1 /* The implementation of exception handling primitives for Objective-C. 2 Copyright (C) 2004-2019 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 __attribute__((target ("general-regs-only"))) 224 PERSONALITY_FUNCTION (_Unwind_State state, 225 struct _Unwind_Exception *ue_header, 226 struct _Unwind_Context *context) 227 #else 228 229 #define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND 230 231 #if defined (__SEH__) && !defined (__USING_SJLJ_EXCEPTIONS__) 232 static 233 #endif 234 _Unwind_Reason_Code 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) 240 #endif 241 { 242 struct ObjcException *xh = (struct ObjcException *) ue_header; 243 244 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; 251 void *return_object; 252 int ip_before_insn = 0; 253 254 #ifdef __ARM_EABI_UNWINDER__ 255 _Unwind_Action actions; 256 257 switch (state & _US_ACTION_MASK) 258 { 259 case _US_VIRTUAL_UNWIND_FRAME: 260 actions = _UA_SEARCH_PHASE; 261 break; 262 263 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; 268 break; 269 270 case _US_UNWIND_FRAME_RESUME: 271 CONTINUE_UNWINDING; 272 break; 273 274 default: 275 abort(); 276 } 277 actions |= state & _US_FORCE_UNWIND; 278 279 /* TODO: Foreign exceptions need some attention (e.g. rethrowing 280 doesn't work). */ 281 foreign_exception = 0; 282 283 /* 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); 289 290 #else /* !__ARM_EABI_UNWINDER. */ 291 /* Interface version check. */ 292 if (version != 1) 293 return _URC_FATAL_PHASE1_ERROR; 294 295 foreign_exception = (exception_class != __objc_exception_class); 296 #endif 297 298 /* Shortcut for phase 2 found handler for domestic exception. */ 299 if (actions == (_UA_CLEANUP_PHASE | _UA_HANDLER_FRAME) 300 && !foreign_exception) 301 { 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]; 305 #else 306 handler_switch_value = xh->handlerSwitchValue; 307 landing_pad = xh->landingPad; 308 #endif 309 goto install_context; 310 } 311 312 language_specific_data = (const unsigned char *) 313 _Unwind_GetLanguageSpecificData (context); 314 315 /* If no LSDA, then there are no handlers or cleanups. */ 316 if (! language_specific_data) 317 CONTINUE_UNWINDING; 318 319 /* 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); 324 #else 325 ip = _Unwind_GetIP (context); 326 #endif 327 if (!ip_before_insn) 328 --ip; 329 landing_pad = 0; 330 action_record = 0; 331 handler_switch_value = 0; 332 333 #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 337 the array. */ 338 if ((int) ip < 0) 339 return _URC_CONTINUE_UNWIND; 340 else 341 { 342 _uleb128_t cs_lp, cs_action; 343 do 344 { 345 p = read_uleb128 (p, &cs_lp); 346 p = read_uleb128 (p, &cs_action); 347 } 348 while (--ip); 349 350 /* 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; 353 if (cs_action) 354 action_record = info.action_table + cs_action - 1; 355 goto found_something; 356 } 357 #else 358 /* Search the call-site table for the action associated with this 359 IP. */ 360 while (p < info.action_table) 361 { 362 _Unwind_Ptr cs_start, cs_len, cs_lp; 363 _uleb128_t cs_action; 364 365 /* Note that all call-site encodings are "absolute" 366 displacements. */ 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); 371 372 /* 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) 376 { 377 if (cs_lp) 378 landing_pad = info.LPStart + cs_lp; 379 if (cs_action) 380 action_record = info.action_table + cs_action - 1; 381 goto found_something; 382 } 383 } 384 #endif /* __USING_SJLJ_EXCEPTIONS__ */ 385 386 /* 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. */ 389 CONTINUE_UNWINDING; 390 391 found_something: 392 saw_cleanup = 0; 393 saw_handler = 0; 394 395 if (landing_pad == 0) 396 { 397 /* If ip is present, and has a null landing pad, there are no 398 cleanups or handlers to be run. */ 399 } 400 else if (action_record == 0) 401 { 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. */ 405 saw_cleanup = 1; 406 } 407 else 408 { 409 /* Otherwise we have a catch handler. */ 410 _sleb128_t ar_filter, ar_disp; 411 412 while (1) 413 { 414 p = action_record; 415 p = read_sleb128 (p, &ar_filter); 416 read_sleb128 (p, &ar_disp); 417 418 if (ar_filter == 0) 419 { 420 /* Zero filter values are cleanups. */ 421 saw_cleanup = 1; 422 } 423 424 /* During forced unwinding, we only run cleanups. With a 425 foreign exception class, we have no class info to 426 match. */ 427 else if ((actions & _UA_FORCE_UNWIND) || foreign_exception) 428 ; 429 430 else if (ar_filter > 0) 431 { 432 /* Positive filter values are handlers. */ 433 Class catch_type = get_ttype_entry (&info, ar_filter); 434 435 if ((*__objc_exception_matcher) (catch_type, xh->value)) 436 { 437 handler_switch_value = ar_filter; 438 saw_handler = 1; 439 break; 440 } 441 } 442 else 443 { 444 /* Negative filter values are exception specifications, 445 which Objective-C does not use. */ 446 abort (); 447 } 448 449 if (ar_disp == 0) 450 break; 451 action_record = p + ar_disp; 452 } 453 } 454 455 if (! saw_handler && ! saw_cleanup) 456 CONTINUE_UNWINDING; 457 458 if (actions & _UA_SEARCH_PHASE) 459 { 460 if (!saw_handler) 461 CONTINUE_UNWINDING; 462 463 /* For domestic exceptions, we cache data from phase 1 for phase 464 2. */ 465 if (!foreign_exception) 466 { 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; 471 #else 472 xh->handlerSwitchValue = handler_switch_value; 473 xh->landingPad = landing_pad; 474 #endif 475 } 476 return _URC_HANDLER_FOUND; 477 } 478 479 install_context: 480 if (saw_cleanup == 0) 481 { 482 return_object = xh->value; 483 if (!(actions & _UA_SEARCH_PHASE)) 484 _Unwind_DeleteException(&xh->base); 485 } 486 487 _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; 493 } 494 495 static void 496 __objc_exception_cleanup (_Unwind_Reason_Code code __attribute__((unused)), 497 struct _Unwind_Exception *exc) 498 { 499 free (exc); 500 } 501 502 void 503 objc_exception_throw (id exception) 504 { 505 struct ObjcException *header = calloc (1, sizeof (*header)); 506 507 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; 511 512 #ifdef __USING_SJLJ_EXCEPTIONS__ 513 _Unwind_SjLj_RaiseException (&header->base); 514 #else 515 _Unwind_RaiseException (&header->base); 516 #endif 517 518 /* No exception handler was installed. Call the uncaught exception 519 handler if any is defined. */ 520 if (__objc_uncaught_exception_handler != 0) 521 { 522 (*__objc_uncaught_exception_handler) (exception); 523 } 524 525 abort (); 526 } 527 528 #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) 533 { 534 return _GCC_specific_handler (ms_exc, this_frame, ms_orig_context, 535 ms_disp, __gnu_objc_personality_imp); 536 } 537 #endif 538