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"
48 const char* program_name;
51 gold_exit(bool status)
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);
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.
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.
74 ssize_t len = write(2, program_name, strlen(program_name));
77 const char* const s = ": out of memory\n";
78 len = write(2, s, strlen(s));
83 // Handle an unreachable case.
86 do_gold_unreachable(const char* filename, int lineno, const char* function)
88 fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
89 program_name, function, filename, lineno);
93 // This class arranges to run the functions done in the middle of the
94 // link. It is just a closure.
96 class Middle_runner : public Task_function_runner
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)
108 run(Workqueue*, const Task*);
111 const General_options& options_;
112 const Input_objects* input_objects_;
113 Symbol_table* symtab_;
119 Middle_runner::run(Workqueue* workqueue, const Task* task)
121 queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
122 this->layout_, workqueue, this->mapfile_);
125 // This class arranges the tasks to process the relocs for garbage collection.
127 class Gc_runner : public Task_function_runner
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)
139 run(Workqueue*, const Task*);
142 const General_options& options_;
143 const Input_objects* input_objects_;
144 Symbol_table* symtab_;
150 Gc_runner::run(Workqueue* workqueue, const Task* task)
152 queue_middle_gc_tasks(this->options_, task, this->input_objects_,
153 this->symtab_, this->layout_, workqueue,
157 // Queue up the initial set of tasks for this link job.
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)
166 if (cmdline.begin() == cmdline.end())
168 if (options.printed_version())
170 gold_fatal(_("no input files"));
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);
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();
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;
195 if (options.has_plugins())
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,
202 this_blocker = next_blocker;
205 if (parameters->options().relocatable()
206 && parameters->options().gc_sections())
207 gold_error(_("cannot mix -r with garbage collection"));
209 if (parameters->options().gc_sections())
211 workqueue->queue(new Task_function(new Gc_runner(options,
217 "Task_function Gc_runner"));
221 workqueue->queue(new Task_function(new Middle_runner(options,
227 "Task_function Middle_runner"));
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.
238 queue_middle_gc_tasks(const General_options& options,
240 const Input_objects* input_objects,
241 Symbol_table* symtab,
243 Workqueue* workqueue,
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();
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));
260 Task_token* this_blocker = new Task_token(true);
261 workqueue->queue(new Task_function(new Middle_runner(options,
267 "Task_function Middle_runner"));
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.
275 queue_middle_tasks(const General_options& options,
277 const Input_objects* input_objects,
278 Symbol_table* symtab,
280 Workqueue* workqueue,
283 // Add any symbols named with -u options to the symbol table.
284 symtab->add_undefined_symbols_from_command_line();
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
289 if (parameters->options().gc_sections())
291 // Find the start symbol if any.
293 if (parameters->options().entry())
294 start_sym = symtab->lookup(parameters->options().entry());
296 start_sym = symtab->lookup("_start");
297 if (start_sym !=NULL)
300 unsigned int shndx = start_sym->shndx(&is_ordinary);
303 symtab->gc()->worklist().push(
304 Section_id(start_sym->object(), shndx));
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();
318 (*p)->layout(symtab, layout, NULL);
321 // Layout deferred objects due to plugins.
322 if (parameters->options().has_plugins())
324 Plugin_manager* plugins = parameters->options().plugins();
325 gold_assert(plugins != NULL);
326 plugins->layout_deferred_objects();
328 if (parameters->options().gc_sections())
330 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
331 p != input_objects->relobj_end();
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();
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);
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(¶meters->default_target());
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);
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())
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());
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());
378 if (is_debugging_enabled(DEBUG_SCRIPT))
379 layout->script_options()->print(stderr);
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();
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());
389 // Create any automatic note sections.
390 layout->create_notes();
392 // Create any output sections required by any linker script.
393 layout->create_script_sections();
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);
399 // Define symbols from any linker scripts.
400 layout->define_script_symbols(symtab);
402 // Attach sections to segments.
403 layout->attach_sections_to_segments();
405 if (!parameters->options().relocatable())
407 // Predefine standard symbols.
408 define_standard_symbols(symtab, layout);
410 // Define __start and __stop symbols for output sections where
412 layout->define_section_symbols(symtab);
415 // Make sure we have symbols for any required group signatures.
416 layout->define_group_signatures(symtab);
418 Task_token* blocker = new Task_token(true);
419 Task_token* symtab_lock = new Task_token(false);
421 // If doing garbage collection, the relocations have already been read.
422 // Otherwise, read and scan the relocations.
423 if (parameters->options().gc_sections())
425 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
426 p != input_objects->relobj_end();
429 blocker->add_blocker();
430 workqueue->queue(new Scan_relocs(options, symtab, layout, *p,
431 (*p)->get_relocs_data(),symtab_lock, blocker));
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.
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();
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));
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())
466 blocker->add_blocker();
467 workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
468 symtab_lock, blocker));
471 // When all those tasks are complete, we can start laying out the
473 // TODO(csilvers): figure out a more principled way to get the target
474 Target* target = const_cast<Target*>(¶meters->target());
475 workqueue->queue(new Task_function(new Layout_task_runner(options,
482 "Task_function Layout_task_runner"));
485 // Queue up the final set of tasks. This is called at the end of
489 queue_final_tasks(const General_options& options,
490 const Input_objects* input_objects,
491 const Symbol_table* symtab,
493 Workqueue* workqueue,
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);
501 bool any_postprocessing_sections = layout->any_postprocessing_sections();
503 // Use a blocker to wait until all the input sections have been
505 Task_token* input_sections_blocker = NULL;
506 if (!any_postprocessing_sections)
507 input_sections_blocker = new Task_token(true);
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);
513 // Use a blocker to block the final cleanup task.
514 Task_token* final_blocker = new Task_token(true);
516 // Queue a task to write out the symbol table.
517 final_blocker->add_blocker();
518 workqueue->queue(new Write_symbols_task(layout,
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,
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));
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();
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,
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
555 if (!any_postprocessing_sections)
557 final_blocker->add_blocker();
558 Task* t = new Write_after_input_sections_task(layout, of,
559 input_sections_blocker,
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,
571 final_blocker = new_final_blocker;
574 // Queue a task to close the output file. This will be blocked by
576 workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
579 "Task_function Close_task_runner"));
582 } // End namespace gold.