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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_METRICS_HISTOGRAM_SHARED_MEMORY_H_
#define BASE_METRICS_HISTOGRAM_SHARED_MEMORY_H_
#include <optional>
#include <string_view>
#include "base/base_export.h"
#include "base/command_line.h"
#include "base/feature_list.h"
#include "base/memory/shared_memory_switch.h"
#include "base/memory/unsafe_shared_memory_region.h"
#include "base/metrics/persistent_memory_allocator.h"
#include "base/process/launch.h"
#include "build/build_config.h"
#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
#include "base/files/platform_file.h"
#include "base/posix/global_descriptors.h"
#endif
#if !BUILDFLAG(USE_BLINK)
#error "This is only intended for platforms that use blink."
#endif
namespace base {
BASE_EXPORT BASE_DECLARE_FEATURE(kPassHistogramSharedMemoryOnLaunch);
// Helper structure to create and return a shared memory region and a histogram
// allocator over top of it. Once returned it is expected that the caller will
// move both the memory regions and the allocator out of the struct and into
// it's own appropriate state variables. Note that the memory region must
// outlive the allocator.
struct BASE_EXPORT HistogramSharedMemory {
HistogramSharedMemory() = delete;
~HistogramSharedMemory() = delete;
HistogramSharedMemory(HistogramSharedMemory&) = delete;
HistogramSharedMemory(HistogramSharedMemory&&) = delete;
HistogramSharedMemory& operator=(HistogramSharedMemory&) = delete;
HistogramSharedMemory& operator=(HistogramSharedMemory&&) = delete;
// Configuration with which to create a histogram shared memory region and
// allocator. Note the expectation that this be initialized with static
// data for the allocator name (i.e., a string literal or static constant
// character array).
struct BASE_EXPORT Config {
const int process_type; // See: content/public/common/process_type.h
const std::string_view allocator_name;
const size_t memory_size_bytes;
};
// Temporary structure used to return the shared memory region and allocator
// created by the |Create| factory function. The caller is expected to move
// the returned values out of this struct.
struct BASE_EXPORT SharedMemory {
UnsafeSharedMemoryRegion region;
std::unique_ptr<PersistentMemoryAllocator> allocator;
SharedMemory(UnsafeSharedMemoryRegion,
std::unique_ptr<PersistentMemoryAllocator>);
~SharedMemory();
// Movable
SharedMemory(SharedMemory&&);
SharedMemory& operator=(SharedMemory&&);
// Not copyable
SharedMemory(SharedMemory&) = delete;
SharedMemory& operator=(SharedMemory&) = delete;
};
// Factory to initialize a shared |memory_region| and |allocator| for
// |process_id| based on |config|. On success, returns true and updates
// the values of |memory_region| and |allocator|. On failure, returns false
// and |memory_region| and |allocator| are unchanged.
static std::optional<SharedMemory> Create(int process_id,
const Config& config);
#if BUILDFLAG(IS_APPLE)
// Exposed for testing.
static const shared_memory::SharedMemoryMachPortRendezvousKey kRendezvousKey;
#endif
// Returns true if passing the shared memory handle via command-line arguments
// is enabled. |process_type| values should come from content:::ProcessType.
static bool PassOnCommandLineIsEnabled(int process_type);
// Updates the launch parameters to share |unsafe_memory_region| to a
// child process that is about to be launched. This should be called in the
// parent process as a part of setting up the launch conditions of the child.
// This call will update the |command_line| and |launch_options|. On posix,
// where we prefer to use a zygote instead of using the launch_options to
// launch a new process, the platform |descriptor_to_share| is returned. The
// caller is expected to transmit the descriptor to the launch flow for the
// zygote.
static void AddToLaunchParameters(
const UnsafeSharedMemoryRegion& unsafe_memory_region,
#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
GlobalDescriptors::Key descriptor_key,
ScopedFD& descriptor_to_share,
#endif
CommandLine* command_line,
LaunchOptions* launch_options);
// Initialize the (global) histogram shared memory from the launch parameters.
// This should be called in the child process before any histogram samples are
// recorded.
static void InitFromLaunchParameters(const CommandLine& command_line);
};
} // namespace base
#endif // BASE_METRICS_HISTOGRAM_SHARED_MEMORY_H_
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