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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_CORE_CHANNEL_LINUX_H_
#define MOJO_CORE_CHANNEL_LINUX_H_
#include <atomic>
#include <memory>
#include "base/task/single_thread_task_runner.h"
#include "build/build_config.h"
#include "mojo/core/channel_posix.h"
namespace mojo {
namespace core {
class DataAvailableNotifier;
// ChannelLinux is a specialization of ChannelPosix which has support for shared
// memory via Mojo channel upgrades. By default on Linux, CrOS, and Android
// every channel will be of type ChannelLinux which can be upgraded at runtime
// to take advantage of shared memory when all required kernel features are
// present.
class MOJO_SYSTEM_IMPL_EXPORT ChannelLinux : public ChannelPosix {
public:
ChannelLinux(Delegate* delegate,
ConnectionParams connection_params,
HandlePolicy handle_policy,
scoped_refptr<base::SingleThreadTaskRunner> io_task_runner);
ChannelLinux(const ChannelLinux&) = delete;
ChannelLinux& operator=(const ChannelLinux&) = delete;
// KernelSupportsUpgradeRequirements will return true if the kernel supports
// the features necessary to use an upgrade channel. How the channel will be
// upgraded is an implementation detail and this just tells the caller that
// calling Channel::UpgradeChannel() will have some effect.
static bool KernelSupportsUpgradeRequirements();
// Will return true if at least one feature that is available via upgrade is
// enabled.
static bool UpgradesEnabled();
// SetSharedMemParams will control whether shared memory is used for this
// channel.
static void SetSharedMemParameters(bool enabled,
uint32_t num_pages,
bool use_zero_on_wake);
// ChannelPosix impl:
void Write(MessagePtr message) override;
void OfferSharedMemUpgrade();
bool OnControlMessage(Message::MessageType message_type,
const void* payload,
size_t payload_size,
std::vector<PlatformHandle> handles) override;
void OnWriteError(Error error) override;
void StartOnIOThread() override;
void ShutDownOnIOThread() override;
private:
~ChannelLinux() override;
class SharedBuffer;
void OfferSharedMemUpgradeInternal();
void SharedMemReadReady();
// We only offer once, we use an atomic flag to guarantee no races to offer.
std::atomic_flag offered_{false};
// This flag keeps track of whether or not we've established a shared memory
// channel with the remote. If false we always fall back to the PosixChannel
// (socket).
std::atomic_bool shared_mem_writer_{false};
std::unique_ptr<DataAvailableNotifier> write_notifier_;
std::unique_ptr<SharedBuffer> write_buffer_;
std::unique_ptr<DataAvailableNotifier> read_notifier_;
std::unique_ptr<SharedBuffer> read_buffer_;
uint32_t num_pages_ = 0;
std::atomic_bool reject_writes_{false};
// This is a temporary buffer we use to remove messages from the shared buffer
// for validation and dispatching.
std::vector<uint8_t> read_buf_;
};
} // namespace core
} // namespace mojo
#endif // MOJO_CORE_CHANNEL_LINUX_H_
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