gold/x86_64.cc

   1 // x86_64.cc -- x86_64 target support for gold.
   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
   9 // modify it under the terms of the GNU Library General Public License
  10 // as published by the Free Software Foundation; either version 2, or
  11 // (at your option) any later version.
  12
  13 // In addition to the permissions in the GNU Library General Public
  14 // License, the Free Software Foundation gives you unlimited
  15 // permission to link the compiled version of this file into
  16 // combinations with other programs, and to distribute those
  17 // combinations without any restriction coming from the use of this
  18 // file.  (The Library Public License restrictions do apply in other
  19 // respects; for example, they cover modification of the file, and
  20 /// distribution when not linked into a combined executable.)
  21
  22 // This program is distributed in the hope that it will be useful, but
  23 // WITHOUT ANY WARRANTY; without even the implied warranty of
  24 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  25 // Library General Public License for more details.
  26
  27 // You should have received a copy of the GNU Library General Public
  28 // License along with this program; if not, write to the Free Software
  29 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
  30 // 02110-1301, USA.
  31
  32 #include "gold.h"
  33
  34 #include <cstring>
  35
  36 #include "elfcpp.h"
  37 #include "parameters.h"
  38 #include "reloc.h"
  39 #include "x86_64.h"
  40 #include "object.h"
  41 #include "symtab.h"
  42 #include "layout.h"
  43 #include "output.h"
  44 #include "target.h"
  45 #include "target-reloc.h"
  46 #include "target-select.h"
  47 #include "tls.h"
  48
  49 namespace
  50 {
  51
  52 using namespace gold;
  53
  54 class Output_data_plt_x86_64;
  55
  56 // The x86_64 target class.
  57 // See the ABI at
  58 //   http://www.x86-64.org/documentation/abi.pdf
  59 // TLS info comes from
  60 //   http://people.redhat.com/drepper/tls.pdf
  61 //   http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt
  62
  63 class Target_x86_64 : public Sized_target<64, false>
  64 {
  65  public:
  66   // In the x86_64 ABI (p 68), it says "The AMD64 ABI architectures
  67   // uses only Elf64_Rela relocation entries with explicit addends."
  68   typedef Output_data_reloc<elfcpp::SHT_RELA, true, 64, false> Reloc_section;
  69
  70   Target_x86_64()
  71     : Sized_target<64, false>(&x86_64_info),
  72       got_(NULL), plt_(NULL), got_plt_(NULL), rela_dyn_(NULL),
  73       copy_relocs_(NULL), dynbss_(NULL)
  74   { }
  75
  76   // Scan the relocations to look for symbol adjustments.
  77   void
  78   scan_relocs(const General_options& options,
  79               Symbol_table* symtab,
  80               Layout* layout,
  81               Sized_relobj<64, false>* object,
  82               unsigned int data_shndx,
  83               unsigned int sh_type,
  84               const unsigned char* prelocs,
  85               size_t reloc_count,
  86               Output_section* output_section,
  87               bool needs_special_offset_handling,
  88               size_t local_symbol_count,
  89               const unsigned char* plocal_symbols);
  90
  91   // Finalize the sections.
  92   void
  93   do_finalize_sections(Layout*);
  94
  95   // Return the value to use for a dynamic which requires special
  96   // treatment.
  97   uint64_t
  98   do_dynsym_value(const Symbol*) const;
  99
 100   // Relocate a section.
 101   void
 102   relocate_section(const Relocate_info<64, false>*,
 103                    unsigned int sh_type,
 104                    const unsigned char* prelocs,
 105                    size_t reloc_count,
 106                    Output_section* output_section,
 107                    bool needs_special_offset_handling,
 108                    unsigned char* view,
 109                    elfcpp::Elf_types<64>::Elf_Addr view_address,
 110                    off_t view_size);
 111
 112   // Return a string used to fill a code section with nops.
 113   std::string
 114   do_code_fill(off_t length);
 115
 116   // Return whether SYM is defined by the ABI.
 117   bool
 118   do_is_defined_by_abi(Symbol* sym) const
 119   { return strcmp(sym->name(), "__tls_get_addr") == 0; }
 120
 121   // Return the size of the GOT section.
 122   off_t
 123   got_size()
 124   {
 125     gold_assert(this->got_ != NULL);
 126     return this->got_->data_size();
 127   }
 128
 129  private:
 130   // The class which scans relocations.
 131   struct Scan
 132   {
 133     inline void
 134     local(const General_options& options, Symbol_table* symtab,
 135           Layout* layout, Target_x86_64* target,
 136           Sized_relobj<64, false>* object,
 137           unsigned int data_shndx,
 138           Output_section* output_section,
 139           const elfcpp::Rela<64, false>& reloc, unsigned int r_type,
 140           const elfcpp::Sym<64, false>& lsym);
 141
 142     inline void
 143     global(const General_options& options, Symbol_table* symtab,
 144            Layout* layout, Target_x86_64* target,
 145            Sized_relobj<64, false>* object,
 146            unsigned int data_shndx,
 147            Output_section* output_section,
 148            const elfcpp::Rela<64, false>& reloc, unsigned int r_type,
 149            Symbol* gsym);
 150
 151     static void
 152     unsupported_reloc_local(Sized_relobj<64, false>*, unsigned int r_type);
 153
 154     static void
 155     unsupported_reloc_global(Sized_relobj<64, false>*, unsigned int r_type,
 156                              Symbol*);
 157   };
 158
 159   // The class which implements relocation.
 160   class Relocate
 161   {
 162    public:
 163     Relocate()
 164       : skip_call_tls_get_addr_(false)
 165     { }
 166
 167     ~Relocate()
 168     {
 169       if (this->skip_call_tls_get_addr_)
 170         {
 171           // FIXME: This needs to specify the location somehow.
 172           gold_error(_("missing expected TLS relocation"));
 173         }
 174     }
 175
 176     // Do a relocation.  Return false if the caller should not issue
 177     // any warnings about this relocation.
 178     inline bool
 179     relocate(const Relocate_info<64, false>*, Target_x86_64*, size_t relnum,
 180              const elfcpp::Rela<64, false>&,
 181              unsigned int r_type, const Sized_symbol<64>*,
 182              const Symbol_value<64>*,
 183              unsigned char*, elfcpp::Elf_types<64>::Elf_Addr,
 184              off_t);
 185
 186    private:
 187     // Do a TLS relocation.
 188     inline void
 189     relocate_tls(const Relocate_info<64, false>*, size_t relnum,
 190                  const elfcpp::Rela<64, false>&,
 191                  unsigned int r_type, const Sized_symbol<64>*,
 192                  const Symbol_value<64>*,
 193                  unsigned char*, elfcpp::Elf_types<64>::Elf_Addr, off_t);
 194
 195     // Do a TLS General-Dynamic to Local-Exec transition.
 196     inline void
 197     tls_gd_to_le(const Relocate_info<64, false>*, size_t relnum,
 198                  Output_segment* tls_segment,
 199                  const elfcpp::Rela<64, false>&, unsigned int r_type,
 200                  elfcpp::Elf_types<64>::Elf_Addr value,
 201                  unsigned char* view,
 202                  off_t view_size);
 203
 204     // Do a TLS Local-Dynamic to Local-Exec transition.
 205     inline void
 206     tls_ld_to_le(const Relocate_info<64, false>*, size_t relnum,
 207                  Output_segment* tls_segment,
 208                  const elfcpp::Rela<64, false>&, unsigned int r_type,
 209                  elfcpp::Elf_types<64>::Elf_Addr value,
 210                  unsigned char* view,
 211                  off_t view_size);
 212
 213     // Do a TLS Initial-Exec to Local-Exec transition.
 214     static inline void
 215     tls_ie_to_le(const Relocate_info<64, false>*, size_t relnum,
 216                  Output_segment* tls_segment,
 217                  const elfcpp::Rela<64, false>&, unsigned int r_type,
 218                  elfcpp::Elf_types<64>::Elf_Addr value,
 219                  unsigned char* view,
 220                  off_t view_size);
 221
 222     // This is set if we should skip the next reloc, which should be a
 223     // PLT32 reloc against ___tls_get_addr.
 224     bool skip_call_tls_get_addr_;
 225   };
 226
 227   // Adjust TLS relocation type based on the options and whether this
 228   // is a local symbol.
 229   static tls::Tls_optimization
 230   optimize_tls_reloc(bool is_final, int r_type);
 231
 232   // Get the GOT section, creating it if necessary.
 233   Output_data_got<64, false>*
 234   got_section(Symbol_table*, Layout*);
 235
 236   // Get the GOT PLT section.
 237   Output_data_space*
 238   got_plt_section() const
 239   {
 240     gold_assert(this->got_plt_ != NULL);
 241     return this->got_plt_;
 242   }
 243
 244   // Create a PLT entry for a global symbol.
 245   void
 246   make_plt_entry(Symbol_table*, Layout*, Symbol*);
 247
 248   // Get the PLT section.
 249   Output_data_plt_x86_64*
 250   plt_section() const
 251   {
 252     gold_assert(this->plt_ != NULL);
 253     return this->plt_;
 254   }
 255
 256   // Get the dynamic reloc section, creating it if necessary.
 257   Reloc_section*
 258   rela_dyn_section(Layout*);
 259
 260   // Return true if the symbol may need a COPY relocation.
 261   // References from an executable object to non-function symbols
 262   // defined in a dynamic object may need a COPY relocation.
 263   bool
 264   may_need_copy_reloc(Symbol* gsym)
 265   {
 266     return (!parameters->output_is_shared()
 267             && gsym->is_from_dynobj()
 268             && gsym->type() != elfcpp::STT_FUNC);
 269   }
 270
 271   // Copy a relocation against a global symbol.
 272   void
 273   copy_reloc(const General_options*, Symbol_table*, Layout*,
 274              Sized_relobj<64, false>*, unsigned int,
 275              Output_section*, Symbol*, const elfcpp::Rela<64, false>&);
 276
 277   // Information about this specific target which we pass to the
 278   // general Target structure.
 279   static const Target::Target_info x86_64_info;
 280
 281   // The GOT section.
 282   Output_data_got<64, false>* got_;
 283   // The PLT section.
 284   Output_data_plt_x86_64* plt_;
 285   // The GOT PLT section.
 286   Output_data_space* got_plt_;
 287   // The dynamic reloc section.
 288   Reloc_section* rela_dyn_;
 289   // Relocs saved to avoid a COPY reloc.
 290   Copy_relocs<64, false>* copy_relocs_;
 291   // Space for variables copied with a COPY reloc.
 292   Output_data_space* dynbss_;
 293 };
 294
 295 const Target::Target_info Target_x86_64::x86_64_info =
 296 {
 297   64,                   // size
 298   false,                // is_big_endian
 299   elfcpp::EM_X86_64,    // machine_code
 300   false,                // has_make_symbol
 301   false,                // has_resolve
 302   true,                 // has_code_fill
 303   true,                 // is_default_stack_executable
 304   "/lib/ld64.so.1",     // program interpreter
 305   0x400000,             // default_text_segment_address
 306   0x1000,               // abi_pagesize
 307   0x1000                // common_pagesize
 308 };
 309
 310 // Get the GOT section, creating it if necessary.
 311
 312 Output_data_got<64, false>*
 313 Target_x86_64::got_section(Symbol_table* symtab, Layout* layout)
 314 {
 315   if (this->got_ == NULL)
 316     {
 317       gold_assert(symtab != NULL && layout != NULL);
 318
 319       this->got_ = new Output_data_got<64, false>();
 320
 321       layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
 322                                       elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
 323                                       this->got_);
 324
 325       // The old GNU linker creates a .got.plt section.  We just
 326       // create another set of data in the .got section.  Note that we
 327       // always create a PLT if we create a GOT, although the PLT
 328       // might be empty.
 329       this->got_plt_ = new Output_data_space(8);
 330       layout->add_output_section_data(".got", elfcpp::SHT_PROGBITS,
 331                                       elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
 332                                       this->got_plt_);
 333
 334       // The first three entries are reserved.
 335       this->got_plt_->set_current_data_size(3 * 8);
 336
 337       // Define _GLOBAL_OFFSET_TABLE_ at the start of the PLT.
 338       symtab->define_in_output_data(this, "_GLOBAL_OFFSET_TABLE_", NULL,
 339                                     this->got_plt_,
 340                                     0, 0, elfcpp::STT_OBJECT,
 341                                     elfcpp::STB_LOCAL,
 342                                     elfcpp::STV_HIDDEN, 0,
 343                                     false, false);
 344     }
 345
 346   return this->got_;
 347 }
 348
 349 // Get the dynamic reloc section, creating it if necessary.
 350
 351 Target_x86_64::Reloc_section*
 352 Target_x86_64::rela_dyn_section(Layout* layout)
 353 {
 354   if (this->rela_dyn_ == NULL)
 355     {
 356       gold_assert(layout != NULL);
 357       this->rela_dyn_ = new Reloc_section();
 358       layout->add_output_section_data(".rela.dyn", elfcpp::SHT_RELA,
 359                                       elfcpp::SHF_ALLOC, this->rela_dyn_);
 360     }
 361   return this->rela_dyn_;
 362 }
 363
 364 // A class to handle the PLT data.
 365
 366 class Output_data_plt_x86_64 : public Output_section_data
 367 {
 368  public:
 369   typedef Output_data_reloc<elfcpp::SHT_RELA, true, 64, false> Reloc_section;
 370
 371   Output_data_plt_x86_64(Layout*, Output_data_space*);
 372
 373   // Add an entry to the PLT.
 374   void
 375   add_entry(Symbol* gsym);
 376
 377   // Return the .rel.plt section data.
 378   const Reloc_section*
 379   rel_plt() const
 380   { return this->rel_; }
 381
 382  protected:
 383   void
 384   do_adjust_output_section(Output_section* os);
 385
 386  private:
 387   // The size of an entry in the PLT.
 388   static const int plt_entry_size = 16;
 389
 390   // The first entry in the PLT.
 391   // From the AMD64 ABI: "Unlike Intel386 ABI, this ABI uses the same
 392   // procedure linkage table for both programs and shared objects."
 393   static unsigned char first_plt_entry[plt_entry_size];
 394
 395   // Other entries in the PLT for an executable.
 396   static unsigned char plt_entry[plt_entry_size];
 397
 398   // Set the final size.
 399   void
 400   set_final_data_size()
 401   { this->set_data_size((this->count_ + 1) * plt_entry_size); }
 402
 403   // Write out the PLT data.
 404   void
 405   do_write(Output_file*);
 406
 407   // The reloc section.
 408   Reloc_section* rel_;
 409   // The .got.plt section.
 410   Output_data_space* got_plt_;
 411   // The number of PLT entries.
 412   unsigned int count_;
 413 };
 414
 415 // Create the PLT section.  The ordinary .got section is an argument,
 416 // since we need to refer to the start.  We also create our own .got
 417 // section just for PLT entries.
 418
 419 Output_data_plt_x86_64::Output_data_plt_x86_64(Layout* layout,
 420                                                Output_data_space* got_plt)
 421   : Output_section_data(8), got_plt_(got_plt), count_(0)
 422 {
 423   this->rel_ = new Reloc_section();
 424   layout->add_output_section_data(".rela.plt", elfcpp::SHT_RELA,
 425                                   elfcpp::SHF_ALLOC, this->rel_);
 426 }
 427
 428 void
 429 Output_data_plt_x86_64::do_adjust_output_section(Output_section* os)
 430 {
 431   // UnixWare sets the entsize of .plt to 4, and so does the old GNU
 432   // linker, and so do we.
 433   os->set_entsize(4);
 434 }
 435
 436 // Add an entry to the PLT.
 437
 438 void
 439 Output_data_plt_x86_64::add_entry(Symbol* gsym)
 440 {
 441   gold_assert(!gsym->has_plt_offset());
 442
 443   // Note that when setting the PLT offset we skip the initial
 444   // reserved PLT entry.
 445   gsym->set_plt_offset((this->count_ + 1) * plt_entry_size);
 446
 447   ++this->count_;
 448
 449   off_t got_offset = this->got_plt_->current_data_size();
 450
 451   // Every PLT entry needs a GOT entry which points back to the PLT
 452   // entry (this will be changed by the dynamic linker, normally
 453   // lazily when the function is called).
 454   this->got_plt_->set_current_data_size(got_offset + 8);
 455
 456   // Every PLT entry needs a reloc.
 457   gsym->set_needs_dynsym_entry();
 458   this->rel_->add_global(gsym, elfcpp::R_X86_64_JUMP_SLOT, this->got_plt_,
 459                          got_offset, 0);
 460
 461   // Note that we don't need to save the symbol.  The contents of the
 462   // PLT are independent of which symbols are used.  The symbols only
 463   // appear in the relocations.
 464 }
 465
 466 // The first entry in the PLT for an executable.
 467
 468 unsigned char Output_data_plt_x86_64::first_plt_entry[plt_entry_size] =
 469 {
 470   // From AMD64 ABI Draft 0.98, page 76
 471   0xff, 0x35,   // pushq contents of memory address
 472   0, 0, 0, 0,   // replaced with address of .got + 4
 473   0xff, 0x25,   // jmp indirect
 474   0, 0, 0, 0,   // replaced with address of .got + 8
 475   0x90, 0x90, 0x90, 0x90   // noop (x4)
 476 };
 477
 478 // Subsequent entries in the PLT for an executable.
 479
 480 unsigned char Output_data_plt_x86_64::plt_entry[plt_entry_size] =
 481 {
 482   // From AMD64 ABI Draft 0.98, page 76
 483   0xff, 0x25,   // jmpq indirect
 484   0, 0, 0, 0,   // replaced with address of symbol in .got
 485   0x68,         // pushq immediate
 486   0, 0, 0, 0,   // replaced with offset into relocation table
 487   0xe9,         // jmpq relative
 488   0, 0, 0, 0    // replaced with offset to start of .plt
 489 };
 490
 491 // Write out the PLT.  This uses the hand-coded instructions above,
 492 // and adjusts them as needed.  This is specified by the AMD64 ABI.
 493
 494 void
 495 Output_data_plt_x86_64::do_write(Output_file* of)
 496 {
 497   const off_t offset = this->offset();
 498   const off_t oview_size = this->data_size();
 499   unsigned char* const oview = of->get_output_view(offset, oview_size);
 500
 501   const off_t got_file_offset = this->got_plt_->offset();
 502   const off_t got_size = this->got_plt_->data_size();
 503   unsigned char* const got_view = of->get_output_view(got_file_offset,
 504                                                       got_size);
 505
 506   unsigned char* pov = oview;
 507
 508   elfcpp::Elf_types<32>::Elf_Addr plt_address = this->address();
 509   elfcpp::Elf_types<32>::Elf_Addr got_address = this->got_plt_->address();
 510
 511   memcpy(pov, first_plt_entry, plt_entry_size);
 512   if (!parameters->output_is_shared())
 513     {
 514       // We do a jmp relative to the PC at the end of this instruction.
 515       elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_address + 8
 516                                                   - (plt_address + 6));
 517       elfcpp::Swap<32, false>::writeval(pov + 8, got_address + 16
 518                                         - (plt_address + 12));
 519     }
 520   pov += plt_entry_size;
 521
 522   unsigned char* got_pov = got_view;
 523
 524   memset(got_pov, 0, 24);
 525   got_pov += 24;
 526
 527   unsigned int plt_offset = plt_entry_size;
 528   unsigned int got_offset = 24;
 529   const unsigned int count = this->count_;
 530   for (unsigned int plt_index = 0;
 531        plt_index < count;
 532        ++plt_index,
 533          pov += plt_entry_size,
 534          got_pov += 8,
 535          plt_offset += plt_entry_size,
 536          got_offset += 8)
 537     {
 538       // Set and adjust the PLT entry itself.
 539       memcpy(pov, plt_entry, plt_entry_size);
 540       if (parameters->output_is_shared())
 541         // FIXME(csilvers): what's the right thing to write here?
 542         elfcpp::Swap_unaligned<32, false>::writeval(pov + 2, got_offset);
 543       else
 544         elfcpp::Swap_unaligned<32, false>::writeval(pov + 2,
 545                                                     (got_address + got_offset
 546                                                      - (plt_address + plt_offset
 547                                                         + 6)));
 548
 549       elfcpp::Swap_unaligned<32, false>::writeval(pov + 7, plt_index);
 550       elfcpp::Swap<32, false>::writeval(pov + 12,
 551                                         - (plt_offset + plt_entry_size));
 552
 553       // Set the entry in the GOT.
 554       elfcpp::Swap<64, false>::writeval(got_pov, plt_address + plt_offset + 6);
 555     }
 556
 557   gold_assert(pov - oview == oview_size);
 558   gold_assert(got_pov - got_view == got_size);
 559
 560   of->write_output_view(offset, oview_size, oview);
 561   of->write_output_view(got_file_offset, got_size, got_view);
 562 }
 563
 564 // Create a PLT entry for a global symbol.
 565
 566 void
 567 Target_x86_64::make_plt_entry(Symbol_table* symtab, Layout* layout,
 568                               Symbol* gsym)
 569 {
 570   if (gsym->has_plt_offset())
 571     return;
 572
 573   if (this->plt_ == NULL)
 574     {
 575       // Create the GOT sections first.
 576       this->got_section(symtab, layout);
 577
 578       this->plt_ = new Output_data_plt_x86_64(layout, this->got_plt_);
 579       layout->add_output_section_data(".plt", elfcpp::SHT_PROGBITS,
 580                                       (elfcpp::SHF_ALLOC
 581                                        | elfcpp::SHF_EXECINSTR),
 582                                       this->plt_);
 583     }
 584
 585   this->plt_->add_entry(gsym);
 586 }
 587
 588 // Handle a relocation against a non-function symbol defined in a
 589 // dynamic object.  The traditional way to handle this is to generate
 590 // a COPY relocation to copy the variable at runtime from the shared
 591 // object into the executable's data segment.  However, this is
 592 // undesirable in general, as if the size of the object changes in the
 593 // dynamic object, the executable will no longer work correctly.  If
 594 // this relocation is in a writable section, then we can create a
 595 // dynamic reloc and the dynamic linker will resolve it to the correct
 596 // address at runtime.  However, we do not want do that if the
 597 // relocation is in a read-only section, as it would prevent the
 598 // readonly segment from being shared.  And if we have to eventually
 599 // generate a COPY reloc, then any dynamic relocations will be
 600 // useless.  So this means that if this is a writable section, we need
 601 // to save the relocation until we see whether we have to create a
 602 // COPY relocation for this symbol for any other relocation.
 603
 604 void
 605 Target_x86_64::copy_reloc(const General_options* options,
 606                           Symbol_table* symtab,
 607                           Layout* layout,
 608                           Sized_relobj<64, false>* object,
 609                           unsigned int data_shndx,
 610                           Output_section* output_section,
 611                           Symbol* gsym,
 612                           const elfcpp::Rela<64, false>& rela)
 613 {
 614   Sized_symbol<64>* ssym;
 615   ssym = symtab->get_sized_symbol SELECT_SIZE_NAME(64) (gsym
 616                                                         SELECT_SIZE(64));
 617
 618   if (!Copy_relocs<64, false>::need_copy_reloc(options, object,
 619                                                data_shndx, ssym))
 620     {
 621       // So far we do not need a COPY reloc.  Save this relocation.
 622       // If it turns out that we never need a COPY reloc for this
 623       // symbol, then we will emit the relocation.
 624       if (this->copy_relocs_ == NULL)
 625         this->copy_relocs_ = new Copy_relocs<64, false>();
 626       this->copy_relocs_->save(ssym, object, data_shndx, output_section, rela);
 627     }
 628   else
 629     {
 630       // Allocate space for this symbol in the .bss section.
 631
 632       elfcpp::Elf_types<64>::Elf_WXword symsize = ssym->symsize();
 633
 634       // There is no defined way to determine the required alignment
 635       // of the symbol.  We pick the alignment based on the size.  We
 636       // set an arbitrary maximum of 256.
 637       unsigned int align;
 638       for (align = 1; align < 512; align <<= 1)
 639         if ((symsize & align) != 0)
 640           break;
 641
 642       if (this->dynbss_ == NULL)
 643         {
 644           this->dynbss_ = new Output_data_space(align);
 645           layout->add_output_section_data(".bss",
 646                                           elfcpp::SHT_NOBITS,
 647                                           (elfcpp::SHF_ALLOC
 648                                            | elfcpp::SHF_WRITE),
 649                                           this->dynbss_);
 650         }
 651
 652       Output_data_space* dynbss = this->dynbss_;
 653
 654       if (align > dynbss->addralign())
 655         dynbss->set_space_alignment(align);
 656
 657       off_t dynbss_size = dynbss->current_data_size();
 658       dynbss_size = align_address(dynbss_size, align);
 659       off_t offset = dynbss_size;
 660       dynbss->set_current_data_size(dynbss_size + symsize);
 661
 662       symtab->define_with_copy_reloc(this, ssym, dynbss, offset);
 663
 664       // Add the COPY reloc.
 665       Reloc_section* rela_dyn = this->rela_dyn_section(layout);
 666       rela_dyn->add_global(ssym, elfcpp::R_X86_64_COPY, dynbss, offset, 0);
 667     }
 668 }
 669
 670
 671 // Optimize the TLS relocation type based on what we know about the
 672 // symbol.  IS_FINAL is true if the final address of this symbol is
 673 // known at link time.
 674
 675 tls::Tls_optimization
 676 Target_x86_64::optimize_tls_reloc(bool is_final, int r_type)
 677 {
 678   // If we are generating a shared library, then we can't do anything
 679   // in the linker.
 680   if (parameters->output_is_shared())
 681     return tls::TLSOPT_NONE;
 682
 683   switch (r_type)
 684     {
 685     case elfcpp::R_X86_64_TLSGD:
 686     case elfcpp::R_X86_64_GOTPC32_TLSDESC:
 687     case elfcpp::R_X86_64_TLSDESC_CALL:
 688       // These are General-Dynamic which permits fully general TLS
 689       // access.  Since we know that we are generating an executable,
 690       // we can convert this to Initial-Exec.  If we also know that
 691       // this is a local symbol, we can further switch to Local-Exec.
 692       if (is_final)
 693         return tls::TLSOPT_TO_LE;
 694       return tls::TLSOPT_TO_IE;
 695
 696     case elfcpp::R_X86_64_TLSLD:
 697       // This is Local-Dynamic, which refers to a local symbol in the
 698       // dynamic TLS block.  Since we know that we generating an
 699       // executable, we can switch to Local-Exec.
 700       return tls::TLSOPT_TO_LE;
 701
 702     case elfcpp::R_X86_64_DTPOFF32:
 703     case elfcpp::R_X86_64_DTPOFF64:
 704       // Another Local-Dynamic reloc.
 705       return tls::TLSOPT_TO_LE;
 706
 707     case elfcpp::R_X86_64_GOTTPOFF:
 708       // These are Initial-Exec relocs which get the thread offset
 709       // from the GOT.  If we know that we are linking against the
 710       // local symbol, we can switch to Local-Exec, which links the
 711       // thread offset into the instruction.
 712       if (is_final)
 713         return tls::TLSOPT_TO_LE;
 714       return tls::TLSOPT_NONE;
 715
 716     case elfcpp::R_X86_64_TPOFF32:
 717       // When we already have Local-Exec, there is nothing further we
 718       // can do.
 719       return tls::TLSOPT_NONE;
 720
 721     default:
 722       gold_unreachable();
 723     }
 724 }
 725
 726 // Report an unsupported relocation against a local symbol.
 727
 728 void
 729 Target_x86_64::Scan::unsupported_reloc_local(Sized_relobj<64, false>* object,
 730                                              unsigned int r_type)
 731 {
 732   gold_error(_("%s: unsupported reloc %u against local symbol"),
 733              object->name().c_str(), r_type);
 734 }
 735
 736 // Scan a relocation for a local symbol.
 737
 738 inline void
 739 Target_x86_64::Scan::local(const General_options&,
 740                            Symbol_table* symtab,
 741                            Layout* layout,
 742                            Target_x86_64* target,
 743                            Sized_relobj<64, false>* object,
 744                            unsigned int data_shndx,
 745                            Output_section* output_section,
 746                            const elfcpp::Rela<64, false>& reloc,
 747                            unsigned int r_type,
 748                            const elfcpp::Sym<64, false>&)
 749 {
 750   switch (r_type)
 751     {
 752     case elfcpp::R_X86_64_NONE:
 753     case elfcpp::R_386_GNU_VTINHERIT:
 754     case elfcpp::R_386_GNU_VTENTRY:
 755       break;
 756
 757     case elfcpp::R_X86_64_64:
 758       // If building a shared library (or a position-independent
 759       // executable), we need to create a dynamic relocation for
 760       // this location. The relocation applied at link time will
 761       // apply the link-time value, so we flag the location with
 762       // an R_386_RELATIVE relocation so the dynamic loader can
 763       // relocate it easily.
 764       if (parameters->output_is_position_independent())
 765         {
 766           Reloc_section* rela_dyn = target->rela_dyn_section(layout);
 767           rela_dyn->add_local(object, 0, elfcpp::R_X86_64_RELATIVE,
 768                               output_section, data_shndx,
 769                               reloc.get_r_offset(), 0);
 770         }
 771       break;
 772
 773     case elfcpp::R_X86_64_32:
 774     case elfcpp::R_X86_64_32S:
 775     case elfcpp::R_X86_64_16:
 776     case elfcpp::R_X86_64_8:
 777       // If building a shared library (or a position-independent
 778       // executable), we need to create a dynamic relocation for
 779       // this location. The relocation applied at link time will
 780       // apply the link-time value, so we flag the location with
 781       // an R_386_RELATIVE relocation so the dynamic loader can
 782       // relocate it easily.
 783       if (parameters->output_is_position_independent())
 784         {
 785           Reloc_section* rela_dyn = target->rela_dyn_section(layout);
 786           unsigned int r_sym = elfcpp::elf_r_sym<64>(reloc.get_r_info());
 787           rela_dyn->add_local(object, r_sym, r_type, output_section,
 788                               data_shndx, reloc.get_r_offset(),
 789                               reloc.get_r_addend());
 790         }
 791       break;
 792
 793     case elfcpp::R_X86_64_PC64:
 794     case elfcpp::R_X86_64_PC32:
 795     case elfcpp::R_X86_64_PC16:
 796     case elfcpp::R_X86_64_PC8:
 797       break;
 798
 799     case elfcpp::R_X86_64_PLT32:
 800       // Since we know this is a local symbol, we can handle this as a
 801       // PC32 reloc.
 802       break;
 803
 804     case elfcpp::R_X86_64_GOTPC32:
 805     case elfcpp::R_X86_64_GOTOFF64:
 806     case elfcpp::R_X86_64_GOTPC64:
 807     case elfcpp::R_X86_64_PLTOFF64:
 808       // We need a GOT section.
 809       target->got_section(symtab, layout);
 810       // For PLTOFF64, we'd normally want a PLT section, but since we
 811       // know this is a local symbol, no PLT is needed.
 812       break;
 813
 814     case elfcpp::R_X86_64_GOT64:
 815     case elfcpp::R_X86_64_GOT32:
 816     case elfcpp::R_X86_64_GOTPCREL64:
 817     case elfcpp::R_X86_64_GOTPCREL:
 818     case elfcpp::R_X86_64_GOTPLT64:
 819       {
 820         // The symbol requires a GOT entry.
 821         Output_data_got<64, false>* got = target->got_section(symtab, layout);
 822         unsigned int r_sym = elfcpp::elf_r_sym<64>(reloc.get_r_info());
 823         if (got->add_local(object, r_sym))
 824           {
 825             // If we are generating a shared object, we need to add a
 826             // dynamic RELATIVE relocation for this symbol.
 827             if (parameters->output_is_position_independent())
 828               {
 829                 // FIXME: R_X86_64_RELATIVE assumes a 64-bit relocation.
 830                 gold_assert(r_type != elfcpp::R_X86_64_GOT32);
 831
 832                 Reloc_section* rela_dyn = target->rela_dyn_section(layout);
 833                 rela_dyn->add_local(object, 0, elfcpp::R_X86_64_RELATIVE,
 834                                     output_section, data_shndx,
 835                                     reloc.get_r_offset(), 0);
 836               }
 837           }
 838         // For GOTPLT64, we'd normally want a PLT section, but since
 839         // we know this is a local symbol, no PLT is needed.
 840       }
 841       break;
 842
 843     case elfcpp::R_X86_64_COPY:
 844     case elfcpp::R_X86_64_GLOB_DAT:
 845     case elfcpp::R_X86_64_JUMP_SLOT:
 846     case elfcpp::R_X86_64_RELATIVE:
 847       // These are outstanding tls relocs, which are unexpected when linking
 848     case elfcpp::R_X86_64_TPOFF64:
 849     case elfcpp::R_X86_64_DTPMOD64:
 850     case elfcpp::R_X86_64_TLSDESC:
 851       gold_error(_("%s: unexpected reloc %u in object file"),
 852                  object->name().c_str(), r_type);
 853       break;
 854
 855       // These are initial tls relocs, which are expected when linking
 856     case elfcpp::R_X86_64_TLSGD:            // Global-dynamic
 857     case elfcpp::R_X86_64_GOTPC32_TLSDESC:  // Global-dynamic (from ~oliva url)
 858     case elfcpp::R_X86_64_TLSDESC_CALL:
 859     case elfcpp::R_X86_64_TLSLD:            // Local-dynamic
 860     case elfcpp::R_X86_64_DTPOFF32:
 861     case elfcpp::R_X86_64_DTPOFF64:
 862     case elfcpp::R_X86_64_GOTTPOFF:         // Initial-exec
 863     case elfcpp::R_X86_64_TPOFF32:          // Local-exec
 864       {
 865         bool output_is_shared = parameters->output_is_shared();
 866         const tls::Tls_optimization optimized_type
 867             = Target_x86_64::optimize_tls_reloc(!output_is_shared, r_type);
 868         switch (r_type)
 869           {
 870           case elfcpp::R_X86_64_TLSGD:       // General-dynamic
 871           case elfcpp::R_X86_64_GOTPC32_TLSDESC:
 872           case elfcpp::R_X86_64_TLSDESC_CALL:
 873             // FIXME: If not relaxing to LE, we need to generate
 874             // DTPMOD64 and DTPOFF64 relocs.
 875             if (optimized_type != tls::TLSOPT_TO_LE)
 876               unsupported_reloc_local(object, r_type);
 877             break;
 878
 879           case elfcpp::R_X86_64_TLSLD:       // Local-dynamic
 880           case elfcpp::R_X86_64_DTPOFF32:
 881           case elfcpp::R_X86_64_DTPOFF64:
 882             // FIXME: If not relaxing to LE, we need to generate a
 883             // DTPMOD64 reloc.
 884             if (optimized_type != tls::TLSOPT_TO_LE)
 885               unsupported_reloc_local(object, r_type);
 886             break;
 887
 888           case elfcpp::R_X86_64_GOTTPOFF:    // Initial-exec
 889             // FIXME: If not relaxing to LE, we need to generate a
 890             // TPOFF64 reloc.
 891             if (optimized_type != tls::TLSOPT_TO_LE)
 892               unsupported_reloc_local(object, r_type);
 893             break;
 894
 895           case elfcpp::R_X86_64_TPOFF32:     // Local-exec
 896             // FIXME: If generating a shared object, we need to copy
 897             // this relocation into the object.
 898             gold_assert(!output_is_shared);
 899             break;
 900
 901           default:
 902             gold_unreachable();
 903           }
 904       }
 905       break;
 906
 907     case elfcpp::R_X86_64_SIZE32:
 908     case elfcpp::R_X86_64_SIZE64:
 909     default:
 910       gold_error(_("%s: unsupported reloc %u against local symbol"),
 911                  object->name().c_str(), r_type);
 912       break;
 913     }
 914 }
 915
 916
 917 // Report an unsupported relocation against a global symbol.
 918
 919 void
 920 Target_x86_64::Scan::unsupported_reloc_global(Sized_relobj<64, false>* object,
 921                                               unsigned int r_type,
 922                                               Symbol* gsym)
 923 {
 924   gold_error(_("%s: unsupported reloc %u against global symbol %s"),
 925              object->name().c_str(), r_type, gsym->demangled_name().c_str());
 926 }
 927
 928 // Scan a relocation for a global symbol.
 929
 930 inline void
 931 Target_x86_64::Scan::global(const General_options& options,
 932                             Symbol_table* symtab,
 933                             Layout* layout,
 934                             Target_x86_64* target,
 935                             Sized_relobj<64, false>* object,
 936                             unsigned int data_shndx,
 937                             Output_section* output_section,
 938                             const elfcpp::Rela<64, false>& reloc,
 939                             unsigned int r_type,
 940                             Symbol* gsym)
 941 {
 942   switch (r_type)
 943     {
 944     case elfcpp::R_X86_64_NONE:
 945     case elfcpp::R_386_GNU_VTINHERIT:
 946     case elfcpp::R_386_GNU_VTENTRY:
 947       break;
 948
 949     case elfcpp::R_X86_64_64:
 950     case elfcpp::R_X86_64_32:
 951     case elfcpp::R_X86_64_32S:
 952     case elfcpp::R_X86_64_16:
 953     case elfcpp::R_X86_64_8:
 954       {
 955         // Make a PLT entry if necessary.
 956         if (gsym->needs_plt_entry())
 957           {
 958             target->make_plt_entry(symtab, layout, gsym);
 959             // Since this is not a PC-relative relocation, we may be
 960             // taking the address of a function. In that case we need to
 961             // set the entry in the dynamic symbol table to the address of
 962             // the PLT entry.
 963             if (gsym->is_from_dynobj())
 964               gsym->set_needs_dynsym_value();
 965           }
 966         // Make a dynamic relocation if necessary.
 967         if (gsym->needs_dynamic_reloc(true, false))
 968           {
 969             if (target->may_need_copy_reloc(gsym))
 970               {
 971                 target->copy_reloc(&options, symtab, layout, object, data_shndx,
 972                                    output_section, gsym, reloc);
 973               }
 974             else if (r_type == elfcpp::R_X86_64_64
 975                      && gsym->can_use_relative_reloc(false))
 976               {
 977                 Reloc_section* rela_dyn = target->rela_dyn_section(layout);
 978                 rela_dyn->add_local(object, 0, elfcpp::R_X86_64_RELATIVE,
 979                                     output_section, data_shndx,
 980                                     reloc.get_r_offset(), 0);
 981               }
 982             else
 983               {
 984                 Reloc_section* rela_dyn = target->rela_dyn_section(layout);
 985                 rela_dyn->add_global(gsym, r_type, output_section, object,
 986                                      data_shndx, reloc.get_r_offset(),
 987                                      reloc.get_r_addend());
 988               }
 989           }
 990       }
 991       break;
 992
 993     case elfcpp::R_X86_64_PC64:
 994     case elfcpp::R_X86_64_PC32:
 995     case elfcpp::R_X86_64_PC16:
 996     case elfcpp::R_X86_64_PC8:
 997       {
 998         // Make a PLT entry if necessary.
 999         if (gsym->needs_plt_entry())
1000           target->make_plt_entry(symtab, layout, gsym);
1001         // Make a dynamic relocation if necessary.
1002         bool is_function_call = (gsym->type() == elfcpp::STT_FUNC);
1003         if (gsym->needs_dynamic_reloc(true, is_function_call))
1004           {
1005             if (target->may_need_copy_reloc(gsym))
1006               {
1007                 target->copy_reloc(&options, symtab, layout, object, data_shndx,
1008                                    output_section, gsym, reloc);
1009               }
1010             else
1011               {
1012                 Reloc_section* rela_dyn = target->rela_dyn_section(layout);
1013                 rela_dyn->add_global(gsym, r_type, output_section, object,
1014                                      data_shndx, reloc.get_r_offset(),
1015                                      reloc.get_r_addend());
1016               }
1017           }
1018       }
1019       break;
1020
1021     case elfcpp::R_X86_64_GOT64:
1022     case elfcpp::R_X86_64_GOT32:
1023     case elfcpp::R_X86_64_GOTPCREL64:
1024     case elfcpp::R_X86_64_GOTPCREL:
1025     case elfcpp::R_X86_64_GOTPLT64:
1026       {
1027         // The symbol requires a GOT entry.
1028         Output_data_got<64, false>* got = target->got_section(symtab, layout);
1029         if (got->add_global(gsym))
1030           {
1031             // If this symbol is not fully resolved, we need to add a
1032             // dynamic relocation for it.
1033             if (!gsym->final_value_is_known())
1034               {
1035                 Reloc_section* rela_dyn = target->rela_dyn_section(layout);
1036                 if (gsym->is_from_dynobj()
1037                     || gsym->is_preemptible())
1038                   rela_dyn->add_global(gsym, elfcpp::R_X86_64_GLOB_DAT, got,
1039                                        gsym->got_offset(), 0);
1040                 else
1041                   {
1042                     rela_dyn->add_local(object, 0, elfcpp::R_X86_64_RELATIVE,
1043                                         got, gsym->got_offset(), 0);
1044                     // Make sure we write the link-time value to the GOT.
1045                     gsym->set_needs_value_in_got();
1046                   }
1047               }
1048           }
1049         // For GOTPLT64, we also need a PLT entry (but only if the
1050         // symbol is not fully resolved).
1051         if (r_type == elfcpp::R_X86_64_GOTPLT64
1052             && !gsym->final_value_is_known())
1053           target->make_plt_entry(symtab, layout, gsym);
1054       }
1055       break;
1056
1057     case elfcpp::R_X86_64_PLT32:
1058       // If the symbol is fully resolved, this is just a PC32 reloc.
1059       // Otherwise we need a PLT entry.
1060       if (gsym->final_value_is_known())
1061         break;
1062       // If building a shared library, we can also skip the PLT entry
1063       // if the symbol is defined in the output file and is protected
1064       // or hidden.
1065       if (gsym->is_defined()
1066           && !gsym->is_from_dynobj()
1067           && !gsym->is_preemptible())
1068         break;
1069       target->make_plt_entry(symtab, layout, gsym);
1070       break;
1071
1072     case elfcpp::R_X86_64_GOTPC32:
1073     case elfcpp::R_X86_64_GOTOFF64:
1074     case elfcpp::R_X86_64_GOTPC64:
1075     case elfcpp::R_X86_64_PLTOFF64:
1076       // We need a GOT section.
1077       target->got_section(symtab, layout);
1078       // For PLTOFF64, we also need a PLT entry (but only if the
1079       // symbol is not fully resolved).
1080       if (r_type == elfcpp::R_X86_64_PLTOFF64
1081           && !gsym->final_value_is_known())
1082         target->make_plt_entry(symtab, layout, gsym);
1083       break;
1084
1085     case elfcpp::R_X86_64_COPY:
1086     case elfcpp::R_X86_64_GLOB_DAT:
1087     case elfcpp::R_X86_64_JUMP_SLOT:
1088     case elfcpp::R_X86_64_RELATIVE:
1089       // These are outstanding tls relocs, which are unexpected when linking
1090     case elfcpp::R_X86_64_TPOFF64:
1091     case elfcpp::R_X86_64_DTPMOD64:
1092     case elfcpp::R_X86_64_TLSDESC:
1093       gold_error(_("%s: unexpected reloc %u in object file"),
1094                  object->name().c_str(), r_type);
1095       break;
1096
1097       // These are initial tls relocs, which are expected for global()
1098     case elfcpp::R_X86_64_TLSGD:            // Global-dynamic
1099     case elfcpp::R_X86_64_GOTPC32_TLSDESC:  // Global-dynamic (from ~oliva url)
1100     case elfcpp::R_X86_64_TLSDESC_CALL:
1101     case elfcpp::R_X86_64_TLSLD:            // Local-dynamic
1102     case elfcpp::R_X86_64_DTPOFF32:
1103     case elfcpp::R_X86_64_DTPOFF64:
1104     case elfcpp::R_X86_64_GOTTPOFF:         // Initial-exec
1105     case elfcpp::R_X86_64_TPOFF32:          // Local-exec
1106       {
1107         const bool is_final = gsym->final_value_is_known();
1108         const tls::Tls_optimization optimized_type
1109             = Target_x86_64::optimize_tls_reloc(is_final, r_type);
1110         switch (r_type)
1111           {
1112           case elfcpp::R_X86_64_TLSGD:       // General-dynamic
1113           case elfcpp::R_X86_64_GOTPC32_TLSDESC:
1114           case elfcpp::R_X86_64_TLSDESC_CALL:
1115             // FIXME: If not relaxing to LE, we need to generate
1116             // DTPMOD64 and DTPOFF64, or TLSDESC, relocs.
1117             if (optimized_type != tls::TLSOPT_TO_LE)
1118               unsupported_reloc_global(object, r_type, gsym);
1119             break;
1120
1121           case elfcpp::R_X86_64_TLSLD:       // Local-dynamic
1122           case elfcpp::R_X86_64_DTPOFF32:
1123           case elfcpp::R_X86_64_DTPOFF64:
1124             // FIXME: If not relaxing to LE, we need to generate a
1125             // DTPMOD64 reloc.
1126             if (optimized_type != tls::TLSOPT_TO_LE)
1127               unsupported_reloc_global(object, r_type, gsym);
1128             break;
1129
1130           case elfcpp::R_X86_64_GOTTPOFF:    // Initial-exec
1131             // FIXME: If not relaxing to LE, we need to generate a
1132             // TPOFF64 reloc.
1133             if (optimized_type != tls::TLSOPT_TO_LE)
1134               unsupported_reloc_global(object, r_type, gsym);
1135             break;
1136
1137           case elfcpp::R_X86_64_TPOFF32:     // Local-exec
1138             // FIXME: If generating a shared object, we need to copy
1139             // this relocation into the object.
1140             gold_assert(is_final);
1141             break;
1142
1143           default:
1144             gold_unreachable();
1145           }
1146       }
1147       break;
1148
1149     case elfcpp::R_X86_64_SIZE32:
1150     case elfcpp::R_X86_64_SIZE64:
1151     default:
1152       gold_error(_("%s: unsupported reloc %u against global symbol %s"),
1153                  object->name().c_str(), r_type,
1154                  gsym->demangled_name().c_str());
1155       break;
1156     }
1157 }
1158
1159 // Scan relocations for a section.
1160
1161 void
1162 Target_x86_64::scan_relocs(const General_options& options,
1163                            Symbol_table* symtab,
1164                            Layout* layout,
1165                            Sized_relobj<64, false>* object,
1166                            unsigned int data_shndx,
1167                            unsigned int sh_type,
1168                            const unsigned char* prelocs,
1169                            size_t reloc_count,
1170                            Output_section* output_section,
1171                            bool needs_special_offset_handling,
1172                            size_t local_symbol_count,
1173                            const unsigned char* plocal_symbols)
1174 {
1175   if (sh_type == elfcpp::SHT_REL)
1176     {
1177       gold_error(_("%s: unsupported REL reloc section"),
1178                  object->name().c_str());
1179       return;
1180     }
1181
1182   gold::scan_relocs<64, false, Target_x86_64, elfcpp::SHT_RELA,
1183       Target_x86_64::Scan>(
1184     options,
1185     symtab,
1186     layout,
1187     this,
1188     object,
1189     data_shndx,
1190     prelocs,
1191     reloc_count,
1192     output_section,
1193     needs_special_offset_handling,
1194     local_symbol_count,
1195     plocal_symbols);
1196 }
1197
1198 // Finalize the sections.
1199
1200 void
1201 Target_x86_64::do_finalize_sections(Layout* layout)
1202 {
1203   // Fill in some more dynamic tags.
1204   Output_data_dynamic* const odyn = layout->dynamic_data();
1205   if (odyn != NULL)
1206     {
1207       if (this->got_plt_ != NULL)
1208         odyn->add_section_address(elfcpp::DT_PLTGOT, this->got_plt_);
1209
1210       if (this->plt_ != NULL)
1211         {
1212           const Output_data* od = this->plt_->rel_plt();
1213           odyn->add_section_size(elfcpp::DT_PLTRELSZ, od);
1214           odyn->add_section_address(elfcpp::DT_JMPREL, od);
1215           odyn->add_constant(elfcpp::DT_PLTREL, elfcpp::DT_RELA);
1216         }
1217
1218       if (this->rela_dyn_ != NULL)
1219         {
1220           const Output_data* od = this->rela_dyn_;
1221           odyn->add_section_address(elfcpp::DT_RELA, od);
1222           odyn->add_section_size(elfcpp::DT_RELASZ, od);
1223           odyn->add_constant(elfcpp::DT_RELAENT,
1224                              elfcpp::Elf_sizes<64>::rela_size);
1225         }
1226
1227       if (!parameters->output_is_shared())
1228         {
1229           // The value of the DT_DEBUG tag is filled in by the dynamic
1230           // linker at run time, and used by the debugger.
1231           odyn->add_constant(elfcpp::DT_DEBUG, 0);
1232         }
1233     }
1234
1235   // Emit any relocs we saved in an attempt to avoid generating COPY
1236   // relocs.
1237   if (this->copy_relocs_ == NULL)
1238     return;
1239   if (this->copy_relocs_->any_to_emit())
1240     {
1241       Reloc_section* rela_dyn = this->rela_dyn_section(layout);
1242       this->copy_relocs_->emit(rela_dyn);
1243     }
1244   delete this->copy_relocs_;
1245   this->copy_relocs_ = NULL;
1246 }
1247
1248 // Perform a relocation.
1249
1250 inline bool
1251 Target_x86_64::Relocate::relocate(const Relocate_info<64, false>* relinfo,
1252                                   Target_x86_64* target,
1253                                   size_t relnum,
1254                                   const elfcpp::Rela<64, false>& rela,
1255                                   unsigned int r_type,
1256                                   const Sized_symbol<64>* gsym,
1257                                   const Symbol_value<64>* psymval,
1258                                   unsigned char* view,
1259                                   elfcpp::Elf_types<64>::Elf_Addr address,
1260                                   off_t view_size)
1261 {
1262   if (this->skip_call_tls_get_addr_)
1263     {
1264       if (r_type != elfcpp::R_X86_64_PLT32
1265           || gsym == NULL
1266           || strcmp(gsym->name(), "__tls_get_addr") != 0)
1267         {
1268           gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1269                                  _("missing expected TLS relocation"));
1270         }
1271       else
1272         {
1273           this->skip_call_tls_get_addr_ = false;
1274           return false;
1275         }
1276     }
1277
1278   // Pick the value to use for symbols defined in shared objects.
1279   Symbol_value<64> symval;
1280   if (gsym != NULL
1281       && (gsym->is_from_dynobj()
1282           || (parameters->output_is_shared()
1283               && gsym->is_preemptible()))
1284       && gsym->has_plt_offset())
1285     {
1286       symval.set_output_value(target->plt_section()->address()
1287                               + gsym->plt_offset());
1288       psymval = &symval;
1289     }
1290
1291   const Sized_relobj<64, false>* object = relinfo->object;
1292   const elfcpp::Elf_Xword addend = rela.get_r_addend();
1293
1294   // Get the GOT offset if needed.
1295   // The GOT pointer points to the end of the GOT section.
1296   // We need to subtract the size of the GOT section to get
1297   // the actual offset to use in the relocation.
1298   bool have_got_offset = false;
1299   unsigned int got_offset = 0;
1300   switch (r_type)
1301     {
1302     case elfcpp::R_X86_64_GOT32:
1303     case elfcpp::R_X86_64_GOT64:
1304     case elfcpp::R_X86_64_GOTPLT64:
1305     case elfcpp::R_X86_64_GOTPCREL:
1306     case elfcpp::R_X86_64_GOTPCREL64:
1307       if (gsym != NULL)
1308         {
1309           gold_assert(gsym->has_got_offset());
1310           got_offset = gsym->got_offset() - target->got_size();
1311         }
1312       else
1313         {
1314           unsigned int r_sym = elfcpp::elf_r_sym<64>(rela.get_r_info());
1315           got_offset = object->local_got_offset(r_sym) - target->got_size();
1316         }
1317       have_got_offset = true;
1318       break;
1319
1320     default:
1321       break;
1322     }
1323
1324   switch (r_type)
1325     {
1326     case elfcpp::R_X86_64_NONE:
1327     case elfcpp::R_386_GNU_VTINHERIT:
1328     case elfcpp::R_386_GNU_VTENTRY:
1329       break;
1330
1331     case elfcpp::R_X86_64_64:
1332       Relocate_functions<64, false>::rela64(view, object, psymval, addend);
1333       break;
1334
1335     case elfcpp::R_X86_64_PC64:
1336       Relocate_functions<64, false>::pcrela64(view, object, psymval, addend,
1337                                               address);
1338       break;
1339
1340     case elfcpp::R_X86_64_32:
1341       // FIXME: we need to verify that value + addend fits into 32 bits:
1342       //    uint64_t x = value + addend;
1343       //    x == static_cast<uint64_t>(static_cast<uint32_t>(x))
1344       // Likewise for other <=32-bit relocations (but see R_X86_64_32S).
1345       Relocate_functions<64, false>::rela32(view, object, psymval, addend);
1346       break;
1347
1348     case elfcpp::R_X86_64_32S:
1349       // FIXME: we need to verify that value + addend fits into 32 bits:
1350       //    int64_t x = value + addend;   // note this quantity is signed!
1351       //    x == static_cast<int64_t>(static_cast<int32_t>(x))
1352       Relocate_functions<64, false>::rela32(view, object, psymval, addend);
1353       break;
1354
1355     case elfcpp::R_X86_64_PC32:
1356       Relocate_functions<64, false>::pcrela32(view, object, psymval, addend,
1357                                               address);
1358       break;
1359
1360     case elfcpp::R_X86_64_16:
1361       Relocate_functions<64, false>::rela16(view, object, psymval, addend);
1362       break;
1363
1364     case elfcpp::R_X86_64_PC16:
1365       Relocate_functions<64, false>::pcrela16(view, object, psymval, addend,
1366                                               address);
1367       break;
1368
1369     case elfcpp::R_X86_64_8:
1370       Relocate_functions<64, false>::rela8(view, object, psymval, addend);
1371       break;
1372
1373     case elfcpp::R_X86_64_PC8:
1374       Relocate_functions<64, false>::pcrela8(view, object, psymval, addend,
1375                                              address);
1376       break;
1377
1378     case elfcpp::R_X86_64_PLT32:
1379       gold_assert(gsym == NULL
1380                   || gsym->has_plt_offset()
1381                   || gsym->final_value_is_known());
1382       // Note: while this code looks the same as for R_X86_64_PC32, it
1383       // behaves differently because psymval was set to point to
1384       // the PLT entry, rather than the symbol, in Scan::global().
1385       Relocate_functions<64, false>::pcrela32(view, object, psymval, addend,
1386                                               address);
1387       break;
1388
1389     case elfcpp::R_X86_64_PLTOFF64:
1390       {
1391         gold_assert(gsym);
1392         gold_assert(gsym->has_plt_offset()
1393                     || gsym->final_value_is_known());
1394         elfcpp::Elf_types<64>::Elf_Addr got_address;
1395         got_address = target->got_section(NULL, NULL)->address();
1396         Relocate_functions<64, false>::rela64(view, object, psymval,
1397                                               addend - got_address);
1398       }
1399
1400     case elfcpp::R_X86_64_GOT32:
1401       gold_assert(have_got_offset);
1402       Relocate_functions<64, false>::rela32(view, got_offset, addend);
1403       break;
1404
1405     case elfcpp::R_X86_64_GOTPC32:
1406       {
1407         gold_assert(gsym);
1408         elfcpp::Elf_types<64>::Elf_Addr value;
1409         value = target->got_plt_section()->address();
1410         Relocate_functions<64, false>::pcrela32(view, value, addend, address);
1411       }
1412       break;
1413
1414     case elfcpp::R_X86_64_GOT64:
1415       // The ABI doc says "Like GOT64, but indicates a PLT entry is needed."
1416       // Since we always add a PLT entry, this is equivalent.
1417     case elfcpp::R_X86_64_GOTPLT64:
1418       gold_assert(have_got_offset);
1419       Relocate_functions<64, false>::rela64(view, got_offset, addend);
1420       break;
1421
1422     case elfcpp::R_X86_64_GOTPC64:
1423       {
1424         gold_assert(gsym);
1425         elfcpp::Elf_types<64>::Elf_Addr value;
1426         value = target->got_plt_section()->address();
1427         Relocate_functions<64, false>::pcrela64(view, value, addend, address);
1428       }
1429       break;
1430
1431     case elfcpp::R_X86_64_GOTOFF64:
1432       {
1433         elfcpp::Elf_types<64>::Elf_Addr value;
1434         value = (psymval->value(object, 0)
1435                  - target->got_plt_section()->address());
1436         Relocate_functions<64, false>::rela64(view, value, addend);
1437       }
1438       break;
1439
1440     case elfcpp::R_X86_64_GOTPCREL:
1441       {
1442         gold_assert(have_got_offset);
1443         elfcpp::Elf_types<64>::Elf_Addr value;
1444         value = target->got_plt_section()->address() + got_offset;
1445         Relocate_functions<64, false>::pcrela32(view, value, addend, address);
1446       }
1447       break;
1448
1449     case elfcpp::R_X86_64_GOTPCREL64:
1450       {
1451         gold_assert(have_got_offset);
1452         elfcpp::Elf_types<64>::Elf_Addr value;
1453         value = target->got_plt_section()->address() + got_offset;
1454         Relocate_functions<64, false>::pcrela64(view, value, addend, address);
1455       }
1456       break;
1457
1458     case elfcpp::R_X86_64_COPY:
1459     case elfcpp::R_X86_64_GLOB_DAT:
1460     case elfcpp::R_X86_64_JUMP_SLOT:
1461     case elfcpp::R_X86_64_RELATIVE:
1462       // These are outstanding tls relocs, which are unexpected when linking
1463     case elfcpp::R_X86_64_TPOFF64:
1464     case elfcpp::R_X86_64_DTPMOD64:
1465     case elfcpp::R_X86_64_TLSDESC:
1466       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1467                              _("unexpected reloc %u in object file"),
1468                              r_type);
1469       break;
1470
1471       // These are initial tls relocs, which are expected when linking
1472     case elfcpp::R_X86_64_TLSGD:            // Global-dynamic
1473     case elfcpp::R_X86_64_GOTPC32_TLSDESC:  // Global-dynamic (from ~oliva url)
1474     case elfcpp::R_X86_64_TLSDESC_CALL:
1475     case elfcpp::R_X86_64_TLSLD:            // Local-dynamic
1476     case elfcpp::R_X86_64_DTPOFF32:
1477     case elfcpp::R_X86_64_DTPOFF64:
1478     case elfcpp::R_X86_64_GOTTPOFF:         // Initial-exec
1479     case elfcpp::R_X86_64_TPOFF32:          // Local-exec
1480       this->relocate_tls(relinfo, relnum, rela, r_type, gsym, psymval, view,
1481                          address, view_size);
1482       break;
1483
1484     case elfcpp::R_X86_64_SIZE32:
1485     case elfcpp::R_X86_64_SIZE64:
1486     default:
1487       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1488                              _("unsupported reloc %u"),
1489                              r_type);
1490       break;
1491     }
1492
1493   return true;
1494 }
1495
1496 // Perform a TLS relocation.
1497
1498 inline void
1499 Target_x86_64::Relocate::relocate_tls(const Relocate_info<64, false>* relinfo,
1500                                       size_t relnum,
1501                                       const elfcpp::Rela<64, false>& rela,
1502                                       unsigned int r_type,
1503                                       const Sized_symbol<64>* gsym,
1504                                       const Symbol_value<64>* psymval,
1505                                       unsigned char* view,
1506                                       elfcpp::Elf_types<64>::Elf_Addr,
1507                                       off_t view_size)
1508 {
1509   Output_segment* tls_segment = relinfo->layout->tls_segment();
1510   if (tls_segment == NULL)
1511     {
1512       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1513                              _("TLS reloc but no TLS segment"));
1514       return;
1515     }
1516
1517   elfcpp::Elf_types<64>::Elf_Addr value = psymval->value(relinfo->object, 0);
1518
1519   const bool is_final = (gsym == NULL
1520                          ? !parameters->output_is_position_independent()
1521                          : gsym->final_value_is_known());
1522   const tls::Tls_optimization optimized_type
1523       = Target_x86_64::optimize_tls_reloc(is_final, r_type);
1524   switch (r_type)
1525     {
1526     case elfcpp::R_X86_64_TLSGD:            // Global-dynamic
1527     case elfcpp::R_X86_64_GOTPC32_TLSDESC:  // Global-dynamic (from ~oliva url)
1528     case elfcpp::R_X86_64_TLSDESC_CALL:
1529       if (optimized_type == tls::TLSOPT_TO_LE)
1530         {
1531           this->tls_gd_to_le(relinfo, relnum, tls_segment,
1532                              rela, r_type, value, view,
1533                              view_size);
1534           break;
1535         }
1536       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1537                              _("unsupported reloc %u"), r_type);
1538       break;
1539
1540     case elfcpp::R_X86_64_TLSLD:            // Local-dynamic
1541       if (optimized_type == tls::TLSOPT_TO_LE)
1542         {
1543           this->tls_ld_to_le(relinfo, relnum, tls_segment, rela, r_type,
1544                              value, view, view_size);
1545           break;
1546         }
1547       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1548                              _("unsupported reloc %u"), r_type);
1549       break;
1550
1551     case elfcpp::R_X86_64_DTPOFF32:
1552       if (optimized_type == tls::TLSOPT_TO_LE)
1553         value = value - (tls_segment->vaddr() + tls_segment->memsz());
1554       else
1555         value = value - tls_segment->vaddr();
1556       Relocate_functions<64, false>::rel32(view, value);
1557       break;
1558
1559     case elfcpp::R_X86_64_DTPOFF64:
1560       if (optimized_type == tls::TLSOPT_TO_LE)
1561         value = value - (tls_segment->vaddr() + tls_segment->memsz());
1562       else
1563         value = value - tls_segment->vaddr();
1564       Relocate_functions<64, false>::rel64(view, value);
1565       break;
1566
1567     case elfcpp::R_X86_64_GOTTPOFF:         // Initial-exec
1568       if (optimized_type == tls::TLSOPT_TO_LE)
1569         {
1570           Target_x86_64::Relocate::tls_ie_to_le(relinfo, relnum, tls_segment,
1571                                                 rela, r_type, value, view,
1572                                                 view_size);
1573           break;
1574         }
1575       gold_error_at_location(relinfo, relnum, rela.get_r_offset(),
1576                              _("unsupported reloc type %u"),
1577                              r_type);
1578       break;
1579
1580     case elfcpp::R_X86_64_TPOFF32:          // Local-exec
1581       value = value - (tls_segment->vaddr() + tls_segment->memsz());
1582       Relocate_functions<64, false>::rel32(view, value);
1583       break;
1584     }
1585 }
1586
1587 // Do a relocation in which we convert a TLS General-Dynamic to a
1588 // Local-Exec.
1589
1590 inline void
1591 Target_x86_64::Relocate::tls_gd_to_le(const Relocate_info<64, false>* relinfo,
1592                                       size_t relnum,
1593                                       Output_segment* tls_segment,
1594                                       const elfcpp::Rela<64, false>& rela,
1595                                       unsigned int,
1596                                       elfcpp::Elf_types<64>::Elf_Addr value,
1597                                       unsigned char* view,
1598                                       off_t view_size)
1599 {
1600   // .byte 0x66; leaq foo@tlsgd(%rip),%rdi;
1601   // .word 0x6666; rex64; call __tls_get_addr
1602   // ==> movq %fs:0,%rax; leaq x@tpoff(%rax),%rax
1603
1604   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -4);
1605   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 12);
1606
1607   tls::check_tls(relinfo, relnum, rela.get_r_offset(),
1608                  (memcmp(view - 4, "\x66\x48\x8d\x3d", 4) == 0));
1609   tls::check_tls(relinfo, relnum, rela.get_r_offset(),
1610                  (memcmp(view + 4, "\x66\x66\x48\xe8", 4) == 0));
1611
1612   memcpy(view - 4, "\x64\x48\x8b\x04\x25\0\0\0\0\x48\x8d\x80\0\0\0\0", 16);
1613
1614   value = value - (tls_segment->vaddr() + tls_segment->memsz());
1615   Relocate_functions<64, false>::rela32(view + 8, value, 0);
1616
1617   // The next reloc should be a PLT32 reloc against __tls_get_addr.
1618   // We can skip it.
1619   this->skip_call_tls_get_addr_ = true;
1620 }
1621
1622 inline void
1623 Target_x86_64::Relocate::tls_ld_to_le(const Relocate_info<64, false>* relinfo,
1624                                       size_t relnum,
1625                                       Output_segment*,
1626                                       const elfcpp::Rela<64, false>& rela,
1627                                       unsigned int,
1628                                       elfcpp::Elf_types<64>::Elf_Addr,
1629                                       unsigned char* view,
1630                                       off_t view_size)
1631 {
1632   // leaq foo@tlsld(%rip),%rdi; call __tls_get_addr@plt;
1633   // ... leq foo@dtpoff(%rax),%reg
1634   // ==> .word 0x6666; .byte 0x66; movq %fs:0,%rax ... leaq x@tpoff(%rax),%rdx
1635
1636   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
1637   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 9);
1638
1639   tls::check_tls(relinfo, relnum, rela.get_r_offset(),
1640                  view[-3] == 0x48 && view[-2] == 0x8d && view[-1] == 0x3d);
1641
1642   tls::check_tls(relinfo, relnum, rela.get_r_offset(), view[4] == 0xe8);
1643
1644   memcpy(view - 3, "\x66\x66\x66\x64\x48\x8b\x04\x25\0\0\0\0", 12);
1645
1646   // The next reloc should be a PLT32 reloc against __tls_get_addr.
1647   // We can skip it.
1648   this->skip_call_tls_get_addr_ = true;
1649 }
1650
1651 // Do a relocation in which we convert a TLS Initial-Exec to a
1652 // Local-Exec.
1653
1654 inline void
1655 Target_x86_64::Relocate::tls_ie_to_le(const Relocate_info<64, false>* relinfo,
1656                                       size_t relnum,
1657                                       Output_segment* tls_segment,
1658                                       const elfcpp::Rela<64, false>& rela,
1659                                       unsigned int,
1660                                       elfcpp::Elf_types<64>::Elf_Addr value,
1661                                       unsigned char* view,
1662                                       off_t view_size)
1663 {
1664   // We need to examine the opcodes to figure out which instruction we
1665   // are looking at.
1666
1667   // movq foo@gottpoff(%rip),%reg  ==>  movq $YY,%reg
1668   // addq foo@gottpoff(%rip),%reg  ==>  addq $YY,%reg
1669
1670   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, -3);
1671   tls::check_range(relinfo, relnum, rela.get_r_offset(), view_size, 4);
1672
1673   unsigned char op1 = view[-3];
1674   unsigned char op2 = view[-2];
1675   unsigned char op3 = view[-1];
1676   unsigned char reg = op3 >> 3;
1677
1678   if (op2 == 0x8b)
1679     {
1680       // movq
1681       if (op1 == 0x4c)
1682         view[-3] = 0x49;
1683       view[-2] = 0xc7;
1684       view[-1] = 0xc0 | reg;
1685     }
1686   else if (reg == 4)
1687     {
1688       // Special handling for %rsp.
1689       if (op1 == 0x4c)
1690         view[-3] = 0x49;
1691       view[-2] = 0x81;
1692       view[-1] = 0xc0 | reg;
1693     }
1694   else
1695     {
1696       // addq
1697       if (op1 == 0x4c)
1698         view[-3] = 0x4d;
1699       view[-2] = 0x8d;
1700       view[-1] = 0x80 | reg | (reg << 3);
1701     }
1702
1703   value = value - (tls_segment->vaddr() + tls_segment->memsz());
1704   Relocate_functions<64, false>::rela32(view, value, 0);
1705 }
1706
1707 // Relocate section data.
1708
1709 void
1710 Target_x86_64::relocate_section(const Relocate_info<64, false>* relinfo,
1711                                 unsigned int sh_type,
1712                                 const unsigned char* prelocs,
1713                                 size_t reloc_count,
1714                                 Output_section* output_section,
1715                                 bool needs_special_offset_handling,
1716                                 unsigned char* view,
1717                                 elfcpp::Elf_types<64>::Elf_Addr address,
1718                                 off_t view_size)
1719 {
1720   gold_assert(sh_type == elfcpp::SHT_RELA);
1721
1722   gold::relocate_section<64, false, Target_x86_64, elfcpp::SHT_RELA,
1723                          Target_x86_64::Relocate>(
1724     relinfo,
1725     this,
1726     prelocs,
1727     reloc_count,
1728     output_section,
1729     needs_special_offset_handling,
1730     view,
1731     address,
1732     view_size);
1733 }
1734
1735 // Return the value to use for a dynamic which requires special
1736 // treatment.  This is how we support equality comparisons of function
1737 // pointers across shared library boundaries, as described in the
1738 // processor specific ABI supplement.
1739
1740 uint64_t
1741 Target_x86_64::do_dynsym_value(const Symbol* gsym) const
1742 {
1743   gold_assert(gsym->is_from_dynobj() && gsym->has_plt_offset());
1744   return this->plt_section()->address() + gsym->plt_offset();
1745 }
1746
1747 // Return a string used to fill a code section with nops to take up
1748 // the specified length.
1749
1750 std::string
1751 Target_x86_64::do_code_fill(off_t length)
1752 {
1753   if (length >= 16)
1754     {
1755       // Build a jmpq instruction to skip over the bytes.
1756       unsigned char jmp[5];
1757       jmp[0] = 0xe9;
1758       elfcpp::Swap_unaligned<64, false>::writeval(jmp + 1, length - 5);
1759       return (std::string(reinterpret_cast<char*>(&jmp[0]), 5)
1760               + std::string(length - 5, '\0'));
1761     }
1762
1763   // Nop sequences of various lengths.
1764   const char nop1[1] = { 0x90 };                   // nop
1765   const char nop2[2] = { 0x66, 0x90 };             // xchg %ax %ax
1766   const char nop3[3] = { 0x8d, 0x76, 0x00 };       // leal 0(%esi),%esi
1767   const char nop4[4] = { 0x8d, 0x74, 0x26, 0x00};  // leal 0(%esi,1),%esi
1768   const char nop5[5] = { 0x90, 0x8d, 0x74, 0x26,   // nop
1769                          0x00 };                   // leal 0(%esi,1),%esi
1770   const char nop6[6] = { 0x8d, 0xb6, 0x00, 0x00,   // leal 0L(%esi),%esi
1771                          0x00, 0x00 };
1772   const char nop7[7] = { 0x8d, 0xb4, 0x26, 0x00,   // leal 0L(%esi,1),%esi
1773                          0x00, 0x00, 0x00 };
1774   const char nop8[8] = { 0x90, 0x8d, 0xb4, 0x26,   // nop
1775                          0x00, 0x00, 0x00, 0x00 }; // leal 0L(%esi,1),%esi
1776   const char nop9[9] = { 0x89, 0xf6, 0x8d, 0xbc,   // movl %esi,%esi
1777                          0x27, 0x00, 0x00, 0x00,   // leal 0L(%edi,1),%edi
1778                          0x00 };
1779   const char nop10[10] = { 0x8d, 0x76, 0x00, 0x8d, // leal 0(%esi),%esi
1780                            0xbc, 0x27, 0x00, 0x00, // leal 0L(%edi,1),%edi
1781                            0x00, 0x00 };
1782   const char nop11[11] = { 0x8d, 0x74, 0x26, 0x00, // leal 0(%esi,1),%esi
1783                            0x8d, 0xbc, 0x27, 0x00, // leal 0L(%edi,1),%edi
1784                            0x00, 0x00, 0x00 };
1785   const char nop12[12] = { 0x8d, 0xb6, 0x00, 0x00, // leal 0L(%esi),%esi
1786                            0x00, 0x00, 0x8d, 0xbf, // leal 0L(%edi),%edi
1787                            0x00, 0x00, 0x00, 0x00 };
1788   const char nop13[13] = { 0x8d, 0xb6, 0x00, 0x00, // leal 0L(%esi),%esi
1789                            0x00, 0x00, 0x8d, 0xbc, // leal 0L(%edi,1),%edi
1790                            0x27, 0x00, 0x00, 0x00,
1791                            0x00 };
1792   const char nop14[14] = { 0x8d, 0xb4, 0x26, 0x00, // leal 0L(%esi,1),%esi
1793                            0x00, 0x00, 0x00, 0x8d, // leal 0L(%edi,1),%edi
1794                            0xbc, 0x27, 0x00, 0x00,
1795                            0x00, 0x00 };
1796   const char nop15[15] = { 0xeb, 0x0d, 0x90, 0x90, // jmp .+15
1797                            0x90, 0x90, 0x90, 0x90, // nop,nop,nop,...
1798                            0x90, 0x90, 0x90, 0x90,
1799                            0x90, 0x90, 0x90 };
1800
1801   const char* nops[16] = {
1802     NULL,
1803     nop1, nop2, nop3, nop4, nop5, nop6, nop7,
1804     nop8, nop9, nop10, nop11, nop12, nop13, nop14, nop15
1805   };
1806
1807   return std::string(nops[length], length);
1808 }
1809
1810 // The selector for x86_64 object files.
1811
1812 class Target_selector_x86_64 : public Target_selector
1813 {
1814 public:
1815   Target_selector_x86_64()
1816     : Target_selector(elfcpp::EM_X86_64, 64, false)
1817   { }
1818
1819   Target*
1820   recognize(int machine, int osabi, int abiversion);
1821
1822  private:
1823   Target_x86_64* target_;
1824 };
1825
1826 // Recognize an x86_64 object file when we already know that the machine
1827 // number is EM_X86_64.
1828
1829 Target*
1830 Target_selector_x86_64::recognize(int, int, int)
1831 {
1832   if (this->target_ == NULL)
1833     this->target_ = new Target_x86_64();
1834   return this->target_;
1835 }
1836
1837 Target_selector_x86_64 target_selector_x86_64;
1838
1839 } // End anonymous namespace.