LXR qemu/scripts/signrom.py

   1from __future__ import print_function
   2#
   3# Option ROM signing utility
   4#
   5# Authors:
   6#  Jan Kiszka <jan.kiszka@siemens.com>
   7#
   8# This work is licensed under the terms of the GNU GPL, version 2 or later.
   9# See the COPYING file in the top-level directory.
  10
  11import sys
  12import struct
  13
  14if len(sys.argv) < 3:
  15    print('usage: signrom.py input output')
  16    sys.exit(1)
  17
  18fin = open(sys.argv[1], 'rb')
  19fout = open(sys.argv[2], 'wb')
  20
  21magic = fin.read(2)
  22if magic != b'\x55\xaa':
  23    sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1])
  24
  25size_byte = ord(fin.read(1))
  26fin.seek(0)
  27data = fin.read()
  28
  29size = size_byte * 512
  30if len(data) > size:
  31    sys.stderr.write('error: ROM is too large (%d > %d)\n' % (len(data), size))
  32    sys.exit(1)
  33elif len(data) < size:
  34    # Add padding if necessary, rounding the whole input to a multiple of
  35    # 512 bytes according to the third byte of the input.
  36    # size-1 because a final byte is added below to store the checksum.
  37    data = data.ljust(size-1, b'\0')
  38else:
  39    if ord(data[-1:]) != 0:
  40        sys.stderr.write('WARNING: ROM includes nonzero checksum\n')
  41    data = data[:size-1]
  42
  43fout.write(data)
  44
  45checksum = 0
  46for b in data:
  47    # catch Python 2 vs. 3 differences
  48    if isinstance(b, int):
  49        checksum += b
  50    else:
  51        checksum += ord(b)
  52checksum = (256 - checksum) % 256
  53
  54# Python 3 no longer allows chr(checksum)
  55fout.write(struct.pack('B', checksum))
  56
  57fin.close()
  58fout.close()
  59