1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright (C) 2006-2020 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 // Return the name of the corresponding uncompressed debug section.
71 corresponding_uncompressed_section_name(std::string secname
);
73 // Maintain a list of free space within a section, segment, or file.
74 // Used for incremental update links.
81 Free_list_node(off_t start
, off_t end
)
82 : start_(start
), end_(end
)
87 typedef std::list
<Free_list_node
>::const_iterator Const_iterator
;
90 : list_(), last_remove_(list_
.begin()), extend_(false), length_(0),
94 // Initialize the free list for a section of length LEN.
95 // If EXTEND is true, free space may be allocated past the end.
97 init(off_t len
, bool extend
);
99 // Set the minimum hole size that is allowed when allocating
100 // from the free list.
102 set_min_hole_size(off_t min_hole
)
103 { this->min_hole_
= min_hole
; }
105 // Remove a chunk from the free list.
107 remove(off_t start
, off_t end
);
109 // Allocate a chunk of space from the free list of length LEN,
110 // with alignment ALIGN, and minimum offset MINOFF.
112 allocate(off_t len
, uint64_t align
, off_t minoff
);
114 // Return an iterator for the beginning of the free list.
117 { return this->list_
.begin(); }
119 // Return an iterator for the end of the free list.
122 { return this->list_
.end(); }
124 // Dump the free list (for debugging).
128 // Print usage statistics.
133 typedef std::list
<Free_list_node
>::iterator Iterator
;
136 std::list
<Free_list_node
> list_
;
138 // The last node visited during a remove operation.
139 Iterator last_remove_
;
141 // Whether we can extend past the original length.
144 // The total length of the section, segment, or file.
147 // The minimum hole size allowed. When allocating from the free list,
148 // we must not leave a hole smaller than this.
152 // The total number of free lists used.
153 static unsigned int num_lists
;
154 // The total number of free list nodes used.
155 static unsigned int num_nodes
;
156 // The total number of calls to Free_list::remove.
157 static unsigned int num_removes
;
158 // The total number of nodes visited during calls to Free_list::remove.
159 static unsigned int num_remove_visits
;
160 // The total number of calls to Free_list::allocate.
161 static unsigned int num_allocates
;
162 // The total number of nodes visited during calls to Free_list::allocate.
163 static unsigned int num_allocate_visits
;
166 // This task function handles mapping the input sections to output
167 // sections and laying them out in memory.
169 class Layout_task_runner
: public Task_function_runner
172 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
173 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
175 Layout_task_runner(const General_options
& options
,
176 const Input_objects
* input_objects
,
177 Symbol_table
* symtab
,
181 : options_(options
), input_objects_(input_objects
), symtab_(symtab
),
182 target_(target
), layout_(layout
), mapfile_(mapfile
)
185 // Run the operation.
187 run(Workqueue
*, const Task
*);
190 Layout_task_runner(const Layout_task_runner
&);
191 Layout_task_runner
& operator=(const Layout_task_runner
&);
193 const General_options
& options_
;
194 const Input_objects
* input_objects_
;
195 Symbol_table
* symtab_
;
201 // This class holds information about the comdat group or
202 // .gnu.linkonce section that will be kept for a given signature.
207 // For a comdat group, we build a mapping from the name of each
208 // section in the group to the section index and the size in object.
209 // When we discard a group in some other object file, we use this
210 // map to figure out which kept section the discarded section is
211 // associated with. We then use that mapping when processing relocs
212 // against discarded sections.
213 struct Comdat_section_info
215 // The section index.
220 Comdat_section_info(unsigned int a_shndx
, uint64_t a_size
)
221 : shndx(a_shndx
), size(a_size
)
225 // Most comdat groups have only one or two sections, so we use a
226 // std::map rather than an Unordered_map to optimize for that case
227 // without paying too heavily for groups with more sections.
228 typedef std::map
<std::string
, Comdat_section_info
> Comdat_group
;
232 : object_(NULL
), shndx_(0), is_comdat_(false), is_group_name_(false)
233 { this->u_
.linkonce_size
= 0; }
235 // We need to support copies for the signature map in the Layout
236 // object, but we should never copy an object after it has been
237 // marked as a comdat section.
238 Kept_section(const Kept_section
& k
)
239 : object_(k
.object_
), shndx_(k
.shndx_
), is_comdat_(false),
240 is_group_name_(k
.is_group_name_
)
242 gold_assert(!k
.is_comdat_
);
243 this->u_
.linkonce_size
= 0;
248 if (this->is_comdat_
)
249 delete this->u_
.group_sections
;
252 // The object where this section lives.
255 { return this->object_
; }
259 set_object(Relobj
* object
)
261 gold_assert(this->object_
== NULL
);
262 this->object_
= object
;
265 // The section index.
268 { return this->shndx_
; }
270 // Set the section index.
272 set_shndx(unsigned int shndx
)
274 gold_assert(this->shndx_
== 0);
275 this->shndx_
= shndx
;
278 // Whether this is a comdat group.
281 { return this->is_comdat_
; }
283 // Set that this is a comdat group.
287 gold_assert(!this->is_comdat_
);
288 this->is_comdat_
= true;
289 this->u_
.group_sections
= new Comdat_group();
292 // Whether this is associated with the name of a group or section
293 // rather than the symbol name derived from a linkonce section.
295 is_group_name() const
296 { return this->is_group_name_
; }
298 // Note that this represents a comdat group rather than a single
302 { this->is_group_name_
= true; }
304 // Add a section to the group list.
306 add_comdat_section(const std::string
& name
, unsigned int shndx
,
309 gold_assert(this->is_comdat_
);
310 Comdat_section_info
sinfo(shndx
, size
);
311 this->u_
.group_sections
->insert(std::make_pair(name
, sinfo
));
314 // Look for a section name in the group list, and return whether it
315 // was found. If found, returns the section index and size.
317 find_comdat_section(const std::string
& name
, unsigned int* pshndx
,
318 uint64_t* psize
) const
320 gold_assert(this->is_comdat_
);
321 Comdat_group::const_iterator p
= this->u_
.group_sections
->find(name
);
322 if (p
== this->u_
.group_sections
->end())
324 *pshndx
= p
->second
.shndx
;
325 *psize
= p
->second
.size
;
329 // If there is only one section in the group list, return true, and
330 // return the section index and size.
332 find_single_comdat_section(unsigned int* pshndx
, uint64_t* psize
) const
334 gold_assert(this->is_comdat_
);
335 if (this->u_
.group_sections
->size() != 1)
337 Comdat_group::const_iterator p
= this->u_
.group_sections
->begin();
338 *pshndx
= p
->second
.shndx
;
339 *psize
= p
->second
.size
;
343 // Return the size of a linkonce section.
345 linkonce_size() const
347 gold_assert(!this->is_comdat_
);
348 return this->u_
.linkonce_size
;
351 // Set the size of a linkonce section.
353 set_linkonce_size(uint64_t size
)
355 gold_assert(!this->is_comdat_
);
356 this->u_
.linkonce_size
= size
;
361 Kept_section
& operator=(const Kept_section
&);
363 // The object containing the comdat group or .gnu.linkonce section.
365 // Index of the group section for comdats and the section itself for
368 // True if this is for a comdat group rather than a .gnu.linkonce
371 // The Kept_sections are values of a mapping, that maps names to
372 // them. This field is true if this struct is associated with the
373 // name of a comdat or .gnu.linkonce, false if it is associated with
374 // the name of a symbol obtained from the .gnu.linkonce.* name
375 // through some heuristics.
379 // If the is_comdat_ field is true, this holds a map from names of
380 // the sections in the group to section indexes in object_ and to
382 Comdat_group
* group_sections
;
383 // If the is_comdat_ field is false, this holds the size of the
385 uint64_t linkonce_size
;
389 // The ordering for output sections. This controls how output
390 // sections are ordered within a PT_LOAD output segment.
392 enum Output_section_order
394 // Unspecified. Used for non-load segments. Also used for the file
395 // and segment headers.
398 // The PT_INTERP section should come first, so that the dynamic
399 // linker can pick it up quickly.
402 // Loadable read-only note sections come next so that the PT_NOTE
403 // segment is on the first page of the executable.
406 // Put read-only sections used by the dynamic linker early in the
407 // executable to minimize paging.
408 ORDER_DYNAMIC_LINKER
,
410 // Put reloc sections used by the dynamic linker after other
411 // sections used by the dynamic linker; otherwise, objcopy and strip
413 ORDER_DYNAMIC_RELOCS
,
415 // Put the PLT reloc section after the other dynamic relocs;
416 // otherwise, prelink gets confused.
417 ORDER_DYNAMIC_PLT_RELOCS
,
419 // The .init section.
425 // The hot text sections, prefixed by .text.hot.
428 // The regular text sections.
431 // The startup text sections, prefixed by .text.startup.
434 // The startup text sections, prefixed by .text.startup.
437 // The unlikely text sections, prefixed by .text.unlikely.
440 // The .fini section.
443 // The read-only sections.
446 // The exception frame sections.
449 // The TLS sections come first in the data section.
453 // Local RELRO (read-only after relocation) sections come before
454 // non-local RELRO sections. This data will be fully resolved by
458 // Non-local RELRO sections are grouped together after local RELRO
459 // sections. All RELRO sections must be adjacent so that they can
460 // all be put into a PT_GNU_RELRO segment.
463 // We permit marking exactly one output section as the last RELRO
464 // section. We do this so that the read-only GOT can be adjacent to
468 // Similarly, we permit marking exactly one output section as the
469 // first non-RELRO section.
470 ORDER_NON_RELRO_FIRST
,
472 // The regular data sections come after the RELRO sections.
475 // Large data sections normally go in large data segments.
478 // Group writable notes so that we can have a single PT_NOTE
482 // The small data sections must be at the end of the data sections,
483 // so that they can be adjacent to the small BSS sections.
486 // The BSS sections start here.
488 // The small BSS sections must be at the start of the BSS sections,
489 // so that they can be adjacent to the small data sections.
492 // The regular BSS sections.
495 // The large BSS sections come after the other BSS sections.
502 // This class handles the details of laying out input sections.
507 Layout(int number_of_input_files
, Script_options
*);
511 delete this->relaxation_debug_check_
;
512 delete this->segment_states_
;
515 // For incremental links, record the base file to be modified.
517 set_incremental_base(Incremental_binary
* base
);
521 { return this->incremental_base_
; }
523 // For incremental links, record the initial fixed layout of a section
524 // from the base file, and return a pointer to the Output_section.
525 template<int size
, bool big_endian
>
527 init_fixed_output_section(const char*, elfcpp::Shdr
<size
, big_endian
>&);
529 // Given an input section SHNDX, named NAME, with data in SHDR, from
530 // the object file OBJECT, return the output section where this
531 // input section should go. RELOC_SHNDX is the index of a
532 // relocation section which applies to this section, or 0 if none,
533 // or -1U if more than one. RELOC_TYPE is the type of the
534 // relocation section if there is one. Set *OFFSET to the offset
535 // within the output section.
536 template<int size
, bool big_endian
>
538 layout(Sized_relobj_file
<size
, big_endian
> *object
, unsigned int shndx
,
539 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
540 unsigned int sh_type
, unsigned int reloc_shndx
,
541 unsigned int reloc_type
, off_t
* offset
);
543 std::map
<Section_id
, unsigned int>*
544 get_section_order_map()
545 { return &this->section_order_map_
; }
547 // Struct to store segment info when mapping some input sections to
548 // unique segments using linker plugins. Mapping an input section to
549 // a unique segment is done by first placing such input sections in
550 // unique output sections and then mapping the output section to a
551 // unique segment. NAME is the name of the output section. FLAGS
552 // and ALIGN are the extra flags and alignment of the segment.
553 struct Unique_segment_info
555 // Identifier for the segment. ELF segments don't have names. This
556 // is used as the name of the output section mapped to the segment.
558 // Additional segment flags.
560 // Segment alignment.
564 // Mapping from input section to segment.
565 typedef std::map
<Const_section_id
, Unique_segment_info
*>
568 // Maps section SECN to SEGMENT s.
570 insert_section_segment_map(Const_section_id secn
, Unique_segment_info
*s
);
572 // Some input sections require special ordering, for compatibility
573 // with GNU ld. Given the name of an input section, return -1 if it
574 // does not require special ordering. Otherwise, return the index
575 // by which it should be ordered compared to other input sections
576 // that require special ordering.
578 special_ordering_of_input_section(const char* name
);
581 is_section_ordering_specified()
582 { return this->section_ordering_specified_
; }
585 set_section_ordering_specified()
586 { this->section_ordering_specified_
= true; }
589 is_unique_segment_for_sections_specified() const
590 { return this->unique_segment_for_sections_specified_
; }
593 set_unique_segment_for_sections_specified()
594 { this->unique_segment_for_sections_specified_
= true; }
597 is_lto_slim_object () const
598 { return this->lto_slim_object_
; }
601 set_lto_slim_object ()
602 { this->lto_slim_object_
= true; }
604 // For incremental updates, allocate a block of memory from the
605 // free list. Find a block starting at or after MINOFF.
607 allocate(off_t len
, uint64_t align
, off_t minoff
)
608 { return this->free_list_
.allocate(len
, align
, minoff
); }
611 find_section_order_index(const std::string
&);
613 // Read the sequence of input sections from the file specified with
614 // linker option --section-ordering-file.
616 read_layout_from_file();
618 // Layout an input reloc section when doing a relocatable link. The
619 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
620 // DATA_SECTION is the reloc section to which it refers. RR is the
621 // relocatable information.
622 template<int size
, bool big_endian
>
624 layout_reloc(Sized_relobj_file
<size
, big_endian
>* object
,
625 unsigned int reloc_shndx
,
626 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
627 Output_section
* data_section
,
628 Relocatable_relocs
* rr
);
630 // Layout a group section when doing a relocatable link.
631 template<int size
, bool big_endian
>
633 layout_group(Symbol_table
* symtab
,
634 Sized_relobj_file
<size
, big_endian
>* object
,
635 unsigned int group_shndx
,
636 const char* group_section_name
,
637 const char* signature
,
638 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
639 elfcpp::Elf_Word flags
,
640 std::vector
<unsigned int>* shndxes
);
642 // Like layout, only for exception frame sections. OBJECT is an
643 // object file. SYMBOLS is the contents of the symbol table
644 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
645 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
646 // .eh_frame section in OBJECT. SHDR is the section header.
647 // RELOC_SHNDX is the index of a relocation section which applies to
648 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
649 // is the type of the relocation section if there is one. This
650 // returns the output section, and sets *OFFSET to the offset.
651 template<int size
, bool big_endian
>
653 layout_eh_frame(Sized_relobj_file
<size
, big_endian
>* object
,
654 const unsigned char* symbols
,
656 const unsigned char* symbol_names
,
657 off_t symbol_names_size
,
659 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
660 unsigned int reloc_shndx
, unsigned int reloc_type
,
663 // After processing all input files, we call this to make sure that
664 // the optimized .eh_frame sections have been added to the output
667 finalize_eh_frame_section();
669 // Add .eh_frame information for a PLT. The FDE must start with a
670 // 4-byte PC-relative reference to the start of the PLT, followed by
671 // a 4-byte size of PLT.
673 add_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
674 size_t cie_length
, const unsigned char* fde_data
,
677 // Remove all post-map .eh_frame information for a PLT.
679 remove_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
682 // Scan a .debug_info or .debug_types section, and add summary
683 // information to the .gdb_index section.
684 template<int size
, bool big_endian
>
686 add_to_gdb_index(bool is_type_unit
,
687 Sized_relobj
<size
, big_endian
>* object
,
688 const unsigned char* symbols
,
691 unsigned int reloc_shndx
,
692 unsigned int reloc_type
);
694 // Handle a GNU stack note. This is called once per input object
695 // file. SEEN_GNU_STACK is true if the object file has a
696 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
697 // from that section if there was one.
699 layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
,
702 // Layout a .note.gnu.property section.
704 layout_gnu_property(unsigned int note_type
,
705 unsigned int pr_type
,
707 const unsigned char* pr_data
,
708 const Object
* object
);
710 // Merge per-object properties with program properties.
712 merge_gnu_properties(const Object
* object
);
714 // Add a target-specific property for the output .note.gnu.property section.
716 add_gnu_property(unsigned int note_type
,
717 unsigned int pr_type
,
719 const unsigned char* pr_data
);
721 // Add an Output_section_data to the layout. This is used for
722 // special sections like the GOT section. ORDER is where the
723 // section should wind up in the output segment. IS_RELRO is true
724 // for relro sections.
726 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
727 elfcpp::Elf_Xword flags
,
728 Output_section_data
*, Output_section_order order
,
731 // Increase the size of the relro segment by this much.
733 increase_relro(unsigned int s
)
734 { this->increase_relro_
+= s
; }
736 // Create dynamic sections if necessary.
738 create_initial_dynamic_sections(Symbol_table
*);
740 // Define __start and __stop symbols for output sections.
742 define_section_symbols(Symbol_table
*);
744 // Create automatic note sections.
748 // Create sections for linker scripts.
750 create_script_sections()
751 { this->script_options_
->create_script_sections(this); }
753 // Define symbols from any linker script.
755 define_script_symbols(Symbol_table
* symtab
)
756 { this->script_options_
->add_symbols_to_table(symtab
); }
758 // Define symbols for group signatures.
760 define_group_signatures(Symbol_table
*);
762 // Return the Stringpool used for symbol names.
765 { return &this->sympool_
; }
767 // Return the Stringpool used for dynamic symbol names and dynamic
771 { return &this->dynpool_
; }
773 // Return the .dynamic output section. This is only valid after the
774 // layout has been finalized.
776 dynamic_section() const
777 { return this->dynamic_section_
; }
779 // Return the symtab_xindex section used to hold large section
780 // indexes for the normal symbol table.
781 Output_symtab_xindex
*
782 symtab_xindex() const
783 { return this->symtab_xindex_
; }
785 // Return the dynsym_xindex section used to hold large section
786 // indexes for the dynamic symbol table.
787 Output_symtab_xindex
*
788 dynsym_xindex() const
789 { return this->dynsym_xindex_
; }
791 // Return whether a section is a .gnu.linkonce section, given the
794 is_linkonce(const char* name
)
795 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
797 // Whether we have added an input section.
799 have_added_input_section() const
800 { return this->have_added_input_section_
; }
802 // Return true if a section is a debugging section.
804 is_debug_info_section(const char* name
)
806 // Debugging sections can only be recognized by name.
807 return (strncmp(name
, ".debug", sizeof(".debug") - 1) == 0
808 || strncmp(name
, ".zdebug", sizeof(".zdebug") - 1) == 0
809 || strncmp(name
, ".gnu.linkonce.wi.",
810 sizeof(".gnu.linkonce.wi.") - 1) == 0
811 || strncmp(name
, ".line", sizeof(".line") - 1) == 0
812 || strncmp(name
, ".stab", sizeof(".stab") - 1) == 0
813 || strncmp(name
, ".pdr", sizeof(".pdr") - 1) == 0);
816 // Return true if RELOBJ is an input file whose base name matches
817 // FILE_NAME. The base name must have an extension of ".o", and
818 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
820 match_file_name(const Relobj
* relobj
, const char* file_name
);
822 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
823 // with more than one word being mapped to a .init_array/.fini_array
826 is_ctors_in_init_array(Relobj
* relobj
, unsigned int shndx
) const;
828 // Check if a comdat group or .gnu.linkonce section with the given
829 // NAME is selected for the link. If there is already a section,
830 // *KEPT_SECTION is set to point to the signature and the function
831 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
832 // IS_GROUP_NAME are recorded for this NAME in the layout object,
833 // *KEPT_SECTION is set to the internal copy and the function return
836 find_or_add_kept_section(const std::string
& name
, Relobj
* object
,
837 unsigned int shndx
, bool is_comdat
,
838 bool is_group_name
, Kept_section
** kept_section
);
840 // Finalize the layout after all the input sections have been added.
842 finalize(const Input_objects
*, Symbol_table
*, Target
*, const Task
*);
844 // Return whether any sections require postprocessing.
846 any_postprocessing_sections() const
847 { return this->any_postprocessing_sections_
; }
849 // Return the size of the output file.
851 output_file_size() const
852 { return this->output_file_size_
; }
854 // Return the TLS segment. This will return NULL if there isn't
858 { return this->tls_segment_
; }
860 // Return the normal symbol table.
862 symtab_section() const
864 gold_assert(this->symtab_section_
!= NULL
);
865 return this->symtab_section_
;
868 // Return the file offset of the normal symbol table.
870 symtab_section_offset() const;
872 // Return the section index of the normal symbol tabl.e
874 symtab_section_shndx() const;
876 // Return the dynamic symbol table.
878 dynsym_section() const
880 gold_assert(this->dynsym_section_
!= NULL
);
881 return this->dynsym_section_
;
884 // Return the dynamic tags.
887 { return this->dynamic_data_
; }
889 // Write out the output sections.
891 write_output_sections(Output_file
* of
) const;
893 // Write out data not associated with an input file or the symbol
896 write_data(const Symbol_table
*, Output_file
*) const;
898 // Write out output sections which can not be written until all the
899 // input sections are complete.
901 write_sections_after_input_sections(Output_file
* of
);
903 // Return an output section named NAME, or NULL if there is none.
905 find_output_section(const char* name
) const;
907 // Return an output segment of type TYPE, with segment flags SET set
908 // and segment flags CLEAR clear. Return NULL if there is none.
910 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
911 elfcpp::Elf_Word clear
) const;
913 // Return the number of segments we expect to produce.
915 expected_segment_count() const;
917 // Set a flag to indicate that an object file uses the static TLS model.
920 { this->has_static_tls_
= true; }
922 // Return true if any object file uses the static TLS model.
924 has_static_tls() const
925 { return this->has_static_tls_
; }
927 // Return the options which may be set by a linker script.
930 { return this->script_options_
; }
932 const Script_options
*
933 script_options() const
934 { return this->script_options_
; }
936 // Return the object managing inputs in incremental build. NULL in
937 // non-incremental builds.
939 incremental_inputs() const
940 { return this->incremental_inputs_
; }
942 // For the target-specific code to add dynamic tags which are common
945 add_target_dynamic_tags(bool use_rel
, const Output_data
* plt_got
,
946 const Output_data
* plt_rel
,
947 const Output_data_reloc_generic
* dyn_rel
,
948 bool add_debug
, bool dynrel_includes_plt
);
950 // Add a target-specific dynamic tag with constant value.
952 add_target_specific_dynamic_tag(elfcpp::DT tag
, unsigned int val
);
954 // Compute and write out the build ID if needed.
956 write_build_id(Output_file
*, unsigned char*, size_t) const;
958 // Rewrite output file in binary format.
960 write_binary(Output_file
* in
) const;
962 // Print output sections to the map file.
964 print_to_mapfile(Mapfile
*) const;
966 // Dump statistical information to stderr.
970 // A list of segments.
972 typedef std::vector
<Output_segment
*> Segment_list
;
974 // A list of sections.
976 typedef std::vector
<Output_section
*> Section_list
;
978 // The list of information to write out which is not attached to
979 // either a section or a segment.
980 typedef std::vector
<Output_data
*> Data_list
;
982 // Store the allocated sections into the section list. This is used
983 // by the linker script code.
985 get_allocated_sections(Section_list
*) const;
987 // Store the executable sections into the section list.
989 get_executable_sections(Section_list
*) const;
991 // Make a section for a linker script to hold data.
993 make_output_section_for_script(const char* name
,
994 Script_sections::Section_type section_type
);
996 // Make a segment. This is used by the linker script code.
998 make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
);
1000 // Return the number of segments.
1002 segment_count() const
1003 { return this->segment_list_
.size(); }
1005 // Map from section flags to segment flags.
1006 static elfcpp::Elf_Word
1007 section_flags_to_segment(elfcpp::Elf_Xword flags
);
1009 // Attach sections to segments.
1011 attach_sections_to_segments(const Target
*);
1013 // For relaxation clean up, we need to know output section data created
1014 // from a linker script.
1016 new_output_section_data_from_script(Output_section_data
* posd
)
1018 if (this->record_output_section_data_from_script_
)
1019 this->script_output_section_data_list_
.push_back(posd
);
1022 // Return section list.
1024 section_list() const
1025 { return this->section_list_
; }
1027 // Returns TRUE iff NAME (an input section from RELOBJ) will
1028 // be mapped to an output section that should be KEPT.
1030 keep_input_section(const Relobj
*, const char*);
1032 // Add a special output object that will be recreated afresh
1033 // if there is another relaxation iteration.
1035 add_relax_output(Output_data
* data
)
1036 { this->relax_output_list_
.push_back(data
); }
1038 // Clear out (and free) everything added by add_relax_output.
1040 reset_relax_output();
1043 Layout(const Layout
&);
1044 Layout
& operator=(const Layout
&);
1046 // Mapping from input section names to output section names.
1047 struct Section_name_mapping
1054 static const Section_name_mapping section_name_mapping
[];
1055 static const int section_name_mapping_count
;
1056 static const Section_name_mapping text_section_name_mapping
[];
1057 static const int text_section_name_mapping_count
;
1059 // Find section name NAME in map and return the mapped name if found
1060 // with the length set in PLEN.
1061 static const char* match_section_name(const Section_name_mapping
* map
,
1062 const int count
, const char* name
,
1065 // During a relocatable link, a list of group sections and
1067 struct Group_signature
1069 // The group section.
1070 Output_section
* section
;
1072 const char* signature
;
1075 : section(NULL
), signature(NULL
)
1078 Group_signature(Output_section
* sectiona
, const char* signaturea
)
1079 : section(sectiona
), signature(signaturea
)
1082 typedef std::vector
<Group_signature
> Group_signatures
;
1084 // Create a note section, filling in the header.
1086 create_note(const char* name
, int note_type
, const char* section_name
,
1087 size_t descsz
, bool allocate
, size_t* trailing_padding
);
1089 // Create a note section for gnu program properties.
1091 create_gnu_properties_note();
1093 // Create a note section for gold version.
1097 // Record whether the stack must be executable, and a user-supplied size.
1099 create_stack_segment();
1101 // Create a build ID note if needed.
1105 // Link .stab and .stabstr sections.
1107 link_stabs_sections();
1109 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1110 // for the next run of incremental linking to check what has changed.
1112 create_incremental_info_sections(Symbol_table
*);
1114 // Find the first read-only PT_LOAD segment, creating one if
1117 find_first_load_seg(const Target
*);
1119 // Count the local symbols in the regular symbol table and the dynamic
1120 // symbol table, and build the respective string pools.
1122 count_local_symbols(const Task
*, const Input_objects
*);
1124 // Create the output sections for the symbol table.
1126 create_symtab_sections(const Input_objects
*, Symbol_table
*,
1127 unsigned int, off_t
*, unsigned int);
1129 // Create the .shstrtab section.
1133 // Create the section header table.
1135 create_shdrs(const Output_section
* shstrtab_section
, off_t
*);
1137 // Create the dynamic symbol table.
1139 create_dynamic_symtab(const Input_objects
*, Symbol_table
*,
1140 Output_section
** pdynstr
,
1141 unsigned int* plocal_dynamic_count
,
1142 unsigned int* pforced_local_dynamic_count
,
1143 std::vector
<Symbol
*>* pdynamic_symbols
,
1144 Versions
* versions
);
1146 // Assign offsets to each local portion of the dynamic symbol table.
1148 assign_local_dynsym_offsets(const Input_objects
*);
1150 // Finish the .dynamic section and PT_DYNAMIC segment.
1152 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
1154 // Set the size of the _DYNAMIC symbol.
1156 set_dynamic_symbol_size(const Symbol_table
*);
1158 // Create the .interp section and PT_INTERP segment.
1160 create_interp(const Target
* target
);
1162 // Create the version sections.
1164 create_version_sections(const Versions
*,
1165 const Symbol_table
*,
1166 unsigned int local_symcount
,
1167 const std::vector
<Symbol
*>& dynamic_symbols
,
1168 const Output_section
* dynstr
);
1170 template<int size
, bool big_endian
>
1172 sized_create_version_sections(const Versions
* versions
,
1173 const Symbol_table
*,
1174 unsigned int local_symcount
,
1175 const std::vector
<Symbol
*>& dynamic_symbols
,
1176 const Output_section
* dynstr
);
1178 // Return whether to include this section in the link.
1179 template<int size
, bool big_endian
>
1181 include_section(Sized_relobj_file
<size
, big_endian
>* object
, const char* name
,
1182 const elfcpp::Shdr
<size
, big_endian
>&);
1184 // Return the output section name to use given an input section
1185 // name. Set *PLEN to the length of the name. *PLEN must be
1186 // initialized to the length of NAME.
1188 output_section_name(const Relobj
*, const char* name
, size_t* plen
);
1190 // Return the number of allocated output sections.
1192 allocated_output_section_count() const;
1194 // Return the output section for NAME, TYPE and FLAGS.
1196 get_output_section(const char* name
, Stringpool::Key name_key
,
1197 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1198 Output_section_order order
, bool is_relro
);
1200 // Clear the input section flags that should not be copied to the
1203 get_output_section_flags (elfcpp::Elf_Xword input_section_flags
);
1205 // Choose the output section for NAME in RELOBJ.
1207 choose_output_section(const Relobj
* relobj
, const char* name
,
1208 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1209 bool is_input_section
, Output_section_order order
,
1210 bool is_relro
, bool is_reloc
, bool match_input_spec
);
1212 // Create a new Output_section.
1214 make_output_section(const char* name
, elfcpp::Elf_Word type
,
1215 elfcpp::Elf_Xword flags
, Output_section_order order
,
1218 // Attach a section to a segment.
1220 attach_section_to_segment(const Target
*, Output_section
*);
1222 // Get section order.
1223 Output_section_order
1224 default_section_order(Output_section
*, bool is_relro_local
);
1226 // Attach an allocated section to a segment.
1228 attach_allocated_section_to_segment(const Target
*, Output_section
*);
1230 // Make the .eh_frame section.
1232 make_eh_frame_section(const Relobj
*);
1234 // Set the final file offsets of all the segments.
1236 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
1238 // Set the file offsets of the sections when doing a relocatable
1241 set_relocatable_section_offsets(Output_data
*, unsigned int* pshndx
);
1243 // Set the final file offsets of all the sections not associated
1244 // with a segment. We set section offsets in three passes: the
1245 // first handles all allocated sections, the second sections that
1246 // require postprocessing, and the last the late-bound STRTAB
1247 // sections (probably only shstrtab, which is the one we care about
1248 // because it holds section names).
1249 enum Section_offset_pass
1251 BEFORE_INPUT_SECTIONS_PASS
,
1252 POSTPROCESSING_SECTIONS_PASS
,
1253 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1256 set_section_offsets(off_t
, Section_offset_pass pass
);
1258 // Set the final section indexes of all the sections not associated
1259 // with a segment. Returns the next unused index.
1261 set_section_indexes(unsigned int pshndx
);
1263 // Set the section addresses when using a script.
1265 set_section_addresses_from_script(Symbol_table
*);
1267 // Find appropriate places or orphan sections in a script.
1269 place_orphan_sections_in_script();
1271 // Return whether SEG1 comes before SEG2 in the output file.
1273 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
1275 // Use to save and restore segments during relaxation.
1276 typedef Unordered_map
<const Output_segment
*, const Output_segment
*>
1279 // Save states of current output segments.
1281 save_segments(Segment_states
*);
1283 // Restore output segment states.
1285 restore_segments(const Segment_states
*);
1287 // Clean up after relaxation so that it is possible to lay out the
1288 // sections and segments again.
1290 clean_up_after_relaxation();
1292 // Doing preparation work for relaxation. This is factored out to make
1293 // Layout::finalized a bit smaller and easier to read.
1295 prepare_for_relaxation();
1297 // Main body of the relaxation loop, which lays out the section.
1299 relaxation_loop_body(int, Target
*, Symbol_table
*, Output_segment
**,
1300 Output_segment
*, Output_segment_headers
*,
1301 Output_file_header
*, unsigned int*);
1303 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1304 typedef Unordered_map
<std::string
, Kept_section
> Signatures
;
1306 // Mapping from input section name/type/flags to output section. We
1307 // use canonicalized strings here.
1309 typedef std::pair
<Stringpool::Key
,
1310 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
1315 operator()(const Key
& k
) const;
1318 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
1320 // A comparison class for segments.
1322 class Compare_segments
1325 Compare_segments(Layout
* layout
)
1330 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
1331 { return this->layout_
->segment_precedes(seg1
, seg2
); }
1337 typedef std::vector
<Output_section_data
*> Output_section_data_list
;
1339 // Debug checker class.
1340 class Relaxation_debug_check
1343 Relaxation_debug_check()
1347 // Check that sections and special data are in reset states.
1349 check_output_data_for_reset_values(const Layout::Section_list
&,
1350 const Layout::Data_list
& special_outputs
,
1351 const Layout::Data_list
& relax_outputs
);
1353 // Record information of a section list.
1355 read_sections(const Layout::Section_list
&);
1357 // Verify a section list with recorded information.
1359 verify_sections(const Layout::Section_list
&);
1362 // Information we care about a section.
1365 // Output section described by this.
1366 Output_section
* output_section
;
1375 // Section information.
1376 std::vector
<Section_info
> section_infos_
;
1379 // Program properties from .note.gnu.property sections.
1383 unsigned char* pr_data
;
1385 typedef std::map
<unsigned int, Gnu_property
> Gnu_properties
;
1387 // The number of input files, for sizing tables.
1388 int number_of_input_files_
;
1389 // Information set by scripts or by command line options.
1390 Script_options
* script_options_
;
1391 // The output section names.
1392 Stringpool namepool_
;
1393 // The output symbol names.
1394 Stringpool sympool_
;
1395 // The dynamic strings, if needed.
1396 Stringpool dynpool_
;
1397 // The list of group sections and linkonce sections which we have seen.
1398 Signatures signatures_
;
1399 // The mapping from input section name/type/flags to output sections.
1400 Section_name_map section_name_map_
;
1401 // The list of output segments.
1402 Segment_list segment_list_
;
1403 // The list of output sections.
1404 Section_list section_list_
;
1405 // The list of output sections which are not attached to any output
1407 Section_list unattached_section_list_
;
1408 // The list of unattached Output_data objects which require special
1409 // handling because they are not Output_sections.
1410 Data_list special_output_list_
;
1411 // Like special_output_list_, but cleared and recreated on each
1412 // iteration of relaxation.
1413 Data_list relax_output_list_
;
1414 // The section headers.
1415 Output_section_headers
* section_headers_
;
1416 // A pointer to the PT_TLS segment if there is one.
1417 Output_segment
* tls_segment_
;
1418 // A pointer to the PT_GNU_RELRO segment if there is one.
1419 Output_segment
* relro_segment_
;
1420 // A pointer to the PT_INTERP segment if there is one.
1421 Output_segment
* interp_segment_
;
1422 // A backend may increase the size of the PT_GNU_RELRO segment if
1423 // there is one. This is the amount to increase it by.
1424 unsigned int increase_relro_
;
1425 // The SHT_SYMTAB output section.
1426 Output_section
* symtab_section_
;
1427 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1428 Output_symtab_xindex
* symtab_xindex_
;
1429 // The SHT_DYNSYM output section if there is one.
1430 Output_section
* dynsym_section_
;
1431 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1432 Output_symtab_xindex
* dynsym_xindex_
;
1433 // The SHT_DYNAMIC output section if there is one.
1434 Output_section
* dynamic_section_
;
1435 // The _DYNAMIC symbol if there is one.
1436 Symbol
* dynamic_symbol_
;
1437 // The dynamic data which goes into dynamic_section_.
1438 Output_data_dynamic
* dynamic_data_
;
1439 // The exception frame output section if there is one.
1440 Output_section
* eh_frame_section_
;
1441 // The exception frame data for eh_frame_section_.
1442 Eh_frame
* eh_frame_data_
;
1443 // Whether we have added eh_frame_data_ to the .eh_frame section.
1444 bool added_eh_frame_data_
;
1445 // The exception frame header output section if there is one.
1446 Output_section
* eh_frame_hdr_section_
;
1447 // The data for the .gdb_index section.
1448 Gdb_index
* gdb_index_data_
;
1449 // The space for the build ID checksum if there is one.
1450 Output_section_data
* build_id_note_
;
1451 // The output section containing dwarf abbreviations
1452 Output_reduced_debug_abbrev_section
* debug_abbrev_
;
1453 // The output section containing the dwarf debug info tree
1454 Output_reduced_debug_info_section
* debug_info_
;
1455 // A list of group sections and their signatures.
1456 Group_signatures group_signatures_
;
1457 // The size of the output file.
1458 off_t output_file_size_
;
1459 // Whether we have added an input section to an output section.
1460 bool have_added_input_section_
;
1461 // Whether we have attached the sections to the segments.
1462 bool sections_are_attached_
;
1463 // Whether we have seen an object file marked to require an
1464 // executable stack.
1465 bool input_requires_executable_stack_
;
1466 // Whether we have seen at least one object file with an executable
1468 bool input_with_gnu_stack_note_
;
1469 // Whether we have seen at least one object file without an
1470 // executable stack marker.
1471 bool input_without_gnu_stack_note_
;
1472 // Whether we have seen an object file that uses the static TLS model.
1473 bool has_static_tls_
;
1474 // Whether any sections require postprocessing.
1475 bool any_postprocessing_sections_
;
1476 // Whether we have resized the signatures_ hash table.
1477 bool resized_signatures_
;
1478 // Whether we have created a .stab*str output section.
1479 bool have_stabstr_section_
;
1480 // True if the input sections in the output sections should be sorted
1481 // as specified in a section ordering file.
1482 bool section_ordering_specified_
;
1483 // True if some input sections need to be mapped to a unique segment,
1484 // after being mapped to a unique Output_section.
1485 bool unique_segment_for_sections_specified_
;
1486 // In incremental build, holds information check the inputs and build the
1487 // .gnu_incremental_inputs section.
1488 Incremental_inputs
* incremental_inputs_
;
1489 // Whether we record output section data created in script
1490 bool record_output_section_data_from_script_
;
1491 // Set if this is a slim LTO object not loaded with a compiler plugin
1492 bool lto_slim_object_
;
1493 // List of output data that needs to be removed at relaxation clean up.
1494 Output_section_data_list script_output_section_data_list_
;
1495 // Structure to save segment states before entering the relaxation loop.
1496 Segment_states
* segment_states_
;
1497 // A relaxation debug checker. We only create one when in debugging mode.
1498 Relaxation_debug_check
* relaxation_debug_check_
;
1499 // Plugins specify section_ordering using this map. This is set in
1500 // update_section_order in plugin.cc
1501 std::map
<Section_id
, unsigned int> section_order_map_
;
1502 // This maps an input section to a unique segment. This is done by first
1503 // placing such input sections in unique output sections and then mapping
1504 // the output section to a unique segment. Unique_segment_info stores
1505 // any additional flags and alignment of the new segment.
1506 Section_segment_map section_segment_map_
;
1507 // Hash a pattern to its position in the section ordering file.
1508 Unordered_map
<std::string
, unsigned int> input_section_position_
;
1509 // Vector of glob only patterns in the section_ordering file.
1510 std::vector
<std::string
> input_section_glob_
;
1511 // For incremental links, the base file to be modified.
1512 Incremental_binary
* incremental_base_
;
1513 // For incremental links, a list of free space within the file.
1514 Free_list free_list_
;
1515 // Program properties.
1516 Gnu_properties gnu_properties_
;
1519 // This task handles writing out data in output sections which is not
1520 // part of an input section, or which requires special handling. When
1521 // this is done, it unblocks both output_sections_blocker and
1524 class Write_sections_task
: public Task
1527 Write_sections_task(const Layout
* layout
, Output_file
* of
,
1528 Task_token
* output_sections_blocker
,
1529 Task_token
* input_sections_blocker
,
1530 Task_token
* final_blocker
)
1531 : layout_(layout
), of_(of
),
1532 output_sections_blocker_(output_sections_blocker
),
1533 input_sections_blocker_(input_sections_blocker
),
1534 final_blocker_(final_blocker
)
1537 // The standard Task methods.
1543 locks(Task_locker
*);
1550 { return "Write_sections_task"; }
1553 class Write_sections_locker
;
1555 const Layout
* layout_
;
1557 Task_token
* output_sections_blocker_
;
1558 Task_token
* input_sections_blocker_
;
1559 Task_token
* final_blocker_
;
1562 // This task handles writing out data which is not part of a section
1565 class Write_data_task
: public Task
1568 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
1569 Output_file
* of
, Task_token
* final_blocker
)
1570 : layout_(layout
), symtab_(symtab
), of_(of
), final_blocker_(final_blocker
)
1573 // The standard Task methods.
1579 locks(Task_locker
*);
1586 { return "Write_data_task"; }
1589 const Layout
* layout_
;
1590 const Symbol_table
* symtab_
;
1592 Task_token
* final_blocker_
;
1595 // This task handles writing out the global symbols.
1597 class Write_symbols_task
: public Task
1600 Write_symbols_task(const Layout
* layout
, const Symbol_table
* symtab
,
1601 const Input_objects
* /*input_objects*/,
1602 const Stringpool
* sympool
, const Stringpool
* dynpool
,
1603 Output_file
* of
, Task_token
* final_blocker
)
1604 : layout_(layout
), symtab_(symtab
),
1605 sympool_(sympool
), dynpool_(dynpool
), of_(of
),
1606 final_blocker_(final_blocker
)
1609 // The standard Task methods.
1615 locks(Task_locker
*);
1622 { return "Write_symbols_task"; }
1625 const Layout
* layout_
;
1626 const Symbol_table
* symtab_
;
1627 const Stringpool
* sympool_
;
1628 const Stringpool
* dynpool_
;
1630 Task_token
* final_blocker_
;
1633 // This task handles writing out data in output sections which can't
1634 // be written out until all the input sections have been handled.
1635 // This is for sections whose contents is based on the contents of
1636 // other output sections.
1638 class Write_after_input_sections_task
: public Task
1641 Write_after_input_sections_task(Layout
* layout
, Output_file
* of
,
1642 Task_token
* input_sections_blocker
,
1643 Task_token
* final_blocker
)
1644 : layout_(layout
), of_(of
),
1645 input_sections_blocker_(input_sections_blocker
),
1646 final_blocker_(final_blocker
)
1649 // The standard Task methods.
1655 locks(Task_locker
*);
1662 { return "Write_after_input_sections_task"; }
1667 Task_token
* input_sections_blocker_
;
1668 Task_token
* final_blocker_
;
1671 // This task function handles computation of the build id.
1672 // When using --build-id=tree, it schedules the tasks that
1673 // compute the hashes for each chunk of the file. This task
1674 // cannot run until we have finalized the size of the output
1675 // file, after the completion of Write_after_input_sections_task.
1677 class Build_id_task_runner
: public Task_function_runner
1680 Build_id_task_runner(const General_options
* options
, const Layout
* layout
,
1682 : options_(options
), layout_(layout
), of_(of
)
1685 // Run the operation.
1687 run(Workqueue
*, const Task
*);
1690 const General_options
* options_
;
1691 const Layout
* layout_
;
1695 // This task function handles closing the file.
1697 class Close_task_runner
: public Task_function_runner
1700 Close_task_runner(const General_options
* options
, const Layout
* layout
,
1701 Output_file
* of
, unsigned char* array_of_hashes
,
1702 size_t size_of_hashes
)
1703 : options_(options
), layout_(layout
), of_(of
),
1704 array_of_hashes_(array_of_hashes
), size_of_hashes_(size_of_hashes
)
1707 // Run the operation.
1709 run(Workqueue
*, const Task
*);
1712 const General_options
* options_
;
1713 const Layout
* layout_
;
1715 unsigned char* const array_of_hashes_
;
1716 const size_t size_of_hashes_
;
1719 // A small helper function to align an address.
1722 align_address(uint64_t address
, uint64_t addralign
)
1725 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
1729 } // End namespace gold.
1731 #endif // !defined(GOLD_LAYOUT_H)