270 lines
8.2 KiB
Go
270 lines
8.2 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fsutil
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import (
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"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
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"gvisor.googlesource.com/gvisor/pkg/sentry/context"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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"gvisor.googlesource.com/gvisor/pkg/syserror"
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"gvisor.googlesource.com/gvisor/pkg/waiter"
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)
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// NoopRelease implements FileOperations.Release for files that have no
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// resources to release.
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type NoopRelease struct{}
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// Release is a no-op.
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func (NoopRelease) Release() {}
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// SeekWithDirCursor is used to implement fs.FileOperations.Seek. If dirCursor
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// is not nil and the seek was on a directory, the cursor will be updated.
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//
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// Currently only seeking to 0 on a directory is supported.
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//
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// FIXME: Lift directory seeking limitations.
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func SeekWithDirCursor(ctx context.Context, file *fs.File, whence fs.SeekWhence, offset int64, dirCursor *string) (int64, error) {
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inode := file.Dirent.Inode
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current := file.Offset()
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// Does the Inode represents a non-seekable type?
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if fs.IsPipe(inode.StableAttr) || fs.IsSocket(inode.StableAttr) {
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return current, syserror.ESPIPE
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}
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// Does the Inode represent a character device?
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if fs.IsCharDevice(inode.StableAttr) {
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// Ignore seek requests.
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//
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// FIXME: This preserves existing
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// behavior but is not universally correct.
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return 0, nil
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}
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// Otherwise compute the new offset.
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switch whence {
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case fs.SeekSet:
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switch inode.StableAttr.Type {
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case fs.RegularFile, fs.SpecialFile, fs.BlockDevice:
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if offset < 0 {
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return current, syserror.EINVAL
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}
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return offset, nil
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case fs.Directory, fs.SpecialDirectory:
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if offset != 0 {
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return current, syserror.EINVAL
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}
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// SEEK_SET to 0 moves the directory "cursor" to the beginning.
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if dirCursor != nil {
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*dirCursor = ""
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}
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return 0, nil
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default:
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return current, syserror.EINVAL
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}
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case fs.SeekCurrent:
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switch inode.StableAttr.Type {
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case fs.RegularFile, fs.SpecialFile, fs.BlockDevice:
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if current+offset < 0 {
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return current, syserror.EINVAL
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}
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return current + offset, nil
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case fs.Directory, fs.SpecialDirectory:
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if offset != 0 {
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return current, syserror.EINVAL
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}
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return current, nil
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default:
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return current, syserror.EINVAL
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}
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case fs.SeekEnd:
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switch inode.StableAttr.Type {
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case fs.RegularFile, fs.BlockDevice:
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// Allow the file to determine the end.
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uattr, err := inode.UnstableAttr(ctx)
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if err != nil {
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return current, err
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}
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sz := uattr.Size
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if sz+offset < 0 {
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return current, syserror.EINVAL
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}
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return sz + offset, nil
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// FIXME: This is not universally correct.
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// Remove SpecialDirectory.
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case fs.SpecialDirectory:
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if offset != 0 {
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return current, syserror.EINVAL
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}
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// SEEK_END to 0 moves the directory "cursor" to the end.
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//
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// FIXME: The ensures that after the seek,
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// reading on the directory will get EOF. But it is not
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// correct in general because the directory can grow in
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// size; attempting to read those new entries will be
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// futile (EOF will always be the result).
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return fs.FileMaxOffset, nil
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default:
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return current, syserror.EINVAL
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}
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}
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// Not a valid seek request.
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return current, syserror.EINVAL
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}
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// GenericSeek implements FileOperations.Seek for files that use a generic
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// seek implementation.
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type GenericSeek struct{}
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// Seek implements fs.FileOperations.Seek.
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func (GenericSeek) Seek(ctx context.Context, file *fs.File, whence fs.SeekWhence, offset int64) (int64, error) {
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return SeekWithDirCursor(ctx, file, whence, offset, nil)
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}
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// ZeroSeek implements FileOperations.Seek for files that maintain a constant
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// zero-value offset and require a no-op Seek.
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type ZeroSeek struct{}
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// Seek implements FileOperations.Seek.
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func (ZeroSeek) Seek(context.Context, *fs.File, fs.SeekWhence, int64) (int64, error) {
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return 0, nil
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}
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// PipeSeek implements FileOperations.Seek and can be used for files that behave
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// like pipes (seeking is not supported).
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type PipeSeek struct{}
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// Seek implements FileOperations.Seek.
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func (PipeSeek) Seek(context.Context, *fs.File, fs.SeekWhence, int64) (int64, error) {
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return 0, syserror.ESPIPE
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}
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// NotDirReaddir implements FileOperations.Readdir for non-directories.
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type NotDirReaddir struct{}
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// Readdir implements FileOperations.NotDirReaddir.
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func (NotDirReaddir) Readdir(context.Context, *fs.File, fs.DentrySerializer) (int64, error) {
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return 0, syserror.ENOTDIR
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}
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// NoFsync implements FileOperations.Fsync for files that don't support syncing.
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type NoFsync struct{}
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// Fsync implements FileOperations.Fsync.
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func (NoFsync) Fsync(context.Context, *fs.File, int64, int64, fs.SyncType) error {
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return syserror.EINVAL
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}
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// NoopFsync implements FileOperations.Fsync for files that don't need to synced.
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type NoopFsync struct{}
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// Fsync implements FileOperations.Fsync.
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func (NoopFsync) Fsync(context.Context, *fs.File, int64, int64, fs.SyncType) error {
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return nil
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}
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// NoopFlush implements FileOperations.Flush as a no-op.
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type NoopFlush struct{}
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// Flush implements FileOperations.Flush.
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func (NoopFlush) Flush(context.Context, *fs.File) error {
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return nil
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}
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// NoMMap implements fs.FileOperations.Mappable for files that cannot
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// be memory mapped.
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type NoMMap struct{}
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// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
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func (NoMMap) ConfigureMMap(context.Context, *fs.File, *memmap.MMapOpts) error {
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return syserror.ENODEV
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}
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// GenericConfigureMMap implements fs.FileOperations.ConfigureMMap for most
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// filesystems that support memory mapping.
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func GenericConfigureMMap(file *fs.File, m memmap.Mappable, opts *memmap.MMapOpts) error {
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opts.Mappable = m
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opts.MappingIdentity = file
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file.IncRef()
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return nil
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}
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// NoIoctl implements fs.FileOperations.Ioctl for files that don't implement
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// the ioctl syscall.
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type NoIoctl struct{}
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// Ioctl implements fs.FileOperations.Ioctl.
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func (NoIoctl) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
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return 0, syserror.ENOTTY
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}
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// DirFileOperations implements FileOperations for directories.
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//
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// +stateify savable
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type DirFileOperations struct {
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waiter.AlwaysReady `state:"nosave"`
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NoopRelease `state:"nosave"`
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GenericSeek `state:"nosave"`
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NoFsync `state:"nosave"`
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NoopFlush `state:"nosave"`
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NoMMap `state:"nosave"`
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NoIoctl `state:"nosave"`
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// dentryMap is a SortedDentryMap used to implement Readdir.
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dentryMap *fs.SortedDentryMap
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// dirCursor contains the name of the last directory entry that was
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// serialized.
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dirCursor string
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}
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// NewDirFileOperations returns a new DirFileOperations that will iterate the
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// given denty map.
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func NewDirFileOperations(dentries *fs.SortedDentryMap) *DirFileOperations {
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return &DirFileOperations{
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dentryMap: dentries,
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}
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}
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// IterateDir implements DirIterator.IterateDir.
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func (dfo *DirFileOperations) IterateDir(ctx context.Context, dirCtx *fs.DirCtx, offset int) (int, error) {
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n, err := fs.GenericReaddir(dirCtx, dfo.dentryMap)
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return offset + n, err
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}
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// Readdir implements FileOperations.Readdir.
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func (dfo *DirFileOperations) Readdir(ctx context.Context, file *fs.File, serializer fs.DentrySerializer) (int64, error) {
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root := fs.RootFromContext(ctx)
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defer root.DecRef()
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dirCtx := &fs.DirCtx{
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Serializer: serializer,
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DirCursor: &dfo.dirCursor,
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}
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return fs.DirentReaddir(ctx, file.Dirent, dfo, root, dirCtx, file.Offset())
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}
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// Read implements FileOperations.Read
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func (*DirFileOperations) Read(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
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return 0, syserror.EISDIR
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}
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// Write implements FileOperations.Write.
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func (*DirFileOperations) Write(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
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return 0, syserror.EISDIR
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}
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