gold/reloc.h

   1 // reloc.h -- relocate input files for gold   -*- C++ -*-
   2
   3 #ifndef GOLD_RELOC_H
   4 #define GOLD_RELOC_H
   5
   6 #include <byteswap.h>
   7
   8 #include "workqueue.h"
   9
  10 namespace gold
  11 {
  12
  13 class General_options;
  14 class Relobj;
  15 class Read_relocs_data;
  16 class Symbol;
  17 class Layout;
  18
  19 template<int size>
  20 class Sized_symbol;
  21
  22 template<int size, bool big_endian>
  23 class Sized_relobj;
  24
  25 template<int size>
  26 class Symbol_value;
  27
  28 template<int sh_type, bool dynamic, int size, bool big_endian>
  29 class Output_data_reloc;
  30
  31 // A class to read the relocations for an object file, and then queue
  32 // up a task to see if they require any GOT/PLT/COPY relocations in
  33 // the symbol table.
  34
  35 class Read_relocs : public Task
  36 {
  37  public:
  38   // SYMTAB_LOCK is used to lock the symbol table.  BLOCKER should be
  39   // unblocked when the Scan_relocs task completes.
  40   Read_relocs(const General_options& options, Symbol_table* symtab,
  41               Layout* layout, Relobj* object, Task_token* symtab_lock,
  42               Task_token* blocker)
  43     : options_(options), symtab_(symtab), layout_(layout), object_(object),
  44       symtab_lock_(symtab_lock), blocker_(blocker)
  45   { }
  46
  47   // The standard Task methods.
  48
  49   Is_runnable_type
  50   is_runnable(Workqueue*);
  51
  52   Task_locker*
  53   locks(Workqueue*);
  54
  55   void
  56   run(Workqueue*);
  57
  58  private:
  59   const General_options& options_;
  60   Symbol_table* symtab_;
  61   Layout* layout_;
  62   Relobj* object_;
  63   Task_token* symtab_lock_;
  64   Task_token* blocker_;
  65 };
  66
  67 // Scan the relocations for an object to see if they require any
  68 // GOT/PLT/COPY relocations.
  69
  70 class Scan_relocs : public Task
  71 {
  72  public:
  73   // SYMTAB_LOCK is used to lock the symbol table.  BLOCKER should be
  74   // unblocked when the task completes.
  75   Scan_relocs(const General_options& options, Symbol_table* symtab,
  76               Layout* layout, Relobj* object, Read_relocs_data* rd,
  77               Task_token* symtab_lock, Task_token* blocker)
  78     : options_(options), symtab_(symtab), layout_(layout), object_(object),
  79       rd_(rd), symtab_lock_(symtab_lock), blocker_(blocker)
  80   { }
  81
  82   // The standard Task methods.
  83
  84   Is_runnable_type
  85   is_runnable(Workqueue*);
  86
  87   Task_locker*
  88   locks(Workqueue*);
  89
  90   void
  91   run(Workqueue*);
  92
  93  private:
  94   class Scan_relocs_locker;
  95
  96   const General_options& options_;
  97   Symbol_table* symtab_;
  98   Layout* layout_;
  99   Relobj* object_;
 100   Read_relocs_data* rd_;
 101   Task_token* symtab_lock_;
 102   Task_token* blocker_;
 103 };
 104
 105 // A class to perform all the relocations for an object file.
 106
 107 class Relocate_task : public Task
 108 {
 109  public:
 110   Relocate_task(const General_options& options, const Symbol_table* symtab,
 111                 const Layout* layout, Relobj* object, Output_file* of,
 112                 Task_token* final_blocker)
 113     : options_(options), symtab_(symtab), layout_(layout), object_(object),
 114       of_(of), final_blocker_(final_blocker)
 115   { }
 116
 117   // The standard Task methods.
 118
 119   Is_runnable_type
 120   is_runnable(Workqueue*);
 121
 122   Task_locker*
 123   locks(Workqueue*);
 124
 125   void
 126   run(Workqueue*);
 127
 128  private:
 129   class Relocate_locker;
 130
 131   const General_options& options_;
 132   const Symbol_table* symtab_;
 133   const Layout* layout_;
 134   Relobj* object_;
 135   Output_file* of_;
 136   Task_token* final_blocker_;
 137 };
 138
 139 // Standard relocation routines which are used on many targets.  Here
 140 // SIZE and BIG_ENDIAN refer to the target, not the relocation type.
 141
 142 template<int size, bool big_endian>
 143 class Relocate_functions
 144 {
 145 private:
 146   // Do a simple relocation with the addend in the section contents.
 147   // VALSIZE is the size of the value.
 148   template<int valsize>
 149   static inline void
 150   rel(unsigned char* view,
 151       typename elfcpp::Swap<valsize, big_endian>::Valtype value)
 152   {
 153     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 154     Valtype* wv = reinterpret_cast<Valtype*>(view);
 155     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 156     elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value);
 157   }
 158
 159   // Do a simple relocation using a Symbol_value with the addend in
 160   // the section contents.  VALSIZE is the size of the value to
 161   // relocate.
 162   template<int valsize>
 163   static inline void
 164   rel(unsigned char* view,
 165       const Sized_relobj<size, big_endian>* object,
 166       const Symbol_value<size>* psymval)
 167   {
 168     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 169     Valtype* wv = reinterpret_cast<Valtype*>(view);
 170     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 171     x = psymval->value(object, x);
 172     elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
 173   }
 174
 175   // Do a simple PC relative relocation with the addend in the section
 176   // contents.  VALSIZE is the size of the value.
 177   template<int valsize>
 178   static inline void
 179   pcrel(unsigned char* view,
 180         typename elfcpp::Swap<valsize, big_endian>::Valtype value,
 181         typename elfcpp::Elf_types<size>::Elf_Addr address)
 182   {
 183     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 184     Valtype* wv = reinterpret_cast<Valtype*>(view);
 185     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 186     elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address);
 187   }
 188
 189   // Do a simple PC relative relocation with a Symbol_value with the
 190   // addend in the section contents.  VALSIZE is the size of the
 191   // value.
 192   template<int valsize>
 193   static inline void
 194   pcrel(unsigned char* view,
 195         const Sized_relobj<size, big_endian>* object,
 196         const Symbol_value<size>* psymval,
 197         typename elfcpp::Elf_types<size>::Elf_Addr address)
 198   {
 199     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 200     Valtype* wv = reinterpret_cast<Valtype*>(view);
 201     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 202     x = psymval->value(object, x);
 203     elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
 204   }
 205
 206   typedef Relocate_functions<size, big_endian> This;
 207
 208 public:
 209   // Do a simple 8-bit REL relocation with the addend in the section
 210   // contents.
 211   static inline void
 212   rel8(unsigned char* view, unsigned char value)
 213   { This::template rel<8>(view, value); }
 214
 215   static inline void
 216   rel8(unsigned char* view,
 217        const Sized_relobj<size, big_endian>* object,
 218        const Symbol_value<size>* psymval)
 219   { This::template rel<8>(view, object, psymval); }
 220
 221   // Do a simple 8-bit PC relative relocation with the addend in the
 222   // section contents.
 223   static inline void
 224   pcrel8(unsigned char* view, unsigned char value,
 225          typename elfcpp::Elf_types<size>::Elf_Addr address)
 226   { This::template pcrel<8>(view, value, address); }
 227
 228   static inline void
 229   pcrel8(unsigned char* view,
 230          const Sized_relobj<size, big_endian>* object,
 231          const Symbol_value<size>* psymval,
 232          typename elfcpp::Elf_types<size>::Elf_Addr address)
 233   { This::template pcrel<8>(view, object, psymval, address); }
 234
 235   // Do a simple 16-bit REL relocation with the addend in the section
 236   // contents.
 237   static inline void
 238   rel16(unsigned char* view, elfcpp::Elf_Half value)
 239   { This::template rel<16>(view, value); }
 240
 241   static inline void
 242   rel16(unsigned char* view,
 243         const Sized_relobj<size, big_endian>* object,
 244         const Symbol_value<size>* psymval)
 245   { This::template rel<16>(view, object, psymval); }
 246
 247   // Do a simple 32-bit PC relative REL relocation with the addend in
 248   // the section contents.
 249   static inline void
 250   pcrel16(unsigned char* view, elfcpp::Elf_Word value,
 251           typename elfcpp::Elf_types<size>::Elf_Addr address)
 252   { This::template pcrel<16>(view, value, address); }
 253
 254   static inline void
 255   pcrel16(unsigned char* view,
 256           const Sized_relobj<size, big_endian>* object,
 257           const Symbol_value<size>* psymval,
 258           typename elfcpp::Elf_types<size>::Elf_Addr address)
 259   { This::template pcrel<16>(view, object, psymval, address); }
 260
 261   // Do a simple 32-bit REL relocation with the addend in the section
 262   // contents.
 263   static inline void
 264   rel32(unsigned char* view, elfcpp::Elf_Word value)
 265   { This::template rel<32>(view, value); }
 266
 267   static inline void
 268   rel32(unsigned char* view,
 269         const Sized_relobj<size, big_endian>* object,
 270         const Symbol_value<size>* psymval)
 271   { This::template rel<32>(view, object, psymval); }
 272
 273   // Do a simple 32-bit PC relative REL relocation with the addend in
 274   // the section contents.
 275   static inline void
 276   pcrel32(unsigned char* view, elfcpp::Elf_Word value,
 277           typename elfcpp::Elf_types<size>::Elf_Addr address)
 278   { This::template pcrel<32>(view, value, address); }
 279
 280   static inline void
 281   pcrel32(unsigned char* view,
 282           const Sized_relobj<size, big_endian>* object,
 283           const Symbol_value<size>* psymval,
 284           typename elfcpp::Elf_types<size>::Elf_Addr address)
 285   { This::template pcrel<32>(view, object, psymval, address); }
 286
 287   // Do a simple 64-bit REL relocation with the addend in the section
 288   // contents.
 289   static inline void
 290   rel64(unsigned char* view, elfcpp::Elf_Xword value)
 291   { This::template rel<64>(view, value); }
 292
 293   static inline void
 294   rel64(unsigned char* view,
 295         const Sized_relobj<size, big_endian>* object,
 296         const Symbol_value<size>* psymval)
 297   { This::template rel<64>(view, object, psymval); }
 298
 299   // Do a simple 64-bit PC relative REL relocation with the addend in
 300   // the section contents.
 301   static inline void
 302   pcrel64(unsigned char* view, elfcpp::Elf_Xword value,
 303           typename elfcpp::Elf_types<size>::Elf_Addr address)
 304   { This::template pcrel<64>(view, value, address); }
 305
 306   static inline void
 307   pcrel64(unsigned char* view,
 308           const Sized_relobj<size, big_endian>* object,
 309           const Symbol_value<size>* psymval,
 310           typename elfcpp::Elf_types<size>::Elf_Addr address)
 311   { This::template pcrel<64>(view, object, psymval, address); }
 312 };
 313
 314 // We try to avoid COPY relocations when possible.  A COPY relocation
 315 // may be required when an executable refers to a variable defined in
 316 // a shared library.  COPY relocations are problematic because they
 317 // tie the executable to the exact size of the variable in the shared
 318 // library.  We can avoid them if all the references to the variable
 319 // are in a writeable section.  In that case we can simply use dynamic
 320 // relocations.  However, when scanning relocs, we don't know when we
 321 // see the relocation whether we will be forced to use a COPY
 322 // relocation or not.  So we have to save the relocation during the
 323 // reloc scanning, and then emit it as a dynamic relocation if
 324 // necessary.  This class implements that.  It is used by the target
 325 // specific code.
 326
 327 template<int size, bool big_endian>
 328 class Copy_relocs
 329 {
 330  public:
 331   Copy_relocs()
 332     : entries_()
 333   { }
 334
 335   // Return whether we need a COPY reloc for a reloc against GSYM,
 336   // which is being applied to section SHNDX in OBJECT.
 337   static bool
 338   need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx,
 339                   Sized_symbol<size>* gsym);
 340
 341   // Save a Rel against SYM for possible emission later.  SHNDX is the
 342   // index of the section to which the reloc is being applied.
 343   void
 344   save(Symbol* sym, Relobj*, unsigned int shndx,
 345        const elfcpp::Rel<size, big_endian>&);
 346
 347   // Save a Rela against SYM for possible emission later.
 348   void
 349   save(Symbol* sym, Relobj*, unsigned int shndx,
 350        const elfcpp::Rela<size, big_endian>&);
 351
 352   // Return whether there are any relocs to emit.  This also discards
 353   // entries which need not be emitted.
 354   bool
 355   any_to_emit();
 356
 357   // Emit relocs for each symbol which did not get a COPY reloc (i.e.,
 358   // is still defined in the dynamic object).
 359   template<int sh_type>
 360   void
 361   emit(Output_data_reloc<sh_type, true, size, big_endian>*);
 362
 363  private:
 364   typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
 365   typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
 366
 367   // This POD class holds the entries we are saving.
 368   class Copy_reloc_entry
 369   {
 370    public:
 371     Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
 372                      Relobj* relobj, unsigned int shndx,
 373                      Address address, Addend addend)
 374       : sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
 375         shndx_(shndx), address_(address), addend_(addend)
 376     { }
 377
 378     // Return whether we should emit this reloc.  If we should not
 379     // emit, we clear it.
 380     bool
 381     should_emit();
 382
 383     // Emit this reloc.
 384
 385     void
 386     emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*);
 387
 388     void
 389     emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*);
 390
 391    private:
 392     Symbol* sym_;
 393     unsigned int reloc_type_;
 394     Relobj* relobj_;
 395     unsigned int shndx_;
 396     Address address_;
 397     Addend addend_;
 398   };
 399
 400   // A list of relocs to be saved.
 401   typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
 402
 403   // The list of relocs we are saving.
 404   Copy_reloc_entries entries_;
 405 };
 406
 407 } // End namespace gold.
 408
 409 #endif // !defined(GOLD_RELOC_H)