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"
49 const char* program_name
;
52 gold_exit(bool status
)
54 if (parameters
!= NULL
55 && parameters
->options_valid()
56 && parameters
->options().has_plugins())
57 parameters
->options().plugins()->cleanup();
58 if (!status
&& parameters
!= NULL
&& parameters
->options_valid())
59 unlink_if_ordinary(parameters
->options().output_file_name());
60 exit(status
? EXIT_SUCCESS
: EXIT_FAILURE
);
66 // We are out of memory, so try hard to print a reasonable message.
67 // Note that we don't try to translate this message, since the
68 // translation process itself will require memory.
70 // LEN only exists to avoid a pointless warning when write is
71 // declared with warn_use_result, as when compiling with
72 // -D_USE_FORTIFY on GNU/Linux. Casting to void does not appear to
73 // work, at least not with gcc 4.3.0.
75 ssize_t len
= write(2, program_name
, strlen(program_name
));
78 const char* const s
= ": out of memory\n";
79 len
= write(2, s
, strlen(s
));
84 // Handle an unreachable case.
87 do_gold_unreachable(const char* filename
, int lineno
, const char* function
)
89 fprintf(stderr
, _("%s: internal error in %s, at %s:%d\n"),
90 program_name
, function
, filename
, lineno
);
94 // This class arranges to run the functions done in the middle of the
95 // link. It is just a closure.
97 class Middle_runner
: public Task_function_runner
100 Middle_runner(const General_options
& options
,
101 const Input_objects
* input_objects
,
102 Symbol_table
* symtab
,
103 Layout
* layout
, Mapfile
* mapfile
)
104 : options_(options
), input_objects_(input_objects
), symtab_(symtab
),
105 layout_(layout
), mapfile_(mapfile
)
109 run(Workqueue
*, const Task
*);
112 const General_options
& options_
;
113 const Input_objects
* input_objects_
;
114 Symbol_table
* symtab_
;
120 Middle_runner::run(Workqueue
* workqueue
, const Task
* task
)
122 queue_middle_tasks(this->options_
, task
, this->input_objects_
, this->symtab_
,
123 this->layout_
, workqueue
, this->mapfile_
);
126 // This class arranges the tasks to process the relocs for garbage collection.
128 class Gc_runner
: public Task_function_runner
131 Gc_runner(const General_options
& options
,
132 const Input_objects
* input_objects
,
133 Symbol_table
* symtab
,
134 Layout
* layout
, Mapfile
* mapfile
)
135 : options_(options
), input_objects_(input_objects
), symtab_(symtab
),
136 layout_(layout
), mapfile_(mapfile
)
140 run(Workqueue
*, const Task
*);
143 const General_options
& options_
;
144 const Input_objects
* input_objects_
;
145 Symbol_table
* symtab_
;
151 Gc_runner::run(Workqueue
* workqueue
, const Task
* task
)
153 queue_middle_gc_tasks(this->options_
, task
, this->input_objects_
,
154 this->symtab_
, this->layout_
, workqueue
,
158 // Queue up the initial set of tasks for this link job.
161 queue_initial_tasks(const General_options
& options
,
162 Dirsearch
& search_path
,
163 const Command_line
& cmdline
,
164 Workqueue
* workqueue
, Input_objects
* input_objects
,
165 Symbol_table
* symtab
, Layout
* layout
, Mapfile
* mapfile
)
167 if (cmdline
.begin() == cmdline
.end())
169 if (options
.printed_version())
171 gold_fatal(_("no input files"));
174 int thread_count
= options
.thread_count_initial();
175 if (thread_count
== 0)
176 thread_count
= cmdline
.number_of_input_files();
177 workqueue
->set_thread_count(thread_count
);
179 // Read the input files. We have to add the symbols to the symbol
180 // table in order. We do this by creating a separate blocker for
181 // each input file. We associate the blocker with the following
182 // input file, to give us a convenient place to delete it.
183 Task_token
* this_blocker
= NULL
;
184 for (Command_line::const_iterator p
= cmdline
.begin();
188 Task_token
* next_blocker
= new Task_token(true);
189 next_blocker
->add_blocker();
190 workqueue
->queue(new Read_symbols(input_objects
, symtab
, layout
,
191 &search_path
, 0, mapfile
, &*p
, NULL
,
192 this_blocker
, next_blocker
));
193 this_blocker
= next_blocker
;
196 if (options
.has_plugins())
198 Task_token
* next_blocker
= new Task_token(true);
199 next_blocker
->add_blocker();
200 workqueue
->queue(new Plugin_hook(options
, input_objects
, symtab
, layout
,
201 &search_path
, mapfile
, this_blocker
,
203 this_blocker
= next_blocker
;
206 if (parameters
->options().relocatable()
207 && (parameters
->options().gc_sections() || parameters
->options().icf()))
208 gold_error(_("cannot mix -r with --gc-sections or --icf"));
210 if (parameters
->options().gc_sections() || parameters
->options().icf())
212 workqueue
->queue(new Task_function(new Gc_runner(options
,
218 "Task_function Gc_runner"));
222 workqueue
->queue(new Task_function(new Middle_runner(options
,
228 "Task_function Middle_runner"));
232 // Queue up a set of tasks to be done before queueing the middle set
233 // of tasks. This is only necessary when garbage collection
234 // (--gc-sections) of unused sections is desired. The relocs are read
235 // and processed here early to determine the garbage sections before the
236 // relocs can be scanned in later tasks.
239 queue_middle_gc_tasks(const General_options
& options
,
241 const Input_objects
* input_objects
,
242 Symbol_table
* symtab
,
244 Workqueue
* workqueue
,
247 // Read_relocs for all the objects must be done and processed to find
248 // unused sections before any scanning of the relocs can take place.
249 Task_token
* blocker
= new Task_token(true);
250 Task_token
* symtab_lock
= new Task_token(false);
251 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
252 p
!= input_objects
->relobj_end();
255 // We can read and process the relocations in any order.
256 blocker
->add_blocker();
257 workqueue
->queue(new Read_relocs(options
, symtab
, layout
, *p
,
258 symtab_lock
, blocker
));
261 Task_token
* this_blocker
= new Task_token(true);
262 workqueue
->queue(new Task_function(new Middle_runner(options
,
268 "Task_function Middle_runner"));
271 // Queue up the middle set of tasks. These are the tasks which run
272 // after all the input objects have been found and all the symbols
273 // have been read, but before we lay out the output file.
276 queue_middle_tasks(const General_options
& options
,
278 const Input_objects
* input_objects
,
279 Symbol_table
* symtab
,
281 Workqueue
* workqueue
,
284 // Add any symbols named with -u options to the symbol table.
285 symtab
->add_undefined_symbols_from_command_line();
287 // If garbage collection was chosen, relocs have been read and processed
288 // at this point by pre_middle_tasks. Layout can then be done for all
290 if (parameters
->options().gc_sections())
292 // Find the start symbol if any.
294 if (parameters
->options().entry())
295 start_sym
= symtab
->lookup(parameters
->options().entry());
297 start_sym
= symtab
->lookup("_start");
298 if (start_sym
!=NULL
)
301 unsigned int shndx
= start_sym
->shndx(&is_ordinary
);
304 symtab
->gc()->worklist().push(
305 Section_id(start_sym
->object(), shndx
));
308 // Symbols named with -u should not be considered garbage.
309 symtab
->gc_mark_undef_symbols();
310 gold_assert(symtab
->gc() != NULL
);
311 // Do a transitive closure on all references to determine the worklist.
312 symtab
->gc()->do_transitive_closure();
315 // If identical code folding (--icf) is chosen it makes sense to do it
316 // only after garbage collection (--gc-sections) as we do not want to
317 // be folding sections that will be garbage.
318 if (parameters
->options().icf())
320 symtab
->icf()->find_identical_sections(input_objects
, symtab
);
323 // Call Object::layout for the second time to determine the
324 // output_sections for all referenced input sections. When
325 // --gc-sections or --icf is turned on, Object::layout is
326 // called twice. It is called the first time when the
327 // symbols are added.
328 if (parameters
->options().gc_sections() || parameters
->options().icf())
330 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
331 p
!= input_objects
->relobj_end();
334 (*p
)->layout(symtab
, layout
, NULL
);
338 // Layout deferred objects due to plugins.
339 if (parameters
->options().has_plugins())
341 Plugin_manager
* plugins
= parameters
->options().plugins();
342 gold_assert(plugins
!= NULL
);
343 plugins
->layout_deferred_objects();
346 if (parameters
->options().gc_sections() || parameters
->options().icf())
348 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
349 p
!= input_objects
->relobj_end();
352 // Update the value of output_section stored in rd.
353 Read_relocs_data
*rd
= (*p
)->get_relocs_data();
354 for (Read_relocs_data::Relocs_list::iterator q
= rd
->relocs
.begin();
355 q
!= rd
->relocs
.end();
358 q
->output_section
= (*p
)->output_section(q
->data_shndx
);
359 q
->needs_special_offset_handling
=
360 (*p
)->is_output_section_offset_invalid(q
->data_shndx
);
365 // We have to support the case of not seeing any input objects, and
366 // generate an empty file. Existing builds depend on being able to
367 // pass an empty archive to the linker and get an empty object file
368 // out. In order to do this we need to use a default target.
369 if (input_objects
->number_of_input_objects() == 0)
370 set_parameters_target(¶meters
->default_target());
372 int thread_count
= options
.thread_count_middle();
373 if (thread_count
== 0)
374 thread_count
= std::max(2, input_objects
->number_of_input_objects());
375 workqueue
->set_thread_count(thread_count
);
377 // Now we have seen all the input files.
378 const bool doing_static_link
= (!input_objects
->any_dynamic()
379 && !parameters
->options().shared());
380 set_parameters_doing_static_link(doing_static_link
);
381 if (!doing_static_link
&& options
.is_static())
383 // We print out just the first .so we see; there may be others.
384 gold_assert(input_objects
->dynobj_begin() != input_objects
->dynobj_end());
385 gold_error(_("cannot mix -static with dynamic object %s"),
386 (*input_objects
->dynobj_begin())->name().c_str());
388 if (!doing_static_link
&& parameters
->options().relocatable())
389 gold_fatal(_("cannot mix -r with dynamic object %s"),
390 (*input_objects
->dynobj_begin())->name().c_str());
391 if (!doing_static_link
392 && options
.oformat_enum() != General_options::OBJECT_FORMAT_ELF
)
393 gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
394 (*input_objects
->dynobj_begin())->name().c_str());
396 if (is_debugging_enabled(DEBUG_SCRIPT
))
397 layout
->script_options()->print(stderr
);
399 // For each dynamic object, record whether we've seen all the
400 // dynamic objects that it depends upon.
401 input_objects
->check_dynamic_dependencies();
403 // See if any of the input definitions violate the One Definition Rule.
404 // TODO: if this is too slow, do this as a task, rather than inline.
405 symtab
->detect_odr_violations(task
, options
.output_file_name());
407 // Create any automatic note sections.
408 layout
->create_notes();
410 // Create any output sections required by any linker script.
411 layout
->create_script_sections();
413 // Define some sections and symbols needed for a dynamic link. This
414 // handles some cases we want to see before we read the relocs.
415 layout
->create_initial_dynamic_sections(symtab
);
417 // Define symbols from any linker scripts.
418 layout
->define_script_symbols(symtab
);
420 // Attach sections to segments.
421 layout
->attach_sections_to_segments();
423 if (!parameters
->options().relocatable())
425 // Predefine standard symbols.
426 define_standard_symbols(symtab
, layout
);
428 // Define __start and __stop symbols for output sections where
430 layout
->define_section_symbols(symtab
);
433 // Make sure we have symbols for any required group signatures.
434 layout
->define_group_signatures(symtab
);
436 Task_token
* blocker
= new Task_token(true);
437 Task_token
* symtab_lock
= new Task_token(false);
439 // If doing garbage collection, the relocations have already been read.
440 // Otherwise, read and scan the relocations.
441 if (parameters
->options().gc_sections() || parameters
->options().icf())
443 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
444 p
!= input_objects
->relobj_end();
447 blocker
->add_blocker();
448 workqueue
->queue(new Scan_relocs(options
, symtab
, layout
, *p
,
449 (*p
)->get_relocs_data(),symtab_lock
, blocker
));
454 // Read the relocations of the input files. We do this to find
455 // which symbols are used by relocations which require a GOT and/or
456 // a PLT entry, or a COPY reloc. When we implement garbage
457 // collection we will do it here by reading the relocations in a
458 // breadth first search by references.
460 // We could also read the relocations during the first pass, and
461 // mark symbols at that time. That is how the old GNU linker works.
462 // Doing that is more complex, since we may later decide to discard
463 // some of the sections, and thus change our minds about the types
464 // of references made to the symbols.
465 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
466 p
!= input_objects
->relobj_end();
469 // We can read and process the relocations in any order. But we
470 // only want one task to write to the symbol table at a time.
471 // So we queue up a task for each object to read the
472 // relocations. That task will in turn queue a task to wait
473 // until it can write to the symbol table.
474 blocker
->add_blocker();
475 workqueue
->queue(new Read_relocs(options
, symtab
, layout
, *p
,
476 symtab_lock
, blocker
));
480 // Allocate common symbols. This requires write access to the
481 // symbol table, but is independent of the relocation processing.
482 if (parameters
->options().define_common())
484 blocker
->add_blocker();
485 workqueue
->queue(new Allocate_commons_task(symtab
, layout
, mapfile
,
486 symtab_lock
, blocker
));
489 // When all those tasks are complete, we can start laying out the
491 // TODO(csilvers): figure out a more principled way to get the target
492 Target
* target
= const_cast<Target
*>(¶meters
->target());
493 workqueue
->queue(new Task_function(new Layout_task_runner(options
,
500 "Task_function Layout_task_runner"));
503 // Queue up the final set of tasks. This is called at the end of
507 queue_final_tasks(const General_options
& options
,
508 const Input_objects
* input_objects
,
509 const Symbol_table
* symtab
,
511 Workqueue
* workqueue
,
514 int thread_count
= options
.thread_count_final();
515 if (thread_count
== 0)
516 thread_count
= std::max(2, input_objects
->number_of_input_objects());
517 workqueue
->set_thread_count(thread_count
);
519 bool any_postprocessing_sections
= layout
->any_postprocessing_sections();
521 // Use a blocker to wait until all the input sections have been
523 Task_token
* input_sections_blocker
= NULL
;
524 if (!any_postprocessing_sections
)
525 input_sections_blocker
= new Task_token(true);
527 // Use a blocker to block any objects which have to wait for the
528 // output sections to complete before they can apply relocations.
529 Task_token
* output_sections_blocker
= new Task_token(true);
531 // Use a blocker to block the final cleanup task.
532 Task_token
* final_blocker
= new Task_token(true);
534 // Queue a task to write out the symbol table.
535 final_blocker
->add_blocker();
536 workqueue
->queue(new Write_symbols_task(layout
,
544 // Queue a task to write out the output sections.
545 output_sections_blocker
->add_blocker();
546 final_blocker
->add_blocker();
547 workqueue
->queue(new Write_sections_task(layout
, of
, output_sections_blocker
,
550 // Queue a task to write out everything else.
551 final_blocker
->add_blocker();
552 workqueue
->queue(new Write_data_task(layout
, symtab
, of
, final_blocker
));
554 // Queue a task for each input object to relocate the sections and
555 // write out the local symbols.
556 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
557 p
!= input_objects
->relobj_end();
560 if (input_sections_blocker
!= NULL
)
561 input_sections_blocker
->add_blocker();
562 final_blocker
->add_blocker();
563 workqueue
->queue(new Relocate_task(options
, symtab
, layout
, *p
, of
,
564 input_sections_blocker
,
565 output_sections_blocker
,
569 // Queue a task to write out the output sections which depend on
570 // input sections. If there are any sections which require
571 // postprocessing, then we need to do this last, since it may resize
573 if (!any_postprocessing_sections
)
575 final_blocker
->add_blocker();
576 Task
* t
= new Write_after_input_sections_task(layout
, of
,
577 input_sections_blocker
,
583 Task_token
*new_final_blocker
= new Task_token(true);
584 new_final_blocker
->add_blocker();
585 Task
* t
= new Write_after_input_sections_task(layout
, of
,
589 final_blocker
= new_final_blocker
;
592 // Queue a task to close the output file. This will be blocked by
594 workqueue
->queue(new Task_function(new Close_task_runner(&options
, layout
,
597 "Task_function Close_task_runner"));
600 } // End namespace gold.