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/Support/COFF.h" 30 #include "llvm/Support/Debug.h" 31 #include "llvm/Support/ErrorHandling.h" 32 #include "llvm/Support/TimeValue.h" 33 #include <cstdio> 34 35 using namespace llvm; 36 37 #define DEBUG_TYPE "WinCOFFObjectWriter" 38 39 namespace { 40 typedef SmallString<COFF::NameSize> name; 41 42 enum AuxiliaryType { 43 ATFunctionDefinition, 44 ATbfAndefSymbol, 45 ATWeakExternal, 46 ATFile, 47 ATSectionDefinition 48 }; 49 50 struct AuxSymbol { 51 AuxiliaryType AuxType; 52 COFF::Auxiliary Aux; 53 }; 54 55 class COFFSymbol; 56 class COFFSection; 57 58 class COFFSymbol { 59 public: 60 COFF::symbol Data; 61 62 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols; 63 64 name Name; 65 int Index; 66 AuxiliarySymbols Aux; 67 COFFSymbol *Other; 68 COFFSection *Section; 69 int Relocations; 70 71 MCSymbolData const *MCData; 72 73 COFFSymbol(StringRef name); 74 size_t size() const; 75 void set_name_offset(uint32_t Offset); 76 77 bool should_keep() const; 78 }; 79 80 // This class contains staging data for a COFF relocation entry. 81 struct COFFRelocation { 82 COFF::relocation Data; 83 COFFSymbol *Symb; 84 85 COFFRelocation() : Symb(nullptr) {} 86 static size_t size() { return COFF::RelocationSize; } 87 }; 88 89 typedef std::vector<COFFRelocation> relocations; 90 91 class COFFSection { 92 public: 93 COFF::section Header; 94 95 std::string Name; 96 int Number; 97 MCSectionData const *MCData; 98 COFFSymbol *Symbol; 99 relocations Relocations; 100 101 COFFSection(StringRef name); 102 static size_t size(); 103 }; 104 105 // This class holds the COFF string table. 106 class StringTable { 107 typedef StringMap<size_t> map; 108 map Map; 109 110 void update_length(); 111 public: 112 std::vector<char> Data; 113 114 StringTable(); 115 size_t size() const; 116 size_t insert(StringRef String); 117 }; 118 119 class WinCOFFObjectWriter : public MCObjectWriter { 120 public: 121 122 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols; 123 typedef std::vector<std::unique_ptr<COFFSection>> sections; 124 125 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map; 126 typedef DenseMap<MCSection const *, COFFSection *> section_map; 127 128 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter; 129 130 // Root level file contents. 131 COFF::header Header; 132 sections Sections; 133 symbols Symbols; 134 StringTable Strings; 135 136 // Maps used during object file creation. 137 section_map SectionMap; 138 symbol_map SymbolMap; 139 140 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS); 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 MakeSymbolReal(COFFSymbol &S, size_t Index); 154 void MakeSectionReal(COFFSection &S, size_t Number); 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 const &Value) { 183 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data); 184 Ptr[0] = (Value & 0x000000FF) >> 0; 185 Ptr[1] = (Value & 0x0000FF00) >> 8; 186 Ptr[2] = (Value & 0x00FF0000) >> 16; 187 Ptr[3] = (Value & 0xFF000000) >> 24; 188 } 189 190 //------------------------------------------------------------------------------ 191 // Symbol class implementation 192 193 COFFSymbol::COFFSymbol(StringRef name) 194 : Name(name.begin(), name.end()) 195 , Other(nullptr) 196 , Section(nullptr) 197 , Relocations(0) 198 , MCData(nullptr) { 199 memset(&Data, 0, sizeof(Data)); 200 } 201 202 size_t COFFSymbol::size() const { 203 return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize); 204 } 205 206 // In the case that the name does not fit within 8 bytes, the offset 207 // into the string table is stored in the last 4 bytes instead, leaving 208 // the first 4 bytes as 0. 209 void COFFSymbol::set_name_offset(uint32_t Offset) { 210 write_uint32_le(Data.Name + 0, 0); 211 write_uint32_le(Data.Name + 4, Offset); 212 } 213 214 /// logic to decide if the symbol should be reported in the symbol table 215 bool COFFSymbol::should_keep() const { 216 // no section means its external, keep it 217 if (!Section) 218 return true; 219 220 // if it has relocations pointing at it, keep it 221 if (Relocations > 0) { 222 assert(Section->Number != -1 && "Sections with relocations must be real!"); 223 return true; 224 } 225 226 // if the section its in is being droped, drop it 227 if (Section->Number == -1) 228 return false; 229 230 // if it is the section symbol, keep it 231 if (Section->Symbol == this) 232 return true; 233 234 // if its temporary, drop it 235 if (MCData && MCData->getSymbol().isTemporary()) 236 return false; 237 238 // otherwise, keep it 239 return true; 240 } 241 242 //------------------------------------------------------------------------------ 243 // Section class implementation 244 245 COFFSection::COFFSection(StringRef name) 246 : Name(name) 247 , MCData(nullptr) 248 , Symbol(nullptr) { 249 memset(&Header, 0, sizeof(Header)); 250 } 251 252 size_t COFFSection::size() { 253 return COFF::SectionSize; 254 } 255 256 //------------------------------------------------------------------------------ 257 // StringTable class implementation 258 259 /// Write the length of the string table into Data. 260 /// The length of the string table includes uint32 length header. 261 void StringTable::update_length() { 262 write_uint32_le(&Data.front(), Data.size()); 263 } 264 265 StringTable::StringTable() { 266 // The string table data begins with the length of the entire string table 267 // including the length header. Allocate space for this header. 268 Data.resize(4); 269 update_length(); 270 } 271 272 size_t StringTable::size() const { 273 return Data.size(); 274 } 275 276 /// Add String to the table iff it is not already there. 277 /// @returns the index into the string table where the string is now located. 278 size_t StringTable::insert(StringRef String) { 279 map::iterator i = Map.find(String); 280 281 if (i != Map.end()) 282 return i->second; 283 284 size_t Offset = Data.size(); 285 286 // Insert string data into string table. 287 Data.insert(Data.end(), String.begin(), String.end()); 288 Data.push_back('\0'); 289 290 // Put a reference to it in the map. 291 Map[String] = Offset; 292 293 // Update the internal length field. 294 update_length(); 295 296 return Offset; 297 } 298 299 //------------------------------------------------------------------------------ 300 // WinCOFFObjectWriter class implementation 301 302 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 303 raw_ostream &OS) 304 : MCObjectWriter(OS, true) 305 , TargetObjectWriter(MOTW) { 306 memset(&Header, 0, sizeof(Header)); 307 308 Header.Machine = TargetObjectWriter->getMachine(); 309 } 310 311 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { 312 return createCOFFEntity<COFFSymbol>(Name, Symbols); 313 } 314 315 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){ 316 symbol_map::iterator i = SymbolMap.find(Symbol); 317 if (i != SymbolMap.end()) 318 return i->second; 319 COFFSymbol *RetSymbol 320 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols); 321 SymbolMap[Symbol] = RetSymbol; 322 return RetSymbol; 323 } 324 325 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { 326 return createCOFFEntity<COFFSection>(Name, Sections); 327 } 328 329 /// A template used to lookup or create a symbol/section, and initialize it if 330 /// needed. 331 template <typename object_t, typename list_t> 332 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, 333 list_t &List) { 334 List.push_back(make_unique<object_t>(Name)); 335 336 return List.back().get(); 337 } 338 339 /// This function takes a section data object from the assembler 340 /// and creates the associated COFF section staging object. 341 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) { 342 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF 343 && "Got non-COFF section in the COFF backend!"); 344 // FIXME: Not sure how to verify this (at least in a debug build). 345 MCSectionCOFF const &Sec = 346 static_cast<MCSectionCOFF const &>(SectionData.getSection()); 347 348 COFFSection *coff_section = createSection(Sec.getSectionName()); 349 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName()); 350 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { 351 if (const MCSymbol *S = Sec.getCOMDATSymbol()) { 352 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); 353 if (COMDATSymbol->Section) 354 report_fatal_error("two sections have the same comdat"); 355 COMDATSymbol->Section = coff_section; 356 } 357 } 358 359 coff_section->Symbol = coff_symbol; 360 coff_symbol->Section = coff_section; 361 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; 362 363 // In this case the auxiliary symbol is a Section Definition. 364 coff_symbol->Aux.resize(1); 365 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 366 coff_symbol->Aux[0].AuxType = ATSectionDefinition; 367 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection(); 368 369 coff_section->Header.Characteristics = Sec.getCharacteristics(); 370 371 uint32_t &Characteristics = coff_section->Header.Characteristics; 372 switch (SectionData.getAlignment()) { 373 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break; 374 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break; 375 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break; 376 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break; 377 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break; 378 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break; 379 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break; 380 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break; 381 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break; 382 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break; 383 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break; 384 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break; 385 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break; 386 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break; 387 default: 388 llvm_unreachable("unsupported section alignment"); 389 } 390 391 // Bind internal COFF section to MC section. 392 coff_section->MCData = &SectionData; 393 SectionMap[&SectionData.getSection()] = coff_section; 394 } 395 396 static uint64_t getSymbolValue(const MCSymbolData &Data, 397 const MCAsmLayout &Layout) { 398 if (Data.isCommon() && Data.isExternal()) 399 return Data.getCommonSize(); 400 401 uint64_t Res; 402 if (!Layout.getSymbolOffset(&Data, Res)) 403 return 0; 404 405 return Res; 406 } 407 408 /// This function takes a symbol data object from the assembler 409 /// and creates the associated COFF symbol staging object. 410 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData, 411 MCAssembler &Assembler, 412 const MCAsmLayout &Layout) { 413 MCSymbol const &Symbol = SymbolData.getSymbol(); 414 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol); 415 SymbolMap[&Symbol] = coff_symbol; 416 417 if (SymbolData.getFlags() & COFF::SF_WeakExternal) { 418 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; 419 420 if (Symbol.isVariable()) { 421 const MCSymbolRefExpr *SymRef = 422 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); 423 424 if (!SymRef) 425 report_fatal_error("Weak externals may only alias symbols"); 426 427 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol()); 428 } else { 429 std::string WeakName = std::string(".weak.") 430 + Symbol.getName().str() 431 + ".default"; 432 COFFSymbol *WeakDefault = createSymbol(WeakName); 433 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 434 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL; 435 WeakDefault->Data.Type = 0; 436 WeakDefault->Data.Value = 0; 437 coff_symbol->Other = WeakDefault; 438 } 439 440 // Setup the Weak External auxiliary symbol. 441 coff_symbol->Aux.resize(1); 442 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0])); 443 coff_symbol->Aux[0].AuxType = ATWeakExternal; 444 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0; 445 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics = 446 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; 447 448 coff_symbol->MCData = &SymbolData; 449 } else { 450 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol); 451 const MCSymbol *Base = Layout.getBaseSymbol(Symbol); 452 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout); 453 454 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0; 455 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16; 456 457 // If no storage class was specified in the streamer, define it here. 458 if (coff_symbol->Data.StorageClass == 0) { 459 bool IsExternal = 460 ResSymData.isExternal() || 461 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable()); 462 463 coff_symbol->Data.StorageClass = IsExternal 464 ? COFF::IMAGE_SYM_CLASS_EXTERNAL 465 : COFF::IMAGE_SYM_CLASS_STATIC; 466 } 467 468 if (!Base) { 469 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 470 } else { 471 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base); 472 if (BaseData.Fragment) { 473 COFFSection *Sec = 474 SectionMap[&BaseData.Fragment->getParent()->getSection()]; 475 476 if (coff_symbol->Section && coff_symbol->Section != Sec) 477 report_fatal_error("conflicting sections for symbol"); 478 479 coff_symbol->Section = Sec; 480 } 481 } 482 483 coff_symbol->MCData = &ResSymData; 484 } 485 } 486 487 // Maximum offsets for different string table entry encodings. 488 static const unsigned Max6DecimalOffset = 999999; 489 static const unsigned Max7DecimalOffset = 9999999; 490 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 491 492 // Encode a string table entry offset in base 64, padded to 6 chars, and 493 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 494 // Buffer must be at least 8 bytes large. No terminating null appended. 495 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) { 496 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 497 "Illegal section name encoding for value"); 498 499 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 500 "abcdefghijklmnopqrstuvwxyz" 501 "0123456789+/"; 502 503 Buffer[0] = '/'; 504 Buffer[1] = '/'; 505 506 char* Ptr = Buffer + 7; 507 for (unsigned i = 0; i < 6; ++i) { 508 unsigned Rem = Value % 64; 509 Value /= 64; 510 *(Ptr--) = Alphabet[Rem]; 511 } 512 } 513 514 /// making a section real involves assigned it a number and putting 515 /// name into the string table if needed 516 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) { 517 if (S.Name.size() > COFF::NameSize) { 518 uint64_t StringTableEntry = Strings.insert(S.Name.c_str()); 519 520 if (StringTableEntry <= Max6DecimalOffset) { 521 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 522 } else if (StringTableEntry <= Max7DecimalOffset) { 523 // With seven digits, we have to skip the terminating null. Because 524 // sprintf always appends it, we use a larger temporary buffer. 525 char buffer[9] = { }; 526 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 527 std::memcpy(S.Header.Name, buffer, 8); 528 } else if (StringTableEntry <= MaxBase64Offset) { 529 // Starting with 10,000,000, offsets are encoded as base64. 530 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 531 } else { 532 report_fatal_error("COFF string table is greater than 64 GB."); 533 } 534 } else 535 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 536 537 S.Number = Number; 538 S.Symbol->Data.SectionNumber = S.Number; 539 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number; 540 } 541 542 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) { 543 if (S.Name.size() > COFF::NameSize) { 544 size_t StringTableEntry = Strings.insert(S.Name.c_str()); 545 546 S.set_name_offset(StringTableEntry); 547 } else 548 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 549 S.Index = Index; 550 } 551 552 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol, 553 MCAssembler &Asm) { 554 // This doesn't seem to be right. Strings referred to from the .data section 555 // need symbols so they can be linked to code in the .text section right? 556 557 // return Asm.isSymbolLinkerVisible(Symbol); 558 559 // Non-temporary labels should always be visible to the linker. 560 if (!Symbol.isTemporary()) 561 return true; 562 563 // Absolute temporary labels are never visible. 564 if (!Symbol.isInSection()) 565 return false; 566 567 // For now, all non-variable symbols are exported, 568 // the linker will sort the rest out for us. 569 return !Symbol.isVariable(); 570 } 571 572 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 573 return (S->Header.Characteristics 574 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0; 575 } 576 577 //------------------------------------------------------------------------------ 578 // entity writing methods 579 580 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 581 WriteLE16(Header.Machine); 582 WriteLE16(Header.NumberOfSections); 583 WriteLE32(Header.TimeDateStamp); 584 WriteLE32(Header.PointerToSymbolTable); 585 WriteLE32(Header.NumberOfSymbols); 586 WriteLE16(Header.SizeOfOptionalHeader); 587 WriteLE16(Header.Characteristics); 588 } 589 590 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 591 WriteBytes(StringRef(S.Data.Name, COFF::NameSize)); 592 WriteLE32(S.Data.Value); 593 WriteLE16(S.Data.SectionNumber); 594 WriteLE16(S.Data.Type); 595 Write8(S.Data.StorageClass); 596 Write8(S.Data.NumberOfAuxSymbols); 597 WriteAuxiliarySymbols(S.Aux); 598 } 599 600 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 601 const COFFSymbol::AuxiliarySymbols &S) { 602 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 603 i != e; ++i) { 604 switch(i->AuxType) { 605 case ATFunctionDefinition: 606 WriteLE32(i->Aux.FunctionDefinition.TagIndex); 607 WriteLE32(i->Aux.FunctionDefinition.TotalSize); 608 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 609 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 610 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 611 break; 612 case ATbfAndefSymbol: 613 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 614 WriteLE16(i->Aux.bfAndefSymbol.Linenumber); 615 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 616 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 617 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 618 break; 619 case ATWeakExternal: 620 WriteLE32(i->Aux.WeakExternal.TagIndex); 621 WriteLE32(i->Aux.WeakExternal.Characteristics); 622 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 623 break; 624 case ATFile: 625 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName), 626 sizeof(i->Aux.File.FileName))); 627 break; 628 case ATSectionDefinition: 629 WriteLE32(i->Aux.SectionDefinition.Length); 630 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations); 631 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 632 WriteLE32(i->Aux.SectionDefinition.CheckSum); 633 WriteLE16(i->Aux.SectionDefinition.Number); 634 Write8(i->Aux.SectionDefinition.Selection); 635 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 636 break; 637 } 638 } 639 } 640 641 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) { 642 WriteBytes(StringRef(S.Name, COFF::NameSize)); 643 644 WriteLE32(S.VirtualSize); 645 WriteLE32(S.VirtualAddress); 646 WriteLE32(S.SizeOfRawData); 647 WriteLE32(S.PointerToRawData); 648 WriteLE32(S.PointerToRelocations); 649 WriteLE32(S.PointerToLineNumbers); 650 WriteLE16(S.NumberOfRelocations); 651 WriteLE16(S.NumberOfLineNumbers); 652 WriteLE32(S.Characteristics); 653 } 654 655 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 656 WriteLE32(R.VirtualAddress); 657 WriteLE32(R.SymbolTableIndex); 658 WriteLE16(R.Type); 659 } 660 661 //////////////////////////////////////////////////////////////////////////////// 662 // MCObjectWriter interface implementations 663 664 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 665 const MCAsmLayout &Layout) { 666 // "Define" each section & symbol. This creates section & symbol 667 // entries in the staging area. 668 669 static_assert(sizeof(((COFF::AuxiliaryFile *)nullptr)->FileName) == COFF::SymbolSize, 670 "size mismatch for COFF::AuxiliaryFile::FileName"); 671 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end(); 672 FI != FE; ++FI) { 673 // round up to calculate the number of auxiliary symbols required 674 unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize; 675 676 COFFSymbol *file = createSymbol(".file"); 677 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 678 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 679 file->Aux.resize(Count); 680 681 unsigned Offset = 0; 682 unsigned Length = FI->size(); 683 for (auto & Aux : file->Aux) { 684 Aux.AuxType = ATFile; 685 686 if (Length > COFF::SymbolSize) { 687 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize); 688 Length = Length - COFF::SymbolSize; 689 } else { 690 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length); 691 memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length); 692 Length = 0; 693 } 694 695 Offset = Offset + COFF::SymbolSize; 696 } 697 } 698 699 for (const auto & Section : Asm) 700 DefineSection(Section); 701 702 for (MCSymbolData &SD : Asm.symbols()) 703 if (ExportSymbol(SD.getSymbol(), Asm)) 704 DefineSymbol(SD, Asm, Layout); 705 } 706 707 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm, 708 const MCAsmLayout &Layout, 709 const MCFragment *Fragment, 710 const MCFixup &Fixup, 711 MCValue Target, 712 bool &IsPCRel, 713 uint64_t &FixedValue) { 714 assert(Target.getSymA() && "Relocation must reference a symbol!"); 715 716 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 717 const MCSymbol &A = Symbol.AliasedSymbol(); 718 if (!Asm.hasSymbolData(A)) 719 Asm.getContext().FatalError( 720 Fixup.getLoc(), 721 Twine("symbol '") + A.getName() + "' can not be undefined"); 722 723 const MCSymbolData &A_SD = Asm.getSymbolData(A); 724 725 MCSectionData const *SectionData = Fragment->getParent(); 726 727 // Mark this symbol as requiring an entry in the symbol table. 728 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && 729 "Section must already have been defined in ExecutePostLayoutBinding!"); 730 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && 731 "Symbol must already have been defined in ExecutePostLayoutBinding!"); 732 733 COFFSection *coff_section = SectionMap[&SectionData->getSection()]; 734 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; 735 const MCSymbolRefExpr *SymB = Target.getSymB(); 736 bool CrossSection = false; 737 738 if (SymB) { 739 const MCSymbol *B = &SymB->getSymbol(); 740 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 741 if (!B_SD.getFragment()) 742 Asm.getContext().FatalError( 743 Fixup.getLoc(), 744 Twine("symbol '") + B->getName() + 745 "' can not be undefined in a subtraction expression"); 746 747 if (!A_SD.getFragment()) 748 Asm.getContext().FatalError( 749 Fixup.getLoc(), 750 Twine("symbol '") + Symbol.getName() + 751 "' can not be undefined in a subtraction expression"); 752 753 CrossSection = &Symbol.getSection() != &B->getSection(); 754 755 // Offset of the symbol in the section 756 int64_t a = Layout.getSymbolOffset(&B_SD); 757 758 // Ofeset of the relocation in the section 759 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 760 761 FixedValue = b - a; 762 // In the case where we have SymbA and SymB, we just need to store the delta 763 // between the two symbols. Update FixedValue to account for the delta, and 764 // skip recording the relocation. 765 if (!CrossSection) 766 return; 767 } else { 768 FixedValue = Target.getConstant(); 769 } 770 771 COFFRelocation Reloc; 772 773 Reloc.Data.SymbolTableIndex = 0; 774 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 775 776 // Turn relocations for temporary symbols into section relocations. 777 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { 778 Reloc.Symb = coff_symbol->Section->Symbol; 779 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment) 780 + coff_symbol->MCData->getOffset(); 781 } else 782 Reloc.Symb = coff_symbol; 783 784 ++Reloc.Symb->Relocations; 785 786 Reloc.Data.VirtualAddress += Fixup.getOffset(); 787 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup, 788 CrossSection); 789 790 // FIXME: Can anyone explain what this does other than adjust for the size 791 // of the offset? 792 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 793 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 794 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 795 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 796 FixedValue += 4; 797 798 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 799 switch (Reloc.Data.Type) { 800 case COFF::IMAGE_REL_ARM_ABSOLUTE: 801 case COFF::IMAGE_REL_ARM_ADDR32: 802 case COFF::IMAGE_REL_ARM_ADDR32NB: 803 case COFF::IMAGE_REL_ARM_TOKEN: 804 case COFF::IMAGE_REL_ARM_SECTION: 805 case COFF::IMAGE_REL_ARM_SECREL: 806 break; 807 case COFF::IMAGE_REL_ARM_BRANCH11: 808 case COFF::IMAGE_REL_ARM_BLX11: 809 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 810 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 811 // for Windows CE). 812 case COFF::IMAGE_REL_ARM_BRANCH24: 813 case COFF::IMAGE_REL_ARM_BLX24: 814 case COFF::IMAGE_REL_ARM_MOV32A: 815 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 816 // only used for ARM mode code, which is documented as being unsupported 817 // by Windows on ARM. Empirical proof indicates that masm is able to 818 // generate the relocations however the rest of the MSVC toolchain is 819 // unable to handle it. 820 llvm_unreachable("unsupported relocation"); 821 break; 822 case COFF::IMAGE_REL_ARM_MOV32T: 823 break; 824 case COFF::IMAGE_REL_ARM_BRANCH20T: 825 case COFF::IMAGE_REL_ARM_BRANCH24T: 826 case COFF::IMAGE_REL_ARM_BLX23T: 827 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 828 // perform a 4 byte adjustment to the relocation. Relative branches are 829 // offset by 4 on ARM, however, because there is no RELA relocations, all 830 // branches are offset by 4. 831 FixedValue = FixedValue + 4; 832 break; 833 } 834 } 835 836 if (TargetObjectWriter->recordRelocation(Fixup)) 837 coff_section->Relocations.push_back(Reloc); 838 } 839 840 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm, 841 const MCAsmLayout &Layout) { 842 // Assign symbol and section indexes and offsets. 843 Header.NumberOfSections = 0; 844 845 DenseMap<COFFSection *, uint16_t> SectionIndices; 846 for (auto & Section : Sections) { 847 size_t Number = ++Header.NumberOfSections; 848 SectionIndices[Section.get()] = Number; 849 MakeSectionReal(*Section, Number); 850 } 851 852 Header.NumberOfSymbols = 0; 853 854 for (auto & Symbol : Symbols) { 855 // Update section number & offset for symbols that have them. 856 if (Symbol->Section) 857 Symbol->Data.SectionNumber = Symbol->Section->Number; 858 859 if (Symbol->should_keep()) { 860 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++); 861 862 // Update auxiliary symbol info. 863 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 864 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 865 } else 866 Symbol->Index = -1; 867 } 868 869 // Fixup weak external references. 870 for (auto & Symbol : Symbols) { 871 if (Symbol->Other) { 872 assert(Symbol->Index != -1); 873 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 874 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 875 "Symbol's aux symbol must be a Weak External!"); 876 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index; 877 } 878 } 879 880 // Fixup associative COMDAT sections. 881 for (auto & Section : Sections) { 882 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 883 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 884 continue; 885 886 const MCSectionCOFF &MCSec = 887 static_cast<const MCSectionCOFF &>(Section->MCData->getSection()); 888 889 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 890 assert(COMDAT); 891 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 892 assert(COMDATSymbol); 893 COFFSection *Assoc = COMDATSymbol->Section; 894 if (!Assoc) 895 report_fatal_error( 896 Twine("Missing associated COMDAT section for section ") + 897 MCSec.getSectionName()); 898 899 // Skip this section if the associated section is unused. 900 if (Assoc->Number == -1) 901 continue; 902 903 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc]; 904 } 905 906 907 // Assign file offsets to COFF object file structures. 908 909 unsigned offset = 0; 910 911 offset += COFF::HeaderSize; 912 offset += COFF::SectionSize * Header.NumberOfSections; 913 914 for (const auto & Section : Asm) { 915 COFFSection *Sec = SectionMap[&Section.getSection()]; 916 917 if (Sec->Number == -1) 918 continue; 919 920 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 921 922 if (IsPhysicalSection(Sec)) { 923 Sec->Header.PointerToRawData = offset; 924 925 offset += Sec->Header.SizeOfRawData; 926 } 927 928 if (Sec->Relocations.size() > 0) { 929 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 930 931 if (RelocationsOverflow) { 932 // Signal overflow by setting NumberOfSections to max value. Actual 933 // size is found in reloc #0. Microsoft tools understand this. 934 Sec->Header.NumberOfRelocations = 0xffff; 935 } else { 936 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 937 } 938 Sec->Header.PointerToRelocations = offset; 939 940 if (RelocationsOverflow) { 941 // Reloc #0 will contain actual count, so make room for it. 942 offset += COFF::RelocationSize; 943 } 944 945 offset += COFF::RelocationSize * Sec->Relocations.size(); 946 947 for (auto & Relocation : Sec->Relocations) { 948 assert(Relocation.Symb->Index != -1); 949 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index; 950 } 951 } 952 953 assert(Sec->Symbol->Aux.size() == 1 && 954 "Section's symbol must have one aux!"); 955 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 956 assert(Aux.AuxType == ATSectionDefinition && 957 "Section's symbol's aux symbol must be a Section Definition!"); 958 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 959 Aux.Aux.SectionDefinition.NumberOfRelocations = 960 Sec->Header.NumberOfRelocations; 961 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 962 Sec->Header.NumberOfLineNumbers; 963 } 964 965 Header.PointerToSymbolTable = offset; 966 967 // We want a deterministic output. It looks like GNU as also writes 0 in here. 968 Header.TimeDateStamp = 0; 969 970 // Write it all to disk... 971 WriteFileHeader(Header); 972 973 { 974 sections::iterator i, ie; 975 MCAssembler::const_iterator j, je; 976 977 for (auto & Section : Sections) { 978 if (Section->Number != -1) { 979 if (Section->Relocations.size() >= 0xffff) 980 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 981 WriteSectionHeader(Section->Header); 982 } 983 } 984 985 for (i = Sections.begin(), ie = Sections.end(), 986 j = Asm.begin(), je = Asm.end(); 987 (i != ie) && (j != je); ++i, ++j) { 988 989 if ((*i)->Number == -1) 990 continue; 991 992 if ((*i)->Header.PointerToRawData != 0) { 993 assert(OS.tell() == (*i)->Header.PointerToRawData && 994 "Section::PointerToRawData is insane!"); 995 996 Asm.writeSectionData(j, Layout); 997 } 998 999 if ((*i)->Relocations.size() > 0) { 1000 assert(OS.tell() == (*i)->Header.PointerToRelocations && 1001 "Section::PointerToRelocations is insane!"); 1002 1003 if ((*i)->Relocations.size() >= 0xffff) { 1004 // In case of overflow, write actual relocation count as first 1005 // relocation. Including the synthetic reloc itself (+ 1). 1006 COFF::relocation r; 1007 r.VirtualAddress = (*i)->Relocations.size() + 1; 1008 r.SymbolTableIndex = 0; 1009 r.Type = 0; 1010 WriteRelocation(r); 1011 } 1012 1013 for (const auto & Relocation : (*i)->Relocations) 1014 WriteRelocation(Relocation.Data); 1015 } else 1016 assert((*i)->Header.PointerToRelocations == 0 && 1017 "Section::PointerToRelocations is insane!"); 1018 } 1019 } 1020 1021 assert(OS.tell() == Header.PointerToSymbolTable && 1022 "Header::PointerToSymbolTable is insane!"); 1023 1024 for (auto & Symbol : Symbols) 1025 if (Symbol->Index != -1) 1026 WriteSymbol(*Symbol); 1027 1028 OS.write((char const *)&Strings.Data.front(), Strings.Data.size()); 1029 } 1030 1031 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) : 1032 Machine(Machine_) { 1033 } 1034 1035 // Pin the vtable to this file. 1036 void MCWinCOFFObjectTargetWriter::anchor() {} 1037 1038 //------------------------------------------------------------------------------ 1039 // WinCOFFObjectWriter factory function 1040 1041 namespace llvm { 1042 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1043 raw_ostream &OS) { 1044 return new WinCOFFObjectWriter(MOTW, OS); 1045 } 1046 } 1047