tools/patch_libmalloc.py

   1 #!/usr/bin/env python
   2 #
   3 # Patches the malloc() function in libmalloc.so to allocate more than the
   4 # specified number of bytes. This is needed to work around issues with the
   5 # compiler occasionally crashing.
   6 #
   7 # This script replaces the "move a1, a0" (00 80 28 25) instruction with
   8 # "addiu a1, a0, n" (24 85 nn nn), which causes the malloc function to add n to
   9 # the size parameter that was passed in.
  10
  11 import hashlib
  12 import os.path
  13 import sys
  14
  15 # file to patch
  16 filename = 'tools/ido5.3_compiler/lib/libmalloc.so'
  17 # Expected (unpatched) hash of file
  18 filehash = 'adde672b5d79b52ca3cce9a47c7cb648'
  19 # location in file to patch
  20 address = 0xAB4
  21
  22 # Get parameter
  23 if len(sys.argv) != 2:
  24     print('Usage: ' + sys.argv[0] + ' n\n    where n is the number of extra bytes to allocate in malloc()')
  25     exit(1)
  26 n = int(sys.argv[1])
  27
  28 # Original instruction "move a1, a0"
  29 oldinsn = bytearray([0x00, 0x80, 0x28, 0x25])
  30
  31 # New instruction "addiu a1, a0, n"
  32 newinsn = bytearray([0x24, 0x85, (n >> 8) & 0xFF, (n & 0xFF)])
  33
  34 # Patch the file
  35 try:
  36     with open(filename, 'rb+') as f:
  37         # Read file contents
  38         contents = bytearray(f.read())
  39
  40         # Unpatch the file by restoring original instruction
  41         contents[address:address+4] = oldinsn
  42
  43         # Verify the (unpatched) hash of the file
  44         md5 = hashlib.md5()
  45         md5.update(contents)
  46         if md5.hexdigest() != filehash:
  47             print('Error: ' + filename + ' does not appear to be the correct version.')
  48             exit(1)
  49
  50         # Patch the file
  51         if n != 0:
  52             contents[address:address+4] = newinsn
  53
  54         # Write file
  55         f.seek(0, os.SEEK_SET)
  56         f.write(contents)
  57 except IOError as e:
  58     print('Error: Could not open library file for writing: ' + str(e))