kbuild: add support for squashing uid/gid in gen_initramfs_list.sh

Sometimes it is useful to squash all uid's/gid's to 0:0 regardless of
current owner.  For example, in build systems that get run as arbitrary
users (uClinux-dist).  This adds a special "squash" keyword so you can do
'-g squash -u squash' and have ownership squashed to root.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: vapier

scripts/gen_initramfs_list.sh

@@ -19,11 +19,11 @@ $0 [-o <file>] [-u <uid>] [-g <gid>] {-d | <cpio_source>} ...
 	-o <file>      Create gzipped initramfs file named <file> using
 		       gen_init_cpio and gzip
 	-u <uid>       User ID to map to user ID 0 (root).
-		       <uid> is only meaningful if <cpio_source>
-		       is a directory.
+		       <uid> is only meaningful if <cpio_source> is a
+		       directory.  "squash" forces all files to uid 0.
 	-g <gid>       Group ID to map to group ID 0 (root).
-		       <gid> is only meaningful if <cpio_source>
-		       is a directory.
+		       <gid> is only meaningful if <cpio_source> is a
+		       directory.  "squash" forces all files to gid 0.
 	<cpio_source>  File list or directory for cpio archive.
 		       If <cpio_source> is a .cpio file it will be used
 		       as direct input to initramfs.
@@ -113,8 +113,8 @@ parse() {
 	local gid="$4"
 	local ftype=$(filetype "${location}")
 	# remap uid/gid to 0 if necessary
-	[ "$uid" -eq "$root_uid" ] && uid=0
-	[ "$gid" -eq "$root_gid" ] && gid=0
+	[ "$root_uid" = "squash" ] && uid=0 || [ "$uid" -eq "$root_uid" ] && uid=0
+	[ "$root_gid" = "squash" ] && gid=0 || [ "$gid" -eq "$root_gid" ] && gid=0
 	local str="${mode} ${uid} ${gid}"
 
 	[ "${ftype}" == "invalid" ] && return 0