stub(*): support dynamic initrds

With this feature, it is now possible to load dynamic initrds (possibly read from filesystem or generated on the fly)
and extend existing initrds.

This feature will be useful to implement addons in the future.

rust/uefi/stub/src/fat.rs

@@ -40,7 +40,11 @@ impl EmbeddedConfiguration {
     }
 }
 
-pub fn boot_linux(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
+pub fn boot_linux(
+    handle: Handle,
+    mut system_table: SystemTable<Boot>,
+    dynamic_initrds: Vec<Vec<u8>>,
+) -> Status {
     uefi_services::init(&mut system_table).unwrap();
 
     // SAFETY: We get a slice that represents our currently running

rust/uefi/stub/src/main.rs

@@ -15,6 +15,7 @@ mod thin;
 #[cfg(all(feature = "fat", feature = "thin"))]
 compile_error!("A thin and fat stub cannot be produced at the same time, disable either `thin` or `fat` feature");
 
+use alloc::vec::Vec;
 use linux_bootloader::efivars::{export_efi_variables, get_loader_features, EfiLoaderFeatures};
 use linux_bootloader::measure::measure_image;
 use linux_bootloader::tpm::tpm_available;
@@ -69,15 +70,18 @@ fn main(handle: Handle, mut system_table: SystemTable<Boot>) -> Status {
     export_efi_variables(STUB_NAME, &system_table).expect("Failed to export stub EFI variables");
 
     let status;
+    // A list of dynamically assembled initrds, e.g. credential initrds or system extension
+    // initrds.
+    let dynamic_initrds: Vec<Vec<u8>> = Vec::new();
 
     #[cfg(feature = "fat")]
     {
-        status = fat::boot_linux(handle, system_table)
+        status = fat::boot_linux(handle, system_table, dynamic_initrds)
     }
 
     #[cfg(feature = "thin")]
     {
-        status = thin::boot_linux(handle, system_table).status()
+        status = thin::boot_linux(handle, system_table, dynamic_initrds).status()
     }
 
     status

rust/uefi/stub/src/thin.rs

@@ -1,3 +1,4 @@
+use alloc::vec::Vec;
 use log::{error, warn};
 use sha2::{Digest, Sha256};
 use uefi::{fs::FileSystem, prelude::*, CString16, Result};
@@ -75,7 +76,11 @@ fn check_hash(data: &[u8], expected_hash: Hash, name: &str, secure_boot: bool) -
     Ok(())
 }
 
-pub fn boot_linux(handle: Handle, mut system_table: SystemTable<Boot>) -> uefi::Result<()> {
+pub fn boot_linux(
+    handle: Handle,
+    mut system_table: SystemTable<Boot>,
+    dynamic_initrds: Vec<Vec<u8>>,
+) -> uefi::Result<()> {
     uefi_services::init(&mut system_table).unwrap();
 
     // SAFETY: We get a slice that represents our currently running