#!/bin/bash

# Uncompress LZMA-packed firmware kernel. This is a functional, but
# quick & dirty version of the Perl script by Enrik Berkhan shown and explained
# at http://www.wehavemorefun.de/fritzbox/index.php/EVA. There is no CRC
# calculation for the time being and also no other kind of error checking,
# always assuming the source file is okay. The advantage of this version is
# that we do not need Perl and especially no exotic LZMA package which is
# unavailable as a Debian image, for example. The opposite is true for unlzma
# which is installed on most Linux systems in general and part of busybox-tools
# as a part of Freetz in particular.

case $# in
	2)
		;;
	*)
		echo "usage: $(basename "$0") <kernel_img> <uncomp_file>" >&2
		echo "    kernel_img  - file starting with compressed kernel image," >&2
		echo "                  e.g. kernel.image or kernel.raw" >&2
		echo "    uncomp_file - uncompressed kernel output file name" >&2
		echo >&2
		echo "This tool also prints the kernel's load and entry addresses in a format which" >&2
		echo "can be parsed and re-used as parameters for tools/lzma2eva:" >&2
		echo "    load=0x94100000 entry=0x94411F50" >&2
		exit 1
esac

(
	# Get LZMA properties + dictionary size
	dd if="$1" bs=1 count=5 skip=28 2>/dev/null
	# Get uncompressed length (32-bit little-endian), pad to 64-bit
	dd if="$1" bs=1 count=4 skip=20 2>/dev/null
	dd if=/dev/zero bs=1 count=4 2>/dev/null
	# Jump to compressed data, pipe into output stream
	dd if="$1" bs=36 skip=1 2>/dev/null
) | $(dirname "$0")/unlzma > "$2" 2>/dev/null

[ $? -ne 0 ] && echo "$(basename "$0") ERROR: could not unpack kernel image" >&2 && exit 1

tmp=$(dd if="$1" bs=4 count=2 skip=1 2>/dev/null | hexdump -C | head -n 1)
length=$(printf "%d" "0x${tmp:19:2}${tmp:16:2}${tmp:13:2}${tmp:10:2}")
load_addr=$(printf "0x%X" "0x${tmp:31:2}${tmp:28:2}${tmp:25:2}${tmp:22:2}")
tmp=$(dd if="$1" bs=1 count=4 skip=$((20+length)) 2>/dev/null | hexdump -C | head -n 1)
entry_addr=$(printf "0x%X" "0x${tmp:19:2}${tmp:16:2}${tmp:13:2}${tmp:10:2}")
echo "load=$load_addr entry=$entry_addr"