gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008, 2009 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
  45 namespace gold
  46 {
  47
  48 const char* program_name;
  49
  50 void
  51 gold_exit(bool status)
  52 {
  53   if (parameters != NULL
  54       && parameters->options_valid()
  55       && parameters->options().has_plugins())
  56     parameters->options().plugins()->cleanup();
  57   if (!status && parameters != NULL && parameters->options_valid())
  58     unlink_if_ordinary(parameters->options().output_file_name());
  59   exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
  60 }
  61
  62 void
  63 gold_nomem()
  64 {
  65   // We are out of memory, so try hard to print a reasonable message.
  66   // Note that we don't try to translate this message, since the
  67   // translation process itself will require memory.
  68
  69   // LEN only exists to avoid a pointless warning when write is
  70   // declared with warn_use_result, as when compiling with
  71   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  72   // work, at least not with gcc 4.3.0.
  73
  74   ssize_t len = write(2, program_name, strlen(program_name));
  75   if (len >= 0)
  76     {
  77       const char* const s = ": out of memory\n";
  78       len = write(2, s, strlen(s));
  79     }
  80   gold_exit(false);
  81 }
  82
  83 // Handle an unreachable case.
  84
  85 void
  86 do_gold_unreachable(const char* filename, int lineno, const char* function)
  87 {
  88   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
  89           program_name, function, filename, lineno);
  90   gold_exit(false);
  91 }
  92
  93 // This class arranges to run the functions done in the middle of the
  94 // link.  It is just a closure.
  95
  96 class Middle_runner : public Task_function_runner
  97 {
  98  public:
  99   Middle_runner(const General_options& options,
 100                 const Input_objects* input_objects,
 101                 Symbol_table* symtab,
 102                 Layout* layout, Mapfile* mapfile)
 103     : options_(options), input_objects_(input_objects), symtab_(symtab),
 104       layout_(layout), mapfile_(mapfile)
 105   { }
 106
 107   void
 108   run(Workqueue*, const Task*);
 109
 110  private:
 111   const General_options& options_;
 112   const Input_objects* input_objects_;
 113   Symbol_table* symtab_;
 114   Layout* layout_;
 115   Mapfile* mapfile_;
 116 };
 117
 118 void
 119 Middle_runner::run(Workqueue* workqueue, const Task* task)
 120 {
 121   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 122                      this->layout_, workqueue, this->mapfile_);
 123 }
 124
 125 // This class arranges the tasks to process the relocs for garbage collection.
 126
 127 class Gc_runner : public Task_function_runner
 128 {
 129   public:
 130    Gc_runner(const General_options& options,
 131              const Input_objects* input_objects,
 132              Symbol_table* symtab,
 133              Layout* layout, Mapfile* mapfile)
 134     : options_(options), input_objects_(input_objects), symtab_(symtab),
 135       layout_(layout), mapfile_(mapfile)
 136    { }
 137
 138   void
 139   run(Workqueue*, const Task*);
 140
 141  private:
 142   const General_options& options_;
 143   const Input_objects* input_objects_;
 144   Symbol_table* symtab_;
 145   Layout* layout_;
 146   Mapfile* mapfile_;
 147 };
 148
 149 void
 150 Gc_runner::run(Workqueue* workqueue, const Task* task)
 151 {
 152   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 153                         this->symtab_, this->layout_, workqueue,
 154                         this->mapfile_);
 155 }
 156
 157 // Queue up the initial set of tasks for this link job.
 158
 159 void
 160 queue_initial_tasks(const General_options& options,
 161                     Dirsearch& search_path,
 162                     const Command_line& cmdline,
 163                     Workqueue* workqueue, Input_objects* input_objects,
 164                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 165 {
 166   if (cmdline.begin() == cmdline.end())
 167     {
 168       if (options.printed_version())
 169         gold_exit(true);
 170       gold_fatal(_("no input files"));
 171     }
 172
 173   int thread_count = options.thread_count_initial();
 174   if (thread_count == 0)
 175     thread_count = cmdline.number_of_input_files();
 176   workqueue->set_thread_count(thread_count);
 177
 178   // Read the input files.  We have to add the symbols to the symbol
 179   // table in order.  We do this by creating a separate blocker for
 180   // each input file.  We associate the blocker with the following
 181   // input file, to give us a convenient place to delete it.
 182   Task_token* this_blocker = NULL;
 183   for (Command_line::const_iterator p = cmdline.begin();
 184        p != cmdline.end();
 185        ++p)
 186     {
 187       Task_token* next_blocker = new Task_token(true);
 188       next_blocker->add_blocker();
 189       workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 190                                         &search_path, 0, mapfile, &*p, NULL,
 191                                         this_blocker, next_blocker));
 192       this_blocker = next_blocker;
 193     }
 194
 195   if (options.has_plugins())
 196     {
 197       Task_token* next_blocker = new Task_token(true);
 198       next_blocker->add_blocker();
 199       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 200                                        &search_path, mapfile, this_blocker,
 201                                        next_blocker));
 202       this_blocker = next_blocker;
 203     }
 204
 205   if (parameters->options().relocatable()
 206       && parameters->options().gc_sections())
 207     gold_error(_("cannot mix -r with garbage collection"));
 208
 209   if (parameters->options().gc_sections())
 210     {
 211       workqueue->queue(new Task_function(new Gc_runner(options,
 212                                                        input_objects,
 213                                                        symtab,
 214                                                        layout,
 215                                                        mapfile),
 216                                          this_blocker,
 217                                          "Task_function Gc_runner"));
 218     }
 219   else
 220     {
 221       workqueue->queue(new Task_function(new Middle_runner(options,
 222                                                            input_objects,
 223                                                            symtab,
 224                                                            layout,
 225                                                            mapfile),
 226                                          this_blocker,
 227                                          "Task_function Middle_runner"));
 228     }
 229 }
 230
 231 // Queue up a set of tasks to be done before queueing the middle set
 232 // of tasks.  This is only necessary when garbage collection
 233 // (--gc-sections) of unused sections is desired.  The relocs are read
 234 // and processed here early to determine the garbage sections before the
 235 // relocs can be scanned in later tasks.
 236
 237 void
 238 queue_middle_gc_tasks(const General_options& options,
 239                       const Task* ,
 240                       const Input_objects* input_objects,
 241                       Symbol_table* symtab,
 242                       Layout* layout,
 243                       Workqueue* workqueue,
 244                       Mapfile* mapfile)
 245 {
 246   // Read_relocs for all the objects must be done and processed to find
 247   // unused sections before any scanning of the relocs can take place.
 248   Task_token* blocker = new Task_token(true);
 249   Task_token* symtab_lock = new Task_token(false);
 250   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 251        p != input_objects->relobj_end();
 252        ++p)
 253     {
 254       // We can read and process the relocations in any order.
 255       blocker->add_blocker();
 256       workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 257                                        symtab_lock, blocker));
 258     }
 259
 260   Task_token* this_blocker = new Task_token(true);
 261   workqueue->queue(new Task_function(new Middle_runner(options,
 262                                                        input_objects,
 263                                                        symtab,
 264                                                        layout,
 265                                                        mapfile),
 266                                      this_blocker,
 267                                      "Task_function Middle_runner"));
 268 }
 269
 270 // Queue up the middle set of tasks.  These are the tasks which run
 271 // after all the input objects have been found and all the symbols
 272 // have been read, but before we lay out the output file.
 273
 274 void
 275 queue_middle_tasks(const General_options& options,
 276                    const Task* task,
 277                    const Input_objects* input_objects,
 278                    Symbol_table* symtab,
 279                    Layout* layout,
 280                    Workqueue* workqueue,
 281                    Mapfile* mapfile)
 282 {
 283   // Add any symbols named with -u options to the symbol table.
 284   symtab->add_undefined_symbols_from_command_line();
 285
 286   // If garbage collection was chosen, relocs have been read and processed
 287   // at this point by pre_middle_tasks.  Layout can then be done for all
 288   // objects.
 289   if (parameters->options().gc_sections())
 290     {
 291       // Find the start symbol if any.
 292       Symbol* start_sym;
 293       if (parameters->options().entry())
 294         start_sym = symtab->lookup(parameters->options().entry());
 295       else
 296         start_sym = symtab->lookup("_start");
 297       if (start_sym !=NULL)
 298         {
 299           bool is_ordinary;
 300           unsigned int shndx = start_sym->shndx(&is_ordinary);
 301           if (is_ordinary)
 302             {
 303               symtab->gc()->worklist().push(
 304                 Section_id(start_sym->object(), shndx));
 305             }
 306         }
 307       // Symbols named with -u should not be considered garbage.
 308       symtab->gc_mark_undef_symbols();
 309       gold_assert(symtab->gc() != NULL);
 310       // Do a transitive closure on all references to determine the worklist.
 311       symtab->gc()->do_transitive_closure();
 312       // Call do_layout again to determine the output_sections for all
 313       // referenced input sections.
 314       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 315            p != input_objects->relobj_end();
 316            ++p)
 317         {
 318           (*p)->layout(symtab, layout, NULL);
 319         }
 320     }
 321   // Layout deferred objects due to plugins.
 322   if (parameters->options().has_plugins())
 323     {
 324       Plugin_manager* plugins = parameters->options().plugins();
 325       gold_assert(plugins != NULL);
 326       plugins->layout_deferred_objects();
 327     }
 328   if (parameters->options().gc_sections())
 329     {
 330       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 331            p != input_objects->relobj_end();
 332            ++p)
 333         {
 334           // Update the value of output_section stored in rd.
 335           Read_relocs_data *rd = (*p)->get_relocs_data();
 336           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 337                q != rd->relocs.end();
 338                ++q)
 339             {
 340               q->output_section = (*p)->output_section(q->data_shndx);
 341               q->needs_special_offset_handling =
 342                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 343             }
 344         }
 345     }
 346
 347   // We have to support the case of not seeing any input objects, and
 348   // generate an empty file.  Existing builds depend on being able to
 349   // pass an empty archive to the linker and get an empty object file
 350   // out.  In order to do this we need to use a default target.
 351   if (input_objects->number_of_input_objects() == 0)
 352     set_parameters_target(&parameters->default_target());
 353
 354   int thread_count = options.thread_count_middle();
 355   if (thread_count == 0)
 356     thread_count = std::max(2, input_objects->number_of_input_objects());
 357   workqueue->set_thread_count(thread_count);
 358
 359   // Now we have seen all the input files.
 360   const bool doing_static_link = (!input_objects->any_dynamic()
 361                                   && !parameters->options().shared());
 362   set_parameters_doing_static_link(doing_static_link);
 363   if (!doing_static_link && options.is_static())
 364     {
 365       // We print out just the first .so we see; there may be others.
 366       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 367       gold_error(_("cannot mix -static with dynamic object %s"),
 368                  (*input_objects->dynobj_begin())->name().c_str());
 369     }
 370   if (!doing_static_link && parameters->options().relocatable())
 371     gold_fatal(_("cannot mix -r with dynamic object %s"),
 372                (*input_objects->dynobj_begin())->name().c_str());
 373   if (!doing_static_link
 374       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 375     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 376                (*input_objects->dynobj_begin())->name().c_str());
 377
 378   if (is_debugging_enabled(DEBUG_SCRIPT))
 379     layout->script_options()->print(stderr);
 380
 381   // For each dynamic object, record whether we've seen all the
 382   // dynamic objects that it depends upon.
 383   input_objects->check_dynamic_dependencies();
 384
 385   // See if any of the input definitions violate the One Definition Rule.
 386   // TODO: if this is too slow, do this as a task, rather than inline.
 387   symtab->detect_odr_violations(task, options.output_file_name());
 388
 389   // Create any automatic note sections.
 390   layout->create_notes();
 391
 392   // Create any output sections required by any linker script.
 393   layout->create_script_sections();
 394
 395   // Define some sections and symbols needed for a dynamic link.  This
 396   // handles some cases we want to see before we read the relocs.
 397   layout->create_initial_dynamic_sections(symtab);
 398
 399   // Define symbols from any linker scripts.
 400   layout->define_script_symbols(symtab);
 401
 402   // Attach sections to segments.
 403   layout->attach_sections_to_segments();
 404
 405   if (!parameters->options().relocatable())
 406     {
 407       // Predefine standard symbols.
 408       define_standard_symbols(symtab, layout);
 409
 410       // Define __start and __stop symbols for output sections where
 411       // appropriate.
 412       layout->define_section_symbols(symtab);
 413     }
 414
 415   // Make sure we have symbols for any required group signatures.
 416   layout->define_group_signatures(symtab);
 417
 418   Task_token* blocker = new Task_token(true);
 419   Task_token* symtab_lock = new Task_token(false);
 420
 421   // If doing garbage collection, the relocations have already been read.
 422   // Otherwise, read and scan the relocations.
 423   if (parameters->options().gc_sections())
 424     {
 425       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 426            p != input_objects->relobj_end();
 427            ++p)
 428         {
 429           blocker->add_blocker();
 430           workqueue->queue(new Scan_relocs(options, symtab, layout, *p,
 431                            (*p)->get_relocs_data(),symtab_lock, blocker));
 432         }
 433     }
 434   else
 435     {
 436       // Read the relocations of the input files.  We do this to find
 437       // which symbols are used by relocations which require a GOT and/or
 438       // a PLT entry, or a COPY reloc.  When we implement garbage
 439       // collection we will do it here by reading the relocations in a
 440       // breadth first search by references.
 441       //
 442       // We could also read the relocations during the first pass, and
 443       // mark symbols at that time.  That is how the old GNU linker works.
 444       // Doing that is more complex, since we may later decide to discard
 445       // some of the sections, and thus change our minds about the types
 446       // of references made to the symbols.
 447       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 448            p != input_objects->relobj_end();
 449            ++p)
 450         {
 451           // We can read and process the relocations in any order.  But we
 452           // only want one task to write to the symbol table at a time.
 453           // So we queue up a task for each object to read the
 454           // relocations.  That task will in turn queue a task to wait
 455           // until it can write to the symbol table.
 456           blocker->add_blocker();
 457           workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 458                    symtab_lock, blocker));
 459         }
 460     }
 461
 462   // Allocate common symbols.  This requires write access to the
 463   // symbol table, but is independent of the relocation processing.
 464   if (parameters->options().define_common())
 465     {
 466       blocker->add_blocker();
 467       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 468                                                  symtab_lock, blocker));
 469     }
 470
 471   // When all those tasks are complete, we can start laying out the
 472   // output file.
 473   // TODO(csilvers): figure out a more principled way to get the target
 474   Target* target = const_cast<Target*>(&parameters->target());
 475   workqueue->queue(new Task_function(new Layout_task_runner(options,
 476                                                             input_objects,
 477                                                             symtab,
 478                                                             target,
 479                                                             layout,
 480                                                             mapfile),
 481                                      blocker,
 482                                      "Task_function Layout_task_runner"));
 483 }
 484
 485 // Queue up the final set of tasks.  This is called at the end of
 486 // Layout_task.
 487
 488 void
 489 queue_final_tasks(const General_options& options,
 490                   const Input_objects* input_objects,
 491                   const Symbol_table* symtab,
 492                   Layout* layout,
 493                   Workqueue* workqueue,
 494                   Output_file* of)
 495 {
 496   int thread_count = options.thread_count_final();
 497   if (thread_count == 0)
 498     thread_count = std::max(2, input_objects->number_of_input_objects());
 499   workqueue->set_thread_count(thread_count);
 500
 501   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 502
 503   // Use a blocker to wait until all the input sections have been
 504   // written out.
 505   Task_token* input_sections_blocker = NULL;
 506   if (!any_postprocessing_sections)
 507     input_sections_blocker = new Task_token(true);
 508
 509   // Use a blocker to block any objects which have to wait for the
 510   // output sections to complete before they can apply relocations.
 511   Task_token* output_sections_blocker = new Task_token(true);
 512
 513   // Use a blocker to block the final cleanup task.
 514   Task_token* final_blocker = new Task_token(true);
 515
 516   // Queue a task to write out the symbol table.
 517   final_blocker->add_blocker();
 518   workqueue->queue(new Write_symbols_task(layout,
 519                                           symtab,
 520                                           input_objects,
 521                                           layout->sympool(),
 522                                           layout->dynpool(),
 523                                           of,
 524                                           final_blocker));
 525
 526   // Queue a task to write out the output sections.
 527   output_sections_blocker->add_blocker();
 528   final_blocker->add_blocker();
 529   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 530                                            final_blocker));
 531
 532   // Queue a task to write out everything else.
 533   final_blocker->add_blocker();
 534   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 535
 536   // Queue a task for each input object to relocate the sections and
 537   // write out the local symbols.
 538   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 539        p != input_objects->relobj_end();
 540        ++p)
 541     {
 542       if (input_sections_blocker != NULL)
 543         input_sections_blocker->add_blocker();
 544       final_blocker->add_blocker();
 545       workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
 546                                          input_sections_blocker,
 547                                          output_sections_blocker,
 548                                          final_blocker));
 549     }
 550
 551   // Queue a task to write out the output sections which depend on
 552   // input sections.  If there are any sections which require
 553   // postprocessing, then we need to do this last, since it may resize
 554   // the output file.
 555   if (!any_postprocessing_sections)
 556     {
 557       final_blocker->add_blocker();
 558       Task* t = new Write_after_input_sections_task(layout, of,
 559                                                     input_sections_blocker,
 560                                                     final_blocker);
 561       workqueue->queue(t);
 562     }
 563   else
 564     {
 565       Task_token *new_final_blocker = new Task_token(true);
 566       new_final_blocker->add_blocker();
 567       Task* t = new Write_after_input_sections_task(layout, of,
 568                                                     final_blocker,
 569                                                     new_final_blocker);
 570       workqueue->queue(t);
 571       final_blocker = new_final_blocker;
 572     }
 573
 574   // Queue a task to close the output file.  This will be blocked by
 575   // FINAL_BLOCKER.
 576   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 577                                                            of),
 578                                      final_blocker,
 579                                      "Task_function Close_task_runner"));
 580 }
 581
 582 } // End namespace gold.