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 #include "base/macros.h"
24 
25 namespace unwindstack {
26 class Unwinder;
27 }
28 
29 namespace art HIDDEN {
30 
31 // Using libunwindstack
32 class BacktraceCollector {
33  public:
BacktraceCollector(uintptr_t * out_frames,size_t max_depth,size_t skip_count)34   BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count)
35       : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {}
36 
NumFrames()37   size_t NumFrames() const {
38     return num_frames_;
39   }
40 
41   // Collect the backtrace, do not call more than once.
42   void Collect();
43 
44  private:
45   // Try to collect backtrace. Returns false on failure.
46   // It is used to retry backtrace on temporary failure.
47   bool CollectImpl(unwindstack::Unwinder* unwinder);
48 
49   uintptr_t* const out_frames_ = nullptr;
50   size_t num_frames_ = 0u;
51   const size_t max_depth_ = 0u;
52   size_t skip_count_ = 0u;
53 };
54 
55 // A bounded sized backtrace.
56 template <size_t kMaxFrames>
57 class FixedSizeBacktrace {
58  public:
Collect(size_t skip_count)59   void Collect(size_t skip_count) {
60     BacktraceCollector collector(frames_, kMaxFrames, skip_count);
61     collector.Collect();
62     num_frames_ = collector.NumFrames();
63   }
64 
Hash()65   uint64_t Hash() const {
66     uint64_t hash = 9314237;
67     for (size_t i = 0; i < num_frames_; ++i) {
68       hash = hash * 2654435761 + frames_[i];
69       hash += (hash >> 13) ^ (hash << 6);
70     }
71     return hash;
72   }
73 
74  private:
75   uintptr_t frames_[kMaxFrames];
76   size_t num_frames_;
77 };
78 
79 }  // namespace art
80 
81 #endif  // ART_RUNTIME_BACKTRACE_HELPER_H_
82