1 files changed, 59 insertions, 0 deletions
diff --git a/pkg/sentry/fs/ext/symlink.go b/pkg/sentry/fs/ext/symlink.go
new file mode 100644
index 000000000..0ed67c0e4
--- /dev/null
+++ b/pkg/sentry/fs/ext/symlink.go
@@ -0,0 +1,59 @@
+// 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/syserror"
+)
+
+// symlink represents a symlink inode.
+type symlink struct {
+	inode  inode
+	target string // immutable
+}
+
+// newSymlink is the symlink constructor. It reads out the symlink target from
+// the inode (however it might have been stored).
+//
+// Preconditions: Must hold the mutex of the filesystem containing dev.
+func newSymlink(dev io.ReadSeeker, blkSize uint64, inode inode) (*symlink, error) {
+	var file *symlink
+	var link []byte
+
+	// If the symlink target is lesser than 60 bytes, its stores in inode.Data().
+	// Otherwise either extents or block maps will be used to store the link.
+	size := inode.diskInode.Size()
+	if size < 60 {
+		link = inode.diskInode.Data()[:size]
+	} else {
+		// Create a regular file out of this inode and read out the target.
+		regFile, err := newRegularFile(dev, blkSize, inode)
+		if err != nil {
+			return nil, err
+		}
+
+		link = make([]byte, size)
+		reader := regFile.impl.getFileReader(dev, blkSize, 0)
+		if _, err := io.ReadFull(reader, link); err != nil {
+			return nil, syserror.EIO
+		}
+	}
+
+	file = &symlink{inode: inode, target: string(link)}
+	file.inode.impl = file
+	return file, nil
+}