1 files changed, 86 insertions, 0 deletions
diff --git a/runtime/backtrace_helper.h b/runtime/backtrace_helper.h
new file mode 100644
index 0000000000..ace118c50b
--- /dev/null
+++ b/runtime/backtrace_helper.h
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_BACKTRACE_HELPER_H_
+#define ART_RUNTIME_BACKTRACE_HELPER_H_
+
+#include <unwind.h>
+
+namespace art {
+
+// Based on debug malloc logic from libc/bionic/debug_stacktrace.cpp.
+class BacktraceCollector {
+ public:
+  BacktraceCollector(uintptr_t* out_frames, size_t max_depth, size_t skip_count)
+      : out_frames_(out_frames), max_depth_(max_depth), skip_count_(skip_count) {}
+
+  size_t NumFrames() const {
+    return num_frames_;
+  }
+
+  // Collect the backtrace, do not call more than once.
+  void Collect() {
+    _Unwind_Backtrace(&Callback, this);
+  }
+
+ private:
+  static _Unwind_Reason_Code Callback(_Unwind_Context* context, void* arg) {
+    auto* const state = reinterpret_cast<BacktraceCollector*>(arg);
+    const uintptr_t ip = _Unwind_GetIP(context);
+    // The first stack frame is get_backtrace itself. Skip it.
+    if (ip != 0 && state->skip_count_ > 0) {
+      --state->skip_count_;
+      return _URC_NO_REASON;
+    }
+    // ip may be off for ARM but it shouldn't matter since we only use it for hashing.
+    state->out_frames_[state->num_frames_] = ip;
+    state->num_frames_++;
+    return state->num_frames_ >= state->max_depth_ ? _URC_END_OF_STACK : _URC_NO_REASON;
+  }
+
+  uintptr_t* const out_frames_ = nullptr;
+  size_t num_frames_ = 0u;
+  const size_t max_depth_ = 0u;
+  size_t skip_count_ = 0u;
+};
+
+// A bounded sized backtrace.
+template <size_t kMaxFrames>
+class FixedSizeBacktrace {
+ public:
+  void Collect(size_t skip_count) {
+    BacktraceCollector collector(frames_, kMaxFrames, skip_count);
+    collector.Collect();
+    num_frames_ = collector.NumFrames();
+  }
+
+  uint64_t Hash() const {
+    uint64_t hash = 9314237;
+    for (size_t i = 0; i < num_frames_; ++i) {
+      hash = hash * 2654435761 + frames_[i];
+      hash += (hash >> 13) ^ (hash << 6);
+    }
+    return hash;
+  }
+
+ private:
+  uintptr_t frames_[kMaxFrames];
+  size_t num_frames_;
+};
+
+}  // namespace art
+
+#endif  // ART_RUNTIME_BACKTRACE_HELPER_H_