// Copyright 2013 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef V8_V8_PLATFORM_H_ #define V8_V8_PLATFORM_H_ #include <stddef.h> #include <stdint.h> #include <stdlib.h> // For abort. #include <memory> #include <string> #include "v8config.h" // NOLINT(build/include) namespace v8 { class Isolate; /** * A Task represents a unit of work. */ class Task { public: virtual ~Task() = default; virtual void Run() = 0; }; /** * An IdleTask represents a unit of work to be performed in idle time. * The Run method is invoked with an argument that specifies the deadline in * seconds returned by MonotonicallyIncreasingTime(). * The idle task is expected to complete by this deadline. */ class IdleTask { public: virtual ~IdleTask() = default; virtual void Run(double deadline_in_seconds) = 0; }; /** * A TaskRunner allows scheduling of tasks. The TaskRunner may still be used to * post tasks after the isolate gets destructed, but these tasks may not get * executed anymore. All tasks posted to a given TaskRunner will be invoked in * sequence. Tasks can be posted from any thread. */ class TaskRunner { public: /** * Schedules a task to be invoked by this TaskRunner. The TaskRunner * implementation takes ownership of |task|. */ virtual void PostTask(std::unique_ptr<Task> task) = 0; /** * Schedules a task to be invoked by this TaskRunner. The TaskRunner * implementation takes ownership of |task|. The |task| cannot be nested * within other task executions. * * Requires that |TaskRunner::NonNestableTasksEnabled()| is true. */ virtual void PostNonNestableTask(std::unique_ptr<Task> task) {} /** * Schedules a task to be invoked by this TaskRunner. The task is scheduled * after the given number of seconds |delay_in_seconds|. The TaskRunner * implementation takes ownership of |task|. */ virtual void PostDelayedTask(std::unique_ptr<Task> task, double delay_in_seconds) = 0; /** * Schedules an idle task to be invoked by this TaskRunner. The task is * scheduled when the embedder is idle. Requires that * |TaskRunner::IdleTasksEnabled()| is true. Idle tasks may be reordered * relative to other task types and may be starved for an arbitrarily long * time if no idle time is available. The TaskRunner implementation takes * ownership of |task|. */ virtual void PostIdleTask(std::unique_ptr<IdleTask> task) = 0; /** * Returns true if idle tasks are enabled for this TaskRunner. */ virtual bool IdleTasksEnabled() = 0; /** * Returns true if non-nestable tasks are enabled for this TaskRunner. */ virtual bool NonNestableTasksEnabled() const { return false; } TaskRunner() = default; virtual ~TaskRunner() = default; private: TaskRunner(const TaskRunner&) = delete; TaskRunner& operator=(const TaskRunner&) = delete; }; /** * The interface represents complex arguments to trace events. */ class ConvertableToTraceFormat { public: virtual ~ConvertableToTraceFormat() = default; /** * Append the class info to the provided |out| string. The appended * data must be a valid JSON object. Strings must be properly quoted, and * escaped. There is no processing applied to the content after it is * appended. */ virtual void AppendAsTraceFormat(std::string* out) const = 0; }; /** * V8 Tracing controller. * * Can be implemented by an embedder to record trace events from V8. */ class TracingController { public: virtual ~TracingController() = default; /** * Called by TRACE_EVENT* macros, don't call this directly. * The name parameter is a category group for example: * TRACE_EVENT0("v8,parse", "V8.Parse") * The pointer returned points to a value with zero or more of the bits * defined in CategoryGroupEnabledFlags. **/ virtual const uint8_t* GetCategoryGroupEnabled(const char* name) { static uint8_t no = 0; return &no; } /** * Adds a trace event to the platform tracing system. These function calls are * usually the result of a TRACE_* macro from trace_event_common.h when * tracing and the category of the particular trace are enabled. It is not * advisable to call these functions on their own; they are really only meant * to be used by the trace macros. The returned handle can be used by * UpdateTraceEventDuration to update the duration of COMPLETE events. */ virtual uint64_t AddTraceEvent( char phase, const uint8_t* category_enabled_flag, const char* name, const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args, const char** arg_names, const uint8_t* arg_types, const uint64_t* arg_values, std::unique_ptr<ConvertableToTraceFormat>* arg_convertables, unsigned int flags) { return 0; } virtual uint64_t AddTraceEventWithTimestamp( char phase, const uint8_t* category_enabled_flag, const char* name, const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args, const char** arg_names, const uint8_t* arg_types, const uint64_t* arg_values, std::unique_ptr<ConvertableToTraceFormat>* arg_convertables, unsigned int flags, int64_t timestamp) { return 0; } /** * Sets the duration field of a COMPLETE trace event. It must be called with * the handle returned from AddTraceEvent(). **/ virtual void UpdateTraceEventDuration(const uint8_t* category_enabled_flag, const char* name, uint64_t handle) {} class TraceStateObserver { public: virtual ~TraceStateObserver() = default; virtual void OnTraceEnabled() = 0; virtual void OnTraceDisabled() = 0; }; /** Adds tracing state change observer. */ virtual void AddTraceStateObserver(TraceStateObserver*) {} /** Removes tracing state change observer. */ virtual void RemoveTraceStateObserver(TraceStateObserver*) {} }; /** * A V8 memory page allocator. * * Can be implemented by an embedder to manage large host OS allocations. */ class PageAllocator { public: virtual ~PageAllocator() = default; /** * Gets the page granularity for AllocatePages and FreePages. Addresses and * lengths for those calls should be multiples of AllocatePageSize(). */ virtual size_t AllocatePageSize() = 0; /** * Gets the page granularity for SetPermissions and ReleasePages. Addresses * and lengths for those calls should be multiples of CommitPageSize(). */ virtual size_t CommitPageSize() = 0; /** * Sets the random seed so that GetRandomMmapAddr() will generate repeatable * sequences of random mmap addresses. */ virtual void SetRandomMmapSeed(int64_t seed) = 0; /** * Returns a randomized address, suitable for memory allocation under ASLR. * The address will be aligned to AllocatePageSize. */ virtual void* GetRandomMmapAddr() = 0; /** * Memory permissions. */ enum Permission { kNoAccess, kRead, kReadWrite, // TODO(hpayer): Remove this flag. Memory should never be rwx. kReadWriteExecute, kReadExecute }; /** * Allocates memory in range with the given alignment and permission. */ virtual void* AllocatePages(void* address, size_t length, size_t alignment, Permission permissions) = 0; /** * Frees memory in a range that was allocated by a call to AllocatePages. */ virtual bool FreePages(void* address, size_t length) = 0; /** * Releases memory in a range that was allocated by a call to AllocatePages. */ virtual bool ReleasePages(void* address, size_t length, size_t new_length) = 0; /** * Sets permissions on pages in an allocated range. */ virtual bool SetPermissions(void* address, size_t length, Permission permissions) = 0; /** * Frees memory in the given [address, address + size) range. address and size * should be operating system page-aligned. The next write to this * memory area brings the memory transparently back. */ virtual bool DiscardSystemPages(void* address, size_t size) { return true; } }; /** * V8 Platform abstraction layer. * * The embedder has to provide an implementation of this interface before * initializing the rest of V8. */ class Platform { public: virtual ~Platform() = default; /** * Allows the embedder to manage memory page allocations. */ virtual PageAllocator* GetPageAllocator() { // TODO(bbudge) Make this abstract after all embedders implement this. return nullptr; } /** * Enables the embedder to respond in cases where V8 can't allocate large * blocks of memory. V8 retries the failed allocation once after calling this * method. On success, execution continues; otherwise V8 exits with a fatal * error. * Embedder overrides of this function must NOT call back into V8. */ virtual void OnCriticalMemoryPressure() { // TODO(bbudge) Remove this when embedders override the following method. // See crbug.com/634547. } /** * Enables the embedder to respond in cases where V8 can't allocate large * memory regions. The |length| parameter is the amount of memory needed. * Returns true if memory is now available. Returns false if no memory could * be made available. V8 will retry allocations until this method returns * false. * * Embedder overrides of this function must NOT call back into V8. */ virtual bool OnCriticalMemoryPressure(size_t length) { return false; } /** * Gets the number of worker threads used by * Call(BlockingTask)OnWorkerThread(). This can be used to estimate the number * of tasks a work package should be split into. A return value of 0 means * that there are no worker threads available. Note that a value of 0 won't * prohibit V8 from posting tasks using |CallOnWorkerThread|. */ virtual int NumberOfWorkerThreads() = 0; /** * Returns a TaskRunner which can be used to post a task on the foreground. * This function should only be called from a foreground thread. */ virtual std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner( Isolate* isolate) = 0; /** * Schedules a task to be invoked on a worker thread. */ virtual void CallOnWorkerThread(std::unique_ptr<Task> task) = 0; /** * Schedules a task that blocks the main thread to be invoked with * high-priority on a worker thread. */ virtual void CallBlockingTaskOnWorkerThread(std::unique_ptr<Task> task) { // Embedders may optionally override this to process these tasks in a high // priority pool. CallOnWorkerThread(std::move(task)); } /** * Schedules a task to be invoked on a worker thread after |delay_in_seconds| * expires. */ virtual void CallDelayedOnWorkerThread(std::unique_ptr<Task> task, double delay_in_seconds) = 0; /** * Schedules a task to be invoked on a foreground thread wrt a specific * |isolate|. Tasks posted for the same isolate should be execute in order of * scheduling. The definition of "foreground" is opaque to V8. */ V8_DEPRECATE_SOON( "Use a taskrunner acquired by GetForegroundTaskRunner instead.", virtual void CallOnForegroundThread(Isolate* isolate, Task* task)) = 0; /** * Schedules a task to be invoked on a foreground thread wrt a specific * |isolate| after the given number of seconds |delay_in_seconds|. * Tasks posted for the same isolate should be execute in order of * scheduling. The definition of "foreground" is opaque to V8. */ V8_DEPRECATE_SOON( "Use a taskrunner acquired by GetForegroundTaskRunner instead.", virtual void CallDelayedOnForegroundThread(Isolate* isolate, Task* task, double delay_in_seconds)) = 0; /** * Schedules a task to be invoked on a foreground thread wrt a specific * |isolate| when the embedder is idle. * Requires that SupportsIdleTasks(isolate) is true. * Idle tasks may be reordered relative to other task types and may be * starved for an arbitrarily long time if no idle time is available. * The definition of "foreground" is opaque to V8. */ V8_DEPRECATE_SOON( "Use a taskrunner acquired by GetForegroundTaskRunner instead.", virtual void CallIdleOnForegroundThread(Isolate* isolate, IdleTask* task)) { // This must be overriden if |IdleTasksEnabled()|. abort(); } /** * Returns true if idle tasks are enabled for the given |isolate|. */ virtual bool IdleTasksEnabled(Isolate* isolate) { return false; } /** * Monotonically increasing time in seconds from an arbitrary fixed point in * the past. This function is expected to return at least * millisecond-precision values. For this reason, * it is recommended that the fixed point be no further in the past than * the epoch. **/ virtual double MonotonicallyIncreasingTime() = 0; /** * Current wall-clock time in milliseconds since epoch. * This function is expected to return at least millisecond-precision values. */ virtual double CurrentClockTimeMillis() = 0; typedef void (*StackTracePrinter)(); /** * Returns a function pointer that print a stack trace of the current stack * on invocation. Disables printing of the stack trace if nullptr. */ virtual StackTracePrinter GetStackTracePrinter() { return nullptr; } /** * Returns an instance of a v8::TracingController. This must be non-nullptr. */ virtual TracingController* GetTracingController() = 0; /** * Tells the embedder to generate and upload a crashdump during an unexpected * but non-critical scenario. */ virtual void DumpWithoutCrashing() {} protected: /** * Default implementation of current wall-clock time in milliseconds * since epoch. Useful for implementing |CurrentClockTimeMillis| if * nothing special needed. */ static double SystemClockTimeMillis(); }; } // namespace v8 #endif // V8_V8_PLATFORM_H_