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   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 the
 139      virtual IP register point at the UCB.  */
 140   ip = (_Unwind_Ptr) ue_header;
 141   _Unwind_SetGR (context, 12, 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   ip = _Unwind_GetIPInfo (context, &ip_before_insn);
 161   if (! ip_before_insn)
 162     --ip;
 163   landing_pad = 0;
 164
 165 #ifdef __USING_SJLJ_EXCEPTIONS__
 166   /* The given "IP" is an index into the call-site table, with two
 167      exceptions -- -1 means no-action, and 0 means terminate.  But
 168      since we're using uleb128 values, we've not got random access
 169      to the array.  */
 170   if ((int) ip <= 0)
 171     return _URC_CONTINUE_UNWIND;
 172   else
 173     {
 174       _Unwind_Word cs_lp, cs_action;
 175       do
 176         {
 177           p = read_uleb128 (p, &cs_lp);
 178           p = read_uleb128 (p, &cs_action);
 179         }
 180       while (--ip);
 181
 182       /* Can never have null landing pad for sjlj -- that would have
 183          been indicated by a -1 call site index.  */
 184       landing_pad = cs_lp + 1;
 185       if (cs_action)
 186         action_record = info.action_table + cs_action - 1;
 187       goto found_something;
 188     }
 189 #else
 190   /* Search the call-site table for the action associated with this IP.  */
 191   while (p < info.action_table)
 192     {
 193       _Unwind_Ptr cs_start, cs_len, cs_lp;
 194       _Unwind_Word cs_action;
 195
 196       /* Note that all call-site encodings are "absolute" displacements.  */
 197       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
 198       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
 199       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 200       p = read_uleb128 (p, &cs_action);
 201
 202       /* The table is sorted, so if we've passed the ip, stop.  */
 203       if (ip < info.Start + cs_start)
 204         p = info.action_table;
 205       else if (ip < info.Start + cs_start + cs_len)
 206         {
 207           if (cs_lp)
 208             landing_pad = info.LPStart + cs_lp;
 209           if (cs_action)
 210             action_record = info.action_table + cs_action - 1;
 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 }