mojo/edk/system/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/edk/system/shared_buffer_dispatcher.h"

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

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

#include "base/logging.h"
#include "mojo/edk/embedder/embedder_internal.h"
#include "mojo/edk/system/configuration.h"
#include "mojo/edk/system/node_controller.h"
#include "mojo/edk/system/options_validation.h"

namespace mojo {
namespace edk {

namespace {

#pragma pack(push, 1)

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

const uint32_t kSerializedStateFlagsReadOnly = 1 << 0;

#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_OPTIONS_FLAG_NONE};

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

  scoped_refptr<PlatformSharedBuffer> shared_buffer;
  if (node_controller) {
    shared_buffer =
        node_controller->CreateSharedBuffer(static_cast<size_t>(num_bytes));
  } else {
    shared_buffer =
        PlatformSharedBuffer::Create(static_cast<size_t>(num_bytes));
  }
  if (!shared_buffer)
    return MOJO_RESULT_RESOURCE_EXHAUSTED;

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

// static
MojoResult SharedBufferDispatcher::CreateFromPlatformSharedBuffer(
    const scoped_refptr<PlatformSharedBuffer>& shared_buffer,
    scoped_refptr<SharedBufferDispatcher>* result) {
  if (!shared_buffer)
    return MOJO_RESULT_INVALID_ARGUMENT;

  *result = CreateInternal(shared_buffer);
  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,
    ScopedPlatformHandle* 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_platform_handles != 1 || num_ports) {
    LOG(ERROR)
        << "Invalid serialized shared buffer dispatcher (missing handles)";
    return nullptr;
  }

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

  bool read_only = (serialized_state->flags & kSerializedStateFlagsReadOnly);
  scoped_refptr<PlatformSharedBuffer> shared_buffer(
      PlatformSharedBuffer::CreateFromPlatformHandle(
          static_cast<size_t>(serialized_state->num_bytes), read_only, guid,
          std::move(platform_handles[0])));
  if (!shared_buffer) {
    LOG(ERROR)
        << "Invalid serialized shared buffer dispatcher (invalid num_bytes?)";
    return nullptr;
  }

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

scoped_refptr<PlatformSharedBuffer>
SharedBufferDispatcher::PassPlatformSharedBuffer() {
  base::AutoLock lock(lock_);
  if (!shared_buffer_ || in_transit_)
    return nullptr;

  scoped_refptr<PlatformSharedBuffer> retval = shared_buffer_;
  shared_buffer_ = nullptr;
  return retval;
}

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

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

  shared_buffer_ = nullptr;
  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;

  // Note: Since this is "duplicate", we keep our ref to |shared_buffer_|.
  base::AutoLock lock(lock_);
  if (in_transit_)
    return MOJO_RESULT_INVALID_ARGUMENT;

  if ((validated_options.flags &
       MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_READ_ONLY) &&
      (!shared_buffer_->IsReadOnly())) {
    // If a read-only duplicate is requested and |shared_buffer_| is not
    // read-only, make a read-only duplicate of |shared_buffer_|.
    scoped_refptr<PlatformSharedBuffer> read_only_buffer =
        shared_buffer_->CreateReadOnlyDuplicate();
    if (!read_only_buffer)
      return MOJO_RESULT_FAILED_PRECONDITION;
    DCHECK(read_only_buffer->IsReadOnly());
    *new_dispatcher = CreateInternal(std::move(read_only_buffer));
    return MOJO_RESULT_OK;
  }

  *new_dispatcher = CreateInternal(shared_buffer_);
  return MOJO_RESULT_OK;
}

MojoResult SharedBufferDispatcher::MapBuffer(
    uint64_t offset,
    uint64_t num_bytes,
    MojoMapBufferFlags flags,
    std::unique_ptr<PlatformSharedBufferMapping>* 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(shared_buffer_);
  if (in_transit_ ||
      !shared_buffer_->IsValidMap(static_cast<size_t>(offset),
                                  static_cast<size_t>(num_bytes))) {
    return MOJO_RESULT_INVALID_ARGUMENT;
  }

  DCHECK(mapping);
  *mapping = shared_buffer_->MapNoCheck(static_cast<size_t>(offset),
                                        static_cast<size_t>(num_bytes));
  if (!*mapping) {
    LOG(ERROR) << "Unable to map: read_only" << shared_buffer_->IsReadOnly();
    return MOJO_RESULT_RESOURCE_EXHAUSTED;
  }

  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;
}

bool SharedBufferDispatcher::EndSerialize(void* destination,
                                          ports::PortName* ports,
                                          ScopedPlatformHandle* handles) {
  SerializedState* serialized_state =
      static_cast<SerializedState*>(destination);
  base::AutoLock lock(lock_);
  serialized_state->num_bytes =
      static_cast<uint64_t>(shared_buffer_->GetNumBytes());
  serialized_state->flags =
      (shared_buffer_->IsReadOnly() ? kSerializedStateFlagsReadOnly : 0);
  base::UnguessableToken guid = shared_buffer_->GetGUID();
  serialized_state->guid_high = guid.GetHighForSerialization();
  serialized_state->guid_low = guid.GetLowForSerialization();
  serialized_state->padding = 0;

  handles[0] = shared_buffer_->DuplicatePlatformHandleForIPC();
  if (!handles[0].is_valid()) {
    shared_buffer_ = nullptr;
    return false;
  }
  return true;
}

bool SharedBufferDispatcher::BeginTransit() {
  base::AutoLock lock(lock_);
  if (in_transit_)
    return false;
  in_transit_ = static_cast<bool>(shared_buffer_);
  return in_transit_;
}

void SharedBufferDispatcher::CompleteTransitAndClose() {
  base::AutoLock lock(lock_);
  in_transit_ = false;
  shared_buffer_ = nullptr;
  ignore_result(handle_for_transit_.release());
}

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

SharedBufferDispatcher::SharedBufferDispatcher(
    scoped_refptr<PlatformSharedBuffer> shared_buffer)
    : shared_buffer_(shared_buffer) {
  DCHECK(shared_buffer_);
}

SharedBufferDispatcher::~SharedBufferDispatcher() {
  DCHECK(!shared_buffer_ && !in_transit_);
}

// static
MojoResult SharedBufferDispatcher::ValidateDuplicateOptions(
    const MojoDuplicateBufferHandleOptions* in_options,
    MojoDuplicateBufferHandleOptions* out_options) {
  const MojoDuplicateBufferHandleOptionsFlags kKnownFlags =
      MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_READ_ONLY;
  static const MojoDuplicateBufferHandleOptions kDefaultOptions = {
      static_cast<uint32_t>(sizeof(MojoDuplicateBufferHandleOptions)),
      MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_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 edk
}  // namespace mojo