160 lines
4.7 KiB
Go
160 lines
4.7 KiB
Go
// Copyright 2019 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 ext
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import (
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"io"
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"sync"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/memmap"
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"gvisor.dev/gvisor/pkg/sentry/safemem"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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// regularFile represents a regular file's inode. This too follows the
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// inheritance pattern prevelant in the vfs layer described in
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// pkg/sentry/vfs/README.md.
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type regularFile struct {
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inode inode
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// This is immutable. The first field of fileReader implementations must be
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// regularFile to ensure temporality.
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// io.ReaderAt is more strict than io.Reader in the sense that a partial read
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// is always accompanied by an error. If a read spans past the end of file, a
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// partial read (within file range) is done and io.EOF is returned.
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impl io.ReaderAt
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}
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// newRegularFile is the regularFile constructor. It figures out what kind of
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// file this is and initializes the fileReader.
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func newRegularFile(inode inode) (*regularFile, error) {
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regFile := regularFile{
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inode: inode,
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}
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inodeFlags := inode.diskInode.Flags()
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if inodeFlags.Extents {
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file, err := newExtentFile(regFile)
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if err != nil {
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return nil, err
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}
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file.regFile.inode.impl = &file.regFile
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return &file.regFile, nil
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}
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file, err := newBlockMapFile(regFile)
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if err != nil {
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return nil, err
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}
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file.regFile.inode.impl = &file.regFile
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return &file.regFile, nil
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}
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func (in *inode) isRegular() bool {
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_, ok := in.impl.(*regularFile)
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return ok
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}
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// directoryFD represents a directory file description. It implements
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// vfs.FileDescriptionImpl.
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type regularFileFD struct {
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fileDescription
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// off is the file offset. off is accessed using atomic memory operations.
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off int64
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// offMu serializes operations that may mutate off.
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offMu sync.Mutex
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}
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// Release implements vfs.FileDescriptionImpl.Release.
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func (fd *regularFileFD) Release() {}
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// PRead implements vfs.FileDescriptionImpl.PRead.
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func (fd *regularFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
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safeReader := safemem.FromIOReaderAt{
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ReaderAt: fd.inode().impl.(*regularFile).impl,
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Offset: offset,
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}
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// Copies data from disk directly into usermem without any intermediate
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// allocations (if dst is converted into BlockSeq such that it does not need
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// safe copying).
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return dst.CopyOutFrom(ctx, safeReader)
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}
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// Read implements vfs.FileDescriptionImpl.Read.
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func (fd *regularFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
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n, err := fd.PRead(ctx, dst, fd.off, opts)
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fd.offMu.Lock()
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fd.off += n
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fd.offMu.Unlock()
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return n, err
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}
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// PWrite implements vfs.FileDescriptionImpl.PWrite.
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func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
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// write(2) specifies that EBADF must be returned if the fd is not open for
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// writing.
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return 0, syserror.EBADF
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}
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// Write implements vfs.FileDescriptionImpl.Write.
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func (fd *regularFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
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n, err := fd.PWrite(ctx, src, fd.off, opts)
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fd.offMu.Lock()
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fd.off += n
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fd.offMu.Unlock()
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return n, err
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}
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// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
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func (fd *regularFileFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
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return syserror.ENOTDIR
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}
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// Seek implements vfs.FileDescriptionImpl.Seek.
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func (fd *regularFileFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
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fd.offMu.Lock()
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defer fd.offMu.Unlock()
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switch whence {
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case linux.SEEK_SET:
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// Use offset as specified.
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case linux.SEEK_CUR:
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offset += fd.off
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case linux.SEEK_END:
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offset += int64(fd.inode().diskInode.Size())
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default:
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return 0, syserror.EINVAL
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}
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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fd.off = offset
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return offset, nil
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}
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// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
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func (fd *regularFileFD) ConfigureMMap(ctx context.Context, opts memmap.MMapOpts) error {
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// TODO(b/134676337): Implement mmap(2).
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return syserror.ENODEV
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}
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