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  1. /* Supporting functions for C exception handling.
  2.    Copyright (C) 2002-2015 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 */
  245.