3 files changed, 125 insertions, 2 deletions
diff --git a/pkg/sentry/fsimpl/mqfs/BUILD b/pkg/sentry/fsimpl/mqfs/BUILD
index 6b22ffabd..6892c6c25 100644
--- a/pkg/sentry/fsimpl/mqfs/BUILD
+++ b/pkg/sentry/fsimpl/mqfs/BUILD
@@ -20,6 +20,7 @@ go_library(
         "mqfs.go",
         "root.go",
         "queue.go",
+        "registry.go",
         "root_inode_refs.go",
     ],
     visibility = ["//pkg/sentry:internal"],
@@ -32,6 +33,7 @@ go_library(
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/mq",
         "//pkg/sentry/vfs",
+        "//pkg/sync",
         "//pkg/usermem",
         "//pkg/waiter",
     ],
diff --git a/pkg/sentry/fsimpl/mqfs/mqfs.go b/pkg/sentry/fsimpl/mqfs/mqfs.go
index 18bc66134..a92012deb 100644
--- a/pkg/sentry/fsimpl/mqfs/mqfs.go
+++ b/pkg/sentry/fsimpl/mqfs/mqfs.go
@@ -28,7 +28,7 @@ import (
 )
 
 const (
-	fsName                   = "mqueue"
+	Name                     = "mqueue"
 	defaultMaxCachedDentries = uint64(1000)
 )
 
@@ -39,7 +39,7 @@ type FilesystemType struct{}
 
 // Name implements vfs.FilesystemType.Name.
 func (FilesystemType) Name() string {
-	return fsName
+	return Name
 }
 
 // Release implements vfs.FilesystemType.Release.
diff --git a/pkg/sentry/fsimpl/mqfs/registry.go b/pkg/sentry/fsimpl/mqfs/registry.go
new file mode 100644
index 000000000..3875b39ee
--- /dev/null
+++ b/pkg/sentry/fsimpl/mqfs/registry.go
@@ -0,0 +1,121 @@
+// Copyright 2021 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 mqfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// RegistryImpl implements mq.RegistryImpl. It implements the interface using
+// the message queue filesystem, and is provided to mq.Registry at
+// initialization.
+//
+// +stateify savable
+type RegistryImpl struct {
+	// mu protects all fields below.
+	mu sync.Mutex
+
+	// root is the root dentry of the mq filesystem. Its main usage is to
+	// retreive the root inode, which we use to add, remove, and lookup message
+	// queues.
+	//
+	// We hold a reference on root and release when the registry is destroyed.
+	root *kernfs.Dentry
+
+	// fs is the filesystem backing this registry, used mainly to initialize
+	// new inodes.
+	fs *filesystem
+
+	// mount is the mount point used for this filesystem.
+	mount *vfs.Mount
+}
+
+// NewRegistryImpl returns a new, initialized RegistryImpl, and takes a
+// reference on root.
+func NewRegistryImpl(root *kernfs.Dentry, fs *filesystem) *RegistryImpl {
+	root.IncRef()
+	return &RegistryImpl{
+		root: root,
+		fs:   fs,
+	}
+}
+
+// Lookup implements mq.RegistryImpl.Lookup.
+func (r *RegistryImpl) Lookup(ctx context.Context, name string) *mq.Queue {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	inode, err := r.lookup(ctx, name)
+	if err != nil {
+		return nil
+	}
+	return inode.(*queueInode).queue
+}
+
+// New implements mq.RegistryImpl.New.
+func (r *RegistryImpl) New(ctx context.Context, name string, q *mq.Queue, perm linux.FileMode) (*vfs.FileDescription, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	root := r.root.Inode().(*rootInode)
+	qInode := r.fs.newQueueInode(ctx, auth.CredentialsFromContext(ctx), q, perm).(*queueInode)
+	err := root.Insert(name, qInode)
+	if err != nil {
+		return nil, err
+	}
+
+	fd := &queueFD{queue: q}
+	err = fd.Init(r.mount, r.root, qInode.data, &qInode.locks, 0 /* flags */)
+	if err != nil {
+		return nil, err
+	}
+	return fd.VFSFileDescription(), nil
+}
+
+// Unlink implements mq.RegistryImpl.Unlink.
+func (r *RegistryImpl) Unlink(ctx context.Context, name string) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	root := r.root.Inode().(*rootInode)
+	inode, err := r.lookup(ctx, name)
+	if err != nil {
+		return err
+	}
+	return root.Unlink(ctx, name, inode)
+}
+
+// lookup retreives a kernfs.Inode using a name.
+//
+// Precondition: r.mu must be held.
+func (r *RegistryImpl) lookup(ctx context.Context, name string) (kernfs.Inode, error) {
+	inode := r.root.Inode().(*rootInode)
+	lookup, err := inode.Lookup(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	return lookup, nil
+}
+
+// Destroy implements mq.RegistryImpl.Destroy.
+func (r *RegistryImpl) Destroy(ctx context.Context) {
+	r.root.DecRef(ctx)
+}