1 // gold.cc -- main linker functions
3 // Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
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.
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.
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.
30 #include "libiberty.h"
34 #include "workqueue.h"
35 #include "dirsearch.h"
45 #include "incremental.h"
50 const char* program_name;
53 gold_exit(bool status)
55 if (parameters != NULL
56 && parameters->options_valid()
57 && parameters->options().has_plugins())
58 parameters->options().plugins()->cleanup();
59 if (!status && parameters != NULL && parameters->options_valid())
60 unlink_if_ordinary(parameters->options().output_file_name());
61 exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
67 // We are out of memory, so try hard to print a reasonable message.
68 // Note that we don't try to translate this message, since the
69 // translation process itself will require memory.
71 // LEN only exists to avoid a pointless warning when write is
72 // declared with warn_use_result, as when compiling with
73 // -D_USE_FORTIFY on GNU/Linux. Casting to void does not appear to
74 // work, at least not with gcc 4.3.0.
76 ssize_t len = write(2, program_name, strlen(program_name));
79 const char* const s = ": out of memory\n";
80 len = write(2, s, strlen(s));
85 // Handle an unreachable case.
88 do_gold_unreachable(const char* filename, int lineno, const char* function)
90 fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
91 program_name, function, filename, lineno);
95 // This class arranges to run the functions done in the middle of the
96 // link. It is just a closure.
98 class Middle_runner : public Task_function_runner
101 Middle_runner(const General_options& options,
102 const Input_objects* input_objects,
103 Symbol_table* symtab,
104 Layout* layout, Mapfile* mapfile)
105 : options_(options), input_objects_(input_objects), symtab_(symtab),
106 layout_(layout), mapfile_(mapfile)
110 run(Workqueue*, const Task*);
113 const General_options& options_;
114 const Input_objects* input_objects_;
115 Symbol_table* symtab_;
121 Middle_runner::run(Workqueue* workqueue, const Task* task)
123 queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
124 this->layout_, workqueue, this->mapfile_);
127 // This class arranges the tasks to process the relocs for garbage collection.
129 class Gc_runner : public Task_function_runner
132 Gc_runner(const General_options& options,
133 const Input_objects* input_objects,
134 Symbol_table* symtab,
135 Layout* layout, Mapfile* mapfile)
136 : options_(options), input_objects_(input_objects), symtab_(symtab),
137 layout_(layout), mapfile_(mapfile)
141 run(Workqueue*, const Task*);
144 const General_options& options_;
145 const Input_objects* input_objects_;
146 Symbol_table* symtab_;
152 Gc_runner::run(Workqueue* workqueue, const Task* task)
154 queue_middle_gc_tasks(this->options_, task, this->input_objects_,
155 this->symtab_, this->layout_, workqueue,
159 // Queue up the initial set of tasks for this link job.
162 queue_initial_tasks(const General_options& options,
163 Dirsearch& search_path,
164 const Command_line& cmdline,
165 Workqueue* workqueue, Input_objects* input_objects,
166 Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
168 if (cmdline.begin() == cmdline.end())
170 if (options.printed_version())
172 gold_fatal(_("no input files"));
175 int thread_count = options.thread_count_initial();
176 if (thread_count == 0)
177 thread_count = cmdline.number_of_input_files();
178 workqueue->set_thread_count(thread_count);
180 if (cmdline.options().incremental())
182 Incremental_checker incremental_checker(
183 parameters->options().output_file_name());
184 if (incremental_checker.can_incrementally_link_output_file())
186 // TODO: remove when incremental linking implemented.
187 printf("Incremental linking might be possible "
188 "(not implemented yet)\n");
190 // TODO: If we decide on an incremental build, fewer tasks
191 // should be scheduled.
194 // Read the input files. We have to add the symbols to the symbol
195 // table in order. We do this by creating a separate blocker for
196 // each input file. We associate the blocker with the following
197 // input file, to give us a convenient place to delete it.
198 Task_token* this_blocker = NULL;
199 for (Command_line::const_iterator p = cmdline.begin();
203 Task_token* next_blocker = new Task_token(true);
204 next_blocker->add_blocker();
205 workqueue->queue(new Read_symbols(input_objects, symtab, layout,
206 &search_path, 0, mapfile, &*p, NULL,
207 this_blocker, next_blocker));
208 this_blocker = next_blocker;
211 if (options.has_plugins())
213 Task_token* next_blocker = new Task_token(true);
214 next_blocker->add_blocker();
215 workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
216 &search_path, mapfile, this_blocker,
218 this_blocker = next_blocker;
221 if (parameters->options().relocatable()
222 && (parameters->options().gc_sections() || parameters->options().icf()))
223 gold_error(_("cannot mix -r with --gc-sections or --icf"));
225 if (parameters->options().gc_sections() || parameters->options().icf())
227 workqueue->queue(new Task_function(new Gc_runner(options,
233 "Task_function Gc_runner"));
237 workqueue->queue(new Task_function(new Middle_runner(options,
243 "Task_function Middle_runner"));
247 // Queue up a set of tasks to be done before queueing the middle set
248 // of tasks. This is only necessary when garbage collection
249 // (--gc-sections) of unused sections is desired. The relocs are read
250 // and processed here early to determine the garbage sections before the
251 // relocs can be scanned in later tasks.
254 queue_middle_gc_tasks(const General_options& options,
256 const Input_objects* input_objects,
257 Symbol_table* symtab,
259 Workqueue* workqueue,
262 // Read_relocs for all the objects must be done and processed to find
263 // unused sections before any scanning of the relocs can take place.
264 Task_token* blocker = new Task_token(true);
265 Task_token* symtab_lock = new Task_token(false);
266 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
267 p != input_objects->relobj_end();
270 // We can read and process the relocations in any order.
271 blocker->add_blocker();
272 workqueue->queue(new Read_relocs(options, symtab, layout, *p,
273 symtab_lock, blocker));
276 Task_token* this_blocker = new Task_token(true);
277 workqueue->queue(new Task_function(new Middle_runner(options,
283 "Task_function Middle_runner"));
286 // Queue up the middle set of tasks. These are the tasks which run
287 // after all the input objects have been found and all the symbols
288 // have been read, but before we lay out the output file.
291 queue_middle_tasks(const General_options& options,
293 const Input_objects* input_objects,
294 Symbol_table* symtab,
296 Workqueue* workqueue,
299 // Add any symbols named with -u options to the symbol table.
300 symtab->add_undefined_symbols_from_command_line();
302 // If garbage collection was chosen, relocs have been read and processed
303 // at this point by pre_middle_tasks. Layout can then be done for all
305 if (parameters->options().gc_sections())
307 // Find the start symbol if any.
309 if (parameters->options().entry())
310 start_sym = symtab->lookup(parameters->options().entry());
312 start_sym = symtab->lookup("_start");
313 if (start_sym !=NULL)
316 unsigned int shndx = start_sym->shndx(&is_ordinary);
319 symtab->gc()->worklist().push(
320 Section_id(start_sym->object(), shndx));
323 // Symbols named with -u should not be considered garbage.
324 symtab->gc_mark_undef_symbols();
325 gold_assert(symtab->gc() != NULL);
326 // Do a transitive closure on all references to determine the worklist.
327 symtab->gc()->do_transitive_closure();
330 // If identical code folding (--icf) is chosen it makes sense to do it
331 // only after garbage collection (--gc-sections) as we do not want to
332 // be folding sections that will be garbage.
333 if (parameters->options().icf())
335 symtab->icf()->find_identical_sections(input_objects, symtab);
338 // Call Object::layout for the second time to determine the
339 // output_sections for all referenced input sections. When
340 // --gc-sections or --icf is turned on, Object::layout is
341 // called twice. It is called the first time when the
342 // symbols are added.
343 if (parameters->options().gc_sections() || parameters->options().icf())
345 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
346 p != input_objects->relobj_end();
349 (*p)->layout(symtab, layout, NULL);
353 // Layout deferred objects due to plugins.
354 if (parameters->options().has_plugins())
356 Plugin_manager* plugins = parameters->options().plugins();
357 gold_assert(plugins != NULL);
358 plugins->layout_deferred_objects();
361 if (parameters->options().gc_sections() || parameters->options().icf())
363 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
364 p != input_objects->relobj_end();
367 // Update the value of output_section stored in rd.
368 Read_relocs_data *rd = (*p)->get_relocs_data();
369 for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
370 q != rd->relocs.end();
373 q->output_section = (*p)->output_section(q->data_shndx);
374 q->needs_special_offset_handling =
375 (*p)->is_output_section_offset_invalid(q->data_shndx);
380 // We have to support the case of not seeing any input objects, and
381 // generate an empty file. Existing builds depend on being able to
382 // pass an empty archive to the linker and get an empty object file
383 // out. In order to do this we need to use a default target.
384 if (input_objects->number_of_input_objects() == 0)
385 set_parameters_target(¶meters->default_target());
387 int thread_count = options.thread_count_middle();
388 if (thread_count == 0)
389 thread_count = std::max(2, input_objects->number_of_input_objects());
390 workqueue->set_thread_count(thread_count);
392 // Now we have seen all the input files.
393 const bool doing_static_link = (!input_objects->any_dynamic()
394 && !parameters->options().shared());
395 set_parameters_doing_static_link(doing_static_link);
396 if (!doing_static_link && options.is_static())
398 // We print out just the first .so we see; there may be others.
399 gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
400 gold_error(_("cannot mix -static with dynamic object %s"),
401 (*input_objects->dynobj_begin())->name().c_str());
403 if (!doing_static_link && parameters->options().relocatable())
404 gold_fatal(_("cannot mix -r with dynamic object %s"),
405 (*input_objects->dynobj_begin())->name().c_str());
406 if (!doing_static_link
407 && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
408 gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
409 (*input_objects->dynobj_begin())->name().c_str());
411 if (is_debugging_enabled(DEBUG_SCRIPT))
412 layout->script_options()->print(stderr);
414 // For each dynamic object, record whether we've seen all the
415 // dynamic objects that it depends upon.
416 input_objects->check_dynamic_dependencies();
418 // See if any of the input definitions violate the One Definition Rule.
419 // TODO: if this is too slow, do this as a task, rather than inline.
420 symtab->detect_odr_violations(task, options.output_file_name());
422 // Create any automatic note sections.
423 layout->create_notes();
425 // Create any output sections required by any linker script.
426 layout->create_script_sections();
428 // Define some sections and symbols needed for a dynamic link. This
429 // handles some cases we want to see before we read the relocs.
430 layout->create_initial_dynamic_sections(symtab);
432 // Define symbols from any linker scripts.
433 layout->define_script_symbols(symtab);
435 // Attach sections to segments.
436 layout->attach_sections_to_segments();
438 if (!parameters->options().relocatable())
440 // Predefine standard symbols.
441 define_standard_symbols(symtab, layout);
443 // Define __start and __stop symbols for output sections where
445 layout->define_section_symbols(symtab);
448 // Make sure we have symbols for any required group signatures.
449 layout->define_group_signatures(symtab);
451 Task_token* blocker = new Task_token(true);
452 Task_token* symtab_lock = new Task_token(false);
454 // If doing garbage collection, the relocations have already been read.
455 // Otherwise, read and scan the relocations.
456 if (parameters->options().gc_sections() || parameters->options().icf())
458 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
459 p != input_objects->relobj_end();
462 blocker->add_blocker();
463 workqueue->queue(new Scan_relocs(options, symtab, layout, *p,
464 (*p)->get_relocs_data(),symtab_lock, blocker));
469 // Read the relocations of the input files. We do this to find
470 // which symbols are used by relocations which require a GOT and/or
471 // a PLT entry, or a COPY reloc. When we implement garbage
472 // collection we will do it here by reading the relocations in a
473 // breadth first search by references.
475 // We could also read the relocations during the first pass, and
476 // mark symbols at that time. That is how the old GNU linker works.
477 // Doing that is more complex, since we may later decide to discard
478 // some of the sections, and thus change our minds about the types
479 // of references made to the symbols.
480 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
481 p != input_objects->relobj_end();
484 // We can read and process the relocations in any order. But we
485 // only want one task to write to the symbol table at a time.
486 // So we queue up a task for each object to read the
487 // relocations. That task will in turn queue a task to wait
488 // until it can write to the symbol table.
489 blocker->add_blocker();
490 workqueue->queue(new Read_relocs(options, symtab, layout, *p,
491 symtab_lock, blocker));
495 // Allocate common symbols. This requires write access to the
496 // symbol table, but is independent of the relocation processing.
497 if (parameters->options().define_common())
499 blocker->add_blocker();
500 workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
501 symtab_lock, blocker));
504 // When all those tasks are complete, we can start laying out the
506 // TODO(csilvers): figure out a more principled way to get the target
507 Target* target = const_cast<Target*>(¶meters->target());
508 workqueue->queue(new Task_function(new Layout_task_runner(options,
515 "Task_function Layout_task_runner"));
518 // Queue up the final set of tasks. This is called at the end of
522 queue_final_tasks(const General_options& options,
523 const Input_objects* input_objects,
524 const Symbol_table* symtab,
526 Workqueue* workqueue,
529 int thread_count = options.thread_count_final();
530 if (thread_count == 0)
531 thread_count = std::max(2, input_objects->number_of_input_objects());
532 workqueue->set_thread_count(thread_count);
534 bool any_postprocessing_sections = layout->any_postprocessing_sections();
536 // Use a blocker to wait until all the input sections have been
538 Task_token* input_sections_blocker = NULL;
539 if (!any_postprocessing_sections)
540 input_sections_blocker = new Task_token(true);
542 // Use a blocker to block any objects which have to wait for the
543 // output sections to complete before they can apply relocations.
544 Task_token* output_sections_blocker = new Task_token(true);
546 // Use a blocker to block the final cleanup task.
547 Task_token* final_blocker = new Task_token(true);
549 // Queue a task to write out the symbol table.
550 final_blocker->add_blocker();
551 workqueue->queue(new Write_symbols_task(layout,
559 // Queue a task to write out the output sections.
560 output_sections_blocker->add_blocker();
561 final_blocker->add_blocker();
562 workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
565 // Queue a task to write out everything else.
566 final_blocker->add_blocker();
567 workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
569 // Queue a task for each input object to relocate the sections and
570 // write out the local symbols.
571 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
572 p != input_objects->relobj_end();
575 if (input_sections_blocker != NULL)
576 input_sections_blocker->add_blocker();
577 final_blocker->add_blocker();
578 workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
579 input_sections_blocker,
580 output_sections_blocker,
584 // Queue a task to write out the output sections which depend on
585 // input sections. If there are any sections which require
586 // postprocessing, then we need to do this last, since it may resize
588 if (!any_postprocessing_sections)
590 final_blocker->add_blocker();
591 Task* t = new Write_after_input_sections_task(layout, of,
592 input_sections_blocker,
598 Task_token *new_final_blocker = new Task_token(true);
599 new_final_blocker->add_blocker();
600 Task* t = new Write_after_input_sections_task(layout, of,
604 final_blocker = new_final_blocker;
607 // Queue a task to close the output file. This will be blocked by
609 workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
612 "Task_function Close_task_runner"));
615 } // End namespace gold.