1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
30 #include "parameters.h"
35 #include "compressed_output.h"
41 // Layout_task_runner methods.
43 // Lay out the sections. This is called after all the input objects
47 Layout_task_runner::run(Workqueue
* workqueue
)
49 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
52 // Now we know the final size of the output file and we know where
53 // each piece of information goes.
54 Output_file
* of
= new Output_file(this->options_
,
55 this->input_objects_
->target());
58 // Queue up the final set of tasks.
59 gold::queue_final_tasks(this->options_
, this->input_objects_
,
60 this->symtab_
, this->layout_
, workqueue
, of
);
65 Layout::Layout(const General_options
& options
)
66 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
67 section_name_map_(), segment_list_(), section_list_(),
68 unattached_section_list_(), special_output_list_(),
69 section_headers_(NULL
), tls_segment_(NULL
), symtab_section_(NULL
),
70 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
),
71 eh_frame_section_(NULL
), output_file_size_(-1),
72 input_requires_executable_stack_(false),
73 input_with_gnu_stack_note_(false),
74 input_without_gnu_stack_note_(false)
76 // Make space for more than enough segments for a typical file.
77 // This is just for efficiency--it's OK if we wind up needing more.
78 this->segment_list_
.reserve(12);
80 // We expect two unattached Output_data objects: the file header and
81 // the segment headers.
82 this->special_output_list_
.reserve(2);
85 // Hash a key we use to look up an output section mapping.
88 Layout::Hash_key::operator()(const Layout::Key
& k
) const
90 return k
.first
+ k
.second
.first
+ k
.second
.second
;
93 // Return whether PREFIX is a prefix of STR.
96 is_prefix_of(const char* prefix
, const char* str
)
98 return strncmp(prefix
, str
, strlen(prefix
)) == 0;
101 // Returns whether the given section is in the list of
102 // debug-sections-used-by-some-version-of-gdb. Currently,
103 // we've checked versions of gdb up to and including 6.7.1.
105 static const char* gdb_sections
[] =
107 // ".debug_aranges", // not used by gdb as of 6.7.1
113 // ".debug_pubnames", // not used by gdb as of 6.7.1
119 is_gdb_debug_section(const char* str
)
121 // We can do this faster: binary search or a hashtable. But why bother?
122 for (size_t i
= 0; i
< sizeof(gdb_sections
)/sizeof(*gdb_sections
); ++i
)
123 if (strcmp(str
, gdb_sections
[i
]) == 0)
128 // Whether to include this section in the link.
130 template<int size
, bool big_endian
>
132 Layout::include_section(Sized_relobj
<size
, big_endian
>*, const char* name
,
133 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
135 // Some section types are never linked. Some are only linked when
136 // doing a relocateable link.
137 switch (shdr
.get_sh_type())
139 case elfcpp::SHT_NULL
:
140 case elfcpp::SHT_SYMTAB
:
141 case elfcpp::SHT_DYNSYM
:
142 case elfcpp::SHT_STRTAB
:
143 case elfcpp::SHT_HASH
:
144 case elfcpp::SHT_DYNAMIC
:
145 case elfcpp::SHT_SYMTAB_SHNDX
:
148 case elfcpp::SHT_RELA
:
149 case elfcpp::SHT_REL
:
150 case elfcpp::SHT_GROUP
:
151 return parameters
->output_is_object();
153 case elfcpp::SHT_PROGBITS
:
154 if (parameters
->strip_debug()
155 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
157 // Debugging sections can only be recognized by name.
158 if (is_prefix_of(".debug", name
)
159 || is_prefix_of(".gnu.linkonce.wi.", name
)
160 || is_prefix_of(".line", name
)
161 || is_prefix_of(".stab", name
))
164 if (parameters
->strip_debug_gdb()
165 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
167 // Debugging sections can only be recognized by name.
168 if (is_prefix_of(".debug", name
)
169 && !is_gdb_debug_section(name
))
179 // Return an output section named NAME, or NULL if there is none.
182 Layout::find_output_section(const char* name
) const
184 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
185 p
!= this->section_name_map_
.end();
187 if (strcmp(p
->second
->name(), name
) == 0)
192 // Return an output segment of type TYPE, with segment flags SET set
193 // and segment flags CLEAR clear. Return NULL if there is none.
196 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
197 elfcpp::Elf_Word clear
) const
199 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
200 p
!= this->segment_list_
.end();
202 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
203 && ((*p
)->flags() & set
) == set
204 && ((*p
)->flags() & clear
) == 0)
209 // Return the output section to use for section NAME with type TYPE
210 // and section flags FLAGS.
213 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
214 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
216 // We should ignore some flags.
217 flags
&= ~ (elfcpp::SHF_INFO_LINK
218 | elfcpp::SHF_LINK_ORDER
221 | elfcpp::SHF_STRINGS
);
223 const Key
key(name_key
, std::make_pair(type
, flags
));
224 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
225 std::pair
<Section_name_map::iterator
, bool> ins(
226 this->section_name_map_
.insert(v
));
229 return ins
.first
->second
;
232 // This is the first time we've seen this name/type/flags
234 Output_section
* os
= this->make_output_section(name
, type
, flags
);
235 ins
.first
->second
= os
;
240 // Return the output section to use for input section SHNDX, with name
241 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
242 // index of a relocation section which applies to this section, or 0
243 // if none, or -1U if more than one. RELOC_TYPE is the type of the
244 // relocation section if there is one. Set *OFF to the offset of this
245 // input section without the output section. Return NULL if the
246 // section should be discarded. Set *OFF to -1 if the section
247 // contents should not be written directly to the output file, but
248 // will instead receive special handling.
250 template<int size
, bool big_endian
>
252 Layout::layout(Sized_relobj
<size
, big_endian
>* object
, unsigned int shndx
,
253 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
254 unsigned int reloc_shndx
, unsigned int, off_t
* off
)
256 if (!this->include_section(object
, name
, shdr
))
259 // If we are not doing a relocateable link, choose the name to use
260 // for the output section.
261 size_t len
= strlen(name
);
262 if (!parameters
->output_is_object())
263 name
= Layout::output_section_name(name
, &len
);
265 // FIXME: Handle SHF_OS_NONCONFORMING here.
267 // Canonicalize the section name.
268 Stringpool::Key name_key
;
269 name
= this->namepool_
.add_prefix(name
, len
, &name_key
);
271 // Find the output section. The output section is selected based on
272 // the section name, type, and flags.
273 Output_section
* os
= this->get_output_section(name
, name_key
,
275 shdr
.get_sh_flags());
277 // FIXME: Handle SHF_LINK_ORDER somewhere.
279 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
284 // Special GNU handling of sections name .eh_frame. They will
285 // normally hold exception frame data as defined by the C++ ABI
286 // (http://codesourcery.com/cxx-abi/).
288 template<int size
, bool big_endian
>
290 Layout::layout_eh_frame(Sized_relobj
<size
, big_endian
>* object
,
291 const unsigned char* symbols
,
293 const unsigned char* symbol_names
,
294 off_t symbol_names_size
,
296 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
297 unsigned int reloc_shndx
, unsigned int reloc_type
,
300 gold_assert(shdr
.get_sh_type() == elfcpp::SHT_PROGBITS
);
301 gold_assert(shdr
.get_sh_flags() == elfcpp::SHF_ALLOC
);
303 Stringpool::Key name_key
;
304 const char* name
= this->namepool_
.add(".eh_frame", false, &name_key
);
306 Output_section
* os
= this->get_output_section(name
, name_key
,
307 elfcpp::SHT_PROGBITS
,
310 if (this->eh_frame_section_
== NULL
)
312 this->eh_frame_section_
= os
;
313 this->eh_frame_data_
= new Eh_frame();
314 os
->add_output_section_data(this->eh_frame_data_
);
316 if (this->options_
.create_eh_frame_hdr())
318 Stringpool::Key hdr_name_key
;
319 const char* hdr_name
= this->namepool_
.add(".eh_frame_hdr",
322 Output_section
* hdr_os
=
323 this->get_output_section(hdr_name
, hdr_name_key
,
324 elfcpp::SHT_PROGBITS
,
327 Eh_frame_hdr
* hdr_posd
= new Eh_frame_hdr(os
, this->eh_frame_data_
);
328 hdr_os
->add_output_section_data(hdr_posd
);
330 hdr_os
->set_after_input_sections();
332 Output_segment
* hdr_oseg
=
333 new Output_segment(elfcpp::PT_GNU_EH_FRAME
, elfcpp::PF_R
);
334 this->segment_list_
.push_back(hdr_oseg
);
335 hdr_oseg
->add_output_section(hdr_os
, elfcpp::PF_R
);
337 this->eh_frame_data_
->set_eh_frame_hdr(hdr_posd
);
341 gold_assert(this->eh_frame_section_
== os
);
343 if (this->eh_frame_data_
->add_ehframe_input_section(object
,
354 // We couldn't handle this .eh_frame section for some reason.
355 // Add it as a normal section.
356 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
362 // Add POSD to an output section using NAME, TYPE, and FLAGS.
365 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
366 elfcpp::Elf_Xword flags
,
367 Output_section_data
* posd
)
369 // Canonicalize the name.
370 Stringpool::Key name_key
;
371 name
= this->namepool_
.add(name
, true, &name_key
);
373 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
374 os
->add_output_section_data(posd
);
377 // Map section flags to segment flags.
380 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
382 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
383 if ((flags
& elfcpp::SHF_WRITE
) != 0)
385 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
390 // Sometimes we compress sections. This is typically done for
391 // sections that are not part of normal program execution (such as
392 // .debug_* sections), and where the readers of these sections know
393 // how to deal with compressed sections. (To make it easier for them,
394 // we will rename the ouput section in such cases from .foo to
395 // .foo.zlib.nnnn, where nnnn is the uncompressed size.) This routine
396 // doesn't say for certain whether we'll compress -- it depends on
397 // commandline options as well -- just whether this section is a
398 // candidate for compression.
401 is_compressible_debug_section(const char* secname
)
403 return (strncmp(secname
, ".debug", sizeof(".debug") - 1) == 0);
406 // Make a new Output_section, and attach it to segments as
410 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
411 elfcpp::Elf_Xword flags
)
414 if ((flags
& elfcpp::SHF_ALLOC
) == 0
415 && this->options_
.compress_debug_sections()
416 && is_compressible_debug_section(name
))
417 os
= new Output_compressed_section(&this->options_
, name
, type
, flags
);
419 os
= new Output_section(name
, type
, flags
);
421 this->section_list_
.push_back(os
);
423 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
424 this->unattached_section_list_
.push_back(os
);
427 // This output section goes into a PT_LOAD segment.
429 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
431 // The only thing we really care about for PT_LOAD segments is
432 // whether or not they are writable, so that is how we search
433 // for them. People who need segments sorted on some other
434 // basis will have to wait until we implement a mechanism for
435 // them to describe the segments they want.
437 Segment_list::const_iterator p
;
438 for (p
= this->segment_list_
.begin();
439 p
!= this->segment_list_
.end();
442 if ((*p
)->type() == elfcpp::PT_LOAD
443 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
445 (*p
)->add_output_section(os
, seg_flags
);
450 if (p
== this->segment_list_
.end())
452 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
454 this->segment_list_
.push_back(oseg
);
455 oseg
->add_output_section(os
, seg_flags
);
458 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
460 if (type
== elfcpp::SHT_NOTE
)
462 // See if we already have an equivalent PT_NOTE segment.
463 for (p
= this->segment_list_
.begin();
464 p
!= segment_list_
.end();
467 if ((*p
)->type() == elfcpp::PT_NOTE
468 && (((*p
)->flags() & elfcpp::PF_W
)
469 == (seg_flags
& elfcpp::PF_W
)))
471 (*p
)->add_output_section(os
, seg_flags
);
476 if (p
== this->segment_list_
.end())
478 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
480 this->segment_list_
.push_back(oseg
);
481 oseg
->add_output_section(os
, seg_flags
);
485 // If we see a loadable SHF_TLS section, we create a PT_TLS
486 // segment. There can only be one such segment.
487 if ((flags
& elfcpp::SHF_TLS
) != 0)
489 if (this->tls_segment_
== NULL
)
491 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
493 this->segment_list_
.push_back(this->tls_segment_
);
495 this->tls_segment_
->add_output_section(os
, seg_flags
);
502 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
503 // is whether we saw a .note.GNU-stack section in the object file.
504 // GNU_STACK_FLAGS is the section flags. The flags give the
505 // protection required for stack memory. We record this in an
506 // executable as a PT_GNU_STACK segment. If an object file does not
507 // have a .note.GNU-stack segment, we must assume that it is an old
508 // object. On some targets that will force an executable stack.
511 Layout::layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
)
514 this->input_without_gnu_stack_note_
= true;
517 this->input_with_gnu_stack_note_
= true;
518 if ((gnu_stack_flags
& elfcpp::SHF_EXECINSTR
) != 0)
519 this->input_requires_executable_stack_
= true;
523 // Create the dynamic sections which are needed before we read the
527 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
528 Symbol_table
* symtab
)
530 if (parameters
->doing_static_link())
533 const char* dynamic_name
= this->namepool_
.add(".dynamic", false, NULL
);
534 this->dynamic_section_
= this->make_output_section(dynamic_name
,
537 | elfcpp::SHF_WRITE
));
539 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC", NULL
,
540 this->dynamic_section_
, 0, 0,
541 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
542 elfcpp::STV_HIDDEN
, 0, false, false);
544 this->dynamic_data_
= new Output_data_dynamic(&this->dynpool_
);
546 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
549 // For each output section whose name can be represented as C symbol,
550 // define __start and __stop symbols for the section. This is a GNU
554 Layout::define_section_symbols(Symbol_table
* symtab
, const Target
* target
)
556 for (Section_list::const_iterator p
= this->section_list_
.begin();
557 p
!= this->section_list_
.end();
560 const char* const name
= (*p
)->name();
561 if (name
[strspn(name
,
563 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
564 "abcdefghijklmnopqrstuvwxyz"
568 const std::string
name_string(name
);
569 const std::string
start_name("__start_" + name_string
);
570 const std::string
stop_name("__stop_" + name_string
);
572 symtab
->define_in_output_data(target
,
582 false, // offset_is_from_end
583 false); // only_if_ref
585 symtab
->define_in_output_data(target
,
595 true, // offset_is_from_end
596 false); // only_if_ref
601 // Find the first read-only PT_LOAD segment, creating one if
605 Layout::find_first_load_seg()
607 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
608 p
!= this->segment_list_
.end();
611 if ((*p
)->type() == elfcpp::PT_LOAD
612 && ((*p
)->flags() & elfcpp::PF_R
) != 0
613 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
617 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
618 this->segment_list_
.push_back(load_seg
);
622 // Finalize the layout. When this is called, we have created all the
623 // output sections and all the output segments which are based on
624 // input sections. We have several things to do, and we have to do
625 // them in the right order, so that we get the right results correctly
628 // 1) Finalize the list of output segments and create the segment
631 // 2) Finalize the dynamic symbol table and associated sections.
633 // 3) Determine the final file offset of all the output segments.
635 // 4) Determine the final file offset of all the SHF_ALLOC output
638 // 5) Create the symbol table sections and the section name table
641 // 6) Finalize the symbol table: set symbol values to their final
642 // value and make a final determination of which symbols are going
643 // into the output symbol table.
645 // 7) Create the section table header.
647 // 8) Determine the final file offset of all the output sections which
648 // are not SHF_ALLOC, including the section table header.
650 // 9) Finalize the ELF file header.
652 // This function returns the size of the output file.
655 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
)
657 Target
* const target
= input_objects
->target();
659 target
->finalize_sections(this);
661 this->count_local_symbols(input_objects
);
663 this->create_gold_note();
664 this->create_executable_stack_info(target
);
666 Output_segment
* phdr_seg
= NULL
;
667 if (!parameters
->doing_static_link())
669 // There was a dynamic object in the link. We need to create
670 // some information for the dynamic linker.
672 // Create the PT_PHDR segment which will hold the program
674 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
675 this->segment_list_
.push_back(phdr_seg
);
677 // Create the dynamic symbol table, including the hash table.
678 Output_section
* dynstr
;
679 std::vector
<Symbol
*> dynamic_symbols
;
680 unsigned int local_dynamic_count
;
682 this->create_dynamic_symtab(input_objects
, target
, symtab
, &dynstr
,
683 &local_dynamic_count
, &dynamic_symbols
,
686 // Create the .interp section to hold the name of the
687 // interpreter, and put it in a PT_INTERP segment.
688 if (!parameters
->output_is_shared())
689 this->create_interp(target
);
691 // Finish the .dynamic section to hold the dynamic data, and put
692 // it in a PT_DYNAMIC segment.
693 this->finish_dynamic_section(input_objects
, symtab
);
695 // We should have added everything we need to the dynamic string
697 this->dynpool_
.set_string_offsets();
699 // Create the version sections. We can't do this until the
700 // dynamic string table is complete.
701 this->create_version_sections(&versions
, symtab
, local_dynamic_count
,
702 dynamic_symbols
, dynstr
);
705 // FIXME: Handle PT_GNU_STACK.
707 Output_segment
* load_seg
= this->find_first_load_seg();
709 // Lay out the segment headers.
710 Output_segment_headers
* segment_headers
;
711 segment_headers
= new Output_segment_headers(this->segment_list_
);
712 load_seg
->add_initial_output_data(segment_headers
);
713 this->special_output_list_
.push_back(segment_headers
);
714 if (phdr_seg
!= NULL
)
715 phdr_seg
->add_initial_output_data(segment_headers
);
717 // Lay out the file header.
718 Output_file_header
* file_header
;
719 file_header
= new Output_file_header(target
, symtab
, segment_headers
);
720 load_seg
->add_initial_output_data(file_header
);
721 this->special_output_list_
.push_back(file_header
);
723 // We set the output section indexes in set_segment_offsets and
724 // set_section_indexes.
725 unsigned int shndx
= 1;
727 // Set the file offsets of all the segments, and all the sections
729 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
731 // Create the symbol table sections.
732 this->create_symtab_sections(input_objects
, symtab
, &off
);
733 if (!parameters
->doing_static_link())
734 this->assign_local_dynsym_offsets(input_objects
);
736 // Create the .shstrtab section.
737 Output_section
* shstrtab_section
= this->create_shstrtab();
739 // Set the file offsets of all the non-data sections which don't
740 // have to wait for the input sections.
741 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
743 // Now that all sections have been created, set the section indexes.
744 shndx
= this->set_section_indexes(shndx
);
746 // Create the section table header.
747 this->create_shdrs(&off
);
749 file_header
->set_section_info(this->section_headers_
, shstrtab_section
);
751 // Now we know exactly where everything goes in the output file
752 // (except for non-allocated sections which require postprocessing).
753 Output_data::layout_complete();
755 this->output_file_size_
= off
;
760 // Create a .note section for an executable or shared library. This
761 // records the version of gold used to create the binary.
764 Layout::create_gold_note()
766 if (parameters
->output_is_object())
769 // Authorities all agree that the values in a .note field should
770 // be aligned on 4-byte boundaries for 32-bit binaries. However,
771 // they differ on what the alignment is for 64-bit binaries.
772 // The GABI says unambiguously they take 8-byte alignment:
773 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
774 // Other documentation says alignment should always be 4 bytes:
775 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
776 // GNU ld and GNU readelf both support the latter (at least as of
777 // version 2.16.91), and glibc always generates the latter for
778 // .note.ABI-tag (as of version 1.6), so that's the one we go with
780 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
781 const int size
= parameters
->get_size();
786 // The contents of the .note section.
787 const char* name
= "GNU";
788 std::string
desc(std::string("gold ") + gold::get_version_string());
789 size_t namesz
= strlen(name
) + 1;
790 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
791 size_t descsz
= desc
.length() + 1;
792 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
793 const int note_type
= 4;
795 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
797 unsigned char buffer
[128];
798 gold_assert(sizeof buffer
>= notesz
);
799 memset(buffer
, 0, notesz
);
801 bool is_big_endian
= parameters
->is_big_endian();
807 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
808 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
809 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
813 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
814 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
815 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
822 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
823 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
824 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
828 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
829 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
830 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
836 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
837 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
839 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
840 Output_section
* os
= this->make_output_section(note_name
,
843 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
845 os
->add_output_section_data(posd
);
848 // Record whether the stack should be executable. This can be set
849 // from the command line using the -z execstack or -z noexecstack
850 // options. Otherwise, if any input file has a .note.GNU-stack
851 // section with the SHF_EXECINSTR flag set, the stack should be
852 // executable. Otherwise, if at least one input file a
853 // .note.GNU-stack section, and some input file has no .note.GNU-stack
854 // section, we use the target default for whether the stack should be
855 // executable. Otherwise, we don't generate a stack note. When
856 // generating a object file, we create a .note.GNU-stack section with
857 // the appropriate marking. When generating an executable or shared
858 // library, we create a PT_GNU_STACK segment.
861 Layout::create_executable_stack_info(const Target
* target
)
863 bool is_stack_executable
;
864 if (this->options_
.is_execstack_set())
865 is_stack_executable
= this->options_
.is_stack_executable();
866 else if (!this->input_with_gnu_stack_note_
)
870 if (this->input_requires_executable_stack_
)
871 is_stack_executable
= true;
872 else if (this->input_without_gnu_stack_note_
)
873 is_stack_executable
= target
->is_default_stack_executable();
875 is_stack_executable
= false;
878 if (parameters
->output_is_object())
880 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
881 elfcpp::Elf_Xword flags
= 0;
882 if (is_stack_executable
)
883 flags
|= elfcpp::SHF_EXECINSTR
;
884 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
888 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
889 if (is_stack_executable
)
890 flags
|= elfcpp::PF_X
;
891 Output_segment
* oseg
= new Output_segment(elfcpp::PT_GNU_STACK
, flags
);
892 this->segment_list_
.push_back(oseg
);
896 // Return whether SEG1 should be before SEG2 in the output file. This
897 // is based entirely on the segment type and flags. When this is
898 // called the segment addresses has normally not yet been set.
901 Layout::segment_precedes(const Output_segment
* seg1
,
902 const Output_segment
* seg2
)
904 elfcpp::Elf_Word type1
= seg1
->type();
905 elfcpp::Elf_Word type2
= seg2
->type();
907 // The single PT_PHDR segment is required to precede any loadable
908 // segment. We simply make it always first.
909 if (type1
== elfcpp::PT_PHDR
)
911 gold_assert(type2
!= elfcpp::PT_PHDR
);
914 if (type2
== elfcpp::PT_PHDR
)
917 // The single PT_INTERP segment is required to precede any loadable
918 // segment. We simply make it always second.
919 if (type1
== elfcpp::PT_INTERP
)
921 gold_assert(type2
!= elfcpp::PT_INTERP
);
924 if (type2
== elfcpp::PT_INTERP
)
927 // We then put PT_LOAD segments before any other segments.
928 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
930 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
933 // We put the PT_TLS segment last, because that is where the dynamic
934 // linker expects to find it (this is just for efficiency; other
935 // positions would also work correctly).
936 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
938 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
941 const elfcpp::Elf_Word flags1
= seg1
->flags();
942 const elfcpp::Elf_Word flags2
= seg2
->flags();
944 // The order of non-PT_LOAD segments is unimportant. We simply sort
945 // by the numeric segment type and flags values. There should not
946 // be more than one segment with the same type and flags.
947 if (type1
!= elfcpp::PT_LOAD
)
950 return type1
< type2
;
951 gold_assert(flags1
!= flags2
);
952 return flags1
< flags2
;
955 // We sort PT_LOAD segments based on the flags. Readonly segments
956 // come before writable segments. Then executable segments come
957 // before non-executable segments. Then the unlikely case of a
958 // non-readable segment comes before the normal case of a readable
959 // segment. If there are multiple segments with the same type and
960 // flags, we require that the address be set, and we sort by
961 // virtual address and then physical address.
962 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
963 return (flags1
& elfcpp::PF_W
) == 0;
964 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
965 return (flags1
& elfcpp::PF_X
) != 0;
966 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
967 return (flags1
& elfcpp::PF_R
) == 0;
969 uint64_t vaddr1
= seg1
->vaddr();
970 uint64_t vaddr2
= seg2
->vaddr();
971 if (vaddr1
!= vaddr2
)
972 return vaddr1
< vaddr2
;
974 uint64_t paddr1
= seg1
->paddr();
975 uint64_t paddr2
= seg2
->paddr();
976 gold_assert(paddr1
!= paddr2
);
977 return paddr1
< paddr2
;
980 // Set the file offsets of all the segments, and all the sections they
981 // contain. They have all been created. LOAD_SEG must be be laid out
982 // first. Return the offset of the data to follow.
985 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
986 unsigned int *pshndx
)
988 // Sort them into the final order.
989 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
990 Layout::Compare_segments());
992 // Find the PT_LOAD segments, and set their addresses and offsets
993 // and their section's addresses and offsets.
995 if (parameters
->output_is_shared())
997 else if (options_
.user_set_text_segment_address())
998 addr
= options_
.text_segment_address();
1000 addr
= target
->default_text_segment_address();
1002 bool was_readonly
= false;
1003 for (Segment_list::iterator p
= this->segment_list_
.begin();
1004 p
!= this->segment_list_
.end();
1007 if ((*p
)->type() == elfcpp::PT_LOAD
)
1009 if (load_seg
!= NULL
&& load_seg
!= *p
)
1013 // If the last segment was readonly, and this one is not,
1014 // then skip the address forward one page, maintaining the
1015 // same position within the page. This lets us store both
1016 // segments overlapping on a single page in the file, but
1017 // the loader will put them on different pages in memory.
1019 uint64_t orig_addr
= addr
;
1020 uint64_t orig_off
= off
;
1022 uint64_t aligned_addr
= addr
;
1023 uint64_t abi_pagesize
= target
->abi_pagesize();
1025 // FIXME: This should depend on the -n and -N options.
1026 (*p
)->set_minimum_addralign(target
->common_pagesize());
1028 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
1030 uint64_t align
= (*p
)->addralign();
1032 addr
= align_address(addr
, align
);
1033 aligned_addr
= addr
;
1034 if ((addr
& (abi_pagesize
- 1)) != 0)
1035 addr
= addr
+ abi_pagesize
;
1038 unsigned int shndx_hold
= *pshndx
;
1039 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1040 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1042 // Now that we know the size of this segment, we may be able
1043 // to save a page in memory, at the cost of wasting some
1044 // file space, by instead aligning to the start of a new
1045 // page. Here we use the real machine page size rather than
1046 // the ABI mandated page size.
1048 if (aligned_addr
!= addr
)
1050 uint64_t common_pagesize
= target
->common_pagesize();
1051 uint64_t first_off
= (common_pagesize
1053 & (common_pagesize
- 1)));
1054 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
1057 && ((aligned_addr
& ~ (common_pagesize
- 1))
1058 != (new_addr
& ~ (common_pagesize
- 1)))
1059 && first_off
+ last_off
<= common_pagesize
)
1061 *pshndx
= shndx_hold
;
1062 addr
= align_address(aligned_addr
, common_pagesize
);
1063 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1064 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1070 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
1071 was_readonly
= true;
1075 // Handle the non-PT_LOAD segments, setting their offsets from their
1076 // section's offsets.
1077 for (Segment_list::iterator p
= this->segment_list_
.begin();
1078 p
!= this->segment_list_
.end();
1081 if ((*p
)->type() != elfcpp::PT_LOAD
)
1085 // Set the TLS offsets for each section in the PT_TLS segment.
1086 if (this->tls_segment_
!= NULL
)
1087 this->tls_segment_
->set_tls_offsets();
1092 // Set the file offset of all the sections not associated with a
1096 Layout::set_section_offsets(off_t off
, Layout::Section_offset_pass pass
)
1098 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1099 p
!= this->unattached_section_list_
.end();
1102 // The symtab section is handled in create_symtab_sections.
1103 if (*p
== this->symtab_section_
)
1106 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1107 && (*p
)->requires_postprocessing())
1108 (*p
)->create_postprocessing_buffer();
1110 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1111 && (*p
)->after_input_sections())
1113 else if (pass
== AFTER_INPUT_SECTIONS_PASS
1114 && (!(*p
)->after_input_sections()
1115 || (*p
)->type() == elfcpp::SHT_STRTAB
))
1117 else if (pass
== STRTAB_AFTER_INPUT_SECTIONS_PASS
1118 && (!(*p
)->after_input_sections()
1119 || (*p
)->type() != elfcpp::SHT_STRTAB
))
1122 off
= align_address(off
, (*p
)->addralign());
1123 (*p
)->set_file_offset(off
);
1124 (*p
)->finalize_data_size();
1125 off
+= (*p
)->data_size();
1127 // At this point the name must be set.
1128 if (pass
!= STRTAB_AFTER_INPUT_SECTIONS_PASS
)
1129 this->namepool_
.add((*p
)->name(), false, NULL
);
1134 // Set the section indexes of all the sections not associated with a
1138 Layout::set_section_indexes(unsigned int shndx
)
1140 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1141 p
!= this->unattached_section_list_
.end();
1144 (*p
)->set_out_shndx(shndx
);
1150 // Count the local symbols in the regular symbol table and the dynamic
1151 // symbol table, and build the respective string pools.
1154 Layout::count_local_symbols(const Input_objects
* input_objects
)
1156 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1157 p
!= input_objects
->relobj_end();
1160 Task_lock_obj
<Object
> tlo(**p
);
1161 (*p
)->count_local_symbols(&this->sympool_
, &this->dynpool_
);
1165 // Create the symbol table sections. Here we also set the final
1166 // values of the symbols. At this point all the loadable sections are
1170 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1171 Symbol_table
* symtab
,
1176 if (parameters
->get_size() == 32)
1178 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1181 else if (parameters
->get_size() == 64)
1183 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1190 off
= align_address(off
, align
);
1191 off_t startoff
= off
;
1193 // Save space for the dummy symbol at the start of the section. We
1194 // never bother to write this out--it will just be left as zero.
1196 unsigned int local_symbol_index
= 1;
1198 // Add STT_SECTION symbols for each Output section which needs one.
1199 for (Section_list::iterator p
= this->section_list_
.begin();
1200 p
!= this->section_list_
.end();
1203 if (!(*p
)->needs_symtab_index())
1204 (*p
)->set_symtab_index(-1U);
1207 (*p
)->set_symtab_index(local_symbol_index
);
1208 ++local_symbol_index
;
1213 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1214 p
!= input_objects
->relobj_end();
1217 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1219 off
+= (index
- local_symbol_index
) * symsize
;
1220 local_symbol_index
= index
;
1223 unsigned int local_symcount
= local_symbol_index
;
1224 gold_assert(local_symcount
* symsize
== off
- startoff
);
1227 size_t dyn_global_index
;
1229 if (this->dynsym_section_
== NULL
)
1232 dyn_global_index
= 0;
1237 dyn_global_index
= this->dynsym_section_
->info();
1238 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1239 dynoff
= this->dynsym_section_
->offset() + locsize
;
1240 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1241 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1242 == this->dynsym_section_
->data_size() - locsize
);
1245 off
= symtab
->finalize(local_symcount
, off
, dynoff
, dyn_global_index
,
1246 dyncount
, &this->sympool_
);
1248 if (!parameters
->strip_all())
1250 this->sympool_
.set_string_offsets();
1252 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1253 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1256 this->symtab_section_
= osymtab
;
1258 Output_section_data
* pos
= new Output_data_fixed_space(off
- startoff
,
1260 osymtab
->add_output_section_data(pos
);
1262 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1263 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1267 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1268 ostrtab
->add_output_section_data(pstr
);
1270 osymtab
->set_file_offset(startoff
);
1271 osymtab
->finalize_data_size();
1272 osymtab
->set_link_section(ostrtab
);
1273 osymtab
->set_info(local_symcount
);
1274 osymtab
->set_entsize(symsize
);
1280 // Create the .shstrtab section, which holds the names of the
1281 // sections. At the time this is called, we have created all the
1282 // output sections except .shstrtab itself.
1285 Layout::create_shstrtab()
1287 // FIXME: We don't need to create a .shstrtab section if we are
1288 // stripping everything.
1290 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1292 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1294 // We can't write out this section until we've set all the section
1295 // names, and we don't set the names of compressed output sections
1296 // until relocations are complete.
1297 os
->set_after_input_sections();
1299 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1300 os
->add_output_section_data(posd
);
1305 // Create the section headers. SIZE is 32 or 64. OFF is the file
1309 Layout::create_shdrs(off_t
* poff
)
1311 Output_section_headers
* oshdrs
;
1312 oshdrs
= new Output_section_headers(this,
1313 &this->segment_list_
,
1314 &this->unattached_section_list_
,
1316 off_t off
= align_address(*poff
, oshdrs
->addralign());
1317 oshdrs
->set_address_and_file_offset(0, off
);
1318 off
+= oshdrs
->data_size();
1320 this->section_headers_
= oshdrs
;
1323 // Create the dynamic symbol table.
1326 Layout::create_dynamic_symtab(const Input_objects
* input_objects
,
1327 const Target
* target
, Symbol_table
* symtab
,
1328 Output_section
**pdynstr
,
1329 unsigned int* plocal_dynamic_count
,
1330 std::vector
<Symbol
*>* pdynamic_symbols
,
1331 Versions
* pversions
)
1333 // Count all the symbols in the dynamic symbol table, and set the
1334 // dynamic symbol indexes.
1336 // Skip symbol 0, which is always all zeroes.
1337 unsigned int index
= 1;
1339 // Add STT_SECTION symbols for each Output section which needs one.
1340 for (Section_list::iterator p
= this->section_list_
.begin();
1341 p
!= this->section_list_
.end();
1344 if (!(*p
)->needs_dynsym_index())
1345 (*p
)->set_dynsym_index(-1U);
1348 (*p
)->set_dynsym_index(index
);
1353 // Count the local symbols that need to go in the dynamic symbol table,
1354 // and set the dynamic symbol indexes.
1355 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1356 p
!= input_objects
->relobj_end();
1359 unsigned int new_index
= (*p
)->set_local_dynsym_indexes(index
);
1363 unsigned int local_symcount
= index
;
1364 *plocal_dynamic_count
= local_symcount
;
1366 // FIXME: We have to tell set_dynsym_indexes whether the
1367 // -E/--export-dynamic option was used.
1368 index
= symtab
->set_dynsym_indexes(target
, index
, pdynamic_symbols
,
1369 &this->dynpool_
, pversions
);
1373 const int size
= parameters
->get_size();
1376 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1379 else if (size
== 64)
1381 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1387 // Create the dynamic symbol table section.
1389 const char* dynsym_name
= this->namepool_
.add(".dynsym", false, NULL
);
1390 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
1394 Output_section_data
* odata
= new Output_data_fixed_space(index
* symsize
,
1396 dynsym
->add_output_section_data(odata
);
1398 dynsym
->set_info(local_symcount
);
1399 dynsym
->set_entsize(symsize
);
1400 dynsym
->set_addralign(align
);
1402 this->dynsym_section_
= dynsym
;
1404 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1405 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1406 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1408 // Create the dynamic string table section.
1410 const char* dynstr_name
= this->namepool_
.add(".dynstr", false, NULL
);
1411 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
1415 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1416 dynstr
->add_output_section_data(strdata
);
1418 dynsym
->set_link_section(dynstr
);
1419 this->dynamic_section_
->set_link_section(dynstr
);
1421 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1422 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1426 // Create the hash tables.
1428 // FIXME: We need an option to create a GNU hash table.
1430 unsigned char* phash
;
1431 unsigned int hashlen
;
1432 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1435 const char* hash_name
= this->namepool_
.add(".hash", false, NULL
);
1436 Output_section
* hashsec
= this->make_output_section(hash_name
,
1440 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1443 hashsec
->add_output_section_data(hashdata
);
1445 hashsec
->set_link_section(dynsym
);
1446 hashsec
->set_entsize(4);
1448 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1451 // Assign offsets to each local portion of the dynamic symbol table.
1454 Layout::assign_local_dynsym_offsets(const Input_objects
* input_objects
)
1456 Output_section
* dynsym
= this->dynsym_section_
;
1457 gold_assert(dynsym
!= NULL
);
1459 off_t off
= dynsym
->offset();
1461 // Skip the dummy symbol at the start of the section.
1462 off
+= dynsym
->entsize();
1464 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1465 p
!= input_objects
->relobj_end();
1468 unsigned int count
= (*p
)->set_local_dynsym_offset(off
);
1469 off
+= count
* dynsym
->entsize();
1473 // Create the version sections.
1476 Layout::create_version_sections(const Versions
* versions
,
1477 const Symbol_table
* symtab
,
1478 unsigned int local_symcount
,
1479 const std::vector
<Symbol
*>& dynamic_symbols
,
1480 const Output_section
* dynstr
)
1482 if (!versions
->any_defs() && !versions
->any_needs())
1485 if (parameters
->get_size() == 32)
1487 if (parameters
->is_big_endian())
1489 #ifdef HAVE_TARGET_32_BIG
1490 this->sized_create_version_sections
1491 SELECT_SIZE_ENDIAN_NAME(32, true)(
1492 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1493 SELECT_SIZE_ENDIAN(32, true));
1500 #ifdef HAVE_TARGET_32_LITTLE
1501 this->sized_create_version_sections
1502 SELECT_SIZE_ENDIAN_NAME(32, false)(
1503 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1504 SELECT_SIZE_ENDIAN(32, false));
1510 else if (parameters
->get_size() == 64)
1512 if (parameters
->is_big_endian())
1514 #ifdef HAVE_TARGET_64_BIG
1515 this->sized_create_version_sections
1516 SELECT_SIZE_ENDIAN_NAME(64, true)(
1517 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1518 SELECT_SIZE_ENDIAN(64, true));
1525 #ifdef HAVE_TARGET_64_LITTLE
1526 this->sized_create_version_sections
1527 SELECT_SIZE_ENDIAN_NAME(64, false)(
1528 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1529 SELECT_SIZE_ENDIAN(64, false));
1539 // Create the version sections, sized version.
1541 template<int size
, bool big_endian
>
1543 Layout::sized_create_version_sections(
1544 const Versions
* versions
,
1545 const Symbol_table
* symtab
,
1546 unsigned int local_symcount
,
1547 const std::vector
<Symbol
*>& dynamic_symbols
,
1548 const Output_section
* dynstr
1551 const char* vname
= this->namepool_
.add(".gnu.version", false, NULL
);
1552 Output_section
* vsec
= this->make_output_section(vname
,
1553 elfcpp::SHT_GNU_versym
,
1556 unsigned char* vbuf
;
1558 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1559 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1560 SELECT_SIZE_ENDIAN(size
, big_endian
));
1562 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1564 vsec
->add_output_section_data(vdata
);
1565 vsec
->set_entsize(2);
1566 vsec
->set_link_section(this->dynsym_section_
);
1568 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1569 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1571 if (versions
->any_defs())
1573 const char* vdname
= this->namepool_
.add(".gnu.version_d", false, NULL
);
1574 Output_section
*vdsec
;
1575 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1578 unsigned char* vdbuf
;
1579 unsigned int vdsize
;
1580 unsigned int vdentries
;
1581 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1582 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1583 SELECT_SIZE_ENDIAN(size
, big_endian
));
1585 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1589 vdsec
->add_output_section_data(vddata
);
1590 vdsec
->set_link_section(dynstr
);
1591 vdsec
->set_info(vdentries
);
1593 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1594 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1597 if (versions
->any_needs())
1599 const char* vnname
= this->namepool_
.add(".gnu.version_r", false, NULL
);
1600 Output_section
* vnsec
;
1601 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1604 unsigned char* vnbuf
;
1605 unsigned int vnsize
;
1606 unsigned int vnentries
;
1607 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1608 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1609 SELECT_SIZE_ENDIAN(size
, big_endian
));
1611 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1615 vnsec
->add_output_section_data(vndata
);
1616 vnsec
->set_link_section(dynstr
);
1617 vnsec
->set_info(vnentries
);
1619 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1620 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1624 // Create the .interp section and PT_INTERP segment.
1627 Layout::create_interp(const Target
* target
)
1629 const char* interp
= this->options_
.dynamic_linker();
1632 interp
= target
->dynamic_linker();
1633 gold_assert(interp
!= NULL
);
1636 size_t len
= strlen(interp
) + 1;
1638 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1640 const char* interp_name
= this->namepool_
.add(".interp", false, NULL
);
1641 Output_section
* osec
= this->make_output_section(interp_name
,
1642 elfcpp::SHT_PROGBITS
,
1644 osec
->add_output_section_data(odata
);
1646 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1647 this->segment_list_
.push_back(oseg
);
1648 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1651 // Finish the .dynamic section and PT_DYNAMIC segment.
1654 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1655 const Symbol_table
* symtab
)
1657 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1658 elfcpp::PF_R
| elfcpp::PF_W
);
1659 this->segment_list_
.push_back(oseg
);
1660 oseg
->add_initial_output_section(this->dynamic_section_
,
1661 elfcpp::PF_R
| elfcpp::PF_W
);
1663 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1665 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1666 p
!= input_objects
->dynobj_end();
1669 // FIXME: Handle --as-needed.
1670 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1673 // FIXME: Support --init and --fini.
1674 Symbol
* sym
= symtab
->lookup("_init");
1675 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1676 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1678 sym
= symtab
->lookup("_fini");
1679 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1680 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1682 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1684 // Add a DT_RPATH entry if needed.
1685 const General_options::Dir_list
& rpath(this->options_
.rpath());
1688 std::string rpath_val
;
1689 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1693 if (rpath_val
.empty())
1694 rpath_val
= p
->name();
1697 // Eliminate duplicates.
1698 General_options::Dir_list::const_iterator q
;
1699 for (q
= rpath
.begin(); q
!= p
; ++q
)
1700 if (q
->name() == p
->name())
1705 rpath_val
+= p
->name();
1710 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1713 // Look for text segments that have dynamic relocations.
1714 bool have_textrel
= false;
1715 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
1716 p
!= this->segment_list_
.end();
1719 if (((*p
)->flags() & elfcpp::PF_W
) == 0
1720 && (*p
)->dynamic_reloc_count() > 0)
1722 have_textrel
= true;
1727 // Add a DT_FLAGS entry. We add it even if no flags are set so that
1728 // post-link tools can easily modify these flags if desired.
1729 unsigned int flags
= 0;
1732 // Add a DT_TEXTREL for compatibility with older loaders.
1733 odyn
->add_constant(elfcpp::DT_TEXTREL
, 0);
1734 flags
|= elfcpp::DF_TEXTREL
;
1736 odyn
->add_constant(elfcpp::DT_FLAGS
, flags
);
1739 // The mapping of .gnu.linkonce section names to real section names.
1741 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1742 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1744 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1745 MAPPING_INIT("t", ".text"),
1746 MAPPING_INIT("r", ".rodata"),
1747 MAPPING_INIT("d", ".data"),
1748 MAPPING_INIT("b", ".bss"),
1749 MAPPING_INIT("s", ".sdata"),
1750 MAPPING_INIT("sb", ".sbss"),
1751 MAPPING_INIT("s2", ".sdata2"),
1752 MAPPING_INIT("sb2", ".sbss2"),
1753 MAPPING_INIT("wi", ".debug_info"),
1754 MAPPING_INIT("td", ".tdata"),
1755 MAPPING_INIT("tb", ".tbss"),
1756 MAPPING_INIT("lr", ".lrodata"),
1757 MAPPING_INIT("l", ".ldata"),
1758 MAPPING_INIT("lb", ".lbss"),
1762 const int Layout::linkonce_mapping_count
=
1763 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1765 // Return the name of the output section to use for a .gnu.linkonce
1766 // section. This is based on the default ELF linker script of the old
1767 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1768 // to ".text". Set *PLEN to the length of the name. *PLEN is
1769 // initialized to the length of NAME.
1772 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1774 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1778 const Linkonce_mapping
* plm
= linkonce_mapping
;
1779 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1781 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1790 // Choose the output section name to use given an input section name.
1791 // Set *PLEN to the length of the name. *PLEN is initialized to the
1795 Layout::output_section_name(const char* name
, size_t* plen
)
1797 if (Layout::is_linkonce(name
))
1799 // .gnu.linkonce sections are laid out as though they were named
1800 // for the sections are placed into.
1801 return Layout::linkonce_output_name(name
, plen
);
1804 // gcc 4.3 generates the following sorts of section names when it
1805 // needs a section name specific to a function:
1811 // .data.rel.local.FN
1813 // .data.rel.ro.local.FN
1820 // The GNU linker maps all of those to the part before the .FN,
1821 // except that .data.rel.local.FN is mapped to .data, and
1822 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1823 // beginning with .data.rel.ro.local are grouped together.
1825 // For an anonymous namespace, the string FN can contain a '.'.
1827 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1828 // GNU linker maps to .rodata.
1830 // The .data.rel.ro sections enable a security feature triggered by
1831 // the -z relro option. Section which need to be relocated at
1832 // program startup time but which may be readonly after startup are
1833 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1834 // segment. The dynamic linker will make that segment writable,
1835 // perform relocations, and then make it read-only. FIXME: We do
1836 // not yet implement this optimization.
1838 // It is hard to handle this in a principled way.
1840 // These are the rules we follow:
1842 // If the section name has no initial '.', or no dot other than an
1843 // initial '.', we use the name unchanged (i.e., "mysection" and
1844 // ".text" are unchanged).
1846 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1848 // Otherwise, we drop the second '.' and everything that comes after
1849 // it (i.e., ".text.XXX" becomes ".text").
1851 const char* s
= name
;
1855 const char* sdot
= strchr(s
, '.');
1859 const char* const data_rel_ro
= ".data.rel.ro";
1860 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
1862 *plen
= strlen(data_rel_ro
);
1866 *plen
= sdot
- name
;
1870 // Record the signature of a comdat section, and return whether to
1871 // include it in the link. If GROUP is true, this is a regular
1872 // section group. If GROUP is false, this is a group signature
1873 // derived from the name of a linkonce section. We want linkonce
1874 // signatures and group signatures to block each other, but we don't
1875 // want a linkonce signature to block another linkonce signature.
1878 Layout::add_comdat(const char* signature
, bool group
)
1880 std::string
sig(signature
);
1881 std::pair
<Signatures::iterator
, bool> ins(
1882 this->signatures_
.insert(std::make_pair(sig
, group
)));
1886 // This is the first time we've seen this signature.
1890 if (ins
.first
->second
)
1892 // We've already seen a real section group with this signature.
1897 // This is a real section group, and we've already seen a
1898 // linkonce section with this signature. Record that we've seen
1899 // a section group, and don't include this section group.
1900 ins
.first
->second
= true;
1905 // We've already seen a linkonce section and this is a linkonce
1906 // section. These don't block each other--this may be the same
1907 // symbol name with different section types.
1912 // Write out the Output_sections. Most won't have anything to write,
1913 // since most of the data will come from input sections which are
1914 // handled elsewhere. But some Output_sections do have Output_data.
1917 Layout::write_output_sections(Output_file
* of
) const
1919 for (Section_list::const_iterator p
= this->section_list_
.begin();
1920 p
!= this->section_list_
.end();
1923 if (!(*p
)->after_input_sections())
1928 // Write out data not associated with a section or the symbol table.
1931 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
1933 if (!parameters
->strip_all())
1935 const Output_section
* symtab_section
= this->symtab_section_
;
1936 for (Section_list::const_iterator p
= this->section_list_
.begin();
1937 p
!= this->section_list_
.end();
1940 if ((*p
)->needs_symtab_index())
1942 gold_assert(symtab_section
!= NULL
);
1943 unsigned int index
= (*p
)->symtab_index();
1944 gold_assert(index
> 0 && index
!= -1U);
1945 off_t off
= (symtab_section
->offset()
1946 + index
* symtab_section
->entsize());
1947 symtab
->write_section_symbol(*p
, of
, off
);
1952 const Output_section
* dynsym_section
= this->dynsym_section_
;
1953 for (Section_list::const_iterator p
= this->section_list_
.begin();
1954 p
!= this->section_list_
.end();
1957 if ((*p
)->needs_dynsym_index())
1959 gold_assert(dynsym_section
!= NULL
);
1960 unsigned int index
= (*p
)->dynsym_index();
1961 gold_assert(index
> 0 && index
!= -1U);
1962 off_t off
= (dynsym_section
->offset()
1963 + index
* dynsym_section
->entsize());
1964 symtab
->write_section_symbol(*p
, of
, off
);
1968 // Write out the Output_data which are not in an Output_section.
1969 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
1970 p
!= this->special_output_list_
.end();
1975 // Write out the Output_sections which can only be written after the
1976 // input sections are complete.
1979 Layout::write_sections_after_input_sections(Output_file
* of
)
1981 // Determine the final section offsets, and thus the final output
1982 // file size. Note we finalize the .shstrab last, to allow the
1983 // after_input_section sections to modify their section-names before
1985 off_t off
= this->output_file_size_
;
1986 off
= this->set_section_offsets(off
, AFTER_INPUT_SECTIONS_PASS
);
1988 // Now that we've finalized the names, we can finalize the shstrab.
1989 off
= this->set_section_offsets(off
, STRTAB_AFTER_INPUT_SECTIONS_PASS
);
1991 if (off
> this->output_file_size_
)
1994 this->output_file_size_
= off
;
1997 for (Section_list::const_iterator p
= this->section_list_
.begin();
1998 p
!= this->section_list_
.end();
2001 if ((*p
)->after_input_sections())
2005 for (Section_list::const_iterator p
= this->unattached_section_list_
.begin();
2006 p
!= this->unattached_section_list_
.end();
2009 if ((*p
)->after_input_sections())
2013 this->section_headers_
->write(of
);
2016 // Print statistical information to stderr. This is used for --stats.
2019 Layout::print_stats() const
2021 this->namepool_
.print_stats("section name pool");
2022 this->sympool_
.print_stats("output symbol name pool");
2023 this->dynpool_
.print_stats("dynamic name pool");
2026 // Write_sections_task methods.
2028 // We can always run this task.
2030 Task::Is_runnable_type
2031 Write_sections_task::is_runnable(Workqueue
*)
2036 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
2039 class Write_sections_task::Write_sections_locker
: public Task_locker
2042 Write_sections_locker(Task_token
& output_sections_blocker
,
2043 Task_token
& final_blocker
,
2044 Workqueue
* workqueue
)
2045 : output_sections_block_(output_sections_blocker
, workqueue
),
2046 final_block_(final_blocker
, workqueue
)
2050 Task_block_token output_sections_block_
;
2051 Task_block_token final_block_
;
2055 Write_sections_task::locks(Workqueue
* workqueue
)
2057 return new Write_sections_locker(*this->output_sections_blocker_
,
2058 *this->final_blocker_
,
2062 // Run the task--write out the data.
2065 Write_sections_task::run(Workqueue
*)
2067 this->layout_
->write_output_sections(this->of_
);
2070 // Write_data_task methods.
2072 // We can always run this task.
2074 Task::Is_runnable_type
2075 Write_data_task::is_runnable(Workqueue
*)
2080 // We need to unlock FINAL_BLOCKER when finished.
2083 Write_data_task::locks(Workqueue
* workqueue
)
2085 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2088 // Run the task--write out the data.
2091 Write_data_task::run(Workqueue
*)
2093 this->layout_
->write_data(this->symtab_
, this->of_
);
2096 // Write_symbols_task methods.
2098 // We can always run this task.
2100 Task::Is_runnable_type
2101 Write_symbols_task::is_runnable(Workqueue
*)
2106 // We need to unlock FINAL_BLOCKER when finished.
2109 Write_symbols_task::locks(Workqueue
* workqueue
)
2111 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2114 // Run the task--write out the symbols.
2117 Write_symbols_task::run(Workqueue
*)
2119 this->symtab_
->write_globals(this->input_objects_
, this->sympool_
,
2120 this->dynpool_
, this->of_
);
2123 // Write_after_input_sections_task methods.
2125 // We can only run this task after the input sections have completed.
2127 Task::Is_runnable_type
2128 Write_after_input_sections_task::is_runnable(Workqueue
*)
2130 if (this->input_sections_blocker_
->is_blocked())
2135 // We need to unlock FINAL_BLOCKER when finished.
2138 Write_after_input_sections_task::locks(Workqueue
* workqueue
)
2140 return new Task_locker_block(*this->final_blocker_
, workqueue
);
2146 Write_after_input_sections_task::run(Workqueue
*)
2148 this->layout_
->write_sections_after_input_sections(this->of_
);
2151 // Close_task_runner methods.
2153 // Run the task--close the file.
2156 Close_task_runner::run(Workqueue
*)
2161 // Instantiate the templates we need. We could use the configure
2162 // script to restrict this to only the ones for implemented targets.
2164 #ifdef HAVE_TARGET_32_LITTLE
2167 Layout::layout
<32, false>(Sized_relobj
<32, false>* object
, unsigned int shndx
,
2169 const elfcpp::Shdr
<32, false>& shdr
,
2170 unsigned int, unsigned int, off_t
*);
2173 #ifdef HAVE_TARGET_32_BIG
2176 Layout::layout
<32, true>(Sized_relobj
<32, true>* object
, unsigned int shndx
,
2178 const elfcpp::Shdr
<32, true>& shdr
,
2179 unsigned int, unsigned int, off_t
*);
2182 #ifdef HAVE_TARGET_64_LITTLE
2185 Layout::layout
<64, false>(Sized_relobj
<64, false>* object
, unsigned int shndx
,
2187 const elfcpp::Shdr
<64, false>& shdr
,
2188 unsigned int, unsigned int, off_t
*);
2191 #ifdef HAVE_TARGET_64_BIG
2194 Layout::layout
<64, true>(Sized_relobj
<64, true>* object
, unsigned int shndx
,
2196 const elfcpp::Shdr
<64, true>& shdr
,
2197 unsigned int, unsigned int, off_t
*);
2200 #ifdef HAVE_TARGET_32_LITTLE
2203 Layout::layout_eh_frame
<32, false>(Sized_relobj
<32, false>* object
,
2204 const unsigned char* symbols
,
2206 const unsigned char* symbol_names
,
2207 off_t symbol_names_size
,
2209 const elfcpp::Shdr
<32, false>& shdr
,
2210 unsigned int reloc_shndx
,
2211 unsigned int reloc_type
,
2215 #ifdef HAVE_TARGET_32_BIG
2218 Layout::layout_eh_frame
<32, true>(Sized_relobj
<32, true>* object
,
2219 const unsigned char* symbols
,
2221 const unsigned char* symbol_names
,
2222 off_t symbol_names_size
,
2224 const elfcpp::Shdr
<32, true>& shdr
,
2225 unsigned int reloc_shndx
,
2226 unsigned int reloc_type
,
2230 #ifdef HAVE_TARGET_64_LITTLE
2233 Layout::layout_eh_frame
<64, false>(Sized_relobj
<64, false>* object
,
2234 const unsigned char* symbols
,
2236 const unsigned char* symbol_names
,
2237 off_t symbol_names_size
,
2239 const elfcpp::Shdr
<64, false>& shdr
,
2240 unsigned int reloc_shndx
,
2241 unsigned int reloc_type
,
2245 #ifdef HAVE_TARGET_64_BIG
2248 Layout::layout_eh_frame
<64, true>(Sized_relobj
<64, true>* object
,
2249 const unsigned char* symbols
,
2251 const unsigned char* symbol_names
,
2252 off_t symbol_names_size
,
2254 const elfcpp::Shdr
<64, true>& shdr
,
2255 unsigned int reloc_shndx
,
2256 unsigned int reloc_type
,
2260 } // End namespace gold.