gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright (C) 2006-2017 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 #include "timer.h"
  49
  50 namespace gold
  51 {
  52
  53 class Object;
  54
  55 const char* program_name;
  56
  57 static Task*
  58 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  59                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  60                           Task_token*, Task_token*);
  61
  62 void
  63 gold_exit(Exit_status status)
  64 {
  65   if (parameters != NULL
  66       && parameters->options_valid()
  67       && parameters->options().has_plugins())
  68     parameters->options().plugins()->cleanup();
  69   if (status != GOLD_OK && parameters != NULL && parameters->options_valid())
  70     unlink_if_ordinary(parameters->options().output_file_name());
  71   exit(status);
  72 }
  73
  74 void
  75 gold_nomem()
  76 {
  77   // We are out of memory, so try hard to print a reasonable message.
  78   // Note that we don't try to translate this message, since the
  79   // translation process itself will require memory.
  80
  81   // LEN only exists to avoid a pointless warning when write is
  82   // declared with warn_use_result, as when compiling with
  83   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  84   // work, at least not with gcc 4.3.0.
  85
  86   ssize_t len = write(2, program_name, strlen(program_name));
  87   if (len >= 0)
  88     {
  89       const char* const s = ": out of memory\n";
  90       len = write(2, s, strlen(s));
  91     }
  92   gold_exit(GOLD_ERR);
  93 }
  94
  95 // Handle an unreachable case.
  96
  97 void
  98 do_gold_unreachable(const char* filename, int lineno, const char* function)
  99 {
 100   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
 101           program_name, function, filename, lineno);
 102   gold_exit(GOLD_ERR);
 103 }
 104
 105 // This class arranges to run the functions done in the middle of the
 106 // link.  It is just a closure.
 107
 108 class Middle_runner : public Task_function_runner
 109 {
 110  public:
 111   Middle_runner(const General_options& options,
 112                 const Input_objects* input_objects,
 113                 Symbol_table* symtab,
 114                 Layout* layout, Mapfile* mapfile)
 115     : options_(options), input_objects_(input_objects), symtab_(symtab),
 116       layout_(layout), mapfile_(mapfile)
 117   { }
 118
 119   void
 120   run(Workqueue*, const Task*);
 121
 122  private:
 123   const General_options& options_;
 124   const Input_objects* input_objects_;
 125   Symbol_table* symtab_;
 126   Layout* layout_;
 127   Mapfile* mapfile_;
 128 };
 129
 130 void
 131 Middle_runner::run(Workqueue* workqueue, const Task* task)
 132 {
 133   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 134                      this->layout_, workqueue, this->mapfile_);
 135 }
 136
 137 // This class arranges the tasks to process the relocs for garbage collection.
 138
 139 class Gc_runner : public Task_function_runner
 140 {
 141   public:
 142    Gc_runner(const General_options& options,
 143              const Input_objects* input_objects,
 144              Symbol_table* symtab,
 145              Layout* layout, Mapfile* mapfile)
 146     : options_(options), input_objects_(input_objects), symtab_(symtab),
 147       layout_(layout), mapfile_(mapfile)
 148    { }
 149
 150   void
 151   run(Workqueue*, const Task*);
 152
 153  private:
 154   const General_options& options_;
 155   const Input_objects* input_objects_;
 156   Symbol_table* symtab_;
 157   Layout* layout_;
 158   Mapfile* mapfile_;
 159 };
 160
 161 void
 162 Gc_runner::run(Workqueue* workqueue, const Task* task)
 163 {
 164   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 165                         this->symtab_, this->layout_, workqueue,
 166                         this->mapfile_);
 167 }
 168
 169 // Queue up the initial set of tasks for this link job.
 170
 171 void
 172 queue_initial_tasks(const General_options& options,
 173                     Dirsearch& search_path,
 174                     const Command_line& cmdline,
 175                     Workqueue* workqueue, Input_objects* input_objects,
 176                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 177 {
 178   if (cmdline.begin() == cmdline.end())
 179     {
 180       bool is_ok = false;
 181       if (options.printed_version())
 182         is_ok = true;
 183       if (options.print_output_format())
 184         {
 185           print_output_format();
 186           is_ok = true;
 187         }
 188       if (is_ok)
 189         gold_exit(GOLD_OK);
 190       gold_fatal(_("no input files"));
 191     }
 192
 193   int thread_count = options.thread_count_initial();
 194   if (thread_count == 0)
 195     thread_count = cmdline.number_of_input_files();
 196   workqueue->set_thread_count(thread_count);
 197
 198   // For incremental links, the base output file.
 199   Incremental_binary* ibase = NULL;
 200
 201   if (parameters->incremental_update())
 202     {
 203       Output_file* of = new Output_file(options.output_file_name());
 204       if (of->open_base_file(options.incremental_base(), true))
 205         {
 206           ibase = open_incremental_binary(of);
 207           if (ibase != NULL
 208               && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 209             ibase->init_layout(layout);
 210           else
 211             {
 212               delete ibase;
 213               ibase = NULL;
 214               of->close();
 215             }
 216         }
 217       if (ibase == NULL)
 218         {
 219           if (set_parameters_incremental_full())
 220             gold_info(_("linking with --incremental-full"));
 221           else
 222             gold_fallback(_("restart link with --incremental-full"));
 223         }
 224     }
 225
 226   // Read the input files.  We have to add the symbols to the symbol
 227   // table in order.  We do this by creating a separate blocker for
 228   // each input file.  We associate the blocker with the following
 229   // input file, to give us a convenient place to delete it.
 230   Task_token* this_blocker = NULL;
 231   if (ibase == NULL)
 232     {
 233       // Normal link.  Queue a Read_symbols task for each input file
 234       // on the command line.
 235       for (Command_line::const_iterator p = cmdline.begin();
 236            p != cmdline.end();
 237            ++p)
 238         {
 239           Task_token* next_blocker = new Task_token(true);
 240           next_blocker->add_blocker();
 241           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 242                                             &search_path, 0, mapfile, &*p, NULL,
 243                                             NULL, this_blocker, next_blocker));
 244           this_blocker = next_blocker;
 245         }
 246     }
 247   else
 248     {
 249       // Incremental update link.  Process the list of input files
 250       // stored in the base file, and queue a task for each file:
 251       // a Read_symbols task for a changed file, and an Add_symbols task
 252       // for an unchanged file.  We need to mark all the space used by
 253       // unchanged files before we can start any tasks running.
 254       unsigned int input_file_count = ibase->input_file_count();
 255       std::vector<Task*> tasks;
 256       tasks.reserve(input_file_count);
 257       for (unsigned int i = 0; i < input_file_count; ++i)
 258         {
 259           Task_token* next_blocker = new Task_token(true);
 260           next_blocker->add_blocker();
 261           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 262                                               layout, &search_path, mapfile,
 263                                               this_blocker, next_blocker);
 264           tasks.push_back(t);
 265           this_blocker = next_blocker;
 266         }
 267       // Now we can queue the tasks.
 268       for (unsigned int i = 0; i < tasks.size(); i++)
 269         workqueue->queue(tasks[i]);
 270     }
 271
 272   if (options.has_plugins())
 273     {
 274       Task_token* next_blocker = new Task_token(true);
 275       next_blocker->add_blocker();
 276       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 277                                        &search_path, mapfile, this_blocker,
 278                                        next_blocker));
 279       this_blocker = next_blocker;
 280     }
 281
 282   if (options.relocatable()
 283       && (options.gc_sections() || options.icf_enabled()))
 284     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 285
 286   if (options.gc_sections() || options.icf_enabled())
 287     {
 288       workqueue->queue(new Task_function(new Gc_runner(options,
 289                                                        input_objects,
 290                                                        symtab,
 291                                                        layout,
 292                                                        mapfile),
 293                                          this_blocker,
 294                                          "Task_function Gc_runner"));
 295     }
 296   else
 297     {
 298       workqueue->queue(new Task_function(new Middle_runner(options,
 299                                                            input_objects,
 300                                                            symtab,
 301                                                            layout,
 302                                                            mapfile),
 303                                          this_blocker,
 304                                          "Task_function Middle_runner"));
 305     }
 306 }
 307
 308 // Process an incremental input file: if it is unchanged from the previous
 309 // link, return a task to add its symbols from the base file's incremental
 310 // info; if it has changed, return a normal Read_symbols task.  We create a
 311 // task for every input file, if only to report the file for rebuilding the
 312 // incremental info.
 313
 314 static Task*
 315 process_incremental_input(Incremental_binary* ibase,
 316                           unsigned int input_file_index,
 317                           Input_objects* input_objects,
 318                           Symbol_table* symtab,
 319                           Layout* layout,
 320                           Dirsearch* search_path,
 321                           Mapfile* mapfile,
 322                           Task_token* this_blocker,
 323                           Task_token* next_blocker)
 324 {
 325   const Incremental_binary::Input_reader* input_reader =
 326       ibase->get_input_reader(input_file_index);
 327   Incremental_input_type input_type = input_reader->type();
 328
 329   // Get the input argument corresponding to this input file, matching on
 330   // the argument serial number.  If the input file cannot be matched
 331   // to an existing input argument, synthesize a new one.
 332   const Input_argument* input_argument =
 333       ibase->get_input_argument(input_file_index);
 334   if (input_argument == NULL)
 335     {
 336       Input_file_argument file(input_reader->filename(),
 337                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 338                                "", false, parameters->options());
 339       Input_argument* arg = new Input_argument(file);
 340       arg->set_script_info(ibase->get_script_info(input_file_index));
 341       input_argument = arg;
 342     }
 343
 344   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 345              input_reader->filename(), input_type);
 346
 347   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 348     {
 349       // Incremental_binary::check_inputs should have cancelled the
 350       // incremental update if the script has changed.
 351       gold_assert(!ibase->file_has_changed(input_file_index));
 352       return new Check_script(layout, ibase, input_file_index, input_reader,
 353                               this_blocker, next_blocker);
 354     }
 355
 356   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 357     {
 358       Incremental_library* lib = ibase->get_library(input_file_index);
 359       gold_assert(lib != NULL);
 360       if (lib->filename() == "/group/"
 361           || !ibase->file_has_changed(input_file_index))
 362         {
 363           // Queue a task to check that no references have been added to any
 364           // of the library's unused symbols.
 365           return new Check_library(symtab, layout, ibase, input_file_index,
 366                                    input_reader, this_blocker, next_blocker);
 367         }
 368       else
 369         {
 370           // Queue a Read_symbols task to process the archive normally.
 371           return new Read_symbols(input_objects, symtab, layout, search_path,
 372                                   0, mapfile, input_argument, NULL, NULL,
 373                                   this_blocker, next_blocker);
 374         }
 375     }
 376
 377   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 378     {
 379       // For archive members, check the timestamp of the containing archive.
 380       Incremental_library* lib = ibase->get_library(input_file_index);
 381       gold_assert(lib != NULL);
 382       // Process members of a --start-lib/--end-lib group as normal objects.
 383       if (lib->filename() != "/group/")
 384         {
 385           if (ibase->file_has_changed(lib->input_file_index()))
 386             {
 387               return new Read_member(input_objects, symtab, layout, mapfile,
 388                                      input_reader, this_blocker, next_blocker);
 389             }
 390           else
 391             {
 392               // The previous contributions from this file will be kept.
 393               // Mark the pieces of output sections contributed by this
 394               // object.
 395               ibase->reserve_layout(input_file_index);
 396               Object* obj = make_sized_incremental_object(ibase,
 397                                                           input_file_index,
 398                                                           input_type,
 399                                                           input_reader);
 400               return new Add_symbols(input_objects, symtab, layout,
 401                                      search_path, 0, mapfile, input_argument,
 402                                      obj, lib, NULL, this_blocker,
 403                                      next_blocker);
 404             }
 405         }
 406     }
 407
 408   // Normal object file or shared library.  Check if the file has changed
 409   // since the last incremental link.
 410   if (ibase->file_has_changed(input_file_index))
 411     {
 412       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 413                               mapfile, input_argument, NULL, NULL,
 414                               this_blocker, next_blocker);
 415     }
 416   else
 417     {
 418       // The previous contributions from this file will be kept.
 419       // Mark the pieces of output sections contributed by this object.
 420       ibase->reserve_layout(input_file_index);
 421       Object* obj = make_sized_incremental_object(ibase,
 422                                                   input_file_index,
 423                                                   input_type,
 424                                                   input_reader);
 425       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 426                              mapfile, input_argument, obj, NULL, NULL,
 427                              this_blocker, next_blocker);
 428     }
 429 }
 430
 431 // Queue up a set of tasks to be done before queueing the middle set
 432 // of tasks.  This is only necessary when garbage collection
 433 // (--gc-sections) of unused sections is desired.  The relocs are read
 434 // and processed here early to determine the garbage sections before the
 435 // relocs can be scanned in later tasks.
 436
 437 void
 438 queue_middle_gc_tasks(const General_options& options,
 439                       const Task* ,
 440                       const Input_objects* input_objects,
 441                       Symbol_table* symtab,
 442                       Layout* layout,
 443                       Workqueue* workqueue,
 444                       Mapfile* mapfile)
 445 {
 446   // Read_relocs for all the objects must be done and processed to find
 447   // unused sections before any scanning of the relocs can take place.
 448   Task_token* this_blocker = NULL;
 449   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 450        p != input_objects->relobj_end();
 451        ++p)
 452     {
 453       Task_token* next_blocker = new Task_token(true);
 454       next_blocker->add_blocker();
 455       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 456                                        next_blocker));
 457       this_blocker = next_blocker;
 458     }
 459
 460   // If we are given only archives in input, we have no regular
 461   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 462   // blocker here so that we can run the middle tasks immediately.
 463   if (this_blocker == NULL)
 464     {
 465       gold_assert(input_objects->number_of_relobjs() == 0);
 466       this_blocker = new Task_token(true);
 467     }
 468
 469   workqueue->queue(new Task_function(new Middle_runner(options,
 470                                                        input_objects,
 471                                                        symtab,
 472                                                        layout,
 473                                                        mapfile),
 474                                      this_blocker,
 475                                      "Task_function Middle_runner"));
 476 }
 477
 478 // Queue up the middle set of tasks.  These are the tasks which run
 479 // after all the input objects have been found and all the symbols
 480 // have been read, but before we lay out the output file.
 481
 482 void
 483 queue_middle_tasks(const General_options& options,
 484                    const Task* task,
 485                    const Input_objects* input_objects,
 486                    Symbol_table* symtab,
 487                    Layout* layout,
 488                    Workqueue* workqueue,
 489                    Mapfile* mapfile)
 490 {
 491   Timer* timer = parameters->timer();
 492   if (timer != NULL)
 493     timer->stamp(0);
 494
 495   // We have to support the case of not seeing any input objects, and
 496   // generate an empty file.  Existing builds depend on being able to
 497   // pass an empty archive to the linker and get an empty object file
 498   // out.  In order to do this we need to use a default target.
 499   if (input_objects->number_of_input_objects() == 0
 500       && layout->incremental_base() == NULL)
 501     parameters_force_valid_target();
 502
 503   // Add any symbols named with -u options to the symbol table.
 504   symtab->add_undefined_symbols_from_command_line(layout);
 505
 506   // If garbage collection was chosen, relocs have been read and processed
 507   // at this point by pre_middle_tasks.  Layout can then be done for all
 508   // objects.
 509   if (parameters->options().gc_sections())
 510     {
 511       // Find the start symbol if any.
 512       Symbol* sym = symtab->lookup(parameters->entry());
 513       if (sym != NULL)
 514         symtab->gc_mark_symbol(sym);
 515       sym = symtab->lookup(parameters->options().init());
 516       if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
 517         symtab->gc_mark_symbol(sym);
 518       sym = symtab->lookup(parameters->options().fini());
 519       if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
 520         symtab->gc_mark_symbol(sym);
 521       // Symbols named with -u should not be considered garbage.
 522       symtab->gc_mark_undef_symbols(layout);
 523       gold_assert(symtab->gc() != NULL);
 524       // Do a transitive closure on all references to determine the worklist.
 525       symtab->gc()->do_transitive_closure();
 526     }
 527
 528   // If identical code folding (--icf) is chosen it makes sense to do it
 529   // only after garbage collection (--gc-sections) as we do not want to
 530   // be folding sections that will be garbage.
 531   if (parameters->options().icf_enabled())
 532     {
 533       symtab->icf()->find_identical_sections(input_objects, symtab);
 534     }
 535
 536   // Call Object::layout for the second time to determine the
 537   // output_sections for all referenced input sections.  When
 538   // --gc-sections or --icf is turned on, or when certain input
 539   // sections have to be mapped to unique segments, Object::layout
 540   // is called twice.  It is called the first time when symbols
 541   // are added.
 542   if (parameters->options().gc_sections()
 543       || parameters->options().icf_enabled()
 544       || layout->is_unique_segment_for_sections_specified())
 545     {
 546       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 547            p != input_objects->relobj_end();
 548            ++p)
 549         {
 550           Task_lock_obj<Object> tlo(task, *p);
 551           (*p)->layout(symtab, layout, NULL);
 552         }
 553     }
 554
 555   // Layout deferred objects due to plugins.
 556   if (parameters->options().has_plugins())
 557     {
 558       Plugin_manager* plugins = parameters->options().plugins();
 559       gold_assert(plugins != NULL);
 560       plugins->layout_deferred_objects();
 561     }
 562
 563   // Finalize the .eh_frame section.
 564   layout->finalize_eh_frame_section();
 565
 566   /* If plugins have specified a section order, re-arrange input sections
 567      according to a specified section order.  If --section-ordering-file is
 568      also specified, do not do anything here.  */
 569   if (parameters->options().has_plugins()
 570       && layout->is_section_ordering_specified()
 571       && !parameters->options().section_ordering_file ())
 572     {
 573       for (Layout::Section_list::const_iterator p
 574              = layout->section_list().begin();
 575            p != layout->section_list().end();
 576            ++p)
 577         (*p)->update_section_layout(layout->get_section_order_map());
 578     }
 579
 580   if (parameters->options().gc_sections()
 581       || parameters->options().icf_enabled())
 582     {
 583       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 584            p != input_objects->relobj_end();
 585            ++p)
 586         {
 587           // Update the value of output_section stored in rd.
 588           Read_relocs_data* rd = (*p)->get_relocs_data();
 589           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 590                q != rd->relocs.end();
 591                ++q)
 592             {
 593               q->output_section = (*p)->output_section(q->data_shndx);
 594               q->needs_special_offset_handling =
 595                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 596             }
 597         }
 598     }
 599
 600   int thread_count = options.thread_count_middle();
 601   if (thread_count == 0)
 602     thread_count = std::max(2, input_objects->number_of_input_objects());
 603   workqueue->set_thread_count(thread_count);
 604
 605   // Now we have seen all the input files.
 606   const bool doing_static_link =
 607     (!input_objects->any_dynamic()
 608      && !parameters->options().output_is_position_independent());
 609   set_parameters_doing_static_link(doing_static_link);
 610   if (!doing_static_link && options.is_static())
 611     {
 612       // We print out just the first .so we see; there may be others.
 613       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 614       gold_error(_("cannot mix -static with dynamic object %s"),
 615                  (*input_objects->dynobj_begin())->name().c_str());
 616     }
 617   if (!doing_static_link && parameters->options().relocatable())
 618     gold_fatal(_("cannot mix -r with dynamic object %s"),
 619                (*input_objects->dynobj_begin())->name().c_str());
 620   if (!doing_static_link
 621       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 622     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 623                (*input_objects->dynobj_begin())->name().c_str());
 624
 625   if (parameters->options().relocatable())
 626     {
 627       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 628       if (p != input_objects->relobj_end())
 629         {
 630           bool uses_split_stack = (*p)->uses_split_stack();
 631           for (++p; p != input_objects->relobj_end(); ++p)
 632             {
 633               if ((*p)->uses_split_stack() != uses_split_stack)
 634                 gold_fatal(_("cannot mix split-stack '%s' and "
 635                              "non-split-stack '%s' when using -r"),
 636                            (*input_objects->relobj_begin())->name().c_str(),
 637                            (*p)->name().c_str());
 638             }
 639         }
 640     }
 641
 642   // For incremental updates, record the existing GOT and PLT entries,
 643   // and the COPY relocations.
 644   if (parameters->incremental_update())
 645     {
 646       Incremental_binary* ibase = layout->incremental_base();
 647       ibase->process_got_plt(symtab, layout);
 648       ibase->emit_copy_relocs(symtab);
 649     }
 650
 651   if (is_debugging_enabled(DEBUG_SCRIPT))
 652     layout->script_options()->print(stderr);
 653
 654   // For each dynamic object, record whether we've seen all the
 655   // dynamic objects that it depends upon.
 656   input_objects->check_dynamic_dependencies();
 657
 658   // Do the --no-undefined-version check.
 659   if (!parameters->options().undefined_version())
 660     {
 661       Script_options* so = layout->script_options();
 662       so->version_script_info()->check_unmatched_names(symtab);
 663     }
 664
 665   // Create any automatic note sections.
 666   layout->create_notes();
 667
 668   // Create any output sections required by any linker script.
 669   layout->create_script_sections();
 670
 671   // Define some sections and symbols needed for a dynamic link.  This
 672   // handles some cases we want to see before we read the relocs.
 673   layout->create_initial_dynamic_sections(symtab);
 674
 675   // Define symbols from any linker scripts.
 676   layout->define_script_symbols(symtab);
 677
 678   // TODO(csilvers): figure out a more principled way to get the target
 679   Target* target = const_cast<Target*>(&parameters->target());
 680
 681   // Attach sections to segments.
 682   layout->attach_sections_to_segments(target);
 683
 684   if (!parameters->options().relocatable())
 685     {
 686       // Predefine standard symbols.
 687       define_standard_symbols(symtab, layout);
 688
 689       // Define __start and __stop symbols for output sections where
 690       // appropriate.
 691       layout->define_section_symbols(symtab);
 692
 693       // Define target-specific symbols.
 694       target->define_standard_symbols(symtab, layout);
 695     }
 696
 697   // Make sure we have symbols for any required group signatures.
 698   layout->define_group_signatures(symtab);
 699
 700   Task_token* this_blocker = NULL;
 701
 702   // Allocate common symbols.  We use a blocker to run this before the
 703   // Scan_relocs tasks, because it writes to the symbol table just as
 704   // they do.
 705   if (parameters->options().define_common())
 706     {
 707       this_blocker = new Task_token(true);
 708       this_blocker->add_blocker();
 709       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 710                                                  this_blocker));
 711     }
 712
 713   // If doing garbage collection, the relocations have already been read.
 714   // Otherwise, read and scan the relocations.
 715   if (parameters->options().gc_sections()
 716       || parameters->options().icf_enabled())
 717     {
 718       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 719            p != input_objects->relobj_end();
 720            ++p)
 721         {
 722           Task_token* next_blocker = new Task_token(true);
 723           next_blocker->add_blocker();
 724           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 725                                            (*p)->get_relocs_data(),
 726                                            this_blocker, next_blocker));
 727           this_blocker = next_blocker;
 728         }
 729     }
 730   else
 731     {
 732       // Read the relocations of the input files.  We do this to find
 733       // which symbols are used by relocations which require a GOT and/or
 734       // a PLT entry, or a COPY reloc.  When we implement garbage
 735       // collection we will do it here by reading the relocations in a
 736       // breadth first search by references.
 737       //
 738       // We could also read the relocations during the first pass, and
 739       // mark symbols at that time.  That is how the old GNU linker works.
 740       // Doing that is more complex, since we may later decide to discard
 741       // some of the sections, and thus change our minds about the types
 742       // of references made to the symbols.
 743       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 744            p != input_objects->relobj_end();
 745            ++p)
 746         {
 747           Task_token* next_blocker = new Task_token(true);
 748           next_blocker->add_blocker();
 749           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 750                                            next_blocker));
 751           this_blocker = next_blocker;
 752         }
 753     }
 754
 755   if (this_blocker == NULL)
 756     {
 757       if (input_objects->number_of_relobjs() == 0)
 758         {
 759           // If we are given only archives in input, we have no regular
 760           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 761           // blocker here so that we can run the layout task immediately.
 762           this_blocker = new Task_token(true);
 763         }
 764       else
 765         {
 766           // If we failed to open any input files, it's possible for
 767           // THIS_BLOCKER to be NULL here.  There's no real point in
 768           // continuing if that happens.
 769           gold_assert(parameters->errors()->error_count() > 0);
 770           gold_exit(GOLD_ERR);
 771         }
 772     }
 773
 774   // When all those tasks are complete, we can start laying out the
 775   // output file.
 776   workqueue->queue(new Task_function(new Layout_task_runner(options,
 777                                                             input_objects,
 778                                                             symtab,
 779                                                             target,
 780                                                             layout,
 781                                                             mapfile),
 782                                      this_blocker,
 783                                      "Task_function Layout_task_runner"));
 784 }
 785
 786 // Queue up the final set of tasks.  This is called at the end of
 787 // Layout_task.
 788
 789 void
 790 queue_final_tasks(const General_options& options,
 791                   const Input_objects* input_objects,
 792                   const Symbol_table* symtab,
 793                   Layout* layout,
 794                   Workqueue* workqueue,
 795                   Output_file* of)
 796 {
 797   Timer* timer = parameters->timer();
 798   if (timer != NULL)
 799     timer->stamp(1);
 800
 801   int thread_count = options.thread_count_final();
 802   if (thread_count == 0)
 803     thread_count = std::max(2, input_objects->number_of_input_objects());
 804   workqueue->set_thread_count(thread_count);
 805
 806   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 807
 808   // Use a blocker to wait until all the input sections have been
 809   // written out.
 810   Task_token* input_sections_blocker = NULL;
 811   if (!any_postprocessing_sections)
 812     {
 813       input_sections_blocker = new Task_token(true);
 814       // Write_symbols_task, Relocate_tasks.
 815       input_sections_blocker->add_blocker();
 816       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 817     }
 818
 819   // Use a blocker to block any objects which have to wait for the
 820   // output sections to complete before they can apply relocations.
 821   Task_token* output_sections_blocker = new Task_token(true);
 822   output_sections_blocker->add_blocker();
 823
 824   // Use a blocker to block the final cleanup task.
 825   Task_token* final_blocker = new Task_token(true);
 826   // Write_symbols_task, Write_sections_task, Write_data_task,
 827   // Relocate_tasks.
 828   final_blocker->add_blockers(3);
 829   final_blocker->add_blockers(input_objects->number_of_relobjs());
 830   if (!any_postprocessing_sections)
 831     final_blocker->add_blocker();
 832
 833   // Queue a task to write out the symbol table.
 834   workqueue->queue(new Write_symbols_task(layout,
 835                                           symtab,
 836                                           input_objects,
 837                                           layout->sympool(),
 838                                           layout->dynpool(),
 839                                           of,
 840                                           final_blocker));
 841
 842   // Queue a task to write out the output sections.
 843   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 844                                            input_sections_blocker,
 845                                            final_blocker));
 846
 847   // Queue a task to write out everything else.
 848   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 849
 850   // Queue a task for each input object to relocate the sections and
 851   // write out the local symbols.
 852   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 853        p != input_objects->relobj_end();
 854        ++p)
 855     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 856                                        input_sections_blocker,
 857                                        output_sections_blocker,
 858                                        final_blocker));
 859
 860   // Queue a task to write out the output sections which depend on
 861   // input sections.  If there are any sections which require
 862   // postprocessing, then we need to do this last, since it may resize
 863   // the output file.
 864   if (!any_postprocessing_sections)
 865     {
 866       Task* t = new Write_after_input_sections_task(layout, of,
 867                                                     input_sections_blocker,
 868                                                     final_blocker);
 869       workqueue->queue(t);
 870     }
 871   else
 872     {
 873       Task_token* new_final_blocker = new Task_token(true);
 874       new_final_blocker->add_blocker();
 875       Task* t = new Write_after_input_sections_task(layout, of,
 876                                                     final_blocker,
 877                                                     new_final_blocker);
 878       workqueue->queue(t);
 879       final_blocker = new_final_blocker;
 880     }
 881
 882   // Create tasks for tree-style build ID computation, if necessary.
 883   if (strcmp(options.build_id(), "tree") == 0)
 884     {
 885       // Queue a task to compute the build id.  This will be blocked by
 886       // FINAL_BLOCKER, and will in turn schedule the task to close
 887       // the output file.
 888       workqueue->queue(new Task_function(new Build_id_task_runner(&options,
 889                                                                   layout,
 890                                                                   of),
 891                                          final_blocker,
 892                                          "Task_function Build_id_task_runner"));
 893     }
 894   else
 895     {
 896       // Queue a task to close the output file.  This will be blocked by
 897       // FINAL_BLOCKER.
 898       workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 899                                                                of, NULL, 0),
 900                                          final_blocker,
 901                                          "Task_function Close_task_runner"));
 902     }
 903
 904 }
 905
 906 } // End namespace gold.