89 lines
2.8 KiB
Go
89 lines
2.8 KiB
Go
|
// Copyright 2020 The gVisor Authors.
|
||
|
//
|
||
|
// 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 memdev
|
||
|
|
||
|
import (
|
||
|
"gvisor.dev/gvisor/pkg/context"
|
||
|
"gvisor.dev/gvisor/pkg/sentry/memmap"
|
||
|
"gvisor.dev/gvisor/pkg/sentry/mm"
|
||
|
"gvisor.dev/gvisor/pkg/sentry/pgalloc"
|
||
|
"gvisor.dev/gvisor/pkg/sentry/vfs"
|
||
|
"gvisor.dev/gvisor/pkg/usermem"
|
||
|
)
|
||
|
|
||
|
const zeroDevMinor = 5
|
||
|
|
||
|
// zeroDevice implements vfs.Device for /dev/zero.
|
||
|
type zeroDevice struct{}
|
||
|
|
||
|
// Open implements vfs.Device.Open.
|
||
|
func (zeroDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
|
||
|
fd := &zeroFD{}
|
||
|
if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
|
||
|
UseDentryMetadata: true,
|
||
|
}); err != nil {
|
||
|
return nil, err
|
||
|
}
|
||
|
return &fd.vfsfd, nil
|
||
|
}
|
||
|
|
||
|
// zeroFD implements vfs.FileDescriptionImpl for /dev/zero.
|
||
|
type zeroFD struct {
|
||
|
vfsfd vfs.FileDescription
|
||
|
vfs.FileDescriptionDefaultImpl
|
||
|
vfs.DentryMetadataFileDescriptionImpl
|
||
|
}
|
||
|
|
||
|
// Release implements vfs.FileDescriptionImpl.Release.
|
||
|
func (fd *zeroFD) Release() {
|
||
|
// noop
|
||
|
}
|
||
|
|
||
|
// PRead implements vfs.FileDescriptionImpl.PRead.
|
||
|
func (fd *zeroFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
|
||
|
return dst.ZeroOut(ctx, dst.NumBytes())
|
||
|
}
|
||
|
|
||
|
// Read implements vfs.FileDescriptionImpl.Read.
|
||
|
func (fd *zeroFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
|
||
|
return dst.ZeroOut(ctx, dst.NumBytes())
|
||
|
}
|
||
|
|
||
|
// PWrite implements vfs.FileDescriptionImpl.PWrite.
|
||
|
func (fd *zeroFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
|
||
|
return src.NumBytes(), nil
|
||
|
}
|
||
|
|
||
|
// Write implements vfs.FileDescriptionImpl.Write.
|
||
|
func (fd *zeroFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
|
||
|
return src.NumBytes(), nil
|
||
|
}
|
||
|
|
||
|
// Seek implements vfs.FileDescriptionImpl.Seek.
|
||
|
func (fd *zeroFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
|
||
|
return 0, nil
|
||
|
}
|
||
|
|
||
|
// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
|
||
|
func (fd *zeroFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
|
||
|
m, err := mm.NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
|
||
|
if err != nil {
|
||
|
return err
|
||
|
}
|
||
|
opts.MappingIdentity = m
|
||
|
opts.Mappable = m
|
||
|
return nil
|
||
|
}
|