#!/usr/bin/python3

# Check ELF program headers for WX segments.

# Copyright (C) 2020 Free Software Foundation, Inc.

# This file is part of the GNU C Library.

#

# The GNU C Library is free software; you can redistribute it and/or

# modify it under the terms of the GNU Lesser General Public

# License as published by the Free Software Foundation; either

# version 2.1 of the License, or (at your option) any later version.

#

# The GNU C Library is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# Lesser General Public License for more details.

#

# You should have received a copy of the GNU Lesser General Public

# License along with the GNU C Library; if not, see

# <https://www.gnu.org/licenses/>.

"""Check that the program headers do not contain write-exec segments."""

import argparse

import os.path

import re

import sys

# Regular expression to extract the RWE flags field.  The

# address/offset columns have varying width.

RE_LOAD = re.compile(

    r'^  LOAD +(?:0x[0-9a-fA-F]+ +){5}([R ][W ][ E]) +0x[0-9a-fA-F]+\n\Z')

def process_file(path, inp, xfail):

    """Analyze one input file."""

    errors = 0

    for line in inp:

        error = None

        if line.startswith('  LOAD '):

            match = RE_LOAD.match(line)

            if match is None:

                error = 'Invalid LOAD line'

            else:

                flags, = match.groups()

                if 'W' in flags and 'E' in flags:

                    if xfail:

                        print('{}: warning: WX segment (as expected)'.format(

                            path))

                    else:

                        error = 'WX segment'

        if error is not None:

            print('{}: error: {}: {!r}'.format(path, error, line.strip()))

            errors += 1

    if xfail and errors == 0:

        print('{}: warning: missing expected WX segment'.format(path))

    return errors

def main():

    """The main entry point."""

    parser = argparse.ArgumentParser(description=__doc__)

    parser.add_argument('--xfail',

                        help='Mark input files as XFAILed ("*" for all)',

                        type=str, default='')

    parser.add_argument('phdrs',

                        help='Files containing readelf -Wl output',

                        nargs='*')

    opts = parser.parse_args(sys.argv)

    xfails = set(opts.xfail.split(' '))

    xfails_all = opts.xfail.strip() == '*'

    errors = 0

    for path in opts.phdrs:

        xfail = ((os.path.basename(path) + '.phdrs') in xfails

                 or xfails_all)

        with open(path) as inp:

            errors += process_file(path, inp, xfail)

    if errors > 0:

        sys.exit(1)

if __name__ == '__main__':

    main()