feat(sprout): implement custom logger which shortens output

crates/sprout/Cargo.toml

@@ -20,7 +20,7 @@ log.workspace = true
 
 [dependencies.uefi]
 workspace = true
-features = ["alloc", "global_allocator", "logger", "panic_handler"]
+features = ["alloc", "global_allocator", "panic_handler"]
 
 [dependencies.uefi-raw]
 workspace = true

crates/sprout/src/logger.rs

@@ -0,0 +1,94 @@
+//! Based on: https://github.com/rust-osdev/uefi-rs/blob/main/uefi/src/helpers/logger.rs
+
+use alloc::format;
+use core::fmt::Write;
+use core::ptr;
+use core::sync::atomic::{AtomicPtr, Ordering};
+use log::{Log, Record};
+use uefi::proto::console::text::Output;
+
+/// The global logger object.
+static LOGGER: Logger = Logger::new();
+
+/// Logging mechanism for Sprout.
+/// Must be initialized to be used, as we use atomic pointers to store the output to write to.
+pub struct Logger {
+    writer: AtomicPtr<Output>,
+}
+
+impl Default for Logger {
+    /// Creates a default logger, which is uninitialized with an output.
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Logger {
+    /// Create a new logger with an output not specified.
+    /// This will cause the logger to not print anything until it is configured.
+    pub const fn new() -> Self {
+        Self {
+            writer: AtomicPtr::new(ptr::null_mut()),
+        }
+    }
+
+    /// Retrieves the pointer to the output.
+    /// SAFETY: This pointer might be null, it should be checked before use.
+    #[must_use]
+    fn output(&self) -> *mut Output {
+        self.writer.load(Ordering::Acquire)
+    }
+
+    /// Sets the output to write to.
+    ///
+    /// # Safety
+    /// This function is unsafe because the output is technically leaked and unmanaged.
+    pub unsafe fn set_output(&self, output: *mut Output) {
+        self.writer.store(output, Ordering::Release);
+    }
+}
+
+impl Log for Logger {
+    /// Enable the logger always.
+    fn enabled(&self, _metadata: &log::Metadata<'_>) -> bool {
+        true
+    }
+
+    /// Log the specified `record` to the output if one is set.
+    fn log(&self, record: &Record) {
+        // Acquire the output. If one is not set, we do nothing.
+        let Some(output) = (unsafe { self.output().as_mut() }) else {
+            return;
+        };
+
+        // Format the log message.
+        let message = format!("{}", record.args());
+
+        // Iterate over every line, formatting the message and writing it to the output.
+        for line in message.lines() {
+            // The format writes the log level in front of every line of text.
+            let _ = writeln!(output, "[{:>5}] {}", record.level(), line);
+        }
+    }
+
+    /// This log is not buffered, so flushing isn't required.
+    fn flush(&self) {}
+}
+
+/// Initialize the logging environment, calling panic if something goes wrong.
+pub fn init() {
+    // Retrieve the stdout handle and set it as the output for the global logger.
+    uefi::system::with_stdout(|stdout| unsafe {
+        // SAFETY: We are using the stdout handle to create a pointer to the output.
+        // The handle is global and is guaranteed to be valid for the lifetime of the program.
+        LOGGER.set_output(stdout);
+    });
+
+    // Set the logger to the global logger.
+    if let Err(error) = log::set_logger(&LOGGER) {
+        panic!("unable to set logger: {}", error);
+    }
+
+    // Set the max level to the level specified by the log features.
+    log::set_max_level(log::STATIC_MAX_LEVEL);
+}

crates/sprout/src/main.rs

@@ -51,18 +51,24 @@ 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;
+/// integrations: Code that interacts with other systems.
+pub mod integrations;
+
+/// logger: Code for the logging mechanism of Sprout.
+pub mod logger;
 
 /// menu: Display a boot menu to select an entry to boot.
 pub mod menu;
 
-/// integrations: Code that interacts with other systems.
-pub mod integrations;
+/// options: Parse the options of the Sprout executable.
+pub mod options;
 
 /// phases: Hooks into specific parts of the boot process.
 pub mod phases;
 
+/// platform: Integration or support code for specific hardware platforms.
+pub mod platform;
+
 /// sbat: Secure Boot Attestation section.
 pub mod sbat;
 
@@ -72,9 +78,6 @@ 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;
 
@@ -385,6 +388,9 @@ fn run() -> Result<()> {
 fn efi_main() -> Status {
     // Initialize the basic UEFI environment.
     // If initialization fails, we will return ABORTED.
+    // NOTE: This function will also initialize the logger.
+    // The logger will panic if it is unable to initialize.
+    // It is guaranteed that if this returns, the logger is initialized.
     if let Err(error) = setup::init() {
         error!("unable to initialize environment: {}", error);
         return Status::ABORTED;
@@ -394,7 +400,7 @@ fn efi_main() -> Status {
     let result = run();
     if let Err(ref error) = result {
         // Print an error trace.
-        error!("sprout encountered an error");
+        error!("sprout encountered an error:");
         for (index, stack) in error.chain().enumerate() {
             error!("[{}]: {}", index, stack);
         }

crates/sprout/src/setup.rs

@@ -1,8 +1,14 @@
+use crate::logger;
 use anyhow::{Context, Result};
 
 /// Initializes the UEFI environment.
 pub fn init() -> Result<()> {
-    // Initialize the uefi internals.
-    uefi::helpers::init().context("unable to initialize uefi")?;
+    // Initialize the logger for Sprout.
+    // NOTE: This cannot use a result type as errors need to be printed
+    // using the logger, which is not initialized until this returns.
+    logger::init();
+
+    // Initialize further UEFI internals.
+    uefi::helpers::init().context("unable to initialize uefi environment")?;
     Ok(())
 }