libgcc/unwind-sjlj.c

   1 /* SJLJ exception handling and frame unwind runtime interface routines.
   2    Copyright (C) 1997-2021 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 #include "tconfig.h"
  26 #include "tsystem.h"
  27 #include "coretypes.h"
  28 #include "tm.h"
  29 #include "libgcc_tm.h"
  30 #include "unwind.h"
  31 #include "gthr.h"
  32
  33 #ifdef __USING_SJLJ_EXCEPTIONS__
  34
  35 #ifdef __LIBGCC_DONT_USE_BUILTIN_SETJMP__
  36 #ifndef inhibit_libc
  37 #include <setjmp.h>
  38 #else
  39 typedef void *jmp_buf[__LIBGCC_JMP_BUF_SIZE__];
  40 extern void longjmp(jmp_buf, int) __attribute__((noreturn));
  41 #endif
  42 #else
  43 #define longjmp __builtin_longjmp
  44 #endif
  45
  46 /* The setjmp side is dealt with in the except.c file.  */
  47 #undef setjmp
  48 #define setjmp setjmp_should_not_be_used_in_this_file
  49
  50
  51 /* This structure is allocated on the stack of the target function.
  52    This must match the definition created in except.c:init_eh.  */
  53 struct SjLj_Function_Context
  54 {
  55   /* This is the chain through all registered contexts.  It is
  56      filled in by _Unwind_SjLj_Register.  */
  57   struct SjLj_Function_Context *prev;
  58
  59   /* This is assigned in by the target function before every call
  60      to the index of the call site in the lsda.  It is assigned by
  61      the personality routine to the landing pad index.  */
  62   int call_site;
  63
  64   /* This is how data is returned from the personality routine to
  65      the target function's handler.  */
  66   _Unwind_Word data[4];
  67
  68   /* These are filled in once by the target function before any
  69      exceptions are expected to be handled.  */
  70   _Unwind_Personality_Fn personality;
  71   void *lsda;
  72
  73 #ifdef __LIBGCC_DONT_USE_BUILTIN_SETJMP__
  74   /* We don't know what sort of alignment requirements the system
  75      jmp_buf has.  We over estimated in except.c, and now we have
  76      to match that here just in case the system *didn't* have more
  77      restrictive requirements.  */
  78   jmp_buf jbuf __attribute__((aligned));
  79 #else
  80   void *jbuf[];
  81 #endif
  82 };
  83
  84 struct _Unwind_Context
  85 {
  86   struct SjLj_Function_Context *fc;
  87 };
  88
  89 typedef struct
  90 {
  91   _Unwind_Personality_Fn personality;
  92 } _Unwind_FrameState;
  93
  94 \f
  95 /* Manage the chain of registered function contexts.  */
  96
  97 /* Single threaded fallback chain.  */
  98 static struct SjLj_Function_Context *fc_static;
  99
 100 #if __GTHREADS
 101 static __gthread_key_t fc_key;
 102 static int use_fc_key = -1;
 103
 104 static void
 105 fc_key_init (void)
 106 {
 107   use_fc_key = __gthread_key_create (&fc_key, 0) == 0;
 108 }
 109
 110 static void
 111 fc_key_init_once (void)
 112 {
 113   static __gthread_once_t once = __GTHREAD_ONCE_INIT;
 114   if (__gthread_once (&once, fc_key_init) != 0 || use_fc_key < 0)
 115     use_fc_key = 0;
 116 }
 117 #endif
 118
 119 void
 120 _Unwind_SjLj_Register (struct SjLj_Function_Context *fc)
 121 {
 122 #if __GTHREADS
 123   if (use_fc_key < 0)
 124     fc_key_init_once ();
 125
 126   if (use_fc_key)
 127     {
 128       fc->prev = __gthread_getspecific (fc_key);
 129       __gthread_setspecific (fc_key, fc);
 130     }
 131   else
 132 #endif
 133     {
 134       fc->prev = fc_static;
 135       fc_static = fc;
 136     }
 137 }
 138
 139 static inline struct SjLj_Function_Context *
 140 _Unwind_SjLj_GetContext (void)
 141 {
 142 #if __GTHREADS
 143   if (use_fc_key < 0)
 144     fc_key_init_once ();
 145
 146   if (use_fc_key)
 147     return __gthread_getspecific (fc_key);
 148 #endif
 149   return fc_static;
 150 }
 151
 152 static inline void
 153 _Unwind_SjLj_SetContext (struct SjLj_Function_Context *fc)
 154 {
 155 #if __GTHREADS
 156   if (use_fc_key < 0)
 157     fc_key_init_once ();
 158
 159   if (use_fc_key)
 160     __gthread_setspecific (fc_key, fc);
 161   else
 162 #endif
 163     fc_static = fc;
 164 }
 165
 166 void
 167 _Unwind_SjLj_Unregister (struct SjLj_Function_Context *fc)
 168 {
 169   _Unwind_SjLj_SetContext (fc->prev);
 170 }
 171
 172 \f
 173 /* Get/set the return data value at INDEX in CONTEXT.  */
 174
 175 _Unwind_Word
 176 _Unwind_GetGR (struct _Unwind_Context *context, int index)
 177 {
 178   return context->fc->data[index];
 179 }
 180
 181 /* Get the value of the CFA as saved in CONTEXT.  */
 182
 183 _Unwind_Word
 184 _Unwind_GetCFA (struct _Unwind_Context *context __attribute__((unused)))
 185 {
 186   /* ??? Ideally __builtin_setjmp places the CFA in the jmpbuf.  */
 187
 188 #ifndef __LIBGCC_DONT_USE_BUILTIN_SETJMP__
 189   /* This is a crude imitation of the CFA: the saved stack pointer.
 190      This is roughly the CFA of the frame before CONTEXT.  When using the
 191      DWARF-2 unwinder _Unwind_GetCFA returns the CFA of the frame described
 192      by CONTEXT instead; but for DWARF-2 the cleanups associated with
 193      CONTEXT have already been run, and for SJLJ they have not yet been.  */
 194   if (context->fc != NULL)
 195     return (_Unwind_Word) context->fc->jbuf[2];
 196 #endif
 197
 198   /* Otherwise we're out of luck for now.  */
 199   return (_Unwind_Word) 0;
 200 }
 201
 202 void
 203 _Unwind_SetGR (struct _Unwind_Context *context, int index, _Unwind_Word val)
 204 {
 205   context->fc->data[index] = val;
 206 }
 207
 208 /* Get the call-site index as saved in CONTEXT.  */
 209
 210 _Unwind_Ptr
 211 _Unwind_GetIP (struct _Unwind_Context *context)
 212 {
 213   return context->fc->call_site + 1;
 214 }
 215
 216 _Unwind_Ptr
 217 _Unwind_GetIPInfo (struct _Unwind_Context *context, int *ip_before_insn)
 218 {
 219   *ip_before_insn = 0;
 220   if (context->fc != NULL)
 221     return context->fc->call_site + 1;
 222   else
 223     return 0;
 224 }
 225
 226 /* Set the return landing pad index in CONTEXT.  */
 227
 228 void
 229 _Unwind_SetIP (struct _Unwind_Context *context, _Unwind_Ptr val)
 230 {
 231   context->fc->call_site = val - 1;
 232 }
 233
 234 void *
 235 _Unwind_GetLanguageSpecificData (struct _Unwind_Context *context)
 236 {
 237   return context->fc->lsda;
 238 }
 239
 240 _Unwind_Ptr
 241 _Unwind_GetRegionStart (struct _Unwind_Context *context __attribute__((unused)) )
 242 {
 243   return 0;
 244 }
 245
 246 void *
 247 _Unwind_FindEnclosingFunction (void *pc __attribute__((unused)))
 248 {
 249   return NULL;
 250 }
 251
 252 #ifndef __ia64__
 253 _Unwind_Ptr
 254 _Unwind_GetDataRelBase (struct _Unwind_Context *context __attribute__((unused)) )
 255 {
 256   return 0;
 257 }
 258
 259 _Unwind_Ptr
 260 _Unwind_GetTextRelBase (struct _Unwind_Context *context __attribute__((unused)) )
 261 {
 262   return 0;
 263 }
 264 #endif
 265 \f
 266 static inline _Unwind_Reason_Code
 267 uw_frame_state_for (struct _Unwind_Context *context, _Unwind_FrameState *fs)
 268 {
 269   if (context->fc == NULL)
 270     {
 271       fs->personality = NULL;
 272       return _URC_END_OF_STACK;
 273     }
 274   else
 275     {
 276       fs->personality = context->fc->personality;
 277       return _URC_NO_REASON;
 278     }
 279 }
 280
 281 static inline void
 282 uw_update_context (struct _Unwind_Context *context,
 283                    _Unwind_FrameState *fs __attribute__((unused)) )
 284 {
 285   context->fc = context->fc->prev;
 286 }
 287
 288 static void
 289 uw_advance_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
 290 {
 291   _Unwind_SjLj_Unregister (context->fc);
 292   uw_update_context (context, fs);
 293 }
 294
 295 static inline void
 296 uw_init_context (struct _Unwind_Context *context)
 297 {
 298   context->fc = _Unwind_SjLj_GetContext ();
 299 }
 300
 301 static void __attribute__((noreturn))
 302 uw_install_context (struct _Unwind_Context *current __attribute__((unused)),
 303                     struct _Unwind_Context *target,
 304                     unsigned long frames __attribute__((unused)))
 305 {
 306   _Unwind_SjLj_SetContext (target->fc);
 307   longjmp (target->fc->jbuf, 1);
 308 }
 309
 310 static inline _Unwind_Ptr
 311 uw_identify_context (struct _Unwind_Context *context)
 312 {
 313   return (_Unwind_Ptr) context->fc;
 314 }
 315
 316
 317 /* Play games with unwind symbols so that we can have call frame
 318    and sjlj symbols in the same shared library.  Not that you can
 319    use them simultaneously...  */
 320 #define _Unwind_RaiseException          _Unwind_SjLj_RaiseException
 321 #define _Unwind_ForcedUnwind            _Unwind_SjLj_ForcedUnwind
 322 #define _Unwind_Resume                  _Unwind_SjLj_Resume
 323 #define _Unwind_Resume_or_Rethrow       _Unwind_SjLj_Resume_or_Rethrow
 324
 325 #include "unwind.inc"
 326
 327 #endif /* USING_SJLJ_EXCEPTIONS */