xref: /freebsd/contrib/llvm-project/libunwind/src/UnwindLevel1.c (revision f81cdf24ba5436367377f7c8e8f51f6df2a75ca7)
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 // Implements C++ ABI Exception Handling Level 1 as documented at:
9 //      https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
10 // using libunwind
11 //
12 //===----------------------------------------------------------------------===//
13 
14 // ARM EHABI does not specify _Unwind_{Get,Set}{GR,IP}().  Thus, we are
15 // defining inline functions to delegate the function calls to
16 // _Unwind_VRS_{Get,Set}().  However, some applications might declare the
17 // function protetype directly (instead of including <unwind.h>), thus we need
18 // to export these functions from libunwind.so as well.
19 #define _LIBUNWIND_UNWIND_LEVEL1_EXTERNAL_LINKAGE 1
20 
21 #include <inttypes.h>
22 #include <stdint.h>
23 #include <stdbool.h>
24 #include <stdlib.h>
25 #include <stdio.h>
26 #include <string.h>
27 
28 #include "cet_unwind.h"
29 #include "config.h"
30 #include "libunwind.h"
31 #include "libunwind_ext.h"
32 #include "unwind.h"
33 
34 #if !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__)
35 
36 #ifndef _LIBUNWIND_SUPPORT_SEH_UNWIND
37 
38 // When CET is enabled, each "call" instruction will push return address to
39 // CET shadow stack, each "ret" instruction will pop current CET shadow stack
40 // top and compare it with target address which program will return.
41 // In exception handing, some stack frames will be skipped before jumping to
42 // landing pad and we must adjust CET shadow stack accordingly.
43 // _LIBUNWIND_POP_CET_SSP is used to adjust CET shadow stack pointer and we
44 // directly jump to __libunwind_Registers_x86/x86_64_jumpto instead of using
45 // a regular function call to avoid pushing to CET shadow stack again.
46 #if !defined(_LIBUNWIND_USE_CET)
47 #define __unw_phase2_resume(cursor, fn)                                        \
48   do {                                                                         \
49     (void)fn;                                                                  \
50     __unw_resume((cursor));                                                    \
51   } while (0)
52 #elif defined(_LIBUNWIND_TARGET_I386)
53 #define __cet_ss_step_size 4
54 #define __unw_phase2_resume(cursor, fn)                                        \
55   do {                                                                         \
56     _LIBUNWIND_POP_CET_SSP((fn));                                              \
57     void *cetRegContext = __libunwind_cet_get_registers((cursor));             \
58     void *cetJumpAddress = __libunwind_cet_get_jump_target();                  \
59     __asm__ volatile("push %%edi\n\t"                                          \
60                      "sub $4, %%esp\n\t"                                       \
61                      "jmp *%%edx\n\t" :: "D"(cetRegContext),                   \
62                      "d"(cetJumpAddress));                                     \
63   } while (0)
64 #elif defined(_LIBUNWIND_TARGET_X86_64)
65 #define __cet_ss_step_size 8
66 #define __unw_phase2_resume(cursor, fn)                                        \
67   do {                                                                         \
68     _LIBUNWIND_POP_CET_SSP((fn));                                              \
69     void *cetRegContext = __libunwind_cet_get_registers((cursor));             \
70     void *cetJumpAddress = __libunwind_cet_get_jump_target();                  \
71     __asm__ volatile("jmpq *%%rdx\n\t" :: "D"(cetRegContext),                  \
72                      "d"(cetJumpAddress));                                     \
73   } while (0)
74 #endif
75 
76 static _Unwind_Reason_Code
77 unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
78   __unw_init_local(cursor, uc);
79 
80   // Walk each frame looking for a place to stop.
81   while (true) {
82     // Ask libunwind to get next frame (skip over first which is
83     // _Unwind_RaiseException).
84     int stepResult = __unw_step(cursor);
85     if (stepResult == 0) {
86       _LIBUNWIND_TRACE_UNWINDING(
87           "unwind_phase1(ex_obj=%p): __unw_step() reached "
88           "bottom => _URC_END_OF_STACK",
89           (void *)exception_object);
90       return _URC_END_OF_STACK;
91     } else if (stepResult < 0) {
92       _LIBUNWIND_TRACE_UNWINDING(
93           "unwind_phase1(ex_obj=%p): __unw_step failed => "
94           "_URC_FATAL_PHASE1_ERROR",
95           (void *)exception_object);
96       return _URC_FATAL_PHASE1_ERROR;
97     }
98 
99     // See if frame has code to run (has personality routine).
100     unw_proc_info_t frameInfo;
101     unw_word_t sp;
102     if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
103       _LIBUNWIND_TRACE_UNWINDING(
104           "unwind_phase1(ex_obj=%p): __unw_get_proc_info "
105           "failed => _URC_FATAL_PHASE1_ERROR",
106           (void *)exception_object);
107       return _URC_FATAL_PHASE1_ERROR;
108     }
109 
110 #ifndef NDEBUG
111     // When tracing, print state information.
112     if (_LIBUNWIND_TRACING_UNWINDING) {
113       char functionBuf[512];
114       const char *functionName = functionBuf;
115       unw_word_t offset;
116       if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
117                                &offset) != UNW_ESUCCESS) ||
118           (frameInfo.start_ip + offset > frameInfo.end_ip))
119         functionName = ".anonymous.";
120       unw_word_t pc;
121       __unw_get_reg(cursor, UNW_REG_IP, &pc);
122       _LIBUNWIND_TRACE_UNWINDING(
123           "unwind_phase1(ex_obj=%p): pc=0x%" PRIxPTR ", start_ip=0x%" PRIxPTR
124           ", func=%s, lsda=0x%" PRIxPTR ", personality=0x%" PRIxPTR "",
125           (void *)exception_object, pc, frameInfo.start_ip, functionName,
126           frameInfo.lsda, frameInfo.handler);
127     }
128 #endif
129 
130     // If there is a personality routine, ask it if it will want to stop at
131     // this frame.
132     if (frameInfo.handler != 0) {
133       _Unwind_Personality_Fn p =
134           (_Unwind_Personality_Fn)(uintptr_t)(frameInfo.handler);
135       _LIBUNWIND_TRACE_UNWINDING(
136           "unwind_phase1(ex_obj=%p): calling personality function %p",
137           (void *)exception_object, (void *)(uintptr_t)p);
138       _Unwind_Reason_Code personalityResult =
139           (*p)(1, _UA_SEARCH_PHASE, exception_object->exception_class,
140                exception_object, (struct _Unwind_Context *)(cursor));
141       switch (personalityResult) {
142       case _URC_HANDLER_FOUND:
143         // found a catch clause or locals that need destructing in this frame
144         // stop search and remember stack pointer at the frame
145         __unw_get_reg(cursor, UNW_REG_SP, &sp);
146         exception_object->private_2 = (uintptr_t)sp;
147         _LIBUNWIND_TRACE_UNWINDING(
148             "unwind_phase1(ex_obj=%p): _URC_HANDLER_FOUND",
149             (void *)exception_object);
150         return _URC_NO_REASON;
151 
152       case _URC_CONTINUE_UNWIND:
153         _LIBUNWIND_TRACE_UNWINDING(
154             "unwind_phase1(ex_obj=%p): _URC_CONTINUE_UNWIND",
155             (void *)exception_object);
156         // continue unwinding
157         break;
158 
159       default:
160         // something went wrong
161         _LIBUNWIND_TRACE_UNWINDING(
162             "unwind_phase1(ex_obj=%p): _URC_FATAL_PHASE1_ERROR",
163             (void *)exception_object);
164         return _URC_FATAL_PHASE1_ERROR;
165       }
166     }
167   }
168   return _URC_NO_REASON;
169 }
170 extern int __unw_step_stage2(unw_cursor_t *);
171 
172 static _Unwind_Reason_Code
173 unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
174   __unw_init_local(cursor, uc);
175 
176   _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p)",
177                              (void *)exception_object);
178 
179   // uc is initialized by __unw_getcontext in the parent frame. The first stack
180   // frame walked is unwind_phase2.
181   unsigned framesWalked = 1;
182 #ifdef _LIBUNWIND_USE_CET
183   unsigned long shadowStackTop = _get_ssp();
184 #endif
185   // Walk each frame until we reach where search phase said to stop.
186   while (true) {
187 
188     // Ask libunwind to get next frame (skip over first which is
189     // _Unwind_RaiseException).
190     int stepResult = __unw_step_stage2(cursor);
191     if (stepResult == 0) {
192       _LIBUNWIND_TRACE_UNWINDING(
193           "unwind_phase2(ex_obj=%p): __unw_step_stage2() reached "
194           "bottom => _URC_END_OF_STACK",
195           (void *)exception_object);
196       return _URC_END_OF_STACK;
197     } else if (stepResult < 0) {
198       _LIBUNWIND_TRACE_UNWINDING(
199           "unwind_phase2(ex_obj=%p): __unw_step_stage2 failed => "
200           "_URC_FATAL_PHASE1_ERROR",
201           (void *)exception_object);
202       return _URC_FATAL_PHASE2_ERROR;
203     }
204 
205     // Get info about this frame.
206     unw_word_t sp;
207     unw_proc_info_t frameInfo;
208     __unw_get_reg(cursor, UNW_REG_SP, &sp);
209     if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
210       _LIBUNWIND_TRACE_UNWINDING(
211           "unwind_phase2(ex_obj=%p): __unw_get_proc_info "
212           "failed => _URC_FATAL_PHASE1_ERROR",
213           (void *)exception_object);
214       return _URC_FATAL_PHASE2_ERROR;
215     }
216 
217 #ifndef NDEBUG
218     // When tracing, print state information.
219     if (_LIBUNWIND_TRACING_UNWINDING) {
220       char functionBuf[512];
221       const char *functionName = functionBuf;
222       unw_word_t offset;
223       if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
224                                &offset) != UNW_ESUCCESS) ||
225           (frameInfo.start_ip + offset > frameInfo.end_ip))
226         functionName = ".anonymous.";
227       _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p): start_ip=0x%" PRIxPTR
228                                  ", func=%s, sp=0x%" PRIxPTR ", lsda=0x%" PRIxPTR
229                                  ", personality=0x%" PRIxPTR,
230                                  (void *)exception_object, frameInfo.start_ip,
231                                  functionName, sp, frameInfo.lsda,
232                                  frameInfo.handler);
233     }
234 #endif
235 
236 // In CET enabled environment, we check return address stored in normal stack
237 // against return address stored in CET shadow stack, if the 2 addresses don't
238 // match, it means return address in normal stack has been corrupted, we return
239 // _URC_FATAL_PHASE2_ERROR.
240 #ifdef _LIBUNWIND_USE_CET
241     if (shadowStackTop != 0) {
242       unw_word_t retInNormalStack;
243       __unw_get_reg(cursor, UNW_REG_IP, &retInNormalStack);
244       unsigned long retInShadowStack = *(
245           unsigned long *)(shadowStackTop + __cet_ss_step_size * framesWalked);
246       if (retInNormalStack != retInShadowStack)
247         return _URC_FATAL_PHASE2_ERROR;
248     }
249 #endif
250     ++framesWalked;
251     // If there is a personality routine, tell it we are unwinding.
252     if (frameInfo.handler != 0) {
253       _Unwind_Personality_Fn p =
254           (_Unwind_Personality_Fn)(uintptr_t)(frameInfo.handler);
255       _Unwind_Action action = _UA_CLEANUP_PHASE;
256       if (sp == exception_object->private_2) {
257         // Tell personality this was the frame it marked in phase 1.
258         action = (_Unwind_Action)(_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME);
259       }
260        _Unwind_Reason_Code personalityResult =
261           (*p)(1, action, exception_object->exception_class, exception_object,
262                (struct _Unwind_Context *)(cursor));
263       switch (personalityResult) {
264       case _URC_CONTINUE_UNWIND:
265         // Continue unwinding
266         _LIBUNWIND_TRACE_UNWINDING(
267             "unwind_phase2(ex_obj=%p): _URC_CONTINUE_UNWIND",
268             (void *)exception_object);
269         if (sp == exception_object->private_2) {
270           // Phase 1 said we would stop at this frame, but we did not...
271           _LIBUNWIND_ABORT("during phase1 personality function said it would "
272                            "stop here, but now in phase2 it did not stop here");
273         }
274         break;
275       case _URC_INSTALL_CONTEXT:
276         _LIBUNWIND_TRACE_UNWINDING(
277             "unwind_phase2(ex_obj=%p): _URC_INSTALL_CONTEXT",
278             (void *)exception_object);
279         // Personality routine says to transfer control to landing pad.
280         // We may get control back if landing pad calls _Unwind_Resume().
281         if (_LIBUNWIND_TRACING_UNWINDING) {
282           unw_word_t pc;
283           __unw_get_reg(cursor, UNW_REG_IP, &pc);
284           __unw_get_reg(cursor, UNW_REG_SP, &sp);
285           _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p): re-entering "
286                                      "user code with ip=0x%" PRIxPTR
287                                      ", sp=0x%" PRIxPTR,
288                                      (void *)exception_object, pc, sp);
289         }
290 
291         __unw_phase2_resume(cursor, framesWalked);
292         // __unw_phase2_resume() only returns if there was an error.
293         return _URC_FATAL_PHASE2_ERROR;
294       default:
295         // Personality routine returned an unknown result code.
296         _LIBUNWIND_DEBUG_LOG("personality function returned unknown result %d",
297                              personalityResult);
298         return _URC_FATAL_PHASE2_ERROR;
299       }
300     }
301   }
302 
303   // Clean up phase did not resume at the frame that the search phase
304   // said it would...
305   return _URC_FATAL_PHASE2_ERROR;
306 }
307 
308 static _Unwind_Reason_Code
309 unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor,
310                      _Unwind_Exception *exception_object,
311                      _Unwind_Stop_Fn stop, void *stop_parameter) {
312   __unw_init_local(cursor, uc);
313 
314   // uc is initialized by __unw_getcontext in the parent frame. The first stack
315   // frame walked is unwind_phase2_forced.
316   unsigned framesWalked = 1;
317   // Walk each frame until we reach where search phase said to stop
318   while (__unw_step_stage2(cursor) > 0) {
319 
320     // Update info about this frame.
321     unw_proc_info_t frameInfo;
322     if (__unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
323       _LIBUNWIND_TRACE_UNWINDING(
324           "unwind_phase2_forced(ex_obj=%p): __unw_get_proc_info "
325           "failed => _URC_END_OF_STACK",
326           (void *)exception_object);
327       return _URC_FATAL_PHASE2_ERROR;
328     }
329 
330 #ifndef NDEBUG
331     // When tracing, print state information.
332     if (_LIBUNWIND_TRACING_UNWINDING) {
333       char functionBuf[512];
334       const char *functionName = functionBuf;
335       unw_word_t offset;
336       if ((__unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
337                                &offset) != UNW_ESUCCESS) ||
338           (frameInfo.start_ip + offset > frameInfo.end_ip))
339         functionName = ".anonymous.";
340       _LIBUNWIND_TRACE_UNWINDING(
341           "unwind_phase2_forced(ex_obj=%p): start_ip=0x%" PRIxPTR
342           ", func=%s, lsda=0x%" PRIxPTR ", personality=0x%" PRIxPTR,
343           (void *)exception_object, frameInfo.start_ip, functionName,
344           frameInfo.lsda, frameInfo.handler);
345     }
346 #endif
347 
348     // Call stop function at each frame.
349     _Unwind_Action action =
350         (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
351     _Unwind_Reason_Code stopResult =
352         (*stop)(1, action, exception_object->exception_class, exception_object,
353                 (struct _Unwind_Context *)(cursor), stop_parameter);
354     _LIBUNWIND_TRACE_UNWINDING(
355         "unwind_phase2_forced(ex_obj=%p): stop function returned %d",
356         (void *)exception_object, stopResult);
357     if (stopResult != _URC_NO_REASON) {
358       _LIBUNWIND_TRACE_UNWINDING(
359           "unwind_phase2_forced(ex_obj=%p): stopped by stop function",
360           (void *)exception_object);
361       return _URC_FATAL_PHASE2_ERROR;
362     }
363 
364     ++framesWalked;
365     // If there is a personality routine, tell it we are unwinding.
366     if (frameInfo.handler != 0) {
367       _Unwind_Personality_Fn p =
368           (_Unwind_Personality_Fn)(intptr_t)(frameInfo.handler);
369       _LIBUNWIND_TRACE_UNWINDING(
370           "unwind_phase2_forced(ex_obj=%p): calling personality function %p",
371           (void *)exception_object, (void *)(uintptr_t)p);
372       _Unwind_Reason_Code personalityResult =
373           (*p)(1, action, exception_object->exception_class, exception_object,
374                (struct _Unwind_Context *)(cursor));
375       switch (personalityResult) {
376       case _URC_CONTINUE_UNWIND:
377         _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
378                                    "personality returned "
379                                    "_URC_CONTINUE_UNWIND",
380                                    (void *)exception_object);
381         // Destructors called, continue unwinding
382         break;
383       case _URC_INSTALL_CONTEXT:
384         _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
385                                    "personality returned "
386                                    "_URC_INSTALL_CONTEXT",
387                                    (void *)exception_object);
388         // We may get control back if landing pad calls _Unwind_Resume().
389         __unw_phase2_resume(cursor, framesWalked);
390         break;
391       default:
392         // Personality routine returned an unknown result code.
393         _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): "
394                                    "personality returned %d, "
395                                    "_URC_FATAL_PHASE2_ERROR",
396                                    (void *)exception_object, personalityResult);
397         return _URC_FATAL_PHASE2_ERROR;
398       }
399     }
400   }
401 
402   // Call stop function one last time and tell it we've reached the end
403   // of the stack.
404   _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_obj=%p): calling stop "
405                              "function with _UA_END_OF_STACK",
406                              (void *)exception_object);
407   _Unwind_Action lastAction =
408       (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
409   (*stop)(1, lastAction, exception_object->exception_class, exception_object,
410           (struct _Unwind_Context *)(cursor), stop_parameter);
411 
412   // Clean up phase did not resume at the frame that the search phase said it
413   // would.
414   return _URC_FATAL_PHASE2_ERROR;
415 }
416 
417 
418 /// Called by __cxa_throw.  Only returns if there is a fatal error.
419 _LIBUNWIND_EXPORT _Unwind_Reason_Code
420 _Unwind_RaiseException(_Unwind_Exception *exception_object) {
421   _LIBUNWIND_TRACE_API("_Unwind_RaiseException(ex_obj=%p)",
422                        (void *)exception_object);
423   unw_context_t uc;
424   unw_cursor_t cursor;
425   __unw_getcontext(&uc);
426 
427   // Mark that this is a non-forced unwind, so _Unwind_Resume()
428   // can do the right thing.
429   exception_object->private_1 = 0;
430   exception_object->private_2 = 0;
431 
432   // phase 1: the search phase
433   _Unwind_Reason_Code phase1 = unwind_phase1(&uc, &cursor, exception_object);
434   if (phase1 != _URC_NO_REASON)
435     return phase1;
436 
437   // phase 2: the clean up phase
438   return unwind_phase2(&uc, &cursor, exception_object);
439 }
440 
441 
442 
443 /// When _Unwind_RaiseException() is in phase2, it hands control
444 /// to the personality function at each frame.  The personality
445 /// may force a jump to a landing pad in that function, the landing
446 /// pad code may then call _Unwind_Resume() to continue with the
447 /// unwinding.  Note: the call to _Unwind_Resume() is from compiler
448 /// generated user code.  All other _Unwind_* routines are called
449 /// by the C++ runtime __cxa_* routines.
450 ///
451 /// Note: re-throwing an exception (as opposed to continuing the unwind)
452 /// is implemented by having the code call __cxa_rethrow() which
453 /// in turn calls _Unwind_Resume_or_Rethrow().
454 _LIBUNWIND_EXPORT void
455 _Unwind_Resume(_Unwind_Exception *exception_object) {
456   _LIBUNWIND_TRACE_API("_Unwind_Resume(ex_obj=%p)", (void *)exception_object);
457   unw_context_t uc;
458   unw_cursor_t cursor;
459   __unw_getcontext(&uc);
460 
461   if (exception_object->private_1 != 0)
462     unwind_phase2_forced(&uc, &cursor, exception_object,
463                          (_Unwind_Stop_Fn) exception_object->private_1,
464                          (void *)exception_object->private_2);
465   else
466     unwind_phase2(&uc, &cursor, exception_object);
467 
468   // Clients assume _Unwind_Resume() does not return, so all we can do is abort.
469   _LIBUNWIND_ABORT("_Unwind_Resume() can't return");
470 }
471 
472 
473 
474 /// Not used by C++.
475 /// Unwinds stack, calling "stop" function at each frame.
476 /// Could be used to implement longjmp().
477 _LIBUNWIND_EXPORT _Unwind_Reason_Code
478 _Unwind_ForcedUnwind(_Unwind_Exception *exception_object,
479                      _Unwind_Stop_Fn stop, void *stop_parameter) {
480   _LIBUNWIND_TRACE_API("_Unwind_ForcedUnwind(ex_obj=%p, stop=%p)",
481                        (void *)exception_object, (void *)(uintptr_t)stop);
482   unw_context_t uc;
483   unw_cursor_t cursor;
484   __unw_getcontext(&uc);
485 
486   // Mark that this is a forced unwind, so _Unwind_Resume() can do
487   // the right thing.
488   exception_object->private_1 = (uintptr_t) stop;
489   exception_object->private_2 = (uintptr_t) stop_parameter;
490 
491   // do it
492   return unwind_phase2_forced(&uc, &cursor, exception_object, stop, stop_parameter);
493 }
494 
495 
496 /// Called by personality handler during phase 2 to get LSDA for current frame.
497 _LIBUNWIND_EXPORT uintptr_t
498 _Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
499   unw_cursor_t *cursor = (unw_cursor_t *)context;
500   unw_proc_info_t frameInfo;
501   uintptr_t result = 0;
502   if (__unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS)
503     result = (uintptr_t)frameInfo.lsda;
504   _LIBUNWIND_TRACE_API(
505       "_Unwind_GetLanguageSpecificData(context=%p) => 0x%" PRIxPTR,
506       (void *)context, result);
507 #if !defined(_LIBUNWIND_SUPPORT_TBTAB_UNWIND)
508   if (result != 0) {
509     if (*((uint8_t *)result) != 0xFF)
510       _LIBUNWIND_DEBUG_LOG("lsda at 0x%" PRIxPTR " does not start with 0xFF",
511                            result);
512   }
513 #endif
514   return result;
515 }
516 
517 
518 /// Called by personality handler during phase 2 to find the start of the
519 /// function.
520 _LIBUNWIND_EXPORT uintptr_t
521 _Unwind_GetRegionStart(struct _Unwind_Context *context) {
522   unw_cursor_t *cursor = (unw_cursor_t *)context;
523   unw_proc_info_t frameInfo;
524   uintptr_t result = 0;
525   if (__unw_get_proc_info(cursor, &frameInfo) == UNW_ESUCCESS)
526     result = (uintptr_t)frameInfo.start_ip;
527   _LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p) => 0x%" PRIxPTR,
528                        (void *)context, result);
529   return result;
530 }
531 
532 #endif // !_LIBUNWIND_SUPPORT_SEH_UNWIND
533 
534 /// Called by personality handler during phase 2 if a foreign exception
535 // is caught.
536 _LIBUNWIND_EXPORT void
537 _Unwind_DeleteException(_Unwind_Exception *exception_object) {
538   _LIBUNWIND_TRACE_API("_Unwind_DeleteException(ex_obj=%p)",
539                        (void *)exception_object);
540   if (exception_object->exception_cleanup != NULL)
541     (*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT,
542                                            exception_object);
543 }
544 
545 /// Called by personality handler during phase 2 to get register values.
546 _LIBUNWIND_EXPORT uintptr_t
547 _Unwind_GetGR(struct _Unwind_Context *context, int index) {
548   unw_cursor_t *cursor = (unw_cursor_t *)context;
549   unw_word_t result;
550   __unw_get_reg(cursor, index, &result);
551   _LIBUNWIND_TRACE_API("_Unwind_GetGR(context=%p, reg=%d) => 0x%" PRIxPTR,
552                        (void *)context, index, result);
553   return (uintptr_t)result;
554 }
555 
556 /// Called by personality handler during phase 2 to alter register values.
557 _LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
558                                      uintptr_t value) {
559   _LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%0" PRIxPTR
560                        ")",
561                        (void *)context, index, value);
562   unw_cursor_t *cursor = (unw_cursor_t *)context;
563   __unw_set_reg(cursor, index, value);
564 }
565 
566 /// Called by personality handler during phase 2 to get instruction pointer.
567 _LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
568   unw_cursor_t *cursor = (unw_cursor_t *)context;
569   unw_word_t result;
570   __unw_get_reg(cursor, UNW_REG_IP, &result);
571   _LIBUNWIND_TRACE_API("_Unwind_GetIP(context=%p) => 0x%" PRIxPTR,
572                        (void *)context, result);
573   return (uintptr_t)result;
574 }
575 
576 /// Called by personality handler during phase 2 to alter instruction pointer,
577 /// such as setting where the landing pad is, so _Unwind_Resume() will
578 /// start executing in the landing pad.
579 _LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
580                                      uintptr_t value) {
581   _LIBUNWIND_TRACE_API("_Unwind_SetIP(context=%p, value=0x%0" PRIxPTR ")",
582                        (void *)context, value);
583   unw_cursor_t *cursor = (unw_cursor_t *)context;
584   __unw_set_reg(cursor, UNW_REG_IP, value);
585 }
586 
587 #endif // !defined(_LIBUNWIND_ARM_EHABI) && !defined(__USING_SJLJ_EXCEPTIONS__)
588