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scripts: add extract-vmlinux

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

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 <corentincj@iksaif.net>
Signed-off-by: Michal Marek <mmarek@suse.cz>
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1 parent 322a8b0 commit 09d481270d445d98342d8ab872f05491b6d23f8b @iksaif iksaif committed with michal42 Aug 16, 2011
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62 scripts/extract-vmlinux
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+#!/bin/sh
+# ----------------------------------------------------------------------
+# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
+#
+# Inspired from extract-ikconfig
+# (c) 2009,2010 Dick Streefland <dick@streefland.net>
+#
+# (c) 2011 Corentin Chary <corentin.chary@gmail.com>
+#
+# Licensed under the GNU General Public License, version 2 (GPLv2).
+# ----------------------------------------------------------------------
+
+check_vmlinux()
+{
+ # Use readelf to check if it's a valid ELF
+ # TODO: find a better to way to check that it's really vmlinux
+ # and not just an elf
+ readelf -h $1 > /dev/null 2>&1 || return 1
+
+ cat $1
+ exit 0
+}
+
+try_decompress()
+{
+ # 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.
+
+ # Try to find the header ($1) and decompress from here
+ 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_vmlinux $tmp
+ done
+}
+
+# Check invocation:
+me=${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_vmlinux $img
+
+# That didn't work, so retry after decompression.
+try_decompress '\037\213\010' xy gunzip
+try_decompress '\3757zXZ\000' abcde unxz
+try_decompress 'BZh' xy bunzip2
+try_decompress '\135\0\0\0' xxx unlzma
+try_decompress '\211\114\132' xy 'lzop -d'
+
+# Bail out:
+echo "$me: Cannot find vmlinux." >&2

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