aboutsummaryrefslogtreecommitdiffstats
path: root/src/Unwind-sjlj.c
blob: 90cac3f8c763818b48efb053828fadf392a46247 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
//===--------------------------- Unwind-sjlj.c ----------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//
//  Implements setjump-longjump based C++ exceptions
//
//===----------------------------------------------------------------------===//

#include <unwind.h>

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>

#include "config.h"

/// With SJLJ based exceptions, any function that has a catch clause or needs to
/// do any clean up when an exception propagates through it, needs to call
/// \c _Unwind_SjLj_Register at the start of the function and
/// \c _Unwind_SjLj_Unregister at the end.  The register function is called with
/// the address of a block of memory in the function's stack frame.  The runtime
/// keeps a linked list (stack) of these blocks - one per thread.  The calling
/// function also sets the personality and lsda fields of the block.

#if defined(_LIBUNWIND_BUILD_SJLJ_APIS)

struct _Unwind_FunctionContext {
  // next function in stack of handlers
  struct _Unwind_FunctionContext *prev;

  // set by calling function before registering to be the landing pad
  uint32_t                        resumeLocation;

  // set by personality handler to be parameters passed to landing pad function
  uint32_t                        resumeParameters[4];

  // set by calling function before registering
  __personality_routine           personality; // arm offset=24
  uintptr_t                       lsda;        // arm offset=28

  // variable length array, contains registers to restore
  // 0 = r7, 1 = pc, 2 = sp
  void                           *jbuf[];
};

#if defined(_LIBUNWIND_HAS_NO_THREADS)
# define _LIBUNWIND_THREAD_LOCAL
#else
# if __STDC_VERSION__ >= 201112L
#  define _LIBUNWIND_THREAD_LOCAL _Thread_local
# elif defined(_WIN32)
#  define _LIBUNWIND_THREAD_LOCAL __declspec(thread)
# elif defined(__GNUC__) || defined(__clang__)
#  define _LIBUNWIND_THREAD_LOCAL __thread
# else
#  error Unable to create thread local storage
# endif
#endif


#if !defined(FOR_DYLD)

#if defined(__APPLE__)
#include <System/pthread_machdep.h>
#else
static _LIBUNWIND_THREAD_LOCAL struct _Unwind_FunctionContext *stack = NULL;
#endif

static struct _Unwind_FunctionContext *__Unwind_SjLj_GetTopOfFunctionStack() {
#if defined(__APPLE__)
  return _pthread_getspecific_direct(__PTK_LIBC_DYLD_Unwind_SjLj_Key);
#else
  return stack;
#endif
}

static void
__Unwind_SjLj_SetTopOfFunctionStack(struct _Unwind_FunctionContext *fc) {
#if defined(__APPLE__)
  _pthread_setspecific_direct(__PTK_LIBC_DYLD_Unwind_SjLj_Key, fc);
#else
  stack = fc;
#endif
}

#endif


/// Called at start of each function that catches exceptions
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Register(struct _Unwind_FunctionContext *fc) {
  fc->prev = __Unwind_SjLj_GetTopOfFunctionStack();
  __Unwind_SjLj_SetTopOfFunctionStack(fc);
}


/// Called at end of each function that catches exceptions
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Unregister(struct _Unwind_FunctionContext *fc) {
  __Unwind_SjLj_SetTopOfFunctionStack(fc->prev);
}


static _Unwind_Reason_Code
unwind_phase1(struct _Unwind_Exception *exception_object) {
  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
  _LIBUNWIND_TRACE_UNWINDING("unwind_phase1: initial function-context=%p", c);

  // walk each frame looking for a place to stop
  for (bool handlerNotFound = true; handlerNotFound; c = c->prev) {

    // check for no more frames
    if (c == NULL) {
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): reached "
                                 "bottom => _URC_END_OF_STACK",
                                  exception_object);
      return _URC_END_OF_STACK;
    }

    _LIBUNWIND_TRACE_UNWINDING("unwind_phase1: function-context=%p", c);
    // if there is a personality routine, ask it if it will want to stop at this
    // frame
    if (c->personality != NULL) {
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): calling "
                                "personality function %p",
                                 exception_object, c->personality);
      _Unwind_Reason_Code personalityResult = (*c->personality)(
          1, _UA_SEARCH_PHASE, exception_object->exception_class,
          exception_object, (struct _Unwind_Context *)c);
      switch (personalityResult) {
      case _URC_HANDLER_FOUND:
        // found a catch clause or locals that need destructing in this frame
        // stop search and remember function context
        handlerNotFound = false;
        exception_object->private_2 = (uintptr_t) c;
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
                                   "_URC_HANDLER_FOUND", exception_object);
        return _URC_NO_REASON;

      case _URC_CONTINUE_UNWIND:
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): "
                                   "_URC_CONTINUE_UNWIND", exception_object);
        // continue unwinding
        break;

      default:
        // something went wrong
        _LIBUNWIND_TRACE_UNWINDING(
            "unwind_phase1(ex_ojb=%p): _URC_FATAL_PHASE1_ERROR",
            exception_object);
        return _URC_FATAL_PHASE1_ERROR;
      }
    }
  }
  return _URC_NO_REASON;
}


static _Unwind_Reason_Code
unwind_phase2(struct _Unwind_Exception *exception_object) {
  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p)", exception_object);

  // walk each frame until we reach where search phase said to stop
  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
  while (true) {
    _LIBUNWIND_TRACE_UNWINDING("unwind_phase2s(ex_ojb=%p): context=%p",
                              exception_object, c);

    // check for no more frames
    if (c == NULL) {
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
                                "bottom => _URC_END_OF_STACK",
                                 exception_object);
      return _URC_END_OF_STACK;
    }

    // if there is a personality routine, tell it we are unwinding
    if (c->personality != NULL) {
      _Unwind_Action action = _UA_CLEANUP_PHASE;
      if ((uintptr_t) c == exception_object->private_2)
        action = (_Unwind_Action)(
            _UA_CLEANUP_PHASE |
            _UA_HANDLER_FRAME); // tell personality this was the frame it marked
                                // in phase 1
      _Unwind_Reason_Code personalityResult =
          (*c->personality)(1, action, exception_object->exception_class,
                            exception_object, (struct _Unwind_Context *)c);
      switch (personalityResult) {
      case _URC_CONTINUE_UNWIND:
        // continue unwinding
        _LIBUNWIND_TRACE_UNWINDING(
            "unwind_phase2(ex_ojb=%p): _URC_CONTINUE_UNWIND",
            exception_object);
        if ((uintptr_t) c == exception_object->private_2) {
          // phase 1 said we would stop at this frame, but we did not...
          _LIBUNWIND_ABORT("during phase1 personality function said it would "
                           "stop here, but now if phase2 it did not stop here");
        }
        break;
      case _URC_INSTALL_CONTEXT:
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): "
                                  "_URC_INSTALL_CONTEXT, will resume at "
                                  "landing pad %p",
                                  exception_object, c->jbuf[1]);
        // personality routine says to transfer control to landing pad
        // we may get control back if landing pad calls _Unwind_Resume()
        __Unwind_SjLj_SetTopOfFunctionStack(c);
        __builtin_longjmp(c->jbuf, 1);
        // unw_resume() only returns if there was an error
        return _URC_FATAL_PHASE2_ERROR;
      default:
        // something went wrong
        _LIBUNWIND_DEBUG_LOG("personality function returned unknown result %d",
                      personalityResult);
        return _URC_FATAL_PHASE2_ERROR;
      }
    }
    c = c->prev;
  }

  // clean up phase did not resume at the frame that the search phase said it
  // would
  return _URC_FATAL_PHASE2_ERROR;
}


static _Unwind_Reason_Code
unwind_phase2_forced(struct _Unwind_Exception *exception_object,
                     _Unwind_Stop_Fn stop, void *stop_parameter) {
  // walk each frame until we reach where search phase said to stop
  _Unwind_FunctionContext_t c = __Unwind_SjLj_GetTopOfFunctionStack();
  while (true) {

    // get next frame (skip over first which is _Unwind_RaiseException)
    if (c == NULL) {
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
                                 "bottom => _URC_END_OF_STACK",
                                 exception_object);
      return _URC_END_OF_STACK;
    }

    // call stop function at each frame
    _Unwind_Action action =
        (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
    _Unwind_Reason_Code stopResult =
        (*stop)(1, action, exception_object->exception_class, exception_object,
                (struct _Unwind_Context *)c, stop_parameter);
    _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
                               "stop function returned %d",
                                exception_object, stopResult);
    if (stopResult != _URC_NO_REASON) {
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
                                 "stopped by stop function",
                                  exception_object);
      return _URC_FATAL_PHASE2_ERROR;
    }

    // if there is a personality routine, tell it we are unwinding
    if (c->personality != NULL) {
      __personality_routine p = (__personality_routine) c->personality;
      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
                                 "calling personality function %p",
                                  exception_object, p);
      _Unwind_Reason_Code personalityResult =
          (*p)(1, action, exception_object->exception_class, exception_object,
               (struct _Unwind_Context *)c);
      switch (personalityResult) {
      case _URC_CONTINUE_UNWIND:
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p):  "
                                   "personality returned _URC_CONTINUE_UNWIND",
                                    exception_object);
        // destructors called, continue unwinding
        break;
      case _URC_INSTALL_CONTEXT:
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
                                   "personality returned _URC_INSTALL_CONTEXT",
                                    exception_object);
        // we may get control back if landing pad calls _Unwind_Resume()
        __Unwind_SjLj_SetTopOfFunctionStack(c);
        __builtin_longjmp(c->jbuf, 1);
        break;
      default:
        // something went wrong
        _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
                                   "personality returned %d, "
                                   "_URC_FATAL_PHASE2_ERROR",
                                    exception_object, personalityResult);
        return _URC_FATAL_PHASE2_ERROR;
      }
    }
    c = c->prev;
  }

  // call stop function one last time and tell it we've reached the end of the
  // stack
  _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): calling stop "
                        "function with _UA_END_OF_STACK",
                        exception_object);
  _Unwind_Action lastAction =
      (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
  (*stop)(1, lastAction, exception_object->exception_class, exception_object,
          (struct _Unwind_Context *)c, stop_parameter);

  // clean up phase did not resume at the frame that the search phase said it
  // would
  return _URC_FATAL_PHASE2_ERROR;
}


/// Called by __cxa_throw.  Only returns if there is a fatal error
_LIBUNWIND_EXPORT _Unwind_Reason_Code
_Unwind_SjLj_RaiseException(struct _Unwind_Exception *exception_object) {
  _LIBUNWIND_TRACE_API("_Unwind_SjLj_RaiseException(ex_obj=%p)", exception_object);

  // mark that this is a non-forced unwind, so _Unwind_Resume() can do the right
  // thing
  exception_object->private_1 = 0;
  exception_object->private_2 = 0;

  // phase 1: the search phase
  _Unwind_Reason_Code phase1 = unwind_phase1(exception_object);
  if (phase1 != _URC_NO_REASON)
    return phase1;

  // phase 2: the clean up phase
  return unwind_phase2(exception_object);
}



/// When _Unwind_RaiseException() is in phase2, it hands control
/// to the personality function at each frame.  The personality
/// may force a jump to a landing pad in that function, the landing
/// pad code may then call _Unwind_Resume() to continue with the
/// unwinding.  Note: the call to _Unwind_Resume() is from compiler
/// geneated user code.  All other _Unwind_* routines are called
/// by the C++ runtime __cxa_* routines.
///
/// Re-throwing an exception is implemented by having the code call
/// __cxa_rethrow() which in turn calls _Unwind_Resume_or_Rethrow()
_LIBUNWIND_EXPORT void
_Unwind_SjLj_Resume(struct _Unwind_Exception *exception_object) {
  _LIBUNWIND_TRACE_API("_Unwind_SjLj_Resume(ex_obj=%p)", exception_object);

  if (exception_object->private_1 != 0)
    unwind_phase2_forced(exception_object,
                         (_Unwind_Stop_Fn) exception_object->private_1,
                         (void *)exception_object->private_2);
  else
    unwind_phase2(exception_object);

  // clients assume _Unwind_Resume() does not return, so all we can do is abort.
  _LIBUNWIND_ABORT("_Unwind_SjLj_Resume() can't return");
}


///  Called by __cxa_rethrow().
_LIBUNWIND_EXPORT _Unwind_Reason_Code
_Unwind_SjLj_Resume_or_Rethrow(struct _Unwind_Exception *exception_object) {
  _LIBUNWIND_TRACE_API("__Unwind_SjLj_Resume_or_Rethrow(ex_obj=%p), "
                             "private_1=%ld",
                              exception_object, exception_object->private_1);
  // If this is non-forced and a stopping place was found, then this is a
  // re-throw.
  // Call _Unwind_RaiseException() as if this was a new exception.
  if (exception_object->private_1 == 0) {
    return _Unwind_SjLj_RaiseException(exception_object);
    // should return if there is no catch clause, so that __cxa_rethrow can call
    // std::terminate()
  }

  // Call through to _Unwind_Resume() which distiguishes between forced and
  // regular exceptions.
  _Unwind_SjLj_Resume(exception_object);
  _LIBUNWIND_ABORT("__Unwind_SjLj_Resume_or_Rethrow() called "
                    "_Unwind_SjLj_Resume() which unexpectedly returned");
}


/// Called by personality handler during phase 2 to get LSDA for current frame.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetLanguageSpecificData(struct _Unwind_Context *context) {
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  _LIBUNWIND_TRACE_API("_Unwind_GetLanguageSpecificData(context=%p) "
                             "=> 0x%0lX",  context, ufc->lsda);
  return ufc->lsda;
}


/// Called by personality handler during phase 2 to get register values.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetGR(struct _Unwind_Context *context,
                                          int index) {
  _LIBUNWIND_TRACE_API("_Unwind_GetGR(context=%p, reg=%d)",
                             context, index);
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  return ufc->resumeParameters[index];
}


/// Called by personality handler during phase 2 to alter register values.
_LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
                                     uintptr_t new_value) {
  _LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%0lX)"
                            , context, index, new_value);
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  ufc->resumeParameters[index] = new_value;
}


/// Called by personality handler during phase 2 to get instruction pointer.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIP(struct _Unwind_Context *context) {
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  _LIBUNWIND_TRACE_API("_Unwind_GetIP(context=%p) => 0x%lX", context,
                  ufc->resumeLocation + 1);
  return ufc->resumeLocation + 1;
}


/// Called by personality handler during phase 2 to get instruction pointer.
/// ipBefore is a boolean that says if IP is already adjusted to be the call
/// site address.  Normally IP is the return address.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
                                              int *ipBefore) {
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  *ipBefore = 0;
  _LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p, %p) => 0x%lX",
                             context, ipBefore, ufc->resumeLocation + 1);
  return ufc->resumeLocation + 1;
}


/// Called by personality handler during phase 2 to alter instruction pointer.
_LIBUNWIND_EXPORT void _Unwind_SetIP(struct _Unwind_Context *context,
                                     uintptr_t new_value) {
  _LIBUNWIND_TRACE_API("_Unwind_SetIP(context=%p, value=0x%0lX)",
                             context, new_value);
  _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
  ufc->resumeLocation = new_value - 1;
}


/// Called by personality handler during phase 2 to find the start of the
/// function.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetRegionStart(struct _Unwind_Context *context) {
  // Not supported or needed for sjlj based unwinding
  (void)context;
  _LIBUNWIND_TRACE_API("_Unwind_GetRegionStart(context=%p)", context);
  return 0;
}


/// Called by personality handler during phase 2 if a foreign exception
/// is caught.
_LIBUNWIND_EXPORT void
_Unwind_DeleteException(struct _Unwind_Exception *exception_object) {
  _LIBUNWIND_TRACE_API("_Unwind_DeleteException(ex_obj=%p)",
                              exception_object);
  if (exception_object->exception_cleanup != NULL)
    (*exception_object->exception_cleanup)(_URC_FOREIGN_EXCEPTION_CAUGHT,
                                           exception_object);
}



/// Called by personality handler during phase 2 to get base address for data
/// relative encodings.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
  // Not supported or needed for sjlj based unwinding
  (void)context;
  _LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", context);
  _LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
}


/// Called by personality handler during phase 2 to get base address for text
/// relative encodings.
_LIBUNWIND_EXPORT uintptr_t
_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
  // Not supported or needed for sjlj based unwinding
  (void)context;
  _LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", context);
  _LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
}


/// Called by personality handler to get "Call Frame Area" for current frame.
_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
  _LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p)", context);
  if (context != NULL) {
    _Unwind_FunctionContext_t ufc = (_Unwind_FunctionContext_t) context;
    // Setjmp/longjmp based exceptions don't have a true CFA.
    // Instead, the SP in the jmpbuf is the closest approximation.
    return (uintptr_t) ufc->jbuf[2];
  }
  return 0;
}

#endif // defined(_LIBUNWIND_BUILD_SJLJ_APIS)