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// 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
}
// AllowUserList allows this filesystem to be listed in /proc/filesystems.
func (*filesystem) AllowUserList() bool {
return true
}
// 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(context.Context, *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() {}
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