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 // Copyright 2021 the V8 project 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 INCLUDE_V8_UNWINDER_H_
 #define INCLUDE_V8_UNWINDER_H_
 
 #include <memory>
 
 #include "v8-embedder-state-scope.h"  // NOLINT(build/include_directory)
 #include "v8config.h"                 // NOLINT(build/include_directory)
 
 namespace v8 {
 // Holds the callee saved registers needed for the stack unwinder. It is the
 // empty struct if no registers are required. Implemented in
 // include/v8-unwinder-state.h.
 struct CalleeSavedRegisters;
 
 // A RegisterState represents the current state of registers used
 // by the sampling profiler API.
 struct V8_EXPORT RegisterState {
   RegisterState();
   ~RegisterState();
   RegisterState(const RegisterState& other);
   RegisterState& operator=(const RegisterState& other);
 
   void* pc;  // Instruction pointer.
   void* sp;  // Stack pointer.
   void* fp;  // Frame pointer.
   void* lr;  // Link register (or nullptr on platforms without a link register).
   // Callee saved registers (or null if no callee saved registers were stored)
   std::unique_ptr<CalleeSavedRegisters> callee_saved;
 };
 
 // A StateTag represents a possible state of the VM.
 enum StateTag : uint16_t {
   JS,
   GC,
   PARSER,
   BYTECODE_COMPILER,
   COMPILER,
   OTHER,
   EXTERNAL,
   ATOMICS_WAIT,
   IDLE
 };
 
 // The output structure filled up by GetStackSample API function.
 struct SampleInfo {
   size_t frames_count;              // Number of frames collected.
   void* external_callback_entry;    // External callback address if VM is
                                     // executing an external callback.
   void* context;                    // Incumbent native context address.
   void* embedder_context;           // Native context address for embedder state
   StateTag vm_state;                // Current VM state.
   EmbedderStateTag embedder_state;  // Current Embedder state
 };
 
 struct MemoryRange {
   const void* start = nullptr;
   size_t length_in_bytes = 0;
 };
 
 struct JSEntryStub {
   MemoryRange code;
 };
 
 struct JSEntryStubs {
   JSEntryStub js_entry_stub;
   JSEntryStub js_construct_entry_stub;
   JSEntryStub js_run_microtasks_entry_stub;
 };
 
 /**
  * Various helpers for skipping over V8 frames in a given stack.
  *
  * The unwinder API is only supported on the x64, ARM64 and ARM32 architectures.
  */
 class V8_EXPORT Unwinder {
  public:
   /**
    * Attempt to unwind the stack to the most recent C++ frame. This function is
    * signal-safe and does not access any V8 state and thus doesn't require an
    * Isolate.
    *
    * The unwinder needs to know the location of the JS Entry Stub (a piece of
    * code that is run when C++ code calls into generated JS code). This is used
    * for edge cases where the current frame is being constructed or torn down
    * when the stack sample occurs.
    *
    * The unwinder also needs the virtual memory range of all possible V8 code
    * objects. There are two ranges required - the heap code range and the range
    * for code embedded in the binary.
    *
    * Available on x64, ARM64 and ARM32.
    *
    * \param code_pages A list of all of the ranges in which V8 has allocated
    * executable code. The caller should obtain this list by calling
    * Isolate::CopyCodePages() during the same interrupt/thread suspension that
    * captures the stack.
    * \param register_state The current registers. This is an in-out param that
    * will be overwritten with the register values after unwinding, on success.
    * \param stack_base The resulting stack pointer and frame pointer values are
    * bounds-checked against the stack_base and the original stack pointer value
    * to ensure that they are valid locations in the given stack. If these values
    * or any intermediate frame pointer values used during unwinding are ever out
    * of these bounds, unwinding will fail.
    *
    * \return True on success.
    */
   static bool TryUnwindV8Frames(const JSEntryStubs& entry_stubs,
                                 size_t code_pages_length,
                                 const MemoryRange* code_pages,
                                 RegisterState* register_state,
                                 const void* stack_base);
 
   /**
    * Whether the PC is within the V8 code range represented by code_pages.
    *
    * If this returns false, then calling UnwindV8Frames() with the same PC
    * and unwind_state will always fail. If it returns true, then unwinding may
    * (but not necessarily) be successful.
    *
    * Available on x64, ARM64 and ARM32
    */
   static bool PCIsInV8(size_t code_pages_length, const MemoryRange* code_pages,
                        void* pc);
 };
 
 }  // namespace v8
 
 #endif  // INCLUDE_V8_UNWINDER_H_

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