path: root/contrib/libs/libunwind/src/UnwindCursor.hpp

//===----------------------------------------------------------------------===//
// 
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// 
// 
// C++ interface to lower levels of libunwind
//===----------------------------------------------------------------------===// 
 
#ifndef __UNWINDCURSOR_HPP__ 
#define __UNWINDCURSOR_HPP__ 
 
#include "cet_unwind.h"
#include <stdint.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <unwind.h> 
 
#ifdef _WIN32
  #include <windows.h>
  #include <ntverp.h>
#endif
#ifdef __APPLE__ 
  #include <mach-o/dyld.h> 
#endif 
 
#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
// Provide a definition for the DISPATCHER_CONTEXT struct for old (Win7 and
// earlier) SDKs.
// MinGW-w64 has always provided this struct.
  #if defined(_WIN32) && defined(_LIBUNWIND_TARGET_X86_64) && \
      !defined(__MINGW32__) && VER_PRODUCTBUILD < 8000
struct _DISPATCHER_CONTEXT {
  ULONG64 ControlPc;
  ULONG64 ImageBase;
  PRUNTIME_FUNCTION FunctionEntry;
  ULONG64 EstablisherFrame;
  ULONG64 TargetIp;
  PCONTEXT ContextRecord;
  PEXCEPTION_ROUTINE LanguageHandler;
  PVOID HandlerData;
  PUNWIND_HISTORY_TABLE HistoryTable;
  ULONG ScopeIndex;
  ULONG Fill0;
};
  #endif

struct UNWIND_INFO {
  uint8_t Version : 3;
  uint8_t Flags : 5;
  uint8_t SizeOfProlog;
  uint8_t CountOfCodes;
  uint8_t FrameRegister : 4;
  uint8_t FrameOffset : 4;
  uint16_t UnwindCodes[2];
};

extern "C" _Unwind_Reason_Code __libunwind_seh_personality(
    int, _Unwind_Action, uint64_t, _Unwind_Exception *,
    struct _Unwind_Context *);

#endif

#include "config.h" 
 
#include "AddressSpace.hpp" 
#include "CompactUnwinder.hpp" 
#include "config.h" 
#include "DwarfInstructions.hpp" 
#include "EHHeaderParser.hpp" 
#include "libunwind.h" 
#include "Registers.hpp" 
#include "RWMutex.hpp"
#include "Unwind-EHABI.h" 
 
namespace libunwind { 
 
#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
/// Cache of recently found FDEs. 
template <typename A> 
class _LIBUNWIND_HIDDEN DwarfFDECache { 
  typedef typename A::pint_t pint_t; 
public: 
  static constexpr pint_t kSearchAll = static_cast<pint_t>(-1);
  static pint_t findFDE(pint_t mh, pint_t pc); 
  static void add(pint_t mh, pint_t ip_start, pint_t ip_end, pint_t fde); 
  static void removeAllIn(pint_t mh); 
  static void iterateCacheEntries(void (*func)(unw_word_t ip_start, 
                                               unw_word_t ip_end, 
                                               unw_word_t fde, unw_word_t mh)); 
 
private: 
 
  struct entry { 
    pint_t mh; 
    pint_t ip_start; 
    pint_t ip_end; 
    pint_t fde; 
  }; 
 
  // These fields are all static to avoid needing an initializer. 
  // There is only one instance of this class per process. 
  static RWMutex _lock;
#ifdef __APPLE__ 
  static void dyldUnloadHook(const struct mach_header *mh, intptr_t slide); 
  static bool _registeredForDyldUnloads; 
#endif 
  static entry *_buffer; 
  static entry *_bufferUsed; 
  static entry *_bufferEnd; 
  static entry _initialBuffer[64]; 
}; 
 
template <typename A> 
typename DwarfFDECache<A>::entry * 
DwarfFDECache<A>::_buffer = _initialBuffer; 
 
template <typename A> 
typename DwarfFDECache<A>::entry * 
DwarfFDECache<A>::_bufferUsed = _initialBuffer; 
 
template <typename A> 
typename DwarfFDECache<A>::entry * 
DwarfFDECache<A>::_bufferEnd = &_initialBuffer[64]; 
 
template <typename A> 
typename DwarfFDECache<A>::entry DwarfFDECache<A>::_initialBuffer[64]; 
 
template <typename A> 
RWMutex DwarfFDECache<A>::_lock;
 
#ifdef __APPLE__ 
template <typename A> 
bool DwarfFDECache<A>::_registeredForDyldUnloads = false; 
#endif 
 
template <typename A> 
typename A::pint_t DwarfFDECache<A>::findFDE(pint_t mh, pint_t pc) { 
  pint_t result = 0; 
  _LIBUNWIND_LOG_IF_FALSE(_lock.lock_shared());
  for (entry *p = _buffer; p < _bufferUsed; ++p) { 
    if ((mh == p->mh) || (mh == kSearchAll)) {
      if ((p->ip_start <= pc) && (pc < p->ip_end)) { 
        result = p->fde; 
        break; 
      } 
    } 
  } 
  _LIBUNWIND_LOG_IF_FALSE(_lock.unlock_shared());
  return result; 
} 
 
template <typename A> 
void DwarfFDECache<A>::add(pint_t mh, pint_t ip_start, pint_t ip_end, 
                           pint_t fde) { 
#if !defined(_LIBUNWIND_NO_HEAP) 
  _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
  if (_bufferUsed >= _bufferEnd) { 
    size_t oldSize = (size_t)(_bufferEnd - _buffer); 
    size_t newSize = oldSize * 4; 
    // Can't use operator new (we are below it). 
    entry *newBuffer = (entry *)malloc(newSize * sizeof(entry)); 
    memcpy(newBuffer, _buffer, oldSize * sizeof(entry)); 
    if (_buffer != _initialBuffer) 
      free(_buffer); 
    _buffer = newBuffer; 
    _bufferUsed = &newBuffer[oldSize]; 
    _bufferEnd = &newBuffer[newSize]; 
  } 
  _bufferUsed->mh = mh; 
  _bufferUsed->ip_start = ip_start; 
  _bufferUsed->ip_end = ip_end; 
  _bufferUsed->fde = fde; 
  ++_bufferUsed; 
#ifdef __APPLE__ 
  if (!_registeredForDyldUnloads) { 
    _dyld_register_func_for_remove_image(&dyldUnloadHook); 
    _registeredForDyldUnloads = true; 
  } 
#endif 
  _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
#endif 
} 
 
template <typename A> 
void DwarfFDECache<A>::removeAllIn(pint_t mh) { 
  _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
  entry *d = _buffer; 
  for (const entry *s = _buffer; s < _bufferUsed; ++s) { 
    if (s->mh != mh) { 
      if (d != s) 
        *d = *s; 
      ++d; 
    } 
  } 
  _bufferUsed = d; 
  _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
} 
 
#ifdef __APPLE__ 
template <typename A> 
void DwarfFDECache<A>::dyldUnloadHook(const struct mach_header *mh, intptr_t ) { 
  removeAllIn((pint_t) mh); 
} 
#endif 
 
template <typename A> 
void DwarfFDECache<A>::iterateCacheEntries(void (*func)( 
    unw_word_t ip_start, unw_word_t ip_end, unw_word_t fde, unw_word_t mh)) { 
  _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
  for (entry *p = _buffer; p < _bufferUsed; ++p) { 
    (*func)(p->ip_start, p->ip_end, p->fde, p->mh); 
  } 
  _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
} 
#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
 
#define arrayoffsetof(type, index, field) ((size_t)(&((type *)0)[index].field)) 
 
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
template <typename A> class UnwindSectionHeader { 
public: 
  UnwindSectionHeader(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t version() const { 
    return _addressSpace.get32(_addr + 
                               offsetof(unwind_info_section_header, version)); 
  } 
  uint32_t commonEncodingsArraySectionOffset() const { 
    return _addressSpace.get32(_addr + 
                               offsetof(unwind_info_section_header, 
                                        commonEncodingsArraySectionOffset)); 
  } 
  uint32_t commonEncodingsArrayCount() const { 
    return _addressSpace.get32(_addr + offsetof(unwind_info_section_header, 
                                                commonEncodingsArrayCount)); 
  } 
  uint32_t personalityArraySectionOffset() const { 
    return _addressSpace.get32(_addr + offsetof(unwind_info_section_header, 
                                                personalityArraySectionOffset)); 
  } 
  uint32_t personalityArrayCount() const { 
    return _addressSpace.get32( 
        _addr + offsetof(unwind_info_section_header, personalityArrayCount)); 
  } 
  uint32_t indexSectionOffset() const { 
    return _addressSpace.get32( 
        _addr + offsetof(unwind_info_section_header, indexSectionOffset)); 
  } 
  uint32_t indexCount() const { 
    return _addressSpace.get32( 
        _addr + offsetof(unwind_info_section_header, indexCount)); 
  } 
 
private: 
  A                     &_addressSpace; 
  typename A::pint_t     _addr; 
}; 
 
template <typename A> class UnwindSectionIndexArray { 
public: 
  UnwindSectionIndexArray(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t functionOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_section_header_index_entry, index, 
                              functionOffset)); 
  } 
  uint32_t secondLevelPagesSectionOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_section_header_index_entry, index, 
                              secondLevelPagesSectionOffset)); 
  } 
  uint32_t lsdaIndexArraySectionOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_section_header_index_entry, index, 
                              lsdaIndexArraySectionOffset)); 
  } 
 
private: 
  A                   &_addressSpace; 
  typename A::pint_t   _addr; 
}; 
 
template <typename A> class UnwindSectionRegularPageHeader { 
public: 
  UnwindSectionRegularPageHeader(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t kind() const { 
    return _addressSpace.get32( 
        _addr + offsetof(unwind_info_regular_second_level_page_header, kind)); 
  } 
  uint16_t entryPageOffset() const { 
    return _addressSpace.get16( 
        _addr + offsetof(unwind_info_regular_second_level_page_header, 
                         entryPageOffset)); 
  } 
  uint16_t entryCount() const { 
    return _addressSpace.get16( 
        _addr + 
        offsetof(unwind_info_regular_second_level_page_header, entryCount)); 
  } 
 
private: 
  A &_addressSpace; 
  typename A::pint_t _addr; 
}; 
 
template <typename A> class UnwindSectionRegularArray { 
public: 
  UnwindSectionRegularArray(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t functionOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_regular_second_level_entry, index, 
                              functionOffset)); 
  } 
  uint32_t encoding(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + 
        arrayoffsetof(unwind_info_regular_second_level_entry, index, encoding)); 
  } 
 
private: 
  A &_addressSpace; 
  typename A::pint_t _addr; 
}; 
 
template <typename A> class UnwindSectionCompressedPageHeader { 
public: 
  UnwindSectionCompressedPageHeader(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t kind() const { 
    return _addressSpace.get32( 
        _addr + 
        offsetof(unwind_info_compressed_second_level_page_header, kind)); 
  } 
  uint16_t entryPageOffset() const { 
    return _addressSpace.get16( 
        _addr + offsetof(unwind_info_compressed_second_level_page_header, 
                         entryPageOffset)); 
  } 
  uint16_t entryCount() const { 
    return _addressSpace.get16( 
        _addr + 
        offsetof(unwind_info_compressed_second_level_page_header, entryCount)); 
  } 
  uint16_t encodingsPageOffset() const { 
    return _addressSpace.get16( 
        _addr + offsetof(unwind_info_compressed_second_level_page_header, 
                         encodingsPageOffset)); 
  } 
  uint16_t encodingsCount() const { 
    return _addressSpace.get16( 
        _addr + offsetof(unwind_info_compressed_second_level_page_header, 
                         encodingsCount)); 
  } 
 
private: 
  A &_addressSpace; 
  typename A::pint_t _addr; 
}; 
 
template <typename A> class UnwindSectionCompressedArray { 
public: 
  UnwindSectionCompressedArray(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t functionOffset(uint32_t index) const { 
    return UNWIND_INFO_COMPRESSED_ENTRY_FUNC_OFFSET( 
        _addressSpace.get32(_addr + index * sizeof(uint32_t))); 
  } 
  uint16_t encodingIndex(uint32_t index) const { 
    return UNWIND_INFO_COMPRESSED_ENTRY_ENCODING_INDEX( 
        _addressSpace.get32(_addr + index * sizeof(uint32_t))); 
  } 
 
private: 
  A &_addressSpace; 
  typename A::pint_t _addr; 
}; 
 
template <typename A> class UnwindSectionLsdaArray { 
public: 
  UnwindSectionLsdaArray(A &addressSpace, typename A::pint_t addr) 
      : _addressSpace(addressSpace), _addr(addr) {} 
 
  uint32_t functionOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_section_header_lsda_index_entry, 
                              index, functionOffset)); 
  } 
  uint32_t lsdaOffset(uint32_t index) const { 
    return _addressSpace.get32( 
        _addr + arrayoffsetof(unwind_info_section_header_lsda_index_entry, 
                              index, lsdaOffset)); 
  } 
 
private: 
  A                   &_addressSpace; 
  typename A::pint_t   _addr; 
}; 
#endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
 
class _LIBUNWIND_HIDDEN AbstractUnwindCursor { 
public: 
  // NOTE: provide a class specific placement deallocation function (S5.3.4 p20) 
  // This avoids an unnecessary dependency to libc++abi. 
  void operator delete(void *, size_t) {} 
 
  virtual ~AbstractUnwindCursor() {} 
  virtual bool validReg(int) { _LIBUNWIND_ABORT("validReg not implemented"); } 
  virtual unw_word_t getReg(int) { _LIBUNWIND_ABORT("getReg not implemented"); } 
  virtual void setReg(int, unw_word_t) { 
    _LIBUNWIND_ABORT("setReg not implemented"); 
  } 
  virtual bool validFloatReg(int) { 
    _LIBUNWIND_ABORT("validFloatReg not implemented"); 
  } 
  virtual unw_fpreg_t getFloatReg(int) { 
    _LIBUNWIND_ABORT("getFloatReg not implemented"); 
  } 
  virtual void setFloatReg(int, unw_fpreg_t) { 
    _LIBUNWIND_ABORT("setFloatReg not implemented"); 
  } 
  virtual int step() { _LIBUNWIND_ABORT("step not implemented"); } 
  virtual void getInfo(unw_proc_info_t *) { 
    _LIBUNWIND_ABORT("getInfo not implemented"); 
  } 
  virtual void jumpto() { _LIBUNWIND_ABORT("jumpto not implemented"); } 
  virtual bool isSignalFrame() { 
    _LIBUNWIND_ABORT("isSignalFrame not implemented"); 
  } 
  virtual bool getFunctionName(char *, size_t, unw_word_t *) { 
    _LIBUNWIND_ABORT("getFunctionName not implemented"); 
  } 
  virtual void setInfoBasedOnIPRegister(bool = false) { 
    _LIBUNWIND_ABORT("setInfoBasedOnIPRegister not implemented"); 
  } 
  virtual const char *getRegisterName(int) { 
    _LIBUNWIND_ABORT("getRegisterName not implemented"); 
  } 
#ifdef __arm__ 
  virtual void saveVFPAsX() { _LIBUNWIND_ABORT("saveVFPAsX not implemented"); } 
#endif 

#if defined(_LIBUNWIND_USE_CET)
  virtual void *get_registers() {
    _LIBUNWIND_ABORT("get_registers not implemented");
  }
#endif
}; 
 
#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) && defined(_WIN32)

/// \c UnwindCursor contains all state (including all register values) during
/// an unwind.  This is normally stack-allocated inside a unw_cursor_t.
template <typename A, typename R>
class UnwindCursor : public AbstractUnwindCursor {
  typedef typename A::pint_t pint_t;
public:
                      UnwindCursor(unw_context_t *context, A &as);
                      UnwindCursor(CONTEXT *context, A &as);
                      UnwindCursor(A &as, void *threadArg);
  virtual             ~UnwindCursor() {}
  virtual bool        validReg(int);
  virtual unw_word_t  getReg(int);
  virtual void        setReg(int, unw_word_t);
  virtual bool        validFloatReg(int);
  virtual unw_fpreg_t getFloatReg(int);
  virtual void        setFloatReg(int, unw_fpreg_t);
  virtual int         step();
  virtual void        getInfo(unw_proc_info_t *);
  virtual void        jumpto();
  virtual bool        isSignalFrame();
  virtual bool        getFunctionName(char *buf, size_t len, unw_word_t *off);
  virtual void        setInfoBasedOnIPRegister(bool isReturnAddress = false);
  virtual const char *getRegisterName(int num);
#ifdef __arm__
  virtual void        saveVFPAsX();
#endif

  DISPATCHER_CONTEXT *getDispatcherContext() { return &_dispContext; }
  void setDispatcherContext(DISPATCHER_CONTEXT *disp) { _dispContext = *disp; }

  // libunwind does not and should not depend on C++ library which means that we
  // need our own defition of inline placement new.
  static void *operator new(size_t, UnwindCursor<A, R> *p) { return p; }

private:

  pint_t getLastPC() const { return _dispContext.ControlPc; }
  void setLastPC(pint_t pc) { _dispContext.ControlPc = pc; }
  RUNTIME_FUNCTION *lookUpSEHUnwindInfo(pint_t pc, pint_t *base) {
    _dispContext.FunctionEntry = RtlLookupFunctionEntry(pc,
                                                        &_dispContext.ImageBase,
                                                        _dispContext.HistoryTable);
    *base = _dispContext.ImageBase;
    return _dispContext.FunctionEntry;
  }
  bool getInfoFromSEH(pint_t pc);
  int stepWithSEHData() {
    _dispContext.LanguageHandler = RtlVirtualUnwind(UNW_FLAG_UHANDLER,
                                                    _dispContext.ImageBase,
                                                    _dispContext.ControlPc,
                                                    _dispContext.FunctionEntry,
                                                    _dispContext.ContextRecord,
                                                    &_dispContext.HandlerData,
                                                    &_dispContext.EstablisherFrame,
                                                    NULL);
    // Update some fields of the unwind info now, since we have them.
    _info.lsda = reinterpret_cast<unw_word_t>(_dispContext.HandlerData);
    if (_dispContext.LanguageHandler) {
      _info.handler = reinterpret_cast<unw_word_t>(__libunwind_seh_personality);
    } else
      _info.handler = 0;
    return UNW_STEP_SUCCESS;
  }

  A                   &_addressSpace;
  unw_proc_info_t      _info;
  DISPATCHER_CONTEXT   _dispContext;
  CONTEXT              _msContext;
  UNWIND_HISTORY_TABLE _histTable;
  bool                 _unwindInfoMissing;
};


template <typename A, typename R>
UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
    : _addressSpace(as), _unwindInfoMissing(false) {
  static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
                "UnwindCursor<> does not fit in unw_cursor_t");
  static_assert((alignof(UnwindCursor<A, R>) <= alignof(unw_cursor_t)),
                "UnwindCursor<> requires more alignment than unw_cursor_t");
  memset(&_info, 0, sizeof(_info));
  memset(&_histTable, 0, sizeof(_histTable));
  _dispContext.ContextRecord = &_msContext;
  _dispContext.HistoryTable = &_histTable;
  // Initialize MS context from ours.
  R r(context);
  _msContext.ContextFlags = CONTEXT_CONTROL|CONTEXT_INTEGER|CONTEXT_FLOATING_POINT;
#if defined(_LIBUNWIND_TARGET_X86_64)
  _msContext.Rax = r.getRegister(UNW_X86_64_RAX);
  _msContext.Rcx = r.getRegister(UNW_X86_64_RCX);
  _msContext.Rdx = r.getRegister(UNW_X86_64_RDX);
  _msContext.Rbx = r.getRegister(UNW_X86_64_RBX);
  _msContext.Rsp = r.getRegister(UNW_X86_64_RSP);
  _msContext.Rbp = r.getRegister(UNW_X86_64_RBP);
  _msContext.Rsi = r.getRegister(UNW_X86_64_RSI);
  _msContext.Rdi = r.getRegister(UNW_X86_64_RDI);
  _msContext.R8 = r.getRegister(UNW_X86_64_R8);
  _msContext.R9 = r.getRegister(UNW_X86_64_R9);
  _msContext.R10 = r.getRegister(UNW_X86_64_R10);
  _msContext.R11 = r.getRegister(UNW_X86_64_R11);
  _msContext.R12 = r.getRegister(UNW_X86_64_R12);
  _msContext.R13 = r.getRegister(UNW_X86_64_R13);
  _msContext.R14 = r.getRegister(UNW_X86_64_R14);
  _msContext.R15 = r.getRegister(UNW_X86_64_R15);
  _msContext.Rip = r.getRegister(UNW_REG_IP);
  union {
    v128 v;
    M128A m;
  } t;
  t.v = r.getVectorRegister(UNW_X86_64_XMM0);
  _msContext.Xmm0 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM1);
  _msContext.Xmm1 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM2);
  _msContext.Xmm2 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM3);
  _msContext.Xmm3 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM4);
  _msContext.Xmm4 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM5);
  _msContext.Xmm5 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM6);
  _msContext.Xmm6 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM7);
  _msContext.Xmm7 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM8);
  _msContext.Xmm8 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM9);
  _msContext.Xmm9 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM10);
  _msContext.Xmm10 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM11);
  _msContext.Xmm11 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM12);
  _msContext.Xmm12 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM13);
  _msContext.Xmm13 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM14);
  _msContext.Xmm14 = t.m;
  t.v = r.getVectorRegister(UNW_X86_64_XMM15);
  _msContext.Xmm15 = t.m;
#elif defined(_LIBUNWIND_TARGET_ARM)
  _msContext.R0 = r.getRegister(UNW_ARM_R0);
  _msContext.R1 = r.getRegister(UNW_ARM_R1);
  _msContext.R2 = r.getRegister(UNW_ARM_R2);
  _msContext.R3 = r.getRegister(UNW_ARM_R3);
  _msContext.R4 = r.getRegister(UNW_ARM_R4);
  _msContext.R5 = r.getRegister(UNW_ARM_R5);
  _msContext.R6 = r.getRegister(UNW_ARM_R6);
  _msContext.R7 = r.getRegister(UNW_ARM_R7);
  _msContext.R8 = r.getRegister(UNW_ARM_R8);
  _msContext.R9 = r.getRegister(UNW_ARM_R9);
  _msContext.R10 = r.getRegister(UNW_ARM_R10);
  _msContext.R11 = r.getRegister(UNW_ARM_R11);
  _msContext.R12 = r.getRegister(UNW_ARM_R12);
  _msContext.Sp = r.getRegister(UNW_ARM_SP);
  _msContext.Lr = r.getRegister(UNW_ARM_LR);
  _msContext.Pc = r.getRegister(UNW_ARM_IP);
  for (int i = UNW_ARM_D0; i <= UNW_ARM_D31; ++i) {
    union {
      uint64_t w;
      double d;
    } d;
    d.d = r.getFloatRegister(i);
    _msContext.D[i - UNW_ARM_D0] = d.w;
  }
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  for (int i = UNW_AARCH64_X0; i <= UNW_ARM64_X30; ++i)
    _msContext.X[i - UNW_AARCH64_X0] = r.getRegister(i);
  _msContext.Sp = r.getRegister(UNW_REG_SP);
  _msContext.Pc = r.getRegister(UNW_REG_IP);
  for (int i = UNW_AARCH64_V0; i <= UNW_ARM64_D31; ++i)
    _msContext.V[i - UNW_AARCH64_V0].D[0] = r.getFloatRegister(i);
#endif
}

template <typename A, typename R>
UnwindCursor<A, R>::UnwindCursor(CONTEXT *context, A &as)
    : _addressSpace(as), _unwindInfoMissing(false) {
  static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
                "UnwindCursor<> does not fit in unw_cursor_t");
  memset(&_info, 0, sizeof(_info));
  memset(&_histTable, 0, sizeof(_histTable));
  _dispContext.ContextRecord = &_msContext;
  _dispContext.HistoryTable = &_histTable;
  _msContext = *context;
}


template <typename A, typename R>
bool UnwindCursor<A, R>::validReg(int regNum) {
  if (regNum == UNW_REG_IP || regNum == UNW_REG_SP) return true;
#if defined(_LIBUNWIND_TARGET_X86_64)
  if (regNum >= UNW_X86_64_RAX && regNum <= UNW_X86_64_R15) return true;
#elif defined(_LIBUNWIND_TARGET_ARM)
  if ((regNum >= UNW_ARM_R0 && regNum <= UNW_ARM_R15) ||
      regNum == UNW_ARM_RA_AUTH_CODE)
    return true;
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  if (regNum >= UNW_AARCH64_X0 && regNum <= UNW_ARM64_X30) return true;
#endif
  return false;
}

template <typename A, typename R>
unw_word_t UnwindCursor<A, R>::getReg(int regNum) {
  switch (regNum) {
#if defined(_LIBUNWIND_TARGET_X86_64)
  case UNW_REG_IP: return _msContext.Rip;
  case UNW_X86_64_RAX: return _msContext.Rax;
  case UNW_X86_64_RDX: return _msContext.Rdx;
  case UNW_X86_64_RCX: return _msContext.Rcx;
  case UNW_X86_64_RBX: return _msContext.Rbx;
  case UNW_REG_SP:
  case UNW_X86_64_RSP: return _msContext.Rsp;
  case UNW_X86_64_RBP: return _msContext.Rbp;
  case UNW_X86_64_RSI: return _msContext.Rsi;
  case UNW_X86_64_RDI: return _msContext.Rdi;
  case UNW_X86_64_R8: return _msContext.R8;
  case UNW_X86_64_R9: return _msContext.R9;
  case UNW_X86_64_R10: return _msContext.R10;
  case UNW_X86_64_R11: return _msContext.R11;
  case UNW_X86_64_R12: return _msContext.R12;
  case UNW_X86_64_R13: return _msContext.R13;
  case UNW_X86_64_R14: return _msContext.R14;
  case UNW_X86_64_R15: return _msContext.R15;
#elif defined(_LIBUNWIND_TARGET_ARM)
  case UNW_ARM_R0: return _msContext.R0;
  case UNW_ARM_R1: return _msContext.R1;
  case UNW_ARM_R2: return _msContext.R2;
  case UNW_ARM_R3: return _msContext.R3;
  case UNW_ARM_R4: return _msContext.R4;
  case UNW_ARM_R5: return _msContext.R5;
  case UNW_ARM_R6: return _msContext.R6;
  case UNW_ARM_R7: return _msContext.R7;
  case UNW_ARM_R8: return _msContext.R8;
  case UNW_ARM_R9: return _msContext.R9;
  case UNW_ARM_R10: return _msContext.R10;
  case UNW_ARM_R11: return _msContext.R11;
  case UNW_ARM_R12: return _msContext.R12;
  case UNW_REG_SP:
  case UNW_ARM_SP: return _msContext.Sp;
  case UNW_ARM_LR: return _msContext.Lr;
  case UNW_REG_IP:
  case UNW_ARM_IP: return _msContext.Pc;
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  case UNW_REG_SP: return _msContext.Sp;
  case UNW_REG_IP: return _msContext.Pc;
  default: return _msContext.X[regNum - UNW_AARCH64_X0];
#endif
  }
  _LIBUNWIND_ABORT("unsupported register");
}

template <typename A, typename R>
void UnwindCursor<A, R>::setReg(int regNum, unw_word_t value) {
  switch (regNum) {
#if defined(_LIBUNWIND_TARGET_X86_64)
  case UNW_REG_IP: _msContext.Rip = value; break;
  case UNW_X86_64_RAX: _msContext.Rax = value; break;
  case UNW_X86_64_RDX: _msContext.Rdx = value; break;
  case UNW_X86_64_RCX: _msContext.Rcx = value; break;
  case UNW_X86_64_RBX: _msContext.Rbx = value; break;
  case UNW_REG_SP:
  case UNW_X86_64_RSP: _msContext.Rsp = value; break;
  case UNW_X86_64_RBP: _msContext.Rbp = value; break;
  case UNW_X86_64_RSI: _msContext.Rsi = value; break;
  case UNW_X86_64_RDI: _msContext.Rdi = value; break;
  case UNW_X86_64_R8: _msContext.R8 = value; break;
  case UNW_X86_64_R9: _msContext.R9 = value; break;
  case UNW_X86_64_R10: _msContext.R10 = value; break;
  case UNW_X86_64_R11: _msContext.R11 = value; break;
  case UNW_X86_64_R12: _msContext.R12 = value; break;
  case UNW_X86_64_R13: _msContext.R13 = value; break;
  case UNW_X86_64_R14: _msContext.R14 = value; break;
  case UNW_X86_64_R15: _msContext.R15 = value; break;
#elif defined(_LIBUNWIND_TARGET_ARM)
  case UNW_ARM_R0: _msContext.R0 = value; break;
  case UNW_ARM_R1: _msContext.R1 = value; break;
  case UNW_ARM_R2: _msContext.R2 = value; break;
  case UNW_ARM_R3: _msContext.R3 = value; break;
  case UNW_ARM_R4: _msContext.R4 = value; break;
  case UNW_ARM_R5: _msContext.R5 = value; break;
  case UNW_ARM_R6: _msContext.R6 = value; break;
  case UNW_ARM_R7: _msContext.R7 = value; break;
  case UNW_ARM_R8: _msContext.R8 = value; break;
  case UNW_ARM_R9: _msContext.R9 = value; break;
  case UNW_ARM_R10: _msContext.R10 = value; break;
  case UNW_ARM_R11: _msContext.R11 = value; break;
  case UNW_ARM_R12: _msContext.R12 = value; break;
  case UNW_REG_SP:
  case UNW_ARM_SP: _msContext.Sp = value; break;
  case UNW_ARM_LR: _msContext.Lr = value; break;
  case UNW_REG_IP:
  case UNW_ARM_IP: _msContext.Pc = value; break;
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  case UNW_REG_SP: _msContext.Sp = value; break;
  case UNW_REG_IP: _msContext.Pc = value; break;
  case UNW_AARCH64_X0:
  case UNW_AARCH64_X1:
  case UNW_AARCH64_X2:
  case UNW_AARCH64_X3:
  case UNW_AARCH64_X4:
  case UNW_AARCH64_X5:
  case UNW_AARCH64_X6:
  case UNW_AARCH64_X7:
  case UNW_AARCH64_X8:
  case UNW_AARCH64_X9:
  case UNW_AARCH64_X10:
  case UNW_AARCH64_X11:
  case UNW_AARCH64_X12:
  case UNW_AARCH64_X13:
  case UNW_AARCH64_X14:
  case UNW_AARCH64_X15:
  case UNW_AARCH64_X16:
  case UNW_AARCH64_X17:
  case UNW_AARCH64_X18:
  case UNW_AARCH64_X19:
  case UNW_AARCH64_X20:
  case UNW_AARCH64_X21:
  case UNW_AARCH64_X22:
  case UNW_AARCH64_X23:
  case UNW_AARCH64_X24:
  case UNW_AARCH64_X25:
  case UNW_AARCH64_X26:
  case UNW_AARCH64_X27:
  case UNW_AARCH64_X28:
  case UNW_AARCH64_FP:
  case UNW_AARCH64_LR: _msContext.X[regNum - UNW_ARM64_X0] = value; break;
#endif
  default:
    _LIBUNWIND_ABORT("unsupported register");
  }
}

template <typename A, typename R>
bool UnwindCursor<A, R>::validFloatReg(int regNum) {
#if defined(_LIBUNWIND_TARGET_ARM)
  if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) return true;
  if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) return true;
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  if (regNum >= UNW_AARCH64_V0 && regNum <= UNW_ARM64_D31) return true;
#else
  (void)regNum;
#endif
  return false;
}

template <typename A, typename R>
unw_fpreg_t UnwindCursor<A, R>::getFloatReg(int regNum) {
#if defined(_LIBUNWIND_TARGET_ARM)
  if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) {
    union {
      uint32_t w;
      float f;
    } d;
    d.w = _msContext.S[regNum - UNW_ARM_S0];
    return d.f;
  }
  if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) {
    union {
      uint64_t w;
      double d;
    } d;
    d.w = _msContext.D[regNum - UNW_ARM_D0];
    return d.d;
  }
  _LIBUNWIND_ABORT("unsupported float register");
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  return _msContext.V[regNum - UNW_AARCH64_V0].D[0];
#else
  (void)regNum;
  _LIBUNWIND_ABORT("float registers unimplemented");
#endif
}

template <typename A, typename R>
void UnwindCursor<A, R>::setFloatReg(int regNum, unw_fpreg_t value) {
#if defined(_LIBUNWIND_TARGET_ARM)
  if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) {
    union {
      uint32_t w;
      float f;
    } d;
    d.f = value;
    _msContext.S[regNum - UNW_ARM_S0] = d.w;
  }
  if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) {
    union {
      uint64_t w;
      double d;
    } d;
    d.d = value;
    _msContext.D[regNum - UNW_ARM_D0] = d.w;
  }
  _LIBUNWIND_ABORT("unsupported float register");
#elif defined(_LIBUNWIND_TARGET_AARCH64)
  _msContext.V[regNum - UNW_AARCH64_V0].D[0] = value;
#else
  (void)regNum;
  (void)value;
  _LIBUNWIND_ABORT("float registers unimplemented");
#endif
}

template <typename A, typename R> void UnwindCursor<A, R>::jumpto() {
  RtlRestoreContext(&_msContext, nullptr);
}

#ifdef __arm__
template <typename A, typename R> void UnwindCursor<A, R>::saveVFPAsX() {}
#endif

template <typename A, typename R>
const char *UnwindCursor<A, R>::getRegisterName(int regNum) {
  return R::getRegisterName(regNum);
}

template <typename A, typename R> bool UnwindCursor<A, R>::isSignalFrame() {
  return false;
}

#else  // !defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) || !defined(_WIN32)

/// UnwindCursor contains all state (including all register values) during 
/// an unwind.  This is normally stack allocated inside a unw_cursor_t. 
template <typename A, typename R> 
class UnwindCursor : public AbstractUnwindCursor{ 
  typedef typename A::pint_t pint_t; 
public: 
                      UnwindCursor(unw_context_t *context, A &as); 
                      UnwindCursor(A &as, void *threadArg); 
  virtual             ~UnwindCursor() {} 
  virtual bool        validReg(int); 
  virtual unw_word_t  getReg(int); 
  virtual void        setReg(int, unw_word_t); 
  virtual bool        validFloatReg(int); 
  virtual unw_fpreg_t getFloatReg(int); 
  virtual void        setFloatReg(int, unw_fpreg_t); 
  virtual int         step(); 
  virtual void        getInfo(unw_proc_info_t *); 
  virtual void        jumpto(); 
  virtual bool        isSignalFrame(); 
  virtual bool        getFunctionName(char *buf, size_t len, unw_word_t *off); 
  virtual void        setInfoBasedOnIPRegister(bool isReturnAddress = false); 
  virtual const char *getRegisterName(int num); 
#ifdef __arm__ 
  virtual void        saveVFPAsX(); 
#endif 
 
#if defined(_LIBUNWIND_USE_CET)
  virtual void *get_registers() { return &_registers; }
#endif
  // libunwind does not and should not depend on C++ library which means that we
  // need our own defition of inline placement new.
  static void *operator new(size_t, UnwindCursor<A, R> *p) { return p; }

private: 
 
#if defined(_LIBUNWIND_ARM_EHABI)
  bool getInfoFromEHABISection(pint_t pc, const UnwindInfoSections &sects); 
 
  int stepWithEHABI() { 
    size_t len = 0; 
    size_t off = 0; 
    // FIXME: Calling decode_eht_entry() here is violating the libunwind 
    // abstraction layer. 
    const uint32_t *ehtp = 
        decode_eht_entry(reinterpret_cast<const uint32_t *>(_info.unwind_info), 
                         &off, &len); 
    if (_Unwind_VRS_Interpret((_Unwind_Context *)this, ehtp, off, len) != 
            _URC_CONTINUE_UNWIND) 
      return UNW_STEP_END; 
    return UNW_STEP_SUCCESS; 
  } 
#endif 
 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
  bool setInfoForSigReturn() {
    R dummy;
    return setInfoForSigReturn(dummy);
  }
  int stepThroughSigReturn() {
    R dummy;
    return stepThroughSigReturn(dummy);
  }
  bool setInfoForSigReturn(Registers_arm64 &);
  int stepThroughSigReturn(Registers_arm64 &);
  template <typename Registers> bool setInfoForSigReturn(Registers &) {
    return false;
  }
  template <typename Registers> int stepThroughSigReturn(Registers &) {
    return UNW_STEP_END;
  }
#endif

#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  bool getInfoFromFdeCie(const typename CFI_Parser<A>::FDE_Info &fdeInfo,
                         const typename CFI_Parser<A>::CIE_Info &cieInfo,
                         pint_t pc, uintptr_t dso_base);
  bool getInfoFromDwarfSection(pint_t pc, const UnwindInfoSections &sects, 
                                            uint32_t fdeSectionOffsetHint=0); 
  int stepWithDwarfFDE() { 
    return DwarfInstructions<A, R>::stepWithDwarf(_addressSpace, 
                                              (pint_t)this->getReg(UNW_REG_IP), 
                                              (pint_t)_info.unwind_info, 
                                              _registers, _isSignalFrame);
  } 
#endif 
 
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
  bool getInfoFromCompactEncodingSection(pint_t pc, 
                                            const UnwindInfoSections &sects); 
  int stepWithCompactEncoding() { 
  #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
    if ( compactSaysUseDwarf() ) 
      return stepWithDwarfFDE(); 
  #endif 
    R dummy; 
    return stepWithCompactEncoding(dummy); 
  } 
 
#if defined(_LIBUNWIND_TARGET_X86_64)
  int stepWithCompactEncoding(Registers_x86_64 &) { 
    return CompactUnwinder_x86_64<A>::stepWithCompactEncoding( 
        _info.format, _info.start_ip, _addressSpace, _registers); 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_I386)
  int stepWithCompactEncoding(Registers_x86 &) { 
    return CompactUnwinder_x86<A>::stepWithCompactEncoding( 
        _info.format, (uint32_t)_info.start_ip, _addressSpace, _registers); 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC)
  int stepWithCompactEncoding(Registers_ppc &) { 
    return UNW_EINVAL; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC64)
  int stepWithCompactEncoding(Registers_ppc64 &) {
    return UNW_EINVAL;
  }
#endif


#if defined(_LIBUNWIND_TARGET_AARCH64)
  int stepWithCompactEncoding(Registers_arm64 &) { 
    return CompactUnwinder_arm64<A>::stepWithCompactEncoding( 
        _info.format, _info.start_ip, _addressSpace, _registers); 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_MIPS_O32)
  int stepWithCompactEncoding(Registers_mips_o32 &) {
    return UNW_EINVAL;
  }
#endif

#if defined(_LIBUNWIND_TARGET_MIPS_NEWABI)
  int stepWithCompactEncoding(Registers_mips_newabi &) {
    return UNW_EINVAL;
  }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC)
  int stepWithCompactEncoding(Registers_sparc &) { return UNW_EINVAL; }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC64)
  int stepWithCompactEncoding(Registers_sparc64 &) { return UNW_EINVAL; }
#endif

#if defined (_LIBUNWIND_TARGET_RISCV)
  int stepWithCompactEncoding(Registers_riscv &) {
    return UNW_EINVAL;
  }
#endif

  bool compactSaysUseDwarf(uint32_t *offset=NULL) const { 
    R dummy; 
    return compactSaysUseDwarf(dummy, offset); 
  } 
 
#if defined(_LIBUNWIND_TARGET_X86_64)
  bool compactSaysUseDwarf(Registers_x86_64 &, uint32_t *offset) const { 
    if ((_info.format & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_DWARF) { 
      if (offset) 
        *offset = (_info.format & UNWIND_X86_64_DWARF_SECTION_OFFSET); 
      return true; 
    } 
    return false; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_I386)
  bool compactSaysUseDwarf(Registers_x86 &, uint32_t *offset) const { 
    if ((_info.format & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF) { 
      if (offset) 
        *offset = (_info.format & UNWIND_X86_DWARF_SECTION_OFFSET); 
      return true; 
    } 
    return false; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC)
  bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const { 
    return true; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC64)
  bool compactSaysUseDwarf(Registers_ppc64 &, uint32_t *) const {
    return true;
  }
#endif

#if defined(_LIBUNWIND_TARGET_AARCH64)
  bool compactSaysUseDwarf(Registers_arm64 &, uint32_t *offset) const { 
    if ((_info.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF) { 
      if (offset) 
        *offset = (_info.format & UNWIND_ARM64_DWARF_SECTION_OFFSET); 
      return true; 
    } 
    return false; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_MIPS_O32)
  bool compactSaysUseDwarf(Registers_mips_o32 &, uint32_t *) const {
    return true;
  }
#endif

#if defined(_LIBUNWIND_TARGET_MIPS_NEWABI)
  bool compactSaysUseDwarf(Registers_mips_newabi &, uint32_t *) const {
    return true;
  }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC)
  bool compactSaysUseDwarf(Registers_sparc &, uint32_t *) const { return true; }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC64)
  bool compactSaysUseDwarf(Registers_sparc64 &, uint32_t *) const {
    return true;
  }
#endif

#if defined (_LIBUNWIND_TARGET_RISCV)
  bool compactSaysUseDwarf(Registers_riscv &, uint32_t *) const {
    return true;
  }
#endif

#endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)

#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  compact_unwind_encoding_t dwarfEncoding() const { 
    R dummy; 
    return dwarfEncoding(dummy); 
  } 
 
#if defined(_LIBUNWIND_TARGET_X86_64)
  compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const { 
    return UNWIND_X86_64_MODE_DWARF; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_I386)
  compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const { 
    return UNWIND_X86_MODE_DWARF; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC)
  compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const { 
    return 0; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_PPC64)
  compact_unwind_encoding_t dwarfEncoding(Registers_ppc64 &) const {
    return 0;
  }
#endif

#if defined(_LIBUNWIND_TARGET_AARCH64)
  compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const { 
    return UNWIND_ARM64_MODE_DWARF; 
  } 
#endif
 
#if defined(_LIBUNWIND_TARGET_ARM)
  compact_unwind_encoding_t dwarfEncoding(Registers_arm &) const {
    return 0;
  }
#endif

#if defined (_LIBUNWIND_TARGET_OR1K)
  compact_unwind_encoding_t dwarfEncoding(Registers_or1k &) const { 
    return 0; 
  } 
#endif
 
#if defined (_LIBUNWIND_TARGET_HEXAGON)
  compact_unwind_encoding_t dwarfEncoding(Registers_hexagon &) const {
    return 0;
  }
#endif

#if defined (_LIBUNWIND_TARGET_MIPS_O32)
  compact_unwind_encoding_t dwarfEncoding(Registers_mips_o32 &) const {
    return 0;
  }
#endif
 
#if defined (_LIBUNWIND_TARGET_MIPS_NEWABI)
  compact_unwind_encoding_t dwarfEncoding(Registers_mips_newabi &) const {
    return 0;
  }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC)
  compact_unwind_encoding_t dwarfEncoding(Registers_sparc &) const { return 0; }
#endif

#if defined(_LIBUNWIND_TARGET_SPARC64)
  compact_unwind_encoding_t dwarfEncoding(Registers_sparc64 &) const {
    return 0;
  }
#endif

#if defined (_LIBUNWIND_TARGET_RISCV)
  compact_unwind_encoding_t dwarfEncoding(Registers_riscv &) const {
    return 0;
  }
#endif

#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
  // For runtime environments using SEH unwind data without Windows runtime
  // support.
  pint_t getLastPC() const { /* FIXME: Implement */ return 0; }
  void setLastPC(pint_t pc) { /* FIXME: Implement */ }
  RUNTIME_FUNCTION *lookUpSEHUnwindInfo(pint_t pc, pint_t *base) {
    /* FIXME: Implement */
    *base = 0;
    return nullptr;
  }
  bool getInfoFromSEH(pint_t pc);
  int stepWithSEHData() { /* FIXME: Implement */ return 0; }
#endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)


  A               &_addressSpace; 
  R                _registers; 
  unw_proc_info_t  _info; 
  bool             _unwindInfoMissing; 
  bool             _isSignalFrame; 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
  bool             _isSigReturn = false;
#endif
}; 
 
 
template <typename A, typename R> 
UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as) 
    : _addressSpace(as), _registers(context), _unwindInfoMissing(false), 
      _isSignalFrame(false) { 
  static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
                "UnwindCursor<> does not fit in unw_cursor_t"); 
  static_assert((alignof(UnwindCursor<A, R>) <= alignof(unw_cursor_t)),
                "UnwindCursor<> requires more alignment than unw_cursor_t");
  memset(&_info, 0, sizeof(_info)); 
} 
 
template <typename A, typename R> 
UnwindCursor<A, R>::UnwindCursor(A &as, void *) 
    : _addressSpace(as), _unwindInfoMissing(false), _isSignalFrame(false) { 
  memset(&_info, 0, sizeof(_info)); 
  // FIXME 
  // fill in _registers from thread arg 
} 
 
 
template <typename A, typename R> 
bool UnwindCursor<A, R>::validReg(int regNum) { 
  return _registers.validRegister(regNum); 
} 
 
template <typename A, typename R> 
unw_word_t UnwindCursor<A, R>::getReg(int regNum) { 
  return _registers.getRegister(regNum); 
} 
 
template <typename A, typename R> 
void UnwindCursor<A, R>::setReg(int regNum, unw_word_t value) { 
  _registers.setRegister(regNum, (typename A::pint_t)value); 
} 
 
template <typename A, typename R> 
bool UnwindCursor<A, R>::validFloatReg(int regNum) { 
  return _registers.validFloatRegister(regNum); 
} 
 
template <typename A, typename R> 
unw_fpreg_t UnwindCursor<A, R>::getFloatReg(int regNum) { 
  return _registers.getFloatRegister(regNum); 
} 
 
template <typename A, typename R> 
void UnwindCursor<A, R>::setFloatReg(int regNum, unw_fpreg_t value) { 
  _registers.setFloatRegister(regNum, value); 
} 
 
template <typename A, typename R> void UnwindCursor<A, R>::jumpto() { 
  _registers.jumpto(); 
} 
 
#ifdef __arm__ 
template <typename A, typename R> void UnwindCursor<A, R>::saveVFPAsX() { 
  _registers.saveVFPAsX(); 
} 
#endif 
 
template <typename A, typename R> 
const char *UnwindCursor<A, R>::getRegisterName(int regNum) { 
  return _registers.getRegisterName(regNum); 
} 
 
template <typename A, typename R> bool UnwindCursor<A, R>::isSignalFrame() { 
  return _isSignalFrame; 
} 
 
#endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)

#if defined(_LIBUNWIND_ARM_EHABI)
template<typename A> 
struct EHABISectionIterator { 
  typedef EHABISectionIterator _Self; 
 
  typedef typename A::pint_t value_type; 
  typedef typename A::pint_t* pointer; 
  typedef typename A::pint_t& reference; 
  typedef size_t size_type; 
  typedef size_t difference_type; 
 
  static _Self begin(A& addressSpace, const UnwindInfoSections& sects) { 
    return _Self(addressSpace, sects, 0); 
  } 
  static _Self end(A& addressSpace, const UnwindInfoSections& sects) { 
    return _Self(addressSpace, sects,
                 sects.arm_section_length / sizeof(EHABIIndexEntry));
  } 
 
  EHABISectionIterator(A& addressSpace, const UnwindInfoSections& sects, size_t i) 
      : _i(i), _addressSpace(&addressSpace), _sects(&sects) {} 
 
  _Self& operator++() { ++_i; return *this; } 
  _Self& operator+=(size_t a) { _i += a; return *this; } 
  _Self& operator--() { assert(_i > 0); --_i; return *this; } 
  _Self& operator-=(size_t a) { assert(_i >= a); _i -= a; return *this; } 
 
  _Self operator+(size_t a) { _Self out = *this; out._i += a; return out; } 
  _Self operator-(size_t a) { assert(_i >= a); _Self out = *this; out._i -= a; return out; } 
 
  size_t operator-(const _Self& other) const { return _i - other._i; }
 
  bool operator==(const _Self& other) const { 
    assert(_addressSpace == other._addressSpace); 
    assert(_sects == other._sects); 
    return _i == other._i; 
  } 
 
  bool operator!=(const _Self& other) const {
    assert(_addressSpace == other._addressSpace);
    assert(_sects == other._sects);
    return _i != other._i;
  }

  typename A::pint_t operator*() const { return functionAddress(); } 
 
  typename A::pint_t functionAddress() const { 
    typename A::pint_t indexAddr = _sects->arm_section + arrayoffsetof( 
        EHABIIndexEntry, _i, functionOffset); 
    return indexAddr + signExtendPrel31(_addressSpace->get32(indexAddr)); 
  } 
 
  typename A::pint_t dataAddress() { 
    typename A::pint_t indexAddr = _sects->arm_section + arrayoffsetof( 
        EHABIIndexEntry, _i, data); 
    return indexAddr; 
  } 
 
 private: 
  size_t _i; 
  A* _addressSpace; 
  const UnwindInfoSections* _sects; 
}; 
 
namespace {

template <typename A>
EHABISectionIterator<A> EHABISectionUpperBound(
    EHABISectionIterator<A> first,
    EHABISectionIterator<A> last,
    typename A::pint_t value) {
  size_t len = last - first;
  while (len > 0) {
    size_t l2 = len / 2;
    EHABISectionIterator<A> m = first + l2;
    if (value < *m) {
        len = l2;
    } else {
        first = ++m;
        len -= l2 + 1;
    }
  }
  return first;
}

}

template <typename A, typename R> 
bool UnwindCursor<A, R>::getInfoFromEHABISection( 
    pint_t pc, 
    const UnwindInfoSections &sects) { 
  EHABISectionIterator<A> begin = 
      EHABISectionIterator<A>::begin(_addressSpace, sects); 
  EHABISectionIterator<A> end = 
      EHABISectionIterator<A>::end(_addressSpace, sects); 
  if (begin == end)
    return false;
 
  EHABISectionIterator<A> itNextPC = EHABISectionUpperBound(begin, end, pc);
  if (itNextPC == begin)
    return false; 
  EHABISectionIterator<A> itThisPC = itNextPC - 1; 
 
  pint_t thisPC = itThisPC.functionAddress(); 
  // If an exception is thrown from a function, corresponding to the last entry
  // in the table, we don't really know the function extent and have to choose a
  // value for nextPC. Choosing max() will allow the range check during trace to
  // succeed.
  pint_t nextPC = (itNextPC == end) ? UINTPTR_MAX : itNextPC.functionAddress();
  pint_t indexDataAddr = itThisPC.dataAddress(); 
 
  if (indexDataAddr == 0) 
    return false; 
 
  uint32_t indexData = _addressSpace.get32(indexDataAddr); 
  if (indexData == UNW_EXIDX_CANTUNWIND) 
    return false; 
 
  // If the high bit is set, the exception handling table entry is inline inside 
  // the index table entry on the second word (aka |indexDataAddr|). Otherwise, 
  // the table points at an offset in the exception handling table (section 5
  // EHABI).
  pint_t exceptionTableAddr; 
  uint32_t exceptionTableData; 
  bool isSingleWordEHT; 
  if (indexData & 0x80000000) { 
    exceptionTableAddr = indexDataAddr; 
    // TODO(ajwong): Should this data be 0? 
    exceptionTableData = indexData; 
    isSingleWordEHT = true; 
  } else { 
    exceptionTableAddr = indexDataAddr + signExtendPrel31(indexData); 
    exceptionTableData = _addressSpace.get32(exceptionTableAddr); 
    isSingleWordEHT = false; 
  } 
 
  // Now we know the 3 things: 
  //   exceptionTableAddr -- exception handler table entry. 
  //   exceptionTableData -- the data inside the first word of the eht entry. 
  //   isSingleWordEHT -- whether the entry is in the index. 
  unw_word_t personalityRoutine = 0xbadf00d; 
  bool scope32 = false; 
  uintptr_t lsda; 
 
  // If the high bit in the exception handling table entry is set, the entry is 
  // in compact form (section 6.3 EHABI). 
  if (exceptionTableData & 0x80000000) { 
    // Grab the index of the personality routine from the compact form. 
    uint32_t choice = (exceptionTableData & 0x0f000000) >> 24; 
    uint32_t extraWords = 0; 
    switch (choice) { 
      case 0: 
        personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr0; 
        extraWords = 0; 
        scope32 = false; 
        lsda = isSingleWordEHT ? 0 : (exceptionTableAddr + 4); 
        break; 
      case 1: 
        personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr1; 
        extraWords = (exceptionTableData & 0x00ff0000) >> 16; 
        scope32 = false; 
        lsda = exceptionTableAddr + (extraWords + 1) * 4; 
        break; 
      case 2: 
        personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr2; 
        extraWords = (exceptionTableData & 0x00ff0000) >> 16; 
        scope32 = true; 
        lsda = exceptionTableAddr + (extraWords + 1) * 4; 
        break; 
      default: 
        _LIBUNWIND_ABORT("unknown personality routine"); 
        return false; 
    } 
 
    if (isSingleWordEHT) { 
      if (extraWords != 0) { 
        _LIBUNWIND_ABORT("index inlined table detected but pr function " 
                         "requires extra words"); 
        return false; 
      } 
    } 
  } else { 
    pint_t personalityAddr = 
        exceptionTableAddr + signExtendPrel31(exceptionTableData); 
    personalityRoutine = personalityAddr; 
 
    // ARM EHABI # 6.2, # 9.2 
    // 
    //  +---- ehtp 
    //  v 
    // +--------------------------------------+ 
    // | +--------+--------+--------+-------+ | 
    // | |0| prel31 to personalityRoutine   | | 
    // | +--------+--------+--------+-------+ | 
    // | |      N |      unwind opcodes     | |  <-- UnwindData 
    // | +--------+--------+--------+-------+ | 
    // | | Word 2        unwind opcodes     | | 
    // | +--------+--------+--------+-------+ | 
    // | ...                                  | 
    // | +--------+--------+--------+-------+ | 
    // | | Word N        unwind opcodes     | | 
    // | +--------+--------+--------+-------+ | 
    // | | LSDA                             | |  <-- lsda 
    // | | ...                              | | 
    // | +--------+--------+--------+-------+ | 
    // +--------------------------------------+ 
 
    uint32_t *UnwindData = reinterpret_cast<uint32_t*>(exceptionTableAddr) + 1; 
    uint32_t FirstDataWord = *UnwindData; 
    size_t N = ((FirstDataWord >> 24) & 0xff); 
    size_t NDataWords = N + 1; 
    lsda = reinterpret_cast<uintptr_t>(UnwindData + NDataWords); 
  } 
 
  _info.start_ip = thisPC; 
  _info.end_ip = nextPC; 
  _info.handler = personalityRoutine; 
  _info.unwind_info = exceptionTableAddr; 
  _info.lsda = lsda; 
  // flags is pr_cache.additional. See EHABI #7.2 for definition of bit 0. 
  _info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?
 
  return true; 
} 
#endif 
 
#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
template <typename A, typename R> 
bool UnwindCursor<A, R>::getInfoFromFdeCie(
    const typename CFI_Parser<A>::FDE_Info &fdeInfo,
    const typename CFI_Parser<A>::CIE_Info &cieInfo, pint_t pc,
    uintptr_t dso_base) {
  typename CFI_Parser<A>::PrologInfo prolog;
  if (CFI_Parser<A>::parseFDEInstructions(_addressSpace, fdeInfo, cieInfo, pc,
                                          R::getArch(), &prolog)) {
    // Save off parsed FDE info
    _info.start_ip          = fdeInfo.pcStart;
    _info.end_ip            = fdeInfo.pcEnd;
    _info.lsda              = fdeInfo.lsda;
    _info.handler           = cieInfo.personality;
    // Some frameless functions need SP altered when resuming in function, so
    // propagate spExtraArgSize.
    _info.gp                = prolog.spExtraArgSize;
    _info.flags             = 0;
    _info.format            = dwarfEncoding();
    _info.unwind_info       = fdeInfo.fdeStart;
    _info.unwind_info_size  = static_cast<uint32_t>(fdeInfo.fdeLength);
    _info.extra             = static_cast<unw_word_t>(dso_base);
    return true;
  }
  return false;
}

template <typename A, typename R>
bool UnwindCursor<A, R>::getInfoFromDwarfSection(pint_t pc, 
                                                const UnwindInfoSections &sects, 
                                                uint32_t fdeSectionOffsetHint) { 
  typename CFI_Parser<A>::FDE_Info fdeInfo; 
  typename CFI_Parser<A>::CIE_Info cieInfo; 
  bool foundFDE = false; 
  bool foundInCache = false; 
  // If compact encoding table gave offset into dwarf section, go directly there 
  if (fdeSectionOffsetHint != 0) { 
    foundFDE = CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section, 
                                    sects.dwarf_section_length,
                                    sects.dwarf_section + fdeSectionOffsetHint, 
                                    &fdeInfo, &cieInfo); 
  } 
#if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
  if (!foundFDE && (sects.dwarf_index_section != 0)) { 
    foundFDE = EHHeaderParser<A>::findFDE( 
        _addressSpace, pc, sects.dwarf_index_section, 
        (uint32_t)sects.dwarf_index_section_length, &fdeInfo, &cieInfo); 
  } 
#endif 
  if (!foundFDE) { 
    // otherwise, search cache of previously found FDEs. 
    pint_t cachedFDE = DwarfFDECache<A>::findFDE(sects.dso_base, pc); 
    if (cachedFDE != 0) { 
      foundFDE = 
          CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section, 
                                 sects.dwarf_section_length,
                                 cachedFDE, &fdeInfo, &cieInfo); 
      foundInCache = foundFDE; 
    } 
  } 
  if (!foundFDE) { 
    // Still not found, do full scan of __eh_frame section. 
    foundFDE = CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section, 
                                      sects.dwarf_section_length, 0,
                                      &fdeInfo, &cieInfo); 
  } 
  if (foundFDE) { 
    if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, sects.dso_base)) {
      // Add to cache (to make next lookup faster) if we had no hint 
      // and there was no index. 
      if (!foundInCache && (fdeSectionOffsetHint == 0)) { 
  #if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
        if (sects.dwarf_index_section == 0) 
  #endif 
        DwarfFDECache<A>::add(sects.dso_base, fdeInfo.pcStart, fdeInfo.pcEnd, 
                              fdeInfo.fdeStart); 
      } 
      return true; 
    } 
  } 
  //_LIBUNWIND_DEBUG_LOG("can't find/use FDE for pc=0x%llX", (uint64_t)pc);
  return false; 
} 
#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
 
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
template <typename A, typename R> 
bool UnwindCursor<A, R>::getInfoFromCompactEncodingSection(pint_t pc, 
                                              const UnwindInfoSections &sects) { 
  const bool log = false; 
  if (log) 
    fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX, mh=0x%llX)\n", 
            (uint64_t)pc, (uint64_t)sects.dso_base); 
 
  const UnwindSectionHeader<A> sectionHeader(_addressSpace, 
                                                sects.compact_unwind_section); 
  if (sectionHeader.version() != UNWIND_SECTION_VERSION) 
    return false; 
 
  // do a binary search of top level index to find page with unwind info 
  pint_t targetFunctionOffset = pc - sects.dso_base; 
  const UnwindSectionIndexArray<A> topIndex(_addressSpace, 
                                           sects.compact_unwind_section 
                                         + sectionHeader.indexSectionOffset()); 
  uint32_t low = 0; 
  uint32_t high = sectionHeader.indexCount(); 
  uint32_t last = high - 1; 
  while (low < high) { 
    uint32_t mid = (low + high) / 2; 
    //if ( log ) fprintf(stderr, "\tmid=%d, low=%d, high=%d, *mid=0x%08X\n", 
    //mid, low, high, topIndex.functionOffset(mid)); 
    if (topIndex.functionOffset(mid) <= targetFunctionOffset) { 
      if ((mid == last) || 
          (topIndex.functionOffset(mid + 1) > targetFunctionOffset)) { 
        low = mid; 
        break; 
      } else { 
        low = mid + 1; 
      } 
    } else { 
      high = mid; 
    } 
  } 
  const uint32_t firstLevelFunctionOffset = topIndex.functionOffset(low); 
  const uint32_t firstLevelNextPageFunctionOffset = 
      topIndex.functionOffset(low + 1); 
  const pint_t secondLevelAddr = 
      sects.compact_unwind_section + topIndex.secondLevelPagesSectionOffset(low); 
  const pint_t lsdaArrayStartAddr = 
      sects.compact_unwind_section + topIndex.lsdaIndexArraySectionOffset(low); 
  const pint_t lsdaArrayEndAddr = 
      sects.compact_unwind_section + topIndex.lsdaIndexArraySectionOffset(low+1); 
  if (log) 
    fprintf(stderr, "\tfirst level search for result index=%d " 
                    "to secondLevelAddr=0x%llX\n", 
                    low, (uint64_t) secondLevelAddr); 
  // do a binary search of second level page index 
  uint32_t encoding = 0; 
  pint_t funcStart = 0; 
  pint_t funcEnd = 0; 
  pint_t lsda = 0; 
  pint_t personality = 0; 
  uint32_t pageKind = _addressSpace.get32(secondLevelAddr); 
  if (pageKind == UNWIND_SECOND_LEVEL_REGULAR) { 
    // regular page 
    UnwindSectionRegularPageHeader<A> pageHeader(_addressSpace, 
                                                 secondLevelAddr); 
    UnwindSectionRegularArray<A> pageIndex( 
        _addressSpace, secondLevelAddr + pageHeader.entryPageOffset()); 
    // binary search looks for entry with e where index[e].offset <= pc < 
    // index[e+1].offset 
    if (log) 
      fprintf(stderr, "\tbinary search for targetFunctionOffset=0x%08llX in " 
                      "regular page starting at secondLevelAddr=0x%llX\n", 
              (uint64_t) targetFunctionOffset, (uint64_t) secondLevelAddr); 
    low = 0; 
    high = pageHeader.entryCount(); 
    while (low < high) { 
      uint32_t mid = (low + high) / 2; 
      if (pageIndex.functionOffset(mid) <= targetFunctionOffset) { 
        if (mid == (uint32_t)(pageHeader.entryCount() - 1)) { 
          // at end of table 
          low = mid; 
          funcEnd = firstLevelNextPageFunctionOffset + sects.dso_base; 
          break; 
        } else if (pageIndex.functionOffset(mid + 1) > targetFunctionOffset) { 
          // next is too big, so we found it 
          low = mid; 
          funcEnd = pageIndex.functionOffset(low + 1) + sects.dso_base; 
          break; 
        } else { 
          low = mid + 1; 
        } 
      } else { 
        high = mid; 
      } 
    } 
    encoding = pageIndex.encoding(low); 
    funcStart = pageIndex.functionOffset(low) + sects.dso_base; 
    if (pc < funcStart) { 
      if (log) 
        fprintf( 
            stderr, 
            "\tpc not in table, pc=0x%llX, funcStart=0x%llX, funcEnd=0x%llX\n", 
            (uint64_t) pc, (uint64_t) funcStart, (uint64_t) funcEnd); 
      return false; 
    } 
    if (pc > funcEnd) { 
      if (log) 
        fprintf( 
            stderr, 
            "\tpc not in table, pc=0x%llX, funcStart=0x%llX, funcEnd=0x%llX\n", 
            (uint64_t) pc, (uint64_t) funcStart, (uint64_t) funcEnd); 
      return false; 
    } 
  } else if (pageKind == UNWIND_SECOND_LEVEL_COMPRESSED) { 
    // compressed page 
    UnwindSectionCompressedPageHeader<A> pageHeader(_addressSpace, 
                                                    secondLevelAddr); 
    UnwindSectionCompressedArray<A> pageIndex( 
        _addressSpace, secondLevelAddr + pageHeader.entryPageOffset()); 
    const uint32_t targetFunctionPageOffset = 
        (uint32_t)(targetFunctionOffset - firstLevelFunctionOffset); 
    // binary search looks for entry with e where index[e].offset <= pc < 
    // index[e+1].offset 
    if (log) 
      fprintf(stderr, "\tbinary search of compressed page starting at " 
                      "secondLevelAddr=0x%llX\n", 
              (uint64_t) secondLevelAddr); 
    low = 0; 
    last = pageHeader.entryCount() - 1; 
    high = pageHeader.entryCount(); 
    while (low < high) { 
      uint32_t mid = (low + high) / 2; 
      if (pageIndex.functionOffset(mid) <= targetFunctionPageOffset) { 
        if ((mid == last) || 
            (pageIndex.functionOffset(mid + 1) > targetFunctionPageOffset)) { 
          low = mid; 
          break; 
        } else { 
          low = mid + 1; 
        } 
      } else { 
        high = mid; 
      } 
    } 
    funcStart = pageIndex.functionOffset(low) + firstLevelFunctionOffset 
                                                              + sects.dso_base; 
    if (low < last) 
      funcEnd = 
          pageIndex.functionOffset(low + 1) + firstLevelFunctionOffset 
                                                              + sects.dso_base; 
    else 
      funcEnd = firstLevelNextPageFunctionOffset + sects.dso_base; 
    if (pc < funcStart) { 
      _LIBUNWIND_DEBUG_LOG("malformed __unwind_info, pc=0x%llX "
                           "not in second level compressed unwind table. "
                           "funcStart=0x%llX",
                            (uint64_t) pc, (uint64_t) funcStart); 
      return false; 
    } 
    if (pc > funcEnd) { 
      _LIBUNWIND_DEBUG_LOG("malformed __unwind_info, pc=0x%llX "
                           "not in second level compressed unwind table. "
                           "funcEnd=0x%llX",
                           (uint64_t) pc, (uint64_t) funcEnd); 
      return false; 
    } 
    uint16_t encodingIndex = pageIndex.encodingIndex(low); 
    if (encodingIndex < sectionHeader.commonEncodingsArrayCount()) { 
      // encoding is in common table in section header 
      encoding = _addressSpace.get32( 
          sects.compact_unwind_section + 
          sectionHeader.commonEncodingsArraySectionOffset() + 
          encodingIndex * sizeof(uint32_t)); 
    } else { 
      // encoding is in page specific table 
      uint16_t pageEncodingIndex = 
          encodingIndex - (uint16_t)sectionHeader.commonEncodingsArrayCount(); 
      encoding = _addressSpace.get32(secondLevelAddr + 
                                     pageHeader.encodingsPageOffset() + 
                                     pageEncodingIndex * sizeof(uint32_t)); 
    } 
  } else { 
    _LIBUNWIND_DEBUG_LOG(
        "malformed __unwind_info at 0x%0llX bad second level page",
        (uint64_t)sects.compact_unwind_section);
    return false; 
  } 
 
  // look up LSDA, if encoding says function has one 
  if (encoding & UNWIND_HAS_LSDA) { 
    UnwindSectionLsdaArray<A> lsdaIndex(_addressSpace, lsdaArrayStartAddr); 
    uint32_t funcStartOffset = (uint32_t)(funcStart - sects.dso_base); 
    low = 0; 
    high = (uint32_t)(lsdaArrayEndAddr - lsdaArrayStartAddr) / 
                    sizeof(unwind_info_section_header_lsda_index_entry); 
    // binary search looks for entry with exact match for functionOffset 
    if (log) 
      fprintf(stderr, 
              "\tbinary search of lsda table for targetFunctionOffset=0x%08X\n", 
              funcStartOffset); 
    while (low < high) { 
      uint32_t mid = (low + high) / 2; 
      if (lsdaIndex.functionOffset(mid) == funcStartOffset) { 
        lsda = lsdaIndex.lsdaOffset(mid) + sects.dso_base; 
        break; 
      } else if (lsdaIndex.functionOffset(mid) < funcStartOffset) { 
        low = mid + 1; 
      } else { 
        high = mid; 
      } 
    } 
    if (lsda == 0) { 
      _LIBUNWIND_DEBUG_LOG("found encoding 0x%08X with HAS_LSDA bit set for " 
                    "pc=0x%0llX, but lsda table has no entry",
                    encoding, (uint64_t) pc); 
      return false; 
    } 
  } 
 
  // extract personality routine, if encoding says function has one
  uint32_t personalityIndex = (encoding & UNWIND_PERSONALITY_MASK) >> 
                              (__builtin_ctz(UNWIND_PERSONALITY_MASK)); 
  if (personalityIndex != 0) { 
    --personalityIndex; // change 1-based to zero-based index 
    if (personalityIndex >= sectionHeader.personalityArrayCount()) {
      _LIBUNWIND_DEBUG_LOG("found encoding 0x%08X with personality index %d,  " 
                            "but personality table has only %d entries",
                            encoding, personalityIndex, 
                            sectionHeader.personalityArrayCount()); 
      return false; 
    } 
    int32_t personalityDelta = (int32_t)_addressSpace.get32( 
        sects.compact_unwind_section + 
        sectionHeader.personalityArraySectionOffset() + 
        personalityIndex * sizeof(uint32_t)); 
    pint_t personalityPointer = sects.dso_base + (pint_t)personalityDelta; 
    personality = _addressSpace.getP(personalityPointer); 
    if (log) 
      fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX), " 
                      "personalityDelta=0x%08X, personality=0x%08llX\n", 
              (uint64_t) pc, personalityDelta, (uint64_t) personality); 
  } 
 
  if (log) 
    fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX), " 
                    "encoding=0x%08X, lsda=0x%08llX for funcStart=0x%llX\n", 
            (uint64_t) pc, encoding, (uint64_t) lsda, (uint64_t) funcStart); 
  _info.start_ip = funcStart; 
  _info.end_ip = funcEnd; 
  _info.lsda = lsda; 
  _info.handler = personality; 
  _info.gp = 0; 
  _info.flags = 0; 
  _info.format = encoding; 
  _info.unwind_info = 0; 
  _info.unwind_info_size = 0; 
  _info.extra = sects.dso_base; 
  return true; 
} 
#endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
 
 
#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
template <typename A, typename R> 
bool UnwindCursor<A, R>::getInfoFromSEH(pint_t pc) {
  pint_t base;
  RUNTIME_FUNCTION *unwindEntry = lookUpSEHUnwindInfo(pc, &base);
  if (!unwindEntry) {
    _LIBUNWIND_DEBUG_LOG("\tpc not in table, pc=0x%llX", (uint64_t) pc);
    return false;
  }
  _info.gp = 0;
  _info.flags = 0;
  _info.format = 0;
  _info.unwind_info_size = sizeof(RUNTIME_FUNCTION);
  _info.unwind_info = reinterpret_cast<unw_word_t>(unwindEntry);
  _info.extra = base;
  _info.start_ip = base + unwindEntry->BeginAddress;
#ifdef _LIBUNWIND_TARGET_X86_64
  _info.end_ip = base + unwindEntry->EndAddress;
  // Only fill in the handler and LSDA if they're stale.
  if (pc != getLastPC()) {
    UNWIND_INFO *xdata = reinterpret_cast<UNWIND_INFO *>(base + unwindEntry->UnwindData);
    if (xdata->Flags & (UNW_FLAG_EHANDLER|UNW_FLAG_UHANDLER)) {
      // The personality is given in the UNWIND_INFO itself. The LSDA immediately
      // follows the UNWIND_INFO. (This follows how both Clang and MSVC emit
      // these structures.)
      // N.B. UNWIND_INFO structs are DWORD-aligned.
      uint32_t lastcode = (xdata->CountOfCodes + 1) & ~1;
      const uint32_t *handler = reinterpret_cast<uint32_t *>(&xdata->UnwindCodes[lastcode]);
      _info.lsda = reinterpret_cast<unw_word_t>(handler+1);
      if (*handler) {
        _info.handler = reinterpret_cast<unw_word_t>(__libunwind_seh_personality);
      } else
        _info.handler = 0;
    } else {
      _info.lsda = 0;
      _info.handler = 0;
    }
  }
#elif defined(_LIBUNWIND_TARGET_ARM)
  _info.end_ip = _info.start_ip + unwindEntry->FunctionLength;
  _info.lsda = 0; // FIXME
  _info.handler = 0; // FIXME
#endif
  setLastPC(pc);
  return true;
}
#endif


template <typename A, typename R>
void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) { 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
  _isSigReturn = false;
#endif

  pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
#if defined(_LIBUNWIND_ARM_EHABI)
  // Remove the thumb bit so the IP represents the actual instruction address. 
  // This matches the behaviour of _Unwind_GetIP on arm. 
  pc &= (pint_t)~0x1; 
#endif 
 
  // Exit early if at the top of the stack.
  if (pc == 0) {
    _unwindInfoMissing = true;
    return;
  }

  // If the last line of a function is a "throw" the compiler sometimes 
  // emits no instructions after the call to __cxa_throw.  This means 
  // the return address is actually the start of the next function. 
  // To disambiguate this, back up the pc when we know it is a return 
  // address. 
  if (isReturnAddress) 
    --pc; 
 
  // Ask address space object to find unwind sections for this pc. 
  UnwindInfoSections sects; 
  if (_addressSpace.findUnwindSections(pc, sects)) { 
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
    // If there is a compact unwind encoding table, look there first. 
    if (sects.compact_unwind_section != 0) { 
      if (this->getInfoFromCompactEncodingSection(pc, sects)) { 
  #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
        // Found info in table, done unless encoding says to use dwarf. 
        uint32_t dwarfOffset; 
        if ((sects.dwarf_section != 0) && compactSaysUseDwarf(&dwarfOffset)) { 
          if (this->getInfoFromDwarfSection(pc, sects, dwarfOffset)) { 
            // found info in dwarf, done 
            return; 
          } 
        } 
  #endif 
        // If unwind table has entry, but entry says there is no unwind info, 
        // record that we have no unwind info. 
        if (_info.format == 0) 
          _unwindInfoMissing = true; 
        return; 
      } 
    } 
#endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
 
#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
    // If there is SEH unwind info, look there next.
    if (this->getInfoFromSEH(pc))
      return;
#endif

#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
    // If there is dwarf unwind info, look there next. 
    if (sects.dwarf_section != 0) { 
      if (this->getInfoFromDwarfSection(pc, sects)) { 
        // found info in dwarf, done 
        return; 
      } 
    } 
#endif 
 
#if defined(_LIBUNWIND_ARM_EHABI)
    // If there is ARM EHABI unwind info, look there next. 
    if (sects.arm_section != 0 && this->getInfoFromEHABISection(pc, sects)) 
      return; 
#endif 
  } 
 
#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
  // There is no static unwind info for this pc. Look to see if an FDE was 
  // dynamically registered for it. 
  pint_t cachedFDE = DwarfFDECache<A>::findFDE(DwarfFDECache<A>::kSearchAll,
                                               pc);
  if (cachedFDE != 0) { 
    typename CFI_Parser<A>::FDE_Info fdeInfo;
    typename CFI_Parser<A>::CIE_Info cieInfo;
    if (!CFI_Parser<A>::decodeFDE(_addressSpace, cachedFDE, &fdeInfo, &cieInfo))
      if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, 0))
        return; 
  } 
 
  // Lastly, ask AddressSpace object about platform specific ways to locate 
  // other FDEs. 
  pint_t fde; 
  if (_addressSpace.findOtherFDE(pc, fde)) { 
    typename CFI_Parser<A>::FDE_Info fdeInfo;
    typename CFI_Parser<A>::CIE_Info cieInfo;
    if (!CFI_Parser<A>::decodeFDE(_addressSpace, fde, &fdeInfo, &cieInfo)) { 
      // Double check this FDE is for a function that includes the pc. 
      if ((fdeInfo.pcStart <= pc) && (pc < fdeInfo.pcEnd))
        if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, 0))
          return; 
    } 
  } 
#endif // #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
  if (setInfoForSigReturn())
    return;
#endif

  // no unwind info, flag that we can't reliably unwind 
  _unwindInfoMissing = true; 
} 
 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
template <typename A, typename R> 
bool UnwindCursor<A, R>::setInfoForSigReturn(Registers_arm64 &) {
  // Look for the sigreturn trampoline. The trampoline's body is two
  // specific instructions (see below). Typically the trampoline comes from the
  // vDSO[1] (i.e. the __kernel_rt_sigreturn function). A libc might provide its
  // own restorer function, though, or user-mode QEMU might write a trampoline
  // onto the stack.
  //
  // This special code path is a fallback that is only used if the trampoline
  // lacks proper (e.g. DWARF) unwind info. On AArch64, a new DWARF register
  // constant for the PC needs to be defined before DWARF can handle a signal
  // trampoline. This code may segfault if the target PC is unreadable, e.g.:
  //  - The PC points at a function compiled without unwind info, and which is
  //    part of an execute-only mapping (e.g. using -Wl,--execute-only).
  //  - The PC is invalid and happens to point to unreadable or unmapped memory.
  //
  // [1] https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/vdso/sigreturn.S
  const pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
  // Look for instructions: mov x8, #0x8b; svc #0x0
  if (_addressSpace.get32(pc) == 0xd2801168 &&
      _addressSpace.get32(pc + 4) == 0xd4000001) {
    _info = {};
    _isSigReturn = true;
    return true;
  }
  return false;
}

template <typename A, typename R>
int UnwindCursor<A, R>::stepThroughSigReturn(Registers_arm64 &) {
  // In the signal trampoline frame, sp points to an rt_sigframe[1], which is:
  //  - 128-byte siginfo struct
  //  - ucontext struct:
  //     - 8-byte long (uc_flags)
  //     - 8-byte pointer (uc_link)
  //     - 24-byte stack_t
  //     - 128-byte signal set
  //     - 8 bytes of padding because sigcontext has 16-byte alignment
  //     - sigcontext/mcontext_t
  // [1] https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/signal.c
  const pint_t kOffsetSpToSigcontext = (128 + 8 + 8 + 24 + 128 + 8); // 304

  // Offsets from sigcontext to each register.
  const pint_t kOffsetGprs = 8; // offset to "__u64 regs[31]" field
  const pint_t kOffsetSp = 256; // offset to "__u64 sp" field
  const pint_t kOffsetPc = 264; // offset to "__u64 pc" field

  pint_t sigctx = _registers.getSP() + kOffsetSpToSigcontext;

  for (int i = 0; i <= 30; ++i) {
    uint64_t value = _addressSpace.get64(sigctx + kOffsetGprs +
                                         static_cast<pint_t>(i * 8));
    _registers.setRegister(UNW_AARCH64_X0 + i, value);
  }
  _registers.setSP(_addressSpace.get64(sigctx + kOffsetSp));
  _registers.setIP(_addressSpace.get64(sigctx + kOffsetPc));
  _isSignalFrame = true;
  return UNW_STEP_SUCCESS;
}
#endif // defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)

template <typename A, typename R>
int UnwindCursor<A, R>::step() { 
  // Bottom of stack is defined is when unwind info cannot be found. 
  if (_unwindInfoMissing) 
    return UNW_STEP_END; 
 
  // Use unwinding info to modify register set as if function returned. 
  int result; 
#if defined(_LIBUNWIND_TARGET_LINUX) && defined(_LIBUNWIND_TARGET_AARCH64)
  if (_isSigReturn) {
    result = this->stepThroughSigReturn();
  } else
#endif
  {
#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
    result = this->stepWithCompactEncoding();
#elif defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
    result = this->stepWithSEHData();
#elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
    result = this->stepWithDwarfFDE();
#elif defined(_LIBUNWIND_ARM_EHABI)
    result = this->stepWithEHABI();
#else 
  #error Need _LIBUNWIND_SUPPORT_COMPACT_UNWIND or \ 
              _LIBUNWIND_SUPPORT_SEH_UNWIND or \
              _LIBUNWIND_SUPPORT_DWARF_UNWIND or \ 
              _LIBUNWIND_ARM_EHABI 
#endif 
  }
 
  // update info based on new PC 
  if (result == UNW_STEP_SUCCESS) { 
    this->setInfoBasedOnIPRegister(true); 
    if (_unwindInfoMissing) 
      return UNW_STEP_END; 
  } 
 
  return result; 
} 
 
template <typename A, typename R> 
void UnwindCursor<A, R>::getInfo(unw_proc_info_t *info) { 
  if (_unwindInfoMissing)
    memset(info, 0, sizeof(*info));
  else
    *info = _info;
} 
 
template <typename A, typename R> 
bool UnwindCursor<A, R>::getFunctionName(char *buf, size_t bufLen, 
                                                           unw_word_t *offset) { 
  return _addressSpace.findFunctionName((pint_t)this->getReg(UNW_REG_IP), 
                                         buf, bufLen, offset); 
} 
 
#if defined(_LIBUNWIND_USE_CET)
extern "C" void *__libunwind_cet_get_registers(unw_cursor_t *cursor) {
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->get_registers();
}
#endif
} // namespace libunwind 
 
#endif // __UNWINDCURSOR_HPP__