1 // Copyright 2013 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef V8_V8_PLATFORM_H_
6 #define V8_V8_PLATFORM_H_
7
8 #include <stddef.h>
9 #include <stdint.h>
10 #include <stdlib.h> // For abort.
11 #include <memory>
12 #include <string>
13
14 #include "v8config.h" // NOLINT(build/include)
15
16 namespace v8 {
17
18 class Isolate;
19
20 /**
21 * A Task represents a unit of work.
22 */
23 class Task {
24 public:
25 virtual ~Task() = default;
26
27 virtual void Run() = 0;
28 };
29
30 /**
31 * An IdleTask represents a unit of work to be performed in idle time.
32 * The Run method is invoked with an argument that specifies the deadline in
33 * seconds returned by MonotonicallyIncreasingTime().
34 * The idle task is expected to complete by this deadline.
35 */
36 class IdleTask {
37 public:
StringView()38 virtual ~IdleTask() = default;
39 virtual void Run(double deadline_in_seconds) = 0;
StringView(const uint8_t * characters,size_t length)40 };
41
42 /**
StringView(const uint16_t * characters,size_t length)43 * A TaskRunner allows scheduling of tasks. The TaskRunner may still be used to
44 * post tasks after the isolate gets destructed, but these tasks may not get
45 * executed anymore. All tasks posted to a given TaskRunner will be invoked in
46 * sequence. Tasks can be posted from any thread.
47 */
48 class TaskRunner {
49 public:
50 /**
51 * Schedules a task to be invoked by this TaskRunner. The TaskRunner
52 * implementation takes ownership of |task|.
53 */
54 virtual void PostTask(std::unique_ptr<Task> task) = 0;
55
56 /**
57 * Schedules a task to be invoked by this TaskRunner. The task is scheduled
58 * after the given number of seconds |delay_in_seconds|. The TaskRunner
59 * implementation takes ownership of |task|.
60 */
61 virtual void PostDelayedTask(std::unique_ptr<Task> task,
62 double delay_in_seconds) = 0;
63
64 /**
65 * Schedules an idle task to be invoked by this TaskRunner. The task is
66 * scheduled when the embedder is idle. Requires that
67 * TaskRunner::SupportsIdleTasks(isolate) is true. Idle tasks may be reordered
68 * relative to other task types and may be starved for an arbitrarily long
69 * time if no idle time is available. The TaskRunner implementation takes
70 * ownership of |task|.
71 */
72 virtual void PostIdleTask(std::unique_ptr<IdleTask> task) = 0;
73
74 /**
75 * Returns true if idle tasks are enabled for this TaskRunner.
76 */
77 virtual bool IdleTasksEnabled() = 0;
78
79 TaskRunner() = default;
80 virtual ~TaskRunner() = default;
81
82 private:
83 TaskRunner(const TaskRunner&) = delete;
84 TaskRunner& operator=(const TaskRunner&) = delete;
85 };
86
87 /**
88 * The interface represents complex arguments to trace events.
89 */
90 class ConvertableToTraceFormat {
91 public:
92 virtual ~ConvertableToTraceFormat() = default;
93
94 /**
95 * Append the class info to the provided |out| string. The appended
96 * data must be a valid JSON object. Strings must be properly quoted, and
97 * escaped. There is no processing applied to the content after it is
98 * appended.
99 */
100 virtual void AppendAsTraceFormat(std::string* out) const = 0;
101 };
102
103 /**
104 * V8 Tracing controller.
105 *
106 * Can be implemented by an embedder to record trace events from V8.
107 */
108 class TracingController {
~V8StackTrace()109 public:
110 virtual ~TracingController() = default;
111
112 /**
113 * Called by TRACE_EVENT* macros, don't call this directly.
114 * The name parameter is a category group for example:
115 * TRACE_EVENT0("v8,parse", "V8.Parse")
116 * The pointer returned points to a value with zero or more of the bits
117 * defined in CategoryGroupEnabledFlags.
118 **/
119 virtual const uint8_t* GetCategoryGroupEnabled(const char* name) {
~V8InspectorSession()120 static uint8_t no = 0;
121 return &no;
122 }
123
124 /**
125 * Adds a trace event to the platform tracing system. These function calls are
~Inspectable()126 * usually the result of a TRACE_* macro from trace_event_common.h when
127 * tracing and the category of the particular trace are enabled. It is not
128 * advisable to call these functions on their own; they are really only meant
129 * to be used by the trace macros. The returned handle can be used by
130 * UpdateTraceEventDuration to update the duration of COMPLETE events.
131 */
132 virtual uint64_t AddTraceEvent(
133 char phase, const uint8_t* category_enabled_flag, const char* name,
134 const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
135 const char** arg_names, const uint8_t* arg_types,
136 const uint64_t* arg_values,
137 std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
138 unsigned int flags) {
139 return 0;
140 }
141 virtual uint64_t AddTraceEventWithTimestamp(
142 char phase, const uint8_t* category_enabled_flag, const char* name,
143 const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
144 const char** arg_names, const uint8_t* arg_types,
145 const uint64_t* arg_values,
146 std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
147 unsigned int flags, int64_t timestamp) {
148 return 0;
149 }
150
151 /**
152 * Sets the duration field of a COMPLETE trace event. It must be called with
153 * the handle returned from AddTraceEvent().
154 **/
155 virtual void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
156 const char* name, uint64_t handle) {}
157
158 class TraceStateObserver {
159 public:
160 virtual ~TraceStateObserver() = default;
161 virtual void OnTraceEnabled() = 0;
162 virtual void OnTraceDisabled() = 0;
163 };
~V8InspectorClient()164
165 /** Adds tracing state change observer. */
166 virtual void AddTraceStateObserver(TraceStateObserver*) {}
quitMessageLoopOnPause()167
168 /** Removes tracing state change observer. */
169 virtual void RemoveTraceStateObserver(TraceStateObserver*) {}
muteMetrics(int contextGroupId)170 };
unmuteMetrics(int contextGroupId)171
172 /**
173 * A V8 memory page allocator.
174 *
175 * Can be implemented by an embedder to manage large host OS allocations.
176 */
177 class PageAllocator {
178 public:
179 virtual ~PageAllocator() = default;
180
181 /**
182 * Gets the page granularity for AllocatePages and FreePages. Addresses and
183 * lengths for those calls should be multiples of AllocatePageSize().
184 */
185 virtual size_t AllocatePageSize() = 0;
186
187 /**
188 * Gets the page granularity for SetPermissions and ReleasePages. Addresses
189 * and lengths for those calls should be multiples of CommitPageSize().
190 */
191 virtual size_t CommitPageSize() = 0;
192
193 /**
194 * Sets the random seed so that GetRandomMmapAddr() will generate repeatable
195 * sequences of random mmap addresses.
196 */
197 virtual void SetRandomMmapSeed(int64_t seed) = 0;
198
199 /**
200 * Returns a randomized address, suitable for memory allocation under ASLR.
201 * The address will be aligned to AllocatePageSize.
202 */
203 virtual void* GetRandomMmapAddr() = 0;
204
205 /**
206 * Memory permissions.
207 */
208 enum Permission {
209 kNoAccess,
210 kRead,
211 kReadWrite,
212 // TODO(hpayer): Remove this flag. Memory should never be rwx.
213 kReadWriteExecute,
214 kReadExecute
215 };
216
217 /**
218 * Allocates memory in range with the given alignment and permission.
219 */
220 virtual void* AllocatePages(void* address, size_t length, size_t alignment,
221 Permission permissions) = 0;
222
223 /**
224 * Frees memory in a range that was allocated by a call to AllocatePages.
225 */
226 virtual bool FreePages(void* address, size_t length) = 0;
227
228 /**
229 * Releases memory in a range that was allocated by a call to AllocatePages.
230 */
231 virtual bool ReleasePages(void* address, size_t length,
232 size_t new_length) = 0;
233
234 /**
235 * Sets permissions on pages in an allocated range.
236 */
237 virtual bool SetPermissions(void* address, size_t length,
238 Permission permissions) = 0;
239 };
240
~V8Inspector()241 /**
242 * V8 Platform abstraction layer.
243 *
244 * The embedder has to provide an implementation of this interface before
245 * initializing the rest of V8.
246 */
247 class Platform {
248 public:
249 /**
250 * This enum is used to indicate whether a task is potentially long running,
251 * or causes a long wait. The embedder might want to use this hint to decide
252 * whether to execute the task on a dedicated thread.
253 */
254 enum ExpectedRuntime {
255 kShortRunningTask,
256 kLongRunningTask
257 };
258
259 virtual ~Platform() = default;
260
261 /**
262 * Allows the embedder to manage memory page allocations.
263 */
264 virtual PageAllocator* GetPageAllocator() {
265 // TODO(bbudge) Make this abstract after all embedders implement this.
266 return nullptr;
267 }
268
269 /**
270 * Enables the embedder to respond in cases where V8 can't allocate large
271 * blocks of memory. V8 retries the failed allocation once after calling this
272 * method. On success, execution continues; otherwise V8 exits with a fatal
273 * error.
274 * Embedder overrides of this function must NOT call back into V8.
275 */
276 virtual void OnCriticalMemoryPressure() {
277 // TODO(bbudge) Remove this when embedders override the following method.
278 // See crbug.com/634547.
279 }
280
281 /**
282 * Enables the embedder to respond in cases where V8 can't allocate large
283 * memory regions. The |length| parameter is the amount of memory needed.
284 * Returns true if memory is now available. Returns false if no memory could
285 * be made available. V8 will retry allocations until this method returns
286 * false.
287 *
288 * Embedder overrides of this function must NOT call back into V8.
289 */
290 virtual bool OnCriticalMemoryPressure(size_t length) { return false; }
291
292 /**
293 * Gets the number of worker threads used by GetWorkerThreadsTaskRunner() and
294 * CallOnWorkerThread(). This can be used to estimate the number of tasks a
295 * work package should be split into. A return value of 0 means that there are
296 * no worker threads available. Note that a value of 0 won't prohibit V8 from
297 * posting tasks using |CallOnWorkerThread|.
298 */
299 virtual int NumberOfWorkerThreads() {
300 return static_cast<int>(NumberOfAvailableBackgroundThreads());
301 }
302
303 /**
304 * Deprecated. Use NumberOfWorkerThreads() instead.
305 * TODO(gab): Remove this when all embedders override
306 * NumberOfWorkerThreads() instead.
307 */
308 V8_DEPRECATE_SOON(
309 "NumberOfAvailableBackgroundThreads() is deprecated, use "
310 "NumberOfAvailableBackgroundThreads() instead.",
311 virtual size_t NumberOfAvailableBackgroundThreads()) {
312 return 0;
313 }
314
315 /**
316 * Returns a TaskRunner which can be used to post a task on the foreground.
317 * This function should only be called from a foreground thread.
318 */
319 virtual std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner(
320 Isolate* isolate) {
321 // TODO(ahaas): Make this function abstract after it got implemented on all
322 // platforms.
323 return {};
324 }
325
326 /**
327 * Returns a TaskRunner which can be used to post a task on a background.
328 * This function should only be called from a foreground thread.
329 */
330 V8_DEPRECATE_SOON(
331 "GetBackgroundTaskRunner() is deprecated, use "
332 "GetWorkerThreadsTaskRunner() "
333 "instead.",
334 virtual std::shared_ptr<v8::TaskRunner> GetBackgroundTaskRunner(
335 Isolate* isolate)) {
336 // TODO(gab): Remove this method when all embedders have moved to
337 // GetWorkerThreadsTaskRunner().
338
339 // An implementation needs to be provided here because this is called by the
340 // default GetWorkerThreadsTaskRunner() implementation below. In practice
341 // however, all code either:
342 // - Overrides GetWorkerThreadsTaskRunner() (thus not making this call) --
343 // i.e. all v8 code.
344 // - Overrides this method (thus not making this call) -- i.e. all
345 // unadapted embedders.
346 abort();
347 }
348
349 /**
350 * Returns a TaskRunner which can be used to post async tasks on a worker.
351 * This function should only be called from a foreground thread.
352 */
353 virtual std::shared_ptr<v8::TaskRunner> GetWorkerThreadsTaskRunner(
354 Isolate* isolate) {
355 // TODO(gab): Make this function abstract after it got implemented on all
356 // platforms.
357 return GetBackgroundTaskRunner(isolate);
358 }
359
360 /**
361 * Schedules a task to be invoked on a background thread. |expected_runtime|
362 * indicates that the task will run a long time. The Platform implementation
363 * takes ownership of |task|. There is no guarantee about order of execution
364 * of tasks wrt order of scheduling, nor is there a guarantee about the
365 * thread the task will be run on.
366 */
367 V8_DEPRECATE_SOON(
368 "ExpectedRuntime is deprecated, use CallOnWorkerThread() instead.",
369 virtual void CallOnBackgroundThread(Task* task,
370 ExpectedRuntime expected_runtime)) {
371 // An implementation needs to be provided here because this is called by the
372 // default implementation below. In practice however, all code either:
373 // - Overrides the new method (thus not making this call) -- i.e. all v8
374 // code.
375 // - Overrides this method (thus not making this call) -- i.e. all
376 // unadapted embedders.
377 abort();
378 }
379
380 /**
381 * Schedules a task to be invoked on a worker thread.
382 * TODO(gab): Make pure virtual when all embedders override this instead of
383 * CallOnBackgroundThread().
384 */
385 virtual void CallOnWorkerThread(std::unique_ptr<Task> task) {
386 CallOnBackgroundThread(task.release(), kShortRunningTask);
387 }
388
389 /**
390 * Schedules a task that blocks the main thread to be invoked with
391 * high-priority on a worker thread.
392 */
393 virtual void CallBlockingTaskOnWorkerThread(std::unique_ptr<Task> task) {
394 // Embedders may optionally override this to process these tasks in a high
395 // priority pool.
396 CallOnWorkerThread(std::move(task));
397 }
398
399 /**
400 * Schedules a task to be invoked on a foreground thread wrt a specific
401 * |isolate|. Tasks posted for the same isolate should be execute in order of
402 * scheduling. The definition of "foreground" is opaque to V8.
403 */
404 virtual void CallOnForegroundThread(Isolate* isolate, Task* task) = 0;
405
406 /**
407 * Schedules a task to be invoked on a foreground thread wrt a specific
408 * |isolate| after the given number of seconds |delay_in_seconds|.
409 * Tasks posted for the same isolate should be execute in order of
410 * scheduling. The definition of "foreground" is opaque to V8.
411 */
412 virtual void CallDelayedOnForegroundThread(Isolate* isolate, Task* task,
413 double delay_in_seconds) = 0;
414
415 /**
416 * Schedules a task to be invoked on a foreground thread wrt a specific
417 * |isolate| when the embedder is idle.
418 * Requires that SupportsIdleTasks(isolate) is true.
419 * Idle tasks may be reordered relative to other task types and may be
420 * starved for an arbitrarily long time if no idle time is available.
421 * The definition of "foreground" is opaque to V8.
422 */
423 virtual void CallIdleOnForegroundThread(Isolate* isolate, IdleTask* task) {
424 // TODO(ulan): Make this function abstract after V8 roll in Chromium.
425 }
426
427 /**
428 * Returns true if idle tasks are enabled for the given |isolate|.
429 */
430 virtual bool IdleTasksEnabled(Isolate* isolate) {
431 // TODO(ulan): Make this function abstract after V8 roll in Chromium.
432 return false;
433 }
434
435 /**
436 * Monotonically increasing time in seconds from an arbitrary fixed point in
437 * the past. This function is expected to return at least
438 * millisecond-precision values. For this reason,
439 * it is recommended that the fixed point be no further in the past than
440 * the epoch.
441 **/
442 virtual double MonotonicallyIncreasingTime() = 0;
443
444 /**
445 * Current wall-clock time in milliseconds since epoch.
446 * This function is expected to return at least millisecond-precision values.
447 */
448 virtual double CurrentClockTimeMillis() = 0;
449
450 typedef void (*StackTracePrinter)();
451
452 /**
453 * Returns a function pointer that print a stack trace of the current stack
454 * on invocation. Disables printing of the stack trace if nullptr.
455 */
456 virtual StackTracePrinter GetStackTracePrinter() { return nullptr; }
457
458 /**
459 * Returns an instance of a v8::TracingController. This must be non-nullptr.
460 */
461 virtual TracingController* GetTracingController() = 0;
462
463 protected:
464 /**
465 * Default implementation of current wall-clock time in milliseconds
466 * since epoch. Useful for implementing |CurrentClockTimeMillis| if
467 * nothing special needed.
468 */
469 static double SystemClockTimeMillis();
470 };
471
472 } // namespace v8
473
474 #endif // V8_V8_PLATFORM_H_
475