1 //===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains an implementation of a Win32 COFF object file writer. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/MC/MCWinCOFFObjectWriter.h" 15 #include "llvm/ADT/DenseMap.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/StringMap.h" 18 #include "llvm/ADT/StringRef.h" 19 #include "llvm/ADT/Twine.h" 20 #include "llvm/Config/config.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/MCObjectFileInfo.h" 26 #include "llvm/MC/MCObjectWriter.h" 27 #include "llvm/MC/MCSection.h" 28 #include "llvm/MC/MCSectionCOFF.h" 29 #include "llvm/MC/MCSymbolCOFF.h" 30 #include "llvm/MC/MCValue.h" 31 #include "llvm/MC/StringTableBuilder.h" 32 #include "llvm/Support/COFF.h" 33 #include "llvm/Support/Debug.h" 34 #include "llvm/Support/Endian.h" 35 #include "llvm/Support/ErrorHandling.h" 36 #include "llvm/Support/JamCRC.h" 37 #include "llvm/Support/TimeValue.h" 38 #include <cstdio> 39 #include <ctime> 40 41 using namespace llvm; 42 43 #define DEBUG_TYPE "WinCOFFObjectWriter" 44 45 namespace { 46 typedef SmallString<COFF::NameSize> name; 47 48 enum AuxiliaryType { 49 ATFunctionDefinition, 50 ATbfAndefSymbol, 51 ATWeakExternal, 52 ATFile, 53 ATSectionDefinition 54 }; 55 56 struct AuxSymbol { 57 AuxiliaryType AuxType; 58 COFF::Auxiliary Aux; 59 }; 60 61 class COFFSymbol; 62 class COFFSection; 63 64 class COFFSymbol { 65 public: 66 COFF::symbol Data; 67 68 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols; 69 70 name Name; 71 int Index; 72 AuxiliarySymbols Aux; 73 COFFSymbol *Other; 74 COFFSection *Section; 75 int Relocations; 76 77 const MCSymbol *MC; 78 79 COFFSymbol(StringRef name); 80 void set_name_offset(uint32_t Offset); 81 82 int64_t getIndex() const { return Index; } 83 void setIndex(int Value) { 84 Index = Value; 85 if (MC) 86 MC->setIndex(static_cast<uint32_t>(Value)); 87 } 88 }; 89 90 // This class contains staging data for a COFF relocation entry. 91 struct COFFRelocation { 92 COFF::relocation Data; 93 COFFSymbol *Symb; 94 95 COFFRelocation() : Symb(nullptr) {} 96 static size_t size() { return COFF::RelocationSize; } 97 }; 98 99 typedef std::vector<COFFRelocation> relocations; 100 101 class COFFSection { 102 public: 103 COFF::section Header; 104 105 std::string Name; 106 int Number; 107 MCSectionCOFF const *MCSection; 108 COFFSymbol *Symbol; 109 relocations Relocations; 110 111 COFFSection(StringRef name); 112 static size_t size(); 113 }; 114 115 class WinCOFFObjectWriter : public MCObjectWriter { 116 public: 117 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols; 118 typedef std::vector<std::unique_ptr<COFFSection>> sections; 119 120 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map; 121 typedef DenseMap<MCSection const *, COFFSection *> section_map; 122 123 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter; 124 125 // Root level file contents. 126 COFF::header Header; 127 sections Sections; 128 symbols Symbols; 129 StringTableBuilder Strings{StringTableBuilder::WinCOFF}; 130 131 // Maps used during object file creation. 132 section_map SectionMap; 133 symbol_map SymbolMap; 134 135 bool UseBigObj; 136 137 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS); 138 139 void reset() override { 140 memset(&Header, 0, sizeof(Header)); 141 Header.Machine = TargetObjectWriter->getMachine(); 142 Sections.clear(); 143 Symbols.clear(); 144 Strings.clear(); 145 SectionMap.clear(); 146 SymbolMap.clear(); 147 MCObjectWriter::reset(); 148 } 149 150 COFFSymbol *createSymbol(StringRef Name); 151 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol); 152 COFFSection *createSection(StringRef Name); 153 154 template <typename object_t, typename list_t> 155 object_t *createCOFFEntity(StringRef Name, list_t &List); 156 157 void defineSection(MCSectionCOFF const &Sec); 158 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler, 159 const MCAsmLayout &Layout); 160 161 void SetSymbolName(COFFSymbol &S); 162 void SetSectionName(COFFSection &S); 163 164 bool IsPhysicalSection(COFFSection *S); 165 166 // Entity writing methods. 167 168 void WriteFileHeader(const COFF::header &Header); 169 void WriteSymbol(const COFFSymbol &S); 170 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S); 171 void writeSectionHeader(const COFF::section &S); 172 void WriteRelocation(const COFF::relocation &R); 173 174 // MCObjectWriter interface implementation. 175 176 void executePostLayoutBinding(MCAssembler &Asm, 177 const MCAsmLayout &Layout) override; 178 179 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 180 const MCSymbol &SymA, 181 const MCFragment &FB, bool InSet, 182 bool IsPCRel) const override; 183 184 bool isWeak(const MCSymbol &Sym) const override; 185 186 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 187 const MCFragment *Fragment, const MCFixup &Fixup, 188 MCValue Target, bool &IsPCRel, 189 uint64_t &FixedValue) override; 190 191 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 192 }; 193 } 194 195 static inline void write_uint32_le(void *Data, uint32_t Value) { 196 support::endian::write<uint32_t, support::little, support::unaligned>(Data, 197 Value); 198 } 199 200 //------------------------------------------------------------------------------ 201 // Symbol class implementation 202 203 COFFSymbol::COFFSymbol(StringRef name) 204 : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr), 205 Relocations(0), MC(nullptr) { 206 memset(&Data, 0, sizeof(Data)); 207 } 208 209 // In the case that the name does not fit within 8 bytes, the offset 210 // into the string table is stored in the last 4 bytes instead, leaving 211 // the first 4 bytes as 0. 212 void COFFSymbol::set_name_offset(uint32_t Offset) { 213 write_uint32_le(Data.Name + 0, 0); 214 write_uint32_le(Data.Name + 4, Offset); 215 } 216 217 //------------------------------------------------------------------------------ 218 // Section class implementation 219 220 COFFSection::COFFSection(StringRef name) 221 : Name(name), MCSection(nullptr), Symbol(nullptr) { 222 memset(&Header, 0, sizeof(Header)); 223 } 224 225 size_t COFFSection::size() { return COFF::SectionSize; } 226 227 //------------------------------------------------------------------------------ 228 // WinCOFFObjectWriter class implementation 229 230 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 231 raw_pwrite_stream &OS) 232 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { 233 memset(&Header, 0, sizeof(Header)); 234 235 Header.Machine = TargetObjectWriter->getMachine(); 236 } 237 238 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 239 return createCOFFEntity<COFFSymbol>(Name, Symbols); 240 } 241 242 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) { 243 symbol_map::iterator i = SymbolMap.find(Symbol); 244 if (i != SymbolMap.end()) 245 return i->second; 246 COFFSymbol *RetSymbol = 247 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 248 SymbolMap[Symbol] = RetSymbol; 249 return RetSymbol; 250 } 251 252 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 253 return createCOFFEntity<COFFSection>(Name, Sections); 254 } 255 256 /// A template used to lookup or create a symbol/section, and initialize it if 257 /// needed. 258 template <typename object_t, typename list_t> 259 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) { 260 List.push_back(make_unique<object_t>(Name)); 261 262 return List.back().get(); 263 } 264 265 /// This function takes a section data object from the assembler 266 /// and creates the associated COFF section staging object. 267 void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) { 268 COFFSection *coff_section = createSection(Sec.getSectionName()); 269 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 270 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 271 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 272 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 273 if (COMDATSymbol->Section) 274 report_fatal_error("two sections have the same comdat"); 275 COMDATSymbol->Section = coff_section; 276 } 277 } 278 279 coff_section->Symbol = coff_symbol; 280 coff_symbol->Section = coff_section; 281 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 282 283 // In this case the auxiliary symbol is a Section Definition. 284 coff_symbol->Aux.resize(1); 285 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 286 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 287 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 288 289 coff_section->Header.Characteristics = Sec.getCharacteristics(); 290 291 uint32_t &Characteristics = coff_section->Header.Characteristics; 292 switch (Sec.getAlignment()) { 293 case 1: 294 Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; 295 break; 296 case 2: 297 Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; 298 break; 299 case 4: 300 Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; 301 break; 302 case 8: 303 Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; 304 break; 305 case 16: 306 Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; 307 break; 308 case 32: 309 Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; 310 break; 311 case 64: 312 Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; 313 break; 314 case 128: 315 Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; 316 break; 317 case 256: 318 Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; 319 break; 320 case 512: 321 Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; 322 break; 323 case 1024: 324 Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; 325 break; 326 case 2048: 327 Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; 328 break; 329 case 4096: 330 Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; 331 break; 332 case 8192: 333 Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; 334 break; 335 default: 336 llvm_unreachable("unsupported section alignment"); 337 } 338 339 // Bind internal COFF section to MC section. 340 coff_section->MCSection = &Sec; 341 SectionMap[&Sec] = coff_section; 342 } 343 344 static uint64_t getSymbolValue(const MCSymbol &Symbol, 345 const MCAsmLayout &Layout) { 346 if (Symbol.isCommon() && Symbol.isExternal()) 347 return Symbol.getCommonSize(); 348 349 uint64_t Res; 350 if (!Layout.getSymbolOffset(Symbol, Res)) 351 return 0; 352 353 return Res; 354 } 355 356 /// This function takes a symbol data object from the assembler 357 /// and creates the associated COFF symbol staging object. 358 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol, 359 MCAssembler &Assembler, 360 const MCAsmLayout &Layout) { 361 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 362 363 if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) { 364 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 365 366 if (Symbol.isVariable()) { 367 const MCSymbolRefExpr *SymRef = 368 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 369 370 if (!SymRef) 371 report_fatal_error("Weak externals may only alias symbols"); 372 373 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 374 } else { 375 std::string WeakName = (".weak." + Symbol.getName() + ".default").str(); 376 COFFSymbol *WeakDefault = createSymbol(WeakName); 377 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 378 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 379 WeakDefault->Data.Type = 0; 380 WeakDefault->Data.Value = 0; 381 coff_symbol->Other = WeakDefault; 382 } 383 384 // Setup the Weak External auxiliary symbol. 385 coff_symbol->Aux.resize(1); 386 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 387 coff_symbol->Aux[0].AuxType = ATWeakExternal; 388 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 389 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 390 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 391 392 coff_symbol->MC = &Symbol; 393 } else { 394 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 395 coff_symbol->Data.Value = getSymbolValue(Symbol, Layout); 396 397 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol); 398 coff_symbol->Data.Type = SymbolCOFF.getType(); 399 coff_symbol->Data.StorageClass = SymbolCOFF.getClass(); 400 401 // If no storage class was specified in the streamer, define it here. 402 if (coff_symbol->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) { 403 bool IsExternal = Symbol.isExternal() || 404 (!Symbol.getFragment() && !Symbol.isVariable()); 405 406 coff_symbol->Data.StorageClass = IsExternal 407 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 408 : COFF::IMAGE_SYM_CLASS_STATIC; 409 } 410 411 if (!Base) { 412 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 413 } else { 414 if (Base->getFragment()) { 415 COFFSection *Sec = SectionMap[Base->getFragment()->getParent()]; 416 417 if (coff_symbol->Section && coff_symbol->Section != Sec) 418 report_fatal_error("conflicting sections for symbol"); 419 420 coff_symbol->Section = Sec; 421 } 422 } 423 424 coff_symbol->MC = &Symbol; 425 } 426 } 427 428 // Maximum offsets for different string table entry encodings. 429 enum : unsigned { Max7DecimalOffset = 9999999U }; 430 enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0 431 432 // Encode a string table entry offset in base 64, padded to 6 chars, and 433 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 434 // Buffer must be at least 8 bytes large. No terminating null appended. 435 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) { 436 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 437 "Illegal section name encoding for value"); 438 439 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 440 "abcdefghijklmnopqrstuvwxyz" 441 "0123456789+/"; 442 443 Buffer[0] = '/'; 444 Buffer[1] = '/'; 445 446 char *Ptr = Buffer + 7; 447 for (unsigned i = 0; i < 6; ++i) { 448 unsigned Rem = Value % 64; 449 Value /= 64; 450 *(Ptr--) = Alphabet[Rem]; 451 } 452 } 453 454 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { 455 if (S.Name.size() > COFF::NameSize) { 456 uint64_t StringTableEntry = Strings.getOffset(S.Name); 457 458 if (StringTableEntry <= Max7DecimalOffset) { 459 SmallVector<char, COFF::NameSize> Buffer; 460 Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer); 461 assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2); 462 463 std::memcpy(S.Header.Name, Buffer.data(), Buffer.size()); 464 } else if (StringTableEntry <= MaxBase64Offset) { 465 // Starting with 10,000,000, offsets are encoded as base64. 466 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 467 } else { 468 report_fatal_error("COFF string table is greater than 64 GB."); 469 } 470 } else { 471 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 472 } 473 } 474 475 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { 476 if (S.Name.size() > COFF::NameSize) 477 S.set_name_offset(Strings.getOffset(S.Name)); 478 else 479 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 480 } 481 482 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 483 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 484 0; 485 } 486 487 //------------------------------------------------------------------------------ 488 // entity writing methods 489 490 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 491 if (UseBigObj) { 492 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); 493 writeLE16(0xFFFF); 494 writeLE16(COFF::BigObjHeader::MinBigObjectVersion); 495 writeLE16(Header.Machine); 496 writeLE32(Header.TimeDateStamp); 497 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic))); 498 writeLE32(0); 499 writeLE32(0); 500 writeLE32(0); 501 writeLE32(0); 502 writeLE32(Header.NumberOfSections); 503 writeLE32(Header.PointerToSymbolTable); 504 writeLE32(Header.NumberOfSymbols); 505 } else { 506 writeLE16(Header.Machine); 507 writeLE16(static_cast<int16_t>(Header.NumberOfSections)); 508 writeLE32(Header.TimeDateStamp); 509 writeLE32(Header.PointerToSymbolTable); 510 writeLE32(Header.NumberOfSymbols); 511 writeLE16(Header.SizeOfOptionalHeader); 512 writeLE16(Header.Characteristics); 513 } 514 } 515 516 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 517 writeBytes(StringRef(S.Data.Name, COFF::NameSize)); 518 writeLE32(S.Data.Value); 519 if (UseBigObj) 520 writeLE32(S.Data.SectionNumber); 521 else 522 writeLE16(static_cast<int16_t>(S.Data.SectionNumber)); 523 writeLE16(S.Data.Type); 524 write8(S.Data.StorageClass); 525 write8(S.Data.NumberOfAuxSymbols); 526 WriteAuxiliarySymbols(S.Aux); 527 } 528 529 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 530 const COFFSymbol::AuxiliarySymbols &S) { 531 for (COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 532 i != e; ++i) { 533 switch (i->AuxType) { 534 case ATFunctionDefinition: 535 writeLE32(i->Aux.FunctionDefinition.TagIndex); 536 writeLE32(i->Aux.FunctionDefinition.TotalSize); 537 writeLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 538 writeLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 539 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 540 if (UseBigObj) 541 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 542 break; 543 case ATbfAndefSymbol: 544 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 545 writeLE16(i->Aux.bfAndefSymbol.Linenumber); 546 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 547 writeLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 548 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 549 if (UseBigObj) 550 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 551 break; 552 case ATWeakExternal: 553 writeLE32(i->Aux.WeakExternal.TagIndex); 554 writeLE32(i->Aux.WeakExternal.Characteristics); 555 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 556 if (UseBigObj) 557 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 558 break; 559 case ATFile: 560 writeBytes( 561 StringRef(reinterpret_cast<const char *>(&i->Aux), 562 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); 563 break; 564 case ATSectionDefinition: 565 writeLE32(i->Aux.SectionDefinition.Length); 566 writeLE16(i->Aux.SectionDefinition.NumberOfRelocations); 567 writeLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 568 writeLE32(i->Aux.SectionDefinition.CheckSum); 569 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number)); 570 write8(i->Aux.SectionDefinition.Selection); 571 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 572 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16)); 573 if (UseBigObj) 574 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 575 break; 576 } 577 } 578 } 579 580 void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) { 581 writeBytes(StringRef(S.Name, COFF::NameSize)); 582 583 writeLE32(S.VirtualSize); 584 writeLE32(S.VirtualAddress); 585 writeLE32(S.SizeOfRawData); 586 writeLE32(S.PointerToRawData); 587 writeLE32(S.PointerToRelocations); 588 writeLE32(S.PointerToLineNumbers); 589 writeLE16(S.NumberOfRelocations); 590 writeLE16(S.NumberOfLineNumbers); 591 writeLE32(S.Characteristics); 592 } 593 594 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 595 writeLE32(R.VirtualAddress); 596 writeLE32(R.SymbolTableIndex); 597 writeLE16(R.Type); 598 } 599 600 //////////////////////////////////////////////////////////////////////////////// 601 // MCObjectWriter interface implementations 602 603 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm, 604 const MCAsmLayout &Layout) { 605 // "Define" each section & symbol. This creates section & symbol 606 // entries in the staging area. 607 for (const auto &Section : Asm) 608 defineSection(static_cast<const MCSectionCOFF &>(Section)); 609 610 for (const MCSymbol &Symbol : Asm.symbols()) 611 if (!Symbol.isTemporary()) 612 DefineSymbol(Symbol, Asm, Layout); 613 } 614 615 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl( 616 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB, 617 bool InSet, bool IsPCRel) const { 618 // MS LINK expects to be able to replace all references to a function with a 619 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize 620 // away any relocations to functions. 621 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType(); 622 if (Asm.isIncrementalLinkerCompatible() && 623 (Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION) 624 return false; 625 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB, 626 InSet, IsPCRel); 627 } 628 629 bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const { 630 if (!Sym.isExternal()) 631 return false; 632 633 if (!Sym.isInSection()) 634 return false; 635 636 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection()); 637 if (!Sec.getCOMDATSymbol()) 638 return false; 639 640 // It looks like for COFF it is invalid to replace a reference to a global 641 // in a comdat with a reference to a local. 642 // FIXME: Add a specification reference if available. 643 return true; 644 } 645 646 void WinCOFFObjectWriter::recordRelocation( 647 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, 648 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { 649 assert(Target.getSymA() && "Relocation must reference a symbol!"); 650 651 const MCSymbol &A = Target.getSymA()->getSymbol(); 652 if (!A.isRegistered()) { 653 Asm.getContext().reportError(Fixup.getLoc(), 654 Twine("symbol '") + A.getName() + 655 "' can not be undefined"); 656 return; 657 } 658 if (A.isTemporary() && A.isUndefined()) { 659 Asm.getContext().reportError(Fixup.getLoc(), 660 Twine("assembler label '") + A.getName() + 661 "' can not be undefined"); 662 return; 663 } 664 665 MCSection *Section = Fragment->getParent(); 666 667 // Mark this symbol as requiring an entry in the symbol table. 668 assert(SectionMap.find(Section) != SectionMap.end() && 669 "Section must already have been defined in executePostLayoutBinding!"); 670 671 COFFSection *coff_section = SectionMap[Section]; 672 const MCSymbolRefExpr *SymB = Target.getSymB(); 673 bool CrossSection = false; 674 675 if (SymB) { 676 const MCSymbol *B = &SymB->getSymbol(); 677 if (!B->getFragment()) { 678 Asm.getContext().reportError( 679 Fixup.getLoc(), 680 Twine("symbol '") + B->getName() + 681 "' can not be undefined in a subtraction expression"); 682 return; 683 } 684 685 if (!A.getFragment()) { 686 Asm.getContext().reportError( 687 Fixup.getLoc(), 688 Twine("symbol '") + A.getName() + 689 "' can not be undefined in a subtraction expression"); 690 return; 691 } 692 693 CrossSection = &A.getSection() != &B->getSection(); 694 695 // Offset of the symbol in the section 696 int64_t OffsetOfB = Layout.getSymbolOffset(*B); 697 698 // In the case where we have SymbA and SymB, we just need to store the delta 699 // between the two symbols. Update FixedValue to account for the delta, and 700 // skip recording the relocation. 701 if (!CrossSection) { 702 int64_t OffsetOfA = Layout.getSymbolOffset(A); 703 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant(); 704 return; 705 } 706 707 // Offset of the relocation in the section 708 int64_t OffsetOfRelocation = 709 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 710 711 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant(); 712 } else { 713 FixedValue = Target.getConstant(); 714 } 715 716 COFFRelocation Reloc; 717 718 Reloc.Data.SymbolTableIndex = 0; 719 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 720 721 // Turn relocations for temporary symbols into section relocations. 722 if (A.isTemporary() || CrossSection) { 723 MCSection *TargetSection = &A.getSection(); 724 assert( 725 SectionMap.find(TargetSection) != SectionMap.end() && 726 "Section must already have been defined in executePostLayoutBinding!"); 727 Reloc.Symb = SectionMap[TargetSection]->Symbol; 728 FixedValue += Layout.getSymbolOffset(A); 729 } else { 730 assert( 731 SymbolMap.find(&A) != SymbolMap.end() && 732 "Symbol must already have been defined in executePostLayoutBinding!"); 733 Reloc.Symb = SymbolMap[&A]; 734 } 735 736 ++Reloc.Symb->Relocations; 737 738 Reloc.Data.VirtualAddress += Fixup.getOffset(); 739 Reloc.Data.Type = TargetObjectWriter->getRelocType( 740 Target, Fixup, CrossSection, Asm.getBackend()); 741 742 // FIXME: Can anyone explain what this does other than adjust for the size 743 // of the offset? 744 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 745 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 746 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 747 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 748 FixedValue += 4; 749 750 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 751 switch (Reloc.Data.Type) { 752 case COFF::IMAGE_REL_ARM_ABSOLUTE: 753 case COFF::IMAGE_REL_ARM_ADDR32: 754 case COFF::IMAGE_REL_ARM_ADDR32NB: 755 case COFF::IMAGE_REL_ARM_TOKEN: 756 case COFF::IMAGE_REL_ARM_SECTION: 757 case COFF::IMAGE_REL_ARM_SECREL: 758 break; 759 case COFF::IMAGE_REL_ARM_BRANCH11: 760 case COFF::IMAGE_REL_ARM_BLX11: 761 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 762 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 763 // for Windows CE). 764 case COFF::IMAGE_REL_ARM_BRANCH24: 765 case COFF::IMAGE_REL_ARM_BLX24: 766 case COFF::IMAGE_REL_ARM_MOV32A: 767 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 768 // only used for ARM mode code, which is documented as being unsupported 769 // by Windows on ARM. Empirical proof indicates that masm is able to 770 // generate the relocations however the rest of the MSVC toolchain is 771 // unable to handle it. 772 llvm_unreachable("unsupported relocation"); 773 break; 774 case COFF::IMAGE_REL_ARM_MOV32T: 775 break; 776 case COFF::IMAGE_REL_ARM_BRANCH20T: 777 case COFF::IMAGE_REL_ARM_BRANCH24T: 778 case COFF::IMAGE_REL_ARM_BLX23T: 779 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 780 // perform a 4 byte adjustment to the relocation. Relative branches are 781 // offset by 4 on ARM, however, because there is no RELA relocations, all 782 // branches are offset by 4. 783 FixedValue = FixedValue + 4; 784 break; 785 } 786 } 787 788 if (TargetObjectWriter->recordRelocation(Fixup)) 789 coff_section->Relocations.push_back(Reloc); 790 } 791 792 void WinCOFFObjectWriter::writeObject(MCAssembler &Asm, 793 const MCAsmLayout &Layout) { 794 size_t SectionsSize = Sections.size(); 795 if (SectionsSize > static_cast<size_t>(INT32_MAX)) 796 report_fatal_error( 797 "PE COFF object files can't have more than 2147483647 sections"); 798 799 // Assign symbol and section indexes and offsets. 800 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize); 801 802 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16; 803 804 // Assign section numbers. 805 size_t Number = 1; 806 for (const auto &Section : Sections) { 807 Section->Number = Number; 808 Section->Symbol->Data.SectionNumber = Number; 809 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number; 810 ++Number; 811 } 812 813 Header.NumberOfSections = NumberOfSections; 814 Header.NumberOfSymbols = 0; 815 816 for (const std::string &Name : Asm.getFileNames()) { 817 // round up to calculate the number of auxiliary symbols required 818 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; 819 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize; 820 821 COFFSymbol *file = createSymbol(".file"); 822 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 823 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 824 file->Aux.resize(Count); 825 826 unsigned Offset = 0; 827 unsigned Length = Name.size(); 828 for (auto &Aux : file->Aux) { 829 Aux.AuxType = ATFile; 830 831 if (Length > SymbolSize) { 832 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize); 833 Length = Length - SymbolSize; 834 } else { 835 memcpy(&Aux.Aux, Name.c_str() + Offset, Length); 836 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); 837 break; 838 } 839 840 Offset += SymbolSize; 841 } 842 } 843 844 for (auto &Symbol : Symbols) { 845 // Update section number & offset for symbols that have them. 846 if (Symbol->Section) 847 Symbol->Data.SectionNumber = Symbol->Section->Number; 848 Symbol->setIndex(Header.NumberOfSymbols++); 849 // Update auxiliary symbol info. 850 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 851 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 852 } 853 854 // Build string table. 855 for (const auto &S : Sections) 856 if (S->Name.size() > COFF::NameSize) 857 Strings.add(S->Name); 858 for (const auto &S : Symbols) 859 if (S->Name.size() > COFF::NameSize) 860 Strings.add(S->Name); 861 Strings.finalize(); 862 863 // Set names. 864 for (const auto &S : Sections) 865 SetSectionName(*S); 866 for (auto &S : Symbols) 867 SetSymbolName(*S); 868 869 // Fixup weak external references. 870 for (auto &Symbol : Symbols) { 871 if (Symbol->Other) { 872 assert(Symbol->getIndex() != -1); 873 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 874 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 875 "Symbol's aux symbol must be a Weak External!"); 876 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex(); 877 } 878 } 879 880 // Fixup associative COMDAT sections. 881 for (auto &Section : Sections) { 882 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 883 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 884 continue; 885 886 const MCSectionCOFF &MCSec = *Section->MCSection; 887 888 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 889 assert(COMDAT); 890 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 891 assert(COMDATSymbol); 892 COFFSection *Assoc = COMDATSymbol->Section; 893 if (!Assoc) 894 report_fatal_error( 895 Twine("Missing associated COMDAT section for section ") + 896 MCSec.getSectionName()); 897 898 // Skip this section if the associated section is unused. 899 if (Assoc->Number == -1) 900 continue; 901 902 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number; 903 } 904 905 // Assign file offsets to COFF object file structures. 906 907 unsigned offset = getInitialOffset(); 908 909 if (UseBigObj) 910 offset += COFF::Header32Size; 911 else 912 offset += COFF::Header16Size; 913 offset += COFF::SectionSize * Header.NumberOfSections; 914 915 for (const auto &Section : Asm) { 916 COFFSection *Sec = SectionMap[&Section]; 917 918 if (Sec->Number == -1) 919 continue; 920 921 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 922 923 if (IsPhysicalSection(Sec)) { 924 // Align the section data to a four byte boundary. 925 offset = alignTo(offset, 4); 926 Sec->Header.PointerToRawData = offset; 927 928 offset += Sec->Header.SizeOfRawData; 929 } 930 931 if (Sec->Relocations.size() > 0) { 932 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 933 934 if (RelocationsOverflow) { 935 // Signal overflow by setting NumberOfRelocations to max value. Actual 936 // size is found in reloc #0. Microsoft tools understand this. 937 Sec->Header.NumberOfRelocations = 0xffff; 938 } else { 939 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 940 } 941 Sec->Header.PointerToRelocations = offset; 942 943 if (RelocationsOverflow) { 944 // Reloc #0 will contain actual count, so make room for it. 945 offset += COFF::RelocationSize; 946 } 947 948 offset += COFF::RelocationSize * Sec->Relocations.size(); 949 950 for (auto &Relocation : Sec->Relocations) { 951 assert(Relocation.Symb->getIndex() != -1); 952 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex(); 953 } 954 } 955 956 assert(Sec->Symbol->Aux.size() == 1 && 957 "Section's symbol must have one aux!"); 958 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 959 assert(Aux.AuxType == ATSectionDefinition && 960 "Section's symbol's aux symbol must be a Section Definition!"); 961 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 962 Aux.Aux.SectionDefinition.NumberOfRelocations = 963 Sec->Header.NumberOfRelocations; 964 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 965 Sec->Header.NumberOfLineNumbers; 966 } 967 968 Header.PointerToSymbolTable = offset; 969 970 // MS LINK expects to be able to use this timestamp to implement their 971 // /INCREMENTAL feature. 972 if (Asm.isIncrementalLinkerCompatible()) { 973 std::time_t Now = time(nullptr); 974 if (Now < 0 || !isUInt<32>(Now)) 975 Now = UINT32_MAX; 976 Header.TimeDateStamp = Now; 977 } else { 978 // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU. 979 Header.TimeDateStamp = 0; 980 } 981 982 // Write it all to disk... 983 WriteFileHeader(Header); 984 985 { 986 sections::iterator i, ie; 987 MCAssembler::iterator j, je; 988 989 for (auto &Section : Sections) { 990 if (Section->Number != -1) { 991 if (Section->Relocations.size() >= 0xffff) 992 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 993 writeSectionHeader(Section->Header); 994 } 995 } 996 997 SmallVector<char, 128> SectionContents; 998 for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(), 999 je = Asm.end(); 1000 (i != ie) && (j != je); ++i, ++j) { 1001 1002 if ((*i)->Number == -1) 1003 continue; 1004 1005 if ((*i)->Header.PointerToRawData != 0) { 1006 assert(getStream().tell() <= (*i)->Header.PointerToRawData && 1007 "Section::PointerToRawData is insane!"); 1008 1009 unsigned SectionDataPadding = 1010 (*i)->Header.PointerToRawData - getStream().tell(); 1011 assert(SectionDataPadding < 4 && 1012 "Should only need at most three bytes of padding!"); 1013 1014 WriteZeros(SectionDataPadding); 1015 1016 // Save the contents of the section to a temporary buffer, we need this 1017 // to CRC the data before we dump it into the object file. 1018 SectionContents.clear(); 1019 raw_svector_ostream VecOS(SectionContents); 1020 raw_pwrite_stream &OldStream = getStream(); 1021 // Redirect the output stream to our buffer. 1022 setStream(VecOS); 1023 // Fill our buffer with the section data. 1024 Asm.writeSectionData(&*j, Layout); 1025 // Reset the stream back to what it was before. 1026 setStream(OldStream); 1027 1028 // Calculate our CRC with an initial value of '0', this is not how 1029 // JamCRC is specified but it aligns with the expected output. 1030 JamCRC JC(/*Init=*/0x00000000U); 1031 JC.update(SectionContents); 1032 1033 // Write the section contents to the object file. 1034 getStream() << SectionContents; 1035 1036 // Update the section definition auxiliary symbol to record the CRC. 1037 COFFSection *Sec = SectionMap[&*j]; 1038 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux; 1039 assert(AuxSyms.size() == 1 && 1040 AuxSyms[0].AuxType == ATSectionDefinition); 1041 AuxSymbol &SecDef = AuxSyms[0]; 1042 SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC(); 1043 } 1044 1045 if ((*i)->Relocations.size() > 0) { 1046 assert(getStream().tell() == (*i)->Header.PointerToRelocations && 1047 "Section::PointerToRelocations is insane!"); 1048 1049 if ((*i)->Relocations.size() >= 0xffff) { 1050 // In case of overflow, write actual relocation count as first 1051 // relocation. Including the synthetic reloc itself (+ 1). 1052 COFF::relocation r; 1053 r.VirtualAddress = (*i)->Relocations.size() + 1; 1054 r.SymbolTableIndex = 0; 1055 r.Type = 0; 1056 WriteRelocation(r); 1057 } 1058 1059 for (const auto &Relocation : (*i)->Relocations) 1060 WriteRelocation(Relocation.Data); 1061 } else 1062 assert((*i)->Header.PointerToRelocations == 0 && 1063 "Section::PointerToRelocations is insane!"); 1064 } 1065 } 1066 1067 assert(getStream().tell() == Header.PointerToSymbolTable && 1068 "Header::PointerToSymbolTable is insane!"); 1069 1070 for (auto &Symbol : Symbols) 1071 if (Symbol->getIndex() != -1) 1072 WriteSymbol(*Symbol); 1073 1074 getStream().write(Strings.data().data(), Strings.data().size()); 1075 } 1076 1077 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) 1078 : Machine(Machine_) {} 1079 1080 // Pin the vtable to this file. 1081 void MCWinCOFFObjectTargetWriter::anchor() {} 1082 1083 //------------------------------------------------------------------------------ 1084 // WinCOFFObjectWriter factory function 1085 1086 MCObjectWriter * 1087 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1088 raw_pwrite_stream &OS) { 1089 return new WinCOFFObjectWriter(MOTW, OS); 1090 } 1091