#!/usr/bin/env bash
#
# Copyright (C) 2022 Ing <https://github.com/wjz304>
#
# This is free software, licensed under the MIT License.
# See /LICENSE for more information.
#
# Based on code and ideas from @jumkey

[ -z "${WORK_PATH}" ] || [ ! -d "${WORK_PATH}/include" ] && WORK_PATH="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"

calculate_run_size() {
  NUM='\([0-9a-fA-F]*[ \t]*\)'
  OUT=$(sed -n 's/^[ \t0-9]*.b[sr][sk][ \t]*'"${NUM}${NUM}${NUM}${NUM}"'.*/0x\1 0x\4/p')

  if [ -z "${OUT}" ]; then
    echo "Never found .bss or .brk file offset" >&2
    return 1
  fi

  read -r sizeA offsetA sizeB offsetB <<<"$(echo ${OUT} | awk '{printf "%d %d %d %d", strtonum($1), strtonum($2), strtonum($3), strtonum($4)}')"

  runSize=$((offsetA + sizeA + sizeB))

  # BFD linker shows the same file offset in ELF.
  if [ "${offsetA}" -ne "${offsetB}" ]; then
    # Gold linker shows them as consecutive.
    endSize=$((offsetB + sizeB))
    if [ "${endSize}" -ne "${runSize}" ]; then
      printf "sizeA: 0x%x\n" ${sizeA} >&2
      printf "offsetA: 0x%x\n" ${offsetA} >&2
      printf "sizeB: 0x%x\n" ${sizeB} >&2
      printf "offsetB: 0x%x\n" ${offsetB} >&2
      echo ".bss and .brk are non-contiguous" >&2
      return 1
    fi
  fi

  printf "%d\n" ${runSize}
  return 0
}

# Adapted from: scripts/Makefile.lib
# Usage: size_append FILE [FILE2] [FILEn]...
# Output: LE HEX with size of file in bytes (to STDOUT)
file_size_le() {
  printf "$(
    local dec_size=0
    for F in "$@"; do dec_size=$((dec_size + $(stat -c "%s" "${F}"))); done
    printf "%08x\n" "${dec_size}" | sed 's/\(..\)/\1 /g' | {
      read -r ch0 ch1 ch2 ch3
      for ch in "${ch3}" "${ch2}" "${ch1}" "${ch0}"; do printf '%s%03o' '\' "$((0x${ch}))"; done
    }
  )"
}

size_le() {
  printf "$(
    printf "%08x\n" "${@}" | sed 's/\(..\)/\1 /g' | {
      read -r ch0 ch1 ch2 ch3
      for ch in "${ch3}" "${ch2}" "${ch1}" "${ch0}"; do printf '%s%03o' '\' "$((0x${ch}))"; done
    }
  )"
}

VMLINUX_MOD=${1}
ZIMAGE_MOD=${2}

KVER=$(strings "${VMLINUX_MOD}" | grep -Eo "Linux version [0-9]+\.[0-9]+\.[0-9]+" | head -1 | awk '{print $3}')
if [ "$(echo "${KVER:-4}" | cut -d'.' -f1)" -lt 5 ]; then
  # Kernel version 4.x or 3.x (bromolow)
  # zImage_head           16494
  # payload(
  #   vmlinux.bin         x
  #   padding             0xf00000-x
  #   vmlinux.bin size    4
  # )                     0xf00004
  # zImage_tail(
  #   unknown             72
  #   run_size            4
  #   unknown             30
  #   vmlinux.bin size    4
  #   unknown             114460
  # )                     114570
  # crc32                 4
  gzip -dc "${WORK_PATH}/bzImage-template-v4.gz" >"${ZIMAGE_MOD}" || exit 1

  dd if="${VMLINUX_MOD}" of="${ZIMAGE_MOD}" bs=16494 seek=1 conv=notrunc || exit 1
  file_size_le "${VMLINUX_MOD}" | dd of="${ZIMAGE_MOD}" bs=15745134 seek=1 conv=notrunc || exit 1
  file_size_le "${VMLINUX_MOD}" | dd of="${ZIMAGE_MOD}" bs=15745244 seek=1 conv=notrunc || exit 1

  RUN_SIZE=$(objdump -h "${VMLINUX_MOD}" | calc_run_size)
  size_le "${RUN_SIZE}" | dd of="${ZIMAGE_MOD}" bs=15745210 seek=1 conv=notrunc || exit 1
  size_le "$((16#$(crc32 "${ZIMAGE_MOD}" | awk '{print $1}') ^ 0xFFFFFFFF))" | dd of="${ZIMAGE_MOD}" conv=notrunc oflag=append || exit 1
else
  # Kernel version 5.x
  gzip -dc "${WORK_PATH}/bzImage-template-v5.gz" >"${ZIMAGE_MOD}" || exit 1

  dd if="${VMLINUX_MOD}" of="${ZIMAGE_MOD}" bs=14561 seek=1 conv=notrunc || exit 1
  file_size_le "${VMLINUX_MOD}" | dd of="${ZIMAGE_MOD}" bs=34463421 seek=1 conv=notrunc || exit 1
  file_size_le "${VMLINUX_MOD}" | dd of="${ZIMAGE_MOD}" bs=34479132 seek=1 conv=notrunc || exit 1
  #  RUN_SIZE=$(objdump -h "${VMLINUX_MOD}" | calc_run_size)
  #  size_le "${RUN_SIZE}" | dd of="${ZIMAGE_MOD}" bs=34626904 seek=1 conv=notrunc || exit 1
  size_le "$((16#$(crc32 "${ZIMAGE_MOD}" | awk '{print $1}') ^ 0xFFFFFFFF))" | dd of="${ZIMAGE_MOD}" conv=notrunc oflag=append || exit 1
fi