unwinding-info-win64.cc

// Copyright 2019 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.

#include "src/diagnostics/unwinding-info-win64.h"

#include "src/codegen/macro-assembler.h"
#include "src/utils/allocation.h"

#if defined(V8_OS_WIN_X64)
#include "src/codegen/x64/assembler-x64.h"
#elif defined(V8_OS_WIN_ARM64)
#include "src/codegen/arm64/assembler-arm64-inl.h"
#include "src/codegen/arm64/macro-assembler-arm64-inl.h"
#else
#error "Unsupported OS"
#endif  // V8_OS_WIN_X64

#include <windows.h>

// This has to come after windows.h.
#include <versionhelpers.h>  // For IsWindows8OrGreater().

namespace v8 {
namespace internal {
namespace win64_unwindinfo {

bool CanEmitUnwindInfoForBuiltins() { return FLAG_win64_unwinding_info; }

bool CanRegisterUnwindInfoForNonABICompliantCodeRange() {
  return !FLAG_jitless;
}

bool RegisterUnwindInfoForExceptionHandlingOnly() {
  DCHECK(CanRegisterUnwindInfoForNonABICompliantCodeRange());
#if defined(V8_OS_WIN_ARM64)
  return !FLAG_win64_unwinding_info;
#else
  return !IsWindows8OrGreater() || !FLAG_win64_unwinding_info;
#endif
}

v8::UnhandledExceptionCallback unhandled_exception_callback_g = nullptr;

void SetUnhandledExceptionCallback(
    v8::UnhandledExceptionCallback unhandled_exception_callback) {
  unhandled_exception_callback_g = unhandled_exception_callback;
}

// This function is registered as exception handler for V8-generated code as
// part of the registration of unwinding info. It is referenced by
// RegisterNonABICompliantCodeRange(), below, and by the unwinding info for
// builtins declared in the embedded blob.
extern "C" __declspec(dllexport) int CRASH_HANDLER_FUNCTION_NAME(
    PEXCEPTION_RECORD ExceptionRecord, ULONG64 EstablisherFrame,
    PCONTEXT ContextRecord, PDISPATCHER_CONTEXT DispatcherContext) {
  if (unhandled_exception_callback_g != nullptr) {
    EXCEPTION_POINTERS info = {ExceptionRecord, ContextRecord};
    return unhandled_exception_callback_g(&info);
  }
  return ExceptionContinueSearch;
}

#if defined(V8_OS_WIN_X64)

#pragma pack(push, 1)

/*
 * From Windows SDK ehdata.h, which does not compile with Clang.
 * See https://msdn.microsoft.com/en-us/library/ddssxxy8.aspx.
 */
union UNWIND_CODE {
  struct {
    unsigned char CodeOffset;
    unsigned char UnwindOp : 4;
    unsigned char OpInfo : 4;
  };
  uint16_t FrameOffset;
};

struct UNWIND_INFO {
  unsigned char Version : 3;
  unsigned char Flags : 5;
  unsigned char SizeOfProlog;
  unsigned char CountOfCodes;
  unsigned char FrameRegister : 4;
  unsigned char FrameOffset : 4;
};

static constexpr int kNumberOfUnwindCodes = 2;
static constexpr int kMaxExceptionThunkSize = 12;

struct V8UnwindData {
  UNWIND_INFO unwind_info;
  UNWIND_CODE unwind_codes[kNumberOfUnwindCodes];

  V8UnwindData() {
    static constexpr int kOpPushNonvol = 0;
    static constexpr int kOpSetFPReg = 3;

    unwind_info.Version = 1;
    unwind_info.Flags = UNW_FLAG_EHANDLER;
    unwind_info.SizeOfProlog = kRbpPrefixLength;
    unwind_info.CountOfCodes = kRbpPrefixCodes;
    unwind_info.FrameRegister = rbp.code();
    unwind_info.FrameOffset = 0;

    unwind_codes[0].CodeOffset = kRbpPrefixLength;  // movq rbp, rsp
    unwind_codes[0].UnwindOp = kOpSetFPReg;
    unwind_codes[0].OpInfo = 0;

    unwind_codes[1].CodeOffset = kPushRbpInstructionLength;  // push rbp
    unwind_codes[1].UnwindOp = kOpPushNonvol;
    unwind_codes[1].OpInfo = rbp.code();
  }
};

struct ExceptionHandlerUnwindData {
  UNWIND_INFO unwind_info;

  ExceptionHandlerUnwindData() {
    unwind_info.Version = 1;
    unwind_info.Flags = UNW_FLAG_EHANDLER;
    unwind_info.SizeOfProlog = 0;
    unwind_info.CountOfCodes = 0;
    unwind_info.FrameRegister = 0;
    unwind_info.FrameOffset = 0;
  }
};

struct CodeRangeUnwindingRecord {
  void* dynamic_table;
  uint32_t runtime_function_count;
  V8UnwindData unwind_info;
  uint32_t exception_handler;
  uint8_t exception_thunk[kMaxExceptionThunkSize];
  RUNTIME_FUNCTION runtime_function[kDefaultRuntimeFunctionCount];
};

struct ExceptionHandlerRecord {
  uint32_t runtime_function_count;
  RUNTIME_FUNCTION runtime_function[kDefaultRuntimeFunctionCount];
  ExceptionHandlerUnwindData unwind_info;
  uint32_t exception_handler;
  uint8_t exception_thunk[kMaxExceptionThunkSize];
};

#pragma pack(pop)

std::vector<uint8_t> GetUnwindInfoForBuiltinFunctions() {
  V8UnwindData xdata;
  return std::vector<uint8_t>(
      reinterpret_cast<uint8_t*>(&xdata),
      reinterpret_cast<uint8_t*>(&xdata) + sizeof(xdata));
}

template <typename Record>
void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
  // We assume that the first page of the code range is executable and
  // committed and reserved to contain PDATA/XDATA.

  // All addresses are 32bit relative offsets to start.
  record->runtime_function[0].BeginAddress = 0;
  record->runtime_function[0].EndAddress =
      static_cast<DWORD>(code_size_in_bytes);
  record->runtime_function[0].UnwindData = offsetof(Record, unwind_info);
  record->runtime_function_count = 1;
  record->exception_handler = offsetof(Record, exception_thunk);

  // Hardcoded thunk.
  AssemblerOptions options;
  options.record_reloc_info_for_serialization = false;
  MacroAssembler masm(nullptr, options, CodeObjectRequired::kNo,
                      NewAssemblerBuffer(64));
  masm.movq(rax, reinterpret_cast<uint64_t>(&CRASH_HANDLER_FUNCTION_NAME));
  masm.jmp(rax);
  DCHECK_LE(masm.instruction_size(), sizeof(record->exception_thunk));
  memcpy(&record->exception_thunk[0], masm.buffer_start(),
         masm.instruction_size());
}

#elif defined(V8_OS_WIN_ARM64)

#pragma pack(push, 1)

// ARM64 unwind codes are defined in below doc.
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling#unwind-codes
enum UnwindOp8Bit {
  OpNop = 0xE3,
  OpAllocS = 0x00,
  OpSaveFpLr = 0x40,
  OpSaveFpLrX = 0x80,
  OpSetFp = 0xE1,
  OpAddFp = 0xE2,
  OpEnd = 0xE4,
};

typedef uint32_t UNWIND_CODE;

constexpr UNWIND_CODE Combine8BitUnwindCodes(uint8_t code0 = OpNop,
                                             uint8_t code1 = OpNop,
                                             uint8_t code2 = OpNop,
                                             uint8_t code3 = OpNop) {
  return static_cast<uint32_t>(code0) | (static_cast<uint32_t>(code1) << 8) |
         (static_cast<uint32_t>(code2) << 16) |
         (static_cast<uint32_t>(code3) << 24);
}

// UNWIND_INFO defines the static part (first 32-bit) of the .xdata record in
// below doc.
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling#xdata-records
struct UNWIND_INFO {
  uint32_t FunctionLength : 18;
  uint32_t Version : 2;
  uint32_t X : 1;
  uint32_t E : 1;
  uint32_t EpilogCount : 5;
  uint32_t CodeWords : 5;
};

static constexpr int kDefaultNumberOfUnwindCodeWords = 1;
static constexpr int kMaxExceptionThunkSize = 16;
static constexpr int kFunctionLengthShiftSize = 2;
static constexpr int kFunctionLengthMask = (1 << kFunctionLengthShiftSize) - 1;
static constexpr int kAllocStackShiftSize = 4;
static constexpr int kAllocStackShiftMask = (1 << kAllocStackShiftSize) - 1;

// Generate an unwind code for "stp fp, lr, [sp, #pre_index_offset]!".
uint8_t MakeOpSaveFpLrX(int pre_index_offset) {
  // See unwind code save_fplr_x in
  // https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling#unwind-codes
  DCHECK_LE(pre_index_offset, -8);
  DCHECK_GE(pre_index_offset, -512);
  constexpr int kShiftSize = 3;
  constexpr int kShiftMask = (1 << kShiftSize) - 1;
  DCHECK_EQ(pre_index_offset & kShiftMask, 0);
  USE(kShiftMask);
  // Solve for Z where -(Z+1)*8 = pre_index_offset.
  int encoded_value = (-pre_index_offset >> kShiftSize) - 1;
  return OpSaveFpLrX | encoded_value;
}

// Generate an unwind code for "sub sp, sp, #stack_space".
uint8_t MakeOpAllocS(int stack_space) {
  // See unwind code alloc_s in
  // https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling#unwind-codes
  DCHECK_GE(stack_space, 0);
  DCHECK_LT(stack_space, 512);
  DCHECK_EQ(stack_space & kAllocStackShiftMask, 0);
  return OpAllocS | (stack_space >> kAllocStackShiftSize);
}

// Generate the second byte of the unwind code for "add fp, sp, #offset".
uint8_t MakeOpAddFpArgument(int offset) {
  // See unwind code add_fp in
  // https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling#unwind-codes
  DCHECK_GE(offset, 0);
  constexpr int kShiftSize = 3;
  constexpr int kShiftMask = (1 << kShiftSize) - 1;
  DCHECK_EQ(offset & kShiftMask, 0);
  USE(kShiftMask);
  int encoded_value = offset >> kShiftSize;
  // Encoded value must fit in 8 bits.
  DCHECK_LE(encoded_value, 0xff);
  return encoded_value;
}

template <int kNumberOfUnwindCodeWords = kDefaultNumberOfUnwindCodeWords>
struct V8UnwindData {
  UNWIND_INFO unwind_info;
  UNWIND_CODE unwind_codes[kNumberOfUnwindCodeWords];

  V8UnwindData() {
    memset(&unwind_info, 0, sizeof(UNWIND_INFO));
    unwind_info.X = 1;  // has exception handler after unwind-codes.
    unwind_info.CodeWords = kNumberOfUnwindCodeWords;

    // Generate unwind codes for the following prolog:
    //
    // stp fp, lr, [sp, #-kCallerSPOffset]!
    // mov fp, sp
    //
    // This is a very rough approximation of the actual function prologs used in
    // V8. In particular, we often push other data before the (fp, lr) pair,
    // meaning the stack pointer computed for the caller frame is wrong. That
    // error is acceptable when the unwinding info for the caller frame also
    // depends on fp rather than sp, as is the case for V8 builtins and runtime-
    // generated code.
    static_assert(kNumberOfUnwindCodeWords >= 1);
    unwind_codes[0] = Combine8BitUnwindCodes(
        OpSetFp, MakeOpSaveFpLrX(-CommonFrameConstants::kCallerSPOffset),
        OpEnd);

    // Fill the rest with nops.
    for (int i = 1; i < kNumberOfUnwindCodeWords; ++i) {
      unwind_codes[i] = Combine8BitUnwindCodes();
    }
  }
};

struct CodeRangeUnwindingRecord {
  void* dynamic_table;
  uint32_t runtime_function_count;
  V8UnwindData<> unwind_info;
  uint32_t exception_handler;

  // For Windows ARM64 unwinding, register 2 unwind_info for each code range,
  // unwind_info for all full size ranges (1MB - 4 bytes) and unwind_info1 for
  // the remaining non full size range. There is at most 1 range which is less
  // than full size.
  V8UnwindData<> unwind_info1;
  uint32_t exception_handler1;
  uint8_t exception_thunk[kMaxExceptionThunkSize];

  // More RUNTIME_FUNCTION structs could follow below array because the number
  // of RUNTIME_FUNCTION needed to cover given code range is computed at
  // runtime.
  RUNTIME_FUNCTION runtime_function[kDefaultRuntimeFunctionCount];
};

#pragma pack(pop)

FrameOffsets::FrameOffsets()
    : fp_to_saved_caller_fp(CommonFrameConstants::kCallerFPOffset),
      fp_to_caller_sp(CommonFrameConstants::kCallerSPOffset) {}
bool FrameOffsets::IsDefault() const {
  FrameOffsets other;
  return fp_to_saved_caller_fp == other.fp_to_saved_caller_fp &&
         fp_to_caller_sp == other.fp_to_caller_sp;
}

std::vector<uint8_t> GetUnwindInfoForBuiltinFunction(
    uint32_t func_len, FrameOffsets fp_adjustment) {
  DCHECK_LE(func_len, kMaxFunctionLength);
  DCHECK_EQ((func_len & kFunctionLengthMask), 0);
  USE(kFunctionLengthMask);

  // The largest size of unwind data required for all options below.
  constexpr int kMaxNumberOfUnwindCodeWords = 2;

  V8UnwindData<kMaxNumberOfUnwindCodeWords> xdata;
  // FunctionLength is ensured to be aligned at instruction size and Windows
  // ARM64 doesn't encoding its 2 LSB.
  xdata.unwind_info.FunctionLength = func_len >> kFunctionLengthShiftSize;

  if (fp_adjustment.IsDefault()) {
    // One code word is plenty.
    static_assert(kDefaultNumberOfUnwindCodeWords <
                  kMaxNumberOfUnwindCodeWords);
    xdata.unwind_info.CodeWords = kDefaultNumberOfUnwindCodeWords;
  } else {
    // We want to convey the following facts:
    // 1. The caller's fp is found at [fp + fp_to_saved_caller_fp].
    // 2. The caller's pc is found at [fp + fp_to_saved_caller_fp + 8].
    // 3. The caller's sp is equal to fp + fp_to_caller_sp.
    //
    // An imaginary prolog that would establish those relationships might look
    // like the following, with appropriate values for the various constants:
    //
    // stp fp, lr, [sp, #pre_index_amount]!
    // sub sp, sp, #stack_space
    // add fp, sp, offset_from_stack_top
    //
    // Why do we need offset_from_stack_top? The unwinding encoding for
    // allocating stack space has 16-byte granularity, and the frame pointer has
    // only 8-byte alignment.
    int pre_index_amount =
        fp_adjustment.fp_to_saved_caller_fp - fp_adjustment.fp_to_caller_sp;
    int stack_space = fp_adjustment.fp_to_saved_caller_fp;
    int offset_from_stack_top = stack_space & kAllocStackShiftMask;
    stack_space += offset_from_stack_top;

    xdata.unwind_codes[0] = Combine8BitUnwindCodes(
        OpAddFp, MakeOpAddFpArgument(offset_from_stack_top),
        MakeOpAllocS(stack_space), MakeOpSaveFpLrX(pre_index_amount));
    xdata.unwind_codes[1] = Combine8BitUnwindCodes(OpEnd);
  }

  return std::vector<uint8_t>(
      reinterpret_cast<uint8_t*>(&xdata),
      reinterpret_cast<uint8_t*>(
          &xdata.unwind_codes[xdata.unwind_info.CodeWords]));
}

template <typename Record>
void InitUnwindingRecord(Record* record, size_t code_size_in_bytes) {
  // We assume that the first page of the code range is executable and
  // committed and reserved to contain multiple PDATA/XDATA to cover the whole
  // range. All addresses are 32bit relative offsets to start.

  // Maximum RUNTIME_FUNCTION count available in reserved memory, this includes
  // static part in Record as kDefaultRuntimeFunctionCount plus dynamic part in
  // the remaining reserved memory.
  constexpr uint32_t max_runtime_function_count = static_cast<uint32_t>(
      (kOSPageSize - sizeof(Record)) / sizeof(RUNTIME_FUNCTION) +
      kDefaultRuntimeFunctionCount);

  uint32_t runtime_function_index = 0;
  uint32_t current_unwind_start_address = 0;
  int64_t remaining_size_in_bytes = static_cast<int64_t>(code_size_in_bytes);

  // Divide the code range into chunks in size kMaxFunctionLength and create a
  // RUNTIME_FUNCTION for each of them. All the chunks in the same size can
  // share 1 unwind_info struct, but a separate unwind_info is needed for the
  // last chunk if it is smaller than kMaxFunctionLength, because unlike X64,
  // unwind_info encodes the function/chunk length.
  while (remaining_size_in_bytes >= kMaxFunctionLength &&
         runtime_function_index < max_runtime_function_count) {
    record->runtime_function[runtime_function_index].BeginAddress =
        current_unwind_start_address;
    record->runtime_function[runtime_function_index].UnwindData =
        static_cast<DWORD>(offsetof(Record, unwind_info));

    runtime_function_index++;
    current_unwind_start_address += kMaxFunctionLength;
    remaining_size_in_bytes -= kMaxFunctionLength;
  }
  // FunctionLength is ensured to be aligned at instruction size and Windows
  // ARM64 doesn't encoding 2 LSB.
  record->unwind_info.unwind_info.FunctionLength = kMaxFunctionLength >> 2;

  if (remaining_size_in_bytes > 0 &&
      runtime_function_index < max_runtime_function_count) {
    DCHECK_EQ(remaining_size_in_bytes % kInstrSize, 0);

    record->unwind_info1.unwind_info.FunctionLength = static_cast<uint32_t>(
        remaining_size_in_bytes >> kFunctionLengthShiftSize);
    record->runtime_function[runtime_function_index].BeginAddress =
        current_unwind_start_address;
    record->runtime_function[runtime_function_index].UnwindData =
        static_cast<DWORD>(offsetof(Record, unwind_info1));

    remaining_size_in_bytes -= kMaxFunctionLength;
    record->exception_handler1 = offsetof(Record, exception_thunk);
    record->runtime_function_count = runtime_function_index + 1;
  } else {
    record->runtime_function_count = runtime_function_index;
  }

  // 1 page can cover kMaximalCodeRangeSize for ARM64 (128MB). If
  // kMaximalCodeRangeSize is changed for ARM64 and makes 1 page insufficient to
  // cover it, more pages will need to reserved for unwind data.
  DCHECK_LE(remaining_size_in_bytes, 0);

  record->exception_handler = offsetof(Record, exception_thunk);

  // Hardcoded thunk.
  AssemblerOptions options;
  options.record_reloc_info_for_serialization = false;
  TurboAssembler masm(nullptr, options, CodeObjectRequired::kNo,
                      NewAssemblerBuffer(64));
  masm.Mov(x16,
           Operand(reinterpret_cast<uint64_t>(&CRASH_HANDLER_FUNCTION_NAME)));
  masm.Br(x16);
  DCHECK_LE(masm.instruction_size(), sizeof(record->exception_thunk));
  memcpy(&record->exception_thunk[0], masm.buffer_start(),
         masm.instruction_size());
}

#endif  // V8_OS_WIN_X64

namespace {

V8_DECLARE_ONCE(load_ntdll_unwinding_functions_once);
static decltype(
    &::RtlAddGrowableFunctionTable) add_growable_function_table_func = nullptr;
static decltype(
    &::RtlDeleteGrowableFunctionTable) delete_growable_function_table_func =
    nullptr;

void LoadNtdllUnwindingFunctionsOnce() {
  // Load functions from the ntdll.dll module.
  HMODULE ntdll_module =
      LoadLibraryEx(L"ntdll.dll", nullptr, LOAD_LIBRARY_SEARCH_SYSTEM32);
  DCHECK_NOT_NULL(ntdll_module);

  // This fails on Windows 7.
  add_growable_function_table_func =
      reinterpret_cast<decltype(&::RtlAddGrowableFunctionTable)>(
          ::GetProcAddress(ntdll_module, "RtlAddGrowableFunctionTable"));
  DCHECK_IMPLIES(IsWindows8OrGreater(), add_growable_function_table_func);

  delete_growable_function_table_func =
      reinterpret_cast<decltype(&::RtlDeleteGrowableFunctionTable)>(
          ::GetProcAddress(ntdll_module, "RtlDeleteGrowableFunctionTable"));
  DCHECK_IMPLIES(IsWindows8OrGreater(), delete_growable_function_table_func);
}

void LoadNtdllUnwindingFunctions() {
  base::CallOnce(&load_ntdll_unwinding_functions_once,
                 &LoadNtdllUnwindingFunctionsOnce);
}

bool AddGrowableFunctionTable(PVOID* DynamicTable,
                              PRUNTIME_FUNCTION FunctionTable, DWORD EntryCount,
                              DWORD MaximumEntryCount, ULONG_PTR RangeBase,
                              ULONG_PTR RangeEnd) {
  DCHECK(::IsWindows8OrGreater());

  LoadNtdllUnwindingFunctions();
  DCHECK_NOT_NULL(add_growable_function_table_func);

  *DynamicTable = nullptr;
  DWORD status =
      add_growable_function_table_func(DynamicTable, FunctionTable, EntryCount,
                                       MaximumEntryCount, RangeBase, RangeEnd);
  DCHECK((status == 0 && *DynamicTable != nullptr) ||
         status == 0xC000009A);  // STATUS_INSUFFICIENT_RESOURCES
  return (status == 0);
}

void DeleteGrowableFunctionTable(PVOID dynamic_table) {
  DCHECK(::IsWindows8OrGreater());

  LoadNtdllUnwindingFunctions();
  DCHECK_NOT_NULL(delete_growable_function_table_func);

  delete_growable_function_table_func(dynamic_table);
}

}  // namespace

void RegisterNonABICompliantCodeRange(void* start, size_t size_in_bytes) {
  DCHECK(CanRegisterUnwindInfoForNonABICompliantCodeRange());

  // When the --win64-unwinding-info flag is set, we call
  // RtlAddGrowableFunctionTable to register unwinding info for the whole code
  // range of an isolate or Wasm module. This enables the Windows OS stack
  // unwinder to work correctly with V8-generated code, enabling stack walking
  // in Windows debuggers and performance tools. However, the
  // RtlAddGrowableFunctionTable API is only supported on Windows 8 and above.
  //
  // On Windows 7, or when --win64-unwinding-info is not set, we may still need
  // to call RtlAddFunctionTable to register a custom exception handler passed
  // by the embedder (like Crashpad).

  if (RegisterUnwindInfoForExceptionHandlingOnly()) {
#if defined(V8_OS_WIN_X64)
    // Windows ARM64 starts since 1709 Windows build, no need to have exception
    // handling only unwind info for compatibility.
    if (unhandled_exception_callback_g) {
      ExceptionHandlerRecord* record = new (start) ExceptionHandlerRecord();
      InitUnwindingRecord(record, size_in_bytes);

      CHECK(::RtlAddFunctionTable(record->runtime_function,
                                  kDefaultRuntimeFunctionCount,
                                  reinterpret_cast<DWORD64>(start)));

      // Protect reserved page against modifications.
      DWORD old_protect;
      CHECK(VirtualProtect(start, sizeof(ExceptionHandlerRecord),
                           PAGE_EXECUTE_READ, &old_protect));
    }
#endif  // V8_OS_WIN_X64
  } else {
    CodeRangeUnwindingRecord* record = new (start) CodeRangeUnwindingRecord();
    InitUnwindingRecord(record, size_in_bytes);

    CHECK(AddGrowableFunctionTable(
        &record->dynamic_table, record->runtime_function,
        record->runtime_function_count, record->runtime_function_count,
        reinterpret_cast<DWORD64>(start),
        reinterpret_cast<DWORD64>(reinterpret_cast<uint8_t*>(start) +
                                  size_in_bytes)));

    // Protect reserved page against modifications.
    DWORD old_protect;
    CHECK(VirtualProtect(start, sizeof(CodeRangeUnwindingRecord),
                         PAGE_EXECUTE_READ, &old_protect));
  }
}

void UnregisterNonABICompliantCodeRange(void* start) {
  DCHECK(CanRegisterUnwindInfoForNonABICompliantCodeRange());

  if (RegisterUnwindInfoForExceptionHandlingOnly()) {
#if defined(V8_OS_WIN_X64)
    // Windows ARM64 starts since 1709 Windows build, no need to have exception
    // handling only unwind info for compatibility.
    if (unhandled_exception_callback_g) {
      ExceptionHandlerRecord* record =
          reinterpret_cast<ExceptionHandlerRecord*>(start);
      CHECK(::RtlDeleteFunctionTable(record->runtime_function));

      // Unprotect reserved page.
      DWORD old_protect;
      CHECK(VirtualProtect(start, sizeof(ExceptionHandlerRecord),
                           PAGE_READWRITE, &old_protect));
    }
#endif  // V8_OS_WIN_X64
  } else {
    CodeRangeUnwindingRecord* record =
        reinterpret_cast<CodeRangeUnwindingRecord*>(start);
    if (record->dynamic_table) {
      DeleteGrowableFunctionTable(record->dynamic_table);
    }

    // Unprotect reserved page.
    DWORD old_protect;
    CHECK(VirtualProtect(start, sizeof(CodeRangeUnwindingRecord),
                         PAGE_READWRITE, &old_protect));
  }
}

#if defined(V8_OS_WIN_X64)

void XdataEncoder::onPushRbp() {
  current_frame_code_offset_ =
      assembler_.pc_offset() - kPushRbpInstructionLength;
}

void XdataEncoder::onMovRbpRsp() {
  if (current_frame_code_offset_ >= 0 &&
      current_frame_code_offset_ == assembler_.pc_offset() - kRbpPrefixLength) {
    fp_offsets_.push_back(current_frame_code_offset_);
  }
}

#elif defined(V8_OS_WIN_ARM64)

void XdataEncoder::onSaveFpLr() {
  current_frame_code_offset_ = assembler_.pc_offset() - 4;
  fp_offsets_.push_back(current_frame_code_offset_);
  fp_adjustments_.push_back(current_frame_adjustment_);
  current_frame_adjustment_ = FrameOffsets();
}

void XdataEncoder::onFramePointerAdjustment(int fp_to_saved_caller_fp,
                                            int fp_to_caller_sp) {
  current_frame_adjustment_.fp_to_saved_caller_fp = fp_to_saved_caller_fp;
  current_frame_adjustment_.fp_to_caller_sp = fp_to_caller_sp;
}

#endif  // V8_OS_WIN_X64

}  // namespace win64_unwindinfo
}  // namespace internal
}  // namespace v8