1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright (C) 2006-2015 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_
; }
530 // Struct to store segment info when mapping some input sections to
531 // unique segments using linker plugins. Mapping an input section to
532 // a unique segment is done by first placing such input sections in
533 // unique output sections and then mapping the output section to a
534 // unique segment. NAME is the name of the output section. FLAGS
535 // and ALIGN are the extra flags and alignment of the segment.
536 struct Unique_segment_info
538 // Identifier for the segment. ELF segments dont have names. This
539 // is used as the name of the output section mapped to the segment.
541 // Additional segment flags.
543 // Segment alignment.
547 // Mapping from input section to segment.
548 typedef std::map
<Const_section_id
, Unique_segment_info
*>
551 // Maps section SECN to SEGMENT s.
553 insert_section_segment_map(Const_section_id secn
, Unique_segment_info
*s
);
555 // Some input sections require special ordering, for compatibility
556 // with GNU ld. Given the name of an input section, return -1 if it
557 // does not require special ordering. Otherwise, return the index
558 // by which it should be ordered compared to other input sections
559 // that require special ordering.
561 special_ordering_of_input_section(const char* name
);
564 is_section_ordering_specified()
565 { return this->section_ordering_specified_
; }
568 set_section_ordering_specified()
569 { this->section_ordering_specified_
= true; }
572 is_unique_segment_for_sections_specified() const
573 { return this->unique_segment_for_sections_specified_
; }
576 set_unique_segment_for_sections_specified()
577 { this->unique_segment_for_sections_specified_
= true; }
579 // For incremental updates, allocate a block of memory from the
580 // free list. Find a block starting at or after MINOFF.
582 allocate(off_t len
, uint64_t align
, off_t minoff
)
583 { return this->free_list_
.allocate(len
, align
, minoff
); }
586 find_section_order_index(const std::string
&);
588 // Read the sequence of input sections from the file specified with
589 // linker option --section-ordering-file.
591 read_layout_from_file();
593 // Layout an input reloc section when doing a relocatable link. The
594 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
595 // DATA_SECTION is the reloc section to which it refers. RR is the
596 // relocatable information.
597 template<int size
, bool big_endian
>
599 layout_reloc(Sized_relobj_file
<size
, big_endian
>* object
,
600 unsigned int reloc_shndx
,
601 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
602 Output_section
* data_section
,
603 Relocatable_relocs
* rr
);
605 // Layout a group section when doing a relocatable link.
606 template<int size
, bool big_endian
>
608 layout_group(Symbol_table
* symtab
,
609 Sized_relobj_file
<size
, big_endian
>* object
,
610 unsigned int group_shndx
,
611 const char* group_section_name
,
612 const char* signature
,
613 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
614 elfcpp::Elf_Word flags
,
615 std::vector
<unsigned int>* shndxes
);
617 // Like layout, only for exception frame sections. OBJECT is an
618 // object file. SYMBOLS is the contents of the symbol table
619 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
620 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
621 // .eh_frame section in OBJECT. SHDR is the section header.
622 // RELOC_SHNDX is the index of a relocation section which applies to
623 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
624 // is the type of the relocation section if there is one. This
625 // returns the output section, and sets *OFFSET to the offset.
626 template<int size
, bool big_endian
>
628 layout_eh_frame(Sized_relobj_file
<size
, big_endian
>* object
,
629 const unsigned char* symbols
,
631 const unsigned char* symbol_names
,
632 off_t symbol_names_size
,
634 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
635 unsigned int reloc_shndx
, unsigned int reloc_type
,
638 // After processing all input files, we call this to make sure that
639 // the optimized .eh_frame sections have been added to the output
642 finalize_eh_frame_section();
644 // Add .eh_frame information for a PLT. The FDE must start with a
645 // 4-byte PC-relative reference to the start of the PLT, followed by
646 // a 4-byte size of PLT.
648 add_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
649 size_t cie_length
, const unsigned char* fde_data
,
652 // Scan a .debug_info or .debug_types section, and add summary
653 // information to the .gdb_index section.
654 template<int size
, bool big_endian
>
656 add_to_gdb_index(bool is_type_unit
,
657 Sized_relobj
<size
, big_endian
>* object
,
658 const unsigned char* symbols
,
661 unsigned int reloc_shndx
,
662 unsigned int reloc_type
);
664 // Handle a GNU stack note. This is called once per input object
665 // file. SEEN_GNU_STACK is true if the object file has a
666 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
667 // from that section if there was one.
669 layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
,
672 // Add an Output_section_data to the layout. This is used for
673 // special sections like the GOT section. ORDER is where the
674 // section should wind up in the output segment. IS_RELRO is true
675 // for relro sections.
677 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
678 elfcpp::Elf_Xword flags
,
679 Output_section_data
*, Output_section_order order
,
682 // Increase the size of the relro segment by this much.
684 increase_relro(unsigned int s
)
685 { this->increase_relro_
+= s
; }
687 // Create dynamic sections if necessary.
689 create_initial_dynamic_sections(Symbol_table
*);
691 // Define __start and __stop symbols for output sections.
693 define_section_symbols(Symbol_table
*);
695 // Create automatic note sections.
699 // Create sections for linker scripts.
701 create_script_sections()
702 { this->script_options_
->create_script_sections(this); }
704 // Define symbols from any linker script.
706 define_script_symbols(Symbol_table
* symtab
)
707 { this->script_options_
->add_symbols_to_table(symtab
); }
709 // Define symbols for group signatures.
711 define_group_signatures(Symbol_table
*);
713 // Return the Stringpool used for symbol names.
716 { return &this->sympool_
; }
718 // Return the Stringpool used for dynamic symbol names and dynamic
722 { return &this->dynpool_
; }
724 // Return the .dynamic output section. This is only valid after the
725 // layout has been finalized.
727 dynamic_section() const
728 { return this->dynamic_section_
; }
730 // Return the symtab_xindex section used to hold large section
731 // indexes for the normal symbol table.
732 Output_symtab_xindex
*
733 symtab_xindex() const
734 { return this->symtab_xindex_
; }
736 // Return the dynsym_xindex section used to hold large section
737 // indexes for the dynamic symbol table.
738 Output_symtab_xindex
*
739 dynsym_xindex() const
740 { return this->dynsym_xindex_
; }
742 // Return whether a section is a .gnu.linkonce section, given the
745 is_linkonce(const char* name
)
746 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
748 // Whether we have added an input section.
750 have_added_input_section() const
751 { return this->have_added_input_section_
; }
753 // Return true if a section is a debugging section.
755 is_debug_info_section(const char* name
)
757 // Debugging sections can only be recognized by name.
758 return (strncmp(name
, ".debug", sizeof(".debug") - 1) == 0
759 || strncmp(name
, ".zdebug", sizeof(".zdebug") - 1) == 0
760 || strncmp(name
, ".gnu.linkonce.wi.",
761 sizeof(".gnu.linkonce.wi.") - 1) == 0
762 || strncmp(name
, ".line", sizeof(".line") - 1) == 0
763 || strncmp(name
, ".stab", sizeof(".stab") - 1) == 0);
766 // Return true if RELOBJ is an input file whose base name matches
767 // FILE_NAME. The base name must have an extension of ".o", and
768 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
770 match_file_name(const Relobj
* relobj
, const char* file_name
);
772 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
773 // with more than one word being mapped to a .init_array/.fini_array
776 is_ctors_in_init_array(Relobj
* relobj
, unsigned int shndx
) const;
778 // Check if a comdat group or .gnu.linkonce section with the given
779 // NAME is selected for the link. If there is already a section,
780 // *KEPT_SECTION is set to point to the signature and the function
781 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
782 // IS_GROUP_NAME are recorded for this NAME in the layout object,
783 // *KEPT_SECTION is set to the internal copy and the function return
786 find_or_add_kept_section(const std::string
& name
, Relobj
* object
,
787 unsigned int shndx
, bool is_comdat
,
788 bool is_group_name
, Kept_section
** kept_section
);
790 // Finalize the layout after all the input sections have been added.
792 finalize(const Input_objects
*, Symbol_table
*, Target
*, const Task
*);
794 // Return whether any sections require postprocessing.
796 any_postprocessing_sections() const
797 { return this->any_postprocessing_sections_
; }
799 // Return the size of the output file.
801 output_file_size() const
802 { return this->output_file_size_
; }
804 // Return the TLS segment. This will return NULL if there isn't
808 { return this->tls_segment_
; }
810 // Return the normal symbol table.
812 symtab_section() const
814 gold_assert(this->symtab_section_
!= NULL
);
815 return this->symtab_section_
;
818 // Return the file offset of the normal symbol table.
820 symtab_section_offset() const;
822 // Return the section index of the normal symbol tabl.e
824 symtab_section_shndx() const;
826 // Return the dynamic symbol table.
828 dynsym_section() const
830 gold_assert(this->dynsym_section_
!= NULL
);
831 return this->dynsym_section_
;
834 // Return the dynamic tags.
837 { return this->dynamic_data_
; }
839 // Write out the output sections.
841 write_output_sections(Output_file
* of
) const;
843 // Write out data not associated with an input file or the symbol
846 write_data(const Symbol_table
*, Output_file
*) const;
848 // Write out output sections which can not be written until all the
849 // input sections are complete.
851 write_sections_after_input_sections(Output_file
* of
);
853 // Return an output section named NAME, or NULL if there is none.
855 find_output_section(const char* name
) const;
857 // Return an output segment of type TYPE, with segment flags SET set
858 // and segment flags CLEAR clear. Return NULL if there is none.
860 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
861 elfcpp::Elf_Word clear
) const;
863 // Return the number of segments we expect to produce.
865 expected_segment_count() const;
867 // Set a flag to indicate that an object file uses the static TLS model.
870 { this->has_static_tls_
= true; }
872 // Return true if any object file uses the static TLS model.
874 has_static_tls() const
875 { return this->has_static_tls_
; }
877 // Return the options which may be set by a linker script.
880 { return this->script_options_
; }
882 const Script_options
*
883 script_options() const
884 { return this->script_options_
; }
886 // Return the object managing inputs in incremental build. NULL in
887 // non-incremental builds.
889 incremental_inputs() const
890 { return this->incremental_inputs_
; }
892 // For the target-specific code to add dynamic tags which are common
895 add_target_dynamic_tags(bool use_rel
, const Output_data
* plt_got
,
896 const Output_data
* plt_rel
,
897 const Output_data_reloc_generic
* dyn_rel
,
898 bool add_debug
, bool dynrel_includes_plt
);
900 // Compute and write out the build ID if needed.
902 write_build_id(Output_file
*, unsigned char*, size_t) const;
904 // Rewrite output file in binary format.
906 write_binary(Output_file
* in
) const;
908 // Print output sections to the map file.
910 print_to_mapfile(Mapfile
*) const;
912 // Dump statistical information to stderr.
916 // A list of segments.
918 typedef std::vector
<Output_segment
*> Segment_list
;
920 // A list of sections.
922 typedef std::vector
<Output_section
*> Section_list
;
924 // The list of information to write out which is not attached to
925 // either a section or a segment.
926 typedef std::vector
<Output_data
*> Data_list
;
928 // Store the allocated sections into the section list. This is used
929 // by the linker script code.
931 get_allocated_sections(Section_list
*) const;
933 // Store the executable sections into the section list.
935 get_executable_sections(Section_list
*) const;
937 // Make a section for a linker script to hold data.
939 make_output_section_for_script(const char* name
,
940 Script_sections::Section_type section_type
);
942 // Make a segment. This is used by the linker script code.
944 make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
);
946 // Return the number of segments.
948 segment_count() const
949 { return this->segment_list_
.size(); }
951 // Map from section flags to segment flags.
952 static elfcpp::Elf_Word
953 section_flags_to_segment(elfcpp::Elf_Xword flags
);
955 // Attach sections to segments.
957 attach_sections_to_segments(const Target
*);
959 // For relaxation clean up, we need to know output section data created
960 // from a linker script.
962 new_output_section_data_from_script(Output_section_data
* posd
)
964 if (this->record_output_section_data_from_script_
)
965 this->script_output_section_data_list_
.push_back(posd
);
968 // Return section list.
971 { return this->section_list_
; }
973 // Returns TRUE iff NAME (an input section from RELOBJ) will
974 // be mapped to an output section that should be KEPT.
976 keep_input_section(const Relobj
*, const char*);
978 // Add a special output object that will be recreated afresh
979 // if there is another relaxation iteration.
981 add_relax_output(Output_data
* data
)
982 { this->relax_output_list_
.push_back(data
); }
984 // Clear out (and free) everything added by add_relax_output.
986 reset_relax_output();
989 Layout(const Layout
&);
990 Layout
& operator=(const Layout
&);
992 // Mapping from input section names to output section names.
993 struct Section_name_mapping
1000 static const Section_name_mapping section_name_mapping
[];
1001 static const int section_name_mapping_count
;
1003 // During a relocatable link, a list of group sections and
1005 struct Group_signature
1007 // The group section.
1008 Output_section
* section
;
1010 const char* signature
;
1013 : section(NULL
), signature(NULL
)
1016 Group_signature(Output_section
* sectiona
, const char* signaturea
)
1017 : section(sectiona
), signature(signaturea
)
1020 typedef std::vector
<Group_signature
> Group_signatures
;
1022 // Create a note section, filling in the header.
1024 create_note(const char* name
, int note_type
, const char* section_name
,
1025 size_t descsz
, bool allocate
, size_t* trailing_padding
);
1027 // Create a note section for gold version.
1031 // Record whether the stack must be executable.
1033 create_executable_stack_info();
1035 // Create a build ID note if needed.
1039 // Link .stab and .stabstr sections.
1041 link_stabs_sections();
1043 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1044 // for the next run of incremental linking to check what has changed.
1046 create_incremental_info_sections(Symbol_table
*);
1048 // Find the first read-only PT_LOAD segment, creating one if
1051 find_first_load_seg(const Target
*);
1053 // Count the local symbols in the regular symbol table and the dynamic
1054 // symbol table, and build the respective string pools.
1056 count_local_symbols(const Task
*, const Input_objects
*);
1058 // Create the output sections for the symbol table.
1060 create_symtab_sections(const Input_objects
*, Symbol_table
*,
1061 unsigned int, off_t
*);
1063 // Create the .shstrtab section.
1067 // Create the section header table.
1069 create_shdrs(const Output_section
* shstrtab_section
, off_t
*);
1071 // Create the dynamic symbol table.
1073 create_dynamic_symtab(const Input_objects
*, Symbol_table
*,
1074 Output_section
** pdynstr
,
1075 unsigned int* plocal_dynamic_count
,
1076 std::vector
<Symbol
*>* pdynamic_symbols
,
1077 Versions
* versions
);
1079 // Assign offsets to each local portion of the dynamic symbol table.
1081 assign_local_dynsym_offsets(const Input_objects
*);
1083 // Finish the .dynamic section and PT_DYNAMIC segment.
1085 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
1087 // Set the size of the _DYNAMIC symbol.
1089 set_dynamic_symbol_size(const Symbol_table
*);
1091 // Create the .interp section and PT_INTERP segment.
1093 create_interp(const Target
* target
);
1095 // Create the version sections.
1097 create_version_sections(const Versions
*,
1098 const Symbol_table
*,
1099 unsigned int local_symcount
,
1100 const std::vector
<Symbol
*>& dynamic_symbols
,
1101 const Output_section
* dynstr
);
1103 template<int size
, bool big_endian
>
1105 sized_create_version_sections(const Versions
* versions
,
1106 const Symbol_table
*,
1107 unsigned int local_symcount
,
1108 const std::vector
<Symbol
*>& dynamic_symbols
,
1109 const Output_section
* dynstr
);
1111 // Return whether to include this section in the link.
1112 template<int size
, bool big_endian
>
1114 include_section(Sized_relobj_file
<size
, big_endian
>* object
, const char* name
,
1115 const elfcpp::Shdr
<size
, big_endian
>&);
1117 // Return the output section name to use given an input section
1118 // name. Set *PLEN to the length of the name. *PLEN must be
1119 // initialized to the length of NAME.
1121 output_section_name(const Relobj
*, const char* name
, size_t* plen
);
1123 // Return the number of allocated output sections.
1125 allocated_output_section_count() const;
1127 // Return the output section for NAME, TYPE and FLAGS.
1129 get_output_section(const char* name
, Stringpool::Key name_key
,
1130 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1131 Output_section_order order
, bool is_relro
);
1133 // Clear the input section flags that should not be copied to the
1136 get_output_section_flags (elfcpp::Elf_Xword input_section_flags
);
1138 // Choose the output section for NAME in RELOBJ.
1140 choose_output_section(const Relobj
* relobj
, const char* name
,
1141 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1142 bool is_input_section
, Output_section_order order
,
1145 // Create a new Output_section.
1147 make_output_section(const char* name
, elfcpp::Elf_Word type
,
1148 elfcpp::Elf_Xword flags
, Output_section_order order
,
1151 // Attach a section to a segment.
1153 attach_section_to_segment(const Target
*, Output_section
*);
1155 // Get section order.
1156 Output_section_order
1157 default_section_order(Output_section
*, bool is_relro_local
);
1159 // Attach an allocated section to a segment.
1161 attach_allocated_section_to_segment(const Target
*, Output_section
*);
1163 // Make the .eh_frame section.
1165 make_eh_frame_section(const Relobj
*);
1167 // Set the final file offsets of all the segments.
1169 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
1171 // Set the file offsets of the sections when doing a relocatable
1174 set_relocatable_section_offsets(Output_data
*, unsigned int* pshndx
);
1176 // Set the final file offsets of all the sections not associated
1177 // with a segment. We set section offsets in three passes: the
1178 // first handles all allocated sections, the second sections that
1179 // require postprocessing, and the last the late-bound STRTAB
1180 // sections (probably only shstrtab, which is the one we care about
1181 // because it holds section names).
1182 enum Section_offset_pass
1184 BEFORE_INPUT_SECTIONS_PASS
,
1185 POSTPROCESSING_SECTIONS_PASS
,
1186 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1189 set_section_offsets(off_t
, Section_offset_pass pass
);
1191 // Set the final section indexes of all the sections not associated
1192 // with a segment. Returns the next unused index.
1194 set_section_indexes(unsigned int pshndx
);
1196 // Set the section addresses when using a script.
1198 set_section_addresses_from_script(Symbol_table
*);
1200 // Find appropriate places or orphan sections in a script.
1202 place_orphan_sections_in_script();
1204 // Return whether SEG1 comes before SEG2 in the output file.
1206 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
1208 // Use to save and restore segments during relaxation.
1209 typedef Unordered_map
<const Output_segment
*, const Output_segment
*>
1212 // Save states of current output segments.
1214 save_segments(Segment_states
*);
1216 // Restore output segment states.
1218 restore_segments(const Segment_states
*);
1220 // Clean up after relaxation so that it is possible to lay out the
1221 // sections and segments again.
1223 clean_up_after_relaxation();
1225 // Doing preparation work for relaxation. This is factored out to make
1226 // Layout::finalized a bit smaller and easier to read.
1228 prepare_for_relaxation();
1230 // Main body of the relaxation loop, which lays out the section.
1232 relaxation_loop_body(int, Target
*, Symbol_table
*, Output_segment
**,
1233 Output_segment
*, Output_segment_headers
*,
1234 Output_file_header
*, unsigned int*);
1236 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1237 typedef Unordered_map
<std::string
, Kept_section
> Signatures
;
1239 // Mapping from input section name/type/flags to output section. We
1240 // use canonicalized strings here.
1242 typedef std::pair
<Stringpool::Key
,
1243 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
1248 operator()(const Key
& k
) const;
1251 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
1253 // A comparison class for segments.
1255 class Compare_segments
1258 Compare_segments(Layout
* layout
)
1263 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
1264 { return this->layout_
->segment_precedes(seg1
, seg2
); }
1270 typedef std::vector
<Output_section_data
*> Output_section_data_list
;
1272 // Debug checker class.
1273 class Relaxation_debug_check
1276 Relaxation_debug_check()
1280 // Check that sections and special data are in reset states.
1282 check_output_data_for_reset_values(const Layout::Section_list
&,
1283 const Layout::Data_list
& special_outputs
,
1284 const Layout::Data_list
& relax_outputs
);
1286 // Record information of a section list.
1288 read_sections(const Layout::Section_list
&);
1290 // Verify a section list with recorded information.
1292 verify_sections(const Layout::Section_list
&);
1295 // Information we care about a section.
1298 // Output section described by this.
1299 Output_section
* output_section
;
1308 // Section information.
1309 std::vector
<Section_info
> section_infos_
;
1312 // The number of input files, for sizing tables.
1313 int number_of_input_files_
;
1314 // Information set by scripts or by command line options.
1315 Script_options
* script_options_
;
1316 // The output section names.
1317 Stringpool namepool_
;
1318 // The output symbol names.
1319 Stringpool sympool_
;
1320 // The dynamic strings, if needed.
1321 Stringpool dynpool_
;
1322 // The list of group sections and linkonce sections which we have seen.
1323 Signatures signatures_
;
1324 // The mapping from input section name/type/flags to output sections.
1325 Section_name_map section_name_map_
;
1326 // The list of output segments.
1327 Segment_list segment_list_
;
1328 // The list of output sections.
1329 Section_list section_list_
;
1330 // The list of output sections which are not attached to any output
1332 Section_list unattached_section_list_
;
1333 // The list of unattached Output_data objects which require special
1334 // handling because they are not Output_sections.
1335 Data_list special_output_list_
;
1336 // Like special_output_list_, but cleared and recreated on each
1337 // iteration of relaxation.
1338 Data_list relax_output_list_
;
1339 // The section headers.
1340 Output_section_headers
* section_headers_
;
1341 // A pointer to the PT_TLS segment if there is one.
1342 Output_segment
* tls_segment_
;
1343 // A pointer to the PT_GNU_RELRO segment if there is one.
1344 Output_segment
* relro_segment_
;
1345 // A pointer to the PT_INTERP segment if there is one.
1346 Output_segment
* interp_segment_
;
1347 // A backend may increase the size of the PT_GNU_RELRO segment if
1348 // there is one. This is the amount to increase it by.
1349 unsigned int increase_relro_
;
1350 // The SHT_SYMTAB output section.
1351 Output_section
* symtab_section_
;
1352 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1353 Output_symtab_xindex
* symtab_xindex_
;
1354 // The SHT_DYNSYM output section if there is one.
1355 Output_section
* dynsym_section_
;
1356 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1357 Output_symtab_xindex
* dynsym_xindex_
;
1358 // The SHT_DYNAMIC output section if there is one.
1359 Output_section
* dynamic_section_
;
1360 // The _DYNAMIC symbol if there is one.
1361 Symbol
* dynamic_symbol_
;
1362 // The dynamic data which goes into dynamic_section_.
1363 Output_data_dynamic
* dynamic_data_
;
1364 // The exception frame output section if there is one.
1365 Output_section
* eh_frame_section_
;
1366 // The exception frame data for eh_frame_section_.
1367 Eh_frame
* eh_frame_data_
;
1368 // Whether we have added eh_frame_data_ to the .eh_frame section.
1369 bool added_eh_frame_data_
;
1370 // The exception frame header output section if there is one.
1371 Output_section
* eh_frame_hdr_section_
;
1372 // The data for the .gdb_index section.
1373 Gdb_index
* gdb_index_data_
;
1374 // The space for the build ID checksum if there is one.
1375 Output_section_data
* build_id_note_
;
1376 // The output section containing dwarf abbreviations
1377 Output_reduced_debug_abbrev_section
* debug_abbrev_
;
1378 // The output section containing the dwarf debug info tree
1379 Output_reduced_debug_info_section
* debug_info_
;
1380 // A list of group sections and their signatures.
1381 Group_signatures group_signatures_
;
1382 // The size of the output file.
1383 off_t output_file_size_
;
1384 // Whether we have added an input section to an output section.
1385 bool have_added_input_section_
;
1386 // Whether we have attached the sections to the segments.
1387 bool sections_are_attached_
;
1388 // Whether we have seen an object file marked to require an
1389 // executable stack.
1390 bool input_requires_executable_stack_
;
1391 // Whether we have seen at least one object file with an executable
1393 bool input_with_gnu_stack_note_
;
1394 // Whether we have seen at least one object file without an
1395 // executable stack marker.
1396 bool input_without_gnu_stack_note_
;
1397 // Whether we have seen an object file that uses the static TLS model.
1398 bool has_static_tls_
;
1399 // Whether any sections require postprocessing.
1400 bool any_postprocessing_sections_
;
1401 // Whether we have resized the signatures_ hash table.
1402 bool resized_signatures_
;
1403 // Whether we have created a .stab*str output section.
1404 bool have_stabstr_section_
;
1405 // True if the input sections in the output sections should be sorted
1406 // as specified in a section ordering file.
1407 bool section_ordering_specified_
;
1408 // True if some input sections need to be mapped to a unique segment,
1409 // after being mapped to a unique Output_section.
1410 bool unique_segment_for_sections_specified_
;
1411 // In incremental build, holds information check the inputs and build the
1412 // .gnu_incremental_inputs section.
1413 Incremental_inputs
* incremental_inputs_
;
1414 // Whether we record output section data created in script
1415 bool record_output_section_data_from_script_
;
1416 // List of output data that needs to be removed at relaxation clean up.
1417 Output_section_data_list script_output_section_data_list_
;
1418 // Structure to save segment states before entering the relaxation loop.
1419 Segment_states
* segment_states_
;
1420 // A relaxation debug checker. We only create one when in debugging mode.
1421 Relaxation_debug_check
* relaxation_debug_check_
;
1422 // Plugins specify section_ordering using this map. This is set in
1423 // update_section_order in plugin.cc
1424 std::map
<Section_id
, unsigned int> section_order_map_
;
1425 // This maps an input section to a unique segment. This is done by first
1426 // placing such input sections in unique output sections and then mapping
1427 // the output section to a unique segment. Unique_segment_info stores
1428 // any additional flags and alignment of the new segment.
1429 Section_segment_map section_segment_map_
;
1430 // Hash a pattern to its position in the section ordering file.
1431 Unordered_map
<std::string
, unsigned int> input_section_position_
;
1432 // Vector of glob only patterns in the section_ordering file.
1433 std::vector
<std::string
> input_section_glob_
;
1434 // For incremental links, the base file to be modified.
1435 Incremental_binary
* incremental_base_
;
1436 // For incremental links, a list of free space within the file.
1437 Free_list free_list_
;
1440 // This task handles writing out data in output sections which is not
1441 // part of an input section, or which requires special handling. When
1442 // this is done, it unblocks both output_sections_blocker and
1445 class Write_sections_task
: public Task
1448 Write_sections_task(const Layout
* layout
, Output_file
* of
,
1449 Task_token
* output_sections_blocker
,
1450 Task_token
* input_sections_blocker
,
1451 Task_token
* final_blocker
)
1452 : layout_(layout
), of_(of
),
1453 output_sections_blocker_(output_sections_blocker
),
1454 input_sections_blocker_(input_sections_blocker
),
1455 final_blocker_(final_blocker
)
1458 // The standard Task methods.
1464 locks(Task_locker
*);
1471 { return "Write_sections_task"; }
1474 class Write_sections_locker
;
1476 const Layout
* layout_
;
1478 Task_token
* output_sections_blocker_
;
1479 Task_token
* input_sections_blocker_
;
1480 Task_token
* final_blocker_
;
1483 // This task handles writing out data which is not part of a section
1486 class Write_data_task
: public Task
1489 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
1490 Output_file
* of
, Task_token
* final_blocker
)
1491 : layout_(layout
), symtab_(symtab
), of_(of
), final_blocker_(final_blocker
)
1494 // The standard Task methods.
1500 locks(Task_locker
*);
1507 { return "Write_data_task"; }
1510 const Layout
* layout_
;
1511 const Symbol_table
* symtab_
;
1513 Task_token
* final_blocker_
;
1516 // This task handles writing out the global symbols.
1518 class Write_symbols_task
: public Task
1521 Write_symbols_task(const Layout
* layout
, const Symbol_table
* symtab
,
1522 const Input_objects
* /*input_objects*/,
1523 const Stringpool
* sympool
, const Stringpool
* dynpool
,
1524 Output_file
* of
, Task_token
* final_blocker
)
1525 : layout_(layout
), symtab_(symtab
),
1526 sympool_(sympool
), dynpool_(dynpool
), of_(of
),
1527 final_blocker_(final_blocker
)
1530 // The standard Task methods.
1536 locks(Task_locker
*);
1543 { return "Write_symbols_task"; }
1546 const Layout
* layout_
;
1547 const Symbol_table
* symtab_
;
1548 const Stringpool
* sympool_
;
1549 const Stringpool
* dynpool_
;
1551 Task_token
* final_blocker_
;
1554 // This task handles writing out data in output sections which can't
1555 // be written out until all the input sections have been handled.
1556 // This is for sections whose contents is based on the contents of
1557 // other output sections.
1559 class Write_after_input_sections_task
: public Task
1562 Write_after_input_sections_task(Layout
* layout
, Output_file
* of
,
1563 Task_token
* input_sections_blocker
,
1564 Task_token
* final_blocker
)
1565 : layout_(layout
), of_(of
),
1566 input_sections_blocker_(input_sections_blocker
),
1567 final_blocker_(final_blocker
)
1570 // The standard Task methods.
1576 locks(Task_locker
*);
1583 { return "Write_after_input_sections_task"; }
1588 Task_token
* input_sections_blocker_
;
1589 Task_token
* final_blocker_
;
1592 // This task function handles computation of the build id.
1593 // When using --build-id=tree, it schedules the tasks that
1594 // compute the hashes for each chunk of the file. This task
1595 // cannot run until we have finalized the size of the output
1596 // file, after the completion of Write_after_input_sections_task.
1598 class Build_id_task_runner
: public Task_function_runner
1601 Build_id_task_runner(const General_options
* options
, const Layout
* layout
,
1603 : options_(options
), layout_(layout
), of_(of
)
1606 // Run the operation.
1608 run(Workqueue
*, const Task
*);
1611 const General_options
* options_
;
1612 const Layout
* layout_
;
1616 // This task function handles closing the file.
1618 class Close_task_runner
: public Task_function_runner
1621 Close_task_runner(const General_options
* options
, const Layout
* layout
,
1622 Output_file
* of
, unsigned char* array_of_hashes
,
1623 size_t size_of_hashes
)
1624 : options_(options
), layout_(layout
), of_(of
),
1625 array_of_hashes_(array_of_hashes
), size_of_hashes_(size_of_hashes
)
1628 // Run the operation.
1630 run(Workqueue
*, const Task
*);
1633 const General_options
* options_
;
1634 const Layout
* layout_
;
1636 unsigned char* const array_of_hashes_
;
1637 const size_t size_of_hashes_
;
1640 // A small helper function to align an address.
1643 align_address(uint64_t address
, uint64_t addralign
)
1646 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
1650 } // End namespace gold.
1652 #endif // !defined(GOLD_LAYOUT_H)