1 // layout.cc -- lay out output file sections for gold
10 #include "parameters.h"
19 // Layout_task_runner methods.
21 // Lay out the sections. This is called after all the input objects
25 Layout_task_runner::run(Workqueue
* workqueue
)
27 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
30 // Now we know the final size of the output file and we know where
31 // each piece of information goes.
32 Output_file
* of
= new Output_file(this->options_
,
33 this->input_objects_
->target());
36 // Queue up the final set of tasks.
37 gold::queue_final_tasks(this->options_
, this->input_objects_
,
38 this->symtab_
, this->layout_
, workqueue
, of
);
43 Layout::Layout(const General_options
& options
)
44 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
45 section_name_map_(), segment_list_(), section_list_(),
46 unattached_section_list_(), special_output_list_(),
47 tls_segment_(NULL
), symtab_section_(NULL
),
48 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
)
50 // Make space for more than enough segments for a typical file.
51 // This is just for efficiency--it's OK if we wind up needing more.
52 this->segment_list_
.reserve(12);
54 // We expect three unattached Output_data objects: the file header,
55 // the segment headers, and the section headers.
56 this->special_output_list_
.reserve(3);
59 // Hash a key we use to look up an output section mapping.
62 Layout::Hash_key::operator()(const Layout::Key
& k
) const
64 return k
.first
+ k
.second
.first
+ k
.second
.second
;
67 // Whether to include this section in the link.
69 template<int size
, bool big_endian
>
71 Layout::include_section(Object
*, const char*,
72 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
74 // Some section types are never linked. Some are only linked when
75 // doing a relocateable link.
76 switch (shdr
.get_sh_type())
78 case elfcpp::SHT_NULL
:
79 case elfcpp::SHT_SYMTAB
:
80 case elfcpp::SHT_DYNSYM
:
81 case elfcpp::SHT_STRTAB
:
82 case elfcpp::SHT_HASH
:
83 case elfcpp::SHT_DYNAMIC
:
84 case elfcpp::SHT_SYMTAB_SHNDX
:
87 case elfcpp::SHT_RELA
:
89 case elfcpp::SHT_GROUP
:
90 return parameters
->output_is_object();
93 // FIXME: Handle stripping debug sections here.
98 // Return an output section named NAME, or NULL if there is none.
101 Layout::find_output_section(const char* name
) const
103 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
104 p
!= this->section_name_map_
.end();
106 if (strcmp(p
->second
->name(), name
) == 0)
111 // Return an output segment of type TYPE, with segment flags SET set
112 // and segment flags CLEAR clear. Return NULL if there is none.
115 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
116 elfcpp::Elf_Word clear
) const
118 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
119 p
!= this->segment_list_
.end();
121 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
122 && ((*p
)->flags() & set
) == set
123 && ((*p
)->flags() & clear
) == 0)
128 // Return the output section to use for section NAME with type TYPE
129 // and section flags FLAGS.
132 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
133 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
135 // We should ignore some flags.
136 flags
&= ~ (elfcpp::SHF_INFO_LINK
137 | elfcpp::SHF_LINK_ORDER
140 | elfcpp::SHF_STRINGS
);
142 const Key
key(name_key
, std::make_pair(type
, flags
));
143 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
144 std::pair
<Section_name_map::iterator
, bool> ins(
145 this->section_name_map_
.insert(v
));
148 return ins
.first
->second
;
151 // This is the first time we've seen this name/type/flags
153 Output_section
* os
= this->make_output_section(name
, type
, flags
);
154 ins
.first
->second
= os
;
159 // Return the output section to use for input section SHNDX, with name
160 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
161 // offset of this input section without the output section.
163 template<int size
, bool big_endian
>
165 Layout::layout(Relobj
* object
, unsigned int shndx
, const char* name
,
166 const elfcpp::Shdr
<size
, big_endian
>& shdr
, off_t
* off
)
168 if (!this->include_section(object
, name
, shdr
))
171 // If we are not doing a relocateable link, choose the name to use
172 // for the output section.
173 size_t len
= strlen(name
);
174 if (!parameters
->output_is_object())
175 name
= Layout::output_section_name(name
, &len
);
177 // FIXME: Handle SHF_OS_NONCONFORMING here.
179 // Canonicalize the section name.
180 Stringpool::Key name_key
;
181 name
= this->namepool_
.add(name
, len
, &name_key
);
183 // Find the output section. The output section is selected based on
184 // the section name, type, and flags.
185 Output_section
* os
= this->get_output_section(name
, name_key
,
187 shdr
.get_sh_flags());
189 // FIXME: Handle SHF_LINK_ORDER somewhere.
191 *off
= os
->add_input_section(object
, shndx
, name
, shdr
);
196 // Add POSD to an output section using NAME, TYPE, and FLAGS.
199 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
200 elfcpp::Elf_Xword flags
,
201 Output_section_data
* posd
)
203 // Canonicalize the name.
204 Stringpool::Key name_key
;
205 name
= this->namepool_
.add(name
, &name_key
);
207 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
208 os
->add_output_section_data(posd
);
211 // Map section flags to segment flags.
214 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
216 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
217 if ((flags
& elfcpp::SHF_WRITE
) != 0)
219 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
224 // Make a new Output_section, and attach it to segments as
228 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
229 elfcpp::Elf_Xword flags
)
231 Output_section
* os
= new Output_section(name
, type
, flags
);
232 this->section_list_
.push_back(os
);
234 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
235 this->unattached_section_list_
.push_back(os
);
238 // This output section goes into a PT_LOAD segment.
240 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
242 // The only thing we really care about for PT_LOAD segments is
243 // whether or not they are writable, so that is how we search
244 // for them. People who need segments sorted on some other
245 // basis will have to wait until we implement a mechanism for
246 // them to describe the segments they want.
248 Segment_list::const_iterator p
;
249 for (p
= this->segment_list_
.begin();
250 p
!= this->segment_list_
.end();
253 if ((*p
)->type() == elfcpp::PT_LOAD
254 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
256 (*p
)->add_output_section(os
, seg_flags
);
261 if (p
== this->segment_list_
.end())
263 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
265 this->segment_list_
.push_back(oseg
);
266 oseg
->add_output_section(os
, seg_flags
);
269 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
271 if (type
== elfcpp::SHT_NOTE
)
273 // See if we already have an equivalent PT_NOTE segment.
274 for (p
= this->segment_list_
.begin();
275 p
!= segment_list_
.end();
278 if ((*p
)->type() == elfcpp::PT_NOTE
279 && (((*p
)->flags() & elfcpp::PF_W
)
280 == (seg_flags
& elfcpp::PF_W
)))
282 (*p
)->add_output_section(os
, seg_flags
);
287 if (p
== this->segment_list_
.end())
289 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
291 this->segment_list_
.push_back(oseg
);
292 oseg
->add_output_section(os
, seg_flags
);
296 // If we see a loadable SHF_TLS section, we create a PT_TLS
297 // segment. There can only be one such segment.
298 if ((flags
& elfcpp::SHF_TLS
) != 0)
300 if (this->tls_segment_
== NULL
)
302 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
304 this->segment_list_
.push_back(this->tls_segment_
);
306 this->tls_segment_
->add_output_section(os
, seg_flags
);
313 // Create the dynamic sections which are needed before we read the
317 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
318 Symbol_table
* symtab
)
320 if (!input_objects
->any_dynamic())
323 const char* dynamic_name
= this->namepool_
.add(".dynamic", NULL
);
324 this->dynamic_section_
= this->make_output_section(dynamic_name
,
327 | elfcpp::SHF_WRITE
));
329 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC", NULL
,
330 this->dynamic_section_
, 0, 0,
331 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
332 elfcpp::STV_HIDDEN
, 0, false, false);
334 this->dynamic_data_
= new Output_data_dynamic(input_objects
->target(),
337 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
340 // Find the first read-only PT_LOAD segment, creating one if
344 Layout::find_first_load_seg()
346 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
347 p
!= this->segment_list_
.end();
350 if ((*p
)->type() == elfcpp::PT_LOAD
351 && ((*p
)->flags() & elfcpp::PF_R
) != 0
352 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
356 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
357 this->segment_list_
.push_back(load_seg
);
361 // Finalize the layout. When this is called, we have created all the
362 // output sections and all the output segments which are based on
363 // input sections. We have several things to do, and we have to do
364 // them in the right order, so that we get the right results correctly
367 // 1) Finalize the list of output segments and create the segment
370 // 2) Finalize the dynamic symbol table and associated sections.
372 // 3) Determine the final file offset of all the output segments.
374 // 4) Determine the final file offset of all the SHF_ALLOC output
377 // 5) Create the symbol table sections and the section name table
380 // 6) Finalize the symbol table: set symbol values to their final
381 // value and make a final determination of which symbols are going
382 // into the output symbol table.
384 // 7) Create the section table header.
386 // 8) Determine the final file offset of all the output sections which
387 // are not SHF_ALLOC, including the section table header.
389 // 9) Finalize the ELF file header.
391 // This function returns the size of the output file.
394 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
)
396 Target
* const target
= input_objects
->target();
397 const int size
= target
->get_size();
399 target
->finalize_sections(this);
401 Output_segment
* phdr_seg
= NULL
;
402 if (input_objects
->any_dynamic())
404 // There was a dynamic object in the link. We need to create
405 // some information for the dynamic linker.
407 // Create the PT_PHDR segment which will hold the program
409 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
410 this->segment_list_
.push_back(phdr_seg
);
412 // Create the dynamic symbol table, including the hash table.
413 Output_section
* dynstr
;
414 std::vector
<Symbol
*> dynamic_symbols
;
415 unsigned int local_dynamic_count
;
417 this->create_dynamic_symtab(target
, symtab
, &dynstr
,
418 &local_dynamic_count
, &dynamic_symbols
,
421 // Create the .interp section to hold the name of the
422 // interpreter, and put it in a PT_INTERP segment.
423 this->create_interp(target
);
425 // Finish the .dynamic section to hold the dynamic data, and put
426 // it in a PT_DYNAMIC segment.
427 this->finish_dynamic_section(input_objects
, symtab
);
429 // We should have added everything we need to the dynamic string
431 this->dynpool_
.set_string_offsets();
433 // Create the version sections. We can't do this until the
434 // dynamic string table is complete.
435 this->create_version_sections(target
, &versions
, local_dynamic_count
,
436 dynamic_symbols
, dynstr
);
439 // FIXME: Handle PT_GNU_STACK.
441 Output_segment
* load_seg
= this->find_first_load_seg();
443 // Lay out the segment headers.
444 bool big_endian
= target
->is_big_endian();
445 Output_segment_headers
* segment_headers
;
446 segment_headers
= new Output_segment_headers(size
, big_endian
,
447 this->segment_list_
);
448 load_seg
->add_initial_output_data(segment_headers
);
449 this->special_output_list_
.push_back(segment_headers
);
450 if (phdr_seg
!= NULL
)
451 phdr_seg
->add_initial_output_data(segment_headers
);
453 // Lay out the file header.
454 Output_file_header
* file_header
;
455 file_header
= new Output_file_header(size
,
460 load_seg
->add_initial_output_data(file_header
);
461 this->special_output_list_
.push_back(file_header
);
463 // We set the output section indexes in set_segment_offsets and
464 // set_section_offsets.
465 unsigned int shndx
= 1;
467 // Set the file offsets of all the segments, and all the sections
469 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
471 // Create the symbol table sections.
472 this->create_symtab_sections(size
, input_objects
, symtab
, &off
);
474 // Create the .shstrtab section.
475 Output_section
* shstrtab_section
= this->create_shstrtab();
477 // Set the file offsets of all the sections not associated with
479 off
= this->set_section_offsets(off
, &shndx
);
481 // Create the section table header.
482 Output_section_headers
* oshdrs
= this->create_shdrs(size
, big_endian
, &off
);
484 file_header
->set_section_info(oshdrs
, shstrtab_section
);
486 // Now we know exactly where everything goes in the output file.
487 Output_data::layout_complete();
492 // Return whether SEG1 should be before SEG2 in the output file. This
493 // is based entirely on the segment type and flags. When this is
494 // called the segment addresses has normally not yet been set.
497 Layout::segment_precedes(const Output_segment
* seg1
,
498 const Output_segment
* seg2
)
500 elfcpp::Elf_Word type1
= seg1
->type();
501 elfcpp::Elf_Word type2
= seg2
->type();
503 // The single PT_PHDR segment is required to precede any loadable
504 // segment. We simply make it always first.
505 if (type1
== elfcpp::PT_PHDR
)
507 gold_assert(type2
!= elfcpp::PT_PHDR
);
510 if (type2
== elfcpp::PT_PHDR
)
513 // The single PT_INTERP segment is required to precede any loadable
514 // segment. We simply make it always second.
515 if (type1
== elfcpp::PT_INTERP
)
517 gold_assert(type2
!= elfcpp::PT_INTERP
);
520 if (type2
== elfcpp::PT_INTERP
)
523 // We then put PT_LOAD segments before any other segments.
524 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
526 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
529 // We put the PT_TLS segment last, because that is where the dynamic
530 // linker expects to find it (this is just for efficiency; other
531 // positions would also work correctly).
532 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
534 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
537 const elfcpp::Elf_Word flags1
= seg1
->flags();
538 const elfcpp::Elf_Word flags2
= seg2
->flags();
540 // The order of non-PT_LOAD segments is unimportant. We simply sort
541 // by the numeric segment type and flags values. There should not
542 // be more than one segment with the same type and flags.
543 if (type1
!= elfcpp::PT_LOAD
)
546 return type1
< type2
;
547 gold_assert(flags1
!= flags2
);
548 return flags1
< flags2
;
551 // We sort PT_LOAD segments based on the flags. Readonly segments
552 // come before writable segments. Then executable segments come
553 // before non-executable segments. Then the unlikely case of a
554 // non-readable segment comes before the normal case of a readable
555 // segment. If there are multiple segments with the same type and
556 // flags, we require that the address be set, and we sort by
557 // virtual address and then physical address.
558 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
559 return (flags1
& elfcpp::PF_W
) == 0;
560 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
561 return (flags1
& elfcpp::PF_X
) != 0;
562 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
563 return (flags1
& elfcpp::PF_R
) == 0;
565 uint64_t vaddr1
= seg1
->vaddr();
566 uint64_t vaddr2
= seg2
->vaddr();
567 if (vaddr1
!= vaddr2
)
568 return vaddr1
< vaddr2
;
570 uint64_t paddr1
= seg1
->paddr();
571 uint64_t paddr2
= seg2
->paddr();
572 gold_assert(paddr1
!= paddr2
);
573 return paddr1
< paddr2
;
576 // Set the file offsets of all the segments, and all the sections they
577 // contain. They have all been created. LOAD_SEG must be be laid out
578 // first. Return the offset of the data to follow.
581 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
582 unsigned int *pshndx
)
584 // Sort them into the final order.
585 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
586 Layout::Compare_segments());
588 // Find the PT_LOAD segments, and set their addresses and offsets
589 // and their section's addresses and offsets.
590 uint64_t addr
= target
->text_segment_address();
592 bool was_readonly
= false;
593 for (Segment_list::iterator p
= this->segment_list_
.begin();
594 p
!= this->segment_list_
.end();
597 if ((*p
)->type() == elfcpp::PT_LOAD
)
599 if (load_seg
!= NULL
&& load_seg
!= *p
)
603 // If the last segment was readonly, and this one is not,
604 // then skip the address forward one page, maintaining the
605 // same position within the page. This lets us store both
606 // segments overlapping on a single page in the file, but
607 // the loader will put them on different pages in memory.
609 uint64_t orig_addr
= addr
;
610 uint64_t orig_off
= off
;
612 uint64_t aligned_addr
= addr
;
613 uint64_t abi_pagesize
= target
->abi_pagesize();
615 // FIXME: This should depend on the -n and -N options.
616 (*p
)->set_minimum_addralign(target
->common_pagesize());
618 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
620 uint64_t align
= (*p
)->addralign();
622 addr
= align_address(addr
, align
);
624 if ((addr
& (abi_pagesize
- 1)) != 0)
625 addr
= addr
+ abi_pagesize
;
628 unsigned int shndx_hold
= *pshndx
;
629 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
630 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
632 // Now that we know the size of this segment, we may be able
633 // to save a page in memory, at the cost of wasting some
634 // file space, by instead aligning to the start of a new
635 // page. Here we use the real machine page size rather than
636 // the ABI mandated page size.
638 if (aligned_addr
!= addr
)
640 uint64_t common_pagesize
= target
->common_pagesize();
641 uint64_t first_off
= (common_pagesize
643 & (common_pagesize
- 1)));
644 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
647 && ((aligned_addr
& ~ (common_pagesize
- 1))
648 != (new_addr
& ~ (common_pagesize
- 1)))
649 && first_off
+ last_off
<= common_pagesize
)
651 *pshndx
= shndx_hold
;
652 addr
= align_address(aligned_addr
, common_pagesize
);
653 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
654 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
660 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
665 // Handle the non-PT_LOAD segments, setting their offsets from their
666 // section's offsets.
667 for (Segment_list::iterator p
= this->segment_list_
.begin();
668 p
!= this->segment_list_
.end();
671 if ((*p
)->type() != elfcpp::PT_LOAD
)
678 // Set the file offset of all the sections not associated with a
682 Layout::set_section_offsets(off_t off
, unsigned int* pshndx
)
684 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
685 p
!= this->unattached_section_list_
.end();
688 (*p
)->set_out_shndx(*pshndx
);
690 if ((*p
)->offset() != -1)
692 off
= align_address(off
, (*p
)->addralign());
693 (*p
)->set_address(0, off
);
694 off
+= (*p
)->data_size();
699 // Create the symbol table sections. Here we also set the final
700 // values of the symbols. At this point all the loadable sections are
704 Layout::create_symtab_sections(int size
, const Input_objects
* input_objects
,
705 Symbol_table
* symtab
,
712 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
717 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
724 off
= align_address(off
, align
);
725 off_t startoff
= off
;
727 // Save space for the dummy symbol at the start of the section. We
728 // never bother to write this out--it will just be left as zero.
730 unsigned int local_symbol_index
= 1;
732 // Add STT_SECTION symbols for each Output section which needs one.
733 for (Section_list::iterator p
= this->section_list_
.begin();
734 p
!= this->section_list_
.end();
737 if (!(*p
)->needs_symtab_index())
738 (*p
)->set_symtab_index(-1U);
741 (*p
)->set_symtab_index(local_symbol_index
);
742 ++local_symbol_index
;
747 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
748 p
!= input_objects
->relobj_end();
751 Task_lock_obj
<Object
> tlo(**p
);
752 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
755 off
+= (index
- local_symbol_index
) * symsize
;
756 local_symbol_index
= index
;
759 unsigned int local_symcount
= local_symbol_index
;
760 gold_assert(local_symcount
* symsize
== off
- startoff
);
763 size_t dyn_global_index
;
765 if (this->dynsym_section_
== NULL
)
768 dyn_global_index
= 0;
773 dyn_global_index
= this->dynsym_section_
->info();
774 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
775 dynoff
= this->dynsym_section_
->offset() + locsize
;
776 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
777 gold_assert(dyncount
* symsize
778 == this->dynsym_section_
->data_size() - locsize
);
781 off
= symtab
->finalize(local_symcount
, off
, dynoff
, dyn_global_index
,
782 dyncount
, &this->sympool_
);
784 this->sympool_
.set_string_offsets();
786 const char* symtab_name
= this->namepool_
.add(".symtab", NULL
);
787 Output_section
* osymtab
= this->make_output_section(symtab_name
,
790 this->symtab_section_
= osymtab
;
792 Output_section_data
* pos
= new Output_data_space(off
- startoff
,
794 osymtab
->add_output_section_data(pos
);
796 const char* strtab_name
= this->namepool_
.add(".strtab", NULL
);
797 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
801 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
802 ostrtab
->add_output_section_data(pstr
);
804 osymtab
->set_address(0, startoff
);
805 osymtab
->set_link_section(ostrtab
);
806 osymtab
->set_info(local_symcount
);
807 osymtab
->set_entsize(symsize
);
812 // Create the .shstrtab section, which holds the names of the
813 // sections. At the time this is called, we have created all the
814 // output sections except .shstrtab itself.
817 Layout::create_shstrtab()
819 // FIXME: We don't need to create a .shstrtab section if we are
820 // stripping everything.
822 const char* name
= this->namepool_
.add(".shstrtab", NULL
);
824 this->namepool_
.set_string_offsets();
826 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
828 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
829 os
->add_output_section_data(posd
);
834 // Create the section headers. SIZE is 32 or 64. OFF is the file
837 Output_section_headers
*
838 Layout::create_shdrs(int size
, bool big_endian
, off_t
* poff
)
840 Output_section_headers
* oshdrs
;
841 oshdrs
= new Output_section_headers(size
, big_endian
, this,
842 &this->segment_list_
,
843 &this->unattached_section_list_
,
845 off_t off
= align_address(*poff
, oshdrs
->addralign());
846 oshdrs
->set_address(0, off
);
847 off
+= oshdrs
->data_size();
849 this->special_output_list_
.push_back(oshdrs
);
853 // Create the dynamic symbol table.
856 Layout::create_dynamic_symtab(const Target
* target
, Symbol_table
* symtab
,
857 Output_section
**pdynstr
,
858 unsigned int* plocal_dynamic_count
,
859 std::vector
<Symbol
*>* pdynamic_symbols
,
862 // Count all the symbols in the dynamic symbol table, and set the
863 // dynamic symbol indexes.
865 // Skip symbol 0, which is always all zeroes.
866 unsigned int index
= 1;
868 // Add STT_SECTION symbols for each Output section which needs one.
869 for (Section_list::iterator p
= this->section_list_
.begin();
870 p
!= this->section_list_
.end();
873 if (!(*p
)->needs_dynsym_index())
874 (*p
)->set_dynsym_index(-1U);
877 (*p
)->set_dynsym_index(index
);
882 // FIXME: Some targets apparently require local symbols in the
883 // dynamic symbol table. Here is where we will have to count them,
884 // and set the dynamic symbol indexes, and add the names to
887 unsigned int local_symcount
= index
;
888 *plocal_dynamic_count
= local_symcount
;
890 // FIXME: We have to tell set_dynsym_indexes whether the
891 // -E/--export-dynamic option was used.
892 index
= symtab
->set_dynsym_indexes(&this->options_
, target
, index
,
893 pdynamic_symbols
, &this->dynpool_
,
898 const int size
= target
->get_size();
901 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
906 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
912 // Create the dynamic symbol table section.
914 const char* dynsym_name
= this->namepool_
.add(".dynsym", NULL
);
915 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
919 Output_section_data
* odata
= new Output_data_space(index
* symsize
,
921 dynsym
->add_output_section_data(odata
);
923 dynsym
->set_info(local_symcount
);
924 dynsym
->set_entsize(symsize
);
925 dynsym
->set_addralign(align
);
927 this->dynsym_section_
= dynsym
;
929 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
930 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
931 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
933 // Create the dynamic string table section.
935 const char* dynstr_name
= this->namepool_
.add(".dynstr", NULL
);
936 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
940 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
941 dynstr
->add_output_section_data(strdata
);
943 dynsym
->set_link_section(dynstr
);
944 this->dynamic_section_
->set_link_section(dynstr
);
946 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
947 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
951 // Create the hash tables.
953 // FIXME: We need an option to create a GNU hash table.
955 unsigned char* phash
;
956 unsigned int hashlen
;
957 Dynobj::create_elf_hash_table(target
, *pdynamic_symbols
, local_symcount
,
960 const char* hash_name
= this->namepool_
.add(".hash", NULL
);
961 Output_section
* hashsec
= this->make_output_section(hash_name
,
965 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
968 hashsec
->add_output_section_data(hashdata
);
970 hashsec
->set_link_section(dynsym
);
971 hashsec
->set_entsize(4);
973 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
976 // Create the version sections.
979 Layout::create_version_sections(const Target
* target
, const Versions
* versions
,
980 unsigned int local_symcount
,
981 const std::vector
<Symbol
*>& dynamic_symbols
,
982 const Output_section
* dynstr
)
984 if (!versions
->any_defs() && !versions
->any_needs())
987 if (target
->get_size() == 32)
989 if (target
->is_big_endian())
991 #ifdef HAVE_TARGET_32_BIG
992 this->sized_create_version_sections
993 SELECT_SIZE_ENDIAN_NAME(32, true)(
994 versions
, local_symcount
, dynamic_symbols
, dynstr
995 SELECT_SIZE_ENDIAN(32, true));
1002 #ifdef HAVE_TARGET_32_LITTLE
1003 this->sized_create_version_sections
1004 SELECT_SIZE_ENDIAN_NAME(32, false)(
1005 versions
, local_symcount
, dynamic_symbols
, dynstr
1006 SELECT_SIZE_ENDIAN(32, false));
1012 else if (target
->get_size() == 64)
1014 if (target
->is_big_endian())
1016 #ifdef HAVE_TARGET_64_BIG
1017 this->sized_create_version_sections
1018 SELECT_SIZE_ENDIAN_NAME(64, true)(
1019 versions
, local_symcount
, dynamic_symbols
, dynstr
1020 SELECT_SIZE_ENDIAN(64, true));
1027 #ifdef HAVE_TARGET_64_LITTLE
1028 this->sized_create_version_sections
1029 SELECT_SIZE_ENDIAN_NAME(64, false)(
1030 versions
, local_symcount
, dynamic_symbols
, dynstr
1031 SELECT_SIZE_ENDIAN(64, false));
1041 // Create the version sections, sized version.
1043 template<int size
, bool big_endian
>
1045 Layout::sized_create_version_sections(
1046 const Versions
* versions
,
1047 unsigned int local_symcount
,
1048 const std::vector
<Symbol
*>& dynamic_symbols
,
1049 const Output_section
* dynstr
1052 const char* vname
= this->namepool_
.add(".gnu.version", NULL
);
1053 Output_section
* vsec
= this->make_output_section(vname
,
1054 elfcpp::SHT_GNU_versym
,
1057 unsigned char* vbuf
;
1059 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1060 &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1061 SELECT_SIZE_ENDIAN(size
, big_endian
));
1063 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1065 vsec
->add_output_section_data(vdata
);
1066 vsec
->set_entsize(2);
1067 vsec
->set_link_section(this->dynsym_section_
);
1069 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1070 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1072 if (versions
->any_defs())
1074 const char* vdname
= this->namepool_
.add(".gnu.version_d", NULL
);
1075 Output_section
*vdsec
;
1076 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1079 unsigned char* vdbuf
;
1080 unsigned int vdsize
;
1081 unsigned int vdentries
;
1082 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1083 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1084 SELECT_SIZE_ENDIAN(size
, big_endian
));
1086 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1090 vdsec
->add_output_section_data(vddata
);
1091 vdsec
->set_link_section(dynstr
);
1092 vdsec
->set_info(vdentries
);
1094 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1095 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1098 if (versions
->any_needs())
1100 const char* vnname
= this->namepool_
.add(".gnu.version_r", NULL
);
1101 Output_section
* vnsec
;
1102 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1105 unsigned char* vnbuf
;
1106 unsigned int vnsize
;
1107 unsigned int vnentries
;
1108 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1109 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1110 SELECT_SIZE_ENDIAN(size
, big_endian
));
1112 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1116 vnsec
->add_output_section_data(vndata
);
1117 vnsec
->set_link_section(dynstr
);
1118 vnsec
->set_info(vnentries
);
1120 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1121 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1125 // Create the .interp section and PT_INTERP segment.
1128 Layout::create_interp(const Target
* target
)
1130 const char* interp
= this->options_
.dynamic_linker();
1133 interp
= target
->dynamic_linker();
1134 gold_assert(interp
!= NULL
);
1137 size_t len
= strlen(interp
) + 1;
1139 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1141 const char* interp_name
= this->namepool_
.add(".interp", NULL
);
1142 Output_section
* osec
= this->make_output_section(interp_name
,
1143 elfcpp::SHT_PROGBITS
,
1145 osec
->add_output_section_data(odata
);
1147 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1148 this->segment_list_
.push_back(oseg
);
1149 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1152 // Finish the .dynamic section and PT_DYNAMIC segment.
1155 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1156 const Symbol_table
* symtab
)
1158 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1159 elfcpp::PF_R
| elfcpp::PF_W
);
1160 this->segment_list_
.push_back(oseg
);
1161 oseg
->add_initial_output_section(this->dynamic_section_
,
1162 elfcpp::PF_R
| elfcpp::PF_W
);
1164 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1166 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1167 p
!= input_objects
->dynobj_end();
1170 // FIXME: Handle --as-needed.
1171 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1174 // FIXME: Support --init and --fini.
1175 Symbol
* sym
= symtab
->lookup("_init");
1176 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1177 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1179 sym
= symtab
->lookup("_fini");
1180 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1181 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1183 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1185 // Add a DT_RPATH entry if needed.
1186 const General_options::Dir_list
& rpath(this->options_
.rpath());
1189 std::string rpath_val
;
1190 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1194 if (rpath_val
.empty())
1198 // Eliminate duplicates.
1199 General_options::Dir_list::const_iterator q
;
1200 for (q
= rpath
.begin(); q
!= p
; ++q
)
1201 if (strcmp(*q
, *p
) == 0)
1211 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1215 // The mapping of .gnu.linkonce section names to real section names.
1217 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1218 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1220 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1221 MAPPING_INIT("t", ".text"),
1222 MAPPING_INIT("r", ".rodata"),
1223 MAPPING_INIT("d", ".data"),
1224 MAPPING_INIT("b", ".bss"),
1225 MAPPING_INIT("s", ".sdata"),
1226 MAPPING_INIT("sb", ".sbss"),
1227 MAPPING_INIT("s2", ".sdata2"),
1228 MAPPING_INIT("sb2", ".sbss2"),
1229 MAPPING_INIT("wi", ".debug_info"),
1230 MAPPING_INIT("td", ".tdata"),
1231 MAPPING_INIT("tb", ".tbss"),
1232 MAPPING_INIT("lr", ".lrodata"),
1233 MAPPING_INIT("l", ".ldata"),
1234 MAPPING_INIT("lb", ".lbss"),
1238 const int Layout::linkonce_mapping_count
=
1239 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1241 // Return the name of the output section to use for a .gnu.linkonce
1242 // section. This is based on the default ELF linker script of the old
1243 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1244 // to ".text". Set *PLEN to the length of the name. *PLEN is
1245 // initialized to the length of NAME.
1248 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1250 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1254 const Linkonce_mapping
* plm
= linkonce_mapping
;
1255 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1257 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1266 // Choose the output section name to use given an input section name.
1267 // Set *PLEN to the length of the name. *PLEN is initialized to the
1271 Layout::output_section_name(const char* name
, size_t* plen
)
1273 if (Layout::is_linkonce(name
))
1275 // .gnu.linkonce sections are laid out as though they were named
1276 // for the sections are placed into.
1277 return Layout::linkonce_output_name(name
, plen
);
1280 // If the section name has no '.', or only an initial '.', we use
1281 // the name unchanged (i.e., ".text" is unchanged).
1283 // Otherwise, if the section name does not include ".rel", we drop
1284 // the last '.' and everything that follows (i.e., ".text.XXX"
1285 // becomes ".text").
1287 // Otherwise, if the section name has zero or one '.' after the
1288 // ".rel", we use the name unchanged (i.e., ".rel.text" is
1291 // Otherwise, we drop the last '.' and everything that follows
1292 // (i.e., ".rel.text.XXX" becomes ".rel.text").
1294 const char* s
= name
;
1297 const char* sdot
= strchr(s
, '.');
1301 const char* srel
= strstr(s
, ".rel");
1304 *plen
= sdot
- name
;
1308 sdot
= strchr(srel
+ 1, '.');
1311 sdot
= strchr(sdot
+ 1, '.');
1315 *plen
= sdot
- name
;
1319 // Record the signature of a comdat section, and return whether to
1320 // include it in the link. If GROUP is true, this is a regular
1321 // section group. If GROUP is false, this is a group signature
1322 // derived from the name of a linkonce section. We want linkonce
1323 // signatures and group signatures to block each other, but we don't
1324 // want a linkonce signature to block another linkonce signature.
1327 Layout::add_comdat(const char* signature
, bool group
)
1329 std::string
sig(signature
);
1330 std::pair
<Signatures::iterator
, bool> ins(
1331 this->signatures_
.insert(std::make_pair(sig
, group
)));
1335 // This is the first time we've seen this signature.
1339 if (ins
.first
->second
)
1341 // We've already seen a real section group with this signature.
1346 // This is a real section group, and we've already seen a
1347 // linkonce section with tihs signature. Record that we've seen
1348 // a section group, and don't include this section group.
1349 ins
.first
->second
= true;
1354 // We've already seen a linkonce section and this is a linkonce
1355 // section. These don't block each other--this may be the same
1356 // symbol name with different section types.
1361 // Write out data not associated with a section or the symbol table.
1364 Layout::write_data(const Symbol_table
* symtab
, const Target
* target
,
1365 Output_file
* of
) const
1367 const Output_section
* symtab_section
= this->symtab_section_
;
1368 for (Section_list::const_iterator p
= this->section_list_
.begin();
1369 p
!= this->section_list_
.end();
1372 if ((*p
)->needs_symtab_index())
1374 gold_assert(symtab_section
!= NULL
);
1375 unsigned int index
= (*p
)->symtab_index();
1376 gold_assert(index
> 0 && index
!= -1U);
1377 off_t off
= (symtab_section
->offset()
1378 + index
* symtab_section
->entsize());
1379 symtab
->write_section_symbol(target
, *p
, of
, off
);
1383 const Output_section
* dynsym_section
= this->dynsym_section_
;
1384 for (Section_list::const_iterator p
= this->section_list_
.begin();
1385 p
!= this->section_list_
.end();
1388 if ((*p
)->needs_dynsym_index())
1390 gold_assert(dynsym_section
!= NULL
);
1391 unsigned int index
= (*p
)->dynsym_index();
1392 gold_assert(index
> 0 && index
!= -1U);
1393 off_t off
= (dynsym_section
->offset()
1394 + index
* dynsym_section
->entsize());
1395 symtab
->write_section_symbol(target
, *p
, of
, off
);
1399 // Write out the Output_sections. Most won't have anything to
1400 // write, since most of the data will come from input sections which
1401 // are handled elsewhere. But some Output_sections do have
1403 for (Section_list::const_iterator p
= this->section_list_
.begin();
1404 p
!= this->section_list_
.end();
1408 // Write out the Output_data which are not in an Output_section.
1409 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
1410 p
!= this->special_output_list_
.end();
1415 // Write_data_task methods.
1417 // We can always run this task.
1419 Task::Is_runnable_type
1420 Write_data_task::is_runnable(Workqueue
*)
1425 // We need to unlock FINAL_BLOCKER when finished.
1428 Write_data_task::locks(Workqueue
* workqueue
)
1430 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1433 // Run the task--write out the data.
1436 Write_data_task::run(Workqueue
*)
1438 this->layout_
->write_data(this->symtab_
, this->target_
, this->of_
);
1441 // Write_symbols_task methods.
1443 // We can always run this task.
1445 Task::Is_runnable_type
1446 Write_symbols_task::is_runnable(Workqueue
*)
1451 // We need to unlock FINAL_BLOCKER when finished.
1454 Write_symbols_task::locks(Workqueue
* workqueue
)
1456 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1459 // Run the task--write out the symbols.
1462 Write_symbols_task::run(Workqueue
*)
1464 this->symtab_
->write_globals(this->target_
, this->sympool_
, this->dynpool_
,
1468 // Close_task_runner methods.
1470 // Run the task--close the file.
1473 Close_task_runner::run(Workqueue
*)
1478 // Instantiate the templates we need. We could use the configure
1479 // script to restrict this to only the ones for implemented targets.
1481 #ifdef HAVE_TARGET_32_LITTLE
1484 Layout::layout
<32, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1485 const elfcpp::Shdr
<32, false>& shdr
, off_t
*);
1488 #ifdef HAVE_TARGET_32_BIG
1491 Layout::layout
<32, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1492 const elfcpp::Shdr
<32, true>& shdr
, off_t
*);
1495 #ifdef HAVE_TARGET_64_LITTLE
1498 Layout::layout
<64, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1499 const elfcpp::Shdr
<64, false>& shdr
, off_t
*);
1502 #ifdef HAVE_TARGET_64_BIG
1505 Layout::layout
<64, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1506 const elfcpp::Shdr
<64, true>& shdr
, off_t
*);
1510 } // End namespace gold.