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