scripts: add extract-vmlinux

#!/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