gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include <cstdlib>
  26 #include <cstdio>
  27 #include <cstring>
  28 #include <unistd.h>
  29 #include <algorithm>
  30 #include "libiberty.h"
  31
  32 #include "options.h"
  33 #include "debug.h"
  34 #include "workqueue.h"
  35 #include "dirsearch.h"
  36 #include "readsyms.h"
  37 #include "symtab.h"
  38 #include "common.h"
  39 #include "object.h"
  40 #include "layout.h"
  41 #include "reloc.h"
  42 #include "defstd.h"
  43 #include "plugin.h"
  44 #include "gc.h"
  45 #include "icf.h"
  46 #include "incremental.h"
  47
  48 namespace gold
  49 {
  50
  51 class Object;
  52
  53 const char* program_name;
  54
  55 static Task*
  56 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  57                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  58                           Task_token*, Task_token*);
  59
  60 void
  61 gold_exit(bool status)
  62 {
  63   if (parameters != NULL
  64       && parameters->options_valid()
  65       && parameters->options().has_plugins())
  66     parameters->options().plugins()->cleanup();
  67   if (!status && parameters != NULL && parameters->options_valid())
  68     unlink_if_ordinary(parameters->options().output_file_name());
  69   exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
  70 }
  71
  72 void
  73 gold_nomem()
  74 {
  75   // We are out of memory, so try hard to print a reasonable message.
  76   // Note that we don't try to translate this message, since the
  77   // translation process itself will require memory.
  78
  79   // LEN only exists to avoid a pointless warning when write is
  80   // declared with warn_use_result, as when compiling with
  81   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  82   // work, at least not with gcc 4.3.0.
  83
  84   ssize_t len = write(2, program_name, strlen(program_name));
  85   if (len >= 0)
  86     {
  87       const char* const s = ": out of memory\n";
  88       len = write(2, s, strlen(s));
  89     }
  90   gold_exit(false);
  91 }
  92
  93 // Handle an unreachable case.
  94
  95 void
  96 do_gold_unreachable(const char* filename, int lineno, const char* function)
  97 {
  98   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
  99           program_name, function, filename, lineno);
 100   gold_exit(false);
 101 }
 102
 103 // This class arranges to run the functions done in the middle of the
 104 // link.  It is just a closure.
 105
 106 class Middle_runner : public Task_function_runner
 107 {
 108  public:
 109   Middle_runner(const General_options& options,
 110                 const Input_objects* input_objects,
 111                 Symbol_table* symtab,
 112                 Layout* layout, Mapfile* mapfile)
 113     : options_(options), input_objects_(input_objects), symtab_(symtab),
 114       layout_(layout), mapfile_(mapfile)
 115   { }
 116
 117   void
 118   run(Workqueue*, const Task*);
 119
 120  private:
 121   const General_options& options_;
 122   const Input_objects* input_objects_;
 123   Symbol_table* symtab_;
 124   Layout* layout_;
 125   Mapfile* mapfile_;
 126 };
 127
 128 void
 129 Middle_runner::run(Workqueue* workqueue, const Task* task)
 130 {
 131   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 132                      this->layout_, workqueue, this->mapfile_);
 133 }
 134
 135 // This class arranges the tasks to process the relocs for garbage collection.
 136
 137 class Gc_runner : public Task_function_runner
 138 {
 139   public:
 140    Gc_runner(const General_options& options,
 141              const Input_objects* input_objects,
 142              Symbol_table* symtab,
 143              Layout* layout, Mapfile* mapfile)
 144     : options_(options), input_objects_(input_objects), symtab_(symtab),
 145       layout_(layout), mapfile_(mapfile)
 146    { }
 147
 148   void
 149   run(Workqueue*, const Task*);
 150
 151  private:
 152   const General_options& options_;
 153   const Input_objects* input_objects_;
 154   Symbol_table* symtab_;
 155   Layout* layout_;
 156   Mapfile* mapfile_;
 157 };
 158
 159 void
 160 Gc_runner::run(Workqueue* workqueue, const Task* task)
 161 {
 162   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 163                         this->symtab_, this->layout_, workqueue,
 164                         this->mapfile_);
 165 }
 166
 167 // Queue up the initial set of tasks for this link job.
 168
 169 void
 170 queue_initial_tasks(const General_options& options,
 171                     Dirsearch& search_path,
 172                     const Command_line& cmdline,
 173                     Workqueue* workqueue, Input_objects* input_objects,
 174                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 175 {
 176   if (cmdline.begin() == cmdline.end())
 177     {
 178       if (options.printed_version())
 179         gold_exit(true);
 180       gold_fatal(_("no input files"));
 181     }
 182
 183   int thread_count = options.thread_count_initial();
 184   if (thread_count == 0)
 185     thread_count = cmdline.number_of_input_files();
 186   workqueue->set_thread_count(thread_count);
 187
 188   // For incremental links, the base output file.
 189   Incremental_binary* ibase = NULL;
 190
 191   if (parameters->incremental())
 192     {
 193       if (options.relocatable())
 194         gold_error(_("incremental linking is incompatible with -r"));
 195       if (options.emit_relocs())
 196         gold_error(_("incremental linking is incompatible with --emit-relocs"));
 197       if (options.gc_sections())
 198         gold_error(_("incremental linking is incompatible with --gc-sections"));
 199       if (options.icf_enabled())
 200         gold_error(_("incremental linking is incompatible with --icf"));
 201       if (options.has_plugins())
 202         gold_error(_("incremental linking is incompatible with --plugin"));
 203
 204       if (parameters->incremental_update())
 205         {
 206           Output_file* of = new Output_file(options.output_file_name());
 207           if (!of->open_for_modification())
 208             gold_info(_("incremental update not possible: "
 209                         "cannot open %s"),
 210                       options.output_file_name());
 211           else
 212             {
 213               ibase = open_incremental_binary(of);
 214               if (ibase != NULL
 215                   && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 216                 ibase->init_layout(layout);
 217               else
 218                 {
 219                   delete ibase;
 220                   ibase = NULL;
 221                   of->close();
 222                 }
 223             }
 224           if (ibase == NULL)
 225             {
 226               if (set_parameters_incremental_full())
 227                 gold_info(_("linking with --incremental-full"));
 228               else
 229                 gold_fatal(_("restart link with --incremental-full"));
 230             }
 231         }
 232     }
 233
 234   // Read the input files.  We have to add the symbols to the symbol
 235   // table in order.  We do this by creating a separate blocker for
 236   // each input file.  We associate the blocker with the following
 237   // input file, to give us a convenient place to delete it.
 238   Task_token* this_blocker = NULL;
 239   if (ibase == NULL)
 240     {
 241       // Normal link.  Queue a Read_symbols task for each input file
 242       // on the command line.
 243       for (Command_line::const_iterator p = cmdline.begin();
 244            p != cmdline.end();
 245            ++p)
 246         {
 247           Task_token* next_blocker = new Task_token(true);
 248           next_blocker->add_blocker();
 249           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 250                                             &search_path, 0, mapfile, &*p, NULL,
 251                                             NULL, this_blocker, next_blocker));
 252           this_blocker = next_blocker;
 253         }
 254     }
 255   else
 256     {
 257       // Incremental update link.  Process the list of input files
 258       // stored in the base file, and queue a task for each file:
 259       // a Read_symbols task for a changed file, and an Add_symbols task
 260       // for an unchanged file.  We need to mark all the space used by
 261       // unchanged files before we can start any tasks running.
 262       unsigned int input_file_count = ibase->input_file_count();
 263       std::vector<Task*> tasks;
 264       tasks.reserve(input_file_count);
 265       for (unsigned int i = 0; i < input_file_count; ++i)
 266         {
 267           Task_token* next_blocker = new Task_token(true);
 268           next_blocker->add_blocker();
 269           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 270                                               layout, &search_path, mapfile,
 271                                               this_blocker, next_blocker);
 272           tasks.push_back(t);
 273           this_blocker = next_blocker;
 274         }
 275       // Now we can queue the tasks.
 276       for (unsigned int i = 0; i < tasks.size(); i++)
 277         workqueue->queue(tasks[i]);
 278     }
 279
 280   if (options.has_plugins())
 281     {
 282       Task_token* next_blocker = new Task_token(true);
 283       next_blocker->add_blocker();
 284       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 285                                        &search_path, mapfile, this_blocker,
 286                                        next_blocker));
 287       this_blocker = next_blocker;
 288     }
 289
 290   if (options.relocatable()
 291       && (options.gc_sections() || options.icf_enabled()))
 292     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 293
 294   if (options.gc_sections() || options.icf_enabled())
 295     {
 296       workqueue->queue(new Task_function(new Gc_runner(options,
 297                                                        input_objects,
 298                                                        symtab,
 299                                                        layout,
 300                                                        mapfile),
 301                                          this_blocker,
 302                                          "Task_function Gc_runner"));
 303     }
 304   else
 305     {
 306       workqueue->queue(new Task_function(new Middle_runner(options,
 307                                                            input_objects,
 308                                                            symtab,
 309                                                            layout,
 310                                                            mapfile),
 311                                          this_blocker,
 312                                          "Task_function Middle_runner"));
 313     }
 314 }
 315
 316 // Process an incremental input file: if it is unchanged from the previous
 317 // link, return a task to add its symbols from the base file's incremental
 318 // info; if it has changed, return a normal Read_symbols task.  We create a
 319 // task for every input file, if only to report the file for rebuilding the
 320 // incremental info.
 321
 322 static Task*
 323 process_incremental_input(Incremental_binary* ibase,
 324                           unsigned int input_file_index,
 325                           Input_objects* input_objects,
 326                           Symbol_table* symtab,
 327                           Layout* layout,
 328                           Dirsearch* search_path,
 329                           Mapfile* mapfile,
 330                           Task_token* this_blocker,
 331                           Task_token* next_blocker)
 332 {
 333   const Incremental_binary::Input_reader* input_reader =
 334       ibase->get_input_reader(input_file_index);
 335   Incremental_input_type input_type = input_reader->type();
 336
 337   // Get the input argument corresponding to this input file, matching on
 338   // the argument serial number.  If the input file cannot be matched
 339   // to an existing input argument, synthesize a new one.
 340   const Input_argument* input_argument =
 341       ibase->get_input_argument(input_file_index);
 342   if (input_argument == NULL)
 343     {
 344       Input_file_argument file(input_reader->filename(),
 345                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 346                                "", false, parameters->options());
 347       Input_argument* arg = new Input_argument(file);
 348       arg->set_script_info(ibase->get_script_info(input_file_index));
 349       input_argument = arg;
 350     }
 351
 352   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 353              input_reader->filename(), input_type);
 354
 355   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 356     {
 357       // Incremental_binary::check_inputs should have cancelled the
 358       // incremental update if the script has changed.
 359       gold_assert(!ibase->file_has_changed(input_file_index));
 360       return new Check_script(layout, ibase, input_file_index, input_reader,
 361                               this_blocker, next_blocker);
 362     }
 363
 364   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 365     {
 366       Incremental_library* lib = ibase->get_library(input_file_index);
 367       gold_assert(lib != NULL);
 368       if (lib->filename() == "/group/"
 369           || !ibase->file_has_changed(input_file_index))
 370         {
 371           // Queue a task to check that no references have been added to any
 372           // of the library's unused symbols.
 373           return new Check_library(symtab, layout, ibase, input_file_index,
 374                                    input_reader, this_blocker, next_blocker);
 375         }
 376       else
 377         {
 378           // Queue a Read_symbols task to process the archive normally.
 379           return new Read_symbols(input_objects, symtab, layout, search_path,
 380                                   0, mapfile, input_argument, NULL, NULL,
 381                                   this_blocker, next_blocker);
 382         }
 383     }
 384
 385   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 386     {
 387       // For archive members, check the timestamp of the containing archive.
 388       Incremental_library* lib = ibase->get_library(input_file_index);
 389       gold_assert(lib != NULL);
 390       // Process members of a --start-lib/--end-lib group as normal objects.
 391       if (lib->filename() != "/group/")
 392         {
 393           if (ibase->file_has_changed(lib->input_file_index()))
 394             {
 395               return new Read_member(input_objects, symtab, layout, mapfile,
 396                                      input_reader, this_blocker, next_blocker);
 397             }
 398           else
 399             {
 400               // The previous contributions from this file will be kept.
 401               // Mark the pieces of output sections contributed by this
 402               // object.
 403               ibase->reserve_layout(input_file_index);
 404               Object* obj = make_sized_incremental_object(ibase,
 405                                                           input_file_index,
 406                                                           input_type,
 407                                                           input_reader);
 408               return new Add_symbols(input_objects, symtab, layout,
 409                                      search_path, 0, mapfile, input_argument,
 410                                      obj, lib, NULL, this_blocker,
 411                                      next_blocker);
 412             }
 413         }
 414     }
 415
 416   // Normal object file or shared library.  Check if the file has changed
 417   // since the last incremental link.
 418   if (ibase->file_has_changed(input_file_index))
 419     {
 420       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 421                               mapfile, input_argument, NULL, NULL,
 422                               this_blocker, next_blocker);
 423     }
 424   else
 425     {
 426       // The previous contributions from this file will be kept.
 427       // Mark the pieces of output sections contributed by this object.
 428       ibase->reserve_layout(input_file_index);
 429       Object* obj = make_sized_incremental_object(ibase,
 430                                                   input_file_index,
 431                                                   input_type,
 432                                                   input_reader);
 433       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 434                              mapfile, input_argument, obj, NULL, NULL,
 435                              this_blocker, next_blocker);
 436     }
 437 }
 438
 439 // Queue up a set of tasks to be done before queueing the middle set
 440 // of tasks.  This is only necessary when garbage collection
 441 // (--gc-sections) of unused sections is desired.  The relocs are read
 442 // and processed here early to determine the garbage sections before the
 443 // relocs can be scanned in later tasks.
 444
 445 void
 446 queue_middle_gc_tasks(const General_options& options,
 447                       const Task* ,
 448                       const Input_objects* input_objects,
 449                       Symbol_table* symtab,
 450                       Layout* layout,
 451                       Workqueue* workqueue,
 452                       Mapfile* mapfile)
 453 {
 454   // Read_relocs for all the objects must be done and processed to find
 455   // unused sections before any scanning of the relocs can take place.
 456   Task_token* this_blocker = NULL;
 457   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 458        p != input_objects->relobj_end();
 459        ++p)
 460     {
 461       Task_token* next_blocker = new Task_token(true);
 462       next_blocker->add_blocker();
 463       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 464                                        next_blocker));
 465       this_blocker = next_blocker;
 466     }
 467
 468   // If we are given only archives in input, we have no regular
 469   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 470   // blocker here so that we can run the middle tasks immediately.
 471   if (this_blocker == NULL)
 472     {
 473       gold_assert(input_objects->number_of_relobjs() == 0);
 474       this_blocker = new Task_token(true);
 475     }
 476
 477   workqueue->queue(new Task_function(new Middle_runner(options,
 478                                                        input_objects,
 479                                                        symtab,
 480                                                        layout,
 481                                                        mapfile),
 482                                      this_blocker,
 483                                      "Task_function Middle_runner"));
 484 }
 485
 486 // Queue up the middle set of tasks.  These are the tasks which run
 487 // after all the input objects have been found and all the symbols
 488 // have been read, but before we lay out the output file.
 489
 490 void
 491 queue_middle_tasks(const General_options& options,
 492                    const Task* task,
 493                    const Input_objects* input_objects,
 494                    Symbol_table* symtab,
 495                    Layout* layout,
 496                    Workqueue* workqueue,
 497                    Mapfile* mapfile)
 498 {
 499   // Add any symbols named with -u options to the symbol table.
 500   symtab->add_undefined_symbols_from_command_line(layout);
 501
 502   // If garbage collection was chosen, relocs have been read and processed
 503   // at this point by pre_middle_tasks.  Layout can then be done for all
 504   // objects.
 505   if (parameters->options().gc_sections())
 506     {
 507       // Find the start symbol if any.
 508       Symbol* start_sym;
 509       if (parameters->options().entry())
 510         start_sym = symtab->lookup(parameters->options().entry());
 511       else
 512         start_sym = symtab->lookup("_start");
 513       if (start_sym != NULL)
 514         {
 515           bool is_ordinary;
 516           unsigned int shndx = start_sym->shndx(&is_ordinary);
 517           if (is_ordinary)
 518             {
 519               symtab->gc()->worklist().push(
 520                 Section_id(start_sym->object(), shndx));
 521             }
 522         }
 523       // Symbols named with -u should not be considered garbage.
 524       symtab->gc_mark_undef_symbols(layout);
 525       gold_assert(symtab->gc() != NULL);
 526       // Do a transitive closure on all references to determine the worklist.
 527       symtab->gc()->do_transitive_closure();
 528     }
 529
 530   // If identical code folding (--icf) is chosen it makes sense to do it
 531   // only after garbage collection (--gc-sections) as we do not want to
 532   // be folding sections that will be garbage.
 533   if (parameters->options().icf_enabled())
 534     {
 535       symtab->icf()->find_identical_sections(input_objects, symtab);
 536     }
 537
 538   // Call Object::layout for the second time to determine the
 539   // output_sections for all referenced input sections.  When
 540   // --gc-sections or --icf is turned on, Object::layout is
 541   // called twice.  It is called the first time when the
 542   // symbols are added.
 543   if (parameters->options().gc_sections()
 544       || parameters->options().icf_enabled())
 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   if (parameters->options().gc_sections()
 564       || parameters->options().icf_enabled())
 565     {
 566       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 567            p != input_objects->relobj_end();
 568            ++p)
 569         {
 570           // Update the value of output_section stored in rd.
 571           Read_relocs_data* rd = (*p)->get_relocs_data();
 572           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 573                q != rd->relocs.end();
 574                ++q)
 575             {
 576               q->output_section = (*p)->output_section(q->data_shndx);
 577               q->needs_special_offset_handling =
 578                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 579             }
 580         }
 581     }
 582
 583   // We have to support the case of not seeing any input objects, and
 584   // generate an empty file.  Existing builds depend on being able to
 585   // pass an empty archive to the linker and get an empty object file
 586   // out.  In order to do this we need to use a default target.
 587   if (input_objects->number_of_input_objects() == 0
 588       && layout->incremental_base() == NULL)
 589     parameters_force_valid_target();
 590
 591   int thread_count = options.thread_count_middle();
 592   if (thread_count == 0)
 593     thread_count = std::max(2, input_objects->number_of_input_objects());
 594   workqueue->set_thread_count(thread_count);
 595
 596   // Now we have seen all the input files.
 597   const bool doing_static_link =
 598     (!input_objects->any_dynamic()
 599      && !parameters->options().output_is_position_independent());
 600   set_parameters_doing_static_link(doing_static_link);
 601   if (!doing_static_link && options.is_static())
 602     {
 603       // We print out just the first .so we see; there may be others.
 604       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 605       gold_error(_("cannot mix -static with dynamic object %s"),
 606                  (*input_objects->dynobj_begin())->name().c_str());
 607     }
 608   if (!doing_static_link && parameters->options().relocatable())
 609     gold_fatal(_("cannot mix -r with dynamic object %s"),
 610                (*input_objects->dynobj_begin())->name().c_str());
 611   if (!doing_static_link
 612       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 613     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 614                (*input_objects->dynobj_begin())->name().c_str());
 615
 616   if (parameters->options().relocatable())
 617     {
 618       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 619       if (p != input_objects->relobj_end())
 620         {
 621           bool uses_split_stack = (*p)->uses_split_stack();
 622           for (++p; p != input_objects->relobj_end(); ++p)
 623             {
 624               if ((*p)->uses_split_stack() != uses_split_stack)
 625                 gold_fatal(_("cannot mix split-stack '%s' and "
 626                              "non-split-stack '%s' when using -r"),
 627                            (*input_objects->relobj_begin())->name().c_str(),
 628                            (*p)->name().c_str());
 629             }
 630         }
 631     }
 632
 633   if (is_debugging_enabled(DEBUG_SCRIPT))
 634     layout->script_options()->print(stderr);
 635
 636   // For each dynamic object, record whether we've seen all the
 637   // dynamic objects that it depends upon.
 638   input_objects->check_dynamic_dependencies();
 639
 640   // See if any of the input definitions violate the One Definition Rule.
 641   // TODO: if this is too slow, do this as a task, rather than inline.
 642   symtab->detect_odr_violations(task, options.output_file_name());
 643
 644   // Do the --no-undefined-version check.
 645   if (!parameters->options().undefined_version())
 646     {
 647       Script_options* so = layout->script_options();
 648       so->version_script_info()->check_unmatched_names(symtab);
 649     }
 650
 651   // Create any automatic note sections.
 652   layout->create_notes();
 653
 654   // Create any output sections required by any linker script.
 655   layout->create_script_sections();
 656
 657   // Define some sections and symbols needed for a dynamic link.  This
 658   // handles some cases we want to see before we read the relocs.
 659   layout->create_initial_dynamic_sections(symtab);
 660
 661   // Define symbols from any linker scripts.
 662   layout->define_script_symbols(symtab);
 663
 664   // Attach sections to segments.
 665   layout->attach_sections_to_segments();
 666
 667   if (!parameters->options().relocatable())
 668     {
 669       // Predefine standard symbols.
 670       define_standard_symbols(symtab, layout);
 671
 672       // Define __start and __stop symbols for output sections where
 673       // appropriate.
 674       layout->define_section_symbols(symtab);
 675     }
 676
 677   // Make sure we have symbols for any required group signatures.
 678   layout->define_group_signatures(symtab);
 679
 680   Task_token* this_blocker = NULL;
 681
 682   // Allocate common symbols.  We use a blocker to run this before the
 683   // Scan_relocs tasks, because it writes to the symbol table just as
 684   // they do.
 685   if (parameters->options().define_common())
 686     {
 687       this_blocker = new Task_token(true);
 688       this_blocker->add_blocker();
 689       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 690                                                  this_blocker));
 691     }
 692
 693   // If doing garbage collection, the relocations have already been read.
 694   // Otherwise, read and scan the relocations.
 695   if (parameters->options().gc_sections()
 696       || parameters->options().icf_enabled())
 697     {
 698       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 699            p != input_objects->relobj_end();
 700            ++p)
 701         {
 702           Task_token* next_blocker = new Task_token(true);
 703           next_blocker->add_blocker();
 704           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 705                                            (*p)->get_relocs_data(),
 706                                            this_blocker, next_blocker));
 707           this_blocker = next_blocker;
 708         }
 709     }
 710   else
 711     {
 712       // Read the relocations of the input files.  We do this to find
 713       // which symbols are used by relocations which require a GOT and/or
 714       // a PLT entry, or a COPY reloc.  When we implement garbage
 715       // collection we will do it here by reading the relocations in a
 716       // breadth first search by references.
 717       //
 718       // We could also read the relocations during the first pass, and
 719       // mark symbols at that time.  That is how the old GNU linker works.
 720       // Doing that is more complex, since we may later decide to discard
 721       // some of the sections, and thus change our minds about the types
 722       // of references made to the symbols.
 723       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 724            p != input_objects->relobj_end();
 725            ++p)
 726         {
 727           Task_token* next_blocker = new Task_token(true);
 728           next_blocker->add_blocker();
 729           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 730                                            next_blocker));
 731           this_blocker = next_blocker;
 732         }
 733     }
 734
 735   if (this_blocker == NULL)
 736     {
 737       if (input_objects->number_of_relobjs() == 0)
 738         {
 739           // If we are given only archives in input, we have no regular
 740           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 741           // blocker here so that we can run the layout task immediately.
 742           this_blocker = new Task_token(true);
 743         }
 744       else
 745         {
 746           // If we failed to open any input files, it's possible for
 747           // THIS_BLOCKER to be NULL here.  There's no real point in
 748           // continuing if that happens.
 749           gold_assert(parameters->errors()->error_count() > 0);
 750           gold_exit(false);
 751         }
 752     }
 753
 754   // When all those tasks are complete, we can start laying out the
 755   // output file.
 756   // TODO(csilvers): figure out a more principled way to get the target
 757   Target* target = const_cast<Target*>(&parameters->target());
 758   workqueue->queue(new Task_function(new Layout_task_runner(options,
 759                                                             input_objects,
 760                                                             symtab,
 761                                                             target,
 762                                                             layout,
 763                                                             mapfile),
 764                                      this_blocker,
 765                                      "Task_function Layout_task_runner"));
 766 }
 767
 768 // Queue up the final set of tasks.  This is called at the end of
 769 // Layout_task.
 770
 771 void
 772 queue_final_tasks(const General_options& options,
 773                   const Input_objects* input_objects,
 774                   const Symbol_table* symtab,
 775                   Layout* layout,
 776                   Workqueue* workqueue,
 777                   Output_file* of)
 778 {
 779   int thread_count = options.thread_count_final();
 780   if (thread_count == 0)
 781     thread_count = std::max(2, input_objects->number_of_input_objects());
 782   workqueue->set_thread_count(thread_count);
 783
 784   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 785
 786   // Use a blocker to wait until all the input sections have been
 787   // written out.
 788   Task_token* input_sections_blocker = NULL;
 789   if (!any_postprocessing_sections)
 790     {
 791       input_sections_blocker = new Task_token(true);
 792       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 793     }
 794
 795   // Use a blocker to block any objects which have to wait for the
 796   // output sections to complete before they can apply relocations.
 797   Task_token* output_sections_blocker = new Task_token(true);
 798   output_sections_blocker->add_blocker();
 799
 800   // Use a blocker to block the final cleanup task.
 801   Task_token* final_blocker = new Task_token(true);
 802   // Write_symbols_task, Write_sections_task, Write_data_task,
 803   // Relocate_tasks.
 804   final_blocker->add_blockers(3);
 805   final_blocker->add_blockers(input_objects->number_of_relobjs());
 806   if (!any_postprocessing_sections)
 807     final_blocker->add_blocker();
 808
 809   // Queue a task to write out the symbol table.
 810   workqueue->queue(new Write_symbols_task(layout,
 811                                           symtab,
 812                                           input_objects,
 813                                           layout->sympool(),
 814                                           layout->dynpool(),
 815                                           of,
 816                                           final_blocker));
 817
 818   // Queue a task to write out the output sections.
 819   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 820                                            final_blocker));
 821
 822   // Queue a task to write out everything else.
 823   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 824
 825   // Queue a task for each input object to relocate the sections and
 826   // write out the local symbols.
 827   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 828        p != input_objects->relobj_end();
 829        ++p)
 830     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 831                                        input_sections_blocker,
 832                                        output_sections_blocker,
 833                                        final_blocker));
 834
 835   // Queue a task to write out the output sections which depend on
 836   // input sections.  If there are any sections which require
 837   // postprocessing, then we need to do this last, since it may resize
 838   // the output file.
 839   if (!any_postprocessing_sections)
 840     {
 841       Task* t = new Write_after_input_sections_task(layout, of,
 842                                                     input_sections_blocker,
 843                                                     final_blocker);
 844       workqueue->queue(t);
 845     }
 846   else
 847     {
 848       Task_token* new_final_blocker = new Task_token(true);
 849       new_final_blocker->add_blocker();
 850       Task* t = new Write_after_input_sections_task(layout, of,
 851                                                     final_blocker,
 852                                                     new_final_blocker);
 853       workqueue->queue(t);
 854       final_blocker = new_final_blocker;
 855     }
 856
 857   // Queue a task to close the output file.  This will be blocked by
 858   // FINAL_BLOCKER.
 859   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 860                                                            of),
 861                                      final_blocker,
 862                                      "Task_function Close_task_runner"));
 863 }
 864
 865 } // End namespace gold.