1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright (C) 2006-2018 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant@google.com>. 5 6 // This file is part of gold. 7 8 // This program is free software; you can redistribute it and/or modify 9 // it under the terms of the GNU General Public License as published by 10 // the Free Software Foundation; either version 3 of the License, or 11 // (at your option) any later version. 12 13 // This program is distributed in the hope that it will be useful, 14 // but WITHOUT ANY WARRANTY; without even the implied warranty of 15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 // GNU General Public License for more details. 17 18 // You should have received a copy of the GNU General Public License 19 // along with this program; if not, write to the Free Software 20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21 // MA 02110-1301, USA. 22 23 #include "gold.h" 24 25 #include "elfcpp.h" 26 #include "target.h" 27 #include "object.h" 28 #include "symtab.h" 29 #include "plugin.h" 30 31 namespace gold 32 { 33 34 // Symbol methods used in this file. 35 36 // This symbol is being overridden by another symbol whose version is 37 // VERSION. Update the VERSION_ field accordingly. 38 39 inline void 40 Symbol::override_version(const char* version) 41 { 42 if (version == NULL) 43 { 44 // This is the case where this symbol is NAME/VERSION, and the 45 // version was not marked as hidden. That makes it the default 46 // version, so we create NAME/NULL. Later we see another symbol 47 // NAME/NULL, and that symbol is overriding this one. In this 48 // case, since NAME/VERSION is the default, we make NAME/NULL 49 // override NAME/VERSION as well. They are already the same 50 // Symbol structure. Setting the VERSION_ field to NULL ensures 51 // that it will be output with the correct, empty, version. 52 this->version_ = version; 53 } 54 else 55 { 56 // This is the case where this symbol is NAME/VERSION_ONE, and 57 // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is 58 // overriding NAME. If VERSION_ONE and VERSION_TWO are 59 // different, then this can only happen when VERSION_ONE is NULL 60 // and VERSION_TWO is not hidden. 61 gold_assert(this->version_ == version || this->version_ == NULL); 62 this->version_ = version; 63 } 64 } 65 66 // This symbol is being overidden by another symbol whose visibility 67 // is VISIBILITY. Updated the VISIBILITY_ field accordingly. 68 69 inline void 70 Symbol::override_visibility(elfcpp::STV visibility) 71 { 72 // The rule for combining visibility is that we always choose the 73 // most constrained visibility. In order of increasing constraint, 74 // visibility goes PROTECTED, HIDDEN, INTERNAL. This is the reverse 75 // of the numeric values, so the effect is that we always want the 76 // smallest non-zero value. 77 if (visibility != elfcpp::STV_DEFAULT) 78 { 79 if (this->visibility_ == elfcpp::STV_DEFAULT) 80 this->visibility_ = visibility; 81 else if (this->visibility_ > visibility) 82 this->visibility_ = visibility; 83 } 84 } 85 86 // Override the fields in Symbol. 87 88 template<int size, bool big_endian> 89 void 90 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym, 91 unsigned int st_shndx, bool is_ordinary, 92 Object* object, const char* version) 93 { 94 gold_assert(this->source_ == FROM_OBJECT); 95 this->u1_.object = object; 96 this->override_version(version); 97 this->u2_.shndx = st_shndx; 98 this->is_ordinary_shndx_ = is_ordinary; 99 // Don't override st_type from plugin placeholder symbols. 100 if (object->pluginobj() == NULL) 101 this->type_ = sym.get_st_type(); 102 this->binding_ = sym.get_st_bind(); 103 this->override_visibility(sym.get_st_visibility()); 104 this->nonvis_ = sym.get_st_nonvis(); 105 if (object->is_dynamic()) 106 this->in_dyn_ = true; 107 else 108 this->in_reg_ = true; 109 } 110 111 // Override the fields in Sized_symbol. 112 113 template<int size> 114 template<bool big_endian> 115 void 116 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym, 117 unsigned st_shndx, bool is_ordinary, 118 Object* object, const char* version) 119 { 120 this->override_base(sym, st_shndx, is_ordinary, object, version); 121 this->value_ = sym.get_st_value(); 122 this->symsize_ = sym.get_st_size(); 123 } 124 125 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version 126 // VERSION. This handles all aliases of TOSYM. 127 128 template<int size, bool big_endian> 129 void 130 Symbol_table::override(Sized_symbol<size>* tosym, 131 const elfcpp::Sym<size, big_endian>& fromsym, 132 unsigned int st_shndx, bool is_ordinary, 133 Object* object, const char* version) 134 { 135 tosym->override(fromsym, st_shndx, is_ordinary, object, version); 136 if (tosym->has_alias()) 137 { 138 Symbol* sym = this->weak_aliases_[tosym]; 139 gold_assert(sym != NULL); 140 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 141 do 142 { 143 ssym->override(fromsym, st_shndx, is_ordinary, object, version); 144 sym = this->weak_aliases_[ssym]; 145 gold_assert(sym != NULL); 146 ssym = this->get_sized_symbol<size>(sym); 147 } 148 while (ssym != tosym); 149 } 150 } 151 152 // The resolve functions build a little code for each symbol. 153 // Bit 0: 0 for global, 1 for weak. 154 // Bit 1: 0 for regular object, 1 for shared object 155 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common 156 // This gives us values from 0 to 11. 157 158 static const int global_or_weak_shift = 0; 159 static const unsigned int global_flag = 0 << global_or_weak_shift; 160 static const unsigned int weak_flag = 1 << global_or_weak_shift; 161 162 static const int regular_or_dynamic_shift = 1; 163 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift; 164 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift; 165 166 static const int def_undef_or_common_shift = 2; 167 static const unsigned int def_flag = 0 << def_undef_or_common_shift; 168 static const unsigned int undef_flag = 1 << def_undef_or_common_shift; 169 static const unsigned int common_flag = 2 << def_undef_or_common_shift; 170 171 // This convenience function combines all the flags based on facts 172 // about the symbol. 173 174 static unsigned int 175 symbol_to_bits(elfcpp::STB binding, bool is_dynamic, 176 unsigned int shndx, bool is_ordinary) 177 { 178 unsigned int bits; 179 180 switch (binding) 181 { 182 case elfcpp::STB_GLOBAL: 183 case elfcpp::STB_GNU_UNIQUE: 184 bits = global_flag; 185 break; 186 187 case elfcpp::STB_WEAK: 188 bits = weak_flag; 189 break; 190 191 case elfcpp::STB_LOCAL: 192 // We should only see externally visible symbols in the symbol 193 // table. 194 gold_error(_("invalid STB_LOCAL symbol in external symbols")); 195 bits = global_flag; 196 break; 197 198 default: 199 // Any target which wants to handle STB_LOOS, etc., needs to 200 // define a resolve method. 201 gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding)); 202 bits = global_flag; 203 } 204 205 if (is_dynamic) 206 bits |= dynamic_flag; 207 else 208 bits |= regular_flag; 209 210 switch (shndx) 211 { 212 case elfcpp::SHN_UNDEF: 213 bits |= undef_flag; 214 break; 215 216 case elfcpp::SHN_COMMON: 217 if (!is_ordinary) 218 bits |= common_flag; 219 break; 220 221 default: 222 if (!is_ordinary && Symbol::is_common_shndx(shndx)) 223 bits |= common_flag; 224 else 225 bits |= def_flag; 226 break; 227 } 228 229 return bits; 230 } 231 232 // Resolve a symbol. This is called the second and subsequent times 233 // we see a symbol. TO is the pre-existing symbol. ST_SHNDX is the 234 // section index for SYM, possibly adjusted for many sections. 235 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather 236 // than a special code. ORIG_ST_SHNDX is the original section index, 237 // before any munging because of discarded sections, except that all 238 // non-ordinary section indexes are mapped to SHN_UNDEF. VERSION is 239 // the version of SYM. 240 241 template<int size, bool big_endian> 242 void 243 Symbol_table::resolve(Sized_symbol<size>* to, 244 const elfcpp::Sym<size, big_endian>& sym, 245 unsigned int st_shndx, bool is_ordinary, 246 unsigned int orig_st_shndx, 247 Object* object, const char* version, 248 bool is_default_version) 249 { 250 bool to_is_ordinary; 251 const unsigned int to_shndx = to->shndx(&to_is_ordinary); 252 253 // It's possible for a symbol to be defined in an object file 254 // using .symver to give it a version, and for there to also be 255 // a linker script giving that symbol the same version. We 256 // don't want to give a multiple-definition error for this 257 // harmless redefinition. 258 if (to->source() == Symbol::FROM_OBJECT 259 && to->object() == object 260 && to->is_defined() 261 && is_ordinary 262 && to_is_ordinary 263 && to_shndx == st_shndx 264 && to->value() == sym.get_st_value()) 265 return; 266 267 // Likewise for an absolute symbol defined twice with the same value. 268 if (!is_ordinary 269 && st_shndx == elfcpp::SHN_ABS 270 && !to_is_ordinary 271 && to_shndx == elfcpp::SHN_ABS 272 && to->value() == sym.get_st_value()) 273 return; 274 275 if (parameters->target().has_resolve()) 276 { 277 Sized_target<size, big_endian>* sized_target; 278 sized_target = parameters->sized_target<size, big_endian>(); 279 if (sized_target->resolve(to, sym, object, version)) 280 return; 281 } 282 283 if (!object->is_dynamic()) 284 { 285 if (sym.get_st_type() == elfcpp::STT_COMMON 286 && (is_ordinary || !Symbol::is_common_shndx(st_shndx))) 287 { 288 gold_warning(_("STT_COMMON symbol '%s' in %s " 289 "is not in a common section"), 290 to->demangled_name().c_str(), 291 to->object()->name().c_str()); 292 return; 293 } 294 // Record that we've seen this symbol in a regular object. 295 to->set_in_reg(); 296 } 297 else if (st_shndx == elfcpp::SHN_UNDEF 298 && (to->visibility() == elfcpp::STV_HIDDEN 299 || to->visibility() == elfcpp::STV_INTERNAL)) 300 { 301 // The symbol is hidden, so a reference from a shared object 302 // cannot bind to it. We tried issuing a warning in this case, 303 // but that produces false positives when the symbol is 304 // actually resolved in a different shared object (PR 15574). 305 return; 306 } 307 else 308 { 309 // Record that we've seen this symbol in a dynamic object. 310 to->set_in_dyn(); 311 } 312 313 // Record if we've seen this symbol in a real ELF object (i.e., the 314 // symbol is referenced from outside the world known to the plugin). 315 if (object->pluginobj() == NULL && !object->is_dynamic()) 316 to->set_in_real_elf(); 317 318 // If we're processing replacement files, allow new symbols to override 319 // the placeholders from the plugin objects. 320 // Treat common symbols specially since it is possible that an ELF 321 // file increased the size of the alignment. 322 if (to->source() == Symbol::FROM_OBJECT) 323 { 324 Pluginobj* obj = to->object()->pluginobj(); 325 if (obj != NULL 326 && parameters->options().plugins()->in_replacement_phase()) 327 { 328 bool adjust_common = false; 329 typename Sized_symbol<size>::Size_type tosize = 0; 330 typename Sized_symbol<size>::Value_type tovalue = 0; 331 if (to->is_common() 332 && !is_ordinary && Symbol::is_common_shndx(st_shndx)) 333 { 334 adjust_common = true; 335 tosize = to->symsize(); 336 tovalue = to->value(); 337 } 338 this->override(to, sym, st_shndx, is_ordinary, object, version); 339 if (adjust_common) 340 { 341 if (tosize > to->symsize()) 342 to->set_symsize(tosize); 343 if (tovalue > to->value()) 344 to->set_value(tovalue); 345 } 346 return; 347 } 348 } 349 350 // A new weak undefined reference, merging with an old weak 351 // reference, could be a One Definition Rule (ODR) violation -- 352 // especially if the types or sizes of the references differ. We'll 353 // store such pairs and look them up later to make sure they 354 // actually refer to the same lines of code. We also check 355 // combinations of weak and strong, which might occur if one case is 356 // inline and the other is not. (Note: not all ODR violations can 357 // be found this way, and not everything this finds is an ODR 358 // violation. But it's helpful to warn about.) 359 if (parameters->options().detect_odr_violations() 360 && (sym.get_st_bind() == elfcpp::STB_WEAK 361 || to->binding() == elfcpp::STB_WEAK) 362 && orig_st_shndx != elfcpp::SHN_UNDEF 363 && to_is_ordinary 364 && to_shndx != elfcpp::SHN_UNDEF 365 && sym.get_st_size() != 0 // Ignore weird 0-sized symbols. 366 && to->symsize() != 0 367 && (sym.get_st_type() != to->type() 368 || sym.get_st_size() != to->symsize()) 369 // C does not have a concept of ODR, so we only need to do this 370 // on C++ symbols. These have (mangled) names starting with _Z. 371 && to->name()[0] == '_' && to->name()[1] == 'Z') 372 { 373 Symbol_location fromloc 374 = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) }; 375 Symbol_location toloc = { to->object(), to_shndx, 376 static_cast<off_t>(to->value()) }; 377 this->candidate_odr_violations_[to->name()].insert(fromloc); 378 this->candidate_odr_violations_[to->name()].insert(toloc); 379 } 380 381 // Plugins don't provide a symbol type, so adopt the existing type 382 // if the FROM symbol is from a plugin. 383 elfcpp::STT fromtype = (object->pluginobj() != NULL 384 ? to->type() 385 : sym.get_st_type()); 386 unsigned int frombits = symbol_to_bits(sym.get_st_bind(), 387 object->is_dynamic(), 388 st_shndx, is_ordinary); 389 390 bool adjust_common_sizes; 391 bool adjust_dyndef; 392 typename Sized_symbol<size>::Size_type tosize = to->symsize(); 393 if (Symbol_table::should_override(to, frombits, fromtype, OBJECT, 394 object, &adjust_common_sizes, 395 &adjust_dyndef, is_default_version)) 396 { 397 elfcpp::STB tobinding = to->binding(); 398 typename Sized_symbol<size>::Value_type tovalue = to->value(); 399 this->override(to, sym, st_shndx, is_ordinary, object, version); 400 if (adjust_common_sizes) 401 { 402 if (tosize > to->symsize()) 403 to->set_symsize(tosize); 404 if (tovalue > to->value()) 405 to->set_value(tovalue); 406 } 407 if (adjust_dyndef) 408 { 409 // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF. 410 // Remember which kind of UNDEF it was for future reference. 411 to->set_undef_binding(tobinding); 412 } 413 } 414 else 415 { 416 if (adjust_common_sizes) 417 { 418 if (sym.get_st_size() > tosize) 419 to->set_symsize(sym.get_st_size()); 420 if (sym.get_st_value() > to->value()) 421 to->set_value(sym.get_st_value()); 422 } 423 if (adjust_dyndef) 424 { 425 // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF. 426 // Remember which kind of UNDEF it was. 427 to->set_undef_binding(sym.get_st_bind()); 428 } 429 // The ELF ABI says that even for a reference to a symbol we 430 // merge the visibility. 431 to->override_visibility(sym.get_st_visibility()); 432 } 433 434 if (adjust_common_sizes && parameters->options().warn_common()) 435 { 436 if (tosize > sym.get_st_size()) 437 Symbol_table::report_resolve_problem(false, 438 _("common of '%s' overriding " 439 "smaller common"), 440 to, OBJECT, object); 441 else if (tosize < sym.get_st_size()) 442 Symbol_table::report_resolve_problem(false, 443 _("common of '%s' overidden by " 444 "larger common"), 445 to, OBJECT, object); 446 else 447 Symbol_table::report_resolve_problem(false, 448 _("multiple common of '%s'"), 449 to, OBJECT, object); 450 } 451 } 452 453 // Handle the core of symbol resolution. This is called with the 454 // existing symbol, TO, and a bitflag describing the new symbol. This 455 // returns true if we should override the existing symbol with the new 456 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 457 // true if we should set the symbol size to the maximum of the TO and 458 // FROM sizes. It handles error conditions. 459 460 bool 461 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 462 elfcpp::STT fromtype, Defined defined, 463 Object* object, bool* adjust_common_sizes, 464 bool* adjust_dyndef, bool is_default_version) 465 { 466 *adjust_common_sizes = false; 467 *adjust_dyndef = false; 468 469 unsigned int tobits; 470 if (to->source() == Symbol::IS_UNDEFINED) 471 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true); 472 else if (to->source() != Symbol::FROM_OBJECT) 473 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false); 474 else 475 { 476 bool is_ordinary; 477 unsigned int shndx = to->shndx(&is_ordinary); 478 tobits = symbol_to_bits(to->binding(), 479 to->object()->is_dynamic(), 480 shndx, 481 is_ordinary); 482 } 483 484 if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS) 485 && !to->is_placeholder()) 486 Symbol_table::report_resolve_problem(true, 487 _("symbol '%s' used as both __thread " 488 "and non-__thread"), 489 to, defined, object); 490 491 // We use a giant switch table for symbol resolution. This code is 492 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 493 // cases; 3) it is easy to change the handling of a particular case. 494 // The alternative would be a series of conditionals, but it is easy 495 // to get the ordering wrong. This could also be done as a table, 496 // but that is no easier to understand than this large switch 497 // statement. 498 499 // These are the values generated by the bit codes. 500 enum 501 { 502 DEF = global_flag | regular_flag | def_flag, 503 WEAK_DEF = weak_flag | regular_flag | def_flag, 504 DYN_DEF = global_flag | dynamic_flag | def_flag, 505 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 506 UNDEF = global_flag | regular_flag | undef_flag, 507 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 508 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 509 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 510 COMMON = global_flag | regular_flag | common_flag, 511 WEAK_COMMON = weak_flag | regular_flag | common_flag, 512 DYN_COMMON = global_flag | dynamic_flag | common_flag, 513 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 514 }; 515 516 switch (tobits * 16 + frombits) 517 { 518 case DEF * 16 + DEF: 519 // Two definitions of the same symbol. 520 521 // If either symbol is defined by an object included using 522 // --just-symbols, then don't warn. This is for compatibility 523 // with the GNU linker. FIXME: This is a hack. 524 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 525 || (object != NULL && object->just_symbols())) 526 return false; 527 528 if (!parameters->options().muldefs()) 529 Symbol_table::report_resolve_problem(true, 530 _("multiple definition of '%s'"), 531 to, defined, object); 532 return false; 533 534 case WEAK_DEF * 16 + DEF: 535 // We've seen a weak definition, and now we see a strong 536 // definition. In the original SVR4 linker, this was treated as 537 // a multiple definition error. In the Solaris linker and the 538 // GNU linker, a weak definition followed by a regular 539 // definition causes the weak definition to be overridden. We 540 // are currently compatible with the GNU linker. In the future 541 // we should add a target specific option to change this. 542 // FIXME. 543 return true; 544 545 case DYN_DEF * 16 + DEF: 546 case DYN_WEAK_DEF * 16 + DEF: 547 // We've seen a definition in a dynamic object, and now we see a 548 // definition in a regular object. The definition in the 549 // regular object overrides the definition in the dynamic 550 // object. 551 return true; 552 553 case UNDEF * 16 + DEF: 554 case WEAK_UNDEF * 16 + DEF: 555 case DYN_UNDEF * 16 + DEF: 556 case DYN_WEAK_UNDEF * 16 + DEF: 557 // We've seen an undefined reference, and now we see a 558 // definition. We use the definition. 559 return true; 560 561 case COMMON * 16 + DEF: 562 case WEAK_COMMON * 16 + DEF: 563 case DYN_COMMON * 16 + DEF: 564 case DYN_WEAK_COMMON * 16 + DEF: 565 // We've seen a common symbol and now we see a definition. The 566 // definition overrides. 567 if (parameters->options().warn_common()) 568 Symbol_table::report_resolve_problem(false, 569 _("definition of '%s' overriding " 570 "common"), 571 to, defined, object); 572 return true; 573 574 case DEF * 16 + WEAK_DEF: 575 case WEAK_DEF * 16 + WEAK_DEF: 576 // We've seen a definition and now we see a weak definition. We 577 // ignore the new weak definition. 578 return false; 579 580 case DYN_DEF * 16 + WEAK_DEF: 581 case DYN_WEAK_DEF * 16 + WEAK_DEF: 582 // We've seen a dynamic definition and now we see a regular weak 583 // definition. The regular weak definition overrides. 584 return true; 585 586 case UNDEF * 16 + WEAK_DEF: 587 case WEAK_UNDEF * 16 + WEAK_DEF: 588 case DYN_UNDEF * 16 + WEAK_DEF: 589 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 590 // A weak definition of a currently undefined symbol. 591 return true; 592 593 case COMMON * 16 + WEAK_DEF: 594 case WEAK_COMMON * 16 + WEAK_DEF: 595 // A weak definition does not override a common definition. 596 return false; 597 598 case DYN_COMMON * 16 + WEAK_DEF: 599 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 600 // A weak definition does override a definition in a dynamic 601 // object. 602 if (parameters->options().warn_common()) 603 Symbol_table::report_resolve_problem(false, 604 _("definition of '%s' overriding " 605 "dynamic common definition"), 606 to, defined, object); 607 return true; 608 609 case DEF * 16 + DYN_DEF: 610 case WEAK_DEF * 16 + DYN_DEF: 611 // Ignore a dynamic definition if we already have a definition. 612 return false; 613 614 case DYN_DEF * 16 + DYN_DEF: 615 case DYN_WEAK_DEF * 16 + DYN_DEF: 616 // Ignore a dynamic definition if we already have a definition, 617 // unless the existing definition is an unversioned definition 618 // in the same dynamic object, and the new definition is a 619 // default version. 620 if (to->object() == object 621 && to->version() == NULL 622 && is_default_version) 623 return true; 624 return false; 625 626 case UNDEF * 16 + DYN_DEF: 627 case DYN_UNDEF * 16 + DYN_DEF: 628 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 629 // Use a dynamic definition if we have a reference. 630 return true; 631 632 case WEAK_UNDEF * 16 + DYN_DEF: 633 // When overriding a weak undef by a dynamic definition, 634 // we need to remember that the original undef was weak. 635 *adjust_dyndef = true; 636 return true; 637 638 case COMMON * 16 + DYN_DEF: 639 case WEAK_COMMON * 16 + DYN_DEF: 640 case DYN_COMMON * 16 + DYN_DEF: 641 case DYN_WEAK_COMMON * 16 + DYN_DEF: 642 // Ignore a dynamic definition if we already have a common 643 // definition. 644 return false; 645 646 case DEF * 16 + DYN_WEAK_DEF: 647 case WEAK_DEF * 16 + DYN_WEAK_DEF: 648 case DYN_DEF * 16 + DYN_WEAK_DEF: 649 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 650 // Ignore a weak dynamic definition if we already have a 651 // definition. 652 return false; 653 654 case UNDEF * 16 + DYN_WEAK_DEF: 655 // When overriding an undef by a dynamic weak definition, 656 // we need to remember that the original undef was not weak. 657 *adjust_dyndef = true; 658 return true; 659 660 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 661 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 662 // Use a weak dynamic definition if we have a reference. 663 return true; 664 665 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 666 // When overriding a weak undef by a dynamic definition, 667 // we need to remember that the original undef was weak. 668 *adjust_dyndef = true; 669 return true; 670 671 case COMMON * 16 + DYN_WEAK_DEF: 672 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 673 case DYN_COMMON * 16 + DYN_WEAK_DEF: 674 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 675 // Ignore a weak dynamic definition if we already have a common 676 // definition. 677 return false; 678 679 case DEF * 16 + UNDEF: 680 case WEAK_DEF * 16 + UNDEF: 681 case UNDEF * 16 + UNDEF: 682 // A new undefined reference tells us nothing. 683 return false; 684 685 case DYN_DEF * 16 + UNDEF: 686 case DYN_WEAK_DEF * 16 + UNDEF: 687 // For a dynamic def, we need to remember which kind of undef we see. 688 *adjust_dyndef = true; 689 return false; 690 691 case WEAK_UNDEF * 16 + UNDEF: 692 case DYN_UNDEF * 16 + UNDEF: 693 case DYN_WEAK_UNDEF * 16 + UNDEF: 694 // A strong undef overrides a dynamic or weak undef. 695 return true; 696 697 case COMMON * 16 + UNDEF: 698 case WEAK_COMMON * 16 + UNDEF: 699 case DYN_COMMON * 16 + UNDEF: 700 case DYN_WEAK_COMMON * 16 + UNDEF: 701 // A new undefined reference tells us nothing. 702 return false; 703 704 case DEF * 16 + WEAK_UNDEF: 705 case WEAK_DEF * 16 + WEAK_UNDEF: 706 case UNDEF * 16 + WEAK_UNDEF: 707 case WEAK_UNDEF * 16 + WEAK_UNDEF: 708 case DYN_UNDEF * 16 + WEAK_UNDEF: 709 case COMMON * 16 + WEAK_UNDEF: 710 case WEAK_COMMON * 16 + WEAK_UNDEF: 711 case DYN_COMMON * 16 + WEAK_UNDEF: 712 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 713 // A new weak undefined reference tells us nothing unless the 714 // exisiting symbol is a dynamic weak reference. 715 return false; 716 717 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 718 // A new weak reference overrides an existing dynamic weak reference. 719 // This is necessary because a dynamic weak reference remembers 720 // the old binding, which may not be weak. If we keeps the existing 721 // dynamic weak reference, the weakness may be dropped in the output. 722 return true; 723 724 case DYN_DEF * 16 + WEAK_UNDEF: 725 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 726 // For a dynamic def, we need to remember which kind of undef we see. 727 *adjust_dyndef = true; 728 return false; 729 730 case DEF * 16 + DYN_UNDEF: 731 case WEAK_DEF * 16 + DYN_UNDEF: 732 case DYN_DEF * 16 + DYN_UNDEF: 733 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 734 case UNDEF * 16 + DYN_UNDEF: 735 case WEAK_UNDEF * 16 + DYN_UNDEF: 736 case DYN_UNDEF * 16 + DYN_UNDEF: 737 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 738 case COMMON * 16 + DYN_UNDEF: 739 case WEAK_COMMON * 16 + DYN_UNDEF: 740 case DYN_COMMON * 16 + DYN_UNDEF: 741 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 742 // A new dynamic undefined reference tells us nothing. 743 return false; 744 745 case DEF * 16 + DYN_WEAK_UNDEF: 746 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 747 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 748 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 749 case UNDEF * 16 + DYN_WEAK_UNDEF: 750 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 751 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 752 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 753 case COMMON * 16 + DYN_WEAK_UNDEF: 754 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 755 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 756 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 757 // A new weak dynamic undefined reference tells us nothing. 758 return false; 759 760 case DEF * 16 + COMMON: 761 // A common symbol does not override a definition. 762 if (parameters->options().warn_common()) 763 Symbol_table::report_resolve_problem(false, 764 _("common '%s' overridden by " 765 "previous definition"), 766 to, defined, object); 767 return false; 768 769 case WEAK_DEF * 16 + COMMON: 770 case DYN_DEF * 16 + COMMON: 771 case DYN_WEAK_DEF * 16 + COMMON: 772 // A common symbol does override a weak definition or a dynamic 773 // definition. 774 return true; 775 776 case UNDEF * 16 + COMMON: 777 case WEAK_UNDEF * 16 + COMMON: 778 case DYN_UNDEF * 16 + COMMON: 779 case DYN_WEAK_UNDEF * 16 + COMMON: 780 // A common symbol is a definition for a reference. 781 return true; 782 783 case COMMON * 16 + COMMON: 784 // Set the size to the maximum. 785 *adjust_common_sizes = true; 786 return false; 787 788 case WEAK_COMMON * 16 + COMMON: 789 // I'm not sure just what a weak common symbol means, but 790 // presumably it can be overridden by a regular common symbol. 791 return true; 792 793 case DYN_COMMON * 16 + COMMON: 794 case DYN_WEAK_COMMON * 16 + COMMON: 795 // Use the real common symbol, but adjust the size if necessary. 796 *adjust_common_sizes = true; 797 return true; 798 799 case DEF * 16 + WEAK_COMMON: 800 case WEAK_DEF * 16 + WEAK_COMMON: 801 case DYN_DEF * 16 + WEAK_COMMON: 802 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 803 // Whatever a weak common symbol is, it won't override a 804 // definition. 805 return false; 806 807 case UNDEF * 16 + WEAK_COMMON: 808 case WEAK_UNDEF * 16 + WEAK_COMMON: 809 case DYN_UNDEF * 16 + WEAK_COMMON: 810 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 811 // A weak common symbol is better than an undefined symbol. 812 return true; 813 814 case COMMON * 16 + WEAK_COMMON: 815 case WEAK_COMMON * 16 + WEAK_COMMON: 816 case DYN_COMMON * 16 + WEAK_COMMON: 817 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 818 // Ignore a weak common symbol in the presence of a real common 819 // symbol. 820 return false; 821 822 case DEF * 16 + DYN_COMMON: 823 case WEAK_DEF * 16 + DYN_COMMON: 824 case DYN_DEF * 16 + DYN_COMMON: 825 case DYN_WEAK_DEF * 16 + DYN_COMMON: 826 // Ignore a dynamic common symbol in the presence of a 827 // definition. 828 return false; 829 830 case UNDEF * 16 + DYN_COMMON: 831 case WEAK_UNDEF * 16 + DYN_COMMON: 832 case DYN_UNDEF * 16 + DYN_COMMON: 833 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 834 // A dynamic common symbol is a definition of sorts. 835 return true; 836 837 case COMMON * 16 + DYN_COMMON: 838 case WEAK_COMMON * 16 + DYN_COMMON: 839 case DYN_COMMON * 16 + DYN_COMMON: 840 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 841 // Set the size to the maximum. 842 *adjust_common_sizes = true; 843 return false; 844 845 case DEF * 16 + DYN_WEAK_COMMON: 846 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 847 case DYN_DEF * 16 + DYN_WEAK_COMMON: 848 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 849 // A common symbol is ignored in the face of a definition. 850 return false; 851 852 case UNDEF * 16 + DYN_WEAK_COMMON: 853 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 854 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 855 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 856 // I guess a weak common symbol is better than a definition. 857 return true; 858 859 case COMMON * 16 + DYN_WEAK_COMMON: 860 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 861 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 862 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 863 // Set the size to the maximum. 864 *adjust_common_sizes = true; 865 return false; 866 867 default: 868 gold_unreachable(); 869 } 870 } 871 872 // Issue an error or warning due to symbol resolution. IS_ERROR 873 // indicates an error rather than a warning. MSG is the error 874 // message; it is expected to have a %s for the symbol name. TO is 875 // the existing symbol. DEFINED/OBJECT is where the new symbol was 876 // found. 877 878 // FIXME: We should have better location information here. When the 879 // symbol is defined, we should be able to pull the location from the 880 // debug info if there is any. 881 882 void 883 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 884 const Symbol* to, Defined defined, 885 Object* object) 886 { 887 std::string demangled(to->demangled_name()); 888 size_t len = strlen(msg) + demangled.length() + 10; 889 char* buf = new char[len]; 890 snprintf(buf, len, msg, demangled.c_str()); 891 892 const char* objname; 893 switch (defined) 894 { 895 case OBJECT: 896 objname = object->name().c_str(); 897 break; 898 case COPY: 899 objname = _("COPY reloc"); 900 break; 901 case DEFSYM: 902 case UNDEFINED: 903 objname = _("command line"); 904 break; 905 case SCRIPT: 906 objname = _("linker script"); 907 break; 908 case PREDEFINED: 909 case INCREMENTAL_BASE: 910 objname = _("linker defined"); 911 break; 912 default: 913 gold_unreachable(); 914 } 915 916 if (is_error) 917 gold_error("%s: %s", objname, buf); 918 else 919 gold_warning("%s: %s", objname, buf); 920 921 delete[] buf; 922 923 if (to->source() == Symbol::FROM_OBJECT) 924 objname = to->object()->name().c_str(); 925 else 926 objname = _("command line"); 927 gold_info("%s: %s: previous definition here", program_name, objname); 928 } 929 930 // Completely override existing symbol. Everything bar name_, 931 // version_, and is_forced_local_ flag are copied. version_ is 932 // cleared if from->version_ is clear. Returns true if this symbol 933 // should be forced local. 934 bool 935 Symbol::clone(const Symbol* from) 936 { 937 // Don't allow cloning after dynamic linking info is attached to symbols. 938 // We aren't prepared to merge such. 939 gold_assert(!this->has_symtab_index() && !from->has_symtab_index()); 940 gold_assert(!this->has_dynsym_index() && !from->has_dynsym_index()); 941 gold_assert(this->got_offset_list() == NULL 942 && from->got_offset_list() == NULL); 943 gold_assert(!this->has_plt_offset() && !from->has_plt_offset()); 944 945 if (!from->version_) 946 this->version_ = from->version_; 947 this->u1_ = from->u1_; 948 this->u2_ = from->u2_; 949 this->type_ = from->type_; 950 this->binding_ = from->binding_; 951 this->visibility_ = from->visibility_; 952 this->nonvis_ = from->nonvis_; 953 this->source_ = from->source_; 954 this->is_def_ = from->is_def_; 955 this->is_forwarder_ = from->is_forwarder_; 956 this->has_alias_ = from->has_alias_; 957 this->needs_dynsym_entry_ = from->needs_dynsym_entry_; 958 this->in_reg_ = from->in_reg_; 959 this->in_dyn_ = from->in_dyn_; 960 this->needs_dynsym_value_ = from->needs_dynsym_value_; 961 this->has_warning_ = from->has_warning_; 962 this->is_copied_from_dynobj_ = from->is_copied_from_dynobj_; 963 this->is_ordinary_shndx_ = from->is_ordinary_shndx_; 964 this->in_real_elf_ = from->in_real_elf_; 965 this->is_defined_in_discarded_section_ 966 = from->is_defined_in_discarded_section_; 967 this->undef_binding_set_ = from->undef_binding_set_; 968 this->undef_binding_weak_ = from->undef_binding_weak_; 969 this->is_predefined_ = from->is_predefined_; 970 this->is_protected_ = from->is_protected_; 971 this->non_zero_localentry_ = from->non_zero_localentry_; 972 973 return !this->is_forced_local_ && from->is_forced_local_; 974 } 975 976 template <int size> 977 bool 978 Sized_symbol<size>::clone(const Sized_symbol<size>* from) 979 { 980 this->value_ = from->value_; 981 this->symsize_ = from->symsize_; 982 return Symbol::clone(from); 983 } 984 985 // A special case of should_override which is only called for a strong 986 // defined symbol from a regular object file. This is used when 987 // defining special symbols. 988 989 bool 990 Symbol_table::should_override_with_special(const Symbol* to, 991 elfcpp::STT fromtype, 992 Defined defined) 993 { 994 bool adjust_common_sizes; 995 bool adjust_dyn_def; 996 unsigned int frombits = global_flag | regular_flag | def_flag; 997 bool ret = Symbol_table::should_override(to, frombits, fromtype, defined, 998 NULL, &adjust_common_sizes, 999 &adjust_dyn_def, false); 1000 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 1001 return ret; 1002 } 1003 1004 // Override symbol base with a special symbol. 1005 1006 void 1007 Symbol::override_base_with_special(const Symbol* from) 1008 { 1009 bool same_name = this->name_ == from->name_; 1010 gold_assert(same_name || this->has_alias()); 1011 1012 // If we are overriding an undef, remember the original binding. 1013 if (this->is_undefined()) 1014 this->set_undef_binding(this->binding_); 1015 1016 this->source_ = from->source_; 1017 switch (from->source_) 1018 { 1019 case FROM_OBJECT: 1020 case IN_OUTPUT_DATA: 1021 case IN_OUTPUT_SEGMENT: 1022 this->u1_ = from->u1_; 1023 this->u2_ = from->u2_; 1024 break; 1025 case IS_CONSTANT: 1026 case IS_UNDEFINED: 1027 break; 1028 default: 1029 gold_unreachable(); 1030 break; 1031 } 1032 1033 if (same_name) 1034 { 1035 // When overriding a versioned symbol with a special symbol, we 1036 // may be changing the version. This will happen if we see a 1037 // special symbol such as "_end" defined in a shared object with 1038 // one version (from a version script), but we want to define it 1039 // here with a different version (from a different version 1040 // script). 1041 this->version_ = from->version_; 1042 } 1043 this->type_ = from->type_; 1044 this->binding_ = from->binding_; 1045 this->override_visibility(from->visibility_); 1046 this->nonvis_ = from->nonvis_; 1047 1048 // Special symbols are always considered to be regular symbols. 1049 this->in_reg_ = true; 1050 1051 if (from->needs_dynsym_entry_) 1052 this->needs_dynsym_entry_ = true; 1053 if (from->needs_dynsym_value_) 1054 this->needs_dynsym_value_ = true; 1055 1056 this->is_predefined_ = from->is_predefined_; 1057 1058 // We shouldn't see these flags. If we do, we need to handle them 1059 // somehow. 1060 gold_assert(!from->is_forwarder_); 1061 gold_assert(!from->has_plt_offset()); 1062 gold_assert(!from->has_warning_); 1063 gold_assert(!from->is_copied_from_dynobj_); 1064 gold_assert(!from->is_forced_local_); 1065 } 1066 1067 // Override a symbol with a special symbol. 1068 1069 template<int size> 1070 void 1071 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 1072 { 1073 this->override_base_with_special(from); 1074 this->value_ = from->value_; 1075 this->symsize_ = from->symsize_; 1076 } 1077 1078 // Override TOSYM with the special symbol FROMSYM. This handles all 1079 // aliases of TOSYM. 1080 1081 template<int size> 1082 void 1083 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 1084 const Sized_symbol<size>* fromsym) 1085 { 1086 tosym->override_with_special(fromsym); 1087 if (tosym->has_alias()) 1088 { 1089 Symbol* sym = this->weak_aliases_[tosym]; 1090 gold_assert(sym != NULL); 1091 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 1092 do 1093 { 1094 ssym->override_with_special(fromsym); 1095 sym = this->weak_aliases_[ssym]; 1096 gold_assert(sym != NULL); 1097 ssym = this->get_sized_symbol<size>(sym); 1098 } 1099 while (ssym != tosym); 1100 } 1101 if (tosym->binding() == elfcpp::STB_LOCAL 1102 || ((tosym->visibility() == elfcpp::STV_HIDDEN 1103 || tosym->visibility() == elfcpp::STV_INTERNAL) 1104 && (tosym->binding() == elfcpp::STB_GLOBAL 1105 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 1106 || tosym->binding() == elfcpp::STB_WEAK) 1107 && !parameters->options().relocatable())) 1108 this->force_local(tosym); 1109 } 1110 1111 // Instantiate the templates we need. We could use the configure 1112 // script to restrict this to only the ones needed for implemented 1113 // targets. 1114 1115 // We have to instantiate both big and little endian versions because 1116 // these are used by other templates that depends on size only. 1117 1118 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1119 template 1120 void 1121 Symbol_table::resolve<32, false>( 1122 Sized_symbol<32>* to, 1123 const elfcpp::Sym<32, false>& sym, 1124 unsigned int st_shndx, 1125 bool is_ordinary, 1126 unsigned int orig_st_shndx, 1127 Object* object, 1128 const char* version, 1129 bool is_default_version); 1130 1131 template 1132 void 1133 Symbol_table::resolve<32, true>( 1134 Sized_symbol<32>* to, 1135 const elfcpp::Sym<32, true>& sym, 1136 unsigned int st_shndx, 1137 bool is_ordinary, 1138 unsigned int orig_st_shndx, 1139 Object* object, 1140 const char* version, 1141 bool is_default_version); 1142 #endif 1143 1144 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1145 template 1146 void 1147 Symbol_table::resolve<64, false>( 1148 Sized_symbol<64>* to, 1149 const elfcpp::Sym<64, false>& sym, 1150 unsigned int st_shndx, 1151 bool is_ordinary, 1152 unsigned int orig_st_shndx, 1153 Object* object, 1154 const char* version, 1155 bool is_default_version); 1156 1157 template 1158 void 1159 Symbol_table::resolve<64, true>( 1160 Sized_symbol<64>* to, 1161 const elfcpp::Sym<64, true>& sym, 1162 unsigned int st_shndx, 1163 bool is_ordinary, 1164 unsigned int orig_st_shndx, 1165 Object* object, 1166 const char* version, 1167 bool is_default_version); 1168 #endif 1169 1170 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1171 template 1172 void 1173 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1174 const Sized_symbol<32>*); 1175 #endif 1176 1177 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1178 template 1179 void 1180 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1181 const Sized_symbol<64>*); 1182 #endif 1183 1184 template 1185 bool 1186 Sized_symbol<32>::clone(const Sized_symbol<32>*); 1187 1188 template 1189 bool 1190 Sized_symbol<64>::clone(const Sized_symbol<64>*); 1191 } // End namespace gold. 1192