LPC.py

00001 """
00002 mbed SDK
00003 Copyright (c) 2011-2013 ARM Limited
00004 
00005 Licensed under the Apache License, Version 2.0 (the "License");
00006 you may not use this file except in compliance with the License.
00007 You may obtain a copy of the License at
00008 
00009     http://www.apache.org/licenses/LICENSE-2.0
00010 
00011 Unless required by applicable law or agreed to in writing, software
00012 distributed under the License is distributed on an "AS IS" BASIS,
00013 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00014 See the License for the specific language governing permissions and
00015 limitations under the License.
00016 
00017 
00018 http://www.nxp.com/documents/user_manual/UM10360.pdf
00019 
00020 32.3.1.1 Criterion for Valid User Code
00021 The reserved Cortex-M3 exception vector location 7 (offset 0x1C in the vector table)
00022 should contain the 2's complement of the check-sum of table entries 0 through 6. This
00023 causes the checksum of the first 8 table entries to be 0. The boot loader code checksums
00024 the first 8 locations in sector 0 of the flash. If the result is 0, then execution control is
00025 transferred to the user code.
00026 """
00027 from struct import unpack, pack
00028 
00029 
00030 def patch(bin_path):
00031     with open(bin_path, 'r+b') as bin:
00032         # Read entries 0 through 6 (Little Endian 32bits words)
00033         vector = [unpack('<I', bin.read(4))[0] for _ in range(7)]
00034 
00035         # location 7 (offset 0x1C in the vector table) should contain the 2's
00036         # complement of the check-sum of table entries 0 through 6
00037         bin.seek(0x1C)
00038         bin.write(pack('<I', (~sum(vector) + 1) & 0xFFFFFFFF))
00039 
00040 
00041 def is_patched(bin_path):
00042     with open(bin_path, 'rb') as bin:
00043         # The checksum of the first 8 table entries should be 0
00044         return (sum([unpack('<I', bin.read(4))[0] for _ in range(8)]) & 0xFFFFFFFF) == 0
00045 
00046 
00047 if __name__ == '__main__':
00048     bin_path = "C:/Users/emimon01/releases/emilmont/build/test/LPC1768/ARM/MBED_A1/basic.bin"
00049     patch(bin_path)
00050     assert is_patched(bin_path), "The file is not patched"