1 /*
2  * Copyright (C) 2018 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 #include "backtrace_helper.h"
18 
19 #if defined(__linux__)
20 
21 #include <backtrace/Backtrace.h>
22 #include <backtrace/BacktraceMap.h>
23 
24 #include <unistd.h>
25 #include <sys/types.h>
26 
27 #include "thread-inl.h"
28 
29 #else
30 
31 // For UNUSED
32 #include "base/macros.h"
33 
34 #endif
35 
36 namespace art {
37 
38 // We only really support libbacktrace on linux which is unfortunate but since this is only for
39 // gcstress this isn't a huge deal.
40 #if defined(__linux__)
41 
42 static const char* kBacktraceCollectorTlsKey = "BacktraceCollectorTlsKey";
43 
44 struct BacktraceMapHolder : public TLSData {
BacktraceMapHolderart::BacktraceMapHolder45   BacktraceMapHolder() : map_(BacktraceMap::Create(getpid())) {}
46 
47   std::unique_ptr<BacktraceMap> map_;
48 };
49 
GetMap(Thread * self)50 static BacktraceMap* GetMap(Thread* self) {
51   BacktraceMapHolder* map_holder =
52       reinterpret_cast<BacktraceMapHolder*>(self->GetCustomTLS(kBacktraceCollectorTlsKey));
53   if (map_holder == nullptr) {
54     map_holder = new BacktraceMapHolder;
55     // We don't care about the function names. Turning this off makes everything significantly
56     // faster.
57     map_holder->map_->SetResolveNames(false);
58     // Only created and queried on Thread::Current so no sync needed.
59     self->SetCustomTLS(kBacktraceCollectorTlsKey, map_holder);
60   }
61 
62   return map_holder->map_.get();
63 }
64 
Collect()65 void BacktraceCollector::Collect() {
66   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(BACKTRACE_CURRENT_PROCESS,
67                                                          BACKTRACE_CURRENT_THREAD,
68                                                          GetMap(Thread::Current())));
69   backtrace->SetSkipFrames(true);
70   if (!backtrace->Unwind(skip_count_, nullptr)) {
71     return;
72   }
73   for (Backtrace::const_iterator it = backtrace->begin();
74        max_depth_ > num_frames_ && it != backtrace->end();
75        ++it) {
76     out_frames_[num_frames_++] = static_cast<uintptr_t>(it->pc);
77   }
78 }
79 
80 #else
81 
82 #pragma clang diagnostic push
83 #pragma clang diagnostic warning "-W#warnings"
84 #warning "Backtrace collector is not implemented. GCStress cannot be used."
85 #pragma clang diagnostic pop
86 
87 // We only have an implementation for linux. On other plaforms just return nothing. This is not
88 // really correct but we only use this for hashing and gcstress so it's not too big a deal.
89 void BacktraceCollector::Collect() {
90   UNUSED(skip_count_);
91   UNUSED(out_frames_);
92   UNUSED(max_depth_);
93   num_frames_ = 0;
94 }
95 
96 #endif
97 
98 }  // namespace art
99