scripts/extract-vmlinux

   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 me=${0##*/}
  14
  15 check_vmlinux()
  16 {
  17         if file "$1" | grep -q 'Linux kernel.*boot executable' ||
  18                 readelf -h "$1" > /dev/null 2>&1
  19         then
  20                 cat "$1"
  21                 echo "$me: Extracted vmlinux using '$2' from offset $3" >&2
  22                 exit 0
  23         fi
  24 }
  25
  26 try_decompress()
  27 {
  28         # The obscure use of the "tr" filter is to work around older versions of
  29         # "grep" that report the byte offset of the line instead of the pattern.
  30
  31         # Try to find the header ($1) and decompress from here
  32         for     pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
  33         do
  34                 pos=${pos%%:*}
  35                 tail -c+$pos "$img" | $3 > $tmp 2> /dev/null
  36                 check_vmlinux $tmp "$3" $pos
  37         done
  38 }
  39
  40 # Check invocation:
  41 img=$1
  42 if      [ $# -ne 1 -o ! -s "$img" ]
  43 then
  44         echo "Usage: $me <kernel-image>" >&2
  45         exit 2
  46 fi
  47
  48 # Prepare temp files:
  49 tmp=$(mktemp /tmp/vmlinux-XXX)
  50 trap "rm -f $tmp" 0
  51
  52 # That didn't work, so retry after decompression.
  53 try_decompress '\037\213\010' xy    gunzip
  54 try_decompress '\3757zXZ\000' abcde unxz
  55 try_decompress 'BZh'          xy    bunzip2
  56 try_decompress '\135\0\0\0'   xxx   unlzma
  57 try_decompress '\211\114\132' xy    'lzop -d'
  58 try_decompress '\002!L\030'   xxx   'lz4 -d'
  59 try_decompress '(\265/\375'   xxx   unzstd
  60
  61 # Finally check for uncompressed images or objects:
  62 check_vmlinux "$img" cat 0
  63
  64 # Bail out:
  65 echo "$me: Cannot find vmlinux." >&2