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