1 /*
2  * Copyright (C) 2011 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include "trace.h"
18 
19 #include <sys/uio.h>
20 #include <unistd.h>
21 
22 #define ATRACE_TAG ATRACE_TAG_DALVIK
23 #include "cutils/trace.h"
24 
25 #include "art_method-inl.h"
26 #include "base/casts.h"
27 #include "base/stl_util.h"
28 #include "base/time_utils.h"
29 #include "base/unix_file/fd_file.h"
30 #include "class_linker.h"
31 #include "common_throws.h"
32 #include "debugger.h"
33 #include "dex_file-inl.h"
34 #include "instrumentation.h"
35 #include "mirror/class-inl.h"
36 #include "mirror/dex_cache-inl.h"
37 #include "mirror/object_array-inl.h"
38 #include "mirror/object-inl.h"
39 #include "os.h"
40 #include "scoped_thread_state_change.h"
41 #include "ScopedLocalRef.h"
42 #include "thread.h"
43 #include "thread_list.h"
44 #include "utils.h"
45 #include "entrypoints/quick/quick_entrypoints.h"
46 
47 namespace art {
48 
49 static constexpr size_t TraceActionBits = MinimumBitsToStore(
50     static_cast<size_t>(kTraceMethodActionMask));
51 static constexpr uint8_t kOpNewMethod = 1U;
52 static constexpr uint8_t kOpNewThread = 2U;
53 
54 class BuildStackTraceVisitor : public StackVisitor {
55  public:
BuildStackTraceVisitor(Thread * thread)56   explicit BuildStackTraceVisitor(Thread* thread)
57       : StackVisitor(thread, nullptr, StackVisitor::StackWalkKind::kIncludeInlinedFrames),
58         method_trace_(Trace::AllocStackTrace()) {}
59 
VisitFrame()60   bool VisitFrame() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
61     ArtMethod* m = GetMethod();
62     // Ignore runtime frames (in particular callee save).
63     if (!m->IsRuntimeMethod()) {
64       method_trace_->push_back(m);
65     }
66     return true;
67   }
68 
69   // Returns a stack trace where the topmost frame corresponds with the first element of the vector.
GetStackTrace() const70   std::vector<ArtMethod*>* GetStackTrace() const {
71     return method_trace_;
72   }
73 
74  private:
75   std::vector<ArtMethod*>* const method_trace_;
76 };
77 
78 static const char     kTraceTokenChar             = '*';
79 static const uint16_t kTraceHeaderLength          = 32;
80 static const uint32_t kTraceMagicValue            = 0x574f4c53;
81 static const uint16_t kTraceVersionSingleClock    = 2;
82 static const uint16_t kTraceVersionDualClock      = 3;
83 static const uint16_t kTraceRecordSizeSingleClock = 10;  // using v2
84 static const uint16_t kTraceRecordSizeDualClock   = 14;  // using v3 with two timestamps
85 
86 TraceClockSource Trace::default_clock_source_ = kDefaultTraceClockSource;
87 
88 Trace* volatile Trace::the_trace_ = nullptr;
89 pthread_t Trace::sampling_pthread_ = 0U;
90 std::unique_ptr<std::vector<ArtMethod*>> Trace::temp_stack_trace_;
91 
92 // The key identifying the tracer to update instrumentation.
93 static constexpr const char* kTracerInstrumentationKey = "Tracer";
94 
DecodeTraceAction(uint32_t tmid)95 static TraceAction DecodeTraceAction(uint32_t tmid) {
96   return static_cast<TraceAction>(tmid & kTraceMethodActionMask);
97 }
98 
DecodeTraceMethod(uint32_t tmid)99 ArtMethod* Trace::DecodeTraceMethod(uint32_t tmid) {
100   MutexLock mu(Thread::Current(), *unique_methods_lock_);
101   return unique_methods_[tmid >> TraceActionBits];
102 }
103 
EncodeTraceMethod(ArtMethod * method)104 uint32_t Trace::EncodeTraceMethod(ArtMethod* method) {
105   MutexLock mu(Thread::Current(), *unique_methods_lock_);
106   uint32_t idx;
107   auto it = art_method_id_map_.find(method);
108   if (it != art_method_id_map_.end()) {
109     idx = it->second;
110   } else {
111     unique_methods_.push_back(method);
112     idx = unique_methods_.size() - 1;
113     art_method_id_map_.emplace(method, idx);
114   }
115   DCHECK_LT(idx, unique_methods_.size());
116   DCHECK_EQ(unique_methods_[idx], method);
117   return idx;
118 }
119 
EncodeTraceMethodAndAction(ArtMethod * method,TraceAction action)120 uint32_t Trace::EncodeTraceMethodAndAction(ArtMethod* method, TraceAction action) {
121   uint32_t tmid = (EncodeTraceMethod(method) << TraceActionBits) | action;
122   DCHECK_EQ(method, DecodeTraceMethod(tmid));
123   return tmid;
124 }
125 
AllocStackTrace()126 std::vector<ArtMethod*>* Trace::AllocStackTrace() {
127   return (temp_stack_trace_.get() != nullptr)  ? temp_stack_trace_.release() :
128       new std::vector<ArtMethod*>();
129 }
130 
FreeStackTrace(std::vector<ArtMethod * > * stack_trace)131 void Trace::FreeStackTrace(std::vector<ArtMethod*>* stack_trace) {
132   stack_trace->clear();
133   temp_stack_trace_.reset(stack_trace);
134 }
135 
SetDefaultClockSource(TraceClockSource clock_source)136 void Trace::SetDefaultClockSource(TraceClockSource clock_source) {
137 #if defined(__linux__)
138   default_clock_source_ = clock_source;
139 #else
140   if (clock_source != TraceClockSource::kWall) {
141     LOG(WARNING) << "Ignoring tracing request to use CPU time.";
142   }
143 #endif
144 }
145 
GetTraceVersion(TraceClockSource clock_source)146 static uint16_t GetTraceVersion(TraceClockSource clock_source) {
147   return (clock_source == TraceClockSource::kDual) ? kTraceVersionDualClock
148                                                     : kTraceVersionSingleClock;
149 }
150 
GetRecordSize(TraceClockSource clock_source)151 static uint16_t GetRecordSize(TraceClockSource clock_source) {
152   return (clock_source == TraceClockSource::kDual) ? kTraceRecordSizeDualClock
153                                                     : kTraceRecordSizeSingleClock;
154 }
155 
UseThreadCpuClock()156 bool Trace::UseThreadCpuClock() {
157   return (clock_source_ == TraceClockSource::kThreadCpu) ||
158       (clock_source_ == TraceClockSource::kDual);
159 }
160 
UseWallClock()161 bool Trace::UseWallClock() {
162   return (clock_source_ == TraceClockSource::kWall) ||
163       (clock_source_ == TraceClockSource::kDual);
164 }
165 
MeasureClockOverhead()166 void Trace::MeasureClockOverhead() {
167   if (UseThreadCpuClock()) {
168     Thread::Current()->GetCpuMicroTime();
169   }
170   if (UseWallClock()) {
171     MicroTime();
172   }
173 }
174 
175 // Compute an average time taken to measure clocks.
GetClockOverheadNanoSeconds()176 uint32_t Trace::GetClockOverheadNanoSeconds() {
177   Thread* self = Thread::Current();
178   uint64_t start = self->GetCpuMicroTime();
179 
180   for (int i = 4000; i > 0; i--) {
181     MeasureClockOverhead();
182     MeasureClockOverhead();
183     MeasureClockOverhead();
184     MeasureClockOverhead();
185     MeasureClockOverhead();
186     MeasureClockOverhead();
187     MeasureClockOverhead();
188     MeasureClockOverhead();
189   }
190 
191   uint64_t elapsed_us = self->GetCpuMicroTime() - start;
192   return static_cast<uint32_t>(elapsed_us / 32);
193 }
194 
195 // TODO: put this somewhere with the big-endian equivalent used by JDWP.
Append2LE(uint8_t * buf,uint16_t val)196 static void Append2LE(uint8_t* buf, uint16_t val) {
197   *buf++ = static_cast<uint8_t>(val);
198   *buf++ = static_cast<uint8_t>(val >> 8);
199 }
200 
201 // TODO: put this somewhere with the big-endian equivalent used by JDWP.
Append4LE(uint8_t * buf,uint32_t val)202 static void Append4LE(uint8_t* buf, uint32_t val) {
203   *buf++ = static_cast<uint8_t>(val);
204   *buf++ = static_cast<uint8_t>(val >> 8);
205   *buf++ = static_cast<uint8_t>(val >> 16);
206   *buf++ = static_cast<uint8_t>(val >> 24);
207 }
208 
209 // TODO: put this somewhere with the big-endian equivalent used by JDWP.
Append8LE(uint8_t * buf,uint64_t val)210 static void Append8LE(uint8_t* buf, uint64_t val) {
211   *buf++ = static_cast<uint8_t>(val);
212   *buf++ = static_cast<uint8_t>(val >> 8);
213   *buf++ = static_cast<uint8_t>(val >> 16);
214   *buf++ = static_cast<uint8_t>(val >> 24);
215   *buf++ = static_cast<uint8_t>(val >> 32);
216   *buf++ = static_cast<uint8_t>(val >> 40);
217   *buf++ = static_cast<uint8_t>(val >> 48);
218   *buf++ = static_cast<uint8_t>(val >> 56);
219 }
220 
GetSample(Thread * thread,void * arg)221 static void GetSample(Thread* thread, void* arg) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
222   BuildStackTraceVisitor build_trace_visitor(thread);
223   build_trace_visitor.WalkStack();
224   std::vector<ArtMethod*>* stack_trace = build_trace_visitor.GetStackTrace();
225   Trace* the_trace = reinterpret_cast<Trace*>(arg);
226   the_trace->CompareAndUpdateStackTrace(thread, stack_trace);
227 }
228 
ClearThreadStackTraceAndClockBase(Thread * thread,void * arg ATTRIBUTE_UNUSED)229 static void ClearThreadStackTraceAndClockBase(Thread* thread, void* arg ATTRIBUTE_UNUSED) {
230   thread->SetTraceClockBase(0);
231   std::vector<ArtMethod*>* stack_trace = thread->GetStackTraceSample();
232   thread->SetStackTraceSample(nullptr);
233   delete stack_trace;
234 }
235 
CompareAndUpdateStackTrace(Thread * thread,std::vector<ArtMethod * > * stack_trace)236 void Trace::CompareAndUpdateStackTrace(Thread* thread,
237                                        std::vector<ArtMethod*>* stack_trace) {
238   CHECK_EQ(pthread_self(), sampling_pthread_);
239   std::vector<ArtMethod*>* old_stack_trace = thread->GetStackTraceSample();
240   // Update the thread's stack trace sample.
241   thread->SetStackTraceSample(stack_trace);
242   // Read timer clocks to use for all events in this trace.
243   uint32_t thread_clock_diff = 0;
244   uint32_t wall_clock_diff = 0;
245   ReadClocks(thread, &thread_clock_diff, &wall_clock_diff);
246   if (old_stack_trace == nullptr) {
247     // If there's no previous stack trace sample for this thread, log an entry event for all
248     // methods in the trace.
249     for (auto rit = stack_trace->rbegin(); rit != stack_trace->rend(); ++rit) {
250       LogMethodTraceEvent(thread, *rit, instrumentation::Instrumentation::kMethodEntered,
251                           thread_clock_diff, wall_clock_diff);
252     }
253   } else {
254     // If there's a previous stack trace for this thread, diff the traces and emit entry and exit
255     // events accordingly.
256     auto old_rit = old_stack_trace->rbegin();
257     auto rit = stack_trace->rbegin();
258     // Iterate bottom-up over both traces until there's a difference between them.
259     while (old_rit != old_stack_trace->rend() && rit != stack_trace->rend() && *old_rit == *rit) {
260       old_rit++;
261       rit++;
262     }
263     // Iterate top-down over the old trace until the point where they differ, emitting exit events.
264     for (auto old_it = old_stack_trace->begin(); old_it != old_rit.base(); ++old_it) {
265       LogMethodTraceEvent(thread, *old_it, instrumentation::Instrumentation::kMethodExited,
266                           thread_clock_diff, wall_clock_diff);
267     }
268     // Iterate bottom-up over the new trace from the point where they differ, emitting entry events.
269     for (; rit != stack_trace->rend(); ++rit) {
270       LogMethodTraceEvent(thread, *rit, instrumentation::Instrumentation::kMethodEntered,
271                           thread_clock_diff, wall_clock_diff);
272     }
273     FreeStackTrace(old_stack_trace);
274   }
275 }
276 
RunSamplingThread(void * arg)277 void* Trace::RunSamplingThread(void* arg) {
278   Runtime* runtime = Runtime::Current();
279   intptr_t interval_us = reinterpret_cast<intptr_t>(arg);
280   CHECK_GE(interval_us, 0);
281   CHECK(runtime->AttachCurrentThread("Sampling Profiler", true, runtime->GetSystemThreadGroup(),
282                                      !runtime->IsAotCompiler()));
283 
284   while (true) {
285     usleep(interval_us);
286     ATRACE_BEGIN("Profile sampling");
287     Thread* self = Thread::Current();
288     Trace* the_trace;
289     {
290       MutexLock mu(self, *Locks::trace_lock_);
291       the_trace = the_trace_;
292       if (the_trace == nullptr) {
293         break;
294       }
295     }
296 
297     runtime->GetThreadList()->SuspendAll(__FUNCTION__);
298     {
299       MutexLock mu(self, *Locks::thread_list_lock_);
300       runtime->GetThreadList()->ForEach(GetSample, the_trace);
301     }
302     runtime->GetThreadList()->ResumeAll();
303     ATRACE_END();
304   }
305 
306   runtime->DetachCurrentThread();
307   return nullptr;
308 }
309 
Start(const char * trace_filename,int trace_fd,size_t buffer_size,int flags,TraceOutputMode output_mode,TraceMode trace_mode,int interval_us)310 void Trace::Start(const char* trace_filename, int trace_fd, size_t buffer_size, int flags,
311                   TraceOutputMode output_mode, TraceMode trace_mode, int interval_us) {
312   Thread* self = Thread::Current();
313   {
314     MutexLock mu(self, *Locks::trace_lock_);
315     if (the_trace_ != nullptr) {
316       LOG(ERROR) << "Trace already in progress, ignoring this request";
317       return;
318     }
319   }
320 
321   // Check interval if sampling is enabled
322   if (trace_mode == TraceMode::kSampling && interval_us <= 0) {
323     LOG(ERROR) << "Invalid sampling interval: " << interval_us;
324     ScopedObjectAccess soa(self);
325     ThrowRuntimeException("Invalid sampling interval: %d", interval_us);
326     return;
327   }
328 
329   // Open trace file if not going directly to ddms.
330   std::unique_ptr<File> trace_file;
331   if (output_mode != TraceOutputMode::kDDMS) {
332     if (trace_fd < 0) {
333       trace_file.reset(OS::CreateEmptyFile(trace_filename));
334     } else {
335       trace_file.reset(new File(trace_fd, "tracefile"));
336       trace_file->DisableAutoClose();
337     }
338     if (trace_file.get() == nullptr) {
339       PLOG(ERROR) << "Unable to open trace file '" << trace_filename << "'";
340       ScopedObjectAccess soa(self);
341       ThrowRuntimeException("Unable to open trace file '%s'", trace_filename);
342       return;
343     }
344   }
345 
346   Runtime* runtime = Runtime::Current();
347 
348   // Enable count of allocs if specified in the flags.
349   bool enable_stats = false;
350 
351   runtime->GetThreadList()->SuspendAll(__FUNCTION__);
352 
353   // Create Trace object.
354   {
355     MutexLock mu(self, *Locks::trace_lock_);
356     if (the_trace_ != nullptr) {
357       LOG(ERROR) << "Trace already in progress, ignoring this request";
358     } else {
359       enable_stats = (flags && kTraceCountAllocs) != 0;
360       the_trace_ = new Trace(trace_file.release(), trace_filename, buffer_size, flags, output_mode,
361                              trace_mode);
362       if (trace_mode == TraceMode::kSampling) {
363         CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, nullptr, &RunSamplingThread,
364                                             reinterpret_cast<void*>(interval_us)),
365                                             "Sampling profiler thread");
366         the_trace_->interval_us_ = interval_us;
367       } else {
368         runtime->GetInstrumentation()->AddListener(the_trace_,
369                                                    instrumentation::Instrumentation::kMethodEntered |
370                                                    instrumentation::Instrumentation::kMethodExited |
371                                                    instrumentation::Instrumentation::kMethodUnwind);
372         // TODO: In full-PIC mode, we don't need to fully deopt.
373         runtime->GetInstrumentation()->EnableMethodTracing(kTracerInstrumentationKey);
374       }
375     }
376   }
377 
378   runtime->GetThreadList()->ResumeAll();
379 
380   // Can't call this when holding the mutator lock.
381   if (enable_stats) {
382     runtime->SetStatsEnabled(true);
383   }
384 }
385 
StopTracing(bool finish_tracing,bool flush_file)386 void Trace::StopTracing(bool finish_tracing, bool flush_file) {
387   bool stop_alloc_counting = false;
388   Runtime* const runtime = Runtime::Current();
389   Trace* the_trace = nullptr;
390   pthread_t sampling_pthread = 0U;
391   {
392     MutexLock mu(Thread::Current(), *Locks::trace_lock_);
393     if (the_trace_ == nullptr) {
394       LOG(ERROR) << "Trace stop requested, but no trace currently running";
395     } else {
396       the_trace = the_trace_;
397       the_trace_ = nullptr;
398       sampling_pthread = sampling_pthread_;
399     }
400   }
401   // Make sure that we join before we delete the trace since we don't want to have
402   // the sampling thread access a stale pointer. This finishes since the sampling thread exits when
403   // the_trace_ is null.
404   if (sampling_pthread != 0U) {
405     CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, nullptr), "sampling thread shutdown");
406     sampling_pthread_ = 0U;
407   }
408   runtime->GetThreadList()->SuspendAll(__FUNCTION__);
409 
410   if (the_trace != nullptr) {
411     stop_alloc_counting = (the_trace->flags_ & Trace::kTraceCountAllocs) != 0;
412     if (finish_tracing) {
413       the_trace->FinishTracing();
414     }
415 
416     if (the_trace->trace_mode_ == TraceMode::kSampling) {
417       MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
418       runtime->GetThreadList()->ForEach(ClearThreadStackTraceAndClockBase, nullptr);
419     } else {
420       runtime->GetInstrumentation()->DisableMethodTracing(kTracerInstrumentationKey);
421       runtime->GetInstrumentation()->RemoveListener(
422           the_trace, instrumentation::Instrumentation::kMethodEntered |
423           instrumentation::Instrumentation::kMethodExited |
424           instrumentation::Instrumentation::kMethodUnwind);
425     }
426     if (the_trace->trace_file_.get() != nullptr) {
427       // Do not try to erase, so flush and close explicitly.
428       if (flush_file) {
429         if (the_trace->trace_file_->Flush() != 0) {
430           PLOG(WARNING) << "Could not flush trace file.";
431         }
432       } else {
433         the_trace->trace_file_->MarkUnchecked();  // Do not trigger guard.
434       }
435       if (the_trace->trace_file_->Close() != 0) {
436         PLOG(ERROR) << "Could not close trace file.";
437       }
438     }
439     delete the_trace;
440   }
441   runtime->GetThreadList()->ResumeAll();
442   if (stop_alloc_counting) {
443     // Can be racy since SetStatsEnabled is not guarded by any locks.
444     runtime->SetStatsEnabled(false);
445   }
446 }
447 
Abort()448 void Trace::Abort() {
449   // Do not write anything anymore.
450   StopTracing(false, false);
451 }
452 
Stop()453 void Trace::Stop() {
454   // Finish writing.
455   StopTracing(true, true);
456 }
457 
Shutdown()458 void Trace::Shutdown() {
459   if (GetMethodTracingMode() != kTracingInactive) {
460     Stop();
461   }
462 }
463 
Pause()464 void Trace::Pause() {
465   bool stop_alloc_counting = false;
466   Runtime* runtime = Runtime::Current();
467   Trace* the_trace = nullptr;
468 
469   pthread_t sampling_pthread = 0U;
470   {
471     MutexLock mu(Thread::Current(), *Locks::trace_lock_);
472     if (the_trace_ == nullptr) {
473       LOG(ERROR) << "Trace pause requested, but no trace currently running";
474       return;
475     } else {
476       the_trace = the_trace_;
477       sampling_pthread = sampling_pthread_;
478     }
479   }
480 
481   if (sampling_pthread != 0U) {
482     {
483       MutexLock mu(Thread::Current(), *Locks::trace_lock_);
484       the_trace_ = nullptr;
485     }
486     CHECK_PTHREAD_CALL(pthread_join, (sampling_pthread, nullptr), "sampling thread shutdown");
487     sampling_pthread_ = 0U;
488     {
489       MutexLock mu(Thread::Current(), *Locks::trace_lock_);
490       the_trace_ = the_trace;
491     }
492   }
493 
494   if (the_trace != nullptr) {
495     runtime->GetThreadList()->SuspendAll(__FUNCTION__);
496     stop_alloc_counting = (the_trace->flags_ & Trace::kTraceCountAllocs) != 0;
497 
498     if (the_trace->trace_mode_ == TraceMode::kSampling) {
499       MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
500       runtime->GetThreadList()->ForEach(ClearThreadStackTraceAndClockBase, nullptr);
501     } else {
502       runtime->GetInstrumentation()->DisableMethodTracing(kTracerInstrumentationKey);
503       runtime->GetInstrumentation()->RemoveListener(the_trace,
504                                                     instrumentation::Instrumentation::kMethodEntered |
505                                                     instrumentation::Instrumentation::kMethodExited |
506                                                     instrumentation::Instrumentation::kMethodUnwind);
507     }
508     runtime->GetThreadList()->ResumeAll();
509   }
510 
511   if (stop_alloc_counting) {
512     // Can be racy since SetStatsEnabled is not guarded by any locks.
513     Runtime::Current()->SetStatsEnabled(false);
514   }
515 }
516 
Resume()517 void Trace::Resume() {
518   Thread* self = Thread::Current();
519   Trace* the_trace;
520   {
521     MutexLock mu(self, *Locks::trace_lock_);
522     if (the_trace_ == nullptr) {
523       LOG(ERROR) << "No trace to resume (or sampling mode), ignoring this request";
524       return;
525     }
526     the_trace = the_trace_;
527   }
528 
529   Runtime* runtime = Runtime::Current();
530 
531   // Enable count of allocs if specified in the flags.
532   bool enable_stats = (the_trace->flags_ && kTraceCountAllocs) != 0;
533 
534   runtime->GetThreadList()->SuspendAll(__FUNCTION__);
535 
536   // Reenable.
537   if (the_trace->trace_mode_ == TraceMode::kSampling) {
538     CHECK_PTHREAD_CALL(pthread_create, (&sampling_pthread_, nullptr, &RunSamplingThread,
539         reinterpret_cast<void*>(the_trace->interval_us_)), "Sampling profiler thread");
540   } else {
541     runtime->GetInstrumentation()->AddListener(the_trace,
542                                                instrumentation::Instrumentation::kMethodEntered |
543                                                instrumentation::Instrumentation::kMethodExited |
544                                                instrumentation::Instrumentation::kMethodUnwind);
545     // TODO: In full-PIC mode, we don't need to fully deopt.
546     runtime->GetInstrumentation()->EnableMethodTracing(kTracerInstrumentationKey);
547   }
548 
549   runtime->GetThreadList()->ResumeAll();
550 
551   // Can't call this when holding the mutator lock.
552   if (enable_stats) {
553     runtime->SetStatsEnabled(true);
554   }
555 }
556 
GetMethodTracingMode()557 TracingMode Trace::GetMethodTracingMode() {
558   MutexLock mu(Thread::Current(), *Locks::trace_lock_);
559   if (the_trace_ == nullptr) {
560     return kTracingInactive;
561   } else {
562     switch (the_trace_->trace_mode_) {
563       case TraceMode::kSampling:
564         return kSampleProfilingActive;
565       case TraceMode::kMethodTracing:
566         return kMethodTracingActive;
567     }
568     LOG(FATAL) << "Unreachable";
569     UNREACHABLE();
570   }
571 }
572 
573 static constexpr size_t kMinBufSize = 18U;  // Trace header is up to 18B.
574 
Trace(File * trace_file,const char * trace_name,size_t buffer_size,int flags,TraceOutputMode output_mode,TraceMode trace_mode)575 Trace::Trace(File* trace_file, const char* trace_name, size_t buffer_size, int flags,
576              TraceOutputMode output_mode, TraceMode trace_mode)
577     : trace_file_(trace_file),
578       buf_(new uint8_t[std::max(kMinBufSize, buffer_size)]()),
579       flags_(flags), trace_output_mode_(output_mode), trace_mode_(trace_mode),
580       clock_source_(default_clock_source_),
581       buffer_size_(std::max(kMinBufSize, buffer_size)),
582       start_time_(MicroTime()), clock_overhead_ns_(GetClockOverheadNanoSeconds()), cur_offset_(0),
583       overflow_(false), interval_us_(0), streaming_lock_(nullptr),
584       unique_methods_lock_(new Mutex("unique methods lock", kTracingUniqueMethodsLock)) {
585   uint16_t trace_version = GetTraceVersion(clock_source_);
586   if (output_mode == TraceOutputMode::kStreaming) {
587     trace_version |= 0xF0U;
588   }
589   // Set up the beginning of the trace.
590   memset(buf_.get(), 0, kTraceHeaderLength);
591   Append4LE(buf_.get(), kTraceMagicValue);
592   Append2LE(buf_.get() + 4, trace_version);
593   Append2LE(buf_.get() + 6, kTraceHeaderLength);
594   Append8LE(buf_.get() + 8, start_time_);
595   if (trace_version >= kTraceVersionDualClock) {
596     uint16_t record_size = GetRecordSize(clock_source_);
597     Append2LE(buf_.get() + 16, record_size);
598   }
599   static_assert(18 <= kMinBufSize, "Minimum buffer size not large enough for trace header");
600 
601   // Update current offset.
602   cur_offset_.StoreRelaxed(kTraceHeaderLength);
603 
604   if (output_mode == TraceOutputMode::kStreaming) {
605     streaming_file_name_ = trace_name;
606     streaming_lock_ = new Mutex("tracing lock", LockLevel::kTracingStreamingLock);
607     seen_threads_.reset(new ThreadIDBitSet());
608   }
609 }
610 
~Trace()611 Trace::~Trace() {
612   delete streaming_lock_;
613   delete unique_methods_lock_;
614 }
615 
ReadBytes(uint8_t * buf,size_t bytes)616 static uint64_t ReadBytes(uint8_t* buf, size_t bytes) {
617   uint64_t ret = 0;
618   for (size_t i = 0; i < bytes; ++i) {
619     ret |= static_cast<uint64_t>(buf[i]) << (i * 8);
620   }
621   return ret;
622 }
623 
DumpBuf(uint8_t * buf,size_t buf_size,TraceClockSource clock_source)624 void Trace::DumpBuf(uint8_t* buf, size_t buf_size, TraceClockSource clock_source) {
625   uint8_t* ptr = buf + kTraceHeaderLength;
626   uint8_t* end = buf + buf_size;
627 
628   while (ptr < end) {
629     uint32_t tmid = ReadBytes(ptr + 2, sizeof(tmid));
630     ArtMethod* method = DecodeTraceMethod(tmid);
631     TraceAction action = DecodeTraceAction(tmid);
632     LOG(INFO) << PrettyMethod(method) << " " << static_cast<int>(action);
633     ptr += GetRecordSize(clock_source);
634   }
635 }
636 
GetVisitedMethodsFromBitSets(const std::map<const DexFile *,DexIndexBitSet * > & seen_methods,std::set<ArtMethod * > * visited_methods)637 static void GetVisitedMethodsFromBitSets(
638     const std::map<const DexFile*, DexIndexBitSet*>& seen_methods,
639     std::set<ArtMethod*>* visited_methods) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
640   ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
641   for (auto& e : seen_methods) {
642     DexIndexBitSet* bit_set = e.second;
643     mirror::DexCache* dex_cache = class_linker->FindDexCache(*e.first);
644     for (uint32_t i = 0; i < bit_set->size(); ++i) {
645       if ((*bit_set)[i]) {
646         visited_methods->insert(dex_cache->GetResolvedMethod(i, sizeof(void*)));
647       }
648     }
649   }
650 }
651 
FinishTracing()652 void Trace::FinishTracing() {
653   size_t final_offset = 0;
654 
655   std::set<ArtMethod*> visited_methods;
656   if (trace_output_mode_ == TraceOutputMode::kStreaming) {
657     // Write the secondary file with all the method names.
658     GetVisitedMethodsFromBitSets(seen_methods_, &visited_methods);
659 
660     // Clean up.
661     STLDeleteValues(&seen_methods_);
662   } else {
663     final_offset = cur_offset_.LoadRelaxed();
664     GetVisitedMethods(final_offset, &visited_methods);
665   }
666 
667   // Compute elapsed time.
668   uint64_t elapsed = MicroTime() - start_time_;
669 
670   std::ostringstream os;
671 
672   os << StringPrintf("%cversion\n", kTraceTokenChar);
673   os << StringPrintf("%d\n", GetTraceVersion(clock_source_));
674   os << StringPrintf("data-file-overflow=%s\n", overflow_ ? "true" : "false");
675   if (UseThreadCpuClock()) {
676     if (UseWallClock()) {
677       os << StringPrintf("clock=dual\n");
678     } else {
679       os << StringPrintf("clock=thread-cpu\n");
680     }
681   } else {
682     os << StringPrintf("clock=wall\n");
683   }
684   os << StringPrintf("elapsed-time-usec=%" PRIu64 "\n", elapsed);
685   if (trace_output_mode_ != TraceOutputMode::kStreaming) {
686     size_t num_records = (final_offset - kTraceHeaderLength) / GetRecordSize(clock_source_);
687     os << StringPrintf("num-method-calls=%zd\n", num_records);
688   }
689   os << StringPrintf("clock-call-overhead-nsec=%d\n", clock_overhead_ns_);
690   os << StringPrintf("vm=art\n");
691   os << StringPrintf("pid=%d\n", getpid());
692   if ((flags_ & kTraceCountAllocs) != 0) {
693     os << StringPrintf("alloc-count=%d\n", Runtime::Current()->GetStat(KIND_ALLOCATED_OBJECTS));
694     os << StringPrintf("alloc-size=%d\n", Runtime::Current()->GetStat(KIND_ALLOCATED_BYTES));
695     os << StringPrintf("gc-count=%d\n", Runtime::Current()->GetStat(KIND_GC_INVOCATIONS));
696   }
697   os << StringPrintf("%cthreads\n", kTraceTokenChar);
698   DumpThreadList(os);
699   os << StringPrintf("%cmethods\n", kTraceTokenChar);
700   DumpMethodList(os, visited_methods);
701   os << StringPrintf("%cend\n", kTraceTokenChar);
702   std::string header(os.str());
703 
704   if (trace_output_mode_ == TraceOutputMode::kStreaming) {
705     File file;
706     if (!file.Open(streaming_file_name_ + ".sec", O_CREAT | O_WRONLY)) {
707       LOG(WARNING) << "Could not open secondary trace file!";
708       return;
709     }
710     if (!file.WriteFully(header.c_str(), header.length())) {
711       file.Erase();
712       std::string detail(StringPrintf("Trace data write failed: %s", strerror(errno)));
713       PLOG(ERROR) << detail;
714       ThrowRuntimeException("%s", detail.c_str());
715     }
716     if (file.FlushCloseOrErase() != 0) {
717       PLOG(ERROR) << "Could not write secondary file";
718     }
719   } else {
720     if (trace_file_.get() == nullptr) {
721       iovec iov[2];
722       iov[0].iov_base = reinterpret_cast<void*>(const_cast<char*>(header.c_str()));
723       iov[0].iov_len = header.length();
724       iov[1].iov_base = buf_.get();
725       iov[1].iov_len = final_offset;
726       Dbg::DdmSendChunkV(CHUNK_TYPE("MPSE"), iov, 2);
727       const bool kDumpTraceInfo = false;
728       if (kDumpTraceInfo) {
729         LOG(INFO) << "Trace sent:\n" << header;
730         DumpBuf(buf_.get(), final_offset, clock_source_);
731       }
732     } else {
733       if (!trace_file_->WriteFully(header.c_str(), header.length()) ||
734           !trace_file_->WriteFully(buf_.get(), final_offset)) {
735         std::string detail(StringPrintf("Trace data write failed: %s", strerror(errno)));
736         PLOG(ERROR) << detail;
737         ThrowRuntimeException("%s", detail.c_str());
738       }
739     }
740   }
741 }
742 
DexPcMoved(Thread * thread,mirror::Object * this_object,ArtMethod * method,uint32_t new_dex_pc)743 void Trace::DexPcMoved(Thread* thread, mirror::Object* this_object,
744                        ArtMethod* method, uint32_t new_dex_pc) {
745   UNUSED(thread, this_object, method, new_dex_pc);
746   // We're not recorded to listen to this kind of event, so complain.
747   LOG(ERROR) << "Unexpected dex PC event in tracing " << PrettyMethod(method) << " " << new_dex_pc;
748 }
749 
FieldRead(Thread * thread,mirror::Object * this_object,ArtMethod * method,uint32_t dex_pc,ArtField * field)750 void Trace::FieldRead(Thread* thread, mirror::Object* this_object,
751                        ArtMethod* method, uint32_t dex_pc, ArtField* field)
752     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
753   UNUSED(thread, this_object, method, dex_pc, field);
754   // We're not recorded to listen to this kind of event, so complain.
755   LOG(ERROR) << "Unexpected field read event in tracing " << PrettyMethod(method) << " " << dex_pc;
756 }
757 
FieldWritten(Thread * thread,mirror::Object * this_object,ArtMethod * method,uint32_t dex_pc,ArtField * field,const JValue & field_value)758 void Trace::FieldWritten(Thread* thread, mirror::Object* this_object,
759                           ArtMethod* method, uint32_t dex_pc, ArtField* field,
760                           const JValue& field_value)
761     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
762   UNUSED(thread, this_object, method, dex_pc, field, field_value);
763   // We're not recorded to listen to this kind of event, so complain.
764   LOG(ERROR) << "Unexpected field write event in tracing " << PrettyMethod(method) << " " << dex_pc;
765 }
766 
MethodEntered(Thread * thread,mirror::Object * this_object ATTRIBUTE_UNUSED,ArtMethod * method,uint32_t dex_pc ATTRIBUTE_UNUSED)767 void Trace::MethodEntered(Thread* thread, mirror::Object* this_object ATTRIBUTE_UNUSED,
768                           ArtMethod* method, uint32_t dex_pc ATTRIBUTE_UNUSED) {
769   uint32_t thread_clock_diff = 0;
770   uint32_t wall_clock_diff = 0;
771   ReadClocks(thread, &thread_clock_diff, &wall_clock_diff);
772   LogMethodTraceEvent(thread, method, instrumentation::Instrumentation::kMethodEntered,
773                       thread_clock_diff, wall_clock_diff);
774 }
775 
MethodExited(Thread * thread,mirror::Object * this_object ATTRIBUTE_UNUSED,ArtMethod * method,uint32_t dex_pc ATTRIBUTE_UNUSED,const JValue & return_value ATTRIBUTE_UNUSED)776 void Trace::MethodExited(Thread* thread, mirror::Object* this_object ATTRIBUTE_UNUSED,
777                          ArtMethod* method, uint32_t dex_pc ATTRIBUTE_UNUSED,
778                          const JValue& return_value ATTRIBUTE_UNUSED) {
779   uint32_t thread_clock_diff = 0;
780   uint32_t wall_clock_diff = 0;
781   ReadClocks(thread, &thread_clock_diff, &wall_clock_diff);
782   LogMethodTraceEvent(thread, method, instrumentation::Instrumentation::kMethodExited,
783                       thread_clock_diff, wall_clock_diff);
784 }
785 
MethodUnwind(Thread * thread,mirror::Object * this_object ATTRIBUTE_UNUSED,ArtMethod * method,uint32_t dex_pc ATTRIBUTE_UNUSED)786 void Trace::MethodUnwind(Thread* thread, mirror::Object* this_object ATTRIBUTE_UNUSED,
787                          ArtMethod* method, uint32_t dex_pc ATTRIBUTE_UNUSED) {
788   uint32_t thread_clock_diff = 0;
789   uint32_t wall_clock_diff = 0;
790   ReadClocks(thread, &thread_clock_diff, &wall_clock_diff);
791   LogMethodTraceEvent(thread, method, instrumentation::Instrumentation::kMethodUnwind,
792                       thread_clock_diff, wall_clock_diff);
793 }
794 
ExceptionCaught(Thread * thread,mirror::Throwable * exception_object)795 void Trace::ExceptionCaught(Thread* thread, mirror::Throwable* exception_object)
796     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
797   UNUSED(thread, exception_object);
798   LOG(ERROR) << "Unexpected exception caught event in tracing";
799 }
800 
BackwardBranch(Thread *,ArtMethod * method,int32_t)801 void Trace::BackwardBranch(Thread* /*thread*/, ArtMethod* method,
802                            int32_t /*dex_pc_offset*/)
803       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
804   LOG(ERROR) << "Unexpected backward branch event in tracing" << PrettyMethod(method);
805 }
806 
ReadClocks(Thread * thread,uint32_t * thread_clock_diff,uint32_t * wall_clock_diff)807 void Trace::ReadClocks(Thread* thread, uint32_t* thread_clock_diff, uint32_t* wall_clock_diff) {
808   if (UseThreadCpuClock()) {
809     uint64_t clock_base = thread->GetTraceClockBase();
810     if (UNLIKELY(clock_base == 0)) {
811       // First event, record the base time in the map.
812       uint64_t time = thread->GetCpuMicroTime();
813       thread->SetTraceClockBase(time);
814     } else {
815       *thread_clock_diff = thread->GetCpuMicroTime() - clock_base;
816     }
817   }
818   if (UseWallClock()) {
819     *wall_clock_diff = MicroTime() - start_time_;
820   }
821 }
822 
RegisterMethod(ArtMethod * method)823 bool Trace::RegisterMethod(ArtMethod* method) {
824   mirror::DexCache* dex_cache = method->GetDexCache();
825   const DexFile* dex_file = dex_cache->GetDexFile();
826   auto* resolved_method = dex_cache->GetResolvedMethod(method->GetDexMethodIndex(), sizeof(void*));
827   if (resolved_method != method) {
828     DCHECK(resolved_method == nullptr);
829     dex_cache->SetResolvedMethod(method->GetDexMethodIndex(), method, sizeof(void*));
830   }
831   if (seen_methods_.find(dex_file) == seen_methods_.end()) {
832     seen_methods_.insert(std::make_pair(dex_file, new DexIndexBitSet()));
833   }
834   DexIndexBitSet* bit_set = seen_methods_.find(dex_file)->second;
835   if (!(*bit_set)[method->GetDexMethodIndex()]) {
836     bit_set->set(method->GetDexMethodIndex());
837     return true;
838   }
839   return false;
840 }
841 
RegisterThread(Thread * thread)842 bool Trace::RegisterThread(Thread* thread) {
843   pid_t tid = thread->GetTid();
844   CHECK_LT(0U, static_cast<uint32_t>(tid));
845   CHECK_LT(static_cast<uint32_t>(tid), 65536U);
846 
847   if (!(*seen_threads_)[tid]) {
848     seen_threads_->set(tid);
849     return true;
850   }
851   return false;
852 }
853 
GetMethodLine(ArtMethod * method)854 std::string Trace::GetMethodLine(ArtMethod* method) {
855   method = method->GetInterfaceMethodIfProxy(sizeof(void*));
856   return StringPrintf("%p\t%s\t%s\t%s\t%s\n",
857                       reinterpret_cast<void*>((EncodeTraceMethod(method) << TraceActionBits)),
858       PrettyDescriptor(method->GetDeclaringClassDescriptor()).c_str(), method->GetName(),
859       method->GetSignature().ToString().c_str(), method->GetDeclaringClassSourceFile());
860 }
861 
WriteToBuf(const uint8_t * src,size_t src_size)862 void Trace::WriteToBuf(const uint8_t* src, size_t src_size) {
863   int32_t old_offset = cur_offset_.LoadRelaxed();
864   int32_t new_offset = old_offset + static_cast<int32_t>(src_size);
865   if (dchecked_integral_cast<size_t>(new_offset) > buffer_size_) {
866     // Flush buffer.
867     if (!trace_file_->WriteFully(buf_.get(), old_offset)) {
868       PLOG(WARNING) << "Failed streaming a tracing event.";
869     }
870 
871     // Check whether the data is too large for the buffer, then write immediately.
872     if (src_size >= buffer_size_) {
873       if (!trace_file_->WriteFully(src, src_size)) {
874         PLOG(WARNING) << "Failed streaming a tracing event.";
875       }
876       cur_offset_.StoreRelease(0);  // Buffer is empty now.
877       return;
878     }
879 
880     old_offset = 0;
881     new_offset = static_cast<int32_t>(src_size);
882   }
883   cur_offset_.StoreRelease(new_offset);
884   // Fill in data.
885   memcpy(buf_.get() + old_offset, src, src_size);
886 }
887 
LogMethodTraceEvent(Thread * thread,ArtMethod * method,instrumentation::Instrumentation::InstrumentationEvent event,uint32_t thread_clock_diff,uint32_t wall_clock_diff)888 void Trace::LogMethodTraceEvent(Thread* thread, ArtMethod* method,
889                                 instrumentation::Instrumentation::InstrumentationEvent event,
890                                 uint32_t thread_clock_diff, uint32_t wall_clock_diff) {
891   // Advance cur_offset_ atomically.
892   int32_t new_offset;
893   int32_t old_offset = 0;
894 
895   // We do a busy loop here trying to acquire the next offset.
896   if (trace_output_mode_ != TraceOutputMode::kStreaming) {
897     do {
898       old_offset = cur_offset_.LoadRelaxed();
899       new_offset = old_offset + GetRecordSize(clock_source_);
900       if (static_cast<size_t>(new_offset) > buffer_size_) {
901         overflow_ = true;
902         return;
903       }
904     } while (!cur_offset_.CompareExchangeWeakSequentiallyConsistent(old_offset, new_offset));
905   }
906 
907   TraceAction action = kTraceMethodEnter;
908   switch (event) {
909     case instrumentation::Instrumentation::kMethodEntered:
910       action = kTraceMethodEnter;
911       break;
912     case instrumentation::Instrumentation::kMethodExited:
913       action = kTraceMethodExit;
914       break;
915     case instrumentation::Instrumentation::kMethodUnwind:
916       action = kTraceUnroll;
917       break;
918     default:
919       UNIMPLEMENTED(FATAL) << "Unexpected event: " << event;
920   }
921 
922   uint32_t method_value = EncodeTraceMethodAndAction(method, action);
923 
924   // Write data
925   uint8_t* ptr;
926   static constexpr size_t kPacketSize = 14U;  // The maximum size of data in a packet.
927   uint8_t stack_buf[kPacketSize];             // Space to store a packet when in streaming mode.
928   if (trace_output_mode_ == TraceOutputMode::kStreaming) {
929     ptr = stack_buf;
930   } else {
931     ptr = buf_.get() + old_offset;
932   }
933 
934   Append2LE(ptr, thread->GetTid());
935   Append4LE(ptr + 2, method_value);
936   ptr += 6;
937 
938   if (UseThreadCpuClock()) {
939     Append4LE(ptr, thread_clock_diff);
940     ptr += 4;
941   }
942   if (UseWallClock()) {
943     Append4LE(ptr, wall_clock_diff);
944   }
945   static_assert(kPacketSize == 2 + 4 + 4 + 4, "Packet size incorrect.");
946 
947   if (trace_output_mode_ == TraceOutputMode::kStreaming) {
948     MutexLock mu(Thread::Current(), *streaming_lock_);  // To serialize writing.
949     if (RegisterMethod(method)) {
950       // Write a special block with the name.
951       std::string method_line(GetMethodLine(method));
952       uint8_t buf2[5];
953       Append2LE(buf2, 0);
954       buf2[2] = kOpNewMethod;
955       Append2LE(buf2 + 3, static_cast<uint16_t>(method_line.length()));
956       WriteToBuf(buf2, sizeof(buf2));
957       WriteToBuf(reinterpret_cast<const uint8_t*>(method_line.c_str()), method_line.length());
958     }
959     if (RegisterThread(thread)) {
960       // It might be better to postpone this. Threads might not have received names...
961       std::string thread_name;
962       thread->GetThreadName(thread_name);
963       uint8_t buf2[7];
964       Append2LE(buf2, 0);
965       buf2[2] = kOpNewThread;
966       Append2LE(buf2 + 3, static_cast<uint16_t>(thread->GetTid()));
967       Append2LE(buf2 + 5, static_cast<uint16_t>(thread_name.length()));
968       WriteToBuf(buf2, sizeof(buf2));
969       WriteToBuf(reinterpret_cast<const uint8_t*>(thread_name.c_str()), thread_name.length());
970     }
971     WriteToBuf(stack_buf, sizeof(stack_buf));
972   }
973 }
974 
GetVisitedMethods(size_t buf_size,std::set<ArtMethod * > * visited_methods)975 void Trace::GetVisitedMethods(size_t buf_size,
976                               std::set<ArtMethod*>* visited_methods) {
977   uint8_t* ptr = buf_.get() + kTraceHeaderLength;
978   uint8_t* end = buf_.get() + buf_size;
979 
980   while (ptr < end) {
981     uint32_t tmid = ReadBytes(ptr + 2, sizeof(tmid));
982     ArtMethod* method = DecodeTraceMethod(tmid);
983     visited_methods->insert(method);
984     ptr += GetRecordSize(clock_source_);
985   }
986 }
987 
DumpMethodList(std::ostream & os,const std::set<ArtMethod * > & visited_methods)988 void Trace::DumpMethodList(std::ostream& os, const std::set<ArtMethod*>& visited_methods) {
989   for (const auto& method : visited_methods) {
990     os << GetMethodLine(method);
991   }
992 }
993 
DumpThread(Thread * t,void * arg)994 static void DumpThread(Thread* t, void* arg) {
995   std::ostream& os = *reinterpret_cast<std::ostream*>(arg);
996   std::string name;
997   t->GetThreadName(name);
998   os << t->GetTid() << "\t" << name << "\n";
999 }
1000 
DumpThreadList(std::ostream & os)1001 void Trace::DumpThreadList(std::ostream& os) {
1002   Thread* self = Thread::Current();
1003   for (auto it : exited_threads_) {
1004     os << it.first << "\t" << it.second << "\n";
1005   }
1006   Locks::thread_list_lock_->AssertNotHeld(self);
1007   MutexLock mu(self, *Locks::thread_list_lock_);
1008   Runtime::Current()->GetThreadList()->ForEach(DumpThread, &os);
1009 }
1010 
StoreExitingThreadInfo(Thread * thread)1011 void Trace::StoreExitingThreadInfo(Thread* thread) {
1012   MutexLock mu(thread, *Locks::trace_lock_);
1013   if (the_trace_ != nullptr) {
1014     std::string name;
1015     thread->GetThreadName(name);
1016     // The same thread/tid may be used multiple times. As SafeMap::Put does not allow to override
1017     // a previous mapping, use SafeMap::Overwrite.
1018     the_trace_->exited_threads_.Overwrite(thread->GetTid(), name);
1019   }
1020 }
1021 
GetOutputMode()1022 Trace::TraceOutputMode Trace::GetOutputMode() {
1023   MutexLock mu(Thread::Current(), *Locks::trace_lock_);
1024   CHECK(the_trace_ != nullptr) << "Trace output mode requested, but no trace currently running";
1025   return the_trace_->trace_output_mode_;
1026 }
1027 
GetMode()1028 Trace::TraceMode Trace::GetMode() {
1029   MutexLock mu(Thread::Current(), *Locks::trace_lock_);
1030   CHECK(the_trace_ != nullptr) << "Trace mode requested, but no trace currently running";
1031   return the_trace_->trace_mode_;
1032 }
1033 
GetBufferSize()1034 size_t Trace::GetBufferSize() {
1035   MutexLock mu(Thread::Current(), *Locks::trace_lock_);
1036   CHECK(the_trace_ != nullptr) << "Trace mode requested, but no trace currently running";
1037   return the_trace_->buffer_size_;
1038 }
1039 
1040 }  // namespace art
1041