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 <cstdint>
  45 #include <cstring>
  46 #include <ctime>
  47 #include <memory>
  48 #include <string>
  49 #include <vector>
  50
  51 using namespace llvm;
  52 using llvm::support::endian::write32le;
  53
  54 #define DEBUG_TYPE "WinCOFFObjectWriter"
  55
  56 namespace {
  57
  58 constexpr int OffsetLabelIntervalBits = 20;
  59
  60 using name = SmallString<COFF::NameSize>;
  61
  62 enum AuxiliaryType {
  63   ATWeakExternal,
  64   ATFile,
  65   ATSectionDefinition
  66 };
  67
  68 struct AuxSymbol {
  69   AuxiliaryType AuxType;
  70   COFF::Auxiliary Aux;
  71 };
  72
  73 class COFFSection;
  74
  75 class COFFSymbol {
  76 public:
  77   COFF::symbol Data = {};
  78
  79   using AuxiliarySymbols = SmallVector<AuxSymbol, 1>;
  80
  81   name Name;
  82   int Index = 0;
  83   AuxiliarySymbols Aux;
  84   COFFSymbol *Other = nullptr;
  85   COFFSection *Section = nullptr;
  86   int Relocations = 0;
  87   const MCSymbol *MC = nullptr;
  88
  89   COFFSymbol(StringRef Name) : Name(Name) {}
  90
  91   void set_name_offset(uint32_t Offset);
  92
  93   int64_t getIndex() const { return Index; }
  94   void setIndex(int Value) {
  95     Index = Value;
  96     if (MC)
  97       MC->setIndex(static_cast<uint32_t>(Value));
  98   }
  99 };
 100
 101 // This class contains staging data for a COFF relocation entry.
 102 struct COFFRelocation {
 103   COFF::relocation Data;
 104   COFFSymbol *Symb = nullptr;
 105
 106   COFFRelocation() = default;
 107
 108   static size_t size() { return COFF::RelocationSize; }
 109 };
 110
 111 using relocations = std::vector<COFFRelocation>;
 112
 113 class COFFSection {
 114 public:
 115   COFF::section Header = {};
 116
 117   std::string Name;
 118   int Number = 0;
 119   MCSectionCOFF const *MCSection = nullptr;
 120   COFFSymbol *Symbol = nullptr;
 121   relocations Relocations;
 122
 123   COFFSection(StringRef Name) : Name(std::string(Name)) {}
 124
 125   SmallVector<COFFSymbol *, 1> OffsetSymbols;
 126 };
 127
 128 class WinCOFFObjectWriter : public MCObjectWriter {
 129 public:
 130   support::endian::Writer W;
 131
 132   using symbols = std::vector<std::unique_ptr<COFFSymbol>>;
 133   using sections = std::vector<std::unique_ptr<COFFSection>>;
 134
 135   using symbol_map = DenseMap<MCSymbol const *, COFFSymbol *>;
 136   using section_map = DenseMap<MCSection const *, COFFSection *>;
 137
 138   using symbol_list = DenseSet<COFFSymbol *>;
 139
 140   std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
 141
 142   // Root level file contents.
 143   COFF::header Header = {};
 144   sections Sections;
 145   symbols Symbols;
 146   StringTableBuilder Strings{StringTableBuilder::WinCOFF};
 147
 148   // Maps used during object file creation.
 149   section_map SectionMap;
 150   symbol_map SymbolMap;
 151
 152   symbol_list WeakDefaults;
 153
 154   bool UseBigObj;
 155   bool UseOffsetLabels = false;
 156
 157   MCSectionCOFF *AddrsigSection = nullptr;
 158
 159   MCSectionCOFF *CGProfileSection = nullptr;
 160
 161   WinCOFFObjectWriter(std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW,
 162                       raw_pwrite_stream &OS);
 163
 164   void reset() override {
 165     memset(&Header, 0, sizeof(Header));
 166     Header.Machine = TargetObjectWriter->getMachine();
 167     Sections.clear();
 168     Symbols.clear();
 169     Strings.clear();
 170     SectionMap.clear();
 171     SymbolMap.clear();
 172     WeakDefaults.clear();
 173     MCObjectWriter::reset();
 174   }
 175
 176   COFFSymbol *createSymbol(StringRef Name);
 177   COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
 178   COFFSection *createSection(StringRef Name);
 179
 180   void defineSection(MCSectionCOFF const &Sec, const MCAsmLayout &Layout);
 181
 182   COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
 183   void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
 184                     const MCAsmLayout &Layout);
 185
 186   void SetSymbolName(COFFSymbol &S);
 187   void SetSectionName(COFFSection &S);
 188
 189   bool IsPhysicalSection(COFFSection *S);
 190
 191   // Entity writing methods.
 192
 193   void WriteFileHeader(const COFF::header &Header);
 194   void WriteSymbol(const COFFSymbol &S);
 195   void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
 196   void writeSectionHeaders();
 197   void WriteRelocation(const COFF::relocation &R);
 198   uint32_t writeSectionContents(MCAssembler &Asm, const MCAsmLayout &Layout,
 199                                 const MCSection &MCSec);
 200   void writeSection(MCAssembler &Asm, const MCAsmLayout &Layout,
 201                     const COFFSection &Sec, const MCSection &MCSec);
 202
 203   // MCObjectWriter interface implementation.
 204
 205   void executePostLayoutBinding(MCAssembler &Asm,
 206                                 const MCAsmLayout &Layout) override;
 207
 208   bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
 209                                               const MCSymbol &SymA,
 210                                               const MCFragment &FB, bool InSet,
 211                                               bool IsPCRel) const override;
 212
 213   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
 214                         const MCFragment *Fragment, const MCFixup &Fixup,
 215                         MCValue Target, uint64_t &FixedValue) override;
 216
 217   void createFileSymbols(MCAssembler &Asm);
 218   void setWeakDefaultNames();
 219   void assignSectionNumbers();
 220   void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout);
 221
 222   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 223 };
 224
 225 } // end anonymous namespace
 226
 227 //------------------------------------------------------------------------------
 228 // Symbol class implementation
 229
 230 // In the case that the name does not fit within 8 bytes, the offset
 231 // into the string table is stored in the last 4 bytes instead, leaving
 232 // the first 4 bytes as 0.
 233 void COFFSymbol::set_name_offset(uint32_t Offset) {
 234   write32le(Data.Name + 0, 0);
 235   write32le(Data.Name + 4, Offset);
 236 }
 237
 238 //------------------------------------------------------------------------------
 239 // WinCOFFObjectWriter class implementation
 240
 241 WinCOFFObjectWriter::WinCOFFObjectWriter(
 242     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
 243     : W(OS, support::little), TargetObjectWriter(std::move(MOTW)) {
 244   Header.Machine = TargetObjectWriter->getMachine();
 245   // Some relocations on ARM64 (the 21 bit ADRP relocations) have a slightly
 246   // limited range for the immediate offset (+/- 1 MB); create extra offset
 247   // label symbols with regular intervals to allow referencing a
 248   // non-temporary symbol that is close enough.
 249   UseOffsetLabels = Header.Machine == COFF::IMAGE_FILE_MACHINE_ARM64;
 250 }
 251
 252 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
 253   Symbols.push_back(std::make_unique<COFFSymbol>(Name));
 254   return Symbols.back().get();
 255 }
 256
 257 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
 258   COFFSymbol *&Ret = SymbolMap[Symbol];
 259   if (!Ret)
 260     Ret = createSymbol(Symbol->getName());
 261   return Ret;
 262 }
 263
 264 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
 265   Sections.emplace_back(std::make_unique<COFFSection>(Name));
 266   return Sections.back().get();
 267 }
 268
 269 static uint32_t getAlignment(const MCSectionCOFF &Sec) {
 270   switch (Sec.getAlign().value()) {
 271   case 1:
 272     return COFF::IMAGE_SCN_ALIGN_1BYTES;
 273   case 2:
 274     return COFF::IMAGE_SCN_ALIGN_2BYTES;
 275   case 4:
 276     return COFF::IMAGE_SCN_ALIGN_4BYTES;
 277   case 8:
 278     return COFF::IMAGE_SCN_ALIGN_8BYTES;
 279   case 16:
 280     return COFF::IMAGE_SCN_ALIGN_16BYTES;
 281   case 32:
 282     return COFF::IMAGE_SCN_ALIGN_32BYTES;
 283   case 64:
 284     return COFF::IMAGE_SCN_ALIGN_64BYTES;
 285   case 128:
 286     return COFF::IMAGE_SCN_ALIGN_128BYTES;
 287   case 256:
 288     return COFF::IMAGE_SCN_ALIGN_256BYTES;
 289   case 512:
 290     return COFF::IMAGE_SCN_ALIGN_512BYTES;
 291   case 1024:
 292     return COFF::IMAGE_SCN_ALIGN_1024BYTES;
 293   case 2048:
 294     return COFF::IMAGE_SCN_ALIGN_2048BYTES;
 295   case 4096:
 296     return COFF::IMAGE_SCN_ALIGN_4096BYTES;
 297   case 8192:
 298     return COFF::IMAGE_SCN_ALIGN_8192BYTES;
 299   }
 300   llvm_unreachable("unsupported section alignment");
 301 }
 302
 303 /// This function takes a section data object from the assembler
 304 /// and creates the associated COFF section staging object.
 305 void WinCOFFObjectWriter::defineSection(const MCSectionCOFF &MCSec,
 306                                         const MCAsmLayout &Layout) {
 307   COFFSection *Section = createSection(MCSec.getName());
 308   COFFSymbol *Symbol = createSymbol(MCSec.getName());
 309   Section->Symbol = Symbol;
 310   Symbol->Section = Section;
 311   Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
 312
 313   // Create a COMDAT symbol if needed.
 314   if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
 315     if (const MCSymbol *S = MCSec.getCOMDATSymbol()) {
 316       COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
 317       if (COMDATSymbol->Section)
 318         report_fatal_error("two sections have the same comdat");
 319       COMDATSymbol->Section = Section;
 320     }
 321   }
 322
 323   // In this case the auxiliary symbol is a Section Definition.
 324   Symbol->Aux.resize(1);
 325   Symbol->Aux[0] = {};
 326   Symbol->Aux[0].AuxType = ATSectionDefinition;
 327   Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection();
 328
 329   // Set section alignment.
 330   Section->Header.Characteristics = MCSec.getCharacteristics();
 331   Section->Header.Characteristics |= getAlignment(MCSec);
 332
 333   // Bind internal COFF section to MC section.
 334   Section->MCSection = &MCSec;
 335   SectionMap[&MCSec] = Section;
 336
 337   if (UseOffsetLabels && !MCSec.getFragmentList().empty()) {
 338     const uint32_t Interval = 1 << OffsetLabelIntervalBits;
 339     uint32_t N = 1;
 340     for (uint32_t Off = Interval, E = Layout.getSectionAddressSize(&MCSec);
 341          Off < E; Off += Interval) {
 342       auto Name = ("$L" + MCSec.getName() + "_" + Twine(N++)).str();
 343       COFFSymbol *Label = createSymbol(Name);
 344       Label->Section = Section;
 345       Label->Data.StorageClass = COFF::IMAGE_SYM_CLASS_LABEL;
 346       Label->Data.Value = Off;
 347       Section->OffsetSymbols.push_back(Label);
 348     }
 349   }
 350 }
 351
 352 static uint64_t getSymbolValue(const MCSymbol &Symbol,
 353                                const MCAsmLayout &Layout) {
 354   if (Symbol.isCommon() && Symbol.isExternal())
 355     return Symbol.getCommonSize();
 356
 357   uint64_t Res;
 358   if (!Layout.getSymbolOffset(Symbol, Res))
 359     return 0;
 360
 361   return Res;
 362 }
 363
 364 COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
 365   if (!Symbol.isVariable())
 366     return nullptr;
 367
 368   const MCSymbolRefExpr *SymRef =
 369       dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
 370   if (!SymRef)
 371     return nullptr;
 372
 373   const MCSymbol &Aliasee = SymRef->getSymbol();
 374   if (Aliasee.isUndefined() || Aliasee.isExternal())
 375     return GetOrCreateCOFFSymbol(&Aliasee);
 376   else
 377     return nullptr;
 378 }
 379
 380 /// This function takes a symbol data object from the assembler
 381 /// and creates the associated COFF symbol staging object.
 382 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
 383                                        MCAssembler &Assembler,
 384                                        const MCAsmLayout &Layout) {
 385   COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym);
 386   const MCSymbol *Base = Layout.getBaseSymbol(MCSym);
 387   COFFSection *Sec = nullptr;
 388   if (Base && Base->getFragment()) {
 389     Sec = SectionMap[Base->getFragment()->getParent()];
 390     if (Sym->Section && Sym->Section != Sec)
 391       report_fatal_error("conflicting sections for symbol");
 392   }
 393
 394   COFFSymbol *Local = nullptr;
 395   if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
 396     Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
 397     Sym->Section = nullptr;
 398
 399     COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
 400     if (!WeakDefault) {
 401       std::string WeakName = (".weak." + MCSym.getName() + ".default").str();
 402       WeakDefault = createSymbol(WeakName);
 403       if (!Sec)
 404         WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 405       else
 406         WeakDefault->Section = Sec;
 407       WeakDefaults.insert(WeakDefault);
 408       Local = WeakDefault;
 409     }
 410
 411     Sym->Other = WeakDefault;
 412
 413     // Setup the Weak External auxiliary symbol.
 414     Sym->Aux.resize(1);
 415     memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
 416     Sym->Aux[0].AuxType = ATWeakExternal;
 417     Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
 418     Sym->Aux[0].Aux.WeakExternal.Characteristics =
 419         COFF::IMAGE_WEAK_EXTERN_SEARCH_ALIAS;
 420   } else {
 421     if (!Base)
 422       Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 423     else
 424       Sym->Section = Sec;
 425     Local = Sym;
 426   }
 427
 428   if (Local) {
 429     Local->Data.Value = getSymbolValue(MCSym, Layout);
 430
 431     const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym);
 432     Local->Data.Type = SymbolCOFF.getType();
 433     Local->Data.StorageClass = SymbolCOFF.getClass();
 434
 435     // If no storage class was specified in the streamer, define it here.
 436     if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
 437       bool IsExternal = MCSym.isExternal() ||
 438                         (!MCSym.getFragment() && !MCSym.isVariable());
 439
 440       Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
 441                                             : COFF::IMAGE_SYM_CLASS_STATIC;
 442     }
 443   }
 444
 445   Sym->MC = &MCSym;
 446 }
 447
 448 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
 449   if (S.Name.size() <= COFF::NameSize) {
 450     std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
 451     return;
 452   }
 453
 454   uint64_t StringTableEntry = Strings.getOffset(S.Name);
 455   if (!COFF::encodeSectionName(S.Header.Name, StringTableEntry))
 456     report_fatal_error("COFF string table is greater than 64 GB.");
 457 }
 458
 459 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
 460   if (S.Name.size() > COFF::NameSize)
 461     S.set_name_offset(Strings.getOffset(S.Name));
 462   else
 463     std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
 464 }
 465
 466 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
 467   return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
 468          0;
 469 }
 470
 471 //------------------------------------------------------------------------------
 472 // entity writing methods
 473
 474 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
 475   if (UseBigObj) {
 476     W.write<uint16_t>(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
 477     W.write<uint16_t>(0xFFFF);
 478     W.write<uint16_t>(COFF::BigObjHeader::MinBigObjectVersion);
 479     W.write<uint16_t>(Header.Machine);
 480     W.write<uint32_t>(Header.TimeDateStamp);
 481     W.OS.write(COFF::BigObjMagic, sizeof(COFF::BigObjMagic));
 482     W.write<uint32_t>(0);
 483     W.write<uint32_t>(0);
 484     W.write<uint32_t>(0);
 485     W.write<uint32_t>(0);
 486     W.write<uint32_t>(Header.NumberOfSections);
 487     W.write<uint32_t>(Header.PointerToSymbolTable);
 488     W.write<uint32_t>(Header.NumberOfSymbols);
 489   } else {
 490     W.write<uint16_t>(Header.Machine);
 491     W.write<uint16_t>(static_cast<int16_t>(Header.NumberOfSections));
 492     W.write<uint32_t>(Header.TimeDateStamp);
 493     W.write<uint32_t>(Header.PointerToSymbolTable);
 494     W.write<uint32_t>(Header.NumberOfSymbols);
 495     W.write<uint16_t>(Header.SizeOfOptionalHeader);
 496     W.write<uint16_t>(Header.Characteristics);
 497   }
 498 }
 499
 500 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
 501   W.OS.write(S.Data.Name, COFF::NameSize);
 502   W.write<uint32_t>(S.Data.Value);
 503   if (UseBigObj)
 504     W.write<uint32_t>(S.Data.SectionNumber);
 505   else
 506     W.write<uint16_t>(static_cast<int16_t>(S.Data.SectionNumber));
 507   W.write<uint16_t>(S.Data.Type);
 508   W.OS << char(S.Data.StorageClass);
 509   W.OS << char(S.Data.NumberOfAuxSymbols);
 510   WriteAuxiliarySymbols(S.Aux);
 511 }
 512
 513 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
 514     const COFFSymbol::AuxiliarySymbols &S) {
 515   for (const AuxSymbol &i : S) {
 516     switch (i.AuxType) {
 517     case ATWeakExternal:
 518       W.write<uint32_t>(i.Aux.WeakExternal.TagIndex);
 519       W.write<uint32_t>(i.Aux.WeakExternal.Characteristics);
 520       W.OS.write_zeros(sizeof(i.Aux.WeakExternal.unused));
 521       if (UseBigObj)
 522         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 523       break;
 524     case ATFile:
 525       W.OS.write(reinterpret_cast<const char *>(&i.Aux),
 526                         UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size);
 527       break;
 528     case ATSectionDefinition:
 529       W.write<uint32_t>(i.Aux.SectionDefinition.Length);
 530       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfRelocations);
 531       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfLinenumbers);
 532       W.write<uint32_t>(i.Aux.SectionDefinition.CheckSum);
 533       W.write<uint16_t>(static_cast<int16_t>(i.Aux.SectionDefinition.Number));
 534       W.OS << char(i.Aux.SectionDefinition.Selection);
 535       W.OS.write_zeros(sizeof(i.Aux.SectionDefinition.unused));
 536       W.write<uint16_t>(static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16));
 537       if (UseBigObj)
 538         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 539       break;
 540     }
 541   }
 542 }
 543
 544 // Write the section header.
 545 void WinCOFFObjectWriter::writeSectionHeaders() {
 546   // Section numbers must be monotonically increasing in the section
 547   // header, but our Sections array is not sorted by section number,
 548   // so make a copy of Sections and sort it.
 549   std::vector<COFFSection *> Arr;
 550   for (auto &Section : Sections)
 551     Arr.push_back(Section.get());
 552   llvm::sort(Arr, [](const COFFSection *A, const COFFSection *B) {
 553     return A->Number < B->Number;
 554   });
 555
 556   for (auto &Section : Arr) {
 557     if (Section->Number == -1)
 558       continue;
 559
 560     COFF::section &S = Section->Header;
 561     if (Section->Relocations.size() >= 0xffff)
 562       S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
 563     W.OS.write(S.Name, COFF::NameSize);
 564     W.write<uint32_t>(S.VirtualSize);
 565     W.write<uint32_t>(S.VirtualAddress);
 566     W.write<uint32_t>(S.SizeOfRawData);
 567     W.write<uint32_t>(S.PointerToRawData);
 568     W.write<uint32_t>(S.PointerToRelocations);
 569     W.write<uint32_t>(S.PointerToLineNumbers);
 570     W.write<uint16_t>(S.NumberOfRelocations);
 571     W.write<uint16_t>(S.NumberOfLineNumbers);
 572     W.write<uint32_t>(S.Characteristics);
 573   }
 574 }
 575
 576 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
 577   W.write<uint32_t>(R.VirtualAddress);
 578   W.write<uint32_t>(R.SymbolTableIndex);
 579   W.write<uint16_t>(R.Type);
 580 }
 581
 582 // Write MCSec's contents. What this function does is essentially
 583 // "Asm.writeSectionData(&MCSec, Layout)", but it's a bit complicated
 584 // because it needs to compute a CRC.
 585 uint32_t WinCOFFObjectWriter::writeSectionContents(MCAssembler &Asm,
 586                                                    const MCAsmLayout &Layout,
 587                                                    const MCSection &MCSec) {
 588   // Save the contents of the section to a temporary buffer, we need this
 589   // to CRC the data before we dump it into the object file.
 590   SmallVector<char, 128> Buf;
 591   raw_svector_ostream VecOS(Buf);
 592   Asm.writeSectionData(VecOS, &MCSec, Layout);
 593
 594   // Write the section contents to the object file.
 595   W.OS << Buf;
 596
 597   // Calculate our CRC with an initial value of '0', this is not how
 598   // JamCRC is specified but it aligns with the expected output.
 599   JamCRC JC(/*Init=*/0);
 600   JC.update(ArrayRef(reinterpret_cast<uint8_t *>(Buf.data()), Buf.size()));
 601   return JC.getCRC();
 602 }
 603
 604 void WinCOFFObjectWriter::writeSection(MCAssembler &Asm,
 605                                        const MCAsmLayout &Layout,
 606                                        const COFFSection &Sec,
 607                                        const MCSection &MCSec) {
 608   if (Sec.Number == -1)
 609     return;
 610
 611   // Write the section contents.
 612   if (Sec.Header.PointerToRawData != 0) {
 613     assert(W.OS.tell() == Sec.Header.PointerToRawData &&
 614            "Section::PointerToRawData is insane!");
 615
 616     uint32_t CRC = writeSectionContents(Asm, Layout, MCSec);
 617
 618     // Update the section definition auxiliary symbol to record the CRC.
 619     COFFSection *Sec = SectionMap[&MCSec];
 620     COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
 621     assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition);
 622     AuxSymbol &SecDef = AuxSyms[0];
 623     SecDef.Aux.SectionDefinition.CheckSum = CRC;
 624   }
 625
 626   // Write relocations for this section.
 627   if (Sec.Relocations.empty()) {
 628     assert(Sec.Header.PointerToRelocations == 0 &&
 629            "Section::PointerToRelocations is insane!");
 630     return;
 631   }
 632
 633   assert(W.OS.tell() == Sec.Header.PointerToRelocations &&
 634          "Section::PointerToRelocations is insane!");
 635
 636   if (Sec.Relocations.size() >= 0xffff) {
 637     // In case of overflow, write actual relocation count as first
 638     // relocation. Including the synthetic reloc itself (+ 1).
 639     COFF::relocation R;
 640     R.VirtualAddress = Sec.Relocations.size() + 1;
 641     R.SymbolTableIndex = 0;
 642     R.Type = 0;
 643     WriteRelocation(R);
 644   }
 645
 646   for (const auto &Relocation : Sec.Relocations)
 647     WriteRelocation(Relocation.Data);
 648 }
 649
 650 ////////////////////////////////////////////////////////////////////////////////
 651 // MCObjectWriter interface implementations
 652
 653 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
 654                                                    const MCAsmLayout &Layout) {
 655   if (EmitAddrsigSection) {
 656     AddrsigSection = Asm.getContext().getCOFFSection(
 657         ".llvm_addrsig", COFF::IMAGE_SCN_LNK_REMOVE,
 658         SectionKind::getMetadata());
 659     Asm.registerSection(*AddrsigSection);
 660   }
 661
 662   if (!Asm.CGProfile.empty()) {
 663     CGProfileSection = Asm.getContext().getCOFFSection(
 664         ".llvm.call-graph-profile", COFF::IMAGE_SCN_LNK_REMOVE,
 665         SectionKind::getMetadata());
 666     Asm.registerSection(*CGProfileSection);
 667   }
 668
 669   // "Define" each section & symbol. This creates section & symbol
 670   // entries in the staging area.
 671   for (const auto &Section : Asm)
 672     defineSection(static_cast<const MCSectionCOFF &>(Section), Layout);
 673
 674   for (const MCSymbol &Symbol : Asm.symbols())
 675     if (!Symbol.isTemporary())
 676       DefineSymbol(Symbol, Asm, Layout);
 677 }
 678
 679 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
 680     const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
 681     bool InSet, bool IsPCRel) const {
 682   // Don't drop relocations between functions, even if they are in the same text
 683   // section. Multiple Visual C++ linker features depend on having the
 684   // relocations present. The /INCREMENTAL flag will cause these relocations to
 685   // point to thunks, and the /GUARD:CF flag assumes that it can use relocations
 686   // to approximate the set of all address taken functions. LLD's implementation
 687   // of /GUARD:CF also relies on the existance of these relocations.
 688   uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
 689   if ((Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
 690     return false;
 691   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
 692                                                                 InSet, IsPCRel);
 693 }
 694
 695 void WinCOFFObjectWriter::recordRelocation(MCAssembler &Asm,
 696                                            const MCAsmLayout &Layout,
 697                                            const MCFragment *Fragment,
 698                                            const MCFixup &Fixup, MCValue Target,
 699                                            uint64_t &FixedValue) {
 700   assert(Target.getSymA() && "Relocation must reference a symbol!");
 701
 702   const MCSymbol &A = Target.getSymA()->getSymbol();
 703   if (!A.isRegistered()) {
 704     Asm.getContext().reportError(Fixup.getLoc(),
 705                                       Twine("symbol '") + A.getName() +
 706                                           "' can not be undefined");
 707     return;
 708   }
 709   if (A.isTemporary() && A.isUndefined()) {
 710     Asm.getContext().reportError(Fixup.getLoc(),
 711                                       Twine("assembler label '") + A.getName() +
 712                                           "' can not be undefined");
 713     return;
 714   }
 715
 716   MCSection *MCSec = Fragment->getParent();
 717
 718   // Mark this symbol as requiring an entry in the symbol table.
 719   assert(SectionMap.contains(MCSec) &&
 720          "Section must already have been defined in executePostLayoutBinding!");
 721
 722   COFFSection *Sec = SectionMap[MCSec];
 723   const MCSymbolRefExpr *SymB = Target.getSymB();
 724
 725   if (SymB) {
 726     const MCSymbol *B = &SymB->getSymbol();
 727     if (!B->getFragment()) {
 728       Asm.getContext().reportError(
 729           Fixup.getLoc(),
 730           Twine("symbol '") + B->getName() +
 731               "' can not be undefined in a subtraction expression");
 732       return;
 733     }
 734
 735     // Offset of the symbol in the section
 736     int64_t OffsetOfB = Layout.getSymbolOffset(*B);
 737
 738     // Offset of the relocation in the section
 739     int64_t OffsetOfRelocation =
 740         Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
 741
 742     FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
 743   } else {
 744     FixedValue = Target.getConstant();
 745   }
 746
 747   COFFRelocation Reloc;
 748
 749   Reloc.Data.SymbolTableIndex = 0;
 750   Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
 751
 752   // Turn relocations for temporary symbols into section relocations.
 753   if (A.isTemporary()) {
 754     MCSection *TargetSection = &A.getSection();
 755     assert(
 756         SectionMap.contains(TargetSection) &&
 757         "Section must already have been defined in executePostLayoutBinding!");
 758     COFFSection *Section = SectionMap[TargetSection];
 759     Reloc.Symb = Section->Symbol;
 760     FixedValue += Layout.getSymbolOffset(A);
 761     // Technically, we should do the final adjustments of FixedValue (below)
 762     // before picking an offset symbol, otherwise we might choose one which
 763     // is slightly too far away. The relocations where it really matters
 764     // (arm64 adrp relocations) don't get any offset though.
 765     if (UseOffsetLabels && !Section->OffsetSymbols.empty()) {
 766       uint64_t LabelIndex = FixedValue >> OffsetLabelIntervalBits;
 767       if (LabelIndex > 0) {
 768         if (LabelIndex <= Section->OffsetSymbols.size())
 769           Reloc.Symb = Section->OffsetSymbols[LabelIndex - 1];
 770         else
 771           Reloc.Symb = Section->OffsetSymbols.back();
 772         FixedValue -= Reloc.Symb->Data.Value;
 773       }
 774     }
 775   } else {
 776     assert(
 777         SymbolMap.contains(&A) &&
 778         "Symbol must already have been defined in executePostLayoutBinding!");
 779     Reloc.Symb = SymbolMap[&A];
 780   }
 781
 782   ++Reloc.Symb->Relocations;
 783
 784   Reloc.Data.VirtualAddress += Fixup.getOffset();
 785   Reloc.Data.Type = TargetObjectWriter->getRelocType(
 786       Asm.getContext(), Target, Fixup, SymB, Asm.getBackend());
 787
 788   // The *_REL32 relocations are relative to the end of the relocation,
 789   // not to the start.
 790   if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
 791        Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
 792       (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
 793        Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32) ||
 794       (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT &&
 795        Reloc.Data.Type == COFF::IMAGE_REL_ARM_REL32) ||
 796       (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARM64 &&
 797        Reloc.Data.Type == COFF::IMAGE_REL_ARM64_REL32))
 798     FixedValue += 4;
 799
 800   if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
 801     switch (Reloc.Data.Type) {
 802     case COFF::IMAGE_REL_ARM_ABSOLUTE:
 803     case COFF::IMAGE_REL_ARM_ADDR32:
 804     case COFF::IMAGE_REL_ARM_ADDR32NB:
 805     case COFF::IMAGE_REL_ARM_TOKEN:
 806     case COFF::IMAGE_REL_ARM_SECTION:
 807     case COFF::IMAGE_REL_ARM_SECREL:
 808       break;
 809     case COFF::IMAGE_REL_ARM_BRANCH11:
 810     case COFF::IMAGE_REL_ARM_BLX11:
 811     // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
 812     // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
 813     // for Windows CE).
 814     case COFF::IMAGE_REL_ARM_BRANCH24:
 815     case COFF::IMAGE_REL_ARM_BLX24:
 816     case COFF::IMAGE_REL_ARM_MOV32A:
 817       // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
 818       // only used for ARM mode code, which is documented as being unsupported
 819       // by Windows on ARM.  Empirical proof indicates that masm is able to
 820       // generate the relocations however the rest of the MSVC toolchain is
 821       // unable to handle it.
 822       llvm_unreachable("unsupported relocation");
 823       break;
 824     case COFF::IMAGE_REL_ARM_MOV32T:
 825       break;
 826     case COFF::IMAGE_REL_ARM_BRANCH20T:
 827     case COFF::IMAGE_REL_ARM_BRANCH24T:
 828     case COFF::IMAGE_REL_ARM_BLX23T:
 829       // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
 830       // perform a 4 byte adjustment to the relocation.  Relative branches are
 831       // offset by 4 on ARM, however, because there is no RELA relocations, all
 832       // branches are offset by 4.
 833       FixedValue = FixedValue + 4;
 834       break;
 835     }
 836   }
 837
 838   // The fixed value never makes sense for section indices, ignore it.
 839   if (Fixup.getKind() == FK_SecRel_2)
 840     FixedValue = 0;
 841
 842   if (TargetObjectWriter->recordRelocation(Fixup))
 843     Sec->Relocations.push_back(Reloc);
 844 }
 845
 846 static std::time_t getTime() {
 847   std::time_t Now = time(nullptr);
 848   if (Now < 0 || !isUInt<32>(Now))
 849     return UINT32_MAX;
 850   return Now;
 851 }
 852
 853 // Create .file symbols.
 854 void WinCOFFObjectWriter::createFileSymbols(MCAssembler &Asm) {
 855   for (const std::pair<std::string, size_t> &It : Asm.getFileNames()) {
 856     // round up to calculate the number of auxiliary symbols required
 857     const std::string &Name = It.first;
 858     unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
 859     unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
 860
 861     COFFSymbol *File = createSymbol(".file");
 862     File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
 863     File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
 864     File->Aux.resize(Count);
 865
 866     unsigned Offset = 0;
 867     unsigned Length = Name.size();
 868     for (auto &Aux : File->Aux) {
 869       Aux.AuxType = ATFile;
 870
 871       if (Length > SymbolSize) {
 872         memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
 873         Length = Length - SymbolSize;
 874       } else {
 875         memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
 876         memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
 877         break;
 878       }
 879
 880       Offset += SymbolSize;
 881     }
 882   }
 883 }
 884
 885 void WinCOFFObjectWriter::setWeakDefaultNames() {
 886   if (WeakDefaults.empty())
 887     return;
 888
 889   // If multiple object files use a weak symbol (either with a regular
 890   // defined default, or an absolute zero symbol as default), the defaults
 891   // cause duplicate definitions unless their names are made unique. Look
 892   // for a defined extern symbol, that isn't comdat - that should be unique
 893   // unless there are other duplicate definitions. And if none is found,
 894   // allow picking a comdat symbol, as that's still better than nothing.
 895
 896   COFFSymbol *Unique = nullptr;
 897   for (bool AllowComdat : {false, true}) {
 898     for (auto &Sym : Symbols) {
 899       // Don't include the names of the defaults themselves
 900       if (WeakDefaults.count(Sym.get()))
 901         continue;
 902       // Only consider external symbols
 903       if (Sym->Data.StorageClass != COFF::IMAGE_SYM_CLASS_EXTERNAL)
 904         continue;
 905       // Only consider symbols defined in a section or that are absolute
 906       if (!Sym->Section && Sym->Data.SectionNumber != COFF::IMAGE_SYM_ABSOLUTE)
 907         continue;
 908       if (!AllowComdat && Sym->Section &&
 909           Sym->Section->Header.Characteristics & COFF::IMAGE_SCN_LNK_COMDAT)
 910         continue;
 911       Unique = Sym.get();
 912       break;
 913     }
 914     if (Unique)
 915       break;
 916   }
 917   // If we didn't find any unique symbol to use for the names, just skip this.
 918   if (!Unique)
 919     return;
 920   for (auto *Sym : WeakDefaults) {
 921     Sym->Name.append(".");
 922     Sym->Name.append(Unique->Name);
 923   }
 924 }
 925
 926 static bool isAssociative(const COFFSection &Section) {
 927   return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection ==
 928          COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
 929 }
 930
 931 void WinCOFFObjectWriter::assignSectionNumbers() {
 932   size_t I = 1;
 933   auto Assign = [&](COFFSection &Section) {
 934     Section.Number = I;
 935     Section.Symbol->Data.SectionNumber = I;
 936     Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I;
 937     ++I;
 938   };
 939
 940   // Although it is not explicitly requested by the Microsoft COFF spec,
 941   // we should avoid emitting forward associative section references,
 942   // because MSVC link.exe as of 2017 cannot handle that.
 943   for (const std::unique_ptr<COFFSection> &Section : Sections)
 944     if (!isAssociative(*Section))
 945       Assign(*Section);
 946   for (const std::unique_ptr<COFFSection> &Section : Sections)
 947     if (isAssociative(*Section))
 948       Assign(*Section);
 949 }
 950
 951 // Assign file offsets to COFF object file structures.
 952 void WinCOFFObjectWriter::assignFileOffsets(MCAssembler &Asm,
 953                                             const MCAsmLayout &Layout) {
 954   unsigned Offset = W.OS.tell();
 955
 956   Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size;
 957   Offset += COFF::SectionSize * Header.NumberOfSections;
 958
 959   for (const auto &Section : Asm) {
 960     COFFSection *Sec = SectionMap[&Section];
 961
 962     if (!Sec || Sec->Number == -1)
 963       continue;
 964
 965     Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
 966
 967     if (IsPhysicalSection(Sec)) {
 968       Sec->Header.PointerToRawData = Offset;
 969       Offset += Sec->Header.SizeOfRawData;
 970     }
 971
 972     if (!Sec->Relocations.empty()) {
 973       bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
 974
 975       if (RelocationsOverflow) {
 976         // Signal overflow by setting NumberOfRelocations to max value. Actual
 977         // size is found in reloc #0. Microsoft tools understand this.
 978         Sec->Header.NumberOfRelocations = 0xffff;
 979       } else {
 980         Sec->Header.NumberOfRelocations = Sec->Relocations.size();
 981       }
 982       Sec->Header.PointerToRelocations = Offset;
 983
 984       if (RelocationsOverflow) {
 985         // Reloc #0 will contain actual count, so make room for it.
 986         Offset += COFF::RelocationSize;
 987       }
 988
 989       Offset += COFF::RelocationSize * Sec->Relocations.size();
 990
 991       for (auto &Relocation : Sec->Relocations) {
 992         assert(Relocation.Symb->getIndex() != -1);
 993         Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
 994       }
 995     }
 996
 997     assert(Sec->Symbol->Aux.size() == 1 &&
 998            "Section's symbol must have one aux!");
 999     AuxSymbol &Aux = Sec->Symbol->Aux[0];
1000     assert(Aux.AuxType == ATSectionDefinition &&
1001            "Section's symbol's aux symbol must be a Section Definition!");
1002     Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
1003     Aux.Aux.SectionDefinition.NumberOfRelocations =
1004         Sec->Header.NumberOfRelocations;
1005     Aux.Aux.SectionDefinition.NumberOfLinenumbers =
1006         Sec->Header.NumberOfLineNumbers;
1007   }
1008
1009   Header.PointerToSymbolTable = Offset;
1010 }
1011
1012 uint64_t WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
1013                                           const MCAsmLayout &Layout) {
1014   uint64_t StartOffset = W.OS.tell();
1015
1016   if (Sections.size() > INT32_MAX)
1017     report_fatal_error(
1018         "PE COFF object files can't have more than 2147483647 sections");
1019
1020   UseBigObj = Sections.size() > COFF::MaxNumberOfSections16;
1021   Header.NumberOfSections = Sections.size();
1022   Header.NumberOfSymbols = 0;
1023
1024   setWeakDefaultNames();
1025   assignSectionNumbers();
1026   createFileSymbols(Asm);
1027
1028   for (auto &Symbol : Symbols) {
1029     // Update section number & offset for symbols that have them.
1030     if (Symbol->Section)
1031       Symbol->Data.SectionNumber = Symbol->Section->Number;
1032     Symbol->setIndex(Header.NumberOfSymbols++);
1033     // Update auxiliary symbol info.
1034     Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
1035     Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
1036   }
1037
1038   // Build string table.
1039   for (const auto &S : Sections)
1040     if (S->Name.size() > COFF::NameSize)
1041       Strings.add(S->Name);
1042   for (const auto &S : Symbols)
1043     if (S->Name.size() > COFF::NameSize)
1044       Strings.add(S->Name);
1045   Strings.finalize();
1046
1047   // Set names.
1048   for (const auto &S : Sections)
1049     SetSectionName(*S);
1050   for (auto &S : Symbols)
1051     SetSymbolName(*S);
1052
1053   // Fixup weak external references.
1054   for (auto &Symbol : Symbols) {
1055     if (Symbol->Other) {
1056       assert(Symbol->getIndex() != -1);
1057       assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
1058       assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
1059              "Symbol's aux symbol must be a Weak External!");
1060       Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
1061     }
1062   }
1063
1064   // Fixup associative COMDAT sections.
1065   for (auto &Section : Sections) {
1066     if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
1067         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1068       continue;
1069
1070     const MCSectionCOFF &MCSec = *Section->MCSection;
1071     const MCSymbol *AssocMCSym = MCSec.getCOMDATSymbol();
1072     assert(AssocMCSym);
1073
1074     // It's an error to try to associate with an undefined symbol or a symbol
1075     // without a section.
1076     if (!AssocMCSym->isInSection()) {
1077       Asm.getContext().reportError(
1078           SMLoc(), Twine("cannot make section ") + MCSec.getName() +
1079                        Twine(" associative with sectionless symbol ") +
1080                        AssocMCSym->getName());
1081       continue;
1082     }
1083
1084     const auto *AssocMCSec = cast<MCSectionCOFF>(&AssocMCSym->getSection());
1085     assert(SectionMap.count(AssocMCSec));
1086     COFFSection *AssocSec = SectionMap[AssocMCSec];
1087
1088     // Skip this section if the associated section is unused.
1089     if (AssocSec->Number == -1)
1090       continue;
1091
1092     Section->Symbol->Aux[0].Aux.SectionDefinition.Number = AssocSec->Number;
1093   }
1094
1095   // Create the contents of the .llvm_addrsig section.
1096   if (EmitAddrsigSection) {
1097     auto Frag = new MCDataFragment(AddrsigSection);
1098     Frag->setLayoutOrder(0);
1099     raw_svector_ostream OS(Frag->getContents());
1100     for (const MCSymbol *S : AddrsigSyms) {
1101       if (!S->isRegistered())
1102         continue;
1103       if (!S->isTemporary()) {
1104         encodeULEB128(S->getIndex(), OS);
1105         continue;
1106       }
1107
1108       MCSection *TargetSection = &S->getSection();
1109       assert(SectionMap.contains(TargetSection) &&
1110              "Section must already have been defined in "
1111              "executePostLayoutBinding!");
1112       encodeULEB128(SectionMap[TargetSection]->Symbol->getIndex(), OS);
1113     }
1114   }
1115
1116   // Create the contents of the .llvm.call-graph-profile section.
1117   if (CGProfileSection) {
1118     auto *Frag = new MCDataFragment(CGProfileSection);
1119     Frag->setLayoutOrder(0);
1120     raw_svector_ostream OS(Frag->getContents());
1121     for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
1122       uint32_t FromIndex = CGPE.From->getSymbol().getIndex();
1123       uint32_t ToIndex = CGPE.To->getSymbol().getIndex();
1124       support::endian::write(OS, FromIndex, W.Endian);
1125       support::endian::write(OS, ToIndex, W.Endian);
1126       support::endian::write(OS, CGPE.Count, W.Endian);
1127     }
1128   }
1129
1130   assignFileOffsets(Asm, Layout);
1131
1132   // MS LINK expects to be able to use this timestamp to implement their
1133   // /INCREMENTAL feature.
1134   if (Asm.isIncrementalLinkerCompatible()) {
1135     Header.TimeDateStamp = getTime();
1136   } else {
1137     // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
1138     Header.TimeDateStamp = 0;
1139   }
1140
1141   // Write it all to disk...
1142   WriteFileHeader(Header);
1143   writeSectionHeaders();
1144
1145   // Write section contents.
1146   sections::iterator I = Sections.begin();
1147   sections::iterator IE = Sections.end();
1148   MCAssembler::iterator J = Asm.begin();
1149   MCAssembler::iterator JE = Asm.end();
1150   for (; I != IE && J != JE; ++I, ++J)
1151     writeSection(Asm, Layout, **I, *J);
1152
1153   assert(W.OS.tell() == Header.PointerToSymbolTable &&
1154          "Header::PointerToSymbolTable is insane!");
1155
1156   // Write a symbol table.
1157   for (auto &Symbol : Symbols)
1158     if (Symbol->getIndex() != -1)
1159       WriteSymbol(*Symbol);
1160
1161   // Write a string table, which completes the entire COFF file.
1162   Strings.write(W.OS);
1163
1164   return W.OS.tell() - StartOffset;
1165 }
1166
1167 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1168     : Machine(Machine_) {}
1169
1170 // Pin the vtable to this file.
1171 void MCWinCOFFObjectTargetWriter::anchor() {}
1172
1173 //------------------------------------------------------------------------------
1174 // WinCOFFObjectWriter factory function
1175
1176 std::unique_ptr<MCObjectWriter> llvm::createWinCOFFObjectWriter(
1177     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS) {
1178   return std::make_unique<WinCOFFObjectWriter>(std::move(MOTW), OS);
1179 }