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