contrib/binutils-2.22/gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 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 "target-select.h"
  34 #include "debug.h"
  35 #include "workqueue.h"
  36 #include "dirsearch.h"
  37 #include "readsyms.h"
  38 #include "symtab.h"
  39 #include "common.h"
  40 #include "object.h"
  41 #include "layout.h"
  42 #include "reloc.h"
  43 #include "defstd.h"
  44 #include "plugin.h"
  45 #include "gc.h"
  46 #include "icf.h"
  47 #include "incremental.h"
  48
  49 namespace gold
  50 {
  51
  52 class Object;
  53
  54 const char* program_name;
  55
  56 static Task*
  57 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  58                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  59                           Task_token*, Task_token*);
  60
  61 void
  62 gold_exit(Exit_status status)
  63 {
  64   if (parameters != NULL
  65       && parameters->options_valid()
  66       && parameters->options().has_plugins())
  67     parameters->options().plugins()->cleanup();
  68   if (status != GOLD_OK && parameters != NULL && parameters->options_valid())
  69     unlink_if_ordinary(parameters->options().output_file_name());
  70   exit(status);
  71 }
  72
  73 void
  74 gold_nomem()
  75 {
  76   // We are out of memory, so try hard to print a reasonable message.
  77   // Note that we don't try to translate this message, since the
  78   // translation process itself will require memory.
  79
  80   // LEN only exists to avoid a pointless warning when write is
  81   // declared with warn_use_result, as when compiling with
  82   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  83   // work, at least not with gcc 4.3.0.
  84
  85   ssize_t len = write(2, program_name, strlen(program_name));
  86   if (len >= 0)
  87     {
  88       const char* const s = ": out of memory\n";
  89       len = write(2, s, strlen(s));
  90     }
  91   gold_exit(GOLD_ERR);
  92 }
  93
  94 // Handle an unreachable case.
  95
  96 void
  97 do_gold_unreachable(const char* filename, int lineno, const char* function)
  98 {
  99   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
 100           program_name, function, filename, lineno);
 101   gold_exit(GOLD_ERR);
 102 }
 103
 104 // This class arranges to run the functions done in the middle of the
 105 // link.  It is just a closure.
 106
 107 class Middle_runner : public Task_function_runner
 108 {
 109  public:
 110   Middle_runner(const General_options& options,
 111                 const Input_objects* input_objects,
 112                 Symbol_table* symtab,
 113                 Layout* layout, Mapfile* mapfile)
 114     : options_(options), input_objects_(input_objects), symtab_(symtab),
 115       layout_(layout), mapfile_(mapfile)
 116   { }
 117
 118   void
 119   run(Workqueue*, const Task*);
 120
 121  private:
 122   const General_options& options_;
 123   const Input_objects* input_objects_;
 124   Symbol_table* symtab_;
 125   Layout* layout_;
 126   Mapfile* mapfile_;
 127 };
 128
 129 void
 130 Middle_runner::run(Workqueue* workqueue, const Task* task)
 131 {
 132   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 133                      this->layout_, workqueue, this->mapfile_);
 134 }
 135
 136 // This class arranges the tasks to process the relocs for garbage collection.
 137
 138 class Gc_runner : public Task_function_runner
 139 {
 140   public:
 141    Gc_runner(const General_options& options,
 142              const Input_objects* input_objects,
 143              Symbol_table* symtab,
 144              Layout* layout, Mapfile* mapfile)
 145     : options_(options), input_objects_(input_objects), symtab_(symtab),
 146       layout_(layout), mapfile_(mapfile)
 147    { }
 148
 149   void
 150   run(Workqueue*, const Task*);
 151
 152  private:
 153   const General_options& options_;
 154   const Input_objects* input_objects_;
 155   Symbol_table* symtab_;
 156   Layout* layout_;
 157   Mapfile* mapfile_;
 158 };
 159
 160 void
 161 Gc_runner::run(Workqueue* workqueue, const Task* task)
 162 {
 163   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 164                         this->symtab_, this->layout_, workqueue,
 165                         this->mapfile_);
 166 }
 167
 168 // Queue up the initial set of tasks for this link job.
 169
 170 void
 171 queue_initial_tasks(const General_options& options,
 172                     Dirsearch& search_path,
 173                     const Command_line& cmdline,
 174                     Workqueue* workqueue, Input_objects* input_objects,
 175                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 176 {
 177   if (cmdline.begin() == cmdline.end())
 178     {
 179       bool is_ok = false;
 180       if (options.printed_version())
 181         is_ok = true;
 182       if (options.print_output_format())
 183         {
 184           print_output_format();
 185           is_ok = true;
 186         }
 187       if (is_ok)
 188         gold_exit(GOLD_OK);
 189       gold_fatal(_("no input files"));
 190     }
 191
 192   int thread_count = options.thread_count_initial();
 193   if (thread_count == 0)
 194     thread_count = cmdline.number_of_input_files();
 195   workqueue->set_thread_count(thread_count);
 196
 197   // For incremental links, the base output file.
 198   Incremental_binary* ibase = NULL;
 199
 200   if (parameters->incremental())
 201     {
 202       if (options.relocatable())
 203         gold_error(_("incremental linking is incompatible with -r"));
 204       if (options.emit_relocs())
 205         gold_error(_("incremental linking is incompatible with --emit-relocs"));
 206       if (options.gc_sections())
 207         gold_error(_("incremental linking is incompatible with --gc-sections"));
 208       if (options.icf_enabled())
 209         gold_error(_("incremental linking is incompatible with --icf"));
 210       if (options.has_plugins())
 211         gold_error(_("incremental linking is incompatible with --plugin"));
 212       if (strcmp(options.compress_debug_sections(), "none") != 0)
 213         gold_error(_("incremental linking is incompatible with "
 214                      "--compress-debug-sections"));
 215
 216       if (parameters->incremental_update())
 217         {
 218           Output_file* of = new Output_file(options.output_file_name());
 219           if (of->open_base_file(options.incremental_base(), true))
 220             {
 221               ibase = open_incremental_binary(of);
 222               if (ibase != NULL
 223                   && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 224                 ibase->init_layout(layout);
 225               else
 226                 {
 227                   delete ibase;
 228                   ibase = NULL;
 229                   of->close();
 230                 }
 231             }
 232           if (ibase == NULL)
 233             {
 234               if (set_parameters_incremental_full())
 235                 gold_info(_("linking with --incremental-full"));
 236               else
 237                 gold_fallback(_("restart link with --incremental-full"));
 238             }
 239         }
 240     }
 241
 242   // Read the input files.  We have to add the symbols to the symbol
 243   // table in order.  We do this by creating a separate blocker for
 244   // each input file.  We associate the blocker with the following
 245   // input file, to give us a convenient place to delete it.
 246   Task_token* this_blocker = NULL;
 247   if (ibase == NULL)
 248     {
 249       // Normal link.  Queue a Read_symbols task for each input file
 250       // on the command line.
 251       for (Command_line::const_iterator p = cmdline.begin();
 252            p != cmdline.end();
 253            ++p)
 254         {
 255           Task_token* next_blocker = new Task_token(true);
 256           next_blocker->add_blocker();
 257           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 258                                             &search_path, 0, mapfile, &*p, NULL,
 259                                             NULL, this_blocker, next_blocker));
 260           this_blocker = next_blocker;
 261         }
 262     }
 263   else
 264     {
 265       // Incremental update link.  Process the list of input files
 266       // stored in the base file, and queue a task for each file:
 267       // a Read_symbols task for a changed file, and an Add_symbols task
 268       // for an unchanged file.  We need to mark all the space used by
 269       // unchanged files before we can start any tasks running.
 270       unsigned int input_file_count = ibase->input_file_count();
 271       std::vector<Task*> tasks;
 272       tasks.reserve(input_file_count);
 273       for (unsigned int i = 0; i < input_file_count; ++i)
 274         {
 275           Task_token* next_blocker = new Task_token(true);
 276           next_blocker->add_blocker();
 277           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 278                                               layout, &search_path, mapfile,
 279                                               this_blocker, next_blocker);
 280           tasks.push_back(t);
 281           this_blocker = next_blocker;
 282         }
 283       // Now we can queue the tasks.
 284       for (unsigned int i = 0; i < tasks.size(); i++)
 285         workqueue->queue(tasks[i]);
 286     }
 287
 288   if (options.has_plugins())
 289     {
 290       Task_token* next_blocker = new Task_token(true);
 291       next_blocker->add_blocker();
 292       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 293                                        &search_path, mapfile, this_blocker,
 294                                        next_blocker));
 295       this_blocker = next_blocker;
 296     }
 297
 298   if (options.relocatable()
 299       && (options.gc_sections() || options.icf_enabled()))
 300     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 301
 302   if (options.gc_sections() || options.icf_enabled())
 303     {
 304       workqueue->queue(new Task_function(new Gc_runner(options,
 305                                                        input_objects,
 306                                                        symtab,
 307                                                        layout,
 308                                                        mapfile),
 309                                          this_blocker,
 310                                          "Task_function Gc_runner"));
 311     }
 312   else
 313     {
 314       workqueue->queue(new Task_function(new Middle_runner(options,
 315                                                            input_objects,
 316                                                            symtab,
 317                                                            layout,
 318                                                            mapfile),
 319                                          this_blocker,
 320                                          "Task_function Middle_runner"));
 321     }
 322 }
 323
 324 // Process an incremental input file: if it is unchanged from the previous
 325 // link, return a task to add its symbols from the base file's incremental
 326 // info; if it has changed, return a normal Read_symbols task.  We create a
 327 // task for every input file, if only to report the file for rebuilding the
 328 // incremental info.
 329
 330 static Task*
 331 process_incremental_input(Incremental_binary* ibase,
 332                           unsigned int input_file_index,
 333                           Input_objects* input_objects,
 334                           Symbol_table* symtab,
 335                           Layout* layout,
 336                           Dirsearch* search_path,
 337                           Mapfile* mapfile,
 338                           Task_token* this_blocker,
 339                           Task_token* next_blocker)
 340 {
 341   const Incremental_binary::Input_reader* input_reader =
 342       ibase->get_input_reader(input_file_index);
 343   Incremental_input_type input_type = input_reader->type();
 344
 345   // Get the input argument corresponding to this input file, matching on
 346   // the argument serial number.  If the input file cannot be matched
 347   // to an existing input argument, synthesize a new one.
 348   const Input_argument* input_argument =
 349       ibase->get_input_argument(input_file_index);
 350   if (input_argument == NULL)
 351     {
 352       Input_file_argument file(input_reader->filename(),
 353                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 354                                "", false, parameters->options());
 355       Input_argument* arg = new Input_argument(file);
 356       arg->set_script_info(ibase->get_script_info(input_file_index));
 357       input_argument = arg;
 358     }
 359
 360   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 361              input_reader->filename(), input_type);
 362
 363   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 364     {
 365       // Incremental_binary::check_inputs should have cancelled the
 366       // incremental update if the script has changed.
 367       gold_assert(!ibase->file_has_changed(input_file_index));
 368       return new Check_script(layout, ibase, input_file_index, input_reader,
 369                               this_blocker, next_blocker);
 370     }
 371
 372   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 373     {
 374       Incremental_library* lib = ibase->get_library(input_file_index);
 375       gold_assert(lib != NULL);
 376       if (lib->filename() == "/group/"
 377           || !ibase->file_has_changed(input_file_index))
 378         {
 379           // Queue a task to check that no references have been added to any
 380           // of the library's unused symbols.
 381           return new Check_library(symtab, layout, ibase, input_file_index,
 382                                    input_reader, this_blocker, next_blocker);
 383         }
 384       else
 385         {
 386           // Queue a Read_symbols task to process the archive normally.
 387           return new Read_symbols(input_objects, symtab, layout, search_path,
 388                                   0, mapfile, input_argument, NULL, NULL,
 389                                   this_blocker, next_blocker);
 390         }
 391     }
 392
 393   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 394     {
 395       // For archive members, check the timestamp of the containing archive.
 396       Incremental_library* lib = ibase->get_library(input_file_index);
 397       gold_assert(lib != NULL);
 398       // Process members of a --start-lib/--end-lib group as normal objects.
 399       if (lib->filename() != "/group/")
 400         {
 401           if (ibase->file_has_changed(lib->input_file_index()))
 402             {
 403               return new Read_member(input_objects, symtab, layout, mapfile,
 404                                      input_reader, this_blocker, next_blocker);
 405             }
 406           else
 407             {
 408               // The previous contributions from this file will be kept.
 409               // Mark the pieces of output sections contributed by this
 410               // object.
 411               ibase->reserve_layout(input_file_index);
 412               Object* obj = make_sized_incremental_object(ibase,
 413                                                           input_file_index,
 414                                                           input_type,
 415                                                           input_reader);
 416               return new Add_symbols(input_objects, symtab, layout,
 417                                      search_path, 0, mapfile, input_argument,
 418                                      obj, lib, NULL, this_blocker,
 419                                      next_blocker);
 420             }
 421         }
 422     }
 423
 424   // Normal object file or shared library.  Check if the file has changed
 425   // since the last incremental link.
 426   if (ibase->file_has_changed(input_file_index))
 427     {
 428       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 429                               mapfile, input_argument, NULL, NULL,
 430                               this_blocker, next_blocker);
 431     }
 432   else
 433     {
 434       // The previous contributions from this file will be kept.
 435       // Mark the pieces of output sections contributed by this object.
 436       ibase->reserve_layout(input_file_index);
 437       Object* obj = make_sized_incremental_object(ibase,
 438                                                   input_file_index,
 439                                                   input_type,
 440                                                   input_reader);
 441       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 442                              mapfile, input_argument, obj, NULL, NULL,
 443                              this_blocker, next_blocker);
 444     }
 445 }
 446
 447 // Queue up a set of tasks to be done before queueing the middle set
 448 // of tasks.  This is only necessary when garbage collection
 449 // (--gc-sections) of unused sections is desired.  The relocs are read
 450 // and processed here early to determine the garbage sections before the
 451 // relocs can be scanned in later tasks.
 452
 453 void
 454 queue_middle_gc_tasks(const General_options& options,
 455                       const Task* ,
 456                       const Input_objects* input_objects,
 457                       Symbol_table* symtab,
 458                       Layout* layout,
 459                       Workqueue* workqueue,
 460                       Mapfile* mapfile)
 461 {
 462   // Read_relocs for all the objects must be done and processed to find
 463   // unused sections before any scanning of the relocs can take place.
 464   Task_token* this_blocker = NULL;
 465   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 466        p != input_objects->relobj_end();
 467        ++p)
 468     {
 469       Task_token* next_blocker = new Task_token(true);
 470       next_blocker->add_blocker();
 471       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 472                                        next_blocker));
 473       this_blocker = next_blocker;
 474     }
 475
 476   // If we are given only archives in input, we have no regular
 477   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 478   // blocker here so that we can run the middle tasks immediately.
 479   if (this_blocker == NULL)
 480     {
 481       gold_assert(input_objects->number_of_relobjs() == 0);
 482       this_blocker = new Task_token(true);
 483     }
 484
 485   workqueue->queue(new Task_function(new Middle_runner(options,
 486                                                        input_objects,
 487                                                        symtab,
 488                                                        layout,
 489                                                        mapfile),
 490                                      this_blocker,
 491                                      "Task_function Middle_runner"));
 492 }
 493
 494 // Queue up the middle set of tasks.  These are the tasks which run
 495 // after all the input objects have been found and all the symbols
 496 // have been read, but before we lay out the output file.
 497
 498 void
 499 queue_middle_tasks(const General_options& options,
 500                    const Task* task,
 501                    const Input_objects* input_objects,
 502                    Symbol_table* symtab,
 503                    Layout* layout,
 504                    Workqueue* workqueue,
 505                    Mapfile* mapfile)
 506 {
 507   // Add any symbols named with -u options to the symbol table.
 508   symtab->add_undefined_symbols_from_command_line(layout);
 509
 510   // If garbage collection was chosen, relocs have been read and processed
 511   // at this point by pre_middle_tasks.  Layout can then be done for all
 512   // objects.
 513   if (parameters->options().gc_sections())
 514     {
 515       // Find the start symbol if any.
 516       Symbol* start_sym = symtab->lookup(parameters->entry());
 517       if (start_sym != NULL)
 518         {
 519           bool is_ordinary;
 520           unsigned int shndx = start_sym->shndx(&is_ordinary);
 521           if (is_ordinary)
 522             {
 523               symtab->gc()->worklist().push(
 524                 Section_id(start_sym->object(), shndx));
 525             }
 526         }
 527       // Symbols named with -u should not be considered garbage.
 528       symtab->gc_mark_undef_symbols(layout);
 529       gold_assert(symtab->gc() != NULL);
 530       // Do a transitive closure on all references to determine the worklist.
 531       symtab->gc()->do_transitive_closure();
 532     }
 533
 534   // If identical code folding (--icf) is chosen it makes sense to do it
 535   // only after garbage collection (--gc-sections) as we do not want to
 536   // be folding sections that will be garbage.
 537   if (parameters->options().icf_enabled())
 538     {
 539       symtab->icf()->find_identical_sections(input_objects, symtab);
 540     }
 541
 542   // Call Object::layout for the second time to determine the
 543   // output_sections for all referenced input sections.  When
 544   // --gc-sections or --icf is turned on, Object::layout is
 545   // called twice.  It is called the first time when the
 546   // symbols are added.
 547   if (parameters->options().gc_sections()
 548       || parameters->options().icf_enabled())
 549     {
 550       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 551            p != input_objects->relobj_end();
 552            ++p)
 553         {
 554           Task_lock_obj<Object> tlo(task, *p);
 555           (*p)->layout(symtab, layout, NULL);
 556         }
 557     }
 558
 559   // Layout deferred objects due to plugins.
 560   if (parameters->options().has_plugins())
 561     {
 562       Plugin_manager* plugins = parameters->options().plugins();
 563       gold_assert(plugins != NULL);
 564       plugins->layout_deferred_objects();
 565     }
 566
 567   if (parameters->options().gc_sections()
 568       || parameters->options().icf_enabled())
 569     {
 570       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 571            p != input_objects->relobj_end();
 572            ++p)
 573         {
 574           // Update the value of output_section stored in rd.
 575           Read_relocs_data* rd = (*p)->get_relocs_data();
 576           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 577                q != rd->relocs.end();
 578                ++q)
 579             {
 580               q->output_section = (*p)->output_section(q->data_shndx);
 581               q->needs_special_offset_handling =
 582                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 583             }
 584         }
 585     }
 586
 587   // We have to support the case of not seeing any input objects, and
 588   // generate an empty file.  Existing builds depend on being able to
 589   // pass an empty archive to the linker and get an empty object file
 590   // out.  In order to do this we need to use a default target.
 591   if (input_objects->number_of_input_objects() == 0
 592       && layout->incremental_base() == NULL)
 593     parameters_force_valid_target();
 594
 595   int thread_count = options.thread_count_middle();
 596   if (thread_count == 0)
 597     thread_count = std::max(2, input_objects->number_of_input_objects());
 598   workqueue->set_thread_count(thread_count);
 599
 600   // Now we have seen all the input files.
 601   const bool doing_static_link =
 602     (!input_objects->any_dynamic()
 603      && !parameters->options().output_is_position_independent());
 604   set_parameters_doing_static_link(doing_static_link);
 605   if (!doing_static_link && options.is_static())
 606     {
 607       // We print out just the first .so we see; there may be others.
 608       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 609       gold_error(_("cannot mix -static with dynamic object %s"),
 610                  (*input_objects->dynobj_begin())->name().c_str());
 611     }
 612   if (!doing_static_link && parameters->options().relocatable())
 613     gold_fatal(_("cannot mix -r with dynamic object %s"),
 614                (*input_objects->dynobj_begin())->name().c_str());
 615   if (!doing_static_link
 616       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 617     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 618                (*input_objects->dynobj_begin())->name().c_str());
 619
 620   if (parameters->options().relocatable())
 621     {
 622       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 623       if (p != input_objects->relobj_end())
 624         {
 625           bool uses_split_stack = (*p)->uses_split_stack();
 626           for (++p; p != input_objects->relobj_end(); ++p)
 627             {
 628               if ((*p)->uses_split_stack() != uses_split_stack)
 629                 gold_fatal(_("cannot mix split-stack '%s' and "
 630                              "non-split-stack '%s' when using -r"),
 631                            (*input_objects->relobj_begin())->name().c_str(),
 632                            (*p)->name().c_str());
 633             }
 634         }
 635     }
 636
 637   // For incremental updates, record the existing GOT and PLT entries,
 638   // and the COPY relocations.
 639   if (parameters->incremental_update())
 640     {
 641       Incremental_binary* ibase = layout->incremental_base();
 642       ibase->process_got_plt(symtab, layout);
 643       ibase->emit_copy_relocs(symtab);
 644     }
 645
 646   if (is_debugging_enabled(DEBUG_SCRIPT))
 647     layout->script_options()->print(stderr);
 648
 649   // For each dynamic object, record whether we've seen all the
 650   // dynamic objects that it depends upon.
 651   input_objects->check_dynamic_dependencies();
 652
 653   // See if any of the input definitions violate the One Definition Rule.
 654   // TODO: if this is too slow, do this as a task, rather than inline.
 655   symtab->detect_odr_violations(task, options.output_file_name());
 656
 657   // Do the --no-undefined-version check.
 658   if (!parameters->options().undefined_version())
 659     {
 660       Script_options* so = layout->script_options();
 661       so->version_script_info()->check_unmatched_names(symtab);
 662     }
 663
 664   // Create any automatic note sections.
 665   layout->create_notes();
 666
 667   // Create any output sections required by any linker script.
 668   layout->create_script_sections();
 669
 670   // Define some sections and symbols needed for a dynamic link.  This
 671   // handles some cases we want to see before we read the relocs.
 672   layout->create_initial_dynamic_sections(symtab);
 673
 674   // Define symbols from any linker scripts.
 675   layout->define_script_symbols(symtab);
 676
 677   // Attach sections to segments.
 678   layout->attach_sections_to_segments();
 679
 680   if (!parameters->options().relocatable())
 681     {
 682       // Predefine standard symbols.
 683       define_standard_symbols(symtab, layout);
 684
 685       // Define __start and __stop symbols for output sections where
 686       // appropriate.
 687       layout->define_section_symbols(symtab);
 688     }
 689
 690   // Make sure we have symbols for any required group signatures.
 691   layout->define_group_signatures(symtab);
 692
 693   Task_token* this_blocker = NULL;
 694
 695   // Allocate common symbols.  We use a blocker to run this before the
 696   // Scan_relocs tasks, because it writes to the symbol table just as
 697   // they do.
 698   if (parameters->options().define_common())
 699     {
 700       this_blocker = new Task_token(true);
 701       this_blocker->add_blocker();
 702       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 703                                                  this_blocker));
 704     }
 705
 706   // If doing garbage collection, the relocations have already been read.
 707   // Otherwise, read and scan the relocations.
 708   if (parameters->options().gc_sections()
 709       || parameters->options().icf_enabled())
 710     {
 711       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 712            p != input_objects->relobj_end();
 713            ++p)
 714         {
 715           Task_token* next_blocker = new Task_token(true);
 716           next_blocker->add_blocker();
 717           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 718                                            (*p)->get_relocs_data(),
 719                                            this_blocker, next_blocker));
 720           this_blocker = next_blocker;
 721         }
 722     }
 723   else
 724     {
 725       // Read the relocations of the input files.  We do this to find
 726       // which symbols are used by relocations which require a GOT and/or
 727       // a PLT entry, or a COPY reloc.  When we implement garbage
 728       // collection we will do it here by reading the relocations in a
 729       // breadth first search by references.
 730       //
 731       // We could also read the relocations during the first pass, and
 732       // mark symbols at that time.  That is how the old GNU linker works.
 733       // Doing that is more complex, since we may later decide to discard
 734       // some of the sections, and thus change our minds about the types
 735       // of references made to the symbols.
 736       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 737            p != input_objects->relobj_end();
 738            ++p)
 739         {
 740           Task_token* next_blocker = new Task_token(true);
 741           next_blocker->add_blocker();
 742           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 743                                            next_blocker));
 744           this_blocker = next_blocker;
 745         }
 746     }
 747
 748   if (this_blocker == NULL)
 749     {
 750       if (input_objects->number_of_relobjs() == 0)
 751         {
 752           // If we are given only archives in input, we have no regular
 753           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 754           // blocker here so that we can run the layout task immediately.
 755           this_blocker = new Task_token(true);
 756         }
 757       else
 758         {
 759           // If we failed to open any input files, it's possible for
 760           // THIS_BLOCKER to be NULL here.  There's no real point in
 761           // continuing if that happens.
 762           gold_assert(parameters->errors()->error_count() > 0);
 763           gold_exit(GOLD_ERR);
 764         }
 765     }
 766
 767   // When all those tasks are complete, we can start laying out the
 768   // output file.
 769   // TODO(csilvers): figure out a more principled way to get the target
 770   Target* target = const_cast<Target*>(&parameters->target());
 771   workqueue->queue(new Task_function(new Layout_task_runner(options,
 772                                                             input_objects,
 773                                                             symtab,
 774                                                             target,
 775                                                             layout,
 776                                                             mapfile),
 777                                      this_blocker,
 778                                      "Task_function Layout_task_runner"));
 779 }
 780
 781 // Queue up the final set of tasks.  This is called at the end of
 782 // Layout_task.
 783
 784 void
 785 queue_final_tasks(const General_options& options,
 786                   const Input_objects* input_objects,
 787                   const Symbol_table* symtab,
 788                   Layout* layout,
 789                   Workqueue* workqueue,
 790                   Output_file* of)
 791 {
 792   int thread_count = options.thread_count_final();
 793   if (thread_count == 0)
 794     thread_count = std::max(2, input_objects->number_of_input_objects());
 795   workqueue->set_thread_count(thread_count);
 796
 797   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 798
 799   // Use a blocker to wait until all the input sections have been
 800   // written out.
 801   Task_token* input_sections_blocker = NULL;
 802   if (!any_postprocessing_sections)
 803     {
 804       input_sections_blocker = new Task_token(true);
 805       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 806     }
 807
 808   // Use a blocker to block any objects which have to wait for the
 809   // output sections to complete before they can apply relocations.
 810   Task_token* output_sections_blocker = new Task_token(true);
 811   output_sections_blocker->add_blocker();
 812
 813   // Use a blocker to block the final cleanup task.
 814   Task_token* final_blocker = new Task_token(true);
 815   // Write_symbols_task, Write_sections_task, Write_data_task,
 816   // Relocate_tasks.
 817   final_blocker->add_blockers(3);
 818   final_blocker->add_blockers(input_objects->number_of_relobjs());
 819   if (!any_postprocessing_sections)
 820     final_blocker->add_blocker();
 821
 822   // Queue a task to write out the symbol table.
 823   workqueue->queue(new Write_symbols_task(layout,
 824                                           symtab,
 825                                           input_objects,
 826                                           layout->sympool(),
 827                                           layout->dynpool(),
 828                                           of,
 829                                           final_blocker));
 830
 831   // Queue a task to write out the output sections.
 832   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 833                                            final_blocker));
 834
 835   // Queue a task to write out everything else.
 836   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 837
 838   // Queue a task for each input object to relocate the sections and
 839   // write out the local symbols.
 840   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 841        p != input_objects->relobj_end();
 842        ++p)
 843     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 844                                        input_sections_blocker,
 845                                        output_sections_blocker,
 846                                        final_blocker));
 847
 848   // Queue a task to write out the output sections which depend on
 849   // input sections.  If there are any sections which require
 850   // postprocessing, then we need to do this last, since it may resize
 851   // the output file.
 852   if (!any_postprocessing_sections)
 853     {
 854       Task* t = new Write_after_input_sections_task(layout, of,
 855                                                     input_sections_blocker,
 856                                                     final_blocker);
 857       workqueue->queue(t);
 858     }
 859   else
 860     {
 861       Task_token* new_final_blocker = new Task_token(true);
 862       new_final_blocker->add_blocker();
 863       Task* t = new Write_after_input_sections_task(layout, of,
 864                                                     final_blocker,
 865                                                     new_final_blocker);
 866       workqueue->queue(t);
 867       final_blocker = new_final_blocker;
 868     }
 869
 870   // Queue a task to close the output file.  This will be blocked by
 871   // FINAL_BLOCKER.
 872   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 873                                                            of),
 874                                      final_blocker,
 875                                      "Task_function Close_task_runner"));
 876 }
 877
 878 } // End namespace gold.