1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright (C) 2006-2020 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 orig_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(orig_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 we have a non-WEAK reference from a regular object to a 435 // dynamic object, mark the dynamic object as needed. 436 if (to->is_from_dynobj() && to->in_reg() && !to->is_undef_binding_weak()) 437 to->object()->set_is_needed(); 438 439 if (adjust_common_sizes && parameters->options().warn_common()) 440 { 441 if (tosize > sym.get_st_size()) 442 Symbol_table::report_resolve_problem(false, 443 _("common of '%s' overriding " 444 "smaller common"), 445 to, OBJECT, object); 446 else if (tosize < sym.get_st_size()) 447 Symbol_table::report_resolve_problem(false, 448 _("common of '%s' overidden by " 449 "larger common"), 450 to, OBJECT, object); 451 else 452 Symbol_table::report_resolve_problem(false, 453 _("multiple common of '%s'"), 454 to, OBJECT, object); 455 } 456 } 457 458 // Handle the core of symbol resolution. This is called with the 459 // existing symbol, TO, and a bitflag describing the new symbol. This 460 // returns true if we should override the existing symbol with the new 461 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 462 // true if we should set the symbol size to the maximum of the TO and 463 // FROM sizes. It handles error conditions. 464 465 bool 466 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 467 elfcpp::STT fromtype, Defined defined, 468 Object* object, bool* adjust_common_sizes, 469 bool* adjust_dyndef, bool is_default_version) 470 { 471 *adjust_common_sizes = false; 472 *adjust_dyndef = false; 473 474 unsigned int tobits; 475 if (to->source() == Symbol::IS_UNDEFINED) 476 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true); 477 else if (to->source() != Symbol::FROM_OBJECT) 478 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false); 479 else 480 { 481 bool is_ordinary; 482 unsigned int shndx = to->shndx(&is_ordinary); 483 tobits = symbol_to_bits(to->binding(), 484 to->object()->is_dynamic(), 485 shndx, 486 is_ordinary); 487 } 488 489 if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS) 490 && !to->is_placeholder()) 491 Symbol_table::report_resolve_problem(true, 492 _("symbol '%s' used as both __thread " 493 "and non-__thread"), 494 to, defined, object); 495 496 // We use a giant switch table for symbol resolution. This code is 497 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 498 // cases; 3) it is easy to change the handling of a particular case. 499 // The alternative would be a series of conditionals, but it is easy 500 // to get the ordering wrong. This could also be done as a table, 501 // but that is no easier to understand than this large switch 502 // statement. 503 504 // These are the values generated by the bit codes. 505 enum 506 { 507 DEF = global_flag | regular_flag | def_flag, 508 WEAK_DEF = weak_flag | regular_flag | def_flag, 509 DYN_DEF = global_flag | dynamic_flag | def_flag, 510 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 511 UNDEF = global_flag | regular_flag | undef_flag, 512 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 513 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 514 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 515 COMMON = global_flag | regular_flag | common_flag, 516 WEAK_COMMON = weak_flag | regular_flag | common_flag, 517 DYN_COMMON = global_flag | dynamic_flag | common_flag, 518 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 519 }; 520 521 switch (tobits * 16 + frombits) 522 { 523 case DEF * 16 + DEF: 524 // Two definitions of the same symbol. 525 526 // If either symbol is defined by an object included using 527 // --just-symbols, then don't warn. This is for compatibility 528 // with the GNU linker. FIXME: This is a hack. 529 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 530 || (object != NULL && object->just_symbols())) 531 return false; 532 533 if (!parameters->options().muldefs()) 534 Symbol_table::report_resolve_problem(true, 535 _("multiple definition of '%s'"), 536 to, defined, object); 537 return false; 538 539 case WEAK_DEF * 16 + DEF: 540 // We've seen a weak definition, and now we see a strong 541 // definition. In the original SVR4 linker, this was treated as 542 // a multiple definition error. In the Solaris linker and the 543 // GNU linker, a weak definition followed by a regular 544 // definition causes the weak definition to be overridden. We 545 // are currently compatible with the GNU linker. In the future 546 // we should add a target specific option to change this. 547 // FIXME. 548 return true; 549 550 case DYN_DEF * 16 + DEF: 551 case DYN_WEAK_DEF * 16 + DEF: 552 // We've seen a definition in a dynamic object, and now we see a 553 // definition in a regular object. The definition in the 554 // regular object overrides the definition in the dynamic 555 // object. 556 return true; 557 558 case UNDEF * 16 + DEF: 559 case WEAK_UNDEF * 16 + DEF: 560 case DYN_UNDEF * 16 + DEF: 561 case DYN_WEAK_UNDEF * 16 + DEF: 562 // We've seen an undefined reference, and now we see a 563 // definition. We use the definition. 564 return true; 565 566 case COMMON * 16 + DEF: 567 case WEAK_COMMON * 16 + DEF: 568 case DYN_COMMON * 16 + DEF: 569 case DYN_WEAK_COMMON * 16 + DEF: 570 // We've seen a common symbol and now we see a definition. The 571 // definition overrides. 572 if (parameters->options().warn_common()) 573 Symbol_table::report_resolve_problem(false, 574 _("definition of '%s' overriding " 575 "common"), 576 to, defined, object); 577 return true; 578 579 case DEF * 16 + WEAK_DEF: 580 case WEAK_DEF * 16 + WEAK_DEF: 581 // We've seen a definition and now we see a weak definition. We 582 // ignore the new weak definition. 583 return false; 584 585 case DYN_DEF * 16 + WEAK_DEF: 586 case DYN_WEAK_DEF * 16 + WEAK_DEF: 587 // We've seen a dynamic definition and now we see a regular weak 588 // definition. The regular weak definition overrides. 589 return true; 590 591 case UNDEF * 16 + WEAK_DEF: 592 case WEAK_UNDEF * 16 + WEAK_DEF: 593 case DYN_UNDEF * 16 + WEAK_DEF: 594 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 595 // A weak definition of a currently undefined symbol. 596 return true; 597 598 case COMMON * 16 + WEAK_DEF: 599 case WEAK_COMMON * 16 + WEAK_DEF: 600 // A weak definition does not override a common definition. 601 return false; 602 603 case DYN_COMMON * 16 + WEAK_DEF: 604 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 605 // A weak definition does override a definition in a dynamic 606 // object. 607 if (parameters->options().warn_common()) 608 Symbol_table::report_resolve_problem(false, 609 _("definition of '%s' overriding " 610 "dynamic common definition"), 611 to, defined, object); 612 return true; 613 614 case DEF * 16 + DYN_DEF: 615 case WEAK_DEF * 16 + DYN_DEF: 616 // Ignore a dynamic definition if we already have a definition. 617 return false; 618 619 case DYN_DEF * 16 + DYN_DEF: 620 case DYN_WEAK_DEF * 16 + DYN_DEF: 621 // Ignore a dynamic definition if we already have a definition, 622 // unless the existing definition is an unversioned definition 623 // in the same dynamic object, and the new definition is a 624 // default version. 625 if (to->object() == object 626 && to->version() == NULL 627 && is_default_version) 628 return true; 629 // Or, if the existing definition is in an unused --as-needed library, 630 // and the reference is weak, let the new definition override. 631 if (to->in_reg() 632 && to->is_undef_binding_weak() 633 && to->object()->as_needed() 634 && !to->object()->is_needed()) 635 return true; 636 return false; 637 638 case UNDEF * 16 + DYN_DEF: 639 case DYN_UNDEF * 16 + DYN_DEF: 640 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 641 // Use a dynamic definition if we have a reference. 642 return true; 643 644 case WEAK_UNDEF * 16 + DYN_DEF: 645 // When overriding a weak undef by a dynamic definition, 646 // we need to remember that the original undef was weak. 647 *adjust_dyndef = true; 648 return true; 649 650 case COMMON * 16 + DYN_DEF: 651 case WEAK_COMMON * 16 + DYN_DEF: 652 // Ignore a dynamic definition if we already have a common 653 // definition. 654 return false; 655 656 case DEF * 16 + DYN_WEAK_DEF: 657 case WEAK_DEF * 16 + DYN_WEAK_DEF: 658 // Ignore a weak dynamic definition if we already have a 659 // definition. 660 return false; 661 662 case UNDEF * 16 + DYN_WEAK_DEF: 663 // When overriding an undef by a dynamic weak definition, 664 // we need to remember that the original undef was not weak. 665 *adjust_dyndef = true; 666 return true; 667 668 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 669 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 670 // Use a weak dynamic definition if we have a reference. 671 return true; 672 673 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 674 // When overriding a weak undef by a dynamic definition, 675 // we need to remember that the original undef was weak. 676 *adjust_dyndef = true; 677 return true; 678 679 case COMMON * 16 + DYN_WEAK_DEF: 680 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 681 // Ignore a weak dynamic definition if we already have a common 682 // definition. 683 return false; 684 685 case DYN_COMMON * 16 + DYN_DEF: 686 case DYN_WEAK_COMMON * 16 + DYN_DEF: 687 case DYN_DEF * 16 + DYN_WEAK_DEF: 688 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 689 case DYN_COMMON * 16 + DYN_WEAK_DEF: 690 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 691 // If the existing definition is in an unused --as-needed library, 692 // and the reference is weak, let a new dynamic definition override. 693 if (to->in_reg() 694 && to->is_undef_binding_weak() 695 && to->object()->as_needed() 696 && !to->object()->is_needed()) 697 return true; 698 return false; 699 700 case DEF * 16 + UNDEF: 701 case WEAK_DEF * 16 + UNDEF: 702 case UNDEF * 16 + UNDEF: 703 // A new undefined reference tells us nothing. 704 return false; 705 706 case DYN_DEF * 16 + UNDEF: 707 case DYN_WEAK_DEF * 16 + UNDEF: 708 // For a dynamic def, we need to remember which kind of undef we see. 709 *adjust_dyndef = true; 710 return false; 711 712 case WEAK_UNDEF * 16 + UNDEF: 713 case DYN_UNDEF * 16 + UNDEF: 714 case DYN_WEAK_UNDEF * 16 + UNDEF: 715 // A strong undef overrides a dynamic or weak undef. 716 return true; 717 718 case COMMON * 16 + UNDEF: 719 case WEAK_COMMON * 16 + UNDEF: 720 case DYN_COMMON * 16 + UNDEF: 721 case DYN_WEAK_COMMON * 16 + UNDEF: 722 // A new undefined reference tells us nothing. 723 return false; 724 725 case DEF * 16 + WEAK_UNDEF: 726 case WEAK_DEF * 16 + WEAK_UNDEF: 727 case UNDEF * 16 + WEAK_UNDEF: 728 case WEAK_UNDEF * 16 + WEAK_UNDEF: 729 case DYN_UNDEF * 16 + WEAK_UNDEF: 730 case COMMON * 16 + WEAK_UNDEF: 731 case WEAK_COMMON * 16 + WEAK_UNDEF: 732 case DYN_COMMON * 16 + WEAK_UNDEF: 733 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 734 // A new weak undefined reference tells us nothing unless the 735 // exisiting symbol is a dynamic weak reference. 736 return false; 737 738 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 739 // A new weak reference overrides an existing dynamic weak reference. 740 // This is necessary because a dynamic weak reference remembers 741 // the old binding, which may not be weak. If we keeps the existing 742 // dynamic weak reference, the weakness may be dropped in the output. 743 return true; 744 745 case DYN_DEF * 16 + WEAK_UNDEF: 746 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 747 // For a dynamic def, we need to remember which kind of undef we see. 748 *adjust_dyndef = true; 749 return false; 750 751 case DEF * 16 + DYN_UNDEF: 752 case WEAK_DEF * 16 + DYN_UNDEF: 753 case DYN_DEF * 16 + DYN_UNDEF: 754 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 755 case UNDEF * 16 + DYN_UNDEF: 756 case WEAK_UNDEF * 16 + DYN_UNDEF: 757 case DYN_UNDEF * 16 + DYN_UNDEF: 758 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 759 case COMMON * 16 + DYN_UNDEF: 760 case WEAK_COMMON * 16 + DYN_UNDEF: 761 case DYN_COMMON * 16 + DYN_UNDEF: 762 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 763 // A new dynamic undefined reference tells us nothing. 764 return false; 765 766 case DEF * 16 + DYN_WEAK_UNDEF: 767 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 768 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 769 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 770 case UNDEF * 16 + DYN_WEAK_UNDEF: 771 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 772 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 773 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 774 case COMMON * 16 + DYN_WEAK_UNDEF: 775 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 776 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 777 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 778 // A new weak dynamic undefined reference tells us nothing. 779 return false; 780 781 case DEF * 16 + COMMON: 782 // A common symbol does not override a definition. 783 if (parameters->options().warn_common()) 784 Symbol_table::report_resolve_problem(false, 785 _("common '%s' overridden by " 786 "previous definition"), 787 to, defined, object); 788 return false; 789 790 case WEAK_DEF * 16 + COMMON: 791 case DYN_DEF * 16 + COMMON: 792 case DYN_WEAK_DEF * 16 + COMMON: 793 // A common symbol does override a weak definition or a dynamic 794 // definition. 795 return true; 796 797 case UNDEF * 16 + COMMON: 798 case WEAK_UNDEF * 16 + COMMON: 799 case DYN_UNDEF * 16 + COMMON: 800 case DYN_WEAK_UNDEF * 16 + COMMON: 801 // A common symbol is a definition for a reference. 802 return true; 803 804 case COMMON * 16 + COMMON: 805 // Set the size to the maximum. 806 *adjust_common_sizes = true; 807 return false; 808 809 case WEAK_COMMON * 16 + COMMON: 810 // I'm not sure just what a weak common symbol means, but 811 // presumably it can be overridden by a regular common symbol. 812 return true; 813 814 case DYN_COMMON * 16 + COMMON: 815 case DYN_WEAK_COMMON * 16 + COMMON: 816 // Use the real common symbol, but adjust the size if necessary. 817 *adjust_common_sizes = true; 818 return true; 819 820 case DEF * 16 + WEAK_COMMON: 821 case WEAK_DEF * 16 + WEAK_COMMON: 822 case DYN_DEF * 16 + WEAK_COMMON: 823 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 824 // Whatever a weak common symbol is, it won't override a 825 // definition. 826 return false; 827 828 case UNDEF * 16 + WEAK_COMMON: 829 case WEAK_UNDEF * 16 + WEAK_COMMON: 830 case DYN_UNDEF * 16 + WEAK_COMMON: 831 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 832 // A weak common symbol is better than an undefined symbol. 833 return true; 834 835 case COMMON * 16 + WEAK_COMMON: 836 case WEAK_COMMON * 16 + WEAK_COMMON: 837 case DYN_COMMON * 16 + WEAK_COMMON: 838 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 839 // Ignore a weak common symbol in the presence of a real common 840 // symbol. 841 return false; 842 843 case DEF * 16 + DYN_COMMON: 844 case WEAK_DEF * 16 + DYN_COMMON: 845 case DYN_DEF * 16 + DYN_COMMON: 846 case DYN_WEAK_DEF * 16 + DYN_COMMON: 847 // Ignore a dynamic common symbol in the presence of a 848 // definition. 849 return false; 850 851 case UNDEF * 16 + DYN_COMMON: 852 case WEAK_UNDEF * 16 + DYN_COMMON: 853 case DYN_UNDEF * 16 + DYN_COMMON: 854 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 855 // A dynamic common symbol is a definition of sorts. 856 return true; 857 858 case COMMON * 16 + DYN_COMMON: 859 case WEAK_COMMON * 16 + DYN_COMMON: 860 case DYN_COMMON * 16 + DYN_COMMON: 861 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 862 // Set the size to the maximum. 863 *adjust_common_sizes = true; 864 return false; 865 866 case DEF * 16 + DYN_WEAK_COMMON: 867 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 868 case DYN_DEF * 16 + DYN_WEAK_COMMON: 869 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 870 // A common symbol is ignored in the face of a definition. 871 return false; 872 873 case UNDEF * 16 + DYN_WEAK_COMMON: 874 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 875 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 876 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 877 // I guess a weak common symbol is better than a definition. 878 return true; 879 880 case COMMON * 16 + DYN_WEAK_COMMON: 881 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 882 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 883 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 884 // Set the size to the maximum. 885 *adjust_common_sizes = true; 886 return false; 887 888 default: 889 gold_unreachable(); 890 } 891 } 892 893 // Issue an error or warning due to symbol resolution. IS_ERROR 894 // indicates an error rather than a warning. MSG is the error 895 // message; it is expected to have a %s for the symbol name. TO is 896 // the existing symbol. DEFINED/OBJECT is where the new symbol was 897 // found. 898 899 // FIXME: We should have better location information here. When the 900 // symbol is defined, we should be able to pull the location from the 901 // debug info if there is any. 902 903 void 904 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 905 const Symbol* to, Defined defined, 906 Object* object) 907 { 908 std::string demangled(to->demangled_name()); 909 size_t len = strlen(msg) + demangled.length() + 10; 910 char* buf = new char[len]; 911 snprintf(buf, len, msg, demangled.c_str()); 912 913 const char* objname; 914 switch (defined) 915 { 916 case OBJECT: 917 objname = object->name().c_str(); 918 break; 919 case COPY: 920 objname = _("COPY reloc"); 921 break; 922 case DEFSYM: 923 case UNDEFINED: 924 objname = _("command line"); 925 break; 926 case SCRIPT: 927 objname = _("linker script"); 928 break; 929 case PREDEFINED: 930 case INCREMENTAL_BASE: 931 objname = _("linker defined"); 932 break; 933 default: 934 gold_unreachable(); 935 } 936 937 if (is_error) 938 gold_error("%s: %s", objname, buf); 939 else 940 gold_warning("%s: %s", objname, buf); 941 942 delete[] buf; 943 944 if (to->source() == Symbol::FROM_OBJECT) 945 objname = to->object()->name().c_str(); 946 else 947 objname = _("command line"); 948 gold_info("%s: %s: previous definition here", program_name, objname); 949 } 950 951 // Completely override existing symbol. Everything bar name_, 952 // version_, and is_forced_local_ flag are copied. version_ is 953 // cleared if from->version_ is clear. Returns true if this symbol 954 // should be forced local. 955 bool 956 Symbol::clone(const Symbol* from) 957 { 958 // Don't allow cloning after dynamic linking info is attached to symbols. 959 // We aren't prepared to merge such. 960 gold_assert(!this->has_symtab_index() && !from->has_symtab_index()); 961 gold_assert(!this->has_dynsym_index() && !from->has_dynsym_index()); 962 gold_assert(this->got_offset_list() == NULL 963 && from->got_offset_list() == NULL); 964 gold_assert(!this->has_plt_offset() && !from->has_plt_offset()); 965 966 if (!from->version_) 967 this->version_ = from->version_; 968 this->u1_ = from->u1_; 969 this->u2_ = from->u2_; 970 this->type_ = from->type_; 971 this->binding_ = from->binding_; 972 this->visibility_ = from->visibility_; 973 this->nonvis_ = from->nonvis_; 974 this->source_ = from->source_; 975 this->is_def_ = from->is_def_; 976 this->is_forwarder_ = from->is_forwarder_; 977 this->has_alias_ = from->has_alias_; 978 this->needs_dynsym_entry_ = from->needs_dynsym_entry_; 979 this->in_reg_ = from->in_reg_; 980 this->in_dyn_ = from->in_dyn_; 981 this->needs_dynsym_value_ = from->needs_dynsym_value_; 982 this->has_warning_ = from->has_warning_; 983 this->is_copied_from_dynobj_ = from->is_copied_from_dynobj_; 984 this->is_ordinary_shndx_ = from->is_ordinary_shndx_; 985 this->in_real_elf_ = from->in_real_elf_; 986 this->is_defined_in_discarded_section_ 987 = from->is_defined_in_discarded_section_; 988 this->undef_binding_set_ = from->undef_binding_set_; 989 this->undef_binding_weak_ = from->undef_binding_weak_; 990 this->is_predefined_ = from->is_predefined_; 991 this->is_protected_ = from->is_protected_; 992 this->non_zero_localentry_ = from->non_zero_localentry_; 993 994 return !this->is_forced_local_ && from->is_forced_local_; 995 } 996 997 template <int size> 998 bool 999 Sized_symbol<size>::clone(const Sized_symbol<size>* from) 1000 { 1001 this->value_ = from->value_; 1002 this->symsize_ = from->symsize_; 1003 return Symbol::clone(from); 1004 } 1005 1006 // A special case of should_override which is only called for a strong 1007 // defined symbol from a regular object file. This is used when 1008 // defining special symbols. 1009 1010 bool 1011 Symbol_table::should_override_with_special(const Symbol* to, 1012 elfcpp::STT fromtype, 1013 Defined defined) 1014 { 1015 bool adjust_common_sizes; 1016 bool adjust_dyn_def; 1017 unsigned int frombits = global_flag | regular_flag | def_flag; 1018 bool ret = Symbol_table::should_override(to, frombits, fromtype, defined, 1019 NULL, &adjust_common_sizes, 1020 &adjust_dyn_def, false); 1021 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 1022 return ret; 1023 } 1024 1025 // Override symbol base with a special symbol. 1026 1027 void 1028 Symbol::override_base_with_special(const Symbol* from) 1029 { 1030 bool same_name = this->name_ == from->name_; 1031 gold_assert(same_name || this->has_alias()); 1032 1033 // If we are overriding an undef, remember the original binding. 1034 if (this->is_undefined()) 1035 this->set_undef_binding(this->binding_); 1036 1037 this->source_ = from->source_; 1038 switch (from->source_) 1039 { 1040 case FROM_OBJECT: 1041 case IN_OUTPUT_DATA: 1042 case IN_OUTPUT_SEGMENT: 1043 this->u1_ = from->u1_; 1044 this->u2_ = from->u2_; 1045 break; 1046 case IS_CONSTANT: 1047 case IS_UNDEFINED: 1048 break; 1049 default: 1050 gold_unreachable(); 1051 break; 1052 } 1053 1054 if (same_name) 1055 { 1056 // When overriding a versioned symbol with a special symbol, we 1057 // may be changing the version. This will happen if we see a 1058 // special symbol such as "_end" defined in a shared object with 1059 // one version (from a version script), but we want to define it 1060 // here with a different version (from a different version 1061 // script). 1062 this->version_ = from->version_; 1063 } 1064 this->type_ = from->type_; 1065 this->binding_ = from->binding_; 1066 this->override_visibility(from->visibility_); 1067 this->nonvis_ = from->nonvis_; 1068 1069 // Special symbols are always considered to be regular symbols. 1070 this->in_reg_ = true; 1071 1072 if (from->needs_dynsym_entry_) 1073 this->needs_dynsym_entry_ = true; 1074 if (from->needs_dynsym_value_) 1075 this->needs_dynsym_value_ = true; 1076 1077 this->is_predefined_ = from->is_predefined_; 1078 1079 // We shouldn't see these flags. If we do, we need to handle them 1080 // somehow. 1081 gold_assert(!from->is_forwarder_); 1082 gold_assert(!from->has_plt_offset()); 1083 gold_assert(!from->has_warning_); 1084 gold_assert(!from->is_copied_from_dynobj_); 1085 gold_assert(!from->is_forced_local_); 1086 } 1087 1088 // Override a symbol with a special symbol. 1089 1090 template<int size> 1091 void 1092 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 1093 { 1094 this->override_base_with_special(from); 1095 this->value_ = from->value_; 1096 this->symsize_ = from->symsize_; 1097 } 1098 1099 // Override TOSYM with the special symbol FROMSYM. This handles all 1100 // aliases of TOSYM. 1101 1102 template<int size> 1103 void 1104 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 1105 const Sized_symbol<size>* fromsym) 1106 { 1107 tosym->override_with_special(fromsym); 1108 if (tosym->has_alias()) 1109 { 1110 Symbol* sym = this->weak_aliases_[tosym]; 1111 gold_assert(sym != NULL); 1112 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 1113 do 1114 { 1115 ssym->override_with_special(fromsym); 1116 sym = this->weak_aliases_[ssym]; 1117 gold_assert(sym != NULL); 1118 ssym = this->get_sized_symbol<size>(sym); 1119 } 1120 while (ssym != tosym); 1121 } 1122 if (tosym->binding() == elfcpp::STB_LOCAL 1123 || ((tosym->visibility() == elfcpp::STV_HIDDEN 1124 || tosym->visibility() == elfcpp::STV_INTERNAL) 1125 && (tosym->binding() == elfcpp::STB_GLOBAL 1126 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 1127 || tosym->binding() == elfcpp::STB_WEAK) 1128 && !parameters->options().relocatable())) 1129 this->force_local(tosym); 1130 } 1131 1132 // Instantiate the templates we need. We could use the configure 1133 // script to restrict this to only the ones needed for implemented 1134 // targets. 1135 1136 // We have to instantiate both big and little endian versions because 1137 // these are used by other templates that depends on size only. 1138 1139 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1140 template 1141 void 1142 Symbol_table::resolve<32, false>( 1143 Sized_symbol<32>* to, 1144 const elfcpp::Sym<32, false>& sym, 1145 unsigned int st_shndx, 1146 bool is_ordinary, 1147 unsigned int orig_st_shndx, 1148 Object* object, 1149 const char* version, 1150 bool is_default_version); 1151 1152 template 1153 void 1154 Symbol_table::resolve<32, true>( 1155 Sized_symbol<32>* to, 1156 const elfcpp::Sym<32, true>& sym, 1157 unsigned int st_shndx, 1158 bool is_ordinary, 1159 unsigned int orig_st_shndx, 1160 Object* object, 1161 const char* version, 1162 bool is_default_version); 1163 #endif 1164 1165 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1166 template 1167 void 1168 Symbol_table::resolve<64, false>( 1169 Sized_symbol<64>* to, 1170 const elfcpp::Sym<64, false>& sym, 1171 unsigned int st_shndx, 1172 bool is_ordinary, 1173 unsigned int orig_st_shndx, 1174 Object* object, 1175 const char* version, 1176 bool is_default_version); 1177 1178 template 1179 void 1180 Symbol_table::resolve<64, true>( 1181 Sized_symbol<64>* to, 1182 const elfcpp::Sym<64, true>& sym, 1183 unsigned int st_shndx, 1184 bool is_ordinary, 1185 unsigned int orig_st_shndx, 1186 Object* object, 1187 const char* version, 1188 bool is_default_version); 1189 #endif 1190 1191 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1192 template 1193 void 1194 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1195 const Sized_symbol<32>*); 1196 #endif 1197 1198 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1199 template 1200 void 1201 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1202 const Sized_symbol<64>*); 1203 #endif 1204 1205 template 1206 bool 1207 Sized_symbol<32>::clone(const Sized_symbol<32>*); 1208 1209 template 1210 bool 1211 Sized_symbol<64>::clone(const Sized_symbol<64>*); 1212 } // End namespace gold. 1213