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, 59 Temple Place - Suite 330, Boston, MA
  30 02111-1307, 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 __USING_SJLJ_EXCEPTIONS__
  85 #define PERSONALITY_FUNCTION    __gcc_personality_sj0
  86 #define __builtin_eh_return_data_regno(x) x
  87 #else
  88 #define PERSONALITY_FUNCTION    __gcc_personality_v0
  89 #endif
  90
  91 _Unwind_Reason_Code
  92 PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
  93                       struct _Unwind_Exception *, struct _Unwind_Context *);
  94
  95 _Unwind_Reason_Code
  96 PERSONALITY_FUNCTION (int version,
  97                       _Unwind_Action actions,
  98                       _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
  99                       struct _Unwind_Exception *ue_header,
 100                       struct _Unwind_Context *context)
 101 {
 102   lsda_header_info info;
 103   const unsigned char *language_specific_data, *p, *action_record;
 104   _Unwind_Ptr landing_pad, ip;
 105
 106   if (version != 1)
 107     return _URC_FATAL_PHASE1_ERROR;
 108
 109   /* Currently we only support cleanups for C.  */
 110   if ((actions & _UA_CLEANUP_PHASE) == 0)
 111     return _URC_CONTINUE_UNWIND;
 112
 113   language_specific_data = (const unsigned char *)
 114     _Unwind_GetLanguageSpecificData (context);
 115
 116   /* If no LSDA, then there are no handlers or cleanups.  */
 117   if (! language_specific_data)
 118     return _URC_CONTINUE_UNWIND;
 119
 120   /* Parse the LSDA header.  */
 121   p = parse_lsda_header (context, language_specific_data, &info);
 122   ip = _Unwind_GetIP (context) - 1;
 123   landing_pad = 0;
 124
 125 #ifdef __USING_SJLJ_EXCEPTIONS__
 126   /* The given "IP" is an index into the call-site table, with two
 127      exceptions -- -1 means no-action, and 0 means terminate.  But
 128      since we're using uleb128 values, we've not got random access
 129      to the array.  */
 130   if ((int) ip <= 0)
 131     return _URC_CONTINUE_UNWIND;
 132   else
 133     {
 134       _Unwind_Word cs_lp, cs_action;
 135       do
 136         {
 137           p = read_uleb128 (p, &cs_lp);
 138           p = read_uleb128 (p, &cs_action);
 139         }
 140       while (--ip);
 141
 142       /* Can never have null landing pad for sjlj -- that would have
 143          been indicated by a -1 call site index.  */
 144       landing_pad = cs_lp + 1;
 145       if (cs_action)
 146         action_record = info.action_table + cs_action - 1;
 147       goto found_something;
 148     }
 149 #else
 150   /* Search the call-site table for the action associated with this IP.  */
 151   while (p < info.action_table)
 152     {
 153       _Unwind_Ptr cs_start, cs_len, cs_lp;
 154       _Unwind_Word cs_action;
 155
 156       /* Note that all call-site encodings are "absolute" displacements.  */
 157       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 158       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 159       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 160       p = read_uleb128 (p, &cs_action);
 161
 162       /* The table is sorted, so if we've passed the ip, stop.  */
 163       if (ip < info.Start + cs_start)
 164         p = info.action_table;
 165       else if (ip < info.Start + cs_start + cs_len)
 166         {
 167           if (cs_lp)
 168             landing_pad = info.LPStart + cs_lp;
 169           if (cs_action)
 170             action_record = info.action_table + cs_action - 1;
 171           goto found_something;
 172         }
 173     }
 174
 175 #endif
 176
 177   /* IP is not in table.  No associated cleanups.  */
 178   /* ??? This is where C++ calls std::terminate to catch throw
 179      from a destructor.  */
 180   return _URC_CONTINUE_UNWIND;
 181
 182  found_something:
 183   if (landing_pad == 0)
 184     {
 185       /* IP is present, but has a null landing pad.
 186          No handler to be run.  */
 187       return _URC_CONTINUE_UNWIND;
 188     }
 189
 190   _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
 191                  (_Unwind_Ptr) ue_header);
 192   _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
 193   _Unwind_SetIP (context, landing_pad);
 194   return _URC_INSTALL_CONTEXT;
 195 }