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 
13 check_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 
32 try_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 $tmp
43 	done
44 }
45 
46 # Check invocation:
47 me=${0##*/}
48 img=$1
49 if	[ $# -ne 1 -o ! -s "$img" ]
50 then
51 	echo "Usage: $me <kernel-image>" >&2
52 	exit 2
53 fi
54 
55 # Prepare temp files:
56 tmp=$(mktemp /tmp/vmlinux-XXX)
57 trap "rm -f $tmp" 0
58 
59 # That didn't work, so retry after decompression.
60 try_decompress '\037\213\010' xy    gunzip
61 try_decompress '\3757zXZ\000' abcde unxz
62 try_decompress 'BZh'          xy    bunzip2
63 try_decompress '\135\0\0\0'   xxx   unlzma
64 try_decompress '\211\114\132' xy    'lzop -d'
65 try_decompress '\004\"M\030'  xxx   'lz4 -d'
66 try_decompress '\002!L\030'   xxx   'lz4 -d'
67 try_decompress '(\265/\375'   xxx   unzstd
68 
69 # Finally check for uncompressed images or objects:
70 check_vmlinux $img
71 
72 # Bail out:
73 echo "$me: Cannot find vmlinux." >&2
74