395 lines
12 KiB
Go
395 lines
12 KiB
Go
// Copyright 2018 The gVisor Authors.
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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.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/fs"
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"gvisor.dev/gvisor/pkg/sentry/memmap"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/syserror"
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"gvisor.dev/gvisor/pkg/waiter"
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)
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// FileNoopRelease implements fs.FileOperations.Release for files that have no
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// resources to release.
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type FileNoopRelease struct{}
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// Release is a no-op.
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func (FileNoopRelease) 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(b/33075855): 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(b/34716638): 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(b/34778850): 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(b/35442290): 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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// FileGenericSeek implements fs.FileOperations.Seek for files that use a
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// generic seek implementation.
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type FileGenericSeek struct{}
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// Seek implements fs.FileOperations.Seek.
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func (FileGenericSeek) 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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// FileZeroSeek implements fs.FileOperations.Seek for files that maintain a
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// constant zero-value offset and require a no-op Seek.
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type FileZeroSeek struct{}
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// Seek implements fs.FileOperations.Seek.
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func (FileZeroSeek) 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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// FileNoSeek implements fs.FileOperations.Seek to return EINVAL.
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type FileNoSeek struct{}
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// Seek implements fs.FileOperations.Seek.
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func (FileNoSeek) Seek(context.Context, *fs.File, fs.SeekWhence, int64) (int64, error) {
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return 0, syserror.EINVAL
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}
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// FilePipeSeek implements fs.FileOperations.Seek and can be used for files
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// that behave like pipes (seeking is not supported).
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type FilePipeSeek struct{}
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// Seek implements fs.FileOperations.Seek.
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func (FilePipeSeek) 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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// FileNotDirReaddir implements fs.FileOperations.Readdir for non-directories.
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type FileNotDirReaddir struct{}
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// Readdir implements fs.FileOperations.FileNotDirReaddir.
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func (FileNotDirReaddir) 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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// FileNoFsync implements fs.FileOperations.Fsync for files that don't support
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// syncing.
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type FileNoFsync struct{}
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// Fsync implements fs.FileOperations.Fsync.
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func (FileNoFsync) 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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// FileNoopFsync implements fs.FileOperations.Fsync for files that don't need
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// to synced.
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type FileNoopFsync struct{}
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// Fsync implements fs.FileOperations.Fsync.
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func (FileNoopFsync) Fsync(context.Context, *fs.File, int64, int64, fs.SyncType) error {
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return nil
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}
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// FileNoopFlush implements fs.FileOperations.Flush as a no-op.
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type FileNoopFlush struct{}
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// Flush implements fs.FileOperations.Flush.
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func (FileNoopFlush) Flush(context.Context, *fs.File) error {
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return nil
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}
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// FileNoMMap implements fs.FileOperations.Mappable for files that cannot
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// be memory mapped.
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type FileNoMMap struct{}
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// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
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func (FileNoMMap) 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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// FileNoIoctl implements fs.FileOperations.Ioctl for files that don't
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// implement the ioctl syscall.
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type FileNoIoctl struct{}
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// Ioctl implements fs.FileOperations.Ioctl.
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func (FileNoIoctl) Ioctl(context.Context, *fs.File, usermem.IO, arch.SyscallArguments) (uintptr, error) {
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return 0, syserror.ENOTTY
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}
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// FileNoSplice implements fs.FileOperations.ReadFrom and
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// fs.FileOperations.WriteTo for files that don't support splice.
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type FileNoSplice struct{}
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// WriteTo implements fs.FileOperations.WriteTo.
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func (FileNoSplice) WriteTo(context.Context, *fs.File, *fs.File, fs.SpliceOpts) (int64, error) {
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return 0, syserror.ENOSYS
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}
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// ReadFrom implements fs.FileOperations.ReadFrom.
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func (FileNoSplice) ReadFrom(context.Context, *fs.File, *fs.File, fs.SpliceOpts) (int64, error) {
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return 0, syserror.ENOSYS
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}
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// DirFileOperations implements most of fs.FileOperations for directories,
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// except for Readdir and UnstableAttr which the embedding type must implement.
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type DirFileOperations struct {
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waiter.AlwaysReady
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FileGenericSeek
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FileNoIoctl
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FileNoMMap
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FileNoopFlush
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FileNoopFsync
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FileNoopRelease
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FileNoSplice
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}
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// Read implements fs.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 fs.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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// StaticDirFileOperations implements fs.FileOperations for directories with
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// static children.
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//
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// +stateify savable
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type StaticDirFileOperations struct {
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DirFileOperations `state:"nosave"`
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FileUseInodeUnstableAttr `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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// NewStaticDirFileOperations returns a new StaticDirFileOperations that will
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// iterate the given denty map.
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func NewStaticDirFileOperations(dentries *fs.SortedDentryMap) *StaticDirFileOperations {
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return &StaticDirFileOperations{
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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 (sdfo *StaticDirFileOperations) IterateDir(ctx context.Context, d *fs.Dirent, dirCtx *fs.DirCtx, offset int) (int, error) {
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n, err := fs.GenericReaddir(dirCtx, sdfo.dentryMap)
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return offset + n, err
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}
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// Readdir implements fs.FileOperations.Readdir.
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func (sdfo *StaticDirFileOperations) Readdir(ctx context.Context, file *fs.File, serializer fs.DentrySerializer) (int64, error) {
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root := fs.RootFromContext(ctx)
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if root != nil {
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defer root.DecRef()
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}
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dirCtx := &fs.DirCtx{
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Serializer: serializer,
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DirCursor: &sdfo.dirCursor,
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}
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return fs.DirentReaddir(ctx, file.Dirent, sdfo, root, dirCtx, file.Offset())
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}
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// NoReadWriteFile is a file that does not support reading or writing.
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//
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// +stateify savable
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type NoReadWriteFile struct {
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waiter.AlwaysReady `state:"nosave"`
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FileGenericSeek `state:"nosave"`
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FileNoIoctl `state:"nosave"`
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FileNoMMap `state:"nosave"`
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FileNoopFsync `state:"nosave"`
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FileNoopFlush `state:"nosave"`
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FileNoopRelease `state:"nosave"`
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FileNoRead `state:"nosave"`
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FileNoWrite `state:"nosave"`
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FileNotDirReaddir `state:"nosave"`
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FileUseInodeUnstableAttr `state:"nosave"`
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FileNoSplice `state:"nosave"`
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}
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var _ fs.FileOperations = (*NoReadWriteFile)(nil)
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// FileStaticContentReader is a helper to implement fs.FileOperations.Read with
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// static content.
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//
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// +stateify savable
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type FileStaticContentReader struct {
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// content is immutable.
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content []byte
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}
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// NewFileStaticContentReader initializes a FileStaticContentReader with the
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// given content.
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func NewFileStaticContentReader(b []byte) FileStaticContentReader {
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return FileStaticContentReader{
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content: b,
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}
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}
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// Read implements fs.FileOperations.Read.
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func (scr *FileStaticContentReader) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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if offset >= int64(len(scr.content)) {
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return 0, nil
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}
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n, err := dst.CopyOut(ctx, scr.content[offset:])
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return int64(n), err
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}
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// FileNoopWrite implements fs.FileOperations.Write as a noop.
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type FileNoopWrite struct{}
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// Write implements fs.FileOperations.Write.
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func (FileNoopWrite) Write(_ context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
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return src.NumBytes(), nil
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}
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// FileNoRead implements fs.FileOperations.Read to return EINVAL.
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type FileNoRead struct{}
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// Read implements fs.FileOperations.Read.
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func (FileNoRead) Read(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
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return 0, syserror.EINVAL
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}
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// FileNoWrite implements fs.FileOperations.Write to return EINVAL.
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type FileNoWrite struct{}
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// Write implements fs.FileOperations.Write.
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func (FileNoWrite) Write(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
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return 0, syserror.EINVAL
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}
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// FileNoopRead implement fs.FileOperations.Read as a noop.
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type FileNoopRead struct{}
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// Read implements fs.FileOperations.Read.
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func (FileNoopRead) Read(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
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return 0, nil
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}
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// FileUseInodeUnstableAttr implements fs.FileOperations.UnstableAttr by calling
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// InodeOperations.UnstableAttr.
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type FileUseInodeUnstableAttr struct{}
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// UnstableAttr implements fs.FileOperations.UnstableAttr.
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func (FileUseInodeUnstableAttr) UnstableAttr(ctx context.Context, file *fs.File) (fs.UnstableAttr, error) {
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return file.Dirent.Inode.UnstableAttr(ctx)
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}
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