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// Copyright 2019 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 ext
import (
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
// symlink represents a symlink inode.
type symlink struct {
inode inode
target string // immutable
}
// newSymlink is the symlink constructor. It reads out the symlink target from
// the inode (however it might have been stored).
func newSymlink(args inodeArgs) (*symlink, error) {
var link []byte
// If the symlink target is lesser than 60 bytes, its stores in inode.Data().
// Otherwise either extents or block maps will be used to store the link.
size := args.diskInode.Size()
if size < 60 {
link = args.diskInode.Data()[:size]
} else {
// Create a regular file out of this inode and read out the target.
regFile, err := newRegularFile(args)
if err != nil {
return nil, err
}
link = make([]byte, size)
if n, err := regFile.impl.ReadAt(link, 0); uint64(n) < size {
return nil, err
}
}
file := &symlink{target: string(link)}
file.inode.init(args, file)
return file, nil
}
func (in *inode) isSymlink() bool {
_, ok := in.impl.(*symlink)
return ok
}
// symlinkFD represents a symlink file description and implements
// vfs.FileDescriptionImpl. which may only be used if open options contains
// O_PATH. For this reason most of the functions return EBADF.
type symlinkFD struct {
fileDescription
vfs.NoLockFD
}
// Compiles only if symlinkFD implements vfs.FileDescriptionImpl.
var _ vfs.FileDescriptionImpl = (*symlinkFD)(nil)
// Release implements vfs.FileDescriptionImpl.Release.
func (fd *symlinkFD) Release(context.Context) {}
// PRead implements vfs.FileDescriptionImpl.PRead.
func (fd *symlinkFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
return 0, syserror.EBADF
}
// Read implements vfs.FileDescriptionImpl.Read.
func (fd *symlinkFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
return 0, syserror.EBADF
}
// PWrite implements vfs.FileDescriptionImpl.PWrite.
func (fd *symlinkFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
return 0, syserror.EBADF
}
// Write implements vfs.FileDescriptionImpl.Write.
func (fd *symlinkFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
return 0, syserror.EBADF
}
// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
func (fd *symlinkFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
return syserror.ENOTDIR
}
// Seek implements vfs.FileDescriptionImpl.Seek.
func (fd *symlinkFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
return 0, syserror.EBADF
}
// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
func (fd *symlinkFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
return syserror.EBADF
}
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