FreeBSD/Linux Kernel Cross Reference
sys/scripts/extract-vmlinux

     #!/bin/sh
     # ----------------------------------------------------------------------
     # extract-vmlinux - Extract uncompressed vmlinux from a kernel image
     #
     # Inspired from extract-ikconfig
     # (c) 2009,2010 Dick Streefland <dick@streefland.net>
     #
     # (c) 2011      Corentin Chary <corentin.chary@gmail.com>
     #
    # Licensed under the GNU General Public License, version 2 (GPLv2).
    # ----------------------------------------------------------------------
    
    check_vmlinux()
    {
            # Use readelf to check if it's a valid ELF
            # TODO: find a better to way to check that it's really vmlinux
            #       and not just an elf
            readelf -h $1 > /dev/null 2>&1 || return 1
    
            cat $1
            exit 0
    }
    
    try_decompress()
    {
            # The obscure use of the "tr" filter is to work around older versions of
            # "grep" that report the byte offset of the line instead of the pattern.
    
            # Try to find the header ($1) and decompress from here
            for     pos in `tr "$1\n$2" "\n$2=" < "$img" | grep -abo "^$2"`
            do
                    pos=${pos%%:*}
                    tail -c+$pos "$img" | $3 > $tmp 2> /dev/null
                    check_vmlinux $tmp
            done
    }
    
    # Check invocation:
    me=${0##*/}
    img=$1
    if      [ $# -ne 1 -o ! -s "$img" ]
    then
            echo "Usage: $me <kernel-image>" >&2
            exit 2
    fi
    
    # Prepare temp files:
    tmp=$(mktemp /tmp/vmlinux-XXX)
    trap "rm -f $tmp" 0
    
    # Initial attempt for uncompressed images or objects:
    check_vmlinux $img
    
    # That didn't work, so retry after decompression.
    try_decompress '\037\213\010' xy    gunzip
    try_decompress '\3757zXZ\000' abcde unxz
    try_decompress 'BZh'          xy    bunzip2
    try_decompress '\135\0\0\0'   xxx   unlzma
    try_decompress '\211\114\132' xy    'lzop -d'
    
    # Bail out:
    echo "$me: Cannot find vmlinux." >&2

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