1 // gold.cc -- main linker functions
3 // Copyright 2006, 2007, 2008, 2009, 2010 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"
46 #include "incremental.h"
53 const char* program_name;
56 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
57 Symbol_table*, Layout*, Dirsearch*, Mapfile*,
58 Task_token*, Task_token*);
61 gold_exit(bool status)
63 if (parameters != NULL
64 && parameters->options_valid()
65 && parameters->options().has_plugins())
66 parameters->options().plugins()->cleanup();
67 if (!status && parameters != NULL && parameters->options_valid())
68 unlink_if_ordinary(parameters->options().output_file_name());
69 exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
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.
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.
84 ssize_t len = write(2, program_name, strlen(program_name));
87 const char* const s = ": out of memory\n";
88 len = write(2, s, strlen(s));
93 // Handle an unreachable case.
96 do_gold_unreachable(const char* filename, int lineno, const char* function)
98 fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
99 program_name, function, filename, lineno);
103 // This class arranges to run the functions done in the middle of the
104 // link. It is just a closure.
106 class Middle_runner : public Task_function_runner
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)
118 run(Workqueue*, const Task*);
121 const General_options& options_;
122 const Input_objects* input_objects_;
123 Symbol_table* symtab_;
129 Middle_runner::run(Workqueue* workqueue, const Task* task)
131 queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
132 this->layout_, workqueue, this->mapfile_);
135 // This class arranges the tasks to process the relocs for garbage collection.
137 class Gc_runner : public Task_function_runner
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)
149 run(Workqueue*, const Task*);
152 const General_options& options_;
153 const Input_objects* input_objects_;
154 Symbol_table* symtab_;
160 Gc_runner::run(Workqueue* workqueue, const Task* task)
162 queue_middle_gc_tasks(this->options_, task, this->input_objects_,
163 this->symtab_, this->layout_, workqueue,
167 // Queue up the initial set of tasks for this link job.
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)
176 if (cmdline.begin() == cmdline.end())
178 if (options.printed_version())
180 gold_fatal(_("no input files"));
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);
188 // For incremental links, the base output file.
189 Incremental_binary* ibase = NULL;
191 if (parameters->incremental())
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"));
204 if (parameters->incremental_update())
206 Output_file* of = new Output_file(options.output_file_name());
207 if (of->open_base_file(options.incremental_base(), true))
209 ibase = open_incremental_binary(of);
211 && ibase->check_inputs(cmdline, layout->incremental_inputs()))
212 ibase->init_layout(layout);
222 if (set_parameters_incremental_full())
223 gold_info(_("linking with --incremental-full"));
225 gold_fatal(_("restart link with --incremental-full"));
230 // Read the input files. We have to add the symbols to the symbol
231 // table in order. We do this by creating a separate blocker for
232 // each input file. We associate the blocker with the following
233 // input file, to give us a convenient place to delete it.
234 Task_token* this_blocker = NULL;
237 // Normal link. Queue a Read_symbols task for each input file
238 // on the command line.
239 for (Command_line::const_iterator p = cmdline.begin();
243 Task_token* next_blocker = new Task_token(true);
244 next_blocker->add_blocker();
245 workqueue->queue(new Read_symbols(input_objects, symtab, layout,
246 &search_path, 0, mapfile, &*p, NULL,
247 NULL, this_blocker, next_blocker));
248 this_blocker = next_blocker;
253 // Incremental update link. Process the list of input files
254 // stored in the base file, and queue a task for each file:
255 // a Read_symbols task for a changed file, and an Add_symbols task
256 // for an unchanged file. We need to mark all the space used by
257 // unchanged files before we can start any tasks running.
258 unsigned int input_file_count = ibase->input_file_count();
259 std::vector<Task*> tasks;
260 tasks.reserve(input_file_count);
261 for (unsigned int i = 0; i < input_file_count; ++i)
263 Task_token* next_blocker = new Task_token(true);
264 next_blocker->add_blocker();
265 Task* t = process_incremental_input(ibase, i, input_objects, symtab,
266 layout, &search_path, mapfile,
267 this_blocker, next_blocker);
269 this_blocker = next_blocker;
271 // Now we can queue the tasks.
272 for (unsigned int i = 0; i < tasks.size(); i++)
273 workqueue->queue(tasks[i]);
276 if (options.has_plugins())
278 Task_token* next_blocker = new Task_token(true);
279 next_blocker->add_blocker();
280 workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
281 &search_path, mapfile, this_blocker,
283 this_blocker = next_blocker;
286 if (options.relocatable()
287 && (options.gc_sections() || options.icf_enabled()))
288 gold_error(_("cannot mix -r with --gc-sections or --icf"));
290 if (options.gc_sections() || options.icf_enabled())
292 workqueue->queue(new Task_function(new Gc_runner(options,
298 "Task_function Gc_runner"));
302 workqueue->queue(new Task_function(new Middle_runner(options,
308 "Task_function Middle_runner"));
312 // Process an incremental input file: if it is unchanged from the previous
313 // link, return a task to add its symbols from the base file's incremental
314 // info; if it has changed, return a normal Read_symbols task. We create a
315 // task for every input file, if only to report the file for rebuilding the
319 process_incremental_input(Incremental_binary* ibase,
320 unsigned int input_file_index,
321 Input_objects* input_objects,
322 Symbol_table* symtab,
324 Dirsearch* search_path,
326 Task_token* this_blocker,
327 Task_token* next_blocker)
329 const Incremental_binary::Input_reader* input_reader =
330 ibase->get_input_reader(input_file_index);
331 Incremental_input_type input_type = input_reader->type();
333 // Get the input argument corresponding to this input file, matching on
334 // the argument serial number. If the input file cannot be matched
335 // to an existing input argument, synthesize a new one.
336 const Input_argument* input_argument =
337 ibase->get_input_argument(input_file_index);
338 if (input_argument == NULL)
340 Input_file_argument file(input_reader->filename(),
341 Input_file_argument::INPUT_FILE_TYPE_FILE,
342 "", false, parameters->options());
343 Input_argument* arg = new Input_argument(file);
344 arg->set_script_info(ibase->get_script_info(input_file_index));
345 input_argument = arg;
348 gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
349 input_reader->filename(), input_type);
351 if (input_type == INCREMENTAL_INPUT_SCRIPT)
353 // Incremental_binary::check_inputs should have cancelled the
354 // incremental update if the script has changed.
355 gold_assert(!ibase->file_has_changed(input_file_index));
356 return new Check_script(layout, ibase, input_file_index, input_reader,
357 this_blocker, next_blocker);
360 if (input_type == INCREMENTAL_INPUT_ARCHIVE)
362 Incremental_library* lib = ibase->get_library(input_file_index);
363 gold_assert(lib != NULL);
364 if (lib->filename() == "/group/"
365 || !ibase->file_has_changed(input_file_index))
367 // Queue a task to check that no references have been added to any
368 // of the library's unused symbols.
369 return new Check_library(symtab, layout, ibase, input_file_index,
370 input_reader, this_blocker, next_blocker);
374 // Queue a Read_symbols task to process the archive normally.
375 return new Read_symbols(input_objects, symtab, layout, search_path,
376 0, mapfile, input_argument, NULL, NULL,
377 this_blocker, next_blocker);
381 if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
383 // For archive members, check the timestamp of the containing archive.
384 Incremental_library* lib = ibase->get_library(input_file_index);
385 gold_assert(lib != NULL);
386 // Process members of a --start-lib/--end-lib group as normal objects.
387 if (lib->filename() != "/group/")
389 if (ibase->file_has_changed(lib->input_file_index()))
391 return new Read_member(input_objects, symtab, layout, mapfile,
392 input_reader, this_blocker, next_blocker);
396 // The previous contributions from this file will be kept.
397 // Mark the pieces of output sections contributed by this
399 ibase->reserve_layout(input_file_index);
400 Object* obj = make_sized_incremental_object(ibase,
404 return new Add_symbols(input_objects, symtab, layout,
405 search_path, 0, mapfile, input_argument,
406 obj, lib, NULL, this_blocker,
412 // Normal object file or shared library. Check if the file has changed
413 // since the last incremental link.
414 if (ibase->file_has_changed(input_file_index))
416 return new Read_symbols(input_objects, symtab, layout, search_path, 0,
417 mapfile, input_argument, NULL, NULL,
418 this_blocker, next_blocker);
422 // The previous contributions from this file will be kept.
423 // Mark the pieces of output sections contributed by this object.
424 ibase->reserve_layout(input_file_index);
425 Object* obj = make_sized_incremental_object(ibase,
429 return new Add_symbols(input_objects, symtab, layout, search_path, 0,
430 mapfile, input_argument, obj, NULL, NULL,
431 this_blocker, next_blocker);
435 // Queue up a set of tasks to be done before queueing the middle set
436 // of tasks. This is only necessary when garbage collection
437 // (--gc-sections) of unused sections is desired. The relocs are read
438 // and processed here early to determine the garbage sections before the
439 // relocs can be scanned in later tasks.
442 queue_middle_gc_tasks(const General_options& options,
444 const Input_objects* input_objects,
445 Symbol_table* symtab,
447 Workqueue* workqueue,
450 // Read_relocs for all the objects must be done and processed to find
451 // unused sections before any scanning of the relocs can take place.
452 Task_token* this_blocker = NULL;
453 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
454 p != input_objects->relobj_end();
457 Task_token* next_blocker = new Task_token(true);
458 next_blocker->add_blocker();
459 workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
461 this_blocker = next_blocker;
464 // If we are given only archives in input, we have no regular
465 // objects and THIS_BLOCKER is NULL here. Create a dummy
466 // blocker here so that we can run the middle tasks immediately.
467 if (this_blocker == NULL)
469 gold_assert(input_objects->number_of_relobjs() == 0);
470 this_blocker = new Task_token(true);
473 workqueue->queue(new Task_function(new Middle_runner(options,
479 "Task_function Middle_runner"));
482 // Queue up the middle set of tasks. These are the tasks which run
483 // after all the input objects have been found and all the symbols
484 // have been read, but before we lay out the output file.
487 queue_middle_tasks(const General_options& options,
489 const Input_objects* input_objects,
490 Symbol_table* symtab,
492 Workqueue* workqueue,
495 // Add any symbols named with -u options to the symbol table.
496 symtab->add_undefined_symbols_from_command_line(layout);
498 // If garbage collection was chosen, relocs have been read and processed
499 // at this point by pre_middle_tasks. Layout can then be done for all
501 if (parameters->options().gc_sections())
503 // Find the start symbol if any.
504 Symbol* start_sym = symtab->lookup(parameters->entry());
505 if (start_sym != NULL)
508 unsigned int shndx = start_sym->shndx(&is_ordinary);
511 symtab->gc()->worklist().push(
512 Section_id(start_sym->object(), shndx));
515 // Symbols named with -u should not be considered garbage.
516 symtab->gc_mark_undef_symbols(layout);
517 gold_assert(symtab->gc() != NULL);
518 // Do a transitive closure on all references to determine the worklist.
519 symtab->gc()->do_transitive_closure();
522 // If identical code folding (--icf) is chosen it makes sense to do it
523 // only after garbage collection (--gc-sections) as we do not want to
524 // be folding sections that will be garbage.
525 if (parameters->options().icf_enabled())
527 symtab->icf()->find_identical_sections(input_objects, symtab);
530 // Call Object::layout for the second time to determine the
531 // output_sections for all referenced input sections. When
532 // --gc-sections or --icf is turned on, Object::layout is
533 // called twice. It is called the first time when the
534 // symbols are added.
535 if (parameters->options().gc_sections()
536 || parameters->options().icf_enabled())
538 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
539 p != input_objects->relobj_end();
542 Task_lock_obj<Object> tlo(task, *p);
543 (*p)->layout(symtab, layout, NULL);
547 // Layout deferred objects due to plugins.
548 if (parameters->options().has_plugins())
550 Plugin_manager* plugins = parameters->options().plugins();
551 gold_assert(plugins != NULL);
552 plugins->layout_deferred_objects();
555 if (parameters->options().gc_sections()
556 || parameters->options().icf_enabled())
558 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
559 p != input_objects->relobj_end();
562 // Update the value of output_section stored in rd.
563 Read_relocs_data* rd = (*p)->get_relocs_data();
564 for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
565 q != rd->relocs.end();
568 q->output_section = (*p)->output_section(q->data_shndx);
569 q->needs_special_offset_handling =
570 (*p)->is_output_section_offset_invalid(q->data_shndx);
575 // We have to support the case of not seeing any input objects, and
576 // generate an empty file. Existing builds depend on being able to
577 // pass an empty archive to the linker and get an empty object file
578 // out. In order to do this we need to use a default target.
579 if (input_objects->number_of_input_objects() == 0
580 && layout->incremental_base() == NULL)
581 parameters_force_valid_target();
583 int thread_count = options.thread_count_middle();
584 if (thread_count == 0)
585 thread_count = std::max(2, input_objects->number_of_input_objects());
586 workqueue->set_thread_count(thread_count);
588 // Now we have seen all the input files.
589 const bool doing_static_link =
590 (!input_objects->any_dynamic()
591 && !parameters->options().output_is_position_independent());
592 set_parameters_doing_static_link(doing_static_link);
593 if (!doing_static_link && options.is_static())
595 // We print out just the first .so we see; there may be others.
596 gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
597 gold_error(_("cannot mix -static with dynamic object %s"),
598 (*input_objects->dynobj_begin())->name().c_str());
600 if (!doing_static_link && parameters->options().relocatable())
601 gold_fatal(_("cannot mix -r with dynamic object %s"),
602 (*input_objects->dynobj_begin())->name().c_str());
603 if (!doing_static_link
604 && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
605 gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
606 (*input_objects->dynobj_begin())->name().c_str());
608 if (parameters->options().relocatable())
610 Input_objects::Relobj_iterator p = input_objects->relobj_begin();
611 if (p != input_objects->relobj_end())
613 bool uses_split_stack = (*p)->uses_split_stack();
614 for (++p; p != input_objects->relobj_end(); ++p)
616 if ((*p)->uses_split_stack() != uses_split_stack)
617 gold_fatal(_("cannot mix split-stack '%s' and "
618 "non-split-stack '%s' when using -r"),
619 (*input_objects->relobj_begin())->name().c_str(),
620 (*p)->name().c_str());
625 // For incremental updates, record the existing GOT and PLT entries,
626 // and the COPY relocations.
627 if (parameters->incremental_update())
629 Incremental_binary* ibase = layout->incremental_base();
630 ibase->process_got_plt(symtab, layout);
631 ibase->emit_copy_relocs(symtab);
634 if (is_debugging_enabled(DEBUG_SCRIPT))
635 layout->script_options()->print(stderr);
637 // For each dynamic object, record whether we've seen all the
638 // dynamic objects that it depends upon.
639 input_objects->check_dynamic_dependencies();
641 // See if any of the input definitions violate the One Definition Rule.
642 // TODO: if this is too slow, do this as a task, rather than inline.
643 symtab->detect_odr_violations(task, options.output_file_name());
645 // Do the --no-undefined-version check.
646 if (!parameters->options().undefined_version())
648 Script_options* so = layout->script_options();
649 so->version_script_info()->check_unmatched_names(symtab);
652 // Create any automatic note sections.
653 layout->create_notes();
655 // Create any output sections required by any linker script.
656 layout->create_script_sections();
658 // Define some sections and symbols needed for a dynamic link. This
659 // handles some cases we want to see before we read the relocs.
660 layout->create_initial_dynamic_sections(symtab);
662 // Define symbols from any linker scripts.
663 layout->define_script_symbols(symtab);
665 // Attach sections to segments.
666 layout->attach_sections_to_segments();
668 if (!parameters->options().relocatable())
670 // Predefine standard symbols.
671 define_standard_symbols(symtab, layout);
673 // Define __start and __stop symbols for output sections where
675 layout->define_section_symbols(symtab);
678 // Make sure we have symbols for any required group signatures.
679 layout->define_group_signatures(symtab);
681 Task_token* this_blocker = NULL;
683 // Allocate common symbols. We use a blocker to run this before the
684 // Scan_relocs tasks, because it writes to the symbol table just as
686 if (parameters->options().define_common())
688 this_blocker = new Task_token(true);
689 this_blocker->add_blocker();
690 workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
694 // If doing garbage collection, the relocations have already been read.
695 // Otherwise, read and scan the relocations.
696 if (parameters->options().gc_sections()
697 || parameters->options().icf_enabled())
699 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
700 p != input_objects->relobj_end();
703 Task_token* next_blocker = new Task_token(true);
704 next_blocker->add_blocker();
705 workqueue->queue(new Scan_relocs(symtab, layout, *p,
706 (*p)->get_relocs_data(),
707 this_blocker, next_blocker));
708 this_blocker = next_blocker;
713 // Read the relocations of the input files. We do this to find
714 // which symbols are used by relocations which require a GOT and/or
715 // a PLT entry, or a COPY reloc. When we implement garbage
716 // collection we will do it here by reading the relocations in a
717 // breadth first search by references.
719 // We could also read the relocations during the first pass, and
720 // mark symbols at that time. That is how the old GNU linker works.
721 // Doing that is more complex, since we may later decide to discard
722 // some of the sections, and thus change our minds about the types
723 // of references made to the symbols.
724 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
725 p != input_objects->relobj_end();
728 Task_token* next_blocker = new Task_token(true);
729 next_blocker->add_blocker();
730 workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
732 this_blocker = next_blocker;
736 if (this_blocker == NULL)
738 if (input_objects->number_of_relobjs() == 0)
740 // If we are given only archives in input, we have no regular
741 // objects and THIS_BLOCKER is NULL here. Create a dummy
742 // blocker here so that we can run the layout task immediately.
743 this_blocker = new Task_token(true);
747 // If we failed to open any input files, it's possible for
748 // THIS_BLOCKER to be NULL here. There's no real point in
749 // continuing if that happens.
750 gold_assert(parameters->errors()->error_count() > 0);
755 // When all those tasks are complete, we can start laying out the
757 // TODO(csilvers): figure out a more principled way to get the target
758 Target* target = const_cast<Target*>(¶meters->target());
759 workqueue->queue(new Task_function(new Layout_task_runner(options,
766 "Task_function Layout_task_runner"));
769 // Queue up the final set of tasks. This is called at the end of
773 queue_final_tasks(const General_options& options,
774 const Input_objects* input_objects,
775 const Symbol_table* symtab,
777 Workqueue* workqueue,
780 int thread_count = options.thread_count_final();
781 if (thread_count == 0)
782 thread_count = std::max(2, input_objects->number_of_input_objects());
783 workqueue->set_thread_count(thread_count);
785 bool any_postprocessing_sections = layout->any_postprocessing_sections();
787 // Use a blocker to wait until all the input sections have been
789 Task_token* input_sections_blocker = NULL;
790 if (!any_postprocessing_sections)
792 input_sections_blocker = new Task_token(true);
793 input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
796 // Use a blocker to block any objects which have to wait for the
797 // output sections to complete before they can apply relocations.
798 Task_token* output_sections_blocker = new Task_token(true);
799 output_sections_blocker->add_blocker();
801 // Use a blocker to block the final cleanup task.
802 Task_token* final_blocker = new Task_token(true);
803 // Write_symbols_task, Write_sections_task, Write_data_task,
805 final_blocker->add_blockers(3);
806 final_blocker->add_blockers(input_objects->number_of_relobjs());
807 if (!any_postprocessing_sections)
808 final_blocker->add_blocker();
810 // Queue a task to write out the symbol table.
811 workqueue->queue(new Write_symbols_task(layout,
819 // Queue a task to write out the output sections.
820 workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
823 // Queue a task to write out everything else.
824 workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
826 // Queue a task for each input object to relocate the sections and
827 // write out the local symbols.
828 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
829 p != input_objects->relobj_end();
831 workqueue->queue(new Relocate_task(symtab, layout, *p, of,
832 input_sections_blocker,
833 output_sections_blocker,
836 // Queue a task to write out the output sections which depend on
837 // input sections. If there are any sections which require
838 // postprocessing, then we need to do this last, since it may resize
840 if (!any_postprocessing_sections)
842 Task* t = new Write_after_input_sections_task(layout, of,
843 input_sections_blocker,
849 Task_token* new_final_blocker = new Task_token(true);
850 new_final_blocker->add_blocker();
851 Task* t = new Write_after_input_sections_task(layout, of,
855 final_blocker = new_final_blocker;
858 // Queue a task to close the output file. This will be blocked by
860 workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
863 "Task_function Close_task_runner"));
866 } // End namespace gold.