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