gold/reloc.cc

   1 // reloc.cc -- relocate input files for gold.
   2
   3 // Copyright 2006, 2007, 2008, 2009 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 <algorithm>
  26
  27 #include "workqueue.h"
  28 #include "symtab.h"
  29 #include "output.h"
  30 #include "merge.h"
  31 #include "object.h"
  32 #include "target-reloc.h"
  33 #include "reloc.h"
  34
  35 namespace gold
  36 {
  37
  38 // Read_relocs methods.
  39
  40 // These tasks just read the relocation information from the file.
  41 // After reading it, the start another task to process the
  42 // information.  These tasks requires access to the file.
  43
  44 Task_token*
  45 Read_relocs::is_runnable()
  46 {
  47   return this->object_->is_locked() ? this->object_->token() : NULL;
  48 }
  49
  50 // Lock the file.
  51
  52 void
  53 Read_relocs::locks(Task_locker* tl)
  54 {
  55   tl->add(this, this->object_->token());
  56 }
  57
  58 // Read the relocations and then start a Scan_relocs_task.
  59
  60 void
  61 Read_relocs::run(Workqueue* workqueue)
  62 {
  63   Read_relocs_data *rd = new Read_relocs_data;
  64   this->object_->read_relocs(rd);
  65   this->object_->set_relocs_data(rd);
  66   this->object_->release();
  67
  68   // If garbage collection or identical comdat folding is desired, we
  69   // process the relocs first before scanning them.  Scanning of relocs is
  70   // done only after garbage or identical sections is identified.
  71   if (parameters->options().gc_sections() || parameters->options().icf())
  72     {
  73       workqueue->queue_next(new Gc_process_relocs(this->options_,
  74                                                   this->symtab_,
  75                                                   this->layout_,
  76                                                   this->object_, rd,
  77                                                   this->symtab_lock_,
  78                                                   this->blocker_));
  79     }
  80   else
  81     {
  82       workqueue->queue_next(new Scan_relocs(this->options_, this->symtab_,
  83                                             this->layout_, this->object_, rd,
  84                                             this->symtab_lock_,
  85                                             this->blocker_));
  86     }
  87 }
  88
  89 // Return a debugging name for the task.
  90
  91 std::string
  92 Read_relocs::get_name() const
  93 {
  94   return "Read_relocs " + this->object_->name();
  95 }
  96
  97 // Gc_process_relocs methods.
  98
  99 // These tasks process the relocations read by Read_relocs and
 100 // determine which sections are referenced and which are garbage.
 101 // This task is done only when --gc-sections is used.
 102
 103 Task_token*
 104 Gc_process_relocs::is_runnable()
 105 {
 106   if (this->object_->is_locked())
 107     return this->object_->token();
 108   return NULL;
 109 }
 110
 111 void
 112 Gc_process_relocs::locks(Task_locker* tl)
 113 {
 114   tl->add(this, this->object_->token());
 115   tl->add(this, this->blocker_);
 116 }
 117
 118 void
 119 Gc_process_relocs::run(Workqueue*)
 120 {
 121   this->object_->gc_process_relocs(this->options_, this->symtab_, this->layout_,
 122                      this->rd_);
 123   this->object_->release();
 124 }
 125
 126 // Return a debugging name for the task.
 127
 128 std::string
 129 Gc_process_relocs::get_name() const
 130 {
 131   return "Gc_process_relocs " + this->object_->name();
 132 }
 133
 134 // Scan_relocs methods.
 135
 136 // These tasks scan the relocations read by Read_relocs and mark up
 137 // the symbol table to indicate which relocations are required.  We
 138 // use a lock on the symbol table to keep them from interfering with
 139 // each other.
 140
 141 Task_token*
 142 Scan_relocs::is_runnable()
 143 {
 144   if (!this->symtab_lock_->is_writable())
 145     return this->symtab_lock_;
 146   if (this->object_->is_locked())
 147     return this->object_->token();
 148   return NULL;
 149 }
 150
 151 // Return the locks we hold: one on the file, one on the symbol table
 152 // and one blocker.
 153
 154 void
 155 Scan_relocs::locks(Task_locker* tl)
 156 {
 157   tl->add(this, this->object_->token());
 158   tl->add(this, this->symtab_lock_);
 159   tl->add(this, this->blocker_);
 160 }
 161
 162 // Scan the relocs.
 163
 164 void
 165 Scan_relocs::run(Workqueue*)
 166 {
 167   this->object_->scan_relocs(this->options_, this->symtab_, this->layout_,
 168                              this->rd_);
 169   this->object_->release();
 170   delete this->rd_;
 171   this->rd_ = NULL;
 172 }
 173
 174 // Return a debugging name for the task.
 175
 176 std::string
 177 Scan_relocs::get_name() const
 178 {
 179   return "Scan_relocs " + this->object_->name();
 180 }
 181
 182 // Relocate_task methods.
 183
 184 // We may have to wait for the output sections to be written.
 185
 186 Task_token*
 187 Relocate_task::is_runnable()
 188 {
 189   if (this->object_->relocs_must_follow_section_writes()
 190       && this->output_sections_blocker_->is_blocked())
 191     return this->output_sections_blocker_;
 192
 193   if (this->object_->is_locked())
 194     return this->object_->token();
 195
 196   return NULL;
 197 }
 198
 199 // We want to lock the file while we run.  We want to unblock
 200 // INPUT_SECTIONS_BLOCKER and FINAL_BLOCKER when we are done.
 201 // INPUT_SECTIONS_BLOCKER may be NULL.
 202
 203 void
 204 Relocate_task::locks(Task_locker* tl)
 205 {
 206   if (this->input_sections_blocker_ != NULL)
 207     tl->add(this, this->input_sections_blocker_);
 208   tl->add(this, this->final_blocker_);
 209   tl->add(this, this->object_->token());
 210 }
 211
 212 // Run the task.
 213
 214 void
 215 Relocate_task::run(Workqueue*)
 216 {
 217   this->object_->relocate(this->options_, this->symtab_, this->layout_,
 218                           this->of_);
 219
 220   // This is normally the last thing we will do with an object, so
 221   // uncache all views.
 222   this->object_->clear_view_cache_marks();
 223
 224   this->object_->release();
 225 }
 226
 227 // Return a debugging name for the task.
 228
 229 std::string
 230 Relocate_task::get_name() const
 231 {
 232   return "Relocate_task " + this->object_->name();
 233 }
 234
 235 // Read the relocs and local symbols from the object file and store
 236 // the information in RD.
 237
 238 template<int size, bool big_endian>
 239 void
 240 Sized_relobj<size, big_endian>::do_read_relocs(Read_relocs_data* rd)
 241 {
 242   rd->relocs.clear();
 243
 244   unsigned int shnum = this->shnum();
 245   if (shnum == 0)
 246     return;
 247
 248   rd->relocs.reserve(shnum / 2);
 249
 250   const Output_sections& out_sections(this->output_sections());
 251   const std::vector<Address>& out_offsets(this->section_offsets_);
 252
 253   const unsigned char *pshdrs = this->get_view(this->elf_file_.shoff(),
 254                                                shnum * This::shdr_size,
 255                                                true, true);
 256   // Skip the first, dummy, section.
 257   const unsigned char *ps = pshdrs + This::shdr_size;
 258   for (unsigned int i = 1; i < shnum; ++i, ps += This::shdr_size)
 259     {
 260       typename This::Shdr shdr(ps);
 261
 262       unsigned int sh_type = shdr.get_sh_type();
 263       if (sh_type != elfcpp::SHT_REL && sh_type != elfcpp::SHT_RELA)
 264         continue;
 265
 266       unsigned int shndx = this->adjust_shndx(shdr.get_sh_info());
 267       if (shndx >= shnum)
 268         {
 269           this->error(_("relocation section %u has bad info %u"),
 270                       i, shndx);
 271           continue;
 272         }
 273
 274       Output_section* os = out_sections[shndx];
 275       if (os == NULL)
 276         continue;
 277
 278       // We are scanning relocations in order to fill out the GOT and
 279       // PLT sections.  Relocations for sections which are not
 280       // allocated (typically debugging sections) should not add new
 281       // GOT and PLT entries.  So we skip them unless this is a
 282       // relocatable link or we need to emit relocations.  FIXME: What
 283       // should we do if a linker script maps a section with SHF_ALLOC
 284       // clear to a section with SHF_ALLOC set?
 285       typename This::Shdr secshdr(pshdrs + shndx * This::shdr_size);
 286       bool is_section_allocated = ((secshdr.get_sh_flags() & elfcpp::SHF_ALLOC)
 287                                    != 0);
 288       if (!is_section_allocated
 289           && !parameters->options().relocatable()
 290           && !parameters->options().emit_relocs())
 291         continue;
 292
 293       if (this->adjust_shndx(shdr.get_sh_link()) != this->symtab_shndx_)
 294         {
 295           this->error(_("relocation section %u uses unexpected "
 296                         "symbol table %u"),
 297                       i, this->adjust_shndx(shdr.get_sh_link()));
 298           continue;
 299         }
 300
 301       off_t sh_size = shdr.get_sh_size();
 302
 303       unsigned int reloc_size;
 304       if (sh_type == elfcpp::SHT_REL)
 305         reloc_size = elfcpp::Elf_sizes<size>::rel_size;
 306       else
 307         reloc_size = elfcpp::Elf_sizes<size>::rela_size;
 308       if (reloc_size != shdr.get_sh_entsize())
 309         {
 310           this->error(_("unexpected entsize for reloc section %u: %lu != %u"),
 311                       i, static_cast<unsigned long>(shdr.get_sh_entsize()),
 312                       reloc_size);
 313           continue;
 314         }
 315
 316       size_t reloc_count = sh_size / reloc_size;
 317       if (static_cast<off_t>(reloc_count * reloc_size) != sh_size)
 318         {
 319           this->error(_("reloc section %u size %lu uneven"),
 320                       i, static_cast<unsigned long>(sh_size));
 321           continue;
 322         }
 323
 324       rd->relocs.push_back(Section_relocs());
 325       Section_relocs& sr(rd->relocs.back());
 326       sr.reloc_shndx = i;
 327       sr.data_shndx = shndx;
 328       sr.contents = this->get_lasting_view(shdr.get_sh_offset(), sh_size,
 329                                            true, true);
 330       sr.sh_type = sh_type;
 331       sr.reloc_count = reloc_count;
 332       sr.output_section = os;
 333       sr.needs_special_offset_handling = out_offsets[shndx] == invalid_address;
 334       sr.is_data_section_allocated = is_section_allocated;
 335     }
 336
 337   // Read the local symbols.
 338   gold_assert(this->symtab_shndx_ != -1U);
 339   if (this->symtab_shndx_ == 0 || this->local_symbol_count_ == 0)
 340     rd->local_symbols = NULL;
 341   else
 342     {
 343       typename This::Shdr symtabshdr(pshdrs
 344                                      + this->symtab_shndx_ * This::shdr_size);
 345       gold_assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB);
 346       const int sym_size = This::sym_size;
 347       const unsigned int loccount = this->local_symbol_count_;
 348       gold_assert(loccount == symtabshdr.get_sh_info());
 349       off_t locsize = loccount * sym_size;
 350       rd->local_symbols = this->get_lasting_view(symtabshdr.get_sh_offset(),
 351                                                  locsize, true, true);
 352     }
 353 }
 354
 355 // Process the relocs to generate mappings from source sections to referenced
 356 // sections.  This is used during garbage colletion to determine garbage
 357 // sections.
 358
 359 template<int size, bool big_endian>
 360 void
 361 Sized_relobj<size, big_endian>::do_gc_process_relocs(const General_options& options,
 362                                                Symbol_table* symtab,
 363                                                Layout* layout,
 364                                                Read_relocs_data* rd)
 365 {
 366   Sized_target<size, big_endian>* target =
 367     parameters->sized_target<size, big_endian>();
 368
 369   const unsigned char* local_symbols;
 370   if (rd->local_symbols == NULL)
 371     local_symbols = NULL;
 372   else
 373     local_symbols = rd->local_symbols->data();
 374
 375   for (Read_relocs_data::Relocs_list::iterator p = rd->relocs.begin();
 376        p != rd->relocs.end();
 377        ++p)
 378     {
 379       if (!parameters->options().relocatable())
 380           {
 381             // As noted above, when not generating an object file, we
 382             // only scan allocated sections.  We may see a non-allocated
 383             // section here if we are emitting relocs.
 384             if (p->is_data_section_allocated)
 385               target->gc_process_relocs(options, symtab, layout, this,
 386                                         p->data_shndx, p->sh_type,
 387                                         p->contents->data(), p->reloc_count,
 388                                         p->output_section,
 389                                         p->needs_special_offset_handling,
 390                                         this->local_symbol_count_,
 391                                         local_symbols);
 392         }
 393     }
 394 }
 395
 396
 397 // Scan the relocs and adjust the symbol table.  This looks for
 398 // relocations which require GOT/PLT/COPY relocations.
 399
 400 template<int size, bool big_endian>
 401 void
 402 Sized_relobj<size, big_endian>::do_scan_relocs(const General_options& options,
 403                                                Symbol_table* symtab,
 404                                                Layout* layout,
 405                                                Read_relocs_data* rd)
 406 {
 407   Sized_target<size, big_endian>* target =
 408     parameters->sized_target<size, big_endian>();
 409
 410   const unsigned char* local_symbols;
 411   if (rd->local_symbols == NULL)
 412     local_symbols = NULL;
 413   else
 414     local_symbols = rd->local_symbols->data();
 415
 416   for (Read_relocs_data::Relocs_list::iterator p = rd->relocs.begin();
 417        p != rd->relocs.end();
 418        ++p)
 419     {
 420       // When garbage collection is on, unreferenced sections are not included
 421       // in the link that would have been included normally. This is known only
 422       // after Read_relocs hence this check has to be done again.
 423       if (parameters->options().gc_sections() || parameters->options().icf())
 424         {
 425           if (p->output_section == NULL)
 426             continue;
 427         }
 428       if (!parameters->options().relocatable())
 429         {
 430           // As noted above, when not generating an object file, we
 431           // only scan allocated sections.  We may see a non-allocated
 432           // section here if we are emitting relocs.
 433           if (p->is_data_section_allocated)
 434             target->scan_relocs(options, symtab, layout, this, p->data_shndx,
 435                                 p->sh_type, p->contents->data(),
 436                                 p->reloc_count, p->output_section,
 437                                 p->needs_special_offset_handling,
 438                                 this->local_symbol_count_,
 439                                 local_symbols);
 440           if (parameters->options().emit_relocs())
 441             this->emit_relocs_scan(options, symtab, layout, local_symbols, p);
 442         }
 443       else
 444         {
 445           Relocatable_relocs* rr = this->relocatable_relocs(p->reloc_shndx);
 446           gold_assert(rr != NULL);
 447           rr->set_reloc_count(p->reloc_count);
 448           target->scan_relocatable_relocs(options, symtab, layout, this,
 449                                           p->data_shndx, p->sh_type,
 450                                           p->contents->data(),
 451                                           p->reloc_count,
 452                                           p->output_section,
 453                                           p->needs_special_offset_handling,
 454                                           this->local_symbol_count_,
 455                                           local_symbols,
 456                                           rr);
 457         }
 458
 459       delete p->contents;
 460       p->contents = NULL;
 461     }
 462
 463   if (rd->local_symbols != NULL)
 464     {
 465       delete rd->local_symbols;
 466       rd->local_symbols = NULL;
 467     }
 468 }
 469
 470 // This is a strategy class we use when scanning for --emit-relocs.
 471
 472 template<int sh_type>
 473 class Emit_relocs_strategy
 474 {
 475  public:
 476   // A local non-section symbol.
 477   inline Relocatable_relocs::Reloc_strategy
 478   local_non_section_strategy(unsigned int, Relobj*, unsigned int)
 479   { return Relocatable_relocs::RELOC_COPY; }
 480
 481   // A local section symbol.
 482   inline Relocatable_relocs::Reloc_strategy
 483   local_section_strategy(unsigned int, Relobj*)
 484   {
 485     if (sh_type == elfcpp::SHT_RELA)
 486       return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA;
 487     else
 488       {
 489         // The addend is stored in the section contents.  Since this
 490         // is not a relocatable link, we are going to apply the
 491         // relocation contents to the section as usual.  This means
 492         // that we have no way to record the original addend.  If the
 493         // original addend is not zero, there is basically no way for
 494         // the user to handle this correctly.  Caveat emptor.
 495         return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0;
 496       }
 497   }
 498
 499   // A global symbol.
 500   inline Relocatable_relocs::Reloc_strategy
 501   global_strategy(unsigned int, Relobj*, unsigned int)
 502   { return Relocatable_relocs::RELOC_COPY; }
 503 };
 504
 505 // Scan the input relocations for --emit-relocs.
 506
 507 template<int size, bool big_endian>
 508 void
 509 Sized_relobj<size, big_endian>::emit_relocs_scan(
 510     const General_options& options,
 511     Symbol_table* symtab,
 512     Layout* layout,
 513     const unsigned char* plocal_syms,
 514     const Read_relocs_data::Relocs_list::iterator& p)
 515 {
 516   Relocatable_relocs* rr = this->relocatable_relocs(p->reloc_shndx);
 517   gold_assert(rr != NULL);
 518   rr->set_reloc_count(p->reloc_count);
 519
 520   if (p->sh_type == elfcpp::SHT_REL)
 521     this->emit_relocs_scan_reltype<elfcpp::SHT_REL>(options, symtab, layout,
 522                                                     plocal_syms, p, rr);
 523   else
 524     {
 525       gold_assert(p->sh_type == elfcpp::SHT_RELA);
 526       this->emit_relocs_scan_reltype<elfcpp::SHT_RELA>(options, symtab,
 527                                                        layout, plocal_syms, p,
 528                                                        rr);
 529     }
 530 }
 531
 532 // Scan the input relocation for --emit-relocs, templatized on the
 533 // type of the relocation section.
 534
 535 template<int size, bool big_endian>
 536 template<int sh_type>
 537 void
 538 Sized_relobj<size, big_endian>::emit_relocs_scan_reltype(
 539     const General_options& options,
 540     Symbol_table* symtab,
 541     Layout* layout,
 542     const unsigned char* plocal_syms,
 543     const Read_relocs_data::Relocs_list::iterator& p,
 544     Relocatable_relocs* rr)
 545 {
 546   scan_relocatable_relocs<size, big_endian, sh_type,
 547                           Emit_relocs_strategy<sh_type> >(
 548     options,
 549     symtab,
 550     layout,
 551     this,
 552     p->data_shndx,
 553     p->contents->data(),
 554     p->reloc_count,
 555     p->output_section,
 556     p->needs_special_offset_handling,
 557     this->local_symbol_count_,
 558     plocal_syms,
 559     rr);
 560 }
 561
 562 // Relocate the input sections and write out the local symbols.
 563
 564 template<int size, bool big_endian>
 565 void
 566 Sized_relobj<size, big_endian>::do_relocate(const General_options& options,
 567                                             const Symbol_table* symtab,
 568                                             const Layout* layout,
 569                                             Output_file* of)
 570 {
 571   unsigned int shnum = this->shnum();
 572
 573   // Read the section headers.
 574   const unsigned char* pshdrs = this->get_view(this->elf_file_.shoff(),
 575                                                shnum * This::shdr_size,
 576                                                true, true);
 577
 578   Views views;
 579   views.resize(shnum);
 580
 581   // Make two passes over the sections.  The first one copies the
 582   // section data to the output file.  The second one applies
 583   // relocations.
 584
 585   this->write_sections(pshdrs, of, &views);
 586
 587   // To speed up relocations, we set up hash tables for fast lookup of
 588   // input offsets to output addresses.
 589   this->initialize_input_to_output_maps();
 590
 591   // Apply relocations.
 592
 593   this->relocate_sections(options, symtab, layout, pshdrs, &views);
 594
 595   // After we've done the relocations, we release the hash tables,
 596   // since we no longer need them.
 597   this->free_input_to_output_maps();
 598
 599   // Write out the accumulated views.
 600   for (unsigned int i = 1; i < shnum; ++i)
 601     {
 602       if (views[i].view != NULL)
 603         {
 604           if (!views[i].is_postprocessing_view)
 605             {
 606               if (views[i].is_input_output_view)
 607                 of->write_input_output_view(views[i].offset,
 608                                             views[i].view_size,
 609                                             views[i].view);
 610               else
 611                 of->write_output_view(views[i].offset, views[i].view_size,
 612                                       views[i].view);
 613             }
 614         }
 615     }
 616
 617   // Write out the local symbols.
 618   this->write_local_symbols(of, layout->sympool(), layout->dynpool(),
 619                             layout->symtab_xindex(), layout->dynsym_xindex());
 620
 621   // We should no longer need the local symbol values.
 622   this->clear_local_symbols();
 623 }
 624
 625 // Sort a Read_multiple vector by file offset.
 626 struct Read_multiple_compare
 627 {
 628   inline bool
 629   operator()(const File_read::Read_multiple_entry& rme1,
 630              const File_read::Read_multiple_entry& rme2) const
 631   { return rme1.file_offset < rme2.file_offset; }
 632 };
 633
 634 // Write section data to the output file.  PSHDRS points to the
 635 // section headers.  Record the views in *PVIEWS for use when
 636 // relocating.
 637
 638 template<int size, bool big_endian>
 639 void
 640 Sized_relobj<size, big_endian>::write_sections(const unsigned char* pshdrs,
 641                                                Output_file* of,
 642                                                Views* pviews)
 643 {
 644   unsigned int shnum = this->shnum();
 645   const Output_sections& out_sections(this->output_sections());
 646   const std::vector<Address>& out_offsets(this->section_offsets_);
 647
 648   File_read::Read_multiple rm;
 649   bool is_sorted = true;
 650
 651   const unsigned char* p = pshdrs + This::shdr_size;
 652   for (unsigned int i = 1; i < shnum; ++i, p += This::shdr_size)
 653     {
 654       View_size* pvs = &(*pviews)[i];
 655
 656       pvs->view = NULL;
 657
 658       const Output_section* os = out_sections[i];
 659       if (os == NULL)
 660         continue;
 661       Address output_offset = out_offsets[i];
 662
 663       typename This::Shdr shdr(p);
 664
 665       if (shdr.get_sh_type() == elfcpp::SHT_NOBITS)
 666         continue;
 667
 668       if ((parameters->options().relocatable()
 669            || parameters->options().emit_relocs())
 670           && (shdr.get_sh_type() == elfcpp::SHT_REL
 671               || shdr.get_sh_type() == elfcpp::SHT_RELA)
 672           && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
 673         {
 674           // This is a reloc section in a relocatable link or when
 675           // emitting relocs.  We don't need to read the input file.
 676           // The size and file offset are stored in the
 677           // Relocatable_relocs structure.
 678           Relocatable_relocs* rr = this->relocatable_relocs(i);
 679           gold_assert(rr != NULL);
 680           Output_data* posd = rr->output_data();
 681           gold_assert(posd != NULL);
 682
 683           pvs->offset = posd->offset();
 684           pvs->view_size = posd->data_size();
 685           pvs->view = of->get_output_view(pvs->offset, pvs->view_size);
 686           pvs->address = posd->address();
 687           pvs->is_input_output_view = false;
 688           pvs->is_postprocessing_view = false;
 689
 690           continue;
 691         }
 692
 693       // In the normal case, this input section is simply mapped to
 694       // the output section at offset OUTPUT_OFFSET.
 695
 696       // However, if OUTPUT_OFFSET == INVALID_ADDRESS, then input data is
 697       // handled specially--e.g., a .eh_frame section.  The relocation
 698       // routines need to check for each reloc where it should be
 699       // applied.  For this case, we need an input/output view for the
 700       // entire contents of the section in the output file.  We don't
 701       // want to copy the contents of the input section to the output
 702       // section; the output section contents were already written,
 703       // and we waited for them in Relocate_task::is_runnable because
 704       // relocs_must_follow_section_writes is set for the object.
 705
 706       // Regardless of which of the above cases is true, we have to
 707       // check requires_postprocessing of the output section.  If that
 708       // is false, then we work with views of the output file
 709       // directly.  If it is true, then we work with a separate
 710       // buffer, and the output section is responsible for writing the
 711       // final data to the output file.
 712
 713       off_t output_section_offset;
 714       Address output_section_size;
 715       if (!os->requires_postprocessing())
 716         {
 717           output_section_offset = os->offset();
 718           output_section_size = convert_types<Address, off_t>(os->data_size());
 719         }
 720       else
 721         {
 722           output_section_offset = 0;
 723           output_section_size =
 724               convert_types<Address, off_t>(os->postprocessing_buffer_size());
 725         }
 726
 727       off_t view_start;
 728       section_size_type view_size;
 729       if (output_offset != invalid_address)
 730         {
 731           view_start = output_section_offset + output_offset;
 732           view_size = convert_to_section_size_type(shdr.get_sh_size());
 733         }
 734       else
 735         {
 736           view_start = output_section_offset;
 737           view_size = convert_to_section_size_type(output_section_size);
 738         }
 739
 740       if (view_size == 0)
 741         continue;
 742
 743       gold_assert(output_offset == invalid_address
 744                   || output_offset + view_size <= output_section_size);
 745
 746       unsigned char* view;
 747       if (os->requires_postprocessing())
 748         {
 749           unsigned char* buffer = os->postprocessing_buffer();
 750           view = buffer + view_start;
 751           if (output_offset != invalid_address)
 752             {
 753               off_t sh_offset = shdr.get_sh_offset();
 754               if (!rm.empty() && rm.back().file_offset > sh_offset)
 755                 is_sorted = false;
 756               rm.push_back(File_read::Read_multiple_entry(sh_offset,
 757                                                           view_size, view));
 758             }
 759         }
 760       else
 761         {
 762           if (output_offset == invalid_address)
 763             view = of->get_input_output_view(view_start, view_size);
 764           else
 765             {
 766               view = of->get_output_view(view_start, view_size);
 767               off_t sh_offset = shdr.get_sh_offset();
 768               if (!rm.empty() && rm.back().file_offset > sh_offset)
 769                 is_sorted = false;
 770               rm.push_back(File_read::Read_multiple_entry(sh_offset,
 771                                                           view_size, view));
 772             }
 773         }
 774
 775       pvs->view = view;
 776       pvs->address = os->address();
 777       if (output_offset != invalid_address)
 778         pvs->address += output_offset;
 779       pvs->offset = view_start;
 780       pvs->view_size = view_size;
 781       pvs->is_input_output_view = output_offset == invalid_address;
 782       pvs->is_postprocessing_view = os->requires_postprocessing();
 783     }
 784
 785   // Actually read the data.
 786   if (!rm.empty())
 787     {
 788       if (!is_sorted)
 789         std::sort(rm.begin(), rm.end(), Read_multiple_compare());
 790       this->read_multiple(rm);
 791     }
 792 }
 793
 794 // Relocate section data.  VIEWS points to the section data as views
 795 // in the output file.
 796
 797 template<int size, bool big_endian>
 798 void
 799 Sized_relobj<size, big_endian>::relocate_sections(
 800     const General_options& options,
 801     const Symbol_table* symtab,
 802     const Layout* layout,
 803     const unsigned char* pshdrs,
 804     Views* pviews)
 805 {
 806   unsigned int shnum = this->shnum();
 807   Sized_target<size, big_endian>* target =
 808     parameters->sized_target<size, big_endian>();
 809
 810   const Output_sections& out_sections(this->output_sections());
 811   const std::vector<Address>& out_offsets(this->section_offsets_);
 812
 813   Relocate_info<size, big_endian> relinfo;
 814   relinfo.options = &options;
 815   relinfo.symtab = symtab;
 816   relinfo.layout = layout;
 817   relinfo.object = this;
 818
 819   const unsigned char* p = pshdrs + This::shdr_size;
 820   for (unsigned int i = 1; i < shnum; ++i, p += This::shdr_size)
 821     {
 822       typename This::Shdr shdr(p);
 823
 824       unsigned int sh_type = shdr.get_sh_type();
 825       if (sh_type != elfcpp::SHT_REL && sh_type != elfcpp::SHT_RELA)
 826         continue;
 827
 828       off_t sh_size = shdr.get_sh_size();
 829       if (sh_size == 0)
 830         continue;
 831
 832       unsigned int index = this->adjust_shndx(shdr.get_sh_info());
 833       if (index >= this->shnum())
 834         {
 835           this->error(_("relocation section %u has bad info %u"),
 836                       i, index);
 837           continue;
 838         }
 839
 840       Output_section* os = out_sections[index];
 841       if (os == NULL)
 842         {
 843           // This relocation section is against a section which we
 844           // discarded.
 845           continue;
 846         }
 847       Address output_offset = out_offsets[index];
 848
 849       gold_assert((*pviews)[index].view != NULL);
 850       if (parameters->options().relocatable())
 851         gold_assert((*pviews)[i].view != NULL);
 852
 853       if (this->adjust_shndx(shdr.get_sh_link()) != this->symtab_shndx_)
 854         {
 855           gold_error(_("relocation section %u uses unexpected "
 856                        "symbol table %u"),
 857                      i, this->adjust_shndx(shdr.get_sh_link()));
 858           continue;
 859         }
 860
 861       const unsigned char* prelocs = this->get_view(shdr.get_sh_offset(),
 862                                                     sh_size, true, false);
 863
 864       unsigned int reloc_size;
 865       if (sh_type == elfcpp::SHT_REL)
 866         reloc_size = elfcpp::Elf_sizes<size>::rel_size;
 867       else
 868         reloc_size = elfcpp::Elf_sizes<size>::rela_size;
 869
 870       if (reloc_size != shdr.get_sh_entsize())
 871         {
 872           gold_error(_("unexpected entsize for reloc section %u: %lu != %u"),
 873                      i, static_cast<unsigned long>(shdr.get_sh_entsize()),
 874                      reloc_size);
 875           continue;
 876         }
 877
 878       size_t reloc_count = sh_size / reloc_size;
 879       if (static_cast<off_t>(reloc_count * reloc_size) != sh_size)
 880         {
 881           gold_error(_("reloc section %u size %lu uneven"),
 882                      i, static_cast<unsigned long>(sh_size));
 883           continue;
 884         }
 885
 886       gold_assert(output_offset != invalid_address
 887                   || this->relocs_must_follow_section_writes());
 888
 889       relinfo.reloc_shndx = i;
 890       relinfo.data_shndx = index;
 891       if (!parameters->options().relocatable())
 892         {
 893           target->relocate_section(&relinfo,
 894                                    sh_type,
 895                                    prelocs,
 896                                    reloc_count,
 897                                    os,
 898                                    output_offset == invalid_address,
 899                                    (*pviews)[index].view,
 900                                    (*pviews)[index].address,
 901                                    (*pviews)[index].view_size);
 902           if (parameters->options().emit_relocs())
 903             this->emit_relocs(&relinfo, i, sh_type, prelocs, reloc_count,
 904                               os, output_offset,
 905                               (*pviews)[index].view,
 906                               (*pviews)[index].address,
 907                               (*pviews)[index].view_size,
 908                               (*pviews)[i].view,
 909                               (*pviews)[i].view_size);
 910         }
 911       else
 912         {
 913           Relocatable_relocs* rr = this->relocatable_relocs(i);
 914           target->relocate_for_relocatable(&relinfo,
 915                                            sh_type,
 916                                            prelocs,
 917                                            reloc_count,
 918                                            os,
 919                                            output_offset,
 920                                            rr,
 921                                            (*pviews)[index].view,
 922                                            (*pviews)[index].address,
 923                                            (*pviews)[index].view_size,
 924                                            (*pviews)[i].view,
 925                                            (*pviews)[i].view_size);
 926         }
 927     }
 928 }
 929
 930 // Emit the relocs for --emit-relocs.
 931
 932 template<int size, bool big_endian>
 933 void
 934 Sized_relobj<size, big_endian>::emit_relocs(
 935     const Relocate_info<size, big_endian>* relinfo,
 936     unsigned int i,
 937     unsigned int sh_type,
 938     const unsigned char* prelocs,
 939     size_t reloc_count,
 940     Output_section* output_section,
 941     typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
 942     unsigned char* view,
 943     typename elfcpp::Elf_types<size>::Elf_Addr address,
 944     section_size_type view_size,
 945     unsigned char* reloc_view,
 946     section_size_type reloc_view_size)
 947 {
 948   if (sh_type == elfcpp::SHT_REL)
 949     this->emit_relocs_reltype<elfcpp::SHT_REL>(relinfo, i, prelocs,
 950                                                reloc_count, output_section,
 951                                                offset_in_output_section,
 952                                                view, address, view_size,
 953                                                reloc_view, reloc_view_size);
 954   else
 955     {
 956       gold_assert(sh_type == elfcpp::SHT_RELA);
 957       this->emit_relocs_reltype<elfcpp::SHT_RELA>(relinfo, i, prelocs,
 958                                                   reloc_count, output_section,
 959                                                   offset_in_output_section,
 960                                                   view, address, view_size,
 961                                                   reloc_view, reloc_view_size);
 962     }
 963 }
 964
 965 // Emit the relocs for --emit-relocs, templatized on the type of the
 966 // relocation section.
 967
 968 template<int size, bool big_endian>
 969 template<int sh_type>
 970 void
 971 Sized_relobj<size, big_endian>::emit_relocs_reltype(
 972     const Relocate_info<size, big_endian>* relinfo,
 973     unsigned int i,
 974     const unsigned char* prelocs,
 975     size_t reloc_count,
 976     Output_section* output_section,
 977     typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
 978     unsigned char* view,
 979     typename elfcpp::Elf_types<size>::Elf_Addr address,
 980     section_size_type view_size,
 981     unsigned char* reloc_view,
 982     section_size_type reloc_view_size)
 983 {
 984   const Relocatable_relocs* rr = this->relocatable_relocs(i);
 985   relocate_for_relocatable<size, big_endian, sh_type>(
 986     relinfo,
 987     prelocs,
 988     reloc_count,
 989     output_section,
 990     offset_in_output_section,
 991     rr,
 992     view,
 993     address,
 994     view_size,
 995     reloc_view,
 996     reloc_view_size);
 997 }
 998
 999 // Create merge hash tables for the local symbols.  These are used to
1000 // speed up relocations.
1001
1002 template<int size, bool big_endian>
1003 void
1004 Sized_relobj<size, big_endian>::initialize_input_to_output_maps()
1005 {
1006   const unsigned int loccount = this->local_symbol_count_;
1007   for (unsigned int i = 1; i < loccount; ++i)
1008     {
1009       Symbol_value<size>& lv(this->local_values_[i]);
1010       lv.initialize_input_to_output_map(this);
1011     }
1012 }
1013
1014 // Free merge hash tables for the local symbols.
1015
1016 template<int size, bool big_endian>
1017 void
1018 Sized_relobj<size, big_endian>::free_input_to_output_maps()
1019 {
1020   const unsigned int loccount = this->local_symbol_count_;
1021   for (unsigned int i = 1; i < loccount; ++i)
1022     {
1023       Symbol_value<size>& lv(this->local_values_[i]);
1024       lv.free_input_to_output_map();
1025     }
1026 }
1027
1028 // Class Merged_symbol_value.
1029
1030 template<int size>
1031 void
1032 Merged_symbol_value<size>::initialize_input_to_output_map(
1033     const Relobj* object,
1034     unsigned int input_shndx)
1035 {
1036   Object_merge_map* map = object->merge_map();
1037   map->initialize_input_to_output_map<size>(input_shndx,
1038                                             this->output_start_address_,
1039                                             &this->output_addresses_);
1040 }
1041
1042 // Get the output value corresponding to an input offset if we
1043 // couldn't find it in the hash table.
1044
1045 template<int size>
1046 typename elfcpp::Elf_types<size>::Elf_Addr
1047 Merged_symbol_value<size>::value_from_output_section(
1048     const Relobj* object,
1049     unsigned int input_shndx,
1050     typename elfcpp::Elf_types<size>::Elf_Addr input_offset) const
1051 {
1052   section_offset_type output_offset;
1053   bool found = object->merge_map()->get_output_offset(NULL, input_shndx,
1054                                                       input_offset,
1055                                                       &output_offset);
1056
1057   // If this assertion fails, it means that some relocation was
1058   // against a portion of an input merge section which we didn't map
1059   // to the output file and we didn't explicitly discard.  We should
1060   // always map all portions of input merge sections.
1061   gold_assert(found);
1062
1063   if (output_offset == -1)
1064     return 0;
1065   else
1066     return this->output_start_address_ + output_offset;
1067 }
1068
1069 // Track_relocs methods.
1070
1071 // Initialize the class to track the relocs.  This gets the object,
1072 // the reloc section index, and the type of the relocs.  This returns
1073 // false if something goes wrong.
1074
1075 template<int size, bool big_endian>
1076 bool
1077 Track_relocs<size, big_endian>::initialize(
1078     Object* object,
1079     unsigned int reloc_shndx,
1080     unsigned int reloc_type)
1081 {
1082   // If RELOC_SHNDX is -1U, it means there is more than one reloc
1083   // section for the .eh_frame section.  We can't handle that case.
1084   if (reloc_shndx == -1U)
1085     return false;
1086
1087   // If RELOC_SHNDX is 0, there is no reloc section.
1088   if (reloc_shndx == 0)
1089     return true;
1090
1091   // Get the contents of the reloc section.
1092   this->prelocs_ = object->section_contents(reloc_shndx, &this->len_, false);
1093
1094   if (reloc_type == elfcpp::SHT_REL)
1095     this->reloc_size_ = elfcpp::Elf_sizes<size>::rel_size;
1096   else if (reloc_type == elfcpp::SHT_RELA)
1097     this->reloc_size_ = elfcpp::Elf_sizes<size>::rela_size;
1098   else
1099     gold_unreachable();
1100
1101   if (this->len_ % this->reloc_size_ != 0)
1102     {
1103       object->error(_("reloc section size %zu is not a multiple of "
1104                       "reloc size %d\n"),
1105                     static_cast<size_t>(this->len_),
1106                     this->reloc_size_);
1107       return false;
1108     }
1109
1110   return true;
1111 }
1112
1113 // Return the offset of the next reloc, or -1 if there isn't one.
1114
1115 template<int size, bool big_endian>
1116 off_t
1117 Track_relocs<size, big_endian>::next_offset() const
1118 {
1119   if (this->pos_ >= this->len_)
1120     return -1;
1121
1122   // Rel and Rela start out the same, so we can always use Rel to find
1123   // the r_offset value.
1124   elfcpp::Rel<size, big_endian> rel(this->prelocs_ + this->pos_);
1125   return rel.get_r_offset();
1126 }
1127
1128 // Return the index of the symbol referenced by the next reloc, or -1U
1129 // if there aren't any more relocs.
1130
1131 template<int size, bool big_endian>
1132 unsigned int
1133 Track_relocs<size, big_endian>::next_symndx() const
1134 {
1135   if (this->pos_ >= this->len_)
1136     return -1U;
1137
1138   // Rel and Rela start out the same, so we can use Rel to find the
1139   // symbol index.
1140   elfcpp::Rel<size, big_endian> rel(this->prelocs_ + this->pos_);
1141   return elfcpp::elf_r_sym<size>(rel.get_r_info());
1142 }
1143
1144 // Advance to the next reloc whose r_offset is greater than or equal
1145 // to OFFSET.  Return the number of relocs we skip.
1146
1147 template<int size, bool big_endian>
1148 int
1149 Track_relocs<size, big_endian>::advance(off_t offset)
1150 {
1151   int ret = 0;
1152   while (this->pos_ < this->len_)
1153     {
1154       // Rel and Rela start out the same, so we can always use Rel to
1155       // find the r_offset value.
1156       elfcpp::Rel<size, big_endian> rel(this->prelocs_ + this->pos_);
1157       if (static_cast<off_t>(rel.get_r_offset()) >= offset)
1158         break;
1159       ++ret;
1160       this->pos_ += this->reloc_size_;
1161     }
1162   return ret;
1163 }
1164
1165 // Instantiate the templates we need.
1166
1167 #ifdef HAVE_TARGET_32_LITTLE
1168 template
1169 void
1170 Sized_relobj<32, false>::do_read_relocs(Read_relocs_data* rd);
1171 #endif
1172
1173 #ifdef HAVE_TARGET_32_BIG
1174 template
1175 void
1176 Sized_relobj<32, true>::do_read_relocs(Read_relocs_data* rd);
1177 #endif
1178
1179 #ifdef HAVE_TARGET_64_LITTLE
1180 template
1181 void
1182 Sized_relobj<64, false>::do_read_relocs(Read_relocs_data* rd);
1183 #endif
1184
1185 #ifdef HAVE_TARGET_64_BIG
1186 template
1187 void
1188 Sized_relobj<64, true>::do_read_relocs(Read_relocs_data* rd);
1189 #endif
1190
1191 #ifdef HAVE_TARGET_32_LITTLE
1192 template
1193 void
1194 Sized_relobj<32, false>::do_gc_process_relocs(const General_options& options,
1195                                         Symbol_table* symtab,
1196                                         Layout* layout,
1197                                         Read_relocs_data* rd);
1198 #endif
1199
1200 #ifdef HAVE_TARGET_32_BIG
1201 template
1202 void
1203 Sized_relobj<32, true>::do_gc_process_relocs(const General_options& options,
1204                                        Symbol_table* symtab,
1205                                        Layout* layout,
1206                                        Read_relocs_data* rd);
1207 #endif
1208
1209 #ifdef HAVE_TARGET_64_LITTLE
1210 template
1211 void
1212 Sized_relobj<64, false>::do_gc_process_relocs(const General_options& options,
1213                                         Symbol_table* symtab,
1214                                         Layout* layout,
1215                                         Read_relocs_data* rd);
1216 #endif
1217
1218 #ifdef HAVE_TARGET_64_BIG
1219 template
1220 void
1221 Sized_relobj<64, true>::do_gc_process_relocs(const General_options& options,
1222                                        Symbol_table* symtab,
1223                                        Layout* layout,
1224                                        Read_relocs_data* rd);
1225 #endif
1226
1227 #ifdef HAVE_TARGET_32_LITTLE
1228 template
1229 void
1230 Sized_relobj<32, false>::do_scan_relocs(const General_options& options,
1231                                         Symbol_table* symtab,
1232                                         Layout* layout,
1233                                         Read_relocs_data* rd);
1234 #endif
1235
1236 #ifdef HAVE_TARGET_32_BIG
1237 template
1238 void
1239 Sized_relobj<32, true>::do_scan_relocs(const General_options& options,
1240                                        Symbol_table* symtab,
1241                                        Layout* layout,
1242                                        Read_relocs_data* rd);
1243 #endif
1244
1245 #ifdef HAVE_TARGET_64_LITTLE
1246 template
1247 void
1248 Sized_relobj<64, false>::do_scan_relocs(const General_options& options,
1249                                         Symbol_table* symtab,
1250                                         Layout* layout,
1251                                         Read_relocs_data* rd);
1252 #endif
1253
1254 #ifdef HAVE_TARGET_64_BIG
1255 template
1256 void
1257 Sized_relobj<64, true>::do_scan_relocs(const General_options& options,
1258                                        Symbol_table* symtab,
1259                                        Layout* layout,
1260                                        Read_relocs_data* rd);
1261 #endif
1262
1263 #ifdef HAVE_TARGET_32_LITTLE
1264 template
1265 void
1266 Sized_relobj<32, false>::do_relocate(const General_options& options,
1267                                      const Symbol_table* symtab,
1268                                      const Layout* layout,
1269                                      Output_file* of);
1270 #endif
1271
1272 #ifdef HAVE_TARGET_32_BIG
1273 template
1274 void
1275 Sized_relobj<32, true>::do_relocate(const General_options& options,
1276                                     const Symbol_table* symtab,
1277                                     const Layout* layout,
1278                                     Output_file* of);
1279 #endif
1280
1281 #ifdef HAVE_TARGET_64_LITTLE
1282 template
1283 void
1284 Sized_relobj<64, false>::do_relocate(const General_options& options,
1285                                      const Symbol_table* symtab,
1286                                      const Layout* layout,
1287                                      Output_file* of);
1288 #endif
1289
1290 #ifdef HAVE_TARGET_64_BIG
1291 template
1292 void
1293 Sized_relobj<64, true>::do_relocate(const General_options& options,
1294                                     const Symbol_table* symtab,
1295                                     const Layout* layout,
1296                                     Output_file* of);
1297 #endif
1298
1299 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1300 template
1301 class Merged_symbol_value<32>;
1302 #endif
1303
1304 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1305 template
1306 class Merged_symbol_value<64>;
1307 #endif
1308
1309 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1310 template
1311 class Symbol_value<32>;
1312 #endif
1313
1314 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1315 template
1316 class Symbol_value<64>;
1317 #endif
1318
1319 #ifdef HAVE_TARGET_32_LITTLE
1320 template
1321 class Track_relocs<32, false>;
1322 #endif
1323
1324 #ifdef HAVE_TARGET_32_BIG
1325 template
1326 class Track_relocs<32, true>;
1327 #endif
1328
1329 #ifdef HAVE_TARGET_64_LITTLE
1330 template
1331 class Track_relocs<64, false>;
1332 #endif
1333
1334 #ifdef HAVE_TARGET_64_BIG
1335 template
1336 class Track_relocs<64, true>;
1337 #endif
1338
1339 } // End namespace gold.