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 // Some input sections require special ordering, for compatibility
557 // with GNU ld. Given the name of an input section, return -1 if it
558 // does not require special ordering. Otherwise, return the index
559 // by which it should be ordered compared to other input sections
560 // that require special ordering.
562 special_ordering_of_input_section(const char* name
);
565 is_section_ordering_specified()
566 { return this->section_ordering_specified_
; }
569 set_section_ordering_specified()
570 { this->section_ordering_specified_
= true; }
573 is_unique_segment_for_sections_specified() const
574 { return this->unique_segment_for_sections_specified_
; }
577 set_unique_segment_for_sections_specified()
578 { this->unique_segment_for_sections_specified_
= true; }
580 // For incremental updates, allocate a block of memory from the
581 // free list. Find a block starting at or after MINOFF.
583 allocate(off_t len
, uint64_t align
, off_t minoff
)
584 { return this->free_list_
.allocate(len
, align
, minoff
); }
587 find_section_order_index(const std::string
&);
589 // Read the sequence of input sections from the file specified with
590 // linker option --section-ordering-file.
592 read_layout_from_file();
594 // Layout an input reloc section when doing a relocatable link. The
595 // section is RELOC_SHNDX in OBJECT, with data in SHDR.
596 // DATA_SECTION is the reloc section to which it refers. RR is the
597 // relocatable information.
598 template<int size
, bool big_endian
>
600 layout_reloc(Sized_relobj_file
<size
, big_endian
>* object
,
601 unsigned int reloc_shndx
,
602 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
603 Output_section
* data_section
,
604 Relocatable_relocs
* rr
);
606 // Layout a group section when doing a relocatable link.
607 template<int size
, bool big_endian
>
609 layout_group(Symbol_table
* symtab
,
610 Sized_relobj_file
<size
, big_endian
>* object
,
611 unsigned int group_shndx
,
612 const char* group_section_name
,
613 const char* signature
,
614 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
615 elfcpp::Elf_Word flags
,
616 std::vector
<unsigned int>* shndxes
);
618 // Like layout, only for exception frame sections. OBJECT is an
619 // object file. SYMBOLS is the contents of the symbol table
620 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of
621 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a
622 // .eh_frame section in OBJECT. SHDR is the section header.
623 // RELOC_SHNDX is the index of a relocation section which applies to
624 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE
625 // is the type of the relocation section if there is one. This
626 // returns the output section, and sets *OFFSET to the offset.
627 template<int size
, bool big_endian
>
629 layout_eh_frame(Sized_relobj_file
<size
, big_endian
>* object
,
630 const unsigned char* symbols
,
632 const unsigned char* symbol_names
,
633 off_t symbol_names_size
,
635 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
636 unsigned int reloc_shndx
, unsigned int reloc_type
,
639 // Add .eh_frame information for a PLT. The FDE must start with a
640 // 4-byte PC-relative reference to the start of the PLT, followed by
641 // a 4-byte size of PLT.
643 add_eh_frame_for_plt(Output_data
* plt
, const unsigned char* cie_data
,
644 size_t cie_length
, const unsigned char* fde_data
,
647 // Scan a .debug_info or .debug_types section, and add summary
648 // information to the .gdb_index section.
649 template<int size
, bool big_endian
>
651 add_to_gdb_index(bool is_type_unit
,
652 Sized_relobj
<size
, big_endian
>* object
,
653 const unsigned char* symbols
,
656 unsigned int reloc_shndx
,
657 unsigned int reloc_type
);
659 // Handle a GNU stack note. This is called once per input object
660 // file. SEEN_GNU_STACK is true if the object file has a
661 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags
662 // from that section if there was one.
664 layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
,
667 // Add an Output_section_data to the layout. This is used for
668 // special sections like the GOT section. ORDER is where the
669 // section should wind up in the output segment. IS_RELRO is true
670 // for relro sections.
672 add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
673 elfcpp::Elf_Xword flags
,
674 Output_section_data
*, Output_section_order order
,
677 // Increase the size of the relro segment by this much.
679 increase_relro(unsigned int s
)
680 { this->increase_relro_
+= s
; }
682 // Create dynamic sections if necessary.
684 create_initial_dynamic_sections(Symbol_table
*);
686 // Define __start and __stop symbols for output sections.
688 define_section_symbols(Symbol_table
*);
690 // Create automatic note sections.
694 // Create sections for linker scripts.
696 create_script_sections()
697 { this->script_options_
->create_script_sections(this); }
699 // Define symbols from any linker script.
701 define_script_symbols(Symbol_table
* symtab
)
702 { this->script_options_
->add_symbols_to_table(symtab
); }
704 // Define symbols for group signatures.
706 define_group_signatures(Symbol_table
*);
708 // Return the Stringpool used for symbol names.
711 { return &this->sympool_
; }
713 // Return the Stringpool used for dynamic symbol names and dynamic
717 { return &this->dynpool_
; }
719 // Return the .dynamic output section. This is only valid after the
720 // layout has been finalized.
722 dynamic_section() const
723 { return this->dynamic_section_
; }
725 // Return the symtab_xindex section used to hold large section
726 // indexes for the normal symbol table.
727 Output_symtab_xindex
*
728 symtab_xindex() const
729 { return this->symtab_xindex_
; }
731 // Return the dynsym_xindex section used to hold large section
732 // indexes for the dynamic symbol table.
733 Output_symtab_xindex
*
734 dynsym_xindex() const
735 { return this->dynsym_xindex_
; }
737 // Return whether a section is a .gnu.linkonce section, given the
740 is_linkonce(const char* name
)
741 { return strncmp(name
, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
743 // Whether we have added an input section.
745 have_added_input_section() const
746 { return this->have_added_input_section_
; }
748 // Return true if a section is a debugging section.
750 is_debug_info_section(const char* name
)
752 // Debugging sections can only be recognized by name.
753 return (strncmp(name
, ".debug", sizeof(".debug") - 1) == 0
754 || strncmp(name
, ".zdebug", sizeof(".zdebug") - 1) == 0
755 || strncmp(name
, ".gnu.linkonce.wi.",
756 sizeof(".gnu.linkonce.wi.") - 1) == 0
757 || strncmp(name
, ".line", sizeof(".line") - 1) == 0
758 || strncmp(name
, ".stab", sizeof(".stab") - 1) == 0);
761 // Return true if RELOBJ is an input file whose base name matches
762 // FILE_NAME. The base name must have an extension of ".o", and
763 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o".
765 match_file_name(const Relobj
* relobj
, const char* file_name
);
767 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section
768 // with more than one word being mapped to a .init_array/.fini_array
771 is_ctors_in_init_array(Relobj
* relobj
, unsigned int shndx
) const;
773 // Check if a comdat group or .gnu.linkonce section with the given
774 // NAME is selected for the link. If there is already a section,
775 // *KEPT_SECTION is set to point to the signature and the function
776 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and
777 // IS_GROUP_NAME are recorded for this NAME in the layout object,
778 // *KEPT_SECTION is set to the internal copy and the function return
781 find_or_add_kept_section(const std::string
& name
, Relobj
* object
,
782 unsigned int shndx
, bool is_comdat
,
783 bool is_group_name
, Kept_section
** kept_section
);
785 // Finalize the layout after all the input sections have been added.
787 finalize(const Input_objects
*, Symbol_table
*, Target
*, const Task
*);
789 // Return whether any sections require postprocessing.
791 any_postprocessing_sections() const
792 { return this->any_postprocessing_sections_
; }
794 // Return the size of the output file.
796 output_file_size() const
797 { return this->output_file_size_
; }
799 // Return the TLS segment. This will return NULL if there isn't
803 { return this->tls_segment_
; }
805 // Return the normal symbol table.
807 symtab_section() const
809 gold_assert(this->symtab_section_
!= NULL
);
810 return this->symtab_section_
;
813 // Return the file offset of the normal symbol table.
815 symtab_section_offset() const;
817 // Return the section index of the normal symbol tabl.e
819 symtab_section_shndx() const;
821 // Return the dynamic symbol table.
823 dynsym_section() const
825 gold_assert(this->dynsym_section_
!= NULL
);
826 return this->dynsym_section_
;
829 // Return the dynamic tags.
832 { return this->dynamic_data_
; }
834 // Write out the output sections.
836 write_output_sections(Output_file
* of
) const;
838 // Write out data not associated with an input file or the symbol
841 write_data(const Symbol_table
*, Output_file
*) const;
843 // Write out output sections which can not be written until all the
844 // input sections are complete.
846 write_sections_after_input_sections(Output_file
* of
);
848 // Return an output section named NAME, or NULL if there is none.
850 find_output_section(const char* name
) const;
852 // Return an output segment of type TYPE, with segment flags SET set
853 // and segment flags CLEAR clear. Return NULL if there is none.
855 find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
856 elfcpp::Elf_Word clear
) const;
858 // Return the number of segments we expect to produce.
860 expected_segment_count() const;
862 // Set a flag to indicate that an object file uses the static TLS model.
865 { this->has_static_tls_
= true; }
867 // Return true if any object file uses the static TLS model.
869 has_static_tls() const
870 { return this->has_static_tls_
; }
872 // Return the options which may be set by a linker script.
875 { return this->script_options_
; }
877 const Script_options
*
878 script_options() const
879 { return this->script_options_
; }
881 // Return the object managing inputs in incremental build. NULL in
882 // non-incremental builds.
884 incremental_inputs() const
885 { return this->incremental_inputs_
; }
887 // For the target-specific code to add dynamic tags which are common
890 add_target_dynamic_tags(bool use_rel
, const Output_data
* plt_got
,
891 const Output_data
* plt_rel
,
892 const Output_data_reloc_generic
* dyn_rel
,
893 bool add_debug
, bool dynrel_includes_plt
);
895 // Compute and write out the build ID if needed.
897 write_build_id(Output_file
*) const;
899 // Rewrite output file in binary format.
901 write_binary(Output_file
* in
) const;
903 // Print output sections to the map file.
905 print_to_mapfile(Mapfile
*) const;
907 // Dump statistical information to stderr.
911 // A list of segments.
913 typedef std::vector
<Output_segment
*> Segment_list
;
915 // A list of sections.
917 typedef std::vector
<Output_section
*> Section_list
;
919 // The list of information to write out which is not attached to
920 // either a section or a segment.
921 typedef std::vector
<Output_data
*> Data_list
;
923 // Store the allocated sections into the section list. This is used
924 // by the linker script code.
926 get_allocated_sections(Section_list
*) const;
928 // Store the executable sections into the section list.
930 get_executable_sections(Section_list
*) const;
932 // Make a section for a linker script to hold data.
934 make_output_section_for_script(const char* name
,
935 Script_sections::Section_type section_type
);
937 // Make a segment. This is used by the linker script code.
939 make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
);
941 // Return the number of segments.
943 segment_count() const
944 { return this->segment_list_
.size(); }
946 // Map from section flags to segment flags.
947 static elfcpp::Elf_Word
948 section_flags_to_segment(elfcpp::Elf_Xword flags
);
950 // Attach sections to segments.
952 attach_sections_to_segments(const Target
*);
954 // For relaxation clean up, we need to know output section data created
955 // from a linker script.
957 new_output_section_data_from_script(Output_section_data
* posd
)
959 if (this->record_output_section_data_from_script_
)
960 this->script_output_section_data_list_
.push_back(posd
);
963 // Return section list.
966 { return this->section_list_
; }
968 // Returns TRUE iff NAME (an input section from RELOBJ) will
969 // be mapped to an output section that should be KEPT.
971 keep_input_section(const Relobj
*, const char*);
974 Layout(const Layout
&);
975 Layout
& operator=(const Layout
&);
977 // Mapping from input section names to output section names.
978 struct Section_name_mapping
985 static const Section_name_mapping section_name_mapping
[];
986 static const int section_name_mapping_count
;
988 // During a relocatable link, a list of group sections and
990 struct Group_signature
992 // The group section.
993 Output_section
* section
;
995 const char* signature
;
998 : section(NULL
), signature(NULL
)
1001 Group_signature(Output_section
* sectiona
, const char* signaturea
)
1002 : section(sectiona
), signature(signaturea
)
1005 typedef std::vector
<Group_signature
> Group_signatures
;
1007 // Create a note section, filling in the header.
1009 create_note(const char* name
, int note_type
, const char* section_name
,
1010 size_t descsz
, bool allocate
, size_t* trailing_padding
);
1012 // Create a note section for gold version.
1016 // Record whether the stack must be executable.
1018 create_executable_stack_info();
1020 // Create a build ID note if needed.
1024 // Link .stab and .stabstr sections.
1026 link_stabs_sections();
1028 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed
1029 // for the next run of incremental linking to check what has changed.
1031 create_incremental_info_sections(Symbol_table
*);
1033 // Find the first read-only PT_LOAD segment, creating one if
1036 find_first_load_seg(const Target
*);
1038 // Count the local symbols in the regular symbol table and the dynamic
1039 // symbol table, and build the respective string pools.
1041 count_local_symbols(const Task
*, const Input_objects
*);
1043 // Create the output sections for the symbol table.
1045 create_symtab_sections(const Input_objects
*, Symbol_table
*,
1046 unsigned int, off_t
*);
1048 // Create the .shstrtab section.
1052 // Create the section header table.
1054 create_shdrs(const Output_section
* shstrtab_section
, off_t
*);
1056 // Create the dynamic symbol table.
1058 create_dynamic_symtab(const Input_objects
*, Symbol_table
*,
1059 Output_section
** pdynstr
,
1060 unsigned int* plocal_dynamic_count
,
1061 std::vector
<Symbol
*>* pdynamic_symbols
,
1062 Versions
* versions
);
1064 // Assign offsets to each local portion of the dynamic symbol table.
1066 assign_local_dynsym_offsets(const Input_objects
*);
1068 // Finish the .dynamic section and PT_DYNAMIC segment.
1070 finish_dynamic_section(const Input_objects
*, const Symbol_table
*);
1072 // Set the size of the _DYNAMIC symbol.
1074 set_dynamic_symbol_size(const Symbol_table
*);
1076 // Create the .interp section and PT_INTERP segment.
1078 create_interp(const Target
* target
);
1080 // Create the version sections.
1082 create_version_sections(const Versions
*,
1083 const Symbol_table
*,
1084 unsigned int local_symcount
,
1085 const std::vector
<Symbol
*>& dynamic_symbols
,
1086 const Output_section
* dynstr
);
1088 template<int size
, bool big_endian
>
1090 sized_create_version_sections(const Versions
* versions
,
1091 const Symbol_table
*,
1092 unsigned int local_symcount
,
1093 const std::vector
<Symbol
*>& dynamic_symbols
,
1094 const Output_section
* dynstr
);
1096 // Return whether to include this section in the link.
1097 template<int size
, bool big_endian
>
1099 include_section(Sized_relobj_file
<size
, big_endian
>* object
, const char* name
,
1100 const elfcpp::Shdr
<size
, big_endian
>&);
1102 // Return the output section name to use given an input section
1103 // name. Set *PLEN to the length of the name. *PLEN must be
1104 // initialized to the length of NAME.
1106 output_section_name(const Relobj
*, const char* name
, size_t* plen
);
1108 // Return the number of allocated output sections.
1110 allocated_output_section_count() const;
1112 // Return the output section for NAME, TYPE and FLAGS.
1114 get_output_section(const char* name
, Stringpool::Key name_key
,
1115 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1116 Output_section_order order
, bool is_relro
);
1118 // Clear the input section flags that should not be copied to the
1121 get_output_section_flags (elfcpp::Elf_Xword input_section_flags
);
1123 // Choose the output section for NAME in RELOBJ.
1125 choose_output_section(const Relobj
* relobj
, const char* name
,
1126 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
1127 bool is_input_section
, Output_section_order order
,
1130 // Create a new Output_section.
1132 make_output_section(const char* name
, elfcpp::Elf_Word type
,
1133 elfcpp::Elf_Xword flags
, Output_section_order order
,
1136 // Attach a section to a segment.
1138 attach_section_to_segment(const Target
*, Output_section
*);
1140 // Get section order.
1141 Output_section_order
1142 default_section_order(Output_section
*, bool is_relro_local
);
1144 // Attach an allocated section to a segment.
1146 attach_allocated_section_to_segment(const Target
*, Output_section
*);
1148 // Make the .eh_frame section.
1150 make_eh_frame_section(const Relobj
*);
1152 // Set the final file offsets of all the segments.
1154 set_segment_offsets(const Target
*, Output_segment
*, unsigned int* pshndx
);
1156 // Set the file offsets of the sections when doing a relocatable
1159 set_relocatable_section_offsets(Output_data
*, unsigned int* pshndx
);
1161 // Set the final file offsets of all the sections not associated
1162 // with a segment. We set section offsets in three passes: the
1163 // first handles all allocated sections, the second sections that
1164 // require postprocessing, and the last the late-bound STRTAB
1165 // sections (probably only shstrtab, which is the one we care about
1166 // because it holds section names).
1167 enum Section_offset_pass
1169 BEFORE_INPUT_SECTIONS_PASS
,
1170 POSTPROCESSING_SECTIONS_PASS
,
1171 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1174 set_section_offsets(off_t
, Section_offset_pass pass
);
1176 // Set the final section indexes of all the sections not associated
1177 // with a segment. Returns the next unused index.
1179 set_section_indexes(unsigned int pshndx
);
1181 // Set the section addresses when using a script.
1183 set_section_addresses_from_script(Symbol_table
*);
1185 // Find appropriate places or orphan sections in a script.
1187 place_orphan_sections_in_script();
1189 // Return whether SEG1 comes before SEG2 in the output file.
1191 segment_precedes(const Output_segment
* seg1
, const Output_segment
* seg2
);
1193 // Use to save and restore segments during relaxation.
1194 typedef Unordered_map
<const Output_segment
*, const Output_segment
*>
1197 // Save states of current output segments.
1199 save_segments(Segment_states
*);
1201 // Restore output segment states.
1203 restore_segments(const Segment_states
*);
1205 // Clean up after relaxation so that it is possible to lay out the
1206 // sections and segments again.
1208 clean_up_after_relaxation();
1210 // Doing preparation work for relaxation. This is factored out to make
1211 // Layout::finalized a bit smaller and easier to read.
1213 prepare_for_relaxation();
1215 // Main body of the relaxation loop, which lays out the section.
1217 relaxation_loop_body(int, Target
*, Symbol_table
*, Output_segment
**,
1218 Output_segment
*, Output_segment_headers
*,
1219 Output_file_header
*, unsigned int*);
1221 // A mapping used for kept comdats/.gnu.linkonce group signatures.
1222 typedef Unordered_map
<std::string
, Kept_section
> Signatures
;
1224 // Mapping from input section name/type/flags to output section. We
1225 // use canonicalized strings here.
1227 typedef std::pair
<Stringpool::Key
,
1228 std::pair
<elfcpp::Elf_Word
, elfcpp::Elf_Xword
> > Key
;
1233 operator()(const Key
& k
) const;
1236 typedef Unordered_map
<Key
, Output_section
*, Hash_key
> Section_name_map
;
1238 // A comparison class for segments.
1240 class Compare_segments
1243 Compare_segments(Layout
* layout
)
1248 operator()(const Output_segment
* seg1
, const Output_segment
* seg2
)
1249 { return this->layout_
->segment_precedes(seg1
, seg2
); }
1255 typedef std::vector
<Output_section_data
*> Output_section_data_list
;
1257 // Debug checker class.
1258 class Relaxation_debug_check
1261 Relaxation_debug_check()
1265 // Check that sections and special data are in reset states.
1267 check_output_data_for_reset_values(const Layout::Section_list
&,
1268 const Layout::Data_list
&);
1270 // Record information of a section list.
1272 read_sections(const Layout::Section_list
&);
1274 // Verify a section list with recorded information.
1276 verify_sections(const Layout::Section_list
&);
1279 // Information we care about a section.
1282 // Output section described by this.
1283 Output_section
* output_section
;
1292 // Section information.
1293 std::vector
<Section_info
> section_infos_
;
1296 // The number of input files, for sizing tables.
1297 int number_of_input_files_
;
1298 // Information set by scripts or by command line options.
1299 Script_options
* script_options_
;
1300 // The output section names.
1301 Stringpool namepool_
;
1302 // The output symbol names.
1303 Stringpool sympool_
;
1304 // The dynamic strings, if needed.
1305 Stringpool dynpool_
;
1306 // The list of group sections and linkonce sections which we have seen.
1307 Signatures signatures_
;
1308 // The mapping from input section name/type/flags to output sections.
1309 Section_name_map section_name_map_
;
1310 // The list of output segments.
1311 Segment_list segment_list_
;
1312 // The list of output sections.
1313 Section_list section_list_
;
1314 // The list of output sections which are not attached to any output
1316 Section_list unattached_section_list_
;
1317 // The list of unattached Output_data objects which require special
1318 // handling because they are not Output_sections.
1319 Data_list special_output_list_
;
1320 // The section headers.
1321 Output_section_headers
* section_headers_
;
1322 // A pointer to the PT_TLS segment if there is one.
1323 Output_segment
* tls_segment_
;
1324 // A pointer to the PT_GNU_RELRO segment if there is one.
1325 Output_segment
* relro_segment_
;
1326 // A pointer to the PT_INTERP segment if there is one.
1327 Output_segment
* interp_segment_
;
1328 // A backend may increase the size of the PT_GNU_RELRO segment if
1329 // there is one. This is the amount to increase it by.
1330 unsigned int increase_relro_
;
1331 // The SHT_SYMTAB output section.
1332 Output_section
* symtab_section_
;
1333 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one.
1334 Output_symtab_xindex
* symtab_xindex_
;
1335 // The SHT_DYNSYM output section if there is one.
1336 Output_section
* dynsym_section_
;
1337 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one.
1338 Output_symtab_xindex
* dynsym_xindex_
;
1339 // The SHT_DYNAMIC output section if there is one.
1340 Output_section
* dynamic_section_
;
1341 // The _DYNAMIC symbol if there is one.
1342 Symbol
* dynamic_symbol_
;
1343 // The dynamic data which goes into dynamic_section_.
1344 Output_data_dynamic
* dynamic_data_
;
1345 // The exception frame output section if there is one.
1346 Output_section
* eh_frame_section_
;
1347 // The exception frame data for eh_frame_section_.
1348 Eh_frame
* eh_frame_data_
;
1349 // Whether we have added eh_frame_data_ to the .eh_frame section.
1350 bool added_eh_frame_data_
;
1351 // The exception frame header output section if there is one.
1352 Output_section
* eh_frame_hdr_section_
;
1353 // The data for the .gdb_index section.
1354 Gdb_index
* gdb_index_data_
;
1355 // The space for the build ID checksum if there is one.
1356 Output_section_data
* build_id_note_
;
1357 // The output section containing dwarf abbreviations
1358 Output_reduced_debug_abbrev_section
* debug_abbrev_
;
1359 // The output section containing the dwarf debug info tree
1360 Output_reduced_debug_info_section
* debug_info_
;
1361 // A list of group sections and their signatures.
1362 Group_signatures group_signatures_
;
1363 // The size of the output file.
1364 off_t output_file_size_
;
1365 // Whether we have added an input section to an output section.
1366 bool have_added_input_section_
;
1367 // Whether we have attached the sections to the segments.
1368 bool sections_are_attached_
;
1369 // Whether we have seen an object file marked to require an
1370 // executable stack.
1371 bool input_requires_executable_stack_
;
1372 // Whether we have seen at least one object file with an executable
1374 bool input_with_gnu_stack_note_
;
1375 // Whether we have seen at least one object file without an
1376 // executable stack marker.
1377 bool input_without_gnu_stack_note_
;
1378 // Whether we have seen an object file that uses the static TLS model.
1379 bool has_static_tls_
;
1380 // Whether any sections require postprocessing.
1381 bool any_postprocessing_sections_
;
1382 // Whether we have resized the signatures_ hash table.
1383 bool resized_signatures_
;
1384 // Whether we have created a .stab*str output section.
1385 bool have_stabstr_section_
;
1386 // True if the input sections in the output sections should be sorted
1387 // as specified in a section ordering file.
1388 bool section_ordering_specified_
;
1389 // True if some input sections need to be mapped to a unique segment,
1390 // after being mapped to a unique Output_section.
1391 bool unique_segment_for_sections_specified_
;
1392 // In incremental build, holds information check the inputs and build the
1393 // .gnu_incremental_inputs section.
1394 Incremental_inputs
* incremental_inputs_
;
1395 // Whether we record output section data created in script
1396 bool record_output_section_data_from_script_
;
1397 // List of output data that needs to be removed at relaxation clean up.
1398 Output_section_data_list script_output_section_data_list_
;
1399 // Structure to save segment states before entering the relaxation loop.
1400 Segment_states
* segment_states_
;
1401 // A relaxation debug checker. We only create one when in debugging mode.
1402 Relaxation_debug_check
* relaxation_debug_check_
;
1403 // Plugins specify section_ordering using this map. This is set in
1404 // update_section_order in plugin.cc
1405 std::map
<Section_id
, unsigned int> section_order_map_
;
1406 // This maps an input section to a unique segment. This is done by first
1407 // placing such input sections in unique output sections and then mapping
1408 // the output section to a unique segment. Unique_segment_info stores
1409 // any additional flags and alignment of the new segment.
1410 Section_segment_map section_segment_map_
;
1411 // Hash a pattern to its position in the section ordering file.
1412 Unordered_map
<std::string
, unsigned int> input_section_position_
;
1413 // Vector of glob only patterns in the section_ordering file.
1414 std::vector
<std::string
> input_section_glob_
;
1415 // For incremental links, the base file to be modified.
1416 Incremental_binary
* incremental_base_
;
1417 // For incremental links, a list of free space within the file.
1418 Free_list free_list_
;
1421 // This task handles writing out data in output sections which is not
1422 // part of an input section, or which requires special handling. When
1423 // this is done, it unblocks both output_sections_blocker and
1426 class Write_sections_task
: public Task
1429 Write_sections_task(const Layout
* layout
, Output_file
* of
,
1430 Task_token
* output_sections_blocker
,
1431 Task_token
* final_blocker
)
1432 : layout_(layout
), of_(of
),
1433 output_sections_blocker_(output_sections_blocker
),
1434 final_blocker_(final_blocker
)
1437 // The standard Task methods.
1443 locks(Task_locker
*);
1450 { return "Write_sections_task"; }
1453 class Write_sections_locker
;
1455 const Layout
* layout_
;
1457 Task_token
* output_sections_blocker_
;
1458 Task_token
* final_blocker_
;
1461 // This task handles writing out data which is not part of a section
1464 class Write_data_task
: public Task
1467 Write_data_task(const Layout
* layout
, const Symbol_table
* symtab
,
1468 Output_file
* of
, Task_token
* final_blocker
)
1469 : layout_(layout
), symtab_(symtab
), of_(of
), final_blocker_(final_blocker
)
1472 // The standard Task methods.
1478 locks(Task_locker
*);
1485 { return "Write_data_task"; }
1488 const Layout
* layout_
;
1489 const Symbol_table
* symtab_
;
1491 Task_token
* final_blocker_
;
1494 // This task handles writing out the global symbols.
1496 class Write_symbols_task
: public Task
1499 Write_symbols_task(const Layout
* layout
, const Symbol_table
* symtab
,
1500 const Input_objects
* input_objects
,
1501 const Stringpool
* sympool
, const Stringpool
* dynpool
,
1502 Output_file
* of
, Task_token
* final_blocker
)
1503 : layout_(layout
), symtab_(symtab
), input_objects_(input_objects
),
1504 sympool_(sympool
), dynpool_(dynpool
), of_(of
),
1505 final_blocker_(final_blocker
)
1508 // The standard Task methods.
1514 locks(Task_locker
*);
1521 { return "Write_symbols_task"; }
1524 const Layout
* layout_
;
1525 const Symbol_table
* symtab_
;
1526 const Input_objects
* input_objects_
;
1527 const Stringpool
* sympool_
;
1528 const Stringpool
* dynpool_
;
1530 Task_token
* final_blocker_
;
1533 // This task handles writing out data in output sections which can't
1534 // be written out until all the input sections have been handled.
1535 // This is for sections whose contents is based on the contents of
1536 // other output sections.
1538 class Write_after_input_sections_task
: public Task
1541 Write_after_input_sections_task(Layout
* layout
, Output_file
* of
,
1542 Task_token
* input_sections_blocker
,
1543 Task_token
* final_blocker
)
1544 : layout_(layout
), of_(of
),
1545 input_sections_blocker_(input_sections_blocker
),
1546 final_blocker_(final_blocker
)
1549 // The standard Task methods.
1555 locks(Task_locker
*);
1562 { return "Write_after_input_sections_task"; }
1567 Task_token
* input_sections_blocker_
;
1568 Task_token
* final_blocker_
;
1571 // This task function handles closing the file.
1573 class Close_task_runner
: public Task_function_runner
1576 Close_task_runner(const General_options
* options
, const Layout
* layout
,
1578 : options_(options
), layout_(layout
), of_(of
)
1581 // Run the operation.
1583 run(Workqueue
*, const Task
*);
1586 const General_options
* options_
;
1587 const Layout
* layout_
;
1591 // A small helper function to align an address.
1594 align_address(uint64_t address
, uint64_t addralign
)
1597 address
= (address
+ addralign
- 1) &~ (addralign
- 1);
1601 } // End namespace gold.
1603 #endif // !defined(GOLD_LAYOUT_H)