1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 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->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 this->type_ = sym.get_st_type(); 100 this->binding_ = sym.get_st_bind(); 101 this->override_visibility(sym.get_st_visibility()); 102 this->nonvis_ = sym.get_st_nonvis(); 103 if (object->is_dynamic()) 104 this->in_dyn_ = true; 105 else 106 this->in_reg_ = true; 107 } 108 109 // Override the fields in Sized_symbol. 110 111 template<int size> 112 template<bool big_endian> 113 void 114 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym, 115 unsigned st_shndx, bool is_ordinary, 116 Object* object, const char* version) 117 { 118 this->override_base(sym, st_shndx, is_ordinary, object, version); 119 this->value_ = sym.get_st_value(); 120 this->symsize_ = sym.get_st_size(); 121 } 122 123 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version 124 // VERSION. This handles all aliases of TOSYM. 125 126 template<int size, bool big_endian> 127 void 128 Symbol_table::override(Sized_symbol<size>* tosym, 129 const elfcpp::Sym<size, big_endian>& fromsym, 130 unsigned int st_shndx, bool is_ordinary, 131 Object* object, const char* version) 132 { 133 tosym->override(fromsym, st_shndx, is_ordinary, object, version); 134 if (tosym->has_alias()) 135 { 136 Symbol* sym = this->weak_aliases_[tosym]; 137 gold_assert(sym != NULL); 138 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 139 do 140 { 141 ssym->override(fromsym, st_shndx, is_ordinary, object, version); 142 sym = this->weak_aliases_[ssym]; 143 gold_assert(sym != NULL); 144 ssym = this->get_sized_symbol<size>(sym); 145 } 146 while (ssym != tosym); 147 } 148 } 149 150 // The resolve functions build a little code for each symbol. 151 // Bit 0: 0 for global, 1 for weak. 152 // Bit 1: 0 for regular object, 1 for shared object 153 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common 154 // This gives us values from 0 to 11. 155 156 static const int global_or_weak_shift = 0; 157 static const unsigned int global_flag = 0 << global_or_weak_shift; 158 static const unsigned int weak_flag = 1 << global_or_weak_shift; 159 160 static const int regular_or_dynamic_shift = 1; 161 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift; 162 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift; 163 164 static const int def_undef_or_common_shift = 2; 165 static const unsigned int def_flag = 0 << def_undef_or_common_shift; 166 static const unsigned int undef_flag = 1 << def_undef_or_common_shift; 167 static const unsigned int common_flag = 2 << def_undef_or_common_shift; 168 169 // This convenience function combines all the flags based on facts 170 // about the symbol. 171 172 static unsigned int 173 symbol_to_bits(elfcpp::STB binding, bool is_dynamic, 174 unsigned int shndx, bool is_ordinary, elfcpp::STT type) 175 { 176 unsigned int bits; 177 178 switch (binding) 179 { 180 case elfcpp::STB_GLOBAL: 181 case elfcpp::STB_GNU_UNIQUE: 182 bits = global_flag; 183 break; 184 185 case elfcpp::STB_WEAK: 186 bits = weak_flag; 187 break; 188 189 case elfcpp::STB_LOCAL: 190 // We should only see externally visible symbols in the symbol 191 // table. 192 gold_error(_("invalid STB_LOCAL symbol in external symbols")); 193 bits = global_flag; 194 195 default: 196 // Any target which wants to handle STB_LOOS, etc., needs to 197 // define a resolve method. 198 gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding)); 199 bits = global_flag; 200 } 201 202 if (is_dynamic) 203 bits |= dynamic_flag; 204 else 205 bits |= regular_flag; 206 207 switch (shndx) 208 { 209 case elfcpp::SHN_UNDEF: 210 bits |= undef_flag; 211 break; 212 213 case elfcpp::SHN_COMMON: 214 if (!is_ordinary) 215 bits |= common_flag; 216 break; 217 218 default: 219 if (type == elfcpp::STT_COMMON) 220 bits |= common_flag; 221 else 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 { 248 // It's possible for a symbol to be defined in an object file 249 // using .symver to give it a version, and for there to also be 250 // a linker script giving that symbol the same version. We 251 // don't want to give a multiple-definition error for this 252 // harmless redefinition. 253 bool to_is_ordinary; 254 if (to->source() == Symbol::FROM_OBJECT 255 && to->object() == object 256 && is_ordinary 257 && to->is_defined() 258 && to->shndx(&to_is_ordinary) == st_shndx 259 && to_is_ordinary 260 && to->value() == sym.get_st_value()) 261 return; 262 263 if (parameters->target().has_resolve()) 264 { 265 Sized_target<size, big_endian>* sized_target; 266 sized_target = parameters->sized_target<size, big_endian>(); 267 sized_target->resolve(to, sym, object, version); 268 return; 269 } 270 271 if (!object->is_dynamic()) 272 { 273 // Record that we've seen this symbol in a regular object. 274 to->set_in_reg(); 275 } 276 else if (st_shndx == elfcpp::SHN_UNDEF 277 && (to->visibility() == elfcpp::STV_HIDDEN 278 || to->visibility() == elfcpp::STV_INTERNAL)) 279 { 280 // A dynamic object cannot reference a hidden or internal symbol 281 // defined in another object. 282 gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"), 283 (to->visibility() == elfcpp::STV_HIDDEN 284 ? "hidden" 285 : "internal"), 286 to->demangled_name().c_str(), 287 to->object()->name().c_str(), 288 object->name().c_str()); 289 return; 290 } 291 else 292 { 293 // Record that we've seen this symbol in a dynamic object. 294 to->set_in_dyn(); 295 } 296 297 // Record if we've seen this symbol in a real ELF object (i.e., the 298 // symbol is referenced from outside the world known to the plugin). 299 if (object->pluginobj() == NULL && !object->is_dynamic()) 300 to->set_in_real_elf(); 301 302 // If we're processing replacement files, allow new symbols to override 303 // the placeholders from the plugin objects. 304 if (to->source() == Symbol::FROM_OBJECT) 305 { 306 Pluginobj* obj = to->object()->pluginobj(); 307 if (obj != NULL 308 && parameters->options().plugins()->in_replacement_phase()) 309 { 310 this->override(to, sym, st_shndx, is_ordinary, object, version); 311 return; 312 } 313 } 314 315 // A new weak undefined reference, merging with an old weak 316 // reference, could be a One Definition Rule (ODR) violation -- 317 // especially if the types or sizes of the references differ. We'll 318 // store such pairs and look them up later to make sure they 319 // actually refer to the same lines of code. We also check 320 // combinations of weak and strong, which might occur if one case is 321 // inline and the other is not. (Note: not all ODR violations can 322 // be found this way, and not everything this finds is an ODR 323 // violation. But it's helpful to warn about.) 324 if (parameters->options().detect_odr_violations() 325 && (sym.get_st_bind() == elfcpp::STB_WEAK 326 || to->binding() == elfcpp::STB_WEAK) 327 && orig_st_shndx != elfcpp::SHN_UNDEF 328 && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF 329 && to_is_ordinary 330 && sym.get_st_size() != 0 // Ignore weird 0-sized symbols. 331 && to->symsize() != 0 332 && (sym.get_st_type() != to->type() 333 || sym.get_st_size() != to->symsize()) 334 // C does not have a concept of ODR, so we only need to do this 335 // on C++ symbols. These have (mangled) names starting with _Z. 336 && to->name()[0] == '_' && to->name()[1] == 'Z') 337 { 338 Symbol_location fromloc 339 = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) }; 340 Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary), 341 static_cast<off_t>(to->value()) }; 342 this->candidate_odr_violations_[to->name()].insert(fromloc); 343 this->candidate_odr_violations_[to->name()].insert(toloc); 344 } 345 346 unsigned int frombits = symbol_to_bits(sym.get_st_bind(), 347 object->is_dynamic(), 348 st_shndx, is_ordinary, 349 sym.get_st_type()); 350 351 bool adjust_common_sizes; 352 bool adjust_dyndef; 353 typename Sized_symbol<size>::Size_type tosize = to->symsize(); 354 if (Symbol_table::should_override(to, frombits, sym.get_st_type(), OBJECT, 355 object, &adjust_common_sizes, 356 &adjust_dyndef)) 357 { 358 elfcpp::STB tobinding = to->binding(); 359 typename Sized_symbol<size>::Value_type tovalue = to->value(); 360 this->override(to, sym, st_shndx, is_ordinary, object, version); 361 if (adjust_common_sizes) 362 { 363 if (tosize > to->symsize()) 364 to->set_symsize(tosize); 365 if (tovalue > to->value()) 366 to->set_value(tovalue); 367 } 368 if (adjust_dyndef) 369 { 370 // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF. 371 // Remember which kind of UNDEF it was for future reference. 372 to->set_undef_binding(tobinding); 373 } 374 } 375 else 376 { 377 if (adjust_common_sizes) 378 { 379 if (sym.get_st_size() > tosize) 380 to->set_symsize(sym.get_st_size()); 381 if (sym.get_st_value() > to->value()) 382 to->set_value(sym.get_st_value()); 383 } 384 if (adjust_dyndef) 385 { 386 // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF. 387 // Remember which kind of UNDEF it was. 388 to->set_undef_binding(sym.get_st_bind()); 389 } 390 // The ELF ABI says that even for a reference to a symbol we 391 // merge the visibility. 392 to->override_visibility(sym.get_st_visibility()); 393 } 394 395 if (adjust_common_sizes && parameters->options().warn_common()) 396 { 397 if (tosize > sym.get_st_size()) 398 Symbol_table::report_resolve_problem(false, 399 _("common of '%s' overriding " 400 "smaller common"), 401 to, OBJECT, object); 402 else if (tosize < sym.get_st_size()) 403 Symbol_table::report_resolve_problem(false, 404 _("common of '%s' overidden by " 405 "larger common"), 406 to, OBJECT, object); 407 else 408 Symbol_table::report_resolve_problem(false, 409 _("multiple common of '%s'"), 410 to, OBJECT, object); 411 } 412 } 413 414 // Handle the core of symbol resolution. This is called with the 415 // existing symbol, TO, and a bitflag describing the new symbol. This 416 // returns true if we should override the existing symbol with the new 417 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 418 // true if we should set the symbol size to the maximum of the TO and 419 // FROM sizes. It handles error conditions. 420 421 bool 422 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 423 elfcpp::STT fromtype, Defined defined, 424 Object* object, bool* adjust_common_sizes, 425 bool* adjust_dyndef) 426 { 427 *adjust_common_sizes = false; 428 *adjust_dyndef = false; 429 430 unsigned int tobits; 431 if (to->source() == Symbol::IS_UNDEFINED) 432 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true, 433 to->type()); 434 else if (to->source() != Symbol::FROM_OBJECT) 435 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false, 436 to->type()); 437 else 438 { 439 bool is_ordinary; 440 unsigned int shndx = to->shndx(&is_ordinary); 441 tobits = symbol_to_bits(to->binding(), 442 to->object()->is_dynamic(), 443 shndx, 444 is_ordinary, 445 to->type()); 446 } 447 448 if (to->type() == elfcpp::STT_TLS 449 ? fromtype != elfcpp::STT_TLS 450 : fromtype == elfcpp::STT_TLS) 451 Symbol_table::report_resolve_problem(true, 452 _("symbol '%s' used as both __thread " 453 "and non-__thread"), 454 to, defined, object); 455 456 // We use a giant switch table for symbol resolution. This code is 457 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 458 // cases; 3) it is easy to change the handling of a particular case. 459 // The alternative would be a series of conditionals, but it is easy 460 // to get the ordering wrong. This could also be done as a table, 461 // but that is no easier to understand than this large switch 462 // statement. 463 464 // These are the values generated by the bit codes. 465 enum 466 { 467 DEF = global_flag | regular_flag | def_flag, 468 WEAK_DEF = weak_flag | regular_flag | def_flag, 469 DYN_DEF = global_flag | dynamic_flag | def_flag, 470 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 471 UNDEF = global_flag | regular_flag | undef_flag, 472 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 473 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 474 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 475 COMMON = global_flag | regular_flag | common_flag, 476 WEAK_COMMON = weak_flag | regular_flag | common_flag, 477 DYN_COMMON = global_flag | dynamic_flag | common_flag, 478 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 479 }; 480 481 switch (tobits * 16 + frombits) 482 { 483 case DEF * 16 + DEF: 484 // Two definitions of the same symbol. 485 486 // If either symbol is defined by an object included using 487 // --just-symbols, then don't warn. This is for compatibility 488 // with the GNU linker. FIXME: This is a hack. 489 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 490 || (object != NULL && object->just_symbols())) 491 return false; 492 493 if (!parameters->options().muldefs()) 494 Symbol_table::report_resolve_problem(true, 495 _("multiple definition of '%s'"), 496 to, defined, object); 497 return false; 498 499 case WEAK_DEF * 16 + DEF: 500 // We've seen a weak definition, and now we see a strong 501 // definition. In the original SVR4 linker, this was treated as 502 // a multiple definition error. In the Solaris linker and the 503 // GNU linker, a weak definition followed by a regular 504 // definition causes the weak definition to be overridden. We 505 // are currently compatible with the GNU linker. In the future 506 // we should add a target specific option to change this. 507 // FIXME. 508 return true; 509 510 case DYN_DEF * 16 + DEF: 511 case DYN_WEAK_DEF * 16 + DEF: 512 // We've seen a definition in a dynamic object, and now we see a 513 // definition in a regular object. The definition in the 514 // regular object overrides the definition in the dynamic 515 // object. 516 return true; 517 518 case UNDEF * 16 + DEF: 519 case WEAK_UNDEF * 16 + DEF: 520 case DYN_UNDEF * 16 + DEF: 521 case DYN_WEAK_UNDEF * 16 + DEF: 522 // We've seen an undefined reference, and now we see a 523 // definition. We use the definition. 524 return true; 525 526 case COMMON * 16 + DEF: 527 case WEAK_COMMON * 16 + DEF: 528 case DYN_COMMON * 16 + DEF: 529 case DYN_WEAK_COMMON * 16 + DEF: 530 // We've seen a common symbol and now we see a definition. The 531 // definition overrides. 532 if (parameters->options().warn_common()) 533 Symbol_table::report_resolve_problem(false, 534 _("definition of '%s' overriding " 535 "common"), 536 to, defined, object); 537 return true; 538 539 case DEF * 16 + WEAK_DEF: 540 case WEAK_DEF * 16 + WEAK_DEF: 541 // We've seen a definition and now we see a weak definition. We 542 // ignore the new weak definition. 543 return false; 544 545 case DYN_DEF * 16 + WEAK_DEF: 546 case DYN_WEAK_DEF * 16 + WEAK_DEF: 547 // We've seen a dynamic definition and now we see a regular weak 548 // definition. The regular weak definition overrides. 549 return true; 550 551 case UNDEF * 16 + WEAK_DEF: 552 case WEAK_UNDEF * 16 + WEAK_DEF: 553 case DYN_UNDEF * 16 + WEAK_DEF: 554 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 555 // A weak definition of a currently undefined symbol. 556 return true; 557 558 case COMMON * 16 + WEAK_DEF: 559 case WEAK_COMMON * 16 + WEAK_DEF: 560 // A weak definition does not override a common definition. 561 return false; 562 563 case DYN_COMMON * 16 + WEAK_DEF: 564 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 565 // A weak definition does override a definition in a dynamic 566 // object. 567 if (parameters->options().warn_common()) 568 Symbol_table::report_resolve_problem(false, 569 _("definition of '%s' overriding " 570 "dynamic common definition"), 571 to, defined, object); 572 return true; 573 574 case DEF * 16 + DYN_DEF: 575 case WEAK_DEF * 16 + DYN_DEF: 576 case DYN_DEF * 16 + DYN_DEF: 577 case DYN_WEAK_DEF * 16 + DYN_DEF: 578 // Ignore a dynamic definition if we already have a definition. 579 return false; 580 581 case UNDEF * 16 + DYN_DEF: 582 case DYN_UNDEF * 16 + DYN_DEF: 583 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 584 // Use a dynamic definition if we have a reference. 585 return true; 586 587 case WEAK_UNDEF * 16 + DYN_DEF: 588 // When overriding a weak undef by a dynamic definition, 589 // we need to remember that the original undef was weak. 590 *adjust_dyndef = true; 591 return true; 592 593 case COMMON * 16 + DYN_DEF: 594 case WEAK_COMMON * 16 + DYN_DEF: 595 case DYN_COMMON * 16 + DYN_DEF: 596 case DYN_WEAK_COMMON * 16 + DYN_DEF: 597 // Ignore a dynamic definition if we already have a common 598 // definition. 599 return false; 600 601 case DEF * 16 + DYN_WEAK_DEF: 602 case WEAK_DEF * 16 + DYN_WEAK_DEF: 603 case DYN_DEF * 16 + DYN_WEAK_DEF: 604 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 605 // Ignore a weak dynamic definition if we already have a 606 // definition. 607 return false; 608 609 case UNDEF * 16 + DYN_WEAK_DEF: 610 // When overriding an undef by a dynamic weak definition, 611 // we need to remember that the original undef was not weak. 612 *adjust_dyndef = true; 613 return true; 614 615 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 616 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 617 // Use a weak dynamic definition if we have a reference. 618 return true; 619 620 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 621 // When overriding a weak undef by a dynamic definition, 622 // we need to remember that the original undef was weak. 623 *adjust_dyndef = true; 624 return true; 625 626 case COMMON * 16 + DYN_WEAK_DEF: 627 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 628 case DYN_COMMON * 16 + DYN_WEAK_DEF: 629 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 630 // Ignore a weak dynamic definition if we already have a common 631 // definition. 632 return false; 633 634 case DEF * 16 + UNDEF: 635 case WEAK_DEF * 16 + UNDEF: 636 case UNDEF * 16 + UNDEF: 637 // A new undefined reference tells us nothing. 638 return false; 639 640 case DYN_DEF * 16 + UNDEF: 641 case DYN_WEAK_DEF * 16 + UNDEF: 642 // For a dynamic def, we need to remember which kind of undef we see. 643 *adjust_dyndef = true; 644 return false; 645 646 case WEAK_UNDEF * 16 + UNDEF: 647 case DYN_UNDEF * 16 + UNDEF: 648 case DYN_WEAK_UNDEF * 16 + UNDEF: 649 // A strong undef overrides a dynamic or weak undef. 650 return true; 651 652 case COMMON * 16 + UNDEF: 653 case WEAK_COMMON * 16 + UNDEF: 654 case DYN_COMMON * 16 + UNDEF: 655 case DYN_WEAK_COMMON * 16 + UNDEF: 656 // A new undefined reference tells us nothing. 657 return false; 658 659 case DEF * 16 + WEAK_UNDEF: 660 case WEAK_DEF * 16 + WEAK_UNDEF: 661 case UNDEF * 16 + WEAK_UNDEF: 662 case WEAK_UNDEF * 16 + WEAK_UNDEF: 663 case DYN_UNDEF * 16 + WEAK_UNDEF: 664 case COMMON * 16 + WEAK_UNDEF: 665 case WEAK_COMMON * 16 + WEAK_UNDEF: 666 case DYN_COMMON * 16 + WEAK_UNDEF: 667 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 668 // A new weak undefined reference tells us nothing unless the 669 // exisiting symbol is a dynamic weak reference. 670 return false; 671 672 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 673 // A new weak reference overrides an existing dynamic weak reference. 674 // This is necessary because a dynamic weak reference remembers 675 // the old binding, which may not be weak. If we keeps the existing 676 // dynamic weak reference, the weakness may be dropped in the output. 677 return true; 678 679 case DYN_DEF * 16 + WEAK_UNDEF: 680 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 681 // For a dynamic def, we need to remember which kind of undef we see. 682 *adjust_dyndef = true; 683 return false; 684 685 case DEF * 16 + DYN_UNDEF: 686 case WEAK_DEF * 16 + DYN_UNDEF: 687 case DYN_DEF * 16 + DYN_UNDEF: 688 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 689 case UNDEF * 16 + DYN_UNDEF: 690 case WEAK_UNDEF * 16 + DYN_UNDEF: 691 case DYN_UNDEF * 16 + DYN_UNDEF: 692 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 693 case COMMON * 16 + DYN_UNDEF: 694 case WEAK_COMMON * 16 + DYN_UNDEF: 695 case DYN_COMMON * 16 + DYN_UNDEF: 696 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 697 // A new dynamic undefined reference tells us nothing. 698 return false; 699 700 case DEF * 16 + DYN_WEAK_UNDEF: 701 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 702 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 703 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 704 case UNDEF * 16 + DYN_WEAK_UNDEF: 705 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 706 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 707 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 708 case COMMON * 16 + DYN_WEAK_UNDEF: 709 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 710 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 711 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 712 // A new weak dynamic undefined reference tells us nothing. 713 return false; 714 715 case DEF * 16 + COMMON: 716 // A common symbol does not override a definition. 717 if (parameters->options().warn_common()) 718 Symbol_table::report_resolve_problem(false, 719 _("common '%s' overridden by " 720 "previous definition"), 721 to, defined, object); 722 return false; 723 724 case WEAK_DEF * 16 + COMMON: 725 case DYN_DEF * 16 + COMMON: 726 case DYN_WEAK_DEF * 16 + COMMON: 727 // A common symbol does override a weak definition or a dynamic 728 // definition. 729 return true; 730 731 case UNDEF * 16 + COMMON: 732 case WEAK_UNDEF * 16 + COMMON: 733 case DYN_UNDEF * 16 + COMMON: 734 case DYN_WEAK_UNDEF * 16 + COMMON: 735 // A common symbol is a definition for a reference. 736 return true; 737 738 case COMMON * 16 + COMMON: 739 // Set the size to the maximum. 740 *adjust_common_sizes = true; 741 return false; 742 743 case WEAK_COMMON * 16 + COMMON: 744 // I'm not sure just what a weak common symbol means, but 745 // presumably it can be overridden by a regular common symbol. 746 return true; 747 748 case DYN_COMMON * 16 + COMMON: 749 case DYN_WEAK_COMMON * 16 + COMMON: 750 // Use the real common symbol, but adjust the size if necessary. 751 *adjust_common_sizes = true; 752 return true; 753 754 case DEF * 16 + WEAK_COMMON: 755 case WEAK_DEF * 16 + WEAK_COMMON: 756 case DYN_DEF * 16 + WEAK_COMMON: 757 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 758 // Whatever a weak common symbol is, it won't override a 759 // definition. 760 return false; 761 762 case UNDEF * 16 + WEAK_COMMON: 763 case WEAK_UNDEF * 16 + WEAK_COMMON: 764 case DYN_UNDEF * 16 + WEAK_COMMON: 765 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 766 // A weak common symbol is better than an undefined symbol. 767 return true; 768 769 case COMMON * 16 + WEAK_COMMON: 770 case WEAK_COMMON * 16 + WEAK_COMMON: 771 case DYN_COMMON * 16 + WEAK_COMMON: 772 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 773 // Ignore a weak common symbol in the presence of a real common 774 // symbol. 775 return false; 776 777 case DEF * 16 + DYN_COMMON: 778 case WEAK_DEF * 16 + DYN_COMMON: 779 case DYN_DEF * 16 + DYN_COMMON: 780 case DYN_WEAK_DEF * 16 + DYN_COMMON: 781 // Ignore a dynamic common symbol in the presence of a 782 // definition. 783 return false; 784 785 case UNDEF * 16 + DYN_COMMON: 786 case WEAK_UNDEF * 16 + DYN_COMMON: 787 case DYN_UNDEF * 16 + DYN_COMMON: 788 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 789 // A dynamic common symbol is a definition of sorts. 790 return true; 791 792 case COMMON * 16 + DYN_COMMON: 793 case WEAK_COMMON * 16 + DYN_COMMON: 794 case DYN_COMMON * 16 + DYN_COMMON: 795 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 796 // Set the size to the maximum. 797 *adjust_common_sizes = true; 798 return false; 799 800 case DEF * 16 + DYN_WEAK_COMMON: 801 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 802 case DYN_DEF * 16 + DYN_WEAK_COMMON: 803 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 804 // A common symbol is ignored in the face of a definition. 805 return false; 806 807 case UNDEF * 16 + DYN_WEAK_COMMON: 808 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 809 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 810 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 811 // I guess a weak common symbol is better than a definition. 812 return true; 813 814 case COMMON * 16 + DYN_WEAK_COMMON: 815 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 816 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 817 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 818 // Set the size to the maximum. 819 *adjust_common_sizes = true; 820 return false; 821 822 default: 823 gold_unreachable(); 824 } 825 } 826 827 // Issue an error or warning due to symbol resolution. IS_ERROR 828 // indicates an error rather than a warning. MSG is the error 829 // message; it is expected to have a %s for the symbol name. TO is 830 // the existing symbol. DEFINED/OBJECT is where the new symbol was 831 // found. 832 833 // FIXME: We should have better location information here. When the 834 // symbol is defined, we should be able to pull the location from the 835 // debug info if there is any. 836 837 void 838 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 839 const Symbol* to, Defined defined, 840 Object* object) 841 { 842 std::string demangled(to->demangled_name()); 843 size_t len = strlen(msg) + demangled.length() + 10; 844 char* buf = new char[len]; 845 snprintf(buf, len, msg, demangled.c_str()); 846 847 const char* objname; 848 switch (defined) 849 { 850 case OBJECT: 851 objname = object->name().c_str(); 852 break; 853 case COPY: 854 objname = _("COPY reloc"); 855 break; 856 case DEFSYM: 857 case UNDEFINED: 858 objname = _("command line"); 859 break; 860 case SCRIPT: 861 objname = _("linker script"); 862 break; 863 case PREDEFINED: 864 case INCREMENTAL_BASE: 865 objname = _("linker defined"); 866 break; 867 default: 868 gold_unreachable(); 869 } 870 871 if (is_error) 872 gold_error("%s: %s", objname, buf); 873 else 874 gold_warning("%s: %s", objname, buf); 875 876 delete[] buf; 877 878 if (to->source() == Symbol::FROM_OBJECT) 879 objname = to->object()->name().c_str(); 880 else 881 objname = _("command line"); 882 gold_info("%s: %s: previous definition here", program_name, objname); 883 } 884 885 // A special case of should_override which is only called for a strong 886 // defined symbol from a regular object file. This is used when 887 // defining special symbols. 888 889 bool 890 Symbol_table::should_override_with_special(const Symbol* to, 891 elfcpp::STT fromtype, 892 Defined defined) 893 { 894 bool adjust_common_sizes; 895 bool adjust_dyn_def; 896 unsigned int frombits = global_flag | regular_flag | def_flag; 897 bool ret = Symbol_table::should_override(to, frombits, fromtype, defined, 898 NULL, &adjust_common_sizes, 899 &adjust_dyn_def); 900 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 901 return ret; 902 } 903 904 // Override symbol base with a special symbol. 905 906 void 907 Symbol::override_base_with_special(const Symbol* from) 908 { 909 bool same_name = this->name_ == from->name_; 910 gold_assert(same_name || this->has_alias()); 911 912 this->source_ = from->source_; 913 switch (from->source_) 914 { 915 case FROM_OBJECT: 916 this->u_.from_object = from->u_.from_object; 917 break; 918 case IN_OUTPUT_DATA: 919 this->u_.in_output_data = from->u_.in_output_data; 920 break; 921 case IN_OUTPUT_SEGMENT: 922 this->u_.in_output_segment = from->u_.in_output_segment; 923 break; 924 case IS_CONSTANT: 925 case IS_UNDEFINED: 926 break; 927 default: 928 gold_unreachable(); 929 break; 930 } 931 932 if (same_name) 933 { 934 // When overriding a versioned symbol with a special symbol, we 935 // may be changing the version. This will happen if we see a 936 // special symbol such as "_end" defined in a shared object with 937 // one version (from a version script), but we want to define it 938 // here with a different version (from a different version 939 // script). 940 this->version_ = from->version_; 941 } 942 this->type_ = from->type_; 943 this->binding_ = from->binding_; 944 this->override_visibility(from->visibility_); 945 this->nonvis_ = from->nonvis_; 946 947 // Special symbols are always considered to be regular symbols. 948 this->in_reg_ = true; 949 950 if (from->needs_dynsym_entry_) 951 this->needs_dynsym_entry_ = true; 952 if (from->needs_dynsym_value_) 953 this->needs_dynsym_value_ = true; 954 955 this->is_predefined_ = from->is_predefined_; 956 957 // We shouldn't see these flags. If we do, we need to handle them 958 // somehow. 959 gold_assert(!from->is_forwarder_); 960 gold_assert(!from->has_plt_offset()); 961 gold_assert(!from->has_warning_); 962 gold_assert(!from->is_copied_from_dynobj_); 963 gold_assert(!from->is_forced_local_); 964 } 965 966 // Override a symbol with a special symbol. 967 968 template<int size> 969 void 970 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 971 { 972 this->override_base_with_special(from); 973 this->value_ = from->value_; 974 this->symsize_ = from->symsize_; 975 } 976 977 // Override TOSYM with the special symbol FROMSYM. This handles all 978 // aliases of TOSYM. 979 980 template<int size> 981 void 982 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 983 const Sized_symbol<size>* fromsym) 984 { 985 tosym->override_with_special(fromsym); 986 if (tosym->has_alias()) 987 { 988 Symbol* sym = this->weak_aliases_[tosym]; 989 gold_assert(sym != NULL); 990 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 991 do 992 { 993 ssym->override_with_special(fromsym); 994 sym = this->weak_aliases_[ssym]; 995 gold_assert(sym != NULL); 996 ssym = this->get_sized_symbol<size>(sym); 997 } 998 while (ssym != tosym); 999 } 1000 if (tosym->binding() == elfcpp::STB_LOCAL 1001 || ((tosym->visibility() == elfcpp::STV_HIDDEN 1002 || tosym->visibility() == elfcpp::STV_INTERNAL) 1003 && (tosym->binding() == elfcpp::STB_GLOBAL 1004 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 1005 || tosym->binding() == elfcpp::STB_WEAK) 1006 && !parameters->options().relocatable())) 1007 this->force_local(tosym); 1008 } 1009 1010 // Instantiate the templates we need. We could use the configure 1011 // script to restrict this to only the ones needed for implemented 1012 // targets. 1013 1014 // We have to instantiate both big and little endian versions because 1015 // these are used by other templates that depends on size only. 1016 1017 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1018 template 1019 void 1020 Symbol_table::resolve<32, false>( 1021 Sized_symbol<32>* to, 1022 const elfcpp::Sym<32, false>& sym, 1023 unsigned int st_shndx, 1024 bool is_ordinary, 1025 unsigned int orig_st_shndx, 1026 Object* object, 1027 const char* version); 1028 1029 template 1030 void 1031 Symbol_table::resolve<32, true>( 1032 Sized_symbol<32>* to, 1033 const elfcpp::Sym<32, true>& sym, 1034 unsigned int st_shndx, 1035 bool is_ordinary, 1036 unsigned int orig_st_shndx, 1037 Object* object, 1038 const char* version); 1039 #endif 1040 1041 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1042 template 1043 void 1044 Symbol_table::resolve<64, false>( 1045 Sized_symbol<64>* to, 1046 const elfcpp::Sym<64, false>& sym, 1047 unsigned int st_shndx, 1048 bool is_ordinary, 1049 unsigned int orig_st_shndx, 1050 Object* object, 1051 const char* version); 1052 1053 template 1054 void 1055 Symbol_table::resolve<64, true>( 1056 Sized_symbol<64>* to, 1057 const elfcpp::Sym<64, true>& sym, 1058 unsigned int st_shndx, 1059 bool is_ordinary, 1060 unsigned int orig_st_shndx, 1061 Object* object, 1062 const char* version); 1063 #endif 1064 1065 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1066 template 1067 void 1068 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1069 const Sized_symbol<32>*); 1070 #endif 1071 1072 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1073 template 1074 void 1075 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1076 const Sized_symbol<64>*); 1077 #endif 1078 1079 } // End namespace gold. 1080