chore(code): move sprout code to crates/sprout and remove splash support for minimalism

crates/sprout/Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+name = "edera-sprout"
+description = "Modern UEFI bootloader"
+license = "Apache-2.0"
+version = "0.0.17"
+homepage = "https://sprout.edera.dev"
+repository = "https://github.com/edera-dev/sprout"
+edition = "2024"
+
+[dependencies]
+anyhow = "1.0.100"
+bitflags = "2.10.0"
+toml = "0.9.8"
+log = "0.4.28"
+
+[dependencies.serde]
+version = "1.0.228"
+features = ["derive"]
+
+[dependencies.sha256]
+version = "1.6.0"
+default-features = false
+
+[dependencies.uefi]
+version = "0.36.0"
+features = ["alloc", "logger"]
+
+[dependencies.uefi-raw]
+version = "0.12.0"
+
+[[bin]]
+name = "sprout"
+path = "src/main.rs"

crates/sprout/README.md

@@ -0,0 +1,3 @@
+# Sprout Bootloader
+
+The main bootable crate of the Sprout bootloader.

crates/sprout/build.rs

@@ -0,0 +1,57 @@
+use std::path::PathBuf;
+use std::{env, fs};
+
+/// The size of the sbat.csv file.
+const SBAT_SIZE: usize = 512;
+
+/// Generate the sbat.csv for the .sbat link section.
+///
+/// We intake a sbat.template.tsv and output a sbat.csv which is included by src/sbat.rs
+fn generate_sbat_csv() {
+    // Notify Cargo that if the Sprout version changes, we need to regenerate the sbat.csv.
+    println!("cargo:rerun-if-env-changed=CARGO_PKG_VERSION");
+
+    // The version of the sprout crate.
+    let sprout_version = env::var("CARGO_PKG_VERSION").expect("CARGO_PKG_VERSION not set");
+
+    // The output directory to place the sbat.csv into.
+    let output_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR not set"));
+
+    // The output path to the sbat.csv.
+    let output_file = output_dir.join("sbat.csv");
+
+    // The path to the root of the sprout crate.
+    let sprout_root =
+        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set"));
+
+    // The path to the sbat.template.tsv file is in the source directory of the sprout crate.
+    let template_path = sprout_root.join("src/sbat.template.csv");
+
+    // Read the sbat.csv template file.
+    let template = fs::read_to_string(&template_path).expect("unable to read template file");
+
+    // Replace the version placeholder in the template with the actual version.
+    let sbat = template.replace("{version}", &sprout_version);
+
+    // Encode the sbat.csv as bytes.
+    let mut encoded = sbat.as_bytes().to_vec();
+
+    if encoded.len() > SBAT_SIZE {
+        panic!("sbat.csv is too large");
+    }
+
+    // Pad the sbat.csv to the required size.
+    while encoded.len() < SBAT_SIZE {
+        encoded.push(0);
+    }
+
+    // Write the sbat.csv to the output directory.
+    fs::write(&output_file, encoded).expect("unable to write sbat.csv");
+}
+
+/// Build script entry point.
+/// Right now, all we need to do is generate the sbat.csv file.
+fn main() {
+    // Generate the sbat.csv file.
+    generate_sbat_csv();
+}

crates/sprout/src/actions.rs

@@ -0,0 +1,65 @@
+use crate::context::SproutContext;
+use anyhow::{Context, Result, bail};
+use serde::{Deserialize, Serialize};
+use std::rc::Rc;
+
+/// EFI chainloader action.
+pub mod chainload;
+/// Edera hypervisor action.
+pub mod edera;
+/// EFI console print action.
+pub mod print;
+
+/// Declares an action that sprout can execute.
+/// Actions allow configuring sprout's internal runtime mechanisms with values
+/// that you can specify via other concepts.
+///
+/// Actions are the main work that Sprout gets done, like booting Linux.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct ActionDeclaration {
+    /// Chainload to another EFI application.
+    /// This allows you to load any EFI application, either to boot an operating system
+    /// or to perform more EFI actions and return to sprout.
+    #[serde(default)]
+    pub chainload: Option<chainload::ChainloadConfiguration>,
+    /// Print a string to the EFI console.
+    #[serde(default)]
+    pub print: Option<print::PrintConfiguration>,
+    /// Boot the Edera hypervisor and the root operating system.
+    /// This action is an extension on top of the Xen EFI stub that
+    /// is specific to Edera.
+    #[serde(default, rename = "edera")]
+    pub edera: Option<edera::EderaConfiguration>,
+}
+
+/// Execute the action specified by `name` which should be stored in the
+/// root context of the provided `context`. This function may not return
+/// if the provided action executes an operating system or an EFI application
+/// that does not return control to sprout.
+pub fn execute(context: Rc<SproutContext>, name: impl AsRef<str>) -> Result<()> {
+    // Retrieve the action from the root context.
+    let Some(action) = context.root().actions().get(name.as_ref()) else {
+        bail!("unknown action '{}'", name.as_ref());
+    };
+    // Finalize the context and freeze it.
+    let context = context
+        .finalize()
+        .context("unable to finalize context")?
+        .freeze();
+
+    // Execute the action.
+    if let Some(chainload) = &action.chainload {
+        chainload::chainload(context.clone(), chainload)?;
+        return Ok(());
+    } else if let Some(print) = &action.print {
+        print::print(context.clone(), print)?;
+        return Ok(());
+    } else if let Some(edera) = &action.edera {
+        edera::edera(context.clone(), edera)?;
+        return Ok(());
+    }
+
+    // If we reach here, we don't know how to execute the action that was configured.
+    // This is likely unreachable, but we should still return an error just in case.
+    bail!("unknown action configuration");
+}

crates/sprout/src/actions/chainload.rs

@@ -0,0 +1,122 @@
+use crate::context::SproutContext;
+use crate::integrations::bootloader_interface::BootloaderInterface;
+use crate::integrations::shim::{ShimInput, ShimSupport};
+use crate::utils;
+use crate::utils::media_loader::MediaLoaderHandle;
+use crate::utils::media_loader::constants::linux::LINUX_EFI_INITRD_MEDIA_GUID;
+use anyhow::{Context, Result, bail};
+use log::error;
+use serde::{Deserialize, Serialize};
+use std::rc::Rc;
+use uefi::CString16;
+use uefi::proto::loaded_image::LoadedImage;
+
+/// The configuration of the chainload action.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct ChainloadConfiguration {
+    /// The path to the image to chainload.
+    /// This can be a Linux EFI stub (vmlinuz usually) or a standard EFI executable.
+    pub path: String,
+    /// The options to pass to the image.
+    /// The options are concatenated by a space and then passed to the EFI application.
+    #[serde(default)]
+    pub options: Vec<String>,
+    /// An optional path to a Linux initrd.
+    /// This uses the [LINUX_EFI_INITRD_MEDIA_GUID] mechanism to load the initrd into the EFI stack.
+    /// For Linux, you can also use initrd=\path\to\initrd as an option, but this option is
+    /// generally better and safer as it can support additional load options in the future.
+    #[serde(default, rename = "linux-initrd")]
+    pub linux_initrd: Option<String>,
+}
+
+/// Executes the chainload action using the specified `configuration` inside the provided `context`.
+pub fn chainload(context: Rc<SproutContext>, configuration: &ChainloadConfiguration) -> Result<()> {
+    // Retrieve the current image handle of sprout.
+    let sprout_image = uefi::boot::image_handle();
+
+    // Resolve the path to the image to chainload.
+    let resolved = utils::resolve_path(
+        Some(context.root().loaded_image_path()?),
+        &context.stamp(&configuration.path),
+    )
+    .context("unable to resolve chainload path")?;
+
+    // Load the image to chainload using the shim support integration.
+    // It will determine if the image needs to be loaded via the shim or can be loaded directly.
+    let image = ShimSupport::load(sprout_image, ShimInput::ResolvedPath(&resolved))?;
+
+    // Open the LoadedImage protocol of the image to chainload.
+    let mut loaded_image_protocol = uefi::boot::open_protocol_exclusive::<LoadedImage>(image)
+        .context("unable to open loaded image protocol")?;
+
+    // Stamp and combine the options to pass to the image.
+    let options =
+        utils::combine_options(configuration.options.iter().map(|item| context.stamp(item)));
+
+    // Pass the load options to the image.
+    // If no options are provided, the resulting string will be empty.
+    // The options are pinned and boxed to ensure that they are valid for the lifetime of this
+    // function, which ensures the lifetime of the options for the image runtime.
+    let options = Box::pin(
+        CString16::try_from(&options[..])
+            .context("unable to convert chainloader options to CString16")?,
+    );
+
+    if options.num_bytes() > u32::MAX as usize {
+        bail!("chainloader options too large");
+    }
+
+    // SAFETY: option size is checked to validate it is safe to pass.
+    // Additionally, the pointer is allocated and retained on heap, which makes
+    // passing the `options` pointer safe to the next image.
+    unsafe {
+        loaded_image_protocol
+            .set_load_options(options.as_ptr() as *const u8, options.num_bytes() as u32);
+    }
+
+    // Stamp the initrd path, if provided.
+    let initrd = configuration
+        .linux_initrd
+        .as_ref()
+        .map(|item| context.stamp(item));
+    // The initrd can be None or empty, so we need to collapse that into a single Option.
+    let initrd = utils::empty_is_none(initrd);
+
+    // If an initrd is provided, register it with the EFI stack.
+    let mut initrd_handle = None;
+    if let Some(linux_initrd) = initrd {
+        let content =
+            utils::read_file_contents(Some(context.root().loaded_image_path()?), &linux_initrd)
+                .context("unable to read linux initrd")?;
+        let handle =
+            MediaLoaderHandle::register(LINUX_EFI_INITRD_MEDIA_GUID, content.into_boxed_slice())
+                .context("unable to register linux initrd")?;
+        initrd_handle = Some(handle);
+    }
+
+    // Mark execution of an entry in the bootloader interface.
+    BootloaderInterface::mark_exec(context.root().timer())
+        .context("unable to mark execution of boot entry in bootloader interface")?;
+
+    // Start the loaded image.
+    // This call might return, or it may pass full control to another image that will never return.
+    // Capture the result to ensure we can return an error if the image fails to start, but only
+    // after the optional initrd has been unregistered.
+    let result = uefi::boot::start_image(image);
+
+    // Unregister the initrd if it was registered.
+    if let Some(initrd_handle) = initrd_handle
+        && let Err(error) = initrd_handle.unregister()
+    {
+        error!("unable to unregister linux initrd: {}", error);
+    }
+
+    // Assert there was no error starting the image.
+    result.context("unable to start image")?;
+
+    // Explicitly drop the options to clarify the lifetime.
+    drop(options);
+
+    // Return control to sprout.
+    Ok(())
+}

crates/sprout/src/actions/edera.rs

@@ -0,0 +1,158 @@
+use std::rc::Rc;
+
+use anyhow::{Context, Result};
+use log::error;
+use serde::{Deserialize, Serialize};
+use uefi::Guid;
+
+use crate::{
+    actions::{self, chainload::ChainloadConfiguration},
+    context::SproutContext,
+    utils::{
+        self,
+        media_loader::{
+            MediaLoaderHandle,
+            constants::xen::{
+                XEN_EFI_CONFIG_MEDIA_GUID, XEN_EFI_KERNEL_MEDIA_GUID, XEN_EFI_RAMDISK_MEDIA_GUID,
+            },
+        },
+    },
+};
+
+/// The configuration of the edera action which boots the Edera hypervisor.
+/// Edera is based on Xen but modified significantly with a Rust stack.
+/// Sprout is a component of the Edera stack and provides the boot functionality of Xen.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct EderaConfiguration {
+    /// The path to the Xen hypervisor EFI image.
+    pub xen: String,
+    /// The path to the kernel to boot for dom0.
+    pub kernel: String,
+    /// The path to the initrd to load for dom0.
+    #[serde(default)]
+    pub initrd: Option<String>,
+    /// The options to pass to the kernel.
+    #[serde(default, rename = "kernel-options")]
+    pub kernel_options: Vec<String>,
+    /// The options to pass to the Xen hypervisor.
+    #[serde(default, rename = "xen-options")]
+    pub xen_options: Vec<String>,
+}
+
+/// Builds a configuration string for the Xen EFI stub using the specified `configuration`.
+fn build_xen_config(context: Rc<SproutContext>, configuration: &EderaConfiguration) -> String {
+    // Stamp xen options and combine them.
+    let xen_options = utils::combine_options(
+        configuration
+            .xen_options
+            .iter()
+            .map(|item| context.stamp(item)),
+    );
+
+    // Stamp kernel options and combine them.
+    let kernel_options = utils::combine_options(
+        configuration
+            .kernel_options
+            .iter()
+            .map(|item| context.stamp(item)),
+    );
+
+    // xen config file format is ini-like
+    [
+        // global section
+        "[global]".to_string(),
+        // default configuration section
+        "default=sprout".to_string(),
+        // configuration section for sprout
+        "[sprout]".to_string(),
+        // xen options
+        format!("options={}", xen_options),
+        // kernel options, stub replaces the kernel path
+        // the kernel is provided via media loader
+        format!("kernel=stub {}", kernel_options),
+        // required or else the last line will be ignored
+        "".to_string(),
+    ]
+    .join("\n")
+}
+
+/// Register a media loader for some `text` with the vendor `guid`.
+/// `what` should indicate some identifying value for error messages
+/// like `config` or `kernel`.
+/// Provides a [MediaLoaderHandle] that can be used to unregister the media loader.
+fn register_media_loader_text(guid: Guid, what: &str, text: String) -> Result<MediaLoaderHandle> {
+    MediaLoaderHandle::register(guid, text.as_bytes().to_vec().into_boxed_slice())
+        .context(format!("unable to register {} media loader", what)) /*  */
+}
+
+/// Register a media loader for the file `path` with the vendor `guid`.
+/// `what` should indicate some identifying value for error messages
+/// like `config` or `kernel`.
+/// Provides a [MediaLoaderHandle] that can be used to unregister the media loader.
+fn register_media_loader_file(
+    context: &Rc<SproutContext>,
+    guid: Guid,
+    what: &str,
+    path: &str,
+) -> Result<MediaLoaderHandle> {
+    // Stamp the path to the file.
+    let path = context.stamp(path);
+    // Read the file contents.
+    let content = utils::read_file_contents(Some(context.root().loaded_image_path()?), &path)
+        .context(format!("unable to read {} file", what))?;
+    // Register the media loader.
+    let handle = MediaLoaderHandle::register(guid, content.into_boxed_slice())
+        .context(format!("unable to register {} media loader", what))?;
+    Ok(handle)
+}
+
+/// Executes the edera action which will boot the Edera hypervisor with the specified
+/// `configuration` and `context`. This action uses Edera-specific Xen EFI stub functionality.
+pub fn edera(context: Rc<SproutContext>, configuration: &EderaConfiguration) -> Result<()> {
+    // Build the Xen config file content for this configuration.
+    let config = build_xen_config(context.clone(), configuration);
+
+    // Register the media loader for the config.
+    let config = register_media_loader_text(XEN_EFI_CONFIG_MEDIA_GUID, "config", config)
+        .context("unable to register config media loader")?;
+
+    // Register the media loaders for the kernel.
+    let kernel = register_media_loader_file(
+        &context,
+        XEN_EFI_KERNEL_MEDIA_GUID,
+        "kernel",
+        &configuration.kernel,
+    )
+    .context("unable to register kernel media loader")?;
+
+    // Create a vector of media loaders to unregister on error.
+    let mut media_loaders = vec![config, kernel];
+
+    // Register the initrd if it is provided.
+    if let Some(initrd) = utils::empty_is_none(configuration.initrd.as_ref()) {
+        let initrd =
+            register_media_loader_file(&context, XEN_EFI_RAMDISK_MEDIA_GUID, "initrd", initrd)
+                .context("unable to register initrd media loader")?;
+        media_loaders.push(initrd);
+    }
+
+    // Chainload to the Xen EFI stub.
+    let result = actions::chainload::chainload(
+        context.clone(),
+        &ChainloadConfiguration {
+            path: configuration.xen.clone(),
+            options: vec![],
+            linux_initrd: None,
+        },
+    )
+    .context("unable to chainload to xen");
+
+    // Unregister the media loaders when an error happens.
+    for media_loader in media_loaders {
+        if let Err(error) = media_loader.unregister() {
+            error!("unable to unregister media loader: {}", error);
+        }
+    }
+
+    result
+}

crates/sprout/src/actions/print.rs

@@ -0,0 +1,19 @@
+use crate::context::SproutContext;
+use anyhow::Result;
+use log::info;
+use serde::{Deserialize, Serialize};
+use std::rc::Rc;
+
+/// The configuration of the print action.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct PrintConfiguration {
+    /// The text to print to the console.
+    #[serde(default)]
+    pub text: String,
+}
+
+/// Executes the print action with the specified `configuration` inside the provided `context`.
+pub fn print(context: Rc<SproutContext>, configuration: &PrintConfiguration) -> Result<()> {
+    info!("{}", context.stamp(&configuration.text));
+    Ok(())
+}

crates/sprout/src/autoconfigure.rs

@@ -0,0 +1,57 @@
+use crate::config::RootConfiguration;
+use anyhow::{Context, Result};
+use uefi::fs::FileSystem;
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::media::fs::SimpleFileSystem;
+
+/// bls: autodetect and configure BLS-enabled filesystems.
+pub mod bls;
+
+/// linux: autodetect and configure Linux kernels.
+/// This autoconfiguration module should not be activated
+/// on BLS-enabled filesystems as it may make duplicate entries.
+pub mod linux;
+
+/// windows: autodetect and configure Windows boot configurations.
+pub mod windows;
+
+/// Generate a [RootConfiguration] based on the environment.
+/// Intakes a `config` to use as the basis of the autoconfiguration.
+pub fn autoconfigure(config: &mut RootConfiguration) -> Result<()> {
+    // Find all the filesystems that are on the system.
+    let filesystem_handles =
+        uefi::boot::find_handles::<SimpleFileSystem>().context("unable to scan filesystems")?;
+
+    // For each filesystem that was detected, scan it for supported autoconfig mechanisms.
+    for handle in filesystem_handles {
+        // Acquire the device path root for the filesystem.
+        let root = {
+            uefi::boot::open_protocol_exclusive::<DevicePath>(handle)
+                .context("unable to get root for filesystem")?
+                .to_boxed()
+        };
+
+        // Open the filesystem that was detected.
+        let filesystem = uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(handle)
+            .context("unable to open filesystem")?;
+
+        // Trade the filesystem protocol for the uefi filesystem helper.
+        let mut filesystem = FileSystem::new(filesystem);
+
+        // Scan the filesystem for BLS supported configurations.
+        let bls_found = bls::scan(&mut filesystem, &root, config)
+            .context("unable to scan for bls configurations")?;
+
+        // If BLS was not found, scan for Linux configurations.
+        if !bls_found {
+            linux::scan(&mut filesystem, &root, config)
+                .context("unable to scan for linux configurations")?;
+        }
+
+        // Always look for Windows configurations.
+        windows::scan(&mut filesystem, &root, config)
+            .context("unable to scan for windows configurations")?;
+    }
+
+    Ok(())
+}

crates/sprout/src/autoconfigure/bls.rs

@@ -0,0 +1,101 @@
+use crate::actions::ActionDeclaration;
+use crate::actions::chainload::ChainloadConfiguration;
+use crate::config::RootConfiguration;
+use crate::entries::EntryDeclaration;
+use crate::generators::GeneratorDeclaration;
+use crate::generators::bls::BlsConfiguration;
+use crate::utils;
+use anyhow::{Context, Result};
+use uefi::cstr16;
+use uefi::fs::{FileSystem, Path};
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+
+/// The name prefix of the BLS chainload action that will be used
+/// by the BLS generator to chainload entries.
+const BLS_CHAINLOAD_ACTION_PREFIX: &str = "bls-chainload-";
+
+/// Scan the specified `filesystem` for BLS configurations.
+pub fn scan(
+    filesystem: &mut FileSystem,
+    root: &DevicePath,
+    config: &mut RootConfiguration,
+) -> Result<bool> {
+    // BLS has a loader.conf file that can specify its own auto-entries mechanism.
+    let bls_loader_conf_path = Path::new(cstr16!("\\loader\\loader.conf"));
+    // BLS also has an entries directory that can specify explicit entries.
+    let bls_entries_path = Path::new(cstr16!("\\loader\\entries"));
+
+    // Convert the device path root to a string we can use in the configuration.
+    let mut root = root
+        .to_string(DisplayOnly(false), AllowShortcuts(false))
+        .context("unable to convert device root to string")?
+        .to_string();
+    // Add a trailing forward-slash to the root to ensure the device root is completed.
+    root.push('/');
+
+    // Generate a unique hash of the root path.
+    let root_unique_hash = utils::unique_hash(&root);
+
+    // Whether we have a loader.conf file.
+    let has_loader_conf = filesystem
+        .try_exists(bls_loader_conf_path)
+        .context("unable to check for BLS loader.conf file")?;
+
+    // Whether we have an entries directory.
+    // We actually iterate the entries to see if there are any.
+    let has_entries_dir = filesystem
+        .read_dir(bls_entries_path)
+        .ok()
+        .and_then(|mut iterator| iterator.next())
+        .map(|entry| entry.is_ok())
+        .unwrap_or(false);
+
+    // Detect if a BLS supported configuration is on this filesystem.
+    // We check both loader.conf and entries directory as only one of them is required.
+    if !(has_loader_conf || has_entries_dir) {
+        return Ok(false);
+    }
+
+    // Generate a unique name for the BLS chainload action.
+    let chainload_action_name = format!("{}{}", BLS_CHAINLOAD_ACTION_PREFIX, root_unique_hash,);
+
+    // BLS is now detected, generate a configuration for it.
+    let generator = BlsConfiguration {
+        entry: EntryDeclaration {
+            title: "$title".to_string(),
+            actions: vec![chainload_action_name.clone()],
+            ..Default::default()
+        },
+        path: format!("{}\\loader", root),
+    };
+
+    // Generate a unique name for the BLS generator and insert the generator into the configuration.
+    config.generators.insert(
+        format!("auto-bls-{}", root_unique_hash),
+        GeneratorDeclaration {
+            bls: Some(generator),
+            ..Default::default()
+        },
+    );
+
+    // Generate a chainload configuration for BLS.
+    // BLS will provide these values to us.
+    let chainload = ChainloadConfiguration {
+        path: format!("{}\\$chainload", root),
+        options: vec!["$options".to_string()],
+        linux_initrd: Some(format!("{}\\$initrd", root)),
+    };
+
+    // Insert the chainload action into the configuration.
+    config.actions.insert(
+        chainload_action_name,
+        ActionDeclaration {
+            chainload: Some(chainload),
+            ..Default::default()
+        },
+    );
+
+    // We had a BLS supported configuration, so return true.
+    Ok(true)
+}

crates/sprout/src/autoconfigure/linux.rs

@@ -0,0 +1,254 @@
+use crate::actions::ActionDeclaration;
+use crate::actions::chainload::ChainloadConfiguration;
+use crate::config::RootConfiguration;
+use crate::entries::EntryDeclaration;
+use crate::generators::GeneratorDeclaration;
+use crate::generators::list::ListConfiguration;
+use crate::utils;
+use crate::utils::vercmp;
+use anyhow::{Context, Result};
+use std::collections::BTreeMap;
+use uefi::CString16;
+use uefi::fs::{FileSystem, Path, PathBuf};
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+
+/// The name prefix of the Linux chainload action that will be used to boot Linux.
+const LINUX_CHAINLOAD_ACTION_PREFIX: &str = "linux-chainload-";
+
+/// The locations to scan for kernel pairs.
+/// We will check for symlinks and if this directory is a symlink, we will skip it.
+/// The empty string represents the root of the filesystem.
+const SCAN_LOCATIONS: &[&str] = &["\\boot", "\\"];
+
+/// Prefixes of kernel files to scan for.
+const KERNEL_PREFIXES: &[&str] = &["vmlinuz"];
+
+/// Prefixes of initramfs files to match to.
+const INITRAMFS_PREFIXES: &[&str] = &["initramfs", "initrd", "initrd.img"];
+
+/// This is really silly, but if what we are booting is the Canonical stubble stub,
+/// there is a chance it will assert that the load options are non-empty.
+/// Technically speaking, load options can be empty. However, it assumes load options
+/// have something in it. Canonical's stubble copied code from systemd that does this
+/// and then uses that code improperly by asserting that the pointer is non-null.
+/// To give a good user experience, we place a placeholder value here to ensure it's non-empty.
+/// For stubble, this code ensures the command line pointer becomes null:
+/// https://github.com/ubuntu/stubble/blob/e56643979addfb98982266018e08921c07424a0c/stub.c#L61-L64
+/// Then this code asserts on it, stopping the boot process:
+/// https://github.com/ubuntu/stubble/blob/e56643979addfb98982266018e08921c07424a0c/stub.c#L27
+const DEFAULT_LINUX_OPTIONS: &str = "placeholder";
+
+/// Pair of kernel and initramfs.
+/// This is what scanning a directory is meant to find.
+struct KernelPair {
+    /// The path to a kernel.
+    kernel: String,
+    /// The path to an initramfs, if any.
+    initramfs: Option<String>,
+}
+
+/// Scan the specified `filesystem` at `path` for [KernelPair] results.
+fn scan_directory(filesystem: &mut FileSystem, path: &str) -> Result<Vec<KernelPair>> {
+    // All the discovered kernel pairs.
+    let mut pairs = Vec::new();
+
+    // We have to special-case the root directory due to path logic in the uefi crate.
+    let is_root = path.is_empty() || path == "\\";
+
+    // Construct a filesystem path from the path string.
+    let path = CString16::try_from(path).context("unable to convert path to CString16")?;
+    let path = Path::new(&path);
+    let path = path.to_path_buf();
+
+    // Check if the path exists and is a directory.
+    let exists = filesystem
+        .metadata(&path)
+        .ok()
+        .map(|metadata| metadata.is_directory())
+        .unwrap_or(false);
+
+    // If the path does not exist, return an empty list.
+    if !exists {
+        return Ok(pairs);
+    }
+
+    // Open a directory iterator on the path to scan.
+    // Ignore errors here as in some scenarios this might fail due to symlinks.
+    let Some(directory) = filesystem.read_dir(&path).ok() else {
+        return Ok(pairs);
+    };
+
+    // Create a new path used for joining file names below.
+    // All attempts to derive paths for the files in the directory should use this instead.
+    // The uefi crate does not handle push correctly for the root directory.
+    // It will add a second slash, which will cause our path logic to fail.
+    let path_for_join = if is_root {
+        PathBuf::new()
+    } else {
+        path.clone()
+    };
+
+    // For each item in the directory, find a kernel.
+    for item in directory {
+        let item = item.context("unable to read directory item")?;
+
+        // Skip over any items that are not regular files.
+        if !item.is_regular_file() {
+            continue;
+        }
+
+        // Convert the name from a CString16 to a String.
+        let name = item.file_name().to_string();
+
+        // Convert the name to lowercase to make all of this case-insensitive.
+        let name_for_match = name.to_lowercase();
+
+        // Find a kernel prefix that matches, if any.
+        // This is case-insensitive to ensure we pick up all possibilities.
+        let Some(prefix) = KERNEL_PREFIXES.iter().find(|prefix| {
+            name_for_match == **prefix || name_for_match.starts_with(&format!("{}-", prefix))
+        }) else {
+            // Skip over anything that doesn't match a kernel prefix.
+            continue;
+        };
+
+        // Acquire the suffix of the name, this will be used to match an initramfs.
+        let suffix = &name[prefix.len()..];
+
+        // Find a matching initramfs, if any.
+        let mut initramfs_prefix_iter = INITRAMFS_PREFIXES.iter();
+        let matched_initramfs_path = loop {
+            let Some(prefix) = initramfs_prefix_iter.next() else {
+                break None;
+            };
+            // Construct an initramfs path.
+            let initramfs = format!("{}{}", prefix, suffix);
+            let initramfs = CString16::try_from(initramfs.as_str())
+                .context("unable to convert initramfs name to CString16")?;
+            let mut initramfs_path = path_for_join.clone();
+            initramfs_path.push(Path::new(&initramfs));
+
+            // Check if the initramfs path exists, if it does, break out of the loop.
+            if filesystem
+                .try_exists(&initramfs_path)
+                .context("unable to check if initramfs path exists")?
+            {
+                break Some(initramfs_path);
+            }
+        };
+
+        // Construct a kernel path from the kernel name.
+        let mut kernel = path_for_join.clone();
+        kernel.push(Path::new(&item.file_name()));
+        let kernel = kernel.to_string();
+        let initramfs = matched_initramfs_path.map(|initramfs_path| initramfs_path.to_string());
+
+        // Produce a kernel pair.
+        let pair = KernelPair { kernel, initramfs };
+        pairs.push(pair);
+    }
+
+    Ok(pairs)
+}
+
+/// Scan the specified `filesystem` for Linux kernels and matching initramfs.
+pub fn scan(
+    filesystem: &mut FileSystem,
+    root: &DevicePath,
+    config: &mut RootConfiguration,
+) -> Result<bool> {
+    let mut pairs = Vec::new();
+
+    // Convert the device path root to a string we can use in the configuration.
+    let mut root = root
+        .to_string(DisplayOnly(false), AllowShortcuts(false))
+        .context("unable to convert device root to string")?
+        .to_string();
+    // Add a trailing forward-slash to the root to ensure the device root is completed.
+    root.push('/');
+
+    // Generate a unique hash of the root path.
+    let root_unique_hash = utils::unique_hash(&root);
+
+    // Scan all locations for kernel pairs, adding them to the list.
+    for location in SCAN_LOCATIONS {
+        let scanned = scan_directory(filesystem, location)
+            .with_context(|| format!("unable to scan directory {}", location))?;
+        pairs.extend(scanned);
+    }
+
+    // If no kernel pairs were found, return false.
+    if pairs.is_empty() {
+        return Ok(false);
+    }
+
+    // Sort the kernel pairs by kernel version, if it has one, newer kernels first.
+    pairs.sort_by(|a, b| vercmp::compare_versions(&a.kernel, &b.kernel).reverse());
+
+    // Generate a unique name for the linux chainload action.
+    let chainload_action_name = format!("{}{}", LINUX_CHAINLOAD_ACTION_PREFIX, root_unique_hash,);
+
+    // Kernel pairs are detected, generate a list configuration for it.
+    let generator = ListConfiguration {
+        entry: EntryDeclaration {
+            title: "Boot Linux $name".to_string(),
+            actions: vec![chainload_action_name.clone()],
+            ..Default::default()
+        },
+        values: pairs
+            .into_iter()
+            .map(|pair| {
+                BTreeMap::from_iter(vec![
+                    ("name".to_string(), pair.kernel.clone()),
+                    ("kernel".to_string(), format!("{}{}", root, pair.kernel)),
+                    (
+                        "initrd".to_string(),
+                        pair.initramfs
+                            .map(|initramfs| format!("{}{}", root, initramfs))
+                            .unwrap_or_default(),
+                    ),
+                ])
+            })
+            .collect(),
+    };
+
+    // Generate a unique name for the Linux generator and insert the generator into the configuration.
+    config.generators.insert(
+        format!("auto-linux-{}", root_unique_hash),
+        GeneratorDeclaration {
+            list: Some(generator),
+            ..Default::default()
+        },
+    );
+
+    // Insert a default value for the linux-options if it doesn't exist.
+    if !config.values.contains_key("linux-options") {
+        config.values.insert(
+            "linux-options".to_string(),
+            DEFAULT_LINUX_OPTIONS.to_string(),
+        );
+    }
+
+    // Generate a chainload configuration for the list generator.
+    // The list will provide these values to us.
+    // Note that we don't need an extra \\ in the paths here.
+    // The root already contains a trailing slash.
+    let chainload = ChainloadConfiguration {
+        path: "$kernel".to_string(),
+        options: vec!["$linux-options".to_string()],
+        linux_initrd: Some("$initrd".to_string()),
+    };
+
+    // Insert the chainload action into the configuration.
+    config.actions.insert(
+        chainload_action_name,
+        ActionDeclaration {
+            chainload: Some(chainload),
+            ..Default::default()
+        },
+    );
+
+    // We had a Linux kernel, so return true to indicate something was found.
+    Ok(true)
+}

crates/sprout/src/autoconfigure/windows.rs

@@ -0,0 +1,80 @@
+use crate::actions::ActionDeclaration;
+use crate::actions::chainload::ChainloadConfiguration;
+use crate::config::RootConfiguration;
+use crate::entries::EntryDeclaration;
+use crate::utils;
+use anyhow::{Context, Result};
+use uefi::CString16;
+use uefi::fs::{FileSystem, Path};
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+
+/// The name prefix of the Windows chainload action that will be used to boot Windows.
+const WINDOWS_CHAINLOAD_ACTION_PREFIX: &str = "windows-chainload-";
+
+/// Windows boot manager path.
+const BOOTMGR_FW_PATH: &str = "\\EFI\\Microsoft\\Boot\\bootmgfw.efi";
+
+/// Scan the specified `filesystem` for Windows configurations.
+pub fn scan(
+    filesystem: &mut FileSystem,
+    root: &DevicePath,
+    config: &mut RootConfiguration,
+) -> Result<bool> {
+    // Convert the boot manager firmware path to a path.
+    let bootmgr_fw_path =
+        CString16::try_from(BOOTMGR_FW_PATH).context("unable to convert path to CString16")?;
+    let bootmgr_fw_path = Path::new(&bootmgr_fw_path);
+
+    // Check if the boot manager firmware path exists, if it doesn't, return false.
+    if !filesystem
+        .try_exists(bootmgr_fw_path)
+        .context("unable to check if bootmgr firmware path exists")?
+    {
+        return Ok(false);
+    }
+
+    // Convert the device path root to a string we can use in the configuration.
+    let mut root = root
+        .to_string(DisplayOnly(false), AllowShortcuts(false))
+        .context("unable to convert device root to string")?
+        .to_string();
+    // Add a trailing forward-slash to the root to ensure the device root is completed.
+    root.push('/');
+
+    // Generate a unique hash of the root path.
+    let root_unique_hash = utils::unique_hash(&root);
+
+    // Generate a unique name for the Windows chainload action.
+    let chainload_action_name = format!("{}{}", WINDOWS_CHAINLOAD_ACTION_PREFIX, root_unique_hash,);
+
+    // Generate an entry name for Windows.
+    let entry_name = format!("auto-windows-{}", root_unique_hash,);
+
+    // Create an entry for Windows and insert it into the configuration.
+    let entry = EntryDeclaration {
+        title: "Boot Windows".to_string(),
+        actions: vec![chainload_action_name.clone()],
+        values: Default::default(),
+    };
+    config.entries.insert(entry_name, entry);
+
+    // Generate a chainload configuration for Windows.
+    let chainload = ChainloadConfiguration {
+        path: format!("{}{}", root, bootmgr_fw_path),
+        options: vec![],
+        ..Default::default()
+    };
+
+    // Insert the chainload action into the configuration.
+    config.actions.insert(
+        chainload_action_name,
+        ActionDeclaration {
+            chainload: Some(chainload),
+            ..Default::default()
+        },
+    );
+
+    // We have a Windows boot entry, so return true to indicate something was found.
+    Ok(true)
+}

crates/sprout/src/config.rs

@@ -0,0 +1,89 @@
+use crate::actions::ActionDeclaration;
+use crate::drivers::DriverDeclaration;
+use crate::entries::EntryDeclaration;
+use crate::extractors::ExtractorDeclaration;
+use crate::generators::GeneratorDeclaration;
+use crate::phases::PhasesConfiguration;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+
+/// The configuration loader mechanisms.
+pub mod loader;
+
+/// This is the latest version of the sprout configuration format.
+/// This must be incremented when the configuration breaks compatibility.
+pub const LATEST_VERSION: u32 = 1;
+
+/// The default timeout for the boot menu in seconds.
+pub const DEFAULT_MENU_TIMEOUT_SECONDS: u64 = 10;
+
+/// The Sprout configuration format.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct RootConfiguration {
+    /// The version of the configuration. This should always be declared
+    /// and be the latest version that is supported. If not specified, it is assumed
+    /// the configuration is the latest version.
+    #[serde(default = "latest_version")]
+    pub version: u32,
+    /// Default options for Sprout.
+    #[serde(default)]
+    pub options: OptionsConfiguration,
+    /// Values to be inserted into the root sprout context.
+    #[serde(default)]
+    pub values: BTreeMap<String, String>,
+    /// Drivers to load.
+    /// These drivers provide extra functionality like filesystem support to Sprout.
+    /// Each driver has a name which uniquely identifies it inside Sprout.
+    #[serde(default)]
+    pub drivers: BTreeMap<String, DriverDeclaration>,
+    /// Declares the extractors that add values to the sprout context that are calculated
+    /// at runtime. Each extractor has a name which corresponds to the value it will set
+    /// inside the sprout context.
+    #[serde(default)]
+    pub extractors: BTreeMap<String, ExtractorDeclaration>,
+    /// Declares the actions that can execute operations for sprout.
+    /// Actions are executable modules in sprout that take in specific structured values.
+    /// Actions are responsible for ensuring that passed strings are stamped to replace values
+    /// at runtime.
+    /// Each action has a name that can be referenced by other base concepts like entries.
+    #[serde(default)]
+    pub actions: BTreeMap<String, ActionDeclaration>,
+    /// Declares the entries that are displayed on the boot menu. These entries are static
+    /// but can still use values from the sprout context.
+    #[serde(default)]
+    pub entries: BTreeMap<String, EntryDeclaration>,
+    /// Declares the generators that are used to generate entries at runtime.
+    /// Each generator has its own logic for generating entries, but generally they intake
+    /// a template entry and stamp that template entry over some values determined at runtime.
+    /// Each generator has an associated name used to differentiate it across sprout.
+    #[serde(default)]
+    pub generators: BTreeMap<String, GeneratorDeclaration>,
+    /// Configures the various phases of sprout. This allows you to hook into specific parts
+    /// of the boot process to execute actions, for example, you can show a boot splash during
+    /// the early phase.
+    #[serde(default)]
+    pub phases: PhasesConfiguration,
+}
+
+/// Options configuration for Sprout, used when the corresponding options are not specified.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct OptionsConfiguration {
+    /// The entry to boot without showing the boot menu.
+    /// If not specified, a boot menu is shown.
+    #[serde(rename = "default-entry", default)]
+    pub default_entry: Option<String>,
+    /// The timeout of the boot menu.
+    #[serde(rename = "menu-timeout", default = "default_menu_timeout")]
+    pub menu_timeout: u64,
+    /// Enables autoconfiguration of Sprout based on the environment.
+    #[serde(default)]
+    pub autoconfigure: bool,
+}
+
+fn latest_version() -> u32 {
+    LATEST_VERSION
+}
+
+fn default_menu_timeout() -> u64 {
+    DEFAULT_MENU_TIMEOUT_SECONDS
+}

crates/sprout/src/config/loader.rs

@@ -0,0 +1,68 @@
+use crate::config::{RootConfiguration, latest_version};
+use crate::options::SproutOptions;
+use crate::platform::tpm::PlatformTpm;
+use crate::utils;
+use anyhow::{Context, Result, bail};
+use log::info;
+use std::ops::Deref;
+use toml::Value;
+use uefi::proto::device_path::LoadedImageDevicePath;
+
+/// Loads the raw configuration from the sprout config file as data.
+fn load_raw_config(options: &SproutOptions) -> Result<Vec<u8>> {
+    // Open the LoadedImageDevicePath protocol to get the path to the current image.
+    let current_image_device_path_protocol =
+        uefi::boot::open_protocol_exclusive::<LoadedImageDevicePath>(uefi::boot::image_handle())
+            .context("unable to get loaded image device path")?;
+    // Acquire the device path as a boxed device path.
+    let path = current_image_device_path_protocol.deref().to_boxed();
+
+    info!("configuration file: {}", options.config);
+
+    // Read the contents of the sprout config file.
+    let content = utils::read_file_contents(Some(&path), &options.config)
+        .context("unable to read sprout config file")?;
+
+    // Measure the sprout.toml into the TPM, if needed and possible.
+    PlatformTpm::log_event(
+        PlatformTpm::PCR_BOOT_LOADER_CONFIG,
+        &content,
+        "sprout: configuration file",
+    )
+    .context("unable to measure the sprout.toml file into the TPM")?;
+
+    // Return the contents of the sprout config file.
+    Ok(content)
+}
+
+/// Loads the [RootConfiguration] for Sprout.
+pub fn load(options: &SproutOptions) -> Result<RootConfiguration> {
+    // Load the raw configuration from the sprout config file.
+    let content = load_raw_config(options)?;
+    // Parse the raw configuration into a toml::Value which can represent any TOML file.
+    let value: Value = toml::from_slice(&content).context("unable to parse sprout config file")?;
+
+    // Check the version of the configuration without parsing the full configuration.
+    let version = value
+        .get("version")
+        .cloned()
+        .unwrap_or_else(|| Value::Integer(latest_version() as i64));
+
+    // Parse the version into an u32.
+    let version: u32 = version
+        .try_into()
+        .context("unable to get configuration version")?;
+
+    // Check if the version is supported.
+    if version != latest_version() {
+        bail!("unsupported configuration version: {}", version);
+    }
+
+    // If the version is supported, parse the full configuration.
+    let config: RootConfiguration = value
+        .try_into()
+        .context("unable to parse sprout.toml file")?;
+
+    // Return the parsed configuration.
+    Ok(config)
+}

crates/sprout/src/context.rs

@@ -0,0 +1,273 @@
+use crate::actions::ActionDeclaration;
+use crate::options::SproutOptions;
+use crate::platform::timer::PlatformTimer;
+use anyhow::anyhow;
+use anyhow::{Result, bail};
+use std::cmp::Reverse;
+use std::collections::{BTreeMap, BTreeSet};
+use std::rc::Rc;
+use uefi::proto::device_path::DevicePath;
+
+/// The maximum number of iterations that can be performed in [SproutContext::finalize].
+const CONTEXT_FINALIZE_ITERATION_LIMIT: usize = 100;
+
+/// Declares a root context for Sprout.
+/// This contains data that needs to be shared across Sprout.
+pub struct RootContext {
+    /// The actions that are available in Sprout.
+    actions: BTreeMap<String, ActionDeclaration>,
+    /// The device path of the loaded Sprout image.
+    loaded_image_path: Option<Box<DevicePath>>,
+    /// Platform timer started at the beginning of the boot process.
+    timer: PlatformTimer,
+    /// The global options of Sprout.
+    options: SproutOptions,
+}
+
+impl RootContext {
+    /// Creates a new root context with the `loaded_image_device_path` which will be stored
+    /// in the context for easy access. We also provide a `timer` which is used to measure elapsed
+    /// time for the bootloader.
+    pub fn new(
+        loaded_image_device_path: Box<DevicePath>,
+        timer: PlatformTimer,
+        options: SproutOptions,
+    ) -> Self {
+        Self {
+            actions: BTreeMap::new(),
+            timer,
+            loaded_image_path: Some(loaded_image_device_path),
+            options,
+        }
+    }
+
+    /// Access the actions configured inside Sprout.
+    pub fn actions(&self) -> &BTreeMap<String, ActionDeclaration> {
+        &self.actions
+    }
+
+    /// Access the actions configured inside Sprout mutably for modification.
+    pub fn actions_mut(&mut self) -> &mut BTreeMap<String, ActionDeclaration> {
+        &mut self.actions
+    }
+
+    /// Access the platform timer that is started at the beginning of the boot process.
+    pub fn timer(&self) -> &PlatformTimer {
+        &self.timer
+    }
+
+    /// Access the device path of the loaded Sprout image.
+    pub fn loaded_image_path(&self) -> Result<&DevicePath> {
+        self.loaded_image_path
+            .as_deref()
+            .ok_or_else(|| anyhow!("no loaded image path"))
+    }
+
+    /// Access the global Sprout options.
+    pub fn options(&self) -> &SproutOptions {
+        &self.options
+    }
+}
+
+/// A context of Sprout. This is passed around different parts of Sprout and represents
+/// a [RootContext] which is data that is shared globally, and [SproutContext] which works
+/// sort of like a tree of values. You can cheaply clone a [SproutContext] and modify it with
+/// new values, which override the values of contexts above it.
+///
+/// This is a core part of the value mechanism in Sprout which makes templating possible.
+pub struct SproutContext {
+    root: Rc<RootContext>,
+    parent: Option<Rc<SproutContext>>,
+    values: BTreeMap<String, String>,
+}
+
+impl SproutContext {
+    /// Create a new [SproutContext] using `root` as the root context.
+    pub fn new(root: RootContext) -> Self {
+        Self {
+            root: Rc::new(root),
+            parent: None,
+            values: BTreeMap::new(),
+        }
+    }
+
+    /// Access the root context of this context.
+    pub fn root(&self) -> &RootContext {
+        self.root.as_ref()
+    }
+
+    /// Access the root context to modify it, if possible.
+    pub fn root_mut(&mut self) -> Option<&mut RootContext> {
+        Rc::get_mut(&mut self.root)
+    }
+
+    /// Retrieve the value specified by `key` from this context or its parents.
+    /// Returns `None` if the value is not found.
+    pub fn get(&self, key: impl AsRef<str>) -> Option<&String> {
+        self.values.get(key.as_ref()).or_else(|| {
+            self.parent
+                .as_ref()
+                .and_then(|parent| parent.get(key.as_ref()))
+        })
+    }
+
+    /// Collects all keys that are present in this context or its parents.
+    /// This is useful for iterating over all keys in a context.
+    pub fn all_keys(&self) -> Vec<String> {
+        let mut keys = BTreeSet::new();
+
+        for key in self.values.keys() {
+            keys.insert(key.clone());
+        }
+
+        if let Some(parent) = &self.parent {
+            keys.extend(parent.all_keys());
+        }
+        keys.into_iter().collect()
+    }
+
+    /// Collects all values that are present in this context or its parents.
+    /// This is useful for iterating over all values in a context.
+    pub fn all_values(&self) -> BTreeMap<String, String> {
+        let mut values = BTreeMap::new();
+        for key in self.all_keys() {
+            // Acquire the value from the context. Since retrieving all the keys will give us
+            // a full view of the context, we can be sure that the key exists.
+            let value = self.get(&key).cloned().unwrap_or_default();
+            values.insert(key.clone(), value);
+        }
+        values
+    }
+
+    /// Sets the value `key` to the value specified by `value` in this context.
+    /// If the parent context has this key, this will override that key.
+    pub fn set(&mut self, key: impl AsRef<str>, value: impl ToString) {
+        self.values
+            .insert(key.as_ref().to_string(), value.to_string());
+    }
+
+    /// Inserts all the specified `values` into this context.
+    /// These values will take precedence over its parent context.
+    pub fn insert(&mut self, values: &BTreeMap<String, String>) {
+        for (key, value) in values {
+            self.values.insert(key.clone(), value.clone());
+        }
+    }
+
+    /// Forks this context as an owned [SproutContext]. This makes it possible
+    /// to cheaply modify a context without cloning the parent context map.
+    /// The parent of the returned context is [self].
+    pub fn fork(self: &Rc<SproutContext>) -> Self {
+        Self {
+            root: self.root.clone(),
+            parent: Some(self.clone()),
+            values: BTreeMap::new(),
+        }
+    }
+
+    /// Freezes this context into a [Rc] which makes it possible to cheaply clone
+    /// and makes it less easy to modify a context. This can be used to pass the context
+    /// to various other parts of Sprout and ensure it won't be modified. Instead, once
+    /// a context is frozen, it should be [self.fork]'d to be modified.
+    pub fn freeze(self) -> Rc<SproutContext> {
+        Rc::new(self)
+    }
+
+    /// Finalizes a context by producing a context with no parent that contains all the values
+    /// of all parent contexts merged. This makes it possible to ensure [SproutContext] has no
+    /// inheritance with other [SproutContext]s. It will still contain a [RootContext] however.
+    pub fn finalize(&self) -> Result<SproutContext> {
+        // Collect all the values from the context and its parents.
+        let mut current_values = self.all_values();
+
+        // To ensure that there is no possible infinite loop, we need to check
+        // the number of iterations. If it exceeds CONTEXT_FINALIZE_ITERATION_LIMIT, we bail.
+        let mut iterations: usize = 0;
+        loop {
+            iterations += 1;
+
+            if iterations > CONTEXT_FINALIZE_ITERATION_LIMIT {
+                bail!("maximum number of replacement iterations reached while finalizing context");
+            }
+
+            let mut did_change = false;
+            let mut values = BTreeMap::new();
+            for (key, value) in &current_values {
+                let (changed, result) = Self::stamp_values(&current_values, value);
+                if changed {
+                    // If the value changed, we need to re-stamp it.
+                    did_change = true;
+                }
+                // Insert the new value into the value map.
+                values.insert(key.clone(), result);
+            }
+            current_values = values;
+
+            // If the values did not change, we can stop.
+            if !did_change {
+                break;
+            }
+        }
+
+        // Produce the final context.
+        Ok(Self {
+            root: self.root.clone(),
+            parent: None,
+            values: current_values,
+        })
+    }
+
+    /// Stamps the `text` value with the specified `values` map. The returned value indicates
+    /// whether the `text` has been changed and the value that was stamped and changed.
+    ///
+    /// Stamping works like this:
+    /// - Start with the input text.
+    /// - Sort all the keys in reverse length order (longest keys first)
+    /// - For each key, if the key is not empty, replace $KEY in the text.
+    /// - Each follow-up iteration acts upon the last iterations result.
+    /// - We keep track if the text changes during the replacement.
+    /// - We return both whether the text changed during any iteration and the final result.
+    fn stamp_values(values: &BTreeMap<String, String>, text: impl AsRef<str>) -> (bool, String) {
+        let mut result = text.as_ref().to_string();
+        let mut did_change = false;
+
+        // Sort the keys by length. This is to ensure that we stamp the longest keys first.
+        // If we did not do this, "$abc" could be stamped by "$a" into an invalid result.
+        let mut keys = values.keys().collect::<Vec<_>>();
+
+        // Sort by key length, reversed. This results in the longest keys appearing first.
+        keys.sort_by_key(|key| Reverse(key.len()));
+
+        for key in keys {
+            // Empty keys are not supported.
+            if key.is_empty() {
+                continue;
+            }
+
+            // We can fetch the value from the map. It is verifiable that the key exists.
+            let Some(value) = values.get(key) else {
+                unreachable!("keys iterated over is collected on a map that cannot be modified");
+            };
+
+            let next_result = result.replace(&format!("${key}"), value);
+            if result != next_result {
+                did_change = true;
+            }
+            result = next_result;
+        }
+        (did_change, result)
+    }
+
+    /// Stamps the input `text` with all the values in this [SproutContext] and it's parents.
+    /// For example, if this context contains {"a":"b"}, and the text "hello\\$a", it will produce
+    /// "hello\\b" as an output string.
+    pub fn stamp(&self, text: impl AsRef<str>) -> String {
+        Self::stamp_values(&self.all_values(), text.as_ref()).1
+    }
+
+    /// Unloads a [SproutContext] back into an owned context. This
+    /// may not succeed if something else is holding onto the value.
+    pub fn unload(self: Rc<SproutContext>) -> Option<SproutContext> {
+        Rc::into_inner(self)
+    }
+}

crates/sprout/src/drivers.rs

@@ -0,0 +1,89 @@
+use crate::context::SproutContext;
+use crate::integrations::shim::{ShimInput, ShimSupport};
+use crate::utils;
+use anyhow::{Context, Result};
+use log::info;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::rc::Rc;
+use uefi::boot::SearchType;
+
+/// Declares a driver configuration.
+/// Drivers allow extending the functionality of Sprout.
+/// Drivers are loaded at runtime and can provide extra functionality like filesystem support.
+/// Drivers are loaded by their name, which is used to reference them in other concepts.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct DriverDeclaration {
+    /// The filesystem path to the driver.
+    /// This file should be an EFI executable that can be located and executed.
+    pub path: String,
+}
+
+/// Loads the driver specified by the `driver` declaration.
+fn load_driver(context: Rc<SproutContext>, driver: &DriverDeclaration) -> Result<()> {
+    // Acquire the handle and device path of the loaded image.
+    let sprout_image = uefi::boot::image_handle();
+
+    // Resolve the path to the driver image.
+    let resolved = utils::resolve_path(
+        Some(context.root().loaded_image_path()?),
+        &context.stamp(&driver.path),
+    )
+    .context("unable to resolve path to driver")?;
+
+    // Load the driver image using the shim support integration.
+    // It will determine if the image needs to be loaded via the shim or can be loaded directly.
+    let image = ShimSupport::load(sprout_image, ShimInput::ResolvedPath(&resolved))?;
+
+    // Start the driver image, this is expected to return control to sprout.
+    // There is no guarantee that the driver will actually return control as it is
+    // just a standard EFI image.
+    uefi::boot::start_image(image).context("unable to start driver image")?;
+
+    Ok(())
+}
+
+/// Reconnects all handles to their controllers.
+/// This is effectively a UEFI stack reload in a sense.
+/// After we load all the drivers, we need to reconnect all of their handles
+/// so that filesystems are recognized again.
+fn reconnect() -> Result<()> {
+    // Locate all of the handles in the UEFI stack.
+    let handles = uefi::boot::locate_handle_buffer(SearchType::AllHandles)
+        .context("unable to locate handles buffer")?;
+
+    for handle in handles.iter() {
+        // Ignore the result as there is nothing we can do if reconnecting a controller fails.
+        // This is also likely to fail in some cases but should fail safely.
+        let _ = uefi::boot::connect_controller(*handle, None, None, true);
+    }
+
+    Ok(())
+}
+
+/// Load all the drivers specified in `drivers`.
+/// There is no driver order currently. This will reconnect all the controllers
+/// to all handles if at least one driver was loaded.
+pub fn load(
+    context: Rc<SproutContext>,
+    drivers: &BTreeMap<String, DriverDeclaration>,
+) -> Result<()> {
+    // If there are no drivers, we don't need to do anything.
+    if drivers.is_empty() {
+        return Ok(());
+    }
+
+    info!("loading drivers");
+
+    // Load all the drivers in no particular order.
+    for (name, driver) in drivers {
+        load_driver(context.clone(), driver).context(format!("unable to load driver: {}", name))?;
+    }
+
+    // Reconnect all the controllers to all handles.
+    reconnect().context("unable to reconnect drivers")?;
+    info!("loaded drivers");
+
+    // We've now loaded all the drivers, so we can return.
+    Ok(())
+}

crates/sprout/src/entries.rs

@@ -0,0 +1,128 @@
+use crate::context::SproutContext;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+/// Declares a boot entry to display in the boot menu.
+///
+/// Entries are the user-facing concept of Sprout, making it possible
+/// to run a set of actions with a specific context.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct EntryDeclaration {
+    /// The title of the entry which will be display in the boot menu.
+    /// This is the pre-stamped value.
+    pub title: String,
+    /// The actions to run when the entry is selected.
+    #[serde(default)]
+    pub actions: Vec<String>,
+    /// The values to insert into the context when the entry is selected.
+    #[serde(default)]
+    pub values: BTreeMap<String, String>,
+}
+
+/// Represents an entry that is stamped and ready to be booted.
+#[derive(Clone)]
+pub struct BootableEntry {
+    name: String,
+    title: String,
+    context: Rc<SproutContext>,
+    declaration: EntryDeclaration,
+    default: bool,
+    pin_name: bool,
+}
+
+impl BootableEntry {
+    /// Create a new bootable entry to represent the full context of an entry.
+    pub fn new(
+        name: String,
+        title: String,
+        context: Rc<SproutContext>,
+        declaration: EntryDeclaration,
+    ) -> Self {
+        Self {
+            name,
+            title,
+            context,
+            declaration,
+            default: false,
+            pin_name: false,
+        }
+    }
+
+    /// Fetch the name of the entry. This is usually a machine-identifiable key.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Fetch the title of the entry. This is usually a human-readable key.
+    pub fn title(&self) -> &str {
+        &self.title
+    }
+
+    /// Fetch the full context of the entry.
+    pub fn context(&self) -> Rc<SproutContext> {
+        Rc::clone(&self.context)
+    }
+
+    /// Fetch the declaration of the entry.
+    pub fn declaration(&self) -> &EntryDeclaration {
+        &self.declaration
+    }
+
+    /// Fetch whether the entry is the default entry.
+    pub fn is_default(&self) -> bool {
+        self.default
+    }
+
+    /// Fetch whether the entry is pinned, which prevents prefixing.
+    pub fn is_pin_name(&self) -> bool {
+        self.pin_name
+    }
+
+    /// Swap out the context of the entry.
+    pub fn swap_context(&mut self, context: Rc<SproutContext>) {
+        self.context = context;
+    }
+
+    /// Restamp the title with the current context.
+    pub fn restamp_title(&mut self) {
+        self.title = self.context.stamp(&self.title);
+    }
+
+    /// Mark this entry as the default entry.
+    pub fn mark_default(&mut self) {
+        self.default = true;
+    }
+
+    // Unmark this entry as the default entry.
+    pub fn unmark_default(&mut self) {
+        self.default = false;
+    }
+
+    /// Mark this entry as being pinned, which prevents prefixing.
+    pub fn mark_pin_name(&mut self) {
+        self.pin_name = true;
+    }
+
+    /// Prepend the name of the entry with `prefix`.
+    pub fn prepend_name_prefix(&mut self, prefix: &str) {
+        self.name.insert_str(0, prefix);
+    }
+
+    /// Determine if this entry matches `needle` by comparing to the name or title of the entry.
+    pub fn is_match(&self, needle: &str) -> bool {
+        self.name == needle || self.title == needle
+    }
+
+    /// Find an entry by `needle` inside the entry iterator `haystack`.
+    /// This will search for an entry by name, title, or index.
+    pub fn find<'a>(
+        needle: &str,
+        haystack: impl Iterator<Item = &'a BootableEntry>,
+    ) -> Option<&'a BootableEntry> {
+        haystack
+            .enumerate()
+            .find(|(index, entry)| entry.is_match(needle) || index.to_string() == needle)
+            .map(|(_index, entry)| entry)
+    }
+}

crates/sprout/src/extractors.rs

@@ -0,0 +1,32 @@
+use crate::context::SproutContext;
+use crate::extractors::filesystem_device_match::FilesystemDeviceMatchExtractor;
+use anyhow::{Result, bail};
+use serde::{Deserialize, Serialize};
+use std::rc::Rc;
+
+/// The filesystem device match extractor.
+pub mod filesystem_device_match;
+
+/// Declares an extractor configuration.
+/// Extractors allow calculating values at runtime
+/// using built-in sprout modules.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct ExtractorDeclaration {
+    /// The filesystem device match extractor.
+    /// This extractor finds a filesystem using some search criteria and returns
+    /// the device root path that can concatenated with subpaths to access files
+    /// on a particular filesystem.
+    #[serde(default, rename = "filesystem-device-match")]
+    pub filesystem_device_match: Option<FilesystemDeviceMatchExtractor>,
+}
+
+/// Extracts the value using the specified `extractor` under the provided `context`.
+/// The extractor must return a value, and if a value cannot be determined, an error
+/// should be returned.
+pub fn extract(context: Rc<SproutContext>, extractor: &ExtractorDeclaration) -> Result<String> {
+    if let Some(filesystem) = &extractor.filesystem_device_match {
+        filesystem_device_match::extract(context, filesystem)
+    } else {
+        bail!("unknown extractor configuration");
+    }
+}

crates/sprout/src/extractors/filesystem_device_match.rs

@@ -0,0 +1,173 @@
+use crate::context::SproutContext;
+use crate::utils;
+use anyhow::{Context, Result, anyhow, bail};
+use serde::{Deserialize, Serialize};
+use std::ops::Deref;
+use std::rc::Rc;
+use std::str::FromStr;
+use uefi::fs::{FileSystem, Path};
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::media::file::{File, FileSystemVolumeLabel};
+use uefi::proto::media::fs::SimpleFileSystem;
+use uefi::{CString16, Guid};
+
+/// The filesystem device match extractor.
+/// This extractor finds a filesystem using some search criteria and returns
+/// the device root path that can concatenated with subpaths to access files
+/// on a particular filesystem.
+/// The fallback value can be used to provide a value if no match is found.
+///
+/// This extractor requires all the criteria to match. If no criteria is provided,
+/// an error is returned.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct FilesystemDeviceMatchExtractor {
+    /// Matches a filesystem that has the specified label.
+    #[serde(default, rename = "has-label")]
+    pub has_label: Option<String>,
+    /// Matches a filesystem that has the specified item.
+    /// An item is either a directory or file.
+    #[serde(default, rename = "has-item")]
+    pub has_item: Option<String>,
+    /// Matches a filesystem that has the specified partition UUID.
+    #[serde(default, rename = "has-partition-uuid")]
+    pub has_partition_uuid: Option<String>,
+    /// Matches a filesystem that has the specified partition type UUID.
+    #[serde(default, rename = "has-partition-type-uuid")]
+    pub has_partition_type_uuid: Option<String>,
+    /// The fallback value to use if no filesystem matches the criteria.
+    #[serde(default)]
+    pub fallback: Option<String>,
+}
+
+/// Extract a filesystem device path using the specified `context` and `extractor` configuration.
+pub fn extract(
+    context: Rc<SproutContext>,
+    extractor: &FilesystemDeviceMatchExtractor,
+) -> Result<String> {
+    // If no criteria are provided, bail with an error.
+    if extractor.has_label.is_none()
+        && extractor.has_item.is_none()
+        && extractor.has_partition_uuid.is_none()
+        && extractor.has_partition_type_uuid.is_none()
+    {
+        bail!("at least one criteria is required for filesystem-device-match");
+    }
+
+    // Find all the filesystems inside the UEFI stack.
+    let handles = uefi::boot::find_handles::<SimpleFileSystem>()
+        .context("unable to find filesystem handles")?;
+
+    // Iterate over all the filesystems and check if they match the criteria.
+    for handle in handles {
+        // This defines whether a match has been found.
+        let mut has_match = false;
+
+        // Check if the partition info matches partition uuid criteria.
+        if let Some(ref has_partition_uuid) = extractor.has_partition_uuid {
+            // Parse the partition uuid from the extractor.
+            let parsed_uuid = Guid::from_str(has_partition_uuid)
+                .map_err(|e| anyhow!("unable to parse has-partition-uuid: {}", e))?;
+
+            // Fetch the root of the device.
+            let root = uefi::boot::open_protocol_exclusive::<DevicePath>(handle)
+                .context("unable to fetch the device path of the filesystem")?
+                .deref()
+                .to_boxed();
+
+            // Fetch the partition uuid for this filesystem.
+            let partition_uuid = utils::partition_guid(&root, utils::PartitionGuidForm::Partition)
+                .context("unable to fetch the partition uuid of the filesystem")?;
+
+            // Compare the partition uuid to the parsed uuid.
+            // If it does not match, continue to the next filesystem.
+            if partition_uuid != Some(parsed_uuid) {
+                continue;
+            }
+            has_match = true;
+        }
+
+        // Check if the partition info matches partition type uuid criteria.
+        if let Some(ref has_partition_type_uuid) = extractor.has_partition_type_uuid {
+            // Parse the partition type uuid from the extractor.
+            let parsed_uuid = Guid::from_str(has_partition_type_uuid)
+                .map_err(|e| anyhow!("unable to parse has-partition-type-uuid: {}", e))?;
+
+            // Fetch the root of the device.
+            let root = uefi::boot::open_protocol_exclusive::<DevicePath>(handle)
+                .context("unable to fetch the device path of the filesystem")?
+                .deref()
+                .to_boxed();
+
+            // Fetch the partition type uuid for this filesystem.
+            let partition_type_uuid =
+                utils::partition_guid(&root, utils::PartitionGuidForm::PartitionType)
+                    .context("unable to fetch the partition uuid of the filesystem")?;
+            // Compare the partition type uuid to the parsed uuid.
+            // If it does not match, continue to the next filesystem.
+            if partition_type_uuid != Some(parsed_uuid) {
+                continue;
+            }
+            has_match = true;
+        }
+
+        // Open the filesystem protocol for this handle.
+        let mut filesystem = uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(handle)
+            .context("unable to open filesystem protocol")?;
+
+        // Check if the filesystem matches label criteria.
+        if let Some(ref label) = extractor.has_label {
+            let want_label = CString16::try_from(context.stamp(label).as_str())
+                .context("unable to convert label to CString16")?;
+            let mut root = filesystem
+                .open_volume()
+                .context("unable to open filesystem volume")?;
+            let label = root
+                .get_boxed_info::<FileSystemVolumeLabel>()
+                .context("unable to get filesystem volume label")?;
+
+            if label.volume_label() != want_label {
+                continue;
+            }
+            has_match = true;
+        }
+
+        // Check if the filesystem matches item criteria.
+        if let Some(ref item) = extractor.has_item {
+            let want_item = CString16::try_from(context.stamp(item).as_str())
+                .context("unable to convert item to CString16")?;
+            let mut filesystem = FileSystem::new(filesystem);
+
+            // Check the metadata of the item.
+            // Ignore filesystem errors as we can't do anything useful with the error.
+            let Some(metadata) = filesystem.metadata(Path::new(&want_item)).ok() else {
+                continue;
+            };
+
+            // Only check directories and files.
+            if !(metadata.is_directory() || metadata.is_regular_file()) {
+                continue;
+            }
+            has_match = true;
+        }
+
+        // If there is no match, continue to the next filesystem.
+        if !has_match {
+            continue;
+        }
+
+        // If we have a match, return the device root path.
+        let path = uefi::boot::open_protocol_exclusive::<DevicePath>(handle)
+            .context("unable to open filesystem device path")?;
+        let path = path.deref();
+        // Acquire the device path root as a string.
+        return utils::device_path_root(path).context("unable to get device path root");
+    }
+
+    // If there is a fallback value, use it at this point.
+    if let Some(fallback) = &extractor.fallback {
+        return Ok(fallback.clone());
+    }
+
+    // Without a fallback, we can't continue, so bail.
+    bail!("unable to find matching filesystem")
+}

crates/sprout/src/generators.rs

@@ -0,0 +1,58 @@
+use crate::context::SproutContext;
+use crate::entries::BootableEntry;
+use crate::generators::bls::BlsConfiguration;
+use crate::generators::list::ListConfiguration;
+use crate::generators::matrix::MatrixConfiguration;
+use anyhow::Result;
+use anyhow::bail;
+use serde::{Deserialize, Serialize};
+use std::rc::Rc;
+
+pub mod bls;
+pub mod list;
+pub mod matrix;
+
+/// Declares a generator configuration.
+/// Generators allow generating entries at runtime based on a set of data.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct GeneratorDeclaration {
+    /// Matrix generator configuration.
+    /// Matrix allows you to specify multiple value-key values as arrays.
+    /// This allows multiplying the number of entries by any number of possible
+    /// configuration options. For example,
+    /// data.x = ["a", "b"]
+    /// data.y = ["c", "d"]
+    /// would generate an entry for each of these combinations:
+    /// x = a, y = c
+    /// x = a, y = d
+    /// x = b, y = c
+    /// x = b, y = d
+    #[serde(default)]
+    pub matrix: Option<MatrixConfiguration>,
+    /// BLS generator configuration.
+    /// BLS allows you to pass a filesystem path that contains a set of BLS entries.
+    /// It will generate a sprout entry for every supported BLS entry.
+    #[serde(default)]
+    pub bls: Option<BlsConfiguration>,
+    /// List generator configuration.
+    /// Allows you to specify a list of values to generate an entry from.
+    pub list: Option<ListConfiguration>,
+}
+
+/// Runs the generator specified by the `generator` option.
+/// It uses the specified `context` as the parent context for
+/// the generated entries, injecting more values if needed.
+pub fn generate(
+    context: Rc<SproutContext>,
+    generator: &GeneratorDeclaration,
+) -> Result<Vec<BootableEntry>> {
+    if let Some(matrix) = &generator.matrix {
+        matrix::generate(context, matrix)
+    } else if let Some(bls) = &generator.bls {
+        bls::generate(context, bls)
+    } else if let Some(list) = &generator.list {
+        list::generate(context, list)
+    } else {
+        bail!("unknown generator configuration");
+    }
+}

crates/sprout/src/generators/bls.rs

@@ -0,0 +1,227 @@
+use crate::context::SproutContext;
+use crate::entries::{BootableEntry, EntryDeclaration};
+use crate::generators::bls::entry::BlsEntry;
+use crate::utils;
+use crate::utils::vercmp;
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::cmp::Ordering;
+use std::rc::Rc;
+use std::str::FromStr;
+use uefi::cstr16;
+use uefi::fs::{FileSystem, PathBuf};
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+use uefi::proto::media::fs::SimpleFileSystem;
+
+/// BLS entry parser.
+mod entry;
+
+/// The default path to the BLS directory.
+const BLS_TEMPLATE_PATH: &str = "\\loader";
+
+/// The configuration of the BLS generator.
+/// The BLS uses the Bootloader Specification to produce
+/// entries from an input template.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct BlsConfiguration {
+    /// The entry to use for as a template.
+    pub entry: EntryDeclaration,
+    /// The path to the BLS directory.
+    #[serde(default = "default_bls_path")]
+    pub path: String,
+}
+
+fn default_bls_path() -> String {
+    BLS_TEMPLATE_PATH.to_string()
+}
+
+// TODO(azenla): remove this once variable substitution is implemented.
+/// This function is used to remove the `tuned_initrd` variable from entry values.
+/// Fedora uses tuned which adds an initrd that shouldn't be used.
+fn quirk_initrd_remove_tuned(input: String) -> String {
+    input.replace("$tuned_initrd", "").trim().to_string()
+}
+
+/// Sorts two entries according to the BLS sort system.
+/// Reference: https://uapi-group.org/specifications/specs/boot_loader_specification/#sorting
+fn sort_entries(a: &(BlsEntry, BootableEntry), b: &(BlsEntry, BootableEntry)) -> Ordering {
+    // Grab the components of both entries.
+    let (a_bls, a_boot) = a;
+    let (b_bls, b_boot) = b;
+
+    // Grab the sort keys from both entries.
+    let a_sort_key = a_bls.sort_key();
+    let b_sort_key = b_bls.sort_key();
+
+    // Compare the sort keys of both entries.
+    match a_sort_key.cmp(&b_sort_key) {
+        // If A and B sort keys are equal, sort by machine-id.
+        Ordering::Equal => {
+            // Grab the machine-id from both entries.
+            let a_machine_id = a_bls.machine_id();
+            let b_machine_id = b_bls.machine_id();
+
+            // Compare the machine-id of both entries.
+            match a_machine_id.cmp(&b_machine_id) {
+                // If both machine-id values are equal, sort by version.
+                Ordering::Equal => {
+                    // Grab the version from both entries.
+                    let a_version = a_bls.version();
+                    let b_version = b_bls.version();
+
+                    // Compare the version of both entries, sorting newer versions first.
+                    match vercmp::compare_versions_optional(
+                        a_version.as_deref(),
+                        b_version.as_deref(),
+                    )
+                    .reverse()
+                    {
+                        // If both versions are equal, sort by file name in reverse order.
+                        Ordering::Equal => {
+                            // Grab the file name from both entries.
+                            let a_name = a_boot.name();
+                            let b_name = b_boot.name();
+
+                            // Compare the file names of both entries, sorting newer entries first.
+                            vercmp::compare_versions(a_name, b_name).reverse()
+                        }
+                        other => other,
+                    }
+                }
+                other => other,
+            }
+        }
+
+        other => other,
+    }
+}
+
+/// Generates entries from the BLS entries directory using the specified `bls` configuration and
+/// `context`. The BLS conversion is best-effort and will ignore any unsupported entries.
+pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Vec<BootableEntry>> {
+    let mut entries = Vec::new();
+
+    // Stamp the path to the BLS directory.
+    let path = context.stamp(&bls.path);
+
+    // Resolve the path to the BLS directory.
+    let bls_resolved = utils::resolve_path(Some(context.root().loaded_image_path()?), &path)
+        .context("unable to resolve bls path")?;
+
+    // Construct a filesystem path to the BLS entries directory.
+    let mut entries_path = PathBuf::from(
+        bls_resolved
+            .sub_path
+            .to_string(DisplayOnly(false), AllowShortcuts(false))
+            .context("unable to convert bls path to string")?,
+    );
+    entries_path.push(cstr16!("entries"));
+
+    // Open exclusive access to the BLS filesystem.
+    let fs =
+        uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(bls_resolved.filesystem_handle)
+            .context("unable to open bls filesystem")?;
+    let mut fs = FileSystem::new(fs);
+
+    // Read the BLS entries directory.
+    let entries_iter = fs
+        .read_dir(&entries_path)
+        .context("unable to read bls entries")?;
+
+    // For each entry in the BLS entries directory, parse the entry and add it to the list.
+    for entry in entries_iter {
+        // Unwrap the entry file info.
+        let entry = entry.context("unable to read bls item entry")?;
+
+        // Skip items that are not regular files.
+        if !entry.is_regular_file() {
+            continue;
+        }
+
+        // Get the file name of the filesystem item.
+        let mut name = entry.file_name().to_string();
+
+        // Ignore files that are not .conf files.
+        if !name.to_lowercase().ends_with(".conf") {
+            continue;
+        }
+
+        // Remove the .conf extension.
+        name.truncate(name.len() - 5);
+
+        // Skip over files that are named just ".conf" as they are not valid entry files.
+        if name.is_empty() {
+            continue;
+        }
+
+        // Create a mutable path so we can append the file name to produce the full path.
+        let mut full_entry_path = entries_path.to_path_buf();
+        full_entry_path.push(entry.file_name());
+
+        // Read the entry file.
+        let content = fs
+            .read(full_entry_path)
+            .context("unable to read bls file")?;
+
+        // Parse the entry file as a UTF-8 string.
+        let content = String::from_utf8(content).context("unable to read bls entry as utf8")?;
+
+        // Parse the entry file as a BLS entry.
+        let entry = BlsEntry::from_str(&content).context("unable to parse bls entry")?;
+
+        // Ignore entries that are not valid for Sprout.
+        if !entry.is_valid() {
+            continue;
+        }
+
+        // Produce a new sprout context for the entry with the extracted values.
+        let mut context = context.fork();
+
+        let title_base = entry.title().unwrap_or_else(|| name.clone());
+        let chainload = entry.chainload_path().unwrap_or_default();
+        let options = entry.options().unwrap_or_default();
+        let version = entry.version().unwrap_or_default();
+        let machine_id = entry.machine_id().unwrap_or_default();
+
+        // Put the initrd through a quirk modifier to support Fedora.
+        let initrd = quirk_initrd_remove_tuned(entry.initrd_path().unwrap_or_default());
+
+        // Combine the title with the version if a version is present, except if it already contains it.
+        // Sometimes BLS will have a version in the title already, and this makes it unique.
+        let title_full = if !version.is_empty() && !title_base.contains(&version) {
+            format!("{} {}", title_base, version)
+        } else {
+            title_base.clone()
+        };
+
+        context.set("title-base", title_base);
+        context.set("title", title_full);
+        context.set("chainload", chainload);
+        context.set("options", options);
+        context.set("initrd", initrd);
+        context.set("version", version);
+        context.set("machine-id", machine_id);
+
+        // Produce a new bootable entry.
+        let mut boot = BootableEntry::new(
+            name,
+            bls.entry.title.clone(),
+            context.freeze(),
+            bls.entry.clone(),
+        );
+
+        // Pin the entry name to prevent prefixing.
+        // This is needed as the bootloader interface requires the name to be
+        // the same as the entry file name, minus the .conf extension.
+        boot.mark_pin_name();
+
+        // Add the BLS entry to the list, along with the bootable entry.
+        entries.push((entry, boot));
+    }
+
+    // Sort all the entries according to the BLS sort system.
+    entries.sort_by(sort_entries);
+
+    // Collect all the bootable entries and return them.
+    Ok(entries.into_iter().map(|(_, boot)| boot).collect())
+}

crates/sprout/src/generators/bls/entry.rs

@@ -0,0 +1,167 @@
+use anyhow::{Error, Result};
+use std::str::FromStr;
+
+/// Represents a parsed BLS entry.
+/// Fields unrelated to Sprout are not included.
+#[derive(Default, Debug, Clone)]
+pub struct BlsEntry {
+    /// The title of the entry.
+    pub title: Option<String>,
+    /// The options to pass to the entry.
+    pub options: Option<String>,
+    /// The path to the linux kernel.
+    pub linux: Option<String>,
+    /// The path to the initrd.
+    pub initrd: Option<String>,
+    /// The path to an EFI image.
+    pub efi: Option<String>,
+    /// The sort key for the entry.
+    pub sort_key: Option<String>,
+    /// The version of the entry.
+    pub version: Option<String>,
+    /// The machine id of the entry.
+    pub machine_id: Option<String>,
+}
+
+/// Parser for a BLS entry.
+impl FromStr for BlsEntry {
+    type Err = Error;
+
+    /// Parses the `input` as a BLS entry file.
+    fn from_str(input: &str) -> Result<Self> {
+        // All the fields in a BLS entry we understand.
+        // Set all to None initially.
+        let mut title: Option<String> = None;
+        let mut options: Option<String> = None;
+        let mut linux: Option<String> = None;
+        let mut initrd: Option<String> = None;
+        let mut efi: Option<String> = None;
+        let mut sort_key: Option<String> = None;
+        let mut version: Option<String> = None;
+        let mut machine_id: Option<String> = None;
+
+        // Iterate over each line in the input and parse it.
+        for line in input.lines() {
+            // Trim the line.
+            let line = line.trim();
+
+            // Skip over empty lines and comments.
+            if line.is_empty() || line.starts_with('#') {
+                continue;
+            }
+
+            // Split the line once by whitespace. This technically includes newlines but since
+            // the lines iterator is used, there should never be a newline here.
+            let Some((key, value)) = line.split_once(char::is_whitespace) else {
+                continue;
+            };
+
+            // Match the key to a field we understand.
+            match key {
+                // The title of the entry.
+                "title" => {
+                    title = Some(value.trim().to_string());
+                }
+
+                // The options to pass to the entry.
+                "options" => {
+                    options = Some(value.trim().to_string());
+                }
+
+                // The path to the linux kernel.
+                "linux" => {
+                    linux = Some(value.trim().to_string());
+                }
+
+                // The path to the initrd.
+                "initrd" => {
+                    initrd = Some(value.trim().to_string());
+                }
+
+                // The path to an EFI image.
+                "efi" => {
+                    efi = Some(value.trim().to_string());
+                }
+
+                "sort-key" => {
+                    sort_key = Some(value.trim().to_string());
+                }
+
+                "version" => {
+                    version = Some(value.trim().to_string());
+                }
+
+                "machine-id" => {
+                    machine_id = Some(value.trim().to_string());
+                }
+
+                // Ignore any other key.
+                _ => {
+                    continue;
+                }
+            }
+        }
+
+        // Produce a BLS entry from the parsed fields.
+        Ok(Self {
+            title,
+            options,
+            linux,
+            initrd,
+            efi,
+            sort_key,
+            version,
+            machine_id,
+        })
+    }
+}
+
+impl BlsEntry {
+    /// Checks if this BLS entry is something we can actually boot in Sprout.
+    pub fn is_valid(&self) -> bool {
+        self.linux.is_some() || self.efi.is_some()
+    }
+
+    /// Fetches the path to an EFI bootable image to boot, if any.
+    /// This prioritizes the linux field over efi.
+    /// It also converts / to \\ to match EFI path style.
+    pub fn chainload_path(&self) -> Option<String> {
+        self.linux
+            .clone()
+            .or(self.efi.clone())
+            .map(|path| path.replace('/', "\\").trim_start_matches('\\').to_string())
+    }
+
+    /// Fetches the path to an initrd to pass to the kernel, if any.
+    /// It also converts / to \\ to match EFI path style.
+    pub fn initrd_path(&self) -> Option<String> {
+        self.initrd
+            .clone()
+            .map(|path| path.replace('/', "\\").trim_start_matches('\\').to_string())
+    }
+
+    /// Fetches the options to pass to the kernel, if any.
+    pub fn options(&self) -> Option<String> {
+        self.options.clone()
+    }
+
+    /// Fetches the title of the entry, if any.
+    pub fn title(&self) -> Option<String> {
+        self.title.clone()
+    }
+
+    /// Fetches the sort key of the entry, if any.
+    pub fn sort_key(&self) -> Option<String> {
+        self.sort_key.clone()
+    }
+
+    /// Fetches the version of the entry, if any.
+    pub fn version(&self) -> Option<String> {
+        self.version.clone()
+    }
+
+    /// Fetches the machine id of the entry, if any.
+    pub fn machine_id(&self) -> Option<String> {
+        self.machine_id.clone()
+    }
+}

crates/sprout/src/generators/list.rs

@@ -0,0 +1,52 @@
+use crate::context::SproutContext;
+use crate::entries::{BootableEntry, EntryDeclaration};
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+/// List generator configuration.
+/// The list generator produces multiple entries based
+/// on a set of input maps.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct ListConfiguration {
+    /// The template entry to use for each generated entry.
+    #[serde(default)]
+    pub entry: EntryDeclaration,
+    /// The values to use as the input for the matrix.
+    #[serde(default)]
+    pub values: Vec<BTreeMap<String, String>>,
+}
+
+/// Generates a set of entries using the specified `list` configuration in the `context`.
+pub fn generate(
+    context: Rc<SproutContext>,
+    list: &ListConfiguration,
+) -> Result<Vec<BootableEntry>> {
+    let mut entries = Vec::new();
+
+    // For each combination, create a new context and entry.
+    for (index, combination) in list.values.iter().enumerate() {
+        let mut context = context.fork();
+        // Insert the combination into the context.
+        context.insert(combination);
+        let context = context.freeze();
+
+        // Stamp the entry title and actions from the template.
+        let mut entry = list.entry.clone();
+        entry.actions = entry
+            .actions
+            .into_iter()
+            .map(|action| context.stamp(action))
+            .collect();
+        // Push the entry into the list with the new context.
+        entries.push(BootableEntry::new(
+            index.to_string(),
+            entry.title.clone(),
+            context,
+            entry,
+        ));
+    }
+
+    Ok(entries)
+}

crates/sprout/src/generators/matrix.rs

@@ -0,0 +1,69 @@
+use crate::context::SproutContext;
+use crate::entries::{BootableEntry, EntryDeclaration};
+use crate::generators::list;
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+/// Matrix generator configuration.
+/// The matrix generator produces multiple entries based
+/// on input values multiplicatively.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct MatrixConfiguration {
+    /// The template entry to use for each generated entry.
+    #[serde(default)]
+    pub entry: EntryDeclaration,
+    /// The values to use as the input for the matrix.
+    #[serde(default)]
+    pub values: BTreeMap<String, Vec<String>>,
+}
+
+/// Builds out multiple generations of `input` based on a matrix style.
+/// For example, if input is: {"x": ["a", "b"], "y": ["c", "d"]}
+/// It will produce:
+/// x: a, y: c
+/// x: a, y: d
+/// x: b, y: c
+/// x: b, y: d
+fn build_matrix(input: &BTreeMap<String, Vec<String>>) -> Vec<BTreeMap<String, String>> {
+    // Convert the input into a vector of tuples.
+    let items: Vec<(String, Vec<String>)> = input.clone().into_iter().collect();
+
+    // The result is a vector of maps.
+    let mut result: Vec<BTreeMap<String, String>> = vec![BTreeMap::new()];
+
+    for (key, values) in items {
+        let mut new_result = Vec::new();
+
+        // Produce all the combinations of the input values.
+        for combination in &result {
+            for value in &values {
+                let mut new_combination = combination.clone();
+                new_combination.insert(key.clone(), value.clone());
+                new_result.push(new_combination);
+            }
+        }
+
+        result = new_result;
+    }
+
+    result.into_iter().filter(|item| !item.is_empty()).collect()
+}
+
+/// Generates a set of entries using the specified `matrix` configuration in the `context`.
+pub fn generate(
+    context: Rc<SproutContext>,
+    matrix: &MatrixConfiguration,
+) -> Result<Vec<BootableEntry>> {
+    // Produce all the combinations of the input values.
+    let combinations = build_matrix(&matrix.values);
+    // Use the list generator to generate entries for each combination.
+    list::generate(
+        context,
+        &list::ListConfiguration {
+            entry: matrix.entry.clone(),
+            values: combinations,
+        },
+    )
+}

crates/sprout/src/integrations.rs

@@ -0,0 +1,4 @@
+/// Implements support for the bootloader interface specification.
+pub mod bootloader_interface;
+/// Implements support for the shim loader application for Secure Boot.
+pub mod shim;

crates/sprout/src/integrations/bootloader_interface.rs

@@ -0,0 +1,314 @@
+use crate::integrations::bootloader_interface::bitflags::LoaderFeatures;
+use crate::platform::timer::PlatformTimer;
+use crate::utils::device_path_subpath;
+use crate::utils::variables::{VariableClass, VariableController};
+use anyhow::{Context, Result};
+use uefi::proto::device_path::DevicePath;
+use uefi::{Guid, guid};
+use uefi_raw::table::runtime::VariableVendor;
+
+/// bitflags: LoaderFeatures bitflags.
+mod bitflags;
+
+/// The name of the bootloader to tell the system.
+const LOADER_NAME: &str = "Sprout";
+
+/// Represents the configured timeout for the bootloader interface.
+pub enum BootloaderInterfaceTimeout {
+    /// Force the menu to be shown.
+    MenuForce,
+    /// Hide the menu.
+    MenuHidden,
+    /// Disable the menu.
+    MenuDisabled,
+    /// Set a timeout for the menu.
+    Timeout(u64),
+    /// Timeout is unspecified.
+    Unspecified,
+}
+
+/// Bootloader Interface support.
+pub struct BootloaderInterface;
+
+impl BootloaderInterface {
+    /// Bootloader Interface GUID from https://systemd.io/BOOT_LOADER_INTERFACE
+    const VENDOR: VariableController = VariableController::new(VariableVendor(guid!(
+        "4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"
+    )));
+
+    /// The feature we support in Sprout.
+    fn features() -> LoaderFeatures {
+        LoaderFeatures::Xbootldr
+            | LoaderFeatures::LoadDriver
+            | LoaderFeatures::Tpm2ActivePcrBanks
+            | LoaderFeatures::RetainShim
+            | LoaderFeatures::ConfigTimeout
+            | LoaderFeatures::ConfigTimeoutOneShot
+            | LoaderFeatures::MenuDisable
+            | LoaderFeatures::EntryDefault
+            | LoaderFeatures::EntryOneShot
+    }
+
+    /// Tell the system that Sprout was initialized at the current time.
+    pub fn mark_init(timer: &PlatformTimer) -> Result<()> {
+        Self::mark_time("LoaderTimeInitUSec", timer)
+    }
+
+    /// Tell the system that Sprout is about to execute the boot entry.
+    pub fn mark_exec(timer: &PlatformTimer) -> Result<()> {
+        Self::mark_time("LoaderTimeExecUSec", timer)
+    }
+
+    /// Tell the system that Sprout is about to display the menu.
+    pub fn mark_menu(timer: &PlatformTimer) -> Result<()> {
+        Self::mark_time("LoaderTimeMenuUSec", timer)
+    }
+
+    /// Tell the system about the current time as measured by the platform timer.
+    /// Sets the variable specified by `key` to the number of microseconds.
+    fn mark_time(key: &str, timer: &PlatformTimer) -> Result<()> {
+        // Measure the elapsed time since the hardware timer was started.
+        let elapsed = timer.elapsed_since_lifetime();
+        Self::VENDOR.set_cstr16(
+            key,
+            &elapsed.as_micros().to_string(),
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system what loader is being used and our features.
+    pub fn set_loader_info() -> Result<()> {
+        // Set the LoaderInfo variable with the name of the loader.
+        Self::VENDOR
+            .set_cstr16(
+                "LoaderInfo",
+                LOADER_NAME,
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to set loader info variable")?;
+
+        // Set the LoaderFeatures variable with the features we support.
+        Self::VENDOR
+            .set_u64le(
+                "LoaderFeatures",
+                Self::features().bits(),
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to set loader features variable")?;
+        Ok(())
+    }
+
+    /// Tell the system the relative path to the partition root of the current bootloader.
+    pub fn set_loader_path(path: &DevicePath) -> Result<()> {
+        let subpath = device_path_subpath(path).context("unable to get loader path subpath")?;
+        Self::VENDOR.set_cstr16(
+            "LoaderImageIdentifier",
+            &subpath,
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system what the partition GUID of the ESP Sprout was booted from is.
+    pub fn set_partition_guid(guid: &Guid) -> Result<()> {
+        Self::VENDOR.set_cstr16(
+            "LoaderDevicePartUUID",
+            &guid.to_string(),
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system what boot entries are available.
+    pub fn set_entries<N: AsRef<str>>(entries: impl Iterator<Item = N>) -> Result<()> {
+        // Entries are stored as a null-terminated list of CString16 strings back to back.
+        // Iterate over the entries and convert them to CString16 placing them into data.
+        let mut data = Vec::new();
+        for entry in entries {
+            // Convert the entry to CString16 little endian.
+            let encoded = entry
+                .as_ref()
+                .encode_utf16()
+                .flat_map(|c| c.to_le_bytes())
+                .collect::<Vec<u8>>();
+            // Write the bytes into the data buffer.
+            data.extend_from_slice(&encoded);
+            // Add a null terminator to the end of the entry.
+            data.extend_from_slice(&[0, 0]);
+        }
+
+        // If no data was generated, we will do nothing.
+        if data.is_empty() {
+            return Ok(());
+        }
+
+        Self::VENDOR.set(
+            "LoaderEntries",
+            &data,
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system what the selected boot entry is.
+    pub fn set_selected_entry(entry: String) -> Result<()> {
+        Self::VENDOR.set_cstr16(
+            "LoaderEntrySelected",
+            &entry,
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system about the UEFI firmware we are running on.
+    pub fn set_firmware_info() -> Result<()> {
+        // Access the firmware revision.
+        let firmware_revision = uefi::system::firmware_revision();
+
+        // Access the UEFI revision.
+        let uefi_revision = uefi::system::uefi_revision();
+
+        // Format the firmware information string into something human-readable.
+        let firmware_info = format!(
+            "{} {}.{:02}",
+            uefi::system::firmware_vendor(),
+            firmware_revision >> 16,
+            firmware_revision & 0xffff,
+        );
+        Self::VENDOR.set_cstr16(
+            "LoaderFirmwareInfo",
+            &firmware_info,
+            VariableClass::BootAndRuntimeTemporary,
+        )?;
+
+        // Format the firmware revision into something human-readable.
+        let firmware_type = format!(
+            "UEFI {}.{:02}",
+            uefi_revision.major(),
+            uefi_revision.minor()
+        );
+        Self::VENDOR.set_cstr16(
+            "LoaderFirmwareType",
+            &firmware_type,
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Tell the system what the number of active PCR banks is.
+    /// If this is zero, that is okay.
+    pub fn set_tpm2_active_pcr_banks(value: u32) -> Result<()> {
+        // Format the value into the specification format.
+        let value = format!("0x{:08x}", value);
+        Self::VENDOR.set_cstr16(
+            "LoaderTpm2ActivePcrBanks",
+            &value,
+            VariableClass::BootAndRuntimeTemporary,
+        )
+    }
+
+    /// Retrieve the timeout value from the bootloader interface, using the specified `key`.
+    /// `remove` indicates whether, when found, we remove the variable.
+    fn get_timeout_value(key: &str, remove: bool) -> Result<Option<BootloaderInterfaceTimeout>> {
+        // Retrieve the timeout value from the bootloader interface.
+        let Some(value) = Self::VENDOR
+            .get_cstr16(key)
+            .context("unable to get timeout value")?
+        else {
+            return Ok(None);
+        };
+
+        // If we reach here, we know the value was specified.
+        // If `remove` is true, remove the variable.
+        if remove {
+            Self::VENDOR
+                .remove(key)
+                .context("unable to remove timeout variable")?;
+        }
+
+        // If the value is empty, return Unspecified.
+        if value.is_empty() {
+            return Ok(Some(BootloaderInterfaceTimeout::Unspecified));
+        }
+
+        // If the value is "menu-force", return MenuForce.
+        if value == "menu-force" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuForce));
+        }
+
+        // If the value is "menu-hidden", return MenuHidden.
+        if value == "menu-hidden" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuHidden));
+        }
+
+        // If the value is "menu-disabled", return MenuDisabled.
+        if value == "menu-disabled" {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuDisabled));
+        }
+
+        // Parse the value as a u64 to decode an numeric value.
+        let value = value
+            .parse::<u64>()
+            .context("unable to parse timeout value")?;
+
+        // The specification says that a value of 0 means that the menu should be hidden.
+        if value == 0 {
+            return Ok(Some(BootloaderInterfaceTimeout::MenuHidden));
+        }
+
+        // If we reach here, we know it must be a real timeout value.
+        Ok(Some(BootloaderInterfaceTimeout::Timeout(value)))
+    }
+
+    /// Get the timeout from the bootloader interface.
+    /// This indicates how the menu should behave.
+    /// If no values are set, Unspecified is returned.
+    pub fn get_timeout() -> Result<BootloaderInterfaceTimeout> {
+        // Attempt to acquire the value of the LoaderConfigTimeoutOneShot variable.
+        // This should take precedence over the LoaderConfigTimeout variable.
+        let oneshot = Self::get_timeout_value("LoaderConfigTimeoutOneShot", true)
+            .context("unable to check for LoaderConfigTimeoutOneShot variable")?;
+
+        // If oneshot was found, return it.
+        if let Some(oneshot) = oneshot {
+            return Ok(oneshot);
+        }
+
+        // Attempt to acquire the value of the LoaderConfigTimeout variable.
+        // This will be used if the LoaderConfigTimeoutOneShot variable is not set.
+        let direct = Self::get_timeout_value("LoaderConfigTimeout", false)
+            .context("unable to check for LoaderConfigTimeout variable")?;
+
+        // If direct was found, return it.
+        if let Some(direct) = direct {
+            return Ok(direct);
+        }
+
+        // If we reach here, we know that neither variable was set.
+        // We provide the unspecified value instead.
+        Ok(BootloaderInterfaceTimeout::Unspecified)
+    }
+
+    /// Get the default entry set by the bootloader interface.
+    pub fn get_default_entry() -> Result<Option<String>> {
+        Self::VENDOR
+            .get_cstr16("LoaderEntryDefault")
+            .context("unable to get default entry from bootloader interface")
+    }
+
+    /// Get the oneshot entry set by the bootloader interface.
+    /// This should be the entry we boot.
+    pub fn get_oneshot_entry() -> Result<Option<String>> {
+        // Acquire the value of the LoaderEntryOneShot variable.
+        // If it is not set, return None.
+        let Some(value) = Self::VENDOR
+            .get_cstr16("LoaderEntryOneShot")
+            .context("unable to get oneshot entry from bootloader interface")?
+        else {
+            return Ok(None);
+        };
+
+        // Remove the oneshot entry from the bootloader interface.
+        Self::VENDOR
+            .remove("LoaderEntryOneShot")
+            .context("unable to remove oneshot entry")?;
+
+        // Return the oneshot value.
+        Ok(Some(value))
+    }
+}

crates/sprout/src/integrations/bootloader_interface/bitflags.rs

@@ -0,0 +1,46 @@
+use bitflags::bitflags;
+
+bitflags! {
+    /// Feature bitflags for the bootloader interface.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+    pub struct LoaderFeatures: u64 {
+        /// Bootloader supports LoaderConfigTimeout.
+        const ConfigTimeout = 1 << 0;
+        /// Bootloader supports LoaderConfigTimeoutOneShot.
+        const ConfigTimeoutOneShot = 1 << 1;
+        /// Bootloader supports LoaderEntryDefault.
+        const EntryDefault = 1 << 2;
+        /// Bootloader supports LoaderEntryOneShot.
+        const EntryOneShot = 1 << 3;
+        /// Bootloader supports boot counting.
+        const BootCounting = 1 << 4;
+        /// Bootloader supports detection from XBOOTLDR partitions.
+        const Xbootldr = 1 << 5;
+        /// Bootloader supports the handling of random seeds.
+        const RandomSeed = 1 << 6;
+        /// Bootloader supports loading drivers.
+        const LoadDriver = 1 << 7;
+        /// Bootloader supports sort keys.
+        const SortKey = 1 << 8;
+        /// Bootloader supports saved entries.
+        const SavedEntry = 1 << 9;
+        /// Bootloader supports device trees.
+        const DeviceTree = 1 << 10;
+        /// Bootloader supports secure boot enroll.
+        const SecureBootEnroll = 1 << 11;
+        /// Bootloader retains the shim.
+        const RetainShim = 1 << 12;
+        /// Bootloader supports disabling the menu via the menu timeout variable.
+        const MenuDisable = 1 << 13;
+        /// Bootloader supports multi-profile UKI.
+        const MultiProfileUki = 1 << 14;
+        /// Bootloader reports URLs.
+        const ReportUrl = 1 << 15;
+        /// Bootloader supports type-1 UKIs.
+        const Type1Uki = 1 << 16;
+        /// Bootloader supports type-1 UKI urls.
+        const Type1UkiUrl = 1 << 17;
+        /// Bootloader indicates TPM2 active PCR banks.
+        const Tpm2ActivePcrBanks = 1 << 18;
+    }
+}

crates/sprout/src/integrations/shim.rs

@@ -0,0 +1,316 @@
+use crate::integrations::shim::hook::SecurityHook;
+use crate::secure::SecureBoot;
+use crate::utils;
+use crate::utils::ResolvedPath;
+use crate::utils::variables::{VariableClass, VariableController};
+use anyhow::{Context, Result, anyhow, bail};
+use log::warn;
+use std::ffi::c_void;
+use std::pin::Pin;
+use uefi::Handle;
+use uefi::boot::LoadImageSource;
+use uefi::proto::device_path::text::{AllowShortcuts, DisplayOnly};
+use uefi::proto::device_path::{DevicePath, FfiDevicePath};
+use uefi::proto::unsafe_protocol;
+use uefi_raw::table::runtime::VariableVendor;
+use uefi_raw::{Guid, Status, guid};
+
+/// Security hook support.
+mod hook;
+
+/// Support for the shim loader application for Secure Boot.
+pub struct ShimSupport;
+
+/// Input to the shim mechanisms.
+pub enum ShimInput<'a> {
+    /// Data loaded into a buffer and ready to be verified, owned.
+    OwnedDataBuffer(Option<&'a ResolvedPath>, Pin<Box<[u8]>>),
+    /// Data loaded into a buffer and ready to be verified.
+    DataBuffer(Option<&'a ResolvedPath>, &'a [u8]),
+    /// Low-level data buffer provided by the security hook.
+    SecurityHookBuffer(Option<*const FfiDevicePath>, &'a [u8]),
+    /// Low-level owned data buffer provided by the security hook.
+    SecurityHookOwnedBuffer(Option<*const FfiDevicePath>, Pin<Box<[u8]>>),
+    /// Low-level path provided by the security hook.
+    SecurityHookPath(*const FfiDevicePath),
+    /// Data is provided as a resolved path. We will need to load the data to verify it.
+    /// The output will them return the loaded data.
+    ResolvedPath(&'a ResolvedPath),
+}
+
+impl<'a> ShimInput<'a> {
+    /// Accesses the buffer behind the shim input, if available.
+    pub fn buffer(&self) -> Option<&[u8]> {
+        match self {
+            ShimInput::OwnedDataBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookOwnedBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookBuffer(_, data) => Some(data),
+            ShimInput::SecurityHookPath(_) => None,
+            ShimInput::DataBuffer(_, data) => Some(data),
+            ShimInput::ResolvedPath(_) => None,
+        }
+    }
+
+    /// Accesses the full device path to the input.
+    pub fn file_path(&self) -> Option<&DevicePath> {
+        match self {
+            ShimInput::OwnedDataBuffer(path, _) => path.as_ref().map(|it| it.full_path.as_ref()),
+            ShimInput::DataBuffer(path, _) => path.as_ref().map(|it| it.full_path.as_ref()),
+            ShimInput::SecurityHookBuffer(path, _) => {
+                path.map(|it| unsafe { DevicePath::from_ffi_ptr(it) })
+            }
+            ShimInput::SecurityHookPath(path) => unsafe { Some(DevicePath::from_ffi_ptr(*path)) },
+            ShimInput::ResolvedPath(path) => Some(path.full_path.as_ref()),
+            ShimInput::SecurityHookOwnedBuffer(path, _) => {
+                path.map(|it| unsafe { DevicePath::from_ffi_ptr(it) })
+            }
+        }
+    }
+
+    /// Converts this input into an owned data buffer, where the data is loaded.
+    /// For ResolvedPath, this will read the file.
+    pub fn into_owned_data_buffer(self) -> Result<ShimInput<'a>> {
+        match self {
+            ShimInput::OwnedDataBuffer(root, data) => Ok(ShimInput::OwnedDataBuffer(root, data)),
+
+            ShimInput::DataBuffer(root, data) => Ok(ShimInput::OwnedDataBuffer(
+                root,
+                Box::into_pin(data.to_vec().into_boxed_slice()),
+            )),
+
+            ShimInput::SecurityHookPath(ffi_path) => {
+                // Acquire the file path.
+                let Some(path) = self.file_path() else {
+                    bail!("unable to convert security hook path to device path");
+                };
+                // Convert the underlying path to a string.
+                let path = path
+                    .to_string(DisplayOnly(false), AllowShortcuts(false))
+                    .context("unable to convert device path to string")?;
+                let path = utils::resolve_path(None, &path.to_string())
+                    .context("unable to resolve path")?;
+                // Read the file path.
+                let data = path.read_file()?;
+                Ok(ShimInput::SecurityHookOwnedBuffer(
+                    Some(ffi_path),
+                    Box::into_pin(data.to_vec().into_boxed_slice()),
+                ))
+            }
+
+            ShimInput::SecurityHookBuffer(_, _) => {
+                bail!("unable to convert security hook buffer to owned data buffer")
+            }
+
+            ShimInput::ResolvedPath(path) => {
+                // Read the file path.
+                let data = path.read_file()?;
+                Ok(ShimInput::OwnedDataBuffer(
+                    Some(path),
+                    Box::into_pin(data.to_vec().into_boxed_slice()),
+                ))
+            }
+
+            ShimInput::SecurityHookOwnedBuffer(path, data) => {
+                Ok(ShimInput::SecurityHookOwnedBuffer(path, data))
+            }
+        }
+    }
+}
+
+/// Output of the shim verification function.
+/// Since the shim needs to load the data from disk, we will optimize by using that as the data
+/// to actually boot.
+pub enum ShimVerificationOutput {
+    /// The verification failed.
+    VerificationFailed(Status),
+    /// The data provided to the verifier was already a buffer.
+    VerifiedDataNotLoaded,
+    /// Verifying the data resulted in loading the data from the source.
+    /// This contains the data that was loaded, so it won't need to be loaded again.
+    VerifiedDataBuffer(Vec<u8>),
+}
+
+/// The shim lock protocol as defined by the shim loader application.
+#[unsafe_protocol(ShimSupport::SHIM_LOCK_GUID)]
+struct ShimLockProtocol {
+    /// Verify the data in `buffer` with the size `buffer_size` to determine if it is valid.
+    /// NOTE: On x86_64, this function uses SYSV calling conventions. On aarch64 it uses the
+    /// efiapi calling convention. This is truly wild, but you can verify it yourself by
+    /// looking at: https://github.com/rhboot/shim/blob/15.8/shim.h#L207-L212
+    /// There is no calling convention declared like there should be.
+    #[cfg(target_arch = "x86_64")]
+    pub shim_verify: unsafe extern "sysv64" fn(buffer: *const c_void, buffer_size: u32) -> Status,
+    #[cfg(target_arch = "aarch64")]
+    pub shim_verify: unsafe extern "efiapi" fn(buffer: *const c_void, buffer_size: u32) -> Status,
+    /// Unused function that is defined by the shim.
+    _generate_header: *mut c_void,
+    /// Unused function that is defined by the shim.
+    _read_header: *mut c_void,
+}
+
+impl ShimSupport {
+    /// Variable controller for the shim lock.
+    const SHIM_LOCK_VARIABLES: VariableController =
+        VariableController::new(VariableVendor(Self::SHIM_LOCK_GUID));
+
+    /// GUID for the shim lock protocol.
+    const SHIM_LOCK_GUID: Guid = guid!("605dab50-e046-4300-abb6-3dd810dd8b23");
+    /// GUID for the shim image loader protocol.
+    const SHIM_IMAGE_LOADER_GUID: Guid = guid!("1f492041-fadb-4e59-9e57-7cafe73a55ab");
+
+    /// Determines whether the shim is loaded.
+    pub fn loaded() -> Result<bool> {
+        Ok(utils::find_handle(&Self::SHIM_LOCK_GUID)
+            .context("unable to find shim lock protocol")?
+            .is_some())
+    }
+
+    /// Determines whether the shim loader is available.
+    pub fn loader_available() -> Result<bool> {
+        Ok(utils::find_handle(&Self::SHIM_IMAGE_LOADER_GUID)
+            .context("unable to find shim image loader protocol")?
+            .is_some())
+    }
+
+    /// Use the shim to validate the `input`, returning [ShimVerificationOutput] when complete.
+    pub fn verify(input: ShimInput) -> Result<ShimVerificationOutput> {
+        // Acquire the handle to the shim lock protocol.
+        let handle = utils::find_handle(&Self::SHIM_LOCK_GUID)
+            .context("unable to find shim lock protocol")?
+            .ok_or_else(|| anyhow!("unable to find shim lock protocol"))?;
+        // Acquire the protocol exclusively to the shim lock.
+        let protocol = uefi::boot::open_protocol_exclusive::<ShimLockProtocol>(handle)
+            .context("unable to open shim lock protocol")?;
+
+        // If the input type is a device path, we need to load the data.
+        let maybe_loaded_data = match input {
+            ShimInput::OwnedDataBuffer(_, _data) => {
+                bail!("owned data buffer is not supported in the verification function");
+            }
+            ShimInput::SecurityHookBuffer(_, _) => None,
+            ShimInput::SecurityHookOwnedBuffer(_, _) => None,
+            ShimInput::DataBuffer(_, _) => None,
+            ShimInput::ResolvedPath(path) => Some(path.read_file()?),
+            ShimInput::SecurityHookPath(_) => None,
+        };
+
+        // Convert the input to a buffer.
+        // If the input provides the data buffer, we will use that.
+        // Otherwise, we will use the data loaded by this function.
+        let buffer = match &input {
+            ShimInput::OwnedDataBuffer(_root, data) => data,
+            ShimInput::DataBuffer(_root, data) => *data,
+            ShimInput::ResolvedPath(_path) => maybe_loaded_data
+                .as_deref()
+                .context("expected data buffer to be loaded already")?,
+            ShimInput::SecurityHookBuffer(_, data) => data,
+            ShimInput::SecurityHookOwnedBuffer(_, data) => data,
+            ShimInput::SecurityHookPath(_) => {
+                bail!("security hook path input not supported in the verification function")
+            }
+        };
+
+        // Check if the buffer is too large to verify.
+        if buffer.len() > u32::MAX as usize {
+            bail!("buffer is too large to verify with shim lock protocol");
+        }
+
+        // Call the shim verify function.
+        // SAFETY: The shim verify function is specified by the shim lock protocol.
+        // Calling this function is considered safe because the shim verify function is
+        // guaranteed to be defined by the environment if we are able to acquire the protocol.
+        let status = unsafe {
+            (protocol.shim_verify)(buffer.as_ptr() as *const c_void, buffer.len() as u32)
+        };
+
+        // If the verification failed, return the verification failure output.
+        if !status.is_success() {
+            return Ok(ShimVerificationOutput::VerificationFailed(status));
+        }
+
+        // If verification succeeded, return the validation output,
+        // which might include the loaded data.
+        Ok(maybe_loaded_data
+            .map(ShimVerificationOutput::VerifiedDataBuffer)
+            .unwrap_or(ShimVerificationOutput::VerifiedDataNotLoaded))
+    }
+
+    /// Load the image specified by the `input` and returns an image handle.
+    pub fn load(current_image: Handle, input: ShimInput) -> Result<Handle> {
+        // Determine whether Secure Boot is enabled.
+        let secure_boot =
+            SecureBoot::enabled().context("unable to determine if secure boot is enabled")?;
+
+        // Determine whether the shim is loaded.
+        let shim_loaded = Self::loaded().context("unable to determine if shim is loaded")?;
+
+        // Determine whether the shim loader is available.
+        let shim_loader_available =
+            Self::loader_available().context("unable to determine if shim loader is available")?;
+
+        // Determines whether LoadImage in Boot Services must be patched.
+        // Version 16 of the shim doesn't require extra effort to load Secure Boot binaries.
+        // If the image loader is installed, we can skip over the security hook.
+        let requires_security_hook = secure_boot && shim_loaded && !shim_loader_available;
+
+        // If the security hook is required, we will bail for now.
+        if requires_security_hook {
+            // Install the security hook, if possible. If it's not, this is necessary to continue,
+            // so we should bail.
+            let installed = SecurityHook::install().context("unable to install security hook")?;
+            if !installed {
+                bail!("unable to install security hook required for this platform");
+            }
+        }
+
+        // If the shim is loaded, we will need to retain the shim protocol to allow
+        // loading multiple images.
+        if shim_loaded {
+            // Retain the shim protocol after loading the image.
+            Self::retain()?;
+        }
+
+        // Converts the shim input to an owned data buffer.
+        let input = input
+            .into_owned_data_buffer()
+            .context("unable to convert input to loaded data buffer")?;
+
+        // Constructs a LoadImageSource from the input.
+        let source = LoadImageSource::FromBuffer {
+            buffer: input.buffer().context("unable to get buffer from input")?,
+            file_path: input.file_path(),
+        };
+
+        // Loads the image using Boot Services LoadImage function.
+        let result = uefi::boot::load_image(current_image, source).context("unable to load image");
+
+        // If the security override is required, we will uninstall the security hook.
+        if requires_security_hook {
+            let uninstall_result = SecurityHook::uninstall();
+            // Ensure we don't mask load image errors if uninstalling fails.
+            if result.is_err()
+                && let Err(uninstall_error) = &uninstall_result
+            {
+                // Warn on the error since the load image error is more important.
+                warn!("unable to uninstall security hook: {}", uninstall_error);
+            } else {
+                // Otherwise, ensure we handle the original uninstallation result.
+                uninstall_result?;
+            }
+        }
+        result
+    }
+
+    /// Set the ShimRetainProtocol variable to indicate that shim should retain the protocols
+    /// for the full lifetime of boot services.
+    pub fn retain() -> Result<()> {
+        Self::SHIM_LOCK_VARIABLES
+            .set_bool(
+                "ShimRetainProtocol",
+                true,
+                VariableClass::BootAndRuntimeTemporary,
+            )
+            .context("unable to retain shim protocol")?;
+        Ok(())
+    }
+}

crates/sprout/src/integrations/shim/hook.rs

@@ -0,0 +1,293 @@
+use crate::integrations::shim::{ShimInput, ShimSupport, ShimVerificationOutput};
+use crate::utils;
+use anyhow::{Context, Result, bail};
+use log::warn;
+use std::sync::{LazyLock, Mutex};
+use uefi::proto::device_path::FfiDevicePath;
+use uefi::proto::unsafe_protocol;
+use uefi::{Guid, guid};
+use uefi_raw::Status;
+
+/// GUID for the EFI_SECURITY_ARCH protocol.
+const SECURITY_ARCH_GUID: Guid = guid!("a46423e3-4617-49f1-b9ff-d1bfa9115839");
+/// GUID for the EFI_SECURITY_ARCH2 protocol.
+const SECURITY_ARCH2_GUID: Guid = guid!("94ab2f58-1438-4ef1-9152-18941a3a0e68");
+
+/// EFI_SECURITY_ARCH protocol definition.
+#[unsafe_protocol(SECURITY_ARCH_GUID)]
+pub struct SecurityArchProtocol {
+    /// Determines the file authentication state.
+    pub file_authentication_state: unsafe extern "efiapi" fn(
+        this: *const SecurityArchProtocol,
+        status: u32,
+        path: *const FfiDevicePath,
+    ) -> Status,
+}
+
+/// EFI_SECURITY_ARCH2 protocol definition.
+#[unsafe_protocol(SECURITY_ARCH2_GUID)]
+pub struct SecurityArch2Protocol {
+    /// Determines the file authentication.
+    pub file_authentication: unsafe extern "efiapi" fn(
+        this: *const SecurityArch2Protocol,
+        path: *const FfiDevicePath,
+        file_buffer: *const u8,
+        file_size: usize,
+        boot_policy: bool,
+    ) -> Status,
+}
+
+/// Global state for the security hook.
+struct SecurityHookState {
+    original_hook: SecurityArchProtocol,
+    original_hook2: SecurityArch2Protocol,
+}
+
+/// Global state for the security hook.
+/// This is messy, but it is safe given the mutex.
+static GLOBAL_HOOK_STATE: LazyLock<Mutex<Option<SecurityHookState>>> =
+    LazyLock::new(|| Mutex::new(None));
+
+/// Security hook helper.
+pub struct SecurityHook;
+
+impl SecurityHook {
+    /// Shared verifier logic for both hook types.
+    #[must_use]
+    fn verify(input: ShimInput) -> bool {
+        // Verify the input and convert the result to a status.
+        let status = match ShimSupport::verify(input) {
+            Ok(output) => match output {
+                // If the verification failed, return the access-denied status.
+                ShimVerificationOutput::VerificationFailed(status) => status,
+                // If the verification succeeded, return the success status.
+                ShimVerificationOutput::VerifiedDataNotLoaded => Status::SUCCESS,
+                ShimVerificationOutput::VerifiedDataBuffer(_) => Status::SUCCESS,
+            },
+
+            // If an error occurs, log the error since we can't return a better error.
+            // Then return the access-denied status.
+            Err(error) => {
+                warn!("unable to verify image: {}", error);
+                Status::ACCESS_DENIED
+            }
+        };
+
+        // If the status is not a success, log the status.
+        if !status.is_success() {
+            warn!("shim verification failed: {}", status);
+        }
+        // Return whether the status is a success.
+        // If it's not a success, the original hook should be called.
+        status.is_success()
+    }
+
+    /// File authentication state verifier for the EFI_SECURITY_ARCH protocol.
+    /// Takes the `path` and determines the verification.
+    unsafe extern "efiapi" fn arch_file_authentication_state(
+        this: *const SecurityArchProtocol,
+        status: u32,
+        path: *const FfiDevicePath,
+    ) -> Status {
+        // Verify the path is not null.
+        if path.is_null() {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // Construct a shim input from the path.
+        let input = ShimInput::SecurityHookPath(path);
+
+        // Convert the input to an owned data buffer.
+        let input = match input.into_owned_data_buffer() {
+            Ok(input) => input,
+            // If an error occurs, log the error and return the not found status.
+            Err(error) => {
+                warn!("unable to read data to be authenticated: {}", error);
+                return Status::NOT_FOUND;
+            }
+        };
+
+        // Verify the input, if it fails, call the original hook.
+        if !Self::verify(input) {
+            // Acquire the global hook state to grab the original hook.
+            let function = match GLOBAL_HOOK_STATE.lock() {
+                // We have acquired the lock, so we can find the original hook.
+                Ok(state) => match state.as_ref() {
+                    // The hook state is available, so we can acquire the original hook.
+                    Some(state) => state.original_hook.file_authentication_state,
+
+                    // The hook state is not available, so we can't call the original hook.
+                    None => {
+                        warn!("global hook state is not available, unable to call original hook");
+                        return Status::LOAD_ERROR;
+                    }
+                },
+
+                Err(error) => {
+                    warn!(
+                        "unable to acquire global hook state lock to call original hook: {}",
+                        error,
+                    );
+                    return Status::LOAD_ERROR;
+                }
+            };
+
+            // Call the original hook function to see what it reports.
+            // SAFETY: This function is safe to call as it is stored by us and is required
+            // in the UEFI specification.
+            unsafe { function(this, status, path) }
+        } else {
+            Status::SUCCESS
+        }
+    }
+
+    /// File authentication verifier for the EFI_SECURITY_ARCH2 protocol.
+    /// Takes the `path` and a file buffer to determine the verification.
+    unsafe extern "efiapi" fn arch2_file_authentication(
+        this: *const SecurityArch2Protocol,
+        path: *const FfiDevicePath,
+        file_buffer: *const u8,
+        file_size: usize,
+        boot_policy: bool,
+    ) -> Status {
+        // Verify the path and file buffer are not null.
+        if path.is_null() || file_buffer.is_null() {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // If the boot policy is true, we can't continue as we don't support that.
+        if boot_policy {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // Construct a slice out of the file buffer and size.
+        let buffer = unsafe { std::slice::from_raw_parts(file_buffer, file_size) };
+
+        // Construct a shim input from the path.
+        let input = ShimInput::SecurityHookBuffer(Some(path), buffer);
+
+        // Verify the input, if it fails, call the original hook.
+        if !Self::verify(input) {
+            // Acquire the global hook state to grab the original hook.
+            let function = match GLOBAL_HOOK_STATE.lock() {
+                // We have acquired the lock, so we can find the original hook.
+                Ok(state) => match state.as_ref() {
+                    // The hook state is available, so we can acquire the original hook.
+                    Some(state) => state.original_hook2.file_authentication,
+
+                    // The hook state is not available, so we can't call the original hook.
+                    None => {
+                        warn!("global hook state is not available, unable to call original hook");
+                        return Status::LOAD_ERROR;
+                    }
+                },
+
+                Err(error) => {
+                    warn!(
+                        "unable to acquire global hook state lock to call original hook: {}",
+                        error
+                    );
+                    return Status::LOAD_ERROR;
+                }
+            };
+
+            // Call the original hook function to see what it reports.
+            // SAFETY: This function is safe to call as it is stored by us and is required
+            // in the UEFI specification.
+            unsafe { function(this, path, file_buffer, file_size, boot_policy) }
+        } else {
+            Status::SUCCESS
+        }
+    }
+
+    /// Install the security hook if needed.
+    pub fn install() -> Result<bool> {
+        // Find the security arch protocol. If we can't find it, we will return false.
+        let Some(hook_arch) = utils::find_handle(&SECURITY_ARCH_GUID)
+            .context("unable to check security arch existence")?
+        else {
+            return Ok(false);
+        };
+
+        // Find the security arch2 protocol. If we can't find it, we will return false.
+        let Some(hook_arch2) = utils::find_handle(&SECURITY_ARCH2_GUID)
+            .context("unable to check security arch2 existence")?
+        else {
+            return Ok(false);
+        };
+
+        // Open the security arch protocol.
+        let mut arch_protocol =
+            uefi::boot::open_protocol_exclusive::<SecurityArchProtocol>(hook_arch)
+                .context("unable to open security arch protocol")?;
+
+        // Open the security arch2 protocol.
+        let mut arch_protocol2 =
+            uefi::boot::open_protocol_exclusive::<SecurityArch2Protocol>(hook_arch2)
+                .context("unable to open security arch2 protocol")?;
+
+        // Construct the global state to store.
+        let state = SecurityHookState {
+            original_hook: SecurityArchProtocol {
+                file_authentication_state: arch_protocol.file_authentication_state,
+            },
+            original_hook2: SecurityArch2Protocol {
+                file_authentication: arch_protocol2.file_authentication,
+            },
+        };
+
+        // Acquire the lock to the global state and replace it.
+        let Ok(mut global_state) = GLOBAL_HOOK_STATE.lock() else {
+            bail!("unable to acquire global hook state lock");
+        };
+        global_state.replace(state);
+
+        // Install the hooks into the UEFI stack.
+        arch_protocol.file_authentication_state = Self::arch_file_authentication_state;
+        arch_protocol2.file_authentication = Self::arch2_file_authentication;
+
+        Ok(true)
+    }
+
+    /// Uninstalls the global security hook, if installed.
+    pub fn uninstall() -> Result<()> {
+        // Find the security arch protocol. If we can't find it, we will do nothing.
+        let Some(hook_arch) = utils::find_handle(&SECURITY_ARCH_GUID)
+            .context("unable to check security arch existence")?
+        else {
+            return Ok(());
+        };
+
+        // Find the security arch2 protocol. If we can't find it, we will do nothing.
+        let Some(hook_arch2) = utils::find_handle(&SECURITY_ARCH2_GUID)
+            .context("unable to check security arch2 existence")?
+        else {
+            return Ok(());
+        };
+
+        // Open the security arch protocol.
+        let mut arch_protocol =
+            uefi::boot::open_protocol_exclusive::<SecurityArchProtocol>(hook_arch)
+                .context("unable to open security arch protocol")?;
+
+        // Open the security arch2 protocol.
+        let mut arch_protocol2 =
+            uefi::boot::open_protocol_exclusive::<SecurityArch2Protocol>(hook_arch2)
+                .context("unable to open security arch2 protocol")?;
+
+        // Acquire the lock to the global state.
+        let Ok(mut global_state) = GLOBAL_HOOK_STATE.lock() else {
+            bail!("unable to acquire global hook state lock");
+        };
+
+        // Take the state and replace the original functions.
+        let Some(state) = global_state.take() else {
+            return Ok(());
+        };
+
+        // Reinstall the original functions.
+        arch_protocol.file_authentication_state = state.original_hook.file_authentication_state;
+        arch_protocol2.file_authentication = state.original_hook2.file_authentication;
+        Ok(())
+    }
+}

crates/sprout/src/main.rs

@@ -0,0 +1,395 @@
+#![doc = include_str!("../README.md")]
+#![feature(uefi_std)]
+
+/// The delay to wait for when an error occurs in Sprout.
+const DELAY_ON_ERROR: Duration = Duration::from_secs(10);
+
+use crate::config::RootConfiguration;
+use crate::context::{RootContext, SproutContext};
+use crate::entries::BootableEntry;
+use crate::integrations::bootloader_interface::{BootloaderInterface, BootloaderInterfaceTimeout};
+use crate::options::SproutOptions;
+use crate::options::parser::OptionsRepresentable;
+use crate::phases::phase;
+use crate::platform::timer::PlatformTimer;
+use crate::platform::tpm::PlatformTpm;
+use crate::secure::SecureBoot;
+use crate::utils::PartitionGuidForm;
+use anyhow::{Context, Result, bail};
+use log::{error, info, warn};
+use std::collections::BTreeMap;
+use std::ops::Deref;
+use std::time::Duration;
+use uefi::proto::device_path::LoadedImageDevicePath;
+
+/// actions: Code that can be configured and executed by Sprout.
+pub mod actions;
+
+/// autoconfigure: Autoconfigure Sprout based on the detected environment.
+pub mod autoconfigure;
+
+/// config: Sprout configuration mechanism.
+pub mod config;
+
+/// context: Stored values that can be cheaply forked and cloned.
+pub mod context;
+
+/// drivers: EFI drivers to load and provide extra functionality.
+pub mod drivers;
+
+/// entries: Boot menu entries that have a title and can execute actions.
+pub mod entries;
+
+/// extractors: Runtime code that can extract values into the Sprout context.
+pub mod extractors;
+
+/// generators: Runtime code that can generate entries with specific values.
+pub mod generators;
+
+/// platform: Integration or support code for specific hardware platforms.
+pub mod platform;
+
+/// menu: Display a boot menu to select an entry to boot.
+pub mod menu;
+
+/// integrations: Code that interacts with other systems.
+pub mod integrations;
+
+/// phases: Hooks into specific parts of the boot process.
+pub mod phases;
+
+/// sbat: Secure Boot Attestation section.
+pub mod sbat;
+
+/// secure: Secure Boot support.
+pub mod secure;
+
+/// setup: Code that initializes the UEFI environment for Sprout.
+pub mod setup;
+
+/// options: Parse the options of the Sprout executable.
+pub mod options;
+
+/// utils: Utility functions that are used by other parts of Sprout.
+pub mod utils;
+
+/// Run Sprout, returning an error if one occurs.
+fn run() -> Result<()> {
+    // For safety reasons, we will note that Secure Boot is in beta on Sprout.
+    if SecureBoot::enabled().context("unable to determine Secure Boot status")? {
+        warn!("Secure Boot is enabled. Sprout Secure Boot is in beta.");
+    }
+
+    // Start the platform timer.
+    let timer = PlatformTimer::start();
+
+    // Mark the initialization of Sprout in the bootloader interface.
+    BootloaderInterface::mark_init(&timer)
+        .context("unable to mark initialization in bootloader interface")?;
+
+    // Tell the bootloader interface what firmware we are running on.
+    BootloaderInterface::set_firmware_info()
+        .context("unable to set firmware info in bootloader interface")?;
+
+    // Tell the bootloader interface what loader is being used.
+    BootloaderInterface::set_loader_info()
+        .context("unable to set loader info in bootloader interface")?;
+
+    // Acquire the number of active PCR banks on the TPM.
+    // If no TPM is available, this will return zero.
+    let active_pcr_banks = PlatformTpm::active_pcr_banks()?;
+    // Tell the bootloader interface what the number of active PCR banks is.
+    BootloaderInterface::set_tpm2_active_pcr_banks(active_pcr_banks)
+        .context("unable to set tpm2 active PCR banks in bootloader interface")?;
+
+    // Parse the options to the sprout executable.
+    let options = SproutOptions::parse().context("unable to parse options")?;
+
+    // If --autoconfigure is specified, we use a stub configuration.
+    let mut config = if options.autoconfigure {
+        info!("autoconfiguration enabled, configuration file will be ignored");
+        RootConfiguration::default()
+    } else {
+        // Load the configuration of sprout.
+        // At this point, the configuration has been validated and the specified
+        // version is checked to ensure compatibility.
+        config::loader::load(&options)?
+    };
+
+    // Grab the sprout.efi loaded image path.
+    // This is done in a block to ensure the release of the LoadedImageDevicePath protocol.
+    let loaded_image_path = {
+        let current_image_device_path_protocol = uefi::boot::open_protocol_exclusive::<
+            LoadedImageDevicePath,
+        >(uefi::boot::image_handle())
+        .context("unable to get loaded image device path")?;
+        current_image_device_path_protocol.deref().to_boxed()
+    };
+
+    // Grab the partition GUID of the ESP that sprout was loaded from.
+    let loaded_image_partition_guid =
+        utils::partition_guid(&loaded_image_path, PartitionGuidForm::Partition)
+            .context("unable to retrieve loaded image partition guid")?;
+
+    // Set the partition GUID of the ESP that sprout was loaded from in the bootloader interface.
+    if let Some(loaded_image_partition_guid) = loaded_image_partition_guid {
+        // Tell the system about the partition GUID.
+        BootloaderInterface::set_partition_guid(&loaded_image_partition_guid)
+            .context("unable to set partition guid in bootloader interface")?;
+    }
+
+    // Tell the bootloader interface what the loaded image path is.
+    BootloaderInterface::set_loader_path(&loaded_image_path)
+        .context("unable to set loader path in bootloader interface")?;
+
+    // Create the root context.
+    let mut root = RootContext::new(loaded_image_path, timer, options);
+
+    // Insert the configuration actions into the root context.
+    root.actions_mut().extend(config.actions.clone());
+
+    // Create a new sprout context with the root context.
+    let mut context = SproutContext::new(root);
+
+    // Insert the configuration values into the sprout context.
+    context.insert(&config.values);
+
+    // Freeze the sprout context so it can be shared and cheaply cloned.
+    let context = context.freeze();
+
+    // Execute the early phase.
+    phase(context.clone(), &config.phases.early).context("unable to execute early phase")?;
+
+    // Load all configured drivers.
+    drivers::load(context.clone(), &config.drivers).context("unable to load drivers")?;
+
+    // If --autoconfigure is specified or the loaded configuration has autoconfigure enabled,
+    // trigger the autoconfiguration mechanism.
+    if context.root().options().autoconfigure || config.options.autoconfigure {
+        autoconfigure::autoconfigure(&mut config).context("unable to autoconfigure")?;
+    }
+
+    // Unload the context so that it can be modified.
+    let Some(mut context) = context.unload() else {
+        bail!("context safety violation while trying to unload context");
+    };
+
+    // Perform root context modification in a block to release the modification when complete.
+    {
+        // Modify the root context to include the autoconfigured actions.
+        let Some(root) = context.root_mut() else {
+            bail!("context safety violation while trying to modify root context");
+        };
+
+        // Extend the root context with the autoconfigured actions.
+        root.actions_mut().extend(config.actions);
+
+        // Insert any modified root values.
+        context.insert(&config.values);
+    }
+
+    // Refreeze the context to ensure that further operations can share the context.
+    let context = context.freeze();
+
+    // Run all the extractors declared in the configuration.
+    let mut extracted = BTreeMap::new();
+    for (name, extractor) in &config.extractors {
+        let value = extractors::extract(context.clone(), extractor)
+            .context(format!("unable to extract value {}", name))?;
+        info!("extracted value {}: {}", name, value);
+        extracted.insert(name.clone(), value);
+    }
+    let mut context = context.fork();
+    // Insert the extracted values into the sprout context.
+    context.insert(&extracted);
+    let context = context.freeze();
+
+    // Execute the startup phase.
+    phase(context.clone(), &config.phases.startup).context("unable to execute startup phase")?;
+
+    let mut entries = Vec::new();
+
+    // Insert all the static entries from the configuration into the entry list.
+    for (name, entry) in config.entries {
+        // Associate the main context with the static entry.
+        entries.push(BootableEntry::new(
+            name,
+            entry.title.clone(),
+            context.clone(),
+            entry,
+        ));
+    }
+
+    // Run all the generators declared in the configuration.
+    for (name, generator) in config.generators {
+        let context = context.fork().freeze();
+
+        // We will prefix all entries with [name]-, provided the name is not pinned.
+        let prefix = format!("{}-", name);
+
+        // Add all the entries generated by the generator to the entry list.
+        // The generator specifies the context associated with the entry.
+        for mut entry in generators::generate(context.clone(), &generator)? {
+            // If the entry name is not pinned, prepend the name prefix.
+            if !entry.is_pin_name() {
+                entry.prepend_name_prefix(&prefix);
+            }
+
+            entries.push(entry);
+        }
+    }
+
+    for entry in &mut entries {
+        let mut context = entry.context().fork();
+        // Insert the values from the entry configuration into the
+        // sprout context to use with the entry itself.
+        context.insert(&entry.declaration().values);
+        let context = context
+            .finalize()
+            .context("unable to finalize context")?
+            .freeze();
+        // Provide the new context to the bootable entry.
+        entry.swap_context(context);
+        // Restamp the title with any values.
+        entry.restamp_title();
+
+        // Mark this entry as the default entry if it is declared as such.
+        if let Some(ref default_entry) = config.options.default_entry {
+            // If the entry matches the default entry, mark it as the default entry.
+            if entry.is_match(default_entry) {
+                entry.mark_default();
+            }
+        }
+    }
+
+    // Tell the bootloader interface what entries are available.
+    BootloaderInterface::set_entries(entries.iter().map(|entry| entry.name()))
+        .context("unable to set entries in bootloader interface")?;
+
+    // Execute the late phase.
+    phase(context.clone(), &config.phases.late).context("unable to execute late phase")?;
+
+    // Acquire the timeout setting from the bootloader interface.
+    let bootloader_interface_timeout =
+        BootloaderInterface::get_timeout().context("unable to get bootloader interface timeout")?;
+
+    // Acquire the default entry from the bootloader interface.
+    let bootloader_interface_default_entry = BootloaderInterface::get_default_entry()
+        .context("unable to get bootloader interface default entry")?;
+
+    // Acquire the oneshot entry from the bootloader interface.
+    let bootloader_interface_oneshot_entry = BootloaderInterface::get_oneshot_entry()
+        .context("unable to get bootloader interface oneshot entry")?;
+
+    // If --boot is specified, boot that entry immediately.
+    let mut force_boot_entry = context.root().options().boot.clone();
+    // If --force-menu is specified, show the boot menu regardless of the value of --boot.
+    let mut force_boot_menu = context.root().options().force_menu;
+
+    // Determine the menu timeout in seconds based on the options or configuration.
+    // We prefer the options over the configuration to allow for overriding.
+    let mut menu_timeout = context
+        .root()
+        .options()
+        .menu_timeout
+        .unwrap_or(config.options.menu_timeout);
+
+    // Apply bootloader interface timeout settings.
+    match bootloader_interface_timeout {
+        BootloaderInterfaceTimeout::MenuForce => {
+            // Force the boot menu.
+            force_boot_menu = true;
+        }
+
+        BootloaderInterfaceTimeout::MenuHidden | BootloaderInterfaceTimeout::MenuDisabled => {
+            // Hide the boot menu by setting the timeout to zero.
+            menu_timeout = 0;
+        }
+
+        BootloaderInterfaceTimeout::Timeout(timeout) => {
+            // Configure the timeout to the specified value.
+            menu_timeout = timeout;
+        }
+
+        BootloaderInterfaceTimeout::Unspecified => {
+            // Do nothing.
+        }
+    }
+
+    // Apply bootloader interface default entry settings.
+    if let Some(ref bootloader_interface_default_entry) = bootloader_interface_default_entry {
+        // Iterate over all the entries and mark the default entry as the one specified.
+        for entry in &mut entries {
+            // Mark the entry as the default entry if it matches the specified entry.
+            // If the entry does not match the specified entry, unmark it as the default entry.
+            if entry.is_match(bootloader_interface_default_entry) {
+                entry.mark_default();
+            } else {
+                entry.unmark_default();
+            }
+        }
+    }
+
+    // Apply bootloader interface oneshot entry settings.
+    // If set, we will force booting the oneshot entry.
+    if let Some(ref bootloader_interface_oneshot_entry) = bootloader_interface_oneshot_entry {
+        force_boot_entry = Some(bootloader_interface_oneshot_entry.clone());
+    }
+
+    // If no entries were the default, pick the first entry as the default entry.
+    if entries.iter().all(|entry| !entry.is_default())
+        && let Some(entry) = entries.first_mut()
+    {
+        entry.mark_default();
+    }
+
+    // Convert the menu timeout to a duration.
+    let menu_timeout = Duration::from_secs(menu_timeout);
+
+    // Use the forced boot entry if possible, otherwise pick the first entry using a boot menu.
+    let entry = if !force_boot_menu && let Some(ref force_boot_entry) = force_boot_entry {
+        BootableEntry::find(force_boot_entry, entries.iter())
+            .context(format!("unable to find entry: {force_boot_entry}"))?
+    } else {
+        // Delegate to the menu to select an entry to boot.
+        menu::select(&timer, menu_timeout, &entries)
+            .context("unable to select entry via boot menu")?
+    };
+
+    // Tell the bootloader interface what the selected entry is.
+    BootloaderInterface::set_selected_entry(entry.name().to_string())
+        .context("unable to set selected entry in bootloader interface")?;
+
+    // Execute all the actions for the selected entry.
+    for action in &entry.declaration().actions {
+        let action = entry.context().stamp(action);
+        actions::execute(entry.context().clone(), &action)
+            .context(format!("unable to execute action '{}'", action))?;
+    }
+
+    Ok(())
+}
+
+/// The main entrypoint of sprout.
+/// It is possible this function will not return if actions that are executed
+/// exit boot services or do not return control to sprout.
+fn main() -> Result<()> {
+    // Initialize the basic UEFI environment.
+    setup::init()?;
+
+    // Run Sprout, then handle the error.
+    let result = run();
+    if let Err(ref error) = result {
+        // Print an error trace.
+        error!("sprout encountered an error");
+        for (index, stack) in error.chain().enumerate() {
+            error!("[{}]: {}", index, stack);
+        }
+        // Sleep to allow the user to read the error.
+        uefi::boot::stall(DELAY_ON_ERROR);
+    }
+
+    // Sprout doesn't necessarily guarantee anything was booted.
+    // If we reach here, we will exit back to whoever called us.
+    Ok(())
+}

crates/sprout/src/menu.rs

@@ -0,0 +1,197 @@
+use crate::entries::BootableEntry;
+use crate::integrations::bootloader_interface::BootloaderInterface;
+use crate::platform::timer::PlatformTimer;
+use anyhow::{Context, Result, bail};
+use log::{info, warn};
+use std::time::Duration;
+use uefi::ResultExt;
+use uefi::boot::TimerTrigger;
+use uefi::proto::console::text::{Input, Key, ScanCode};
+use uefi_raw::table::boot::{EventType, Tpl};
+
+/// The characters that can be used to select an entry from keys.
+const ENTRY_NUMBER_TABLE: &[char] = &['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
+
+/// Represents the operation that can be performed by the boot menu.
+#[derive(PartialEq, Eq)]
+enum MenuOperation {
+    /// The user selected a numbered entry.
+    Number(usize),
+    /// The user selected the escape key to exit the boot menu.
+    Exit,
+    /// The user selected the enter key to display the entries again.
+    Continue,
+    /// Timeout occurred.
+    Timeout,
+    /// No operation should be performed.
+    Nop,
+}
+
+/// Read a key from the input device with a duration, returning the [MenuOperation] that was
+/// performed.
+fn read(input: &mut Input, timeout: &Duration) -> Result<MenuOperation> {
+    // The event to wait for a key press.
+    let key_event = input
+        .wait_for_key_event()
+        .context("unable to acquire key event")?;
+
+    // Timer event for timeout.
+    // SAFETY: The timer event creation allocated a timer pointer on the UEFI heap.
+    // This is validated safe as long as we are in boot services.
+    let timer_event = unsafe {
+        uefi::boot::create_event_ex(EventType::TIMER, Tpl::CALLBACK, None, None, None)
+            .context("unable to create timer event")?
+    };
+
+    // The timeout is in increments of 100 nanoseconds.
+    let timeout_hundred_nanos = timeout.as_nanos() / 100;
+
+    // Check if the timeout is too large to fit into an u64.
+    if timeout_hundred_nanos > u64::MAX as u128 {
+        bail!("timeout duration overflow");
+    }
+
+    // Set a timer to trigger after the specified duration.
+    let trigger = TimerTrigger::Relative(timeout_hundred_nanos as u64);
+    uefi::boot::set_timer(&timer_event, trigger).context("unable to set timeout timer")?;
+
+    let mut events = vec![timer_event, key_event];
+
+    // Wait for either the timer event or the key event to trigger.
+    // Store the result so that we can free the timer event.
+    let event_result = uefi::boot::wait_for_event(&mut events)
+        .discard_errdata()
+        .context("unable to wait for event");
+
+    // Close the timer event that we acquired.
+    // We don't need to close the key event because it is owned globally.
+    if let Some(timer_event) = events.into_iter().next() {
+        // Store the result of the close event so we can determine if we can safely assert it.
+        let close_event_result =
+            uefi::boot::close_event(timer_event).context("unable to close timer event");
+        if event_result.is_err()
+            && let Err(ref close_event_error) = close_event_result
+        {
+            // Log a warning if we failed to close the timer event.
+            // This is done to ensure we don't mask the wait_for_event error.
+            warn!("unable to close timer event: {}", close_event_error);
+        } else {
+            // If we reach here, we can safely assert that the close event succeeded without
+            // masking the wait_for_event error.
+            close_event_result?;
+        }
+    }
+
+    // Acquire the event that triggered.
+    let event = event_result?;
+
+    // The first event is the timer event.
+    // If it has triggered, the user did not select a numbered entry.
+    if event == 0 {
+        return Ok(MenuOperation::Timeout);
+    }
+
+    // If we reach here, there is a key event.
+    let Some(key) = input.read_key().context("unable to read key")? else {
+        bail!("no key was pressed");
+    };
+
+    match key {
+        Key::Printable(c) => {
+            // If the key is not ascii, we can't process it.
+            if !c.is_ascii() {
+                return Ok(MenuOperation::Continue);
+            }
+            // Convert the key to a char.
+            let c: char = c.into();
+            // Find the key pressed in the entry number table or continue.
+            Ok(ENTRY_NUMBER_TABLE
+                .iter()
+                .position(|&x| x == c)
+                .map(MenuOperation::Number)
+                .unwrap_or(MenuOperation::Continue))
+        }
+
+        // The escape key is used to exit the boot menu.
+        Key::Special(ScanCode::ESCAPE) => Ok(MenuOperation::Exit),
+
+        // If the special key is unknown, do nothing.
+        Key::Special(_) => Ok(MenuOperation::Nop),
+    }
+}
+
+/// Selects an entry from the list of entries using the boot menu.
+fn select_with_input<'a>(
+    input: &mut Input,
+    timeout: Duration,
+    entries: &'a [BootableEntry],
+) -> Result<&'a BootableEntry> {
+    loop {
+        // If the timeout is not zero, let's display the boot menu.
+        if !timeout.is_zero() {
+            // Until a pretty menu is available, we just print all the entries.
+            info!("Boot Menu:");
+            for (index, entry) in entries.iter().enumerate() {
+                let title = entry.context().stamp(&entry.declaration().title);
+                info!("  [{}] {}", index, title);
+            }
+        }
+
+        // Read from input until a valid operation is selected.
+        let operation = loop {
+            // If the timeout is zero, we can exit immediately because there is nothing to do.
+            if timeout.is_zero() {
+                break MenuOperation::Exit;
+            }
+
+            info!("Select a boot entry using the number keys.");
+            info!("Press Escape to exit and enter to display the entries again.");
+
+            let operation = read(input, &timeout)?;
+            if operation != MenuOperation::Nop {
+                break operation;
+            }
+        };
+
+        match operation {
+            // Entry was selected by number. If the number is invalid, we continue.
+            MenuOperation::Number(index) => {
+                let Some(entry) = entries.get(index) else {
+                    info!("invalid entry number");
+                    continue;
+                };
+                return Ok(entry);
+            }
+
+            // When the user exits the boot menu or a timeout occurs, we should
+            // boot the default entry, if any.
+            MenuOperation::Exit | MenuOperation::Timeout => {
+                return entries
+                    .iter()
+                    .find(|item| item.is_default())
+                    .context("no default entry available");
+            }
+
+            // If the operation is to continue or nop, we can just run the loop again.
+            MenuOperation::Continue | MenuOperation::Nop => {
+                continue;
+            }
+        }
+    }
+}
+
+/// Shows a boot menu to select a bootable entry to boot.
+/// The actual work is done internally in [select_with_input] which is called
+/// within the context of the standard input device.
+pub fn select<'live>(
+    timer: &'live PlatformTimer,
+    timeout: Duration,
+    entries: &'live [BootableEntry],
+) -> Result<&'live BootableEntry> {
+    // Notify the bootloader interface that we are about to display the menu.
+    BootloaderInterface::mark_menu(timer)
+        .context("unable to mark menu display in bootloader interface")?;
+
+    // Acquire the standard input device and run the boot menu.
+    uefi::system::with_stdin(move |input| select_with_input(input, timeout, entries))
+}

crates/sprout/src/options.rs

@@ -0,0 +1,133 @@
+use crate::options::parser::{OptionDescription, OptionForm, OptionsRepresentable};
+use anyhow::{Context, Result, bail};
+use std::collections::BTreeMap;
+
+/// The Sprout options parser.
+pub mod parser;
+
+/// Default configuration file path.
+const DEFAULT_CONFIG_PATH: &str = "\\sprout.toml";
+
+/// The parsed options of sprout.
+#[derive(Debug)]
+pub struct SproutOptions {
+    /// Configures Sprout automatically based on the environment.
+    pub autoconfigure: bool,
+    /// Path to a configuration file to load.
+    pub config: String,
+    /// Entry to boot without showing the boot menu.
+    pub boot: Option<String>,
+    /// Force display of the boot menu.
+    pub force_menu: bool,
+    /// The timeout for the boot menu in seconds.
+    pub menu_timeout: Option<u64>,
+}
+
+/// The default Sprout options.
+impl Default for SproutOptions {
+    fn default() -> Self {
+        Self {
+            autoconfigure: false,
+            config: DEFAULT_CONFIG_PATH.to_string(),
+            boot: None,
+            force_menu: false,
+            menu_timeout: None,
+        }
+    }
+}
+
+/// The options parser mechanism for Sprout.
+impl OptionsRepresentable for SproutOptions {
+    /// Produce the [SproutOptions] structure.
+    type Output = Self;
+
+    /// All the Sprout options that are defined.
+    fn options() -> &'static [(&'static str, OptionDescription<'static>)] {
+        &[
+            (
+                "autoconfigure",
+                OptionDescription {
+                    description: "Enable Sprout Autoconfiguration",
+                    form: OptionForm::Flag,
+                },
+            ),
+            (
+                "config",
+                OptionDescription {
+                    description: "Path to Sprout configuration file",
+                    form: OptionForm::Value,
+                },
+            ),
+            (
+                "boot",
+                OptionDescription {
+                    description: "Entry to boot, bypassing the menu",
+                    form: OptionForm::Value,
+                },
+            ),
+            (
+                "force-menu",
+                OptionDescription {
+                    description: "Force showing of the boot menu",
+                    form: OptionForm::Flag,
+                },
+            ),
+            (
+                "menu-timeout",
+                OptionDescription {
+                    description: "Boot menu timeout, in seconds",
+                    form: OptionForm::Value,
+                },
+            ),
+            (
+                "help",
+                OptionDescription {
+                    description: "Display Sprout Help",
+                    form: OptionForm::Help,
+                },
+            ),
+        ]
+    }
+
+    /// Produces [SproutOptions] from the parsed raw `options` map.
+    fn produce(options: BTreeMap<String, Option<String>>) -> Result<Self> {
+        // Use the default value of sprout options and have the raw options be parsed into it.
+        let mut result = Self::default();
+
+        for (key, value) in options {
+            match key.as_str() {
+                "autoconfigure" => {
+                    // Enable autoconfiguration.
+                    result.autoconfigure = true;
+                }
+
+                "config" => {
+                    // The configuration file to load.
+                    result.config = value.context("--config option requires a value")?;
+                }
+
+                "boot" => {
+                    // The entry to boot.
+                    result.boot = Some(value.context("--boot option requires a value")?);
+                }
+
+                "force-menu" => {
+                    // Force showing of the boot menu.
+                    result.force_menu = true;
+                }
+
+                "menu-timeout" => {
+                    // The timeout for the boot menu in seconds.
+                    let value = value.context("--menu-timeout option requires a value")?;
+                    let value = value
+                        .parse::<u64>()
+                        .context("menu-timeout must be a number")?;
+                    result.menu_timeout = Some(value);
+                }
+
+                _ => bail!("unknown option: --{key}"),
+            }
+        }
+        Ok(result)
+    }
+}

crates/sprout/src/options/parser.rs

@@ -0,0 +1,163 @@
+use anyhow::{Context, Result, bail};
+use log::info;
+use std::collections::BTreeMap;
+
+/// The type of option. This disambiguates different behavior
+/// of how options are handled.
+#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq)]
+pub enum OptionForm {
+    /// A flag, like --verbose.
+    Flag,
+    /// A value, in the form --abc 123 or --abc=123.
+    Value,
+    /// Help flag, like --help.
+    Help,
+}
+
+/// The description of an option, used in the options parser
+/// to make decisions about how to progress.
+#[derive(Debug, Clone)]
+pub struct OptionDescription<'a> {
+    /// The description of the option.
+    pub description: &'a str,
+    /// The type of option to parse as.
+    pub form: OptionForm,
+}
+
+/// Represents a type that can be parsed from command line arguments.
+/// This is a super minimal options parser mechanism just for Sprout.
+pub trait OptionsRepresentable {
+    /// The output type that parsing will produce.
+    type Output;
+
+    /// The configured options for this type. This should describe all the options
+    /// that are valid to produce the type. The left hand side is the name of the option,
+    /// and the right hand side is the description.
+    fn options() -> &'static [(&'static str, OptionDescription<'static>)];
+
+    /// Produces the type by taking the `options` and processing it into the output.
+    fn produce(options: BTreeMap<String, Option<String>>) -> Result<Self::Output>;
+
+    /// For minimalism, we don't want a full argument parser. Instead, we use
+    /// a simple --xyz = xyz: None and --abc 123 = abc: Some("123") format.
+    /// We also support --abc=123 = abc: Some("123") format.
+    fn parse_raw() -> Result<BTreeMap<String, Option<String>>> {
+        // Access the configured options for this type.
+        let configured: BTreeMap<_, _> = BTreeMap::from_iter(Self::options().to_vec());
+
+        // Collect all the arguments to Sprout.
+        // Skip the first argument, which is the path to our executable.
+        let mut args = std::env::args().skip(1).collect::<Vec<_>>();
+
+        // Correct firmware that may add invalid arguments at the start.
+        // Witnessed this on a Dell Precision 5690 when direct booting.
+        loop {
+            // Grab the first argument or break.
+            let Some(arg) = args.first() else {
+                break;
+            };
+
+            // If the argument starts with a tilde, remove it.
+            if arg.starts_with("`") {
+                args.remove(0);
+                continue;
+            }
+            break;
+        }
+
+        // Represent options as key-value pairs.
+        let mut options = BTreeMap::new();
+
+        // Iterators makes this way easier.
+        let mut iterator = args.into_iter().peekable();
+
+        loop {
+            // Consume the next option, if any.
+            let Some(option) = iterator.next() else {
+                break;
+            };
+
+            // If the doesn't start with --, that is invalid.
+            if !option.starts_with("--") {
+                bail!("invalid option: {option}");
+            }
+
+            // Strip the -- prefix off.
+            let mut option = option["--".len()..].trim().to_string();
+
+            // An optional value.
+            let mut value = None;
+
+            // Check if the option is of the form --abc=123
+            if let Some((part_key, part_value)) = option.split_once('=') {
+                let part_key = part_key.to_string();
+                let part_value = part_value.to_string();
+                option = part_key;
+                value = Some(part_value);
+            }
+
+            // Error on empty option names.
+            if option.is_empty() {
+                bail!("invalid empty option");
+            }
+
+            // Find the description of the configured option, if any.
+            let Some(description) = configured.get(option.as_str()) else {
+                bail!("invalid option: --{option}");
+            };
+
+            // Check if the option requires a value and error if none was provided.
+            if description.form == OptionForm::Value && value.is_none() {
+                // Check for the next value.
+                let maybe_next = iterator.peek();
+
+                // If the next value isn't another option, set the value to the next value.
+                // Otherwise, it is None.
+                value = if let Some(next) = maybe_next
+                    && !next.starts_with("--")
+                {
+                    iterator.next()
+                } else {
+                    None
+                };
+            }
+
+            // If the option form does not support a value and there is a value, error.
+            if description.form != OptionForm::Value && value.is_some() {
+                bail!("option --{} does not take a value", option);
+            }
+
+            // Handle the --help flag case.
+            if description.form == OptionForm::Help {
+                // Generic configured options output.
+                info!("Configured Options:");
+                for (name, description) in &configured {
+                    info!(
+                        "  --{}{}: {}",
+                        name,
+                        if description.form == OptionForm::Value {
+                            " <value>"
+                        } else {
+                            ""
+                        },
+                        description.description
+                    );
+                }
+                // Exit because the help has been displayed.
+                std::process::exit(0);
+            }
+
+            // Insert the option and the value into the map.
+            options.insert(option, value);
+        }
+        Ok(options)
+    }
+
+    /// Parses the program arguments as a [Self::Output], calling [Self::parse_raw] and [Self::produce].
+    fn parse() -> Result<Self::Output> {
+        // Parse the program arguments into a raw map.
+        let options = Self::parse_raw().context("unable to parse options")?;
+        // Produce the options from the map.
+        Self::produce(options)
+    }
+}

crates/sprout/src/phases.rs

@@ -0,0 +1,54 @@
+use crate::actions;
+use crate::context::SproutContext;
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+/// Configures the various phases of the boot process.
+/// This allows hooking various phases to run actions.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct PhasesConfiguration {
+    /// The early phase is run before drivers are loaded.
+    #[serde(default)]
+    pub early: Vec<PhaseConfiguration>,
+    /// The startup phase is run after drivers are loaded, but before entries are displayed.
+    #[serde(default)]
+    pub startup: Vec<PhaseConfiguration>,
+    /// The late phase is run after the entry is chosen, but before the actions are executed.
+    #[serde(default)]
+    pub late: Vec<PhaseConfiguration>,
+}
+
+/// Configures a single phase of the boot process.
+/// There can be multiple phase configurations that are
+/// executed sequentially.
+#[derive(Serialize, Deserialize, Debug, Default, Clone)]
+pub struct PhaseConfiguration {
+    /// The actions to run when the phase is executed.
+    #[serde(default)]
+    pub actions: Vec<String>,
+    /// The values to insert into the context when the phase is executed.
+    #[serde(default)]
+    pub values: BTreeMap<String, String>,
+}
+
+/// Executes the specified [phase] of the boot process.
+/// The value [phase] should be a reference of a specific phase in the [PhasesConfiguration].
+/// Any error from the actions is propagated into the [Result] and will interrupt further
+/// execution of phase actions.
+pub fn phase(context: Rc<SproutContext>, phase: &[PhaseConfiguration]) -> Result<()> {
+    for item in phase {
+        let mut context = context.fork();
+        // Insert the values into the context.
+        context.insert(&item.values);
+        let context = context.freeze();
+
+        // Execute all the actions in this phase configuration.
+        for action in item.actions.iter() {
+            actions::execute(context.clone(), action)
+                .context(format!("unable to execute action '{}'", action))?;
+        }
+    }
+    Ok(())
+}

crates/sprout/src/platform.rs

@@ -0,0 +1,4 @@
+/// timer: Platform timer support.
+pub mod timer;
+/// tpm: Platform TPM support.
+pub mod tpm;

crates/sprout/src/platform/timer.rs

@@ -0,0 +1,94 @@
+// Referenced https://github.com/sheroz/tick_counter (MIT license) as a baseline.
+// Architecturally modified to support UEFI and remove x86 (32-bit) support.
+
+use std::time::Duration;
+
+/// Support for aarch64 timers.
+#[cfg(target_arch = "aarch64")]
+pub mod aarch64;
+
+/// Support for x86_64 timers.
+#[cfg(target_arch = "x86_64")]
+pub mod x86_64;
+
+/// The tick frequency of the platform.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TickFrequency {
+    /// The platform provides the tick frequency.
+    Hardware(u64),
+    /// The tick frequency is measured internally.
+    Measured(u64, Duration),
+}
+
+impl TickFrequency {
+    /// Acquire the tick frequency reported by the platform.
+    fn ticks(&self) -> u64 {
+        match self {
+            TickFrequency::Hardware(frequency) => *frequency,
+            TickFrequency::Measured(frequency, _) => *frequency,
+        }
+    }
+
+    /// Calculate the nanoseconds represented by a tick.
+    fn nanos(&self) -> f64 {
+        1.0e9_f64 / (self.ticks() as f64)
+    }
+
+    /// Produce a duration from the provided elapsed `ticks` value.
+    fn duration(&self, ticks: u64) -> Duration {
+        let accuracy = self.nanos();
+        let nanos = ticks as f64 * accuracy;
+        Duration::from_nanos(nanos as u64)
+    }
+}
+
+/// Acquire the tick value reported by the platform.
+fn arch_ticks() -> u64 {
+    #[cfg(target_arch = "aarch64")]
+    return aarch64::ticks();
+    #[cfg(target_arch = "x86_64")]
+    return x86_64::ticks();
+}
+
+/// Acquire the tick frequency reported by the platform.
+fn arch_frequency() -> TickFrequency {
+    #[cfg(target_arch = "aarch64")]
+    let frequency = aarch64::frequency();
+    #[cfg(target_arch = "x86_64")]
+    let frequency = x86_64::frequency();
+    // If the frequency is 0, then something went very wrong and we should panic.
+    if frequency.ticks() == 0 {
+        panic!("timer frequency is zero");
+    }
+    frequency
+}
+
+/// Platform timer that allows measurement of the elapsed time.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct PlatformTimer {
+    /// The start tick value.
+    start: u64,
+    /// The tick frequency of the platform.
+    frequency: TickFrequency,
+}
+
+impl PlatformTimer {
+    /// Start a platform timer at the current instant.
+    pub fn start() -> Self {
+        Self {
+            start: arch_ticks(),
+            frequency: arch_frequency(),
+        }
+    }
+
+    /// Measure the elapsed duration since the hardware started ticking upwards.
+    pub fn elapsed_since_lifetime(&self) -> Duration {
+        self.frequency.duration(arch_ticks())
+    }
+
+    /// Measure the elapsed duration since the timer was started.
+    pub fn elapsed_since_start(&self) -> Duration {
+        let duration = arch_ticks().wrapping_sub(self.start);
+        self.frequency.duration(duration)
+    }
+}

crates/sprout/src/platform/timer/aarch64.rs

@@ -0,0 +1,33 @@
+use crate::platform::timer::TickFrequency;
+use std::arch::asm;
+
+/// Reads the cntvct_el0 counter and returns the value.
+pub fn ticks() -> u64 {
+    let counter: u64;
+    unsafe {
+        asm!("mrs x0, cntvct_el0", out("x0") counter);
+    }
+    counter
+}
+
+/// We can use the actual ticks value as our start value.
+pub fn start() -> u64 {
+    ticks()
+}
+
+/// We can use the actual ticks value as our stop value.
+pub fn stop() -> u64 {
+    ticks()
+}
+
+/// Our frequency is provided by cntfrq_el0 on the platform.
+pub fn frequency() -> TickFrequency {
+    let frequency: u64;
+    unsafe {
+        asm!(
+            "mrs x0, cntfrq_el0",
+            out("x0") frequency
+        );
+    }
+    TickFrequency::Hardware(frequency)
+}

crates/sprout/src/platform/timer/x86_64.rs

@@ -0,0 +1,66 @@
+use crate::platform::timer::TickFrequency;
+use core::arch::asm;
+use std::time::Duration;
+
+/// We will measure the frequency of the timer based on 1000 microseconds.
+/// This will result in a call to BS->Stall(1000) in the end.
+const MEASURE_FREQUENCY_DURATION: Duration = Duration::from_micros(1000);
+
+/// Read the number of ticks from the platform timer.
+pub fn ticks() -> u64 {
+    let mut eax: u32;
+    let mut edx: u32;
+
+    unsafe {
+        asm!("rdtsc", out("eax") eax, out("edx") edx);
+    }
+
+    (edx as u64) << 32 | eax as u64
+}
+
+/// Read the starting number of ticks from the platform timer.
+pub fn start() -> u64 {
+    let rax: u64;
+    unsafe {
+        asm!(
+            "mfence",
+            "lfence",
+            "rdtsc",
+            "shl rdx, 32",
+            "or rax, rdx",
+            out("rax") rax
+        );
+    }
+    rax
+}
+
+/// Read the ending number of ticks from the platform timer.
+pub fn stop() -> u64 {
+    let rax: u64;
+    unsafe {
+        asm!(
+        "rdtsc",
+        "lfence",
+        "shl rdx, 32",
+        "or rax, rdx",
+        out("rax") rax
+        );
+    }
+    rax
+}
+
+/// Measure the frequency of the platform timer.
+fn measure_frequency() -> u64 {
+    let start = start();
+    uefi::boot::stall(MEASURE_FREQUENCY_DURATION);
+    let stop = stop();
+    let elapsed = stop.wrapping_sub(start) as f64;
+    (elapsed / MEASURE_FREQUENCY_DURATION.as_secs_f64()) as u64
+}
+
+/// Acquire the platform timer frequency.
+/// On x86_64, this is slightly expensive, so it should be done once.
+pub fn frequency() -> TickFrequency {
+    let frequency = measure_frequency();
+    TickFrequency::Measured(frequency, MEASURE_FREQUENCY_DURATION)
+}

crates/sprout/src/platform/tpm.rs

@@ -0,0 +1,128 @@
+use crate::utils;
+use anyhow::{Context, Result};
+use uefi::ResultExt;
+use uefi::boot::ScopedProtocol;
+use uefi::proto::tcg::PcrIndex;
+use uefi::proto::tcg::v2::{PcrEventInputs, Tcg};
+use uefi_raw::protocol::tcg::EventType;
+use uefi_raw::protocol::tcg::v2::{Tcg2HashLogExtendEventFlags, Tcg2Protocol, Tcg2Version};
+
+/// Represents the platform TPM.
+pub struct PlatformTpm;
+
+/// Represents an open TPM handle.
+pub struct TpmProtocolHandle {
+    /// The version of the TPM protocol.
+    version: Tcg2Version,
+    /// The protocol itself.
+    protocol: ScopedProtocol<Tcg>,
+}
+
+impl TpmProtocolHandle {
+    /// Construct a new [TpmProtocolHandle] from the `version` and `protocol`.
+    pub fn new(version: Tcg2Version, protocol: ScopedProtocol<Tcg>) -> Self {
+        Self { version, protocol }
+    }
+
+    /// Access the version provided by the tcg2 protocol.
+    pub fn version(&self) -> Tcg2Version {
+        self.version
+    }
+
+    /// Access the protocol interface for tcg2.
+    pub fn protocol(&mut self) -> &mut ScopedProtocol<Tcg> {
+        &mut self.protocol
+    }
+}
+
+impl PlatformTpm {
+    /// The PCR for measuring the bootloader configuration into.
+    pub const PCR_BOOT_LOADER_CONFIG: PcrIndex = PcrIndex(5);
+
+    /// Acquire access to the TPM protocol handle, if possible.
+    /// Returns None if TPM is not available.
+    fn protocol() -> Result<Option<TpmProtocolHandle>> {
+        // Attempt to acquire the TCG2 protocol handle. If it's not available, return None.
+        let Some(handle) =
+            utils::find_handle(&Tcg2Protocol::GUID).context("unable to determine tpm presence")?
+        else {
+            return Ok(None);
+        };
+
+        // If we reach here, we've already validated that the handle
+        // implements the TCG2 protocol.
+        let mut protocol = uefi::boot::open_protocol_exclusive::<Tcg>(handle)
+            .context("unable to open tcg2 protocol")?;
+
+        // Acquire the capabilities of the TPM.
+        let capability = protocol
+            .get_capability()
+            .context("unable to get tcg2 boot service capability")?;
+
+        // If the TPM is not present, return None.
+        if !capability.tpm_present() {
+            return Ok(None);
+        }
+
+        // If the TPM is present, we need to determine the version of the TPM.
+        let version = capability.protocol_version;
+
+        // We have a TPM, so return the protocol version and the protocol handle.
+        Ok(Some(TpmProtocolHandle::new(version, protocol)))
+    }
+
+    /// Determines whether the platform TPM is present.
+    pub fn present() -> Result<bool> {
+        Ok(PlatformTpm::protocol()?.is_some())
+    }
+
+    /// Determine the number of active PCR banks on the TPM.
+    /// If no TPM is available, this will return zero.
+    pub fn active_pcr_banks() -> Result<u32> {
+        // Acquire access to the TPM protocol handle.
+        let Some(mut handle) = PlatformTpm::protocol()? else {
+            return Ok(0);
+        };
+
+        // Check if the TPM supports `GetActivePcrBanks`, and if it doesn't return zero.
+        if handle.version().major < 1 || handle.version().major == 1 && handle.version().minor < 1 {
+            return Ok(0);
+        }
+
+        // The safe wrapper for this function will decode the bitmap.
+        // Strictly speaking, it's not future-proof to re-encode that, but in practice it will work.
+        let banks = handle
+            .protocol()
+            .get_active_pcr_banks()
+            .context("unable to get active pcr banks")?;
+
+        // Return the number of active PCR banks.
+        Ok(banks.bits())
+    }
+
+    /// Log an event into the TPM pcr `pcr_index` with `buffer` as data. The `description`
+    /// is used to describe what the event is.
+    ///
+    /// If a TPM is not available, this will do nothing.
+    pub fn log_event(pcr_index: PcrIndex, buffer: &[u8], description: &str) -> Result<()> {
+        // Acquire access to the TPM protocol handle.
+        let Some(mut handle) = PlatformTpm::protocol()? else {
+            return Ok(());
+        };
+
+        // Encode the description as UTF-8.
+        let description = description.as_bytes().to_vec();
+
+        // Construct an event input for the TPM.
+        let event = PcrEventInputs::new_in_box(pcr_index, EventType::IPL, &description)
+            .discard_errdata()
+            .context("unable to construct pcr event inputs")?;
+
+        // Log the event into the TPM.
+        handle
+            .protocol()
+            .hash_log_extend_event(Tcg2HashLogExtendEventFlags::empty(), buffer, &event)
+            .context("unable to log event to tpm")?;
+        Ok(())
+    }
+}

crates/sprout/src/sbat.rs

@@ -0,0 +1,11 @@
+/// SBAT must be aligned by 512 bytes.
+const SBAT_SIZE: usize = 512;
+
+/// Define the SBAT attestation by including the sbat.csv file.
+/// See this document for more details: https://github.com/rhboot/shim/blob/main/SBAT.md
+/// NOTE: Alignment can't be enforced by an attribute, so instead the alignment is currently
+/// enforced by the SBAT_SIZE being 512. The build.rs will ensure that the sbat.csv is padded.
+/// This code will not compile if the sbat.csv is a different size than SBAT_SIZE.
+#[used]
+#[unsafe(link_section = ".sbat")]
+static SBAT: [u8; SBAT_SIZE] = *include_bytes!(concat!(env!("OUT_DIR"), "/sbat.csv"));

crates/sprout/src/sbat.template.csv

@@ -0,0 +1,2 @@
+sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
+sprout,1,Edera,sprout,{version},https://sprout.edera.dev

crates/sprout/src/secure.rs

@@ -0,0 +1,14 @@
+use crate::utils::variables::VariableController;
+use anyhow::Result;
+
+/// Secure boot services.
+pub struct SecureBoot;
+
+impl SecureBoot {
+    /// Checks if Secure Boot is enabled on the system.
+    /// This might fail if retrieving the variable fails in an irrecoverable way.
+    pub fn enabled() -> Result<bool> {
+        // The SecureBoot variable will tell us whether Secure Boot is enabled at all.
+        VariableController::GLOBAL.get_bool("SecureBoot")
+    }
+}

crates/sprout/src/setup.rs

@@ -0,0 +1,27 @@
+use anyhow::{Context, Result};
+use std::os::uefi as uefi_std;
+
+/// Initializes the UEFI environment.
+///
+/// This fetches the system table and current image handle from uefi_std and injects
+/// them into the uefi crate.
+pub fn init() -> Result<()> {
+    // Acquire the system table and image handle from the uefi_std environment.
+    let system_table = uefi_std::env::system_table();
+    let image_handle = uefi_std::env::image_handle();
+
+    // SAFETY: The UEFI variables above come from the Rust std.
+    // These variables are not-null and calling the uefi crates with these values is validated
+    // to be corrected by hand.
+    unsafe {
+        // Set the system table and image handle.
+        uefi::table::set_system_table(system_table.as_ptr().cast());
+        let handle = uefi::Handle::from_ptr(image_handle.as_ptr().cast())
+            .context("unable to resolve image handle")?;
+        uefi::boot::set_image_handle(handle);
+    }
+
+    // Initialize the uefi logger mechanism and other helpers.
+    uefi::helpers::init().context("unable to initialize uefi")?;
+    Ok(())
+}

crates/sprout/src/utils.rs

@@ -0,0 +1,296 @@
+use anyhow::{Context, Result, bail};
+use std::ops::Deref;
+use uefi::boot::SearchType;
+use uefi::fs::{FileSystem, Path};
+use uefi::proto::device_path::text::{AllowShortcuts, DevicePathFromText, DisplayOnly};
+use uefi::proto::device_path::{DevicePath, PoolDevicePath};
+use uefi::proto::media::fs::SimpleFileSystem;
+use uefi::proto::media::partition::PartitionInfo;
+use uefi::{CString16, Guid, Handle};
+use uefi_raw::Status;
+
+/// Support code for the EFI framebuffer.
+pub mod framebuffer;
+
+/// Support code for the media loader protocol.
+pub mod media_loader;
+
+/// Support code for EFI variables.
+pub mod variables;
+
+/// Implements a version comparison algorithm according to the BLS specification.
+pub mod vercmp;
+
+/// Parses the input `path` as a [DevicePath].
+/// Uses the [DevicePathFromText] protocol exclusively, and will fail if it cannot acquire the protocol.
+pub fn text_to_device_path(path: &str) -> Result<PoolDevicePath> {
+    let path = CString16::try_from(path).context("unable to convert path to CString16")?;
+    let device_path_from_text = uefi::boot::open_protocol_exclusive::<DevicePathFromText>(
+        uefi::boot::get_handle_for_protocol::<DevicePathFromText>()
+            .context("no device path from text protocol")?,
+    )
+    .context("unable to open device path from text protocol")?;
+
+    device_path_from_text
+        .convert_text_to_device_path(&path)
+        .context("unable to convert text to device path")
+}
+
+/// Checks if a [CString16] contains a char `c`.
+/// We need to call to_string() because CString16 doesn't support `contains` with a char.
+fn cstring16_contains_char(string: &CString16, c: char) -> bool {
+    string.to_string().contains(c)
+}
+
+/// Grabs the root part of the `path`.
+/// For example, given "PciRoot(0x0)/Pci(0x4,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)/HD(1,MBR,0xBE1AFDFA,0x3F,0xFBFC1)/\EFI\BOOT\BOOTX64.efi"
+/// it will give "PciRoot(0x0)/Pci(0x4,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)/HD(1,MBR,0xBE1AFDFA,0x3F,0xFBFC1)"
+pub fn device_path_root(path: &DevicePath) -> Result<String> {
+    let mut path = path
+        .node_iter()
+        .filter_map(|item| {
+            let item = item.to_string(DisplayOnly(false), AllowShortcuts(false));
+            if item
+                .as_ref()
+                .map(|item| cstring16_contains_char(item, '('))
+                .unwrap_or(false)
+            {
+                Some(item.unwrap_or_default())
+            } else {
+                None
+            }
+        })
+        .map(|item| item.to_string())
+        .collect::<Vec<_>>()
+        .join("/");
+    path.push('/');
+    Ok(path)
+}
+
+/// Grabs the part of the `path` after the root.
+/// For example, given "PciRoot(0x0)/Pci(0x4,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)/HD(1,MBR,0xBE1AFDFA,0x3F,0xFBFC1)/\EFI\BOOT\BOOTX64.efi"
+/// it will give "\EFI\BOOT\BOOTX64.efi"
+pub fn device_path_subpath(path: &DevicePath) -> Result<String> {
+    let path = path
+        .node_iter()
+        .filter_map(|item| {
+            let item = item.to_string(DisplayOnly(false), AllowShortcuts(false));
+            if item
+                .as_ref()
+                .map(|item| cstring16_contains_char(item, '('))
+                .unwrap_or(false)
+            {
+                None
+            } else {
+                Some(item.unwrap_or_default())
+            }
+        })
+        .map(|item| item.to_string())
+        .collect::<Vec<_>>()
+        .join("\\");
+    Ok(path)
+}
+
+/// Represents the components of a resolved path.
+pub struct ResolvedPath {
+    /// The root path of the resolved path. This is the device itself.
+    /// For example, "PciRoot(0x0)/Pci(0x4,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)/HD(1,MBR,0xBE1AFDFA,0x3F,0xFBFC1)/"
+    pub root_path: Box<DevicePath>,
+    /// The subpath of the resolved path. This is the path to the file.
+    /// For example, "\EFI\BOOT\BOOTX64.efi"
+    pub sub_path: Box<DevicePath>,
+    /// The full path of the resolved path. This is the safest path to use.
+    /// For example, "PciRoot(0x0)/Pci(0x4,0x0)/NVMe(0x1,00-00-00-00-00-00-00-00)/HD(1,MBR,0xBE1AFDFA,0x3F,0xFBFC1)/\EFI\BOOT\BOOTX64.efi"
+    pub full_path: Box<DevicePath>,
+    /// The handle of the filesystem containing the path.
+    /// This can be used to acquire a [SimpleFileSystem] protocol to read the file.
+    pub filesystem_handle: Handle,
+}
+
+impl ResolvedPath {
+    /// Read the file specified by this path into a buffer and return it.
+    pub fn read_file(&self) -> Result<Vec<u8>> {
+        let fs = uefi::boot::open_protocol_exclusive::<SimpleFileSystem>(self.filesystem_handle)
+            .context("unable to open filesystem protocol")?;
+        let mut fs = FileSystem::new(fs);
+        let path = self
+            .sub_path
+            .to_string(DisplayOnly(false), AllowShortcuts(false))?;
+        let content = fs.read(Path::new(&path));
+        content.context("unable to read file contents")
+    }
+}
+
+/// Resolve a path specified by `input` to its various components.
+/// Uses `default_root_path` as the base root if one is not specified in the path.
+/// Returns [ResolvedPath] which contains the resolved components.
+pub fn resolve_path(default_root_path: Option<&DevicePath>, input: &str) -> Result<ResolvedPath> {
+    let mut path = text_to_device_path(input).context("unable to convert text to path")?;
+    let path_has_device = path
+        .node_iter()
+        .next()
+        .map(|it| {
+            it.to_string(DisplayOnly(false), AllowShortcuts(false))
+                .unwrap_or_default()
+        })
+        .map(|it| it.to_string().contains('('))
+        .unwrap_or(false);
+    if !path_has_device {
+        let mut input = input.to_string();
+        if !input.starts_with('\\') {
+            input.insert(0, '\\');
+        }
+
+        let default_root_path = default_root_path.context("unable to get default root path")?;
+
+        input.insert_str(
+            0,
+            device_path_root(default_root_path)
+                .context("unable to get loaded image device root")?
+                .as_str(),
+        );
+        path = text_to_device_path(input.as_str()).context("unable to convert text to path")?;
+    }
+
+    let path = path.to_boxed();
+    let root = device_path_root(path.as_ref()).context("unable to convert root to path")?;
+    let root_path = text_to_device_path(root.as_str())
+        .context("unable to convert root to path")?
+        .to_boxed();
+    let root_path = root_path.as_ref();
+
+    // locate_device_path modifies the path, so we need to clone it.
+    let root_path_modifiable = root_path.to_owned();
+    let handle = uefi::boot::locate_device_path::<SimpleFileSystem>(&mut &*root_path_modifiable)
+        .context("unable to locate filesystem device path")?;
+    let subpath = device_path_subpath(path.deref()).context("unable to get device subpath")?;
+    Ok(ResolvedPath {
+        root_path: root_path.to_boxed(),
+        sub_path: text_to_device_path(subpath.as_str())?.to_boxed(),
+        full_path: path,
+        filesystem_handle: handle,
+    })
+}
+
+/// Read the contents of a file at the location specified with the `input` path.
+/// Internally, this uses [resolve_path] to resolve the path to its various components.
+/// [resolve_path] is passed the `default_root_path` which should specify a base root.
+///
+/// This acquires exclusive protocol access to the [SimpleFileSystem] protocol of the resolved
+/// filesystem handle, so care must be taken to call this function outside a scope with
+/// the filesystem handle protocol acquired.
+pub fn read_file_contents(default_root_path: Option<&DevicePath>, input: &str) -> Result<Vec<u8>> {
+    let resolved = resolve_path(default_root_path, input)?;
+    resolved.read_file()
+}
+
+/// Filter a string-like Option `input` such that an empty string is [None].
+pub fn empty_is_none<T: AsRef<str>>(input: Option<T>) -> Option<T> {
+    input.filter(|input| !input.as_ref().is_empty())
+}
+
+/// Combine a sequence of strings into a single string, separated by spaces, ignoring empty strings.
+pub fn combine_options<T: AsRef<str>>(options: impl Iterator<Item = T>) -> String {
+    options
+        .flat_map(|item| empty_is_none(Some(item)))
+        .map(|item| item.as_ref().to_string())
+        .collect::<Vec<_>>()
+        .join(" ")
+}
+
+/// Produce a unique hash for the input.
+/// This uses SHA-256, which is unique enough but relatively short.
+pub fn unique_hash(input: &str) -> String {
+    sha256::digest(input.as_bytes())
+}
+
+/// Represents the type of partition GUID that can be retrieved.
+#[derive(PartialEq, Eq)]
+pub enum PartitionGuidForm {
+    /// The partition GUID is the unique partition GUID.
+    Partition,
+    /// The partition GUID is the partition type GUID.
+    PartitionType,
+}
+
+/// Retrieve the partition / partition type GUID of the device root `path`.
+/// This only works on GPT partitions. If the root is not a GPT partition, None is returned.
+/// If the GUID is all zeros, this will return None.
+pub fn partition_guid(path: &DevicePath, form: PartitionGuidForm) -> Result<Option<Guid>> {
+    // Clone the path so we can pass it to the UEFI stack.
+    let path = path.to_boxed();
+    let result = uefi::boot::locate_device_path::<PartitionInfo>(&mut &*path);
+    let handle = match result {
+        Ok(handle) => Ok(Some(handle)),
+        Err(error) => {
+            // If the error is NOT_FOUND or UNSUPPORTED, we can return None.
+            // These are non-fatal errors.
+            if error.status() == Status::NOT_FOUND || error.status() == Status::UNSUPPORTED {
+                Ok(None)
+            } else {
+                Err(error)
+            }
+        }
+    }
+    .context("unable to locate device path")?;
+
+    // If we have the handle, we can try to open the partition info protocol.
+    if let Some(handle) = handle {
+        // Open the partition info protocol.
+        let partition_info = uefi::boot::open_protocol_exclusive::<PartitionInfo>(handle)
+            .context("unable to open partition info protocol")?;
+        // Find the unique partition GUID.
+        // If this is not a GPT partition, this will produce None.
+        Ok(partition_info
+            .gpt_partition_entry()
+            .map(|entry| match form {
+                // Match the form of the partition GUID.
+                PartitionGuidForm::Partition => entry.unique_partition_guid,
+                PartitionGuidForm::PartitionType => entry.partition_type_guid.0,
+            })
+            .filter(|guid| !guid.is_zero()))
+    } else {
+        Ok(None)
+    }
+}
+
+/// Find a handle that provides the specified `protocol`.
+pub fn find_handle(protocol: &Guid) -> Result<Option<Handle>> {
+    // Locate the requested protocol handle.
+    match uefi::boot::locate_handle_buffer(SearchType::ByProtocol(protocol)) {
+        // If a handle is found, the protocol is available.
+        Ok(handles) => Ok(if handles.is_empty() {
+            None
+        } else {
+            Some(handles[0])
+        }),
+        // If an error occurs, check if it is because the protocol is not available.
+        // If so, return false. Otherwise, return the error.
+        Err(error) => {
+            if error.status() == Status::NOT_FOUND {
+                Ok(None)
+            } else {
+                Err(error).context("unable to determine if the protocol is available")
+            }
+        }
+    }
+}
+
+/// Convert a byte slice into a CString16.
+pub fn utf16_bytes_to_cstring16(bytes: &[u8]) -> Result<CString16> {
+    // Validate the input bytes are the right length.
+    if !bytes.len().is_multiple_of(2) {
+        bail!("utf16 bytes must be a multiple of 2");
+    }
+
+    // Convert the bytes to UTF-16 data.
+    let data = bytes
+        // Chunk everything into two bytes.
+        .chunks_exact(2)
+        // Reinterpret the bytes as u16 little-endian.
+        .map(|chunk| u16::from_le_bytes([chunk[0], chunk[1]]))
+        // Collect the result into a vector.
+        .collect::<Vec<_>>();
+
+    CString16::try_from(data).context("unable to convert utf16 bytes to CString16")
+}

crates/sprout/src/utils/framebuffer.rs

@@ -0,0 +1,56 @@
+use anyhow::{Context, Result};
+use uefi::proto::console::gop::{BltOp, BltPixel, BltRegion, GraphicsOutput};
+
+/// Represents the EFI framebuffer.
+pub struct Framebuffer {
+    /// The width of the framebuffer in pixels.
+    width: usize,
+    /// The height of the framebuffer in pixels.
+    height: usize,
+    /// The pixels of the framebuffer.
+    pixels: Vec<BltPixel>,
+}
+
+impl Framebuffer {
+    /// Creates a new framebuffer of the specified `width` and `height`.
+    pub fn new(width: usize, height: usize) -> Result<Self> {
+        // Verify that the size is valid during multiplication.
+        let size = width
+            .checked_mul(height)
+            .context("framebuffer size overflow")?;
+
+        // Initialize the pixel buffer with black pixels, with the verified size.
+        let pixels = vec![BltPixel::new(0, 0, 0); size];
+
+        Ok(Framebuffer {
+            width,
+            height,
+            pixels,
+        })
+    }
+
+    /// Mutably acquires a pixel of the framebuffer at the specified `x` and `y` coordinate.
+    pub fn pixel(&mut self, x: usize, y: usize) -> Option<&mut BltPixel> {
+        // Verify that the coordinates are within the bounds of the framebuffer.
+        if x >= self.width || y >= self.height {
+            return None;
+        }
+
+        // Calculate the index of the pixel safely, returning None if it overflows.
+        let index = y.checked_mul(self.width)?.checked_add(x)?;
+        // Return the pixel at the index. If the index is out of bounds, this will return None.
+        self.pixels.get_mut(index)
+    }
+
+    /// Blit the framebuffer to the specified `gop` [GraphicsOutput].
+    pub fn blit(&self, gop: &mut GraphicsOutput) -> Result<()> {
+        gop.blt(BltOp::BufferToVideo {
+            buffer: &self.pixels,
+            src: BltRegion::Full,
+            dest: (0, 0),
+            dims: (self.width, self.height),
+        })
+        .context("unable to blit framebuffer")?;
+        Ok(())
+    }
+}

crates/sprout/src/utils/media_loader.rs

@@ -0,0 +1,276 @@
+use anyhow::{Context, Result, bail};
+use std::ffi::c_void;
+use uefi::proto::device_path::DevicePath;
+use uefi::proto::device_path::build::DevicePathBuilder;
+use uefi::proto::device_path::build::media::Vendor;
+use uefi::proto::media::load_file::LoadFile2;
+use uefi::{Guid, Handle};
+use uefi_raw::protocol::device_path::DevicePathProtocol;
+use uefi_raw::protocol::media::LoadFile2Protocol;
+use uefi_raw::{Boolean, Status};
+
+pub mod constants;
+
+/// The media loader protocol.
+#[derive(Debug)]
+#[repr(C)]
+struct MediaLoaderProtocol {
+    /// This is the standard EFI LoadFile2 protocol.
+    pub load_file: unsafe extern "efiapi" fn(
+        this: *mut MediaLoaderProtocol,
+        file_path: *const DevicePathProtocol,
+        boot_policy: Boolean,
+        buffer_size: *mut usize,
+        buffer: *mut c_void,
+    ) -> Status,
+    /// A pointer to a Box<[u8]> containing the data to load.
+    pub address: *mut c_void,
+    /// The length of the data to load.
+    pub length: usize,
+}
+
+/// Represents a media loader which has been registered in the UEFI stack.
+/// You MUST call [MediaLoaderHandle::unregister] when ready to unregister.
+/// [Drop] is not implemented for this type.
+pub struct MediaLoaderHandle {
+    /// The handle of the media loader in the UEFI stack.
+    handle: Handle,
+    /// The protocol interface pointer.
+    protocol: *mut MediaLoaderProtocol,
+    /// The device path pointer.
+    path: *mut DevicePath,
+}
+
+impl MediaLoaderHandle {
+    /// The behavior of this function is derived from how Linux calls it.
+    ///
+    /// Linux calls this function by first passing a NULL `buffer`.
+    /// We must set the size of the buffer it should allocate in `buffer_size`.
+    /// The next call will pass a buffer of the right size, and we should copy
+    /// data into that buffer, checking whether it is safe to copy based on
+    /// the buffer size.
+    ///
+    /// SAFETY: `this.address` and `this.length` are set by leaking a Box<[u8]>, so we can
+    /// be sure their pointers are valid when this is called. The caller must call this function
+    /// while inside UEFI boot services to ensure pointers are valid. Copying to `buffer` is
+    /// assumed valid because the caller must ensure `buffer` is valid by function contract.
+    unsafe extern "efiapi" fn load_file(
+        this: *mut MediaLoaderProtocol,
+        file_path: *const DevicePathProtocol,
+        boot_policy: Boolean,
+        buffer_size: *mut usize,
+        buffer: *mut c_void,
+    ) -> Status {
+        // Check if the pointers are non-null first.
+        if this.is_null() || buffer_size.is_null() || file_path.is_null() {
+            return Status::INVALID_PARAMETER;
+        }
+
+        // Boot policy must not be true, and if it is, that is special behavior that is irrelevant
+        // for the media loader concept.
+        if boot_policy == Boolean::TRUE {
+            return Status::UNSUPPORTED;
+        }
+
+        // SAFETY: Validated as safe because this is checked to be non-null. It is the caller's
+        // responsibility to ensure that the right pointer is passed for [this].
+        unsafe {
+            // Check if the length and address are valid.
+            if (*this).length == 0 || (*this).address.is_null() {
+                return Status::NOT_FOUND;
+            }
+
+            // Check if the buffer is large enough.
+            // If it is not, we need to set the buffer size to the length of the data.
+            // This is the way that Linux calls this function, to check the size to allocate
+            // for the buffer that holds the data.
+            if buffer.is_null() || *buffer_size < (*this).length {
+                *buffer_size = (*this).length;
+                return Status::BUFFER_TOO_SMALL;
+            }
+
+            // Copy the data into the buffer.
+            buffer.copy_from((*this).address, (*this).length);
+            // Set the buffer size to the length of the data.
+            *buffer_size = (*this).length;
+        }
+
+        // We've successfully loaded the data.
+        Status::SUCCESS
+    }
+
+    /// Creates a new device path for the media loader based on a vendor `guid`.
+    fn device_path(guid: Guid) -> Result<Box<DevicePath>> {
+        // The buffer for the device path.
+        let mut path = Vec::new();
+        // Build a device path for the media loader with a vendor-specific guid.
+        let path = DevicePathBuilder::with_vec(&mut path)
+            .push(&Vendor {
+                vendor_guid: guid,
+                vendor_defined_data: &[],
+            })
+            .context("unable to produce device path")?
+            .finalize()
+            .context("unable to produce device path")?;
+        // Convert the device path to a boxed device path.
+        // This is safer than dealing with a pooled device path.
+        Ok(path.to_boxed())
+    }
+
+    /// Checks if the media loader is already registered with the UEFI stack.
+    fn already_registered(guid: Guid) -> Result<bool> {
+        // Acquire the device path for the media loader.
+        let path = Self::device_path(guid)?;
+
+        let mut existing_path = path.as_ref();
+
+        // Locate the LoadFile2 protocol for the media loader based on the device path.
+        let result = uefi::boot::locate_device_path::<LoadFile2>(&mut existing_path);
+
+        // If the result is okay, the media loader is already registered.
+        if result.is_ok() {
+            return Ok(true);
+        } else if let Err(error) = result
+            && error.status() != Status::NOT_FOUND
+        // If the error is not found, that means it's not registered.
+        {
+            bail!("unable to locate media loader device path: {}", error);
+        }
+        // The media loader is not registered.
+        Ok(false)
+    }
+
+    /// Registers the provided `data` with the UEFI stack as media loader.
+    /// This uses a special device path that other EFI programs will look at
+    /// to load the data from.
+    pub fn register(guid: Guid, data: Box<[u8]>) -> Result<MediaLoaderHandle> {
+        // Acquire the vendor device path for the media loader.
+        let path = Self::device_path(guid)?;
+
+        // Check if the media loader is already registered.
+        // If it is, we can't register it again safely.
+        if Self::already_registered(guid)? {
+            bail!("media loader already registered");
+        }
+
+        // Leak the device path to pass it to the UEFI stack.
+        let path = Box::leak(path);
+
+        // Install a protocol interface for the device path.
+        // This ensures it can be located by other EFI programs.
+        let primary_handle = unsafe {
+            uefi::boot::install_protocol_interface(
+                None,
+                &DevicePathProtocol::GUID,
+                path.as_ffi_ptr() as *mut c_void,
+            )
+        }
+        .context("unable to install media loader device path handle")?;
+
+        // Leak the data we need to pass to the UEFI stack.
+        let data = Box::leak(data);
+
+        // Allocate a new box for the protocol interface.
+        let protocol = Box::new(MediaLoaderProtocol {
+            load_file: Self::load_file,
+            address: data.as_ptr() as *mut _,
+            length: data.len(),
+        });
+
+        // Leak the protocol interface to pass it to the UEFI stack.
+        let protocol = Box::leak(protocol);
+
+        // Install a protocol interface for the load file protocol for the media loader protocol.
+        let secondary_handle = unsafe {
+            uefi::boot::install_protocol_interface(
+                Some(primary_handle),
+                &LoadFile2Protocol::GUID,
+                // The UEFI API expects an opaque pointer here.
+                protocol as *mut MediaLoaderProtocol as *mut c_void,
+            )
+        };
+
+        // If installing the second protocol interface failed, we need to clean up after ourselves.
+        if secondary_handle.is_err() {
+            // Uninstall the protocol interface for the device path protocol.
+            // SAFETY: If we have reached this point, we know that the protocol is registered.
+            // If this fails, we have no choice but to leak memory. The error will be shown
+            // to the user, so at least they can see it. In most cases, catching this error
+            // will exit, so leaking is safe.
+            unsafe {
+                uefi::boot::uninstall_protocol_interface(
+                    primary_handle,
+                    &DevicePathProtocol::GUID,
+                    path.as_ffi_ptr() as *mut c_void,
+                )
+                .context(
+                    "unable to uninstall media loader device path handle, this will leak memory",
+                )?;
+            }
+
+            // SAFETY: We know that the protocol is leaked, so we can safely take a reference to it.
+            let protocol = unsafe { Box::from_raw(protocol) };
+            // SAFETY: We know that the data is leaked, so we can safely take a reference to it.
+            let data = unsafe { Box::from_raw(data) };
+            // SAFETY: We know that the path is leaked, so we can safely take a reference to it.
+            let path = unsafe { Box::from_raw(path) };
+
+            // Drop all the allocations explicitly to clarify the lifetime.
+            drop(protocol);
+            drop(data);
+            drop(path);
+        }
+
+        // If installing the second protocol interface failed, this will return the error.
+        // We should have already cleaned up after ourselves, so this is safe.
+        secondary_handle.context("unable to install media loader load file handle")?;
+
+        // Return a handle to the media loader.
+        Ok(Self {
+            handle: primary_handle,
+            protocol,
+            path,
+        })
+    }
+
+    /// Unregisters a media loader from the UEFI stack.
+    /// This will free the memory allocated by the passed data.
+    pub fn unregister(self) -> Result<()> {
+        // SAFETY: We know that the media loader is registered if the handle is valid,
+        // so we can safely uninstall it.
+        // We should have allocated the pointers involved, so we can safely free them.
+        unsafe {
+            // Uninstall the protocol interface for the device path protocol.
+            uefi::boot::uninstall_protocol_interface(
+                self.handle,
+                &DevicePathProtocol::GUID,
+                self.path as *mut c_void,
+            )
+            .context("unable to uninstall media loader device path handle")?;
+
+            // Uninstall the protocol interface for the load file protocol.
+            uefi::boot::uninstall_protocol_interface(
+                self.handle,
+                &LoadFile2Protocol::GUID,
+                self.protocol as *mut _ as *mut c_void,
+            )
+            .context("unable to uninstall media loader load file handle")?;
+
+            // Retrieve a box for the device path and protocols.
+            let path = Box::from_raw(self.path);
+            let protocol = Box::from_raw(self.protocol);
+
+            // Retrieve a box for the data we passed in.
+            let slice =
+                std::ptr::slice_from_raw_parts_mut(protocol.address as *mut u8, protocol.length);
+            let data = Box::from_raw(slice);
+
+            // Drop all the allocations explicitly, as we don't want to leak them.
+            drop(path);
+            drop(protocol);
+            drop(data);
+        }
+
+        Ok(())
+    }
+}

crates/sprout/src/utils/media_loader/constants.rs

@@ -0,0 +1,20 @@
+/// These GUIDs are specific to Linux itself.
+pub mod linux {
+    use uefi::{Guid, guid};
+
+    /// The device path GUID for the Linux EFI initrd.
+    pub const LINUX_EFI_INITRD_MEDIA_GUID: Guid = guid!("5568e427-68fc-4f3d-ac74-ca555231cc68");
+}
+
+/// These GUIDs were created by Edera to support Xen loading data
+/// from Sprout and other EFI bootloaders.
+pub mod xen {
+    use uefi::{Guid, guid};
+
+    /// The device path GUID for the Xen EFI config.
+    pub const XEN_EFI_CONFIG_MEDIA_GUID: Guid = guid!("bf61f458-a28e-46cd-93d7-07dac5e8cd66");
+    /// The device path GUID for the Xen EFI kernel.
+    pub const XEN_EFI_KERNEL_MEDIA_GUID: Guid = guid!("4010c8bf-6ced-40f5-a53f-e820aee8f34b");
+    /// The device path GUID for the Xen EFI ramdisk.
+    pub const XEN_EFI_RAMDISK_MEDIA_GUID: Guid = guid!("5db1fd01-c3cb-4812-b2ba-8791e52d4a89");
+}

crates/sprout/src/utils/variables.rs

@@ -0,0 +1,152 @@
+use crate::utils;
+use anyhow::{Context, Result};
+use log::warn;
+use uefi::{CString16, guid};
+use uefi_raw::Status;
+use uefi_raw::table::runtime::{VariableAttributes, VariableVendor};
+
+/// The classification of a variable.
+/// This is an abstraction over various variable attributes.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum VariableClass {
+    /// The variable is available in Boot Services and Runtime Services and is not persistent.
+    BootAndRuntimeTemporary,
+}
+
+impl VariableClass {
+    /// The [VariableAttributes] for this classification.
+    fn attributes(&self) -> VariableAttributes {
+        match self {
+            VariableClass::BootAndRuntimeTemporary => {
+                VariableAttributes::BOOTSERVICE_ACCESS | VariableAttributes::RUNTIME_ACCESS
+            }
+        }
+    }
+}
+
+/// Provides access to a particular set of vendor variables.
+pub struct VariableController {
+    /// The GUID of the vendor.
+    vendor: VariableVendor,
+}
+
+impl VariableController {
+    /// Global variables.
+    pub const GLOBAL: VariableController = VariableController::new(VariableVendor(guid!(
+        "8be4df61-93ca-11d2-aa0d-00e098032b8c"
+    )));
+
+    /// Create a new [VariableController] for the `vendor`.
+    pub const fn new(vendor: VariableVendor) -> Self {
+        Self { vendor }
+    }
+
+    /// Convert `key` to a variable name as a CString16.
+    fn name(key: &str) -> Result<CString16> {
+        CString16::try_from(key).context("unable to convert variable name to CString16")
+    }
+
+    /// Retrieve the cstr16 value specified by the `key`.
+    /// Returns None if the value isn't set.
+    /// If the value is not decodable, we will return None and log a warning.
+    pub fn get_cstr16(&self, key: &str) -> Result<Option<String>> {
+        let name = Self::name(key)?;
+
+        // Retrieve the variable data, handling variable not existing as None.
+        match uefi::runtime::get_variable_boxed(&name, &self.vendor) {
+            Ok((data, _)) => {
+                // Try to decode UTF-16 bytes to a CString16.
+                match utils::utf16_bytes_to_cstring16(&data) {
+                    Ok(value) => {
+                        // We have a value, so return the UTF-8 value.
+                        Ok(Some(value.to_string()))
+                    }
+
+                    Err(error) => {
+                        // We encountered an error, so warn and return None.
+                        warn!("efi variable '{}' is not valid UTF-16: {}", key, error);
+                        Ok(None)
+                    }
+                }
+            }
+
+            Err(error) => {
+                // If the variable does not exist, we will return None.
+                if error.status() == Status::NOT_FOUND {
+                    Ok(None)
+                } else {
+                    Err(error).with_context(|| format!("unable to get efi variable {}", key))
+                }
+            }
+        }
+    }
+
+    /// Retrieve a boolean value specified by the `key`.
+    pub fn get_bool(&self, key: &str) -> Result<bool> {
+        let name = Self::name(key)?;
+
+        // Retrieve the variable data, handling variable not existing as false.
+        match uefi::runtime::get_variable_boxed(&name, &self.vendor) {
+            Ok((data, _)) => {
+                // If the variable is zero-length, we treat it as false.
+                if data.is_empty() {
+                    Ok(false)
+                } else {
+                    // We treat the variable as true if the first byte is non-zero.
+                    Ok(data[0] > 0)
+                }
+            }
+
+            Err(error) => {
+                // If the variable does not exist, we treat it as false.
+                if error.status() == Status::NOT_FOUND {
+                    Ok(false)
+                } else {
+                    Err(error).with_context(|| format!("unable to get efi variable {}", key))
+                }
+            }
+        }
+    }
+
+    /// Set a variable specified by `key` to `value`.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set(&self, key: &str, value: &[u8], class: VariableClass) -> Result<()> {
+        let name = Self::name(key)?;
+        uefi::runtime::set_variable(&name, &self.vendor, class.attributes(), value)
+            .with_context(|| format!("unable to set efi variable {}", key))?;
+        Ok(())
+    }
+
+    /// Set a variable specified by `key` to `value`, converting the value to
+    /// a [CString16]. The variable `class` controls the attributes for the variable.
+    pub fn set_cstr16(&self, key: &str, value: &str, class: VariableClass) -> Result<()> {
+        // Encode the value as a CString16 little endian.
+        let mut encoded = value
+            .encode_utf16()
+            .flat_map(|c| c.to_le_bytes())
+            .collect::<Vec<u8>>();
+        // Add a null terminator to the end of the value.
+        encoded.extend_from_slice(&[0, 0]);
+        self.set(key, &encoded, class)
+    }
+
+    /// Set a boolean variable specified by `key` to `value`, converting the value.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set_bool(&self, key: &str, value: bool, class: VariableClass) -> Result<()> {
+        self.set(key, &[value as u8], class)
+    }
+
+    /// Set the u64 little-endian variable specified by `key` to `value`.
+    /// The variable `class` controls the attributes for the variable.
+    pub fn set_u64le(&self, key: &str, value: u64, class: VariableClass) -> Result<()> {
+        self.set(key, &value.to_le_bytes(), class)
+    }
+
+    pub fn remove(&self, key: &str) -> Result<()> {
+        let name = Self::name(key)?;
+
+        // Delete the variable from UEFI.
+        uefi::runtime::delete_variable(&name, &self.vendor)
+            .with_context(|| format!("unable to remove efi variable {}", key))
+    }
+}

crates/sprout/src/utils/vercmp.rs

@@ -0,0 +1,184 @@
+use std::cmp::Ordering;
+use std::iter::Peekable;
+
+/// Handles single character advancement and comparison.
+macro_rules! handle_single_char {
+    ($ca: expr, $cb:expr, $a_chars:expr, $b_chars:expr, $c:expr) => {
+        match ($ca == $c, $cb == $c) {
+            (true, false) => return Ordering::Less,
+            (false, true) => return Ordering::Greater,
+            (true, true) => {
+                $a_chars.next();
+                $b_chars.next();
+                continue;
+            }
+            _ => {}
+        }
+    };
+}
+
+/// Compares two strings using the BLS version comparison specification.
+/// Handles optional values as well by comparing only if both are specified.
+pub fn compare_versions_optional(a: Option<&str>, b: Option<&str>) -> Ordering {
+    match (a, b) {
+        // If both have values, compare them.
+        (Some(a), Some(b)) => compare_versions(a, b),
+        // If the second value is None, return that it is less than the first.
+        (Some(_a), None) => Ordering::Less,
+        // If the first value is None, return that it is greater than the second.
+        (None, Some(_b)) => Ordering::Greater,
+        // If both values are None, return that they are equal.
+        (None, None) => Ordering::Equal,
+    }
+}
+
+/// Compares two strings using the BLS version comparison specification.
+/// See: https://uapi-group.org/specifications/specs/version_format_specification/
+pub fn compare_versions(a: &str, b: &str) -> Ordering {
+    // Acquire a peekable iterator for each string.
+    let mut a_chars = a.chars().peekable();
+    let mut b_chars = b.chars().peekable();
+
+    // Loop until we have reached the end of one of the strings.
+    loop {
+        // Skip invalid characters in both strings.
+        skip_invalid(&mut a_chars);
+        skip_invalid(&mut b_chars);
+
+        // Check if either string has ended.
+        match (a_chars.peek(), b_chars.peek()) {
+            // No more characters in either string.
+            (None, None) => return Ordering::Equal,
+            // One string has ended, the other hasn't.
+            (None, Some(_)) => return Ordering::Less,
+            (Some(_), None) => return Ordering::Greater,
+            // Both strings have characters left.
+            (Some(&ca), Some(&cb)) => {
+                // Handle the ~ character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '~');
+
+                // Handle '-' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '-');
+
+                // Handle the '^' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '^');
+
+                // Handle the '.' character.
+                handle_single_char!(ca, cb, a_chars, b_chars, '.');
+
+                // Handle digits with numerical comparison.
+                // We key off of the A character being a digit intentionally as we presume
+                // this indicates it will be the same at this position.
+                if ca.is_ascii_digit() || cb.is_ascii_digit() {
+                    let result = compare_numeric(&mut a_chars, &mut b_chars);
+                    if result != Ordering::Equal {
+                        return result;
+                    }
+                    continue;
+                }
+
+                // Handle letters with alphabetical comparison.
+                // We key off of the A character being alphabetical intentionally as we presume
+                // this indicates it will be the same at this position.
+                if ca.is_ascii_alphabetic() || cb.is_ascii_alphabetic() {
+                    let result = compare_alphabetic(&mut a_chars, &mut b_chars);
+                    if result != Ordering::Equal {
+                        return result;
+                    }
+                    continue;
+                }
+            }
+        }
+    }
+}
+
+/// Skips characters that are not in the valid character set.
+fn skip_invalid<I: Iterator<Item = char>>(iter: &mut Peekable<I>) {
+    while let Some(&c) = iter.peek() {
+        if is_valid_char(c) {
+            break;
+        }
+        iter.next();
+    }
+}
+
+/// Checks if a character is in the valid character set for comparison.
+fn is_valid_char(c: char) -> bool {
+    matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '.' | '~' | '^')
+}
+
+/// Compares numerical prefixes by extracting numbers.
+fn compare_numeric<I: Iterator<Item = char>>(
+    iter_a: &mut Peekable<I>,
+    iter_b: &mut Peekable<I>,
+) -> Ordering {
+    let num_a = extract_number(iter_a);
+    let num_b = extract_number(iter_b);
+
+    num_a.cmp(&num_b)
+}
+
+/// Extracts a number from the iterator, skipping leading zeros.
+fn extract_number<I: Iterator<Item = char>>(iter: &mut Peekable<I>) -> u64 {
+    // Skip leading zeros
+    while let Some(&'0') = iter.peek() {
+        iter.next();
+    }
+
+    let mut num = 0u64;
+    while let Some(&c) = iter.peek() {
+        if c.is_ascii_digit() {
+            iter.next();
+            num = num.saturating_mul(10).saturating_add(c as u64 - '0' as u64);
+        } else {
+            break;
+        }
+    }
+
+    num
+}
+
+/// Compares alphabetical prefixes
+/// Capital letters compare lower than lowercase letters (B < a)
+fn compare_alphabetic<I: Iterator<Item = char>>(
+    iter_a: &mut Peekable<I>,
+    iter_b: &mut Peekable<I>,
+) -> Ordering {
+    loop {
+        return match (iter_a.peek(), iter_b.peek()) {
+            (Some(&ca), Some(&cb)) if ca.is_ascii_alphabetic() && cb.is_ascii_alphabetic() => {
+                if ca == cb {
+                    // Same character, we should continue.
+                    iter_a.next();
+                    iter_b.next();
+                    continue;
+                }
+
+                // Different characters found.
+                // All capital letters compare lower than lowercase letters.
+                match (ca.is_ascii_uppercase(), cb.is_ascii_uppercase()) {
+                    (true, false) => Ordering::Less,    // uppercase < lowercase
+                    (false, true) => Ordering::Greater, // lowercase > uppercase
+                    (true, true) => ca.cmp(&cb),        // both are uppercase
+                    (false, false) => ca.cmp(&cb),      // both are lowercase
+                }
+            }
+
+            (Some(&ca), Some(_)) if ca.is_ascii_alphabetic() => {
+                // a has letters, b doesn't
+                Ordering::Greater
+            }
+
+            (Some(_), Some(&cb)) if cb.is_ascii_alphabetic() => {
+                // b has letters, a doesn't
+                Ordering::Less
+            }
+
+            (Some(&ca), None) if ca.is_ascii_alphabetic() => Ordering::Greater,
+
+            (None, Some(&cb)) if cb.is_ascii_alphabetic() => Ordering::Less,
+
+            _ => Ordering::Equal,
+        };
+    }
+}