1/* Supporting functions for C exception handling.
2   Copyright (C) 2002, 2003, 2009 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#else
97#define PERSONALITY_FUNCTION    __gcc_personality_v0
98#endif
99
100#ifdef __ARM_EABI_UNWINDER__
101_Unwind_Reason_Code
102PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
103		      struct _Unwind_Context *);
104
105_Unwind_Reason_Code
106PERSONALITY_FUNCTION (_Unwind_State state,
107		      struct _Unwind_Exception * ue_header,
108		      struct _Unwind_Context * context)
109#else
110_Unwind_Reason_Code
111PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
112		      struct _Unwind_Exception *, struct _Unwind_Context *);
113
114_Unwind_Reason_Code
115PERSONALITY_FUNCTION (int version,
116		      _Unwind_Action actions,
117		      _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
118		      struct _Unwind_Exception *ue_header,
119		      struct _Unwind_Context *context)
120#endif
121{
122  lsda_header_info info;
123  const unsigned char *language_specific_data, *p;
124  _Unwind_Ptr landing_pad, ip;
125  int ip_before_insn = 0;
126
127#ifdef __ARM_EABI_UNWINDER__
128  if ((state & _US_ACTION_MASK) != _US_UNWIND_FRAME_STARTING)
129    CONTINUE_UNWINDING;
130
131  /* The dwarf unwinder assumes the context structure holds things like the
132     function and LSDA pointers.  The ARM implementation caches these in
133     the exception header (UCB).  To avoid rewriting everything we make the
134     virtual IP register point at the UCB.  */
135  ip = (_Unwind_Ptr) ue_header;
136  _Unwind_SetGR (context, 12, ip);
137#else
138  if (version != 1)
139    return _URC_FATAL_PHASE1_ERROR;
140
141  /* Currently we only support cleanups for C.  */
142  if ((actions & _UA_CLEANUP_PHASE) == 0)
143    CONTINUE_UNWINDING;
144#endif
145
146  language_specific_data = (const unsigned char *)
147    _Unwind_GetLanguageSpecificData (context);
148
149  /* If no LSDA, then there are no handlers or cleanups.  */
150  if (! language_specific_data)
151    CONTINUE_UNWINDING;
152
153  /* Parse the LSDA header.  */
154  p = parse_lsda_header (context, language_specific_data, &info);
155#ifdef HAVE_GETIPINFO
156  ip = _Unwind_GetIPInfo (context, &ip_before_insn);
157#else
158  ip = _Unwind_GetIP (context);
159#endif
160  if (! ip_before_insn)
161    --ip;
162  landing_pad = 0;
163
164#ifdef __USING_SJLJ_EXCEPTIONS__
165  /* The given "IP" is an index into the call-site table, with two
166     exceptions -- -1 means no-action, and 0 means terminate.  But
167     since we're using uleb128 values, we've not got random access
168     to the array.  */
169  if ((int) ip <= 0)
170    return _URC_CONTINUE_UNWIND;
171  else
172    {
173      _uleb128_t cs_lp, cs_action;
174      do
175	{
176	  p = read_uleb128 (p, &cs_lp);
177	  p = read_uleb128 (p, &cs_action);
178	}
179      while (--ip);
180
181      /* Can never have null landing pad for sjlj -- that would have
182	 been indicated by a -1 call site index.  */
183      landing_pad = (_Unwind_Ptr)cs_lp + 1;
184      goto found_something;
185    }
186#else
187  /* Search the call-site table for the action associated with this IP.  */
188  while (p < info.action_table)
189    {
190      _Unwind_Ptr cs_start, cs_len, cs_lp;
191      _uleb128_t cs_action;
192
193      /* Note that all call-site encodings are "absolute" displacements.  */
194      p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
195      p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
196      p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
197      p = read_uleb128 (p, &cs_action);
198
199      /* The table is sorted, so if we've passed the ip, stop.  */
200      if (ip < info.Start + cs_start)
201	p = info.action_table;
202      else if (ip < info.Start + cs_start + cs_len)
203	{
204	  if (cs_lp)
205	    landing_pad = info.LPStart + cs_lp;
206	  goto found_something;
207	}
208    }
209#endif
210
211  /* IP is not in table.  No associated cleanups.  */
212  /* ??? This is where C++ calls std::terminate to catch throw
213     from a destructor.  */
214  CONTINUE_UNWINDING;
215
216 found_something:
217  if (landing_pad == 0)
218    {
219      /* IP is present, but has a null landing pad.
220	 No handler to be run.  */
221      CONTINUE_UNWINDING;
222    }
223
224  _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
225		 (_Unwind_Ptr) ue_header);
226  _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
227  _Unwind_SetIP (context, landing_pad);
228  return _URC_INSTALL_CONTEXT;
229}
230