1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright (C) 2006-2017 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 regular text sections.
428 // The .fini section.
431 // The read-only sections.
434 // The exception frame sections.
437 // The TLS sections come first in the data section.
441 // Local RELRO (read-only after relocation) sections come before
442 // non-local RELRO sections. This data will be fully resolved by
446 // Non-local RELRO sections are grouped together after local RELRO
447 // sections. All RELRO sections must be adjacent so that they can
448 // all be put into a PT_GNU_RELRO segment.
451 // We permit marking exactly one output section as the last RELRO
452 // section. We do this so that the read-only GOT can be adjacent to
456 // Similarly, we permit marking exactly one output section as the
457 // first non-RELRO section.
458 ORDER_NON_RELRO_FIRST
,
460 // The regular data sections come after the RELRO sections.
463 // Large data sections normally go in large data segments.
466 // Group writable notes so that we can have a single PT_NOTE
470 // The small data sections must be at the end of the data sections,
471 // so that they can be adjacent to the small BSS sections.
474 // The BSS sections start here.
476 // The small BSS sections must be at the start of the BSS sections,
477 // so that they can be adjacent to the small data sections.
480 // The regular BSS sections.
483 // The large BSS sections come after the other BSS sections.
490 // This class handles the details of laying out input sections.
495 Layout(int number_of_input_files
, Script_options
*);
499 delete this->relaxation_debug_check_
;
500 delete this->segment_states_
;
503 // For incremental links, record the base file to be modified.
505 set_incremental_base(Incremental_binary
* base
);
509 { return this->incremental_base_
; }
511 // For incremental links, record the initial fixed layout of a section
512 // from the base file, and return a pointer to the Output_section.
513 template<int size
, bool big_endian
>
515 init_fixed_output_section(const char*, elfcpp::Shdr
<size
, big_endian
>&);
517 // Given an input section SHNDX, named NAME, with data in SHDR, from
518 // the object file OBJECT, return the output section where this
519 // input section should go. RELOC_SHNDX is the index of a
520 // relocation section which applies to this section, or 0 if none,
521 // or -1U if more than one. RELOC_TYPE is the type of the
522 // relocation section if there is one. Set *OFFSET to the offset
523 // within the output section.
524 template<int size
, bool big_endian
>
526 layout(Sized_relobj_file
<size
, big_endian
> *object
, unsigned int shndx
,
527 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
528 unsigned int reloc_shndx
, unsigned int reloc_type
, off_t
* offset
);
530 std::map
<Section_id
, unsigned int>*
531 get_section_order_map()
532 { return &this->section_order_map_
; }
534 // Struct to store segment info when mapping some input sections to
535 // unique segments using linker plugins. Mapping an input section to
536 // a unique segment is done by first placing such input sections in
537 // unique output sections and then mapping the output section to a
538 // unique segment. NAME is the name of the output section. FLAGS
539 // and ALIGN are the extra flags and alignment of the segment.
540 struct Unique_segment_info
542 // Identifier for the segment. ELF segments don't have names. This
543 // is used as the name of the output section mapped to the segment.
545 // Additional segment flags.
547 // Segment alignment.
551 // Mapping from input section to segment.
552 typedef std::map
<Const_section_id
, Unique_segment_info
*>
555 // Maps section SECN to SEGMENT s.
557 insert_section_segment_map(Const_section_id secn
, Unique_segment_info
*s
);
559 // Some input sections require special ordering, for compatibility
560 // with GNU ld. Given the name of an input section, return -1 if it
561 // does not require special ordering. Otherwise, return the index
562 // by which it should be ordered compared to other input sections
563 // that require special ordering.
565 special_ordering_of_input_section(const char* name
);
568 is_section_ordering_specified()
569 { return this->section_ordering_specified_
; }
572 set_section_ordering_specified()
573 { this->section_ordering_specified_
= true; }
576 is_unique_segment_for_sections_specified() const
577 { return this->unique_segment_for_sections_specified_
; }
580 set_unique_segment_for_sections_specified()
581 { this->unique_segment_for_sections_specified_
= true; }
583 // For incremental updates, allocate a block of memory from the
584 // free list. Find a block starting at or after MINOFF.
586 allocate(off_t len
, uint64_t align
, off_t minoff
)
587 { return this->free_list_
.allocate(len
, align
, minoff
); }
590 find_section_order_index(const std::string
&);
592 // Read the sequence of input sections from the file specified with
593 // linker option --section-ordering-file.
595 read_layout_from_file();
597 // Layout an input reloc section when doing a relocatable link. The
598 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
599 // DATA_SECTION is the reloc section to which it refers. RR is the
600 // relocatable information.
601 template<int size
, bool big_endian
>
603 layout_reloc(Sized_relobj_file
<size
, big_endian
>* object
,
604 unsigned int reloc_shndx
,
605 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
606 Output_section
* data_section
,
607 Relocatable_relocs
* rr
);
609 // Layout a group section when doing a relocatable link.
610 template<int size
, bool big_endian
>
612 layout_group(Symbol_table
* symtab
,
613 Sized_relobj_file
<size
, big_endian
>* object
,
614 unsigned int group_shndx
,
615 const char* group_section_name
,
616 const char* signature
,
617 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
618 elfcpp::Elf_Word flags
,
619 std::vector
<unsigned int>* shndxes
);
621 // Like layout, only for exception frame sections. OBJECT is an
622 // object file. SYMBOLS is the contents of the symbol table
623 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
624 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
625 // .eh_frame section in OBJECT. SHDR is the section header.
626 // RELOC_SHNDX is the index of a relocation section which applies to
627 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
628 // is the type of the relocation section if there is one. This
629 // returns the output section, and sets *OFFSET to the offset.
630 template<int size
, bool big_endian
>
632 layout_eh_frame(Sized_relobj_file
<size
, big_endian
>* object
,
633 const unsigned char* symbols
,
635 const unsigned char* symbol_names
,
636 off_t symbol_names_size
,
638 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
639 unsigned int reloc_shndx
, unsigned int reloc_type
,
642 // After processing all input files, we call this to make sure that
643 // the optimized .eh_frame sections have been added to the output
646 finalize_eh_frame_section();
648 // Add .eh_frame information for a PLT. The FDE must start with a
649 // 4-byte PC-relative reference to the start of the PLT, followed by
650 // a 4-byte size of PLT.
652 add_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
653 size_t cie_length
, const unsigned char* fde_data
,
656 // Remove .eh_frame information for a PLT. FDEs using the CIE must
657 // be removed in reverse order to the order they were added.
659 remove_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
660 size_t cie_length
, const unsigned char* fde_data
,
663 // Scan a .debug_info or .debug_types section, and add summary
664 // information to the .gdb_index section.
665 template<int size
, bool big_endian
>
667 add_to_gdb_index(bool is_type_unit
,
668 Sized_relobj
<size
, big_endian
>* object
,
669 const unsigned char* symbols
,
672 unsigned int reloc_shndx
,
673 unsigned int reloc_type
);
675 // Handle a GNU stack note. This is called once per input object
676 // file. SEEN_GNU_STACK is true if the object file has a
677 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
678 // from that section if there was one.
680 layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
,
683 // Add an Output_section_data to the layout. This is used for
684 // special sections like the GOT section. ORDER is where the
685 // section should wind up in the output segment. IS_RELRO is true
686 // for relro sections.
688 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
689 elfcpp::Elf_Xword flags
,
690 Output_section_data
*, Output_section_order order
,
693 // Increase the size of the relro segment by this much.
695 increase_relro(unsigned int s
)
696 { this->increase_relro_
+= s
; }
698 // Create dynamic sections if necessary.
700 create_initial_dynamic_sections(Symbol_table
*);
702 // Define __start and __stop symbols for output sections.
704 define_section_symbols(Symbol_table
*);
706 // Create automatic note sections.
710 // Create sections for linker scripts.
712 create_script_sections()
713 { this->script_options_
->create_script_sections(this); }
715 // Define symbols from any linker script.
717 define_script_symbols(Symbol_table
* symtab
)
718 { this->script_options_
->add_symbols_to_table(symtab
); }
720 // Define symbols for group signatures.
722 define_group_signatures(Symbol_table
*);
724 // Return the Stringpool used for symbol names.
727 { return &this->sympool_
; }
729 // Return the Stringpool used for dynamic symbol names and dynamic
733 { return &this->dynpool_
; }
735 // Return the .dynamic output section. This is only valid after the
736 // layout has been finalized.
738 dynamic_section() const
739 { return this->dynamic_section_
; }
741 // Return the symtab_xindex section used to hold large section
742 // indexes for the normal symbol table.
743 Output_symtab_xindex
*
744 symtab_xindex() const
745 { return this->symtab_xindex_
; }
747 // Return the dynsym_xindex section used to hold large section
748 // indexes for the dynamic symbol table.
749 Output_symtab_xindex
*
750 dynsym_xindex() const
751 { return this->dynsym_xindex_
; }
753 // Return whether a section is a .gnu.linkonce section, given the
756 is_linkonce(const char* name
)
757 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
759 // Whether we have added an input section.
761 have_added_input_section() const
762 { return this->have_added_input_section_
; }
764 // Return true if a section is a debugging section.
766 is_debug_info_section(const char* name
)
768 // Debugging sections can only be recognized by name.
769 return (strncmp(name
, ".debug", sizeof(".debug") - 1) == 0
770 || strncmp(name
, ".zdebug", sizeof(".zdebug") - 1) == 0
771 || strncmp(name
, ".gnu.linkonce.wi.",
772 sizeof(".gnu.linkonce.wi.") - 1) == 0
773 || strncmp(name
, ".line", sizeof(".line") - 1) == 0
774 || strncmp(name
, ".stab", sizeof(".stab") - 1) == 0
775 || strncmp(name
, ".pdr", sizeof(".pdr") - 1) == 0);
778 // Return true if RELOBJ is an input file whose base name matches
779 // FILE_NAME. The base name must have an extension of ".o", and
780 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
782 match_file_name(const Relobj
* relobj
, const char* file_name
);
784 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
785 // with more than one word being mapped to a .init_array/.fini_array
788 is_ctors_in_init_array(Relobj
* relobj
, unsigned int shndx
) const;
790 // Check if a comdat group or .gnu.linkonce section with the given
791 // NAME is selected for the link. If there is already a section,
792 // *KEPT_SECTION is set to point to the signature and the function
793 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
794 // IS_GROUP_NAME are recorded for this NAME in the layout object,
795 // *KEPT_SECTION is set to the internal copy and the function return
798 find_or_add_kept_section(const std::string
& name
, Relobj
* object
,
799 unsigned int shndx
, bool is_comdat
,
800 bool is_group_name
, Kept_section
** kept_section
);
802 // Finalize the layout after all the input sections have been added.
804 finalize(const Input_objects
*, Symbol_table
*, Target
*, const Task
*);
806 // Return whether any sections require postprocessing.
808 any_postprocessing_sections() const
809 { return this->any_postprocessing_sections_
; }
811 // Return the size of the output file.
813 output_file_size() const
814 { return this->output_file_size_
; }
816 // Return the TLS segment. This will return NULL if there isn't
820 { return this->tls_segment_
; }
822 // Return the normal symbol table.
824 symtab_section() const
826 gold_assert(this->symtab_section_
!= NULL
);
827 return this->symtab_section_
;
830 // Return the file offset of the normal symbol table.
832 symtab_section_offset() const;
834 // Return the section index of the normal symbol tabl.e
836 symtab_section_shndx() const;
838 // Return the dynamic symbol table.
840 dynsym_section() const
842 gold_assert(this->dynsym_section_
!= NULL
);
843 return this->dynsym_section_
;
846 // Return the dynamic tags.
849 { return this->dynamic_data_
; }
851 // Write out the output sections.
853 write_output_sections(Output_file
* of
) const;
855 // Write out data not associated with an input file or the symbol
858 write_data(const Symbol_table
*, Output_file
*) const;
860 // Write out output sections which can not be written until all the
861 // input sections are complete.
863 write_sections_after_input_sections(Output_file
* of
);
865 // Return an output section named NAME, or NULL if there is none.
867 find_output_section(const char* name
) const;
869 // Return an output segment of type TYPE, with segment flags SET set
870 // and segment flags CLEAR clear. Return NULL if there is none.
872 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
873 elfcpp::Elf_Word clear
) const;
875 // Return the number of segments we expect to produce.
877 expected_segment_count() const;
879 // Set a flag to indicate that an object file uses the static TLS model.
882 { this->has_static_tls_
= true; }
884 // Return true if any object file uses the static TLS model.
886 has_static_tls() const
887 { return this->has_static_tls_
; }
889 // Return the options which may be set by a linker script.
892 { return this->script_options_
; }
894 const Script_options
*
895 script_options() const
896 { return this->script_options_
; }
898 // Return the object managing inputs in incremental build. NULL in
899 // non-incremental builds.
901 incremental_inputs() const
902 { return this->incremental_inputs_
; }
904 // For the target-specific code to add dynamic tags which are common
907 add_target_dynamic_tags(bool use_rel
, const Output_data
* plt_got
,
908 const Output_data
* plt_rel
,
909 const Output_data_reloc_generic
* dyn_rel
,
910 bool add_debug
, bool dynrel_includes_plt
);
912 // Add a target-specific dynamic tag with constant value.
914 add_target_specific_dynamic_tag(elfcpp::DT tag
, unsigned int val
);
916 // Compute and write out the build ID if needed.
918 write_build_id(Output_file
*, unsigned char*, size_t) const;
920 // Rewrite output file in binary format.
922 write_binary(Output_file
* in
) const;
924 // Print output sections to the map file.
926 print_to_mapfile(Mapfile
*) const;
928 // Dump statistical information to stderr.
932 // A list of segments.
934 typedef std::vector
<Output_segment
*> Segment_list
;
936 // A list of sections.
938 typedef std::vector
<Output_section
*> Section_list
;
940 // The list of information to write out which is not attached to
941 // either a section or a segment.
942 typedef std::vector
<Output_data
*> Data_list
;
944 // Store the allocated sections into the section list. This is used
945 // by the linker script code.
947 get_allocated_sections(Section_list
*) const;
949 // Store the executable sections into the section list.
951 get_executable_sections(Section_list
*) const;
953 // Make a section for a linker script to hold data.
955 make_output_section_for_script(const char* name
,
956 Script_sections::Section_type section_type
);
958 // Make a segment. This is used by the linker script code.
960 make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
);
962 // Return the number of segments.
964 segment_count() const
965 { return this->segment_list_
.size(); }
967 // Map from section flags to segment flags.
968 static elfcpp::Elf_Word
969 section_flags_to_segment(elfcpp::Elf_Xword flags
);
971 // Attach sections to segments.
973 attach_sections_to_segments(const Target
*);
975 // For relaxation clean up, we need to know output section data created
976 // from a linker script.
978 new_output_section_data_from_script(Output_section_data
* posd
)
980 if (this->record_output_section_data_from_script_
)
981 this->script_output_section_data_list_
.push_back(posd
);
984 // Return section list.
987 { return this->section_list_
; }
989 // Returns TRUE iff NAME (an input section from RELOBJ) will
990 // be mapped to an output section that should be KEPT.
992 keep_input_section(const Relobj
*, const char*);
994 // Add a special output object that will be recreated afresh
995 // if there is another relaxation iteration.
997 add_relax_output(Output_data
* data
)
998 { this->relax_output_list_
.push_back(data
); }
1000 // Clear out (and free) everything added by add_relax_output.
1002 reset_relax_output();
1005 Layout(const Layout
&);
1006 Layout
& operator=(const Layout
&);
1008 // Mapping from input section names to output section names.
1009 struct Section_name_mapping
1016 static const Section_name_mapping section_name_mapping
[];
1017 static const int section_name_mapping_count
;
1019 // During a relocatable link, a list of group sections and
1021 struct Group_signature
1023 // The group section.
1024 Output_section
* section
;
1026 const char* signature
;
1029 : section(NULL
), signature(NULL
)
1032 Group_signature(Output_section
* sectiona
, const char* signaturea
)
1033 : section(sectiona
), signature(signaturea
)
1036 typedef std::vector
<Group_signature
> Group_signatures
;
1038 // Create a note section, filling in the header.
1040 create_note(const char* name
, int note_type
, const char* section_name
,
1041 size_t descsz
, bool allocate
, size_t* trailing_padding
);
1043 // Create a note section for gold version.
1047 // Record whether the stack must be executable, and a user-supplied size.
1049 create_stack_segment();
1051 // Create a build ID note if needed.
1055 // Link .stab and .stabstr sections.
1057 link_stabs_sections();
1059 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1060 // for the next run of incremental linking to check what has changed.
1062 create_incremental_info_sections(Symbol_table
*);
1064 // Find the first read-only PT_LOAD segment, creating one if
1067 find_first_load_seg(const Target
*);
1069 // Count the local symbols in the regular symbol table and the dynamic
1070 // symbol table, and build the respective string pools.
1072 count_local_symbols(const Task
*, const Input_objects
*);
1074 // Create the output sections for the symbol table.
1076 create_symtab_sections(const Input_objects
*, Symbol_table
*,
1077 unsigned int, off_t
*, unsigned int);
1079 // Create the .shstrtab section.
1083 // Create the section header table.
1085 create_shdrs(const Output_section
* shstrtab_section
, off_t
*);
1087 // Create the dynamic symbol table.
1089 create_dynamic_symtab(const Input_objects
*, Symbol_table
*,
1090 Output_section
** pdynstr
,
1091 unsigned int* plocal_dynamic_count
,
1092 unsigned int* pforced_local_dynamic_count
,
1093 std::vector
<Symbol
*>* pdynamic_symbols
,
1094 Versions
* versions
);
1096 // Assign offsets to each local portion of the dynamic symbol table.
1098 assign_local_dynsym_offsets(const Input_objects
*);
1100 // Finish the .dynamic section and PT_DYNAMIC segment.
1102 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
1104 // Set the size of the _DYNAMIC symbol.
1106 set_dynamic_symbol_size(const Symbol_table
*);
1108 // Create the .interp section and PT_INTERP segment.
1110 create_interp(const Target
* target
);
1112 // Create the version sections.
1114 create_version_sections(const Versions
*,
1115 const Symbol_table
*,
1116 unsigned int local_symcount
,
1117 const std::vector
<Symbol
*>& dynamic_symbols
,
1118 const Output_section
* dynstr
);
1120 template<int size
, bool big_endian
>
1122 sized_create_version_sections(const Versions
* versions
,
1123 const Symbol_table
*,
1124 unsigned int local_symcount
,
1125 const std::vector
<Symbol
*>& dynamic_symbols
,
1126 const Output_section
* dynstr
);
1128 // Return whether to include this section in the link.
1129 template<int size
, bool big_endian
>
1131 include_section(Sized_relobj_file
<size
, big_endian
>* object
, const char* name
,
1132 const elfcpp::Shdr
<size
, big_endian
>&);
1134 // Return the output section name to use given an input section
1135 // name. Set *PLEN to the length of the name. *PLEN must be
1136 // initialized to the length of NAME.
1138 output_section_name(const Relobj
*, const char* name
, size_t* plen
);
1140 // Return the number of allocated output sections.
1142 allocated_output_section_count() const;
1144 // Return the output section for NAME, TYPE and FLAGS.
1146 get_output_section(const char* name
, Stringpool::Key name_key
,
1147 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1148 Output_section_order order
, bool is_relro
);
1150 // Clear the input section flags that should not be copied to the
1153 get_output_section_flags (elfcpp::Elf_Xword input_section_flags
);
1155 // Choose the output section for NAME in RELOBJ.
1157 choose_output_section(const Relobj
* relobj
, const char* name
,
1158 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1159 bool is_input_section
, Output_section_order order
,
1160 bool is_relro
, bool is_reloc
, bool match_input_spec
);
1162 // Create a new Output_section.
1164 make_output_section(const char* name
, elfcpp::Elf_Word type
,
1165 elfcpp::Elf_Xword flags
, Output_section_order order
,
1168 // Attach a section to a segment.
1170 attach_section_to_segment(const Target
*, Output_section
*);
1172 // Get section order.
1173 Output_section_order
1174 default_section_order(Output_section
*, bool is_relro_local
);
1176 // Attach an allocated section to a segment.
1178 attach_allocated_section_to_segment(const Target
*, Output_section
*);
1180 // Make the .eh_frame section.
1182 make_eh_frame_section(const Relobj
*);
1184 // Set the final file offsets of all the segments.
1186 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
1188 // Set the file offsets of the sections when doing a relocatable
1191 set_relocatable_section_offsets(Output_data
*, unsigned int* pshndx
);
1193 // Set the final file offsets of all the sections not associated
1194 // with a segment. We set section offsets in three passes: the
1195 // first handles all allocated sections, the second sections that
1196 // require postprocessing, and the last the late-bound STRTAB
1197 // sections (probably only shstrtab, which is the one we care about
1198 // because it holds section names).
1199 enum Section_offset_pass
1201 BEFORE_INPUT_SECTIONS_PASS
,
1202 POSTPROCESSING_SECTIONS_PASS
,
1203 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1206 set_section_offsets(off_t
, Section_offset_pass pass
);
1208 // Set the final section indexes of all the sections not associated
1209 // with a segment. Returns the next unused index.
1211 set_section_indexes(unsigned int pshndx
);
1213 // Set the section addresses when using a script.
1215 set_section_addresses_from_script(Symbol_table
*);
1217 // Find appropriate places or orphan sections in a script.
1219 place_orphan_sections_in_script();
1221 // Return whether SEG1 comes before SEG2 in the output file.
1223 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
1225 // Use to save and restore segments during relaxation.
1226 typedef Unordered_map
<const Output_segment
*, const Output_segment
*>
1229 // Save states of current output segments.
1231 save_segments(Segment_states
*);
1233 // Restore output segment states.
1235 restore_segments(const Segment_states
*);
1237 // Clean up after relaxation so that it is possible to lay out the
1238 // sections and segments again.
1240 clean_up_after_relaxation();
1242 // Doing preparation work for relaxation. This is factored out to make
1243 // Layout::finalized a bit smaller and easier to read.
1245 prepare_for_relaxation();
1247 // Main body of the relaxation loop, which lays out the section.
1249 relaxation_loop_body(int, Target
*, Symbol_table
*, Output_segment
**,
1250 Output_segment
*, Output_segment_headers
*,
1251 Output_file_header
*, unsigned int*);
1253 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1254 typedef Unordered_map
<std::string
, Kept_section
> Signatures
;
1256 // Mapping from input section name/type/flags to output section. We
1257 // use canonicalized strings here.
1259 typedef std::pair
<Stringpool::Key
,
1260 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
1265 operator()(const Key
& k
) const;
1268 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
1270 // A comparison class for segments.
1272 class Compare_segments
1275 Compare_segments(Layout
* layout
)
1280 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
1281 { return this->layout_
->segment_precedes(seg1
, seg2
); }
1287 typedef std::vector
<Output_section_data
*> Output_section_data_list
;
1289 // Debug checker class.
1290 class Relaxation_debug_check
1293 Relaxation_debug_check()
1297 // Check that sections and special data are in reset states.
1299 check_output_data_for_reset_values(const Layout::Section_list
&,
1300 const Layout::Data_list
& special_outputs
,
1301 const Layout::Data_list
& relax_outputs
);
1303 // Record information of a section list.
1305 read_sections(const Layout::Section_list
&);
1307 // Verify a section list with recorded information.
1309 verify_sections(const Layout::Section_list
&);
1312 // Information we care about a section.
1315 // Output section described by this.
1316 Output_section
* output_section
;
1325 // Section information.
1326 std::vector
<Section_info
> section_infos_
;
1329 // The number of input files, for sizing tables.
1330 int number_of_input_files_
;
1331 // Information set by scripts or by command line options.
1332 Script_options
* script_options_
;
1333 // The output section names.
1334 Stringpool namepool_
;
1335 // The output symbol names.
1336 Stringpool sympool_
;
1337 // The dynamic strings, if needed.
1338 Stringpool dynpool_
;
1339 // The list of group sections and linkonce sections which we have seen.
1340 Signatures signatures_
;
1341 // The mapping from input section name/type/flags to output sections.
1342 Section_name_map section_name_map_
;
1343 // The list of output segments.
1344 Segment_list segment_list_
;
1345 // The list of output sections.
1346 Section_list section_list_
;
1347 // The list of output sections which are not attached to any output
1349 Section_list unattached_section_list_
;
1350 // The list of unattached Output_data objects which require special
1351 // handling because they are not Output_sections.
1352 Data_list special_output_list_
;
1353 // Like special_output_list_, but cleared and recreated on each
1354 // iteration of relaxation.
1355 Data_list relax_output_list_
;
1356 // The section headers.
1357 Output_section_headers
* section_headers_
;
1358 // A pointer to the PT_TLS segment if there is one.
1359 Output_segment
* tls_segment_
;
1360 // A pointer to the PT_GNU_RELRO segment if there is one.
1361 Output_segment
* relro_segment_
;
1362 // A pointer to the PT_INTERP segment if there is one.
1363 Output_segment
* interp_segment_
;
1364 // A backend may increase the size of the PT_GNU_RELRO segment if
1365 // there is one. This is the amount to increase it by.
1366 unsigned int increase_relro_
;
1367 // The SHT_SYMTAB output section.
1368 Output_section
* symtab_section_
;
1369 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1370 Output_symtab_xindex
* symtab_xindex_
;
1371 // The SHT_DYNSYM output section if there is one.
1372 Output_section
* dynsym_section_
;
1373 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1374 Output_symtab_xindex
* dynsym_xindex_
;
1375 // The SHT_DYNAMIC output section if there is one.
1376 Output_section
* dynamic_section_
;
1377 // The _DYNAMIC symbol if there is one.
1378 Symbol
* dynamic_symbol_
;
1379 // The dynamic data which goes into dynamic_section_.
1380 Output_data_dynamic
* dynamic_data_
;
1381 // The exception frame output section if there is one.
1382 Output_section
* eh_frame_section_
;
1383 // The exception frame data for eh_frame_section_.
1384 Eh_frame
* eh_frame_data_
;
1385 // Whether we have added eh_frame_data_ to the .eh_frame section.
1386 bool added_eh_frame_data_
;
1387 // The exception frame header output section if there is one.
1388 Output_section
* eh_frame_hdr_section_
;
1389 // The data for the .gdb_index section.
1390 Gdb_index
* gdb_index_data_
;
1391 // The space for the build ID checksum if there is one.
1392 Output_section_data
* build_id_note_
;
1393 // The output section containing dwarf abbreviations
1394 Output_reduced_debug_abbrev_section
* debug_abbrev_
;
1395 // The output section containing the dwarf debug info tree
1396 Output_reduced_debug_info_section
* debug_info_
;
1397 // A list of group sections and their signatures.
1398 Group_signatures group_signatures_
;
1399 // The size of the output file.
1400 off_t output_file_size_
;
1401 // Whether we have added an input section to an output section.
1402 bool have_added_input_section_
;
1403 // Whether we have attached the sections to the segments.
1404 bool sections_are_attached_
;
1405 // Whether we have seen an object file marked to require an
1406 // executable stack.
1407 bool input_requires_executable_stack_
;
1408 // Whether we have seen at least one object file with an executable
1410 bool input_with_gnu_stack_note_
;
1411 // Whether we have seen at least one object file without an
1412 // executable stack marker.
1413 bool input_without_gnu_stack_note_
;
1414 // Whether we have seen an object file that uses the static TLS model.
1415 bool has_static_tls_
;
1416 // Whether any sections require postprocessing.
1417 bool any_postprocessing_sections_
;
1418 // Whether we have resized the signatures_ hash table.
1419 bool resized_signatures_
;
1420 // Whether we have created a .stab*str output section.
1421 bool have_stabstr_section_
;
1422 // True if the input sections in the output sections should be sorted
1423 // as specified in a section ordering file.
1424 bool section_ordering_specified_
;
1425 // True if some input sections need to be mapped to a unique segment,
1426 // after being mapped to a unique Output_section.
1427 bool unique_segment_for_sections_specified_
;
1428 // In incremental build, holds information check the inputs and build the
1429 // .gnu_incremental_inputs section.
1430 Incremental_inputs
* incremental_inputs_
;
1431 // Whether we record output section data created in script
1432 bool record_output_section_data_from_script_
;
1433 // List of output data that needs to be removed at relaxation clean up.
1434 Output_section_data_list script_output_section_data_list_
;
1435 // Structure to save segment states before entering the relaxation loop.
1436 Segment_states
* segment_states_
;
1437 // A relaxation debug checker. We only create one when in debugging mode.
1438 Relaxation_debug_check
* relaxation_debug_check_
;
1439 // Plugins specify section_ordering using this map. This is set in
1440 // update_section_order in plugin.cc
1441 std::map
<Section_id
, unsigned int> section_order_map_
;
1442 // This maps an input section to a unique segment. This is done by first
1443 // placing such input sections in unique output sections and then mapping
1444 // the output section to a unique segment. Unique_segment_info stores
1445 // any additional flags and alignment of the new segment.
1446 Section_segment_map section_segment_map_
;
1447 // Hash a pattern to its position in the section ordering file.
1448 Unordered_map
<std::string
, unsigned int> input_section_position_
;
1449 // Vector of glob only patterns in the section_ordering file.
1450 std::vector
<std::string
> input_section_glob_
;
1451 // For incremental links, the base file to be modified.
1452 Incremental_binary
* incremental_base_
;
1453 // For incremental links, a list of free space within the file.
1454 Free_list free_list_
;
1457 // This task handles writing out data in output sections which is not
1458 // part of an input section, or which requires special handling. When
1459 // this is done, it unblocks both output_sections_blocker and
1462 class Write_sections_task
: public Task
1465 Write_sections_task(const Layout
* layout
, Output_file
* of
,
1466 Task_token
* output_sections_blocker
,
1467 Task_token
* input_sections_blocker
,
1468 Task_token
* final_blocker
)
1469 : layout_(layout
), of_(of
),
1470 output_sections_blocker_(output_sections_blocker
),
1471 input_sections_blocker_(input_sections_blocker
),
1472 final_blocker_(final_blocker
)
1475 // The standard Task methods.
1481 locks(Task_locker
*);
1488 { return "Write_sections_task"; }
1491 class Write_sections_locker
;
1493 const Layout
* layout_
;
1495 Task_token
* output_sections_blocker_
;
1496 Task_token
* input_sections_blocker_
;
1497 Task_token
* final_blocker_
;
1500 // This task handles writing out data which is not part of a section
1503 class Write_data_task
: public Task
1506 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
1507 Output_file
* of
, Task_token
* final_blocker
)
1508 : layout_(layout
), symtab_(symtab
), of_(of
), final_blocker_(final_blocker
)
1511 // The standard Task methods.
1517 locks(Task_locker
*);
1524 { return "Write_data_task"; }
1527 const Layout
* layout_
;
1528 const Symbol_table
* symtab_
;
1530 Task_token
* final_blocker_
;
1533 // This task handles writing out the global symbols.
1535 class Write_symbols_task
: public Task
1538 Write_symbols_task(const Layout
* layout
, const Symbol_table
* symtab
,
1539 const Input_objects
* /*input_objects*/,
1540 const Stringpool
* sympool
, const Stringpool
* dynpool
,
1541 Output_file
* of
, Task_token
* final_blocker
)
1542 : layout_(layout
), symtab_(symtab
),
1543 sympool_(sympool
), dynpool_(dynpool
), of_(of
),
1544 final_blocker_(final_blocker
)
1547 // The standard Task methods.
1553 locks(Task_locker
*);
1560 { return "Write_symbols_task"; }
1563 const Layout
* layout_
;
1564 const Symbol_table
* symtab_
;
1565 const Stringpool
* sympool_
;
1566 const Stringpool
* dynpool_
;
1568 Task_token
* final_blocker_
;
1571 // This task handles writing out data in output sections which can't
1572 // be written out until all the input sections have been handled.
1573 // This is for sections whose contents is based on the contents of
1574 // other output sections.
1576 class Write_after_input_sections_task
: public Task
1579 Write_after_input_sections_task(Layout
* layout
, Output_file
* of
,
1580 Task_token
* input_sections_blocker
,
1581 Task_token
* final_blocker
)
1582 : layout_(layout
), of_(of
),
1583 input_sections_blocker_(input_sections_blocker
),
1584 final_blocker_(final_blocker
)
1587 // The standard Task methods.
1593 locks(Task_locker
*);
1600 { return "Write_after_input_sections_task"; }
1605 Task_token
* input_sections_blocker_
;
1606 Task_token
* final_blocker_
;
1609 // This task function handles computation of the build id.
1610 // When using --build-id=tree, it schedules the tasks that
1611 // compute the hashes for each chunk of the file. This task
1612 // cannot run until we have finalized the size of the output
1613 // file, after the completion of Write_after_input_sections_task.
1615 class Build_id_task_runner
: public Task_function_runner
1618 Build_id_task_runner(const General_options
* options
, const Layout
* layout
,
1620 : options_(options
), layout_(layout
), of_(of
)
1623 // Run the operation.
1625 run(Workqueue
*, const Task
*);
1628 const General_options
* options_
;
1629 const Layout
* layout_
;
1633 // This task function handles closing the file.
1635 class Close_task_runner
: public Task_function_runner
1638 Close_task_runner(const General_options
* options
, const Layout
* layout
,
1639 Output_file
* of
, unsigned char* array_of_hashes
,
1640 size_t size_of_hashes
)
1641 : options_(options
), layout_(layout
), of_(of
),
1642 array_of_hashes_(array_of_hashes
), size_of_hashes_(size_of_hashes
)
1645 // Run the operation.
1647 run(Workqueue
*, const Task
*);
1650 const General_options
* options_
;
1651 const Layout
* layout_
;
1653 unsigned char* const array_of_hashes_
;
1654 const size_t size_of_hashes_
;
1657 // A small helper function to align an address.
1660 align_address(uint64_t address
, uint64_t addralign
)
1663 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
1667 } // End namespace gold.
1669 #endif // !defined(GOLD_LAYOUT_H)