scripts/extract-ikconfig

   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, Dick Streefland <dick@streefland.net>
  11 # Licensed under the terms of the GNU General Public License.
  12 # ----------------------------------------------------------------------
  13
  14 gz1='\037\213\010'
  15 gz2='01'
  16 cf1='IKCFG_ST\037\213\010'
  17 cf2='0123456789'
  18
  19 dump_config()
  20 {
  21         if      pos=`tr "$cf1\n$cf2" "\n$cf2=" < "$1" | grep -abo "^$cf2"`
  22         then
  23                 pos=${pos%%:*}
  24                 tail -c+$(($pos+8)) "$1" | zcat -q
  25                 exit 0
  26         fi
  27 }
  28
  29 # Check invocation:
  30 me=${0##*/}
  31 img=$1
  32 if      [ $# -ne 1 -o ! -s "$img" ]
  33 then
  34         echo "Usage: $me <kernel-image>" >&2
  35         exit 2
  36 fi
  37
  38 # Initial attempt for uncompressed images or objects:
  39 dump_config "$img"
  40
  41 # That didn't work, so decompress and try again:
  42 tmp=/tmp/ikconfig$$
  43 trap "rm -f $tmp" 0
  44 for     pos in `tr "$gz1\n$gz2" "\n$gz2=" < "$img" | grep -abo "^$gz2"`
  45 do
  46         pos=${pos%%:*}
  47         tail -c+$pos "$img" | zcat 2> /dev/null > $tmp
  48         dump_config $tmp
  49 done
  50
  51 # Bail out:
  52 echo "$me: Cannot find kernel config." >&2
  53 exit 1