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 *
parse_lsda_header(struct _Unwind_Context * context,const unsigned char * p,lsda_header_info * info)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
PERSONALITY_FUNCTION(_Unwind_State state,struct _Unwind_Exception * ue_header,struct _Unwind_Context * context)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 #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 _Unwind_Word 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 = cs_lp + 1;
189 if (cs_action)
190 action_record = info.action_table + cs_action - 1;
191 goto found_something;
192 }
193 #else
194 /* Search the call-site table for the action associated with this IP. */
195 while (p < info.action_table)
196 {
197 _Unwind_Ptr cs_start, cs_len, cs_lp;
198 _Unwind_Word cs_action;
199
200 /* Note that all call-site encodings are "absolute" displacements. */
201 p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
202 p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
203 p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
204 p = read_uleb128 (p, &cs_action);
205
206 /* The table is sorted, so if we've passed the ip, stop. */
207 if (ip < info.Start + cs_start)
208 p = info.action_table;
209 else if (ip < info.Start + cs_start + cs_len)
210 {
211 if (cs_lp)
212 landing_pad = info.LPStart + cs_lp;
213 if (cs_action)
214 action_record = info.action_table + cs_action - 1;
215 goto found_something;
216 }
217 }
218 #endif
219
220 /* IP is not in table. No associated cleanups. */
221 /* ??? This is where C++ calls std::terminate to catch throw
222 from a destructor. */
223 CONTINUE_UNWINDING;
224
225 found_something:
226 if (landing_pad == 0)
227 {
228 /* IP is present, but has a null landing pad.
229 No handler to be run. */
230 CONTINUE_UNWINDING;
231 }
232
233 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
234 (_Unwind_Ptr) ue_header);
235 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
236 _Unwind_SetIP (context, landing_pad);
237 return _URC_INSTALL_CONTEXT;
238 }
239