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 unwindstack {
24 class Unwinder;
25 }
26 
27 namespace art {
28 
29 // Using libbacktrace
30 class BacktraceCollector {
31  public:
BacktraceCollector(uintptr_t * out_frames,size_t max_depth,size_t skip_count)32   BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count)
33       : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {}
34 
NumFrames()35   size_t NumFrames() const {
36     return num_frames_;
37   }
38 
39   // Collect the backtrace, do not call more than once.
40   void Collect();
41 
42  private:
43   // Try to collect backtrace. Returns false on failure.
44   // It is used to retry backtrace on temporary failure.
45   bool CollectImpl(unwindstack::Unwinder* unwinder);
46 
47   uintptr_t* const out_frames_ = nullptr;
48   size_t num_frames_ = 0u;
49   const size_t max_depth_ = 0u;
50   size_t skip_count_ = 0u;
51 };
52 
53 // A bounded sized backtrace.
54 template <size_t kMaxFrames>
55 class FixedSizeBacktrace {
56  public:
Collect(size_t skip_count)57   void Collect(size_t skip_count) {
58     BacktraceCollector collector(frames_, kMaxFrames, skip_count);
59     collector.Collect();
60     num_frames_ = collector.NumFrames();
61   }
62 
Hash()63   uint64_t Hash() const {
64     uint64_t hash = 9314237;
65     for (size_t i = 0; i < num_frames_; ++i) {
66       hash = hash * 2654435761 + frames_[i];
67       hash += (hash >> 13) ^ (hash << 6);
68     }
69     return hash;
70   }
71 
72  private:
73   uintptr_t frames_[kMaxFrames];
74   size_t num_frames_;
75 };
76 
77 }  // namespace art
78 
79 #endif  // ART_RUNTIME_BACKTRACE_HELPER_H_
80