Add linux-aarch64 kernel compatibility shim

.github/workflows/test.yml

@@ -25,9 +25,16 @@ jobs:
             -w /workspace \
             archlinux:base-devel bash -lc '
               set -euo pipefail
-              pacman -Syu --noconfirm git jq
+              pacman -Syu --noconfirm git jq python-yaml xz zstd
               ./bin/sync-upstream self-test
               ./bin/sync-rebuilds --self-test
               ./bin/omarchy-pkgs self-test
               ./bin/omarchy-release self-test
+              shopt -s nullglob
+              for test in pkgbuilds/*/test.sh; do
+                bash "$test"
+              done
+              if [[ -d test ]]; then
+                runuser -u nobody -- python -m unittest discover -s test -v
+              fi
             '

pkgbuilds/linux-aarch64-pkgbase-shim/.omarchy/package.json

@@ -0,0 +1,3 @@
+{
+  "source": "local"
+}

pkgbuilds/linux-aarch64-pkgbase-shim/85-linux-aarch64-pkgbase-shim.hook

@@ -0,0 +1,19 @@
+# Run before mkinitcpio and Limine discover installed kernels.
+[Trigger]
+Type = Path
+Operation = Install
+Operation = Upgrade
+Operation = Remove
+Target = usr/lib/modules/*/
+
+[Trigger]
+Type = Package
+Operation = Install
+Operation = Upgrade
+Target = linux-aarch64-pkgbase-shim
+
+[Action]
+Description = Writing pkgbase and vmlinuz for Arch Linux ARM kernels...
+When = PostTransaction
+Exec = /usr/share/libalpm/scripts/linux-aarch64-pkgbase-shim
+NeedsTargets

pkgbuilds/linux-aarch64-pkgbase-shim/PKGBUILD

@@ -0,0 +1,26 @@
+# Maintainer: Jimmy Van Veen
+
+# Add kernel metadata required by mkinitcpio and Limine on Arch Linux ARM.
+
+pkgname=linux-aarch64-pkgbase-shim
+pkgver=1
+pkgrel=3
+pkgdesc="Writes usr/lib/modules/<ver>/{pkgbase,vmlinuz} for Arch Linux ARM kernels so mkinitcpio and Limine hooks find them"
+arch=('aarch64')
+url="https://github.com/omacom/omarchy-pkgs"
+license=('MIT')
+depends=('bash' 'diffutils' 'pacman')
+optdepends=('limine-mkinitcpio-hook: rebuild the UKI and Limine entry when the shim is installed after the kernel')
+options=('!debug')
+source=(
+  '85-linux-aarch64-pkgbase-shim.hook'
+  'linux-aarch64-pkgbase-shim'
+  'README.package.md'
+)
+sha256sums=('SKIP' 'SKIP' 'SKIP')
+
+package() {
+  install -Dm644 85-linux-aarch64-pkgbase-shim.hook "${pkgdir}/usr/share/libalpm/hooks/85-linux-aarch64-pkgbase-shim.hook"
+  install -Dm755 linux-aarch64-pkgbase-shim "${pkgdir}/usr/share/libalpm/scripts/linux-aarch64-pkgbase-shim"
+  install -Dm644 README.package.md "${pkgdir}/usr/share/doc/${pkgname}/README.md"
+}

pkgbuilds/linux-aarch64-pkgbase-shim/README.package.md

@@ -0,0 +1,28 @@
+# linux-aarch64-pkgbase-shim
+
+Arch Linux ARM installs its kernel as `/boot/Image` instead of
+`usr/lib/modules/<ver>/vmlinuz`. Limine discovers the kernel through
+`modules.builtin`, but needs `vmlinuz` beside it to build a boot entry.
+
+This package is one pacman hook. After a kernel package is installed or
+upgraded (`usr/lib/modules/*/`), and when the shim itself is installed, it
+writes into each package-owned modules directory without native kernel metadata:
+
+- `pkgbase`: compatibility metadata naming the package that owns the directory
+- `vmlinuz`: a copy of `/boot/Image` (the owner must own that too)
+
+Reinstalling a kernel refreshes the shim's copy when the image changes, even
+if the module-directory version is unchanged. Package-owned files are preserved.
+
+It runs as `85-`, before `90-mkinitcpio-install`, so the usual hook then builds
+the initramfs/UKI and the Limine entry. If that hook would not run in the same
+transaction (the shim installed after the kernel, or a kernel package that
+does not touch `usr/lib/initcpio/`), the script runs
+`limine-mkinitcpio-install` itself. Leftover directories of removed kernels
+that hold nothing but these two files are cleaned up.
+
+## Retirement
+
+Delete this package when `linux-aarch64` ships `vmlinuz` in its kernel module
+directory. Package-owned metadata is never modified, so both approaches can coexist
+during the transition.

pkgbuilds/linux-aarch64-pkgbase-shim/linux-aarch64-pkgbase-shim

@@ -0,0 +1,103 @@
+#!/bin/bash
+# Supply pkgbase and vmlinuz metadata missing from Arch Linux ARM kernels.
+set -uo pipefail
+
+readonly SELF=linux-aarch64-pkgbase-shim
+readonly ROOT=${OMARCHY_KERNEL_SHIM_ROOT:-}
+readonly IMAGE=$ROOT/boot/Image
+readonly LIMINE_INSTALL_SCRIPT=$ROOT/usr/share/libalpm/scripts/limine-mkinitcpio-install
+
+declare -A DIRS=()
+modules_in_transaction=0
+self_in_transaction=0
+rebuild=0
+failed=0
+
+owner_of() {
+	pacman -Qqo "${1#"$ROOT"}" 2>/dev/null
+}
+
+# NeedsTargets requires consuming every line from stdin.
+while IFS= read -r line; do
+	case $line in
+	usr/lib/modules/*)
+		v=${line#usr/lib/modules/}
+		v=${v%%/*}
+		[[ -n $v ]] && DIRS["$ROOT/usr/lib/modules/$v"]=1
+		modules_in_transaction=1
+		;;
+	"$SELF")
+		self_in_transaction=1
+		;;
+	esac
+done
+
+# Cover kernels already present when the shim itself is installed.
+if ((self_in_transaction)); then
+	for d in "$ROOT"/usr/lib/modules/*/; do
+		[[ -d $d ]] && DIRS["${d%/}"]=1
+	done
+fi
+
+for dir in "${!DIRS[@]}"; do
+	[[ -d $dir ]] || continue
+	# Not a packaged kernel (a leftover or DKMS-only directory).
+	owner=$(owner_of "$dir") || continue
+	if [[ $(owner_of "$IMAGE") != "$owner" ]]; then
+		echo "$SELF: $owner owns $dir but not $IMAGE, leaving it alone" >&2
+		continue
+	fi
+	# Preserve package-owned files; refresh metadata previously written by the shim.
+	owner_of "$dir/pkgbase" >/dev/null && continue
+	owner_of "$dir/vmlinuz" >/dev/null && continue
+	if [[ -e $dir/pkgbase && $(<"$dir/pkgbase") != "$owner" ]]; then
+		continue
+	fi
+	if [[ -f $dir/pkgbase ]] && cmp -s "$IMAGE" "$dir/vmlinuz"; then
+		continue
+	fi
+	image_tmp=$(mktemp "$dir/.vmlinuz.XXXXXX") || { failed=1; continue; }
+	if ! cp --preserve=mode "$IMAGE" "$image_tmp" || ! mv -f "$image_tmp" "$dir/vmlinuz"; then
+		echo "$SELF: failed to copy $IMAGE to $dir/vmlinuz" >&2
+		rm -f "$image_tmp"
+		failed=1
+		continue
+	fi
+	if ! printf '%s\n' "$owner" >"$dir/pkgbase"; then
+		failed=1
+		continue
+	fi
+	echo "$SELF: wrote pkgbase ($owner) and vmlinuz in $dir"
+	# Rebuild when the transaction will not trigger mkinitcpio itself.
+	if ! ((modules_in_transaction)) || ! pacman -Qlq "$owner" 2>/dev/null | grep '^/usr/lib/initcpio/' >/dev/null; then
+		rebuild=1
+	fi
+done
+
+# Remove directories containing only stale shim metadata.
+for dir in "$ROOT"/usr/lib/modules/*/; do
+	dir=${dir%/}
+	[[ -f $dir/pkgbase && -f $dir/vmlinuz ]] || continue
+	owner_of "$dir" >/dev/null && continue
+	owner_of "$dir/pkgbase" >/dev/null && continue
+	owner_of "$dir/vmlinuz" >/dev/null && continue
+	[[ -z $(find "$dir" -mindepth 1 ! -name pkgbase ! -name vmlinuz -print -quit) ]] || continue
+	rm -f "$dir/pkgbase" "$dir/vmlinuz" && rmdir "$dir" && echo "$SELF: removed leftover $dir"
+done
+
+# Respect the installer's deferred boot-image build.
+deferred_hook=$ROOT/etc/pacman.d/hooks/90-mkinitcpio-install.hook
+if ((rebuild)) && [[ -L $deferred_hook && $(readlink "$deferred_hook") == /dev/null ]]; then
+	echo "$SELF: $deferred_hook is masked, leaving the rebuild to limine-update"
+	rebuild=0
+fi
+
+if ((rebuild)); then
+	if [[ -x $LIMINE_INSTALL_SCRIPT ]]; then
+		echo rebuild | "$LIMINE_INSTALL_SCRIPT" || failed=1
+	else
+		echo "$SELF: $LIMINE_INSTALL_SCRIPT not found; run mkinitcpio for the new kernel yourself" >&2
+	fi
+fi
+
+exit "$failed"

pkgbuilds/linux-aarch64-pkgbase-shim/test.sh

@@ -0,0 +1,107 @@
+#!/bin/bash
+set -euo pipefail
+
+package_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+scratch=$(mktemp -d)
+trap 'rm -rf "$scratch"' EXIT
+export OMARCHY_KERNEL_SHIM_ROOT=$scratch
+export SHIM_NATIVE=0 SHIM_KERNEL_PRESENT=1
+export SHIM_IMAGE_OWNER=linux-aarch64
+
+pacman() {
+  if [[ $1 == -Qlq ]]; then
+    printf '/usr/lib/initcpio/install/test\n'
+    return 0
+  fi
+  case $2 in
+    /boot/Image)
+      printf '%s\n' "$SHIM_IMAGE_OWNER"
+      ;;
+    /usr/lib/modules/test)
+      ((SHIM_KERNEL_PRESENT)) || return 1
+      printf 'linux-aarch64\n'
+      ;;
+    /usr/lib/modules/test/pkgbase | /usr/lib/modules/test/vmlinuz)
+      [[ $SHIM_NATIVE == 1 || $2 == /usr/lib/modules/test/"$SHIM_NATIVE" ]] || return 1
+      printf 'linux-aarch64\n'
+      ;;
+    *) return 1 ;;
+  esac
+}
+export -f pacman
+
+modules=$scratch/usr/lib/modules/test
+mkdir -p "$modules" "$scratch/boot" "$scratch/etc/pacman.d/hooks" \
+  "$scratch/usr/share/libalpm/scripts"
+printf 'first-kernel' >"$scratch/boot/Image"
+cat >"$scratch/usr/share/libalpm/scripts/limine-mkinitcpio-install" <<'SCRIPT'
+#!/bin/bash
+cat >>"$OMARCHY_KERNEL_SHIM_ROOT/rebuilds"
+SCRIPT
+chmod +x "$scratch/usr/share/libalpm/scripts/limine-mkinitcpio-install"
+
+run_shim() {
+  printf '%s\n' "$1" | bash "$package_dir/linux-aarch64-pkgbase-shim"
+}
+
+run_shim usr/lib/modules/test/
+[[ $(<"$modules/pkgbase") == linux-aarch64 ]]
+cmp "$scratch/boot/Image" "$modules/vmlinuz"
+[[ $(stat -c %a "$modules/vmlinuz") == $(stat -c %a "$scratch/boot/Image") ]]
+[[ ! -e $scratch/rebuilds ]]
+echo 'ok - kernel installation supplies metadata before the normal rebuild hook'
+
+printf 'replacement-kernel' >"$scratch/boot/Image"
+run_shim usr/lib/modules/test/
+cmp "$scratch/boot/Image" "$modules/vmlinuz"
+echo 'ok - reinstalling the same kernel version refreshes its image'
+
+printf 'shim-upgrade' >"$scratch/boot/Image"
+run_shim linux-aarch64-pkgbase-shim
+[[ $(<"$scratch/rebuilds") == rebuild ]]
+run_shim linux-aarch64-pkgbase-shim
+[[ $(wc -l <"$scratch/rebuilds") == 1 ]]
+echo 'ok - unchanged images do not trigger redundant rebuilds'
+
+ln -s /dev/null "$scratch/etc/pacman.d/hooks/90-mkinitcpio-install.hook"
+printf 'deferred-kernel' >"$scratch/boot/Image"
+run_shim linux-aarch64-pkgbase-shim
+cmp "$scratch/boot/Image" "$modules/vmlinuz"
+[[ $(wc -l <"$scratch/rebuilds") == 1 ]]
+echo 'ok - the installer can defer boot-image regeneration'
+
+for SHIM_NATIVE in pkgbase vmlinuz; do
+  printf 'package-owned' >"$modules/vmlinuz"
+  run_shim usr/lib/modules/test/
+  [[ $(<"$modules/vmlinuz") == package-owned ]]
+done
+echo 'ok - either package-owned metadata file prevents replacement'
+
+SHIM_NATIVE=0
+SHIM_IMAGE_OWNER=another-kernel
+run_shim usr/lib/modules/test/
+[[ $(<"$modules/vmlinuz") == package-owned ]]
+SHIM_IMAGE_OWNER=linux-aarch64
+echo 'ok - a different kernel image owner prevents replacement'
+
+(
+  # shellcheck disable=SC2329 # Invoked by the shim in a child shell.
+  cp() { return 1; }
+  export -f cp
+  if run_shim usr/lib/modules/test/; then
+    echo 'not ok - a failed image copy was accepted' >&2
+    exit 1
+  fi
+  [[ $(<"$modules/vmlinuz") == package-owned ]]
+)
+echo 'ok - failed copies preserve the previous kernel image'
+
+SHIM_KERNEL_PRESENT=0
+mkdir -p "$modules/updates/dkms"
+run_shim usr/lib/modules/test/
+[[ -d $modules/updates/dkms && -f $modules/vmlinuz ]]
+rmdir "$modules/updates/dkms" "$modules/updates"
+echo 'ok - kernel removal preserves DKMS leftovers'
+run_shim usr/lib/modules/test/
+[[ ! -d $modules ]]
+echo 'ok - kernel removal cleans up leftover shim metadata'