1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright (C) 2006-2016 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant (at) 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->u_.from_object.object = object; 96 this->override_version(version); 97 this->u_.from_object.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; 196 197 default: 198 // Any target which wants to handle STB_LOOS, etc., needs to 199 // define a resolve method. 200 gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding)); 201 bits = global_flag; 202 } 203 204 if (is_dynamic) 205 bits |= dynamic_flag; 206 else 207 bits |= regular_flag; 208 209 switch (shndx) 210 { 211 case elfcpp::SHN_UNDEF: 212 bits |= undef_flag; 213 break; 214 215 case elfcpp::SHN_COMMON: 216 if (!is_ordinary) 217 bits |= common_flag; 218 break; 219 220 default: 221 if (!is_ordinary && Symbol::is_common_shndx(shndx)) 222 bits |= common_flag; 223 else 224 bits |= def_flag; 225 break; 226 } 227 228 return bits; 229 } 230 231 // Resolve a symbol. This is called the second and subsequent times 232 // we see a symbol. TO is the pre-existing symbol. ST_SHNDX is the 233 // section index for SYM, possibly adjusted for many sections. 234 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather 235 // than a special code. ORIG_ST_SHNDX is the original section index, 236 // before any munging because of discarded sections, except that all 237 // non-ordinary section indexes are mapped to SHN_UNDEF. VERSION is 238 // the version of SYM. 239 240 template<int size, bool big_endian> 241 void 242 Symbol_table::resolve(Sized_symbol<size>* to, 243 const elfcpp::Sym<size, big_endian>& sym, 244 unsigned int st_shndx, bool is_ordinary, 245 unsigned int orig_st_shndx, 246 Object* object, const char* version, 247 bool is_default_version) 248 { 249 // It's possible for a symbol to be defined in an object file 250 // using .symver to give it a version, and for there to also be 251 // a linker script giving that symbol the same version. We 252 // don't want to give a multiple-definition error for this 253 // harmless redefinition. 254 bool to_is_ordinary; 255 if (to->source() == Symbol::FROM_OBJECT 256 && to->object() == object 257 && is_ordinary 258 && to->is_defined() 259 && to->shndx(&to_is_ordinary) == st_shndx 260 && to_is_ordinary 261 && to->value() == sym.get_st_value()) 262 return; 263 264 if (parameters->target().has_resolve()) 265 { 266 Sized_target<size, big_endian>* sized_target; 267 sized_target = parameters->sized_target<size, big_endian>(); 268 sized_target->resolve(to, sym, object, version); 269 return; 270 } 271 272 if (!object->is_dynamic()) 273 { 274 if (sym.get_st_type() == elfcpp::STT_COMMON 275 && (is_ordinary || !Symbol::is_common_shndx(st_shndx))) 276 { 277 gold_warning(_("STT_COMMON symbol '%s' in %s " 278 "is not in a common section"), 279 to->demangled_name().c_str(), 280 to->object()->name().c_str()); 281 return; 282 } 283 // Record that we've seen this symbol in a regular object. 284 to->set_in_reg(); 285 } 286 else if (st_shndx == elfcpp::SHN_UNDEF 287 && (to->visibility() == elfcpp::STV_HIDDEN 288 || to->visibility() == elfcpp::STV_INTERNAL)) 289 { 290 // The symbol is hidden, so a reference from a shared object 291 // cannot bind to it. We tried issuing a warning in this case, 292 // but that produces false positives when the symbol is 293 // actually resolved in a different shared object (PR 15574). 294 return; 295 } 296 else 297 { 298 // Record that we've seen this symbol in a dynamic object. 299 to->set_in_dyn(); 300 } 301 302 // Record if we've seen this symbol in a real ELF object (i.e., the 303 // symbol is referenced from outside the world known to the plugin). 304 if (object->pluginobj() == NULL && !object->is_dynamic()) 305 to->set_in_real_elf(); 306 307 // If we're processing replacement files, allow new symbols to override 308 // the placeholders from the plugin objects. 309 // Treat common symbols specially since it is possible that an ELF 310 // file increased the size of the alignment. 311 if (to->source() == Symbol::FROM_OBJECT) 312 { 313 Pluginobj* obj = to->object()->pluginobj(); 314 if (obj != NULL 315 && parameters->options().plugins()->in_replacement_phase()) 316 { 317 bool adjust_common = false; 318 typename Sized_symbol<size>::Size_type tosize = 0; 319 typename Sized_symbol<size>::Value_type tovalue = 0; 320 if (to->is_common() 321 && !is_ordinary && Symbol::is_common_shndx(st_shndx)) 322 { 323 adjust_common = true; 324 tosize = to->symsize(); 325 tovalue = to->value(); 326 } 327 this->override(to, sym, st_shndx, is_ordinary, object, version); 328 if (adjust_common) 329 { 330 if (tosize > to->symsize()) 331 to->set_symsize(tosize); 332 if (tovalue > to->value()) 333 to->set_value(tovalue); 334 } 335 return; 336 } 337 } 338 339 // A new weak undefined reference, merging with an old weak 340 // reference, could be a One Definition Rule (ODR) violation -- 341 // especially if the types or sizes of the references differ. We'll 342 // store such pairs and look them up later to make sure they 343 // actually refer to the same lines of code. We also check 344 // combinations of weak and strong, which might occur if one case is 345 // inline and the other is not. (Note: not all ODR violations can 346 // be found this way, and not everything this finds is an ODR 347 // violation. But it's helpful to warn about.) 348 if (parameters->options().detect_odr_violations() 349 && (sym.get_st_bind() == elfcpp::STB_WEAK 350 || to->binding() == elfcpp::STB_WEAK) 351 && orig_st_shndx != elfcpp::SHN_UNDEF 352 && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF 353 && to_is_ordinary 354 && sym.get_st_size() != 0 // Ignore weird 0-sized symbols. 355 && to->symsize() != 0 356 && (sym.get_st_type() != to->type() 357 || sym.get_st_size() != to->symsize()) 358 // C does not have a concept of ODR, so we only need to do this 359 // on C++ symbols. These have (mangled) names starting with _Z. 360 && to->name()[0] == '_' && to->name()[1] == 'Z') 361 { 362 Symbol_location fromloc 363 = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) }; 364 Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary), 365 static_cast<off_t>(to->value()) }; 366 this->candidate_odr_violations_[to->name()].insert(fromloc); 367 this->candidate_odr_violations_[to->name()].insert(toloc); 368 } 369 370 // Plugins don't provide a symbol type, so adopt the existing type 371 // if the FROM symbol is from a plugin. 372 elfcpp::STT fromtype = (object->pluginobj() != NULL 373 ? to->type() 374 : sym.get_st_type()); 375 unsigned int frombits = symbol_to_bits(sym.get_st_bind(), 376 object->is_dynamic(), 377 st_shndx, is_ordinary); 378 379 bool adjust_common_sizes; 380 bool adjust_dyndef; 381 typename Sized_symbol<size>::Size_type tosize = to->symsize(); 382 if (Symbol_table::should_override(to, frombits, fromtype, OBJECT, 383 object, &adjust_common_sizes, 384 &adjust_dyndef, is_default_version)) 385 { 386 elfcpp::STB tobinding = to->binding(); 387 typename Sized_symbol<size>::Value_type tovalue = to->value(); 388 this->override(to, sym, st_shndx, is_ordinary, object, version); 389 if (adjust_common_sizes) 390 { 391 if (tosize > to->symsize()) 392 to->set_symsize(tosize); 393 if (tovalue > to->value()) 394 to->set_value(tovalue); 395 } 396 if (adjust_dyndef) 397 { 398 // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF. 399 // Remember which kind of UNDEF it was for future reference. 400 to->set_undef_binding(tobinding); 401 } 402 } 403 else 404 { 405 if (adjust_common_sizes) 406 { 407 if (sym.get_st_size() > tosize) 408 to->set_symsize(sym.get_st_size()); 409 if (sym.get_st_value() > to->value()) 410 to->set_value(sym.get_st_value()); 411 } 412 if (adjust_dyndef) 413 { 414 // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF. 415 // Remember which kind of UNDEF it was. 416 to->set_undef_binding(sym.get_st_bind()); 417 } 418 // The ELF ABI says that even for a reference to a symbol we 419 // merge the visibility. 420 to->override_visibility(sym.get_st_visibility()); 421 } 422 423 if (adjust_common_sizes && parameters->options().warn_common()) 424 { 425 if (tosize > sym.get_st_size()) 426 Symbol_table::report_resolve_problem(false, 427 _("common of '%s' overriding " 428 "smaller common"), 429 to, OBJECT, object); 430 else if (tosize < sym.get_st_size()) 431 Symbol_table::report_resolve_problem(false, 432 _("common of '%s' overidden by " 433 "larger common"), 434 to, OBJECT, object); 435 else 436 Symbol_table::report_resolve_problem(false, 437 _("multiple common of '%s'"), 438 to, OBJECT, object); 439 } 440 } 441 442 // Handle the core of symbol resolution. This is called with the 443 // existing symbol, TO, and a bitflag describing the new symbol. This 444 // returns true if we should override the existing symbol with the new 445 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 446 // true if we should set the symbol size to the maximum of the TO and 447 // FROM sizes. It handles error conditions. 448 449 bool 450 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 451 elfcpp::STT fromtype, Defined defined, 452 Object* object, bool* adjust_common_sizes, 453 bool* adjust_dyndef, bool is_default_version) 454 { 455 *adjust_common_sizes = false; 456 *adjust_dyndef = false; 457 458 unsigned int tobits; 459 if (to->source() == Symbol::IS_UNDEFINED) 460 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true); 461 else if (to->source() != Symbol::FROM_OBJECT) 462 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false); 463 else 464 { 465 bool is_ordinary; 466 unsigned int shndx = to->shndx(&is_ordinary); 467 tobits = symbol_to_bits(to->binding(), 468 to->object()->is_dynamic(), 469 shndx, 470 is_ordinary); 471 } 472 473 if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS) 474 && !to->is_placeholder()) 475 Symbol_table::report_resolve_problem(true, 476 _("symbol '%s' used as both __thread " 477 "and non-__thread"), 478 to, defined, object); 479 480 // We use a giant switch table for symbol resolution. This code is 481 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 482 // cases; 3) it is easy to change the handling of a particular case. 483 // The alternative would be a series of conditionals, but it is easy 484 // to get the ordering wrong. This could also be done as a table, 485 // but that is no easier to understand than this large switch 486 // statement. 487 488 // These are the values generated by the bit codes. 489 enum 490 { 491 DEF = global_flag | regular_flag | def_flag, 492 WEAK_DEF = weak_flag | regular_flag | def_flag, 493 DYN_DEF = global_flag | dynamic_flag | def_flag, 494 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 495 UNDEF = global_flag | regular_flag | undef_flag, 496 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 497 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 498 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 499 COMMON = global_flag | regular_flag | common_flag, 500 WEAK_COMMON = weak_flag | regular_flag | common_flag, 501 DYN_COMMON = global_flag | dynamic_flag | common_flag, 502 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 503 }; 504 505 switch (tobits * 16 + frombits) 506 { 507 case DEF * 16 + DEF: 508 // Two definitions of the same symbol. 509 510 // If either symbol is defined by an object included using 511 // --just-symbols, then don't warn. This is for compatibility 512 // with the GNU linker. FIXME: This is a hack. 513 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 514 || (object != NULL && object->just_symbols())) 515 return false; 516 517 if (!parameters->options().muldefs()) 518 Symbol_table::report_resolve_problem(true, 519 _("multiple definition of '%s'"), 520 to, defined, object); 521 return false; 522 523 case WEAK_DEF * 16 + DEF: 524 // We've seen a weak definition, and now we see a strong 525 // definition. In the original SVR4 linker, this was treated as 526 // a multiple definition error. In the Solaris linker and the 527 // GNU linker, a weak definition followed by a regular 528 // definition causes the weak definition to be overridden. We 529 // are currently compatible with the GNU linker. In the future 530 // we should add a target specific option to change this. 531 // FIXME. 532 return true; 533 534 case DYN_DEF * 16 + DEF: 535 case DYN_WEAK_DEF * 16 + DEF: 536 // We've seen a definition in a dynamic object, and now we see a 537 // definition in a regular object. The definition in the 538 // regular object overrides the definition in the dynamic 539 // object. 540 return true; 541 542 case UNDEF * 16 + DEF: 543 case WEAK_UNDEF * 16 + DEF: 544 case DYN_UNDEF * 16 + DEF: 545 case DYN_WEAK_UNDEF * 16 + DEF: 546 // We've seen an undefined reference, and now we see a 547 // definition. We use the definition. 548 return true; 549 550 case COMMON * 16 + DEF: 551 case WEAK_COMMON * 16 + DEF: 552 case DYN_COMMON * 16 + DEF: 553 case DYN_WEAK_COMMON * 16 + DEF: 554 // We've seen a common symbol and now we see a definition. The 555 // definition overrides. 556 if (parameters->options().warn_common()) 557 Symbol_table::report_resolve_problem(false, 558 _("definition of '%s' overriding " 559 "common"), 560 to, defined, object); 561 return true; 562 563 case DEF * 16 + WEAK_DEF: 564 case WEAK_DEF * 16 + WEAK_DEF: 565 // We've seen a definition and now we see a weak definition. We 566 // ignore the new weak definition. 567 return false; 568 569 case DYN_DEF * 16 + WEAK_DEF: 570 case DYN_WEAK_DEF * 16 + WEAK_DEF: 571 // We've seen a dynamic definition and now we see a regular weak 572 // definition. The regular weak definition overrides. 573 return true; 574 575 case UNDEF * 16 + WEAK_DEF: 576 case WEAK_UNDEF * 16 + WEAK_DEF: 577 case DYN_UNDEF * 16 + WEAK_DEF: 578 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 579 // A weak definition of a currently undefined symbol. 580 return true; 581 582 case COMMON * 16 + WEAK_DEF: 583 case WEAK_COMMON * 16 + WEAK_DEF: 584 // A weak definition does not override a common definition. 585 return false; 586 587 case DYN_COMMON * 16 + WEAK_DEF: 588 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 589 // A weak definition does override a definition in a dynamic 590 // object. 591 if (parameters->options().warn_common()) 592 Symbol_table::report_resolve_problem(false, 593 _("definition of '%s' overriding " 594 "dynamic common definition"), 595 to, defined, object); 596 return true; 597 598 case DEF * 16 + DYN_DEF: 599 case WEAK_DEF * 16 + DYN_DEF: 600 // Ignore a dynamic definition if we already have a definition. 601 return false; 602 603 case DYN_DEF * 16 + DYN_DEF: 604 case DYN_WEAK_DEF * 16 + DYN_DEF: 605 // Ignore a dynamic definition if we already have a definition, 606 // unless the existing definition is an unversioned definition 607 // in the same dynamic object, and the new definition is a 608 // default version. 609 if (to->object() == object 610 && to->version() == NULL 611 && is_default_version) 612 return true; 613 return false; 614 615 case UNDEF * 16 + DYN_DEF: 616 case DYN_UNDEF * 16 + DYN_DEF: 617 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 618 // Use a dynamic definition if we have a reference. 619 return true; 620 621 case WEAK_UNDEF * 16 + DYN_DEF: 622 // When overriding a weak undef by a dynamic definition, 623 // we need to remember that the original undef was weak. 624 *adjust_dyndef = true; 625 return true; 626 627 case COMMON * 16 + DYN_DEF: 628 case WEAK_COMMON * 16 + DYN_DEF: 629 case DYN_COMMON * 16 + DYN_DEF: 630 case DYN_WEAK_COMMON * 16 + DYN_DEF: 631 // Ignore a dynamic definition if we already have a common 632 // definition. 633 return false; 634 635 case DEF * 16 + DYN_WEAK_DEF: 636 case WEAK_DEF * 16 + DYN_WEAK_DEF: 637 case DYN_DEF * 16 + DYN_WEAK_DEF: 638 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 639 // Ignore a weak dynamic definition if we already have a 640 // definition. 641 return false; 642 643 case UNDEF * 16 + DYN_WEAK_DEF: 644 // When overriding an undef by a dynamic weak definition, 645 // we need to remember that the original undef was not weak. 646 *adjust_dyndef = true; 647 return true; 648 649 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 650 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 651 // Use a weak dynamic definition if we have a reference. 652 return true; 653 654 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 655 // When overriding a weak undef by a dynamic definition, 656 // we need to remember that the original undef was weak. 657 *adjust_dyndef = true; 658 return true; 659 660 case COMMON * 16 + DYN_WEAK_DEF: 661 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 662 case DYN_COMMON * 16 + DYN_WEAK_DEF: 663 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 664 // Ignore a weak dynamic definition if we already have a common 665 // definition. 666 return false; 667 668 case DEF * 16 + UNDEF: 669 case WEAK_DEF * 16 + UNDEF: 670 case UNDEF * 16 + UNDEF: 671 // A new undefined reference tells us nothing. 672 return false; 673 674 case DYN_DEF * 16 + UNDEF: 675 case DYN_WEAK_DEF * 16 + UNDEF: 676 // For a dynamic def, we need to remember which kind of undef we see. 677 *adjust_dyndef = true; 678 return false; 679 680 case WEAK_UNDEF * 16 + UNDEF: 681 case DYN_UNDEF * 16 + UNDEF: 682 case DYN_WEAK_UNDEF * 16 + UNDEF: 683 // A strong undef overrides a dynamic or weak undef. 684 return true; 685 686 case COMMON * 16 + UNDEF: 687 case WEAK_COMMON * 16 + UNDEF: 688 case DYN_COMMON * 16 + UNDEF: 689 case DYN_WEAK_COMMON * 16 + UNDEF: 690 // A new undefined reference tells us nothing. 691 return false; 692 693 case DEF * 16 + WEAK_UNDEF: 694 case WEAK_DEF * 16 + WEAK_UNDEF: 695 case UNDEF * 16 + WEAK_UNDEF: 696 case WEAK_UNDEF * 16 + WEAK_UNDEF: 697 case DYN_UNDEF * 16 + WEAK_UNDEF: 698 case COMMON * 16 + WEAK_UNDEF: 699 case WEAK_COMMON * 16 + WEAK_UNDEF: 700 case DYN_COMMON * 16 + WEAK_UNDEF: 701 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 702 // A new weak undefined reference tells us nothing unless the 703 // exisiting symbol is a dynamic weak reference. 704 return false; 705 706 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 707 // A new weak reference overrides an existing dynamic weak reference. 708 // This is necessary because a dynamic weak reference remembers 709 // the old binding, which may not be weak. If we keeps the existing 710 // dynamic weak reference, the weakness may be dropped in the output. 711 return true; 712 713 case DYN_DEF * 16 + WEAK_UNDEF: 714 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 715 // For a dynamic def, we need to remember which kind of undef we see. 716 *adjust_dyndef = true; 717 return false; 718 719 case DEF * 16 + DYN_UNDEF: 720 case WEAK_DEF * 16 + DYN_UNDEF: 721 case DYN_DEF * 16 + DYN_UNDEF: 722 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 723 case UNDEF * 16 + DYN_UNDEF: 724 case WEAK_UNDEF * 16 + DYN_UNDEF: 725 case DYN_UNDEF * 16 + DYN_UNDEF: 726 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 727 case COMMON * 16 + DYN_UNDEF: 728 case WEAK_COMMON * 16 + DYN_UNDEF: 729 case DYN_COMMON * 16 + DYN_UNDEF: 730 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 731 // A new dynamic undefined reference tells us nothing. 732 return false; 733 734 case DEF * 16 + DYN_WEAK_UNDEF: 735 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 736 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 737 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 738 case UNDEF * 16 + DYN_WEAK_UNDEF: 739 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 740 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 741 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 742 case COMMON * 16 + DYN_WEAK_UNDEF: 743 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 744 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 745 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 746 // A new weak dynamic undefined reference tells us nothing. 747 return false; 748 749 case DEF * 16 + COMMON: 750 // A common symbol does not override a definition. 751 if (parameters->options().warn_common()) 752 Symbol_table::report_resolve_problem(false, 753 _("common '%s' overridden by " 754 "previous definition"), 755 to, defined, object); 756 return false; 757 758 case WEAK_DEF * 16 + COMMON: 759 case DYN_DEF * 16 + COMMON: 760 case DYN_WEAK_DEF * 16 + COMMON: 761 // A common symbol does override a weak definition or a dynamic 762 // definition. 763 return true; 764 765 case UNDEF * 16 + COMMON: 766 case WEAK_UNDEF * 16 + COMMON: 767 case DYN_UNDEF * 16 + COMMON: 768 case DYN_WEAK_UNDEF * 16 + COMMON: 769 // A common symbol is a definition for a reference. 770 return true; 771 772 case COMMON * 16 + COMMON: 773 // Set the size to the maximum. 774 *adjust_common_sizes = true; 775 return false; 776 777 case WEAK_COMMON * 16 + COMMON: 778 // I'm not sure just what a weak common symbol means, but 779 // presumably it can be overridden by a regular common symbol. 780 return true; 781 782 case DYN_COMMON * 16 + COMMON: 783 case DYN_WEAK_COMMON * 16 + COMMON: 784 // Use the real common symbol, but adjust the size if necessary. 785 *adjust_common_sizes = true; 786 return true; 787 788 case DEF * 16 + WEAK_COMMON: 789 case WEAK_DEF * 16 + WEAK_COMMON: 790 case DYN_DEF * 16 + WEAK_COMMON: 791 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 792 // Whatever a weak common symbol is, it won't override a 793 // definition. 794 return false; 795 796 case UNDEF * 16 + WEAK_COMMON: 797 case WEAK_UNDEF * 16 + WEAK_COMMON: 798 case DYN_UNDEF * 16 + WEAK_COMMON: 799 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 800 // A weak common symbol is better than an undefined symbol. 801 return true; 802 803 case COMMON * 16 + WEAK_COMMON: 804 case WEAK_COMMON * 16 + WEAK_COMMON: 805 case DYN_COMMON * 16 + WEAK_COMMON: 806 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 807 // Ignore a weak common symbol in the presence of a real common 808 // symbol. 809 return false; 810 811 case DEF * 16 + DYN_COMMON: 812 case WEAK_DEF * 16 + DYN_COMMON: 813 case DYN_DEF * 16 + DYN_COMMON: 814 case DYN_WEAK_DEF * 16 + DYN_COMMON: 815 // Ignore a dynamic common symbol in the presence of a 816 // definition. 817 return false; 818 819 case UNDEF * 16 + DYN_COMMON: 820 case WEAK_UNDEF * 16 + DYN_COMMON: 821 case DYN_UNDEF * 16 + DYN_COMMON: 822 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 823 // A dynamic common symbol is a definition of sorts. 824 return true; 825 826 case COMMON * 16 + DYN_COMMON: 827 case WEAK_COMMON * 16 + DYN_COMMON: 828 case DYN_COMMON * 16 + DYN_COMMON: 829 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 830 // Set the size to the maximum. 831 *adjust_common_sizes = true; 832 return false; 833 834 case DEF * 16 + DYN_WEAK_COMMON: 835 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 836 case DYN_DEF * 16 + DYN_WEAK_COMMON: 837 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 838 // A common symbol is ignored in the face of a definition. 839 return false; 840 841 case UNDEF * 16 + DYN_WEAK_COMMON: 842 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 843 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 844 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 845 // I guess a weak common symbol is better than a definition. 846 return true; 847 848 case COMMON * 16 + DYN_WEAK_COMMON: 849 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 850 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 851 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 852 // Set the size to the maximum. 853 *adjust_common_sizes = true; 854 return false; 855 856 default: 857 gold_unreachable(); 858 } 859 } 860 861 // Issue an error or warning due to symbol resolution. IS_ERROR 862 // indicates an error rather than a warning. MSG is the error 863 // message; it is expected to have a %s for the symbol name. TO is 864 // the existing symbol. DEFINED/OBJECT is where the new symbol was 865 // found. 866 867 // FIXME: We should have better location information here. When the 868 // symbol is defined, we should be able to pull the location from the 869 // debug info if there is any. 870 871 void 872 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 873 const Symbol* to, Defined defined, 874 Object* object) 875 { 876 std::string demangled(to->demangled_name()); 877 size_t len = strlen(msg) + demangled.length() + 10; 878 char* buf = new char[len]; 879 snprintf(buf, len, msg, demangled.c_str()); 880 881 const char* objname; 882 switch (defined) 883 { 884 case OBJECT: 885 objname = object->name().c_str(); 886 break; 887 case COPY: 888 objname = _("COPY reloc"); 889 break; 890 case DEFSYM: 891 case UNDEFINED: 892 objname = _("command line"); 893 break; 894 case SCRIPT: 895 objname = _("linker script"); 896 break; 897 case PREDEFINED: 898 case INCREMENTAL_BASE: 899 objname = _("linker defined"); 900 break; 901 default: 902 gold_unreachable(); 903 } 904 905 if (is_error) 906 gold_error("%s: %s", objname, buf); 907 else 908 gold_warning("%s: %s", objname, buf); 909 910 delete[] buf; 911 912 if (to->source() == Symbol::FROM_OBJECT) 913 objname = to->object()->name().c_str(); 914 else 915 objname = _("command line"); 916 gold_info("%s: %s: previous definition here", program_name, objname); 917 } 918 919 // A special case of should_override which is only called for a strong 920 // defined symbol from a regular object file. This is used when 921 // defining special symbols. 922 923 bool 924 Symbol_table::should_override_with_special(const Symbol* to, 925 elfcpp::STT fromtype, 926 Defined defined) 927 { 928 bool adjust_common_sizes; 929 bool adjust_dyn_def; 930 unsigned int frombits = global_flag | regular_flag | def_flag; 931 bool ret = Symbol_table::should_override(to, frombits, fromtype, defined, 932 NULL, &adjust_common_sizes, 933 &adjust_dyn_def, false); 934 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 935 return ret; 936 } 937 938 // Override symbol base with a special symbol. 939 940 void 941 Symbol::override_base_with_special(const Symbol* from) 942 { 943 bool same_name = this->name_ == from->name_; 944 gold_assert(same_name || this->has_alias()); 945 946 // If we are overriding an undef, remember the original binding. 947 if (this->is_undefined()) 948 this->set_undef_binding(this->binding_); 949 950 this->source_ = from->source_; 951 switch (from->source_) 952 { 953 case FROM_OBJECT: 954 this->u_.from_object = from->u_.from_object; 955 break; 956 case IN_OUTPUT_DATA: 957 this->u_.in_output_data = from->u_.in_output_data; 958 break; 959 case IN_OUTPUT_SEGMENT: 960 this->u_.in_output_segment = from->u_.in_output_segment; 961 break; 962 case IS_CONSTANT: 963 case IS_UNDEFINED: 964 break; 965 default: 966 gold_unreachable(); 967 break; 968 } 969 970 if (same_name) 971 { 972 // When overriding a versioned symbol with a special symbol, we 973 // may be changing the version. This will happen if we see a 974 // special symbol such as "_end" defined in a shared object with 975 // one version (from a version script), but we want to define it 976 // here with a different version (from a different version 977 // script). 978 this->version_ = from->version_; 979 } 980 this->type_ = from->type_; 981 this->binding_ = from->binding_; 982 this->override_visibility(from->visibility_); 983 this->nonvis_ = from->nonvis_; 984 985 // Special symbols are always considered to be regular symbols. 986 this->in_reg_ = true; 987 988 if (from->needs_dynsym_entry_) 989 this->needs_dynsym_entry_ = true; 990 if (from->needs_dynsym_value_) 991 this->needs_dynsym_value_ = true; 992 993 this->is_predefined_ = from->is_predefined_; 994 995 // We shouldn't see these flags. If we do, we need to handle them 996 // somehow. 997 gold_assert(!from->is_forwarder_); 998 gold_assert(!from->has_plt_offset()); 999 gold_assert(!from->has_warning_); 1000 gold_assert(!from->is_copied_from_dynobj_); 1001 gold_assert(!from->is_forced_local_); 1002 } 1003 1004 // Override a symbol with a special symbol. 1005 1006 template<int size> 1007 void 1008 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 1009 { 1010 this->override_base_with_special(from); 1011 this->value_ = from->value_; 1012 this->symsize_ = from->symsize_; 1013 } 1014 1015 // Override TOSYM with the special symbol FROMSYM. This handles all 1016 // aliases of TOSYM. 1017 1018 template<int size> 1019 void 1020 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 1021 const Sized_symbol<size>* fromsym) 1022 { 1023 tosym->override_with_special(fromsym); 1024 if (tosym->has_alias()) 1025 { 1026 Symbol* sym = this->weak_aliases_[tosym]; 1027 gold_assert(sym != NULL); 1028 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 1029 do 1030 { 1031 ssym->override_with_special(fromsym); 1032 sym = this->weak_aliases_[ssym]; 1033 gold_assert(sym != NULL); 1034 ssym = this->get_sized_symbol<size>(sym); 1035 } 1036 while (ssym != tosym); 1037 } 1038 if (tosym->binding() == elfcpp::STB_LOCAL 1039 || ((tosym->visibility() == elfcpp::STV_HIDDEN 1040 || tosym->visibility() == elfcpp::STV_INTERNAL) 1041 && (tosym->binding() == elfcpp::STB_GLOBAL 1042 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 1043 || tosym->binding() == elfcpp::STB_WEAK) 1044 && !parameters->options().relocatable())) 1045 this->force_local(tosym); 1046 } 1047 1048 // Instantiate the templates we need. We could use the configure 1049 // script to restrict this to only the ones needed for implemented 1050 // targets. 1051 1052 // We have to instantiate both big and little endian versions because 1053 // these are used by other templates that depends on size only. 1054 1055 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1056 template 1057 void 1058 Symbol_table::resolve<32, false>( 1059 Sized_symbol<32>* to, 1060 const elfcpp::Sym<32, false>& sym, 1061 unsigned int st_shndx, 1062 bool is_ordinary, 1063 unsigned int orig_st_shndx, 1064 Object* object, 1065 const char* version, 1066 bool is_default_version); 1067 1068 template 1069 void 1070 Symbol_table::resolve<32, true>( 1071 Sized_symbol<32>* to, 1072 const elfcpp::Sym<32, true>& sym, 1073 unsigned int st_shndx, 1074 bool is_ordinary, 1075 unsigned int orig_st_shndx, 1076 Object* object, 1077 const char* version, 1078 bool is_default_version); 1079 #endif 1080 1081 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1082 template 1083 void 1084 Symbol_table::resolve<64, false>( 1085 Sized_symbol<64>* to, 1086 const elfcpp::Sym<64, false>& sym, 1087 unsigned int st_shndx, 1088 bool is_ordinary, 1089 unsigned int orig_st_shndx, 1090 Object* object, 1091 const char* version, 1092 bool is_default_version); 1093 1094 template 1095 void 1096 Symbol_table::resolve<64, true>( 1097 Sized_symbol<64>* to, 1098 const elfcpp::Sym<64, true>& sym, 1099 unsigned int st_shndx, 1100 bool is_ordinary, 1101 unsigned int orig_st_shndx, 1102 Object* object, 1103 const char* version, 1104 bool is_default_version); 1105 #endif 1106 1107 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1108 template 1109 void 1110 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1111 const Sized_symbol<32>*); 1112 #endif 1113 1114 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1115 template 1116 void 1117 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1118 const Sized_symbol<64>*); 1119 #endif 1120 1121 } // End namespace gold. 1122
