libgcc/unwind-c.c

   1 /* Supporting functions for C exception handling.
   2    Copyright (C) 2002-2024 Free Software Foundation, Inc.
   3    Contributed by Aldy Hernandez <aldy@quesejoda.com>.
   4    Shamelessly stolen from the Java front end.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 Under Section 7 of GPL version 3, you are granted additional
  19 permissions described in the GCC Runtime Library Exception, version
  20 3.1, as published by the Free Software Foundation.
  21
  22 You should have received a copy of the GNU General Public License and
  23 a copy of the GCC Runtime Library Exception along with this program;
  24 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 <http://www.gnu.org/licenses/>.  */
  26
  27 #include "tconfig.h"
  28 #include "tsystem.h"
  29 #include "auto-target.h"
  30 #include "unwind.h"
  31 #define NO_SIZE_OF_ENCODED_VALUE
  32 #include "unwind-pe.h"
  33
  34 typedef struct
  35 {
  36   _Unwind_Ptr Start;
  37   _Unwind_Ptr LPStart;
  38   _Unwind_Ptr ttype_base;
  39   const unsigned char *TType;
  40   const unsigned char *action_table;
  41   unsigned char ttype_encoding;
  42   unsigned char call_site_encoding;
  43 } lsda_header_info;
  44
  45 static const unsigned char *
  46 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
  47                    lsda_header_info *info)
  48 {
  49   _uleb128_t tmp;
  50   unsigned char lpstart_encoding;
  51
  52   info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
  53
  54   /* Find @LPStart, the base to which landing pad offsets are relative.  */
  55   lpstart_encoding = *p++;
  56   if (lpstart_encoding != DW_EH_PE_omit)
  57     p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
  58   else
  59     info->LPStart = info->Start;
  60
  61   /* Find @TType, the base of the handler and exception spec type data.  */
  62   info->ttype_encoding = *p++;
  63   if (info->ttype_encoding != DW_EH_PE_omit)
  64     {
  65       p = read_uleb128 (p, &tmp);
  66       info->TType = p + tmp;
  67     }
  68   else
  69     info->TType = 0;
  70
  71   /* The encoding and length of the call-site table; the action table
  72      immediately follows.  */
  73   info->call_site_encoding = *p++;
  74   p = read_uleb128 (p, &tmp);
  75   info->action_table = p + tmp;
  76
  77   return p;
  78 }
  79
  80 #ifdef __ARM_EABI_UNWINDER__
  81 /* ARM EABI personality routines must also unwind the stack.  */
  82 #define CONTINUE_UNWINDING \
  83   do                                                            \
  84     {                                                           \
  85       if (__gnu_unwind_frame (ue_header, context) != _URC_OK)   \
  86         return _URC_FAILURE;                                    \
  87       return _URC_CONTINUE_UNWIND;                              \
  88     }                                                           \
  89   while (0)
  90 #else
  91 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
  92 #endif
  93
  94 #ifdef __USING_SJLJ_EXCEPTIONS__
  95 #define PERSONALITY_FUNCTION    __gcc_personality_sj0
  96 #define __builtin_eh_return_data_regno(x) x
  97 #elif defined(__SEH__)
  98 #define PERSONALITY_FUNCTION    __gcc_personality_imp
  99 #else
 100 #define PERSONALITY_FUNCTION    __gcc_personality_v0
 101 #endif
 102
 103 #ifdef __ARM_EABI_UNWINDER__
 104 _Unwind_Reason_Code
 105 PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
 106                       struct _Unwind_Context *);
 107
 108 _Unwind_Reason_Code
 109 __attribute__((target ("general-regs-only")))
 110 PERSONALITY_FUNCTION (_Unwind_State state,
 111                       struct _Unwind_Exception * ue_header,
 112                       struct _Unwind_Context * context)
 113 #else
 114 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
 115 static
 116 #endif
 117 _Unwind_Reason_Code
 118 PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
 119                       struct _Unwind_Exception *, struct _Unwind_Context *);
 120
 121 _Unwind_Reason_Code
 122 PERSONALITY_FUNCTION (int version,
 123                       _Unwind_Action actions,
 124                       _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
 125                       struct _Unwind_Exception *ue_header,
 126                       struct _Unwind_Context *context)
 127 #endif
 128 {
 129   lsda_header_info info;
 130   const unsigned char *language_specific_data, *p;
 131   _Unwind_Ptr landing_pad, ip;
 132   int ip_before_insn = 0;
 133
 134 #ifdef __ARM_EABI_UNWINDER__
 135   if ((state & _US_ACTION_MASK) != _US_UNWIND_FRAME_STARTING)
 136     CONTINUE_UNWINDING;
 137
 138   /* The dwarf unwinder assumes the context structure holds things like the
 139      function and LSDA pointers.  The ARM implementation caches these in
 140      the exception header (UCB).  To avoid rewriting everything we make a
 141      virtual scratch register point at the UCB.  */
 142   ip = (_Unwind_Ptr) ue_header;
 143   _Unwind_SetGR (context, UNWIND_POINTER_REG, ip);
 144 #else
 145   if (version != 1)
 146     return _URC_FATAL_PHASE1_ERROR;
 147
 148   /* Currently we only support cleanups for C.  */
 149   if ((actions & _UA_CLEANUP_PHASE) == 0)
 150     CONTINUE_UNWINDING;
 151 #endif
 152
 153   language_specific_data = (const unsigned char *)
 154     _Unwind_GetLanguageSpecificData (context);
 155
 156   /* If no LSDA, then there are no handlers or cleanups.  */
 157   if (! language_specific_data)
 158     CONTINUE_UNWINDING;
 159
 160   /* Parse the LSDA header.  */
 161   p = parse_lsda_header (context, language_specific_data, &info);
 162 #ifdef HAVE_GETIPINFO
 163   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 164 #else
 165   ip = _Unwind_GetIP (context);
 166 #endif
 167   if (! ip_before_insn)
 168     --ip;
 169   landing_pad = 0;
 170
 171 #ifdef __USING_SJLJ_EXCEPTIONS__
 172   /* The given "IP" is an index into the call-site table, with two
 173      exceptions -- -1 means no-action, and 0 means terminate.  But
 174      since we're using uleb128 values, we've not got random access
 175      to the array.  */
 176   if ((int) ip <= 0)
 177     return _URC_CONTINUE_UNWIND;
 178   else
 179     {
 180       _uleb128_t cs_lp, cs_action;
 181       do
 182         {
 183           p = read_uleb128 (p, &cs_lp);
 184           p = read_uleb128 (p, &cs_action);
 185         }
 186       while (--ip);
 187
 188       /* Can never have null landing pad for sjlj -- that would have
 189          been indicated by a -1 call site index.  */
 190       landing_pad = (_Unwind_Ptr)cs_lp + 1;
 191       goto found_something;
 192     }
 193 #else
 194   /* Search the call-site table for the action associated with this IP.  */
 195   while (p < info.action_table)
 196     {
 197       _Unwind_Ptr cs_start, cs_len, cs_lp;
 198       _uleb128_t cs_action;
 199
 200       /* Note that all call-site encodings are "absolute" displacements.  */
 201       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 202       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 203       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 204       p = read_uleb128 (p, &cs_action);
 205
 206       /* The table is sorted, so if we've passed the ip, stop.  */
 207       if (ip < info.Start + cs_start)
 208         p = info.action_table;
 209       else if (ip < info.Start + cs_start + cs_len)
 210         {
 211           if (cs_lp)
 212             landing_pad = info.LPStart + cs_lp;
 213           goto found_something;
 214         }
 215     }
 216 #endif
 217
 218   /* IP is not in table.  No associated cleanups.  */
 219   /* ??? This is where C++ calls std::terminate to catch throw
 220      from a destructor.  */
 221   CONTINUE_UNWINDING;
 222
 223  found_something:
 224   if (landing_pad == 0)
 225     {
 226       /* IP is present, but has a null landing pad.
 227          No handler to be run.  */
 228       CONTINUE_UNWINDING;
 229     }
 230
 231   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 232                  (_Unwind_Ptr) ue_header);
 233   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
 234   _Unwind_SetIP (context, landing_pad);
 235   return _URC_INSTALL_CONTEXT;
 236 }
 237
 238 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
 239 EXCEPTION_DISPOSITION
 240 __gcc_personality_seh0 (PEXCEPTION_RECORD ms_exc, void *this_frame,
 241                         PCONTEXT ms_orig_context, PDISPATCHER_CONTEXT ms_disp)
 242 {
 243   return _GCC_specific_handler (ms_exc, this_frame, ms_orig_context,
 244                                 ms_disp, __gcc_personality_imp);
 245 }
 246 #endif /* SEH */