lib/MC/ELFObjectWriter.cpp

   1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements ELF object file writer information.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/ADT/SmallPtrSet.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/StringMap.h"
  17 #include "llvm/ADT/Twine.h"
  18 #include "llvm/MC/MCAssembler.h"
  19 #include "llvm/MC/MCAsmLayout.h"
  20 #include "llvm/MC/MCContext.h"
  21 #include "llvm/MC/MCELFSymbolFlags.h"
  22 #include "llvm/MC/MCExpr.h"
  23 #include "llvm/MC/MCELFObjectWriter.h"
  24 #include "llvm/MC/MCObjectWriter.h"
  25 #include "llvm/MC/MCSectionELF.h"
  26 #include "llvm/MC/MCSymbol.h"
  27 #include "llvm/MC/MCValue.h"
  28 #include "llvm/Support/Debug.h"
  29 #include "llvm/Support/ErrorHandling.h"
  30 #include "llvm/Support/ELF.h"
  31 #include "llvm/Target/TargetAsmBackend.h"
  32
  33 #include "../Target/X86/X86FixupKinds.h"
  34 #include "../Target/ARM/ARMFixupKinds.h"
  35
  36 #include <vector>
  37 using namespace llvm;
  38
  39 static unsigned GetType(const MCSymbolData &SD) {
  40   uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
  41   assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
  42          Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
  43          Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
  44          Type == ELF::STT_TLS);
  45   return Type;
  46 }
  47
  48 static unsigned GetBinding(const MCSymbolData &SD) {
  49   uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
  50   assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
  51          Binding == ELF::STB_WEAK);
  52   return Binding;
  53 }
  54
  55 static void SetBinding(MCSymbolData &SD, unsigned Binding) {
  56   assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
  57          Binding == ELF::STB_WEAK);
  58   uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
  59   SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
  60 }
  61
  62 static unsigned GetVisibility(MCSymbolData &SD) {
  63   unsigned Visibility =
  64     (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
  65   assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
  66          Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
  67   return Visibility;
  68 }
  69
  70
  71 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
  72   switch (Variant) {
  73   default:
  74     return false;
  75   case MCSymbolRefExpr::VK_GOT:
  76   case MCSymbolRefExpr::VK_PLT:
  77   case MCSymbolRefExpr::VK_GOTPCREL:
  78   case MCSymbolRefExpr::VK_TPOFF:
  79   case MCSymbolRefExpr::VK_TLSGD:
  80   case MCSymbolRefExpr::VK_GOTTPOFF:
  81   case MCSymbolRefExpr::VK_INDNTPOFF:
  82   case MCSymbolRefExpr::VK_NTPOFF:
  83   case MCSymbolRefExpr::VK_GOTNTPOFF:
  84   case MCSymbolRefExpr::VK_TLSLDM:
  85   case MCSymbolRefExpr::VK_DTPOFF:
  86   case MCSymbolRefExpr::VK_TLSLD:
  87     return true;
  88   }
  89 }
  90
  91 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
  92   const MCFixupKindInfo &FKI =
  93     Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
  94
  95   return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
  96 }
  97
  98 namespace {
  99   class ELFObjectWriter : public MCObjectWriter {
 100   protected:
 101     /*static bool isFixupKindX86RIPRel(unsigned Kind) {
 102       return Kind == X86::reloc_riprel_4byte ||
 103         Kind == X86::reloc_riprel_4byte_movq_load;
 104     }*/
 105
 106
 107     /// ELFSymbolData - Helper struct for containing some precomputed information
 108     /// on symbols.
 109     struct ELFSymbolData {
 110       MCSymbolData *SymbolData;
 111       uint64_t StringIndex;
 112       uint32_t SectionIndex;
 113
 114       // Support lexicographic sorting.
 115       bool operator<(const ELFSymbolData &RHS) const {
 116         if (GetType(*SymbolData) == ELF::STT_FILE)
 117           return true;
 118         if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
 119           return false;
 120         return SymbolData->getSymbol().getName() <
 121                RHS.SymbolData->getSymbol().getName();
 122       }
 123     };
 124
 125     /// @name Relocation Data
 126     /// @{
 127
 128     struct ELFRelocationEntry {
 129       // Make these big enough for both 32-bit and 64-bit
 130       uint64_t r_offset;
 131       int Index;
 132       unsigned Type;
 133       const MCSymbol *Symbol;
 134       uint64_t r_addend;
 135
 136       ELFRelocationEntry()
 137         : r_offset(0), Index(0), Type(0), Symbol(0), r_addend(0) {}
 138
 139       ELFRelocationEntry(uint64_t RelocOffset, int Idx,
 140                          unsigned RelType, const MCSymbol *Sym,
 141                          uint64_t Addend)
 142         : r_offset(RelocOffset), Index(Idx), Type(RelType),
 143           Symbol(Sym), r_addend(Addend) {}
 144
 145       // Support lexicographic sorting.
 146       bool operator<(const ELFRelocationEntry &RE) const {
 147         return RE.r_offset < r_offset;
 148       }
 149     };
 150
 151     SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
 152     SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
 153     DenseMap<const MCSymbol *, const MCSymbol *> Renames;
 154
 155     llvm::DenseMap<const MCSectionData*,
 156                    std::vector<ELFRelocationEntry> > Relocations;
 157     DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
 158
 159     /// @}
 160     /// @name Symbol Table Data
 161     /// @{
 162
 163     SmallString<256> StringTable;
 164     std::vector<ELFSymbolData> LocalSymbolData;
 165     std::vector<ELFSymbolData> ExternalSymbolData;
 166     std::vector<ELFSymbolData> UndefinedSymbolData;
 167
 168     /// @}
 169
 170     bool NeedsGOT;
 171
 172     bool NeedsSymtabShndx;
 173
 174     unsigned Is64Bit : 1;
 175
 176     bool HasRelocationAddend;
 177
 178     Triple::OSType OSType;
 179
 180     uint16_t EMachine;
 181
 182     // This holds the symbol table index of the last local symbol.
 183     unsigned LastLocalSymbolIndex;
 184     // This holds the .strtab section index.
 185     unsigned StringTableIndex;
 186     // This holds the .symtab section index.
 187     unsigned SymbolTableIndex;
 188
 189     unsigned ShstrtabIndex;
 190
 191
 192     const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
 193                                   const MCValue &Target,
 194                                   const MCFragment &F) const;
 195
 196   public:
 197     ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
 198                     uint16_t _EMachine, bool _HasRelAddend,
 199                     Triple::OSType _OSType)
 200       : MCObjectWriter(_OS, IsLittleEndian),
 201         NeedsGOT(false), NeedsSymtabShndx(false),
 202         Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
 203         OSType(_OSType), EMachine(_EMachine) {
 204     }
 205
 206     virtual ~ELFObjectWriter();
 207
 208     void WriteWord(uint64_t W) {
 209       if (Is64Bit)
 210         Write64(W);
 211       else
 212         Write32(W);
 213     }
 214
 215     void StringLE16(char *buf, uint16_t Value) {
 216       buf[0] = char(Value >> 0);
 217       buf[1] = char(Value >> 8);
 218     }
 219
 220     void StringLE32(char *buf, uint32_t Value) {
 221       StringLE16(buf, uint16_t(Value >> 0));
 222       StringLE16(buf + 2, uint16_t(Value >> 16));
 223     }
 224
 225     void StringLE64(char *buf, uint64_t Value) {
 226       StringLE32(buf, uint32_t(Value >> 0));
 227       StringLE32(buf + 4, uint32_t(Value >> 32));
 228     }
 229
 230     void StringBE16(char *buf ,uint16_t Value) {
 231       buf[0] = char(Value >> 8);
 232       buf[1] = char(Value >> 0);
 233     }
 234
 235     void StringBE32(char *buf, uint32_t Value) {
 236       StringBE16(buf, uint16_t(Value >> 16));
 237       StringBE16(buf + 2, uint16_t(Value >> 0));
 238     }
 239
 240     void StringBE64(char *buf, uint64_t Value) {
 241       StringBE32(buf, uint32_t(Value >> 32));
 242       StringBE32(buf + 4, uint32_t(Value >> 0));
 243     }
 244
 245     void String8(MCDataFragment &F, uint8_t Value) {
 246       char buf[1];
 247       buf[0] = Value;
 248       F.getContents() += StringRef(buf, 1);
 249     }
 250
 251     void String16(MCDataFragment &F, uint16_t Value) {
 252       char buf[2];
 253       if (isLittleEndian())
 254         StringLE16(buf, Value);
 255       else
 256         StringBE16(buf, Value);
 257       F.getContents() += StringRef(buf, 2);
 258     }
 259
 260     void String32(MCDataFragment &F, uint32_t Value) {
 261       char buf[4];
 262       if (isLittleEndian())
 263         StringLE32(buf, Value);
 264       else
 265         StringBE32(buf, Value);
 266       F.getContents() += StringRef(buf, 4);
 267     }
 268
 269     void String64(MCDataFragment &F, uint64_t Value) {
 270       char buf[8];
 271       if (isLittleEndian())
 272         StringLE64(buf, Value);
 273       else
 274         StringBE64(buf, Value);
 275       F.getContents() += StringRef(buf, 8);
 276     }
 277
 278     virtual void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
 279
 280     virtual void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
 281                           uint64_t name, uint8_t info,
 282                           uint64_t value, uint64_t size,
 283                           uint8_t other, uint32_t shndx,
 284                           bool Reserved);
 285
 286     virtual void WriteSymbol(MCDataFragment *SymtabF,  MCDataFragment *ShndxF,
 287                      ELFSymbolData &MSD,
 288                      const MCAsmLayout &Layout);
 289
 290     typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
 291     virtual void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
 292                           const MCAssembler &Asm,
 293                           const MCAsmLayout &Layout,
 294                           const SectionIndexMapTy &SectionIndexMap);
 295
 296     virtual void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
 297                                   const MCFragment *Fragment, const MCFixup &Fixup,
 298                                   MCValue Target, uint64_t &FixedValue);
 299
 300     virtual uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
 301                                          const MCSymbol *S);
 302
 303     // Map from a group section to the signature symbol
 304     typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
 305     // Map from a signature symbol to the group section
 306     typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
 307
 308     /// ComputeSymbolTable - Compute the symbol table data
 309     ///
 310     /// \param StringTable [out] - The string table data.
 311     /// \param StringIndexMap [out] - Map from symbol names to offsets in the
 312     /// string table.
 313     virtual void ComputeSymbolTable(MCAssembler &Asm,
 314                             const SectionIndexMapTy &SectionIndexMap,
 315                             RevGroupMapTy RevGroupMap);
 316
 317     virtual void ComputeIndexMap(MCAssembler &Asm,
 318                          SectionIndexMapTy &SectionIndexMap);
 319
 320     virtual void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
 321                          const MCSectionData &SD);
 322
 323     virtual void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
 324       for (MCAssembler::const_iterator it = Asm.begin(),
 325              ie = Asm.end(); it != ie; ++it) {
 326         WriteRelocation(Asm, Layout, *it);
 327       }
 328     }
 329
 330     virtual void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
 331                                 const SectionIndexMapTy &SectionIndexMap);
 332
 333     virtual void CreateGroupSections(MCAssembler &Asm, MCAsmLayout &Layout,
 334                              GroupMapTy &GroupMap, RevGroupMapTy &RevGroupMap);
 335
 336     virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
 337                                           const MCAsmLayout &Layout);
 338
 339     virtual void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
 340                           uint64_t Address, uint64_t Offset,
 341                           uint64_t Size, uint32_t Link, uint32_t Info,
 342                           uint64_t Alignment, uint64_t EntrySize);
 343
 344     virtual void WriteRelocationsFragment(const MCAssembler &Asm,
 345                                           MCDataFragment *F,
 346                                           const MCSectionData *SD);
 347
 348     virtual bool
 349     IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
 350                                        const MCSymbolRefExpr *A,
 351                                        const MCSymbolRefExpr *B) const {
 352       // FIXME: Implement this!
 353       return false;
 354     }
 355
 356     virtual bool IsFixupFullyResolved(const MCAssembler &Asm,
 357                               const MCValue Target,
 358                               bool IsPCRel,
 359                               const MCFragment *DF) const;
 360
 361     virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
 362     virtual void WriteSection(MCAssembler &Asm,
 363                       const SectionIndexMapTy &SectionIndexMap,
 364                       uint32_t GroupSymbolIndex,
 365                       uint64_t Offset, uint64_t Size, uint64_t Alignment,
 366                       const MCSectionELF &Section);
 367
 368   protected:
 369     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 370                                   bool IsPCRel, bool IsRelocWithSymbol,
 371                                   int64_t Addend) = 0;
 372   };
 373
 374   //===- X86ELFObjectWriter -------------------------------------------===//
 375
 376   class X86ELFObjectWriter : public ELFObjectWriter {
 377   public:
 378     X86ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
 379                        uint16_t _EMachine, bool _HasRelAddend,
 380                        Triple::OSType _OSType);
 381
 382     virtual ~X86ELFObjectWriter();
 383   protected:
 384     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 385                                   bool IsPCRel, bool IsRelocWithSymbol,
 386                                   int64_t Addend);
 387   };
 388
 389
 390   //===- ARMELFObjectWriter -------------------------------------------===//
 391
 392   class ARMELFObjectWriter : public ELFObjectWriter {
 393   public:
 394     ARMELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
 395                        uint16_t _EMachine, bool _HasRelAddend,
 396                        Triple::OSType _OSType);
 397
 398     virtual ~ARMELFObjectWriter();
 399   protected:
 400     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 401                                   bool IsPCRel, bool IsRelocWithSymbol,
 402                                   int64_t Addend);
 403   };
 404
 405   //===- MBlazeELFObjectWriter -------------------------------------------===//
 406
 407   class MBlazeELFObjectWriter : public ELFObjectWriter {
 408   public:
 409     MBlazeELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
 410                           uint16_t _EMachine, bool _HasRelAddend,
 411                           Triple::OSType _OSType);
 412
 413     virtual ~MBlazeELFObjectWriter();
 414   protected:
 415     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 416                                   bool IsPCRel, bool IsRelocWithSymbol,
 417                                   int64_t Addend);
 418   };
 419 }
 420
 421 ELFObjectWriter::~ELFObjectWriter()
 422 {}
 423
 424 // Emit the ELF header.
 425 void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize,
 426                                   unsigned NumberOfSections) {
 427   // ELF Header
 428   // ----------
 429   //
 430   // Note
 431   // ----
 432   // emitWord method behaves differently for ELF32 and ELF64, writing
 433   // 4 bytes in the former and 8 in the latter.
 434
 435   Write8(0x7f); // e_ident[EI_MAG0]
 436   Write8('E');  // e_ident[EI_MAG1]
 437   Write8('L');  // e_ident[EI_MAG2]
 438   Write8('F');  // e_ident[EI_MAG3]
 439
 440   Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
 441
 442   // e_ident[EI_DATA]
 443   Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
 444
 445   Write8(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
 446   // e_ident[EI_OSABI]
 447   switch (OSType) {
 448     case Triple::FreeBSD:  Write8(ELF::ELFOSABI_FREEBSD); break;
 449     case Triple::Linux:    Write8(ELF::ELFOSABI_LINUX); break;
 450     default:               Write8(ELF::ELFOSABI_NONE); break;
 451   }
 452   Write8(0);                  // e_ident[EI_ABIVERSION]
 453
 454   WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
 455
 456   Write16(ELF::ET_REL);             // e_type
 457
 458   Write16(EMachine); // e_machine = target
 459
 460   Write32(ELF::EV_CURRENT);         // e_version
 461   WriteWord(0);                    // e_entry, no entry point in .o file
 462   WriteWord(0);                    // e_phoff, no program header for .o
 463   WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
 464             sizeof(ELF::Elf32_Ehdr)));  // e_shoff = sec hdr table off in bytes
 465
 466   // FIXME: Make this configurable.
 467   Write32(0);   // e_flags = whatever the target wants
 468
 469   // e_ehsize = ELF header size
 470   Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
 471
 472   Write16(0);                  // e_phentsize = prog header entry size
 473   Write16(0);                  // e_phnum = # prog header entries = 0
 474
 475   // e_shentsize = Section header entry size
 476   Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
 477
 478   // e_shnum     = # of section header ents
 479   if (NumberOfSections >= ELF::SHN_LORESERVE)
 480     Write16(0);
 481   else
 482     Write16(NumberOfSections);
 483
 484   // e_shstrndx  = Section # of '.shstrtab'
 485   if (NumberOfSections >= ELF::SHN_LORESERVE)
 486     Write16(ELF::SHN_XINDEX);
 487   else
 488     Write16(ShstrtabIndex);
 489 }
 490
 491 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
 492                                        MCDataFragment *ShndxF,
 493                                        uint64_t name,
 494                                        uint8_t info, uint64_t value,
 495                                        uint64_t size, uint8_t other,
 496                                        uint32_t shndx,
 497                                        bool Reserved) {
 498   if (ShndxF) {
 499     if (shndx >= ELF::SHN_LORESERVE && !Reserved)
 500       String32(*ShndxF, shndx);
 501     else
 502       String32(*ShndxF, 0);
 503   }
 504
 505   uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
 506     uint16_t(ELF::SHN_XINDEX) : shndx;
 507
 508   if (Is64Bit) {
 509     String32(*SymtabF, name);  // st_name
 510     String8(*SymtabF, info);   // st_info
 511     String8(*SymtabF, other);  // st_other
 512     String16(*SymtabF, Index); // st_shndx
 513     String64(*SymtabF, value); // st_value
 514     String64(*SymtabF, size);  // st_size
 515   } else {
 516     String32(*SymtabF, name);  // st_name
 517     String32(*SymtabF, value); // st_value
 518     String32(*SymtabF, size);  // st_size
 519     String8(*SymtabF, info);   // st_info
 520     String8(*SymtabF, other);  // st_other
 521     String16(*SymtabF, Index); // st_shndx
 522   }
 523 }
 524
 525 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) {
 526   if (Data.isCommon() && Data.isExternal())
 527     return Data.getCommonAlignment();
 528
 529   const MCSymbol &Symbol = Data.getSymbol();
 530   if (!Symbol.isInSection())
 531     return 0;
 532
 533   if (Data.getFragment())
 534     return Layout.getSymbolOffset(&Data);
 535
 536   return 0;
 537 }
 538
 539 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
 540                                                const MCAsmLayout &Layout) {
 541   // The presence of symbol versions causes undefined symbols and
 542   // versions declared with @@@ to be renamed.
 543
 544   for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
 545          ie = Asm.symbol_end(); it != ie; ++it) {
 546     const MCSymbol &Alias = it->getSymbol();
 547     const MCSymbol &Symbol = Alias.AliasedSymbol();
 548     MCSymbolData &SD = Asm.getSymbolData(Symbol);
 549
 550     // Not an alias.
 551     if (&Symbol == &Alias)
 552       continue;
 553
 554     StringRef AliasName = Alias.getName();
 555     size_t Pos = AliasName.find('@');
 556     if (Pos == StringRef::npos)
 557       continue;
 558
 559     // Aliases defined with .symvar copy the binding from the symbol they alias.
 560     // This is the first place we are able to copy this information.
 561     it->setExternal(SD.isExternal());
 562     SetBinding(*it, GetBinding(SD));
 563
 564     StringRef Rest = AliasName.substr(Pos);
 565     if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
 566       continue;
 567
 568     // FIXME: produce a better error message.
 569     if (Symbol.isUndefined() && Rest.startswith("@@") &&
 570         !Rest.startswith("@@@"))
 571       report_fatal_error("A @@ version cannot be undefined");
 572
 573     Renames.insert(std::make_pair(&Symbol, &Alias));
 574   }
 575 }
 576
 577 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
 578                                   MCDataFragment *ShndxF,
 579                                   ELFSymbolData &MSD,
 580                                   const MCAsmLayout &Layout) {
 581   MCSymbolData &OrigData = *MSD.SymbolData;
 582   MCSymbolData &Data =
 583     Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
 584
 585   bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
 586     Data.getSymbol().isVariable();
 587
 588   uint8_t Binding = GetBinding(OrigData);
 589   uint8_t Visibility = GetVisibility(OrigData);
 590   uint8_t Type = GetType(Data);
 591
 592   uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
 593   uint8_t Other = Visibility;
 594
 595   uint64_t Value = SymbolValue(Data, Layout);
 596   uint64_t Size = 0;
 597   const MCExpr *ESize;
 598
 599   assert(!(Data.isCommon() && !Data.isExternal()));
 600
 601   ESize = Data.getSize();
 602   if (Data.getSize()) {
 603     MCValue Res;
 604     if (ESize->getKind() == MCExpr::Binary) {
 605       const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
 606
 607       if (BE->EvaluateAsRelocatable(Res, &Layout)) {
 608         assert(!Res.getSymA() || !Res.getSymA()->getSymbol().isDefined());
 609         assert(!Res.getSymB() || !Res.getSymB()->getSymbol().isDefined());
 610         Size = Res.getConstant();
 611       }
 612     } else if (ESize->getKind() == MCExpr::Constant) {
 613       Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
 614     } else {
 615       assert(0 && "Unsupported size expression");
 616     }
 617   }
 618
 619   // Write out the symbol table entry
 620   WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
 621                    Size, Other, MSD.SectionIndex, IsReserved);
 622 }
 623
 624 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
 625                                        MCDataFragment *ShndxF,
 626                                        const MCAssembler &Asm,
 627                                        const MCAsmLayout &Layout,
 628                                      const SectionIndexMapTy &SectionIndexMap) {
 629   // The string table must be emitted first because we need the index
 630   // into the string table for all the symbol names.
 631   assert(StringTable.size() && "Missing string table");
 632
 633   // FIXME: Make sure the start of the symbol table is aligned.
 634
 635   // The first entry is the undefined symbol entry.
 636   WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
 637
 638   // Write the symbol table entries.
 639   LastLocalSymbolIndex = LocalSymbolData.size() + 1;
 640   for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
 641     ELFSymbolData &MSD = LocalSymbolData[i];
 642     WriteSymbol(SymtabF, ShndxF, MSD, Layout);
 643   }
 644
 645   // Write out a symbol table entry for each regular section.
 646   for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
 647        ++i) {
 648     const MCSectionELF &Section =
 649       static_cast<const MCSectionELF&>(i->getSection());
 650     if (Section.getType() == ELF::SHT_RELA ||
 651         Section.getType() == ELF::SHT_REL ||
 652         Section.getType() == ELF::SHT_STRTAB ||
 653         Section.getType() == ELF::SHT_SYMTAB)
 654       continue;
 655     WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
 656                      ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false);
 657     LastLocalSymbolIndex++;
 658   }
 659
 660   for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
 661     ELFSymbolData &MSD = ExternalSymbolData[i];
 662     MCSymbolData &Data = *MSD.SymbolData;
 663     assert(((Data.getFlags() & ELF_STB_Global) ||
 664             (Data.getFlags() & ELF_STB_Weak)) &&
 665            "External symbol requires STB_GLOBAL or STB_WEAK flag");
 666     WriteSymbol(SymtabF, ShndxF, MSD, Layout);
 667     if (GetBinding(Data) == ELF::STB_LOCAL)
 668       LastLocalSymbolIndex++;
 669   }
 670
 671   for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
 672     ELFSymbolData &MSD = UndefinedSymbolData[i];
 673     MCSymbolData &Data = *MSD.SymbolData;
 674     WriteSymbol(SymtabF, ShndxF, MSD, Layout);
 675     if (GetBinding(Data) == ELF::STB_LOCAL)
 676       LastLocalSymbolIndex++;
 677   }
 678 }
 679
 680 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
 681                                                const MCValue &Target,
 682                                                const MCFragment &F) const {
 683   const MCSymbol &Symbol = Target.getSymA()->getSymbol();
 684   const MCSymbol &ASymbol = Symbol.AliasedSymbol();
 685   const MCSymbol *Renamed = Renames.lookup(&Symbol);
 686   const MCSymbolData &SD = Asm.getSymbolData(Symbol);
 687
 688   if (ASymbol.isUndefined()) {
 689     if (Renamed)
 690       return Renamed;
 691     return &ASymbol;
 692   }
 693
 694   if (SD.isExternal()) {
 695     if (Renamed)
 696       return Renamed;
 697     return &Symbol;
 698   }
 699
 700   const MCSectionELF &Section =
 701     static_cast<const MCSectionELF&>(ASymbol.getSection());
 702   const SectionKind secKind = Section.getKind();
 703
 704   if (secKind.isBSS())
 705     return NULL;
 706
 707   if (secKind.isThreadLocal()) {
 708     if (Renamed)
 709       return Renamed;
 710     return &Symbol;
 711   }
 712
 713   MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
 714   const MCSectionELF &Sec2 =
 715     static_cast<const MCSectionELF&>(F.getParent()->getSection());
 716
 717   if (&Sec2 != &Section &&
 718       (Kind == MCSymbolRefExpr::VK_PLT ||
 719        Kind == MCSymbolRefExpr::VK_GOTPCREL ||
 720        Kind == MCSymbolRefExpr::VK_GOTOFF)) {
 721     if (Renamed)
 722       return Renamed;
 723     return &Symbol;
 724   }
 725
 726   if (Section.getFlags() & MCSectionELF::SHF_MERGE) {
 727     if (Target.getConstant() == 0)
 728       return NULL;
 729     if (Renamed)
 730       return Renamed;
 731     return &Symbol;
 732   }
 733
 734   return NULL;
 735 }
 736
 737
 738 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
 739                                        const MCAsmLayout &Layout,
 740                                        const MCFragment *Fragment,
 741                                        const MCFixup &Fixup,
 742                                        MCValue Target,
 743                                        uint64_t &FixedValue) {
 744   int64_t Addend = 0;
 745   int Index = 0;
 746   int64_t Value = Target.getConstant();
 747   const MCSymbol *RelocSymbol = NULL;
 748
 749   bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
 750   if (!Target.isAbsolute()) {
 751     const MCSymbol &Symbol = Target.getSymA()->getSymbol();
 752     const MCSymbol &ASymbol = Symbol.AliasedSymbol();
 753     RelocSymbol = SymbolToReloc(Asm, Target, *Fragment);
 754
 755     if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
 756       const MCSymbol &SymbolB = RefB->getSymbol();
 757       MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
 758       IsPCRel = true;
 759
 760       // Offset of the symbol in the section
 761       int64_t a = Layout.getSymbolOffset(&SDB);
 762
 763       // Ofeset of the relocation in the section
 764       int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
 765       Value += b - a;
 766     }
 767
 768     if (!RelocSymbol) {
 769       MCSymbolData &SD = Asm.getSymbolData(ASymbol);
 770       MCFragment *F = SD.getFragment();
 771
 772       Index = F->getParent()->getOrdinal() + 1;
 773
 774       // Offset of the symbol in the section
 775       Value += Layout.getSymbolOffset(&SD);
 776     } else {
 777       if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
 778         WeakrefUsedInReloc.insert(RelocSymbol);
 779       else
 780         UsedInReloc.insert(RelocSymbol);
 781       Index = -1;
 782     }
 783     Addend = Value;
 784     // Compensate for the addend on i386.
 785     if (Is64Bit)
 786       Value = 0;
 787   }
 788
 789   FixedValue = Value;
 790   unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
 791                                (RelocSymbol != 0), Addend);
 792
 793   uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
 794     Fixup.getOffset();
 795
 796   if (!HasRelocationAddend) Addend = 0;
 797   ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend);
 798   Relocations[Fragment->getParent()].push_back(ERE);
 799 }
 800
 801
 802 uint64_t
 803 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
 804                                              const MCSymbol *S) {
 805   MCSymbolData &SD = Asm.getSymbolData(*S);
 806   return SD.getIndex();
 807 }
 808
 809 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
 810                        bool Used, bool Renamed) {
 811   if (Data.getFlags() & ELF_Other_Weakref)
 812     return false;
 813
 814   if (Used)
 815     return true;
 816
 817   if (Renamed)
 818     return false;
 819
 820   const MCSymbol &Symbol = Data.getSymbol();
 821
 822   if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
 823     return true;
 824
 825   const MCSymbol &A = Symbol.AliasedSymbol();
 826   if (!A.isVariable() && A.isUndefined() && !Data.isCommon())
 827     return false;
 828
 829   if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
 830     return false;
 831
 832   if (Symbol.isTemporary())
 833     return false;
 834
 835   return true;
 836 }
 837
 838 static bool isLocal(const MCSymbolData &Data, bool isSignature,
 839                     bool isUsedInReloc) {
 840   if (Data.isExternal())
 841     return false;
 842
 843   const MCSymbol &Symbol = Data.getSymbol();
 844   const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
 845
 846   if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
 847     if (isSignature && !isUsedInReloc)
 848       return true;
 849
 850     return false;
 851   }
 852
 853   return true;
 854 }
 855
 856 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
 857                                       SectionIndexMapTy &SectionIndexMap) {
 858   unsigned Index = 1;
 859   for (MCAssembler::iterator it = Asm.begin(),
 860          ie = Asm.end(); it != ie; ++it) {
 861     const MCSectionELF &Section =
 862       static_cast<const MCSectionELF &>(it->getSection());
 863     if (Section.getType() != ELF::SHT_GROUP)
 864       continue;
 865     SectionIndexMap[&Section] = Index++;
 866   }
 867
 868   for (MCAssembler::iterator it = Asm.begin(),
 869          ie = Asm.end(); it != ie; ++it) {
 870     const MCSectionELF &Section =
 871       static_cast<const MCSectionELF &>(it->getSection());
 872     if (Section.getType() == ELF::SHT_GROUP)
 873       continue;
 874     SectionIndexMap[&Section] = Index++;
 875   }
 876 }
 877
 878 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
 879                                       const SectionIndexMapTy &SectionIndexMap,
 880                                       RevGroupMapTy RevGroupMap) {
 881   // FIXME: Is this the correct place to do this?
 882   if (NeedsGOT) {
 883     llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_";
 884     MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
 885     MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
 886     Data.setExternal(true);
 887     SetBinding(Data, ELF::STB_GLOBAL);
 888   }
 889
 890   // Build section lookup table.
 891   int NumRegularSections = Asm.size();
 892
 893   // Index 0 is always the empty string.
 894   StringMap<uint64_t> StringIndexMap;
 895   StringTable += '\x00';
 896
 897   // Add the data for the symbols.
 898   for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
 899          ie = Asm.symbol_end(); it != ie; ++it) {
 900     const MCSymbol &Symbol = it->getSymbol();
 901
 902     bool Used = UsedInReloc.count(&Symbol);
 903     bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
 904     bool isSignature = RevGroupMap.count(&Symbol);
 905
 906     if (!isInSymtab(Asm, *it,
 907                     Used || WeakrefUsed || isSignature,
 908                     Renames.count(&Symbol)))
 909       continue;
 910
 911     ELFSymbolData MSD;
 912     MSD.SymbolData = it;
 913     const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
 914
 915     // Undefined symbols are global, but this is the first place we
 916     // are able to set it.
 917     bool Local = isLocal(*it, isSignature, Used);
 918     if (!Local && GetBinding(*it) == ELF::STB_LOCAL) {
 919       MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
 920       SetBinding(*it, ELF::STB_GLOBAL);
 921       SetBinding(SD, ELF::STB_GLOBAL);
 922     }
 923
 924     if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
 925       SetBinding(*it, ELF::STB_WEAK);
 926
 927     if (it->isCommon()) {
 928       assert(!Local);
 929       MSD.SectionIndex = ELF::SHN_COMMON;
 930     } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
 931       MSD.SectionIndex = ELF::SHN_ABS;
 932     } else if (RefSymbol.isUndefined()) {
 933       if (isSignature && !Used)
 934         MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
 935       else
 936         MSD.SectionIndex = ELF::SHN_UNDEF;
 937     } else {
 938       const MCSectionELF &Section =
 939         static_cast<const MCSectionELF&>(RefSymbol.getSection());
 940       MSD.SectionIndex = SectionIndexMap.lookup(&Section);
 941       if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
 942         NeedsSymtabShndx = true;
 943       assert(MSD.SectionIndex && "Invalid section index!");
 944     }
 945
 946     // The @@@ in symbol version is replaced with @ in undefined symbols and
 947     // @@ in defined ones.
 948     StringRef Name = Symbol.getName();
 949     SmallString<32> Buf;
 950
 951     size_t Pos = Name.find("@@@");
 952     if (Pos != StringRef::npos) {
 953       Buf += Name.substr(0, Pos);
 954       unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
 955       Buf += Name.substr(Pos + Skip);
 956       Name = Buf;
 957     }
 958
 959     uint64_t &Entry = StringIndexMap[Name];
 960     if (!Entry) {
 961       Entry = StringTable.size();
 962       StringTable += Name;
 963       StringTable += '\x00';
 964     }
 965     MSD.StringIndex = Entry;
 966     if (MSD.SectionIndex == ELF::SHN_UNDEF)
 967       UndefinedSymbolData.push_back(MSD);
 968     else if (Local)
 969       LocalSymbolData.push_back(MSD);
 970     else
 971       ExternalSymbolData.push_back(MSD);
 972   }
 973
 974   // Symbols are required to be in lexicographic order.
 975   array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
 976   array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
 977   array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
 978
 979   // Set the symbol indices. Local symbols must come before all other
 980   // symbols with non-local bindings.
 981   unsigned Index = 1;
 982   for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
 983     LocalSymbolData[i].SymbolData->setIndex(Index++);
 984
 985   Index += NumRegularSections;
 986
 987   for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
 988     ExternalSymbolData[i].SymbolData->setIndex(Index++);
 989   for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
 990     UndefinedSymbolData[i].SymbolData->setIndex(Index++);
 991 }
 992
 993 void ELFObjectWriter::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
 994                                       const MCSectionData &SD) {
 995   if (!Relocations[&SD].empty()) {
 996     MCContext &Ctx = Asm.getContext();
 997     const MCSectionELF *RelaSection;
 998     const MCSectionELF &Section =
 999       static_cast<const MCSectionELF&>(SD.getSection());
1000
1001     const StringRef SectionName = Section.getSectionName();
1002     std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
1003     RelaSectionName += SectionName;
1004
1005     unsigned EntrySize;
1006     if (HasRelocationAddend)
1007       EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1008     else
1009       EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1010
1011     RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
1012                                     ELF::SHT_RELA : ELF::SHT_REL, 0,
1013                                     SectionKind::getReadOnly(),
1014                                     EntrySize, "");
1015
1016     MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1017     RelaSD.setAlignment(Is64Bit ? 8 : 4);
1018
1019     MCDataFragment *F = new MCDataFragment(&RelaSD);
1020
1021     WriteRelocationsFragment(Asm, F, &SD);
1022   }
1023 }
1024
1025 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1026                                        uint64_t Flags, uint64_t Address,
1027                                        uint64_t Offset, uint64_t Size,
1028                                        uint32_t Link, uint32_t Info,
1029                                        uint64_t Alignment,
1030                                        uint64_t EntrySize) {
1031   Write32(Name);        // sh_name: index into string table
1032   Write32(Type);        // sh_type
1033   WriteWord(Flags);     // sh_flags
1034   WriteWord(Address);   // sh_addr
1035   WriteWord(Offset);    // sh_offset
1036   WriteWord(Size);      // sh_size
1037   Write32(Link);        // sh_link
1038   Write32(Info);        // sh_info
1039   WriteWord(Alignment); // sh_addralign
1040   WriteWord(EntrySize); // sh_entsize
1041 }
1042
1043 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1044                                                MCDataFragment *F,
1045                                                const MCSectionData *SD) {
1046   std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1047   // sort by the r_offset just like gnu as does
1048   array_pod_sort(Relocs.begin(), Relocs.end());
1049
1050   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1051     ELFRelocationEntry entry = Relocs[e - i - 1];
1052
1053     if (!entry.Index)
1054       ;
1055     else if (entry.Index < 0)
1056       entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1057     else
1058       entry.Index += LocalSymbolData.size();
1059     if (Is64Bit) {
1060       String64(*F, entry.r_offset);
1061
1062       struct ELF::Elf64_Rela ERE64;
1063       ERE64.setSymbolAndType(entry.Index, entry.Type);
1064       String64(*F, ERE64.r_info);
1065
1066       if (HasRelocationAddend)
1067         String64(*F, entry.r_addend);
1068     } else {
1069       String32(*F, entry.r_offset);
1070
1071       struct ELF::Elf32_Rela ERE32;
1072       ERE32.setSymbolAndType(entry.Index, entry.Type);
1073       String32(*F, ERE32.r_info);
1074
1075       if (HasRelocationAddend)
1076         String32(*F, entry.r_addend);
1077     }
1078   }
1079 }
1080
1081 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1082                                              MCAsmLayout &Layout,
1083                                     const SectionIndexMapTy &SectionIndexMap) {
1084   MCContext &Ctx = Asm.getContext();
1085   MCDataFragment *F;
1086
1087   unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1088
1089   // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1090   const MCSectionELF *ShstrtabSection =
1091     Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1092                       SectionKind::getReadOnly());
1093   MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1094   ShstrtabSD.setAlignment(1);
1095   ShstrtabIndex = Asm.size();
1096
1097   const MCSectionELF *SymtabSection =
1098     Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1099                       SectionKind::getReadOnly(),
1100                       EntrySize, "");
1101   MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1102   SymtabSD.setAlignment(Is64Bit ? 8 : 4);
1103   SymbolTableIndex = Asm.size();
1104
1105   MCSectionData *SymtabShndxSD = NULL;
1106
1107   if (NeedsSymtabShndx) {
1108     const MCSectionELF *SymtabShndxSection =
1109       Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1110                         SectionKind::getReadOnly(), 4, "");
1111     SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1112     SymtabShndxSD->setAlignment(4);
1113   }
1114
1115   const MCSection *StrtabSection;
1116   StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1117                                     SectionKind::getReadOnly());
1118   MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1119   StrtabSD.setAlignment(1);
1120   StringTableIndex = Asm.size();
1121
1122   WriteRelocations(Asm, Layout);
1123
1124   // Symbol table
1125   F = new MCDataFragment(&SymtabSD);
1126   MCDataFragment *ShndxF = NULL;
1127   if (NeedsSymtabShndx) {
1128     ShndxF = new MCDataFragment(SymtabShndxSD);
1129   }
1130   WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1131
1132   F = new MCDataFragment(&StrtabSD);
1133   F->getContents().append(StringTable.begin(), StringTable.end());
1134
1135   F = new MCDataFragment(&ShstrtabSD);
1136
1137   // Section header string table.
1138   //
1139   // The first entry of a string table holds a null character so skip
1140   // section 0.
1141   uint64_t Index = 1;
1142   F->getContents() += '\x00';
1143
1144   StringMap<uint64_t> SecStringMap;
1145   for (MCAssembler::const_iterator it = Asm.begin(),
1146          ie = Asm.end(); it != ie; ++it) {
1147     const MCSectionELF &Section =
1148       static_cast<const MCSectionELF&>(it->getSection());
1149     // FIXME: We could merge suffixes like in .text and .rela.text.
1150
1151     StringRef Name = Section.getSectionName();
1152     if (SecStringMap.count(Name)) {
1153       SectionStringTableIndex[&Section] =  SecStringMap[Name];
1154       continue;
1155     }
1156     // Remember the index into the string table so we can write it
1157     // into the sh_name field of the section header table.
1158     SectionStringTableIndex[&Section] = Index;
1159     SecStringMap[Name] = Index;
1160
1161     Index += Name.size() + 1;
1162     F->getContents() += Name;
1163     F->getContents() += '\x00';
1164   }
1165 }
1166
1167 bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm,
1168                                            const MCValue Target,
1169                                            bool IsPCRel,
1170                                            const MCFragment *DF) const {
1171   // If this is a PCrel relocation, find the section this fixup value is
1172   // relative to.
1173   const MCSection *BaseSection = 0;
1174   if (IsPCRel) {
1175     BaseSection = &DF->getParent()->getSection();
1176     assert(BaseSection);
1177   }
1178
1179   const MCSection *SectionA = 0;
1180   const MCSymbol *SymbolA = 0;
1181   if (const MCSymbolRefExpr *A = Target.getSymA()) {
1182     SymbolA = &A->getSymbol();
1183     SectionA = &SymbolA->AliasedSymbol().getSection();
1184   }
1185
1186   const MCSection *SectionB = 0;
1187   const MCSymbol *SymbolB = 0;
1188   if (const MCSymbolRefExpr *B = Target.getSymB()) {
1189     SymbolB = &B->getSymbol();
1190     SectionB = &SymbolB->AliasedSymbol().getSection();
1191   }
1192
1193   if (!BaseSection)
1194     return SectionA == SectionB;
1195
1196   if (SymbolB)
1197     return false;
1198
1199   // Absolute address but PCrel instruction, so we need a relocation.
1200   if (!SymbolA)
1201     return false;
1202
1203   // FIXME: This is in here just to match gnu as output. If the two ends
1204   // are in the same section, there is nothing that the linker can do to
1205   // break it.
1206   const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA);
1207   if (DataA.isExternal())
1208     return false;
1209
1210   return BaseSection == SectionA;
1211 }
1212
1213 void ELFObjectWriter::CreateGroupSections(MCAssembler &Asm,
1214                                           MCAsmLayout &Layout,
1215                                           GroupMapTy &GroupMap,
1216                                           RevGroupMapTy &RevGroupMap) {
1217   // Build the groups
1218   for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1219        it != ie; ++it) {
1220     const MCSectionELF &Section =
1221       static_cast<const MCSectionELF&>(it->getSection());
1222     if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1223       continue;
1224
1225     const MCSymbol *SignatureSymbol = Section.getGroup();
1226     Asm.getOrCreateSymbolData(*SignatureSymbol);
1227     const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1228     if (!Group) {
1229       Group = Asm.getContext().CreateELFGroupSection();
1230       MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1231       Data.setAlignment(4);
1232       MCDataFragment *F = new MCDataFragment(&Data);
1233       String32(*F, ELF::GRP_COMDAT);
1234     }
1235     GroupMap[Group] = SignatureSymbol;
1236   }
1237
1238   // Add sections to the groups
1239   unsigned Index = 1;
1240   unsigned NumGroups = RevGroupMap.size();
1241   for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1242        it != ie; ++it, ++Index) {
1243     const MCSectionELF &Section =
1244       static_cast<const MCSectionELF&>(it->getSection());
1245     if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1246       continue;
1247     const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1248     MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1249     // FIXME: we could use the previous fragment
1250     MCDataFragment *F = new MCDataFragment(&Data);
1251     String32(*F, NumGroups + Index);
1252   }
1253 }
1254
1255 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1256                                    const SectionIndexMapTy &SectionIndexMap,
1257                                    uint32_t GroupSymbolIndex,
1258                                    uint64_t Offset, uint64_t Size,
1259                                    uint64_t Alignment,
1260                                    const MCSectionELF &Section) {
1261   uint64_t sh_link = 0;
1262   uint64_t sh_info = 0;
1263
1264   switch(Section.getType()) {
1265   case ELF::SHT_DYNAMIC:
1266     sh_link = SectionStringTableIndex[&Section];
1267     sh_info = 0;
1268     break;
1269
1270   case ELF::SHT_REL:
1271   case ELF::SHT_RELA: {
1272     const MCSectionELF *SymtabSection;
1273     const MCSectionELF *InfoSection;
1274     SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1275                                                    0,
1276                                                    SectionKind::getReadOnly());
1277     sh_link = SectionIndexMap.lookup(SymtabSection);
1278     assert(sh_link && ".symtab not found");
1279
1280     // Remove ".rel" and ".rela" prefixes.
1281     unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1282     StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1283
1284     InfoSection = Asm.getContext().getELFSection(SectionName,
1285                                                  ELF::SHT_PROGBITS, 0,
1286                                                  SectionKind::getReadOnly());
1287     sh_info = SectionIndexMap.lookup(InfoSection);
1288     break;
1289   }
1290
1291   case ELF::SHT_SYMTAB:
1292   case ELF::SHT_DYNSYM:
1293     sh_link = StringTableIndex;
1294     sh_info = LastLocalSymbolIndex;
1295     break;
1296
1297   case ELF::SHT_SYMTAB_SHNDX:
1298     sh_link = SymbolTableIndex;
1299     break;
1300
1301   case ELF::SHT_PROGBITS:
1302   case ELF::SHT_STRTAB:
1303   case ELF::SHT_NOBITS:
1304   case ELF::SHT_NULL:
1305   case ELF::SHT_ARM_ATTRIBUTES:
1306     // Nothing to do.
1307     break;
1308
1309   case ELF::SHT_GROUP: {
1310     sh_link = SymbolTableIndex;
1311     sh_info = GroupSymbolIndex;
1312     break;
1313   }
1314
1315   default:
1316     assert(0 && "FIXME: sh_type value not supported!");
1317     break;
1318   }
1319
1320   WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1321                    Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1322                    Alignment, Section.getEntrySize());
1323 }
1324
1325 static bool IsELFMetaDataSection(const MCSectionData &SD) {
1326   return SD.getOrdinal() == ~UINT32_C(0) &&
1327     !SD.getSection().isVirtualSection();
1328 }
1329
1330 static uint64_t DataSectionSize(const MCSectionData &SD) {
1331   uint64_t Ret = 0;
1332   for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1333        ++i) {
1334     const MCFragment &F = *i;
1335     assert(F.getKind() == MCFragment::FT_Data);
1336     Ret += cast<MCDataFragment>(F).getContents().size();
1337   }
1338   return Ret;
1339 }
1340
1341 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
1342                                    const MCSectionData &SD) {
1343   if (IsELFMetaDataSection(SD))
1344     return DataSectionSize(SD);
1345   return Layout.getSectionFileSize(&SD);
1346 }
1347
1348 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
1349                                       const MCSectionData &SD) {
1350   if (IsELFMetaDataSection(SD))
1351     return DataSectionSize(SD);
1352   return Layout.getSectionAddressSize(&SD);
1353 }
1354
1355 static void WriteDataSectionData(ELFObjectWriter *W, const MCSectionData &SD) {
1356   for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1357        ++i) {
1358     const MCFragment &F = *i;
1359     assert(F.getKind() == MCFragment::FT_Data);
1360     W->WriteBytes(cast<MCDataFragment>(F).getContents().str());
1361   }
1362 }
1363
1364 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1365                                   const MCAsmLayout &Layout) {
1366   GroupMapTy GroupMap;
1367   RevGroupMapTy RevGroupMap;
1368   CreateGroupSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1369                       RevGroupMap);
1370
1371   SectionIndexMapTy SectionIndexMap;
1372
1373   ComputeIndexMap(Asm, SectionIndexMap);
1374
1375   // Compute symbol table information.
1376   ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap);
1377
1378   CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1379                          const_cast<MCAsmLayout&>(Layout),
1380                          SectionIndexMap);
1381
1382   // Update to include the metadata sections.
1383   ComputeIndexMap(Asm, SectionIndexMap);
1384
1385   // Add 1 for the null section.
1386   unsigned NumSections = Asm.size() + 1;
1387   uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
1388   uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
1389   uint64_t FileOff = HeaderSize;
1390
1391   std::vector<const MCSectionELF*> Sections;
1392   Sections.resize(NumSections);
1393
1394   for (SectionIndexMapTy::const_iterator i=
1395          SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1396     const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1397     Sections[p.second] = p.first;
1398   }
1399
1400   for (unsigned i = 1; i < NumSections; ++i) {
1401     const MCSectionELF &Section = *Sections[i];
1402     const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1403
1404     FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1405
1406     // Get the size of the section in the output file (including padding).
1407     FileOff += GetSectionFileSize(Layout, SD);
1408   }
1409
1410   FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1411
1412   // Write out the ELF header ...
1413   WriteHeader(FileOff - HeaderSize, NumSections);
1414
1415   FileOff = HeaderSize;
1416
1417   // ... then all of the sections ...
1418   DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
1419
1420   for (unsigned i = 1; i < NumSections; ++i) {
1421     const MCSectionELF &Section = *Sections[i];
1422     const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1423
1424     uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
1425     WriteZeros(Padding);
1426     FileOff += Padding;
1427
1428     // Remember the offset into the file for this section.
1429     SectionOffsetMap[&Section] = FileOff;
1430
1431     FileOff += GetSectionFileSize(Layout, SD);
1432
1433     if (IsELFMetaDataSection(SD))
1434       WriteDataSectionData(this, SD);
1435     else
1436       Asm.WriteSectionData(&SD, Layout);
1437   }
1438
1439   uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
1440   WriteZeros(Padding);
1441   FileOff += Padding;
1442
1443   // ... and then the section header table.
1444   // Should we align the section header table?
1445   //
1446   // Null section first.
1447   uint64_t FirstSectionSize =
1448     NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1449   uint32_t FirstSectionLink =
1450     ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1451   WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1452
1453   for (unsigned i = 1; i < NumSections; ++i) {
1454     const MCSectionELF &Section = *Sections[i];
1455     const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1456     uint32_t GroupSymbolIndex;
1457     if (Section.getType() != ELF::SHT_GROUP)
1458       GroupSymbolIndex = 0;
1459     else
1460       GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, GroupMap[&Section]);
1461
1462     uint64_t Size = GetSectionAddressSize(Layout, SD);
1463
1464     WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1465                  SectionOffsetMap[&Section], Size,
1466                  SD.getAlignment(), Section);
1467   }
1468 }
1469
1470 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1471                                             raw_ostream &OS,
1472                                             bool Is64Bit,
1473                                             Triple::OSType OSType,
1474                                             uint16_t EMachine,
1475                                             bool IsLittleEndian,
1476                                             bool HasRelocationAddend) {
1477   switch (EMachine) {
1478     case ELF::EM_386:
1479     case ELF::EM_X86_64:
1480       return new X86ELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1481                                     HasRelocationAddend, OSType); break;
1482     case ELF::EM_ARM:
1483       return new ARMELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1484                                     HasRelocationAddend, OSType); break;
1485     case ELF::EM_MBLAZE:
1486       return new MBlazeELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1487                                        HasRelocationAddend, OSType); break;
1488     default: llvm_unreachable("Unsupported architecture"); break;
1489   }
1490 }
1491
1492
1493 /// START OF SUBCLASSES for ELFObjectWriter
1494 //===- ARMELFObjectWriter -------------------------------------------===//
1495
1496 ARMELFObjectWriter::ARMELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1497                                        bool _IsLittleEndian,
1498                                        uint16_t _EMachine, bool _HasRelocationAddend,
1499                                        Triple::OSType _OSType)
1500   : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1501                     _HasRelocationAddend, _OSType)
1502 {}
1503
1504 ARMELFObjectWriter::~ARMELFObjectWriter()
1505 {}
1506
1507 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
1508                                           const MCFixup &Fixup,
1509                                           bool IsPCRel,
1510                                           bool IsRelocWithSymbol,
1511                                           int64_t Addend) {
1512   MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
1513     MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
1514
1515   unsigned Type = 0;
1516   if (IsPCRel) {
1517     switch ((unsigned)Fixup.getKind()) {
1518     default: assert(0 && "Unimplemented");
1519     case FK_Data_4:
1520       switch (Modifier) {
1521       default: llvm_unreachable("Unsupported Modifier");
1522       case MCSymbolRefExpr::VK_None:
1523         Type = ELF::R_ARM_BASE_PREL; break;
1524       case MCSymbolRefExpr::VK_ARM_TLSGD:
1525         assert(0 && "unimplemented"); break;
1526       case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
1527         Type = ELF::R_ARM_TLS_IE32;
1528       } break;
1529     case ARM::fixup_arm_branch:
1530       switch (Modifier) {
1531       case MCSymbolRefExpr::VK_ARM_PLT:
1532         Type = ELF::R_ARM_PLT32; break;
1533       default:
1534         Type = ELF::R_ARM_CALL; break;
1535       } break;
1536     }
1537   } else {
1538     switch ((unsigned)Fixup.getKind()) {
1539     default: llvm_unreachable("invalid fixup kind!");
1540     case FK_Data_4:
1541       switch (Modifier) {
1542       default: llvm_unreachable("Unsupported Modifier"); break;
1543       case MCSymbolRefExpr::VK_ARM_GOT:
1544         Type = ELF::R_ARM_GOT_BREL; break;
1545       case MCSymbolRefExpr::VK_ARM_TLSGD:
1546         Type = ELF::R_ARM_TLS_GD32; break;
1547       case MCSymbolRefExpr::VK_ARM_TPOFF:
1548         Type = ELF::R_ARM_TLS_LE32; break;
1549       case MCSymbolRefExpr::VK_ARM_GOTTPOFF:
1550         Type = ELF::R_ARM_TLS_IE32; break;
1551       case MCSymbolRefExpr::VK_None:
1552         Type = ELF::R_ARM_ABS32; break;
1553       case MCSymbolRefExpr::VK_ARM_GOTOFF:
1554         Type = ELF::R_ARM_GOTOFF32; break;
1555       } break;
1556     case ARM::fixup_arm_ldst_pcrel_12:
1557     case ARM::fixup_arm_pcrel_10:
1558     case ARM::fixup_arm_adr_pcrel_12:
1559     case ARM::fixup_arm_thumb_bl:
1560     case ARM::fixup_arm_thumb_cb:
1561     case ARM::fixup_arm_thumb_cp:
1562     case ARM::fixup_arm_thumb_br:
1563       assert(0 && "Unimplemented"); break;
1564     case ARM::fixup_arm_branch:
1565       // FIXME: Differentiate between R_ARM_CALL and
1566       // R_ARM_JUMP24 (latter used for conditional jumps)
1567       Type = ELF::R_ARM_CALL; break;
1568     case ARM::fixup_arm_movt_hi16:
1569       Type = ELF::R_ARM_MOVT_ABS; break;
1570     case ARM::fixup_arm_movw_lo16:
1571       Type = ELF::R_ARM_MOVW_ABS_NC; break;
1572     }
1573   }
1574
1575   if (RelocNeedsGOT(Modifier))
1576     NeedsGOT = true;
1577
1578   return Type;
1579 }
1580
1581 //===- MBlazeELFObjectWriter -------------------------------------------===//
1582
1583 MBlazeELFObjectWriter::MBlazeELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1584                                              bool _IsLittleEndian,
1585                                              uint16_t _EMachine,
1586                                              bool _HasRelocationAddend,
1587                                              Triple::OSType _OSType)
1588   : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1589                     _HasRelocationAddend, _OSType) {
1590 }
1591
1592 MBlazeELFObjectWriter::~MBlazeELFObjectWriter() {
1593 }
1594
1595 unsigned MBlazeELFObjectWriter::GetRelocType(const MCValue &Target,
1596                                              const MCFixup &Fixup,
1597                                              bool IsPCRel,
1598                                              bool IsRelocWithSymbol,
1599                                              int64_t Addend) {
1600   // determine the type of the relocation
1601   unsigned Type;
1602   if (IsPCRel) {
1603     switch ((unsigned)Fixup.getKind()) {
1604     default:
1605       llvm_unreachable("Unimplemented");
1606     case FK_PCRel_4:
1607       Type = ELF::R_MICROBLAZE_64_PCREL;
1608       break;
1609     case FK_PCRel_2:
1610       Type = ELF::R_MICROBLAZE_32_PCREL;
1611       break;
1612     }
1613   } else {
1614     switch ((unsigned)Fixup.getKind()) {
1615     default: llvm_unreachable("invalid fixup kind!");
1616     case FK_Data_4:
1617       Type = ((IsRelocWithSymbol || Addend !=0)
1618               ? ELF::R_MICROBLAZE_32
1619               : ELF::R_MICROBLAZE_64);
1620       break;
1621     case FK_Data_2:
1622       Type = ELF::R_MICROBLAZE_32;
1623       break;
1624     }
1625   }
1626   return Type;
1627 }
1628
1629 //===- X86ELFObjectWriter -------------------------------------------===//
1630
1631
1632 X86ELFObjectWriter::X86ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1633                                        bool _IsLittleEndian,
1634                                        uint16_t _EMachine, bool _HasRelocationAddend,
1635                                        Triple::OSType _OSType)
1636   : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1637                     _HasRelocationAddend, _OSType)
1638 {}
1639
1640 X86ELFObjectWriter::~X86ELFObjectWriter()
1641 {}
1642
1643 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target,
1644                                           const MCFixup &Fixup,
1645                                           bool IsPCRel,
1646                                           bool IsRelocWithSymbol,
1647                                           int64_t Addend) {
1648   // determine the type of the relocation
1649
1650   MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
1651     MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
1652   unsigned Type;
1653   if (Is64Bit) {
1654     if (IsPCRel) {
1655       switch (Modifier) {
1656       default:
1657         llvm_unreachable("Unimplemented");
1658       case MCSymbolRefExpr::VK_None:
1659         Type = ELF::R_X86_64_PC32;
1660         break;
1661       case MCSymbolRefExpr::VK_PLT:
1662         Type = ELF::R_X86_64_PLT32;
1663         break;
1664       case MCSymbolRefExpr::VK_GOTPCREL:
1665         Type = ELF::R_X86_64_GOTPCREL;
1666         break;
1667       case MCSymbolRefExpr::VK_GOTTPOFF:
1668         Type = ELF::R_X86_64_GOTTPOFF;
1669         break;
1670       case MCSymbolRefExpr::VK_TLSGD:
1671         Type = ELF::R_X86_64_TLSGD;
1672         break;
1673       case MCSymbolRefExpr::VK_TLSLD:
1674         Type = ELF::R_X86_64_TLSLD;
1675         break;
1676       }
1677     } else {
1678       switch ((unsigned)Fixup.getKind()) {
1679       default: llvm_unreachable("invalid fixup kind!");
1680       case FK_Data_8: Type = ELF::R_X86_64_64; break;
1681       case X86::reloc_signed_4byte:
1682       case FK_PCRel_4:
1683         assert(isInt<32>(Target.getConstant()));
1684         switch (Modifier) {
1685         default:
1686           llvm_unreachable("Unimplemented");
1687         case MCSymbolRefExpr::VK_None:
1688           Type = ELF::R_X86_64_32S;
1689           break;
1690         case MCSymbolRefExpr::VK_GOT:
1691           Type = ELF::R_X86_64_GOT32;
1692           break;
1693         case MCSymbolRefExpr::VK_GOTPCREL:
1694           Type = ELF::R_X86_64_GOTPCREL;
1695           break;
1696         case MCSymbolRefExpr::VK_TPOFF:
1697           Type = ELF::R_X86_64_TPOFF32;
1698           break;
1699         case MCSymbolRefExpr::VK_DTPOFF:
1700           Type = ELF::R_X86_64_DTPOFF32;
1701           break;
1702         }
1703         break;
1704       case FK_Data_4:
1705         Type = ELF::R_X86_64_32;
1706         break;
1707       case FK_Data_2: Type = ELF::R_X86_64_16; break;
1708       case FK_PCRel_1:
1709       case FK_Data_1: Type = ELF::R_X86_64_8; break;
1710       }
1711     }
1712   } else {
1713     if (IsPCRel) {
1714       switch (Modifier) {
1715       default:
1716         llvm_unreachable("Unimplemented");
1717       case MCSymbolRefExpr::VK_None:
1718         Type = ELF::R_386_PC32;
1719         break;
1720       case MCSymbolRefExpr::VK_PLT:
1721         Type = ELF::R_386_PLT32;
1722         break;
1723       }
1724     } else {
1725       switch ((unsigned)Fixup.getKind()) {
1726       default: llvm_unreachable("invalid fixup kind!");
1727
1728       case X86::reloc_global_offset_table:
1729         Type = ELF::R_386_GOTPC;
1730         break;
1731
1732       // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode
1733       // instead?
1734       case X86::reloc_signed_4byte:
1735       case FK_PCRel_4:
1736       case FK_Data_4:
1737         switch (Modifier) {
1738         default:
1739           llvm_unreachable("Unimplemented");
1740         case MCSymbolRefExpr::VK_None:
1741           Type = ELF::R_386_32;
1742           break;
1743         case MCSymbolRefExpr::VK_GOT:
1744           Type = ELF::R_386_GOT32;
1745           break;
1746         case MCSymbolRefExpr::VK_GOTOFF:
1747           Type = ELF::R_386_GOTOFF;
1748           break;
1749         case MCSymbolRefExpr::VK_TLSGD:
1750           Type = ELF::R_386_TLS_GD;
1751           break;
1752         case MCSymbolRefExpr::VK_TPOFF:
1753           Type = ELF::R_386_TLS_LE_32;
1754           break;
1755         case MCSymbolRefExpr::VK_INDNTPOFF:
1756           Type = ELF::R_386_TLS_IE;
1757           break;
1758         case MCSymbolRefExpr::VK_NTPOFF:
1759           Type = ELF::R_386_TLS_LE;
1760           break;
1761         case MCSymbolRefExpr::VK_GOTNTPOFF:
1762           Type = ELF::R_386_TLS_GOTIE;
1763           break;
1764         case MCSymbolRefExpr::VK_TLSLDM:
1765           Type = ELF::R_386_TLS_LDM;
1766           break;
1767         case MCSymbolRefExpr::VK_DTPOFF:
1768           Type = ELF::R_386_TLS_LDO_32;
1769           break;
1770         }
1771         break;
1772       case FK_Data_2: Type = ELF::R_386_16; break;
1773       case FK_PCRel_1:
1774       case FK_Data_1: Type = ELF::R_386_8; break;
1775       }
1776     }
1777   }
1778
1779   if (RelocNeedsGOT(Modifier))
1780     NeedsGOT = true;
1781
1782   return Type;
1783 }