gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011, 2012
   4 // Free Software Foundation, Inc.
   5 // Written by Ian Lance Taylor <iant@google.com>.
   6
   7 // This file is part of gold.
   8
   9 // This program is free software; you can redistribute it and/or modify
  10 // it under the terms of the GNU General Public License as published by
  11 // the Free Software Foundation; either version 3 of the License, or
  12 // (at your option) any later version.
  13
  14 // This program is distributed in the hope that it will be useful,
  15 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 // GNU General Public License for more details.
  18
  19 // You should have received a copy of the GNU General Public License
  20 // along with this program; if not, write to the Free Software
  21 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  22 // MA 02110-1301, USA.
  23
  24 #include "gold.h"
  25
  26 #include <cstdlib>
  27 #include <cstdio>
  28 #include <cstring>
  29 #include <unistd.h>
  30 #include <algorithm>
  31 #include "libiberty.h"
  32
  33 #include "options.h"
  34 #include "target-select.h"
  35 #include "debug.h"
  36 #include "workqueue.h"
  37 #include "dirsearch.h"
  38 #include "readsyms.h"
  39 #include "symtab.h"
  40 #include "common.h"
  41 #include "object.h"
  42 #include "layout.h"
  43 #include "reloc.h"
  44 #include "defstd.h"
  45 #include "plugin.h"
  46 #include "gc.h"
  47 #include "icf.h"
  48 #include "incremental.h"
  49 #include "timer.h"
  50
  51 namespace gold
  52 {
  53
  54 class Object;
  55
  56 const char* program_name;
  57
  58 static Task*
  59 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  60                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  61                           Task_token*, Task_token*);
  62
  63 void
  64 gold_exit(Exit_status status)
  65 {
  66   if (parameters != NULL
  67       && parameters->options_valid()
  68       && parameters->options().has_plugins())
  69     parameters->options().plugins()->cleanup();
  70   if (status != GOLD_OK && parameters != NULL && parameters->options_valid())
  71     unlink_if_ordinary(parameters->options().output_file_name());
  72   exit(status);
  73 }
  74
  75 void
  76 gold_nomem()
  77 {
  78   // We are out of memory, so try hard to print a reasonable message.
  79   // Note that we don't try to translate this message, since the
  80   // translation process itself will require memory.
  81
  82   // LEN only exists to avoid a pointless warning when write is
  83   // declared with warn_use_result, as when compiling with
  84   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  85   // work, at least not with gcc 4.3.0.
  86
  87   ssize_t len = write(2, program_name, strlen(program_name));
  88   if (len >= 0)
  89     {
  90       const char* const s = ": out of memory\n";
  91       len = write(2, s, strlen(s));
  92     }
  93   gold_exit(GOLD_ERR);
  94 }
  95
  96 // Handle an unreachable case.
  97
  98 void
  99 do_gold_unreachable(const char* filename, int lineno, const char* function)
 100 {
 101   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
 102           program_name, function, filename, lineno);
 103   gold_exit(GOLD_ERR);
 104 }
 105
 106 // This class arranges to run the functions done in the middle of the
 107 // link.  It is just a closure.
 108
 109 class Middle_runner : public Task_function_runner
 110 {
 111  public:
 112   Middle_runner(const General_options& options,
 113                 const Input_objects* input_objects,
 114                 Symbol_table* symtab,
 115                 Layout* layout, Mapfile* mapfile)
 116     : options_(options), input_objects_(input_objects), symtab_(symtab),
 117       layout_(layout), mapfile_(mapfile)
 118   { }
 119
 120   void
 121   run(Workqueue*, const Task*);
 122
 123  private:
 124   const General_options& options_;
 125   const Input_objects* input_objects_;
 126   Symbol_table* symtab_;
 127   Layout* layout_;
 128   Mapfile* mapfile_;
 129 };
 130
 131 void
 132 Middle_runner::run(Workqueue* workqueue, const Task* task)
 133 {
 134   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 135                      this->layout_, workqueue, this->mapfile_);
 136 }
 137
 138 // This class arranges the tasks to process the relocs for garbage collection.
 139
 140 class Gc_runner : public Task_function_runner
 141 {
 142   public:
 143    Gc_runner(const General_options& options,
 144              const Input_objects* input_objects,
 145              Symbol_table* symtab,
 146              Layout* layout, Mapfile* mapfile)
 147     : options_(options), input_objects_(input_objects), symtab_(symtab),
 148       layout_(layout), mapfile_(mapfile)
 149    { }
 150
 151   void
 152   run(Workqueue*, const Task*);
 153
 154  private:
 155   const General_options& options_;
 156   const Input_objects* input_objects_;
 157   Symbol_table* symtab_;
 158   Layout* layout_;
 159   Mapfile* mapfile_;
 160 };
 161
 162 void
 163 Gc_runner::run(Workqueue* workqueue, const Task* task)
 164 {
 165   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 166                         this->symtab_, this->layout_, workqueue,
 167                         this->mapfile_);
 168 }
 169
 170 // Queue up the initial set of tasks for this link job.
 171
 172 void
 173 queue_initial_tasks(const General_options& options,
 174                     Dirsearch& search_path,
 175                     const Command_line& cmdline,
 176                     Workqueue* workqueue, Input_objects* input_objects,
 177                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 178 {
 179   if (cmdline.begin() == cmdline.end())
 180     {
 181       bool is_ok = false;
 182       if (options.printed_version())
 183         is_ok = true;
 184       if (options.print_output_format())
 185         {
 186           print_output_format();
 187           is_ok = true;
 188         }
 189       if (is_ok)
 190         gold_exit(GOLD_OK);
 191       gold_fatal(_("no input files"));
 192     }
 193
 194   int thread_count = options.thread_count_initial();
 195   if (thread_count == 0)
 196     thread_count = cmdline.number_of_input_files();
 197   workqueue->set_thread_count(thread_count);
 198
 199   // For incremental links, the base output file.
 200   Incremental_binary* ibase = NULL;
 201
 202   if (parameters->incremental_update())
 203     {
 204       Output_file* of = new Output_file(options.output_file_name());
 205       if (of->open_base_file(options.incremental_base(), true))
 206         {
 207           ibase = open_incremental_binary(of);
 208           if (ibase != NULL
 209               && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 210             ibase->init_layout(layout);
 211           else
 212             {
 213               delete ibase;
 214               ibase = NULL;
 215               of->close();
 216             }
 217         }
 218       if (ibase == NULL)
 219         {
 220           if (set_parameters_incremental_full())
 221             gold_info(_("linking with --incremental-full"));
 222           else
 223             gold_fallback(_("restart link with --incremental-full"));
 224         }
 225     }
 226
 227   // Read the input files.  We have to add the symbols to the symbol
 228   // table in order.  We do this by creating a separate blocker for
 229   // each input file.  We associate the blocker with the following
 230   // input file, to give us a convenient place to delete it.
 231   Task_token* this_blocker = NULL;
 232   if (ibase == NULL)
 233     {
 234       // Normal link.  Queue a Read_symbols task for each input file
 235       // on the command line.
 236       for (Command_line::const_iterator p = cmdline.begin();
 237            p != cmdline.end();
 238            ++p)
 239         {
 240           Task_token* next_blocker = new Task_token(true);
 241           next_blocker->add_blocker();
 242           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 243                                             &search_path, 0, mapfile, &*p, NULL,
 244                                             NULL, this_blocker, next_blocker));
 245           this_blocker = next_blocker;
 246         }
 247     }
 248   else
 249     {
 250       // Incremental update link.  Process the list of input files
 251       // stored in the base file, and queue a task for each file:
 252       // a Read_symbols task for a changed file, and an Add_symbols task
 253       // for an unchanged file.  We need to mark all the space used by
 254       // unchanged files before we can start any tasks running.
 255       unsigned int input_file_count = ibase->input_file_count();
 256       std::vector<Task*> tasks;
 257       tasks.reserve(input_file_count);
 258       for (unsigned int i = 0; i < input_file_count; ++i)
 259         {
 260           Task_token* next_blocker = new Task_token(true);
 261           next_blocker->add_blocker();
 262           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 263                                               layout, &search_path, mapfile,
 264                                               this_blocker, next_blocker);
 265           tasks.push_back(t);
 266           this_blocker = next_blocker;
 267         }
 268       // Now we can queue the tasks.
 269       for (unsigned int i = 0; i < tasks.size(); i++)
 270         workqueue->queue(tasks[i]);
 271     }
 272
 273   if (options.has_plugins())
 274     {
 275       Task_token* next_blocker = new Task_token(true);
 276       next_blocker->add_blocker();
 277       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 278                                        &search_path, mapfile, this_blocker,
 279                                        next_blocker));
 280       this_blocker = next_blocker;
 281     }
 282
 283   if (options.relocatable()
 284       && (options.gc_sections() || options.icf_enabled()))
 285     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 286
 287   if (options.gc_sections() || options.icf_enabled())
 288     {
 289       workqueue->queue(new Task_function(new Gc_runner(options,
 290                                                        input_objects,
 291                                                        symtab,
 292                                                        layout,
 293                                                        mapfile),
 294                                          this_blocker,
 295                                          "Task_function Gc_runner"));
 296     }
 297   else
 298     {
 299       workqueue->queue(new Task_function(new Middle_runner(options,
 300                                                            input_objects,
 301                                                            symtab,
 302                                                            layout,
 303                                                            mapfile),
 304                                          this_blocker,
 305                                          "Task_function Middle_runner"));
 306     }
 307 }
 308
 309 // Process an incremental input file: if it is unchanged from the previous
 310 // link, return a task to add its symbols from the base file's incremental
 311 // info; if it has changed, return a normal Read_symbols task.  We create a
 312 // task for every input file, if only to report the file for rebuilding the
 313 // incremental info.
 314
 315 static Task*
 316 process_incremental_input(Incremental_binary* ibase,
 317                           unsigned int input_file_index,
 318                           Input_objects* input_objects,
 319                           Symbol_table* symtab,
 320                           Layout* layout,
 321                           Dirsearch* search_path,
 322                           Mapfile* mapfile,
 323                           Task_token* this_blocker,
 324                           Task_token* next_blocker)
 325 {
 326   const Incremental_binary::Input_reader* input_reader =
 327       ibase->get_input_reader(input_file_index);
 328   Incremental_input_type input_type = input_reader->type();
 329
 330   // Get the input argument corresponding to this input file, matching on
 331   // the argument serial number.  If the input file cannot be matched
 332   // to an existing input argument, synthesize a new one.
 333   const Input_argument* input_argument =
 334       ibase->get_input_argument(input_file_index);
 335   if (input_argument == NULL)
 336     {
 337       Input_file_argument file(input_reader->filename(),
 338                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 339                                "", false, parameters->options());
 340       Input_argument* arg = new Input_argument(file);
 341       arg->set_script_info(ibase->get_script_info(input_file_index));
 342       input_argument = arg;
 343     }
 344
 345   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 346              input_reader->filename(), input_type);
 347
 348   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 349     {
 350       // Incremental_binary::check_inputs should have cancelled the
 351       // incremental update if the script has changed.
 352       gold_assert(!ibase->file_has_changed(input_file_index));
 353       return new Check_script(layout, ibase, input_file_index, input_reader,
 354                               this_blocker, next_blocker);
 355     }
 356
 357   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 358     {
 359       Incremental_library* lib = ibase->get_library(input_file_index);
 360       gold_assert(lib != NULL);
 361       if (lib->filename() == "/group/"
 362           || !ibase->file_has_changed(input_file_index))
 363         {
 364           // Queue a task to check that no references have been added to any
 365           // of the library's unused symbols.
 366           return new Check_library(symtab, layout, ibase, input_file_index,
 367                                    input_reader, this_blocker, next_blocker);
 368         }
 369       else
 370         {
 371           // Queue a Read_symbols task to process the archive normally.
 372           return new Read_symbols(input_objects, symtab, layout, search_path,
 373                                   0, mapfile, input_argument, NULL, NULL,
 374                                   this_blocker, next_blocker);
 375         }
 376     }
 377
 378   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 379     {
 380       // For archive members, check the timestamp of the containing archive.
 381       Incremental_library* lib = ibase->get_library(input_file_index);
 382       gold_assert(lib != NULL);
 383       // Process members of a --start-lib/--end-lib group as normal objects.
 384       if (lib->filename() != "/group/")
 385         {
 386           if (ibase->file_has_changed(lib->input_file_index()))
 387             {
 388               return new Read_member(input_objects, symtab, layout, mapfile,
 389                                      input_reader, this_blocker, next_blocker);
 390             }
 391           else
 392             {
 393               // The previous contributions from this file will be kept.
 394               // Mark the pieces of output sections contributed by this
 395               // object.
 396               ibase->reserve_layout(input_file_index);
 397               Object* obj = make_sized_incremental_object(ibase,
 398                                                           input_file_index,
 399                                                           input_type,
 400                                                           input_reader);
 401               return new Add_symbols(input_objects, symtab, layout,
 402                                      search_path, 0, mapfile, input_argument,
 403                                      obj, lib, NULL, this_blocker,
 404                                      next_blocker);
 405             }
 406         }
 407     }
 408
 409   // Normal object file or shared library.  Check if the file has changed
 410   // since the last incremental link.
 411   if (ibase->file_has_changed(input_file_index))
 412     {
 413       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 414                               mapfile, input_argument, NULL, NULL,
 415                               this_blocker, next_blocker);
 416     }
 417   else
 418     {
 419       // The previous contributions from this file will be kept.
 420       // Mark the pieces of output sections contributed by this object.
 421       ibase->reserve_layout(input_file_index);
 422       Object* obj = make_sized_incremental_object(ibase,
 423                                                   input_file_index,
 424                                                   input_type,
 425                                                   input_reader);
 426       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 427                              mapfile, input_argument, obj, NULL, NULL,
 428                              this_blocker, next_blocker);
 429     }
 430 }
 431
 432 // Queue up a set of tasks to be done before queueing the middle set
 433 // of tasks.  This is only necessary when garbage collection
 434 // (--gc-sections) of unused sections is desired.  The relocs are read
 435 // and processed here early to determine the garbage sections before the
 436 // relocs can be scanned in later tasks.
 437
 438 void
 439 queue_middle_gc_tasks(const General_options& options,
 440                       const Task* ,
 441                       const Input_objects* input_objects,
 442                       Symbol_table* symtab,
 443                       Layout* layout,
 444                       Workqueue* workqueue,
 445                       Mapfile* mapfile)
 446 {
 447   // Read_relocs for all the objects must be done and processed to find
 448   // unused sections before any scanning of the relocs can take place.
 449   Task_token* this_blocker = NULL;
 450   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 451        p != input_objects->relobj_end();
 452        ++p)
 453     {
 454       Task_token* next_blocker = new Task_token(true);
 455       next_blocker->add_blocker();
 456       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 457                                        next_blocker));
 458       this_blocker = next_blocker;
 459     }
 460
 461   // If we are given only archives in input, we have no regular
 462   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 463   // blocker here so that we can run the middle tasks immediately.
 464   if (this_blocker == NULL)
 465     {
 466       gold_assert(input_objects->number_of_relobjs() == 0);
 467       this_blocker = new Task_token(true);
 468     }
 469
 470   workqueue->queue(new Task_function(new Middle_runner(options,
 471                                                        input_objects,
 472                                                        symtab,
 473                                                        layout,
 474                                                        mapfile),
 475                                      this_blocker,
 476                                      "Task_function Middle_runner"));
 477 }
 478
 479 // Queue up the middle set of tasks.  These are the tasks which run
 480 // after all the input objects have been found and all the symbols
 481 // have been read, but before we lay out the output file.
 482
 483 void
 484 queue_middle_tasks(const General_options& options,
 485                    const Task* task,
 486                    const Input_objects* input_objects,
 487                    Symbol_table* symtab,
 488                    Layout* layout,
 489                    Workqueue* workqueue,
 490                    Mapfile* mapfile)
 491 {
 492   Timer* timer = parameters->timer();
 493   if (timer != NULL)
 494     timer->stamp(0);
 495
 496   // Add any symbols named with -u options to the symbol table.
 497   symtab->add_undefined_symbols_from_command_line(layout);
 498
 499   // If garbage collection was chosen, relocs have been read and processed
 500   // at this point by pre_middle_tasks.  Layout can then be done for all
 501   // objects.
 502   if (parameters->options().gc_sections())
 503     {
 504       // Find the start symbol if any.
 505       Symbol* start_sym = symtab->lookup(parameters->entry());
 506       if (start_sym != NULL)
 507         symtab->gc_mark_symbol(start_sym);
 508       // Symbols named with -u should not be considered garbage.
 509       symtab->gc_mark_undef_symbols(layout);
 510       gold_assert(symtab->gc() != NULL);
 511       // Do a transitive closure on all references to determine the worklist.
 512       symtab->gc()->do_transitive_closure();
 513     }
 514
 515   // If identical code folding (--icf) is chosen it makes sense to do it
 516   // only after garbage collection (--gc-sections) as we do not want to
 517   // be folding sections that will be garbage.
 518   if (parameters->options().icf_enabled())
 519     {
 520       symtab->icf()->find_identical_sections(input_objects, symtab);
 521     }
 522
 523   // Call Object::layout for the second time to determine the
 524   // output_sections for all referenced input sections.  When
 525   // --gc-sections or --icf is turned on, or when certain input
 526   // sections have to be mapped to unique segments, Object::layout
 527   // is called twice.  It is called the first time when symbols
 528   // are added.
 529   if (parameters->options().gc_sections()
 530       || parameters->options().icf_enabled()
 531       || layout->is_unique_segment_for_sections_specified())
 532     {
 533       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 534            p != input_objects->relobj_end();
 535            ++p)
 536         {
 537           Task_lock_obj<Object> tlo(task, *p);
 538           (*p)->layout(symtab, layout, NULL);
 539         }
 540     }
 541
 542   // Layout deferred objects due to plugins.
 543   if (parameters->options().has_plugins())
 544     {
 545       Plugin_manager* plugins = parameters->options().plugins();
 546       gold_assert(plugins != NULL);
 547       plugins->layout_deferred_objects();
 548     }
 549
 550   /* If plugins have specified a section order, re-arrange input sections
 551      according to a specified section order.  If --section-ordering-file is
 552      also specified, do not do anything here.  */
 553   if (parameters->options().has_plugins()
 554       && layout->is_section_ordering_specified()
 555       && !parameters->options().section_ordering_file ())
 556     {
 557       for (Layout::Section_list::const_iterator p
 558              = layout->section_list().begin();
 559            p != layout->section_list().end();
 560            ++p)
 561         (*p)->update_section_layout(layout->get_section_order_map());
 562     }
 563
 564   if (parameters->options().gc_sections()
 565       || parameters->options().icf_enabled())
 566     {
 567       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 568            p != input_objects->relobj_end();
 569            ++p)
 570         {
 571           // Update the value of output_section stored in rd.
 572           Read_relocs_data* rd = (*p)->get_relocs_data();
 573           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 574                q != rd->relocs.end();
 575                ++q)
 576             {
 577               q->output_section = (*p)->output_section(q->data_shndx);
 578               q->needs_special_offset_handling =
 579                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 580             }
 581         }
 582     }
 583
 584   // We have to support the case of not seeing any input objects, and
 585   // generate an empty file.  Existing builds depend on being able to
 586   // pass an empty archive to the linker and get an empty object file
 587   // out.  In order to do this we need to use a default target.
 588   if (input_objects->number_of_input_objects() == 0
 589       && layout->incremental_base() == NULL)
 590     parameters_force_valid_target();
 591
 592   int thread_count = options.thread_count_middle();
 593   if (thread_count == 0)
 594     thread_count = std::max(2, input_objects->number_of_input_objects());
 595   workqueue->set_thread_count(thread_count);
 596
 597   // Now we have seen all the input files.
 598   const bool doing_static_link =
 599     (!input_objects->any_dynamic()
 600      && !parameters->options().output_is_position_independent());
 601   set_parameters_doing_static_link(doing_static_link);
 602   if (!doing_static_link && options.is_static())
 603     {
 604       // We print out just the first .so we see; there may be others.
 605       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 606       gold_error(_("cannot mix -static with dynamic object %s"),
 607                  (*input_objects->dynobj_begin())->name().c_str());
 608     }
 609   if (!doing_static_link && parameters->options().relocatable())
 610     gold_fatal(_("cannot mix -r with dynamic object %s"),
 611                (*input_objects->dynobj_begin())->name().c_str());
 612   if (!doing_static_link
 613       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 614     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 615                (*input_objects->dynobj_begin())->name().c_str());
 616
 617   if (parameters->options().relocatable())
 618     {
 619       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 620       if (p != input_objects->relobj_end())
 621         {
 622           bool uses_split_stack = (*p)->uses_split_stack();
 623           for (++p; p != input_objects->relobj_end(); ++p)
 624             {
 625               if ((*p)->uses_split_stack() != uses_split_stack)
 626                 gold_fatal(_("cannot mix split-stack '%s' and "
 627                              "non-split-stack '%s' when using -r"),
 628                            (*input_objects->relobj_begin())->name().c_str(),
 629                            (*p)->name().c_str());
 630             }
 631         }
 632     }
 633
 634   // For incremental updates, record the existing GOT and PLT entries,
 635   // and the COPY relocations.
 636   if (parameters->incremental_update())
 637     {
 638       Incremental_binary* ibase = layout->incremental_base();
 639       ibase->process_got_plt(symtab, layout);
 640       ibase->emit_copy_relocs(symtab);
 641     }
 642
 643   if (is_debugging_enabled(DEBUG_SCRIPT))
 644     layout->script_options()->print(stderr);
 645
 646   // For each dynamic object, record whether we've seen all the
 647   // dynamic objects that it depends upon.
 648   input_objects->check_dynamic_dependencies();
 649
 650   // See if any of the input definitions violate the One Definition Rule.
 651   // TODO: if this is too slow, do this as a task, rather than inline.
 652   symtab->detect_odr_violations(task, options.output_file_name());
 653
 654   // Do the --no-undefined-version check.
 655   if (!parameters->options().undefined_version())
 656     {
 657       Script_options* so = layout->script_options();
 658       so->version_script_info()->check_unmatched_names(symtab);
 659     }
 660
 661   // Create any automatic note sections.
 662   layout->create_notes();
 663
 664   // Create any output sections required by any linker script.
 665   layout->create_script_sections();
 666
 667   // Define some sections and symbols needed for a dynamic link.  This
 668   // handles some cases we want to see before we read the relocs.
 669   layout->create_initial_dynamic_sections(symtab);
 670
 671   // Define symbols from any linker scripts.
 672   layout->define_script_symbols(symtab);
 673
 674   // TODO(csilvers): figure out a more principled way to get the target
 675   Target* target = const_cast<Target*>(&parameters->target());
 676
 677   // Attach sections to segments.
 678   layout->attach_sections_to_segments(target);
 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       // Define target-specific symbols.
 690       target->define_standard_symbols(symtab, layout);
 691     }
 692
 693   // Make sure we have symbols for any required group signatures.
 694   layout->define_group_signatures(symtab);
 695
 696   Task_token* this_blocker = NULL;
 697
 698   // Allocate common symbols.  We use a blocker to run this before the
 699   // Scan_relocs tasks, because it writes to the symbol table just as
 700   // they do.
 701   if (parameters->options().define_common())
 702     {
 703       this_blocker = new Task_token(true);
 704       this_blocker->add_blocker();
 705       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 706                                                  this_blocker));
 707     }
 708
 709   // If doing garbage collection, the relocations have already been read.
 710   // Otherwise, read and scan the relocations.
 711   if (parameters->options().gc_sections()
 712       || parameters->options().icf_enabled())
 713     {
 714       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 715            p != input_objects->relobj_end();
 716            ++p)
 717         {
 718           Task_token* next_blocker = new Task_token(true);
 719           next_blocker->add_blocker();
 720           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 721                                            (*p)->get_relocs_data(),
 722                                            this_blocker, next_blocker));
 723           this_blocker = next_blocker;
 724         }
 725     }
 726   else
 727     {
 728       // Read the relocations of the input files.  We do this to find
 729       // which symbols are used by relocations which require a GOT and/or
 730       // a PLT entry, or a COPY reloc.  When we implement garbage
 731       // collection we will do it here by reading the relocations in a
 732       // breadth first search by references.
 733       //
 734       // We could also read the relocations during the first pass, and
 735       // mark symbols at that time.  That is how the old GNU linker works.
 736       // Doing that is more complex, since we may later decide to discard
 737       // some of the sections, and thus change our minds about the types
 738       // of references made to the symbols.
 739       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 740            p != input_objects->relobj_end();
 741            ++p)
 742         {
 743           Task_token* next_blocker = new Task_token(true);
 744           next_blocker->add_blocker();
 745           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 746                                            next_blocker));
 747           this_blocker = next_blocker;
 748         }
 749     }
 750
 751   if (this_blocker == NULL)
 752     {
 753       if (input_objects->number_of_relobjs() == 0)
 754         {
 755           // If we are given only archives in input, we have no regular
 756           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 757           // blocker here so that we can run the layout task immediately.
 758           this_blocker = new Task_token(true);
 759         }
 760       else
 761         {
 762           // If we failed to open any input files, it's possible for
 763           // THIS_BLOCKER to be NULL here.  There's no real point in
 764           // continuing if that happens.
 765           gold_assert(parameters->errors()->error_count() > 0);
 766           gold_exit(GOLD_ERR);
 767         }
 768     }
 769
 770   // When all those tasks are complete, we can start laying out the
 771   // output file.
 772   workqueue->queue(new Task_function(new Layout_task_runner(options,
 773                                                             input_objects,
 774                                                             symtab,
 775                                                             target,
 776                                                             layout,
 777                                                             mapfile),
 778                                      this_blocker,
 779                                      "Task_function Layout_task_runner"));
 780 }
 781
 782 // Queue up the final set of tasks.  This is called at the end of
 783 // Layout_task.
 784
 785 void
 786 queue_final_tasks(const General_options& options,
 787                   const Input_objects* input_objects,
 788                   const Symbol_table* symtab,
 789                   Layout* layout,
 790                   Workqueue* workqueue,
 791                   Output_file* of)
 792 {
 793   Timer* timer = parameters->timer();
 794   if (timer != NULL)
 795     timer->stamp(1);
 796
 797   int thread_count = options.thread_count_final();
 798   if (thread_count == 0)
 799     thread_count = std::max(2, input_objects->number_of_input_objects());
 800   workqueue->set_thread_count(thread_count);
 801
 802   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 803
 804   // Use a blocker to wait until all the input sections have been
 805   // written out.
 806   Task_token* input_sections_blocker = NULL;
 807   if (!any_postprocessing_sections)
 808     {
 809       input_sections_blocker = new Task_token(true);
 810       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 811     }
 812
 813   // Use a blocker to block any objects which have to wait for the
 814   // output sections to complete before they can apply relocations.
 815   Task_token* output_sections_blocker = new Task_token(true);
 816   output_sections_blocker->add_blocker();
 817
 818   // Use a blocker to block the final cleanup task.
 819   Task_token* final_blocker = new Task_token(true);
 820   // Write_symbols_task, Write_sections_task, Write_data_task,
 821   // Relocate_tasks.
 822   final_blocker->add_blockers(3);
 823   final_blocker->add_blockers(input_objects->number_of_relobjs());
 824   if (!any_postprocessing_sections)
 825     final_blocker->add_blocker();
 826
 827   // Queue a task to write out the symbol table.
 828   workqueue->queue(new Write_symbols_task(layout,
 829                                           symtab,
 830                                           input_objects,
 831                                           layout->sympool(),
 832                                           layout->dynpool(),
 833                                           of,
 834                                           final_blocker));
 835
 836   // Queue a task to write out the output sections.
 837   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 838                                            final_blocker));
 839
 840   // Queue a task to write out everything else.
 841   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 842
 843   // Queue a task for each input object to relocate the sections and
 844   // write out the local symbols.
 845   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 846        p != input_objects->relobj_end();
 847        ++p)
 848     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 849                                        input_sections_blocker,
 850                                        output_sections_blocker,
 851                                        final_blocker));
 852
 853   // Queue a task to write out the output sections which depend on
 854   // input sections.  If there are any sections which require
 855   // postprocessing, then we need to do this last, since it may resize
 856   // the output file.
 857   if (!any_postprocessing_sections)
 858     {
 859       Task* t = new Write_after_input_sections_task(layout, of,
 860                                                     input_sections_blocker,
 861                                                     final_blocker);
 862       workqueue->queue(t);
 863     }
 864   else
 865     {
 866       Task_token* new_final_blocker = new Task_token(true);
 867       new_final_blocker->add_blocker();
 868       Task* t = new Write_after_input_sections_task(layout, of,
 869                                                     final_blocker,
 870                                                     new_final_blocker);
 871       workqueue->queue(t);
 872       final_blocker = new_final_blocker;
 873     }
 874
 875   // Queue a task to close the output file.  This will be blocked by
 876   // FINAL_BLOCKER.
 877   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 878                                                            of),
 879                                      final_blocker,
 880                                      "Task_function Close_task_runner"));
 881 }
 882
 883 } // End namespace gold.