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/MC/MCAsmLayout.h" 21 #include "llvm/MC/MCAssembler.h" 22 #include "llvm/MC/MCContext.h" 23 #include "llvm/MC/MCExpr.h" 24 #include "llvm/MC/MCObjectWriter.h" 25 #include "llvm/MC/MCSection.h" 26 #include "llvm/MC/MCSectionCOFF.h" 27 #include "llvm/MC/MCSymbol.h" 28 #include "llvm/MC/MCValue.h" 29 #include "llvm/MC/StringTableBuilder.h" 30 #include "llvm/Support/COFF.h" 31 #include "llvm/Support/Debug.h" 32 #include "llvm/Support/Endian.h" 33 #include "llvm/Support/ErrorHandling.h" 34 #include "llvm/Support/TimeValue.h" 35 #include <cstdio> 36 37 using namespace llvm; 38 39 #define DEBUG_TYPE "WinCOFFObjectWriter" 40 41 namespace { 42 typedef SmallString<COFF::NameSize> name; 43 44 enum AuxiliaryType { 45 ATFunctionDefinition, 46 ATbfAndefSymbol, 47 ATWeakExternal, 48 ATFile, 49 ATSectionDefinition 50 }; 51 52 struct AuxSymbol { 53 AuxiliaryType AuxType; 54 COFF::Auxiliary Aux; 55 }; 56 57 class COFFSymbol; 58 class COFFSection; 59 60 class COFFSymbol { 61 public: 62 COFF::symbol Data; 63 64 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols; 65 66 name Name; 67 int Index; 68 AuxiliarySymbols Aux; 69 COFFSymbol *Other; 70 COFFSection *Section; 71 int Relocations; 72 73 MCSymbolData const *MCData; 74 75 COFFSymbol(StringRef name); 76 void set_name_offset(uint32_t Offset); 77 78 bool should_keep() const; 79 }; 80 81 // This class contains staging data for a COFF relocation entry. 82 struct COFFRelocation { 83 COFF::relocation Data; 84 COFFSymbol *Symb; 85 86 COFFRelocation() : Symb(nullptr) {} 87 static size_t size() { return COFF::RelocationSize; } 88 }; 89 90 typedef std::vector<COFFRelocation> relocations; 91 92 class COFFSection { 93 public: 94 COFF::section Header; 95 96 std::string Name; 97 int Number; 98 MCSectionData const *MCData; 99 COFFSymbol *Symbol; 100 relocations Relocations; 101 102 COFFSection(StringRef name); 103 static size_t size(); 104 }; 105 106 class WinCOFFObjectWriter : public MCObjectWriter { 107 public: 108 109 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols; 110 typedef std::vector<std::unique_ptr<COFFSection>> sections; 111 112 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map; 113 typedef DenseMap<MCSection const *, COFFSection *> section_map; 114 115 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter; 116 117 // Root level file contents. 118 COFF::header Header; 119 sections Sections; 120 symbols Symbols; 121 StringTableBuilder Strings; 122 123 // Maps used during object file creation. 124 section_map SectionMap; 125 symbol_map SymbolMap; 126 127 bool UseBigObj; 128 129 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS); 130 131 void reset() override { 132 memset(&Header, 0, sizeof(Header)); 133 Header.Machine = TargetObjectWriter->getMachine(); 134 Sections.clear(); 135 Symbols.clear(); 136 Strings.clear(); 137 SectionMap.clear(); 138 SymbolMap.clear(); 139 MCObjectWriter::reset(); 140 } 141 142 COFFSymbol *createSymbol(StringRef Name); 143 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol); 144 COFFSection *createSection(StringRef Name); 145 146 template <typename object_t, typename list_t> 147 object_t *createCOFFEntity(StringRef Name, list_t &List); 148 149 void DefineSection(MCSectionData const &SectionData); 150 void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler, 151 const MCAsmLayout &Layout); 152 153 void SetSymbolName(COFFSymbol &S); 154 void SetSectionName(COFFSection &S); 155 156 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm); 157 158 bool IsPhysicalSection(COFFSection *S); 159 160 // Entity writing methods. 161 162 void WriteFileHeader(const COFF::header &Header); 163 void WriteSymbol(const COFFSymbol &S); 164 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S); 165 void WriteSectionHeader(const COFF::section &S); 166 void WriteRelocation(const COFF::relocation &R); 167 168 // MCObjectWriter interface implementation. 169 170 void ExecutePostLayoutBinding(MCAssembler &Asm, 171 const MCAsmLayout &Layout) override; 172 173 bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 174 const MCSymbol &SymA, 175 const MCFragment &FB, bool InSet, 176 bool IsPCRel) const override; 177 178 bool isWeak(const MCSymbolData &SD) const override; 179 180 void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 181 const MCFragment *Fragment, const MCFixup &Fixup, 182 MCValue Target, bool &IsPCRel, 183 uint64_t &FixedValue) override; 184 185 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 186 }; 187 } 188 189 static inline void write_uint32_le(void *Data, uint32_t Value) { 190 support::endian::write<uint32_t, support::little, support::unaligned>(Data, 191 Value); 192 } 193 194 //------------------------------------------------------------------------------ 195 // Symbol class implementation 196 197 COFFSymbol::COFFSymbol(StringRef name) 198 : Name(name.begin(), name.end()) 199 , Other(nullptr) 200 , Section(nullptr) 201 , Relocations(0) 202 , MCData(nullptr) { 203 memset(&Data, 0, sizeof(Data)); 204 } 205 206 // In the case that the name does not fit within 8 bytes, the offset 207 // into the string table is stored in the last 4 bytes instead, leaving 208 // the first 4 bytes as 0. 209 void COFFSymbol::set_name_offset(uint32_t Offset) { 210 write_uint32_le(Data.Name + 0, 0); 211 write_uint32_le(Data.Name + 4, Offset); 212 } 213 214 /// logic to decide if the symbol should be reported in the symbol table 215 bool COFFSymbol::should_keep() const { 216 // no section means its external, keep it 217 if (!Section) 218 return true; 219 220 // if it has relocations pointing at it, keep it 221 if (Relocations > 0) { 222 assert(Section->Number != -1 && "Sections with relocations must be real!"); 223 return true; 224 } 225 226 // if the section its in is being droped, drop it 227 if (Section->Number == -1) 228 return false; 229 230 // if it is the section symbol, keep it 231 if (Section->Symbol == this) 232 return true; 233 234 // if its temporary, drop it 235 if (MCData && MCData->getSymbol().isTemporary()) 236 return false; 237 238 // otherwise, keep it 239 return true; 240 } 241 242 //------------------------------------------------------------------------------ 243 // Section class implementation 244 245 COFFSection::COFFSection(StringRef name) 246 : Name(name) 247 , MCData(nullptr) 248 , Symbol(nullptr) { 249 memset(&Header, 0, sizeof(Header)); 250 } 251 252 size_t COFFSection::size() { 253 return COFF::SectionSize; 254 } 255 256 //------------------------------------------------------------------------------ 257 // WinCOFFObjectWriter class implementation 258 259 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 260 raw_pwrite_stream &OS) 261 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { 262 memset(&Header, 0, sizeof(Header)); 263 264 Header.Machine = TargetObjectWriter->getMachine(); 265 } 266 267 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 268 return createCOFFEntity<COFFSymbol>(Name, Symbols); 269 } 270 271 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) { 272 symbol_map::iterator i = SymbolMap.find(Symbol); 273 if (i != SymbolMap.end()) 274 return i->second; 275 COFFSymbol *RetSymbol = 276 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 277 SymbolMap[Symbol] = RetSymbol; 278 return RetSymbol; 279 } 280 281 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 282 return createCOFFEntity<COFFSection>(Name, Sections); 283 } 284 285 /// A template used to lookup or create a symbol/section, and initialize it if 286 /// needed. 287 template <typename object_t, typename list_t> 288 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, 289 list_t &List) { 290 List.push_back(make_unique<object_t>(Name)); 291 292 return List.back().get(); 293 } 294 295 /// This function takes a section data object from the assembler 296 /// and creates the associated COFF section staging object. 297 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) { 298 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF 299 && "Got non-COFF section in the COFF backend!"); 300 // FIXME: Not sure how to verify this (at least in a debug build). 301 MCSectionCOFF const &Sec = 302 static_cast<MCSectionCOFF const &>(SectionData.getSection()); 303 304 COFFSection *coff_section = createSection(Sec.getSectionName()); 305 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 306 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 307 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 308 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 309 if (COMDATSymbol->Section) 310 report_fatal_error("two sections have the same comdat"); 311 COMDATSymbol->Section = coff_section; 312 } 313 } 314 315 coff_section->Symbol = coff_symbol; 316 coff_symbol->Section = coff_section; 317 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 318 319 // In this case the auxiliary symbol is a Section Definition. 320 coff_symbol->Aux.resize(1); 321 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 322 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 323 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 324 325 coff_section->Header.Characteristics = Sec.getCharacteristics(); 326 327 uint32_t &Characteristics = coff_section->Header.Characteristics; 328 switch (SectionData.getAlignment()) { 329 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break; 330 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break; 331 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break; 332 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break; 333 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break; 334 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break; 335 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break; 336 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break; 337 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break; 338 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break; 339 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break; 340 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break; 341 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break; 342 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break; 343 default: 344 llvm_unreachable("unsupported section alignment"); 345 } 346 347 // Bind internal COFF section to MC section. 348 coff_section->MCData = &SectionData; 349 SectionMap[&SectionData.getSection()] = coff_section; 350 } 351 352 static uint64_t getSymbolValue(const MCSymbolData &Data, 353 const MCAsmLayout &Layout) { 354 if (Data.isCommon() && Data.isExternal()) 355 return Data.getCommonSize(); 356 357 uint64_t Res; 358 if (!Layout.getSymbolOffset(&Data, Res)) 359 return 0; 360 361 return Res; 362 } 363 364 /// This function takes a symbol data object from the assembler 365 /// and creates the associated COFF symbol staging object. 366 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData, 367 MCAssembler &Assembler, 368 const MCAsmLayout &Layout) { 369 MCSymbol const &Symbol = SymbolData.getSymbol(); 370 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 371 SymbolMap[&Symbol] = coff_symbol; 372 373 if (SymbolData.getFlags() & COFF::SF_WeakExternal) { 374 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 375 376 if (Symbol.isVariable()) { 377 const MCSymbolRefExpr *SymRef = 378 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 379 380 if (!SymRef) 381 report_fatal_error("Weak externals may only alias symbols"); 382 383 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 384 } else { 385 std::string WeakName = (".weak." + Symbol.getName() + ".default").str(); 386 COFFSymbol *WeakDefault = createSymbol(WeakName); 387 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 388 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 389 WeakDefault->Data.Type = 0; 390 WeakDefault->Data.Value = 0; 391 coff_symbol->Other = WeakDefault; 392 } 393 394 // Setup the Weak External auxiliary symbol. 395 coff_symbol->Aux.resize(1); 396 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 397 coff_symbol->Aux[0].AuxType = ATWeakExternal; 398 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 399 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 400 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 401 402 coff_symbol->MCData = &SymbolData; 403 } else { 404 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol); 405 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 406 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout); 407 408 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0; 409 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16; 410 411 // If no storage class was specified in the streamer, define it here. 412 if (coff_symbol->Data.StorageClass == 0) { 413 bool IsExternal = 414 ResSymData.isExternal() || 415 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable()); 416 417 coff_symbol->Data.StorageClass = IsExternal 418 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 419 : COFF::IMAGE_SYM_CLASS_STATIC; 420 } 421 422 if (!Base) { 423 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 424 } else { 425 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base); 426 if (BaseData.getFragment()) { 427 COFFSection *Sec = 428 SectionMap[&BaseData.getFragment()->getParent()->getSection()]; 429 430 if (coff_symbol->Section && coff_symbol->Section != Sec) 431 report_fatal_error("conflicting sections for symbol"); 432 433 coff_symbol->Section = Sec; 434 } 435 } 436 437 coff_symbol->MCData = &ResSymData; 438 } 439 } 440 441 // Maximum offsets for different string table entry encodings. 442 static const unsigned Max6DecimalOffset = 999999; 443 static const unsigned Max7DecimalOffset = 9999999; 444 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 445 446 // Encode a string table entry offset in base 64, padded to 6 chars, and 447 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 448 // Buffer must be at least 8 bytes large. No terminating null appended. 449 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) { 450 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 451 "Illegal section name encoding for value"); 452 453 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 454 "abcdefghijklmnopqrstuvwxyz" 455 "0123456789+/"; 456 457 Buffer[0] = '/'; 458 Buffer[1] = '/'; 459 460 char* Ptr = Buffer + 7; 461 for (unsigned i = 0; i < 6; ++i) { 462 unsigned Rem = Value % 64; 463 Value /= 64; 464 *(Ptr--) = Alphabet[Rem]; 465 } 466 } 467 468 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { 469 if (S.Name.size() > COFF::NameSize) { 470 uint64_t StringTableEntry = Strings.getOffset(S.Name); 471 472 if (StringTableEntry <= Max6DecimalOffset) { 473 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 474 } else if (StringTableEntry <= Max7DecimalOffset) { 475 // With seven digits, we have to skip the terminating null. Because 476 // sprintf always appends it, we use a larger temporary buffer. 477 char buffer[9] = { }; 478 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 479 std::memcpy(S.Header.Name, buffer, 8); 480 } else if (StringTableEntry <= MaxBase64Offset) { 481 // Starting with 10,000,000, offsets are encoded as base64. 482 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 483 } else { 484 report_fatal_error("COFF string table is greater than 64 GB."); 485 } 486 } else 487 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 488 } 489 490 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { 491 if (S.Name.size() > COFF::NameSize) 492 S.set_name_offset(Strings.getOffset(S.Name)); 493 else 494 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 495 } 496 497 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol, 498 MCAssembler &Asm) { 499 // This doesn't seem to be right. Strings referred to from the .data section 500 // need symbols so they can be linked to code in the .text section right? 501 502 // return Asm.isSymbolLinkerVisible(Symbol); 503 504 // Non-temporary labels should always be visible to the linker. 505 if (!Symbol.isTemporary()) 506 return true; 507 508 // Absolute temporary labels are never visible. 509 if (!Symbol.isInSection()) 510 return false; 511 512 // For now, all non-variable symbols are exported, 513 // the linker will sort the rest out for us. 514 return !Symbol.isVariable(); 515 } 516 517 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 518 return (S->Header.Characteristics 519 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0; 520 } 521 522 //------------------------------------------------------------------------------ 523 // entity writing methods 524 525 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 526 if (UseBigObj) { 527 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); 528 WriteLE16(0xFFFF); 529 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion); 530 WriteLE16(Header.Machine); 531 WriteLE32(Header.TimeDateStamp); 532 WriteBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic))); 533 WriteLE32(0); 534 WriteLE32(0); 535 WriteLE32(0); 536 WriteLE32(0); 537 WriteLE32(Header.NumberOfSections); 538 WriteLE32(Header.PointerToSymbolTable); 539 WriteLE32(Header.NumberOfSymbols); 540 } else { 541 WriteLE16(Header.Machine); 542 WriteLE16(static_cast<int16_t>(Header.NumberOfSections)); 543 WriteLE32(Header.TimeDateStamp); 544 WriteLE32(Header.PointerToSymbolTable); 545 WriteLE32(Header.NumberOfSymbols); 546 WriteLE16(Header.SizeOfOptionalHeader); 547 WriteLE16(Header.Characteristics); 548 } 549 } 550 551 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 552 WriteBytes(StringRef(S.Data.Name, COFF::NameSize)); 553 WriteLE32(S.Data.Value); 554 if (UseBigObj) 555 WriteLE32(S.Data.SectionNumber); 556 else 557 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber)); 558 WriteLE16(S.Data.Type); 559 Write8(S.Data.StorageClass); 560 Write8(S.Data.NumberOfAuxSymbols); 561 WriteAuxiliarySymbols(S.Aux); 562 } 563 564 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 565 const COFFSymbol::AuxiliarySymbols &S) { 566 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 567 i != e; ++i) { 568 switch(i->AuxType) { 569 case ATFunctionDefinition: 570 WriteLE32(i->Aux.FunctionDefinition.TagIndex); 571 WriteLE32(i->Aux.FunctionDefinition.TotalSize); 572 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 573 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 574 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 575 if (UseBigObj) 576 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 577 break; 578 case ATbfAndefSymbol: 579 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 580 WriteLE16(i->Aux.bfAndefSymbol.Linenumber); 581 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 582 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 583 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 584 if (UseBigObj) 585 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 586 break; 587 case ATWeakExternal: 588 WriteLE32(i->Aux.WeakExternal.TagIndex); 589 WriteLE32(i->Aux.WeakExternal.Characteristics); 590 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 591 if (UseBigObj) 592 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 593 break; 594 case ATFile: 595 WriteBytes( 596 StringRef(reinterpret_cast<const char *>(&i->Aux), 597 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); 598 break; 599 case ATSectionDefinition: 600 WriteLE32(i->Aux.SectionDefinition.Length); 601 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations); 602 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 603 WriteLE32(i->Aux.SectionDefinition.CheckSum); 604 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number)); 605 Write8(i->Aux.SectionDefinition.Selection); 606 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 607 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16)); 608 if (UseBigObj) 609 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 610 break; 611 } 612 } 613 } 614 615 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) { 616 WriteBytes(StringRef(S.Name, COFF::NameSize)); 617 618 WriteLE32(S.VirtualSize); 619 WriteLE32(S.VirtualAddress); 620 WriteLE32(S.SizeOfRawData); 621 WriteLE32(S.PointerToRawData); 622 WriteLE32(S.PointerToRelocations); 623 WriteLE32(S.PointerToLineNumbers); 624 WriteLE16(S.NumberOfRelocations); 625 WriteLE16(S.NumberOfLineNumbers); 626 WriteLE32(S.Characteristics); 627 } 628 629 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 630 WriteLE32(R.VirtualAddress); 631 WriteLE32(R.SymbolTableIndex); 632 WriteLE16(R.Type); 633 } 634 635 //////////////////////////////////////////////////////////////////////////////// 636 // MCObjectWriter interface implementations 637 638 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 639 const MCAsmLayout &Layout) { 640 // "Define" each section & symbol. This creates section & symbol 641 // entries in the staging area. 642 for (const auto &Section : Asm) 643 DefineSection(Section); 644 645 for (const MCSymbol &Symbol : Asm.symbols()) 646 if (ExportSymbol(Symbol, Asm)) 647 DefineSymbol(Symbol.getData(), Asm, Layout); 648 } 649 650 bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 651 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB, 652 bool InSet, bool IsPCRel) const { 653 // MS LINK expects to be able to replace all references to a function with a 654 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize 655 // away any relocations to functions. 656 if ((((SymA.getData().getFlags() & COFF::SF_TypeMask) >> 657 COFF::SF_TypeShift) >> 658 COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION) 659 return false; 660 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB, 661 InSet, IsPCRel); 662 } 663 664 bool WinCOFFObjectWriter::isWeak(const MCSymbolData &SD) const { 665 if (!SD.isExternal()) 666 return false; 667 668 const MCSymbol &Sym = SD.getSymbol(); 669 if (!Sym.isInSection()) 670 return false; 671 672 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection()); 673 if (!Sec.getCOMDATSymbol()) 674 return false; 675 676 // It looks like for COFF it is invalid to replace a reference to a global 677 // in a comdat with a reference to a local. 678 // FIXME: Add a specification reference if available. 679 return true; 680 } 681 682 void WinCOFFObjectWriter::RecordRelocation( 683 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, 684 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { 685 assert(Target.getSymA() && "Relocation must reference a symbol!"); 686 687 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 688 const MCSymbol &A = Symbol; 689 if (!Asm.hasSymbolData(A)) 690 Asm.getContext().reportFatalError( 691 Fixup.getLoc(), 692 Twine("symbol '") + A.getName() + "' can not be undefined"); 693 694 const MCSymbolData &A_SD = Asm.getSymbolData(A); 695 696 MCSectionData const *SectionData = Fragment->getParent(); 697 698 // Mark this symbol as requiring an entry in the symbol table. 699 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && 700 "Section must already have been defined in ExecutePostLayoutBinding!"); 701 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && 702 "Symbol must already have been defined in ExecutePostLayoutBinding!"); 703 704 COFFSection *coff_section = SectionMap[&SectionData->getSection()]; 705 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; 706 const MCSymbolRefExpr *SymB = Target.getSymB(); 707 bool CrossSection = false; 708 709 if (SymB) { 710 const MCSymbol *B = &SymB->getSymbol(); 711 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 712 if (!B_SD.getFragment()) 713 Asm.getContext().reportFatalError( 714 Fixup.getLoc(), 715 Twine("symbol '") + B->getName() + 716 "' can not be undefined in a subtraction expression"); 717 718 if (!A_SD.getFragment()) 719 Asm.getContext().reportFatalError( 720 Fixup.getLoc(), 721 Twine("symbol '") + Symbol.getName() + 722 "' can not be undefined in a subtraction expression"); 723 724 CrossSection = &Symbol.getSection() != &B->getSection(); 725 726 // Offset of the symbol in the section 727 int64_t OffsetOfB = Layout.getSymbolOffset(&B_SD); 728 729 // In the case where we have SymbA and SymB, we just need to store the delta 730 // between the two symbols. Update FixedValue to account for the delta, and 731 // skip recording the relocation. 732 if (!CrossSection) { 733 int64_t OffsetOfA = Layout.getSymbolOffset(&A_SD); 734 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant(); 735 return; 736 } 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 (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { 754 Reloc.Symb = coff_symbol->Section->Symbol; 755 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->getFragment()) + 756 coff_symbol->MCData->getOffset(); 757 } else 758 Reloc.Symb = coff_symbol; 759 760 ++Reloc.Symb->Relocations; 761 762 Reloc.Data.VirtualAddress += Fixup.getOffset(); 763 Reloc.Data.Type = 764 TargetObjectWriter->getRelocType(Target, Fixup, CrossSection, 765 Asm.getBackend()); 766 767 // FIXME: Can anyone explain what this does other than adjust for the size 768 // of the offset? 769 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 770 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 771 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 772 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 773 FixedValue += 4; 774 775 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 776 switch (Reloc.Data.Type) { 777 case COFF::IMAGE_REL_ARM_ABSOLUTE: 778 case COFF::IMAGE_REL_ARM_ADDR32: 779 case COFF::IMAGE_REL_ARM_ADDR32NB: 780 case COFF::IMAGE_REL_ARM_TOKEN: 781 case COFF::IMAGE_REL_ARM_SECTION: 782 case COFF::IMAGE_REL_ARM_SECREL: 783 break; 784 case COFF::IMAGE_REL_ARM_BRANCH11: 785 case COFF::IMAGE_REL_ARM_BLX11: 786 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 787 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 788 // for Windows CE). 789 case COFF::IMAGE_REL_ARM_BRANCH24: 790 case COFF::IMAGE_REL_ARM_BLX24: 791 case COFF::IMAGE_REL_ARM_MOV32A: 792 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 793 // only used for ARM mode code, which is documented as being unsupported 794 // by Windows on ARM. Empirical proof indicates that masm is able to 795 // generate the relocations however the rest of the MSVC toolchain is 796 // unable to handle it. 797 llvm_unreachable("unsupported relocation"); 798 break; 799 case COFF::IMAGE_REL_ARM_MOV32T: 800 break; 801 case COFF::IMAGE_REL_ARM_BRANCH20T: 802 case COFF::IMAGE_REL_ARM_BRANCH24T: 803 case COFF::IMAGE_REL_ARM_BLX23T: 804 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 805 // perform a 4 byte adjustment to the relocation. Relative branches are 806 // offset by 4 on ARM, however, because there is no RELA relocations, all 807 // branches are offset by 4. 808 FixedValue = FixedValue + 4; 809 break; 810 } 811 } 812 813 if (TargetObjectWriter->recordRelocation(Fixup)) 814 coff_section->Relocations.push_back(Reloc); 815 } 816 817 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm, 818 const MCAsmLayout &Layout) { 819 size_t SectionsSize = Sections.size(); 820 if (SectionsSize > static_cast<size_t>(INT32_MAX)) 821 report_fatal_error( 822 "PE COFF object files can't have more than 2147483647 sections"); 823 824 // Assign symbol and section indexes and offsets. 825 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize); 826 827 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16; 828 829 DenseMap<COFFSection *, int32_t> SectionIndices( 830 NextPowerOf2(NumberOfSections)); 831 832 // Assign section numbers. 833 size_t Number = 1; 834 for (const auto &Section : Sections) { 835 SectionIndices[Section.get()] = Number; 836 Section->Number = Number; 837 Section->Symbol->Data.SectionNumber = Number; 838 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number; 839 ++Number; 840 } 841 842 Header.NumberOfSections = NumberOfSections; 843 Header.NumberOfSymbols = 0; 844 845 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end(); 846 FI != FE; ++FI) { 847 // round up to calculate the number of auxiliary symbols required 848 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; 849 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize; 850 851 COFFSymbol *file = createSymbol(".file"); 852 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 853 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 854 file->Aux.resize(Count); 855 856 unsigned Offset = 0; 857 unsigned Length = FI->size(); 858 for (auto &Aux : file->Aux) { 859 Aux.AuxType = ATFile; 860 861 if (Length > SymbolSize) { 862 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize); 863 Length = Length - SymbolSize; 864 } else { 865 memcpy(&Aux.Aux, FI->c_str() + Offset, Length); 866 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); 867 break; 868 } 869 870 Offset += SymbolSize; 871 } 872 } 873 874 for (auto &Symbol : Symbols) { 875 // Update section number & offset for symbols that have them. 876 if (Symbol->Section) 877 Symbol->Data.SectionNumber = Symbol->Section->Number; 878 if (Symbol->should_keep()) { 879 Symbol->Index = Header.NumberOfSymbols++; 880 // Update auxiliary symbol info. 881 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 882 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 883 } else 884 Symbol->Index = -1; 885 } 886 887 // Build string table. 888 for (const auto &S : Sections) 889 if (S->Name.size() > COFF::NameSize) 890 Strings.add(S->Name); 891 for (const auto &S : Symbols) 892 if (S->should_keep() && S->Name.size() > COFF::NameSize) 893 Strings.add(S->Name); 894 Strings.finalize(StringTableBuilder::WinCOFF); 895 896 // Set names. 897 for (const auto &S : Sections) 898 SetSectionName(*S); 899 for (auto &S : Symbols) 900 if (S->should_keep()) 901 SetSymbolName(*S); 902 903 // Fixup weak external references. 904 for (auto &Symbol : Symbols) { 905 if (Symbol->Other) { 906 assert(Symbol->Index != -1); 907 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 908 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 909 "Symbol's aux symbol must be a Weak External!"); 910 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index; 911 } 912 } 913 914 // Fixup associative COMDAT sections. 915 for (auto &Section : Sections) { 916 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 917 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 918 continue; 919 920 const MCSectionCOFF &MCSec = 921 static_cast<const MCSectionCOFF &>(Section->MCData->getSection()); 922 923 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 924 assert(COMDAT); 925 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 926 assert(COMDATSymbol); 927 COFFSection *Assoc = COMDATSymbol->Section; 928 if (!Assoc) 929 report_fatal_error( 930 Twine("Missing associated COMDAT section for section ") + 931 MCSec.getSectionName()); 932 933 // Skip this section if the associated section is unused. 934 if (Assoc->Number == -1) 935 continue; 936 937 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc]; 938 } 939 940 941 // Assign file offsets to COFF object file structures. 942 943 unsigned offset = 0; 944 945 if (UseBigObj) 946 offset += COFF::Header32Size; 947 else 948 offset += COFF::Header16Size; 949 offset += COFF::SectionSize * Header.NumberOfSections; 950 951 for (const auto &Section : Asm) { 952 COFFSection *Sec = SectionMap[&Section.getSection()]; 953 954 if (Sec->Number == -1) 955 continue; 956 957 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 958 959 if (IsPhysicalSection(Sec)) { 960 // Align the section data to a four byte boundary. 961 offset = RoundUpToAlignment(offset, 4); 962 Sec->Header.PointerToRawData = offset; 963 964 offset += Sec->Header.SizeOfRawData; 965 } 966 967 if (Sec->Relocations.size() > 0) { 968 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 969 970 if (RelocationsOverflow) { 971 // Signal overflow by setting NumberOfRelocations to max value. Actual 972 // size is found in reloc #0. Microsoft tools understand this. 973 Sec->Header.NumberOfRelocations = 0xffff; 974 } else { 975 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 976 } 977 Sec->Header.PointerToRelocations = offset; 978 979 if (RelocationsOverflow) { 980 // Reloc #0 will contain actual count, so make room for it. 981 offset += COFF::RelocationSize; 982 } 983 984 offset += COFF::RelocationSize * Sec->Relocations.size(); 985 986 for (auto &Relocation : Sec->Relocations) { 987 assert(Relocation.Symb->Index != -1); 988 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index; 989 } 990 } 991 992 assert(Sec->Symbol->Aux.size() == 1 && 993 "Section's symbol must have one aux!"); 994 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 995 assert(Aux.AuxType == ATSectionDefinition && 996 "Section's symbol's aux symbol must be a Section Definition!"); 997 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 998 Aux.Aux.SectionDefinition.NumberOfRelocations = 999 Sec->Header.NumberOfRelocations; 1000 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 1001 Sec->Header.NumberOfLineNumbers; 1002 } 1003 1004 Header.PointerToSymbolTable = offset; 1005 1006 // We want a deterministic output. It looks like GNU as also writes 0 in here. 1007 Header.TimeDateStamp = 0; 1008 1009 // Write it all to disk... 1010 WriteFileHeader(Header); 1011 1012 { 1013 sections::iterator i, ie; 1014 MCAssembler::const_iterator j, je; 1015 1016 for (auto &Section : Sections) { 1017 if (Section->Number != -1) { 1018 if (Section->Relocations.size() >= 0xffff) 1019 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 1020 WriteSectionHeader(Section->Header); 1021 } 1022 } 1023 1024 for (i = Sections.begin(), ie = Sections.end(), 1025 j = Asm.begin(), je = Asm.end(); 1026 (i != ie) && (j != je); ++i, ++j) { 1027 1028 if ((*i)->Number == -1) 1029 continue; 1030 1031 if ((*i)->Header.PointerToRawData != 0) { 1032 assert(OS.tell() <= (*i)->Header.PointerToRawData && 1033 "Section::PointerToRawData is insane!"); 1034 1035 unsigned SectionDataPadding = (*i)->Header.PointerToRawData - OS.tell(); 1036 assert(SectionDataPadding < 4 && 1037 "Should only need at most three bytes of padding!"); 1038 1039 WriteZeros(SectionDataPadding); 1040 1041 Asm.writeSectionData(j, Layout); 1042 } 1043 1044 if ((*i)->Relocations.size() > 0) { 1045 assert(OS.tell() == (*i)->Header.PointerToRelocations && 1046 "Section::PointerToRelocations is insane!"); 1047 1048 if ((*i)->Relocations.size() >= 0xffff) { 1049 // In case of overflow, write actual relocation count as first 1050 // relocation. Including the synthetic reloc itself (+ 1). 1051 COFF::relocation r; 1052 r.VirtualAddress = (*i)->Relocations.size() + 1; 1053 r.SymbolTableIndex = 0; 1054 r.Type = 0; 1055 WriteRelocation(r); 1056 } 1057 1058 for (const auto &Relocation : (*i)->Relocations) 1059 WriteRelocation(Relocation.Data); 1060 } else 1061 assert((*i)->Header.PointerToRelocations == 0 && 1062 "Section::PointerToRelocations is insane!"); 1063 } 1064 } 1065 1066 assert(OS.tell() == Header.PointerToSymbolTable && 1067 "Header::PointerToSymbolTable is insane!"); 1068 1069 for (auto &Symbol : Symbols) 1070 if (Symbol->Index != -1) 1071 WriteSymbol(*Symbol); 1072 1073 OS.write(Strings.data().data(), Strings.data().size()); 1074 } 1075 1076 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) : 1077 Machine(Machine_) { 1078 } 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