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