1 // layout.cc -- lay out output file sections for gold
18 // Layout_task_runner methods.
20 // Lay out the sections. This is called after all the input objects
24 Layout_task_runner::run(Workqueue* workqueue)
26 off_t file_size = this->layout_->finalize(this->input_objects_,
29 // Now we know the final size of the output file and we know where
30 // each piece of information goes.
31 Output_file* of = new Output_file(this->options_);
34 // Queue up the final set of tasks.
35 gold::queue_final_tasks(this->options_, this->input_objects_,
36 this->symtab_, this->layout_, workqueue, of);
41 Layout::Layout(const General_options& options)
42 : options_(options), namepool_(), sympool_(), dynpool_(), signatures_(),
43 section_name_map_(), segment_list_(), section_list_(),
44 unattached_section_list_(), special_output_list_(),
45 tls_segment_(NULL), symtab_section_(NULL),
46 dynsym_section_(NULL), dynamic_section_(NULL), dynamic_data_(NULL)
48 // Make space for more than enough segments for a typical file.
49 // This is just for efficiency--it's OK if we wind up needing more.
50 this->segment_list_.reserve(12);
52 // We expect three unattached Output_data objects: the file header,
53 // the segment headers, and the section headers.
54 this->special_output_list_.reserve(3);
57 // Hash a key we use to look up an output section mapping.
60 Layout::Hash_key::operator()(const Layout::Key& k) const
62 return k.first + k.second.first + k.second.second;
65 // Whether to include this section in the link.
67 template<int size, bool big_endian>
69 Layout::include_section(Object*, const char*,
70 const elfcpp::Shdr<size, big_endian>& shdr)
72 // Some section types are never linked. Some are only linked when
73 // doing a relocateable link.
74 switch (shdr.get_sh_type())
76 case elfcpp::SHT_NULL:
77 case elfcpp::SHT_SYMTAB:
78 case elfcpp::SHT_DYNSYM:
79 case elfcpp::SHT_STRTAB:
80 case elfcpp::SHT_HASH:
81 case elfcpp::SHT_DYNAMIC:
82 case elfcpp::SHT_SYMTAB_SHNDX:
85 case elfcpp::SHT_RELA:
87 case elfcpp::SHT_GROUP:
88 return this->options_.is_relocatable();
91 // FIXME: Handle stripping debug sections here.
96 // Return an output section named NAME, or NULL if there is none.
99 Layout::find_output_section(const char* name) const
101 for (Section_name_map::const_iterator p = this->section_name_map_.begin();
102 p != this->section_name_map_.end();
104 if (strcmp(p->second->name(), name) == 0)
109 // Return an output segment of type TYPE, with segment flags SET set
110 // and segment flags CLEAR clear. Return NULL if there is none.
113 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
114 elfcpp::Elf_Word clear) const
116 for (Segment_list::const_iterator p = this->segment_list_.begin();
117 p != this->segment_list_.end();
119 if (static_cast<elfcpp::PT>((*p)->type()) == type
120 && ((*p)->flags() & set) == set
121 && ((*p)->flags() & clear) == 0)
126 // Return the output section to use for section NAME with type TYPE
127 // and section flags FLAGS.
130 Layout::get_output_section(const char* name, Stringpool::Key name_key,
131 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
133 // We should ignore some flags.
134 flags &= ~ (elfcpp::SHF_INFO_LINK
135 | elfcpp::SHF_LINK_ORDER
138 | elfcpp::SHF_STRINGS);
140 const Key key(name_key, std::make_pair(type, flags));
141 const std::pair<Key, Output_section*> v(key, NULL);
142 std::pair<Section_name_map::iterator, bool> ins(
143 this->section_name_map_.insert(v));
146 return ins.first->second;
149 // This is the first time we've seen this name/type/flags
151 Output_section* os = this->make_output_section(name, type, flags);
152 ins.first->second = os;
157 // Return the output section to use for input section SHNDX, with name
158 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
159 // offset of this input section without the output section.
161 template<int size, bool big_endian>
163 Layout::layout(Relobj* object, unsigned int shndx, const char* name,
164 const elfcpp::Shdr<size, big_endian>& shdr, off_t* off)
166 if (!this->include_section(object, name, shdr))
169 // If we are not doing a relocateable link, choose the name to use
170 // for the output section.
171 size_t len = strlen(name);
172 if (!this->options_.is_relocatable())
173 name = Layout::output_section_name(name, &len);
175 // FIXME: Handle SHF_OS_NONCONFORMING here.
177 // Canonicalize the section name.
178 Stringpool::Key name_key;
179 name = this->namepool_.add(name, len, &name_key);
181 // Find the output section. The output section is selected based on
182 // the section name, type, and flags.
183 Output_section* os = this->get_output_section(name, name_key,
185 shdr.get_sh_flags());
187 // FIXME: Handle SHF_LINK_ORDER somewhere.
189 *off = os->add_input_section(object, shndx, name, shdr);
194 // Add POSD to an output section using NAME, TYPE, and FLAGS.
197 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
198 elfcpp::Elf_Xword flags,
199 Output_section_data* posd)
201 // Canonicalize the name.
202 Stringpool::Key name_key;
203 name = this->namepool_.add(name, &name_key);
205 Output_section* os = this->get_output_section(name, name_key, type, flags);
206 os->add_output_section_data(posd);
209 // Map section flags to segment flags.
212 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
214 elfcpp::Elf_Word ret = elfcpp::PF_R;
215 if ((flags & elfcpp::SHF_WRITE) != 0)
217 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
222 // Make a new Output_section, and attach it to segments as
226 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
227 elfcpp::Elf_Xword flags)
229 Output_section* os = new Output_section(name, type, flags);
230 this->section_list_.push_back(os);
232 if ((flags & elfcpp::SHF_ALLOC) == 0)
233 this->unattached_section_list_.push_back(os);
236 // This output section goes into a PT_LOAD segment.
238 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
240 // The only thing we really care about for PT_LOAD segments is
241 // whether or not they are writable, so that is how we search
242 // for them. People who need segments sorted on some other
243 // basis will have to wait until we implement a mechanism for
244 // them to describe the segments they want.
246 Segment_list::const_iterator p;
247 for (p = this->segment_list_.begin();
248 p != this->segment_list_.end();
251 if ((*p)->type() == elfcpp::PT_LOAD
252 && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
254 (*p)->add_output_section(os, seg_flags);
259 if (p == this->segment_list_.end())
261 Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
263 this->segment_list_.push_back(oseg);
264 oseg->add_output_section(os, seg_flags);
267 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
269 if (type == elfcpp::SHT_NOTE)
271 // See if we already have an equivalent PT_NOTE segment.
272 for (p = this->segment_list_.begin();
273 p != segment_list_.end();
276 if ((*p)->type() == elfcpp::PT_NOTE
277 && (((*p)->flags() & elfcpp::PF_W)
278 == (seg_flags & elfcpp::PF_W)))
280 (*p)->add_output_section(os, seg_flags);
285 if (p == this->segment_list_.end())
287 Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
289 this->segment_list_.push_back(oseg);
290 oseg->add_output_section(os, seg_flags);
294 // If we see a loadable SHF_TLS section, we create a PT_TLS
295 // segment. There can only be one such segment.
296 if ((flags & elfcpp::SHF_TLS) != 0)
298 if (this->tls_segment_ == NULL)
300 this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
302 this->segment_list_.push_back(this->tls_segment_);
304 this->tls_segment_->add_output_section(os, seg_flags);
311 // Create the dynamic sections which are needed before we read the
315 Layout::create_initial_dynamic_sections(const Input_objects* input_objects,
316 Symbol_table* symtab)
318 if (!input_objects->any_dynamic())
321 const char* dynamic_name = this->namepool_.add(".dynamic", NULL);
322 this->dynamic_section_ = this->make_output_section(dynamic_name,
325 | elfcpp::SHF_WRITE));
327 symtab->define_in_output_data(input_objects->target(), "_DYNAMIC", NULL,
328 this->dynamic_section_, 0, 0,
329 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
330 elfcpp::STV_HIDDEN, 0, false, false);
332 this->dynamic_data_ = new Output_data_dynamic(input_objects->target(),
335 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
338 // Find the first read-only PT_LOAD segment, creating one if
342 Layout::find_first_load_seg()
344 for (Segment_list::const_iterator p = this->segment_list_.begin();
345 p != this->segment_list_.end();
348 if ((*p)->type() == elfcpp::PT_LOAD
349 && ((*p)->flags() & elfcpp::PF_R) != 0
350 && ((*p)->flags() & elfcpp::PF_W) == 0)
354 Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
355 this->segment_list_.push_back(load_seg);
359 // Finalize the layout. When this is called, we have created all the
360 // output sections and all the output segments which are based on
361 // input sections. We have several things to do, and we have to do
362 // them in the right order, so that we get the right results correctly
365 // 1) Finalize the list of output segments and create the segment
368 // 2) Finalize the dynamic symbol table and associated sections.
370 // 3) Determine the final file offset of all the output segments.
372 // 4) Determine the final file offset of all the SHF_ALLOC output
375 // 5) Create the symbol table sections and the section name table
378 // 6) Finalize the symbol table: set symbol values to their final
379 // value and make a final determination of which symbols are going
380 // into the output symbol table.
382 // 7) Create the section table header.
384 // 8) Determine the final file offset of all the output sections which
385 // are not SHF_ALLOC, including the section table header.
387 // 9) Finalize the ELF file header.
389 // This function returns the size of the output file.
392 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab)
394 Target* const target = input_objects->target();
395 const int size = target->get_size();
397 target->finalize_sections(&this->options_, this);
399 Output_segment* phdr_seg = NULL;
400 if (input_objects->any_dynamic())
402 // There was a dynamic object in the link. We need to create
403 // some information for the dynamic linker.
405 // Create the PT_PHDR segment which will hold the program
407 phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
408 this->segment_list_.push_back(phdr_seg);
410 // Create the dynamic symbol table, including the hash table.
411 Output_section* dynstr;
412 std::vector<Symbol*> dynamic_symbols;
413 unsigned int local_dynamic_count;
415 this->create_dynamic_symtab(target, symtab, &dynstr,
416 &local_dynamic_count, &dynamic_symbols,
419 // Create the .interp section to hold the name of the
420 // interpreter, and put it in a PT_INTERP segment.
421 this->create_interp(target);
423 // Finish the .dynamic section to hold the dynamic data, and put
424 // it in a PT_DYNAMIC segment.
425 this->finish_dynamic_section(input_objects, symtab);
427 // We should have added everything we need to the dynamic string
429 this->dynpool_.set_string_offsets();
431 // Create the version sections. We can't do this until the
432 // dynamic string table is complete.
433 this->create_version_sections(target, &versions, local_dynamic_count,
434 dynamic_symbols, dynstr);
437 // FIXME: Handle PT_GNU_STACK.
439 Output_segment* load_seg = this->find_first_load_seg();
441 // Lay out the segment headers.
442 bool big_endian = target->is_big_endian();
443 Output_segment_headers* segment_headers;
444 segment_headers = new Output_segment_headers(size, big_endian,
445 this->segment_list_);
446 load_seg->add_initial_output_data(segment_headers);
447 this->special_output_list_.push_back(segment_headers);
448 if (phdr_seg != NULL)
449 phdr_seg->add_initial_output_data(segment_headers);
451 // Lay out the file header.
452 Output_file_header* file_header;
453 file_header = new Output_file_header(size,
459 load_seg->add_initial_output_data(file_header);
460 this->special_output_list_.push_back(file_header);
462 // We set the output section indexes in set_segment_offsets and
463 // set_section_offsets.
464 unsigned int shndx = 1;
466 // Set the file offsets of all the segments, and all the sections
468 off_t off = this->set_segment_offsets(target, load_seg, &shndx);
470 // Create the symbol table sections.
471 this->create_symtab_sections(size, input_objects, symtab, &off);
473 // Create the .shstrtab section.
474 Output_section* shstrtab_section = this->create_shstrtab();
476 // Set the file offsets of all the sections not associated with
478 off = this->set_section_offsets(off, &shndx);
480 // Create the section table header.
481 Output_section_headers* oshdrs = this->create_shdrs(size, big_endian, &off);
483 file_header->set_section_info(oshdrs, shstrtab_section);
485 // Now we know exactly where everything goes in the output file.
486 Output_data::layout_complete();
491 // Return whether SEG1 should be before SEG2 in the output file. This
492 // is based entirely on the segment type and flags. When this is
493 // called the segment addresses has normally not yet been set.
496 Layout::segment_precedes(const Output_segment* seg1,
497 const Output_segment* seg2)
499 elfcpp::Elf_Word type1 = seg1->type();
500 elfcpp::Elf_Word type2 = seg2->type();
502 // The single PT_PHDR segment is required to precede any loadable
503 // segment. We simply make it always first.
504 if (type1 == elfcpp::PT_PHDR)
506 gold_assert(type2 != elfcpp::PT_PHDR);
509 if (type2 == elfcpp::PT_PHDR)
512 // The single PT_INTERP segment is required to precede any loadable
513 // segment. We simply make it always second.
514 if (type1 == elfcpp::PT_INTERP)
516 gold_assert(type2 != elfcpp::PT_INTERP);
519 if (type2 == elfcpp::PT_INTERP)
522 // We then put PT_LOAD segments before any other segments.
523 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
525 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
528 // We put the PT_TLS segment last, because that is where the dynamic
529 // linker expects to find it (this is just for efficiency; other
530 // positions would also work correctly).
531 if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
533 if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
536 const elfcpp::Elf_Word flags1 = seg1->flags();
537 const elfcpp::Elf_Word flags2 = seg2->flags();
539 // The order of non-PT_LOAD segments is unimportant. We simply sort
540 // by the numeric segment type and flags values. There should not
541 // be more than one segment with the same type and flags.
542 if (type1 != elfcpp::PT_LOAD)
545 return type1 < type2;
546 gold_assert(flags1 != flags2);
547 return flags1 < flags2;
550 // We sort PT_LOAD segments based on the flags. Readonly segments
551 // come before writable segments. Then executable segments come
552 // before non-executable segments. Then the unlikely case of a
553 // non-readable segment comes before the normal case of a readable
554 // segment. If there are multiple segments with the same type and
555 // flags, we require that the address be set, and we sort by
556 // virtual address and then physical address.
557 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
558 return (flags1 & elfcpp::PF_W) == 0;
559 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
560 return (flags1 & elfcpp::PF_X) != 0;
561 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
562 return (flags1 & elfcpp::PF_R) == 0;
564 uint64_t vaddr1 = seg1->vaddr();
565 uint64_t vaddr2 = seg2->vaddr();
566 if (vaddr1 != vaddr2)
567 return vaddr1 < vaddr2;
569 uint64_t paddr1 = seg1->paddr();
570 uint64_t paddr2 = seg2->paddr();
571 gold_assert(paddr1 != paddr2);
572 return paddr1 < paddr2;
575 // Set the file offsets of all the segments, and all the sections they
576 // contain. They have all been created. LOAD_SEG must be be laid out
577 // first. Return the offset of the data to follow.
580 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
581 unsigned int *pshndx)
583 // Sort them into the final order.
584 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
585 Layout::Compare_segments());
587 // Find the PT_LOAD segments, and set their addresses and offsets
588 // and their section's addresses and offsets.
589 uint64_t addr = target->text_segment_address();
591 bool was_readonly = false;
592 for (Segment_list::iterator p = this->segment_list_.begin();
593 p != this->segment_list_.end();
596 if ((*p)->type() == elfcpp::PT_LOAD)
598 if (load_seg != NULL && load_seg != *p)
602 // If the last segment was readonly, and this one is not,
603 // then skip the address forward one page, maintaining the
604 // same position within the page. This lets us store both
605 // segments overlapping on a single page in the file, but
606 // the loader will put them on different pages in memory.
608 uint64_t orig_addr = addr;
609 uint64_t orig_off = off;
611 uint64_t aligned_addr = addr;
612 uint64_t abi_pagesize = target->abi_pagesize();
613 if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
615 uint64_t align = (*p)->addralign();
617 addr = align_address(addr, align);
619 if ((addr & (abi_pagesize - 1)) != 0)
620 addr = addr + abi_pagesize;
623 unsigned int shndx_hold = *pshndx;
624 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
625 uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
627 // Now that we know the size of this segment, we may be able
628 // to save a page in memory, at the cost of wasting some
629 // file space, by instead aligning to the start of a new
630 // page. Here we use the real machine page size rather than
631 // the ABI mandated page size.
633 if (aligned_addr != addr)
635 uint64_t common_pagesize = target->common_pagesize();
636 uint64_t first_off = (common_pagesize
638 & (common_pagesize - 1)));
639 uint64_t last_off = new_addr & (common_pagesize - 1);
642 && ((aligned_addr & ~ (common_pagesize - 1))
643 != (new_addr & ~ (common_pagesize - 1)))
644 && first_off + last_off <= common_pagesize)
646 *pshndx = shndx_hold;
647 addr = align_address(aligned_addr, common_pagesize);
648 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
649 new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
655 if (((*p)->flags() & elfcpp::PF_W) == 0)
660 // Handle the non-PT_LOAD segments, setting their offsets from their
661 // section's offsets.
662 for (Segment_list::iterator p = this->segment_list_.begin();
663 p != this->segment_list_.end();
666 if ((*p)->type() != elfcpp::PT_LOAD)
673 // Set the file offset of all the sections not associated with a
677 Layout::set_section_offsets(off_t off, unsigned int* pshndx)
679 for (Section_list::iterator p = this->unattached_section_list_.begin();
680 p != this->unattached_section_list_.end();
683 (*p)->set_out_shndx(*pshndx);
685 if ((*p)->offset() != -1)
687 off = align_address(off, (*p)->addralign());
688 (*p)->set_address(0, off);
689 off += (*p)->data_size();
694 // Create the symbol table sections. Here we also set the final
695 // values of the symbols. At this point all the loadable sections are
699 Layout::create_symtab_sections(int size, const Input_objects* input_objects,
700 Symbol_table* symtab,
707 symsize = elfcpp::Elf_sizes<32>::sym_size;
712 symsize = elfcpp::Elf_sizes<64>::sym_size;
719 off = align_address(off, align);
720 off_t startoff = off;
722 // Save space for the dummy symbol at the start of the section. We
723 // never bother to write this out--it will just be left as zero.
725 unsigned int local_symbol_index = 1;
727 // Add STT_SECTION symbols for each Output section which needs one.
728 for (Section_list::iterator p = this->section_list_.begin();
729 p != this->section_list_.end();
732 if (!(*p)->needs_symtab_index())
733 (*p)->set_symtab_index(-1U);
736 (*p)->set_symtab_index(local_symbol_index);
737 ++local_symbol_index;
742 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
743 p != input_objects->relobj_end();
746 Task_lock_obj<Object> tlo(**p);
747 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
750 off += (index - local_symbol_index) * symsize;
751 local_symbol_index = index;
754 unsigned int local_symcount = local_symbol_index;
755 gold_assert(local_symcount * symsize == off - startoff);
758 size_t dyn_global_index;
760 if (this->dynsym_section_ == NULL)
763 dyn_global_index = 0;
768 dyn_global_index = this->dynsym_section_->info();
769 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
770 dynoff = this->dynsym_section_->offset() + locsize;
771 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
772 gold_assert(dyncount * symsize
773 == this->dynsym_section_->data_size() - locsize);
776 off = symtab->finalize(local_symcount, off, dynoff, dyn_global_index,
777 dyncount, &this->sympool_);
779 this->sympool_.set_string_offsets();
781 const char* symtab_name = this->namepool_.add(".symtab", NULL);
782 Output_section* osymtab = this->make_output_section(symtab_name,
785 this->symtab_section_ = osymtab;
787 Output_section_data* pos = new Output_data_space(off - startoff,
789 osymtab->add_output_section_data(pos);
791 const char* strtab_name = this->namepool_.add(".strtab", NULL);
792 Output_section* ostrtab = this->make_output_section(strtab_name,
796 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
797 ostrtab->add_output_section_data(pstr);
799 osymtab->set_address(0, startoff);
800 osymtab->set_link_section(ostrtab);
801 osymtab->set_info(local_symcount);
802 osymtab->set_entsize(symsize);
807 // Create the .shstrtab section, which holds the names of the
808 // sections. At the time this is called, we have created all the
809 // output sections except .shstrtab itself.
812 Layout::create_shstrtab()
814 // FIXME: We don't need to create a .shstrtab section if we are
815 // stripping everything.
817 const char* name = this->namepool_.add(".shstrtab", NULL);
819 this->namepool_.set_string_offsets();
821 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0);
823 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
824 os->add_output_section_data(posd);
829 // Create the section headers. SIZE is 32 or 64. OFF is the file
832 Output_section_headers*
833 Layout::create_shdrs(int size, bool big_endian, off_t* poff)
835 Output_section_headers* oshdrs;
836 oshdrs = new Output_section_headers(size, big_endian, this,
837 &this->segment_list_,
838 &this->unattached_section_list_,
840 off_t off = align_address(*poff, oshdrs->addralign());
841 oshdrs->set_address(0, off);
842 off += oshdrs->data_size();
844 this->special_output_list_.push_back(oshdrs);
848 // Create the dynamic symbol table.
851 Layout::create_dynamic_symtab(const Target* target, Symbol_table* symtab,
852 Output_section **pdynstr,
853 unsigned int* plocal_dynamic_count,
854 std::vector<Symbol*>* pdynamic_symbols,
857 // Count all the symbols in the dynamic symbol table, and set the
858 // dynamic symbol indexes.
860 // Skip symbol 0, which is always all zeroes.
861 unsigned int index = 1;
863 // Add STT_SECTION symbols for each Output section which needs one.
864 for (Section_list::iterator p = this->section_list_.begin();
865 p != this->section_list_.end();
868 if (!(*p)->needs_dynsym_index())
869 (*p)->set_dynsym_index(-1U);
872 (*p)->set_dynsym_index(index);
877 // FIXME: Some targets apparently require local symbols in the
878 // dynamic symbol table. Here is where we will have to count them,
879 // and set the dynamic symbol indexes, and add the names to
882 unsigned int local_symcount = index;
883 *plocal_dynamic_count = local_symcount;
885 // FIXME: We have to tell set_dynsym_indexes whether the
886 // -E/--export-dynamic option was used.
887 index = symtab->set_dynsym_indexes(&this->options_, target, index,
888 pdynamic_symbols, &this->dynpool_,
893 const int size = target->get_size();
896 symsize = elfcpp::Elf_sizes<32>::sym_size;
901 symsize = elfcpp::Elf_sizes<64>::sym_size;
907 // Create the dynamic symbol table section.
909 const char* dynsym_name = this->namepool_.add(".dynsym", NULL);
910 Output_section* dynsym = this->make_output_section(dynsym_name,
914 Output_section_data* odata = new Output_data_space(index * symsize,
916 dynsym->add_output_section_data(odata);
918 dynsym->set_info(local_symcount);
919 dynsym->set_entsize(symsize);
920 dynsym->set_addralign(align);
922 this->dynsym_section_ = dynsym;
924 Output_data_dynamic* const odyn = this->dynamic_data_;
925 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
926 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
928 // Create the dynamic string table section.
930 const char* dynstr_name = this->namepool_.add(".dynstr", NULL);
931 Output_section* dynstr = this->make_output_section(dynstr_name,
935 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
936 dynstr->add_output_section_data(strdata);
938 dynsym->set_link_section(dynstr);
939 this->dynamic_section_->set_link_section(dynstr);
941 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
942 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
946 // Create the hash tables.
948 // FIXME: We need an option to create a GNU hash table.
950 unsigned char* phash;
951 unsigned int hashlen;
952 Dynobj::create_elf_hash_table(target, *pdynamic_symbols, local_symcount,
955 const char* hash_name = this->namepool_.add(".hash", NULL);
956 Output_section* hashsec = this->make_output_section(hash_name,
960 Output_section_data* hashdata = new Output_data_const_buffer(phash,
963 hashsec->add_output_section_data(hashdata);
965 hashsec->set_link_section(dynsym);
966 hashsec->set_entsize(4);
968 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
971 // Create the version sections.
974 Layout::create_version_sections(const Target* target, const Versions* versions,
975 unsigned int local_symcount,
976 const std::vector<Symbol*>& dynamic_symbols,
977 const Output_section* dynstr)
979 if (!versions->any_defs() && !versions->any_needs())
982 if (target->get_size() == 32)
984 if (target->is_big_endian())
985 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(32, true)(
986 versions, local_symcount, dynamic_symbols, dynstr
987 SELECT_SIZE_ENDIAN(32, true));
989 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(32, false)(
990 versions, local_symcount, dynamic_symbols, dynstr
991 SELECT_SIZE_ENDIAN(32, false));
993 else if (target->get_size() == 64)
995 if (target->is_big_endian())
996 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(64, true)(
997 versions, local_symcount, dynamic_symbols, dynstr
998 SELECT_SIZE_ENDIAN(64, true));
1000 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(64, false)(
1001 versions, local_symcount, dynamic_symbols, dynstr
1002 SELECT_SIZE_ENDIAN(64, false));
1008 // Create the version sections, sized version.
1010 template<int size, bool big_endian>
1012 Layout::sized_create_version_sections(
1013 const Versions* versions,
1014 unsigned int local_symcount,
1015 const std::vector<Symbol*>& dynamic_symbols,
1016 const Output_section* dynstr
1019 const char* vname = this->namepool_.add(".gnu.version", NULL);
1020 Output_section* vsec = this->make_output_section(vname,
1021 elfcpp::SHT_GNU_versym,
1024 unsigned char* vbuf;
1026 versions->symbol_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1027 &this->dynpool_, local_symcount, dynamic_symbols, &vbuf, &vsize
1028 SELECT_SIZE_ENDIAN(size, big_endian));
1030 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2);
1032 vsec->add_output_section_data(vdata);
1033 vsec->set_entsize(2);
1034 vsec->set_link_section(this->dynsym_section_);
1036 Output_data_dynamic* const odyn = this->dynamic_data_;
1037 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
1039 if (versions->any_defs())
1041 const char* vdname = this->namepool_.add(".gnu.version_d", NULL);
1042 Output_section *vdsec;
1043 vdsec = this->make_output_section(vdname, elfcpp::SHT_GNU_verdef,
1046 unsigned char* vdbuf;
1047 unsigned int vdsize;
1048 unsigned int vdentries;
1049 versions->def_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1050 &this->dynpool_, &vdbuf, &vdsize, &vdentries
1051 SELECT_SIZE_ENDIAN(size, big_endian));
1053 Output_section_data* vddata = new Output_data_const_buffer(vdbuf,
1057 vdsec->add_output_section_data(vddata);
1058 vdsec->set_link_section(dynstr);
1059 vdsec->set_info(vdentries);
1061 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
1062 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
1065 if (versions->any_needs())
1067 const char* vnname = this->namepool_.add(".gnu.version_r", NULL);
1068 Output_section* vnsec;
1069 vnsec = this->make_output_section(vnname, elfcpp::SHT_GNU_verneed,
1072 unsigned char* vnbuf;
1073 unsigned int vnsize;
1074 unsigned int vnentries;
1075 versions->need_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)
1076 (&this->dynpool_, &vnbuf, &vnsize, &vnentries
1077 SELECT_SIZE_ENDIAN(size, big_endian));
1079 Output_section_data* vndata = new Output_data_const_buffer(vnbuf,
1083 vnsec->add_output_section_data(vndata);
1084 vnsec->set_link_section(dynstr);
1085 vnsec->set_info(vnentries);
1087 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
1088 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
1092 // Create the .interp section and PT_INTERP segment.
1095 Layout::create_interp(const Target* target)
1097 const char* interp = this->options_.dynamic_linker();
1100 interp = target->dynamic_linker();
1101 gold_assert(interp != NULL);
1104 size_t len = strlen(interp) + 1;
1106 Output_section_data* odata = new Output_data_const(interp, len, 1);
1108 const char* interp_name = this->namepool_.add(".interp", NULL);
1109 Output_section* osec = this->make_output_section(interp_name,
1110 elfcpp::SHT_PROGBITS,
1112 osec->add_output_section_data(odata);
1114 Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
1115 this->segment_list_.push_back(oseg);
1116 oseg->add_initial_output_section(osec, elfcpp::PF_R);
1119 // Finish the .dynamic section and PT_DYNAMIC segment.
1122 Layout::finish_dynamic_section(const Input_objects* input_objects,
1123 const Symbol_table* symtab)
1125 Output_segment* oseg = new Output_segment(elfcpp::PT_DYNAMIC,
1126 elfcpp::PF_R | elfcpp::PF_W);
1127 this->segment_list_.push_back(oseg);
1128 oseg->add_initial_output_section(this->dynamic_section_,
1129 elfcpp::PF_R | elfcpp::PF_W);
1131 Output_data_dynamic* const odyn = this->dynamic_data_;
1133 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
1134 p != input_objects->dynobj_end();
1137 // FIXME: Handle --as-needed.
1138 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
1141 // FIXME: Support --init and --fini.
1142 Symbol* sym = symtab->lookup("_init");
1143 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1144 odyn->add_symbol(elfcpp::DT_INIT, sym);
1146 sym = symtab->lookup("_fini");
1147 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1148 odyn->add_symbol(elfcpp::DT_FINI, sym);
1150 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1153 // The mapping of .gnu.linkonce section names to real section names.
1155 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1156 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
1158 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1159 MAPPING_INIT("t", ".text"),
1160 MAPPING_INIT("r", ".rodata"),
1161 MAPPING_INIT("d", ".data"),
1162 MAPPING_INIT("b", ".bss"),
1163 MAPPING_INIT("s", ".sdata"),
1164 MAPPING_INIT("sb", ".sbss"),
1165 MAPPING_INIT("s2", ".sdata2"),
1166 MAPPING_INIT("sb2", ".sbss2"),
1167 MAPPING_INIT("wi", ".debug_info"),
1168 MAPPING_INIT("td", ".tdata"),
1169 MAPPING_INIT("tb", ".tbss"),
1170 MAPPING_INIT("lr", ".lrodata"),
1171 MAPPING_INIT("l", ".ldata"),
1172 MAPPING_INIT("lb", ".lbss"),
1176 const int Layout::linkonce_mapping_count =
1177 sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
1179 // Return the name of the output section to use for a .gnu.linkonce
1180 // section. This is based on the default ELF linker script of the old
1181 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1182 // to ".text". Set *PLEN to the length of the name. *PLEN is
1183 // initialized to the length of NAME.
1186 Layout::linkonce_output_name(const char* name, size_t *plen)
1188 const char* s = name + sizeof(".gnu.linkonce") - 1;
1192 const Linkonce_mapping* plm = linkonce_mapping;
1193 for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
1195 if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
1204 // Choose the output section name to use given an input section name.
1205 // Set *PLEN to the length of the name. *PLEN is initialized to the
1209 Layout::output_section_name(const char* name, size_t* plen)
1211 if (Layout::is_linkonce(name))
1213 // .gnu.linkonce sections are laid out as though they were named
1214 // for the sections are placed into.
1215 return Layout::linkonce_output_name(name, plen);
1218 // If the section name has no '.', or only an initial '.', we use
1219 // the name unchanged (i.e., ".text" is unchanged).
1221 // Otherwise, if the section name does not include ".rel", we drop
1222 // the last '.' and everything that follows (i.e., ".text.XXX"
1223 // becomes ".text").
1225 // Otherwise, if the section name has zero or one '.' after the
1226 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1229 // Otherwise, we drop the last '.' and everything that follows
1230 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1232 const char* s = name;
1235 const char* sdot = strchr(s, '.');
1239 const char* srel = strstr(s, ".rel");
1242 *plen = sdot - name;
1246 sdot = strchr(srel + 1, '.');
1249 sdot = strchr(sdot + 1, '.');
1253 *plen = sdot - name;
1257 // Record the signature of a comdat section, and return whether to
1258 // include it in the link. If GROUP is true, this is a regular
1259 // section group. If GROUP is false, this is a group signature
1260 // derived from the name of a linkonce section. We want linkonce
1261 // signatures and group signatures to block each other, but we don't
1262 // want a linkonce signature to block another linkonce signature.
1265 Layout::add_comdat(const char* signature, bool group)
1267 std::string sig(signature);
1268 std::pair<Signatures::iterator, bool> ins(
1269 this->signatures_.insert(std::make_pair(sig, group)));
1273 // This is the first time we've seen this signature.
1277 if (ins.first->second)
1279 // We've already seen a real section group with this signature.
1284 // This is a real section group, and we've already seen a
1285 // linkonce section with tihs signature. Record that we've seen
1286 // a section group, and don't include this section group.
1287 ins.first->second = true;
1292 // We've already seen a linkonce section and this is a linkonce
1293 // section. These don't block each other--this may be the same
1294 // symbol name with different section types.
1299 // Write out data not associated with a section or the symbol table.
1302 Layout::write_data(const Symbol_table* symtab, const Target* target,
1303 Output_file* of) const
1305 const Output_section* symtab_section = this->symtab_section_;
1306 for (Section_list::const_iterator p = this->section_list_.begin();
1307 p != this->section_list_.end();
1310 if ((*p)->needs_symtab_index())
1312 gold_assert(symtab_section != NULL);
1313 unsigned int index = (*p)->symtab_index();
1314 gold_assert(index > 0 && index != -1U);
1315 off_t off = (symtab_section->offset()
1316 + index * symtab_section->entsize());
1317 symtab->write_section_symbol(target, *p, of, off);
1321 const Output_section* dynsym_section = this->dynsym_section_;
1322 for (Section_list::const_iterator p = this->section_list_.begin();
1323 p != this->section_list_.end();
1326 if ((*p)->needs_dynsym_index())
1328 gold_assert(dynsym_section != NULL);
1329 unsigned int index = (*p)->dynsym_index();
1330 gold_assert(index > 0 && index != -1U);
1331 off_t off = (dynsym_section->offset()
1332 + index * dynsym_section->entsize());
1333 symtab->write_section_symbol(target, *p, of, off);
1337 // Write out the Output_sections. Most won't have anything to
1338 // write, since most of the data will come from input sections which
1339 // are handled elsewhere. But some Output_sections do have
1341 for (Section_list::const_iterator p = this->section_list_.begin();
1342 p != this->section_list_.end();
1346 // Write out the Output_data which are not in an Output_section.
1347 for (Data_list::const_iterator p = this->special_output_list_.begin();
1348 p != this->special_output_list_.end();
1353 // Write_data_task methods.
1355 // We can always run this task.
1357 Task::Is_runnable_type
1358 Write_data_task::is_runnable(Workqueue*)
1363 // We need to unlock FINAL_BLOCKER when finished.
1366 Write_data_task::locks(Workqueue* workqueue)
1368 return new Task_locker_block(*this->final_blocker_, workqueue);
1371 // Run the task--write out the data.
1374 Write_data_task::run(Workqueue*)
1376 this->layout_->write_data(this->symtab_, this->target_, this->of_);
1379 // Write_symbols_task methods.
1381 // We can always run this task.
1383 Task::Is_runnable_type
1384 Write_symbols_task::is_runnable(Workqueue*)
1389 // We need to unlock FINAL_BLOCKER when finished.
1392 Write_symbols_task::locks(Workqueue* workqueue)
1394 return new Task_locker_block(*this->final_blocker_, workqueue);
1397 // Run the task--write out the symbols.
1400 Write_symbols_task::run(Workqueue*)
1402 this->symtab_->write_globals(this->target_, this->sympool_, this->dynpool_,
1406 // Close_task_runner methods.
1408 // Run the task--close the file.
1411 Close_task_runner::run(Workqueue*)
1416 // Instantiate the templates we need. We could use the configure
1417 // script to restrict this to only the ones for implemented targets.
1421 Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name,
1422 const elfcpp::Shdr<32, false>& shdr, off_t*);
1426 Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name,
1427 const elfcpp::Shdr<32, true>& shdr, off_t*);
1431 Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name,
1432 const elfcpp::Shdr<64, false>& shdr, off_t*);
1436 Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name,
1437 const elfcpp::Shdr<64, true>& shdr, off_t*);
1440 } // End namespace gold.