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_update())
 201     {
 202       Output_file* of = new Output_file(options.output_file_name());
 203       if (of->open_base_file(options.incremental_base(), true))
 204         {
 205           ibase = open_incremental_binary(of);
 206           if (ibase != NULL
 207               && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 208             ibase->init_layout(layout);
 209           else
 210             {
 211               delete ibase;
 212               ibase = NULL;
 213               of->close();
 214             }
 215         }
 216       if (ibase == NULL)
 217         {
 218           if (set_parameters_incremental_full())
 219             gold_info(_("linking with --incremental-full"));
 220           else
 221             gold_fallback(_("restart link with --incremental-full"));
 222         }
 223     }
 224
 225   // Read the input files.  We have to add the symbols to the symbol
 226   // table in order.  We do this by creating a separate blocker for
 227   // each input file.  We associate the blocker with the following
 228   // input file, to give us a convenient place to delete it.
 229   Task_token* this_blocker = NULL;
 230   if (ibase == NULL)
 231     {
 232       // Normal link.  Queue a Read_symbols task for each input file
 233       // on the command line.
 234       for (Command_line::const_iterator p = cmdline.begin();
 235            p != cmdline.end();
 236            ++p)
 237         {
 238           Task_token* next_blocker = new Task_token(true);
 239           next_blocker->add_blocker();
 240           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 241                                             &search_path, 0, mapfile, &*p, NULL,
 242                                             NULL, this_blocker, next_blocker));
 243           this_blocker = next_blocker;
 244         }
 245     }
 246   else
 247     {
 248       // Incremental update link.  Process the list of input files
 249       // stored in the base file, and queue a task for each file:
 250       // a Read_symbols task for a changed file, and an Add_symbols task
 251       // for an unchanged file.  We need to mark all the space used by
 252       // unchanged files before we can start any tasks running.
 253       unsigned int input_file_count = ibase->input_file_count();
 254       std::vector<Task*> tasks;
 255       tasks.reserve(input_file_count);
 256       for (unsigned int i = 0; i < input_file_count; ++i)
 257         {
 258           Task_token* next_blocker = new Task_token(true);
 259           next_blocker->add_blocker();
 260           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 261                                               layout, &search_path, mapfile,
 262                                               this_blocker, next_blocker);
 263           tasks.push_back(t);
 264           this_blocker = next_blocker;
 265         }
 266       // Now we can queue the tasks.
 267       for (unsigned int i = 0; i < tasks.size(); i++)
 268         workqueue->queue(tasks[i]);
 269     }
 270
 271   if (options.has_plugins())
 272     {
 273       Task_token* next_blocker = new Task_token(true);
 274       next_blocker->add_blocker();
 275       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 276                                        &search_path, mapfile, this_blocker,
 277                                        next_blocker));
 278       this_blocker = next_blocker;
 279     }
 280
 281   if (options.relocatable()
 282       && (options.gc_sections() || options.icf_enabled()))
 283     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 284
 285   if (options.gc_sections() || options.icf_enabled())
 286     {
 287       workqueue->queue(new Task_function(new Gc_runner(options,
 288                                                        input_objects,
 289                                                        symtab,
 290                                                        layout,
 291                                                        mapfile),
 292                                          this_blocker,
 293                                          "Task_function Gc_runner"));
 294     }
 295   else
 296     {
 297       workqueue->queue(new Task_function(new Middle_runner(options,
 298                                                            input_objects,
 299                                                            symtab,
 300                                                            layout,
 301                                                            mapfile),
 302                                          this_blocker,
 303                                          "Task_function Middle_runner"));
 304     }
 305 }
 306
 307 // Process an incremental input file: if it is unchanged from the previous
 308 // link, return a task to add its symbols from the base file's incremental
 309 // info; if it has changed, return a normal Read_symbols task.  We create a
 310 // task for every input file, if only to report the file for rebuilding the
 311 // incremental info.
 312
 313 static Task*
 314 process_incremental_input(Incremental_binary* ibase,
 315                           unsigned int input_file_index,
 316                           Input_objects* input_objects,
 317                           Symbol_table* symtab,
 318                           Layout* layout,
 319                           Dirsearch* search_path,
 320                           Mapfile* mapfile,
 321                           Task_token* this_blocker,
 322                           Task_token* next_blocker)
 323 {
 324   const Incremental_binary::Input_reader* input_reader =
 325       ibase->get_input_reader(input_file_index);
 326   Incremental_input_type input_type = input_reader->type();
 327
 328   // Get the input argument corresponding to this input file, matching on
 329   // the argument serial number.  If the input file cannot be matched
 330   // to an existing input argument, synthesize a new one.
 331   const Input_argument* input_argument =
 332       ibase->get_input_argument(input_file_index);
 333   if (input_argument == NULL)
 334     {
 335       Input_file_argument file(input_reader->filename(),
 336                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 337                                "", false, parameters->options());
 338       Input_argument* arg = new Input_argument(file);
 339       arg->set_script_info(ibase->get_script_info(input_file_index));
 340       input_argument = arg;
 341     }
 342
 343   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 344              input_reader->filename(), input_type);
 345
 346   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 347     {
 348       // Incremental_binary::check_inputs should have cancelled the
 349       // incremental update if the script has changed.
 350       gold_assert(!ibase->file_has_changed(input_file_index));
 351       return new Check_script(layout, ibase, input_file_index, input_reader,
 352                               this_blocker, next_blocker);
 353     }
 354
 355   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 356     {
 357       Incremental_library* lib = ibase->get_library(input_file_index);
 358       gold_assert(lib != NULL);
 359       if (lib->filename() == "/group/"
 360           || !ibase->file_has_changed(input_file_index))
 361         {
 362           // Queue a task to check that no references have been added to any
 363           // of the library's unused symbols.
 364           return new Check_library(symtab, layout, ibase, input_file_index,
 365                                    input_reader, this_blocker, next_blocker);
 366         }
 367       else
 368         {
 369           // Queue a Read_symbols task to process the archive normally.
 370           return new Read_symbols(input_objects, symtab, layout, search_path,
 371                                   0, mapfile, input_argument, NULL, NULL,
 372                                   this_blocker, next_blocker);
 373         }
 374     }
 375
 376   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 377     {
 378       // For archive members, check the timestamp of the containing archive.
 379       Incremental_library* lib = ibase->get_library(input_file_index);
 380       gold_assert(lib != NULL);
 381       // Process members of a --start-lib/--end-lib group as normal objects.
 382       if (lib->filename() != "/group/")
 383         {
 384           if (ibase->file_has_changed(lib->input_file_index()))
 385             {
 386               return new Read_member(input_objects, symtab, layout, mapfile,
 387                                      input_reader, this_blocker, next_blocker);
 388             }
 389           else
 390             {
 391               // The previous contributions from this file will be kept.
 392               // Mark the pieces of output sections contributed by this
 393               // object.
 394               ibase->reserve_layout(input_file_index);
 395               Object* obj = make_sized_incremental_object(ibase,
 396                                                           input_file_index,
 397                                                           input_type,
 398                                                           input_reader);
 399               return new Add_symbols(input_objects, symtab, layout,
 400                                      search_path, 0, mapfile, input_argument,
 401                                      obj, lib, NULL, this_blocker,
 402                                      next_blocker);
 403             }
 404         }
 405     }
 406
 407   // Normal object file or shared library.  Check if the file has changed
 408   // since the last incremental link.
 409   if (ibase->file_has_changed(input_file_index))
 410     {
 411       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 412                               mapfile, input_argument, NULL, NULL,
 413                               this_blocker, next_blocker);
 414     }
 415   else
 416     {
 417       // The previous contributions from this file will be kept.
 418       // Mark the pieces of output sections contributed by this object.
 419       ibase->reserve_layout(input_file_index);
 420       Object* obj = make_sized_incremental_object(ibase,
 421                                                   input_file_index,
 422                                                   input_type,
 423                                                   input_reader);
 424       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 425                              mapfile, input_argument, obj, NULL, NULL,
 426                              this_blocker, next_blocker);
 427     }
 428 }
 429
 430 // Queue up a set of tasks to be done before queueing the middle set
 431 // of tasks.  This is only necessary when garbage collection
 432 // (--gc-sections) of unused sections is desired.  The relocs are read
 433 // and processed here early to determine the garbage sections before the
 434 // relocs can be scanned in later tasks.
 435
 436 void
 437 queue_middle_gc_tasks(const General_options& options,
 438                       const Task* ,
 439                       const Input_objects* input_objects,
 440                       Symbol_table* symtab,
 441                       Layout* layout,
 442                       Workqueue* workqueue,
 443                       Mapfile* mapfile)
 444 {
 445   // Read_relocs for all the objects must be done and processed to find
 446   // unused sections before any scanning of the relocs can take place.
 447   Task_token* this_blocker = NULL;
 448   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 449        p != input_objects->relobj_end();
 450        ++p)
 451     {
 452       Task_token* next_blocker = new Task_token(true);
 453       next_blocker->add_blocker();
 454       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 455                                        next_blocker));
 456       this_blocker = next_blocker;
 457     }
 458
 459   // If we are given only archives in input, we have no regular
 460   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 461   // blocker here so that we can run the middle tasks immediately.
 462   if (this_blocker == NULL)
 463     {
 464       gold_assert(input_objects->number_of_relobjs() == 0);
 465       this_blocker = new Task_token(true);
 466     }
 467
 468   workqueue->queue(new Task_function(new Middle_runner(options,
 469                                                        input_objects,
 470                                                        symtab,
 471                                                        layout,
 472                                                        mapfile),
 473                                      this_blocker,
 474                                      "Task_function Middle_runner"));
 475 }
 476
 477 // Queue up the middle set of tasks.  These are the tasks which run
 478 // after all the input objects have been found and all the symbols
 479 // have been read, but before we lay out the output file.
 480
 481 void
 482 queue_middle_tasks(const General_options& options,
 483                    const Task* task,
 484                    const Input_objects* input_objects,
 485                    Symbol_table* symtab,
 486                    Layout* layout,
 487                    Workqueue* workqueue,
 488                    Mapfile* mapfile)
 489 {
 490   // Add any symbols named with -u options to the symbol table.
 491   symtab->add_undefined_symbols_from_command_line(layout);
 492
 493   // If garbage collection was chosen, relocs have been read and processed
 494   // at this point by pre_middle_tasks.  Layout can then be done for all
 495   // objects.
 496   if (parameters->options().gc_sections())
 497     {
 498       // Find the start symbol if any.
 499       Symbol* start_sym = symtab->lookup(parameters->entry());
 500       if (start_sym != NULL)
 501         {
 502           bool is_ordinary;
 503           unsigned int shndx = start_sym->shndx(&is_ordinary);
 504           if (is_ordinary)
 505             {
 506               symtab->gc()->worklist().push(
 507                 Section_id(start_sym->object(), shndx));
 508             }
 509         }
 510       // Symbols named with -u should not be considered garbage.
 511       symtab->gc_mark_undef_symbols(layout);
 512       gold_assert(symtab->gc() != NULL);
 513       // Do a transitive closure on all references to determine the worklist.
 514       symtab->gc()->do_transitive_closure();
 515     }
 516
 517   // If identical code folding (--icf) is chosen it makes sense to do it
 518   // only after garbage collection (--gc-sections) as we do not want to
 519   // be folding sections that will be garbage.
 520   if (parameters->options().icf_enabled())
 521     {
 522       symtab->icf()->find_identical_sections(input_objects, symtab);
 523     }
 524
 525   // Call Object::layout for the second time to determine the
 526   // output_sections for all referenced input sections.  When
 527   // --gc-sections or --icf is turned on, Object::layout is
 528   // called twice.  It is called the first time when the
 529   // symbols are added.
 530   if (parameters->options().gc_sections()
 531       || parameters->options().icf_enabled())
 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   /* If plugins have specified a section order, re-arrange input sections
 543      according to a specified section order.  If --section-ordering-file is
 544      also specified, do not do anything here.  */
 545   if (parameters->options().has_plugins()
 546       && layout->is_section_ordering_specified()
 547       && !parameters->options().section_ordering_file ())
 548     {
 549       for (Layout::Section_list::const_iterator p
 550              = layout->section_list().begin();
 551            p != layout->section_list().end();
 552            ++p)
 553         (*p)->update_section_layout(layout->get_section_order_map());
 554     }
 555
 556   // Layout deferred objects due to plugins.
 557   if (parameters->options().has_plugins())
 558     {
 559       Plugin_manager* plugins = parameters->options().plugins();
 560       gold_assert(plugins != NULL);
 561       plugins->layout_deferred_objects();
 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   // Attach sections to segments.
 675   layout->attach_sections_to_segments();
 676
 677   if (!parameters->options().relocatable())
 678     {
 679       // Predefine standard symbols.
 680       define_standard_symbols(symtab, layout);
 681
 682       // Define __start and __stop symbols for output sections where
 683       // appropriate.
 684       layout->define_section_symbols(symtab);
 685     }
 686
 687   // Make sure we have symbols for any required group signatures.
 688   layout->define_group_signatures(symtab);
 689
 690   Task_token* this_blocker = NULL;
 691
 692   // Allocate common symbols.  We use a blocker to run this before the
 693   // Scan_relocs tasks, because it writes to the symbol table just as
 694   // they do.
 695   if (parameters->options().define_common())
 696     {
 697       this_blocker = new Task_token(true);
 698       this_blocker->add_blocker();
 699       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 700                                                  this_blocker));
 701     }
 702
 703   // If doing garbage collection, the relocations have already been read.
 704   // Otherwise, read and scan the relocations.
 705   if (parameters->options().gc_sections()
 706       || parameters->options().icf_enabled())
 707     {
 708       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 709            p != input_objects->relobj_end();
 710            ++p)
 711         {
 712           Task_token* next_blocker = new Task_token(true);
 713           next_blocker->add_blocker();
 714           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 715                                            (*p)->get_relocs_data(),
 716                                            this_blocker, next_blocker));
 717           this_blocker = next_blocker;
 718         }
 719     }
 720   else
 721     {
 722       // Read the relocations of the input files.  We do this to find
 723       // which symbols are used by relocations which require a GOT and/or
 724       // a PLT entry, or a COPY reloc.  When we implement garbage
 725       // collection we will do it here by reading the relocations in a
 726       // breadth first search by references.
 727       //
 728       // We could also read the relocations during the first pass, and
 729       // mark symbols at that time.  That is how the old GNU linker works.
 730       // Doing that is more complex, since we may later decide to discard
 731       // some of the sections, and thus change our minds about the types
 732       // of references made to the symbols.
 733       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 734            p != input_objects->relobj_end();
 735            ++p)
 736         {
 737           Task_token* next_blocker = new Task_token(true);
 738           next_blocker->add_blocker();
 739           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 740                                            next_blocker));
 741           this_blocker = next_blocker;
 742         }
 743     }
 744
 745   if (this_blocker == NULL)
 746     {
 747       if (input_objects->number_of_relobjs() == 0)
 748         {
 749           // If we are given only archives in input, we have no regular
 750           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 751           // blocker here so that we can run the layout task immediately.
 752           this_blocker = new Task_token(true);
 753         }
 754       else
 755         {
 756           // If we failed to open any input files, it's possible for
 757           // THIS_BLOCKER to be NULL here.  There's no real point in
 758           // continuing if that happens.
 759           gold_assert(parameters->errors()->error_count() > 0);
 760           gold_exit(GOLD_ERR);
 761         }
 762     }
 763
 764   // When all those tasks are complete, we can start laying out the
 765   // output file.
 766   // TODO(csilvers): figure out a more principled way to get the target
 767   Target* target = const_cast<Target*>(&parameters->target());
 768   workqueue->queue(new Task_function(new Layout_task_runner(options,
 769                                                             input_objects,
 770                                                             symtab,
 771                                                             target,
 772                                                             layout,
 773                                                             mapfile),
 774                                      this_blocker,
 775                                      "Task_function Layout_task_runner"));
 776 }
 777
 778 // Queue up the final set of tasks.  This is called at the end of
 779 // Layout_task.
 780
 781 void
 782 queue_final_tasks(const General_options& options,
 783                   const Input_objects* input_objects,
 784                   const Symbol_table* symtab,
 785                   Layout* layout,
 786                   Workqueue* workqueue,
 787                   Output_file* of)
 788 {
 789   int thread_count = options.thread_count_final();
 790   if (thread_count == 0)
 791     thread_count = std::max(2, input_objects->number_of_input_objects());
 792   workqueue->set_thread_count(thread_count);
 793
 794   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 795
 796   // Use a blocker to wait until all the input sections have been
 797   // written out.
 798   Task_token* input_sections_blocker = NULL;
 799   if (!any_postprocessing_sections)
 800     {
 801       input_sections_blocker = new Task_token(true);
 802       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 803     }
 804
 805   // Use a blocker to block any objects which have to wait for the
 806   // output sections to complete before they can apply relocations.
 807   Task_token* output_sections_blocker = new Task_token(true);
 808   output_sections_blocker->add_blocker();
 809
 810   // Use a blocker to block the final cleanup task.
 811   Task_token* final_blocker = new Task_token(true);
 812   // Write_symbols_task, Write_sections_task, Write_data_task,
 813   // Relocate_tasks.
 814   final_blocker->add_blockers(3);
 815   final_blocker->add_blockers(input_objects->number_of_relobjs());
 816   if (!any_postprocessing_sections)
 817     final_blocker->add_blocker();
 818
 819   // Queue a task to write out the symbol table.
 820   workqueue->queue(new Write_symbols_task(layout,
 821                                           symtab,
 822                                           input_objects,
 823                                           layout->sympool(),
 824                                           layout->dynpool(),
 825                                           of,
 826                                           final_blocker));
 827
 828   // Queue a task to write out the output sections.
 829   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 830                                            final_blocker));
 831
 832   // Queue a task to write out everything else.
 833   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 834
 835   // Queue a task for each input object to relocate the sections and
 836   // write out the local symbols.
 837   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 838        p != input_objects->relobj_end();
 839        ++p)
 840     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 841                                        input_sections_blocker,
 842                                        output_sections_blocker,
 843                                        final_blocker));
 844
 845   // Queue a task to write out the output sections which depend on
 846   // input sections.  If there are any sections which require
 847   // postprocessing, then we need to do this last, since it may resize
 848   // the output file.
 849   if (!any_postprocessing_sections)
 850     {
 851       Task* t = new Write_after_input_sections_task(layout, of,
 852                                                     input_sections_blocker,
 853                                                     final_blocker);
 854       workqueue->queue(t);
 855     }
 856   else
 857     {
 858       Task_token* new_final_blocker = new Task_token(true);
 859       new_final_blocker->add_blocker();
 860       Task* t = new Write_after_input_sections_task(layout, of,
 861                                                     final_blocker,
 862                                                     new_final_blocker);
 863       workqueue->queue(t);
 864       final_blocker = new_final_blocker;
 865     }
 866
 867   // Queue a task to close the output file.  This will be blocked by
 868   // FINAL_BLOCKER.
 869   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 870                                                            of),
 871                                      final_blocker,
 872                                      "Task_function Close_task_runner"));
 873 }
 874
 875 } // End namespace gold.