1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011, 2012
4 // Free Software Foundation, Inc.
5 // Written by Ian Lance Taylor <iant@google.com>.
7 // This file is part of gold.
9 // This program is free software; you can redistribute it and/or modify
10 // it under the terms of the GNU General Public License as published by
11 // the Free Software Foundation; either version 3 of the License, or
12 // (at your option) any later version.
14 // This program is distributed in the hope that it will be useful,
15 // but WITHOUT ANY WARRANTY; without even the implied warranty of
16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 // GNU General Public License for more details.
19 // You should have received a copy of the GNU General Public License
20 // along with this program; if not, write to the Free Software
21 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
22 // MA 02110-1301, USA.
35 #include "libiberty.h"
39 #include "parameters.h"
43 #include "script-sections.h"
48 #include "gdb-index.h"
49 #include "compressed_output.h"
50 #include "reduced_debug_output.h"
53 #include "descriptors.h"
55 #include "incremental.h"
63 // The total number of free lists used.
64 unsigned int Free_list::num_lists = 0;
65 // The total number of free list nodes used.
66 unsigned int Free_list::num_nodes = 0;
67 // The total number of calls to Free_list::remove.
68 unsigned int Free_list::num_removes = 0;
69 // The total number of nodes visited during calls to Free_list::remove.
70 unsigned int Free_list::num_remove_visits = 0;
71 // The total number of calls to Free_list::allocate.
72 unsigned int Free_list::num_allocates = 0;
73 // The total number of nodes visited during calls to Free_list::allocate.
74 unsigned int Free_list::num_allocate_visits = 0;
76 // Initialize the free list. Creates a single free list node that
77 // describes the entire region of length LEN. If EXTEND is true,
78 // allocate() is allowed to extend the region beyond its initial
82 Free_list::init(off_t len, bool extend)
84 this->list_.push_front(Free_list_node(0, len));
85 this->last_remove_ = this->list_.begin();
86 this->extend_ = extend;
88 ++Free_list::num_lists;
89 ++Free_list::num_nodes;
92 // Remove a chunk from the free list. Because we start with a single
93 // node that covers the entire section, and remove chunks from it one
94 // at a time, we do not need to coalesce chunks or handle cases that
95 // span more than one free node. We expect to remove chunks from the
96 // free list in order, and we expect to have only a few chunks of free
97 // space left (corresponding to files that have changed since the last
98 // incremental link), so a simple linear list should provide sufficient
102 Free_list::remove(off_t start, off_t end)
106 gold_assert(start < end);
108 ++Free_list::num_removes;
110 Iterator p = this->last_remove_;
111 if (p->start_ > start)
112 p = this->list_.begin();
114 for (; p != this->list_.end(); ++p)
116 ++Free_list::num_remove_visits;
117 // Find a node that wholly contains the indicated region.
118 if (p->start_ <= start && p->end_ >= end)
120 // Case 1: the indicated region spans the whole node.
121 // Add some fuzz to avoid creating tiny free chunks.
122 if (p->start_ + 3 >= start && p->end_ <= end + 3)
123 p = this->list_.erase(p);
124 // Case 2: remove a chunk from the start of the node.
125 else if (p->start_ + 3 >= start)
127 // Case 3: remove a chunk from the end of the node.
128 else if (p->end_ <= end + 3)
130 // Case 4: remove a chunk from the middle, and split
131 // the node into two.
134 Free_list_node newnode(p->start_, start);
136 this->list_.insert(p, newnode);
137 ++Free_list::num_nodes;
139 this->last_remove_ = p;
144 // Did not find a node containing the given chunk. This could happen
145 // because a small chunk was already removed due to the fuzz.
146 gold_debug(DEBUG_INCREMENTAL,
147 "Free_list::remove(%d,%d) not found",
148 static_cast<int>(start), static_cast<int>(end));
151 // Allocate a chunk of size LEN from the free list. Returns -1ULL
152 // if a sufficiently large chunk of free space is not found.
153 // We use a simple first-fit algorithm.
156 Free_list::allocate(off_t len, uint64_t align, off_t minoff)
158 gold_debug(DEBUG_INCREMENTAL,
159 "Free_list::allocate(%08lx, %d, %08lx)",
160 static_cast<long>(len), static_cast<int>(align),
161 static_cast<long>(minoff));
163 return align_address(minoff, align);
165 ++Free_list::num_allocates;
167 // We usually want to drop free chunks smaller than 4 bytes.
168 // If we need to guarantee a minimum hole size, though, we need
169 // to keep track of all free chunks.
170 const int fuzz = this->min_hole_ > 0 ? 0 : 3;
172 for (Iterator p = this->list_.begin(); p != this->list_.end(); ++p)
174 ++Free_list::num_allocate_visits;
175 off_t start = p->start_ > minoff ? p->start_ : minoff;
176 start = align_address(start, align);
177 off_t end = start + len;
178 if (end > p->end_ && p->end_ == this->length_ && this->extend_)
183 if (end == p->end_ || (end <= p->end_ - this->min_hole_))
185 if (p->start_ + fuzz >= start && p->end_ <= end + fuzz)
186 this->list_.erase(p);
187 else if (p->start_ + fuzz >= start)
189 else if (p->end_ <= end + fuzz)
193 Free_list_node newnode(p->start_, start);
195 this->list_.insert(p, newnode);
196 ++Free_list::num_nodes;
203 off_t start = align_address(this->length_, align);
204 this->length_ = start + len;
210 // Dump the free list (for debugging).
214 gold_info("Free list:\n start end length\n");
215 for (Iterator p = this->list_.begin(); p != this->list_.end(); ++p)
216 gold_info(" %08lx %08lx %08lx", static_cast<long>(p->start_),
217 static_cast<long>(p->end_),
218 static_cast<long>(p->end_ - p->start_));
221 // Print the statistics for the free lists.
223 Free_list::print_stats()
225 fprintf(stderr, _("%s: total free lists: %u\n"),
226 program_name, Free_list::num_lists);
227 fprintf(stderr, _("%s: total free list nodes: %u\n"),
228 program_name, Free_list::num_nodes);
229 fprintf(stderr, _("%s: calls to Free_list::remove: %u\n"),
230 program_name, Free_list::num_removes);
231 fprintf(stderr, _("%s: nodes visited: %u\n"),
232 program_name, Free_list::num_remove_visits);
233 fprintf(stderr, _("%s: calls to Free_list::allocate: %u\n"),
234 program_name, Free_list::num_allocates);
235 fprintf(stderr, _("%s: nodes visited: %u\n"),
236 program_name, Free_list::num_allocate_visits);
239 // Layout::Relaxation_debug_check methods.
241 // Check that sections and special data are in reset states.
242 // We do not save states for Output_sections and special Output_data.
243 // So we check that they have not assigned any addresses or offsets.
244 // clean_up_after_relaxation simply resets their addresses and offsets.
246 Layout::Relaxation_debug_check::check_output_data_for_reset_values(
247 const Layout::Section_list& sections,
248 const Layout::Data_list& special_outputs)
250 for(Layout::Section_list::const_iterator p = sections.begin();
253 gold_assert((*p)->address_and_file_offset_have_reset_values());
255 for(Layout::Data_list::const_iterator p = special_outputs.begin();
256 p != special_outputs.end();
258 gold_assert((*p)->address_and_file_offset_have_reset_values());
261 // Save information of SECTIONS for checking later.
264 Layout::Relaxation_debug_check::read_sections(
265 const Layout::Section_list& sections)
267 for(Layout::Section_list::const_iterator p = sections.begin();
271 Output_section* os = *p;
273 info.output_section = os;
274 info.address = os->is_address_valid() ? os->address() : 0;
275 info.data_size = os->is_data_size_valid() ? os->data_size() : -1;
276 info.offset = os->is_offset_valid()? os->offset() : -1 ;
277 this->section_infos_.push_back(info);
281 // Verify SECTIONS using previously recorded information.
284 Layout::Relaxation_debug_check::verify_sections(
285 const Layout::Section_list& sections)
288 for(Layout::Section_list::const_iterator p = sections.begin();
292 Output_section* os = *p;
293 uint64_t address = os->is_address_valid() ? os->address() : 0;
294 off_t data_size = os->is_data_size_valid() ? os->data_size() : -1;
295 off_t offset = os->is_offset_valid()? os->offset() : -1 ;
297 if (i >= this->section_infos_.size())
299 gold_fatal("Section_info of %s missing.\n", os->name());
301 const Section_info& info = this->section_infos_[i];
302 if (os != info.output_section)
303 gold_fatal("Section order changed. Expecting %s but see %s\n",
304 info.output_section->name(), os->name());
305 if (address != info.address
306 || data_size != info.data_size
307 || offset != info.offset)
308 gold_fatal("Section %s changed.\n", os->name());
312 // Layout_task_runner methods.
314 // Lay out the sections. This is called after all the input objects
318 Layout_task_runner::run(Workqueue* workqueue, const Task* task)
320 Layout* layout = this->layout_;
321 off_t file_size = layout->finalize(this->input_objects_,
326 // Now we know the final size of the output file and we know where
327 // each piece of information goes.
329 if (this->mapfile_ != NULL)
331 this->mapfile_->print_discarded_sections(this->input_objects_);
332 layout->print_to_mapfile(this->mapfile_);
336 if (layout->incremental_base() == NULL)
338 of = new Output_file(parameters->options().output_file_name());
339 if (this->options_.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
340 of->set_is_temporary();
345 of = layout->incremental_base()->output_file();
347 // Apply the incremental relocations for symbols whose values
348 // have changed. We do this before we resize the file and start
349 // writing anything else to it, so that we can read the old
350 // incremental information from the file before (possibly)
352 if (parameters->incremental_update())
353 layout->incremental_base()->apply_incremental_relocs(this->symtab_,
357 of->resize(file_size);
360 // Queue up the final set of tasks.
361 gold::queue_final_tasks(this->options_, this->input_objects_,
362 this->symtab_, layout, workqueue, of);
367 Layout::Layout(int number_of_input_files, Script_options* script_options)
368 : number_of_input_files_(number_of_input_files),
369 script_options_(script_options),
377 unattached_section_list_(),
378 special_output_list_(),
379 section_headers_(NULL),
381 relro_segment_(NULL),
382 interp_segment_(NULL),
384 symtab_section_(NULL),
385 symtab_xindex_(NULL),
386 dynsym_section_(NULL),
387 dynsym_xindex_(NULL),
388 dynamic_section_(NULL),
389 dynamic_symbol_(NULL),
391 eh_frame_section_(NULL),
392 eh_frame_data_(NULL),
393 added_eh_frame_data_(false),
394 eh_frame_hdr_section_(NULL),
395 gdb_index_data_(NULL),
396 build_id_note_(NULL),
400 output_file_size_(-1),
401 have_added_input_section_(false),
402 sections_are_attached_(false),
403 input_requires_executable_stack_(false),
404 input_with_gnu_stack_note_(false),
405 input_without_gnu_stack_note_(false),
406 has_static_tls_(false),
407 any_postprocessing_sections_(false),
408 resized_signatures_(false),
409 have_stabstr_section_(false),
410 section_ordering_specified_(false),
411 incremental_inputs_(NULL),
412 record_output_section_data_from_script_(false),
413 script_output_section_data_list_(),
414 segment_states_(NULL),
415 relaxation_debug_check_(NULL),
416 section_order_map_(),
417 input_section_position_(),
418 input_section_glob_(),
419 incremental_base_(NULL),
422 // Make space for more than enough segments for a typical file.
423 // This is just for efficiency--it's OK if we wind up needing more.
424 this->segment_list_.reserve(12);
426 // We expect two unattached Output_data objects: the file header and
427 // the segment headers.
428 this->special_output_list_.reserve(2);
430 // Initialize structure needed for an incremental build.
431 if (parameters->incremental())
432 this->incremental_inputs_ = new Incremental_inputs;
434 // The section name pool is worth optimizing in all cases, because
435 // it is small, but there are often overlaps due to .rel sections.
436 this->namepool_.set_optimize();
439 // For incremental links, record the base file to be modified.
442 Layout::set_incremental_base(Incremental_binary* base)
444 this->incremental_base_ = base;
445 this->free_list_.init(base->output_file()->filesize(), true);
448 // Hash a key we use to look up an output section mapping.
451 Layout::Hash_key::operator()(const Layout::Key& k) const
453 return k.first + k.second.first + k.second.second;
456 // These are the debug sections that are actually used by gdb.
457 // Currently, we've checked versions of gdb up to and including 7.4.
458 // We only check the part of the name that follows ".debug_" or
461 static const char* gdb_sections[] =
464 "addr", // Fission extension
465 // "aranges", // not used by gdb as of 7.4
473 // "pubnames", // not used by gdb as of 7.4
474 // "pubtypes", // not used by gdb as of 7.4
479 // This is the minimum set of sections needed for line numbers.
481 static const char* lines_only_debug_sections[] =
484 // "addr", // Fission extension
485 // "aranges", // not used by gdb as of 7.4
493 // "pubnames", // not used by gdb as of 7.4
494 // "pubtypes", // not used by gdb as of 7.4
499 // These sections are the DWARF fast-lookup tables, and are not needed
500 // when building a .gdb_index section.
502 static const char* gdb_fast_lookup_sections[] =
509 // Returns whether the given debug section is in the list of
510 // debug-sections-used-by-some-version-of-gdb. SUFFIX is the
511 // portion of the name following ".debug_" or ".zdebug_".
514 is_gdb_debug_section(const char* suffix)
516 // We can do this faster: binary search or a hashtable. But why bother?
517 for (size_t i = 0; i < sizeof(gdb_sections)/sizeof(*gdb_sections); ++i)
518 if (strcmp(suffix, gdb_sections[i]) == 0)
523 // Returns whether the given section is needed for lines-only debugging.
526 is_lines_only_debug_section(const char* suffix)
528 // We can do this faster: binary search or a hashtable. But why bother?
530 i < sizeof(lines_only_debug_sections)/sizeof(*lines_only_debug_sections);
532 if (strcmp(suffix, lines_only_debug_sections[i]) == 0)
537 // Returns whether the given section is a fast-lookup section that
538 // will not be needed when building a .gdb_index section.
541 is_gdb_fast_lookup_section(const char* suffix)
543 // We can do this faster: binary search or a hashtable. But why bother?
545 i < sizeof(gdb_fast_lookup_sections)/sizeof(*gdb_fast_lookup_sections);
547 if (strcmp(suffix, gdb_fast_lookup_sections[i]) == 0)
552 // Sometimes we compress sections. This is typically done for
553 // sections that are not part of normal program execution (such as
554 // .debug_* sections), and where the readers of these sections know
555 // how to deal with compressed sections. This routine doesn't say for
556 // certain whether we'll compress -- it depends on commandline options
557 // as well -- just whether this section is a candidate for compression.
558 // (The Output_compressed_section class decides whether to compress
559 // a given section, and picks the name of the compressed section.)
562 is_compressible_debug_section(const char* secname)
564 return (is_prefix_of(".debug", secname));
567 // We may see compressed debug sections in input files. Return TRUE
568 // if this is the name of a compressed debug section.
571 is_compressed_debug_section(const char* secname)
573 return (is_prefix_of(".zdebug", secname));
576 // Whether to include this section in the link.
578 template<int size, bool big_endian>
580 Layout::include_section(Sized_relobj_file<size, big_endian>*, const char* name,
581 const elfcpp::Shdr<size, big_endian>& shdr)
583 if (shdr.get_sh_flags() & elfcpp::SHF_EXCLUDE)
586 switch (shdr.get_sh_type())
588 case elfcpp::SHT_NULL:
589 case elfcpp::SHT_SYMTAB:
590 case elfcpp::SHT_DYNSYM:
591 case elfcpp::SHT_HASH:
592 case elfcpp::SHT_DYNAMIC:
593 case elfcpp::SHT_SYMTAB_SHNDX:
596 case elfcpp::SHT_STRTAB:
597 // Discard the sections which have special meanings in the ELF
598 // ABI. Keep others (e.g., .stabstr). We could also do this by
599 // checking the sh_link fields of the appropriate sections.
600 return (strcmp(name, ".dynstr") != 0
601 && strcmp(name, ".strtab") != 0
602 && strcmp(name, ".shstrtab") != 0);
604 case elfcpp::SHT_RELA:
605 case elfcpp::SHT_REL:
606 case elfcpp::SHT_GROUP:
607 // If we are emitting relocations these should be handled
609 gold_assert(!parameters->options().relocatable()
610 && !parameters->options().emit_relocs());
613 case elfcpp::SHT_PROGBITS:
614 if (parameters->options().strip_debug()
615 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
617 if (is_debug_info_section(name))
620 if (parameters->options().strip_debug_non_line()
621 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
623 // Debugging sections can only be recognized by name.
624 if (is_prefix_of(".debug_", name)
625 && !is_lines_only_debug_section(name + 7))
627 if (is_prefix_of(".zdebug_", name)
628 && !is_lines_only_debug_section(name + 8))
631 if (parameters->options().strip_debug_gdb()
632 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
634 // Debugging sections can only be recognized by name.
635 if (is_prefix_of(".debug_", name)
636 && !is_gdb_debug_section(name + 7))
638 if (is_prefix_of(".zdebug_", name)
639 && !is_gdb_debug_section(name + 8))
642 if (parameters->options().gdb_index()
643 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
645 // When building .gdb_index, we can strip .debug_pubnames,
646 // .debug_pubtypes, and .debug_aranges sections.
647 if (is_prefix_of(".debug_", name)
648 && is_gdb_fast_lookup_section(name + 7))
650 if (is_prefix_of(".zdebug_", name)
651 && is_gdb_fast_lookup_section(name + 8))
654 if (parameters->options().strip_lto_sections()
655 && !parameters->options().relocatable()
656 && (shdr.get_sh_flags() & elfcpp::SHF_ALLOC) == 0)
658 // Ignore LTO sections containing intermediate code.
659 if (is_prefix_of(".gnu.lto_", name))
662 // The GNU linker strips .gnu_debuglink sections, so we do too.
663 // This is a feature used to keep debugging information in
665 if (strcmp(name, ".gnu_debuglink") == 0)
674 // Return an output section named NAME, or NULL if there is none.
677 Layout::find_output_section(const char* name) const
679 for (Section_list::const_iterator p = this->section_list_.begin();
680 p != this->section_list_.end();
682 if (strcmp((*p)->name(), name) == 0)
687 // Return an output segment of type TYPE, with segment flags SET set
688 // and segment flags CLEAR clear. Return NULL if there is none.
691 Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
692 elfcpp::Elf_Word clear) const
694 for (Segment_list::const_iterator p = this->segment_list_.begin();
695 p != this->segment_list_.end();
697 if (static_cast<elfcpp::PT>((*p)->type()) == type
698 && ((*p)->flags() & set) == set
699 && ((*p)->flags() & clear) == 0)
704 // When we put a .ctors or .dtors section with more than one word into
705 // a .init_array or .fini_array section, we need to reverse the words
706 // in the .ctors/.dtors section. This is because .init_array executes
707 // constructors front to back, where .ctors executes them back to
708 // front, and vice-versa for .fini_array/.dtors. Although we do want
709 // to remap .ctors/.dtors into .init_array/.fini_array because it can
710 // be more efficient, we don't want to change the order in which
711 // constructors/destructors are run. This set just keeps track of
712 // these sections which need to be reversed. It is only changed by
713 // Layout::layout. It should be a private member of Layout, but that
714 // would require layout.h to #include object.h to get the definition
716 static Unordered_set<Section_id, Section_id_hash> ctors_sections_in_init_array;
718 // Return whether OBJECT/SHNDX is a .ctors/.dtors section mapped to a
719 // .init_array/.fini_array section.
722 Layout::is_ctors_in_init_array(Relobj* relobj, unsigned int shndx) const
724 return (ctors_sections_in_init_array.find(Section_id(relobj, shndx))
725 != ctors_sections_in_init_array.end());
728 // Return the output section to use for section NAME with type TYPE
729 // and section flags FLAGS. NAME must be canonicalized in the string
730 // pool, and NAME_KEY is the key. ORDER is where this should appear
731 // in the output sections. IS_RELRO is true for a relro section.
734 Layout::get_output_section(const char* name, Stringpool::Key name_key,
735 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
736 Output_section_order order, bool is_relro)
738 elfcpp::Elf_Word lookup_type = type;
740 // For lookup purposes, treat INIT_ARRAY, FINI_ARRAY, and
741 // PREINIT_ARRAY like PROGBITS. This ensures that we combine
742 // .init_array, .fini_array, and .preinit_array sections by name
743 // whatever their type in the input file. We do this because the
744 // types are not always right in the input files.
745 if (lookup_type == elfcpp::SHT_INIT_ARRAY
746 || lookup_type == elfcpp::SHT_FINI_ARRAY
747 || lookup_type == elfcpp::SHT_PREINIT_ARRAY)
748 lookup_type = elfcpp::SHT_PROGBITS;
750 elfcpp::Elf_Xword lookup_flags = flags;
752 // Ignoring SHF_WRITE and SHF_EXECINSTR here means that we combine
753 // read-write with read-only sections. Some other ELF linkers do
754 // not do this. FIXME: Perhaps there should be an option
756 lookup_flags &= ~(elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
758 const Key key(name_key, std::make_pair(lookup_type, lookup_flags));
759 const std::pair<Key, Output_section*> v(key, NULL);
760 std::pair<Section_name_map::iterator, bool> ins(
761 this->section_name_map_.insert(v));
764 return ins.first->second;
767 // This is the first time we've seen this name/type/flags
768 // combination. For compatibility with the GNU linker, we
769 // combine sections with contents and zero flags with sections
770 // with non-zero flags. This is a workaround for cases where
771 // assembler code forgets to set section flags. FIXME: Perhaps
772 // there should be an option to control this.
773 Output_section* os = NULL;
775 if (lookup_type == elfcpp::SHT_PROGBITS)
779 Output_section* same_name = this->find_output_section(name);
780 if (same_name != NULL
781 && (same_name->type() == elfcpp::SHT_PROGBITS
782 || same_name->type() == elfcpp::SHT_INIT_ARRAY
783 || same_name->type() == elfcpp::SHT_FINI_ARRAY
784 || same_name->type() == elfcpp::SHT_PREINIT_ARRAY)
785 && (same_name->flags() & elfcpp::SHF_TLS) == 0)
788 else if ((flags & elfcpp::SHF_TLS) == 0)
790 elfcpp::Elf_Xword zero_flags = 0;
791 const Key zero_key(name_key, std::make_pair(lookup_type,
793 Section_name_map::iterator p =
794 this->section_name_map_.find(zero_key);
795 if (p != this->section_name_map_.end())
801 os = this->make_output_section(name, type, flags, order, is_relro);
803 ins.first->second = os;
808 // Pick the output section to use for section NAME, in input file
809 // RELOBJ, with type TYPE and flags FLAGS. RELOBJ may be NULL for a
810 // linker created section. IS_INPUT_SECTION is true if we are
811 // choosing an output section for an input section found in a input
812 // file. ORDER is where this section should appear in the output
813 // sections. IS_RELRO is true for a relro section. This will return
814 // NULL if the input section should be discarded.
817 Layout::choose_output_section(const Relobj* relobj, const char* name,
818 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
819 bool is_input_section, Output_section_order order,
822 // We should not see any input sections after we have attached
823 // sections to segments.
824 gold_assert(!is_input_section || !this->sections_are_attached_);
826 // Some flags in the input section should not be automatically
827 // copied to the output section.
828 flags &= ~ (elfcpp::SHF_INFO_LINK
831 | elfcpp::SHF_STRINGS);
833 // We only clear the SHF_LINK_ORDER flag in for
834 // a non-relocatable link.
835 if (!parameters->options().relocatable())
836 flags &= ~elfcpp::SHF_LINK_ORDER;
838 if (this->script_options_->saw_sections_clause())
840 // We are using a SECTIONS clause, so the output section is
841 // chosen based only on the name.
843 Script_sections* ss = this->script_options_->script_sections();
844 const char* file_name = relobj == NULL ? NULL : relobj->name().c_str();
845 Output_section** output_section_slot;
846 Script_sections::Section_type script_section_type;
847 const char* orig_name = name;
848 name = ss->output_section_name(file_name, name, &output_section_slot,
849 &script_section_type);
852 gold_debug(DEBUG_SCRIPT, _("Unable to create output section '%s' "
853 "because it is not allowed by the "
854 "SECTIONS clause of the linker script"),
856 // The SECTIONS clause says to discard this input section.
860 // We can only handle script section types ST_NONE and ST_NOLOAD.
861 switch (script_section_type)
863 case Script_sections::ST_NONE:
865 case Script_sections::ST_NOLOAD:
866 flags &= elfcpp::SHF_ALLOC;
872 // If this is an orphan section--one not mentioned in the linker
873 // script--then OUTPUT_SECTION_SLOT will be NULL, and we do the
874 // default processing below.
876 if (output_section_slot != NULL)
878 if (*output_section_slot != NULL)
880 (*output_section_slot)->update_flags_for_input_section(flags);
881 return *output_section_slot;
884 // We don't put sections found in the linker script into
885 // SECTION_NAME_MAP_. That keeps us from getting confused
886 // if an orphan section is mapped to a section with the same
887 // name as one in the linker script.
889 name = this->namepool_.add(name, false, NULL);
891 Output_section* os = this->make_output_section(name, type, flags,
894 os->set_found_in_sections_clause();
896 // Special handling for NOLOAD sections.
897 if (script_section_type == Script_sections::ST_NOLOAD)
901 // The constructor of Output_section sets addresses of non-ALLOC
902 // sections to 0 by default. We don't want that for NOLOAD
903 // sections even if they have no SHF_ALLOC flag.
904 if ((os->flags() & elfcpp::SHF_ALLOC) == 0
905 && os->is_address_valid())
907 gold_assert(os->address() == 0
908 && !os->is_offset_valid()
909 && !os->is_data_size_valid());
910 os->reset_address_and_file_offset();
914 *output_section_slot = os;
919 // FIXME: Handle SHF_OS_NONCONFORMING somewhere.
921 size_t len = strlen(name);
922 char* uncompressed_name = NULL;
924 // Compressed debug sections should be mapped to the corresponding
925 // uncompressed section.
926 if (is_compressed_debug_section(name))
928 uncompressed_name = new char[len];
929 uncompressed_name[0] = '.';
930 gold_assert(name[0] == '.' && name[1] == 'z');
931 strncpy(&uncompressed_name[1], &name[2], len - 2);
932 uncompressed_name[len - 1] = '\0';
934 name = uncompressed_name;
937 // Turn NAME from the name of the input section into the name of the
940 && !this->script_options_->saw_sections_clause()
941 && !parameters->options().relocatable())
942 name = Layout::output_section_name(relobj, name, &len);
944 Stringpool::Key name_key;
945 name = this->namepool_.add_with_length(name, len, true, &name_key);
947 if (uncompressed_name != NULL)
948 delete[] uncompressed_name;
950 // Find or make the output section. The output section is selected
951 // based on the section name, type, and flags.
952 return this->get_output_section(name, name_key, type, flags, order, is_relro);
955 // For incremental links, record the initial fixed layout of a section
956 // from the base file, and return a pointer to the Output_section.
958 template<int size, bool big_endian>
960 Layout::init_fixed_output_section(const char* name,
961 elfcpp::Shdr<size, big_endian>& shdr)
963 unsigned int sh_type = shdr.get_sh_type();
965 // We preserve the layout of PROGBITS, NOBITS, INIT_ARRAY, FINI_ARRAY,
966 // PRE_INIT_ARRAY, and NOTE sections.
967 // All others will be created from scratch and reallocated.
968 if (!can_incremental_update(sh_type))
971 // If we're generating a .gdb_index section, we need to regenerate
973 if (parameters->options().gdb_index()
974 && sh_type == elfcpp::SHT_PROGBITS
975 && strcmp(name, ".gdb_index") == 0)
978 typename elfcpp::Elf_types<size>::Elf_Addr sh_addr = shdr.get_sh_addr();
979 typename elfcpp::Elf_types<size>::Elf_Off sh_offset = shdr.get_sh_offset();
980 typename elfcpp::Elf_types<size>::Elf_WXword sh_size = shdr.get_sh_size();
981 typename elfcpp::Elf_types<size>::Elf_WXword sh_flags = shdr.get_sh_flags();
982 typename elfcpp::Elf_types<size>::Elf_WXword sh_addralign =
983 shdr.get_sh_addralign();
985 // Make the output section.
986 Stringpool::Key name_key;
987 name = this->namepool_.add(name, true, &name_key);
988 Output_section* os = this->get_output_section(name, name_key, sh_type,
989 sh_flags, ORDER_INVALID, false);
990 os->set_fixed_layout(sh_addr, sh_offset, sh_size, sh_addralign);
991 if (sh_type != elfcpp::SHT_NOBITS)
992 this->free_list_.remove(sh_offset, sh_offset + sh_size);
996 // Return the output section to use for input section SHNDX, with name
997 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
998 // index of a relocation section which applies to this section, or 0
999 // if none, or -1U if more than one. RELOC_TYPE is the type of the
1000 // relocation section if there is one. Set *OFF to the offset of this
1001 // input section without the output section. Return NULL if the
1002 // section should be discarded. Set *OFF to -1 if the section
1003 // contents should not be written directly to the output file, but
1004 // will instead receive special handling.
1006 template<int size, bool big_endian>
1008 Layout::layout(Sized_relobj_file<size, big_endian>* object, unsigned int shndx,
1009 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
1010 unsigned int reloc_shndx, unsigned int, off_t* off)
1014 if (!this->include_section(object, name, shdr))
1017 elfcpp::Elf_Word sh_type = shdr.get_sh_type();
1019 // In a relocatable link a grouped section must not be combined with
1020 // any other sections.
1022 if (parameters->options().relocatable()
1023 && (shdr.get_sh_flags() & elfcpp::SHF_GROUP) != 0)
1025 name = this->namepool_.add(name, true, NULL);
1026 os = this->make_output_section(name, sh_type, shdr.get_sh_flags(),
1027 ORDER_INVALID, false);
1031 os = this->choose_output_section(object, name, sh_type,
1032 shdr.get_sh_flags(), true,
1033 ORDER_INVALID, false);
1038 // By default the GNU linker sorts input sections whose names match
1039 // .ctors.*, .dtors.*, .init_array.*, or .fini_array.*. The
1040 // sections are sorted by name. This is used to implement
1041 // constructor priority ordering. We are compatible. When we put
1042 // .ctor sections in .init_array and .dtor sections in .fini_array,
1043 // we must also sort plain .ctor and .dtor sections.
1044 if (!this->script_options_->saw_sections_clause()
1045 && !parameters->options().relocatable()
1046 && (is_prefix_of(".ctors.", name)
1047 || is_prefix_of(".dtors.", name)
1048 || is_prefix_of(".init_array.", name)
1049 || is_prefix_of(".fini_array.", name)
1050 || (parameters->options().ctors_in_init_array()
1051 && (strcmp(name, ".ctors") == 0
1052 || strcmp(name, ".dtors") == 0))))
1053 os->set_must_sort_attached_input_sections();
1055 // If this is a .ctors or .ctors.* section being mapped to a
1056 // .init_array section, or a .dtors or .dtors.* section being mapped
1057 // to a .fini_array section, we will need to reverse the words if
1058 // there is more than one. Record this section for later. See
1059 // ctors_sections_in_init_array above.
1060 if (!this->script_options_->saw_sections_clause()
1061 && !parameters->options().relocatable()
1062 && shdr.get_sh_size() > size / 8
1063 && (((strcmp(name, ".ctors") == 0
1064 || is_prefix_of(".ctors.", name))
1065 && strcmp(os->name(), ".init_array") == 0)
1066 || ((strcmp(name, ".dtors") == 0
1067 || is_prefix_of(".dtors.", name))
1068 && strcmp(os->name(), ".fini_array") == 0)))
1069 ctors_sections_in_init_array.insert(Section_id(object, shndx));
1071 // FIXME: Handle SHF_LINK_ORDER somewhere.
1073 elfcpp::Elf_Xword orig_flags = os->flags();
1075 *off = os->add_input_section(this, object, shndx, name, shdr, reloc_shndx,
1076 this->script_options_->saw_sections_clause());
1078 // If the flags changed, we may have to change the order.
1079 if ((orig_flags & elfcpp::SHF_ALLOC) != 0)
1081 orig_flags &= (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
1082 elfcpp::Elf_Xword new_flags =
1083 os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR);
1084 if (orig_flags != new_flags)
1085 os->set_order(this->default_section_order(os, false));
1088 this->have_added_input_section_ = true;
1093 // Handle a relocation section when doing a relocatable link.
1095 template<int size, bool big_endian>
1097 Layout::layout_reloc(Sized_relobj_file<size, big_endian>* object,
1099 const elfcpp::Shdr<size, big_endian>& shdr,
1100 Output_section* data_section,
1101 Relocatable_relocs* rr)
1103 gold_assert(parameters->options().relocatable()
1104 || parameters->options().emit_relocs());
1106 int sh_type = shdr.get_sh_type();
1109 if (sh_type == elfcpp::SHT_REL)
1111 else if (sh_type == elfcpp::SHT_RELA)
1115 name += data_section->name();
1117 // In a relocatable link relocs for a grouped section must not be
1118 // combined with other reloc sections.
1120 if (!parameters->options().relocatable()
1121 || (data_section->flags() & elfcpp::SHF_GROUP) == 0)
1122 os = this->choose_output_section(object, name.c_str(), sh_type,
1123 shdr.get_sh_flags(), false,
1124 ORDER_INVALID, false);
1127 const char* n = this->namepool_.add(name.c_str(), true, NULL);
1128 os = this->make_output_section(n, sh_type, shdr.get_sh_flags(),
1129 ORDER_INVALID, false);
1132 os->set_should_link_to_symtab();
1133 os->set_info_section(data_section);
1135 Output_section_data* posd;
1136 if (sh_type == elfcpp::SHT_REL)
1138 os->set_entsize(elfcpp::Elf_sizes<size>::rel_size);
1139 posd = new Output_relocatable_relocs<elfcpp::SHT_REL,
1143 else if (sh_type == elfcpp::SHT_RELA)
1145 os->set_entsize(elfcpp::Elf_sizes<size>::rela_size);
1146 posd = new Output_relocatable_relocs<elfcpp::SHT_RELA,
1153 os->add_output_section_data(posd);
1154 rr->set_output_data(posd);
1159 // Handle a group section when doing a relocatable link.
1161 template<int size, bool big_endian>
1163 Layout::layout_group(Symbol_table* symtab,
1164 Sized_relobj_file<size, big_endian>* object,
1166 const char* group_section_name,
1167 const char* signature,
1168 const elfcpp::Shdr<size, big_endian>& shdr,
1169 elfcpp::Elf_Word flags,
1170 std::vector<unsigned int>* shndxes)
1172 gold_assert(parameters->options().relocatable());
1173 gold_assert(shdr.get_sh_type() == elfcpp::SHT_GROUP);
1174 group_section_name = this->namepool_.add(group_section_name, true, NULL);
1175 Output_section* os = this->make_output_section(group_section_name,
1177 shdr.get_sh_flags(),
1178 ORDER_INVALID, false);
1180 // We need to find a symbol with the signature in the symbol table.
1181 // If we don't find one now, we need to look again later.
1182 Symbol* sym = symtab->lookup(signature, NULL);
1184 os->set_info_symndx(sym);
1187 // Reserve some space to minimize reallocations.
1188 if (this->group_signatures_.empty())
1189 this->group_signatures_.reserve(this->number_of_input_files_ * 16);
1191 // We will wind up using a symbol whose name is the signature.
1192 // So just put the signature in the symbol name pool to save it.
1193 signature = symtab->canonicalize_name(signature);
1194 this->group_signatures_.push_back(Group_signature(os, signature));
1197 os->set_should_link_to_symtab();
1200 section_size_type entry_count =
1201 convert_to_section_size_type(shdr.get_sh_size() / 4);
1202 Output_section_data* posd =
1203 new Output_data_group<size, big_endian>(object, entry_count, flags,
1205 os->add_output_section_data(posd);
1208 // Special GNU handling of sections name .eh_frame. They will
1209 // normally hold exception frame data as defined by the C++ ABI
1210 // (http://codesourcery.com/cxx-abi/).
1212 template<int size, bool big_endian>
1214 Layout::layout_eh_frame(Sized_relobj_file<size, big_endian>* object,
1215 const unsigned char* symbols,
1217 const unsigned char* symbol_names,
1218 off_t symbol_names_size,
1220 const elfcpp::Shdr<size, big_endian>& shdr,
1221 unsigned int reloc_shndx, unsigned int reloc_type,
1224 gold_assert(shdr.get_sh_type() == elfcpp::SHT_PROGBITS
1225 || shdr.get_sh_type() == elfcpp::SHT_X86_64_UNWIND);
1226 gold_assert((shdr.get_sh_flags() & elfcpp::SHF_ALLOC) != 0);
1228 Output_section* os = this->make_eh_frame_section(object);
1232 gold_assert(this->eh_frame_section_ == os);
1234 elfcpp::Elf_Xword orig_flags = os->flags();
1236 if (!parameters->incremental()
1237 && this->eh_frame_data_->add_ehframe_input_section(object,
1246 os->update_flags_for_input_section(shdr.get_sh_flags());
1248 // A writable .eh_frame section is a RELRO section.
1249 if ((orig_flags & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR))
1250 != (os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR)))
1253 os->set_order(ORDER_RELRO);
1256 // We found a .eh_frame section we are going to optimize, so now
1257 // we can add the set of optimized sections to the output
1258 // section. We need to postpone adding this until we've found a
1259 // section we can optimize so that the .eh_frame section in
1260 // crtbegin.o winds up at the start of the output section.
1261 if (!this->added_eh_frame_data_)
1263 os->add_output_section_data(this->eh_frame_data_);
1264 this->added_eh_frame_data_ = true;
1270 // We couldn't handle this .eh_frame section for some reason.
1271 // Add it as a normal section.
1272 bool saw_sections_clause = this->script_options_->saw_sections_clause();
1273 *off = os->add_input_section(this, object, shndx, ".eh_frame", shdr,
1274 reloc_shndx, saw_sections_clause);
1275 this->have_added_input_section_ = true;
1277 if ((orig_flags & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR))
1278 != (os->flags() & (elfcpp::SHF_WRITE | elfcpp::SHF_EXECINSTR)))
1279 os->set_order(this->default_section_order(os, false));
1285 // Create and return the magic .eh_frame section. Create
1286 // .eh_frame_hdr also if appropriate. OBJECT is the object with the
1287 // input .eh_frame section; it may be NULL.
1290 Layout::make_eh_frame_section(const Relobj* object)
1292 // FIXME: On x86_64, this could use SHT_X86_64_UNWIND rather than
1294 Output_section* os = this->choose_output_section(object, ".eh_frame",
1295 elfcpp::SHT_PROGBITS,
1296 elfcpp::SHF_ALLOC, false,
1297 ORDER_EHFRAME, false);
1301 if (this->eh_frame_section_ == NULL)
1303 this->eh_frame_section_ = os;
1304 this->eh_frame_data_ = new Eh_frame();
1306 // For incremental linking, we do not optimize .eh_frame sections
1307 // or create a .eh_frame_hdr section.
1308 if (parameters->options().eh_frame_hdr() && !parameters->incremental())
1310 Output_section* hdr_os =
1311 this->choose_output_section(NULL, ".eh_frame_hdr",
1312 elfcpp::SHT_PROGBITS,
1313 elfcpp::SHF_ALLOC, false,
1314 ORDER_EHFRAME, false);
1318 Eh_frame_hdr* hdr_posd = new Eh_frame_hdr(os,
1319 this->eh_frame_data_);
1320 hdr_os->add_output_section_data(hdr_posd);
1322 hdr_os->set_after_input_sections();
1324 if (!this->script_options_->saw_phdrs_clause())
1326 Output_segment* hdr_oseg;
1327 hdr_oseg = this->make_output_segment(elfcpp::PT_GNU_EH_FRAME,
1329 hdr_oseg->add_output_section_to_nonload(hdr_os,
1333 this->eh_frame_data_->set_eh_frame_hdr(hdr_posd);
1341 // Add an exception frame for a PLT. This is called from target code.
1344 Layout::add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
1345 size_t cie_length, const unsigned char* fde_data,
1348 if (parameters->incremental())
1350 // FIXME: Maybe this could work some day....
1353 Output_section* os = this->make_eh_frame_section(NULL);
1356 this->eh_frame_data_->add_ehframe_for_plt(plt, cie_data, cie_length,
1357 fde_data, fde_length);
1358 if (!this->added_eh_frame_data_)
1360 os->add_output_section_data(this->eh_frame_data_);
1361 this->added_eh_frame_data_ = true;
1365 // Scan a .debug_info or .debug_types section, and add summary
1366 // information to the .gdb_index section.
1368 template<int size, bool big_endian>
1370 Layout::add_to_gdb_index(bool is_type_unit,
1371 Sized_relobj<size, big_endian>* object,
1372 const unsigned char* symbols,
1375 unsigned int reloc_shndx,
1376 unsigned int reloc_type)
1378 if (this->gdb_index_data_ == NULL)
1380 Output_section* os = this->choose_output_section(NULL, ".gdb_index",
1381 elfcpp::SHT_PROGBITS, 0,
1382 false, ORDER_INVALID,
1387 this->gdb_index_data_ = new Gdb_index(os);
1388 os->add_output_section_data(this->gdb_index_data_);
1389 os->set_after_input_sections();
1392 this->gdb_index_data_->scan_debug_info(is_type_unit, object, symbols,
1393 symbols_size, shndx, reloc_shndx,
1397 // Add POSD to an output section using NAME, TYPE, and FLAGS. Return
1398 // the output section.
1401 Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type,
1402 elfcpp::Elf_Xword flags,
1403 Output_section_data* posd,
1404 Output_section_order order, bool is_relro)
1406 Output_section* os = this->choose_output_section(NULL, name, type, flags,
1407 false, order, is_relro);
1409 os->add_output_section_data(posd);
1413 // Map section flags to segment flags.
1416 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags)
1418 elfcpp::Elf_Word ret = elfcpp::PF_R;
1419 if ((flags & elfcpp::SHF_WRITE) != 0)
1420 ret |= elfcpp::PF_W;
1421 if ((flags & elfcpp::SHF_EXECINSTR) != 0)
1422 ret |= elfcpp::PF_X;
1426 // Make a new Output_section, and attach it to segments as
1427 // appropriate. ORDER is the order in which this section should
1428 // appear in the output segment. IS_RELRO is true if this is a relro
1429 // (read-only after relocations) section.
1432 Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
1433 elfcpp::Elf_Xword flags,
1434 Output_section_order order, bool is_relro)
1437 if ((flags & elfcpp::SHF_ALLOC) == 0
1438 && strcmp(parameters->options().compress_debug_sections(), "none") != 0
1439 && is_compressible_debug_section(name))
1440 os = new Output_compressed_section(¶meters->options(), name, type,
1442 else if ((flags & elfcpp::SHF_ALLOC) == 0
1443 && parameters->options().strip_debug_non_line()
1444 && strcmp(".debug_abbrev", name) == 0)
1446 os = this->debug_abbrev_ = new Output_reduced_debug_abbrev_section(
1448 if (this->debug_info_)
1449 this->debug_info_->set_abbreviations(this->debug_abbrev_);
1451 else if ((flags & elfcpp::SHF_ALLOC) == 0
1452 && parameters->options().strip_debug_non_line()
1453 && strcmp(".debug_info", name) == 0)
1455 os = this->debug_info_ = new Output_reduced_debug_info_section(
1457 if (this->debug_abbrev_)
1458 this->debug_info_->set_abbreviations(this->debug_abbrev_);
1462 // Sometimes .init_array*, .preinit_array* and .fini_array* do
1463 // not have correct section types. Force them here.
1464 if (type == elfcpp::SHT_PROGBITS)
1466 if (is_prefix_of(".init_array", name))
1467 type = elfcpp::SHT_INIT_ARRAY;
1468 else if (is_prefix_of(".preinit_array", name))
1469 type = elfcpp::SHT_PREINIT_ARRAY;
1470 else if (is_prefix_of(".fini_array", name))
1471 type = elfcpp::SHT_FINI_ARRAY;
1474 // FIXME: const_cast is ugly.
1475 Target* target = const_cast<Target*>(¶meters->target());
1476 os = target->make_output_section(name, type, flags);
1479 // With -z relro, we have to recognize the special sections by name.
1480 // There is no other way.
1481 bool is_relro_local = false;
1482 if (!this->script_options_->saw_sections_clause()
1483 && parameters->options().relro()
1484 && (flags & elfcpp::SHF_ALLOC) != 0
1485 && (flags & elfcpp::SHF_WRITE) != 0)
1487 if (type == elfcpp::SHT_PROGBITS)
1489 if ((flags & elfcpp::SHF_TLS) != 0)
1491 else if (strcmp(name, ".data.rel.ro") == 0)
1493 else if (strcmp(name, ".data.rel.ro.local") == 0)
1496 is_relro_local = true;
1498 else if (strcmp(name, ".ctors") == 0
1499 || strcmp(name, ".dtors") == 0
1500 || strcmp(name, ".jcr") == 0)
1503 else if (type == elfcpp::SHT_INIT_ARRAY
1504 || type == elfcpp::SHT_FINI_ARRAY
1505 || type == elfcpp::SHT_PREINIT_ARRAY)
1512 if (order == ORDER_INVALID && (flags & elfcpp::SHF_ALLOC) != 0)
1513 order = this->default_section_order(os, is_relro_local);
1515 os->set_order(order);
1517 parameters->target().new_output_section(os);
1519 this->section_list_.push_back(os);
1521 // The GNU linker by default sorts some sections by priority, so we
1522 // do the same. We need to know that this might happen before we
1523 // attach any input sections.
1524 if (!this->script_options_->saw_sections_clause()
1525 && !parameters->options().relocatable()
1526 && (strcmp(name, ".init_array") == 0
1527 || strcmp(name, ".fini_array") == 0
1528 || (!parameters->options().ctors_in_init_array()
1529 && (strcmp(name, ".ctors") == 0
1530 || strcmp(name, ".dtors") == 0))))
1531 os->set_may_sort_attached_input_sections();
1533 // Check for .stab*str sections, as .stab* sections need to link to
1535 if (type == elfcpp::SHT_STRTAB
1536 && !this->have_stabstr_section_
1537 && strncmp(name, ".stab", 5) == 0
1538 && strcmp(name + strlen(name) - 3, "str") == 0)
1539 this->have_stabstr_section_ = true;
1541 // During a full incremental link, we add patch space to most
1542 // PROGBITS and NOBITS sections. Flag those that may be
1543 // arbitrarily padded.
1544 if ((type == elfcpp::SHT_PROGBITS || type == elfcpp::SHT_NOBITS)
1545 && order != ORDER_INTERP
1546 && order != ORDER_INIT
1547 && order != ORDER_PLT
1548 && order != ORDER_FINI
1549 && order != ORDER_RELRO_LAST
1550 && order != ORDER_NON_RELRO_FIRST
1551 && strcmp(name, ".eh_frame") != 0
1552 && strcmp(name, ".ctors") != 0
1553 && strcmp(name, ".dtors") != 0
1554 && strcmp(name, ".jcr") != 0)
1556 os->set_is_patch_space_allowed();
1558 // Certain sections require "holes" to be filled with
1559 // specific fill patterns. These fill patterns may have
1560 // a minimum size, so we must prevent allocations from the
1561 // free list that leave a hole smaller than the minimum.
1562 if (strcmp(name, ".debug_info") == 0)
1563 os->set_free_space_fill(new Output_fill_debug_info(false));
1564 else if (strcmp(name, ".debug_types") == 0)
1565 os->set_free_space_fill(new Output_fill_debug_info(true));
1566 else if (strcmp(name, ".debug_line") == 0)
1567 os->set_free_space_fill(new Output_fill_debug_line());
1570 // If we have already attached the sections to segments, then we
1571 // need to attach this one now. This happens for sections created
1572 // directly by the linker.
1573 if (this->sections_are_attached_)
1574 this->attach_section_to_segment(¶meters->target(), os);
1579 // Return the default order in which a section should be placed in an
1580 // output segment. This function captures a lot of the ideas in
1581 // ld/scripttempl/elf.sc in the GNU linker. Note that the order of a
1582 // linker created section is normally set when the section is created;
1583 // this function is used for input sections.
1585 Output_section_order
1586 Layout::default_section_order(Output_section* os, bool is_relro_local)
1588 gold_assert((os->flags() & elfcpp::SHF_ALLOC) != 0);
1589 bool is_write = (os->flags() & elfcpp::SHF_WRITE) != 0;
1590 bool is_execinstr = (os->flags() & elfcpp::SHF_EXECINSTR) != 0;
1591 bool is_bss = false;
1596 case elfcpp::SHT_PROGBITS:
1598 case elfcpp::SHT_NOBITS:
1601 case elfcpp::SHT_RELA:
1602 case elfcpp::SHT_REL:
1604 return ORDER_DYNAMIC_RELOCS;
1606 case elfcpp::SHT_HASH:
1607 case elfcpp::SHT_DYNAMIC:
1608 case elfcpp::SHT_SHLIB:
1609 case elfcpp::SHT_DYNSYM:
1610 case elfcpp::SHT_GNU_HASH:
1611 case elfcpp::SHT_GNU_verdef:
1612 case elfcpp::SHT_GNU_verneed:
1613 case elfcpp::SHT_GNU_versym:
1615 return ORDER_DYNAMIC_LINKER;
1617 case elfcpp::SHT_NOTE:
1618 return is_write ? ORDER_RW_NOTE : ORDER_RO_NOTE;
1621 if ((os->flags() & elfcpp::SHF_TLS) != 0)
1622 return is_bss ? ORDER_TLS_BSS : ORDER_TLS_DATA;
1624 if (!is_bss && !is_write)
1628 if (strcmp(os->name(), ".init") == 0)
1630 else if (strcmp(os->name(), ".fini") == 0)
1633 return is_execinstr ? ORDER_TEXT : ORDER_READONLY;
1637 return is_relro_local ? ORDER_RELRO_LOCAL : ORDER_RELRO;
1639 if (os->is_small_section())
1640 return is_bss ? ORDER_SMALL_BSS : ORDER_SMALL_DATA;
1641 if (os->is_large_section())
1642 return is_bss ? ORDER_LARGE_BSS : ORDER_LARGE_DATA;
1644 return is_bss ? ORDER_BSS : ORDER_DATA;
1647 // Attach output sections to segments. This is called after we have
1648 // seen all the input sections.
1651 Layout::attach_sections_to_segments(const Target* target)
1653 for (Section_list::iterator p = this->section_list_.begin();
1654 p != this->section_list_.end();
1656 this->attach_section_to_segment(target, *p);
1658 this->sections_are_attached_ = true;
1661 // Attach an output section to a segment.
1664 Layout::attach_section_to_segment(const Target* target, Output_section* os)
1666 if ((os->flags() & elfcpp::SHF_ALLOC) == 0)
1667 this->unattached_section_list_.push_back(os);
1669 this->attach_allocated_section_to_segment(target, os);
1672 // Attach an allocated output section to a segment.
1675 Layout::attach_allocated_section_to_segment(const Target* target,
1678 elfcpp::Elf_Xword flags = os->flags();
1679 gold_assert((flags & elfcpp::SHF_ALLOC) != 0);
1681 if (parameters->options().relocatable())
1684 // If we have a SECTIONS clause, we can't handle the attachment to
1685 // segments until after we've seen all the sections.
1686 if (this->script_options_->saw_sections_clause())
1689 gold_assert(!this->script_options_->saw_phdrs_clause());
1691 // This output section goes into a PT_LOAD segment.
1693 elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags);
1695 // Check for --section-start.
1697 bool is_address_set = parameters->options().section_start(os->name(), &addr);
1699 // In general the only thing we really care about for PT_LOAD
1700 // segments is whether or not they are writable or executable,
1701 // so that is how we search for them.
1702 // Large data sections also go into their own PT_LOAD segment.
1703 // People who need segments sorted on some other basis will
1704 // have to use a linker script.
1706 Segment_list::const_iterator p;
1707 for (p = this->segment_list_.begin();
1708 p != this->segment_list_.end();
1711 if ((*p)->type() != elfcpp::PT_LOAD)
1713 if (!parameters->options().omagic()
1714 && ((*p)->flags() & elfcpp::PF_W) != (seg_flags & elfcpp::PF_W))
1716 if ((target->isolate_execinstr() || parameters->options().rosegment())
1717 && ((*p)->flags() & elfcpp::PF_X) != (seg_flags & elfcpp::PF_X))
1719 // If -Tbss was specified, we need to separate the data and BSS
1721 if (parameters->options().user_set_Tbss())
1723 if ((os->type() == elfcpp::SHT_NOBITS)
1724 == (*p)->has_any_data_sections())
1727 if (os->is_large_data_section() && !(*p)->is_large_data_segment())
1732 if ((*p)->are_addresses_set())
1735 (*p)->add_initial_output_data(os);
1736 (*p)->update_flags_for_output_section(seg_flags);
1737 (*p)->set_addresses(addr, addr);
1741 (*p)->add_output_section_to_load(this, os, seg_flags);
1745 if (p == this->segment_list_.end())
1747 Output_segment* oseg = this->make_output_segment(elfcpp::PT_LOAD,
1749 if (os->is_large_data_section())
1750 oseg->set_is_large_data_segment();
1751 oseg->add_output_section_to_load(this, os, seg_flags);
1753 oseg->set_addresses(addr, addr);
1756 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
1758 if (os->type() == elfcpp::SHT_NOTE)
1760 // See if we already have an equivalent PT_NOTE segment.
1761 for (p = this->segment_list_.begin();
1762 p != segment_list_.end();
1765 if ((*p)->type() == elfcpp::PT_NOTE
1766 && (((*p)->flags() & elfcpp::PF_W)
1767 == (seg_flags & elfcpp::PF_W)))
1769 (*p)->add_output_section_to_nonload(os, seg_flags);
1774 if (p == this->segment_list_.end())
1776 Output_segment* oseg = this->make_output_segment(elfcpp::PT_NOTE,
1778 oseg->add_output_section_to_nonload(os, seg_flags);
1782 // If we see a loadable SHF_TLS section, we create a PT_TLS
1783 // segment. There can only be one such segment.
1784 if ((flags & elfcpp::SHF_TLS) != 0)
1786 if (this->tls_segment_ == NULL)
1787 this->make_output_segment(elfcpp::PT_TLS, seg_flags);
1788 this->tls_segment_->add_output_section_to_nonload(os, seg_flags);
1791 // If -z relro is in effect, and we see a relro section, we create a
1792 // PT_GNU_RELRO segment. There can only be one such segment.
1793 if (os->is_relro() && parameters->options().relro())
1795 gold_assert(seg_flags == (elfcpp::PF_R | elfcpp::PF_W));
1796 if (this->relro_segment_ == NULL)
1797 this->make_output_segment(elfcpp::PT_GNU_RELRO, seg_flags);
1798 this->relro_segment_->add_output_section_to_nonload(os, seg_flags);
1801 // If we see a section named .interp, put it into a PT_INTERP
1802 // segment. This seems broken to me, but this is what GNU ld does,
1803 // and glibc expects it.
1804 if (strcmp(os->name(), ".interp") == 0
1805 && !this->script_options_->saw_phdrs_clause())
1807 if (this->interp_segment_ == NULL)
1808 this->make_output_segment(elfcpp::PT_INTERP, seg_flags);
1810 gold_warning(_("multiple '.interp' sections in input files "
1811 "may cause confusing PT_INTERP segment"));
1812 this->interp_segment_->add_output_section_to_nonload(os, seg_flags);
1816 // Make an output section for a script.
1819 Layout::make_output_section_for_script(
1821 Script_sections::Section_type section_type)
1823 name = this->namepool_.add(name, false, NULL);
1824 elfcpp::Elf_Xword sh_flags = elfcpp::SHF_ALLOC;
1825 if (section_type == Script_sections::ST_NOLOAD)
1827 Output_section* os = this->make_output_section(name, elfcpp::SHT_PROGBITS,
1828 sh_flags, ORDER_INVALID,
1830 os->set_found_in_sections_clause();
1831 if (section_type == Script_sections::ST_NOLOAD)
1832 os->set_is_noload();
1836 // Return the number of segments we expect to see.
1839 Layout::expected_segment_count() const
1841 size_t ret = this->segment_list_.size();
1843 // If we didn't see a SECTIONS clause in a linker script, we should
1844 // already have the complete list of segments. Otherwise we ask the
1845 // SECTIONS clause how many segments it expects, and add in the ones
1846 // we already have (PT_GNU_STACK, PT_GNU_EH_FRAME, etc.)
1848 if (!this->script_options_->saw_sections_clause())
1852 const Script_sections* ss = this->script_options_->script_sections();
1853 return ret + ss->expected_segment_count(this);
1857 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
1858 // is whether we saw a .note.GNU-stack section in the object file.
1859 // GNU_STACK_FLAGS is the section flags. The flags give the
1860 // protection required for stack memory. We record this in an
1861 // executable as a PT_GNU_STACK segment. If an object file does not
1862 // have a .note.GNU-stack segment, we must assume that it is an old
1863 // object. On some targets that will force an executable stack.
1866 Layout::layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags,
1869 if (!seen_gnu_stack)
1871 this->input_without_gnu_stack_note_ = true;
1872 if (parameters->options().warn_execstack()
1873 && parameters->target().is_default_stack_executable())
1874 gold_warning(_("%s: missing .note.GNU-stack section"
1875 " implies executable stack"),
1876 obj->name().c_str());
1880 this->input_with_gnu_stack_note_ = true;
1881 if ((gnu_stack_flags & elfcpp::SHF_EXECINSTR) != 0)
1883 this->input_requires_executable_stack_ = true;
1884 if (parameters->options().warn_execstack()
1885 || parameters->options().is_stack_executable())
1886 gold_warning(_("%s: requires executable stack"),
1887 obj->name().c_str());
1892 // Create automatic note sections.
1895 Layout::create_notes()
1897 this->create_gold_note();
1898 this->create_executable_stack_info();
1899 this->create_build_id();
1902 // Create the dynamic sections which are needed before we read the
1906 Layout::create_initial_dynamic_sections(Symbol_table* symtab)
1908 if (parameters->doing_static_link())
1911 this->dynamic_section_ = this->choose_output_section(NULL, ".dynamic",
1912 elfcpp::SHT_DYNAMIC,
1914 | elfcpp::SHF_WRITE),
1918 // A linker script may discard .dynamic, so check for NULL.
1919 if (this->dynamic_section_ != NULL)
1921 this->dynamic_symbol_ =
1922 symtab->define_in_output_data("_DYNAMIC", NULL,
1923 Symbol_table::PREDEFINED,
1924 this->dynamic_section_, 0, 0,
1925 elfcpp::STT_OBJECT, elfcpp::STB_LOCAL,
1926 elfcpp::STV_HIDDEN, 0, false, false);
1928 this->dynamic_data_ = new Output_data_dynamic(&this->dynpool_);
1930 this->dynamic_section_->add_output_section_data(this->dynamic_data_);
1934 // For each output section whose name can be represented as C symbol,
1935 // define __start and __stop symbols for the section. This is a GNU
1939 Layout::define_section_symbols(Symbol_table* symtab)
1941 for (Section_list::const_iterator p = this->section_list_.begin();
1942 p != this->section_list_.end();
1945 const char* const name = (*p)->name();
1946 if (is_cident(name))
1948 const std::string name_string(name);
1949 const std::string start_name(cident_section_start_prefix
1951 const std::string stop_name(cident_section_stop_prefix
1954 symtab->define_in_output_data(start_name.c_str(),
1956 Symbol_table::PREDEFINED,
1962 elfcpp::STV_DEFAULT,
1964 false, // offset_is_from_end
1965 true); // only_if_ref
1967 symtab->define_in_output_data(stop_name.c_str(),
1969 Symbol_table::PREDEFINED,
1975 elfcpp::STV_DEFAULT,
1977 true, // offset_is_from_end
1978 true); // only_if_ref
1983 // Define symbols for group signatures.
1986 Layout::define_group_signatures(Symbol_table* symtab)
1988 for (Group_signatures::iterator p = this->group_signatures_.begin();
1989 p != this->group_signatures_.end();
1992 Symbol* sym = symtab->lookup(p->signature, NULL);
1994 p->section->set_info_symndx(sym);
1997 // Force the name of the group section to the group
1998 // signature, and use the group's section symbol as the
1999 // signature symbol.
2000 if (strcmp(p->section->name(), p->signature) != 0)
2002 const char* name = this->namepool_.add(p->signature,
2004 p->section->set_name(name);
2006 p->section->set_needs_symtab_index();
2007 p->section->set_info_section_symndx(p->section);
2011 this->group_signatures_.clear();
2014 // Find the first read-only PT_LOAD segment, creating one if
2018 Layout::find_first_load_seg(const Target* target)
2020 Output_segment* best = NULL;
2021 for (Segment_list::const_iterator p = this->segment_list_.begin();
2022 p != this->segment_list_.end();
2025 if ((*p)->type() == elfcpp::PT_LOAD
2026 && ((*p)->flags() & elfcpp::PF_R) != 0
2027 && (parameters->options().omagic()
2028 || ((*p)->flags() & elfcpp::PF_W) == 0)
2029 && (!target->isolate_execinstr()
2030 || ((*p)->flags() & elfcpp::PF_X) == 0))
2032 if (best == NULL || this->segment_precedes(*p, best))
2039 gold_assert(!this->script_options_->saw_phdrs_clause());
2041 Output_segment* load_seg = this->make_output_segment(elfcpp::PT_LOAD,
2046 // Save states of all current output segments. Store saved states
2047 // in SEGMENT_STATES.
2050 Layout::save_segments(Segment_states* segment_states)
2052 for (Segment_list::const_iterator p = this->segment_list_.begin();
2053 p != this->segment_list_.end();
2056 Output_segment* segment = *p;
2058 Output_segment* copy = new Output_segment(*segment);
2059 (*segment_states)[segment] = copy;
2063 // Restore states of output segments and delete any segment not found in
2067 Layout::restore_segments(const Segment_states* segment_states)
2069 // Go through the segment list and remove any segment added in the
2071 this->tls_segment_ = NULL;
2072 this->relro_segment_ = NULL;
2073 Segment_list::iterator list_iter = this->segment_list_.begin();
2074 while (list_iter != this->segment_list_.end())
2076 Output_segment* segment = *list_iter;
2077 Segment_states::const_iterator states_iter =
2078 segment_states->find(segment);
2079 if (states_iter != segment_states->end())
2081 const Output_segment* copy = states_iter->second;
2082 // Shallow copy to restore states.
2085 // Also fix up TLS and RELRO segment pointers as appropriate.
2086 if (segment->type() == elfcpp::PT_TLS)
2087 this->tls_segment_ = segment;
2088 else if (segment->type() == elfcpp::PT_GNU_RELRO)
2089 this->relro_segment_ = segment;
2095 list_iter = this->segment_list_.erase(list_iter);
2096 // This is a segment created during section layout. It should be
2097 // safe to remove it since we should have removed all pointers to it.
2103 // Clean up after relaxation so that sections can be laid out again.
2106 Layout::clean_up_after_relaxation()
2108 // Restore the segments to point state just prior to the relaxation loop.
2109 Script_sections* script_section = this->script_options_->script_sections();
2110 script_section->release_segments();
2111 this->restore_segments(this->segment_states_);
2113 // Reset section addresses and file offsets
2114 for (Section_list::iterator p = this->section_list_.begin();
2115 p != this->section_list_.end();
2118 (*p)->restore_states();
2120 // If an input section changes size because of relaxation,
2121 // we need to adjust the section offsets of all input sections.
2122 // after such a section.
2123 if ((*p)->section_offsets_need_adjustment())
2124 (*p)->adjust_section_offsets();
2126 (*p)->reset_address_and_file_offset();
2129 // Reset special output object address and file offsets.
2130 for (Data_list::iterator p = this->special_output_list_.begin();
2131 p != this->special_output_list_.end();
2133 (*p)->reset_address_and_file_offset();
2135 // A linker script may have created some output section data objects.
2136 // They are useless now.
2137 for (Output_section_data_list::const_iterator p =
2138 this->script_output_section_data_list_.begin();
2139 p != this->script_output_section_data_list_.end();
2142 this->script_output_section_data_list_.clear();
2145 // Prepare for relaxation.
2148 Layout::prepare_for_relaxation()
2150 // Create an relaxation debug check if in debugging mode.
2151 if (is_debugging_enabled(DEBUG_RELAXATION))
2152 this->relaxation_debug_check_ = new Relaxation_debug_check();
2154 // Save segment states.
2155 this->segment_states_ = new Segment_states();
2156 this->save_segments(this->segment_states_);
2158 for(Section_list::const_iterator p = this->section_list_.begin();
2159 p != this->section_list_.end();
2161 (*p)->save_states();
2163 if (is_debugging_enabled(DEBUG_RELAXATION))
2164 this->relaxation_debug_check_->check_output_data_for_reset_values(
2165 this->section_list_, this->special_output_list_);
2167 // Also enable recording of output section data from scripts.
2168 this->record_output_section_data_from_script_ = true;
2171 // Relaxation loop body: If target has no relaxation, this runs only once
2172 // Otherwise, the target relaxation hook is called at the end of
2173 // each iteration. If the hook returns true, it means re-layout of
2174 // section is required.
2176 // The number of segments created by a linking script without a PHDRS
2177 // clause may be affected by section sizes and alignments. There is
2178 // a remote chance that relaxation causes different number of PT_LOAD
2179 // segments are created and sections are attached to different segments.
2180 // Therefore, we always throw away all segments created during section
2181 // layout. In order to be able to restart the section layout, we keep
2182 // a copy of the segment list right before the relaxation loop and use
2183 // that to restore the segments.
2185 // PASS is the current relaxation pass number.
2186 // SYMTAB is a symbol table.
2187 // PLOAD_SEG is the address of a pointer for the load segment.
2188 // PHDR_SEG is a pointer to the PHDR segment.
2189 // SEGMENT_HEADERS points to the output segment header.
2190 // FILE_HEADER points to the output file header.
2191 // PSHNDX is the address to store the output section index.
2194 Layout::relaxation_loop_body(
2197 Symbol_table* symtab,
2198 Output_segment** pload_seg,
2199 Output_segment* phdr_seg,
2200 Output_segment_headers* segment_headers,
2201 Output_file_header* file_header,
2202 unsigned int* pshndx)
2204 // If this is not the first iteration, we need to clean up after
2205 // relaxation so that we can lay out the sections again.
2207 this->clean_up_after_relaxation();
2209 // If there is a SECTIONS clause, put all the input sections into
2210 // the required order.
2211 Output_segment* load_seg;
2212 if (this->script_options_->saw_sections_clause())
2213 load_seg = this->set_section_addresses_from_script(symtab);
2214 else if (parameters->options().relocatable())
2217 load_seg = this->find_first_load_seg(target);
2219 if (parameters->options().oformat_enum()
2220 != General_options::OBJECT_FORMAT_ELF)
2223 // If the user set the address of the text segment, that may not be
2224 // compatible with putting the segment headers and file headers into
2226 if (parameters->options().user_set_Ttext()
2227 && parameters->options().Ttext() % target->common_pagesize() != 0)
2233 gold_assert(phdr_seg == NULL
2235 || this->script_options_->saw_sections_clause());
2237 // If the address of the load segment we found has been set by
2238 // --section-start rather than by a script, then adjust the VMA and
2239 // LMA downward if possible to include the file and section headers.
2240 uint64_t header_gap = 0;
2241 if (load_seg != NULL
2242 && load_seg->are_addresses_set()
2243 && !this->script_options_->saw_sections_clause()
2244 && !parameters->options().relocatable())
2246 file_header->finalize_data_size();
2247 segment_headers->finalize_data_size();
2248 size_t sizeof_headers = (file_header->data_size()
2249 + segment_headers->data_size());
2250 const uint64_t abi_pagesize = target->abi_pagesize();
2251 uint64_t hdr_paddr = load_seg->paddr() - sizeof_headers;
2252 hdr_paddr &= ~(abi_pagesize - 1);
2253 uint64_t subtract = load_seg->paddr() - hdr_paddr;
2254 if (load_seg->paddr() < subtract || load_seg->vaddr() < subtract)
2258 load_seg->set_addresses(load_seg->vaddr() - subtract,
2259 load_seg->paddr() - subtract);
2260 header_gap = subtract - sizeof_headers;
2264 // Lay out the segment headers.
2265 if (!parameters->options().relocatable())
2267 gold_assert(segment_headers != NULL);
2268 if (header_gap != 0 && load_seg != NULL)
2270 Output_data_zero_fill* z = new Output_data_zero_fill(header_gap, 1);
2271 load_seg->add_initial_output_data(z);
2273 if (load_seg != NULL)
2274 load_seg->add_initial_output_data(segment_headers);
2275 if (phdr_seg != NULL)
2276 phdr_seg->add_initial_output_data(segment_headers);
2279 // Lay out the file header.
2280 if (load_seg != NULL)
2281 load_seg->add_initial_output_data(file_header);
2283 if (this->script_options_->saw_phdrs_clause()
2284 && !parameters->options().relocatable())
2286 // Support use of FILEHDRS and PHDRS attachments in a PHDRS
2287 // clause in a linker script.
2288 Script_sections* ss = this->script_options_->script_sections();
2289 ss->put_headers_in_phdrs(file_header, segment_headers);
2292 // We set the output section indexes in set_segment_offsets and
2293 // set_section_indexes.
2296 // Set the file offsets of all the segments, and all the sections
2299 if (!parameters->options().relocatable())
2300 off = this->set_segment_offsets(target, load_seg, pshndx);
2302 off = this->set_relocatable_section_offsets(file_header, pshndx);
2304 // Verify that the dummy relaxation does not change anything.
2305 if (is_debugging_enabled(DEBUG_RELAXATION))
2308 this->relaxation_debug_check_->read_sections(this->section_list_);
2310 this->relaxation_debug_check_->verify_sections(this->section_list_);
2313 *pload_seg = load_seg;
2317 // Search the list of patterns and find the postion of the given section
2318 // name in the output section. If the section name matches a glob
2319 // pattern and a non-glob name, then the non-glob position takes
2320 // precedence. Return 0 if no match is found.
2323 Layout::find_section_order_index(const std::string& section_name)
2325 Unordered_map<std::string, unsigned int>::iterator map_it;
2326 map_it = this->input_section_position_.find(section_name);
2327 if (map_it != this->input_section_position_.end())
2328 return map_it->second;
2330 // Absolute match failed. Linear search the glob patterns.
2331 std::vector<std::string>::iterator it;
2332 for (it = this->input_section_glob_.begin();
2333 it != this->input_section_glob_.end();
2336 if (fnmatch((*it).c_str(), section_name.c_str(), FNM_NOESCAPE) == 0)
2338 map_it = this->input_section_position_.find(*it);
2339 gold_assert(map_it != this->input_section_position_.end());
2340 return map_it->second;
2346 // Read the sequence of input sections from the file specified with
2347 // option --section-ordering-file.
2350 Layout::read_layout_from_file()
2352 const char* filename = parameters->options().section_ordering_file();
2358 gold_fatal(_("unable to open --section-ordering-file file %s: %s"),
2359 filename, strerror(errno));
2361 std::getline(in, line); // this chops off the trailing \n, if any
2362 unsigned int position = 1;
2363 this->set_section_ordering_specified();
2367 if (!line.empty() && line[line.length() - 1] == '\r') // Windows
2368 line.resize(line.length() - 1);
2369 // Ignore comments, beginning with '#'
2372 std::getline(in, line);
2375 this->input_section_position_[line] = position;
2376 // Store all glob patterns in a vector.
2377 if (is_wildcard_string(line.c_str()))
2378 this->input_section_glob_.push_back(line);
2380 std::getline(in, line);
2384 // Finalize the layout. When this is called, we have created all the
2385 // output sections and all the output segments which are based on
2386 // input sections. We have several things to do, and we have to do
2387 // them in the right order, so that we get the right results correctly
2390 // 1) Finalize the list of output segments and create the segment
2393 // 2) Finalize the dynamic symbol table and associated sections.
2395 // 3) Determine the final file offset of all the output segments.
2397 // 4) Determine the final file offset of all the SHF_ALLOC output
2400 // 5) Create the symbol table sections and the section name table
2403 // 6) Finalize the symbol table: set symbol values to their final
2404 // value and make a final determination of which symbols are going
2405 // into the output symbol table.
2407 // 7) Create the section table header.
2409 // 8) Determine the final file offset of all the output sections which
2410 // are not SHF_ALLOC, including the section table header.
2412 // 9) Finalize the ELF file header.
2414 // This function returns the size of the output file.
2417 Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab,
2418 Target* target, const Task* task)
2420 target->finalize_sections(this, input_objects, symtab);
2422 this->count_local_symbols(task, input_objects);
2424 this->link_stabs_sections();
2426 Output_segment* phdr_seg = NULL;
2427 if (!parameters->options().relocatable() && !parameters->doing_static_link())
2429 // There was a dynamic object in the link. We need to create
2430 // some information for the dynamic linker.
2432 // Create the PT_PHDR segment which will hold the program
2434 if (!this->script_options_->saw_phdrs_clause())
2435 phdr_seg = this->make_output_segment(elfcpp::PT_PHDR, elfcpp::PF_R);
2437 // Create the dynamic symbol table, including the hash table.
2438 Output_section* dynstr;
2439 std::vector<Symbol*> dynamic_symbols;
2440 unsigned int local_dynamic_count;
2441 Versions versions(*this->script_options()->version_script_info(),
2443 this->create_dynamic_symtab(input_objects, symtab, &dynstr,
2444 &local_dynamic_count, &dynamic_symbols,
2447 // Create the .interp section to hold the name of the
2448 // interpreter, and put it in a PT_INTERP segment. Don't do it
2449 // if we saw a .interp section in an input file.
2450 if ((!parameters->options().shared()
2451 || parameters->options().dynamic_linker() != NULL)
2452 && this->interp_segment_ == NULL)
2453 this->create_interp(target);
2455 // Finish the .dynamic section to hold the dynamic data, and put
2456 // it in a PT_DYNAMIC segment.
2457 this->finish_dynamic_section(input_objects, symtab);
2459 // We should have added everything we need to the dynamic string
2461 this->dynpool_.set_string_offsets();
2463 // Create the version sections. We can't do this until the
2464 // dynamic string table is complete.
2465 this->create_version_sections(&versions, symtab, local_dynamic_count,
2466 dynamic_symbols, dynstr);
2468 // Set the size of the _DYNAMIC symbol. We can't do this until
2469 // after we call create_version_sections.
2470 this->set_dynamic_symbol_size(symtab);
2473 // Create segment headers.
2474 Output_segment_headers* segment_headers =
2475 (parameters->options().relocatable()
2477 : new Output_segment_headers(this->segment_list_));
2479 // Lay out the file header.
2480 Output_file_header* file_header = new Output_file_header(target, symtab,
2483 this->special_output_list_.push_back(file_header);
2484 if (segment_headers != NULL)
2485 this->special_output_list_.push_back(segment_headers);
2487 // Find approriate places for orphan output sections if we are using
2489 if (this->script_options_->saw_sections_clause())
2490 this->place_orphan_sections_in_script();
2492 Output_segment* load_seg;
2497 // Take a snapshot of the section layout as needed.
2498 if (target->may_relax())
2499 this->prepare_for_relaxation();
2501 // Run the relaxation loop to lay out sections.
2504 off = this->relaxation_loop_body(pass, target, symtab, &load_seg,
2505 phdr_seg, segment_headers, file_header,
2509 while (target->may_relax()
2510 && target->relax(pass, input_objects, symtab, this, task));
2512 // If there is a load segment that contains the file and program headers,
2513 // provide a symbol __ehdr_start pointing there.
2514 // A program can use this to examine itself robustly.
2515 if (load_seg != NULL)
2516 symtab->define_in_output_segment("__ehdr_start", NULL,
2517 Symbol_table::PREDEFINED, load_seg, 0, 0,
2518 elfcpp::STT_NOTYPE, elfcpp::STB_GLOBAL,
2519 elfcpp::STV_DEFAULT, 0,
2520 Symbol::SEGMENT_START, true);
2522 // Set the file offsets of all the non-data sections we've seen so
2523 // far which don't have to wait for the input sections. We need
2524 // this in order to finalize local symbols in non-allocated
2526 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
2528 // Set the section indexes of all unallocated sections seen so far,
2529 // in case any of them are somehow referenced by a symbol.
2530 shndx = this->set_section_indexes(shndx);
2532 // Create the symbol table sections.
2533 this->create_symtab_sections(input_objects, symtab, shndx, &off);
2534 if (!parameters->doing_static_link())
2535 this->assign_local_dynsym_offsets(input_objects);
2537 // Process any symbol assignments from a linker script. This must
2538 // be called after the symbol table has been finalized.
2539 this->script_options_->finalize_symbols(symtab, this);
2541 // Create the incremental inputs sections.
2542 if (this->incremental_inputs_)
2544 this->incremental_inputs_->finalize();
2545 this->create_incremental_info_sections(symtab);
2548 // Create the .shstrtab section.
2549 Output_section* shstrtab_section = this->create_shstrtab();
2551 // Set the file offsets of the rest of the non-data sections which
2552 // don't have to wait for the input sections.
2553 off = this->set_section_offsets(off, BEFORE_INPUT_SECTIONS_PASS);
2555 // Now that all sections have been created, set the section indexes
2556 // for any sections which haven't been done yet.
2557 shndx = this->set_section_indexes(shndx);
2559 // Create the section table header.
2560 this->create_shdrs(shstrtab_section, &off);
2562 // If there are no sections which require postprocessing, we can
2563 // handle the section names now, and avoid a resize later.
2564 if (!this->any_postprocessing_sections_)
2566 off = this->set_section_offsets(off,
2567 POSTPROCESSING_SECTIONS_PASS);
2569 this->set_section_offsets(off,
2570 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
2573 file_header->set_section_info(this->section_headers_, shstrtab_section);
2575 // Now we know exactly where everything goes in the output file
2576 // (except for non-allocated sections which require postprocessing).
2577 Output_data::layout_complete();
2579 this->output_file_size_ = off;
2584 // Create a note header following the format defined in the ELF ABI.
2585 // NAME is the name, NOTE_TYPE is the type, SECTION_NAME is the name
2586 // of the section to create, DESCSZ is the size of the descriptor.
2587 // ALLOCATE is true if the section should be allocated in memory.
2588 // This returns the new note section. It sets *TRAILING_PADDING to
2589 // the number of trailing zero bytes required.
2592 Layout::create_note(const char* name, int note_type,
2593 const char* section_name, size_t descsz,
2594 bool allocate, size_t* trailing_padding)
2596 // Authorities all agree that the values in a .note field should
2597 // be aligned on 4-byte boundaries for 32-bit binaries. However,
2598 // they differ on what the alignment is for 64-bit binaries.
2599 // The GABI says unambiguously they take 8-byte alignment:
2600 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
2601 // Other documentation says alignment should always be 4 bytes:
2602 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
2603 // GNU ld and GNU readelf both support the latter (at least as of
2604 // version 2.16.91), and glibc always generates the latter for
2605 // .note.ABI-tag (as of version 1.6), so that's the one we go with
2607 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
2608 const int size = parameters->target().get_size();
2610 const int size = 32;
2613 // The contents of the .note section.
2614 size_t namesz = strlen(name) + 1;
2615 size_t aligned_namesz = align_address(namesz, size / 8);
2616 size_t aligned_descsz = align_address(descsz, size / 8);
2618 size_t notehdrsz = 3 * (size / 8) + aligned_namesz;
2620 unsigned char* buffer = new unsigned char[notehdrsz];
2621 memset(buffer, 0, notehdrsz);
2623 bool is_big_endian = parameters->target().is_big_endian();
2629 elfcpp::Swap<32, false>::writeval(buffer, namesz);
2630 elfcpp::Swap<32, false>::writeval(buffer + 4, descsz);
2631 elfcpp::Swap<32, false>::writeval(buffer + 8, note_type);
2635 elfcpp::Swap<32, true>::writeval(buffer, namesz);
2636 elfcpp::Swap<32, true>::writeval(buffer + 4, descsz);
2637 elfcpp::Swap<32, true>::writeval(buffer + 8, note_type);
2640 else if (size == 64)
2644 elfcpp::Swap<64, false>::writeval(buffer, namesz);
2645 elfcpp::Swap<64, false>::writeval(buffer + 8, descsz);
2646 elfcpp::Swap<64, false>::writeval(buffer + 16, note_type);
2650 elfcpp::Swap<64, true>::writeval(buffer, namesz);
2651 elfcpp::Swap<64, true>::writeval(buffer + 8, descsz);
2652 elfcpp::Swap<64, true>::writeval(buffer + 16, note_type);
2658 memcpy(buffer + 3 * (size / 8), name, namesz);
2660 elfcpp::Elf_Xword flags = 0;
2661 Output_section_order order = ORDER_INVALID;
2664 flags = elfcpp::SHF_ALLOC;
2665 order = ORDER_RO_NOTE;
2667 Output_section* os = this->choose_output_section(NULL, section_name,
2669 flags, false, order, false);
2673 Output_section_data* posd = new Output_data_const_buffer(buffer, notehdrsz,
2676 os->add_output_section_data(posd);
2678 *trailing_padding = aligned_descsz - descsz;
2683 // For an executable or shared library, create a note to record the
2684 // version of gold used to create the binary.
2687 Layout::create_gold_note()
2689 if (parameters->options().relocatable()
2690 || parameters->incremental_update())
2693 std::string desc = std::string("gold ") + gold::get_version_string();
2695 size_t trailing_padding;
2696 Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_GOLD_VERSION,
2697 ".note.gnu.gold-version", desc.size(),
2698 false, &trailing_padding);
2702 Output_section_data* posd = new Output_data_const(desc, 4);
2703 os->add_output_section_data(posd);
2705 if (trailing_padding > 0)
2707 posd = new Output_data_zero_fill(trailing_padding, 0);
2708 os->add_output_section_data(posd);
2712 // Record whether the stack should be executable. This can be set
2713 // from the command line using the -z execstack or -z noexecstack
2714 // options. Otherwise, if any input file has a .note.GNU-stack
2715 // section with the SHF_EXECINSTR flag set, the stack should be
2716 // executable. Otherwise, if at least one input file a
2717 // .note.GNU-stack section, and some input file has no .note.GNU-stack
2718 // section, we use the target default for whether the stack should be
2719 // executable. Otherwise, we don't generate a stack note. When
2720 // generating a object file, we create a .note.GNU-stack section with
2721 // the appropriate marking. When generating an executable or shared
2722 // library, we create a PT_GNU_STACK segment.
2725 Layout::create_executable_stack_info()
2727 bool is_stack_executable;
2728 if (parameters->options().is_execstack_set())
2729 is_stack_executable = parameters->options().is_stack_executable();
2730 else if (!this->input_with_gnu_stack_note_)
2734 if (this->input_requires_executable_stack_)
2735 is_stack_executable = true;
2736 else if (this->input_without_gnu_stack_note_)
2737 is_stack_executable =
2738 parameters->target().is_default_stack_executable();
2740 is_stack_executable = false;
2743 if (parameters->options().relocatable())
2745 const char* name = this->namepool_.add(".note.GNU-stack", false, NULL);
2746 elfcpp::Elf_Xword flags = 0;
2747 if (is_stack_executable)
2748 flags |= elfcpp::SHF_EXECINSTR;
2749 this->make_output_section(name, elfcpp::SHT_PROGBITS, flags,
2750 ORDER_INVALID, false);
2754 if (this->script_options_->saw_phdrs_clause())
2756 int flags = elfcpp::PF_R | elfcpp::PF_W;
2757 if (is_stack_executable)
2758 flags |= elfcpp::PF_X;
2759 this->make_output_segment(elfcpp::PT_GNU_STACK, flags);
2763 // If --build-id was used, set up the build ID note.
2766 Layout::create_build_id()
2768 if (!parameters->options().user_set_build_id())
2771 const char* style = parameters->options().build_id();
2772 if (strcmp(style, "none") == 0)
2775 // Set DESCSZ to the size of the note descriptor. When possible,
2776 // set DESC to the note descriptor contents.
2779 if (strcmp(style, "md5") == 0)
2781 else if (strcmp(style, "sha1") == 0)
2783 else if (strcmp(style, "uuid") == 0)
2785 const size_t uuidsz = 128 / 8;
2787 char buffer[uuidsz];
2788 memset(buffer, 0, uuidsz);
2790 int descriptor = open_descriptor(-1, "/dev/urandom", O_RDONLY);
2792 gold_error(_("--build-id=uuid failed: could not open /dev/urandom: %s"),
2796 ssize_t got = ::read(descriptor, buffer, uuidsz);
2797 release_descriptor(descriptor, true);
2799 gold_error(_("/dev/urandom: read failed: %s"), strerror(errno));
2800 else if (static_cast<size_t>(got) != uuidsz)
2801 gold_error(_("/dev/urandom: expected %zu bytes, got %zd bytes"),
2805 desc.assign(buffer, uuidsz);
2808 else if (strncmp(style, "0x", 2) == 0)
2811 const char* p = style + 2;
2814 if (hex_p(p[0]) && hex_p(p[1]))
2816 char c = (hex_value(p[0]) << 4) | hex_value(p[1]);
2820 else if (*p == '-' || *p == ':')
2823 gold_fatal(_("--build-id argument '%s' not a valid hex number"),
2826 descsz = desc.size();
2829 gold_fatal(_("unrecognized --build-id argument '%s'"), style);
2832 size_t trailing_padding;
2833 Output_section* os = this->create_note("GNU", elfcpp::NT_GNU_BUILD_ID,
2834 ".note.gnu.build-id", descsz, true,
2841 // We know the value already, so we fill it in now.
2842 gold_assert(desc.size() == descsz);
2844 Output_section_data* posd = new Output_data_const(desc, 4);
2845 os->add_output_section_data(posd);
2847 if (trailing_padding != 0)
2849 posd = new Output_data_zero_fill(trailing_padding, 0);
2850 os->add_output_section_data(posd);
2855 // We need to compute a checksum after we have completed the
2857 gold_assert(trailing_padding == 0);
2858 this->build_id_note_ = new Output_data_zero_fill(descsz, 4);
2859 os->add_output_section_data(this->build_id_note_);
2863 // If we have both .stabXX and .stabXXstr sections, then the sh_link
2864 // field of the former should point to the latter. I'm not sure who
2865 // started this, but the GNU linker does it, and some tools depend
2869 Layout::link_stabs_sections()
2871 if (!this->have_stabstr_section_)
2874 for (Section_list::iterator p = this->section_list_.begin();
2875 p != this->section_list_.end();
2878 if ((*p)->type() != elfcpp::SHT_STRTAB)
2881 const char* name = (*p)->name();
2882 if (strncmp(name, ".stab", 5) != 0)
2885 size_t len = strlen(name);
2886 if (strcmp(name + len - 3, "str") != 0)
2889 std::string stab_name(name, len - 3);
2890 Output_section* stab_sec;
2891 stab_sec = this->find_output_section(stab_name.c_str());
2892 if (stab_sec != NULL)
2893 stab_sec->set_link_section(*p);
2897 // Create .gnu_incremental_inputs and related sections needed
2898 // for the next run of incremental linking to check what has changed.
2901 Layout::create_incremental_info_sections(Symbol_table* symtab)
2903 Incremental_inputs* incr = this->incremental_inputs_;
2905 gold_assert(incr != NULL);
2907 // Create the .gnu_incremental_inputs, _symtab, and _relocs input sections.
2908 incr->create_data_sections(symtab);
2910 // Add the .gnu_incremental_inputs section.
2911 const char* incremental_inputs_name =
2912 this->namepool_.add(".gnu_incremental_inputs", false, NULL);
2913 Output_section* incremental_inputs_os =
2914 this->make_output_section(incremental_inputs_name,
2915 elfcpp::SHT_GNU_INCREMENTAL_INPUTS, 0,
2916 ORDER_INVALID, false);
2917 incremental_inputs_os->add_output_section_data(incr->inputs_section());
2919 // Add the .gnu_incremental_symtab section.
2920 const char* incremental_symtab_name =
2921 this->namepool_.add(".gnu_incremental_symtab", false, NULL);
2922 Output_section* incremental_symtab_os =
2923 this->make_output_section(incremental_symtab_name,
2924 elfcpp::SHT_GNU_INCREMENTAL_SYMTAB, 0,
2925 ORDER_INVALID, false);
2926 incremental_symtab_os->add_output_section_data(incr->symtab_section());
2927 incremental_symtab_os->set_entsize(4);
2929 // Add the .gnu_incremental_relocs section.
2930 const char* incremental_relocs_name =
2931 this->namepool_.add(".gnu_incremental_relocs", false, NULL);
2932 Output_section* incremental_relocs_os =
2933 this->make_output_section(incremental_relocs_name,
2934 elfcpp::SHT_GNU_INCREMENTAL_RELOCS, 0,
2935 ORDER_INVALID, false);
2936 incremental_relocs_os->add_output_section_data(incr->relocs_section());
2937 incremental_relocs_os->set_entsize(incr->relocs_entsize());
2939 // Add the .gnu_incremental_got_plt section.
2940 const char* incremental_got_plt_name =
2941 this->namepool_.add(".gnu_incremental_got_plt", false, NULL);
2942 Output_section* incremental_got_plt_os =
2943 this->make_output_section(incremental_got_plt_name,
2944 elfcpp::SHT_GNU_INCREMENTAL_GOT_PLT, 0,
2945 ORDER_INVALID, false);
2946 incremental_got_plt_os->add_output_section_data(incr->got_plt_section());
2948 // Add the .gnu_incremental_strtab section.
2949 const char* incremental_strtab_name =
2950 this->namepool_.add(".gnu_incremental_strtab", false, NULL);
2951 Output_section* incremental_strtab_os = this->make_output_section(incremental_strtab_name,
2952 elfcpp::SHT_STRTAB, 0,
2953 ORDER_INVALID, false);
2954 Output_data_strtab* strtab_data =
2955 new Output_data_strtab(incr->get_stringpool());
2956 incremental_strtab_os->add_output_section_data(strtab_data);
2958 incremental_inputs_os->set_after_input_sections();
2959 incremental_symtab_os->set_after_input_sections();
2960 incremental_relocs_os->set_after_input_sections();
2961 incremental_got_plt_os->set_after_input_sections();
2963 incremental_inputs_os->set_link_section(incremental_strtab_os);
2964 incremental_symtab_os->set_link_section(incremental_inputs_os);
2965 incremental_relocs_os->set_link_section(incremental_inputs_os);
2966 incremental_got_plt_os->set_link_section(incremental_inputs_os);
2969 // Return whether SEG1 should be before SEG2 in the output file. This
2970 // is based entirely on the segment type and flags. When this is
2971 // called the segment addresses have normally not yet been set.
2974 Layout::segment_precedes(const Output_segment* seg1,
2975 const Output_segment* seg2)
2977 elfcpp::Elf_Word type1 = seg1->type();
2978 elfcpp::Elf_Word type2 = seg2->type();
2980 // The single PT_PHDR segment is required to precede any loadable
2981 // segment. We simply make it always first.
2982 if (type1 == elfcpp::PT_PHDR)
2984 gold_assert(type2 != elfcpp::PT_PHDR);
2987 if (type2 == elfcpp::PT_PHDR)
2990 // The single PT_INTERP segment is required to precede any loadable
2991 // segment. We simply make it always second.
2992 if (type1 == elfcpp::PT_INTERP)
2994 gold_assert(type2 != elfcpp::PT_INTERP);
2997 if (type2 == elfcpp::PT_INTERP)
3000 // We then put PT_LOAD segments before any other segments.
3001 if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD)
3003 if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD)
3006 // We put the PT_TLS segment last except for the PT_GNU_RELRO
3007 // segment, because that is where the dynamic linker expects to find
3008 // it (this is just for efficiency; other positions would also work
3010 if (type1 == elfcpp::PT_TLS
3011 && type2 != elfcpp::PT_TLS
3012 && type2 != elfcpp::PT_GNU_RELRO)
3014 if (type2 == elfcpp::PT_TLS
3015 && type1 != elfcpp::PT_TLS
3016 && type1 != elfcpp::PT_GNU_RELRO)
3019 // We put the PT_GNU_RELRO segment last, because that is where the
3020 // dynamic linker expects to find it (as with PT_TLS, this is just
3022 if (type1 == elfcpp::PT_GNU_RELRO && type2 != elfcpp::PT_GNU_RELRO)
3024 if (type2 == elfcpp::PT_GNU_RELRO && type1 != elfcpp::PT_GNU_RELRO)
3027 const elfcpp::Elf_Word flags1 = seg1->flags();
3028 const elfcpp::Elf_Word flags2 = seg2->flags();
3030 // The order of non-PT_LOAD segments is unimportant. We simply sort
3031 // by the numeric segment type and flags values. There should not
3032 // be more than one segment with the same type and flags.
3033 if (type1 != elfcpp::PT_LOAD)
3036 return type1 < type2;
3037 gold_assert(flags1 != flags2);
3038 return flags1 < flags2;
3041 // If the addresses are set already, sort by load address.
3042 if (seg1->are_addresses_set())
3044 if (!seg2->are_addresses_set())
3047 unsigned int section_count1 = seg1->output_section_count();
3048 unsigned int section_count2 = seg2->output_section_count();
3049 if (section_count1 == 0 && section_count2 > 0)
3051 if (section_count1 > 0 && section_count2 == 0)
3054 uint64_t paddr1 = (seg1->are_addresses_set()
3056 : seg1->first_section_load_address());
3057 uint64_t paddr2 = (seg2->are_addresses_set()
3059 : seg2->first_section_load_address());
3061 if (paddr1 != paddr2)
3062 return paddr1 < paddr2;
3064 else if (seg2->are_addresses_set())
3067 // A segment which holds large data comes after a segment which does
3068 // not hold large data.
3069 if (seg1->is_large_data_segment())
3071 if (!seg2->is_large_data_segment())
3074 else if (seg2->is_large_data_segment())
3077 // Otherwise, we sort PT_LOAD segments based on the flags. Readonly
3078 // segments come before writable segments. Then writable segments
3079 // with data come before writable segments without data. Then
3080 // executable segments come before non-executable segments. Then
3081 // the unlikely case of a non-readable segment comes before the
3082 // normal case of a readable segment. If there are multiple
3083 // segments with the same type and flags, we require that the
3084 // address be set, and we sort by virtual address and then physical
3086 if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W))
3087 return (flags1 & elfcpp::PF_W) == 0;
3088 if ((flags1 & elfcpp::PF_W) != 0
3089 && seg1->has_any_data_sections() != seg2->has_any_data_sections())
3090 return seg1->has_any_data_sections();
3091 if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X))
3092 return (flags1 & elfcpp::PF_X) != 0;
3093 if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R))
3094 return (flags1 & elfcpp::PF_R) == 0;
3096 // We shouldn't get here--we shouldn't create segments which we
3097 // can't distinguish. Unless of course we are using a weird linker
3098 // script or overlapping --section-start options.
3099 gold_assert(this->script_options_->saw_phdrs_clause()
3100 || parameters->options().any_section_start());
3104 // Increase OFF so that it is congruent to ADDR modulo ABI_PAGESIZE.
3107 align_file_offset(off_t off, uint64_t addr, uint64_t abi_pagesize)
3109 uint64_t unsigned_off = off;
3110 uint64_t aligned_off = ((unsigned_off & ~(abi_pagesize - 1))
3111 | (addr & (abi_pagesize - 1)));
3112 if (aligned_off < unsigned_off)
3113 aligned_off += abi_pagesize;
3117 // Set the file offsets of all the segments, and all the sections they
3118 // contain. They have all been created. LOAD_SEG must be be laid out
3119 // first. Return the offset of the data to follow.
3122 Layout::set_segment_offsets(const Target* target, Output_segment* load_seg,
3123 unsigned int* pshndx)
3125 // Sort them into the final order. We use a stable sort so that we
3126 // don't randomize the order of indistinguishable segments created
3127 // by linker scripts.
3128 std::stable_sort(this->segment_list_.begin(), this->segment_list_.end(),
3129 Layout::Compare_segments(this));
3131 // Find the PT_LOAD segments, and set their addresses and offsets
3132 // and their section's addresses and offsets.
3133 uint64_t start_addr;
3134 if (parameters->options().user_set_Ttext())
3135 start_addr = parameters->options().Ttext();
3136 else if (parameters->options().output_is_position_independent())
3139 start_addr = target->default_text_segment_address();
3141 uint64_t addr = start_addr;
3144 // If LOAD_SEG is NULL, then the file header and segment headers
3145 // will not be loadable. But they still need to be at offset 0 in
3146 // the file. Set their offsets now.
3147 if (load_seg == NULL)
3149 for (Data_list::iterator p = this->special_output_list_.begin();
3150 p != this->special_output_list_.end();
3153 off = align_address(off, (*p)->addralign());
3154 (*p)->set_address_and_file_offset(0, off);
3155 off += (*p)->data_size();
3159 unsigned int increase_relro = this->increase_relro_;
3160 if (this->script_options_->saw_sections_clause())
3163 const bool check_sections = parameters->options().check_sections();
3164 Output_segment* last_load_segment = NULL;
3166 unsigned int shndx_begin = *pshndx;
3167 unsigned int shndx_load_seg = *pshndx;
3169 for (Segment_list::iterator p = this->segment_list_.begin();
3170 p != this->segment_list_.end();
3173 if ((*p)->type() == elfcpp::PT_LOAD)
3175 if (target->isolate_execinstr())
3177 // When we hit the segment that should contain the
3178 // file headers, reset the file offset so we place
3179 // it and subsequent segments appropriately.
3180 // We'll fix up the preceding segments below.
3188 shndx_load_seg = *pshndx;
3194 // Verify that the file headers fall into the first segment.
3195 if (load_seg != NULL && load_seg != *p)
3200 bool are_addresses_set = (*p)->are_addresses_set();
3201 if (are_addresses_set)
3203 // When it comes to setting file offsets, we care about
3204 // the physical address.
3205 addr = (*p)->paddr();
3207 else if (parameters->options().user_set_Ttext()
3208 && ((*p)->flags() & elfcpp::PF_W) == 0)
3210 are_addresses_set = true;
3212 else if (parameters->options().user_set_Tdata()
3213 && ((*p)->flags() & elfcpp::PF_W) != 0
3214 && (!parameters->options().user_set_Tbss()
3215 || (*p)->has_any_data_sections()))
3217 addr = parameters->options().Tdata();
3218 are_addresses_set = true;
3220 else if (parameters->options().user_set_Tbss()
3221 && ((*p)->flags() & elfcpp::PF_W) != 0
3222 && !(*p)->has_any_data_sections())
3224 addr = parameters->options().Tbss();
3225 are_addresses_set = true;
3228 uint64_t orig_addr = addr;
3229 uint64_t orig_off = off;
3231 uint64_t aligned_addr = 0;
3232 uint64_t abi_pagesize = target->abi_pagesize();
3233 uint64_t common_pagesize = target->common_pagesize();
3235 if (!parameters->options().nmagic()
3236 && !parameters->options().omagic())
3237 (*p)->set_minimum_p_align(common_pagesize);
3239 if (!are_addresses_set)
3241 // Skip the address forward one page, maintaining the same
3242 // position within the page. This lets us store both segments
3243 // overlapping on a single page in the file, but the loader will
3244 // put them on different pages in memory. We will revisit this
3245 // decision once we know the size of the segment.
3247 addr = align_address(addr, (*p)->maximum_alignment());
3248 aligned_addr = addr;
3252 // This is the segment that will contain the file
3253 // headers, so its offset will have to be exactly zero.
3254 gold_assert(orig_off == 0);
3256 // If the target wants a fixed minimum distance from the
3257 // text segment to the read-only segment, move up now.
3258 uint64_t min_addr = start_addr + target->rosegment_gap();
3259 if (addr < min_addr)
3262 // But this is not the first segment! To make its
3263 // address congruent with its offset, that address better
3264 // be aligned to the ABI-mandated page size.
3265 addr = align_address(addr, abi_pagesize);
3266 aligned_addr = addr;
3270 if ((addr & (abi_pagesize - 1)) != 0)
3271 addr = addr + abi_pagesize;
3273 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
3277 if (!parameters->options().nmagic()
3278 && !parameters->options().omagic())
3279 off = align_file_offset(off, addr, abi_pagesize);
3282 // This is -N or -n with a section script which prevents
3283 // us from using a load segment. We need to ensure that
3284 // the file offset is aligned to the alignment of the
3285 // segment. This is because the linker script
3286 // implicitly assumed a zero offset. If we don't align
3287 // here, then the alignment of the sections in the
3288 // linker script may not match the alignment of the
3289 // sections in the set_section_addresses call below,
3290 // causing an error about dot moving backward.
3291 off = align_address(off, (*p)->maximum_alignment());
3294 unsigned int shndx_hold = *pshndx;
3295 bool has_relro = false;
3296 uint64_t new_addr = (*p)->set_section_addresses(this, false, addr,
3301 // Now that we know the size of this segment, we may be able
3302 // to save a page in memory, at the cost of wasting some
3303 // file space, by instead aligning to the start of a new
3304 // page. Here we use the real machine page size rather than
3305 // the ABI mandated page size. If the segment has been
3306 // aligned so that the relro data ends at a page boundary,
3307 // we do not try to realign it.
3309 if (!are_addresses_set
3311 && aligned_addr != addr
3312 && !parameters->incremental())
3314 uint64_t first_off = (common_pagesize
3316 & (common_pagesize - 1)));
3317 uint64_t last_off = new_addr & (common_pagesize - 1);
3320 && ((aligned_addr & ~ (common_pagesize - 1))
3321 != (new_addr & ~ (common_pagesize - 1)))
3322 && first_off + last_off <= common_pagesize)
3324 *pshndx = shndx_hold;
3325 addr = align_address(aligned_addr, common_pagesize);
3326 addr = align_address(addr, (*p)->maximum_alignment());
3327 off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1));
3328 off = align_file_offset(off, addr, abi_pagesize);
3330 increase_relro = this->increase_relro_;
3331 if (this->script_options_->saw_sections_clause())
3335 new_addr = (*p)->set_section_addresses(this, true, addr,
3344 // Implement --check-sections. We know that the segments
3345 // are sorted by LMA.
3346 if (check_sections && last_load_segment != NULL)
3348 gold_assert(last_load_segment->paddr() <= (*p)->paddr());
3349 if (last_load_segment->paddr() + last_load_segment->memsz()
3352 unsigned long long lb1 = last_load_segment->paddr();
3353 unsigned long long le1 = lb1 + last_load_segment->memsz();
3354 unsigned long long lb2 = (*p)->paddr();
3355 unsigned long long le2 = lb2 + (*p)->memsz();
3356 gold_error(_("load segment overlap [0x%llx -> 0x%llx] and "
3357 "[0x%llx -> 0x%llx]"),
3358 lb1, le1, lb2, le2);
3361 last_load_segment = *p;
3365 if (load_seg != NULL && target->isolate_execinstr())
3367 // Process the early segments again, setting their file offsets
3368 // so they land after the segments starting at LOAD_SEG.
3369 off = align_file_offset(off, 0, target->abi_pagesize());
3371 for (Segment_list::iterator p = this->segment_list_.begin();
3375 if ((*p)->type() == elfcpp::PT_LOAD)
3377 // We repeat the whole job of assigning addresses and
3378 // offsets, but we really only want to change the offsets and
3379 // must ensure that the addresses all come out the same as
3380 // they did the first time through.
3381 bool has_relro = false;
3382 const uint64_t old_addr = (*p)->vaddr();
3383 const uint64_t old_end = old_addr + (*p)->memsz();
3384 uint64_t new_addr = (*p)->set_section_addresses(this, true,
3390 gold_assert(new_addr == old_end);
3394 gold_assert(shndx_begin == shndx_load_seg);
3397 // Handle the non-PT_LOAD segments, setting their offsets from their
3398 // section's offsets.
3399 for (Segment_list::iterator p = this->segment_list_.begin();
3400 p != this->segment_list_.end();
3403 if ((*p)->type() != elfcpp::PT_LOAD)
3404 (*p)->set_offset((*p)->type() == elfcpp::PT_GNU_RELRO
3409 // Set the TLS offsets for each section in the PT_TLS segment.
3410 if (this->tls_segment_ != NULL)
3411 this->tls_segment_->set_tls_offsets();
3416 // Set the offsets of all the allocated sections when doing a
3417 // relocatable link. This does the same jobs as set_segment_offsets,
3418 // only for a relocatable link.
3421 Layout::set_relocatable_section_offsets(Output_data* file_header,
3422 unsigned int* pshndx)
3426 file_header->set_address_and_file_offset(0, 0);
3427 off += file_header->data_size();
3429 for (Section_list::iterator p = this->section_list_.begin();
3430 p != this->section_list_.end();
3433 // We skip unallocated sections here, except that group sections
3434 // have to come first.
3435 if (((*p)->flags() & elfcpp::SHF_ALLOC) == 0
3436 && (*p)->type() != elfcpp::SHT_GROUP)
3439 off = align_address(off, (*p)->addralign());
3441 // The linker script might have set the address.
3442 if (!(*p)->is_address_valid())
3443 (*p)->set_address(0);
3444 (*p)->set_file_offset(off);
3445 (*p)->finalize_data_size();
3446 off += (*p)->data_size();
3448 (*p)->set_out_shndx(*pshndx);
3455 // Set the file offset of all the sections not associated with a
3459 Layout::set_section_offsets(off_t off, Layout::Section_offset_pass pass)
3461 off_t startoff = off;
3464 for (Section_list::iterator p = this->unattached_section_list_.begin();
3465 p != this->unattached_section_list_.end();
3468 // The symtab section is handled in create_symtab_sections.
3469 if (*p == this->symtab_section_)
3472 // If we've already set the data size, don't set it again.
3473 if ((*p)->is_offset_valid() && (*p)->is_data_size_valid())
3476 if (pass == BEFORE_INPUT_SECTIONS_PASS
3477 && (*p)->requires_postprocessing())
3479 (*p)->create_postprocessing_buffer();
3480 this->any_postprocessing_sections_ = true;
3483 if (pass == BEFORE_INPUT_SECTIONS_PASS
3484 && (*p)->after_input_sections())
3486 else if (pass == POSTPROCESSING_SECTIONS_PASS
3487 && (!(*p)->after_input_sections()
3488 || (*p)->type() == elfcpp::SHT_STRTAB))
3490 else if (pass == STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
3491 && (!(*p)->after_input_sections()
3492 || (*p)->type() != elfcpp::SHT_STRTAB))
3495 if (!parameters->incremental_update())
3497 off = align_address(off, (*p)->addralign());
3498 (*p)->set_file_offset(off);
3499 (*p)->finalize_data_size();
3503 // Incremental update: allocate file space from free list.
3504 (*p)->pre_finalize_data_size();
3505 off_t current_size = (*p)->current_data_size();
3506 off = this->allocate(current_size, (*p)->addralign(), startoff);
3509 if (is_debugging_enabled(DEBUG_INCREMENTAL))
3510 this->free_list_.dump();
3511 gold_assert((*p)->output_section() != NULL);
3512 gold_fallback(_("out of patch space for section %s; "
3513 "relink with --incremental-full"),
3514 (*p)->output_section()->name());
3516 (*p)->set_file_offset(off);
3517 (*p)->finalize_data_size();
3518 if ((*p)->data_size() > current_size)
3520 gold_assert((*p)->output_section() != NULL);
3521 gold_fallback(_("%s: section changed size; "
3522 "relink with --incremental-full"),
3523 (*p)->output_section()->name());
3525 gold_debug(DEBUG_INCREMENTAL,
3526 "set_section_offsets: %08lx %08lx %s",
3527 static_cast<long>(off),
3528 static_cast<long>((*p)->data_size()),
3529 ((*p)->output_section() != NULL
3530 ? (*p)->output_section()->name() : "(special)"));
3533 off += (*p)->data_size();
3537 // At this point the name must be set.
3538 if (pass != STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS)
3539 this->namepool_.add((*p)->name(), false, NULL);
3544 // Set the section indexes of all the sections not associated with a
3548 Layout::set_section_indexes(unsigned int shndx)
3550 for (Section_list::iterator p = this->unattached_section_list_.begin();
3551 p != this->unattached_section_list_.end();
3554 if (!(*p)->has_out_shndx())
3556 (*p)->set_out_shndx(shndx);
3563 // Set the section addresses according to the linker script. This is
3564 // only called when we see a SECTIONS clause. This returns the
3565 // program segment which should hold the file header and segment
3566 // headers, if any. It will return NULL if they should not be in a
3570 Layout::set_section_addresses_from_script(Symbol_table* symtab)
3572 Script_sections* ss = this->script_options_->script_sections();
3573 gold_assert(ss->saw_sections_clause());
3574 return this->script_options_->set_section_addresses(symtab, this);
3577 // Place the orphan sections in the linker script.
3580 Layout::place_orphan_sections_in_script()
3582 Script_sections* ss = this->script_options_->script_sections();
3583 gold_assert(ss->saw_sections_clause());
3585 // Place each orphaned output section in the script.
3586 for (Section_list::iterator p = this->section_list_.begin();
3587 p != this->section_list_.end();
3590 if (!(*p)->found_in_sections_clause())
3591 ss->place_orphan(*p);
3595 // Count the local symbols in the regular symbol table and the dynamic
3596 // symbol table, and build the respective string pools.
3599 Layout::count_local_symbols(const Task* task,
3600 const Input_objects* input_objects)
3602 // First, figure out an upper bound on the number of symbols we'll
3603 // be inserting into each pool. This helps us create the pools with
3604 // the right size, to avoid unnecessary hashtable resizing.
3605 unsigned int symbol_count = 0;
3606 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3607 p != input_objects->relobj_end();
3609 symbol_count += (*p)->local_symbol_count();
3611 // Go from "upper bound" to "estimate." We overcount for two
3612 // reasons: we double-count symbols that occur in more than one
3613 // object file, and we count symbols that are dropped from the
3614 // output. Add it all together and assume we overcount by 100%.
3617 // We assume all symbols will go into both the sympool and dynpool.
3618 this->sympool_.reserve(symbol_count);
3619 this->dynpool_.reserve(symbol_count);
3621 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3622 p != input_objects->relobj_end();
3625 Task_lock_obj<Object> tlo(task, *p);
3626 (*p)->count_local_symbols(&this->sympool_, &this->dynpool_);
3630 // Create the symbol table sections. Here we also set the final
3631 // values of the symbols. At this point all the loadable sections are
3632 // fully laid out. SHNUM is the number of sections so far.
3635 Layout::create_symtab_sections(const Input_objects* input_objects,
3636 Symbol_table* symtab,
3642 if (parameters->target().get_size() == 32)
3644 symsize = elfcpp::Elf_sizes<32>::sym_size;
3647 else if (parameters->target().get_size() == 64)
3649 symsize = elfcpp::Elf_sizes<64>::sym_size;
3655 // Compute file offsets relative to the start of the symtab section.
3658 // Save space for the dummy symbol at the start of the section. We
3659 // never bother to write this out--it will just be left as zero.
3661 unsigned int local_symbol_index = 1;
3663 // Add STT_SECTION symbols for each Output section which needs one.
3664 for (Section_list::iterator p = this->section_list_.begin();
3665 p != this->section_list_.end();
3668 if (!(*p)->needs_symtab_index())
3669 (*p)->set_symtab_index(-1U);
3672 (*p)->set_symtab_index(local_symbol_index);
3673 ++local_symbol_index;
3678 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3679 p != input_objects->relobj_end();
3682 unsigned int index = (*p)->finalize_local_symbols(local_symbol_index,
3684 off += (index - local_symbol_index) * symsize;
3685 local_symbol_index = index;
3688 unsigned int local_symcount = local_symbol_index;
3689 gold_assert(static_cast<off_t>(local_symcount * symsize) == off);
3692 size_t dyn_global_index;
3694 if (this->dynsym_section_ == NULL)
3697 dyn_global_index = 0;
3702 dyn_global_index = this->dynsym_section_->info();
3703 off_t locsize = dyn_global_index * this->dynsym_section_->entsize();
3704 dynoff = this->dynsym_section_->offset() + locsize;
3705 dyncount = (this->dynsym_section_->data_size() - locsize) / symsize;
3706 gold_assert(static_cast<off_t>(dyncount * symsize)
3707 == this->dynsym_section_->data_size() - locsize);
3710 off_t global_off = off;
3711 off = symtab->finalize(off, dynoff, dyn_global_index, dyncount,
3712 &this->sympool_, &local_symcount);
3714 if (!parameters->options().strip_all())
3716 this->sympool_.set_string_offsets();
3718 const char* symtab_name = this->namepool_.add(".symtab", false, NULL);
3719 Output_section* osymtab = this->make_output_section(symtab_name,
3723 this->symtab_section_ = osymtab;
3725 Output_section_data* pos = new Output_data_fixed_space(off, align,
3727 osymtab->add_output_section_data(pos);
3729 // We generate a .symtab_shndx section if we have more than
3730 // SHN_LORESERVE sections. Technically it is possible that we
3731 // don't need one, because it is possible that there are no
3732 // symbols in any of sections with indexes larger than
3733 // SHN_LORESERVE. That is probably unusual, though, and it is
3734 // easier to always create one than to compute section indexes
3735 // twice (once here, once when writing out the symbols).
3736 if (shnum >= elfcpp::SHN_LORESERVE)
3738 const char* symtab_xindex_name = this->namepool_.add(".symtab_shndx",
3740 Output_section* osymtab_xindex =
3741 this->make_output_section(symtab_xindex_name,
3742 elfcpp::SHT_SYMTAB_SHNDX, 0,
3743 ORDER_INVALID, false);
3745 size_t symcount = off / symsize;
3746 this->symtab_xindex_ = new Output_symtab_xindex(symcount);
3748 osymtab_xindex->add_output_section_data(this->symtab_xindex_);
3750 osymtab_xindex->set_link_section(osymtab);
3751 osymtab_xindex->set_addralign(4);
3752 osymtab_xindex->set_entsize(4);
3754 osymtab_xindex->set_after_input_sections();
3756 // This tells the driver code to wait until the symbol table
3757 // has written out before writing out the postprocessing
3758 // sections, including the .symtab_shndx section.
3759 this->any_postprocessing_sections_ = true;
3762 const char* strtab_name = this->namepool_.add(".strtab", false, NULL);
3763 Output_section* ostrtab = this->make_output_section(strtab_name,
3768 Output_section_data* pstr = new Output_data_strtab(&this->sympool_);
3769 ostrtab->add_output_section_data(pstr);
3772 if (!parameters->incremental_update())
3773 symtab_off = align_address(*poff, align);
3776 symtab_off = this->allocate(off, align, *poff);
3778 gold_fallback(_("out of patch space for symbol table; "
3779 "relink with --incremental-full"));
3780 gold_debug(DEBUG_INCREMENTAL,
3781 "create_symtab_sections: %08lx %08lx .symtab",
3782 static_cast<long>(symtab_off),
3783 static_cast<long>(off));
3786 symtab->set_file_offset(symtab_off + global_off);
3787 osymtab->set_file_offset(symtab_off);
3788 osymtab->finalize_data_size();
3789 osymtab->set_link_section(ostrtab);
3790 osymtab->set_info(local_symcount);
3791 osymtab->set_entsize(symsize);
3793 if (symtab_off + off > *poff)
3794 *poff = symtab_off + off;
3798 // Create the .shstrtab section, which holds the names of the
3799 // sections. At the time this is called, we have created all the
3800 // output sections except .shstrtab itself.
3803 Layout::create_shstrtab()
3805 // FIXME: We don't need to create a .shstrtab section if we are
3806 // stripping everything.
3808 const char* name = this->namepool_.add(".shstrtab", false, NULL);
3810 Output_section* os = this->make_output_section(name, elfcpp::SHT_STRTAB, 0,
3811 ORDER_INVALID, false);
3813 if (strcmp(parameters->options().compress_debug_sections(), "none") != 0)
3815 // We can't write out this section until we've set all the
3816 // section names, and we don't set the names of compressed
3817 // output sections until relocations are complete. FIXME: With
3818 // the current names we use, this is unnecessary.
3819 os->set_after_input_sections();
3822 Output_section_data* posd = new Output_data_strtab(&this->namepool_);
3823 os->add_output_section_data(posd);
3828 // Create the section headers. SIZE is 32 or 64. OFF is the file
3832 Layout::create_shdrs(const Output_section* shstrtab_section, off_t* poff)
3834 Output_section_headers* oshdrs;
3835 oshdrs = new Output_section_headers(this,
3836 &this->segment_list_,
3837 &this->section_list_,
3838 &this->unattached_section_list_,
3842 if (!parameters->incremental_update())
3843 off = align_address(*poff, oshdrs->addralign());
3846 oshdrs->pre_finalize_data_size();
3847 off = this->allocate(oshdrs->data_size(), oshdrs->addralign(), *poff);
3849 gold_fallback(_("out of patch space for section header table; "
3850 "relink with --incremental-full"));
3851 gold_debug(DEBUG_INCREMENTAL,
3852 "create_shdrs: %08lx %08lx (section header table)",
3853 static_cast<long>(off),
3854 static_cast<long>(off + oshdrs->data_size()));
3856 oshdrs->set_address_and_file_offset(0, off);
3857 off += oshdrs->data_size();
3860 this->section_headers_ = oshdrs;
3863 // Count the allocated sections.
3866 Layout::allocated_output_section_count() const
3868 size_t section_count = 0;
3869 for (Segment_list::const_iterator p = this->segment_list_.begin();
3870 p != this->segment_list_.end();
3872 section_count += (*p)->output_section_count();
3873 return section_count;
3876 // Create the dynamic symbol table.
3879 Layout::create_dynamic_symtab(const Input_objects* input_objects,
3880 Symbol_table* symtab,
3881 Output_section** pdynstr,
3882 unsigned int* plocal_dynamic_count,
3883 std::vector<Symbol*>* pdynamic_symbols,
3884 Versions* pversions)
3886 // Count all the symbols in the dynamic symbol table, and set the
3887 // dynamic symbol indexes.
3889 // Skip symbol 0, which is always all zeroes.
3890 unsigned int index = 1;
3892 // Add STT_SECTION symbols for each Output section which needs one.
3893 for (Section_list::iterator p = this->section_list_.begin();
3894 p != this->section_list_.end();
3897 if (!(*p)->needs_dynsym_index())
3898 (*p)->set_dynsym_index(-1U);
3901 (*p)->set_dynsym_index(index);
3906 // Count the local symbols that need to go in the dynamic symbol table,
3907 // and set the dynamic symbol indexes.
3908 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
3909 p != input_objects->relobj_end();
3912 unsigned int new_index = (*p)->set_local_dynsym_indexes(index);
3916 unsigned int local_symcount = index;
3917 *plocal_dynamic_count = local_symcount;
3919 index = symtab->set_dynsym_indexes(index, pdynamic_symbols,
3920 &this->dynpool_, pversions);
3924 const int size = parameters->target().get_size();
3927 symsize = elfcpp::Elf_sizes<32>::sym_size;
3930 else if (size == 64)
3932 symsize = elfcpp::Elf_sizes<64>::sym_size;
3938 // Create the dynamic symbol table section.
3940 Output_section* dynsym = this->choose_output_section(NULL, ".dynsym",
3944 ORDER_DYNAMIC_LINKER,
3947 // Check for NULL as a linker script may discard .dynsym.
3950 Output_section_data* odata = new Output_data_fixed_space(index * symsize,
3953 dynsym->add_output_section_data(odata);
3955 dynsym->set_info(local_symcount);
3956 dynsym->set_entsize(symsize);
3957 dynsym->set_addralign(align);
3959 this->dynsym_section_ = dynsym;
3962 Output_data_dynamic* const odyn = this->dynamic_data_;
3965 odyn->add_section_address(elfcpp::DT_SYMTAB, dynsym);
3966 odyn->add_constant(elfcpp::DT_SYMENT, symsize);
3969 // If there are more than SHN_LORESERVE allocated sections, we
3970 // create a .dynsym_shndx section. It is possible that we don't
3971 // need one, because it is possible that there are no dynamic
3972 // symbols in any of the sections with indexes larger than
3973 // SHN_LORESERVE. This is probably unusual, though, and at this
3974 // time we don't know the actual section indexes so it is
3975 // inconvenient to check.
3976 if (this->allocated_output_section_count() >= elfcpp::SHN_LORESERVE)
3978 Output_section* dynsym_xindex =
3979 this->choose_output_section(NULL, ".dynsym_shndx",
3980 elfcpp::SHT_SYMTAB_SHNDX,
3982 false, ORDER_DYNAMIC_LINKER, false);
3984 if (dynsym_xindex != NULL)
3986 this->dynsym_xindex_ = new Output_symtab_xindex(index);
3988 dynsym_xindex->add_output_section_data(this->dynsym_xindex_);
3990 dynsym_xindex->set_link_section(dynsym);
3991 dynsym_xindex->set_addralign(4);
3992 dynsym_xindex->set_entsize(4);
3994 dynsym_xindex->set_after_input_sections();
3996 // This tells the driver code to wait until the symbol table
3997 // has written out before writing out the postprocessing
3998 // sections, including the .dynsym_shndx section.
3999 this->any_postprocessing_sections_ = true;
4003 // Create the dynamic string table section.
4005 Output_section* dynstr = this->choose_output_section(NULL, ".dynstr",
4009 ORDER_DYNAMIC_LINKER,
4014 Output_section_data* strdata = new Output_data_strtab(&this->dynpool_);
4015 dynstr->add_output_section_data(strdata);
4018 dynsym->set_link_section(dynstr);
4019 if (this->dynamic_section_ != NULL)
4020 this->dynamic_section_->set_link_section(dynstr);
4024 odyn->add_section_address(elfcpp::DT_STRTAB, dynstr);
4025 odyn->add_section_size(elfcpp::DT_STRSZ, dynstr);
4031 // Create the hash tables.
4033 if (strcmp(parameters->options().hash_style(), "sysv") == 0
4034 || strcmp(parameters->options().hash_style(), "both") == 0)
4036 unsigned char* phash;
4037 unsigned int hashlen;
4038 Dynobj::create_elf_hash_table(*pdynamic_symbols, local_symcount,
4041 Output_section* hashsec =
4042 this->choose_output_section(NULL, ".hash", elfcpp::SHT_HASH,
4043 elfcpp::SHF_ALLOC, false,
4044 ORDER_DYNAMIC_LINKER, false);
4046 Output_section_data* hashdata = new Output_data_const_buffer(phash,
4050 if (hashsec != NULL && hashdata != NULL)
4051 hashsec->add_output_section_data(hashdata);
4053 if (hashsec != NULL)
4056 hashsec->set_link_section(dynsym);
4057 hashsec->set_entsize(4);
4061 odyn->add_section_address(elfcpp::DT_HASH, hashsec);
4064 if (strcmp(parameters->options().hash_style(), "gnu") == 0
4065 || strcmp(parameters->options().hash_style(), "both") == 0)
4067 unsigned char* phash;
4068 unsigned int hashlen;
4069 Dynobj::create_gnu_hash_table(*pdynamic_symbols, local_symcount,
4072 Output_section* hashsec =
4073 this->choose_output_section(NULL, ".gnu.hash", elfcpp::SHT_GNU_HASH,
4074 elfcpp::SHF_ALLOC, false,
4075 ORDER_DYNAMIC_LINKER, false);
4077 Output_section_data* hashdata = new Output_data_const_buffer(phash,
4081 if (hashsec != NULL && hashdata != NULL)
4082 hashsec->add_output_section_data(hashdata);
4084 if (hashsec != NULL)
4087 hashsec->set_link_section(dynsym);
4089 // For a 64-bit target, the entries in .gnu.hash do not have
4090 // a uniform size, so we only set the entry size for a
4092 if (parameters->target().get_size() == 32)
4093 hashsec->set_entsize(4);
4096 odyn->add_section_address(elfcpp::DT_GNU_HASH, hashsec);
4101 // Assign offsets to each local portion of the dynamic symbol table.
4104 Layout::assign_local_dynsym_offsets(const Input_objects* input_objects)
4106 Output_section* dynsym = this->dynsym_section_;
4110 off_t off = dynsym->offset();
4112 // Skip the dummy symbol at the start of the section.
4113 off += dynsym->entsize();
4115 for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
4116 p != input_objects->relobj_end();
4119 unsigned int count = (*p)->set_local_dynsym_offset(off);
4120 off += count * dynsym->entsize();
4124 // Create the version sections.
4127 Layout::create_version_sections(const Versions* versions,
4128 const Symbol_table* symtab,
4129 unsigned int local_symcount,
4130 const std::vector<Symbol*>& dynamic_symbols,
4131 const Output_section* dynstr)
4133 if (!versions->any_defs() && !versions->any_needs())
4136 switch (parameters->size_and_endianness())
4138 #ifdef HAVE_TARGET_32_LITTLE
4139 case Parameters::TARGET_32_LITTLE:
4140 this->sized_create_version_sections<32, false>(versions, symtab,
4142 dynamic_symbols, dynstr);
4145 #ifdef HAVE_TARGET_32_BIG
4146 case Parameters::TARGET_32_BIG:
4147 this->sized_create_version_sections<32, true>(versions, symtab,
4149 dynamic_symbols, dynstr);
4152 #ifdef HAVE_TARGET_64_LITTLE
4153 case Parameters::TARGET_64_LITTLE:
4154 this->sized_create_version_sections<64, false>(versions, symtab,
4156 dynamic_symbols, dynstr);
4159 #ifdef HAVE_TARGET_64_BIG
4160 case Parameters::TARGET_64_BIG:
4161 this->sized_create_version_sections<64, true>(versions, symtab,
4163 dynamic_symbols, dynstr);
4171 // Create the version sections, sized version.
4173 template<int size, bool big_endian>
4175 Layout::sized_create_version_sections(
4176 const Versions* versions,
4177 const Symbol_table* symtab,
4178 unsigned int local_symcount,
4179 const std::vector<Symbol*>& dynamic_symbols,
4180 const Output_section* dynstr)
4182 Output_section* vsec = this->choose_output_section(NULL, ".gnu.version",
4183 elfcpp::SHT_GNU_versym,
4186 ORDER_DYNAMIC_LINKER,
4189 // Check for NULL since a linker script may discard this section.
4192 unsigned char* vbuf;
4194 versions->symbol_section_contents<size, big_endian>(symtab,
4200 Output_section_data* vdata = new Output_data_const_buffer(vbuf, vsize, 2,
4203 vsec->add_output_section_data(vdata);
4204 vsec->set_entsize(2);
4205 vsec->set_link_section(this->dynsym_section_);
4208 Output_data_dynamic* const odyn = this->dynamic_data_;
4209 if (odyn != NULL && vsec != NULL)
4210 odyn->add_section_address(elfcpp::DT_VERSYM, vsec);
4212 if (versions->any_defs())
4214 Output_section* vdsec;
4215 vdsec = this->choose_output_section(NULL, ".gnu.version_d",
4216 elfcpp::SHT_GNU_verdef,
4218 false, ORDER_DYNAMIC_LINKER, false);
4222 unsigned char* vdbuf;
4223 unsigned int vdsize;
4224 unsigned int vdentries;
4225 versions->def_section_contents<size, big_endian>(&this->dynpool_,
4229 Output_section_data* vddata =
4230 new Output_data_const_buffer(vdbuf, vdsize, 4, "** version defs");
4232 vdsec->add_output_section_data(vddata);
4233 vdsec->set_link_section(dynstr);
4234 vdsec->set_info(vdentries);
4238 odyn->add_section_address(elfcpp::DT_VERDEF, vdsec);
4239 odyn->add_constant(elfcpp::DT_VERDEFNUM, vdentries);
4244 if (versions->any_needs())
4246 Output_section* vnsec;
4247 vnsec = this->choose_output_section(NULL, ".gnu.version_r",
4248 elfcpp::SHT_GNU_verneed,
4250 false, ORDER_DYNAMIC_LINKER, false);
4254 unsigned char* vnbuf;
4255 unsigned int vnsize;
4256 unsigned int vnentries;
4257 versions->need_section_contents<size, big_endian>(&this->dynpool_,
4261 Output_section_data* vndata =
4262 new Output_data_const_buffer(vnbuf, vnsize, 4, "** version refs");
4264 vnsec->add_output_section_data(vndata);
4265 vnsec->set_link_section(dynstr);
4266 vnsec->set_info(vnentries);
4270 odyn->add_section_address(elfcpp::DT_VERNEED, vnsec);
4271 odyn->add_constant(elfcpp::DT_VERNEEDNUM, vnentries);
4277 // Create the .interp section and PT_INTERP segment.
4280 Layout::create_interp(const Target* target)
4282 gold_assert(this->interp_segment_ == NULL);
4284 const char* interp = parameters->options().dynamic_linker();
4287 interp = target->dynamic_linker();
4288 gold_assert(interp != NULL);
4291 size_t len = strlen(interp) + 1;
4293 Output_section_data* odata = new Output_data_const(interp, len, 1);
4295 Output_section* osec = this->choose_output_section(NULL, ".interp",
4296 elfcpp::SHT_PROGBITS,
4298 false, ORDER_INTERP,
4301 osec->add_output_section_data(odata);
4304 // Add dynamic tags for the PLT and the dynamic relocs. This is
4305 // called by the target-specific code. This does nothing if not doing
4308 // USE_REL is true for REL relocs rather than RELA relocs.
4310 // If PLT_GOT is not NULL, then DT_PLTGOT points to it.
4312 // If PLT_REL is not NULL, it is used for DT_PLTRELSZ, and DT_JMPREL,
4313 // and we also set DT_PLTREL. We use PLT_REL's output section, since
4314 // some targets have multiple reloc sections in PLT_REL.
4316 // If DYN_REL is not NULL, it is used for DT_REL/DT_RELA,
4317 // DT_RELSZ/DT_RELASZ, DT_RELENT/DT_RELAENT. Again we use the output
4320 // If ADD_DEBUG is true, we add a DT_DEBUG entry when generating an
4324 Layout::add_target_dynamic_tags(bool use_rel, const Output_data* plt_got,
4325 const Output_data* plt_rel,
4326 const Output_data_reloc_generic* dyn_rel,
4327 bool add_debug, bool dynrel_includes_plt)
4329 Output_data_dynamic* odyn = this->dynamic_data_;
4333 if (plt_got != NULL && plt_got->output_section() != NULL)
4334 odyn->add_section_address(elfcpp::DT_PLTGOT, plt_got);
4336 if (plt_rel != NULL && plt_rel->output_section() != NULL)
4338 odyn->add_section_size(elfcpp::DT_PLTRELSZ, plt_rel->output_section());
4339 odyn->add_section_address(elfcpp::DT_JMPREL, plt_rel->output_section());
4340 odyn->add_constant(elfcpp::DT_PLTREL,
4341 use_rel ? elfcpp::DT_REL : elfcpp::DT_RELA);
4344 if ((dyn_rel != NULL && dyn_rel->output_section() != NULL)
4345 || (dynrel_includes_plt
4347 && plt_rel->output_section() != NULL))
4349 bool have_dyn_rel = dyn_rel != NULL && dyn_rel->output_section() != NULL;
4350 bool have_plt_rel = plt_rel != NULL && plt_rel->output_section() != NULL;
4351 odyn->add_section_address(use_rel ? elfcpp::DT_REL : elfcpp::DT_RELA,
4353 ? dyn_rel->output_section()
4354 : plt_rel->output_section()));
4355 elfcpp::DT size_tag = use_rel ? elfcpp::DT_RELSZ : elfcpp::DT_RELASZ;
4356 if (have_dyn_rel && have_plt_rel && dynrel_includes_plt)
4357 odyn->add_section_size(size_tag,
4358 dyn_rel->output_section(),
4359 plt_rel->output_section());
4360 else if (have_dyn_rel)
4361 odyn->add_section_size(size_tag, dyn_rel->output_section());
4363 odyn->add_section_size(size_tag, plt_rel->output_section());
4364 const int size = parameters->target().get_size();
4369 rel_tag = elfcpp::DT_RELENT;
4371 rel_size = Reloc_types<elfcpp::SHT_REL, 32, false>::reloc_size;
4372 else if (size == 64)
4373 rel_size = Reloc_types<elfcpp::SHT_REL, 64, false>::reloc_size;
4379 rel_tag = elfcpp::DT_RELAENT;
4381 rel_size = Reloc_types<elfcpp::SHT_RELA, 32, false>::reloc_size;
4382 else if (size == 64)
4383 rel_size = Reloc_types<elfcpp::SHT_RELA, 64, false>::reloc_size;
4387 odyn->add_constant(rel_tag, rel_size);
4389 if (parameters->options().combreloc() && have_dyn_rel)
4391 size_t c = dyn_rel->relative_reloc_count();
4393 odyn->add_constant((use_rel
4394 ? elfcpp::DT_RELCOUNT
4395 : elfcpp::DT_RELACOUNT),
4400 if (add_debug && !parameters->options().shared())
4402 // The value of the DT_DEBUG tag is filled in by the dynamic
4403 // linker at run time, and used by the debugger.
4404 odyn->add_constant(elfcpp::DT_DEBUG, 0);
4408 // Finish the .dynamic section and PT_DYNAMIC segment.
4411 Layout::finish_dynamic_section(const Input_objects* input_objects,
4412 const Symbol_table* symtab)
4414 if (!this->script_options_->saw_phdrs_clause()
4415 && this->dynamic_section_ != NULL)
4417 Output_segment* oseg = this->make_output_segment(elfcpp::PT_DYNAMIC,
4420 oseg->add_output_section_to_nonload(this->dynamic_section_,
4421 elfcpp::PF_R | elfcpp::PF_W);
4424 Output_data_dynamic* const odyn = this->dynamic_data_;
4428 for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
4429 p != input_objects->dynobj_end();
4432 if (!(*p)->is_needed() && (*p)->as_needed())
4434 // This dynamic object was linked with --as-needed, but it
4439 odyn->add_string(elfcpp::DT_NEEDED, (*p)->soname());
4442 if (parameters->options().shared())
4444 const char* soname = parameters->options().soname();
4446 odyn->add_string(elfcpp::DT_SONAME, soname);
4449 Symbol* sym = symtab->lookup(parameters->options().init());
4450 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
4451 odyn->add_symbol(elfcpp::DT_INIT, sym);
4453 sym = symtab->lookup(parameters->options().fini());
4454 if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
4455 odyn->add_symbol(elfcpp::DT_FINI, sym);
4457 // Look for .init_array, .preinit_array and .fini_array by checking
4459 for(Layout::Section_list::const_iterator p = this->section_list_.begin();
4460 p != this->section_list_.end();
4462 switch((*p)->type())
4464 case elfcpp::SHT_FINI_ARRAY:
4465 odyn->add_section_address(elfcpp::DT_FINI_ARRAY, *p);
4466 odyn->add_section_size(elfcpp::DT_FINI_ARRAYSZ, *p);
4468 case elfcpp::SHT_INIT_ARRAY:
4469 odyn->add_section_address(elfcpp::DT_INIT_ARRAY, *p);
4470 odyn->add_section_size(elfcpp::DT_INIT_ARRAYSZ, *p);
4472 case elfcpp::SHT_PREINIT_ARRAY:
4473 odyn->add_section_address(elfcpp::DT_PREINIT_ARRAY, *p);
4474 odyn->add_section_size(elfcpp::DT_PREINIT_ARRAYSZ, *p);
4480 // Add a DT_RPATH entry if needed.
4481 const General_options::Dir_list& rpath(parameters->options().rpath());
4484 std::string rpath_val;
4485 for (General_options::Dir_list::const_iterator p = rpath.begin();
4489 if (rpath_val.empty())
4490 rpath_val = p->name();
4493 // Eliminate duplicates.
4494 General_options::Dir_list::const_iterator q;
4495 for (q = rpath.begin(); q != p; ++q)
4496 if (q->name() == p->name())
4501 rpath_val += p->name();
4506 odyn->add_string(elfcpp::DT_RPATH, rpath_val);
4507 if (parameters->options().enable_new_dtags())
4508 odyn->add_string(elfcpp::DT_RUNPATH, rpath_val);
4511 // Look for text segments that have dynamic relocations.
4512 bool have_textrel = false;
4513 if (!this->script_options_->saw_sections_clause())
4515 for (Segment_list::const_iterator p = this->segment_list_.begin();
4516 p != this->segment_list_.end();
4519 if ((*p)->type() == elfcpp::PT_LOAD
4520 && ((*p)->flags() & elfcpp::PF_W) == 0
4521 && (*p)->has_dynamic_reloc())
4523 have_textrel = true;
4530 // We don't know the section -> segment mapping, so we are
4531 // conservative and just look for readonly sections with
4532 // relocations. If those sections wind up in writable segments,
4533 // then we have created an unnecessary DT_TEXTREL entry.
4534 for (Section_list::const_iterator p = this->section_list_.begin();
4535 p != this->section_list_.end();
4538 if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0
4539 && ((*p)->flags() & elfcpp::SHF_WRITE) == 0
4540 && (*p)->has_dynamic_reloc())
4542 have_textrel = true;
4548 if (parameters->options().filter() != NULL)
4549 odyn->add_string(elfcpp::DT_FILTER, parameters->options().filter());
4550 if (parameters->options().any_auxiliary())
4552 for (options::String_set::const_iterator p =
4553 parameters->options().auxiliary_begin();
4554 p != parameters->options().auxiliary_end();
4556 odyn->add_string(elfcpp::DT_AUXILIARY, *p);
4559 // Add a DT_FLAGS entry if necessary.
4560 unsigned int flags = 0;
4563 // Add a DT_TEXTREL for compatibility with older loaders.
4564 odyn->add_constant(elfcpp::DT_TEXTREL, 0);
4565 flags |= elfcpp::DF_TEXTREL;
4567 if (parameters->options().text())
4568 gold_error(_("read-only segment has dynamic relocations"));
4569 else if (parameters->options().warn_shared_textrel()
4570 && parameters->options().shared())
4571 gold_warning(_("shared library text segment is not shareable"));
4573 if (parameters->options().shared() && this->has_static_tls())
4574 flags |= elfcpp::DF_STATIC_TLS;
4575 if (parameters->options().origin())
4576 flags |= elfcpp::DF_ORIGIN;
4577 if (parameters->options().Bsymbolic())
4579 flags |= elfcpp::DF_SYMBOLIC;
4580 // Add DT_SYMBOLIC for compatibility with older loaders.
4581 odyn->add_constant(elfcpp::DT_SYMBOLIC, 0);
4583 if (parameters->options().now())
4584 flags |= elfcpp::DF_BIND_NOW;
4586 odyn->add_constant(elfcpp::DT_FLAGS, flags);
4589 if (parameters->options().initfirst())
4590 flags |= elfcpp::DF_1_INITFIRST;
4591 if (parameters->options().interpose())
4592 flags |= elfcpp::DF_1_INTERPOSE;
4593 if (parameters->options().loadfltr())
4594 flags |= elfcpp::DF_1_LOADFLTR;
4595 if (parameters->options().nodefaultlib())
4596 flags |= elfcpp::DF_1_NODEFLIB;
4597 if (parameters->options().nodelete())
4598 flags |= elfcpp::DF_1_NODELETE;
4599 if (parameters->options().nodlopen())
4600 flags |= elfcpp::DF_1_NOOPEN;
4601 if (parameters->options().nodump())
4602 flags |= elfcpp::DF_1_NODUMP;
4603 if (!parameters->options().shared())
4604 flags &= ~(elfcpp::DF_1_INITFIRST
4605 | elfcpp::DF_1_NODELETE
4606 | elfcpp::DF_1_NOOPEN);
4607 if (parameters->options().origin())
4608 flags |= elfcpp::DF_1_ORIGIN;
4609 if (parameters->options().now())
4610 flags |= elfcpp::DF_1_NOW;
4611 if (parameters->options().Bgroup())
4612 flags |= elfcpp::DF_1_GROUP;
4614 odyn->add_constant(elfcpp::DT_FLAGS_1, flags);
4617 // Set the size of the _DYNAMIC symbol table to be the size of the
4621 Layout::set_dynamic_symbol_size(const Symbol_table* symtab)
4623 Output_data_dynamic* const odyn = this->dynamic_data_;
4626 odyn->finalize_data_size();
4627 if (this->dynamic_symbol_ == NULL)
4629 off_t data_size = odyn->data_size();
4630 const int size = parameters->target().get_size();
4632 symtab->get_sized_symbol<32>(this->dynamic_symbol_)->set_symsize(data_size);
4633 else if (size == 64)
4634 symtab->get_sized_symbol<64>(this->dynamic_symbol_)->set_symsize(data_size);
4639 // The mapping of input section name prefixes to output section names.
4640 // In some cases one prefix is itself a prefix of another prefix; in
4641 // such a case the longer prefix must come first. These prefixes are
4642 // based on the GNU linker default ELF linker script.
4644 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
4645 #define MAPPING_INIT_EXACT(f, t) { f, 0, t, sizeof(t) - 1 }
4646 const Layout::Section_name_mapping Layout::section_name_mapping[] =
4648 MAPPING_INIT(".text.", ".text"),
4649 MAPPING_INIT(".rodata.", ".rodata"),
4650 MAPPING_INIT(".data.rel.ro.local.", ".data.rel.ro.local"),
4651 MAPPING_INIT_EXACT(".data.rel.ro.local", ".data.rel.ro.local"),
4652 MAPPING_INIT(".data.rel.ro.", ".data.rel.ro"),
4653 MAPPING_INIT_EXACT(".data.rel.ro", ".data.rel.ro"),
4654 MAPPING_INIT(".data.", ".data"),
4655 MAPPING_INIT(".bss.", ".bss"),
4656 MAPPING_INIT(".tdata.", ".tdata"),
4657 MAPPING_INIT(".tbss.", ".tbss"),
4658 MAPPING_INIT(".init_array.", ".init_array"),
4659 MAPPING_INIT(".fini_array.", ".fini_array"),
4660 MAPPING_INIT(".sdata.", ".sdata"),
4661 MAPPING_INIT(".sbss.", ".sbss"),
4662 // FIXME: In the GNU linker, .sbss2 and .sdata2 are handled
4663 // differently depending on whether it is creating a shared library.
4664 MAPPING_INIT(".sdata2.", ".sdata"),
4665 MAPPING_INIT(".sbss2.", ".sbss"),
4666 MAPPING_INIT(".lrodata.", ".lrodata"),
4667 MAPPING_INIT(".ldata.", ".ldata"),
4668 MAPPING_INIT(".lbss.", ".lbss"),
4669 MAPPING_INIT(".gcc_except_table.", ".gcc_except_table"),
4670 MAPPING_INIT(".gnu.linkonce.d.rel.ro.local.", ".data.rel.ro.local"),
4671 MAPPING_INIT(".gnu.linkonce.d.rel.ro.", ".data.rel.ro"),
4672 MAPPING_INIT(".gnu.linkonce.t.", ".text"),
4673 MAPPING_INIT(".gnu.linkonce.r.", ".rodata"),
4674 MAPPING_INIT(".gnu.linkonce.d.", ".data"),
4675 MAPPING_INIT(".gnu.linkonce.b.", ".bss"),
4676 MAPPING_INIT(".gnu.linkonce.s.", ".sdata"),
4677 MAPPING_INIT(".gnu.linkonce.sb.", ".sbss"),
4678 MAPPING_INIT(".gnu.linkonce.s2.", ".sdata"),
4679 MAPPING_INIT(".gnu.linkonce.sb2.", ".sbss"),
4680 MAPPING_INIT(".gnu.linkonce.wi.", ".debug_info"),
4681 MAPPING_INIT(".gnu.linkonce.td.", ".tdata"),
4682 MAPPING_INIT(".gnu.linkonce.tb.", ".tbss"),
4683 MAPPING_INIT(".gnu.linkonce.lr.", ".lrodata"),
4684 MAPPING_INIT(".gnu.linkonce.l.", ".ldata"),
4685 MAPPING_INIT(".gnu.linkonce.lb.", ".lbss"),
4686 MAPPING_INIT(".ARM.extab", ".ARM.extab"),
4687 MAPPING_INIT(".gnu.linkonce.armextab.", ".ARM.extab"),
4688 MAPPING_INIT(".ARM.exidx", ".ARM.exidx"),
4689 MAPPING_INIT(".gnu.linkonce.armexidx.", ".ARM.exidx"),
4692 #undef MAPPING_INIT_EXACT
4694 const int Layout::section_name_mapping_count =
4695 (sizeof(Layout::section_name_mapping)
4696 / sizeof(Layout::section_name_mapping[0]));
4698 // Choose the output section name to use given an input section name.
4699 // Set *PLEN to the length of the name. *PLEN is initialized to the
4703 Layout::output_section_name(const Relobj* relobj, const char* name,
4706 // gcc 4.3 generates the following sorts of section names when it
4707 // needs a section name specific to a function:
4713 // .data.rel.local.FN
4715 // .data.rel.ro.local.FN
4722 // The GNU linker maps all of those to the part before the .FN,
4723 // except that .data.rel.local.FN is mapped to .data, and
4724 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
4725 // beginning with .data.rel.ro.local are grouped together.
4727 // For an anonymous namespace, the string FN can contain a '.'.
4729 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
4730 // GNU linker maps to .rodata.
4732 // The .data.rel.ro sections are used with -z relro. The sections
4733 // are recognized by name. We use the same names that the GNU
4734 // linker does for these sections.
4736 // It is hard to handle this in a principled way, so we don't even
4737 // try. We use a table of mappings. If the input section name is
4738 // not found in the table, we simply use it as the output section
4741 const Section_name_mapping* psnm = section_name_mapping;
4742 for (int i = 0; i < section_name_mapping_count; ++i, ++psnm)
4744 if (psnm->fromlen > 0)
4746 if (strncmp(name, psnm->from, psnm->fromlen) == 0)
4748 *plen = psnm->tolen;
4754 if (strcmp(name, psnm->from) == 0)
4756 *plen = psnm->tolen;
4762 // As an additional complication, .ctors sections are output in
4763 // either .ctors or .init_array sections, and .dtors sections are
4764 // output in either .dtors or .fini_array sections.
4765 if (is_prefix_of(".ctors.", name) || is_prefix_of(".dtors.", name))
4767 if (parameters->options().ctors_in_init_array())
4770 return name[1] == 'c' ? ".init_array" : ".fini_array";
4775 return name[1] == 'c' ? ".ctors" : ".dtors";
4778 if (parameters->options().ctors_in_init_array()
4779 && (strcmp(name, ".ctors") == 0 || strcmp(name, ".dtors") == 0))
4781 // To make .init_array/.fini_array work with gcc we must exclude
4782 // .ctors and .dtors sections from the crtbegin and crtend
4785 || (!Layout::match_file_name(relobj, "crtbegin")
4786 && !Layout::match_file_name(relobj, "crtend")))
4789 return name[1] == 'c' ? ".init_array" : ".fini_array";
4796 // Return true if RELOBJ is an input file whose base name matches
4797 // FILE_NAME. The base name must have an extension of ".o", and must
4798 // be exactly FILE_NAME.o or FILE_NAME, one character, ".o". This is
4799 // to match crtbegin.o as well as crtbeginS.o without getting confused
4800 // by other possibilities. Overall matching the file name this way is
4801 // a dreadful hack, but the GNU linker does it in order to better
4802 // support gcc, and we need to be compatible.
4805 Layout::match_file_name(const Relobj* relobj, const char* match)
4807 const std::string& file_name(relobj->name());
4808 const char* base_name = lbasename(file_name.c_str());
4809 size_t match_len = strlen(match);
4810 if (strncmp(base_name, match, match_len) != 0)
4812 size_t base_len = strlen(base_name);
4813 if (base_len != match_len + 2 && base_len != match_len + 3)
4815 return memcmp(base_name + base_len - 2, ".o", 2) == 0;
4818 // Check if a comdat group or .gnu.linkonce section with the given
4819 // NAME is selected for the link. If there is already a section,
4820 // *KEPT_SECTION is set to point to the existing section and the
4821 // function returns false. Otherwise, OBJECT, SHNDX, IS_COMDAT, and
4822 // IS_GROUP_NAME are recorded for this NAME in the layout object,
4823 // *KEPT_SECTION is set to the internal copy and the function returns
4827 Layout::find_or_add_kept_section(const std::string& name,
4832 Kept_section** kept_section)
4834 // It's normal to see a couple of entries here, for the x86 thunk
4835 // sections. If we see more than a few, we're linking a C++
4836 // program, and we resize to get more space to minimize rehashing.
4837 if (this->signatures_.size() > 4
4838 && !this->resized_signatures_)
4840 reserve_unordered_map(&this->signatures_,
4841 this->number_of_input_files_ * 64);
4842 this->resized_signatures_ = true;
4845 Kept_section candidate;
4846 std::pair<Signatures::iterator, bool> ins =
4847 this->signatures_.insert(std::make_pair(name, candidate));
4849 if (kept_section != NULL)
4850 *kept_section = &ins.first->second;
4853 // This is the first time we've seen this signature.
4854 ins.first->second.set_object(object);
4855 ins.first->second.set_shndx(shndx);
4857 ins.first->second.set_is_comdat();
4859 ins.first->second.set_is_group_name();
4863 // We have already seen this signature.
4865 if (ins.first->second.is_group_name())
4867 // We've already seen a real section group with this signature.
4868 // If the kept group is from a plugin object, and we're in the
4869 // replacement phase, accept the new one as a replacement.
4870 if (ins.first->second.object() == NULL
4871 && parameters->options().plugins()->in_replacement_phase())
4873 ins.first->second.set_object(object);
4874 ins.first->second.set_shndx(shndx);
4879 else if (is_group_name)
4881 // This is a real section group, and we've already seen a
4882 // linkonce section with this signature. Record that we've seen
4883 // a section group, and don't include this section group.
4884 ins.first->second.set_is_group_name();
4889 // We've already seen a linkonce section and this is a linkonce
4890 // section. These don't block each other--this may be the same
4891 // symbol name with different section types.
4896 // Store the allocated sections into the section list.
4899 Layout::get_allocated_sections(Section_list* section_list) const
4901 for (Section_list::const_iterator p = this->section_list_.begin();
4902 p != this->section_list_.end();
4904 if (((*p)->flags() & elfcpp::SHF_ALLOC) != 0)
4905 section_list->push_back(*p);
4908 // Create an output segment.
4911 Layout::make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags)
4913 gold_assert(!parameters->options().relocatable());
4914 Output_segment* oseg = new Output_segment(type, flags);
4915 this->segment_list_.push_back(oseg);
4917 if (type == elfcpp::PT_TLS)
4918 this->tls_segment_ = oseg;
4919 else if (type == elfcpp::PT_GNU_RELRO)
4920 this->relro_segment_ = oseg;
4921 else if (type == elfcpp::PT_INTERP)
4922 this->interp_segment_ = oseg;
4927 // Return the file offset of the normal symbol table.
4930 Layout::symtab_section_offset() const
4932 if (this->symtab_section_ != NULL)
4933 return this->symtab_section_->offset();
4937 // Return the section index of the normal symbol table. It may have
4938 // been stripped by the -s/--strip-all option.
4941 Layout::symtab_section_shndx() const
4943 if (this->symtab_section_ != NULL)
4944 return this->symtab_section_->out_shndx();
4948 // Write out the Output_sections. Most won't have anything to write,
4949 // since most of the data will come from input sections which are
4950 // handled elsewhere. But some Output_sections do have Output_data.
4953 Layout::write_output_sections(Output_file* of) const
4955 for (Section_list::const_iterator p = this->section_list_.begin();
4956 p != this->section_list_.end();
4959 if (!(*p)->after_input_sections())
4964 // Write out data not associated with a section or the symbol table.
4967 Layout::write_data(const Symbol_table* symtab, Output_file* of) const
4969 if (!parameters->options().strip_all())
4971 const Output_section* symtab_section = this->symtab_section_;
4972 for (Section_list::const_iterator p = this->section_list_.begin();
4973 p != this->section_list_.end();
4976 if ((*p)->needs_symtab_index())
4978 gold_assert(symtab_section != NULL);
4979 unsigned int index = (*p)->symtab_index();
4980 gold_assert(index > 0 && index != -1U);
4981 off_t off = (symtab_section->offset()
4982 + index * symtab_section->entsize());
4983 symtab->write_section_symbol(*p, this->symtab_xindex_, of, off);
4988 const Output_section* dynsym_section = this->dynsym_section_;
4989 for (Section_list::const_iterator p = this->section_list_.begin();
4990 p != this->section_list_.end();
4993 if ((*p)->needs_dynsym_index())
4995 gold_assert(dynsym_section != NULL);
4996 unsigned int index = (*p)->dynsym_index();
4997 gold_assert(index > 0 && index != -1U);
4998 off_t off = (dynsym_section->offset()
4999 + index * dynsym_section->entsize());
5000 symtab->write_section_symbol(*p, this->dynsym_xindex_, of, off);
5004 // Write out the Output_data which are not in an Output_section.
5005 for (Data_list::const_iterator p = this->special_output_list_.begin();
5006 p != this->special_output_list_.end();
5011 // Write out the Output_sections which can only be written after the
5012 // input sections are complete.
5015 Layout::write_sections_after_input_sections(Output_file* of)
5017 // Determine the final section offsets, and thus the final output
5018 // file size. Note we finalize the .shstrab last, to allow the
5019 // after_input_section sections to modify their section-names before
5021 if (this->any_postprocessing_sections_)
5023 off_t off = this->output_file_size_;
5024 off = this->set_section_offsets(off, POSTPROCESSING_SECTIONS_PASS);
5026 // Now that we've finalized the names, we can finalize the shstrab.
5028 this->set_section_offsets(off,
5029 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS);
5031 if (off > this->output_file_size_)
5034 this->output_file_size_ = off;
5038 for (Section_list::const_iterator p = this->section_list_.begin();
5039 p != this->section_list_.end();
5042 if ((*p)->after_input_sections())
5046 this->section_headers_->write(of);
5049 // If the build ID requires computing a checksum, do so here, and
5050 // write it out. We compute a checksum over the entire file because
5051 // that is simplest.
5054 Layout::write_build_id(Output_file* of) const
5056 if (this->build_id_note_ == NULL)
5059 const unsigned char* iv = of->get_input_view(0, this->output_file_size_);
5061 unsigned char* ov = of->get_output_view(this->build_id_note_->offset(),
5062 this->build_id_note_->data_size());
5064 const char* style = parameters->options().build_id();
5065 if (strcmp(style, "sha1") == 0)
5068 sha1_init_ctx(&ctx);
5069 sha1_process_bytes(iv, this->output_file_size_, &ctx);
5070 sha1_finish_ctx(&ctx, ov);
5072 else if (strcmp(style, "md5") == 0)
5076 md5_process_bytes(iv, this->output_file_size_, &ctx);
5077 md5_finish_ctx(&ctx, ov);
5082 of->write_output_view(this->build_id_note_->offset(),
5083 this->build_id_note_->data_size(),
5086 of->free_input_view(0, this->output_file_size_, iv);
5089 // Write out a binary file. This is called after the link is
5090 // complete. IN is the temporary output file we used to generate the
5091 // ELF code. We simply walk through the segments, read them from
5092 // their file offset in IN, and write them to their load address in
5093 // the output file. FIXME: with a bit more work, we could support
5094 // S-records and/or Intel hex format here.
5097 Layout::write_binary(Output_file* in) const
5099 gold_assert(parameters->options().oformat_enum()
5100 == General_options::OBJECT_FORMAT_BINARY);
5102 // Get the size of the binary file.
5103 uint64_t max_load_address = 0;
5104 for (Segment_list::const_iterator p = this->segment_list_.begin();
5105 p != this->segment_list_.end();
5108 if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
5110 uint64_t max_paddr = (*p)->paddr() + (*p)->filesz();
5111 if (max_paddr > max_load_address)
5112 max_load_address = max_paddr;
5116 Output_file out(parameters->options().output_file_name());
5117 out.open(max_load_address);
5119 for (Segment_list::const_iterator p = this->segment_list_.begin();
5120 p != this->segment_list_.end();
5123 if ((*p)->type() == elfcpp::PT_LOAD && (*p)->filesz() > 0)
5125 const unsigned char* vin = in->get_input_view((*p)->offset(),
5127 unsigned char* vout = out.get_output_view((*p)->paddr(),
5129 memcpy(vout, vin, (*p)->filesz());
5130 out.write_output_view((*p)->paddr(), (*p)->filesz(), vout);
5131 in->free_input_view((*p)->offset(), (*p)->filesz(), vin);
5138 // Print the output sections to the map file.
5141 Layout::print_to_mapfile(Mapfile* mapfile) const
5143 for (Segment_list::const_iterator p = this->segment_list_.begin();
5144 p != this->segment_list_.end();
5146 (*p)->print_sections_to_mapfile(mapfile);
5149 // Print statistical information to stderr. This is used for --stats.
5152 Layout::print_stats() const
5154 this->namepool_.print_stats("section name pool");
5155 this->sympool_.print_stats("output symbol name pool");
5156 this->dynpool_.print_stats("dynamic name pool");
5158 for (Section_list::const_iterator p = this->section_list_.begin();
5159 p != this->section_list_.end();
5161 (*p)->print_merge_stats();
5164 // Write_sections_task methods.
5166 // We can always run this task.
5169 Write_sections_task::is_runnable()
5174 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
5178 Write_sections_task::locks(Task_locker* tl)
5180 tl->add(this, this->output_sections_blocker_);
5181 tl->add(this, this->final_blocker_);
5184 // Run the task--write out the data.
5187 Write_sections_task::run(Workqueue*)
5189 this->layout_->write_output_sections(this->of_);
5192 // Write_data_task methods.
5194 // We can always run this task.
5197 Write_data_task::is_runnable()
5202 // We need to unlock FINAL_BLOCKER when finished.
5205 Write_data_task::locks(Task_locker* tl)
5207 tl->add(this, this->final_blocker_);
5210 // Run the task--write out the data.
5213 Write_data_task::run(Workqueue*)
5215 this->layout_->write_data(this->symtab_, this->of_);
5218 // Write_symbols_task methods.
5220 // We can always run this task.
5223 Write_symbols_task::is_runnable()
5228 // We need to unlock FINAL_BLOCKER when finished.
5231 Write_symbols_task::locks(Task_locker* tl)
5233 tl->add(this, this->final_blocker_);
5236 // Run the task--write out the symbols.
5239 Write_symbols_task::run(Workqueue*)
5241 this->symtab_->write_globals(this->sympool_, this->dynpool_,
5242 this->layout_->symtab_xindex(),
5243 this->layout_->dynsym_xindex(), this->of_);
5246 // Write_after_input_sections_task methods.
5248 // We can only run this task after the input sections have completed.
5251 Write_after_input_sections_task::is_runnable()
5253 if (this->input_sections_blocker_->is_blocked())
5254 return this->input_sections_blocker_;
5258 // We need to unlock FINAL_BLOCKER when finished.
5261 Write_after_input_sections_task::locks(Task_locker* tl)
5263 tl->add(this, this->final_blocker_);
5269 Write_after_input_sections_task::run(Workqueue*)
5271 this->layout_->write_sections_after_input_sections(this->of_);
5274 // Close_task_runner methods.
5276 // Run the task--close the file.
5279 Close_task_runner::run(Workqueue*, const Task*)
5281 // If we need to compute a checksum for the BUILD if, we do so here.
5282 this->layout_->write_build_id(this->of_);
5284 // If we've been asked to create a binary file, we do so here.
5285 if (this->options_->oformat_enum() != General_options::OBJECT_FORMAT_ELF)
5286 this->layout_->write_binary(this->of_);
5291 // Instantiate the templates we need. We could use the configure
5292 // script to restrict this to only the ones for implemented targets.
5294 #ifdef HAVE_TARGET_32_LITTLE
5297 Layout::init_fixed_output_section<32, false>(
5299 elfcpp::Shdr<32, false>& shdr);
5302 #ifdef HAVE_TARGET_32_BIG
5305 Layout::init_fixed_output_section<32, true>(
5307 elfcpp::Shdr<32, true>& shdr);
5310 #ifdef HAVE_TARGET_64_LITTLE
5313 Layout::init_fixed_output_section<64, false>(
5315 elfcpp::Shdr<64, false>& shdr);
5318 #ifdef HAVE_TARGET_64_BIG
5321 Layout::init_fixed_output_section<64, true>(
5323 elfcpp::Shdr<64, true>& shdr);
5326 #ifdef HAVE_TARGET_32_LITTLE
5329 Layout::layout<32, false>(Sized_relobj_file<32, false>* object,
5332 const elfcpp::Shdr<32, false>& shdr,
5333 unsigned int, unsigned int, off_t*);
5336 #ifdef HAVE_TARGET_32_BIG
5339 Layout::layout<32, true>(Sized_relobj_file<32, true>* object,
5342 const elfcpp::Shdr<32, true>& shdr,
5343 unsigned int, unsigned int, off_t*);
5346 #ifdef HAVE_TARGET_64_LITTLE
5349 Layout::layout<64, false>(Sized_relobj_file<64, false>* object,
5352 const elfcpp::Shdr<64, false>& shdr,
5353 unsigned int, unsigned int, off_t*);
5356 #ifdef HAVE_TARGET_64_BIG
5359 Layout::layout<64, true>(Sized_relobj_file<64, true>* object,
5362 const elfcpp::Shdr<64, true>& shdr,
5363 unsigned int, unsigned int, off_t*);
5366 #ifdef HAVE_TARGET_32_LITTLE
5369 Layout::layout_reloc<32, false>(Sized_relobj_file<32, false>* object,
5370 unsigned int reloc_shndx,
5371 const elfcpp::Shdr<32, false>& shdr,
5372 Output_section* data_section,
5373 Relocatable_relocs* rr);
5376 #ifdef HAVE_TARGET_32_BIG
5379 Layout::layout_reloc<32, true>(Sized_relobj_file<32, true>* object,
5380 unsigned int reloc_shndx,
5381 const elfcpp::Shdr<32, true>& shdr,
5382 Output_section* data_section,
5383 Relocatable_relocs* rr);
5386 #ifdef HAVE_TARGET_64_LITTLE
5389 Layout::layout_reloc<64, false>(Sized_relobj_file<64, false>* object,
5390 unsigned int reloc_shndx,
5391 const elfcpp::Shdr<64, false>& shdr,
5392 Output_section* data_section,
5393 Relocatable_relocs* rr);
5396 #ifdef HAVE_TARGET_64_BIG
5399 Layout::layout_reloc<64, true>(Sized_relobj_file<64, true>* object,
5400 unsigned int reloc_shndx,
5401 const elfcpp::Shdr<64, true>& shdr,
5402 Output_section* data_section,
5403 Relocatable_relocs* rr);
5406 #ifdef HAVE_TARGET_32_LITTLE
5409 Layout::layout_group<32, false>(Symbol_table* symtab,
5410 Sized_relobj_file<32, false>* object,
5412 const char* group_section_name,
5413 const char* signature,
5414 const elfcpp::Shdr<32, false>& shdr,
5415 elfcpp::Elf_Word flags,
5416 std::vector<unsigned int>* shndxes);
5419 #ifdef HAVE_TARGET_32_BIG
5422 Layout::layout_group<32, true>(Symbol_table* symtab,
5423 Sized_relobj_file<32, true>* object,
5425 const char* group_section_name,
5426 const char* signature,
5427 const elfcpp::Shdr<32, true>& shdr,
5428 elfcpp::Elf_Word flags,
5429 std::vector<unsigned int>* shndxes);
5432 #ifdef HAVE_TARGET_64_LITTLE
5435 Layout::layout_group<64, false>(Symbol_table* symtab,
5436 Sized_relobj_file<64, false>* object,
5438 const char* group_section_name,
5439 const char* signature,
5440 const elfcpp::Shdr<64, false>& shdr,
5441 elfcpp::Elf_Word flags,
5442 std::vector<unsigned int>* shndxes);
5445 #ifdef HAVE_TARGET_64_BIG
5448 Layout::layout_group<64, true>(Symbol_table* symtab,
5449 Sized_relobj_file<64, true>* object,
5451 const char* group_section_name,
5452 const char* signature,
5453 const elfcpp::Shdr<64, true>& shdr,
5454 elfcpp::Elf_Word flags,
5455 std::vector<unsigned int>* shndxes);
5458 #ifdef HAVE_TARGET_32_LITTLE
5461 Layout::layout_eh_frame<32, false>(Sized_relobj_file<32, false>* object,
5462 const unsigned char* symbols,
5464 const unsigned char* symbol_names,
5465 off_t symbol_names_size,
5467 const elfcpp::Shdr<32, false>& shdr,
5468 unsigned int reloc_shndx,
5469 unsigned int reloc_type,
5473 #ifdef HAVE_TARGET_32_BIG
5476 Layout::layout_eh_frame<32, true>(Sized_relobj_file<32, true>* object,
5477 const unsigned char* symbols,
5479 const unsigned char* symbol_names,
5480 off_t symbol_names_size,
5482 const elfcpp::Shdr<32, true>& shdr,
5483 unsigned int reloc_shndx,
5484 unsigned int reloc_type,
5488 #ifdef HAVE_TARGET_64_LITTLE
5491 Layout::layout_eh_frame<64, false>(Sized_relobj_file<64, false>* object,
5492 const unsigned char* symbols,
5494 const unsigned char* symbol_names,
5495 off_t symbol_names_size,
5497 const elfcpp::Shdr<64, false>& shdr,
5498 unsigned int reloc_shndx,
5499 unsigned int reloc_type,
5503 #ifdef HAVE_TARGET_64_BIG
5506 Layout::layout_eh_frame<64, true>(Sized_relobj_file<64, true>* object,
5507 const unsigned char* symbols,
5509 const unsigned char* symbol_names,
5510 off_t symbol_names_size,
5512 const elfcpp::Shdr<64, true>& shdr,
5513 unsigned int reloc_shndx,
5514 unsigned int reloc_type,
5518 #ifdef HAVE_TARGET_32_LITTLE
5521 Layout::add_to_gdb_index(bool is_type_unit,
5522 Sized_relobj<32, false>* object,
5523 const unsigned char* symbols,
5526 unsigned int reloc_shndx,
5527 unsigned int reloc_type);
5530 #ifdef HAVE_TARGET_32_BIG
5533 Layout::add_to_gdb_index(bool is_type_unit,
5534 Sized_relobj<32, true>* object,
5535 const unsigned char* symbols,
5538 unsigned int reloc_shndx,
5539 unsigned int reloc_type);
5542 #ifdef HAVE_TARGET_64_LITTLE
5545 Layout::add_to_gdb_index(bool is_type_unit,
5546 Sized_relobj<64, false>* object,
5547 const unsigned char* symbols,
5550 unsigned int reloc_shndx,
5551 unsigned int reloc_type);
5554 #ifdef HAVE_TARGET_64_BIG
5557 Layout::add_to_gdb_index(bool is_type_unit,
5558 Sized_relobj<64, true>* object,
5559 const unsigned char* symbols,
5562 unsigned int reloc_shndx,
5563 unsigned int reloc_type);
5566 } // End namespace gold.