1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008 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.
32 #include "workqueue.h"
35 #include "stringpool.h"
40 class General_options;
43 class Output_section_data;
45 class Output_section_headers;
48 class Output_data_dynamic;
52 // This task function handles mapping the input sections to output
53 // sections and laying them out in memory.
55 class Layout_task_runner : public Task_function_runner
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
61 Layout_task_runner(const General_options& options,
62 const Input_objects* input_objects,
66 : options_(options), input_objects_(input_objects), symtab_(symtab),
67 target_(target), layout_(layout)
72 run(Workqueue*, const Task*);
75 Layout_task_runner(const Layout_task_runner&);
76 Layout_task_runner& operator=(const Layout_task_runner&);
78 const General_options& options_;
79 const Input_objects* input_objects_;
80 Symbol_table* symtab_;
85 // This class handles the details of laying out input sections.
90 Layout(const General_options& options, Script_options*);
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>
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);
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>
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);
117 // Layout a group section when doing a relocatable link.
118 template<int size, bool big_endian>
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);
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>
139 layout_eh_frame(Sized_relobj<size, big_endian>* object,
140 const unsigned char* symbols,
142 const unsigned char* symbol_names,
143 off_t symbol_names_size,
145 const elfcpp::Shdr<size, big_endian>& shdr,
146 unsigned int reloc_shndx, unsigned int reloc_type,
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.
154 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags);
156 // Add an Output_section_data to the layout. This is used for
157 // special sections like the GOT section.
159 add_output_section_data(const char* name, elfcpp::Elf_Word type,
160 elfcpp::Elf_Xword flags,
161 Output_section_data*);
163 // Create dynamic sections if necessary.
165 create_initial_dynamic_sections(Symbol_table*);
167 // Define __start and __stop symbols for output sections.
169 define_section_symbols(Symbol_table*);
171 // Define symbols from any linker script.
173 define_script_symbols(Symbol_table* symtab)
174 { this->script_options_->add_symbols_to_table(symtab); }
176 // Define symbols for group signatures.
178 define_group_signatures(Symbol_table*);
180 // Return the Stringpool used for symbol names.
183 { return &this->sympool_; }
185 // Return the Stringpool used for dynamic symbol names and dynamic
189 { return &this->dynpool_; }
191 // Return whether a section is a .gnu.linkonce section, given the
194 is_linkonce(const char* name)
195 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
197 // Record the signature of a comdat section, and return whether to
198 // include it in the link. The GROUP parameter is true for a
199 // section group signature, false for a signature derived from a
200 // .gnu.linkonce section.
202 add_comdat(const char*, bool group);
204 // Finalize the layout after all the input sections have been added.
206 finalize(const Input_objects*, Symbol_table*, Target*, const Task*);
208 // Return whether any sections require postprocessing.
210 any_postprocessing_sections() const
211 { return this->any_postprocessing_sections_; }
213 // Return the size of the output file.
215 output_file_size() const
216 { return this->output_file_size_; }
218 // Return the TLS segment. This will return NULL if there isn't
222 { return this->tls_segment_; }
224 // Return the normal symbol table.
226 symtab_section() const
228 gold_assert(this->symtab_section_ != NULL);
229 return this->symtab_section_;
232 // Return the dynamic symbol table.
234 dynsym_section() const
236 gold_assert(this->dynsym_section_ != NULL);
237 return this->dynsym_section_;
240 // Return the dynamic tags.
243 { return this->dynamic_data_; }
245 // Write out the output sections.
247 write_output_sections(Output_file* of) const;
249 // Write out data not associated with an input file or the symbol
252 write_data(const Symbol_table*, Output_file*) const;
254 // Write out output sections which can not be written until all the
255 // input sections are complete.
257 write_sections_after_input_sections(Output_file* of);
259 // Return an output section named NAME, or NULL if there is none.
261 find_output_section(const char* name) const;
263 // Return an output segment of type TYPE, with segment flags SET set
264 // and segment flags CLEAR clear. Return NULL if there is none.
266 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
267 elfcpp::Elf_Word clear) const;
269 // Return the number of segments we expect to produce.
271 expected_segment_count() const;
273 // Set a flag to indicate that an object file uses the static TLS model.
276 { this->has_static_tls_ = true; }
278 // Return true if any object file uses the static TLS model.
280 has_static_tls() const
281 { return this->has_static_tls_; }
283 // Return the options which may be set by a linker script.
286 { return this->script_options_; }
288 const Script_options*
289 script_options() const
290 { return this->script_options_; }
292 // Rewrite output file in binary format.
294 write_binary(Output_file* in) const;
296 // Dump statistical information to stderr.
300 // A list of segments.
302 typedef std::vector<Output_segment*> Segment_list;
304 // A list of sections.
306 typedef std::vector<Output_section*> Section_list;
308 // The list of information to write out which is not attached to
309 // either a section or a segment.
310 typedef std::vector<Output_data*> Data_list;
312 // Store the allocated sections into the section list. This is used
313 // by the linker script code.
315 get_allocated_sections(Section_list*) const;
317 // Make a segment. This is used by the linker script code.
319 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);
321 // Return the number of segments.
323 segment_count() const
324 { return this->segment_list_.size(); }
326 // Map from section flags to segment flags.
327 static elfcpp::Elf_Word
328 section_flags_to_segment(elfcpp::Elf_Xword flags);
331 Layout(const Layout&);
332 Layout& operator=(const Layout&);
334 // Mapping from .gnu.linkonce section names to output section names.
335 struct Linkonce_mapping
342 static const Linkonce_mapping linkonce_mapping[];
343 static const int linkonce_mapping_count;
345 // During a relocatable link, a list of group sections and
347 struct Group_signature
349 // The group section.
350 Output_section* section;
352 const char* signature;
355 : section(NULL), signature(NULL)
358 Group_signature(Output_section* sectiona, const char* signaturea)
359 : section(sectiona), signature(signaturea)
362 typedef std::vector<Group_signature> Group_signatures;
364 // Create a .note section for gold.
368 // Record whether the stack must be executable.
370 create_executable_stack_info(const Target*);
372 // Find the first read-only PT_LOAD segment, creating one if
375 find_first_load_seg();
377 // Count the local symbols in the regular symbol table and the dynamic
378 // symbol table, and build the respective string pools.
380 count_local_symbols(const Task*, const Input_objects*);
382 // Create the output sections for the symbol table.
384 create_symtab_sections(const Input_objects*, Symbol_table*, off_t*);
386 // Create the .shstrtab section.
390 // Create the section header table.
392 create_shdrs(off_t*);
394 // Create the dynamic symbol table.
396 create_dynamic_symtab(const Input_objects*, Symbol_table*,
397 Output_section** pdynstr,
398 unsigned int* plocal_dynamic_count,
399 std::vector<Symbol*>* pdynamic_symbols,
402 // Assign offsets to each local portion of the dynamic symbol table.
404 assign_local_dynsym_offsets(const Input_objects*);
406 // Finish the .dynamic section and PT_DYNAMIC segment.
408 finish_dynamic_section(const Input_objects*, const Symbol_table*);
410 // Create the .interp section and PT_INTERP segment.
412 create_interp(const Target* target);
414 // Create the version sections.
416 create_version_sections(const Versions*,
418 unsigned int local_symcount,
419 const std::vector<Symbol*>& dynamic_symbols,
420 const Output_section* dynstr);
422 template<int size, bool big_endian>
424 sized_create_version_sections(const Versions* versions,
426 unsigned int local_symcount,
427 const std::vector<Symbol*>& dynamic_symbols,
428 const Output_section* dynstr
431 // Return whether to include this section in the link.
432 template<int size, bool big_endian>
434 include_section(Sized_relobj<size, big_endian>* object, const char* name,
435 const elfcpp::Shdr<size, big_endian>&);
437 // Return the output section name to use given an input section
438 // name. Set *PLEN to the length of the name. *PLEN must be
439 // initialized to the length of NAME.
441 output_section_name(const char* name, size_t* plen);
443 // Return the output section name to use for a linkonce section
444 // name. PLEN is as for output_section_name.
446 linkonce_output_name(const char* name, size_t* plen);
448 // Return the output section for NAME, TYPE and FLAGS.
450 get_output_section(const char* name, Stringpool::Key name_key,
451 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
453 // Choose the output section for NAME in RELOBJ.
455 choose_output_section(const Relobj* relobj, const char* name,
456 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
459 // Create a new Output_section.
461 make_output_section(const char* name, elfcpp::Elf_Word type,
462 elfcpp::Elf_Xword flags);
464 // Set the final file offsets of all the segments.
466 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
468 // Set the file offsets of the sections when doing a relocatable
471 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx);
473 // Set the final file offsets of all the sections not associated
474 // with a segment. We set section offsets in three passes: the
475 // first handles all allocated sections, the second sections that
476 // require postprocessing, and the last the late-bound STRTAB
477 // sections (probably only shstrtab, which is the one we care about
478 // because it holds section names).
479 enum Section_offset_pass
481 BEFORE_INPUT_SECTIONS_PASS,
482 POSTPROCESSING_SECTIONS_PASS,
483 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
486 set_section_offsets(off_t, Section_offset_pass pass);
488 // Set the final section indexes of all the sections not associated
489 // with a segment. Returns the next unused index.
491 set_section_indexes(unsigned int pshndx);
493 // Set the section addresses when using a script.
495 set_section_addresses_from_script(Symbol_table*);
497 // Return whether SEG1 comes before SEG2 in the output file.
499 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
501 // A mapping used for group signatures.
502 typedef Unordered_map<std::string, bool> Signatures;
504 // Mapping from input section name/type/flags to output section. We
505 // use canonicalized strings here.
507 typedef std::pair<Stringpool::Key,
508 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
513 operator()(const Key& k) const;
516 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
518 // A comparison class for segments.
520 struct Compare_segments
523 operator()(const Output_segment* seg1, const Output_segment* seg2)
524 { return Layout::segment_precedes(seg1, seg2); }
527 // A reference to the options on the command line.
528 const General_options& options_;
529 // Information set by scripts or by command line options.
530 Script_options* script_options_;
531 // The output section names.
532 Stringpool namepool_;
533 // The output symbol names.
535 // The dynamic strings, if needed.
537 // The list of group sections and linkonce sections which we have seen.
538 Signatures signatures_;
539 // The mapping from input section name/type/flags to output sections.
540 Section_name_map section_name_map_;
541 // The list of output segments.
542 Segment_list segment_list_;
543 // The list of output sections.
544 Section_list section_list_;
545 // The list of output sections which are not attached to any output
547 Section_list unattached_section_list_;
548 // The list of unattached Output_data objects which require special
549 // handling because they are not Output_sections.
550 Data_list special_output_list_;
551 // The section headers.
552 Output_section_headers* section_headers_;
553 // A pointer to the PT_TLS segment if there is one.
554 Output_segment* tls_segment_;
555 // The SHT_SYMTAB output section.
556 Output_section* symtab_section_;
557 // The SHT_DYNSYM output section if there is one.
558 Output_section* dynsym_section_;
559 // The SHT_DYNAMIC output section if there is one.
560 Output_section* dynamic_section_;
561 // The dynamic data which goes into dynamic_section_.
562 Output_data_dynamic* dynamic_data_;
563 // The exception frame output section if there is one.
564 Output_section* eh_frame_section_;
565 // The exception frame data for eh_frame_section_.
566 Eh_frame* eh_frame_data_;
567 // The exception frame header output section if there is one.
568 Output_section* eh_frame_hdr_section_;
569 // A list of group sections and their signatures.
570 Group_signatures group_signatures_;
571 // The size of the output file.
572 off_t output_file_size_;
573 // Whether we have seen an object file marked to require an
575 bool input_requires_executable_stack_;
576 // Whether we have seen at least one object file with an executable
578 bool input_with_gnu_stack_note_;
579 // Whether we have seen at least one object file without an
580 // executable stack marker.
581 bool input_without_gnu_stack_note_;
582 // Whether we have seen an object file that uses the static TLS model.
583 bool has_static_tls_;
584 // Whether any sections require postprocessing.
585 bool any_postprocessing_sections_;
588 // This task handles writing out data in output sections which is not
589 // part of an input section, or which requires special handling. When
590 // this is done, it unblocks both output_sections_blocker and
593 class Write_sections_task : public Task
596 Write_sections_task(const Layout* layout, Output_file* of,
597 Task_token* output_sections_blocker,
598 Task_token* final_blocker)
599 : layout_(layout), of_(of),
600 output_sections_blocker_(output_sections_blocker),
601 final_blocker_(final_blocker)
604 // The standard Task methods.
617 { return "Write_sections_task"; }
620 class Write_sections_locker;
622 const Layout* layout_;
624 Task_token* output_sections_blocker_;
625 Task_token* final_blocker_;
628 // This task handles writing out data which is not part of a section
631 class Write_data_task : public Task
634 Write_data_task(const Layout* layout, const Symbol_table* symtab,
635 Output_file* of, Task_token* final_blocker)
636 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
639 // The standard Task methods.
652 { return "Write_data_task"; }
655 const Layout* layout_;
656 const Symbol_table* symtab_;
658 Task_token* final_blocker_;
661 // This task handles writing out the global symbols.
663 class Write_symbols_task : public Task
666 Write_symbols_task(const Symbol_table* symtab,
667 const Input_objects* input_objects,
668 const Stringpool* sympool, const Stringpool* dynpool,
669 Output_file* of, Task_token* final_blocker)
670 : symtab_(symtab), input_objects_(input_objects), sympool_(sympool),
671 dynpool_(dynpool), of_(of), final_blocker_(final_blocker)
674 // The standard Task methods.
687 { return "Write_symbols_task"; }
690 const Symbol_table* symtab_;
691 const Input_objects* input_objects_;
692 const Stringpool* sympool_;
693 const Stringpool* dynpool_;
695 Task_token* final_blocker_;
698 // This task handles writing out data in output sections which can't
699 // be written out until all the input sections have been handled.
700 // This is for sections whose contents is based on the contents of
701 // other output sections.
703 class Write_after_input_sections_task : public Task
706 Write_after_input_sections_task(Layout* layout, Output_file* of,
707 Task_token* input_sections_blocker,
708 Task_token* final_blocker)
709 : layout_(layout), of_(of),
710 input_sections_blocker_(input_sections_blocker),
711 final_blocker_(final_blocker)
714 // The standard Task methods.
727 { return "Write_after_input_sections_task"; }
732 Task_token* input_sections_blocker_;
733 Task_token* final_blocker_;
736 // This task function handles closing the file.
738 class Close_task_runner : public Task_function_runner
741 Close_task_runner(const General_options* options, const Layout* layout,
743 : options_(options), layout_(layout), of_(of)
746 // Run the operation.
748 run(Workqueue*, const Task*);
751 const General_options* options_;
752 const Layout* layout_;
756 // A small helper function to align an address.
759 align_address(uint64_t address, uint64_t addralign)
762 address = (address + addralign - 1) &~ (addralign - 1);
766 } // End namespace gold.
768 #endif // !defined(GOLD_LAYOUT_H)