scripts/extract-ikconfig: add support for bzip2, lzma and lzo

Add support for kernels compressed with bzip2, lzma or lzo to the
extract-ikconfig script.

Fixes kernel bugzilla #19852:
https://bugzilla.kernel.org/show_bug.cgi?id=19852

Signed-off-by: Dick Streefland <dick@streefland.net>
Tested-by: Justin <jlec@gentoo.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/extract-ikconfig

@@ -7,12 +7,10 @@
 # The obscure use of the "tr" filter is to work around older versions of
 # "grep" that report the byte offset of the line instead of the pattern.
 #
-# (c) 2009, Dick Streefland <dick@streefland.net>
+# (c) 2009,2010 Dick Streefland <dick@streefland.net>
 # Licensed under the terms of the GNU General Public License.
 # ----------------------------------------------------------------------
 
-gz1='\037\213\010'
-gz2='01'
 cf1='IKCFG_ST\037\213\010'
 cf2='0123456789'
 
@@ -21,11 +19,25 @@ dump_config()
 	if	pos=`tr "$cf1\n$cf2" "\n$cf2=" < "$1" | grep -abo "^$cf2"`
 	then
 		pos=${pos%%:*}
-		tail -c+$(($pos+8)) "$1" | zcat -q
-		exit 0
+		tail -c+$(($pos+8)) "$1" | zcat > $tmp1 2> /dev/null
+		if	[ $? != 1 ]
+		then	# exit status must be 0 or 2 (trailing garbage warning)
+			cat $tmp1
+			exit 0
+		fi
 	fi
 }
 
+try_decompress()
+{
+	for	pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
+	do
+		pos=${pos%%:*}
+		tail -c+$pos "$img" | $3 > $tmp2 2> /dev/null
+		dump_config $tmp2
+	done
+}
+
 # Check invocation:
 me=${0##*/}
 img=$1
@@ -35,18 +47,19 @@ then
 	exit 2
 fi
 
+# Prepare temp files:
+tmp1=/tmp/ikconfig$$.1
+tmp2=/tmp/ikconfig$$.2
+trap "rm -f $tmp1 $tmp2" 0
+
 # Initial attempt for uncompressed images or objects:
 dump_config "$img"
 
-# That didn't work, so decompress and try again:
-tmp=/tmp/ikconfig$$
-trap "rm -f $tmp" 0
-for	pos in `tr "$gz1\n$gz2" "\n$gz2=" < "$img" | grep -abo "^$gz2"`
-do
-	pos=${pos%%:*}
-	tail -c+$pos "$img" | zcat 2> /dev/null > $tmp
-	dump_config $tmp
-done
+# That didn't work, so retry after decompression.
+try_decompress '\037\213\010' xy  gunzip
+try_decompress 'BZh'          xy  bunzip2
+try_decompress '\135\0\0\0'   xxx unlzma
+try_decompress '\211\114\132' xy  'lzop -d'
 
 # Bail out:
 echo "$me: Cannot find kernel config." >&2