Issue #1829 - Revert "Issue #1751 -- Remove files unused without XP_DARWIN"

This reverts commit cd1f7241353c35627672dc3f6f73eb8bbd5f4925.

3 files changed, 754 insertions, 1 deletions

diff --git a/ipc/glue/SharedMemoryBasic_mach.h b/ipc/glue/SharedMemoryBasic_mach.h
new file mode 100644
index 0000000000..2c54652413
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_mach.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ipc_SharedMemoryBasic_mach_h
+#define mozilla_ipc_SharedMemoryBasic_mach_h
+
+#include "base/file_descriptor_posix.h"
+#include "base/process.h"
+
+#include "SharedMemory.h"
+#include <mach/port.h>
+
+//
+// This is a low-level wrapper around platform shared memory.  Don't
+// use it directly; use Shmem allocated through IPDL interfaces.
+//
+
+class MachPortSender;
+class ReceivePort;
+
+namespace mozilla {
+namespace ipc {
+
+class SharedMemoryBasic final : public SharedMemoryCommon<mach_port_t>
+{
+public:
+  static void SetupMachMemory(pid_t pid,
+                              ReceivePort* listen_port,
+                              MachPortSender* listen_port_ack,
+                              MachPortSender* send_port,
+                              ReceivePort* send_port_ack,
+                              bool pidIsParent);
+
+  static void CleanupForPid(pid_t pid);
+
+  static void Shutdown();
+
+  SharedMemoryBasic();
+
+  virtual bool SetHandle(const Handle& aHandle) override;
+
+  virtual bool Create(size_t aNbytes) override;
+
+  virtual bool Map(size_t nBytes) override;
+
+  virtual void CloseHandle() override;
+
+  virtual void* memory() const override
+  {
+    return mMemory;
+  }
+
+  virtual SharedMemoryType Type() const override
+  {
+    return TYPE_BASIC;
+  }
+
+  static Handle NULLHandle()
+  {
+    return Handle();
+  }
+
+
+  virtual bool IsHandleValid(const Handle &aHandle) const override;
+
+  virtual bool ShareToProcess(base::ProcessId aProcessId,
+                              Handle* aNewHandle) override;
+
+private:
+  ~SharedMemoryBasic();
+
+  void Unmap();
+  mach_port_t mPort;
+  // Pointer to mapped region, null if unmapped.
+  void *mMemory;
+};
+
+} // namespace ipc
+} // namespace mozilla
+
+#endif // ifndef mozilla_ipc_SharedMemoryBasic_mach_h
diff --git a/ipc/glue/SharedMemoryBasic_mach.mm b/ipc/glue/SharedMemoryBasic_mach.mm
new file mode 100644
index 0000000000..3ee5a854d5
--- /dev/null
+++ b/ipc/glue/SharedMemoryBasic_mach.mm
@@ -0,0 +1,664 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <map>
+
+#include <mach/vm_map.h>
+#include <mach/mach_port.h>
+#include <mach/mach_vm.h>
+#include <pthread.h>
+#include <unistd.h>
+#include "SharedMemoryBasic.h"
+#include "chrome/common/mach_ipc_mac.h"
+
+#include "mozilla/StaticMutex.h"
+
+#ifdef DEBUG
+#define LOG_ERROR(str, args...)                 \
+  PR_BEGIN_MACRO                                \
+  char *msg = PR_smprintf(str, ## args);        \
+  NS_WARNING(msg);                              \
+  PR_smprintf_free(msg);                        \
+  PR_END_MACRO
+#else
+#define LOG_ERROR(str, args...) do { /* nothing */ } while(0)
+#endif
+
+#define CHECK_MACH_ERROR(kr, msg)                               \
+  PR_BEGIN_MACRO                                                \
+  if (kr != KERN_SUCCESS) {                                     \
+    LOG_ERROR("%s %s (%x)\n", msg, mach_error_string(kr), kr);  \
+    return false;                                               \
+  }                                                             \
+  PR_END_MACRO
+
+/*
+ * This code is responsible for sharing memory between processes. Memory can be
+ * shared between parent and child or between two children. Each memory region is
+ * referenced via a Mach port. Mach ports are also used for messaging when
+ * sharing a memory region.
+ *
+ * When the parent starts a child, it starts a thread whose only purpose is to
+ * communicate with the child about shared memory. Once the child has started,
+ * it starts a similar thread for communicating with the parent. Each side can
+ * communicate with the thread on the other side via Mach ports. When either
+ * side wants to share memory with the other, it sends a Mach message to the
+ * other side. Attached to the message is the port that references the shared
+ * memory region. When the other side receives the message, it automatically
+ * gets access to the region. It sends a reply (also via a Mach port) so that
+ * the originating side can continue.
+ *
+ * The two sides communicate using four ports. Two ports are used when the
+ * parent shares memory with the child. The other two are used when the child
+ * shares memory with the parent. One of these two ports is used for sending the
+ * "share" message and the other is used for the reply.
+ *
+ * If a child wants to share memory with another child, it sends a "GetPorts"
+ * message to the parent. The parent forwards this GetPorts message to the
+ * target child. The message includes some ports so that the children can talk
+ * directly. Both children start up a thread to communicate with the other child,
+ * similar to the way parent and child communicate. In the future, when these
+ * two children want to communicate, they re-use the channels that were created.
+ *
+ * When a child shuts down, the parent notifies all other children. Those
+ * children then have the opportunity to shut down any threads they might have
+ * been using to communicate directly with that child.
+ */
+
+namespace mozilla {
+namespace ipc {
+
+struct MemoryPorts {
+  MachPortSender* mSender;
+  ReceivePort* mReceiver;
+
+  MemoryPorts() {}
+  MemoryPorts(MachPortSender* sender, ReceivePort* receiver)
+   : mSender(sender), mReceiver(receiver) {}
+};
+
+// Protects gMemoryCommPorts and gThreads.
+static StaticMutex gMutex;
+
+static std::map<pid_t, MemoryPorts> gMemoryCommPorts;
+
+enum {
+  kGetPortsMsg = 1,
+  kSharePortsMsg,
+  kReturnIdMsg,
+  kReturnPortsMsg,
+  kShutdownMsg,
+  kCleanupMsg,
+};
+
+const int kTimeout = 1000;
+const int kLongTimeout = 60 * kTimeout;
+
+pid_t gParentPid = 0;
+
+struct PIDPair {
+  pid_t mRequester;
+  pid_t mRequested;
+
+  PIDPair(pid_t requester, pid_t requested)
+   : mRequester(requester), mRequested(requested) {}
+};
+
+struct ListeningThread {
+  pthread_t mThread;
+  MemoryPorts* mPorts;
+
+  ListeningThread() {}
+  ListeningThread(pthread_t thread, MemoryPorts* ports)
+   : mThread(thread), mPorts(ports) {}
+};
+
+struct SharePortsReply {
+  uint64_t serial;
+  mach_port_t port;
+};
+
+std::map<pid_t, ListeningThread> gThreads;
+
+static void *
+PortServerThread(void *argument);
+
+
+static void
+SetupMachMemory(pid_t pid,
+                ReceivePort* listen_port,
+                MachPortSender* listen_port_ack,
+                MachPortSender* send_port,
+                ReceivePort* send_port_ack,
+                bool pidIsParent)
+{
+  if (pidIsParent) {
+    gParentPid = pid;
+  }
+  MemoryPorts* listen_ports = new MemoryPorts(listen_port_ack, listen_port);
+  pthread_t thread;
+  pthread_attr_t attr;
+  pthread_attr_init(&attr);
+  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+  int err = pthread_create(&thread, &attr, PortServerThread, listen_ports);
+  if (err) {
+    LOG_ERROR("pthread_create failed with %x\n", err);
+    return;
+  }
+
+  gMutex.AssertCurrentThreadOwns();
+  gThreads[pid] = ListeningThread(thread, listen_ports);
+  gMemoryCommPorts[pid] = MemoryPorts(send_port, send_port_ack);
+}
+
+// Send two communication ports to another process along with the pid of the process that is
+// listening on them.
+bool
+SendPortsMessage(MachPortSender* sender,
+                 mach_port_t ports_in_receiver,
+                 mach_port_t ports_out_receiver,
+                 PIDPair pid_pair)
+{
+  MachSendMessage getPortsMsg(kGetPortsMsg);
+  if (!getPortsMsg.AddDescriptor(MachMsgPortDescriptor(ports_in_receiver))) {
+    LOG_ERROR("Adding descriptor to message failed");
+    return false;
+  }
+  if (!getPortsMsg.AddDescriptor(MachMsgPortDescriptor(ports_out_receiver))) {
+    LOG_ERROR("Adding descriptor to message failed");
+    return false;
+  }
+
+  getPortsMsg.SetData(&pid_pair, sizeof(PIDPair));
+  kern_return_t err = sender->SendMessage(getPortsMsg, kTimeout);
+  if (KERN_SUCCESS != err) {
+    LOG_ERROR("Error sending get ports message %s (%x)\n",  mach_error_string(err), err);
+    return false;
+  }
+  return true;
+}
+
+// Receive two communication ports from another process
+bool
+RecvPortsMessage(ReceivePort* receiver, mach_port_t* ports_in_sender, mach_port_t* ports_out_sender)
+{
+  MachReceiveMessage rcvPortsMsg;
+  kern_return_t err = receiver->WaitForMessage(&rcvPortsMsg, kTimeout);
+  if (KERN_SUCCESS != err) {
+    LOG_ERROR("Error receiving get ports message %s (%x)\n",  mach_error_string(err), err);
+  }
+  if (rcvPortsMsg.GetTranslatedPort(0) == MACH_PORT_NULL) {
+    LOG_ERROR("GetTranslatedPort(0) failed");
+    return false;
+  }
+  *ports_in_sender = rcvPortsMsg.GetTranslatedPort(0);
+
+  if (rcvPortsMsg.GetTranslatedPort(1) == MACH_PORT_NULL) {
+    LOG_ERROR("GetTranslatedPort(1) failed");
+    return false;
+  }
+  *ports_out_sender = rcvPortsMsg.GetTranslatedPort(1);
+  return true;
+}
+
+// Send two communication ports to another process and receive two back
+bool
+RequestPorts(const MemoryPorts& request_ports,
+             mach_port_t  ports_in_receiver,
+             mach_port_t* ports_in_sender,
+             mach_port_t* ports_out_sender,
+             mach_port_t ports_out_receiver,
+             PIDPair pid_pair)
+{
+  if (!SendPortsMessage(request_ports.mSender, ports_in_receiver, ports_out_receiver, pid_pair)) {
+    return false;
+  }
+  return RecvPortsMessage(request_ports.mReceiver, ports_in_sender, ports_out_sender);
+}
+
+MemoryPorts*
+GetMemoryPortsForPid(pid_t pid)
+{
+  gMutex.AssertCurrentThreadOwns();
+
+  if (gMemoryCommPorts.find(pid) == gMemoryCommPorts.end()) {
+    // We don't have the ports open to communicate with that pid, so we're going to
+    // ask our parent process over IPC to set them up for us.
+    if (gParentPid == 0) {
+      // If we're the top level parent process, we have no parent to ask.
+      LOG_ERROR("request for ports for pid %d, but we're the chrome process\n", pid);
+      return nullptr;
+    }
+    const MemoryPorts& parent = gMemoryCommPorts[gParentPid];
+
+    // Create two receiving ports in this process to send to the parent. One will be used for
+    // for listening for incoming memory to be shared, the other for getting the Handle of
+    // memory we share to the other process.
+    ReceivePort* ports_in_receiver = new ReceivePort();
+    ReceivePort* ports_out_receiver = new ReceivePort();
+    mach_port_t raw_ports_in_sender, raw_ports_out_sender;
+    if (!RequestPorts(parent,
+                      ports_in_receiver->GetPort(),
+                      &raw_ports_in_sender,
+                      &raw_ports_out_sender,
+                      ports_out_receiver->GetPort(),
+                      PIDPair(getpid(), pid))) {
+      LOG_ERROR("failed to request ports\n");
+      return nullptr;
+    }
+    // Our parent process sent us two ports, one is for sending new memory to, the other
+    // is for replying with the Handle when we receive new memory.
+    MachPortSender* ports_in_sender = new MachPortSender(raw_ports_in_sender);
+    MachPortSender* ports_out_sender = new MachPortSender(raw_ports_out_sender);
+    SetupMachMemory(pid,
+                    ports_in_receiver,
+                    ports_in_sender,
+                    ports_out_sender,
+                    ports_out_receiver,
+                    false);
+    MOZ_ASSERT(gMemoryCommPorts.find(pid) != gMemoryCommPorts.end());
+  }
+  return &gMemoryCommPorts.at(pid);
+}
+
+// We just received a port representing a region of shared memory, reply to
+// the process that set it with the mach_port_t that represents it in this process.
+// That will be the Handle to be shared over normal IPC
+void
+HandleSharePortsMessage(MachReceiveMessage* rmsg, MemoryPorts* ports)
+{
+  mach_port_t port = rmsg->GetTranslatedPort(0);
+  uint64_t* serial = reinterpret_cast<uint64_t*>(rmsg->GetData());
+  MachSendMessage msg(kReturnIdMsg);
+  // Construct the reply message, echoing the serial, and adding the port
+  SharePortsReply replydata;
+  replydata.port = port;
+  replydata.serial = *serial;
+  msg.SetData(&replydata, sizeof(SharePortsReply));
+  kern_return_t err = ports->mSender->SendMessage(msg, kTimeout);
+  if (KERN_SUCCESS != err) {
+    LOG_ERROR("SendMessage failed 0x%x %s\n", err, mach_error_string(err));
+  }
+}
+
+// We were asked by another process to get communications ports to some process. Return
+// those ports via an IPC message.
+bool
+SendReturnPortsMsg(MachPortSender* sender,
+                   mach_port_t raw_ports_in_sender,
+                   mach_port_t raw_ports_out_sender)
+{
+  MachSendMessage getPortsMsg(kReturnPortsMsg);
+  if (!getPortsMsg.AddDescriptor(MachMsgPortDescriptor(raw_ports_in_sender))) {
+    LOG_ERROR("Adding descriptor to message failed");
+    return false;
+  }
+
+  if (!getPortsMsg.AddDescriptor(MachMsgPortDescriptor(raw_ports_out_sender))) {
+    LOG_ERROR("Adding descriptor to message failed");
+    return false;
+  }
+  kern_return_t err = sender->SendMessage(getPortsMsg, kTimeout);
+  if (KERN_SUCCESS != err) {
+    LOG_ERROR("Error sending get ports message %s (%x)\n",  mach_error_string(err), err);
+    return false;
+  }
+  return true;
+}
+
+// We were asked for communcations ports to a process that isn't us. Assuming that process
+// is one of our children, forward that request on.
+void
+ForwardGetPortsMessage(MachReceiveMessage* rmsg, MemoryPorts* ports, PIDPair* pid_pair)
+{
+  if (rmsg->GetTranslatedPort(0) == MACH_PORT_NULL) {
+    LOG_ERROR("GetTranslatedPort(0) failed");
+    return;
+  }
+  if (rmsg->GetTranslatedPort(1) == MACH_PORT_NULL) {
+    LOG_ERROR("GetTranslatedPort(1) failed");
+    return;
+  }
+  mach_port_t raw_ports_in_sender, raw_ports_out_sender;
+  MemoryPorts* requestedPorts = GetMemoryPortsForPid(pid_pair->mRequested);
+  if (!requestedPorts) {
+    LOG_ERROR("failed to find port for process\n");
+    return;
+  }
+  if (!RequestPorts(*requestedPorts, rmsg->GetTranslatedPort(0), &raw_ports_in_sender,
+                    &raw_ports_out_sender, rmsg->GetTranslatedPort(1), *pid_pair)) {
+    LOG_ERROR("failed to request ports\n");
+    return;
+  }
+  SendReturnPortsMsg(ports->mSender, raw_ports_in_sender, raw_ports_out_sender);
+}
+
+// We receieved a message asking us to get communications ports for another process
+void
+HandleGetPortsMessage(MachReceiveMessage* rmsg, MemoryPorts* ports)
+{
+  PIDPair* pid_pair;
+  if (rmsg->GetDataLength() != sizeof(PIDPair)) {
+    LOG_ERROR("Improperly formatted message\n");
+    return;
+  }
+  pid_pair = reinterpret_cast<PIDPair*>(rmsg->GetData());
+  if (pid_pair->mRequested != getpid()) {
+    // This request is for ports to a process that isn't us, forward it to that process
+    ForwardGetPortsMessage(rmsg, ports, pid_pair);
+  } else {
+    if (rmsg->GetTranslatedPort(0) == MACH_PORT_NULL) {
+      LOG_ERROR("GetTranslatedPort(0) failed");
+      return;
+    }
+
+    if (rmsg->GetTranslatedPort(1) == MACH_PORT_NULL) {
+      LOG_ERROR("GetTranslatedPort(1) failed");
+      return;
+    }
+
+    MachPortSender* ports_in_sender = new MachPortSender(rmsg->GetTranslatedPort(0));
+    MachPortSender* ports_out_sender = new MachPortSender(rmsg->GetTranslatedPort(1));
+
+    ReceivePort* ports_in_receiver = new ReceivePort();
+    ReceivePort* ports_out_receiver = new ReceivePort();
+    if (SendReturnPortsMsg(ports->mSender, ports_in_receiver->GetPort(), ports_out_receiver->GetPort())) {
+      SetupMachMemory(pid_pair->mRequester,
+                      ports_out_receiver,
+                      ports_out_sender,
+                      ports_in_sender,
+                      ports_in_receiver,
+                      false);
+    }
+  }
+}
+
+static void *
+PortServerThread(void *argument)
+{
+  MemoryPorts* ports = static_cast<MemoryPorts*>(argument);
+  MachReceiveMessage child_message;
+  while (true) {
+    MachReceiveMessage rmsg;
+    kern_return_t err = ports->mReceiver->WaitForMessage(&rmsg, MACH_MSG_TIMEOUT_NONE);
+    if (err != KERN_SUCCESS) {
+      LOG_ERROR("Wait for message failed 0x%x %s\n", err, mach_error_string(err));
+      continue;
+    }
+    if (rmsg.GetMessageID() == kShutdownMsg) {
+      delete ports->mSender;
+      delete ports->mReceiver;
+      delete ports;
+      return nullptr;
+    }
+    StaticMutexAutoLock smal(gMutex);
+    switch (rmsg.GetMessageID()) {
+    case kSharePortsMsg:
+      HandleSharePortsMessage(&rmsg, ports);
+      break;
+    case kGetPortsMsg:
+      HandleGetPortsMessage(&rmsg, ports);
+      break;
+    case kCleanupMsg:
+     if (gParentPid == 0) {
+       LOG_ERROR("Cleanup message not valid for parent process");
+       continue;
+     }
+
+      pid_t* pid;
+      if (rmsg.GetDataLength() != sizeof(pid_t)) {
+        LOG_ERROR("Improperly formatted message\n");
+        continue;
+      }
+      pid = reinterpret_cast<pid_t*>(rmsg.GetData());
+      SharedMemoryBasic::CleanupForPid(*pid);
+      break;
+    default:
+      LOG_ERROR("Unknown message\n");
+    }
+  }
+}
+
+void
+SharedMemoryBasic::SetupMachMemory(pid_t pid,
+                                   ReceivePort* listen_port,
+                                   MachPortSender* listen_port_ack,
+                                   MachPortSender* send_port,
+                                   ReceivePort* send_port_ack,
+                                   bool pidIsParent)
+{
+  StaticMutexAutoLock smal(gMutex);
+  mozilla::ipc::SetupMachMemory(pid, listen_port, listen_port_ack, send_port, send_port_ack, pidIsParent);
+}
+
+void
+SharedMemoryBasic::Shutdown()
+{
+  StaticMutexAutoLock smal(gMutex);
+
+  for (auto it = gThreads.begin(); it != gThreads.end(); ++it) {
+    MachSendMessage shutdownMsg(kShutdownMsg);
+    it->second.mPorts->mReceiver->SendMessageToSelf(shutdownMsg, kTimeout);
+  }
+  gThreads.clear();
+
+  for (auto it = gMemoryCommPorts.begin(); it != gMemoryCommPorts.end(); ++it) {
+    delete it->second.mSender;
+    delete it->second.mReceiver;
+  }
+  gMemoryCommPorts.clear();
+}
+
+void
+SharedMemoryBasic::CleanupForPid(pid_t pid)
+{
+  if (gThreads.find(pid) == gThreads.end()) {
+    return;
+  }
+  const ListeningThread& listeningThread = gThreads[pid];
+  MachSendMessage shutdownMsg(kShutdownMsg);
+  kern_return_t ret = listeningThread.mPorts->mReceiver->SendMessageToSelf(shutdownMsg, kTimeout);
+  if (ret != KERN_SUCCESS) {
+    LOG_ERROR("sending shutdown msg failed %s %x\n", mach_error_string(ret), ret);
+  }
+  gThreads.erase(pid);
+
+  if (gParentPid == 0) {
+    // We're the parent. Broadcast the cleanup message to everyone else.
+    for (auto it = gMemoryCommPorts.begin(); it != gMemoryCommPorts.end(); ++it) {
+      MachSendMessage msg(kCleanupMsg);
+      msg.SetData(&pid, sizeof(pid));
+      // We don't really care if this fails, we could be trying to send to an already shut down proc
+      it->second.mSender->SendMessage(msg, kTimeout);
+    }
+  }
+
+  MemoryPorts& ports = gMemoryCommPorts[pid];
+  delete ports.mSender;
+  delete ports.mReceiver;
+  gMemoryCommPorts.erase(pid);
+}
+
+SharedMemoryBasic::SharedMemoryBasic()
+  : mPort(MACH_PORT_NULL)
+  , mMemory(nullptr)
+{
+}
+
+SharedMemoryBasic::~SharedMemoryBasic()
+{
+  Unmap();
+  CloseHandle();
+}
+
+bool
+SharedMemoryBasic::SetHandle(const Handle& aHandle)
+{
+  MOZ_ASSERT(mPort == MACH_PORT_NULL, "already initialized");
+
+  mPort = aHandle;
+  return true;
+}
+
+static inline void*
+toPointer(mach_vm_address_t address)
+{
+  return reinterpret_cast<void*>(static_cast<uintptr_t>(address));
+}
+
+static inline mach_vm_address_t
+toVMAddress(void* pointer)
+{
+  return static_cast<mach_vm_address_t>(reinterpret_cast<uintptr_t>(pointer));
+}
+
+bool
+SharedMemoryBasic::Create(size_t size)
+{
+  mach_vm_address_t address;
+
+  kern_return_t kr = mach_vm_allocate(mach_task_self(), &address, round_page(size), VM_FLAGS_ANYWHERE);
+  if (kr != KERN_SUCCESS) {
+    LOG_ERROR("Failed to allocate mach_vm_allocate shared memory (%zu bytes). %s (%x)\n",
+              size, mach_error_string(kr), kr);
+    return false;
+  }
+
+  memory_object_size_t memoryObjectSize = round_page(size);
+
+  kr = mach_make_memory_entry_64(mach_task_self(),
+                                 &memoryObjectSize,
+                                 address,
+                                 VM_PROT_DEFAULT,
+                                 &mPort,
+                                 MACH_PORT_NULL);
+  if (kr != KERN_SUCCESS) {
+    LOG_ERROR("Failed to make memory entry (%zu bytes). %s (%x)\n",
+              size, mach_error_string(kr), kr);
+    return false;
+  }
+
+  mMemory = toPointer(address);
+  Mapped(size);
+  return true;
+}
+
+bool
+SharedMemoryBasic::Map(size_t size)
+{
+  if (mMemory) {
+    return true;
+  }
+
+  if (MACH_PORT_NULL == mPort) {
+    return false;
+  }
+
+  kern_return_t kr;
+  mach_vm_address_t address = 0;
+
+  vm_prot_t vmProtection = VM_PROT_READ | VM_PROT_WRITE;
+
+  kr = mach_vm_map(mach_task_self(), &address, round_page(size), 0, VM_FLAGS_ANYWHERE,
+                   mPort, 0, false, vmProtection, vmProtection, VM_INHERIT_NONE);
+  if (kr != KERN_SUCCESS) {
+    LOG_ERROR("Failed to map shared memory (%zu bytes) into %x, port %x. %s (%x)\n",
+              size, mach_task_self(), mPort, mach_error_string(kr), kr);
+    return false;
+  }
+
+  mMemory = toPointer(address);
+  Mapped(size);
+  return true;
+}
+
+bool
+SharedMemoryBasic::ShareToProcess(base::ProcessId pid,
+                                  Handle* aNewHandle)
+{
+  if (pid == getpid()) {
+    *aNewHandle = mPort;
+    return mach_port_mod_refs(mach_task_self(), *aNewHandle, MACH_PORT_RIGHT_SEND, 1) == KERN_SUCCESS;
+  }
+  StaticMutexAutoLock smal(gMutex);
+
+   // Serially number the messages, to check whether
+  // the reply we get was meant for us.
+  static uint64_t serial = 0;
+  uint64_t my_serial = serial;
+  serial++;
+
+  MemoryPorts* ports = GetMemoryPortsForPid(pid);
+  if (!ports) {
+    LOG_ERROR("Unable to get ports for process.\n");
+    return false;
+  }
+  MachSendMessage smsg(kSharePortsMsg);
+  smsg.AddDescriptor(MachMsgPortDescriptor(mPort, MACH_MSG_TYPE_COPY_SEND));
+  smsg.SetData(&my_serial, sizeof(uint64_t));
+  kern_return_t err = ports->mSender->SendMessage(smsg, kTimeout);
+  if (err != KERN_SUCCESS) {
+    LOG_ERROR("sending port failed %s %x\n", mach_error_string(err), err);
+    return false;
+  }
+  MachReceiveMessage msg;
+  err = ports->mReceiver->WaitForMessage(&msg, kTimeout);
+  if (err != KERN_SUCCESS) {
+    LOG_ERROR("short timeout didn't get an id %s %x\n", mach_error_string(err), err);
+    err = ports->mReceiver->WaitForMessage(&msg, kLongTimeout);
+
+    if (err != KERN_SUCCESS) {
+      LOG_ERROR("long timeout didn't get an id %s %x\n", mach_error_string(err), err);
+      return false;
+    }
+  }
+  if (msg.GetDataLength() != sizeof(SharePortsReply)) {
+    LOG_ERROR("Improperly formatted reply\n");
+    return false;
+  }
+  SharePortsReply* msg_data = reinterpret_cast<SharePortsReply*>(msg.GetData());
+  mach_port_t id = msg_data->port;
+  uint64_t serial_check = msg_data->serial;
+  if (serial_check != my_serial) {
+    LOG_ERROR("Serials do not match up: %d vs %d", serial_check, my_serial);
+    return false;
+  }
+  *aNewHandle = id;
+  return true;
+}
+
+void
+SharedMemoryBasic::Unmap()
+{
+  if (!mMemory) {
+    return;
+  }
+  vm_address_t address = toVMAddress(mMemory);
+  kern_return_t kr = vm_deallocate(mach_task_self(), address, round_page(mMappedSize));
+  if (kr != KERN_SUCCESS) {
+    LOG_ERROR("Failed to deallocate shared memory. %s (%x)\n",  mach_error_string(kr), kr);
+    return;
+  }
+  mMemory = nullptr;
+}
+
+void
+SharedMemoryBasic::CloseHandle()
+{
+  if (mPort != MACH_PORT_NULL) {
+    mach_port_deallocate(mach_task_self(), mPort);
+    mPort = MACH_PORT_NULL;
+  }
+}
+
+bool
+SharedMemoryBasic::IsHandleValid(const Handle& aHandle) const
+{
+  return aHandle > 0;
+}
+
+} // namespace ipc
+} // namespace mozilla
diff --git a/ipc/glue/moz.build b/ipc/glue/moz.build
index d882e3fbd1..426e796668 100644
--- a/ipc/glue/moz.build
+++ b/ipc/glue/moz.build
@@ -77,7 +77,13 @@ else:
         'CrossProcessMutex_unimplemented.cpp',
     ]
 
-EXPORTS.mozilla.ipc += ['SharedMemoryBasic_chromium.h']
+if CONFIG['OS_ARCH'] == 'Darwin':
+    EXPORTS.mozilla.ipc += ['SharedMemoryBasic_mach.h']
+    SOURCES += [
+        'SharedMemoryBasic_mach.mm',
+    ]
+else:
+    EXPORTS.mozilla.ipc += ['SharedMemoryBasic_chromium.h']
 
 if CONFIG['OS_ARCH'] == 'Linux':
     UNIFIED_SOURCES += [