Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 71 insertions, 0 deletions

diff --git a/pkg/sentry/fs/ramfs/tree.go b/pkg/sentry/fs/ramfs/tree.go
new file mode 100644
index 000000000..1fb335f74
--- /dev/null
+++ b/pkg/sentry/fs/ramfs/tree.go
@@ -0,0 +1,71 @@
+// Copyright 2018 Google Inc.
+//
+// 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 ramfs
+
+import (
+	"fmt"
+	"path"
+	"strings"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/anon"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// MakeDirectoryTree constructs a ramfs tree of all directories containing
+// subdirs. Each element of subdir must be a clean path, and cannot be empty or
+// "/".
+func MakeDirectoryTree(ctx context.Context, msrc *fs.MountSource, subdirs []string) (*fs.Inode, error) {
+	root := emptyDir(ctx, msrc)
+	for _, subdir := range subdirs {
+		if path.Clean(subdir) != subdir {
+			return nil, fmt.Errorf("cannot add subdir at an unclean path: %q", subdir)
+		}
+		if subdir == "" || subdir == "/" {
+			return nil, fmt.Errorf("cannot add subdir at %q", subdir)
+		}
+		makeSubdir(ctx, msrc, root.InodeOperations.(*Dir), subdir)
+	}
+	return root, nil
+}
+
+// makeSubdir installs into root each component of subdir. The final component is
+// a *ramfs.Dir.
+func makeSubdir(ctx context.Context, msrc *fs.MountSource, root *Dir, subdir string) {
+	for _, c := range strings.Split(subdir, "/") {
+		if len(c) == 0 {
+			continue
+		}
+		child, ok := root.FindChild(c)
+		if !ok {
+			child = emptyDir(ctx, msrc)
+			root.AddChild(ctx, c, child)
+		}
+		root = child.InodeOperations.(*Dir)
+	}
+}
+
+// emptyDir returns an empty *ramfs.Dir that is traversable but not writable.
+func emptyDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	dir := &Dir{}
+	dir.InitDir(ctx, make(map[string]*fs.Inode), fs.RootOwner, fs.FilePermsFromMode(0555))
+	return fs.NewInode(dir, msrc, fs.StableAttr{
+		DeviceID:  anon.PseudoDevice.DeviceID(),
+		InodeID:   anon.PseudoDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.Directory,
+	})
+}