recoveryboot: chain-load into the recovery partition on BCB request

The RPi firmware can't read the BCB in misc, so 'adb reboot recovery' /
factory reset never reached recovery: init writes boot-recovery and
reboots, the firmware ignores the reboot arg, and Android just boots
normally again.

pawlet-recoveryboot is a vendor oneshot (post-fs-data) that reads the
BCB command field (misc offset 0 — the HAL's PawletBootControl lives at
4096, no overlap) and, on boot-recovery, reboots with arg '3': the
firmware's PM_RSTS partition mechanism (same driver path as the
updater's tryboot) boots GPT partition 3 = recovery once. Stock
recovery reads its args from the untouched BCB, clears it when done,
and the next reboot is normal. A /metadata attempt counter clears the
BCB after 2 failed tries so an unbootable recovery can't wedge the
device.

config/rpi_common.mk

@@ -37,3 +37,11 @@ PRODUCT_PACKAGES += \
     PawletUpdaterRpiOverlay \
     PawletSettings \
     SettingsProviderRpiCommonOverlay
+
+# ---------------------------------------------------------------------------
+# reboot-to-recovery chain-loader — RPi firmware can't read the BCB in misc,
+# so a boot-time oneshot detects "boot-recovery" and reboots into the
+# recovery partition (3) via the firmware's PM_RSTS partition mechanism.
+# ---------------------------------------------------------------------------
+PRODUCT_PACKAGES += \
+    pawlet-recoveryboot

recoveryboot/Android.bp

@@ -0,0 +1,9 @@
+// Copyright (C) 2026 oxmc / PawletOS
+// SPDX-License-Identifier: Apache-2.0
+
+sh_binary {
+    name: "pawlet-recoveryboot",
+    src: "pawlet-recoveryboot.sh",
+    vendor: true,
+    init_rc: ["pawlet-recoveryboot.rc"],
+}

recoveryboot/pawlet-recoveryboot.rc

@@ -0,0 +1,11 @@
+# Chain-load into the recovery partition when the BCB asks for it — see
+# pawlet-recoveryboot.sh. post-fs-data: by-name symlinks and /metadata are
+# guaranteed mounted, and we still reboot before the launcher appears.
+service pawlet_recoveryboot /vendor/bin/pawlet-recoveryboot.sh
+    user root
+    group root system
+    oneshot
+    disabled
+
+on post-fs-data
+    exec_start pawlet_recoveryboot

recoveryboot/pawlet-recoveryboot.sh

@@ -0,0 +1,53 @@
+#!/vendor/bin/sh
+#
+# Copyright (C) 2026 oxmc / PawletOS
+# SPDX-License-Identifier: Apache-2.0
+#
+# Boot-time bootloader-message (BCB) watcher — the RPi firmware cannot read
+# the misc partition, so "reboot recovery" needs an Android-side chain-load:
+#
+#   adb reboot recovery / Settings factory reset
+#     -> framework+init write "boot-recovery" into the BCB command field
+#        (misc offset 0, 32 bytes) and reboot; the firmware ignores the
+#        "recovery" reboot arg and boots normal Android
+#     -> THIS script (oneshot, early in boot) sees the BCB and reboots with
+#        arg "3": the firmware's PM_RSTS partition mechanism (same driver
+#        path as the updater's "tryboot") boots GPT partition 3 = recovery
+#     -> stock recovery reads its args from the BCB, does its work, clears
+#        the BCB, reboots -> normal boot
+#
+# The BCB is left intact for recovery (it carries e.g. --wipe_data). A
+# bootloop breaker in /metadata clears the BCB after repeated failed
+# attempts so an unbootable recovery partition can't wedge the device.
+
+MISC=/dev/block/by-name/misc
+GUARD_DIR=/metadata/pawlet
+GUARD=$GUARD_DIR/recoveryboot.attempts
+TAG=pawlet-recoveryboot
+
+CMD=$(dd if=$MISC bs=1 count=32 2>/dev/null | tr -d '\0')
+
+case "$CMD" in
+  boot-recovery*)
+    mkdir -p $GUARD_DIR
+    N=$(cat $GUARD 2>/dev/null)
+    [ -z "$N" ] && N=0
+    if [ "$N" -ge 2 ]; then
+      # Recovery partition isn't coming up — break the loop: clear the BCB
+      # command field and stay in Android.
+      dd if=/dev/zero of=$MISC bs=1 count=32 conv=notrunc 2>/dev/null
+      rm -f $GUARD
+      log -p e -t $TAG "recovery boot failed $N times; BCB cleared, staying in Android"
+      exit 0
+    fi
+    echo $((N + 1)) > $GUARD
+    log -p i -t $TAG "BCB requests recovery — rebooting to partition 3 (attempt $((N + 1)))"
+    setprop sys.powerctl reboot,3
+    ;;
+  *)
+    # Normal boot: reset the attempt counter.
+    rm -f $GUARD 2>/dev/null
+    ;;
+esac
+
+exit 0