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[binutils.git] / gold / layout.cc
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1 // layout.cc -- lay out output file sections for gold
3 #include "gold.h"
5 #include <cstring>
6 #include <algorithm>
7 #include <iostream>
8 #include <utility>
10 #include "output.h"
11 #include "symtab.h"
12 #include "dynobj.h"
13 #include "layout.h"
15 namespace gold
18 // Layout_task_runner methods.
20 // Lay out the sections. This is called after all the input objects
21 // have been read.
23 void
24 Layout_task_runner::run(Workqueue* workqueue)
26 off_t file_size = this->layout_->finalize(this->input_objects_,
27 this->symtab_);
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_);
32 of->open(file_size);
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);
39 // Layout methods.
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.
59 size_t
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>
68 bool
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:
83 return false;
85 case elfcpp::SHT_RELA:
86 case elfcpp::SHT_REL:
87 case elfcpp::SHT_GROUP:
88 return this->options_.is_relocatable();
90 default:
91 // FIXME: Handle stripping debug sections here.
92 return true;
96 // Return an output section named NAME, or NULL if there is none.
98 Output_section*
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();
103 ++p)
104 if (strcmp(p->second->name(), name) == 0)
105 return p->second;
106 return NULL;
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.
112 Output_segment*
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();
118 ++p)
119 if (static_cast<elfcpp::PT>((*p)->type()) == type
120 && ((*p)->flags() & set) == set
121 && ((*p)->flags() & clear) == 0)
122 return *p;
123 return NULL;
126 // Return the output section to use for section NAME with type TYPE
127 // and section flags FLAGS.
129 Output_section*
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
136 | elfcpp::SHF_GROUP);
138 const Key key(name_key, std::make_pair(type, flags));
139 const std::pair<Key, Output_section*> v(key, NULL);
140 std::pair<Section_name_map::iterator, bool> ins(
141 this->section_name_map_.insert(v));
143 if (!ins.second)
144 return ins.first->second;
145 else
147 // This is the first time we've seen this name/type/flags
148 // combination.
149 Output_section* os = this->make_output_section(name, type, flags);
150 ins.first->second = os;
151 return os;
155 // Return the output section to use for input section SHNDX, with name
156 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
157 // offset of this input section without the output section.
159 template<int size, bool big_endian>
160 Output_section*
161 Layout::layout(Relobj* object, unsigned int shndx, const char* name,
162 const elfcpp::Shdr<size, big_endian>& shdr, off_t* off)
164 if (!this->include_section(object, name, shdr))
165 return NULL;
167 // If we are not doing a relocateable link, choose the name to use
168 // for the output section.
169 size_t len = strlen(name);
170 if (!this->options_.is_relocatable())
171 name = Layout::output_section_name(name, &len);
173 // FIXME: Handle SHF_OS_NONCONFORMING here.
175 // Canonicalize the section name.
176 Stringpool::Key name_key;
177 name = this->namepool_.add(name, len, &name_key);
179 // Find the output section. The output section is selected based on
180 // the section name, type, and flags.
181 Output_section* os = this->get_output_section(name, name_key,
182 shdr.get_sh_type(),
183 shdr.get_sh_flags());
185 // FIXME: Handle SHF_LINK_ORDER somewhere.
187 *off = os->add_input_section(object, shndx, name, shdr);
189 return os;
192 // Add POSD to an output section using NAME, TYPE, and FLAGS.
194 void
195 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
196 elfcpp::Elf_Xword flags,
197 Output_section_data* posd)
199 // Canonicalize the name.
200 Stringpool::Key name_key;
201 name = this->namepool_.add(name, &name_key);
203 Output_section* os = this->get_output_section(name, name_key, type, flags);
204 os->add_output_section_data(posd);
207 // Map section flags to segment flags.
209 elfcpp::Elf_Word
210 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
212 elfcpp::Elf_Word ret = elfcpp::PF_R;
213 if ((flags & elfcpp::SHF_WRITE) != 0)
214 ret |= elfcpp::PF_W;
215 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
216 ret |= elfcpp::PF_X;
217 return ret;
220 // Make a new Output_section, and attach it to segments as
221 // appropriate.
223 Output_section*
224 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
225 elfcpp::Elf_Xword flags)
227 Output_section* os = new Output_section(name, type, flags, true);
228 this->section_list_.push_back(os);
230 if ((flags & elfcpp::SHF_ALLOC) == 0)
231 this->unattached_section_list_.push_back(os);
232 else
234 // This output section goes into a PT_LOAD segment.
236 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
238 // The only thing we really care about for PT_LOAD segments is
239 // whether or not they are writable, so that is how we search
240 // for them. People who need segments sorted on some other
241 // basis will have to wait until we implement a mechanism for
242 // them to describe the segments they want.
244 Segment_list::const_iterator p;
245 for (p = this->segment_list_.begin();
246 p != this->segment_list_.end();
247 ++p)
249 if ((*p)->type() == elfcpp::PT_LOAD
250 && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
252 (*p)->add_output_section(os, seg_flags);
253 break;
257 if (p == this->segment_list_.end())
259 Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
260 seg_flags);
261 this->segment_list_.push_back(oseg);
262 oseg->add_output_section(os, seg_flags);
265 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
266 // segment.
267 if (type == elfcpp::SHT_NOTE)
269 // See if we already have an equivalent PT_NOTE segment.
270 for (p = this->segment_list_.begin();
271 p != segment_list_.end();
272 ++p)
274 if ((*p)->type() == elfcpp::PT_NOTE
275 && (((*p)->flags() & elfcpp::PF_W)
276 == (seg_flags & elfcpp::PF_W)))
278 (*p)->add_output_section(os, seg_flags);
279 break;
283 if (p == this->segment_list_.end())
285 Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
286 seg_flags);
287 this->segment_list_.push_back(oseg);
288 oseg->add_output_section(os, seg_flags);
292 // If we see a loadable SHF_TLS section, we create a PT_TLS
293 // segment. There can only be one such segment.
294 if ((flags & elfcpp::SHF_TLS) != 0)
296 if (this->tls_segment_ == NULL)
298 this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
299 seg_flags);
300 this->segment_list_.push_back(this->tls_segment_);
302 this->tls_segment_->add_output_section(os, seg_flags);
306 return os;
309 // Create the dynamic sections which are needed before we read the
310 // relocs.
312 void
313 Layout::create_initial_dynamic_sections(const Input_objects* input_objects,
314 Symbol_table* symtab)
316 if (!input_objects->any_dynamic())
317 return;
319 const char* dynamic_name = this->namepool_.add(".dynamic", NULL);
320 this->dynamic_section_ = this->make_output_section(dynamic_name,
321 elfcpp::SHT_DYNAMIC,
322 (elfcpp::SHF_ALLOC
323 | elfcpp::SHF_WRITE));
325 symtab->define_in_output_data(input_objects->target(), "_DYNAMIC", NULL,
326 this->dynamic_section_, 0, 0,
327 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
328 elfcpp::STV_HIDDEN, 0, false, false);
330 this->dynamic_data_ = new Output_data_dynamic(input_objects->target(),
331 &this->dynpool_);
333 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
336 // Find the first read-only PT_LOAD segment, creating one if
337 // necessary.
339 Output_segment*
340 Layout::find_first_load_seg()
342 for (Segment_list::const_iterator p = this->segment_list_.begin();
343 p != this->segment_list_.end();
344 ++p)
346 if ((*p)->type() == elfcpp::PT_LOAD
347 && ((*p)->flags() & elfcpp::PF_R) != 0
348 && ((*p)->flags() & elfcpp::PF_W) == 0)
349 return *p;
352 Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
353 this->segment_list_.push_back(load_seg);
354 return load_seg;
357 // Finalize the layout. When this is called, we have created all the
358 // output sections and all the output segments which are based on
359 // input sections. We have several things to do, and we have to do
360 // them in the right order, so that we get the right results correctly
361 // and efficiently.
363 // 1) Finalize the list of output segments and create the segment
364 // table header.
366 // 2) Finalize the dynamic symbol table and associated sections.
368 // 3) Determine the final file offset of all the output segments.
370 // 4) Determine the final file offset of all the SHF_ALLOC output
371 // sections.
373 // 5) Create the symbol table sections and the section name table
374 // section.
376 // 6) Finalize the symbol table: set symbol values to their final
377 // value and make a final determination of which symbols are going
378 // into the output symbol table.
380 // 7) Create the section table header.
382 // 8) Determine the final file offset of all the output sections which
383 // are not SHF_ALLOC, including the section table header.
385 // 9) Finalize the ELF file header.
387 // This function returns the size of the output file.
389 off_t
390 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab)
392 Target* const target = input_objects->target();
393 const int size = target->get_size();
395 target->finalize_sections(&this->options_, this);
397 Output_segment* phdr_seg = NULL;
398 if (input_objects->any_dynamic())
400 // There was a dynamic object in the link. We need to create
401 // some information for the dynamic linker.
403 // Create the PT_PHDR segment which will hold the program
404 // headers.
405 phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
406 this->segment_list_.push_back(phdr_seg);
408 // Create the dynamic symbol table, including the hash table.
409 Output_section* dynstr;
410 std::vector<Symbol*> dynamic_symbols;
411 unsigned int local_dynamic_count;
412 Versions versions;
413 this->create_dynamic_symtab(target, symtab, &dynstr,
414 &local_dynamic_count, &dynamic_symbols,
415 &versions);
417 // Create the .interp section to hold the name of the
418 // interpreter, and put it in a PT_INTERP segment.
419 this->create_interp(target);
421 // Finish the .dynamic section to hold the dynamic data, and put
422 // it in a PT_DYNAMIC segment.
423 this->finish_dynamic_section(input_objects, symtab);
425 // We should have added everything we need to the dynamic string
426 // table.
427 this->dynpool_.set_string_offsets();
429 // Create the version sections. We can't do this until the
430 // dynamic string table is complete.
431 this->create_version_sections(target, &versions, local_dynamic_count,
432 dynamic_symbols, dynstr);
435 // FIXME: Handle PT_GNU_STACK.
437 Output_segment* load_seg = this->find_first_load_seg();
439 // Lay out the segment headers.
440 bool big_endian = target->is_big_endian();
441 Output_segment_headers* segment_headers;
442 segment_headers = new Output_segment_headers(size, big_endian,
443 this->segment_list_);
444 load_seg->add_initial_output_data(segment_headers);
445 this->special_output_list_.push_back(segment_headers);
446 if (phdr_seg != NULL)
447 phdr_seg->add_initial_output_data(segment_headers);
449 // Lay out the file header.
450 Output_file_header* file_header;
451 file_header = new Output_file_header(size,
452 big_endian,
453 this->options_,
454 target,
455 symtab,
456 segment_headers);
457 load_seg->add_initial_output_data(file_header);
458 this->special_output_list_.push_back(file_header);
460 // We set the output section indexes in set_segment_offsets and
461 // set_section_offsets.
462 unsigned int shndx = 1;
464 // Set the file offsets of all the segments, and all the sections
465 // they contain.
466 off_t off = this->set_segment_offsets(target, load_seg, &shndx);
468 // Create the symbol table sections.
469 // FIXME: We don't need to do this if we are stripping symbols.
470 this->create_symtab_sections(size, input_objects, symtab, &off);
472 // Create the .shstrtab section.
473 Output_section* shstrtab_section = this->create_shstrtab();
475 // Set the file offsets of all the sections not associated with
476 // segments.
477 off = this->set_section_offsets(off, &shndx);
479 // Create the section table header.
480 Output_section_headers* oshdrs = this->create_shdrs(size, big_endian, &off);
482 file_header->set_section_info(oshdrs, shstrtab_section);
484 // Now we know exactly where everything goes in the output file.
485 Output_data::layout_complete();
487 return off;
490 // Return whether SEG1 should be before SEG2 in the output file. This
491 // is based entirely on the segment type and flags. When this is
492 // called the segment addresses has normally not yet been set.
494 bool
495 Layout::segment_precedes(const Output_segment* seg1,
496 const Output_segment* seg2)
498 elfcpp::Elf_Word type1 = seg1->type();
499 elfcpp::Elf_Word type2 = seg2->type();
501 // The single PT_PHDR segment is required to precede any loadable
502 // segment. We simply make it always first.
503 if (type1 == elfcpp::PT_PHDR)
505 gold_assert(type2 != elfcpp::PT_PHDR);
506 return true;
508 if (type2 == elfcpp::PT_PHDR)
509 return false;
511 // The single PT_INTERP segment is required to precede any loadable
512 // segment. We simply make it always second.
513 if (type1 == elfcpp::PT_INTERP)
515 gold_assert(type2 != elfcpp::PT_INTERP);
516 return true;
518 if (type2 == elfcpp::PT_INTERP)
519 return false;
521 // We then put PT_LOAD segments before any other segments.
522 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
523 return true;
524 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
525 return false;
527 // We put the PT_TLS segment last, because that is where the dynamic
528 // linker expects to find it (this is just for efficiency; other
529 // positions would also work correctly).
530 if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
531 return false;
532 if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
533 return true;
535 const elfcpp::Elf_Word flags1 = seg1->flags();
536 const elfcpp::Elf_Word flags2 = seg2->flags();
538 // The order of non-PT_LOAD segments is unimportant. We simply sort
539 // by the numeric segment type and flags values. There should not
540 // be more than one segment with the same type and flags.
541 if (type1 != elfcpp::PT_LOAD)
543 if (type1 != type2)
544 return type1 < type2;
545 gold_assert(flags1 != flags2);
546 return flags1 < flags2;
549 // We sort PT_LOAD segments based on the flags. Readonly segments
550 // come before writable segments. Then executable segments come
551 // before non-executable segments. Then the unlikely case of a
552 // non-readable segment comes before the normal case of a readable
553 // segment. If there are multiple segments with the same type and
554 // flags, we require that the address be set, and we sort by
555 // virtual address and then physical address.
556 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
557 return (flags1 & elfcpp::PF_W) == 0;
558 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
559 return (flags1 & elfcpp::PF_X) != 0;
560 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
561 return (flags1 & elfcpp::PF_R) == 0;
563 uint64_t vaddr1 = seg1->vaddr();
564 uint64_t vaddr2 = seg2->vaddr();
565 if (vaddr1 != vaddr2)
566 return vaddr1 < vaddr2;
568 uint64_t paddr1 = seg1->paddr();
569 uint64_t paddr2 = seg2->paddr();
570 gold_assert(paddr1 != paddr2);
571 return paddr1 < paddr2;
574 // Set the file offsets of all the segments, and all the sections they
575 // contain. They have all been created. LOAD_SEG must be be laid out
576 // first. Return the offset of the data to follow.
578 off_t
579 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
580 unsigned int *pshndx)
582 // Sort them into the final order.
583 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
584 Layout::Compare_segments());
586 // Find the PT_LOAD segments, and set their addresses and offsets
587 // and their section's addresses and offsets.
588 uint64_t addr = target->text_segment_address();
589 off_t off = 0;
590 bool was_readonly = false;
591 for (Segment_list::iterator p = this->segment_list_.begin();
592 p != this->segment_list_.end();
593 ++p)
595 if ((*p)->type() == elfcpp::PT_LOAD)
597 if (load_seg != NULL && load_seg != *p)
598 gold_unreachable();
599 load_seg = NULL;
601 // If the last segment was readonly, and this one is not,
602 // then skip the address forward one page, maintaining the
603 // same position within the page. This lets us store both
604 // segments overlapping on a single page in the file, but
605 // the loader will put them on different pages in memory.
607 uint64_t orig_addr = addr;
608 uint64_t orig_off = off;
610 uint64_t aligned_addr = addr;
611 uint64_t abi_pagesize = target->abi_pagesize();
612 if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
614 uint64_t align = (*p)->addralign();
616 addr = align_address(addr, align);
617 aligned_addr = addr;
618 if ((addr & (abi_pagesize - 1)) != 0)
619 addr = addr + abi_pagesize;
622 unsigned int shndx_hold = *pshndx;
623 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
624 uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
626 // Now that we know the size of this segment, we may be able
627 // to save a page in memory, at the cost of wasting some
628 // file space, by instead aligning to the start of a new
629 // page. Here we use the real machine page size rather than
630 // the ABI mandated page size.
632 if (aligned_addr != addr)
634 uint64_t common_pagesize = target->common_pagesize();
635 uint64_t first_off = (common_pagesize
636 - (aligned_addr
637 & (common_pagesize - 1)));
638 uint64_t last_off = new_addr & (common_pagesize - 1);
639 if (first_off > 0
640 && last_off > 0
641 && ((aligned_addr & ~ (common_pagesize - 1))
642 != (new_addr & ~ (common_pagesize - 1)))
643 && first_off + last_off <= common_pagesize)
645 *pshndx = shndx_hold;
646 addr = align_address(aligned_addr, common_pagesize);
647 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
648 new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
652 addr = new_addr;
654 if (((*p)->flags() & elfcpp::PF_W) == 0)
655 was_readonly = true;
659 // Handle the non-PT_LOAD segments, setting their offsets from their
660 // section's offsets.
661 for (Segment_list::iterator p = this->segment_list_.begin();
662 p != this->segment_list_.end();
663 ++p)
665 if ((*p)->type() != elfcpp::PT_LOAD)
666 (*p)->set_offset();
669 return off;
672 // Set the file offset of all the sections not associated with a
673 // segment.
675 off_t
676 Layout::set_section_offsets(off_t off, unsigned int* pshndx)
678 for (Section_list::iterator p = this->unattached_section_list_.begin();
679 p != this->unattached_section_list_.end();
680 ++p)
682 (*p)->set_out_shndx(*pshndx);
683 ++*pshndx;
684 if ((*p)->offset() != -1)
685 continue;
686 off = align_address(off, (*p)->addralign());
687 (*p)->set_address(0, off);
688 off += (*p)->data_size();
690 return off;
693 // Create the symbol table sections.
695 void
696 Layout::create_symtab_sections(int size, const Input_objects* input_objects,
697 Symbol_table* symtab,
698 off_t* poff)
700 int symsize;
701 unsigned int align;
702 if (size == 32)
704 symsize = elfcpp::Elf_sizes<32>::sym_size;
705 align = 4;
707 else if (size == 64)
709 symsize = elfcpp::Elf_sizes<64>::sym_size;
710 align = 8;
712 else
713 gold_unreachable();
715 off_t off = *poff;
716 off = align_address(off, align);
717 off_t startoff = off;
719 // Save space for the dummy symbol at the start of the section. We
720 // never bother to write this out--it will just be left as zero.
721 off += symsize;
722 unsigned int local_symbol_index = 1;
724 // Add STT_SECTION symbols for each Output section which needs one.
725 for (Section_list::iterator p = this->section_list_.begin();
726 p != this->section_list_.end();
727 ++p)
729 if (!(*p)->needs_symtab_index())
730 (*p)->set_symtab_index(-1U);
731 else
733 (*p)->set_symtab_index(local_symbol_index);
734 ++local_symbol_index;
735 off += symsize;
739 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
740 p != input_objects->relobj_end();
741 ++p)
743 Task_lock_obj<Object> tlo(**p);
744 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
745 off,
746 &this->sympool_);
747 off += (index - local_symbol_index) * symsize;
748 local_symbol_index = index;
751 unsigned int local_symcount = local_symbol_index;
752 gold_assert(local_symcount * symsize == off - startoff);
754 off_t dynoff;
755 size_t dyn_global_index;
756 size_t dyncount;
757 if (this->dynsym_section_ == NULL)
759 dynoff = 0;
760 dyn_global_index = 0;
761 dyncount = 0;
763 else
765 dyn_global_index = this->dynsym_section_->info();
766 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
767 dynoff = this->dynsym_section_->offset() + locsize;
768 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
769 gold_assert(dyncount * symsize
770 == this->dynsym_section_->data_size() - locsize);
773 off = symtab->finalize(local_symcount, off, dynoff, dyn_global_index,
774 dyncount, &this->sympool_);
776 this->sympool_.set_string_offsets();
778 const char* symtab_name = this->namepool_.add(".symtab", NULL);
779 Output_section* osymtab = this->make_output_section(symtab_name,
780 elfcpp::SHT_SYMTAB,
782 this->symtab_section_ = osymtab;
784 Output_section_data* pos = new Output_data_space(off - startoff,
785 align);
786 osymtab->add_output_section_data(pos);
788 const char* strtab_name = this->namepool_.add(".strtab", NULL);
789 Output_section* ostrtab = this->make_output_section(strtab_name,
790 elfcpp::SHT_STRTAB,
793 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
794 ostrtab->add_output_section_data(pstr);
796 osymtab->set_address(0, startoff);
797 osymtab->set_link_section(ostrtab);
798 osymtab->set_info(local_symcount);
799 osymtab->set_entsize(symsize);
801 *poff = off;
804 // Create the .shstrtab section, which holds the names of the
805 // sections. At the time this is called, we have created all the
806 // output sections except .shstrtab itself.
808 Output_section*
809 Layout::create_shstrtab()
811 // FIXME: We don't need to create a .shstrtab section if we are
812 // stripping everything.
814 const char* name = this->namepool_.add(".shstrtab", NULL);
816 this->namepool_.set_string_offsets();
818 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0);
820 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
821 os->add_output_section_data(posd);
823 return os;
826 // Create the section headers. SIZE is 32 or 64. OFF is the file
827 // offset.
829 Output_section_headers*
830 Layout::create_shdrs(int size, bool big_endian, off_t* poff)
832 Output_section_headers* oshdrs;
833 oshdrs = new Output_section_headers(size, big_endian, this,
834 &this->segment_list_,
835 &this->unattached_section_list_,
836 &this->namepool_);
837 off_t off = align_address(*poff, oshdrs->addralign());
838 oshdrs->set_address(0, off);
839 off += oshdrs->data_size();
840 *poff = off;
841 this->special_output_list_.push_back(oshdrs);
842 return oshdrs;
845 // Create the dynamic symbol table.
847 void
848 Layout::create_dynamic_symtab(const Target* target, Symbol_table* symtab,
849 Output_section **pdynstr,
850 unsigned int* plocal_dynamic_count,
851 std::vector<Symbol*>* pdynamic_symbols,
852 Versions* pversions)
854 // Count all the symbols in the dynamic symbol table, and set the
855 // dynamic symbol indexes.
857 // Skip symbol 0, which is always all zeroes.
858 unsigned int index = 1;
860 // Add STT_SECTION symbols for each Output section which needs one.
861 for (Section_list::iterator p = this->section_list_.begin();
862 p != this->section_list_.end();
863 ++p)
865 if (!(*p)->needs_dynsym_index())
866 (*p)->set_dynsym_index(-1U);
867 else
869 (*p)->set_dynsym_index(index);
870 ++index;
874 // FIXME: Some targets apparently require local symbols in the
875 // dynamic symbol table. Here is where we will have to count them,
876 // and set the dynamic symbol indexes, and add the names to
877 // this->dynpool_.
879 unsigned int local_symcount = index;
880 *plocal_dynamic_count = local_symcount;
882 // FIXME: We have to tell set_dynsym_indexes whether the
883 // -E/--export-dynamic option was used.
884 index = symtab->set_dynsym_indexes(&this->options_, target, index,
885 pdynamic_symbols, &this->dynpool_,
886 pversions);
888 int symsize;
889 unsigned int align;
890 const int size = target->get_size();
891 if (size == 32)
893 symsize = elfcpp::Elf_sizes<32>::sym_size;
894 align = 4;
896 else if (size == 64)
898 symsize = elfcpp::Elf_sizes<64>::sym_size;
899 align = 8;
901 else
902 gold_unreachable();
904 // Create the dynamic symbol table section.
906 const char* dynsym_name = this->namepool_.add(".dynsym", NULL);
907 Output_section* dynsym = this->make_output_section(dynsym_name,
908 elfcpp::SHT_DYNSYM,
909 elfcpp::SHF_ALLOC);
911 Output_section_data* odata = new Output_data_space(index * symsize,
912 align);
913 dynsym->add_output_section_data(odata);
915 dynsym->set_info(local_symcount);
916 dynsym->set_entsize(symsize);
917 dynsym->set_addralign(align);
919 this->dynsym_section_ = dynsym;
921 Output_data_dynamic* const odyn = this->dynamic_data_;
922 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
923 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
925 // Create the dynamic string table section.
927 const char* dynstr_name = this->namepool_.add(".dynstr", NULL);
928 Output_section* dynstr = this->make_output_section(dynstr_name,
929 elfcpp::SHT_STRTAB,
930 elfcpp::SHF_ALLOC);
932 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
933 dynstr->add_output_section_data(strdata);
935 dynsym->set_link_section(dynstr);
936 this->dynamic_section_->set_link_section(dynstr);
938 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
939 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
941 *pdynstr = dynstr;
943 // Create the hash tables.
945 // FIXME: We need an option to create a GNU hash table.
947 unsigned char* phash;
948 unsigned int hashlen;
949 Dynobj::create_elf_hash_table(target, *pdynamic_symbols, local_symcount,
950 &phash, &hashlen);
952 const char* hash_name = this->namepool_.add(".hash", NULL);
953 Output_section* hashsec = this->make_output_section(hash_name,
954 elfcpp::SHT_HASH,
955 elfcpp::SHF_ALLOC);
957 Output_section_data* hashdata = new Output_data_const_buffer(phash,
958 hashlen,
959 align);
960 hashsec->add_output_section_data(hashdata);
962 hashsec->set_link_section(dynsym);
963 hashsec->set_entsize(4);
965 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
968 // Create the version sections.
970 void
971 Layout::create_version_sections(const Target* target, const Versions* versions,
972 unsigned int local_symcount,
973 const std::vector<Symbol*>& dynamic_symbols,
974 const Output_section* dynstr)
976 if (!versions->any_defs() && !versions->any_needs())
977 return;
979 if (target->get_size() == 32)
981 if (target->is_big_endian())
982 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(32, true)(
983 versions, local_symcount, dynamic_symbols, dynstr
984 SELECT_SIZE_ENDIAN(32, true));
985 else
986 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(32, false)(
987 versions, local_symcount, dynamic_symbols, dynstr
988 SELECT_SIZE_ENDIAN(32, false));
990 else if (target->get_size() == 64)
992 if (target->is_big_endian())
993 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(64, true)(
994 versions, local_symcount, dynamic_symbols, dynstr
995 SELECT_SIZE_ENDIAN(64, true));
996 else
997 this->sized_create_version_sections SELECT_SIZE_ENDIAN_NAME(64, false)(
998 versions, local_symcount, dynamic_symbols, dynstr
999 SELECT_SIZE_ENDIAN(64, false));
1001 else
1002 gold_unreachable();
1005 // Create the version sections, sized version.
1007 template<int size, bool big_endian>
1008 void
1009 Layout::sized_create_version_sections(
1010 const Versions* versions,
1011 unsigned int local_symcount,
1012 const std::vector<Symbol*>& dynamic_symbols,
1013 const Output_section* dynstr
1014 ACCEPT_SIZE_ENDIAN)
1016 const char* vname = this->namepool_.add(".gnu.version", NULL);
1017 Output_section* vsec = this->make_output_section(vname,
1018 elfcpp::SHT_GNU_versym,
1019 elfcpp::SHF_ALLOC);
1021 unsigned char* vbuf;
1022 unsigned int vsize;
1023 versions->symbol_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1024 &this->dynpool_, local_symcount, dynamic_symbols, &vbuf, &vsize
1025 SELECT_SIZE_ENDIAN(size, big_endian));
1027 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2);
1029 vsec->add_output_section_data(vdata);
1030 vsec->set_entsize(2);
1031 vsec->set_link_section(this->dynsym_section_);
1033 Output_data_dynamic* const odyn = this->dynamic_data_;
1034 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
1036 if (versions->any_defs())
1038 const char* vdname = this->namepool_.add(".gnu.version_d", NULL);
1039 Output_section *vdsec;
1040 vdsec = this->make_output_section(vdname, elfcpp::SHT_GNU_verdef,
1041 elfcpp::SHF_ALLOC);
1043 unsigned char* vdbuf;
1044 unsigned int vdsize;
1045 unsigned int vdentries;
1046 versions->def_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1047 &this->dynpool_, &vdbuf, &vdsize, &vdentries
1048 SELECT_SIZE_ENDIAN(size, big_endian));
1050 Output_section_data* vddata = new Output_data_const_buffer(vdbuf,
1051 vdsize,
1054 vdsec->add_output_section_data(vddata);
1055 vdsec->set_link_section(dynstr);
1056 vdsec->set_info(vdentries);
1058 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
1059 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
1062 if (versions->any_needs())
1064 const char* vnname = this->namepool_.add(".gnu.version_r", NULL);
1065 Output_section* vnsec;
1066 vnsec = this->make_output_section(vnname, elfcpp::SHT_GNU_verneed,
1067 elfcpp::SHF_ALLOC);
1069 unsigned char* vnbuf;
1070 unsigned int vnsize;
1071 unsigned int vnentries;
1072 versions->need_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)
1073 (&this->dynpool_, &vnbuf, &vnsize, &vnentries
1074 SELECT_SIZE_ENDIAN(size, big_endian));
1076 Output_section_data* vndata = new Output_data_const_buffer(vnbuf,
1077 vnsize,
1080 vnsec->add_output_section_data(vndata);
1081 vnsec->set_link_section(dynstr);
1082 vnsec->set_info(vnentries);
1084 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
1085 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
1089 // Create the .interp section and PT_INTERP segment.
1091 void
1092 Layout::create_interp(const Target* target)
1094 const char* interp = this->options_.dynamic_linker();
1095 if (interp == NULL)
1097 interp = target->dynamic_linker();
1098 gold_assert(interp != NULL);
1101 size_t len = strlen(interp) + 1;
1103 Output_section_data* odata = new Output_data_const(interp, len, 1);
1105 const char* interp_name = this->namepool_.add(".interp", NULL);
1106 Output_section* osec = this->make_output_section(interp_name,
1107 elfcpp::SHT_PROGBITS,
1108 elfcpp::SHF_ALLOC);
1109 osec->add_output_section_data(odata);
1111 Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
1112 this->segment_list_.push_back(oseg);
1113 oseg->add_initial_output_section(osec, elfcpp::PF_R);
1116 // Finish the .dynamic section and PT_DYNAMIC segment.
1118 void
1119 Layout::finish_dynamic_section(const Input_objects* input_objects,
1120 const Symbol_table* symtab)
1122 Output_segment* oseg = new Output_segment(elfcpp::PT_DYNAMIC,
1123 elfcpp::PF_R | elfcpp::PF_W);
1124 this->segment_list_.push_back(oseg);
1125 oseg->add_initial_output_section(this->dynamic_section_,
1126 elfcpp::PF_R | elfcpp::PF_W);
1128 Output_data_dynamic* const odyn = this->dynamic_data_;
1130 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
1131 p != input_objects->dynobj_end();
1132 ++p)
1134 // FIXME: Handle --as-needed.
1135 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
1138 // FIXME: Support --init and --fini.
1139 Symbol* sym = symtab->lookup("_init");
1140 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1141 odyn->add_symbol(elfcpp::DT_INIT, sym);
1143 sym = symtab->lookup("_fini");
1144 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1145 odyn->add_symbol(elfcpp::DT_FINI, sym);
1147 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1150 // The mapping of .gnu.linkonce section names to real section names.
1152 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1153 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
1155 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1156 MAPPING_INIT("t", ".text"),
1157 MAPPING_INIT("r", ".rodata"),
1158 MAPPING_INIT("d", ".data"),
1159 MAPPING_INIT("b", ".bss"),
1160 MAPPING_INIT("s", ".sdata"),
1161 MAPPING_INIT("sb", ".sbss"),
1162 MAPPING_INIT("s2", ".sdata2"),
1163 MAPPING_INIT("sb2", ".sbss2"),
1164 MAPPING_INIT("wi", ".debug_info"),
1165 MAPPING_INIT("td", ".tdata"),
1166 MAPPING_INIT("tb", ".tbss"),
1167 MAPPING_INIT("lr", ".lrodata"),
1168 MAPPING_INIT("l", ".ldata"),
1169 MAPPING_INIT("lb", ".lbss"),
1171 #undef MAPPING_INIT
1173 const int Layout::linkonce_mapping_count =
1174 sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
1176 // Return the name of the output section to use for a .gnu.linkonce
1177 // section. This is based on the default ELF linker script of the old
1178 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1179 // to ".text". Set *PLEN to the length of the name. *PLEN is
1180 // initialized to the length of NAME.
1182 const char*
1183 Layout::linkonce_output_name(const char* name, size_t *plen)
1185 const char* s = name + sizeof(".gnu.linkonce") - 1;
1186 if (*s != '.')
1187 return name;
1188 ++s;
1189 const Linkonce_mapping* plm = linkonce_mapping;
1190 for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
1192 if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
1194 *plen = plm->tolen;
1195 return plm->to;
1198 return name;
1201 // Choose the output section name to use given an input section name.
1202 // Set *PLEN to the length of the name. *PLEN is initialized to the
1203 // length of NAME.
1205 const char*
1206 Layout::output_section_name(const char* name, size_t* plen)
1208 if (Layout::is_linkonce(name))
1210 // .gnu.linkonce sections are laid out as though they were named
1211 // for the sections are placed into.
1212 return Layout::linkonce_output_name(name, plen);
1215 // If the section name has no '.', or only an initial '.', we use
1216 // the name unchanged (i.e., ".text" is unchanged).
1218 // Otherwise, if the section name does not include ".rel", we drop
1219 // the last '.' and everything that follows (i.e., ".text.XXX"
1220 // becomes ".text").
1222 // Otherwise, if the section name has zero or one '.' after the
1223 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1224 // unchanged).
1226 // Otherwise, we drop the last '.' and everything that follows
1227 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1229 const char* s = name;
1230 if (*s == '.')
1231 ++s;
1232 const char* sdot = strchr(s, '.');
1233 if (sdot == NULL)
1234 return name;
1236 const char* srel = strstr(s, ".rel");
1237 if (srel == NULL)
1239 *plen = sdot - name;
1240 return name;
1243 sdot = strchr(srel + 1, '.');
1244 if (sdot == NULL)
1245 return name;
1246 sdot = strchr(sdot + 1, '.');
1247 if (sdot == NULL)
1248 return name;
1250 *plen = sdot - name;
1251 return name;
1254 // Record the signature of a comdat section, and return whether to
1255 // include it in the link. If GROUP is true, this is a regular
1256 // section group. If GROUP is false, this is a group signature
1257 // derived from the name of a linkonce section. We want linkonce
1258 // signatures and group signatures to block each other, but we don't
1259 // want a linkonce signature to block another linkonce signature.
1261 bool
1262 Layout::add_comdat(const char* signature, bool group)
1264 std::string sig(signature);
1265 std::pair<Signatures::iterator, bool> ins(
1266 this->signatures_.insert(std::make_pair(sig, group)));
1268 if (ins.second)
1270 // This is the first time we've seen this signature.
1271 return true;
1274 if (ins.first->second)
1276 // We've already seen a real section group with this signature.
1277 return false;
1279 else if (group)
1281 // This is a real section group, and we've already seen a
1282 // linkonce section with tihs signature. Record that we've seen
1283 // a section group, and don't include this section group.
1284 ins.first->second = true;
1285 return false;
1287 else
1289 // We've already seen a linkonce section and this is a linkonce
1290 // section. These don't block each other--this may be the same
1291 // symbol name with different section types.
1292 return true;
1296 // Write out data not associated with a section or the symbol table.
1298 void
1299 Layout::write_data(const Symbol_table* symtab, const Target* target,
1300 Output_file* of) const
1302 const Output_section* symtab_section = this->symtab_section_;
1303 for (Section_list::const_iterator p = this->section_list_.begin();
1304 p != this->section_list_.end();
1305 ++p)
1307 if ((*p)->needs_symtab_index())
1309 gold_assert(symtab_section != NULL);
1310 unsigned int index = (*p)->symtab_index();
1311 gold_assert(index > 0 && index != -1U);
1312 off_t off = (symtab_section->offset()
1313 + index * symtab_section->entsize());
1314 symtab->write_section_symbol(target, *p, of, off);
1318 const Output_section* dynsym_section = this->dynsym_section_;
1319 for (Section_list::const_iterator p = this->section_list_.begin();
1320 p != this->section_list_.end();
1321 ++p)
1323 if ((*p)->needs_dynsym_index())
1325 gold_assert(dynsym_section != NULL);
1326 unsigned int index = (*p)->dynsym_index();
1327 gold_assert(index > 0 && index != -1U);
1328 off_t off = (dynsym_section->offset()
1329 + index * dynsym_section->entsize());
1330 symtab->write_section_symbol(target, *p, of, off);
1334 // Write out the Output_sections. Most won't have anything to
1335 // write, since most of the data will come from input sections which
1336 // are handled elsewhere. But some Output_sections do have
1337 // Output_data.
1338 for (Section_list::const_iterator p = this->section_list_.begin();
1339 p != this->section_list_.end();
1340 ++p)
1341 (*p)->write(of);
1343 // Write out the Output_data which are not in an Output_section.
1344 for (Data_list::const_iterator p = this->special_output_list_.begin();
1345 p != this->special_output_list_.end();
1346 ++p)
1347 (*p)->write(of);
1350 // Write_data_task methods.
1352 // We can always run this task.
1354 Task::Is_runnable_type
1355 Write_data_task::is_runnable(Workqueue*)
1357 return IS_RUNNABLE;
1360 // We need to unlock FINAL_BLOCKER when finished.
1362 Task_locker*
1363 Write_data_task::locks(Workqueue* workqueue)
1365 return new Task_locker_block(*this->final_blocker_, workqueue);
1368 // Run the task--write out the data.
1370 void
1371 Write_data_task::run(Workqueue*)
1373 this->layout_->write_data(this->symtab_, this->target_, this->of_);
1376 // Write_symbols_task methods.
1378 // We can always run this task.
1380 Task::Is_runnable_type
1381 Write_symbols_task::is_runnable(Workqueue*)
1383 return IS_RUNNABLE;
1386 // We need to unlock FINAL_BLOCKER when finished.
1388 Task_locker*
1389 Write_symbols_task::locks(Workqueue* workqueue)
1391 return new Task_locker_block(*this->final_blocker_, workqueue);
1394 // Run the task--write out the symbols.
1396 void
1397 Write_symbols_task::run(Workqueue*)
1399 this->symtab_->write_globals(this->target_, this->sympool_, this->dynpool_,
1400 this->of_);
1403 // Close_task_runner methods.
1405 // Run the task--close the file.
1407 void
1408 Close_task_runner::run(Workqueue*)
1410 this->of_->close();
1413 // Instantiate the templates we need. We could use the configure
1414 // script to restrict this to only the ones for implemented targets.
1416 template
1417 Output_section*
1418 Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name,
1419 const elfcpp::Shdr<32, false>& shdr, off_t*);
1421 template
1422 Output_section*
1423 Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name,
1424 const elfcpp::Shdr<32, true>& shdr, off_t*);
1426 template
1427 Output_section*
1428 Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name,
1429 const elfcpp::Shdr<64, false>& shdr, off_t*);
1431 template
1432 Output_section*
1433 Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name,
1434 const elfcpp::Shdr<64, true>& shdr, off_t*);
1437 } // End namespace gold.