Parse uki and aboot files using minimal composefs-boot dependency (#397)

This uses a new feature of composefs-boot to drop all composefs
integration dependencies, making it a very small library with parsers
for boot artifacts (uki, aboot, os-release files). This allows us to
drop the objcopy and android-tools dependency.

Signed-off-by: Alexander Larsson <alexl@redhat.com>

Author: alexlarsson

Cargo.lock

@@ -19,10 +19,8 @@ Requires: podman
 Requires: qemu-img
 Requires: qemu-kvm
 Requires: virtiofsd
-# Extraction and initramfs tools are needed for some ephemeral boot images.
-Recommends: binutils
+# Initramfs tools are needed for some ephemeral boot images.
 Recommends: kernel-tools
-Recommends: android-tools
 # libvirt-client is optional but recommended for 'bcvk libvirt' commands
 Recommends: libvirt-client
 

contrib/packaging/bcvk.spec

@@ -160,7 +160,7 @@ pub enum BootMode {
     /// Direct kernel boot (fast, testing-focused).
     /// Also used for UKI boot after extracting kernel/initramfs from UKI PE sections.
     ///
-    /// Note: For UKI images, we extract kernel/initramfs using objcopy rather than
+    /// Note: For UKI images, we extract kernel/initramfs from PE sections rather than
     /// booting the UKI directly via OVMF. This allows us to append bcvk units to
     /// the initramfs for /etc overlay and /var setup. The tradeoff is that this
     /// breaks the UKI signature chain, so Secure Boot is not supported for

crates/bcvk-qemu/src/qemu.rs

@@ -264,7 +264,7 @@ integration_test!(test_run_ephemeral_instancetype_invalid);
 /// Test that ephemeral VMs can boot from UKI-only images (no separate vmlinuz/initramfs)
 ///
 /// This tests compatibility with bootc images that only ship a Unified Kernel Image,
-/// verifying that bcvk can extract kernel/initramfs from the UKI using objcopy.
+/// verifying that bcvk can extract kernel/initramfs from the UKI.
 fn test_run_ephemeral_uki_only() -> TestResult {
     let sh = shell()?;
     let base_image = get_test_image();

crates/integration-tests/src/tests/run_ephemeral.rs

@@ -50,6 +50,7 @@ bcvk-qemu = { path = "../bcvk-qemu" }
 cap-std-ext = { workspace = true }
 bootc-mount = { package = "bootc-internal-mount", version = "1.16.14" }
 bootc-utils = { package = "bootc-internal-utils", version = "1.16.14" }
+composefs-boot = { version = "0.9.4", default-features = false }
 rustix = { version = "1", features = ["thread", "net", "fs", "pipe", "system", "process", "mount"] }
 vsock = "0.5"
 nix = { version = "0.31", features = ["socket"] }

crates/kit/Cargo.toml

@@ -1428,40 +1428,37 @@ pub(crate) async fn run_impl(opts: RunEphemeralOpts) -> Result<()> {
 
     match kernel_info.kind {
         crate::kernel::KernelKind::Uki => {
-            require_binary("objcopy")?;
             debug!(
                 "Extracting kernel and initramfs from UKI: {:?}",
                 kernel_info.kernel_path
             );
-            for (section, output) in [(".linux", kernel_mount), (".initrd", initramfs_mount)] {
-                Command::new("objcopy")
-                    .args([
-                        "--dump-section",
-                        &format!("{section}={output}"),
-                        kernel_info.kernel_path.as_str(),
-                    ])
-                    .run_capture_stderr()
-                    .map_err(|e| eyre!("Failed to extract {section} from UKI: {e}"))?;
+            let mut uki = File::open(&kernel_info.kernel_path).context("opening UKI")?;
+            for (section, target) in [(".linux", kernel_mount), (".initrd", initramfs_mount)] {
+                // The buffered parser starts at the current position in the image.
+                uki.rewind().context("rewinding UKI")?;
+                let contents = composefs_boot::uki::get_section_buffered(&mut uki, section)
+                    .context(format!("extracting {section} from UKI"))?;
+                fs::write(target, contents).context(format!("writing {section} from UKI"))?;
+                debug!("Extracted {section} from UKI to {target}");
             }
         }
         crate::kernel::KernelKind::AndroidBoot => {
-            require_binary("unpack_bootimg")?;
-            let unpacked = "/run/qemu/aboot-unpacked";
-            fs::create_dir_all(unpacked)?;
-            Command::new("unpack_bootimg")
-                .args([
-                    "--boot_img",
-                    kernel_info.kernel_path.as_str(),
-                    "--out",
-                    unpacked,
-                ])
-                .stdout(Stdio::null())
-                .run_capture_stderr()
-                .map_err(|e| eyre!("Failed to unpack Android boot image: {e}"))?;
-            fs::rename(format!("{unpacked}/kernel"), kernel_mount)
-                .context("Getting kernel from Android boot image")?;
-            fs::rename(format!("{unpacked}/ramdisk"), initramfs_mount)
-                .context("Getting ramdisk from Android boot image")?;
+            use composefs_boot::android_boot::{AndroidBootImage, Component};
+
+            let mut image =
+                File::open(&kernel_info.kernel_path).context("opening Android boot image")?;
+            let header =
+                AndroidBootImage::parse(&mut image).context("parsing Android boot image")?;
+            for (component, name, target) in [
+                (Component::Kernel, "kernel", kernel_mount),
+                (Component::Ramdisk, "ramdisk", initramfs_mount),
+            ] {
+                let contents = header
+                    .component(&mut image, component)
+                    .with_context(|| format!("extracting {name} from Android boot image"))?;
+                fs::write(target, contents)
+                    .with_context(|| format!("writing {name} from Android boot image"))?;
+            }
         }
         crate::kernel::KernelKind::Traditional => {
             let source_initramfs_path = kernel_info

crates/kit/src/run_ephemeral.rs

@@ -22,8 +22,6 @@ For running bcvk:
 - virtiofsd
 - Podman
 - openssh-clients (for libvirt SSH operations)
-- binutils (for extracting UKIs, including ukiboot payloads)
-- android-tools (for extracting Android boot images)
 - kernel-tools (for initramfs bootconfig and ARM64 zstd EFI zboot kernels)
 
 Optional:

docs/src/installation.md

@@ -6,7 +6,7 @@ Tracking issue: https://github.com/bootc-dev/bcvk/issues/161
 
 Ephemeral VMs currently use direct kernel boot via QEMU's `-kernel` and
 `-initrd` options. For UKI-only images, we extract the kernel and initramfs
-from the UKI using `objcopy --dump-section`.
+from the UKI using the `composefs-boot` UKI parser.
 
 ### Where UKIs Live in bootc Images