mojo/core/shared_buffer_dispatcher.cc

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "mojo/core/shared_buffer_dispatcher.h"

#include <stddef.h>
#include <stdint.h>

#include <limits>
#include <memory>
#include <utility>

#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "build/build_config.h"
#include "mojo/core/configuration.h"
#include "mojo/core/node_controller.h"
#include "mojo/core/options_validation.h"
#include "mojo/core/platform_handle_utils.h"
#include "mojo/core/platform_shared_memory_mapping.h"
#include "mojo/public/c/system/platform_handle.h"

namespace mojo {
namespace core {

namespace {

#pragma pack(push, 1)

struct SerializedState {
  uint64_t num_bytes;
  uint32_t access_mode;
  uint64_t guid_high;
  uint64_t guid_low;
  uint32_t padding;
};

#pragma pack(pop)

static_assert(sizeof(SerializedState) % 8 == 0,
              "Invalid SerializedState size.");

}  // namespace

// static
const MojoCreateSharedBufferOptions
    SharedBufferDispatcher::kDefaultCreateOptions = {
        static_cast<uint32_t>(sizeof(MojoCreateSharedBufferOptions)),
        MOJO_CREATE_SHARED_BUFFER_FLAG_NONE};

// static
MojoResult SharedBufferDispatcher::ValidateCreateOptions(
    const MojoCreateSharedBufferOptions* in_options,
    MojoCreateSharedBufferOptions* out_options) {
  const MojoCreateSharedBufferFlags kKnownFlags =
      MOJO_CREATE_SHARED_BUFFER_FLAG_NONE;

  *out_options = kDefaultCreateOptions;
  if (!in_options)
    return MOJO_RESULT_OK;

  UserOptionsReader<MojoCreateSharedBufferOptions> reader(in_options);
  if (!reader.is_valid())
    return MOJO_RESULT_INVALID_ARGUMENT;

  if (!OPTIONS_STRUCT_HAS_MEMBER(MojoCreateSharedBufferOptions, flags, reader))
    return MOJO_RESULT_OK;
  if ((reader.options().flags & ~kKnownFlags))
    return MOJO_RESULT_UNIMPLEMENTED;
  out_options->flags = reader.options().flags;

  // Checks for fields beyond |flags|:

  // (Nothing here yet.)

  return MOJO_RESULT_OK;
}

// static
MojoResult SharedBufferDispatcher::Create(
    const MojoCreateSharedBufferOptions& /*validated_options*/,
    NodeController* node_controller,
    uint64_t num_bytes,
    scoped_refptr<SharedBufferDispatcher>* result) {
  if (!num_bytes)
    return MOJO_RESULT_INVALID_ARGUMENT;
  if (num_bytes > GetConfiguration().max_shared_memory_num_bytes)
    return MOJO_RESULT_RESOURCE_EXHAUSTED;

  base::WritableSharedMemoryRegion writable_region;
  if (node_controller) {
    writable_region =
        node_controller->CreateSharedBuffer(static_cast<size_t>(num_bytes));
  } else {
    writable_region = base::WritableSharedMemoryRegion::Create(
        static_cast<size_t>(num_bytes));
  }
  if (!writable_region.IsValid())
    return MOJO_RESULT_RESOURCE_EXHAUSTED;

  *result = CreateInternal(
      base::WritableSharedMemoryRegion::TakeHandleForSerialization(
          std::move(writable_region)));
  return MOJO_RESULT_OK;
}

// static
MojoResult SharedBufferDispatcher::CreateFromPlatformSharedMemoryRegion(
    base::subtle::PlatformSharedMemoryRegion region,
    scoped_refptr<SharedBufferDispatcher>* result) {
  if (!region.IsValid())
    return MOJO_RESULT_INVALID_ARGUMENT;

  *result = CreateInternal(std::move(region));
  return MOJO_RESULT_OK;
}

// static
scoped_refptr<SharedBufferDispatcher> SharedBufferDispatcher::Deserialize(
    const void* bytes,
    size_t num_bytes,
    const ports::PortName* ports,
    size_t num_ports,
    PlatformHandle* platform_handles,
    size_t num_platform_handles) {
  if (num_bytes != sizeof(SerializedState)) {
    LOG(ERROR) << "Invalid serialized shared buffer dispatcher (bad size)";
    return nullptr;
  }

  const SerializedState* serialized_state =
      static_cast<const SerializedState*>(bytes);
  if (!serialized_state->num_bytes) {
    LOG(ERROR)
        << "Invalid serialized shared buffer dispatcher (invalid num_bytes)";
    return nullptr;
  }

  if (num_ports)
    return nullptr;

  PlatformHandle handles[2];
#if defined(OS_POSIX) && !defined(OS_ANDROID) && \
    (!defined(OS_MACOSX) || defined(OS_IOS))
  if (serialized_state->access_mode ==
      MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_WRITABLE) {
    if (num_platform_handles != 2)
      return nullptr;
    handles[1] = std::move(platform_handles[1]);
  } else {
    if (num_platform_handles != 1)
      return nullptr;
  }
#else
  if (num_platform_handles != 1)
    return nullptr;
#endif
  handles[0] = std::move(platform_handles[0]);

  base::UnguessableToken guid = base::UnguessableToken::Deserialize(
      serialized_state->guid_high, serialized_state->guid_low);

  base::subtle::PlatformSharedMemoryRegion::Mode mode;
  switch (serialized_state->access_mode) {
    case MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_READ_ONLY:
      mode = base::subtle::PlatformSharedMemoryRegion::Mode::kReadOnly;
      break;
    case MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_WRITABLE:
      mode = base::subtle::PlatformSharedMemoryRegion::Mode::kWritable;
      break;
    case MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_UNSAFE:
      mode = base::subtle::PlatformSharedMemoryRegion::Mode::kUnsafe;
      break;
    default:
      LOG(ERROR) << "Invalid serialized shared buffer access mode.";
      return nullptr;
  }

  auto region = base::subtle::PlatformSharedMemoryRegion::Take(
      CreateSharedMemoryRegionHandleFromPlatformHandles(std::move(handles[0]),
                                                        std::move(handles[1])),
      mode, static_cast<size_t>(serialized_state->num_bytes), guid);
  if (!region.IsValid()) {
    LOG(ERROR)
        << "Invalid serialized shared buffer dispatcher (invalid num_bytes?)";
    return nullptr;
  }

  return CreateInternal(std::move(region));
}

base::subtle::PlatformSharedMemoryRegion
SharedBufferDispatcher::PassPlatformSharedMemoryRegion() {
  base::AutoLock lock(lock_);
  if (!region_.IsValid() || in_transit_)
    return base::subtle::PlatformSharedMemoryRegion();

  return std::move(region_);
}

Dispatcher::Type SharedBufferDispatcher::GetType() const {
  return Type::SHARED_BUFFER;
}

MojoResult SharedBufferDispatcher::Close() {
  base::AutoLock lock(lock_);
  if (in_transit_)
    return MOJO_RESULT_INVALID_ARGUMENT;

  region_ = base::subtle::PlatformSharedMemoryRegion();
  return MOJO_RESULT_OK;
}

MojoResult SharedBufferDispatcher::DuplicateBufferHandle(
    const MojoDuplicateBufferHandleOptions* options,
    scoped_refptr<Dispatcher>* new_dispatcher) {
  MojoDuplicateBufferHandleOptions validated_options;
  MojoResult result = ValidateDuplicateOptions(options, &validated_options);
  if (result != MOJO_RESULT_OK)
    return result;

  base::AutoLock lock(lock_);
  if (in_transit_)
    return MOJO_RESULT_INVALID_ARGUMENT;

  if ((validated_options.flags & MOJO_DUPLICATE_BUFFER_HANDLE_FLAG_READ_ONLY)) {
    // If a read-only duplicate is requested and this handle is not already
    // read-only, we need to make it read-only before duplicating. If it's
    // unsafe it can't be made read-only, and we must fail instead.
    if (region_.GetMode() ==
        base::subtle::PlatformSharedMemoryRegion::Mode::kUnsafe) {
      return MOJO_RESULT_FAILED_PRECONDITION;
    } else if (region_.GetMode() ==
               base::subtle::PlatformSharedMemoryRegion::Mode::kWritable) {
      region_ = base::ReadOnlySharedMemoryRegion::TakeHandleForSerialization(
          base::WritableSharedMemoryRegion::ConvertToReadOnly(
              base::WritableSharedMemoryRegion::Deserialize(
                  std::move(region_))));
    }

    DCHECK_EQ(region_.GetMode(),
              base::subtle::PlatformSharedMemoryRegion::Mode::kReadOnly);
  } else {
    // A writable duplicate was requested. If this is already a read-only handle
    // we have to reject. Otherwise we have to convert to unsafe to ensure that
    // no future read-only duplication requests can succeed.
    if (region_.GetMode() ==
        base::subtle::PlatformSharedMemoryRegion::Mode::kReadOnly) {
      return MOJO_RESULT_FAILED_PRECONDITION;
    } else if (region_.GetMode() ==
               base::subtle::PlatformSharedMemoryRegion::Mode::kWritable) {
      auto handle = region_.PassPlatformHandle();
#if defined(OS_POSIX) && !defined(OS_ANDROID) && \
    (!defined(OS_MACOSX) || defined(OS_IOS))
      // On POSIX systems excluding Android, Fuchsia, and OSX, we explicitly
      // wipe out the secondary (read-only) FD from the platform handle to
      // repurpose it for exclusive unsafe usage.
      handle.readonly_fd.reset();
#endif
      region_ = base::subtle::PlatformSharedMemoryRegion::Take(
          std::move(handle),
          base::subtle::PlatformSharedMemoryRegion::Mode::kUnsafe,
          region_.GetSize(), region_.GetGUID());
    }
  }

  *new_dispatcher = CreateInternal(region_.Duplicate());
  return MOJO_RESULT_OK;
}

MojoResult SharedBufferDispatcher::MapBuffer(
    uint64_t offset,
    uint64_t num_bytes,
    std::unique_ptr<PlatformSharedMemoryMapping>* mapping) {
  if (offset > static_cast<uint64_t>(std::numeric_limits<size_t>::max()))
    return MOJO_RESULT_INVALID_ARGUMENT;
  if (num_bytes > static_cast<uint64_t>(std::numeric_limits<size_t>::max()))
    return MOJO_RESULT_INVALID_ARGUMENT;

  base::AutoLock lock(lock_);
  DCHECK(region_.IsValid());
  if (in_transit_ || num_bytes == 0 ||
      static_cast<size_t>(offset + num_bytes) > region_.GetSize()) {
    return MOJO_RESULT_INVALID_ARGUMENT;
  }

  DCHECK(mapping);
  *mapping = std::make_unique<PlatformSharedMemoryMapping>(
      &region_, static_cast<size_t>(offset), static_cast<size_t>(num_bytes));
  if (!(*mapping)->IsValid()) {
    LOG(ERROR) << "Failed to map shared memory region.";
    return MOJO_RESULT_RESOURCE_EXHAUSTED;
  }

  return MOJO_RESULT_OK;
}

MojoResult SharedBufferDispatcher::GetBufferInfo(MojoSharedBufferInfo* info) {
  if (!info)
    return MOJO_RESULT_INVALID_ARGUMENT;

  base::AutoLock lock(lock_);
  info->struct_size = sizeof(*info);
  info->size = region_.GetSize();
  return MOJO_RESULT_OK;
}

void SharedBufferDispatcher::StartSerialize(uint32_t* num_bytes,
                                            uint32_t* num_ports,
                                            uint32_t* num_platform_handles) {
  *num_bytes = sizeof(SerializedState);
  *num_ports = 0;
  *num_platform_handles = 1;
#if defined(OS_POSIX) && !defined(OS_ANDROID) && \
    (!defined(OS_MACOSX) || defined(OS_IOS))
  if (region_.GetMode() ==
      base::subtle::PlatformSharedMemoryRegion::Mode::kWritable) {
    *num_platform_handles = 2;
  }
#endif
}

bool SharedBufferDispatcher::EndSerialize(void* destination,
                                          ports::PortName* ports,
                                          PlatformHandle* handles) {
  SerializedState* serialized_state =
      static_cast<SerializedState*>(destination);
  base::AutoLock lock(lock_);
  serialized_state->num_bytes = region_.GetSize();
  switch (region_.GetMode()) {
    case base::subtle::PlatformSharedMemoryRegion::Mode::kReadOnly:
      serialized_state->access_mode =
          MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_READ_ONLY;
      break;
    case base::subtle::PlatformSharedMemoryRegion::Mode::kWritable:
      serialized_state->access_mode =
          MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_WRITABLE;
      break;
    case base::subtle::PlatformSharedMemoryRegion::Mode::kUnsafe:
      serialized_state->access_mode =
          MOJO_PLATFORM_SHARED_MEMORY_REGION_ACCESS_MODE_UNSAFE;
      break;
    default:
      NOTREACHED();
      return false;
  }

  const base::UnguessableToken& guid = region_.GetGUID();
  serialized_state->guid_high = guid.GetHighForSerialization();
  serialized_state->guid_low = guid.GetLowForSerialization();
  serialized_state->padding = 0;

  auto region = std::move(region_);
#if defined(OS_POSIX) && !defined(OS_ANDROID) && \
    (!defined(OS_MACOSX) || defined(OS_IOS))
  if (region.GetMode() ==
      base::subtle::PlatformSharedMemoryRegion::Mode::kWritable) {
    PlatformHandle platform_handles[2];
    ExtractPlatformHandlesFromSharedMemoryRegionHandle(
        region.PassPlatformHandle(), &platform_handles[0],
        &platform_handles[1]);
    handles[0] = std::move(platform_handles[0]);
    handles[1] = std::move(platform_handles[1]);
    return true;
  }
#endif

  PlatformHandle platform_handle;
  PlatformHandle ignored_handle;
  ExtractPlatformHandlesFromSharedMemoryRegionHandle(
      region.PassPlatformHandle(), &platform_handle, &ignored_handle);
  handles[0] = std::move(platform_handle);
  return true;
}

bool SharedBufferDispatcher::BeginTransit() {
  base::AutoLock lock(lock_);
  if (in_transit_)
    return false;
  in_transit_ = region_.IsValid();
  return in_transit_;
}

void SharedBufferDispatcher::CompleteTransitAndClose() {
  base::AutoLock lock(lock_);
  in_transit_ = false;
  region_ = base::subtle::PlatformSharedMemoryRegion();
}

void SharedBufferDispatcher::CancelTransit() {
  base::AutoLock lock(lock_);
  in_transit_ = false;
}

SharedBufferDispatcher::SharedBufferDispatcher(
    base::subtle::PlatformSharedMemoryRegion region)
    : region_(std::move(region)) {
  DCHECK(region_.IsValid());
}

SharedBufferDispatcher::~SharedBufferDispatcher() {
  DCHECK(!region_.IsValid() && !in_transit_);
}

// static
scoped_refptr<SharedBufferDispatcher> SharedBufferDispatcher::CreateInternal(
    base::subtle::PlatformSharedMemoryRegion region) {
  return base::WrapRefCounted(new SharedBufferDispatcher(std::move(region)));
}

// static
MojoResult SharedBufferDispatcher::ValidateDuplicateOptions(
    const MojoDuplicateBufferHandleOptions* in_options,
    MojoDuplicateBufferHandleOptions* out_options) {
  const MojoDuplicateBufferHandleFlags kKnownFlags =
      MOJO_DUPLICATE_BUFFER_HANDLE_FLAG_READ_ONLY;
  static const MojoDuplicateBufferHandleOptions kDefaultOptions = {
      static_cast<uint32_t>(sizeof(MojoDuplicateBufferHandleOptions)),
      MOJO_DUPLICATE_BUFFER_HANDLE_FLAG_NONE};

  *out_options = kDefaultOptions;
  if (!in_options)
    return MOJO_RESULT_OK;

  UserOptionsReader<MojoDuplicateBufferHandleOptions> reader(in_options);
  if (!reader.is_valid())
    return MOJO_RESULT_INVALID_ARGUMENT;

  if (!OPTIONS_STRUCT_HAS_MEMBER(MojoDuplicateBufferHandleOptions, flags,
                                 reader))
    return MOJO_RESULT_OK;
  if ((reader.options().flags & ~kKnownFlags))
    return MOJO_RESULT_UNIMPLEMENTED;
  out_options->flags = reader.options().flags;

  // Checks for fields beyond |flags|:

  // (Nothing here yet.)

  return MOJO_RESULT_OK;
}

}  // namespace core
}  // namespace mojo