1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //
8 // C++ interface to lower levels of libunwind
9 //===----------------------------------------------------------------------===//
10 
11 #ifndef __UNWINDCURSOR_HPP__
12 #define __UNWINDCURSOR_HPP__
13 
14 #include "cet_unwind.h"
15 #include <stdint.h>
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <unwind.h>
19 
20 #ifdef _WIN32
21   #include <windows.h>
22   #include <ntverp.h>
23 #endif
24 #ifdef __APPLE__
25   #include <mach-o/dyld.h>
26 #endif
27 #ifdef _AIX
28 #include <dlfcn.h>
29 #include <sys/debug.h>
30 #include <sys/pseg.h>
31 #endif
32 
33 #if defined(_LIBUNWIND_TARGET_LINUX) &&                                        \
34     (defined(_LIBUNWIND_TARGET_AARCH64) || defined(_LIBUNWIND_TARGET_S390X))
35 #include <sys/syscall.h>
36 #include <sys/uio.h>
37 #include <unistd.h>
38 #define _LIBUNWIND_CHECK_LINUX_SIGRETURN 1
39 #endif
40 
41 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
42 // Provide a definition for the DISPATCHER_CONTEXT struct for old (Win7 and
43 // earlier) SDKs.
44 // MinGW-w64 has always provided this struct.
45   #if defined(_WIN32) && defined(_LIBUNWIND_TARGET_X86_64) && \
46       !defined(__MINGW32__) && VER_PRODUCTBUILD < 8000
47 struct _DISPATCHER_CONTEXT {
48   ULONG64 ControlPc;
49   ULONG64 ImageBase;
50   PRUNTIME_FUNCTION FunctionEntry;
51   ULONG64 EstablisherFrame;
52   ULONG64 TargetIp;
53   PCONTEXT ContextRecord;
54   PEXCEPTION_ROUTINE LanguageHandler;
55   PVOID HandlerData;
56   PUNWIND_HISTORY_TABLE HistoryTable;
57   ULONG ScopeIndex;
58   ULONG Fill0;
59 };
60   #endif
61 
62 struct UNWIND_INFO {
63   uint8_t Version : 3;
64   uint8_t Flags : 5;
65   uint8_t SizeOfProlog;
66   uint8_t CountOfCodes;
67   uint8_t FrameRegister : 4;
68   uint8_t FrameOffset : 4;
69   uint16_t UnwindCodes[2];
70 };
71 
72 extern "C" _Unwind_Reason_Code __libunwind_seh_personality(
73     int, _Unwind_Action, uint64_t, _Unwind_Exception *,
74     struct _Unwind_Context *);
75 
76 #endif
77 
78 #include "config.h"
79 
80 #include "AddressSpace.hpp"
81 #include "CompactUnwinder.hpp"
82 #include "config.h"
83 #include "DwarfInstructions.hpp"
84 #include "EHHeaderParser.hpp"
85 #include "libunwind.h"
86 #include "Registers.hpp"
87 #include "RWMutex.hpp"
88 #include "Unwind-EHABI.h"
89 
90 namespace libunwind {
91 
92 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
93 /// Cache of recently found FDEs.
94 template <typename A>
95 class _LIBUNWIND_HIDDEN DwarfFDECache {
96   typedef typename A::pint_t pint_t;
97 public:
98   static constexpr pint_t kSearchAll = static_cast<pint_t>(-1);
99   static pint_t findFDE(pint_t mh, pint_t pc);
100   static void add(pint_t mh, pint_t ip_start, pint_t ip_end, pint_t fde);
101   static void removeAllIn(pint_t mh);
102   static void iterateCacheEntries(void (*func)(unw_word_t ip_start,
103                                                unw_word_t ip_end,
104                                                unw_word_t fde, unw_word_t mh));
105 
106 private:
107 
108   struct entry {
109     pint_t mh;
110     pint_t ip_start;
111     pint_t ip_end;
112     pint_t fde;
113   };
114 
115   // These fields are all static to avoid needing an initializer.
116   // There is only one instance of this class per process.
117   static RWMutex _lock;
118 #ifdef __APPLE__
119   static void dyldUnloadHook(const struct mach_header *mh, intptr_t slide);
120   static bool _registeredForDyldUnloads;
121 #endif
122   static entry *_buffer;
123   static entry *_bufferUsed;
124   static entry *_bufferEnd;
125   static entry _initialBuffer[64];
126 };
127 
128 template <typename A>
129 typename DwarfFDECache<A>::entry *
130 DwarfFDECache<A>::_buffer = _initialBuffer;
131 
132 template <typename A>
133 typename DwarfFDECache<A>::entry *
134 DwarfFDECache<A>::_bufferUsed = _initialBuffer;
135 
136 template <typename A>
137 typename DwarfFDECache<A>::entry *
138 DwarfFDECache<A>::_bufferEnd = &_initialBuffer[64];
139 
140 template <typename A>
141 typename DwarfFDECache<A>::entry DwarfFDECache<A>::_initialBuffer[64];
142 
143 template <typename A>
144 RWMutex DwarfFDECache<A>::_lock;
145 
146 #ifdef __APPLE__
147 template <typename A>
148 bool DwarfFDECache<A>::_registeredForDyldUnloads = false;
149 #endif
150 
151 template <typename A>
152 typename A::pint_t DwarfFDECache<A>::findFDE(pint_t mh, pint_t pc) {
153   pint_t result = 0;
154   _LIBUNWIND_LOG_IF_FALSE(_lock.lock_shared());
155   for (entry *p = _buffer; p < _bufferUsed; ++p) {
156     if ((mh == p->mh) || (mh == kSearchAll)) {
157       if ((p->ip_start <= pc) && (pc < p->ip_end)) {
158         result = p->fde;
159         break;
160       }
161     }
162   }
163   _LIBUNWIND_LOG_IF_FALSE(_lock.unlock_shared());
164   return result;
165 }
166 
167 template <typename A>
168 void DwarfFDECache<A>::add(pint_t mh, pint_t ip_start, pint_t ip_end,
169                            pint_t fde) {
170 #if !defined(_LIBUNWIND_NO_HEAP)
171   _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
172   if (_bufferUsed >= _bufferEnd) {
173     size_t oldSize = (size_t)(_bufferEnd - _buffer);
174     size_t newSize = oldSize * 4;
175     // Can't use operator new (we are below it).
176     entry *newBuffer = (entry *)malloc(newSize * sizeof(entry));
177     memcpy(newBuffer, _buffer, oldSize * sizeof(entry));
178     if (_buffer != _initialBuffer)
179       free(_buffer);
180     _buffer = newBuffer;
181     _bufferUsed = &newBuffer[oldSize];
182     _bufferEnd = &newBuffer[newSize];
183   }
184   _bufferUsed->mh = mh;
185   _bufferUsed->ip_start = ip_start;
186   _bufferUsed->ip_end = ip_end;
187   _bufferUsed->fde = fde;
188   ++_bufferUsed;
189 #ifdef __APPLE__
190   if (!_registeredForDyldUnloads) {
191     _dyld_register_func_for_remove_image(&dyldUnloadHook);
192     _registeredForDyldUnloads = true;
193   }
194 #endif
195   _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
196 #endif
197 }
198 
199 template <typename A>
200 void DwarfFDECache<A>::removeAllIn(pint_t mh) {
201   _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
202   entry *d = _buffer;
203   for (const entry *s = _buffer; s < _bufferUsed; ++s) {
204     if (s->mh != mh) {
205       if (d != s)
206         *d = *s;
207       ++d;
208     }
209   }
210   _bufferUsed = d;
211   _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
212 }
213 
214 #ifdef __APPLE__
215 template <typename A>
216 void DwarfFDECache<A>::dyldUnloadHook(const struct mach_header *mh, intptr_t ) {
217   removeAllIn((pint_t) mh);
218 }
219 #endif
220 
221 template <typename A>
222 void DwarfFDECache<A>::iterateCacheEntries(void (*func)(
223     unw_word_t ip_start, unw_word_t ip_end, unw_word_t fde, unw_word_t mh)) {
224   _LIBUNWIND_LOG_IF_FALSE(_lock.lock());
225   for (entry *p = _buffer; p < _bufferUsed; ++p) {
226     (*func)(p->ip_start, p->ip_end, p->fde, p->mh);
227   }
228   _LIBUNWIND_LOG_IF_FALSE(_lock.unlock());
229 }
230 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
231 
232 
233 #define arrayoffsetof(type, index, field) ((size_t)(&((type *)0)[index].field))
234 
235 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
236 template <typename A> class UnwindSectionHeader {
237 public:
238   UnwindSectionHeader(A &addressSpace, typename A::pint_t addr)
239       : _addressSpace(addressSpace), _addr(addr) {}
240 
241   uint32_t version() const {
242     return _addressSpace.get32(_addr +
243                                offsetof(unwind_info_section_header, version));
244   }
245   uint32_t commonEncodingsArraySectionOffset() const {
246     return _addressSpace.get32(_addr +
247                                offsetof(unwind_info_section_header,
248                                         commonEncodingsArraySectionOffset));
249   }
250   uint32_t commonEncodingsArrayCount() const {
251     return _addressSpace.get32(_addr + offsetof(unwind_info_section_header,
252                                                 commonEncodingsArrayCount));
253   }
254   uint32_t personalityArraySectionOffset() const {
255     return _addressSpace.get32(_addr + offsetof(unwind_info_section_header,
256                                                 personalityArraySectionOffset));
257   }
258   uint32_t personalityArrayCount() const {
259     return _addressSpace.get32(
260         _addr + offsetof(unwind_info_section_header, personalityArrayCount));
261   }
262   uint32_t indexSectionOffset() const {
263     return _addressSpace.get32(
264         _addr + offsetof(unwind_info_section_header, indexSectionOffset));
265   }
266   uint32_t indexCount() const {
267     return _addressSpace.get32(
268         _addr + offsetof(unwind_info_section_header, indexCount));
269   }
270 
271 private:
272   A                     &_addressSpace;
273   typename A::pint_t     _addr;
274 };
275 
276 template <typename A> class UnwindSectionIndexArray {
277 public:
278   UnwindSectionIndexArray(A &addressSpace, typename A::pint_t addr)
279       : _addressSpace(addressSpace), _addr(addr) {}
280 
281   uint32_t functionOffset(uint32_t index) const {
282     return _addressSpace.get32(
283         _addr + arrayoffsetof(unwind_info_section_header_index_entry, index,
284                               functionOffset));
285   }
286   uint32_t secondLevelPagesSectionOffset(uint32_t index) const {
287     return _addressSpace.get32(
288         _addr + arrayoffsetof(unwind_info_section_header_index_entry, index,
289                               secondLevelPagesSectionOffset));
290   }
291   uint32_t lsdaIndexArraySectionOffset(uint32_t index) const {
292     return _addressSpace.get32(
293         _addr + arrayoffsetof(unwind_info_section_header_index_entry, index,
294                               lsdaIndexArraySectionOffset));
295   }
296 
297 private:
298   A                   &_addressSpace;
299   typename A::pint_t   _addr;
300 };
301 
302 template <typename A> class UnwindSectionRegularPageHeader {
303 public:
304   UnwindSectionRegularPageHeader(A &addressSpace, typename A::pint_t addr)
305       : _addressSpace(addressSpace), _addr(addr) {}
306 
307   uint32_t kind() const {
308     return _addressSpace.get32(
309         _addr + offsetof(unwind_info_regular_second_level_page_header, kind));
310   }
311   uint16_t entryPageOffset() const {
312     return _addressSpace.get16(
313         _addr + offsetof(unwind_info_regular_second_level_page_header,
314                          entryPageOffset));
315   }
316   uint16_t entryCount() const {
317     return _addressSpace.get16(
318         _addr +
319         offsetof(unwind_info_regular_second_level_page_header, entryCount));
320   }
321 
322 private:
323   A &_addressSpace;
324   typename A::pint_t _addr;
325 };
326 
327 template <typename A> class UnwindSectionRegularArray {
328 public:
329   UnwindSectionRegularArray(A &addressSpace, typename A::pint_t addr)
330       : _addressSpace(addressSpace), _addr(addr) {}
331 
332   uint32_t functionOffset(uint32_t index) const {
333     return _addressSpace.get32(
334         _addr + arrayoffsetof(unwind_info_regular_second_level_entry, index,
335                               functionOffset));
336   }
337   uint32_t encoding(uint32_t index) const {
338     return _addressSpace.get32(
339         _addr +
340         arrayoffsetof(unwind_info_regular_second_level_entry, index, encoding));
341   }
342 
343 private:
344   A &_addressSpace;
345   typename A::pint_t _addr;
346 };
347 
348 template <typename A> class UnwindSectionCompressedPageHeader {
349 public:
350   UnwindSectionCompressedPageHeader(A &addressSpace, typename A::pint_t addr)
351       : _addressSpace(addressSpace), _addr(addr) {}
352 
353   uint32_t kind() const {
354     return _addressSpace.get32(
355         _addr +
356         offsetof(unwind_info_compressed_second_level_page_header, kind));
357   }
358   uint16_t entryPageOffset() const {
359     return _addressSpace.get16(
360         _addr + offsetof(unwind_info_compressed_second_level_page_header,
361                          entryPageOffset));
362   }
363   uint16_t entryCount() const {
364     return _addressSpace.get16(
365         _addr +
366         offsetof(unwind_info_compressed_second_level_page_header, entryCount));
367   }
368   uint16_t encodingsPageOffset() const {
369     return _addressSpace.get16(
370         _addr + offsetof(unwind_info_compressed_second_level_page_header,
371                          encodingsPageOffset));
372   }
373   uint16_t encodingsCount() const {
374     return _addressSpace.get16(
375         _addr + offsetof(unwind_info_compressed_second_level_page_header,
376                          encodingsCount));
377   }
378 
379 private:
380   A &_addressSpace;
381   typename A::pint_t _addr;
382 };
383 
384 template <typename A> class UnwindSectionCompressedArray {
385 public:
386   UnwindSectionCompressedArray(A &addressSpace, typename A::pint_t addr)
387       : _addressSpace(addressSpace), _addr(addr) {}
388 
389   uint32_t functionOffset(uint32_t index) const {
390     return UNWIND_INFO_COMPRESSED_ENTRY_FUNC_OFFSET(
391         _addressSpace.get32(_addr + index * sizeof(uint32_t)));
392   }
393   uint16_t encodingIndex(uint32_t index) const {
394     return UNWIND_INFO_COMPRESSED_ENTRY_ENCODING_INDEX(
395         _addressSpace.get32(_addr + index * sizeof(uint32_t)));
396   }
397 
398 private:
399   A &_addressSpace;
400   typename A::pint_t _addr;
401 };
402 
403 template <typename A> class UnwindSectionLsdaArray {
404 public:
405   UnwindSectionLsdaArray(A &addressSpace, typename A::pint_t addr)
406       : _addressSpace(addressSpace), _addr(addr) {}
407 
408   uint32_t functionOffset(uint32_t index) const {
409     return _addressSpace.get32(
410         _addr + arrayoffsetof(unwind_info_section_header_lsda_index_entry,
411                               index, functionOffset));
412   }
413   uint32_t lsdaOffset(uint32_t index) const {
414     return _addressSpace.get32(
415         _addr + arrayoffsetof(unwind_info_section_header_lsda_index_entry,
416                               index, lsdaOffset));
417   }
418 
419 private:
420   A                   &_addressSpace;
421   typename A::pint_t   _addr;
422 };
423 #endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
424 
425 class _LIBUNWIND_HIDDEN AbstractUnwindCursor {
426 public:
427   // NOTE: provide a class specific placement deallocation function (S5.3.4 p20)
428   // This avoids an unnecessary dependency to libc++abi.
429   void operator delete(void *, size_t) {}
430 
431   virtual ~AbstractUnwindCursor() {}
432   virtual bool validReg(int) { _LIBUNWIND_ABORT("validReg not implemented"); }
433   virtual unw_word_t getReg(int) { _LIBUNWIND_ABORT("getReg not implemented"); }
434   virtual void setReg(int, unw_word_t) {
435     _LIBUNWIND_ABORT("setReg not implemented");
436   }
437   virtual bool validFloatReg(int) {
438     _LIBUNWIND_ABORT("validFloatReg not implemented");
439   }
440   virtual unw_fpreg_t getFloatReg(int) {
441     _LIBUNWIND_ABORT("getFloatReg not implemented");
442   }
443   virtual void setFloatReg(int, unw_fpreg_t) {
444     _LIBUNWIND_ABORT("setFloatReg not implemented");
445   }
446   virtual int step() { _LIBUNWIND_ABORT("step not implemented"); }
447   virtual void getInfo(unw_proc_info_t *) {
448     _LIBUNWIND_ABORT("getInfo not implemented");
449   }
450   virtual void jumpto() { _LIBUNWIND_ABORT("jumpto not implemented"); }
451   virtual bool isSignalFrame() {
452     _LIBUNWIND_ABORT("isSignalFrame not implemented");
453   }
454   virtual bool getFunctionName(char *, size_t, unw_word_t *) {
455     _LIBUNWIND_ABORT("getFunctionName not implemented");
456   }
457   virtual void setInfoBasedOnIPRegister(bool = false) {
458     _LIBUNWIND_ABORT("setInfoBasedOnIPRegister not implemented");
459   }
460   virtual const char *getRegisterName(int) {
461     _LIBUNWIND_ABORT("getRegisterName not implemented");
462   }
463 #ifdef __arm__
464   virtual void saveVFPAsX() { _LIBUNWIND_ABORT("saveVFPAsX not implemented"); }
465 #endif
466 
467 #ifdef _AIX
468   virtual uintptr_t getDataRelBase() {
469     _LIBUNWIND_ABORT("getDataRelBase not implemented");
470   }
471 #endif
472 
473 #if defined(_LIBUNWIND_USE_CET)
474   virtual void *get_registers() {
475     _LIBUNWIND_ABORT("get_registers not implemented");
476   }
477 #endif
478 };
479 
480 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) && defined(_WIN32)
481 
482 /// \c UnwindCursor contains all state (including all register values) during
483 /// an unwind.  This is normally stack-allocated inside a unw_cursor_t.
484 template <typename A, typename R>
485 class UnwindCursor : public AbstractUnwindCursor {
486   typedef typename A::pint_t pint_t;
487 public:
488                       UnwindCursor(unw_context_t *context, A &as);
489                       UnwindCursor(CONTEXT *context, A &as);
490                       UnwindCursor(A &as, void *threadArg);
491   virtual             ~UnwindCursor() {}
492   virtual bool        validReg(int);
493   virtual unw_word_t  getReg(int);
494   virtual void        setReg(int, unw_word_t);
495   virtual bool        validFloatReg(int);
496   virtual unw_fpreg_t getFloatReg(int);
497   virtual void        setFloatReg(int, unw_fpreg_t);
498   virtual int         step();
499   virtual void        getInfo(unw_proc_info_t *);
500   virtual void        jumpto();
501   virtual bool        isSignalFrame();
502   virtual bool        getFunctionName(char *buf, size_t len, unw_word_t *off);
503   virtual void        setInfoBasedOnIPRegister(bool isReturnAddress = false);
504   virtual const char *getRegisterName(int num);
505 #ifdef __arm__
506   virtual void        saveVFPAsX();
507 #endif
508 
509   DISPATCHER_CONTEXT *getDispatcherContext() { return &_dispContext; }
510   void setDispatcherContext(DISPATCHER_CONTEXT *disp) { _dispContext = *disp; }
511 
512   // libunwind does not and should not depend on C++ library which means that we
513   // need our own defition of inline placement new.
514   static void *operator new(size_t, UnwindCursor<A, R> *p) { return p; }
515 
516 private:
517 
518   pint_t getLastPC() const { return _dispContext.ControlPc; }
519   void setLastPC(pint_t pc) { _dispContext.ControlPc = pc; }
520   RUNTIME_FUNCTION *lookUpSEHUnwindInfo(pint_t pc, pint_t *base) {
521     _dispContext.FunctionEntry = RtlLookupFunctionEntry(pc,
522                                                         &_dispContext.ImageBase,
523                                                         _dispContext.HistoryTable);
524     *base = _dispContext.ImageBase;
525     return _dispContext.FunctionEntry;
526   }
527   bool getInfoFromSEH(pint_t pc);
528   int stepWithSEHData() {
529     _dispContext.LanguageHandler = RtlVirtualUnwind(UNW_FLAG_UHANDLER,
530                                                     _dispContext.ImageBase,
531                                                     _dispContext.ControlPc,
532                                                     _dispContext.FunctionEntry,
533                                                     _dispContext.ContextRecord,
534                                                     &_dispContext.HandlerData,
535                                                     &_dispContext.EstablisherFrame,
536                                                     NULL);
537     // Update some fields of the unwind info now, since we have them.
538     _info.lsda = reinterpret_cast<unw_word_t>(_dispContext.HandlerData);
539     if (_dispContext.LanguageHandler) {
540       _info.handler = reinterpret_cast<unw_word_t>(__libunwind_seh_personality);
541     } else
542       _info.handler = 0;
543     return UNW_STEP_SUCCESS;
544   }
545 
546   A                   &_addressSpace;
547   unw_proc_info_t      _info;
548   DISPATCHER_CONTEXT   _dispContext;
549   CONTEXT              _msContext;
550   UNWIND_HISTORY_TABLE _histTable;
551   bool                 _unwindInfoMissing;
552 };
553 
554 
555 template <typename A, typename R>
556 UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
557     : _addressSpace(as), _unwindInfoMissing(false) {
558   static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
559                 "UnwindCursor<> does not fit in unw_cursor_t");
560   static_assert((alignof(UnwindCursor<A, R>) <= alignof(unw_cursor_t)),
561                 "UnwindCursor<> requires more alignment than unw_cursor_t");
562   memset(&_info, 0, sizeof(_info));
563   memset(&_histTable, 0, sizeof(_histTable));
564   _dispContext.ContextRecord = &_msContext;
565   _dispContext.HistoryTable = &_histTable;
566   // Initialize MS context from ours.
567   R r(context);
568   _msContext.ContextFlags = CONTEXT_CONTROL|CONTEXT_INTEGER|CONTEXT_FLOATING_POINT;
569 #if defined(_LIBUNWIND_TARGET_X86_64)
570   _msContext.Rax = r.getRegister(UNW_X86_64_RAX);
571   _msContext.Rcx = r.getRegister(UNW_X86_64_RCX);
572   _msContext.Rdx = r.getRegister(UNW_X86_64_RDX);
573   _msContext.Rbx = r.getRegister(UNW_X86_64_RBX);
574   _msContext.Rsp = r.getRegister(UNW_X86_64_RSP);
575   _msContext.Rbp = r.getRegister(UNW_X86_64_RBP);
576   _msContext.Rsi = r.getRegister(UNW_X86_64_RSI);
577   _msContext.Rdi = r.getRegister(UNW_X86_64_RDI);
578   _msContext.R8 = r.getRegister(UNW_X86_64_R8);
579   _msContext.R9 = r.getRegister(UNW_X86_64_R9);
580   _msContext.R10 = r.getRegister(UNW_X86_64_R10);
581   _msContext.R11 = r.getRegister(UNW_X86_64_R11);
582   _msContext.R12 = r.getRegister(UNW_X86_64_R12);
583   _msContext.R13 = r.getRegister(UNW_X86_64_R13);
584   _msContext.R14 = r.getRegister(UNW_X86_64_R14);
585   _msContext.R15 = r.getRegister(UNW_X86_64_R15);
586   _msContext.Rip = r.getRegister(UNW_REG_IP);
587   union {
588     v128 v;
589     M128A m;
590   } t;
591   t.v = r.getVectorRegister(UNW_X86_64_XMM0);
592   _msContext.Xmm0 = t.m;
593   t.v = r.getVectorRegister(UNW_X86_64_XMM1);
594   _msContext.Xmm1 = t.m;
595   t.v = r.getVectorRegister(UNW_X86_64_XMM2);
596   _msContext.Xmm2 = t.m;
597   t.v = r.getVectorRegister(UNW_X86_64_XMM3);
598   _msContext.Xmm3 = t.m;
599   t.v = r.getVectorRegister(UNW_X86_64_XMM4);
600   _msContext.Xmm4 = t.m;
601   t.v = r.getVectorRegister(UNW_X86_64_XMM5);
602   _msContext.Xmm5 = t.m;
603   t.v = r.getVectorRegister(UNW_X86_64_XMM6);
604   _msContext.Xmm6 = t.m;
605   t.v = r.getVectorRegister(UNW_X86_64_XMM7);
606   _msContext.Xmm7 = t.m;
607   t.v = r.getVectorRegister(UNW_X86_64_XMM8);
608   _msContext.Xmm8 = t.m;
609   t.v = r.getVectorRegister(UNW_X86_64_XMM9);
610   _msContext.Xmm9 = t.m;
611   t.v = r.getVectorRegister(UNW_X86_64_XMM10);
612   _msContext.Xmm10 = t.m;
613   t.v = r.getVectorRegister(UNW_X86_64_XMM11);
614   _msContext.Xmm11 = t.m;
615   t.v = r.getVectorRegister(UNW_X86_64_XMM12);
616   _msContext.Xmm12 = t.m;
617   t.v = r.getVectorRegister(UNW_X86_64_XMM13);
618   _msContext.Xmm13 = t.m;
619   t.v = r.getVectorRegister(UNW_X86_64_XMM14);
620   _msContext.Xmm14 = t.m;
621   t.v = r.getVectorRegister(UNW_X86_64_XMM15);
622   _msContext.Xmm15 = t.m;
623 #elif defined(_LIBUNWIND_TARGET_ARM)
624   _msContext.R0 = r.getRegister(UNW_ARM_R0);
625   _msContext.R1 = r.getRegister(UNW_ARM_R1);
626   _msContext.R2 = r.getRegister(UNW_ARM_R2);
627   _msContext.R3 = r.getRegister(UNW_ARM_R3);
628   _msContext.R4 = r.getRegister(UNW_ARM_R4);
629   _msContext.R5 = r.getRegister(UNW_ARM_R5);
630   _msContext.R6 = r.getRegister(UNW_ARM_R6);
631   _msContext.R7 = r.getRegister(UNW_ARM_R7);
632   _msContext.R8 = r.getRegister(UNW_ARM_R8);
633   _msContext.R9 = r.getRegister(UNW_ARM_R9);
634   _msContext.R10 = r.getRegister(UNW_ARM_R10);
635   _msContext.R11 = r.getRegister(UNW_ARM_R11);
636   _msContext.R12 = r.getRegister(UNW_ARM_R12);
637   _msContext.Sp = r.getRegister(UNW_ARM_SP);
638   _msContext.Lr = r.getRegister(UNW_ARM_LR);
639   _msContext.Pc = r.getRegister(UNW_ARM_IP);
640   for (int i = UNW_ARM_D0; i <= UNW_ARM_D31; ++i) {
641     union {
642       uint64_t w;
643       double d;
644     } d;
645     d.d = r.getFloatRegister(i);
646     _msContext.D[i - UNW_ARM_D0] = d.w;
647   }
648 #elif defined(_LIBUNWIND_TARGET_AARCH64)
649   for (int i = UNW_AARCH64_X0; i <= UNW_ARM64_X30; ++i)
650     _msContext.X[i - UNW_AARCH64_X0] = r.getRegister(i);
651   _msContext.Sp = r.getRegister(UNW_REG_SP);
652   _msContext.Pc = r.getRegister(UNW_REG_IP);
653   for (int i = UNW_AARCH64_V0; i <= UNW_ARM64_D31; ++i)
654     _msContext.V[i - UNW_AARCH64_V0].D[0] = r.getFloatRegister(i);
655 #endif
656 }
657 
658 template <typename A, typename R>
659 UnwindCursor<A, R>::UnwindCursor(CONTEXT *context, A &as)
660     : _addressSpace(as), _unwindInfoMissing(false) {
661   static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
662                 "UnwindCursor<> does not fit in unw_cursor_t");
663   memset(&_info, 0, sizeof(_info));
664   memset(&_histTable, 0, sizeof(_histTable));
665   _dispContext.ContextRecord = &_msContext;
666   _dispContext.HistoryTable = &_histTable;
667   _msContext = *context;
668 }
669 
670 
671 template <typename A, typename R>
672 bool UnwindCursor<A, R>::validReg(int regNum) {
673   if (regNum == UNW_REG_IP || regNum == UNW_REG_SP) return true;
674 #if defined(_LIBUNWIND_TARGET_X86_64)
675   if (regNum >= UNW_X86_64_RAX && regNum <= UNW_X86_64_R15) return true;
676 #elif defined(_LIBUNWIND_TARGET_ARM)
677   if ((regNum >= UNW_ARM_R0 && regNum <= UNW_ARM_R15) ||
678       regNum == UNW_ARM_RA_AUTH_CODE)
679     return true;
680 #elif defined(_LIBUNWIND_TARGET_AARCH64)
681   if (regNum >= UNW_AARCH64_X0 && regNum <= UNW_ARM64_X30) return true;
682 #endif
683   return false;
684 }
685 
686 template <typename A, typename R>
687 unw_word_t UnwindCursor<A, R>::getReg(int regNum) {
688   switch (regNum) {
689 #if defined(_LIBUNWIND_TARGET_X86_64)
690   case UNW_REG_IP: return _msContext.Rip;
691   case UNW_X86_64_RAX: return _msContext.Rax;
692   case UNW_X86_64_RDX: return _msContext.Rdx;
693   case UNW_X86_64_RCX: return _msContext.Rcx;
694   case UNW_X86_64_RBX: return _msContext.Rbx;
695   case UNW_REG_SP:
696   case UNW_X86_64_RSP: return _msContext.Rsp;
697   case UNW_X86_64_RBP: return _msContext.Rbp;
698   case UNW_X86_64_RSI: return _msContext.Rsi;
699   case UNW_X86_64_RDI: return _msContext.Rdi;
700   case UNW_X86_64_R8: return _msContext.R8;
701   case UNW_X86_64_R9: return _msContext.R9;
702   case UNW_X86_64_R10: return _msContext.R10;
703   case UNW_X86_64_R11: return _msContext.R11;
704   case UNW_X86_64_R12: return _msContext.R12;
705   case UNW_X86_64_R13: return _msContext.R13;
706   case UNW_X86_64_R14: return _msContext.R14;
707   case UNW_X86_64_R15: return _msContext.R15;
708 #elif defined(_LIBUNWIND_TARGET_ARM)
709   case UNW_ARM_R0: return _msContext.R0;
710   case UNW_ARM_R1: return _msContext.R1;
711   case UNW_ARM_R2: return _msContext.R2;
712   case UNW_ARM_R3: return _msContext.R3;
713   case UNW_ARM_R4: return _msContext.R4;
714   case UNW_ARM_R5: return _msContext.R5;
715   case UNW_ARM_R6: return _msContext.R6;
716   case UNW_ARM_R7: return _msContext.R7;
717   case UNW_ARM_R8: return _msContext.R8;
718   case UNW_ARM_R9: return _msContext.R9;
719   case UNW_ARM_R10: return _msContext.R10;
720   case UNW_ARM_R11: return _msContext.R11;
721   case UNW_ARM_R12: return _msContext.R12;
722   case UNW_REG_SP:
723   case UNW_ARM_SP: return _msContext.Sp;
724   case UNW_ARM_LR: return _msContext.Lr;
725   case UNW_REG_IP:
726   case UNW_ARM_IP: return _msContext.Pc;
727 #elif defined(_LIBUNWIND_TARGET_AARCH64)
728   case UNW_REG_SP: return _msContext.Sp;
729   case UNW_REG_IP: return _msContext.Pc;
730   default: return _msContext.X[regNum - UNW_AARCH64_X0];
731 #endif
732   }
733   _LIBUNWIND_ABORT("unsupported register");
734 }
735 
736 template <typename A, typename R>
737 void UnwindCursor<A, R>::setReg(int regNum, unw_word_t value) {
738   switch (regNum) {
739 #if defined(_LIBUNWIND_TARGET_X86_64)
740   case UNW_REG_IP: _msContext.Rip = value; break;
741   case UNW_X86_64_RAX: _msContext.Rax = value; break;
742   case UNW_X86_64_RDX: _msContext.Rdx = value; break;
743   case UNW_X86_64_RCX: _msContext.Rcx = value; break;
744   case UNW_X86_64_RBX: _msContext.Rbx = value; break;
745   case UNW_REG_SP:
746   case UNW_X86_64_RSP: _msContext.Rsp = value; break;
747   case UNW_X86_64_RBP: _msContext.Rbp = value; break;
748   case UNW_X86_64_RSI: _msContext.Rsi = value; break;
749   case UNW_X86_64_RDI: _msContext.Rdi = value; break;
750   case UNW_X86_64_R8: _msContext.R8 = value; break;
751   case UNW_X86_64_R9: _msContext.R9 = value; break;
752   case UNW_X86_64_R10: _msContext.R10 = value; break;
753   case UNW_X86_64_R11: _msContext.R11 = value; break;
754   case UNW_X86_64_R12: _msContext.R12 = value; break;
755   case UNW_X86_64_R13: _msContext.R13 = value; break;
756   case UNW_X86_64_R14: _msContext.R14 = value; break;
757   case UNW_X86_64_R15: _msContext.R15 = value; break;
758 #elif defined(_LIBUNWIND_TARGET_ARM)
759   case UNW_ARM_R0: _msContext.R0 = value; break;
760   case UNW_ARM_R1: _msContext.R1 = value; break;
761   case UNW_ARM_R2: _msContext.R2 = value; break;
762   case UNW_ARM_R3: _msContext.R3 = value; break;
763   case UNW_ARM_R4: _msContext.R4 = value; break;
764   case UNW_ARM_R5: _msContext.R5 = value; break;
765   case UNW_ARM_R6: _msContext.R6 = value; break;
766   case UNW_ARM_R7: _msContext.R7 = value; break;
767   case UNW_ARM_R8: _msContext.R8 = value; break;
768   case UNW_ARM_R9: _msContext.R9 = value; break;
769   case UNW_ARM_R10: _msContext.R10 = value; break;
770   case UNW_ARM_R11: _msContext.R11 = value; break;
771   case UNW_ARM_R12: _msContext.R12 = value; break;
772   case UNW_REG_SP:
773   case UNW_ARM_SP: _msContext.Sp = value; break;
774   case UNW_ARM_LR: _msContext.Lr = value; break;
775   case UNW_REG_IP:
776   case UNW_ARM_IP: _msContext.Pc = value; break;
777 #elif defined(_LIBUNWIND_TARGET_AARCH64)
778   case UNW_REG_SP: _msContext.Sp = value; break;
779   case UNW_REG_IP: _msContext.Pc = value; break;
780   case UNW_AARCH64_X0:
781   case UNW_AARCH64_X1:
782   case UNW_AARCH64_X2:
783   case UNW_AARCH64_X3:
784   case UNW_AARCH64_X4:
785   case UNW_AARCH64_X5:
786   case UNW_AARCH64_X6:
787   case UNW_AARCH64_X7:
788   case UNW_AARCH64_X8:
789   case UNW_AARCH64_X9:
790   case UNW_AARCH64_X10:
791   case UNW_AARCH64_X11:
792   case UNW_AARCH64_X12:
793   case UNW_AARCH64_X13:
794   case UNW_AARCH64_X14:
795   case UNW_AARCH64_X15:
796   case UNW_AARCH64_X16:
797   case UNW_AARCH64_X17:
798   case UNW_AARCH64_X18:
799   case UNW_AARCH64_X19:
800   case UNW_AARCH64_X20:
801   case UNW_AARCH64_X21:
802   case UNW_AARCH64_X22:
803   case UNW_AARCH64_X23:
804   case UNW_AARCH64_X24:
805   case UNW_AARCH64_X25:
806   case UNW_AARCH64_X26:
807   case UNW_AARCH64_X27:
808   case UNW_AARCH64_X28:
809   case UNW_AARCH64_FP:
810   case UNW_AARCH64_LR: _msContext.X[regNum - UNW_ARM64_X0] = value; break;
811 #endif
812   default:
813     _LIBUNWIND_ABORT("unsupported register");
814   }
815 }
816 
817 template <typename A, typename R>
818 bool UnwindCursor<A, R>::validFloatReg(int regNum) {
819 #if defined(_LIBUNWIND_TARGET_ARM)
820   if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) return true;
821   if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) return true;
822 #elif defined(_LIBUNWIND_TARGET_AARCH64)
823   if (regNum >= UNW_AARCH64_V0 && regNum <= UNW_ARM64_D31) return true;
824 #else
825   (void)regNum;
826 #endif
827   return false;
828 }
829 
830 template <typename A, typename R>
831 unw_fpreg_t UnwindCursor<A, R>::getFloatReg(int regNum) {
832 #if defined(_LIBUNWIND_TARGET_ARM)
833   if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) {
834     union {
835       uint32_t w;
836       float f;
837     } d;
838     d.w = _msContext.S[regNum - UNW_ARM_S0];
839     return d.f;
840   }
841   if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) {
842     union {
843       uint64_t w;
844       double d;
845     } d;
846     d.w = _msContext.D[regNum - UNW_ARM_D0];
847     return d.d;
848   }
849   _LIBUNWIND_ABORT("unsupported float register");
850 #elif defined(_LIBUNWIND_TARGET_AARCH64)
851   return _msContext.V[regNum - UNW_AARCH64_V0].D[0];
852 #else
853   (void)regNum;
854   _LIBUNWIND_ABORT("float registers unimplemented");
855 #endif
856 }
857 
858 template <typename A, typename R>
859 void UnwindCursor<A, R>::setFloatReg(int regNum, unw_fpreg_t value) {
860 #if defined(_LIBUNWIND_TARGET_ARM)
861   if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) {
862     union {
863       uint32_t w;
864       float f;
865     } d;
866     d.f = value;
867     _msContext.S[regNum - UNW_ARM_S0] = d.w;
868   }
869   if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) {
870     union {
871       uint64_t w;
872       double d;
873     } d;
874     d.d = value;
875     _msContext.D[regNum - UNW_ARM_D0] = d.w;
876   }
877   _LIBUNWIND_ABORT("unsupported float register");
878 #elif defined(_LIBUNWIND_TARGET_AARCH64)
879   _msContext.V[regNum - UNW_AARCH64_V0].D[0] = value;
880 #else
881   (void)regNum;
882   (void)value;
883   _LIBUNWIND_ABORT("float registers unimplemented");
884 #endif
885 }
886 
887 template <typename A, typename R> void UnwindCursor<A, R>::jumpto() {
888   RtlRestoreContext(&_msContext, nullptr);
889 }
890 
891 #ifdef __arm__
892 template <typename A, typename R> void UnwindCursor<A, R>::saveVFPAsX() {}
893 #endif
894 
895 template <typename A, typename R>
896 const char *UnwindCursor<A, R>::getRegisterName(int regNum) {
897   return R::getRegisterName(regNum);
898 }
899 
900 template <typename A, typename R> bool UnwindCursor<A, R>::isSignalFrame() {
901   return false;
902 }
903 
904 #else  // !defined(_LIBUNWIND_SUPPORT_SEH_UNWIND) || !defined(_WIN32)
905 
906 /// UnwindCursor contains all state (including all register values) during
907 /// an unwind.  This is normally stack allocated inside a unw_cursor_t.
908 template <typename A, typename R>
909 class UnwindCursor : public AbstractUnwindCursor{
910   typedef typename A::pint_t pint_t;
911 public:
912                       UnwindCursor(unw_context_t *context, A &as);
913                       UnwindCursor(A &as, void *threadArg);
914   virtual             ~UnwindCursor() {}
915   virtual bool        validReg(int);
916   virtual unw_word_t  getReg(int);
917   virtual void        setReg(int, unw_word_t);
918   virtual bool        validFloatReg(int);
919   virtual unw_fpreg_t getFloatReg(int);
920   virtual void        setFloatReg(int, unw_fpreg_t);
921   virtual int         step();
922   virtual void        getInfo(unw_proc_info_t *);
923   virtual void        jumpto();
924   virtual bool        isSignalFrame();
925   virtual bool        getFunctionName(char *buf, size_t len, unw_word_t *off);
926   virtual void        setInfoBasedOnIPRegister(bool isReturnAddress = false);
927   virtual const char *getRegisterName(int num);
928 #ifdef __arm__
929   virtual void        saveVFPAsX();
930 #endif
931 
932 #ifdef _AIX
933   virtual uintptr_t getDataRelBase();
934 #endif
935 
936 #if defined(_LIBUNWIND_USE_CET)
937   virtual void *get_registers() { return &_registers; }
938 #endif
939 
940   // libunwind does not and should not depend on C++ library which means that we
941   // need our own defition of inline placement new.
942   static void *operator new(size_t, UnwindCursor<A, R> *p) { return p; }
943 
944 private:
945 
946 #if defined(_LIBUNWIND_ARM_EHABI)
947   bool getInfoFromEHABISection(pint_t pc, const UnwindInfoSections &sects);
948 
949   int stepWithEHABI() {
950     size_t len = 0;
951     size_t off = 0;
952     // FIXME: Calling decode_eht_entry() here is violating the libunwind
953     // abstraction layer.
954     const uint32_t *ehtp =
955         decode_eht_entry(reinterpret_cast<const uint32_t *>(_info.unwind_info),
956                          &off, &len);
957     if (_Unwind_VRS_Interpret((_Unwind_Context *)this, ehtp, off, len) !=
958             _URC_CONTINUE_UNWIND)
959       return UNW_STEP_END;
960     return UNW_STEP_SUCCESS;
961   }
962 #endif
963 
964 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN)
965   bool setInfoForSigReturn() {
966     R dummy;
967     return setInfoForSigReturn(dummy);
968   }
969   int stepThroughSigReturn() {
970     R dummy;
971     return stepThroughSigReturn(dummy);
972   }
973 #if defined(_LIBUNWIND_TARGET_AARCH64)
974   bool setInfoForSigReturn(Registers_arm64 &);
975   int stepThroughSigReturn(Registers_arm64 &);
976 #endif
977 #if defined(_LIBUNWIND_TARGET_S390X)
978   bool setInfoForSigReturn(Registers_s390x &);
979   int stepThroughSigReturn(Registers_s390x &);
980 #endif
981   template <typename Registers> bool setInfoForSigReturn(Registers &) {
982     return false;
983   }
984   template <typename Registers> int stepThroughSigReturn(Registers &) {
985     return UNW_STEP_END;
986   }
987 #endif
988 
989 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
990   bool getInfoFromFdeCie(const typename CFI_Parser<A>::FDE_Info &fdeInfo,
991                          const typename CFI_Parser<A>::CIE_Info &cieInfo,
992                          pint_t pc, uintptr_t dso_base);
993   bool getInfoFromDwarfSection(pint_t pc, const UnwindInfoSections &sects,
994                                             uint32_t fdeSectionOffsetHint=0);
995   int stepWithDwarfFDE() {
996     return DwarfInstructions<A, R>::stepWithDwarf(_addressSpace,
997                                               (pint_t)this->getReg(UNW_REG_IP),
998                                               (pint_t)_info.unwind_info,
999                                               _registers, _isSignalFrame);
1000   }
1001 #endif
1002 
1003 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
1004   bool getInfoFromCompactEncodingSection(pint_t pc,
1005                                             const UnwindInfoSections &sects);
1006   int stepWithCompactEncoding() {
1007   #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
1008     if ( compactSaysUseDwarf() )
1009       return stepWithDwarfFDE();
1010   #endif
1011     R dummy;
1012     return stepWithCompactEncoding(dummy);
1013   }
1014 
1015 #if defined(_LIBUNWIND_TARGET_X86_64)
1016   int stepWithCompactEncoding(Registers_x86_64 &) {
1017     return CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
1018         _info.format, _info.start_ip, _addressSpace, _registers);
1019   }
1020 #endif
1021 
1022 #if defined(_LIBUNWIND_TARGET_I386)
1023   int stepWithCompactEncoding(Registers_x86 &) {
1024     return CompactUnwinder_x86<A>::stepWithCompactEncoding(
1025         _info.format, (uint32_t)_info.start_ip, _addressSpace, _registers);
1026   }
1027 #endif
1028 
1029 #if defined(_LIBUNWIND_TARGET_PPC)
1030   int stepWithCompactEncoding(Registers_ppc &) {
1031     return UNW_EINVAL;
1032   }
1033 #endif
1034 
1035 #if defined(_LIBUNWIND_TARGET_PPC64)
1036   int stepWithCompactEncoding(Registers_ppc64 &) {
1037     return UNW_EINVAL;
1038   }
1039 #endif
1040 
1041 
1042 #if defined(_LIBUNWIND_TARGET_AARCH64)
1043   int stepWithCompactEncoding(Registers_arm64 &) {
1044     return CompactUnwinder_arm64<A>::stepWithCompactEncoding(
1045         _info.format, _info.start_ip, _addressSpace, _registers);
1046   }
1047 #endif
1048 
1049 #if defined(_LIBUNWIND_TARGET_MIPS_O32)
1050   int stepWithCompactEncoding(Registers_mips_o32 &) {
1051     return UNW_EINVAL;
1052   }
1053 #endif
1054 
1055 #if defined(_LIBUNWIND_TARGET_MIPS_NEWABI)
1056   int stepWithCompactEncoding(Registers_mips_newabi &) {
1057     return UNW_EINVAL;
1058   }
1059 #endif
1060 
1061 #if defined(_LIBUNWIND_TARGET_SPARC)
1062   int stepWithCompactEncoding(Registers_sparc &) { return UNW_EINVAL; }
1063 #endif
1064 
1065 #if defined(_LIBUNWIND_TARGET_SPARC64)
1066   int stepWithCompactEncoding(Registers_sparc64 &) { return UNW_EINVAL; }
1067 #endif
1068 
1069 #if defined (_LIBUNWIND_TARGET_RISCV)
1070   int stepWithCompactEncoding(Registers_riscv &) {
1071     return UNW_EINVAL;
1072   }
1073 #endif
1074 
1075   bool compactSaysUseDwarf(uint32_t *offset=NULL) const {
1076     R dummy;
1077     return compactSaysUseDwarf(dummy, offset);
1078   }
1079 
1080 #if defined(_LIBUNWIND_TARGET_X86_64)
1081   bool compactSaysUseDwarf(Registers_x86_64 &, uint32_t *offset) const {
1082     if ((_info.format & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_DWARF) {
1083       if (offset)
1084         *offset = (_info.format & UNWIND_X86_64_DWARF_SECTION_OFFSET);
1085       return true;
1086     }
1087     return false;
1088   }
1089 #endif
1090 
1091 #if defined(_LIBUNWIND_TARGET_I386)
1092   bool compactSaysUseDwarf(Registers_x86 &, uint32_t *offset) const {
1093     if ((_info.format & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF) {
1094       if (offset)
1095         *offset = (_info.format & UNWIND_X86_DWARF_SECTION_OFFSET);
1096       return true;
1097     }
1098     return false;
1099   }
1100 #endif
1101 
1102 #if defined(_LIBUNWIND_TARGET_PPC)
1103   bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const {
1104     return true;
1105   }
1106 #endif
1107 
1108 #if defined(_LIBUNWIND_TARGET_PPC64)
1109   bool compactSaysUseDwarf(Registers_ppc64 &, uint32_t *) const {
1110     return true;
1111   }
1112 #endif
1113 
1114 #if defined(_LIBUNWIND_TARGET_AARCH64)
1115   bool compactSaysUseDwarf(Registers_arm64 &, uint32_t *offset) const {
1116     if ((_info.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF) {
1117       if (offset)
1118         *offset = (_info.format & UNWIND_ARM64_DWARF_SECTION_OFFSET);
1119       return true;
1120     }
1121     return false;
1122   }
1123 #endif
1124 
1125 #if defined(_LIBUNWIND_TARGET_MIPS_O32)
1126   bool compactSaysUseDwarf(Registers_mips_o32 &, uint32_t *) const {
1127     return true;
1128   }
1129 #endif
1130 
1131 #if defined(_LIBUNWIND_TARGET_MIPS_NEWABI)
1132   bool compactSaysUseDwarf(Registers_mips_newabi &, uint32_t *) const {
1133     return true;
1134   }
1135 #endif
1136 
1137 #if defined(_LIBUNWIND_TARGET_SPARC)
1138   bool compactSaysUseDwarf(Registers_sparc &, uint32_t *) const { return true; }
1139 #endif
1140 
1141 #if defined(_LIBUNWIND_TARGET_SPARC64)
1142   bool compactSaysUseDwarf(Registers_sparc64 &, uint32_t *) const {
1143     return true;
1144   }
1145 #endif
1146 
1147 #if defined (_LIBUNWIND_TARGET_RISCV)
1148   bool compactSaysUseDwarf(Registers_riscv &, uint32_t *) const {
1149     return true;
1150   }
1151 #endif
1152 
1153 #endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
1154 
1155 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
1156   compact_unwind_encoding_t dwarfEncoding() const {
1157     R dummy;
1158     return dwarfEncoding(dummy);
1159   }
1160 
1161 #if defined(_LIBUNWIND_TARGET_X86_64)
1162   compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const {
1163     return UNWIND_X86_64_MODE_DWARF;
1164   }
1165 #endif
1166 
1167 #if defined(_LIBUNWIND_TARGET_I386)
1168   compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const {
1169     return UNWIND_X86_MODE_DWARF;
1170   }
1171 #endif
1172 
1173 #if defined(_LIBUNWIND_TARGET_PPC)
1174   compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const {
1175     return 0;
1176   }
1177 #endif
1178 
1179 #if defined(_LIBUNWIND_TARGET_PPC64)
1180   compact_unwind_encoding_t dwarfEncoding(Registers_ppc64 &) const {
1181     return 0;
1182   }
1183 #endif
1184 
1185 #if defined(_LIBUNWIND_TARGET_AARCH64)
1186   compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const {
1187     return UNWIND_ARM64_MODE_DWARF;
1188   }
1189 #endif
1190 
1191 #if defined(_LIBUNWIND_TARGET_ARM)
1192   compact_unwind_encoding_t dwarfEncoding(Registers_arm &) const {
1193     return 0;
1194   }
1195 #endif
1196 
1197 #if defined (_LIBUNWIND_TARGET_OR1K)
1198   compact_unwind_encoding_t dwarfEncoding(Registers_or1k &) const {
1199     return 0;
1200   }
1201 #endif
1202 
1203 #if defined (_LIBUNWIND_TARGET_HEXAGON)
1204   compact_unwind_encoding_t dwarfEncoding(Registers_hexagon &) const {
1205     return 0;
1206   }
1207 #endif
1208 
1209 #if defined (_LIBUNWIND_TARGET_MIPS_O32)
1210   compact_unwind_encoding_t dwarfEncoding(Registers_mips_o32 &) const {
1211     return 0;
1212   }
1213 #endif
1214 
1215 #if defined (_LIBUNWIND_TARGET_MIPS_NEWABI)
1216   compact_unwind_encoding_t dwarfEncoding(Registers_mips_newabi &) const {
1217     return 0;
1218   }
1219 #endif
1220 
1221 #if defined(_LIBUNWIND_TARGET_SPARC)
1222   compact_unwind_encoding_t dwarfEncoding(Registers_sparc &) const { return 0; }
1223 #endif
1224 
1225 #if defined(_LIBUNWIND_TARGET_SPARC64)
1226   compact_unwind_encoding_t dwarfEncoding(Registers_sparc64 &) const {
1227     return 0;
1228   }
1229 #endif
1230 
1231 #if defined (_LIBUNWIND_TARGET_RISCV)
1232   compact_unwind_encoding_t dwarfEncoding(Registers_riscv &) const {
1233     return 0;
1234   }
1235 #endif
1236 
1237 #if defined (_LIBUNWIND_TARGET_S390X)
1238   compact_unwind_encoding_t dwarfEncoding(Registers_s390x &) const {
1239     return 0;
1240   }
1241 #endif
1242 
1243 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
1244 
1245 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
1246   // For runtime environments using SEH unwind data without Windows runtime
1247   // support.
1248   pint_t getLastPC() const { /* FIXME: Implement */ return 0; }
1249   void setLastPC(pint_t pc) { /* FIXME: Implement */ }
1250   RUNTIME_FUNCTION *lookUpSEHUnwindInfo(pint_t pc, pint_t *base) {
1251     /* FIXME: Implement */
1252     *base = 0;
1253     return nullptr;
1254   }
1255   bool getInfoFromSEH(pint_t pc);
1256   int stepWithSEHData() { /* FIXME: Implement */ return 0; }
1257 #endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
1258 
1259 #if defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
1260   bool getInfoFromTBTable(pint_t pc, R &registers);
1261   int stepWithTBTable(pint_t pc, tbtable *TBTable, R &registers,
1262                       bool &isSignalFrame);
1263   int stepWithTBTableData() {
1264     return stepWithTBTable(reinterpret_cast<pint_t>(this->getReg(UNW_REG_IP)),
1265                            reinterpret_cast<tbtable *>(_info.unwind_info),
1266                            _registers, _isSignalFrame);
1267   }
1268 #endif // defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
1269 
1270   A               &_addressSpace;
1271   R                _registers;
1272   unw_proc_info_t  _info;
1273   bool             _unwindInfoMissing;
1274   bool             _isSignalFrame;
1275 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN)
1276   bool             _isSigReturn = false;
1277 #endif
1278 };
1279 
1280 
1281 template <typename A, typename R>
1282 UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
1283     : _addressSpace(as), _registers(context), _unwindInfoMissing(false),
1284       _isSignalFrame(false) {
1285   static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
1286                 "UnwindCursor<> does not fit in unw_cursor_t");
1287   static_assert((alignof(UnwindCursor<A, R>) <= alignof(unw_cursor_t)),
1288                 "UnwindCursor<> requires more alignment than unw_cursor_t");
1289   memset(&_info, 0, sizeof(_info));
1290 }
1291 
1292 template <typename A, typename R>
1293 UnwindCursor<A, R>::UnwindCursor(A &as, void *)
1294     : _addressSpace(as), _unwindInfoMissing(false), _isSignalFrame(false) {
1295   memset(&_info, 0, sizeof(_info));
1296   // FIXME
1297   // fill in _registers from thread arg
1298 }
1299 
1300 
1301 template <typename A, typename R>
1302 bool UnwindCursor<A, R>::validReg(int regNum) {
1303   return _registers.validRegister(regNum);
1304 }
1305 
1306 template <typename A, typename R>
1307 unw_word_t UnwindCursor<A, R>::getReg(int regNum) {
1308   return _registers.getRegister(regNum);
1309 }
1310 
1311 template <typename A, typename R>
1312 void UnwindCursor<A, R>::setReg(int regNum, unw_word_t value) {
1313   _registers.setRegister(regNum, (typename A::pint_t)value);
1314 }
1315 
1316 template <typename A, typename R>
1317 bool UnwindCursor<A, R>::validFloatReg(int regNum) {
1318   return _registers.validFloatRegister(regNum);
1319 }
1320 
1321 template <typename A, typename R>
1322 unw_fpreg_t UnwindCursor<A, R>::getFloatReg(int regNum) {
1323   return _registers.getFloatRegister(regNum);
1324 }
1325 
1326 template <typename A, typename R>
1327 void UnwindCursor<A, R>::setFloatReg(int regNum, unw_fpreg_t value) {
1328   _registers.setFloatRegister(regNum, value);
1329 }
1330 
1331 template <typename A, typename R> void UnwindCursor<A, R>::jumpto() {
1332   _registers.jumpto();
1333 }
1334 
1335 #ifdef __arm__
1336 template <typename A, typename R> void UnwindCursor<A, R>::saveVFPAsX() {
1337   _registers.saveVFPAsX();
1338 }
1339 #endif
1340 
1341 #ifdef _AIX
1342 template <typename A, typename R>
1343 uintptr_t UnwindCursor<A, R>::getDataRelBase() {
1344   return reinterpret_cast<uintptr_t>(_info.extra);
1345 }
1346 #endif
1347 
1348 template <typename A, typename R>
1349 const char *UnwindCursor<A, R>::getRegisterName(int regNum) {
1350   return _registers.getRegisterName(regNum);
1351 }
1352 
1353 template <typename A, typename R> bool UnwindCursor<A, R>::isSignalFrame() {
1354   return _isSignalFrame;
1355 }
1356 
1357 #endif // defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
1358 
1359 #if defined(_LIBUNWIND_ARM_EHABI)
1360 template<typename A>
1361 struct EHABISectionIterator {
1362   typedef EHABISectionIterator _Self;
1363 
1364   typedef typename A::pint_t value_type;
1365   typedef typename A::pint_t* pointer;
1366   typedef typename A::pint_t& reference;
1367   typedef size_t size_type;
1368   typedef size_t difference_type;
1369 
1370   static _Self begin(A& addressSpace, const UnwindInfoSections& sects) {
1371     return _Self(addressSpace, sects, 0);
1372   }
1373   static _Self end(A& addressSpace, const UnwindInfoSections& sects) {
1374     return _Self(addressSpace, sects,
1375                  sects.arm_section_length / sizeof(EHABIIndexEntry));
1376   }
1377 
1378   EHABISectionIterator(A& addressSpace, const UnwindInfoSections& sects, size_t i)
1379       : _i(i), _addressSpace(&addressSpace), _sects(&sects) {}
1380 
1381   _Self& operator++() { ++_i; return *this; }
1382   _Self& operator+=(size_t a) { _i += a; return *this; }
1383   _Self& operator--() { assert(_i > 0); --_i; return *this; }
1384   _Self& operator-=(size_t a) { assert(_i >= a); _i -= a; return *this; }
1385 
1386   _Self operator+(size_t a) { _Self out = *this; out._i += a; return out; }
1387   _Self operator-(size_t a) { assert(_i >= a); _Self out = *this; out._i -= a; return out; }
1388 
1389   size_t operator-(const _Self& other) const { return _i - other._i; }
1390 
1391   bool operator==(const _Self& other) const {
1392     assert(_addressSpace == other._addressSpace);
1393     assert(_sects == other._sects);
1394     return _i == other._i;
1395   }
1396 
1397   bool operator!=(const _Self& other) const {
1398     assert(_addressSpace == other._addressSpace);
1399     assert(_sects == other._sects);
1400     return _i != other._i;
1401   }
1402 
1403   typename A::pint_t operator*() const { return functionAddress(); }
1404 
1405   typename A::pint_t functionAddress() const {
1406     typename A::pint_t indexAddr = _sects->arm_section + arrayoffsetof(
1407         EHABIIndexEntry, _i, functionOffset);
1408     return indexAddr + signExtendPrel31(_addressSpace->get32(indexAddr));
1409   }
1410 
1411   typename A::pint_t dataAddress() {
1412     typename A::pint_t indexAddr = _sects->arm_section + arrayoffsetof(
1413         EHABIIndexEntry, _i, data);
1414     return indexAddr;
1415   }
1416 
1417  private:
1418   size_t _i;
1419   A* _addressSpace;
1420   const UnwindInfoSections* _sects;
1421 };
1422 
1423 namespace {
1424 
1425 template <typename A>
1426 EHABISectionIterator<A> EHABISectionUpperBound(
1427     EHABISectionIterator<A> first,
1428     EHABISectionIterator<A> last,
1429     typename A::pint_t value) {
1430   size_t len = last - first;
1431   while (len > 0) {
1432     size_t l2 = len / 2;
1433     EHABISectionIterator<A> m = first + l2;
1434     if (value < *m) {
1435         len = l2;
1436     } else {
1437         first = ++m;
1438         len -= l2 + 1;
1439     }
1440   }
1441   return first;
1442 }
1443 
1444 }
1445 
1446 template <typename A, typename R>
1447 bool UnwindCursor<A, R>::getInfoFromEHABISection(
1448     pint_t pc,
1449     const UnwindInfoSections &sects) {
1450   EHABISectionIterator<A> begin =
1451       EHABISectionIterator<A>::begin(_addressSpace, sects);
1452   EHABISectionIterator<A> end =
1453       EHABISectionIterator<A>::end(_addressSpace, sects);
1454   if (begin == end)
1455     return false;
1456 
1457   EHABISectionIterator<A> itNextPC = EHABISectionUpperBound(begin, end, pc);
1458   if (itNextPC == begin)
1459     return false;
1460   EHABISectionIterator<A> itThisPC = itNextPC - 1;
1461 
1462   pint_t thisPC = itThisPC.functionAddress();
1463   // If an exception is thrown from a function, corresponding to the last entry
1464   // in the table, we don't really know the function extent and have to choose a
1465   // value for nextPC. Choosing max() will allow the range check during trace to
1466   // succeed.
1467   pint_t nextPC = (itNextPC == end) ? UINTPTR_MAX : itNextPC.functionAddress();
1468   pint_t indexDataAddr = itThisPC.dataAddress();
1469 
1470   if (indexDataAddr == 0)
1471     return false;
1472 
1473   uint32_t indexData = _addressSpace.get32(indexDataAddr);
1474   if (indexData == UNW_EXIDX_CANTUNWIND)
1475     return false;
1476 
1477   // If the high bit is set, the exception handling table entry is inline inside
1478   // the index table entry on the second word (aka |indexDataAddr|). Otherwise,
1479   // the table points at an offset in the exception handling table (section 5
1480   // EHABI).
1481   pint_t exceptionTableAddr;
1482   uint32_t exceptionTableData;
1483   bool isSingleWordEHT;
1484   if (indexData & 0x80000000) {
1485     exceptionTableAddr = indexDataAddr;
1486     // TODO(ajwong): Should this data be 0?
1487     exceptionTableData = indexData;
1488     isSingleWordEHT = true;
1489   } else {
1490     exceptionTableAddr = indexDataAddr + signExtendPrel31(indexData);
1491     exceptionTableData = _addressSpace.get32(exceptionTableAddr);
1492     isSingleWordEHT = false;
1493   }
1494 
1495   // Now we know the 3 things:
1496   //   exceptionTableAddr -- exception handler table entry.
1497   //   exceptionTableData -- the data inside the first word of the eht entry.
1498   //   isSingleWordEHT -- whether the entry is in the index.
1499   unw_word_t personalityRoutine = 0xbadf00d;
1500   bool scope32 = false;
1501   uintptr_t lsda;
1502 
1503   // If the high bit in the exception handling table entry is set, the entry is
1504   // in compact form (section 6.3 EHABI).
1505   if (exceptionTableData & 0x80000000) {
1506     // Grab the index of the personality routine from the compact form.
1507     uint32_t choice = (exceptionTableData & 0x0f000000) >> 24;
1508     uint32_t extraWords = 0;
1509     switch (choice) {
1510       case 0:
1511         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr0;
1512         extraWords = 0;
1513         scope32 = false;
1514         lsda = isSingleWordEHT ? 0 : (exceptionTableAddr + 4);
1515         break;
1516       case 1:
1517         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr1;
1518         extraWords = (exceptionTableData & 0x00ff0000) >> 16;
1519         scope32 = false;
1520         lsda = exceptionTableAddr + (extraWords + 1) * 4;
1521         break;
1522       case 2:
1523         personalityRoutine = (unw_word_t) &__aeabi_unwind_cpp_pr2;
1524         extraWords = (exceptionTableData & 0x00ff0000) >> 16;
1525         scope32 = true;
1526         lsda = exceptionTableAddr + (extraWords + 1) * 4;
1527         break;
1528       default:
1529         _LIBUNWIND_ABORT("unknown personality routine");
1530         return false;
1531     }
1532 
1533     if (isSingleWordEHT) {
1534       if (extraWords != 0) {
1535         _LIBUNWIND_ABORT("index inlined table detected but pr function "
1536                          "requires extra words");
1537         return false;
1538       }
1539     }
1540   } else {
1541     pint_t personalityAddr =
1542         exceptionTableAddr + signExtendPrel31(exceptionTableData);
1543     personalityRoutine = personalityAddr;
1544 
1545     // ARM EHABI # 6.2, # 9.2
1546     //
1547     //  +---- ehtp
1548     //  v
1549     // +--------------------------------------+
1550     // | +--------+--------+--------+-------+ |
1551     // | |0| prel31 to personalityRoutine   | |
1552     // | +--------+--------+--------+-------+ |
1553     // | |      N |      unwind opcodes     | |  <-- UnwindData
1554     // | +--------+--------+--------+-------+ |
1555     // | | Word 2        unwind opcodes     | |
1556     // | +--------+--------+--------+-------+ |
1557     // | ...                                  |
1558     // | +--------+--------+--------+-------+ |
1559     // | | Word N        unwind opcodes     | |
1560     // | +--------+--------+--------+-------+ |
1561     // | | LSDA                             | |  <-- lsda
1562     // | | ...                              | |
1563     // | +--------+--------+--------+-------+ |
1564     // +--------------------------------------+
1565 
1566     uint32_t *UnwindData = reinterpret_cast<uint32_t*>(exceptionTableAddr) + 1;
1567     uint32_t FirstDataWord = *UnwindData;
1568     size_t N = ((FirstDataWord >> 24) & 0xff);
1569     size_t NDataWords = N + 1;
1570     lsda = reinterpret_cast<uintptr_t>(UnwindData + NDataWords);
1571   }
1572 
1573   _info.start_ip = thisPC;
1574   _info.end_ip = nextPC;
1575   _info.handler = personalityRoutine;
1576   _info.unwind_info = exceptionTableAddr;
1577   _info.lsda = lsda;
1578   // flags is pr_cache.additional. See EHABI #7.2 for definition of bit 0.
1579   _info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?
1580 
1581   return true;
1582 }
1583 #endif
1584 
1585 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
1586 template <typename A, typename R>
1587 bool UnwindCursor<A, R>::getInfoFromFdeCie(
1588     const typename CFI_Parser<A>::FDE_Info &fdeInfo,
1589     const typename CFI_Parser<A>::CIE_Info &cieInfo, pint_t pc,
1590     uintptr_t dso_base) {
1591   typename CFI_Parser<A>::PrologInfo prolog;
1592   if (CFI_Parser<A>::parseFDEInstructions(_addressSpace, fdeInfo, cieInfo, pc,
1593                                           R::getArch(), &prolog)) {
1594     // Save off parsed FDE info
1595     _info.start_ip          = fdeInfo.pcStart;
1596     _info.end_ip            = fdeInfo.pcEnd;
1597     _info.lsda              = fdeInfo.lsda;
1598     _info.handler           = cieInfo.personality;
1599     // Some frameless functions need SP altered when resuming in function, so
1600     // propagate spExtraArgSize.
1601     _info.gp                = prolog.spExtraArgSize;
1602     _info.flags             = 0;
1603     _info.format            = dwarfEncoding();
1604     _info.unwind_info       = fdeInfo.fdeStart;
1605     _info.unwind_info_size  = static_cast<uint32_t>(fdeInfo.fdeLength);
1606     _info.extra             = static_cast<unw_word_t>(dso_base);
1607     return true;
1608   }
1609   return false;
1610 }
1611 
1612 template <typename A, typename R>
1613 bool UnwindCursor<A, R>::getInfoFromDwarfSection(pint_t pc,
1614                                                 const UnwindInfoSections &sects,
1615                                                 uint32_t fdeSectionOffsetHint) {
1616   typename CFI_Parser<A>::FDE_Info fdeInfo;
1617   typename CFI_Parser<A>::CIE_Info cieInfo;
1618   bool foundFDE = false;
1619   bool foundInCache = false;
1620   // If compact encoding table gave offset into dwarf section, go directly there
1621   if (fdeSectionOffsetHint != 0) {
1622     foundFDE = CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section,
1623                                     sects.dwarf_section_length,
1624                                     sects.dwarf_section + fdeSectionOffsetHint,
1625                                     &fdeInfo, &cieInfo);
1626   }
1627 #if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
1628   if (!foundFDE && (sects.dwarf_index_section != 0)) {
1629     foundFDE = EHHeaderParser<A>::findFDE(
1630         _addressSpace, pc, sects.dwarf_index_section,
1631         (uint32_t)sects.dwarf_index_section_length, &fdeInfo, &cieInfo);
1632   }
1633 #endif
1634   if (!foundFDE) {
1635     // otherwise, search cache of previously found FDEs.
1636     pint_t cachedFDE = DwarfFDECache<A>::findFDE(sects.dso_base, pc);
1637     if (cachedFDE != 0) {
1638       foundFDE =
1639           CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section,
1640                                  sects.dwarf_section_length,
1641                                  cachedFDE, &fdeInfo, &cieInfo);
1642       foundInCache = foundFDE;
1643     }
1644   }
1645   if (!foundFDE) {
1646     // Still not found, do full scan of __eh_frame section.
1647     foundFDE = CFI_Parser<A>::findFDE(_addressSpace, pc, sects.dwarf_section,
1648                                       sects.dwarf_section_length, 0,
1649                                       &fdeInfo, &cieInfo);
1650   }
1651   if (foundFDE) {
1652     if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, sects.dso_base)) {
1653       // Add to cache (to make next lookup faster) if we had no hint
1654       // and there was no index.
1655       if (!foundInCache && (fdeSectionOffsetHint == 0)) {
1656   #if defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
1657         if (sects.dwarf_index_section == 0)
1658   #endif
1659         DwarfFDECache<A>::add(sects.dso_base, fdeInfo.pcStart, fdeInfo.pcEnd,
1660                               fdeInfo.fdeStart);
1661       }
1662       return true;
1663     }
1664   }
1665   //_LIBUNWIND_DEBUG_LOG("can't find/use FDE for pc=0x%llX", (uint64_t)pc);
1666   return false;
1667 }
1668 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
1669 
1670 
1671 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
1672 template <typename A, typename R>
1673 bool UnwindCursor<A, R>::getInfoFromCompactEncodingSection(pint_t pc,
1674                                               const UnwindInfoSections &sects) {
1675   const bool log = false;
1676   if (log)
1677     fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX, mh=0x%llX)\n",
1678             (uint64_t)pc, (uint64_t)sects.dso_base);
1679 
1680   const UnwindSectionHeader<A> sectionHeader(_addressSpace,
1681                                                 sects.compact_unwind_section);
1682   if (sectionHeader.version() != UNWIND_SECTION_VERSION)
1683     return false;
1684 
1685   // do a binary search of top level index to find page with unwind info
1686   pint_t targetFunctionOffset = pc - sects.dso_base;
1687   const UnwindSectionIndexArray<A> topIndex(_addressSpace,
1688                                            sects.compact_unwind_section
1689                                          + sectionHeader.indexSectionOffset());
1690   uint32_t low = 0;
1691   uint32_t high = sectionHeader.indexCount();
1692   uint32_t last = high - 1;
1693   while (low < high) {
1694     uint32_t mid = (low + high) / 2;
1695     //if ( log ) fprintf(stderr, "\tmid=%d, low=%d, high=%d, *mid=0x%08X\n",
1696     //mid, low, high, topIndex.functionOffset(mid));
1697     if (topIndex.functionOffset(mid) <= targetFunctionOffset) {
1698       if ((mid == last) ||
1699           (topIndex.functionOffset(mid + 1) > targetFunctionOffset)) {
1700         low = mid;
1701         break;
1702       } else {
1703         low = mid + 1;
1704       }
1705     } else {
1706       high = mid;
1707     }
1708   }
1709   const uint32_t firstLevelFunctionOffset = topIndex.functionOffset(low);
1710   const uint32_t firstLevelNextPageFunctionOffset =
1711       topIndex.functionOffset(low + 1);
1712   const pint_t secondLevelAddr =
1713       sects.compact_unwind_section + topIndex.secondLevelPagesSectionOffset(low);
1714   const pint_t lsdaArrayStartAddr =
1715       sects.compact_unwind_section + topIndex.lsdaIndexArraySectionOffset(low);
1716   const pint_t lsdaArrayEndAddr =
1717       sects.compact_unwind_section + topIndex.lsdaIndexArraySectionOffset(low+1);
1718   if (log)
1719     fprintf(stderr, "\tfirst level search for result index=%d "
1720                     "to secondLevelAddr=0x%llX\n",
1721                     low, (uint64_t) secondLevelAddr);
1722   // do a binary search of second level page index
1723   uint32_t encoding = 0;
1724   pint_t funcStart = 0;
1725   pint_t funcEnd = 0;
1726   pint_t lsda = 0;
1727   pint_t personality = 0;
1728   uint32_t pageKind = _addressSpace.get32(secondLevelAddr);
1729   if (pageKind == UNWIND_SECOND_LEVEL_REGULAR) {
1730     // regular page
1731     UnwindSectionRegularPageHeader<A> pageHeader(_addressSpace,
1732                                                  secondLevelAddr);
1733     UnwindSectionRegularArray<A> pageIndex(
1734         _addressSpace, secondLevelAddr + pageHeader.entryPageOffset());
1735     // binary search looks for entry with e where index[e].offset <= pc <
1736     // index[e+1].offset
1737     if (log)
1738       fprintf(stderr, "\tbinary search for targetFunctionOffset=0x%08llX in "
1739                       "regular page starting at secondLevelAddr=0x%llX\n",
1740               (uint64_t) targetFunctionOffset, (uint64_t) secondLevelAddr);
1741     low = 0;
1742     high = pageHeader.entryCount();
1743     while (low < high) {
1744       uint32_t mid = (low + high) / 2;
1745       if (pageIndex.functionOffset(mid) <= targetFunctionOffset) {
1746         if (mid == (uint32_t)(pageHeader.entryCount() - 1)) {
1747           // at end of table
1748           low = mid;
1749           funcEnd = firstLevelNextPageFunctionOffset + sects.dso_base;
1750           break;
1751         } else if (pageIndex.functionOffset(mid + 1) > targetFunctionOffset) {
1752           // next is too big, so we found it
1753           low = mid;
1754           funcEnd = pageIndex.functionOffset(low + 1) + sects.dso_base;
1755           break;
1756         } else {
1757           low = mid + 1;
1758         }
1759       } else {
1760         high = mid;
1761       }
1762     }
1763     encoding = pageIndex.encoding(low);
1764     funcStart = pageIndex.functionOffset(low) + sects.dso_base;
1765     if (pc < funcStart) {
1766       if (log)
1767         fprintf(
1768             stderr,
1769             "\tpc not in table, pc=0x%llX, funcStart=0x%llX, funcEnd=0x%llX\n",
1770             (uint64_t) pc, (uint64_t) funcStart, (uint64_t) funcEnd);
1771       return false;
1772     }
1773     if (pc > funcEnd) {
1774       if (log)
1775         fprintf(
1776             stderr,
1777             "\tpc not in table, pc=0x%llX, funcStart=0x%llX, funcEnd=0x%llX\n",
1778             (uint64_t) pc, (uint64_t) funcStart, (uint64_t) funcEnd);
1779       return false;
1780     }
1781   } else if (pageKind == UNWIND_SECOND_LEVEL_COMPRESSED) {
1782     // compressed page
1783     UnwindSectionCompressedPageHeader<A> pageHeader(_addressSpace,
1784                                                     secondLevelAddr);
1785     UnwindSectionCompressedArray<A> pageIndex(
1786         _addressSpace, secondLevelAddr + pageHeader.entryPageOffset());
1787     const uint32_t targetFunctionPageOffset =
1788         (uint32_t)(targetFunctionOffset - firstLevelFunctionOffset);
1789     // binary search looks for entry with e where index[e].offset <= pc <
1790     // index[e+1].offset
1791     if (log)
1792       fprintf(stderr, "\tbinary search of compressed page starting at "
1793                       "secondLevelAddr=0x%llX\n",
1794               (uint64_t) secondLevelAddr);
1795     low = 0;
1796     last = pageHeader.entryCount() - 1;
1797     high = pageHeader.entryCount();
1798     while (low < high) {
1799       uint32_t mid = (low + high) / 2;
1800       if (pageIndex.functionOffset(mid) <= targetFunctionPageOffset) {
1801         if ((mid == last) ||
1802             (pageIndex.functionOffset(mid + 1) > targetFunctionPageOffset)) {
1803           low = mid;
1804           break;
1805         } else {
1806           low = mid + 1;
1807         }
1808       } else {
1809         high = mid;
1810       }
1811     }
1812     funcStart = pageIndex.functionOffset(low) + firstLevelFunctionOffset
1813                                                               + sects.dso_base;
1814     if (low < last)
1815       funcEnd =
1816           pageIndex.functionOffset(low + 1) + firstLevelFunctionOffset
1817                                                               + sects.dso_base;
1818     else
1819       funcEnd = firstLevelNextPageFunctionOffset + sects.dso_base;
1820     if (pc < funcStart) {
1821       _LIBUNWIND_DEBUG_LOG("malformed __unwind_info, pc=0x%llX "
1822                            "not in second level compressed unwind table. "
1823                            "funcStart=0x%llX",
1824                             (uint64_t) pc, (uint64_t) funcStart);
1825       return false;
1826     }
1827     if (pc > funcEnd) {
1828       _LIBUNWIND_DEBUG_LOG("malformed __unwind_info, pc=0x%llX "
1829                            "not in second level compressed unwind table. "
1830                            "funcEnd=0x%llX",
1831                            (uint64_t) pc, (uint64_t) funcEnd);
1832       return false;
1833     }
1834     uint16_t encodingIndex = pageIndex.encodingIndex(low);
1835     if (encodingIndex < sectionHeader.commonEncodingsArrayCount()) {
1836       // encoding is in common table in section header
1837       encoding = _addressSpace.get32(
1838           sects.compact_unwind_section +
1839           sectionHeader.commonEncodingsArraySectionOffset() +
1840           encodingIndex * sizeof(uint32_t));
1841     } else {
1842       // encoding is in page specific table
1843       uint16_t pageEncodingIndex =
1844           encodingIndex - (uint16_t)sectionHeader.commonEncodingsArrayCount();
1845       encoding = _addressSpace.get32(secondLevelAddr +
1846                                      pageHeader.encodingsPageOffset() +
1847                                      pageEncodingIndex * sizeof(uint32_t));
1848     }
1849   } else {
1850     _LIBUNWIND_DEBUG_LOG(
1851         "malformed __unwind_info at 0x%0llX bad second level page",
1852         (uint64_t)sects.compact_unwind_section);
1853     return false;
1854   }
1855 
1856   // look up LSDA, if encoding says function has one
1857   if (encoding & UNWIND_HAS_LSDA) {
1858     UnwindSectionLsdaArray<A> lsdaIndex(_addressSpace, lsdaArrayStartAddr);
1859     uint32_t funcStartOffset = (uint32_t)(funcStart - sects.dso_base);
1860     low = 0;
1861     high = (uint32_t)(lsdaArrayEndAddr - lsdaArrayStartAddr) /
1862                     sizeof(unwind_info_section_header_lsda_index_entry);
1863     // binary search looks for entry with exact match for functionOffset
1864     if (log)
1865       fprintf(stderr,
1866               "\tbinary search of lsda table for targetFunctionOffset=0x%08X\n",
1867               funcStartOffset);
1868     while (low < high) {
1869       uint32_t mid = (low + high) / 2;
1870       if (lsdaIndex.functionOffset(mid) == funcStartOffset) {
1871         lsda = lsdaIndex.lsdaOffset(mid) + sects.dso_base;
1872         break;
1873       } else if (lsdaIndex.functionOffset(mid) < funcStartOffset) {
1874         low = mid + 1;
1875       } else {
1876         high = mid;
1877       }
1878     }
1879     if (lsda == 0) {
1880       _LIBUNWIND_DEBUG_LOG("found encoding 0x%08X with HAS_LSDA bit set for "
1881                     "pc=0x%0llX, but lsda table has no entry",
1882                     encoding, (uint64_t) pc);
1883       return false;
1884     }
1885   }
1886 
1887   // extract personality routine, if encoding says function has one
1888   uint32_t personalityIndex = (encoding & UNWIND_PERSONALITY_MASK) >>
1889                               (__builtin_ctz(UNWIND_PERSONALITY_MASK));
1890   if (personalityIndex != 0) {
1891     --personalityIndex; // change 1-based to zero-based index
1892     if (personalityIndex >= sectionHeader.personalityArrayCount()) {
1893       _LIBUNWIND_DEBUG_LOG("found encoding 0x%08X with personality index %d,  "
1894                             "but personality table has only %d entries",
1895                             encoding, personalityIndex,
1896                             sectionHeader.personalityArrayCount());
1897       return false;
1898     }
1899     int32_t personalityDelta = (int32_t)_addressSpace.get32(
1900         sects.compact_unwind_section +
1901         sectionHeader.personalityArraySectionOffset() +
1902         personalityIndex * sizeof(uint32_t));
1903     pint_t personalityPointer = sects.dso_base + (pint_t)personalityDelta;
1904     personality = _addressSpace.getP(personalityPointer);
1905     if (log)
1906       fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX), "
1907                       "personalityDelta=0x%08X, personality=0x%08llX\n",
1908               (uint64_t) pc, personalityDelta, (uint64_t) personality);
1909   }
1910 
1911   if (log)
1912     fprintf(stderr, "getInfoFromCompactEncodingSection(pc=0x%llX), "
1913                     "encoding=0x%08X, lsda=0x%08llX for funcStart=0x%llX\n",
1914             (uint64_t) pc, encoding, (uint64_t) lsda, (uint64_t) funcStart);
1915   _info.start_ip = funcStart;
1916   _info.end_ip = funcEnd;
1917   _info.lsda = lsda;
1918   _info.handler = personality;
1919   _info.gp = 0;
1920   _info.flags = 0;
1921   _info.format = encoding;
1922   _info.unwind_info = 0;
1923   _info.unwind_info_size = 0;
1924   _info.extra = sects.dso_base;
1925   return true;
1926 }
1927 #endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
1928 
1929 
1930 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
1931 template <typename A, typename R>
1932 bool UnwindCursor<A, R>::getInfoFromSEH(pint_t pc) {
1933   pint_t base;
1934   RUNTIME_FUNCTION *unwindEntry = lookUpSEHUnwindInfo(pc, &base);
1935   if (!unwindEntry) {
1936     _LIBUNWIND_DEBUG_LOG("\tpc not in table, pc=0x%llX", (uint64_t) pc);
1937     return false;
1938   }
1939   _info.gp = 0;
1940   _info.flags = 0;
1941   _info.format = 0;
1942   _info.unwind_info_size = sizeof(RUNTIME_FUNCTION);
1943   _info.unwind_info = reinterpret_cast<unw_word_t>(unwindEntry);
1944   _info.extra = base;
1945   _info.start_ip = base + unwindEntry->BeginAddress;
1946 #ifdef _LIBUNWIND_TARGET_X86_64
1947   _info.end_ip = base + unwindEntry->EndAddress;
1948   // Only fill in the handler and LSDA if they're stale.
1949   if (pc != getLastPC()) {
1950     UNWIND_INFO *xdata = reinterpret_cast<UNWIND_INFO *>(base + unwindEntry->UnwindData);
1951     if (xdata->Flags & (UNW_FLAG_EHANDLER|UNW_FLAG_UHANDLER)) {
1952       // The personality is given in the UNWIND_INFO itself. The LSDA immediately
1953       // follows the UNWIND_INFO. (This follows how both Clang and MSVC emit
1954       // these structures.)
1955       // N.B. UNWIND_INFO structs are DWORD-aligned.
1956       uint32_t lastcode = (xdata->CountOfCodes + 1) & ~1;
1957       const uint32_t *handler = reinterpret_cast<uint32_t *>(&xdata->UnwindCodes[lastcode]);
1958       _info.lsda = reinterpret_cast<unw_word_t>(handler+1);
1959       if (*handler) {
1960         _info.handler = reinterpret_cast<unw_word_t>(__libunwind_seh_personality);
1961       } else
1962         _info.handler = 0;
1963     } else {
1964       _info.lsda = 0;
1965       _info.handler = 0;
1966     }
1967   }
1968 #elif defined(_LIBUNWIND_TARGET_ARM)
1969   _info.end_ip = _info.start_ip + unwindEntry->FunctionLength;
1970   _info.lsda = 0; // FIXME
1971   _info.handler = 0; // FIXME
1972 #endif
1973   setLastPC(pc);
1974   return true;
1975 }
1976 #endif
1977 
1978 #if defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
1979 // Masks for traceback table field xtbtable.
1980 enum xTBTableMask : uint8_t {
1981   reservedBit = 0x02, // The traceback table was incorrectly generated if set
1982                       // (see comments in function getInfoFromTBTable().
1983   ehInfoBit = 0x08    // Exception handling info is present if set
1984 };
1985 
1986 enum frameType : unw_word_t {
1987   frameWithXLEHStateTable = 0,
1988   frameWithEHInfo = 1
1989 };
1990 
1991 extern "C" {
1992 typedef _Unwind_Reason_Code __xlcxx_personality_v0_t(int, _Unwind_Action,
1993                                                      uint64_t,
1994                                                      _Unwind_Exception *,
1995                                                      struct _Unwind_Context *);
1996 __attribute__((__weak__)) __xlcxx_personality_v0_t __xlcxx_personality_v0;
1997 }
1998 
1999 static __xlcxx_personality_v0_t *xlcPersonalityV0;
2000 static RWMutex xlcPersonalityV0InitLock;
2001 
2002 template <typename A, typename R>
2003 bool UnwindCursor<A, R>::getInfoFromTBTable(pint_t pc, R &registers) {
2004   uint32_t *p = reinterpret_cast<uint32_t *>(pc);
2005 
2006   // Keep looking forward until a word of 0 is found. The traceback
2007   // table starts at the following word.
2008   while (*p)
2009     ++p;
2010   tbtable *TBTable = reinterpret_cast<tbtable *>(p + 1);
2011 
2012   if (_LIBUNWIND_TRACING_UNWINDING) {
2013     char functionBuf[512];
2014     const char *functionName = functionBuf;
2015     unw_word_t offset;
2016     if (!getFunctionName(functionBuf, sizeof(functionBuf), &offset)) {
2017       functionName = ".anonymous.";
2018     }
2019     _LIBUNWIND_TRACE_UNWINDING("%s: Look up traceback table of func=%s at %p",
2020                                __func__, functionName,
2021                                reinterpret_cast<void *>(TBTable));
2022   }
2023 
2024   // If the traceback table does not contain necessary info, bypass this frame.
2025   if (!TBTable->tb.has_tboff)
2026     return false;
2027 
2028   // Structure tbtable_ext contains important data we are looking for.
2029   p = reinterpret_cast<uint32_t *>(&TBTable->tb_ext);
2030 
2031   // Skip field parminfo if it exists.
2032   if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
2033     ++p;
2034 
2035   // p now points to tb_offset, the offset from start of function to TB table.
2036   unw_word_t start_ip =
2037       reinterpret_cast<unw_word_t>(TBTable) - *p - sizeof(uint32_t);
2038   unw_word_t end_ip = reinterpret_cast<unw_word_t>(TBTable);
2039   ++p;
2040 
2041   _LIBUNWIND_TRACE_UNWINDING("start_ip=%p, end_ip=%p\n",
2042                              reinterpret_cast<void *>(start_ip),
2043                              reinterpret_cast<void *>(end_ip));
2044 
2045   // Skip field hand_mask if it exists.
2046   if (TBTable->tb.int_hndl)
2047     ++p;
2048 
2049   unw_word_t lsda = 0;
2050   unw_word_t handler = 0;
2051   unw_word_t flags = frameType::frameWithXLEHStateTable;
2052 
2053   if (TBTable->tb.lang == TB_CPLUSPLUS && TBTable->tb.has_ctl) {
2054     // State table info is available. The ctl_info field indicates the
2055     // number of CTL anchors. There should be only one entry for the C++
2056     // state table.
2057     assert(*p == 1 && "libunwind: there must be only one ctl_info entry");
2058     ++p;
2059     // p points to the offset of the state table into the stack.
2060     pint_t stateTableOffset = *p++;
2061 
2062     int framePointerReg;
2063 
2064     // Skip fields name_len and name if exist.
2065     if (TBTable->tb.name_present) {
2066       const uint16_t name_len = *(reinterpret_cast<uint16_t *>(p));
2067       p = reinterpret_cast<uint32_t *>(reinterpret_cast<char *>(p) + name_len +
2068                                        sizeof(uint16_t));
2069     }
2070 
2071     if (TBTable->tb.uses_alloca)
2072       framePointerReg = *(reinterpret_cast<char *>(p));
2073     else
2074       framePointerReg = 1; // default frame pointer == SP
2075 
2076     _LIBUNWIND_TRACE_UNWINDING(
2077         "framePointerReg=%d, framePointer=%p, "
2078         "stateTableOffset=%#lx\n",
2079         framePointerReg,
2080         reinterpret_cast<void *>(_registers.getRegister(framePointerReg)),
2081         stateTableOffset);
2082     lsda = _registers.getRegister(framePointerReg) + stateTableOffset;
2083 
2084     // Since the traceback table generated by the legacy XLC++ does not
2085     // provide the location of the personality for the state table,
2086     // function __xlcxx_personality_v0(), which is the personality for the state
2087     // table and is exported from libc++abi, is directly assigned as the
2088     // handler here. When a legacy XLC++ frame is encountered, the symbol
2089     // is resolved dynamically using dlopen() to avoid hard dependency from
2090     // libunwind on libc++abi.
2091 
2092     // Resolve the function pointer to the state table personality if it has
2093     // not already.
2094     if (xlcPersonalityV0 == NULL) {
2095       xlcPersonalityV0InitLock.lock();
2096       if (xlcPersonalityV0 == NULL) {
2097         // If libc++abi is statically linked in, symbol __xlcxx_personality_v0
2098         // has been resolved at the link time.
2099         xlcPersonalityV0 = &__xlcxx_personality_v0;
2100         if (xlcPersonalityV0 == NULL) {
2101           // libc++abi is dynamically linked. Resolve __xlcxx_personality_v0
2102           // using dlopen().
2103           const char libcxxabi[] = "libc++abi.a(libc++abi.so.1)";
2104           void *libHandle;
2105           libHandle = dlopen(libcxxabi, RTLD_MEMBER | RTLD_NOW);
2106           if (libHandle == NULL) {
2107             _LIBUNWIND_TRACE_UNWINDING("dlopen() failed with errno=%d\n",
2108                                        errno);
2109             assert(0 && "dlopen() failed");
2110           }
2111           xlcPersonalityV0 = reinterpret_cast<__xlcxx_personality_v0_t *>(
2112               dlsym(libHandle, "__xlcxx_personality_v0"));
2113           if (xlcPersonalityV0 == NULL) {
2114             _LIBUNWIND_TRACE_UNWINDING("dlsym() failed with errno=%d\n", errno);
2115             assert(0 && "dlsym() failed");
2116           }
2117           dlclose(libHandle);
2118         }
2119       }
2120       xlcPersonalityV0InitLock.unlock();
2121     }
2122     handler = reinterpret_cast<unw_word_t>(xlcPersonalityV0);
2123     _LIBUNWIND_TRACE_UNWINDING("State table: LSDA=%p, Personality=%p\n",
2124                                reinterpret_cast<void *>(lsda),
2125                                reinterpret_cast<void *>(handler));
2126   } else if (TBTable->tb.longtbtable) {
2127     // This frame has the traceback table extension. Possible cases are
2128     // 1) a C++ frame that has the 'eh_info' structure; 2) a C++ frame that
2129     // is not EH aware; or, 3) a frame of other languages. We need to figure out
2130     // if the traceback table extension contains the 'eh_info' structure.
2131     //
2132     // We also need to deal with the complexity arising from some XL compiler
2133     // versions use the wrong ordering of 'longtbtable' and 'has_vec' bits
2134     // where the 'longtbtable' bit is meant to be the 'has_vec' bit and vice
2135     // versa. For frames of code generated by those compilers, the 'longtbtable'
2136     // bit may be set but there isn't really a traceback table extension.
2137     //
2138     // In </usr/include/sys/debug.h>, there is the following definition of
2139     // 'struct tbtable_ext'. It is not really a structure but a dummy to
2140     // collect the description of optional parts of the traceback table.
2141     //
2142     // struct tbtable_ext {
2143     //   ...
2144     //   char alloca_reg;        /* Register for alloca automatic storage */
2145     //   struct vec_ext vec_ext; /* Vector extension (if has_vec is set) */
2146     //   unsigned char xtbtable; /* More tbtable fields, if longtbtable is set*/
2147     // };
2148     //
2149     // Depending on how the 'has_vec'/'longtbtable' bit is interpreted, the data
2150     // following 'alloca_reg' can be treated either as 'struct vec_ext' or
2151     // 'unsigned char xtbtable'. 'xtbtable' bits are defined in
2152     // </usr/include/sys/debug.h> as flags. The 7th bit '0x02' is currently
2153     // unused and should not be set. 'struct vec_ext' is defined in
2154     // </usr/include/sys/debug.h> as follows:
2155     //
2156     // struct vec_ext {
2157     //   unsigned vr_saved:6;      /* Number of non-volatile vector regs saved
2158     //   */
2159     //                             /* first register saved is assumed to be */
2160     //                             /* 32 - vr_saved                         */
2161     //   unsigned saves_vrsave:1;  /* Set if vrsave is saved on the stack */
2162     //   unsigned has_varargs:1;
2163     //   ...
2164     // };
2165     //
2166     // Here, the 7th bit is used as 'saves_vrsave'. To determine whether it
2167     // is 'struct vec_ext' or 'xtbtable' that follows 'alloca_reg',
2168     // we checks if the 7th bit is set or not because 'xtbtable' should
2169     // never have the 7th bit set. The 7th bit of 'xtbtable' will be reserved
2170     // in the future to make sure the mitigation works. This mitigation
2171     // is not 100% bullet proof because 'struct vec_ext' may not always have
2172     // 'saves_vrsave' bit set.
2173     //
2174     // 'reservedBit' is defined in enum 'xTBTableMask' above as the mask for
2175     // checking the 7th bit.
2176 
2177     // p points to field name len.
2178     uint8_t *charPtr = reinterpret_cast<uint8_t *>(p);
2179 
2180     // Skip fields name_len and name if they exist.
2181     if (TBTable->tb.name_present) {
2182       const uint16_t name_len = *(reinterpret_cast<uint16_t *>(charPtr));
2183       charPtr = charPtr + name_len + sizeof(uint16_t);
2184     }
2185 
2186     // Skip field alloc_reg if it exists.
2187     if (TBTable->tb.uses_alloca)
2188       ++charPtr;
2189 
2190     // Check traceback table bit has_vec. Skip struct vec_ext if it exists.
2191     if (TBTable->tb.has_vec)
2192       // Note struct vec_ext does exist at this point because whether the
2193       // ordering of longtbtable and has_vec bits is correct or not, both
2194       // are set.
2195       charPtr += sizeof(struct vec_ext);
2196 
2197     // charPtr points to field 'xtbtable'. Check if the EH info is available.
2198     // Also check if the reserved bit of the extended traceback table field
2199     // 'xtbtable' is set. If it is, the traceback table was incorrectly
2200     // generated by an XL compiler that uses the wrong ordering of 'longtbtable'
2201     // and 'has_vec' bits and this is in fact 'struct vec_ext'. So skip the
2202     // frame.
2203     if ((*charPtr & xTBTableMask::ehInfoBit) &&
2204         !(*charPtr & xTBTableMask::reservedBit)) {
2205       // Mark this frame has the new EH info.
2206       flags = frameType::frameWithEHInfo;
2207 
2208       // eh_info is available.
2209       charPtr++;
2210       // The pointer is 4-byte aligned.
2211       if (reinterpret_cast<uintptr_t>(charPtr) % 4)
2212         charPtr += 4 - reinterpret_cast<uintptr_t>(charPtr) % 4;
2213       uintptr_t *ehInfo =
2214           reinterpret_cast<uintptr_t *>(*(reinterpret_cast<uintptr_t *>(
2215               registers.getRegister(2) +
2216               *(reinterpret_cast<uintptr_t *>(charPtr)))));
2217 
2218       // ehInfo points to structure en_info. The first member is version.
2219       // Only version 0 is currently supported.
2220       assert(*(reinterpret_cast<uint32_t *>(ehInfo)) == 0 &&
2221              "libunwind: ehInfo version other than 0 is not supported");
2222 
2223       // Increment ehInfo to point to member lsda.
2224       ++ehInfo;
2225       lsda = *ehInfo++;
2226 
2227       // enInfo now points to member personality.
2228       handler = *ehInfo;
2229 
2230       _LIBUNWIND_TRACE_UNWINDING("Range table: LSDA=%#lx, Personality=%#lx\n",
2231                                  lsda, handler);
2232     }
2233   }
2234 
2235   _info.start_ip = start_ip;
2236   _info.end_ip = end_ip;
2237   _info.lsda = lsda;
2238   _info.handler = handler;
2239   _info.gp = 0;
2240   _info.flags = flags;
2241   _info.format = 0;
2242   _info.unwind_info = reinterpret_cast<unw_word_t>(TBTable);
2243   _info.unwind_info_size = 0;
2244   _info.extra = registers.getRegister(2);
2245 
2246   return true;
2247 }
2248 
2249 // Step back up the stack following the frame back link.
2250 template <typename A, typename R>
2251 int UnwindCursor<A, R>::stepWithTBTable(pint_t pc, tbtable *TBTable,
2252                                         R &registers, bool &isSignalFrame) {
2253   if (_LIBUNWIND_TRACING_UNWINDING) {
2254     char functionBuf[512];
2255     const char *functionName = functionBuf;
2256     unw_word_t offset;
2257     if (!getFunctionName(functionBuf, sizeof(functionBuf), &offset)) {
2258       functionName = ".anonymous.";
2259     }
2260     _LIBUNWIND_TRACE_UNWINDING("%s: Look up traceback table of func=%s at %p",
2261                                __func__, functionName,
2262                                reinterpret_cast<void *>(TBTable));
2263   }
2264 
2265 #if defined(__powerpc64__)
2266   // Instruction to reload TOC register "l r2,40(r1)"
2267   const uint32_t loadTOCRegInst = 0xe8410028;
2268   const int32_t unwPPCF0Index = UNW_PPC64_F0;
2269   const int32_t unwPPCV0Index = UNW_PPC64_V0;
2270 #else
2271   // Instruction to reload TOC register "l r2,20(r1)"
2272   const uint32_t loadTOCRegInst = 0x80410014;
2273   const int32_t unwPPCF0Index = UNW_PPC_F0;
2274   const int32_t unwPPCV0Index = UNW_PPC_V0;
2275 #endif
2276 
2277   R newRegisters = registers;
2278 
2279   // lastStack points to the stack frame of the next routine up.
2280   pint_t lastStack = *(reinterpret_cast<pint_t *>(registers.getSP()));
2281 
2282   // Return address is the address after call site instruction.
2283   pint_t returnAddress;
2284 
2285   if (isSignalFrame) {
2286     _LIBUNWIND_TRACE_UNWINDING("Possible signal handler frame: lastStack=%p",
2287                                reinterpret_cast<void *>(lastStack));
2288 
2289     sigcontext *sigContext = reinterpret_cast<sigcontext *>(
2290         reinterpret_cast<char *>(lastStack) + STKMIN);
2291     returnAddress = sigContext->sc_jmpbuf.jmp_context.iar;
2292 
2293     _LIBUNWIND_TRACE_UNWINDING("From sigContext=%p, returnAddress=%p\n",
2294                                reinterpret_cast<void *>(sigContext),
2295                                reinterpret_cast<void *>(returnAddress));
2296 
2297     if (returnAddress < 0x10000000) {
2298       // Try again using STKMINALIGN
2299       sigContext = reinterpret_cast<sigcontext *>(
2300           reinterpret_cast<char *>(lastStack) + STKMINALIGN);
2301       returnAddress = sigContext->sc_jmpbuf.jmp_context.iar;
2302       if (returnAddress < 0x10000000) {
2303         _LIBUNWIND_TRACE_UNWINDING("Bad returnAddress=%p\n",
2304                                    reinterpret_cast<void *>(returnAddress));
2305         return UNW_EBADFRAME;
2306       } else {
2307         _LIBUNWIND_TRACE_UNWINDING("Tried again using STKMINALIGN: "
2308                                    "sigContext=%p, returnAddress=%p. "
2309                                    "Seems to be a valid address\n",
2310                                    reinterpret_cast<void *>(sigContext),
2311                                    reinterpret_cast<void *>(returnAddress));
2312       }
2313     }
2314     // Restore the condition register from sigcontext.
2315     newRegisters.setCR(sigContext->sc_jmpbuf.jmp_context.cr);
2316 
2317     // Restore GPRs from sigcontext.
2318     for (int i = 0; i < 32; ++i)
2319       newRegisters.setRegister(i, sigContext->sc_jmpbuf.jmp_context.gpr[i]);
2320 
2321     // Restore FPRs from sigcontext.
2322     for (int i = 0; i < 32; ++i)
2323       newRegisters.setFloatRegister(i + unwPPCF0Index,
2324                                     sigContext->sc_jmpbuf.jmp_context.fpr[i]);
2325 
2326     // Restore vector registers if there is an associated extended context
2327     // structure.
2328     if (sigContext->sc_jmpbuf.jmp_context.msr & __EXTCTX) {
2329       ucontext_t *uContext = reinterpret_cast<ucontext_t *>(sigContext);
2330       if (uContext->__extctx->__extctx_magic == __EXTCTX_MAGIC) {
2331         for (int i = 0; i < 32; ++i)
2332           newRegisters.setVectorRegister(
2333               i + unwPPCV0Index, *(reinterpret_cast<v128 *>(
2334                                      &(uContext->__extctx->__vmx.__vr[i]))));
2335       }
2336     }
2337   } else {
2338     // Step up a normal frame.
2339     returnAddress = reinterpret_cast<pint_t *>(lastStack)[2];
2340 
2341     _LIBUNWIND_TRACE_UNWINDING("Extract info from lastStack=%p, "
2342                                "returnAddress=%p\n",
2343                                reinterpret_cast<void *>(lastStack),
2344                                reinterpret_cast<void *>(returnAddress));
2345     _LIBUNWIND_TRACE_UNWINDING("fpr_regs=%d, gpr_regs=%d, saves_cr=%d\n",
2346                                TBTable->tb.fpr_saved, TBTable->tb.gpr_saved,
2347                                TBTable->tb.saves_cr);
2348 
2349     // Restore FP registers.
2350     char *ptrToRegs = reinterpret_cast<char *>(lastStack);
2351     double *FPRegs = reinterpret_cast<double *>(
2352         ptrToRegs - (TBTable->tb.fpr_saved * sizeof(double)));
2353     for (int i = 0; i < TBTable->tb.fpr_saved; ++i)
2354       newRegisters.setFloatRegister(
2355           32 - TBTable->tb.fpr_saved + i + unwPPCF0Index, FPRegs[i]);
2356 
2357     // Restore GP registers.
2358     ptrToRegs = reinterpret_cast<char *>(FPRegs);
2359     uintptr_t *GPRegs = reinterpret_cast<uintptr_t *>(
2360         ptrToRegs - (TBTable->tb.gpr_saved * sizeof(uintptr_t)));
2361     for (int i = 0; i < TBTable->tb.gpr_saved; ++i)
2362       newRegisters.setRegister(32 - TBTable->tb.gpr_saved + i, GPRegs[i]);
2363 
2364     // Restore Vector registers.
2365     ptrToRegs = reinterpret_cast<char *>(GPRegs);
2366 
2367     // Restore vector registers only if this is a Clang frame. Also
2368     // check if traceback table bit has_vec is set. If it is, structure
2369     // vec_ext is available.
2370     if (_info.flags == frameType::frameWithEHInfo && TBTable->tb.has_vec) {
2371 
2372       // Get to the vec_ext structure to check if vector registers are saved.
2373       uint32_t *p = reinterpret_cast<uint32_t *>(&TBTable->tb_ext);
2374 
2375       // Skip field parminfo if exists.
2376       if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
2377         ++p;
2378 
2379       // Skip field tb_offset if exists.
2380       if (TBTable->tb.has_tboff)
2381         ++p;
2382 
2383       // Skip field hand_mask if exists.
2384       if (TBTable->tb.int_hndl)
2385         ++p;
2386 
2387       // Skip fields ctl_info and ctl_info_disp if exist.
2388       if (TBTable->tb.has_ctl) {
2389         // Skip field ctl_info.
2390         ++p;
2391         // Skip field ctl_info_disp.
2392         ++p;
2393       }
2394 
2395       // Skip fields name_len and name if exist.
2396       // p is supposed to point to field name_len now.
2397       uint8_t *charPtr = reinterpret_cast<uint8_t *>(p);
2398       if (TBTable->tb.name_present) {
2399         const uint16_t name_len = *(reinterpret_cast<uint16_t *>(charPtr));
2400         charPtr = charPtr + name_len + sizeof(uint16_t);
2401       }
2402 
2403       // Skip field alloc_reg if it exists.
2404       if (TBTable->tb.uses_alloca)
2405         ++charPtr;
2406 
2407       struct vec_ext *vec_ext = reinterpret_cast<struct vec_ext *>(charPtr);
2408 
2409       _LIBUNWIND_TRACE_UNWINDING("vr_saved=%d\n", vec_ext->vr_saved);
2410 
2411       // Restore vector register(s) if saved on the stack.
2412       if (vec_ext->vr_saved) {
2413         // Saved vector registers are 16-byte aligned.
2414         if (reinterpret_cast<uintptr_t>(ptrToRegs) % 16)
2415           ptrToRegs -= reinterpret_cast<uintptr_t>(ptrToRegs) % 16;
2416         v128 *VecRegs = reinterpret_cast<v128 *>(ptrToRegs - vec_ext->vr_saved *
2417                                                                  sizeof(v128));
2418         for (int i = 0; i < vec_ext->vr_saved; ++i) {
2419           newRegisters.setVectorRegister(
2420               32 - vec_ext->vr_saved + i + unwPPCV0Index, VecRegs[i]);
2421         }
2422       }
2423     }
2424     if (TBTable->tb.saves_cr) {
2425       // Get the saved condition register. The condition register is only
2426       // a single word.
2427       newRegisters.setCR(
2428           *(reinterpret_cast<uint32_t *>(lastStack + sizeof(uintptr_t))));
2429     }
2430 
2431     // Restore the SP.
2432     newRegisters.setSP(lastStack);
2433 
2434     // The first instruction after return.
2435     uint32_t firstInstruction = *(reinterpret_cast<uint32_t *>(returnAddress));
2436 
2437     // Do we need to set the TOC register?
2438     _LIBUNWIND_TRACE_UNWINDING(
2439         "Current gpr2=%p\n",
2440         reinterpret_cast<void *>(newRegisters.getRegister(2)));
2441     if (firstInstruction == loadTOCRegInst) {
2442       _LIBUNWIND_TRACE_UNWINDING(
2443           "Set gpr2=%p from frame\n",
2444           reinterpret_cast<void *>(reinterpret_cast<pint_t *>(lastStack)[5]));
2445       newRegisters.setRegister(2, reinterpret_cast<pint_t *>(lastStack)[5]);
2446     }
2447   }
2448   _LIBUNWIND_TRACE_UNWINDING("lastStack=%p, returnAddress=%p, pc=%p\n",
2449                              reinterpret_cast<void *>(lastStack),
2450                              reinterpret_cast<void *>(returnAddress),
2451                              reinterpret_cast<void *>(pc));
2452 
2453   // The return address is the address after call site instruction, so
2454   // setting IP to that simualates a return.
2455   newRegisters.setIP(reinterpret_cast<uintptr_t>(returnAddress));
2456 
2457   // Simulate the step by replacing the register set with the new ones.
2458   registers = newRegisters;
2459 
2460   // Check if the next frame is a signal frame.
2461   pint_t nextStack = *(reinterpret_cast<pint_t *>(registers.getSP()));
2462 
2463   // Return address is the address after call site instruction.
2464   pint_t nextReturnAddress = reinterpret_cast<pint_t *>(nextStack)[2];
2465 
2466   if (nextReturnAddress > 0x01 && nextReturnAddress < 0x10000) {
2467     _LIBUNWIND_TRACE_UNWINDING("The next is a signal handler frame: "
2468                                "nextStack=%p, next return address=%p\n",
2469                                reinterpret_cast<void *>(nextStack),
2470                                reinterpret_cast<void *>(nextReturnAddress));
2471     isSignalFrame = true;
2472   } else {
2473     isSignalFrame = false;
2474   }
2475 
2476   return UNW_STEP_SUCCESS;
2477 }
2478 #endif // defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
2479 
2480 template <typename A, typename R>
2481 void UnwindCursor<A, R>::setInfoBasedOnIPRegister(bool isReturnAddress) {
2482 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN)
2483   _isSigReturn = false;
2484 #endif
2485 
2486   pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
2487 #if defined(_LIBUNWIND_ARM_EHABI)
2488   // Remove the thumb bit so the IP represents the actual instruction address.
2489   // This matches the behaviour of _Unwind_GetIP on arm.
2490   pc &= (pint_t)~0x1;
2491 #endif
2492 
2493   // Exit early if at the top of the stack.
2494   if (pc == 0) {
2495     _unwindInfoMissing = true;
2496     return;
2497   }
2498 
2499   // If the last line of a function is a "throw" the compiler sometimes
2500   // emits no instructions after the call to __cxa_throw.  This means
2501   // the return address is actually the start of the next function.
2502   // To disambiguate this, back up the pc when we know it is a return
2503   // address.
2504   if (isReturnAddress)
2505 #if defined(_AIX)
2506     // PC needs to be a 4-byte aligned address to be able to look for a
2507     // word of 0 that indicates the start of the traceback table at the end
2508     // of a function on AIX.
2509     pc -= 4;
2510 #else
2511     --pc;
2512 #endif
2513 
2514   // Ask address space object to find unwind sections for this pc.
2515   UnwindInfoSections sects;
2516   if (_addressSpace.findUnwindSections(pc, sects)) {
2517 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
2518     // If there is a compact unwind encoding table, look there first.
2519     if (sects.compact_unwind_section != 0) {
2520       if (this->getInfoFromCompactEncodingSection(pc, sects)) {
2521   #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
2522         // Found info in table, done unless encoding says to use dwarf.
2523         uint32_t dwarfOffset;
2524         if ((sects.dwarf_section != 0) && compactSaysUseDwarf(&dwarfOffset)) {
2525           if (this->getInfoFromDwarfSection(pc, sects, dwarfOffset)) {
2526             // found info in dwarf, done
2527             return;
2528           }
2529         }
2530   #endif
2531         // If unwind table has entry, but entry says there is no unwind info,
2532         // record that we have no unwind info.
2533         if (_info.format == 0)
2534           _unwindInfoMissing = true;
2535         return;
2536       }
2537     }
2538 #endif // defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
2539 
2540 #if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
2541     // If there is SEH unwind info, look there next.
2542     if (this->getInfoFromSEH(pc))
2543       return;
2544 #endif
2545 
2546 #if defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
2547     // If there is unwind info in the traceback table, look there next.
2548     if (this->getInfoFromTBTable(pc, _registers))
2549       return;
2550 #endif
2551 
2552 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
2553     // If there is dwarf unwind info, look there next.
2554     if (sects.dwarf_section != 0) {
2555       if (this->getInfoFromDwarfSection(pc, sects)) {
2556         // found info in dwarf, done
2557         return;
2558       }
2559     }
2560 #endif
2561 
2562 #if defined(_LIBUNWIND_ARM_EHABI)
2563     // If there is ARM EHABI unwind info, look there next.
2564     if (sects.arm_section != 0 && this->getInfoFromEHABISection(pc, sects))
2565       return;
2566 #endif
2567   }
2568 
2569 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
2570   // There is no static unwind info for this pc. Look to see if an FDE was
2571   // dynamically registered for it.
2572   pint_t cachedFDE = DwarfFDECache<A>::findFDE(DwarfFDECache<A>::kSearchAll,
2573                                                pc);
2574   if (cachedFDE != 0) {
2575     typename CFI_Parser<A>::FDE_Info fdeInfo;
2576     typename CFI_Parser<A>::CIE_Info cieInfo;
2577     if (!CFI_Parser<A>::decodeFDE(_addressSpace, cachedFDE, &fdeInfo, &cieInfo))
2578       if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, 0))
2579         return;
2580   }
2581 
2582   // Lastly, ask AddressSpace object about platform specific ways to locate
2583   // other FDEs.
2584   pint_t fde;
2585   if (_addressSpace.findOtherFDE(pc, fde)) {
2586     typename CFI_Parser<A>::FDE_Info fdeInfo;
2587     typename CFI_Parser<A>::CIE_Info cieInfo;
2588     if (!CFI_Parser<A>::decodeFDE(_addressSpace, fde, &fdeInfo, &cieInfo)) {
2589       // Double check this FDE is for a function that includes the pc.
2590       if ((fdeInfo.pcStart <= pc) && (pc < fdeInfo.pcEnd))
2591         if (getInfoFromFdeCie(fdeInfo, cieInfo, pc, 0))
2592           return;
2593     }
2594   }
2595 #endif // #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
2596 
2597 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN)
2598   if (setInfoForSigReturn())
2599     return;
2600 #endif
2601 
2602   // no unwind info, flag that we can't reliably unwind
2603   _unwindInfoMissing = true;
2604 }
2605 
2606 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&                               \
2607     defined(_LIBUNWIND_TARGET_AARCH64)
2608 template <typename A, typename R>
2609 bool UnwindCursor<A, R>::setInfoForSigReturn(Registers_arm64 &) {
2610   // Look for the sigreturn trampoline. The trampoline's body is two
2611   // specific instructions (see below). Typically the trampoline comes from the
2612   // vDSO[1] (i.e. the __kernel_rt_sigreturn function). A libc might provide its
2613   // own restorer function, though, or user-mode QEMU might write a trampoline
2614   // onto the stack.
2615   //
2616   // This special code path is a fallback that is only used if the trampoline
2617   // lacks proper (e.g. DWARF) unwind info. On AArch64, a new DWARF register
2618   // constant for the PC needs to be defined before DWARF can handle a signal
2619   // trampoline. This code may segfault if the target PC is unreadable, e.g.:
2620   //  - The PC points at a function compiled without unwind info, and which is
2621   //    part of an execute-only mapping (e.g. using -Wl,--execute-only).
2622   //  - The PC is invalid and happens to point to unreadable or unmapped memory.
2623   //
2624   // [1] https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/vdso/sigreturn.S
2625   const pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
2626   // The PC might contain an invalid address if the unwind info is bad, so
2627   // directly accessing it could cause a segfault. Use process_vm_readv to read
2628   // the memory safely instead. process_vm_readv was added in Linux 3.2, and
2629   // AArch64 supported was added in Linux 3.7, so the syscall is guaranteed to
2630   // be present. Unfortunately, there are Linux AArch64 environments where the
2631   // libc wrapper for the syscall might not be present (e.g. Android 5), so call
2632   // the syscall directly instead.
2633   uint32_t instructions[2];
2634   struct iovec local_iov = {&instructions, sizeof instructions};
2635   struct iovec remote_iov = {reinterpret_cast<void *>(pc), sizeof instructions};
2636   long bytesRead =
2637       syscall(SYS_process_vm_readv, getpid(), &local_iov, 1, &remote_iov, 1, 0);
2638   // Look for instructions: mov x8, #0x8b; svc #0x0
2639   if (bytesRead != sizeof instructions || instructions[0] != 0xd2801168 ||
2640       instructions[1] != 0xd4000001)
2641     return false;
2642 
2643   _info = {};
2644   _info.start_ip = pc;
2645   _info.end_ip = pc + 4;
2646   _isSigReturn = true;
2647   return true;
2648 }
2649 
2650 template <typename A, typename R>
2651 int UnwindCursor<A, R>::stepThroughSigReturn(Registers_arm64 &) {
2652   // In the signal trampoline frame, sp points to an rt_sigframe[1], which is:
2653   //  - 128-byte siginfo struct
2654   //  - ucontext struct:
2655   //     - 8-byte long (uc_flags)
2656   //     - 8-byte pointer (uc_link)
2657   //     - 24-byte stack_t
2658   //     - 128-byte signal set
2659   //     - 8 bytes of padding because sigcontext has 16-byte alignment
2660   //     - sigcontext/mcontext_t
2661   // [1] https://github.com/torvalds/linux/blob/master/arch/arm64/kernel/signal.c
2662   const pint_t kOffsetSpToSigcontext = (128 + 8 + 8 + 24 + 128 + 8); // 304
2663 
2664   // Offsets from sigcontext to each register.
2665   const pint_t kOffsetGprs = 8; // offset to "__u64 regs[31]" field
2666   const pint_t kOffsetSp = 256; // offset to "__u64 sp" field
2667   const pint_t kOffsetPc = 264; // offset to "__u64 pc" field
2668 
2669   pint_t sigctx = _registers.getSP() + kOffsetSpToSigcontext;
2670 
2671   for (int i = 0; i <= 30; ++i) {
2672     uint64_t value = _addressSpace.get64(sigctx + kOffsetGprs +
2673                                          static_cast<pint_t>(i * 8));
2674     _registers.setRegister(UNW_AARCH64_X0 + i, value);
2675   }
2676   _registers.setSP(_addressSpace.get64(sigctx + kOffsetSp));
2677   _registers.setIP(_addressSpace.get64(sigctx + kOffsetPc));
2678   _isSignalFrame = true;
2679   return UNW_STEP_SUCCESS;
2680 }
2681 #endif // defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&
2682        // defined(_LIBUNWIND_TARGET_AARCH64)
2683 
2684 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&                               \
2685     defined(_LIBUNWIND_TARGET_S390X)
2686 template <typename A, typename R>
2687 bool UnwindCursor<A, R>::setInfoForSigReturn(Registers_s390x &) {
2688   // Look for the sigreturn trampoline. The trampoline's body is a
2689   // specific instruction (see below). Typically the trampoline comes from the
2690   // vDSO (i.e. the __kernel_[rt_]sigreturn function). A libc might provide its
2691   // own restorer function, though, or user-mode QEMU might write a trampoline
2692   // onto the stack.
2693   const pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
2694   const uint16_t inst = _addressSpace.get16(pc);
2695   if (inst == 0x0a77 || inst == 0x0aad) {
2696     _info = {};
2697     _info.start_ip = pc;
2698     _info.end_ip = pc + 2;
2699     _isSigReturn = true;
2700     return true;
2701   }
2702   return false;
2703 }
2704 
2705 template <typename A, typename R>
2706 int UnwindCursor<A, R>::stepThroughSigReturn(Registers_s390x &) {
2707   // Determine current SP.
2708   const pint_t sp = static_cast<pint_t>(this->getReg(UNW_REG_SP));
2709   // According to the s390x ABI, the CFA is at (incoming) SP + 160.
2710   const pint_t cfa = sp + 160;
2711 
2712   // Determine current PC and instruction there (this must be either
2713   // a "svc __NR_sigreturn" or "svc __NR_rt_sigreturn").
2714   const pint_t pc = static_cast<pint_t>(this->getReg(UNW_REG_IP));
2715   const uint16_t inst = _addressSpace.get16(pc);
2716 
2717   // Find the addresses of the signo and sigcontext in the frame.
2718   pint_t pSigctx = 0;
2719   pint_t pSigno = 0;
2720 
2721   // "svc __NR_sigreturn" uses a non-RT signal trampoline frame.
2722   if (inst == 0x0a77) {
2723     // Layout of a non-RT signal trampoline frame, starting at the CFA:
2724     //  - 8-byte signal mask
2725     //  - 8-byte pointer to sigcontext, followed by signo
2726     //  - 4-byte signo
2727     pSigctx = _addressSpace.get64(cfa + 8);
2728     pSigno = pSigctx + 344;
2729   }
2730 
2731   // "svc __NR_rt_sigreturn" uses a RT signal trampoline frame.
2732   if (inst == 0x0aad) {
2733     // Layout of a RT signal trampoline frame, starting at the CFA:
2734     //  - 8-byte retcode (+ alignment)
2735     //  - 128-byte siginfo struct (starts with signo)
2736     //  - ucontext struct:
2737     //     - 8-byte long (uc_flags)
2738     //     - 8-byte pointer (uc_link)
2739     //     - 24-byte stack_t
2740     //     - 8 bytes of padding because sigcontext has 16-byte alignment
2741     //     - sigcontext/mcontext_t
2742     pSigctx = cfa + 8 + 128 + 8 + 8 + 24 + 8;
2743     pSigno = cfa + 8;
2744   }
2745 
2746   assert(pSigctx != 0);
2747   assert(pSigno != 0);
2748 
2749   // Offsets from sigcontext to each register.
2750   const pint_t kOffsetPc = 8;
2751   const pint_t kOffsetGprs = 16;
2752   const pint_t kOffsetFprs = 216;
2753 
2754   // Restore all registers.
2755   for (int i = 0; i < 16; ++i) {
2756     uint64_t value = _addressSpace.get64(pSigctx + kOffsetGprs +
2757                                          static_cast<pint_t>(i * 8));
2758     _registers.setRegister(UNW_S390X_R0 + i, value);
2759   }
2760   for (int i = 0; i < 16; ++i) {
2761     static const int fpr[16] = {
2762       UNW_S390X_F0, UNW_S390X_F1, UNW_S390X_F2, UNW_S390X_F3,
2763       UNW_S390X_F4, UNW_S390X_F5, UNW_S390X_F6, UNW_S390X_F7,
2764       UNW_S390X_F8, UNW_S390X_F9, UNW_S390X_F10, UNW_S390X_F11,
2765       UNW_S390X_F12, UNW_S390X_F13, UNW_S390X_F14, UNW_S390X_F15
2766     };
2767     double value = _addressSpace.getDouble(pSigctx + kOffsetFprs +
2768                                            static_cast<pint_t>(i * 8));
2769     _registers.setFloatRegister(fpr[i], value);
2770   }
2771   _registers.setIP(_addressSpace.get64(pSigctx + kOffsetPc));
2772 
2773   // SIGILL, SIGFPE and SIGTRAP are delivered with psw_addr
2774   // after the faulting instruction rather than before it.
2775   // Do not set _isSignalFrame in that case.
2776   uint32_t signo = _addressSpace.get32(pSigno);
2777   _isSignalFrame = (signo != 4 && signo != 5 && signo != 8);
2778 
2779   return UNW_STEP_SUCCESS;
2780 }
2781 #endif // defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN) &&
2782        // defined(_LIBUNWIND_TARGET_S390X)
2783 
2784 template <typename A, typename R>
2785 int UnwindCursor<A, R>::step() {
2786   // Bottom of stack is defined is when unwind info cannot be found.
2787   if (_unwindInfoMissing)
2788     return UNW_STEP_END;
2789 
2790   // Use unwinding info to modify register set as if function returned.
2791   int result;
2792 #if defined(_LIBUNWIND_CHECK_LINUX_SIGRETURN)
2793   if (_isSigReturn) {
2794     result = this->stepThroughSigReturn();
2795   } else
2796 #endif
2797   {
2798 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
2799     result = this->stepWithCompactEncoding();
2800 #elif defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
2801     result = this->stepWithSEHData();
2802 #elif defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
2803     result = this->stepWithTBTableData();
2804 #elif defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
2805     result = this->stepWithDwarfFDE();
2806 #elif defined(_LIBUNWIND_ARM_EHABI)
2807     result = this->stepWithEHABI();
2808 #else
2809   #error Need _LIBUNWIND_SUPPORT_COMPACT_UNWIND or \
2810               _LIBUNWIND_SUPPORT_SEH_UNWIND or \
2811               _LIBUNWIND_SUPPORT_DWARF_UNWIND or \
2812               _LIBUNWIND_ARM_EHABI
2813 #endif
2814   }
2815 
2816   // update info based on new PC
2817   if (result == UNW_STEP_SUCCESS) {
2818     this->setInfoBasedOnIPRegister(true);
2819     if (_unwindInfoMissing)
2820       return UNW_STEP_END;
2821   }
2822 
2823   return result;
2824 }
2825 
2826 template <typename A, typename R>
2827 void UnwindCursor<A, R>::getInfo(unw_proc_info_t *info) {
2828   if (_unwindInfoMissing)
2829     memset(info, 0, sizeof(*info));
2830   else
2831     *info = _info;
2832 }
2833 
2834 template <typename A, typename R>
2835 bool UnwindCursor<A, R>::getFunctionName(char *buf, size_t bufLen,
2836                                                            unw_word_t *offset) {
2837   return _addressSpace.findFunctionName((pint_t)this->getReg(UNW_REG_IP),
2838                                          buf, bufLen, offset);
2839 }
2840 
2841 #if defined(_LIBUNWIND_USE_CET)
2842 extern "C" void *__libunwind_cet_get_registers(unw_cursor_t *cursor) {
2843   AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
2844   return co->get_registers();
2845 }
2846 #endif
2847 } // namespace libunwind
2848 
2849 #endif // __UNWINDCURSOR_HPP__
2850