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1 // Copyright 2017 The Chromium 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 #include "base/profiler/native_stack_sampler.h" | |
6 | |
7 #include <dlfcn.h> | |
8 #include <libkern/OSByteOrder.h> | |
9 #include <libunwind.h> | |
10 #include <mach-o/swap.h> | |
11 #include <mach/kern_return.h> | |
12 #include <mach/mach.h> | |
13 #include <mach/thread_act.h> | |
14 #include <pthread.h> | |
15 #include <sys/resource.h> | |
16 #include <sys/syslimits.h> | |
17 | |
18 #include <algorithm> | |
19 #include <map> | |
20 #include <memory> | |
21 | |
22 #include "base/logging.h" | |
23 #include "base/mac/mach_logging.h" | |
24 #include "base/macros.h" | |
25 #include "base/memory/ptr_util.h" | |
26 #include "base/strings/string_number_conversions.h" | |
27 | |
28 namespace base { | |
29 | |
30 namespace { | |
31 | |
32 // Miscellaneous -------------------------------------------------------------- | |
33 | |
34 size_t StackCopyBufferSize() { | |
35 static size_t stack_size = 0; | |
36 if (stack_size) | |
37 return stack_size; | |
38 | |
39 // In platform_thread_mac's GetDefaultThreadStackSize(), RLIMIT_STACK is used | |
40 // for all stacks, not just the main thread's, so it is good for use here. | |
41 struct rlimit stack_rlimit; | |
42 if (getrlimit(RLIMIT_STACK, &stack_rlimit) == 0 && | |
43 stack_rlimit.rlim_cur != RLIM_INFINITY) { | |
44 stack_size = stack_rlimit.rlim_cur; | |
45 return stack_size; | |
46 } | |
47 | |
48 // If getrlimit somehow fails, return the default macOS main thread stack size | |
49 // of 8 MB (DFLSSIZ in <i386/vmparam.h>) with extra wiggle room. | |
50 return 12 * 1024 * 1024; | |
51 } | |
52 | |
53 // Stack walking -------------------------------------------------------------- | |
54 | |
55 // Fills |state| with |target_thread|'s context. | |
56 // | |
57 // Note that this is called while a thread is suspended. Make very very sure | |
58 // that no shared resources (e.g. memory allocators) are used for the duration | |
59 // of this function. | |
60 bool GetThreadState(thread_act_t target_thread, x86_thread_state64_t* state) { | |
61 mach_msg_type_number_t count = | |
62 static_cast<mach_msg_type_number_t>(x86_THREAD_STATE64_COUNT); | |
63 return thread_get_state(target_thread, x86_THREAD_STATE64, | |
64 reinterpret_cast<thread_state_t>(state), | |
65 &count) == KERN_SUCCESS; | |
66 } | |
67 | |
68 // If the value at |pointer| points to the original stack, rewrites it to point | |
69 // to the corresponding location in the copied stack. | |
70 // | |
71 // Note that this is called while a thread is suspended. Make very very sure | |
72 // that no shared resources (e.g. memory allocators) are used for the duration | |
73 // of this function. | |
74 uintptr_t RewritePointerIfInOriginalStack( | |
75 const uintptr_t* original_stack_bottom, | |
76 const uintptr_t* original_stack_top, | |
77 uintptr_t* stack_copy_bottom, | |
78 uintptr_t pointer) { | |
79 uintptr_t original_stack_bottom_int = | |
80 reinterpret_cast<uintptr_t>(original_stack_bottom); | |
81 uintptr_t original_stack_top_int = | |
82 reinterpret_cast<uintptr_t>(original_stack_top); | |
83 uintptr_t stack_copy_bottom_int = | |
84 reinterpret_cast<uintptr_t>(stack_copy_bottom); | |
85 | |
86 if ((pointer < original_stack_bottom_int) || | |
87 (pointer >= original_stack_top_int)) { | |
88 return pointer; | |
89 } | |
90 | |
91 return stack_copy_bottom_int + (pointer - original_stack_bottom_int); | |
92 } | |
93 | |
94 // Copies the stack to a buffer while rewriting possible pointers to locations | |
95 // within the stack to point to the corresponding locations in the copy. This is | |
96 // necessary to handle stack frames with dynamic stack allocation, where a | |
97 // pointer to the beginning of the dynamic allocation area is stored on the | |
98 // stack and/or in a non-volatile register. | |
99 // | |
100 // Eager rewriting of anything that looks like a pointer to the stack, as done | |
101 // in this function, does not adversely affect the stack unwinding. The only | |
102 // other values on the stack the unwinding depends on are return addresses, | |
103 // which should not point within the stack memory. The rewriting is guaranteed | |
104 // to catch all pointers because the stacks are guaranteed by the ABI to be | |
105 // sizeof(void*) aligned. | |
106 // | |
107 // Note that this is called while a thread is suspended. Make very very sure | |
108 // that no shared resources (e.g. memory allocators) are used for the duration | |
109 // of this function. | |
110 void CopyStackAndRewritePointers(uintptr_t* stack_copy_bottom, | |
111 const uintptr_t* original_stack_bottom, | |
112 const uintptr_t* original_stack_top, | |
113 x86_thread_state64_t* thread_state) | |
114 NO_SANITIZE("address") { | |
115 size_t count = original_stack_top - original_stack_bottom; | |
116 for (size_t pos = 0; pos < count; ++pos) { | |
117 stack_copy_bottom[pos] = RewritePointerIfInOriginalStack( | |
118 original_stack_bottom, original_stack_top, stack_copy_bottom, | |
119 original_stack_bottom[pos]); | |
120 } | |
121 | |
122 uint64_t* rewrite_registers[] = {&thread_state->__rbx, &thread_state->__rbp, | |
123 &thread_state->__rsp, &thread_state->__r12, | |
124 &thread_state->__r13, &thread_state->__r14, | |
125 &thread_state->__r15}; | |
126 for (auto* reg : rewrite_registers) { | |
127 *reg = RewritePointerIfInOriginalStack( | |
128 original_stack_bottom, original_stack_top, stack_copy_bottom, *reg); | |
129 } | |
130 } | |
131 | |
132 // Walks the stack represented by |unwind_context|, calling back to the provided | |
133 // lambda for each frame. Returns false if an error occurred, otherwise returns | |
134 // true. | |
135 template <typename StackFrameCallback> | |
136 bool WalkStackFromContext(unw_context_t* unwind_context, | |
137 size_t* frame_count, | |
138 const StackFrameCallback& callback) { | |
139 unw_cursor_t unwind_cursor; | |
140 unw_init_local(&unwind_cursor, unwind_context); | |
141 | |
142 int step_result; | |
143 unw_word_t ip; | |
144 do { | |
145 ++(*frame_count); | |
146 unw_get_reg(&unwind_cursor, UNW_REG_IP, &ip); | |
147 | |
148 callback(static_cast<uintptr_t>(ip)); | |
149 | |
150 step_result = unw_step(&unwind_cursor); | |
151 } while (step_result > 0); | |
152 | |
153 if (step_result != 0) | |
154 return false; | |
155 | |
156 return true; | |
157 } | |
158 | |
159 bool IsIPInValidImage(unw_context_t* unwind_context) { | |
160 unw_cursor_t unwind_cursor; | |
161 unw_init_local(&unwind_cursor, unwind_context); | |
162 unw_proc_info_t proc_info; | |
163 unw_get_proc_info(&unwind_cursor, &proc_info); | |
164 return proc_info.extra != 0; | |
165 } | |
166 | |
167 // Walks the stack represented by |thread_state|, calling back to the provided | |
168 // lambda for each frame. | |
169 template <typename StackFrameCallback> | |
170 void WalkStack(const x86_thread_state64_t& thread_state, | |
171 uintptr_t stack_top, | |
172 const StackFrameCallback& callback) { | |
173 size_t frame_count = 0; | |
174 // This uses libunwind to walk the stack. libunwind is designed to be used for | |
175 // a thread to walk its own stack. This creates two problems. | |
176 | |
177 // Problem 1: There is no official way to create a unw_context other than to | |
178 // create it from the current state of the current thread's stack. To get | |
179 // around this, forge a context. A unw_context is just a copy of the 16 main | |
180 // registers followed by the instruction pointer, nothing more. | |
181 // Coincidentally, the first 17 items of the x86_thread_state64_t type are | |
182 // exactly those registers in exactly the same order, so just bulk copy them | |
183 // over. | |
184 unw_context_t unwind_context; | |
185 memcpy(&unwind_context, &thread_state, sizeof(uintptr_t) * 17); | |
186 bool result = WalkStackFromContext(&unwind_context, &frame_count, callback); | |
187 | |
188 if (!result) | |
189 return; | |
190 | |
191 if (frame_count == 1) { | |
192 // Problem 2: Because libunwind is designed to be triggered by user code on | |
193 // their own thread, if it hits a library that has no unwind info for the | |
194 // function that is being executed, it just stops. This isn't a problem in | |
195 // the normal case, but in this case, it's quite possible that the stack | |
196 // being walked is stopped in a function that bridges to the kernel and thus | |
197 // is missing the unwind info. | |
198 // | |
199 // If so, cheat by scanning the stack and trying again. Only do this if the | |
200 // first time using libunwind fails after one frame. | |
201 bool ip_in_valid_image = false; | |
202 auto& rsp = unwind_context.data[7]; | |
203 auto& rip = unwind_context.data[16]; | |
204 const uintptr_t kMaxScanDepthWords = 16; | |
205 uintptr_t scan_limit = std::min<uintptr_t>( | |
206 stack_top, rsp + kMaxScanDepthWords * sizeof(uintptr_t)); | |
207 do { | |
208 rip = *reinterpret_cast<uintptr_t*>(rsp); // rip = *rsp | |
209 rsp += sizeof(uintptr_t); // rsp++ | |
210 if (rsp % sizeof(uintptr_t)) { | |
211 // The "stack pointer" isn't aligned. Just give up. | |
212 return; | |
213 } | |
214 | |
215 ip_in_valid_image = IsIPInValidImage(&unwind_context); | |
216 } while (!ip_in_valid_image && rsp < scan_limit); | |
217 | |
218 if (ip_in_valid_image) | |
219 WalkStackFromContext(&unwind_context, &frame_count, callback); | |
220 } | |
221 } | |
222 | |
223 // Module identifiers --------------------------------------------------------- | |
224 | |
225 // Returns the hex encoding of a 16-byte ID for the binary loaded at | |
226 // |module_addr|. Returns an empty string if the UUID cannot be found at | |
227 // |module_addr|. | |
228 std::string GetUniqueId(const void* module_addr) { | |
229 const mach_header_64* mach_header = | |
230 reinterpret_cast<const mach_header_64*>(module_addr); | |
231 DCHECK_EQ(MH_MAGIC_64, mach_header->magic); | |
232 | |
233 size_t offset = sizeof(mach_header_64); | |
234 size_t offset_limit = sizeof(mach_header_64) + mach_header->sizeofcmds; | |
235 for (uint32_t i = 0; (i < mach_header->ncmds) && | |
236 (offset + sizeof(load_command) < offset_limit); | |
237 ++i) { | |
238 const load_command* current_cmd = reinterpret_cast<const load_command*>( | |
239 reinterpret_cast<const uint8_t*>(mach_header) + offset); | |
240 | |
241 if (offset + current_cmd->cmdsize > offset_limit) { | |
242 // This command runs off the end of the command list. This is malformed. | |
243 return std::string(); | |
244 } | |
245 | |
246 if (current_cmd->cmd == LC_UUID) { | |
247 if (current_cmd->cmdsize < sizeof(uuid_command)) { | |
248 // This "UUID command" is too small. This is malformed. | |
249 return std::string(); | |
250 } | |
251 | |
252 const uuid_command* uuid_cmd = | |
253 reinterpret_cast<const uuid_command*>(current_cmd); | |
254 static_assert(sizeof(uuid_cmd->uuid) == sizeof(uuid_t), | |
255 "UUID field of UUID command should be 16 bytes."); | |
256 return HexEncode(&uuid_cmd->uuid, sizeof(uuid_cmd->uuid)); | |
257 } | |
258 offset += current_cmd->cmdsize; | |
259 } | |
260 return std::string(); | |
261 } | |
262 | |
263 // Gets the index for the Module containing |instruction_pointer| in | |
264 // |modules|, adding it if it's not already present. Returns | |
265 // StackSamplingProfiler::Frame::kUnknownModuleIndex if no Module can be | |
266 // determined for |module|. | |
267 size_t GetModuleIndex(const uintptr_t instruction_pointer, | |
268 std::vector<StackSamplingProfiler::Module>* modules, | |
269 std::map<const void*, size_t>* profile_module_index) { | |
270 Dl_info inf; | |
271 if (!dladdr(reinterpret_cast<const void*>(instruction_pointer), &inf)) | |
272 return StackSamplingProfiler::Frame::kUnknownModuleIndex; | |
273 | |
274 auto module_index = profile_module_index->find(inf.dli_fbase); | |
275 if (module_index == profile_module_index->end()) { | |
276 StackSamplingProfiler::Module module( | |
277 reinterpret_cast<uintptr_t>(inf.dli_fbase), GetUniqueId(inf.dli_fbase), | |
278 base::FilePath(inf.dli_fname)); | |
279 modules->push_back(module); | |
280 module_index = | |
281 profile_module_index | |
282 ->insert(std::make_pair(inf.dli_fbase, modules->size() - 1)) | |
283 .first; | |
284 } | |
285 return module_index->second; | |
286 } | |
287 | |
288 // ScopedSuspendThread -------------------------------------------------------- | |
289 | |
290 // Suspends a thread for the lifetime of the object. | |
291 class ScopedSuspendThread { | |
292 public: | |
293 explicit ScopedSuspendThread(mach_port_t thread_port) | |
294 : thread_port_(thread_suspend(thread_port) == KERN_SUCCESS | |
295 ? thread_port | |
296 : MACH_PORT_NULL) {} | |
297 | |
298 ~ScopedSuspendThread() { | |
299 if (!was_successful()) | |
300 return; | |
301 | |
302 kern_return_t kr = thread_resume(thread_port_); | |
303 MACH_CHECK(kr == KERN_SUCCESS, kr) << "thread_resume"; | |
304 } | |
305 | |
306 bool was_successful() const { return thread_port_ != MACH_PORT_NULL; } | |
307 | |
308 private: | |
309 mach_port_t thread_port_; | |
310 | |
311 DISALLOW_COPY_AND_ASSIGN(ScopedSuspendThread); | |
312 }; | |
313 | |
314 // NativeStackSamplerMac ------------------------------------------------------ | |
315 | |
316 class NativeStackSamplerMac : public NativeStackSampler { | |
317 public: | |
318 NativeStackSamplerMac(mach_port_t thread_port, | |
319 AnnotateCallback annotator, | |
320 NativeStackSamplerTestDelegate* test_delegate); | |
321 ~NativeStackSamplerMac() override; | |
322 | |
323 // StackSamplingProfiler::NativeStackSampler: | |
324 void ProfileRecordingStarting( | |
325 std::vector<StackSamplingProfiler::Module>* modules) override; | |
326 void RecordStackSample(StackSamplingProfiler::Sample* sample) override; | |
327 void ProfileRecordingStopped() override; | |
328 | |
329 private: | |
330 // Suspends the thread with |thread_port_|, copies its stack and resumes the | |
331 // thread, then records the stack frames and associated modules into |sample|. | |
332 void SuspendThreadAndRecordStack(StackSamplingProfiler::Sample* sample); | |
333 | |
334 // Weak reference: Mach port for thread being profiled. | |
335 mach_port_t thread_port_; | |
336 | |
337 const AnnotateCallback annotator_; | |
338 | |
339 NativeStackSamplerTestDelegate* const test_delegate_; | |
340 | |
341 // The stack base address corresponding to |thread_handle_|. | |
342 const void* const thread_stack_base_address_; | |
343 | |
344 // The size of the |stack_copy_buffer_|. | |
345 const size_t stack_copy_buffer_size_; | |
346 | |
347 // Buffer to use for copies of the stack. We use the same buffer for all the | |
348 // samples to avoid the overhead of multiple allocations and frees. | |
349 const std::unique_ptr<unsigned char[]> stack_copy_buffer_; | |
350 | |
351 // Weak. Points to the modules associated with the profile being recorded | |
352 // between ProfileRecordingStarting() and ProfileRecordingStopped(). | |
353 std::vector<StackSamplingProfiler::Module>* current_modules_ = nullptr; | |
354 | |
355 // Maps a module's base address to the corresponding Module's index within | |
356 // current_modules_. | |
357 std::map<const void*, size_t> profile_module_index_; | |
358 | |
359 DISALLOW_COPY_AND_ASSIGN(NativeStackSamplerMac); | |
360 }; | |
361 | |
362 NativeStackSamplerMac::NativeStackSamplerMac( | |
363 mach_port_t thread_port, | |
364 AnnotateCallback annotator, | |
365 NativeStackSamplerTestDelegate* test_delegate) | |
366 : thread_port_(thread_port), | |
367 annotator_(annotator), | |
368 test_delegate_(test_delegate), | |
369 thread_stack_base_address_( | |
370 pthread_get_stackaddr_np(pthread_from_mach_thread_np(thread_port))), | |
371 stack_copy_buffer_size_(StackCopyBufferSize()), | |
372 stack_copy_buffer_(new unsigned char[stack_copy_buffer_size_]) { | |
373 DCHECK(annotator_); | |
374 | |
375 // This class suspends threads, and those threads might be suspended in dyld. | |
376 // Therefore, for all the system functions that might be linked in dynamically | |
377 // that are used while threads are suspended, make calls to them to make sure | |
378 // that they are linked up. | |
379 x86_thread_state64_t thread_state; | |
380 GetThreadState(thread_port_, &thread_state); | |
381 } | |
382 | |
383 NativeStackSamplerMac::~NativeStackSamplerMac() {} | |
384 | |
385 void NativeStackSamplerMac::ProfileRecordingStarting( | |
386 std::vector<StackSamplingProfiler::Module>* modules) { | |
387 current_modules_ = modules; | |
388 profile_module_index_.clear(); | |
389 } | |
390 | |
391 void NativeStackSamplerMac::RecordStackSample( | |
392 StackSamplingProfiler::Sample* sample) { | |
393 DCHECK(current_modules_); | |
394 | |
395 SuspendThreadAndRecordStack(sample); | |
396 } | |
397 | |
398 void NativeStackSamplerMac::ProfileRecordingStopped() { | |
399 current_modules_ = nullptr; | |
400 } | |
401 | |
402 void NativeStackSamplerMac::SuspendThreadAndRecordStack( | |
403 StackSamplingProfiler::Sample* sample) { | |
404 x86_thread_state64_t thread_state; | |
405 | |
406 // Copy the stack. | |
407 | |
408 uintptr_t new_stack_top = 0; | |
409 { | |
410 // IMPORTANT NOTE: Do not do ANYTHING in this in this scope that might | |
411 // allocate memory, including indirectly via use of DCHECK/CHECK or other | |
412 // logging statements. Otherwise this code can deadlock on heap locks in the | |
413 // default heap acquired by the target thread before it was suspended. | |
414 ScopedSuspendThread suspend_thread(thread_port_); | |
415 if (!suspend_thread.was_successful()) | |
416 return; | |
417 | |
418 if (!GetThreadState(thread_port_, &thread_state)) | |
419 return; | |
420 uintptr_t stack_top = | |
421 reinterpret_cast<uintptr_t>(thread_stack_base_address_); | |
422 uintptr_t stack_bottom = thread_state.__rsp; | |
423 if (stack_bottom >= stack_top) | |
424 return; | |
425 uintptr_t stack_size = stack_top - stack_bottom; | |
426 | |
427 if (stack_size > stack_copy_buffer_size_) | |
428 return; | |
429 | |
430 (*annotator_)(sample); | |
431 | |
432 CopyStackAndRewritePointers( | |
433 reinterpret_cast<uintptr_t*>(stack_copy_buffer_.get()), | |
434 reinterpret_cast<uintptr_t*>(stack_bottom), | |
435 reinterpret_cast<uintptr_t*>(stack_top), &thread_state); | |
436 | |
437 new_stack_top = | |
438 reinterpret_cast<uintptr_t>(stack_copy_buffer_.get()) + stack_size; | |
439 } // ScopedSuspendThread | |
440 | |
441 if (test_delegate_) | |
442 test_delegate_->OnPreStackWalk(); | |
443 | |
444 // Walk the stack and record it. | |
445 | |
446 // Reserve enough memory for most stacks, to avoid repeated allocations. | |
447 // Approximately 99.9% of recorded stacks are 128 frames or fewer. | |
448 sample->frames.reserve(128); | |
449 | |
450 auto* current_modules = current_modules_; | |
451 auto* profile_module_index = &profile_module_index_; | |
452 WalkStack( | |
453 thread_state, new_stack_top, | |
454 [sample, current_modules, profile_module_index](uintptr_t frame_ip) { | |
455 sample->frames.push_back(StackSamplingProfiler::Frame( | |
456 frame_ip, | |
457 GetModuleIndex(frame_ip, current_modules, profile_module_index))); | |
458 }); | |
459 } | |
460 | |
461 } // namespace | |
462 | |
463 std::unique_ptr<NativeStackSampler> NativeStackSampler::Create( | |
464 PlatformThreadId thread_id, | |
465 AnnotateCallback annotator, | |
466 NativeStackSamplerTestDelegate* test_delegate) { | |
467 return base::MakeUnique<NativeStackSamplerMac>(thread_id, annotator, | |
468 test_delegate); | |
469 } | |
470 | |
471 } // namespace base | |
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