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   // Like rel(), but sign-extends the value to SIZE.
 196   template<int valsize>
 197   static inline void
 198   signedrel(unsigned char* view,
 199             const Sized_relobj<size, big_endian>* object,
 200             const Symbol_value<size>* psymval)
 201   {
 202     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 203     typedef typename elfcpp::Swap<size, big_endian>::Valtype Sizetype;
 204     Valtype* wv = reinterpret_cast<Valtype*>(view);
 205     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 206     // Fancy formula to sign-extend x to size.
 207     const Sizetype mask = 1U << (sizeof(valsize) * 8 - 1);
 208     Sizetype sign_extended_x = x;
 209     sign_extended_x = (sign_extended_x ^ mask) - mask;
 210     x = psymval->value(object, sign_extended_x);
 211     elfcpp::Swap<valsize, big_endian>::writeval(wv, x);
 212   }
 213
 214   // Do a simple PC relative relocation with the addend in the section
 215   // contents.  VALSIZE is the size of the value.
 216   template<int valsize>
 217   static inline void
 218   pcrel(unsigned char* view,
 219         typename elfcpp::Swap<valsize, big_endian>::Valtype value,
 220         typename elfcpp::Elf_types<size>::Elf_Addr address)
 221   {
 222     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 223     Valtype* wv = reinterpret_cast<Valtype*>(view);
 224     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 225     elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address);
 226   }
 227
 228   // Do a simple PC relative relocation with a Symbol_value with the
 229   // addend in the section contents.  VALSIZE is the size of the
 230   // value.
 231   template<int valsize>
 232   static inline void
 233   pcrel(unsigned char* view,
 234         const Sized_relobj<size, big_endian>* object,
 235         const Symbol_value<size>* psymval,
 236         typename elfcpp::Elf_types<size>::Elf_Addr address)
 237   {
 238     typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype;
 239     Valtype* wv = reinterpret_cast<Valtype*>(view);
 240     Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv);
 241     x = psymval->value(object, x);
 242     elfcpp::Swap<valsize, big_endian>::writeval(wv, x - address);
 243   }
 244
 245   typedef Relocate_functions<size, big_endian> This;
 246
 247 public:
 248   // Do a simple 8-bit REL relocation with the addend in the section
 249   // contents.
 250   static inline void
 251   rel8(unsigned char* view, unsigned char value)
 252   { This::template rel<8>(view, value); }
 253
 254   static inline void
 255   rel8(unsigned char* view,
 256        const Sized_relobj<size, big_endian>* object,
 257        const Symbol_value<size>* psymval)
 258   { This::template rel<8>(view, object, psymval); }
 259
 260   // Do an 8-bit REL relocation, sign extending the addend to SIZE.
 261   static inline void
 262   rel8s(unsigned char* view,
 263          const Sized_relobj<size, big_endian>* object,
 264          const Symbol_value<size>* psymval)
 265   { This::template signedrel<8>(view, object, psymval); }
 266
 267   // Do a simple 8-bit PC relative relocation with the addend in the
 268   // section contents.
 269   static inline void
 270   pcrel8(unsigned char* view, unsigned char value,
 271          typename elfcpp::Elf_types<size>::Elf_Addr address)
 272   { This::template pcrel<8>(view, value, address); }
 273
 274   static inline void
 275   pcrel8(unsigned char* view,
 276          const Sized_relobj<size, big_endian>* object,
 277          const Symbol_value<size>* psymval,
 278          typename elfcpp::Elf_types<size>::Elf_Addr address)
 279   { This::template pcrel<8>(view, object, psymval, address); }
 280
 281   // Do a simple 16-bit REL relocation with the addend in the section
 282   // contents.
 283   static inline void
 284   rel16(unsigned char* view, elfcpp::Elf_Half value)
 285   { This::template rel<16>(view, value); }
 286
 287   static inline void
 288   rel16(unsigned char* view,
 289         const Sized_relobj<size, big_endian>* object,
 290         const Symbol_value<size>* psymval)
 291   { This::template rel<16>(view, object, psymval); }
 292
 293   // Do a 16-bit REL relocation, sign extending the addend to SIZE.
 294   static inline void
 295   rel16s(unsigned char* view,
 296          const Sized_relobj<size, big_endian>* object,
 297          const Symbol_value<size>* psymval)
 298   { This::template signedrel<16>(view, object, psymval); }
 299
 300   // Do a simple 32-bit PC relative REL relocation with the addend in
 301   // the section contents.
 302   static inline void
 303   pcrel16(unsigned char* view, elfcpp::Elf_Word value,
 304           typename elfcpp::Elf_types<size>::Elf_Addr address)
 305   { This::template pcrel<16>(view, value, address); }
 306
 307   static inline void
 308   pcrel16(unsigned char* view,
 309           const Sized_relobj<size, big_endian>* object,
 310           const Symbol_value<size>* psymval,
 311           typename elfcpp::Elf_types<size>::Elf_Addr address)
 312   { This::template pcrel<16>(view, object, psymval, address); }
 313
 314   // Do a simple 32-bit REL relocation with the addend in the section
 315   // contents.
 316   static inline void
 317   rel32(unsigned char* view, elfcpp::Elf_Word value)
 318   { This::template rel<32>(view, value); }
 319
 320   static inline void
 321   rel32(unsigned char* view,
 322         const Sized_relobj<size, big_endian>* object,
 323         const Symbol_value<size>* psymval)
 324   { This::template rel<32>(view, object, psymval); }
 325
 326   // Do a 32-bit REL relocation, sign extending the addend to SIZE.
 327   static inline void
 328   rel32s(unsigned char* view,
 329          const Sized_relobj<size, big_endian>* object,
 330          const Symbol_value<size>* psymval)
 331   { This::template signedrel<32>(view, object, psymval); }
 332
 333   // Do a simple 32-bit PC relative REL relocation with the addend in
 334   // the section contents.
 335   static inline void
 336   pcrel32(unsigned char* view, elfcpp::Elf_Word value,
 337           typename elfcpp::Elf_types<size>::Elf_Addr address)
 338   { This::template pcrel<32>(view, value, address); }
 339
 340   static inline void
 341   pcrel32(unsigned char* view,
 342           const Sized_relobj<size, big_endian>* object,
 343           const Symbol_value<size>* psymval,
 344           typename elfcpp::Elf_types<size>::Elf_Addr address)
 345   { This::template pcrel<32>(view, object, psymval, address); }
 346
 347   // Do a simple 64-bit REL relocation with the addend in the section
 348   // contents.
 349   static inline void
 350   rel64(unsigned char* view, elfcpp::Elf_Xword value)
 351   { This::template rel<64>(view, value); }
 352
 353   static inline void
 354   rel64(unsigned char* view,
 355         const Sized_relobj<size, big_endian>* object,
 356         const Symbol_value<size>* psymval)
 357   { This::template rel<64>(view, object, psymval); }
 358
 359   // Do a simple 64-bit PC relative REL relocation with the addend in
 360   // the section contents.
 361   static inline void
 362   pcrel64(unsigned char* view, elfcpp::Elf_Xword value,
 363           typename elfcpp::Elf_types<size>::Elf_Addr address)
 364   { This::template pcrel<64>(view, value, address); }
 365
 366   static inline void
 367   pcrel64(unsigned char* view,
 368           const Sized_relobj<size, big_endian>* object,
 369           const Symbol_value<size>* psymval,
 370           typename elfcpp::Elf_types<size>::Elf_Addr address)
 371   { This::template pcrel<64>(view, object, psymval, address); }
 372 };
 373
 374 // We try to avoid COPY relocations when possible.  A COPY relocation
 375 // may be required when an executable refers to a variable defined in
 376 // a shared library.  COPY relocations are problematic because they
 377 // tie the executable to the exact size of the variable in the shared
 378 // library.  We can avoid them if all the references to the variable
 379 // are in a writeable section.  In that case we can simply use dynamic
 380 // relocations.  However, when scanning relocs, we don't know when we
 381 // see the relocation whether we will be forced to use a COPY
 382 // relocation or not.  So we have to save the relocation during the
 383 // reloc scanning, and then emit it as a dynamic relocation if
 384 // necessary.  This class implements that.  It is used by the target
 385 // specific code.
 386
 387 template<int size, bool big_endian>
 388 class Copy_relocs
 389 {
 390  public:
 391   Copy_relocs()
 392     : entries_()
 393   { }
 394
 395   // Return whether we need a COPY reloc for a reloc against GSYM,
 396   // which is being applied to section SHNDX in OBJECT.
 397   static bool
 398   need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx,
 399                   Sized_symbol<size>* gsym);
 400
 401   // Save a Rel against SYM for possible emission later.  SHNDX is the
 402   // index of the section to which the reloc is being applied.
 403   void
 404   save(Symbol* sym, Relobj*, unsigned int shndx,
 405        const elfcpp::Rel<size, big_endian>&);
 406
 407   // Save a Rela against SYM for possible emission later.
 408   void
 409   save(Symbol* sym, Relobj*, unsigned int shndx,
 410        const elfcpp::Rela<size, big_endian>&);
 411
 412   // Return whether there are any relocs to emit.  This also discards
 413   // entries which need not be emitted.
 414   bool
 415   any_to_emit();
 416
 417   // Emit relocs for each symbol which did not get a COPY reloc (i.e.,
 418   // is still defined in the dynamic object).
 419   template<int sh_type>
 420   void
 421   emit(Output_data_reloc<sh_type, true, size, big_endian>*);
 422
 423  private:
 424   typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
 425   typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
 426
 427   // This POD class holds the entries we are saving.
 428   class Copy_reloc_entry
 429   {
 430    public:
 431     Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
 432                      Relobj* relobj, unsigned int shndx,
 433                      Address address, Addend addend)
 434       : sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
 435         shndx_(shndx), address_(address), addend_(addend)
 436     { }
 437
 438     // Return whether we should emit this reloc.  If we should not
 439     // emit, we clear it.
 440     bool
 441     should_emit();
 442
 443     // Emit this reloc.
 444
 445     void
 446     emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*);
 447
 448     void
 449     emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*);
 450
 451    private:
 452     Symbol* sym_;
 453     unsigned int reloc_type_;
 454     Relobj* relobj_;
 455     unsigned int shndx_;
 456     Address address_;
 457     Addend addend_;
 458   };
 459
 460   // A list of relocs to be saved.
 461   typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
 462
 463   // The list of relocs we are saving.
 464   Copy_reloc_entries entries_;
 465 };
 466
 467 } // End namespace gold.
 468
 469 #endif // !defined(GOLD_RELOC_H)