gold/object.h

   1 // object.h -- support for an object file for linking in gold  -*- C++ -*-
   2
   3 #ifndef GOLD_OBJECT_H
   4 #define GOLD_OBJECT_H
   5
   6 #include <cassert>
   7 #include <string>
   8 #include <vector>
   9
  10 #include "elfcpp.h"
  11 #include "elfcpp_file.h"
  12 #include "fileread.h"
  13 #include "target.h"
  14
  15 namespace gold
  16 {
  17
  18 class General_options;
  19 class Stringpool;
  20 class Layout;
  21 class Output_section;
  22 class Output_file;
  23 class Dynobj;
  24
  25 // Data to pass from read_symbols() to add_symbols().
  26
  27 struct Read_symbols_data
  28 {
  29   // Section headers.
  30   File_view* section_headers;
  31   // Section names.
  32   File_view* section_names;
  33   // Size of section name data in bytes.
  34   off_t section_names_size;
  35   // Symbol data.
  36   File_view* symbols;
  37   // Size of symbol data in bytes.
  38   off_t symbols_size;
  39   // Symbol names.
  40   File_view* symbol_names;
  41   // Size of symbol name data in bytes.
  42   off_t symbol_names_size;
  43 };
  44
  45 // Data about a single relocation section.  This is read in
  46 // read_relocs and processed in scan_relocs.
  47
  48 struct Section_relocs
  49 {
  50   // Index of reloc section.
  51   unsigned int reloc_shndx;
  52   // Index of section that relocs apply to.
  53   unsigned int data_shndx;
  54   // Contents of reloc section.
  55   File_view* contents;
  56   // Reloc section type.
  57   unsigned int sh_type;
  58   // Number of reloc entries.
  59   size_t reloc_count;
  60 };
  61
  62 // Relocations in an object file.  This is read in read_relocs and
  63 // processed in scan_relocs.
  64
  65 struct Read_relocs_data
  66 {
  67   typedef std::vector<Section_relocs> Relocs_list;
  68   // The relocations.
  69   Relocs_list relocs;
  70   // The local symbols.
  71   File_view* local_symbols;
  72 };
  73
  74 // Object is an abstract base class which represents either a 32-bit
  75 // or a 64-bit input object.  This can be a regular object file
  76 // (ET_REL) or a shared object (ET_DYN).
  77
  78 class Object
  79 {
  80  public:
  81   // NAME is the name of the object as we would report it to the user
  82   // (e.g., libfoo.a(bar.o) if this is in an archive.  INPUT_FILE is
  83   // used to read the file.  OFFSET is the offset within the input
  84   // file--0 for a .o or .so file, something else for a .a file.
  85   Object(const std::string& name, Input_file* input_file, bool is_dynamic,
  86          off_t offset = 0)
  87     : name_(name), input_file_(input_file), offset_(offset),
  88       is_dynamic_(is_dynamic), target_(NULL)
  89   { }
  90
  91   virtual ~Object()
  92   { }
  93
  94   // Return the name of the object as we would report it to the tuser.
  95   const std::string&
  96   name() const
  97   { return this->name_; }
  98
  99   // Return whether this is a dynamic object.
 100   bool
 101   is_dynamic() const
 102   { return this->is_dynamic_; }
 103
 104   // Return the target structure associated with this object.
 105   Target*
 106   target() const
 107   { return this->target_; }
 108
 109   // Lock the underlying file.
 110   void
 111   lock()
 112   { this->input_file_->file().lock(); }
 113
 114   // Unlock the underlying file.
 115   void
 116   unlock()
 117   { this->input_file_->file().unlock(); }
 118
 119   // Return whether the underlying file is locked.
 120   bool
 121   is_locked() const
 122   { return this->input_file_->file().is_locked(); }
 123
 124   // Return the sized target structure associated with this object.
 125   // This is like the target method but it returns a pointer of
 126   // appropriate checked type.
 127   template<int size, bool big_endian>
 128   Sized_target<size, big_endian>*
 129   sized_target(ACCEPT_SIZE_ENDIAN_ONLY);
 130
 131   // Read the symbol information.
 132   void
 133   read_symbols(Read_symbols_data* sd)
 134   { return this->do_read_symbols(sd); }
 135
 136   // Pass sections which should be included in the link to the Layout
 137   // object, and record where the sections go in the output file.
 138   void
 139   layout(const General_options& options, Symbol_table* symtab,
 140          Layout* layout, Read_symbols_data* sd)
 141   { this->do_layout(options, symtab, layout, sd); }
 142
 143   // Add symbol information to the global symbol table.
 144   void
 145   add_symbols(Symbol_table* symtab, Read_symbols_data* sd)
 146   { this->do_add_symbols(symtab, sd); }
 147
 148   // Return a view of the contents of a section.  Set *PLEN to the
 149   // size.
 150   const unsigned char*
 151   section_contents(unsigned int shndx, off_t* plen);
 152
 153   // Return the name of a section given a section index.  This is only
 154   // used for error messages.
 155   std::string
 156   section_name(unsigned int shnum)
 157   { return this->do_section_name(shnum); }
 158
 159   // Functions and types for the elfcpp::Elf_file interface.  This
 160   // permit us to use Object as the File template parameter for
 161   // elfcpp::Elf_file.
 162
 163   // The View class is returned by view.  It must support a single
 164   // method, data().  This is trivial, because get_view does what we
 165   // need.
 166   class View
 167   {
 168    public:
 169     View(const unsigned char* p)
 170       : p_(p)
 171     { }
 172
 173     const unsigned char*
 174     data() const
 175     { return this->p_; }
 176
 177    private:
 178     const unsigned char* p_;
 179   };
 180
 181   // Return a View.
 182   View
 183   view(off_t file_offset, off_t data_size)
 184   { return View(this->get_view(file_offset, data_size)); }
 185
 186   // Report an error.
 187   void
 188   error(const char* format, ...) ATTRIBUTE_PRINTF_2;
 189
 190   // A location in the file.
 191   struct Location
 192   {
 193     off_t file_offset;
 194     off_t data_size;
 195
 196     Location(off_t fo, off_t ds)
 197       : file_offset(fo), data_size(ds)
 198     { }
 199   };
 200
 201   // Get a View given a Location.
 202   View view(Location loc)
 203   { return View(this->get_view(loc.file_offset, loc.data_size)); }
 204
 205  protected:
 206   // Read the symbols--implemented by child class.
 207   virtual void
 208   do_read_symbols(Read_symbols_data*) = 0;
 209
 210   // Lay out sections--implemented by child class.
 211   virtual void
 212   do_layout(const General_options&, Symbol_table*, Layout*,
 213             Read_symbols_data*) = 0;
 214
 215   // Add symbol information to the global symbol table--implemented by
 216   // child class.
 217   virtual void
 218   do_add_symbols(Symbol_table*, Read_symbols_data*) = 0;
 219
 220   // Return the location of the contents of a section.  Implemented by
 221   // child class.
 222   virtual Location
 223   do_section_contents(unsigned int shnum) = 0;
 224
 225   // Get the name of a section--implemented by child class.
 226   virtual std::string
 227   do_section_name(unsigned int shnum) = 0;
 228
 229   // Get the file.
 230   Input_file*
 231   input_file() const
 232   { return this->input_file_; }
 233
 234   // Get the offset into the file.
 235   off_t
 236   offset() const
 237   { return this->offset_; }
 238
 239   // Get a view into the underlying file.
 240   const unsigned char*
 241   get_view(off_t start, off_t size)
 242   { return this->input_file_->file().get_view(start + this->offset_, size); }
 243
 244   // Get a lasting view into the underlying file.
 245   File_view*
 246   get_lasting_view(off_t start, off_t size)
 247   {
 248     return this->input_file_->file().get_lasting_view(start + this->offset_,
 249                                                       size);
 250   }
 251
 252   // Read data from the underlying file.
 253   void
 254   read(off_t start, off_t size, void* p)
 255   { this->input_file_->file().read(start + this->offset_, size, p); }
 256
 257   // Set the target.
 258   void
 259   set_target(Target* target)
 260   { this->target_ = target; }
 261
 262  private:
 263   // This class may not be copied.
 264   Object(const Object&);
 265   Object& operator=(const Object&);
 266
 267   // Name of object as printed to user.
 268   std::string name_;
 269   // For reading the file.
 270   Input_file* input_file_;
 271   // Offset within the file--0 for an object file, non-0 for an
 272   // archive.
 273   off_t offset_;
 274   // Whether this is a dynamic object.
 275   bool is_dynamic_;
 276   // Target functions--may be NULL if the target is not known.
 277   Target* target_;
 278 };
 279
 280 // Implement sized_target inline for efficiency.  This approach breaks
 281 // static type checking, but is made safe using asserts.
 282
 283 template<int size, bool big_endian>
 284 inline Sized_target<size, big_endian>*
 285 Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY)
 286 {
 287   assert(this->target_->get_size() == size);
 288   assert(this->target_->is_big_endian() ? big_endian : !big_endian);
 289   return static_cast<Sized_target<size, big_endian>*>(this->target_);
 290 }
 291
 292 // A regular object (ET_REL).  This is an abstract base class itself.
 293 // The implementations is the template class Sized_relobj.
 294
 295 class Relobj : public Object
 296 {
 297  public:
 298   Relobj(const std::string& name, Input_file* input_file, off_t offset = 0)
 299     : Object(name, input_file, false, offset)
 300   { }
 301
 302   // Read the relocs.
 303   void
 304   read_relocs(Read_relocs_data* rd)
 305   { return this->do_read_relocs(rd); }
 306
 307   // Scan the relocs and adjust the symbol table.
 308   void
 309   scan_relocs(const General_options& options, Symbol_table* symtab,
 310               Layout* layout, Read_relocs_data* rd)
 311   { return this->do_scan_relocs(options, symtab, layout, rd); }
 312
 313   // Initial local symbol processing: set the offset where local
 314   // symbol information will be stored; add local symbol names to
 315   // *POOL; return the offset following the local symbols.
 316   off_t
 317   finalize_local_symbols(off_t off, Stringpool* pool)
 318   { return this->do_finalize_local_symbols(off, pool); }
 319
 320   // Relocate the input sections and write out the local symbols.
 321   void
 322   relocate(const General_options& options, const Symbol_table* symtab,
 323            const Layout* layout, Output_file* of)
 324   { return this->do_relocate(options, symtab, layout, of); }
 325
 326   // Return whether an input section is being included in the link.
 327   bool
 328   is_section_included(unsigned int shnum) const
 329   {
 330     assert(shnum < this->map_to_output_.size());
 331     return this->map_to_output_[shnum].output_section != NULL;
 332   }
 333
 334   // Given a section index, return the corresponding Output_section
 335   // (which will be NULL if the section is not included in the link)
 336   // and set *POFF to the offset within that section.
 337   inline Output_section*
 338   output_section(unsigned int shnum, off_t* poff);
 339
 340   // Set the offset of an input section within its output section.
 341   void
 342   set_section_offset(unsigned int shndx, off_t off)
 343   {
 344     assert(shndx < this->map_to_output_.size());
 345     this->map_to_output_[shndx].offset = off;
 346   }
 347
 348  protected:
 349   // What we need to know to map an input section to an output
 350   // section.  We keep an array of these, one for each input section,
 351   // indexed by the input section number.
 352   struct Map_to_output
 353   {
 354     // The output section.  This is NULL if the input section is to be
 355     // discarded.
 356     Output_section* output_section;
 357     // The offset within the output section.
 358     off_t offset;
 359   };
 360
 361   // Read the relocs--implemented by child class.
 362   virtual void
 363   do_read_relocs(Read_relocs_data*) = 0;
 364
 365   // Scan the relocs--implemented by child class.
 366   virtual void
 367   do_scan_relocs(const General_options&, Symbol_table*, Layout*,
 368                  Read_relocs_data*) = 0;
 369
 370   // Finalize local symbols--implemented by child class.
 371   virtual off_t
 372   do_finalize_local_symbols(off_t, Stringpool*) = 0;
 373
 374   // Relocate the input sections and write out the local
 375   // symbols--implemented by child class.
 376   virtual void
 377   do_relocate(const General_options& options, const Symbol_table* symtab,
 378               const Layout*, Output_file* of) = 0;
 379
 380   // Get the number of sections.
 381   unsigned int
 382   shnum() const
 383   { return this->shnum_; }
 384
 385   // Set the number of sections.
 386   void
 387   set_shnum(int shnum)
 388   { this->shnum_ = shnum; }
 389
 390   // Return the vector mapping input sections to output sections.
 391   std::vector<Map_to_output>&
 392   map_to_output()
 393   { return this->map_to_output_; }
 394
 395  private:
 396   // Number of input sections.
 397   unsigned int shnum_;
 398   // Mapping from input sections to output section.
 399   std::vector<Map_to_output> map_to_output_;
 400 };
 401
 402 // Implement Object::output_section inline for efficiency.
 403 inline Output_section*
 404 Relobj::output_section(unsigned int shnum, off_t* poff)
 405 {
 406   assert(shnum < this->map_to_output_.size());
 407   const Map_to_output& mo(this->map_to_output_[shnum]);
 408   *poff = mo.offset;
 409   return mo.output_section;
 410 }
 411
 412 // A regular object file.  This is size and endian specific.
 413
 414 template<int size, bool big_endian>
 415 class Sized_relobj : public Relobj
 416 {
 417  public:
 418   Sized_relobj(const std::string& name, Input_file* input_file, off_t offset,
 419                const typename elfcpp::Ehdr<size, big_endian>&);
 420
 421   ~Sized_relobj();
 422
 423   // Set up the object file based on the ELF header.
 424   void
 425   setup(const typename elfcpp::Ehdr<size, big_endian>&);
 426
 427   // Read the symbols.
 428   void
 429   do_read_symbols(Read_symbols_data*);
 430
 431   // Add the symbols to the symbol table.
 432   void
 433   do_add_symbols(Symbol_table*, Read_symbols_data*);
 434
 435   // Read the relocs.
 436   void
 437   do_read_relocs(Read_relocs_data*);
 438
 439   // Scan the relocs and adjust the symbol table.
 440   void
 441   do_scan_relocs(const General_options&, Symbol_table*, Layout*,
 442                  Read_relocs_data*);
 443
 444   // Lay out the input sections.
 445   void
 446   do_layout(const General_options&, Symbol_table*, Layout*,
 447             Read_symbols_data*);
 448
 449   // Finalize the local symbols.
 450   off_t
 451   do_finalize_local_symbols(off_t, Stringpool*);
 452
 453   // Relocate the input sections and write out the local symbols.
 454   void
 455   do_relocate(const General_options& options, const Symbol_table* symtab,
 456               const Layout*, Output_file* of);
 457
 458   // Get the name of a section.
 459   std::string
 460   do_section_name(unsigned int shndx)
 461   { return this->elf_file_.section_name(shndx); }
 462
 463   // Return the location of the contents of a section.
 464   Location
 465   do_section_contents(unsigned int shndx)
 466   { return this->elf_file_.section_contents(shndx); }
 467
 468   // Return the appropriate Sized_target structure.
 469   Sized_target<size, big_endian>*
 470   sized_target()
 471   {
 472     return this->Object::sized_target
 473       SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
 474           SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
 475   }
 476
 477  private:
 478   // For convenience.
 479   typedef Sized_relobj<size, big_endian> This;
 480   static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
 481   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 482   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 483   typedef elfcpp::Shdr<size, big_endian> Shdr;
 484
 485   // Whether to include a section group in the link.
 486   bool
 487   include_section_group(Layout*, unsigned int,
 488                         const elfcpp::Shdr<size, big_endian>&,
 489                         std::vector<bool>*);
 490
 491   // Whether to include a linkonce section in the link.
 492   bool
 493   include_linkonce_section(Layout*, const char*,
 494                            const elfcpp::Shdr<size, big_endian>&);
 495
 496   // Views and sizes when relocating.
 497   struct View_size
 498   {
 499     unsigned char* view;
 500     typename elfcpp::Elf_types<size>::Elf_Addr address;
 501     off_t offset;
 502     off_t view_size;
 503   };
 504
 505   typedef std::vector<View_size> Views;
 506
 507   // Write section data to the output file.  Record the views and
 508   // sizes in VIEWS for use when relocating.
 509   void
 510   write_sections(const unsigned char* pshdrs, Output_file*, Views*);
 511
 512   // Relocate the sections in the output file.
 513   void
 514   relocate_sections(const General_options& options, const Symbol_table*,
 515                     const Layout*, const unsigned char* pshdrs, Views*);
 516
 517   // Write out the local symbols.
 518   void
 519   write_local_symbols(Output_file*, const Stringpool*);
 520
 521   // General access to the ELF file.
 522   elfcpp::Elf_file<size, big_endian, Object> elf_file_;
 523   // If non-NULL, a view of the section header data.
 524   File_view* section_headers_;
 525   // Index of SHT_SYMTAB section.
 526   unsigned int symtab_shndx_;
 527   // The number of local symbols.
 528   unsigned int local_symbol_count_;
 529   // The number of local symbols which go into the output file.
 530   unsigned int output_local_symbol_count_;
 531   // The entries in the symbol table for the external symbols.
 532   Symbol** symbols_;
 533   // File offset for local symbols.
 534   off_t local_symbol_offset_;
 535   // Values of local symbols.
 536   typename elfcpp::Elf_types<size>::Elf_Addr *values_;
 537 };
 538
 539 // A class to manage the list of all objects.
 540
 541 class Input_objects
 542 {
 543  public:
 544   Input_objects()
 545     : relobj_list_(), target_(NULL)
 546   { }
 547
 548   // The type of the list of input relocateable objects.
 549   typedef std::vector<Relobj*> Relobj_list;
 550   typedef Relobj_list::const_iterator Relobj_iterator;
 551
 552   // The type of the list of input dynamic objects.
 553   typedef std::vector<Dynobj*> Dynobj_list;
 554   typedef Dynobj_list::const_iterator Dynobj_iterator;
 555
 556   // Add an object to the list.
 557   void
 558   add_object(Object*);
 559
 560   // Get the target we should use for the output file.
 561   Target*
 562   target() const
 563   { return this->target_; }
 564
 565   // Iterate over all regular objects.
 566
 567   Relobj_iterator
 568   relobj_begin() const
 569   { return this->relobj_list_.begin(); }
 570
 571   Relobj_iterator
 572   relobj_end() const
 573   { return this->relobj_list_.end(); }
 574
 575   // Iterate over all dynamic objects.
 576
 577   Dynobj_iterator
 578   dynobj_begin() const
 579   { return this->dynobj_list_.begin(); }
 580
 581   Dynobj_iterator
 582   dynobj_end() const
 583   { return this->dynobj_list_.end(); }
 584
 585   // Return whether we have seen any dynamic objects.
 586   bool
 587   any_dynamic() const
 588   { return !this->dynobj_list_.empty(); }
 589
 590  private:
 591   Input_objects(const Input_objects&);
 592   Input_objects& operator=(const Input_objects&);
 593
 594   Relobj_list relobj_list_;
 595   Dynobj_list dynobj_list_;
 596   Target* target_;
 597 };
 598
 599 // Some of the information we pass to the relocation routines.  We
 600 // group this together to avoid passing a dozen different arguments.
 601
 602 template<int size, bool big_endian>
 603 struct Relocate_info
 604 {
 605   // Command line options.
 606   const General_options* options;
 607   // Symbol table.
 608   const Symbol_table* symtab;
 609   // Layout.
 610   const Layout* layout;
 611   // Object being relocated.
 612   Sized_relobj<size, big_endian>* object;
 613   // Number of local symbols.
 614   unsigned int local_symbol_count;
 615   // Values of local symbols.
 616   typename elfcpp::Elf_types<size>::Elf_Addr *values;
 617   // Global symbols.
 618   Symbol** symbols;
 619   // Section index of relocation section.
 620   unsigned int reloc_shndx;
 621   // Section index of section being relocated.
 622   unsigned int data_shndx;
 623
 624   // Return a string showing the location of a relocation.  This is
 625   // only used for error messages.
 626   std::string
 627   location(size_t relnum, off_t reloffset) const;
 628 };
 629
 630 // Return an Object appropriate for the input file.  P is BYTES long,
 631 // and holds the ELF header.
 632
 633 extern Object*
 634 make_elf_object(const std::string& name, Input_file*,
 635                 off_t offset, const unsigned char* p,
 636                 off_t bytes);
 637
 638 } // end namespace gold
 639
 640 #endif // !defined(GOLD_OBJECT_H)