1 /* The implementation of exception handling primitives for Objective-C. 2 Copyright (C) 2004-2016 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 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 9 later version. 10 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. 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 #include "objc-private/common.h" 26 #include <stdlib.h> 27 #include "config.h" 28 #include "objc/runtime.h" 29 #include "objc/objc-exception.h" 30 #include "unwind.h" 31 #include "unwind-pe.h" 32 #include <string.h> /* For memcpy */ 33 34 /* 'is_kind_of_exception_matcher' is our default exception matcher - 35 it determines if the object 'exception' is of class 'catch_class', 36 or of a subclass. */ 37 static int 38 is_kind_of_exception_matcher (Class catch_class, id exception) 39 { 40 /* NULL catch_class is catch-all (eg, @catch (id object)). */ 41 if (catch_class == Nil) 42 return 1; 43 44 /* If exception is nil (eg, @throw nil;), then it can only be 45 catched by a catch-all (eg, @catch (id object)). */ 46 if (exception != nil) 47 { 48 Class c; 49 50 for (c = exception->class_pointer; c != Nil; 51 c = class_getSuperclass (c)) 52 if (c == catch_class) 53 return 1; 54 } 55 return 0; 56 } 57 58 /* The exception matcher currently in use. */ 59 static objc_exception_matcher 60 __objc_exception_matcher = is_kind_of_exception_matcher; 61 62 objc_exception_matcher 63 objc_setExceptionMatcher (objc_exception_matcher new_matcher) 64 { 65 objc_exception_matcher old_matcher = __objc_exception_matcher; 66 __objc_exception_matcher = new_matcher; 67 return old_matcher; 68 } 69 70 /* The uncaught exception handler currently in use. */ 71 static objc_uncaught_exception_handler 72 __objc_uncaught_exception_handler = NULL; 73 74 objc_uncaught_exception_handler 75 objc_setUncaughtExceptionHandler (objc_uncaught_exception_handler 76 new_handler) 77 { 78 objc_uncaught_exception_handler old_handler 79 = __objc_uncaught_exception_handler; 80 __objc_uncaught_exception_handler = new_handler; 81 return old_handler; 82 } 83 84 85 86 #ifdef __ARM_EABI_UNWINDER__ 87 88 const _Unwind_Exception_Class __objc_exception_class 89 = {'G', 'N', 'U', 'C', 'O', 'B', 'J', 'C'}; 90 91 #else 92 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'); 103 104 #endif 105 106 /* This is the object that is passed around by the Objective C runtime 107 to represent the exception in flight. */ 108 struct ObjcException 109 { 110 /* This bit is needed in order to interact with the unwind runtime. */ 111 struct _Unwind_Exception base; 112 113 /* The actual object we want to throw. Note: must come immediately 114 after unwind header. */ 115 id value; 116 117 #ifdef __ARM_EABI_UNWINDER__ 118 /* Note: we use the barrier cache defined in the unwind control 119 block for ARM EABI. */ 120 #else 121 /* Cache some internal unwind data between phase 1 and phase 2. */ 122 _Unwind_Ptr landingPad; 123 int handlerSwitchValue; 124 #endif 125 }; 126 127 128 129 struct lsda_header_info 130 { 131 _Unwind_Ptr Start; 132 _Unwind_Ptr LPStart; 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; 138 }; 139 140 static const unsigned char * 141 parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p, 142 struct lsda_header_info *info) 143 { 144 _uleb128_t tmp; 145 unsigned char lpstart_encoding; 146 147 info->Start = (context ? _Unwind_GetRegionStart (context) : 0); 148 149 /* Find @LPStart, the base to which landing pad offsets are 150 relative. */ 151 lpstart_encoding = *p++; 152 if (lpstart_encoding != DW_EH_PE_omit) 153 p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart); 154 else 155 info->LPStart = info->Start; 156 157 /* Find @TType, the base of the handler and exception spec type 158 data. */ 159 info->ttype_encoding = *p++; 160 if (info->ttype_encoding != DW_EH_PE_omit) 161 { 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; 166 #endif 167 p = read_uleb128 (p, &tmp); 168 info->TType = p + tmp; 169 } 170 else 171 info->TType = 0; 172 173 /* 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; 178 179 return p; 180 } 181 182 static Class 183 get_ttype_entry (struct lsda_header_info *info, _Unwind_Word i) 184 { 185 _Unwind_Ptr ptr; 186 187 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); 190 191 /* NULL ptr means catch-all. Note that if the class is not found, 192 this will abort the program. */ 193 if (ptr) 194 return objc_getRequiredClass ((const char *) ptr); 195 else 196 return 0; 197 } 198 199 /* Using a different personality function name causes link failures 200 when trying to mix code using different exception handling 201 models. */ 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 207 #else 208 #define PERSONALITY_FUNCTION __gnu_objc_personality_v0 209 #endif 210 211 #ifdef __ARM_EABI_UNWINDER__ 212 213 #define CONTINUE_UNWINDING \ 214 do \ 215 { \ 216 if (__gnu_unwind_frame(ue_header, context) != _URC_OK) \ 217 return _URC_FAILURE; \ 218 return _URC_CONTINUE_UNWIND; \ 219 } \ 220 while (0) 221 222 _Unwind_Reason_Code 223 PERSONALITY_FUNCTION (_Unwind_State state, 224 struct _Unwind_Exception *ue_header, 225 struct _Unwind_Context *context) 226 #else 227 228 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND 229 230 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__) 231 static 232 #endif 233 _Unwind_Reason_Code 234 PERSONALITY_FUNCTION (int version, 235 _Unwind_Action actions, 236 _Unwind_Exception_Class exception_class, 237 struct _Unwind_Exception *ue_header, 238 struct _Unwind_Context *context) 239 #endif 240 { 241 struct ObjcException *xh = (struct ObjcException *) ue_header; 242 243 struct lsda_header_info info; 244 const unsigned char *language_specific_data; 245 const unsigned char *action_record; 246 const unsigned char *p; 247 _Unwind_Ptr landing_pad, ip; 248 int handler_switch_value; 249 int saw_cleanup = 0, saw_handler, foreign_exception; 250 void *return_object; 251 int ip_before_insn = 0; 252 253 #ifdef __ARM_EABI_UNWINDER__ 254 _Unwind_Action actions; 255 256 switch (state & _US_ACTION_MASK) 257 { 258 case _US_VIRTUAL_UNWIND_FRAME: 259 actions = _UA_SEARCH_PHASE; 260 break; 261 262 case _US_UNWIND_FRAME_STARTING: 263 actions = _UA_CLEANUP_PHASE; 264 if (!(state & _US_FORCE_UNWIND) 265 && ue_header->barrier_cache.sp == _Unwind_GetGR (context, 13)) 266 actions |= _UA_HANDLER_FRAME; 267 break; 268 269 case _US_UNWIND_FRAME_RESUME: 270 CONTINUE_UNWINDING; 271 break; 272 273 default: 274 abort(); 275 } 276 actions |= state & _US_FORCE_UNWIND; 277 278 /* TODO: Foreign exceptions need some attention (e.g. rethrowing 279 doesn't work). */ 280 foreign_exception = 0; 281 282 /* The dwarf unwinder assumes the context structure holds things 283 like the function and LSDA pointers. The ARM implementation 284 caches these in the exception header (UCB). To avoid rewriting 285 everything we make the virtual IP register point at the UCB. */ 286 ip = (_Unwind_Ptr) ue_header; 287 _Unwind_SetGR (context, 12, ip); 288 289 #else /* !__ARM_EABI_UNWINDER. */ 290 /* Interface version check. */ 291 if (version != 1) 292 return _URC_FATAL_PHASE1_ERROR; 293 294 foreign_exception = (exception_class != __objc_exception_class); 295 #endif 296 297 /* Shortcut for phase 2 found handler for domestic exception. */ 298 if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME) 299 && !foreign_exception) 300 { 301 #ifdef __ARM_EABI_UNWINDER__ 302 handler_switch_value = (int) ue_header->barrier_cache.bitpattern[1]; 303 landing_pad = (_Unwind_Ptr) ue_header->barrier_cache.bitpattern[3]; 304 #else 305 handler_switch_value = xh->handlerSwitchValue; 306 landing_pad = xh->landingPad; 307 #endif 308 goto install_context; 309 } 310 311 language_specific_data = (const unsigned char *) 312 _Unwind_GetLanguageSpecificData (context); 313 314 /* If no LSDA, then there are no handlers or cleanups. */ 315 if (! language_specific_data) 316 CONTINUE_UNWINDING; 317 318 /* Parse the LSDA header. */ 319 p = parse_lsda_header (context, language_specific_data, &info); 320 info.ttype_base = base_of_encoded_value (info.ttype_encoding, context); 321 #ifdef HAVE_GETIPINFO 322 ip = _Unwind_GetIPInfo (context, &ip_before_insn); 323 #else 324 ip = _Unwind_GetIP (context); 325 #endif 326 if (!ip_before_insn) 327 --ip; 328 landing_pad = 0; 329 action_record = 0; 330 handler_switch_value = 0; 331 332 #ifdef __USING_SJLJ_EXCEPTIONS__ 333 /* The given "IP" is an index into the call-site table, with two 334 exceptions -- -1 means no-action, and 0 means terminate. But 335 since we're using uleb128 values, we've not got random access to 336 the array. */ 337 if ((int) ip < 0) 338 return _URC_CONTINUE_UNWIND; 339 else 340 { 341 _uleb128_t cs_lp, cs_action; 342 do 343 { 344 p = read_uleb128 (p, &cs_lp); 345 p = read_uleb128 (p, &cs_action); 346 } 347 while (--ip); 348 349 /* Can never have null landing pad for sjlj -- that would have 350 been indicated by a -1 call site index. */ 351 landing_pad = cs_lp + 1; 352 if (cs_action) 353 action_record = info.action_table + cs_action - 1; 354 goto found_something; 355 } 356 #else 357 /* Search the call-site table for the action associated with this 358 IP. */ 359 while (p < info.action_table) 360 { 361 _Unwind_Ptr cs_start, cs_len, cs_lp; 362 _uleb128_t cs_action; 363 364 /* Note that all call-site encodings are "absolute" 365 displacements. */ 366 p = read_encoded_value (0, info.call_site_encoding, p, &cs_start); 367 p = read_encoded_value (0, info.call_site_encoding, p, &cs_len); 368 p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp); 369 p = read_uleb128 (p, &cs_action); 370 371 /* The table is sorted, so if we've passed the ip, stop. */ 372 if (ip < info.Start + cs_start) 373 p = info.action_table; 374 else if (ip < info.Start + cs_start + cs_len) 375 { 376 if (cs_lp) 377 landing_pad = info.LPStart + cs_lp; 378 if (cs_action) 379 action_record = info.action_table + cs_action - 1; 380 goto found_something; 381 } 382 } 383 #endif /* __USING_SJLJ_EXCEPTIONS__ */ 384 385 /* If ip is not present in the table, C++ would call terminate. */ 386 /* ??? As with Java, it's perhaps better to tweek the LSDA to that 387 no-action is mapped to no-entry. */ 388 CONTINUE_UNWINDING; 389 390 found_something: 391 saw_cleanup = 0; 392 saw_handler = 0; 393 394 if (landing_pad == 0) 395 { 396 /* If ip is present, and has a null landing pad, there are no 397 cleanups or handlers to be run. */ 398 } 399 else if (action_record == 0) 400 { 401 /* If ip is present, has a non-null landing pad, and a null 402 action table offset, then there are only cleanups present. 403 Cleanups use a zero switch value, as set above. */ 404 saw_cleanup = 1; 405 } 406 else 407 { 408 /* Otherwise we have a catch handler. */ 409 _sleb128_t ar_filter, ar_disp; 410 411 while (1) 412 { 413 p = action_record; 414 p = read_sleb128 (p, &ar_filter); 415 read_sleb128 (p, &ar_disp); 416 417 if (ar_filter == 0) 418 { 419 /* Zero filter values are cleanups. */ 420 saw_cleanup = 1; 421 } 422 423 /* During forced unwinding, we only run cleanups. With a 424 foreign exception class, we have no class info to 425 match. */ 426 else if ((actions & _UA_FORCE_UNWIND) || foreign_exception) 427 ; 428 429 else if (ar_filter > 0) 430 { 431 /* Positive filter values are handlers. */ 432 Class catch_type = get_ttype_entry (&info, ar_filter); 433 434 if ((*__objc_exception_matcher) (catch_type, xh->value)) 435 { 436 handler_switch_value = ar_filter; 437 saw_handler = 1; 438 break; 439 } 440 } 441 else 442 { 443 /* Negative filter values are exception specifications, 444 which Objective-C does not use. */ 445 abort (); 446 } 447 448 if (ar_disp == 0) 449 break; 450 action_record = p + ar_disp; 451 } 452 } 453 454 if (! saw_handler && ! saw_cleanup) 455 CONTINUE_UNWINDING; 456 457 if (actions & _UA_SEARCH_PHASE) 458 { 459 if (!saw_handler) 460 CONTINUE_UNWINDING; 461 462 /* For domestic exceptions, we cache data from phase 1 for phase 463 2. */ 464 if (!foreign_exception) 465 { 466 #ifdef __ARM_EABI_UNWINDER__ 467 ue_header->barrier_cache.sp = _Unwind_GetGR (context, 13); 468 ue_header->barrier_cache.bitpattern[1] = (_uw) handler_switch_value; 469 ue_header->barrier_cache.bitpattern[3] = (_uw) landing_pad; 470 #else 471 xh->handlerSwitchValue = handler_switch_value; 472 xh->landingPad = landing_pad; 473 #endif 474 } 475 return _URC_HANDLER_FOUND; 476 } 477 478 install_context: 479 if (saw_cleanup == 0) 480 { 481 return_object = xh->value; 482 if (!(actions & _UA_SEARCH_PHASE)) 483 _Unwind_DeleteException(&xh->base); 484 } 485 486 _Unwind_SetGR (context, __builtin_eh_return_data_regno (0), 487 __builtin_extend_pointer (saw_cleanup ? xh : return_object)); 488 _Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 489 handler_switch_value); 490 _Unwind_SetIP (context, landing_pad); 491 return _URC_INSTALL_CONTEXT; 492 } 493 494 static void 495 __objc_exception_cleanup (_Unwind_Reason_Code code __attribute__((unused)), 496 struct _Unwind_Exception *exc) 497 { 498 free (exc); 499 } 500 501 void 502 objc_exception_throw (id exception) 503 { 504 struct ObjcException *header = calloc (1, sizeof (*header)); 505 506 memcpy (&header->base.exception_class, &__objc_exception_class, 507 sizeof (__objc_exception_class)); 508 header->base.exception_cleanup = __objc_exception_cleanup; 509 header->value = exception; 510 511 #ifdef __USING_SJLJ_EXCEPTIONS__ 512 _Unwind_SjLj_RaiseException (&header->base); 513 #else 514 _Unwind_RaiseException (&header->base); 515 #endif 516 517 /* No exception handler was installed. Call the uncaught exception 518 handler if any is defined. */ 519 if (__objc_uncaught_exception_handler != 0) 520 { 521 (*__objc_uncaught_exception_handler) (exception); 522 } 523 524 abort (); 525 } 526 527 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__) 528 EXCEPTION_DISPOSITION 529 __gnu_objc_personality_seh0 (PEXCEPTION_RECORD ms_exc, void *this_frame, 530 PCONTEXT ms_orig_context, 531 PDISPATCHER_CONTEXT ms_disp) 532 { 533 return _GCC_specific_handler (ms_exc, this_frame, ms_orig_context, 534 ms_disp, __gnu_objc_personality_imp); 535 } 536 #endif 537