libgcc/unwind.inc

   1 /* Exception handling and frame unwind runtime interface routines. -*- C -*-
   2    Copyright (C) 2001-2017 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 {
  41   _Unwind_Reason_Code code;
  42
  43   while (1)
  44     {
  45       _Unwind_FrameState fs;
  46       int match_handler;
  47
  48       code = uw_frame_state_for (context, &fs);
  49
  50       /* Identify when we've reached the designated handler context.  */
  51       match_handler = (uw_identify_context (context) == exc->private_2
  52                        ? _UA_HANDLER_FRAME : 0);
  53
  54       if (code != _URC_NO_REASON)
  55         /* Some error encountered.  Usually the unwinder doesn't
  56            diagnose these and merely crashes.  */
  57         return _URC_FATAL_PHASE2_ERROR;
  58
  59       /* Unwind successful.  Run the personality routine, if any.  */
  60       if (fs.personality)
  61         {
  62           code = (*fs.personality) (1, _UA_CLEANUP_PHASE | match_handler,
  63                                     exc->exception_class, exc, context);
  64           if (code == _URC_INSTALL_CONTEXT)
  65             break;
  66           if (code != _URC_CONTINUE_UNWIND)
  67             return _URC_FATAL_PHASE2_ERROR;
  68         }
  69
  70       /* Don't let us unwind past the handler context.  */
  71       gcc_assert (!match_handler);
  72
  73       uw_update_context (context, &fs);
  74     }
  75
  76   return code;
  77 }
  78
  79 /* Raise an exception, passing along the given exception object.  */
  80
  81 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
  82 _Unwind_RaiseException(struct _Unwind_Exception *exc)
  83 {
  84   struct _Unwind_Context this_context, cur_context;
  85   _Unwind_Reason_Code code;
  86
  87   /* Set up this_context to describe the current stack frame.  */
  88   uw_init_context (&this_context);
  89   cur_context = this_context;
  90
  91   /* Phase 1: Search.  Unwind the stack, calling the personality routine
  92      with the _UA_SEARCH_PHASE flag set.  Do not modify the stack yet.  */
  93   while (1)
  94     {
  95       _Unwind_FrameState fs;
  96
  97       /* Set up fs to describe the FDE for the caller of cur_context.  The
  98          first time through the loop, that means __cxa_throw.  */
  99       code = uw_frame_state_for (&cur_context, &fs);
 100
 101       if (code == _URC_END_OF_STACK)
 102         /* Hit end of stack with no handler found.  */
 103         return _URC_END_OF_STACK;
 104
 105       if (code != _URC_NO_REASON)
 106         /* Some error encountered.  Usually the unwinder doesn't
 107            diagnose these and merely crashes.  */
 108         return _URC_FATAL_PHASE1_ERROR;
 109
 110       /* Unwind successful.  Run the personality routine, if any.  */
 111       if (fs.personality)
 112         {
 113           code = (*fs.personality) (1, _UA_SEARCH_PHASE, exc->exception_class,
 114                                     exc, &cur_context);
 115           if (code == _URC_HANDLER_FOUND)
 116             break;
 117           else if (code != _URC_CONTINUE_UNWIND)
 118             return _URC_FATAL_PHASE1_ERROR;
 119         }
 120
 121       /* Update cur_context to describe the same frame as fs.  */
 122       uw_update_context (&cur_context, &fs);
 123     }
 124
 125   /* Indicate to _Unwind_Resume and associated subroutines that this
 126      is not a forced unwind.  Further, note where we found a handler.  */
 127   exc->private_1 = 0;
 128   exc->private_2 = uw_identify_context (&cur_context);
 129
 130   cur_context = this_context;
 131   code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
 132   if (code != _URC_INSTALL_CONTEXT)
 133     return code;
 134
 135   uw_install_context (&this_context, &cur_context);
 136 }
 137
 138
 139 /* Subroutine of _Unwind_ForcedUnwind also invoked from _Unwind_Resume.  */
 140
 141 static _Unwind_Reason_Code
 142 _Unwind_ForcedUnwind_Phase2 (struct _Unwind_Exception *exc,
 143                              struct _Unwind_Context *context)
 144 {
 145   _Unwind_Stop_Fn stop = (_Unwind_Stop_Fn) (_Unwind_Ptr) exc->private_1;
 146   void *stop_argument = (void *) (_Unwind_Ptr) exc->private_2;
 147   _Unwind_Reason_Code code, stop_code;
 148
 149   while (1)
 150     {
 151       _Unwind_FrameState fs;
 152       int action;
 153
 154       /* Set up fs to describe the FDE for the caller of cur_context.  */
 155       code = uw_frame_state_for (context, &fs);
 156       if (code != _URC_NO_REASON && code != _URC_END_OF_STACK)
 157         return _URC_FATAL_PHASE2_ERROR;
 158
 159       /* Unwind successful.  */
 160       action = _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE;
 161       if (code == _URC_END_OF_STACK)
 162         action |= _UA_END_OF_STACK;
 163       stop_code = (*stop) (1, action, exc->exception_class, exc,
 164                            context, stop_argument);
 165       if (stop_code != _URC_NO_REASON)
 166         return _URC_FATAL_PHASE2_ERROR;
 167
 168       /* Stop didn't want to do anything.  Invoke the personality
 169          handler, if applicable, to run cleanups.  */
 170       if (code == _URC_END_OF_STACK)
 171         break;
 172
 173       if (fs.personality)
 174         {
 175           code = (*fs.personality) (1, _UA_FORCE_UNWIND | _UA_CLEANUP_PHASE,
 176                                     exc->exception_class, exc, context);
 177           if (code == _URC_INSTALL_CONTEXT)
 178             break;
 179           if (code != _URC_CONTINUE_UNWIND)
 180             return _URC_FATAL_PHASE2_ERROR;
 181         }
 182
 183       /* Update cur_context to describe the same frame as fs, and discard
 184          the previous context if necessary.  */
 185       uw_advance_context (context, &fs);
 186     }
 187
 188   return code;
 189 }
 190
 191
 192 /* Raise an exception for forced unwinding.  */
 193
 194 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 195 _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
 196                       _Unwind_Stop_Fn stop, void * stop_argument)
 197 {
 198   struct _Unwind_Context this_context, cur_context;
 199   _Unwind_Reason_Code code;
 200
 201   uw_init_context (&this_context);
 202   cur_context = this_context;
 203
 204   exc->private_1 = (_Unwind_Ptr) stop;
 205   exc->private_2 = (_Unwind_Ptr) stop_argument;
 206
 207   code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
 208   if (code != _URC_INSTALL_CONTEXT)
 209     return code;
 210
 211   uw_install_context (&this_context, &cur_context);
 212 }
 213
 214
 215 /* Resume propagation of an existing exception.  This is used after
 216    e.g. executing cleanup code, and not to implement rethrowing.  */
 217
 218 void LIBGCC2_UNWIND_ATTRIBUTE
 219 _Unwind_Resume (struct _Unwind_Exception *exc)
 220 {
 221   struct _Unwind_Context this_context, cur_context;
 222   _Unwind_Reason_Code code;
 223
 224   uw_init_context (&this_context);
 225   cur_context = this_context;
 226
 227   /* Choose between continuing to process _Unwind_RaiseException
 228      or _Unwind_ForcedUnwind.  */
 229   if (exc->private_1 == 0)
 230     code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
 231   else
 232     code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
 233
 234   gcc_assert (code == _URC_INSTALL_CONTEXT);
 235
 236   uw_install_context (&this_context, &cur_context);
 237 }
 238
 239
 240 /* Resume propagation of an FORCE_UNWIND exception, or to rethrow
 241    a normal exception that was handled.  */
 242
 243 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 244 _Unwind_Resume_or_Rethrow (struct _Unwind_Exception *exc)
 245 {
 246   struct _Unwind_Context this_context, cur_context;
 247   _Unwind_Reason_Code code;
 248
 249   /* Choose between continuing to process _Unwind_RaiseException
 250      or _Unwind_ForcedUnwind.  */
 251   if (exc->private_1 == 0)
 252     return _Unwind_RaiseException (exc);
 253
 254   uw_init_context (&this_context);
 255   cur_context = this_context;
 256
 257   code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
 258
 259   gcc_assert (code == _URC_INSTALL_CONTEXT);
 260
 261   uw_install_context (&this_context, &cur_context);
 262 }
 263
 264
 265 /* A convenience function that calls the exception_cleanup field.  */
 266
 267 void
 268 _Unwind_DeleteException (struct _Unwind_Exception *exc)
 269 {
 270   if (exc->exception_cleanup)
 271     (*exc->exception_cleanup) (_URC_FOREIGN_EXCEPTION_CAUGHT, exc);
 272 }
 273
 274
 275 /* Perform stack backtrace through unwind data.  */
 276
 277 _Unwind_Reason_Code LIBGCC2_UNWIND_ATTRIBUTE
 278 _Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument)
 279 {
 280   struct _Unwind_Context context;
 281   _Unwind_Reason_Code code;
 282
 283   uw_init_context (&context);
 284
 285   while (1)
 286     {
 287       _Unwind_FrameState fs;
 288
 289       /* Set up fs to describe the FDE for the caller of context.  */
 290       code = uw_frame_state_for (&context, &fs);
 291       if (code != _URC_NO_REASON && code != _URC_END_OF_STACK)
 292         return _URC_FATAL_PHASE1_ERROR;
 293
 294       /* Call trace function.  */
 295       if ((*trace) (&context, trace_argument) != _URC_NO_REASON)
 296         return _URC_FATAL_PHASE1_ERROR;
 297
 298       /* We're done at end of stack.  */
 299       if (code == _URC_END_OF_STACK)
 300         break;
 301
 302       /* Update context to describe the same frame as fs.  */
 303       uw_update_context (&context, &fs);
 304     }
 305
 306   return code;
 307 }