unwind: move src/Unwind, include/, and test/ unwind content

This moves the majority of the unwind sources into the new project layout for
libunwind.  This was previously discussed on llvmdev at [1].  This is a
purely movement related change, with the build infrastructure currently still
residing in the libc++abi repository.

[1] http://lists.cs.uiuc.edu/pipermail/llvmdev/2015-January/081507.html

llvm-svn: 235758

1 files changed, 1317 insertions, 0 deletions

diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
new file mode 100644
index 00000000000..b4d413f4f32
--- /dev/null
+++ b/libunwind/src/UnwindCursor.hpp
@@ -0,0 +1,1317 @@
+//===------------------------- UnwindCursor.hpp ---------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//
+// C++ interface to lower levels of libuwind
+//===----------------------------------------------------------------------===//
+
+#ifndef __UNWINDCURSOR_HPP__
+#define __UNWINDCURSOR_HPP__
+
+#include <algorithm>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <unwind.h>
+
+#ifdef __APPLE__
+  #include <mach-o/dyld.h>
+#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 "Unwind-EHABI.h"
+
+namespace libunwind {
+
+#if _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 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 pthread_rwlock_t _lock;
+#ifdef __APPLE__
+  static void dyldUnloadHook(const struct mach_header *mh, intptr_t slide);
+  static bool _registeredForDyldUnloads;
+#endif
+  // Can't use std::vector<> here because this code is below libc++.
+  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>
+pthread_rwlock_t DwarfFDECache<A>::_lock = PTHREAD_RWLOCK_INITIALIZER;
+
+#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_NON_ZERO(::pthread_rwlock_rdlock(&_lock));
+  for (entry *p = _buffer; p < _bufferUsed; ++p) {
+    if ((mh == p->mh) || (mh == 0)) {
+      if ((p->ip_start <= pc) && (pc < p->ip_end)) {
+        result = p->fde;
+        break;
+      }
+    }
+  }
+  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_unlock(&_lock));
+  return result;
+}
+
+template <typename A>
+void DwarfFDECache<A>::add(pint_t mh, pint_t ip_start, pint_t ip_end,
+                           pint_t fde) {
+  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_wrlock(&_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_NON_ZERO(::pthread_rwlock_unlock(&_lock));
+}
+
+template <typename A>
+void DwarfFDECache<A>::removeAllIn(pint_t mh) {
+  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_wrlock(&_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_NON_ZERO(::pthread_rwlock_unlock(&_lock));
+}
+
+#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_NON_ZERO(::pthread_rwlock_wrlock(&_lock));
+  for (entry *p = _buffer; p < _bufferUsed; ++p) {
+    (*func)(p->ip_start, p->ip_end, p->fde, p->mh);
+  }
+  _LIBUNWIND_LOG_NON_ZERO(::pthread_rwlock_unlock(&_lock));
+}
+#endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
+
+
+#define arrayoffsetof(type, index, field) ((size_t)(&((type *)0)[index].field))
+
+#if _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 // _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
+};
+
+/// 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
+
+private:
+
+#if LIBCXXABI_ARM_EHABI
+  bool getInfoFromEHABISection(pint_t pc, const UnwindInfoSections &sects);
+#endif
+
+#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
+  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);
+  }
+#endif
+
+#if _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+  bool getInfoFromCompactEncodingSection(pint_t pc,
+                                            const UnwindInfoSections &sects);
+  int stepWithCompactEncoding() {
+  #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
+    if ( compactSaysUseDwarf() )
+      return stepWithDwarfFDE();
+  #endif
+    R dummy;
+    return stepWithCompactEncoding(dummy);
+  }
+
+  int stepWithCompactEncoding(Registers_x86_64 &) {
+    return CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
+        _info.format, _info.start_ip, _addressSpace, _registers);
+  }
+
+  int stepWithCompactEncoding(Registers_x86 &) {
+    return CompactUnwinder_x86<A>::stepWithCompactEncoding(
+        _info.format, (uint32_t)_info.start_ip, _addressSpace, _registers);
+  }
+
+  int stepWithCompactEncoding(Registers_ppc &) {
+    return UNW_EINVAL;
+  }
+
+  int stepWithCompactEncoding(Registers_arm64 &) {
+    return CompactUnwinder_arm64<A>::stepWithCompactEncoding(
+        _info.format, _info.start_ip, _addressSpace, _registers);
+  }
+
+  bool compactSaysUseDwarf(uint32_t *offset=NULL) const {
+    R dummy;
+    return compactSaysUseDwarf(dummy, offset);
+  }
+
+  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;
+  }
+
+  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;
+  }
+
+  bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const {
+    return true;
+  }
+
+  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 // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+
+#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
+  compact_unwind_encoding_t dwarfEncoding() const {
+    R dummy;
+    return dwarfEncoding(dummy);
+  }
+
+  compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const {
+    return UNWIND_X86_64_MODE_DWARF;
+  }
+
+  compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const {
+    return UNWIND_X86_MODE_DWARF;
+  }
+
+  compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const {
+    return 0;
+  }
+
+  compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const {
+    return UNWIND_ARM64_MODE_DWARF;
+  }
+#endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
+
+
+  A               &_addressSpace;
+  R                _registers;
+  unw_proc_info_t  _info;
+  bool             _unwindInfoMissing;
+  bool             _isSignalFrame;
+};
+
+
+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(sizeof(UnwindCursor<A, R>) < sizeof(unw_cursor_t),
+                "UnwindCursor<> does not fit in 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;
+}
+
+#if LIBCXXABI_ARM_EHABI
+struct EHABIIndexEntry {
+  uint32_t functionOffset;
+  uint32_t data;
+};
+
+template<typename A>
+struct EHABISectionIterator {
+  typedef EHABISectionIterator _Self;
+
+  typedef std::random_access_iterator_tag iterator_category;
+  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);
+  }
+
+  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) { 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;
+};
+
+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);
+
+  EHABISectionIterator<A> itNextPC = std::upper_bound(begin, end, pc);
+  if (itNextPC == begin || itNextPC == end)
+    return false;
+  EHABISectionIterator<A> itThisPC = itNextPC - 1;
+
+  pint_t thisPC = itThisPC.functionAddress();
+  pint_t nextPC = 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 = 0xbadf00d;
+
+  // 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;
+        break;
+      case 1:
+        personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr1;
+        extraWords = (exceptionTableData & 0x00ff0000) >> 16;
+        scope32 = false;
+        break;
+      case 2:
+        personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr2;
+        extraWords = (exceptionTableData & 0x00ff0000) >> 16;
+        scope32 = true;
+        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 _LIBUNWIND_SUPPORT_DWARF_UNWIND
+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,
+                                    (uint32_t)sects.dwarf_section_length,
+                                    sects.dwarf_section + fdeSectionOffsetHint,
+                                    &fdeInfo, &cieInfo);
+  }
+#if _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,
+                                 (uint32_t)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,
+                                      (uint32_t)sects.dwarf_section_length, 0,
+                                      &fdeInfo, &cieInfo);
+  }
+  if (foundFDE) {
+    typename CFI_Parser<A>::PrologInfo prolog;
+    if (CFI_Parser<A>::parseFDEInstructions(_addressSpace, fdeInfo, cieInfo, pc,
+                                            &prolog)) {
+      // Save off parsed FDE info
+      _info.start_ip          = fdeInfo.pcStart;
+      _info.end_ip            = fdeInfo.pcEnd;
+      _info.lsda              = fdeInfo.lsda;
+      _info.handler           = cieInfo.personality;
+      _info.gp                = prolog.spExtraArgSize;
+      _info.flags             = 0;
+      _info.format            = dwarfEncoding();
+      _info.unwind_info       = fdeInfo.fdeStart;
+      _info.unwind_info_size  = (uint32_t)fdeInfo.fdeLength;
+      _info.extra             = (unw_word_t) 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 _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\n", (uint64_t)pc);
+  return false;
+}
+#endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
+
+
+#if _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\n",
+                            (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\n",
+                           (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\n",
+                          (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\n",
+                    encoding, (uint64_t) pc);
+      return false;
+    }
+  }
+
+  // extact 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 entires\n",
+                            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 // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+
+
+template <typename A, typename R>
+void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
+  pint_t pc = (pint_t)this->getReg(UNW_REG_IP);
+#if LIBCXXABI_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
+
+  // 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 _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 _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 // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+
+#if _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 LIBCXXABI_ARM_EHABI
+    // If there is ARM EHABI unwind info, look there next.
+    if (sects.arm_section != 0 && this->getInfoFromEHABISection(pc, sects))
+      return;
+#endif
+  }
+
+#if _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(0, pc);
+  if (cachedFDE != 0) {
+    CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
+    CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
+    const char *msg = CFI_Parser<A>::decodeFDE(_addressSpace,
+                                                cachedFDE, &fdeInfo, &cieInfo);
+    if (msg == NULL) {
+      typename CFI_Parser<A>::PrologInfo prolog;
+      if (CFI_Parser<A>::parseFDEInstructions(_addressSpace, fdeInfo, cieInfo,
+                                                                pc, &prolog)) {
+        // save off parsed FDE info
+        _info.start_ip         = fdeInfo.pcStart;
+        _info.end_ip           = fdeInfo.pcEnd;
+        _info.lsda             = fdeInfo.lsda;
+        _info.handler          = cieInfo.personality;
+        _info.gp               = prolog.spExtraArgSize;
+                                  // Some frameless functions need SP
+                                  // altered when resuming in function.
+        _info.flags            = 0;
+        _info.format           = dwarfEncoding();
+        _info.unwind_info      = fdeInfo.fdeStart;
+        _info.unwind_info_size = (uint32_t)fdeInfo.fdeLength;
+        _info.extra            = 0;
+        return;
+      }
+    }
+  }
+
+  // Lastly, ask AddressSpace object about platform specific ways to locate
+  // other FDEs.
+  pint_t fde;
+  if (_addressSpace.findOtherFDE(pc, fde)) {
+    CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
+    CFI_Parser<LocalAddressSpace>::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)) {
+        typename CFI_Parser<A>::PrologInfo prolog;
+        if (CFI_Parser<A>::parseFDEInstructions(_addressSpace, fdeInfo,
+                                                cieInfo, pc, &prolog)) {
+          // save off parsed FDE info
+          _info.start_ip         = fdeInfo.pcStart;
+          _info.end_ip           = fdeInfo.pcEnd;
+          _info.lsda             = fdeInfo.lsda;
+          _info.handler          = cieInfo.personality;
+          _info.gp               = prolog.spExtraArgSize;
+          _info.flags            = 0;
+          _info.format           = dwarfEncoding();
+          _info.unwind_info      = fdeInfo.fdeStart;
+          _info.unwind_info_size = (uint32_t)fdeInfo.fdeLength;
+          _info.extra            = 0;
+          return;
+        }
+      }
+    }
+  }
+#endif // #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
+
+  // no unwind info, flag that we can't reliably unwind
+  _unwindInfoMissing = true;
+}
+
+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 _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+  result = this->stepWithCompactEncoding();
+#elif _LIBUNWIND_SUPPORT_DWARF_UNWIND
+  result = this->stepWithDwarfFDE();
+#elif LIBCXXABI_ARM_EHABI
+  result = UNW_STEP_SUCCESS;
+#else
+  #error Need _LIBUNWIND_SUPPORT_COMPACT_UNWIND or \
+              _LIBUNWIND_SUPPORT_DWARF_UNWIND or \
+              LIBCXXABI_ARM_EHABI
+#endif
+
+  // update info based on new PC
+  if (result == UNW_STEP_SUCCESS) {
+    this->setInfoBasedOnIPRegister(true);
+    if (_unwindInfoMissing)
+      return UNW_STEP_END;
+    if (_info.gp)
+      setReg(UNW_REG_SP, getReg(UNW_REG_SP) + _info.gp);
+  }
+
+  return result;
+}
+
+template <typename A, typename R>
+void UnwindCursor<A, R>::getInfo(unw_proc_info_t *info) {
+  *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);
+}
+
+} // namespace libunwind
+
+#endif // __UNWINDCURSOR_HPP__