gcc/unwind-c.c

   1 /* Supporting functions for C exception handling.
   2    Copyright (C) 2002, 2003 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 2, or (at your option) any later
  11 version.
  12
  13 In addition to the permissions in the GNU General Public License, the
  14 Free Software Foundation gives you unlimited permission to link the
  15 compiled version of this file into combinations with other programs,
  16 and to distribute those combinations without any restriction coming
  17 from the use of this file.  (The General Public License restrictions
  18 do apply in other respects; for example, they cover modification of
  19 the file, and distribution when not linked into a combined
  20 executable.)
  21
  22 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  23 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  24 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  25 for more details.
  26
  27 You should have received a copy of the GNU General Public License
  28 along with GCC; see the file COPYING.  If not, write to the Free
  29 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  30 02110-1301, USA.  */
  31
  32 #include "tconfig.h"
  33 #include "tsystem.h"
  34 #include "unwind.h"
  35 #define NO_SIZE_OF_ENCODED_VALUE
  36 #include "unwind-pe.h"
  37
  38 typedef struct
  39 {
  40   _Unwind_Ptr Start;
  41   _Unwind_Ptr LPStart;
  42   _Unwind_Ptr ttype_base;
  43   const unsigned char *TType;
  44   const unsigned char *action_table;
  45   unsigned char ttype_encoding;
  46   unsigned char call_site_encoding;
  47 } lsda_header_info;
  48
  49 static const unsigned char *
  50 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
  51                    lsda_header_info *info)
  52 {
  53   _Unwind_Word tmp;
  54   unsigned char lpstart_encoding;
  55
  56   info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
  57
  58   /* Find @LPStart, the base to which landing pad offsets are relative.  */
  59   lpstart_encoding = *p++;
  60   if (lpstart_encoding != DW_EH_PE_omit)
  61     p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
  62   else
  63     info->LPStart = info->Start;
  64
  65   /* Find @TType, the base of the handler and exception spec type data.  */
  66   info->ttype_encoding = *p++;
  67   if (info->ttype_encoding != DW_EH_PE_omit)
  68     {
  69       p = read_uleb128 (p, &tmp);
  70       info->TType = p + tmp;
  71     }
  72   else
  73     info->TType = 0;
  74
  75   /* The encoding and length of the call-site table; the action table
  76      immediately follows.  */
  77   info->call_site_encoding = *p++;
  78   p = read_uleb128 (p, &tmp);
  79   info->action_table = p + tmp;
  80
  81   return p;
  82 }
  83
  84 #ifdef __ARM_EABI_UNWINDER__
  85 /* ARM EABI personality routines must also unwind the stack.  */
  86 #define CONTINUE_UNWINDING \
  87   do                                                            \
  88     {                                                           \
  89       if (__gnu_unwind_frame (ue_header, context) != _URC_OK)   \
  90         return _URC_FAILURE;                                    \
  91       return _URC_CONTINUE_UNWIND;                              \
  92     }                                                           \
  93   while (0)
  94 #else
  95 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
  96 #endif
  97
  98 #ifdef __USING_SJLJ_EXCEPTIONS__
  99 #define PERSONALITY_FUNCTION    __gcc_personality_sj0
 100 #define __builtin_eh_return_data_regno(x) x
 101 #else
 102 #define PERSONALITY_FUNCTION    __gcc_personality_v0
 103 #endif
 104
 105 #ifdef __ARM_EABI_UNWINDER__
 106 _Unwind_Reason_Code
 107 PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
 108                       struct _Unwind_Context *);
 109
 110 _Unwind_Reason_Code
 111 PERSONALITY_FUNCTION (_Unwind_State state,
 112                       struct _Unwind_Exception * ue_header,
 113                       struct _Unwind_Context * context)
 114 #else
 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, *action_record;
 129   _Unwind_Ptr landing_pad, ip;
 130
 131 #ifdef __ARM_EABI_UNWINDER__
 132   if (state != _US_UNWIND_FRAME_STARTING)
 133     CONTINUE_UNWINDING;
 134
 135   /* The dwarf unwinder assumes the context structure holds things like the
 136      function and LSDA pointers.  The ARM implementation caches these in
 137      the exception header (UCB).  To avoid rewriting everything we make the
 138      virtual IP register point at the UCB.  */
 139   ip = (_Unwind_Ptr) ue_header;
 140   _Unwind_SetGR (context, 12, ip);
 141 #else
 142   if (version != 1)
 143     return _URC_FATAL_PHASE1_ERROR;
 144
 145   /* Currently we only support cleanups for C.  */
 146   if ((actions & _UA_CLEANUP_PHASE) == 0)
 147     CONTINUE_UNWINDING;
 148 #endif
 149
 150   language_specific_data = (const unsigned char *)
 151     _Unwind_GetLanguageSpecificData (context);
 152
 153   /* If no LSDA, then there are no handlers or cleanups.  */
 154   if (! language_specific_data)
 155     CONTINUE_UNWINDING;
 156
 157   /* Parse the LSDA header.  */
 158   p = parse_lsda_header (context, language_specific_data, &info);
 159   ip = _Unwind_GetIP (context) - 1;
 160   landing_pad = 0;
 161
 162 #ifdef __USING_SJLJ_EXCEPTIONS__
 163   /* The given "IP" is an index into the call-site table, with two
 164      exceptions -- -1 means no-action, and 0 means terminate.  But
 165      since we're using uleb128 values, we've not got random access
 166      to the array.  */
 167   if ((int) ip <= 0)
 168     return _URC_CONTINUE_UNWIND;
 169   else
 170     {
 171       _Unwind_Word cs_lp, cs_action;
 172       do
 173         {
 174           p = read_uleb128 (p, &cs_lp);
 175           p = read_uleb128 (p, &cs_action);
 176         }
 177       while (--ip);
 178
 179       /* Can never have null landing pad for sjlj -- that would have
 180          been indicated by a -1 call site index.  */
 181       landing_pad = cs_lp + 1;
 182       if (cs_action)
 183         action_record = info.action_table + cs_action - 1;
 184       goto found_something;
 185     }
 186 #else
 187   /* Search the call-site table for the action associated with this IP.  */
 188   while (p < info.action_table)
 189     {
 190       _Unwind_Ptr cs_start, cs_len, cs_lp;
 191       _Unwind_Word cs_action;
 192
 193       /* Note that all call-site encodings are "absolute" displacements.  */
 194       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 195       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 196       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 197       p = read_uleb128 (p, &cs_action);
 198
 199       /* The table is sorted, so if we've passed the ip, stop.  */
 200       if (ip < info.Start + cs_start)
 201         p = info.action_table;
 202       else if (ip < info.Start + cs_start + cs_len)
 203         {
 204           if (cs_lp)
 205             landing_pad = info.LPStart + cs_lp;
 206           if (cs_action)
 207             action_record = info.action_table + cs_action - 1;
 208           goto found_something;
 209         }
 210     }
 211 #endif
 212
 213   /* IP is not in table.  No associated cleanups.  */
 214   /* ??? This is where C++ calls std::terminate to catch throw
 215      from a destructor.  */
 216   CONTINUE_UNWINDING;
 217
 218  found_something:
 219   if (landing_pad == 0)
 220     {
 221       /* IP is present, but has a null landing pad.
 222          No handler to be run.  */
 223       CONTINUE_UNWINDING;
 224     }
 225
 226   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 227                  (_Unwind_Ptr) ue_header);
 228   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
 229   _Unwind_SetIP (context, landing_pad);
 230   return _URC_INSTALL_CONTEXT;
 231 }