feat(bls): basic support for boot loader interface

src/entries.rs

@@ -28,6 +28,7 @@ pub struct BootableEntry {
     context: Rc<SproutContext>,
     declaration: EntryDeclaration,
     default: bool,
+    pin_name: bool,
 }
 
 impl BootableEntry {
@@ -44,6 +45,7 @@ impl BootableEntry {
             context,
             declaration,
             default: false,
+            pin_name: false,
         }
     }
 
@@ -72,6 +74,11 @@ impl BootableEntry {
         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;
@@ -87,6 +94,11 @@ impl BootableEntry {
         self.default = true;
     }
 
+    /// 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);

src/generators/bls.rs

@@ -83,13 +83,16 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
         }
 
         // Get the file name of the filesystem item.
-        let name = entry.file_name().to_string();
+        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);
+
         // 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());
@@ -125,13 +128,21 @@ pub fn generate(context: Rc<SproutContext>, bls: &BlsConfiguration) -> Result<Ve
         context.set("options", options);
         context.set("initrd", initrd);
 
-        // Add the entry to the list with a frozen context.
-        entries.push(BootableEntry::new(
+        // Produce a new bootable entry.
+        let mut entry = 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.
+        entry.mark_pin_name();
+
+        // Add the entry to the list with a frozen context.
+        entries.push(entry);
     }
 
     Ok(entries)

src/integrations/bootloader_interface.rs

@@ -1,10 +1,14 @@
-use anyhow::Result;
-use uefi::Guid;
+use anyhow::{Context, Result};
+use uefi::{CString16, Guid, guid};
+use uefi_raw::table::runtime::{VariableAttributes, VariableVendor};
 
 /// Bootloader Interface support.
 pub struct BootloaderInterface;
 
 impl BootloaderInterface {
+    /// Bootloader Interface GUID from https://systemd.io/BOOT_LOADER_INTERFACE
+    const VENDOR: VariableVendor = VariableVendor(guid!("4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"));
+
     /// Tell the system that Sprout was initialized at the current time.
     pub fn mark_init() -> Result<()> {
         // TODO(azenla): Implement support for LoaderTimeInitUSec here.
@@ -18,26 +22,54 @@ impl BootloaderInterface {
     }
 
     /// Tell the system what the partition GUID of the ESP Sprout was booted from is.
-    pub fn set_partition_guid(_guid: &Guid) -> Result<()> {
-        // TODO(azenla): Implement support for LoaderDevicePartUUID here.
-        Ok(())
+    pub fn set_partition_guid(guid: &Guid) -> Result<()> {
+        Self::set_cstr16("LoaderDevicePartUUID", &guid.to_string())
     }
 
     /// Tell the system what boot entries are available.
-    pub fn set_entries<N: AsRef<str>>(_entries: impl Iterator<Item = N>) -> Result<()> {
-        // TODO(azenla): Implement support for LoaderEntries here.
-        Ok(())
+    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 a CString16.
+            let entry = CString16::try_from(entry.as_ref())
+                .context("unable to convert entry to CString16")?;
+            // Write the bytes (including the null terminator) into the data buffer.
+            data.extend_from_slice(entry.as_bytes());
+        }
+        Self::set("LoaderEntries", &data)
     }
 
     /// Tell the system what the default boot entry is.
-    pub fn set_default_entry(_entry: String) -> Result<()> {
-        // TODO(azenla): Implement support for LoaderEntryDefault here.
-        Ok(())
+    pub fn set_default_entry(entry: String) -> Result<()> {
+        Self::set_cstr16("LoaderEntryDefault", &entry)
     }
 
     /// Tell the system what the selected boot entry is.
-    pub fn set_selected_entry(_entry: String) -> Result<()> {
-        // TODO(azenla): Implement support for LoaderEntrySelected here.
+    pub fn set_selected_entry(entry: String) -> Result<()> {
+        Self::set_cstr16("LoaderEntrySelected", &entry)
+    }
+
+    /// The [VariableAttributes] for bootloader interface variables.
+    fn attributes() -> VariableAttributes {
+        VariableAttributes::BOOTSERVICE_ACCESS | VariableAttributes::RUNTIME_ACCESS
+    }
+
+    /// Set a bootloader interface variable specified by `key` to `value`.
+    fn set(key: &str, value: &[u8]) -> Result<()> {
+        let name =
+            CString16::try_from(key).context("unable to convert variable name to CString16")?;
+        uefi::runtime::set_variable(&name, &Self::VENDOR, Self::attributes(), value)
+            .with_context(|| format!("unable to set efi variable {}", key))?;
         Ok(())
     }
+
+    /// Set a bootloader interface variable specified by `key` to `value`, converting the value to
+    /// a [CString16].
+    fn set_cstr16(key: &str, value: &str) -> Result<()> {
+        let value =
+            CString16::try_from(value).context("unable to convert variable value to CString16")?;
+        Self::set(key, value.as_bytes())
+    }
 }

src/main.rs

@@ -182,13 +182,17 @@ fn run() -> Result<()> {
     for (name, generator) in config.generators {
         let context = context.fork().freeze();
 
-        // We will prefix all entries with [name]-.
+        // 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)? {
-            entry.prepend_name_prefix(&prefix);
+            // If the entry name is not pinned, prepend the name prefix.
+            if !entry.is_pin_name() {
+                entry.prepend_name_prefix(&prefix);
+            }
+
             entries.push(entry);
         }
     }