#!/bin/bash
#
# extract-ikconfig -- a more human readable script to extract kernel config.gz
#
# Author: Wu Zhangjin <lzufalcon@163.com>, 2019.07.19
# Copyright (C) 2016-2021 Wu Zhangjin <falcon@ruma.tech>
#
# ref: kernel/configs.c: .rodata ( ... IKCFG_ST.........................IKCFG_ED ... )
#                                              ^ kernel/config_data.gz ^
#      scripts/extract-ikconfig
#

# Check invocation:
me=${0##*/}
img=$1
if [ $# -ne 1 -o ! -s "$img" ]; then
  echo "Usage: $me <kernel-image>" >&2
  exit 2
fi

pos=$(grep -abo "IKCFG_ST" $img)
[ $? -ne 0 ] && echo "$me: Cannot find kernel config." >&2 && exit 1

pos=${pos%%:*}
kcfg_start=$(($pos+8))

pos=$(grep -abo "IKCFG_ED" $img)
pos=${pos%%:*}
kcfg_end=$(($pos-1))

kcfg_bytes=$(($kcfg_end-$kcfg_start+1))

dd if=$img bs=1 skip=$kcfg_start count=$kcfg_bytes | zcat