1 files changed, 159 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
new file mode 100644
index 000000000..08c691c47
--- /dev/null
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -0,0 +1,159 @@
+// 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 gofer
+
+import (
+	"sync"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/safemem"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// specialFileFD implements vfs.FileDescriptionImpl for files other than
+// regular files, directories, and symlinks: pipes, sockets, etc. It is also
+// used for regular files when filesystemOptions.specialRegularFiles is in
+// effect. specialFileFD differs from regularFileFD by using per-FD handles
+// instead of shared per-dentry handles, and never buffering I/O.
+type specialFileFD struct {
+	fileDescription
+
+	// handle is immutable.
+	handle handle
+
+	// off is the file offset. off is protected by mu. (POSIX 2.9.7 only
+	// requires operations using the file offset to be atomic for regular files
+	// and symlinks; however, since specialFileFD may be used for regular
+	// files, we apply this atomicity unconditionally.)
+	mu  sync.Mutex
+	off int64
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *specialFileFD) Release() {
+	fd.handle.close(context.Background())
+	fs := fd.vfsfd.Mount().Filesystem().Impl().(*filesystem)
+	fs.syncMu.Lock()
+	delete(fs.specialFileFDs, fd)
+	fs.syncMu.Unlock()
+}
+
+// OnClose implements vfs.FileDescriptionImpl.OnClose.
+func (fd *specialFileFD) OnClose(ctx context.Context) error {
+	if !fd.vfsfd.IsWritable() {
+		return nil
+	}
+	return fd.handle.file.flush(ctx)
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	if opts.Flags != 0 {
+		return 0, syserror.EOPNOTSUPP
+	}
+
+	// Going through dst.CopyOutFrom() holds MM locks around file operations of
+	// unknown duration. For regularFileFD, doing so is necessary to support
+	// mmap due to lock ordering; MM locks precede dentry.dataMu. That doesn't
+	// hold here since specialFileFD doesn't client-cache data. Just buffer the
+	// read instead.
+	if d := fd.dentry(); d.fs.opts.interop != InteropModeShared {
+		d.touchAtime(ctx, fd.vfsfd.Mount())
+	}
+	buf := make([]byte, dst.NumBytes())
+	n, err := fd.handle.readToBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
+	if n == 0 {
+		return 0, err
+	}
+	if cp, cperr := dst.CopyOut(ctx, buf[:n]); cperr != nil {
+		return int64(cp), cperr
+	}
+	return int64(n), err
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *specialFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	fd.mu.Lock()
+	n, err := fd.PRead(ctx, dst, fd.off, opts)
+	fd.off += n
+	fd.mu.Unlock()
+	return n, err
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *specialFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	if opts.Flags != 0 {
+		return 0, syserror.EOPNOTSUPP
+	}
+
+	// Do a buffered write. See rationale in PRead.
+	if d := fd.dentry(); d.fs.opts.interop != InteropModeShared {
+		d.touchCMtime(ctx)
+	}
+	buf := make([]byte, src.NumBytes())
+	// Don't do partial writes if we get a partial read from src.
+	if _, err := src.CopyIn(ctx, buf); err != nil {
+		return 0, err
+	}
+	n, err := fd.handle.writeFromBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
+	return int64(n), err
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *specialFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	fd.mu.Lock()
+	n, err := fd.PWrite(ctx, src, fd.off, opts)
+	fd.off += n
+	fd.mu.Unlock()
+	return n, err
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *specialFileFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	fd.mu.Lock()
+	defer fd.mu.Unlock()
+	switch whence {
+	case linux.SEEK_SET:
+		// Use offset as given.
+	case linux.SEEK_CUR:
+		offset += fd.off
+	default:
+		// SEEK_END, SEEK_DATA, and SEEK_HOLE aren't supported since it's not
+		// clear that file size is even meaningful for these files.
+		return 0, syserror.EINVAL
+	}
+	if offset < 0 {
+		return 0, syserror.EINVAL
+	}
+	fd.off = offset
+	return offset, nil
+}
+
+// Sync implements vfs.FileDescriptionImpl.Sync.
+func (fd *specialFileFD) Sync(ctx context.Context) error {
+	if !fd.vfsfd.IsWritable() {
+		return nil
+	}
+	return fd.handle.sync(ctx)
+}