Don't check assertions until symbols are finalized. Create an output
[deliverable/binutils-gdb.git] / gold / layout.h
1 // layout.h -- lay out output file sections for gold -*- C++ -*-
2
3 // Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
5
6 // This file is part of gold.
7
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.
12
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.
17
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.
22
23 #ifndef GOLD_LAYOUT_H
24 #define GOLD_LAYOUT_H
25
26 #include <list>
27 #include <string>
28 #include <utility>
29 #include <vector>
30
31 #include "script.h"
32 #include "workqueue.h"
33 #include "object.h"
34 #include "dynobj.h"
35 #include "stringpool.h"
36
37 namespace gold
38 {
39
40 class General_options;
41 class Input_objects;
42 class Symbol_table;
43 class Output_section_data;
44 class Output_section;
45 class Output_section_headers;
46 class Output_segment;
47 class Output_data;
48 class Output_data_dynamic;
49 class Eh_frame;
50 class Target;
51
52 // This task function handles mapping the input sections to output
53 // sections and laying them out in memory.
54
55 class Layout_task_runner : public Task_function_runner
56 {
57 public:
58 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
59 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
60 // object.
61 Layout_task_runner(const General_options& options,
62 const Input_objects* input_objects,
63 Symbol_table* symtab,
64 Target* target,
65 Layout* layout)
66 : options_(options), input_objects_(input_objects), symtab_(symtab),
67 target_(target), layout_(layout)
68 { }
69
70 // Run the operation.
71 void
72 run(Workqueue*, const Task*);
73
74 private:
75 Layout_task_runner(const Layout_task_runner&);
76 Layout_task_runner& operator=(const Layout_task_runner&);
77
78 const General_options& options_;
79 const Input_objects* input_objects_;
80 Symbol_table* symtab_;
81 Target* target_;
82 Layout* layout_;
83 };
84
85 // This class handles the details of laying out input sections.
86
87 class Layout
88 {
89 public:
90 Layout(const General_options& options, Script_options*);
91
92 // Given an input section SHNDX, named NAME, with data in SHDR, from
93 // the object file OBJECT, return the output section where this
94 // input section should go. RELOC_SHNDX is the index of a
95 // relocation section which applies to this section, or 0 if none,
96 // or -1U if more than one. RELOC_TYPE is the type of the
97 // relocation section if there is one. Set *OFFSET to the offset
98 // within the output section.
99 template<int size, bool big_endian>
100 Output_section*
101 layout(Sized_relobj<size, big_endian> *object, unsigned int shndx,
102 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
103 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);
104
105 // Layout an input reloc section when doing a relocatable link. The
106 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
107 // DATA_SECTION is the reloc section to which it refers. RR is the
108 // relocatable information.
109 template<int size, bool big_endian>
110 Output_section*
111 layout_reloc(Sized_relobj<size, big_endian>* object,
112 unsigned int reloc_shndx,
113 const elfcpp::Shdr<size, big_endian>& shdr,
114 Output_section* data_section,
115 Relocatable_relocs* rr);
116
117 // Layout a group section when doing a relocatable link.
118 template<int size, bool big_endian>
119 void
120 layout_group(Symbol_table* symtab,
121 Sized_relobj<size, big_endian>* object,
122 unsigned int group_shndx,
123 const char* group_section_name,
124 const char* signature,
125 const elfcpp::Shdr<size, big_endian>& shdr,
126 const elfcpp::Elf_Word* contents);
127
128 // Like layout, only for exception frame sections. OBJECT is an
129 // object file. SYMBOLS is the contents of the symbol table
130 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
131 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
132 // .eh_frame section in OBJECT. SHDR is the section header.
133 // RELOC_SHNDX is the index of a relocation section which applies to
134 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
135 // is the type of the relocation section if there is one. This
136 // returns the output section, and sets *OFFSET to the offset.
137 template<int size, bool big_endian>
138 Output_section*
139 layout_eh_frame(Sized_relobj<size, big_endian>* object,
140 const unsigned char* symbols,
141 off_t symbols_size,
142 const unsigned char* symbol_names,
143 off_t symbol_names_size,
144 unsigned int shndx,
145 const elfcpp::Shdr<size, big_endian>& shdr,
146 unsigned int reloc_shndx, unsigned int reloc_type,
147 off_t* offset);
148
149 // Handle a GNU stack note. This is called once per input object
150 // file. SEEN_GNU_STACK is true if the object file has a
151 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
152 // from that section if there was one.
153 void
154 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags);
155
156 // Add an Output_section_data to the layout. This is used for
157 // special sections like the GOT section.
158 void
159 add_output_section_data(const char* name, elfcpp::Elf_Word type,
160 elfcpp::Elf_Xword flags,
161 Output_section_data*);
162
163 // Create dynamic sections if necessary.
164 void
165 create_initial_dynamic_sections(Symbol_table*);
166
167 // Define __start and __stop symbols for output sections.
168 void
169 define_section_symbols(Symbol_table*);
170
171 // Create sections for linker scripts.
172 void
173 create_script_sections()
174 { this->script_options_->create_script_sections(this); }
175
176 // Define symbols from any linker script.
177 void
178 define_script_symbols(Symbol_table* symtab)
179 { this->script_options_->add_symbols_to_table(symtab); }
180
181 // Define symbols for group signatures.
182 void
183 define_group_signatures(Symbol_table*);
184
185 // Return the Stringpool used for symbol names.
186 const Stringpool*
187 sympool() const
188 { return &this->sympool_; }
189
190 // Return the Stringpool used for dynamic symbol names and dynamic
191 // tags.
192 const Stringpool*
193 dynpool() const
194 { return &this->dynpool_; }
195
196 // Return whether a section is a .gnu.linkonce section, given the
197 // section name.
198 static inline bool
199 is_linkonce(const char* name)
200 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
201
202 // Record the signature of a comdat section, and return whether to
203 // include it in the link. The GROUP parameter is true for a
204 // section group signature, false for a signature derived from a
205 // .gnu.linkonce section.
206 bool
207 add_comdat(const char*, bool group);
208
209 // Finalize the layout after all the input sections have been added.
210 off_t
211 finalize(const Input_objects*, Symbol_table*, Target*, const Task*);
212
213 // Return whether any sections require postprocessing.
214 bool
215 any_postprocessing_sections() const
216 { return this->any_postprocessing_sections_; }
217
218 // Return the size of the output file.
219 off_t
220 output_file_size() const
221 { return this->output_file_size_; }
222
223 // Return the TLS segment. This will return NULL if there isn't
224 // one.
225 Output_segment*
226 tls_segment() const
227 { return this->tls_segment_; }
228
229 // Return the normal symbol table.
230 Output_section*
231 symtab_section() const
232 {
233 gold_assert(this->symtab_section_ != NULL);
234 return this->symtab_section_;
235 }
236
237 // Return the dynamic symbol table.
238 Output_section*
239 dynsym_section() const
240 {
241 gold_assert(this->dynsym_section_ != NULL);
242 return this->dynsym_section_;
243 }
244
245 // Return the dynamic tags.
246 Output_data_dynamic*
247 dynamic_data() const
248 { return this->dynamic_data_; }
249
250 // Write out the output sections.
251 void
252 write_output_sections(Output_file* of) const;
253
254 // Write out data not associated with an input file or the symbol
255 // table.
256 void
257 write_data(const Symbol_table*, Output_file*) const;
258
259 // Write out output sections which can not be written until all the
260 // input sections are complete.
261 void
262 write_sections_after_input_sections(Output_file* of);
263
264 // Return an output section named NAME, or NULL if there is none.
265 Output_section*
266 find_output_section(const char* name) const;
267
268 // Return an output segment of type TYPE, with segment flags SET set
269 // and segment flags CLEAR clear. Return NULL if there is none.
270 Output_segment*
271 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
272 elfcpp::Elf_Word clear) const;
273
274 // Return the number of segments we expect to produce.
275 size_t
276 expected_segment_count() const;
277
278 // Set a flag to indicate that an object file uses the static TLS model.
279 void
280 set_has_static_tls()
281 { this->has_static_tls_ = true; }
282
283 // Return true if any object file uses the static TLS model.
284 bool
285 has_static_tls() const
286 { return this->has_static_tls_; }
287
288 // Return the options which may be set by a linker script.
289 Script_options*
290 script_options()
291 { return this->script_options_; }
292
293 const Script_options*
294 script_options() const
295 { return this->script_options_; }
296
297 // Rewrite output file in binary format.
298 void
299 write_binary(Output_file* in) const;
300
301 // Dump statistical information to stderr.
302 void
303 print_stats() const;
304
305 // A list of segments.
306
307 typedef std::vector<Output_segment*> Segment_list;
308
309 // A list of sections.
310
311 typedef std::vector<Output_section*> Section_list;
312
313 // The list of information to write out which is not attached to
314 // either a section or a segment.
315 typedef std::vector<Output_data*> Data_list;
316
317 // Store the allocated sections into the section list. This is used
318 // by the linker script code.
319 void
320 get_allocated_sections(Section_list*) const;
321
322 // Make a section for a linker script to hold data.
323 Output_section*
324 make_output_section_for_script(const char* name);
325
326 // Make a segment. This is used by the linker script code.
327 Output_segment*
328 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);
329
330 // Return the number of segments.
331 size_t
332 segment_count() const
333 { return this->segment_list_.size(); }
334
335 // Map from section flags to segment flags.
336 static elfcpp::Elf_Word
337 section_flags_to_segment(elfcpp::Elf_Xword flags);
338
339 private:
340 Layout(const Layout&);
341 Layout& operator=(const Layout&);
342
343 // Mapping from .gnu.linkonce section names to output section names.
344 struct Linkonce_mapping
345 {
346 const char* from;
347 int fromlen;
348 const char* to;
349 int tolen;
350 };
351 static const Linkonce_mapping linkonce_mapping[];
352 static const int linkonce_mapping_count;
353
354 // During a relocatable link, a list of group sections and
355 // signatures.
356 struct Group_signature
357 {
358 // The group section.
359 Output_section* section;
360 // The signature.
361 const char* signature;
362
363 Group_signature()
364 : section(NULL), signature(NULL)
365 { }
366
367 Group_signature(Output_section* sectiona, const char* signaturea)
368 : section(sectiona), signature(signaturea)
369 { }
370 };
371 typedef std::vector<Group_signature> Group_signatures;
372
373 // Create a .note section for gold.
374 void
375 create_gold_note();
376
377 // Record whether the stack must be executable.
378 void
379 create_executable_stack_info(const Target*);
380
381 // Find the first read-only PT_LOAD segment, creating one if
382 // necessary.
383 Output_segment*
384 find_first_load_seg();
385
386 // Count the local symbols in the regular symbol table and the dynamic
387 // symbol table, and build the respective string pools.
388 void
389 count_local_symbols(const Task*, const Input_objects*);
390
391 // Create the output sections for the symbol table.
392 void
393 create_symtab_sections(const Input_objects*, Symbol_table*, off_t*);
394
395 // Create the .shstrtab section.
396 Output_section*
397 create_shstrtab();
398
399 // Create the section header table.
400 void
401 create_shdrs(off_t*);
402
403 // Create the dynamic symbol table.
404 void
405 create_dynamic_symtab(const Input_objects*, Symbol_table*,
406 Output_section** pdynstr,
407 unsigned int* plocal_dynamic_count,
408 std::vector<Symbol*>* pdynamic_symbols,
409 Versions* versions);
410
411 // Assign offsets to each local portion of the dynamic symbol table.
412 void
413 assign_local_dynsym_offsets(const Input_objects*);
414
415 // Finish the .dynamic section and PT_DYNAMIC segment.
416 void
417 finish_dynamic_section(const Input_objects*, const Symbol_table*);
418
419 // Create the .interp section and PT_INTERP segment.
420 void
421 create_interp(const Target* target);
422
423 // Create the version sections.
424 void
425 create_version_sections(const Versions*,
426 const Symbol_table*,
427 unsigned int local_symcount,
428 const std::vector<Symbol*>& dynamic_symbols,
429 const Output_section* dynstr);
430
431 template<int size, bool big_endian>
432 void
433 sized_create_version_sections(const Versions* versions,
434 const Symbol_table*,
435 unsigned int local_symcount,
436 const std::vector<Symbol*>& dynamic_symbols,
437 const Output_section* dynstr
438 ACCEPT_SIZE_ENDIAN);
439
440 // Return whether to include this section in the link.
441 template<int size, bool big_endian>
442 bool
443 include_section(Sized_relobj<size, big_endian>* object, const char* name,
444 const elfcpp::Shdr<size, big_endian>&);
445
446 // Return the output section name to use given an input section
447 // name. Set *PLEN to the length of the name. *PLEN must be
448 // initialized to the length of NAME.
449 static const char*
450 output_section_name(const char* name, size_t* plen);
451
452 // Return the output section name to use for a linkonce section
453 // name. PLEN is as for output_section_name.
454 static const char*
455 linkonce_output_name(const char* name, size_t* plen);
456
457 // Return the output section for NAME, TYPE and FLAGS.
458 Output_section*
459 get_output_section(const char* name, Stringpool::Key name_key,
460 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
461
462 // Choose the output section for NAME in RELOBJ.
463 Output_section*
464 choose_output_section(const Relobj* relobj, const char* name,
465 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
466 bool adjust_name);
467
468 // Create a new Output_section.
469 Output_section*
470 make_output_section(const char* name, elfcpp::Elf_Word type,
471 elfcpp::Elf_Xword flags);
472
473 // Set the final file offsets of all the segments.
474 off_t
475 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
476
477 // Set the file offsets of the sections when doing a relocatable
478 // link.
479 off_t
480 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx);
481
482 // Set the final file offsets of all the sections not associated
483 // with a segment. We set section offsets in three passes: the
484 // first handles all allocated sections, the second sections that
485 // require postprocessing, and the last the late-bound STRTAB
486 // sections (probably only shstrtab, which is the one we care about
487 // because it holds section names).
488 enum Section_offset_pass
489 {
490 BEFORE_INPUT_SECTIONS_PASS,
491 POSTPROCESSING_SECTIONS_PASS,
492 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
493 };
494 off_t
495 set_section_offsets(off_t, Section_offset_pass pass);
496
497 // Set the final section indexes of all the sections not associated
498 // with a segment. Returns the next unused index.
499 unsigned int
500 set_section_indexes(unsigned int pshndx);
501
502 // Set the section addresses when using a script.
503 Output_segment*
504 set_section_addresses_from_script(Symbol_table*);
505
506 // Return whether SEG1 comes before SEG2 in the output file.
507 static bool
508 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
509
510 // A mapping used for group signatures.
511 typedef Unordered_map<std::string, bool> Signatures;
512
513 // Mapping from input section name/type/flags to output section. We
514 // use canonicalized strings here.
515
516 typedef std::pair<Stringpool::Key,
517 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
518
519 struct Hash_key
520 {
521 size_t
522 operator()(const Key& k) const;
523 };
524
525 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
526
527 // A comparison class for segments.
528
529 struct Compare_segments
530 {
531 bool
532 operator()(const Output_segment* seg1, const Output_segment* seg2)
533 { return Layout::segment_precedes(seg1, seg2); }
534 };
535
536 // A reference to the options on the command line.
537 const General_options& options_;
538 // Information set by scripts or by command line options.
539 Script_options* script_options_;
540 // The output section names.
541 Stringpool namepool_;
542 // The output symbol names.
543 Stringpool sympool_;
544 // The dynamic strings, if needed.
545 Stringpool dynpool_;
546 // The list of group sections and linkonce sections which we have seen.
547 Signatures signatures_;
548 // The mapping from input section name/type/flags to output sections.
549 Section_name_map section_name_map_;
550 // The list of output segments.
551 Segment_list segment_list_;
552 // The list of output sections.
553 Section_list section_list_;
554 // The list of output sections which are not attached to any output
555 // segment.
556 Section_list unattached_section_list_;
557 // The list of unattached Output_data objects which require special
558 // handling because they are not Output_sections.
559 Data_list special_output_list_;
560 // The section headers.
561 Output_section_headers* section_headers_;
562 // A pointer to the PT_TLS segment if there is one.
563 Output_segment* tls_segment_;
564 // The SHT_SYMTAB output section.
565 Output_section* symtab_section_;
566 // The SHT_DYNSYM output section if there is one.
567 Output_section* dynsym_section_;
568 // The SHT_DYNAMIC output section if there is one.
569 Output_section* dynamic_section_;
570 // The dynamic data which goes into dynamic_section_.
571 Output_data_dynamic* dynamic_data_;
572 // The exception frame output section if there is one.
573 Output_section* eh_frame_section_;
574 // The exception frame data for eh_frame_section_.
575 Eh_frame* eh_frame_data_;
576 // The exception frame header output section if there is one.
577 Output_section* eh_frame_hdr_section_;
578 // A list of group sections and their signatures.
579 Group_signatures group_signatures_;
580 // The size of the output file.
581 off_t output_file_size_;
582 // Whether we have seen an object file marked to require an
583 // executable stack.
584 bool input_requires_executable_stack_;
585 // Whether we have seen at least one object file with an executable
586 // stack marker.
587 bool input_with_gnu_stack_note_;
588 // Whether we have seen at least one object file without an
589 // executable stack marker.
590 bool input_without_gnu_stack_note_;
591 // Whether we have seen an object file that uses the static TLS model.
592 bool has_static_tls_;
593 // Whether any sections require postprocessing.
594 bool any_postprocessing_sections_;
595 };
596
597 // This task handles writing out data in output sections which is not
598 // part of an input section, or which requires special handling. When
599 // this is done, it unblocks both output_sections_blocker and
600 // final_blocker.
601
602 class Write_sections_task : public Task
603 {
604 public:
605 Write_sections_task(const Layout* layout, Output_file* of,
606 Task_token* output_sections_blocker,
607 Task_token* final_blocker)
608 : layout_(layout), of_(of),
609 output_sections_blocker_(output_sections_blocker),
610 final_blocker_(final_blocker)
611 { }
612
613 // The standard Task methods.
614
615 Task_token*
616 is_runnable();
617
618 void
619 locks(Task_locker*);
620
621 void
622 run(Workqueue*);
623
624 std::string
625 get_name() const
626 { return "Write_sections_task"; }
627
628 private:
629 class Write_sections_locker;
630
631 const Layout* layout_;
632 Output_file* of_;
633 Task_token* output_sections_blocker_;
634 Task_token* final_blocker_;
635 };
636
637 // This task handles writing out data which is not part of a section
638 // or segment.
639
640 class Write_data_task : public Task
641 {
642 public:
643 Write_data_task(const Layout* layout, const Symbol_table* symtab,
644 Output_file* of, Task_token* final_blocker)
645 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
646 { }
647
648 // The standard Task methods.
649
650 Task_token*
651 is_runnable();
652
653 void
654 locks(Task_locker*);
655
656 void
657 run(Workqueue*);
658
659 std::string
660 get_name() const
661 { return "Write_data_task"; }
662
663 private:
664 const Layout* layout_;
665 const Symbol_table* symtab_;
666 Output_file* of_;
667 Task_token* final_blocker_;
668 };
669
670 // This task handles writing out the global symbols.
671
672 class Write_symbols_task : public Task
673 {
674 public:
675 Write_symbols_task(const Symbol_table* symtab,
676 const Input_objects* input_objects,
677 const Stringpool* sympool, const Stringpool* dynpool,
678 Output_file* of, Task_token* final_blocker)
679 : symtab_(symtab), input_objects_(input_objects), sympool_(sympool),
680 dynpool_(dynpool), of_(of), final_blocker_(final_blocker)
681 { }
682
683 // The standard Task methods.
684
685 Task_token*
686 is_runnable();
687
688 void
689 locks(Task_locker*);
690
691 void
692 run(Workqueue*);
693
694 std::string
695 get_name() const
696 { return "Write_symbols_task"; }
697
698 private:
699 const Symbol_table* symtab_;
700 const Input_objects* input_objects_;
701 const Stringpool* sympool_;
702 const Stringpool* dynpool_;
703 Output_file* of_;
704 Task_token* final_blocker_;
705 };
706
707 // This task handles writing out data in output sections which can't
708 // be written out until all the input sections have been handled.
709 // This is for sections whose contents is based on the contents of
710 // other output sections.
711
712 class Write_after_input_sections_task : public Task
713 {
714 public:
715 Write_after_input_sections_task(Layout* layout, Output_file* of,
716 Task_token* input_sections_blocker,
717 Task_token* final_blocker)
718 : layout_(layout), of_(of),
719 input_sections_blocker_(input_sections_blocker),
720 final_blocker_(final_blocker)
721 { }
722
723 // The standard Task methods.
724
725 Task_token*
726 is_runnable();
727
728 void
729 locks(Task_locker*);
730
731 void
732 run(Workqueue*);
733
734 std::string
735 get_name() const
736 { return "Write_after_input_sections_task"; }
737
738 private:
739 Layout* layout_;
740 Output_file* of_;
741 Task_token* input_sections_blocker_;
742 Task_token* final_blocker_;
743 };
744
745 // This task function handles closing the file.
746
747 class Close_task_runner : public Task_function_runner
748 {
749 public:
750 Close_task_runner(const General_options* options, const Layout* layout,
751 Output_file* of)
752 : options_(options), layout_(layout), of_(of)
753 { }
754
755 // Run the operation.
756 void
757 run(Workqueue*, const Task*);
758
759 private:
760 const General_options* options_;
761 const Layout* layout_;
762 Output_file* of_;
763 };
764
765 // A small helper function to align an address.
766
767 inline uint64_t
768 align_address(uint64_t address, uint64_t addralign)
769 {
770 if (addralign != 0)
771 address = (address + addralign - 1) &~ (addralign - 1);
772 return address;
773 }
774
775 } // End namespace gold.
776
777 #endif // !defined(GOLD_LAYOUT_H)
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