1 files changed, 66 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/kernfs/symlink.go b/pkg/sentry/fsimpl/kernfs/symlink.go
new file mode 100644
index 000000000..0aa6dc979
--- /dev/null
+++ b/pkg/sentry/fsimpl/kernfs/symlink.go
@@ -0,0 +1,66 @@
+// 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 kernfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// StaticSymlink provides an Inode implementation for symlinks that point to
+// a immutable target.
+type StaticSymlink struct {
+	InodeAttrs
+	InodeNoopRefCount
+	InodeSymlink
+
+	target string
+}
+
+var _ Inode = (*StaticSymlink)(nil)
+
+// NewStaticSymlink creates a new symlink file pointing to 'target'.
+func NewStaticSymlink(creds *auth.Credentials, ino uint64, target string) *Dentry {
+	inode := &StaticSymlink{}
+	inode.Init(creds, ino, target)
+
+	d := &Dentry{}
+	d.Init(inode)
+	return d
+}
+
+// Init initializes the instance.
+func (s *StaticSymlink) Init(creds *auth.Credentials, ino uint64, target string) {
+	s.target = target
+	s.InodeAttrs.Init(creds, ino, linux.ModeSymlink|0777)
+}
+
+// Readlink implements Inode.
+func (s *StaticSymlink) Readlink(_ context.Context) (string, error) {
+	return s.target, nil
+}
+
+// Getlink implements Inode.Getlink.
+func (s *StaticSymlink) Getlink(context.Context, *vfs.Mount) (vfs.VirtualDentry, string, error) {
+	return vfs.VirtualDentry{}, s.target, nil
+}
+
+// SetStat implements Inode.SetStat not allowing inode attributes to be changed.
+func (*StaticSymlink) SetStat(context.Context, *vfs.Filesystem, *auth.Credentials, vfs.SetStatOptions) error {
+	return syserror.EPERM
+}