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 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 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING.  If not, write to the Free
  20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  21 02111-1307, USA.  */
  22
  23 #include "tconfig.h"
  24 #include "tsystem.h"
  25 #include "unwind.h"
  26 #define NO_SIZE_OF_ENCODED_VALUE
  27 #include "unwind-pe.h"
  28
  29 typedef struct
  30 {
  31   _Unwind_Ptr Start;
  32   _Unwind_Ptr LPStart;
  33   _Unwind_Ptr ttype_base;
  34   const unsigned char *TType;
  35   const unsigned char *action_table;
  36   unsigned char ttype_encoding;
  37   unsigned char call_site_encoding;
  38 } lsda_header_info;
  39
  40 static const unsigned char *
  41 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
  42                    lsda_header_info *info)
  43 {
  44   _Unwind_Word tmp;
  45   unsigned char lpstart_encoding;
  46
  47   info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
  48
  49   /* Find @LPStart, the base to which landing pad offsets are relative.  */
  50   lpstart_encoding = *p++;
  51   if (lpstart_encoding != DW_EH_PE_omit)
  52     p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
  53   else
  54     info->LPStart = info->Start;
  55
  56   /* Find @TType, the base of the handler and exception spec type data.  */
  57   info->ttype_encoding = *p++;
  58   if (info->ttype_encoding != DW_EH_PE_omit)
  59     {
  60       p = read_uleb128 (p, &tmp);
  61       info->TType = p + tmp;
  62     }
  63   else
  64     info->TType = 0;
  65
  66   /* The encoding and length of the call-site table; the action table
  67      immediately follows.  */
  68   info->call_site_encoding = *p++;
  69   p = read_uleb128 (p, &tmp);
  70   info->action_table = p + tmp;
  71
  72   return p;
  73 }
  74
  75 #ifdef __USING_SJLJ_EXCEPTIONS__
  76 #define PERSONALITY_FUNCTION    __gcc_personality_sj0
  77 #define __builtin_eh_return_data_regno(x) x
  78 #else
  79 #define PERSONALITY_FUNCTION    __gcc_personality_v0
  80 #endif
  81
  82 _Unwind_Reason_Code
  83 PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
  84                       struct _Unwind_Exception *, struct _Unwind_Context *);
  85
  86 _Unwind_Reason_Code
  87 PERSONALITY_FUNCTION (int version,
  88                       _Unwind_Action actions,
  89                       _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
  90                       struct _Unwind_Exception *ue_header,
  91                       struct _Unwind_Context *context)
  92 {
  93   lsda_header_info info;
  94   const unsigned char *language_specific_data, *p, *action_record;
  95   _Unwind_Ptr landing_pad, ip;
  96
  97   if (version != 1)
  98     return _URC_FATAL_PHASE1_ERROR;
  99
 100   /* Currently we only support cleanups for C.  */
 101   if ((actions & _UA_CLEANUP_PHASE) == 0)
 102     return _URC_CONTINUE_UNWIND;
 103
 104   language_specific_data = (const unsigned char *)
 105     _Unwind_GetLanguageSpecificData (context);
 106
 107   /* If no LSDA, then there are no handlers or cleanups.  */
 108   if (! language_specific_data)
 109     return _URC_CONTINUE_UNWIND;
 110
 111   /* Parse the LSDA header.  */
 112   p = parse_lsda_header (context, language_specific_data, &info);
 113   ip = _Unwind_GetIP (context) - 1;
 114   landing_pad = 0;
 115
 116 #ifdef __USING_SJLJ_EXCEPTIONS__
 117   /* The given "IP" is an index into the call-site table, with two
 118      exceptions -- -1 means no-action, and 0 means terminate.  But
 119      since we're using uleb128 values, we've not got random access
 120      to the array.  */
 121   if ((int) ip <= 0)
 122     return _URC_CONTINUE_UNWIND;
 123   else
 124     {
 125       _Unwind_Word cs_lp, cs_action;
 126       do
 127         {
 128           p = read_uleb128 (p, &cs_lp);
 129           p = read_uleb128 (p, &cs_action);
 130         }
 131       while (--ip);
 132
 133       /* Can never have null landing pad for sjlj -- that would have
 134          been indicated by a -1 call site index.  */
 135       landing_pad = cs_lp + 1;
 136       if (cs_action)
 137         action_record = info.action_table + cs_action - 1;
 138       goto found_something;
 139     }
 140 #else
 141   /* Search the call-site table for the action associated with this IP.  */
 142   while (p < info.action_table)
 143     {
 144       _Unwind_Ptr cs_start, cs_len, cs_lp;
 145       _Unwind_Word cs_action;
 146
 147       /* Note that all call-site encodings are "absolute" displacements.  */
 148       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 149       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 150       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 151       p = read_uleb128 (p, &cs_action);
 152
 153       /* The table is sorted, so if we've passed the ip, stop.  */
 154       if (ip < info.Start + cs_start)
 155         p = info.action_table;
 156       else if (ip < info.Start + cs_start + cs_len)
 157         {
 158           if (cs_lp)
 159             landing_pad = info.LPStart + cs_lp;
 160           if (cs_action)
 161             action_record = info.action_table + cs_action - 1;
 162           goto found_something;
 163         }
 164     }
 165
 166 #endif
 167
 168   /* IP is not in table.  No associated cleanups.  */
 169   /* ??? This is where C++ calls std::terminate to catch throw
 170      from a destructor.  */
 171   return _URC_CONTINUE_UNWIND;
 172
 173  found_something:
 174   if (landing_pad == 0)
 175     {
 176       /* IP is present, but has a null landing pad.
 177          No handler to be run.  */
 178       return _URC_CONTINUE_UNWIND;
 179     }
 180
 181   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 182                  (_Unwind_Ptr) ue_header);
 183   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
 184   _Unwind_SetIP (context, landing_pad);
 185   return _URC_INSTALL_CONTEXT;
 186 }