1#!/bin/sh
2# SPDX-License-Identifier: GPL-2.0-only
3# ----------------------------------------------------------------------
4# extract-vmlinux - Extract uncompressed vmlinux from a kernel image
5#
6# Inspired from extract-ikconfig
7# (c) 2009,2010 Dick Streefland <dick@streefland.net>
8#
9# (c) 2011      Corentin Chary <corentin.chary@gmail.com>
10#
11# ----------------------------------------------------------------------
12
13check_vmlinux()
14{
15	# Use readelf to check if it's a valid ELF
16	# TODO: find a better to way to check that it's really vmlinux
17	#       and not just an elf
18	readelf -h $1 > /dev/null 2>&1
19	if [ $? -ne 0 ]; then
20		# On ARM64, the kernel might be a PE file instead
21		# and output of file command might be something like following:
22		# $ file cuttlefish_assembly/vmlinux
23		# cuttlefish_assembly/vmlinux: MS-DOS executable PE32+ executable (EFI application) Aarch64 (stripped to external PDB), for MS Windows
24		# $
25		file $1 | grep -q "MS-DOS executable" || return 1
26	fi
27
28	cat $1
29	exit 0
30}
31
32try_decompress()
33{
34	# The obscure use of the "tr" filter is to work around older versions of
35	# "grep" that report the byte offset of the line instead of the pattern.
36
37	# Try to find the header ($1) and decompress from here
38	for	pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
39	do
40		pos=${pos%%:*}
41		tail -c+$pos "$img" | $3 > $tmp 2> /dev/null
42		check_vmlinux $tmp
43	done
44}
45
46# Check invocation:
47me=${0##*/}
48img=$1
49if	[ $# -ne 1 -o ! -s "$img" ]
50then
51	echo "Usage: $me <kernel-image>" >&2
52	exit 2
53fi
54
55# Prepare temp files:
56tmp=$(mktemp /tmp/vmlinux-XXX)
57trap "rm -f $tmp" 0
58
59# That didn't work, so retry after decompression.
60try_decompress '\037\213\010' xy    gunzip
61try_decompress '\3757zXZ\000' abcde unxz
62try_decompress 'BZh'          xy    bunzip2
63try_decompress '\135\0\0\0'   xxx   unlzma
64try_decompress '\211\114\132' xy    'lzop -d'
65try_decompress '\004\"M\030'  xxx   'lz4 -d'
66try_decompress '\002!L\030'   xxx   'lz4 -d'
67try_decompress '(\265/\375'   xxx   unzstd
68
69# Finally check for uncompressed images or objects:
70check_vmlinux $img
71
72# Bail out:
73echo "$me: Cannot find vmlinux." >&2
74