1//===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file contains an implementation of a Win32 COFF object file writer. 11// 12//===----------------------------------------------------------------------===// 13 14#include "llvm/MC/MCWinCOFFObjectWriter.h" 15#include "llvm/ADT/DenseMap.h" 16#include "llvm/ADT/STLExtras.h" 17#include "llvm/ADT/StringMap.h" 18#include "llvm/ADT/StringRef.h" 19#include "llvm/ADT/Twine.h" 20#include "llvm/Config/config.h" 21#include "llvm/MC/MCAsmLayout.h" 22#include "llvm/MC/MCAssembler.h" 23#include "llvm/MC/MCContext.h" 24#include "llvm/MC/MCExpr.h" 25#include "llvm/MC/MCObjectFileInfo.h" 26#include "llvm/MC/MCObjectWriter.h" 27#include "llvm/MC/MCSection.h" 28#include "llvm/MC/MCSectionCOFF.h" 29#include "llvm/MC/MCSymbolCOFF.h" 30#include "llvm/MC/MCValue.h" 31#include "llvm/MC/StringTableBuilder.h" 32#include "llvm/Support/COFF.h" 33#include "llvm/Support/Debug.h" 34#include "llvm/Support/Endian.h" 35#include "llvm/Support/ErrorHandling.h" 36#include "llvm/Support/JamCRC.h" 37#include "llvm/Support/TimeValue.h" 38#include <cstdio> 39#include <ctime> 40 41using namespace llvm; 42 43#define DEBUG_TYPE "WinCOFFObjectWriter" 44 45namespace { 46typedef SmallString<COFF::NameSize> name; 47 48enum AuxiliaryType { 49 ATFunctionDefinition, 50 ATbfAndefSymbol, 51 ATWeakExternal, 52 ATFile, 53 ATSectionDefinition 54}; 55 56struct AuxSymbol { 57 AuxiliaryType AuxType; 58 COFF::Auxiliary Aux; 59}; 60 61class COFFSymbol; 62class COFFSection; 63 64class COFFSymbol { 65public: 66 COFF::symbol Data; 67 68 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols; 69 70 name Name; 71 int Index; 72 AuxiliarySymbols Aux; 73 COFFSymbol *Other; 74 COFFSection *Section; 75 int Relocations; 76 77 const MCSymbol *MC; 78 79 COFFSymbol(StringRef name); 80 void set_name_offset(uint32_t Offset); 81 82 int64_t getIndex() const { return Index; } 83 void setIndex(int Value) { 84 Index = Value; 85 if (MC) 86 MC->setIndex(static_cast<uint32_t>(Value)); 87 } 88}; 89 90// This class contains staging data for a COFF relocation entry. 91struct COFFRelocation { 92 COFF::relocation Data; 93 COFFSymbol *Symb; 94 95 COFFRelocation() : Symb(nullptr) {} 96 static size_t size() { return COFF::RelocationSize; } 97}; 98 99typedef std::vector<COFFRelocation> relocations; 100 101class COFFSection { 102public: 103 COFF::section Header; 104 105 std::string Name; 106 int Number; 107 MCSectionCOFF const *MCSection; 108 COFFSymbol *Symbol; 109 relocations Relocations; 110 111 COFFSection(StringRef name); 112 static size_t size(); 113}; 114 115class WinCOFFObjectWriter : public MCObjectWriter { 116public: 117 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols; 118 typedef std::vector<std::unique_ptr<COFFSection>> sections; 119 120 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map; 121 typedef DenseMap<MCSection const *, COFFSection *> section_map; 122 123 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter; 124 125 // Root level file contents. 126 COFF::header Header; 127 sections Sections; 128 symbols Symbols; 129 StringTableBuilder Strings{StringTableBuilder::WinCOFF}; 130 131 // Maps used during object file creation. 132 section_map SectionMap; 133 symbol_map SymbolMap; 134 135 bool UseBigObj; 136 137 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS); 138 139 void reset() override { 140 memset(&Header, 0, sizeof(Header)); 141 Header.Machine = TargetObjectWriter->getMachine(); 142 Sections.clear(); 143 Symbols.clear(); 144 Strings.clear(); 145 SectionMap.clear(); 146 SymbolMap.clear(); 147 MCObjectWriter::reset(); 148 } 149 150 COFFSymbol *createSymbol(StringRef Name); 151 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol); 152 COFFSection *createSection(StringRef Name); 153 154 template <typename object_t, typename list_t> 155 object_t *createCOFFEntity(StringRef Name, list_t &List); 156 157 void defineSection(MCSectionCOFF const &Sec); 158 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler, 159 const MCAsmLayout &Layout); 160 161 void SetSymbolName(COFFSymbol &S); 162 void SetSectionName(COFFSection &S); 163 164 bool IsPhysicalSection(COFFSection *S); 165 166 // Entity writing methods. 167 168 void WriteFileHeader(const COFF::header &Header); 169 void WriteSymbol(const COFFSymbol &S); 170 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S); 171 void writeSectionHeader(const COFF::section &S); 172 void WriteRelocation(const COFF::relocation &R); 173 174 // MCObjectWriter interface implementation. 175 176 void executePostLayoutBinding(MCAssembler &Asm, 177 const MCAsmLayout &Layout) override; 178 179 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 180 const MCSymbol &SymA, 181 const MCFragment &FB, bool InSet, 182 bool IsPCRel) const override; 183 184 bool isWeak(const MCSymbol &Sym) const override; 185 186 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 187 const MCFragment *Fragment, const MCFixup &Fixup, 188 MCValue Target, bool &IsPCRel, 189 uint64_t &FixedValue) override; 190 191 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 192}; 193} 194 195static inline void write_uint32_le(void *Data, uint32_t Value) { 196 support::endian::write<uint32_t, support::little, support::unaligned>(Data, 197 Value); 198} 199 200//------------------------------------------------------------------------------ 201// Symbol class implementation 202 203COFFSymbol::COFFSymbol(StringRef name) 204 : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr), 205 Relocations(0), MC(nullptr) { 206 memset(&Data, 0, sizeof(Data)); 207} 208 209// In the case that the name does not fit within 8 bytes, the offset 210// into the string table is stored in the last 4 bytes instead, leaving 211// the first 4 bytes as 0. 212void COFFSymbol::set_name_offset(uint32_t Offset) { 213 write_uint32_le(Data.Name + 0, 0); 214 write_uint32_le(Data.Name + 4, Offset); 215} 216 217//------------------------------------------------------------------------------ 218// Section class implementation 219 220COFFSection::COFFSection(StringRef name) 221 : Name(name), MCSection(nullptr), Symbol(nullptr) { 222 memset(&Header, 0, sizeof(Header)); 223} 224 225size_t COFFSection::size() { return COFF::SectionSize; } 226 227//------------------------------------------------------------------------------ 228// WinCOFFObjectWriter class implementation 229 230WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 231 raw_pwrite_stream &OS) 232 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { 233 memset(&Header, 0, sizeof(Header)); 234 235 Header.Machine = TargetObjectWriter->getMachine(); 236} 237 238COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 239 return createCOFFEntity<COFFSymbol>(Name, Symbols); 240} 241 242COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) { 243 symbol_map::iterator i = SymbolMap.find(Symbol); 244 if (i != SymbolMap.end()) 245 return i->second; 246 COFFSymbol *RetSymbol = 247 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 248 SymbolMap[Symbol] = RetSymbol; 249 return RetSymbol; 250} 251 252COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 253 return createCOFFEntity<COFFSection>(Name, Sections); 254} 255 256/// A template used to lookup or create a symbol/section, and initialize it if 257/// needed. 258template <typename object_t, typename list_t> 259object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) { 260 List.push_back(make_unique<object_t>(Name)); 261 262 return List.back().get(); 263} 264 265/// This function takes a section data object from the assembler 266/// and creates the associated COFF section staging object. 267void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) { 268 COFFSection *coff_section = createSection(Sec.getSectionName()); 269 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 270 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 271 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 272 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 273 if (COMDATSymbol->Section) 274 report_fatal_error("two sections have the same comdat"); 275 COMDATSymbol->Section = coff_section; 276 } 277 } 278 279 coff_section->Symbol = coff_symbol; 280 coff_symbol->Section = coff_section; 281 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 282 283 // In this case the auxiliary symbol is a Section Definition. 284 coff_symbol->Aux.resize(1); 285 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 286 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 287 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 288 289 coff_section->Header.Characteristics = Sec.getCharacteristics(); 290 291 uint32_t &Characteristics = coff_section->Header.Characteristics; 292 switch (Sec.getAlignment()) { 293 case 1: 294 Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; 295 break; 296 case 2: 297 Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; 298 break; 299 case 4: 300 Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; 301 break; 302 case 8: 303 Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; 304 break; 305 case 16: 306 Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; 307 break; 308 case 32: 309 Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; 310 break; 311 case 64: 312 Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; 313 break; 314 case 128: 315 Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; 316 break; 317 case 256: 318 Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; 319 break; 320 case 512: 321 Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; 322 break; 323 case 1024: 324 Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; 325 break; 326 case 2048: 327 Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; 328 break; 329 case 4096: 330 Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; 331 break; 332 case 8192: 333 Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; 334 break; 335 default: 336 llvm_unreachable("unsupported section alignment"); 337 } 338 339 // Bind internal COFF section to MC section. 340 coff_section->MCSection = &Sec; 341 SectionMap[&Sec] = coff_section; 342} 343 344static uint64_t getSymbolValue(const MCSymbol &Symbol, 345 const MCAsmLayout &Layout) { 346 if (Symbol.isCommon() && Symbol.isExternal()) 347 return Symbol.getCommonSize(); 348 349 uint64_t Res; 350 if (!Layout.getSymbolOffset(Symbol, Res)) 351 return 0; 352 353 return Res; 354} 355 356/// This function takes a symbol data object from the assembler 357/// and creates the associated COFF symbol staging object. 358void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol, 359 MCAssembler &Assembler, 360 const MCAsmLayout &Layout) { 361 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 362 363 if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) { 364 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 365 366 if (Symbol.isVariable()) { 367 const MCSymbolRefExpr *SymRef = 368 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 369 370 if (!SymRef) 371 report_fatal_error("Weak externals may only alias symbols"); 372 373 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 374 } else { 375 std::string WeakName = (".weak." + Symbol.getName() + ".default").str(); 376 COFFSymbol *WeakDefault = createSymbol(WeakName); 377 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 378 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 379 WeakDefault->Data.Type = 0; 380 WeakDefault->Data.Value = 0; 381 coff_symbol->Other = WeakDefault; 382 } 383 384 // Setup the Weak External auxiliary symbol. 385 coff_symbol->Aux.resize(1); 386 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 387 coff_symbol->Aux[0].AuxType = ATWeakExternal; 388 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 389 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 390 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 391 392 coff_symbol->MC = &Symbol; 393 } else { 394 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 395 coff_symbol->Data.Value = getSymbolValue(Symbol, Layout); 396 397 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol); 398 coff_symbol->Data.Type = SymbolCOFF.getType(); 399 coff_symbol->Data.StorageClass = SymbolCOFF.getClass(); 400 401 // If no storage class was specified in the streamer, define it here. 402 if (coff_symbol->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) { 403 bool IsExternal = Symbol.isExternal() || 404 (!Symbol.getFragment() && !Symbol.isVariable()); 405 406 coff_symbol->Data.StorageClass = IsExternal 407 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 408 : COFF::IMAGE_SYM_CLASS_STATIC; 409 } 410 411 if (!Base) { 412 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 413 } else { 414 if (Base->getFragment()) { 415 COFFSection *Sec = SectionMap[Base->getFragment()->getParent()]; 416 417 if (coff_symbol->Section && coff_symbol->Section != Sec) 418 report_fatal_error("conflicting sections for symbol"); 419 420 coff_symbol->Section = Sec; 421 } 422 } 423 424 coff_symbol->MC = &Symbol; 425 } 426} 427 428// Maximum offsets for different string table entry encodings. 429static const unsigned Max6DecimalOffset = 999999; 430static const unsigned Max7DecimalOffset = 9999999; 431static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 432 433// Encode a string table entry offset in base 64, padded to 6 chars, and 434// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 435// Buffer must be at least 8 bytes large. No terminating null appended. 436static void encodeBase64StringEntry(char *Buffer, uint64_t Value) { 437 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 438 "Illegal section name encoding for value"); 439 440 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 441 "abcdefghijklmnopqrstuvwxyz" 442 "0123456789+/"; 443 444 Buffer[0] = '/'; 445 Buffer[1] = '/'; 446 447 char *Ptr = Buffer + 7; 448 for (unsigned i = 0; i < 6; ++i) { 449 unsigned Rem = Value % 64; 450 Value /= 64; 451 *(Ptr--) = Alphabet[Rem]; 452 } 453} 454 455void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { 456 if (S.Name.size() > COFF::NameSize) { 457 uint64_t StringTableEntry = Strings.getOffset(S.Name); 458 459 if (StringTableEntry <= Max6DecimalOffset) { 460 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 461 } else if (StringTableEntry <= Max7DecimalOffset) { 462 // With seven digits, we have to skip the terminating null. Because 463 // sprintf always appends it, we use a larger temporary buffer. 464 char buffer[9] = {}; 465 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 466 std::memcpy(S.Header.Name, buffer, 8); 467 } else if (StringTableEntry <= MaxBase64Offset) { 468 // Starting with 10,000,000, offsets are encoded as base64. 469 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 470 } else { 471 report_fatal_error("COFF string table is greater than 64 GB."); 472 } 473 } else 474 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 475} 476 477void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { 478 if (S.Name.size() > COFF::NameSize) 479 S.set_name_offset(Strings.getOffset(S.Name)); 480 else 481 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 482} 483 484bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 485 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 486 0; 487} 488 489//------------------------------------------------------------------------------ 490// entity writing methods 491 492void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 493 if (UseBigObj) { 494 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); 495 writeLE16(0xFFFF); 496 writeLE16(COFF::BigObjHeader::MinBigObjectVersion); 497 writeLE16(Header.Machine); 498 writeLE32(Header.TimeDateStamp); 499 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic))); 500 writeLE32(0); 501 writeLE32(0); 502 writeLE32(0); 503 writeLE32(0); 504 writeLE32(Header.NumberOfSections); 505 writeLE32(Header.PointerToSymbolTable); 506 writeLE32(Header.NumberOfSymbols); 507 } else { 508 writeLE16(Header.Machine); 509 writeLE16(static_cast<int16_t>(Header.NumberOfSections)); 510 writeLE32(Header.TimeDateStamp); 511 writeLE32(Header.PointerToSymbolTable); 512 writeLE32(Header.NumberOfSymbols); 513 writeLE16(Header.SizeOfOptionalHeader); 514 writeLE16(Header.Characteristics); 515 } 516} 517 518void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 519 writeBytes(StringRef(S.Data.Name, COFF::NameSize)); 520 writeLE32(S.Data.Value); 521 if (UseBigObj) 522 writeLE32(S.Data.SectionNumber); 523 else 524 writeLE16(static_cast<int16_t>(S.Data.SectionNumber)); 525 writeLE16(S.Data.Type); 526 write8(S.Data.StorageClass); 527 write8(S.Data.NumberOfAuxSymbols); 528 WriteAuxiliarySymbols(S.Aux); 529} 530 531void WinCOFFObjectWriter::WriteAuxiliarySymbols( 532 const COFFSymbol::AuxiliarySymbols &S) { 533 for (COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 534 i != e; ++i) { 535 switch (i->AuxType) { 536 case ATFunctionDefinition: 537 writeLE32(i->Aux.FunctionDefinition.TagIndex); 538 writeLE32(i->Aux.FunctionDefinition.TotalSize); 539 writeLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 540 writeLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 541 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 542 if (UseBigObj) 543 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 544 break; 545 case ATbfAndefSymbol: 546 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 547 writeLE16(i->Aux.bfAndefSymbol.Linenumber); 548 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 549 writeLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 550 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 551 if (UseBigObj) 552 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 553 break; 554 case ATWeakExternal: 555 writeLE32(i->Aux.WeakExternal.TagIndex); 556 writeLE32(i->Aux.WeakExternal.Characteristics); 557 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 558 if (UseBigObj) 559 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 560 break; 561 case ATFile: 562 writeBytes( 563 StringRef(reinterpret_cast<const char *>(&i->Aux), 564 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); 565 break; 566 case ATSectionDefinition: 567 writeLE32(i->Aux.SectionDefinition.Length); 568 writeLE16(i->Aux.SectionDefinition.NumberOfRelocations); 569 writeLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 570 writeLE32(i->Aux.SectionDefinition.CheckSum); 571 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number)); 572 write8(i->Aux.SectionDefinition.Selection); 573 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 574 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16)); 575 if (UseBigObj) 576 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); 577 break; 578 } 579 } 580} 581 582void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) { 583 writeBytes(StringRef(S.Name, COFF::NameSize)); 584 585 writeLE32(S.VirtualSize); 586 writeLE32(S.VirtualAddress); 587 writeLE32(S.SizeOfRawData); 588 writeLE32(S.PointerToRawData); 589 writeLE32(S.PointerToRelocations); 590 writeLE32(S.PointerToLineNumbers); 591 writeLE16(S.NumberOfRelocations); 592 writeLE16(S.NumberOfLineNumbers); 593 writeLE32(S.Characteristics); 594} 595 596void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 597 writeLE32(R.VirtualAddress); 598 writeLE32(R.SymbolTableIndex); 599 writeLE16(R.Type); 600} 601 602//////////////////////////////////////////////////////////////////////////////// 603// MCObjectWriter interface implementations 604 605void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm, 606 const MCAsmLayout &Layout) { 607 // "Define" each section & symbol. This creates section & symbol 608 // entries in the staging area. 609 for (const auto &Section : Asm) 610 defineSection(static_cast<const MCSectionCOFF &>(Section)); 611 612 for (const MCSymbol &Symbol : Asm.symbols()) 613 if (!Symbol.isTemporary()) 614 DefineSymbol(Symbol, Asm, Layout); 615} 616 617bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl( 618 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB, 619 bool InSet, bool IsPCRel) const { 620 // MS LINK expects to be able to replace all references to a function with a 621 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize 622 // away any relocations to functions. 623 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType(); 624 if (Asm.isIncrementalLinkerCompatible() && 625 (Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION) 626 return false; 627 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB, 628 InSet, IsPCRel); 629} 630 631bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const { 632 if (!Sym.isExternal()) 633 return false; 634 635 if (!Sym.isInSection()) 636 return false; 637 638 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection()); 639 if (!Sec.getCOMDATSymbol()) 640 return false; 641 642 // It looks like for COFF it is invalid to replace a reference to a global 643 // in a comdat with a reference to a local. 644 // FIXME: Add a specification reference if available. 645 return true; 646} 647 648void WinCOFFObjectWriter::recordRelocation( 649 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, 650 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { 651 assert(Target.getSymA() && "Relocation must reference a symbol!"); 652 653 const MCSymbol &A = Target.getSymA()->getSymbol(); 654 if (!A.isRegistered()) { 655 Asm.getContext().reportError(Fixup.getLoc(), 656 Twine("symbol '") + A.getName() + 657 "' can not be undefined"); 658 return; 659 } 660 if (A.isTemporary() && A.isUndefined()) { 661 Asm.getContext().reportError(Fixup.getLoc(), 662 Twine("assembler label '") + A.getName() + 663 "' can not be undefined"); 664 return; 665 } 666 667 MCSection *Section = Fragment->getParent(); 668 669 // Mark this symbol as requiring an entry in the symbol table. 670 assert(SectionMap.find(Section) != SectionMap.end() && 671 "Section must already have been defined in executePostLayoutBinding!"); 672 673 COFFSection *coff_section = SectionMap[Section]; 674 const MCSymbolRefExpr *SymB = Target.getSymB(); 675 bool CrossSection = false; 676 677 if (SymB) { 678 const MCSymbol *B = &SymB->getSymbol(); 679 if (!B->getFragment()) { 680 Asm.getContext().reportError( 681 Fixup.getLoc(), 682 Twine("symbol '") + B->getName() + 683 "' can not be undefined in a subtraction expression"); 684 return; 685 } 686 687 if (!A.getFragment()) { 688 Asm.getContext().reportError( 689 Fixup.getLoc(), 690 Twine("symbol '") + A.getName() + 691 "' can not be undefined in a subtraction expression"); 692 return; 693 } 694 695 CrossSection = &A.getSection() != &B->getSection(); 696 697 // Offset of the symbol in the section 698 int64_t OffsetOfB = Layout.getSymbolOffset(*B); 699 700 // In the case where we have SymbA and SymB, we just need to store the delta 701 // between the two symbols. Update FixedValue to account for the delta, and 702 // skip recording the relocation. 703 if (!CrossSection) { 704 int64_t OffsetOfA = Layout.getSymbolOffset(A); 705 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant(); 706 return; 707 } 708 709 // Offset of the relocation in the section 710 int64_t OffsetOfRelocation = 711 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 712 713 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant(); 714 } else { 715 FixedValue = Target.getConstant(); 716 } 717 718 COFFRelocation Reloc; 719 720 Reloc.Data.SymbolTableIndex = 0; 721 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 722 723 // Turn relocations for temporary symbols into section relocations. 724 if (A.isTemporary() || CrossSection) { 725 MCSection *TargetSection = &A.getSection(); 726 assert( 727 SectionMap.find(TargetSection) != SectionMap.end() && 728 "Section must already have been defined in executePostLayoutBinding!"); 729 Reloc.Symb = SectionMap[TargetSection]->Symbol; 730 FixedValue += Layout.getSymbolOffset(A); 731 } else { 732 assert( 733 SymbolMap.find(&A) != SymbolMap.end() && 734 "Symbol must already have been defined in executePostLayoutBinding!"); 735 Reloc.Symb = SymbolMap[&A]; 736 } 737 738 ++Reloc.Symb->Relocations; 739 740 Reloc.Data.VirtualAddress += Fixup.getOffset(); 741 Reloc.Data.Type = TargetObjectWriter->getRelocType( 742 Target, Fixup, CrossSection, Asm.getBackend()); 743 744 // FIXME: Can anyone explain what this does other than adjust for the size 745 // of the offset? 746 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 747 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 748 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 749 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 750 FixedValue += 4; 751 752 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 753 switch (Reloc.Data.Type) { 754 case COFF::IMAGE_REL_ARM_ABSOLUTE: 755 case COFF::IMAGE_REL_ARM_ADDR32: 756 case COFF::IMAGE_REL_ARM_ADDR32NB: 757 case COFF::IMAGE_REL_ARM_TOKEN: 758 case COFF::IMAGE_REL_ARM_SECTION: 759 case COFF::IMAGE_REL_ARM_SECREL: 760 break; 761 case COFF::IMAGE_REL_ARM_BRANCH11: 762 case COFF::IMAGE_REL_ARM_BLX11: 763 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 764 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 765 // for Windows CE). 766 case COFF::IMAGE_REL_ARM_BRANCH24: 767 case COFF::IMAGE_REL_ARM_BLX24: 768 case COFF::IMAGE_REL_ARM_MOV32A: 769 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 770 // only used for ARM mode code, which is documented as being unsupported 771 // by Windows on ARM. Empirical proof indicates that masm is able to 772 // generate the relocations however the rest of the MSVC toolchain is 773 // unable to handle it. 774 llvm_unreachable("unsupported relocation"); 775 break; 776 case COFF::IMAGE_REL_ARM_MOV32T: 777 break; 778 case COFF::IMAGE_REL_ARM_BRANCH20T: 779 case COFF::IMAGE_REL_ARM_BRANCH24T: 780 case COFF::IMAGE_REL_ARM_BLX23T: 781 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 782 // perform a 4 byte adjustment to the relocation. Relative branches are 783 // offset by 4 on ARM, however, because there is no RELA relocations, all 784 // branches are offset by 4. 785 FixedValue = FixedValue + 4; 786 break; 787 } 788 } 789 790 if (TargetObjectWriter->recordRelocation(Fixup)) 791 coff_section->Relocations.push_back(Reloc); 792} 793 794void WinCOFFObjectWriter::writeObject(MCAssembler &Asm, 795 const MCAsmLayout &Layout) { 796 size_t SectionsSize = Sections.size(); 797 if (SectionsSize > static_cast<size_t>(INT32_MAX)) 798 report_fatal_error( 799 "PE COFF object files can't have more than 2147483647 sections"); 800 801 // Assign symbol and section indexes and offsets. 802 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize); 803 804 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16; 805 806 // Assign section numbers. 807 size_t Number = 1; 808 for (const auto &Section : Sections) { 809 Section->Number = Number; 810 Section->Symbol->Data.SectionNumber = Number; 811 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number; 812 ++Number; 813 } 814 815 Header.NumberOfSections = NumberOfSections; 816 Header.NumberOfSymbols = 0; 817 818 for (const std::string &Name : Asm.getFileNames()) { 819 // round up to calculate the number of auxiliary symbols required 820 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; 821 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize; 822 823 COFFSymbol *file = createSymbol(".file"); 824 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 825 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 826 file->Aux.resize(Count); 827 828 unsigned Offset = 0; 829 unsigned Length = Name.size(); 830 for (auto &Aux : file->Aux) { 831 Aux.AuxType = ATFile; 832 833 if (Length > SymbolSize) { 834 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize); 835 Length = Length - SymbolSize; 836 } else { 837 memcpy(&Aux.Aux, Name.c_str() + Offset, Length); 838 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); 839 break; 840 } 841 842 Offset += SymbolSize; 843 } 844 } 845 846 for (auto &Symbol : Symbols) { 847 // Update section number & offset for symbols that have them. 848 if (Symbol->Section) 849 Symbol->Data.SectionNumber = Symbol->Section->Number; 850 Symbol->setIndex(Header.NumberOfSymbols++); 851 // Update auxiliary symbol info. 852 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 853 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 854 } 855 856 // Build string table. 857 for (const auto &S : Sections) 858 if (S->Name.size() > COFF::NameSize) 859 Strings.add(S->Name); 860 for (const auto &S : Symbols) 861 if (S->Name.size() > COFF::NameSize) 862 Strings.add(S->Name); 863 Strings.finalize(); 864 865 // Set names. 866 for (const auto &S : Sections) 867 SetSectionName(*S); 868 for (auto &S : Symbols) 869 SetSymbolName(*S); 870 871 // Fixup weak external references. 872 for (auto &Symbol : Symbols) { 873 if (Symbol->Other) { 874 assert(Symbol->getIndex() != -1); 875 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 876 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 877 "Symbol's aux symbol must be a Weak External!"); 878 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex(); 879 } 880 } 881 882 // Fixup associative COMDAT sections. 883 for (auto &Section : Sections) { 884 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 885 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 886 continue; 887 888 const MCSectionCOFF &MCSec = *Section->MCSection; 889 890 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 891 assert(COMDAT); 892 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 893 assert(COMDATSymbol); 894 COFFSection *Assoc = COMDATSymbol->Section; 895 if (!Assoc) 896 report_fatal_error( 897 Twine("Missing associated COMDAT section for section ") + 898 MCSec.getSectionName()); 899 900 // Skip this section if the associated section is unused. 901 if (Assoc->Number == -1) 902 continue; 903 904 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number; 905 } 906 907 // Assign file offsets to COFF object file structures. 908 909 unsigned offset = getInitialOffset(); 910 911 if (UseBigObj) 912 offset += COFF::Header32Size; 913 else 914 offset += COFF::Header16Size; 915 offset += COFF::SectionSize * Header.NumberOfSections; 916 917 for (const auto &Section : Asm) { 918 COFFSection *Sec = SectionMap[&Section]; 919 920 if (Sec->Number == -1) 921 continue; 922 923 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 924 925 if (IsPhysicalSection(Sec)) { 926 // Align the section data to a four byte boundary. 927 offset = RoundUpToAlignment(offset, 4); 928 Sec->Header.PointerToRawData = offset; 929 930 offset += Sec->Header.SizeOfRawData; 931 } 932 933 if (Sec->Relocations.size() > 0) { 934 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 935 936 if (RelocationsOverflow) { 937 // Signal overflow by setting NumberOfRelocations to max value. Actual 938 // size is found in reloc #0. Microsoft tools understand this. 939 Sec->Header.NumberOfRelocations = 0xffff; 940 } else { 941 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 942 } 943 Sec->Header.PointerToRelocations = offset; 944 945 if (RelocationsOverflow) { 946 // Reloc #0 will contain actual count, so make room for it. 947 offset += COFF::RelocationSize; 948 } 949 950 offset += COFF::RelocationSize * Sec->Relocations.size(); 951 952 for (auto &Relocation : Sec->Relocations) { 953 assert(Relocation.Symb->getIndex() != -1); 954 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex(); 955 } 956 } 957 958 assert(Sec->Symbol->Aux.size() == 1 && 959 "Section's symbol must have one aux!"); 960 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 961 assert(Aux.AuxType == ATSectionDefinition && 962 "Section's symbol's aux symbol must be a Section Definition!"); 963 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 964 Aux.Aux.SectionDefinition.NumberOfRelocations = 965 Sec->Header.NumberOfRelocations; 966 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 967 Sec->Header.NumberOfLineNumbers; 968 } 969 970 Header.PointerToSymbolTable = offset; 971 972 // FIXME: Remove the #else branch and make the #if branch unconditional once 973 // LLVM's self host configuration is aware of /Brepro. 974#if (ENABLE_TIMESTAMPS == 1) 975 // MS LINK expects to be able to use this timestamp to implement their 976 // /INCREMENTAL feature. 977 if (Asm.isIncrementalLinkerCompatible()) { 978 std::time_t Now = time(nullptr); 979 if (Now < 0 || !isUInt<32>(Now)) 980 Now = UINT32_MAX; 981 Header.TimeDateStamp = Now; 982 } else { 983 Header.TimeDateStamp = 0; 984 } 985#else 986 // We want a deterministic output. It looks like GNU as also writes 0 in here. 987 Header.TimeDateStamp = 0; 988#endif 989 990 // Write it all to disk... 991 WriteFileHeader(Header); 992 993 { 994 sections::iterator i, ie; 995 MCAssembler::iterator j, je; 996 997 for (auto &Section : Sections) { 998 if (Section->Number != -1) { 999 if (Section->Relocations.size() >= 0xffff) 1000 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 1001 writeSectionHeader(Section->Header); 1002 } 1003 } 1004 1005 SmallVector<char, 128> SectionContents; 1006 for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(), 1007 je = Asm.end(); 1008 (i != ie) && (j != je); ++i, ++j) { 1009 1010 if ((*i)->Number == -1) 1011 continue; 1012 1013 if ((*i)->Header.PointerToRawData != 0) { 1014 assert(getStream().tell() <= (*i)->Header.PointerToRawData && 1015 "Section::PointerToRawData is insane!"); 1016 1017 unsigned SectionDataPadding = 1018 (*i)->Header.PointerToRawData - getStream().tell(); 1019 assert(SectionDataPadding < 4 && 1020 "Should only need at most three bytes of padding!"); 1021 1022 WriteZeros(SectionDataPadding); 1023 1024 // Save the contents of the section to a temporary buffer, we need this 1025 // to CRC the data before we dump it into the object file. 1026 SectionContents.clear(); 1027 raw_svector_ostream VecOS(SectionContents); 1028 raw_pwrite_stream &OldStream = getStream(); 1029 // Redirect the output stream to our buffer. 1030 setStream(VecOS); 1031 // Fill our buffer with the section data. 1032 Asm.writeSectionData(&*j, Layout); 1033 // Reset the stream back to what it was before. 1034 setStream(OldStream); 1035 1036 // Calculate our CRC with an initial value of '0', this is not how 1037 // JamCRC is specified but it aligns with the expected output. 1038 JamCRC JC(/*Init=*/0x00000000U); 1039 JC.update(SectionContents); 1040 1041 // Write the section contents to the object file. 1042 getStream() << SectionContents; 1043 1044 // Update the section definition auxiliary symbol to record the CRC. 1045 COFFSection *Sec = SectionMap[&*j]; 1046 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux; 1047 assert(AuxSyms.size() == 1 && 1048 AuxSyms[0].AuxType == ATSectionDefinition); 1049 AuxSymbol &SecDef = AuxSyms[0]; 1050 SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC(); 1051 } 1052 1053 if ((*i)->Relocations.size() > 0) { 1054 assert(getStream().tell() == (*i)->Header.PointerToRelocations && 1055 "Section::PointerToRelocations is insane!"); 1056 1057 if ((*i)->Relocations.size() >= 0xffff) { 1058 // In case of overflow, write actual relocation count as first 1059 // relocation. Including the synthetic reloc itself (+ 1). 1060 COFF::relocation r; 1061 r.VirtualAddress = (*i)->Relocations.size() + 1; 1062 r.SymbolTableIndex = 0; 1063 r.Type = 0; 1064 WriteRelocation(r); 1065 } 1066 1067 for (const auto &Relocation : (*i)->Relocations) 1068 WriteRelocation(Relocation.Data); 1069 } else 1070 assert((*i)->Header.PointerToRelocations == 0 && 1071 "Section::PointerToRelocations is insane!"); 1072 } 1073 } 1074 1075 assert(getStream().tell() == Header.PointerToSymbolTable && 1076 "Header::PointerToSymbolTable is insane!"); 1077 1078 for (auto &Symbol : Symbols) 1079 if (Symbol->getIndex() != -1) 1080 WriteSymbol(*Symbol); 1081 1082 getStream().write(Strings.data().data(), Strings.data().size()); 1083} 1084 1085MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) 1086 : Machine(Machine_) {} 1087 1088// Pin the vtable to this file. 1089void MCWinCOFFObjectTargetWriter::anchor() {} 1090 1091//------------------------------------------------------------------------------ 1092// WinCOFFObjectWriter factory function 1093 1094MCObjectWriter * 1095llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1096 raw_pwrite_stream &OS) { 1097 return new WinCOFFObjectWriter(MOTW, OS); 1098} 1099