1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
34 #include "workqueue.h"
37 #include "stringpool.h"
42 class General_options;
43 class Incremental_inputs;
44 class Incremental_binary;
48 class Output_section_data;
50 class Output_section_headers;
51 class Output_segment_headers;
52 class Output_file_header;
55 class Output_data_reloc_generic;
56 class Output_data_dynamic;
57 class Output_symtab_xindex;
58 class Output_reduced_debug_abbrev_section;
59 class Output_reduced_debug_info_section;
65 // Return TRUE if SECNAME is the name of a compressed debug section.
67 is_compressed_debug_section(const char* secname);
69 // Maintain a list of free space within a section, segment, or file.
70 // Used for incremental update links.
77 Free_list_node(off_t start, off_t end)
78 : start_(start), end_(end)
83 typedef std::list<Free_list_node>::const_iterator Const_iterator;
86 : list_(), last_remove_(list_.begin()), extend_(false), length_(0),
90 // Initialize the free list for a section of length LEN.
91 // If EXTEND is true, free space may be allocated past the end.
93 init(off_t len, bool extend);
95 // Set the minimum hole size that is allowed when allocating
96 // from the free list.
98 set_min_hole_size(off_t min_hole)
99 { this->min_hole_ = min_hole; }
101 // Remove a chunk from the free list.
103 remove(off_t start, off_t end);
105 // Allocate a chunk of space from the free list of length LEN,
106 // with alignment ALIGN, and minimum offset MINOFF.
108 allocate(off_t len, uint64_t align, off_t minoff);
110 // Return an iterator for the beginning of the free list.
113 { return this->list_.begin(); }
115 // Return an iterator for the end of the free list.
118 { return this->list_.end(); }
120 // Dump the free list (for debugging).
124 // Print usage statistics.
129 typedef std::list<Free_list_node>::iterator Iterator;
132 std::list<Free_list_node> list_;
134 // The last node visited during a remove operation.
135 Iterator last_remove_;
137 // Whether we can extend past the original length.
140 // The total length of the section, segment, or file.
143 // The minimum hole size allowed. When allocating from the free list,
144 // we must not leave a hole smaller than this.
148 // The total number of free lists used.
149 static unsigned int num_lists;
150 // The total number of free list nodes used.
151 static unsigned int num_nodes;
152 // The total number of calls to Free_list::remove.
153 static unsigned int num_removes;
154 // The total number of nodes visited during calls to Free_list::remove.
155 static unsigned int num_remove_visits;
156 // The total number of calls to Free_list::allocate.
157 static unsigned int num_allocates;
158 // The total number of nodes visited during calls to Free_list::allocate.
159 static unsigned int num_allocate_visits;
162 // This task function handles mapping the input sections to output
163 // sections and laying them out in memory.
165 class Layout_task_runner : public Task_function_runner
168 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
169 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
171 Layout_task_runner(const General_options& options,
172 const Input_objects* input_objects,
173 Symbol_table* symtab,
177 : options_(options), input_objects_(input_objects), symtab_(symtab),
178 target_(target), layout_(layout), mapfile_(mapfile)
181 // Run the operation.
183 run(Workqueue*, const Task*);
186 Layout_task_runner(const Layout_task_runner&);
187 Layout_task_runner& operator=(const Layout_task_runner&);
189 const General_options& options_;
190 const Input_objects* input_objects_;
191 Symbol_table* symtab_;
197 // This class holds information about the comdat group or
198 // .gnu.linkonce section that will be kept for a given signature.
203 // For a comdat group, we build a mapping from the name of each
204 // section in the group to the section index and the size in object.
205 // When we discard a group in some other object file, we use this
206 // map to figure out which kept section the discarded section is
207 // associated with. We then use that mapping when processing relocs
208 // against discarded sections.
209 struct Comdat_section_info
211 // The section index.
216 Comdat_section_info(unsigned int a_shndx, uint64_t a_size)
217 : shndx(a_shndx), size(a_size)
221 // Most comdat groups have only one or two sections, so we use a
222 // std::map rather than an Unordered_map to optimize for that case
223 // without paying too heavily for groups with more sections.
224 typedef std::map<std::string, Comdat_section_info> Comdat_group;
228 : object_(NULL), shndx_(0), is_comdat_(false), is_group_name_(false)
229 { this->u_.linkonce_size = 0; }
231 // We need to support copies for the signature map in the Layout
232 // object, but we should never copy an object after it has been
233 // marked as a comdat section.
234 Kept_section(const Kept_section& k)
235 : object_(k.object_), shndx_(k.shndx_), is_comdat_(false),
236 is_group_name_(k.is_group_name_)
238 gold_assert(!k.is_comdat_);
239 this->u_.linkonce_size = 0;
244 if (this->is_comdat_)
245 delete this->u_.group_sections;
248 // The object where this section lives.
251 { return this->object_; }
255 set_object(Relobj* object)
257 gold_assert(this->object_ == NULL);
258 this->object_ = object;
261 // The section index.
264 { return this->shndx_; }
266 // Set the section index.
268 set_shndx(unsigned int shndx)
270 gold_assert(this->shndx_ == 0);
271 this->shndx_ = shndx;
274 // Whether this is a comdat group.
277 { return this->is_comdat_; }
279 // Set that this is a comdat group.
283 gold_assert(!this->is_comdat_);
284 this->is_comdat_ = true;
285 this->u_.group_sections = new Comdat_group();
288 // Whether this is associated with the name of a group or section
289 // rather than the symbol name derived from a linkonce section.
291 is_group_name() const
292 { return this->is_group_name_; }
294 // Note that this represents a comdat group rather than a single
298 { this->is_group_name_ = true; }
300 // Add a section to the group list.
302 add_comdat_section(const std::string& name, unsigned int shndx,
305 gold_assert(this->is_comdat_);
306 Comdat_section_info sinfo(shndx, size);
307 this->u_.group_sections->insert(std::make_pair(name, sinfo));
310 // Look for a section name in the group list, and return whether it
311 // was found. If found, returns the section index and size.
313 find_comdat_section(const std::string& name, unsigned int* pshndx,
314 uint64_t* psize) const
316 gold_assert(this->is_comdat_);
317 Comdat_group::const_iterator p = this->u_.group_sections->find(name);
318 if (p == this->u_.group_sections->end())
320 *pshndx = p->second.shndx;
321 *psize = p->second.size;
325 // If there is only one section in the group list, return true, and
326 // return the section index and size.
328 find_single_comdat_section(unsigned int* pshndx, uint64_t* psize) const
330 gold_assert(this->is_comdat_);
331 if (this->u_.group_sections->size() != 1)
333 Comdat_group::const_iterator p = this->u_.group_sections->begin();
334 *pshndx = p->second.shndx;
335 *psize = p->second.size;
339 // Return the size of a linkonce section.
341 linkonce_size() const
343 gold_assert(!this->is_comdat_);
344 return this->u_.linkonce_size;
347 // Set the size of a linkonce section.
349 set_linkonce_size(uint64_t size)
351 gold_assert(!this->is_comdat_);
352 this->u_.linkonce_size = size;
357 Kept_section& operator=(const Kept_section&);
359 // The object containing the comdat group or .gnu.linkonce section.
361 // Index of the group section for comdats and the section itself for
364 // True if this is for a comdat group rather than a .gnu.linkonce
367 // The Kept_sections are values of a mapping, that maps names to
368 // them. This field is true if this struct is associated with the
369 // name of a comdat or .gnu.linkonce, false if it is associated with
370 // the name of a symbol obtained from the .gnu.linkonce.* name
371 // through some heuristics.
375 // If the is_comdat_ field is true, this holds a map from names of
376 // the sections in the group to section indexes in object_ and to
378 Comdat_group* group_sections;
379 // If the is_comdat_ field is false, this holds the size of the
381 uint64_t linkonce_size;
385 // The ordering for output sections. This controls how output
386 // sections are ordered within a PT_LOAD output segment.
388 enum Output_section_order
390 // Unspecified. Used for non-load segments. Also used for the file
391 // and segment headers.
394 // The PT_INTERP section should come first, so that the dynamic
395 // linker can pick it up quickly.
398 // Loadable read-only note sections come next so that the PT_NOTE
399 // segment is on the first page of the executable.
402 // Put read-only sections used by the dynamic linker early in the
403 // executable to minimize paging.
404 ORDER_DYNAMIC_LINKER,
406 // Put reloc sections used by the dynamic linker after other
407 // sections used by the dynamic linker; otherwise, objcopy and strip
409 ORDER_DYNAMIC_RELOCS,
411 // Put the PLT reloc section after the other dynamic relocs;
412 // otherwise, prelink gets confused.
413 ORDER_DYNAMIC_PLT_RELOCS,
415 // The .init section.
421 // The regular text sections.
424 // The .fini section.
427 // The read-only sections.
430 // The exception frame sections.
433 // The TLS sections come first in the data section.
437 // Local RELRO (read-only after relocation) sections come before
438 // non-local RELRO sections. This data will be fully resolved by
442 // Non-local RELRO sections are grouped together after local RELRO
443 // sections. All RELRO sections must be adjacent so that they can
444 // all be put into a PT_GNU_RELRO segment.
447 // We permit marking exactly one output section as the last RELRO
448 // section. We do this so that the read-only GOT can be adjacent to
452 // Similarly, we permit marking exactly one output section as the
453 // first non-RELRO section.
454 ORDER_NON_RELRO_FIRST,
456 // The regular data sections come after the RELRO sections.
459 // Large data sections normally go in large data segments.
462 // Group writable notes so that we can have a single PT_NOTE
466 // The small data sections must be at the end of the data sections,
467 // so that they can be adjacent to the small BSS sections.
470 // The BSS sections start here.
472 // The small BSS sections must be at the start of the BSS sections,
473 // so that they can be adjacent to the small data sections.
476 // The regular BSS sections.
479 // The large BSS sections come after the other BSS sections.
486 // This class handles the details of laying out input sections.
491 Layout(int number_of_input_files, Script_options*);
495 delete this->relaxation_debug_check_;
496 delete this->segment_states_;
499 // For incremental links, record the base file to be modified.
501 set_incremental_base(Incremental_binary* base);
505 { return this->incremental_base_; }
507 // For incremental links, record the initial fixed layout of a section
508 // from the base file, and return a pointer to the Output_section.
509 template<int size, bool big_endian>
511 init_fixed_output_section(const char*, elfcpp::Shdr<size, big_endian>&);
513 // Given an input section SHNDX, named NAME, with data in SHDR, from
514 // the object file OBJECT, return the output section where this
515 // input section should go. RELOC_SHNDX is the index of a
516 // relocation section which applies to this section, or 0 if none,
517 // or -1U if more than one. RELOC_TYPE is the type of the
518 // relocation section if there is one. Set *OFFSET to the offset
519 // within the output section.
520 template<int size, bool big_endian>
522 layout(Sized_relobj_file<size, big_endian> *object, unsigned int shndx,
523 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
524 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);
526 std::map<Section_id, unsigned int>*
527 get_section_order_map()
528 { return &this->section_order_map_; }
531 is_section_ordering_specified()
532 { return this->section_ordering_specified_; }
535 set_section_ordering_specified()
536 { this->section_ordering_specified_ = true; }
538 // For incremental updates, allocate a block of memory from the
539 // free list. Find a block starting at or after MINOFF.
541 allocate(off_t len, uint64_t align, off_t minoff)
542 { return this->free_list_.allocate(len, align, minoff); }
545 find_section_order_index(const std::string&);
547 // Read the sequence of input sections from the file specified with
548 // linker option --section-ordering-file.
550 read_layout_from_file();
552 // Layout an input reloc section when doing a relocatable link. The
553 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
554 // DATA_SECTION is the reloc section to which it refers. RR is the
555 // relocatable information.
556 template<int size, bool big_endian>
558 layout_reloc(Sized_relobj_file<size, big_endian>* object,
559 unsigned int reloc_shndx,
560 const elfcpp::Shdr<size, big_endian>& shdr,
561 Output_section* data_section,
562 Relocatable_relocs* rr);
564 // Layout a group section when doing a relocatable link.
565 template<int size, bool big_endian>
567 layout_group(Symbol_table* symtab,
568 Sized_relobj_file<size, big_endian>* object,
569 unsigned int group_shndx,
570 const char* group_section_name,
571 const char* signature,
572 const elfcpp::Shdr<size, big_endian>& shdr,
573 elfcpp::Elf_Word flags,
574 std::vector<unsigned int>* shndxes);
576 // Like layout, only for exception frame sections. OBJECT is an
577 // object file. SYMBOLS is the contents of the symbol table
578 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
579 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
580 // .eh_frame section in OBJECT. SHDR is the section header.
581 // RELOC_SHNDX is the index of a relocation section which applies to
582 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
583 // is the type of the relocation section if there is one. This
584 // returns the output section, and sets *OFFSET to the offset.
585 template<int size, bool big_endian>
587 layout_eh_frame(Sized_relobj_file<size, big_endian>* object,
588 const unsigned char* symbols,
590 const unsigned char* symbol_names,
591 off_t symbol_names_size,
593 const elfcpp::Shdr<size, big_endian>& shdr,
594 unsigned int reloc_shndx, unsigned int reloc_type,
597 // Add .eh_frame information for a PLT. The FDE must start with a
598 // 4-byte PC-relative reference to the start of the PLT, followed by
599 // a 4-byte size of PLT.
601 add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
602 size_t cie_length, const unsigned char* fde_data,
605 // Scan a .debug_info or .debug_types section, and add summary
606 // information to the .gdb_index section.
607 template<int size, bool big_endian>
609 add_to_gdb_index(bool is_type_unit,
610 Sized_relobj<size, big_endian>* object,
611 const unsigned char* symbols,
614 unsigned int reloc_shndx,
615 unsigned int reloc_type);
617 // Handle a GNU stack note. This is called once per input object
618 // file. SEEN_GNU_STACK is true if the object file has a
619 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
620 // from that section if there was one.
622 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags,
625 // Add an Output_section_data to the layout. This is used for
626 // special sections like the GOT section. ORDER is where the
627 // section should wind up in the output segment. IS_RELRO is true
628 // for relro sections.
630 add_output_section_data(const char* name, elfcpp::Elf_Word type,
631 elfcpp::Elf_Xword flags,
632 Output_section_data*, Output_section_order order,
635 // Increase the size of the relro segment by this much.
637 increase_relro(unsigned int s)
638 { this->increase_relro_ += s; }
640 // Create dynamic sections if necessary.
642 create_initial_dynamic_sections(Symbol_table*);
644 // Define __start and __stop symbols for output sections.
646 define_section_symbols(Symbol_table*);
648 // Create automatic note sections.
652 // Create sections for linker scripts.
654 create_script_sections()
655 { this->script_options_->create_script_sections(this); }
657 // Define symbols from any linker script.
659 define_script_symbols(Symbol_table* symtab)
660 { this->script_options_->add_symbols_to_table(symtab); }
662 // Define symbols for group signatures.
664 define_group_signatures(Symbol_table*);
666 // Return the Stringpool used for symbol names.
669 { return &this->sympool_; }
671 // Return the Stringpool used for dynamic symbol names and dynamic
675 { return &this->dynpool_; }
677 // Return the .dynamic output section. This is only valid after the
678 // layout has been finalized.
680 dynamic_section() const
681 { return this->dynamic_section_; }
683 // Return the symtab_xindex section used to hold large section
684 // indexes for the normal symbol table.
685 Output_symtab_xindex*
686 symtab_xindex() const
687 { return this->symtab_xindex_; }
689 // Return the dynsym_xindex section used to hold large section
690 // indexes for the dynamic symbol table.
691 Output_symtab_xindex*
692 dynsym_xindex() const
693 { return this->dynsym_xindex_; }
695 // Return whether a section is a .gnu.linkonce section, given the
698 is_linkonce(const char* name)
699 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
701 // Whether we have added an input section.
703 have_added_input_section() const
704 { return this->have_added_input_section_; }
706 // Return true if a section is a debugging section.
708 is_debug_info_section(const char* name)
710 // Debugging sections can only be recognized by name.
711 return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0
712 || strncmp(name, ".zdebug", sizeof(".zdebug") - 1) == 0
713 || strncmp(name, ".gnu.linkonce.wi.",
714 sizeof(".gnu.linkonce.wi.") - 1) == 0
715 || strncmp(name, ".line", sizeof(".line") - 1) == 0
716 || strncmp(name, ".stab", sizeof(".stab") - 1) == 0);
719 // Return true if RELOBJ is an input file whose base name matches
720 // FILE_NAME. The base name must have an extension of ".o", and
721 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
723 match_file_name(const Relobj* relobj, const char* file_name);
725 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
726 // with more than one word being mapped to a .init_array/.fini_array
729 is_ctors_in_init_array(Relobj* relobj, unsigned int shndx) const;
731 // Check if a comdat group or .gnu.linkonce section with the given
732 // NAME is selected for the link. If there is already a section,
733 // *KEPT_SECTION is set to point to the signature and the function
734 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
735 // IS_GROUP_NAME are recorded for this NAME in the layout object,
736 // *KEPT_SECTION is set to the internal copy and the function return
739 find_or_add_kept_section(const std::string& name, Relobj* object,
740 unsigned int shndx, bool is_comdat,
741 bool is_group_name, Kept_section** kept_section);
743 // Finalize the layout after all the input sections have been added.
745 finalize(const Input_objects*, Symbol_table*, Target*, const Task*);
747 // Return whether any sections require postprocessing.
749 any_postprocessing_sections() const
750 { return this->any_postprocessing_sections_; }
752 // Return the size of the output file.
754 output_file_size() const
755 { return this->output_file_size_; }
757 // Return the TLS segment. This will return NULL if there isn't
761 { return this->tls_segment_; }
763 // Return the normal symbol table.
765 symtab_section() const
767 gold_assert(this->symtab_section_ != NULL);
768 return this->symtab_section_;
771 // Return the file offset of the normal symbol table.
773 symtab_section_offset() const;
775 // Return the section index of the normal symbol tabl.e
777 symtab_section_shndx() const;
779 // Return the dynamic symbol table.
781 dynsym_section() const
783 gold_assert(this->dynsym_section_ != NULL);
784 return this->dynsym_section_;
787 // Return the dynamic tags.
790 { return this->dynamic_data_; }
792 // Write out the output sections.
794 write_output_sections(Output_file* of) const;
796 // Write out data not associated with an input file or the symbol
799 write_data(const Symbol_table*, Output_file*) const;
801 // Write out output sections which can not be written until all the
802 // input sections are complete.
804 write_sections_after_input_sections(Output_file* of);
806 // Return an output section named NAME, or NULL if there is none.
808 find_output_section(const char* name) const;
810 // Return an output segment of type TYPE, with segment flags SET set
811 // and segment flags CLEAR clear. Return NULL if there is none.
813 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
814 elfcpp::Elf_Word clear) const;
816 // Return the number of segments we expect to produce.
818 expected_segment_count() const;
820 // Set a flag to indicate that an object file uses the static TLS model.
823 { this->has_static_tls_ = true; }
825 // Return true if any object file uses the static TLS model.
827 has_static_tls() const
828 { return this->has_static_tls_; }
830 // Return the options which may be set by a linker script.
833 { return this->script_options_; }
835 const Script_options*
836 script_options() const
837 { return this->script_options_; }
839 // Return the object managing inputs in incremental build. NULL in
840 // non-incremental builds.
842 incremental_inputs() const
843 { return this->incremental_inputs_; }
845 // For the target-specific code to add dynamic tags which are common
848 add_target_dynamic_tags(bool use_rel, const Output_data* plt_got,
849 const Output_data* plt_rel,
850 const Output_data_reloc_generic* dyn_rel,
851 bool add_debug, bool dynrel_includes_plt);
853 // Compute and write out the build ID if needed.
855 write_build_id(Output_file*) const;
857 // Rewrite output file in binary format.
859 write_binary(Output_file* in) const;
861 // Print output sections to the map file.
863 print_to_mapfile(Mapfile*) const;
865 // Dump statistical information to stderr.
869 // A list of segments.
871 typedef std::vector<Output_segment*> Segment_list;
873 // A list of sections.
875 typedef std::vector<Output_section*> Section_list;
877 // The list of information to write out which is not attached to
878 // either a section or a segment.
879 typedef std::vector<Output_data*> Data_list;
881 // Store the allocated sections into the section list. This is used
882 // by the linker script code.
884 get_allocated_sections(Section_list*) const;
886 // Make a section for a linker script to hold data.
888 make_output_section_for_script(const char* name,
889 Script_sections::Section_type section_type);
891 // Make a segment. This is used by the linker script code.
893 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);
895 // Return the number of segments.
897 segment_count() const
898 { return this->segment_list_.size(); }
900 // Map from section flags to segment flags.
901 static elfcpp::Elf_Word
902 section_flags_to_segment(elfcpp::Elf_Xword flags);
904 // Attach sections to segments.
906 attach_sections_to_segments();
908 // For relaxation clean up, we need to know output section data created
909 // from a linker script.
911 new_output_section_data_from_script(Output_section_data* posd)
913 if (this->record_output_section_data_from_script_)
914 this->script_output_section_data_list_.push_back(posd);
917 // Return section list.
920 { return this->section_list_; }
923 Layout(const Layout&);
924 Layout& operator=(const Layout&);
926 // Mapping from input section names to output section names.
927 struct Section_name_mapping
934 static const Section_name_mapping section_name_mapping[];
935 static const int section_name_mapping_count;
937 // During a relocatable link, a list of group sections and
939 struct Group_signature
941 // The group section.
942 Output_section* section;
944 const char* signature;
947 : section(NULL), signature(NULL)
950 Group_signature(Output_section* sectiona, const char* signaturea)
951 : section(sectiona), signature(signaturea)
954 typedef std::vector<Group_signature> Group_signatures;
956 // Create a note section, filling in the header.
958 create_note(const char* name, int note_type, const char* section_name,
959 size_t descsz, bool allocate, size_t* trailing_padding);
961 // Create a note section for gold version.
965 // Record whether the stack must be executable.
967 create_executable_stack_info();
969 // Create a build ID note if needed.
973 // Link .stab and .stabstr sections.
975 link_stabs_sections();
977 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
978 // for the next run of incremental linking to check what has changed.
980 create_incremental_info_sections(Symbol_table*);
982 // Find the first read-only PT_LOAD segment, creating one if
985 find_first_load_seg();
987 // Count the local symbols in the regular symbol table and the dynamic
988 // symbol table, and build the respective string pools.
990 count_local_symbols(const Task*, const Input_objects*);
992 // Create the output sections for the symbol table.
994 create_symtab_sections(const Input_objects*, Symbol_table*,
995 unsigned int, off_t*);
997 // Create the .shstrtab section.
1001 // Create the section header table.
1003 create_shdrs(const Output_section* shstrtab_section, off_t*);
1005 // Create the dynamic symbol table.
1007 create_dynamic_symtab(const Input_objects*, Symbol_table*,
1008 Output_section** pdynstr,
1009 unsigned int* plocal_dynamic_count,
1010 std::vector<Symbol*>* pdynamic_symbols,
1011 Versions* versions);
1013 // Assign offsets to each local portion of the dynamic symbol table.
1015 assign_local_dynsym_offsets(const Input_objects*);
1017 // Finish the .dynamic section and PT_DYNAMIC segment.
1019 finish_dynamic_section(const Input_objects*, const Symbol_table*);
1021 // Set the size of the _DYNAMIC symbol.
1023 set_dynamic_symbol_size(const Symbol_table*);
1025 // Create the .interp section and PT_INTERP segment.
1027 create_interp(const Target* target);
1029 // Create the version sections.
1031 create_version_sections(const Versions*,
1032 const Symbol_table*,
1033 unsigned int local_symcount,
1034 const std::vector<Symbol*>& dynamic_symbols,
1035 const Output_section* dynstr);
1037 template<int size, bool big_endian>
1039 sized_create_version_sections(const Versions* versions,
1040 const Symbol_table*,
1041 unsigned int local_symcount,
1042 const std::vector<Symbol*>& dynamic_symbols,
1043 const Output_section* dynstr);
1045 // Return whether to include this section in the link.
1046 template<int size, bool big_endian>
1048 include_section(Sized_relobj_file<size, big_endian>* object, const char* name,
1049 const elfcpp::Shdr<size, big_endian>&);
1051 // Return the output section name to use given an input section
1052 // name. Set *PLEN to the length of the name. *PLEN must be
1053 // initialized to the length of NAME.
1055 output_section_name(const Relobj*, const char* name, size_t* plen);
1057 // Return the number of allocated output sections.
1059 allocated_output_section_count() const;
1061 // Return the output section for NAME, TYPE and FLAGS.
1063 get_output_section(const char* name, Stringpool::Key name_key,
1064 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
1065 Output_section_order order, bool is_relro);
1067 // Choose the output section for NAME in RELOBJ.
1069 choose_output_section(const Relobj* relobj, const char* name,
1070 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
1071 bool is_input_section, Output_section_order order,
1074 // Create a new Output_section.
1076 make_output_section(const char* name, elfcpp::Elf_Word type,
1077 elfcpp::Elf_Xword flags, Output_section_order order,
1080 // Attach a section to a segment.
1082 attach_section_to_segment(Output_section*);
1084 // Get section order.
1085 Output_section_order
1086 default_section_order(Output_section*, bool is_relro_local);
1088 // Attach an allocated section to a segment.
1090 attach_allocated_section_to_segment(Output_section*);
1092 // Make the .eh_frame section.
1094 make_eh_frame_section(const Relobj*);
1096 // Set the final file offsets of all the segments.
1098 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
1100 // Set the file offsets of the sections when doing a relocatable
1103 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx);
1105 // Set the final file offsets of all the sections not associated
1106 // with a segment. We set section offsets in three passes: the
1107 // first handles all allocated sections, the second sections that
1108 // require postprocessing, and the last the late-bound STRTAB
1109 // sections (probably only shstrtab, which is the one we care about
1110 // because it holds section names).
1111 enum Section_offset_pass
1113 BEFORE_INPUT_SECTIONS_PASS,
1114 POSTPROCESSING_SECTIONS_PASS,
1115 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1118 set_section_offsets(off_t, Section_offset_pass pass);
1120 // Set the final section indexes of all the sections not associated
1121 // with a segment. Returns the next unused index.
1123 set_section_indexes(unsigned int pshndx);
1125 // Set the section addresses when using a script.
1127 set_section_addresses_from_script(Symbol_table*);
1129 // Find appropriate places or orphan sections in a script.
1131 place_orphan_sections_in_script();
1133 // Return whether SEG1 comes before SEG2 in the output file.
1135 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
1137 // Use to save and restore segments during relaxation.
1138 typedef Unordered_map<const Output_segment*, const Output_segment*>
1141 // Save states of current output segments.
1143 save_segments(Segment_states*);
1145 // Restore output segment states.
1147 restore_segments(const Segment_states*);
1149 // Clean up after relaxation so that it is possible to lay out the
1150 // sections and segments again.
1152 clean_up_after_relaxation();
1154 // Doing preparation work for relaxation. This is factored out to make
1155 // Layout::finalized a bit smaller and easier to read.
1157 prepare_for_relaxation();
1159 // Main body of the relaxation loop, which lays out the section.
1161 relaxation_loop_body(int, Target*, Symbol_table*, Output_segment**,
1162 Output_segment*, Output_segment_headers*,
1163 Output_file_header*, unsigned int*);
1165 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1166 typedef Unordered_map<std::string, Kept_section> Signatures;
1168 // Mapping from input section name/type/flags to output section. We
1169 // use canonicalized strings here.
1171 typedef std::pair<Stringpool::Key,
1172 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
1177 operator()(const Key& k) const;
1180 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
1182 // A comparison class for segments.
1184 class Compare_segments
1187 Compare_segments(Layout* layout)
1192 operator()(const Output_segment* seg1, const Output_segment* seg2)
1193 { return this->layout_->segment_precedes(seg1, seg2); }
1199 typedef std::vector<Output_section_data*> Output_section_data_list;
1201 // Debug checker class.
1202 class Relaxation_debug_check
1205 Relaxation_debug_check()
1209 // Check that sections and special data are in reset states.
1211 check_output_data_for_reset_values(const Layout::Section_list&,
1212 const Layout::Data_list&);
1214 // Record information of a section list.
1216 read_sections(const Layout::Section_list&);
1218 // Verify a section list with recorded information.
1220 verify_sections(const Layout::Section_list&);
1223 // Information we care about a section.
1226 // Output section described by this.
1227 Output_section* output_section;
1236 // Section information.
1237 std::vector<Section_info> section_infos_;
1240 // The number of input files, for sizing tables.
1241 int number_of_input_files_;
1242 // Information set by scripts or by command line options.
1243 Script_options* script_options_;
1244 // The output section names.
1245 Stringpool namepool_;
1246 // The output symbol names.
1247 Stringpool sympool_;
1248 // The dynamic strings, if needed.
1249 Stringpool dynpool_;
1250 // The list of group sections and linkonce sections which we have seen.
1251 Signatures signatures_;
1252 // The mapping from input section name/type/flags to output sections.
1253 Section_name_map section_name_map_;
1254 // The list of output segments.
1255 Segment_list segment_list_;
1256 // The list of output sections.
1257 Section_list section_list_;
1258 // The list of output sections which are not attached to any output
1260 Section_list unattached_section_list_;
1261 // The list of unattached Output_data objects which require special
1262 // handling because they are not Output_sections.
1263 Data_list special_output_list_;
1264 // The section headers.
1265 Output_section_headers* section_headers_;
1266 // A pointer to the PT_TLS segment if there is one.
1267 Output_segment* tls_segment_;
1268 // A pointer to the PT_GNU_RELRO segment if there is one.
1269 Output_segment* relro_segment_;
1270 // A pointer to the PT_INTERP segment if there is one.
1271 Output_segment* interp_segment_;
1272 // A backend may increase the size of the PT_GNU_RELRO segment if
1273 // there is one. This is the amount to increase it by.
1274 unsigned int increase_relro_;
1275 // The SHT_SYMTAB output section.
1276 Output_section* symtab_section_;
1277 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1278 Output_symtab_xindex* symtab_xindex_;
1279 // The SHT_DYNSYM output section if there is one.
1280 Output_section* dynsym_section_;
1281 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1282 Output_symtab_xindex* dynsym_xindex_;
1283 // The SHT_DYNAMIC output section if there is one.
1284 Output_section* dynamic_section_;
1285 // The _DYNAMIC symbol if there is one.
1286 Symbol* dynamic_symbol_;
1287 // The dynamic data which goes into dynamic_section_.
1288 Output_data_dynamic* dynamic_data_;
1289 // The exception frame output section if there is one.
1290 Output_section* eh_frame_section_;
1291 // The exception frame data for eh_frame_section_.
1292 Eh_frame* eh_frame_data_;
1293 // Whether we have added eh_frame_data_ to the .eh_frame section.
1294 bool added_eh_frame_data_;
1295 // The exception frame header output section if there is one.
1296 Output_section* eh_frame_hdr_section_;
1297 // The data for the .gdb_index section.
1298 Gdb_index* gdb_index_data_;
1299 // The space for the build ID checksum if there is one.
1300 Output_section_data* build_id_note_;
1301 // The output section containing dwarf abbreviations
1302 Output_reduced_debug_abbrev_section* debug_abbrev_;
1303 // The output section containing the dwarf debug info tree
1304 Output_reduced_debug_info_section* debug_info_;
1305 // A list of group sections and their signatures.
1306 Group_signatures group_signatures_;
1307 // The size of the output file.
1308 off_t output_file_size_;
1309 // Whether we have added an input section to an output section.
1310 bool have_added_input_section_;
1311 // Whether we have attached the sections to the segments.
1312 bool sections_are_attached_;
1313 // Whether we have seen an object file marked to require an
1314 // executable stack.
1315 bool input_requires_executable_stack_;
1316 // Whether we have seen at least one object file with an executable
1318 bool input_with_gnu_stack_note_;
1319 // Whether we have seen at least one object file without an
1320 // executable stack marker.
1321 bool input_without_gnu_stack_note_;
1322 // Whether we have seen an object file that uses the static TLS model.
1323 bool has_static_tls_;
1324 // Whether any sections require postprocessing.
1325 bool any_postprocessing_sections_;
1326 // Whether we have resized the signatures_ hash table.
1327 bool resized_signatures_;
1328 // Whether we have created a .stab*str output section.
1329 bool have_stabstr_section_;
1330 // True if the input sections in the output sections should be sorted
1331 // as specified in a section ordering file.
1332 bool section_ordering_specified_;
1333 // In incremental build, holds information check the inputs and build the
1334 // .gnu_incremental_inputs section.
1335 Incremental_inputs* incremental_inputs_;
1336 // Whether we record output section data created in script
1337 bool record_output_section_data_from_script_;
1338 // List of output data that needs to be removed at relaxation clean up.
1339 Output_section_data_list script_output_section_data_list_;
1340 // Structure to save segment states before entering the relaxation loop.
1341 Segment_states* segment_states_;
1342 // A relaxation debug checker. We only create one when in debugging mode.
1343 Relaxation_debug_check* relaxation_debug_check_;
1344 // Plugins specify section_ordering using this map. This is set in
1345 // update_section_order in plugin.cc
1346 std::map<Section_id, unsigned int> section_order_map_;
1347 // Hash a pattern to its position in the section ordering file.
1348 Unordered_map<std::string, unsigned int> input_section_position_;
1349 // Vector of glob only patterns in the section_ordering file.
1350 std::vector<std::string> input_section_glob_;
1351 // For incremental links, the base file to be modified.
1352 Incremental_binary* incremental_base_;
1353 // For incremental links, a list of free space within the file.
1354 Free_list free_list_;
1357 // This task handles writing out data in output sections which is not
1358 // part of an input section, or which requires special handling. When
1359 // this is done, it unblocks both output_sections_blocker and
1362 class Write_sections_task : public Task
1365 Write_sections_task(const Layout* layout, Output_file* of,
1366 Task_token* output_sections_blocker,
1367 Task_token* final_blocker)
1368 : layout_(layout), of_(of),
1369 output_sections_blocker_(output_sections_blocker),
1370 final_blocker_(final_blocker)
1373 // The standard Task methods.
1379 locks(Task_locker*);
1386 { return "Write_sections_task"; }
1389 class Write_sections_locker;
1391 const Layout* layout_;
1393 Task_token* output_sections_blocker_;
1394 Task_token* final_blocker_;
1397 // This task handles writing out data which is not part of a section
1400 class Write_data_task : public Task
1403 Write_data_task(const Layout* layout, const Symbol_table* symtab,
1404 Output_file* of, Task_token* final_blocker)
1405 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
1408 // The standard Task methods.
1414 locks(Task_locker*);
1421 { return "Write_data_task"; }
1424 const Layout* layout_;
1425 const Symbol_table* symtab_;
1427 Task_token* final_blocker_;
1430 // This task handles writing out the global symbols.
1432 class Write_symbols_task : public Task
1435 Write_symbols_task(const Layout* layout, const Symbol_table* symtab,
1436 const Input_objects* input_objects,
1437 const Stringpool* sympool, const Stringpool* dynpool,
1438 Output_file* of, Task_token* final_blocker)
1439 : layout_(layout), symtab_(symtab), input_objects_(input_objects),
1440 sympool_(sympool), dynpool_(dynpool), of_(of),
1441 final_blocker_(final_blocker)
1444 // The standard Task methods.
1450 locks(Task_locker*);
1457 { return "Write_symbols_task"; }
1460 const Layout* layout_;
1461 const Symbol_table* symtab_;
1462 const Input_objects* input_objects_;
1463 const Stringpool* sympool_;
1464 const Stringpool* dynpool_;
1466 Task_token* final_blocker_;
1469 // This task handles writing out data in output sections which can't
1470 // be written out until all the input sections have been handled.
1471 // This is for sections whose contents is based on the contents of
1472 // other output sections.
1474 class Write_after_input_sections_task : public Task
1477 Write_after_input_sections_task(Layout* layout, Output_file* of,
1478 Task_token* input_sections_blocker,
1479 Task_token* final_blocker)
1480 : layout_(layout), of_(of),
1481 input_sections_blocker_(input_sections_blocker),
1482 final_blocker_(final_blocker)
1485 // The standard Task methods.
1491 locks(Task_locker*);
1498 { return "Write_after_input_sections_task"; }
1503 Task_token* input_sections_blocker_;
1504 Task_token* final_blocker_;
1507 // This task function handles closing the file.
1509 class Close_task_runner : public Task_function_runner
1512 Close_task_runner(const General_options* options, const Layout* layout,
1514 : options_(options), layout_(layout), of_(of)
1517 // Run the operation.
1519 run(Workqueue*, const Task*);
1522 const General_options* options_;
1523 const Layout* layout_;
1527 // A small helper function to align an address.
1530 align_address(uint64_t address, uint64_t addralign)
1533 address = (address + addralign - 1) &~ (addralign - 1);
1537 } // End namespace gold.
1539 #endif // !defined(GOLD_LAYOUT_H)