1 files changed, 155 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/memfs/regular_file.go b/pkg/sentry/fsimpl/memfs/regular_file.go
new file mode 100644
index 000000000..4a3603cc8
--- /dev/null
+++ b/pkg/sentry/fsimpl/memfs/regular_file.go
@@ -0,0 +1,155 @@
+// 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 memfs
+
+import (
+	"io"
+	"sync"
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/context"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+type regularFile struct {
+	inode Inode
+
+	mu   sync.RWMutex
+	data []byte
+	// dataLen is len(data), but accessed using atomic memory operations to
+	// avoid locking in Inode.stat().
+	dataLen int64
+}
+
+func (fs *Filesystem) newRegularFile(creds *auth.Credentials, mode uint16) *Inode {
+	file := &regularFile{}
+	file.inode.init(file, fs, creds, mode)
+	file.inode.nlink = 1 // from parent directory
+	return &file.inode
+}
+
+type regularFileFD struct {
+	fileDescription
+	vfs.FileDescriptionDefaultImpl
+
+	// These are immutable.
+	readable bool
+	writable bool
+
+	// off is the file offset. off is accessed using atomic memory operations.
+	// offMu serializes operations that may mutate off.
+	off   int64
+	offMu sync.Mutex
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *regularFileFD) Release() {
+	if fd.writable {
+		fd.vfsfd.VirtualDentry().Mount().EndWrite()
+	}
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *regularFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	if !fd.readable {
+		return 0, syserror.EINVAL
+	}
+	f := fd.inode().impl.(*regularFile)
+	f.mu.RLock()
+	if offset >= int64(len(f.data)) {
+		f.mu.RUnlock()
+		return 0, io.EOF
+	}
+	n, err := dst.CopyOut(ctx, f.data[offset:])
+	f.mu.RUnlock()
+	return int64(n), err
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *regularFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	fd.offMu.Lock()
+	n, err := fd.PRead(ctx, dst, fd.off, opts)
+	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) {
+	if !fd.writable {
+		return 0, syserror.EINVAL
+	}
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	srclen := src.NumBytes()
+	if srclen == 0 {
+		return 0, nil
+	}
+	f := fd.inode().impl.(*regularFile)
+	f.mu.Lock()
+	end := offset + srclen
+	if end < offset {
+		// Overflow.
+		f.mu.Unlock()
+		return 0, syserror.EFBIG
+	}
+	if end > f.dataLen {
+		f.data = append(f.data, make([]byte, end-f.dataLen)...)
+		atomic.StoreInt64(&f.dataLen, end)
+	}
+	n, err := src.CopyIn(ctx, f.data[offset:end])
+	f.mu.Unlock()
+	return int64(n), err
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *regularFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	fd.offMu.Lock()
+	n, err := fd.PWrite(ctx, src, fd.off, opts)
+	fd.off += n
+	fd.offMu.Unlock()
+	return n, err
+}
+
+// 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 += atomic.LoadInt64(&fd.inode().impl.(*regularFile).dataLen)
+	default:
+		return 0, syserror.EINVAL
+	}
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	fd.off = offset
+	return offset, nil
+}
+
+// Sync implements vfs.FileDescriptionImpl.Sync.
+func (fd *regularFileFD) Sync(ctx context.Context) error {
+	return nil
+}