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 <vector>
   8
   9 #include "elfcpp.h"
  10 #include "fileread.h"
  11 #include "target.h"
  12 #include "symtab.h"
  13
  14 namespace gold
  15 {
  16
  17 class Stringpool;
  18 class Layout;
  19 class Output_section;
  20 class Output_file;
  21
  22 // Data to pass from read_symbols() to add_symbols().
  23
  24 struct Read_symbols_data
  25 {
  26   // Symbol data.
  27   File_view* symbols;
  28   // Size of symbol data in bytes.
  29   off_t symbols_size;
  30   // Symbol names.
  31   File_view* symbol_names;
  32   // Size of symbol name data in bytes.
  33   off_t symbol_names_size;
  34 };
  35
  36 // Object is an interface which represents either a 32-bit or a 64-bit
  37 // input object.  This can be a regular object file (ET_REL) or a
  38 // shared object (ET_DYN).  The actual instantiations are
  39 // Sized_object<32> and Sized_object<64>
  40
  41 class Object
  42 {
  43  public:
  44   // NAME is the name of the object as we would report it to the user
  45   // (e.g., libfoo.a(bar.o) if this is in an archive.  INPUT_FILE is
  46   // used to read the file.  OFFSET is the offset within the input
  47   // file--0 for a .o or .so file, something else for a .a file.
  48   Object(const std::string& name, Input_file* input_file, bool is_dynamic,
  49          off_t offset = 0)
  50     : name_(name), input_file_(input_file), offset_(offset),
  51       shnum_(0), is_dynamic_(is_dynamic), target_(NULL),
  52       map_to_output_()
  53   { }
  54
  55   virtual ~Object()
  56   { }
  57
  58   // Return the name of the object as we would report it to the tuser.
  59   const std::string&
  60   name() const
  61   { return this->name_; }
  62
  63   // Return whether this is a dynamic object.
  64   bool
  65   is_dynamic() const
  66   { return this->is_dynamic_; }
  67
  68   // Return the target structure associated with this object.
  69   Target*
  70   target() const
  71   { return this->target_; }
  72
  73   // Lock the underlying file.
  74   void
  75   lock()
  76   { this->input_file_->file().lock(); }
  77
  78   // Unlock the underlying file.
  79   void
  80   unlock()
  81   { this->input_file_->file().unlock(); }
  82
  83   // Return whether the underlying file is locked.
  84   bool
  85   is_locked() const
  86   { return this->input_file_->file().is_locked(); }
  87
  88 #ifdef HAVE_MEMBER_TEMPLATE_SPECIFICATIONS
  89   // Return the sized target structure associated with this object.
  90   // This is like the target method but it returns a pointer of
  91   // appropriate checked type.
  92   template<int size, bool big_endian>
  93   Sized_target<size, big_endian>*
  94   sized_target();
  95 #endif
  96
  97   // Read the symbol and relocation information.
  98   Read_symbols_data
  99   read_symbols()
 100   { return this->do_read_symbols(); }
 101
 102   // Add symbol information to the global symbol table.
 103   void
 104   add_symbols(Symbol_table* symtab, Read_symbols_data rd)
 105   { this->do_add_symbols(symtab, rd); }
 106
 107   // Pass sections which should be included in the link to the Layout
 108   // object, and record where the sections go in the output file.
 109   void
 110   layout(Layout* lay)
 111   { this->do_layout(lay); }
 112
 113   // Initial local symbol processing: set the offset where local
 114   // symbol information will be stored; add local symbol names to
 115   // *POOL; return the offset following the local symbols.
 116   off_t
 117   finalize_local_symbols(off_t off, Stringpool* pool)
 118   { return this->do_finalize_local_symbols(off, pool); }
 119
 120   // Relocate the input sections and write out the local symbols.
 121   void
 122   relocate(const General_options& options, const Symbol_table* symtab,
 123            const Stringpool* sympool, Output_file* of)
 124   { return this->do_relocate(options, symtab, sympool, of); }
 125
 126   // What we need to know to map an input section to an output
 127   // section.  We keep an array of these, one for each input section,
 128   // indexed by the input section number.
 129   struct Map_to_output
 130   {
 131     // The output section.  This is NULL if the input section is to be
 132     // discarded.
 133     Output_section* output_section;
 134     // The offset within the output section.
 135     off_t offset;
 136   };
 137
 138   // Given a section index, return the corresponding Map_to_output
 139   // information.
 140   const Map_to_output*
 141   section_output_info(unsigned int shnum) const
 142   {
 143     assert(shnum < this->map_to_output_.size());
 144     return &this->map_to_output_[shnum];
 145   }
 146
 147  protected:
 148   // Read the symbols--implemented by child class.
 149   virtual Read_symbols_data
 150   do_read_symbols() = 0;
 151
 152   // Add symbol information to the global symbol table--implemented by
 153   // child class.
 154   virtual void
 155   do_add_symbols(Symbol_table*, Read_symbols_data) = 0;
 156
 157   // Lay out sections--implemented by child class.
 158   virtual void
 159   do_layout(Layout*) = 0;
 160
 161   // Finalize local symbols--implemented by child class.
 162   virtual off_t
 163   do_finalize_local_symbols(off_t, Stringpool*) = 0;
 164
 165   // Relocate the input sections and write out the local
 166   // symbols--implemented by child class.
 167   virtual void
 168   do_relocate(const General_options& options, const Symbol_table* symtab,
 169               const Stringpool*, Output_file* of) = 0;
 170
 171   // Get the file.
 172   Input_file*
 173   input_file() const
 174   { return this->input_file_; }
 175
 176   // Get the offset into the file.
 177   off_t
 178   offset() const
 179   { return this->offset_; }
 180
 181   // Get a view into the underlying file.
 182   const unsigned char*
 183   get_view(off_t start, off_t size);
 184
 185   // Get the number of sections.
 186   unsigned int
 187   shnum() const
 188   { return this->shnum_; }
 189
 190   // Set the number of sections.
 191   void
 192   set_shnum(int shnum)
 193   { this->shnum_ = shnum; }
 194
 195   // Set the target.
 196   void
 197   set_target(Target* target)
 198   { this->target_ = target; }
 199
 200   // Read data from the underlying file.
 201   void
 202   read(off_t start, off_t size, void* p);
 203
 204   // Get a lasting view into the underlying file.
 205   File_view*
 206   get_lasting_view(off_t start, off_t size);
 207
 208   // Return the vector mapping input sections to output sections.
 209   std::vector<Map_to_output>&
 210   map_to_output()
 211   { return this->map_to_output_; }
 212
 213  private:
 214   // This class may not be copied.
 215   Object(const Object&);
 216   Object& operator=(const Object&);
 217
 218   // Name of object as printed to user.
 219   std::string name_;
 220   // For reading the file.
 221   Input_file* input_file_;
 222   // Offset within the file--0 for an object file, non-0 for an
 223   // archive.
 224   off_t offset_;
 225   // Number of input sections.
 226   unsigned int shnum_;
 227   // Whether this is a dynamic object.
 228   bool is_dynamic_;
 229   // Target functions--may be NULL if the target is not known.
 230   Target* target_;
 231   // Mapping from input sections to output section.
 232   std::vector<Map_to_output> map_to_output_;
 233 };
 234
 235 #ifdef HAVE_MEMBER_TEMPLATE_SPECIFICATIONS
 236
 237 // Implement sized_target inline for efficiency.  This approach breaks
 238 // static type checking, but is made safe using asserts.
 239
 240 template<int size, bool big_endian>
 241 inline Sized_target<size, big_endian>*
 242 Object::sized_target()
 243 {
 244   assert(this->target_->get_size() == size);
 245   assert(this->target_->is_big_endian() ? big_endian : !big_endian);
 246   return static_cast<Sized_target<size, big_endian>*>(this->target_);
 247 }
 248
 249 #endif
 250
 251 // A regular object file.  This is size and endian specific.
 252
 253 template<int size, bool big_endian>
 254 class Sized_object : public Object
 255 {
 256  public:
 257   Sized_object(const std::string& name, Input_file* input_file, off_t offset,
 258                const typename elfcpp::Ehdr<size, big_endian>&);
 259
 260   ~Sized_object();
 261
 262   // Set up the object file based on the ELF header.
 263   void
 264   setup(const typename elfcpp::Ehdr<size, big_endian>&);
 265
 266   // Read the symbols.
 267   Read_symbols_data
 268   do_read_symbols();
 269
 270   // Add the symbols to the symbol table.
 271   void
 272   do_add_symbols(Symbol_table*, Read_symbols_data);
 273
 274   // Lay out the input sections.
 275   void
 276   do_layout(Layout*);
 277
 278   // Finalize the local symbols.
 279   off_t
 280   do_finalize_local_symbols(off_t, Stringpool*);
 281
 282   // Relocate the input sections and write out the local symbols.
 283   void
 284   do_relocate(const General_options& options, const Symbol_table* symtab,
 285               const Stringpool*, Output_file* of);
 286
 287   // Return the appropriate Sized_target structure.
 288   Sized_target<size, big_endian>*
 289   sized_target()
 290   {
 291 #ifdef HAVE_MEMBER_TEMPLATE_SPECIFICATIONS
 292     return this->Object::sized_target<size, big_endian>();
 293 #else
 294     return static_cast<Sized_target<size, big_endian>*>(this->target());
 295 #endif
 296   }
 297
 298  private:
 299   // This object may not be copied.
 300   Sized_object(const Sized_object&);
 301   Sized_object& operator=(const Sized_object&);
 302
 303   // For convenience.
 304   typedef Sized_object<size, big_endian> This;
 305   static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size;
 306   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 307   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 308   typedef elfcpp::Shdr<size, big_endian> Shdr;
 309
 310   // Read the section header for section SHNUM.
 311   const unsigned char*
 312   section_header(unsigned int shnum);
 313
 314   // Whether to include a section group in the link.
 315   bool
 316   include_section_group(Layout*, unsigned int,
 317                         const elfcpp::Shdr<size, big_endian>&,
 318                         std::vector<bool>*);
 319
 320   // Whether to include a linkonce section in the link.
 321   bool
 322   include_linkonce_section(Layout*, const char*,
 323                            const elfcpp::Shdr<size, big_endian>&);
 324
 325   // Views and sizes when relocating.
 326   struct View_size
 327   {
 328     unsigned char* view;
 329     typename elfcpp::Elf_types<size>::Elf_Addr address;
 330     off_t offset;
 331     off_t view_size;
 332   };
 333
 334   typedef std::vector<View_size> Views;
 335
 336   // Write section data to the output file.  Record the views and
 337   // sizes in VIEWS for use when relocating.
 338   void
 339   write_sections(const unsigned char* pshdrs, Output_file*, Views*);
 340
 341   // Relocate the sections in the output file.
 342   void
 343   relocate_sections(const Symbol_table*, const unsigned char* pshdrs, Views*);
 344
 345   // Write out the local symbols.
 346   void
 347   write_local_symbols(Output_file*, const Stringpool*);
 348
 349   // ELF file header e_flags field.
 350   unsigned int flags_;
 351   // File offset of section header table.
 352   off_t shoff_;
 353   // Offset of SHT_STRTAB section holding section names.
 354   unsigned int shstrndx_;
 355   // Index of SHT_SYMTAB section.
 356   unsigned int symtab_shnum_;
 357   // The number of local symbols.
 358   unsigned int local_symbol_count_;
 359   // The number of local symbols which go into the output file.
 360   unsigned int output_local_symbol_count_;
 361   // The entries in the symbol table for the external symbols.
 362   Symbol** symbols_;
 363   // File offset for local symbols.
 364   off_t local_symbol_offset_;
 365   // Values of local symbols.
 366   typename elfcpp::Elf_types<size>::Elf_Addr *values_;
 367 };
 368
 369 // A class to manage the list of all objects.
 370
 371 class Input_objects
 372 {
 373  public:
 374   Input_objects()
 375     : object_list_(), target_(NULL), any_dynamic_(false)
 376   { }
 377
 378   // The type of the list of input objects.
 379   typedef std::list<Object*> Object_list;
 380
 381   // Add an object to the list.
 382   void
 383   add_object(Object*);
 384
 385   // Get the target we should use for the output file.
 386   Target*
 387   target() const
 388   { return this->target_; }
 389
 390   // Iterate over all objects.
 391   Object_list::const_iterator
 392   begin() const
 393   { return this->object_list_.begin(); }
 394
 395   Object_list::const_iterator
 396   end() const
 397   { return this->object_list_.end(); }
 398
 399   // Return whether we have seen any dynamic objects.
 400   bool
 401   any_dynamic() const
 402   { return this->any_dynamic_; }
 403
 404  private:
 405   Input_objects(const Input_objects&);
 406   Input_objects& operator=(const Input_objects&);
 407
 408   Object_list object_list_;
 409   Target* target_;
 410   bool any_dynamic_;
 411 };
 412
 413 // Return an Object appropriate for the input file.  P is BYTES long,
 414 // and holds the ELF header.
 415
 416 extern Object*
 417 make_elf_object(const std::string& name, Input_file*,
 418                 off_t offset, const unsigned char* p,
 419                 off_t bytes);
 420
 421 } // end namespace gold
 422
 423 #endif // !defined(GOLD_OBJECT_H)