Fix ensure_bb implementation

Close #2549, close #2560

Author: topjohnwu

scripts/util_functions.sh

@@ -86,23 +86,40 @@ setup_flashable() {
 }
 
 ensure_bb() {
-  [ -o standalone ] && return
-  set -o standalone 2>/dev/null && return
+  if set -o | grep -q standalone; then
+    # We are definitely in busybox ash
+    set -o standalone
+    return
+  fi
 
-  # At this point, we are not running in BusyBox ash
   # Find our busybox binary
-  local BUSYBOX
+  local bb
   if [ -f $TMPDIR/busybox ]; then
-    BUSYBOX=$TMPDIR/busybox
+    bb=$TMPDIR/busybox
   elif [ -f $MAGISKBIN/busybox ]; then
-    BUSYBOX=$MAGISKBIN/busybox
+    bb=$MAGISKBIN/busybox
   else
     abort "! Cannot find BusyBox"
   fi
+  chmod 755 $bb
+
+  # Find our current arguments
+  # Run in busybox environment to ensure consistent results
+  # /proc/<pid>/cmdline shall be <interpreter> <script> <arguments...>
+  local cmds=$($bb sh -o standalone -c "
+  tr '\0' '\n' < /proc/$$/cmdline | (while read -r arg; do
+    if [ -z \"\$cmds\" ]; then
+      # Skip the first argument as we want to change the interpreter
+      cmds=\"sh -o standalone\"
+    else
+      cmds=\"\$cmds '\$arg'\"
+    fi
+  done
+  echo \$cmds)")
 
   # Re-exec our script
-  chmod 755 $BUSYBOX
-  exec $BUSYBOX sh -o standalone $0 "$@"
+  echo $cmds | $bb xargs $bb
+  exit
 }
 
 recovery_actions() {