1 #!/bin/sh
2 # ----------------------------------------------------------------------
3 # extract-ikconfig - Extract the .config file from a kernel image
4 #
5 # This will only work when the kernel was compiled with CONFIG_IKCONFIG.
6 #
7 # The obscure use of the "tr" filter is to work around older versions of
8 # "grep" that report the byte offset of the line instead of the pattern.
9 #
10 # (c) 2009,2010 Dick Streefland <dick@streefland.net>
11 # Licensed under the terms of the GNU General Public License.
12 # ----------------------------------------------------------------------
13
14 cf1='IKCFG_ST\037\213\010'
15 cf2='0123456789'
16
17 dump_config()
18 {
19 if pos=`tr "$cf1\n$cf2" "\n$cf2=" < "$1" | grep -abo "^$cf2"`
20 then
21 pos=${pos%%:*}
22 tail -c+$(($pos+8)) "$1" | zcat > $tmp1 2> /dev/null
23 if [ $? != 1 ]
24 then # exit status must be 0 or 2 (trailing garbage warning)
25 cat $tmp1
26 exit 0
27 fi
28 fi
29 }
30
31 try_decompress()
32 {
33 for pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
34 do
35 pos=${pos%%:*}
36 tail -c+$pos "$img" | $3 > $tmp2 2> /dev/null
37 dump_config $tmp2
38 done
39 }
40
41 # Check invocation:
42 me=${0##*/}
43 img=$1
44 if [ $# -ne 1 -o ! -s "$img" ]
45 then
46 echo "Usage: $me <kernel-image>" >&2
47 exit 2
48 fi
49
50 # Prepare temp files:
51 tmp1=/tmp/ikconfig$$.1
52 tmp2=/tmp/ikconfig$$.2
53 trap "rm -f $tmp1 $tmp2" 0
54
55 # Initial attempt for uncompressed images or objects:
56 dump_config "$img"
57
58 # That didn't work, so retry after decompression.
59 try_decompress '\037\213\010' xy gunzip
60 try_decompress '\3757zXZ\000' abcde unxz
61 try_decompress 'BZh' xy bunzip2
62 try_decompress '\135\0\0\0' xxx unlzma
63 try_decompress '\211\114\132' xy 'lzop -d'
64 try_decompress '\002\041\114\030' xyy 'lz4 -d -l'
65 try_decompress '\050\265\057\375' xxx unzstd
66
67 # Bail out:
68 echo "$me: Cannot find kernel config." >&2
69 exit 1
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