Fix ARM64 initramfs: write complete archiso mkinitcpio hooks inline

The archiso git repo doesn't ship the hooks as standalone files, and
ALARM has no archiso package. Write the hooks directly in the entrypoint
with the correct three-phase structure:

- run_earlyhook: modprobe squashfs/overlay/iso9660/loop/vfat before udev
- run_hook: parse archisolabel/archisobasedir from /proc/cmdline, set
  mount_handler="archiso_mount_handler"
- archiso_mount_handler: find ISO by label (fallback to TYPE=iso9660),
  mount it, mount squashfs at arch/$(uname -m)/airootfs.sfs, set up
  tmpfs cowspace, mount overlay to /new_root

install hook: add all required modules (squashfs, overlay, iso9660,
loop, vfat, nls_*) and binaries (blkid, losetup, sleep, uname).
Each mount step prints its progress and bails with a clear error message
on failure so boot panics are diagnosable.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/docker/Dockerfile.arm64

@@ -65,8 +65,6 @@ RUN git clone --depth=1 https://gitlab.archlinux.org/archlinux/archiso.git /tmp/
     install -Dm755 /tmp/archiso/scripts/run_archiso.sh /usr/bin/run_archiso && \
     install -d /usr/share/archiso && \
     cp -a /tmp/archiso/configs /usr/share/archiso/ && \
-    echo "=== archiso hook locations ===" && \
-    find /tmp/archiso -name "archiso" -not -path "*/\.git/*" | sort && \
     rm -rf /tmp/archiso
 
 # Pre-download linux-aarch64 and create a local pacman repo so mkarchiso

iso/docker/entrypoint-arm64.sh

@@ -146,31 +146,128 @@ rm -f "$PROFILE/packages.x86_64"
 # ── 3. airootfs overlay — files that land in the live system ─────────
 AIROOTFS="$PROFILE/airootfs"
 
-# The archiso mkinitcpio hooks must be in the airootfs chroot so mkinitcpio
-# can build a working initramfs. ALARM has no archiso package, so we find
-# the hooks from the archiso source we copied into /usr/share/archiso/.
+# The archiso mkinitcpio hooks are not shipped as separate files in the
+# archiso git repo. ALARM has no archiso package. Write them here with
+# correct module loading, device detection, and overlay setup.
 mkdir -p "$AIROOTFS/usr/lib/initcpio/hooks" "$AIROOTFS/usr/lib/initcpio/install"
 
-_find_hook() {
-    # Try releng airootfs first, then any other location under /usr/share/archiso
-    local name="$1"
-    local found
-    found=$(find /usr/share/archiso -path "*/initcpio/${name}/archiso" | head -1)
-    echo "${found}"
+cat > "$AIROOTFS/usr/lib/initcpio/hooks/archiso" <<'HOOK'
+#!/usr/bin/ash
+
+run_earlyhook() {
+    # Load all modules needed for live boot before udev runs
+    modprobe -q squashfs 2>/dev/null || true
+    modprobe -q overlay  2>/dev/null || true
+    modprobe -q iso9660  2>/dev/null || true
+    modprobe -q loop     2>/dev/null || true
+    modprobe -q vfat     2>/dev/null || true
 }
 
-_hook_runtime=$(_find_hook "hooks")
-_hook_install=$(_find_hook "install")
+run_hook() {
+    # Read kernel cmdline parameters
+    for _param in $(cat /proc/cmdline); do
+        case "${_param}" in
+            archisobasedir=*) archisobasedir="${_param#archisobasedir=}" ;;
+            archisolabel=*)   archisolabel="${_param#archisolabel=}"     ;;
+        esac
+    done
+    [ -z "${archisobasedir}" ] && archisobasedir="arch"
+    export mount_handler="archiso_mount_handler"
+}
 
-if [[ -n "$_hook_runtime" && -n "$_hook_install" ]]; then
-    install -m755 "$_hook_runtime" "$AIROOTFS/usr/lib/initcpio/hooks/archiso"
-    install -m755 "$_hook_install" "$AIROOTFS/usr/lib/initcpio/install/archiso"
-    echo ">>> Official archiso mkinitcpio hooks installed (from $_hook_runtime)"
-else
-    echo "ERROR: archiso mkinitcpio hooks not found under /usr/share/archiso — listing:"
-    find /usr/share/archiso -name "archiso" 2>/dev/null | sort
-    exit 1
+archiso_mount_handler() {
+    local _newroot="${1}"
+    local _dev _sfs _arch _i
+
+    # Find ISO device by label; fall back to any iso9660 device
+    _i=0
+    while [ "${_i}" -lt 30 ]; do
+        if [ -n "${archisolabel}" ]; then
+            _dev=$(blkid -l -t "LABEL=${archisolabel}" -o device 2>/dev/null)
         fi
+        [ -z "${_dev}" ] && \
+            _dev=$(blkid -t TYPE=iso9660 -o device 2>/dev/null | head -1)
+        [ -n "${_dev}" ] && break
+        sleep 1
+        _i=$(( _i + 1 ))
+    done
+
+    if [ -z "${_dev}" ]; then
+        echo "ERROR: archiso: cannot find ISO device (label=${archisolabel})"
+        return 1
+    fi
+    echo ":: archiso: found device ${_dev}"
+
+    mkdir -p /run/archiso/bootmnt
+    mount -r "${_dev}" /run/archiso/bootmnt || {
+        echo "ERROR: archiso: cannot mount ${_dev}"
+        return 1
+    }
+
+    # Squashfs path: arch/<uname -m>/airootfs.sfs
+    _arch=$(uname -m)
+    _sfs="/run/archiso/bootmnt/${archisobasedir}/${_arch}/airootfs.sfs"
+    echo ":: archiso: mounting squashfs ${_sfs}"
+
+    mkdir -p /run/archiso/airootfs
+    if ! mount -r -t squashfs "${_sfs}" /run/archiso/airootfs; then
+        echo "ERROR: archiso: cannot mount squashfs ${_sfs}"
+        echo "       contents of /run/archiso/bootmnt/${archisobasedir}/:"
+        ls "/run/archiso/bootmnt/${archisobasedir}/" 2>/dev/null || true
+        return 1
+    fi
+
+    # Writable overlay on top of the read-only squashfs
+    mkdir -p /run/archiso/cowspace
+    mount -t tmpfs -o size=75%,mode=0755 tmpfs /run/archiso/cowspace
+    mkdir -p /run/archiso/cowspace/upper /run/archiso/cowspace/work
+
+    mount -t overlay overlay \
+        -o "lowerdir=/run/archiso/airootfs,upperdir=/run/archiso/cowspace/upper,workdir=/run/archiso/cowspace/work" \
+        "${_newroot}" || {
+        echo "ERROR: archiso: overlay mount failed"
+        return 1
+    }
+    echo ":: archiso: overlay ready"
+}
+HOOK
+chmod 755 "$AIROOTFS/usr/lib/initcpio/hooks/archiso"
+
+cat > "$AIROOTFS/usr/lib/initcpio/install/archiso" <<'INSTALL'
+#!/bin/bash
+
+build() {
+    add_runscript
+
+    # Filesystems for the live medium
+    add_module squashfs
+    add_module overlay
+    add_module iso9660
+    add_module loop
+    add_module vfat
+    add_module fat
+    add_module nls_cp437
+    add_module nls_iso8859_1
+    add_module nls_utf8
+
+    # Required binaries
+    add_binary blkid
+    add_binary losetup
+    add_binary sleep
+    add_binary uname
+
+    # Pre-create mount points so the initramfs has them
+    add_dir /run/archiso/bootmnt
+    add_dir /run/archiso/airootfs
+    add_dir /run/archiso/cowspace
+}
+
+help() {
+    echo "Mounts the archiso squashfs live root via overlay."
+}
+INSTALL
+chmod 755 "$AIROOTFS/usr/lib/initcpio/install/archiso"
+echo ">>> archiso mkinitcpio hooks written to airootfs"
 
 mkdir -p "$AIROOTFS/etc/mkinitcpio.conf.d"
 cat > "$AIROOTFS/etc/mkinitcpio.conf.d/archiso.conf" <<'MKCONF'