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 layout->incremental_inputs());
185 if (incremental_checker.can_incrementally_link_output_file())
187 // TODO: remove when incremental linking implemented.
188 printf("Incremental linking might be possible "
189 "(not implemented yet)\n");
191 // TODO: If we decide on an incremental build, fewer tasks
192 // should be scheduled.
195 // Read the input files. We have to add the symbols to the symbol
196 // table in order. We do this by creating a separate blocker for
197 // each input file. We associate the blocker with the following
198 // input file, to give us a convenient place to delete it.
199 Task_token* this_blocker = NULL;
200 for (Command_line::const_iterator p = cmdline.begin();
204 Task_token* next_blocker = new Task_token(true);
205 next_blocker->add_blocker();
206 workqueue->queue(new Read_symbols(input_objects, symtab, layout,
207 &search_path, 0, mapfile, &*p, NULL,
208 this_blocker, next_blocker));
209 this_blocker = next_blocker;
212 if (options.has_plugins())
214 Task_token* next_blocker = new Task_token(true);
215 next_blocker->add_blocker();
216 workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
217 &search_path, mapfile, this_blocker,
219 this_blocker = next_blocker;
222 if (parameters->options().relocatable()
223 && (parameters->options().gc_sections() || parameters->options().icf()))
224 gold_error(_("cannot mix -r with --gc-sections or --icf"));
226 if (parameters->options().gc_sections() || parameters->options().icf())
228 workqueue->queue(new Task_function(new Gc_runner(options,
234 "Task_function Gc_runner"));
238 workqueue->queue(new Task_function(new Middle_runner(options,
244 "Task_function Middle_runner"));
248 // Queue up a set of tasks to be done before queueing the middle set
249 // of tasks. This is only necessary when garbage collection
250 // (--gc-sections) of unused sections is desired. The relocs are read
251 // and processed here early to determine the garbage sections before the
252 // relocs can be scanned in later tasks.
255 queue_middle_gc_tasks(const General_options& options,
257 const Input_objects* input_objects,
258 Symbol_table* symtab,
260 Workqueue* workqueue,
263 // Read_relocs for all the objects must be done and processed to find
264 // unused sections before any scanning of the relocs can take place.
265 Task_token* blocker = new Task_token(true);
266 Task_token* symtab_lock = new Task_token(false);
267 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
268 p != input_objects->relobj_end();
271 // We can read and process the relocations in any order.
272 blocker->add_blocker();
273 workqueue->queue(new Read_relocs(options, symtab, layout, *p,
274 symtab_lock, blocker));
277 Task_token* this_blocker = new Task_token(true);
278 workqueue->queue(new Task_function(new Middle_runner(options,
284 "Task_function Middle_runner"));
287 // Queue up the middle set of tasks. These are the tasks which run
288 // after all the input objects have been found and all the symbols
289 // have been read, but before we lay out the output file.
292 queue_middle_tasks(const General_options& options,
294 const Input_objects* input_objects,
295 Symbol_table* symtab,
297 Workqueue* workqueue,
300 // Add any symbols named with -u options to the symbol table.
301 symtab->add_undefined_symbols_from_command_line();
303 // If garbage collection was chosen, relocs have been read and processed
304 // at this point by pre_middle_tasks. Layout can then be done for all
306 if (parameters->options().gc_sections())
308 // Find the start symbol if any.
310 if (parameters->options().entry())
311 start_sym = symtab->lookup(parameters->options().entry());
313 start_sym = symtab->lookup("_start");
314 if (start_sym !=NULL)
317 unsigned int shndx = start_sym->shndx(&is_ordinary);
320 symtab->gc()->worklist().push(
321 Section_id(start_sym->object(), shndx));
324 // Symbols named with -u should not be considered garbage.
325 symtab->gc_mark_undef_symbols();
326 gold_assert(symtab->gc() != NULL);
327 // Do a transitive closure on all references to determine the worklist.
328 symtab->gc()->do_transitive_closure();
331 // If identical code folding (--icf) is chosen it makes sense to do it
332 // only after garbage collection (--gc-sections) as we do not want to
333 // be folding sections that will be garbage.
334 if (parameters->options().icf())
336 symtab->icf()->find_identical_sections(input_objects, symtab);
339 // Call Object::layout for the second time to determine the
340 // output_sections for all referenced input sections. When
341 // --gc-sections or --icf is turned on, Object::layout is
342 // called twice. It is called the first time when the
343 // symbols are added.
344 if (parameters->options().gc_sections() || parameters->options().icf())
346 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
347 p != input_objects->relobj_end();
350 (*p)->layout(symtab, layout, NULL);
354 // Layout deferred objects due to plugins.
355 if (parameters->options().has_plugins())
357 Plugin_manager* plugins = parameters->options().plugins();
358 gold_assert(plugins != NULL);
359 plugins->layout_deferred_objects();
362 if (parameters->options().gc_sections() || parameters->options().icf())
364 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
365 p != input_objects->relobj_end();
368 // Update the value of output_section stored in rd.
369 Read_relocs_data *rd = (*p)->get_relocs_data();
370 for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
371 q != rd->relocs.end();
374 q->output_section = (*p)->output_section(q->data_shndx);
375 q->needs_special_offset_handling =
376 (*p)->is_output_section_offset_invalid(q->data_shndx);
381 // We have to support the case of not seeing any input objects, and
382 // generate an empty file. Existing builds depend on being able to
383 // pass an empty archive to the linker and get an empty object file
384 // out. In order to do this we need to use a default target.
385 if (input_objects->number_of_input_objects() == 0)
386 parameters_force_valid_target();
388 int thread_count = options.thread_count_middle();
389 if (thread_count == 0)
390 thread_count = std::max(2, input_objects->number_of_input_objects());
391 workqueue->set_thread_count(thread_count);
393 // Now we have seen all the input files.
394 const bool doing_static_link = (!input_objects->any_dynamic()
395 && !parameters->options().shared());
396 set_parameters_doing_static_link(doing_static_link);
397 if (!doing_static_link && options.is_static())
399 // We print out just the first .so we see; there may be others.
400 gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
401 gold_error(_("cannot mix -static with dynamic object %s"),
402 (*input_objects->dynobj_begin())->name().c_str());
404 if (!doing_static_link && parameters->options().relocatable())
405 gold_fatal(_("cannot mix -r with dynamic object %s"),
406 (*input_objects->dynobj_begin())->name().c_str());
407 if (!doing_static_link
408 && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
409 gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
410 (*input_objects->dynobj_begin())->name().c_str());
412 if (parameters->options().relocatable())
414 Input_objects::Relobj_iterator p = input_objects->relobj_begin();
415 if (p != input_objects->relobj_end())
417 bool uses_split_stack = (*p)->uses_split_stack();
418 for (++p; p != input_objects->relobj_end(); ++p)
420 if ((*p)->uses_split_stack() != uses_split_stack)
421 gold_fatal(_("cannot mix split-stack '%s' and "
422 "non-split-stack '%s' when using -r"),
423 (*input_objects->relobj_begin())->name().c_str(),
424 (*p)->name().c_str());
429 if (is_debugging_enabled(DEBUG_SCRIPT))
430 layout->script_options()->print(stderr);
432 // For each dynamic object, record whether we've seen all the
433 // dynamic objects that it depends upon.
434 input_objects->check_dynamic_dependencies();
436 // See if any of the input definitions violate the One Definition Rule.
437 // TODO: if this is too slow, do this as a task, rather than inline.
438 symtab->detect_odr_violations(task, options.output_file_name());
440 // Create any automatic note sections.
441 layout->create_notes();
443 // Create any output sections required by any linker script.
444 layout->create_script_sections();
446 // Define some sections and symbols needed for a dynamic link. This
447 // handles some cases we want to see before we read the relocs.
448 layout->create_initial_dynamic_sections(symtab);
450 // Define symbols from any linker scripts.
451 layout->define_script_symbols(symtab);
453 // Attach sections to segments.
454 layout->attach_sections_to_segments();
456 if (!parameters->options().relocatable())
458 // Predefine standard symbols.
459 define_standard_symbols(symtab, layout);
461 // Define __start and __stop symbols for output sections where
463 layout->define_section_symbols(symtab);
466 // Make sure we have symbols for any required group signatures.
467 layout->define_group_signatures(symtab);
469 Task_token* blocker = new Task_token(true);
470 Task_token* symtab_lock = new Task_token(false);
472 // If doing garbage collection, the relocations have already been read.
473 // Otherwise, read and scan the relocations.
474 if (parameters->options().gc_sections() || parameters->options().icf())
476 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
477 p != input_objects->relobj_end();
480 blocker->add_blocker();
481 workqueue->queue(new Scan_relocs(options, symtab, layout, *p,
482 (*p)->get_relocs_data(),symtab_lock, blocker));
487 // Read the relocations of the input files. We do this to find
488 // which symbols are used by relocations which require a GOT and/or
489 // a PLT entry, or a COPY reloc. When we implement garbage
490 // collection we will do it here by reading the relocations in a
491 // breadth first search by references.
493 // We could also read the relocations during the first pass, and
494 // mark symbols at that time. That is how the old GNU linker works.
495 // Doing that is more complex, since we may later decide to discard
496 // some of the sections, and thus change our minds about the types
497 // of references made to the symbols.
498 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
499 p != input_objects->relobj_end();
502 // We can read and process the relocations in any order. But we
503 // only want one task to write to the symbol table at a time.
504 // So we queue up a task for each object to read the
505 // relocations. That task will in turn queue a task to wait
506 // until it can write to the symbol table.
507 blocker->add_blocker();
508 workqueue->queue(new Read_relocs(options, symtab, layout, *p,
509 symtab_lock, blocker));
513 // Allocate common symbols. This requires write access to the
514 // symbol table, but is independent of the relocation processing.
515 if (parameters->options().define_common())
517 blocker->add_blocker();
518 workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
519 symtab_lock, blocker));
522 // When all those tasks are complete, we can start laying out the
524 // TODO(csilvers): figure out a more principled way to get the target
525 Target* target = const_cast<Target*>(¶meters->target());
526 workqueue->queue(new Task_function(new Layout_task_runner(options,
533 "Task_function Layout_task_runner"));
536 // Queue up the final set of tasks. This is called at the end of
540 queue_final_tasks(const General_options& options,
541 const Input_objects* input_objects,
542 const Symbol_table* symtab,
544 Workqueue* workqueue,
547 int thread_count = options.thread_count_final();
548 if (thread_count == 0)
549 thread_count = std::max(2, input_objects->number_of_input_objects());
550 workqueue->set_thread_count(thread_count);
552 bool any_postprocessing_sections = layout->any_postprocessing_sections();
554 // Use a blocker to wait until all the input sections have been
556 Task_token* input_sections_blocker = NULL;
557 if (!any_postprocessing_sections)
558 input_sections_blocker = new Task_token(true);
560 // Use a blocker to block any objects which have to wait for the
561 // output sections to complete before they can apply relocations.
562 Task_token* output_sections_blocker = new Task_token(true);
564 // Use a blocker to block the final cleanup task.
565 Task_token* final_blocker = new Task_token(true);
567 // Queue a task to write out the symbol table.
568 final_blocker->add_blocker();
569 workqueue->queue(new Write_symbols_task(layout,
577 // Queue a task to write out the output sections.
578 output_sections_blocker->add_blocker();
579 final_blocker->add_blocker();
580 workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
583 // Queue a task to write out everything else.
584 final_blocker->add_blocker();
585 workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
587 // Queue a task for each input object to relocate the sections and
588 // write out the local symbols.
589 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
590 p != input_objects->relobj_end();
593 if (input_sections_blocker != NULL)
594 input_sections_blocker->add_blocker();
595 final_blocker->add_blocker();
596 workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
597 input_sections_blocker,
598 output_sections_blocker,
602 // Queue a task to write out the output sections which depend on
603 // input sections. If there are any sections which require
604 // postprocessing, then we need to do this last, since it may resize
606 if (!any_postprocessing_sections)
608 final_blocker->add_blocker();
609 Task* t = new Write_after_input_sections_task(layout, of,
610 input_sections_blocker,
616 Task_token *new_final_blocker = new Task_token(true);
617 new_final_blocker->add_blocker();
618 Task* t = new Write_after_input_sections_task(layout, of,
622 final_blocker = new_final_blocker;
625 // Queue a task to close the output file. This will be blocked by
627 workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
630 "Task_function Close_task_runner"));
633 } // End namespace gold.