libgcc/unwind-c.c

   1 /* Supporting functions for C exception handling.
   2    Copyright (C) 2002-2016 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 "unwind.h"
  30 #define NO_SIZE_OF_ENCODED_VALUE
  31 #include "unwind-pe.h"
  32
  33 typedef struct
  34 {
  35   _Unwind_Ptr Start;
  36   _Unwind_Ptr LPStart;
  37   _Unwind_Ptr ttype_base;
  38   const unsigned char *TType;
  39   const unsigned char *action_table;
  40   unsigned char ttype_encoding;
  41   unsigned char call_site_encoding;
  42 } lsda_header_info;
  43
  44 static const unsigned char *
  45 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
  46                    lsda_header_info *info)
  47 {
  48   _uleb128_t tmp;
  49   unsigned char lpstart_encoding;
  50
  51   info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
  52
  53   /* Find @LPStart, the base to which landing pad offsets are relative.  */
  54   lpstart_encoding = *p++;
  55   if (lpstart_encoding != DW_EH_PE_omit)
  56     p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
  57   else
  58     info->LPStart = info->Start;
  59
  60   /* Find @TType, the base of the handler and exception spec type data.  */
  61   info->ttype_encoding = *p++;
  62   if (info->ttype_encoding != DW_EH_PE_omit)
  63     {
  64       p = read_uleb128 (p, &tmp);
  65       info->TType = p + tmp;
  66     }
  67   else
  68     info->TType = 0;
  69
  70   /* The encoding and length of the call-site table; the action table
  71      immediately follows.  */
  72   info->call_site_encoding = *p++;
  73   p = read_uleb128 (p, &tmp);
  74   info->action_table = p + tmp;
  75
  76   return p;
  77 }
  78
  79 #ifdef __ARM_EABI_UNWINDER__
  80 /* ARM EABI personality routines must also unwind the stack.  */
  81 #define CONTINUE_UNWINDING \
  82   do                                                            \
  83     {                                                           \
  84       if (__gnu_unwind_frame (ue_header, context) != _URC_OK)   \
  85         return _URC_FAILURE;                                    \
  86       return _URC_CONTINUE_UNWIND;                              \
  87     }                                                           \
  88   while (0)
  89 #else
  90 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
  91 #endif
  92
  93 #ifdef __USING_SJLJ_EXCEPTIONS__
  94 #define PERSONALITY_FUNCTION    __gcc_personality_sj0
  95 #define __builtin_eh_return_data_regno(x) x
  96 #elif defined(__SEH__)
  97 #define PERSONALITY_FUNCTION    __gcc_personality_imp
  98 #else
  99 #define PERSONALITY_FUNCTION    __gcc_personality_v0
 100 #endif
 101
 102 #ifdef __ARM_EABI_UNWINDER__
 103 _Unwind_Reason_Code
 104 PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
 105                       struct _Unwind_Context *);
 106
 107 _Unwind_Reason_Code
 108 PERSONALITY_FUNCTION (_Unwind_State state,
 109                       struct _Unwind_Exception * ue_header,
 110                       struct _Unwind_Context * context)
 111 #else
 112 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
 113 static
 114 #endif
 115 _Unwind_Reason_Code
 116 PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
 117                       struct _Unwind_Exception *, struct _Unwind_Context *);
 118
 119 _Unwind_Reason_Code
 120 PERSONALITY_FUNCTION (int version,
 121                       _Unwind_Action actions,
 122                       _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
 123                       struct _Unwind_Exception *ue_header,
 124                       struct _Unwind_Context *context)
 125 #endif
 126 {
 127   lsda_header_info info;
 128   const unsigned char *language_specific_data, *p;
 129   _Unwind_Ptr landing_pad, ip;
 130   int ip_before_insn = 0;
 131
 132 #ifdef __ARM_EABI_UNWINDER__
 133   if ((state & _US_ACTION_MASK) != _US_UNWIND_FRAME_STARTING)
 134     CONTINUE_UNWINDING;
 135
 136   /* The dwarf unwinder assumes the context structure holds things like the
 137      function and LSDA pointers.  The ARM implementation caches these in
 138      the exception header (UCB).  To avoid rewriting everything we make a
 139      virtual scratch register point at the UCB.  */
 140   ip = (_Unwind_Ptr) ue_header;
 141   _Unwind_SetGR (context, UNWIND_POINTER_REG, ip);
 142 #else
 143   if (version != 1)
 144     return _URC_FATAL_PHASE1_ERROR;
 145
 146   /* Currently we only support cleanups for C.  */
 147   if ((actions & _UA_CLEANUP_PHASE) == 0)
 148     CONTINUE_UNWINDING;
 149 #endif
 150
 151   language_specific_data = (const unsigned char *)
 152     _Unwind_GetLanguageSpecificData (context);
 153
 154   /* If no LSDA, then there are no handlers or cleanups.  */
 155   if (! language_specific_data)
 156     CONTINUE_UNWINDING;
 157
 158   /* Parse the LSDA header.  */
 159   p = parse_lsda_header (context, language_specific_data, &info);
 160 #ifdef HAVE_GETIPINFO
 161   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 162 #else
 163   ip = _Unwind_GetIP (context);
 164 #endif
 165   if (! ip_before_insn)
 166     --ip;
 167   landing_pad = 0;
 168
 169 #ifdef __USING_SJLJ_EXCEPTIONS__
 170   /* The given "IP" is an index into the call-site table, with two
 171      exceptions -- -1 means no-action, and 0 means terminate.  But
 172      since we're using uleb128 values, we've not got random access
 173      to the array.  */
 174   if ((int) ip <= 0)
 175     return _URC_CONTINUE_UNWIND;
 176   else
 177     {
 178       _uleb128_t cs_lp, cs_action;
 179       do
 180         {
 181           p = read_uleb128 (p, &cs_lp);
 182           p = read_uleb128 (p, &cs_action);
 183         }
 184       while (--ip);
 185
 186       /* Can never have null landing pad for sjlj -- that would have
 187          been indicated by a -1 call site index.  */
 188       landing_pad = (_Unwind_Ptr)cs_lp + 1;
 189       goto found_something;
 190     }
 191 #else
 192   /* Search the call-site table for the action associated with this IP.  */
 193   while (p < info.action_table)
 194     {
 195       _Unwind_Ptr cs_start, cs_len, cs_lp;
 196       _uleb128_t cs_action;
 197
 198       /* Note that all call-site encodings are "absolute" displacements.  */
 199       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 200       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 201       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 202       p = read_uleb128 (p, &cs_action);
 203
 204       /* The table is sorted, so if we've passed the ip, stop.  */
 205       if (ip < info.Start + cs_start)
 206         p = info.action_table;
 207       else if (ip < info.Start + cs_start + cs_len)
 208         {
 209           if (cs_lp)
 210             landing_pad = info.LPStart + cs_lp;
 211           goto found_something;
 212         }
 213     }
 214 #endif
 215
 216   /* IP is not in table.  No associated cleanups.  */
 217   /* ??? This is where C++ calls std::terminate to catch throw
 218      from a destructor.  */
 219   CONTINUE_UNWINDING;
 220
 221  found_something:
 222   if (landing_pad == 0)
 223     {
 224       /* IP is present, but has a null landing pad.
 225          No handler to be run.  */
 226       CONTINUE_UNWINDING;
 227     }
 228
 229   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 230                  (_Unwind_Ptr) ue_header);
 231   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
 232   _Unwind_SetIP (context, landing_pad);
 233   return _URC_INSTALL_CONTEXT;
 234 }
 235
 236 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
 237 EXCEPTION_DISPOSITION
 238 __gcc_personality_seh0 (PEXCEPTION_RECORD ms_exc, void *this_frame,
 239                         PCONTEXT ms_orig_context, PDISPATCHER_CONTEXT ms_disp)
 240 {
 241   return _GCC_specific_handler (ms_exc, this_frame, ms_orig_context,
 242                                 ms_disp, __gcc_personality_imp);
 243 }
 244 #endif /* SEH */