gecko-dev/ipc/glue/ProtocolUtils.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "base/process_util.h"
#include "base/task.h"

#ifdef OS_POSIX
#include <errno.h>
#endif

#include "mozilla/IntegerPrintfMacros.h"

#include "mozilla/ipc/ProtocolUtils.h"

#include "mozilla/dom/ContentParent.h"
#include "mozilla/ipc/MessageChannel.h"
#include "mozilla/ipc/Transport.h"
#include "mozilla/StaticMutex.h"
#include "mozilla/SystemGroup.h"
#include "mozilla/Unused.h"
#include "nsPrintfCString.h"

#if defined(MOZ_SANDBOX) && defined(XP_WIN)
#define TARGET_SANDBOX_EXPORTS
#include "mozilla/sandboxTarget.h"
#endif

#if defined(MOZ_CRASHREPORTER) && defined(XP_WIN)
#include "aclapi.h"
#include "sddl.h"

#include "mozilla/TypeTraits.h"
#endif

#include "nsAutoPtr.h"

using namespace IPC;

using base::GetCurrentProcId;
using base::ProcessHandle;
using base::ProcessId;

namespace mozilla {

#if defined(MOZ_CRASHREPORTER) && defined(XP_WIN)
// Generate RAII classes for LPTSTR and PSECURITY_DESCRIPTOR.
MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedLPTStr, \
                                          RemovePointer<LPTSTR>::Type, \
                                          ::LocalFree)
MOZ_TYPE_SPECIFIC_SCOPED_POINTER_TEMPLATE(ScopedPSecurityDescriptor, \
                                          RemovePointer<PSECURITY_DESCRIPTOR>::Type, \
                                          ::LocalFree)
#endif

namespace ipc {

IPCResult
IPCResult::Fail(NotNull<IProtocol*> actor, const char* where, const char* why)
{
  // Calls top-level protocol to handle the error.
  nsPrintfCString errorMsg("%s::%s %s\n", actor->ProtocolName(), where, why);
  actor->GetIPCChannel()->Listener()->ProcessingError(
    HasResultCodes::MsgProcessingError, errorMsg.get());
  return IPCResult(false);
}

class ChannelOpened : public IPC::Message
{
public:
  ChannelOpened(TransportDescriptor aDescriptor,
                ProcessId aOtherProcess,
                ProtocolId aProtocol,
                NestedLevel aNestedLevel = NOT_NESTED)
    : IPC::Message(MSG_ROUTING_CONTROL, // these only go to top-level actors
                   CHANNEL_OPENED_MESSAGE_TYPE,
                   0,
                   HeaderFlags(aNestedLevel))
  {
    IPC::WriteParam(this, aDescriptor);
    IPC::WriteParam(this, aOtherProcess);
    IPC::WriteParam(this, static_cast<uint32_t>(aProtocol));
  }

  static bool Read(const IPC::Message& aMsg,
                   TransportDescriptor* aDescriptor,
                   ProcessId* aOtherProcess,
                   ProtocolId* aProtocol)
  {
    PickleIterator iter(aMsg);
    if (!IPC::ReadParam(&aMsg, &iter, aDescriptor) ||
        !IPC::ReadParam(&aMsg, &iter, aOtherProcess) ||
        !IPC::ReadParam(&aMsg, &iter, reinterpret_cast<uint32_t*>(aProtocol))) {
      return false;
    }
    aMsg.EndRead(iter);
    return true;
  }
};

nsresult
Bridge(const PrivateIPDLInterface&,
       MessageChannel* aParentChannel, ProcessId aParentPid,
       MessageChannel* aChildChannel, ProcessId aChildPid,
       ProtocolId aProtocol, ProtocolId aChildProtocol)
{
  if (!aParentPid || !aChildPid) {
    return NS_ERROR_INVALID_ARG;
  }

  TransportDescriptor parentSide, childSide;
  nsresult rv;
  if (NS_FAILED(rv = CreateTransport(aParentPid, &parentSide, &childSide))) {
    return rv;
  }

  if (!aParentChannel->Send(new ChannelOpened(parentSide,
                                              aChildPid,
                                              aProtocol,
                                              IPC::Message::NESTED_INSIDE_CPOW))) {
    CloseDescriptor(parentSide);
    CloseDescriptor(childSide);
    return NS_ERROR_BRIDGE_OPEN_PARENT;
  }

  if (!aChildChannel->Send(new ChannelOpened(childSide,
                                            aParentPid,
                                            aChildProtocol,
                                            IPC::Message::NESTED_INSIDE_CPOW))) {
    CloseDescriptor(parentSide);
    CloseDescriptor(childSide);
    return NS_ERROR_BRIDGE_OPEN_CHILD;
  }

  return NS_OK;
}

bool
Open(const PrivateIPDLInterface&,
     MessageChannel* aOpenerChannel, ProcessId aOtherProcessId,
     Transport::Mode aOpenerMode,
     ProtocolId aProtocol, ProtocolId aChildProtocol)
{
  bool isParent = (Transport::MODE_SERVER == aOpenerMode);
  ProcessId thisPid = GetCurrentProcId();
  ProcessId parentId = isParent ? thisPid : aOtherProcessId;
  ProcessId childId = !isParent ? thisPid : aOtherProcessId;
  if (!parentId || !childId) {
    return false;
  }

  TransportDescriptor parentSide, childSide;
  if (NS_FAILED(CreateTransport(parentId, &parentSide, &childSide))) {
    return false;
  }

  Message* parentMsg = new ChannelOpened(parentSide, childId, aProtocol);
  Message* childMsg = new ChannelOpened(childSide, parentId, aChildProtocol);
  nsAutoPtr<Message> messageForUs(isParent ? parentMsg : childMsg);
  nsAutoPtr<Message> messageForOtherSide(!isParent ? parentMsg : childMsg);
  if (!aOpenerChannel->Echo(messageForUs.forget()) ||
      !aOpenerChannel->Send(messageForOtherSide.forget())) {
    CloseDescriptor(parentSide);
    CloseDescriptor(childSide);
    return false;
  }
  return true;
}

bool
UnpackChannelOpened(const PrivateIPDLInterface&,
                    const Message& aMsg,
                    TransportDescriptor* aTransport,
                    ProcessId* aOtherProcess,
                    ProtocolId* aProtocol)
{
  return ChannelOpened::Read(aMsg, aTransport, aOtherProcess, aProtocol);
}

#if defined(XP_WIN)
bool DuplicateHandle(HANDLE aSourceHandle,
                     DWORD aTargetProcessId,
                     HANDLE* aTargetHandle,
                     DWORD aDesiredAccess,
                     DWORD aOptions) {
  // If our process is the target just duplicate the handle.
  if (aTargetProcessId == base::GetCurrentProcId()) {
    return !!::DuplicateHandle(::GetCurrentProcess(), aSourceHandle,
                               ::GetCurrentProcess(), aTargetHandle,
                               aDesiredAccess, false, aOptions);

  }

#if defined(MOZ_SANDBOX)
  // Try the broker next (will fail if not sandboxed).
  if (SandboxTarget::Instance()->BrokerDuplicateHandle(aSourceHandle,
                                                       aTargetProcessId,
                                                       aTargetHandle,
                                                       aDesiredAccess,
                                                       aOptions)) {
    return true;
  }
#endif

  // Finally, see if we already have access to the process.
  ScopedProcessHandle targetProcess(OpenProcess(PROCESS_DUP_HANDLE,
                                                FALSE,
                                                aTargetProcessId));
  if (!targetProcess) {
#ifdef MOZ_CRASHREPORTER
    CrashReporter::AnnotateCrashReport(
      NS_LITERAL_CSTRING("IPCTransportFailureReason"),
      NS_LITERAL_CSTRING("Failed to open target process."));
#endif
    return false;
  }

  return !!::DuplicateHandle(::GetCurrentProcess(), aSourceHandle,
                              targetProcess, aTargetHandle,
                              aDesiredAccess, FALSE, aOptions);
}
#endif

#ifdef MOZ_CRASHREPORTER
void
AnnotateSystemError()
{
  int64_t error = 0;
#if defined(XP_WIN)
  error = ::GetLastError();
#elif defined(OS_POSIX)
  error = errno;
#endif
  if (error) {
    CrashReporter::AnnotateCrashReport(
      NS_LITERAL_CSTRING("IPCSystemError"),
      nsPrintfCString("%" PRId64, error));
  }
}
#endif

#if defined(MOZ_CRASHREPORTER) && defined(XP_MACOSX)
void
AnnotateCrashReportWithErrno(const char* tag, int error)
{
  CrashReporter::AnnotateCrashReport(
    nsCString(tag),
    nsPrintfCString("%d", error));
}
#endif

void
LogMessageForProtocol(const char* aTopLevelProtocol, base::ProcessId aOtherPid,
                      const char* aContextDescription,
                      uint32_t aMessageId,
                      MessageDirection aDirection)
{
  nsPrintfCString logMessage("[time: %" PRId64 "][%d%s%d] [%s] %s %s\n",
                             PR_Now(), base::GetCurrentProcId(),
                             aDirection == MessageDirection::eReceiving ? "<-" : "->",
                             aOtherPid, aTopLevelProtocol,
                             aContextDescription,
                             StringFromIPCMessageType(aMessageId));
#ifdef ANDROID
  __android_log_write(ANDROID_LOG_INFO, "GeckoIPC", logMessage.get());
#endif
  fputs(logMessage.get(), stderr);
}

void
ProtocolErrorBreakpoint(const char* aMsg)
{
    // Bugs that generate these error messages can be tough to
    // reproduce.  Log always in the hope that someone finds the error
    // message.
    printf_stderr("IPDL protocol error: %s\n", aMsg);
}

void
FatalError(const char* aProtocolName, const char* aMsg, bool aIsParent)
{
  ProtocolErrorBreakpoint(aMsg);

  nsAutoCString formattedMessage("IPDL error [");
  formattedMessage.AppendASCII(aProtocolName);
  formattedMessage.AppendLiteral("]: \"");
  formattedMessage.AppendASCII(aMsg);
  if (aIsParent) {
#ifdef MOZ_CRASHREPORTER
    // We're going to crash the parent process because at this time
    // there's no other really nice way of getting a minidump out of
    // this process if we're off the main thread.
    formattedMessage.AppendLiteral("\". Intentionally crashing.");
    NS_ERROR(formattedMessage.get());
    CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("IPCFatalErrorProtocol"),
                                       nsDependentCString(aProtocolName));
    CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("IPCFatalErrorMsg"),
                                       nsDependentCString(aMsg));
    AnnotateSystemError();
#endif
    MOZ_CRASH("IPC FatalError in the parent process!");
  } else {
    formattedMessage.AppendLiteral("\". abort()ing as a result.");
    MOZ_CRASH_UNSAFE_OOL(formattedMessage.get());
  }
}

void
LogicError(const char* aMsg)
{
  MOZ_CRASH_UNSAFE_OOL(aMsg);
}

void
ActorIdReadError(const char* aActorDescription)
{
  nsPrintfCString message("Error deserializing id for %s", aActorDescription);
  NS_RUNTIMEABORT(message.get());
}

void
BadActorIdError(const char* aActorDescription)
{
  nsPrintfCString message("bad id for %s", aActorDescription);
  ProtocolErrorBreakpoint(message.get());
}

void
ActorLookupError(const char* aActorDescription)
{
  nsPrintfCString message("could not lookup id for %s", aActorDescription);
  ProtocolErrorBreakpoint(message.get());
}

void
MismatchedActorTypeError(const char* aActorDescription)
{
  nsPrintfCString message("actor that should be of type %s has different type",
                          aActorDescription);
  ProtocolErrorBreakpoint(message.get());
}

void
UnionTypeReadError(const char* aUnionName)
{
  nsPrintfCString message("error deserializing type of union %s", aUnionName);
  NS_RUNTIMEABORT(message.get());
}

void
ArrayLengthReadError(const char* aElementName)
{
  nsPrintfCString message("error deserializing length of %s[]", aElementName);
  NS_RUNTIMEABORT(message.get());
}

void
SentinelReadError(const char* aClassName)
{
  nsPrintfCString message("incorrect sentinel when reading %s", aClassName);
  NS_RUNTIMEABORT(message.get());
}

void
TableToArray(const nsTHashtable<nsPtrHashKey<void>>& aTable,
             nsTArray<void*>& aArray)
{
  uint32_t i = 0;
  void** elements = aArray.AppendElements(aTable.Count());
  for (auto iter = aTable.ConstIter(); !iter.Done(); iter.Next()) {
    elements[i] = iter.Get()->GetKey();
    ++i;
  }
}

Maybe<IProtocol*>
IProtocol::ReadActor(const IPC::Message* aMessage, PickleIterator* aIter, bool aNullable,
                     const char* aActorDescription, int32_t aProtocolTypeId)
{
    int32_t id;
    if (!IPC::ReadParam(aMessage, aIter, &id)) {
        ActorIdReadError(aActorDescription);
        return Nothing();
    }

    if (id == 1 || (id == 0 && !aNullable)) {
        BadActorIdError(aActorDescription);
        return Nothing();
    }

    if (id == 0) {
        return Some(static_cast<IProtocol*>(nullptr));
    }

    IProtocol* listener = this->Lookup(id);
    if (!listener) {
        ActorLookupError(aActorDescription);
        return Nothing();
    }

    if (listener->GetProtocolTypeId() != aProtocolTypeId) {
        MismatchedActorTypeError(aActorDescription);
        return Nothing();
    }

    return Some(listener);
}

int32_t
IProtocol::Register(IProtocol* aRouted)
{
  return Manager()->Register(aRouted);
}

int32_t
IProtocol::RegisterID(IProtocol* aRouted, int32_t aId)
{
  return Manager()->RegisterID(aRouted, aId);
}

IProtocol*
IProtocol::Lookup(int32_t aId)
{
  return Manager()->Lookup(aId);
}

void
IProtocol::Unregister(int32_t aId)
{
  if (mId == aId) {
    mId = kFreedActorId;
  }
  Manager()->Unregister(aId);
}

Shmem::SharedMemory*
IProtocol::CreateSharedMemory(size_t aSize,
                              SharedMemory::SharedMemoryType aType,
                              bool aUnsafe,
                              int32_t* aId)
{
  return Manager()->CreateSharedMemory(aSize, aType, aUnsafe, aId);
}

Shmem::SharedMemory*
IProtocol::LookupSharedMemory(int32_t aId)
{
  return Manager()->LookupSharedMemory(aId);
}

bool
IProtocol::IsTrackingSharedMemory(Shmem::SharedMemory* aSegment)
{
  return Manager()->IsTrackingSharedMemory(aSegment);
}

bool
IProtocol::DestroySharedMemory(Shmem& aShmem)
{
  return Manager()->DestroySharedMemory(aShmem);
}

ProcessId
IProtocol::OtherPid() const
{
  return Manager()->OtherPid();
}

void
IProtocol::FatalError(const char* const aErrorMsg) const
{
  HandleFatalError(ProtocolName(), aErrorMsg);
}

void
IProtocol::HandleFatalError(const char* aProtocolName, const char* aErrorMsg) const
{
  if (IProtocol* manager = Manager()) {
    manager->HandleFatalError(aProtocolName, aErrorMsg);
    return;
  }

  mozilla::ipc::FatalError(aProtocolName, aErrorMsg, mSide == ParentSide);
}

bool
IProtocol::AllocShmem(size_t aSize,
                      Shmem::SharedMemory::SharedMemoryType aType,
                      Shmem* aOutMem)
{
  Shmem::id_t id;
  Shmem::SharedMemory* rawmem(CreateSharedMemory(aSize, aType, false, &id));
  if (!rawmem) {
    return false;
  }

  *aOutMem = Shmem(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), rawmem, id);
  return true;
}

bool
IProtocol::AllocUnsafeShmem(size_t aSize,
                            Shmem::SharedMemory::SharedMemoryType aType,
                            Shmem* aOutMem)
{
  Shmem::id_t id;
  Shmem::SharedMemory* rawmem(CreateSharedMemory(aSize, aType, true, &id));
  if (!rawmem) {
    return false;
  }

  *aOutMem = Shmem(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), rawmem, id);
  return true;
}

bool
IProtocol::DeallocShmem(Shmem& aMem)
{
  bool ok = DestroySharedMemory(aMem);
#ifdef DEBUG
  if (!ok) {
    if (mSide == ChildSide) {
      FatalError("bad Shmem");
    } else {
      NS_WARNING("bad Shmem");
    }
    return false;
  }
#endif // DEBUG
  aMem.forget(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead());
  return ok;
}

void
IProtocol::SetManager(IProtocol* aManager)
{
  MOZ_RELEASE_ASSERT(!mManager || mManager == aManager);
  mManager = aManager;
}

void
IProtocol::SetEventTargetForActor(IProtocol* aActor, nsIEventTarget* aEventTarget)
{
  // Make sure we have a manager for the internal method to access.
  aActor->SetManager(this);
  SetEventTargetForActorInternal(aActor, aEventTarget);
}

void
IProtocol::ReplaceEventTargetForActor(IProtocol* aActor,
                                      nsIEventTarget* aEventTarget)
{
  // Ensure the actor has been registered.
  MOZ_ASSERT(aActor->Manager());
  ReplaceEventTargetForActorInternal(aActor, aEventTarget);
}

void
IProtocol::SetEventTargetForActorInternal(IProtocol* aActor,
                                          nsIEventTarget* aEventTarget)
{
  Manager()->SetEventTargetForActorInternal(aActor, aEventTarget);
}

void
IProtocol::ReplaceEventTargetForActorInternal(IProtocol* aActor,
                                              nsIEventTarget* aEventTarget)
{
  Manager()->ReplaceEventTargetForActorInternal(aActor, aEventTarget);
}

nsIEventTarget*
IProtocol::GetActorEventTarget()
{
  // We should only call this function when this actor has been registered and
  // is not unregistered yet.
  MOZ_RELEASE_ASSERT(mId != kNullActorId && mId != kFreedActorId);
  RefPtr<nsIEventTarget> target = Manager()->GetActorEventTargetInternal(this);
  return target;
}

already_AddRefed<nsIEventTarget>
IProtocol::GetActorEventTargetInternal(IProtocol* aActor)
{
  return Manager()->GetActorEventTargetInternal(aActor);
}

IToplevelProtocol::IToplevelProtocol(ProtocolId aProtoId, Side aSide)
 : IProtocol(aSide),
   mProtocolId(aProtoId),
   mOtherPid(mozilla::ipc::kInvalidProcessId),
   mLastRouteId(aSide == ParentSide ? kFreedActorId : kNullActorId),
   mLastShmemId(aSide == ParentSide ? kFreedActorId : kNullActorId),
   mEventTargetMutex("ProtocolEventTargetMutex")
{
}

IToplevelProtocol::~IToplevelProtocol()
{
  if (mTrans) {
    RefPtr<DeleteTask<Transport>> task = new DeleteTask<Transport>(mTrans.release());
    XRE_GetIOMessageLoop()->PostTask(task.forget());
  }
}

base::ProcessId
IToplevelProtocol::OtherPid() const
{
  return mOtherPid;
}

void
IToplevelProtocol::SetOtherProcessId(base::ProcessId aOtherPid)
{
  mOtherPid = aOtherPid;
}

bool
IToplevelProtocol::TakeMinidump(nsIFile** aDump, uint32_t* aSequence)
{
  MOZ_RELEASE_ASSERT(GetSide() == ParentSide);
#ifdef MOZ_CRASHREPORTER
  return XRE_TakeMinidumpForChild(OtherPid(), aDump, aSequence);
#else
  return false;
#endif
}

bool
IToplevelProtocol::Open(mozilla::ipc::Transport* aTransport,
                        base::ProcessId aOtherPid,
                        MessageLoop* aThread,
                        mozilla::ipc::Side aSide)
{
  SetOtherProcessId(aOtherPid);
  return GetIPCChannel()->Open(aTransport, aThread, aSide);
}

bool
IToplevelProtocol::Open(MessageChannel* aChannel,
                        MessageLoop* aMessageLoop,
                        mozilla::ipc::Side aSide)
{
  SetOtherProcessId(base::GetCurrentProcId());
  return GetIPCChannel()->Open(aChannel, aMessageLoop->SerialEventTarget(), aSide);
}

bool
IToplevelProtocol::Open(MessageChannel* aChannel,
                        nsIEventTarget* aEventTarget,
                        mozilla::ipc::Side aSide)
{
  SetOtherProcessId(base::GetCurrentProcId());
  return GetIPCChannel()->Open(aChannel, aEventTarget, aSide);
}

void
IToplevelProtocol::Close()
{
  GetIPCChannel()->Close();
}

void
IToplevelProtocol::SetReplyTimeoutMs(int32_t aTimeoutMs)
{
  GetIPCChannel()->SetReplyTimeoutMs(aTimeoutMs);
}

bool
IToplevelProtocol::IsOnCxxStack() const
{
  return GetIPCChannel()->IsOnCxxStack();
}

int32_t
IToplevelProtocol::Register(IProtocol* aRouted)
{
  if (aRouted->Id() != kNullActorId && aRouted->Id() != kFreedActorId) {
    // If there's already an ID, just return that.
    return aRouted->Id();
  }
  int32_t id = GetSide() == ParentSide ? ++mLastRouteId : --mLastRouteId;
  mActorMap.AddWithID(aRouted, id);
  aRouted->SetId(id);

  // Inherit our event target from our manager.
  if (IProtocol* manager = aRouted->Manager()) {
    MutexAutoLock lock(mEventTargetMutex);
    if (nsCOMPtr<nsIEventTarget> target = mEventTargetMap.Lookup(manager->Id())) {
      mEventTargetMap.AddWithID(target, id);
    }
  }

  return id;
}

int32_t
IToplevelProtocol::RegisterID(IProtocol* aRouted,
                              int32_t aId)
{
  mActorMap.AddWithID(aRouted, aId);
  aRouted->SetId(aId);
  return aId;
}

IProtocol*
IToplevelProtocol::Lookup(int32_t aId)
{
  return mActorMap.Lookup(aId);
}

void
IToplevelProtocol::Unregister(int32_t aId)
{
  mActorMap.Remove(aId);

  MutexAutoLock lock(mEventTargetMutex);
  mEventTargetMap.RemoveIfPresent(aId);
}

Shmem::SharedMemory*
IToplevelProtocol::CreateSharedMemory(size_t aSize,
                                      Shmem::SharedMemory::SharedMemoryType aType,
                                      bool aUnsafe,
                                      Shmem::id_t* aId)
{
  RefPtr<Shmem::SharedMemory> segment(
    Shmem::Alloc(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), aSize, aType, aUnsafe));
  if (!segment) {
    return nullptr;
  }
  int32_t id = GetSide() == ParentSide ? ++mLastShmemId : --mLastShmemId;
  Shmem shmem(
    Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(),
    segment.get(),
    id);
  Message* descriptor = shmem.ShareTo(
    Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), OtherPid(), MSG_ROUTING_CONTROL);
  if (!descriptor) {
    return nullptr;
  }
  Unused << GetIPCChannel()->Send(descriptor);

  *aId = shmem.Id(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead());
  Shmem::SharedMemory* rawSegment = segment.get();
  mShmemMap.AddWithID(segment.forget().take(), *aId);
  return rawSegment;
}

Shmem::SharedMemory*
IToplevelProtocol::LookupSharedMemory(Shmem::id_t aId)
{
  return mShmemMap.Lookup(aId);
}

bool
IToplevelProtocol::IsTrackingSharedMemory(Shmem::SharedMemory* segment)
{
  return mShmemMap.HasData(segment);
}

bool
IToplevelProtocol::DestroySharedMemory(Shmem& shmem)
{
  Shmem::id_t aId = shmem.Id(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead());
  Shmem::SharedMemory* segment = LookupSharedMemory(aId);
  if (!segment) {
    return false;
  }

  Message* descriptor = shmem.UnshareFrom(
    Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), OtherPid(), MSG_ROUTING_CONTROL);

  mShmemMap.Remove(aId);
  Shmem::Dealloc(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), segment);

  if (!GetIPCChannel()->CanSend()) {
    delete descriptor;
    return true;
  }

  return descriptor && GetIPCChannel()->Send(descriptor);
}

void
IToplevelProtocol::DeallocShmems()
{
  for (IDMap<SharedMemory*>::const_iterator cit = mShmemMap.begin(); cit != mShmemMap.end(); ++cit) {
    Shmem::Dealloc(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), cit->second);
  }
  mShmemMap.Clear();
}

bool
IToplevelProtocol::ShmemCreated(const Message& aMsg)
{
  Shmem::id_t id;
  RefPtr<Shmem::SharedMemory> rawmem(Shmem::OpenExisting(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), aMsg, &id, true));
  if (!rawmem) {
    return false;
  }
  mShmemMap.AddWithID(rawmem.forget().take(), id);
  return true;
}

bool
IToplevelProtocol::ShmemDestroyed(const Message& aMsg)
{
  Shmem::id_t id;
  PickleIterator iter = PickleIterator(aMsg);
  if (!IPC::ReadParam(&aMsg, &iter, &id)) {
    return false;
  }
  aMsg.EndRead(iter);

  Shmem::SharedMemory* rawmem = LookupSharedMemory(id);
  if (rawmem) {
    mShmemMap.Remove(id);
    Shmem::Dealloc(Shmem::IHadBetterBeIPDLCodeCallingThis_OtherwiseIAmADoodyhead(), rawmem);
  }
  return true;
}

already_AddRefed<nsIEventTarget>
IToplevelProtocol::GetMessageEventTarget(const Message& aMsg)
{
  int32_t route = aMsg.routing_id();

  Maybe<MutexAutoLock> lock;
  lock.emplace(mEventTargetMutex);

  nsCOMPtr<nsIEventTarget> target = mEventTargetMap.Lookup(route);

  if (aMsg.is_constructor()) {
    ActorHandle handle;
    PickleIterator iter = PickleIterator(aMsg);
    if (!IPC::ReadParam(&aMsg, &iter, &handle)) {
      return nullptr;
    }

    // Normally a new actor inherits its event target from its manager. If the
    // manager has no event target, we give the subclass a chance to make a new
    // one.
    if (!target) {
      MutexAutoUnlock unlock(mEventTargetMutex);
      target = GetConstructedEventTarget(aMsg);
    }

    mEventTargetMap.AddWithID(target, handle.mId);
  } else if (!target) {
    // We don't need the lock after this point.
    lock.reset();

    target = GetSpecificMessageEventTarget(aMsg);
  }

  return target.forget();
}

already_AddRefed<nsIEventTarget>
IToplevelProtocol::GetActorEventTargetInternal(IProtocol* aActor)
{
  MOZ_RELEASE_ASSERT(aActor->Id() != kNullActorId && aActor->Id() != kFreedActorId);

  MutexAutoLock lock(mEventTargetMutex);
  nsCOMPtr<nsIEventTarget> target = mEventTargetMap.Lookup(aActor->Id());
  return target.forget();
}

already_AddRefed<nsIEventTarget>
IToplevelProtocol::GetActorEventTarget(IProtocol* aActor)
{
  return GetActorEventTargetInternal(aActor);
}

nsIEventTarget*
IToplevelProtocol::GetActorEventTarget()
{
  // The EventTarget of a ToplevelProtocol shall never be set.
  return nullptr;
}

void
IToplevelProtocol::SetEventTargetForActorInternal(IProtocol* aActor,
                                                  nsIEventTarget* aEventTarget)
{
  // The EventTarget of a ToplevelProtocol shall never be set.
  MOZ_RELEASE_ASSERT(aActor != this);

  // We should only call this function on actors that haven't been used for IPC
  // code yet. Otherwise we'll be posting stuff to the wrong event target before
  // we're called.
  MOZ_RELEASE_ASSERT(aActor->Id() == kNullActorId || aActor->Id() == kFreedActorId);

  // Register the actor early. When it's registered again, it will keep the same
  // ID.
  int32_t id = Register(aActor);
  aActor->SetId(id);

  MutexAutoLock lock(mEventTargetMutex);
  mEventTargetMap.AddWithID(aEventTarget, id);
}

void
IToplevelProtocol::ReplaceEventTargetForActorInternal(
  IProtocol* aActor,
  nsIEventTarget* aEventTarget)
{
  // The EventTarget of a ToplevelProtocol shall never be set.
  MOZ_RELEASE_ASSERT(aActor != this);

  int32_t id = aActor->Id();
  // The ID of the actor should have existed.
  MOZ_RELEASE_ASSERT(id!= kNullActorId && id!= kFreedActorId);

  MutexAutoLock lock(mEventTargetMutex);
  mEventTargetMap.ReplaceWithID(aEventTarget, id);
}

} // namespace ipc
} // namespace mozilla