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