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)