1 /* Supporting functions for C exception handling.
2 Copyright (C) 2002-2023 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 "auto-target.h"
30 #include "unwind.h"
31 #define NO_SIZE_OF_ENCODED_VALUE
32 #include "unwind-pe.h"
33
34 typedef struct
35 {
36 _Unwind_Ptr Start;
37 _Unwind_Ptr LPStart;
38 _Unwind_Ptr ttype_base;
39 const unsigned char *TType;
40 const unsigned char *action_table;
41 unsigned char ttype_encoding;
42 unsigned char call_site_encoding;
43 } lsda_header_info;
44
45 static const unsigned char *
46 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
47 lsda_header_info *info)
48 {
49 _uleb128_t tmp;
50 unsigned char lpstart_encoding;
51
52 info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
53
54 /* Find @LPStart, the base to which landing pad offsets are relative. */
55 lpstart_encoding = *p++;
56 if (lpstart_encoding != DW_EH_PE_omit)
57 p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
58 else
59 info->LPStart = info->Start;
60
61 /* Find @TType, the base of the handler and exception spec type data. */
62 info->ttype_encoding = *p++;
63 if (info->ttype_encoding != DW_EH_PE_omit)
64 {
65 p = read_uleb128 (p, &tmp);
66 info->TType = p + tmp;
67 }
68 else
69 info->TType = 0;
70
71 /* The encoding and length of the call-site table; the action table
72 immediately follows. */
73 info->call_site_encoding = *p++;
74 p = read_uleb128 (p, &tmp);
75 info->action_table = p + tmp;
76
77 return p;
78 }
79
80 #ifdef __ARM_EABI_UNWINDER__
81 /* ARM EABI personality routines must also unwind the stack. */
82 #define CONTINUE_UNWINDING \
83 do \
84 { \
85 if (__gnu_unwind_frame (ue_header, context) != _URC_OK) \
86 return _URC_FAILURE; \
87 return _URC_CONTINUE_UNWIND; \
88 } \
89 while (0)
90 #else
91 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
92 #endif
93
94 #ifdef __USING_SJLJ_EXCEPTIONS__
95 #define PERSONALITY_FUNCTION __gcc_personality_sj0
96 #define __builtin_eh_return_data_regno(x) x
97 #elif defined(__SEH__)
98 #define PERSONALITY_FUNCTION __gcc_personality_imp
99 #else
100 #define PERSONALITY_FUNCTION __gcc_personality_v0
101 #endif
102
103 #ifdef __ARM_EABI_UNWINDER__
104 _Unwind_Reason_Code
105 PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
106 struct _Unwind_Context *);
107
108 _Unwind_Reason_Code
109 __attribute__((target ("general-regs-only")))
110 PERSONALITY_FUNCTION (_Unwind_State state,
111 struct _Unwind_Exception * ue_header,
112 struct _Unwind_Context * context)
113 #else
114 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
115 static
116 #endif
117 _Unwind_Reason_Code
118 PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
119 struct _Unwind_Exception *, struct _Unwind_Context *);
120
121 _Unwind_Reason_Code
122 PERSONALITY_FUNCTION (int version,
123 _Unwind_Action actions,
124 _Unwind_Exception_Class exception_class ATTRIBUTE_UNUSED,
125 struct _Unwind_Exception *ue_header,
126 struct _Unwind_Context *context)
127 #endif
128 {
129 lsda_header_info info;
130 const unsigned char *language_specific_data, *p;
131 _Unwind_Ptr landing_pad, ip;
132 int ip_before_insn = 0;
133
134 #ifdef __ARM_EABI_UNWINDER__
135 if ((state & _US_ACTION_MASK) != _US_UNWIND_FRAME_STARTING)
136 CONTINUE_UNWINDING;
137
138 /* The dwarf unwinder assumes the context structure holds things like the
139 function and LSDA pointers. The ARM implementation caches these in
140 the exception header (UCB). To avoid rewriting everything we make a
141 virtual scratch register point at the UCB. */
142 ip = (_Unwind_Ptr) ue_header;
143 _Unwind_SetGR (context, UNWIND_POINTER_REG, ip);
144 #else
145 if (version != 1)
146 return _URC_FATAL_PHASE1_ERROR;
147
148 /* Currently we only support cleanups for C. */
149 if ((actions & _UA_CLEANUP_PHASE) == 0)
150 CONTINUE_UNWINDING;
151 #endif
152
153 language_specific_data = (const unsigned char *)
154 _Unwind_GetLanguageSpecificData (context);
155
156 /* If no LSDA, then there are no handlers or cleanups. */
157 if (! language_specific_data)
158 CONTINUE_UNWINDING;
159
160 /* Parse the LSDA header. */
161 p = parse_lsda_header (context, language_specific_data, &info);
162 #ifdef HAVE_GETIPINFO
163 ip = _Unwind_GetIPInfo (context, &ip_before_insn);
164 #else
165 ip = _Unwind_GetIP (context);
166 #endif
167 if (! ip_before_insn)
168 --ip;
169 landing_pad = 0;
170
171 #ifdef __USING_SJLJ_EXCEPTIONS__
172 /* The given "IP" is an index into the call-site table, with two
173 exceptions -- -1 means no-action, and 0 means terminate. But
174 since we're using uleb128 values, we've not got random access
175 to the array. */
176 if ((int) ip <= 0)
177 return _URC_CONTINUE_UNWIND;
178 else
179 {
180 _uleb128_t cs_lp, cs_action;
181 do
182 {
183 p = read_uleb128 (p, &cs_lp);
184 p = read_uleb128 (p, &cs_action);
185 }
186 while (--ip);
187
188 /* Can never have null landing pad for sjlj -- that would have
189 been indicated by a -1 call site index. */
190 landing_pad = (_Unwind_Ptr)cs_lp + 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 _uleb128_t 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 goto found_something;
214 }
215 }
216 #endif
217
218 /* IP is not in table. No associated cleanups. */
219 /* ??? This is where C++ calls std::terminate to catch throw
220 from a destructor. */
221 CONTINUE_UNWINDING;
222
223 found_something:
224 if (landing_pad == 0)
225 {
226 /* IP is present, but has a null landing pad.
227 No handler to be run. */
228 CONTINUE_UNWINDING;
229 }
230
231 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
232 (_Unwind_Ptr) ue_header);
233 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
234 _Unwind_SetIP (context, landing_pad);
235 return _URC_INSTALL_CONTEXT;
236 }
237
238 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
239 EXCEPTION_DISPOSITION
240 __gcc_personality_seh0 (PEXCEPTION_RECORD ms_exc, void *this_frame,
241 PCONTEXT ms_orig_context, PDISPATCHER_CONTEXT ms_disp)
242 {
243 return _GCC_specific_handler (ms_exc, this_frame, ms_orig_context,
244 ms_disp, __gcc_personality_imp);
245 }
246 #endif /* SEH */