#!/bin/sh
# ----------------------------------------------------------------------
# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
#
# Inspired from extract-ikconfig
# (c) 2009,2010 Dick Streefland <[email protected]>
#
# (c) 2011 Corentin Chary <[email protected]>
#
# 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