LXR qemu/scripts/signrom.py

   1#!/usr/bin/env python3
   2
   3#
   4# Option ROM signing utility
   5#
   6# Authors:
   7#  Jan Kiszka <jan.kiszka@siemens.com>
   8#
   9# This work is licensed under the terms of the GNU GPL, version 2 or later.
  10# See the COPYING file in the top-level directory.
  11
  12import sys
  13import struct
  14
  15if len(sys.argv) < 3:
  16    print('usage: signrom.py input output')
  17    sys.exit(1)
  18
  19fin = open(sys.argv[1], 'rb')
  20fout = open(sys.argv[2], 'wb')
  21
  22magic = fin.read(2)
  23if magic != b'\x55\xaa':
  24    sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1])
  25
  26size_byte = ord(fin.read(1))
  27fin.seek(0)
  28data = fin.read()
  29
  30size = size_byte * 512
  31if len(data) > size:
  32    sys.stderr.write('error: ROM is too large (%d > %d)\n' % (len(data), size))
  33    sys.exit(1)
  34elif len(data) < size:
  35    # Add padding if necessary, rounding the whole input to a multiple of
  36    # 512 bytes according to the third byte of the input.
  37    # size-1 because a final byte is added below to store the checksum.
  38    data = data.ljust(size-1, b'\0')
  39else:
  40    if ord(data[-1:]) != 0:
  41        sys.stderr.write('WARNING: ROM includes nonzero checksum\n')
  42    data = data[:size-1]
  43
  44fout.write(data)
  45
  46checksum = 0
  47for b in data:
  48    checksum = (checksum - b) & 255
  49
  50fout.write(struct.pack('B', checksum))
  51
  52fin.close()
  53fout.close()
  54