#!/bin/sh

  # SPDX-License-Identifier: GPL-2.0-only

  # ----------------------------------------------------------------------
  # 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>
  #

  # ----------------------------------------------------------------------
  
  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
  $2" "
  $2=" < "$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

  # 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'

  try_decompress '\002!L\030'   xxx   'lz4 -d'
  try_decompress '(\265/\375'   xxx   unzstd

  # Finally check for uncompressed images or objects:
  check_vmlinux $img

  # Bail out:
  echo "$me: Cannot find vmlinux." >&2