backuptool: Support seamless backup and restore to extra partitions

For scripts declaring ADDOND_VERSION=3 automatically mount
vendor, product, system_ext and others (when they're dedicated partitions).

Also expose the get_output_path() function to get the path to where
a file is mounted in case it lives in a dedicated partition.

ab exapmles:
get_output_path "system/product/priv-app/MyApp.apk"  = "/postinstall/product/priv-app/MyApk.apk"
get_output_path "system/app/MySystemApp.apk"         = "/postinstall/system/app/MySystemApp.apk"

a-only examples:
get_output_path "/mnt/system/system/product/priv-app/MyApp.apk" = "/mnt/system/system/product/priv-app/MyApp.apk"

******************************************************************
Instead of cycling all scripts for each stage, run
pre-backup -> backup -> post-backup in quick succession
(and likewise for restore), to ensure backwards compatibility
with scripts that wrongly assumed their environment not to
change between steps.
This is needed because we want to undo any mounting done for V3
scripts when executing V2 scripts. If a V2 script did mounting in
pre-restore and expected things to still be mounted in restore,
we would break their (yes incorrect) assumption.

Change-Id: I73fbad6f45824fed99e4482128769435348588f5

prebuilt/common/bin/backuptool.sh

@@ -8,9 +8,20 @@ export SYSDEV="$(readlink -nf "$2")"
 export SYSFS="$3"
 export V=18.1
 
+export ADDOND_VERSION=3
+
+# Partitions to mount for backup/restore in V3
+export all_V3_partitions="vendor product system_ext"
+
 # Scripts in /system/addon.d expect to find backuptool.functions in /tmp
 cp -f /tmp/install/bin/backuptool.functions /tmp
 
+get_script_version() {
+  version=$(grep "^# ADDOND_VERSION=" $1 | cut -d= -f2)
+  [ -z "$version" ] && version=1
+  echo $version
+}
+
 # Preserve /system/addon.d in /tmp/addon.d
 preserve_addon_d() {
   if [ -d $S/addon.d/ ]; then
@@ -43,15 +54,31 @@ fi
 return 0
 }
 
-# Execute /system/addon.d/*.sh scripts with $1 parameter
-run_stage() {
+# Execute /system/addon.d/*.sh scripts with each $@ parameter
+run_stages() {
 if [ -d /tmp/addon.d/ ]; then
   for script in $(find /tmp/addon.d/ -name '*.sh' |sort -n); do
-    $script $1
+    v=$(get_script_version $script)
+    if [ $v -ge 3 ]; then
+      mount_extra $all_V3_partitions
+    else
+      umount_extra $all_V3_partitions
+    fi
+
+    for stage in $@; do
+      if [ $v -ge 3 ]; then
+        $script $stage
+      else
+        ADDOND_VERSION=2 $script $stage
+      fi
+    done
   done
 fi
 }
 
+#####################
+### Mount helpers ###
+#####################
 determine_system_mount() {
   if grep -q -e"^$SYSDEV" /proc/mounts; then
     umount $(grep -e"^$SYSDEV" /proc/mounts | cut -d" " -f2)
@@ -76,26 +103,77 @@ unmount_system() {
   umount $SYSMOUNT
 }
 
+get_block_for_mount_point() {
+  grep -v "^#" /etc/recovery.fstab | grep " $1 " | tail -n1 | tr -s ' ' | cut -d' ' -f1
+}
+
+find_block() {
+  local name="$1"
+  local fstab_entry=$(get_block_for_mount_point "/$name")
+  # P-SAR hacks
+  [ -z "$fstab_entry" ] && [ "$name" = "system" ] && fstab_entry=$(get_block_for_mount_point "/")
+  [ -z "$fstab_entry" ] && [ "$name" = "system" ] && fstab_entry=$(get_block_for_mount_point "/system_root")
+
+  local dev
+  if [ "$DYNAMIC_PARTITIONS" = "true" ]; then
+    if [ -n "$fstab_entry" ]; then
+      dev="${BLK_PATH}/${fstab_entry}"
+    else
+      dev="${BLK_PATH}/${name}"
+    fi
+  else
+    if [ -n "$fstab_entry" ]; then
+      dev="$fstab_entry"
+    else
+      dev="${BLK_PATH}/${name}"
+    fi
+  fi
+
+  if [ -b "$dev" ]; then
+    echo "$dev"
+  fi
+}
+
 determine_system_mount
 
+DYNAMIC_PARTITIONS=$(getprop ro.boot.dynamic_partitions)
+BLK_PATH=$(dirname "$SYSDEV")
+
+mount_extra() {
+  for partition in $@; do
+    mnt_point="/$partition"
+    mountpoint "$mnt_point" >/dev/null 2>&1 && break
+
+    blk_dev=$(find_block "$partition")
+    if [ -e "$blk_dev" ]; then
+      [ "$DYNAMIC_PARTITIONS" = "true" ] && blockdev --setrw "$blk_dev"
+      mkdir -p "$mnt_point"
+      mount -o rw "$blk_dev" "$mnt_point"
+    fi
+  done
+}
+
+umount_extra() {
+  for partition in $@; do
+    umount -l "/$partition" 2>/dev/null
+  done
+}
+
 case "$1" in
   backup)
     mount_system
     if check_prereq; then
       mkdir -p $C
       preserve_addon_d
-      run_stage pre-backup
-      run_stage backup
-      run_stage post-backup
+      run_stages pre-backup backup post-backup
     fi
     unmount_system
   ;;
   restore)
     mount_system
     if check_prereq; then
-      run_stage pre-restore
-      run_stage restore
-      run_stage post-restore
+      run_stages pre-restore restore post-restore
+      umount_extra $all_V3_partitions
       restore_addon_d
       rm -rf $C
       sync