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
6This file is part of GCC.
7
8GCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
16for more details.
17
18Under Section 7 of GPL version 3, you are granted additional
19permissions described in the GCC Runtime Library Exception, version
203.1, as published by the Free Software Foundation.
21
22You should have received a copy of the GNU General Public License and
23a copy of the GCC Runtime Library Exception along with this program;
24see 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
33typedef 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
44static const unsigned char *
45parse_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
104PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
105		      struct _Unwind_Context *);
106
107_Unwind_Reason_Code
108PERSONALITY_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__)
113static
114#endif
115_Unwind_Reason_Code
116PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
117		      struct _Unwind_Exception *, struct _Unwind_Context *);
118
119_Unwind_Reason_Code
120PERSONALITY_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__)
237EXCEPTION_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