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/StringMap.h" 17 #include "llvm/ADT/StringRef.h" 18 #include "llvm/ADT/STLExtras.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_ostream &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 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 174 const MCFragment *Fragment, const MCFixup &Fixup, 175 MCValue Target, bool &IsPCRel, 176 uint64_t &FixedValue) override; 177 178 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 179 }; 180 } 181 182 static inline void write_uint32_le(void *Data, uint32_t Value) { 183 support::endian::write<uint32_t, support::little, support::unaligned>(Data, 184 Value); 185 } 186 187 //------------------------------------------------------------------------------ 188 // Symbol class implementation 189 190 COFFSymbol::COFFSymbol(StringRef name) 191 : Name(name.begin(), name.end()) 192 , Other(nullptr) 193 , Section(nullptr) 194 , Relocations(0) 195 , MCData(nullptr) { 196 memset(&Data, 0, sizeof(Data)); 197 } 198 199 // In the case that the name does not fit within 8 bytes, the offset 200 // into the string table is stored in the last 4 bytes instead, leaving 201 // the first 4 bytes as 0. 202 void COFFSymbol::set_name_offset(uint32_t Offset) { 203 write_uint32_le(Data.Name + 0, 0); 204 write_uint32_le(Data.Name + 4, Offset); 205 } 206 207 /// logic to decide if the symbol should be reported in the symbol table 208 bool COFFSymbol::should_keep() const { 209 // no section means its external, keep it 210 if (!Section) 211 return true; 212 213 // if it has relocations pointing at it, keep it 214 if (Relocations > 0) { 215 assert(Section->Number != -1 && "Sections with relocations must be real!"); 216 return true; 217 } 218 219 // if the section its in is being droped, drop it 220 if (Section->Number == -1) 221 return false; 222 223 // if it is the section symbol, keep it 224 if (Section->Symbol == this) 225 return true; 226 227 // if its temporary, drop it 228 if (MCData && MCData->getSymbol().isTemporary()) 229 return false; 230 231 // otherwise, keep it 232 return true; 233 } 234 235 //------------------------------------------------------------------------------ 236 // Section class implementation 237 238 COFFSection::COFFSection(StringRef name) 239 : Name(name) 240 , MCData(nullptr) 241 , Symbol(nullptr) { 242 memset(&Header, 0, sizeof(Header)); 243 } 244 245 size_t COFFSection::size() { 246 return COFF::SectionSize; 247 } 248 249 //------------------------------------------------------------------------------ 250 // WinCOFFObjectWriter class implementation 251 252 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 253 raw_ostream &OS) 254 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { 255 memset(&Header, 0, sizeof(Header)); 256 257 Header.Machine = TargetObjectWriter->getMachine(); 258 } 259 260 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 261 return createCOFFEntity<COFFSymbol>(Name, Symbols); 262 } 263 264 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){ 265 symbol_map::iterator i = SymbolMap.find(Symbol); 266 if (i != SymbolMap.end()) 267 return i->second; 268 COFFSymbol *RetSymbol 269 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 270 SymbolMap[Symbol] = RetSymbol; 271 return RetSymbol; 272 } 273 274 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 275 return createCOFFEntity<COFFSection>(Name, Sections); 276 } 277 278 /// A template used to lookup or create a symbol/section, and initialize it if 279 /// needed. 280 template <typename object_t, typename list_t> 281 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, 282 list_t &List) { 283 List.push_back(make_unique<object_t>(Name)); 284 285 return List.back().get(); 286 } 287 288 /// This function takes a section data object from the assembler 289 /// and creates the associated COFF section staging object. 290 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) { 291 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF 292 && "Got non-COFF section in the COFF backend!"); 293 // FIXME: Not sure how to verify this (at least in a debug build). 294 MCSectionCOFF const &Sec = 295 static_cast<MCSectionCOFF const &>(SectionData.getSection()); 296 297 COFFSection *coff_section = createSection(Sec.getSectionName()); 298 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 299 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 300 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 301 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 302 if (COMDATSymbol->Section) 303 report_fatal_error("two sections have the same comdat"); 304 COMDATSymbol->Section = coff_section; 305 } 306 } 307 308 coff_section->Symbol = coff_symbol; 309 coff_symbol->Section = coff_section; 310 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 311 312 // In this case the auxiliary symbol is a Section Definition. 313 coff_symbol->Aux.resize(1); 314 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 315 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 316 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 317 318 coff_section->Header.Characteristics = Sec.getCharacteristics(); 319 320 uint32_t &Characteristics = coff_section->Header.Characteristics; 321 switch (SectionData.getAlignment()) { 322 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break; 323 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break; 324 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break; 325 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break; 326 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break; 327 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break; 328 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break; 329 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break; 330 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break; 331 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break; 332 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break; 333 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break; 334 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break; 335 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break; 336 default: 337 llvm_unreachable("unsupported section alignment"); 338 } 339 340 // Bind internal COFF section to MC section. 341 coff_section->MCData = &SectionData; 342 SectionMap[&SectionData.getSection()] = coff_section; 343 } 344 345 static uint64_t getSymbolValue(const MCSymbolData &Data, 346 const MCAsmLayout &Layout) { 347 if (Data.isCommon() && Data.isExternal()) 348 return Data.getCommonSize(); 349 350 uint64_t Res; 351 if (!Layout.getSymbolOffset(&Data, Res)) 352 return 0; 353 354 return Res; 355 } 356 357 /// This function takes a symbol data object from the assembler 358 /// and creates the associated COFF symbol staging object. 359 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData, 360 MCAssembler &Assembler, 361 const MCAsmLayout &Layout) { 362 MCSymbol const &Symbol = SymbolData.getSymbol(); 363 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 364 SymbolMap[&Symbol] = coff_symbol; 365 366 if (SymbolData.getFlags() & COFF::SF_WeakExternal) { 367 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 368 369 if (Symbol.isVariable()) { 370 const MCSymbolRefExpr *SymRef = 371 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 372 373 if (!SymRef) 374 report_fatal_error("Weak externals may only alias symbols"); 375 376 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 377 } else { 378 std::string WeakName = std::string(".weak.") 379 + Symbol.getName().str() 380 + ".default"; 381 COFFSymbol *WeakDefault = createSymbol(WeakName); 382 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 383 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 384 WeakDefault->Data.Type = 0; 385 WeakDefault->Data.Value = 0; 386 coff_symbol->Other = WeakDefault; 387 } 388 389 // Setup the Weak External auxiliary symbol. 390 coff_symbol->Aux.resize(1); 391 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 392 coff_symbol->Aux[0].AuxType = ATWeakExternal; 393 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 394 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 395 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 396 397 coff_symbol->MCData = &SymbolData; 398 } else { 399 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol); 400 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 401 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout); 402 403 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0; 404 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16; 405 406 // If no storage class was specified in the streamer, define it here. 407 if (coff_symbol->Data.StorageClass == 0) { 408 bool IsExternal = 409 ResSymData.isExternal() || 410 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable()); 411 412 coff_symbol->Data.StorageClass = IsExternal 413 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 414 : COFF::IMAGE_SYM_CLASS_STATIC; 415 } 416 417 if (!Base) { 418 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 419 } else { 420 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base); 421 if (BaseData.getFragment()) { 422 COFFSection *Sec = 423 SectionMap[&BaseData.getFragment()->getParent()->getSection()]; 424 425 if (coff_symbol->Section && coff_symbol->Section != Sec) 426 report_fatal_error("conflicting sections for symbol"); 427 428 coff_symbol->Section = Sec; 429 } 430 } 431 432 coff_symbol->MCData = &ResSymData; 433 } 434 } 435 436 // Maximum offsets for different string table entry encodings. 437 static const unsigned Max6DecimalOffset = 999999; 438 static const unsigned Max7DecimalOffset = 9999999; 439 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 440 441 // Encode a string table entry offset in base 64, padded to 6 chars, and 442 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 443 // Buffer must be at least 8 bytes large. No terminating null appended. 444 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) { 445 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 446 "Illegal section name encoding for value"); 447 448 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 449 "abcdefghijklmnopqrstuvwxyz" 450 "0123456789+/"; 451 452 Buffer[0] = '/'; 453 Buffer[1] = '/'; 454 455 char* Ptr = Buffer + 7; 456 for (unsigned i = 0; i < 6; ++i) { 457 unsigned Rem = Value % 64; 458 Value /= 64; 459 *(Ptr--) = Alphabet[Rem]; 460 } 461 } 462 463 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { 464 if (S.Name.size() > COFF::NameSize) { 465 uint64_t StringTableEntry = Strings.getOffset(S.Name); 466 467 if (StringTableEntry <= Max6DecimalOffset) { 468 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 469 } else if (StringTableEntry <= Max7DecimalOffset) { 470 // With seven digits, we have to skip the terminating null. Because 471 // sprintf always appends it, we use a larger temporary buffer. 472 char buffer[9] = { }; 473 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 474 std::memcpy(S.Header.Name, buffer, 8); 475 } else if (StringTableEntry <= MaxBase64Offset) { 476 // Starting with 10,000,000, offsets are encoded as base64. 477 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 478 } else { 479 report_fatal_error("COFF string table is greater than 64 GB."); 480 } 481 } else 482 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 483 } 484 485 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { 486 if (S.Name.size() > COFF::NameSize) 487 S.set_name_offset(Strings.getOffset(S.Name)); 488 else 489 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 490 } 491 492 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol, 493 MCAssembler &Asm) { 494 // This doesn't seem to be right. Strings referred to from the .data section 495 // need symbols so they can be linked to code in the .text section right? 496 497 // return Asm.isSymbolLinkerVisible(Symbol); 498 499 // Non-temporary labels should always be visible to the linker. 500 if (!Symbol.isTemporary()) 501 return true; 502 503 // Absolute temporary labels are never visible. 504 if (!Symbol.isInSection()) 505 return false; 506 507 // For now, all non-variable symbols are exported, 508 // the linker will sort the rest out for us. 509 return !Symbol.isVariable(); 510 } 511 512 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 513 return (S->Header.Characteristics 514 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0; 515 } 516 517 //------------------------------------------------------------------------------ 518 // entity writing methods 519 520 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 521 if (UseBigObj) { 522 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); 523 WriteLE16(0xFFFF); 524 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion); 525 WriteLE16(Header.Machine); 526 WriteLE32(Header.TimeDateStamp); 527 for (uint8_t MagicChar : COFF::BigObjMagic) 528 Write8(MagicChar); 529 WriteLE32(0); 530 WriteLE32(0); 531 WriteLE32(0); 532 WriteLE32(0); 533 WriteLE32(Header.NumberOfSections); 534 WriteLE32(Header.PointerToSymbolTable); 535 WriteLE32(Header.NumberOfSymbols); 536 } else { 537 WriteLE16(Header.Machine); 538 WriteLE16(static_cast<int16_t>(Header.NumberOfSections)); 539 WriteLE32(Header.TimeDateStamp); 540 WriteLE32(Header.PointerToSymbolTable); 541 WriteLE32(Header.NumberOfSymbols); 542 WriteLE16(Header.SizeOfOptionalHeader); 543 WriteLE16(Header.Characteristics); 544 } 545 } 546 547 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 548 WriteBytes(StringRef(S.Data.Name, COFF::NameSize)); 549 WriteLE32(S.Data.Value); 550 if (UseBigObj) 551 WriteLE32(S.Data.SectionNumber); 552 else 553 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber)); 554 WriteLE16(S.Data.Type); 555 Write8(S.Data.StorageClass); 556 Write8(S.Data.NumberOfAuxSymbols); 557 WriteAuxiliarySymbols(S.Aux); 558 } 559 560 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 561 const COFFSymbol::AuxiliarySymbols &S) { 562 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 563 i != e; ++i) { 564 switch(i->AuxType) { 565 case ATFunctionDefinition: 566 WriteLE32(i->Aux.FunctionDefinition.TagIndex); 567 WriteLE32(i->Aux.FunctionDefinition.TotalSize); 568 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 569 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 570 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 571 if (UseBigObj) 572 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 573 break; 574 case ATbfAndefSymbol: 575 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 576 WriteLE16(i->Aux.bfAndefSymbol.Linenumber); 577 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 578 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 579 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 580 if (UseBigObj) 581 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 582 break; 583 case ATWeakExternal: 584 WriteLE32(i->Aux.WeakExternal.TagIndex); 585 WriteLE32(i->Aux.WeakExternal.Characteristics); 586 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 587 if (UseBigObj) 588 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 589 break; 590 case ATFile: 591 WriteBytes( 592 StringRef(reinterpret_cast<const char *>(&i->Aux), 593 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); 594 break; 595 case ATSectionDefinition: 596 WriteLE32(i->Aux.SectionDefinition.Length); 597 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations); 598 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 599 WriteLE32(i->Aux.SectionDefinition.CheckSum); 600 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number)); 601 Write8(i->Aux.SectionDefinition.Selection); 602 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 603 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16)); 604 if (UseBigObj) 605 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 606 break; 607 } 608 } 609 } 610 611 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) { 612 WriteBytes(StringRef(S.Name, COFF::NameSize)); 613 614 WriteLE32(S.VirtualSize); 615 WriteLE32(S.VirtualAddress); 616 WriteLE32(S.SizeOfRawData); 617 WriteLE32(S.PointerToRawData); 618 WriteLE32(S.PointerToRelocations); 619 WriteLE32(S.PointerToLineNumbers); 620 WriteLE16(S.NumberOfRelocations); 621 WriteLE16(S.NumberOfLineNumbers); 622 WriteLE32(S.Characteristics); 623 } 624 625 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 626 WriteLE32(R.VirtualAddress); 627 WriteLE32(R.SymbolTableIndex); 628 WriteLE16(R.Type); 629 } 630 631 //////////////////////////////////////////////////////////////////////////////// 632 // MCObjectWriter interface implementations 633 634 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 635 const MCAsmLayout &Layout) { 636 // "Define" each section & symbol. This creates section & symbol 637 // entries in the staging area. 638 for (const auto & Section : Asm) 639 DefineSection(Section); 640 641 for (MCSymbolData &SD : Asm.symbols()) 642 if (ExportSymbol(SD.getSymbol(), Asm)) 643 DefineSymbol(SD, Asm, Layout); 644 } 645 646 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm, 647 const MCAsmLayout &Layout, 648 const MCFragment *Fragment, 649 const MCFixup &Fixup, 650 MCValue Target, 651 bool &IsPCRel, 652 uint64_t &FixedValue) { 653 assert(Target.getSymA() && "Relocation must reference a symbol!"); 654 655 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 656 const MCSymbol &A = Symbol.AliasedSymbol(); 657 if (!Asm.hasSymbolData(A)) 658 Asm.getContext().FatalError( 659 Fixup.getLoc(), 660 Twine("symbol '") + A.getName() + "' can not be undefined"); 661 662 const MCSymbolData &A_SD = Asm.getSymbolData(A); 663 664 MCSectionData const *SectionData = Fragment->getParent(); 665 666 // Mark this symbol as requiring an entry in the symbol table. 667 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && 668 "Section must already have been defined in ExecutePostLayoutBinding!"); 669 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && 670 "Symbol must already have been defined in ExecutePostLayoutBinding!"); 671 672 COFFSection *coff_section = SectionMap[&SectionData->getSection()]; 673 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; 674 const MCSymbolRefExpr *SymB = Target.getSymB(); 675 bool CrossSection = false; 676 677 if (SymB) { 678 const MCSymbol *B = &SymB->getSymbol(); 679 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 680 if (!B_SD.getFragment()) 681 Asm.getContext().FatalError( 682 Fixup.getLoc(), 683 Twine("symbol '") + B->getName() + 684 "' can not be undefined in a subtraction expression"); 685 686 if (!A_SD.getFragment()) 687 Asm.getContext().FatalError( 688 Fixup.getLoc(), 689 Twine("symbol '") + Symbol.getName() + 690 "' can not be undefined in a subtraction expression"); 691 692 CrossSection = &Symbol.getSection() != &B->getSection(); 693 694 // Offset of the symbol in the section 695 int64_t a = Layout.getSymbolOffset(&B_SD); 696 697 // Ofeset of the relocation in the section 698 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 699 700 FixedValue = b - a; 701 // In the case where we have SymbA and SymB, we just need to store the delta 702 // between the two symbols. Update FixedValue to account for the delta, and 703 // skip recording the relocation. 704 if (!CrossSection) 705 return; 706 } else { 707 FixedValue = Target.getConstant(); 708 } 709 710 COFFRelocation Reloc; 711 712 Reloc.Data.SymbolTableIndex = 0; 713 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 714 715 // Turn relocations for temporary symbols into section relocations. 716 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { 717 Reloc.Symb = coff_symbol->Section->Symbol; 718 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->getFragment()) + 719 coff_symbol->MCData->getOffset(); 720 } else 721 Reloc.Symb = coff_symbol; 722 723 ++Reloc.Symb->Relocations; 724 725 Reloc.Data.VirtualAddress += Fixup.getOffset(); 726 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup, 727 CrossSection); 728 729 // FIXME: Can anyone explain what this does other than adjust for the size 730 // of the offset? 731 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 732 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 733 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 734 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 735 FixedValue += 4; 736 737 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 738 switch (Reloc.Data.Type) { 739 case COFF::IMAGE_REL_ARM_ABSOLUTE: 740 case COFF::IMAGE_REL_ARM_ADDR32: 741 case COFF::IMAGE_REL_ARM_ADDR32NB: 742 case COFF::IMAGE_REL_ARM_TOKEN: 743 case COFF::IMAGE_REL_ARM_SECTION: 744 case COFF::IMAGE_REL_ARM_SECREL: 745 break; 746 case COFF::IMAGE_REL_ARM_BRANCH11: 747 case COFF::IMAGE_REL_ARM_BLX11: 748 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 749 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 750 // for Windows CE). 751 case COFF::IMAGE_REL_ARM_BRANCH24: 752 case COFF::IMAGE_REL_ARM_BLX24: 753 case COFF::IMAGE_REL_ARM_MOV32A: 754 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 755 // only used for ARM mode code, which is documented as being unsupported 756 // by Windows on ARM. Empirical proof indicates that masm is able to 757 // generate the relocations however the rest of the MSVC toolchain is 758 // unable to handle it. 759 llvm_unreachable("unsupported relocation"); 760 break; 761 case COFF::IMAGE_REL_ARM_MOV32T: 762 break; 763 case COFF::IMAGE_REL_ARM_BRANCH20T: 764 case COFF::IMAGE_REL_ARM_BRANCH24T: 765 case COFF::IMAGE_REL_ARM_BLX23T: 766 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 767 // perform a 4 byte adjustment to the relocation. Relative branches are 768 // offset by 4 on ARM, however, because there is no RELA relocations, all 769 // branches are offset by 4. 770 FixedValue = FixedValue + 4; 771 break; 772 } 773 } 774 775 if (TargetObjectWriter->recordRelocation(Fixup)) 776 coff_section->Relocations.push_back(Reloc); 777 } 778 779 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm, 780 const MCAsmLayout &Layout) { 781 size_t SectionsSize = Sections.size(); 782 if (SectionsSize > static_cast<size_t>(INT32_MAX)) 783 report_fatal_error( 784 "PE COFF object files can't have more than 2147483647 sections"); 785 786 // Assign symbol and section indexes and offsets. 787 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize); 788 789 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16; 790 791 DenseMap<COFFSection *, int32_t> SectionIndices( 792 NextPowerOf2(NumberOfSections)); 793 794 // Assign section numbers. 795 size_t Number = 1; 796 for (const auto &Section : Sections) { 797 SectionIndices[Section.get()] = Number; 798 Section->Number = Number; 799 Section->Symbol->Data.SectionNumber = Number; 800 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number; 801 ++Number; 802 } 803 804 Header.NumberOfSections = NumberOfSections; 805 Header.NumberOfSymbols = 0; 806 807 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end(); 808 FI != FE; ++FI) { 809 // round up to calculate the number of auxiliary symbols required 810 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; 811 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize; 812 813 COFFSymbol *file = createSymbol(".file"); 814 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 815 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 816 file->Aux.resize(Count); 817 818 unsigned Offset = 0; 819 unsigned Length = FI->size(); 820 for (auto & Aux : file->Aux) { 821 Aux.AuxType = ATFile; 822 823 if (Length > SymbolSize) { 824 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize); 825 Length = Length - SymbolSize; 826 } else { 827 memcpy(&Aux.Aux, FI->c_str() + Offset, Length); 828 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); 829 break; 830 } 831 832 Offset += SymbolSize; 833 } 834 } 835 836 for (auto &Symbol : Symbols) { 837 // Update section number & offset for symbols that have them. 838 if (Symbol->Section) 839 Symbol->Data.SectionNumber = Symbol->Section->Number; 840 if (Symbol->should_keep()) { 841 Symbol->Index = Header.NumberOfSymbols++; 842 // Update auxiliary symbol info. 843 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 844 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 845 } else 846 Symbol->Index = -1; 847 } 848 849 // Build string table. 850 for (const auto &S : Sections) 851 if (S->Name.size() > COFF::NameSize) 852 Strings.add(S->Name); 853 for (const auto &S : Symbols) 854 if (S->should_keep() && S->Name.size() > COFF::NameSize) 855 Strings.add(S->Name); 856 Strings.finalize(StringTableBuilder::WinCOFF); 857 858 // Set names. 859 for (const auto &S : Sections) 860 SetSectionName(*S); 861 for (auto &S : Symbols) 862 if (S->should_keep()) 863 SetSymbolName(*S); 864 865 // Fixup weak external references. 866 for (auto & Symbol : Symbols) { 867 if (Symbol->Other) { 868 assert(Symbol->Index != -1); 869 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 870 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 871 "Symbol's aux symbol must be a Weak External!"); 872 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index; 873 } 874 } 875 876 // Fixup associative COMDAT sections. 877 for (auto & Section : Sections) { 878 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 879 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 880 continue; 881 882 const MCSectionCOFF &MCSec = 883 static_cast<const MCSectionCOFF &>(Section->MCData->getSection()); 884 885 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 886 assert(COMDAT); 887 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 888 assert(COMDATSymbol); 889 COFFSection *Assoc = COMDATSymbol->Section; 890 if (!Assoc) 891 report_fatal_error( 892 Twine("Missing associated COMDAT section for section ") + 893 MCSec.getSectionName()); 894 895 // Skip this section if the associated section is unused. 896 if (Assoc->Number == -1) 897 continue; 898 899 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc]; 900 } 901 902 903 // Assign file offsets to COFF object file structures. 904 905 unsigned offset = 0; 906 907 if (UseBigObj) 908 offset += COFF::Header32Size; 909 else 910 offset += COFF::Header16Size; 911 offset += COFF::SectionSize * Header.NumberOfSections; 912 913 for (const auto & Section : Asm) { 914 COFFSection *Sec = SectionMap[&Section.getSection()]; 915 916 if (Sec->Number == -1) 917 continue; 918 919 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 920 921 if (IsPhysicalSection(Sec)) { 922 Sec->Header.PointerToRawData = offset; 923 924 offset += Sec->Header.SizeOfRawData; 925 } 926 927 if (Sec->Relocations.size() > 0) { 928 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 929 930 if (RelocationsOverflow) { 931 // Signal overflow by setting NumberOfRelocations to max value. Actual 932 // size is found in reloc #0. Microsoft tools understand this. 933 Sec->Header.NumberOfRelocations = 0xffff; 934 } else { 935 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 936 } 937 Sec->Header.PointerToRelocations = offset; 938 939 if (RelocationsOverflow) { 940 // Reloc #0 will contain actual count, so make room for it. 941 offset += COFF::RelocationSize; 942 } 943 944 offset += COFF::RelocationSize * Sec->Relocations.size(); 945 946 for (auto & Relocation : Sec->Relocations) { 947 assert(Relocation.Symb->Index != -1); 948 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index; 949 } 950 } 951 952 assert(Sec->Symbol->Aux.size() == 1 && 953 "Section's symbol must have one aux!"); 954 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 955 assert(Aux.AuxType == ATSectionDefinition && 956 "Section's symbol's aux symbol must be a Section Definition!"); 957 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 958 Aux.Aux.SectionDefinition.NumberOfRelocations = 959 Sec->Header.NumberOfRelocations; 960 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 961 Sec->Header.NumberOfLineNumbers; 962 } 963 964 Header.PointerToSymbolTable = offset; 965 966 // We want a deterministic output. It looks like GNU as also writes 0 in here. 967 Header.TimeDateStamp = 0; 968 969 // Write it all to disk... 970 WriteFileHeader(Header); 971 972 { 973 sections::iterator i, ie; 974 MCAssembler::const_iterator j, je; 975 976 for (auto & Section : Sections) { 977 if (Section->Number != -1) { 978 if (Section->Relocations.size() >= 0xffff) 979 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 980 WriteSectionHeader(Section->Header); 981 } 982 } 983 984 for (i = Sections.begin(), ie = Sections.end(), 985 j = Asm.begin(), je = Asm.end(); 986 (i != ie) && (j != je); ++i, ++j) { 987 988 if ((*i)->Number == -1) 989 continue; 990 991 if ((*i)->Header.PointerToRawData != 0) { 992 assert(OS.tell() == (*i)->Header.PointerToRawData && 993 "Section::PointerToRawData is insane!"); 994 995 Asm.writeSectionData(j, Layout); 996 } 997 998 if ((*i)->Relocations.size() > 0) { 999 assert(OS.tell() == (*i)->Header.PointerToRelocations && 1000 "Section::PointerToRelocations is insane!"); 1001 1002 if ((*i)->Relocations.size() >= 0xffff) { 1003 // In case of overflow, write actual relocation count as first 1004 // relocation. Including the synthetic reloc itself (+ 1). 1005 COFF::relocation r; 1006 r.VirtualAddress = (*i)->Relocations.size() + 1; 1007 r.SymbolTableIndex = 0; 1008 r.Type = 0; 1009 WriteRelocation(r); 1010 } 1011 1012 for (const auto & Relocation : (*i)->Relocations) 1013 WriteRelocation(Relocation.Data); 1014 } else 1015 assert((*i)->Header.PointerToRelocations == 0 && 1016 "Section::PointerToRelocations is insane!"); 1017 } 1018 } 1019 1020 assert(OS.tell() == Header.PointerToSymbolTable && 1021 "Header::PointerToSymbolTable is insane!"); 1022 1023 for (auto & Symbol : Symbols) 1024 if (Symbol->Index != -1) 1025 WriteSymbol(*Symbol); 1026 1027 OS.write(Strings.data().data(), Strings.data().size()); 1028 } 1029 1030 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) : 1031 Machine(Machine_) { 1032 } 1033 1034 // Pin the vtable to this file. 1035 void MCWinCOFFObjectTargetWriter::anchor() {} 1036 1037 //------------------------------------------------------------------------------ 1038 // WinCOFFObjectWriter factory function 1039 1040 namespace llvm { 1041 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1042 raw_ostream &OS) { 1043 return new WinCOFFObjectWriter(MOTW, OS); 1044 } 1045 } 1046