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"
40 // Layout_task_runner methods.
42 // Lay out the sections. This is called after all the input objects
46 Layout_task_runner::run(Workqueue
* workqueue
)
48 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
51 // Now we know the final size of the output file and we know where
52 // each piece of information goes.
53 Output_file
* of
= new Output_file(this->options_
,
54 this->input_objects_
->target());
57 // Queue up the final set of tasks.
58 gold::queue_final_tasks(this->options_
, this->input_objects_
,
59 this->symtab_
, this->layout_
, workqueue
, of
);
64 Layout::Layout(const General_options
& options
)
65 : options_(options
), namepool_(), sympool_(), dynpool_(), signatures_(),
66 section_name_map_(), segment_list_(), section_list_(),
67 unattached_section_list_(), special_output_list_(),
68 tls_segment_(NULL
), symtab_section_(NULL
),
69 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
),
70 eh_frame_section_(NULL
), output_file_size_(-1),
71 input_requires_executable_stack_(false),
72 input_with_gnu_stack_note_(false),
73 input_without_gnu_stack_note_(false)
75 // Make space for more than enough segments for a typical file.
76 // This is just for efficiency--it's OK if we wind up needing more.
77 this->segment_list_
.reserve(12);
79 // We expect three unattached Output_data objects: the file header,
80 // the segment headers, and the section headers.
81 this->special_output_list_
.reserve(3);
84 // Hash a key we use to look up an output section mapping.
87 Layout::Hash_key::operator()(const Layout::Key
& k
) const
89 return k
.first
+ k
.second
.first
+ k
.second
.second
;
92 // Return whether PREFIX is a prefix of STR.
95 is_prefix_of(const char* prefix
, const char* str
)
97 return strncmp(prefix
, str
, strlen(prefix
)) == 0;
100 // Whether to include this section in the link.
102 template<int size
, bool big_endian
>
104 Layout::include_section(Object
*, const char* name
,
105 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
107 // Some section types are never linked. Some are only linked when
108 // doing a relocateable link.
109 switch (shdr
.get_sh_type())
111 case elfcpp::SHT_NULL
:
112 case elfcpp::SHT_SYMTAB
:
113 case elfcpp::SHT_DYNSYM
:
114 case elfcpp::SHT_STRTAB
:
115 case elfcpp::SHT_HASH
:
116 case elfcpp::SHT_DYNAMIC
:
117 case elfcpp::SHT_SYMTAB_SHNDX
:
120 case elfcpp::SHT_RELA
:
121 case elfcpp::SHT_REL
:
122 case elfcpp::SHT_GROUP
:
123 return parameters
->output_is_object();
125 case elfcpp::SHT_PROGBITS
:
126 if (parameters
->strip_debug()
127 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
129 // Debugging sections can only be recognized by name.
130 if (is_prefix_of(".debug", name
)
131 || is_prefix_of(".gnu.linkonce.wi.", name
)
132 || is_prefix_of(".line", name
)
133 || is_prefix_of(".stab", name
))
143 // Return an output section named NAME, or NULL if there is none.
146 Layout::find_output_section(const char* name
) const
148 for (Section_name_map::const_iterator p
= this->section_name_map_
.begin();
149 p
!= this->section_name_map_
.end();
151 if (strcmp(p
->second
->name(), name
) == 0)
156 // Return an output segment of type TYPE, with segment flags SET set
157 // and segment flags CLEAR clear. Return NULL if there is none.
160 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
161 elfcpp::Elf_Word clear
) const
163 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
164 p
!= this->segment_list_
.end();
166 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
167 && ((*p
)->flags() & set
) == set
168 && ((*p
)->flags() & clear
) == 0)
173 // Return the output section to use for section NAME with type TYPE
174 // and section flags FLAGS.
177 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
178 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
180 // We should ignore some flags.
181 flags
&= ~ (elfcpp::SHF_INFO_LINK
182 | elfcpp::SHF_LINK_ORDER
185 | elfcpp::SHF_STRINGS
);
187 const Key
key(name_key
, std::make_pair(type
, flags
));
188 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
189 std::pair
<Section_name_map::iterator
, bool> ins(
190 this->section_name_map_
.insert(v
));
193 return ins
.first
->second
;
196 // This is the first time we've seen this name/type/flags
198 Output_section
* os
= this->make_output_section(name
, type
, flags
);
199 ins
.first
->second
= os
;
204 // Return the output section to use for input section SHNDX, with name
205 // NAME, with header HEADER, from object OBJECT. Set *OFF to the
206 // offset of this input section without the output section.
208 template<int size
, bool big_endian
>
210 Layout::layout(Relobj
* object
, unsigned int shndx
, const char* name
,
211 const elfcpp::Shdr
<size
, big_endian
>& shdr
, off_t
* off
)
213 if (!this->include_section(object
, name
, shdr
))
216 // If we are not doing a relocateable link, choose the name to use
217 // for the output section.
218 size_t len
= strlen(name
);
219 if (!parameters
->output_is_object())
220 name
= Layout::output_section_name(name
, &len
);
222 // FIXME: Handle SHF_OS_NONCONFORMING here.
224 // Canonicalize the section name.
225 Stringpool::Key name_key
;
226 name
= this->namepool_
.add_prefix(name
, len
, &name_key
);
228 // Find the output section. The output section is selected based on
229 // the section name, type, and flags.
230 Output_section
* os
= this->get_output_section(name
, name_key
,
232 shdr
.get_sh_flags());
234 // Special GNU handling of sections named .eh_frame.
235 if (!parameters
->output_is_object()
236 && strcmp(name
, ".eh_frame") == 0
237 && shdr
.get_sh_size() > 0
238 && shdr
.get_sh_type() == elfcpp::SHT_PROGBITS
239 && shdr
.get_sh_flags() == elfcpp::SHF_ALLOC
)
241 this->layout_eh_frame(object
, shndx
, name
, shdr
, os
, off
);
245 // FIXME: Handle SHF_LINK_ORDER somewhere.
247 *off
= os
->add_input_section(object
, shndx
, name
, shdr
);
252 // Special GNU handling of sections named .eh_frame. They will
253 // normally hold exception frame data.
255 template<int size
, bool big_endian
>
257 Layout::layout_eh_frame(Relobj
* object
,
260 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
261 Output_section
* os
, off_t
* off
)
263 if (this->eh_frame_section_
== NULL
)
265 this->eh_frame_section_
= os
;
267 if (this->options_
.create_eh_frame_hdr())
269 Stringpool::Key hdr_name_key
;
270 const char* hdr_name
= this->namepool_
.add(".eh_frame_hdr",
273 Output_section
* hdr_os
=
274 this->get_output_section(hdr_name
, hdr_name_key
,
275 elfcpp::SHT_PROGBITS
,
278 Eh_frame_hdr
* hdr_posd
= new Eh_frame_hdr(os
);
279 hdr_os
->add_output_section_data(hdr_posd
);
281 Output_segment
* hdr_oseg
=
282 new Output_segment(elfcpp::PT_GNU_EH_FRAME
, elfcpp::PF_R
);
283 this->segment_list_
.push_back(hdr_oseg
);
284 hdr_oseg
->add_output_section(hdr_os
, elfcpp::PF_R
);
288 gold_assert(this->eh_frame_section_
== os
);
290 *off
= os
->add_input_section(object
, shndx
, name
, shdr
);
293 // Add POSD to an output section using NAME, TYPE, and FLAGS.
296 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
297 elfcpp::Elf_Xword flags
,
298 Output_section_data
* posd
)
300 // Canonicalize the name.
301 Stringpool::Key name_key
;
302 name
= this->namepool_
.add(name
, true, &name_key
);
304 Output_section
* os
= this->get_output_section(name
, name_key
, type
, flags
);
305 os
->add_output_section_data(posd
);
308 // Map section flags to segment flags.
311 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
313 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
314 if ((flags
& elfcpp::SHF_WRITE
) != 0)
316 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
321 // Make a new Output_section, and attach it to segments as
325 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
326 elfcpp::Elf_Xword flags
)
328 Output_section
* os
= new Output_section(name
, type
, flags
);
329 this->section_list_
.push_back(os
);
331 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
332 this->unattached_section_list_
.push_back(os
);
335 // This output section goes into a PT_LOAD segment.
337 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
339 // The only thing we really care about for PT_LOAD segments is
340 // whether or not they are writable, so that is how we search
341 // for them. People who need segments sorted on some other
342 // basis will have to wait until we implement a mechanism for
343 // them to describe the segments they want.
345 Segment_list::const_iterator p
;
346 for (p
= this->segment_list_
.begin();
347 p
!= this->segment_list_
.end();
350 if ((*p
)->type() == elfcpp::PT_LOAD
351 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
353 (*p
)->add_output_section(os
, seg_flags
);
358 if (p
== this->segment_list_
.end())
360 Output_segment
* oseg
= new Output_segment(elfcpp::PT_LOAD
,
362 this->segment_list_
.push_back(oseg
);
363 oseg
->add_output_section(os
, seg_flags
);
366 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
368 if (type
== elfcpp::SHT_NOTE
)
370 // See if we already have an equivalent PT_NOTE segment.
371 for (p
= this->segment_list_
.begin();
372 p
!= segment_list_
.end();
375 if ((*p
)->type() == elfcpp::PT_NOTE
376 && (((*p
)->flags() & elfcpp::PF_W
)
377 == (seg_flags
& elfcpp::PF_W
)))
379 (*p
)->add_output_section(os
, seg_flags
);
384 if (p
== this->segment_list_
.end())
386 Output_segment
* oseg
= new Output_segment(elfcpp::PT_NOTE
,
388 this->segment_list_
.push_back(oseg
);
389 oseg
->add_output_section(os
, seg_flags
);
393 // If we see a loadable SHF_TLS section, we create a PT_TLS
394 // segment. There can only be one such segment.
395 if ((flags
& elfcpp::SHF_TLS
) != 0)
397 if (this->tls_segment_
== NULL
)
399 this->tls_segment_
= new Output_segment(elfcpp::PT_TLS
,
401 this->segment_list_
.push_back(this->tls_segment_
);
403 this->tls_segment_
->add_output_section(os
, seg_flags
);
410 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
411 // is whether we saw a .note.GNU-stack section in the object file.
412 // GNU_STACK_FLAGS is the section flags. The flags give the
413 // protection required for stack memory. We record this in an
414 // executable as a PT_GNU_STACK segment. If an object file does not
415 // have a .note.GNU-stack segment, we must assume that it is an old
416 // object. On some targets that will force an executable stack.
419 Layout::layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
)
422 this->input_without_gnu_stack_note_
= true;
425 this->input_with_gnu_stack_note_
= true;
426 if ((gnu_stack_flags
& elfcpp::SHF_EXECINSTR
) != 0)
427 this->input_requires_executable_stack_
= true;
431 // Create the dynamic sections which are needed before we read the
435 Layout::create_initial_dynamic_sections(const Input_objects
* input_objects
,
436 Symbol_table
* symtab
)
438 if (parameters
->doing_static_link())
441 const char* dynamic_name
= this->namepool_
.add(".dynamic", false, NULL
);
442 this->dynamic_section_
= this->make_output_section(dynamic_name
,
445 | elfcpp::SHF_WRITE
));
447 symtab
->define_in_output_data(input_objects
->target(), "_DYNAMIC", NULL
,
448 this->dynamic_section_
, 0, 0,
449 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
450 elfcpp::STV_HIDDEN
, 0, false, false);
452 this->dynamic_data_
= new Output_data_dynamic(&this->dynpool_
);
454 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
457 // For each output section whose name can be represented as C symbol,
458 // define __start and __stop symbols for the section. This is a GNU
462 Layout::define_section_symbols(Symbol_table
* symtab
, const Target
* target
)
464 for (Section_list::const_iterator p
= this->section_list_
.begin();
465 p
!= this->section_list_
.end();
468 const char* const name
= (*p
)->name();
469 if (name
[strspn(name
,
471 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
472 "abcdefghijklmnopqrstuvwxyz"
476 const std::string
name_string(name
);
477 const std::string
start_name("__start_" + name_string
);
478 const std::string
stop_name("__stop_" + name_string
);
480 symtab
->define_in_output_data(target
,
490 false, // offset_is_from_end
491 false); // only_if_ref
493 symtab
->define_in_output_data(target
,
503 true, // offset_is_from_end
504 false); // only_if_ref
509 // Find the first read-only PT_LOAD segment, creating one if
513 Layout::find_first_load_seg()
515 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
516 p
!= this->segment_list_
.end();
519 if ((*p
)->type() == elfcpp::PT_LOAD
520 && ((*p
)->flags() & elfcpp::PF_R
) != 0
521 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
525 Output_segment
* load_seg
= new Output_segment(elfcpp::PT_LOAD
, elfcpp::PF_R
);
526 this->segment_list_
.push_back(load_seg
);
530 // Finalize the layout. When this is called, we have created all the
531 // output sections and all the output segments which are based on
532 // input sections. We have several things to do, and we have to do
533 // them in the right order, so that we get the right results correctly
536 // 1) Finalize the list of output segments and create the segment
539 // 2) Finalize the dynamic symbol table and associated sections.
541 // 3) Determine the final file offset of all the output segments.
543 // 4) Determine the final file offset of all the SHF_ALLOC output
546 // 5) Create the symbol table sections and the section name table
549 // 6) Finalize the symbol table: set symbol values to their final
550 // value and make a final determination of which symbols are going
551 // into the output symbol table.
553 // 7) Create the section table header.
555 // 8) Determine the final file offset of all the output sections which
556 // are not SHF_ALLOC, including the section table header.
558 // 9) Finalize the ELF file header.
560 // This function returns the size of the output file.
563 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
)
565 Target
* const target
= input_objects
->target();
567 target
->finalize_sections(this);
569 this->create_gold_note();
570 this->create_executable_stack_info(target
);
572 Output_segment
* phdr_seg
= NULL
;
573 if (!parameters
->doing_static_link())
575 // There was a dynamic object in the link. We need to create
576 // some information for the dynamic linker.
578 // Create the PT_PHDR segment which will hold the program
580 phdr_seg
= new Output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
581 this->segment_list_
.push_back(phdr_seg
);
583 // Create the dynamic symbol table, including the hash table.
584 Output_section
* dynstr
;
585 std::vector
<Symbol
*> dynamic_symbols
;
586 unsigned int local_dynamic_count
;
588 this->create_dynamic_symtab(target
, symtab
, &dynstr
,
589 &local_dynamic_count
, &dynamic_symbols
,
592 // Create the .interp section to hold the name of the
593 // interpreter, and put it in a PT_INTERP segment.
594 this->create_interp(target
);
596 // Finish the .dynamic section to hold the dynamic data, and put
597 // it in a PT_DYNAMIC segment.
598 this->finish_dynamic_section(input_objects
, symtab
);
600 // We should have added everything we need to the dynamic string
602 this->dynpool_
.set_string_offsets();
604 // Create the version sections. We can't do this until the
605 // dynamic string table is complete.
606 this->create_version_sections(&versions
, symtab
, local_dynamic_count
,
607 dynamic_symbols
, dynstr
);
610 // FIXME: Handle PT_GNU_STACK.
612 Output_segment
* load_seg
= this->find_first_load_seg();
614 // Lay out the segment headers.
615 Output_segment_headers
* segment_headers
;
616 segment_headers
= new Output_segment_headers(this->segment_list_
);
617 load_seg
->add_initial_output_data(segment_headers
);
618 this->special_output_list_
.push_back(segment_headers
);
619 if (phdr_seg
!= NULL
)
620 phdr_seg
->add_initial_output_data(segment_headers
);
622 // Lay out the file header.
623 Output_file_header
* file_header
;
624 file_header
= new Output_file_header(target
, symtab
, segment_headers
);
625 load_seg
->add_initial_output_data(file_header
);
626 this->special_output_list_
.push_back(file_header
);
628 // We set the output section indexes in set_segment_offsets and
629 // set_section_offsets.
630 unsigned int shndx
= 1;
632 // Set the file offsets of all the segments, and all the sections
634 off_t off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
636 // Create the symbol table sections.
637 this->create_symtab_sections(input_objects
, symtab
, &off
);
639 // Create the .shstrtab section.
640 Output_section
* shstrtab_section
= this->create_shstrtab();
642 // Set the file offsets of all the sections not associated with
644 off
= this->set_section_offsets(off
, &shndx
);
646 // Create the section table header.
647 Output_section_headers
* oshdrs
= this->create_shdrs(&off
);
649 file_header
->set_section_info(oshdrs
, shstrtab_section
);
651 // Now we know exactly where everything goes in the output file.
652 Output_data::layout_complete();
654 this->output_file_size_
= off
;
659 // Create a .note section for an executable or shared library. This
660 // records the version of gold used to create the binary.
663 Layout::create_gold_note()
665 if (parameters
->output_is_object())
668 // Authorities all agree that the values in a .note field should
669 // be aligned on 4-byte boundaries for 32-bit binaries. However,
670 // they differ on what the alignment is for 64-bit binaries.
671 // The GABI says unambiguously they take 8-byte alignment:
672 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
673 // Other documentation says alignment should always be 4 bytes:
674 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
675 // GNU ld and GNU readelf both support the latter (at least as of
676 // version 2.16.91), and glibc always generates the latter for
677 // .note.ABI-tag (as of version 1.6), so that's the one we go with
679 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
680 const int size
= parameters
->get_size();
685 // The contents of the .note section.
686 const char* name
= "GNU";
687 std::string
desc(std::string("gold ") + gold::get_version_string());
688 size_t namesz
= strlen(name
) + 1;
689 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
690 size_t descsz
= desc
.length() + 1;
691 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
692 const int note_type
= 4;
694 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
696 unsigned char buffer
[128];
697 gold_assert(sizeof buffer
>= notesz
);
698 memset(buffer
, 0, notesz
);
700 bool is_big_endian
= parameters
->is_big_endian();
706 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
707 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
708 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
712 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
713 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
714 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
721 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
722 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
723 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
727 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
728 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
729 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
735 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
736 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
738 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
739 Output_section
* os
= this->make_output_section(note_name
,
742 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
744 os
->add_output_section_data(posd
);
747 // Record whether the stack should be executable. This can be set
748 // from the command line using the -z execstack or -z noexecstack
749 // options. Otherwise, if any input file has a .note.GNU-stack
750 // section with the SHF_EXECINSTR flag set, the stack should be
751 // executable. Otherwise, if at least one input file a
752 // .note.GNU-stack section, and some input file has no .note.GNU-stack
753 // section, we use the target default for whether the stack should be
754 // executable. Otherwise, we don't generate a stack note. When
755 // generating a object file, we create a .note.GNU-stack section with
756 // the appropriate marking. When generating an executable or shared
757 // library, we create a PT_GNU_STACK segment.
760 Layout::create_executable_stack_info(const Target
* target
)
762 bool is_stack_executable
;
763 if (this->options_
.is_execstack_set())
764 is_stack_executable
= this->options_
.is_stack_executable();
765 else if (!this->input_with_gnu_stack_note_
)
769 if (this->input_requires_executable_stack_
)
770 is_stack_executable
= true;
771 else if (this->input_without_gnu_stack_note_
)
772 is_stack_executable
= target
->is_default_stack_executable();
774 is_stack_executable
= false;
777 if (parameters
->output_is_object())
779 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
780 elfcpp::Elf_Xword flags
= 0;
781 if (is_stack_executable
)
782 flags
|= elfcpp::SHF_EXECINSTR
;
783 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
787 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
788 if (is_stack_executable
)
789 flags
|= elfcpp::PF_X
;
790 Output_segment
* oseg
= new Output_segment(elfcpp::PT_GNU_STACK
, flags
);
791 this->segment_list_
.push_back(oseg
);
795 // Return whether SEG1 should be before SEG2 in the output file. This
796 // is based entirely on the segment type and flags. When this is
797 // called the segment addresses has normally not yet been set.
800 Layout::segment_precedes(const Output_segment
* seg1
,
801 const Output_segment
* seg2
)
803 elfcpp::Elf_Word type1
= seg1
->type();
804 elfcpp::Elf_Word type2
= seg2
->type();
806 // The single PT_PHDR segment is required to precede any loadable
807 // segment. We simply make it always first.
808 if (type1
== elfcpp::PT_PHDR
)
810 gold_assert(type2
!= elfcpp::PT_PHDR
);
813 if (type2
== elfcpp::PT_PHDR
)
816 // The single PT_INTERP segment is required to precede any loadable
817 // segment. We simply make it always second.
818 if (type1
== elfcpp::PT_INTERP
)
820 gold_assert(type2
!= elfcpp::PT_INTERP
);
823 if (type2
== elfcpp::PT_INTERP
)
826 // We then put PT_LOAD segments before any other segments.
827 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
829 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
832 // We put the PT_TLS segment last, because that is where the dynamic
833 // linker expects to find it (this is just for efficiency; other
834 // positions would also work correctly).
835 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
837 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
840 const elfcpp::Elf_Word flags1
= seg1
->flags();
841 const elfcpp::Elf_Word flags2
= seg2
->flags();
843 // The order of non-PT_LOAD segments is unimportant. We simply sort
844 // by the numeric segment type and flags values. There should not
845 // be more than one segment with the same type and flags.
846 if (type1
!= elfcpp::PT_LOAD
)
849 return type1
< type2
;
850 gold_assert(flags1
!= flags2
);
851 return flags1
< flags2
;
854 // We sort PT_LOAD segments based on the flags. Readonly segments
855 // come before writable segments. Then executable segments come
856 // before non-executable segments. Then the unlikely case of a
857 // non-readable segment comes before the normal case of a readable
858 // segment. If there are multiple segments with the same type and
859 // flags, we require that the address be set, and we sort by
860 // virtual address and then physical address.
861 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
862 return (flags1
& elfcpp::PF_W
) == 0;
863 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
864 return (flags1
& elfcpp::PF_X
) != 0;
865 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
866 return (flags1
& elfcpp::PF_R
) == 0;
868 uint64_t vaddr1
= seg1
->vaddr();
869 uint64_t vaddr2
= seg2
->vaddr();
870 if (vaddr1
!= vaddr2
)
871 return vaddr1
< vaddr2
;
873 uint64_t paddr1
= seg1
->paddr();
874 uint64_t paddr2
= seg2
->paddr();
875 gold_assert(paddr1
!= paddr2
);
876 return paddr1
< paddr2
;
879 // Set the file offsets of all the segments, and all the sections they
880 // contain. They have all been created. LOAD_SEG must be be laid out
881 // first. Return the offset of the data to follow.
884 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
885 unsigned int *pshndx
)
887 // Sort them into the final order.
888 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
889 Layout::Compare_segments());
891 // Find the PT_LOAD segments, and set their addresses and offsets
892 // and their section's addresses and offsets.
894 if (options_
.user_set_text_segment_address())
895 addr
= options_
.text_segment_address();
897 addr
= target
->default_text_segment_address();
899 bool was_readonly
= false;
900 for (Segment_list::iterator p
= this->segment_list_
.begin();
901 p
!= this->segment_list_
.end();
904 if ((*p
)->type() == elfcpp::PT_LOAD
)
906 if (load_seg
!= NULL
&& load_seg
!= *p
)
910 // If the last segment was readonly, and this one is not,
911 // then skip the address forward one page, maintaining the
912 // same position within the page. This lets us store both
913 // segments overlapping on a single page in the file, but
914 // the loader will put them on different pages in memory.
916 uint64_t orig_addr
= addr
;
917 uint64_t orig_off
= off
;
919 uint64_t aligned_addr
= addr
;
920 uint64_t abi_pagesize
= target
->abi_pagesize();
922 // FIXME: This should depend on the -n and -N options.
923 (*p
)->set_minimum_addralign(target
->common_pagesize());
925 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
927 uint64_t align
= (*p
)->addralign();
929 addr
= align_address(addr
, align
);
931 if ((addr
& (abi_pagesize
- 1)) != 0)
932 addr
= addr
+ abi_pagesize
;
935 unsigned int shndx_hold
= *pshndx
;
936 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
937 uint64_t new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
939 // Now that we know the size of this segment, we may be able
940 // to save a page in memory, at the cost of wasting some
941 // file space, by instead aligning to the start of a new
942 // page. Here we use the real machine page size rather than
943 // the ABI mandated page size.
945 if (aligned_addr
!= addr
)
947 uint64_t common_pagesize
= target
->common_pagesize();
948 uint64_t first_off
= (common_pagesize
950 & (common_pagesize
- 1)));
951 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
954 && ((aligned_addr
& ~ (common_pagesize
- 1))
955 != (new_addr
& ~ (common_pagesize
- 1)))
956 && first_off
+ last_off
<= common_pagesize
)
958 *pshndx
= shndx_hold
;
959 addr
= align_address(aligned_addr
, common_pagesize
);
960 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
961 new_addr
= (*p
)->set_section_addresses(addr
, &off
, pshndx
);
967 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
972 // Handle the non-PT_LOAD segments, setting their offsets from their
973 // section's offsets.
974 for (Segment_list::iterator p
= this->segment_list_
.begin();
975 p
!= this->segment_list_
.end();
978 if ((*p
)->type() != elfcpp::PT_LOAD
)
985 // Set the file offset of all the sections not associated with a
989 Layout::set_section_offsets(off_t off
, unsigned int* pshndx
)
991 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
992 p
!= this->unattached_section_list_
.end();
995 (*p
)->set_out_shndx(*pshndx
);
997 if ((*p
)->offset() != -1)
999 off
= align_address(off
, (*p
)->addralign());
1000 (*p
)->set_address(0, off
);
1001 off
+= (*p
)->data_size();
1006 // Create the symbol table sections. Here we also set the final
1007 // values of the symbols. At this point all the loadable sections are
1011 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1012 Symbol_table
* symtab
,
1017 if (parameters
->get_size() == 32)
1019 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1022 else if (parameters
->get_size() == 64)
1024 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1031 off
= align_address(off
, align
);
1032 off_t startoff
= off
;
1034 // Save space for the dummy symbol at the start of the section. We
1035 // never bother to write this out--it will just be left as zero.
1037 unsigned int local_symbol_index
= 1;
1039 // Add STT_SECTION symbols for each Output section which needs one.
1040 for (Section_list::iterator p
= this->section_list_
.begin();
1041 p
!= this->section_list_
.end();
1044 if (!(*p
)->needs_symtab_index())
1045 (*p
)->set_symtab_index(-1U);
1048 (*p
)->set_symtab_index(local_symbol_index
);
1049 ++local_symbol_index
;
1054 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1055 p
!= input_objects
->relobj_end();
1058 Task_lock_obj
<Object
> tlo(**p
);
1059 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1062 off
+= (index
- local_symbol_index
) * symsize
;
1063 local_symbol_index
= index
;
1066 unsigned int local_symcount
= local_symbol_index
;
1067 gold_assert(local_symcount
* symsize
== off
- startoff
);
1070 size_t dyn_global_index
;
1072 if (this->dynsym_section_
== NULL
)
1075 dyn_global_index
= 0;
1080 dyn_global_index
= this->dynsym_section_
->info();
1081 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1082 dynoff
= this->dynsym_section_
->offset() + locsize
;
1083 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1084 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1085 == this->dynsym_section_
->data_size() - locsize
);
1088 off
= symtab
->finalize(local_symcount
, off
, dynoff
, dyn_global_index
,
1089 dyncount
, &this->sympool_
);
1091 if (!parameters
->strip_all())
1093 this->sympool_
.set_string_offsets();
1095 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1096 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1099 this->symtab_section_
= osymtab
;
1101 Output_section_data
* pos
= new Output_data_space(off
- startoff
,
1103 osymtab
->add_output_section_data(pos
);
1105 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1106 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1110 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1111 ostrtab
->add_output_section_data(pstr
);
1113 osymtab
->set_address(0, startoff
);
1114 osymtab
->set_link_section(ostrtab
);
1115 osymtab
->set_info(local_symcount
);
1116 osymtab
->set_entsize(symsize
);
1122 // Create the .shstrtab section, which holds the names of the
1123 // sections. At the time this is called, we have created all the
1124 // output sections except .shstrtab itself.
1127 Layout::create_shstrtab()
1129 // FIXME: We don't need to create a .shstrtab section if we are
1130 // stripping everything.
1132 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1134 this->namepool_
.set_string_offsets();
1136 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1138 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1139 os
->add_output_section_data(posd
);
1144 // Create the section headers. SIZE is 32 or 64. OFF is the file
1147 Output_section_headers
*
1148 Layout::create_shdrs(off_t
* poff
)
1150 Output_section_headers
* oshdrs
;
1151 oshdrs
= new Output_section_headers(this,
1152 &this->segment_list_
,
1153 &this->unattached_section_list_
,
1155 off_t off
= align_address(*poff
, oshdrs
->addralign());
1156 oshdrs
->set_address(0, off
);
1157 off
+= oshdrs
->data_size();
1159 this->special_output_list_
.push_back(oshdrs
);
1163 // Create the dynamic symbol table.
1166 Layout::create_dynamic_symtab(const Target
* target
, Symbol_table
* symtab
,
1167 Output_section
**pdynstr
,
1168 unsigned int* plocal_dynamic_count
,
1169 std::vector
<Symbol
*>* pdynamic_symbols
,
1170 Versions
* pversions
)
1172 // Count all the symbols in the dynamic symbol table, and set the
1173 // dynamic symbol indexes.
1175 // Skip symbol 0, which is always all zeroes.
1176 unsigned int index
= 1;
1178 // Add STT_SECTION symbols for each Output section which needs one.
1179 for (Section_list::iterator p
= this->section_list_
.begin();
1180 p
!= this->section_list_
.end();
1183 if (!(*p
)->needs_dynsym_index())
1184 (*p
)->set_dynsym_index(-1U);
1187 (*p
)->set_dynsym_index(index
);
1192 // FIXME: Some targets apparently require local symbols in the
1193 // dynamic symbol table. Here is where we will have to count them,
1194 // and set the dynamic symbol indexes, and add the names to
1197 unsigned int local_symcount
= index
;
1198 *plocal_dynamic_count
= local_symcount
;
1200 // FIXME: We have to tell set_dynsym_indexes whether the
1201 // -E/--export-dynamic option was used.
1202 index
= symtab
->set_dynsym_indexes(target
, index
, pdynamic_symbols
,
1203 &this->dynpool_
, pversions
);
1207 const int size
= parameters
->get_size();
1210 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1213 else if (size
== 64)
1215 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1221 // Create the dynamic symbol table section.
1223 const char* dynsym_name
= this->namepool_
.add(".dynsym", false, NULL
);
1224 Output_section
* dynsym
= this->make_output_section(dynsym_name
,
1228 Output_section_data
* odata
= new Output_data_space(index
* symsize
,
1230 dynsym
->add_output_section_data(odata
);
1232 dynsym
->set_info(local_symcount
);
1233 dynsym
->set_entsize(symsize
);
1234 dynsym
->set_addralign(align
);
1236 this->dynsym_section_
= dynsym
;
1238 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1239 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1240 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1242 // Create the dynamic string table section.
1244 const char* dynstr_name
= this->namepool_
.add(".dynstr", false, NULL
);
1245 Output_section
* dynstr
= this->make_output_section(dynstr_name
,
1249 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1250 dynstr
->add_output_section_data(strdata
);
1252 dynsym
->set_link_section(dynstr
);
1253 this->dynamic_section_
->set_link_section(dynstr
);
1255 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1256 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1260 // Create the hash tables.
1262 // FIXME: We need an option to create a GNU hash table.
1264 unsigned char* phash
;
1265 unsigned int hashlen
;
1266 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1269 const char* hash_name
= this->namepool_
.add(".hash", false, NULL
);
1270 Output_section
* hashsec
= this->make_output_section(hash_name
,
1274 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1277 hashsec
->add_output_section_data(hashdata
);
1279 hashsec
->set_link_section(dynsym
);
1280 hashsec
->set_entsize(4);
1282 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1285 // Create the version sections.
1288 Layout::create_version_sections(const Versions
* versions
,
1289 const Symbol_table
* symtab
,
1290 unsigned int local_symcount
,
1291 const std::vector
<Symbol
*>& dynamic_symbols
,
1292 const Output_section
* dynstr
)
1294 if (!versions
->any_defs() && !versions
->any_needs())
1297 if (parameters
->get_size() == 32)
1299 if (parameters
->is_big_endian())
1301 #ifdef HAVE_TARGET_32_BIG
1302 this->sized_create_version_sections
1303 SELECT_SIZE_ENDIAN_NAME(32, true)(
1304 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1305 SELECT_SIZE_ENDIAN(32, true));
1312 #ifdef HAVE_TARGET_32_LITTLE
1313 this->sized_create_version_sections
1314 SELECT_SIZE_ENDIAN_NAME(32, false)(
1315 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1316 SELECT_SIZE_ENDIAN(32, false));
1322 else if (parameters
->get_size() == 64)
1324 if (parameters
->is_big_endian())
1326 #ifdef HAVE_TARGET_64_BIG
1327 this->sized_create_version_sections
1328 SELECT_SIZE_ENDIAN_NAME(64, true)(
1329 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1330 SELECT_SIZE_ENDIAN(64, true));
1337 #ifdef HAVE_TARGET_64_LITTLE
1338 this->sized_create_version_sections
1339 SELECT_SIZE_ENDIAN_NAME(64, false)(
1340 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1341 SELECT_SIZE_ENDIAN(64, false));
1351 // Create the version sections, sized version.
1353 template<int size
, bool big_endian
>
1355 Layout::sized_create_version_sections(
1356 const Versions
* versions
,
1357 const Symbol_table
* symtab
,
1358 unsigned int local_symcount
,
1359 const std::vector
<Symbol
*>& dynamic_symbols
,
1360 const Output_section
* dynstr
1363 const char* vname
= this->namepool_
.add(".gnu.version", false, NULL
);
1364 Output_section
* vsec
= this->make_output_section(vname
,
1365 elfcpp::SHT_GNU_versym
,
1368 unsigned char* vbuf
;
1370 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1371 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
1372 SELECT_SIZE_ENDIAN(size
, big_endian
));
1374 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
1376 vsec
->add_output_section_data(vdata
);
1377 vsec
->set_entsize(2);
1378 vsec
->set_link_section(this->dynsym_section_
);
1380 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1381 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
1383 if (versions
->any_defs())
1385 const char* vdname
= this->namepool_
.add(".gnu.version_d", false, NULL
);
1386 Output_section
*vdsec
;
1387 vdsec
= this->make_output_section(vdname
, elfcpp::SHT_GNU_verdef
,
1390 unsigned char* vdbuf
;
1391 unsigned int vdsize
;
1392 unsigned int vdentries
;
1393 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
1394 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
1395 SELECT_SIZE_ENDIAN(size
, big_endian
));
1397 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
1401 vdsec
->add_output_section_data(vddata
);
1402 vdsec
->set_link_section(dynstr
);
1403 vdsec
->set_info(vdentries
);
1405 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
1406 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
1409 if (versions
->any_needs())
1411 const char* vnname
= this->namepool_
.add(".gnu.version_r", false, NULL
);
1412 Output_section
* vnsec
;
1413 vnsec
= this->make_output_section(vnname
, elfcpp::SHT_GNU_verneed
,
1416 unsigned char* vnbuf
;
1417 unsigned int vnsize
;
1418 unsigned int vnentries
;
1419 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
1420 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
1421 SELECT_SIZE_ENDIAN(size
, big_endian
));
1423 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
1427 vnsec
->add_output_section_data(vndata
);
1428 vnsec
->set_link_section(dynstr
);
1429 vnsec
->set_info(vnentries
);
1431 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
1432 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
1436 // Create the .interp section and PT_INTERP segment.
1439 Layout::create_interp(const Target
* target
)
1441 const char* interp
= this->options_
.dynamic_linker();
1444 interp
= target
->dynamic_linker();
1445 gold_assert(interp
!= NULL
);
1448 size_t len
= strlen(interp
) + 1;
1450 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
1452 const char* interp_name
= this->namepool_
.add(".interp", false, NULL
);
1453 Output_section
* osec
= this->make_output_section(interp_name
,
1454 elfcpp::SHT_PROGBITS
,
1456 osec
->add_output_section_data(odata
);
1458 Output_segment
* oseg
= new Output_segment(elfcpp::PT_INTERP
, elfcpp::PF_R
);
1459 this->segment_list_
.push_back(oseg
);
1460 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
1463 // Finish the .dynamic section and PT_DYNAMIC segment.
1466 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
1467 const Symbol_table
* symtab
)
1469 Output_segment
* oseg
= new Output_segment(elfcpp::PT_DYNAMIC
,
1470 elfcpp::PF_R
| elfcpp::PF_W
);
1471 this->segment_list_
.push_back(oseg
);
1472 oseg
->add_initial_output_section(this->dynamic_section_
,
1473 elfcpp::PF_R
| elfcpp::PF_W
);
1475 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1477 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
1478 p
!= input_objects
->dynobj_end();
1481 // FIXME: Handle --as-needed.
1482 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
1485 // FIXME: Support --init and --fini.
1486 Symbol
* sym
= symtab
->lookup("_init");
1487 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1488 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
1490 sym
= symtab
->lookup("_fini");
1491 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
1492 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
1494 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
1496 // Add a DT_RPATH entry if needed.
1497 const General_options::Dir_list
& rpath(this->options_
.rpath());
1500 std::string rpath_val
;
1501 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
1505 if (rpath_val
.empty())
1506 rpath_val
= p
->name();
1509 // Eliminate duplicates.
1510 General_options::Dir_list::const_iterator q
;
1511 for (q
= rpath
.begin(); q
!= p
; ++q
)
1512 if (q
->name() == p
->name())
1517 rpath_val
+= p
->name();
1522 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
1526 // The mapping of .gnu.linkonce section names to real section names.
1528 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
1529 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
1531 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
1532 MAPPING_INIT("t", ".text"),
1533 MAPPING_INIT("r", ".rodata"),
1534 MAPPING_INIT("d", ".data"),
1535 MAPPING_INIT("b", ".bss"),
1536 MAPPING_INIT("s", ".sdata"),
1537 MAPPING_INIT("sb", ".sbss"),
1538 MAPPING_INIT("s2", ".sdata2"),
1539 MAPPING_INIT("sb2", ".sbss2"),
1540 MAPPING_INIT("wi", ".debug_info"),
1541 MAPPING_INIT("td", ".tdata"),
1542 MAPPING_INIT("tb", ".tbss"),
1543 MAPPING_INIT("lr", ".lrodata"),
1544 MAPPING_INIT("l", ".ldata"),
1545 MAPPING_INIT("lb", ".lbss"),
1549 const int Layout::linkonce_mapping_count
=
1550 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
1552 // Return the name of the output section to use for a .gnu.linkonce
1553 // section. This is based on the default ELF linker script of the old
1554 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
1555 // to ".text". Set *PLEN to the length of the name. *PLEN is
1556 // initialized to the length of NAME.
1559 Layout::linkonce_output_name(const char* name
, size_t *plen
)
1561 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
1565 const Linkonce_mapping
* plm
= linkonce_mapping
;
1566 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
1568 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
1577 // Choose the output section name to use given an input section name.
1578 // Set *PLEN to the length of the name. *PLEN is initialized to the
1582 Layout::output_section_name(const char* name
, size_t* plen
)
1584 if (Layout::is_linkonce(name
))
1586 // .gnu.linkonce sections are laid out as though they were named
1587 // for the sections are placed into.
1588 return Layout::linkonce_output_name(name
, plen
);
1591 // gcc 4.3 generates the following sorts of section names when it
1592 // needs a section name specific to a function:
1598 // .data.rel.local.FN
1600 // .data.rel.ro.local.FN
1607 // The GNU linker maps all of those to the part before the .FN,
1608 // except that .data.rel.local.FN is mapped to .data, and
1609 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
1610 // beginning with .data.rel.ro.local are grouped together.
1612 // For an anonymous namespace, the string FN can contain a '.'.
1614 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
1615 // GNU linker maps to .rodata.
1617 // The .data.rel.ro sections enable a security feature triggered by
1618 // the -z relro option. Section which need to be relocated at
1619 // program startup time but which may be readonly after startup are
1620 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
1621 // segment. The dynamic linker will make that segment writable,
1622 // perform relocations, and then make it read-only. FIXME: We do
1623 // not yet implement this optimization.
1625 // It is hard to handle this in a principled way.
1627 // These are the rules we follow:
1629 // If the section name has no initial '.', or no dot other than an
1630 // initial '.', we use the name unchanged (i.e., "mysection" and
1631 // ".text" are unchanged).
1633 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
1635 // Otherwise, we drop the second '.' and everything that comes after
1636 // it (i.e., ".text.XXX" becomes ".text").
1638 const char* s
= name
;
1642 const char* sdot
= strchr(s
, '.');
1646 const char* const data_rel_ro
= ".data.rel.ro";
1647 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
1649 *plen
= strlen(data_rel_ro
);
1653 *plen
= sdot
- name
;
1657 // Record the signature of a comdat section, and return whether to
1658 // include it in the link. If GROUP is true, this is a regular
1659 // section group. If GROUP is false, this is a group signature
1660 // derived from the name of a linkonce section. We want linkonce
1661 // signatures and group signatures to block each other, but we don't
1662 // want a linkonce signature to block another linkonce signature.
1665 Layout::add_comdat(const char* signature
, bool group
)
1667 std::string
sig(signature
);
1668 std::pair
<Signatures::iterator
, bool> ins(
1669 this->signatures_
.insert(std::make_pair(sig
, group
)));
1673 // This is the first time we've seen this signature.
1677 if (ins
.first
->second
)
1679 // We've already seen a real section group with this signature.
1684 // This is a real section group, and we've already seen a
1685 // linkonce section with this signature. Record that we've seen
1686 // a section group, and don't include this section group.
1687 ins
.first
->second
= true;
1692 // We've already seen a linkonce section and this is a linkonce
1693 // section. These don't block each other--this may be the same
1694 // symbol name with different section types.
1699 // Write out data not associated with a section or the symbol table.
1702 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
1704 if (!parameters
->strip_all())
1706 const Output_section
* symtab_section
= this->symtab_section_
;
1707 for (Section_list::const_iterator p
= this->section_list_
.begin();
1708 p
!= this->section_list_
.end();
1711 if ((*p
)->needs_symtab_index())
1713 gold_assert(symtab_section
!= NULL
);
1714 unsigned int index
= (*p
)->symtab_index();
1715 gold_assert(index
> 0 && index
!= -1U);
1716 off_t off
= (symtab_section
->offset()
1717 + index
* symtab_section
->entsize());
1718 symtab
->write_section_symbol(*p
, of
, off
);
1723 const Output_section
* dynsym_section
= this->dynsym_section_
;
1724 for (Section_list::const_iterator p
= this->section_list_
.begin();
1725 p
!= this->section_list_
.end();
1728 if ((*p
)->needs_dynsym_index())
1730 gold_assert(dynsym_section
!= NULL
);
1731 unsigned int index
= (*p
)->dynsym_index();
1732 gold_assert(index
> 0 && index
!= -1U);
1733 off_t off
= (dynsym_section
->offset()
1734 + index
* dynsym_section
->entsize());
1735 symtab
->write_section_symbol(*p
, of
, off
);
1739 // Write out the Output_sections. Most won't have anything to
1740 // write, since most of the data will come from input sections which
1741 // are handled elsewhere. But some Output_sections do have
1743 for (Section_list::const_iterator p
= this->section_list_
.begin();
1744 p
!= this->section_list_
.end();
1748 // Write out the Output_data which are not in an Output_section.
1749 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
1750 p
!= this->special_output_list_
.end();
1755 // Write_data_task methods.
1757 // We can always run this task.
1759 Task::Is_runnable_type
1760 Write_data_task::is_runnable(Workqueue
*)
1765 // We need to unlock FINAL_BLOCKER when finished.
1768 Write_data_task::locks(Workqueue
* workqueue
)
1770 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1773 // Run the task--write out the data.
1776 Write_data_task::run(Workqueue
*)
1778 this->layout_
->write_data(this->symtab_
, this->of_
);
1781 // Write_symbols_task methods.
1783 // We can always run this task.
1785 Task::Is_runnable_type
1786 Write_symbols_task::is_runnable(Workqueue
*)
1791 // We need to unlock FINAL_BLOCKER when finished.
1794 Write_symbols_task::locks(Workqueue
* workqueue
)
1796 return new Task_locker_block(*this->final_blocker_
, workqueue
);
1799 // Run the task--write out the symbols.
1802 Write_symbols_task::run(Workqueue
*)
1804 this->symtab_
->write_globals(this->target_
, this->sympool_
, this->dynpool_
,
1808 // Close_task_runner methods.
1810 // Run the task--close the file.
1813 Close_task_runner::run(Workqueue
*)
1818 // Instantiate the templates we need. We could use the configure
1819 // script to restrict this to only the ones for implemented targets.
1821 #ifdef HAVE_TARGET_32_LITTLE
1824 Layout::layout
<32, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1825 const elfcpp::Shdr
<32, false>& shdr
, off_t
*);
1828 #ifdef HAVE_TARGET_32_BIG
1831 Layout::layout
<32, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1832 const elfcpp::Shdr
<32, true>& shdr
, off_t
*);
1835 #ifdef HAVE_TARGET_64_LITTLE
1838 Layout::layout
<64, false>(Relobj
* object
, unsigned int shndx
, const char* name
,
1839 const elfcpp::Shdr
<64, false>& shdr
, off_t
*);
1842 #ifdef HAVE_TARGET_64_BIG
1845 Layout::layout
<64, true>(Relobj
* object
, unsigned int shndx
, const char* name
,
1846 const elfcpp::Shdr
<64, true>& shdr
, off_t
*);
1850 } // End namespace gold.