sys-devel/gcc/files/sysroot_wrapper.hardened

#!/usr/bin/python

# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# This script is a meta-driver for the toolchain. It transforms the command
# line to allow the following:
# 1. This script ensures that '--sysroot' is passed to whatever it is wrapping.
#
# 2. It adds hardened flags to gcc invocation. The hardened flags are:
#   -fstack-protector-strong
#   -fPIE
#   -pie
#   -D_FORTIFY_SOURCE=2
#
# It can disable -fPIE -pie by checking if -nopie is passed to gcc. In this
# case it removes -nopie as it is a non-standard flag.
#
# 3. Enable clang diagnostics with -clang-syntax option
#
# 4. Add new -print-cmdline option to print the command line before executon
#
# 5. Enable clang codegen.
# This is currently implemented as two loops on the list of arguments. The
# first loop # identifies hardening flags, as well as determining if clang
# invocation is specified. The second loop build command line for clang
# invocation as well adjusting gcc command line.
#
# This implementation ensure compile time of default path remains mostly
# the same.
#
# There is a similar hardening wrapper that wraps ld and adds -z now -z relro
# to the link command line (see ldwrapper).
#
# To use:
#   mv <tool> <tool>.real
#   ln -s <path_to_sysroot_wrapper> <tool>

from __future__ import print_function

import errno
import os
import re
import sys

# Get target architecture, 'armv7a-cros-linux-gnueabi' or
# 'x86_64-cros-linux-gnu', etc.
gcc_comp = os.path.basename(sys.argv[0])
arch = '-'.join(gcc_comp.split('-')[0:-1])

# Full hardening. Some/all of these may be discarded depending on
# other flags.
# Temporarily disable function splitting because of chromium:434751.
flags_to_add = set(['-fstack-protector-strong', '-fPIE', '-pie',
                    '-D_FORTIFY_SOURCE=2',
                    '-fno-omit-frame-pointer',
                    '-Wno-deprecated-declarations'])
x86_disable_flags = set(['-mno-movbe'])

gcc_flags = ['-frecord-gcc-switches',
             '-fno-reorder-blocks-and-partition',
             '-Wno-unused-local-typedefs',
             '-Wno-maybe-uninitialized',
            ]

# Only FORTIFY_SOURCE hardening flag is applicable for clang.
clang_flags = ['-Qunused-arguments']

# If -clang-syntax is present or the command line uses clang instead of gcc.
invoke_clang = False

# If -print-cmdline is present.
print_cmdline = False

# If ccache should be used automatically.
use_ccache = True  # @CCACHE_DEFAULT@ Keep this comment for code.

fstack = set(['-D__KERNEL__', '-fno-stack-protector', '-nodefaultlibs',
              '-nostdlib'])
fPIE = set(['-D__KERNEL__', '-fPIC', '-fPIE', '-fno-PIC', '-fno-PIE',
            '-fno-pic', '-fno-pie', '-fpic', '-fpie', '-nopie',
            '-nostartfiles', '-nostdlib', '-pie', '-static'])
pie = set(['-D__KERNEL__', '-A', '-fno-PIC', '-fno-PIE', '-fno-pic', '-fno-pie',
           '-nopie', '-nostartfiles', '-nostdlib', '-pie', '-r', '--shared',
           '-shared', '-static'])
sse = set(['-msse3', '-mssse3', '-msse4.1', '-msse4.2', '-msse4', '-msse4a'])
wrapper_only_options = set(['-clang-syntax', '-print-cmdline',
                            '-nopie', '-noccache'])

myargs = sys.argv[1:]

if fstack.intersection(myargs):
  flags_to_add.remove('-fstack-protector-strong')
  flags_to_add.add('-fno-stack-protector')
if fPIE.intersection(myargs):
  flags_to_add.remove('-fPIE')
if pie.intersection(myargs):
  flags_to_add.remove('-pie')
print_cmdline = '-print-cmdline' in myargs
clang_cmdline = clang_flags + list(flags_to_add)
gcc_flags += list(flags_to_add)
clang_codegen = sys.argv[0].split('-')[-1] in ('clang', 'clang++')
if '-fstack-check' in myargs:
  print('Option "-fstack-check" is not supported. See crbug.com/485492',
        file=sys.stderr)
  sys.exit(1)

# We will start to enable ASAN for cros-workon packages.
# For ASAN, if a library is built with ASAN, then all the binaries that use
# this library should at lease link against ASAN.
# Our solution is to add '-fsanitize=address' to LDFLAGS for asan bot.
# This causes another problem. Packages that are built with gcc.real have the
# '-fsanitize=address' option in the link time. We use clang for all asan
# built. This is a conflict. Our solution is if we see a gcc command with
# '-fsanitize=address', we first try to run it without '-fsanitize=address'.
# If it is successful, then we are fine. otherwise, we check the output of the
# command, if it contains some thing like undefinited symbol "asan_init", we
# invoke clang and run again. If there is an error in the gcc command, that is
# not related to ASAN, we just exit.

ASAN_FLAG = '-fsanitize=address'
# some package will transfer '-fsanitize=address' to '-Wl,-fsanitize=address'.
myargs = [ASAN_FLAG if ASAN_FLAG in x else x for x in myargs]
link_with_asan = not clang_codegen and ASAN_FLAG in myargs
clang_codegen |= link_with_asan
invoke_clang = '-clang-syntax' in myargs or clang_codegen

if '-noccache' in myargs or clang_codegen and not link_with_asan:
  # TODO make clang work with ccache.
  # Clang does not work with ccache well. At lease it fails at
  # package adhd.

  # Only explicitly disable so we can set defaults up top.
  use_ccache = False
cmdline = [x for x in myargs if x not in wrapper_only_options]

if re.match(r'i.86|x86_64', os.path.basename(sys.argv[0])):
  cmdline.extend(x86_disable_flags)

if not invoke_clang:
  gcc_cmdline = cmdline
else:
  import subprocess
  # Gcc flags to remove from the clang command line.
  # TODO: Once clang supports gcc compatibility mode, remove
  # these checks.
  #
  # Use of -Qunused-arguments allows this set to be small, just those
  # that clang still warns about.
  clang_unsupported = set(['-pass-exit-codes', '-Ofast', '-Wclobbered',
                           '-Wunsafe-loop-optimizations', '-Wlogical-op',
                           '-Wmissing-parameter-type', '-Woverride-init',
                           '-Wold-style-declaration', '-Wno-psabi',
                           '-Wno-unused-local-typedefs',
                           '-mno-movbe',
                          ])
  clang_unsupported_prefixes = ('-Wstrict-aliasing=', '-finline-limit=')

  # clang with '-ftrapv' generates 'call __mulodi4', which is only implemented
  # in compiler-rt library. However compiler-rt library only has i386/x86_64
  # backends (see '/usr/lib/clang/3.7.0/lib/linux/libclang_rt.*'). Gcc, on the
  # other hand, generate 'call __mulvdi3', which is implemented in libgcc. See
  # bug chromium:503229.
  clang_arm_options_to_be_discarded = set(['-ftrapv'])

  # Clang may use different options for the same or similar functionality.
  gcc_to_clang = {
      '-Wno-error=unused-but-set-variable': '-Wno-error=unused-variable',
      '-Wno-error=maybe-uninitialized': '-Wno-error=uninitialized',
      '-Wno-unused-but-set-variable': '-Wno-unused-variable',
      '-Wunused-but-set-variable': '-Wunused-variable',
      '-fstack-protector-strong': '-fstack-protector-all',
      '-fvisibility=internal': '-fvisibility=hidden',
      '-Wno-error=cpp': '-Wno-#warnings',
  }

  # If these options are specified, do not run clang, even if -clang-syntax is
  # specified.
  # This is mainly for utilities that depend on compiler output.
  skip_clang_prefixes = ('-print-', '-dump', '@')
  skip_clang_set = set(['-', '-E', '-M'])

  # Reset gcc cmdline too. Only change is to remove -Xclang-only
  # options if specified.
  gcc_cmdline = []

  skip_clang = False
  for flag in cmdline:
    if (not clang_codegen and
        (flag.startswith(skip_clang_prefixes) or
         flag in skip_clang_set or
         flag.endswith('.S'))):
      skip_clang = True
    elif not (flag in clang_unsupported or
              flag.startswith(clang_unsupported_prefixes)):
      # Strip off -Xclang-only= if present.
      if flag.startswith('-Xclang-only='):
        opt = flag.partition('=')[2]
        clang_cmdline.append(opt)
        # No need to add to gcc_cmdline.
        continue
      elif flag in gcc_to_clang.keys():
        clang_cmdline.append(gcc_to_clang[flag])
      elif (not (arch == 'armv7a-cros-linux-gnueabi' and
                 flag in clang_arm_options_to_be_discarded)):
        clang_cmdline.append(flag)
    gcc_cmdline.append(flag)


def get_proc_cmdline(pid):
  with open('/proc/%i/cmdline' % pid) as fp:
    return fp.read().replace('\0', ' ')
  return None


def get_proc_status(pid, item):
  with open('/proc/%i/status' % pid) as fp:
    for line in fp:
      m = re.match(r'%s:\s*(.*)' % re.escape(item), line)
      if m:
        return m.group(1)
  return None


def log_parent_process_tree(log, ppid):
  depth = 0

  while ppid > 1:
    cmd = get_proc_cmdline(ppid)
    log.warning(' %*s {%5i}: %s' % (depth, '', ppid, cmd))

    ppid = get_proc_status(ppid, 'PPid')
    if not ppid:
      break
    ppid = int(ppid)
    depth += 2


def get_linker_path(cmd):
  """Return the a directory which contains an 'ld' that gcc is using.

  We need to provide a directory that contains the right ld for clang.
  If we use realpath for this function, it will return the dirctory that
  the 'ld' inside it is a symbolic link to ld.bfd. By default, clang will
  use the 'ld' inside the directory after '-B', So clang will use bfd
  linker even gcc uses gold linker. To make clang use the same linker as gcc,
  We use readlink so that we provide a directory that contains 'ld' which is
  a symbolick link pointing to the real linker that gcc is using.
  """

  for path in os.environ['PATH'].split(':'):
    cmd_path = os.path.join(path, cmd)
    if os.path.exists(cmd_path):
      cmd_full = os.readlink(cmd_path)
      return os.path.dirname(cmd_full)
  return None


def link_asan():
  """link process when '-fsanitize=address' appears in a gcc command."""
  orig_gcc_cmdline = [x for x in gcc_cmdline if ASAN_FLAG not in x]
  gcc_execargs = (execargs + [real_gcc] + gcc_flags + orig_gcc_cmdline)

  p = subprocess.Popen(gcc_execargs,
                       stdout=subprocess.PIPE,
                       stderr=subprocess.PIPE)
  out, err = p.communicate()
  errorcode = p.returncode
  found_clang_undef = False
  if (out and '__asan_' in out or
      err and '__asan_' in err):
    found_clang_undef = True

  if errorcode != 0 and found_clang_undef:
    if print_cmdline:
      print('%s %s\n' % (clang_comp, ' '.join(clang_cmdline)))
    clang_execargs = [clang_comp] + clang_cmdline
    sys.stdout.flush()
    os.execv(clang_comp, clang_execargs)
  else:
    if print_cmdline:
      print('[%s] %s' % (argv0, ' '.join(gcc_execargs)))
    if out:
      print(out)
    if err:
      print(err, file=sys.stderr)
    sys.exit(errorcode)


def get_gomacc_command():
  """Return the gomacc command if it is found in $GOMACC_PATH."""
  gomacc = os.environ.get('GOMACC_PATH')
  if gomacc and os.path.isfile(gomacc):
    return gomacc
  return None


def syntax_check_with_clang(clang_comp, clang_cmdline):
  """Execute clang for syntax checking."""
  command = [clang_comp] + clang_cmdline
  gomacc = get_gomacc_command()
  if gomacc:
    command.insert(0, gomacc)
  if print_cmdline:
    print('%s\n' % ' '.join(command))
  p = subprocess.Popen(command)
  p.wait()
  if p.returncode != 0:
    sys.exit(p.returncode)


def handle_exec_exception(exc):
  """Analyze compiler execution errors."""
  if use_ccache and exc.errno == errno.ENOENT:
    print('error: make sure you install ccache\n', file=sys.stderr)
  print('error: execution of (%s, %s) failed' % (argv0, execargs), file=sys.stderr)
  raise


def exec_and_bisect(execargs, bisect_stage):
  """Execute compiler, return and invoke bisection driver."""
  import bisect

  try:
    retval = bisect.exec_and_return(execargs)
  except OSError as e:
    handle_exec_exception(e)

  if retval != 0:
    sys.exit(retval)

  bisect.bisect_driver(bisect_stage, execargs)

  sys.exit(0)


sysroot = os.environ.get('SYSROOT', '')
if sysroot:
  clang_cmdline.insert(0, '--sysroot=%s' % sysroot)
  gcc_cmdline.insert(0, '--sysroot=%s' % sysroot)
else:
  import logging
  import logging.handlers
  import traceback

  log_file = '/tmp/sysroot_wrapper.error'

  log = logging.getLogger('sysroot_wrapper')
  log.setLevel(logging.DEBUG)

  handler = logging.handlers.RotatingFileHandler(log_file, maxBytes=0x20000000,
                                                 backupCount=1)
  formatter = logging.Formatter('%(asctime)s %(message)s')
  handler.setFormatter(formatter)
  log.addHandler(handler)

  log.warning('Invocation with missing SYSROOT: %s' % ' '.join(sys.argv))
  try:
    log_parent_process_tree(log, os.getppid())
  except IOError:
    log.error('%s' % traceback.format_exc())

  try:
    # The logging module does not support setting permissions.
    os.chmod(log_file, 0666)
  except OSError:
    pass

if invoke_clang and not skip_clang:
  clang_comp = os.environ.get('CLANG', '/usr/bin/clang')

  # Check for clang or clang++.
  if sys.argv[0].endswith('++'):
    clang_comp += '++'

  # Specify the target for clang.
  linker = arch + '-ld'
  linker_path = get_linker_path(linker)
  clang_cmdline += ['-B' + linker_path]
  if re.match(r'i.86', arch):
    # We can not set -target for x86 because our target is i686-pc-linux-gnu.
    # If the target is set, it will search for libclang_rt.asan-i686.a
    # when linking against ASAN. However, this file does not exist.
    # The libclang_rt.asan-i386.a is there, but we can not set target to
    # i386-pc-linux-gnu, because the i386-pc-linux-gnu-ld does not exist.
    clang_cmdline += ['-m32']
  else:
    clang_cmdline += ['-target', arch]

  # All armv7a systems are built with hardfp, unlike gcc, which has
  # "-mfloat-abi" baked in compiler binaries in configuration phase, for clang,
  # we share the same binary for all backends, so here we enfore hardfp via
  # command line.
  if arch == "armv7a-cros-linux-gnueabi":
    clang_cmdline += ['-mfloat-abi=hard']

  if not clang_codegen:
    clang_cmdline.append('-fsyntax-only')

  if not clang_codegen:
    syntax_check_with_clang(clang_comp, clang_cmdline)

execargs = []
real_gcc = '%s.real' % sys.argv[0]
gomacc = get_gomacc_command()
if gomacc:
  argv0 = gomacc
  execargs += [gomacc]
elif use_ccache:
  # Portage likes to set this for us when it has FEATURES=-ccache.
  # The other vars we need to setup manually because of tools like
  # scons that scrubs the env before we get executed.
  os.environ.pop('CCACHE_DISABLE', None)

  # We should be able to share the objects across compilers as
  # the pre-processed output will differ.  This allows boards
  # that share compiler flags (like x86 boards) to share caches.
  ccache_dir = '/var/cache/distfiles/ccache'
  os.environ['CCACHE_DIR'] = ccache_dir

  # If RESTRICT=sandbox is enabled, then sandbox won't be setup,
  # and the env vars won't be available for appending.
  if 'SANDBOX_WRITE' in os.environ:
    os.environ['SANDBOX_WRITE'] += ':%s' % ccache_dir

  # We need to get ccache to make relative paths from within the
  # sysroot.  This lets us share cached files across boards (if
  # all other things are equal of course like CFLAGS) as well as
  # across versions.  A quick test is something like:
  #   $ export CFLAGS='-O2 -g -pipe' CXXFLAGS='-O2 -g -pipe'
  #   $ BOARD=x86-alex
  #   $ cros_workon-$BOARD stop cros-disks
  #   $ emerge-$BOARD cros-disks
  #   $ cros_workon-$BOARD start cros-disks
  #   $ emerge-$BOARD cros-disks
  #   $ BOARD=amd64-generic
  #   $ cros_workon-$BOARD stop cros-disks
  #   $ emerge-$BOARD cros-disks
  #   $ cros_workon-$BOARD start cros-disks
  #   $ emerge-$BOARD cros-disks
  # All of those will get cache hits (ignoring the first one
  # which will seed the cache) due to this setting.
  if sysroot:
    os.environ['CCACHE_BASEDIR'] = sysroot

  # Minor speed up as we don't care about this in general.
  # os.environ['CCACHE_NOSTATS'] = 'no'
  # Useful for debugging.
  # os.environ['CCACHE_LOG'] = '/dev/stderr'

  # The gcc ebuild takes care of nuking the cache in the whenever it revbumps
  # in a way that matters, so we should be able to disable ccache's check.
  # We've found in practice though that sometimes that doesn't happen.  Since
  # the default check is cheap (it's a stat() in mtime mode), keep it enabled.
  # os.environ['CCACHE_COMPILERCHECK'] = 'none'

  # Make sure we keep the cached files group writable.
  os.environ['CCACHE_UMASK'] = '002'

  argv0 = '/usr/bin/ccache'
  execargs += ['ccache']
else:
  argv0 = real_gcc

if link_with_asan:
  link_asan()

if clang_codegen:
  execargs += [clang_comp] + clang_cmdline
  argv0 = clang_comp
else:
  execargs += [real_gcc] + gcc_flags + gcc_cmdline

if print_cmdline:
  print('[%s] %s' % (argv0, ' '.join(execargs)))

sys.stdout.flush()

bisect_stage = os.environ.get('BISECT_STAGE')
if not bisect_stage:
  try:
    os.execv(argv0, execargs)
  except OSError as e:
    handle_exec_exception(e)

# Only comes here if doing bisection.
exec_and_bisect(execargs, bisect_stage)