1 files changed, 147 insertions, 0 deletions
diff --git a/src/buildstream/sandbox/_mounter.py b/src/buildstream/sandbox/_mounter.py
new file mode 100644
index 000000000..e6054c20d
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+++ b/src/buildstream/sandbox/_mounter.py
@@ -0,0 +1,147 @@
+#
+#  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():
+    @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)