llvm/lib/MC/WinCOFFObjectWriter.cpp

   1 //===- llvm/MC/WinCOFFObjectWriter.cpp ------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains an implementation of a Win32 COFF object file writer.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/ADT/DenseMap.h"
  14 #include "llvm/ADT/DenseSet.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/SmallString.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ADT/Twine.h"
  20 #include "llvm/BinaryFormat/COFF.h"
  21 #include "llvm/MC/MCAsmLayout.h"
  22 #include "llvm/MC/MCAssembler.h"
  23 #include "llvm/MC/MCContext.h"
  24 #include "llvm/MC/MCExpr.h"
  25 #include "llvm/MC/MCFixup.h"
  26 #include "llvm/MC/MCFragment.h"
  27 #include "llvm/MC/MCObjectWriter.h"
  28 #include "llvm/MC/MCSection.h"
  29 #include "llvm/MC/MCSectionCOFF.h"
  30 #include "llvm/MC/MCSymbol.h"
  31 #include "llvm/MC/MCSymbolCOFF.h"
  32 #include "llvm/MC/MCValue.h"
  33 #include "llvm/MC/MCWinCOFFObjectWriter.h"
  34 #include "llvm/MC/StringTableBuilder.h"
  35 #include "llvm/Support/CRC.h"
  36 #include "llvm/Support/Casting.h"
  37 #include "llvm/Support/EndianStream.h"
  38 #include "llvm/Support/ErrorHandling.h"
  39 #include "llvm/Support/LEB128.h"
  40 #include "llvm/Support/MathExtras.h"
  41 #include "llvm/Support/raw_ostream.h"
  42 #include <algorithm>
  43 #include <cassert>
  44 #include <cstddef>
  45 #include <cstdint>
  46 #include <cstring>
  47 #include <ctime>
  48 #include <memory>
  49 #include <string>
  50 #include <vector>
  51
  52 using namespace llvm;
  53 using llvm::support::endian::write32le;
  54
  55 #define DEBUG_TYPE "WinCOFFObjectWriter"
  56
  57 namespace {
  58
  59 using name = SmallString<COFF::NameSize>;
  60
  61 enum AuxiliaryType {
  62   ATWeakExternal,
  63   ATFile,
  64   ATSectionDefinition
  65 };
  66
  67 struct AuxSymbol {
  68   AuxiliaryType AuxType;
  69   COFF::Auxiliary Aux;
  70 };
  71
  72 class COFFSection;
  73
  74 class COFFSymbol {
  75 public:
  76   COFF::symbol Data = {};
  77
  78   using AuxiliarySymbols = SmallVector<AuxSymbol, 1>;
  79
  80   name Name;
  81   int Index;
  82   AuxiliarySymbols Aux;
  83   COFFSymbol *Other = nullptr;
  84   COFFSection *Section = nullptr;
  85   int Relocations = 0;
  86   const MCSymbol *MC = nullptr;
  87
  88   COFFSymbol(StringRef Name) : Name(Name) {}
  89
  90   void set_name_offset(uint32_t Offset);
  91
  92   int64_t getIndex() const { return Index; }
  93   void setIndex(int Value) {
  94     Index = Value;
  95     if (MC)
  96       MC->setIndex(static_cast<uint32_t>(Value));
  97   }
  98 };
  99
 100 // This class contains staging data for a COFF relocation entry.
 101 struct COFFRelocation {
 102   COFF::relocation Data;
 103   COFFSymbol *Symb = nullptr;
 104
 105   COFFRelocation() = default;
 106
 107   static size_t size() { return COFF::RelocationSize; }
 108 };
 109
 110 using relocations = std::vector<COFFRelocation>;
 111
 112 class COFFSection {
 113 public:
 114   COFF::section Header = {};
 115
 116   std::string Name;
 117   int Number;
 118   MCSectionCOFF const *MCSection = nullptr;
 119   COFFSymbol *Symbol = nullptr;
 120   relocations Relocations;
 121
 122   COFFSection(StringRef Name) : Name(std::string(Name)) {}
 123 };
 124
 125 class WinCOFFObjectWriter : public MCObjectWriter {
 126 public:
 127   support::endian::Writer W;
 128
 129   using symbols = std::vector<std::unique_ptr<COFFSymbol>>;
 130   using sections = std::vector<std::unique_ptr<COFFSection>>;
 131
 132   using symbol_map = DenseMap<MCSymbol const *, COFFSymbol *>;
 133   using section_map = DenseMap<MCSection const *, COFFSection *>;
 134
 135   using symbol_list = DenseSet<COFFSymbol *>;
 136
 137   std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
 138
 139   // Root level file contents.
 140   COFF::header Header = {};
 141   sections Sections;
 142   symbols Symbols;
 143   StringTableBuilder Strings{StringTableBuilder::WinCOFF};
 144
 145   // Maps used during object file creation.
 146   section_map SectionMap;
 147   symbol_map SymbolMap;
 148
 149   symbol_list WeakDefaults;
 150
 151   bool UseBigObj;
 152
 153   bool EmitAddrsigSection = false;
 154   MCSectionCOFF *AddrsigSection;
 155   std::vector<const MCSymbol *> AddrsigSyms;
 156
 157   MCSectionCOFF *CGProfileSection = nullptr;
 158
 159   WinCOFFObjectWriter(std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW,
 160                       raw_pwrite_stream &OS);
 161
 162   void reset() override {
 163     memset(&Header, 0, sizeof(Header));
 164     Header.Machine = TargetObjectWriter->getMachine();
 165     Sections.clear();
 166     Symbols.clear();
 167     Strings.clear();
 168     SectionMap.clear();
 169     SymbolMap.clear();
 170     MCObjectWriter::reset();
 171   }
 172
 173   COFFSymbol *createSymbol(StringRef Name);
 174   COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
 175   COFFSection *createSection(StringRef Name);
 176
 177   void defineSection(MCSectionCOFF const &Sec);
 178
 179   COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
 180   void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
 181                     const MCAsmLayout &Layout);
 182
 183   void SetSymbolName(COFFSymbol &S);
 184   void SetSectionName(COFFSection &S);
 185
 186   bool IsPhysicalSection(COFFSection *S);
 187
 188   // Entity writing methods.
 189
 190   void WriteFileHeader(const COFF::header &Header);
 191   void WriteSymbol(const COFFSymbol &S);
 192   void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
 193   void writeSectionHeaders();
 194   void WriteRelocation(const COFF::relocation &R);
 195   uint32_t writeSectionContents(MCAssembler &Asm, const MCAsmLayout &Layout,
 196                                 const MCSection &MCSec);
 197   void writeSection(MCAssembler &Asm, const MCAsmLayout &Layout,
 198                     const COFFSection &Sec, const MCSection &MCSec);
 199
 200   // MCObjectWriter interface implementation.
 201
 202   void executePostLayoutBinding(MCAssembler &Asm,
 203                                 const MCAsmLayout &Layout) override;
 204
 205   bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
 206                                               const MCSymbol &SymA,
 207                                               const MCFragment &FB, bool InSet,
 208                                               bool IsPCRel) const override;
 209
 210   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
 211                         const MCFragment *Fragment, const MCFixup &Fixup,
 212                         MCValue Target, uint64_t &FixedValue) override;
 213
 214   void createFileSymbols(MCAssembler &Asm);
 215   void setWeakDefaultNames();
 216   void assignSectionNumbers();
 217   void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout);
 218
 219   void emitAddrsigSection() override { EmitAddrsigSection = true; }
 220   void addAddrsigSymbol(const MCSymbol *Sym) override {
 221     AddrsigSyms.push_back(Sym);
 222   }
 223
 224   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 225 };
 226
 227 } // end anonymous namespace
 228
 229 //------------------------------------------------------------------------------
 230 // Symbol class implementation
 231
 232 // In the case that the name does not fit within 8 bytes, the offset
 233 // into the string table is stored in the last 4 bytes instead, leaving
 234 // the first 4 bytes as 0.
 235 void COFFSymbol::set_name_offset(uint32_t Offset) {
 236   write32le(Data.Name + 0, 0);
 237   write32le(Data.Name + 4, Offset);
 238 }
 239
 240 //------------------------------------------------------------------------------
 241 // WinCOFFObjectWriter class implementation
 242
 243 WinCOFFObjectWriter::WinCOFFObjectWriter(
 244     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
 245     : W(OS, support::little), TargetObjectWriter(std::move(MOTW)) {
 246   Header.Machine = TargetObjectWriter->getMachine();
 247 }
 248
 249 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
 250   Symbols.push_back(std::make_unique<COFFSymbol>(Name));
 251   return Symbols.back().get();
 252 }
 253
 254 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
 255   COFFSymbol *&Ret = SymbolMap[Symbol];
 256   if (!Ret)
 257     Ret = createSymbol(Symbol->getName());
 258   return Ret;
 259 }
 260
 261 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
 262   Sections.emplace_back(std::make_unique<COFFSection>(Name));
 263   return Sections.back().get();
 264 }
 265
 266 static uint32_t getAlignment(const MCSectionCOFF &Sec) {
 267   switch (Sec.getAlignment()) {
 268   case 1:
 269     return COFF::IMAGE_SCN_ALIGN_1BYTES;
 270   case 2:
 271     return COFF::IMAGE_SCN_ALIGN_2BYTES;
 272   case 4:
 273     return COFF::IMAGE_SCN_ALIGN_4BYTES;
 274   case 8:
 275     return COFF::IMAGE_SCN_ALIGN_8BYTES;
 276   case 16:
 277     return COFF::IMAGE_SCN_ALIGN_16BYTES;
 278   case 32:
 279     return COFF::IMAGE_SCN_ALIGN_32BYTES;
 280   case 64:
 281     return COFF::IMAGE_SCN_ALIGN_64BYTES;
 282   case 128:
 283     return COFF::IMAGE_SCN_ALIGN_128BYTES;
 284   case 256:
 285     return COFF::IMAGE_SCN_ALIGN_256BYTES;
 286   case 512:
 287     return COFF::IMAGE_SCN_ALIGN_512BYTES;
 288   case 1024:
 289     return COFF::IMAGE_SCN_ALIGN_1024BYTES;
 290   case 2048:
 291     return COFF::IMAGE_SCN_ALIGN_2048BYTES;
 292   case 4096:
 293     return COFF::IMAGE_SCN_ALIGN_4096BYTES;
 294   case 8192:
 295     return COFF::IMAGE_SCN_ALIGN_8192BYTES;
 296   }
 297   llvm_unreachable("unsupported section alignment");
 298 }
 299
 300 /// This function takes a section data object from the assembler
 301 /// and creates the associated COFF section staging object.
 302 void WinCOFFObjectWriter::defineSection(const MCSectionCOFF &MCSec) {
 303   COFFSection *Section = createSection(MCSec.getName());
 304   COFFSymbol *Symbol = createSymbol(MCSec.getName());
 305   Section->Symbol = Symbol;
 306   Symbol->Section = Section;
 307   Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
 308
 309   // Create a COMDAT symbol if needed.
 310   if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
 311     if (const MCSymbol *S = MCSec.getCOMDATSymbol()) {
 312       COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
 313       if (COMDATSymbol->Section)
 314         report_fatal_error("two sections have the same comdat");
 315       COMDATSymbol->Section = Section;
 316     }
 317   }
 318
 319   // In this case the auxiliary symbol is a Section Definition.
 320   Symbol->Aux.resize(1);
 321   Symbol->Aux[0] = {};
 322   Symbol->Aux[0].AuxType = ATSectionDefinition;
 323   Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection();
 324
 325   // Set section alignment.
 326   Section->Header.Characteristics = MCSec.getCharacteristics();
 327   Section->Header.Characteristics |= getAlignment(MCSec);
 328
 329   // Bind internal COFF section to MC section.
 330   Section->MCSection = &MCSec;
 331   SectionMap[&MCSec] = Section;
 332 }
 333
 334 static uint64_t getSymbolValue(const MCSymbol &Symbol,
 335                                const MCAsmLayout &Layout) {
 336   if (Symbol.isCommon() && Symbol.isExternal())
 337     return Symbol.getCommonSize();
 338
 339   uint64_t Res;
 340   if (!Layout.getSymbolOffset(Symbol, Res))
 341     return 0;
 342
 343   return Res;
 344 }
 345
 346 COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
 347   if (!Symbol.isVariable())
 348     return nullptr;
 349
 350   const MCSymbolRefExpr *SymRef =
 351       dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
 352   if (!SymRef)
 353     return nullptr;
 354
 355   const MCSymbol &Aliasee = SymRef->getSymbol();
 356   if (Aliasee.isUndefined() || Aliasee.isExternal())
 357     return GetOrCreateCOFFSymbol(&Aliasee);
 358   else
 359     return nullptr;
 360 }
 361
 362 /// This function takes a symbol data object from the assembler
 363 /// and creates the associated COFF symbol staging object.
 364 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
 365                                        MCAssembler &Assembler,
 366                                        const MCAsmLayout &Layout) {
 367   COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym);
 368   const MCSymbol *Base = Layout.getBaseSymbol(MCSym);
 369   COFFSection *Sec = nullptr;
 370   if (Base && Base->getFragment()) {
 371     Sec = SectionMap[Base->getFragment()->getParent()];
 372     if (Sym->Section && Sym->Section != Sec)
 373       report_fatal_error("conflicting sections for symbol");
 374   }
 375
 376   COFFSymbol *Local = nullptr;
 377   if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
 378     Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
 379     Sym->Section = nullptr;
 380
 381     COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
 382     if (!WeakDefault) {
 383       std::string WeakName = (".weak." + MCSym.getName() + ".default").str();
 384       WeakDefault = createSymbol(WeakName);
 385       if (!Sec)
 386         WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 387       else
 388         WeakDefault->Section = Sec;
 389       WeakDefaults.insert(WeakDefault);
 390       Local = WeakDefault;
 391     }
 392
 393     Sym->Other = WeakDefault;
 394
 395     // Setup the Weak External auxiliary symbol.
 396     Sym->Aux.resize(1);
 397     memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
 398     Sym->Aux[0].AuxType = ATWeakExternal;
 399     Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
 400     Sym->Aux[0].Aux.WeakExternal.Characteristics =
 401         COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS;
 402   } else {
 403     if (!Base)
 404       Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 405     else
 406       Sym->Section = Sec;
 407     Local = Sym;
 408   }
 409
 410   if (Local) {
 411     Local->Data.Value = getSymbolValue(MCSym, Layout);
 412
 413     const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym);
 414     Local->Data.Type = SymbolCOFF.getType();
 415     Local->Data.StorageClass = SymbolCOFF.getClass();
 416
 417     // If no storage class was specified in the streamer, define it here.
 418     if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
 419       bool IsExternal = MCSym.isExternal() ||
 420                         (!MCSym.getFragment() && !MCSym.isVariable());
 421
 422       Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
 423                                             : COFF::IMAGE_SYM_CLASS_STATIC;
 424     }
 425   }
 426
 427   Sym->MC = &MCSym;
 428 }
 429
 430 // Maximum offsets for different string table entry encodings.
 431 enum : unsigned { Max7DecimalOffset = 9999999U };
 432 enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0
 433
 434 // Encode a string table entry offset in base 64, padded to 6 chars, and
 435 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
 436 // Buffer must be at least 8 bytes large. No terminating null appended.
 437 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
 438   assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
 439          "Illegal section name encoding for value");
 440
 441   static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 442                                  "abcdefghijklmnopqrstuvwxyz"
 443                                  "0123456789+/";
 444
 445   Buffer[0] = '/';
 446   Buffer[1] = '/';
 447
 448   char *Ptr = Buffer + 7;
 449   for (unsigned i = 0; i < 6; ++i) {
 450     unsigned Rem = Value % 64;
 451     Value /= 64;
 452     *(Ptr--) = Alphabet[Rem];
 453   }
 454 }
 455
 456 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
 457   if (S.Name.size() <= COFF::NameSize) {
 458     std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
 459     return;
 460   }
 461
 462   uint64_t StringTableEntry = Strings.getOffset(S.Name);
 463   if (StringTableEntry <= Max7DecimalOffset) {
 464     SmallVector<char, COFF::NameSize> Buffer;
 465     Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
 466     assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
 467     std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
 468     return;
 469   }
 470   if (StringTableEntry <= MaxBase64Offset) {
 471     // Starting with 10,000,000, offsets are encoded as base64.
 472     encodeBase64StringEntry(S.Header.Name, StringTableEntry);
 473     return;
 474   }
 475   report_fatal_error("COFF string table is greater than 64 GB.");
 476 }
 477
 478 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
 479   if (S.Name.size() > COFF::NameSize)
 480     S.set_name_offset(Strings.getOffset(S.Name));
 481   else
 482     std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
 483 }
 484
 485 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
 486   return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
 487          0;
 488 }
 489
 490 //------------------------------------------------------------------------------
 491 // entity writing methods
 492
 493 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
 494   if (UseBigObj) {
 495     W.write<uint16_t>(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
 496     W.write<uint16_t>(0xFFFF);
 497     W.write<uint16_t>(COFF::BigObjHeader::MinBigObjectVersion);
 498     W.write<uint16_t>(Header.Machine);
 499     W.write<uint32_t>(Header.TimeDateStamp);
 500     W.OS.write(COFF::BigObjMagic, sizeof(COFF::BigObjMagic));
 501     W.write<uint32_t>(0);
 502     W.write<uint32_t>(0);
 503     W.write<uint32_t>(0);
 504     W.write<uint32_t>(0);
 505     W.write<uint32_t>(Header.NumberOfSections);
 506     W.write<uint32_t>(Header.PointerToSymbolTable);
 507     W.write<uint32_t>(Header.NumberOfSymbols);
 508   } else {
 509     W.write<uint16_t>(Header.Machine);
 510     W.write<uint16_t>(static_cast<int16_t>(Header.NumberOfSections));
 511     W.write<uint32_t>(Header.TimeDateStamp);
 512     W.write<uint32_t>(Header.PointerToSymbolTable);
 513     W.write<uint32_t>(Header.NumberOfSymbols);
 514     W.write<uint16_t>(Header.SizeOfOptionalHeader);
 515     W.write<uint16_t>(Header.Characteristics);
 516   }
 517 }
 518
 519 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
 520   W.OS.write(S.Data.Name, COFF::NameSize);
 521   W.write<uint32_t>(S.Data.Value);
 522   if (UseBigObj)
 523     W.write<uint32_t>(S.Data.SectionNumber);
 524   else
 525     W.write<uint16_t>(static_cast<int16_t>(S.Data.SectionNumber));
 526   W.write<uint16_t>(S.Data.Type);
 527   W.OS << char(S.Data.StorageClass);
 528   W.OS << char(S.Data.NumberOfAuxSymbols);
 529   WriteAuxiliarySymbols(S.Aux);
 530 }
 531
 532 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
 533     const COFFSymbol::AuxiliarySymbols &S) {
 534   for (const AuxSymbol &i : S) {
 535     switch (i.AuxType) {
 536     case ATWeakExternal:
 537       W.write<uint32_t>(i.Aux.WeakExternal.TagIndex);
 538       W.write<uint32_t>(i.Aux.WeakExternal.Characteristics);
 539       W.OS.write_zeros(sizeof(i.Aux.WeakExternal.unused));
 540       if (UseBigObj)
 541         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 542       break;
 543     case ATFile:
 544       W.OS.write(reinterpret_cast<const char *>(&i.Aux),
 545                         UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size);
 546       break;
 547     case ATSectionDefinition:
 548       W.write<uint32_t>(i.Aux.SectionDefinition.Length);
 549       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfRelocations);
 550       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfLinenumbers);
 551       W.write<uint32_t>(i.Aux.SectionDefinition.CheckSum);
 552       W.write<uint16_t>(static_cast<int16_t>(i.Aux.SectionDefinition.Number));
 553       W.OS << char(i.Aux.SectionDefinition.Selection);
 554       W.OS.write_zeros(sizeof(i.Aux.SectionDefinition.unused));
 555       W.write<uint16_t>(static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16));
 556       if (UseBigObj)
 557         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 558       break;
 559     }
 560   }
 561 }
 562
 563 // Write the section header.
 564 void WinCOFFObjectWriter::writeSectionHeaders() {
 565   // Section numbers must be monotonically increasing in the section
 566   // header, but our Sections array is not sorted by section number,
 567   // so make a copy of Sections and sort it.
 568   std::vector<COFFSection *> Arr;
 569   for (auto &Section : Sections)
 570     Arr.push_back(Section.get());
 571   llvm::sort(Arr, [](const COFFSection *A, const COFFSection *B) {
 572     return A->Number < B->Number;
 573   });
 574
 575   for (auto &Section : Arr) {
 576     if (Section->Number == -1)
 577       continue;
 578
 579     COFF::section &S = Section->Header;
 580     if (Section->Relocations.size() >= 0xffff)
 581       S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
 582     W.OS.write(S.Name, COFF::NameSize);
 583     W.write<uint32_t>(S.VirtualSize);
 584     W.write<uint32_t>(S.VirtualAddress);
 585     W.write<uint32_t>(S.SizeOfRawData);
 586     W.write<uint32_t>(S.PointerToRawData);
 587     W.write<uint32_t>(S.PointerToRelocations);
 588     W.write<uint32_t>(S.PointerToLineNumbers);
 589     W.write<uint16_t>(S.NumberOfRelocations);
 590     W.write<uint16_t>(S.NumberOfLineNumbers);
 591     W.write<uint32_t>(S.Characteristics);
 592   }
 593 }
 594
 595 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
 596   W.write<uint32_t>(R.VirtualAddress);
 597   W.write<uint32_t>(R.SymbolTableIndex);
 598   W.write<uint16_t>(R.Type);
 599 }
 600
 601 // Write MCSec's contents. What this function does is essentially
 602 // "Asm.writeSectionData(&MCSec, Layout)", but it's a bit complicated
 603 // because it needs to compute a CRC.
 604 uint32_t WinCOFFObjectWriter::writeSectionContents(MCAssembler &Asm,
 605                                                    const MCAsmLayout &Layout,
 606                                                    const MCSection &MCSec) {
 607   // Save the contents of the section to a temporary buffer, we need this
 608   // to CRC the data before we dump it into the object file.
 609   SmallVector<char, 128> Buf;
 610   raw_svector_ostream VecOS(Buf);
 611   Asm.writeSectionData(VecOS, &MCSec, Layout);
 612
 613   // Write the section contents to the object file.
 614   W.OS << Buf;
 615
 616   // Calculate our CRC with an initial value of '0', this is not how
 617   // JamCRC is specified but it aligns with the expected output.
 618   JamCRC JC(/*Init=*/0);
 619   JC.update(makeArrayRef(reinterpret_cast<uint8_t*>(Buf.data()), Buf.size()));
 620   return JC.getCRC();
 621 }
 622
 623 void WinCOFFObjectWriter::writeSection(MCAssembler &Asm,
 624                                        const MCAsmLayout &Layout,
 625                                        const COFFSection &Sec,
 626                                        const MCSection &MCSec) {
 627   if (Sec.Number == -1)
 628     return;
 629
 630   // Write the section contents.
 631   if (Sec.Header.PointerToRawData != 0) {
 632     assert(W.OS.tell() == Sec.Header.PointerToRawData &&
 633            "Section::PointerToRawData is insane!");
 634
 635     uint32_t CRC = writeSectionContents(Asm, Layout, MCSec);
 636
 637     // Update the section definition auxiliary symbol to record the CRC.
 638     COFFSection *Sec = SectionMap[&MCSec];
 639     COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
 640     assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition);
 641     AuxSymbol &SecDef = AuxSyms[0];
 642     SecDef.Aux.SectionDefinition.CheckSum = CRC;
 643   }
 644
 645   // Write relocations for this section.
 646   if (Sec.Relocations.empty()) {
 647     assert(Sec.Header.PointerToRelocations == 0 &&
 648            "Section::PointerToRelocations is insane!");
 649     return;
 650   }
 651
 652   assert(W.OS.tell() == Sec.Header.PointerToRelocations &&
 653          "Section::PointerToRelocations is insane!");
 654
 655   if (Sec.Relocations.size() >= 0xffff) {
 656     // In case of overflow, write actual relocation count as first
 657     // relocation. Including the synthetic reloc itself (+ 1).
 658     COFF::relocation R;
 659     R.VirtualAddress = Sec.Relocations.size() + 1;
 660     R.SymbolTableIndex = 0;
 661     R.Type = 0;
 662     WriteRelocation(R);
 663   }
 664
 665   for (const auto &Relocation : Sec.Relocations)
 666     WriteRelocation(Relocation.Data);
 667 }
 668
 669 ////////////////////////////////////////////////////////////////////////////////
 670 // MCObjectWriter interface implementations
 671
 672 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
 673                                                    const MCAsmLayout &Layout) {
 674   if (EmitAddrsigSection) {
 675     AddrsigSection = Asm.getContext().getCOFFSection(
 676         ".llvm_addrsig", COFF::IMAGE_SCN_LNK_REMOVE,
 677         SectionKind::getMetadata());
 678     Asm.registerSection(*AddrsigSection);
 679   }
 680
 681   if (!Asm.CGProfile.empty()) {
 682     CGProfileSection = Asm.getContext().getCOFFSection(
 683         ".llvm.call-graph-profile", COFF::IMAGE_SCN_LNK_REMOVE,
 684         SectionKind::getMetadata());
 685     Asm.registerSection(*CGProfileSection);
 686   }
 687
 688   // "Define" each section & symbol. This creates section & symbol
 689   // entries in the staging area.
 690   for (const auto &Section : Asm)
 691     defineSection(static_cast<const MCSectionCOFF &>(Section));
 692
 693   for (const MCSymbol &Symbol : Asm.symbols())
 694     if (!Symbol.isTemporary())
 695       DefineSymbol(Symbol, Asm, Layout);
 696 }
 697
 698 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
 699     const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
 700     bool InSet, bool IsPCRel) const {
 701   // Don't drop relocations between functions, even if they are in the same text
 702   // section. Multiple Visual C++ linker features depend on having the
 703   // relocations present. The /INCREMENTAL flag will cause these relocations to
 704   // point to thunks, and the /GUARD:CF flag assumes that it can use relocations
 705   // to approximate the set of all address taken functions. LLD's implementation
 706   // of /GUARD:CF also relies on the existance of these relocations.
 707   uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
 708   if ((Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
 709     return false;
 710   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
 711                                                                 InSet, IsPCRel);
 712 }
 713
 714 void WinCOFFObjectWriter::recordRelocation(MCAssembler &Asm,
 715                                            const MCAsmLayout &Layout,
 716                                            const MCFragment *Fragment,
 717                                            const MCFixup &Fixup, MCValue Target,
 718                                            uint64_t &FixedValue) {
 719   assert(Target.getSymA() && "Relocation must reference a symbol!");
 720
 721   const MCSymbol &A = Target.getSymA()->getSymbol();
 722   if (!A.isRegistered()) {
 723     Asm.getContext().reportError(Fixup.getLoc(),
 724                                       Twine("symbol '") + A.getName() +
 725                                           "' can not be undefined");
 726     return;
 727   }
 728   if (A.isTemporary() && A.isUndefined()) {
 729     Asm.getContext().reportError(Fixup.getLoc(),
 730                                       Twine("assembler label '") + A.getName() +
 731                                           "' can not be undefined");
 732     return;
 733   }
 734
 735   MCSection *MCSec = Fragment->getParent();
 736
 737   // Mark this symbol as requiring an entry in the symbol table.
 738   assert(SectionMap.find(MCSec) != SectionMap.end() &&
 739          "Section must already have been defined in executePostLayoutBinding!");
 740
 741   COFFSection *Sec = SectionMap[MCSec];
 742   const MCSymbolRefExpr *SymB = Target.getSymB();
 743
 744   if (SymB) {
 745     const MCSymbol *B = &SymB->getSymbol();
 746     if (!B->getFragment()) {
 747       Asm.getContext().reportError(
 748           Fixup.getLoc(),
 749           Twine("symbol '") + B->getName() +
 750               "' can not be undefined in a subtraction expression");
 751       return;
 752     }
 753
 754     // Offset of the symbol in the section
 755     int64_t OffsetOfB = Layout.getSymbolOffset(*B);
 756
 757     // Offset of the relocation in the section
 758     int64_t OffsetOfRelocation =
 759         Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
 760
 761     FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
 762   } else {
 763     FixedValue = Target.getConstant();
 764   }
 765
 766   COFFRelocation Reloc;
 767
 768   Reloc.Data.SymbolTableIndex = 0;
 769   Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
 770
 771   // Turn relocations for temporary symbols into section relocations.
 772   if (A.isTemporary()) {
 773     MCSection *TargetSection = &A.getSection();
 774     assert(
 775         SectionMap.find(TargetSection) != SectionMap.end() &&
 776         "Section must already have been defined in executePostLayoutBinding!");
 777     Reloc.Symb = SectionMap[TargetSection]->Symbol;
 778     FixedValue += Layout.getSymbolOffset(A);
 779   } else {
 780     assert(
 781         SymbolMap.find(&A) != SymbolMap.end() &&
 782         "Symbol must already have been defined in executePostLayoutBinding!");
 783     Reloc.Symb = SymbolMap[&A];
 784   }
 785
 786   ++Reloc.Symb->Relocations;
 787
 788   Reloc.Data.VirtualAddress += Fixup.getOffset();
 789   Reloc.Data.Type = TargetObjectWriter->getRelocType(
 790       Asm.getContext(), Target, Fixup, SymB, Asm.getBackend());
 791
 792   // The *_REL32 relocations are relative to the end of the relocation,
 793   // not to the start.
 794   if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
 795        Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
 796       (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
 797        Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32) ||
 798       (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT &&
 799        Reloc.Data.Type == COFF::IMAGE_REL_ARM_REL32) ||
 800       (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARM64 &&
 801        Reloc.Data.Type == COFF::IMAGE_REL_ARM64_REL32))
 802     FixedValue += 4;
 803
 804   if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
 805     switch (Reloc.Data.Type) {
 806     case COFF::IMAGE_REL_ARM_ABSOLUTE:
 807     case COFF::IMAGE_REL_ARM_ADDR32:
 808     case COFF::IMAGE_REL_ARM_ADDR32NB:
 809     case COFF::IMAGE_REL_ARM_TOKEN:
 810     case COFF::IMAGE_REL_ARM_SECTION:
 811     case COFF::IMAGE_REL_ARM_SECREL:
 812       break;
 813     case COFF::IMAGE_REL_ARM_BRANCH11:
 814     case COFF::IMAGE_REL_ARM_BLX11:
 815     // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
 816     // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
 817     // for Windows CE).
 818     case COFF::IMAGE_REL_ARM_BRANCH24:
 819     case COFF::IMAGE_REL_ARM_BLX24:
 820     case COFF::IMAGE_REL_ARM_MOV32A:
 821       // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
 822       // only used for ARM mode code, which is documented as being unsupported
 823       // by Windows on ARM.  Empirical proof indicates that masm is able to
 824       // generate the relocations however the rest of the MSVC toolchain is
 825       // unable to handle it.
 826       llvm_unreachable("unsupported relocation");
 827       break;
 828     case COFF::IMAGE_REL_ARM_MOV32T:
 829       break;
 830     case COFF::IMAGE_REL_ARM_BRANCH20T:
 831     case COFF::IMAGE_REL_ARM_BRANCH24T:
 832     case COFF::IMAGE_REL_ARM_BLX23T:
 833       // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
 834       // perform a 4 byte adjustment to the relocation.  Relative branches are
 835       // offset by 4 on ARM, however, because there is no RELA relocations, all
 836       // branches are offset by 4.
 837       FixedValue = FixedValue + 4;
 838       break;
 839     }
 840   }
 841
 842   // The fixed value never makes sense for section indices, ignore it.
 843   if (Fixup.getKind() == FK_SecRel_2)
 844     FixedValue = 0;
 845
 846   if (TargetObjectWriter->recordRelocation(Fixup))
 847     Sec->Relocations.push_back(Reloc);
 848 }
 849
 850 static std::time_t getTime() {
 851   std::time_t Now = time(nullptr);
 852   if (Now < 0 || !isUInt<32>(Now))
 853     return UINT32_MAX;
 854   return Now;
 855 }
 856
 857 // Create .file symbols.
 858 void WinCOFFObjectWriter::createFileSymbols(MCAssembler &Asm) {
 859   for (const std::pair<std::string, size_t> &It : Asm.getFileNames()) {
 860     // round up to calculate the number of auxiliary symbols required
 861     const std::string &Name = It.first;
 862     unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
 863     unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
 864
 865     COFFSymbol *File = createSymbol(".file");
 866     File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
 867     File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
 868     File->Aux.resize(Count);
 869
 870     unsigned Offset = 0;
 871     unsigned Length = Name.size();
 872     for (auto &Aux : File->Aux) {
 873       Aux.AuxType = ATFile;
 874
 875       if (Length > SymbolSize) {
 876         memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
 877         Length = Length - SymbolSize;
 878       } else {
 879         memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
 880         memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
 881         break;
 882       }
 883
 884       Offset += SymbolSize;
 885     }
 886   }
 887 }
 888
 889 void WinCOFFObjectWriter::setWeakDefaultNames() {
 890   if (WeakDefaults.empty())
 891     return;
 892
 893   // If multiple object files use a weak symbol (either with a regular
 894   // defined default, or an absolute zero symbol as default), the defaults
 895   // cause duplicate definitions unless their names are made unique. Look
 896   // for a defined extern symbol, that isn't comdat - that should be unique
 897   // unless there are other duplicate definitions. And if none is found,
 898   // allow picking a comdat symbol, as that's still better than nothing.
 899
 900   COFFSymbol *Unique = nullptr;
 901   for (bool AllowComdat : {false, true}) {
 902     for (auto &Sym : Symbols) {
 903       // Don't include the names of the defaults themselves
 904       if (WeakDefaults.count(Sym.get()))
 905         continue;
 906       // Only consider external symbols
 907       if (Sym->Data.StorageClass != COFF::IMAGE_SYM_CLASS_EXTERNAL)
 908         continue;
 909       // Only consider symbols defined in a section or that are absolute
 910       if (!Sym->Section && Sym->Data.SectionNumber != COFF::IMAGE_SYM_ABSOLUTE)
 911         continue;
 912       if (!AllowComdat && Sym->Section &&
 913           Sym->Section->Header.Characteristics & COFF::IMAGE_SCN_LNK_COMDAT)
 914         continue;
 915       Unique = Sym.get();
 916       break;
 917     }
 918     if (Unique)
 919       break;
 920   }
 921   // If we didn't find any unique symbol to use for the names, just skip this.
 922   if (!Unique)
 923     return;
 924   for (auto *Sym : WeakDefaults) {
 925     Sym->Name.append(".");
 926     Sym->Name.append(Unique->Name);
 927   }
 928 }
 929
 930 static bool isAssociative(const COFFSection &Section) {
 931   return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection ==
 932          COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
 933 }
 934
 935 void WinCOFFObjectWriter::assignSectionNumbers() {
 936   size_t I = 1;
 937   auto Assign = [&](COFFSection &Section) {
 938     Section.Number = I;
 939     Section.Symbol->Data.SectionNumber = I;
 940     Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I;
 941     ++I;
 942   };
 943
 944   // Although it is not explicitly requested by the Microsoft COFF spec,
 945   // we should avoid emitting forward associative section references,
 946   // because MSVC link.exe as of 2017 cannot handle that.
 947   for (const std::unique_ptr<COFFSection> &Section : Sections)
 948     if (!isAssociative(*Section))
 949       Assign(*Section);
 950   for (const std::unique_ptr<COFFSection> &Section : Sections)
 951     if (isAssociative(*Section))
 952       Assign(*Section);
 953 }
 954
 955 // Assign file offsets to COFF object file structures.
 956 void WinCOFFObjectWriter::assignFileOffsets(MCAssembler &Asm,
 957                                             const MCAsmLayout &Layout) {
 958   unsigned Offset = W.OS.tell();
 959
 960   Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size;
 961   Offset += COFF::SectionSize * Header.NumberOfSections;
 962
 963   for (const auto &Section : Asm) {
 964     COFFSection *Sec = SectionMap[&Section];
 965
 966     if (Sec->Number == -1)
 967       continue;
 968
 969     Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
 970
 971     if (IsPhysicalSection(Sec)) {
 972       Sec->Header.PointerToRawData = Offset;
 973       Offset += Sec->Header.SizeOfRawData;
 974     }
 975
 976     if (!Sec->Relocations.empty()) {
 977       bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
 978
 979       if (RelocationsOverflow) {
 980         // Signal overflow by setting NumberOfRelocations to max value. Actual
 981         // size is found in reloc #0. Microsoft tools understand this.
 982         Sec->Header.NumberOfRelocations = 0xffff;
 983       } else {
 984         Sec->Header.NumberOfRelocations = Sec->Relocations.size();
 985       }
 986       Sec->Header.PointerToRelocations = Offset;
 987
 988       if (RelocationsOverflow) {
 989         // Reloc #0 will contain actual count, so make room for it.
 990         Offset += COFF::RelocationSize;
 991       }
 992
 993       Offset += COFF::RelocationSize * Sec->Relocations.size();
 994
 995       for (auto &Relocation : Sec->Relocations) {
 996         assert(Relocation.Symb->getIndex() != -1);
 997         Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
 998       }
 999     }
1000
1001     assert(Sec->Symbol->Aux.size() == 1 &&
1002            "Section's symbol must have one aux!");
1003     AuxSymbol &Aux = Sec->Symbol->Aux[0];
1004     assert(Aux.AuxType == ATSectionDefinition &&
1005            "Section's symbol's aux symbol must be a Section Definition!");
1006     Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
1007     Aux.Aux.SectionDefinition.NumberOfRelocations =
1008         Sec->Header.NumberOfRelocations;
1009     Aux.Aux.SectionDefinition.NumberOfLinenumbers =
1010         Sec->Header.NumberOfLineNumbers;
1011   }
1012
1013   Header.PointerToSymbolTable = Offset;
1014 }
1015
1016 uint64_t WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
1017                                           const MCAsmLayout &Layout) {
1018   uint64_t StartOffset = W.OS.tell();
1019
1020   if (Sections.size() > INT32_MAX)
1021     report_fatal_error(
1022         "PE COFF object files can't have more than 2147483647 sections");
1023
1024   UseBigObj = Sections.size() > COFF::MaxNumberOfSections16;
1025   Header.NumberOfSections = Sections.size();
1026   Header.NumberOfSymbols = 0;
1027
1028   setWeakDefaultNames();
1029   assignSectionNumbers();
1030   createFileSymbols(Asm);
1031
1032   for (auto &Symbol : Symbols) {
1033     // Update section number & offset for symbols that have them.
1034     if (Symbol->Section)
1035       Symbol->Data.SectionNumber = Symbol->Section->Number;
1036     Symbol->setIndex(Header.NumberOfSymbols++);
1037     // Update auxiliary symbol info.
1038     Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
1039     Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
1040   }
1041
1042   // Build string table.
1043   for (const auto &S : Sections)
1044     if (S->Name.size() > COFF::NameSize)
1045       Strings.add(S->Name);
1046   for (const auto &S : Symbols)
1047     if (S->Name.size() > COFF::NameSize)
1048       Strings.add(S->Name);
1049   Strings.finalize();
1050
1051   // Set names.
1052   for (const auto &S : Sections)
1053     SetSectionName(*S);
1054   for (auto &S : Symbols)
1055     SetSymbolName(*S);
1056
1057   // Fixup weak external references.
1058   for (auto &Symbol : Symbols) {
1059     if (Symbol->Other) {
1060       assert(Symbol->getIndex() != -1);
1061       assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
1062       assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
1063              "Symbol's aux symbol must be a Weak External!");
1064       Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
1065     }
1066   }
1067
1068   // Fixup associative COMDAT sections.
1069   for (auto &Section : Sections) {
1070     if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
1071         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1072       continue;
1073
1074     const MCSectionCOFF &MCSec = *Section->MCSection;
1075     const MCSymbol *AssocMCSym = MCSec.getCOMDATSymbol();
1076     assert(AssocMCSym);
1077
1078     // It's an error to try to associate with an undefined symbol or a symbol
1079     // without a section.
1080     if (!AssocMCSym->isInSection()) {
1081       Asm.getContext().reportError(
1082           SMLoc(), Twine("cannot make section ") + MCSec.getName() +
1083                        Twine(" associative with sectionless symbol ") +
1084                        AssocMCSym->getName());
1085       continue;
1086     }
1087
1088     const auto *AssocMCSec = cast<MCSectionCOFF>(&AssocMCSym->getSection());
1089     assert(SectionMap.count(AssocMCSec));
1090     COFFSection *AssocSec = SectionMap[AssocMCSec];
1091
1092     // Skip this section if the associated section is unused.
1093     if (AssocSec->Number == -1)
1094       continue;
1095
1096     Section->Symbol->Aux[0].Aux.SectionDefinition.Number = AssocSec->Number;
1097   }
1098
1099   // Create the contents of the .llvm_addrsig section.
1100   if (EmitAddrsigSection) {
1101     auto Frag = new MCDataFragment(AddrsigSection);
1102     Frag->setLayoutOrder(0);
1103     raw_svector_ostream OS(Frag->getContents());
1104     for (const MCSymbol *S : AddrsigSyms) {
1105       if (!S->isTemporary()) {
1106         encodeULEB128(S->getIndex(), OS);
1107         continue;
1108       }
1109
1110       MCSection *TargetSection = &S->getSection();
1111       assert(SectionMap.find(TargetSection) != SectionMap.end() &&
1112              "Section must already have been defined in "
1113              "executePostLayoutBinding!");
1114       encodeULEB128(SectionMap[TargetSection]->Symbol->getIndex(), OS);
1115     }
1116   }
1117
1118   // Create the contents of the .llvm.call-graph-profile section.
1119   if (CGProfileSection) {
1120     auto *Frag = new MCDataFragment(CGProfileSection);
1121     Frag->setLayoutOrder(0);
1122     raw_svector_ostream OS(Frag->getContents());
1123     for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
1124       uint32_t FromIndex = CGPE.From->getSymbol().getIndex();
1125       uint32_t ToIndex = CGPE.To->getSymbol().getIndex();
1126       support::endian::write(OS, FromIndex, W.Endian);
1127       support::endian::write(OS, ToIndex, W.Endian);
1128       support::endian::write(OS, CGPE.Count, W.Endian);
1129     }
1130   }
1131
1132   assignFileOffsets(Asm, Layout);
1133
1134   // MS LINK expects to be able to use this timestamp to implement their
1135   // /INCREMENTAL feature.
1136   if (Asm.isIncrementalLinkerCompatible()) {
1137     Header.TimeDateStamp = getTime();
1138   } else {
1139     // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
1140     Header.TimeDateStamp = 0;
1141   }
1142
1143   // Write it all to disk...
1144   WriteFileHeader(Header);
1145   writeSectionHeaders();
1146
1147   // Write section contents.
1148   sections::iterator I = Sections.begin();
1149   sections::iterator IE = Sections.end();
1150   MCAssembler::iterator J = Asm.begin();
1151   MCAssembler::iterator JE = Asm.end();
1152   for (; I != IE && J != JE; ++I, ++J)
1153     writeSection(Asm, Layout, **I, *J);
1154
1155   assert(W.OS.tell() == Header.PointerToSymbolTable &&
1156          "Header::PointerToSymbolTable is insane!");
1157
1158   // Write a symbol table.
1159   for (auto &Symbol : Symbols)
1160     if (Symbol->getIndex() != -1)
1161       WriteSymbol(*Symbol);
1162
1163   // Write a string table, which completes the entire COFF file.
1164   Strings.write(W.OS);
1165
1166   return W.OS.tell() - StartOffset;
1167 }
1168
1169 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1170     : Machine(Machine_) {}
1171
1172 // Pin the vtable to this file.
1173 void MCWinCOFFObjectTargetWriter::anchor() {}
1174
1175 //------------------------------------------------------------------------------
1176 // WinCOFFObjectWriter factory function
1177
1178 std::unique_ptr<MCObjectWriter> llvm::createWinCOFFObjectWriter(
1179     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS) {
1180   return std::make_unique<WinCOFFObjectWriter>(std::move(MOTW), OS);
1181 }