1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright (C) 2006-2014 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, elfcpp::STT type) 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 (type == elfcpp::STT_COMMON) 222 bits |= common_flag; 223 else if (!is_ordinary && Symbol::is_common_shndx(shndx)) 224 bits |= common_flag; 225 else 226 bits |= def_flag; 227 break; 228 } 229 230 return bits; 231 } 232 233 // Resolve a symbol. This is called the second and subsequent times 234 // we see a symbol. TO is the pre-existing symbol. ST_SHNDX is the 235 // section index for SYM, possibly adjusted for many sections. 236 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather 237 // than a special code. ORIG_ST_SHNDX is the original section index, 238 // before any munging because of discarded sections, except that all 239 // non-ordinary section indexes are mapped to SHN_UNDEF. VERSION is 240 // the version of SYM. 241 242 template<int size, bool big_endian> 243 void 244 Symbol_table::resolve(Sized_symbol<size>* to, 245 const elfcpp::Sym<size, big_endian>& sym, 246 unsigned int st_shndx, bool is_ordinary, 247 unsigned int orig_st_shndx, 248 Object* object, const char* version) 249 { 250 // It's possible for a symbol to be defined in an object file 251 // using .symver to give it a version, and for there to also be 252 // a linker script giving that symbol the same version. We 253 // don't want to give a multiple-definition error for this 254 // harmless redefinition. 255 bool to_is_ordinary; 256 if (to->source() == Symbol::FROM_OBJECT 257 && to->object() == object 258 && is_ordinary 259 && to->is_defined() 260 && to->shndx(&to_is_ordinary) == st_shndx 261 && to_is_ordinary 262 && to->value() == sym.get_st_value()) 263 return; 264 265 if (parameters->target().has_resolve()) 266 { 267 Sized_target<size, big_endian>* sized_target; 268 sized_target = parameters->sized_target<size, big_endian>(); 269 sized_target->resolve(to, sym, object, version); 270 return; 271 } 272 273 if (!object->is_dynamic()) 274 { 275 // Record that we've seen this symbol in a regular object. 276 to->set_in_reg(); 277 } 278 else if (st_shndx == elfcpp::SHN_UNDEF 279 && (to->visibility() == elfcpp::STV_HIDDEN 280 || to->visibility() == elfcpp::STV_INTERNAL)) 281 { 282 // The symbol is hidden, so a reference from a shared object 283 // cannot bind to it. We tried issuing a warning in this case, 284 // but that produces false positives when the symbol is 285 // actually resolved in a different shared object (PR 15574). 286 return; 287 } 288 else 289 { 290 // Record that we've seen this symbol in a dynamic object. 291 to->set_in_dyn(); 292 } 293 294 // Record if we've seen this symbol in a real ELF object (i.e., the 295 // symbol is referenced from outside the world known to the plugin). 296 if (object->pluginobj() == NULL && !object->is_dynamic()) 297 to->set_in_real_elf(); 298 299 // If we're processing replacement files, allow new symbols to override 300 // the placeholders from the plugin objects. 301 // Treat common symbols specially since it is possible that an ELF 302 // file increased the size of the alignment. 303 if (to->source() == Symbol::FROM_OBJECT) 304 { 305 Pluginobj* obj = to->object()->pluginobj(); 306 if (obj != NULL 307 && parameters->options().plugins()->in_replacement_phase()) 308 { 309 bool adjust_common = false; 310 typename Sized_symbol<size>::Size_type tosize = 0; 311 typename Sized_symbol<size>::Value_type tovalue = 0; 312 if (to->is_common() && !is_ordinary && st_shndx == elfcpp::SHN_COMMON) 313 { 314 adjust_common = true; 315 tosize = to->symsize(); 316 tovalue = to->value(); 317 } 318 this->override(to, sym, st_shndx, is_ordinary, object, version); 319 if (adjust_common) 320 { 321 if (tosize > to->symsize()) 322 to->set_symsize(tosize); 323 if (tovalue > to->value()) 324 to->set_value(tovalue); 325 } 326 return; 327 } 328 } 329 330 // A new weak undefined reference, merging with an old weak 331 // reference, could be a One Definition Rule (ODR) violation -- 332 // especially if the types or sizes of the references differ. We'll 333 // store such pairs and look them up later to make sure they 334 // actually refer to the same lines of code. We also check 335 // combinations of weak and strong, which might occur if one case is 336 // inline and the other is not. (Note: not all ODR violations can 337 // be found this way, and not everything this finds is an ODR 338 // violation. But it's helpful to warn about.) 339 if (parameters->options().detect_odr_violations() 340 && (sym.get_st_bind() == elfcpp::STB_WEAK 341 || to->binding() == elfcpp::STB_WEAK) 342 && orig_st_shndx != elfcpp::SHN_UNDEF 343 && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF 344 && to_is_ordinary 345 && sym.get_st_size() != 0 // Ignore weird 0-sized symbols. 346 && to->symsize() != 0 347 && (sym.get_st_type() != to->type() 348 || sym.get_st_size() != to->symsize()) 349 // C does not have a concept of ODR, so we only need to do this 350 // on C++ symbols. These have (mangled) names starting with _Z. 351 && to->name()[0] == '_' && to->name()[1] == 'Z') 352 { 353 Symbol_location fromloc 354 = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) }; 355 Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary), 356 static_cast<off_t>(to->value()) }; 357 this->candidate_odr_violations_[to->name()].insert(fromloc); 358 this->candidate_odr_violations_[to->name()].insert(toloc); 359 } 360 361 // Plugins don't provide a symbol type, so adopt the existing type 362 // if the FROM symbol is from a plugin. 363 elfcpp::STT fromtype = (object->pluginobj() != NULL 364 ? to->type() 365 : sym.get_st_type()); 366 unsigned int frombits = symbol_to_bits(sym.get_st_bind(), 367 object->is_dynamic(), 368 st_shndx, is_ordinary, 369 fromtype); 370 371 bool adjust_common_sizes; 372 bool adjust_dyndef; 373 typename Sized_symbol<size>::Size_type tosize = to->symsize(); 374 if (Symbol_table::should_override(to, frombits, fromtype, OBJECT, 375 object, &adjust_common_sizes, 376 &adjust_dyndef)) 377 { 378 elfcpp::STB tobinding = to->binding(); 379 typename Sized_symbol<size>::Value_type tovalue = to->value(); 380 this->override(to, sym, st_shndx, is_ordinary, object, version); 381 if (adjust_common_sizes) 382 { 383 if (tosize > to->symsize()) 384 to->set_symsize(tosize); 385 if (tovalue > to->value()) 386 to->set_value(tovalue); 387 } 388 if (adjust_dyndef) 389 { 390 // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF. 391 // Remember which kind of UNDEF it was for future reference. 392 to->set_undef_binding(tobinding); 393 } 394 } 395 else 396 { 397 if (adjust_common_sizes) 398 { 399 if (sym.get_st_size() > tosize) 400 to->set_symsize(sym.get_st_size()); 401 if (sym.get_st_value() > to->value()) 402 to->set_value(sym.get_st_value()); 403 } 404 if (adjust_dyndef) 405 { 406 // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF. 407 // Remember which kind of UNDEF it was. 408 to->set_undef_binding(sym.get_st_bind()); 409 } 410 // The ELF ABI says that even for a reference to a symbol we 411 // merge the visibility. 412 to->override_visibility(sym.get_st_visibility()); 413 } 414 415 if (adjust_common_sizes && parameters->options().warn_common()) 416 { 417 if (tosize > sym.get_st_size()) 418 Symbol_table::report_resolve_problem(false, 419 _("common of '%s' overriding " 420 "smaller common"), 421 to, OBJECT, object); 422 else if (tosize < sym.get_st_size()) 423 Symbol_table::report_resolve_problem(false, 424 _("common of '%s' overidden by " 425 "larger common"), 426 to, OBJECT, object); 427 else 428 Symbol_table::report_resolve_problem(false, 429 _("multiple common of '%s'"), 430 to, OBJECT, object); 431 } 432 } 433 434 // Handle the core of symbol resolution. This is called with the 435 // existing symbol, TO, and a bitflag describing the new symbol. This 436 // returns true if we should override the existing symbol with the new 437 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 438 // true if we should set the symbol size to the maximum of the TO and 439 // FROM sizes. It handles error conditions. 440 441 bool 442 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 443 elfcpp::STT fromtype, Defined defined, 444 Object* object, bool* adjust_common_sizes, 445 bool* adjust_dyndef) 446 { 447 *adjust_common_sizes = false; 448 *adjust_dyndef = false; 449 450 unsigned int tobits; 451 if (to->source() == Symbol::IS_UNDEFINED) 452 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true, 453 to->type()); 454 else if (to->source() != Symbol::FROM_OBJECT) 455 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false, 456 to->type()); 457 else 458 { 459 bool is_ordinary; 460 unsigned int shndx = to->shndx(&is_ordinary); 461 tobits = symbol_to_bits(to->binding(), 462 to->object()->is_dynamic(), 463 shndx, 464 is_ordinary, 465 to->type()); 466 } 467 468 if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS) 469 && !to->is_placeholder()) 470 Symbol_table::report_resolve_problem(true, 471 _("symbol '%s' used as both __thread " 472 "and non-__thread"), 473 to, defined, object); 474 475 // We use a giant switch table for symbol resolution. This code is 476 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 477 // cases; 3) it is easy to change the handling of a particular case. 478 // The alternative would be a series of conditionals, but it is easy 479 // to get the ordering wrong. This could also be done as a table, 480 // but that is no easier to understand than this large switch 481 // statement. 482 483 // These are the values generated by the bit codes. 484 enum 485 { 486 DEF = global_flag | regular_flag | def_flag, 487 WEAK_DEF = weak_flag | regular_flag | def_flag, 488 DYN_DEF = global_flag | dynamic_flag | def_flag, 489 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 490 UNDEF = global_flag | regular_flag | undef_flag, 491 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 492 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 493 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 494 COMMON = global_flag | regular_flag | common_flag, 495 WEAK_COMMON = weak_flag | regular_flag | common_flag, 496 DYN_COMMON = global_flag | dynamic_flag | common_flag, 497 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 498 }; 499 500 switch (tobits * 16 + frombits) 501 { 502 case DEF * 16 + DEF: 503 // Two definitions of the same symbol. 504 505 // If either symbol is defined by an object included using 506 // --just-symbols, then don't warn. This is for compatibility 507 // with the GNU linker. FIXME: This is a hack. 508 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 509 || (object != NULL && object->just_symbols())) 510 return false; 511 512 if (!parameters->options().muldefs()) 513 Symbol_table::report_resolve_problem(true, 514 _("multiple definition of '%s'"), 515 to, defined, object); 516 return false; 517 518 case WEAK_DEF * 16 + DEF: 519 // We've seen a weak definition, and now we see a strong 520 // definition. In the original SVR4 linker, this was treated as 521 // a multiple definition error. In the Solaris linker and the 522 // GNU linker, a weak definition followed by a regular 523 // definition causes the weak definition to be overridden. We 524 // are currently compatible with the GNU linker. In the future 525 // we should add a target specific option to change this. 526 // FIXME. 527 return true; 528 529 case DYN_DEF * 16 + DEF: 530 case DYN_WEAK_DEF * 16 + DEF: 531 // We've seen a definition in a dynamic object, and now we see a 532 // definition in a regular object. The definition in the 533 // regular object overrides the definition in the dynamic 534 // object. 535 return true; 536 537 case UNDEF * 16 + DEF: 538 case WEAK_UNDEF * 16 + DEF: 539 case DYN_UNDEF * 16 + DEF: 540 case DYN_WEAK_UNDEF * 16 + DEF: 541 // We've seen an undefined reference, and now we see a 542 // definition. We use the definition. 543 return true; 544 545 case COMMON * 16 + DEF: 546 case WEAK_COMMON * 16 + DEF: 547 case DYN_COMMON * 16 + DEF: 548 case DYN_WEAK_COMMON * 16 + DEF: 549 // We've seen a common symbol and now we see a definition. The 550 // definition overrides. 551 if (parameters->options().warn_common()) 552 Symbol_table::report_resolve_problem(false, 553 _("definition of '%s' overriding " 554 "common"), 555 to, defined, object); 556 return true; 557 558 case DEF * 16 + WEAK_DEF: 559 case WEAK_DEF * 16 + WEAK_DEF: 560 // We've seen a definition and now we see a weak definition. We 561 // ignore the new weak definition. 562 return false; 563 564 case DYN_DEF * 16 + WEAK_DEF: 565 case DYN_WEAK_DEF * 16 + WEAK_DEF: 566 // We've seen a dynamic definition and now we see a regular weak 567 // definition. The regular weak definition overrides. 568 return true; 569 570 case UNDEF * 16 + WEAK_DEF: 571 case WEAK_UNDEF * 16 + WEAK_DEF: 572 case DYN_UNDEF * 16 + WEAK_DEF: 573 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 574 // A weak definition of a currently undefined symbol. 575 return true; 576 577 case COMMON * 16 + WEAK_DEF: 578 case WEAK_COMMON * 16 + WEAK_DEF: 579 // A weak definition does not override a common definition. 580 return false; 581 582 case DYN_COMMON * 16 + WEAK_DEF: 583 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 584 // A weak definition does override a definition in a dynamic 585 // object. 586 if (parameters->options().warn_common()) 587 Symbol_table::report_resolve_problem(false, 588 _("definition of '%s' overriding " 589 "dynamic common definition"), 590 to, defined, object); 591 return true; 592 593 case DEF * 16 + DYN_DEF: 594 case WEAK_DEF * 16 + DYN_DEF: 595 case DYN_DEF * 16 + DYN_DEF: 596 case DYN_WEAK_DEF * 16 + DYN_DEF: 597 // Ignore a dynamic definition if we already have a definition. 598 return false; 599 600 case UNDEF * 16 + DYN_DEF: 601 case DYN_UNDEF * 16 + DYN_DEF: 602 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 603 // Use a dynamic definition if we have a reference. 604 return true; 605 606 case WEAK_UNDEF * 16 + DYN_DEF: 607 // When overriding a weak undef by a dynamic definition, 608 // we need to remember that the original undef was weak. 609 *adjust_dyndef = true; 610 return true; 611 612 case COMMON * 16 + DYN_DEF: 613 case WEAK_COMMON * 16 + DYN_DEF: 614 case DYN_COMMON * 16 + DYN_DEF: 615 case DYN_WEAK_COMMON * 16 + DYN_DEF: 616 // Ignore a dynamic definition if we already have a common 617 // definition. 618 return false; 619 620 case DEF * 16 + DYN_WEAK_DEF: 621 case WEAK_DEF * 16 + DYN_WEAK_DEF: 622 case DYN_DEF * 16 + DYN_WEAK_DEF: 623 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 624 // Ignore a weak dynamic definition if we already have a 625 // definition. 626 return false; 627 628 case UNDEF * 16 + DYN_WEAK_DEF: 629 // When overriding an undef by a dynamic weak definition, 630 // we need to remember that the original undef was not weak. 631 *adjust_dyndef = true; 632 return true; 633 634 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 635 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 636 // Use a weak dynamic definition if we have a reference. 637 return true; 638 639 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 640 // When overriding a weak undef by a dynamic definition, 641 // we need to remember that the original undef was weak. 642 *adjust_dyndef = true; 643 return true; 644 645 case COMMON * 16 + DYN_WEAK_DEF: 646 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 647 case DYN_COMMON * 16 + DYN_WEAK_DEF: 648 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 649 // Ignore a weak dynamic definition if we already have a common 650 // definition. 651 return false; 652 653 case DEF * 16 + UNDEF: 654 case WEAK_DEF * 16 + UNDEF: 655 case UNDEF * 16 + UNDEF: 656 // A new undefined reference tells us nothing. 657 return false; 658 659 case DYN_DEF * 16 + UNDEF: 660 case DYN_WEAK_DEF * 16 + UNDEF: 661 // For a dynamic def, we need to remember which kind of undef we see. 662 *adjust_dyndef = true; 663 return false; 664 665 case WEAK_UNDEF * 16 + UNDEF: 666 case DYN_UNDEF * 16 + UNDEF: 667 case DYN_WEAK_UNDEF * 16 + UNDEF: 668 // A strong undef overrides a dynamic or weak undef. 669 return true; 670 671 case COMMON * 16 + UNDEF: 672 case WEAK_COMMON * 16 + UNDEF: 673 case DYN_COMMON * 16 + UNDEF: 674 case DYN_WEAK_COMMON * 16 + UNDEF: 675 // A new undefined reference tells us nothing. 676 return false; 677 678 case DEF * 16 + WEAK_UNDEF: 679 case WEAK_DEF * 16 + WEAK_UNDEF: 680 case UNDEF * 16 + WEAK_UNDEF: 681 case WEAK_UNDEF * 16 + WEAK_UNDEF: 682 case DYN_UNDEF * 16 + WEAK_UNDEF: 683 case COMMON * 16 + WEAK_UNDEF: 684 case WEAK_COMMON * 16 + WEAK_UNDEF: 685 case DYN_COMMON * 16 + WEAK_UNDEF: 686 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 687 // A new weak undefined reference tells us nothing unless the 688 // exisiting symbol is a dynamic weak reference. 689 return false; 690 691 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 692 // A new weak reference overrides an existing dynamic weak reference. 693 // This is necessary because a dynamic weak reference remembers 694 // the old binding, which may not be weak. If we keeps the existing 695 // dynamic weak reference, the weakness may be dropped in the output. 696 return true; 697 698 case DYN_DEF * 16 + WEAK_UNDEF: 699 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 700 // For a dynamic def, we need to remember which kind of undef we see. 701 *adjust_dyndef = true; 702 return false; 703 704 case DEF * 16 + DYN_UNDEF: 705 case WEAK_DEF * 16 + DYN_UNDEF: 706 case DYN_DEF * 16 + DYN_UNDEF: 707 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 708 case UNDEF * 16 + DYN_UNDEF: 709 case WEAK_UNDEF * 16 + DYN_UNDEF: 710 case DYN_UNDEF * 16 + DYN_UNDEF: 711 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 712 case COMMON * 16 + DYN_UNDEF: 713 case WEAK_COMMON * 16 + DYN_UNDEF: 714 case DYN_COMMON * 16 + DYN_UNDEF: 715 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 716 // A new dynamic undefined reference tells us nothing. 717 return false; 718 719 case DEF * 16 + DYN_WEAK_UNDEF: 720 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 721 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 722 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 723 case UNDEF * 16 + DYN_WEAK_UNDEF: 724 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 725 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 726 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 727 case COMMON * 16 + DYN_WEAK_UNDEF: 728 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 729 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 730 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 731 // A new weak dynamic undefined reference tells us nothing. 732 return false; 733 734 case DEF * 16 + COMMON: 735 // A common symbol does not override a definition. 736 if (parameters->options().warn_common()) 737 Symbol_table::report_resolve_problem(false, 738 _("common '%s' overridden by " 739 "previous definition"), 740 to, defined, object); 741 return false; 742 743 case WEAK_DEF * 16 + COMMON: 744 case DYN_DEF * 16 + COMMON: 745 case DYN_WEAK_DEF * 16 + COMMON: 746 // A common symbol does override a weak definition or a dynamic 747 // definition. 748 return true; 749 750 case UNDEF * 16 + COMMON: 751 case WEAK_UNDEF * 16 + COMMON: 752 case DYN_UNDEF * 16 + COMMON: 753 case DYN_WEAK_UNDEF * 16 + COMMON: 754 // A common symbol is a definition for a reference. 755 return true; 756 757 case COMMON * 16 + COMMON: 758 // Set the size to the maximum. 759 *adjust_common_sizes = true; 760 return false; 761 762 case WEAK_COMMON * 16 + COMMON: 763 // I'm not sure just what a weak common symbol means, but 764 // presumably it can be overridden by a regular common symbol. 765 return true; 766 767 case DYN_COMMON * 16 + COMMON: 768 case DYN_WEAK_COMMON * 16 + COMMON: 769 // Use the real common symbol, but adjust the size if necessary. 770 *adjust_common_sizes = true; 771 return true; 772 773 case DEF * 16 + WEAK_COMMON: 774 case WEAK_DEF * 16 + WEAK_COMMON: 775 case DYN_DEF * 16 + WEAK_COMMON: 776 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 777 // Whatever a weak common symbol is, it won't override a 778 // definition. 779 return false; 780 781 case UNDEF * 16 + WEAK_COMMON: 782 case WEAK_UNDEF * 16 + WEAK_COMMON: 783 case DYN_UNDEF * 16 + WEAK_COMMON: 784 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 785 // A weak common symbol is better than an undefined symbol. 786 return true; 787 788 case COMMON * 16 + WEAK_COMMON: 789 case WEAK_COMMON * 16 + WEAK_COMMON: 790 case DYN_COMMON * 16 + WEAK_COMMON: 791 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 792 // Ignore a weak common symbol in the presence of a real common 793 // symbol. 794 return false; 795 796 case DEF * 16 + DYN_COMMON: 797 case WEAK_DEF * 16 + DYN_COMMON: 798 case DYN_DEF * 16 + DYN_COMMON: 799 case DYN_WEAK_DEF * 16 + DYN_COMMON: 800 // Ignore a dynamic common symbol in the presence of a 801 // definition. 802 return false; 803 804 case UNDEF * 16 + DYN_COMMON: 805 case WEAK_UNDEF * 16 + DYN_COMMON: 806 case DYN_UNDEF * 16 + DYN_COMMON: 807 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 808 // A dynamic common symbol is a definition of sorts. 809 return true; 810 811 case COMMON * 16 + DYN_COMMON: 812 case WEAK_COMMON * 16 + DYN_COMMON: 813 case DYN_COMMON * 16 + DYN_COMMON: 814 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 815 // Set the size to the maximum. 816 *adjust_common_sizes = true; 817 return false; 818 819 case DEF * 16 + DYN_WEAK_COMMON: 820 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 821 case DYN_DEF * 16 + DYN_WEAK_COMMON: 822 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 823 // A common symbol is ignored in the face of a definition. 824 return false; 825 826 case UNDEF * 16 + DYN_WEAK_COMMON: 827 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 828 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 829 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 830 // I guess a weak common symbol is better than a definition. 831 return true; 832 833 case COMMON * 16 + DYN_WEAK_COMMON: 834 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 835 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 836 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 837 // Set the size to the maximum. 838 *adjust_common_sizes = true; 839 return false; 840 841 default: 842 gold_unreachable(); 843 } 844 } 845 846 // Issue an error or warning due to symbol resolution. IS_ERROR 847 // indicates an error rather than a warning. MSG is the error 848 // message; it is expected to have a %s for the symbol name. TO is 849 // the existing symbol. DEFINED/OBJECT is where the new symbol was 850 // found. 851 852 // FIXME: We should have better location information here. When the 853 // symbol is defined, we should be able to pull the location from the 854 // debug info if there is any. 855 856 void 857 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 858 const Symbol* to, Defined defined, 859 Object* object) 860 { 861 std::string demangled(to->demangled_name()); 862 size_t len = strlen(msg) + demangled.length() + 10; 863 char* buf = new char[len]; 864 snprintf(buf, len, msg, demangled.c_str()); 865 866 const char* objname; 867 switch (defined) 868 { 869 case OBJECT: 870 objname = object->name().c_str(); 871 break; 872 case COPY: 873 objname = _("COPY reloc"); 874 break; 875 case DEFSYM: 876 case UNDEFINED: 877 objname = _("command line"); 878 break; 879 case SCRIPT: 880 objname = _("linker script"); 881 break; 882 case PREDEFINED: 883 case INCREMENTAL_BASE: 884 objname = _("linker defined"); 885 break; 886 default: 887 gold_unreachable(); 888 } 889 890 if (is_error) 891 gold_error("%s: %s", objname, buf); 892 else 893 gold_warning("%s: %s", objname, buf); 894 895 delete[] buf; 896 897 if (to->source() == Symbol::FROM_OBJECT) 898 objname = to->object()->name().c_str(); 899 else 900 objname = _("command line"); 901 gold_info("%s: %s: previous definition here", program_name, objname); 902 } 903 904 // A special case of should_override which is only called for a strong 905 // defined symbol from a regular object file. This is used when 906 // defining special symbols. 907 908 bool 909 Symbol_table::should_override_with_special(const Symbol* to, 910 elfcpp::STT fromtype, 911 Defined defined) 912 { 913 bool adjust_common_sizes; 914 bool adjust_dyn_def; 915 unsigned int frombits = global_flag | regular_flag | def_flag; 916 bool ret = Symbol_table::should_override(to, frombits, fromtype, defined, 917 NULL, &adjust_common_sizes, 918 &adjust_dyn_def); 919 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 920 return ret; 921 } 922 923 // Override symbol base with a special symbol. 924 925 void 926 Symbol::override_base_with_special(const Symbol* from) 927 { 928 bool same_name = this->name_ == from->name_; 929 gold_assert(same_name || this->has_alias()); 930 931 // If we are overriding an undef, remember the original binding. 932 if (this->is_undefined()) 933 this->set_undef_binding(this->binding_); 934 935 this->source_ = from->source_; 936 switch (from->source_) 937 { 938 case FROM_OBJECT: 939 this->u_.from_object = from->u_.from_object; 940 break; 941 case IN_OUTPUT_DATA: 942 this->u_.in_output_data = from->u_.in_output_data; 943 break; 944 case IN_OUTPUT_SEGMENT: 945 this->u_.in_output_segment = from->u_.in_output_segment; 946 break; 947 case IS_CONSTANT: 948 case IS_UNDEFINED: 949 break; 950 default: 951 gold_unreachable(); 952 break; 953 } 954 955 if (same_name) 956 { 957 // When overriding a versioned symbol with a special symbol, we 958 // may be changing the version. This will happen if we see a 959 // special symbol such as "_end" defined in a shared object with 960 // one version (from a version script), but we want to define it 961 // here with a different version (from a different version 962 // script). 963 this->version_ = from->version_; 964 } 965 this->type_ = from->type_; 966 this->binding_ = from->binding_; 967 this->override_visibility(from->visibility_); 968 this->nonvis_ = from->nonvis_; 969 970 // Special symbols are always considered to be regular symbols. 971 this->in_reg_ = true; 972 973 if (from->needs_dynsym_entry_) 974 this->needs_dynsym_entry_ = true; 975 if (from->needs_dynsym_value_) 976 this->needs_dynsym_value_ = true; 977 978 this->is_predefined_ = from->is_predefined_; 979 980 // We shouldn't see these flags. If we do, we need to handle them 981 // somehow. 982 gold_assert(!from->is_forwarder_); 983 gold_assert(!from->has_plt_offset()); 984 gold_assert(!from->has_warning_); 985 gold_assert(!from->is_copied_from_dynobj_); 986 gold_assert(!from->is_forced_local_); 987 } 988 989 // Override a symbol with a special symbol. 990 991 template<int size> 992 void 993 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 994 { 995 this->override_base_with_special(from); 996 this->value_ = from->value_; 997 this->symsize_ = from->symsize_; 998 } 999 1000 // Override TOSYM with the special symbol FROMSYM. This handles all 1001 // aliases of TOSYM. 1002 1003 template<int size> 1004 void 1005 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 1006 const Sized_symbol<size>* fromsym) 1007 { 1008 tosym->override_with_special(fromsym); 1009 if (tosym->has_alias()) 1010 { 1011 Symbol* sym = this->weak_aliases_[tosym]; 1012 gold_assert(sym != NULL); 1013 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 1014 do 1015 { 1016 ssym->override_with_special(fromsym); 1017 sym = this->weak_aliases_[ssym]; 1018 gold_assert(sym != NULL); 1019 ssym = this->get_sized_symbol<size>(sym); 1020 } 1021 while (ssym != tosym); 1022 } 1023 if (tosym->binding() == elfcpp::STB_LOCAL 1024 || ((tosym->visibility() == elfcpp::STV_HIDDEN 1025 || tosym->visibility() == elfcpp::STV_INTERNAL) 1026 && (tosym->binding() == elfcpp::STB_GLOBAL 1027 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 1028 || tosym->binding() == elfcpp::STB_WEAK) 1029 && !parameters->options().relocatable())) 1030 this->force_local(tosym); 1031 } 1032 1033 // Instantiate the templates we need. We could use the configure 1034 // script to restrict this to only the ones needed for implemented 1035 // targets. 1036 1037 // We have to instantiate both big and little endian versions because 1038 // these are used by other templates that depends on size only. 1039 1040 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1041 template 1042 void 1043 Symbol_table::resolve<32, false>( 1044 Sized_symbol<32>* to, 1045 const elfcpp::Sym<32, false>& sym, 1046 unsigned int st_shndx, 1047 bool is_ordinary, 1048 unsigned int orig_st_shndx, 1049 Object* object, 1050 const char* version); 1051 1052 template 1053 void 1054 Symbol_table::resolve<32, true>( 1055 Sized_symbol<32>* to, 1056 const elfcpp::Sym<32, true>& sym, 1057 unsigned int st_shndx, 1058 bool is_ordinary, 1059 unsigned int orig_st_shndx, 1060 Object* object, 1061 const char* version); 1062 #endif 1063 1064 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1065 template 1066 void 1067 Symbol_table::resolve<64, false>( 1068 Sized_symbol<64>* to, 1069 const elfcpp::Sym<64, false>& sym, 1070 unsigned int st_shndx, 1071 bool is_ordinary, 1072 unsigned int orig_st_shndx, 1073 Object* object, 1074 const char* version); 1075 1076 template 1077 void 1078 Symbol_table::resolve<64, true>( 1079 Sized_symbol<64>* to, 1080 const elfcpp::Sym<64, true>& sym, 1081 unsigned int st_shndx, 1082 bool is_ordinary, 1083 unsigned int orig_st_shndx, 1084 Object* object, 1085 const char* version); 1086 #endif 1087 1088 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1089 template 1090 void 1091 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1092 const Sized_symbol<32>*); 1093 #endif 1094 1095 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1096 template 1097 void 1098 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1099 const Sized_symbol<64>*); 1100 #endif 1101 1102 } // End namespace gold. 1103
