Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 95 insertions, 0 deletions

diff --git a/pkg/sentry/fs/tty/fs.go b/pkg/sentry/fs/tty/fs.go
new file mode 100644
index 000000000..f5e7a3162
--- /dev/null
+++ b/pkg/sentry/fs/tty/fs.go
@@ -0,0 +1,95 @@
+// 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 tty
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/device"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// ptsDevice is the pseudo-filesystem device.
+var ptsDevice = device.NewAnonDevice()
+
+// filesystem is a devpts filesystem.
+//
+// This devpts is always in the new "multi-instance" mode. i.e., it contains a
+// ptmx device tied to this mount.
+type filesystem struct{}
+
+func init() {
+	fs.RegisterFilesystem(&filesystem{})
+}
+
+// Name matches drivers/devpts/indoe.c:devpts_fs_type.name.
+func (*filesystem) Name() string {
+	return "devpts"
+}
+
+// AllowUserMount allows users to mount(2) this file system.
+func (*filesystem) AllowUserMount() bool {
+	// TODO: Users may mount this once the terminals are in a
+	// usable state.
+	return false
+}
+
+// Flags returns that there is nothing special about this file system.
+func (*filesystem) Flags() fs.FilesystemFlags {
+	return 0
+}
+
+// MountSource returns a devpts root 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.
+
+	// No options are supported.
+	if data != "" {
+		return nil, syserror.EINVAL
+	}
+
+	return newDir(ctx, fs.NewMountSource(&superOperations{}, f, flags)), nil
+}
+
+// superOperations implements fs.MountSourceOperations, preventing caching.
+type superOperations struct{}
+
+// Revalidate implements fs.DirentOperations.Revalidate.
+//
+// It always returns true, forcing a Lookup for all entries.
+//
+// Slave entries are dropped from dir when their master is closed, so an
+// existing slave Dirent in the tree is not sufficient to guarantee that it
+// still exists on the filesystem.
+func (superOperations) Revalidate(*fs.Dirent) bool {
+	return true
+}
+
+// Keep implements fs.DirentOperations.Keep.
+//
+// Keep returns false because Revalidate would force a lookup on cached entries
+// anyways.
+func (superOperations) Keep(*fs.Dirent) bool {
+	return false
+}
+
+// ResetInodeMappings implements MountSourceOperations.ResetInodeMappings.
+func (superOperations) ResetInodeMappings() {}
+
+// SaveInodeMapping implements MountSourceOperations.SaveInodeMapping.
+func (superOperations) SaveInodeMapping(*fs.Inode, string) {}
+
+// Destroy implements MountSourceOperations.Destroy.
+func (superOperations) Destroy() {}