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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 const char* LibSystemKernelName() { | |
160 static char path[PATH_MAX]; | |
161 static char* name = nullptr; | |
162 if (name) | |
163 return name; | |
164 | |
165 Dl_info info; | |
166 dladdr(reinterpret_cast<void*>(_exit), &info); | |
167 strncpy(path, info.dli_fname, PATH_MAX); | |
Alexei Svitkine (slow)
2017/05/04 21:01:30
Drive-by nit: prefer strlcpy over strncpy as strnc
Avi (use Gerrit)
2017/05/12 15:59:46
Addressing in https://codereview.chromium.org/2882
| |
168 name = path; | |
169 DCHECK_EQ(std::string(name), | |
170 std::string("/usr/lib/system/libsystem_kernel.dylib")); | |
171 return name; | |
172 } | |
173 | |
174 // Walks the stack represented by |thread_state|, calling back to the provided | |
175 // lambda for each frame. | |
176 template <typename StackFrameCallback> | |
177 void WalkStack(const x86_thread_state64_t& thread_state, | |
178 uintptr_t stack_top, | |
179 const StackFrameCallback& callback) { | |
180 size_t frame_count = 0; | |
181 // This uses libunwind to walk the stack. libunwind is designed to be used for | |
182 // a thread to walk its own stack. This creates two problems. | |
183 | |
184 // Problem 1: There is no official way to create a unw_context other than to | |
185 // create it from the current state of the current thread's stack. To get | |
186 // around this, forge a context. A unw_context is just a copy of the 16 main | |
187 // registers followed by the instruction pointer, nothing more. | |
188 // Coincidentally, the first 17 items of the x86_thread_state64_t type are | |
189 // exactly those registers in exactly the same order, so just bulk copy them | |
190 // over. | |
191 unw_context_t unwind_context; | |
192 memcpy(&unwind_context, &thread_state, sizeof(uintptr_t) * 17); | |
193 bool result = WalkStackFromContext(&unwind_context, &frame_count, callback); | |
194 | |
195 if (!result) | |
196 return; | |
197 | |
198 if (frame_count == 1) { | |
199 // Problem 2: Because libunwind is designed to be triggered by user code on | |
200 // their own thread, if it hits a library that has no unwind info for the | |
201 // function that is being executed, it just stops. This isn't a problem in | |
202 // the normal case, but in this case, it's quite possible that the stack | |
203 // being walked is stopped in a function that bridges to the kernel and thus | |
204 // is missing the unwind info. | |
205 | |
206 // For now, just unwind the single case where the thread is stopped in a | |
207 // function in libsystem_kernel. | |
208 uint64_t& rsp = unwind_context.data[7]; | |
209 uint64_t& rip = unwind_context.data[16]; | |
210 Dl_info info; | |
211 if (dladdr(reinterpret_cast<void*>(rip), &info) != 0 && | |
212 strcmp(info.dli_fname, LibSystemKernelName()) == 0) { | |
213 rip = *reinterpret_cast<uint64_t*>(rsp); | |
214 rsp += 8; | |
215 WalkStackFromContext(&unwind_context, &frame_count, callback); | |
216 } | |
217 } | |
218 } | |
219 | |
220 // Module identifiers --------------------------------------------------------- | |
221 | |
222 // Returns the hex encoding of a 16-byte ID for the binary loaded at | |
223 // |module_addr|. Returns an empty string if the UUID cannot be found at | |
224 // |module_addr|. | |
225 std::string GetUniqueId(const void* module_addr) { | |
226 const mach_header_64* mach_header = | |
227 reinterpret_cast<const mach_header_64*>(module_addr); | |
228 DCHECK_EQ(MH_MAGIC_64, mach_header->magic); | |
229 | |
230 size_t offset = sizeof(mach_header_64); | |
231 size_t offset_limit = sizeof(mach_header_64) + mach_header->sizeofcmds; | |
232 for (uint32_t i = 0; (i < mach_header->ncmds) && | |
233 (offset + sizeof(load_command) < offset_limit); | |
234 ++i) { | |
235 const load_command* current_cmd = reinterpret_cast<const load_command*>( | |
236 reinterpret_cast<const uint8_t*>(mach_header) + offset); | |
237 | |
238 if (offset + current_cmd->cmdsize > offset_limit) { | |
239 // This command runs off the end of the command list. This is malformed. | |
240 return std::string(); | |
241 } | |
242 | |
243 if (current_cmd->cmd == LC_UUID) { | |
244 if (current_cmd->cmdsize < sizeof(uuid_command)) { | |
245 // This "UUID command" is too small. This is malformed. | |
246 return std::string(); | |
247 } | |
248 | |
249 const uuid_command* uuid_cmd = | |
250 reinterpret_cast<const uuid_command*>(current_cmd); | |
251 static_assert(sizeof(uuid_cmd->uuid) == sizeof(uuid_t), | |
252 "UUID field of UUID command should be 16 bytes."); | |
253 return HexEncode(&uuid_cmd->uuid, sizeof(uuid_cmd->uuid)); | |
254 } | |
255 offset += current_cmd->cmdsize; | |
256 } | |
257 return std::string(); | |
258 } | |
259 | |
260 // Gets the index for the Module containing |instruction_pointer| in | |
261 // |modules|, adding it if it's not already present. Returns | |
262 // StackSamplingProfiler::Frame::kUnknownModuleIndex if no Module can be | |
263 // determined for |module|. | |
264 size_t GetModuleIndex(const uintptr_t instruction_pointer, | |
265 std::vector<StackSamplingProfiler::Module>* modules, | |
266 std::map<const void*, size_t>* profile_module_index) { | |
267 Dl_info inf; | |
268 if (!dladdr(reinterpret_cast<const void*>(instruction_pointer), &inf)) | |
269 return StackSamplingProfiler::Frame::kUnknownModuleIndex; | |
270 | |
271 auto module_index = profile_module_index->find(inf.dli_fbase); | |
272 if (module_index == profile_module_index->end()) { | |
273 StackSamplingProfiler::Module module( | |
274 reinterpret_cast<uintptr_t>(inf.dli_fbase), GetUniqueId(inf.dli_fbase), | |
275 base::FilePath(inf.dli_fname)); | |
276 modules->push_back(module); | |
277 module_index = | |
278 profile_module_index | |
279 ->insert(std::make_pair(inf.dli_fbase, modules->size() - 1)) | |
280 .first; | |
281 } | |
282 return module_index->second; | |
283 } | |
284 | |
285 // ScopedSuspendThread -------------------------------------------------------- | |
286 | |
287 // Suspends a thread for the lifetime of the object. | |
288 class ScopedSuspendThread { | |
289 public: | |
290 explicit ScopedSuspendThread(mach_port_t thread_port) | |
291 : thread_port_(thread_suspend(thread_port) == KERN_SUCCESS | |
292 ? thread_port | |
293 : MACH_PORT_NULL) {} | |
294 | |
295 ~ScopedSuspendThread() { | |
296 if (!was_successful()) | |
297 return; | |
298 | |
299 kern_return_t kr = thread_resume(thread_port_); | |
300 MACH_CHECK(kr == KERN_SUCCESS, kr) << "thread_resume"; | |
301 } | |
302 | |
303 bool was_successful() const { return thread_port_ != MACH_PORT_NULL; } | |
304 | |
305 private: | |
306 mach_port_t thread_port_; | |
307 | |
308 DISALLOW_COPY_AND_ASSIGN(ScopedSuspendThread); | |
309 }; | |
310 | |
311 // NativeStackSamplerMac ------------------------------------------------------ | |
312 | |
313 class NativeStackSamplerMac : public NativeStackSampler { | |
314 public: | |
315 NativeStackSamplerMac(mach_port_t thread_port, | |
316 AnnotateCallback annotator, | |
317 NativeStackSamplerTestDelegate* test_delegate); | |
318 ~NativeStackSamplerMac() override; | |
319 | |
320 // StackSamplingProfiler::NativeStackSampler: | |
321 void ProfileRecordingStarting( | |
322 std::vector<StackSamplingProfiler::Module>* modules) override; | |
323 void RecordStackSample(StackSamplingProfiler::Sample* sample) override; | |
324 void ProfileRecordingStopped() override; | |
325 | |
326 private: | |
327 // Suspends the thread with |thread_port_|, copies its stack and resumes the | |
328 // thread, then records the stack frames and associated modules into |sample|. | |
329 void SuspendThreadAndRecordStack(StackSamplingProfiler::Sample* sample); | |
330 | |
331 // Weak reference: Mach port for thread being profiled. | |
332 mach_port_t thread_port_; | |
333 | |
334 const AnnotateCallback annotator_; | |
335 | |
336 NativeStackSamplerTestDelegate* const test_delegate_; | |
337 | |
338 // The stack base address corresponding to |thread_handle_|. | |
339 const void* const thread_stack_base_address_; | |
340 | |
341 // The size of the |stack_copy_buffer_|. | |
342 const size_t stack_copy_buffer_size_; | |
343 | |
344 // Buffer to use for copies of the stack. We use the same buffer for all the | |
345 // samples to avoid the overhead of multiple allocations and frees. | |
346 const std::unique_ptr<unsigned char[]> stack_copy_buffer_; | |
347 | |
348 // Weak. Points to the modules associated with the profile being recorded | |
349 // between ProfileRecordingStarting() and ProfileRecordingStopped(). | |
350 std::vector<StackSamplingProfiler::Module>* current_modules_ = nullptr; | |
351 | |
352 // Maps a module's base address to the corresponding Module's index within | |
353 // current_modules_. | |
354 std::map<const void*, size_t> profile_module_index_; | |
355 | |
356 DISALLOW_COPY_AND_ASSIGN(NativeStackSamplerMac); | |
357 }; | |
358 | |
359 NativeStackSamplerMac::NativeStackSamplerMac( | |
360 mach_port_t thread_port, | |
361 AnnotateCallback annotator, | |
362 NativeStackSamplerTestDelegate* test_delegate) | |
363 : thread_port_(thread_port), | |
364 annotator_(annotator), | |
365 test_delegate_(test_delegate), | |
366 thread_stack_base_address_( | |
367 pthread_get_stackaddr_np(pthread_from_mach_thread_np(thread_port))), | |
368 stack_copy_buffer_size_(StackCopyBufferSize()), | |
369 stack_copy_buffer_(new unsigned char[stack_copy_buffer_size_]) { | |
370 DCHECK(annotator_); | |
371 | |
372 // This class suspends threads, and those threads might be suspended in dyld. | |
373 // Therefore, for all the system functions that might be linked in dynamically | |
374 // that are used while threads are suspended, make calls to them to make sure | |
375 // that they are linked up. | |
376 x86_thread_state64_t thread_state; | |
377 GetThreadState(thread_port_, &thread_state); | |
378 } | |
379 | |
380 NativeStackSamplerMac::~NativeStackSamplerMac() {} | |
381 | |
382 void NativeStackSamplerMac::ProfileRecordingStarting( | |
383 std::vector<StackSamplingProfiler::Module>* modules) { | |
384 current_modules_ = modules; | |
385 profile_module_index_.clear(); | |
386 } | |
387 | |
388 void NativeStackSamplerMac::RecordStackSample( | |
389 StackSamplingProfiler::Sample* sample) { | |
390 DCHECK(current_modules_); | |
391 | |
392 SuspendThreadAndRecordStack(sample); | |
393 } | |
394 | |
395 void NativeStackSamplerMac::ProfileRecordingStopped() { | |
396 current_modules_ = nullptr; | |
397 } | |
398 | |
399 void NativeStackSamplerMac::SuspendThreadAndRecordStack( | |
400 StackSamplingProfiler::Sample* sample) { | |
401 x86_thread_state64_t thread_state; | |
402 | |
403 // Copy the stack. | |
404 | |
405 uintptr_t new_stack_top = 0; | |
406 { | |
407 // IMPORTANT NOTE: Do not do ANYTHING in this in this scope that might | |
408 // allocate memory, including indirectly via use of DCHECK/CHECK or other | |
409 // logging statements. Otherwise this code can deadlock on heap locks in the | |
410 // default heap acquired by the target thread before it was suspended. | |
411 ScopedSuspendThread suspend_thread(thread_port_); | |
412 if (!suspend_thread.was_successful()) | |
413 return; | |
414 | |
415 if (!GetThreadState(thread_port_, &thread_state)) | |
416 return; | |
417 uintptr_t stack_top = | |
418 reinterpret_cast<uintptr_t>(thread_stack_base_address_); | |
419 uintptr_t stack_bottom = thread_state.__rsp; | |
420 if (stack_bottom >= stack_top) | |
421 return; | |
422 uintptr_t stack_size = stack_top - stack_bottom; | |
423 | |
424 if (stack_size > stack_copy_buffer_size_) | |
425 return; | |
426 | |
427 (*annotator_)(sample); | |
428 | |
429 CopyStackAndRewritePointers( | |
430 reinterpret_cast<uintptr_t*>(stack_copy_buffer_.get()), | |
431 reinterpret_cast<uintptr_t*>(stack_bottom), | |
432 reinterpret_cast<uintptr_t*>(stack_top), &thread_state); | |
433 | |
434 new_stack_top = | |
435 reinterpret_cast<uintptr_t>(stack_copy_buffer_.get()) + stack_size; | |
436 } // ScopedSuspendThread | |
437 | |
438 if (test_delegate_) | |
439 test_delegate_->OnPreStackWalk(); | |
440 | |
441 // Walk the stack and record it. | |
442 | |
443 // Reserve enough memory for most stacks, to avoid repeated allocations. | |
444 // Approximately 99.9% of recorded stacks are 128 frames or fewer. | |
445 sample->frames.reserve(128); | |
446 | |
447 auto* current_modules = current_modules_; | |
448 auto* profile_module_index = &profile_module_index_; | |
449 WalkStack( | |
450 thread_state, new_stack_top, | |
451 [sample, current_modules, profile_module_index](uintptr_t frame_ip) { | |
452 sample->frames.push_back(StackSamplingProfiler::Frame( | |
453 frame_ip, | |
454 GetModuleIndex(frame_ip, current_modules, profile_module_index))); | |
455 }); | |
456 } | |
457 | |
458 } // namespace | |
459 | |
460 std::unique_ptr<NativeStackSampler> NativeStackSampler::Create( | |
461 PlatformThreadId thread_id, | |
462 AnnotateCallback annotator, | |
463 NativeStackSamplerTestDelegate* test_delegate) { | |
464 return base::MakeUnique<NativeStackSamplerMac>(thread_id, annotator, | |
465 test_delegate); | |
466 } | |
467 | |
468 } // namespace base | |
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