1 // layout.h -- lay out output file sections for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011, 2012
4 // Free Software Foundation, Inc.
5 // Written by Ian Lance Taylor <iant@google.com>.
7 // This file is part of gold.
9 // This program is free software; you can redistribute it and/or modify
10 // it under the terms of the GNU General Public License as published by
11 // the Free Software Foundation; either version 3 of the License, or
12 // (at your option) any later version.
14 // This program is distributed in the hope that it will be useful,
15 // but WITHOUT ANY WARRANTY; without even the implied warranty of
16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 // GNU General Public License for more details.
19 // You should have received a copy of the GNU General Public License
20 // along with this program; if not, write to the Free Software
21 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
22 // MA 02110-1301, USA.
35 #include "workqueue.h"
38 #include "stringpool.h"
43 class General_options
;
44 class Incremental_inputs
;
45 class Incremental_binary
;
49 class Output_section_data
;
51 class Output_section_headers
;
52 class Output_segment_headers
;
53 class Output_file_header
;
56 class Output_data_reloc_generic
;
57 class Output_data_dynamic
;
58 class Output_symtab_xindex
;
59 class Output_reduced_debug_abbrev_section
;
60 class Output_reduced_debug_info_section
;
66 // Return TRUE if SECNAME is the name of a compressed debug section.
68 is_compressed_debug_section(const char* secname
);
70 // Maintain a list of free space within a section, segment, or file.
71 // Used for incremental update links.
78 Free_list_node(off_t start
, off_t end
)
79 : start_(start
), end_(end
)
84 typedef std::list
<Free_list_node
>::const_iterator Const_iterator
;
87 : list_(), last_remove_(list_
.begin()), extend_(false), length_(0),
91 // Initialize the free list for a section of length LEN.
92 // If EXTEND is true, free space may be allocated past the end.
94 init(off_t len
, bool extend
);
96 // Set the minimum hole size that is allowed when allocating
97 // from the free list.
99 set_min_hole_size(off_t min_hole
)
100 { this->min_hole_
= min_hole
; }
102 // Remove a chunk from the free list.
104 remove(off_t start
, off_t end
);
106 // Allocate a chunk of space from the free list of length LEN,
107 // with alignment ALIGN, and minimum offset MINOFF.
109 allocate(off_t len
, uint64_t align
, off_t minoff
);
111 // Return an iterator for the beginning of the free list.
114 { return this->list_
.begin(); }
116 // Return an iterator for the end of the free list.
119 { return this->list_
.end(); }
121 // Dump the free list (for debugging).
125 // Print usage statistics.
130 typedef std::list
<Free_list_node
>::iterator Iterator
;
133 std::list
<Free_list_node
> list_
;
135 // The last node visited during a remove operation.
136 Iterator last_remove_
;
138 // Whether we can extend past the original length.
141 // The total length of the section, segment, or file.
144 // The minimum hole size allowed. When allocating from the free list,
145 // we must not leave a hole smaller than this.
149 // The total number of free lists used.
150 static unsigned int num_lists
;
151 // The total number of free list nodes used.
152 static unsigned int num_nodes
;
153 // The total number of calls to Free_list::remove.
154 static unsigned int num_removes
;
155 // The total number of nodes visited during calls to Free_list::remove.
156 static unsigned int num_remove_visits
;
157 // The total number of calls to Free_list::allocate.
158 static unsigned int num_allocates
;
159 // The total number of nodes visited during calls to Free_list::allocate.
160 static unsigned int num_allocate_visits
;
163 // This task function handles mapping the input sections to output
164 // sections and laying them out in memory.
166 class Layout_task_runner
: public Task_function_runner
169 // OPTIONS is the command line options, INPUT_OBJECTS is the list of
170 // input objects, SYMTAB is the symbol table, LAYOUT is the layout
172 Layout_task_runner(const General_options
& options
,
173 const Input_objects
* input_objects
,
174 Symbol_table
* symtab
,
178 : options_(options
), input_objects_(input_objects
), symtab_(symtab
),
179 target_(target
), layout_(layout
), mapfile_(mapfile
)
182 // Run the operation.
184 run(Workqueue
*, const Task
*);
187 Layout_task_runner(const Layout_task_runner
&);
188 Layout_task_runner
& operator=(const Layout_task_runner
&);
190 const General_options
& options_
;
191 const Input_objects
* input_objects_
;
192 Symbol_table
* symtab_
;
198 // This class holds information about the comdat group or
199 // .gnu.linkonce section that will be kept for a given signature.
204 // For a comdat group, we build a mapping from the name of each
205 // section in the group to the section index and the size in object.
206 // When we discard a group in some other object file, we use this
207 // map to figure out which kept section the discarded section is
208 // associated with. We then use that mapping when processing relocs
209 // against discarded sections.
210 struct Comdat_section_info
212 // The section index.
217 Comdat_section_info(unsigned int a_shndx
, uint64_t a_size
)
218 : shndx(a_shndx
), size(a_size
)
222 // Most comdat groups have only one or two sections, so we use a
223 // std::map rather than an Unordered_map to optimize for that case
224 // without paying too heavily for groups with more sections.
225 typedef std::map
<std::string
, Comdat_section_info
> Comdat_group
;
229 : object_(NULL
), shndx_(0), is_comdat_(false), is_group_name_(false)
230 { this->u_
.linkonce_size
= 0; }
232 // We need to support copies for the signature map in the Layout
233 // object, but we should never copy an object after it has been
234 // marked as a comdat section.
235 Kept_section(const Kept_section
& k
)
236 : object_(k
.object_
), shndx_(k
.shndx_
), is_comdat_(false),
237 is_group_name_(k
.is_group_name_
)
239 gold_assert(!k
.is_comdat_
);
240 this->u_
.linkonce_size
= 0;
245 if (this->is_comdat_
)
246 delete this->u_
.group_sections
;
249 // The object where this section lives.
252 { return this->object_
; }
256 set_object(Relobj
* object
)
258 gold_assert(this->object_
== NULL
);
259 this->object_
= object
;
262 // The section index.
265 { return this->shndx_
; }
267 // Set the section index.
269 set_shndx(unsigned int shndx
)
271 gold_assert(this->shndx_
== 0);
272 this->shndx_
= shndx
;
275 // Whether this is a comdat group.
278 { return this->is_comdat_
; }
280 // Set that this is a comdat group.
284 gold_assert(!this->is_comdat_
);
285 this->is_comdat_
= true;
286 this->u_
.group_sections
= new Comdat_group();
289 // Whether this is associated with the name of a group or section
290 // rather than the symbol name derived from a linkonce section.
292 is_group_name() const
293 { return this->is_group_name_
; }
295 // Note that this represents a comdat group rather than a single
299 { this->is_group_name_
= true; }
301 // Add a section to the group list.
303 add_comdat_section(const std::string
& name
, unsigned int shndx
,
306 gold_assert(this->is_comdat_
);
307 Comdat_section_info
sinfo(shndx
, size
);
308 this->u_
.group_sections
->insert(std::make_pair(name
, sinfo
));
311 // Look for a section name in the group list, and return whether it
312 // was found. If found, returns the section index and size.
314 find_comdat_section(const std::string
& name
, unsigned int* pshndx
,
315 uint64_t* psize
) const
317 gold_assert(this->is_comdat_
);
318 Comdat_group::const_iterator p
= this->u_
.group_sections
->find(name
);
319 if (p
== this->u_
.group_sections
->end())
321 *pshndx
= p
->second
.shndx
;
322 *psize
= p
->second
.size
;
326 // If there is only one section in the group list, return true, and
327 // return the section index and size.
329 find_single_comdat_section(unsigned int* pshndx
, uint64_t* psize
) const
331 gold_assert(this->is_comdat_
);
332 if (this->u_
.group_sections
->size() != 1)
334 Comdat_group::const_iterator p
= this->u_
.group_sections
->begin();
335 *pshndx
= p
->second
.shndx
;
336 *psize
= p
->second
.size
;
340 // Return the size of a linkonce section.
342 linkonce_size() const
344 gold_assert(!this->is_comdat_
);
345 return this->u_
.linkonce_size
;
348 // Set the size of a linkonce section.
350 set_linkonce_size(uint64_t size
)
352 gold_assert(!this->is_comdat_
);
353 this->u_
.linkonce_size
= size
;
358 Kept_section
& operator=(const Kept_section
&);
360 // The object containing the comdat group or .gnu.linkonce section.
362 // Index of the group section for comdats and the section itself for
365 // True if this is for a comdat group rather than a .gnu.linkonce
368 // The Kept_sections are values of a mapping, that maps names to
369 // them. This field is true if this struct is associated with the
370 // name of a comdat or .gnu.linkonce, false if it is associated with
371 // the name of a symbol obtained from the .gnu.linkonce.* name
372 // through some heuristics.
376 // If the is_comdat_ field is true, this holds a map from names of
377 // the sections in the group to section indexes in object_ and to
379 Comdat_group
* group_sections
;
380 // If the is_comdat_ field is false, this holds the size of the
382 uint64_t linkonce_size
;
386 // The ordering for output sections. This controls how output
387 // sections are ordered within a PT_LOAD output segment.
389 enum Output_section_order
391 // Unspecified. Used for non-load segments. Also used for the file
392 // and segment headers.
395 // The PT_INTERP section should come first, so that the dynamic
396 // linker can pick it up quickly.
399 // Loadable read-only note sections come next so that the PT_NOTE
400 // segment is on the first page of the executable.
403 // Put read-only sections used by the dynamic linker early in the
404 // executable to minimize paging.
405 ORDER_DYNAMIC_LINKER
,
407 // Put reloc sections used by the dynamic linker after other
408 // sections used by the dynamic linker; otherwise, objcopy and strip
410 ORDER_DYNAMIC_RELOCS
,
412 // Put the PLT reloc section after the other dynamic relocs;
413 // otherwise, prelink gets confused.
414 ORDER_DYNAMIC_PLT_RELOCS
,
416 // The .init section.
422 // The regular text sections.
425 // The .fini section.
428 // The read-only sections.
431 // The exception frame sections.
434 // The TLS sections come first in the data section.
438 // Local RELRO (read-only after relocation) sections come before
439 // non-local RELRO sections. This data will be fully resolved by
443 // Non-local RELRO sections are grouped together after local RELRO
444 // sections. All RELRO sections must be adjacent so that they can
445 // all be put into a PT_GNU_RELRO segment.
448 // We permit marking exactly one output section as the last RELRO
449 // section. We do this so that the read-only GOT can be adjacent to
453 // Similarly, we permit marking exactly one output section as the
454 // first non-RELRO section.
455 ORDER_NON_RELRO_FIRST
,
457 // The regular data sections come after the RELRO sections.
460 // Large data sections normally go in large data segments.
463 // Group writable notes so that we can have a single PT_NOTE
467 // The small data sections must be at the end of the data sections,
468 // so that they can be adjacent to the small BSS sections.
471 // The BSS sections start here.
473 // The small BSS sections must be at the start of the BSS sections,
474 // so that they can be adjacent to the small data sections.
477 // The regular BSS sections.
480 // The large BSS sections come after the other BSS sections.
487 // This class handles the details of laying out input sections.
492 Layout(int number_of_input_files
, Script_options
*);
496 delete this->relaxation_debug_check_
;
497 delete this->segment_states_
;
500 // For incremental links, record the base file to be modified.
502 set_incremental_base(Incremental_binary
* base
);
506 { return this->incremental_base_
; }
508 // For incremental links, record the initial fixed layout of a section
509 // from the base file, and return a pointer to the Output_section.
510 template<int size
, bool big_endian
>
512 init_fixed_output_section(const char*, elfcpp::Shdr
<size
, big_endian
>&);
514 // Given an input section SHNDX, named NAME, with data in SHDR, from
515 // the object file OBJECT, return the output section where this
516 // input section should go. RELOC_SHNDX is the index of a
517 // relocation section which applies to this section, or 0 if none,
518 // or -1U if more than one. RELOC_TYPE is the type of the
519 // relocation section if there is one. Set *OFFSET to the offset
520 // within the output section.
521 template<int size
, bool big_endian
>
523 layout(Sized_relobj_file
<size
, big_endian
> *object
, unsigned int shndx
,
524 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
525 unsigned int reloc_shndx
, unsigned int reloc_type
, off_t
* offset
);
527 std::map
<Section_id
, unsigned int>*
528 get_section_order_map()
529 { return &this->section_order_map_
; }
531 // Struct to store segment info when mapping some input sections to
532 // unique segments using linker plugins. Mapping an input section to
533 // a unique segment is done by first placing such input sections in
534 // unique output sections and then mapping the output section to a
535 // unique segment. NAME is the name of the output section. FLAGS
536 // and ALIGN are the extra flags and alignment of the segment.
537 struct Unique_segment_info
539 // Identifier for the segment. ELF segments dont have names. This
540 // is used as the name of the output section mapped to the segment.
542 // Additional segment flags.
544 // Segment alignment.
548 // Mapping from input section to segment.
549 typedef std::map
<Const_section_id
, Unique_segment_info
*>
552 // Maps section SECN to SEGMENT s.
554 insert_section_segment_map(Const_section_id secn
, Unique_segment_info
*s
);
556 // By default, gold groups input sections with certain prefixes. This
557 // function returns true if this section name NAME contains such a prefix.
559 is_section_name_prefix_grouped(const char *name
);
562 is_section_ordering_specified()
563 { return this->section_ordering_specified_
; }
566 set_section_ordering_specified()
567 { this->section_ordering_specified_
= true; }
570 is_unique_segment_for_sections_specified() const
571 { return this->unique_segment_for_sections_specified_
; }
574 set_unique_segment_for_sections_specified()
575 { this->unique_segment_for_sections_specified_
= true; }
577 // For incremental updates, allocate a block of memory from the
578 // free list. Find a block starting at or after MINOFF.
580 allocate(off_t len
, uint64_t align
, off_t minoff
)
581 { return this->free_list_
.allocate(len
, align
, minoff
); }
584 find_section_order_index(const std::string
&);
586 // Read the sequence of input sections from the file specified with
587 // linker option --section-ordering-file.
589 read_layout_from_file();
591 // Layout an input reloc section when doing a relocatable link. The
592 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
593 // DATA_SECTION is the reloc section to which it refers. RR is the
594 // relocatable information.
595 template<int size
, bool big_endian
>
597 layout_reloc(Sized_relobj_file
<size
, big_endian
>* object
,
598 unsigned int reloc_shndx
,
599 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
600 Output_section
* data_section
,
601 Relocatable_relocs
* rr
);
603 // Layout a group section when doing a relocatable link.
604 template<int size
, bool big_endian
>
606 layout_group(Symbol_table
* symtab
,
607 Sized_relobj_file
<size
, big_endian
>* object
,
608 unsigned int group_shndx
,
609 const char* group_section_name
,
610 const char* signature
,
611 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
612 elfcpp::Elf_Word flags
,
613 std::vector
<unsigned int>* shndxes
);
615 // Like layout, only for exception frame sections. OBJECT is an
616 // object file. SYMBOLS is the contents of the symbol table
617 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
618 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
619 // .eh_frame section in OBJECT. SHDR is the section header.
620 // RELOC_SHNDX is the index of a relocation section which applies to
621 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
622 // is the type of the relocation section if there is one. This
623 // returns the output section, and sets *OFFSET to the offset.
624 template<int size
, bool big_endian
>
626 layout_eh_frame(Sized_relobj_file
<size
, big_endian
>* object
,
627 const unsigned char* symbols
,
629 const unsigned char* symbol_names
,
630 off_t symbol_names_size
,
632 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
633 unsigned int reloc_shndx
, unsigned int reloc_type
,
636 // Add .eh_frame information for a PLT. The FDE must start with a
637 // 4-byte PC-relative reference to the start of the PLT, followed by
638 // a 4-byte size of PLT.
640 add_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
641 size_t cie_length
, const unsigned char* fde_data
,
644 // Scan a .debug_info or .debug_types section, and add summary
645 // information to the .gdb_index section.
646 template<int size
, bool big_endian
>
648 add_to_gdb_index(bool is_type_unit
,
649 Sized_relobj
<size
, big_endian
>* object
,
650 const unsigned char* symbols
,
653 unsigned int reloc_shndx
,
654 unsigned int reloc_type
);
656 // Handle a GNU stack note. This is called once per input object
657 // file. SEEN_GNU_STACK is true if the object file has a
658 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
659 // from that section if there was one.
661 layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
,
664 // Add an Output_section_data to the layout. This is used for
665 // special sections like the GOT section. ORDER is where the
666 // section should wind up in the output segment. IS_RELRO is true
667 // for relro sections.
669 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
670 elfcpp::Elf_Xword flags
,
671 Output_section_data
*, Output_section_order order
,
674 // Increase the size of the relro segment by this much.
676 increase_relro(unsigned int s
)
677 { this->increase_relro_
+= s
; }
679 // Create dynamic sections if necessary.
681 create_initial_dynamic_sections(Symbol_table
*);
683 // Define __start and __stop symbols for output sections.
685 define_section_symbols(Symbol_table
*);
687 // Create automatic note sections.
691 // Create sections for linker scripts.
693 create_script_sections()
694 { this->script_options_
->create_script_sections(this); }
696 // Define symbols from any linker script.
698 define_script_symbols(Symbol_table
* symtab
)
699 { this->script_options_
->add_symbols_to_table(symtab
); }
701 // Define symbols for group signatures.
703 define_group_signatures(Symbol_table
*);
705 // Return the Stringpool used for symbol names.
708 { return &this->sympool_
; }
710 // Return the Stringpool used for dynamic symbol names and dynamic
714 { return &this->dynpool_
; }
716 // Return the .dynamic output section. This is only valid after the
717 // layout has been finalized.
719 dynamic_section() const
720 { return this->dynamic_section_
; }
722 // Return the symtab_xindex section used to hold large section
723 // indexes for the normal symbol table.
724 Output_symtab_xindex
*
725 symtab_xindex() const
726 { return this->symtab_xindex_
; }
728 // Return the dynsym_xindex section used to hold large section
729 // indexes for the dynamic symbol table.
730 Output_symtab_xindex
*
731 dynsym_xindex() const
732 { return this->dynsym_xindex_
; }
734 // Return whether a section is a .gnu.linkonce section, given the
737 is_linkonce(const char* name
)
738 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
740 // Whether we have added an input section.
742 have_added_input_section() const
743 { return this->have_added_input_section_
; }
745 // Return true if a section is a debugging section.
747 is_debug_info_section(const char* name
)
749 // Debugging sections can only be recognized by name.
750 return (strncmp(name
, ".debug", sizeof(".debug") - 1) == 0
751 || strncmp(name
, ".zdebug", sizeof(".zdebug") - 1) == 0
752 || strncmp(name
, ".gnu.linkonce.wi.",
753 sizeof(".gnu.linkonce.wi.") - 1) == 0
754 || strncmp(name
, ".line", sizeof(".line") - 1) == 0
755 || strncmp(name
, ".stab", sizeof(".stab") - 1) == 0);
758 // Return true if RELOBJ is an input file whose base name matches
759 // FILE_NAME. The base name must have an extension of ".o", and
760 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
762 match_file_name(const Relobj
* relobj
, const char* file_name
);
764 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
765 // with more than one word being mapped to a .init_array/.fini_array
768 is_ctors_in_init_array(Relobj
* relobj
, unsigned int shndx
) const;
770 // Check if a comdat group or .gnu.linkonce section with the given
771 // NAME is selected for the link. If there is already a section,
772 // *KEPT_SECTION is set to point to the signature and the function
773 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
774 // IS_GROUP_NAME are recorded for this NAME in the layout object,
775 // *KEPT_SECTION is set to the internal copy and the function return
778 find_or_add_kept_section(const std::string
& name
, Relobj
* object
,
779 unsigned int shndx
, bool is_comdat
,
780 bool is_group_name
, Kept_section
** kept_section
);
782 // Finalize the layout after all the input sections have been added.
784 finalize(const Input_objects
*, Symbol_table
*, Target
*, const Task
*);
786 // Return whether any sections require postprocessing.
788 any_postprocessing_sections() const
789 { return this->any_postprocessing_sections_
; }
791 // Return the size of the output file.
793 output_file_size() const
794 { return this->output_file_size_
; }
796 // Return the TLS segment. This will return NULL if there isn't
800 { return this->tls_segment_
; }
802 // Return the normal symbol table.
804 symtab_section() const
806 gold_assert(this->symtab_section_
!= NULL
);
807 return this->symtab_section_
;
810 // Return the file offset of the normal symbol table.
812 symtab_section_offset() const;
814 // Return the section index of the normal symbol tabl.e
816 symtab_section_shndx() const;
818 // Return the dynamic symbol table.
820 dynsym_section() const
822 gold_assert(this->dynsym_section_
!= NULL
);
823 return this->dynsym_section_
;
826 // Return the dynamic tags.
829 { return this->dynamic_data_
; }
831 // Write out the output sections.
833 write_output_sections(Output_file
* of
) const;
835 // Write out data not associated with an input file or the symbol
838 write_data(const Symbol_table
*, Output_file
*) const;
840 // Write out output sections which can not be written until all the
841 // input sections are complete.
843 write_sections_after_input_sections(Output_file
* of
);
845 // Return an output section named NAME, or NULL if there is none.
847 find_output_section(const char* name
) const;
849 // Return an output segment of type TYPE, with segment flags SET set
850 // and segment flags CLEAR clear. Return NULL if there is none.
852 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
853 elfcpp::Elf_Word clear
) const;
855 // Return the number of segments we expect to produce.
857 expected_segment_count() const;
859 // Set a flag to indicate that an object file uses the static TLS model.
862 { this->has_static_tls_
= true; }
864 // Return true if any object file uses the static TLS model.
866 has_static_tls() const
867 { return this->has_static_tls_
; }
869 // Return the options which may be set by a linker script.
872 { return this->script_options_
; }
874 const Script_options
*
875 script_options() const
876 { return this->script_options_
; }
878 // Return the object managing inputs in incremental build. NULL in
879 // non-incremental builds.
881 incremental_inputs() const
882 { return this->incremental_inputs_
; }
884 // For the target-specific code to add dynamic tags which are common
887 add_target_dynamic_tags(bool use_rel
, const Output_data
* plt_got
,
888 const Output_data
* plt_rel
,
889 const Output_data_reloc_generic
* dyn_rel
,
890 bool add_debug
, bool dynrel_includes_plt
);
892 // Compute and write out the build ID if needed.
894 write_build_id(Output_file
*) const;
896 // Rewrite output file in binary format.
898 write_binary(Output_file
* in
) const;
900 // Print output sections to the map file.
902 print_to_mapfile(Mapfile
*) const;
904 // Dump statistical information to stderr.
908 // A list of segments.
910 typedef std::vector
<Output_segment
*> Segment_list
;
912 // A list of sections.
914 typedef std::vector
<Output_section
*> Section_list
;
916 // The list of information to write out which is not attached to
917 // either a section or a segment.
918 typedef std::vector
<Output_data
*> Data_list
;
920 // Store the allocated sections into the section list. This is used
921 // by the linker script code.
923 get_allocated_sections(Section_list
*) const;
925 // Store the executable sections into the section list.
927 get_executable_sections(Section_list
*) const;
929 // Make a section for a linker script to hold data.
931 make_output_section_for_script(const char* name
,
932 Script_sections::Section_type section_type
);
934 // Make a segment. This is used by the linker script code.
936 make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
);
938 // Return the number of segments.
940 segment_count() const
941 { return this->segment_list_
.size(); }
943 // Map from section flags to segment flags.
944 static elfcpp::Elf_Word
945 section_flags_to_segment(elfcpp::Elf_Xword flags
);
947 // Attach sections to segments.
949 attach_sections_to_segments(const Target
*);
951 // For relaxation clean up, we need to know output section data created
952 // from a linker script.
954 new_output_section_data_from_script(Output_section_data
* posd
)
956 if (this->record_output_section_data_from_script_
)
957 this->script_output_section_data_list_
.push_back(posd
);
960 // Return section list.
963 { return this->section_list_
; }
965 // Returns TRUE iff NAME (an input section from RELOBJ) will
966 // be mapped to an output section that should be KEPT.
968 keep_input_section(const Relobj
*, const char*);
971 Layout(const Layout
&);
972 Layout
& operator=(const Layout
&);
974 // Mapping from input section names to output section names.
975 struct Section_name_mapping
982 static const Section_name_mapping section_name_mapping
[];
983 static const int section_name_mapping_count
;
985 // During a relocatable link, a list of group sections and
987 struct Group_signature
989 // The group section.
990 Output_section
* section
;
992 const char* signature
;
995 : section(NULL
), signature(NULL
)
998 Group_signature(Output_section
* sectiona
, const char* signaturea
)
999 : section(sectiona
), signature(signaturea
)
1002 typedef std::vector
<Group_signature
> Group_signatures
;
1004 // Create a note section, filling in the header.
1006 create_note(const char* name
, int note_type
, const char* section_name
,
1007 size_t descsz
, bool allocate
, size_t* trailing_padding
);
1009 // Create a note section for gold version.
1013 // Record whether the stack must be executable.
1015 create_executable_stack_info();
1017 // Create a build ID note if needed.
1021 // Link .stab and .stabstr sections.
1023 link_stabs_sections();
1025 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1026 // for the next run of incremental linking to check what has changed.
1028 create_incremental_info_sections(Symbol_table
*);
1030 // Find the first read-only PT_LOAD segment, creating one if
1033 find_first_load_seg(const Target
*);
1035 // Count the local symbols in the regular symbol table and the dynamic
1036 // symbol table, and build the respective string pools.
1038 count_local_symbols(const Task
*, const Input_objects
*);
1040 // Create the output sections for the symbol table.
1042 create_symtab_sections(const Input_objects
*, Symbol_table
*,
1043 unsigned int, off_t
*);
1045 // Create the .shstrtab section.
1049 // Create the section header table.
1051 create_shdrs(const Output_section
* shstrtab_section
, off_t
*);
1053 // Create the dynamic symbol table.
1055 create_dynamic_symtab(const Input_objects
*, Symbol_table
*,
1056 Output_section
** pdynstr
,
1057 unsigned int* plocal_dynamic_count
,
1058 std::vector
<Symbol
*>* pdynamic_symbols
,
1059 Versions
* versions
);
1061 // Assign offsets to each local portion of the dynamic symbol table.
1063 assign_local_dynsym_offsets(const Input_objects
*);
1065 // Finish the .dynamic section and PT_DYNAMIC segment.
1067 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
1069 // Set the size of the _DYNAMIC symbol.
1071 set_dynamic_symbol_size(const Symbol_table
*);
1073 // Create the .interp section and PT_INTERP segment.
1075 create_interp(const Target
* target
);
1077 // Create the version sections.
1079 create_version_sections(const Versions
*,
1080 const Symbol_table
*,
1081 unsigned int local_symcount
,
1082 const std::vector
<Symbol
*>& dynamic_symbols
,
1083 const Output_section
* dynstr
);
1085 template<int size
, bool big_endian
>
1087 sized_create_version_sections(const Versions
* versions
,
1088 const Symbol_table
*,
1089 unsigned int local_symcount
,
1090 const std::vector
<Symbol
*>& dynamic_symbols
,
1091 const Output_section
* dynstr
);
1093 // Return whether to include this section in the link.
1094 template<int size
, bool big_endian
>
1096 include_section(Sized_relobj_file
<size
, big_endian
>* object
, const char* name
,
1097 const elfcpp::Shdr
<size
, big_endian
>&);
1099 // Return the output section name to use given an input section
1100 // name. Set *PLEN to the length of the name. *PLEN must be
1101 // initialized to the length of NAME.
1103 output_section_name(const Relobj
*, const char* name
, size_t* plen
);
1105 // Return the number of allocated output sections.
1107 allocated_output_section_count() const;
1109 // Return the output section for NAME, TYPE and FLAGS.
1111 get_output_section(const char* name
, Stringpool::Key name_key
,
1112 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1113 Output_section_order order
, bool is_relro
);
1115 // Clear the input section flags that should not be copied to the
1118 get_output_section_flags (elfcpp::Elf_Xword input_section_flags
);
1120 // Choose the output section for NAME in RELOBJ.
1122 choose_output_section(const Relobj
* relobj
, const char* name
,
1123 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1124 bool is_input_section
, Output_section_order order
,
1127 // Create a new Output_section.
1129 make_output_section(const char* name
, elfcpp::Elf_Word type
,
1130 elfcpp::Elf_Xword flags
, Output_section_order order
,
1133 // Attach a section to a segment.
1135 attach_section_to_segment(const Target
*, Output_section
*);
1137 // Get section order.
1138 Output_section_order
1139 default_section_order(Output_section
*, bool is_relro_local
);
1141 // Attach an allocated section to a segment.
1143 attach_allocated_section_to_segment(const Target
*, Output_section
*);
1145 // Make the .eh_frame section.
1147 make_eh_frame_section(const Relobj
*);
1149 // Set the final file offsets of all the segments.
1151 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
1153 // Set the file offsets of the sections when doing a relocatable
1156 set_relocatable_section_offsets(Output_data
*, unsigned int* pshndx
);
1158 // Set the final file offsets of all the sections not associated
1159 // with a segment. We set section offsets in three passes: the
1160 // first handles all allocated sections, the second sections that
1161 // require postprocessing, and the last the late-bound STRTAB
1162 // sections (probably only shstrtab, which is the one we care about
1163 // because it holds section names).
1164 enum Section_offset_pass
1166 BEFORE_INPUT_SECTIONS_PASS
,
1167 POSTPROCESSING_SECTIONS_PASS
,
1168 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1171 set_section_offsets(off_t
, Section_offset_pass pass
);
1173 // Set the final section indexes of all the sections not associated
1174 // with a segment. Returns the next unused index.
1176 set_section_indexes(unsigned int pshndx
);
1178 // Set the section addresses when using a script.
1180 set_section_addresses_from_script(Symbol_table
*);
1182 // Find appropriate places or orphan sections in a script.
1184 place_orphan_sections_in_script();
1186 // Return whether SEG1 comes before SEG2 in the output file.
1188 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
1190 // Use to save and restore segments during relaxation.
1191 typedef Unordered_map
<const Output_segment
*, const Output_segment
*>
1194 // Save states of current output segments.
1196 save_segments(Segment_states
*);
1198 // Restore output segment states.
1200 restore_segments(const Segment_states
*);
1202 // Clean up after relaxation so that it is possible to lay out the
1203 // sections and segments again.
1205 clean_up_after_relaxation();
1207 // Doing preparation work for relaxation. This is factored out to make
1208 // Layout::finalized a bit smaller and easier to read.
1210 prepare_for_relaxation();
1212 // Main body of the relaxation loop, which lays out the section.
1214 relaxation_loop_body(int, Target
*, Symbol_table
*, Output_segment
**,
1215 Output_segment
*, Output_segment_headers
*,
1216 Output_file_header
*, unsigned int*);
1218 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1219 typedef Unordered_map
<std::string
, Kept_section
> Signatures
;
1221 // Mapping from input section name/type/flags to output section. We
1222 // use canonicalized strings here.
1224 typedef std::pair
<Stringpool::Key
,
1225 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
1230 operator()(const Key
& k
) const;
1233 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
1235 // A comparison class for segments.
1237 class Compare_segments
1240 Compare_segments(Layout
* layout
)
1245 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
1246 { return this->layout_
->segment_precedes(seg1
, seg2
); }
1252 typedef std::vector
<Output_section_data
*> Output_section_data_list
;
1254 // Debug checker class.
1255 class Relaxation_debug_check
1258 Relaxation_debug_check()
1262 // Check that sections and special data are in reset states.
1264 check_output_data_for_reset_values(const Layout::Section_list
&,
1265 const Layout::Data_list
&);
1267 // Record information of a section list.
1269 read_sections(const Layout::Section_list
&);
1271 // Verify a section list with recorded information.
1273 verify_sections(const Layout::Section_list
&);
1276 // Information we care about a section.
1279 // Output section described by this.
1280 Output_section
* output_section
;
1289 // Section information.
1290 std::vector
<Section_info
> section_infos_
;
1293 // The number of input files, for sizing tables.
1294 int number_of_input_files_
;
1295 // Information set by scripts or by command line options.
1296 Script_options
* script_options_
;
1297 // The output section names.
1298 Stringpool namepool_
;
1299 // The output symbol names.
1300 Stringpool sympool_
;
1301 // The dynamic strings, if needed.
1302 Stringpool dynpool_
;
1303 // The list of group sections and linkonce sections which we have seen.
1304 Signatures signatures_
;
1305 // The mapping from input section name/type/flags to output sections.
1306 Section_name_map section_name_map_
;
1307 // The list of output segments.
1308 Segment_list segment_list_
;
1309 // The list of output sections.
1310 Section_list section_list_
;
1311 // The list of output sections which are not attached to any output
1313 Section_list unattached_section_list_
;
1314 // The list of unattached Output_data objects which require special
1315 // handling because they are not Output_sections.
1316 Data_list special_output_list_
;
1317 // The section headers.
1318 Output_section_headers
* section_headers_
;
1319 // A pointer to the PT_TLS segment if there is one.
1320 Output_segment
* tls_segment_
;
1321 // A pointer to the PT_GNU_RELRO segment if there is one.
1322 Output_segment
* relro_segment_
;
1323 // A pointer to the PT_INTERP segment if there is one.
1324 Output_segment
* interp_segment_
;
1325 // A backend may increase the size of the PT_GNU_RELRO segment if
1326 // there is one. This is the amount to increase it by.
1327 unsigned int increase_relro_
;
1328 // The SHT_SYMTAB output section.
1329 Output_section
* symtab_section_
;
1330 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1331 Output_symtab_xindex
* symtab_xindex_
;
1332 // The SHT_DYNSYM output section if there is one.
1333 Output_section
* dynsym_section_
;
1334 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1335 Output_symtab_xindex
* dynsym_xindex_
;
1336 // The SHT_DYNAMIC output section if there is one.
1337 Output_section
* dynamic_section_
;
1338 // The _DYNAMIC symbol if there is one.
1339 Symbol
* dynamic_symbol_
;
1340 // The dynamic data which goes into dynamic_section_.
1341 Output_data_dynamic
* dynamic_data_
;
1342 // The exception frame output section if there is one.
1343 Output_section
* eh_frame_section_
;
1344 // The exception frame data for eh_frame_section_.
1345 Eh_frame
* eh_frame_data_
;
1346 // Whether we have added eh_frame_data_ to the .eh_frame section.
1347 bool added_eh_frame_data_
;
1348 // The exception frame header output section if there is one.
1349 Output_section
* eh_frame_hdr_section_
;
1350 // The data for the .gdb_index section.
1351 Gdb_index
* gdb_index_data_
;
1352 // The space for the build ID checksum if there is one.
1353 Output_section_data
* build_id_note_
;
1354 // The output section containing dwarf abbreviations
1355 Output_reduced_debug_abbrev_section
* debug_abbrev_
;
1356 // The output section containing the dwarf debug info tree
1357 Output_reduced_debug_info_section
* debug_info_
;
1358 // A list of group sections and their signatures.
1359 Group_signatures group_signatures_
;
1360 // The size of the output file.
1361 off_t output_file_size_
;
1362 // Whether we have added an input section to an output section.
1363 bool have_added_input_section_
;
1364 // Whether we have attached the sections to the segments.
1365 bool sections_are_attached_
;
1366 // Whether we have seen an object file marked to require an
1367 // executable stack.
1368 bool input_requires_executable_stack_
;
1369 // Whether we have seen at least one object file with an executable
1371 bool input_with_gnu_stack_note_
;
1372 // Whether we have seen at least one object file without an
1373 // executable stack marker.
1374 bool input_without_gnu_stack_note_
;
1375 // Whether we have seen an object file that uses the static TLS model.
1376 bool has_static_tls_
;
1377 // Whether any sections require postprocessing.
1378 bool any_postprocessing_sections_
;
1379 // Whether we have resized the signatures_ hash table.
1380 bool resized_signatures_
;
1381 // Whether we have created a .stab*str output section.
1382 bool have_stabstr_section_
;
1383 // True if the input sections in the output sections should be sorted
1384 // as specified in a section ordering file.
1385 bool section_ordering_specified_
;
1386 // True if some input sections need to be mapped to a unique segment,
1387 // after being mapped to a unique Output_section.
1388 bool unique_segment_for_sections_specified_
;
1389 // In incremental build, holds information check the inputs and build the
1390 // .gnu_incremental_inputs section.
1391 Incremental_inputs
* incremental_inputs_
;
1392 // Whether we record output section data created in script
1393 bool record_output_section_data_from_script_
;
1394 // List of output data that needs to be removed at relaxation clean up.
1395 Output_section_data_list script_output_section_data_list_
;
1396 // Structure to save segment states before entering the relaxation loop.
1397 Segment_states
* segment_states_
;
1398 // A relaxation debug checker. We only create one when in debugging mode.
1399 Relaxation_debug_check
* relaxation_debug_check_
;
1400 // Plugins specify section_ordering using this map. This is set in
1401 // update_section_order in plugin.cc
1402 std::map
<Section_id
, unsigned int> section_order_map_
;
1403 // This maps an input section to a unique segment. This is done by first
1404 // placing such input sections in unique output sections and then mapping
1405 // the output section to a unique segment. Unique_segment_info stores
1406 // any additional flags and alignment of the new segment.
1407 Section_segment_map section_segment_map_
;
1408 // Hash a pattern to its position in the section ordering file.
1409 Unordered_map
<std::string
, unsigned int> input_section_position_
;
1410 // Vector of glob only patterns in the section_ordering file.
1411 std::vector
<std::string
> input_section_glob_
;
1412 // For incremental links, the base file to be modified.
1413 Incremental_binary
* incremental_base_
;
1414 // For incremental links, a list of free space within the file.
1415 Free_list free_list_
;
1418 // This task handles writing out data in output sections which is not
1419 // part of an input section, or which requires special handling. When
1420 // this is done, it unblocks both output_sections_blocker and
1423 class Write_sections_task
: public Task
1426 Write_sections_task(const Layout
* layout
, Output_file
* of
,
1427 Task_token
* output_sections_blocker
,
1428 Task_token
* final_blocker
)
1429 : layout_(layout
), of_(of
),
1430 output_sections_blocker_(output_sections_blocker
),
1431 final_blocker_(final_blocker
)
1434 // The standard Task methods.
1440 locks(Task_locker
*);
1447 { return "Write_sections_task"; }
1450 class Write_sections_locker
;
1452 const Layout
* layout_
;
1454 Task_token
* output_sections_blocker_
;
1455 Task_token
* final_blocker_
;
1458 // This task handles writing out data which is not part of a section
1461 class Write_data_task
: public Task
1464 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
1465 Output_file
* of
, Task_token
* final_blocker
)
1466 : layout_(layout
), symtab_(symtab
), of_(of
), final_blocker_(final_blocker
)
1469 // The standard Task methods.
1475 locks(Task_locker
*);
1482 { return "Write_data_task"; }
1485 const Layout
* layout_
;
1486 const Symbol_table
* symtab_
;
1488 Task_token
* final_blocker_
;
1491 // This task handles writing out the global symbols.
1493 class Write_symbols_task
: public Task
1496 Write_symbols_task(const Layout
* layout
, const Symbol_table
* symtab
,
1497 const Input_objects
* input_objects
,
1498 const Stringpool
* sympool
, const Stringpool
* dynpool
,
1499 Output_file
* of
, Task_token
* final_blocker
)
1500 : layout_(layout
), symtab_(symtab
), input_objects_(input_objects
),
1501 sympool_(sympool
), dynpool_(dynpool
), of_(of
),
1502 final_blocker_(final_blocker
)
1505 // The standard Task methods.
1511 locks(Task_locker
*);
1518 { return "Write_symbols_task"; }
1521 const Layout
* layout_
;
1522 const Symbol_table
* symtab_
;
1523 const Input_objects
* input_objects_
;
1524 const Stringpool
* sympool_
;
1525 const Stringpool
* dynpool_
;
1527 Task_token
* final_blocker_
;
1530 // This task handles writing out data in output sections which can't
1531 // be written out until all the input sections have been handled.
1532 // This is for sections whose contents is based on the contents of
1533 // other output sections.
1535 class Write_after_input_sections_task
: public Task
1538 Write_after_input_sections_task(Layout
* layout
, Output_file
* of
,
1539 Task_token
* input_sections_blocker
,
1540 Task_token
* final_blocker
)
1541 : layout_(layout
), of_(of
),
1542 input_sections_blocker_(input_sections_blocker
),
1543 final_blocker_(final_blocker
)
1546 // The standard Task methods.
1552 locks(Task_locker
*);
1559 { return "Write_after_input_sections_task"; }
1564 Task_token
* input_sections_blocker_
;
1565 Task_token
* final_blocker_
;
1568 // This task function handles closing the file.
1570 class Close_task_runner
: public Task_function_runner
1573 Close_task_runner(const General_options
* options
, const Layout
* layout
,
1575 : options_(options
), layout_(layout
), of_(of
)
1578 // Run the operation.
1580 run(Workqueue
*, const Task
*);
1583 const General_options
* options_
;
1584 const Layout
* layout_
;
1588 // A small helper function to align an address.
1591 align_address(uint64_t address
, uint64_t addralign
)
1594 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
1598 } // End namespace gold.
1600 #endif // !defined(GOLD_LAYOUT_H)