Repo created

TMessagesProj/jni/voip/webrtc/base/profiler/unwinder.h

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+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_PROFILER_UNWINDER_H_
+#define BASE_PROFILER_UNWINDER_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/profiler/frame.h"
+#include "base/profiler/module_cache.h"
+#include "base/profiler/register_context.h"
+
+namespace base {
+
+// The result of attempting to unwind stack frames.
+enum class UnwindResult {
+  // The end of the stack was reached successfully.
+  COMPLETED,
+
+  // The walk reached a frame that it doesn't know how to unwind, but might be
+  // unwindable by the other native/aux unwinder.
+  UNRECOGNIZED_FRAME,
+
+  // The walk was aborted and is not resumable.
+  ABORTED,
+};
+
+// Unwinder provides an interface for stack frame unwinder implementations for
+// use with the StackSamplingProfiler. The profiler is expected to call
+// CanUnwind() to determine if the Unwinder thinks it can unwind from the frame
+// represented by the context values, then TryUnwind() to attempt the
+// unwind.
+class Unwinder {
+ public:
+  virtual ~Unwinder() = default;
+
+  // Invoked to allow the unwinder to add any modules it recognizes to the
+  // ModuleCache.
+  virtual void AddInitialModules(ModuleCache* module_cache) {}
+
+  // Invoked at the time the stack is captured. IMPORTANT NOTE: this function is
+  // invoked while the target thread is suspended. To avoid deadlock it must not
+  // invoke any non-reentrant code that is also invoked by the target thread. In
+  // particular, it may not perform any heap allocation or deallocation,
+  // including indirectly via use of DCHECK/CHECK or other logging statements.
+  virtual void OnStackCapture() {}
+
+  // Allows the unwinder to update ModuleCache with any modules it's responsible
+  // for. Invoked for each sample between OnStackCapture() and the initial
+  // invocations of CanUnwindFrom()/TryUnwind().
+  virtual void UpdateModules(ModuleCache* module_cache) {}
+
+  // Returns true if the unwinder recognizes the code referenced by
+  // |current_frame| as code from which it should be able to unwind. When
+  // multiple unwinders are in use, each should return true for a disjoint set
+  // of frames. Note that if the unwinder returns true it may still legitmately
+  // fail to unwind; e.g. in the case of a native unwind for a function that
+  // doesn't have unwind information.
+  virtual bool CanUnwindFrom(const Frame& current_frame) const = 0;
+
+  // Attempts to unwind the frame represented by the context values.
+  // Walks the native frames on the stack pointed to by the stack pointer in
+  // |thread_context|, appending the frames to |stack|. When invoked
+  // stack->back() contains the frame corresponding to the state in
+  // |thread_context|.
+  // Precondition: RegisterContextStackPointer(thread_context) is less than
+  // |stack_top|.
+  // Postcondition: If the implementation returns UNRECOGNIZED_FRAME, indicating
+  // that it successfully unwound, RegisterContextStackPointer(thread_context)
+  // is greater than the previous value and less than |stack_top|.
+  virtual UnwindResult TryUnwind(RegisterContext* thread_context,
+                                 uintptr_t stack_top,
+                                 ModuleCache* module_cache,
+                                 std::vector<Frame>* stack) const = 0;
+
+  Unwinder(const Unwinder&) = delete;
+  Unwinder& operator=(const Unwinder&) = delete;
+
+ protected:
+  Unwinder() = default;
+};
+
+}  // namespace base
+
+#endif  // BASE_PROFILER_UNWINDER_H_