gold/layout.cc

   1 // layout.cc -- lay out output file sections for gold
   2
   3 #include "gold.h"
   4
   5 #include <cassert>
   6 #include <cstring>
   7 #include <algorithm>
   8 #include <iostream>
   9 #include <utility>
  10
  11 #include "output.h"
  12 #include "symtab.h"
  13 #include "layout.h"
  14
  15 namespace gold
  16 {
  17
  18 // Layout_task_runner methods.
  19
  20 // Lay out the sections.  This is called after all the input objects
  21 // have been read.
  22
  23 void
  24 Layout_task_runner::run(Workqueue* workqueue)
  25 {
  26   off_t file_size = this->layout_->finalize(this->input_objects_,
  27                                             this->symtab_);
  28
  29   // Now we know the final size of the output file and we know where
  30   // each piece of information goes.
  31   Output_file* of = new Output_file(this->options_);
  32   of->open(file_size);
  33
  34   // Queue up the final set of tasks.
  35   gold::queue_final_tasks(this->options_, this->input_objects_,
  36                           this->symtab_, this->layout_, workqueue, of);
  37 }
  38
  39 // Layout methods.
  40
  41 Layout::Layout(const General_options& options)
  42   : options_(options), namepool_(), sympool_(), signatures_(),
  43     section_name_map_(), segment_list_(), section_list_(),
  44     special_output_list_(), tls_segment_(NULL)
  45 {
  46   // Make space for more than enough segments for a typical file.
  47   // This is just for efficiency--it's OK if we wind up needing more.
  48   segment_list_.reserve(12);
  49 }
  50
  51 // Hash a key we use to look up an output section mapping.
  52
  53 size_t
  54 Layout::Hash_key::operator()(const Layout::Key& k) const
  55 {
  56  return k.first + k.second.first + k.second.second;
  57 }
  58
  59 // Whether to include this section in the link.
  60
  61 template<int size, bool big_endian>
  62 bool
  63 Layout::include_section(Object*, const char*,
  64                         const elfcpp::Shdr<size, big_endian>& shdr)
  65 {
  66   // Some section types are never linked.  Some are only linked when
  67   // doing a relocateable link.
  68   switch (shdr.get_sh_type())
  69     {
  70     case elfcpp::SHT_NULL:
  71     case elfcpp::SHT_SYMTAB:
  72     case elfcpp::SHT_DYNSYM:
  73     case elfcpp::SHT_STRTAB:
  74     case elfcpp::SHT_HASH:
  75     case elfcpp::SHT_DYNAMIC:
  76     case elfcpp::SHT_SYMTAB_SHNDX:
  77       return false;
  78
  79     case elfcpp::SHT_RELA:
  80     case elfcpp::SHT_REL:
  81     case elfcpp::SHT_GROUP:
  82       return this->options_.is_relocatable();
  83
  84     default:
  85       // FIXME: Handle stripping debug sections here.
  86       return true;
  87     }
  88 }
  89
  90 // Return an output section named NAME, or NULL if there is none.
  91
  92 Output_section*
  93 Layout::find_output_section(const char* name) const
  94 {
  95   for (Section_name_map::const_iterator p = this->section_name_map_.begin();
  96        p != this->section_name_map_.end();
  97        ++p)
  98     if (strcmp(p->second->name(), name) == 0)
  99       return p->second;
 100   return NULL;
 101 }
 102
 103 // Return an output segment of type TYPE, with segment flags SET set
 104 // and segment flags CLEAR clear.  Return NULL if there is none.
 105
 106 Output_segment*
 107 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
 108                             elfcpp::Elf_Word clear) const
 109 {
 110   for (Segment_list::const_iterator p = this->segment_list_.begin();
 111        p != this->segment_list_.end();
 112        ++p)
 113     if (static_cast<elfcpp::PT>((*p)->type()) == type
 114         && ((*p)->flags() & set) == set
 115         && ((*p)->flags() & clear) == 0)
 116       return *p;
 117   return NULL;
 118 }
 119
 120 // Return the output section to use for section NAME with type TYPE
 121 // and section flags FLAGS.
 122
 123 Output_section*
 124 Layout::get_output_section(const char* name, Stringpool::Key name_key,
 125                            elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
 126 {
 127   // We should ignore some flags.
 128   flags &= ~ (elfcpp::SHF_INFO_LINK
 129               | elfcpp::SHF_LINK_ORDER
 130               | elfcpp::SHF_GROUP);
 131
 132   const Key key(name_key, std::make_pair(type, flags));
 133   const std::pair<Key, Output_section*> v(key, NULL);
 134   std::pair<Section_name_map::iterator, bool> ins(
 135     this->section_name_map_.insert(v));
 136
 137   if (!ins.second)
 138     return ins.first->second;
 139   else
 140     {
 141       // This is the first time we've seen this name/type/flags
 142       // combination.
 143       Output_section* os = this->make_output_section(name, type, flags);
 144       ins.first->second = os;
 145       return os;
 146     }
 147 }
 148
 149 // Return the output section to use for input section SHNDX, with name
 150 // NAME, with header HEADER, from object OBJECT.  Set *OFF to the
 151 // offset of this input section without the output section.
 152
 153 template<int size, bool big_endian>
 154 Output_section*
 155 Layout::layout(Relobj* object, unsigned int shndx, const char* name,
 156                const elfcpp::Shdr<size, big_endian>& shdr, off_t* off)
 157 {
 158   if (!this->include_section(object, name, shdr))
 159     return NULL;
 160
 161   // If we are not doing a relocateable link, choose the name to use
 162   // for the output section.
 163   size_t len = strlen(name);
 164   if (!this->options_.is_relocatable())
 165     name = Layout::output_section_name(name, &len);
 166
 167   // FIXME: Handle SHF_OS_NONCONFORMING here.
 168
 169   // Canonicalize the section name.
 170   Stringpool::Key name_key;
 171   name = this->namepool_.add(name, len, &name_key);
 172
 173   // Find the output section.  The output section is selected based on
 174   // the section name, type, and flags.
 175   Output_section* os = this->get_output_section(name, name_key,
 176                                                 shdr.get_sh_type(),
 177                                                 shdr.get_sh_flags());
 178
 179   // FIXME: Handle SHF_LINK_ORDER somewhere.
 180
 181   *off = os->add_input_section(object, shndx, name, shdr);
 182
 183   return os;
 184 }
 185
 186 // Add POSD to an output section using NAME, TYPE, and FLAGS.
 187
 188 void
 189 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
 190                                 elfcpp::Elf_Xword flags,
 191                                 Output_section_data* posd)
 192 {
 193   // Canonicalize the name.
 194   Stringpool::Key name_key;
 195   name = this->namepool_.add(name, &name_key);
 196
 197   Output_section* os = this->get_output_section(name, name_key, type, flags);
 198   os->add_output_section_data(posd);
 199 }
 200
 201 // Map section flags to segment flags.
 202
 203 elfcpp::Elf_Word
 204 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
 205 {
 206   elfcpp::Elf_Word ret = elfcpp::PF_R;
 207   if ((flags & elfcpp::SHF_WRITE) != 0)
 208     ret |= elfcpp::PF_W;
 209   if ((flags & elfcpp::SHF_EXECINSTR) != 0)
 210     ret |= elfcpp::PF_X;
 211   return ret;
 212 }
 213
 214 // Make a new Output_section, and attach it to segments as
 215 // appropriate.
 216
 217 Output_section*
 218 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
 219                             elfcpp::Elf_Xword flags)
 220 {
 221   Output_section* os = new Output_section(name, type, flags, true);
 222
 223   if ((flags & elfcpp::SHF_ALLOC) == 0)
 224     this->section_list_.push_back(os);
 225   else
 226     {
 227       // This output section goes into a PT_LOAD segment.
 228
 229       elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
 230
 231       // The only thing we really care about for PT_LOAD segments is
 232       // whether or not they are writable, so that is how we search
 233       // for them.  People who need segments sorted on some other
 234       // basis will have to wait until we implement a mechanism for
 235       // them to describe the segments they want.
 236
 237       Segment_list::const_iterator p;
 238       for (p = this->segment_list_.begin();
 239            p != this->segment_list_.end();
 240            ++p)
 241         {
 242           if ((*p)->type() == elfcpp::PT_LOAD
 243               && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
 244             {
 245               (*p)->add_output_section(os, seg_flags);
 246               break;
 247             }
 248         }
 249
 250       if (p == this->segment_list_.end())
 251         {
 252           Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
 253                                                     seg_flags);
 254           this->segment_list_.push_back(oseg);
 255           oseg->add_output_section(os, seg_flags);
 256         }
 257
 258       // If we see a loadable SHT_NOTE section, we create a PT_NOTE
 259       // segment.
 260       if (type == elfcpp::SHT_NOTE)
 261         {
 262           // See if we already have an equivalent PT_NOTE segment.
 263           for (p = this->segment_list_.begin();
 264                p != segment_list_.end();
 265                ++p)
 266             {
 267               if ((*p)->type() == elfcpp::PT_NOTE
 268                   && (((*p)->flags() & elfcpp::PF_W)
 269                       == (seg_flags & elfcpp::PF_W)))
 270                 {
 271                   (*p)->add_output_section(os, seg_flags);
 272                   break;
 273                 }
 274             }
 275
 276           if (p == this->segment_list_.end())
 277             {
 278               Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
 279                                                         seg_flags);
 280               this->segment_list_.push_back(oseg);
 281               oseg->add_output_section(os, seg_flags);
 282             }
 283         }
 284
 285       // If we see a loadable SHF_TLS section, we create a PT_TLS
 286       // segment.  There can only be one such segment.
 287       if ((flags & elfcpp::SHF_TLS) != 0)
 288         {
 289           if (this->tls_segment_ == NULL)
 290             {
 291               this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
 292                                                       seg_flags);
 293               this->segment_list_.push_back(this->tls_segment_);
 294             }
 295           this->tls_segment_->add_output_section(os, seg_flags);
 296         }
 297     }
 298
 299   return os;
 300 }
 301
 302 // Find the first read-only PT_LOAD segment, creating one if
 303 // necessary.
 304
 305 Output_segment*
 306 Layout::find_first_load_seg()
 307 {
 308   for (Segment_list::const_iterator p = this->segment_list_.begin();
 309        p != this->segment_list_.end();
 310        ++p)
 311     {
 312       if ((*p)->type() == elfcpp::PT_LOAD
 313           && ((*p)->flags() & elfcpp::PF_R) != 0
 314           && ((*p)->flags() & elfcpp::PF_W) == 0)
 315         return *p;
 316     }
 317
 318   Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
 319   this->segment_list_.push_back(load_seg);
 320   return load_seg;
 321 }
 322
 323 // Finalize the layout.  When this is called, we have created all the
 324 // output sections and all the output segments which are based on
 325 // input sections.  We have several things to do, and we have to do
 326 // them in the right order, so that we get the right results correctly
 327 // and efficiently.
 328
 329 // 1) Finalize the list of output segments and create the segment
 330 // table header.
 331
 332 // 2) Finalize the dynamic symbol table and associated sections.
 333
 334 // 3) Determine the final file offset of all the output segments.
 335
 336 // 4) Determine the final file offset of all the SHF_ALLOC output
 337 // sections.
 338
 339 // 5) Create the symbol table sections and the section name table
 340 // section.
 341
 342 // 6) Finalize the symbol table: set symbol values to their final
 343 // value and make a final determination of which symbols are going
 344 // into the output symbol table.
 345
 346 // 7) Create the section table header.
 347
 348 // 8) Determine the final file offset of all the output sections which
 349 // are not SHF_ALLOC, including the section table header.
 350
 351 // 9) Finalize the ELF file header.
 352
 353 // This function returns the size of the output file.
 354
 355 off_t
 356 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab)
 357 {
 358   const int size = input_objects->target()->get_size();
 359
 360   Output_segment* phdr_seg = NULL;
 361   if (input_objects->any_dynamic())
 362     {
 363       // There was a dynamic object in the link.  We need to create
 364       // some information for the dynamic linker.
 365
 366       // Create the PT_PHDR segment which will hold the program
 367       // headers.
 368       phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
 369       this->segment_list_.push_back(phdr_seg);
 370
 371       // Create the dynamic symbol table, including the hash table,
 372       // the dynamic relocations, and the version sections.
 373       this->create_dynamic_symtab(size, symtab);
 374
 375       // Create the .dynamic section to hold the dynamic data, and put
 376       // it in a PT_DYNAMIC segment.
 377       this->create_dynamic_section();
 378
 379       // Create the .interp section to hold the name of the
 380       // interpreter, and put it in a PT_INTERP segment.
 381       this->create_interp(input_objects->target());
 382     }
 383
 384   // FIXME: Handle PT_GNU_STACK.
 385
 386   Output_segment* load_seg = this->find_first_load_seg();
 387
 388   // Lay out the segment headers.
 389   bool big_endian = input_objects->target()->is_big_endian();
 390   Output_segment_headers* segment_headers;
 391   segment_headers = new Output_segment_headers(size, big_endian,
 392                                                this->segment_list_);
 393   load_seg->add_initial_output_data(segment_headers);
 394   this->special_output_list_.push_back(segment_headers);
 395   if (phdr_seg != NULL)
 396     phdr_seg->add_initial_output_data(segment_headers);
 397
 398   // Lay out the file header.
 399   Output_file_header* file_header;
 400   file_header = new Output_file_header(size,
 401                                        big_endian,
 402                                        this->options_,
 403                                        input_objects->target(),
 404                                        symtab,
 405                                        segment_headers);
 406   load_seg->add_initial_output_data(file_header);
 407   this->special_output_list_.push_back(file_header);
 408
 409   // We set the output section indexes in set_segment_offsets and
 410   // set_section_offsets.
 411   unsigned int shndx = 1;
 412
 413   // Set the file offsets of all the segments, and all the sections
 414   // they contain.
 415   off_t off = this->set_segment_offsets(input_objects->target(), load_seg,
 416                                         &shndx);
 417
 418   // Create the symbol table sections.
 419   // FIXME: We don't need to do this if we are stripping symbols.
 420   Output_section* osymtab;
 421   Output_section* ostrtab;
 422   this->create_symtab_sections(size, input_objects, symtab, &off,
 423                                &osymtab, &ostrtab);
 424
 425   // Create the .shstrtab section.
 426   Output_section* shstrtab_section = this->create_shstrtab();
 427
 428   // Set the file offsets of all the sections not associated with
 429   // segments.
 430   off = this->set_section_offsets(off, &shndx);
 431
 432   // Now the section index of OSTRTAB is set.
 433   osymtab->set_link(ostrtab->out_shndx());
 434
 435   // Create the section table header.
 436   Output_section_headers* oshdrs = this->create_shdrs(size, big_endian, &off);
 437
 438   file_header->set_section_info(oshdrs, shstrtab_section);
 439
 440   // Now we know exactly where everything goes in the output file.
 441
 442   return off;
 443 }
 444
 445 // Return whether SEG1 should be before SEG2 in the output file.  This
 446 // is based entirely on the segment type and flags.  When this is
 447 // called the segment addresses has normally not yet been set.
 448
 449 bool
 450 Layout::segment_precedes(const Output_segment* seg1,
 451                          const Output_segment* seg2)
 452 {
 453   elfcpp::Elf_Word type1 = seg1->type();
 454   elfcpp::Elf_Word type2 = seg2->type();
 455
 456   // The single PT_PHDR segment is required to precede any loadable
 457   // segment.  We simply make it always first.
 458   if (type1 == elfcpp::PT_PHDR)
 459     {
 460       assert(type2 != elfcpp::PT_PHDR);
 461       return true;
 462     }
 463   if (type2 == elfcpp::PT_PHDR)
 464     return false;
 465
 466   // The single PT_INTERP segment is required to precede any loadable
 467   // segment.  We simply make it always second.
 468   if (type1 == elfcpp::PT_INTERP)
 469     {
 470       assert(type2 != elfcpp::PT_INTERP);
 471       return true;
 472     }
 473   if (type2 == elfcpp::PT_INTERP)
 474     return false;
 475
 476   // We then put PT_LOAD segments before any other segments.
 477   if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
 478     return true;
 479   if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
 480     return false;
 481
 482   // We put the PT_TLS segment last, because that is where the dynamic
 483   // linker expects to find it (this is just for efficiency; other
 484   // positions would also work correctly).
 485   if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
 486     return false;
 487   if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
 488     return true;
 489
 490   const elfcpp::Elf_Word flags1 = seg1->flags();
 491   const elfcpp::Elf_Word flags2 = seg2->flags();
 492
 493   // The order of non-PT_LOAD segments is unimportant.  We simply sort
 494   // by the numeric segment type and flags values.  There should not
 495   // be more than one segment with the same type and flags.
 496   if (type1 != elfcpp::PT_LOAD)
 497     {
 498       if (type1 != type2)
 499         return type1 < type2;
 500       assert(flags1 != flags2);
 501       return flags1 < flags2;
 502     }
 503
 504   // We sort PT_LOAD segments based on the flags.  Readonly segments
 505   // come before writable segments.  Then executable segments come
 506   // before non-executable segments.  Then the unlikely case of a
 507   // non-readable segment comes before the normal case of a readable
 508   // segment.  If there are multiple segments with the same type and
 509   // flags, we require that the address be set, and we sort by
 510   // virtual address and then physical address.
 511   if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
 512     return (flags1 & elfcpp::PF_W) == 0;
 513   if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
 514     return (flags1 & elfcpp::PF_X) != 0;
 515   if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
 516     return (flags1 & elfcpp::PF_R) == 0;
 517
 518   uint64_t vaddr1 = seg1->vaddr();
 519   uint64_t vaddr2 = seg2->vaddr();
 520   if (vaddr1 != vaddr2)
 521     return vaddr1 < vaddr2;
 522
 523   uint64_t paddr1 = seg1->paddr();
 524   uint64_t paddr2 = seg2->paddr();
 525   assert(paddr1 != paddr2);
 526   return paddr1 < paddr2;
 527 }
 528
 529 // Set the file offsets of all the segments, and all the sections they
 530 // contain.  They have all been created.  LOAD_SEG must be be laid out
 531 // first.  Return the offset of the data to follow.
 532
 533 off_t
 534 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
 535                             unsigned int *pshndx)
 536 {
 537   // Sort them into the final order.
 538   std::sort(this->segment_list_.begin(), this->segment_list_.end(),
 539             Layout::Compare_segments());
 540
 541   // Find the PT_LOAD segments, and set their addresses and offsets
 542   // and their section's addresses and offsets.
 543   uint64_t addr = target->text_segment_address();
 544   off_t off = 0;
 545   bool was_readonly = false;
 546   for (Segment_list::iterator p = this->segment_list_.begin();
 547        p != this->segment_list_.end();
 548        ++p)
 549     {
 550       if ((*p)->type() == elfcpp::PT_LOAD)
 551         {
 552           if (load_seg != NULL && load_seg != *p)
 553             abort();
 554           load_seg = NULL;
 555
 556           // If the last segment was readonly, and this one is not,
 557           // then skip the address forward one page, maintaining the
 558           // same position within the page.  This lets us store both
 559           // segments overlapping on a single page in the file, but
 560           // the loader will put them on different pages in memory.
 561
 562           uint64_t orig_addr = addr;
 563           uint64_t orig_off = off;
 564
 565           uint64_t aligned_addr = addr;
 566           uint64_t abi_pagesize = target->abi_pagesize();
 567           if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
 568             {
 569               uint64_t align = (*p)->addralign();
 570
 571               addr = align_address(addr, align);
 572               aligned_addr = addr;
 573               if ((addr & (abi_pagesize - 1)) != 0)
 574                 addr = addr + abi_pagesize;
 575             }
 576
 577           unsigned int shndx_hold = *pshndx;
 578           off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
 579           uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
 580
 581           // Now that we know the size of this segment, we may be able
 582           // to save a page in memory, at the cost of wasting some
 583           // file space, by instead aligning to the start of a new
 584           // page.  Here we use the real machine page size rather than
 585           // the ABI mandated page size.
 586
 587           if (aligned_addr != addr)
 588             {
 589               uint64_t common_pagesize = target->common_pagesize();
 590               uint64_t first_off = (common_pagesize
 591                                     - (aligned_addr
 592                                        & (common_pagesize - 1)));
 593               uint64_t last_off = new_addr & (common_pagesize - 1);
 594               if (first_off > 0
 595                   && last_off > 0
 596                   && ((aligned_addr & ~ (common_pagesize - 1))
 597                       != (new_addr & ~ (common_pagesize - 1)))
 598                   && first_off + last_off <= common_pagesize)
 599                 {
 600                   *pshndx = shndx_hold;
 601                   addr = align_address(aligned_addr, common_pagesize);
 602                   off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
 603                   new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
 604                 }
 605             }
 606
 607           addr = new_addr;
 608
 609           if (((*p)->flags() & elfcpp::PF_W) == 0)
 610             was_readonly = true;
 611         }
 612     }
 613
 614   // Handle the non-PT_LOAD segments, setting their offsets from their
 615   // section's offsets.
 616   for (Segment_list::iterator p = this->segment_list_.begin();
 617        p != this->segment_list_.end();
 618        ++p)
 619     {
 620       if ((*p)->type() != elfcpp::PT_LOAD)
 621         (*p)->set_offset();
 622     }
 623
 624   return off;
 625 }
 626
 627 // Set the file offset of all the sections not associated with a
 628 // segment.
 629
 630 off_t
 631 Layout::set_section_offsets(off_t off, unsigned int* pshndx)
 632 {
 633   for (Layout::Section_list::iterator p = this->section_list_.begin();
 634        p != this->section_list_.end();
 635        ++p)
 636     {
 637       (*p)->set_out_shndx(*pshndx);
 638       ++*pshndx;
 639       if ((*p)->offset() != -1)
 640         continue;
 641       off = align_address(off, (*p)->addralign());
 642       (*p)->set_address(0, off);
 643       off += (*p)->data_size();
 644     }
 645   return off;
 646 }
 647
 648 // Create the symbol table sections.
 649
 650 void
 651 Layout::create_symtab_sections(int size, const Input_objects* input_objects,
 652                                Symbol_table* symtab,
 653                                off_t* poff,
 654                                Output_section** posymtab,
 655                                Output_section** postrtab)
 656 {
 657   int symsize;
 658   unsigned int align;
 659   if (size == 32)
 660     {
 661       symsize = elfcpp::Elf_sizes<32>::sym_size;
 662       align = 4;
 663     }
 664   else if (size == 64)
 665     {
 666       symsize = elfcpp::Elf_sizes<64>::sym_size;
 667       align = 8;
 668     }
 669   else
 670     abort();
 671
 672   off_t off = *poff;
 673   off = align_address(off, align);
 674   off_t startoff = off;
 675
 676   // Save space for the dummy symbol at the start of the section.  We
 677   // never bother to write this out--it will just be left as zero.
 678   off += symsize;
 679   unsigned int local_symbol_index = 1;
 680
 681   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 682        p != input_objects->relobj_end();
 683        ++p)
 684     {
 685       Task_lock_obj<Object> tlo(**p);
 686       unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
 687                                                         off,
 688                                                         &this->sympool_);
 689       off += (index - local_symbol_index) * symsize;
 690       local_symbol_index = index;
 691     }
 692
 693   unsigned int local_symcount = local_symbol_index;
 694   assert(local_symcount * symsize == off - startoff);
 695
 696   off = symtab->finalize(local_symcount, off, &this->sympool_);
 697
 698   this->sympool_.set_string_offsets();
 699
 700   const char* symtab_name = this->namepool_.add(".symtab", NULL);
 701   Output_section* osymtab = new Output_section_symtab(symtab_name,
 702                                                       off - startoff);
 703   this->section_list_.push_back(osymtab);
 704
 705   const char* strtab_name = this->namepool_.add(".strtab", NULL);
 706   Output_section *ostrtab = new Output_section_strtab(strtab_name,
 707                                                       &this->sympool_);
 708   this->section_list_.push_back(ostrtab);
 709   this->special_output_list_.push_back(ostrtab);
 710
 711   osymtab->set_address(0, startoff);
 712   osymtab->set_info(local_symcount);
 713   osymtab->set_entsize(symsize);
 714   osymtab->set_addralign(align);
 715
 716   *poff = off;
 717   *posymtab = osymtab;
 718   *postrtab = ostrtab;
 719 }
 720
 721 // Create the .shstrtab section, which holds the names of the
 722 // sections.  At the time this is called, we have created all the
 723 // output sections except .shstrtab itself.
 724
 725 Output_section*
 726 Layout::create_shstrtab()
 727 {
 728   // FIXME: We don't need to create a .shstrtab section if we are
 729   // stripping everything.
 730
 731   const char* name = this->namepool_.add(".shstrtab", NULL);
 732
 733   this->namepool_.set_string_offsets();
 734
 735   Output_section* os = new Output_section_strtab(name, &this->namepool_);
 736
 737   this->section_list_.push_back(os);
 738   this->special_output_list_.push_back(os);
 739
 740   return os;
 741 }
 742
 743 // Create the section headers.  SIZE is 32 or 64.  OFF is the file
 744 // offset.
 745
 746 Output_section_headers*
 747 Layout::create_shdrs(int size, bool big_endian, off_t* poff)
 748 {
 749   Output_section_headers* oshdrs;
 750   oshdrs = new Output_section_headers(size, big_endian, this->segment_list_,
 751                                       this->section_list_,
 752                                       &this->namepool_);
 753   off_t off = align_address(*poff, oshdrs->addralign());
 754   oshdrs->set_address(0, off);
 755   off += oshdrs->data_size();
 756   *poff = off;
 757   this->special_output_list_.push_back(oshdrs);
 758   return oshdrs;
 759 }
 760
 761 // Create the dynamic symbol table.
 762
 763 void
 764 Layout::create_dynamic_symtab(int, Symbol_table*)
 765 {
 766   abort();
 767 }
 768
 769 // Create the .dynamic section and PT_DYNAMIC segment.
 770
 771 void
 772 Layout::create_dynamic_section()
 773 {
 774   abort();
 775 }
 776
 777 // Create the .interp section and PT_INTERP segment.
 778
 779 void
 780 Layout::create_interp(const Target* target)
 781 {
 782   const char* interp = this->options_.dynamic_linker();
 783   if (interp == NULL)
 784     {
 785       interp = target->dynamic_linker();
 786       assert(interp != NULL);
 787     }
 788
 789   size_t len = strlen(interp) + 1;
 790
 791   Output_section_data* odata = new Output_data_const(interp, len, 1);
 792
 793   const char* interp_name = this->namepool_.add(".interp", NULL);
 794   Output_section* osec = this->make_output_section(interp_name,
 795                                                    elfcpp::SHT_PROGBITS,
 796                                                    elfcpp::SHF_ALLOC);
 797   osec->add_output_section_data(odata);
 798
 799   Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
 800   this->segment_list_.push_back(oseg);
 801   oseg->add_initial_output_section(osec, elfcpp::PF_R);
 802 }
 803
 804 // The mapping of .gnu.linkonce section names to real section names.
 805
 806 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
 807 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
 808 {
 809   MAPPING_INIT("d.rel.ro", ".data.rel.ro"),     // Must be before "d".
 810   MAPPING_INIT("t", ".text"),
 811   MAPPING_INIT("r", ".rodata"),
 812   MAPPING_INIT("d", ".data"),
 813   MAPPING_INIT("b", ".bss"),
 814   MAPPING_INIT("s", ".sdata"),
 815   MAPPING_INIT("sb", ".sbss"),
 816   MAPPING_INIT("s2", ".sdata2"),
 817   MAPPING_INIT("sb2", ".sbss2"),
 818   MAPPING_INIT("wi", ".debug_info"),
 819   MAPPING_INIT("td", ".tdata"),
 820   MAPPING_INIT("tb", ".tbss"),
 821   MAPPING_INIT("lr", ".lrodata"),
 822   MAPPING_INIT("l", ".ldata"),
 823   MAPPING_INIT("lb", ".lbss"),
 824 };
 825 #undef MAPPING_INIT
 826
 827 const int Layout::linkonce_mapping_count =
 828   sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
 829
 830 // Return the name of the output section to use for a .gnu.linkonce
 831 // section.  This is based on the default ELF linker script of the old
 832 // GNU linker.  For example, we map a name like ".gnu.linkonce.t.foo"
 833 // to ".text".  Set *PLEN to the length of the name.  *PLEN is
 834 // initialized to the length of NAME.
 835
 836 const char*
 837 Layout::linkonce_output_name(const char* name, size_t *plen)
 838 {
 839   const char* s = name + sizeof(".gnu.linkonce") - 1;
 840   if (*s != '.')
 841     return name;
 842   ++s;
 843   const Linkonce_mapping* plm = linkonce_mapping;
 844   for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
 845     {
 846       if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
 847         {
 848           *plen = plm->tolen;
 849           return plm->to;
 850         }
 851     }
 852   return name;
 853 }
 854
 855 // Choose the output section name to use given an input section name.
 856 // Set *PLEN to the length of the name.  *PLEN is initialized to the
 857 // length of NAME.
 858
 859 const char*
 860 Layout::output_section_name(const char* name, size_t* plen)
 861 {
 862   if (Layout::is_linkonce(name))
 863     {
 864       // .gnu.linkonce sections are laid out as though they were named
 865       // for the sections are placed into.
 866       return Layout::linkonce_output_name(name, plen);
 867     }
 868
 869   // If the section name has no '.', or only an initial '.', we use
 870   // the name unchanged (i.e., ".text" is unchanged).
 871
 872   // Otherwise, if the section name does not include ".rel", we drop
 873   // the last '.'  and everything that follows (i.e., ".text.XXX"
 874   // becomes ".text").
 875
 876   // Otherwise, if the section name has zero or one '.' after the
 877   // ".rel", we use the name unchanged (i.e., ".rel.text" is
 878   // unchanged).
 879
 880   // Otherwise, we drop the last '.' and everything that follows
 881   // (i.e., ".rel.text.XXX" becomes ".rel.text").
 882
 883   const char* s = name;
 884   if (*s == '.')
 885     ++s;
 886   const char* sdot = strchr(s, '.');
 887   if (sdot == NULL)
 888     return name;
 889
 890   const char* srel = strstr(s, ".rel");
 891   if (srel == NULL)
 892     {
 893       *plen = sdot - name;
 894       return name;
 895     }
 896
 897   sdot = strchr(srel + 1, '.');
 898   if (sdot == NULL)
 899     return name;
 900   sdot = strchr(sdot + 1, '.');
 901   if (sdot == NULL)
 902     return name;
 903
 904   *plen = sdot - name;
 905   return name;
 906 }
 907
 908 // Record the signature of a comdat section, and return whether to
 909 // include it in the link.  If GROUP is true, this is a regular
 910 // section group.  If GROUP is false, this is a group signature
 911 // derived from the name of a linkonce section.  We want linkonce
 912 // signatures and group signatures to block each other, but we don't
 913 // want a linkonce signature to block another linkonce signature.
 914
 915 bool
 916 Layout::add_comdat(const char* signature, bool group)
 917 {
 918   std::string sig(signature);
 919   std::pair<Signatures::iterator, bool> ins(
 920     this->signatures_.insert(std::make_pair(sig, group)));
 921
 922   if (ins.second)
 923     {
 924       // This is the first time we've seen this signature.
 925       return true;
 926     }
 927
 928   if (ins.first->second)
 929     {
 930       // We've already seen a real section group with this signature.
 931       return false;
 932     }
 933   else if (group)
 934     {
 935       // This is a real section group, and we've already seen a
 936       // linkonce section with tihs signature.  Record that we've seen
 937       // a section group, and don't include this section group.
 938       ins.first->second = true;
 939       return false;
 940     }
 941   else
 942     {
 943       // We've already seen a linkonce section and this is a linkonce
 944       // section.  These don't block each other--this may be the same
 945       // symbol name with different section types.
 946       return true;
 947     }
 948 }
 949
 950 // Write out data not associated with a section or the symbol table.
 951
 952 void
 953 Layout::write_data(Output_file* of) const
 954 {
 955   for (Data_list::const_iterator p = this->special_output_list_.begin();
 956        p != this->special_output_list_.end();
 957        ++p)
 958     (*p)->write(of);
 959 }
 960
 961 // Write_data_task methods.
 962
 963 // We can always run this task.
 964
 965 Task::Is_runnable_type
 966 Write_data_task::is_runnable(Workqueue*)
 967 {
 968   return IS_RUNNABLE;
 969 }
 970
 971 // We need to unlock FINAL_BLOCKER when finished.
 972
 973 Task_locker*
 974 Write_data_task::locks(Workqueue* workqueue)
 975 {
 976   return new Task_locker_block(*this->final_blocker_, workqueue);
 977 }
 978
 979 // Run the task--write out the data.
 980
 981 void
 982 Write_data_task::run(Workqueue*)
 983 {
 984   this->layout_->write_data(this->of_);
 985 }
 986
 987 // Write_symbols_task methods.
 988
 989 // We can always run this task.
 990
 991 Task::Is_runnable_type
 992 Write_symbols_task::is_runnable(Workqueue*)
 993 {
 994   return IS_RUNNABLE;
 995 }
 996
 997 // We need to unlock FINAL_BLOCKER when finished.
 998
 999 Task_locker*
1000 Write_symbols_task::locks(Workqueue* workqueue)
1001 {
1002   return new Task_locker_block(*this->final_blocker_, workqueue);
1003 }
1004
1005 // Run the task--write out the symbols.
1006
1007 void
1008 Write_symbols_task::run(Workqueue*)
1009 {
1010   this->symtab_->write_globals(this->target_, this->sympool_, this->of_);
1011 }
1012
1013 // Close_task_runner methods.
1014
1015 // Run the task--close the file.
1016
1017 void
1018 Close_task_runner::run(Workqueue*)
1019 {
1020   this->of_->close();
1021 }
1022
1023 // Instantiate the templates we need.  We could use the configure
1024 // script to restrict this to only the ones for implemented targets.
1025
1026 template
1027 Output_section*
1028 Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name,
1029                           const elfcpp::Shdr<32, false>& shdr, off_t*);
1030
1031 template
1032 Output_section*
1033 Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name,
1034                          const elfcpp::Shdr<32, true>& shdr, off_t*);
1035
1036 template
1037 Output_section*
1038 Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name,
1039                           const elfcpp::Shdr<64, false>& shdr, off_t*);
1040
1041 template
1042 Output_section*
1043 Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name,
1044                          const elfcpp::Shdr<64, true>& shdr, off_t*);
1045
1046
1047 } // End namespace gold.