common/vsoc/shm/base.h

#pragma once
/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Base macros for all layout structures.

#include <type_traits>
#include "common/vsoc/shm/version.h"

#define ASSERT_SHM_COMPATIBLE(T, R)                                   \
  static_assert(sizeof(T) == vsoc::layout::version_info::R::T##_size, \
                "size changed, update the version");                  \
  static_assert(std::is_trivial<T>(), "Class uses features that are unsafe")

#define ASSERT_SHM_CONSTANT_VALUE(T, R)                                 \
  static_assert(T == vsoc::layout::version_info::R::constant_values::T, \
                "Constant value changed")

namespace vsoc {
namespace layout {

/**
 * Base class that should be used for all shared memory objects
 */
class Base {
};
ASSERT_SHM_COMPATIBLE(Base, multi_region);

/**
 * Memory is shared between Guest and Host kernels. In some cases we need
 * flag to indicate which side we're on. In those cases we'll use this
 * simple structure.
 *
 * These are carefully formatted to make Guest and Host a bitfield.
 */
struct Sides : public Base {
  static const uint32_t NoSides = 0;
  static const uint32_t Guest = 1;
  static const uint32_t Host = 2;
  static const uint32_t Both = 3;
#ifdef CUTTLEFISH_HOST
  static const uint32_t OurSide = Host;
  static const uint32_t Peer = Guest;
#else
  static const uint32_t OurSide = Guest;
  static const uint32_t Peer = Host;
#endif

  uint32_t value_;
};
ASSERT_SHM_COMPATIBLE(Sides, multi_region);

/**
 * Base class for all region layout structures.
 */
class RegionLayout : public Base {
};
ASSERT_SHM_COMPATIBLE(RegionLayout, multi_region);

}  // namespace layout
}  // namespace vsoc