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#
# Copyright (C) 2017 Codethink Limited
#
# This program 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 of the License, or (at your option) any later version.
#
# This 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 this library. If not, see <http://www.gnu.org/licenses/>.
#
# Authors:
# Tristan Maat <tristan.maat@codethink.co.uk>
import sys
from contextlib import contextmanager
from .._exceptions import SandboxError
from .. import utils, _signals
# A class to wrap the `mount` and `umount` system commands
class Mounter(object):
@classmethod
def _mount(cls, dest, src=None, mount_type=None,
stdout=sys.stdout, stderr=sys.stderr, options=None,
flags=None):
argv = [utils.get_host_tool('mount')]
if mount_type:
argv.extend(['-t', mount_type])
if options:
argv.extend(['-o', options])
if flags:
argv.extend(flags)
if src is not None:
argv += [src]
argv += [dest]
status, _ = utils._call(
argv,
terminate=True,
stdout=stdout,
stderr=stderr
)
if status != 0:
raise SandboxError('`{}` failed with exit code {}'
.format(' '.join(argv), status))
return dest
@classmethod
def _umount(cls, path, stdout=sys.stdout, stderr=sys.stderr):
cmd = [utils.get_host_tool('umount'), '-R', path]
status, _ = utils._call(
cmd,
terminate=True,
stdout=stdout,
stderr=stderr
)
if status != 0:
raise SandboxError('`{}` failed with exit code {}'
.format(' '.join(cmd), status))
# mount()
#
# A wrapper for the `mount` command. The device is unmounted when
# the context is left.
#
# Args:
# dest (str) - The directory to mount to
# src (str) - The directory to mount
# stdout (file) - stdout
# stderr (file) - stderr
# mount_type (str|None) - The mount type (can be omitted or None)
# kwargs - Arguments to pass to the mount command, such as `ro=True`
#
# Yields:
# (str) The path to the destination
#
@classmethod
@contextmanager
def mount(cls, dest, src=None, stdout=sys.stdout,
stderr=sys.stderr, mount_type=None, **kwargs):
def kill_proc():
cls._umount(dest, stdout, stderr)
options = ','.join([key for key, val in kwargs.items() if val])
path = cls._mount(dest, src, mount_type, stdout=stdout, stderr=stderr, options=options)
try:
with _signals.terminator(kill_proc):
yield path
finally:
cls._umount(dest, stdout, stderr)
# bind_mount()
#
# Mount a directory to a different location (a hardlink for all
# intents and purposes). The directory is unmounted when the
# context is left.
#
# Args:
# dest (str) - The directory to mount to
# src (str) - The directory to mount
# stdout (file) - stdout
# stderr (file) - stderr
# kwargs - Arguments to pass to the mount command, such as `ro=True`
#
# Yields:
# (str) The path to the destination
#
# While this is equivalent to `mount --rbind`, this option may not
# exist and can be dangerous, requiring careful cleanupIt is
# recommended to use this function over a manual mount invocation.
#
@classmethod
@contextmanager
def bind_mount(cls, dest, src=None, stdout=sys.stdout,
stderr=sys.stderr, **kwargs):
def kill_proc():
cls._umount(dest, stdout, stderr)
kwargs['rbind'] = True
options = ','.join([key for key, val in kwargs.items() if val])
path = cls._mount(dest, src, None, stdout, stderr, options)
try:
with _signals.terminator(kill_proc):
# Make the rbind a slave to avoid unmounting vital devices in
# /proc
cls._mount(dest, flags=['--make-rslave'])
yield path
finally:
cls._umount(dest, stdout, stderr)
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