gold/reloc.h

   1 // reloc.h -- relocate input files for gold   -*- C++ -*-
   2
   3 // Copyright 2006, 2007 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   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.
  12
  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.
  17
  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.
  22
  23 #ifndef GOLD_RELOC_H
  24 #define GOLD_RELOC_H
  25
  26 #include <byteswap.h>
  27
  28 #include "workqueue.h"
  29
  30 namespace gold
  31 {
  32
  33 class General_options;
  34 class Relobj;
  35 class Read_relocs_data;
  36 class Symbol;
  37 class Layout;
  38
  39 template<int size>
  40 class Sized_symbol;
  41
  42 template<int size, bool big_endian>
  43 class Sized_relobj;
  44
  45 template<int size>
  46 class Symbol_value;
  47
  48 template<int sh_type, bool dynamic, int size, bool big_endian>
  49 class Output_data_reloc;
  50
  51 // A class to read the relocations for an object file, and then queue
  52 // up a task to see if they require any GOT/PLT/COPY relocations in
  53 // the symbol table.
  54
  55 class Read_relocs : public Task
  56 {
  57  public:
  58   // SYMTAB_LOCK is used to lock the symbol table.  BLOCKER should be
  59   // unblocked when the Scan_relocs task completes.
  60   Read_relocs(const General_options& options, Symbol_table* symtab,
  61               Layout* layout, Relobj* object, Task_token* symtab_lock,
  62               Task_token* blocker)
  63     : options_(options), symtab_(symtab), layout_(layout), object_(object),
  64       symtab_lock_(symtab_lock), blocker_(blocker)
  65   { }
  66
  67   // The standard Task methods.
  68
  69   Is_runnable_type
  70   is_runnable(Workqueue*);
  71
  72   Task_locker*
  73   locks(Workqueue*);
  74
  75   void
  76   run(Workqueue*);
  77
  78  private:
  79   const General_options& options_;
  80   Symbol_table* symtab_;
  81   Layout* layout_;
  82   Relobj* object_;
  83   Task_token* symtab_lock_;
  84   Task_token* blocker_;
  85 };
  86
  87 // Scan the relocations for an object to see if they require any
  88 // GOT/PLT/COPY relocations.
  89
  90 class Scan_relocs : public Task
  91 {
  92  public:
  93   // SYMTAB_LOCK is used to lock the symbol table.  BLOCKER should be
  94   // unblocked when the task completes.
  95   Scan_relocs(const General_options& options, Symbol_table* symtab,
  96               Layout* layout, Relobj* object, Read_relocs_data* rd,
  97               Task_token* symtab_lock, Task_token* blocker)
  98     : options_(options), symtab_(symtab), layout_(layout), object_(object),
  99       rd_(rd), symtab_lock_(symtab_lock), blocker_(blocker)
 100   { }
 101
 102   // The standard Task methods.
 103
 104   Is_runnable_type
 105   is_runnable(Workqueue*);
 106
 107   Task_locker*
 108   locks(Workqueue*);
 109
 110   void
 111   run(Workqueue*);
 112
 113  private:
 114   class Scan_relocs_locker;
 115
 116   const General_options& options_;
 117   Symbol_table* symtab_;
 118   Layout* layout_;
 119   Relobj* object_;
 120   Read_relocs_data* rd_;
 121   Task_token* symtab_lock_;
 122   Task_token* blocker_;
 123 };
 124
 125 // A class to perform all the relocations for an object file.
 126
 127 class Relocate_task : public Task
 128 {
 129  public:
 130   Relocate_task(const General_options& options, const Symbol_table* symtab,
 131                 const Layout* layout, Relobj* object, Output_file* of,
 132                 Task_token* final_blocker)
 133     : options_(options), symtab_(symtab), layout_(layout), object_(object),
 134       of_(of), final_blocker_(final_blocker)
 135   { }
 136
 137   // The standard Task methods.
 138
 139   Is_runnable_type
 140   is_runnable(Workqueue*);
 141
 142   Task_locker*
 143   locks(Workqueue*);
 144
 145   void
 146   run(Workqueue*);
 147
 148  private:
 149   class Relocate_locker;
 150
 151   const General_options& options_;
 152   const Symbol_table* symtab_;
 153   const Layout* layout_;
 154   Relobj* object_;
 155   Output_file* of_;
 156   Task_token* final_blocker_;
 157 };
 158
 159 // Standard relocation routines which are used on many targets.  Here
 160 // SIZE and BIG_ENDIAN refer to the target, not the relocation type.
 161
 162 template<int size, bool big_endian>
 163 class Relocate_functions
 164 {
 165 private:
 166   // Do a simple relocation with the addend in the section contents.
 167   // VALSIZE is the size of the value.
 168   template<int valsize>
 169   static inline void
 170   rel(unsigned char* view,
 171       typename elfcpp::Swap<valsize, big_endian>::Valtype value)
 172   {
 173     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 174     Valtype* wv = reinterpret_cast<Valtype*>(view);
 175     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 176     elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value);
 177   }
 178
 179   // Do a simple relocation using a Symbol_value with the addend in
 180   // the section contents.  VALSIZE is the size of the value to
 181   // relocate.
 182   template<int valsize>
 183   static inline void
 184   rel(unsigned char* view,
 185       const Sized_relobj<size, big_endian>* object,
 186       const Symbol_value<size>* psymval)
 187   {
 188     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 189     Valtype* wv = reinterpret_cast<Valtype*>(view);
 190     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 191     x = psymval->value(object, x);
 192     elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
 193   }
 194
 195   // Do a simple relocation with the addend in the relocation.
 196   // VALSIZE is the size of the value.
 197   template<int valsize>
 198   static inline void
 199   rela(unsigned char* view,
 200        typename elfcpp::Swap<valsize, big_endian>::Valtype value,
 201        typename elfcpp::Swap<valsize, big_endian>::Valtype addend)
 202   {
 203     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 204     Valtype* wv = reinterpret_cast<Valtype*>(view);
 205     elfcpp::Swap<valsize, big_endian>::writeval(wv, value + addend);
 206   }
 207
 208   // Do a simple relocation using a symbol value with the addend in
 209   // the relocation.  VALSIZE is the size of the value.
 210   template<int valsize>
 211   static inline void
 212   rela(unsigned char* view,
 213        const Sized_relobj<size, big_endian>* object,
 214        const Symbol_value<size>* psymval,
 215        typename elfcpp::Swap<valsize, big_endian>::Valtype addend)
 216   {
 217     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 218     Valtype* wv = reinterpret_cast<Valtype*>(view);
 219     Valtype x = psymval->value(object, addend);
 220     elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
 221   }
 222
 223   // Do a simple PC relative relocation with the addend in the section
 224   // contents.  VALSIZE is the size of the value.
 225   template<int valsize>
 226   static inline void
 227   pcrel(unsigned char* view,
 228         typename elfcpp::Swap<valsize, big_endian>::Valtype value,
 229         typename elfcpp::Elf_types<size>::Elf_Addr address)
 230   {
 231     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 232     Valtype* wv = reinterpret_cast<Valtype*>(view);
 233     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 234     elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address);
 235   }
 236
 237   // Do a simple PC relative relocation with a Symbol_value with the
 238   // addend in the section contents.  VALSIZE is the size of the
 239   // value.
 240   template<int valsize>
 241   static inline void
 242   pcrel(unsigned char* view,
 243         const Sized_relobj<size, big_endian>* object,
 244         const Symbol_value<size>* psymval,
 245         typename elfcpp::Elf_types<size>::Elf_Addr address)
 246   {
 247     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 248     Valtype* wv = reinterpret_cast<Valtype*>(view);
 249     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 250     x = psymval->value(object, x);
 251     elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
 252   }
 253
 254   // Do a simple PC relative relocation with the addend in the
 255   // relocation.  VALSIZE is the size of the value.
 256   template<int valsize>
 257   static inline void
 258   pcrela(unsigned char* view,
 259          typename elfcpp::Swap<valsize, big_endian>::Valtype value,
 260          typename elfcpp::Swap<valsize, big_endian>::Valtype addend,
 261          typename elfcpp::Elf_types<size>::Elf_Addr address)
 262   {
 263     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 264     Valtype* wv = reinterpret_cast<Valtype*>(view);
 265     elfcpp::Swap<valsize, big_endian>::writeval(wv, value + addend - address);
 266   }
 267
 268   // Do a simple PC relative relocation with a Symbol_value with the
 269   // addend in the relocation.  VALSIZE is the size of the value.
 270   template<int valsize>
 271   static inline void
 272   pcrela(unsigned char* view,
 273          const Sized_relobj<size, big_endian>* object,
 274          const Symbol_value<size>* psymval,
 275          typename elfcpp::Swap<valsize, big_endian>::Valtype addend,
 276          typename elfcpp::Elf_types<size>::Elf_Addr address)
 277   {
 278     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 279     Valtype* wv = reinterpret_cast<Valtype*>(view);
 280     Valtype x = psymval->value(object, addend);
 281     elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
 282   }
 283
 284   typedef Relocate_functions<size, big_endian> This;
 285
 286 public:
 287   // Do a simple 8-bit REL relocation with the addend in the section
 288   // contents.
 289   static inline void
 290   rel8(unsigned char* view, unsigned char value)
 291   { This::template rel<8>(view, value); }
 292
 293   static inline void
 294   rel8(unsigned char* view,
 295        const Sized_relobj<size, big_endian>* object,
 296        const Symbol_value<size>* psymval)
 297   { This::template rel<8>(view, object, psymval); }
 298
 299   // Do an 8-bit RELA relocation with the addend in the relocation.
 300   static inline void
 301   rela8(unsigned char* view, unsigned char value, unsigned char addend)
 302   { This::template rela<8>(view, value, addend); }
 303
 304   static inline void
 305   rela8(unsigned char* view,
 306         const Sized_relobj<size, big_endian>* object,
 307         const Symbol_value<size>* psymval,
 308         unsigned char addend)
 309   { This::template rela<8>(view, object, psymval, addend); }
 310
 311   // Do a simple 8-bit PC relative relocation with the addend in the
 312   // section contents.
 313   static inline void
 314   pcrel8(unsigned char* view, unsigned char value,
 315          typename elfcpp::Elf_types<size>::Elf_Addr address)
 316   { This::template pcrel<8>(view, value, address); }
 317
 318   static inline void
 319   pcrel8(unsigned char* view,
 320          const Sized_relobj<size, big_endian>* object,
 321          const Symbol_value<size>* psymval,
 322          typename elfcpp::Elf_types<size>::Elf_Addr address)
 323   { This::template pcrel<8>(view, object, psymval, address); }
 324
 325   // Do a simple 8-bit PC relative RELA relocation with the addend in
 326   // the reloc.
 327   static inline void
 328   pcrela8(unsigned char* view, unsigned char value, unsigned char addend,
 329           typename elfcpp::Elf_types<size>::Elf_Addr address)
 330   { This::template pcrela<8>(view, value, addend, address); }
 331
 332   static inline void
 333   pcrela8(unsigned char* view,
 334           const Sized_relobj<size, big_endian>* object,
 335           const Symbol_value<size>* psymval,
 336           unsigned char addend,
 337           typename elfcpp::Elf_types<size>::Elf_Addr address)
 338   { This::template pcrela<8>(view, object, psymval, addend, address); }
 339
 340   // Do a simple 16-bit REL relocation with the addend in the section
 341   // contents.
 342   static inline void
 343   rel16(unsigned char* view, elfcpp::Elf_Half value)
 344   { This::template rel<16>(view, value); }
 345
 346   static inline void
 347   rel16(unsigned char* view,
 348         const Sized_relobj<size, big_endian>* object,
 349         const Symbol_value<size>* psymval)
 350   { This::template rel<16>(view, object, psymval); }
 351
 352   // Do an 16-bit RELA relocation with the addend in the relocation.
 353   static inline void
 354   rela16(unsigned char* view, elfcpp::Elf_Half value, elfcpp::Elf_Half addend)
 355   { This::template rela<16>(view, value, addend); }
 356
 357   static inline void
 358   rela16(unsigned char* view,
 359          const Sized_relobj<size, big_endian>* object,
 360          const Symbol_value<size>* psymval,
 361          elfcpp::Elf_Half addend)
 362   { This::template rela<16>(view, object, psymval, addend); }
 363
 364   // Do a simple 16-bit PC relative REL relocation with the addend in
 365   // the section contents.
 366   static inline void
 367   pcrel16(unsigned char* view, elfcpp::Elf_Half value,
 368           typename elfcpp::Elf_types<size>::Elf_Addr address)
 369   { This::template pcrel<16>(view, value, address); }
 370
 371   static inline void
 372   pcrel16(unsigned char* view,
 373           const Sized_relobj<size, big_endian>* object,
 374           const Symbol_value<size>* psymval,
 375           typename elfcpp::Elf_types<size>::Elf_Addr address)
 376   { This::template pcrel<16>(view, object, psymval, address); }
 377
 378   // Do a simple 16-bit PC relative RELA relocation with the addend in
 379   // the reloc.
 380   static inline void
 381   pcrela16(unsigned char* view, elfcpp::Elf_Half value,
 382            elfcpp::Elf_Half addend,
 383            typename elfcpp::Elf_types<size>::Elf_Addr address)
 384   { This::template pcrela<16>(view, value, addend, address); }
 385
 386   static inline void
 387   pcrela16(unsigned char* view,
 388            const Sized_relobj<size, big_endian>* object,
 389            const Symbol_value<size>* psymval,
 390            elfcpp::Elf_Half addend,
 391            typename elfcpp::Elf_types<size>::Elf_Addr address)
 392   { This::template pcrela<16>(view, object, psymval, addend, address); }
 393
 394   // Do a simple 32-bit REL relocation with the addend in the section
 395   // contents.
 396   static inline void
 397   rel32(unsigned char* view, elfcpp::Elf_Word value)
 398   { This::template rel<32>(view, value); }
 399
 400   static inline void
 401   rel32(unsigned char* view,
 402         const Sized_relobj<size, big_endian>* object,
 403         const Symbol_value<size>* psymval)
 404   { This::template rel<32>(view, object, psymval); }
 405
 406   // Do an 32-bit RELA relocation with the addend in the relocation.
 407   static inline void
 408   rela32(unsigned char* view, elfcpp::Elf_Word value, elfcpp::Elf_Word addend)
 409   { This::template rela<32>(view, value, addend); }
 410
 411   static inline void
 412   rela32(unsigned char* view,
 413          const Sized_relobj<size, big_endian>* object,
 414          const Symbol_value<size>* psymval,
 415          elfcpp::Elf_Word addend)
 416   { This::template rela<32>(view, object, psymval, addend); }
 417
 418   // Do a simple 32-bit PC relative REL relocation with the addend in
 419   // the section contents.
 420   static inline void
 421   pcrel32(unsigned char* view, elfcpp::Elf_Word value,
 422           typename elfcpp::Elf_types<size>::Elf_Addr address)
 423   { This::template pcrel<32>(view, value, address); }
 424
 425   static inline void
 426   pcrel32(unsigned char* view,
 427           const Sized_relobj<size, big_endian>* object,
 428           const Symbol_value<size>* psymval,
 429           typename elfcpp::Elf_types<size>::Elf_Addr address)
 430   { This::template pcrel<32>(view, object, psymval, address); }
 431
 432   // Do a simple 32-bit PC relative RELA relocation with the addend in
 433   // the relocation.
 434   static inline void
 435   pcrela32(unsigned char* view, elfcpp::Elf_Word value,
 436            elfcpp::Elf_Word addend,
 437            typename elfcpp::Elf_types<size>::Elf_Addr address)
 438   { This::template pcrela<32>(view, value, addend, address); }
 439
 440   static inline void
 441   pcrela32(unsigned char* view,
 442            const Sized_relobj<size, big_endian>* object,
 443            const Symbol_value<size>* psymval,
 444            elfcpp::Elf_Word addend,
 445            typename elfcpp::Elf_types<size>::Elf_Addr address)
 446   { This::template pcrela<32>(view, object, psymval, addend, address); }
 447
 448   // Do a simple 64-bit REL relocation with the addend in the section
 449   // contents.
 450   static inline void
 451   rel64(unsigned char* view, elfcpp::Elf_Xword value)
 452   { This::template rel<64>(view, value); }
 453
 454   static inline void
 455   rel64(unsigned char* view,
 456         const Sized_relobj<size, big_endian>* object,
 457         const Symbol_value<size>* psymval)
 458   { This::template rel<64>(view, object, psymval); }
 459
 460   // Do a 64-bit RELA relocation with the addend in the relocation.
 461   static inline void
 462   rela64(unsigned char* view, elfcpp::Elf_Xword value,
 463          elfcpp::Elf_Xword addend)
 464   { This::template rela<64>(view, value, addend); }
 465
 466   static inline void
 467   rela64(unsigned char* view,
 468          const Sized_relobj<size, big_endian>* object,
 469          const Symbol_value<size>* psymval,
 470          elfcpp::Elf_Xword addend)
 471   { This::template rela<64>(view, object, psymval, addend); }
 472
 473   // Do a simple 64-bit PC relative REL relocation with the addend in
 474   // the section contents.
 475   static inline void
 476   pcrel64(unsigned char* view, elfcpp::Elf_Xword value,
 477           typename elfcpp::Elf_types<size>::Elf_Addr address)
 478   { This::template pcrel<64>(view, value, address); }
 479
 480   static inline void
 481   pcrel64(unsigned char* view,
 482           const Sized_relobj<size, big_endian>* object,
 483           const Symbol_value<size>* psymval,
 484           typename elfcpp::Elf_types<size>::Elf_Addr address)
 485   { This::template pcrel<64>(view, object, psymval, address); }
 486
 487   // Do a simple 64-bit PC relative RELA relocation with the addend in
 488   // the relocation.
 489   static inline void
 490   pcrela64(unsigned char* view, elfcpp::Elf_Xword value,
 491            elfcpp::Elf_Xword addend,
 492            typename elfcpp::Elf_types<size>::Elf_Addr address)
 493   { This::template pcrela<64>(view, value, addend, address); }
 494
 495   static inline void
 496   pcrela64(unsigned char* view,
 497            const Sized_relobj<size, big_endian>* object,
 498            const Symbol_value<size>* psymval,
 499            elfcpp::Elf_Xword addend,
 500            typename elfcpp::Elf_types<size>::Elf_Addr address)
 501   { This::template pcrela<64>(view, object, psymval, addend, address); }
 502 };
 503
 504 // We try to avoid COPY relocations when possible.  A COPY relocation
 505 // may be required when an executable refers to a variable defined in
 506 // a shared library.  COPY relocations are problematic because they
 507 // tie the executable to the exact size of the variable in the shared
 508 // library.  We can avoid them if all the references to the variable
 509 // are in a writeable section.  In that case we can simply use dynamic
 510 // relocations.  However, when scanning relocs, we don't know when we
 511 // see the relocation whether we will be forced to use a COPY
 512 // relocation or not.  So we have to save the relocation during the
 513 // reloc scanning, and then emit it as a dynamic relocation if
 514 // necessary.  This class implements that.  It is used by the target
 515 // specific code.
 516
 517 template<int size, bool big_endian>
 518 class Copy_relocs
 519 {
 520  public:
 521   Copy_relocs()
 522     : entries_()
 523   { }
 524
 525   // Return whether we need a COPY reloc for a reloc against GSYM,
 526   // which is being applied to section SHNDX in OBJECT.
 527   static bool
 528   need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx,
 529                   Sized_symbol<size>* gsym);
 530
 531   // Save a Rel against SYM for possible emission later.  SHNDX is the
 532   // index of the section to which the reloc is being applied.
 533   void
 534   save(Symbol* sym, Relobj*, unsigned int shndx,
 535        const elfcpp::Rel<size, big_endian>&);
 536
 537   // Save a Rela against SYM for possible emission later.
 538   void
 539   save(Symbol* sym, Relobj*, unsigned int shndx,
 540        const elfcpp::Rela<size, big_endian>&);
 541
 542   // Return whether there are any relocs to emit.  This also discards
 543   // entries which need not be emitted.
 544   bool
 545   any_to_emit();
 546
 547   // Emit relocs for each symbol which did not get a COPY reloc (i.e.,
 548   // is still defined in the dynamic object).
 549   template<int sh_type>
 550   void
 551   emit(Output_data_reloc<sh_type, true, size, big_endian>*);
 552
 553  private:
 554   typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
 555   typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
 556
 557   // This POD class holds the entries we are saving.
 558   class Copy_reloc_entry
 559   {
 560    public:
 561     Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
 562                      Relobj* relobj, unsigned int shndx,
 563                      Address address, Addend addend)
 564       : sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
 565         shndx_(shndx), address_(address), addend_(addend)
 566     { }
 567
 568     // Return whether we should emit this reloc.  If we should not
 569     // emit, we clear it.
 570     bool
 571     should_emit();
 572
 573     // Emit this reloc.
 574
 575     void
 576     emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*);
 577
 578     void
 579     emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*);
 580
 581    private:
 582     Symbol* sym_;
 583     unsigned int reloc_type_;
 584     Relobj* relobj_;
 585     unsigned int shndx_;
 586     Address address_;
 587     Addend addend_;
 588   };
 589
 590   // A list of relocs to be saved.
 591   typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
 592
 593   // The list of relocs we are saving.
 594   Copy_reloc_entries entries_;
 595 };
 596
 597 } // End namespace gold.
 598
 599 #endif // !defined(GOLD_RELOC_H)