1 // -*- C++ -*- Exception handling and frame unwind runtime interface routines.
2 // Copyright (C) 2001-2023 Free Software Foundation, Inc.
3 //
4 // This file is part of GCC.
5 //
6 // GCC is free software; you can redistribute it and/or modify
7 // it under the terms of the GNU General Public License as published by
8 // the Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 //
11 // GCC is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 //
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 // This is derived from the C++ ABI for IA-64. Where we diverge
26 // for cross-architecture compatibility are noted with "@@@".
27
28 #ifndef _UNWIND_CXX_H
29 #define _UNWIND_CXX_H 1
30
31 // Level 2: C++ ABI
32
33 #include <typeinfo>
34 #include <exception>
35 #include <cstddef>
36 #include "unwind.h"
37 #include <bits/atomic_word.h>
38 #include <cxxabi.h>
39
40 #ifdef _GLIBCXX_HAVE_SYS_SDT_H
41 #include <sys/sdt.h>
42 /* We only want to use stap probes starting with v3. Earlier versions
43 added too much startup cost. */
44 #if defined (STAP_PROBE2) && _SDT_NOTE_TYPE >= 3
45 #define PROBE2(name, arg1, arg2) STAP_PROBE2 (libstdcxx, name, arg1, arg2)
46 #endif
47 #endif
48
49 #ifndef PROBE2
50 #define PROBE2(name, arg1, arg2)
51 #endif
52
53 #pragma GCC visibility push(default)
54
55 namespace __cxxabiv1
56 {
57
58 // A primary C++ exception object consists of a header, which is a wrapper
59 // around an unwind object header with additional C++ specific information,
60 // followed by the exception object itself.
61
62 struct __cxa_exception
63 {
64 // Manage the exception object itself.
65 std::type_info *exceptionType;
66 void (_GLIBCXX_CDTOR_CALLABI *exceptionDestructor)(void *);
67
68 // The C++ standard has entertaining rules wrt calling set_terminate
69 // and set_unexpected in the middle of the exception cleanup process.
70 std::terminate_handler unexpectedHandler;
71 std::terminate_handler terminateHandler;
72
73 // The caught exception stack threads through here.
74 __cxa_exception *nextException;
75
76 // How many nested handlers have caught this exception. A negated
77 // value is a signal that this object has been rethrown.
78 int handlerCount;
79
80 #ifdef __ARM_EABI_UNWINDER__
81 // Stack of exceptions in cleanups.
82 __cxa_exception* nextPropagatingException;
83
84 // The number of active cleanup handlers for this exception.
85 int propagationCount;
86 #else
87 // Cache parsed handler data from the personality routine Phase 1
88 // for Phase 2 and __cxa_call_unexpected.
89 int handlerSwitchValue;
90 const unsigned char *actionRecord;
91 const unsigned char *languageSpecificData;
92 _Unwind_Ptr catchTemp;
93 void *adjustedPtr;
94 #endif
95
96 // The generic exception header. Must be last.
97 _Unwind_Exception unwindHeader;
98 };
99
100 struct __cxa_refcounted_exception
101 {
102 // Manage this header.
103 _Atomic_word referenceCount;
104 // __cxa_exception must be last, and no padding can be after it.
105 __cxa_exception exc;
106 };
107
108 // A dependent C++ exception object consists of a wrapper around an unwind
109 // object header with additional C++ specific information, containing a pointer
110 // to a primary exception object.
111
112 struct __cxa_dependent_exception
113 {
114 // The primary exception this thing depends on.
115 void *primaryException;
116
117 // Unused member to get similar layout to __cxa_exception, otherwise the
118 // alignment requirements of _Unwind_Exception would require padding bytes
119 // before the unwindHeader member.
120 void (_GLIBCXX_CDTOR_CALLABI *__padding)(void *);
121
122 // The C++ standard has entertaining rules wrt calling set_terminate
123 // and set_unexpected in the middle of the exception cleanup process.
124 std::terminate_handler unexpectedHandler;
125 std::terminate_handler terminateHandler;
126
127 // The caught exception stack threads through here.
128 __cxa_exception *nextException;
129
130 // How many nested handlers have caught this exception. A negated
131 // value is a signal that this object has been rethrown.
132 int handlerCount;
133
134 #ifdef __ARM_EABI_UNWINDER__
135 // Stack of exceptions in cleanups.
136 __cxa_exception* nextPropagatingException;
137
138 // The number of active cleanup handlers for this exception.
139 int propagationCount;
140 #else
141 // Cache parsed handler data from the personality routine Phase 1
142 // for Phase 2 and __cxa_call_unexpected.
143 int handlerSwitchValue;
144 const unsigned char *actionRecord;
145 const unsigned char *languageSpecificData;
146 _Unwind_Ptr catchTemp;
147 void *adjustedPtr;
148 #endif
149
150 // The generic exception header. Must be last.
151 _Unwind_Exception unwindHeader;
152 };
153
154 // Each thread in a C++ program has access to a __cxa_eh_globals object.
155 struct __cxa_eh_globals
156 {
157 __cxa_exception *caughtExceptions;
158 unsigned int uncaughtExceptions;
159 #ifdef __ARM_EABI_UNWINDER__
160 __cxa_exception* propagatingExceptions;
161 #endif
162 };
163
164 // @@@ These are not directly specified by the IA-64 C++ ABI.
165
166 // Handles re-checking the exception specification if unexpectedHandler
167 // throws, and if bad_exception needs to be thrown. Called from the
168 // compiler.
169 extern "C" void __cxa_call_unexpected (void *) __attribute__((__noreturn__));
170 extern "C" void __cxa_call_terminate (_Unwind_Exception*) throw ()
171 __attribute__((__noreturn__));
172
173 #ifdef __ARM_EABI_UNWINDER__
174 // Arm EABI specified routines.
175 typedef enum {
176 ctm_failed = 0,
177 ctm_succeeded = 1,
178 ctm_succeeded_with_ptr_to_base = 2
179 } __cxa_type_match_result;
180 extern "C" __cxa_type_match_result __cxa_type_match(_Unwind_Exception*,
181 const std::type_info*,
182 bool, void**);
183 extern "C" bool __cxa_begin_cleanup (_Unwind_Exception*);
184 extern "C" void __cxa_end_cleanup (void);
185 #endif
186
187 // Handles cleanup from transactional memory restart.
188 extern "C" void __cxa_tm_cleanup (void *, void *, unsigned int) throw();
189
190 // Invokes given handler, dying appropriately if the user handler was
191 // so inconsiderate as to return.
192 extern void __terminate(std::terminate_handler) throw ()
193 __attribute__((__noreturn__));
194 extern void __unexpected(std::terminate_handler)
195 __attribute__((__noreturn__));
196
197 // The current installed user handlers.
198 extern std::terminate_handler __terminate_handler;
199 extern std::terminate_handler __unexpected_handler;
200
201 // These are explicitly GNU C++ specific.
202
203 // Acquire the C++ exception header from the C++ object.
204 static inline __cxa_exception *
205 __get_exception_header_from_obj (void *ptr)
206 {
207 return reinterpret_cast<__cxa_exception *>(ptr) - 1;
208 }
209
210 // Acquire the C++ exception header from the generic exception header.
211 static inline __cxa_exception *
212 __get_exception_header_from_ue (_Unwind_Exception *exc)
213 {
214 return reinterpret_cast<__cxa_exception *>(exc + 1) - 1;
215 }
216
217 // Acquire the C++ refcounted exception header from the C++ object.
218 static inline __cxa_refcounted_exception *
219 __get_refcounted_exception_header_from_obj (void *ptr)
220 {
221 return reinterpret_cast<__cxa_refcounted_exception *>(ptr) - 1;
222 }
223
224 // Acquire the C++ refcounted exception header from the generic exception
225 // header.
226 static inline __cxa_refcounted_exception *
227 __get_refcounted_exception_header_from_ue (_Unwind_Exception *exc)
228 {
229 return reinterpret_cast<__cxa_refcounted_exception *>(exc + 1) - 1;
230 }
231
232 static inline __cxa_dependent_exception *
233 __get_dependent_exception_from_ue (_Unwind_Exception *exc)
234 {
235 return reinterpret_cast<__cxa_dependent_exception *>(exc + 1) - 1;
236 }
237
238 #ifdef __ARM_EABI_UNWINDER__
239 static inline bool
240 __is_gxx_exception_class(_Unwind_Exception_Class c)
241 {
242 // TODO: Take advantage of the fact that c will always be word aligned.
243 return c[0] == 'G'
244 && c[1] == 'N'
245 && c[2] == 'U'
246 && c[3] == 'C'
247 && c[4] == 'C'
248 && c[5] == '+'
249 && c[6] == '+'
250 && (c[7] == '\0' || c[7] == '\x01');
251 }
252
253 // Only checks for primary or dependent, but not that it is a C++ exception at
254 // all.
255 static inline bool
256 __is_dependent_exception(_Unwind_Exception_Class c)
257 {
258 return c[7] == '\x01';
259 }
260
261 static inline void
262 __GXX_INIT_PRIMARY_EXCEPTION_CLASS(_Unwind_Exception_Class c)
263 {
264 c[0] = 'G';
265 c[1] = 'N';
266 c[2] = 'U';
267 c[3] = 'C';
268 c[4] = 'C';
269 c[5] = '+';
270 c[6] = '+';
271 c[7] = '\0';
272 }
273
274 static inline void
275 __GXX_INIT_DEPENDENT_EXCEPTION_CLASS(_Unwind_Exception_Class c)
276 {
277 c[0] = 'G';
278 c[1] = 'N';
279 c[2] = 'U';
280 c[3] = 'C';
281 c[4] = 'C';
282 c[5] = '+';
283 c[6] = '+';
284 c[7] = '\x01';
285 }
286
287 static inline bool
288 __is_gxx_forced_unwind_class(_Unwind_Exception_Class c)
289 {
290 return c[0] == 'G'
291 && c[1] == 'N'
292 && c[2] == 'U'
293 && c[3] == 'C'
294 && c[4] == 'F'
295 && c[5] == 'O'
296 && c[6] == 'R'
297 && c[7] == '\0';
298 }
299
300 static inline void
301 __GXX_INIT_FORCED_UNWIND_CLASS(_Unwind_Exception_Class c)
302 {
303 c[0] = 'G';
304 c[1] = 'N';
305 c[2] = 'U';
306 c[3] = 'C';
307 c[4] = 'F';
308 c[5] = 'O';
309 c[6] = 'R';
310 c[7] = '\0';
311 }
312
313 static inline void*
314 __gxx_caught_object(_Unwind_Exception* eo)
315 {
316 return (void*)eo->barrier_cache.bitpattern[0];
317 }
318 #else // !__ARM_EABI_UNWINDER__
319 // This is the primary exception class we report -- "GNUCC++\0".
320 const _Unwind_Exception_Class __gxx_primary_exception_class
321 = ((((((((_Unwind_Exception_Class) 'G'
322 << 8 | (_Unwind_Exception_Class) 'N')
323 << 8 | (_Unwind_Exception_Class) 'U')
324 << 8 | (_Unwind_Exception_Class) 'C')
325 << 8 | (_Unwind_Exception_Class) 'C')
326 << 8 | (_Unwind_Exception_Class) '+')
327 << 8 | (_Unwind_Exception_Class) '+')
328 << 8 | (_Unwind_Exception_Class) '\0');
329
330 // This is the dependent (from std::rethrow_exception) exception class we report
331 // "GNUCC++\x01"
332 const _Unwind_Exception_Class __gxx_dependent_exception_class
333 = ((((((((_Unwind_Exception_Class) 'G'
334 << 8 | (_Unwind_Exception_Class) 'N')
335 << 8 | (_Unwind_Exception_Class) 'U')
336 << 8 | (_Unwind_Exception_Class) 'C')
337 << 8 | (_Unwind_Exception_Class) 'C')
338 << 8 | (_Unwind_Exception_Class) '+')
339 << 8 | (_Unwind_Exception_Class) '+')
340 << 8 | (_Unwind_Exception_Class) '\x01');
341
342 static inline bool
343 __is_gxx_exception_class(_Unwind_Exception_Class c)
344 {
345 return c == __gxx_primary_exception_class
346 || c == __gxx_dependent_exception_class;
347 }
348
349 // Only checks for primary or dependent, but not that it is a C++ exception at
350 // all.
351 static inline bool
352 __is_dependent_exception(_Unwind_Exception_Class c)
353 {
354 return (c & 1);
355 }
356
357 #define __GXX_INIT_PRIMARY_EXCEPTION_CLASS(c) c = __gxx_primary_exception_class
358 #define __GXX_INIT_DEPENDENT_EXCEPTION_CLASS(c) \
359 c = __gxx_dependent_exception_class
360
361 // GNU C++ personality routine, Version 0.
362 extern "C" _Unwind_Reason_Code __gxx_personality_v0
363 (int, _Unwind_Action, _Unwind_Exception_Class,
364 struct _Unwind_Exception *, struct _Unwind_Context *);
365
366 // GNU C++ sjlj personality routine, Version 0.
367 extern "C" _Unwind_Reason_Code __gxx_personality_sj0
368 (int, _Unwind_Action, _Unwind_Exception_Class,
369 struct _Unwind_Exception *, struct _Unwind_Context *);
370
371 static inline void*
372 __gxx_caught_object(_Unwind_Exception* eo)
373 {
374 // Bad as it looks, this actually works for dependent exceptions too.
375 __cxa_exception* header = __get_exception_header_from_ue (eo);
376 return header->adjustedPtr;
377 }
378 #endif // !__ARM_EABI_UNWINDER__
379
380 static inline void*
381 __get_object_from_ue(_Unwind_Exception* eo) throw()
382 {
383 return __is_dependent_exception (eo->exception_class) ?
384 __get_dependent_exception_from_ue (eo)->primaryException :
385 eo + 1;
386 }
387
388 static inline void *
389 __get_object_from_ambiguous_exception(__cxa_exception *p_or_d) throw()
390 {
391 return __get_object_from_ue (&p_or_d->unwindHeader);
392 }
393
394
395 } /* namespace __cxxabiv1 */
396
397 #pragma GCC visibility pop
398
399 #endif // _UNWIND_CXX_H