scripts/check-wx-segment.py

   1 #!/usr/bin/python3
   2 # Check ELF program headers for WX segments.
   3 # Copyright (C) 2020 Free Software Foundation, Inc.
   4 # This file is part of the GNU C Library.
   5 #
   6 # The GNU C Library is free software; you can redistribute it and/or
   7 # modify it under the terms of the GNU Lesser General Public
   8 # License as published by the Free Software Foundation; either
   9 # version 2.1 of the License, or (at your option) any later version.
  10 #
  11 # The GNU C Library is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 # Lesser General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU Lesser General Public
  17 # License along with the GNU C Library; if not, see
  18 # <https://www.gnu.org/licenses/>.
  19
  20 """Check that the program headers do not contain write-exec segments."""
  21
  22 import argparse
  23 import os.path
  24 import re
  25 import sys
  26
  27 # Regular expression to extract the RWE flags field.  The
  28 # address/offset columns have varying width.
  29 RE_LOAD = re.compile(
  30     r'^  LOAD +(?:0x[0-9a-fA-F]+ +){5}([R ][W ][ E]) +0x[0-9a-fA-F]+\n\Z')
  31
  32 def process_file(path, inp, xfail):
  33     """Analyze one input file."""
  34
  35     errors = 0
  36     for line in inp:
  37         error = None
  38         if line.startswith('  LOAD '):
  39             match = RE_LOAD.match(line)
  40             if match is None:
  41                 error = 'Invalid LOAD line'
  42             else:
  43                 flags, = match.groups()
  44                 if 'W' in flags and 'E' in flags:
  45                     if xfail:
  46                         print('{}: warning: WX segment (as expected)'.format(
  47                             path))
  48                     else:
  49                         error = 'WX segment'
  50
  51         if error is not None:
  52             print('{}: error: {}: {!r}'.format(path, error, line.strip()))
  53             errors += 1
  54
  55     if xfail and errors == 0:
  56         print('{}: warning: missing expected WX segment'.format(path))
  57     return errors
  58
  59
  60 def main():
  61     """The main entry point."""
  62     parser = argparse.ArgumentParser(description=__doc__)
  63     parser.add_argument('--xfail',
  64                         help='Mark input files as XFAILed ("*" for all)',
  65                         type=str, default='')
  66     parser.add_argument('phdrs',
  67                         help='Files containing readelf -Wl output',
  68                         nargs='*')
  69     opts = parser.parse_args(sys.argv)
  70
  71     xfails = set(opts.xfail.split(' '))
  72     xfails_all = opts.xfail.strip() == '*'
  73
  74     errors = 0
  75     for path in opts.phdrs:
  76         xfail = ((os.path.basename(path) + '.phdrs') in xfails
  77                  or xfails_all)
  78         with open(path) as inp:
  79             errors += process_file(path, inp, xfail)
  80     if errors > 0:
  81         sys.exit(1)
  82
  83
  84 if __name__ == '__main__':
  85     main()