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 MCSymbolData &DataA, 175 const MCSymbolData *DataB, 176 const MCFragment &FB, bool InSet, 177 bool IsPCRel) const override; 178 179 bool isWeak(const MCSymbolData &SD) const override; 180 181 void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 182 const MCFragment *Fragment, const MCFixup &Fixup, 183 MCValue Target, bool &IsPCRel, 184 uint64_t &FixedValue) override; 185 186 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 187 }; 188 } 189 190 static inline void write_uint32_le(void *Data, uint32_t Value) { 191 support::endian::write<uint32_t, support::little, support::unaligned>(Data, 192 Value); 193 } 194 195 //------------------------------------------------------------------------------ 196 // Symbol class implementation 197 198 COFFSymbol::COFFSymbol(StringRef name) 199 : Name(name.begin(), name.end()) 200 , Other(nullptr) 201 , Section(nullptr) 202 , Relocations(0) 203 , MCData(nullptr) { 204 memset(&Data, 0, sizeof(Data)); 205 } 206 207 // In the case that the name does not fit within 8 bytes, the offset 208 // into the string table is stored in the last 4 bytes instead, leaving 209 // the first 4 bytes as 0. 210 void COFFSymbol::set_name_offset(uint32_t Offset) { 211 write_uint32_le(Data.Name + 0, 0); 212 write_uint32_le(Data.Name + 4, Offset); 213 } 214 215 /// logic to decide if the symbol should be reported in the symbol table 216 bool COFFSymbol::should_keep() const { 217 // no section means its external, keep it 218 if (!Section) 219 return true; 220 221 // if it has relocations pointing at it, keep it 222 if (Relocations > 0) { 223 assert(Section->Number != -1 && "Sections with relocations must be real!"); 224 return true; 225 } 226 227 // if the section its in is being droped, drop it 228 if (Section->Number == -1) 229 return false; 230 231 // if it is the section symbol, keep it 232 if (Section->Symbol == this) 233 return true; 234 235 // if its temporary, drop it 236 if (MCData && MCData->getSymbol().isTemporary()) 237 return false; 238 239 // otherwise, keep it 240 return true; 241 } 242 243 //------------------------------------------------------------------------------ 244 // Section class implementation 245 246 COFFSection::COFFSection(StringRef name) 247 : Name(name) 248 , MCData(nullptr) 249 , Symbol(nullptr) { 250 memset(&Header, 0, sizeof(Header)); 251 } 252 253 size_t COFFSection::size() { 254 return COFF::SectionSize; 255 } 256 257 //------------------------------------------------------------------------------ 258 // WinCOFFObjectWriter class implementation 259 260 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 261 raw_pwrite_stream &OS) 262 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { 263 memset(&Header, 0, sizeof(Header)); 264 265 Header.Machine = TargetObjectWriter->getMachine(); 266 } 267 268 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 269 return createCOFFEntity<COFFSymbol>(Name, Symbols); 270 } 271 272 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) { 273 symbol_map::iterator i = SymbolMap.find(Symbol); 274 if (i != SymbolMap.end()) 275 return i->second; 276 COFFSymbol *RetSymbol = 277 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 278 SymbolMap[Symbol] = RetSymbol; 279 return RetSymbol; 280 } 281 282 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 283 return createCOFFEntity<COFFSection>(Name, Sections); 284 } 285 286 /// A template used to lookup or create a symbol/section, and initialize it if 287 /// needed. 288 template <typename object_t, typename list_t> 289 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, 290 list_t &List) { 291 List.push_back(make_unique<object_t>(Name)); 292 293 return List.back().get(); 294 } 295 296 /// This function takes a section data object from the assembler 297 /// and creates the associated COFF section staging object. 298 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) { 299 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF 300 && "Got non-COFF section in the COFF backend!"); 301 // FIXME: Not sure how to verify this (at least in a debug build). 302 MCSectionCOFF const &Sec = 303 static_cast<MCSectionCOFF const &>(SectionData.getSection()); 304 305 COFFSection *coff_section = createSection(Sec.getSectionName()); 306 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 307 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 308 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 309 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 310 if (COMDATSymbol->Section) 311 report_fatal_error("two sections have the same comdat"); 312 COMDATSymbol->Section = coff_section; 313 } 314 } 315 316 coff_section->Symbol = coff_symbol; 317 coff_symbol->Section = coff_section; 318 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 319 320 // In this case the auxiliary symbol is a Section Definition. 321 coff_symbol->Aux.resize(1); 322 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 323 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 324 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 325 326 coff_section->Header.Characteristics = Sec.getCharacteristics(); 327 328 uint32_t &Characteristics = coff_section->Header.Characteristics; 329 switch (SectionData.getAlignment()) { 330 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break; 331 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break; 332 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break; 333 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break; 334 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break; 335 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break; 336 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break; 337 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break; 338 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break; 339 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break; 340 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break; 341 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break; 342 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break; 343 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break; 344 default: 345 llvm_unreachable("unsupported section alignment"); 346 } 347 348 // Bind internal COFF section to MC section. 349 coff_section->MCData = &SectionData; 350 SectionMap[&SectionData.getSection()] = coff_section; 351 } 352 353 static uint64_t getSymbolValue(const MCSymbolData &Data, 354 const MCAsmLayout &Layout) { 355 if (Data.isCommon() && Data.isExternal()) 356 return Data.getCommonSize(); 357 358 uint64_t Res; 359 if (!Layout.getSymbolOffset(&Data, Res)) 360 return 0; 361 362 return Res; 363 } 364 365 /// This function takes a symbol data object from the assembler 366 /// and creates the associated COFF symbol staging object. 367 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData, 368 MCAssembler &Assembler, 369 const MCAsmLayout &Layout) { 370 MCSymbol const &Symbol = SymbolData.getSymbol(); 371 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 372 SymbolMap[&Symbol] = coff_symbol; 373 374 if (SymbolData.getFlags() & COFF::SF_WeakExternal) { 375 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 376 377 if (Symbol.isVariable()) { 378 const MCSymbolRefExpr *SymRef = 379 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 380 381 if (!SymRef) 382 report_fatal_error("Weak externals may only alias symbols"); 383 384 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 385 } else { 386 std::string WeakName = (".weak." + Symbol.getName() + ".default").str(); 387 COFFSymbol *WeakDefault = createSymbol(WeakName); 388 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 389 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 390 WeakDefault->Data.Type = 0; 391 WeakDefault->Data.Value = 0; 392 coff_symbol->Other = WeakDefault; 393 } 394 395 // Setup the Weak External auxiliary symbol. 396 coff_symbol->Aux.resize(1); 397 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 398 coff_symbol->Aux[0].AuxType = ATWeakExternal; 399 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 400 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 401 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 402 403 coff_symbol->MCData = &SymbolData; 404 } else { 405 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol); 406 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 407 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout); 408 409 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0; 410 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16; 411 412 // If no storage class was specified in the streamer, define it here. 413 if (coff_symbol->Data.StorageClass == 0) { 414 bool IsExternal = 415 ResSymData.isExternal() || 416 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable()); 417 418 coff_symbol->Data.StorageClass = IsExternal 419 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 420 : COFF::IMAGE_SYM_CLASS_STATIC; 421 } 422 423 if (!Base) { 424 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 425 } else { 426 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base); 427 if (BaseData.getFragment()) { 428 COFFSection *Sec = 429 SectionMap[&BaseData.getFragment()->getParent()->getSection()]; 430 431 if (coff_symbol->Section && coff_symbol->Section != Sec) 432 report_fatal_error("conflicting sections for symbol"); 433 434 coff_symbol->Section = Sec; 435 } 436 } 437 438 coff_symbol->MCData = &ResSymData; 439 } 440 } 441 442 // Maximum offsets for different string table entry encodings. 443 static const unsigned Max6DecimalOffset = 999999; 444 static const unsigned Max7DecimalOffset = 9999999; 445 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 446 447 // Encode a string table entry offset in base 64, padded to 6 chars, and 448 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 449 // Buffer must be at least 8 bytes large. No terminating null appended. 450 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) { 451 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 452 "Illegal section name encoding for value"); 453 454 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 455 "abcdefghijklmnopqrstuvwxyz" 456 "0123456789+/"; 457 458 Buffer[0] = '/'; 459 Buffer[1] = '/'; 460 461 char* Ptr = Buffer + 7; 462 for (unsigned i = 0; i < 6; ++i) { 463 unsigned Rem = Value % 64; 464 Value /= 64; 465 *(Ptr--) = Alphabet[Rem]; 466 } 467 } 468 469 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { 470 if (S.Name.size() > COFF::NameSize) { 471 uint64_t StringTableEntry = Strings.getOffset(S.Name); 472 473 if (StringTableEntry <= Max6DecimalOffset) { 474 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 475 } else if (StringTableEntry <= Max7DecimalOffset) { 476 // With seven digits, we have to skip the terminating null. Because 477 // sprintf always appends it, we use a larger temporary buffer. 478 char buffer[9] = { }; 479 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 480 std::memcpy(S.Header.Name, buffer, 8); 481 } else if (StringTableEntry <= MaxBase64Offset) { 482 // Starting with 10,000,000, offsets are encoded as base64. 483 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 484 } else { 485 report_fatal_error("COFF string table is greater than 64 GB."); 486 } 487 } else 488 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 489 } 490 491 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { 492 if (S.Name.size() > COFF::NameSize) 493 S.set_name_offset(Strings.getOffset(S.Name)); 494 else 495 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 496 } 497 498 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol, 499 MCAssembler &Asm) { 500 // This doesn't seem to be right. Strings referred to from the .data section 501 // need symbols so they can be linked to code in the .text section right? 502 503 // return Asm.isSymbolLinkerVisible(Symbol); 504 505 // Non-temporary labels should always be visible to the linker. 506 if (!Symbol.isTemporary()) 507 return true; 508 509 // Absolute temporary labels are never visible. 510 if (!Symbol.isInSection()) 511 return false; 512 513 // For now, all non-variable symbols are exported, 514 // the linker will sort the rest out for us. 515 return !Symbol.isVariable(); 516 } 517 518 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 519 return (S->Header.Characteristics 520 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0; 521 } 522 523 //------------------------------------------------------------------------------ 524 // entity writing methods 525 526 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 527 if (UseBigObj) { 528 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); 529 WriteLE16(0xFFFF); 530 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion); 531 WriteLE16(Header.Machine); 532 WriteLE32(Header.TimeDateStamp); 533 for (uint8_t MagicChar : COFF::BigObjMagic) 534 Write8(MagicChar); 535 WriteLE32(0); 536 WriteLE32(0); 537 WriteLE32(0); 538 WriteLE32(0); 539 WriteLE32(Header.NumberOfSections); 540 WriteLE32(Header.PointerToSymbolTable); 541 WriteLE32(Header.NumberOfSymbols); 542 } else { 543 WriteLE16(Header.Machine); 544 WriteLE16(static_cast<int16_t>(Header.NumberOfSections)); 545 WriteLE32(Header.TimeDateStamp); 546 WriteLE32(Header.PointerToSymbolTable); 547 WriteLE32(Header.NumberOfSymbols); 548 WriteLE16(Header.SizeOfOptionalHeader); 549 WriteLE16(Header.Characteristics); 550 } 551 } 552 553 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 554 WriteBytes(StringRef(S.Data.Name, COFF::NameSize)); 555 WriteLE32(S.Data.Value); 556 if (UseBigObj) 557 WriteLE32(S.Data.SectionNumber); 558 else 559 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber)); 560 WriteLE16(S.Data.Type); 561 Write8(S.Data.StorageClass); 562 Write8(S.Data.NumberOfAuxSymbols); 563 WriteAuxiliarySymbols(S.Aux); 564 } 565 566 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 567 const COFFSymbol::AuxiliarySymbols &S) { 568 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 569 i != e; ++i) { 570 switch(i->AuxType) { 571 case ATFunctionDefinition: 572 WriteLE32(i->Aux.FunctionDefinition.TagIndex); 573 WriteLE32(i->Aux.FunctionDefinition.TotalSize); 574 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 575 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 576 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 577 if (UseBigObj) 578 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 579 break; 580 case ATbfAndefSymbol: 581 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 582 WriteLE16(i->Aux.bfAndefSymbol.Linenumber); 583 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 584 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 585 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 586 if (UseBigObj) 587 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 588 break; 589 case ATWeakExternal: 590 WriteLE32(i->Aux.WeakExternal.TagIndex); 591 WriteLE32(i->Aux.WeakExternal.Characteristics); 592 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 593 if (UseBigObj) 594 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 595 break; 596 case ATFile: 597 WriteBytes( 598 StringRef(reinterpret_cast<const char *>(&i->Aux), 599 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); 600 break; 601 case ATSectionDefinition: 602 WriteLE32(i->Aux.SectionDefinition.Length); 603 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations); 604 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 605 WriteLE32(i->Aux.SectionDefinition.CheckSum); 606 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number)); 607 Write8(i->Aux.SectionDefinition.Selection); 608 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 609 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16)); 610 if (UseBigObj) 611 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 612 break; 613 } 614 } 615 } 616 617 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) { 618 WriteBytes(StringRef(S.Name, COFF::NameSize)); 619 620 WriteLE32(S.VirtualSize); 621 WriteLE32(S.VirtualAddress); 622 WriteLE32(S.SizeOfRawData); 623 WriteLE32(S.PointerToRawData); 624 WriteLE32(S.PointerToRelocations); 625 WriteLE32(S.PointerToLineNumbers); 626 WriteLE16(S.NumberOfRelocations); 627 WriteLE16(S.NumberOfLineNumbers); 628 WriteLE32(S.Characteristics); 629 } 630 631 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 632 WriteLE32(R.VirtualAddress); 633 WriteLE32(R.SymbolTableIndex); 634 WriteLE16(R.Type); 635 } 636 637 //////////////////////////////////////////////////////////////////////////////// 638 // MCObjectWriter interface implementations 639 640 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 641 const MCAsmLayout &Layout) { 642 // "Define" each section & symbol. This creates section & symbol 643 // entries in the staging area. 644 for (const auto &Section : Asm) 645 DefineSection(Section); 646 647 for (MCSymbolData &SD : Asm.symbols()) 648 if (ExportSymbol(SD.getSymbol(), Asm)) 649 DefineSymbol(SD, Asm, Layout); 650 } 651 652 bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 653 const MCAssembler &Asm, const MCSymbolData &DataA, 654 const MCSymbolData *DataB, const MCFragment &FB, bool InSet, 655 bool IsPCRel) const { 656 // MS LINK expects to be able to replace all references to a function with a 657 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize 658 // away any relocations to functions. 659 if ((((DataA.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift) >> 660 COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION) 661 return false; 662 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( 663 Asm, DataA, DataB, FB, InSet, IsPCRel); 664 } 665 666 bool WinCOFFObjectWriter::isWeak(const MCSymbolData &SD) const { 667 // FIXME: this is for PR23025. Write a good description on 668 // why this is needed. 669 return SD.isExternal(); 670 } 671 672 void WinCOFFObjectWriter::RecordRelocation( 673 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, 674 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { 675 assert(Target.getSymA() && "Relocation must reference a symbol!"); 676 677 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 678 const MCSymbol &A = Symbol.AliasedSymbol(); 679 if (!Asm.hasSymbolData(A)) 680 Asm.getContext().FatalError( 681 Fixup.getLoc(), 682 Twine("symbol '") + A.getName() + "' can not be undefined"); 683 684 const MCSymbolData &A_SD = Asm.getSymbolData(A); 685 686 MCSectionData const *SectionData = Fragment->getParent(); 687 688 // Mark this symbol as requiring an entry in the symbol table. 689 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && 690 "Section must already have been defined in ExecutePostLayoutBinding!"); 691 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && 692 "Symbol must already have been defined in ExecutePostLayoutBinding!"); 693 694 COFFSection *coff_section = SectionMap[&SectionData->getSection()]; 695 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; 696 const MCSymbolRefExpr *SymB = Target.getSymB(); 697 bool CrossSection = false; 698 699 if (SymB) { 700 const MCSymbol *B = &SymB->getSymbol(); 701 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 702 if (!B_SD.getFragment()) 703 Asm.getContext().FatalError( 704 Fixup.getLoc(), 705 Twine("symbol '") + B->getName() + 706 "' can not be undefined in a subtraction expression"); 707 708 if (!A_SD.getFragment()) 709 Asm.getContext().FatalError( 710 Fixup.getLoc(), 711 Twine("symbol '") + Symbol.getName() + 712 "' can not be undefined in a subtraction expression"); 713 714 CrossSection = &Symbol.getSection() != &B->getSection(); 715 716 // Offset of the symbol in the section 717 int64_t OffsetOfB = Layout.getSymbolOffset(&B_SD); 718 719 // In the case where we have SymbA and SymB, we just need to store the delta 720 // between the two symbols. Update FixedValue to account for the delta, and 721 // skip recording the relocation. 722 if (!CrossSection) { 723 int64_t OffsetOfA = Layout.getSymbolOffset(&A_SD); 724 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant(); 725 return; 726 } 727 728 // Offset of the relocation in the section 729 int64_t OffsetOfRelocation = 730 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 731 732 FixedValue = OffsetOfRelocation - OffsetOfB; 733 } else { 734 FixedValue = Target.getConstant(); 735 } 736 737 COFFRelocation Reloc; 738 739 Reloc.Data.SymbolTableIndex = 0; 740 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 741 742 // Turn relocations for temporary symbols into section relocations. 743 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { 744 Reloc.Symb = coff_symbol->Section->Symbol; 745 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->getFragment()) + 746 coff_symbol->MCData->getOffset(); 747 } else 748 Reloc.Symb = coff_symbol; 749 750 ++Reloc.Symb->Relocations; 751 752 Reloc.Data.VirtualAddress += Fixup.getOffset(); 753 Reloc.Data.Type = 754 TargetObjectWriter->getRelocType(Target, Fixup, CrossSection, 755 Asm.getBackend()); 756 757 // FIXME: Can anyone explain what this does other than adjust for the size 758 // of the offset? 759 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 760 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 761 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 762 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 763 FixedValue += 4; 764 765 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 766 switch (Reloc.Data.Type) { 767 case COFF::IMAGE_REL_ARM_ABSOLUTE: 768 case COFF::IMAGE_REL_ARM_ADDR32: 769 case COFF::IMAGE_REL_ARM_ADDR32NB: 770 case COFF::IMAGE_REL_ARM_TOKEN: 771 case COFF::IMAGE_REL_ARM_SECTION: 772 case COFF::IMAGE_REL_ARM_SECREL: 773 break; 774 case COFF::IMAGE_REL_ARM_BRANCH11: 775 case COFF::IMAGE_REL_ARM_BLX11: 776 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 777 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 778 // for Windows CE). 779 case COFF::IMAGE_REL_ARM_BRANCH24: 780 case COFF::IMAGE_REL_ARM_BLX24: 781 case COFF::IMAGE_REL_ARM_MOV32A: 782 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 783 // only used for ARM mode code, which is documented as being unsupported 784 // by Windows on ARM. Empirical proof indicates that masm is able to 785 // generate the relocations however the rest of the MSVC toolchain is 786 // unable to handle it. 787 llvm_unreachable("unsupported relocation"); 788 break; 789 case COFF::IMAGE_REL_ARM_MOV32T: 790 break; 791 case COFF::IMAGE_REL_ARM_BRANCH20T: 792 case COFF::IMAGE_REL_ARM_BRANCH24T: 793 case COFF::IMAGE_REL_ARM_BLX23T: 794 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 795 // perform a 4 byte adjustment to the relocation. Relative branches are 796 // offset by 4 on ARM, however, because there is no RELA relocations, all 797 // branches are offset by 4. 798 FixedValue = FixedValue + 4; 799 break; 800 } 801 } 802 803 if (TargetObjectWriter->recordRelocation(Fixup)) 804 coff_section->Relocations.push_back(Reloc); 805 } 806 807 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm, 808 const MCAsmLayout &Layout) { 809 size_t SectionsSize = Sections.size(); 810 if (SectionsSize > static_cast<size_t>(INT32_MAX)) 811 report_fatal_error( 812 "PE COFF object files can't have more than 2147483647 sections"); 813 814 // Assign symbol and section indexes and offsets. 815 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize); 816 817 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16; 818 819 DenseMap<COFFSection *, int32_t> SectionIndices( 820 NextPowerOf2(NumberOfSections)); 821 822 // Assign section numbers. 823 size_t Number = 1; 824 for (const auto &Section : Sections) { 825 SectionIndices[Section.get()] = Number; 826 Section->Number = Number; 827 Section->Symbol->Data.SectionNumber = Number; 828 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number; 829 ++Number; 830 } 831 832 Header.NumberOfSections = NumberOfSections; 833 Header.NumberOfSymbols = 0; 834 835 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end(); 836 FI != FE; ++FI) { 837 // round up to calculate the number of auxiliary symbols required 838 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; 839 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize; 840 841 COFFSymbol *file = createSymbol(".file"); 842 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 843 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 844 file->Aux.resize(Count); 845 846 unsigned Offset = 0; 847 unsigned Length = FI->size(); 848 for (auto &Aux : file->Aux) { 849 Aux.AuxType = ATFile; 850 851 if (Length > SymbolSize) { 852 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize); 853 Length = Length - SymbolSize; 854 } else { 855 memcpy(&Aux.Aux, FI->c_str() + Offset, Length); 856 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); 857 break; 858 } 859 860 Offset += SymbolSize; 861 } 862 } 863 864 for (auto &Symbol : Symbols) { 865 // Update section number & offset for symbols that have them. 866 if (Symbol->Section) 867 Symbol->Data.SectionNumber = Symbol->Section->Number; 868 if (Symbol->should_keep()) { 869 Symbol->Index = Header.NumberOfSymbols++; 870 // Update auxiliary symbol info. 871 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 872 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 873 } else 874 Symbol->Index = -1; 875 } 876 877 // Build string table. 878 for (const auto &S : Sections) 879 if (S->Name.size() > COFF::NameSize) 880 Strings.add(S->Name); 881 for (const auto &S : Symbols) 882 if (S->should_keep() && S->Name.size() > COFF::NameSize) 883 Strings.add(S->Name); 884 Strings.finalize(StringTableBuilder::WinCOFF); 885 886 // Set names. 887 for (const auto &S : Sections) 888 SetSectionName(*S); 889 for (auto &S : Symbols) 890 if (S->should_keep()) 891 SetSymbolName(*S); 892 893 // Fixup weak external references. 894 for (auto &Symbol : Symbols) { 895 if (Symbol->Other) { 896 assert(Symbol->Index != -1); 897 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 898 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 899 "Symbol's aux symbol must be a Weak External!"); 900 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index; 901 } 902 } 903 904 // Fixup associative COMDAT sections. 905 for (auto &Section : Sections) { 906 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 907 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 908 continue; 909 910 const MCSectionCOFF &MCSec = 911 static_cast<const MCSectionCOFF &>(Section->MCData->getSection()); 912 913 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 914 assert(COMDAT); 915 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 916 assert(COMDATSymbol); 917 COFFSection *Assoc = COMDATSymbol->Section; 918 if (!Assoc) 919 report_fatal_error( 920 Twine("Missing associated COMDAT section for section ") + 921 MCSec.getSectionName()); 922 923 // Skip this section if the associated section is unused. 924 if (Assoc->Number == -1) 925 continue; 926 927 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc]; 928 } 929 930 931 // Assign file offsets to COFF object file structures. 932 933 unsigned offset = 0; 934 935 if (UseBigObj) 936 offset += COFF::Header32Size; 937 else 938 offset += COFF::Header16Size; 939 offset += COFF::SectionSize * Header.NumberOfSections; 940 941 for (const auto &Section : Asm) { 942 COFFSection *Sec = SectionMap[&Section.getSection()]; 943 944 if (Sec->Number == -1) 945 continue; 946 947 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 948 949 if (IsPhysicalSection(Sec)) { 950 // Align the section data to a four byte boundary. 951 offset = RoundUpToAlignment(offset, 4); 952 Sec->Header.PointerToRawData = offset; 953 954 offset += Sec->Header.SizeOfRawData; 955 } 956 957 if (Sec->Relocations.size() > 0) { 958 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 959 960 if (RelocationsOverflow) { 961 // Signal overflow by setting NumberOfRelocations to max value. Actual 962 // size is found in reloc #0. Microsoft tools understand this. 963 Sec->Header.NumberOfRelocations = 0xffff; 964 } else { 965 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 966 } 967 Sec->Header.PointerToRelocations = offset; 968 969 if (RelocationsOverflow) { 970 // Reloc #0 will contain actual count, so make room for it. 971 offset += COFF::RelocationSize; 972 } 973 974 offset += COFF::RelocationSize * Sec->Relocations.size(); 975 976 for (auto &Relocation : Sec->Relocations) { 977 assert(Relocation.Symb->Index != -1); 978 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index; 979 } 980 } 981 982 assert(Sec->Symbol->Aux.size() == 1 && 983 "Section's symbol must have one aux!"); 984 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 985 assert(Aux.AuxType == ATSectionDefinition && 986 "Section's symbol's aux symbol must be a Section Definition!"); 987 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 988 Aux.Aux.SectionDefinition.NumberOfRelocations = 989 Sec->Header.NumberOfRelocations; 990 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 991 Sec->Header.NumberOfLineNumbers; 992 } 993 994 Header.PointerToSymbolTable = offset; 995 996 // We want a deterministic output. It looks like GNU as also writes 0 in here. 997 Header.TimeDateStamp = 0; 998 999 // Write it all to disk... 1000 WriteFileHeader(Header); 1001 1002 { 1003 sections::iterator i, ie; 1004 MCAssembler::const_iterator j, je; 1005 1006 for (auto &Section : Sections) { 1007 if (Section->Number != -1) { 1008 if (Section->Relocations.size() >= 0xffff) 1009 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 1010 WriteSectionHeader(Section->Header); 1011 } 1012 } 1013 1014 for (i = Sections.begin(), ie = Sections.end(), 1015 j = Asm.begin(), je = Asm.end(); 1016 (i != ie) && (j != je); ++i, ++j) { 1017 1018 if ((*i)->Number == -1) 1019 continue; 1020 1021 if ((*i)->Header.PointerToRawData != 0) { 1022 assert(OS.tell() <= (*i)->Header.PointerToRawData && 1023 "Section::PointerToRawData is insane!"); 1024 1025 unsigned SectionDataPadding = (*i)->Header.PointerToRawData - OS.tell(); 1026 assert(SectionDataPadding < 4 && 1027 "Should only need at most three bytes of padding!"); 1028 1029 WriteZeros(SectionDataPadding); 1030 1031 Asm.writeSectionData(j, Layout); 1032 } 1033 1034 if ((*i)->Relocations.size() > 0) { 1035 assert(OS.tell() == (*i)->Header.PointerToRelocations && 1036 "Section::PointerToRelocations is insane!"); 1037 1038 if ((*i)->Relocations.size() >= 0xffff) { 1039 // In case of overflow, write actual relocation count as first 1040 // relocation. Including the synthetic reloc itself (+ 1). 1041 COFF::relocation r; 1042 r.VirtualAddress = (*i)->Relocations.size() + 1; 1043 r.SymbolTableIndex = 0; 1044 r.Type = 0; 1045 WriteRelocation(r); 1046 } 1047 1048 for (const auto &Relocation : (*i)->Relocations) 1049 WriteRelocation(Relocation.Data); 1050 } else 1051 assert((*i)->Header.PointerToRelocations == 0 && 1052 "Section::PointerToRelocations is insane!"); 1053 } 1054 } 1055 1056 assert(OS.tell() == Header.PointerToSymbolTable && 1057 "Header::PointerToSymbolTable is insane!"); 1058 1059 for (auto &Symbol : Symbols) 1060 if (Symbol->Index != -1) 1061 WriteSymbol(*Symbol); 1062 1063 OS.write(Strings.data().data(), Strings.data().size()); 1064 } 1065 1066 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) : 1067 Machine(Machine_) { 1068 } 1069 1070 // Pin the vtable to this file. 1071 void MCWinCOFFObjectTargetWriter::anchor() {} 1072 1073 //------------------------------------------------------------------------------ 1074 // WinCOFFObjectWriter factory function 1075 1076 MCObjectWriter * 1077 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1078 raw_pwrite_stream &OS) { 1079 return new WinCOFFObjectWriter(MOTW, OS); 1080 } 1081
