1 // layout.cc -- lay out output file sections for gold
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.
30 #include "parameters.h"
40 // Layout_task_runner methods.
42 // Lay out the sections. This is called after all the input objects
46 Layout_task_runner::run(Workqueue* workqueue)
48 off_t file_size = this->layout_->finalize(this->input_objects_,
51 // Now we know the final size of the output file and we know where
52 // each piece of information goes.
53 Output_file* of = new Output_file(this->options_,
54 this->input_objects_->target());
57 // Queue up the final set of tasks.
58 gold::queue_final_tasks(this->options_, this->input_objects_,
59 this->symtab_, this->layout_, workqueue, of);
64 Layout::Layout(const General_options& options)
65 : options_(options), namepool_(), sympool_(), dynpool_(), signatures_(),
66 section_name_map_(), segment_list_(), section_list_(),
67 unattached_section_list_(), special_output_list_(),
68 tls_segment_(NULL), symtab_section_(NULL),
69 dynsym_section_(NULL), dynamic_section_(NULL), dynamic_data_(NULL),
70 eh_frame_section_(NULL)
72 // Make space for more than enough segments for a typical file.
73 // This is just for efficiency--it's OK if we wind up needing more.
74 this->segment_list_.reserve(12);
76 // We expect three unattached Output_data objects: the file header,
77 // the segment headers, and the section headers.
78 this->special_output_list_.reserve(3);
81 // Hash a key we use to look up an output section mapping.
84 Layout::Hash_key::operator()(const Layout::Key& k) const
86 return k.first + k.second.first + k.second.second;
89 // Whether to include this section in the link.
91 template<int size, bool big_endian>
93 Layout::include_section(Object*, const char*,
94 const elfcpp::Shdr<size, big_endian>& shdr)
96 // Some section types are never linked. Some are only linked when
97 // doing a relocateable link.
98 switch (shdr.get_sh_type())
100 case elfcpp::SHT_NULL:
101 case elfcpp::SHT_SYMTAB:
102 case elfcpp::SHT_DYNSYM:
103 case elfcpp::SHT_STRTAB:
104 case elfcpp::SHT_HASH:
105 case elfcpp::SHT_DYNAMIC:
106 case elfcpp::SHT_SYMTAB_SHNDX:
109 case elfcpp::SHT_RELA:
110 case elfcpp::SHT_REL:
111 case elfcpp::SHT_GROUP:
112 return parameters->output_is_object();
115 // FIXME: Handle stripping debug sections here.
120 // Return an output section named NAME, or NULL if there is none.
123 Layout::find_output_section(const char* name) const
125 for (Section_name_map::const_iterator p = this->section_name_map_.begin();
126 p != this->section_name_map_.end();
128 if (strcmp(p->second->name(), name) == 0)
133 // Return an output segment of type TYPE, with segment flags SET set
134 // and segment flags CLEAR clear. Return NULL if there is none.
137 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
138 elfcpp::Elf_Word clear) const
140 for (Segment_list::const_iterator p = this->segment_list_.begin();
141 p != this->segment_list_.end();
143 if (static_cast<elfcpp::PT>((*p)->type()) == type
144 && ((*p)->flags() & set) == set
145 && ((*p)->flags() & clear) == 0)
150 // Return the output section to use for section NAME with type TYPE
151 // and section flags FLAGS.
154 Layout::get_output_section(const char* name, Stringpool::Key name_key,
155 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
157 // We should ignore some flags.
158 flags &= ~ (elfcpp::SHF_INFO_LINK
159 | elfcpp::SHF_LINK_ORDER
162 | elfcpp::SHF_STRINGS);
164 const Key key(name_key, std::make_pair(type, flags));
165 const std::pair<Key, Output_section*> v(key, NULL);
166 std::pair<Section_name_map::iterator, bool> ins(
167 this->section_name_map_.insert(v));
170 return ins.first->second;
173 // This is the first time we've seen this name/type/flags
175 Output_section* os = this->make_output_section(name, type, flags);
176 ins.first->second = os;
181 // Return the output section to use for input section SHNDX, with name
182 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
183 // offset of this input section without the output section.
185 template<int size, bool big_endian>
187 Layout::layout(Relobj* object, unsigned int shndx, const char* name,
188 const elfcpp::Shdr<size, big_endian>& shdr, off_t* off)
190 if (!this->include_section(object, name, shdr))
193 // If we are not doing a relocateable link, choose the name to use
194 // for the output section.
195 size_t len = strlen(name);
196 if (!parameters->output_is_object())
197 name = Layout::output_section_name(name, &len);
199 // FIXME: Handle SHF_OS_NONCONFORMING here.
201 // Canonicalize the section name.
202 Stringpool::Key name_key;
203 name = this->namepool_.add(name, len, &name_key);
205 // Find the output section. The output section is selected based on
206 // the section name, type, and flags.
207 Output_section* os = this->get_output_section(name, name_key,
209 shdr.get_sh_flags());
211 // Special GNU handling of sections named .eh_frame.
212 if (!parameters->output_is_object()
213 && strcmp(name, ".eh_frame") == 0
214 && shdr.get_sh_size() > 0
215 && shdr.get_sh_type() == elfcpp::SHT_PROGBITS
216 && shdr.get_sh_flags() == elfcpp::SHF_ALLOC)
218 this->layout_eh_frame(object, shndx, name, shdr, os, off);
222 // FIXME: Handle SHF_LINK_ORDER somewhere.
224 *off = os->add_input_section(object, shndx, name, shdr);
229 // Special GNU handling of sections named .eh_frame. They will
230 // normally hold exception frame data.
232 template<int size, bool big_endian>
234 Layout::layout_eh_frame(Relobj* object,
237 const elfcpp::Shdr<size, big_endian>& shdr,
238 Output_section* os, off_t* off)
240 if (this->eh_frame_section_ == NULL)
242 this->eh_frame_section_ = os;
244 if (this->options_.create_eh_frame_hdr())
246 Stringpool::Key hdr_name_key;
247 const char* hdr_name = this->namepool_.add(".eh_frame_hdr",
249 Output_section* hdr_os =
250 this->get_output_section(hdr_name, hdr_name_key,
251 elfcpp::SHT_PROGBITS,
254 Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os);
255 hdr_os->add_output_section_data(hdr_posd);
257 Output_segment* hdr_oseg =
258 new Output_segment(elfcpp::PT_GNU_EH_FRAME, elfcpp::PF_R);
259 this->segment_list_.push_back(hdr_oseg);
260 hdr_oseg->add_output_section(hdr_os, elfcpp::PF_R);
264 gold_assert(this->eh_frame_section_ == os);
266 *off = os->add_input_section(object, shndx, name, shdr);
269 // Add POSD to an output section using NAME, TYPE, and FLAGS.
272 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
273 elfcpp::Elf_Xword flags,
274 Output_section_data* posd)
276 // Canonicalize the name.
277 Stringpool::Key name_key;
278 name = this->namepool_.add(name, &name_key);
280 Output_section* os = this->get_output_section(name, name_key, type, flags);
281 os->add_output_section_data(posd);
284 // Map section flags to segment flags.
287 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
289 elfcpp::Elf_Word ret = elfcpp::PF_R;
290 if ((flags & elfcpp::SHF_WRITE) != 0)
292 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
297 // Make a new Output_section, and attach it to segments as
301 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
302 elfcpp::Elf_Xword flags)
304 Output_section* os = new Output_section(name, type, flags);
305 this->section_list_.push_back(os);
307 if ((flags & elfcpp::SHF_ALLOC) == 0)
308 this->unattached_section_list_.push_back(os);
311 // This output section goes into a PT_LOAD segment.
313 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
315 // The only thing we really care about for PT_LOAD segments is
316 // whether or not they are writable, so that is how we search
317 // for them. People who need segments sorted on some other
318 // basis will have to wait until we implement a mechanism for
319 // them to describe the segments they want.
321 Segment_list::const_iterator p;
322 for (p = this->segment_list_.begin();
323 p != this->segment_list_.end();
326 if ((*p)->type() == elfcpp::PT_LOAD
327 && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
329 (*p)->add_output_section(os, seg_flags);
334 if (p == this->segment_list_.end())
336 Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
338 this->segment_list_.push_back(oseg);
339 oseg->add_output_section(os, seg_flags);
342 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
344 if (type == elfcpp::SHT_NOTE)
346 // See if we already have an equivalent PT_NOTE segment.
347 for (p = this->segment_list_.begin();
348 p != segment_list_.end();
351 if ((*p)->type() == elfcpp::PT_NOTE
352 && (((*p)->flags() & elfcpp::PF_W)
353 == (seg_flags & elfcpp::PF_W)))
355 (*p)->add_output_section(os, seg_flags);
360 if (p == this->segment_list_.end())
362 Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
364 this->segment_list_.push_back(oseg);
365 oseg->add_output_section(os, seg_flags);
369 // If we see a loadable SHF_TLS section, we create a PT_TLS
370 // segment. There can only be one such segment.
371 if ((flags & elfcpp::SHF_TLS) != 0)
373 if (this->tls_segment_ == NULL)
375 this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
377 this->segment_list_.push_back(this->tls_segment_);
379 this->tls_segment_->add_output_section(os, seg_flags);
386 // Create the dynamic sections which are needed before we read the
390 Layout::create_initial_dynamic_sections(const Input_objects* input_objects,
391 Symbol_table* symtab)
393 if (!input_objects->any_dynamic())
396 const char* dynamic_name = this->namepool_.add(".dynamic", NULL);
397 this->dynamic_section_ = this->make_output_section(dynamic_name,
400 | elfcpp::SHF_WRITE));
402 symtab->define_in_output_data(input_objects->target(), "_DYNAMIC", NULL,
403 this->dynamic_section_, 0, 0,
404 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
405 elfcpp::STV_HIDDEN, 0, false, false);
407 this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
409 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
412 // For each output section whose name can be represented as C symbol,
413 // define __start and __stop symbols for the section. This is a GNU
417 Layout::define_section_symbols(Symbol_table* symtab, const Target* target)
419 for (Section_list::const_iterator p = this->section_list_.begin();
420 p != this->section_list_.end();
423 const char* const name = (*p)->name();
424 if (name[strspn(name,
426 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
427 "abcdefghijklmnopqrstuvwxyz"
431 const std::string name_string(name);
432 const std::string start_name("__start_" + name_string);
433 const std::string stop_name("__stop_" + name_string);
435 symtab->define_in_output_data(target,
445 false, // offset_is_from_end
446 false); // only_if_ref
448 symtab->define_in_output_data(target,
458 true, // offset_is_from_end
459 false); // only_if_ref
464 // Find the first read-only PT_LOAD segment, creating one if
468 Layout::find_first_load_seg()
470 for (Segment_list::const_iterator p = this->segment_list_.begin();
471 p != this->segment_list_.end();
474 if ((*p)->type() == elfcpp::PT_LOAD
475 && ((*p)->flags() & elfcpp::PF_R) != 0
476 && ((*p)->flags() & elfcpp::PF_W) == 0)
480 Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
481 this->segment_list_.push_back(load_seg);
485 // Finalize the layout. When this is called, we have created all the
486 // output sections and all the output segments which are based on
487 // input sections. We have several things to do, and we have to do
488 // them in the right order, so that we get the right results correctly
491 // 1) Finalize the list of output segments and create the segment
494 // 2) Finalize the dynamic symbol table and associated sections.
496 // 3) Determine the final file offset of all the output segments.
498 // 4) Determine the final file offset of all the SHF_ALLOC output
501 // 5) Create the symbol table sections and the section name table
504 // 6) Finalize the symbol table: set symbol values to their final
505 // value and make a final determination of which symbols are going
506 // into the output symbol table.
508 // 7) Create the section table header.
510 // 8) Determine the final file offset of all the output sections which
511 // are not SHF_ALLOC, including the section table header.
513 // 9) Finalize the ELF file header.
515 // This function returns the size of the output file.
518 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab)
520 Target* const target = input_objects->target();
522 target->finalize_sections(this);
524 this->create_note_section();
526 Output_segment* phdr_seg = NULL;
527 if (input_objects->any_dynamic())
529 // There was a dynamic object in the link. We need to create
530 // some information for the dynamic linker.
532 // Create the PT_PHDR segment which will hold the program
534 phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
535 this->segment_list_.push_back(phdr_seg);
537 // Create the dynamic symbol table, including the hash table.
538 Output_section* dynstr;
539 std::vector<Symbol*> dynamic_symbols;
540 unsigned int local_dynamic_count;
542 this->create_dynamic_symtab(target, symtab, &dynstr,
543 &local_dynamic_count, &dynamic_symbols,
546 // Create the .interp section to hold the name of the
547 // interpreter, and put it in a PT_INTERP segment.
548 this->create_interp(target);
550 // Finish the .dynamic section to hold the dynamic data, and put
551 // it in a PT_DYNAMIC segment.
552 this->finish_dynamic_section(input_objects, symtab);
554 // We should have added everything we need to the dynamic string
556 this->dynpool_.set_string_offsets();
558 // Create the version sections. We can't do this until the
559 // dynamic string table is complete.
560 this->create_version_sections(&versions, local_dynamic_count,
561 dynamic_symbols, dynstr);
564 // FIXME: Handle PT_GNU_STACK.
566 Output_segment* load_seg = this->find_first_load_seg();
568 // Lay out the segment headers.
569 Output_segment_headers* segment_headers;
570 segment_headers = new Output_segment_headers(this->segment_list_);
571 load_seg->add_initial_output_data(segment_headers);
572 this->special_output_list_.push_back(segment_headers);
573 if (phdr_seg != NULL)
574 phdr_seg->add_initial_output_data(segment_headers);
576 // Lay out the file header.
577 Output_file_header* file_header;
578 file_header = new Output_file_header(target, symtab, segment_headers);
579 load_seg->add_initial_output_data(file_header);
580 this->special_output_list_.push_back(file_header);
582 // We set the output section indexes in set_segment_offsets and
583 // set_section_offsets.
584 unsigned int shndx = 1;
586 // Set the file offsets of all the segments, and all the sections
588 off_t off = this->set_segment_offsets(target, load_seg, &shndx);
590 // Create the symbol table sections.
591 this->create_symtab_sections(input_objects, symtab, &off);
593 // Create the .shstrtab section.
594 Output_section* shstrtab_section = this->create_shstrtab();
596 // Set the file offsets of all the sections not associated with
598 off = this->set_section_offsets(off, &shndx);
600 // Create the section table header.
601 Output_section_headers* oshdrs = this->create_shdrs(&off);
603 file_header->set_section_info(oshdrs, shstrtab_section);
605 // Now we know exactly where everything goes in the output file.
606 Output_data::layout_complete();
611 // Create a .note section for an executable or shared library. This
612 // records the version of gold used to create the binary.
615 Layout::create_note_section()
617 if (parameters->output_is_object())
620 const int size = parameters->get_size();
622 // The contents of the .note section.
623 const char* name = "GNU";
624 std::string desc(std::string("gold ") + gold::get_version_string());
625 size_t namesz = strlen(name) + 1;
626 size_t aligned_namesz = align_address(namesz, size / 8);
627 size_t descsz = desc.length() + 1;
628 size_t aligned_descsz = align_address(descsz, size / 8);
629 const int note_type = 4;
631 size_t notesz = 3 * (size / 8) + aligned_namesz + aligned_descsz;
633 unsigned char buffer[128];
634 gold_assert(sizeof buffer >= notesz);
635 memset(buffer, 0, notesz);
637 bool is_big_endian = parameters->is_big_endian();
643 elfcpp::Swap<32, false>::writeval(buffer, namesz);
644 elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
645 elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
649 elfcpp::Swap<32, true>::writeval(buffer, namesz);
650 elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
651 elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
658 elfcpp::Swap<64, false>::writeval(buffer, namesz);
659 elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
660 elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
664 elfcpp::Swap<64, true>::writeval(buffer, namesz);
665 elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
666 elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
672 memcpy(buffer + 3 * (size / 8), name, namesz);
673 memcpy(buffer + 3 * (size / 8) + aligned_namesz, desc.data(), descsz);
675 const char* note_name = this->namepool_.add(".note", NULL);
676 Output_section* os = this->make_output_section(note_name,
679 Output_section_data* posd = new Output_data_const(buffer, notesz,
681 os->add_output_section_data(posd);
684 // Return whether SEG1 should be before SEG2 in the output file. This
685 // is based entirely on the segment type and flags. When this is
686 // called the segment addresses has normally not yet been set.
689 Layout::segment_precedes(const Output_segment* seg1,
690 const Output_segment* seg2)
692 elfcpp::Elf_Word type1 = seg1->type();
693 elfcpp::Elf_Word type2 = seg2->type();
695 // The single PT_PHDR segment is required to precede any loadable
696 // segment. We simply make it always first.
697 if (type1 == elfcpp::PT_PHDR)
699 gold_assert(type2 != elfcpp::PT_PHDR);
702 if (type2 == elfcpp::PT_PHDR)
705 // The single PT_INTERP segment is required to precede any loadable
706 // segment. We simply make it always second.
707 if (type1 == elfcpp::PT_INTERP)
709 gold_assert(type2 != elfcpp::PT_INTERP);
712 if (type2 == elfcpp::PT_INTERP)
715 // We then put PT_LOAD segments before any other segments.
716 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
718 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
721 // We put the PT_TLS segment last, because that is where the dynamic
722 // linker expects to find it (this is just for efficiency; other
723 // positions would also work correctly).
724 if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
726 if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
729 const elfcpp::Elf_Word flags1 = seg1->flags();
730 const elfcpp::Elf_Word flags2 = seg2->flags();
732 // The order of non-PT_LOAD segments is unimportant. We simply sort
733 // by the numeric segment type and flags values. There should not
734 // be more than one segment with the same type and flags.
735 if (type1 != elfcpp::PT_LOAD)
738 return type1 < type2;
739 gold_assert(flags1 != flags2);
740 return flags1 < flags2;
743 // We sort PT_LOAD segments based on the flags. Readonly segments
744 // come before writable segments. Then executable segments come
745 // before non-executable segments. Then the unlikely case of a
746 // non-readable segment comes before the normal case of a readable
747 // segment. If there are multiple segments with the same type and
748 // flags, we require that the address be set, and we sort by
749 // virtual address and then physical address.
750 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
751 return (flags1 & elfcpp::PF_W) == 0;
752 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
753 return (flags1 & elfcpp::PF_X) != 0;
754 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
755 return (flags1 & elfcpp::PF_R) == 0;
757 uint64_t vaddr1 = seg1->vaddr();
758 uint64_t vaddr2 = seg2->vaddr();
759 if (vaddr1 != vaddr2)
760 return vaddr1 < vaddr2;
762 uint64_t paddr1 = seg1->paddr();
763 uint64_t paddr2 = seg2->paddr();
764 gold_assert(paddr1 != paddr2);
765 return paddr1 < paddr2;
768 // Set the file offsets of all the segments, and all the sections they
769 // contain. They have all been created. LOAD_SEG must be be laid out
770 // first. Return the offset of the data to follow.
773 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
774 unsigned int *pshndx)
776 // Sort them into the final order.
777 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
778 Layout::Compare_segments());
780 // Find the PT_LOAD segments, and set their addresses and offsets
781 // and their section's addresses and offsets.
782 uint64_t addr = target->text_segment_address();
784 bool was_readonly = false;
785 for (Segment_list::iterator p = this->segment_list_.begin();
786 p != this->segment_list_.end();
789 if ((*p)->type() == elfcpp::PT_LOAD)
791 if (load_seg != NULL && load_seg != *p)
795 // If the last segment was readonly, and this one is not,
796 // then skip the address forward one page, maintaining the
797 // same position within the page. This lets us store both
798 // segments overlapping on a single page in the file, but
799 // the loader will put them on different pages in memory.
801 uint64_t orig_addr = addr;
802 uint64_t orig_off = off;
804 uint64_t aligned_addr = addr;
805 uint64_t abi_pagesize = target->abi_pagesize();
807 // FIXME: This should depend on the -n and -N options.
808 (*p)->set_minimum_addralign(target->common_pagesize());
810 if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
812 uint64_t align = (*p)->addralign();
814 addr = align_address(addr, align);
816 if ((addr & (abi_pagesize - 1)) != 0)
817 addr = addr + abi_pagesize;
820 unsigned int shndx_hold = *pshndx;
821 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
822 uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
824 // Now that we know the size of this segment, we may be able
825 // to save a page in memory, at the cost of wasting some
826 // file space, by instead aligning to the start of a new
827 // page. Here we use the real machine page size rather than
828 // the ABI mandated page size.
830 if (aligned_addr != addr)
832 uint64_t common_pagesize = target->common_pagesize();
833 uint64_t first_off = (common_pagesize
835 & (common_pagesize - 1)));
836 uint64_t last_off = new_addr & (common_pagesize - 1);
839 && ((aligned_addr & ~ (common_pagesize - 1))
840 != (new_addr & ~ (common_pagesize - 1)))
841 && first_off + last_off <= common_pagesize)
843 *pshndx = shndx_hold;
844 addr = align_address(aligned_addr, common_pagesize);
845 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
846 new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
852 if (((*p)->flags() & elfcpp::PF_W) == 0)
857 // Handle the non-PT_LOAD segments, setting their offsets from their
858 // section's offsets.
859 for (Segment_list::iterator p = this->segment_list_.begin();
860 p != this->segment_list_.end();
863 if ((*p)->type() != elfcpp::PT_LOAD)
870 // Set the file offset of all the sections not associated with a
874 Layout::set_section_offsets(off_t off, unsigned int* pshndx)
876 for (Section_list::iterator p = this->unattached_section_list_.begin();
877 p != this->unattached_section_list_.end();
880 (*p)->set_out_shndx(*pshndx);
882 if ((*p)->offset() != -1)
884 off = align_address(off, (*p)->addralign());
885 (*p)->set_address(0, off);
886 off += (*p)->data_size();
891 // Create the symbol table sections. Here we also set the final
892 // values of the symbols. At this point all the loadable sections are
896 Layout::create_symtab_sections(const Input_objects* input_objects,
897 Symbol_table* symtab,
902 if (parameters->get_size() == 32)
904 symsize = elfcpp::Elf_sizes<32>::sym_size;
907 else if (parameters->get_size() == 64)
909 symsize = elfcpp::Elf_sizes<64>::sym_size;
916 off = align_address(off, align);
917 off_t startoff = off;
919 // Save space for the dummy symbol at the start of the section. We
920 // never bother to write this out--it will just be left as zero.
922 unsigned int local_symbol_index = 1;
924 // Add STT_SECTION symbols for each Output section which needs one.
925 for (Section_list::iterator p = this->section_list_.begin();
926 p != this->section_list_.end();
929 if (!(*p)->needs_symtab_index())
930 (*p)->set_symtab_index(-1U);
933 (*p)->set_symtab_index(local_symbol_index);
934 ++local_symbol_index;
939 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
940 p != input_objects->relobj_end();
943 Task_lock_obj<Object> tlo(**p);
944 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
947 off += (index - local_symbol_index) * symsize;
948 local_symbol_index = index;
951 unsigned int local_symcount = local_symbol_index;
952 gold_assert(local_symcount * symsize == off - startoff);
955 size_t dyn_global_index;
957 if (this->dynsym_section_ == NULL)
960 dyn_global_index = 0;
965 dyn_global_index = this->dynsym_section_->info();
966 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
967 dynoff = this->dynsym_section_->offset() + locsize;
968 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
969 gold_assert(static_cast<off_t>(dyncount * symsize)
970 == this->dynsym_section_->data_size() - locsize);
973 off = symtab->finalize(local_symcount, off, dynoff, dyn_global_index,
974 dyncount, &this->sympool_);
976 this->sympool_.set_string_offsets();
978 const char* symtab_name = this->namepool_.add(".symtab", NULL);
979 Output_section* osymtab = this->make_output_section(symtab_name,
982 this->symtab_section_ = osymtab;
984 Output_section_data* pos = new Output_data_space(off - startoff,
986 osymtab->add_output_section_data(pos);
988 const char* strtab_name = this->namepool_.add(".strtab", NULL);
989 Output_section* ostrtab = this->make_output_section(strtab_name,
993 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
994 ostrtab->add_output_section_data(pstr);
996 osymtab->set_address(0, startoff);
997 osymtab->set_link_section(ostrtab);
998 osymtab->set_info(local_symcount);
999 osymtab->set_entsize(symsize);
1004 // Create the .shstrtab section, which holds the names of the
1005 // sections. At the time this is called, we have created all the
1006 // output sections except .shstrtab itself.
1009 Layout::create_shstrtab()
1011 // FIXME: We don't need to create a .shstrtab section if we are
1012 // stripping everything.
1014 const char* name = this->namepool_.add(".shstrtab", NULL);
1016 this->namepool_.set_string_offsets();
1018 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0);
1020 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
1021 os->add_output_section_data(posd);
1026 // Create the section headers. SIZE is 32 or 64. OFF is the file
1029 Output_section_headers*
1030 Layout::create_shdrs(off_t* poff)
1032 Output_section_headers* oshdrs;
1033 oshdrs = new Output_section_headers(this,
1034 &this->segment_list_,
1035 &this->unattached_section_list_,
1037 off_t off = align_address(*poff, oshdrs->addralign());
1038 oshdrs->set_address(0, off);
1039 off += oshdrs->data_size();
1041 this->special_output_list_.push_back(oshdrs);
1045 // Create the dynamic symbol table.
1048 Layout::create_dynamic_symtab(const Target* target, Symbol_table* symtab,
1049 Output_section **pdynstr,
1050 unsigned int* plocal_dynamic_count,
1051 std::vector<Symbol*>* pdynamic_symbols,
1052 Versions* pversions)
1054 // Count all the symbols in the dynamic symbol table, and set the
1055 // dynamic symbol indexes.
1057 // Skip symbol 0, which is always all zeroes.
1058 unsigned int index = 1;
1060 // Add STT_SECTION symbols for each Output section which needs one.
1061 for (Section_list::iterator p = this->section_list_.begin();
1062 p != this->section_list_.end();
1065 if (!(*p)->needs_dynsym_index())
1066 (*p)->set_dynsym_index(-1U);
1069 (*p)->set_dynsym_index(index);
1074 // FIXME: Some targets apparently require local symbols in the
1075 // dynamic symbol table. Here is where we will have to count them,
1076 // and set the dynamic symbol indexes, and add the names to
1079 unsigned int local_symcount = index;
1080 *plocal_dynamic_count = local_symcount;
1082 // FIXME: We have to tell set_dynsym_indexes whether the
1083 // -E/--export-dynamic option was used.
1084 index = symtab->set_dynsym_indexes(&this->options_, target, index,
1085 pdynamic_symbols, &this->dynpool_,
1090 const int size = parameters->get_size();
1093 symsize = elfcpp::Elf_sizes<32>::sym_size;
1096 else if (size == 64)
1098 symsize = elfcpp::Elf_sizes<64>::sym_size;
1104 // Create the dynamic symbol table section.
1106 const char* dynsym_name = this->namepool_.add(".dynsym", NULL);
1107 Output_section* dynsym = this->make_output_section(dynsym_name,
1111 Output_section_data* odata = new Output_data_space(index * symsize,
1113 dynsym->add_output_section_data(odata);
1115 dynsym->set_info(local_symcount);
1116 dynsym->set_entsize(symsize);
1117 dynsym->set_addralign(align);
1119 this->dynsym_section_ = dynsym;
1121 Output_data_dynamic* const odyn = this->dynamic_data_;
1122 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
1123 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
1125 // Create the dynamic string table section.
1127 const char* dynstr_name = this->namepool_.add(".dynstr", NULL);
1128 Output_section* dynstr = this->make_output_section(dynstr_name,
1132 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
1133 dynstr->add_output_section_data(strdata);
1135 dynsym->set_link_section(dynstr);
1136 this->dynamic_section_->set_link_section(dynstr);
1138 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
1139 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
1143 // Create the hash tables.
1145 // FIXME: We need an option to create a GNU hash table.
1147 unsigned char* phash;
1148 unsigned int hashlen;
1149 Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
1152 const char* hash_name = this->namepool_.add(".hash", NULL);
1153 Output_section* hashsec = this->make_output_section(hash_name,
1157 Output_section_data* hashdata = new Output_data_const_buffer(phash,
1160 hashsec->add_output_section_data(hashdata);
1162 hashsec->set_link_section(dynsym);
1163 hashsec->set_entsize(4);
1165 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
1168 // Create the version sections.
1171 Layout::create_version_sections(const Versions* versions,
1172 unsigned int local_symcount,
1173 const std::vector<Symbol*>& dynamic_symbols,
1174 const Output_section* dynstr)
1176 if (!versions->any_defs() && !versions->any_needs())
1179 if (parameters->get_size() == 32)
1181 if (parameters->is_big_endian())
1183 #ifdef HAVE_TARGET_32_BIG
1184 this->sized_create_version_sections
1185 SELECT_SIZE_ENDIAN_NAME(32, true)(
1186 versions, local_symcount, dynamic_symbols, dynstr
1187 SELECT_SIZE_ENDIAN(32, true));
1194 #ifdef HAVE_TARGET_32_LITTLE
1195 this->sized_create_version_sections
1196 SELECT_SIZE_ENDIAN_NAME(32, false)(
1197 versions, local_symcount, dynamic_symbols, dynstr
1198 SELECT_SIZE_ENDIAN(32, false));
1204 else if (parameters->get_size() == 64)
1206 if (parameters->is_big_endian())
1208 #ifdef HAVE_TARGET_64_BIG
1209 this->sized_create_version_sections
1210 SELECT_SIZE_ENDIAN_NAME(64, true)(
1211 versions, local_symcount, dynamic_symbols, dynstr
1212 SELECT_SIZE_ENDIAN(64, true));
1219 #ifdef HAVE_TARGET_64_LITTLE
1220 this->sized_create_version_sections
1221 SELECT_SIZE_ENDIAN_NAME(64, false)(
1222 versions, local_symcount, dynamic_symbols, dynstr
1223 SELECT_SIZE_ENDIAN(64, false));
1233 // Create the version sections, sized version.
1235 template<int size, bool big_endian>
1237 Layout::sized_create_version_sections(
1238 const Versions* versions,
1239 unsigned int local_symcount,
1240 const std::vector<Symbol*>& dynamic_symbols,
1241 const Output_section* dynstr
1244 const char* vname = this->namepool_.add(".gnu.version", NULL);
1245 Output_section* vsec = this->make_output_section(vname,
1246 elfcpp::SHT_GNU_versym,
1249 unsigned char* vbuf;
1251 versions->symbol_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1252 &this->dynpool_, local_symcount, dynamic_symbols, &vbuf, &vsize
1253 SELECT_SIZE_ENDIAN(size, big_endian));
1255 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2);
1257 vsec->add_output_section_data(vdata);
1258 vsec->set_entsize(2);
1259 vsec->set_link_section(this->dynsym_section_);
1261 Output_data_dynamic* const odyn = this->dynamic_data_;
1262 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
1264 if (versions->any_defs())
1266 const char* vdname = this->namepool_.add(".gnu.version_d", NULL);
1267 Output_section *vdsec;
1268 vdsec = this->make_output_section(vdname, elfcpp::SHT_GNU_verdef,
1271 unsigned char* vdbuf;
1272 unsigned int vdsize;
1273 unsigned int vdentries;
1274 versions->def_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1275 &this->dynpool_, &vdbuf, &vdsize, &vdentries
1276 SELECT_SIZE_ENDIAN(size, big_endian));
1278 Output_section_data* vddata = new Output_data_const_buffer(vdbuf,
1282 vdsec->add_output_section_data(vddata);
1283 vdsec->set_link_section(dynstr);
1284 vdsec->set_info(vdentries);
1286 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
1287 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
1290 if (versions->any_needs())
1292 const char* vnname = this->namepool_.add(".gnu.version_r", NULL);
1293 Output_section* vnsec;
1294 vnsec = this->make_output_section(vnname, elfcpp::SHT_GNU_verneed,
1297 unsigned char* vnbuf;
1298 unsigned int vnsize;
1299 unsigned int vnentries;
1300 versions->need_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)
1301 (&this->dynpool_, &vnbuf, &vnsize, &vnentries
1302 SELECT_SIZE_ENDIAN(size, big_endian));
1304 Output_section_data* vndata = new Output_data_const_buffer(vnbuf,
1308 vnsec->add_output_section_data(vndata);
1309 vnsec->set_link_section(dynstr);
1310 vnsec->set_info(vnentries);
1312 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
1313 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
1317 // Create the .interp section and PT_INTERP segment.
1320 Layout::create_interp(const Target* target)
1322 const char* interp = this->options_.dynamic_linker();
1325 interp = target->dynamic_linker();
1326 gold_assert(interp != NULL);
1329 size_t len = strlen(interp) + 1;
1331 Output_section_data* odata = new Output_data_const(interp, len, 1);
1333 const char* interp_name = this->namepool_.add(".interp", NULL);
1334 Output_section* osec = this->make_output_section(interp_name,
1335 elfcpp::SHT_PROGBITS,
1337 osec->add_output_section_data(odata);
1339 Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
1340 this->segment_list_.push_back(oseg);
1341 oseg->add_initial_output_section(osec, elfcpp::PF_R);
1344 // Finish the .dynamic section and PT_DYNAMIC segment.
1347 Layout::finish_dynamic_section(const Input_objects* input_objects,
1348 const Symbol_table* symtab)
1350 Output_segment* oseg = new Output_segment(elfcpp::PT_DYNAMIC,
1351 elfcpp::PF_R | elfcpp::PF_W);
1352 this->segment_list_.push_back(oseg);
1353 oseg->add_initial_output_section(this->dynamic_section_,
1354 elfcpp::PF_R | elfcpp::PF_W);
1356 Output_data_dynamic* const odyn = this->dynamic_data_;
1358 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
1359 p != input_objects->dynobj_end();
1362 // FIXME: Handle --as-needed.
1363 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
1366 // FIXME: Support --init and --fini.
1367 Symbol* sym = symtab->lookup("_init");
1368 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1369 odyn->add_symbol(elfcpp::DT_INIT, sym);
1371 sym = symtab->lookup("_fini");
1372 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1373 odyn->add_symbol(elfcpp::DT_FINI, sym);
1375 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1377 // Add a DT_RPATH entry if needed.
1378 const General_options::Dir_list& rpath(this->options_.rpath());
1381 std::string rpath_val;
1382 for (General_options::Dir_list::const_iterator p = rpath.begin();
1386 if (rpath_val.empty())
1387 rpath_val = p->name();
1390 // Eliminate duplicates.
1391 General_options::Dir_list::const_iterator q;
1392 for (q = rpath.begin(); q != p; ++q)
1393 if (q->name() == p->name())
1398 rpath_val += p->name();
1403 odyn->add_string(elfcpp::DT_RPATH, rpath_val);
1407 // The mapping of .gnu.linkonce section names to real section names.
1409 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1410 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
1412 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1413 MAPPING_INIT("t", ".text"),
1414 MAPPING_INIT("r", ".rodata"),
1415 MAPPING_INIT("d", ".data"),
1416 MAPPING_INIT("b", ".bss"),
1417 MAPPING_INIT("s", ".sdata"),
1418 MAPPING_INIT("sb", ".sbss"),
1419 MAPPING_INIT("s2", ".sdata2"),
1420 MAPPING_INIT("sb2", ".sbss2"),
1421 MAPPING_INIT("wi", ".debug_info"),
1422 MAPPING_INIT("td", ".tdata"),
1423 MAPPING_INIT("tb", ".tbss"),
1424 MAPPING_INIT("lr", ".lrodata"),
1425 MAPPING_INIT("l", ".ldata"),
1426 MAPPING_INIT("lb", ".lbss"),
1430 const int Layout::linkonce_mapping_count =
1431 sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
1433 // Return the name of the output section to use for a .gnu.linkonce
1434 // section. This is based on the default ELF linker script of the old
1435 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1436 // to ".text". Set *PLEN to the length of the name. *PLEN is
1437 // initialized to the length of NAME.
1440 Layout::linkonce_output_name(const char* name, size_t *plen)
1442 const char* s = name + sizeof(".gnu.linkonce") - 1;
1446 const Linkonce_mapping* plm = linkonce_mapping;
1447 for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
1449 if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
1458 // Choose the output section name to use given an input section name.
1459 // Set *PLEN to the length of the name. *PLEN is initialized to the
1463 Layout::output_section_name(const char* name, size_t* plen)
1465 if (Layout::is_linkonce(name))
1467 // .gnu.linkonce sections are laid out as though they were named
1468 // for the sections are placed into.
1469 return Layout::linkonce_output_name(name, plen);
1472 // If the section name has no '.', or only an initial '.', we use
1473 // the name unchanged (i.e., ".text" is unchanged).
1475 // Otherwise, if the section name does not include ".rel", we drop
1476 // the last '.' and everything that follows (i.e., ".text.XXX"
1477 // becomes ".text").
1479 // Otherwise, if the section name has zero or one '.' after the
1480 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1483 // Otherwise, we drop the last '.' and everything that follows
1484 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1486 const char* s = name;
1489 const char* sdot = strchr(s, '.');
1493 const char* srel = strstr(s, ".rel");
1496 *plen = sdot - name;
1500 sdot = strchr(srel + 1, '.');
1503 sdot = strchr(sdot + 1, '.');
1507 *plen = sdot - name;
1511 // Record the signature of a comdat section, and return whether to
1512 // include it in the link. If GROUP is true, this is a regular
1513 // section group. If GROUP is false, this is a group signature
1514 // derived from the name of a linkonce section. We want linkonce
1515 // signatures and group signatures to block each other, but we don't
1516 // want a linkonce signature to block another linkonce signature.
1519 Layout::add_comdat(const char* signature, bool group)
1521 std::string sig(signature);
1522 std::pair<Signatures::iterator, bool> ins(
1523 this->signatures_.insert(std::make_pair(sig, group)));
1527 // This is the first time we've seen this signature.
1531 if (ins.first->second)
1533 // We've already seen a real section group with this signature.
1538 // This is a real section group, and we've already seen a
1539 // linkonce section with this signature. Record that we've seen
1540 // a section group, and don't include this section group.
1541 ins.first->second = true;
1546 // We've already seen a linkonce section and this is a linkonce
1547 // section. These don't block each other--this may be the same
1548 // symbol name with different section types.
1553 // Write out data not associated with a section or the symbol table.
1556 Layout::write_data(const Symbol_table* symtab, Output_file* of) const
1558 const Output_section* symtab_section = this->symtab_section_;
1559 for (Section_list::const_iterator p = this->section_list_.begin();
1560 p != this->section_list_.end();
1563 if ((*p)->needs_symtab_index())
1565 gold_assert(symtab_section != NULL);
1566 unsigned int index = (*p)->symtab_index();
1567 gold_assert(index > 0 && index != -1U);
1568 off_t off = (symtab_section->offset()
1569 + index * symtab_section->entsize());
1570 symtab->write_section_symbol(*p, of, off);
1574 const Output_section* dynsym_section = this->dynsym_section_;
1575 for (Section_list::const_iterator p = this->section_list_.begin();
1576 p != this->section_list_.end();
1579 if ((*p)->needs_dynsym_index())
1581 gold_assert(dynsym_section != NULL);
1582 unsigned int index = (*p)->dynsym_index();
1583 gold_assert(index > 0 && index != -1U);
1584 off_t off = (dynsym_section->offset()
1585 + index * dynsym_section->entsize());
1586 symtab->write_section_symbol(*p, of, off);
1590 // Write out the Output_sections. Most won't have anything to
1591 // write, since most of the data will come from input sections which
1592 // are handled elsewhere. But some Output_sections do have
1594 for (Section_list::const_iterator p = this->section_list_.begin();
1595 p != this->section_list_.end();
1599 // Write out the Output_data which are not in an Output_section.
1600 for (Data_list::const_iterator p = this->special_output_list_.begin();
1601 p != this->special_output_list_.end();
1606 // Write_data_task methods.
1608 // We can always run this task.
1610 Task::Is_runnable_type
1611 Write_data_task::is_runnable(Workqueue*)
1616 // We need to unlock FINAL_BLOCKER when finished.
1619 Write_data_task::locks(Workqueue* workqueue)
1621 return new Task_locker_block(*this->final_blocker_, workqueue);
1624 // Run the task--write out the data.
1627 Write_data_task::run(Workqueue*)
1629 this->layout_->write_data(this->symtab_, this->of_);
1632 // Write_symbols_task methods.
1634 // We can always run this task.
1636 Task::Is_runnable_type
1637 Write_symbols_task::is_runnable(Workqueue*)
1642 // We need to unlock FINAL_BLOCKER when finished.
1645 Write_symbols_task::locks(Workqueue* workqueue)
1647 return new Task_locker_block(*this->final_blocker_, workqueue);
1650 // Run the task--write out the symbols.
1653 Write_symbols_task::run(Workqueue*)
1655 this->symtab_->write_globals(this->target_, this->sympool_, this->dynpool_,
1659 // Close_task_runner methods.
1661 // Run the task--close the file.
1664 Close_task_runner::run(Workqueue*)
1669 // Instantiate the templates we need. We could use the configure
1670 // script to restrict this to only the ones for implemented targets.
1672 #ifdef HAVE_TARGET_32_LITTLE
1675 Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name,
1676 const elfcpp::Shdr<32, false>& shdr, off_t*);
1679 #ifdef HAVE_TARGET_32_BIG
1682 Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name,
1683 const elfcpp::Shdr<32, true>& shdr, off_t*);
1686 #ifdef HAVE_TARGET_64_LITTLE
1689 Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name,
1690 const elfcpp::Shdr<64, false>& shdr, off_t*);
1693 #ifdef HAVE_TARGET_64_BIG
1696 Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name,
1697 const elfcpp::Shdr<64, true>& shdr, off_t*);
1701 } // End namespace gold.