1 // object.h -- support for an object file for linking in gold -*- C++ -*-
10 #include "elfcpp_file.h"
17 class General_options;
23 template<typename Stringpool_char>
24 class Stringpool_template;
26 // Data to pass from read_symbols() to add_symbols().
28 struct Read_symbols_data
31 File_view* section_headers;
33 File_view* section_names;
34 // Size of section name data in bytes.
35 off_t section_names_size;
38 // Size of symbol data in bytes.
41 File_view* symbol_names;
42 // Size of symbol name data in bytes.
43 off_t symbol_names_size;
45 // Version information. This is only used on dynamic objects.
46 // Version symbol data (from SHT_GNU_versym section).
49 // Version definition data (from SHT_GNU_verdef section).
52 unsigned int verdef_info;
53 // Needed version data (from SHT_GNU_verneed section).
56 unsigned int verneed_info;
59 // Data about a single relocation section. This is read in
60 // read_relocs and processed in scan_relocs.
64 // Index of reloc section.
65 unsigned int reloc_shndx;
66 // Index of section that relocs apply to.
67 unsigned int data_shndx;
68 // Contents of reloc section.
70 // Reloc section type.
72 // Number of reloc entries.
76 // Relocations in an object file. This is read in read_relocs and
77 // processed in scan_relocs.
79 struct Read_relocs_data
81 typedef std::vector<Section_relocs> Relocs_list;
85 File_view* local_symbols;
88 // Object is an abstract base class which represents either a 32-bit
89 // or a 64-bit input object. This can be a regular object file
90 // (ET_REL) or a shared object (ET_DYN).
95 // NAME is the name of the object as we would report it to the user
96 // (e.g., libfoo.a(bar.o) if this is in an archive. INPUT_FILE is
97 // used to read the file. OFFSET is the offset within the input
98 // file--0 for a .o or .so file, something else for a .a file.
99 Object(const std::string& name, Input_file* input_file, bool is_dynamic,
101 : name_(name), input_file_(input_file), offset_(offset), shnum_(-1U),
102 is_dynamic_(is_dynamic), target_(NULL)
108 // Return the name of the object as we would report it to the tuser.
111 { return this->name_; }
113 // Return whether this is a dynamic object.
116 { return this->is_dynamic_; }
118 // Return the target structure associated with this object.
121 { return this->target_; }
123 // Lock the underlying file.
126 { this->input_file_->file().lock(); }
128 // Unlock the underlying file.
131 { this->input_file_->file().unlock(); }
133 // Return whether the underlying file is locked.
136 { return this->input_file_->file().is_locked(); }
138 // Return the sized target structure associated with this object.
139 // This is like the target method but it returns a pointer of
140 // appropriate checked type.
141 template<int size, bool big_endian>
142 Sized_target<size, big_endian>*
143 sized_target(ACCEPT_SIZE_ENDIAN_ONLY);
145 // Get the number of sections.
148 { return this->shnum_; }
150 // Return a view of the contents of a section. Set *PLEN to the
153 section_contents(unsigned int shndx, off_t* plen);
155 // Return the name of a section given a section index. This is only
156 // used for error messages.
158 section_name(unsigned int shndx)
159 { return this->do_section_name(shndx); }
161 // Return the section flags given a section index.
163 section_flags(unsigned int shndx)
164 { return this->do_section_flags(shndx); }
166 // Read the symbol information.
168 read_symbols(Read_symbols_data* sd)
169 { return this->do_read_symbols(sd); }
171 // Pass sections which should be included in the link to the Layout
172 // object, and record where the sections go in the output file.
174 layout(Symbol_table* symtab, Layout* layout, Read_symbols_data* sd)
175 { this->do_layout(symtab, layout, sd); }
177 // Add symbol information to the global symbol table.
179 add_symbols(Symbol_table* symtab, Read_symbols_data* sd)
180 { this->do_add_symbols(symtab, sd); }
182 // Functions and types for the elfcpp::Elf_file interface. This
183 // permit us to use Object as the File template parameter for
186 // The View class is returned by view. It must support a single
187 // method, data(). This is trivial, because get_view does what we
192 View(const unsigned char* p)
201 const unsigned char* p_;
206 view(off_t file_offset, off_t data_size)
207 { return View(this->get_view(file_offset, data_size)); }
211 error(const char* format, ...) ATTRIBUTE_PRINTF_2;
213 // A location in the file.
219 Location(off_t fo, off_t ds)
220 : file_offset(fo), data_size(ds)
224 // Get a View given a Location.
225 View view(Location loc)
226 { return View(this->get_view(loc.file_offset, loc.data_size)); }
229 // Read the symbols--implemented by child class.
231 do_read_symbols(Read_symbols_data*) = 0;
233 // Lay out sections--implemented by child class.
235 do_layout(Symbol_table*, Layout*, Read_symbols_data*) = 0;
237 // Add symbol information to the global symbol table--implemented by
240 do_add_symbols(Symbol_table*, Read_symbols_data*) = 0;
242 // Return the location of the contents of a section. Implemented by
245 do_section_contents(unsigned int shndx) = 0;
247 // Get the name of a section--implemented by child class.
249 do_section_name(unsigned int shndx) = 0;
251 // Get section flags--implemented by child class.
253 do_section_flags(unsigned int shndx) = 0;
258 { return this->input_file_; }
260 // Get the offset into the file.
263 { return this->offset_; }
265 // Get a view into the underlying file.
267 get_view(off_t start, off_t size)
268 { return this->input_file_->file().get_view(start + this->offset_, size); }
270 // Get a lasting view into the underlying file.
272 get_lasting_view(off_t start, off_t size)
274 return this->input_file_->file().get_lasting_view(start + this->offset_,
278 // Read data from the underlying file.
280 read(off_t start, off_t size, void* p)
281 { this->input_file_->file().read(start + this->offset_, size, p); }
285 set_target(int machine, int size, bool big_endian, int osabi,
288 // Set the number of sections.
291 { this->shnum_ = shnum; }
293 // Functions used by both Sized_relobj and Sized_dynobj.
295 // Read the section data into a Read_symbols_data object.
296 template<int size, bool big_endian>
298 read_section_data(elfcpp::Elf_file<size, big_endian, Object>*,
301 // If NAME is the name of a special .gnu.warning section, arrange
302 // for the warning to be issued. SHNDX is the section index.
303 // Return whether it is a warning section.
305 handle_gnu_warning_section(const char* name, unsigned int shndx,
309 // This class may not be copied.
310 Object(const Object&);
311 Object& operator=(const Object&);
313 // Name of object as printed to user.
315 // For reading the file.
316 Input_file* input_file_;
317 // Offset within the file--0 for an object file, non-0 for an
320 // Number of input sections.
322 // Whether this is a dynamic object.
324 // Target functions--may be NULL if the target is not known.
328 // Implement sized_target inline for efficiency. This approach breaks
329 // static type checking, but is made safe using asserts.
331 template<int size, bool big_endian>
332 inline Sized_target<size, big_endian>*
333 Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY)
335 gold_assert(this->target_->get_size() == size);
336 gold_assert(this->target_->is_big_endian() ? big_endian : !big_endian);
337 return static_cast<Sized_target<size, big_endian>*>(this->target_);
340 // A regular object (ET_REL). This is an abstract base class itself.
341 // The implementation is the template class Sized_relobj.
343 class Relobj : public Object
346 Relobj(const std::string& name, Input_file* input_file, off_t offset = 0)
347 : Object(name, input_file, false, offset)
352 read_relocs(Read_relocs_data* rd)
353 { return this->do_read_relocs(rd); }
355 // Scan the relocs and adjust the symbol table.
357 scan_relocs(const General_options& options, Symbol_table* symtab,
358 Layout* layout, Read_relocs_data* rd)
359 { return this->do_scan_relocs(options, symtab, layout, rd); }
361 // Initial local symbol processing: set the offset where local
362 // symbol information will be stored; add local symbol names to
363 // *POOL; return the new local symbol index.
365 finalize_local_symbols(unsigned int index, off_t off,
366 Stringpool_template<char>* pool)
367 { return this->do_finalize_local_symbols(index, off, pool); }
369 // Relocate the input sections and write out the local symbols.
371 relocate(const General_options& options, const Symbol_table* symtab,
372 const Layout* layout, Output_file* of)
373 { return this->do_relocate(options, symtab, layout, of); }
375 // Return whether an input section is being included in the link.
377 is_section_included(unsigned int shndx) const
379 gold_assert(shndx < this->map_to_output_.size());
380 return this->map_to_output_[shndx].output_section != NULL;
383 // Given a section index, return the corresponding Output_section
384 // (which will be NULL if the section is not included in the link)
385 // and set *POFF to the offset within that section.
386 inline Output_section*
387 output_section(unsigned int shndx, off_t* poff) const;
389 // Set the offset of an input section within its output section.
391 set_section_offset(unsigned int shndx, off_t off)
393 gold_assert(shndx < this->map_to_output_.size());
394 this->map_to_output_[shndx].offset = off;
398 // What we need to know to map an input section to an output
399 // section. We keep an array of these, one for each input section,
400 // indexed by the input section number.
403 // The output section. This is NULL if the input section is to be
405 Output_section* output_section;
406 // The offset within the output section. This is -1 if the
407 // section requires special handling.
411 // Read the relocs--implemented by child class.
413 do_read_relocs(Read_relocs_data*) = 0;
415 // Scan the relocs--implemented by child class.
417 do_scan_relocs(const General_options&, Symbol_table*, Layout*,
418 Read_relocs_data*) = 0;
420 // Finalize local symbols--implemented by child class.
422 do_finalize_local_symbols(unsigned int, off_t,
423 Stringpool_template<char>*) = 0;
425 // Relocate the input sections and write out the local
426 // symbols--implemented by child class.
428 do_relocate(const General_options& options, const Symbol_table* symtab,
429 const Layout*, Output_file* of) = 0;
431 // Return the vector mapping input sections to output sections.
432 std::vector<Map_to_output>&
434 { return this->map_to_output_; }
436 const std::vector<Map_to_output>&
437 map_to_output() const
438 { return this->map_to_output_; }
441 // Mapping from input sections to output section.
442 std::vector<Map_to_output> map_to_output_;
445 // Implement Object::output_section inline for efficiency.
446 inline Output_section*
447 Relobj::output_section(unsigned int shndx, off_t* poff) const
449 gold_assert(shndx < this->map_to_output_.size());
450 const Map_to_output& mo(this->map_to_output_[shndx]);
452 return mo.output_section;
455 // This POD class is holds the value of a symbol. This is used for
456 // local symbols, and for all symbols during relocation processing.
457 // In order to process relocs we need to be able to handle SHF_MERGE
458 // sections correctly.
464 typedef typename elfcpp::Elf_types<size>::Elf_Addr Value;
467 : output_symtab_index_(0), input_shndx_(0), needs_output_address_(false),
471 // Get the value of this symbol. OBJECT is the object in which this
472 // symbol is defined, and ADDEND is an addend to add to the value.
473 template<bool big_endian>
475 value(const Sized_relobj<size, big_endian>* object, Value addend) const
477 if (!this->needs_output_address_)
478 return this->value_ + addend;
479 return object->local_value(this->input_shndx_, this->value_, addend);
482 // Set the value of this symbol in the output symbol table.
484 set_output_value(Value value)
486 this->value_ = value;
487 this->needs_output_address_ = false;
490 // If this symbol is mapped to an output section which requires
491 // special handling to determine the output value, we store the
492 // value of the symbol in the input file. This is used for
493 // SHF_MERGE sections.
495 set_input_value(Value value)
497 this->value_ = value;
498 this->needs_output_address_ = true;
501 // Return whether this symbol should go into the output symbol
504 needs_output_symtab_entry() const
506 gold_assert(this->output_symtab_index_ != 0);
507 return this->output_symtab_index_ != -1U;
510 // Return the index in the output symbol table.
512 output_symtab_index() const
514 gold_assert(this->output_symtab_index_ != 0);
515 return this->output_symtab_index_;
518 // Set the index in the output symbol table.
520 set_output_symtab_index(unsigned int i)
522 gold_assert(this->output_symtab_index_ == 0);
523 this->output_symtab_index_ = i;
526 // Record that this symbol should not go into the output symbol
529 set_no_output_symtab_entry()
531 gold_assert(this->output_symtab_index_ == 0);
532 this->output_symtab_index_ = -1U;
535 // Set the index of the input section in the input file.
537 set_input_shndx(unsigned int i)
538 { this->input_shndx_ = i; }
541 // The index of this local symbol in the output symbol table. This
542 // will be -1 if the symbol should not go into the symbol table.
543 unsigned int output_symtab_index_;
544 // The section index in the input file in which this symbol is
546 unsigned int input_shndx_ : 31;
547 // Whether getting the value of this symbol requires calling an
548 // Output_section method. For example, this will be true of a
549 // STT_SECTION symbol in a SHF_MERGE section.
550 bool needs_output_address_ : 1;
551 // The value of the symbol. If !needs_output_address_, this is the
552 // value in the output file. If needs_output_address_, this is the
553 // value in the input file.
557 // A regular object file. This is size and endian specific.
559 template<int size, bool big_endian>
560 class Sized_relobj : public Relobj
563 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
564 typedef std::vector<Symbol_value<size> > Local_values;
566 Sized_relobj(const std::string& name, Input_file* input_file, off_t offset,
567 const typename elfcpp::Ehdr<size, big_endian>&);
571 // Set up the object file based on the ELF header.
573 setup(const typename elfcpp::Ehdr<size, big_endian>&);
575 // Return the index of local symbol SYM in the ordinary symbol
576 // table. A value of -1U means that the symbol is not being output.
578 symtab_index(unsigned int sym) const
580 gold_assert(sym < this->local_values_.size());
581 return this->local_values_[sym].output_symtab_index();
586 do_read_symbols(Read_symbols_data*);
588 // Lay out the input sections.
590 do_layout(Symbol_table*, Layout*, Read_symbols_data*);
592 // Add the symbols to the symbol table.
594 do_add_symbols(Symbol_table*, Read_symbols_data*);
598 do_read_relocs(Read_relocs_data*);
600 // Scan the relocs and adjust the symbol table.
602 do_scan_relocs(const General_options&, Symbol_table*, Layout*,
605 // Finalize the local symbols.
607 do_finalize_local_symbols(unsigned int, off_t,
608 Stringpool_template<char>*);
610 // Relocate the input sections and write out the local symbols.
612 do_relocate(const General_options& options, const Symbol_table* symtab,
613 const Layout*, Output_file* of);
615 // Get the name of a section.
617 do_section_name(unsigned int shndx)
618 { return this->elf_file_.section_name(shndx); }
620 // Return the location of the contents of a section.
622 do_section_contents(unsigned int shndx)
623 { return this->elf_file_.section_contents(shndx); }
625 // Return section flags.
627 do_section_flags(unsigned int shndx)
628 { return this->elf_file_.section_flags(shndx); }
630 // Return the appropriate Sized_target structure.
631 Sized_target<size, big_endian>*
634 return this->Object::sized_target
635 SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
636 SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
639 // Return the value of a local symbol define in input section SHNDX,
640 // with value VALUE, adding addend ADDEND. This handles SHF_MERGE
643 local_value(unsigned int shndx, Address value, Address addend) const;
647 typedef Sized_relobj<size, big_endian> This;
648 static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
649 static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
650 static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
651 typedef elfcpp::Shdr<size, big_endian> Shdr;
653 // Find the SHT_SYMTAB section, given the section headers.
655 find_symtab(const unsigned char* pshdrs);
657 // Whether to include a section group in the link.
659 include_section_group(Layout*, unsigned int,
660 const elfcpp::Shdr<size, big_endian>&,
663 // Whether to include a linkonce section in the link.
665 include_linkonce_section(Layout*, const char*,
666 const elfcpp::Shdr<size, big_endian>&);
668 // Views and sizes when relocating.
672 typename elfcpp::Elf_types<size>::Elf_Addr address;
677 typedef std::vector<View_size> Views;
679 // Write section data to the output file. Record the views and
680 // sizes in VIEWS for use when relocating.
682 write_sections(const unsigned char* pshdrs, Output_file*, Views*);
684 // Relocate the sections in the output file.
686 relocate_sections(const General_options& options, const Symbol_table*,
687 const Layout*, const unsigned char* pshdrs, Views*);
689 // Write out the local symbols.
691 write_local_symbols(Output_file*,
692 const Stringpool_template<char>*);
694 // General access to the ELF file.
695 elfcpp::Elf_file<size, big_endian, Object> elf_file_;
696 // Index of SHT_SYMTAB section.
697 unsigned int symtab_shndx_;
698 // The number of local symbols.
699 unsigned int local_symbol_count_;
700 // The number of local symbols which go into the output file.
701 unsigned int output_local_symbol_count_;
702 // The entries in the symbol table for the external symbols.
704 // File offset for local symbols.
705 off_t local_symbol_offset_;
706 // Values of local symbols.
707 Local_values local_values_;
710 // A class to manage the list of all objects.
716 : relobj_list_(), dynobj_list_(), target_(NULL), sonames_()
719 // The type of the list of input relocateable objects.
720 typedef std::vector<Relobj*> Relobj_list;
721 typedef Relobj_list::const_iterator Relobj_iterator;
723 // The type of the list of input dynamic objects.
724 typedef std::vector<Dynobj*> Dynobj_list;
725 typedef Dynobj_list::const_iterator Dynobj_iterator;
727 // Add an object to the list. Return true if all is well, or false
728 // if this object should be ignored.
732 // Get the target we should use for the output file.
735 { return this->target_; }
737 // Iterate over all regular objects.
741 { return this->relobj_list_.begin(); }
745 { return this->relobj_list_.end(); }
747 // Iterate over all dynamic objects.
751 { return this->dynobj_list_.begin(); }
755 { return this->dynobj_list_.end(); }
757 // Return whether we have seen any dynamic objects.
760 { return !this->dynobj_list_.empty(); }
763 Input_objects(const Input_objects&);
764 Input_objects& operator=(const Input_objects&);
766 // The list of ordinary objects included in the link.
767 Relobj_list relobj_list_;
768 // The list of dynamic objects included in the link.
769 Dynobj_list dynobj_list_;
772 // SONAMEs that we have seen.
773 Unordered_set<std::string> sonames_;
776 // Some of the information we pass to the relocation routines. We
777 // group this together to avoid passing a dozen different arguments.
779 template<int size, bool big_endian>
782 // Command line options.
783 const General_options* options;
785 const Symbol_table* symtab;
787 const Layout* layout;
788 // Object being relocated.
789 Sized_relobj<size, big_endian>* object;
790 // Number of local symbols.
791 unsigned int local_symbol_count;
792 // Values of local symbols.
793 const typename Sized_relobj<size, big_endian>::Local_values* local_values;
795 const Symbol* const * symbols;
796 // Section index of relocation section.
797 unsigned int reloc_shndx;
798 // Section index of section being relocated.
799 unsigned int data_shndx;
801 // Return a string showing the location of a relocation. This is
802 // only used for error messages.
804 location(size_t relnum, off_t reloffset) const;
807 // Return an Object appropriate for the input file. P is BYTES long,
808 // and holds the ELF header.
811 make_elf_object(const std::string& name, Input_file*,
812 off_t offset, const unsigned char* p,
815 } // end namespace gold
817 #endif // !defined(GOLD_OBJECT_H)