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