1 // object.h -- support for an object file for linking in gold -*- C++ -*-
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 "elfcpp_file.h"
37 class General_options
;
43 template<typename Stringpool_char
>
44 class Stringpool_template
;
46 // Data to pass from read_symbols() to add_symbols().
48 struct Read_symbols_data
51 File_view
* section_headers
;
53 File_view
* section_names
;
54 // Size of section name data in bytes.
55 off_t section_names_size
;
58 // Size of symbol data in bytes.
61 File_view
* symbol_names
;
62 // Size of symbol name data in bytes.
63 off_t symbol_names_size
;
65 // Version information. This is only used on dynamic objects.
66 // Version symbol data (from SHT_GNU_versym section).
69 // Version definition data (from SHT_GNU_verdef section).
72 unsigned int verdef_info
;
73 // Needed version data (from SHT_GNU_verneed section).
76 unsigned int verneed_info
;
79 // Data about a single relocation section. This is read in
80 // read_relocs and processed in scan_relocs.
84 // Index of reloc section.
85 unsigned int reloc_shndx
;
86 // Index of section that relocs apply to.
87 unsigned int data_shndx
;
88 // Contents of reloc section.
90 // Reloc section type.
92 // Number of reloc entries.
96 // Relocations in an object file. This is read in read_relocs and
97 // processed in scan_relocs.
99 struct Read_relocs_data
101 typedef std::vector
<Section_relocs
> Relocs_list
;
104 // The local symbols.
105 File_view
* local_symbols
;
108 // Object is an abstract base class which represents either a 32-bit
109 // or a 64-bit input object. This can be a regular object file
110 // (ET_REL) or a shared object (ET_DYN).
115 // NAME is the name of the object as we would report it to the user
116 // (e.g., libfoo.a(bar.o) if this is in an archive. INPUT_FILE is
117 // used to read the file. OFFSET is the offset within the input
118 // file--0 for a .o or .so file, something else for a .a file.
119 Object(const std::string
& name
, Input_file
* input_file
, bool is_dynamic
,
121 : name_(name
), input_file_(input_file
), offset_(offset
), shnum_(-1U),
122 is_dynamic_(is_dynamic
), target_(NULL
)
128 // Return the name of the object as we would report it to the tuser.
131 { return this->name_
; }
133 // Return whether this is a dynamic object.
136 { return this->is_dynamic_
; }
138 // Return the target structure associated with this object.
141 { return this->target_
; }
143 // Lock the underlying file.
146 { this->input_file_
->file().lock(); }
148 // Unlock the underlying file.
151 { this->input_file_
->file().unlock(); }
153 // Return whether the underlying file is locked.
156 { return this->input_file_
->file().is_locked(); }
158 // Return the sized target structure associated with this object.
159 // This is like the target method but it returns a pointer of
160 // appropriate checked type.
161 template<int size
, bool big_endian
>
162 Sized_target
<size
, big_endian
>*
163 sized_target(ACCEPT_SIZE_ENDIAN_ONLY
);
165 // Get the number of sections.
168 { return this->shnum_
; }
170 // Return a view of the contents of a section. Set *PLEN to the
173 section_contents(unsigned int shndx
, off_t
* plen
);
175 // Return the name of a section given a section index. This is only
176 // used for error messages.
178 section_name(unsigned int shndx
)
179 { return this->do_section_name(shndx
); }
181 // Return the section flags given a section index.
183 section_flags(unsigned int shndx
)
184 { return this->do_section_flags(shndx
); }
186 // Read the symbol information.
188 read_symbols(Read_symbols_data
* sd
)
189 { return this->do_read_symbols(sd
); }
191 // Pass sections which should be included in the link to the Layout
192 // object, and record where the sections go in the output file.
194 layout(Symbol_table
* symtab
, Layout
* layout
, Read_symbols_data
* sd
)
195 { this->do_layout(symtab
, layout
, sd
); }
197 // Add symbol information to the global symbol table.
199 add_symbols(Symbol_table
* symtab
, Read_symbols_data
* sd
)
200 { this->do_add_symbols(symtab
, sd
); }
202 // Functions and types for the elfcpp::Elf_file interface. This
203 // permit us to use Object as the File template parameter for
206 // The View class is returned by view. It must support a single
207 // method, data(). This is trivial, because get_view does what we
212 View(const unsigned char* p
)
221 const unsigned char* p_
;
226 view(off_t file_offset
, off_t data_size
)
227 { return View(this->get_view(file_offset
, data_size
)); }
231 error(const char* format
, ...) ATTRIBUTE_PRINTF_2
;
233 // A location in the file.
239 Location(off_t fo
, off_t ds
)
240 : file_offset(fo
), data_size(ds
)
244 // Get a View given a Location.
245 View
view(Location loc
)
246 { return View(this->get_view(loc
.file_offset
, loc
.data_size
)); }
249 // Read the symbols--implemented by child class.
251 do_read_symbols(Read_symbols_data
*) = 0;
253 // Lay out sections--implemented by child class.
255 do_layout(Symbol_table
*, Layout
*, Read_symbols_data
*) = 0;
257 // Add symbol information to the global symbol table--implemented by
260 do_add_symbols(Symbol_table
*, Read_symbols_data
*) = 0;
262 // Return the location of the contents of a section. Implemented by
265 do_section_contents(unsigned int shndx
) = 0;
267 // Get the name of a section--implemented by child class.
269 do_section_name(unsigned int shndx
) = 0;
271 // Get section flags--implemented by child class.
273 do_section_flags(unsigned int shndx
) = 0;
278 { return this->input_file_
; }
280 // Get the offset into the file.
283 { return this->offset_
; }
285 // Get a view into the underlying file.
287 get_view(off_t start
, off_t size
)
288 { return this->input_file_
->file().get_view(start
+ this->offset_
, size
); }
290 // Get a lasting view into the underlying file.
292 get_lasting_view(off_t start
, off_t size
)
294 return this->input_file_
->file().get_lasting_view(start
+ this->offset_
,
298 // Read data from the underlying file.
300 read(off_t start
, off_t size
, void* p
)
301 { this->input_file_
->file().read(start
+ this->offset_
, size
, p
); }
305 set_target(int machine
, int size
, bool big_endian
, int osabi
,
308 // Set the number of sections.
311 { this->shnum_
= shnum
; }
313 // Functions used by both Sized_relobj and Sized_dynobj.
315 // Read the section data into a Read_symbols_data object.
316 template<int size
, bool big_endian
>
318 read_section_data(elfcpp::Elf_file
<size
, big_endian
, Object
>*,
321 // If NAME is the name of a special .gnu.warning section, arrange
322 // for the warning to be issued. SHNDX is the section index.
323 // Return whether it is a warning section.
325 handle_gnu_warning_section(const char* name
, unsigned int shndx
,
329 // This class may not be copied.
330 Object(const Object
&);
331 Object
& operator=(const Object
&);
333 // Name of object as printed to user.
335 // For reading the file.
336 Input_file
* input_file_
;
337 // Offset within the file--0 for an object file, non-0 for an
340 // Number of input sections.
342 // Whether this is a dynamic object.
344 // Target functions--may be NULL if the target is not known.
348 // Implement sized_target inline for efficiency. This approach breaks
349 // static type checking, but is made safe using asserts.
351 template<int size
, bool big_endian
>
352 inline Sized_target
<size
, big_endian
>*
353 Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY
)
355 gold_assert(this->target_
->get_size() == size
);
356 gold_assert(this->target_
->is_big_endian() ? big_endian
: !big_endian
);
357 return static_cast<Sized_target
<size
, big_endian
>*>(this->target_
);
360 // A regular object (ET_REL). This is an abstract base class itself.
361 // The implementation is the template class Sized_relobj.
363 class Relobj
: public Object
366 Relobj(const std::string
& name
, Input_file
* input_file
, off_t offset
= 0)
367 : Object(name
, input_file
, false, offset
)
372 read_relocs(Read_relocs_data
* rd
)
373 { return this->do_read_relocs(rd
); }
375 // Scan the relocs and adjust the symbol table.
377 scan_relocs(const General_options
& options
, Symbol_table
* symtab
,
378 Layout
* layout
, Read_relocs_data
* rd
)
379 { return this->do_scan_relocs(options
, symtab
, layout
, rd
); }
381 // Initial local symbol processing: set the offset where local
382 // symbol information will be stored; add local symbol names to
383 // *POOL; return the new local symbol index.
385 finalize_local_symbols(unsigned int index
, off_t off
,
386 Stringpool_template
<char>* pool
)
387 { return this->do_finalize_local_symbols(index
, off
, pool
); }
389 // Relocate the input sections and write out the local symbols.
391 relocate(const General_options
& options
, const Symbol_table
* symtab
,
392 const Layout
* layout
, Output_file
* of
)
393 { return this->do_relocate(options
, symtab
, layout
, of
); }
395 // Return whether an input section is being included in the link.
397 is_section_included(unsigned int shndx
) const
399 gold_assert(shndx
< this->map_to_output_
.size());
400 return this->map_to_output_
[shndx
].output_section
!= NULL
;
403 // Given a section index, return the corresponding Output_section
404 // (which will be NULL if the section is not included in the link)
405 // and set *POFF to the offset within that section.
406 inline Output_section
*
407 output_section(unsigned int shndx
, off_t
* poff
) const;
409 // Set the offset of an input section within its output section.
411 set_section_offset(unsigned int shndx
, off_t off
)
413 gold_assert(shndx
< this->map_to_output_
.size());
414 this->map_to_output_
[shndx
].offset
= off
;
418 // What we need to know to map an input section to an output
419 // section. We keep an array of these, one for each input section,
420 // indexed by the input section number.
423 // The output section. This is NULL if the input section is to be
425 Output_section
* output_section
;
426 // The offset within the output section. This is -1 if the
427 // section requires special handling.
431 // Read the relocs--implemented by child class.
433 do_read_relocs(Read_relocs_data
*) = 0;
435 // Scan the relocs--implemented by child class.
437 do_scan_relocs(const General_options
&, Symbol_table
*, Layout
*,
438 Read_relocs_data
*) = 0;
440 // Finalize local symbols--implemented by child class.
442 do_finalize_local_symbols(unsigned int, off_t
,
443 Stringpool_template
<char>*) = 0;
445 // Relocate the input sections and write out the local
446 // symbols--implemented by child class.
448 do_relocate(const General_options
& options
, const Symbol_table
* symtab
,
449 const Layout
*, Output_file
* of
) = 0;
451 // Return the vector mapping input sections to output sections.
452 std::vector
<Map_to_output
>&
454 { return this->map_to_output_
; }
456 const std::vector
<Map_to_output
>&
457 map_to_output() const
458 { return this->map_to_output_
; }
461 // Mapping from input sections to output section.
462 std::vector
<Map_to_output
> map_to_output_
;
465 // Implement Object::output_section inline for efficiency.
466 inline Output_section
*
467 Relobj::output_section(unsigned int shndx
, off_t
* poff
) const
469 gold_assert(shndx
< this->map_to_output_
.size());
470 const Map_to_output
& mo(this->map_to_output_
[shndx
]);
472 return mo
.output_section
;
475 // This POD class is holds the value of a symbol. This is used for
476 // local symbols, and for all symbols during relocation processing.
477 // In order to process relocs we need to be able to handle SHF_MERGE
478 // sections correctly.
484 typedef typename
elfcpp::Elf_types
<size
>::Elf_Addr Value
;
487 : output_symtab_index_(0), input_shndx_(0), needs_output_address_(false),
491 // Get the value of this symbol. OBJECT is the object in which this
492 // symbol is defined, and ADDEND is an addend to add to the value.
493 template<bool big_endian
>
495 value(const Sized_relobj
<size
, big_endian
>* object
, Value addend
) const
497 if (!this->needs_output_address_
)
498 return this->value_
+ addend
;
499 return object
->local_value(this->input_shndx_
, this->value_
, addend
);
502 // Set the value of this symbol in the output symbol table.
504 set_output_value(Value value
)
506 this->value_
= value
;
507 this->needs_output_address_
= false;
510 // If this symbol is mapped to an output section which requires
511 // special handling to determine the output value, we store the
512 // value of the symbol in the input file. This is used for
513 // SHF_MERGE sections.
515 set_input_value(Value value
)
517 this->value_
= value
;
518 this->needs_output_address_
= true;
521 // Return whether this symbol should go into the output symbol
524 needs_output_symtab_entry() const
526 gold_assert(this->output_symtab_index_
!= 0);
527 return this->output_symtab_index_
!= -1U;
530 // Return the index in the output symbol table.
532 output_symtab_index() const
534 gold_assert(this->output_symtab_index_
!= 0);
535 return this->output_symtab_index_
;
538 // Set the index in the output symbol table.
540 set_output_symtab_index(unsigned int i
)
542 gold_assert(this->output_symtab_index_
== 0);
543 this->output_symtab_index_
= i
;
546 // Record that this symbol should not go into the output symbol
549 set_no_output_symtab_entry()
551 gold_assert(this->output_symtab_index_
== 0);
552 this->output_symtab_index_
= -1U;
555 // Set the index of the input section in the input file.
557 set_input_shndx(unsigned int i
)
558 { this->input_shndx_
= i
; }
561 // The index of this local symbol in the output symbol table. This
562 // will be -1 if the symbol should not go into the symbol table.
563 unsigned int output_symtab_index_
;
564 // The section index in the input file in which this symbol is
566 unsigned int input_shndx_
: 31;
567 // Whether getting the value of this symbol requires calling an
568 // Output_section method. For example, this will be true of a
569 // STT_SECTION symbol in a SHF_MERGE section.
570 bool needs_output_address_
: 1;
571 // The value of the symbol. If !needs_output_address_, this is the
572 // value in the output file. If needs_output_address_, this is the
573 // value in the input file.
577 // A regular object file. This is size and endian specific.
579 template<int size
, bool big_endian
>
580 class Sized_relobj
: public Relobj
583 typedef typename
elfcpp::Elf_types
<size
>::Elf_Addr Address
;
584 typedef std::vector
<Symbol_value
<size
> > Local_values
;
586 Sized_relobj(const std::string
& name
, Input_file
* input_file
, off_t offset
,
587 const typename
elfcpp::Ehdr
<size
, big_endian
>&);
591 // Set up the object file based on the ELF header.
593 setup(const typename
elfcpp::Ehdr
<size
, big_endian
>&);
595 // Return the index of local symbol SYM in the ordinary symbol
596 // table. A value of -1U means that the symbol is not being output.
598 symtab_index(unsigned int sym
) const
600 gold_assert(sym
< this->local_values_
.size());
601 return this->local_values_
[sym
].output_symtab_index();
606 do_read_symbols(Read_symbols_data
*);
608 // Lay out the input sections.
610 do_layout(Symbol_table
*, Layout
*, Read_symbols_data
*);
612 // Add the symbols to the symbol table.
614 do_add_symbols(Symbol_table
*, Read_symbols_data
*);
618 do_read_relocs(Read_relocs_data
*);
620 // Scan the relocs and adjust the symbol table.
622 do_scan_relocs(const General_options
&, Symbol_table
*, Layout
*,
625 // Finalize the local symbols.
627 do_finalize_local_symbols(unsigned int, off_t
,
628 Stringpool_template
<char>*);
630 // Relocate the input sections and write out the local symbols.
632 do_relocate(const General_options
& options
, const Symbol_table
* symtab
,
633 const Layout
*, Output_file
* of
);
635 // Get the name of a section.
637 do_section_name(unsigned int shndx
)
638 { return this->elf_file_
.section_name(shndx
); }
640 // Return the location of the contents of a section.
642 do_section_contents(unsigned int shndx
)
643 { return this->elf_file_
.section_contents(shndx
); }
645 // Return section flags.
647 do_section_flags(unsigned int shndx
)
648 { return this->elf_file_
.section_flags(shndx
); }
650 // Return the appropriate Sized_target structure.
651 Sized_target
<size
, big_endian
>*
654 return this->Object::sized_target
655 SELECT_SIZE_ENDIAN_NAME(size
, big_endian
) (
656 SELECT_SIZE_ENDIAN_ONLY(size
, big_endian
));
659 // Return the value of a local symbol define in input section SHNDX,
660 // with value VALUE, adding addend ADDEND. This handles SHF_MERGE
663 local_value(unsigned int shndx
, Address value
, Address addend
) const;
667 typedef Sized_relobj
<size
, big_endian
> This
;
668 static const int ehdr_size
= elfcpp::Elf_sizes
<size
>::ehdr_size
;
669 static const int shdr_size
= elfcpp::Elf_sizes
<size
>::shdr_size
;
670 static const int sym_size
= elfcpp::Elf_sizes
<size
>::sym_size
;
671 typedef elfcpp::Shdr
<size
, big_endian
> Shdr
;
673 // Find the SHT_SYMTAB section, given the section headers.
675 find_symtab(const unsigned char* pshdrs
);
677 // Whether to include a section group in the link.
679 include_section_group(Layout
*, unsigned int,
680 const elfcpp::Shdr
<size
, big_endian
>&,
683 // Whether to include a linkonce section in the link.
685 include_linkonce_section(Layout
*, const char*,
686 const elfcpp::Shdr
<size
, big_endian
>&);
688 // Views and sizes when relocating.
692 typename
elfcpp::Elf_types
<size
>::Elf_Addr address
;
697 typedef std::vector
<View_size
> Views
;
699 // Write section data to the output file. Record the views and
700 // sizes in VIEWS for use when relocating.
702 write_sections(const unsigned char* pshdrs
, Output_file
*, Views
*);
704 // Relocate the sections in the output file.
706 relocate_sections(const General_options
& options
, const Symbol_table
*,
707 const Layout
*, const unsigned char* pshdrs
, Views
*);
709 // Write out the local symbols.
711 write_local_symbols(Output_file
*,
712 const Stringpool_template
<char>*);
714 // General access to the ELF file.
715 elfcpp::Elf_file
<size
, big_endian
, Object
> elf_file_
;
716 // Index of SHT_SYMTAB section.
717 unsigned int symtab_shndx_
;
718 // The number of local symbols.
719 unsigned int local_symbol_count_
;
720 // The number of local symbols which go into the output file.
721 unsigned int output_local_symbol_count_
;
722 // The entries in the symbol table for the external symbols.
724 // File offset for local symbols.
725 off_t local_symbol_offset_
;
726 // Values of local symbols.
727 Local_values local_values_
;
730 // A class to manage the list of all objects.
736 : relobj_list_(), dynobj_list_(), target_(NULL
), sonames_()
739 // The type of the list of input relocateable objects.
740 typedef std::vector
<Relobj
*> Relobj_list
;
741 typedef Relobj_list::const_iterator Relobj_iterator
;
743 // The type of the list of input dynamic objects.
744 typedef std::vector
<Dynobj
*> Dynobj_list
;
745 typedef Dynobj_list::const_iterator Dynobj_iterator
;
747 // Add an object to the list. Return true if all is well, or false
748 // if this object should be ignored.
752 // Get the target we should use for the output file.
755 { return this->target_
; }
757 // Iterate over all regular objects.
761 { return this->relobj_list_
.begin(); }
765 { return this->relobj_list_
.end(); }
767 // Iterate over all dynamic objects.
771 { return this->dynobj_list_
.begin(); }
775 { return this->dynobj_list_
.end(); }
777 // Return whether we have seen any dynamic objects.
780 { return !this->dynobj_list_
.empty(); }
783 Input_objects(const Input_objects
&);
784 Input_objects
& operator=(const Input_objects
&);
786 // The list of ordinary objects included in the link.
787 Relobj_list relobj_list_
;
788 // The list of dynamic objects included in the link.
789 Dynobj_list dynobj_list_
;
792 // SONAMEs that we have seen.
793 Unordered_set
<std::string
> sonames_
;
796 // Some of the information we pass to the relocation routines. We
797 // group this together to avoid passing a dozen different arguments.
799 template<int size
, bool big_endian
>
802 // Command line options.
803 const General_options
* options
;
805 const Symbol_table
* symtab
;
807 const Layout
* layout
;
808 // Object being relocated.
809 Sized_relobj
<size
, big_endian
>* object
;
810 // Number of local symbols.
811 unsigned int local_symbol_count
;
812 // Values of local symbols.
813 const typename Sized_relobj
<size
, big_endian
>::Local_values
* local_values
;
815 const Symbol
* const * symbols
;
816 // Section index of relocation section.
817 unsigned int reloc_shndx
;
818 // Section index of section being relocated.
819 unsigned int data_shndx
;
821 // Return a string showing the location of a relocation. This is
822 // only used for error messages.
824 location(size_t relnum
, off_t reloffset
) const;
827 // Return an Object appropriate for the input file. P is BYTES long,
828 // and holds the ELF header.
831 make_elf_object(const std::string
& name
, Input_file
*,
832 off_t offset
, const unsigned char* p
,
835 } // end namespace gold
837 #endif // !defined(GOLD_OBJECT_H)