1 // layout.cc -- lay out output file sections for gold
18 // Layout_task_runner methods.
20 // Lay out the sections. This is called after all the input objects
24 Layout_task_runner::run(Workqueue
* workqueue
)
26 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
29 // Now we know the final size of the output file and we know where
30 // each piece of information goes.
31 Output_file
* of
= new Output_file(this->options_
);
34 // Queue up the final set of tasks.
35 gold::queue_final_tasks(this->options_
, this->input_objects_
,
36 this->symtab_
, this->layout_
, workqueue
, of
);
41 Layout::Layout(const General_options
& options
)
42 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
43 section_name_map_(), segment_list_(), section_list_(),
44 unattached_section_list_(), special_output_list_(),
45 tls_segment_(NULL
), symtab_section_(NULL
), dynsym_section_(NULL
),
46 dynamic_section_(NULL
), dynamic_data_(NULL
)
48 // Make space for more than enough segments for a typical file.
49 // This is just for efficiency--it's OK if we wind up needing more.
50 this->segment_list_
.reserve(12);
52 // We expect three unattached Output_data objects: the file header,
53 // the segment headers, and the section headers.
54 this->special_output_list_
.reserve(3);
57 // Hash a key we use to look up an output section mapping.
60 Layout::Hash_key::operator()(const Layout::Key
& k
) const
62 return k
.first
+ k
.second
.first
+ k
.second
.second
;
65 // Whether to include this section in the link.
67 template<int size
, bool big_endian
>
69 Layout::include_section(Object
*, const char*,
70 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
72 // Some section types are never linked. Some are only linked when
73 // doing a relocateable link.
74 switch (shdr
.get_sh_type())
76 case elfcpp::SHT_NULL
:
77 case elfcpp::SHT_SYMTAB
:
78 case elfcpp::SHT_DYNSYM
:
79 case elfcpp::SHT_STRTAB
:
80 case elfcpp::SHT_HASH
:
81 case elfcpp::SHT_DYNAMIC
:
82 case elfcpp::SHT_SYMTAB_SHNDX
:
85 case elfcpp::SHT_RELA
:
87 case elfcpp::SHT_GROUP
:
88 return this->options_
.is_relocatable();
91 // FIXME: Handle stripping debug sections here.
96 // Return an output section named NAME, or NULL if there is none.
99 Layout::find_output_section(const char* name
) const
101 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
102 p
!= this->section_name_map_
.end();
104 if (strcmp(p
->second
->name(), name
) == 0)
109 // Return an output segment of type TYPE, with segment flags SET set
110 // and segment flags CLEAR clear. Return NULL if there is none.
113 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
114 elfcpp::Elf_Word clear
) const
116 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
117 p
!= this->segment_list_
.end();
119 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
120 && ((*p
)->flags() & set
) == set
121 && ((*p
)->flags() & clear
) == 0)
126 // Return the output section to use for section NAME with type TYPE
127 // and section flags FLAGS.
130 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
131 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
133 // We should ignore some flags.
134 flags
&= ~ (elfcpp::SHF_INFO_LINK
135 | elfcpp::SHF_LINK_ORDER
136 | elfcpp::SHF_GROUP
);
138 const Key
key(name_key
, std::make_pair(type
, flags
));
139 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
140 std::pair
<Section_name_map::iterator
, bool> ins(
141 this->section_name_map_
.insert(v
));
144 return ins
.first
->second
;
147 // This is the first time we've seen this name/type/flags
149 Output_section
* os
= this->make_output_section(name
, type
, flags
);
150 ins
.first
->second
= os
;
155 // Return the output section to use for input section SHNDX, with name
156 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
157 // offset of this input section without the output section.
159 template<int size
, bool big_endian
>
161 Layout::layout(Relobj
* object
, unsigned int shndx
, const char* name
,
162 const elfcpp::Shdr
<size
, big_endian
>& shdr
, off_t
* off
)
164 if (!this->include_section(object
, name
, shdr
))
167 // If we are not doing a relocateable link, choose the name to use
168 // for the output section.
169 size_t len
= strlen(name
);
170 if (!this->options_
.is_relocatable())
171 name
= Layout::output_section_name(name
, &len
);
173 // FIXME: Handle SHF_OS_NONCONFORMING here.
175 // Canonicalize the section name.
176 Stringpool::Key name_key
;
177 name
= this->namepool_
.add(name
, len
, &name_key
);
179 // Find the output section. The output section is selected based on
180 // the section name, type, and flags.
181 Output_section
* os
= this->get_output_section(name
, name_key
,
183 shdr
.get_sh_flags());
185 // FIXME: Handle SHF_LINK_ORDER somewhere.
187 *off
= os
->add_input_section(object
, shndx
, name
, shdr
);
192 // Add POSD to an output section using NAME, TYPE, and FLAGS.
195 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
196 elfcpp::Elf_Xword flags
,
197 Output_section_data
* posd
)
199 // Canonicalize the name.
200 Stringpool::Key name_key
;
201 name
= this->namepool_
.add(name
, &name_key
);
203 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
204 os
->add_output_section_data(posd
);
207 // Map section flags to segment flags.
210 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
212 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
213 if ((flags
& elfcpp::SHF_WRITE
) != 0)
215 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
220 // Make a new Output_section, and attach it to segments as
224 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
225 elfcpp::Elf_Xword flags
)
227 Output_section
* os
= new Output_section(name
, type
, flags
, true);
228 this->section_list_
.push_back(os
);
230 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
231 this->unattached_section_list_
.push_back(os
);
234 // This output section goes into a PT_LOAD segment.
236 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
238 // The only thing we really care about for PT_LOAD segments is
239 // whether or not they are writable, so that is how we search
240 // for them. People who need segments sorted on some other
241 // basis will have to wait until we implement a mechanism for
242 // them to describe the segments they want.
244 Segment_list::const_iterator p
;
245 for (p
= this->segment_list_
.begin();
246 p
!= this->segment_list_
.end();
249 if ((*p
)->type() == elfcpp::PT_LOAD
250 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
252 (*p
)->add_output_section(os
, seg_flags
);
257 if (p
== this->segment_list_
.end())
259 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
261 this->segment_list_
.push_back(oseg
);
262 oseg
->add_output_section(os
, seg_flags
);
265 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
267 if (type
== elfcpp::SHT_NOTE
)
269 // See if we already have an equivalent PT_NOTE segment.
270 for (p
= this->segment_list_
.begin();
271 p
!= segment_list_
.end();
274 if ((*p
)->type() == elfcpp::PT_NOTE
275 && (((*p
)->flags() & elfcpp::PF_W
)
276 == (seg_flags
& elfcpp::PF_W
)))
278 (*p
)->add_output_section(os
, seg_flags
);
283 if (p
== this->segment_list_
.end())
285 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
287 this->segment_list_
.push_back(oseg
);
288 oseg
->add_output_section(os
, seg_flags
);
292 // If we see a loadable SHF_TLS section, we create a PT_TLS
293 // segment. There can only be one such segment.
294 if ((flags
& elfcpp::SHF_TLS
) != 0)
296 if (this->tls_segment_
== NULL
)
298 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
300 this->segment_list_
.push_back(this->tls_segment_
);
302 this->tls_segment_
->add_output_section(os
, seg_flags
);
309 // Create the dynamic sections which are needed before we read the
313 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
314 Symbol_table
* symtab
)
316 if (!input_objects
->any_dynamic())
319 const char* dynamic_name
= this->namepool_
.add(".dynamic", NULL
);
320 this->dynamic_section_
= this->make_output_section(dynamic_name
,
323 | elfcpp::SHF_WRITE
));
325 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC",
326 this->dynamic_section_
, 0, 0,
327 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
328 elfcpp::STV_HIDDEN
, 0, false, false);
330 this->dynamic_data_
= new Output_data_dynamic(input_objects
->target(),
333 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
336 // Find the first read-only PT_LOAD segment, creating one if
340 Layout::find_first_load_seg()
342 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
343 p
!= this->segment_list_
.end();
346 if ((*p
)->type() == elfcpp::PT_LOAD
347 && ((*p
)->flags() & elfcpp::PF_R
) != 0
348 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
352 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
353 this->segment_list_
.push_back(load_seg
);
357 // Finalize the layout. When this is called, we have created all the
358 // output sections and all the output segments which are based on
359 // input sections. We have several things to do, and we have to do
360 // them in the right order, so that we get the right results correctly
363 // 1) Finalize the list of output segments and create the segment
366 // 2) Finalize the dynamic symbol table and associated sections.
368 // 3) Determine the final file offset of all the output segments.
370 // 4) Determine the final file offset of all the SHF_ALLOC output
373 // 5) Create the symbol table sections and the section name table
376 // 6) Finalize the symbol table: set symbol values to their final
377 // value and make a final determination of which symbols are going
378 // into the output symbol table.
380 // 7) Create the section table header.
382 // 8) Determine the final file offset of all the output sections which
383 // are not SHF_ALLOC, including the section table header.
385 // 9) Finalize the ELF file header.
387 // This function returns the size of the output file.
390 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
)
392 Target
* const target
= input_objects
->target();
393 const int size
= target
->get_size();
395 target
->finalize_sections(&this->options_
, this);
397 Output_segment
* phdr_seg
= NULL
;
398 if (input_objects
->any_dynamic())
400 // There was a dynamic object in the link. We need to create
401 // some information for the dynamic linker.
403 // Create the PT_PHDR segment which will hold the program
405 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
406 this->segment_list_
.push_back(phdr_seg
);
408 // Create the dynamic symbol table, including the hash table,
409 // the dynamic relocations, and the version sections.
410 this->create_dynamic_symtab(target
, symtab
);
412 // Create the .interp section to hold the name of the
413 // interpreter, and put it in a PT_INTERP segment.
414 this->create_interp(target
);
416 // Finish the .dynamic section to hold the dynamic data, and put
417 // it in a PT_DYNAMIC segment.
418 this->finish_dynamic_section(input_objects
, symtab
);
421 // FIXME: Handle PT_GNU_STACK.
423 Output_segment
* load_seg
= this->find_first_load_seg();
425 // Lay out the segment headers.
426 bool big_endian
= target
->is_big_endian();
427 Output_segment_headers
* segment_headers
;
428 segment_headers
= new Output_segment_headers(size
, big_endian
,
429 this->segment_list_
);
430 load_seg
->add_initial_output_data(segment_headers
);
431 this->special_output_list_
.push_back(segment_headers
);
432 if (phdr_seg
!= NULL
)
433 phdr_seg
->add_initial_output_data(segment_headers
);
435 // Lay out the file header.
436 Output_file_header
* file_header
;
437 file_header
= new Output_file_header(size
,
443 load_seg
->add_initial_output_data(file_header
);
444 this->special_output_list_
.push_back(file_header
);
446 // We set the output section indexes in set_segment_offsets and
447 // set_section_offsets.
448 unsigned int shndx
= 1;
450 // Set the file offsets of all the segments, and all the sections
452 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
454 // Create the symbol table sections.
455 // FIXME: We don't need to do this if we are stripping symbols.
456 this->create_symtab_sections(size
, input_objects
, symtab
, &off
);
458 // Create the .shstrtab section.
459 Output_section
* shstrtab_section
= this->create_shstrtab();
461 // Set the file offsets of all the sections not associated with
463 off
= this->set_section_offsets(off
, &shndx
);
465 // Create the section table header.
466 Output_section_headers
* oshdrs
= this->create_shdrs(size
, big_endian
, &off
);
468 file_header
->set_section_info(oshdrs
, shstrtab_section
);
470 // Now we know exactly where everything goes in the output file.
471 Output_data::layout_complete();
476 // Return whether SEG1 should be before SEG2 in the output file. This
477 // is based entirely on the segment type and flags. When this is
478 // called the segment addresses has normally not yet been set.
481 Layout::segment_precedes(const Output_segment
* seg1
,
482 const Output_segment
* seg2
)
484 elfcpp::Elf_Word type1
= seg1
->type();
485 elfcpp::Elf_Word type2
= seg2
->type();
487 // The single PT_PHDR segment is required to precede any loadable
488 // segment. We simply make it always first.
489 if (type1
== elfcpp::PT_PHDR
)
491 gold_assert(type2
!= elfcpp::PT_PHDR
);
494 if (type2
== elfcpp::PT_PHDR
)
497 // The single PT_INTERP segment is required to precede any loadable
498 // segment. We simply make it always second.
499 if (type1
== elfcpp::PT_INTERP
)
501 gold_assert(type2
!= elfcpp::PT_INTERP
);
504 if (type2
== elfcpp::PT_INTERP
)
507 // We then put PT_LOAD segments before any other segments.
508 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
510 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
513 // We put the PT_TLS segment last, because that is where the dynamic
514 // linker expects to find it (this is just for efficiency; other
515 // positions would also work correctly).
516 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
518 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
521 const elfcpp::Elf_Word flags1
= seg1
->flags();
522 const elfcpp::Elf_Word flags2
= seg2
->flags();
524 // The order of non-PT_LOAD segments is unimportant. We simply sort
525 // by the numeric segment type and flags values. There should not
526 // be more than one segment with the same type and flags.
527 if (type1
!= elfcpp::PT_LOAD
)
530 return type1
< type2
;
531 gold_assert(flags1
!= flags2
);
532 return flags1
< flags2
;
535 // We sort PT_LOAD segments based on the flags. Readonly segments
536 // come before writable segments. Then executable segments come
537 // before non-executable segments. Then the unlikely case of a
538 // non-readable segment comes before the normal case of a readable
539 // segment. If there are multiple segments with the same type and
540 // flags, we require that the address be set, and we sort by
541 // virtual address and then physical address.
542 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
543 return (flags1
& elfcpp::PF_W
) == 0;
544 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
545 return (flags1
& elfcpp::PF_X
) != 0;
546 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
547 return (flags1
& elfcpp::PF_R
) == 0;
549 uint64_t vaddr1
= seg1
->vaddr();
550 uint64_t vaddr2
= seg2
->vaddr();
551 if (vaddr1
!= vaddr2
)
552 return vaddr1
< vaddr2
;
554 uint64_t paddr1
= seg1
->paddr();
555 uint64_t paddr2
= seg2
->paddr();
556 gold_assert(paddr1
!= paddr2
);
557 return paddr1
< paddr2
;
560 // Set the file offsets of all the segments, and all the sections they
561 // contain. They have all been created. LOAD_SEG must be be laid out
562 // first. Return the offset of the data to follow.
565 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
566 unsigned int *pshndx
)
568 // Sort them into the final order.
569 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
570 Layout::Compare_segments());
572 // Find the PT_LOAD segments, and set their addresses and offsets
573 // and their section's addresses and offsets.
574 uint64_t addr
= target
->text_segment_address();
576 bool was_readonly
= false;
577 for (Segment_list::iterator p
= this->segment_list_
.begin();
578 p
!= this->segment_list_
.end();
581 if ((*p
)->type() == elfcpp::PT_LOAD
)
583 if (load_seg
!= NULL
&& load_seg
!= *p
)
587 // If the last segment was readonly, and this one is not,
588 // then skip the address forward one page, maintaining the
589 // same position within the page. This lets us store both
590 // segments overlapping on a single page in the file, but
591 // the loader will put them on different pages in memory.
593 uint64_t orig_addr
= addr
;
594 uint64_t orig_off
= off
;
596 uint64_t aligned_addr
= addr
;
597 uint64_t abi_pagesize
= target
->abi_pagesize();
598 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
600 uint64_t align
= (*p
)->addralign();
602 addr
= align_address(addr
, align
);
604 if ((addr
& (abi_pagesize
- 1)) != 0)
605 addr
= addr
+ abi_pagesize
;
608 unsigned int shndx_hold
= *pshndx
;
609 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
610 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
612 // Now that we know the size of this segment, we may be able
613 // to save a page in memory, at the cost of wasting some
614 // file space, by instead aligning to the start of a new
615 // page. Here we use the real machine page size rather than
616 // the ABI mandated page size.
618 if (aligned_addr
!= addr
)
620 uint64_t common_pagesize
= target
->common_pagesize();
621 uint64_t first_off
= (common_pagesize
623 & (common_pagesize
- 1)));
624 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
627 && ((aligned_addr
& ~ (common_pagesize
- 1))
628 != (new_addr
& ~ (common_pagesize
- 1)))
629 && first_off
+ last_off
<= common_pagesize
)
631 *pshndx
= shndx_hold
;
632 addr
= align_address(aligned_addr
, common_pagesize
);
633 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
634 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
640 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
645 // Handle the non-PT_LOAD segments, setting their offsets from their
646 // section's offsets.
647 for (Segment_list::iterator p
= this->segment_list_
.begin();
648 p
!= this->segment_list_
.end();
651 if ((*p
)->type() != elfcpp::PT_LOAD
)
658 // Set the file offset of all the sections not associated with a
662 Layout::set_section_offsets(off_t off
, unsigned int* pshndx
)
664 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
665 p
!= this->unattached_section_list_
.end();
668 (*p
)->set_out_shndx(*pshndx
);
670 if ((*p
)->offset() != -1)
672 off
= align_address(off
, (*p
)->addralign());
673 (*p
)->set_address(0, off
);
674 off
+= (*p
)->data_size();
679 // Create the symbol table sections.
682 Layout::create_symtab_sections(int size
, const Input_objects
* input_objects
,
683 Symbol_table
* symtab
,
690 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
695 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
702 off
= align_address(off
, align
);
703 off_t startoff
= off
;
705 // Save space for the dummy symbol at the start of the section. We
706 // never bother to write this out--it will just be left as zero.
708 unsigned int local_symbol_index
= 1;
710 // Add STT_SECTION symbols for each Output section which needs one.
711 for (Section_list::iterator p
= this->section_list_
.begin();
712 p
!= this->section_list_
.end();
715 if (!(*p
)->needs_symtab_index())
716 (*p
)->set_symtab_index(-1U);
719 (*p
)->set_symtab_index(local_symbol_index
);
720 ++local_symbol_index
;
725 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
726 p
!= input_objects
->relobj_end();
729 Task_lock_obj
<Object
> tlo(**p
);
730 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
733 off
+= (index
- local_symbol_index
) * symsize
;
734 local_symbol_index
= index
;
737 unsigned int local_symcount
= local_symbol_index
;
738 gold_assert(local_symcount
* symsize
== off
- startoff
);
741 size_t dyn_global_index
;
743 if (this->dynsym_section_
== NULL
)
746 dyn_global_index
= 0;
751 dyn_global_index
= this->dynsym_section_
->info();
752 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
753 dynoff
= this->dynsym_section_
->offset() + locsize
;
754 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
755 gold_assert(dyncount
* symsize
756 == this->dynsym_section_
->data_size() - locsize
);
759 off
= symtab
->finalize(local_symcount
, off
, dynoff
, dyn_global_index
,
760 dyncount
, &this->sympool_
);
762 this->sympool_
.set_string_offsets();
764 const char* symtab_name
= this->namepool_
.add(".symtab", NULL
);
765 Output_section
* osymtab
= this->make_output_section(symtab_name
,
768 this->symtab_section_
= osymtab
;
770 Output_section_data
* pos
= new Output_data_space(off
- startoff
,
772 osymtab
->add_output_section_data(pos
);
774 const char* strtab_name
= this->namepool_
.add(".strtab", NULL
);
775 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
779 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
780 ostrtab
->add_output_section_data(pstr
);
782 osymtab
->set_address(0, startoff
);
783 osymtab
->set_link_section(ostrtab
);
784 osymtab
->set_info(local_symcount
);
785 osymtab
->set_entsize(symsize
);
790 // Create the .shstrtab section, which holds the names of the
791 // sections. At the time this is called, we have created all the
792 // output sections except .shstrtab itself.
795 Layout::create_shstrtab()
797 // FIXME: We don't need to create a .shstrtab section if we are
798 // stripping everything.
800 const char* name
= this->namepool_
.add(".shstrtab", NULL
);
802 this->namepool_
.set_string_offsets();
804 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
806 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
807 os
->add_output_section_data(posd
);
812 // Create the section headers. SIZE is 32 or 64. OFF is the file
815 Output_section_headers
*
816 Layout::create_shdrs(int size
, bool big_endian
, off_t
* poff
)
818 Output_section_headers
* oshdrs
;
819 oshdrs
= new Output_section_headers(size
, big_endian
, this,
820 &this->segment_list_
,
821 &this->unattached_section_list_
,
823 off_t off
= align_address(*poff
, oshdrs
->addralign());
824 oshdrs
->set_address(0, off
);
825 off
+= oshdrs
->data_size();
827 this->special_output_list_
.push_back(oshdrs
);
831 // Create the dynamic symbol table.
834 Layout::create_dynamic_symtab(const Target
* target
, Symbol_table
* symtab
)
836 // Count all the symbols in the dynamic symbol table, and set the
837 // dynamic symbol indexes.
839 // Skip symbol 0, which is always all zeroes.
840 unsigned int index
= 1;
842 // Add STT_SECTION symbols for each Output section which needs one.
843 for (Section_list::iterator p
= this->section_list_
.begin();
844 p
!= this->section_list_
.end();
847 if (!(*p
)->needs_dynsym_index())
848 (*p
)->set_dynsym_index(-1U);
851 (*p
)->set_dynsym_index(index
);
856 // FIXME: Some targets apparently require local symbols in the
857 // dynamic symbol table. Here is where we will have to count them,
858 // and set the dynamic symbol indexes, and add the names to
861 unsigned int local_symcount
= index
;
863 std::vector
<Symbol
*> dynamic_symbols
;
865 // FIXME: We have to tell set_dynsym_indexes whether the
866 // -E/--export-dynamic option was used.
867 index
= symtab
->set_dynsym_indexes(index
, &dynamic_symbols
,
872 const int size
= target
->get_size();
875 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
880 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
886 const char* dynsym_name
= this->namepool_
.add(".dynsym", NULL
);
887 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
891 Output_section_data
* odata
= new Output_data_space(index
* symsize
,
893 dynsym
->add_output_section_data(odata
);
895 dynsym
->set_info(local_symcount
);
896 dynsym
->set_entsize(symsize
);
897 dynsym
->set_addralign(align
);
899 this->dynsym_section_
= dynsym
;
901 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
902 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
903 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
905 const char* dynstr_name
= this->namepool_
.add(".dynstr", NULL
);
906 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
910 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
911 dynstr
->add_output_section_data(strdata
);
913 dynsym
->set_link_section(dynstr
);
914 this->dynamic_section_
->set_link_section(dynstr
);
916 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
917 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
919 // FIXME: We need an option to create a GNU hash table.
921 unsigned char* phash
;
922 unsigned int hashlen
;
923 Dynobj::create_elf_hash_table(target
, dynamic_symbols
, local_symcount
,
926 const char* hash_name
= this->namepool_
.add(".hash", NULL
);
927 Output_section
* hashsec
= this->make_output_section(hash_name
,
931 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
934 hashsec
->add_output_section_data(hashdata
);
936 hashsec
->set_link_section(dynsym
);
937 hashsec
->set_entsize(4);
939 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
942 // Create the .interp section and PT_INTERP segment.
945 Layout::create_interp(const Target
* target
)
947 const char* interp
= this->options_
.dynamic_linker();
950 interp
= target
->dynamic_linker();
951 gold_assert(interp
!= NULL
);
954 size_t len
= strlen(interp
) + 1;
956 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
958 const char* interp_name
= this->namepool_
.add(".interp", NULL
);
959 Output_section
* osec
= this->make_output_section(interp_name
,
960 elfcpp::SHT_PROGBITS
,
962 osec
->add_output_section_data(odata
);
964 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
965 this->segment_list_
.push_back(oseg
);
966 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
969 // Finish the .dynamic section and PT_DYNAMIC segment.
972 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
973 const Symbol_table
* symtab
)
975 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
976 elfcpp::PF_R
| elfcpp::PF_W
);
977 this->segment_list_
.push_back(oseg
);
978 oseg
->add_initial_output_section(this->dynamic_section_
,
979 elfcpp::PF_R
| elfcpp::PF_W
);
981 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
983 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
984 p
!= input_objects
->dynobj_end();
987 // FIXME: Handle --as-needed.
988 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
991 // FIXME: Support --init and --fini.
992 Symbol
* sym
= symtab
->lookup("_init");
993 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_defined_in_dynobj())
994 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
996 sym
= symtab
->lookup("_fini");
997 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_defined_in_dynobj())
998 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1000 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1003 // The mapping of .gnu.linkonce section names to real section names.
1005 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1006 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1008 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1009 MAPPING_INIT("t", ".text"),
1010 MAPPING_INIT("r", ".rodata"),
1011 MAPPING_INIT("d", ".data"),
1012 MAPPING_INIT("b", ".bss"),
1013 MAPPING_INIT("s", ".sdata"),
1014 MAPPING_INIT("sb", ".sbss"),
1015 MAPPING_INIT("s2", ".sdata2"),
1016 MAPPING_INIT("sb2", ".sbss2"),
1017 MAPPING_INIT("wi", ".debug_info"),
1018 MAPPING_INIT("td", ".tdata"),
1019 MAPPING_INIT("tb", ".tbss"),
1020 MAPPING_INIT("lr", ".lrodata"),
1021 MAPPING_INIT("l", ".ldata"),
1022 MAPPING_INIT("lb", ".lbss"),
1026 const int Layout::linkonce_mapping_count
=
1027 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1029 // Return the name of the output section to use for a .gnu.linkonce
1030 // section. This is based on the default ELF linker script of the old
1031 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1032 // to ".text". Set *PLEN to the length of the name. *PLEN is
1033 // initialized to the length of NAME.
1036 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1038 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1042 const Linkonce_mapping
* plm
= linkonce_mapping
;
1043 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1045 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1054 // Choose the output section name to use given an input section name.
1055 // Set *PLEN to the length of the name. *PLEN is initialized to the
1059 Layout::output_section_name(const char* name
, size_t* plen
)
1061 if (Layout::is_linkonce(name
))
1063 // .gnu.linkonce sections are laid out as though they were named
1064 // for the sections are placed into.
1065 return Layout::linkonce_output_name(name
, plen
);
1068 // If the section name has no '.', or only an initial '.', we use
1069 // the name unchanged (i.e., ".text" is unchanged).
1071 // Otherwise, if the section name does not include ".rel", we drop
1072 // the last '.' and everything that follows (i.e., ".text.XXX"
1073 // becomes ".text").
1075 // Otherwise, if the section name has zero or one '.' after the
1076 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1079 // Otherwise, we drop the last '.' and everything that follows
1080 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1082 const char* s
= name
;
1085 const char* sdot
= strchr(s
, '.');
1089 const char* srel
= strstr(s
, ".rel");
1092 *plen
= sdot
- name
;
1096 sdot
= strchr(srel
+ 1, '.');
1099 sdot
= strchr(sdot
+ 1, '.');
1103 *plen
= sdot
- name
;
1107 // Record the signature of a comdat section, and return whether to
1108 // include it in the link. If GROUP is true, this is a regular
1109 // section group. If GROUP is false, this is a group signature
1110 // derived from the name of a linkonce section. We want linkonce
1111 // signatures and group signatures to block each other, but we don't
1112 // want a linkonce signature to block another linkonce signature.
1115 Layout::add_comdat(const char* signature
, bool group
)
1117 std::string
sig(signature
);
1118 std::pair
<Signatures::iterator
, bool> ins(
1119 this->signatures_
.insert(std::make_pair(sig
, group
)));
1123 // This is the first time we've seen this signature.
1127 if (ins
.first
->second
)
1129 // We've already seen a real section group with this signature.
1134 // This is a real section group, and we've already seen a
1135 // linkonce section with tihs signature. Record that we've seen
1136 // a section group, and don't include this section group.
1137 ins
.first
->second
= true;
1142 // We've already seen a linkonce section and this is a linkonce
1143 // section. These don't block each other--this may be the same
1144 // symbol name with different section types.
1149 // Write out data not associated with a section or the symbol table.
1152 Layout::write_data(const Symbol_table
* symtab
, const Target
* target
,
1153 Output_file
* of
) const
1155 const Output_section
* symtab_section
= this->symtab_section_
;
1156 for (Section_list::const_iterator p
= this->section_list_
.begin();
1157 p
!= this->section_list_
.end();
1160 if ((*p
)->needs_symtab_index())
1162 gold_assert(symtab_section
!= NULL
);
1163 unsigned int index
= (*p
)->symtab_index();
1164 gold_assert(index
> 0 && index
!= -1U);
1165 off_t off
= (symtab_section
->offset()
1166 + index
* symtab_section
->entsize());
1167 symtab
->write_section_symbol(target
, *p
, of
, off
);
1171 const Output_section
* dynsym_section
= this->dynsym_section_
;
1172 for (Section_list::const_iterator p
= this->section_list_
.begin();
1173 p
!= this->section_list_
.end();
1176 if ((*p
)->needs_dynsym_index())
1178 gold_assert(dynsym_section
!= NULL
);
1179 unsigned int index
= (*p
)->dynsym_index();
1180 gold_assert(index
> 0 && index
!= -1U);
1181 off_t off
= (dynsym_section
->offset()
1182 + index
* dynsym_section
->entsize());
1183 symtab
->write_section_symbol(target
, *p
, of
, off
);
1187 // Write out the Output_sections. Most won't have anything to
1188 // write, since most of the data will come from input sections which
1189 // are handled elsewhere. But some Output_sections do have
1191 for (Section_list::const_iterator p
= this->section_list_
.begin();
1192 p
!= this->section_list_
.end();
1196 // Write out the Output_data which are not in an Output_section.
1197 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
1198 p
!= this->special_output_list_
.end();
1203 // Write_data_task methods.
1205 // We can always run this task.
1207 Task::Is_runnable_type
1208 Write_data_task::is_runnable(Workqueue
*)
1213 // We need to unlock FINAL_BLOCKER when finished.
1216 Write_data_task::locks(Workqueue
* workqueue
)
1218 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1221 // Run the task--write out the data.
1224 Write_data_task::run(Workqueue
*)
1226 this->layout_
->write_data(this->symtab_
, this->target_
, this->of_
);
1229 // Write_symbols_task methods.
1231 // We can always run this task.
1233 Task::Is_runnable_type
1234 Write_symbols_task::is_runnable(Workqueue
*)
1239 // We need to unlock FINAL_BLOCKER when finished.
1242 Write_symbols_task::locks(Workqueue
* workqueue
)
1244 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1247 // Run the task--write out the symbols.
1250 Write_symbols_task::run(Workqueue
*)
1252 this->symtab_
->write_globals(this->target_
, this->sympool_
, this->dynpool_
,
1256 // Close_task_runner methods.
1258 // Run the task--close the file.
1261 Close_task_runner::run(Workqueue
*)
1266 // Instantiate the templates we need. We could use the configure
1267 // script to restrict this to only the ones for implemented targets.
1271 Layout::layout
<32, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1272 const elfcpp::Shdr
<32, false>& shdr
, off_t
*);
1276 Layout::layout
<32, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1277 const elfcpp::Shdr
<32, true>& shdr
, off_t
*);
1281 Layout::layout
<64, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1282 const elfcpp::Shdr
<64, false>& shdr
, off_t
*);
1286 Layout::layout
<64, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1287 const elfcpp::Shdr
<64, true>& shdr
, off_t
*);
1290 } // End namespace gold.