1 // layout.cc -- lay out output file sections for gold
3 // Copyright 2006, 2007, 2008 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"
33 #include "script-sections.h"
38 #include "compressed_output.h"
45 // Layout_task_runner methods.
47 // Lay out the sections. This is called after all the input objects
51 Layout_task_runner::run(Workqueue
* workqueue
, const Task
* task
)
53 off_t file_size
= this->layout_
->finalize(this->input_objects_
,
58 // Now we know the final size of the output file and we know where
59 // each piece of information goes.
60 Output_file
* of
= new Output_file(parameters
->options().output_file_name());
61 if (this->options_
.oformat() != General_options::OBJECT_FORMAT_ELF
)
62 of
->set_is_temporary();
65 // Queue up the final set of tasks.
66 gold::queue_final_tasks(this->options_
, this->input_objects_
,
67 this->symtab_
, this->layout_
, workqueue
, of
);
72 Layout::Layout(const General_options
& options
, Script_options
* script_options
)
73 : options_(options
), script_options_(script_options
), namepool_(),
74 sympool_(), dynpool_(), signatures_(),
75 section_name_map_(), segment_list_(), section_list_(),
76 unattached_section_list_(), special_output_list_(),
77 section_headers_(NULL
), tls_segment_(NULL
), symtab_section_(NULL
),
78 dynsym_section_(NULL
), dynamic_section_(NULL
), dynamic_data_(NULL
),
79 eh_frame_section_(NULL
), group_signatures_(), output_file_size_(-1),
80 input_requires_executable_stack_(false),
81 input_with_gnu_stack_note_(false),
82 input_without_gnu_stack_note_(false),
83 has_static_tls_(false),
84 any_postprocessing_sections_(false)
86 // Make space for more than enough segments for a typical file.
87 // This is just for efficiency--it's OK if we wind up needing more.
88 this->segment_list_
.reserve(12);
90 // We expect two unattached Output_data objects: the file header and
91 // the segment headers.
92 this->special_output_list_
.reserve(2);
95 // Hash a key we use to look up an output section mapping.
98 Layout::Hash_key::operator()(const Layout::Key
& k
) const
100 return k
.first
+ k
.second
.first
+ k
.second
.second
;
103 // Return whether PREFIX is a prefix of STR.
106 is_prefix_of(const char* prefix
, const char* str
)
108 return strncmp(prefix
, str
, strlen(prefix
)) == 0;
111 // Returns whether the given section is in the list of
112 // debug-sections-used-by-some-version-of-gdb. Currently,
113 // we've checked versions of gdb up to and including 6.7.1.
115 static const char* gdb_sections
[] =
117 // ".debug_aranges", // not used by gdb as of 6.7.1
123 // ".debug_pubnames", // not used by gdb as of 6.7.1
129 is_gdb_debug_section(const char* str
)
131 // We can do this faster: binary search or a hashtable. But why bother?
132 for (size_t i
= 0; i
< sizeof(gdb_sections
)/sizeof(*gdb_sections
); ++i
)
133 if (strcmp(str
, gdb_sections
[i
]) == 0)
138 // Whether to include this section in the link.
140 template<int size
, bool big_endian
>
142 Layout::include_section(Sized_relobj
<size
, big_endian
>*, const char* name
,
143 const elfcpp::Shdr
<size
, big_endian
>& shdr
)
145 switch (shdr
.get_sh_type())
147 case elfcpp::SHT_NULL
:
148 case elfcpp::SHT_SYMTAB
:
149 case elfcpp::SHT_DYNSYM
:
150 case elfcpp::SHT_STRTAB
:
151 case elfcpp::SHT_HASH
:
152 case elfcpp::SHT_DYNAMIC
:
153 case elfcpp::SHT_SYMTAB_SHNDX
:
156 case elfcpp::SHT_RELA
:
157 case elfcpp::SHT_REL
:
158 case elfcpp::SHT_GROUP
:
159 // If we are emitting relocations these should be handled
161 gold_assert(!parameters
->options().relocatable()
162 && !parameters
->options().emit_relocs());
165 case elfcpp::SHT_PROGBITS
:
166 if (parameters
->options().strip_debug()
167 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
169 // Debugging sections can only be recognized by name.
170 if (is_prefix_of(".debug", name
)
171 || is_prefix_of(".gnu.linkonce.wi.", name
)
172 || is_prefix_of(".line", name
)
173 || is_prefix_of(".stab", name
))
176 if (parameters
->options().strip_debug_gdb()
177 && (shdr
.get_sh_flags() & elfcpp::SHF_ALLOC
) == 0)
179 // Debugging sections can only be recognized by name.
180 if (is_prefix_of(".debug", name
)
181 && !is_gdb_debug_section(name
))
191 // Return an output section named NAME, or NULL if there is none.
194 Layout::find_output_section(const char* name
) const
196 for (Section_list::const_iterator p
= this->section_list_
.begin();
197 p
!= this->section_list_
.end();
199 if (strcmp((*p
)->name(), name
) == 0)
204 // Return an output segment of type TYPE, with segment flags SET set
205 // and segment flags CLEAR clear. Return NULL if there is none.
208 Layout::find_output_segment(elfcpp::PT type
, elfcpp::Elf_Word set
,
209 elfcpp::Elf_Word clear
) const
211 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
212 p
!= this->segment_list_
.end();
214 if (static_cast<elfcpp::PT
>((*p
)->type()) == type
215 && ((*p
)->flags() & set
) == set
216 && ((*p
)->flags() & clear
) == 0)
221 // Return the output section to use for section NAME with type TYPE
222 // and section flags FLAGS. NAME must be canonicalized in the string
223 // pool, and NAME_KEY is the key.
226 Layout::get_output_section(const char* name
, Stringpool::Key name_key
,
227 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
)
229 const Key
key(name_key
, std::make_pair(type
, flags
));
230 const std::pair
<Key
, Output_section
*> v(key
, NULL
);
231 std::pair
<Section_name_map::iterator
, bool> ins(
232 this->section_name_map_
.insert(v
));
235 return ins
.first
->second
;
238 // This is the first time we've seen this name/type/flags
240 Output_section
* os
= this->make_output_section(name
, type
, flags
);
241 ins
.first
->second
= os
;
246 // Pick the output section to use for section NAME, in input file
247 // RELOBJ, with type TYPE and flags FLAGS. RELOBJ may be NULL for a
248 // linker created section. ADJUST_NAME is true if we should apply the
249 // standard name mappings in Layout::output_section_name. This will
250 // return NULL if the input section should be discarded.
253 Layout::choose_output_section(const Relobj
* relobj
, const char* name
,
254 elfcpp::Elf_Word type
, elfcpp::Elf_Xword flags
,
257 // We should ignore some flags. FIXME: This will need some
258 // adjustment for ld -r.
259 flags
&= ~ (elfcpp::SHF_INFO_LINK
260 | elfcpp::SHF_LINK_ORDER
263 | elfcpp::SHF_STRINGS
);
265 if (this->script_options_
->saw_sections_clause())
267 // We are using a SECTIONS clause, so the output section is
268 // chosen based only on the name.
270 Script_sections
* ss
= this->script_options_
->script_sections();
271 const char* file_name
= relobj
== NULL
? NULL
: relobj
->name().c_str();
272 Output_section
** output_section_slot
;
273 name
= ss
->output_section_name(file_name
, name
, &output_section_slot
);
276 // The SECTIONS clause says to discard this input section.
280 // If this is an orphan section--one not mentioned in the linker
281 // script--then OUTPUT_SECTION_SLOT will be NULL, and we do the
282 // default processing below.
284 if (output_section_slot
!= NULL
)
286 if (*output_section_slot
!= NULL
)
287 return *output_section_slot
;
289 // We don't put sections found in the linker script into
290 // SECTION_NAME_MAP_. That keeps us from getting confused
291 // if an orphan section is mapped to a section with the same
292 // name as one in the linker script.
294 name
= this->namepool_
.add(name
, false, NULL
);
296 Output_section
* os
= this->make_output_section(name
, type
, flags
);
297 os
->set_found_in_sections_clause();
298 *output_section_slot
= os
;
303 // FIXME: Handle SHF_OS_NONCONFORMING somewhere.
305 // Turn NAME from the name of the input section into the name of the
308 size_t len
= strlen(name
);
309 if (adjust_name
&& !parameters
->options().relocatable())
310 name
= Layout::output_section_name(name
, &len
);
312 Stringpool::Key name_key
;
313 name
= this->namepool_
.add_with_length(name
, len
, true, &name_key
);
315 // Find or make the output section. The output section is selected
316 // based on the section name, type, and flags.
317 return this->get_output_section(name
, name_key
, type
, flags
);
320 // Return the output section to use for input section SHNDX, with name
321 // NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
322 // index of a relocation section which applies to this section, or 0
323 // if none, or -1U if more than one. RELOC_TYPE is the type of the
324 // relocation section if there is one. Set *OFF to the offset of this
325 // input section without the output section. Return NULL if the
326 // section should be discarded. Set *OFF to -1 if the section
327 // contents should not be written directly to the output file, but
328 // will instead receive special handling.
330 template<int size
, bool big_endian
>
332 Layout::layout(Sized_relobj
<size
, big_endian
>* object
, unsigned int shndx
,
333 const char* name
, const elfcpp::Shdr
<size
, big_endian
>& shdr
,
334 unsigned int reloc_shndx
, unsigned int, off_t
* off
)
336 if (!this->include_section(object
, name
, shdr
))
341 // In a relocatable link a grouped section must not be combined with
342 // any other sections.
343 if (parameters
->options().relocatable()
344 && (shdr
.get_sh_flags() & elfcpp::SHF_GROUP
) != 0)
346 name
= this->namepool_
.add(name
, true, NULL
);
347 os
= this->make_output_section(name
, shdr
.get_sh_type(),
348 shdr
.get_sh_flags());
352 os
= this->choose_output_section(object
, name
, shdr
.get_sh_type(),
353 shdr
.get_sh_flags(), true);
358 // FIXME: Handle SHF_LINK_ORDER somewhere.
360 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
,
361 this->script_options_
->saw_sections_clause());
366 // Handle a relocation section when doing a relocatable link.
368 template<int size
, bool big_endian
>
370 Layout::layout_reloc(Sized_relobj
<size
, big_endian
>* object
,
372 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
373 Output_section
* data_section
,
374 Relocatable_relocs
* rr
)
376 gold_assert(parameters
->options().relocatable()
377 || parameters
->options().emit_relocs());
379 int sh_type
= shdr
.get_sh_type();
382 if (sh_type
== elfcpp::SHT_REL
)
384 else if (sh_type
== elfcpp::SHT_RELA
)
388 name
+= data_section
->name();
390 Output_section
* os
= this->choose_output_section(object
, name
.c_str(),
395 os
->set_should_link_to_symtab();
396 os
->set_info_section(data_section
);
398 Output_section_data
* posd
;
399 if (sh_type
== elfcpp::SHT_REL
)
401 os
->set_entsize(elfcpp::Elf_sizes
<size
>::rel_size
);
402 posd
= new Output_relocatable_relocs
<elfcpp::SHT_REL
,
406 else if (sh_type
== elfcpp::SHT_RELA
)
408 os
->set_entsize(elfcpp::Elf_sizes
<size
>::rela_size
);
409 posd
= new Output_relocatable_relocs
<elfcpp::SHT_RELA
,
416 os
->add_output_section_data(posd
);
417 rr
->set_output_data(posd
);
422 // Handle a group section when doing a relocatable link.
424 template<int size
, bool big_endian
>
426 Layout::layout_group(Symbol_table
* symtab
,
427 Sized_relobj
<size
, big_endian
>* object
,
429 const char* group_section_name
,
430 const char* signature
,
431 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
432 const elfcpp::Elf_Word
* contents
)
434 gold_assert(parameters
->options().relocatable());
435 gold_assert(shdr
.get_sh_type() == elfcpp::SHT_GROUP
);
436 group_section_name
= this->namepool_
.add(group_section_name
, true, NULL
);
437 Output_section
* os
= this->make_output_section(group_section_name
,
439 shdr
.get_sh_flags());
441 // We need to find a symbol with the signature in the symbol table.
442 // If we don't find one now, we need to look again later.
443 Symbol
* sym
= symtab
->lookup(signature
, NULL
);
445 os
->set_info_symndx(sym
);
448 // We will wind up using a symbol whose name is the signature.
449 // So just put the signature in the symbol name pool to save it.
450 signature
= symtab
->canonicalize_name(signature
);
451 this->group_signatures_
.push_back(Group_signature(os
, signature
));
454 os
->set_should_link_to_symtab();
457 section_size_type entry_count
=
458 convert_to_section_size_type(shdr
.get_sh_size() / 4);
459 Output_section_data
* posd
=
460 new Output_data_group
<size
, big_endian
>(object
, entry_count
, contents
);
461 os
->add_output_section_data(posd
);
464 // Special GNU handling of sections name .eh_frame. They will
465 // normally hold exception frame data as defined by the C++ ABI
466 // (http://codesourcery.com/cxx-abi/).
468 template<int size
, bool big_endian
>
470 Layout::layout_eh_frame(Sized_relobj
<size
, big_endian
>* object
,
471 const unsigned char* symbols
,
473 const unsigned char* symbol_names
,
474 off_t symbol_names_size
,
476 const elfcpp::Shdr
<size
, big_endian
>& shdr
,
477 unsigned int reloc_shndx
, unsigned int reloc_type
,
480 gold_assert(shdr
.get_sh_type() == elfcpp::SHT_PROGBITS
);
481 gold_assert(shdr
.get_sh_flags() == elfcpp::SHF_ALLOC
);
483 const char* const name
= ".eh_frame";
484 Output_section
* os
= this->choose_output_section(object
,
486 elfcpp::SHT_PROGBITS
,
492 if (this->eh_frame_section_
== NULL
)
494 this->eh_frame_section_
= os
;
495 this->eh_frame_data_
= new Eh_frame();
496 os
->add_output_section_data(this->eh_frame_data_
);
498 if (this->options_
.eh_frame_hdr())
500 Output_section
* hdr_os
=
501 this->choose_output_section(NULL
,
503 elfcpp::SHT_PROGBITS
,
509 Eh_frame_hdr
* hdr_posd
= new Eh_frame_hdr(os
,
510 this->eh_frame_data_
);
511 hdr_os
->add_output_section_data(hdr_posd
);
513 hdr_os
->set_after_input_sections();
515 if (!this->script_options_
->saw_phdrs_clause())
517 Output_segment
* hdr_oseg
;
518 hdr_oseg
= this->make_output_segment(elfcpp::PT_GNU_EH_FRAME
,
520 hdr_oseg
->add_output_section(hdr_os
, elfcpp::PF_R
);
523 this->eh_frame_data_
->set_eh_frame_hdr(hdr_posd
);
528 gold_assert(this->eh_frame_section_
== os
);
530 if (this->eh_frame_data_
->add_ehframe_input_section(object
,
541 // We couldn't handle this .eh_frame section for some reason.
542 // Add it as a normal section.
543 bool saw_sections_clause
= this->script_options_
->saw_sections_clause();
544 *off
= os
->add_input_section(object
, shndx
, name
, shdr
, reloc_shndx
,
545 saw_sections_clause
);
551 // Add POSD to an output section using NAME, TYPE, and FLAGS.
554 Layout::add_output_section_data(const char* name
, elfcpp::Elf_Word type
,
555 elfcpp::Elf_Xword flags
,
556 Output_section_data
* posd
)
558 Output_section
* os
= this->choose_output_section(NULL
, name
, type
, flags
,
561 os
->add_output_section_data(posd
);
564 // Map section flags to segment flags.
567 Layout::section_flags_to_segment(elfcpp::Elf_Xword flags
)
569 elfcpp::Elf_Word ret
= elfcpp::PF_R
;
570 if ((flags
& elfcpp::SHF_WRITE
) != 0)
572 if ((flags
& elfcpp::SHF_EXECINSTR
) != 0)
577 // Sometimes we compress sections. This is typically done for
578 // sections that are not part of normal program execution (such as
579 // .debug_* sections), and where the readers of these sections know
580 // how to deal with compressed sections. (To make it easier for them,
581 // we will rename the ouput section in such cases from .foo to
582 // .foo.zlib.nnnn, where nnnn is the uncompressed size.) This routine
583 // doesn't say for certain whether we'll compress -- it depends on
584 // commandline options as well -- just whether this section is a
585 // candidate for compression.
588 is_compressible_debug_section(const char* secname
)
590 return (strncmp(secname
, ".debug", sizeof(".debug") - 1) == 0);
593 // Make a new Output_section, and attach it to segments as
597 Layout::make_output_section(const char* name
, elfcpp::Elf_Word type
,
598 elfcpp::Elf_Xword flags
)
601 if ((flags
& elfcpp::SHF_ALLOC
) == 0
602 && this->options_
.compress_debug_sections()
603 && is_compressible_debug_section(name
))
604 os
= new Output_compressed_section(&this->options_
, name
, type
, flags
);
606 os
= new Output_section(name
, type
, flags
);
608 this->section_list_
.push_back(os
);
610 if ((flags
& elfcpp::SHF_ALLOC
) == 0)
611 this->unattached_section_list_
.push_back(os
);
614 if (parameters
->options().relocatable())
617 // If we have a SECTIONS clause, we can't handle the attachment
618 // to segments until after we've seen all the sections.
619 if (this->script_options_
->saw_sections_clause())
622 gold_assert(!this->script_options_
->saw_phdrs_clause());
624 // This output section goes into a PT_LOAD segment.
626 elfcpp::Elf_Word seg_flags
= Layout::section_flags_to_segment(flags
);
628 // In general the only thing we really care about for PT_LOAD
629 // segments is whether or not they are writable, so that is how
630 // we search for them. People who need segments sorted on some
631 // other basis will have to use a linker script.
633 Segment_list::const_iterator p
;
634 for (p
= this->segment_list_
.begin();
635 p
!= this->segment_list_
.end();
638 if ((*p
)->type() == elfcpp::PT_LOAD
639 && ((*p
)->flags() & elfcpp::PF_W
) == (seg_flags
& elfcpp::PF_W
))
641 // If -Tbss was specified, we need to separate the data
643 if (this->options_
.user_set_Tbss())
645 if ((type
== elfcpp::SHT_NOBITS
)
646 == (*p
)->has_any_data_sections())
650 (*p
)->add_output_section(os
, seg_flags
);
655 if (p
== this->segment_list_
.end())
657 Output_segment
* oseg
= this->make_output_segment(elfcpp::PT_LOAD
,
659 oseg
->add_output_section(os
, seg_flags
);
662 // If we see a loadable SHT_NOTE section, we create a PT_NOTE
664 if (type
== elfcpp::SHT_NOTE
)
666 // See if we already have an equivalent PT_NOTE segment.
667 for (p
= this->segment_list_
.begin();
668 p
!= segment_list_
.end();
671 if ((*p
)->type() == elfcpp::PT_NOTE
672 && (((*p
)->flags() & elfcpp::PF_W
)
673 == (seg_flags
& elfcpp::PF_W
)))
675 (*p
)->add_output_section(os
, seg_flags
);
680 if (p
== this->segment_list_
.end())
682 Output_segment
* oseg
= this->make_output_segment(elfcpp::PT_NOTE
,
684 oseg
->add_output_section(os
, seg_flags
);
688 // If we see a loadable SHF_TLS section, we create a PT_TLS
689 // segment. There can only be one such segment.
690 if ((flags
& elfcpp::SHF_TLS
) != 0)
692 if (this->tls_segment_
== NULL
)
693 this->tls_segment_
= this->make_output_segment(elfcpp::PT_TLS
,
695 this->tls_segment_
->add_output_section(os
, seg_flags
);
702 // Return the number of segments we expect to see.
705 Layout::expected_segment_count() const
707 size_t ret
= this->segment_list_
.size();
709 // If we didn't see a SECTIONS clause in a linker script, we should
710 // already have the complete list of segments. Otherwise we ask the
711 // SECTIONS clause how many segments it expects, and add in the ones
712 // we already have (PT_GNU_STACK, PT_GNU_EH_FRAME, etc.)
714 if (!this->script_options_
->saw_sections_clause())
718 const Script_sections
* ss
= this->script_options_
->script_sections();
719 return ret
+ ss
->expected_segment_count(this);
723 // Handle the .note.GNU-stack section at layout time. SEEN_GNU_STACK
724 // is whether we saw a .note.GNU-stack section in the object file.
725 // GNU_STACK_FLAGS is the section flags. The flags give the
726 // protection required for stack memory. We record this in an
727 // executable as a PT_GNU_STACK segment. If an object file does not
728 // have a .note.GNU-stack segment, we must assume that it is an old
729 // object. On some targets that will force an executable stack.
732 Layout::layout_gnu_stack(bool seen_gnu_stack
, uint64_t gnu_stack_flags
)
735 this->input_without_gnu_stack_note_
= true;
738 this->input_with_gnu_stack_note_
= true;
739 if ((gnu_stack_flags
& elfcpp::SHF_EXECINSTR
) != 0)
740 this->input_requires_executable_stack_
= true;
744 // Create the dynamic sections which are needed before we read the
748 Layout::create_initial_dynamic_sections(Symbol_table
* symtab
)
750 if (parameters
->doing_static_link())
753 this->dynamic_section_
= this->choose_output_section(NULL
, ".dynamic",
756 | elfcpp::SHF_WRITE
),
759 symtab
->define_in_output_data("_DYNAMIC", NULL
, this->dynamic_section_
, 0, 0,
760 elfcpp::STT_OBJECT
, elfcpp::STB_LOCAL
,
761 elfcpp::STV_HIDDEN
, 0, false, false);
763 this->dynamic_data_
= new Output_data_dynamic(&this->dynpool_
);
765 this->dynamic_section_
->add_output_section_data(this->dynamic_data_
);
768 // For each output section whose name can be represented as C symbol,
769 // define __start and __stop symbols for the section. This is a GNU
773 Layout::define_section_symbols(Symbol_table
* symtab
)
775 for (Section_list::const_iterator p
= this->section_list_
.begin();
776 p
!= this->section_list_
.end();
779 const char* const name
= (*p
)->name();
780 if (name
[strspn(name
,
782 "ABCDEFGHIJKLMNOPWRSTUVWXYZ"
783 "abcdefghijklmnopqrstuvwxyz"
787 const std::string
name_string(name
);
788 const std::string
start_name("__start_" + name_string
);
789 const std::string
stop_name("__stop_" + name_string
);
791 symtab
->define_in_output_data(start_name
.c_str(),
800 false, // offset_is_from_end
801 true); // only_if_ref
803 symtab
->define_in_output_data(stop_name
.c_str(),
812 true, // offset_is_from_end
813 true); // only_if_ref
818 // Define symbols for group signatures.
821 Layout::define_group_signatures(Symbol_table
* symtab
)
823 for (Group_signatures::iterator p
= this->group_signatures_
.begin();
824 p
!= this->group_signatures_
.end();
827 Symbol
* sym
= symtab
->lookup(p
->signature
, NULL
);
829 p
->section
->set_info_symndx(sym
);
832 // Force the name of the group section to the group
833 // signature, and use the group's section symbol as the
835 if (strcmp(p
->section
->name(), p
->signature
) != 0)
837 const char* name
= this->namepool_
.add(p
->signature
,
839 p
->section
->set_name(name
);
841 p
->section
->set_needs_symtab_index();
842 p
->section
->set_info_section_symndx(p
->section
);
846 this->group_signatures_
.clear();
849 // Find the first read-only PT_LOAD segment, creating one if
853 Layout::find_first_load_seg()
855 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
856 p
!= this->segment_list_
.end();
859 if ((*p
)->type() == elfcpp::PT_LOAD
860 && ((*p
)->flags() & elfcpp::PF_R
) != 0
861 && ((*p
)->flags() & elfcpp::PF_W
) == 0)
865 gold_assert(!this->script_options_
->saw_phdrs_clause());
867 Output_segment
* load_seg
= this->make_output_segment(elfcpp::PT_LOAD
,
872 // Finalize the layout. When this is called, we have created all the
873 // output sections and all the output segments which are based on
874 // input sections. We have several things to do, and we have to do
875 // them in the right order, so that we get the right results correctly
878 // 1) Finalize the list of output segments and create the segment
881 // 2) Finalize the dynamic symbol table and associated sections.
883 // 3) Determine the final file offset of all the output segments.
885 // 4) Determine the final file offset of all the SHF_ALLOC output
888 // 5) Create the symbol table sections and the section name table
891 // 6) Finalize the symbol table: set symbol values to their final
892 // value and make a final determination of which symbols are going
893 // into the output symbol table.
895 // 7) Create the section table header.
897 // 8) Determine the final file offset of all the output sections which
898 // are not SHF_ALLOC, including the section table header.
900 // 9) Finalize the ELF file header.
902 // This function returns the size of the output file.
905 Layout::finalize(const Input_objects
* input_objects
, Symbol_table
* symtab
,
906 Target
* target
, const Task
* task
)
908 target
->finalize_sections(this);
910 this->count_local_symbols(task
, input_objects
);
912 this->create_gold_note();
913 this->create_executable_stack_info(target
);
915 Output_segment
* phdr_seg
= NULL
;
916 if (!parameters
->options().relocatable() && !parameters
->doing_static_link())
918 // There was a dynamic object in the link. We need to create
919 // some information for the dynamic linker.
921 // Create the PT_PHDR segment which will hold the program
923 if (!this->script_options_
->saw_phdrs_clause())
924 phdr_seg
= this->make_output_segment(elfcpp::PT_PHDR
, elfcpp::PF_R
);
926 // Create the dynamic symbol table, including the hash table.
927 Output_section
* dynstr
;
928 std::vector
<Symbol
*> dynamic_symbols
;
929 unsigned int local_dynamic_count
;
930 Versions
versions(*this->script_options()->version_script_info(),
932 this->create_dynamic_symtab(input_objects
, symtab
, &dynstr
,
933 &local_dynamic_count
, &dynamic_symbols
,
936 // Create the .interp section to hold the name of the
937 // interpreter, and put it in a PT_INTERP segment.
938 if (!parameters
->options().shared())
939 this->create_interp(target
);
941 // Finish the .dynamic section to hold the dynamic data, and put
942 // it in a PT_DYNAMIC segment.
943 this->finish_dynamic_section(input_objects
, symtab
);
945 // We should have added everything we need to the dynamic string
947 this->dynpool_
.set_string_offsets();
949 // Create the version sections. We can't do this until the
950 // dynamic string table is complete.
951 this->create_version_sections(&versions
, symtab
, local_dynamic_count
,
952 dynamic_symbols
, dynstr
);
955 // If there is a SECTIONS clause, put all the input sections into
956 // the required order.
957 Output_segment
* load_seg
;
958 if (this->script_options_
->saw_sections_clause())
959 load_seg
= this->set_section_addresses_from_script(symtab
);
960 else if (parameters
->options().relocatable())
963 load_seg
= this->find_first_load_seg();
965 if (this->options_
.oformat() != General_options::OBJECT_FORMAT_ELF
)
968 gold_assert(phdr_seg
== NULL
|| load_seg
!= NULL
);
970 // Lay out the segment headers.
971 Output_segment_headers
* segment_headers
;
972 if (parameters
->options().relocatable())
973 segment_headers
= NULL
;
976 segment_headers
= new Output_segment_headers(this->segment_list_
);
977 if (load_seg
!= NULL
)
978 load_seg
->add_initial_output_data(segment_headers
);
979 if (phdr_seg
!= NULL
)
980 phdr_seg
->add_initial_output_data(segment_headers
);
983 // Lay out the file header.
984 Output_file_header
* file_header
;
985 file_header
= new Output_file_header(target
, symtab
, segment_headers
,
986 this->options_
.entry());
987 if (load_seg
!= NULL
)
988 load_seg
->add_initial_output_data(file_header
);
990 this->special_output_list_
.push_back(file_header
);
991 if (segment_headers
!= NULL
)
992 this->special_output_list_
.push_back(segment_headers
);
994 if (this->script_options_
->saw_phdrs_clause()
995 && !parameters
->options().relocatable())
997 // Support use of FILEHDRS and PHDRS attachments in a PHDRS
998 // clause in a linker script.
999 Script_sections
* ss
= this->script_options_
->script_sections();
1000 ss
->put_headers_in_phdrs(file_header
, segment_headers
);
1003 // We set the output section indexes in set_segment_offsets and
1004 // set_section_indexes.
1005 unsigned int shndx
= 1;
1007 // Set the file offsets of all the segments, and all the sections
1010 if (!parameters
->options().relocatable())
1011 off
= this->set_segment_offsets(target
, load_seg
, &shndx
);
1013 off
= this->set_relocatable_section_offsets(file_header
, &shndx
);
1015 // Set the file offsets of all the non-data sections we've seen so
1016 // far which don't have to wait for the input sections. We need
1017 // this in order to finalize local symbols in non-allocated
1019 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
1021 // Create the symbol table sections.
1022 this->create_symtab_sections(input_objects
, symtab
, &off
);
1023 if (!parameters
->doing_static_link())
1024 this->assign_local_dynsym_offsets(input_objects
);
1026 // Process any symbol assignments from a linker script. This must
1027 // be called after the symbol table has been finalized.
1028 this->script_options_
->finalize_symbols(symtab
, this);
1030 // Create the .shstrtab section.
1031 Output_section
* shstrtab_section
= this->create_shstrtab();
1033 // Set the file offsets of the rest of the non-data sections which
1034 // don't have to wait for the input sections.
1035 off
= this->set_section_offsets(off
, BEFORE_INPUT_SECTIONS_PASS
);
1037 // Now that all sections have been created, set the section indexes.
1038 shndx
= this->set_section_indexes(shndx
);
1040 // Create the section table header.
1041 this->create_shdrs(&off
);
1043 // If there are no sections which require postprocessing, we can
1044 // handle the section names now, and avoid a resize later.
1045 if (!this->any_postprocessing_sections_
)
1046 off
= this->set_section_offsets(off
,
1047 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
1049 file_header
->set_section_info(this->section_headers_
, shstrtab_section
);
1051 // Now we know exactly where everything goes in the output file
1052 // (except for non-allocated sections which require postprocessing).
1053 Output_data::layout_complete();
1055 this->output_file_size_
= off
;
1060 // Create a .note section for an executable or shared library. This
1061 // records the version of gold used to create the binary.
1064 Layout::create_gold_note()
1066 if (parameters
->options().relocatable())
1069 // Authorities all agree that the values in a .note field should
1070 // be aligned on 4-byte boundaries for 32-bit binaries. However,
1071 // they differ on what the alignment is for 64-bit binaries.
1072 // The GABI says unambiguously they take 8-byte alignment:
1073 // http://sco.com/developers/gabi/latest/ch5.pheader.html#note_section
1074 // Other documentation says alignment should always be 4 bytes:
1075 // http://www.netbsd.org/docs/kernel/elf-notes.html#note-format
1076 // GNU ld and GNU readelf both support the latter (at least as of
1077 // version 2.16.91), and glibc always generates the latter for
1078 // .note.ABI-tag (as of version 1.6), so that's the one we go with
1080 #ifdef GABI_FORMAT_FOR_DOTNOTE_SECTION // This is not defined by default.
1081 const int size
= parameters
->target().get_size();
1083 const int size
= 32;
1086 // The contents of the .note section.
1087 const char* name
= "GNU";
1088 std::string
desc(std::string("gold ") + gold::get_version_string());
1089 size_t namesz
= strlen(name
) + 1;
1090 size_t aligned_namesz
= align_address(namesz
, size
/ 8);
1091 size_t descsz
= desc
.length() + 1;
1092 size_t aligned_descsz
= align_address(descsz
, size
/ 8);
1093 const int note_type
= 4;
1095 size_t notesz
= 3 * (size
/ 8) + aligned_namesz
+ aligned_descsz
;
1097 unsigned char buffer
[128];
1098 gold_assert(sizeof buffer
>= notesz
);
1099 memset(buffer
, 0, notesz
);
1101 bool is_big_endian
= parameters
->target().is_big_endian();
1107 elfcpp::Swap
<32, false>::writeval(buffer
, namesz
);
1108 elfcpp::Swap
<32, false>::writeval(buffer
+ 4, descsz
);
1109 elfcpp::Swap
<32, false>::writeval(buffer
+ 8, note_type
);
1113 elfcpp::Swap
<32, true>::writeval(buffer
, namesz
);
1114 elfcpp::Swap
<32, true>::writeval(buffer
+ 4, descsz
);
1115 elfcpp::Swap
<32, true>::writeval(buffer
+ 8, note_type
);
1118 else if (size
== 64)
1122 elfcpp::Swap
<64, false>::writeval(buffer
, namesz
);
1123 elfcpp::Swap
<64, false>::writeval(buffer
+ 8, descsz
);
1124 elfcpp::Swap
<64, false>::writeval(buffer
+ 16, note_type
);
1128 elfcpp::Swap
<64, true>::writeval(buffer
, namesz
);
1129 elfcpp::Swap
<64, true>::writeval(buffer
+ 8, descsz
);
1130 elfcpp::Swap
<64, true>::writeval(buffer
+ 16, note_type
);
1136 memcpy(buffer
+ 3 * (size
/ 8), name
, namesz
);
1137 memcpy(buffer
+ 3 * (size
/ 8) + aligned_namesz
, desc
.data(), descsz
);
1139 const char* note_name
= this->namepool_
.add(".note", false, NULL
);
1140 Output_section
* os
= this->make_output_section(note_name
,
1143 Output_section_data
* posd
= new Output_data_const(buffer
, notesz
,
1145 os
->add_output_section_data(posd
);
1148 // Record whether the stack should be executable. This can be set
1149 // from the command line using the -z execstack or -z noexecstack
1150 // options. Otherwise, if any input file has a .note.GNU-stack
1151 // section with the SHF_EXECINSTR flag set, the stack should be
1152 // executable. Otherwise, if at least one input file a
1153 // .note.GNU-stack section, and some input file has no .note.GNU-stack
1154 // section, we use the target default for whether the stack should be
1155 // executable. Otherwise, we don't generate a stack note. When
1156 // generating a object file, we create a .note.GNU-stack section with
1157 // the appropriate marking. When generating an executable or shared
1158 // library, we create a PT_GNU_STACK segment.
1161 Layout::create_executable_stack_info(const Target
* target
)
1163 bool is_stack_executable
;
1164 if (this->options_
.is_execstack_set())
1165 is_stack_executable
= this->options_
.is_stack_executable();
1166 else if (!this->input_with_gnu_stack_note_
)
1170 if (this->input_requires_executable_stack_
)
1171 is_stack_executable
= true;
1172 else if (this->input_without_gnu_stack_note_
)
1173 is_stack_executable
= target
->is_default_stack_executable();
1175 is_stack_executable
= false;
1178 if (parameters
->options().relocatable())
1180 const char* name
= this->namepool_
.add(".note.GNU-stack", false, NULL
);
1181 elfcpp::Elf_Xword flags
= 0;
1182 if (is_stack_executable
)
1183 flags
|= elfcpp::SHF_EXECINSTR
;
1184 this->make_output_section(name
, elfcpp::SHT_PROGBITS
, flags
);
1188 if (this->script_options_
->saw_phdrs_clause())
1190 int flags
= elfcpp::PF_R
| elfcpp::PF_W
;
1191 if (is_stack_executable
)
1192 flags
|= elfcpp::PF_X
;
1193 this->make_output_segment(elfcpp::PT_GNU_STACK
, flags
);
1197 // Return whether SEG1 should be before SEG2 in the output file. This
1198 // is based entirely on the segment type and flags. When this is
1199 // called the segment addresses has normally not yet been set.
1202 Layout::segment_precedes(const Output_segment
* seg1
,
1203 const Output_segment
* seg2
)
1205 elfcpp::Elf_Word type1
= seg1
->type();
1206 elfcpp::Elf_Word type2
= seg2
->type();
1208 // The single PT_PHDR segment is required to precede any loadable
1209 // segment. We simply make it always first.
1210 if (type1
== elfcpp::PT_PHDR
)
1212 gold_assert(type2
!= elfcpp::PT_PHDR
);
1215 if (type2
== elfcpp::PT_PHDR
)
1218 // The single PT_INTERP segment is required to precede any loadable
1219 // segment. We simply make it always second.
1220 if (type1
== elfcpp::PT_INTERP
)
1222 gold_assert(type2
!= elfcpp::PT_INTERP
);
1225 if (type2
== elfcpp::PT_INTERP
)
1228 // We then put PT_LOAD segments before any other segments.
1229 if (type1
== elfcpp::PT_LOAD
&& type2
!= elfcpp::PT_LOAD
)
1231 if (type2
== elfcpp::PT_LOAD
&& type1
!= elfcpp::PT_LOAD
)
1234 // We put the PT_TLS segment last, because that is where the dynamic
1235 // linker expects to find it (this is just for efficiency; other
1236 // positions would also work correctly).
1237 if (type1
== elfcpp::PT_TLS
&& type2
!= elfcpp::PT_TLS
)
1239 if (type2
== elfcpp::PT_TLS
&& type1
!= elfcpp::PT_TLS
)
1242 const elfcpp::Elf_Word flags1
= seg1
->flags();
1243 const elfcpp::Elf_Word flags2
= seg2
->flags();
1245 // The order of non-PT_LOAD segments is unimportant. We simply sort
1246 // by the numeric segment type and flags values. There should not
1247 // be more than one segment with the same type and flags.
1248 if (type1
!= elfcpp::PT_LOAD
)
1251 return type1
< type2
;
1252 gold_assert(flags1
!= flags2
);
1253 return flags1
< flags2
;
1256 // If the addresses are set already, sort by load address.
1257 if (seg1
->are_addresses_set())
1259 if (!seg2
->are_addresses_set())
1262 unsigned int section_count1
= seg1
->output_section_count();
1263 unsigned int section_count2
= seg2
->output_section_count();
1264 if (section_count1
== 0 && section_count2
> 0)
1266 if (section_count1
> 0 && section_count2
== 0)
1269 uint64_t paddr1
= seg1
->first_section_load_address();
1270 uint64_t paddr2
= seg2
->first_section_load_address();
1271 if (paddr1
!= paddr2
)
1272 return paddr1
< paddr2
;
1274 else if (seg2
->are_addresses_set())
1277 // We sort PT_LOAD segments based on the flags. Readonly segments
1278 // come before writable segments. Then writable segments with data
1279 // come before writable segments without data. Then executable
1280 // segments come before non-executable segments. Then the unlikely
1281 // case of a non-readable segment comes before the normal case of a
1282 // readable segment. If there are multiple segments with the same
1283 // type and flags, we require that the address be set, and we sort
1284 // by virtual address and then physical address.
1285 if ((flags1
& elfcpp::PF_W
) != (flags2
& elfcpp::PF_W
))
1286 return (flags1
& elfcpp::PF_W
) == 0;
1287 if ((flags1
& elfcpp::PF_W
) != 0
1288 && seg1
->has_any_data_sections() != seg2
->has_any_data_sections())
1289 return seg1
->has_any_data_sections();
1290 if ((flags1
& elfcpp::PF_X
) != (flags2
& elfcpp::PF_X
))
1291 return (flags1
& elfcpp::PF_X
) != 0;
1292 if ((flags1
& elfcpp::PF_R
) != (flags2
& elfcpp::PF_R
))
1293 return (flags1
& elfcpp::PF_R
) == 0;
1295 // We shouldn't get here--we shouldn't create segments which we
1296 // can't distinguish.
1300 // Set the file offsets of all the segments, and all the sections they
1301 // contain. They have all been created. LOAD_SEG must be be laid out
1302 // first. Return the offset of the data to follow.
1305 Layout::set_segment_offsets(const Target
* target
, Output_segment
* load_seg
,
1306 unsigned int *pshndx
)
1308 // Sort them into the final order.
1309 std::sort(this->segment_list_
.begin(), this->segment_list_
.end(),
1310 Layout::Compare_segments());
1312 // Find the PT_LOAD segments, and set their addresses and offsets
1313 // and their section's addresses and offsets.
1315 if (this->options_
.user_set_Ttext())
1316 addr
= this->options_
.Ttext();
1317 else if (parameters
->options().shared())
1320 addr
= target
->default_text_segment_address();
1323 // If LOAD_SEG is NULL, then the file header and segment headers
1324 // will not be loadable. But they still need to be at offset 0 in
1325 // the file. Set their offsets now.
1326 if (load_seg
== NULL
)
1328 for (Data_list::iterator p
= this->special_output_list_
.begin();
1329 p
!= this->special_output_list_
.end();
1332 off
= align_address(off
, (*p
)->addralign());
1333 (*p
)->set_address_and_file_offset(0, off
);
1334 off
+= (*p
)->data_size();
1338 bool was_readonly
= false;
1339 for (Segment_list::iterator p
= this->segment_list_
.begin();
1340 p
!= this->segment_list_
.end();
1343 if ((*p
)->type() == elfcpp::PT_LOAD
)
1345 if (load_seg
!= NULL
&& load_seg
!= *p
)
1349 bool are_addresses_set
= (*p
)->are_addresses_set();
1350 if (are_addresses_set
)
1352 // When it comes to setting file offsets, we care about
1353 // the physical address.
1354 addr
= (*p
)->paddr();
1356 else if (this->options_
.user_set_Tdata()
1357 && ((*p
)->flags() & elfcpp::PF_W
) != 0
1358 && (!this->options_
.user_set_Tbss()
1359 || (*p
)->has_any_data_sections()))
1361 addr
= this->options_
.Tdata();
1362 are_addresses_set
= true;
1364 else if (this->options_
.user_set_Tbss()
1365 && ((*p
)->flags() & elfcpp::PF_W
) != 0
1366 && !(*p
)->has_any_data_sections())
1368 addr
= this->options_
.Tbss();
1369 are_addresses_set
= true;
1372 uint64_t orig_addr
= addr
;
1373 uint64_t orig_off
= off
;
1375 uint64_t aligned_addr
= 0;
1376 uint64_t abi_pagesize
= target
->abi_pagesize();
1378 // FIXME: This should depend on the -n and -N options.
1379 (*p
)->set_minimum_p_align(target
->common_pagesize());
1381 if (are_addresses_set
)
1383 // Adjust the file offset to the same address modulo the
1385 uint64_t unsigned_off
= off
;
1386 uint64_t aligned_off
= ((unsigned_off
& ~(abi_pagesize
- 1))
1387 | (addr
& (abi_pagesize
- 1)));
1388 if (aligned_off
< unsigned_off
)
1389 aligned_off
+= abi_pagesize
;
1394 // If the last segment was readonly, and this one is
1395 // not, then skip the address forward one page,
1396 // maintaining the same position within the page. This
1397 // lets us store both segments overlapping on a single
1398 // page in the file, but the loader will put them on
1399 // different pages in memory.
1401 addr
= align_address(addr
, (*p
)->maximum_alignment());
1402 aligned_addr
= addr
;
1404 if (was_readonly
&& ((*p
)->flags() & elfcpp::PF_W
) != 0)
1406 if ((addr
& (abi_pagesize
- 1)) != 0)
1407 addr
= addr
+ abi_pagesize
;
1410 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1413 unsigned int shndx_hold
= *pshndx
;
1414 uint64_t new_addr
= (*p
)->set_section_addresses(false, addr
, &off
,
1417 // Now that we know the size of this segment, we may be able
1418 // to save a page in memory, at the cost of wasting some
1419 // file space, by instead aligning to the start of a new
1420 // page. Here we use the real machine page size rather than
1421 // the ABI mandated page size.
1423 if (!are_addresses_set
&& aligned_addr
!= addr
)
1425 uint64_t common_pagesize
= target
->common_pagesize();
1426 uint64_t first_off
= (common_pagesize
1428 & (common_pagesize
- 1)));
1429 uint64_t last_off
= new_addr
& (common_pagesize
- 1);
1432 && ((aligned_addr
& ~ (common_pagesize
- 1))
1433 != (new_addr
& ~ (common_pagesize
- 1)))
1434 && first_off
+ last_off
<= common_pagesize
)
1436 *pshndx
= shndx_hold
;
1437 addr
= align_address(aligned_addr
, common_pagesize
);
1438 addr
= align_address(addr
, (*p
)->maximum_alignment());
1439 off
= orig_off
+ ((addr
- orig_addr
) & (abi_pagesize
- 1));
1440 new_addr
= (*p
)->set_section_addresses(true, addr
, &off
,
1447 if (((*p
)->flags() & elfcpp::PF_W
) == 0)
1448 was_readonly
= true;
1452 // Handle the non-PT_LOAD segments, setting their offsets from their
1453 // section's offsets.
1454 for (Segment_list::iterator p
= this->segment_list_
.begin();
1455 p
!= this->segment_list_
.end();
1458 if ((*p
)->type() != elfcpp::PT_LOAD
)
1462 // Set the TLS offsets for each section in the PT_TLS segment.
1463 if (this->tls_segment_
!= NULL
)
1464 this->tls_segment_
->set_tls_offsets();
1469 // Set the offsets of all the allocated sections when doing a
1470 // relocatable link. This does the same jobs as set_segment_offsets,
1471 // only for a relocatable link.
1474 Layout::set_relocatable_section_offsets(Output_data
* file_header
,
1475 unsigned int *pshndx
)
1479 file_header
->set_address_and_file_offset(0, 0);
1480 off
+= file_header
->data_size();
1482 for (Section_list::iterator p
= this->section_list_
.begin();
1483 p
!= this->section_list_
.end();
1486 // We skip unallocated sections here, except that group sections
1487 // have to come first.
1488 if (((*p
)->flags() & elfcpp::SHF_ALLOC
) == 0
1489 && (*p
)->type() != elfcpp::SHT_GROUP
)
1492 off
= align_address(off
, (*p
)->addralign());
1494 // The linker script might have set the address.
1495 if (!(*p
)->is_address_valid())
1496 (*p
)->set_address(0);
1497 (*p
)->set_file_offset(off
);
1498 (*p
)->finalize_data_size();
1499 off
+= (*p
)->data_size();
1501 (*p
)->set_out_shndx(*pshndx
);
1508 // Set the file offset of all the sections not associated with a
1512 Layout::set_section_offsets(off_t off
, Layout::Section_offset_pass pass
)
1514 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1515 p
!= this->unattached_section_list_
.end();
1518 // The symtab section is handled in create_symtab_sections.
1519 if (*p
== this->symtab_section_
)
1522 // If we've already set the data size, don't set it again.
1523 if ((*p
)->is_offset_valid() && (*p
)->is_data_size_valid())
1526 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1527 && (*p
)->requires_postprocessing())
1529 (*p
)->create_postprocessing_buffer();
1530 this->any_postprocessing_sections_
= true;
1533 if (pass
== BEFORE_INPUT_SECTIONS_PASS
1534 && (*p
)->after_input_sections())
1536 else if (pass
== POSTPROCESSING_SECTIONS_PASS
1537 && (!(*p
)->after_input_sections()
1538 || (*p
)->type() == elfcpp::SHT_STRTAB
))
1540 else if (pass
== STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
1541 && (!(*p
)->after_input_sections()
1542 || (*p
)->type() != elfcpp::SHT_STRTAB
))
1545 off
= align_address(off
, (*p
)->addralign());
1546 (*p
)->set_file_offset(off
);
1547 (*p
)->finalize_data_size();
1548 off
+= (*p
)->data_size();
1550 // At this point the name must be set.
1551 if (pass
!= STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
)
1552 this->namepool_
.add((*p
)->name(), false, NULL
);
1557 // Set the section indexes of all the sections not associated with a
1561 Layout::set_section_indexes(unsigned int shndx
)
1563 const bool output_is_object
= parameters
->options().relocatable();
1564 for (Section_list::iterator p
= this->unattached_section_list_
.begin();
1565 p
!= this->unattached_section_list_
.end();
1568 // In a relocatable link, we already did group sections.
1569 if (output_is_object
1570 && (*p
)->type() == elfcpp::SHT_GROUP
)
1573 (*p
)->set_out_shndx(shndx
);
1579 // Set the section addresses according to the linker script. This is
1580 // only called when we see a SECTIONS clause. This returns the
1581 // program segment which should hold the file header and segment
1582 // headers, if any. It will return NULL if they should not be in a
1586 Layout::set_section_addresses_from_script(Symbol_table
* symtab
)
1588 Script_sections
* ss
= this->script_options_
->script_sections();
1589 gold_assert(ss
->saw_sections_clause());
1591 // Place each orphaned output section in the script.
1592 for (Section_list::iterator p
= this->section_list_
.begin();
1593 p
!= this->section_list_
.end();
1596 if (!(*p
)->found_in_sections_clause())
1597 ss
->place_orphan(*p
);
1600 return this->script_options_
->set_section_addresses(symtab
, this);
1603 // Count the local symbols in the regular symbol table and the dynamic
1604 // symbol table, and build the respective string pools.
1607 Layout::count_local_symbols(const Task
* task
,
1608 const Input_objects
* input_objects
)
1610 // First, figure out an upper bound on the number of symbols we'll
1611 // be inserting into each pool. This helps us create the pools with
1612 // the right size, to avoid unnecessary hashtable resizing.
1613 unsigned int symbol_count
= 0;
1614 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1615 p
!= input_objects
->relobj_end();
1617 symbol_count
+= (*p
)->local_symbol_count();
1619 // Go from "upper bound" to "estimate." We overcount for two
1620 // reasons: we double-count symbols that occur in more than one
1621 // object file, and we count symbols that are dropped from the
1622 // output. Add it all together and assume we overcount by 100%.
1625 // We assume all symbols will go into both the sympool and dynpool.
1626 this->sympool_
.reserve(symbol_count
);
1627 this->dynpool_
.reserve(symbol_count
);
1629 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1630 p
!= input_objects
->relobj_end();
1633 Task_lock_obj
<Object
> tlo(task
, *p
);
1634 (*p
)->count_local_symbols(&this->sympool_
, &this->dynpool_
);
1638 // Create the symbol table sections. Here we also set the final
1639 // values of the symbols. At this point all the loadable sections are
1643 Layout::create_symtab_sections(const Input_objects
* input_objects
,
1644 Symbol_table
* symtab
,
1649 if (parameters
->target().get_size() == 32)
1651 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1654 else if (parameters
->target().get_size() == 64)
1656 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1663 off
= align_address(off
, align
);
1664 off_t startoff
= off
;
1666 // Save space for the dummy symbol at the start of the section. We
1667 // never bother to write this out--it will just be left as zero.
1669 unsigned int local_symbol_index
= 1;
1671 // Add STT_SECTION symbols for each Output section which needs one.
1672 for (Section_list::iterator p
= this->section_list_
.begin();
1673 p
!= this->section_list_
.end();
1676 if (!(*p
)->needs_symtab_index())
1677 (*p
)->set_symtab_index(-1U);
1680 (*p
)->set_symtab_index(local_symbol_index
);
1681 ++local_symbol_index
;
1686 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1687 p
!= input_objects
->relobj_end();
1690 unsigned int index
= (*p
)->finalize_local_symbols(local_symbol_index
,
1692 off
+= (index
- local_symbol_index
) * symsize
;
1693 local_symbol_index
= index
;
1696 unsigned int local_symcount
= local_symbol_index
;
1697 gold_assert(local_symcount
* symsize
== off
- startoff
);
1700 size_t dyn_global_index
;
1702 if (this->dynsym_section_
== NULL
)
1705 dyn_global_index
= 0;
1710 dyn_global_index
= this->dynsym_section_
->info();
1711 off_t locsize
= dyn_global_index
* this->dynsym_section_
->entsize();
1712 dynoff
= this->dynsym_section_
->offset() + locsize
;
1713 dyncount
= (this->dynsym_section_
->data_size() - locsize
) / symsize
;
1714 gold_assert(static_cast<off_t
>(dyncount
* symsize
)
1715 == this->dynsym_section_
->data_size() - locsize
);
1718 off
= symtab
->finalize(off
, dynoff
, dyn_global_index
, dyncount
,
1719 &this->sympool_
, &local_symcount
);
1721 if (!parameters
->options().strip_all())
1723 this->sympool_
.set_string_offsets();
1725 const char* symtab_name
= this->namepool_
.add(".symtab", false, NULL
);
1726 Output_section
* osymtab
= this->make_output_section(symtab_name
,
1729 this->symtab_section_
= osymtab
;
1731 Output_section_data
* pos
= new Output_data_fixed_space(off
- startoff
,
1733 osymtab
->add_output_section_data(pos
);
1735 const char* strtab_name
= this->namepool_
.add(".strtab", false, NULL
);
1736 Output_section
* ostrtab
= this->make_output_section(strtab_name
,
1740 Output_section_data
* pstr
= new Output_data_strtab(&this->sympool_
);
1741 ostrtab
->add_output_section_data(pstr
);
1743 osymtab
->set_file_offset(startoff
);
1744 osymtab
->finalize_data_size();
1745 osymtab
->set_link_section(ostrtab
);
1746 osymtab
->set_info(local_symcount
);
1747 osymtab
->set_entsize(symsize
);
1753 // Create the .shstrtab section, which holds the names of the
1754 // sections. At the time this is called, we have created all the
1755 // output sections except .shstrtab itself.
1758 Layout::create_shstrtab()
1760 // FIXME: We don't need to create a .shstrtab section if we are
1761 // stripping everything.
1763 const char* name
= this->namepool_
.add(".shstrtab", false, NULL
);
1765 Output_section
* os
= this->make_output_section(name
, elfcpp::SHT_STRTAB
, 0);
1767 // We can't write out this section until we've set all the section
1768 // names, and we don't set the names of compressed output sections
1769 // until relocations are complete.
1770 os
->set_after_input_sections();
1772 Output_section_data
* posd
= new Output_data_strtab(&this->namepool_
);
1773 os
->add_output_section_data(posd
);
1778 // Create the section headers. SIZE is 32 or 64. OFF is the file
1782 Layout::create_shdrs(off_t
* poff
)
1784 Output_section_headers
* oshdrs
;
1785 oshdrs
= new Output_section_headers(this,
1786 &this->segment_list_
,
1787 &this->section_list_
,
1788 &this->unattached_section_list_
,
1790 off_t off
= align_address(*poff
, oshdrs
->addralign());
1791 oshdrs
->set_address_and_file_offset(0, off
);
1792 off
+= oshdrs
->data_size();
1794 this->section_headers_
= oshdrs
;
1797 // Create the dynamic symbol table.
1800 Layout::create_dynamic_symtab(const Input_objects
* input_objects
,
1801 Symbol_table
* symtab
,
1802 Output_section
**pdynstr
,
1803 unsigned int* plocal_dynamic_count
,
1804 std::vector
<Symbol
*>* pdynamic_symbols
,
1805 Versions
* pversions
)
1807 // Count all the symbols in the dynamic symbol table, and set the
1808 // dynamic symbol indexes.
1810 // Skip symbol 0, which is always all zeroes.
1811 unsigned int index
= 1;
1813 // Add STT_SECTION symbols for each Output section which needs one.
1814 for (Section_list::iterator p
= this->section_list_
.begin();
1815 p
!= this->section_list_
.end();
1818 if (!(*p
)->needs_dynsym_index())
1819 (*p
)->set_dynsym_index(-1U);
1822 (*p
)->set_dynsym_index(index
);
1827 // Count the local symbols that need to go in the dynamic symbol table,
1828 // and set the dynamic symbol indexes.
1829 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1830 p
!= input_objects
->relobj_end();
1833 unsigned int new_index
= (*p
)->set_local_dynsym_indexes(index
);
1837 unsigned int local_symcount
= index
;
1838 *plocal_dynamic_count
= local_symcount
;
1840 // FIXME: We have to tell set_dynsym_indexes whether the
1841 // -E/--export-dynamic option was used.
1842 index
= symtab
->set_dynsym_indexes(index
, pdynamic_symbols
,
1843 &this->dynpool_
, pversions
);
1847 const int size
= parameters
->target().get_size();
1850 symsize
= elfcpp::Elf_sizes
<32>::sym_size
;
1853 else if (size
== 64)
1855 symsize
= elfcpp::Elf_sizes
<64>::sym_size
;
1861 // Create the dynamic symbol table section.
1863 Output_section
* dynsym
= this->choose_output_section(NULL
, ".dynsym",
1868 Output_section_data
* odata
= new Output_data_fixed_space(index
* symsize
,
1870 dynsym
->add_output_section_data(odata
);
1872 dynsym
->set_info(local_symcount
);
1873 dynsym
->set_entsize(symsize
);
1874 dynsym
->set_addralign(align
);
1876 this->dynsym_section_
= dynsym
;
1878 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
1879 odyn
->add_section_address(elfcpp::DT_SYMTAB
, dynsym
);
1880 odyn
->add_constant(elfcpp::DT_SYMENT
, symsize
);
1882 // Create the dynamic string table section.
1884 Output_section
* dynstr
= this->choose_output_section(NULL
, ".dynstr",
1889 Output_section_data
* strdata
= new Output_data_strtab(&this->dynpool_
);
1890 dynstr
->add_output_section_data(strdata
);
1892 dynsym
->set_link_section(dynstr
);
1893 this->dynamic_section_
->set_link_section(dynstr
);
1895 odyn
->add_section_address(elfcpp::DT_STRTAB
, dynstr
);
1896 odyn
->add_section_size(elfcpp::DT_STRSZ
, dynstr
);
1900 // Create the hash tables.
1902 // FIXME: We need an option to create a GNU hash table.
1904 unsigned char* phash
;
1905 unsigned int hashlen
;
1906 Dynobj::create_elf_hash_table(*pdynamic_symbols
, local_symcount
,
1909 Output_section
* hashsec
= this->choose_output_section(NULL
, ".hash",
1914 Output_section_data
* hashdata
= new Output_data_const_buffer(phash
,
1917 hashsec
->add_output_section_data(hashdata
);
1919 hashsec
->set_link_section(dynsym
);
1920 hashsec
->set_entsize(4);
1922 odyn
->add_section_address(elfcpp::DT_HASH
, hashsec
);
1925 // Assign offsets to each local portion of the dynamic symbol table.
1928 Layout::assign_local_dynsym_offsets(const Input_objects
* input_objects
)
1930 Output_section
* dynsym
= this->dynsym_section_
;
1931 gold_assert(dynsym
!= NULL
);
1933 off_t off
= dynsym
->offset();
1935 // Skip the dummy symbol at the start of the section.
1936 off
+= dynsym
->entsize();
1938 for (Input_objects::Relobj_iterator p
= input_objects
->relobj_begin();
1939 p
!= input_objects
->relobj_end();
1942 unsigned int count
= (*p
)->set_local_dynsym_offset(off
);
1943 off
+= count
* dynsym
->entsize();
1947 // Create the version sections.
1950 Layout::create_version_sections(const Versions
* versions
,
1951 const Symbol_table
* symtab
,
1952 unsigned int local_symcount
,
1953 const std::vector
<Symbol
*>& dynamic_symbols
,
1954 const Output_section
* dynstr
)
1956 if (!versions
->any_defs() && !versions
->any_needs())
1959 switch (parameters
->size_and_endianness())
1961 #ifdef HAVE_TARGET_32_LITTLE
1962 case Parameters::TARGET_32_LITTLE
:
1963 this->sized_create_version_sections
1964 SELECT_SIZE_ENDIAN_NAME(32, false)(
1965 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1966 SELECT_SIZE_ENDIAN(32, false));
1969 #ifdef HAVE_TARGET_32_BIG
1970 case Parameters::TARGET_32_BIG
:
1971 this->sized_create_version_sections
1972 SELECT_SIZE_ENDIAN_NAME(32, true)(
1973 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1974 SELECT_SIZE_ENDIAN(32, true));
1977 #ifdef HAVE_TARGET_64_LITTLE
1978 case Parameters::TARGET_64_LITTLE
:
1979 this->sized_create_version_sections
1980 SELECT_SIZE_ENDIAN_NAME(64, false)(
1981 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1982 SELECT_SIZE_ENDIAN(64, false));
1985 #ifdef HAVE_TARGET_64_BIG
1986 case Parameters::TARGET_64_BIG
:
1987 this->sized_create_version_sections
1988 SELECT_SIZE_ENDIAN_NAME(64, true)(
1989 versions
, symtab
, local_symcount
, dynamic_symbols
, dynstr
1990 SELECT_SIZE_ENDIAN(64, true));
1998 // Create the version sections, sized version.
2000 template<int size
, bool big_endian
>
2002 Layout::sized_create_version_sections(
2003 const Versions
* versions
,
2004 const Symbol_table
* symtab
,
2005 unsigned int local_symcount
,
2006 const std::vector
<Symbol
*>& dynamic_symbols
,
2007 const Output_section
* dynstr
2010 Output_section
* vsec
= this->choose_output_section(NULL
, ".gnu.version",
2011 elfcpp::SHT_GNU_versym
,
2015 unsigned char* vbuf
;
2017 versions
->symbol_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
2018 symtab
, &this->dynpool_
, local_symcount
, dynamic_symbols
, &vbuf
, &vsize
2019 SELECT_SIZE_ENDIAN(size
, big_endian
));
2021 Output_section_data
* vdata
= new Output_data_const_buffer(vbuf
, vsize
, 2);
2023 vsec
->add_output_section_data(vdata
);
2024 vsec
->set_entsize(2);
2025 vsec
->set_link_section(this->dynsym_section_
);
2027 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
2028 odyn
->add_section_address(elfcpp::DT_VERSYM
, vsec
);
2030 if (versions
->any_defs())
2032 Output_section
* vdsec
;
2033 vdsec
= this->choose_output_section(NULL
, ".gnu.version_d",
2034 elfcpp::SHT_GNU_verdef
,
2038 unsigned char* vdbuf
;
2039 unsigned int vdsize
;
2040 unsigned int vdentries
;
2041 versions
->def_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)(
2042 &this->dynpool_
, &vdbuf
, &vdsize
, &vdentries
2043 SELECT_SIZE_ENDIAN(size
, big_endian
));
2045 Output_section_data
* vddata
= new Output_data_const_buffer(vdbuf
,
2049 vdsec
->add_output_section_data(vddata
);
2050 vdsec
->set_link_section(dynstr
);
2051 vdsec
->set_info(vdentries
);
2053 odyn
->add_section_address(elfcpp::DT_VERDEF
, vdsec
);
2054 odyn
->add_constant(elfcpp::DT_VERDEFNUM
, vdentries
);
2057 if (versions
->any_needs())
2059 Output_section
* vnsec
;
2060 vnsec
= this->choose_output_section(NULL
, ".gnu.version_r",
2061 elfcpp::SHT_GNU_verneed
,
2065 unsigned char* vnbuf
;
2066 unsigned int vnsize
;
2067 unsigned int vnentries
;
2068 versions
->need_section_contents
SELECT_SIZE_ENDIAN_NAME(size
, big_endian
)
2069 (&this->dynpool_
, &vnbuf
, &vnsize
, &vnentries
2070 SELECT_SIZE_ENDIAN(size
, big_endian
));
2072 Output_section_data
* vndata
= new Output_data_const_buffer(vnbuf
,
2076 vnsec
->add_output_section_data(vndata
);
2077 vnsec
->set_link_section(dynstr
);
2078 vnsec
->set_info(vnentries
);
2080 odyn
->add_section_address(elfcpp::DT_VERNEED
, vnsec
);
2081 odyn
->add_constant(elfcpp::DT_VERNEEDNUM
, vnentries
);
2085 // Create the .interp section and PT_INTERP segment.
2088 Layout::create_interp(const Target
* target
)
2090 const char* interp
= this->options_
.dynamic_linker();
2093 interp
= target
->dynamic_linker();
2094 gold_assert(interp
!= NULL
);
2097 size_t len
= strlen(interp
) + 1;
2099 Output_section_data
* odata
= new Output_data_const(interp
, len
, 1);
2101 Output_section
* osec
= this->choose_output_section(NULL
, ".interp",
2102 elfcpp::SHT_PROGBITS
,
2105 osec
->add_output_section_data(odata
);
2107 if (!this->script_options_
->saw_phdrs_clause())
2109 Output_segment
* oseg
= this->make_output_segment(elfcpp::PT_INTERP
,
2111 oseg
->add_initial_output_section(osec
, elfcpp::PF_R
);
2115 // Finish the .dynamic section and PT_DYNAMIC segment.
2118 Layout::finish_dynamic_section(const Input_objects
* input_objects
,
2119 const Symbol_table
* symtab
)
2121 if (!this->script_options_
->saw_phdrs_clause())
2123 Output_segment
* oseg
= this->make_output_segment(elfcpp::PT_DYNAMIC
,
2126 oseg
->add_initial_output_section(this->dynamic_section_
,
2127 elfcpp::PF_R
| elfcpp::PF_W
);
2130 Output_data_dynamic
* const odyn
= this->dynamic_data_
;
2132 for (Input_objects::Dynobj_iterator p
= input_objects
->dynobj_begin();
2133 p
!= input_objects
->dynobj_end();
2136 // FIXME: Handle --as-needed.
2137 odyn
->add_string(elfcpp::DT_NEEDED
, (*p
)->soname());
2140 if (parameters
->options().shared())
2142 const char* soname
= this->options_
.soname();
2144 odyn
->add_string(elfcpp::DT_SONAME
, soname
);
2147 // FIXME: Support --init and --fini.
2148 Symbol
* sym
= symtab
->lookup("_init");
2149 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
2150 odyn
->add_symbol(elfcpp::DT_INIT
, sym
);
2152 sym
= symtab
->lookup("_fini");
2153 if (sym
!= NULL
&& sym
->is_defined() && !sym
->is_from_dynobj())
2154 odyn
->add_symbol(elfcpp::DT_FINI
, sym
);
2156 // FIXME: Support DT_INIT_ARRAY and DT_FINI_ARRAY.
2158 // Add a DT_RPATH entry if needed.
2159 const General_options::Dir_list
& rpath(this->options_
.rpath());
2162 std::string rpath_val
;
2163 for (General_options::Dir_list::const_iterator p
= rpath
.begin();
2167 if (rpath_val
.empty())
2168 rpath_val
= p
->name();
2171 // Eliminate duplicates.
2172 General_options::Dir_list::const_iterator q
;
2173 for (q
= rpath
.begin(); q
!= p
; ++q
)
2174 if (q
->name() == p
->name())
2179 rpath_val
+= p
->name();
2184 odyn
->add_string(elfcpp::DT_RPATH
, rpath_val
);
2187 // Look for text segments that have dynamic relocations.
2188 bool have_textrel
= false;
2189 if (!this->script_options_
->saw_sections_clause())
2191 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
2192 p
!= this->segment_list_
.end();
2195 if (((*p
)->flags() & elfcpp::PF_W
) == 0
2196 && (*p
)->dynamic_reloc_count() > 0)
2198 have_textrel
= true;
2205 // We don't know the section -> segment mapping, so we are
2206 // conservative and just look for readonly sections with
2207 // relocations. If those sections wind up in writable segments,
2208 // then we have created an unnecessary DT_TEXTREL entry.
2209 for (Section_list::const_iterator p
= this->section_list_
.begin();
2210 p
!= this->section_list_
.end();
2213 if (((*p
)->flags() & elfcpp::SHF_ALLOC
) != 0
2214 && ((*p
)->flags() & elfcpp::SHF_WRITE
) == 0
2215 && ((*p
)->dynamic_reloc_count() > 0))
2217 have_textrel
= true;
2223 // Add a DT_FLAGS entry. We add it even if no flags are set so that
2224 // post-link tools can easily modify these flags if desired.
2225 unsigned int flags
= 0;
2228 // Add a DT_TEXTREL for compatibility with older loaders.
2229 odyn
->add_constant(elfcpp::DT_TEXTREL
, 0);
2230 flags
|= elfcpp::DF_TEXTREL
;
2232 if (parameters
->options().shared() && this->has_static_tls())
2233 flags
|= elfcpp::DF_STATIC_TLS
;
2234 odyn
->add_constant(elfcpp::DT_FLAGS
, flags
);
2237 // The mapping of .gnu.linkonce section names to real section names.
2239 #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 }
2240 const Layout::Linkonce_mapping
Layout::linkonce_mapping
[] =
2242 MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d".
2243 MAPPING_INIT("t", ".text"),
2244 MAPPING_INIT("r", ".rodata"),
2245 MAPPING_INIT("d", ".data"),
2246 MAPPING_INIT("b", ".bss"),
2247 MAPPING_INIT("s", ".sdata"),
2248 MAPPING_INIT("sb", ".sbss"),
2249 MAPPING_INIT("s2", ".sdata2"),
2250 MAPPING_INIT("sb2", ".sbss2"),
2251 MAPPING_INIT("wi", ".debug_info"),
2252 MAPPING_INIT("td", ".tdata"),
2253 MAPPING_INIT("tb", ".tbss"),
2254 MAPPING_INIT("lr", ".lrodata"),
2255 MAPPING_INIT("l", ".ldata"),
2256 MAPPING_INIT("lb", ".lbss"),
2260 const int Layout::linkonce_mapping_count
=
2261 sizeof(Layout::linkonce_mapping
) / sizeof(Layout::linkonce_mapping
[0]);
2263 // Return the name of the output section to use for a .gnu.linkonce
2264 // section. This is based on the default ELF linker script of the old
2265 // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo"
2266 // to ".text". Set *PLEN to the length of the name. *PLEN is
2267 // initialized to the length of NAME.
2270 Layout::linkonce_output_name(const char* name
, size_t *plen
)
2272 const char* s
= name
+ sizeof(".gnu.linkonce") - 1;
2276 const Linkonce_mapping
* plm
= linkonce_mapping
;
2277 for (int i
= 0; i
< linkonce_mapping_count
; ++i
, ++plm
)
2279 if (strncmp(s
, plm
->from
, plm
->fromlen
) == 0 && s
[plm
->fromlen
] == '.')
2288 // Choose the output section name to use given an input section name.
2289 // Set *PLEN to the length of the name. *PLEN is initialized to the
2293 Layout::output_section_name(const char* name
, size_t* plen
)
2295 if (Layout::is_linkonce(name
))
2297 // .gnu.linkonce sections are laid out as though they were named
2298 // for the sections are placed into.
2299 return Layout::linkonce_output_name(name
, plen
);
2302 // gcc 4.3 generates the following sorts of section names when it
2303 // needs a section name specific to a function:
2309 // .data.rel.local.FN
2311 // .data.rel.ro.local.FN
2318 // The GNU linker maps all of those to the part before the .FN,
2319 // except that .data.rel.local.FN is mapped to .data, and
2320 // .data.rel.ro.local.FN is mapped to .data.rel.ro. The sections
2321 // beginning with .data.rel.ro.local are grouped together.
2323 // For an anonymous namespace, the string FN can contain a '.'.
2325 // Also of interest: .rodata.strN.N, .rodata.cstN, both of which the
2326 // GNU linker maps to .rodata.
2328 // The .data.rel.ro sections enable a security feature triggered by
2329 // the -z relro option. Section which need to be relocated at
2330 // program startup time but which may be readonly after startup are
2331 // grouped into .data.rel.ro. They are then put into a PT_GNU_RELRO
2332 // segment. The dynamic linker will make that segment writable,
2333 // perform relocations, and then make it read-only. FIXME: We do
2334 // not yet implement this optimization.
2336 // It is hard to handle this in a principled way.
2338 // These are the rules we follow:
2340 // If the section name has no initial '.', or no dot other than an
2341 // initial '.', we use the name unchanged (i.e., "mysection" and
2342 // ".text" are unchanged).
2344 // If the name starts with ".data.rel.ro" we use ".data.rel.ro".
2346 // Otherwise, we drop the second '.' and everything that comes after
2347 // it (i.e., ".text.XXX" becomes ".text").
2349 const char* s
= name
;
2353 const char* sdot
= strchr(s
, '.');
2357 const char* const data_rel_ro
= ".data.rel.ro";
2358 if (strncmp(name
, data_rel_ro
, strlen(data_rel_ro
)) == 0)
2360 *plen
= strlen(data_rel_ro
);
2364 *plen
= sdot
- name
;
2368 // Record the signature of a comdat section, and return whether to
2369 // include it in the link. If GROUP is true, this is a regular
2370 // section group. If GROUP is false, this is a group signature
2371 // derived from the name of a linkonce section. We want linkonce
2372 // signatures and group signatures to block each other, but we don't
2373 // want a linkonce signature to block another linkonce signature.
2376 Layout::add_comdat(const char* signature
, bool group
)
2378 std::string
sig(signature
);
2379 std::pair
<Signatures::iterator
, bool> ins(
2380 this->signatures_
.insert(std::make_pair(sig
, group
)));
2384 // This is the first time we've seen this signature.
2388 if (ins
.first
->second
)
2390 // We've already seen a real section group with this signature.
2395 // This is a real section group, and we've already seen a
2396 // linkonce section with this signature. Record that we've seen
2397 // a section group, and don't include this section group.
2398 ins
.first
->second
= true;
2403 // We've already seen a linkonce section and this is a linkonce
2404 // section. These don't block each other--this may be the same
2405 // symbol name with different section types.
2410 // Store the allocated sections into the section list.
2413 Layout::get_allocated_sections(Section_list
* section_list
) const
2415 for (Section_list::const_iterator p
= this->section_list_
.begin();
2416 p
!= this->section_list_
.end();
2418 if (((*p
)->flags() & elfcpp::SHF_ALLOC
) != 0)
2419 section_list
->push_back(*p
);
2422 // Create an output segment.
2425 Layout::make_output_segment(elfcpp::Elf_Word type
, elfcpp::Elf_Word flags
)
2427 gold_assert(!parameters
->options().relocatable());
2428 Output_segment
* oseg
= new Output_segment(type
, flags
);
2429 this->segment_list_
.push_back(oseg
);
2433 // Write out the Output_sections. Most won't have anything to write,
2434 // since most of the data will come from input sections which are
2435 // handled elsewhere. But some Output_sections do have Output_data.
2438 Layout::write_output_sections(Output_file
* of
) const
2440 for (Section_list::const_iterator p
= this->section_list_
.begin();
2441 p
!= this->section_list_
.end();
2444 if (!(*p
)->after_input_sections())
2449 // Write out data not associated with a section or the symbol table.
2452 Layout::write_data(const Symbol_table
* symtab
, Output_file
* of
) const
2454 if (!parameters
->options().strip_all())
2456 const Output_section
* symtab_section
= this->symtab_section_
;
2457 for (Section_list::const_iterator p
= this->section_list_
.begin();
2458 p
!= this->section_list_
.end();
2461 if ((*p
)->needs_symtab_index())
2463 gold_assert(symtab_section
!= NULL
);
2464 unsigned int index
= (*p
)->symtab_index();
2465 gold_assert(index
> 0 && index
!= -1U);
2466 off_t off
= (symtab_section
->offset()
2467 + index
* symtab_section
->entsize());
2468 symtab
->write_section_symbol(*p
, of
, off
);
2473 const Output_section
* dynsym_section
= this->dynsym_section_
;
2474 for (Section_list::const_iterator p
= this->section_list_
.begin();
2475 p
!= this->section_list_
.end();
2478 if ((*p
)->needs_dynsym_index())
2480 gold_assert(dynsym_section
!= NULL
);
2481 unsigned int index
= (*p
)->dynsym_index();
2482 gold_assert(index
> 0 && index
!= -1U);
2483 off_t off
= (dynsym_section
->offset()
2484 + index
* dynsym_section
->entsize());
2485 symtab
->write_section_symbol(*p
, of
, off
);
2489 // Write out the Output_data which are not in an Output_section.
2490 for (Data_list::const_iterator p
= this->special_output_list_
.begin();
2491 p
!= this->special_output_list_
.end();
2496 // Write out the Output_sections which can only be written after the
2497 // input sections are complete.
2500 Layout::write_sections_after_input_sections(Output_file
* of
)
2502 // Determine the final section offsets, and thus the final output
2503 // file size. Note we finalize the .shstrab last, to allow the
2504 // after_input_section sections to modify their section-names before
2506 if (this->any_postprocessing_sections_
)
2508 off_t off
= this->output_file_size_
;
2509 off
= this->set_section_offsets(off
, POSTPROCESSING_SECTIONS_PASS
);
2511 // Now that we've finalized the names, we can finalize the shstrab.
2513 this->set_section_offsets(off
,
2514 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS
);
2516 if (off
> this->output_file_size_
)
2519 this->output_file_size_
= off
;
2523 for (Section_list::const_iterator p
= this->section_list_
.begin();
2524 p
!= this->section_list_
.end();
2527 if ((*p
)->after_input_sections())
2531 this->section_headers_
->write(of
);
2534 // Write out a binary file. This is called after the link is
2535 // complete. IN is the temporary output file we used to generate the
2536 // ELF code. We simply walk through the segments, read them from
2537 // their file offset in IN, and write them to their load address in
2538 // the output file. FIXME: with a bit more work, we could support
2539 // S-records and/or Intel hex format here.
2542 Layout::write_binary(Output_file
* in
) const
2544 gold_assert(this->options_
.oformat()
2545 == General_options::OBJECT_FORMAT_BINARY
);
2547 // Get the size of the binary file.
2548 uint64_t max_load_address
= 0;
2549 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
2550 p
!= this->segment_list_
.end();
2553 if ((*p
)->type() == elfcpp::PT_LOAD
&& (*p
)->filesz() > 0)
2555 uint64_t max_paddr
= (*p
)->paddr() + (*p
)->filesz();
2556 if (max_paddr
> max_load_address
)
2557 max_load_address
= max_paddr
;
2561 Output_file
out(parameters
->options().output_file_name());
2562 out
.open(max_load_address
);
2564 for (Segment_list::const_iterator p
= this->segment_list_
.begin();
2565 p
!= this->segment_list_
.end();
2568 if ((*p
)->type() == elfcpp::PT_LOAD
&& (*p
)->filesz() > 0)
2570 const unsigned char* vin
= in
->get_input_view((*p
)->offset(),
2572 unsigned char* vout
= out
.get_output_view((*p
)->paddr(),
2574 memcpy(vout
, vin
, (*p
)->filesz());
2575 out
.write_output_view((*p
)->paddr(), (*p
)->filesz(), vout
);
2576 in
->free_input_view((*p
)->offset(), (*p
)->filesz(), vin
);
2583 // Print statistical information to stderr. This is used for --stats.
2586 Layout::print_stats() const
2588 this->namepool_
.print_stats("section name pool");
2589 this->sympool_
.print_stats("output symbol name pool");
2590 this->dynpool_
.print_stats("dynamic name pool");
2592 for (Section_list::const_iterator p
= this->section_list_
.begin();
2593 p
!= this->section_list_
.end();
2595 (*p
)->print_merge_stats();
2598 // Write_sections_task methods.
2600 // We can always run this task.
2603 Write_sections_task::is_runnable()
2608 // We need to unlock both OUTPUT_SECTIONS_BLOCKER and FINAL_BLOCKER
2612 Write_sections_task::locks(Task_locker
* tl
)
2614 tl
->add(this, this->output_sections_blocker_
);
2615 tl
->add(this, this->final_blocker_
);
2618 // Run the task--write out the data.
2621 Write_sections_task::run(Workqueue
*)
2623 this->layout_
->write_output_sections(this->of_
);
2626 // Write_data_task methods.
2628 // We can always run this task.
2631 Write_data_task::is_runnable()
2636 // We need to unlock FINAL_BLOCKER when finished.
2639 Write_data_task::locks(Task_locker
* tl
)
2641 tl
->add(this, this->final_blocker_
);
2644 // Run the task--write out the data.
2647 Write_data_task::run(Workqueue
*)
2649 this->layout_
->write_data(this->symtab_
, this->of_
);
2652 // Write_symbols_task methods.
2654 // We can always run this task.
2657 Write_symbols_task::is_runnable()
2662 // We need to unlock FINAL_BLOCKER when finished.
2665 Write_symbols_task::locks(Task_locker
* tl
)
2667 tl
->add(this, this->final_blocker_
);
2670 // Run the task--write out the symbols.
2673 Write_symbols_task::run(Workqueue
*)
2675 this->symtab_
->write_globals(this->input_objects_
, this->sympool_
,
2676 this->dynpool_
, this->of_
);
2679 // Write_after_input_sections_task methods.
2681 // We can only run this task after the input sections have completed.
2684 Write_after_input_sections_task::is_runnable()
2686 if (this->input_sections_blocker_
->is_blocked())
2687 return this->input_sections_blocker_
;
2691 // We need to unlock FINAL_BLOCKER when finished.
2694 Write_after_input_sections_task::locks(Task_locker
* tl
)
2696 tl
->add(this, this->final_blocker_
);
2702 Write_after_input_sections_task::run(Workqueue
*)
2704 this->layout_
->write_sections_after_input_sections(this->of_
);
2707 // Close_task_runner methods.
2709 // Run the task--close the file.
2712 Close_task_runner::run(Workqueue
*, const Task
*)
2714 // If we've been asked to create a binary file, we do so here.
2715 if (this->options_
->oformat() != General_options::OBJECT_FORMAT_ELF
)
2716 this->layout_
->write_binary(this->of_
);
2721 // Instantiate the templates we need. We could use the configure
2722 // script to restrict this to only the ones for implemented targets.
2724 #ifdef HAVE_TARGET_32_LITTLE
2727 Layout::layout
<32, false>(Sized_relobj
<32, false>* object
, unsigned int shndx
,
2729 const elfcpp::Shdr
<32, false>& shdr
,
2730 unsigned int, unsigned int, off_t
*);
2733 #ifdef HAVE_TARGET_32_BIG
2736 Layout::layout
<32, true>(Sized_relobj
<32, true>* object
, unsigned int shndx
,
2738 const elfcpp::Shdr
<32, true>& shdr
,
2739 unsigned int, unsigned int, off_t
*);
2742 #ifdef HAVE_TARGET_64_LITTLE
2745 Layout::layout
<64, false>(Sized_relobj
<64, false>* object
, unsigned int shndx
,
2747 const elfcpp::Shdr
<64, false>& shdr
,
2748 unsigned int, unsigned int, off_t
*);
2751 #ifdef HAVE_TARGET_64_BIG
2754 Layout::layout
<64, true>(Sized_relobj
<64, true>* object
, unsigned int shndx
,
2756 const elfcpp::Shdr
<64, true>& shdr
,
2757 unsigned int, unsigned int, off_t
*);
2760 #ifdef HAVE_TARGET_32_LITTLE
2763 Layout::layout_reloc
<32, false>(Sized_relobj
<32, false>* object
,
2764 unsigned int reloc_shndx
,
2765 const elfcpp::Shdr
<32, false>& shdr
,
2766 Output_section
* data_section
,
2767 Relocatable_relocs
* rr
);
2770 #ifdef HAVE_TARGET_32_BIG
2773 Layout::layout_reloc
<32, true>(Sized_relobj
<32, true>* object
,
2774 unsigned int reloc_shndx
,
2775 const elfcpp::Shdr
<32, true>& shdr
,
2776 Output_section
* data_section
,
2777 Relocatable_relocs
* rr
);
2780 #ifdef HAVE_TARGET_64_LITTLE
2783 Layout::layout_reloc
<64, false>(Sized_relobj
<64, false>* object
,
2784 unsigned int reloc_shndx
,
2785 const elfcpp::Shdr
<64, false>& shdr
,
2786 Output_section
* data_section
,
2787 Relocatable_relocs
* rr
);
2790 #ifdef HAVE_TARGET_64_BIG
2793 Layout::layout_reloc
<64, true>(Sized_relobj
<64, true>* object
,
2794 unsigned int reloc_shndx
,
2795 const elfcpp::Shdr
<64, true>& shdr
,
2796 Output_section
* data_section
,
2797 Relocatable_relocs
* rr
);
2800 #ifdef HAVE_TARGET_32_LITTLE
2803 Layout::layout_group
<32, false>(Symbol_table
* symtab
,
2804 Sized_relobj
<32, false>* object
,
2806 const char* group_section_name
,
2807 const char* signature
,
2808 const elfcpp::Shdr
<32, false>& shdr
,
2809 const elfcpp::Elf_Word
* contents
);
2812 #ifdef HAVE_TARGET_32_BIG
2815 Layout::layout_group
<32, true>(Symbol_table
* symtab
,
2816 Sized_relobj
<32, true>* object
,
2818 const char* group_section_name
,
2819 const char* signature
,
2820 const elfcpp::Shdr
<32, true>& shdr
,
2821 const elfcpp::Elf_Word
* contents
);
2824 #ifdef HAVE_TARGET_64_LITTLE
2827 Layout::layout_group
<64, false>(Symbol_table
* symtab
,
2828 Sized_relobj
<64, false>* object
,
2830 const char* group_section_name
,
2831 const char* signature
,
2832 const elfcpp::Shdr
<64, false>& shdr
,
2833 const elfcpp::Elf_Word
* contents
);
2836 #ifdef HAVE_TARGET_64_BIG
2839 Layout::layout_group
<64, true>(Symbol_table
* symtab
,
2840 Sized_relobj
<64, true>* object
,
2842 const char* group_section_name
,
2843 const char* signature
,
2844 const elfcpp::Shdr
<64, true>& shdr
,
2845 const elfcpp::Elf_Word
* contents
);
2848 #ifdef HAVE_TARGET_32_LITTLE
2851 Layout::layout_eh_frame
<32, false>(Sized_relobj
<32, false>* object
,
2852 const unsigned char* symbols
,
2854 const unsigned char* symbol_names
,
2855 off_t symbol_names_size
,
2857 const elfcpp::Shdr
<32, false>& shdr
,
2858 unsigned int reloc_shndx
,
2859 unsigned int reloc_type
,
2863 #ifdef HAVE_TARGET_32_BIG
2866 Layout::layout_eh_frame
<32, true>(Sized_relobj
<32, true>* object
,
2867 const unsigned char* symbols
,
2869 const unsigned char* symbol_names
,
2870 off_t symbol_names_size
,
2872 const elfcpp::Shdr
<32, true>& shdr
,
2873 unsigned int reloc_shndx
,
2874 unsigned int reloc_type
,
2878 #ifdef HAVE_TARGET_64_LITTLE
2881 Layout::layout_eh_frame
<64, false>(Sized_relobj
<64, false>* object
,
2882 const unsigned char* symbols
,
2884 const unsigned char* symbol_names
,
2885 off_t symbol_names_size
,
2887 const elfcpp::Shdr
<64, false>& shdr
,
2888 unsigned int reloc_shndx
,
2889 unsigned int reloc_type
,
2893 #ifdef HAVE_TARGET_64_BIG
2896 Layout::layout_eh_frame
<64, true>(Sized_relobj
<64, true>* object
,
2897 const unsigned char* symbols
,
2899 const unsigned char* symbol_names
,
2900 off_t symbol_names_size
,
2902 const elfcpp::Shdr
<64, true>& shdr
,
2903 unsigned int reloc_shndx
,
2904 unsigned int reloc_type
,
2908 } // End namespace gold.