1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright 2006, 2007 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.
31 #include "workqueue.h"
34 #include "stringpool.h"
39 class General_options;
42 class Output_section_data;
44 class Output_section_headers;
47 class Output_data_dynamic;
51 // This task function handles mapping the input sections to output
52 // sections and laying them out in memory.
54 class Layout_task_runner : public Task_function_runner
57 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
58 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
60 Layout_task_runner(const General_options& options,
61 const Input_objects* input_objects,
64 : options_(options), input_objects_(input_objects), symtab_(symtab),
73 Layout_task_runner(const Layout_task_runner&);
74 Layout_task_runner& operator=(const Layout_task_runner&);
76 const General_options& options_;
77 const Input_objects* input_objects_;
78 Symbol_table* symtab_;
82 // This class handles the details of laying out input sections.
87 Layout(const General_options& options);
89 // Given an input section SHNDX, named NAME, with data in SHDR, from
90 // the object file OBJECT, return the output section where this
91 // input section should go. RELOC_SHNDX is the index of a
92 // relocation section which applies to this section, or 0 if none,
93 // or -1U if more than one. RELOC_TYPE is the type of the
94 // relocation section if there is one. Set *OFFSET to the offset
95 // within the output section.
96 template<int size, bool big_endian>
98 layout(Sized_relobj<size, big_endian> *object, unsigned int shndx,
99 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
100 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);
102 // Like layout, only for exception frame sections. OBJECT is an
103 // object file. SYMBOLS is the contents of the symbol table
104 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
105 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
106 // .eh_frame section in OBJECT. SHDR is the section header.
107 // RELOC_SHNDX is the index of a relocation section which applies to
108 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
109 // is the type of the relocation section if there is one. This
110 // returns the output section, and sets *OFFSET to the offset.
111 template<int size, bool big_endian>
113 layout_eh_frame(Sized_relobj<size, big_endian>* object,
114 const unsigned char* symbols,
116 const unsigned char* symbol_names,
117 off_t symbol_names_size,
119 const elfcpp::Shdr<size, big_endian>& shdr,
120 unsigned int reloc_shndx, unsigned int reloc_type,
123 // Handle a GNU stack note. This is called once per input object
124 // file. SEEN_GNU_STACK is true if the object file has a
125 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
126 // from that section if there was one.
128 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags);
130 // Add an Output_section_data to the layout. This is used for
131 // special sections like the GOT section.
133 add_output_section_data(const char* name, elfcpp::Elf_Word type,
134 elfcpp::Elf_Xword flags,
135 Output_section_data*);
137 // Create dynamic sections if necessary.
139 create_initial_dynamic_sections(const Input_objects*, Symbol_table*);
141 // Define __start and __stop symbols for output sections.
143 define_section_symbols(Symbol_table*, const Target*);
145 // Return the Stringpool used for symbol names.
148 { return &this->sympool_; }
150 // Return the Stringpool used for dynamic symbol names and dynamic
154 { return &this->dynpool_; }
156 // Return whether a section is a .gnu.linkonce section, given the
159 is_linkonce(const char* name)
160 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
162 // Record the signature of a comdat section, and return whether to
163 // include it in the link. The GROUP parameter is true for a
164 // section group signature, false for a signature derived from a
165 // .gnu.linkonce section.
167 add_comdat(const char*, bool group);
169 // Finalize the layout after all the input sections have been added.
171 finalize(const Input_objects*, Symbol_table*);
173 // Return the size of the output file.
175 output_file_size() const
176 { return this->output_file_size_; }
178 // Return the TLS segment. This will return NULL if there isn't
182 { return this->tls_segment_; }
184 // Return the normal symbol table.
186 symtab_section() const
188 gold_assert(this->symtab_section_ != NULL);
189 return this->symtab_section_;
192 // Return the dynamic symbol table.
194 dynsym_section() const
196 gold_assert(this->dynsym_section_ != NULL);
197 return this->dynsym_section_;
200 // Return the dynamic tags.
203 { return this->dynamic_data_; }
205 // Write out the output sections.
207 write_output_sections(Output_file* of) const;
209 // Write out data not associated with an input file or the symbol
212 write_data(const Symbol_table*, Output_file*) const;
214 // Write out output sections which can not be written until all the
215 // input sections are complete.
217 write_sections_after_input_sections(Output_file* of);
219 // Return an output section named NAME, or NULL if there is none.
221 find_output_section(const char* name) const;
223 // Return an output segment of type TYPE, with segment flags SET set
224 // and segment flags CLEAR clear. Return NULL if there is none.
226 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
227 elfcpp::Elf_Word clear) const;
229 // Dump statistical information to stderr.
233 // The list of segments.
235 typedef std::vector<Output_segment*> Segment_list;
237 // The list of sections not attached to a segment.
239 typedef std::vector<Output_section*> Section_list;
241 // The list of information to write out which is not attached to
242 // either a section or a segment.
243 typedef std::vector<Output_data*> Data_list;
246 Layout(const Layout&);
247 Layout& operator=(const Layout&);
249 // Mapping from .gnu.linkonce section names to output section names.
250 struct Linkonce_mapping
257 static const Linkonce_mapping linkonce_mapping[];
258 static const int linkonce_mapping_count;
260 // Create a .note section for gold.
264 // Record whether the stack must be executable.
266 create_executable_stack_info(const Target*);
268 // Find the first read-only PT_LOAD segment, creating one if
271 find_first_load_seg();
273 // Count the local symbols in the regular symbol table and the dynamic
274 // symbol table, and build the respective string pools.
276 count_local_symbols(const Input_objects*);
278 // Create the output sections for the symbol table.
280 create_symtab_sections(const Input_objects*, Symbol_table*, off_t*);
282 // Create the .shstrtab section.
286 // Create the section header table.
288 create_shdrs(off_t*);
290 // Create the dynamic symbol table.
292 create_dynamic_symtab(const Input_objects*, const Target*,
293 Symbol_table*, Output_section** pdynstr,
294 unsigned int* plocal_dynamic_count,
295 std::vector<Symbol*>* pdynamic_symbols,
298 // Assign offsets to each local portion of the dynamic symbol table.
300 assign_local_dynsym_offsets(const Input_objects*);
302 // Finish the .dynamic section and PT_DYNAMIC segment.
304 finish_dynamic_section(const Input_objects*, const Symbol_table*);
306 // Create the .interp section and PT_INTERP segment.
308 create_interp(const Target* target);
310 // Create the version sections.
312 create_version_sections(const Versions*,
314 unsigned int local_symcount,
315 const std::vector<Symbol*>& dynamic_symbols,
316 const Output_section* dynstr);
318 template<int size, bool big_endian>
320 sized_create_version_sections(const Versions* versions,
322 unsigned int local_symcount,
323 const std::vector<Symbol*>& dynamic_symbols,
324 const Output_section* dynstr
327 // Return whether to include this section in the link.
328 template<int size, bool big_endian>
330 include_section(Sized_relobj<size, big_endian>* object, const char* name,
331 const elfcpp::Shdr<size, big_endian>&);
333 // Return the output section name to use given an input section
334 // name. Set *PLEN to the length of the name. *PLEN must be
335 // initialized to the length of NAME.
337 output_section_name(const char* name, size_t* plen);
339 // Return the output section name to use for a linkonce section
340 // name. PLEN is as for output_section_name.
342 linkonce_output_name(const char* name, size_t* plen);
344 // Return the output section for NAME, TYPE and FLAGS.
346 get_output_section(const char* name, Stringpool::Key name_key,
347 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
349 // Create a new Output_section.
351 make_output_section(const char* name, elfcpp::Elf_Word type,
352 elfcpp::Elf_Xword flags);
354 // Set the final file offsets of all the segments.
356 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
358 // Set the final file offsets of all the sections not associated
359 // with a segment. We set section offsets in three passes: the
360 // first handles all allocated sections, the second sections that
361 // can be handled after input-sections are processed, and the last
362 // the late-bound STRTAB sections (probably only shstrtab, which is
363 // the one we care about because it holds section names).
364 enum Section_offset_pass
366 BEFORE_INPUT_SECTIONS_PASS,
367 AFTER_INPUT_SECTIONS_PASS,
368 STRTAB_AFTER_INPUT_SECTIONS_PASS
371 set_section_offsets(off_t, Section_offset_pass pass);
373 // Set the final section indexes of all the sections not associated
374 // with a segment. Returns the next unused index.
376 set_section_indexes(unsigned int pshndx);
378 // Return whether SEG1 comes before SEG2 in the output file.
380 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
382 // Map from section flags to segment flags.
383 static elfcpp::Elf_Word
384 section_flags_to_segment(elfcpp::Elf_Xword flags);
386 // A mapping used for group signatures.
387 typedef Unordered_map<std::string, bool> Signatures;
389 // Mapping from input section name/type/flags to output section. We
390 // use canonicalized strings here.
392 typedef std::pair<Stringpool::Key,
393 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
398 operator()(const Key& k) const;
401 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
403 // A comparison class for segments.
405 struct Compare_segments
408 operator()(const Output_segment* seg1, const Output_segment* seg2)
409 { return Layout::segment_precedes(seg1, seg2); }
412 // A reference to the options on the command line.
413 const General_options& options_;
414 // The output section names.
415 Stringpool namepool_;
416 // The output symbol names.
418 // The dynamic strings, if needed.
420 // The list of group sections and linkonce sections which we have seen.
421 Signatures signatures_;
422 // The mapping from input section name/type/flags to output sections.
423 Section_name_map section_name_map_;
424 // The list of output segments.
425 Segment_list segment_list_;
426 // The list of output sections.
427 Section_list section_list_;
428 // The list of output sections which are not attached to any output
430 Section_list unattached_section_list_;
431 // The list of unattached Output_data objects which require special
432 // handling because they are not Output_sections.
433 Data_list special_output_list_;
434 // The section headers.
435 Output_section_headers* section_headers_;
436 // A pointer to the PT_TLS segment if there is one.
437 Output_segment* tls_segment_;
438 // The SHT_SYMTAB output section.
439 Output_section* symtab_section_;
440 // The SHT_DYNSYM output section if there is one.
441 Output_section* dynsym_section_;
442 // The SHT_DYNAMIC output section if there is one.
443 Output_section* dynamic_section_;
444 // The dynamic data which goes into dynamic_section_.
445 Output_data_dynamic* dynamic_data_;
446 // The exception frame output section if there is one.
447 Output_section* eh_frame_section_;
448 // The exception frame data for eh_frame_section_.
449 Eh_frame* eh_frame_data_;
450 // The exception frame header output section if there is one.
451 Output_section* eh_frame_hdr_section_;
452 // The size of the output file.
453 off_t output_file_size_;
454 // Whether we have seen an object file marked to require an
456 bool input_requires_executable_stack_;
457 // Whether we have seen at least one object file with an executable
459 bool input_with_gnu_stack_note_;
460 // Whether we have seen at least one object file without an
461 // executable stack marker.
462 bool input_without_gnu_stack_note_;
465 // This task handles writing out data in output sections which is not
466 // part of an input section, or which requires special handling. When
467 // this is done, it unblocks both output_sections_blocker and
470 class Write_sections_task : public Task
473 Write_sections_task(const Layout* layout, Output_file* of,
474 Task_token* output_sections_blocker,
475 Task_token* final_blocker)
476 : layout_(layout), of_(of),
477 output_sections_blocker_(output_sections_blocker),
478 final_blocker_(final_blocker)
481 // The standard Task methods.
484 is_runnable(Workqueue*);
494 { return "Write_sections_task"; }
497 class Write_sections_locker;
499 const Layout* layout_;
501 Task_token* output_sections_blocker_;
502 Task_token* final_blocker_;
505 // This task handles writing out data which is not part of a section
508 class Write_data_task : public Task
511 Write_data_task(const Layout* layout, const Symbol_table* symtab,
512 Output_file* of, Task_token* final_blocker)
513 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
516 // The standard Task methods.
519 is_runnable(Workqueue*);
529 { return "Write_data_task"; }
532 const Layout* layout_;
533 const Symbol_table* symtab_;
535 Task_token* final_blocker_;
538 // This task handles writing out the global symbols.
540 class Write_symbols_task : public Task
543 Write_symbols_task(const Symbol_table* symtab,
544 const Input_objects* input_objects,
545 const Stringpool* sympool, const Stringpool* dynpool,
546 Output_file* of, Task_token* final_blocker)
547 : symtab_(symtab), input_objects_(input_objects), sympool_(sympool),
548 dynpool_(dynpool), of_(of), final_blocker_(final_blocker)
551 // The standard Task methods.
554 is_runnable(Workqueue*);
564 { return "Write_symbols_task"; }
567 const Symbol_table* symtab_;
568 const Input_objects* input_objects_;
569 const Stringpool* sympool_;
570 const Stringpool* dynpool_;
572 Task_token* final_blocker_;
575 // This task handles writing out data in output sections which can't
576 // be written out until all the input sections have been handled.
577 // This is for sections whose contents is based on the contents of
578 // other output sections.
580 class Write_after_input_sections_task : public Task
583 Write_after_input_sections_task(Layout* layout, Output_file* of,
584 Task_token* input_sections_blocker,
585 Task_token* final_blocker)
586 : layout_(layout), of_(of),
587 input_sections_blocker_(input_sections_blocker),
588 final_blocker_(final_blocker)
591 // The standard Task methods.
594 is_runnable(Workqueue*);
604 { return "Write_after_input_sections_task"; }
607 class Write_sections_locker;
611 Task_token* input_sections_blocker_;
612 Task_token* final_blocker_;
615 // This task function handles closing the file.
617 class Close_task_runner : public Task_function_runner
620 Close_task_runner(Output_file* of)
624 // Run the operation.
632 // A small helper function to align an address.
635 align_address(uint64_t address, uint64_t addralign)
638 address = (address + addralign - 1) &~ (addralign - 1);
642 } // End namespace gold.
644 #endif // !defined(GOLD_LAYOUT_H)