tubestation/ipc/glue/SharedMemoryHandle.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/. */

/* This source code was derived from Chromium code, and as such is also subject
 * to the [Chromium license](ipc/chromium/src/LICENSE). */

#include "mozilla/ipc/SharedMemoryHandle.h"
#include "mozilla/ipc/SharedMemoryMapping.h"
#include "SharedMemoryPlatform.h"

#include "chrome/common/ipc_message_utils.h"
#include "mozilla/Atomics.h"
#include "nsDebug.h"
#include "nsIMemoryReporter.h"

namespace mozilla::ipc::shared_memory {

// Implementation of the shared memory logger in SharedMemoryPlatform.h.
LazyLogModule gSharedMemoryLog{"SharedMemory"};

class AllocationReporter final : public nsIMemoryReporter {
  ~AllocationReporter() = default;

 public:
  static Atomic<uint64_t> allocated;

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_IMETHOD
  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
                 bool aAnonymize) override {
    MOZ_COLLECT_REPORT(
        "shmem-allocated", KIND_OTHER, UNITS_BYTES, allocated,
        "Memory shared with other processes that is accessible (but not "
        "necessarily mapped).");

    return NS_OK;
  }
};

Atomic<uint64_t> AllocationReporter::allocated;

NS_IMPL_ISUPPORTS(AllocationReporter, nsIMemoryReporter)

static void RegisterMemoryReporter() {
  static Atomic<bool> registered;
  if (registered.compareExchange(false, true)) {
    RegisterStrongMemoryReporter(new AllocationReporter());
  }
}

HandleBase::HandleBase() { RegisterMemoryReporter(); }

HandleBase::~HandleBase() {
  MOZ_ASSERT(AllocationReporter::allocated >= mSize,
             "Can't destroy more than allocated");
  AllocationReporter::allocated -= mSize;
  mHandle = nullptr;
  mSize = 0;
}

HandleBase HandleBase::Clone() const {
  HandleBase hb;
  hb.mHandle = Platform::CloneHandle(mHandle);
  if (hb.mHandle) {
    hb.mSize = mSize;
    // TODO more intelligently handle clones to not count as addition
    // allocations?
    AllocationReporter::allocated += mSize;
  }
  return hb;
}

void HandleBase::ToMessageWriter(IPC::MessageWriter* aWriter) && {
  WriteParam(aWriter, std::move(mHandle));
  WriteParam(aWriter, std::exchange(mSize, 0));
}

bool HandleBase::FromMessageReader(IPC::MessageReader* aReader) {
  mozilla::ipc::shared_memory::PlatformHandle handle;
  if (!ReadParam(aReader, &handle)) {
    return false;
  }
  if (handle && !Platform::IsSafeToMap(handle)) {
    return false;
  }
  mHandle = std::move(handle);
  if (!ReadParam(aReader, &mSize)) {
    return false;
  }
  mozilla::ipc::shared_memory::AllocationReporter::allocated += mSize;
  return true;
}

Mapping Handle::Map(void* aFixedAddress) const {
  return Mapping(*this, aFixedAddress);
}

ReadOnlyMapping ReadOnlyHandle::Map(void* aFixedAddress) const {
  return ReadOnlyMapping(*this, aFixedAddress);
}

FreezableHandle::~FreezableHandle() {
  NS_WARNING_ASSERTION(!IsValid(), "freezable shared memory was never frozen");
}

Handle FreezableHandle::WontFreeze() && {
  return std::move(*this).ConvertTo<Handle>();
}

ReadOnlyHandle FreezableHandle::Freeze() && {
  DebugOnly<const uint64_t> previous_size = Size();
  if (Platform::Freeze(*this)) {
    MOZ_ASSERT(Size() == previous_size);
    return std::move(*this).ConvertTo<ReadOnlyHandle>();
  }
  return nullptr;
}

FreezableMapping FreezableHandle::Map(void* aFixedAddress) && {
  return FreezableMapping(std::move(*this), aFixedAddress);
}

Handle Create(uint64_t aSize) {
  Handle h;
  const auto success = Platform::Create(h, aSize);
  MOZ_ASSERT(success == h.IsValid());
  if (success) {
    MOZ_ASSERT(aSize == h.Size());
    AllocationReporter::allocated += h.Size();
  }
  return h;
}

FreezableHandle CreateFreezable(uint64_t aSize) {
  FreezableHandle h;
  const auto success = Platform::CreateFreezable(h, aSize);
  MOZ_ASSERT(success == h.IsValid());
  if (success) {
    MOZ_ASSERT(aSize == h.Size());
    AllocationReporter::allocated += h.Size();
  }
  return h;
}

}  // namespace mozilla::ipc::shared_memory

namespace IPC {

void ParamTraits<mozilla::ipc::shared_memory::Handle>::Write(
    MessageWriter* aWriter, mozilla::ipc::shared_memory::Handle&& aParam) {
  std::move(aParam).ToMessageWriter(aWriter);
}

bool ParamTraits<mozilla::ipc::shared_memory::Handle>::Read(
    MessageReader* aReader, mozilla::ipc::shared_memory::Handle* aResult) {
  return aResult->FromMessageReader(aReader);
}

void ParamTraits<mozilla::ipc::shared_memory::ReadOnlyHandle>::Write(
    MessageWriter* aWriter,
    mozilla::ipc::shared_memory::ReadOnlyHandle&& aParam) {
  std::move(aParam).ToMessageWriter(aWriter);
}

bool ParamTraits<mozilla::ipc::shared_memory::ReadOnlyHandle>::Read(
    MessageReader* aReader,
    mozilla::ipc::shared_memory::ReadOnlyHandle* aResult) {
  return aResult->FromMessageReader(aReader);
}

}  // namespace IPC