Create package msgqueue.

Create package msgqueue, define primitives to be used for message
queues, and add a msgqueue.Registry to IPCNamespace.

Updates #135

pkg/sentry/kernel/BUILD

@@ -256,6 +256,7 @@ go_library(
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/epoll",
         "//pkg/sentry/kernel/futex",
+        "//pkg/sentry/kernel/msgqueue",
         "//pkg/sentry/kernel/sched",
         "//pkg/sentry/kernel/semaphore",
         "//pkg/sentry/kernel/shm",

pkg/sentry/kernel/ipc_namespace.go

@@ -17,6 +17,7 @@ package kernel
 import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/msgqueue"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/semaphore"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/shm"
 )
@@ -30,6 +31,7 @@ type IPCNamespace struct {
 	// User namespace which owns this IPC namespace. Immutable.
 	userNS *auth.UserNamespace
 
+	queues     *msgqueue.Registry
 	semaphores *semaphore.Registry
 	shms       *shm.Registry
 }
@@ -38,6 +40,7 @@ type IPCNamespace struct {
 func NewIPCNamespace(userNS *auth.UserNamespace) *IPCNamespace {
 	ns := &IPCNamespace{
 		userNS:     userNS,
+		queues:     msgqueue.NewRegistry(userNS),
 		semaphores: semaphore.NewRegistry(userNS),
 		shms:       shm.NewRegistry(userNS),
 	}
@@ -45,6 +48,11 @@ func NewIPCNamespace(userNS *auth.UserNamespace) *IPCNamespace {
 	return ns
 }
 
+// MsgqueueRegistry returns the message queue registry for this namespace.
+func (i *IPCNamespace) MsgqueueRegistry() *msgqueue.Registry {
+	return i.queues
+}
+
 // SemaphoreRegistry returns the semaphore set registry for this namespace.
 func (i *IPCNamespace) SemaphoreRegistry() *semaphore.Registry {
 	return i.semaphores

pkg/sentry/kernel/msgqueue/BUILD

@@ -0,0 +1,32 @@
+load("//tools:defs.bzl", "go_library")
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "message_list",
+    out = "message_list.go",
+    package = "msgqueue",
+    prefix = "msg",
+    template = "//pkg/ilist:generic_list",
+    types = {
+        "Element": "*Message",
+        "Linker": "*Message",
+    },
+)
+
+go_library(
+    name = "msgqueue",
+    srcs = [
+        "msgqueue.go",
+        "message_list.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/kernel/ipc",
+        "//pkg/sentry/kernel/time",
+        "//pkg/waiter",
+        "//pkg/sync",
+    ],
+)

pkg/sentry/kernel/msgqueue/msgqueue.go

@@ -0,0 +1,111 @@
+// 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 msgqueue implements System V message queues.
+package msgqueue
+
+import (
+	"sync"
+
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/ipc"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// Registry contains a set of message queues that can be referenced using keys
+// or IDs.
+//
+// +stateify savable
+type Registry struct {
+	// mu protects all the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// reg defines basic fields and operations needed for all SysV registries.
+	reg *ipc.Registry
+}
+
+// Queue represents a SysV message queue, described by sysvipc(7).
+//
+// +stateify savable
+type Queue struct {
+	// registry is the registry owning this queue. Immutable.
+	registry *Registry
+
+	// mu protects all the fields below.
+	mu sync.Mutex `state:"nosave"`
+
+	// obj defines basic fields that should be included in all SysV IPC objects.
+	obj *ipc.Object
+
+	// senders holds a queue of blocked message senders. Senders are notified
+	// when enough space is available in the queue to insert their message.
+	senders waiter.Queue
+
+	// receivers holds a queue of blocked receivers. Receivers are notified
+	// when a new message is inserted into the queue and can be received.
+	receivers waiter.Queue
+
+	// messages is a list of sent messages.
+	messages msgList
+
+	// sendTime is the last time a msgsnd was perfomed.
+	sendTime ktime.Time
+
+	// receiveTime is the last time a msgrcv was performed.
+	receiveTime ktime.Time
+
+	// changeTime is the last time the queue was modified using msgctl.
+	changeTime ktime.Time
+
+	// byteCount is the current number of message bytes in the queue.
+	byteCount uint64
+
+	// messageCount is the current number of messages in the queue.
+	messageCount uint64
+
+	// maxBytes is the maximum allowed number of bytes in the queue, and is also
+	// used as a limit for the number of total possible messages.
+	maxBytes uint64
+
+	// sendPID is the PID of the process that performed the last msgsnd.
+	sendPID int32
+
+	// receivePID is the PID of the process that performed the last msgrcv.
+	receivePID int32
+}
+
+// Message represents a message exchanged through a Queue via msgsnd(2) and
+// msgrcv(2).
+//
+// +stateify savable
+type Message struct {
+	msgEntry
+
+	// mType is an integer representing the type of the sent message.
+	mType int64
+
+	// mText is an untyped block of memory.
+	mText []byte
+
+	// mSize is the size of mText.
+	mSize uint64
+}
+
+// NewRegistry returns a new Registry ready to be used.
+func NewRegistry(userNS *auth.UserNamespace) *Registry {
+	return &Registry{
+		reg: ipc.NewRegistry(userNS),
+	}
+}