gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010 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 <cstdlib>
  26 #include <cstdio>
  27 #include <cstring>
  28 #include <unistd.h>
  29 #include <algorithm>
  30 #include "libiberty.h"
  31
  32 #include "options.h"
  33 #include "debug.h"
  34 #include "workqueue.h"
  35 #include "dirsearch.h"
  36 #include "readsyms.h"
  37 #include "symtab.h"
  38 #include "common.h"
  39 #include "object.h"
  40 #include "layout.h"
  41 #include "reloc.h"
  42 #include "defstd.h"
  43 #include "plugin.h"
  44 #include "gc.h"
  45 #include "icf.h"
  46 #include "incremental.h"
  47
  48 namespace gold
  49 {
  50
  51 class Object;
  52
  53 const char* program_name;
  54
  55 static Task*
  56 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  57                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  58                           Task_token*, Task_token*);
  59
  60 void
  61 gold_exit(bool status)
  62 {
  63   if (parameters != NULL
  64       && parameters->options_valid()
  65       && parameters->options().has_plugins())
  66     parameters->options().plugins()->cleanup();
  67   if (!status && parameters != NULL && parameters->options_valid())
  68     unlink_if_ordinary(parameters->options().output_file_name());
  69   exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
  70 }
  71
  72 void
  73 gold_nomem()
  74 {
  75   // We are out of memory, so try hard to print a reasonable message.
  76   // Note that we don't try to translate this message, since the
  77   // translation process itself will require memory.
  78
  79   // LEN only exists to avoid a pointless warning when write is
  80   // declared with warn_use_result, as when compiling with
  81   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  82   // work, at least not with gcc 4.3.0.
  83
  84   ssize_t len = write(2, program_name, strlen(program_name));
  85   if (len >= 0)
  86     {
  87       const char* const s = ": out of memory\n";
  88       len = write(2, s, strlen(s));
  89     }
  90   gold_exit(false);
  91 }
  92
  93 // Handle an unreachable case.
  94
  95 void
  96 do_gold_unreachable(const char* filename, int lineno, const char* function)
  97 {
  98   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
  99           program_name, function, filename, lineno);
 100   gold_exit(false);
 101 }
 102
 103 // This class arranges to run the functions done in the middle of the
 104 // link.  It is just a closure.
 105
 106 class Middle_runner : public Task_function_runner
 107 {
 108  public:
 109   Middle_runner(const General_options& options,
 110                 const Input_objects* input_objects,
 111                 Symbol_table* symtab,
 112                 Layout* layout, Mapfile* mapfile)
 113     : options_(options), input_objects_(input_objects), symtab_(symtab),
 114       layout_(layout), mapfile_(mapfile)
 115   { }
 116
 117   void
 118   run(Workqueue*, const Task*);
 119
 120  private:
 121   const General_options& options_;
 122   const Input_objects* input_objects_;
 123   Symbol_table* symtab_;
 124   Layout* layout_;
 125   Mapfile* mapfile_;
 126 };
 127
 128 void
 129 Middle_runner::run(Workqueue* workqueue, const Task* task)
 130 {
 131   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 132                      this->layout_, workqueue, this->mapfile_);
 133 }
 134
 135 // This class arranges the tasks to process the relocs for garbage collection.
 136
 137 class Gc_runner : public Task_function_runner
 138 {
 139   public:
 140    Gc_runner(const General_options& options,
 141              const Input_objects* input_objects,
 142              Symbol_table* symtab,
 143              Layout* layout, Mapfile* mapfile)
 144     : options_(options), input_objects_(input_objects), symtab_(symtab),
 145       layout_(layout), mapfile_(mapfile)
 146    { }
 147
 148   void
 149   run(Workqueue*, const Task*);
 150
 151  private:
 152   const General_options& options_;
 153   const Input_objects* input_objects_;
 154   Symbol_table* symtab_;
 155   Layout* layout_;
 156   Mapfile* mapfile_;
 157 };
 158
 159 void
 160 Gc_runner::run(Workqueue* workqueue, const Task* task)
 161 {
 162   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 163                         this->symtab_, this->layout_, workqueue,
 164                         this->mapfile_);
 165 }
 166
 167 // Queue up the initial set of tasks for this link job.
 168
 169 void
 170 queue_initial_tasks(const General_options& options,
 171                     Dirsearch& search_path,
 172                     const Command_line& cmdline,
 173                     Workqueue* workqueue, Input_objects* input_objects,
 174                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 175 {
 176   if (cmdline.begin() == cmdline.end())
 177     {
 178       if (options.printed_version())
 179         gold_exit(true);
 180       gold_fatal(_("no input files"));
 181     }
 182
 183   int thread_count = options.thread_count_initial();
 184   if (thread_count == 0)
 185     thread_count = cmdline.number_of_input_files();
 186   workqueue->set_thread_count(thread_count);
 187
 188   // For incremental links, the base output file.
 189   Incremental_binary* ibase = NULL;
 190
 191   if (parameters->incremental())
 192     {
 193       if (options.relocatable())
 194         gold_error(_("incremental linking is incompatible with -r"));
 195       if (options.emit_relocs())
 196         gold_error(_("incremental linking is incompatible with --emit-relocs"));
 197       if (options.gc_sections())
 198         gold_error(_("incremental linking is incompatible with --gc-sections"));
 199       if (options.icf_enabled())
 200         gold_error(_("incremental linking is incompatible with --icf"));
 201       if (options.has_plugins())
 202         gold_error(_("incremental linking is incompatible with --plugin"));
 203
 204       if (parameters->incremental_update())
 205         {
 206           Output_file* of = new Output_file(options.output_file_name());
 207           if (of->open_base_file(options.incremental_base(), true))
 208             {
 209               ibase = open_incremental_binary(of);
 210               if (ibase != NULL
 211                   && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 212                 ibase->init_layout(layout);
 213               else
 214                 {
 215                   delete ibase;
 216                   ibase = NULL;
 217                   of->close();
 218                 }
 219             }
 220           if (ibase == NULL)
 221             {
 222               if (set_parameters_incremental_full())
 223                 gold_info(_("linking with --incremental-full"));
 224               else
 225                 gold_fatal(_("restart link with --incremental-full"));
 226             }
 227         }
 228     }
 229
 230   // Read the input files.  We have to add the symbols to the symbol
 231   // table in order.  We do this by creating a separate blocker for
 232   // each input file.  We associate the blocker with the following
 233   // input file, to give us a convenient place to delete it.
 234   Task_token* this_blocker = NULL;
 235   if (ibase == NULL)
 236     {
 237       // Normal link.  Queue a Read_symbols task for each input file
 238       // on the command line.
 239       for (Command_line::const_iterator p = cmdline.begin();
 240            p != cmdline.end();
 241            ++p)
 242         {
 243           Task_token* next_blocker = new Task_token(true);
 244           next_blocker->add_blocker();
 245           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 246                                             &search_path, 0, mapfile, &*p, NULL,
 247                                             NULL, this_blocker, next_blocker));
 248           this_blocker = next_blocker;
 249         }
 250     }
 251   else
 252     {
 253       // Incremental update link.  Process the list of input files
 254       // stored in the base file, and queue a task for each file:
 255       // a Read_symbols task for a changed file, and an Add_symbols task
 256       // for an unchanged file.  We need to mark all the space used by
 257       // unchanged files before we can start any tasks running.
 258       unsigned int input_file_count = ibase->input_file_count();
 259       std::vector<Task*> tasks;
 260       tasks.reserve(input_file_count);
 261       for (unsigned int i = 0; i < input_file_count; ++i)
 262         {
 263           Task_token* next_blocker = new Task_token(true);
 264           next_blocker->add_blocker();
 265           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 266                                               layout, &search_path, mapfile,
 267                                               this_blocker, next_blocker);
 268           tasks.push_back(t);
 269           this_blocker = next_blocker;
 270         }
 271       // Now we can queue the tasks.
 272       for (unsigned int i = 0; i < tasks.size(); i++)
 273         workqueue->queue(tasks[i]);
 274     }
 275
 276   if (options.has_plugins())
 277     {
 278       Task_token* next_blocker = new Task_token(true);
 279       next_blocker->add_blocker();
 280       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 281                                        &search_path, mapfile, this_blocker,
 282                                        next_blocker));
 283       this_blocker = next_blocker;
 284     }
 285
 286   if (options.relocatable()
 287       && (options.gc_sections() || options.icf_enabled()))
 288     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 289
 290   if (options.gc_sections() || options.icf_enabled())
 291     {
 292       workqueue->queue(new Task_function(new Gc_runner(options,
 293                                                        input_objects,
 294                                                        symtab,
 295                                                        layout,
 296                                                        mapfile),
 297                                          this_blocker,
 298                                          "Task_function Gc_runner"));
 299     }
 300   else
 301     {
 302       workqueue->queue(new Task_function(new Middle_runner(options,
 303                                                            input_objects,
 304                                                            symtab,
 305                                                            layout,
 306                                                            mapfile),
 307                                          this_blocker,
 308                                          "Task_function Middle_runner"));
 309     }
 310 }
 311
 312 // Process an incremental input file: if it is unchanged from the previous
 313 // link, return a task to add its symbols from the base file's incremental
 314 // info; if it has changed, return a normal Read_symbols task.  We create a
 315 // task for every input file, if only to report the file for rebuilding the
 316 // incremental info.
 317
 318 static Task*
 319 process_incremental_input(Incremental_binary* ibase,
 320                           unsigned int input_file_index,
 321                           Input_objects* input_objects,
 322                           Symbol_table* symtab,
 323                           Layout* layout,
 324                           Dirsearch* search_path,
 325                           Mapfile* mapfile,
 326                           Task_token* this_blocker,
 327                           Task_token* next_blocker)
 328 {
 329   const Incremental_binary::Input_reader* input_reader =
 330       ibase->get_input_reader(input_file_index);
 331   Incremental_input_type input_type = input_reader->type();
 332
 333   // Get the input argument corresponding to this input file, matching on
 334   // the argument serial number.  If the input file cannot be matched
 335   // to an existing input argument, synthesize a new one.
 336   const Input_argument* input_argument =
 337       ibase->get_input_argument(input_file_index);
 338   if (input_argument == NULL)
 339     {
 340       Input_file_argument file(input_reader->filename(),
 341                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 342                                "", false, parameters->options());
 343       Input_argument* arg = new Input_argument(file);
 344       arg->set_script_info(ibase->get_script_info(input_file_index));
 345       input_argument = arg;
 346     }
 347
 348   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 349              input_reader->filename(), input_type);
 350
 351   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 352     {
 353       // Incremental_binary::check_inputs should have cancelled the
 354       // incremental update if the script has changed.
 355       gold_assert(!ibase->file_has_changed(input_file_index));
 356       return new Check_script(layout, ibase, input_file_index, input_reader,
 357                               this_blocker, next_blocker);
 358     }
 359
 360   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 361     {
 362       Incremental_library* lib = ibase->get_library(input_file_index);
 363       gold_assert(lib != NULL);
 364       if (lib->filename() == "/group/"
 365           || !ibase->file_has_changed(input_file_index))
 366         {
 367           // Queue a task to check that no references have been added to any
 368           // of the library's unused symbols.
 369           return new Check_library(symtab, layout, ibase, input_file_index,
 370                                    input_reader, this_blocker, next_blocker);
 371         }
 372       else
 373         {
 374           // Queue a Read_symbols task to process the archive normally.
 375           return new Read_symbols(input_objects, symtab, layout, search_path,
 376                                   0, mapfile, input_argument, NULL, NULL,
 377                                   this_blocker, next_blocker);
 378         }
 379     }
 380
 381   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 382     {
 383       // For archive members, check the timestamp of the containing archive.
 384       Incremental_library* lib = ibase->get_library(input_file_index);
 385       gold_assert(lib != NULL);
 386       // Process members of a --start-lib/--end-lib group as normal objects.
 387       if (lib->filename() != "/group/")
 388         {
 389           if (ibase->file_has_changed(lib->input_file_index()))
 390             {
 391               return new Read_member(input_objects, symtab, layout, mapfile,
 392                                      input_reader, this_blocker, next_blocker);
 393             }
 394           else
 395             {
 396               // The previous contributions from this file will be kept.
 397               // Mark the pieces of output sections contributed by this
 398               // object.
 399               ibase->reserve_layout(input_file_index);
 400               Object* obj = make_sized_incremental_object(ibase,
 401                                                           input_file_index,
 402                                                           input_type,
 403                                                           input_reader);
 404               return new Add_symbols(input_objects, symtab, layout,
 405                                      search_path, 0, mapfile, input_argument,
 406                                      obj, lib, NULL, this_blocker,
 407                                      next_blocker);
 408             }
 409         }
 410     }
 411
 412   // Normal object file or shared library.  Check if the file has changed
 413   // since the last incremental link.
 414   if (ibase->file_has_changed(input_file_index))
 415     {
 416       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 417                               mapfile, input_argument, NULL, NULL,
 418                               this_blocker, next_blocker);
 419     }
 420   else
 421     {
 422       // The previous contributions from this file will be kept.
 423       // Mark the pieces of output sections contributed by this object.
 424       ibase->reserve_layout(input_file_index);
 425       Object* obj = make_sized_incremental_object(ibase,
 426                                                   input_file_index,
 427                                                   input_type,
 428                                                   input_reader);
 429       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 430                              mapfile, input_argument, obj, NULL, NULL,
 431                              this_blocker, next_blocker);
 432     }
 433 }
 434
 435 // Queue up a set of tasks to be done before queueing the middle set
 436 // of tasks.  This is only necessary when garbage collection
 437 // (--gc-sections) of unused sections is desired.  The relocs are read
 438 // and processed here early to determine the garbage sections before the
 439 // relocs can be scanned in later tasks.
 440
 441 void
 442 queue_middle_gc_tasks(const General_options& options,
 443                       const Task* ,
 444                       const Input_objects* input_objects,
 445                       Symbol_table* symtab,
 446                       Layout* layout,
 447                       Workqueue* workqueue,
 448                       Mapfile* mapfile)
 449 {
 450   // Read_relocs for all the objects must be done and processed to find
 451   // unused sections before any scanning of the relocs can take place.
 452   Task_token* this_blocker = NULL;
 453   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 454        p != input_objects->relobj_end();
 455        ++p)
 456     {
 457       Task_token* next_blocker = new Task_token(true);
 458       next_blocker->add_blocker();
 459       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 460                                        next_blocker));
 461       this_blocker = next_blocker;
 462     }
 463
 464   // If we are given only archives in input, we have no regular
 465   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 466   // blocker here so that we can run the middle tasks immediately.
 467   if (this_blocker == NULL)
 468     {
 469       gold_assert(input_objects->number_of_relobjs() == 0);
 470       this_blocker = new Task_token(true);
 471     }
 472
 473   workqueue->queue(new Task_function(new Middle_runner(options,
 474                                                        input_objects,
 475                                                        symtab,
 476                                                        layout,
 477                                                        mapfile),
 478                                      this_blocker,
 479                                      "Task_function Middle_runner"));
 480 }
 481
 482 // Queue up the middle set of tasks.  These are the tasks which run
 483 // after all the input objects have been found and all the symbols
 484 // have been read, but before we lay out the output file.
 485
 486 void
 487 queue_middle_tasks(const General_options& options,
 488                    const Task* task,
 489                    const Input_objects* input_objects,
 490                    Symbol_table* symtab,
 491                    Layout* layout,
 492                    Workqueue* workqueue,
 493                    Mapfile* mapfile)
 494 {
 495   // Add any symbols named with -u options to the symbol table.
 496   symtab->add_undefined_symbols_from_command_line(layout);
 497
 498   // If garbage collection was chosen, relocs have been read and processed
 499   // at this point by pre_middle_tasks.  Layout can then be done for all
 500   // objects.
 501   if (parameters->options().gc_sections())
 502     {
 503       // Find the start symbol if any.
 504       Symbol* start_sym = symtab->lookup(parameters->entry());
 505       if (start_sym != NULL)
 506         {
 507           bool is_ordinary;
 508           unsigned int shndx = start_sym->shndx(&is_ordinary);
 509           if (is_ordinary)
 510             {
 511               symtab->gc()->worklist().push(
 512                 Section_id(start_sym->object(), shndx));
 513             }
 514         }
 515       // Symbols named with -u should not be considered garbage.
 516       symtab->gc_mark_undef_symbols(layout);
 517       gold_assert(symtab->gc() != NULL);
 518       // Do a transitive closure on all references to determine the worklist.
 519       symtab->gc()->do_transitive_closure();
 520     }
 521
 522   // If identical code folding (--icf) is chosen it makes sense to do it
 523   // only after garbage collection (--gc-sections) as we do not want to
 524   // be folding sections that will be garbage.
 525   if (parameters->options().icf_enabled())
 526     {
 527       symtab->icf()->find_identical_sections(input_objects, symtab);
 528     }
 529
 530   // Call Object::layout for the second time to determine the
 531   // output_sections for all referenced input sections.  When
 532   // --gc-sections or --icf is turned on, Object::layout is
 533   // called twice.  It is called the first time when the
 534   // symbols are added.
 535   if (parameters->options().gc_sections()
 536       || parameters->options().icf_enabled())
 537     {
 538       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 539            p != input_objects->relobj_end();
 540            ++p)
 541         {
 542           Task_lock_obj<Object> tlo(task, *p);
 543           (*p)->layout(symtab, layout, NULL);
 544         }
 545     }
 546
 547   // Layout deferred objects due to plugins.
 548   if (parameters->options().has_plugins())
 549     {
 550       Plugin_manager* plugins = parameters->options().plugins();
 551       gold_assert(plugins != NULL);
 552       plugins->layout_deferred_objects();
 553     }
 554
 555   if (parameters->options().gc_sections()
 556       || parameters->options().icf_enabled())
 557     {
 558       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 559            p != input_objects->relobj_end();
 560            ++p)
 561         {
 562           // Update the value of output_section stored in rd.
 563           Read_relocs_data* rd = (*p)->get_relocs_data();
 564           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 565                q != rd->relocs.end();
 566                ++q)
 567             {
 568               q->output_section = (*p)->output_section(q->data_shndx);
 569               q->needs_special_offset_handling =
 570                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 571             }
 572         }
 573     }
 574
 575   // We have to support the case of not seeing any input objects, and
 576   // generate an empty file.  Existing builds depend on being able to
 577   // pass an empty archive to the linker and get an empty object file
 578   // out.  In order to do this we need to use a default target.
 579   if (input_objects->number_of_input_objects() == 0
 580       && layout->incremental_base() == NULL)
 581     parameters_force_valid_target();
 582
 583   int thread_count = options.thread_count_middle();
 584   if (thread_count == 0)
 585     thread_count = std::max(2, input_objects->number_of_input_objects());
 586   workqueue->set_thread_count(thread_count);
 587
 588   // Now we have seen all the input files.
 589   const bool doing_static_link =
 590     (!input_objects->any_dynamic()
 591      && !parameters->options().output_is_position_independent());
 592   set_parameters_doing_static_link(doing_static_link);
 593   if (!doing_static_link && options.is_static())
 594     {
 595       // We print out just the first .so we see; there may be others.
 596       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 597       gold_error(_("cannot mix -static with dynamic object %s"),
 598                  (*input_objects->dynobj_begin())->name().c_str());
 599     }
 600   if (!doing_static_link && parameters->options().relocatable())
 601     gold_fatal(_("cannot mix -r with dynamic object %s"),
 602                (*input_objects->dynobj_begin())->name().c_str());
 603   if (!doing_static_link
 604       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 605     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 606                (*input_objects->dynobj_begin())->name().c_str());
 607
 608   if (parameters->options().relocatable())
 609     {
 610       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 611       if (p != input_objects->relobj_end())
 612         {
 613           bool uses_split_stack = (*p)->uses_split_stack();
 614           for (++p; p != input_objects->relobj_end(); ++p)
 615             {
 616               if ((*p)->uses_split_stack() != uses_split_stack)
 617                 gold_fatal(_("cannot mix split-stack '%s' and "
 618                              "non-split-stack '%s' when using -r"),
 619                            (*input_objects->relobj_begin())->name().c_str(),
 620                            (*p)->name().c_str());
 621             }
 622         }
 623     }
 624
 625   // For incremental updates, record the existing GOT and PLT entries,
 626   // and the COPY relocations.
 627   if (parameters->incremental_update())
 628     {
 629       Incremental_binary* ibase = layout->incremental_base();
 630       ibase->process_got_plt(symtab, layout);
 631       ibase->emit_copy_relocs(symtab);
 632     }
 633
 634   if (is_debugging_enabled(DEBUG_SCRIPT))
 635     layout->script_options()->print(stderr);
 636
 637   // For each dynamic object, record whether we've seen all the
 638   // dynamic objects that it depends upon.
 639   input_objects->check_dynamic_dependencies();
 640
 641   // See if any of the input definitions violate the One Definition Rule.
 642   // TODO: if this is too slow, do this as a task, rather than inline.
 643   symtab->detect_odr_violations(task, options.output_file_name());
 644
 645   // Do the --no-undefined-version check.
 646   if (!parameters->options().undefined_version())
 647     {
 648       Script_options* so = layout->script_options();
 649       so->version_script_info()->check_unmatched_names(symtab);
 650     }
 651
 652   // Create any automatic note sections.
 653   layout->create_notes();
 654
 655   // Create any output sections required by any linker script.
 656   layout->create_script_sections();
 657
 658   // Define some sections and symbols needed for a dynamic link.  This
 659   // handles some cases we want to see before we read the relocs.
 660   layout->create_initial_dynamic_sections(symtab);
 661
 662   // Define symbols from any linker scripts.
 663   layout->define_script_symbols(symtab);
 664
 665   // Attach sections to segments.
 666   layout->attach_sections_to_segments();
 667
 668   if (!parameters->options().relocatable())
 669     {
 670       // Predefine standard symbols.
 671       define_standard_symbols(symtab, layout);
 672
 673       // Define __start and __stop symbols for output sections where
 674       // appropriate.
 675       layout->define_section_symbols(symtab);
 676     }
 677
 678   // Make sure we have symbols for any required group signatures.
 679   layout->define_group_signatures(symtab);
 680
 681   Task_token* this_blocker = NULL;
 682
 683   // Allocate common symbols.  We use a blocker to run this before the
 684   // Scan_relocs tasks, because it writes to the symbol table just as
 685   // they do.
 686   if (parameters->options().define_common())
 687     {
 688       this_blocker = new Task_token(true);
 689       this_blocker->add_blocker();
 690       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 691                                                  this_blocker));
 692     }
 693
 694   // If doing garbage collection, the relocations have already been read.
 695   // Otherwise, read and scan the relocations.
 696   if (parameters->options().gc_sections()
 697       || parameters->options().icf_enabled())
 698     {
 699       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 700            p != input_objects->relobj_end();
 701            ++p)
 702         {
 703           Task_token* next_blocker = new Task_token(true);
 704           next_blocker->add_blocker();
 705           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 706                                            (*p)->get_relocs_data(),
 707                                            this_blocker, next_blocker));
 708           this_blocker = next_blocker;
 709         }
 710     }
 711   else
 712     {
 713       // Read the relocations of the input files.  We do this to find
 714       // which symbols are used by relocations which require a GOT and/or
 715       // a PLT entry, or a COPY reloc.  When we implement garbage
 716       // collection we will do it here by reading the relocations in a
 717       // breadth first search by references.
 718       //
 719       // We could also read the relocations during the first pass, and
 720       // mark symbols at that time.  That is how the old GNU linker works.
 721       // Doing that is more complex, since we may later decide to discard
 722       // some of the sections, and thus change our minds about the types
 723       // of references made to the symbols.
 724       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 725            p != input_objects->relobj_end();
 726            ++p)
 727         {
 728           Task_token* next_blocker = new Task_token(true);
 729           next_blocker->add_blocker();
 730           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 731                                            next_blocker));
 732           this_blocker = next_blocker;
 733         }
 734     }
 735
 736   if (this_blocker == NULL)
 737     {
 738       if (input_objects->number_of_relobjs() == 0)
 739         {
 740           // If we are given only archives in input, we have no regular
 741           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 742           // blocker here so that we can run the layout task immediately.
 743           this_blocker = new Task_token(true);
 744         }
 745       else
 746         {
 747           // If we failed to open any input files, it's possible for
 748           // THIS_BLOCKER to be NULL here.  There's no real point in
 749           // continuing if that happens.
 750           gold_assert(parameters->errors()->error_count() > 0);
 751           gold_exit(false);
 752         }
 753     }
 754
 755   // When all those tasks are complete, we can start laying out the
 756   // output file.
 757   // TODO(csilvers): figure out a more principled way to get the target
 758   Target* target = const_cast<Target*>(&parameters->target());
 759   workqueue->queue(new Task_function(new Layout_task_runner(options,
 760                                                             input_objects,
 761                                                             symtab,
 762                                                             target,
 763                                                             layout,
 764                                                             mapfile),
 765                                      this_blocker,
 766                                      "Task_function Layout_task_runner"));
 767 }
 768
 769 // Queue up the final set of tasks.  This is called at the end of
 770 // Layout_task.
 771
 772 void
 773 queue_final_tasks(const General_options& options,
 774                   const Input_objects* input_objects,
 775                   const Symbol_table* symtab,
 776                   Layout* layout,
 777                   Workqueue* workqueue,
 778                   Output_file* of)
 779 {
 780   int thread_count = options.thread_count_final();
 781   if (thread_count == 0)
 782     thread_count = std::max(2, input_objects->number_of_input_objects());
 783   workqueue->set_thread_count(thread_count);
 784
 785   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 786
 787   // Use a blocker to wait until all the input sections have been
 788   // written out.
 789   Task_token* input_sections_blocker = NULL;
 790   if (!any_postprocessing_sections)
 791     {
 792       input_sections_blocker = new Task_token(true);
 793       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 794     }
 795
 796   // Use a blocker to block any objects which have to wait for the
 797   // output sections to complete before they can apply relocations.
 798   Task_token* output_sections_blocker = new Task_token(true);
 799   output_sections_blocker->add_blocker();
 800
 801   // Use a blocker to block the final cleanup task.
 802   Task_token* final_blocker = new Task_token(true);
 803   // Write_symbols_task, Write_sections_task, Write_data_task,
 804   // Relocate_tasks.
 805   final_blocker->add_blockers(3);
 806   final_blocker->add_blockers(input_objects->number_of_relobjs());
 807   if (!any_postprocessing_sections)
 808     final_blocker->add_blocker();
 809
 810   // Queue a task to write out the symbol table.
 811   workqueue->queue(new Write_symbols_task(layout,
 812                                           symtab,
 813                                           input_objects,
 814                                           layout->sympool(),
 815                                           layout->dynpool(),
 816                                           of,
 817                                           final_blocker));
 818
 819   // Queue a task to write out the output sections.
 820   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 821                                            final_blocker));
 822
 823   // Queue a task to write out everything else.
 824   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 825
 826   // Queue a task for each input object to relocate the sections and
 827   // write out the local symbols.
 828   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 829        p != input_objects->relobj_end();
 830        ++p)
 831     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 832                                        input_sections_blocker,
 833                                        output_sections_blocker,
 834                                        final_blocker));
 835
 836   // Queue a task to write out the output sections which depend on
 837   // input sections.  If there are any sections which require
 838   // postprocessing, then we need to do this last, since it may resize
 839   // the output file.
 840   if (!any_postprocessing_sections)
 841     {
 842       Task* t = new Write_after_input_sections_task(layout, of,
 843                                                     input_sections_blocker,
 844                                                     final_blocker);
 845       workqueue->queue(t);
 846     }
 847   else
 848     {
 849       Task_token* new_final_blocker = new Task_token(true);
 850       new_final_blocker->add_blocker();
 851       Task* t = new Write_after_input_sections_task(layout, of,
 852                                                     final_blocker,
 853                                                     new_final_blocker);
 854       workqueue->queue(t);
 855       final_blocker = new_final_blocker;
 856     }
 857
 858   // Queue a task to close the output file.  This will be blocked by
 859   // FINAL_BLOCKER.
 860   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 861                                                            of),
 862                                      final_blocker,
 863                                      "Task_function Close_task_runner"));
 864 }
 865
 866 } // End namespace gold.