Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 69 insertions, 0 deletions

diff --git a/pkg/sentry/fs/proc/fs.go b/pkg/sentry/fs/proc/fs.go
new file mode 100644
index 000000000..072d00beb
--- /dev/null
+++ b/pkg/sentry/fs/proc/fs.go
@@ -0,0 +1,69 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package proc
+
+import (
+	"fmt"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+)
+
+// filesystem is a procfs.
+type filesystem struct{}
+
+func init() {
+	fs.RegisterFilesystem(&filesystem{})
+}
+
+// FilesystemName is the name underwhich the filesystem is registered.
+// Name matches fs/proc/root.c:proc_fs_type.name.
+const FilesystemName = "proc"
+
+// Name is the name of the file system.
+func (*filesystem) Name() string {
+	return FilesystemName
+}
+
+// AllowUserMount allows users to mount(2) this file system.
+func (*filesystem) AllowUserMount() bool {
+	return true
+}
+
+// Flags returns that there is nothing special about this file system.
+//
+// In Linux, proc returns FS_USERNS_VISIBLE | FS_USERNS_MOUNT, see fs/proc/root.c.
+func (*filesystem) Flags() fs.FilesystemFlags {
+	return 0
+}
+
+// Mount returns the root of a procfs that can be positioned in the vfs.
+func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSourceFlags, data string) (*fs.Inode, error) {
+	// device is always ignored.
+
+	// Parse generic comma-separated key=value options, this file system expects them.
+	options := fs.GenericMountSourceOptions(data)
+
+	// Proc options parsing checks for either a gid= or hidepid= and barfs on
+	// anything else, see fs/proc/root.c:proc_parse_options. Since we don't know
+	// what to do with gid= or hidepid=, we blow up if we get any options.
+	if len(options) > 0 {
+		return nil, fmt.Errorf("unsupported mount options: %v", options)
+	}
+
+	// Construct the procfs root. Since procfs files are all virtual, we
+	// never want them cached.
+	return New(ctx, fs.NewNonCachingMountSource(f, flags))
+}