1 // layout.h -- lay out output file sections for gold -*- C++ -*-
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 "workqueue.h"
38 #include "stringpool.h"
43 class General_options;
44 class Incremental_inputs;
45 class Incremental_binary;
49 class Output_section_data;
51 class Output_section_headers;
52 class Output_segment_headers;
53 class Output_file_header;
56 class Output_data_reloc_generic;
57 class Output_data_dynamic;
58 class Output_symtab_xindex;
59 class Output_reduced_debug_abbrev_section;
60 class Output_reduced_debug_info_section;
66 // Return TRUE if SECNAME is the name of a compressed debug section.
68 is_compressed_debug_section(const char* secname);
70 // Maintain a list of free space within a section, segment, or file.
71 // Used for incremental update links.
78 Free_list_node(off_t start, off_t end)
79 : start_(start), end_(end)
84 typedef std::list<Free_list_node>::const_iterator Const_iterator;
87 : list_(), last_remove_(list_.begin()), extend_(false), length_(0),
91 // Initialize the free list for a section of length LEN.
92 // If EXTEND is true, free space may be allocated past the end.
94 init(off_t len, bool extend);
96 // Set the minimum hole size that is allowed when allocating
97 // from the free list.
99 set_min_hole_size(off_t min_hole)
100 { this->min_hole_ = min_hole; }
102 // Remove a chunk from the free list.
104 remove(off_t start, off_t end);
106 // Allocate a chunk of space from the free list of length LEN,
107 // with alignment ALIGN, and minimum offset MINOFF.
109 allocate(off_t len, uint64_t align, off_t minoff);
111 // Return an iterator for the beginning of the free list.
114 { return this->list_.begin(); }
116 // Return an iterator for the end of the free list.
119 { return this->list_.end(); }
121 // Dump the free list (for debugging).
125 // Print usage statistics.
130 typedef std::list<Free_list_node>::iterator Iterator;
133 std::list<Free_list_node> list_;
135 // The last node visited during a remove operation.
136 Iterator last_remove_;
138 // Whether we can extend past the original length.
141 // The total length of the section, segment, or file.
144 // The minimum hole size allowed. When allocating from the free list,
145 // we must not leave a hole smaller than this.
149 // The total number of free lists used.
150 static unsigned int num_lists;
151 // The total number of free list nodes used.
152 static unsigned int num_nodes;
153 // The total number of calls to Free_list::remove.
154 static unsigned int num_removes;
155 // The total number of nodes visited during calls to Free_list::remove.
156 static unsigned int num_remove_visits;
157 // The total number of calls to Free_list::allocate.
158 static unsigned int num_allocates;
159 // The total number of nodes visited during calls to Free_list::allocate.
160 static unsigned int num_allocate_visits;
163 // This task function handles mapping the input sections to output
164 // sections and laying them out in memory.
166 class Layout_task_runner : public Task_function_runner
169 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
170 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
172 Layout_task_runner(const General_options& options,
173 const Input_objects* input_objects,
174 Symbol_table* symtab,
178 : options_(options), input_objects_(input_objects), symtab_(symtab),
179 target_(target), layout_(layout), mapfile_(mapfile)
182 // Run the operation.
184 run(Workqueue*, const Task*);
187 Layout_task_runner(const Layout_task_runner&);
188 Layout_task_runner& operator=(const Layout_task_runner&);
190 const General_options& options_;
191 const Input_objects* input_objects_;
192 Symbol_table* symtab_;
198 // This class holds information about the comdat group or
199 // .gnu.linkonce section that will be kept for a given signature.
204 // For a comdat group, we build a mapping from the name of each
205 // section in the group to the section index and the size in object.
206 // When we discard a group in some other object file, we use this
207 // map to figure out which kept section the discarded section is
208 // associated with. We then use that mapping when processing relocs
209 // against discarded sections.
210 struct Comdat_section_info
212 // The section index.
217 Comdat_section_info(unsigned int a_shndx, uint64_t a_size)
218 : shndx(a_shndx), size(a_size)
222 // Most comdat groups have only one or two sections, so we use a
223 // std::map rather than an Unordered_map to optimize for that case
224 // without paying too heavily for groups with more sections.
225 typedef std::map<std::string, Comdat_section_info> Comdat_group;
229 : object_(NULL), shndx_(0), is_comdat_(false), is_group_name_(false)
230 { this->u_.linkonce_size = 0; }
232 // We need to support copies for the signature map in the Layout
233 // object, but we should never copy an object after it has been
234 // marked as a comdat section.
235 Kept_section(const Kept_section& k)
236 : object_(k.object_), shndx_(k.shndx_), is_comdat_(false),
237 is_group_name_(k.is_group_name_)
239 gold_assert(!k.is_comdat_);
240 this->u_.linkonce_size = 0;
245 if (this->is_comdat_)
246 delete this->u_.group_sections;
249 // The object where this section lives.
252 { return this->object_; }
256 set_object(Relobj* object)
258 gold_assert(this->object_ == NULL);
259 this->object_ = object;
262 // The section index.
265 { return this->shndx_; }
267 // Set the section index.
269 set_shndx(unsigned int shndx)
271 gold_assert(this->shndx_ == 0);
272 this->shndx_ = shndx;
275 // Whether this is a comdat group.
278 { return this->is_comdat_; }
280 // Set that this is a comdat group.
284 gold_assert(!this->is_comdat_);
285 this->is_comdat_ = true;
286 this->u_.group_sections = new Comdat_group();
289 // Whether this is associated with the name of a group or section
290 // rather than the symbol name derived from a linkonce section.
292 is_group_name() const
293 { return this->is_group_name_; }
295 // Note that this represents a comdat group rather than a single
299 { this->is_group_name_ = true; }
301 // Add a section to the group list.
303 add_comdat_section(const std::string& name, unsigned int shndx,
306 gold_assert(this->is_comdat_);
307 Comdat_section_info sinfo(shndx, size);
308 this->u_.group_sections->insert(std::make_pair(name, sinfo));
311 // Look for a section name in the group list, and return whether it
312 // was found. If found, returns the section index and size.
314 find_comdat_section(const std::string& name, unsigned int* pshndx,
315 uint64_t* psize) const
317 gold_assert(this->is_comdat_);
318 Comdat_group::const_iterator p = this->u_.group_sections->find(name);
319 if (p == this->u_.group_sections->end())
321 *pshndx = p->second.shndx;
322 *psize = p->second.size;
326 // If there is only one section in the group list, return true, and
327 // return the section index and size.
329 find_single_comdat_section(unsigned int* pshndx, uint64_t* psize) const
331 gold_assert(this->is_comdat_);
332 if (this->u_.group_sections->size() != 1)
334 Comdat_group::const_iterator p = this->u_.group_sections->begin();
335 *pshndx = p->second.shndx;
336 *psize = p->second.size;
340 // Return the size of a linkonce section.
342 linkonce_size() const
344 gold_assert(!this->is_comdat_);
345 return this->u_.linkonce_size;
348 // Set the size of a linkonce section.
350 set_linkonce_size(uint64_t size)
352 gold_assert(!this->is_comdat_);
353 this->u_.linkonce_size = size;
358 Kept_section& operator=(const Kept_section&);
360 // The object containing the comdat group or .gnu.linkonce section.
362 // Index of the group section for comdats and the section itself for
365 // True if this is for a comdat group rather than a .gnu.linkonce
368 // The Kept_sections are values of a mapping, that maps names to
369 // them. This field is true if this struct is associated with the
370 // name of a comdat or .gnu.linkonce, false if it is associated with
371 // the name of a symbol obtained from the .gnu.linkonce.* name
372 // through some heuristics.
376 // If the is_comdat_ field is true, this holds a map from names of
377 // the sections in the group to section indexes in object_ and to
379 Comdat_group* group_sections;
380 // If the is_comdat_ field is false, this holds the size of the
382 uint64_t linkonce_size;
386 // The ordering for output sections. This controls how output
387 // sections are ordered within a PT_LOAD output segment.
389 enum Output_section_order
391 // Unspecified. Used for non-load segments. Also used for the file
392 // and segment headers.
395 // The PT_INTERP section should come first, so that the dynamic
396 // linker can pick it up quickly.
399 // Loadable read-only note sections come next so that the PT_NOTE
400 // segment is on the first page of the executable.
403 // Put read-only sections used by the dynamic linker early in the
404 // executable to minimize paging.
405 ORDER_DYNAMIC_LINKER,
407 // Put reloc sections used by the dynamic linker after other
408 // sections used by the dynamic linker; otherwise, objcopy and strip
410 ORDER_DYNAMIC_RELOCS,
412 // Put the PLT reloc section after the other dynamic relocs;
413 // otherwise, prelink gets confused.
414 ORDER_DYNAMIC_PLT_RELOCS,
416 // The .init section.
422 // The regular text sections.
425 // The .fini section.
428 // The read-only sections.
431 // The exception frame sections.
434 // The TLS sections come first in the data section.
438 // Local RELRO (read-only after relocation) sections come before
439 // non-local RELRO sections. This data will be fully resolved by
443 // Non-local RELRO sections are grouped together after local RELRO
444 // sections. All RELRO sections must be adjacent so that they can
445 // all be put into a PT_GNU_RELRO segment.
448 // We permit marking exactly one output section as the last RELRO
449 // section. We do this so that the read-only GOT can be adjacent to
453 // Similarly, we permit marking exactly one output section as the
454 // first non-RELRO section.
455 ORDER_NON_RELRO_FIRST,
457 // The regular data sections come after the RELRO sections.
460 // Large data sections normally go in large data segments.
463 // Group writable notes so that we can have a single PT_NOTE
467 // The small data sections must be at the end of the data sections,
468 // so that they can be adjacent to the small BSS sections.
471 // The BSS sections start here.
473 // The small BSS sections must be at the start of the BSS sections,
474 // so that they can be adjacent to the small data sections.
477 // The regular BSS sections.
480 // The large BSS sections come after the other BSS sections.
487 // This class handles the details of laying out input sections.
492 Layout(int number_of_input_files, Script_options*);
496 delete this->relaxation_debug_check_;
497 delete this->segment_states_;
500 // For incremental links, record the base file to be modified.
502 set_incremental_base(Incremental_binary* base);
506 { return this->incremental_base_; }
508 // For incremental links, record the initial fixed layout of a section
509 // from the base file, and return a pointer to the Output_section.
510 template<int size, bool big_endian>
512 init_fixed_output_section(const char*, elfcpp::Shdr<size, big_endian>&);
514 // Given an input section SHNDX, named NAME, with data in SHDR, from
515 // the object file OBJECT, return the output section where this
516 // input section should go. RELOC_SHNDX is the index of a
517 // relocation section which applies to this section, or 0 if none,
518 // or -1U if more than one. RELOC_TYPE is the type of the
519 // relocation section if there is one. Set *OFFSET to the offset
520 // within the output section.
521 template<int size, bool big_endian>
523 layout(Sized_relobj_file<size, big_endian> *object, unsigned int shndx,
524 const char* name, const elfcpp::Shdr<size, big_endian>& shdr,
525 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);
527 std::map<Section_id, unsigned int>*
528 get_section_order_map()
529 { return &this->section_order_map_; }
531 // Struct to store segment info when mapping some input sections to
532 // unique segments using linker plugins. Mapping an input section to
533 // a unique segment is done by first placing such input sections in
534 // unique output sections and then mapping the output section to a
535 // unique segment. NAME is the name of the output section. FLAGS
536 // and ALIGN are the extra flags and alignment of the segment.
537 struct Unique_segment_info
539 // Identifier for the segment. ELF segments dont have names. This
540 // is used as the name of the output section mapped to the segment.
542 // Additional segment flags.
544 // Segment alignment.
548 // Mapping from input section to segment.
549 typedef std::map<Const_section_id, Unique_segment_info*>
552 // Maps section SECN to SEGMENT s.
554 insert_section_segment_map(Const_section_id secn, Unique_segment_info *s);
556 // Some input sections require special ordering, for compatibility
557 // with GNU ld. Given the name of an input section, return -1 if it
558 // does not require special ordering. Otherwise, return the index
559 // by which it should be ordered compared to other input sections
560 // that require special ordering.
562 special_ordering_of_input_section(const char* name);
565 is_section_ordering_specified()
566 { return this->section_ordering_specified_; }
569 set_section_ordering_specified()
570 { this->section_ordering_specified_ = true; }
573 is_unique_segment_for_sections_specified() const
574 { return this->unique_segment_for_sections_specified_; }
577 set_unique_segment_for_sections_specified()
578 { this->unique_segment_for_sections_specified_ = true; }
580 // For incremental updates, allocate a block of memory from the
581 // free list. Find a block starting at or after MINOFF.
583 allocate(off_t len, uint64_t align, off_t minoff)
584 { return this->free_list_.allocate(len, align, minoff); }
587 find_section_order_index(const std::string&);
589 // Read the sequence of input sections from the file specified with
590 // linker option --section-ordering-file.
592 read_layout_from_file();
594 // Layout an input reloc section when doing a relocatable link. The
595 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
596 // DATA_SECTION is the reloc section to which it refers. RR is the
597 // relocatable information.
598 template<int size, bool big_endian>
600 layout_reloc(Sized_relobj_file<size, big_endian>* object,
601 unsigned int reloc_shndx,
602 const elfcpp::Shdr<size, big_endian>& shdr,
603 Output_section* data_section,
604 Relocatable_relocs* rr);
606 // Layout a group section when doing a relocatable link.
607 template<int size, bool big_endian>
609 layout_group(Symbol_table* symtab,
610 Sized_relobj_file<size, big_endian>* object,
611 unsigned int group_shndx,
612 const char* group_section_name,
613 const char* signature,
614 const elfcpp::Shdr<size, big_endian>& shdr,
615 elfcpp::Elf_Word flags,
616 std::vector<unsigned int>* shndxes);
618 // Like layout, only for exception frame sections. OBJECT is an
619 // object file. SYMBOLS is the contents of the symbol table
620 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
621 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
622 // .eh_frame section in OBJECT. SHDR is the section header.
623 // RELOC_SHNDX is the index of a relocation section which applies to
624 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
625 // is the type of the relocation section if there is one. This
626 // returns the output section, and sets *OFFSET to the offset.
627 template<int size, bool big_endian>
629 layout_eh_frame(Sized_relobj_file<size, big_endian>* object,
630 const unsigned char* symbols,
632 const unsigned char* symbol_names,
633 off_t symbol_names_size,
635 const elfcpp::Shdr<size, big_endian>& shdr,
636 unsigned int reloc_shndx, unsigned int reloc_type,
639 // Add .eh_frame information for a PLT. The FDE must start with a
640 // 4-byte PC-relative reference to the start of the PLT, followed by
641 // a 4-byte size of PLT.
643 add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data,
644 size_t cie_length, const unsigned char* fde_data,
647 // Scan a .debug_info or .debug_types section, and add summary
648 // information to the .gdb_index section.
649 template<int size, bool big_endian>
651 add_to_gdb_index(bool is_type_unit,
652 Sized_relobj<size, big_endian>* object,
653 const unsigned char* symbols,
656 unsigned int reloc_shndx,
657 unsigned int reloc_type);
659 // Handle a GNU stack note. This is called once per input object
660 // file. SEEN_GNU_STACK is true if the object file has a
661 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
662 // from that section if there was one.
664 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags,
667 // Add an Output_section_data to the layout. This is used for
668 // special sections like the GOT section. ORDER is where the
669 // section should wind up in the output segment. IS_RELRO is true
670 // for relro sections.
672 add_output_section_data(const char* name, elfcpp::Elf_Word type,
673 elfcpp::Elf_Xword flags,
674 Output_section_data*, Output_section_order order,
677 // Increase the size of the relro segment by this much.
679 increase_relro(unsigned int s)
680 { this->increase_relro_ += s; }
682 // Create dynamic sections if necessary.
684 create_initial_dynamic_sections(Symbol_table*);
686 // Define __start and __stop symbols for output sections.
688 define_section_symbols(Symbol_table*);
690 // Create automatic note sections.
694 // Create sections for linker scripts.
696 create_script_sections()
697 { this->script_options_->create_script_sections(this); }
699 // Define symbols from any linker script.
701 define_script_symbols(Symbol_table* symtab)
702 { this->script_options_->add_symbols_to_table(symtab); }
704 // Define symbols for group signatures.
706 define_group_signatures(Symbol_table*);
708 // Return the Stringpool used for symbol names.
711 { return &this->sympool_; }
713 // Return the Stringpool used for dynamic symbol names and dynamic
717 { return &this->dynpool_; }
719 // Return the .dynamic output section. This is only valid after the
720 // layout has been finalized.
722 dynamic_section() const
723 { return this->dynamic_section_; }
725 // Return the symtab_xindex section used to hold large section
726 // indexes for the normal symbol table.
727 Output_symtab_xindex*
728 symtab_xindex() const
729 { return this->symtab_xindex_; }
731 // Return the dynsym_xindex section used to hold large section
732 // indexes for the dynamic symbol table.
733 Output_symtab_xindex*
734 dynsym_xindex() const
735 { return this->dynsym_xindex_; }
737 // Return whether a section is a .gnu.linkonce section, given the
740 is_linkonce(const char* name)
741 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
743 // Whether we have added an input section.
745 have_added_input_section() const
746 { return this->have_added_input_section_; }
748 // Return true if a section is a debugging section.
750 is_debug_info_section(const char* name)
752 // Debugging sections can only be recognized by name.
753 return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0
754 || strncmp(name, ".zdebug", sizeof(".zdebug") - 1) == 0
755 || strncmp(name, ".gnu.linkonce.wi.",
756 sizeof(".gnu.linkonce.wi.") - 1) == 0
757 || strncmp(name, ".line", sizeof(".line") - 1) == 0
758 || strncmp(name, ".stab", sizeof(".stab") - 1) == 0);
761 // Return true if RELOBJ is an input file whose base name matches
762 // FILE_NAME. The base name must have an extension of ".o", and
763 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
765 match_file_name(const Relobj* relobj, const char* file_name);
767 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
768 // with more than one word being mapped to a .init_array/.fini_array
771 is_ctors_in_init_array(Relobj* relobj, unsigned int shndx) const;
773 // Check if a comdat group or .gnu.linkonce section with the given
774 // NAME is selected for the link. If there is already a section,
775 // *KEPT_SECTION is set to point to the signature and the function
776 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
777 // IS_GROUP_NAME are recorded for this NAME in the layout object,
778 // *KEPT_SECTION is set to the internal copy and the function return
781 find_or_add_kept_section(const std::string& name, Relobj* object,
782 unsigned int shndx, bool is_comdat,
783 bool is_group_name, Kept_section** kept_section);
785 // Finalize the layout after all the input sections have been added.
787 finalize(const Input_objects*, Symbol_table*, Target*, const Task*);
789 // Return whether any sections require postprocessing.
791 any_postprocessing_sections() const
792 { return this->any_postprocessing_sections_; }
794 // Return the size of the output file.
796 output_file_size() const
797 { return this->output_file_size_; }
799 // Return the TLS segment. This will return NULL if there isn't
803 { return this->tls_segment_; }
805 // Return the normal symbol table.
807 symtab_section() const
809 gold_assert(this->symtab_section_ != NULL);
810 return this->symtab_section_;
813 // Return the file offset of the normal symbol table.
815 symtab_section_offset() const;
817 // Return the section index of the normal symbol tabl.e
819 symtab_section_shndx() const;
821 // Return the dynamic symbol table.
823 dynsym_section() const
825 gold_assert(this->dynsym_section_ != NULL);
826 return this->dynsym_section_;
829 // Return the dynamic tags.
832 { return this->dynamic_data_; }
834 // Write out the output sections.
836 write_output_sections(Output_file* of) const;
838 // Write out data not associated with an input file or the symbol
841 write_data(const Symbol_table*, Output_file*) const;
843 // Write out output sections which can not be written until all the
844 // input sections are complete.
846 write_sections_after_input_sections(Output_file* of);
848 // Return an output section named NAME, or NULL if there is none.
850 find_output_section(const char* name) const;
852 // Return an output segment of type TYPE, with segment flags SET set
853 // and segment flags CLEAR clear. Return NULL if there is none.
855 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
856 elfcpp::Elf_Word clear) const;
858 // Return the number of segments we expect to produce.
860 expected_segment_count() const;
862 // Set a flag to indicate that an object file uses the static TLS model.
865 { this->has_static_tls_ = true; }
867 // Return true if any object file uses the static TLS model.
869 has_static_tls() const
870 { return this->has_static_tls_; }
872 // Return the options which may be set by a linker script.
875 { return this->script_options_; }
877 const Script_options*
878 script_options() const
879 { return this->script_options_; }
881 // Return the object managing inputs in incremental build. NULL in
882 // non-incremental builds.
884 incremental_inputs() const
885 { return this->incremental_inputs_; }
887 // For the target-specific code to add dynamic tags which are common
890 add_target_dynamic_tags(bool use_rel, const Output_data* plt_got,
891 const Output_data* plt_rel,
892 const Output_data_reloc_generic* dyn_rel,
893 bool add_debug, bool dynrel_includes_plt);
895 // Compute and write out the build ID if needed.
897 write_build_id(Output_file*) const;
899 // Rewrite output file in binary format.
901 write_binary(Output_file* in) const;
903 // Print output sections to the map file.
905 print_to_mapfile(Mapfile*) const;
907 // Dump statistical information to stderr.
911 // A list of segments.
913 typedef std::vector<Output_segment*> Segment_list;
915 // A list of sections.
917 typedef std::vector<Output_section*> Section_list;
919 // The list of information to write out which is not attached to
920 // either a section or a segment.
921 typedef std::vector<Output_data*> Data_list;
923 // Store the allocated sections into the section list. This is used
924 // by the linker script code.
926 get_allocated_sections(Section_list*) const;
928 // Store the executable sections into the section list.
930 get_executable_sections(Section_list*) const;
932 // Make a section for a linker script to hold data.
934 make_output_section_for_script(const char* name,
935 Script_sections::Section_type section_type);
937 // Make a segment. This is used by the linker script code.
939 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);
941 // Return the number of segments.
943 segment_count() const
944 { return this->segment_list_.size(); }
946 // Map from section flags to segment flags.
947 static elfcpp::Elf_Word
948 section_flags_to_segment(elfcpp::Elf_Xword flags);
950 // Attach sections to segments.
952 attach_sections_to_segments(const Target*);
954 // For relaxation clean up, we need to know output section data created
955 // from a linker script.
957 new_output_section_data_from_script(Output_section_data* posd)
959 if (this->record_output_section_data_from_script_)
960 this->script_output_section_data_list_.push_back(posd);
963 // Return section list.
966 { return this->section_list_; }
968 // Returns TRUE iff NAME (an input section from RELOBJ) will
969 // be mapped to an output section that should be KEPT.
971 keep_input_section(const Relobj*, const char*);
974 Layout(const Layout&);
975 Layout& operator=(const Layout&);
977 // Mapping from input section names to output section names.
978 struct Section_name_mapping
985 static const Section_name_mapping section_name_mapping[];
986 static const int section_name_mapping_count;
988 // During a relocatable link, a list of group sections and
990 struct Group_signature
992 // The group section.
993 Output_section* section;
995 const char* signature;
998 : section(NULL), signature(NULL)
1001 Group_signature(Output_section* sectiona, const char* signaturea)
1002 : section(sectiona), signature(signaturea)
1005 typedef std::vector<Group_signature> Group_signatures;
1007 // Create a note section, filling in the header.
1009 create_note(const char* name, int note_type, const char* section_name,
1010 size_t descsz, bool allocate, size_t* trailing_padding);
1012 // Create a note section for gold version.
1016 // Record whether the stack must be executable.
1018 create_executable_stack_info();
1020 // Create a build ID note if needed.
1024 // Link .stab and .stabstr sections.
1026 link_stabs_sections();
1028 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1029 // for the next run of incremental linking to check what has changed.
1031 create_incremental_info_sections(Symbol_table*);
1033 // Find the first read-only PT_LOAD segment, creating one if
1036 find_first_load_seg(const Target*);
1038 // Count the local symbols in the regular symbol table and the dynamic
1039 // symbol table, and build the respective string pools.
1041 count_local_symbols(const Task*, const Input_objects*);
1043 // Create the output sections for the symbol table.
1045 create_symtab_sections(const Input_objects*, Symbol_table*,
1046 unsigned int, off_t*);
1048 // Create the .shstrtab section.
1052 // Create the section header table.
1054 create_shdrs(const Output_section* shstrtab_section, off_t*);
1056 // Create the dynamic symbol table.
1058 create_dynamic_symtab(const Input_objects*, Symbol_table*,
1059 Output_section** pdynstr,
1060 unsigned int* plocal_dynamic_count,
1061 std::vector<Symbol*>* pdynamic_symbols,
1062 Versions* versions);
1064 // Assign offsets to each local portion of the dynamic symbol table.
1066 assign_local_dynsym_offsets(const Input_objects*);
1068 // Finish the .dynamic section and PT_DYNAMIC segment.
1070 finish_dynamic_section(const Input_objects*, const Symbol_table*);
1072 // Set the size of the _DYNAMIC symbol.
1074 set_dynamic_symbol_size(const Symbol_table*);
1076 // Create the .interp section and PT_INTERP segment.
1078 create_interp(const Target* target);
1080 // Create the version sections.
1082 create_version_sections(const Versions*,
1083 const Symbol_table*,
1084 unsigned int local_symcount,
1085 const std::vector<Symbol*>& dynamic_symbols,
1086 const Output_section* dynstr);
1088 template<int size, bool big_endian>
1090 sized_create_version_sections(const Versions* versions,
1091 const Symbol_table*,
1092 unsigned int local_symcount,
1093 const std::vector<Symbol*>& dynamic_symbols,
1094 const Output_section* dynstr);
1096 // Return whether to include this section in the link.
1097 template<int size, bool big_endian>
1099 include_section(Sized_relobj_file<size, big_endian>* object, const char* name,
1100 const elfcpp::Shdr<size, big_endian>&);
1102 // Return the output section name to use given an input section
1103 // name. Set *PLEN to the length of the name. *PLEN must be
1104 // initialized to the length of NAME.
1106 output_section_name(const Relobj*, const char* name, size_t* plen);
1108 // Return the number of allocated output sections.
1110 allocated_output_section_count() const;
1112 // Return the output section for NAME, TYPE and FLAGS.
1114 get_output_section(const char* name, Stringpool::Key name_key,
1115 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
1116 Output_section_order order, bool is_relro);
1118 // Clear the input section flags that should not be copied to the
1121 get_output_section_flags (elfcpp::Elf_Xword input_section_flags);
1123 // Choose the output section for NAME in RELOBJ.
1125 choose_output_section(const Relobj* relobj, const char* name,
1126 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags,
1127 bool is_input_section, Output_section_order order,
1130 // Create a new Output_section.
1132 make_output_section(const char* name, elfcpp::Elf_Word type,
1133 elfcpp::Elf_Xword flags, Output_section_order order,
1136 // Attach a section to a segment.
1138 attach_section_to_segment(const Target*, Output_section*);
1140 // Get section order.
1141 Output_section_order
1142 default_section_order(Output_section*, bool is_relro_local);
1144 // Attach an allocated section to a segment.
1146 attach_allocated_section_to_segment(const Target*, Output_section*);
1148 // Make the .eh_frame section.
1150 make_eh_frame_section(const Relobj*);
1152 // Set the final file offsets of all the segments.
1154 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
1156 // Set the file offsets of the sections when doing a relocatable
1159 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx);
1161 // Set the final file offsets of all the sections not associated
1162 // with a segment. We set section offsets in three passes: the
1163 // first handles all allocated sections, the second sections that
1164 // require postprocessing, and the last the late-bound STRTAB
1165 // sections (probably only shstrtab, which is the one we care about
1166 // because it holds section names).
1167 enum Section_offset_pass
1169 BEFORE_INPUT_SECTIONS_PASS,
1170 POSTPROCESSING_SECTIONS_PASS,
1171 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1174 set_section_offsets(off_t, Section_offset_pass pass);
1176 // Set the final section indexes of all the sections not associated
1177 // with a segment. Returns the next unused index.
1179 set_section_indexes(unsigned int pshndx);
1181 // Set the section addresses when using a script.
1183 set_section_addresses_from_script(Symbol_table*);
1185 // Find appropriate places or orphan sections in a script.
1187 place_orphan_sections_in_script();
1189 // Return whether SEG1 comes before SEG2 in the output file.
1191 segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
1193 // Use to save and restore segments during relaxation.
1194 typedef Unordered_map<const Output_segment*, const Output_segment*>
1197 // Save states of current output segments.
1199 save_segments(Segment_states*);
1201 // Restore output segment states.
1203 restore_segments(const Segment_states*);
1205 // Clean up after relaxation so that it is possible to lay out the
1206 // sections and segments again.
1208 clean_up_after_relaxation();
1210 // Doing preparation work for relaxation. This is factored out to make
1211 // Layout::finalized a bit smaller and easier to read.
1213 prepare_for_relaxation();
1215 // Main body of the relaxation loop, which lays out the section.
1217 relaxation_loop_body(int, Target*, Symbol_table*, Output_segment**,
1218 Output_segment*, Output_segment_headers*,
1219 Output_file_header*, unsigned int*);
1221 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1222 typedef Unordered_map<std::string, Kept_section> Signatures;
1224 // Mapping from input section name/type/flags to output section. We
1225 // use canonicalized strings here.
1227 typedef std::pair<Stringpool::Key,
1228 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
1233 operator()(const Key& k) const;
1236 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
1238 // A comparison class for segments.
1240 class Compare_segments
1243 Compare_segments(Layout* layout)
1248 operator()(const Output_segment* seg1, const Output_segment* seg2)
1249 { return this->layout_->segment_precedes(seg1, seg2); }
1255 typedef std::vector<Output_section_data*> Output_section_data_list;
1257 // Debug checker class.
1258 class Relaxation_debug_check
1261 Relaxation_debug_check()
1265 // Check that sections and special data are in reset states.
1267 check_output_data_for_reset_values(const Layout::Section_list&,
1268 const Layout::Data_list&);
1270 // Record information of a section list.
1272 read_sections(const Layout::Section_list&);
1274 // Verify a section list with recorded information.
1276 verify_sections(const Layout::Section_list&);
1279 // Information we care about a section.
1282 // Output section described by this.
1283 Output_section* output_section;
1292 // Section information.
1293 std::vector<Section_info> section_infos_;
1296 // The number of input files, for sizing tables.
1297 int number_of_input_files_;
1298 // Information set by scripts or by command line options.
1299 Script_options* script_options_;
1300 // The output section names.
1301 Stringpool namepool_;
1302 // The output symbol names.
1303 Stringpool sympool_;
1304 // The dynamic strings, if needed.
1305 Stringpool dynpool_;
1306 // The list of group sections and linkonce sections which we have seen.
1307 Signatures signatures_;
1308 // The mapping from input section name/type/flags to output sections.
1309 Section_name_map section_name_map_;
1310 // The list of output segments.
1311 Segment_list segment_list_;
1312 // The list of output sections.
1313 Section_list section_list_;
1314 // The list of output sections which are not attached to any output
1316 Section_list unattached_section_list_;
1317 // The list of unattached Output_data objects which require special
1318 // handling because they are not Output_sections.
1319 Data_list special_output_list_;
1320 // The section headers.
1321 Output_section_headers* section_headers_;
1322 // A pointer to the PT_TLS segment if there is one.
1323 Output_segment* tls_segment_;
1324 // A pointer to the PT_GNU_RELRO segment if there is one.
1325 Output_segment* relro_segment_;
1326 // A pointer to the PT_INTERP segment if there is one.
1327 Output_segment* interp_segment_;
1328 // A backend may increase the size of the PT_GNU_RELRO segment if
1329 // there is one. This is the amount to increase it by.
1330 unsigned int increase_relro_;
1331 // The SHT_SYMTAB output section.
1332 Output_section* symtab_section_;
1333 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1334 Output_symtab_xindex* symtab_xindex_;
1335 // The SHT_DYNSYM output section if there is one.
1336 Output_section* dynsym_section_;
1337 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1338 Output_symtab_xindex* dynsym_xindex_;
1339 // The SHT_DYNAMIC output section if there is one.
1340 Output_section* dynamic_section_;
1341 // The _DYNAMIC symbol if there is one.
1342 Symbol* dynamic_symbol_;
1343 // The dynamic data which goes into dynamic_section_.
1344 Output_data_dynamic* dynamic_data_;
1345 // The exception frame output section if there is one.
1346 Output_section* eh_frame_section_;
1347 // The exception frame data for eh_frame_section_.
1348 Eh_frame* eh_frame_data_;
1349 // Whether we have added eh_frame_data_ to the .eh_frame section.
1350 bool added_eh_frame_data_;
1351 // The exception frame header output section if there is one.
1352 Output_section* eh_frame_hdr_section_;
1353 // The data for the .gdb_index section.
1354 Gdb_index* gdb_index_data_;
1355 // The space for the build ID checksum if there is one.
1356 Output_section_data* build_id_note_;
1357 // The output section containing dwarf abbreviations
1358 Output_reduced_debug_abbrev_section* debug_abbrev_;
1359 // The output section containing the dwarf debug info tree
1360 Output_reduced_debug_info_section* debug_info_;
1361 // A list of group sections and their signatures.
1362 Group_signatures group_signatures_;
1363 // The size of the output file.
1364 off_t output_file_size_;
1365 // Whether we have added an input section to an output section.
1366 bool have_added_input_section_;
1367 // Whether we have attached the sections to the segments.
1368 bool sections_are_attached_;
1369 // Whether we have seen an object file marked to require an
1370 // executable stack.
1371 bool input_requires_executable_stack_;
1372 // Whether we have seen at least one object file with an executable
1374 bool input_with_gnu_stack_note_;
1375 // Whether we have seen at least one object file without an
1376 // executable stack marker.
1377 bool input_without_gnu_stack_note_;
1378 // Whether we have seen an object file that uses the static TLS model.
1379 bool has_static_tls_;
1380 // Whether any sections require postprocessing.
1381 bool any_postprocessing_sections_;
1382 // Whether we have resized the signatures_ hash table.
1383 bool resized_signatures_;
1384 // Whether we have created a .stab*str output section.
1385 bool have_stabstr_section_;
1386 // True if the input sections in the output sections should be sorted
1387 // as specified in a section ordering file.
1388 bool section_ordering_specified_;
1389 // True if some input sections need to be mapped to a unique segment,
1390 // after being mapped to a unique Output_section.
1391 bool unique_segment_for_sections_specified_;
1392 // In incremental build, holds information check the inputs and build the
1393 // .gnu_incremental_inputs section.
1394 Incremental_inputs* incremental_inputs_;
1395 // Whether we record output section data created in script
1396 bool record_output_section_data_from_script_;
1397 // List of output data that needs to be removed at relaxation clean up.
1398 Output_section_data_list script_output_section_data_list_;
1399 // Structure to save segment states before entering the relaxation loop.
1400 Segment_states* segment_states_;
1401 // A relaxation debug checker. We only create one when in debugging mode.
1402 Relaxation_debug_check* relaxation_debug_check_;
1403 // Plugins specify section_ordering using this map. This is set in
1404 // update_section_order in plugin.cc
1405 std::map<Section_id, unsigned int> section_order_map_;
1406 // This maps an input section to a unique segment. This is done by first
1407 // placing such input sections in unique output sections and then mapping
1408 // the output section to a unique segment. Unique_segment_info stores
1409 // any additional flags and alignment of the new segment.
1410 Section_segment_map section_segment_map_;
1411 // Hash a pattern to its position in the section ordering file.
1412 Unordered_map<std::string, unsigned int> input_section_position_;
1413 // Vector of glob only patterns in the section_ordering file.
1414 std::vector<std::string> input_section_glob_;
1415 // For incremental links, the base file to be modified.
1416 Incremental_binary* incremental_base_;
1417 // For incremental links, a list of free space within the file.
1418 Free_list free_list_;
1421 // This task handles writing out data in output sections which is not
1422 // part of an input section, or which requires special handling. When
1423 // this is done, it unblocks both output_sections_blocker and
1426 class Write_sections_task : public Task
1429 Write_sections_task(const Layout* layout, Output_file* of,
1430 Task_token* output_sections_blocker,
1431 Task_token* final_blocker)
1432 : layout_(layout), of_(of),
1433 output_sections_blocker_(output_sections_blocker),
1434 final_blocker_(final_blocker)
1437 // The standard Task methods.
1443 locks(Task_locker*);
1450 { return "Write_sections_task"; }
1453 class Write_sections_locker;
1455 const Layout* layout_;
1457 Task_token* output_sections_blocker_;
1458 Task_token* final_blocker_;
1461 // This task handles writing out data which is not part of a section
1464 class Write_data_task : public Task
1467 Write_data_task(const Layout* layout, const Symbol_table* symtab,
1468 Output_file* of, Task_token* final_blocker)
1469 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
1472 // The standard Task methods.
1478 locks(Task_locker*);
1485 { return "Write_data_task"; }
1488 const Layout* layout_;
1489 const Symbol_table* symtab_;
1491 Task_token* final_blocker_;
1494 // This task handles writing out the global symbols.
1496 class Write_symbols_task : public Task
1499 Write_symbols_task(const Layout* layout, const Symbol_table* symtab,
1500 const Input_objects* input_objects,
1501 const Stringpool* sympool, const Stringpool* dynpool,
1502 Output_file* of, Task_token* final_blocker)
1503 : layout_(layout), symtab_(symtab), input_objects_(input_objects),
1504 sympool_(sympool), dynpool_(dynpool), of_(of),
1505 final_blocker_(final_blocker)
1508 // The standard Task methods.
1514 locks(Task_locker*);
1521 { return "Write_symbols_task"; }
1524 const Layout* layout_;
1525 const Symbol_table* symtab_;
1526 const Input_objects* input_objects_;
1527 const Stringpool* sympool_;
1528 const Stringpool* dynpool_;
1530 Task_token* final_blocker_;
1533 // This task handles writing out data in output sections which can't
1534 // be written out until all the input sections have been handled.
1535 // This is for sections whose contents is based on the contents of
1536 // other output sections.
1538 class Write_after_input_sections_task : public Task
1541 Write_after_input_sections_task(Layout* layout, Output_file* of,
1542 Task_token* input_sections_blocker,
1543 Task_token* final_blocker)
1544 : layout_(layout), of_(of),
1545 input_sections_blocker_(input_sections_blocker),
1546 final_blocker_(final_blocker)
1549 // The standard Task methods.
1555 locks(Task_locker*);
1562 { return "Write_after_input_sections_task"; }
1567 Task_token* input_sections_blocker_;
1568 Task_token* final_blocker_;
1571 // This task function handles closing the file.
1573 class Close_task_runner : public Task_function_runner
1576 Close_task_runner(const General_options* options, const Layout* layout,
1578 : options_(options), layout_(layout), of_(of)
1581 // Run the operation.
1583 run(Workqueue*, const Task*);
1586 const General_options* options_;
1587 const Layout* layout_;
1591 // A small helper function to align an address.
1594 align_address(uint64_t address, uint64_t addralign)
1597 address = (address + addralign - 1) &~ (addralign - 1);
1601 } // End namespace gold.
1603 #endif // !defined(GOLD_LAYOUT_H)