[PATCH] scripts: add extract-vmlinux

[Corentin Chary]

This script can be used to extract vmlinux from a compressed
kernel image (bzImage, etc..). It's inspired from (a subset of)
extract-ikconfig.

I don't know if this scripts really have this place in the kernel
tree, but it's something a lot of people have been looking for (mainly
people with xen < 4 that doesn't support bzImages at all).

Signed-off-by: Corentin Chary <corentin.chary@xxxxxxxxx>
---
 scripts/extract-vmlinux |   60 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)
 create mode 100755 scripts/extract-vmlinux

diff --git a/scripts/extract-vmlinux b/scripts/extract-vmlinux
new file mode 100755
index 0000000..444f404
--- /dev/null
+++ b/scripts/extract-vmlinux
@@ -0,0 +1,60 @@
+#!/bin/sh
+# ----------------------------------------------------------------------
+# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
+#
+# 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.
+#
+# Inspired from extract-ikconfig
+# (c) 2009,2010 Dick Streefland <dick@xxxxxxxxxxxxxx>
+#
+# (c) 2011      Corentin Chary <corentin.chary@xxxxxxxxx>
+# Licensed under the terms of the GNU General Public License.
+# ----------------------------------------------------------------------
+
+check_elf()
+{
+	# Use readelf to check if it's a valid ELF
+	# There is probably a better way to do that...
+	readelf -h $1 > /dev/null 2>&1 || return 1
+
+	cat $1
+	exit 0
+}
+
+try_decompress()
+{
+	for	pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
+	do
+		pos=${pos%%:*}
+		tail -c+$pos "$img" | $3 > $tmp 2> /dev/null
+		check_elf $tmp
+	done
+}
+
+# Check invocation:
+me=${0##*/}
+img=$1
+if	[ $# -ne 1 -o ! -s "$img" ]
+then
+	echo "Usage: $me <kernel-image>" >&2
+	exit 2
+fi
+
+# Prepare temp files:
+tmp=$(mktemp /tmp/vmlinux-XXX)
+trap "rm -f $tmp" 0
+
+# Initial attempt for uncompressed images or objects:
+check_elf $img
+
+# That didn't work, so retry after decompression.
+try_decompress '\037\213\010' xy    gunzip
+try_decompress '\3757zXZ\000' abcde unxz
+try_decompress 'BZh'          xy    bunzip2
+try_decompress '\135\0\0\0'   xxx   unlzma
+try_decompress '\211\114\132' xy    'lzop -d'
+
+# Bail out:
+echo "$me: Cannot find vmlinux." >&2
+exit 1
-- 
1.7.3.4

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