1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007, 2008, 2009, 2010 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.
34 #include "libiberty.h"
38 #include "parameters.h"
42 #include "script-sections.h"
47 #include "compressed_output.h"
48 #include "reduced_debug_output.h"
50 #include "descriptors.h"
52 #include "incremental.h"
58 // Layout::Relaxation_debug_check methods.
60 // Check that sections and special data are in reset states.
61 // We do not save states for Output_sections and special Output_data.
62 // So we check that they have not assigned any addresses or offsets.
63 // clean_up_after_relaxation simply resets their addresses and offsets.
65 Layout::Relaxation_debug_check::check_output_data_for_reset_values(
66 const Layout::Section_list& sections,
67 const Layout::Data_list& special_outputs)
69 for(Layout::Section_list::const_iterator p = sections.begin();
72 gold_assert((*p)->address_and_file_offset_have_reset_values());
74 for(Layout::Data_list::const_iterator p = special_outputs.begin();
75 p != special_outputs.end();
77 gold_assert((*p)->address_and_file_offset_have_reset_values());
80 // Save information of SECTIONS for checking later.
83 Layout::Relaxation_debug_check::read_sections(
84 const Layout::Section_list& sections)
86 for(Layout::Section_list::const_iterator p = sections.begin();
90 Output_section* os = *p;
92 info.output_section = os;
93 info.address = os->is_address_valid() ? os->address() : 0;
94 info.data_size = os->is_data_size_valid() ? os->data_size() : -1;
95 info.offset = os->is_offset_valid()? os->offset() : -1 ;
96 this->section_infos_.push_back(info);
100 // Verify SECTIONS using previously recorded information.
103 Layout::Relaxation_debug_check::verify_sections(
104 const Layout::Section_list& sections)
107 for(Layout::Section_list::const_iterator p = sections.begin();
111 Output_section* os = *p;
112 uint64_t address = os->is_address_valid() ? os->address() : 0;
113 off_t data_size = os->is_data_size_valid() ? os->data_size() : -1;
114 off_t offset = os->is_offset_valid()? os->offset() : -1 ;
116 if (i >= this->section_infos_.size())
118 gold_fatal("Section_info of %s missing.\n", os->name());
120 const Section_info& info = this->section_infos_[i];
121 if (os != info.output_section)
122 gold_fatal("Section order changed. Expecting %s but see %s\n",
123 info.output_section->name(), os->name());
124 if (address != info.address
125 || data_size != info.data_size
126 || offset != info.offset)
127 gold_fatal("Section %s changed.\n", os->name());
131 // Layout_task_runner methods.
133 // Lay out the sections. This is called after all the input objects
137 Layout_task_runner::run(Workqueue* workqueue, const Task* task)
139 off_t file_size = this->layout_->finalize(this->input_objects_,
144 // Now we know the final size of the output file and we know where
145 // each piece of information goes.
147 if (this->mapfile_ != NULL)
149 this->mapfile_->print_discarded_sections(this->input_objects_);
150 this->layout_->print_to_mapfile(this->mapfile_);
153 Output_file* of = new Output_file(parameters->options().output_file_name());
154 if (this->options_.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
155 of->set_is_temporary();
158 // Queue up the final set of tasks.
159 gold::queue_final_tasks(this->options_, this->input_objects_,
160 this->symtab_, this->layout_, workqueue, of);
165 Layout::Layout(int number_of_input_files, Script_options* script_options)
166 : number_of_input_files_(number_of_input_files),
167 script_options_(script_options),
175 unattached_section_list_(),
176 special_output_list_(),
177 section_headers_(NULL),
179 relro_segment_(NULL),
181 symtab_section_(NULL),
182 symtab_xindex_(NULL),
183 dynsym_section_(NULL),
184 dynsym_xindex_(NULL),
185 dynamic_section_(NULL),
186 dynamic_symbol_(NULL),
188 eh_frame_section_(NULL),
189 eh_frame_data_(NULL),
190 added_eh_frame_data_(false),
191 eh_frame_hdr_section_(NULL),
192 build_id_note_(NULL),
196 output_file_size_(-1),
197 have_added_input_section_(false),
198 sections_are_attached_(false),
199 input_requires_executable_stack_(false),
200 input_with_gnu_stack_note_(false),
201 input_without_gnu_stack_note_(false),
202 has_static_tls_(false),
203 any_postprocessing_sections_(false),
204 resized_signatures_(false),
205 have_stabstr_section_(false),
206 incremental_inputs_(NULL),
207 record_output_section_data_from_script_(false),
208 script_output_section_data_list_(),
209 segment_states_(NULL),
210 relaxation_debug_check_(NULL)
212 // Make space for more than enough segments for a typical file.
213 // This is just for efficiency--it's OK if we wind up needing more.
214 this->segment_list_.reserve(12);
216 // We expect two unattached Output_data objects: the file header and
217 // the segment headers.
218 this->special_output_list_.reserve(2);
220 // Initialize structure needed for an incremental build.
221 if (parameters->options().incremental())
222 this->incremental_inputs_ = new Incremental_inputs;
224 // The section name pool is worth optimizing in all cases, because
225 // it is small, but there are often overlaps due to .rel sections.
226 this->namepool_.set_optimize();
229 // Hash a key we use to look up an output section mapping.
232 Layout::Hash_key::operator()(const Layout::Key& k) const
234 return k.first + k.second.first + k.second.second;
237 // Returns whether the given section is in the list of
238 // debug-sections-used-by-some-version-of-gdb. Currently,
239 // we've checked versions of gdb up to and including 6.7.1.
241 static const char* gdb_sections[] =
243 // ".debug_aranges", // not used by gdb as of 6.7.1
250 // ".debug_pubnames", // not used by gdb as of 6.7.1
255 static const char* lines_only_debug_sections[] =
257 // ".debug_aranges", // not used by gdb as of 6.7.1
264 // ".debug_pubnames", // not used by gdb as of 6.7.1
270 is_gdb_debug_section(const char* str)
272 // We can do this faster: binary search or a hashtable. But why bother?
273 for (size_t i = 0; i < sizeof(gdb_sections)/sizeof(*gdb_sections); ++i)
274 if (strcmp(str, gdb_sections[i]) == 0)
280 is_lines_only_debug_section(const char* str)
282 // We can do this faster: binary search or a hashtable. But why bother?
284 i < sizeof(lines_only_debug_sections)/sizeof(*lines_only_debug_sections);
286 if (strcmp(str, lines_only_debug_sections[i]) == 0)
291 // Whether to include this section in the link.
293 template<int size, bool big_endian>
295 Layout::include_section(Sized_relobj<size, big_endian>*, const char* name,
296 const elfcpp::Shdr<size, big_endian>& shdr)
298 if (shdr.get_sh_flags() & elfcpp::SHF_EXCLUDE)
301 switch (shdr.get_sh_type())
303 case elfcpp::SHT_NULL:
304 case elfcpp::SHT_SYMTAB:
305 case elfcpp::SHT_DYNSYM:
306 case elfcpp::SHT_HASH:
307 case elfcpp::SHT_DYNAMIC:
308 case elfcpp::SHT_SYMTAB_SHNDX:
311 case elfcpp::SHT_STRTAB:
312 // Discard the sections which have special meanings in the ELF
313 // ABI. Keep others (e.g., .stabstr). We could also do this by
314 // checking the sh_link fields of the appropriate sections.
315 return (strcmp(name, ".dynstr") != 0
316 && strcmp(name, ".strtab") != 0
317 && strcmp(name, ".shstrtab") != 0);
319 case elfcpp::SHT_RELA:
320 case elfcpp::SHT_REL:
321 case elfcpp::SHT_GROUP:
322 // If we are emitting relocations these should be handled
324 gold_assert(!parameters->options().relocatable()
325 && !parameters->options().emit_relocs());
328 case elfcpp::SHT_PROGBITS:
329 if (parameters->options().strip_debug()
330 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
332 if (is_debug_info_section(name))
335 if (parameters->options().strip_debug_non_line()
336 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
338 // Debugging sections can only be recognized by name.
339 if (is_prefix_of(".debug", name)
340 && !is_lines_only_debug_section(name))
343 if (parameters->options().strip_debug_gdb()
344 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
346 // Debugging sections can only be recognized by name.
347 if (is_prefix_of(".debug", name)
348 && !is_gdb_debug_section(name))
351 if (parameters->options().strip_lto_sections()
352 && !parameters->options().relocatable()
353 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
355 // Ignore LTO sections containing intermediate code.
356 if (is_prefix_of(".gnu.lto_", name))
359 // The GNU linker strips .gnu_debuglink sections, so we do too.
360 // This is a feature used to keep debugging information in
362 if (strcmp(name, ".gnu_debuglink") == 0)
371 // Return an output section named NAME, or NULL if there is none.
374 Layout::find_output_section(const char* name) const
376 for (Section_list::const_iterator p = this->section_list_.begin();
377 p != this->section_list_.end();
379 if (strcmp((*p)->name(), name) == 0)
384 // Return an output segment of type TYPE, with segment flags SET set
385 // and segment flags CLEAR clear. Return NULL if there is none.
388 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
389 elfcpp::Elf_Word clear) const
391 for (Segment_list::const_iterator p = this->segment_list_.begin();
392 p != this->segment_list_.end();
394 if (static_cast<elfcpp::PT>((*p)->type()) == type
395 && ((*p)->flags() & set) == set
396 && ((*p)->flags() & clear) == 0)
401 // Return the output section to use for section NAME with type TYPE
402 // and section flags FLAGS. NAME must be canonicalized in the string
403 // pool, and NAME_KEY is the key. IS_INTERP is true if this is the
404 // .interp section. IS_DYNAMIC_LINKER_SECTION is true if this section
405 // is used by the dynamic linker. IS_RELRO is true for a relro
406 // section. IS_LAST_RELRO is true for the last relro section.
407 // IS_FIRST_NON_RELRO is true for the first non-relro section.
410 Layout::get_output_section(const char* name, Stringpool::Key name_key,
411 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
412 Output_section_order order, bool is_relro)
414 elfcpp::Elf_Xword lookup_flags = flags;
416 // Ignoring SHF_WRITE and SHF_EXECINSTR here means that we combine
417 // read-write with read-only sections. Some other ELF linkers do
418 // not do this. FIXME: Perhaps there should be an option
420 lookup_flags &= ~(elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
422 const Key key(name_key, std::make_pair(type, lookup_flags));
423 const std::pair<Key, Output_section*> v(key, NULL);
424 std::pair<Section_name_map::iterator, bool> ins(
425 this->section_name_map_.insert(v));
428 return ins.first->second;
431 // This is the first time we've seen this name/type/flags
432 // combination. For compatibility with the GNU linker, we
433 // combine sections with contents and zero flags with sections
434 // with non-zero flags. This is a workaround for cases where
435 // assembler code forgets to set section flags. FIXME: Perhaps
436 // there should be an option to control this.
437 Output_section* os = NULL;
439 if (type == elfcpp::SHT_PROGBITS)
443 Output_section* same_name = this->find_output_section(name);
444 if (same_name != NULL
445 && same_name->type() == elfcpp::SHT_PROGBITS
446 && (same_name->flags() & elfcpp::SHF_TLS) == 0)
449 else if ((flags & elfcpp::SHF_TLS) == 0)
451 elfcpp::Elf_Xword zero_flags = 0;
452 const Key zero_key(name_key, std::make_pair(type, zero_flags));
453 Section_name_map::iterator p =
454 this->section_name_map_.find(zero_key);
455 if (p != this->section_name_map_.end())
461 os = this->make_output_section(name, type, flags, order, is_relro);
463 ins.first->second = os;
468 // Pick the output section to use for section NAME, in input file
469 // RELOBJ, with type TYPE and flags FLAGS. RELOBJ may be NULL for a
470 // linker created section. IS_INPUT_SECTION is true if we are
471 // choosing an output section for an input section found in a input
472 // file. IS_INTERP is true if this is the .interp section.
473 // IS_DYNAMIC_LINKER_SECTION is true if this section is used by the
474 // dynamic linker. IS_RELRO is true for a relro section.
475 // IS_LAST_RELRO is true for the last relro section.
476 // IS_FIRST_NON_RELRO is true for the first non-relro section. This
477 // will return NULL if the input section should be discarded.
480 Layout::choose_output_section(const Relobj* relobj, const char* name,
481 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
482 bool is_input_section, Output_section_order order,
485 // We should not see any input sections after we have attached
486 // sections to segments.
487 gold_assert(!is_input_section || !this->sections_are_attached_);
489 // Some flags in the input section should not be automatically
490 // copied to the output section.
491 flags &= ~ (elfcpp::SHF_INFO_LINK
492 | elfcpp::SHF_LINK_ORDER
495 | elfcpp::SHF_STRINGS);
497 if (this->script_options_->saw_sections_clause())
499 // We are using a SECTIONS clause, so the output section is
500 // chosen based only on the name.
502 Script_sections* ss = this->script_options_->script_sections();
503 const char* file_name = relobj == NULL ? NULL : relobj->name().c_str();
504 Output_section** output_section_slot;
505 Script_sections::Section_type script_section_type;
506 const char* orig_name = name;
507 name = ss->output_section_name(file_name, name, &output_section_slot,
508 &script_section_type);
511 gold_debug(DEBUG_SCRIPT, _("Unable to create output section '%s' "
512 "because it is not allowed by the "
513 "SECTIONS clause of the linker script"),
515 // The SECTIONS clause says to discard this input section.
519 // We can only handle script section types ST_NONE and ST_NOLOAD.
520 switch (script_section_type)
522 case Script_sections::ST_NONE:
524 case Script_sections::ST_NOLOAD:
525 flags &= elfcpp::SHF_ALLOC;
531 // If this is an orphan section--one not mentioned in the linker
532 // script--then OUTPUT_SECTION_SLOT will be NULL, and we do the
533 // default processing below.
535 if (output_section_slot != NULL)
537 if (*output_section_slot != NULL)
539 (*output_section_slot)->update_flags_for_input_section(flags);
540 return *output_section_slot;
543 // We don't put sections found in the linker script into
544 // SECTION_NAME_MAP_. That keeps us from getting confused
545 // if an orphan section is mapped to a section with the same
546 // name as one in the linker script.
548 name = this->namepool_.add(name, false, NULL);
550 Output_section* os = this->make_output_section(name, type, flags,
553 os->set_found_in_sections_clause();
555 // Special handling for NOLOAD sections.
556 if (script_section_type == Script_sections::ST_NOLOAD)
560 // The constructor of Output_section sets addresses of non-ALLOC
561 // sections to 0 by default. We don't want that for NOLOAD
562 // sections even if they have no SHF_ALLOC flag.
563 if ((os->flags() & elfcpp::SHF_ALLOC) == 0
564 && os->is_address_valid())
566 gold_assert(os->address() == 0
567 && !os->is_offset_valid()
568 && !os->is_data_size_valid());
569 os->reset_address_and_file_offset();
573 *output_section_slot = os;
578 // FIXME: Handle SHF_OS_NONCONFORMING somewhere.
580 // Turn NAME from the name of the input section into the name of the
583 size_t len = strlen(name);
585 && !this->script_options_->saw_sections_clause()
586 && !parameters->options().relocatable())
587 name = Layout::output_section_name(name, &len);
589 Stringpool::Key name_key;
590 name = this->namepool_.add_with_length(name, len, true, &name_key);
592 // Find or make the output section. The output section is selected
593 // based on the section name, type, and flags.
594 return this->get_output_section(name, name_key, type, flags, order, is_relro);
597 // Return the output section to use for input section SHNDX, with name
598 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
599 // index of a relocation section which applies to this section, or 0
600 // if none, or -1U if more than one. RELOC_TYPE is the type of the
601 // relocation section if there is one. Set *OFF to the offset of this
602 // input section without the output section. Return NULL if the
603 // section should be discarded. Set *OFF to -1 if the section
604 // contents should not be written directly to the output file, but
605 // will instead receive special handling.
607 template<int size, bool big_endian>
609 Layout::layout(Sized_relobj<size, big_endian>* object, unsigned int shndx,
610 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
611 unsigned int reloc_shndx, unsigned int, off_t* off)
615 if (!this->include_section(object, name, shdr))
620 // Sometimes .init_array*, .preinit_array* and .fini_array* do not have
621 // correct section types. Force them here.
622 elfcpp::Elf_Word sh_type = shdr.get_sh_type();
623 if (sh_type == elfcpp::SHT_PROGBITS)
625 static const char init_array_prefix[] = ".init_array";
626 static const char preinit_array_prefix[] = ".preinit_array";
627 static const char fini_array_prefix[] = ".fini_array";
628 static size_t init_array_prefix_size = sizeof(init_array_prefix) - 1;
629 static size_t preinit_array_prefix_size =
630 sizeof(preinit_array_prefix) - 1;
631 static size_t fini_array_prefix_size = sizeof(fini_array_prefix) - 1;
633 if (strncmp(name, init_array_prefix, init_array_prefix_size) == 0)
634 sh_type = elfcpp::SHT_INIT_ARRAY;
635 else if (strncmp(name, preinit_array_prefix, preinit_array_prefix_size)
637 sh_type = elfcpp::SHT_PREINIT_ARRAY;
638 else if (strncmp(name, fini_array_prefix, fini_array_prefix_size) == 0)
639 sh_type = elfcpp::SHT_FINI_ARRAY;
642 // In a relocatable link a grouped section must not be combined with
643 // any other sections.
644 if (parameters->options().relocatable()
645 && (shdr.get_sh_flags() & elfcpp::SHF_GROUP) != 0)
647 name = this->namepool_.add(name, true, NULL);
648 os = this->make_output_section(name, sh_type, shdr.get_sh_flags(),
649 ORDER_INVALID, false);
653 os = this->choose_output_section(object, name, sh_type,
654 shdr.get_sh_flags(), true,
655 ORDER_INVALID, false);
660 // By default the GNU linker sorts input sections whose names match
661 // .ctor.*, .dtor.*, .init_array.*, or .fini_array.*. The sections
662 // are sorted by name. This is used to implement constructor
663 // priority ordering. We are compatible.
664 if (!this->script_options_->saw_sections_clause()
665 && (is_prefix_of(".ctors.", name)
666 || is_prefix_of(".dtors.", name)
667 || is_prefix_of(".init_array.", name)
668 || is_prefix_of(".fini_array.", name)))
669 os->set_must_sort_attached_input_sections();
671 // FIXME: Handle SHF_LINK_ORDER somewhere.
673 *off = os->add_input_section(this, object, shndx, name, shdr, reloc_shndx,
674 this->script_options_->saw_sections_clause());
675 this->have_added_input_section_ = true;
680 // Handle a relocation section when doing a relocatable link.
682 template<int size, bool big_endian>
684 Layout::layout_reloc(Sized_relobj<size, big_endian>* object,
686 const elfcpp::Shdr<size, big_endian>& shdr,
687 Output_section* data_section,
688 Relocatable_relocs* rr)
690 gold_assert(parameters->options().relocatable()
691 || parameters->options().emit_relocs());
693 int sh_type = shdr.get_sh_type();
696 if (sh_type == elfcpp::SHT_REL)
698 else if (sh_type == elfcpp::SHT_RELA)
702 name += data_section->name();
704 // In a relocatable link relocs for a grouped section must not be
705 // combined with other reloc sections.
707 if (!parameters->options().relocatable()
708 || (data_section->flags() & elfcpp::SHF_GROUP) == 0)
709 os = this->choose_output_section(object, name.c_str(), sh_type,
710 shdr.get_sh_flags(), false,
711 ORDER_INVALID, false);
714 const char* n = this->namepool_.add(name.c_str(), true, NULL);
715 os = this->make_output_section(n, sh_type, shdr.get_sh_flags(),
716 ORDER_INVALID, false);
719 os->set_should_link_to_symtab();
720 os->set_info_section(data_section);
722 Output_section_data* posd;
723 if (sh_type == elfcpp::SHT_REL)
725 os->set_entsize(elfcpp::Elf_sizes<size>::rel_size);
726 posd = new Output_relocatable_relocs<elfcpp::SHT_REL,
730 else if (sh_type == elfcpp::SHT_RELA)
732 os->set_entsize(elfcpp::Elf_sizes<size>::rela_size);
733 posd = new Output_relocatable_relocs<elfcpp::SHT_RELA,
740 os->add_output_section_data(posd);
741 rr->set_output_data(posd);
746 // Handle a group section when doing a relocatable link.
748 template<int size, bool big_endian>
750 Layout::layout_group(Symbol_table* symtab,
751 Sized_relobj<size, big_endian>* object,
753 const char* group_section_name,
754 const char* signature,
755 const elfcpp::Shdr<size, big_endian>& shdr,
756 elfcpp::Elf_Word flags,
757 std::vector<unsigned int>* shndxes)
759 gold_assert(parameters->options().relocatable());
760 gold_assert(shdr.get_sh_type() == elfcpp::SHT_GROUP);
761 group_section_name = this->namepool_.add(group_section_name, true, NULL);
762 Output_section* os = this->make_output_section(group_section_name,
765 ORDER_INVALID, false);
767 // We need to find a symbol with the signature in the symbol table.
768 // If we don't find one now, we need to look again later.
769 Symbol* sym = symtab->lookup(signature, NULL);
771 os->set_info_symndx(sym);
774 // Reserve some space to minimize reallocations.
775 if (this->group_signatures_.empty())
776 this->group_signatures_.reserve(this->number_of_input_files_ * 16);
778 // We will wind up using a symbol whose name is the signature.
779 // So just put the signature in the symbol name pool to save it.
780 signature = symtab->canonicalize_name(signature);
781 this->group_signatures_.push_back(Group_signature(os, signature));
784 os->set_should_link_to_symtab();
787 section_size_type entry_count =
788 convert_to_section_size_type(shdr.get_sh_size() / 4);
789 Output_section_data* posd =
790 new Output_data_group<size, big_endian>(object, entry_count, flags,
792 os->add_output_section_data(posd);
795 // Special GNU handling of sections name .eh_frame. They will
796 // normally hold exception frame data as defined by the C++ ABI
797 // (http://codesourcery.com/cxx-abi/).
799 template<int size, bool big_endian>
801 Layout::layout_eh_frame(Sized_relobj<size, big_endian>* object,
802 const unsigned char* symbols,
804 const unsigned char* symbol_names,
805 off_t symbol_names_size,
807 const elfcpp::Shdr<size, big_endian>& shdr,
808 unsigned int reloc_shndx, unsigned int reloc_type,
811 gold_assert(shdr.get_sh_type() == elfcpp::SHT_PROGBITS);
812 gold_assert((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
814 const char* const name = ".eh_frame";
815 Output_section* os = this->choose_output_section(object, name,
816 elfcpp::SHT_PROGBITS,
817 elfcpp::SHF_ALLOC, false,
818 ORDER_EHFRAME, false);
822 if (this->eh_frame_section_ == NULL)
824 this->eh_frame_section_ = os;
825 this->eh_frame_data_ = new Eh_frame();
827 if (parameters->options().eh_frame_hdr())
829 Output_section* hdr_os =
830 this->choose_output_section(NULL, ".eh_frame_hdr",
831 elfcpp::SHT_PROGBITS,
832 elfcpp::SHF_ALLOC, false,
833 ORDER_EHFRAME, false);
837 Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os,
838 this->eh_frame_data_);
839 hdr_os->add_output_section_data(hdr_posd);
841 hdr_os->set_after_input_sections();
843 if (!this->script_options_->saw_phdrs_clause())
845 Output_segment* hdr_oseg;
846 hdr_oseg = this->make_output_segment(elfcpp::PT_GNU_EH_FRAME,
848 hdr_oseg->add_output_section_to_nonload(hdr_os,
852 this->eh_frame_data_->set_eh_frame_hdr(hdr_posd);
857 gold_assert(this->eh_frame_section_ == os);
859 if (this->eh_frame_data_->add_ehframe_input_section(object,
868 os->update_flags_for_input_section(shdr.get_sh_flags());
870 // We found a .eh_frame section we are going to optimize, so now
871 // we can add the set of optimized sections to the output
872 // section. We need to postpone adding this until we've found a
873 // section we can optimize so that the .eh_frame section in
874 // crtbegin.o winds up at the start of the output section.
875 if (!this->added_eh_frame_data_)
877 os->add_output_section_data(this->eh_frame_data_);
878 this->added_eh_frame_data_ = true;
884 // We couldn't handle this .eh_frame section for some reason.
885 // Add it as a normal section.
886 bool saw_sections_clause = this->script_options_->saw_sections_clause();
887 *off = os->add_input_section(this, object, shndx, name, shdr, reloc_shndx,
888 saw_sections_clause);
889 this->have_added_input_section_ = true;
895 // Add POSD to an output section using NAME, TYPE, and FLAGS. Return
896 // the output section.
899 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
900 elfcpp::Elf_Xword flags,
901 Output_section_data* posd,
902 Output_section_order order, bool is_relro)
904 Output_section* os = this->choose_output_section(NULL, name, type, flags,
905 false, order, is_relro);
907 os->add_output_section_data(posd);
911 // Map section flags to segment flags.
914 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
916 elfcpp::Elf_Word ret = elfcpp::PF_R;
917 if ((flags & elfcpp::SHF_WRITE) != 0)
919 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
924 // Sometimes we compress sections. This is typically done for
925 // sections that are not part of normal program execution (such as
926 // .debug_* sections), and where the readers of these sections know
927 // how to deal with compressed sections. This routine doesn't say for
928 // certain whether we'll compress -- it depends on commandline options
929 // as well -- just whether this section is a candidate for compression.
930 // (The Output_compressed_section class decides whether to compress
931 // a given section, and picks the name of the compressed section.)
934 is_compressible_debug_section(const char* secname)
936 return (is_prefix_of(".debug", secname));
939 // We may see compressed debug sections in input files. Return TRUE
940 // if this is the name of a compressed debug section.
943 is_compressed_debug_section(const char* secname)
945 return (is_prefix_of(".zdebug", secname));
948 // Make a new Output_section, and attach it to segments as
949 // appropriate. ORDER is the order in which this section should
950 // appear in the output segment. IS_RELRO is true if this is a relro
951 // (read-only after relocations) section.
954 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
955 elfcpp::Elf_Xword flags,
956 Output_section_order order, bool is_relro)
959 if ((flags & elfcpp::SHF_ALLOC) == 0
960 && strcmp(parameters->options().compress_debug_sections(), "none") != 0
961 && is_compressible_debug_section(name))
962 os = new Output_compressed_section(¶meters->options(), name, type,
964 else if ((flags & elfcpp::SHF_ALLOC) == 0
965 && parameters->options().strip_debug_non_line()
966 && strcmp(".debug_abbrev", name) == 0)
968 os = this->debug_abbrev_ = new Output_reduced_debug_abbrev_section(
970 if (this->debug_info_)
971 this->debug_info_->set_abbreviations(this->debug_abbrev_);
973 else if ((flags & elfcpp::SHF_ALLOC) == 0
974 && parameters->options().strip_debug_non_line()
975 && strcmp(".debug_info", name) == 0)
977 os = this->debug_info_ = new Output_reduced_debug_info_section(
979 if (this->debug_abbrev_)
980 this->debug_info_->set_abbreviations(this->debug_abbrev_);
984 // FIXME: const_cast is ugly.
985 Target* target = const_cast<Target*>(¶meters->target());
986 os = target->make_output_section(name, type, flags);
989 // With -z relro, we have to recognize the special sections by name.
990 // There is no other way.
991 bool is_relro_local = false;
992 if (!this->script_options_->saw_sections_clause()
993 && parameters->options().relro()
994 && type == elfcpp::SHT_PROGBITS
995 && (flags & elfcpp::SHF_ALLOC) != 0
996 && (flags & elfcpp::SHF_WRITE) != 0)
998 if (strcmp(name, ".data.rel.ro") == 0)
1000 else if (strcmp(name, ".data.rel.ro.local") == 0)
1003 is_relro_local = true;
1005 else if (type == elfcpp::SHT_INIT_ARRAY
1006 || type == elfcpp::SHT_FINI_ARRAY
1007 || type == elfcpp::SHT_PREINIT_ARRAY)
1009 else if (strcmp(name, ".ctors") == 0
1010 || strcmp(name, ".dtors") == 0
1011 || strcmp(name, ".jcr") == 0)
1018 if (order == ORDER_INVALID && (flags & elfcpp::SHF_ALLOC) != 0)
1019 order = this->default_section_order(os, is_relro_local);
1021 os->set_order(order);
1023 parameters->target().new_output_section(os);
1025 this->section_list_.push_back(os);
1027 // The GNU linker by default sorts some sections by priority, so we
1028 // do the same. We need to know that this might happen before we
1029 // attach any input sections.
1030 if (!this->script_options_->saw_sections_clause()
1031 && (strcmp(name, ".ctors") == 0
1032 || strcmp(name, ".dtors") == 0
1033 || strcmp(name, ".init_array") == 0
1034 || strcmp(name, ".fini_array") == 0))
1035 os->set_may_sort_attached_input_sections();
1037 // Check for .stab*str sections, as .stab* sections need to link to
1039 if (type == elfcpp::SHT_STRTAB
1040 && !this->have_stabstr_section_
1041 && strncmp(name, ".stab", 5) == 0
1042 && strcmp(name + strlen(name) - 3, "str") == 0)
1043 this->have_stabstr_section_ = true;
1045 // If we have already attached the sections to segments, then we
1046 // need to attach this one now. This happens for sections created
1047 // directly by the linker.
1048 if (this->sections_are_attached_)
1049 this->attach_section_to_segment(os);
1054 // Return the default order in which a section should be placed in an
1055 // output segment. This function captures a lot of the ideas in
1056 // ld/scripttempl/elf.sc in the GNU linker. Note that the order of a
1057 // linker created section is normally set when the section is created;
1058 // this function is used for input sections.
1060 Output_section_order
1061 Layout::default_section_order(Output_section* os, bool is_relro_local)
1063 gold_assert((os->flags() & elfcpp::SHF_ALLOC) != 0);
1064 bool is_write = (os->flags() & elfcpp::SHF_WRITE) != 0;
1065 bool is_execinstr = (os->flags() & elfcpp::SHF_EXECINSTR) != 0;
1066 bool is_bss = false;
1071 case elfcpp::SHT_PROGBITS:
1073 case elfcpp::SHT_NOBITS:
1076 case elfcpp::SHT_RELA:
1077 case elfcpp::SHT_REL:
1079 return ORDER_DYNAMIC_RELOCS;
1081 case elfcpp::SHT_HASH:
1082 case elfcpp::SHT_DYNAMIC:
1083 case elfcpp::SHT_SHLIB:
1084 case elfcpp::SHT_DYNSYM:
1085 case elfcpp::SHT_GNU_HASH:
1086 case elfcpp::SHT_GNU_verdef:
1087 case elfcpp::SHT_GNU_verneed:
1088 case elfcpp::SHT_GNU_versym:
1090 return ORDER_DYNAMIC_LINKER;
1092 case elfcpp::SHT_NOTE:
1093 return is_write ? ORDER_RW_NOTE : ORDER_RO_NOTE;
1096 if ((os->flags() & elfcpp::SHF_TLS) != 0)
1097 return is_bss ? ORDER_TLS_BSS : ORDER_TLS_DATA;
1099 if (!is_bss && !is_write)
1103 if (strcmp(os->name(), ".init") == 0)
1105 else if (strcmp(os->name(), ".fini") == 0)
1108 return is_execinstr ? ORDER_TEXT : ORDER_READONLY;
1112 return is_relro_local ? ORDER_RELRO_LOCAL : ORDER_RELRO;
1114 if (os->is_small_section())
1115 return is_bss ? ORDER_SMALL_BSS : ORDER_SMALL_DATA;
1116 if (os->is_large_section())
1117 return is_bss ? ORDER_LARGE_BSS : ORDER_LARGE_DATA;
1119 return is_bss ? ORDER_BSS : ORDER_DATA;
1122 // Attach output sections to segments. This is called after we have
1123 // seen all the input sections.
1126 Layout::attach_sections_to_segments()
1128 for (Section_list::iterator p = this->section_list_.begin();
1129 p != this->section_list_.end();
1131 this->attach_section_to_segment(*p);
1133 this->sections_are_attached_ = true;
1136 // Attach an output section to a segment.
1139 Layout::attach_section_to_segment(Output_section* os)
1141 if ((os->flags() & elfcpp::SHF_ALLOC) == 0)
1142 this->unattached_section_list_.push_back(os);
1144 this->attach_allocated_section_to_segment(os);
1147 // Attach an allocated output section to a segment.
1150 Layout::attach_allocated_section_to_segment(Output_section* os)
1152 elfcpp::Elf_Xword flags = os->flags();
1153 gold_assert((flags & elfcpp::SHF_ALLOC) != 0);
1155 if (parameters->options().relocatable())
1158 // If we have a SECTIONS clause, we can't handle the attachment to
1159 // segments until after we've seen all the sections.
1160 if (this->script_options_->saw_sections_clause())
1163 gold_assert(!this->script_options_->saw_phdrs_clause());
1165 // This output section goes into a PT_LOAD segment.
1167 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
1169 // Check for --section-start.
1171 bool is_address_set = parameters->options().section_start(os->name(), &addr);
1173 // In general the only thing we really care about for PT_LOAD
1174 // segments is whether or not they are writable, so that is how we
1175 // search for them. Large data sections also go into their own
1176 // PT_LOAD segment. People who need segments sorted on some other
1177 // basis will have to use a linker script.
1179 Segment_list::const_iterator p;
1180 for (p = this->segment_list_.begin();
1181 p != this->segment_list_.end();
1184 if ((*p)->type() != elfcpp::PT_LOAD)
1186 if (!parameters->options().omagic()
1187 && ((*p)->flags() & elfcpp::PF_W) != (seg_flags & elfcpp::PF_W))
1189 // If -Tbss was specified, we need to separate the data and BSS
1191 if (parameters->options().user_set_Tbss())
1193 if ((os->type() == elfcpp::SHT_NOBITS)
1194 == (*p)->has_any_data_sections())
1197 if (os->is_large_data_section() && !(*p)->is_large_data_segment())
1202 if ((*p)->are_addresses_set())
1205 (*p)->add_initial_output_data(os);
1206 (*p)->update_flags_for_output_section(seg_flags);
1207 (*p)->set_addresses(addr, addr);
1211 (*p)->add_output_section_to_load(this, os, seg_flags);
1215 if (p == this->segment_list_.end())
1217 Output_segment* oseg = this->make_output_segment(elfcpp::PT_LOAD,
1219 if (os->is_large_data_section())
1220 oseg->set_is_large_data_segment();
1221 oseg->add_output_section_to_load(this, os, seg_flags);
1223 oseg->set_addresses(addr, addr);
1226 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
1228 if (os->type() == elfcpp::SHT_NOTE)
1230 // See if we already have an equivalent PT_NOTE segment.
1231 for (p = this->segment_list_.begin();
1232 p != segment_list_.end();
1235 if ((*p)->type() == elfcpp::PT_NOTE
1236 && (((*p)->flags() & elfcpp::PF_W)
1237 == (seg_flags & elfcpp::PF_W)))
1239 (*p)->add_output_section_to_nonload(os, seg_flags);
1244 if (p == this->segment_list_.end())
1246 Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
1248 oseg->add_output_section_to_nonload(os, seg_flags);
1252 // If we see a loadable SHF_TLS section, we create a PT_TLS
1253 // segment. There can only be one such segment.
1254 if ((flags & elfcpp::SHF_TLS) != 0)
1256 if (this->tls_segment_ == NULL)
1257 this->make_output_segment(elfcpp::PT_TLS, seg_flags);
1258 this->tls_segment_->add_output_section_to_nonload(os, seg_flags);
1261 // If -z relro is in effect, and we see a relro section, we create a
1262 // PT_GNU_RELRO segment. There can only be one such segment.
1263 if (os->is_relro() && parameters->options().relro())
1265 gold_assert(seg_flags == (elfcpp::PF_R | elfcpp::PF_W));
1266 if (this->relro_segment_ == NULL)
1267 this->make_output_segment(elfcpp::PT_GNU_RELRO, seg_flags);
1268 this->relro_segment_->add_output_section_to_nonload(os, seg_flags);
1272 // Make an output section for a script.
1275 Layout::make_output_section_for_script(
1277 Script_sections::Section_type section_type)
1279 name = this->namepool_.add(name, false, NULL);
1280 elfcpp::Elf_Xword sh_flags = elfcpp::SHF_ALLOC;
1281 if (section_type == Script_sections::ST_NOLOAD)
1283 Output_section* os = this->make_output_section(name, elfcpp::SHT_PROGBITS,
1284 sh_flags, ORDER_INVALID,
1286 os->set_found_in_sections_clause();
1287 if (section_type == Script_sections::ST_NOLOAD)
1288 os->set_is_noload();
1292 // Return the number of segments we expect to see.
1295 Layout::expected_segment_count() const
1297 size_t ret = this->segment_list_.size();
1299 // If we didn't see a SECTIONS clause in a linker script, we should
1300 // already have the complete list of segments. Otherwise we ask the
1301 // SECTIONS clause how many segments it expects, and add in the ones
1302 // we already have (PT_GNU_STACK, PT_GNU_EH_FRAME, etc.)
1304 if (!this->script_options_->saw_sections_clause())
1308 const Script_sections* ss = this->script_options_->script_sections();
1309 return ret + ss->expected_segment_count(this);
1313 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
1314 // is whether we saw a .note.GNU-stack section in the object file.
1315 // GNU_STACK_FLAGS is the section flags. The flags give the
1316 // protection required for stack memory. We record this in an
1317 // executable as a PT_GNU_STACK segment. If an object file does not
1318 // have a .note.GNU-stack segment, we must assume that it is an old
1319 // object. On some targets that will force an executable stack.
1322 Layout::layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags)
1324 if (!seen_gnu_stack)
1325 this->input_without_gnu_stack_note_ = true;
1328 this->input_with_gnu_stack_note_ = true;
1329 if ((gnu_stack_flags & elfcpp::SHF_EXECINSTR) != 0)
1330 this->input_requires_executable_stack_ = true;
1334 // Create automatic note sections.
1337 Layout::create_notes()
1339 this->create_gold_note();
1340 this->create_executable_stack_info();
1341 this->create_build_id();
1344 // Create the dynamic sections which are needed before we read the
1348 Layout::create_initial_dynamic_sections(Symbol_table* symtab)
1350 if (parameters->doing_static_link())
1353 this->dynamic_section_ = this->choose_output_section(NULL, ".dynamic",
1354 elfcpp::SHT_DYNAMIC,
1356 | elfcpp::SHF_WRITE),
1360 this->dynamic_symbol_ =
1361 symtab->define_in_output_data("_DYNAMIC", NULL, Symbol_table::PREDEFINED,
1362 this->dynamic_section_, 0, 0,
1363 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
1364 elfcpp::STV_HIDDEN, 0, false, false);
1366 this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
1368 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
1371 // For each output section whose name can be represented as C symbol,
1372 // define __start and __stop symbols for the section. This is a GNU
1376 Layout::define_section_symbols(Symbol_table* symtab)
1378 for (Section_list::const_iterator p = this->section_list_.begin();
1379 p != this->section_list_.end();
1382 const char* const name = (*p)->name();
1383 if (is_cident(name))
1385 const std::string name_string(name);
1386 const std::string start_name(cident_section_start_prefix
1388 const std::string stop_name(cident_section_stop_prefix
1391 symtab->define_in_output_data(start_name.c_str(),
1393 Symbol_table::PREDEFINED,
1399 elfcpp::STV_DEFAULT,
1401 false, // offset_is_from_end
1402 true); // only_if_ref
1404 symtab->define_in_output_data(stop_name.c_str(),
1406 Symbol_table::PREDEFINED,
1412 elfcpp::STV_DEFAULT,
1414 true, // offset_is_from_end
1415 true); // only_if_ref
1420 // Define symbols for group signatures.
1423 Layout::define_group_signatures(Symbol_table* symtab)
1425 for (Group_signatures::iterator p = this->group_signatures_.begin();
1426 p != this->group_signatures_.end();
1429 Symbol* sym = symtab->lookup(p->signature, NULL);
1431 p->section->set_info_symndx(sym);
1434 // Force the name of the group section to the group
1435 // signature, and use the group's section symbol as the
1436 // signature symbol.
1437 if (strcmp(p->section->name(), p->signature) != 0)
1439 const char* name = this->namepool_.add(p->signature,
1441 p->section->set_name(name);
1443 p->section->set_needs_symtab_index();
1444 p->section->set_info_section_symndx(p->section);
1448 this->group_signatures_.clear();
1451 // Find the first read-only PT_LOAD segment, creating one if
1455 Layout::find_first_load_seg()
1457 for (Segment_list::const_iterator p = this->segment_list_.begin();
1458 p != this->segment_list_.end();
1461 if ((*p)->type() == elfcpp::PT_LOAD
1462 && ((*p)->flags() & elfcpp::PF_R) != 0
1463 && (parameters->options().omagic()
1464 || ((*p)->flags() & elfcpp::PF_W) == 0))
1468 gold_assert(!this->script_options_->saw_phdrs_clause());
1470 Output_segment* load_seg = this->make_output_segment(elfcpp::PT_LOAD,
1475 // Save states of all current output segments. Store saved states
1476 // in SEGMENT_STATES.
1479 Layout::save_segments(Segment_states* segment_states)
1481 for (Segment_list::const_iterator p = this->segment_list_.begin();
1482 p != this->segment_list_.end();
1485 Output_segment* segment = *p;
1487 Output_segment* copy = new Output_segment(*segment);
1488 (*segment_states)[segment] = copy;
1492 // Restore states of output segments and delete any segment not found in
1496 Layout::restore_segments(const Segment_states* segment_states)
1498 // Go through the segment list and remove any segment added in the
1500 this->tls_segment_ = NULL;
1501 this->relro_segment_ = NULL;
1502 Segment_list::iterator list_iter = this->segment_list_.begin();
1503 while (list_iter != this->segment_list_.end())
1505 Output_segment* segment = *list_iter;
1506 Segment_states::const_iterator states_iter =
1507 segment_states->find(segment);
1508 if (states_iter != segment_states->end())
1510 const Output_segment* copy = states_iter->second;
1511 // Shallow copy to restore states.
1514 // Also fix up TLS and RELRO segment pointers as appropriate.
1515 if (segment->type() == elfcpp::PT_TLS)
1516 this->tls_segment_ = segment;
1517 else if (segment->type() == elfcpp::PT_GNU_RELRO)
1518 this->relro_segment_ = segment;
1524 list_iter = this->segment_list_.erase(list_iter);
1525 // This is a segment created during section layout. It should be
1526 // safe to remove it since we should have removed all pointers to it.
1532 // Clean up after relaxation so that sections can be laid out again.
1535 Layout::clean_up_after_relaxation()
1537 // Restore the segments to point state just prior to the relaxation loop.
1538 Script_sections* script_section = this->script_options_->script_sections();
1539 script_section->release_segments();
1540 this->restore_segments(this->segment_states_);
1542 // Reset section addresses and file offsets
1543 for (Section_list::iterator p = this->section_list_.begin();
1544 p != this->section_list_.end();
1547 (*p)->restore_states();
1549 // If an input section changes size because of relaxation,
1550 // we need to adjust the section offsets of all input sections.
1551 // after such a section.
1552 if ((*p)->section_offsets_need_adjustment())
1553 (*p)->adjust_section_offsets();
1555 (*p)->reset_address_and_file_offset();
1558 // Reset special output object address and file offsets.
1559 for (Data_list::iterator p = this->special_output_list_.begin();
1560 p != this->special_output_list_.end();
1562 (*p)->reset_address_and_file_offset();
1564 // A linker script may have created some output section data objects.
1565 // They are useless now.
1566 for (Output_section_data_list::const_iterator p =
1567 this->script_output_section_data_list_.begin();
1568 p != this->script_output_section_data_list_.end();
1571 this->script_output_section_data_list_.clear();
1574 // Prepare for relaxation.
1577 Layout::prepare_for_relaxation()
1579 // Create an relaxation debug check if in debugging mode.
1580 if (is_debugging_enabled(DEBUG_RELAXATION))
1581 this->relaxation_debug_check_ = new Relaxation_debug_check();
1583 // Save segment states.
1584 this->segment_states_ = new Segment_states();
1585 this->save_segments(this->segment_states_);
1587 for(Section_list::const_iterator p = this->section_list_.begin();
1588 p != this->section_list_.end();
1590 (*p)->save_states();
1592 if (is_debugging_enabled(DEBUG_RELAXATION))
1593 this->relaxation_debug_check_->check_output_data_for_reset_values(
1594 this->section_list_, this->special_output_list_);
1596 // Also enable recording of output section data from scripts.
1597 this->record_output_section_data_from_script_ = true;
1600 // Relaxation loop body: If target has no relaxation, this runs only once
1601 // Otherwise, the target relaxation hook is called at the end of
1602 // each iteration. If the hook returns true, it means re-layout of
1603 // section is required.
1605 // The number of segments created by a linking script without a PHDRS
1606 // clause may be affected by section sizes and alignments. There is
1607 // a remote chance that relaxation causes different number of PT_LOAD
1608 // segments are created and sections are attached to different segments.
1609 // Therefore, we always throw away all segments created during section
1610 // layout. In order to be able to restart the section layout, we keep
1611 // a copy of the segment list right before the relaxation loop and use
1612 // that to restore the segments.
1614 // PASS is the current relaxation pass number.
1615 // SYMTAB is a symbol table.
1616 // PLOAD_SEG is the address of a pointer for the load segment.
1617 // PHDR_SEG is a pointer to the PHDR segment.
1618 // SEGMENT_HEADERS points to the output segment header.
1619 // FILE_HEADER points to the output file header.
1620 // PSHNDX is the address to store the output section index.
1623 Layout::relaxation_loop_body(
1626 Symbol_table* symtab,
1627 Output_segment** pload_seg,
1628 Output_segment* phdr_seg,
1629 Output_segment_headers* segment_headers,
1630 Output_file_header* file_header,
1631 unsigned int* pshndx)
1633 // If this is not the first iteration, we need to clean up after
1634 // relaxation so that we can lay out the sections again.
1636 this->clean_up_after_relaxation();
1638 // If there is a SECTIONS clause, put all the input sections into
1639 // the required order.
1640 Output_segment* load_seg;
1641 if (this->script_options_->saw_sections_clause())
1642 load_seg = this->set_section_addresses_from_script(symtab);
1643 else if (parameters->options().relocatable())
1646 load_seg = this->find_first_load_seg();
1648 if (parameters->options().oformat_enum()
1649 != General_options::OBJECT_FORMAT_ELF)
1652 // If the user set the address of the text segment, that may not be
1653 // compatible with putting the segment headers and file headers into
1655 if (parameters->options().user_set_Ttext())
1658 gold_assert(phdr_seg == NULL
1660 || this->script_options_->saw_sections_clause());
1662 // If the address of the load segment we found has been set by
1663 // --section-start rather than by a script, then adjust the VMA and
1664 // LMA downward if possible to include the file and section headers.
1665 uint64_t header_gap = 0;
1666 if (load_seg != NULL
1667 && load_seg->are_addresses_set()
1668 && !this->script_options_->saw_sections_clause()
1669 && !parameters->options().relocatable())
1671 file_header->finalize_data_size();
1672 segment_headers->finalize_data_size();
1673 size_t sizeof_headers = (file_header->data_size()
1674 + segment_headers->data_size());
1675 const uint64_t abi_pagesize = target->abi_pagesize();
1676 uint64_t hdr_paddr = load_seg->paddr() - sizeof_headers;
1677 hdr_paddr &= ~(abi_pagesize - 1);
1678 uint64_t subtract = load_seg->paddr() - hdr_paddr;
1679 if (load_seg->paddr() < subtract || load_seg->vaddr() < subtract)
1683 load_seg->set_addresses(load_seg->vaddr() - subtract,
1684 load_seg->paddr() - subtract);
1685 header_gap = subtract - sizeof_headers;
1689 // Lay out the segment headers.
1690 if (!parameters->options().relocatable())
1692 gold_assert(segment_headers != NULL);
1693 if (header_gap != 0 && load_seg != NULL)
1695 Output_data_zero_fill* z = new Output_data_zero_fill(header_gap, 1);
1696 load_seg->add_initial_output_data(z);
1698 if (load_seg != NULL)
1699 load_seg->add_initial_output_data(segment_headers);
1700 if (phdr_seg != NULL)
1701 phdr_seg->add_initial_output_data(segment_headers);
1704 // Lay out the file header.
1705 if (load_seg != NULL)
1706 load_seg->add_initial_output_data(file_header);
1708 if (this->script_options_->saw_phdrs_clause()
1709 && !parameters->options().relocatable())
1711 // Support use of FILEHDRS and PHDRS attachments in a PHDRS
1712 // clause in a linker script.
1713 Script_sections* ss = this->script_options_->script_sections();
1714 ss->put_headers_in_phdrs(file_header, segment_headers);
1717 // We set the output section indexes in set_segment_offsets and
1718 // set_section_indexes.
1721 // Set the file offsets of all the segments, and all the sections
1724 if (!parameters->options().relocatable())
1725 off = this->set_segment_offsets(target, load_seg, pshndx);
1727 off = this->set_relocatable_section_offsets(file_header, pshndx);
1729 // Verify that the dummy relaxation does not change anything.
1730 if (is_debugging_enabled(DEBUG_RELAXATION))
1733 this->relaxation_debug_check_->read_sections(this->section_list_);
1735 this->relaxation_debug_check_->verify_sections(this->section_list_);
1738 *pload_seg = load_seg;
1742 // Search the list of patterns and find the postion of the given section
1743 // name in the output section. If the section name matches a glob
1744 // pattern and a non-glob name, then the non-glob position takes
1745 // precedence. Return 0 if no match is found.
1748 Layout::find_section_order_index(const std::string& section_name)
1750 Unordered_map<std::string, unsigned int>::iterator map_it;
1751 map_it = this->input_section_position_.find(section_name);
1752 if (map_it != this->input_section_position_.end())
1753 return map_it->second;
1755 // Absolute match failed. Linear search the glob patterns.
1756 std::vector<std::string>::iterator it;
1757 for (it = this->input_section_glob_.begin();
1758 it != this->input_section_glob_.end();
1761 if (fnmatch((*it).c_str(), section_name.c_str(), FNM_NOESCAPE) == 0)
1763 map_it = this->input_section_position_.find(*it);
1764 gold_assert(map_it != this->input_section_position_.end());
1765 return map_it->second;
1771 // Read the sequence of input sections from the file specified with
1772 // --section-ordering-file.
1775 Layout::read_layout_from_file()
1777 const char* filename = parameters->options().section_ordering_file();
1783 gold_fatal(_("unable to open --section-ordering-file file %s: %s"),
1784 filename, strerror(errno));
1786 std::getline(in, line); // this chops off the trailing \n, if any
1787 unsigned int position = 1;
1791 if (!line.empty() && line[line.length() - 1] == '\r') // Windows
1792 line.resize(line.length() - 1);
1793 // Ignore comments, beginning with '#'
1796 std::getline(in, line);
1799 this->input_section_position_[line] = position;
1800 // Store all glob patterns in a vector.
1801 if (is_wildcard_string(line.c_str()))
1802 this->input_section_glob_.push_back(line);
1804 std::getline(in, line);
1808 // Finalize the layout. When this is called, we have created all the
1809 // output sections and all the output segments which are based on
1810 // input sections. We have several things to do, and we have to do
1811 // them in the right order, so that we get the right results correctly
1814 // 1) Finalize the list of output segments and create the segment
1817 // 2) Finalize the dynamic symbol table and associated sections.
1819 // 3) Determine the final file offset of all the output segments.
1821 // 4) Determine the final file offset of all the SHF_ALLOC output
1824 // 5) Create the symbol table sections and the section name table
1827 // 6) Finalize the symbol table: set symbol values to their final
1828 // value and make a final determination of which symbols are going
1829 // into the output symbol table.
1831 // 7) Create the section table header.
1833 // 8) Determine the final file offset of all the output sections which
1834 // are not SHF_ALLOC, including the section table header.
1836 // 9) Finalize the ELF file header.
1838 // This function returns the size of the output file.
1841 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
1842 Target* target, const Task* task)
1844 target->finalize_sections(this, input_objects, symtab);
1846 this->count_local_symbols(task, input_objects);
1848 this->link_stabs_sections();
1850 Output_segment* phdr_seg = NULL;
1851 if (!parameters->options().relocatable() && !parameters->doing_static_link())
1853 // There was a dynamic object in the link. We need to create
1854 // some information for the dynamic linker.
1856 // Create the PT_PHDR segment which will hold the program
1858 if (!this->script_options_->saw_phdrs_clause())
1859 phdr_seg = this->make_output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
1861 // Create the dynamic symbol table, including the hash table.
1862 Output_section* dynstr;
1863 std::vector<Symbol*> dynamic_symbols;
1864 unsigned int local_dynamic_count;
1865 Versions versions(*this->script_options()->version_script_info(),
1867 this->create_dynamic_symtab(input_objects, symtab, &dynstr,
1868 &local_dynamic_count, &dynamic_symbols,
1871 // Create the .interp section to hold the name of the
1872 // interpreter, and put it in a PT_INTERP segment.
1873 if (!parameters->options().shared())
1874 this->create_interp(target);
1876 // Finish the .dynamic section to hold the dynamic data, and put
1877 // it in a PT_DYNAMIC segment.
1878 this->finish_dynamic_section(input_objects, symtab);
1880 // We should have added everything we need to the dynamic string
1882 this->dynpool_.set_string_offsets();
1884 // Create the version sections. We can't do this until the
1885 // dynamic string table is complete.
1886 this->create_version_sections(&versions, symtab, local_dynamic_count,
1887 dynamic_symbols, dynstr);
1889 // Set the size of the _DYNAMIC symbol. We can't do this until
1890 // after we call create_version_sections.
1891 this->set_dynamic_symbol_size(symtab);
1894 // Create segment headers.
1895 Output_segment_headers* segment_headers =
1896 (parameters->options().relocatable()
1898 : new Output_segment_headers(this->segment_list_));
1900 // Lay out the file header.
1901 Output_file_header* file_header
1902 = new Output_file_header(target, symtab, segment_headers,
1903 parameters->options().entry());
1905 this->special_output_list_.push_back(file_header);
1906 if (segment_headers != NULL)
1907 this->special_output_list_.push_back(segment_headers);
1909 // Find approriate places for orphan output sections if we are using
1911 if (this->script_options_->saw_sections_clause())
1912 this->place_orphan_sections_in_script();
1914 Output_segment* load_seg;
1919 // Take a snapshot of the section layout as needed.
1920 if (target->may_relax())
1921 this->prepare_for_relaxation();
1923 // Run the relaxation loop to lay out sections.
1926 off = this->relaxation_loop_body(pass, target, symtab, &load_seg,
1927 phdr_seg, segment_headers, file_header,
1931 while (target->may_relax()
1932 && target->relax(pass, input_objects, symtab, this));
1934 // Set the file offsets of all the non-data sections we've seen so
1935 // far which don't have to wait for the input sections. We need
1936 // this in order to finalize local symbols in non-allocated
1938 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
1940 // Set the section indexes of all unallocated sections seen so far,
1941 // in case any of them are somehow referenced by a symbol.
1942 shndx = this->set_section_indexes(shndx);
1944 // Create the symbol table sections.
1945 this->create_symtab_sections(input_objects, symtab, shndx, &off);
1946 if (!parameters->doing_static_link())
1947 this->assign_local_dynsym_offsets(input_objects);
1949 // Process any symbol assignments from a linker script. This must
1950 // be called after the symbol table has been finalized.
1951 this->script_options_->finalize_symbols(symtab, this);
1953 // Create the incremental inputs sections.
1954 if (this->incremental_inputs_)
1956 this->incremental_inputs_->finalize();
1957 this->create_incremental_info_sections(symtab);
1960 // Create the .shstrtab section.
1961 Output_section* shstrtab_section = this->create_shstrtab();
1963 // Set the file offsets of the rest of the non-data sections which
1964 // don't have to wait for the input sections.
1965 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
1967 // Now that all sections have been created, set the section indexes
1968 // for any sections which haven't been done yet.
1969 shndx = this->set_section_indexes(shndx);
1971 // Create the section table header.
1972 this->create_shdrs(shstrtab_section, &off);
1974 // If there are no sections which require postprocessing, we can
1975 // handle the section names now, and avoid a resize later.
1976 if (!this->any_postprocessing_sections_)
1978 off = this->set_section_offsets(off,
1979 POSTPROCESSING_SECTIONS_PASS);
1981 this->set_section_offsets(off,
1982 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
1985 file_header->set_section_info(this->section_headers_, shstrtab_section);
1987 // Now we know exactly where everything goes in the output file
1988 // (except for non-allocated sections which require postprocessing).
1989 Output_data::layout_complete();
1991 this->output_file_size_ = off;
1996 // Create a note header following the format defined in the ELF ABI.
1997 // NAME is the name, NOTE_TYPE is the type, SECTION_NAME is the name
1998 // of the section to create, DESCSZ is the size of the descriptor.
1999 // ALLOCATE is true if the section should be allocated in memory.
2000 // This returns the new note section. It sets *TRAILING_PADDING to
2001 // the number of trailing zero bytes required.
2004 Layout::create_note(const char* name, int note_type,
2005 const char* section_name, size_t descsz,
2006 bool allocate, size_t* trailing_padding)
2008 // Authorities all agree that the values in a .note field should
2009 // be aligned on 4-byte boundaries for 32-bit binaries. However,
2010 // they differ on what the alignment is for 64-bit binaries.
2011 // The GABI says unambiguously they take 8-byte alignment:
2012 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
2013 // Other documentation says alignment should always be 4 bytes:
2014 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
2015 // GNU ld and GNU readelf both support the latter (at least as of
2016 // version 2.16.91), and glibc always generates the latter for
2017 // .note.ABI-tag (as of version 1.6), so that's the one we go with
2019 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
2020 const int size = parameters->target().get_size();
2022 const int size = 32;
2025 // The contents of the .note section.
2026 size_t namesz = strlen(name) + 1;
2027 size_t aligned_namesz = align_address(namesz, size / 8);
2028 size_t aligned_descsz = align_address(descsz, size / 8);
2030 size_t notehdrsz = 3 * (size / 8) + aligned_namesz;
2032 unsigned char* buffer = new unsigned char[notehdrsz];
2033 memset(buffer, 0, notehdrsz);
2035 bool is_big_endian = parameters->target().is_big_endian();
2041 elfcpp::Swap<32, false>::writeval(buffer, namesz);
2042 elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
2043 elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
2047 elfcpp::Swap<32, true>::writeval(buffer, namesz);
2048 elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
2049 elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
2052 else if (size == 64)
2056 elfcpp::Swap<64, false>::writeval(buffer, namesz);
2057 elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
2058 elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
2062 elfcpp::Swap<64, true>::writeval(buffer, namesz);
2063 elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
2064 elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
2070 memcpy(buffer + 3 * (size / 8), name, namesz);
2072 elfcpp::Elf_Xword flags = 0;
2073 Output_section_order order = ORDER_INVALID;
2076 flags = elfcpp::SHF_ALLOC;
2077 order = ORDER_RO_NOTE;
2079 Output_section* os = this->choose_output_section(NULL, section_name,
2081 flags, false, order, false);
2085 Output_section_data* posd = new Output_data_const_buffer(buffer, notehdrsz,
2088 os->add_output_section_data(posd);
2090 *trailing_padding = aligned_descsz - descsz;
2095 // For an executable or shared library, create a note to record the
2096 // version of gold used to create the binary.
2099 Layout::create_gold_note()
2101 if (parameters->options().relocatable())
2104 std::string desc = std::string("gold ") + gold::get_version_string();
2106 size_t trailing_padding;
2107 Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_GOLD_VERSION,
2108 ".note.gnu.gold-version", desc.size(),
2109 false, &trailing_padding);
2113 Output_section_data* posd = new Output_data_const(desc, 4);
2114 os->add_output_section_data(posd);
2116 if (trailing_padding > 0)
2118 posd = new Output_data_zero_fill(trailing_padding, 0);
2119 os->add_output_section_data(posd);
2123 // Record whether the stack should be executable. This can be set
2124 // from the command line using the -z execstack or -z noexecstack
2125 // options. Otherwise, if any input file has a .note.GNU-stack
2126 // section with the SHF_EXECINSTR flag set, the stack should be
2127 // executable. Otherwise, if at least one input file a
2128 // .note.GNU-stack section, and some input file has no .note.GNU-stack
2129 // section, we use the target default for whether the stack should be
2130 // executable. Otherwise, we don't generate a stack note. When
2131 // generating a object file, we create a .note.GNU-stack section with
2132 // the appropriate marking. When generating an executable or shared
2133 // library, we create a PT_GNU_STACK segment.
2136 Layout::create_executable_stack_info()
2138 bool is_stack_executable;
2139 if (parameters->options().is_execstack_set())
2140 is_stack_executable = parameters->options().is_stack_executable();
2141 else if (!this->input_with_gnu_stack_note_)
2145 if (this->input_requires_executable_stack_)
2146 is_stack_executable = true;
2147 else if (this->input_without_gnu_stack_note_)
2148 is_stack_executable =
2149 parameters->target().is_default_stack_executable();
2151 is_stack_executable = false;
2154 if (parameters->options().relocatable())
2156 const char* name = this->namepool_.add(".note.GNU-stack", false, NULL);
2157 elfcpp::Elf_Xword flags = 0;
2158 if (is_stack_executable)
2159 flags |= elfcpp::SHF_EXECINSTR;
2160 this->make_output_section(name, elfcpp::SHT_PROGBITS, flags,
2161 ORDER_INVALID, false);
2165 if (this->script_options_->saw_phdrs_clause())
2167 int flags = elfcpp::PF_R | elfcpp::PF_W;
2168 if (is_stack_executable)
2169 flags |= elfcpp::PF_X;
2170 this->make_output_segment(elfcpp::PT_GNU_STACK, flags);
2174 // If --build-id was used, set up the build ID note.
2177 Layout::create_build_id()
2179 if (!parameters->options().user_set_build_id())
2182 const char* style = parameters->options().build_id();
2183 if (strcmp(style, "none") == 0)
2186 // Set DESCSZ to the size of the note descriptor. When possible,
2187 // set DESC to the note descriptor contents.
2190 if (strcmp(style, "md5") == 0)
2192 else if (strcmp(style, "sha1") == 0)
2194 else if (strcmp(style, "uuid") == 0)
2196 const size_t uuidsz = 128 / 8;
2198 char buffer[uuidsz];
2199 memset(buffer, 0, uuidsz);
2201 int descriptor = open_descriptor(-1, "/dev/urandom", O_RDONLY);
2203 gold_error(_("--build-id=uuid failed: could not open /dev/urandom: %s"),
2207 ssize_t got = ::read(descriptor, buffer, uuidsz);
2208 release_descriptor(descriptor, true);
2210 gold_error(_("/dev/urandom: read failed: %s"), strerror(errno));
2211 else if (static_cast<size_t>(got) != uuidsz)
2212 gold_error(_("/dev/urandom: expected %zu bytes, got %zd bytes"),
2216 desc.assign(buffer, uuidsz);
2219 else if (strncmp(style, "0x", 2) == 0)
2222 const char* p = style + 2;
2225 if (hex_p(p[0]) && hex_p(p[1]))
2227 char c = (hex_value(p[0]) << 4) | hex_value(p[1]);
2231 else if (*p == '-' || *p == ':')
2234 gold_fatal(_("--build-id argument '%s' not a valid hex number"),
2237 descsz = desc.size();
2240 gold_fatal(_("unrecognized --build-id argument '%s'"), style);
2243 size_t trailing_padding;
2244 Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_BUILD_ID,
2245 ".note.gnu.build-id", descsz, true,
2252 // We know the value already, so we fill it in now.
2253 gold_assert(desc.size() == descsz);
2255 Output_section_data* posd = new Output_data_const(desc, 4);
2256 os->add_output_section_data(posd);
2258 if (trailing_padding != 0)
2260 posd = new Output_data_zero_fill(trailing_padding, 0);
2261 os->add_output_section_data(posd);
2266 // We need to compute a checksum after we have completed the
2268 gold_assert(trailing_padding == 0);
2269 this->build_id_note_ = new Output_data_zero_fill(descsz, 4);
2270 os->add_output_section_data(this->build_id_note_);
2274 // If we have both .stabXX and .stabXXstr sections, then the sh_link
2275 // field of the former should point to the latter. I'm not sure who
2276 // started this, but the GNU linker does it, and some tools depend
2280 Layout::link_stabs_sections()
2282 if (!this->have_stabstr_section_)
2285 for (Section_list::iterator p = this->section_list_.begin();
2286 p != this->section_list_.end();
2289 if ((*p)->type() != elfcpp::SHT_STRTAB)
2292 const char* name = (*p)->name();
2293 if (strncmp(name, ".stab", 5) != 0)
2296 size_t len = strlen(name);
2297 if (strcmp(name + len - 3, "str") != 0)
2300 std::string stab_name(name, len - 3);
2301 Output_section* stab_sec;
2302 stab_sec = this->find_output_section(stab_name.c_str());
2303 if (stab_sec != NULL)
2304 stab_sec->set_link_section(*p);
2308 // Create .gnu_incremental_inputs and related sections needed
2309 // for the next run of incremental linking to check what has changed.
2312 Layout::create_incremental_info_sections(Symbol_table* symtab)
2314 Incremental_inputs* incr = this->incremental_inputs_;
2316 gold_assert(incr != NULL);
2318 // Create the .gnu_incremental_inputs, _symtab, and _relocs input sections.
2319 incr->create_data_sections(symtab);
2321 // Add the .gnu_incremental_inputs section.
2322 const char* incremental_inputs_name =
2323 this->namepool_.add(".gnu_incremental_inputs", false, NULL);
2324 Output_section* incremental_inputs_os =
2325 this->make_output_section(incremental_inputs_name,
2326 elfcpp::SHT_GNU_INCREMENTAL_INPUTS, 0,
2327 ORDER_INVALID, false);
2328 incremental_inputs_os->add_output_section_data(incr->inputs_section());
2330 // Add the .gnu_incremental_symtab section.
2331 const char* incremental_symtab_name =
2332 this->namepool_.add(".gnu_incremental_symtab", false, NULL);
2333 Output_section* incremental_symtab_os =
2334 this->make_output_section(incremental_symtab_name,
2335 elfcpp::SHT_GNU_INCREMENTAL_SYMTAB, 0,
2336 ORDER_INVALID, false);
2337 incremental_symtab_os->add_output_section_data(incr->symtab_section());
2338 incremental_symtab_os->set_entsize(4);
2340 // Add the .gnu_incremental_relocs section.
2341 const char* incremental_relocs_name =
2342 this->namepool_.add(".gnu_incremental_relocs", false, NULL);
2343 Output_section* incremental_relocs_os =
2344 this->make_output_section(incremental_relocs_name,
2345 elfcpp::SHT_GNU_INCREMENTAL_RELOCS, 0,
2346 ORDER_INVALID, false);
2347 incremental_relocs_os->add_output_section_data(incr->relocs_section());
2348 incremental_relocs_os->set_entsize(incr->relocs_entsize());
2350 // Add the .gnu_incremental_got_plt section.
2351 const char* incremental_got_plt_name =
2352 this->namepool_.add(".gnu_incremental_got_plt", false, NULL);
2353 Output_section* incremental_got_plt_os =
2354 this->make_output_section(incremental_got_plt_name,
2355 elfcpp::SHT_GNU_INCREMENTAL_GOT_PLT, 0,
2356 ORDER_INVALID, false);
2357 incremental_got_plt_os->add_output_section_data(incr->got_plt_section());
2359 // Add the .gnu_incremental_strtab section.
2360 const char* incremental_strtab_name =
2361 this->namepool_.add(".gnu_incremental_strtab", false, NULL);
2362 Output_section* incremental_strtab_os = this->make_output_section(incremental_strtab_name,
2363 elfcpp::SHT_STRTAB, 0,
2364 ORDER_INVALID, false);
2365 Output_data_strtab* strtab_data =
2366 new Output_data_strtab(incr->get_stringpool());
2367 incremental_strtab_os->add_output_section_data(strtab_data);
2369 incremental_inputs_os->set_after_input_sections();
2370 incremental_symtab_os->set_after_input_sections();
2371 incremental_relocs_os->set_after_input_sections();
2372 incremental_got_plt_os->set_after_input_sections();
2374 incremental_inputs_os->set_link_section(incremental_strtab_os);
2375 incremental_symtab_os->set_link_section(incremental_inputs_os);
2376 incremental_relocs_os->set_link_section(incremental_inputs_os);
2377 incremental_got_plt_os->set_link_section(incremental_inputs_os);
2380 // Return whether SEG1 should be before SEG2 in the output file. This
2381 // is based entirely on the segment type and flags. When this is
2382 // called the segment addresses has normally not yet been set.
2385 Layout::segment_precedes(const Output_segment* seg1,
2386 const Output_segment* seg2)
2388 elfcpp::Elf_Word type1 = seg1->type();
2389 elfcpp::Elf_Word type2 = seg2->type();
2391 // The single PT_PHDR segment is required to precede any loadable
2392 // segment. We simply make it always first.
2393 if (type1 == elfcpp::PT_PHDR)
2395 gold_assert(type2 != elfcpp::PT_PHDR);
2398 if (type2 == elfcpp::PT_PHDR)
2401 // The single PT_INTERP segment is required to precede any loadable
2402 // segment. We simply make it always second.
2403 if (type1 == elfcpp::PT_INTERP)
2405 gold_assert(type2 != elfcpp::PT_INTERP);
2408 if (type2 == elfcpp::PT_INTERP)
2411 // We then put PT_LOAD segments before any other segments.
2412 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
2414 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
2417 // We put the PT_TLS segment last except for the PT_GNU_RELRO
2418 // segment, because that is where the dynamic linker expects to find
2419 // it (this is just for efficiency; other positions would also work
2421 if (type1 == elfcpp::PT_TLS
2422 && type2 != elfcpp::PT_TLS
2423 && type2 != elfcpp::PT_GNU_RELRO)
2425 if (type2 == elfcpp::PT_TLS
2426 && type1 != elfcpp::PT_TLS
2427 && type1 != elfcpp::PT_GNU_RELRO)
2430 // We put the PT_GNU_RELRO segment last, because that is where the
2431 // dynamic linker expects to find it (as with PT_TLS, this is just
2433 if (type1 == elfcpp::PT_GNU_RELRO && type2 != elfcpp::PT_GNU_RELRO)
2435 if (type2 == elfcpp::PT_GNU_RELRO && type1 != elfcpp::PT_GNU_RELRO)
2438 const elfcpp::Elf_Word flags1 = seg1->flags();
2439 const elfcpp::Elf_Word flags2 = seg2->flags();
2441 // The order of non-PT_LOAD segments is unimportant. We simply sort
2442 // by the numeric segment type and flags values. There should not
2443 // be more than one segment with the same type and flags.
2444 if (type1 != elfcpp::PT_LOAD)
2447 return type1 < type2;
2448 gold_assert(flags1 != flags2);
2449 return flags1 < flags2;
2452 // If the addresses are set already, sort by load address.
2453 if (seg1->are_addresses_set())
2455 if (!seg2->are_addresses_set())
2458 unsigned int section_count1 = seg1->output_section_count();
2459 unsigned int section_count2 = seg2->output_section_count();
2460 if (section_count1 == 0 && section_count2 > 0)
2462 if (section_count1 > 0 && section_count2 == 0)
2465 uint64_t paddr1 = (seg1->are_addresses_set()
2467 : seg1->first_section_load_address());
2468 uint64_t paddr2 = (seg2->are_addresses_set()
2470 : seg2->first_section_load_address());
2472 if (paddr1 != paddr2)
2473 return paddr1 < paddr2;
2475 else if (seg2->are_addresses_set())
2478 // A segment which holds large data comes after a segment which does
2479 // not hold large data.
2480 if (seg1->is_large_data_segment())
2482 if (!seg2->is_large_data_segment())
2485 else if (seg2->is_large_data_segment())
2488 // Otherwise, we sort PT_LOAD segments based on the flags. Readonly
2489 // segments come before writable segments. Then writable segments
2490 // with data come before writable segments without data. Then
2491 // executable segments come before non-executable segments. Then
2492 // the unlikely case of a non-readable segment comes before the
2493 // normal case of a readable segment. If there are multiple
2494 // segments with the same type and flags, we require that the
2495 // address be set, and we sort by virtual address and then physical
2497 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
2498 return (flags1 & elfcpp::PF_W) == 0;
2499 if ((flags1 & elfcpp::PF_W) != 0
2500 && seg1->has_any_data_sections() != seg2->has_any_data_sections())
2501 return seg1->has_any_data_sections();
2502 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
2503 return (flags1 & elfcpp::PF_X) != 0;
2504 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
2505 return (flags1 & elfcpp::PF_R) == 0;
2507 // We shouldn't get here--we shouldn't create segments which we
2508 // can't distinguish.
2512 // Increase OFF so that it is congruent to ADDR modulo ABI_PAGESIZE.
2515 align_file_offset(off_t off, uint64_t addr, uint64_t abi_pagesize)
2517 uint64_t unsigned_off = off;
2518 uint64_t aligned_off = ((unsigned_off & ~(abi_pagesize - 1))
2519 | (addr & (abi_pagesize - 1)));
2520 if (aligned_off < unsigned_off)
2521 aligned_off += abi_pagesize;
2525 // Set the file offsets of all the segments, and all the sections they
2526 // contain. They have all been created. LOAD_SEG must be be laid out
2527 // first. Return the offset of the data to follow.
2530 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
2531 unsigned int* pshndx)
2533 // Sort them into the final order.
2534 std::sort(this->segment_list_.begin(), this->segment_list_.end(),
2535 Layout::Compare_segments());
2537 // Find the PT_LOAD segments, and set their addresses and offsets
2538 // and their section's addresses and offsets.
2540 if (parameters->options().user_set_Ttext())
2541 addr = parameters->options().Ttext();
2542 else if (parameters->options().output_is_position_independent())
2545 addr = target->default_text_segment_address();
2548 // If LOAD_SEG is NULL, then the file header and segment headers
2549 // will not be loadable. But they still need to be at offset 0 in
2550 // the file. Set their offsets now.
2551 if (load_seg == NULL)
2553 for (Data_list::iterator p = this->special_output_list_.begin();
2554 p != this->special_output_list_.end();
2557 off = align_address(off, (*p)->addralign());
2558 (*p)->set_address_and_file_offset(0, off);
2559 off += (*p)->data_size();
2563 unsigned int increase_relro = this->increase_relro_;
2564 if (this->script_options_->saw_sections_clause())
2567 const bool check_sections = parameters->options().check_sections();
2568 Output_segment* last_load_segment = NULL;
2570 for (Segment_list::iterator p = this->segment_list_.begin();
2571 p != this->segment_list_.end();
2574 if ((*p)->type() == elfcpp::PT_LOAD)
2576 if (load_seg != NULL && load_seg != *p)
2580 bool are_addresses_set = (*p)->are_addresses_set();
2581 if (are_addresses_set)
2583 // When it comes to setting file offsets, we care about
2584 // the physical address.
2585 addr = (*p)->paddr();
2587 else if (parameters->options().user_set_Tdata()
2588 && ((*p)->flags() & elfcpp::PF_W) != 0
2589 && (!parameters->options().user_set_Tbss()
2590 || (*p)->has_any_data_sections()))
2592 addr = parameters->options().Tdata();
2593 are_addresses_set = true;
2595 else if (parameters->options().user_set_Tbss()
2596 && ((*p)->flags() & elfcpp::PF_W) != 0
2597 && !(*p)->has_any_data_sections())
2599 addr = parameters->options().Tbss();
2600 are_addresses_set = true;
2603 uint64_t orig_addr = addr;
2604 uint64_t orig_off = off;
2606 uint64_t aligned_addr = 0;
2607 uint64_t abi_pagesize = target->abi_pagesize();
2608 uint64_t common_pagesize = target->common_pagesize();
2610 if (!parameters->options().nmagic()
2611 && !parameters->options().omagic())
2612 (*p)->set_minimum_p_align(common_pagesize);
2614 if (!are_addresses_set)
2616 // Skip the address forward one page, maintaining the same
2617 // position within the page. This lets us store both segments
2618 // overlapping on a single page in the file, but the loader will
2619 // put them on different pages in memory. We will revisit this
2620 // decision once we know the size of the segment.
2622 addr = align_address(addr, (*p)->maximum_alignment());
2623 aligned_addr = addr;
2625 if ((addr & (abi_pagesize - 1)) != 0)
2626 addr = addr + abi_pagesize;
2628 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
2631 if (!parameters->options().nmagic()
2632 && !parameters->options().omagic())
2633 off = align_file_offset(off, addr, abi_pagesize);
2634 else if (load_seg == NULL)
2636 // This is -N or -n with a section script which prevents
2637 // us from using a load segment. We need to ensure that
2638 // the file offset is aligned to the alignment of the
2639 // segment. This is because the linker script
2640 // implicitly assumed a zero offset. If we don't align
2641 // here, then the alignment of the sections in the
2642 // linker script may not match the alignment of the
2643 // sections in the set_section_addresses call below,
2644 // causing an error about dot moving backward.
2645 off = align_address(off, (*p)->maximum_alignment());
2648 unsigned int shndx_hold = *pshndx;
2649 uint64_t new_addr = (*p)->set_section_addresses(this, false, addr,
2653 // Now that we know the size of this segment, we may be able
2654 // to save a page in memory, at the cost of wasting some
2655 // file space, by instead aligning to the start of a new
2656 // page. Here we use the real machine page size rather than
2657 // the ABI mandated page size.
2659 if (!are_addresses_set && aligned_addr != addr)
2661 uint64_t first_off = (common_pagesize
2663 & (common_pagesize - 1)));
2664 uint64_t last_off = new_addr & (common_pagesize - 1);
2667 && ((aligned_addr & ~ (common_pagesize - 1))
2668 != (new_addr & ~ (common_pagesize - 1)))
2669 && first_off + last_off <= common_pagesize)
2671 *pshndx = shndx_hold;
2672 addr = align_address(aligned_addr, common_pagesize);
2673 addr = align_address(addr, (*p)->maximum_alignment());
2674 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
2675 off = align_file_offset(off, addr, abi_pagesize);
2676 new_addr = (*p)->set_section_addresses(this, true, addr,
2684 // Implement --check-sections. We know that the segments
2685 // are sorted by LMA.
2686 if (check_sections && last_load_segment != NULL)
2688 gold_assert(last_load_segment->paddr() <= (*p)->paddr());
2689 if (last_load_segment->paddr() + last_load_segment->memsz()
2692 unsigned long long lb1 = last_load_segment->paddr();
2693 unsigned long long le1 = lb1 + last_load_segment->memsz();
2694 unsigned long long lb2 = (*p)->paddr();
2695 unsigned long long le2 = lb2 + (*p)->memsz();
2696 gold_error(_("load segment overlap [0x%llx -> 0x%llx] and "
2697 "[0x%llx -> 0x%llx]"),
2698 lb1, le1, lb2, le2);
2701 last_load_segment = *p;
2705 // Handle the non-PT_LOAD segments, setting their offsets from their
2706 // section's offsets.
2707 for (Segment_list::iterator p = this->segment_list_.begin();
2708 p != this->segment_list_.end();
2711 if ((*p)->type() != elfcpp::PT_LOAD)
2712 (*p)->set_offset((*p)->type() == elfcpp::PT_GNU_RELRO
2717 // Set the TLS offsets for each section in the PT_TLS segment.
2718 if (this->tls_segment_ != NULL)
2719 this->tls_segment_->set_tls_offsets();
2724 // Set the offsets of all the allocated sections when doing a
2725 // relocatable link. This does the same jobs as set_segment_offsets,
2726 // only for a relocatable link.
2729 Layout::set_relocatable_section_offsets(Output_data* file_header,
2730 unsigned int* pshndx)
2734 file_header->set_address_and_file_offset(0, 0);
2735 off += file_header->data_size();
2737 for (Section_list::iterator p = this->section_list_.begin();
2738 p != this->section_list_.end();
2741 // We skip unallocated sections here, except that group sections
2742 // have to come first.
2743 if (((*p)->flags() & elfcpp::SHF_ALLOC) == 0
2744 && (*p)->type() != elfcpp::SHT_GROUP)
2747 off = align_address(off, (*p)->addralign());
2749 // The linker script might have set the address.
2750 if (!(*p)->is_address_valid())
2751 (*p)->set_address(0);
2752 (*p)->set_file_offset(off);
2753 (*p)->finalize_data_size();
2754 off += (*p)->data_size();
2756 (*p)->set_out_shndx(*pshndx);
2763 // Set the file offset of all the sections not associated with a
2767 Layout::set_section_offsets(off_t off, Layout::Section_offset_pass pass)
2769 for (Section_list::iterator p = this->unattached_section_list_.begin();
2770 p != this->unattached_section_list_.end();
2773 // The symtab section is handled in create_symtab_sections.
2774 if (*p == this->symtab_section_)
2777 // If we've already set the data size, don't set it again.
2778 if ((*p)->is_offset_valid() && (*p)->is_data_size_valid())
2781 if (pass == BEFORE_INPUT_SECTIONS_PASS
2782 && (*p)->requires_postprocessing())
2784 (*p)->create_postprocessing_buffer();
2785 this->any_postprocessing_sections_ = true;
2788 if (pass == BEFORE_INPUT_SECTIONS_PASS
2789 && (*p)->after_input_sections())
2791 else if (pass == POSTPROCESSING_SECTIONS_PASS
2792 && (!(*p)->after_input_sections()
2793 || (*p)->type() == elfcpp::SHT_STRTAB))
2795 else if (pass == STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
2796 && (!(*p)->after_input_sections()
2797 || (*p)->type() != elfcpp::SHT_STRTAB))
2800 off = align_address(off, (*p)->addralign());
2801 (*p)->set_file_offset(off);
2802 (*p)->finalize_data_size();
2803 off += (*p)->data_size();
2805 // At this point the name must be set.
2806 if (pass != STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS)
2807 this->namepool_.add((*p)->name(), false, NULL);
2812 // Set the section indexes of all the sections not associated with a
2816 Layout::set_section_indexes(unsigned int shndx)
2818 for (Section_list::iterator p = this->unattached_section_list_.begin();
2819 p != this->unattached_section_list_.end();
2822 if (!(*p)->has_out_shndx())
2824 (*p)->set_out_shndx(shndx);
2831 // Set the section addresses according to the linker script. This is
2832 // only called when we see a SECTIONS clause. This returns the
2833 // program segment which should hold the file header and segment
2834 // headers, if any. It will return NULL if they should not be in a
2838 Layout::set_section_addresses_from_script(Symbol_table* symtab)
2840 Script_sections* ss = this->script_options_->script_sections();
2841 gold_assert(ss->saw_sections_clause());
2842 return this->script_options_->set_section_addresses(symtab, this);
2845 // Place the orphan sections in the linker script.
2848 Layout::place_orphan_sections_in_script()
2850 Script_sections* ss = this->script_options_->script_sections();
2851 gold_assert(ss->saw_sections_clause());
2853 // Place each orphaned output section in the script.
2854 for (Section_list::iterator p = this->section_list_.begin();
2855 p != this->section_list_.end();
2858 if (!(*p)->found_in_sections_clause())
2859 ss->place_orphan(*p);
2863 // Count the local symbols in the regular symbol table and the dynamic
2864 // symbol table, and build the respective string pools.
2867 Layout::count_local_symbols(const Task* task,
2868 const Input_objects* input_objects)
2870 // First, figure out an upper bound on the number of symbols we'll
2871 // be inserting into each pool. This helps us create the pools with
2872 // the right size, to avoid unnecessary hashtable resizing.
2873 unsigned int symbol_count = 0;
2874 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
2875 p != input_objects->relobj_end();
2877 symbol_count += (*p)->local_symbol_count();
2879 // Go from "upper bound" to "estimate." We overcount for two
2880 // reasons: we double-count symbols that occur in more than one
2881 // object file, and we count symbols that are dropped from the
2882 // output. Add it all together and assume we overcount by 100%.
2885 // We assume all symbols will go into both the sympool and dynpool.
2886 this->sympool_.reserve(symbol_count);
2887 this->dynpool_.reserve(symbol_count);
2889 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
2890 p != input_objects->relobj_end();
2893 Task_lock_obj<Object> tlo(task, *p);
2894 (*p)->count_local_symbols(&this->sympool_, &this->dynpool_);
2898 // Create the symbol table sections. Here we also set the final
2899 // values of the symbols. At this point all the loadable sections are
2900 // fully laid out. SHNUM is the number of sections so far.
2903 Layout::create_symtab_sections(const Input_objects* input_objects,
2904 Symbol_table* symtab,
2910 if (parameters->target().get_size() == 32)
2912 symsize = elfcpp::Elf_sizes<32>::sym_size;
2915 else if (parameters->target().get_size() == 64)
2917 symsize = elfcpp::Elf_sizes<64>::sym_size;
2924 off = align_address(off, align);
2925 off_t startoff = off;
2927 // Save space for the dummy symbol at the start of the section. We
2928 // never bother to write this out--it will just be left as zero.
2930 unsigned int local_symbol_index = 1;
2932 // Add STT_SECTION symbols for each Output section which needs one.
2933 for (Section_list::iterator p = this->section_list_.begin();
2934 p != this->section_list_.end();
2937 if (!(*p)->needs_symtab_index())
2938 (*p)->set_symtab_index(-1U);
2941 (*p)->set_symtab_index(local_symbol_index);
2942 ++local_symbol_index;
2947 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
2948 p != input_objects->relobj_end();
2951 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
2953 off += (index - local_symbol_index) * symsize;
2954 local_symbol_index = index;
2957 unsigned int local_symcount = local_symbol_index;
2958 gold_assert(static_cast<off_t>(local_symcount * symsize) == off - startoff);
2961 size_t dyn_global_index;
2963 if (this->dynsym_section_ == NULL)
2966 dyn_global_index = 0;
2971 dyn_global_index = this->dynsym_section_->info();
2972 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
2973 dynoff = this->dynsym_section_->offset() + locsize;
2974 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
2975 gold_assert(static_cast<off_t>(dyncount * symsize)
2976 == this->dynsym_section_->data_size() - locsize);
2979 off = symtab->finalize(off, dynoff, dyn_global_index, dyncount,
2980 &this->sympool_, &local_symcount);
2982 if (!parameters->options().strip_all())
2984 this->sympool_.set_string_offsets();
2986 const char* symtab_name = this->namepool_.add(".symtab", false, NULL);
2987 Output_section* osymtab = this->make_output_section(symtab_name,
2991 this->symtab_section_ = osymtab;
2993 Output_section_data* pos = new Output_data_fixed_space(off - startoff,
2996 osymtab->add_output_section_data(pos);
2998 // We generate a .symtab_shndx section if we have more than
2999 // SHN_LORESERVE sections. Technically it is possible that we
3000 // don't need one, because it is possible that there are no
3001 // symbols in any of sections with indexes larger than
3002 // SHN_LORESERVE. That is probably unusual, though, and it is
3003 // easier to always create one than to compute section indexes
3004 // twice (once here, once when writing out the symbols).
3005 if (shnum >= elfcpp::SHN_LORESERVE)
3007 const char* symtab_xindex_name = this->namepool_.add(".symtab_shndx",
3009 Output_section* osymtab_xindex =
3010 this->make_output_section(symtab_xindex_name,
3011 elfcpp::SHT_SYMTAB_SHNDX, 0,
3012 ORDER_INVALID, false);
3014 size_t symcount = (off - startoff) / symsize;
3015 this->symtab_xindex_ = new Output_symtab_xindex(symcount);
3017 osymtab_xindex->add_output_section_data(this->symtab_xindex_);
3019 osymtab_xindex->set_link_section(osymtab);
3020 osymtab_xindex->set_addralign(4);
3021 osymtab_xindex->set_entsize(4);
3023 osymtab_xindex->set_after_input_sections();
3025 // This tells the driver code to wait until the symbol table
3026 // has written out before writing out the postprocessing
3027 // sections, including the .symtab_shndx section.
3028 this->any_postprocessing_sections_ = true;
3031 const char* strtab_name = this->namepool_.add(".strtab", false, NULL);
3032 Output_section* ostrtab = this->make_output_section(strtab_name,
3037 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
3038 ostrtab->add_output_section_data(pstr);
3040 osymtab->set_file_offset(startoff);
3041 osymtab->finalize_data_size();
3042 osymtab->set_link_section(ostrtab);
3043 osymtab->set_info(local_symcount);
3044 osymtab->set_entsize(symsize);
3050 // Create the .shstrtab section, which holds the names of the
3051 // sections. At the time this is called, we have created all the
3052 // output sections except .shstrtab itself.
3055 Layout::create_shstrtab()
3057 // FIXME: We don't need to create a .shstrtab section if we are
3058 // stripping everything.
3060 const char* name = this->namepool_.add(".shstrtab", false, NULL);
3062 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0,
3063 ORDER_INVALID, false);
3065 if (strcmp(parameters->options().compress_debug_sections(), "none") != 0)
3067 // We can't write out this section until we've set all the
3068 // section names, and we don't set the names of compressed
3069 // output sections until relocations are complete. FIXME: With
3070 // the current names we use, this is unnecessary.
3071 os->set_after_input_sections();
3074 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
3075 os->add_output_section_data(posd);
3080 // Create the section headers. SIZE is 32 or 64. OFF is the file
3084 Layout::create_shdrs(const Output_section* shstrtab_section, off_t* poff)
3086 Output_section_headers* oshdrs;
3087 oshdrs = new Output_section_headers(this,
3088 &this->segment_list_,
3089 &this->section_list_,
3090 &this->unattached_section_list_,
3093 off_t off = align_address(*poff, oshdrs->addralign());
3094 oshdrs->set_address_and_file_offset(0, off);
3095 off += oshdrs->data_size();
3097 this->section_headers_ = oshdrs;
3100 // Count the allocated sections.
3103 Layout::allocated_output_section_count() const
3105 size_t section_count = 0;
3106 for (Segment_list::const_iterator p = this->segment_list_.begin();
3107 p != this->segment_list_.end();
3109 section_count += (*p)->output_section_count();
3110 return section_count;
3113 // Create the dynamic symbol table.
3116 Layout::create_dynamic_symtab(const Input_objects* input_objects,
3117 Symbol_table* symtab,
3118 Output_section** pdynstr,
3119 unsigned int* plocal_dynamic_count,
3120 std::vector<Symbol*>* pdynamic_symbols,
3121 Versions* pversions)
3123 // Count all the symbols in the dynamic symbol table, and set the
3124 // dynamic symbol indexes.
3126 // Skip symbol 0, which is always all zeroes.
3127 unsigned int index = 1;
3129 // Add STT_SECTION symbols for each Output section which needs one.
3130 for (Section_list::iterator p = this->section_list_.begin();
3131 p != this->section_list_.end();
3134 if (!(*p)->needs_dynsym_index())
3135 (*p)->set_dynsym_index(-1U);
3138 (*p)->set_dynsym_index(index);
3143 // Count the local symbols that need to go in the dynamic symbol table,
3144 // and set the dynamic symbol indexes.
3145 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3146 p != input_objects->relobj_end();
3149 unsigned int new_index = (*p)->set_local_dynsym_indexes(index);
3153 unsigned int local_symcount = index;
3154 *plocal_dynamic_count = local_symcount;
3156 index = symtab->set_dynsym_indexes(index, pdynamic_symbols,
3157 &this->dynpool_, pversions);
3161 const int size = parameters->target().get_size();
3164 symsize = elfcpp::Elf_sizes<32>::sym_size;
3167 else if (size == 64)
3169 symsize = elfcpp::Elf_sizes<64>::sym_size;
3175 // Create the dynamic symbol table section.
3177 Output_section* dynsym = this->choose_output_section(NULL, ".dynsym",
3181 ORDER_DYNAMIC_LINKER,
3184 Output_section_data* odata = new Output_data_fixed_space(index * symsize,
3187 dynsym->add_output_section_data(odata);
3189 dynsym->set_info(local_symcount);
3190 dynsym->set_entsize(symsize);
3191 dynsym->set_addralign(align);
3193 this->dynsym_section_ = dynsym;
3195 Output_data_dynamic* const odyn = this->dynamic_data_;
3196 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
3197 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
3199 // If there are more than SHN_LORESERVE allocated sections, we
3200 // create a .dynsym_shndx section. It is possible that we don't
3201 // need one, because it is possible that there are no dynamic
3202 // symbols in any of the sections with indexes larger than
3203 // SHN_LORESERVE. This is probably unusual, though, and at this
3204 // time we don't know the actual section indexes so it is
3205 // inconvenient to check.
3206 if (this->allocated_output_section_count() >= elfcpp::SHN_LORESERVE)
3208 Output_section* dynsym_xindex =
3209 this->choose_output_section(NULL, ".dynsym_shndx",
3210 elfcpp::SHT_SYMTAB_SHNDX,
3212 false, ORDER_DYNAMIC_LINKER, false);
3214 this->dynsym_xindex_ = new Output_symtab_xindex(index);
3216 dynsym_xindex->add_output_section_data(this->dynsym_xindex_);
3218 dynsym_xindex->set_link_section(dynsym);
3219 dynsym_xindex->set_addralign(4);
3220 dynsym_xindex->set_entsize(4);
3222 dynsym_xindex->set_after_input_sections();
3224 // This tells the driver code to wait until the symbol table has
3225 // written out before writing out the postprocessing sections,
3226 // including the .dynsym_shndx section.
3227 this->any_postprocessing_sections_ = true;
3230 // Create the dynamic string table section.
3232 Output_section* dynstr = this->choose_output_section(NULL, ".dynstr",
3236 ORDER_DYNAMIC_LINKER,
3239 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
3240 dynstr->add_output_section_data(strdata);
3242 dynsym->set_link_section(dynstr);
3243 this->dynamic_section_->set_link_section(dynstr);
3245 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
3246 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
3250 // Create the hash tables.
3252 if (strcmp(parameters->options().hash_style(), "sysv") == 0
3253 || strcmp(parameters->options().hash_style(), "both") == 0)
3255 unsigned char* phash;
3256 unsigned int hashlen;
3257 Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
3260 Output_section* hashsec =
3261 this->choose_output_section(NULL, ".hash", elfcpp::SHT_HASH,
3262 elfcpp::SHF_ALLOC, false,
3263 ORDER_DYNAMIC_LINKER, false);
3265 Output_section_data* hashdata = new Output_data_const_buffer(phash,
3269 hashsec->add_output_section_data(hashdata);
3271 hashsec->set_link_section(dynsym);
3272 hashsec->set_entsize(4);
3274 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
3277 if (strcmp(parameters->options().hash_style(), "gnu") == 0
3278 || strcmp(parameters->options().hash_style(), "both") == 0)
3280 unsigned char* phash;
3281 unsigned int hashlen;
3282 Dynobj::create_gnu_hash_table(*pdynamic_symbols, local_symcount,
3285 Output_section* hashsec =
3286 this->choose_output_section(NULL, ".gnu.hash", elfcpp::SHT_GNU_HASH,
3287 elfcpp::SHF_ALLOC, false,
3288 ORDER_DYNAMIC_LINKER, false);
3290 Output_section_data* hashdata = new Output_data_const_buffer(phash,
3294 hashsec->add_output_section_data(hashdata);
3296 hashsec->set_link_section(dynsym);
3298 // For a 64-bit target, the entries in .gnu.hash do not have a
3299 // uniform size, so we only set the entry size for a 32-bit
3301 if (parameters->target().get_size() == 32)
3302 hashsec->set_entsize(4);
3304 odyn->add_section_address(elfcpp::DT_GNU_HASH, hashsec);
3308 // Assign offsets to each local portion of the dynamic symbol table.
3311 Layout::assign_local_dynsym_offsets(const Input_objects* input_objects)
3313 Output_section* dynsym = this->dynsym_section_;
3314 gold_assert(dynsym != NULL);
3316 off_t off = dynsym->offset();
3318 // Skip the dummy symbol at the start of the section.
3319 off += dynsym->entsize();
3321 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3322 p != input_objects->relobj_end();
3325 unsigned int count = (*p)->set_local_dynsym_offset(off);
3326 off += count * dynsym->entsize();
3330 // Create the version sections.
3333 Layout::create_version_sections(const Versions* versions,
3334 const Symbol_table* symtab,
3335 unsigned int local_symcount,
3336 const std::vector<Symbol*>& dynamic_symbols,
3337 const Output_section* dynstr)
3339 if (!versions->any_defs() && !versions->any_needs())
3342 switch (parameters->size_and_endianness())
3344 #ifdef HAVE_TARGET_32_LITTLE
3345 case Parameters::TARGET_32_LITTLE:
3346 this->sized_create_version_sections<32, false>(versions, symtab,
3348 dynamic_symbols, dynstr);
3351 #ifdef HAVE_TARGET_32_BIG
3352 case Parameters::TARGET_32_BIG:
3353 this->sized_create_version_sections<32, true>(versions, symtab,
3355 dynamic_symbols, dynstr);
3358 #ifdef HAVE_TARGET_64_LITTLE
3359 case Parameters::TARGET_64_LITTLE:
3360 this->sized_create_version_sections<64, false>(versions, symtab,
3362 dynamic_symbols, dynstr);
3365 #ifdef HAVE_TARGET_64_BIG
3366 case Parameters::TARGET_64_BIG:
3367 this->sized_create_version_sections<64, true>(versions, symtab,
3369 dynamic_symbols, dynstr);
3377 // Create the version sections, sized version.
3379 template<int size, bool big_endian>
3381 Layout::sized_create_version_sections(
3382 const Versions* versions,
3383 const Symbol_table* symtab,
3384 unsigned int local_symcount,
3385 const std::vector<Symbol*>& dynamic_symbols,
3386 const Output_section* dynstr)
3388 Output_section* vsec = this->choose_output_section(NULL, ".gnu.version",
3389 elfcpp::SHT_GNU_versym,
3392 ORDER_DYNAMIC_LINKER,
3395 unsigned char* vbuf;
3397 versions->symbol_section_contents<size, big_endian>(symtab, &this->dynpool_,
3402 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2,
3405 vsec->add_output_section_data(vdata);
3406 vsec->set_entsize(2);
3407 vsec->set_link_section(this->dynsym_section_);
3409 Output_data_dynamic* const odyn = this->dynamic_data_;
3410 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
3412 if (versions->any_defs())
3414 Output_section* vdsec;
3415 vdsec= this->choose_output_section(NULL, ".gnu.version_d",
3416 elfcpp::SHT_GNU_verdef,
3418 false, ORDER_DYNAMIC_LINKER, false);
3420 unsigned char* vdbuf;
3421 unsigned int vdsize;
3422 unsigned int vdentries;
3423 versions->def_section_contents<size, big_endian>(&this->dynpool_, &vdbuf,
3424 &vdsize, &vdentries);
3426 Output_section_data* vddata =
3427 new Output_data_const_buffer(vdbuf, vdsize, 4, "** version defs");
3429 vdsec->add_output_section_data(vddata);
3430 vdsec->set_link_section(dynstr);
3431 vdsec->set_info(vdentries);
3433 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
3434 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
3437 if (versions->any_needs())
3439 Output_section* vnsec;
3440 vnsec = this->choose_output_section(NULL, ".gnu.version_r",
3441 elfcpp::SHT_GNU_verneed,
3443 false, ORDER_DYNAMIC_LINKER, false);
3445 unsigned char* vnbuf;
3446 unsigned int vnsize;
3447 unsigned int vnentries;
3448 versions->need_section_contents<size, big_endian>(&this->dynpool_,
3452 Output_section_data* vndata =
3453 new Output_data_const_buffer(vnbuf, vnsize, 4, "** version refs");
3455 vnsec->add_output_section_data(vndata);
3456 vnsec->set_link_section(dynstr);
3457 vnsec->set_info(vnentries);
3459 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
3460 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
3464 // Create the .interp section and PT_INTERP segment.
3467 Layout::create_interp(const Target* target)
3469 const char* interp = parameters->options().dynamic_linker();
3472 interp = target->dynamic_linker();
3473 gold_assert(interp != NULL);
3476 size_t len = strlen(interp) + 1;
3478 Output_section_data* odata = new Output_data_const(interp, len, 1);
3480 Output_section* osec = this->choose_output_section(NULL, ".interp",
3481 elfcpp::SHT_PROGBITS,
3483 false, ORDER_INTERP,
3485 osec->add_output_section_data(odata);
3487 if (!this->script_options_->saw_phdrs_clause())
3489 Output_segment* oseg = this->make_output_segment(elfcpp::PT_INTERP,
3491 oseg->add_output_section_to_nonload(osec, elfcpp::PF_R);
3495 // Add dynamic tags for the PLT and the dynamic relocs. This is
3496 // called by the target-specific code. This does nothing if not doing
3499 // USE_REL is true for REL relocs rather than RELA relocs.
3501 // If PLT_GOT is not NULL, then DT_PLTGOT points to it.
3503 // If PLT_REL is not NULL, it is used for DT_PLTRELSZ, and DT_JMPREL,
3504 // and we also set DT_PLTREL. We use PLT_REL's output section, since
3505 // some targets have multiple reloc sections in PLT_REL.
3507 // If DYN_REL is not NULL, it is used for DT_REL/DT_RELA,
3508 // DT_RELSZ/DT_RELASZ, DT_RELENT/DT_RELAENT.
3510 // If ADD_DEBUG is true, we add a DT_DEBUG entry when generating an
3514 Layout::add_target_dynamic_tags(bool use_rel, const Output_data* plt_got,
3515 const Output_data* plt_rel,
3516 const Output_data_reloc_generic* dyn_rel,
3517 bool add_debug, bool dynrel_includes_plt)
3519 Output_data_dynamic* odyn = this->dynamic_data_;
3523 if (plt_got != NULL && plt_got->output_section() != NULL)
3524 odyn->add_section_address(elfcpp::DT_PLTGOT, plt_got);
3526 if (plt_rel != NULL && plt_rel->output_section() != NULL)
3528 odyn->add_section_size(elfcpp::DT_PLTRELSZ, plt_rel->output_section());
3529 odyn->add_section_address(elfcpp::DT_JMPREL, plt_rel->output_section());
3530 odyn->add_constant(elfcpp::DT_PLTREL,
3531 use_rel ? elfcpp::DT_REL : elfcpp::DT_RELA);
3534 if (dyn_rel != NULL && dyn_rel->output_section() != NULL)
3536 odyn->add_section_address(use_rel ? elfcpp::DT_REL : elfcpp::DT_RELA,
3538 if (plt_rel != NULL && dynrel_includes_plt)
3539 odyn->add_section_size(use_rel ? elfcpp::DT_RELSZ : elfcpp::DT_RELASZ,
3542 odyn->add_section_size(use_rel ? elfcpp::DT_RELSZ : elfcpp::DT_RELASZ,
3544 const int size = parameters->target().get_size();
3549 rel_tag = elfcpp::DT_RELENT;
3551 rel_size = Reloc_types<elfcpp::SHT_REL, 32, false>::reloc_size;
3552 else if (size == 64)
3553 rel_size = Reloc_types<elfcpp::SHT_REL, 64, false>::reloc_size;
3559 rel_tag = elfcpp::DT_RELAENT;
3561 rel_size = Reloc_types<elfcpp::SHT_RELA, 32, false>::reloc_size;
3562 else if (size == 64)
3563 rel_size = Reloc_types<elfcpp::SHT_RELA, 64, false>::reloc_size;
3567 odyn->add_constant(rel_tag, rel_size);
3569 if (parameters->options().combreloc())
3571 size_t c = dyn_rel->relative_reloc_count();
3573 odyn->add_constant((use_rel
3574 ? elfcpp::DT_RELCOUNT
3575 : elfcpp::DT_RELACOUNT),
3580 if (add_debug && !parameters->options().shared())
3582 // The value of the DT_DEBUG tag is filled in by the dynamic
3583 // linker at run time, and used by the debugger.
3584 odyn->add_constant(elfcpp::DT_DEBUG, 0);
3588 // Finish the .dynamic section and PT_DYNAMIC segment.
3591 Layout::finish_dynamic_section(const Input_objects* input_objects,
3592 const Symbol_table* symtab)
3594 if (!this->script_options_->saw_phdrs_clause())
3596 Output_segment* oseg = this->make_output_segment(elfcpp::PT_DYNAMIC,
3599 oseg->add_output_section_to_nonload(this->dynamic_section_,
3600 elfcpp::PF_R | elfcpp::PF_W);
3603 Output_data_dynamic* const odyn = this->dynamic_data_;
3605 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
3606 p != input_objects->dynobj_end();
3609 if (!(*p)->is_needed()
3610 && (*p)->input_file()->options().as_needed())
3612 // This dynamic object was linked with --as-needed, but it
3617 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
3620 if (parameters->options().shared())
3622 const char* soname = parameters->options().soname();
3624 odyn->add_string(elfcpp::DT_SONAME, soname);
3627 Symbol* sym = symtab->lookup(parameters->options().init());
3628 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
3629 odyn->add_symbol(elfcpp::DT_INIT, sym);
3631 sym = symtab->lookup(parameters->options().fini());
3632 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
3633 odyn->add_symbol(elfcpp::DT_FINI, sym);
3635 // Look for .init_array, .preinit_array and .fini_array by checking
3637 for(Layout::Section_list::const_iterator p = this->section_list_.begin();
3638 p != this->section_list_.end();
3640 switch((*p)->type())
3642 case elfcpp::SHT_FINI_ARRAY:
3643 odyn->add_section_address(elfcpp::DT_FINI_ARRAY, *p);
3644 odyn->add_section_size(elfcpp::DT_FINI_ARRAYSZ, *p);
3646 case elfcpp::SHT_INIT_ARRAY:
3647 odyn->add_section_address(elfcpp::DT_INIT_ARRAY, *p);
3648 odyn->add_section_size(elfcpp::DT_INIT_ARRAYSZ, *p);
3650 case elfcpp::SHT_PREINIT_ARRAY:
3651 odyn->add_section_address(elfcpp::DT_PREINIT_ARRAY, *p);
3652 odyn->add_section_size(elfcpp::DT_PREINIT_ARRAYSZ, *p);
3658 // Add a DT_RPATH entry if needed.
3659 const General_options::Dir_list& rpath(parameters->options().rpath());
3662 std::string rpath_val;
3663 for (General_options::Dir_list::const_iterator p = rpath.begin();
3667 if (rpath_val.empty())
3668 rpath_val = p->name();
3671 // Eliminate duplicates.
3672 General_options::Dir_list::const_iterator q;
3673 for (q = rpath.begin(); q != p; ++q)
3674 if (q->name() == p->name())
3679 rpath_val += p->name();
3684 odyn->add_string(elfcpp::DT_RPATH, rpath_val);
3685 if (parameters->options().enable_new_dtags())
3686 odyn->add_string(elfcpp::DT_RUNPATH, rpath_val);
3689 // Look for text segments that have dynamic relocations.
3690 bool have_textrel = false;
3691 if (!this->script_options_->saw_sections_clause())
3693 for (Segment_list::const_iterator p = this->segment_list_.begin();
3694 p != this->segment_list_.end();
3697 if (((*p)->flags() & elfcpp::PF_W) == 0
3698 && (*p)->has_dynamic_reloc())
3700 have_textrel = true;
3707 // We don't know the section -> segment mapping, so we are
3708 // conservative and just look for readonly sections with
3709 // relocations. If those sections wind up in writable segments,
3710 // then we have created an unnecessary DT_TEXTREL entry.
3711 for (Section_list::const_iterator p = this->section_list_.begin();
3712 p != this->section_list_.end();
3715 if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0
3716 && ((*p)->flags() & elfcpp::SHF_WRITE) == 0
3717 && ((*p)->has_dynamic_reloc()))
3719 have_textrel = true;
3725 // Add a DT_FLAGS entry. We add it even if no flags are set so that
3726 // post-link tools can easily modify these flags if desired.
3727 unsigned int flags = 0;
3730 // Add a DT_TEXTREL for compatibility with older loaders.
3731 odyn->add_constant(elfcpp::DT_TEXTREL, 0);
3732 flags |= elfcpp::DF_TEXTREL;
3734 if (parameters->options().text())
3735 gold_error(_("read-only segment has dynamic relocations"));
3736 else if (parameters->options().warn_shared_textrel()
3737 && parameters->options().shared())
3738 gold_warning(_("shared library text segment is not shareable"));
3740 if (parameters->options().shared() && this->has_static_tls())
3741 flags |= elfcpp::DF_STATIC_TLS;
3742 if (parameters->options().origin())
3743 flags |= elfcpp::DF_ORIGIN;
3744 if (parameters->options().Bsymbolic())
3746 flags |= elfcpp::DF_SYMBOLIC;
3747 // Add DT_SYMBOLIC for compatibility with older loaders.
3748 odyn->add_constant(elfcpp::DT_SYMBOLIC, 0);
3750 if (parameters->options().now())
3751 flags |= elfcpp::DF_BIND_NOW;
3752 odyn->add_constant(elfcpp::DT_FLAGS, flags);
3755 if (parameters->options().initfirst())
3756 flags |= elfcpp::DF_1_INITFIRST;
3757 if (parameters->options().interpose())
3758 flags |= elfcpp::DF_1_INTERPOSE;
3759 if (parameters->options().loadfltr())
3760 flags |= elfcpp::DF_1_LOADFLTR;
3761 if (parameters->options().nodefaultlib())
3762 flags |= elfcpp::DF_1_NODEFLIB;
3763 if (parameters->options().nodelete())
3764 flags |= elfcpp::DF_1_NODELETE;
3765 if (parameters->options().nodlopen())
3766 flags |= elfcpp::DF_1_NOOPEN;
3767 if (parameters->options().nodump())
3768 flags |= elfcpp::DF_1_NODUMP;
3769 if (!parameters->options().shared())
3770 flags &= ~(elfcpp::DF_1_INITFIRST
3771 | elfcpp::DF_1_NODELETE
3772 | elfcpp::DF_1_NOOPEN);
3773 if (parameters->options().origin())
3774 flags |= elfcpp::DF_1_ORIGIN;
3775 if (parameters->options().now())
3776 flags |= elfcpp::DF_1_NOW;
3778 odyn->add_constant(elfcpp::DT_FLAGS_1, flags);
3781 // Set the size of the _DYNAMIC symbol table to be the size of the
3785 Layout::set_dynamic_symbol_size(const Symbol_table* symtab)
3787 Output_data_dynamic* const odyn = this->dynamic_data_;
3788 odyn->finalize_data_size();
3789 off_t data_size = odyn->data_size();
3790 const int size = parameters->target().get_size();
3792 symtab->get_sized_symbol<32>(this->dynamic_symbol_)->set_symsize(data_size);
3793 else if (size == 64)
3794 symtab->get_sized_symbol<64>(this->dynamic_symbol_)->set_symsize(data_size);
3799 // The mapping of input section name prefixes to output section names.
3800 // In some cases one prefix is itself a prefix of another prefix; in
3801 // such a case the longer prefix must come first. These prefixes are
3802 // based on the GNU linker default ELF linker script.
3804 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
3805 const Layout::Section_name_mapping Layout::section_name_mapping[] =
3807 MAPPING_INIT(".text.", ".text"),
3808 MAPPING_INIT(".ctors.", ".ctors"),
3809 MAPPING_INIT(".dtors.", ".dtors"),
3810 MAPPING_INIT(".rodata.", ".rodata"),
3811 MAPPING_INIT(".data.rel.ro.local", ".data.rel.ro.local"),
3812 MAPPING_INIT(".data.rel.ro", ".data.rel.ro"),
3813 MAPPING_INIT(".data.", ".data"),
3814 MAPPING_INIT(".bss.", ".bss"),
3815 MAPPING_INIT(".tdata.", ".tdata"),
3816 MAPPING_INIT(".tbss.", ".tbss"),
3817 MAPPING_INIT(".init_array.", ".init_array"),
3818 MAPPING_INIT(".fini_array.", ".fini_array"),
3819 MAPPING_INIT(".sdata.", ".sdata"),
3820 MAPPING_INIT(".sbss.", ".sbss"),
3821 // FIXME: In the GNU linker, .sbss2 and .sdata2 are handled
3822 // differently depending on whether it is creating a shared library.
3823 MAPPING_INIT(".sdata2.", ".sdata"),
3824 MAPPING_INIT(".sbss2.", ".sbss"),
3825 MAPPING_INIT(".lrodata.", ".lrodata"),
3826 MAPPING_INIT(".ldata.", ".ldata"),
3827 MAPPING_INIT(".lbss.", ".lbss"),
3828 MAPPING_INIT(".gcc_except_table.", ".gcc_except_table"),
3829 MAPPING_INIT(".gnu.linkonce.d.rel.ro.local.", ".data.rel.ro.local"),
3830 MAPPING_INIT(".gnu.linkonce.d.rel.ro.", ".data.rel.ro"),
3831 MAPPING_INIT(".gnu.linkonce.t.", ".text"),
3832 MAPPING_INIT(".gnu.linkonce.r.", ".rodata"),
3833 MAPPING_INIT(".gnu.linkonce.d.", ".data"),
3834 MAPPING_INIT(".gnu.linkonce.b.", ".bss"),
3835 MAPPING_INIT(".gnu.linkonce.s.", ".sdata"),
3836 MAPPING_INIT(".gnu.linkonce.sb.", ".sbss"),
3837 MAPPING_INIT(".gnu.linkonce.s2.", ".sdata"),
3838 MAPPING_INIT(".gnu.linkonce.sb2.", ".sbss"),
3839 MAPPING_INIT(".gnu.linkonce.wi.", ".debug_info"),
3840 MAPPING_INIT(".gnu.linkonce.td.", ".tdata"),
3841 MAPPING_INIT(".gnu.linkonce.tb.", ".tbss"),
3842 MAPPING_INIT(".gnu.linkonce.lr.", ".lrodata"),
3843 MAPPING_INIT(".gnu.linkonce.l.", ".ldata"),
3844 MAPPING_INIT(".gnu.linkonce.lb.", ".lbss"),
3845 MAPPING_INIT(".ARM.extab", ".ARM.extab"),
3846 MAPPING_INIT(".gnu.linkonce.armextab.", ".ARM.extab"),
3847 MAPPING_INIT(".ARM.exidx", ".ARM.exidx"),
3848 MAPPING_INIT(".gnu.linkonce.armexidx.", ".ARM.exidx"),
3852 const int Layout::section_name_mapping_count =
3853 (sizeof(Layout::section_name_mapping)
3854 / sizeof(Layout::section_name_mapping[0]));
3856 // Choose the output section name to use given an input section name.
3857 // Set *PLEN to the length of the name. *PLEN is initialized to the
3861 Layout::output_section_name(const char* name, size_t* plen)
3863 // gcc 4.3 generates the following sorts of section names when it
3864 // needs a section name specific to a function:
3870 // .data.rel.local.FN
3872 // .data.rel.ro.local.FN
3879 // The GNU linker maps all of those to the part before the .FN,
3880 // except that .data.rel.local.FN is mapped to .data, and
3881 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
3882 // beginning with .data.rel.ro.local are grouped together.
3884 // For an anonymous namespace, the string FN can contain a '.'.
3886 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
3887 // GNU linker maps to .rodata.
3889 // The .data.rel.ro sections are used with -z relro. The sections
3890 // are recognized by name. We use the same names that the GNU
3891 // linker does for these sections.
3893 // It is hard to handle this in a principled way, so we don't even
3894 // try. We use a table of mappings. If the input section name is
3895 // not found in the table, we simply use it as the output section
3898 const Section_name_mapping* psnm = section_name_mapping;
3899 for (int i = 0; i < section_name_mapping_count; ++i, ++psnm)
3901 if (strncmp(name, psnm->from, psnm->fromlen) == 0)
3903 *plen = psnm->tolen;
3908 // Compressed debug sections should be mapped to the corresponding
3909 // uncompressed section.
3910 if (is_compressed_debug_section(name))
3912 size_t len = strlen(name);
3913 char* uncompressed_name = new char[len];
3914 uncompressed_name[0] = '.';
3915 gold_assert(name[0] == '.' && name[1] == 'z');
3916 strncpy(&uncompressed_name[1], &name[2], len - 2);
3917 uncompressed_name[len - 1] = '\0';
3919 return uncompressed_name;
3925 // Check if a comdat group or .gnu.linkonce section with the given
3926 // NAME is selected for the link. If there is already a section,
3927 // *KEPT_SECTION is set to point to the existing section and the
3928 // function returns false. Otherwise, OBJECT, SHNDX, IS_COMDAT, and
3929 // IS_GROUP_NAME are recorded for this NAME in the layout object,
3930 // *KEPT_SECTION is set to the internal copy and the function returns
3934 Layout::find_or_add_kept_section(const std::string& name,
3939 Kept_section** kept_section)
3941 // It's normal to see a couple of entries here, for the x86 thunk
3942 // sections. If we see more than a few, we're linking a C++
3943 // program, and we resize to get more space to minimize rehashing.
3944 if (this->signatures_.size() > 4
3945 && !this->resized_signatures_)
3947 reserve_unordered_map(&this->signatures_,
3948 this->number_of_input_files_ * 64);
3949 this->resized_signatures_ = true;
3952 Kept_section candidate;
3953 std::pair<Signatures::iterator, bool> ins =
3954 this->signatures_.insert(std::make_pair(name, candidate));
3956 if (kept_section != NULL)
3957 *kept_section = &ins.first->second;
3960 // This is the first time we've seen this signature.
3961 ins.first->second.set_object(object);
3962 ins.first->second.set_shndx(shndx);
3964 ins.first->second.set_is_comdat();
3966 ins.first->second.set_is_group_name();
3970 // We have already seen this signature.
3972 if (ins.first->second.is_group_name())
3974 // We've already seen a real section group with this signature.
3975 // If the kept group is from a plugin object, and we're in the
3976 // replacement phase, accept the new one as a replacement.
3977 if (ins.first->second.object() == NULL
3978 && parameters->options().plugins()->in_replacement_phase())
3980 ins.first->second.set_object(object);
3981 ins.first->second.set_shndx(shndx);
3986 else if (is_group_name)
3988 // This is a real section group, and we've already seen a
3989 // linkonce section with this signature. Record that we've seen
3990 // a section group, and don't include this section group.
3991 ins.first->second.set_is_group_name();
3996 // We've already seen a linkonce section and this is a linkonce
3997 // section. These don't block each other--this may be the same
3998 // symbol name with different section types.
4003 // Store the allocated sections into the section list.
4006 Layout::get_allocated_sections(Section_list* section_list) const
4008 for (Section_list::const_iterator p = this->section_list_.begin();
4009 p != this->section_list_.end();
4011 if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0)
4012 section_list->push_back(*p);
4015 // Create an output segment.
4018 Layout::make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags)
4020 gold_assert(!parameters->options().relocatable());
4021 Output_segment* oseg = new Output_segment(type, flags);
4022 this->segment_list_.push_back(oseg);
4024 if (type == elfcpp::PT_TLS)
4025 this->tls_segment_ = oseg;
4026 else if (type == elfcpp::PT_GNU_RELRO)
4027 this->relro_segment_ = oseg;
4032 // Write out the Output_sections. Most won't have anything to write,
4033 // since most of the data will come from input sections which are
4034 // handled elsewhere. But some Output_sections do have Output_data.
4037 Layout::write_output_sections(Output_file* of) const
4039 for (Section_list::const_iterator p = this->section_list_.begin();
4040 p != this->section_list_.end();
4043 if (!(*p)->after_input_sections())
4048 // Write out data not associated with a section or the symbol table.
4051 Layout::write_data(const Symbol_table* symtab, Output_file* of) const
4053 if (!parameters->options().strip_all())
4055 const Output_section* symtab_section = this->symtab_section_;
4056 for (Section_list::const_iterator p = this->section_list_.begin();
4057 p != this->section_list_.end();
4060 if ((*p)->needs_symtab_index())
4062 gold_assert(symtab_section != NULL);
4063 unsigned int index = (*p)->symtab_index();
4064 gold_assert(index > 0 && index != -1U);
4065 off_t off = (symtab_section->offset()
4066 + index * symtab_section->entsize());
4067 symtab->write_section_symbol(*p, this->symtab_xindex_, of, off);
4072 const Output_section* dynsym_section = this->dynsym_section_;
4073 for (Section_list::const_iterator p = this->section_list_.begin();
4074 p != this->section_list_.end();
4077 if ((*p)->needs_dynsym_index())
4079 gold_assert(dynsym_section != NULL);
4080 unsigned int index = (*p)->dynsym_index();
4081 gold_assert(index > 0 && index != -1U);
4082 off_t off = (dynsym_section->offset()
4083 + index * dynsym_section->entsize());
4084 symtab->write_section_symbol(*p, this->dynsym_xindex_, of, off);
4088 // Write out the Output_data which are not in an Output_section.
4089 for (Data_list::const_iterator p = this->special_output_list_.begin();
4090 p != this->special_output_list_.end();
4095 // Write out the Output_sections which can only be written after the
4096 // input sections are complete.
4099 Layout::write_sections_after_input_sections(Output_file* of)
4101 // Determine the final section offsets, and thus the final output
4102 // file size. Note we finalize the .shstrab last, to allow the
4103 // after_input_section sections to modify their section-names before
4105 if (this->any_postprocessing_sections_)
4107 off_t off = this->output_file_size_;
4108 off = this->set_section_offsets(off, POSTPROCESSING_SECTIONS_PASS);
4110 // Now that we've finalized the names, we can finalize the shstrab.
4112 this->set_section_offsets(off,
4113 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
4115 if (off > this->output_file_size_)
4118 this->output_file_size_ = off;
4122 for (Section_list::const_iterator p = this->section_list_.begin();
4123 p != this->section_list_.end();
4126 if ((*p)->after_input_sections())
4130 this->section_headers_->write(of);
4133 // If the build ID requires computing a checksum, do so here, and
4134 // write it out. We compute a checksum over the entire file because
4135 // that is simplest.
4138 Layout::write_build_id(Output_file* of) const
4140 if (this->build_id_note_ == NULL)
4143 const unsigned char* iv = of->get_input_view(0, this->output_file_size_);
4145 unsigned char* ov = of->get_output_view(this->build_id_note_->offset(),
4146 this->build_id_note_->data_size());
4148 const char* style = parameters->options().build_id();
4149 if (strcmp(style, "sha1") == 0)
4152 sha1_init_ctx(&ctx);
4153 sha1_process_bytes(iv, this->output_file_size_, &ctx);
4154 sha1_finish_ctx(&ctx, ov);
4156 else if (strcmp(style, "md5") == 0)
4160 md5_process_bytes(iv, this->output_file_size_, &ctx);
4161 md5_finish_ctx(&ctx, ov);
4166 of->write_output_view(this->build_id_note_->offset(),
4167 this->build_id_note_->data_size(),
4170 of->free_input_view(0, this->output_file_size_, iv);
4173 // Write out a binary file. This is called after the link is
4174 // complete. IN is the temporary output file we used to generate the
4175 // ELF code. We simply walk through the segments, read them from
4176 // their file offset in IN, and write them to their load address in
4177 // the output file. FIXME: with a bit more work, we could support
4178 // S-records and/or Intel hex format here.
4181 Layout::write_binary(Output_file* in) const
4183 gold_assert(parameters->options().oformat_enum()
4184 == General_options::OBJECT_FORMAT_BINARY);
4186 // Get the size of the binary file.
4187 uint64_t max_load_address = 0;
4188 for (Segment_list::const_iterator p = this->segment_list_.begin();
4189 p != this->segment_list_.end();
4192 if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
4194 uint64_t max_paddr = (*p)->paddr() + (*p)->filesz();
4195 if (max_paddr > max_load_address)
4196 max_load_address = max_paddr;
4200 Output_file out(parameters->options().output_file_name());
4201 out.open(max_load_address);
4203 for (Segment_list::const_iterator p = this->segment_list_.begin();
4204 p != this->segment_list_.end();
4207 if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
4209 const unsigned char* vin = in->get_input_view((*p)->offset(),
4211 unsigned char* vout = out.get_output_view((*p)->paddr(),
4213 memcpy(vout, vin, (*p)->filesz());
4214 out.write_output_view((*p)->paddr(), (*p)->filesz(), vout);
4215 in->free_input_view((*p)->offset(), (*p)->filesz(), vin);
4222 // Print the output sections to the map file.
4225 Layout::print_to_mapfile(Mapfile* mapfile) const
4227 for (Segment_list::const_iterator p = this->segment_list_.begin();
4228 p != this->segment_list_.end();
4230 (*p)->print_sections_to_mapfile(mapfile);
4233 // Print statistical information to stderr. This is used for --stats.
4236 Layout::print_stats() const
4238 this->namepool_.print_stats("section name pool");
4239 this->sympool_.print_stats("output symbol name pool");
4240 this->dynpool_.print_stats("dynamic name pool");
4242 for (Section_list::const_iterator p = this->section_list_.begin();
4243 p != this->section_list_.end();
4245 (*p)->print_merge_stats();
4248 // Write_sections_task methods.
4250 // We can always run this task.
4253 Write_sections_task::is_runnable()
4258 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
4262 Write_sections_task::locks(Task_locker* tl)
4264 tl->add(this, this->output_sections_blocker_);
4265 tl->add(this, this->final_blocker_);
4268 // Run the task--write out the data.
4271 Write_sections_task::run(Workqueue*)
4273 this->layout_->write_output_sections(this->of_);
4276 // Write_data_task methods.
4278 // We can always run this task.
4281 Write_data_task::is_runnable()
4286 // We need to unlock FINAL_BLOCKER when finished.
4289 Write_data_task::locks(Task_locker* tl)
4291 tl->add(this, this->final_blocker_);
4294 // Run the task--write out the data.
4297 Write_data_task::run(Workqueue*)
4299 this->layout_->write_data(this->symtab_, this->of_);
4302 // Write_symbols_task methods.
4304 // We can always run this task.
4307 Write_symbols_task::is_runnable()
4312 // We need to unlock FINAL_BLOCKER when finished.
4315 Write_symbols_task::locks(Task_locker* tl)
4317 tl->add(this, this->final_blocker_);
4320 // Run the task--write out the symbols.
4323 Write_symbols_task::run(Workqueue*)
4325 this->symtab_->write_globals(this->sympool_, this->dynpool_,
4326 this->layout_->symtab_xindex(),
4327 this->layout_->dynsym_xindex(), this->of_);
4330 // Write_after_input_sections_task methods.
4332 // We can only run this task after the input sections have completed.
4335 Write_after_input_sections_task::is_runnable()
4337 if (this->input_sections_blocker_->is_blocked())
4338 return this->input_sections_blocker_;
4342 // We need to unlock FINAL_BLOCKER when finished.
4345 Write_after_input_sections_task::locks(Task_locker* tl)
4347 tl->add(this, this->final_blocker_);
4353 Write_after_input_sections_task::run(Workqueue*)
4355 this->layout_->write_sections_after_input_sections(this->of_);
4358 // Close_task_runner methods.
4360 // Run the task--close the file.
4363 Close_task_runner::run(Workqueue*, const Task*)
4365 // If we need to compute a checksum for the BUILD if, we do so here.
4366 this->layout_->write_build_id(this->of_);
4368 // If we've been asked to create a binary file, we do so here.
4369 if (this->options_->oformat_enum() != General_options::OBJECT_FORMAT_ELF)
4370 this->layout_->write_binary(this->of_);
4375 // Instantiate the templates we need. We could use the configure
4376 // script to restrict this to only the ones for implemented targets.
4378 #ifdef HAVE_TARGET_32_LITTLE
4381 Layout::layout<32, false>(Sized_relobj<32, false>* object, unsigned int shndx,
4383 const elfcpp::Shdr<32, false>& shdr,
4384 unsigned int, unsigned int, off_t*);
4387 #ifdef HAVE_TARGET_32_BIG
4390 Layout::layout<32, true>(Sized_relobj<32, true>* object, unsigned int shndx,
4392 const elfcpp::Shdr<32, true>& shdr,
4393 unsigned int, unsigned int, off_t*);
4396 #ifdef HAVE_TARGET_64_LITTLE
4399 Layout::layout<64, false>(Sized_relobj<64, false>* object, unsigned int shndx,
4401 const elfcpp::Shdr<64, false>& shdr,
4402 unsigned int, unsigned int, off_t*);
4405 #ifdef HAVE_TARGET_64_BIG
4408 Layout::layout<64, true>(Sized_relobj<64, true>* object, unsigned int shndx,
4410 const elfcpp::Shdr<64, true>& shdr,
4411 unsigned int, unsigned int, off_t*);
4414 #ifdef HAVE_TARGET_32_LITTLE
4417 Layout::layout_reloc<32, false>(Sized_relobj<32, false>* object,
4418 unsigned int reloc_shndx,
4419 const elfcpp::Shdr<32, false>& shdr,
4420 Output_section* data_section,
4421 Relocatable_relocs* rr);
4424 #ifdef HAVE_TARGET_32_BIG
4427 Layout::layout_reloc<32, true>(Sized_relobj<32, true>* object,
4428 unsigned int reloc_shndx,
4429 const elfcpp::Shdr<32, true>& shdr,
4430 Output_section* data_section,
4431 Relocatable_relocs* rr);
4434 #ifdef HAVE_TARGET_64_LITTLE
4437 Layout::layout_reloc<64, false>(Sized_relobj<64, false>* object,
4438 unsigned int reloc_shndx,
4439 const elfcpp::Shdr<64, false>& shdr,
4440 Output_section* data_section,
4441 Relocatable_relocs* rr);
4444 #ifdef HAVE_TARGET_64_BIG
4447 Layout::layout_reloc<64, true>(Sized_relobj<64, true>* object,
4448 unsigned int reloc_shndx,
4449 const elfcpp::Shdr<64, true>& shdr,
4450 Output_section* data_section,
4451 Relocatable_relocs* rr);
4454 #ifdef HAVE_TARGET_32_LITTLE
4457 Layout::layout_group<32, false>(Symbol_table* symtab,
4458 Sized_relobj<32, false>* object,
4460 const char* group_section_name,
4461 const char* signature,
4462 const elfcpp::Shdr<32, false>& shdr,
4463 elfcpp::Elf_Word flags,
4464 std::vector<unsigned int>* shndxes);
4467 #ifdef HAVE_TARGET_32_BIG
4470 Layout::layout_group<32, true>(Symbol_table* symtab,
4471 Sized_relobj<32, true>* object,
4473 const char* group_section_name,
4474 const char* signature,
4475 const elfcpp::Shdr<32, true>& shdr,
4476 elfcpp::Elf_Word flags,
4477 std::vector<unsigned int>* shndxes);
4480 #ifdef HAVE_TARGET_64_LITTLE
4483 Layout::layout_group<64, false>(Symbol_table* symtab,
4484 Sized_relobj<64, false>* object,
4486 const char* group_section_name,
4487 const char* signature,
4488 const elfcpp::Shdr<64, false>& shdr,
4489 elfcpp::Elf_Word flags,
4490 std::vector<unsigned int>* shndxes);
4493 #ifdef HAVE_TARGET_64_BIG
4496 Layout::layout_group<64, true>(Symbol_table* symtab,
4497 Sized_relobj<64, true>* object,
4499 const char* group_section_name,
4500 const char* signature,
4501 const elfcpp::Shdr<64, true>& shdr,
4502 elfcpp::Elf_Word flags,
4503 std::vector<unsigned int>* shndxes);
4506 #ifdef HAVE_TARGET_32_LITTLE
4509 Layout::layout_eh_frame<32, false>(Sized_relobj<32, false>* object,
4510 const unsigned char* symbols,
4512 const unsigned char* symbol_names,
4513 off_t symbol_names_size,
4515 const elfcpp::Shdr<32, false>& shdr,
4516 unsigned int reloc_shndx,
4517 unsigned int reloc_type,
4521 #ifdef HAVE_TARGET_32_BIG
4524 Layout::layout_eh_frame<32, true>(Sized_relobj<32, true>* object,
4525 const unsigned char* symbols,
4527 const unsigned char* symbol_names,
4528 off_t symbol_names_size,
4530 const elfcpp::Shdr<32, true>& shdr,
4531 unsigned int reloc_shndx,
4532 unsigned int reloc_type,
4536 #ifdef HAVE_TARGET_64_LITTLE
4539 Layout::layout_eh_frame<64, false>(Sized_relobj<64, false>* object,
4540 const unsigned char* symbols,
4542 const unsigned char* symbol_names,
4543 off_t symbol_names_size,
4545 const elfcpp::Shdr<64, false>& shdr,
4546 unsigned int reloc_shndx,
4547 unsigned int reloc_type,
4551 #ifdef HAVE_TARGET_64_BIG
4554 Layout::layout_eh_frame<64, true>(Sized_relobj<64, true>* object,
4555 const unsigned char* symbols,
4557 const unsigned char* symbol_names,
4558 off_t symbol_names_size,
4560 const elfcpp::Shdr<64, true>& shdr,
4561 unsigned int reloc_shndx,
4562 unsigned int reloc_type,
4566 } // End namespace gold.