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 <stddef.h>
21 #include <stdint.h>
22 
23 namespace art {
24 
25 // Using libbacktrace
26 class BacktraceCollector {
27  public:
BacktraceCollector(uintptr_t * out_frames,size_t max_depth,size_t skip_count)28   BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count)
29       : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {}
30 
NumFrames()31   size_t NumFrames() const {
32     return num_frames_;
33   }
34 
35   // Collect the backtrace, do not call more than once.
36   void Collect();
37 
38  private:
39   // Try to collect backtrace. Returns false on failure.
40   // It is used to retry backtrace on temporary failure.
41   bool CollectImpl();
42 
43   uintptr_t* const out_frames_ = nullptr;
44   size_t num_frames_ = 0u;
45   const size_t max_depth_ = 0u;
46   size_t skip_count_ = 0u;
47 };
48 
49 // A bounded sized backtrace.
50 template <size_t kMaxFrames>
51 class FixedSizeBacktrace {
52  public:
Collect(size_t skip_count)53   void Collect(size_t skip_count) {
54     BacktraceCollector collector(frames_, kMaxFrames, skip_count);
55     collector.Collect();
56     num_frames_ = collector.NumFrames();
57   }
58 
Hash()59   uint64_t Hash() const {
60     uint64_t hash = 9314237;
61     for (size_t i = 0; i < num_frames_; ++i) {
62       hash = hash * 2654435761 + frames_[i];
63       hash += (hash >> 13) ^ (hash << 6);
64     }
65     return hash;
66   }
67 
68  private:
69   uintptr_t frames_[kMaxFrames];
70   size_t num_frames_;
71 };
72 
73 }  // namespace art
74 
75 #endif  // ART_RUNTIME_BACKTRACE_HELPER_H_
76