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
, const Task
* task
)
49 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
53 // Now we know the final size of the output file and we know where
54 // each piece of information goes.
55 Output_file
* of
= new Output_file(this->options_
,
56 this->input_objects_
->target());
59 // Queue up the final set of tasks.
60 gold::queue_final_tasks(this->options_
, this->input_objects_
,
61 this->symtab_
, this->layout_
, workqueue
, of
);
66 Layout::Layout(const General_options
& options
)
67 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
68 section_name_map_(), segment_list_(), section_list_(),
69 unattached_section_list_(), special_output_list_(),
70 section_headers_(NULL
), tls_segment_(NULL
), symtab_section_(NULL
),
71 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
),
72 eh_frame_section_(NULL
), output_file_size_(-1),
73 input_requires_executable_stack_(false),
74 input_with_gnu_stack_note_(false),
75 input_without_gnu_stack_note_(false),
76 has_static_tls_(false),
77 any_postprocessing_sections_(false)
79 // Make space for more than enough segments for a typical file.
80 // This is just for efficiency--it's OK if we wind up needing more.
81 this->segment_list_
.reserve(12);
83 // We expect two unattached Output_data objects: the file header and
84 // the segment headers.
85 this->special_output_list_
.reserve(2);
88 // Hash a key we use to look up an output section mapping.
91 Layout::Hash_key::operator()(const Layout::Key
& k
) const
93 return k
.first
+ k
.second
.first
+ k
.second
.second
;
96 // Return whether PREFIX is a prefix of STR.
99 is_prefix_of(const char* prefix
, const char* str
)
101 return strncmp(prefix
, str
, strlen(prefix
)) == 0;
104 // Returns whether the given section is in the list of
105 // debug-sections-used-by-some-version-of-gdb. Currently,
106 // we've checked versions of gdb up to and including 6.7.1.
108 static const char* gdb_sections
[] =
110 // ".debug_aranges", // not used by gdb as of 6.7.1
116 // ".debug_pubnames", // not used by gdb as of 6.7.1
122 is_gdb_debug_section(const char* str
)
124 // We can do this faster: binary search or a hashtable. But why bother?
125 for (size_t i
= 0; i
< sizeof(gdb_sections
)/sizeof(*gdb_sections
); ++i
)
126 if (strcmp(str
, gdb_sections
[i
]) == 0)
131 // Whether to include this section in the link.
133 template<int size
, bool big_endian
>
135 Layout::include_section(Sized_relobj
<size
, big_endian
>*, const char* name
,
136 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
138 // Some section types are never linked. Some are only linked when
139 // doing a relocateable link.
140 switch (shdr
.get_sh_type())
142 case elfcpp::SHT_NULL
:
143 case elfcpp::SHT_SYMTAB
:
144 case elfcpp::SHT_DYNSYM
:
145 case elfcpp::SHT_STRTAB
:
146 case elfcpp::SHT_HASH
:
147 case elfcpp::SHT_DYNAMIC
:
148 case elfcpp::SHT_SYMTAB_SHNDX
:
151 case elfcpp::SHT_RELA
:
152 case elfcpp::SHT_REL
:
153 case elfcpp::SHT_GROUP
:
154 return parameters
->output_is_object();
156 case elfcpp::SHT_PROGBITS
:
157 if (parameters
->strip_debug()
158 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
160 // Debugging sections can only be recognized by name.
161 if (is_prefix_of(".debug", name
)
162 || is_prefix_of(".gnu.linkonce.wi.", name
)
163 || is_prefix_of(".line", name
)
164 || is_prefix_of(".stab", name
))
167 if (parameters
->strip_debug_gdb()
168 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
170 // Debugging sections can only be recognized by name.
171 if (is_prefix_of(".debug", name
)
172 && !is_gdb_debug_section(name
))
182 // Return an output section named NAME, or NULL if there is none.
185 Layout::find_output_section(const char* name
) const
187 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
188 p
!= this->section_name_map_
.end();
190 if (strcmp(p
->second
->name(), name
) == 0)
195 // Return an output segment of type TYPE, with segment flags SET set
196 // and segment flags CLEAR clear. Return NULL if there is none.
199 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
200 elfcpp::Elf_Word clear
) const
202 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
203 p
!= this->segment_list_
.end();
205 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
206 && ((*p
)->flags() & set
) == set
207 && ((*p
)->flags() & clear
) == 0)
212 // Return the output section to use for section NAME with type TYPE
213 // and section flags FLAGS.
216 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
217 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
219 // We should ignore some flags.
220 flags
&= ~ (elfcpp::SHF_INFO_LINK
221 | elfcpp::SHF_LINK_ORDER
224 | elfcpp::SHF_STRINGS
);
226 const Key
key(name_key
, std::make_pair(type
, flags
));
227 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
228 std::pair
<Section_name_map::iterator
, bool> ins(
229 this->section_name_map_
.insert(v
));
232 return ins
.first
->second
;
235 // This is the first time we've seen this name/type/flags
237 Output_section
* os
= this->make_output_section(name
, type
, flags
);
238 ins
.first
->second
= os
;
243 // Return the output section to use for input section SHNDX, with name
244 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
245 // index of a relocation section which applies to this section, or 0
246 // if none, or -1U if more than one. RELOC_TYPE is the type of the
247 // relocation section if there is one. Set *OFF to the offset of this
248 // input section without the output section. Return NULL if the
249 // section should be discarded. Set *OFF to -1 if the section
250 // contents should not be written directly to the output file, but
251 // will instead receive special handling.
253 template<int size
, bool big_endian
>
255 Layout::layout(Sized_relobj
<size
, big_endian
>* object
, unsigned int shndx
,
256 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
257 unsigned int reloc_shndx
, unsigned int, off_t
* off
)
259 if (!this->include_section(object
, name
, shdr
))
262 // If we are not doing a relocateable link, choose the name to use
263 // for the output section.
264 size_t len
= strlen(name
);
265 if (!parameters
->output_is_object())
266 name
= Layout::output_section_name(name
, &len
);
268 // FIXME: Handle SHF_OS_NONCONFORMING here.
270 // Canonicalize the section name.
271 Stringpool::Key name_key
;
272 name
= this->namepool_
.add_with_length(name
, len
, true, &name_key
);
274 // Find the output section. The output section is selected based on
275 // the section name, type, and flags.
276 Output_section
* os
= this->get_output_section(name
, name_key
,
278 shdr
.get_sh_flags());
280 // FIXME: Handle SHF_LINK_ORDER somewhere.
282 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
287 // Special GNU handling of sections name .eh_frame. They will
288 // normally hold exception frame data as defined by the C++ ABI
289 // (http://codesourcery.com/cxx-abi/).
291 template<int size
, bool big_endian
>
293 Layout::layout_eh_frame(Sized_relobj
<size
, big_endian
>* object
,
294 const unsigned char* symbols
,
296 const unsigned char* symbol_names
,
297 off_t symbol_names_size
,
299 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
300 unsigned int reloc_shndx
, unsigned int reloc_type
,
303 gold_assert(shdr
.get_sh_type() == elfcpp::SHT_PROGBITS
);
304 gold_assert(shdr
.get_sh_flags() == elfcpp::SHF_ALLOC
);
306 Stringpool::Key name_key
;
307 const char* name
= this->namepool_
.add(".eh_frame", false, &name_key
);
309 Output_section
* os
= this->get_output_section(name
, name_key
,
310 elfcpp::SHT_PROGBITS
,
313 if (this->eh_frame_section_
== NULL
)
315 this->eh_frame_section_
= os
;
316 this->eh_frame_data_
= new Eh_frame();
317 os
->add_output_section_data(this->eh_frame_data_
);
319 if (this->options_
.create_eh_frame_hdr())
321 Stringpool::Key hdr_name_key
;
322 const char* hdr_name
= this->namepool_
.add(".eh_frame_hdr",
325 Output_section
* hdr_os
=
326 this->get_output_section(hdr_name
, hdr_name_key
,
327 elfcpp::SHT_PROGBITS
,
330 Eh_frame_hdr
* hdr_posd
= new Eh_frame_hdr(os
, this->eh_frame_data_
);
331 hdr_os
->add_output_section_data(hdr_posd
);
333 hdr_os
->set_after_input_sections();
335 Output_segment
* hdr_oseg
=
336 new Output_segment(elfcpp::PT_GNU_EH_FRAME
, elfcpp::PF_R
);
337 this->segment_list_
.push_back(hdr_oseg
);
338 hdr_oseg
->add_output_section(hdr_os
, elfcpp::PF_R
);
340 this->eh_frame_data_
->set_eh_frame_hdr(hdr_posd
);
344 gold_assert(this->eh_frame_section_
== os
);
346 if (this->eh_frame_data_
->add_ehframe_input_section(object
,
357 // We couldn't handle this .eh_frame section for some reason.
358 // Add it as a normal section.
359 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
);
365 // Add POSD to an output section using NAME, TYPE, and FLAGS.
368 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
369 elfcpp::Elf_Xword flags
,
370 Output_section_data
* posd
)
372 // Canonicalize the name.
373 Stringpool::Key name_key
;
374 name
= this->namepool_
.add(name
, true, &name_key
);
376 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
377 os
->add_output_section_data(posd
);
380 // Map section flags to segment flags.
383 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
385 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
386 if ((flags
& elfcpp::SHF_WRITE
) != 0)
388 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
393 // Sometimes we compress sections. This is typically done for
394 // sections that are not part of normal program execution (such as
395 // .debug_* sections), and where the readers of these sections know
396 // how to deal with compressed sections. (To make it easier for them,
397 // we will rename the ouput section in such cases from .foo to
398 // .foo.zlib.nnnn, where nnnn is the uncompressed size.) This routine
399 // doesn't say for certain whether we'll compress -- it depends on
400 // commandline options as well -- just whether this section is a
401 // candidate for compression.
404 is_compressible_debug_section(const char* secname
)
406 return (strncmp(secname
, ".debug", sizeof(".debug") - 1) == 0);
409 // Make a new Output_section, and attach it to segments as
413 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
414 elfcpp::Elf_Xword flags
)
417 if ((flags
& elfcpp::SHF_ALLOC
) == 0
418 && this->options_
.compress_debug_sections()
419 && is_compressible_debug_section(name
))
420 os
= new Output_compressed_section(&this->options_
, name
, type
, flags
);
422 os
= new Output_section(name
, type
, flags
);
424 this->section_list_
.push_back(os
);
426 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
427 this->unattached_section_list_
.push_back(os
);
430 // This output section goes into a PT_LOAD segment.
432 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
434 // The only thing we really care about for PT_LOAD segments is
435 // whether or not they are writable, so that is how we search
436 // for them. People who need segments sorted on some other
437 // basis will have to wait until we implement a mechanism for
438 // them to describe the segments they want.
440 Segment_list::const_iterator p
;
441 for (p
= this->segment_list_
.begin();
442 p
!= this->segment_list_
.end();
445 if ((*p
)->type() == elfcpp::PT_LOAD
446 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
448 (*p
)->add_output_section(os
, seg_flags
);
453 if (p
== this->segment_list_
.end())
455 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
457 this->segment_list_
.push_back(oseg
);
458 oseg
->add_output_section(os
, seg_flags
);
461 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
463 if (type
== elfcpp::SHT_NOTE
)
465 // See if we already have an equivalent PT_NOTE segment.
466 for (p
= this->segment_list_
.begin();
467 p
!= segment_list_
.end();
470 if ((*p
)->type() == elfcpp::PT_NOTE
471 && (((*p
)->flags() & elfcpp::PF_W
)
472 == (seg_flags
& elfcpp::PF_W
)))
474 (*p
)->add_output_section(os
, seg_flags
);
479 if (p
== this->segment_list_
.end())
481 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
483 this->segment_list_
.push_back(oseg
);
484 oseg
->add_output_section(os
, seg_flags
);
488 // If we see a loadable SHF_TLS section, we create a PT_TLS
489 // segment. There can only be one such segment.
490 if ((flags
& elfcpp::SHF_TLS
) != 0)
492 if (this->tls_segment_
== NULL
)
494 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
496 this->segment_list_
.push_back(this->tls_segment_
);
498 this->tls_segment_
->add_output_section(os
, seg_flags
);
505 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
506 // is whether we saw a .note.GNU-stack section in the object file.
507 // GNU_STACK_FLAGS is the section flags. The flags give the
508 // protection required for stack memory. We record this in an
509 // executable as a PT_GNU_STACK segment. If an object file does not
510 // have a .note.GNU-stack segment, we must assume that it is an old
511 // object. On some targets that will force an executable stack.
514 Layout::layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
)
517 this->input_without_gnu_stack_note_
= true;
520 this->input_with_gnu_stack_note_
= true;
521 if ((gnu_stack_flags
& elfcpp::SHF_EXECINSTR
) != 0)
522 this->input_requires_executable_stack_
= true;
526 // Create the dynamic sections which are needed before we read the
530 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
531 Symbol_table
* symtab
)
533 if (parameters
->doing_static_link())
536 const char* dynamic_name
= this->namepool_
.add(".dynamic", false, NULL
);
537 this->dynamic_section_
= this->make_output_section(dynamic_name
,
540 | elfcpp::SHF_WRITE
));
542 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC", NULL
,
543 this->dynamic_section_
, 0, 0,
544 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
545 elfcpp::STV_HIDDEN
, 0, false, false);
547 this->dynamic_data_
= new Output_data_dynamic(&this->dynpool_
);
549 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
552 // For each output section whose name can be represented as C symbol,
553 // define __start and __stop symbols for the section. This is a GNU
557 Layout::define_section_symbols(Symbol_table
* symtab
, const Target
* target
)
559 for (Section_list::const_iterator p
= this->section_list_
.begin();
560 p
!= this->section_list_
.end();
563 const char* const name
= (*p
)->name();
564 if (name
[strspn(name
,
566 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
567 "abcdefghijklmnopqrstuvwxyz"
571 const std::string
name_string(name
);
572 const std::string
start_name("__start_" + name_string
);
573 const std::string
stop_name("__stop_" + name_string
);
575 symtab
->define_in_output_data(target
,
585 false, // offset_is_from_end
586 false); // only_if_ref
588 symtab
->define_in_output_data(target
,
598 true, // offset_is_from_end
599 false); // only_if_ref
604 // Find the first read-only PT_LOAD segment, creating one if
608 Layout::find_first_load_seg()
610 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
611 p
!= this->segment_list_
.end();
614 if ((*p
)->type() == elfcpp::PT_LOAD
615 && ((*p
)->flags() & elfcpp::PF_R
) != 0
616 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
620 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
621 this->segment_list_
.push_back(load_seg
);
625 // Finalize the layout. When this is called, we have created all the
626 // output sections and all the output segments which are based on
627 // input sections. We have several things to do, and we have to do
628 // them in the right order, so that we get the right results correctly
631 // 1) Finalize the list of output segments and create the segment
634 // 2) Finalize the dynamic symbol table and associated sections.
636 // 3) Determine the final file offset of all the output segments.
638 // 4) Determine the final file offset of all the SHF_ALLOC output
641 // 5) Create the symbol table sections and the section name table
644 // 6) Finalize the symbol table: set symbol values to their final
645 // value and make a final determination of which symbols are going
646 // into the output symbol table.
648 // 7) Create the section table header.
650 // 8) Determine the final file offset of all the output sections which
651 // are not SHF_ALLOC, including the section table header.
653 // 9) Finalize the ELF file header.
655 // This function returns the size of the output file.
658 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
,
661 Target
* const target
= input_objects
->target();
663 target
->finalize_sections(this);
665 this->count_local_symbols(task
, input_objects
);
667 this->create_gold_note();
668 this->create_executable_stack_info(target
);
670 Output_segment
* phdr_seg
= NULL
;
671 if (!parameters
->doing_static_link())
673 // There was a dynamic object in the link. We need to create
674 // some information for the dynamic linker.
676 // Create the PT_PHDR segment which will hold the program
678 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
679 this->segment_list_
.push_back(phdr_seg
);
681 // Create the dynamic symbol table, including the hash table.
682 Output_section
* dynstr
;
683 std::vector
<Symbol
*> dynamic_symbols
;
684 unsigned int local_dynamic_count
;
686 this->create_dynamic_symtab(input_objects
, target
, symtab
, &dynstr
,
687 &local_dynamic_count
, &dynamic_symbols
,
690 // Create the .interp section to hold the name of the
691 // interpreter, and put it in a PT_INTERP segment.
692 if (!parameters
->output_is_shared())
693 this->create_interp(target
);
695 // Finish the .dynamic section to hold the dynamic data, and put
696 // it in a PT_DYNAMIC segment.
697 this->finish_dynamic_section(input_objects
, symtab
);
699 // We should have added everything we need to the dynamic string
701 this->dynpool_
.set_string_offsets();
703 // Create the version sections. We can't do this until the
704 // dynamic string table is complete.
705 this->create_version_sections(&versions
, symtab
, local_dynamic_count
,
706 dynamic_symbols
, dynstr
);
709 // FIXME: Handle PT_GNU_STACK.
711 Output_segment
* load_seg
= this->find_first_load_seg();
713 // Lay out the segment headers.
714 Output_segment_headers
* segment_headers
;
715 segment_headers
= new Output_segment_headers(this->segment_list_
);
716 load_seg
->add_initial_output_data(segment_headers
);
717 this->special_output_list_
.push_back(segment_headers
);
718 if (phdr_seg
!= NULL
)
719 phdr_seg
->add_initial_output_data(segment_headers
);
721 // Lay out the file header.
722 Output_file_header
* file_header
;
723 file_header
= new Output_file_header(target
, symtab
, segment_headers
);
724 load_seg
->add_initial_output_data(file_header
);
725 this->special_output_list_
.push_back(file_header
);
727 // We set the output section indexes in set_segment_offsets and
728 // set_section_indexes.
729 unsigned int shndx
= 1;
731 // Set the file offsets of all the segments, and all the sections
733 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
735 // Create the symbol table sections.
736 this->create_symtab_sections(input_objects
, symtab
, task
, &off
);
737 if (!parameters
->doing_static_link())
738 this->assign_local_dynsym_offsets(input_objects
);
740 // Create the .shstrtab section.
741 Output_section
* shstrtab_section
= this->create_shstrtab();
743 // Set the file offsets of all the non-data sections which don't
744 // have to wait for the input sections.
745 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
747 // Now that all sections have been created, set the section indexes.
748 shndx
= this->set_section_indexes(shndx
);
750 // Create the section table header.
751 this->create_shdrs(&off
);
753 // If there are no sections which require postprocessing, we can
754 // handle the section names now, and avoid a resize later.
755 if (!this->any_postprocessing_sections_
)
756 off
= this->set_section_offsets(off
,
757 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
759 file_header
->set_section_info(this->section_headers_
, shstrtab_section
);
761 // Now we know exactly where everything goes in the output file
762 // (except for non-allocated sections which require postprocessing).
763 Output_data::layout_complete();
765 this->output_file_size_
= off
;
770 // Create a .note section for an executable or shared library. This
771 // records the version of gold used to create the binary.
774 Layout::create_gold_note()
776 if (parameters
->output_is_object())
779 // Authorities all agree that the values in a .note field should
780 // be aligned on 4-byte boundaries for 32-bit binaries. However,
781 // they differ on what the alignment is for 64-bit binaries.
782 // The GABI says unambiguously they take 8-byte alignment:
783 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
784 // Other documentation says alignment should always be 4 bytes:
785 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
786 // GNU ld and GNU readelf both support the latter (at least as of
787 // version 2.16.91), and glibc always generates the latter for
788 // .note.ABI-tag (as of version 1.6), so that's the one we go with
790 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
791 const int size
= parameters
->get_size();
796 // The contents of the .note section.
797 const char* name
= "GNU";
798 std::string
desc(std::string("gold ") + gold::get_version_string());
799 size_t namesz
= strlen(name
) + 1;
800 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
801 size_t descsz
= desc
.length() + 1;
802 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
803 const int note_type
= 4;
805 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
807 unsigned char buffer
[128];
808 gold_assert(sizeof buffer
>= notesz
);
809 memset(buffer
, 0, notesz
);
811 bool is_big_endian
= parameters
->is_big_endian();
817 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
818 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
819 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
823 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
824 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
825 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
832 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
833 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
834 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
838 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
839 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
840 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
846 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
847 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
849 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
850 Output_section
* os
= this->make_output_section(note_name
,
853 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
855 os
->add_output_section_data(posd
);
858 // Record whether the stack should be executable. This can be set
859 // from the command line using the -z execstack or -z noexecstack
860 // options. Otherwise, if any input file has a .note.GNU-stack
861 // section with the SHF_EXECINSTR flag set, the stack should be
862 // executable. Otherwise, if at least one input file a
863 // .note.GNU-stack section, and some input file has no .note.GNU-stack
864 // section, we use the target default for whether the stack should be
865 // executable. Otherwise, we don't generate a stack note. When
866 // generating a object file, we create a .note.GNU-stack section with
867 // the appropriate marking. When generating an executable or shared
868 // library, we create a PT_GNU_STACK segment.
871 Layout::create_executable_stack_info(const Target
* target
)
873 bool is_stack_executable
;
874 if (this->options_
.is_execstack_set())
875 is_stack_executable
= this->options_
.is_stack_executable();
876 else if (!this->input_with_gnu_stack_note_
)
880 if (this->input_requires_executable_stack_
)
881 is_stack_executable
= true;
882 else if (this->input_without_gnu_stack_note_
)
883 is_stack_executable
= target
->is_default_stack_executable();
885 is_stack_executable
= false;
888 if (parameters
->output_is_object())
890 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
891 elfcpp::Elf_Xword flags
= 0;
892 if (is_stack_executable
)
893 flags
|= elfcpp::SHF_EXECINSTR
;
894 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
898 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
899 if (is_stack_executable
)
900 flags
|= elfcpp::PF_X
;
901 Output_segment
* oseg
= new Output_segment(elfcpp::PT_GNU_STACK
, flags
);
902 this->segment_list_
.push_back(oseg
);
906 // Return whether SEG1 should be before SEG2 in the output file. This
907 // is based entirely on the segment type and flags. When this is
908 // called the segment addresses has normally not yet been set.
911 Layout::segment_precedes(const Output_segment
* seg1
,
912 const Output_segment
* seg2
)
914 elfcpp::Elf_Word type1
= seg1
->type();
915 elfcpp::Elf_Word type2
= seg2
->type();
917 // The single PT_PHDR segment is required to precede any loadable
918 // segment. We simply make it always first.
919 if (type1
== elfcpp::PT_PHDR
)
921 gold_assert(type2
!= elfcpp::PT_PHDR
);
924 if (type2
== elfcpp::PT_PHDR
)
927 // The single PT_INTERP segment is required to precede any loadable
928 // segment. We simply make it always second.
929 if (type1
== elfcpp::PT_INTERP
)
931 gold_assert(type2
!= elfcpp::PT_INTERP
);
934 if (type2
== elfcpp::PT_INTERP
)
937 // We then put PT_LOAD segments before any other segments.
938 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
940 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
943 // We put the PT_TLS segment last, because that is where the dynamic
944 // linker expects to find it (this is just for efficiency; other
945 // positions would also work correctly).
946 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
948 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
951 const elfcpp::Elf_Word flags1
= seg1
->flags();
952 const elfcpp::Elf_Word flags2
= seg2
->flags();
954 // The order of non-PT_LOAD segments is unimportant. We simply sort
955 // by the numeric segment type and flags values. There should not
956 // be more than one segment with the same type and flags.
957 if (type1
!= elfcpp::PT_LOAD
)
960 return type1
< type2
;
961 gold_assert(flags1
!= flags2
);
962 return flags1
< flags2
;
965 // We sort PT_LOAD segments based on the flags. Readonly segments
966 // come before writable segments. Then executable segments come
967 // before non-executable segments. Then the unlikely case of a
968 // non-readable segment comes before the normal case of a readable
969 // segment. If there are multiple segments with the same type and
970 // flags, we require that the address be set, and we sort by
971 // virtual address and then physical address.
972 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
973 return (flags1
& elfcpp::PF_W
) == 0;
974 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
975 return (flags1
& elfcpp::PF_X
) != 0;
976 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
977 return (flags1
& elfcpp::PF_R
) == 0;
979 uint64_t vaddr1
= seg1
->vaddr();
980 uint64_t vaddr2
= seg2
->vaddr();
981 if (vaddr1
!= vaddr2
)
982 return vaddr1
< vaddr2
;
984 uint64_t paddr1
= seg1
->paddr();
985 uint64_t paddr2
= seg2
->paddr();
986 gold_assert(paddr1
!= paddr2
);
987 return paddr1
< paddr2
;
990 // Set the file offsets of all the segments, and all the sections they
991 // contain. They have all been created. LOAD_SEG must be be laid out
992 // first. Return the offset of the data to follow.
995 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
996 unsigned int *pshndx
)
998 // Sort them into the final order.
999 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
1000 Layout::Compare_segments());
1002 // Find the PT_LOAD segments, and set their addresses and offsets
1003 // and their section's addresses and offsets.
1005 if (parameters
->output_is_shared())
1007 else if (options_
.user_set_text_segment_address())
1008 addr
= options_
.text_segment_address();
1010 addr
= target
->default_text_segment_address();
1012 bool was_readonly
= false;
1013 for (Segment_list::iterator p
= this->segment_list_
.begin();
1014 p
!= this->segment_list_
.end();
1017 if ((*p
)->type() == elfcpp::PT_LOAD
)
1019 if (load_seg
!= NULL
&& load_seg
!= *p
)
1023 // If the last segment was readonly, and this one is not,
1024 // then skip the address forward one page, maintaining the
1025 // same position within the page. This lets us store both
1026 // segments overlapping on a single page in the file, but
1027 // the loader will put them on different pages in memory.
1029 uint64_t orig_addr
= addr
;
1030 uint64_t orig_off
= off
;
1032 uint64_t aligned_addr
= addr
;
1033 uint64_t abi_pagesize
= target
->abi_pagesize();
1035 // FIXME: This should depend on the -n and -N options.
1036 (*p
)->set_minimum_addralign(target
->common_pagesize());
1038 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
1040 uint64_t align
= (*p
)->addralign();
1042 addr
= align_address(addr
, align
);
1043 aligned_addr
= addr
;
1044 if ((addr
& (abi_pagesize
- 1)) != 0)
1045 addr
= addr
+ abi_pagesize
;
1048 unsigned int shndx_hold
= *pshndx
;
1049 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1050 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1052 // Now that we know the size of this segment, we may be able
1053 // to save a page in memory, at the cost of wasting some
1054 // file space, by instead aligning to the start of a new
1055 // page. Here we use the real machine page size rather than
1056 // the ABI mandated page size.
1058 if (aligned_addr
!= addr
)
1060 uint64_t common_pagesize
= target
->common_pagesize();
1061 uint64_t first_off
= (common_pagesize
1063 & (common_pagesize
- 1)));
1064 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
1067 && ((aligned_addr
& ~ (common_pagesize
- 1))
1068 != (new_addr
& ~ (common_pagesize
- 1)))
1069 && first_off
+ last_off
<= common_pagesize
)
1071 *pshndx
= shndx_hold
;
1072 addr
= align_address(aligned_addr
, common_pagesize
);
1073 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1074 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1080 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
1081 was_readonly
= true;
1085 // Handle the non-PT_LOAD segments, setting their offsets from their
1086 // section's offsets.
1087 for (Segment_list::iterator p
= this->segment_list_
.begin();
1088 p
!= this->segment_list_
.end();
1091 if ((*p
)->type() != elfcpp::PT_LOAD
)
1095 // Set the TLS offsets for each section in the PT_TLS segment.
1096 if (this->tls_segment_
!= NULL
)
1097 this->tls_segment_
->set_tls_offsets();
1102 // Set the file offset of all the sections not associated with a
1106 Layout::set_section_offsets(off_t off
, Layout::Section_offset_pass pass
)
1108 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1109 p
!= this->unattached_section_list_
.end();
1112 // The symtab section is handled in create_symtab_sections.
1113 if (*p
== this->symtab_section_
)
1116 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1117 && (*p
)->requires_postprocessing())
1119 (*p
)->create_postprocessing_buffer();
1120 this->any_postprocessing_sections_
= true;
1123 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1124 && (*p
)->after_input_sections())
1126 else if (pass
== POSTPROCESSING_SECTIONS_PASS
1127 && (!(*p
)->after_input_sections()
1128 || (*p
)->type() == elfcpp::SHT_STRTAB
))
1130 else if (pass
== STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1131 && (!(*p
)->after_input_sections()
1132 || (*p
)->type() != elfcpp::SHT_STRTAB
))
1135 off
= align_address(off
, (*p
)->addralign());
1136 (*p
)->set_file_offset(off
);
1137 (*p
)->finalize_data_size();
1138 off
+= (*p
)->data_size();
1140 // At this point the name must be set.
1141 if (pass
!= STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
)
1142 this->namepool_
.add((*p
)->name(), false, NULL
);
1147 // Set the section indexes of all the sections not associated with a
1151 Layout::set_section_indexes(unsigned int shndx
)
1153 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1154 p
!= this->unattached_section_list_
.end();
1157 (*p
)->set_out_shndx(shndx
);
1163 // Count the local symbols in the regular symbol table and the dynamic
1164 // symbol table, and build the respective string pools.
1167 Layout::count_local_symbols(const Task
* task
,
1168 const Input_objects
* input_objects
)
1170 // First, figure out an upper bound on the number of symbols we'll
1171 // be inserting into each pool. This helps us create the pools with
1172 // the right size, to avoid unnecessary hashtable resizing.
1173 unsigned int symbol_count
= 0;
1174 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1175 p
!= input_objects
->relobj_end();
1177 symbol_count
+= (*p
)->local_symbol_count();
1179 // Go from "upper bound" to "estimate." We overcount for two
1180 // reasons: we double-count symbols that occur in more than one
1181 // object file, and we count symbols that are dropped from the
1182 // output. Add it all together and assume we overcount by 100%.
1185 // We assume all symbols will go into both the sympool and dynpool.
1186 this->sympool_
.reserve(symbol_count
);
1187 this->dynpool_
.reserve(symbol_count
);
1189 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1190 p
!= input_objects
->relobj_end();
1193 Task_lock_obj
<Object
> tlo(task
, *p
);
1194 (*p
)->count_local_symbols(&this->sympool_
, &this->dynpool_
);
1198 // Create the symbol table sections. Here we also set the final
1199 // values of the symbols. At this point all the loadable sections are
1203 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1204 Symbol_table
* symtab
,
1210 if (parameters
->get_size() == 32)
1212 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1215 else if (parameters
->get_size() == 64)
1217 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1224 off
= align_address(off
, align
);
1225 off_t startoff
= off
;
1227 // Save space for the dummy symbol at the start of the section. We
1228 // never bother to write this out--it will just be left as zero.
1230 unsigned int local_symbol_index
= 1;
1232 // Add STT_SECTION symbols for each Output section which needs one.
1233 for (Section_list::iterator p
= this->section_list_
.begin();
1234 p
!= this->section_list_
.end();
1237 if (!(*p
)->needs_symtab_index())
1238 (*p
)->set_symtab_index(-1U);
1241 (*p
)->set_symtab_index(local_symbol_index
);
1242 ++local_symbol_index
;
1247 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1248 p
!= input_objects
->relobj_end();
1251 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1253 off
+= (index
- local_symbol_index
) * symsize
;
1254 local_symbol_index
= index
;
1257 unsigned int local_symcount
= local_symbol_index
;
1258 gold_assert(local_symcount
* symsize
== off
- startoff
);
1261 size_t dyn_global_index
;
1263 if (this->dynsym_section_
== NULL
)
1266 dyn_global_index
= 0;
1271 dyn_global_index
= this->dynsym_section_
->info();
1272 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1273 dynoff
= this->dynsym_section_
->offset() + locsize
;
1274 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1275 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1276 == this->dynsym_section_
->data_size() - locsize
);
1279 off
= symtab
->finalize(task
, local_symcount
, off
, dynoff
, dyn_global_index
,
1280 dyncount
, &this->sympool_
);
1282 if (!parameters
->strip_all())
1284 this->sympool_
.set_string_offsets();
1286 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1287 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1290 this->symtab_section_
= osymtab
;
1292 Output_section_data
* pos
= new Output_data_fixed_space(off
- startoff
,
1294 osymtab
->add_output_section_data(pos
);
1296 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1297 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1301 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1302 ostrtab
->add_output_section_data(pstr
);
1304 osymtab
->set_file_offset(startoff
);
1305 osymtab
->finalize_data_size();
1306 osymtab
->set_link_section(ostrtab
);
1307 osymtab
->set_info(local_symcount
);
1308 osymtab
->set_entsize(symsize
);
1314 // Create the .shstrtab section, which holds the names of the
1315 // sections. At the time this is called, we have created all the
1316 // output sections except .shstrtab itself.
1319 Layout::create_shstrtab()
1321 // FIXME: We don't need to create a .shstrtab section if we are
1322 // stripping everything.
1324 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1326 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1328 // We can't write out this section until we've set all the section
1329 // names, and we don't set the names of compressed output sections
1330 // until relocations are complete.
1331 os
->set_after_input_sections();
1333 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1334 os
->add_output_section_data(posd
);
1339 // Create the section headers. SIZE is 32 or 64. OFF is the file
1343 Layout::create_shdrs(off_t
* poff
)
1345 Output_section_headers
* oshdrs
;
1346 oshdrs
= new Output_section_headers(this,
1347 &this->segment_list_
,
1348 &this->unattached_section_list_
,
1350 off_t off
= align_address(*poff
, oshdrs
->addralign());
1351 oshdrs
->set_address_and_file_offset(0, off
);
1352 off
+= oshdrs
->data_size();
1354 this->section_headers_
= oshdrs
;
1357 // Create the dynamic symbol table.
1360 Layout::create_dynamic_symtab(const Input_objects
* input_objects
,
1361 const Target
* target
, Symbol_table
* symtab
,
1362 Output_section
**pdynstr
,
1363 unsigned int* plocal_dynamic_count
,
1364 std::vector
<Symbol
*>* pdynamic_symbols
,
1365 Versions
* pversions
)
1367 // Count all the symbols in the dynamic symbol table, and set the
1368 // dynamic symbol indexes.
1370 // Skip symbol 0, which is always all zeroes.
1371 unsigned int index
= 1;
1373 // Add STT_SECTION symbols for each Output section which needs one.
1374 for (Section_list::iterator p
= this->section_list_
.begin();
1375 p
!= this->section_list_
.end();
1378 if (!(*p
)->needs_dynsym_index())
1379 (*p
)->set_dynsym_index(-1U);
1382 (*p
)->set_dynsym_index(index
);
1387 // Count the local symbols that need to go in the dynamic symbol table,
1388 // and set the dynamic symbol indexes.
1389 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1390 p
!= input_objects
->relobj_end();
1393 unsigned int new_index
= (*p
)->set_local_dynsym_indexes(index
);
1397 unsigned int local_symcount
= index
;
1398 *plocal_dynamic_count
= local_symcount
;
1400 // FIXME: We have to tell set_dynsym_indexes whether the
1401 // -E/--export-dynamic option was used.
1402 index
= symtab
->set_dynsym_indexes(target
, index
, pdynamic_symbols
,
1403 &this->dynpool_
, pversions
);
1407 const int size
= parameters
->get_size();
1410 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1413 else if (size
== 64)
1415 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1421 // Create the dynamic symbol table section.
1423 const char* dynsym_name
= this->namepool_
.add(".dynsym", false, NULL
);
1424 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
1428 Output_section_data
* odata
= new Output_data_fixed_space(index
* symsize
,
1430 dynsym
->add_output_section_data(odata
);
1432 dynsym
->set_info(local_symcount
);
1433 dynsym
->set_entsize(symsize
);
1434 dynsym
->set_addralign(align
);
1436 this->dynsym_section_
= dynsym
;
1438 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1439 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1440 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1442 // Create the dynamic string table section.
1444 const char* dynstr_name
= this->namepool_
.add(".dynstr", false, NULL
);
1445 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
1449 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1450 dynstr
->add_output_section_data(strdata
);
1452 dynsym
->set_link_section(dynstr
);
1453 this->dynamic_section_
->set_link_section(dynstr
);
1455 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1456 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1460 // Create the hash tables.
1462 // FIXME: We need an option to create a GNU hash table.
1464 unsigned char* phash
;
1465 unsigned int hashlen
;
1466 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1469 const char* hash_name
= this->namepool_
.add(".hash", false, NULL
);
1470 Output_section
* hashsec
= this->make_output_section(hash_name
,
1474 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1477 hashsec
->add_output_section_data(hashdata
);
1479 hashsec
->set_link_section(dynsym
);
1480 hashsec
->set_entsize(4);
1482 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1485 // Assign offsets to each local portion of the dynamic symbol table.
1488 Layout::assign_local_dynsym_offsets(const Input_objects
* input_objects
)
1490 Output_section
* dynsym
= this->dynsym_section_
;
1491 gold_assert(dynsym
!= NULL
);
1493 off_t off
= dynsym
->offset();
1495 // Skip the dummy symbol at the start of the section.
1496 off
+= dynsym
->entsize();
1498 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1499 p
!= input_objects
->relobj_end();
1502 unsigned int count
= (*p
)->set_local_dynsym_offset(off
);
1503 off
+= count
* dynsym
->entsize();
1507 // Create the version sections.
1510 Layout::create_version_sections(const Versions
* versions
,
1511 const Symbol_table
* symtab
,
1512 unsigned int local_symcount
,
1513 const std::vector
<Symbol
*>& dynamic_symbols
,
1514 const Output_section
* dynstr
)
1516 if (!versions
->any_defs() && !versions
->any_needs())
1519 if (parameters
->get_size() == 32)
1521 if (parameters
->is_big_endian())
1523 #ifdef HAVE_TARGET_32_BIG
1524 this->sized_create_version_sections
1525 SELECT_SIZE_ENDIAN_NAME(32, true)(
1526 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1527 SELECT_SIZE_ENDIAN(32, true));
1534 #ifdef HAVE_TARGET_32_LITTLE
1535 this->sized_create_version_sections
1536 SELECT_SIZE_ENDIAN_NAME(32, false)(
1537 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1538 SELECT_SIZE_ENDIAN(32, false));
1544 else if (parameters
->get_size() == 64)
1546 if (parameters
->is_big_endian())
1548 #ifdef HAVE_TARGET_64_BIG
1549 this->sized_create_version_sections
1550 SELECT_SIZE_ENDIAN_NAME(64, true)(
1551 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1552 SELECT_SIZE_ENDIAN(64, true));
1559 #ifdef HAVE_TARGET_64_LITTLE
1560 this->sized_create_version_sections
1561 SELECT_SIZE_ENDIAN_NAME(64, false)(
1562 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1563 SELECT_SIZE_ENDIAN(64, false));
1573 // Create the version sections, sized version.
1575 template<int size
, bool big_endian
>
1577 Layout::sized_create_version_sections(
1578 const Versions
* versions
,
1579 const Symbol_table
* symtab
,
1580 unsigned int local_symcount
,
1581 const std::vector
<Symbol
*>& dynamic_symbols
,
1582 const Output_section
* dynstr
1585 const char* vname
= this->namepool_
.add(".gnu.version", false, NULL
);
1586 Output_section
* vsec
= this->make_output_section(vname
,
1587 elfcpp::SHT_GNU_versym
,
1590 unsigned char* vbuf
;
1592 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1593 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1594 SELECT_SIZE_ENDIAN(size
, big_endian
));
1596 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1598 vsec
->add_output_section_data(vdata
);
1599 vsec
->set_entsize(2);
1600 vsec
->set_link_section(this->dynsym_section_
);
1602 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1603 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1605 if (versions
->any_defs())
1607 const char* vdname
= this->namepool_
.add(".gnu.version_d", false, NULL
);
1608 Output_section
*vdsec
;
1609 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1612 unsigned char* vdbuf
;
1613 unsigned int vdsize
;
1614 unsigned int vdentries
;
1615 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1616 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1617 SELECT_SIZE_ENDIAN(size
, big_endian
));
1619 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1623 vdsec
->add_output_section_data(vddata
);
1624 vdsec
->set_link_section(dynstr
);
1625 vdsec
->set_info(vdentries
);
1627 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1628 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1631 if (versions
->any_needs())
1633 const char* vnname
= this->namepool_
.add(".gnu.version_r", false, NULL
);
1634 Output_section
* vnsec
;
1635 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1638 unsigned char* vnbuf
;
1639 unsigned int vnsize
;
1640 unsigned int vnentries
;
1641 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1642 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1643 SELECT_SIZE_ENDIAN(size
, big_endian
));
1645 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1649 vnsec
->add_output_section_data(vndata
);
1650 vnsec
->set_link_section(dynstr
);
1651 vnsec
->set_info(vnentries
);
1653 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1654 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1658 // Create the .interp section and PT_INTERP segment.
1661 Layout::create_interp(const Target
* target
)
1663 const char* interp
= this->options_
.dynamic_linker();
1666 interp
= target
->dynamic_linker();
1667 gold_assert(interp
!= NULL
);
1670 size_t len
= strlen(interp
) + 1;
1672 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1674 const char* interp_name
= this->namepool_
.add(".interp", false, NULL
);
1675 Output_section
* osec
= this->make_output_section(interp_name
,
1676 elfcpp::SHT_PROGBITS
,
1678 osec
->add_output_section_data(odata
);
1680 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1681 this->segment_list_
.push_back(oseg
);
1682 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1685 // Finish the .dynamic section and PT_DYNAMIC segment.
1688 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1689 const Symbol_table
* symtab
)
1691 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1692 elfcpp::PF_R
| elfcpp::PF_W
);
1693 this->segment_list_
.push_back(oseg
);
1694 oseg
->add_initial_output_section(this->dynamic_section_
,
1695 elfcpp::PF_R
| elfcpp::PF_W
);
1697 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1699 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1700 p
!= input_objects
->dynobj_end();
1703 // FIXME: Handle --as-needed.
1704 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1707 // FIXME: Support --init and --fini.
1708 Symbol
* sym
= symtab
->lookup("_init");
1709 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1710 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1712 sym
= symtab
->lookup("_fini");
1713 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1714 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1716 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1718 // Add a DT_RPATH entry if needed.
1719 const General_options::Dir_list
& rpath(this->options_
.rpath());
1722 std::string rpath_val
;
1723 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1727 if (rpath_val
.empty())
1728 rpath_val
= p
->name();
1731 // Eliminate duplicates.
1732 General_options::Dir_list::const_iterator q
;
1733 for (q
= rpath
.begin(); q
!= p
; ++q
)
1734 if (q
->name() == p
->name())
1739 rpath_val
+= p
->name();
1744 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1747 // Look for text segments that have dynamic relocations.
1748 bool have_textrel
= false;
1749 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
1750 p
!= this->segment_list_
.end();
1753 if (((*p
)->flags() & elfcpp::PF_W
) == 0
1754 && (*p
)->dynamic_reloc_count() > 0)
1756 have_textrel
= true;
1761 // Add a DT_FLAGS entry. We add it even if no flags are set so that
1762 // post-link tools can easily modify these flags if desired.
1763 unsigned int flags
= 0;
1766 // Add a DT_TEXTREL for compatibility with older loaders.
1767 odyn
->add_constant(elfcpp::DT_TEXTREL
, 0);
1768 flags
|= elfcpp::DF_TEXTREL
;
1770 if (parameters
->output_is_shared() && this->has_static_tls())
1771 flags
|= elfcpp::DF_STATIC_TLS
;
1772 odyn
->add_constant(elfcpp::DT_FLAGS
, flags
);
1775 // The mapping of .gnu.linkonce section names to real section names.
1777 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1778 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1780 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1781 MAPPING_INIT("t", ".text"),
1782 MAPPING_INIT("r", ".rodata"),
1783 MAPPING_INIT("d", ".data"),
1784 MAPPING_INIT("b", ".bss"),
1785 MAPPING_INIT("s", ".sdata"),
1786 MAPPING_INIT("sb", ".sbss"),
1787 MAPPING_INIT("s2", ".sdata2"),
1788 MAPPING_INIT("sb2", ".sbss2"),
1789 MAPPING_INIT("wi", ".debug_info"),
1790 MAPPING_INIT("td", ".tdata"),
1791 MAPPING_INIT("tb", ".tbss"),
1792 MAPPING_INIT("lr", ".lrodata"),
1793 MAPPING_INIT("l", ".ldata"),
1794 MAPPING_INIT("lb", ".lbss"),
1798 const int Layout::linkonce_mapping_count
=
1799 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1801 // Return the name of the output section to use for a .gnu.linkonce
1802 // section. This is based on the default ELF linker script of the old
1803 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1804 // to ".text". Set *PLEN to the length of the name. *PLEN is
1805 // initialized to the length of NAME.
1808 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1810 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1814 const Linkonce_mapping
* plm
= linkonce_mapping
;
1815 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1817 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1826 // Choose the output section name to use given an input section name.
1827 // Set *PLEN to the length of the name. *PLEN is initialized to the
1831 Layout::output_section_name(const char* name
, size_t* plen
)
1833 if (Layout::is_linkonce(name
))
1835 // .gnu.linkonce sections are laid out as though they were named
1836 // for the sections are placed into.
1837 return Layout::linkonce_output_name(name
, plen
);
1840 // gcc 4.3 generates the following sorts of section names when it
1841 // needs a section name specific to a function:
1847 // .data.rel.local.FN
1849 // .data.rel.ro.local.FN
1856 // The GNU linker maps all of those to the part before the .FN,
1857 // except that .data.rel.local.FN is mapped to .data, and
1858 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1859 // beginning with .data.rel.ro.local are grouped together.
1861 // For an anonymous namespace, the string FN can contain a '.'.
1863 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1864 // GNU linker maps to .rodata.
1866 // The .data.rel.ro sections enable a security feature triggered by
1867 // the -z relro option. Section which need to be relocated at
1868 // program startup time but which may be readonly after startup are
1869 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1870 // segment. The dynamic linker will make that segment writable,
1871 // perform relocations, and then make it read-only. FIXME: We do
1872 // not yet implement this optimization.
1874 // It is hard to handle this in a principled way.
1876 // These are the rules we follow:
1878 // If the section name has no initial '.', or no dot other than an
1879 // initial '.', we use the name unchanged (i.e., "mysection" and
1880 // ".text" are unchanged).
1882 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1884 // Otherwise, we drop the second '.' and everything that comes after
1885 // it (i.e., ".text.XXX" becomes ".text").
1887 const char* s
= name
;
1891 const char* sdot
= strchr(s
, '.');
1895 const char* const data_rel_ro
= ".data.rel.ro";
1896 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
1898 *plen
= strlen(data_rel_ro
);
1902 *plen
= sdot
- name
;
1906 // Record the signature of a comdat section, and return whether to
1907 // include it in the link. If GROUP is true, this is a regular
1908 // section group. If GROUP is false, this is a group signature
1909 // derived from the name of a linkonce section. We want linkonce
1910 // signatures and group signatures to block each other, but we don't
1911 // want a linkonce signature to block another linkonce signature.
1914 Layout::add_comdat(const char* signature
, bool group
)
1916 std::string
sig(signature
);
1917 std::pair
<Signatures::iterator
, bool> ins(
1918 this->signatures_
.insert(std::make_pair(sig
, group
)));
1922 // This is the first time we've seen this signature.
1926 if (ins
.first
->second
)
1928 // We've already seen a real section group with this signature.
1933 // This is a real section group, and we've already seen a
1934 // linkonce section with this signature. Record that we've seen
1935 // a section group, and don't include this section group.
1936 ins
.first
->second
= true;
1941 // We've already seen a linkonce section and this is a linkonce
1942 // section. These don't block each other--this may be the same
1943 // symbol name with different section types.
1948 // Write out the Output_sections. Most won't have anything to write,
1949 // since most of the data will come from input sections which are
1950 // handled elsewhere. But some Output_sections do have Output_data.
1953 Layout::write_output_sections(Output_file
* of
) const
1955 for (Section_list::const_iterator p
= this->section_list_
.begin();
1956 p
!= this->section_list_
.end();
1959 if (!(*p
)->after_input_sections())
1964 // Write out data not associated with a section or the symbol table.
1967 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
1969 if (!parameters
->strip_all())
1971 const Output_section
* symtab_section
= this->symtab_section_
;
1972 for (Section_list::const_iterator p
= this->section_list_
.begin();
1973 p
!= this->section_list_
.end();
1976 if ((*p
)->needs_symtab_index())
1978 gold_assert(symtab_section
!= NULL
);
1979 unsigned int index
= (*p
)->symtab_index();
1980 gold_assert(index
> 0 && index
!= -1U);
1981 off_t off
= (symtab_section
->offset()
1982 + index
* symtab_section
->entsize());
1983 symtab
->write_section_symbol(*p
, of
, off
);
1988 const Output_section
* dynsym_section
= this->dynsym_section_
;
1989 for (Section_list::const_iterator p
= this->section_list_
.begin();
1990 p
!= this->section_list_
.end();
1993 if ((*p
)->needs_dynsym_index())
1995 gold_assert(dynsym_section
!= NULL
);
1996 unsigned int index
= (*p
)->dynsym_index();
1997 gold_assert(index
> 0 && index
!= -1U);
1998 off_t off
= (dynsym_section
->offset()
1999 + index
* dynsym_section
->entsize());
2000 symtab
->write_section_symbol(*p
, of
, off
);
2004 // Write out the Output_data which are not in an Output_section.
2005 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
2006 p
!= this->special_output_list_
.end();
2011 // Write out the Output_sections which can only be written after the
2012 // input sections are complete.
2015 Layout::write_sections_after_input_sections(Output_file
* of
)
2017 // Determine the final section offsets, and thus the final output
2018 // file size. Note we finalize the .shstrab last, to allow the
2019 // after_input_section sections to modify their section-names before
2021 if (this->any_postprocessing_sections_
)
2023 off_t off
= this->output_file_size_
;
2024 off
= this->set_section_offsets(off
, POSTPROCESSING_SECTIONS_PASS
);
2026 // Now that we've finalized the names, we can finalize the shstrab.
2028 this->set_section_offsets(off
,
2029 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
2031 if (off
> this->output_file_size_
)
2034 this->output_file_size_
= off
;
2038 for (Section_list::const_iterator p
= this->section_list_
.begin();
2039 p
!= this->section_list_
.end();
2042 if ((*p
)->after_input_sections())
2046 this->section_headers_
->write(of
);
2049 // Print statistical information to stderr. This is used for --stats.
2052 Layout::print_stats() const
2054 this->namepool_
.print_stats("section name pool");
2055 this->sympool_
.print_stats("output symbol name pool");
2056 this->dynpool_
.print_stats("dynamic name pool");
2058 for (Section_list::const_iterator p
= this->section_list_
.begin();
2059 p
!= this->section_list_
.end();
2061 (*p
)->print_merge_stats();
2064 // Write_sections_task methods.
2066 // We can always run this task.
2069 Write_sections_task::is_runnable()
2074 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
2078 Write_sections_task::locks(Task_locker
* tl
)
2080 tl
->add(this, this->output_sections_blocker_
);
2081 tl
->add(this, this->final_blocker_
);
2084 // Run the task--write out the data.
2087 Write_sections_task::run(Workqueue
*)
2089 this->layout_
->write_output_sections(this->of_
);
2092 // Write_data_task methods.
2094 // We can always run this task.
2097 Write_data_task::is_runnable()
2102 // We need to unlock FINAL_BLOCKER when finished.
2105 Write_data_task::locks(Task_locker
* tl
)
2107 tl
->add(this, this->final_blocker_
);
2110 // Run the task--write out the data.
2113 Write_data_task::run(Workqueue
*)
2115 this->layout_
->write_data(this->symtab_
, this->of_
);
2118 // Write_symbols_task methods.
2120 // We can always run this task.
2123 Write_symbols_task::is_runnable()
2128 // We need to unlock FINAL_BLOCKER when finished.
2131 Write_symbols_task::locks(Task_locker
* tl
)
2133 tl
->add(this, this->final_blocker_
);
2136 // Run the task--write out the symbols.
2139 Write_symbols_task::run(Workqueue
*)
2141 this->symtab_
->write_globals(this->input_objects_
, this->sympool_
,
2142 this->dynpool_
, this->of_
);
2145 // Write_after_input_sections_task methods.
2147 // We can only run this task after the input sections have completed.
2150 Write_after_input_sections_task::is_runnable()
2152 if (this->input_sections_blocker_
->is_blocked())
2153 return this->input_sections_blocker_
;
2157 // We need to unlock FINAL_BLOCKER when finished.
2160 Write_after_input_sections_task::locks(Task_locker
* tl
)
2162 tl
->add(this, this->final_blocker_
);
2168 Write_after_input_sections_task::run(Workqueue
*)
2170 this->layout_
->write_sections_after_input_sections(this->of_
);
2173 // Close_task_runner methods.
2175 // Run the task--close the file.
2178 Close_task_runner::run(Workqueue
*, const Task
*)
2183 // Instantiate the templates we need. We could use the configure
2184 // script to restrict this to only the ones for implemented targets.
2186 #ifdef HAVE_TARGET_32_LITTLE
2189 Layout::layout
<32, false>(Sized_relobj
<32, false>* object
, unsigned int shndx
,
2191 const elfcpp::Shdr
<32, false>& shdr
,
2192 unsigned int, unsigned int, off_t
*);
2195 #ifdef HAVE_TARGET_32_BIG
2198 Layout::layout
<32, true>(Sized_relobj
<32, true>* object
, unsigned int shndx
,
2200 const elfcpp::Shdr
<32, true>& shdr
,
2201 unsigned int, unsigned int, off_t
*);
2204 #ifdef HAVE_TARGET_64_LITTLE
2207 Layout::layout
<64, false>(Sized_relobj
<64, false>* object
, unsigned int shndx
,
2209 const elfcpp::Shdr
<64, false>& shdr
,
2210 unsigned int, unsigned int, off_t
*);
2213 #ifdef HAVE_TARGET_64_BIG
2216 Layout::layout
<64, true>(Sized_relobj
<64, true>* object
, unsigned int shndx
,
2218 const elfcpp::Shdr
<64, true>& shdr
,
2219 unsigned int, unsigned int, off_t
*);
2222 #ifdef HAVE_TARGET_32_LITTLE
2225 Layout::layout_eh_frame
<32, false>(Sized_relobj
<32, false>* object
,
2226 const unsigned char* symbols
,
2228 const unsigned char* symbol_names
,
2229 off_t symbol_names_size
,
2231 const elfcpp::Shdr
<32, false>& shdr
,
2232 unsigned int reloc_shndx
,
2233 unsigned int reloc_type
,
2237 #ifdef HAVE_TARGET_32_BIG
2240 Layout::layout_eh_frame
<32, true>(Sized_relobj
<32, true>* object
,
2241 const unsigned char* symbols
,
2243 const unsigned char* symbol_names
,
2244 off_t symbol_names_size
,
2246 const elfcpp::Shdr
<32, true>& shdr
,
2247 unsigned int reloc_shndx
,
2248 unsigned int reloc_type
,
2252 #ifdef HAVE_TARGET_64_LITTLE
2255 Layout::layout_eh_frame
<64, false>(Sized_relobj
<64, false>* object
,
2256 const unsigned char* symbols
,
2258 const unsigned char* symbol_names
,
2259 off_t symbol_names_size
,
2261 const elfcpp::Shdr
<64, false>& shdr
,
2262 unsigned int reloc_shndx
,
2263 unsigned int reloc_type
,
2267 #ifdef HAVE_TARGET_64_BIG
2270 Layout::layout_eh_frame
<64, true>(Sized_relobj
<64, true>* object
,
2271 const unsigned char* symbols
,
2273 const unsigned char* symbol_names
,
2274 off_t symbol_names_size
,
2276 const elfcpp::Shdr
<64, true>& shdr
,
2277 unsigned int reloc_shndx
,
2278 unsigned int reloc_type
,
2282 } // End namespace gold.