1 /* 2 * Copyright (C) 2017 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 #ifndef ART_RUNTIME_BACKTRACE_HELPER_H_ 18 #define ART_RUNTIME_BACKTRACE_HELPER_H_ 19 20 #include <unwind.h> 21 22 namespace art { 23 24 // Based on debug malloc logic from libc/bionic/debug_stacktrace.cpp. 25 class BacktraceCollector { 26 public: BacktraceCollector(uintptr_t * out_frames,size_t max_depth,size_t skip_count)27 BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count) 28 : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {} 29 NumFrames()30 size_t NumFrames() const { 31 return num_frames_; 32 } 33 34 // Collect the backtrace, do not call more than once. Collect()35 void Collect() { 36 _Unwind_Backtrace(&Callback, this); 37 } 38 39 private: Callback(_Unwind_Context * context,void * arg)40 static _Unwind_Reason_Code Callback(_Unwind_Context* context, void* arg) { 41 auto* const state = reinterpret_cast<BacktraceCollector*>(arg); 42 const uintptr_t ip = _Unwind_GetIP(context); 43 // The first stack frame is get_backtrace itself. Skip it. 44 if (ip != 0 && state->skip_count_ > 0) { 45 --state->skip_count_; 46 return _URC_NO_REASON; 47 } 48 // ip may be off for ARM but it shouldn't matter since we only use it for hashing. 49 state->out_frames_[state->num_frames_] = ip; 50 state->num_frames_++; 51 return state->num_frames_ >= state->max_depth_ ? _URC_END_OF_STACK : _URC_NO_REASON; 52 } 53 54 uintptr_t* const out_frames_ = nullptr; 55 size_t num_frames_ = 0u; 56 const size_t max_depth_ = 0u; 57 size_t skip_count_ = 0u; 58 }; 59 60 // A bounded sized backtrace. 61 template <size_t kMaxFrames> 62 class FixedSizeBacktrace { 63 public: Collect(size_t skip_count)64 void Collect(size_t skip_count) { 65 BacktraceCollector collector(frames_, kMaxFrames, skip_count); 66 collector.Collect(); 67 num_frames_ = collector.NumFrames(); 68 } 69 Hash()70 uint64_t Hash() const { 71 uint64_t hash = 9314237; 72 for (size_t i = 0; i < num_frames_; ++i) { 73 hash = hash * 2654435761 + frames_[i]; 74 hash += (hash >> 13) ^ (hash << 6); 75 } 76 return hash; 77 } 78 79 private: 80 uintptr_t frames_[kMaxFrames]; 81 size_t num_frames_; 82 }; 83 84 } // namespace art 85 86 #endif // ART_RUNTIME_BACKTRACE_HELPER_H_ 87