1 // target-reloc.h -- target specific relocation support -*- C++ -*- 2 3 // Copyright (C) 2006-2020 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant@google.com>. 5 6 // This file is part of gold. 7 8 // This program is free software; you can redistribute it and/or modify 9 // it under the terms of the GNU General Public License as published by 10 // the Free Software Foundation; either version 3 of the License, or 11 // (at your option) any later version. 12 13 // This program is distributed in the hope that it will be useful, 14 // but WITHOUT ANY WARRANTY; without even the implied warranty of 15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 // GNU General Public License for more details. 17 18 // You should have received a copy of the GNU General Public License 19 // along with this program; if not, write to the Free Software 20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21 // MA 02110-1301, USA. 22 23 #ifndef GOLD_TARGET_RELOC_H 24 #define GOLD_TARGET_RELOC_H 25 26 #include "elfcpp.h" 27 #include "symtab.h" 28 #include "object.h" 29 #include "reloc.h" 30 #include "reloc-types.h" 31 32 namespace gold 33 { 34 35 // This function implements the generic part of reloc scanning. The 36 // template parameter Scan must be a class type which provides two 37 // functions: local() and global(). Those functions implement the 38 // machine specific part of scanning. We do it this way to 39 // avoid making a function call for each relocation, and to avoid 40 // repeating the generic code for each target. 41 42 template<int size, bool big_endian, typename Target_type, 43 typename Scan, typename Classify_reloc> 44 inline void 45 scan_relocs( 46 Symbol_table* symtab, 47 Layout* layout, 48 Target_type* target, 49 Sized_relobj_file<size, big_endian>* object, 50 unsigned int data_shndx, 51 const unsigned char* prelocs, 52 size_t reloc_count, 53 Output_section* output_section, 54 bool needs_special_offset_handling, 55 size_t local_count, 56 const unsigned char* plocal_syms) 57 { 58 typedef typename Classify_reloc::Reltype Reltype; 59 const int reloc_size = Classify_reloc::reloc_size; 60 const int sym_size = elfcpp::Elf_sizes<size>::sym_size; 61 Scan scan; 62 63 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) 64 { 65 Reltype reloc(prelocs); 66 67 if (needs_special_offset_handling 68 && !output_section->is_input_address_mapped(object, data_shndx, 69 reloc.get_r_offset())) 70 continue; 71 72 unsigned int r_sym = Classify_reloc::get_r_sym(&reloc); 73 unsigned int r_type = Classify_reloc::get_r_type(&reloc); 74 75 if (r_sym < local_count) 76 { 77 gold_assert(plocal_syms != NULL); 78 typename elfcpp::Sym<size, big_endian> lsym(plocal_syms 79 + r_sym * sym_size); 80 unsigned int shndx = lsym.get_st_shndx(); 81 bool is_ordinary; 82 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary); 83 // If RELOC is a relocation against a local symbol in a 84 // section we are discarding then we can ignore it. It will 85 // eventually become a reloc against the value zero. 86 // 87 // FIXME: We should issue a warning if this is an 88 // allocated section; is this the best place to do it? 89 // 90 // FIXME: The old GNU linker would in some cases look 91 // for the linkonce section which caused this section to 92 // be discarded, and, if the other section was the same 93 // size, change the reloc to refer to the other section. 94 // That seems risky and weird to me, and I don't know of 95 // any case where it is actually required. 96 bool is_discarded = (is_ordinary 97 && shndx != elfcpp::SHN_UNDEF 98 && !object->is_section_included(shndx) 99 && !symtab->is_section_folded(object, shndx)); 100 scan.local(symtab, layout, target, object, data_shndx, 101 output_section, reloc, r_type, lsym, is_discarded); 102 } 103 else 104 { 105 Symbol* gsym = object->global_symbol(r_sym); 106 gold_assert(gsym != NULL); 107 if (gsym->is_forwarder()) 108 gsym = symtab->resolve_forwards(gsym); 109 110 scan.global(symtab, layout, target, object, data_shndx, 111 output_section, reloc, r_type, gsym); 112 } 113 } 114 } 115 116 // Behavior for relocations to discarded comdat sections. 117 118 enum Comdat_behavior 119 { 120 CB_UNDETERMINED, // Not yet determined -- need to look at section name. 121 CB_PRETEND, // Attempt to map to the corresponding kept section. 122 CB_IGNORE, // Ignore the relocation. 123 CB_ERROR // Print an error. 124 }; 125 126 class Default_comdat_behavior 127 { 128 public: 129 // Decide what the linker should do for relocations that refer to 130 // discarded comdat sections. This decision is based on the name of 131 // the section being relocated. 132 133 inline Comdat_behavior 134 get(const char* name) 135 { 136 if (Layout::is_debug_info_section(name)) 137 return CB_PRETEND; 138 if (strcmp(name, ".eh_frame") == 0 139 || strcmp(name, ".gcc_except_table") == 0) 140 return CB_IGNORE; 141 return CB_ERROR; 142 } 143 }; 144 145 // Give an error for a symbol with non-default visibility which is not 146 // defined locally. 147 148 inline void 149 visibility_error(const Symbol* sym) 150 { 151 const char* v; 152 switch (sym->visibility()) 153 { 154 case elfcpp::STV_INTERNAL: 155 v = _("internal"); 156 break; 157 case elfcpp::STV_HIDDEN: 158 v = _("hidden"); 159 break; 160 case elfcpp::STV_PROTECTED: 161 v = _("protected"); 162 break; 163 default: 164 gold_unreachable(); 165 } 166 gold_error(_("%s symbol '%s' is not defined locally"), 167 v, sym->name()); 168 } 169 170 // Return true if we are should issue an error saying that SYM is an 171 // undefined symbol. This is called if there is a relocation against 172 // SYM. 173 174 inline bool 175 issue_undefined_symbol_error(const Symbol* sym) 176 { 177 // We only report global symbols. 178 if (sym == NULL) 179 return false; 180 181 // We only report undefined symbols. 182 if (!sym->is_undefined() && !sym->is_placeholder()) 183 return false; 184 185 // We don't report weak symbols. 186 if (sym->is_weak_undefined()) 187 return false; 188 189 // We don't report symbols defined in discarded sections, 190 // unless they're placeholder symbols that should have been 191 // provided by a plugin. 192 if (sym->is_defined_in_discarded_section() && !sym->is_placeholder()) 193 return false; 194 195 // If the target defines this symbol, don't report it here. 196 if (parameters->target().is_defined_by_abi(sym)) 197 return false; 198 199 // See if we've been told to ignore whether this symbol is 200 // undefined. 201 const char* const u = parameters->options().unresolved_symbols(); 202 if (u != NULL) 203 { 204 if (strcmp(u, "ignore-all") == 0) 205 return false; 206 if (strcmp(u, "report-all") == 0) 207 return true; 208 if (strcmp(u, "ignore-in-object-files") == 0 && !sym->in_dyn()) 209 return false; 210 if (strcmp(u, "ignore-in-shared-libs") == 0 && !sym->in_reg()) 211 return false; 212 } 213 214 // If the symbol is hidden, report it. 215 if (sym->visibility() == elfcpp::STV_HIDDEN) 216 return true; 217 218 // When creating a shared library, only report unresolved symbols if 219 // -z defs was used. 220 if (parameters->options().shared() && !parameters->options().defs()) 221 return false; 222 223 // Otherwise issue a warning. 224 return true; 225 } 226 227 template<int size, bool big_endian> 228 inline void 229 issue_discarded_error( 230 const Relocate_info<size, big_endian>* relinfo, 231 size_t shndx, 232 section_offset_type offset, 233 unsigned int r_sym, 234 const Symbol* gsym) 235 { 236 Sized_relobj_file<size, big_endian>* object = relinfo->object; 237 238 if (gsym == NULL) 239 { 240 gold_error_at_location( 241 relinfo, shndx, offset, 242 _("relocation refers to local symbol \"%s\" [%u], " 243 "which is defined in a discarded section"), 244 object->get_symbol_name(r_sym), r_sym); 245 } 246 else 247 { 248 gold_error_at_location( 249 relinfo, shndx, offset, 250 _("relocation refers to global symbol \"%s\", " 251 "which is defined in a discarded section"), 252 gsym->demangled_name().c_str()); 253 } 254 255 bool is_ordinary; 256 typename elfcpp::Elf_types<size>::Elf_Addr value; 257 unsigned int orig_shndx = object->symbol_section_and_value(r_sym, &value, 258 &is_ordinary); 259 if (orig_shndx != elfcpp::SHN_UNDEF) 260 { 261 unsigned int key_symndx; 262 Relobj* kept_obj = object->find_kept_section_object(orig_shndx, 263 &key_symndx); 264 if (key_symndx != 0) 265 gold_info(_(" section group signature: \"%s\""), 266 object->get_symbol_name(key_symndx)); 267 if (kept_obj != NULL) 268 gold_info(_(" prevailing definition is from %s"), 269 kept_obj->name().c_str()); 270 } 271 } 272 273 // This function implements the generic part of relocation processing. 274 // The template parameter Relocate must be a class type which provides 275 // a single function, relocate(), which implements the machine 276 // specific part of a relocation. 277 278 // The template parameter Relocate_comdat_behavior is a class type 279 // which provides a single function, get(), which determines what the 280 // linker should do for relocations that refer to discarded comdat 281 // sections. 282 283 // SIZE is the ELF size: 32 or 64. BIG_ENDIAN is the endianness of 284 // the data. SH_TYPE is the section type: SHT_REL or SHT_RELA. 285 // RELOCATE implements operator() to do a relocation. 286 287 // PRELOCS points to the relocation data. RELOC_COUNT is the number 288 // of relocs. OUTPUT_SECTION is the output section. 289 // NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be 290 // mapped to output offsets. 291 292 // VIEW is the section data, VIEW_ADDRESS is its memory address, and 293 // VIEW_SIZE is the size. These refer to the input section, unless 294 // NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to 295 // the output section. 296 297 // RELOC_SYMBOL_CHANGES is used for -fsplit-stack support. If it is 298 // not NULL, it is a vector indexed by relocation index. If that 299 // entry is not NULL, it points to a global symbol which used as the 300 // symbol for the relocation, ignoring the symbol index in the 301 // relocation. 302 303 template<int size, bool big_endian, typename Target_type, 304 typename Relocate, 305 typename Relocate_comdat_behavior, 306 typename Classify_reloc> 307 inline void 308 relocate_section( 309 const Relocate_info<size, big_endian>* relinfo, 310 Target_type* target, 311 const unsigned char* prelocs, 312 size_t reloc_count, 313 Output_section* output_section, 314 bool needs_special_offset_handling, 315 unsigned char* view, 316 typename elfcpp::Elf_types<size>::Elf_Addr view_address, 317 section_size_type view_size, 318 const Reloc_symbol_changes* reloc_symbol_changes) 319 { 320 typedef typename Classify_reloc::Reltype Reltype; 321 const int reloc_size = Classify_reloc::reloc_size; 322 Relocate relocate; 323 Relocate_comdat_behavior relocate_comdat_behavior; 324 325 Sized_relobj_file<size, big_endian>* object = relinfo->object; 326 unsigned int local_count = object->local_symbol_count(); 327 328 Comdat_behavior comdat_behavior = CB_UNDETERMINED; 329 330 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) 331 { 332 Reltype reloc(prelocs); 333 334 section_offset_type offset = 335 convert_to_section_size_type(reloc.get_r_offset()); 336 337 if (needs_special_offset_handling) 338 { 339 offset = output_section->output_offset(relinfo->object, 340 relinfo->data_shndx, 341 offset); 342 if (offset == -1) 343 continue; 344 } 345 346 unsigned int r_sym = Classify_reloc::get_r_sym(&reloc); 347 348 const Sized_symbol<size>* sym; 349 350 Symbol_value<size> symval; 351 const Symbol_value<size> *psymval; 352 bool is_defined_in_discarded_section; 353 unsigned int shndx; 354 const Symbol* gsym = NULL; 355 if (r_sym < local_count 356 && (reloc_symbol_changes == NULL 357 || (*reloc_symbol_changes)[i] == NULL)) 358 { 359 sym = NULL; 360 psymval = object->local_symbol(r_sym); 361 362 // If the local symbol belongs to a section we are discarding, 363 // and that section is a debug section, try to find the 364 // corresponding kept section and map this symbol to its 365 // counterpart in the kept section. The symbol must not 366 // correspond to a section we are folding. 367 bool is_ordinary; 368 shndx = psymval->input_shndx(&is_ordinary); 369 is_defined_in_discarded_section = 370 (is_ordinary 371 && shndx != elfcpp::SHN_UNDEF 372 && !object->is_section_included(shndx) 373 && !relinfo->symtab->is_section_folded(object, shndx)); 374 } 375 else 376 { 377 if (reloc_symbol_changes != NULL 378 && (*reloc_symbol_changes)[i] != NULL) 379 gsym = (*reloc_symbol_changes)[i]; 380 else 381 { 382 gsym = object->global_symbol(r_sym); 383 gold_assert(gsym != NULL); 384 if (gsym->is_forwarder()) 385 gsym = relinfo->symtab->resolve_forwards(gsym); 386 } 387 388 sym = static_cast<const Sized_symbol<size>*>(gsym); 389 if (sym->has_symtab_index() && sym->symtab_index() != -1U) 390 symval.set_output_symtab_index(sym->symtab_index()); 391 else 392 symval.set_no_output_symtab_entry(); 393 symval.set_output_value(sym->value()); 394 if (gsym->type() == elfcpp::STT_TLS) 395 symval.set_is_tls_symbol(); 396 else if (gsym->type() == elfcpp::STT_GNU_IFUNC) 397 symval.set_is_ifunc_symbol(); 398 psymval = &symval; 399 400 is_defined_in_discarded_section = 401 (gsym->is_defined_in_discarded_section() 402 && gsym->is_undefined()); 403 shndx = 0; 404 } 405 406 Symbol_value<size> symval2; 407 if (is_defined_in_discarded_section) 408 { 409 std::string name = object->section_name(relinfo->data_shndx); 410 411 if (comdat_behavior == CB_UNDETERMINED) 412 comdat_behavior = relocate_comdat_behavior.get(name.c_str()); 413 414 if (comdat_behavior == CB_PRETEND) 415 { 416 // FIXME: This case does not work for global symbols. 417 // We have no place to store the original section index. 418 // Fortunately this does not matter for comdat sections, 419 // only for sections explicitly discarded by a linker 420 // script. 421 bool found; 422 typename elfcpp::Elf_types<size>::Elf_Addr value = 423 object->map_to_kept_section(shndx, name, &found); 424 if (found) 425 symval2.set_output_value(value + psymval->input_value()); 426 else 427 symval2.set_output_value(0); 428 } 429 else 430 { 431 if (comdat_behavior == CB_ERROR) 432 issue_discarded_error(relinfo, i, offset, r_sym, gsym); 433 symval2.set_output_value(0); 434 } 435 symval2.set_no_output_symtab_entry(); 436 psymval = &symval2; 437 } 438 439 // If OFFSET is out of range, still let the target decide to 440 // ignore the relocation. Pass in NULL as the VIEW argument so 441 // that it can return quickly without trashing an invalid memory 442 // address. 443 unsigned char *v = view + offset; 444 if (offset < 0 || static_cast<section_size_type>(offset) >= view_size) 445 v = NULL; 446 447 if (!relocate.relocate(relinfo, Classify_reloc::sh_type, target, 448 output_section, i, prelocs, sym, psymval, 449 v, view_address + offset, view_size)) 450 continue; 451 452 if (v == NULL) 453 { 454 gold_error_at_location(relinfo, i, offset, 455 _("reloc has bad offset %zu"), 456 static_cast<size_t>(offset)); 457 continue; 458 } 459 460 if (issue_undefined_symbol_error(sym)) 461 gold_undefined_symbol_at_location(sym, relinfo, i, offset); 462 else if (sym != NULL 463 && sym->visibility() != elfcpp::STV_DEFAULT 464 && (sym->is_strong_undefined() || sym->is_from_dynobj())) 465 visibility_error(sym); 466 467 if (sym != NULL && sym->has_warning()) 468 relinfo->symtab->issue_warning(sym, relinfo, i, offset); 469 } 470 } 471 472 // Apply an incremental relocation. 473 474 template<int size, bool big_endian, typename Target_type, 475 typename Relocate> 476 void 477 apply_relocation(const Relocate_info<size, big_endian>* relinfo, 478 Target_type* target, 479 typename elfcpp::Elf_types<size>::Elf_Addr r_offset, 480 unsigned int r_type, 481 typename elfcpp::Elf_types<size>::Elf_Swxword r_addend, 482 const Symbol* gsym, 483 unsigned char* view, 484 typename elfcpp::Elf_types<size>::Elf_Addr address, 485 section_size_type view_size) 486 { 487 // Construct the ELF relocation in a temporary buffer. 488 const int reloc_size = elfcpp::Elf_sizes<size>::rela_size; 489 unsigned char relbuf[reloc_size]; 490 elfcpp::Rela_write<size, big_endian> orel(relbuf); 491 orel.put_r_offset(r_offset); 492 orel.put_r_info(elfcpp::elf_r_info<size>(0, r_type)); 493 orel.put_r_addend(r_addend); 494 495 // Setup a Symbol_value for the global symbol. 496 const Sized_symbol<size>* sym = static_cast<const Sized_symbol<size>*>(gsym); 497 Symbol_value<size> symval; 498 gold_assert(sym->has_symtab_index() && sym->symtab_index() != -1U); 499 symval.set_output_symtab_index(sym->symtab_index()); 500 symval.set_output_value(sym->value()); 501 if (gsym->type() == elfcpp::STT_TLS) 502 symval.set_is_tls_symbol(); 503 else if (gsym->type() == elfcpp::STT_GNU_IFUNC) 504 symval.set_is_ifunc_symbol(); 505 506 Relocate relocate; 507 relocate.relocate(relinfo, elfcpp::SHT_RELA, target, NULL, 508 -1U, relbuf, sym, &symval, 509 view + r_offset, address + r_offset, view_size); 510 } 511 512 // A class for inquiring about properties of a relocation, 513 // used while scanning relocs during a relocatable link and 514 // garbage collection. This class may be used as the default 515 // for SHT_RELA targets, but SHT_REL targets must implement 516 // a derived class that overrides get_size_for_reloc. 517 // The MIPS-64 target also needs to override the methods 518 // for accessing the r_sym and r_type fields of a relocation, 519 // due to its non-standard use of the r_info field. 520 521 template<int sh_type_, int size, bool big_endian> 522 class Default_classify_reloc 523 { 524 public: 525 typedef typename Reloc_types<sh_type_, size, big_endian>::Reloc 526 Reltype; 527 typedef typename Reloc_types<sh_type_, size, big_endian>::Reloc_write 528 Reltype_write; 529 static const int reloc_size = 530 Reloc_types<sh_type_, size, big_endian>::reloc_size; 531 static const int sh_type = sh_type_; 532 533 // Return the symbol referred to by the relocation. 534 static inline unsigned int 535 get_r_sym(const Reltype* reloc) 536 { return elfcpp::elf_r_sym<size>(reloc->get_r_info()); } 537 538 // Return the type of the relocation. 539 static inline unsigned int 540 get_r_type(const Reltype* reloc) 541 { return elfcpp::elf_r_type<size>(reloc->get_r_info()); } 542 543 // Return the explicit addend of the relocation (return 0 for SHT_REL). 544 static inline typename elfcpp::Elf_types<size>::Elf_Swxword 545 get_r_addend(const Reltype* reloc) 546 { return Reloc_types<sh_type_, size, big_endian>::get_reloc_addend(reloc); } 547 548 // Write the r_info field to a new reloc, using the r_info field from 549 // the original reloc, replacing the r_sym field with R_SYM. 550 static inline void 551 put_r_info(Reltype_write* new_reloc, Reltype* reloc, unsigned int r_sym) 552 { 553 unsigned int r_type = elfcpp::elf_r_type<size>(reloc->get_r_info()); 554 new_reloc->put_r_info(elfcpp::elf_r_info<size>(r_sym, r_type)); 555 } 556 557 // Write the r_addend field to a new reloc. 558 static inline void 559 put_r_addend(Reltype_write* to, 560 typename elfcpp::Elf_types<size>::Elf_Swxword addend) 561 { Reloc_types<sh_type_, size, big_endian>::set_reloc_addend(to, addend); } 562 563 // Return the size of the addend of the relocation (only used for SHT_REL). 564 static unsigned int 565 get_size_for_reloc(unsigned int, Relobj*) 566 { 567 gold_unreachable(); 568 return 0; 569 } 570 }; 571 572 // This class may be used as a typical class for the 573 // Scan_relocatable_reloc parameter to scan_relocatable_relocs. 574 // This class is intended to capture the most typical target behaviour, 575 // while still permitting targets to define their own independent class 576 // for Scan_relocatable_reloc. 577 578 template<typename Classify_reloc> 579 class Default_scan_relocatable_relocs 580 { 581 public: 582 typedef typename Classify_reloc::Reltype Reltype; 583 static const int reloc_size = Classify_reloc::reloc_size; 584 static const int sh_type = Classify_reloc::sh_type; 585 586 // Return the symbol referred to by the relocation. 587 static inline unsigned int 588 get_r_sym(const Reltype* reloc) 589 { return Classify_reloc::get_r_sym(reloc); } 590 591 // Return the type of the relocation. 592 static inline unsigned int 593 get_r_type(const Reltype* reloc) 594 { return Classify_reloc::get_r_type(reloc); } 595 596 // Return the strategy to use for a local symbol which is not a 597 // section symbol, given the relocation type. 598 inline Relocatable_relocs::Reloc_strategy 599 local_non_section_strategy(unsigned int r_type, Relobj*, unsigned int r_sym) 600 { 601 // We assume that relocation type 0 is NONE. Targets which are 602 // different must override. 603 if (r_type == 0 && r_sym == 0) 604 return Relocatable_relocs::RELOC_DISCARD; 605 return Relocatable_relocs::RELOC_COPY; 606 } 607 608 // Return the strategy to use for a local symbol which is a section 609 // symbol, given the relocation type. 610 inline Relocatable_relocs::Reloc_strategy 611 local_section_strategy(unsigned int r_type, Relobj* object) 612 { 613 if (sh_type == elfcpp::SHT_RELA) 614 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA; 615 else 616 { 617 switch (Classify_reloc::get_size_for_reloc(r_type, object)) 618 { 619 case 0: 620 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0; 621 case 1: 622 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1; 623 case 2: 624 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2; 625 case 4: 626 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4; 627 case 8: 628 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8; 629 default: 630 gold_unreachable(); 631 } 632 } 633 } 634 635 // Return the strategy to use for a global symbol, given the 636 // relocation type, the object, and the symbol index. 637 inline Relocatable_relocs::Reloc_strategy 638 global_strategy(unsigned int, Relobj*, unsigned int) 639 { return Relocatable_relocs::RELOC_COPY; } 640 }; 641 642 // This is a strategy class used with scan_relocatable_relocs 643 // and --emit-relocs. 644 645 template<typename Classify_reloc> 646 class Default_emit_relocs_strategy 647 { 648 public: 649 typedef typename Classify_reloc::Reltype Reltype; 650 static const int reloc_size = Classify_reloc::reloc_size; 651 static const int sh_type = Classify_reloc::sh_type; 652 653 // Return the symbol referred to by the relocation. 654 static inline unsigned int 655 get_r_sym(const Reltype* reloc) 656 { return Classify_reloc::get_r_sym(reloc); } 657 658 // Return the type of the relocation. 659 static inline unsigned int 660 get_r_type(const Reltype* reloc) 661 { return Classify_reloc::get_r_type(reloc); } 662 663 // A local non-section symbol. 664 inline Relocatable_relocs::Reloc_strategy 665 local_non_section_strategy(unsigned int, Relobj*, unsigned int) 666 { return Relocatable_relocs::RELOC_COPY; } 667 668 // A local section symbol. 669 inline Relocatable_relocs::Reloc_strategy 670 local_section_strategy(unsigned int, Relobj*) 671 { 672 if (sh_type == elfcpp::SHT_RELA) 673 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA; 674 else 675 { 676 // The addend is stored in the section contents. Since this 677 // is not a relocatable link, we are going to apply the 678 // relocation contents to the section as usual. This means 679 // that we have no way to record the original addend. If the 680 // original addend is not zero, there is basically no way for 681 // the user to handle this correctly. Caveat emptor. 682 return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0; 683 } 684 } 685 686 // A global symbol. 687 inline Relocatable_relocs::Reloc_strategy 688 global_strategy(unsigned int, Relobj*, unsigned int) 689 { return Relocatable_relocs::RELOC_COPY; } 690 }; 691 692 // Scan relocs during a relocatable link. This is a default 693 // definition which should work for most targets. 694 // Scan_relocatable_reloc must name a class type which provides three 695 // functions which return a Relocatable_relocs::Reloc_strategy code: 696 // global_strategy, local_non_section_strategy, and 697 // local_section_strategy. Most targets should be able to use 698 // Default_scan_relocatable_relocs as this class. 699 700 template<int size, bool big_endian, typename Scan_relocatable_reloc> 701 void 702 scan_relocatable_relocs( 703 Symbol_table*, 704 Layout*, 705 Sized_relobj_file<size, big_endian>* object, 706 unsigned int data_shndx, 707 const unsigned char* prelocs, 708 size_t reloc_count, 709 Output_section* output_section, 710 bool needs_special_offset_handling, 711 size_t local_symbol_count, 712 const unsigned char* plocal_syms, 713 Relocatable_relocs* rr) 714 { 715 typedef typename Scan_relocatable_reloc::Reltype Reltype; 716 const int reloc_size = Scan_relocatable_reloc::reloc_size; 717 const int sym_size = elfcpp::Elf_sizes<size>::sym_size; 718 Scan_relocatable_reloc scan; 719 720 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) 721 { 722 Reltype reloc(prelocs); 723 724 Relocatable_relocs::Reloc_strategy strategy; 725 726 if (needs_special_offset_handling 727 && !output_section->is_input_address_mapped(object, data_shndx, 728 reloc.get_r_offset())) 729 strategy = Relocatable_relocs::RELOC_DISCARD; 730 else 731 { 732 const unsigned int r_sym = Scan_relocatable_reloc::get_r_sym(&reloc); 733 const unsigned int r_type = 734 Scan_relocatable_reloc::get_r_type(&reloc); 735 736 if (r_sym >= local_symbol_count) 737 strategy = scan.global_strategy(r_type, object, r_sym); 738 else 739 { 740 gold_assert(plocal_syms != NULL); 741 typename elfcpp::Sym<size, big_endian> lsym(plocal_syms 742 + r_sym * sym_size); 743 unsigned int shndx = lsym.get_st_shndx(); 744 bool is_ordinary; 745 shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary); 746 if (is_ordinary 747 && shndx != elfcpp::SHN_UNDEF 748 && !object->is_section_included(shndx)) 749 { 750 // RELOC is a relocation against a local symbol 751 // defined in a section we are discarding. Discard 752 // the reloc. FIXME: Should we issue a warning? 753 strategy = Relocatable_relocs::RELOC_DISCARD; 754 } 755 else if (lsym.get_st_type() != elfcpp::STT_SECTION) 756 strategy = scan.local_non_section_strategy(r_type, object, 757 r_sym); 758 else 759 { 760 strategy = scan.local_section_strategy(r_type, object); 761 if (strategy != Relocatable_relocs::RELOC_DISCARD) 762 object->output_section(shndx)->set_needs_symtab_index(); 763 } 764 765 if (strategy == Relocatable_relocs::RELOC_COPY) 766 object->set_must_have_output_symtab_entry(r_sym); 767 } 768 } 769 770 rr->set_next_reloc_strategy(strategy); 771 } 772 } 773 774 // Relocate relocs. Called for a relocatable link, and for --emit-relocs. 775 // This is a default definition which should work for most targets. 776 777 template<int size, bool big_endian, typename Classify_reloc> 778 void 779 relocate_relocs( 780 const Relocate_info<size, big_endian>* relinfo, 781 const unsigned char* prelocs, 782 size_t reloc_count, 783 Output_section* output_section, 784 typename elfcpp::Elf_types<size>::Elf_Off offset_in_output_section, 785 unsigned char* view, 786 typename elfcpp::Elf_types<size>::Elf_Addr view_address, 787 section_size_type view_size, 788 unsigned char* reloc_view, 789 section_size_type reloc_view_size) 790 { 791 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address; 792 typedef typename Classify_reloc::Reltype Reltype; 793 typedef typename Classify_reloc::Reltype_write Reltype_write; 794 const int reloc_size = Classify_reloc::reloc_size; 795 const Address invalid_address = static_cast<Address>(0) - 1; 796 797 Sized_relobj_file<size, big_endian>* const object = relinfo->object; 798 const unsigned int local_count = object->local_symbol_count(); 799 800 unsigned char* pwrite = reloc_view; 801 802 const bool relocatable = parameters->options().relocatable(); 803 804 for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) 805 { 806 Relocatable_relocs::Reloc_strategy strategy = relinfo->rr->strategy(i); 807 if (strategy == Relocatable_relocs::RELOC_DISCARD) 808 continue; 809 810 if (strategy == Relocatable_relocs::RELOC_SPECIAL) 811 { 812 // Target wants to handle this relocation. 813 Sized_target<size, big_endian>* target = 814 parameters->sized_target<size, big_endian>(); 815 target->relocate_special_relocatable(relinfo, Classify_reloc::sh_type, 816 prelocs, i, output_section, 817 offset_in_output_section, 818 view, view_address, 819 view_size, pwrite); 820 pwrite += reloc_size; 821 continue; 822 } 823 Reltype reloc(prelocs); 824 Reltype_write reloc_write(pwrite); 825 826 const unsigned int r_sym = Classify_reloc::get_r_sym(&reloc); 827 828 // Get the new symbol index. 829 830 Output_section* os = NULL; 831 unsigned int new_symndx; 832 if (r_sym < local_count) 833 { 834 switch (strategy) 835 { 836 case Relocatable_relocs::RELOC_COPY: 837 if (r_sym == 0) 838 new_symndx = 0; 839 else 840 { 841 new_symndx = object->symtab_index(r_sym); 842 gold_assert(new_symndx != -1U); 843 } 844 break; 845 846 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA: 847 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0: 848 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1: 849 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2: 850 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4: 851 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8: 852 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4_UNALIGNED: 853 { 854 // We are adjusting a section symbol. We need to find 855 // the symbol table index of the section symbol for 856 // the output section corresponding to input section 857 // in which this symbol is defined. 858 gold_assert(r_sym < local_count); 859 bool is_ordinary; 860 unsigned int shndx = 861 object->local_symbol_input_shndx(r_sym, &is_ordinary); 862 gold_assert(is_ordinary); 863 os = object->output_section(shndx); 864 gold_assert(os != NULL); 865 gold_assert(os->needs_symtab_index()); 866 new_symndx = os->symtab_index(); 867 } 868 break; 869 870 default: 871 gold_unreachable(); 872 } 873 } 874 else 875 { 876 const Symbol* gsym = object->global_symbol(r_sym); 877 gold_assert(gsym != NULL); 878 if (gsym->is_forwarder()) 879 gsym = relinfo->symtab->resolve_forwards(gsym); 880 881 gold_assert(gsym->has_symtab_index()); 882 new_symndx = gsym->symtab_index(); 883 } 884 885 // Get the new offset--the location in the output section where 886 // this relocation should be applied. 887 888 Address offset = reloc.get_r_offset(); 889 Address new_offset; 890 if (offset_in_output_section != invalid_address) 891 new_offset = offset + offset_in_output_section; 892 else 893 { 894 section_offset_type sot_offset = 895 convert_types<section_offset_type, Address>(offset); 896 section_offset_type new_sot_offset = 897 output_section->output_offset(object, relinfo->data_shndx, 898 sot_offset); 899 gold_assert(new_sot_offset != -1); 900 new_offset = new_sot_offset; 901 } 902 903 // In an object file, r_offset is an offset within the section. 904 // In an executable or dynamic object, generated by 905 // --emit-relocs, r_offset is an absolute address. 906 if (!relocatable) 907 { 908 new_offset += view_address; 909 if (offset_in_output_section != invalid_address) 910 new_offset -= offset_in_output_section; 911 } 912 913 reloc_write.put_r_offset(new_offset); 914 Classify_reloc::put_r_info(&reloc_write, &reloc, new_symndx); 915 916 // Handle the reloc addend based on the strategy. 917 918 if (strategy == Relocatable_relocs::RELOC_COPY) 919 { 920 if (Classify_reloc::sh_type == elfcpp::SHT_RELA) 921 Classify_reloc::put_r_addend(&reloc_write, 922 Classify_reloc::get_r_addend(&reloc)); 923 } 924 else 925 { 926 // The relocation uses a section symbol in the input file. 927 // We are adjusting it to use a section symbol in the output 928 // file. The input section symbol refers to some address in 929 // the input section. We need the relocation in the output 930 // file to refer to that same address. This adjustment to 931 // the addend is the same calculation we use for a simple 932 // absolute relocation for the input section symbol. 933 934 const Symbol_value<size>* psymval = object->local_symbol(r_sym); 935 936 unsigned char* padd = view + offset; 937 switch (strategy) 938 { 939 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA: 940 { 941 typename elfcpp::Elf_types<size>::Elf_Swxword addend 942 = Classify_reloc::get_r_addend(&reloc); 943 addend = psymval->value(object, addend); 944 // In a relocatable link, the symbol value is relative to 945 // the start of the output section. For a non-relocatable 946 // link, we need to adjust the addend. 947 if (!relocatable) 948 { 949 gold_assert(os != NULL); 950 addend -= os->address(); 951 } 952 Classify_reloc::put_r_addend(&reloc_write, addend); 953 } 954 break; 955 956 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0: 957 break; 958 959 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1: 960 Relocate_functions<size, big_endian>::rel8(padd, object, 961 psymval); 962 break; 963 964 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2: 965 Relocate_functions<size, big_endian>::rel16(padd, object, 966 psymval); 967 break; 968 969 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4: 970 Relocate_functions<size, big_endian>::rel32(padd, object, 971 psymval); 972 break; 973 974 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8: 975 Relocate_functions<size, big_endian>::rel64(padd, object, 976 psymval); 977 break; 978 979 case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4_UNALIGNED: 980 Relocate_functions<size, big_endian>::rel32_unaligned(padd, 981 object, 982 psymval); 983 break; 984 985 default: 986 gold_unreachable(); 987 } 988 } 989 990 pwrite += reloc_size; 991 } 992 993 gold_assert(static_cast<section_size_type>(pwrite - reloc_view) 994 == reloc_view_size); 995 } 996 997 } // End namespace gold. 998 999 #endif // !defined(GOLD_TARGET_RELOC_H) 1000