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
171 // size. CACHE is a hint as in File_read::get_view.
173 section_contents(unsigned int shndx, off_t* plen, bool cache);
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, true)); }
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, true)); }
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, bool cache)
289 return this->input_file_->file().get_view(start + this->offset_, size,
293 // Get a lasting view into the underlying file.
295 get_lasting_view(off_t start, off_t size, bool cache)
297 return this->input_file_->file().get_lasting_view(start + this->offset_,
301 // Read data from the underlying file.
303 read(off_t start, off_t size, void* p)
304 { this->input_file_->file().read(start + this->offset_, size, p); }
308 set_target(int machine, int size, bool big_endian, int osabi,
311 // Set the number of sections.
314 { this->shnum_ = shnum; }
316 // Functions used by both Sized_relobj and Sized_dynobj.
318 // Read the section data into a Read_symbols_data object.
319 template<int size, bool big_endian>
321 read_section_data(elfcpp::Elf_file<size, big_endian, Object>*,
324 // If NAME is the name of a special .gnu.warning section, arrange
325 // for the warning to be issued. SHNDX is the section index.
326 // Return whether it is a warning section.
328 handle_gnu_warning_section(const char* name, unsigned int shndx,
332 // This class may not be copied.
333 Object(const Object&);
334 Object& operator=(const Object&);
336 // Name of object as printed to user.
338 // For reading the file.
339 Input_file* input_file_;
340 // Offset within the file--0 for an object file, non-0 for an
343 // Number of input sections.
345 // Whether this is a dynamic object.
347 // Target functions--may be NULL if the target is not known.
351 // Implement sized_target inline for efficiency. This approach breaks
352 // static type checking, but is made safe using asserts.
354 template<int size, bool big_endian>
355 inline Sized_target<size, big_endian>*
356 Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY)
358 gold_assert(this->target_->get_size() == size);
359 gold_assert(this->target_->is_big_endian() ? big_endian : !big_endian);
360 return static_cast<Sized_target<size, big_endian>*>(this->target_);
363 // A regular object (ET_REL). This is an abstract base class itself.
364 // The implementation is the template class Sized_relobj.
366 class Relobj : public Object
369 Relobj(const std::string& name, Input_file* input_file, off_t offset = 0)
370 : Object(name, input_file, false, offset)
375 read_relocs(Read_relocs_data* rd)
376 { return this->do_read_relocs(rd); }
378 // Scan the relocs and adjust the symbol table.
380 scan_relocs(const General_options& options, Symbol_table* symtab,
381 Layout* layout, Read_relocs_data* rd)
382 { return this->do_scan_relocs(options, symtab, layout, rd); }
384 // Initial local symbol processing: set the offset where local
385 // symbol information will be stored; add local symbol names to
386 // *POOL; return the new local symbol index.
388 finalize_local_symbols(unsigned int index, off_t off,
389 Stringpool_template<char>* pool)
390 { return this->do_finalize_local_symbols(index, off, pool); }
392 // Relocate the input sections and write out the local symbols.
394 relocate(const General_options& options, const Symbol_table* symtab,
395 const Layout* layout, Output_file* of)
396 { return this->do_relocate(options, symtab, layout, of); }
398 // Return whether an input section is being included in the link.
400 is_section_included(unsigned int shndx) const
402 gold_assert(shndx < this->map_to_output_.size());
403 return this->map_to_output_[shndx].output_section != NULL;
406 // Given a section index, return the corresponding Output_section
407 // (which will be NULL if the section is not included in the link)
408 // and set *POFF to the offset within that section.
409 inline Output_section*
410 output_section(unsigned int shndx, off_t* poff) const;
412 // Set the offset of an input section within its output section.
414 set_section_offset(unsigned int shndx, off_t off)
416 gold_assert(shndx < this->map_to_output_.size());
417 this->map_to_output_[shndx].offset = off;
421 // What we need to know to map an input section to an output
422 // section. We keep an array of these, one for each input section,
423 // indexed by the input section number.
426 // The output section. This is NULL if the input section is to be
428 Output_section* output_section;
429 // The offset within the output section. This is -1 if the
430 // section requires special handling.
434 // Read the relocs--implemented by child class.
436 do_read_relocs(Read_relocs_data*) = 0;
438 // Scan the relocs--implemented by child class.
440 do_scan_relocs(const General_options&, Symbol_table*, Layout*,
441 Read_relocs_data*) = 0;
443 // Finalize local symbols--implemented by child class.
445 do_finalize_local_symbols(unsigned int, off_t,
446 Stringpool_template<char>*) = 0;
448 // Relocate the input sections and write out the local
449 // symbols--implemented by child class.
451 do_relocate(const General_options& options, const Symbol_table* symtab,
452 const Layout*, Output_file* of) = 0;
454 // Return the vector mapping input sections to output sections.
455 std::vector<Map_to_output>&
457 { return this->map_to_output_; }
459 const std::vector<Map_to_output>&
460 map_to_output() const
461 { return this->map_to_output_; }
464 // Mapping from input sections to output section.
465 std::vector<Map_to_output> map_to_output_;
468 // Implement Object::output_section inline for efficiency.
469 inline Output_section*
470 Relobj::output_section(unsigned int shndx, off_t* poff) const
472 gold_assert(shndx < this->map_to_output_.size());
473 const Map_to_output& mo(this->map_to_output_[shndx]);
475 return mo.output_section;
478 // This POD class is holds the value of a symbol. This is used for
479 // local symbols, and for all symbols during relocation processing.
480 // In order to process relocs we need to be able to handle SHF_MERGE
481 // sections correctly.
487 typedef typename elfcpp::Elf_types<size>::Elf_Addr Value;
490 : output_symtab_index_(0), input_shndx_(0), is_section_symbol_(false),
491 needs_output_address_(false), value_(0)
494 // Get the value of this symbol. OBJECT is the object in which this
495 // symbol is defined, and ADDEND is an addend to add to the value.
496 template<bool big_endian>
498 value(const Sized_relobj<size, big_endian>* object, Value addend) const
500 if (!this->needs_output_address_)
501 return this->value_ + addend;
502 return object->local_value(this->input_shndx_, this->value_,
503 this->is_section_symbol_, addend);
506 // Set the value of this symbol in the output symbol table.
508 set_output_value(Value value)
510 this->value_ = value;
511 this->needs_output_address_ = false;
514 // If this symbol is mapped to an output section which requires
515 // special handling to determine the output value, we store the
516 // value of the symbol in the input file. This is used for
517 // SHF_MERGE sections.
519 set_input_value(Value value)
521 this->value_ = value;
522 this->needs_output_address_ = true;
525 // Return whether this symbol should go into the output symbol
528 needs_output_symtab_entry() const
530 gold_assert(this->output_symtab_index_ != 0);
531 return this->output_symtab_index_ != -1U;
534 // Return the index in the output symbol table.
536 output_symtab_index() const
538 gold_assert(this->output_symtab_index_ != 0);
539 return this->output_symtab_index_;
542 // Set the index in the output symbol table.
544 set_output_symtab_index(unsigned int i)
546 gold_assert(this->output_symtab_index_ == 0);
547 this->output_symtab_index_ = i;
550 // Record that this symbol should not go into the output symbol
553 set_no_output_symtab_entry()
555 gold_assert(this->output_symtab_index_ == 0);
556 this->output_symtab_index_ = -1U;
559 // Set the index of the input section in the input file.
561 set_input_shndx(unsigned int i)
562 { this->input_shndx_ = i; }
564 // Record that this is a section symbol.
566 set_is_section_symbol()
567 { this->is_section_symbol_ = true; }
570 // The index of this local symbol in the output symbol table. This
571 // will be -1 if the symbol should not go into the symbol table.
572 unsigned int output_symtab_index_;
573 // The section index in the input file in which this symbol is
575 unsigned int input_shndx_ : 30;
576 // Whether this is a STT_SECTION symbol.
577 bool is_section_symbol_ : 1;
578 // Whether getting the value of this symbol requires calling an
579 // Output_section method. For example, this will be true of a
580 // symbol in a SHF_MERGE section.
581 bool needs_output_address_ : 1;
582 // The value of the symbol. If !needs_output_address_, this is the
583 // value in the output file. If needs_output_address_, this is the
584 // value in the input file.
588 // A regular object file. This is size and endian specific.
590 template<int size, bool big_endian>
591 class Sized_relobj : public Relobj
594 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
595 typedef std::vector<Symbol_value<size> > Local_values;
597 Sized_relobj(const std::string& name, Input_file* input_file, off_t offset,
598 const typename elfcpp::Ehdr<size, big_endian>&);
602 // Set up the object file based on the ELF header.
604 setup(const typename elfcpp::Ehdr<size, big_endian>&);
606 // Return the index of local symbol SYM in the ordinary symbol
607 // table. A value of -1U means that the symbol is not being output.
609 symtab_index(unsigned int sym) const
611 gold_assert(sym < this->local_values_.size());
612 return this->local_values_[sym].output_symtab_index();
617 do_read_symbols(Read_symbols_data*);
619 // Lay out the input sections.
621 do_layout(Symbol_table*, Layout*, Read_symbols_data*);
623 // Add the symbols to the symbol table.
625 do_add_symbols(Symbol_table*, Read_symbols_data*);
629 do_read_relocs(Read_relocs_data*);
631 // Scan the relocs and adjust the symbol table.
633 do_scan_relocs(const General_options&, Symbol_table*, Layout*,
636 // Finalize the local symbols.
638 do_finalize_local_symbols(unsigned int, off_t,
639 Stringpool_template<char>*);
641 // Relocate the input sections and write out the local symbols.
643 do_relocate(const General_options& options, const Symbol_table* symtab,
644 const Layout*, Output_file* of);
646 // Get the name of a section.
648 do_section_name(unsigned int shndx)
649 { return this->elf_file_.section_name(shndx); }
651 // Return the location of the contents of a section.
653 do_section_contents(unsigned int shndx)
654 { return this->elf_file_.section_contents(shndx); }
656 // Return section flags.
658 do_section_flags(unsigned int shndx)
659 { return this->elf_file_.section_flags(shndx); }
661 // Return the appropriate Sized_target structure.
662 Sized_target<size, big_endian>*
665 return this->Object::sized_target
666 SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
667 SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
670 // Return the value of a local symbol define in input section SHNDX,
671 // with value VALUE, adding addend ADDEND. IS_SECTION_SYMBOL
672 // indicates whether the symbol is a section symbol. This handles
673 // SHF_MERGE sections.
675 local_value(unsigned int shndx, Address value, bool is_section_symbol,
676 Address addend) const;
680 typedef Sized_relobj<size, big_endian> This;
681 static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
682 static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
683 static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
684 typedef elfcpp::Shdr<size, big_endian> Shdr;
686 // Find the SHT_SYMTAB section, given the section headers.
688 find_symtab(const unsigned char* pshdrs);
690 // Whether to include a section group in the link.
692 include_section_group(Layout*, unsigned int,
693 const elfcpp::Shdr<size, big_endian>&,
696 // Whether to include a linkonce section in the link.
698 include_linkonce_section(Layout*, const char*,
699 const elfcpp::Shdr<size, big_endian>&);
701 // Views and sizes when relocating.
705 typename elfcpp::Elf_types<size>::Elf_Addr address;
710 typedef std::vector<View_size> Views;
712 // Write section data to the output file. Record the views and
713 // sizes in VIEWS for use when relocating.
715 write_sections(const unsigned char* pshdrs, Output_file*, Views*);
717 // Relocate the sections in the output file.
719 relocate_sections(const General_options& options, const Symbol_table*,
720 const Layout*, const unsigned char* pshdrs, Views*);
722 // Write out the local symbols.
724 write_local_symbols(Output_file*,
725 const Stringpool_template<char>*);
727 // General access to the ELF file.
728 elfcpp::Elf_file<size, big_endian, Object> elf_file_;
729 // Index of SHT_SYMTAB section.
730 unsigned int symtab_shndx_;
731 // The number of local symbols.
732 unsigned int local_symbol_count_;
733 // The number of local symbols which go into the output file.
734 unsigned int output_local_symbol_count_;
735 // The entries in the symbol table for the external symbols.
737 // File offset for local symbols.
738 off_t local_symbol_offset_;
739 // Values of local symbols.
740 Local_values local_values_;
743 // A class to manage the list of all objects.
749 : relobj_list_(), dynobj_list_(), target_(NULL), sonames_()
752 // The type of the list of input relocateable objects.
753 typedef std::vector<Relobj*> Relobj_list;
754 typedef Relobj_list::const_iterator Relobj_iterator;
756 // The type of the list of input dynamic objects.
757 typedef std::vector<Dynobj*> Dynobj_list;
758 typedef Dynobj_list::const_iterator Dynobj_iterator;
760 // Add an object to the list. Return true if all is well, or false
761 // if this object should be ignored.
765 // Get the target we should use for the output file.
768 { return this->target_; }
770 // Iterate over all regular objects.
774 { return this->relobj_list_.begin(); }
778 { return this->relobj_list_.end(); }
780 // Iterate over all dynamic objects.
784 { return this->dynobj_list_.begin(); }
788 { return this->dynobj_list_.end(); }
790 // Return whether we have seen any dynamic objects.
793 { return !this->dynobj_list_.empty(); }
796 Input_objects(const Input_objects&);
797 Input_objects& operator=(const Input_objects&);
799 // The list of ordinary objects included in the link.
800 Relobj_list relobj_list_;
801 // The list of dynamic objects included in the link.
802 Dynobj_list dynobj_list_;
805 // SONAMEs that we have seen.
806 Unordered_set<std::string> sonames_;
809 // Some of the information we pass to the relocation routines. We
810 // group this together to avoid passing a dozen different arguments.
812 template<int size, bool big_endian>
815 // Command line options.
816 const General_options* options;
818 const Symbol_table* symtab;
820 const Layout* layout;
821 // Object being relocated.
822 Sized_relobj<size, big_endian>* object;
823 // Number of local symbols.
824 unsigned int local_symbol_count;
825 // Values of local symbols.
826 const typename Sized_relobj<size, big_endian>::Local_values* local_values;
828 const Symbol* const * symbols;
829 // Section index of relocation section.
830 unsigned int reloc_shndx;
831 // Section index of section being relocated.
832 unsigned int data_shndx;
834 // Return a string showing the location of a relocation. This is
835 // only used for error messages.
837 location(size_t relnum, off_t reloffset) const;
840 // Return an Object appropriate for the input file. P is BYTES long,
841 // and holds the ELF header.
844 make_elf_object(const std::string& name, Input_file*,
845 off_t offset, const unsigned char* p,
848 } // end namespace gold
850 #endif // !defined(GOLD_OBJECT_H)