1 files changed, 69 insertions, 0 deletions
diff --git a/pkg/sentry/vfs/filesystem_impl_util.go b/pkg/sentry/vfs/filesystem_impl_util.go
new file mode 100644
index 000000000..7315a588e
--- /dev/null
+++ b/pkg/sentry/vfs/filesystem_impl_util.go
@@ -0,0 +1,69 @@
+// 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 vfs
+
+import (
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/fspath"
+)
+
+// GenericParseMountOptions parses a comma-separated list of options of the
+// form "key" or "key=value", where neither key nor value contain commas, and
+// returns it as a map. If str contains duplicate keys, then the last value
+// wins. For example:
+//
+// str = "key0=value0,key1,key2=value2,key0=value3" -> map{'key0':'value3','key1':'','key2':'value2'}
+//
+// GenericParseMountOptions is not appropriate if values may contain commas,
+// e.g. in the case of the mpol mount option for tmpfs(5).
+func GenericParseMountOptions(str string) map[string]string {
+	m := make(map[string]string)
+	for _, opt := range strings.Split(str, ",") {
+		if len(opt) > 0 {
+			res := strings.SplitN(opt, "=", 2)
+			if len(res) == 2 {
+				m[res[0]] = res[1]
+			} else {
+				m[opt] = ""
+			}
+		}
+	}
+	return m
+}
+
+// GenericPrependPath may be used by implementations of
+// FilesystemImpl.PrependPath() for which a single statically-determined lock
+// or set of locks is sufficient to ensure its preconditions (as opposed to
+// e.g. per-Dentry locks).
+//
+// Preconditions: Dentry.Name() and Dentry.Parent() must be held constant for
+// vd.Dentry() and all of its ancestors.
+func GenericPrependPath(vfsroot, vd VirtualDentry, b *fspath.Builder) error {
+	mnt, d := vd.mount, vd.dentry
+	for {
+		if mnt == vfsroot.mount && d == vfsroot.dentry {
+			return PrependPathAtVFSRootError{}
+		}
+		if d == mnt.root {
+			return nil
+		}
+		if d.parent == nil {
+			return PrependPathAtNonMountRootError{}
+		}
+		b.PrependComponent(d.name)
+		d = d.parent
+	}
+}