1 /* The implementation of exception handling primitives for Objective-C.
2 Copyright (C) 2004-2020 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
14 License for more details.
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.
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/>. */
25 #include "objc-private/common.h"
28 #include "objc/runtime.h"
29 #include "objc/objc-exception.h"
31 #include "unwind-pe.h"
32 #include <string.h> /* For memcpy */
34 /* 'is_kind_of_exception_matcher' is our default exception matcher -
35 it determines if the object 'exception' is of class 'catch_class',
38 is_kind_of_exception_matcher (Class catch_class
, id exception
)
40 /* NULL catch_class is catch-all (eg, @catch (id object)). */
41 if (catch_class
== Nil
)
44 /* If exception is nil (eg, @throw nil;), then it can only be
45 catched by a catch-all (eg, @catch (id object)). */
50 for (c
= exception
->class_pointer
; c
!= Nil
;
51 c
= class_getSuperclass (c
))
58 /* The exception matcher currently in use. */
59 static objc_exception_matcher
60 __objc_exception_matcher
= is_kind_of_exception_matcher
;
62 objc_exception_matcher
63 objc_setExceptionMatcher (objc_exception_matcher new_matcher
)
65 objc_exception_matcher old_matcher
= __objc_exception_matcher
;
66 __objc_exception_matcher
= new_matcher
;
70 /* The uncaught exception handler currently in use. */
71 static objc_uncaught_exception_handler
72 __objc_uncaught_exception_handler
= NULL
;
74 objc_uncaught_exception_handler
75 objc_setUncaughtExceptionHandler (objc_uncaught_exception_handler
78 objc_uncaught_exception_handler old_handler
79 = __objc_uncaught_exception_handler
;
80 __objc_uncaught_exception_handler
= new_handler
;
86 #ifdef __ARM_EABI_UNWINDER__
88 const _Unwind_Exception_Class __objc_exception_class
89 = {'G', 'N', 'U', 'C', 'O', 'B', 'J', 'C'};
93 /* This is the exception class we report -- "GNUCOBJC". */
94 static const _Unwind_Exception_Class __objc_exception_class
95 = ((((((((_Unwind_Exception_Class
) 'G'
96 << 8 | (_Unwind_Exception_Class
) 'N')
97 << 8 | (_Unwind_Exception_Class
) 'U')
98 << 8 | (_Unwind_Exception_Class
) 'C')
99 << 8 | (_Unwind_Exception_Class
) 'O')
100 << 8 | (_Unwind_Exception_Class
) 'B')
101 << 8 | (_Unwind_Exception_Class
) 'J')
102 << 8 | (_Unwind_Exception_Class
) 'C');
106 /* This is the object that is passed around by the Objective C runtime
107 to represent the exception in flight. */
110 /* This bit is needed in order to interact with the unwind runtime. */
111 struct _Unwind_Exception base
;
113 /* The actual object we want to throw. Note: must come immediately
114 after unwind header. */
117 #ifdef __ARM_EABI_UNWINDER__
118 /* Note: we use the barrier cache defined in the unwind control
119 block for ARM EABI. */
121 /* Cache some internal unwind data between phase 1 and phase 2. */
122 _Unwind_Ptr landingPad
;
123 int handlerSwitchValue
;
129 struct lsda_header_info
133 _Unwind_Ptr ttype_base
;
134 const unsigned char *TType
;
135 const unsigned char *action_table
;
136 unsigned char ttype_encoding
;
137 unsigned char call_site_encoding
;
140 static const unsigned char *
141 parse_lsda_header (struct _Unwind_Context
*context
, const unsigned char *p
,
142 struct lsda_header_info
*info
)
145 unsigned char lpstart_encoding
;
147 info
->Start
= (context
? _Unwind_GetRegionStart (context
) : 0);
149 /* Find @LPStart, the base to which landing pad offsets are
151 lpstart_encoding
= *p
++;
152 if (lpstart_encoding
!= DW_EH_PE_omit
)
153 p
= read_encoded_value (context
, lpstart_encoding
, p
, &info
->LPStart
);
155 info
->LPStart
= info
->Start
;
157 /* Find @TType, the base of the handler and exception spec type
159 info
->ttype_encoding
= *p
++;
160 if (info
->ttype_encoding
!= DW_EH_PE_omit
)
162 #if _GLIBCXX_OVERRIDE_TTYPE_ENCODING
163 /* Older ARM EABI toolchains set this value incorrectly, so use a
164 hardcoded OS-specific format. */
165 info
->ttype_encoding
= _GLIBCXX_OVERRIDE_TTYPE_ENCODING
;
167 p
= read_uleb128 (p
, &tmp
);
168 info
->TType
= p
+ tmp
;
173 /* The encoding and length of the call-site table; the action table
174 immediately follows. */
175 info
->call_site_encoding
= *p
++;
176 p
= read_uleb128 (p
, &tmp
);
177 info
->action_table
= p
+ tmp
;
183 get_ttype_entry (struct lsda_header_info
*info
, _Unwind_Word i
)
187 i
*= size_of_encoded_value (info
->ttype_encoding
);
188 read_encoded_value_with_base (info
->ttype_encoding
, info
->ttype_base
,
189 info
->TType
- i
, &ptr
);
191 /* NULL ptr means catch-all. Note that if the class is not found,
192 this will abort the program. */
194 return objc_getRequiredClass ((const char *) ptr
);
199 /* Using a different personality function name causes link failures
200 when trying to mix code using different exception handling
202 #ifdef __USING_SJLJ_EXCEPTIONS__
203 #define PERSONALITY_FUNCTION __gnu_objc_personality_sj0
204 #define __builtin_eh_return_data_regno(x) x
205 #elif defined(__SEH__)
206 #define PERSONALITY_FUNCTION __gnu_objc_personality_imp
208 #define PERSONALITY_FUNCTION __gnu_objc_personality_v0
211 #ifdef __ARM_EABI_UNWINDER__
213 #define CONTINUE_UNWINDING \
216 if (__gnu_unwind_frame(ue_header, context) != _URC_OK) \
217 return _URC_FAILURE; \
218 return _URC_CONTINUE_UNWIND; \
223 __attribute__((target ("general-regs-only")))
224 PERSONALITY_FUNCTION (_Unwind_State state
,
225 struct _Unwind_Exception
*ue_header
,
226 struct _Unwind_Context
*context
)
229 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
231 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
235 PERSONALITY_FUNCTION (int version
,
236 _Unwind_Action actions
,
237 _Unwind_Exception_Class exception_class
,
238 struct _Unwind_Exception
*ue_header
,
239 struct _Unwind_Context
*context
)
242 struct ObjcException
*xh
= (struct ObjcException
*) ue_header
;
244 struct lsda_header_info info
;
245 const unsigned char *language_specific_data
;
246 const unsigned char *action_record
;
247 const unsigned char *p
;
248 _Unwind_Ptr landing_pad
, ip
;
249 int handler_switch_value
;
250 int saw_cleanup
= 0, saw_handler
, foreign_exception
;
252 int ip_before_insn
= 0;
254 #ifdef __ARM_EABI_UNWINDER__
255 _Unwind_Action actions
;
257 switch (state
& _US_ACTION_MASK
)
259 case _US_VIRTUAL_UNWIND_FRAME
:
260 actions
= _UA_SEARCH_PHASE
;
263 case _US_UNWIND_FRAME_STARTING
:
264 actions
= _UA_CLEANUP_PHASE
;
265 if (!(state
& _US_FORCE_UNWIND
)
266 && ue_header
->barrier_cache
.sp
== _Unwind_GetGR (context
, 13))
267 actions
|= _UA_HANDLER_FRAME
;
270 case _US_UNWIND_FRAME_RESUME
:
277 actions
|= state
& _US_FORCE_UNWIND
;
279 /* TODO: Foreign exceptions need some attention (e.g. rethrowing
281 foreign_exception
= 0;
283 /* The dwarf unwinder assumes the context structure holds things
284 like the function and LSDA pointers. The ARM implementation
285 caches these in the exception header (UCB). To avoid rewriting
286 everything we make the virtual IP register point at the UCB. */
287 ip
= (_Unwind_Ptr
) ue_header
;
288 _Unwind_SetGR (context
, 12, ip
);
290 #else /* !__ARM_EABI_UNWINDER. */
291 /* Interface version check. */
293 return _URC_FATAL_PHASE1_ERROR
;
295 foreign_exception
= (exception_class
!= __objc_exception_class
);
298 /* Shortcut for phase 2 found handler for domestic exception. */
299 if (actions
== (_UA_CLEANUP_PHASE
| _UA_HANDLER_FRAME
)
300 && !foreign_exception
)
302 #ifdef __ARM_EABI_UNWINDER__
303 handler_switch_value
= (int) ue_header
->barrier_cache
.bitpattern
[1];
304 landing_pad
= (_Unwind_Ptr
) ue_header
->barrier_cache
.bitpattern
[3];
306 handler_switch_value
= xh
->handlerSwitchValue
;
307 landing_pad
= xh
->landingPad
;
309 goto install_context
;
312 language_specific_data
= (const unsigned char *)
313 _Unwind_GetLanguageSpecificData (context
);
315 /* If no LSDA, then there are no handlers or cleanups. */
316 if (! language_specific_data
)
319 /* Parse the LSDA header. */
320 p
= parse_lsda_header (context
, language_specific_data
, &info
);
321 info
.ttype_base
= base_of_encoded_value (info
.ttype_encoding
, context
);
322 #ifdef HAVE_GETIPINFO
323 ip
= _Unwind_GetIPInfo (context
, &ip_before_insn
);
325 ip
= _Unwind_GetIP (context
);
331 handler_switch_value
= 0;
333 #ifdef __USING_SJLJ_EXCEPTIONS__
334 /* The given "IP" is an index into the call-site table, with two
335 exceptions -- -1 means no-action, and 0 means terminate. But
336 since we're using uleb128 values, we've not got random access to
339 return _URC_CONTINUE_UNWIND
;
342 _uleb128_t cs_lp
, cs_action
;
345 p
= read_uleb128 (p
, &cs_lp
);
346 p
= read_uleb128 (p
, &cs_action
);
350 /* Can never have null landing pad for sjlj -- that would have
351 been indicated by a -1 call site index. */
352 landing_pad
= cs_lp
+ 1;
354 action_record
= info
.action_table
+ cs_action
- 1;
355 goto found_something
;
358 /* Search the call-site table for the action associated with this
360 while (p
< info
.action_table
)
362 _Unwind_Ptr cs_start
, cs_len
, cs_lp
;
363 _uleb128_t cs_action
;
365 /* Note that all call-site encodings are "absolute"
367 p
= read_encoded_value (0, info
.call_site_encoding
, p
, &cs_start
);
368 p
= read_encoded_value (0, info
.call_site_encoding
, p
, &cs_len
);
369 p
= read_encoded_value (0, info
.call_site_encoding
, p
, &cs_lp
);
370 p
= read_uleb128 (p
, &cs_action
);
372 /* The table is sorted, so if we've passed the ip, stop. */
373 if (ip
< info
.Start
+ cs_start
)
374 p
= info
.action_table
;
375 else if (ip
< info
.Start
+ cs_start
+ cs_len
)
378 landing_pad
= info
.LPStart
+ cs_lp
;
380 action_record
= info
.action_table
+ cs_action
- 1;
381 goto found_something
;
384 #endif /* __USING_SJLJ_EXCEPTIONS__ */
386 /* If ip is not present in the table, C++ would call terminate. */
387 /* ??? As with Java, it's perhaps better to tweek the LSDA to that
388 no-action is mapped to no-entry. */
395 if (landing_pad
== 0)
397 /* If ip is present, and has a null landing pad, there are no
398 cleanups or handlers to be run. */
400 else if (action_record
== 0)
402 /* If ip is present, has a non-null landing pad, and a null
403 action table offset, then there are only cleanups present.
404 Cleanups use a zero switch value, as set above. */
409 /* Otherwise we have a catch handler. */
410 _sleb128_t ar_filter
, ar_disp
;
415 p
= read_sleb128 (p
, &ar_filter
);
416 read_sleb128 (p
, &ar_disp
);
420 /* Zero filter values are cleanups. */
424 /* During forced unwinding, we only run cleanups. With a
425 foreign exception class, we have no class info to
427 else if ((actions
& _UA_FORCE_UNWIND
) || foreign_exception
)
430 else if (ar_filter
> 0)
432 /* Positive filter values are handlers. */
433 Class catch_type
= get_ttype_entry (&info
, ar_filter
);
435 if ((*__objc_exception_matcher
) (catch_type
, xh
->value
))
437 handler_switch_value
= ar_filter
;
444 /* Negative filter values are exception specifications,
445 which Objective-C does not use. */
451 action_record
= p
+ ar_disp
;
455 if (! saw_handler
&& ! saw_cleanup
)
458 if (actions
& _UA_SEARCH_PHASE
)
463 /* For domestic exceptions, we cache data from phase 1 for phase
465 if (!foreign_exception
)
467 #ifdef __ARM_EABI_UNWINDER__
468 ue_header
->barrier_cache
.sp
= _Unwind_GetGR (context
, 13);
469 ue_header
->barrier_cache
.bitpattern
[1] = (_uw
) handler_switch_value
;
470 ue_header
->barrier_cache
.bitpattern
[3] = (_uw
) landing_pad
;
472 xh
->handlerSwitchValue
= handler_switch_value
;
473 xh
->landingPad
= landing_pad
;
476 return _URC_HANDLER_FOUND
;
480 if (saw_cleanup
== 0)
482 return_object
= xh
->value
;
483 if (!(actions
& _UA_SEARCH_PHASE
))
484 _Unwind_DeleteException(&xh
->base
);
487 _Unwind_SetGR (context
, __builtin_eh_return_data_regno (0),
488 __builtin_extend_pointer (saw_cleanup
? xh
: return_object
));
489 _Unwind_SetGR (context
, __builtin_eh_return_data_regno (1),
490 handler_switch_value
);
491 _Unwind_SetIP (context
, landing_pad
);
492 return _URC_INSTALL_CONTEXT
;
496 __objc_exception_cleanup (_Unwind_Reason_Code code
__attribute__((unused
)),
497 struct _Unwind_Exception
*exc
)
503 objc_exception_throw (id exception
)
505 struct ObjcException
*header
= calloc (1, sizeof (*header
));
507 memcpy (&header
->base
.exception_class
, &__objc_exception_class
,
508 sizeof (__objc_exception_class
));
509 header
->base
.exception_cleanup
= __objc_exception_cleanup
;
510 header
->value
= exception
;
512 #ifdef __USING_SJLJ_EXCEPTIONS__
513 _Unwind_SjLj_RaiseException (&header
->base
);
515 _Unwind_RaiseException (&header
->base
);
518 /* No exception handler was installed. Call the uncaught exception
519 handler if any is defined. */
520 if (__objc_uncaught_exception_handler
!= 0)
522 (*__objc_uncaught_exception_handler
) (exception
);
528 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__)
529 EXCEPTION_DISPOSITION
530 __gnu_objc_personality_seh0 (PEXCEPTION_RECORD ms_exc
, void *this_frame
,
531 PCONTEXT ms_orig_context
,
532 PDISPATCHER_CONTEXT ms_disp
)
534 return _GCC_specific_handler (ms_exc
, this_frame
, ms_orig_context
,
535 ms_disp
, __gnu_objc_personality_imp
);