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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 ashmem implements Android ashmem module (Anonymus Shared Memory).
package ashmem
import (
"sync"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
)
// Device implements fs.InodeOperations.
//
// +stateify savable
type Device struct {
fsutil.DeprecatedFileOperations `state:"nosave"`
fsutil.InodeNoExtendedAttributes `state:"nosave"`
fsutil.InodeNotDirectory `state:"nosave"`
fsutil.InodeNotRenameable `state:"nosave"`
fsutil.InodeNotSocket `state:"nosave"`
fsutil.InodeNotSymlink `state:"nosave"`
fsutil.NoFsync `state:"nosave"`
fsutil.NoMappable `state:"nosave"`
fsutil.NoopWriteOut `state:"nosave"`
fsutil.NotDirReaddir `state:"nosave"`
mu sync.Mutex `state:"nosave"`
unstable fs.UnstableAttr
}
// NewDevice creates and intializes a Device structure.
func NewDevice(ctx context.Context, owner fs.FileOwner, fp fs.FilePermissions) *Device {
return &Device{
unstable: fs.WithCurrentTime(ctx, fs.UnstableAttr{
Owner: owner,
Perms: fp,
Links: 1,
}),
}
}
// Release implements fs.InodeOperations.Release.
func (ad *Device) Release(context.Context) {}
// GetFile implements fs.InodeOperations.GetFile.
func (ad *Device) GetFile(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
return fs.NewFile(ctx, d, flags, &Area{
ad: ad,
tmpfsFile: nil,
perms: usermem.AnyAccess,
}), nil
}
// UnstableAttr implements fs.InodeOperations.UnstableAttr.
func (ad *Device) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
ad.mu.Lock()
defer ad.mu.Unlock()
return ad.unstable, nil
}
// Check implements fs.InodeOperations.Check.
func (ad *Device) Check(ctx context.Context, inode *fs.Inode, p fs.PermMask) bool {
return fs.ContextCanAccessFile(ctx, inode, p)
}
// SetPermissions implements fs.InodeOperations.SetPermissions.
func (ad *Device) SetPermissions(ctx context.Context, inode *fs.Inode, fp fs.FilePermissions) bool {
ad.mu.Lock()
defer ad.mu.Unlock()
ad.unstable.Perms = fp
ad.unstable.StatusChangeTime = time.NowFromContext(ctx)
return true
}
// SetOwner implements fs.InodeOperations.SetOwner.
func (ad *Device) SetOwner(ctx context.Context, inode *fs.Inode, owner fs.FileOwner) error {
ad.mu.Lock()
defer ad.mu.Unlock()
if owner.UID.Ok() {
ad.unstable.Owner.UID = owner.UID
}
if owner.GID.Ok() {
ad.unstable.Owner.GID = owner.GID
}
return nil
}
// SetTimestamps implements fs.InodeOperations.SetTimestamps.
func (ad *Device) SetTimestamps(ctx context.Context, inode *fs.Inode, ts fs.TimeSpec) error {
if ts.ATimeOmit && ts.MTimeOmit {
return nil
}
ad.mu.Lock()
defer ad.mu.Unlock()
now := time.NowFromContext(ctx)
if !ts.ATimeOmit {
if ts.ATimeSetSystemTime {
ad.unstable.AccessTime = now
} else {
ad.unstable.AccessTime = ts.ATime
}
}
if !ts.MTimeOmit {
if ts.MTimeSetSystemTime {
ad.unstable.ModificationTime = now
} else {
ad.unstable.ModificationTime = ts.MTime
}
}
ad.unstable.StatusChangeTime = now
return nil
}
// Truncate implements fs.InodeOperations.WriteOut.
//
// Ignored by ashmem.
func (ad *Device) Truncate(ctx context.Context, inode *fs.Inode, size int64) error {
return nil
}
// AddLink implements fs.InodeOperations.AddLink.
//
// Ashmem doesn't support links, no-op.
func (ad *Device) AddLink() {}
// DropLink implements fs.InodeOperations.DropLink.
//
// Ashmem doesn't support links, no-op.
func (ad *Device) DropLink() {}
// NotifyStatusChange implements fs.InodeOperations.NotifyStatusChange.
func (ad *Device) NotifyStatusChange(ctx context.Context) {
ad.mu.Lock()
defer ad.mu.Unlock()
now := time.NowFromContext(ctx)
ad.unstable.ModificationTime = now
ad.unstable.StatusChangeTime = now
}
// IsVirtual implements fs.InodeOperations.IsVirtual.
//
// Ashmem is virtual.
func (ad *Device) IsVirtual() bool {
return true
}
// StatFS implements fs.InodeOperations.StatFS.
//
// Ashmem doesn't support querying for filesystem info.
func (ad *Device) StatFS(context.Context) (fs.Info, error) {
return fs.Info{}, syserror.ENOSYS
}
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