libgcc/unwind.inc

   1 /* Exception handling and frame unwind runtime interface routines. -*- C -*-
   2    Copyright (C) 2001-2024 Free Software Foundation, Inc.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GCC is distributed in the hope that it will be useful, but WITHOUT
  12    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  14    License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* This is derived from the C++ ABI for IA-64.  Where we diverge
  26    for cross-architecture compatibility are noted with "@@@".
  27    This file is included from unwind-dw2.c, unwind-sjlj.c or
  28    unwind-ia64.c.  */
  29
  30 /* Subroutine of _Unwind_RaiseException also invoked from _Unwind_Resume.
  31
  32    Unwind the stack calling the personality routine to find both the
  33    exception handler and intermediary cleanup code.  We'll only locate
  34    the first such frame here.  Cleanup code will call back into
  35    _Unwind_Resume and we'll continue Phase 2 there.  */
  36
  37 static _Unwind_Reason_Code
  38 _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
  39                               struct _Unwind_Context *context,
  40                               unsigned long *frames_p)
  41 {
  42   _Unwind_Reason_Code code;
  43   unsigned long frames = 1;
  44
  45   while (1)
  46     {
  47       _Unwind_FrameState fs;
  48       int match_handler;
  49
  50       code = uw_frame_state_for (context, &fs);
  51
  52       /* Identify when we've reached the designated handler context.  */
  53       match_handler = (uw_identify_context (context) == exc->private_2
  54                        ? _UA_HANDLER_FRAME : 0);
  55
  56       if (code != _URC_NO_REASON)
  57         /* Some error encountered.  Usually the unwinder doesn't
  58            diagnose these and merely crashes.  */
  59         return _URC_FATAL_PHASE2_ERROR;
  60
  61       /* Unwind successful.  Run the personality routine, if any.  */
  62       if (fs.personality)
  63         {
  64           code = (*fs.personality) (1, _UA_CLEANUP_PHASE | match_handler,
  65                                     exc->exception_class, exc, context);
  66           if (code == _URC_INSTALL_CONTEXT)
  67             break;
  68           if (code != _URC_CONTINUE_UNWIND)
  69             return _URC_FATAL_PHASE2_ERROR;
  70         }
  71
  72       /* Don't let us unwind past the handler context.  */
  73       gcc_assert (!match_handler);
  74
  75       uw_update_context (context, &fs);
  76       _Unwind_Frames_Increment (exc, context, frames);
  77     }
  78
  79   *frames_p = frames;
  80   return code;
  81 }
  82
  83 /* Raise an exception, passing along the given exception object.  */
  84
  85 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
  86 _Unwind_RaiseException(struct _Unwind_Exception *exc)
  87 {
  88   struct _Unwind_Context this_context, cur_context;
  89   _Unwind_Reason_Code code;
  90   unsigned long frames;
  91
  92   /* Set up this_context to describe the current stack frame.  */
  93   uw_init_context (&this_context);
  94   cur_context = this_context;
  95
  96   /* Phase 1: Search.  Unwind the stack, calling the personality routine
  97      with the _UA_SEARCH_PHASE flag set.  Do not modify the stack yet.  */
  98   while (1)
  99     {
 100       _Unwind_FrameState fs;
 101
 102       /* Set up fs to describe the FDE for the caller of cur_context.  The
 103          first time through the loop, that means __cxa_throw.  */
 104       code = uw_frame_state_for (&cur_context, &fs);
 105
 106       if (code == _URC_END_OF_STACK)
 107         /* Hit end of stack with no handler found.  */
 108         return _URC_END_OF_STACK;
 109
 110       if (code != _URC_NO_REASON)
 111         /* Some error encountered.  Usually the unwinder doesn't
 112            diagnose these and merely crashes.  */
 113         return _URC_FATAL_PHASE1_ERROR;
 114
 115       /* Unwind successful.  Run the personality routine, if any.  */
 116       if (fs.personality)
 117         {
 118           code = (*fs.personality) (1, _UA_SEARCH_PHASE, exc->exception_class,
 119                                     exc, &cur_context);
 120           if (code == _URC_HANDLER_FOUND)
 121             break;
 122           else if (code != _URC_CONTINUE_UNWIND)
 123             return _URC_FATAL_PHASE1_ERROR;
 124         }
 125
 126       /* Update cur_context to describe the same frame as fs.  */
 127       uw_update_context (&cur_context, &fs);
 128     }
 129
 130   /* Indicate to _Unwind_Resume and associated subroutines that this
 131      is not a forced unwind.  Further, note where we found a handler.  */
 132   exc->private_1 = 0;
 133   exc->private_2 = uw_identify_context (&cur_context);
 134
 135   cur_context = this_context;
 136   code = _Unwind_RaiseException_Phase2 (exc, &cur_context, &frames);
 137   if (code != _URC_INSTALL_CONTEXT)
 138     return code;
 139
 140   uw_install_context (&this_context, &cur_context, frames);
 141 }
 142
 143
 144 /* Subroutine of _Unwind_ForcedUnwind also invoked from _Unwind_Resume.  */
 145
 146 static _Unwind_Reason_Code
 147 _Unwind_ForcedUnwind_Phase2 (struct _Unwind_Exception *exc,
 148                              struct _Unwind_Context *context,
 149                              unsigned long *frames_p)
 150 {
 151   _Unwind_Stop_Fn stop = (_Unwind_Stop_Fn) (_Unwind_Ptr) exc->private_1;
 152   void *stop_argument = (void *) (_Unwind_Ptr) exc->private_2;
 153   _Unwind_Reason_Code code, stop_code;
 154   unsigned long frames = 1;
 155
 156   while (1)
 157     {
 158       _Unwind_FrameState fs;
 159       int action;
 160
 161       /* Set up fs to describe the FDE for the caller of cur_context.  */
 162       code = uw_frame_state_for (context, &fs);
 163       if (code != _URC_NO_REASON && code != _URC_END_OF_STACK
 164           && code != _URC_NORMAL_STOP)
 165         return _URC_FATAL_PHASE2_ERROR;
 166
 167       /* Unwind successful.  */
 168       action = _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE;
 169       if (code == _URC_END_OF_STACK || code == _URC_NORMAL_STOP)
 170         action |= _UA_END_OF_STACK;
 171       stop_code = (*stop) (1, action, exc->exception_class, exc,
 172                            context, stop_argument);
 173       if (stop_code != _URC_NO_REASON)
 174         return _URC_FATAL_PHASE2_ERROR;
 175
 176       /* Stop didn't want to do anything.  Invoke the personality
 177          handler, if applicable, to run cleanups.  */
 178       if (code == _URC_END_OF_STACK)
 179         break;
 180
 181       if (fs.personality)
 182         {
 183           code = (*fs.personality) (1, _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE,
 184                                     exc->exception_class, exc, context);
 185           if (code == _URC_INSTALL_CONTEXT)
 186             break;
 187           if (code != _URC_CONTINUE_UNWIND)
 188             return _URC_FATAL_PHASE2_ERROR;
 189         }
 190
 191       /* Update cur_context to describe the same frame as fs, and discard
 192          the previous context if necessary.  */
 193       uw_advance_context (context, &fs);
 194       _Unwind_Frames_Increment (exc, context, frames);
 195     }
 196
 197   *frames_p = frames;
 198   return code;
 199 }
 200
 201
 202 /* Raise an exception for forced unwinding.  */
 203
 204 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 205 _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
 206                       _Unwind_Stop_Fn stop, void * stop_argument)
 207 {
 208   struct _Unwind_Context this_context, cur_context;
 209   _Unwind_Reason_Code code;
 210   unsigned long frames;
 211
 212   uw_init_context (&this_context);
 213   cur_context = this_context;
 214
 215   exc->private_1 = (_Unwind_Ptr) stop;
 216   exc->private_2 = (_Unwind_Ptr) stop_argument;
 217
 218   code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
 219   if (code != _URC_INSTALL_CONTEXT)
 220     return code;
 221
 222   uw_install_context (&this_context, &cur_context, frames);
 223 }
 224
 225
 226 /* Resume propagation of an existing exception.  This is used after
 227    e.g. executing cleanup code, and not to implement rethrowing.  */
 228
 229 void LIBGCC2_UNWIND_ATTRIBUTE
 230 _Unwind_Resume (struct _Unwind_Exception *exc)
 231 {
 232   struct _Unwind_Context this_context, cur_context;
 233   _Unwind_Reason_Code code;
 234   unsigned long frames;
 235
 236   uw_init_context (&this_context);
 237   cur_context = this_context;
 238
 239   /* Choose between continuing to process _Unwind_RaiseException
 240      or _Unwind_ForcedUnwind.  */
 241   if (exc->private_1 == 0)
 242     code = _Unwind_RaiseException_Phase2 (exc, &cur_context, &frames);
 243   else
 244     code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
 245
 246   gcc_assert (code == _URC_INSTALL_CONTEXT);
 247
 248   uw_install_context (&this_context, &cur_context, frames);
 249 }
 250
 251
 252 /* Resume propagation of an FORCE_UNWIND exception, or to rethrow
 253    a normal exception that was handled.  */
 254
 255 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 256 _Unwind_Resume_or_Rethrow (struct _Unwind_Exception *exc)
 257 {
 258   struct _Unwind_Context this_context, cur_context;
 259   _Unwind_Reason_Code code;
 260   unsigned long frames;
 261
 262   /* Choose between continuing to process _Unwind_RaiseException
 263      or _Unwind_ForcedUnwind.  */
 264   if (exc->private_1 == 0)
 265     return _Unwind_RaiseException (exc);
 266
 267   uw_init_context (&this_context);
 268   cur_context = this_context;
 269
 270   code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
 271
 272   gcc_assert (code == _URC_INSTALL_CONTEXT);
 273
 274   uw_install_context (&this_context, &cur_context, frames);
 275 }
 276
 277
 278 /* A convenience function that calls the exception_cleanup field.  */
 279
 280 void
 281 _Unwind_DeleteException (struct _Unwind_Exception *exc)
 282 {
 283   if (exc->exception_cleanup)
 284     (*exc->exception_cleanup) (_URC_FOREIGN_EXCEPTION_CAUGHT, exc);
 285 }
 286
 287
 288 /* Perform stack backtrace through unwind data.  */
 289
 290 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 291 _Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument)
 292 {
 293   struct _Unwind_Context context;
 294   _Unwind_Reason_Code code;
 295
 296   uw_init_context (&context);
 297
 298   while (1)
 299     {
 300       _Unwind_FrameState fs;
 301
 302       /* Set up fs to describe the FDE for the caller of context.  */
 303       code = uw_frame_state_for (&context, &fs);
 304       if (code != _URC_NO_REASON && code != _URC_END_OF_STACK
 305           && code != _URC_NORMAL_STOP)
 306         return _URC_FATAL_PHASE1_ERROR;
 307
 308       /* Call trace function.  */
 309       if ((*trace) (&context, trace_argument) != _URC_NO_REASON)
 310         return _URC_FATAL_PHASE1_ERROR;
 311
 312 #ifdef MD_BACKCHAIN_FALLBACK
 313       /* Do a backchain if there is no DWARF data.  */
 314       if (code == _URC_NORMAL_STOP)
 315         {
 316           MD_BACKCHAIN_FALLBACK(&context, trace_argument);
 317           break;
 318         }
 319 #endif
 320
 321       /* We're done at end of stack.  */
 322       if (code == _URC_END_OF_STACK)
 323         break;
 324
 325       /* Update context to describe the same frame as fs.  */
 326       uw_update_context (&context, &fs);
 327     }
 328
 329   return code;
 330 }