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 // Return whether PREFIX is a prefix of STR.
92 is_prefix_of(const char* prefix, const char* str)
94 return strncmp(prefix, str, strlen(prefix)) == 0;
97 // Whether to include this section in the link.
99 template<int size, bool big_endian>
101 Layout::include_section(Object*, const char* name,
102 const elfcpp::Shdr<size, big_endian>& shdr)
104 // Some section types are never linked. Some are only linked when
105 // doing a relocateable link.
106 switch (shdr.get_sh_type())
108 case elfcpp::SHT_NULL:
109 case elfcpp::SHT_SYMTAB:
110 case elfcpp::SHT_DYNSYM:
111 case elfcpp::SHT_STRTAB:
112 case elfcpp::SHT_HASH:
113 case elfcpp::SHT_DYNAMIC:
114 case elfcpp::SHT_SYMTAB_SHNDX:
117 case elfcpp::SHT_RELA:
118 case elfcpp::SHT_REL:
119 case elfcpp::SHT_GROUP:
120 return parameters->output_is_object();
122 case elfcpp::SHT_PROGBITS:
123 if (parameters->strip_debug()
124 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
126 // Debugging sections can only be recognized by name.
127 if (is_prefix_of(".debug", name)
128 || is_prefix_of(".gnu.linkonce.wi.", name)
129 || is_prefix_of(".line", name)
130 || is_prefix_of(".stab", name))
140 // Return an output section named NAME, or NULL if there is none.
143 Layout::find_output_section(const char* name) const
145 for (Section_name_map::const_iterator p = this->section_name_map_.begin();
146 p != this->section_name_map_.end();
148 if (strcmp(p->second->name(), name) == 0)
153 // Return an output segment of type TYPE, with segment flags SET set
154 // and segment flags CLEAR clear. Return NULL if there is none.
157 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
158 elfcpp::Elf_Word clear) const
160 for (Segment_list::const_iterator p = this->segment_list_.begin();
161 p != this->segment_list_.end();
163 if (static_cast<elfcpp::PT>((*p)->type()) == type
164 && ((*p)->flags() & set) == set
165 && ((*p)->flags() & clear) == 0)
170 // Return the output section to use for section NAME with type TYPE
171 // and section flags FLAGS.
174 Layout::get_output_section(const char* name, Stringpool::Key name_key,
175 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
177 // We should ignore some flags.
178 flags &= ~ (elfcpp::SHF_INFO_LINK
179 | elfcpp::SHF_LINK_ORDER
182 | elfcpp::SHF_STRINGS);
184 const Key key(name_key, std::make_pair(type, flags));
185 const std::pair<Key, Output_section*> v(key, NULL);
186 std::pair<Section_name_map::iterator, bool> ins(
187 this->section_name_map_.insert(v));
190 return ins.first->second;
193 // This is the first time we've seen this name/type/flags
195 Output_section* os = this->make_output_section(name, type, flags);
196 ins.first->second = os;
201 // Return the output section to use for input section SHNDX, with name
202 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
203 // offset of this input section without the output section.
205 template<int size, bool big_endian>
207 Layout::layout(Relobj* object, unsigned int shndx, const char* name,
208 const elfcpp::Shdr<size, big_endian>& shdr, off_t* off)
210 if (!this->include_section(object, name, shdr))
213 // If we are not doing a relocateable link, choose the name to use
214 // for the output section.
215 size_t len = strlen(name);
216 if (!parameters->output_is_object())
217 name = Layout::output_section_name(name, &len);
219 // FIXME: Handle SHF_OS_NONCONFORMING here.
221 // Canonicalize the section name.
222 Stringpool::Key name_key;
223 name = this->namepool_.add(name, len, &name_key);
225 // Find the output section. The output section is selected based on
226 // the section name, type, and flags.
227 Output_section* os = this->get_output_section(name, name_key,
229 shdr.get_sh_flags());
231 // Special GNU handling of sections named .eh_frame.
232 if (!parameters->output_is_object()
233 && strcmp(name, ".eh_frame") == 0
234 && shdr.get_sh_size() > 0
235 && shdr.get_sh_type() == elfcpp::SHT_PROGBITS
236 && shdr.get_sh_flags() == elfcpp::SHF_ALLOC)
238 this->layout_eh_frame(object, shndx, name, shdr, os, off);
242 // FIXME: Handle SHF_LINK_ORDER somewhere.
244 *off = os->add_input_section(object, shndx, name, shdr);
249 // Special GNU handling of sections named .eh_frame. They will
250 // normally hold exception frame data.
252 template<int size, bool big_endian>
254 Layout::layout_eh_frame(Relobj* object,
257 const elfcpp::Shdr<size, big_endian>& shdr,
258 Output_section* os, off_t* off)
260 if (this->eh_frame_section_ == NULL)
262 this->eh_frame_section_ = os;
264 if (this->options_.create_eh_frame_hdr())
266 Stringpool::Key hdr_name_key;
267 const char* hdr_name = this->namepool_.add(".eh_frame_hdr",
269 Output_section* hdr_os =
270 this->get_output_section(hdr_name, hdr_name_key,
271 elfcpp::SHT_PROGBITS,
274 Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os);
275 hdr_os->add_output_section_data(hdr_posd);
277 Output_segment* hdr_oseg =
278 new Output_segment(elfcpp::PT_GNU_EH_FRAME, elfcpp::PF_R);
279 this->segment_list_.push_back(hdr_oseg);
280 hdr_oseg->add_output_section(hdr_os, elfcpp::PF_R);
284 gold_assert(this->eh_frame_section_ == os);
286 *off = os->add_input_section(object, shndx, name, shdr);
289 // Add POSD to an output section using NAME, TYPE, and FLAGS.
292 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
293 elfcpp::Elf_Xword flags,
294 Output_section_data* posd)
296 // Canonicalize the name.
297 Stringpool::Key name_key;
298 name = this->namepool_.add(name, &name_key);
300 Output_section* os = this->get_output_section(name, name_key, type, flags);
301 os->add_output_section_data(posd);
304 // Map section flags to segment flags.
307 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
309 elfcpp::Elf_Word ret = elfcpp::PF_R;
310 if ((flags & elfcpp::SHF_WRITE) != 0)
312 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
317 // Make a new Output_section, and attach it to segments as
321 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
322 elfcpp::Elf_Xword flags)
324 Output_section* os = new Output_section(name, type, flags);
325 this->section_list_.push_back(os);
327 if ((flags & elfcpp::SHF_ALLOC) == 0)
328 this->unattached_section_list_.push_back(os);
331 // This output section goes into a PT_LOAD segment.
333 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
335 // The only thing we really care about for PT_LOAD segments is
336 // whether or not they are writable, so that is how we search
337 // for them. People who need segments sorted on some other
338 // basis will have to wait until we implement a mechanism for
339 // them to describe the segments they want.
341 Segment_list::const_iterator p;
342 for (p = this->segment_list_.begin();
343 p != this->segment_list_.end();
346 if ((*p)->type() == elfcpp::PT_LOAD
347 && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
349 (*p)->add_output_section(os, seg_flags);
354 if (p == this->segment_list_.end())
356 Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
358 this->segment_list_.push_back(oseg);
359 oseg->add_output_section(os, seg_flags);
362 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
364 if (type == elfcpp::SHT_NOTE)
366 // See if we already have an equivalent PT_NOTE segment.
367 for (p = this->segment_list_.begin();
368 p != segment_list_.end();
371 if ((*p)->type() == elfcpp::PT_NOTE
372 && (((*p)->flags() & elfcpp::PF_W)
373 == (seg_flags & elfcpp::PF_W)))
375 (*p)->add_output_section(os, seg_flags);
380 if (p == this->segment_list_.end())
382 Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
384 this->segment_list_.push_back(oseg);
385 oseg->add_output_section(os, seg_flags);
389 // If we see a loadable SHF_TLS section, we create a PT_TLS
390 // segment. There can only be one such segment.
391 if ((flags & elfcpp::SHF_TLS) != 0)
393 if (this->tls_segment_ == NULL)
395 this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
397 this->segment_list_.push_back(this->tls_segment_);
399 this->tls_segment_->add_output_section(os, seg_flags);
406 // Create the dynamic sections which are needed before we read the
410 Layout::create_initial_dynamic_sections(const Input_objects* input_objects,
411 Symbol_table* symtab)
413 if (!input_objects->any_dynamic())
416 const char* dynamic_name = this->namepool_.add(".dynamic", NULL);
417 this->dynamic_section_ = this->make_output_section(dynamic_name,
420 | elfcpp::SHF_WRITE));
422 symtab->define_in_output_data(input_objects->target(), "_DYNAMIC", NULL,
423 this->dynamic_section_, 0, 0,
424 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
425 elfcpp::STV_HIDDEN, 0, false, false);
427 this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
429 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
432 // For each output section whose name can be represented as C symbol,
433 // define __start and __stop symbols for the section. This is a GNU
437 Layout::define_section_symbols(Symbol_table* symtab, const Target* target)
439 for (Section_list::const_iterator p = this->section_list_.begin();
440 p != this->section_list_.end();
443 const char* const name = (*p)->name();
444 if (name[strspn(name,
446 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
447 "abcdefghijklmnopqrstuvwxyz"
451 const std::string name_string(name);
452 const std::string start_name("__start_" + name_string);
453 const std::string stop_name("__stop_" + name_string);
455 symtab->define_in_output_data(target,
465 false, // offset_is_from_end
466 false); // only_if_ref
468 symtab->define_in_output_data(target,
478 true, // offset_is_from_end
479 false); // only_if_ref
484 // Find the first read-only PT_LOAD segment, creating one if
488 Layout::find_first_load_seg()
490 for (Segment_list::const_iterator p = this->segment_list_.begin();
491 p != this->segment_list_.end();
494 if ((*p)->type() == elfcpp::PT_LOAD
495 && ((*p)->flags() & elfcpp::PF_R) != 0
496 && ((*p)->flags() & elfcpp::PF_W) == 0)
500 Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
501 this->segment_list_.push_back(load_seg);
505 // Finalize the layout. When this is called, we have created all the
506 // output sections and all the output segments which are based on
507 // input sections. We have several things to do, and we have to do
508 // them in the right order, so that we get the right results correctly
511 // 1) Finalize the list of output segments and create the segment
514 // 2) Finalize the dynamic symbol table and associated sections.
516 // 3) Determine the final file offset of all the output segments.
518 // 4) Determine the final file offset of all the SHF_ALLOC output
521 // 5) Create the symbol table sections and the section name table
524 // 6) Finalize the symbol table: set symbol values to their final
525 // value and make a final determination of which symbols are going
526 // into the output symbol table.
528 // 7) Create the section table header.
530 // 8) Determine the final file offset of all the output sections which
531 // are not SHF_ALLOC, including the section table header.
533 // 9) Finalize the ELF file header.
535 // This function returns the size of the output file.
538 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab)
540 Target* const target = input_objects->target();
542 target->finalize_sections(this);
544 this->create_note_section();
546 Output_segment* phdr_seg = NULL;
547 if (input_objects->any_dynamic())
549 // There was a dynamic object in the link. We need to create
550 // some information for the dynamic linker.
552 // Create the PT_PHDR segment which will hold the program
554 phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
555 this->segment_list_.push_back(phdr_seg);
557 // Create the dynamic symbol table, including the hash table.
558 Output_section* dynstr;
559 std::vector<Symbol*> dynamic_symbols;
560 unsigned int local_dynamic_count;
562 this->create_dynamic_symtab(target, symtab, &dynstr,
563 &local_dynamic_count, &dynamic_symbols,
566 // Create the .interp section to hold the name of the
567 // interpreter, and put it in a PT_INTERP segment.
568 this->create_interp(target);
570 // Finish the .dynamic section to hold the dynamic data, and put
571 // it in a PT_DYNAMIC segment.
572 this->finish_dynamic_section(input_objects, symtab);
574 // We should have added everything we need to the dynamic string
576 this->dynpool_.set_string_offsets();
578 // Create the version sections. We can't do this until the
579 // dynamic string table is complete.
580 this->create_version_sections(&versions, local_dynamic_count,
581 dynamic_symbols, dynstr);
584 // FIXME: Handle PT_GNU_STACK.
586 Output_segment* load_seg = this->find_first_load_seg();
588 // Lay out the segment headers.
589 Output_segment_headers* segment_headers;
590 segment_headers = new Output_segment_headers(this->segment_list_);
591 load_seg->add_initial_output_data(segment_headers);
592 this->special_output_list_.push_back(segment_headers);
593 if (phdr_seg != NULL)
594 phdr_seg->add_initial_output_data(segment_headers);
596 // Lay out the file header.
597 Output_file_header* file_header;
598 file_header = new Output_file_header(target, symtab, segment_headers);
599 load_seg->add_initial_output_data(file_header);
600 this->special_output_list_.push_back(file_header);
602 // We set the output section indexes in set_segment_offsets and
603 // set_section_offsets.
604 unsigned int shndx = 1;
606 // Set the file offsets of all the segments, and all the sections
608 off_t off = this->set_segment_offsets(target, load_seg, &shndx);
610 // Create the symbol table sections.
611 this->create_symtab_sections(input_objects, symtab, &off);
613 // Create the .shstrtab section.
614 Output_section* shstrtab_section = this->create_shstrtab();
616 // Set the file offsets of all the sections not associated with
618 off = this->set_section_offsets(off, &shndx);
620 // Create the section table header.
621 Output_section_headers* oshdrs = this->create_shdrs(&off);
623 file_header->set_section_info(oshdrs, shstrtab_section);
625 // Now we know exactly where everything goes in the output file.
626 Output_data::layout_complete();
631 // Create a .note section for an executable or shared library. This
632 // records the version of gold used to create the binary.
635 Layout::create_note_section()
637 if (parameters->output_is_object())
640 const int size = parameters->get_size();
642 // The contents of the .note section.
643 const char* name = "GNU";
644 std::string desc(std::string("gold ") + gold::get_version_string());
645 size_t namesz = strlen(name) + 1;
646 size_t aligned_namesz = align_address(namesz, size / 8);
647 size_t descsz = desc.length() + 1;
648 size_t aligned_descsz = align_address(descsz, size / 8);
649 const int note_type = 4;
651 size_t notesz = 3 * (size / 8) + aligned_namesz + aligned_descsz;
653 unsigned char buffer[128];
654 gold_assert(sizeof buffer >= notesz);
655 memset(buffer, 0, notesz);
657 bool is_big_endian = parameters->is_big_endian();
663 elfcpp::Swap<32, false>::writeval(buffer, namesz);
664 elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
665 elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
669 elfcpp::Swap<32, true>::writeval(buffer, namesz);
670 elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
671 elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
678 elfcpp::Swap<64, false>::writeval(buffer, namesz);
679 elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
680 elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
684 elfcpp::Swap<64, true>::writeval(buffer, namesz);
685 elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
686 elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
692 memcpy(buffer + 3 * (size / 8), name, namesz);
693 memcpy(buffer + 3 * (size / 8) + aligned_namesz, desc.data(), descsz);
695 const char* note_name = this->namepool_.add(".note", NULL);
696 Output_section* os = this->make_output_section(note_name,
699 Output_section_data* posd = new Output_data_const(buffer, notesz,
701 os->add_output_section_data(posd);
704 // Return whether SEG1 should be before SEG2 in the output file. This
705 // is based entirely on the segment type and flags. When this is
706 // called the segment addresses has normally not yet been set.
709 Layout::segment_precedes(const Output_segment* seg1,
710 const Output_segment* seg2)
712 elfcpp::Elf_Word type1 = seg1->type();
713 elfcpp::Elf_Word type2 = seg2->type();
715 // The single PT_PHDR segment is required to precede any loadable
716 // segment. We simply make it always first.
717 if (type1 == elfcpp::PT_PHDR)
719 gold_assert(type2 != elfcpp::PT_PHDR);
722 if (type2 == elfcpp::PT_PHDR)
725 // The single PT_INTERP segment is required to precede any loadable
726 // segment. We simply make it always second.
727 if (type1 == elfcpp::PT_INTERP)
729 gold_assert(type2 != elfcpp::PT_INTERP);
732 if (type2 == elfcpp::PT_INTERP)
735 // We then put PT_LOAD segments before any other segments.
736 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
738 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
741 // We put the PT_TLS segment last, because that is where the dynamic
742 // linker expects to find it (this is just for efficiency; other
743 // positions would also work correctly).
744 if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
746 if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
749 const elfcpp::Elf_Word flags1 = seg1->flags();
750 const elfcpp::Elf_Word flags2 = seg2->flags();
752 // The order of non-PT_LOAD segments is unimportant. We simply sort
753 // by the numeric segment type and flags values. There should not
754 // be more than one segment with the same type and flags.
755 if (type1 != elfcpp::PT_LOAD)
758 return type1 < type2;
759 gold_assert(flags1 != flags2);
760 return flags1 < flags2;
763 // We sort PT_LOAD segments based on the flags. Readonly segments
764 // come before writable segments. Then executable segments come
765 // before non-executable segments. Then the unlikely case of a
766 // non-readable segment comes before the normal case of a readable
767 // segment. If there are multiple segments with the same type and
768 // flags, we require that the address be set, and we sort by
769 // virtual address and then physical address.
770 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
771 return (flags1 & elfcpp::PF_W) == 0;
772 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
773 return (flags1 & elfcpp::PF_X) != 0;
774 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
775 return (flags1 & elfcpp::PF_R) == 0;
777 uint64_t vaddr1 = seg1->vaddr();
778 uint64_t vaddr2 = seg2->vaddr();
779 if (vaddr1 != vaddr2)
780 return vaddr1 < vaddr2;
782 uint64_t paddr1 = seg1->paddr();
783 uint64_t paddr2 = seg2->paddr();
784 gold_assert(paddr1 != paddr2);
785 return paddr1 < paddr2;
788 // Set the file offsets of all the segments, and all the sections they
789 // contain. They have all been created. LOAD_SEG must be be laid out
790 // first. Return the offset of the data to follow.
793 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
794 unsigned int *pshndx)
796 // Sort them into the final order.
797 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
798 Layout::Compare_segments());
800 // Find the PT_LOAD segments, and set their addresses and offsets
801 // and their section's addresses and offsets.
802 uint64_t addr = target->text_segment_address();
804 bool was_readonly = false;
805 for (Segment_list::iterator p = this->segment_list_.begin();
806 p != this->segment_list_.end();
809 if ((*p)->type() == elfcpp::PT_LOAD)
811 if (load_seg != NULL && load_seg != *p)
815 // If the last segment was readonly, and this one is not,
816 // then skip the address forward one page, maintaining the
817 // same position within the page. This lets us store both
818 // segments overlapping on a single page in the file, but
819 // the loader will put them on different pages in memory.
821 uint64_t orig_addr = addr;
822 uint64_t orig_off = off;
824 uint64_t aligned_addr = addr;
825 uint64_t abi_pagesize = target->abi_pagesize();
827 // FIXME: This should depend on the -n and -N options.
828 (*p)->set_minimum_addralign(target->common_pagesize());
830 if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
832 uint64_t align = (*p)->addralign();
834 addr = align_address(addr, align);
836 if ((addr & (abi_pagesize - 1)) != 0)
837 addr = addr + abi_pagesize;
840 unsigned int shndx_hold = *pshndx;
841 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
842 uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
844 // Now that we know the size of this segment, we may be able
845 // to save a page in memory, at the cost of wasting some
846 // file space, by instead aligning to the start of a new
847 // page. Here we use the real machine page size rather than
848 // the ABI mandated page size.
850 if (aligned_addr != addr)
852 uint64_t common_pagesize = target->common_pagesize();
853 uint64_t first_off = (common_pagesize
855 & (common_pagesize - 1)));
856 uint64_t last_off = new_addr & (common_pagesize - 1);
859 && ((aligned_addr & ~ (common_pagesize - 1))
860 != (new_addr & ~ (common_pagesize - 1)))
861 && first_off + last_off <= common_pagesize)
863 *pshndx = shndx_hold;
864 addr = align_address(aligned_addr, common_pagesize);
865 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
866 new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
872 if (((*p)->flags() & elfcpp::PF_W) == 0)
877 // Handle the non-PT_LOAD segments, setting their offsets from their
878 // section's offsets.
879 for (Segment_list::iterator p = this->segment_list_.begin();
880 p != this->segment_list_.end();
883 if ((*p)->type() != elfcpp::PT_LOAD)
890 // Set the file offset of all the sections not associated with a
894 Layout::set_section_offsets(off_t off, unsigned int* pshndx)
896 for (Section_list::iterator p = this->unattached_section_list_.begin();
897 p != this->unattached_section_list_.end();
900 (*p)->set_out_shndx(*pshndx);
902 if ((*p)->offset() != -1)
904 off = align_address(off, (*p)->addralign());
905 (*p)->set_address(0, off);
906 off += (*p)->data_size();
911 // Create the symbol table sections. Here we also set the final
912 // values of the symbols. At this point all the loadable sections are
916 Layout::create_symtab_sections(const Input_objects* input_objects,
917 Symbol_table* symtab,
922 if (parameters->get_size() == 32)
924 symsize = elfcpp::Elf_sizes<32>::sym_size;
927 else if (parameters->get_size() == 64)
929 symsize = elfcpp::Elf_sizes<64>::sym_size;
936 off = align_address(off, align);
937 off_t startoff = off;
939 // Save space for the dummy symbol at the start of the section. We
940 // never bother to write this out--it will just be left as zero.
942 unsigned int local_symbol_index = 1;
944 // Add STT_SECTION symbols for each Output section which needs one.
945 for (Section_list::iterator p = this->section_list_.begin();
946 p != this->section_list_.end();
949 if (!(*p)->needs_symtab_index())
950 (*p)->set_symtab_index(-1U);
953 (*p)->set_symtab_index(local_symbol_index);
954 ++local_symbol_index;
959 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
960 p != input_objects->relobj_end();
963 Task_lock_obj<Object> tlo(**p);
964 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
967 off += (index - local_symbol_index) * symsize;
968 local_symbol_index = index;
971 unsigned int local_symcount = local_symbol_index;
972 gold_assert(local_symcount * symsize == off - startoff);
975 size_t dyn_global_index;
977 if (this->dynsym_section_ == NULL)
980 dyn_global_index = 0;
985 dyn_global_index = this->dynsym_section_->info();
986 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
987 dynoff = this->dynsym_section_->offset() + locsize;
988 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
989 gold_assert(static_cast<off_t>(dyncount * symsize)
990 == this->dynsym_section_->data_size() - locsize);
993 off = symtab->finalize(local_symcount, off, dynoff, dyn_global_index,
994 dyncount, &this->sympool_);
996 if (!parameters->strip_all())
998 this->sympool_.set_string_offsets();
1000 const char* symtab_name = this->namepool_.add(".symtab", NULL);
1001 Output_section* osymtab = this->make_output_section(symtab_name,
1004 this->symtab_section_ = osymtab;
1006 Output_section_data* pos = new Output_data_space(off - startoff,
1008 osymtab->add_output_section_data(pos);
1010 const char* strtab_name = this->namepool_.add(".strtab", NULL);
1011 Output_section* ostrtab = this->make_output_section(strtab_name,
1015 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
1016 ostrtab->add_output_section_data(pstr);
1018 osymtab->set_address(0, startoff);
1019 osymtab->set_link_section(ostrtab);
1020 osymtab->set_info(local_symcount);
1021 osymtab->set_entsize(symsize);
1027 // Create the .shstrtab section, which holds the names of the
1028 // sections. At the time this is called, we have created all the
1029 // output sections except .shstrtab itself.
1032 Layout::create_shstrtab()
1034 // FIXME: We don't need to create a .shstrtab section if we are
1035 // stripping everything.
1037 const char* name = this->namepool_.add(".shstrtab", NULL);
1039 this->namepool_.set_string_offsets();
1041 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0);
1043 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
1044 os->add_output_section_data(posd);
1049 // Create the section headers. SIZE is 32 or 64. OFF is the file
1052 Output_section_headers*
1053 Layout::create_shdrs(off_t* poff)
1055 Output_section_headers* oshdrs;
1056 oshdrs = new Output_section_headers(this,
1057 &this->segment_list_,
1058 &this->unattached_section_list_,
1060 off_t off = align_address(*poff, oshdrs->addralign());
1061 oshdrs->set_address(0, off);
1062 off += oshdrs->data_size();
1064 this->special_output_list_.push_back(oshdrs);
1068 // Create the dynamic symbol table.
1071 Layout::create_dynamic_symtab(const Target* target, Symbol_table* symtab,
1072 Output_section **pdynstr,
1073 unsigned int* plocal_dynamic_count,
1074 std::vector<Symbol*>* pdynamic_symbols,
1075 Versions* pversions)
1077 // Count all the symbols in the dynamic symbol table, and set the
1078 // dynamic symbol indexes.
1080 // Skip symbol 0, which is always all zeroes.
1081 unsigned int index = 1;
1083 // Add STT_SECTION symbols for each Output section which needs one.
1084 for (Section_list::iterator p = this->section_list_.begin();
1085 p != this->section_list_.end();
1088 if (!(*p)->needs_dynsym_index())
1089 (*p)->set_dynsym_index(-1U);
1092 (*p)->set_dynsym_index(index);
1097 // FIXME: Some targets apparently require local symbols in the
1098 // dynamic symbol table. Here is where we will have to count them,
1099 // and set the dynamic symbol indexes, and add the names to
1102 unsigned int local_symcount = index;
1103 *plocal_dynamic_count = local_symcount;
1105 // FIXME: We have to tell set_dynsym_indexes whether the
1106 // -E/--export-dynamic option was used.
1107 index = symtab->set_dynsym_indexes(&this->options_, target, index,
1108 pdynamic_symbols, &this->dynpool_,
1113 const int size = parameters->get_size();
1116 symsize = elfcpp::Elf_sizes<32>::sym_size;
1119 else if (size == 64)
1121 symsize = elfcpp::Elf_sizes<64>::sym_size;
1127 // Create the dynamic symbol table section.
1129 const char* dynsym_name = this->namepool_.add(".dynsym", NULL);
1130 Output_section* dynsym = this->make_output_section(dynsym_name,
1134 Output_section_data* odata = new Output_data_space(index * symsize,
1136 dynsym->add_output_section_data(odata);
1138 dynsym->set_info(local_symcount);
1139 dynsym->set_entsize(symsize);
1140 dynsym->set_addralign(align);
1142 this->dynsym_section_ = dynsym;
1144 Output_data_dynamic* const odyn = this->dynamic_data_;
1145 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
1146 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
1148 // Create the dynamic string table section.
1150 const char* dynstr_name = this->namepool_.add(".dynstr", NULL);
1151 Output_section* dynstr = this->make_output_section(dynstr_name,
1155 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
1156 dynstr->add_output_section_data(strdata);
1158 dynsym->set_link_section(dynstr);
1159 this->dynamic_section_->set_link_section(dynstr);
1161 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
1162 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
1166 // Create the hash tables.
1168 // FIXME: We need an option to create a GNU hash table.
1170 unsigned char* phash;
1171 unsigned int hashlen;
1172 Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
1175 const char* hash_name = this->namepool_.add(".hash", NULL);
1176 Output_section* hashsec = this->make_output_section(hash_name,
1180 Output_section_data* hashdata = new Output_data_const_buffer(phash,
1183 hashsec->add_output_section_data(hashdata);
1185 hashsec->set_link_section(dynsym);
1186 hashsec->set_entsize(4);
1188 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
1191 // Create the version sections.
1194 Layout::create_version_sections(const Versions* versions,
1195 unsigned int local_symcount,
1196 const std::vector<Symbol*>& dynamic_symbols,
1197 const Output_section* dynstr)
1199 if (!versions->any_defs() && !versions->any_needs())
1202 if (parameters->get_size() == 32)
1204 if (parameters->is_big_endian())
1206 #ifdef HAVE_TARGET_32_BIG
1207 this->sized_create_version_sections
1208 SELECT_SIZE_ENDIAN_NAME(32, true)(
1209 versions, local_symcount, dynamic_symbols, dynstr
1210 SELECT_SIZE_ENDIAN(32, true));
1217 #ifdef HAVE_TARGET_32_LITTLE
1218 this->sized_create_version_sections
1219 SELECT_SIZE_ENDIAN_NAME(32, false)(
1220 versions, local_symcount, dynamic_symbols, dynstr
1221 SELECT_SIZE_ENDIAN(32, false));
1227 else if (parameters->get_size() == 64)
1229 if (parameters->is_big_endian())
1231 #ifdef HAVE_TARGET_64_BIG
1232 this->sized_create_version_sections
1233 SELECT_SIZE_ENDIAN_NAME(64, true)(
1234 versions, local_symcount, dynamic_symbols, dynstr
1235 SELECT_SIZE_ENDIAN(64, true));
1242 #ifdef HAVE_TARGET_64_LITTLE
1243 this->sized_create_version_sections
1244 SELECT_SIZE_ENDIAN_NAME(64, false)(
1245 versions, local_symcount, dynamic_symbols, dynstr
1246 SELECT_SIZE_ENDIAN(64, false));
1256 // Create the version sections, sized version.
1258 template<int size, bool big_endian>
1260 Layout::sized_create_version_sections(
1261 const Versions* versions,
1262 unsigned int local_symcount,
1263 const std::vector<Symbol*>& dynamic_symbols,
1264 const Output_section* dynstr
1267 const char* vname = this->namepool_.add(".gnu.version", NULL);
1268 Output_section* vsec = this->make_output_section(vname,
1269 elfcpp::SHT_GNU_versym,
1272 unsigned char* vbuf;
1274 versions->symbol_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1275 &this->dynpool_, local_symcount, dynamic_symbols, &vbuf, &vsize
1276 SELECT_SIZE_ENDIAN(size, big_endian));
1278 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2);
1280 vsec->add_output_section_data(vdata);
1281 vsec->set_entsize(2);
1282 vsec->set_link_section(this->dynsym_section_);
1284 Output_data_dynamic* const odyn = this->dynamic_data_;
1285 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
1287 if (versions->any_defs())
1289 const char* vdname = this->namepool_.add(".gnu.version_d", NULL);
1290 Output_section *vdsec;
1291 vdsec = this->make_output_section(vdname, elfcpp::SHT_GNU_verdef,
1294 unsigned char* vdbuf;
1295 unsigned int vdsize;
1296 unsigned int vdentries;
1297 versions->def_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1298 &this->dynpool_, &vdbuf, &vdsize, &vdentries
1299 SELECT_SIZE_ENDIAN(size, big_endian));
1301 Output_section_data* vddata = new Output_data_const_buffer(vdbuf,
1305 vdsec->add_output_section_data(vddata);
1306 vdsec->set_link_section(dynstr);
1307 vdsec->set_info(vdentries);
1309 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
1310 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
1313 if (versions->any_needs())
1315 const char* vnname = this->namepool_.add(".gnu.version_r", NULL);
1316 Output_section* vnsec;
1317 vnsec = this->make_output_section(vnname, elfcpp::SHT_GNU_verneed,
1320 unsigned char* vnbuf;
1321 unsigned int vnsize;
1322 unsigned int vnentries;
1323 versions->need_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)
1324 (&this->dynpool_, &vnbuf, &vnsize, &vnentries
1325 SELECT_SIZE_ENDIAN(size, big_endian));
1327 Output_section_data* vndata = new Output_data_const_buffer(vnbuf,
1331 vnsec->add_output_section_data(vndata);
1332 vnsec->set_link_section(dynstr);
1333 vnsec->set_info(vnentries);
1335 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
1336 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
1340 // Create the .interp section and PT_INTERP segment.
1343 Layout::create_interp(const Target* target)
1345 const char* interp = this->options_.dynamic_linker();
1348 interp = target->dynamic_linker();
1349 gold_assert(interp != NULL);
1352 size_t len = strlen(interp) + 1;
1354 Output_section_data* odata = new Output_data_const(interp, len, 1);
1356 const char* interp_name = this->namepool_.add(".interp", NULL);
1357 Output_section* osec = this->make_output_section(interp_name,
1358 elfcpp::SHT_PROGBITS,
1360 osec->add_output_section_data(odata);
1362 Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
1363 this->segment_list_.push_back(oseg);
1364 oseg->add_initial_output_section(osec, elfcpp::PF_R);
1367 // Finish the .dynamic section and PT_DYNAMIC segment.
1370 Layout::finish_dynamic_section(const Input_objects* input_objects,
1371 const Symbol_table* symtab)
1373 Output_segment* oseg = new Output_segment(elfcpp::PT_DYNAMIC,
1374 elfcpp::PF_R | elfcpp::PF_W);
1375 this->segment_list_.push_back(oseg);
1376 oseg->add_initial_output_section(this->dynamic_section_,
1377 elfcpp::PF_R | elfcpp::PF_W);
1379 Output_data_dynamic* const odyn = this->dynamic_data_;
1381 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
1382 p != input_objects->dynobj_end();
1385 // FIXME: Handle --as-needed.
1386 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
1389 // FIXME: Support --init and --fini.
1390 Symbol* sym = symtab->lookup("_init");
1391 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1392 odyn->add_symbol(elfcpp::DT_INIT, sym);
1394 sym = symtab->lookup("_fini");
1395 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1396 odyn->add_symbol(elfcpp::DT_FINI, sym);
1398 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1400 // Add a DT_RPATH entry if needed.
1401 const General_options::Dir_list& rpath(this->options_.rpath());
1404 std::string rpath_val;
1405 for (General_options::Dir_list::const_iterator p = rpath.begin();
1409 if (rpath_val.empty())
1410 rpath_val = p->name();
1413 // Eliminate duplicates.
1414 General_options::Dir_list::const_iterator q;
1415 for (q = rpath.begin(); q != p; ++q)
1416 if (q->name() == p->name())
1421 rpath_val += p->name();
1426 odyn->add_string(elfcpp::DT_RPATH, rpath_val);
1430 // The mapping of .gnu.linkonce section names to real section names.
1432 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1433 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
1435 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1436 MAPPING_INIT("t", ".text"),
1437 MAPPING_INIT("r", ".rodata"),
1438 MAPPING_INIT("d", ".data"),
1439 MAPPING_INIT("b", ".bss"),
1440 MAPPING_INIT("s", ".sdata"),
1441 MAPPING_INIT("sb", ".sbss"),
1442 MAPPING_INIT("s2", ".sdata2"),
1443 MAPPING_INIT("sb2", ".sbss2"),
1444 MAPPING_INIT("wi", ".debug_info"),
1445 MAPPING_INIT("td", ".tdata"),
1446 MAPPING_INIT("tb", ".tbss"),
1447 MAPPING_INIT("lr", ".lrodata"),
1448 MAPPING_INIT("l", ".ldata"),
1449 MAPPING_INIT("lb", ".lbss"),
1453 const int Layout::linkonce_mapping_count =
1454 sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
1456 // Return the name of the output section to use for a .gnu.linkonce
1457 // section. This is based on the default ELF linker script of the old
1458 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1459 // to ".text". Set *PLEN to the length of the name. *PLEN is
1460 // initialized to the length of NAME.
1463 Layout::linkonce_output_name(const char* name, size_t *plen)
1465 const char* s = name + sizeof(".gnu.linkonce") - 1;
1469 const Linkonce_mapping* plm = linkonce_mapping;
1470 for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
1472 if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
1481 // Choose the output section name to use given an input section name.
1482 // Set *PLEN to the length of the name. *PLEN is initialized to the
1486 Layout::output_section_name(const char* name, size_t* plen)
1488 if (Layout::is_linkonce(name))
1490 // .gnu.linkonce sections are laid out as though they were named
1491 // for the sections are placed into.
1492 return Layout::linkonce_output_name(name, plen);
1495 // If the section name has no '.', or only an initial '.', we use
1496 // the name unchanged (i.e., ".text" is unchanged).
1498 // Otherwise, if the section name does not include ".rel", we drop
1499 // the last '.' and everything that follows (i.e., ".text.XXX"
1500 // becomes ".text").
1502 // Otherwise, if the section name has zero or one '.' after the
1503 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1506 // Otherwise, we drop the last '.' and everything that follows
1507 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1509 const char* s = name;
1512 const char* sdot = strchr(s, '.');
1516 const char* srel = strstr(s, ".rel");
1519 *plen = sdot - name;
1523 sdot = strchr(srel + 1, '.');
1526 sdot = strchr(sdot + 1, '.');
1530 *plen = sdot - name;
1534 // Record the signature of a comdat section, and return whether to
1535 // include it in the link. If GROUP is true, this is a regular
1536 // section group. If GROUP is false, this is a group signature
1537 // derived from the name of a linkonce section. We want linkonce
1538 // signatures and group signatures to block each other, but we don't
1539 // want a linkonce signature to block another linkonce signature.
1542 Layout::add_comdat(const char* signature, bool group)
1544 std::string sig(signature);
1545 std::pair<Signatures::iterator, bool> ins(
1546 this->signatures_.insert(std::make_pair(sig, group)));
1550 // This is the first time we've seen this signature.
1554 if (ins.first->second)
1556 // We've already seen a real section group with this signature.
1561 // This is a real section group, and we've already seen a
1562 // linkonce section with this signature. Record that we've seen
1563 // a section group, and don't include this section group.
1564 ins.first->second = true;
1569 // We've already seen a linkonce section and this is a linkonce
1570 // section. These don't block each other--this may be the same
1571 // symbol name with different section types.
1576 // Write out data not associated with a section or the symbol table.
1579 Layout::write_data(const Symbol_table* symtab, Output_file* of) const
1581 if (!parameters->strip_all())
1583 const Output_section* symtab_section = this->symtab_section_;
1584 for (Section_list::const_iterator p = this->section_list_.begin();
1585 p != this->section_list_.end();
1588 if ((*p)->needs_symtab_index())
1590 gold_assert(symtab_section != NULL);
1591 unsigned int index = (*p)->symtab_index();
1592 gold_assert(index > 0 && index != -1U);
1593 off_t off = (symtab_section->offset()
1594 + index * symtab_section->entsize());
1595 symtab->write_section_symbol(*p, of, off);
1600 const Output_section* dynsym_section = this->dynsym_section_;
1601 for (Section_list::const_iterator p = this->section_list_.begin();
1602 p != this->section_list_.end();
1605 if ((*p)->needs_dynsym_index())
1607 gold_assert(dynsym_section != NULL);
1608 unsigned int index = (*p)->dynsym_index();
1609 gold_assert(index > 0 && index != -1U);
1610 off_t off = (dynsym_section->offset()
1611 + index * dynsym_section->entsize());
1612 symtab->write_section_symbol(*p, of, off);
1616 // Write out the Output_sections. Most won't have anything to
1617 // write, since most of the data will come from input sections which
1618 // are handled elsewhere. But some Output_sections do have
1620 for (Section_list::const_iterator p = this->section_list_.begin();
1621 p != this->section_list_.end();
1625 // Write out the Output_data which are not in an Output_section.
1626 for (Data_list::const_iterator p = this->special_output_list_.begin();
1627 p != this->special_output_list_.end();
1632 // Write_data_task methods.
1634 // We can always run this task.
1636 Task::Is_runnable_type
1637 Write_data_task::is_runnable(Workqueue*)
1642 // We need to unlock FINAL_BLOCKER when finished.
1645 Write_data_task::locks(Workqueue* workqueue)
1647 return new Task_locker_block(*this->final_blocker_, workqueue);
1650 // Run the task--write out the data.
1653 Write_data_task::run(Workqueue*)
1655 this->layout_->write_data(this->symtab_, this->of_);
1658 // Write_symbols_task methods.
1660 // We can always run this task.
1662 Task::Is_runnable_type
1663 Write_symbols_task::is_runnable(Workqueue*)
1668 // We need to unlock FINAL_BLOCKER when finished.
1671 Write_symbols_task::locks(Workqueue* workqueue)
1673 return new Task_locker_block(*this->final_blocker_, workqueue);
1676 // Run the task--write out the symbols.
1679 Write_symbols_task::run(Workqueue*)
1681 this->symtab_->write_globals(this->target_, this->sympool_, this->dynpool_,
1685 // Close_task_runner methods.
1687 // Run the task--close the file.
1690 Close_task_runner::run(Workqueue*)
1695 // Instantiate the templates we need. We could use the configure
1696 // script to restrict this to only the ones for implemented targets.
1698 #ifdef HAVE_TARGET_32_LITTLE
1701 Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name,
1702 const elfcpp::Shdr<32, false>& shdr, off_t*);
1705 #ifdef HAVE_TARGET_32_BIG
1708 Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name,
1709 const elfcpp::Shdr<32, true>& shdr, off_t*);
1712 #ifdef HAVE_TARGET_64_LITTLE
1715 Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name,
1716 const elfcpp::Shdr<64, false>& shdr, off_t*);
1719 #ifdef HAVE_TARGET_64_BIG
1722 Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name,
1723 const elfcpp::Shdr<64, true>& shdr, off_t*);
1727 } // End namespace gold.