util/exynos/fixed_cksum.py

   1 #!/usr/bin/env python3
   2 #
   3 # SPDX-License-Identifier: BSD-3-Clause
   4
   5 """
   6 This utility computes and fills Exynos ROM checksum (for BL1 or BL2).
   7 (Algorithm from U-Boot: tools/mkexynosspl.c)
   8
   9 Input: IN OUT DATA_SIZE
  10
  11 Output:
  12
  13   IN padded out to DATA_SIZE, checksum at the end, written to OUT.
  14 """
  15
  16 import struct
  17 import sys
  18
  19 def main(argv):
  20   if len(argv) != 4:
  21     exit('usage: %s IN OUT DATA_SIZE' % argv[0])
  22
  23   in_name, out_name = argv[1:3]
  24   size = int(argv[3], 0)
  25   checksum_format = "<I"
  26   with open(in_name, "rb") as in_file, open(out_name, "wb") as out_file:
  27     data = in_file.read()
  28     checksum_size = struct.calcsize(checksum_format)
  29     data_size = size - checksum_size
  30     assert len(data) <= data_size
  31     checksum = struct.pack(checksum_format, sum(data))
  32     out_file.write(data + bytearray(data_size - len(data)) + checksum)
  33
  34
  35 if __name__ == '__main__':
  36   main(sys.argv)