1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007, 2008 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"
36 #include "compressed_output.h"
42 // Layout_task_runner methods.
44 // Lay out the sections. This is called after all the input objects
48 Layout_task_runner::run(Workqueue* workqueue, const Task* task)
50 off_t file_size = this->layout_->finalize(this->input_objects_,
54 // Now we know the final size of the output file and we know where
55 // each piece of information goes.
56 Output_file* of = new Output_file(parameters->output_file_name());
59 // Queue up the final set of tasks.
60 gold::queue_final_tasks(this->options_, this->input_objects_,
61 this->symtab_, this->layout_, workqueue, of);
66 Layout::Layout(const General_options& options, Script_options* script_options)
67 : options_(options), script_options_(script_options), namepool_(),
68 sympool_(), dynpool_(), signatures_(),
69 section_name_map_(), segment_list_(), section_list_(),
70 unattached_section_list_(), special_output_list_(),
71 section_headers_(NULL), tls_segment_(NULL), symtab_section_(NULL),
72 dynsym_section_(NULL), dynamic_section_(NULL), dynamic_data_(NULL),
73 eh_frame_section_(NULL), output_file_size_(-1),
74 input_requires_executable_stack_(false),
75 input_with_gnu_stack_note_(false),
76 input_without_gnu_stack_note_(false),
77 has_static_tls_(false),
78 any_postprocessing_sections_(false)
80 // Make space for more than enough segments for a typical file.
81 // This is just for efficiency--it's OK if we wind up needing more.
82 this->segment_list_.reserve(12);
84 // We expect two unattached Output_data objects: the file header and
85 // the segment headers.
86 this->special_output_list_.reserve(2);
89 // Hash a key we use to look up an output section mapping.
92 Layout::Hash_key::operator()(const Layout::Key& k) const
94 return k.first + k.second.first + k.second.second;
97 // Return whether PREFIX is a prefix of STR.
100 is_prefix_of(const char* prefix, const char* str)
102 return strncmp(prefix, str, strlen(prefix)) == 0;
105 // Returns whether the given section is in the list of
106 // debug-sections-used-by-some-version-of-gdb. Currently,
107 // we've checked versions of gdb up to and including 6.7.1.
109 static const char* gdb_sections[] =
111 // ".debug_aranges", // not used by gdb as of 6.7.1
117 // ".debug_pubnames", // not used by gdb as of 6.7.1
123 is_gdb_debug_section(const char* str)
125 // We can do this faster: binary search or a hashtable. But why bother?
126 for (size_t i = 0; i < sizeof(gdb_sections)/sizeof(*gdb_sections); ++i)
127 if (strcmp(str, gdb_sections[i]) == 0)
132 // Whether to include this section in the link.
134 template<int size, bool big_endian>
136 Layout::include_section(Sized_relobj<size, big_endian>*, const char* name,
137 const elfcpp::Shdr<size, big_endian>& shdr)
139 // Some section types are never linked. Some are only linked when
140 // doing a relocateable link.
141 switch (shdr.get_sh_type())
143 case elfcpp::SHT_NULL:
144 case elfcpp::SHT_SYMTAB:
145 case elfcpp::SHT_DYNSYM:
146 case elfcpp::SHT_STRTAB:
147 case elfcpp::SHT_HASH:
148 case elfcpp::SHT_DYNAMIC:
149 case elfcpp::SHT_SYMTAB_SHNDX:
152 case elfcpp::SHT_RELA:
153 case elfcpp::SHT_REL:
154 case elfcpp::SHT_GROUP:
155 return parameters->output_is_object();
157 case elfcpp::SHT_PROGBITS:
158 if (parameters->strip_debug()
159 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
161 // Debugging sections can only be recognized by name.
162 if (is_prefix_of(".debug", name)
163 || is_prefix_of(".gnu.linkonce.wi.", name)
164 || is_prefix_of(".line", name)
165 || is_prefix_of(".stab", name))
168 if (parameters->strip_debug_gdb()
169 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
171 // Debugging sections can only be recognized by name.
172 if (is_prefix_of(".debug", name)
173 && !is_gdb_debug_section(name))
183 // Return an output section named NAME, or NULL if there is none.
186 Layout::find_output_section(const char* name) const
188 for (Section_name_map::const_iterator p = this->section_name_map_.begin();
189 p != this->section_name_map_.end();
191 if (strcmp(p->second->name(), name) == 0)
196 // Return an output segment of type TYPE, with segment flags SET set
197 // and segment flags CLEAR clear. Return NULL if there is none.
200 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
201 elfcpp::Elf_Word clear) const
203 for (Segment_list::const_iterator p = this->segment_list_.begin();
204 p != this->segment_list_.end();
206 if (static_cast<elfcpp::PT>((*p)->type()) == type
207 && ((*p)->flags() & set) == set
208 && ((*p)->flags() & clear) == 0)
213 // Return the output section to use for section NAME with type TYPE
214 // and section flags FLAGS.
217 Layout::get_output_section(const char* name, Stringpool::Key name_key,
218 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags)
220 // We should ignore some flags.
221 flags &= ~ (elfcpp::SHF_INFO_LINK
222 | elfcpp::SHF_LINK_ORDER
225 | elfcpp::SHF_STRINGS);
227 const Key key(name_key, std::make_pair(type, flags));
228 const std::pair<Key, Output_section*> v(key, NULL);
229 std::pair<Section_name_map::iterator, bool> ins(
230 this->section_name_map_.insert(v));
233 return ins.first->second;
236 // This is the first time we've seen this name/type/flags
238 Output_section* os = this->make_output_section(name, type, flags);
239 ins.first->second = os;
244 // Return the output section to use for input section SHNDX, with name
245 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
246 // index of a relocation section which applies to this section, or 0
247 // if none, or -1U if more than one. RELOC_TYPE is the type of the
248 // relocation section if there is one. Set *OFF to the offset of this
249 // input section without the output section. Return NULL if the
250 // section should be discarded. Set *OFF to -1 if the section
251 // contents should not be written directly to the output file, but
252 // will instead receive special handling.
254 template<int size, bool big_endian>
256 Layout::layout(Sized_relobj<size, big_endian>* object, unsigned int shndx,
257 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
258 unsigned int reloc_shndx, unsigned int, off_t* off)
260 if (!this->include_section(object, name, shdr))
263 // If we are not doing a relocateable link, choose the name to use
264 // for the output section.
265 size_t len = strlen(name);
266 if (!parameters->output_is_object())
267 name = Layout::output_section_name(name, &len);
269 // FIXME: Handle SHF_OS_NONCONFORMING here.
271 // Canonicalize the section name.
272 Stringpool::Key name_key;
273 name = this->namepool_.add_with_length(name, len, true, &name_key);
275 // Find the output section. The output section is selected based on
276 // the section name, type, and flags.
277 Output_section* os = this->get_output_section(name, name_key,
279 shdr.get_sh_flags());
281 // FIXME: Handle SHF_LINK_ORDER somewhere.
283 *off = os->add_input_section(object, shndx, name, shdr, reloc_shndx);
288 // Special GNU handling of sections name .eh_frame. They will
289 // normally hold exception frame data as defined by the C++ ABI
290 // (http://codesourcery.com/cxx-abi/).
292 template<int size, bool big_endian>
294 Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
295 const unsigned char* symbols,
297 const unsigned char* symbol_names,
298 off_t symbol_names_size,
300 const elfcpp::Shdr<size, big_endian>& shdr,
301 unsigned int reloc_shndx, unsigned int reloc_type,
304 gold_assert(shdr.get_sh_type() == elfcpp::SHT_PROGBITS);
305 gold_assert(shdr.get_sh_flags() == elfcpp::SHF_ALLOC);
307 Stringpool::Key name_key;
308 const char* name = this->namepool_.add(".eh_frame", false, &name_key);
310 Output_section* os = this->get_output_section(name, name_key,
311 elfcpp::SHT_PROGBITS,
314 if (this->eh_frame_section_ == NULL)
316 this->eh_frame_section_ = os;
317 this->eh_frame_data_ = new Eh_frame();
318 os->add_output_section_data(this->eh_frame_data_);
320 if (this->options_.create_eh_frame_hdr())
322 Stringpool::Key hdr_name_key;
323 const char* hdr_name = this->namepool_.add(".eh_frame_hdr",
326 Output_section* hdr_os =
327 this->get_output_section(hdr_name, hdr_name_key,
328 elfcpp::SHT_PROGBITS,
331 Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os, this->eh_frame_data_);
332 hdr_os->add_output_section_data(hdr_posd);
334 hdr_os->set_after_input_sections();
336 Output_segment* hdr_oseg =
337 new Output_segment(elfcpp::PT_GNU_EH_FRAME, elfcpp::PF_R);
338 this->segment_list_.push_back(hdr_oseg);
339 hdr_oseg->add_output_section(hdr_os, elfcpp::PF_R);
341 this->eh_frame_data_->set_eh_frame_hdr(hdr_posd);
345 gold_assert(this->eh_frame_section_ == os);
347 if (this->eh_frame_data_->add_ehframe_input_section(object,
358 // We couldn't handle this .eh_frame section for some reason.
359 // Add it as a normal section.
360 *off = os->add_input_section(object, shndx, name, shdr, reloc_shndx);
366 // Add POSD to an output section using NAME, TYPE, and FLAGS.
369 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
370 elfcpp::Elf_Xword flags,
371 Output_section_data* posd)
373 // Canonicalize the name.
374 Stringpool::Key name_key;
375 name = this->namepool_.add(name, true, &name_key);
377 Output_section* os = this->get_output_section(name, name_key, type, flags);
378 os->add_output_section_data(posd);
381 // Map section flags to segment flags.
384 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
386 elfcpp::Elf_Word ret = elfcpp::PF_R;
387 if ((flags & elfcpp::SHF_WRITE) != 0)
389 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
394 // Sometimes we compress sections. This is typically done for
395 // sections that are not part of normal program execution (such as
396 // .debug_* sections), and where the readers of these sections know
397 // how to deal with compressed sections. (To make it easier for them,
398 // we will rename the ouput section in such cases from .foo to
399 // .foo.zlib.nnnn, where nnnn is the uncompressed size.) This routine
400 // doesn't say for certain whether we'll compress -- it depends on
401 // commandline options as well -- just whether this section is a
402 // candidate for compression.
405 is_compressible_debug_section(const char* secname)
407 return (strncmp(secname, ".debug", sizeof(".debug") - 1) == 0);
410 // Make a new Output_section, and attach it to segments as
414 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
415 elfcpp::Elf_Xword flags)
418 if ((flags & elfcpp::SHF_ALLOC) == 0
419 && this->options_.compress_debug_sections()
420 && is_compressible_debug_section(name))
421 os = new Output_compressed_section(&this->options_, name, type, flags);
423 os = new Output_section(name, type, flags);
425 this->section_list_.push_back(os);
427 if ((flags & elfcpp::SHF_ALLOC) == 0)
428 this->unattached_section_list_.push_back(os);
431 // This output section goes into a PT_LOAD segment.
433 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
435 // The only thing we really care about for PT_LOAD segments is
436 // whether or not they are writable, so that is how we search
437 // for them. People who need segments sorted on some other
438 // basis will have to wait until we implement a mechanism for
439 // them to describe the segments they want.
441 Segment_list::const_iterator p;
442 for (p = this->segment_list_.begin();
443 p != this->segment_list_.end();
446 if ((*p)->type() == elfcpp::PT_LOAD
447 && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W))
449 (*p)->add_output_section(os, seg_flags);
454 if (p == this->segment_list_.end())
456 Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD,
458 this->segment_list_.push_back(oseg);
459 oseg->add_output_section(os, seg_flags);
462 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
464 if (type == elfcpp::SHT_NOTE)
466 // See if we already have an equivalent PT_NOTE segment.
467 for (p = this->segment_list_.begin();
468 p != segment_list_.end();
471 if ((*p)->type() == elfcpp::PT_NOTE
472 && (((*p)->flags() & elfcpp::PF_W)
473 == (seg_flags & elfcpp::PF_W)))
475 (*p)->add_output_section(os, seg_flags);
480 if (p == this->segment_list_.end())
482 Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE,
484 this->segment_list_.push_back(oseg);
485 oseg->add_output_section(os, seg_flags);
489 // If we see a loadable SHF_TLS section, we create a PT_TLS
490 // segment. There can only be one such segment.
491 if ((flags & elfcpp::SHF_TLS) != 0)
493 if (this->tls_segment_ == NULL)
495 this->tls_segment_ = new Output_segment(elfcpp::PT_TLS,
497 this->segment_list_.push_back(this->tls_segment_);
499 this->tls_segment_->add_output_section(os, seg_flags);
506 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
507 // is whether we saw a .note.GNU-stack section in the object file.
508 // GNU_STACK_FLAGS is the section flags. The flags give the
509 // protection required for stack memory. We record this in an
510 // executable as a PT_GNU_STACK segment. If an object file does not
511 // have a .note.GNU-stack segment, we must assume that it is an old
512 // object. On some targets that will force an executable stack.
515 Layout::layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags)
518 this->input_without_gnu_stack_note_ = true;
521 this->input_with_gnu_stack_note_ = true;
522 if ((gnu_stack_flags & elfcpp::SHF_EXECINSTR) != 0)
523 this->input_requires_executable_stack_ = true;
527 // Create the dynamic sections which are needed before we read the
531 Layout::create_initial_dynamic_sections(Symbol_table* symtab)
533 if (parameters->doing_static_link())
536 const char* dynamic_name = this->namepool_.add(".dynamic", false, NULL);
537 this->dynamic_section_ = this->make_output_section(dynamic_name,
540 | elfcpp::SHF_WRITE));
542 symtab->define_in_output_data("_DYNAMIC", NULL, this->dynamic_section_, 0, 0,
543 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
544 elfcpp::STV_HIDDEN, 0, false, false);
546 this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
548 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
551 // For each output section whose name can be represented as C symbol,
552 // define __start and __stop symbols for the section. This is a GNU
556 Layout::define_section_symbols(Symbol_table* symtab)
558 for (Section_list::const_iterator p = this->section_list_.begin();
559 p != this->section_list_.end();
562 const char* const name = (*p)->name();
563 if (name[strspn(name,
565 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
566 "abcdefghijklmnopqrstuvwxyz"
570 const std::string name_string(name);
571 const std::string start_name("__start_" + name_string);
572 const std::string stop_name("__stop_" + name_string);
574 symtab->define_in_output_data(start_name.c_str(),
583 false, // offset_is_from_end
584 false); // only_if_ref
586 symtab->define_in_output_data(stop_name.c_str(),
595 true, // offset_is_from_end
596 false); // only_if_ref
601 // Find the first read-only PT_LOAD segment, creating one if
605 Layout::find_first_load_seg()
607 for (Segment_list::const_iterator p = this->segment_list_.begin();
608 p != this->segment_list_.end();
611 if ((*p)->type() == elfcpp::PT_LOAD
612 && ((*p)->flags() & elfcpp::PF_R) != 0
613 && ((*p)->flags() & elfcpp::PF_W) == 0)
617 Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R);
618 this->segment_list_.push_back(load_seg);
622 // Finalize the layout. When this is called, we have created all the
623 // output sections and all the output segments which are based on
624 // input sections. We have several things to do, and we have to do
625 // them in the right order, so that we get the right results correctly
628 // 1) Finalize the list of output segments and create the segment
631 // 2) Finalize the dynamic symbol table and associated sections.
633 // 3) Determine the final file offset of all the output segments.
635 // 4) Determine the final file offset of all the SHF_ALLOC output
638 // 5) Create the symbol table sections and the section name table
641 // 6) Finalize the symbol table: set symbol values to their final
642 // value and make a final determination of which symbols are going
643 // into the output symbol table.
645 // 7) Create the section table header.
647 // 8) Determine the final file offset of all the output sections which
648 // are not SHF_ALLOC, including the section table header.
650 // 9) Finalize the ELF file header.
652 // This function returns the size of the output file.
655 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
658 Target* const target = input_objects->target();
660 target->finalize_sections(this);
662 this->count_local_symbols(task, input_objects);
664 this->create_gold_note();
665 this->create_executable_stack_info(target);
667 Output_segment* phdr_seg = NULL;
668 if (!parameters->doing_static_link())
670 // There was a dynamic object in the link. We need to create
671 // some information for the dynamic linker.
673 // Create the PT_PHDR segment which will hold the program
675 phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
676 this->segment_list_.push_back(phdr_seg);
678 // Create the dynamic symbol table, including the hash table.
679 Output_section* dynstr;
680 std::vector<Symbol*> dynamic_symbols;
681 unsigned int local_dynamic_count;
682 Versions versions(this->options_, &this->dynpool_);
683 this->create_dynamic_symtab(input_objects, symtab, &dynstr,
684 &local_dynamic_count, &dynamic_symbols,
687 // Create the .interp section to hold the name of the
688 // interpreter, and put it in a PT_INTERP segment.
689 if (!parameters->output_is_shared())
690 this->create_interp(target);
692 // Finish the .dynamic section to hold the dynamic data, and put
693 // it in a PT_DYNAMIC segment.
694 this->finish_dynamic_section(input_objects, symtab);
696 // We should have added everything we need to the dynamic string
698 this->dynpool_.set_string_offsets();
700 // Create the version sections. We can't do this until the
701 // dynamic string table is complete.
702 this->create_version_sections(&versions, symtab, local_dynamic_count,
703 dynamic_symbols, dynstr);
706 // FIXME: Handle PT_GNU_STACK.
708 Output_segment* load_seg = this->find_first_load_seg();
710 // Lay out the segment headers.
711 Output_segment_headers* segment_headers;
712 segment_headers = new Output_segment_headers(this->segment_list_);
713 load_seg->add_initial_output_data(segment_headers);
714 this->special_output_list_.push_back(segment_headers);
715 if (phdr_seg != NULL)
716 phdr_seg->add_initial_output_data(segment_headers);
718 // Lay out the file header.
719 Output_file_header* file_header;
720 file_header = new Output_file_header(target, symtab, segment_headers,
721 this->script_options_->entry());
722 load_seg->add_initial_output_data(file_header);
723 this->special_output_list_.push_back(file_header);
725 // We set the output section indexes in set_segment_offsets and
726 // set_section_indexes.
727 unsigned int shndx = 1;
729 // Set the file offsets of all the segments, and all the sections
731 off_t off = this->set_segment_offsets(target, load_seg, &shndx);
733 // Set the file offsets of all the non-data sections we've seen so
734 // far which don't have to wait for the input sections. We need
735 // this in order to finalize local symbols in non-allocated
737 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
739 // Create the symbol table sections.
740 this->create_symtab_sections(input_objects, symtab, &off);
741 if (!parameters->doing_static_link())
742 this->assign_local_dynsym_offsets(input_objects);
744 // Process any symbol assignments from a linker script. This must
745 // be called after the symbol table has been finalized.
746 this->script_options_->finalize_symbols(symtab, this);
748 // Create the .shstrtab section.
749 Output_section* shstrtab_section = this->create_shstrtab();
751 // Set the file offsets of the rest of the non-data sections which
752 // don't have to wait for the input sections.
753 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
755 // Now that all sections have been created, set the section indexes.
756 shndx = this->set_section_indexes(shndx);
758 // Create the section table header.
759 this->create_shdrs(&off);
761 // If there are no sections which require postprocessing, we can
762 // handle the section names now, and avoid a resize later.
763 if (!this->any_postprocessing_sections_)
764 off = this->set_section_offsets(off,
765 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
767 file_header->set_section_info(this->section_headers_, shstrtab_section);
769 // Now we know exactly where everything goes in the output file
770 // (except for non-allocated sections which require postprocessing).
771 Output_data::layout_complete();
773 this->output_file_size_ = off;
778 // Create a .note section for an executable or shared library. This
779 // records the version of gold used to create the binary.
782 Layout::create_gold_note()
784 if (parameters->output_is_object())
787 // Authorities all agree that the values in a .note field should
788 // be aligned on 4-byte boundaries for 32-bit binaries. However,
789 // they differ on what the alignment is for 64-bit binaries.
790 // The GABI says unambiguously they take 8-byte alignment:
791 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
792 // Other documentation says alignment should always be 4 bytes:
793 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
794 // GNU ld and GNU readelf both support the latter (at least as of
795 // version 2.16.91), and glibc always generates the latter for
796 // .note.ABI-tag (as of version 1.6), so that's the one we go with
798 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
799 const int size = parameters->get_size();
804 // The contents of the .note section.
805 const char* name = "GNU";
806 std::string desc(std::string("gold ") + gold::get_version_string());
807 size_t namesz = strlen(name) + 1;
808 size_t aligned_namesz = align_address(namesz, size / 8);
809 size_t descsz = desc.length() + 1;
810 size_t aligned_descsz = align_address(descsz, size / 8);
811 const int note_type = 4;
813 size_t notesz = 3 * (size / 8) + aligned_namesz + aligned_descsz;
815 unsigned char buffer[128];
816 gold_assert(sizeof buffer >= notesz);
817 memset(buffer, 0, notesz);
819 bool is_big_endian = parameters->is_big_endian();
825 elfcpp::Swap<32, false>::writeval(buffer, namesz);
826 elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
827 elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
831 elfcpp::Swap<32, true>::writeval(buffer, namesz);
832 elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
833 elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
840 elfcpp::Swap<64, false>::writeval(buffer, namesz);
841 elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
842 elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
846 elfcpp::Swap<64, true>::writeval(buffer, namesz);
847 elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
848 elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
854 memcpy(buffer + 3 * (size / 8), name, namesz);
855 memcpy(buffer + 3 * (size / 8) + aligned_namesz, desc.data(), descsz);
857 const char* note_name = this->namepool_.add(".note", false, NULL);
858 Output_section* os = this->make_output_section(note_name,
861 Output_section_data* posd = new Output_data_const(buffer, notesz,
863 os->add_output_section_data(posd);
866 // Record whether the stack should be executable. This can be set
867 // from the command line using the -z execstack or -z noexecstack
868 // options. Otherwise, if any input file has a .note.GNU-stack
869 // section with the SHF_EXECINSTR flag set, the stack should be
870 // executable. Otherwise, if at least one input file a
871 // .note.GNU-stack section, and some input file has no .note.GNU-stack
872 // section, we use the target default for whether the stack should be
873 // executable. Otherwise, we don't generate a stack note. When
874 // generating a object file, we create a .note.GNU-stack section with
875 // the appropriate marking. When generating an executable or shared
876 // library, we create a PT_GNU_STACK segment.
879 Layout::create_executable_stack_info(const Target* target)
881 bool is_stack_executable;
882 if (this->options_.is_execstack_set())
883 is_stack_executable = this->options_.is_stack_executable();
884 else if (!this->input_with_gnu_stack_note_)
888 if (this->input_requires_executable_stack_)
889 is_stack_executable = true;
890 else if (this->input_without_gnu_stack_note_)
891 is_stack_executable = target->is_default_stack_executable();
893 is_stack_executable = false;
896 if (parameters->output_is_object())
898 const char* name = this->namepool_.add(".note.GNU-stack", false, NULL);
899 elfcpp::Elf_Xword flags = 0;
900 if (is_stack_executable)
901 flags |= elfcpp::SHF_EXECINSTR;
902 this->make_output_section(name, elfcpp::SHT_PROGBITS, flags);
906 int flags = elfcpp::PF_R | elfcpp::PF_W;
907 if (is_stack_executable)
908 flags |= elfcpp::PF_X;
909 Output_segment* oseg = new Output_segment(elfcpp::PT_GNU_STACK, flags);
910 this->segment_list_.push_back(oseg);
914 // Return whether SEG1 should be before SEG2 in the output file. This
915 // is based entirely on the segment type and flags. When this is
916 // called the segment addresses has normally not yet been set.
919 Layout::segment_precedes(const Output_segment* seg1,
920 const Output_segment* seg2)
922 elfcpp::Elf_Word type1 = seg1->type();
923 elfcpp::Elf_Word type2 = seg2->type();
925 // The single PT_PHDR segment is required to precede any loadable
926 // segment. We simply make it always first.
927 if (type1 == elfcpp::PT_PHDR)
929 gold_assert(type2 != elfcpp::PT_PHDR);
932 if (type2 == elfcpp::PT_PHDR)
935 // The single PT_INTERP segment is required to precede any loadable
936 // segment. We simply make it always second.
937 if (type1 == elfcpp::PT_INTERP)
939 gold_assert(type2 != elfcpp::PT_INTERP);
942 if (type2 == elfcpp::PT_INTERP)
945 // We then put PT_LOAD segments before any other segments.
946 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
948 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
951 // We put the PT_TLS segment last, because that is where the dynamic
952 // linker expects to find it (this is just for efficiency; other
953 // positions would also work correctly).
954 if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS)
956 if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS)
959 const elfcpp::Elf_Word flags1 = seg1->flags();
960 const elfcpp::Elf_Word flags2 = seg2->flags();
962 // The order of non-PT_LOAD segments is unimportant. We simply sort
963 // by the numeric segment type and flags values. There should not
964 // be more than one segment with the same type and flags.
965 if (type1 != elfcpp::PT_LOAD)
968 return type1 < type2;
969 gold_assert(flags1 != flags2);
970 return flags1 < flags2;
973 // We sort PT_LOAD segments based on the flags. Readonly segments
974 // come before writable segments. Then executable segments come
975 // before non-executable segments. Then the unlikely case of a
976 // non-readable segment comes before the normal case of a readable
977 // segment. If there are multiple segments with the same type and
978 // flags, we require that the address be set, and we sort by
979 // virtual address and then physical address.
980 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
981 return (flags1 & elfcpp::PF_W) == 0;
982 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
983 return (flags1 & elfcpp::PF_X) != 0;
984 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
985 return (flags1 & elfcpp::PF_R) == 0;
987 uint64_t vaddr1 = seg1->vaddr();
988 uint64_t vaddr2 = seg2->vaddr();
989 if (vaddr1 != vaddr2)
990 return vaddr1 < vaddr2;
992 uint64_t paddr1 = seg1->paddr();
993 uint64_t paddr2 = seg2->paddr();
994 gold_assert(paddr1 != paddr2);
995 return paddr1 < paddr2;
998 // Set the file offsets of all the segments, and all the sections they
999 // contain. They have all been created. LOAD_SEG must be be laid out
1000 // first. Return the offset of the data to follow.
1003 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
1004 unsigned int *pshndx)
1006 // Sort them into the final order.
1007 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
1008 Layout::Compare_segments());
1010 // Find the PT_LOAD segments, and set their addresses and offsets
1011 // and their section's addresses and offsets.
1013 if (parameters->output_is_shared())
1015 else if (options_.user_set_text_segment_address())
1016 addr = options_.text_segment_address();
1018 addr = target->default_text_segment_address();
1020 bool was_readonly = false;
1021 for (Segment_list::iterator p = this->segment_list_.begin();
1022 p != this->segment_list_.end();
1025 if ((*p)->type() == elfcpp::PT_LOAD)
1027 if (load_seg != NULL && load_seg != *p)
1031 // If the last segment was readonly, and this one is not,
1032 // then skip the address forward one page, maintaining the
1033 // same position within the page. This lets us store both
1034 // segments overlapping on a single page in the file, but
1035 // the loader will put them on different pages in memory.
1037 uint64_t orig_addr = addr;
1038 uint64_t orig_off = off;
1040 uint64_t aligned_addr = addr;
1041 uint64_t abi_pagesize = target->abi_pagesize();
1043 // FIXME: This should depend on the -n and -N options.
1044 (*p)->set_minimum_addralign(target->common_pagesize());
1046 if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0)
1048 uint64_t align = (*p)->addralign();
1050 addr = align_address(addr, align);
1051 aligned_addr = addr;
1052 if ((addr & (abi_pagesize - 1)) != 0)
1053 addr = addr + abi_pagesize;
1056 unsigned int shndx_hold = *pshndx;
1057 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
1058 uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
1060 // Now that we know the size of this segment, we may be able
1061 // to save a page in memory, at the cost of wasting some
1062 // file space, by instead aligning to the start of a new
1063 // page. Here we use the real machine page size rather than
1064 // the ABI mandated page size.
1066 if (aligned_addr != addr)
1068 uint64_t common_pagesize = target->common_pagesize();
1069 uint64_t first_off = (common_pagesize
1071 & (common_pagesize - 1)));
1072 uint64_t last_off = new_addr & (common_pagesize - 1);
1075 && ((aligned_addr & ~ (common_pagesize - 1))
1076 != (new_addr & ~ (common_pagesize - 1)))
1077 && first_off + last_off <= common_pagesize)
1079 *pshndx = shndx_hold;
1080 addr = align_address(aligned_addr, common_pagesize);
1081 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
1082 new_addr = (*p)->set_section_addresses(addr, &off, pshndx);
1088 if (((*p)->flags() & elfcpp::PF_W) == 0)
1089 was_readonly = true;
1093 // Handle the non-PT_LOAD segments, setting their offsets from their
1094 // section's offsets.
1095 for (Segment_list::iterator p = this->segment_list_.begin();
1096 p != this->segment_list_.end();
1099 if ((*p)->type() != elfcpp::PT_LOAD)
1103 // Set the TLS offsets for each section in the PT_TLS segment.
1104 if (this->tls_segment_ != NULL)
1105 this->tls_segment_->set_tls_offsets();
1110 // Set the file offset of all the sections not associated with a
1114 Layout::set_section_offsets(off_t off, Layout::Section_offset_pass pass)
1116 for (Section_list::iterator p = this->unattached_section_list_.begin();
1117 p != this->unattached_section_list_.end();
1120 // The symtab section is handled in create_symtab_sections.
1121 if (*p == this->symtab_section_)
1124 // If we've already set the data size, don't set it again.
1125 if ((*p)->is_offset_valid() && (*p)->is_data_size_valid())
1128 if (pass == BEFORE_INPUT_SECTIONS_PASS
1129 && (*p)->requires_postprocessing())
1131 (*p)->create_postprocessing_buffer();
1132 this->any_postprocessing_sections_ = true;
1135 if (pass == BEFORE_INPUT_SECTIONS_PASS
1136 && (*p)->after_input_sections())
1138 else if (pass == POSTPROCESSING_SECTIONS_PASS
1139 && (!(*p)->after_input_sections()
1140 || (*p)->type() == elfcpp::SHT_STRTAB))
1142 else if (pass == STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1143 && (!(*p)->after_input_sections()
1144 || (*p)->type() != elfcpp::SHT_STRTAB))
1147 off = align_address(off, (*p)->addralign());
1148 (*p)->set_file_offset(off);
1149 (*p)->finalize_data_size();
1150 off += (*p)->data_size();
1152 // At this point the name must be set.
1153 if (pass != STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS)
1154 this->namepool_.add((*p)->name(), false, NULL);
1159 // Set the section indexes of all the sections not associated with a
1163 Layout::set_section_indexes(unsigned int shndx)
1165 for (Section_list::iterator p = this->unattached_section_list_.begin();
1166 p != this->unattached_section_list_.end();
1169 (*p)->set_out_shndx(shndx);
1175 // Count the local symbols in the regular symbol table and the dynamic
1176 // symbol table, and build the respective string pools.
1179 Layout::count_local_symbols(const Task* task,
1180 const Input_objects* input_objects)
1182 // First, figure out an upper bound on the number of symbols we'll
1183 // be inserting into each pool. This helps us create the pools with
1184 // the right size, to avoid unnecessary hashtable resizing.
1185 unsigned int symbol_count = 0;
1186 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
1187 p != input_objects->relobj_end();
1189 symbol_count += (*p)->local_symbol_count();
1191 // Go from "upper bound" to "estimate." We overcount for two
1192 // reasons: we double-count symbols that occur in more than one
1193 // object file, and we count symbols that are dropped from the
1194 // output. Add it all together and assume we overcount by 100%.
1197 // We assume all symbols will go into both the sympool and dynpool.
1198 this->sympool_.reserve(symbol_count);
1199 this->dynpool_.reserve(symbol_count);
1201 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
1202 p != input_objects->relobj_end();
1205 Task_lock_obj<Object> tlo(task, *p);
1206 (*p)->count_local_symbols(&this->sympool_, &this->dynpool_);
1210 // Create the symbol table sections. Here we also set the final
1211 // values of the symbols. At this point all the loadable sections are
1215 Layout::create_symtab_sections(const Input_objects* input_objects,
1216 Symbol_table* symtab,
1221 if (parameters->get_size() == 32)
1223 symsize = elfcpp::Elf_sizes<32>::sym_size;
1226 else if (parameters->get_size() == 64)
1228 symsize = elfcpp::Elf_sizes<64>::sym_size;
1235 off = align_address(off, align);
1236 off_t startoff = off;
1238 // Save space for the dummy symbol at the start of the section. We
1239 // never bother to write this out--it will just be left as zero.
1241 unsigned int local_symbol_index = 1;
1243 // Add STT_SECTION symbols for each Output section which needs one.
1244 for (Section_list::iterator p = this->section_list_.begin();
1245 p != this->section_list_.end();
1248 if (!(*p)->needs_symtab_index())
1249 (*p)->set_symtab_index(-1U);
1252 (*p)->set_symtab_index(local_symbol_index);
1253 ++local_symbol_index;
1258 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
1259 p != input_objects->relobj_end();
1262 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
1264 off += (index - local_symbol_index) * symsize;
1265 local_symbol_index = index;
1268 unsigned int local_symcount = local_symbol_index;
1269 gold_assert(local_symcount * symsize == off - startoff);
1272 size_t dyn_global_index;
1274 if (this->dynsym_section_ == NULL)
1277 dyn_global_index = 0;
1282 dyn_global_index = this->dynsym_section_->info();
1283 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
1284 dynoff = this->dynsym_section_->offset() + locsize;
1285 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
1286 gold_assert(static_cast<off_t>(dyncount * symsize)
1287 == this->dynsym_section_->data_size() - locsize);
1290 off = symtab->finalize(off, dynoff, dyn_global_index, dyncount,
1291 &this->sympool_, &local_symcount);
1293 if (!parameters->strip_all())
1295 this->sympool_.set_string_offsets();
1297 const char* symtab_name = this->namepool_.add(".symtab", false, NULL);
1298 Output_section* osymtab = this->make_output_section(symtab_name,
1301 this->symtab_section_ = osymtab;
1303 Output_section_data* pos = new Output_data_fixed_space(off - startoff,
1305 osymtab->add_output_section_data(pos);
1307 const char* strtab_name = this->namepool_.add(".strtab", false, NULL);
1308 Output_section* ostrtab = this->make_output_section(strtab_name,
1312 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
1313 ostrtab->add_output_section_data(pstr);
1315 osymtab->set_file_offset(startoff);
1316 osymtab->finalize_data_size();
1317 osymtab->set_link_section(ostrtab);
1318 osymtab->set_info(local_symcount);
1319 osymtab->set_entsize(symsize);
1325 // Create the .shstrtab section, which holds the names of the
1326 // sections. At the time this is called, we have created all the
1327 // output sections except .shstrtab itself.
1330 Layout::create_shstrtab()
1332 // FIXME: We don't need to create a .shstrtab section if we are
1333 // stripping everything.
1335 const char* name = this->namepool_.add(".shstrtab", false, NULL);
1337 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0);
1339 // We can't write out this section until we've set all the section
1340 // names, and we don't set the names of compressed output sections
1341 // until relocations are complete.
1342 os->set_after_input_sections();
1344 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
1345 os->add_output_section_data(posd);
1350 // Create the section headers. SIZE is 32 or 64. OFF is the file
1354 Layout::create_shdrs(off_t* poff)
1356 Output_section_headers* oshdrs;
1357 oshdrs = new Output_section_headers(this,
1358 &this->segment_list_,
1359 &this->unattached_section_list_,
1361 off_t off = align_address(*poff, oshdrs->addralign());
1362 oshdrs->set_address_and_file_offset(0, off);
1363 off += oshdrs->data_size();
1365 this->section_headers_ = oshdrs;
1368 // Create the dynamic symbol table.
1371 Layout::create_dynamic_symtab(const Input_objects* input_objects,
1372 Symbol_table* symtab,
1373 Output_section **pdynstr,
1374 unsigned int* plocal_dynamic_count,
1375 std::vector<Symbol*>* pdynamic_symbols,
1376 Versions* pversions)
1378 // Count all the symbols in the dynamic symbol table, and set the
1379 // dynamic symbol indexes.
1381 // Skip symbol 0, which is always all zeroes.
1382 unsigned int index = 1;
1384 // Add STT_SECTION symbols for each Output section which needs one.
1385 for (Section_list::iterator p = this->section_list_.begin();
1386 p != this->section_list_.end();
1389 if (!(*p)->needs_dynsym_index())
1390 (*p)->set_dynsym_index(-1U);
1393 (*p)->set_dynsym_index(index);
1398 // Count the local symbols that need to go in the dynamic symbol table,
1399 // and set the dynamic symbol indexes.
1400 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
1401 p != input_objects->relobj_end();
1404 unsigned int new_index = (*p)->set_local_dynsym_indexes(index);
1408 unsigned int local_symcount = index;
1409 *plocal_dynamic_count = local_symcount;
1411 // FIXME: We have to tell set_dynsym_indexes whether the
1412 // -E/--export-dynamic option was used.
1413 index = symtab->set_dynsym_indexes(index, pdynamic_symbols,
1414 &this->dynpool_, pversions);
1418 const int size = parameters->get_size();
1421 symsize = elfcpp::Elf_sizes<32>::sym_size;
1424 else if (size == 64)
1426 symsize = elfcpp::Elf_sizes<64>::sym_size;
1432 // Create the dynamic symbol table section.
1434 const char* dynsym_name = this->namepool_.add(".dynsym", false, NULL);
1435 Output_section* dynsym = this->make_output_section(dynsym_name,
1439 Output_section_data* odata = new Output_data_fixed_space(index * symsize,
1441 dynsym->add_output_section_data(odata);
1443 dynsym->set_info(local_symcount);
1444 dynsym->set_entsize(symsize);
1445 dynsym->set_addralign(align);
1447 this->dynsym_section_ = dynsym;
1449 Output_data_dynamic* const odyn = this->dynamic_data_;
1450 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
1451 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
1453 // Create the dynamic string table section.
1455 const char* dynstr_name = this->namepool_.add(".dynstr", false, NULL);
1456 Output_section* dynstr = this->make_output_section(dynstr_name,
1460 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
1461 dynstr->add_output_section_data(strdata);
1463 dynsym->set_link_section(dynstr);
1464 this->dynamic_section_->set_link_section(dynstr);
1466 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
1467 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
1471 // Create the hash tables.
1473 // FIXME: We need an option to create a GNU hash table.
1475 unsigned char* phash;
1476 unsigned int hashlen;
1477 Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
1480 const char* hash_name = this->namepool_.add(".hash", false, NULL);
1481 Output_section* hashsec = this->make_output_section(hash_name,
1485 Output_section_data* hashdata = new Output_data_const_buffer(phash,
1488 hashsec->add_output_section_data(hashdata);
1490 hashsec->set_link_section(dynsym);
1491 hashsec->set_entsize(4);
1493 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
1496 // Assign offsets to each local portion of the dynamic symbol table.
1499 Layout::assign_local_dynsym_offsets(const Input_objects* input_objects)
1501 Output_section* dynsym = this->dynsym_section_;
1502 gold_assert(dynsym != NULL);
1504 off_t off = dynsym->offset();
1506 // Skip the dummy symbol at the start of the section.
1507 off += dynsym->entsize();
1509 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
1510 p != input_objects->relobj_end();
1513 unsigned int count = (*p)->set_local_dynsym_offset(off);
1514 off += count * dynsym->entsize();
1518 // Create the version sections.
1521 Layout::create_version_sections(const Versions* versions,
1522 const Symbol_table* symtab,
1523 unsigned int local_symcount,
1524 const std::vector<Symbol*>& dynamic_symbols,
1525 const Output_section* dynstr)
1527 if (!versions->any_defs() && !versions->any_needs())
1530 if (parameters->get_size() == 32)
1532 if (parameters->is_big_endian())
1534 #ifdef HAVE_TARGET_32_BIG
1535 this->sized_create_version_sections
1536 SELECT_SIZE_ENDIAN_NAME(32, true)(
1537 versions, symtab, local_symcount, dynamic_symbols, dynstr
1538 SELECT_SIZE_ENDIAN(32, true));
1545 #ifdef HAVE_TARGET_32_LITTLE
1546 this->sized_create_version_sections
1547 SELECT_SIZE_ENDIAN_NAME(32, false)(
1548 versions, symtab, local_symcount, dynamic_symbols, dynstr
1549 SELECT_SIZE_ENDIAN(32, false));
1555 else if (parameters->get_size() == 64)
1557 if (parameters->is_big_endian())
1559 #ifdef HAVE_TARGET_64_BIG
1560 this->sized_create_version_sections
1561 SELECT_SIZE_ENDIAN_NAME(64, true)(
1562 versions, symtab, local_symcount, dynamic_symbols, dynstr
1563 SELECT_SIZE_ENDIAN(64, true));
1570 #ifdef HAVE_TARGET_64_LITTLE
1571 this->sized_create_version_sections
1572 SELECT_SIZE_ENDIAN_NAME(64, false)(
1573 versions, symtab, local_symcount, dynamic_symbols, dynstr
1574 SELECT_SIZE_ENDIAN(64, false));
1584 // Create the version sections, sized version.
1586 template<int size, bool big_endian>
1588 Layout::sized_create_version_sections(
1589 const Versions* versions,
1590 const Symbol_table* symtab,
1591 unsigned int local_symcount,
1592 const std::vector<Symbol*>& dynamic_symbols,
1593 const Output_section* dynstr
1596 const char* vname = this->namepool_.add(".gnu.version", false, NULL);
1597 Output_section* vsec = this->make_output_section(vname,
1598 elfcpp::SHT_GNU_versym,
1601 unsigned char* vbuf;
1603 versions->symbol_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1604 symtab, &this->dynpool_, local_symcount, dynamic_symbols, &vbuf, &vsize
1605 SELECT_SIZE_ENDIAN(size, big_endian));
1607 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2);
1609 vsec->add_output_section_data(vdata);
1610 vsec->set_entsize(2);
1611 vsec->set_link_section(this->dynsym_section_);
1613 Output_data_dynamic* const odyn = this->dynamic_data_;
1614 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
1616 if (versions->any_defs())
1618 const char* vdname = this->namepool_.add(".gnu.version_d", false, NULL);
1619 Output_section *vdsec;
1620 vdsec = this->make_output_section(vdname, elfcpp::SHT_GNU_verdef,
1623 unsigned char* vdbuf;
1624 unsigned int vdsize;
1625 unsigned int vdentries;
1626 versions->def_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)(
1627 &this->dynpool_, &vdbuf, &vdsize, &vdentries
1628 SELECT_SIZE_ENDIAN(size, big_endian));
1630 Output_section_data* vddata = new Output_data_const_buffer(vdbuf,
1634 vdsec->add_output_section_data(vddata);
1635 vdsec->set_link_section(dynstr);
1636 vdsec->set_info(vdentries);
1638 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
1639 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
1642 if (versions->any_needs())
1644 const char* vnname = this->namepool_.add(".gnu.version_r", false, NULL);
1645 Output_section* vnsec;
1646 vnsec = this->make_output_section(vnname, elfcpp::SHT_GNU_verneed,
1649 unsigned char* vnbuf;
1650 unsigned int vnsize;
1651 unsigned int vnentries;
1652 versions->need_section_contents SELECT_SIZE_ENDIAN_NAME(size, big_endian)
1653 (&this->dynpool_, &vnbuf, &vnsize, &vnentries
1654 SELECT_SIZE_ENDIAN(size, big_endian));
1656 Output_section_data* vndata = new Output_data_const_buffer(vnbuf,
1660 vnsec->add_output_section_data(vndata);
1661 vnsec->set_link_section(dynstr);
1662 vnsec->set_info(vnentries);
1664 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
1665 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
1669 // Create the .interp section and PT_INTERP segment.
1672 Layout::create_interp(const Target* target)
1674 const char* interp = this->options_.dynamic_linker();
1677 interp = target->dynamic_linker();
1678 gold_assert(interp != NULL);
1681 size_t len = strlen(interp) + 1;
1683 Output_section_data* odata = new Output_data_const(interp, len, 1);
1685 const char* interp_name = this->namepool_.add(".interp", false, NULL);
1686 Output_section* osec = this->make_output_section(interp_name,
1687 elfcpp::SHT_PROGBITS,
1689 osec->add_output_section_data(odata);
1691 Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R);
1692 this->segment_list_.push_back(oseg);
1693 oseg->add_initial_output_section(osec, elfcpp::PF_R);
1696 // Finish the .dynamic section and PT_DYNAMIC segment.
1699 Layout::finish_dynamic_section(const Input_objects* input_objects,
1700 const Symbol_table* symtab)
1702 Output_segment* oseg = new Output_segment(elfcpp::PT_DYNAMIC,
1703 elfcpp::PF_R | elfcpp::PF_W);
1704 this->segment_list_.push_back(oseg);
1705 oseg->add_initial_output_section(this->dynamic_section_,
1706 elfcpp::PF_R | elfcpp::PF_W);
1708 Output_data_dynamic* const odyn = this->dynamic_data_;
1710 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
1711 p != input_objects->dynobj_end();
1714 // FIXME: Handle --as-needed.
1715 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
1718 if (parameters->output_is_shared())
1720 const char* soname = this->options_.soname();
1722 odyn->add_string(elfcpp::DT_SONAME, soname);
1725 // FIXME: Support --init and --fini.
1726 Symbol* sym = symtab->lookup("_init");
1727 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1728 odyn->add_symbol(elfcpp::DT_INIT, sym);
1730 sym = symtab->lookup("_fini");
1731 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
1732 odyn->add_symbol(elfcpp::DT_FINI, sym);
1734 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1736 // Add a DT_RPATH entry if needed.
1737 const General_options::Dir_list& rpath(this->options_.rpath());
1740 std::string rpath_val;
1741 for (General_options::Dir_list::const_iterator p = rpath.begin();
1745 if (rpath_val.empty())
1746 rpath_val = p->name();
1749 // Eliminate duplicates.
1750 General_options::Dir_list::const_iterator q;
1751 for (q = rpath.begin(); q != p; ++q)
1752 if (q->name() == p->name())
1757 rpath_val += p->name();
1762 odyn->add_string(elfcpp::DT_RPATH, rpath_val);
1765 // Look for text segments that have dynamic relocations.
1766 bool have_textrel = false;
1767 for (Segment_list::const_iterator p = this->segment_list_.begin();
1768 p != this->segment_list_.end();
1771 if (((*p)->flags() & elfcpp::PF_W) == 0
1772 && (*p)->dynamic_reloc_count() > 0)
1774 have_textrel = true;
1779 // Add a DT_FLAGS entry. We add it even if no flags are set so that
1780 // post-link tools can easily modify these flags if desired.
1781 unsigned int flags = 0;
1784 // Add a DT_TEXTREL for compatibility with older loaders.
1785 odyn->add_constant(elfcpp::DT_TEXTREL, 0);
1786 flags |= elfcpp::DF_TEXTREL;
1788 if (parameters->output_is_shared() && this->has_static_tls())
1789 flags |= elfcpp::DF_STATIC_TLS;
1790 odyn->add_constant(elfcpp::DT_FLAGS, flags);
1793 // The mapping of .gnu.linkonce section names to real section names.
1795 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1796 const Layout::Linkonce_mapping Layout::linkonce_mapping[] =
1798 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1799 MAPPING_INIT("t", ".text"),
1800 MAPPING_INIT("r", ".rodata"),
1801 MAPPING_INIT("d", ".data"),
1802 MAPPING_INIT("b", ".bss"),
1803 MAPPING_INIT("s", ".sdata"),
1804 MAPPING_INIT("sb", ".sbss"),
1805 MAPPING_INIT("s2", ".sdata2"),
1806 MAPPING_INIT("sb2", ".sbss2"),
1807 MAPPING_INIT("wi", ".debug_info"),
1808 MAPPING_INIT("td", ".tdata"),
1809 MAPPING_INIT("tb", ".tbss"),
1810 MAPPING_INIT("lr", ".lrodata"),
1811 MAPPING_INIT("l", ".ldata"),
1812 MAPPING_INIT("lb", ".lbss"),
1816 const int Layout::linkonce_mapping_count =
1817 sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]);
1819 // Return the name of the output section to use for a .gnu.linkonce
1820 // section. This is based on the default ELF linker script of the old
1821 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1822 // to ".text". Set *PLEN to the length of the name. *PLEN is
1823 // initialized to the length of NAME.
1826 Layout::linkonce_output_name(const char* name, size_t *plen)
1828 const char* s = name + sizeof(".gnu.linkonce") - 1;
1832 const Linkonce_mapping* plm = linkonce_mapping;
1833 for (int i = 0; i < linkonce_mapping_count; ++i, ++plm)
1835 if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.')
1844 // Choose the output section name to use given an input section name.
1845 // Set *PLEN to the length of the name. *PLEN is initialized to the
1849 Layout::output_section_name(const char* name, size_t* plen)
1851 if (Layout::is_linkonce(name))
1853 // .gnu.linkonce sections are laid out as though they were named
1854 // for the sections are placed into.
1855 return Layout::linkonce_output_name(name, plen);
1858 // gcc 4.3 generates the following sorts of section names when it
1859 // needs a section name specific to a function:
1865 // .data.rel.local.FN
1867 // .data.rel.ro.local.FN
1874 // The GNU linker maps all of those to the part before the .FN,
1875 // except that .data.rel.local.FN is mapped to .data, and
1876 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1877 // beginning with .data.rel.ro.local are grouped together.
1879 // For an anonymous namespace, the string FN can contain a '.'.
1881 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1882 // GNU linker maps to .rodata.
1884 // The .data.rel.ro sections enable a security feature triggered by
1885 // the -z relro option. Section which need to be relocated at
1886 // program startup time but which may be readonly after startup are
1887 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1888 // segment. The dynamic linker will make that segment writable,
1889 // perform relocations, and then make it read-only. FIXME: We do
1890 // not yet implement this optimization.
1892 // It is hard to handle this in a principled way.
1894 // These are the rules we follow:
1896 // If the section name has no initial '.', or no dot other than an
1897 // initial '.', we use the name unchanged (i.e., "mysection" and
1898 // ".text" are unchanged).
1900 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1902 // Otherwise, we drop the second '.' and everything that comes after
1903 // it (i.e., ".text.XXX" becomes ".text").
1905 const char* s = name;
1909 const char* sdot = strchr(s, '.');
1913 const char* const data_rel_ro = ".data.rel.ro";
1914 if (strncmp(name, data_rel_ro, strlen(data_rel_ro)) == 0)
1916 *plen = strlen(data_rel_ro);
1920 *plen = sdot - name;
1924 // Record the signature of a comdat section, and return whether to
1925 // include it in the link. If GROUP is true, this is a regular
1926 // section group. If GROUP is false, this is a group signature
1927 // derived from the name of a linkonce section. We want linkonce
1928 // signatures and group signatures to block each other, but we don't
1929 // want a linkonce signature to block another linkonce signature.
1932 Layout::add_comdat(const char* signature, bool group)
1934 std::string sig(signature);
1935 std::pair<Signatures::iterator, bool> ins(
1936 this->signatures_.insert(std::make_pair(sig, group)));
1940 // This is the first time we've seen this signature.
1944 if (ins.first->second)
1946 // We've already seen a real section group with this signature.
1951 // This is a real section group, and we've already seen a
1952 // linkonce section with this signature. Record that we've seen
1953 // a section group, and don't include this section group.
1954 ins.first->second = true;
1959 // We've already seen a linkonce section and this is a linkonce
1960 // section. These don't block each other--this may be the same
1961 // symbol name with different section types.
1966 // Write out the Output_sections. Most won't have anything to write,
1967 // since most of the data will come from input sections which are
1968 // handled elsewhere. But some Output_sections do have Output_data.
1971 Layout::write_output_sections(Output_file* of) const
1973 for (Section_list::const_iterator p = this->section_list_.begin();
1974 p != this->section_list_.end();
1977 if (!(*p)->after_input_sections())
1982 // Write out data not associated with a section or the symbol table.
1985 Layout::write_data(const Symbol_table* symtab, Output_file* of) const
1987 if (!parameters->strip_all())
1989 const Output_section* symtab_section = this->symtab_section_;
1990 for (Section_list::const_iterator p = this->section_list_.begin();
1991 p != this->section_list_.end();
1994 if ((*p)->needs_symtab_index())
1996 gold_assert(symtab_section != NULL);
1997 unsigned int index = (*p)->symtab_index();
1998 gold_assert(index > 0 && index != -1U);
1999 off_t off = (symtab_section->offset()
2000 + index * symtab_section->entsize());
2001 symtab->write_section_symbol(*p, of, off);
2006 const Output_section* dynsym_section = this->dynsym_section_;
2007 for (Section_list::const_iterator p = this->section_list_.begin();
2008 p != this->section_list_.end();
2011 if ((*p)->needs_dynsym_index())
2013 gold_assert(dynsym_section != NULL);
2014 unsigned int index = (*p)->dynsym_index();
2015 gold_assert(index > 0 && index != -1U);
2016 off_t off = (dynsym_section->offset()
2017 + index * dynsym_section->entsize());
2018 symtab->write_section_symbol(*p, of, off);
2022 // Write out the Output_data which are not in an Output_section.
2023 for (Data_list::const_iterator p = this->special_output_list_.begin();
2024 p != this->special_output_list_.end();
2029 // Write out the Output_sections which can only be written after the
2030 // input sections are complete.
2033 Layout::write_sections_after_input_sections(Output_file* of)
2035 // Determine the final section offsets, and thus the final output
2036 // file size. Note we finalize the .shstrab last, to allow the
2037 // after_input_section sections to modify their section-names before
2039 if (this->any_postprocessing_sections_)
2041 off_t off = this->output_file_size_;
2042 off = this->set_section_offsets(off, POSTPROCESSING_SECTIONS_PASS);
2044 // Now that we've finalized the names, we can finalize the shstrab.
2046 this->set_section_offsets(off,
2047 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
2049 if (off > this->output_file_size_)
2052 this->output_file_size_ = off;
2056 for (Section_list::const_iterator p = this->section_list_.begin();
2057 p != this->section_list_.end();
2060 if ((*p)->after_input_sections())
2064 this->section_headers_->write(of);
2067 // Print statistical information to stderr. This is used for --stats.
2070 Layout::print_stats() const
2072 this->namepool_.print_stats("section name pool");
2073 this->sympool_.print_stats("output symbol name pool");
2074 this->dynpool_.print_stats("dynamic name pool");
2076 for (Section_list::const_iterator p = this->section_list_.begin();
2077 p != this->section_list_.end();
2079 (*p)->print_merge_stats();
2082 // Write_sections_task methods.
2084 // We can always run this task.
2087 Write_sections_task::is_runnable()
2092 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
2096 Write_sections_task::locks(Task_locker* tl)
2098 tl->add(this, this->output_sections_blocker_);
2099 tl->add(this, this->final_blocker_);
2102 // Run the task--write out the data.
2105 Write_sections_task::run(Workqueue*)
2107 this->layout_->write_output_sections(this->of_);
2110 // Write_data_task methods.
2112 // We can always run this task.
2115 Write_data_task::is_runnable()
2120 // We need to unlock FINAL_BLOCKER when finished.
2123 Write_data_task::locks(Task_locker* tl)
2125 tl->add(this, this->final_blocker_);
2128 // Run the task--write out the data.
2131 Write_data_task::run(Workqueue*)
2133 this->layout_->write_data(this->symtab_, this->of_);
2136 // Write_symbols_task methods.
2138 // We can always run this task.
2141 Write_symbols_task::is_runnable()
2146 // We need to unlock FINAL_BLOCKER when finished.
2149 Write_symbols_task::locks(Task_locker* tl)
2151 tl->add(this, this->final_blocker_);
2154 // Run the task--write out the symbols.
2157 Write_symbols_task::run(Workqueue*)
2159 this->symtab_->write_globals(this->input_objects_, this->sympool_,
2160 this->dynpool_, this->of_);
2163 // Write_after_input_sections_task methods.
2165 // We can only run this task after the input sections have completed.
2168 Write_after_input_sections_task::is_runnable()
2170 if (this->input_sections_blocker_->is_blocked())
2171 return this->input_sections_blocker_;
2175 // We need to unlock FINAL_BLOCKER when finished.
2178 Write_after_input_sections_task::locks(Task_locker* tl)
2180 tl->add(this, this->final_blocker_);
2186 Write_after_input_sections_task::run(Workqueue*)
2188 this->layout_->write_sections_after_input_sections(this->of_);
2191 // Close_task_runner methods.
2193 // Run the task--close the file.
2196 Close_task_runner::run(Workqueue*, const Task*)
2201 // Instantiate the templates we need. We could use the configure
2202 // script to restrict this to only the ones for implemented targets.
2204 #ifdef HAVE_TARGET_32_LITTLE
2207 Layout::layout<32, false>(Sized_relobj<32, false>* object, unsigned int shndx,
2209 const elfcpp::Shdr<32, false>& shdr,
2210 unsigned int, unsigned int, off_t*);
2213 #ifdef HAVE_TARGET_32_BIG
2216 Layout::layout<32, true>(Sized_relobj<32, true>* object, unsigned int shndx,
2218 const elfcpp::Shdr<32, true>& shdr,
2219 unsigned int, unsigned int, off_t*);
2222 #ifdef HAVE_TARGET_64_LITTLE
2225 Layout::layout<64, false>(Sized_relobj<64, false>* object, unsigned int shndx,
2227 const elfcpp::Shdr<64, false>& shdr,
2228 unsigned int, unsigned int, off_t*);
2231 #ifdef HAVE_TARGET_64_BIG
2234 Layout::layout<64, true>(Sized_relobj<64, true>* object, unsigned int shndx,
2236 const elfcpp::Shdr<64, true>& shdr,
2237 unsigned int, unsigned int, off_t*);
2240 #ifdef HAVE_TARGET_32_LITTLE
2243 Layout::layout_eh_frame<32, false>(Sized_relobj<32, false>* object,
2244 const unsigned char* symbols,
2246 const unsigned char* symbol_names,
2247 off_t symbol_names_size,
2249 const elfcpp::Shdr<32, false>& shdr,
2250 unsigned int reloc_shndx,
2251 unsigned int reloc_type,
2255 #ifdef HAVE_TARGET_32_BIG
2258 Layout::layout_eh_frame<32, true>(Sized_relobj<32, true>* object,
2259 const unsigned char* symbols,
2261 const unsigned char* symbol_names,
2262 off_t symbol_names_size,
2264 const elfcpp::Shdr<32, true>& shdr,
2265 unsigned int reloc_shndx,
2266 unsigned int reloc_type,
2270 #ifdef HAVE_TARGET_64_LITTLE
2273 Layout::layout_eh_frame<64, false>(Sized_relobj<64, false>* object,
2274 const unsigned char* symbols,
2276 const unsigned char* symbol_names,
2277 off_t symbol_names_size,
2279 const elfcpp::Shdr<64, false>& shdr,
2280 unsigned int reloc_shndx,
2281 unsigned int reloc_type,
2285 #ifdef HAVE_TARGET_64_BIG
2288 Layout::layout_eh_frame<64, true>(Sized_relobj<64, true>* object,
2289 const unsigned char* symbols,
2291 const unsigned char* symbol_names,
2292 off_t symbol_names_size,
2294 const elfcpp::Shdr<64, true>& shdr,
2295 unsigned int reloc_shndx,
2296 unsigned int reloc_type,
2300 } // End namespace gold.