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 // Set the file offsets of all the non-data sections we've seen so
736 // far which don't have to wait for the input sections. We need
737 // this in order to finalize local symbols in non-allocated
739 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
741 // Create the symbol table sections.
742 this->create_symtab_sections(input_objects
, symtab
, task
, &off
);
743 if (!parameters
->doing_static_link())
744 this->assign_local_dynsym_offsets(input_objects
);
746 // Create the .shstrtab section.
747 Output_section
* shstrtab_section
= this->create_shstrtab();
749 // Set the file offsets of the rest of the non-data sections which
750 // don't have to wait for the input sections.
751 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
753 // Now that all sections have been created, set the section indexes.
754 shndx
= this->set_section_indexes(shndx
);
756 // Create the section table header.
757 this->create_shdrs(&off
);
759 // If there are no sections which require postprocessing, we can
760 // handle the section names now, and avoid a resize later.
761 if (!this->any_postprocessing_sections_
)
762 off
= this->set_section_offsets(off
,
763 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
765 file_header
->set_section_info(this->section_headers_
, shstrtab_section
);
767 // Now we know exactly where everything goes in the output file
768 // (except for non-allocated sections which require postprocessing).
769 Output_data::layout_complete();
771 this->output_file_size_
= off
;
776 // Create a .note section for an executable or shared library. This
777 // records the version of gold used to create the binary.
780 Layout::create_gold_note()
782 if (parameters
->output_is_object())
785 // Authorities all agree that the values in a .note field should
786 // be aligned on 4-byte boundaries for 32-bit binaries. However,
787 // they differ on what the alignment is for 64-bit binaries.
788 // The GABI says unambiguously they take 8-byte alignment:
789 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
790 // Other documentation says alignment should always be 4 bytes:
791 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
792 // GNU ld and GNU readelf both support the latter (at least as of
793 // version 2.16.91), and glibc always generates the latter for
794 // .note.ABI-tag (as of version 1.6), so that's the one we go with
796 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
797 const int size
= parameters
->get_size();
802 // The contents of the .note section.
803 const char* name
= "GNU";
804 std::string
desc(std::string("gold ") + gold::get_version_string());
805 size_t namesz
= strlen(name
) + 1;
806 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
807 size_t descsz
= desc
.length() + 1;
808 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
809 const int note_type
= 4;
811 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
813 unsigned char buffer
[128];
814 gold_assert(sizeof buffer
>= notesz
);
815 memset(buffer
, 0, notesz
);
817 bool is_big_endian
= parameters
->is_big_endian();
823 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
824 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
825 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
829 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
830 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
831 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
838 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
839 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
840 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
844 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
845 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
846 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
852 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
853 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
855 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
856 Output_section
* os
= this->make_output_section(note_name
,
859 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
861 os
->add_output_section_data(posd
);
864 // Record whether the stack should be executable. This can be set
865 // from the command line using the -z execstack or -z noexecstack
866 // options. Otherwise, if any input file has a .note.GNU-stack
867 // section with the SHF_EXECINSTR flag set, the stack should be
868 // executable. Otherwise, if at least one input file a
869 // .note.GNU-stack section, and some input file has no .note.GNU-stack
870 // section, we use the target default for whether the stack should be
871 // executable. Otherwise, we don't generate a stack note. When
872 // generating a object file, we create a .note.GNU-stack section with
873 // the appropriate marking. When generating an executable or shared
874 // library, we create a PT_GNU_STACK segment.
877 Layout::create_executable_stack_info(const Target
* target
)
879 bool is_stack_executable
;
880 if (this->options_
.is_execstack_set())
881 is_stack_executable
= this->options_
.is_stack_executable();
882 else if (!this->input_with_gnu_stack_note_
)
886 if (this->input_requires_executable_stack_
)
887 is_stack_executable
= true;
888 else if (this->input_without_gnu_stack_note_
)
889 is_stack_executable
= target
->is_default_stack_executable();
891 is_stack_executable
= false;
894 if (parameters
->output_is_object())
896 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
897 elfcpp::Elf_Xword flags
= 0;
898 if (is_stack_executable
)
899 flags
|= elfcpp::SHF_EXECINSTR
;
900 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
904 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
905 if (is_stack_executable
)
906 flags
|= elfcpp::PF_X
;
907 Output_segment
* oseg
= new Output_segment(elfcpp::PT_GNU_STACK
, flags
);
908 this->segment_list_
.push_back(oseg
);
912 // Return whether SEG1 should be before SEG2 in the output file. This
913 // is based entirely on the segment type and flags. When this is
914 // called the segment addresses has normally not yet been set.
917 Layout::segment_precedes(const Output_segment
* seg1
,
918 const Output_segment
* seg2
)
920 elfcpp::Elf_Word type1
= seg1
->type();
921 elfcpp::Elf_Word type2
= seg2
->type();
923 // The single PT_PHDR segment is required to precede any loadable
924 // segment. We simply make it always first.
925 if (type1
== elfcpp::PT_PHDR
)
927 gold_assert(type2
!= elfcpp::PT_PHDR
);
930 if (type2
== elfcpp::PT_PHDR
)
933 // The single PT_INTERP segment is required to precede any loadable
934 // segment. We simply make it always second.
935 if (type1
== elfcpp::PT_INTERP
)
937 gold_assert(type2
!= elfcpp::PT_INTERP
);
940 if (type2
== elfcpp::PT_INTERP
)
943 // We then put PT_LOAD segments before any other segments.
944 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
946 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
949 // We put the PT_TLS segment last, because that is where the dynamic
950 // linker expects to find it (this is just for efficiency; other
951 // positions would also work correctly).
952 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
954 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
957 const elfcpp::Elf_Word flags1
= seg1
->flags();
958 const elfcpp::Elf_Word flags2
= seg2
->flags();
960 // The order of non-PT_LOAD segments is unimportant. We simply sort
961 // by the numeric segment type and flags values. There should not
962 // be more than one segment with the same type and flags.
963 if (type1
!= elfcpp::PT_LOAD
)
966 return type1
< type2
;
967 gold_assert(flags1
!= flags2
);
968 return flags1
< flags2
;
971 // We sort PT_LOAD segments based on the flags. Readonly segments
972 // come before writable segments. Then executable segments come
973 // before non-executable segments. Then the unlikely case of a
974 // non-readable segment comes before the normal case of a readable
975 // segment. If there are multiple segments with the same type and
976 // flags, we require that the address be set, and we sort by
977 // virtual address and then physical address.
978 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
979 return (flags1
& elfcpp::PF_W
) == 0;
980 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
981 return (flags1
& elfcpp::PF_X
) != 0;
982 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
983 return (flags1
& elfcpp::PF_R
) == 0;
985 uint64_t vaddr1
= seg1
->vaddr();
986 uint64_t vaddr2
= seg2
->vaddr();
987 if (vaddr1
!= vaddr2
)
988 return vaddr1
< vaddr2
;
990 uint64_t paddr1
= seg1
->paddr();
991 uint64_t paddr2
= seg2
->paddr();
992 gold_assert(paddr1
!= paddr2
);
993 return paddr1
< paddr2
;
996 // Set the file offsets of all the segments, and all the sections they
997 // contain. They have all been created. LOAD_SEG must be be laid out
998 // first. Return the offset of the data to follow.
1001 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
1002 unsigned int *pshndx
)
1004 // Sort them into the final order.
1005 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
1006 Layout::Compare_segments());
1008 // Find the PT_LOAD segments, and set their addresses and offsets
1009 // and their section's addresses and offsets.
1011 if (parameters
->output_is_shared())
1013 else if (options_
.user_set_text_segment_address())
1014 addr
= options_
.text_segment_address();
1016 addr
= target
->default_text_segment_address();
1018 bool was_readonly
= false;
1019 for (Segment_list::iterator p
= this->segment_list_
.begin();
1020 p
!= this->segment_list_
.end();
1023 if ((*p
)->type() == elfcpp::PT_LOAD
)
1025 if (load_seg
!= NULL
&& load_seg
!= *p
)
1029 // If the last segment was readonly, and this one is not,
1030 // then skip the address forward one page, maintaining the
1031 // same position within the page. This lets us store both
1032 // segments overlapping on a single page in the file, but
1033 // the loader will put them on different pages in memory.
1035 uint64_t orig_addr
= addr
;
1036 uint64_t orig_off
= off
;
1038 uint64_t aligned_addr
= addr
;
1039 uint64_t abi_pagesize
= target
->abi_pagesize();
1041 // FIXME: This should depend on the -n and -N options.
1042 (*p
)->set_minimum_addralign(target
->common_pagesize());
1044 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
1046 uint64_t align
= (*p
)->addralign();
1048 addr
= align_address(addr
, align
);
1049 aligned_addr
= addr
;
1050 if ((addr
& (abi_pagesize
- 1)) != 0)
1051 addr
= addr
+ abi_pagesize
;
1054 unsigned int shndx_hold
= *pshndx
;
1055 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1056 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1058 // Now that we know the size of this segment, we may be able
1059 // to save a page in memory, at the cost of wasting some
1060 // file space, by instead aligning to the start of a new
1061 // page. Here we use the real machine page size rather than
1062 // the ABI mandated page size.
1064 if (aligned_addr
!= addr
)
1066 uint64_t common_pagesize
= target
->common_pagesize();
1067 uint64_t first_off
= (common_pagesize
1069 & (common_pagesize
- 1)));
1070 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
1073 && ((aligned_addr
& ~ (common_pagesize
- 1))
1074 != (new_addr
& ~ (common_pagesize
- 1)))
1075 && first_off
+ last_off
<= common_pagesize
)
1077 *pshndx
= shndx_hold
;
1078 addr
= align_address(aligned_addr
, common_pagesize
);
1079 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1080 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
1086 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
1087 was_readonly
= true;
1091 // Handle the non-PT_LOAD segments, setting their offsets from their
1092 // section's offsets.
1093 for (Segment_list::iterator p
= this->segment_list_
.begin();
1094 p
!= this->segment_list_
.end();
1097 if ((*p
)->type() != elfcpp::PT_LOAD
)
1101 // Set the TLS offsets for each section in the PT_TLS segment.
1102 if (this->tls_segment_
!= NULL
)
1103 this->tls_segment_
->set_tls_offsets();
1108 // Set the file offset of all the sections not associated with a
1112 Layout::set_section_offsets(off_t off
, Layout::Section_offset_pass pass
)
1114 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1115 p
!= this->unattached_section_list_
.end();
1118 // The symtab section is handled in create_symtab_sections.
1119 if (*p
== this->symtab_section_
)
1122 // If we've already set the data size, don't set it again.
1123 if ((*p
)->is_offset_valid() && (*p
)->is_data_size_valid())
1126 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1127 && (*p
)->requires_postprocessing())
1129 (*p
)->create_postprocessing_buffer();
1130 this->any_postprocessing_sections_
= true;
1133 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1134 && (*p
)->after_input_sections())
1136 else if (pass
== POSTPROCESSING_SECTIONS_PASS
1137 && (!(*p
)->after_input_sections()
1138 || (*p
)->type() == elfcpp::SHT_STRTAB
))
1140 else if (pass
== STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1141 && (!(*p
)->after_input_sections()
1142 || (*p
)->type() != elfcpp::SHT_STRTAB
))
1145 off
= align_address(off
, (*p
)->addralign());
1146 (*p
)->set_file_offset(off
);
1147 (*p
)->finalize_data_size();
1148 off
+= (*p
)->data_size();
1150 // At this point the name must be set.
1151 if (pass
!= STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
)
1152 this->namepool_
.add((*p
)->name(), false, NULL
);
1157 // Set the section indexes of all the sections not associated with a
1161 Layout::set_section_indexes(unsigned int shndx
)
1163 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1164 p
!= this->unattached_section_list_
.end();
1167 (*p
)->set_out_shndx(shndx
);
1173 // Count the local symbols in the regular symbol table and the dynamic
1174 // symbol table, and build the respective string pools.
1177 Layout::count_local_symbols(const Task
* task
,
1178 const Input_objects
* input_objects
)
1180 // First, figure out an upper bound on the number of symbols we'll
1181 // be inserting into each pool. This helps us create the pools with
1182 // the right size, to avoid unnecessary hashtable resizing.
1183 unsigned int symbol_count
= 0;
1184 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1185 p
!= input_objects
->relobj_end();
1187 symbol_count
+= (*p
)->local_symbol_count();
1189 // Go from "upper bound" to "estimate." We overcount for two
1190 // reasons: we double-count symbols that occur in more than one
1191 // object file, and we count symbols that are dropped from the
1192 // output. Add it all together and assume we overcount by 100%.
1195 // We assume all symbols will go into both the sympool and dynpool.
1196 this->sympool_
.reserve(symbol_count
);
1197 this->dynpool_
.reserve(symbol_count
);
1199 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1200 p
!= input_objects
->relobj_end();
1203 Task_lock_obj
<Object
> tlo(task
, *p
);
1204 (*p
)->count_local_symbols(&this->sympool_
, &this->dynpool_
);
1208 // Create the symbol table sections. Here we also set the final
1209 // values of the symbols. At this point all the loadable sections are
1213 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1214 Symbol_table
* symtab
,
1220 if (parameters
->get_size() == 32)
1222 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1225 else if (parameters
->get_size() == 64)
1227 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1234 off
= align_address(off
, align
);
1235 off_t startoff
= off
;
1237 // Save space for the dummy symbol at the start of the section. We
1238 // never bother to write this out--it will just be left as zero.
1240 unsigned int local_symbol_index
= 1;
1242 // Add STT_SECTION symbols for each Output section which needs one.
1243 for (Section_list::iterator p
= this->section_list_
.begin();
1244 p
!= this->section_list_
.end();
1247 if (!(*p
)->needs_symtab_index())
1248 (*p
)->set_symtab_index(-1U);
1251 (*p
)->set_symtab_index(local_symbol_index
);
1252 ++local_symbol_index
;
1257 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1258 p
!= input_objects
->relobj_end();
1261 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1263 off
+= (index
- local_symbol_index
) * symsize
;
1264 local_symbol_index
= index
;
1267 unsigned int local_symcount
= local_symbol_index
;
1268 gold_assert(local_symcount
* symsize
== off
- startoff
);
1271 size_t dyn_global_index
;
1273 if (this->dynsym_section_
== NULL
)
1276 dyn_global_index
= 0;
1281 dyn_global_index
= this->dynsym_section_
->info();
1282 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1283 dynoff
= this->dynsym_section_
->offset() + locsize
;
1284 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1285 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1286 == this->dynsym_section_
->data_size() - locsize
);
1289 off
= symtab
->finalize(task
, local_symcount
, off
, dynoff
, dyn_global_index
,
1290 dyncount
, &this->sympool_
);
1292 if (!parameters
->strip_all())
1294 this->sympool_
.set_string_offsets();
1296 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1297 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1300 this->symtab_section_
= osymtab
;
1302 Output_section_data
* pos
= new Output_data_fixed_space(off
- startoff
,
1304 osymtab
->add_output_section_data(pos
);
1306 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1307 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1311 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1312 ostrtab
->add_output_section_data(pstr
);
1314 osymtab
->set_file_offset(startoff
);
1315 osymtab
->finalize_data_size();
1316 osymtab
->set_link_section(ostrtab
);
1317 osymtab
->set_info(local_symcount
);
1318 osymtab
->set_entsize(symsize
);
1324 // Create the .shstrtab section, which holds the names of the
1325 // sections. At the time this is called, we have created all the
1326 // output sections except .shstrtab itself.
1329 Layout::create_shstrtab()
1331 // FIXME: We don't need to create a .shstrtab section if we are
1332 // stripping everything.
1334 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1336 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1338 // We can't write out this section until we've set all the section
1339 // names, and we don't set the names of compressed output sections
1340 // until relocations are complete.
1341 os
->set_after_input_sections();
1343 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1344 os
->add_output_section_data(posd
);
1349 // Create the section headers. SIZE is 32 or 64. OFF is the file
1353 Layout::create_shdrs(off_t
* poff
)
1355 Output_section_headers
* oshdrs
;
1356 oshdrs
= new Output_section_headers(this,
1357 &this->segment_list_
,
1358 &this->unattached_section_list_
,
1360 off_t off
= align_address(*poff
, oshdrs
->addralign());
1361 oshdrs
->set_address_and_file_offset(0, off
);
1362 off
+= oshdrs
->data_size();
1364 this->section_headers_
= oshdrs
;
1367 // Create the dynamic symbol table.
1370 Layout::create_dynamic_symtab(const Input_objects
* input_objects
,
1371 const Target
* target
, Symbol_table
* symtab
,
1372 Output_section
**pdynstr
,
1373 unsigned int* plocal_dynamic_count
,
1374 std::vector
<Symbol
*>* pdynamic_symbols
,
1375 Versions
* pversions
)
1377 // Count all the symbols in the dynamic symbol table, and set the
1378 // dynamic symbol indexes.
1380 // Skip symbol 0, which is always all zeroes.
1381 unsigned int index
= 1;
1383 // Add STT_SECTION symbols for each Output section which needs one.
1384 for (Section_list::iterator p
= this->section_list_
.begin();
1385 p
!= this->section_list_
.end();
1388 if (!(*p
)->needs_dynsym_index())
1389 (*p
)->set_dynsym_index(-1U);
1392 (*p
)->set_dynsym_index(index
);
1397 // Count the local symbols that need to go in the dynamic symbol table,
1398 // and set the dynamic symbol indexes.
1399 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1400 p
!= input_objects
->relobj_end();
1403 unsigned int new_index
= (*p
)->set_local_dynsym_indexes(index
);
1407 unsigned int local_symcount
= index
;
1408 *plocal_dynamic_count
= local_symcount
;
1410 // FIXME: We have to tell set_dynsym_indexes whether the
1411 // -E/--export-dynamic option was used.
1412 index
= symtab
->set_dynsym_indexes(target
, index
, pdynamic_symbols
,
1413 &this->dynpool_
, pversions
);
1417 const int size
= parameters
->get_size();
1420 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1423 else if (size
== 64)
1425 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1431 // Create the dynamic symbol table section.
1433 const char* dynsym_name
= this->namepool_
.add(".dynsym", false, NULL
);
1434 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
1438 Output_section_data
* odata
= new Output_data_fixed_space(index
* symsize
,
1440 dynsym
->add_output_section_data(odata
);
1442 dynsym
->set_info(local_symcount
);
1443 dynsym
->set_entsize(symsize
);
1444 dynsym
->set_addralign(align
);
1446 this->dynsym_section_
= dynsym
;
1448 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1449 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1450 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1452 // Create the dynamic string table section.
1454 const char* dynstr_name
= this->namepool_
.add(".dynstr", false, NULL
);
1455 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
1459 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1460 dynstr
->add_output_section_data(strdata
);
1462 dynsym
->set_link_section(dynstr
);
1463 this->dynamic_section_
->set_link_section(dynstr
);
1465 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1466 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1470 // Create the hash tables.
1472 // FIXME: We need an option to create a GNU hash table.
1474 unsigned char* phash
;
1475 unsigned int hashlen
;
1476 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1479 const char* hash_name
= this->namepool_
.add(".hash", false, NULL
);
1480 Output_section
* hashsec
= this->make_output_section(hash_name
,
1484 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1487 hashsec
->add_output_section_data(hashdata
);
1489 hashsec
->set_link_section(dynsym
);
1490 hashsec
->set_entsize(4);
1492 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1495 // Assign offsets to each local portion of the dynamic symbol table.
1498 Layout::assign_local_dynsym_offsets(const Input_objects
* input_objects
)
1500 Output_section
* dynsym
= this->dynsym_section_
;
1501 gold_assert(dynsym
!= NULL
);
1503 off_t off
= dynsym
->offset();
1505 // Skip the dummy symbol at the start of the section.
1506 off
+= dynsym
->entsize();
1508 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1509 p
!= input_objects
->relobj_end();
1512 unsigned int count
= (*p
)->set_local_dynsym_offset(off
);
1513 off
+= count
* dynsym
->entsize();
1517 // Create the version sections.
1520 Layout::create_version_sections(const Versions
* versions
,
1521 const Symbol_table
* symtab
,
1522 unsigned int local_symcount
,
1523 const std::vector
<Symbol
*>& dynamic_symbols
,
1524 const Output_section
* dynstr
)
1526 if (!versions
->any_defs() && !versions
->any_needs())
1529 if (parameters
->get_size() == 32)
1531 if (parameters
->is_big_endian())
1533 #ifdef HAVE_TARGET_32_BIG
1534 this->sized_create_version_sections
1535 SELECT_SIZE_ENDIAN_NAME(32, true)(
1536 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1537 SELECT_SIZE_ENDIAN(32, true));
1544 #ifdef HAVE_TARGET_32_LITTLE
1545 this->sized_create_version_sections
1546 SELECT_SIZE_ENDIAN_NAME(32, false)(
1547 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1548 SELECT_SIZE_ENDIAN(32, false));
1554 else if (parameters
->get_size() == 64)
1556 if (parameters
->is_big_endian())
1558 #ifdef HAVE_TARGET_64_BIG
1559 this->sized_create_version_sections
1560 SELECT_SIZE_ENDIAN_NAME(64, true)(
1561 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1562 SELECT_SIZE_ENDIAN(64, true));
1569 #ifdef HAVE_TARGET_64_LITTLE
1570 this->sized_create_version_sections
1571 SELECT_SIZE_ENDIAN_NAME(64, false)(
1572 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1573 SELECT_SIZE_ENDIAN(64, false));
1583 // Create the version sections, sized version.
1585 template<int size
, bool big_endian
>
1587 Layout::sized_create_version_sections(
1588 const Versions
* versions
,
1589 const Symbol_table
* symtab
,
1590 unsigned int local_symcount
,
1591 const std::vector
<Symbol
*>& dynamic_symbols
,
1592 const Output_section
* dynstr
1595 const char* vname
= this->namepool_
.add(".gnu.version", false, NULL
);
1596 Output_section
* vsec
= this->make_output_section(vname
,
1597 elfcpp::SHT_GNU_versym
,
1600 unsigned char* vbuf
;
1602 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1603 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1604 SELECT_SIZE_ENDIAN(size
, big_endian
));
1606 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1608 vsec
->add_output_section_data(vdata
);
1609 vsec
->set_entsize(2);
1610 vsec
->set_link_section(this->dynsym_section_
);
1612 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1613 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1615 if (versions
->any_defs())
1617 const char* vdname
= this->namepool_
.add(".gnu.version_d", false, NULL
);
1618 Output_section
*vdsec
;
1619 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1622 unsigned char* vdbuf
;
1623 unsigned int vdsize
;
1624 unsigned int vdentries
;
1625 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1626 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1627 SELECT_SIZE_ENDIAN(size
, big_endian
));
1629 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1633 vdsec
->add_output_section_data(vddata
);
1634 vdsec
->set_link_section(dynstr
);
1635 vdsec
->set_info(vdentries
);
1637 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1638 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1641 if (versions
->any_needs())
1643 const char* vnname
= this->namepool_
.add(".gnu.version_r", false, NULL
);
1644 Output_section
* vnsec
;
1645 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1648 unsigned char* vnbuf
;
1649 unsigned int vnsize
;
1650 unsigned int vnentries
;
1651 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1652 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1653 SELECT_SIZE_ENDIAN(size
, big_endian
));
1655 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1659 vnsec
->add_output_section_data(vndata
);
1660 vnsec
->set_link_section(dynstr
);
1661 vnsec
->set_info(vnentries
);
1663 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1664 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1668 // Create the .interp section and PT_INTERP segment.
1671 Layout::create_interp(const Target
* target
)
1673 const char* interp
= this->options_
.dynamic_linker();
1676 interp
= target
->dynamic_linker();
1677 gold_assert(interp
!= NULL
);
1680 size_t len
= strlen(interp
) + 1;
1682 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1684 const char* interp_name
= this->namepool_
.add(".interp", false, NULL
);
1685 Output_section
* osec
= this->make_output_section(interp_name
,
1686 elfcpp::SHT_PROGBITS
,
1688 osec
->add_output_section_data(odata
);
1690 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1691 this->segment_list_
.push_back(oseg
);
1692 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1695 // Finish the .dynamic section and PT_DYNAMIC segment.
1698 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1699 const Symbol_table
* symtab
)
1701 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1702 elfcpp::PF_R
| elfcpp::PF_W
);
1703 this->segment_list_
.push_back(oseg
);
1704 oseg
->add_initial_output_section(this->dynamic_section_
,
1705 elfcpp::PF_R
| elfcpp::PF_W
);
1707 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1709 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1710 p
!= input_objects
->dynobj_end();
1713 // FIXME: Handle --as-needed.
1714 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1717 // FIXME: Support --init and --fini.
1718 Symbol
* sym
= symtab
->lookup("_init");
1719 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1720 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1722 sym
= symtab
->lookup("_fini");
1723 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1724 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1726 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1728 // Add a DT_RPATH entry if needed.
1729 const General_options::Dir_list
& rpath(this->options_
.rpath());
1732 std::string rpath_val
;
1733 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1737 if (rpath_val
.empty())
1738 rpath_val
= p
->name();
1741 // Eliminate duplicates.
1742 General_options::Dir_list::const_iterator q
;
1743 for (q
= rpath
.begin(); q
!= p
; ++q
)
1744 if (q
->name() == p
->name())
1749 rpath_val
+= p
->name();
1754 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1757 // Look for text segments that have dynamic relocations.
1758 bool have_textrel
= false;
1759 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
1760 p
!= this->segment_list_
.end();
1763 if (((*p
)->flags() & elfcpp::PF_W
) == 0
1764 && (*p
)->dynamic_reloc_count() > 0)
1766 have_textrel
= true;
1771 // Add a DT_FLAGS entry. We add it even if no flags are set so that
1772 // post-link tools can easily modify these flags if desired.
1773 unsigned int flags
= 0;
1776 // Add a DT_TEXTREL for compatibility with older loaders.
1777 odyn
->add_constant(elfcpp::DT_TEXTREL
, 0);
1778 flags
|= elfcpp::DF_TEXTREL
;
1780 if (parameters
->output_is_shared() && this->has_static_tls())
1781 flags
|= elfcpp::DF_STATIC_TLS
;
1782 odyn
->add_constant(elfcpp::DT_FLAGS
, flags
);
1785 // The mapping of .gnu.linkonce section names to real section names.
1787 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1788 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1790 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1791 MAPPING_INIT("t", ".text"),
1792 MAPPING_INIT("r", ".rodata"),
1793 MAPPING_INIT("d", ".data"),
1794 MAPPING_INIT("b", ".bss"),
1795 MAPPING_INIT("s", ".sdata"),
1796 MAPPING_INIT("sb", ".sbss"),
1797 MAPPING_INIT("s2", ".sdata2"),
1798 MAPPING_INIT("sb2", ".sbss2"),
1799 MAPPING_INIT("wi", ".debug_info"),
1800 MAPPING_INIT("td", ".tdata"),
1801 MAPPING_INIT("tb", ".tbss"),
1802 MAPPING_INIT("lr", ".lrodata"),
1803 MAPPING_INIT("l", ".ldata"),
1804 MAPPING_INIT("lb", ".lbss"),
1808 const int Layout::linkonce_mapping_count
=
1809 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1811 // Return the name of the output section to use for a .gnu.linkonce
1812 // section. This is based on the default ELF linker script of the old
1813 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1814 // to ".text". Set *PLEN to the length of the name. *PLEN is
1815 // initialized to the length of NAME.
1818 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1820 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1824 const Linkonce_mapping
* plm
= linkonce_mapping
;
1825 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1827 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1836 // Choose the output section name to use given an input section name.
1837 // Set *PLEN to the length of the name. *PLEN is initialized to the
1841 Layout::output_section_name(const char* name
, size_t* plen
)
1843 if (Layout::is_linkonce(name
))
1845 // .gnu.linkonce sections are laid out as though they were named
1846 // for the sections are placed into.
1847 return Layout::linkonce_output_name(name
, plen
);
1850 // gcc 4.3 generates the following sorts of section names when it
1851 // needs a section name specific to a function:
1857 // .data.rel.local.FN
1859 // .data.rel.ro.local.FN
1866 // The GNU linker maps all of those to the part before the .FN,
1867 // except that .data.rel.local.FN is mapped to .data, and
1868 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1869 // beginning with .data.rel.ro.local are grouped together.
1871 // For an anonymous namespace, the string FN can contain a '.'.
1873 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1874 // GNU linker maps to .rodata.
1876 // The .data.rel.ro sections enable a security feature triggered by
1877 // the -z relro option. Section which need to be relocated at
1878 // program startup time but which may be readonly after startup are
1879 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1880 // segment. The dynamic linker will make that segment writable,
1881 // perform relocations, and then make it read-only. FIXME: We do
1882 // not yet implement this optimization.
1884 // It is hard to handle this in a principled way.
1886 // These are the rules we follow:
1888 // If the section name has no initial '.', or no dot other than an
1889 // initial '.', we use the name unchanged (i.e., "mysection" and
1890 // ".text" are unchanged).
1892 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1894 // Otherwise, we drop the second '.' and everything that comes after
1895 // it (i.e., ".text.XXX" becomes ".text").
1897 const char* s
= name
;
1901 const char* sdot
= strchr(s
, '.');
1905 const char* const data_rel_ro
= ".data.rel.ro";
1906 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
1908 *plen
= strlen(data_rel_ro
);
1912 *plen
= sdot
- name
;
1916 // Record the signature of a comdat section, and return whether to
1917 // include it in the link. If GROUP is true, this is a regular
1918 // section group. If GROUP is false, this is a group signature
1919 // derived from the name of a linkonce section. We want linkonce
1920 // signatures and group signatures to block each other, but we don't
1921 // want a linkonce signature to block another linkonce signature.
1924 Layout::add_comdat(const char* signature
, bool group
)
1926 std::string
sig(signature
);
1927 std::pair
<Signatures::iterator
, bool> ins(
1928 this->signatures_
.insert(std::make_pair(sig
, group
)));
1932 // This is the first time we've seen this signature.
1936 if (ins
.first
->second
)
1938 // We've already seen a real section group with this signature.
1943 // This is a real section group, and we've already seen a
1944 // linkonce section with this signature. Record that we've seen
1945 // a section group, and don't include this section group.
1946 ins
.first
->second
= true;
1951 // We've already seen a linkonce section and this is a linkonce
1952 // section. These don't block each other--this may be the same
1953 // symbol name with different section types.
1958 // Write out the Output_sections. Most won't have anything to write,
1959 // since most of the data will come from input sections which are
1960 // handled elsewhere. But some Output_sections do have Output_data.
1963 Layout::write_output_sections(Output_file
* of
) const
1965 for (Section_list::const_iterator p
= this->section_list_
.begin();
1966 p
!= this->section_list_
.end();
1969 if (!(*p
)->after_input_sections())
1974 // Write out data not associated with a section or the symbol table.
1977 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
1979 if (!parameters
->strip_all())
1981 const Output_section
* symtab_section
= this->symtab_section_
;
1982 for (Section_list::const_iterator p
= this->section_list_
.begin();
1983 p
!= this->section_list_
.end();
1986 if ((*p
)->needs_symtab_index())
1988 gold_assert(symtab_section
!= NULL
);
1989 unsigned int index
= (*p
)->symtab_index();
1990 gold_assert(index
> 0 && index
!= -1U);
1991 off_t off
= (symtab_section
->offset()
1992 + index
* symtab_section
->entsize());
1993 symtab
->write_section_symbol(*p
, of
, off
);
1998 const Output_section
* dynsym_section
= this->dynsym_section_
;
1999 for (Section_list::const_iterator p
= this->section_list_
.begin();
2000 p
!= this->section_list_
.end();
2003 if ((*p
)->needs_dynsym_index())
2005 gold_assert(dynsym_section
!= NULL
);
2006 unsigned int index
= (*p
)->dynsym_index();
2007 gold_assert(index
> 0 && index
!= -1U);
2008 off_t off
= (dynsym_section
->offset()
2009 + index
* dynsym_section
->entsize());
2010 symtab
->write_section_symbol(*p
, of
, off
);
2014 // Write out the Output_data which are not in an Output_section.
2015 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
2016 p
!= this->special_output_list_
.end();
2021 // Write out the Output_sections which can only be written after the
2022 // input sections are complete.
2025 Layout::write_sections_after_input_sections(Output_file
* of
)
2027 // Determine the final section offsets, and thus the final output
2028 // file size. Note we finalize the .shstrab last, to allow the
2029 // after_input_section sections to modify their section-names before
2031 if (this->any_postprocessing_sections_
)
2033 off_t off
= this->output_file_size_
;
2034 off
= this->set_section_offsets(off
, POSTPROCESSING_SECTIONS_PASS
);
2036 // Now that we've finalized the names, we can finalize the shstrab.
2038 this->set_section_offsets(off
,
2039 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
2041 if (off
> this->output_file_size_
)
2044 this->output_file_size_
= off
;
2048 for (Section_list::const_iterator p
= this->section_list_
.begin();
2049 p
!= this->section_list_
.end();
2052 if ((*p
)->after_input_sections())
2056 this->section_headers_
->write(of
);
2059 // Print statistical information to stderr. This is used for --stats.
2062 Layout::print_stats() const
2064 this->namepool_
.print_stats("section name pool");
2065 this->sympool_
.print_stats("output symbol name pool");
2066 this->dynpool_
.print_stats("dynamic name pool");
2068 for (Section_list::const_iterator p
= this->section_list_
.begin();
2069 p
!= this->section_list_
.end();
2071 (*p
)->print_merge_stats();
2074 // Write_sections_task methods.
2076 // We can always run this task.
2079 Write_sections_task::is_runnable()
2084 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
2088 Write_sections_task::locks(Task_locker
* tl
)
2090 tl
->add(this, this->output_sections_blocker_
);
2091 tl
->add(this, this->final_blocker_
);
2094 // Run the task--write out the data.
2097 Write_sections_task::run(Workqueue
*)
2099 this->layout_
->write_output_sections(this->of_
);
2102 // Write_data_task methods.
2104 // We can always run this task.
2107 Write_data_task::is_runnable()
2112 // We need to unlock FINAL_BLOCKER when finished.
2115 Write_data_task::locks(Task_locker
* tl
)
2117 tl
->add(this, this->final_blocker_
);
2120 // Run the task--write out the data.
2123 Write_data_task::run(Workqueue
*)
2125 this->layout_
->write_data(this->symtab_
, this->of_
);
2128 // Write_symbols_task methods.
2130 // We can always run this task.
2133 Write_symbols_task::is_runnable()
2138 // We need to unlock FINAL_BLOCKER when finished.
2141 Write_symbols_task::locks(Task_locker
* tl
)
2143 tl
->add(this, this->final_blocker_
);
2146 // Run the task--write out the symbols.
2149 Write_symbols_task::run(Workqueue
*)
2151 this->symtab_
->write_globals(this->input_objects_
, this->sympool_
,
2152 this->dynpool_
, this->of_
);
2155 // Write_after_input_sections_task methods.
2157 // We can only run this task after the input sections have completed.
2160 Write_after_input_sections_task::is_runnable()
2162 if (this->input_sections_blocker_
->is_blocked())
2163 return this->input_sections_blocker_
;
2167 // We need to unlock FINAL_BLOCKER when finished.
2170 Write_after_input_sections_task::locks(Task_locker
* tl
)
2172 tl
->add(this, this->final_blocker_
);
2178 Write_after_input_sections_task::run(Workqueue
*)
2180 this->layout_
->write_sections_after_input_sections(this->of_
);
2183 // Close_task_runner methods.
2185 // Run the task--close the file.
2188 Close_task_runner::run(Workqueue
*, const Task
*)
2193 // Instantiate the templates we need. We could use the configure
2194 // script to restrict this to only the ones for implemented targets.
2196 #ifdef HAVE_TARGET_32_LITTLE
2199 Layout::layout
<32, false>(Sized_relobj
<32, false>* object
, unsigned int shndx
,
2201 const elfcpp::Shdr
<32, false>& shdr
,
2202 unsigned int, unsigned int, off_t
*);
2205 #ifdef HAVE_TARGET_32_BIG
2208 Layout::layout
<32, true>(Sized_relobj
<32, true>* object
, unsigned int shndx
,
2210 const elfcpp::Shdr
<32, true>& shdr
,
2211 unsigned int, unsigned int, off_t
*);
2214 #ifdef HAVE_TARGET_64_LITTLE
2217 Layout::layout
<64, false>(Sized_relobj
<64, false>* object
, unsigned int shndx
,
2219 const elfcpp::Shdr
<64, false>& shdr
,
2220 unsigned int, unsigned int, off_t
*);
2223 #ifdef HAVE_TARGET_64_BIG
2226 Layout::layout
<64, true>(Sized_relobj
<64, true>* object
, unsigned int shndx
,
2228 const elfcpp::Shdr
<64, true>& shdr
,
2229 unsigned int, unsigned int, off_t
*);
2232 #ifdef HAVE_TARGET_32_LITTLE
2235 Layout::layout_eh_frame
<32, false>(Sized_relobj
<32, false>* object
,
2236 const unsigned char* symbols
,
2238 const unsigned char* symbol_names
,
2239 off_t symbol_names_size
,
2241 const elfcpp::Shdr
<32, false>& shdr
,
2242 unsigned int reloc_shndx
,
2243 unsigned int reloc_type
,
2247 #ifdef HAVE_TARGET_32_BIG
2250 Layout::layout_eh_frame
<32, true>(Sized_relobj
<32, true>* object
,
2251 const unsigned char* symbols
,
2253 const unsigned char* symbol_names
,
2254 off_t symbol_names_size
,
2256 const elfcpp::Shdr
<32, true>& shdr
,
2257 unsigned int reloc_shndx
,
2258 unsigned int reloc_type
,
2262 #ifdef HAVE_TARGET_64_LITTLE
2265 Layout::layout_eh_frame
<64, false>(Sized_relobj
<64, false>* object
,
2266 const unsigned char* symbols
,
2268 const unsigned char* symbol_names
,
2269 off_t symbol_names_size
,
2271 const elfcpp::Shdr
<64, false>& shdr
,
2272 unsigned int reloc_shndx
,
2273 unsigned int reloc_type
,
2277 #ifdef HAVE_TARGET_64_BIG
2280 Layout::layout_eh_frame
<64, true>(Sized_relobj
<64, true>* object
,
2281 const unsigned char* symbols
,
2283 const unsigned char* symbol_names
,
2284 off_t symbol_names_size
,
2286 const elfcpp::Shdr
<64, true>& shdr
,
2287 unsigned int reloc_shndx
,
2288 unsigned int reloc_type
,
2292 } // End namespace gold.