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