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;
64 // Return TRUE if SECNAME is the name of a compressed debug section.
66 is_compressed_debug_section(const char* secname);
68 // Maintain a list of free space within a section, segment, or file.
69 // Used for incremental update links.
75 : list_(), last_remove_(list_.begin()), extend_(false), length_(0)
79 init(off_t len, bool extend);
82 remove(off_t start, off_t end);
85 allocate(off_t len, uint64_t align, off_t minoff);
96 Free_list_node(off_t start, off_t end)
97 : start_(start), end_(end)
102 typedef std::list<Free_list_node>::iterator Iterator;
105 std::list<Free_list_node> list_;
107 // The last node visited during a remove operation.
108 Iterator last_remove_;
110 // Whether we can extend past the original length.
113 // The total length of the section, segment, or file.
117 // The total number of free lists used.
118 static unsigned int num_lists;
119 // The total number of free list nodes used.
120 static unsigned int num_nodes;
121 // The total number of calls to Free_list::remove.
122 static unsigned int num_removes;
123 // The total number of nodes visited during calls to Free_list::remove.
124 static unsigned int num_remove_visits;
125 // The total number of calls to Free_list::allocate.
126 static unsigned int num_allocates;
127 // The total number of nodes visited during calls to Free_list::allocate.
128 static unsigned int num_allocate_visits;
131 // This task function handles mapping the input sections to output
132 // sections and laying them out in memory.
134 class Layout_task_runner : public Task_function_runner
137 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
138 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
140 Layout_task_runner(const General_options& options,
141 const Input_objects* input_objects,
142 Symbol_table* symtab,
146 : options_(options), input_objects_(input_objects), symtab_(symtab),
147 target_(target), layout_(layout), mapfile_(mapfile)
150 // Run the operation.
152 run(Workqueue*, const Task*);
155 Layout_task_runner(const Layout_task_runner&);
156 Layout_task_runner& operator=(const Layout_task_runner&);
158 const General_options& options_;
159 const Input_objects* input_objects_;
160 Symbol_table* symtab_;
166 // This class holds information about the comdat group or
167 // .gnu.linkonce section that will be kept for a given signature.
172 // For a comdat group, we build a mapping from the name of each
173 // section in the group to the section index and the size in object.
174 // When we discard a group in some other object file, we use this
175 // map to figure out which kept section the discarded section is
176 // associated with. We then use that mapping when processing relocs
177 // against discarded sections.
178 struct Comdat_section_info
180 // The section index.
185 Comdat_section_info(unsigned int a_shndx, uint64_t a_size)
186 : shndx(a_shndx), size(a_size)
190 // Most comdat groups have only one or two sections, so we use a
191 // std::map rather than an Unordered_map to optimize for that case
192 // without paying too heavily for groups with more sections.
193 typedef std::map<std::string, Comdat_section_info> Comdat_group;
197 : object_(NULL), shndx_(0), is_comdat_(false), is_group_name_(false)
198 { this->u_.linkonce_size = 0; }
200 // We need to support copies for the signature map in the Layout
201 // object, but we should never copy an object after it has been
202 // marked as a comdat section.
203 Kept_section(const Kept_section& k)
204 : object_(k.object_), shndx_(k.shndx_), is_comdat_(false),
205 is_group_name_(k.is_group_name_)
207 gold_assert(!k.is_comdat_);
208 this->u_.linkonce_size = 0;
213 if (this->is_comdat_)
214 delete this->u_.group_sections;
217 // The object where this section lives.
220 { return this->object_; }
224 set_object(Relobj* object)
226 gold_assert(this->object_ == NULL);
227 this->object_ = object;
230 // The section index.
233 { return this->shndx_; }
235 // Set the section index.
237 set_shndx(unsigned int shndx)
239 gold_assert(this->shndx_ == 0);
240 this->shndx_ = shndx;
243 // Whether this is a comdat group.
246 { return this->is_comdat_; }
248 // Set that this is a comdat group.
252 gold_assert(!this->is_comdat_);
253 this->is_comdat_ = true;
254 this->u_.group_sections = new Comdat_group();
257 // Whether this is associated with the name of a group or section
258 // rather than the symbol name derived from a linkonce section.
260 is_group_name() const
261 { return this->is_group_name_; }
263 // Note that this represents a comdat group rather than a single
267 { this->is_group_name_ = true; }
269 // Add a section to the group list.
271 add_comdat_section(const std::string& name, unsigned int shndx,
274 gold_assert(this->is_comdat_);
275 Comdat_section_info sinfo(shndx, size);
276 this->u_.group_sections->insert(std::make_pair(name, sinfo));
279 // Look for a section name in the group list, and return whether it
280 // was found. If found, returns the section index and size.
282 find_comdat_section(const std::string& name, unsigned int* pshndx,
283 uint64_t* psize) const
285 gold_assert(this->is_comdat_);
286 Comdat_group::const_iterator p = this->u_.group_sections->find(name);
287 if (p == this->u_.group_sections->end())
289 *pshndx = p->second.shndx;
290 *psize = p->second.size;
294 // If there is only one section in the group list, return true, and
295 // return the section index and size.
297 find_single_comdat_section(unsigned int* pshndx, uint64_t* psize) const
299 gold_assert(this->is_comdat_);
300 if (this->u_.group_sections->size() != 1)
302 Comdat_group::const_iterator p = this->u_.group_sections->begin();
303 *pshndx = p->second.shndx;
304 *psize = p->second.size;
308 // Return the size of a linkonce section.
310 linkonce_size() const
312 gold_assert(!this->is_comdat_);
313 return this->u_.linkonce_size;
316 // Set the size of a linkonce section.
318 set_linkonce_size(uint64_t size)
320 gold_assert(!this->is_comdat_);
321 this->u_.linkonce_size = size;
326 Kept_section& operator=(const Kept_section&);
328 // The object containing the comdat group or .gnu.linkonce section.
330 // Index of the group section for comdats and the section itself for
333 // True if this is for a comdat group rather than a .gnu.linkonce
336 // The Kept_sections are values of a mapping, that maps names to
337 // them. This field is true if this struct is associated with the
338 // name of a comdat or .gnu.linkonce, false if it is associated with
339 // the name of a symbol obtained from the .gnu.linkonce.* name
340 // through some heuristics.
344 // If the is_comdat_ field is true, this holds a map from names of
345 // the sections in the group to section indexes in object_ and to
347 Comdat_group* group_sections;
348 // If the is_comdat_ field is false, this holds the size of the
350 uint64_t linkonce_size;
354 // The ordering for output sections. This controls how output
355 // sections are ordered within a PT_LOAD output segment.
357 enum Output_section_order
359 // Unspecified. Used for non-load segments. Also used for the file
360 // and segment headers.
363 // The PT_INTERP section should come first, so that the dynamic
364 // linker can pick it up quickly.
367 // Loadable read-only note sections come next so that the PT_NOTE
368 // segment is on the first page of the executable.
371 // Put read-only sections used by the dynamic linker early in the
372 // executable to minimize paging.
373 ORDER_DYNAMIC_LINKER,
375 // Put reloc sections used by the dynamic linker after other
376 // sections used by the dynamic linker; otherwise, objcopy and strip
378 ORDER_DYNAMIC_RELOCS,
380 // Put the PLT reloc section after the other dynamic relocs;
381 // otherwise, prelink gets confused.
382 ORDER_DYNAMIC_PLT_RELOCS,
384 // The .init section.
390 // The regular text sections.
393 // The .fini section.
396 // The read-only sections.
399 // The exception frame sections.
402 // The TLS sections come first in the data section.
406 // Local RELRO (read-only after relocation) sections come before
407 // non-local RELRO sections. This data will be fully resolved by
411 // Non-local RELRO sections are grouped together after local RELRO
412 // sections. All RELRO sections must be adjacent so that they can
413 // all be put into a PT_GNU_RELRO segment.
416 // We permit marking exactly one output section as the last RELRO
417 // section. We do this so that the read-only GOT can be adjacent to
421 // Similarly, we permit marking exactly one output section as the
422 // first non-RELRO section.
423 ORDER_NON_RELRO_FIRST,
425 // The regular data sections come after the RELRO sections.
428 // Large data sections normally go in large data segments.
431 // Group writable notes so that we can have a single PT_NOTE
435 // The small data sections must be at the end of the data sections,
436 // so that they can be adjacent to the small BSS sections.
439 // The BSS sections start here.
441 // The small BSS sections must be at the start of the BSS sections,
442 // so that they can be adjacent to the small data sections.
445 // The regular BSS sections.
448 // The large BSS sections come after the other BSS sections.
455 // This class handles the details of laying out input sections.
460 Layout(int number_of_input_files, Script_options*);
464 delete this->relaxation_debug_check_;
465 delete this->segment_states_;
468 // For incremental links, record the base file to be modified.
470 set_incremental_base(Incremental_binary* base);
474 { return this->incremental_base_; }
476 // For incremental links, record the initial fixed layout of a section
477 // from the base file, and return a pointer to the Output_section.
478 template<int size, bool big_endian>
480 init_fixed_output_section(const char*, elfcpp::Shdr<size, big_endian>&);
482 // Given an input section SHNDX, named NAME, with data in SHDR, from
483 // the object file OBJECT, return the output section where this
484 // input section should go. RELOC_SHNDX is the index of a
485 // relocation section which applies to this section, or 0 if none,
486 // or -1U if more than one. RELOC_TYPE is the type of the
487 // relocation section if there is one. Set *OFFSET to the offset
488 // within the output section.
489 template<int size, bool big_endian>
491 layout(Sized_relobj_file<size, big_endian> *object, unsigned int shndx,
492 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
493 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);
495 // For incremental updates, allocate a block of memory from the
496 // free list. Find a block starting at or after MINOFF.
498 allocate(off_t len, uint64_t align, off_t minoff)
499 { return this->free_list_.allocate(len, align, minoff); }
502 find_section_order_index(const std::string&);
505 read_layout_from_file();
507 // Layout an input reloc section when doing a relocatable link. The
508 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
509 // DATA_SECTION is the reloc section to which it refers. RR is the
510 // relocatable information.
511 template<int size, bool big_endian>
513 layout_reloc(Sized_relobj_file<size, big_endian>* object,
514 unsigned int reloc_shndx,
515 const elfcpp::Shdr<size, big_endian>& shdr,
516 Output_section* data_section,
517 Relocatable_relocs* rr);
519 // Layout a group section when doing a relocatable link.
520 template<int size, bool big_endian>
522 layout_group(Symbol_table* symtab,
523 Sized_relobj_file<size, big_endian>* object,
524 unsigned int group_shndx,
525 const char* group_section_name,
526 const char* signature,
527 const elfcpp::Shdr<size, big_endian>& shdr,
528 elfcpp::Elf_Word flags,
529 std::vector<unsigned int>* shndxes);
531 // Like layout, only for exception frame sections. OBJECT is an
532 // object file. SYMBOLS is the contents of the symbol table
533 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
534 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
535 // .eh_frame section in OBJECT. SHDR is the section header.
536 // RELOC_SHNDX is the index of a relocation section which applies to
537 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
538 // is the type of the relocation section if there is one. This
539 // returns the output section, and sets *OFFSET to the offset.
540 template<int size, bool big_endian>
542 layout_eh_frame(Sized_relobj_file<size, big_endian>* object,
543 const unsigned char* symbols,
545 const unsigned char* symbol_names,
546 off_t symbol_names_size,
548 const elfcpp::Shdr<size, big_endian>& shdr,
549 unsigned int reloc_shndx, unsigned int reloc_type,
552 // Handle a GNU stack note. This is called once per input object
553 // file. SEEN_GNU_STACK is true if the object file has a
554 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
555 // from that section if there was one.
557 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags,
560 // Add an Output_section_data to the layout. This is used for
561 // special sections like the GOT section. ORDER is where the
562 // section should wind up in the output segment. IS_RELRO is true
563 // for relro sections.
565 add_output_section_data(const char* name, elfcpp::Elf_Word type,
566 elfcpp::Elf_Xword flags,
567 Output_section_data*, Output_section_order order,
570 // Increase the size of the relro segment by this much.
572 increase_relro(unsigned int s)
573 { this->increase_relro_ += s; }
575 // Create dynamic sections if necessary.
577 create_initial_dynamic_sections(Symbol_table*);
579 // Define __start and __stop symbols for output sections.
581 define_section_symbols(Symbol_table*);
583 // Create automatic note sections.
587 // Create sections for linker scripts.
589 create_script_sections()
590 { this->script_options_->create_script_sections(this); }
592 // Define symbols from any linker script.
594 define_script_symbols(Symbol_table* symtab)
595 { this->script_options_->add_symbols_to_table(symtab); }
597 // Define symbols for group signatures.
599 define_group_signatures(Symbol_table*);
601 // Return the Stringpool used for symbol names.
604 { return &this->sympool_; }
606 // Return the Stringpool used for dynamic symbol names and dynamic
610 { return &this->dynpool_; }
612 // Return the symtab_xindex section used to hold large section
613 // indexes for the normal symbol table.
614 Output_symtab_xindex*
615 symtab_xindex() const
616 { return this->symtab_xindex_; }
618 // Return the dynsym_xindex section used to hold large section
619 // indexes for the dynamic symbol table.
620 Output_symtab_xindex*
621 dynsym_xindex() const
622 { return this->dynsym_xindex_; }
624 // Return whether a section is a .gnu.linkonce section, given the
627 is_linkonce(const char* name)
628 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
630 // Whether we have added an input section.
632 have_added_input_section() const
633 { return this->have_added_input_section_; }
635 // Return true if a section is a debugging section.
637 is_debug_info_section(const char* name)
639 // Debugging sections can only be recognized by name.
640 return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0
641 || strncmp(name, ".zdebug", sizeof(".zdebug") - 1) == 0
642 || strncmp(name, ".gnu.linkonce.wi.",
643 sizeof(".gnu.linkonce.wi.") - 1) == 0
644 || strncmp(name, ".line", sizeof(".line") - 1) == 0
645 || strncmp(name, ".stab", sizeof(".stab") - 1) == 0);
648 // Return true if RELOBJ is an input file whose base name matches
649 // FILE_NAME. The base name must have an extension of ".o", and
650 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
652 match_file_name(const Relobj* relobj, const char* file_name);
654 // Check if a comdat group or .gnu.linkonce section with the given
655 // NAME is selected for the link. If there is already a section,
656 // *KEPT_SECTION is set to point to the signature and the function
657 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
658 // IS_GROUP_NAME are recorded for this NAME in the layout object,
659 // *KEPT_SECTION is set to the internal copy and the function return
662 find_or_add_kept_section(const std::string& name, Relobj* object,
663 unsigned int shndx, bool is_comdat,
664 bool is_group_name, Kept_section** kept_section);
666 // Finalize the layout after all the input sections have been added.
668 finalize(const Input_objects*, Symbol_table*, Target*, const Task*);
670 // Return whether any sections require postprocessing.
672 any_postprocessing_sections() const
673 { return this->any_postprocessing_sections_; }
675 // Return the size of the output file.
677 output_file_size() const
678 { return this->output_file_size_; }
680 // Return the TLS segment. This will return NULL if there isn't
684 { return this->tls_segment_; }
686 // Return the normal symbol table.
688 symtab_section() const
690 gold_assert(this->symtab_section_ != NULL);
691 return this->symtab_section_;
694 // Return the file offset of the normal symbol table.
696 symtab_section_offset() const;
698 // Return the dynamic symbol table.
700 dynsym_section() const
702 gold_assert(this->dynsym_section_ != NULL);
703 return this->dynsym_section_;
706 // Return the dynamic tags.
709 { return this->dynamic_data_; }
711 // Write out the output sections.
713 write_output_sections(Output_file* of) const;
715 // Write out data not associated with an input file or the symbol
718 write_data(const Symbol_table*, Output_file*) const;
720 // Write out output sections which can not be written until all the
721 // input sections are complete.
723 write_sections_after_input_sections(Output_file* of);
725 // Return an output section named NAME, or NULL if there is none.
727 find_output_section(const char* name) const;
729 // Return an output segment of type TYPE, with segment flags SET set
730 // and segment flags CLEAR clear. Return NULL if there is none.
732 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
733 elfcpp::Elf_Word clear) const;
735 // Return the number of segments we expect to produce.
737 expected_segment_count() const;
739 // Set a flag to indicate that an object file uses the static TLS model.
742 { this->has_static_tls_ = true; }
744 // Return true if any object file uses the static TLS model.
746 has_static_tls() const
747 { return this->has_static_tls_; }
749 // Return the options which may be set by a linker script.
752 { return this->script_options_; }
754 const Script_options*
755 script_options() const
756 { return this->script_options_; }
758 // Return the object managing inputs in incremental build. NULL in
759 // non-incremental builds.
761 incremental_inputs() const
762 { return this->incremental_inputs_; }
764 // For the target-specific code to add dynamic tags which are common
767 add_target_dynamic_tags(bool use_rel, const Output_data* plt_got,
768 const Output_data* plt_rel,
769 const Output_data_reloc_generic* dyn_rel,
770 bool add_debug, bool dynrel_includes_plt);
772 // Compute and write out the build ID if needed.
774 write_build_id(Output_file*) const;
776 // Rewrite output file in binary format.
778 write_binary(Output_file* in) const;
780 // Print output sections to the map file.
782 print_to_mapfile(Mapfile*) const;
784 // Dump statistical information to stderr.
788 // A list of segments.
790 typedef std::vector<Output_segment*> Segment_list;
792 // A list of sections.
794 typedef std::vector<Output_section*> Section_list;
796 // The list of information to write out which is not attached to
797 // either a section or a segment.
798 typedef std::vector<Output_data*> Data_list;
800 // Store the allocated sections into the section list. This is used
801 // by the linker script code.
803 get_allocated_sections(Section_list*) const;
805 // Make a section for a linker script to hold data.
807 make_output_section_for_script(const char* name,
808 Script_sections::Section_type section_type);
810 // Make a segment. This is used by the linker script code.
812 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);
814 // Return the number of segments.
816 segment_count() const
817 { return this->segment_list_.size(); }
819 // Map from section flags to segment flags.
820 static elfcpp::Elf_Word
821 section_flags_to_segment(elfcpp::Elf_Xword flags);
823 // Attach sections to segments.
825 attach_sections_to_segments();
827 // For relaxation clean up, we need to know output section data created
828 // from a linker script.
830 new_output_section_data_from_script(Output_section_data* posd)
832 if (this->record_output_section_data_from_script_)
833 this->script_output_section_data_list_.push_back(posd);
836 // Return section list.
839 { return this->section_list_; }
842 Layout(const Layout&);
843 Layout& operator=(const Layout&);
845 // Mapping from input section names to output section names.
846 struct Section_name_mapping
853 static const Section_name_mapping section_name_mapping[];
854 static const int section_name_mapping_count;
856 // During a relocatable link, a list of group sections and
858 struct Group_signature
860 // The group section.
861 Output_section* section;
863 const char* signature;
866 : section(NULL), signature(NULL)
869 Group_signature(Output_section* sectiona, const char* signaturea)
870 : section(sectiona), signature(signaturea)
873 typedef std::vector<Group_signature> Group_signatures;
875 // Create a note section, filling in the header.
877 create_note(const char* name, int note_type, const char* section_name,
878 size_t descsz, bool allocate, size_t* trailing_padding);
880 // Create a note section for gold version.
884 // Record whether the stack must be executable.
886 create_executable_stack_info();
888 // Create a build ID note if needed.
892 // Link .stab and .stabstr sections.
894 link_stabs_sections();
896 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
897 // for the next run of incremental linking to check what has changed.
899 create_incremental_info_sections(Symbol_table*);
901 // Find the first read-only PT_LOAD segment, creating one if
904 find_first_load_seg();
906 // Count the local symbols in the regular symbol table and the dynamic
907 // symbol table, and build the respective string pools.
909 count_local_symbols(const Task*, const Input_objects*);
911 // Create the output sections for the symbol table.
913 create_symtab_sections(const Input_objects*, Symbol_table*,
914 unsigned int, off_t*);
916 // Create the .shstrtab section.
920 // Create the section header table.
922 create_shdrs(const Output_section* shstrtab_section, off_t*);
924 // Create the dynamic symbol table.
926 create_dynamic_symtab(const Input_objects*, Symbol_table*,
927 Output_section** pdynstr,
928 unsigned int* plocal_dynamic_count,
929 std::vector<Symbol*>* pdynamic_symbols,
932 // Assign offsets to each local portion of the dynamic symbol table.
934 assign_local_dynsym_offsets(const Input_objects*);
936 // Finish the .dynamic section and PT_DYNAMIC segment.
938 finish_dynamic_section(const Input_objects*, const Symbol_table*);
940 // Set the size of the _DYNAMIC symbol.
942 set_dynamic_symbol_size(const Symbol_table*);
944 // Create the .interp section and PT_INTERP segment.
946 create_interp(const Target* target);
948 // Create the version sections.
950 create_version_sections(const Versions*,
952 unsigned int local_symcount,
953 const std::vector<Symbol*>& dynamic_symbols,
954 const Output_section* dynstr);
956 template<int size, bool big_endian>
958 sized_create_version_sections(const Versions* versions,
960 unsigned int local_symcount,
961 const std::vector<Symbol*>& dynamic_symbols,
962 const Output_section* dynstr);
964 // Return whether to include this section in the link.
965 template<int size, bool big_endian>
967 include_section(Sized_relobj_file<size, big_endian>* object, const char* name,
968 const elfcpp::Shdr<size, big_endian>&);
970 // Return the output section name to use given an input section
971 // name. Set *PLEN to the length of the name. *PLEN must be
972 // initialized to the length of NAME.
974 output_section_name(const Relobj*, const char* name, size_t* plen);
976 // Return the number of allocated output sections.
978 allocated_output_section_count() const;
980 // Return the output section for NAME, TYPE and FLAGS.
982 get_output_section(const char* name, Stringpool::Key name_key,
983 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
984 Output_section_order order, bool is_relro);
986 // Choose the output section for NAME in RELOBJ.
988 choose_output_section(const Relobj* relobj, const char* name,
989 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
990 bool is_input_section, Output_section_order order,
993 // Create a new Output_section.
995 make_output_section(const char* name, elfcpp::Elf_Word type,
996 elfcpp::Elf_Xword flags, Output_section_order order,
999 // Attach a section to a segment.
1001 attach_section_to_segment(Output_section*);
1003 // Get section order.
1004 Output_section_order
1005 default_section_order(Output_section*, bool is_relro_local);
1007 // Attach an allocated section to a segment.
1009 attach_allocated_section_to_segment(Output_section*);
1011 // Set the final file offsets of all the segments.
1013 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
1015 // Set the file offsets of the sections when doing a relocatable
1018 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx);
1020 // Set the final file offsets of all the sections not associated
1021 // with a segment. We set section offsets in three passes: the
1022 // first handles all allocated sections, the second sections that
1023 // require postprocessing, and the last the late-bound STRTAB
1024 // sections (probably only shstrtab, which is the one we care about
1025 // because it holds section names).
1026 enum Section_offset_pass
1028 BEFORE_INPUT_SECTIONS_PASS,
1029 POSTPROCESSING_SECTIONS_PASS,
1030 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1033 set_section_offsets(off_t, Section_offset_pass pass);
1035 // Set the final section indexes of all the sections not associated
1036 // with a segment. Returns the next unused index.
1038 set_section_indexes(unsigned int pshndx);
1040 // Set the section addresses when using a script.
1042 set_section_addresses_from_script(Symbol_table*);
1044 // Find appropriate places or orphan sections in a script.
1046 place_orphan_sections_in_script();
1048 // Return whether SEG1 comes before SEG2 in the output file.
1050 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
1052 // Use to save and restore segments during relaxation.
1053 typedef Unordered_map<const Output_segment*, const Output_segment*>
1056 // Save states of current output segments.
1058 save_segments(Segment_states*);
1060 // Restore output segment states.
1062 restore_segments(const Segment_states*);
1064 // Clean up after relaxation so that it is possible to lay out the
1065 // sections and segments again.
1067 clean_up_after_relaxation();
1069 // Doing preparation work for relaxation. This is factored out to make
1070 // Layout::finalized a bit smaller and easier to read.
1072 prepare_for_relaxation();
1074 // Main body of the relaxation loop, which lays out the section.
1076 relaxation_loop_body(int, Target*, Symbol_table*, Output_segment**,
1077 Output_segment*, Output_segment_headers*,
1078 Output_file_header*, unsigned int*);
1080 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1081 typedef Unordered_map<std::string, Kept_section> Signatures;
1083 // Mapping from input section name/type/flags to output section. We
1084 // use canonicalized strings here.
1086 typedef std::pair<Stringpool::Key,
1087 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
1092 operator()(const Key& k) const;
1095 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
1097 // A comparison class for segments.
1099 struct Compare_segments
1102 operator()(const Output_segment* seg1, const Output_segment* seg2)
1103 { return Layout::segment_precedes(seg1, seg2); }
1106 typedef std::vector<Output_section_data*> Output_section_data_list;
1108 // Debug checker class.
1109 class Relaxation_debug_check
1112 Relaxation_debug_check()
1116 // Check that sections and special data are in reset states.
1118 check_output_data_for_reset_values(const Layout::Section_list&,
1119 const Layout::Data_list&);
1121 // Record information of a section list.
1123 read_sections(const Layout::Section_list&);
1125 // Verify a section list with recorded information.
1127 verify_sections(const Layout::Section_list&);
1130 // Information we care about a section.
1133 // Output section described by this.
1134 Output_section* output_section;
1143 // Section information.
1144 std::vector<Section_info> section_infos_;
1147 // The number of input files, for sizing tables.
1148 int number_of_input_files_;
1149 // Information set by scripts or by command line options.
1150 Script_options* script_options_;
1151 // The output section names.
1152 Stringpool namepool_;
1153 // The output symbol names.
1154 Stringpool sympool_;
1155 // The dynamic strings, if needed.
1156 Stringpool dynpool_;
1157 // The list of group sections and linkonce sections which we have seen.
1158 Signatures signatures_;
1159 // The mapping from input section name/type/flags to output sections.
1160 Section_name_map section_name_map_;
1161 // The list of output segments.
1162 Segment_list segment_list_;
1163 // The list of output sections.
1164 Section_list section_list_;
1165 // The list of output sections which are not attached to any output
1167 Section_list unattached_section_list_;
1168 // The list of unattached Output_data objects which require special
1169 // handling because they are not Output_sections.
1170 Data_list special_output_list_;
1171 // The section headers.
1172 Output_section_headers* section_headers_;
1173 // A pointer to the PT_TLS segment if there is one.
1174 Output_segment* tls_segment_;
1175 // A pointer to the PT_GNU_RELRO segment if there is one.
1176 Output_segment* relro_segment_;
1177 // A pointer to the PT_INTERP segment if there is one.
1178 Output_segment* interp_segment_;
1179 // A backend may increase the size of the PT_GNU_RELRO segment if
1180 // there is one. This is the amount to increase it by.
1181 unsigned int increase_relro_;
1182 // The SHT_SYMTAB output section.
1183 Output_section* symtab_section_;
1184 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1185 Output_symtab_xindex* symtab_xindex_;
1186 // The SHT_DYNSYM output section if there is one.
1187 Output_section* dynsym_section_;
1188 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1189 Output_symtab_xindex* dynsym_xindex_;
1190 // The SHT_DYNAMIC output section if there is one.
1191 Output_section* dynamic_section_;
1192 // The _DYNAMIC symbol if there is one.
1193 Symbol* dynamic_symbol_;
1194 // The dynamic data which goes into dynamic_section_.
1195 Output_data_dynamic* dynamic_data_;
1196 // The exception frame output section if there is one.
1197 Output_section* eh_frame_section_;
1198 // The exception frame data for eh_frame_section_.
1199 Eh_frame* eh_frame_data_;
1200 // Whether we have added eh_frame_data_ to the .eh_frame section.
1201 bool added_eh_frame_data_;
1202 // The exception frame header output section if there is one.
1203 Output_section* eh_frame_hdr_section_;
1204 // The space for the build ID checksum if there is one.
1205 Output_section_data* build_id_note_;
1206 // The output section containing dwarf abbreviations
1207 Output_reduced_debug_abbrev_section* debug_abbrev_;
1208 // The output section containing the dwarf debug info tree
1209 Output_reduced_debug_info_section* debug_info_;
1210 // A list of group sections and their signatures.
1211 Group_signatures group_signatures_;
1212 // The size of the output file.
1213 off_t output_file_size_;
1214 // Whether we have added an input section to an output section.
1215 bool have_added_input_section_;
1216 // Whether we have attached the sections to the segments.
1217 bool sections_are_attached_;
1218 // Whether we have seen an object file marked to require an
1219 // executable stack.
1220 bool input_requires_executable_stack_;
1221 // Whether we have seen at least one object file with an executable
1223 bool input_with_gnu_stack_note_;
1224 // Whether we have seen at least one object file without an
1225 // executable stack marker.
1226 bool input_without_gnu_stack_note_;
1227 // Whether we have seen an object file that uses the static TLS model.
1228 bool has_static_tls_;
1229 // Whether any sections require postprocessing.
1230 bool any_postprocessing_sections_;
1231 // Whether we have resized the signatures_ hash table.
1232 bool resized_signatures_;
1233 // Whether we have created a .stab*str output section.
1234 bool have_stabstr_section_;
1235 // In incremental build, holds information check the inputs and build the
1236 // .gnu_incremental_inputs section.
1237 Incremental_inputs* incremental_inputs_;
1238 // Whether we record output section data created in script
1239 bool record_output_section_data_from_script_;
1240 // List of output data that needs to be removed at relaxation clean up.
1241 Output_section_data_list script_output_section_data_list_;
1242 // Structure to save segment states before entering the relaxation loop.
1243 Segment_states* segment_states_;
1244 // A relaxation debug checker. We only create one when in debugging mode.
1245 Relaxation_debug_check* relaxation_debug_check_;
1246 // Hash a pattern to its position in the section ordering file.
1247 Unordered_map<std::string, unsigned int> input_section_position_;
1248 // Vector of glob only patterns in the section_ordering file.
1249 std::vector<std::string> input_section_glob_;
1250 // For incremental links, the base file to be modified.
1251 Incremental_binary* incremental_base_;
1252 // For incremental links, a list of free space within the file.
1253 Free_list free_list_;
1256 // This task handles writing out data in output sections which is not
1257 // part of an input section, or which requires special handling. When
1258 // this is done, it unblocks both output_sections_blocker and
1261 class Write_sections_task : public Task
1264 Write_sections_task(const Layout* layout, Output_file* of,
1265 Task_token* output_sections_blocker,
1266 Task_token* final_blocker)
1267 : layout_(layout), of_(of),
1268 output_sections_blocker_(output_sections_blocker),
1269 final_blocker_(final_blocker)
1272 // The standard Task methods.
1278 locks(Task_locker*);
1285 { return "Write_sections_task"; }
1288 class Write_sections_locker;
1290 const Layout* layout_;
1292 Task_token* output_sections_blocker_;
1293 Task_token* final_blocker_;
1296 // This task handles writing out data which is not part of a section
1299 class Write_data_task : public Task
1302 Write_data_task(const Layout* layout, const Symbol_table* symtab,
1303 Output_file* of, Task_token* final_blocker)
1304 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
1307 // The standard Task methods.
1313 locks(Task_locker*);
1320 { return "Write_data_task"; }
1323 const Layout* layout_;
1324 const Symbol_table* symtab_;
1326 Task_token* final_blocker_;
1329 // This task handles writing out the global symbols.
1331 class Write_symbols_task : public Task
1334 Write_symbols_task(const Layout* layout, const Symbol_table* symtab,
1335 const Input_objects* input_objects,
1336 const Stringpool* sympool, const Stringpool* dynpool,
1337 Output_file* of, Task_token* final_blocker)
1338 : layout_(layout), symtab_(symtab), input_objects_(input_objects),
1339 sympool_(sympool), dynpool_(dynpool), of_(of),
1340 final_blocker_(final_blocker)
1343 // The standard Task methods.
1349 locks(Task_locker*);
1356 { return "Write_symbols_task"; }
1359 const Layout* layout_;
1360 const Symbol_table* symtab_;
1361 const Input_objects* input_objects_;
1362 const Stringpool* sympool_;
1363 const Stringpool* dynpool_;
1365 Task_token* final_blocker_;
1368 // This task handles writing out data in output sections which can't
1369 // be written out until all the input sections have been handled.
1370 // This is for sections whose contents is based on the contents of
1371 // other output sections.
1373 class Write_after_input_sections_task : public Task
1376 Write_after_input_sections_task(Layout* layout, Output_file* of,
1377 Task_token* input_sections_blocker,
1378 Task_token* final_blocker)
1379 : layout_(layout), of_(of),
1380 input_sections_blocker_(input_sections_blocker),
1381 final_blocker_(final_blocker)
1384 // The standard Task methods.
1390 locks(Task_locker*);
1397 { return "Write_after_input_sections_task"; }
1402 Task_token* input_sections_blocker_;
1403 Task_token* final_blocker_;
1406 // This task function handles closing the file.
1408 class Close_task_runner : public Task_function_runner
1411 Close_task_runner(const General_options* options, const Layout* layout,
1413 : options_(options), layout_(layout), of_(of)
1416 // Run the operation.
1418 run(Workqueue*, const Task*);
1421 const General_options* options_;
1422 const Layout* layout_;
1426 // A small helper function to align an address.
1429 align_address(uint64_t address, uint64_t addralign)
1432 address = (address + addralign - 1) &~ (addralign - 1);
1436 } // End namespace gold.
1438 #endif // !defined(GOLD_LAYOUT_H)