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(MCSymbolData const &SymbolData, 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 external = ResSymData.isExternal() || !ResSymData.Fragment; 460 461 coff_symbol->Data.StorageClass = 462 external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC; 463 } 464 465 if (!Base) { 466 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; 467 } else { 468 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base); 469 if (BaseData.Fragment) { 470 COFFSection *Sec = 471 SectionMap[&BaseData.Fragment->getParent()->getSection()]; 472 473 if (coff_symbol->Section && coff_symbol->Section != Sec) 474 report_fatal_error("conflicting sections for symbol"); 475 476 coff_symbol->Section = Sec; 477 } 478 } 479 480 coff_symbol->MCData = &ResSymData; 481 } 482 } 483 484 // Maximum offsets for different string table entry encodings. 485 static const unsigned Max6DecimalOffset = 999999; 486 static const unsigned Max7DecimalOffset = 9999999; 487 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0 488 489 // Encode a string table entry offset in base 64, padded to 6 chars, and 490 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... 491 // Buffer must be at least 8 bytes large. No terminating null appended. 492 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) { 493 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && 494 "Illegal section name encoding for value"); 495 496 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" 497 "abcdefghijklmnopqrstuvwxyz" 498 "0123456789+/"; 499 500 Buffer[0] = '/'; 501 Buffer[1] = '/'; 502 503 char* Ptr = Buffer + 7; 504 for (unsigned i = 0; i < 6; ++i) { 505 unsigned Rem = Value % 64; 506 Value /= 64; 507 *(Ptr--) = Alphabet[Rem]; 508 } 509 } 510 511 /// making a section real involves assigned it a number and putting 512 /// name into the string table if needed 513 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) { 514 if (S.Name.size() > COFF::NameSize) { 515 uint64_t StringTableEntry = Strings.insert(S.Name.c_str()); 516 517 if (StringTableEntry <= Max6DecimalOffset) { 518 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry)); 519 } else if (StringTableEntry <= Max7DecimalOffset) { 520 // With seven digits, we have to skip the terminating null. Because 521 // sprintf always appends it, we use a larger temporary buffer. 522 char buffer[9] = { }; 523 std::sprintf(buffer, "/%d", unsigned(StringTableEntry)); 524 std::memcpy(S.Header.Name, buffer, 8); 525 } else if (StringTableEntry <= MaxBase64Offset) { 526 // Starting with 10,000,000, offsets are encoded as base64. 527 encodeBase64StringEntry(S.Header.Name, StringTableEntry); 528 } else { 529 report_fatal_error("COFF string table is greater than 64 GB."); 530 } 531 } else 532 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); 533 534 S.Number = Number; 535 S.Symbol->Data.SectionNumber = S.Number; 536 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number; 537 } 538 539 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) { 540 if (S.Name.size() > COFF::NameSize) { 541 size_t StringTableEntry = Strings.insert(S.Name.c_str()); 542 543 S.set_name_offset(StringTableEntry); 544 } else 545 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); 546 S.Index = Index; 547 } 548 549 bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData, 550 MCAssembler &Asm) { 551 // This doesn't seem to be right. Strings referred to from the .data section 552 // need symbols so they can be linked to code in the .text section right? 553 554 // return Asm.isSymbolLinkerVisible(SymbolData.getSymbol()); 555 556 // For now, all non-variable symbols are exported, 557 // the linker will sort the rest out for us. 558 return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable(); 559 } 560 561 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { 562 return (S->Header.Characteristics 563 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0; 564 } 565 566 //------------------------------------------------------------------------------ 567 // entity writing methods 568 569 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { 570 WriteLE16(Header.Machine); 571 WriteLE16(Header.NumberOfSections); 572 WriteLE32(Header.TimeDateStamp); 573 WriteLE32(Header.PointerToSymbolTable); 574 WriteLE32(Header.NumberOfSymbols); 575 WriteLE16(Header.SizeOfOptionalHeader); 576 WriteLE16(Header.Characteristics); 577 } 578 579 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { 580 WriteBytes(StringRef(S.Data.Name, COFF::NameSize)); 581 WriteLE32(S.Data.Value); 582 WriteLE16(S.Data.SectionNumber); 583 WriteLE16(S.Data.Type); 584 Write8(S.Data.StorageClass); 585 Write8(S.Data.NumberOfAuxSymbols); 586 WriteAuxiliarySymbols(S.Aux); 587 } 588 589 void WinCOFFObjectWriter::WriteAuxiliarySymbols( 590 const COFFSymbol::AuxiliarySymbols &S) { 591 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end(); 592 i != e; ++i) { 593 switch(i->AuxType) { 594 case ATFunctionDefinition: 595 WriteLE32(i->Aux.FunctionDefinition.TagIndex); 596 WriteLE32(i->Aux.FunctionDefinition.TotalSize); 597 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber); 598 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction); 599 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused)); 600 break; 601 case ATbfAndefSymbol: 602 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1)); 603 WriteLE16(i->Aux.bfAndefSymbol.Linenumber); 604 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2)); 605 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction); 606 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3)); 607 break; 608 case ATWeakExternal: 609 WriteLE32(i->Aux.WeakExternal.TagIndex); 610 WriteLE32(i->Aux.WeakExternal.Characteristics); 611 WriteZeros(sizeof(i->Aux.WeakExternal.unused)); 612 break; 613 case ATFile: 614 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName), 615 sizeof(i->Aux.File.FileName))); 616 break; 617 case ATSectionDefinition: 618 WriteLE32(i->Aux.SectionDefinition.Length); 619 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations); 620 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers); 621 WriteLE32(i->Aux.SectionDefinition.CheckSum); 622 WriteLE16(i->Aux.SectionDefinition.Number); 623 Write8(i->Aux.SectionDefinition.Selection); 624 WriteZeros(sizeof(i->Aux.SectionDefinition.unused)); 625 break; 626 } 627 } 628 } 629 630 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) { 631 WriteBytes(StringRef(S.Name, COFF::NameSize)); 632 633 WriteLE32(S.VirtualSize); 634 WriteLE32(S.VirtualAddress); 635 WriteLE32(S.SizeOfRawData); 636 WriteLE32(S.PointerToRawData); 637 WriteLE32(S.PointerToRelocations); 638 WriteLE32(S.PointerToLineNumbers); 639 WriteLE16(S.NumberOfRelocations); 640 WriteLE16(S.NumberOfLineNumbers); 641 WriteLE32(S.Characteristics); 642 } 643 644 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { 645 WriteLE32(R.VirtualAddress); 646 WriteLE32(R.SymbolTableIndex); 647 WriteLE16(R.Type); 648 } 649 650 //////////////////////////////////////////////////////////////////////////////// 651 // MCObjectWriter interface implementations 652 653 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, 654 const MCAsmLayout &Layout) { 655 // "Define" each section & symbol. This creates section & symbol 656 // entries in the staging area. 657 658 static_assert(sizeof(((COFF::AuxiliaryFile *)nullptr)->FileName) == COFF::SymbolSize, 659 "size mismatch for COFF::AuxiliaryFile::FileName"); 660 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end(); 661 FI != FE; ++FI) { 662 // round up to calculate the number of auxiliary symbols required 663 unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize; 664 665 COFFSymbol *file = createSymbol(".file"); 666 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; 667 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; 668 file->Aux.resize(Count); 669 670 unsigned Offset = 0; 671 unsigned Length = FI->size(); 672 for (auto & Aux : file->Aux) { 673 Aux.AuxType = ATFile; 674 675 if (Length > COFF::SymbolSize) { 676 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize); 677 Length = Length - COFF::SymbolSize; 678 } else { 679 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length); 680 memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length); 681 Length = 0; 682 } 683 684 Offset = Offset + COFF::SymbolSize; 685 } 686 } 687 688 for (const auto & Section : Asm) 689 DefineSection(Section); 690 691 for (MCSymbolData &SD : Asm.symbols()) 692 if (ExportSymbol(SD, Asm)) 693 DefineSymbol(SD, Asm, Layout); 694 } 695 696 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm, 697 const MCAsmLayout &Layout, 698 const MCFragment *Fragment, 699 const MCFixup &Fixup, 700 MCValue Target, 701 bool &IsPCRel, 702 uint64_t &FixedValue) { 703 assert(Target.getSymA() && "Relocation must reference a symbol!"); 704 705 const MCSymbol &Symbol = Target.getSymA()->getSymbol(); 706 const MCSymbol &A = Symbol.AliasedSymbol(); 707 if (!Asm.hasSymbolData(A)) 708 Asm.getContext().FatalError( 709 Fixup.getLoc(), 710 Twine("symbol '") + A.getName() + "' can not be undefined"); 711 712 const MCSymbolData &A_SD = Asm.getSymbolData(A); 713 714 MCSectionData const *SectionData = Fragment->getParent(); 715 716 // Mark this symbol as requiring an entry in the symbol table. 717 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && 718 "Section must already have been defined in ExecutePostLayoutBinding!"); 719 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && 720 "Symbol must already have been defined in ExecutePostLayoutBinding!"); 721 722 COFFSection *coff_section = SectionMap[&SectionData->getSection()]; 723 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; 724 const MCSymbolRefExpr *SymB = Target.getSymB(); 725 bool CrossSection = false; 726 727 if (SymB) { 728 const MCSymbol *B = &SymB->getSymbol(); 729 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 730 if (!B_SD.getFragment()) 731 Asm.getContext().FatalError( 732 Fixup.getLoc(), 733 Twine("symbol '") + B->getName() + 734 "' can not be undefined in a subtraction expression"); 735 736 if (!A_SD.getFragment()) 737 Asm.getContext().FatalError( 738 Fixup.getLoc(), 739 Twine("symbol '") + Symbol.getName() + 740 "' can not be undefined in a subtraction expression"); 741 742 CrossSection = &Symbol.getSection() != &B->getSection(); 743 744 // Offset of the symbol in the section 745 int64_t a = Layout.getSymbolOffset(&B_SD); 746 747 // Ofeset of the relocation in the section 748 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 749 750 FixedValue = b - a; 751 // In the case where we have SymbA and SymB, we just need to store the delta 752 // between the two symbols. Update FixedValue to account for the delta, and 753 // skip recording the relocation. 754 if (!CrossSection) 755 return; 756 } else { 757 FixedValue = Target.getConstant(); 758 } 759 760 COFFRelocation Reloc; 761 762 Reloc.Data.SymbolTableIndex = 0; 763 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); 764 765 // Turn relocations for temporary symbols into section relocations. 766 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { 767 Reloc.Symb = coff_symbol->Section->Symbol; 768 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment) 769 + coff_symbol->MCData->getOffset(); 770 } else 771 Reloc.Symb = coff_symbol; 772 773 ++Reloc.Symb->Relocations; 774 775 Reloc.Data.VirtualAddress += Fixup.getOffset(); 776 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup, 777 CrossSection); 778 779 // FIXME: Can anyone explain what this does other than adjust for the size 780 // of the offset? 781 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && 782 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || 783 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && 784 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) 785 FixedValue += 4; 786 787 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { 788 switch (Reloc.Data.Type) { 789 case COFF::IMAGE_REL_ARM_ABSOLUTE: 790 case COFF::IMAGE_REL_ARM_ADDR32: 791 case COFF::IMAGE_REL_ARM_ADDR32NB: 792 case COFF::IMAGE_REL_ARM_TOKEN: 793 case COFF::IMAGE_REL_ARM_SECTION: 794 case COFF::IMAGE_REL_ARM_SECREL: 795 break; 796 case COFF::IMAGE_REL_ARM_BRANCH11: 797 case COFF::IMAGE_REL_ARM_BLX11: 798 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for 799 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid 800 // for Windows CE). 801 case COFF::IMAGE_REL_ARM_BRANCH24: 802 case COFF::IMAGE_REL_ARM_BLX24: 803 case COFF::IMAGE_REL_ARM_MOV32A: 804 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are 805 // only used for ARM mode code, which is documented as being unsupported 806 // by Windows on ARM. Empirical proof indicates that masm is able to 807 // generate the relocations however the rest of the MSVC toolchain is 808 // unable to handle it. 809 llvm_unreachable("unsupported relocation"); 810 break; 811 case COFF::IMAGE_REL_ARM_MOV32T: 812 break; 813 case COFF::IMAGE_REL_ARM_BRANCH20T: 814 case COFF::IMAGE_REL_ARM_BRANCH24T: 815 case COFF::IMAGE_REL_ARM_BLX23T: 816 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all 817 // perform a 4 byte adjustment to the relocation. Relative branches are 818 // offset by 4 on ARM, however, because there is no RELA relocations, all 819 // branches are offset by 4. 820 FixedValue = FixedValue + 4; 821 break; 822 } 823 } 824 825 if (TargetObjectWriter->recordRelocation(Fixup)) 826 coff_section->Relocations.push_back(Reloc); 827 } 828 829 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm, 830 const MCAsmLayout &Layout) { 831 // Assign symbol and section indexes and offsets. 832 Header.NumberOfSections = 0; 833 834 DenseMap<COFFSection *, uint16_t> SectionIndices; 835 for (auto & Section : Sections) { 836 size_t Number = ++Header.NumberOfSections; 837 SectionIndices[Section.get()] = Number; 838 MakeSectionReal(*Section, Number); 839 } 840 841 Header.NumberOfSymbols = 0; 842 843 for (auto & Symbol : Symbols) { 844 // Update section number & offset for symbols that have them. 845 if (Symbol->Section) 846 Symbol->Data.SectionNumber = Symbol->Section->Number; 847 848 if (Symbol->should_keep()) { 849 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++); 850 851 // Update auxiliary symbol info. 852 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); 853 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; 854 } else 855 Symbol->Index = -1; 856 } 857 858 // Fixup weak external references. 859 for (auto & Symbol : Symbols) { 860 if (Symbol->Other) { 861 assert(Symbol->Index != -1); 862 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); 863 assert(Symbol->Aux[0].AuxType == ATWeakExternal && 864 "Symbol's aux symbol must be a Weak External!"); 865 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index; 866 } 867 } 868 869 // Fixup associative COMDAT sections. 870 for (auto & Section : Sections) { 871 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != 872 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) 873 continue; 874 875 const MCSectionCOFF &MCSec = 876 static_cast<const MCSectionCOFF &>(Section->MCData->getSection()); 877 878 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); 879 assert(COMDAT); 880 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); 881 assert(COMDATSymbol); 882 COFFSection *Assoc = COMDATSymbol->Section; 883 if (!Assoc) 884 report_fatal_error( 885 Twine("Missing associated COMDAT section for section ") + 886 MCSec.getSectionName()); 887 888 // Skip this section if the associated section is unused. 889 if (Assoc->Number == -1) 890 continue; 891 892 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc]; 893 } 894 895 896 // Assign file offsets to COFF object file structures. 897 898 unsigned offset = 0; 899 900 offset += COFF::HeaderSize; 901 offset += COFF::SectionSize * Header.NumberOfSections; 902 903 for (const auto & Section : Asm) { 904 COFFSection *Sec = SectionMap[&Section.getSection()]; 905 906 if (Sec->Number == -1) 907 continue; 908 909 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); 910 911 if (IsPhysicalSection(Sec)) { 912 Sec->Header.PointerToRawData = offset; 913 914 offset += Sec->Header.SizeOfRawData; 915 } 916 917 if (Sec->Relocations.size() > 0) { 918 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; 919 920 if (RelocationsOverflow) { 921 // Signal overflow by setting NumberOfSections to max value. Actual 922 // size is found in reloc #0. Microsoft tools understand this. 923 Sec->Header.NumberOfRelocations = 0xffff; 924 } else { 925 Sec->Header.NumberOfRelocations = Sec->Relocations.size(); 926 } 927 Sec->Header.PointerToRelocations = offset; 928 929 if (RelocationsOverflow) { 930 // Reloc #0 will contain actual count, so make room for it. 931 offset += COFF::RelocationSize; 932 } 933 934 offset += COFF::RelocationSize * Sec->Relocations.size(); 935 936 for (auto & Relocation : Sec->Relocations) { 937 assert(Relocation.Symb->Index != -1); 938 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index; 939 } 940 } 941 942 assert(Sec->Symbol->Aux.size() == 1 && 943 "Section's symbol must have one aux!"); 944 AuxSymbol &Aux = Sec->Symbol->Aux[0]; 945 assert(Aux.AuxType == ATSectionDefinition && 946 "Section's symbol's aux symbol must be a Section Definition!"); 947 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; 948 Aux.Aux.SectionDefinition.NumberOfRelocations = 949 Sec->Header.NumberOfRelocations; 950 Aux.Aux.SectionDefinition.NumberOfLinenumbers = 951 Sec->Header.NumberOfLineNumbers; 952 } 953 954 Header.PointerToSymbolTable = offset; 955 956 // We want a deterministic output. It looks like GNU as also writes 0 in here. 957 Header.TimeDateStamp = 0; 958 959 // Write it all to disk... 960 WriteFileHeader(Header); 961 962 { 963 sections::iterator i, ie; 964 MCAssembler::const_iterator j, je; 965 966 for (auto & Section : Sections) { 967 if (Section->Number != -1) { 968 if (Section->Relocations.size() >= 0xffff) 969 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; 970 WriteSectionHeader(Section->Header); 971 } 972 } 973 974 for (i = Sections.begin(), ie = Sections.end(), 975 j = Asm.begin(), je = Asm.end(); 976 (i != ie) && (j != je); ++i, ++j) { 977 978 if ((*i)->Number == -1) 979 continue; 980 981 if ((*i)->Header.PointerToRawData != 0) { 982 assert(OS.tell() == (*i)->Header.PointerToRawData && 983 "Section::PointerToRawData is insane!"); 984 985 Asm.writeSectionData(j, Layout); 986 } 987 988 if ((*i)->Relocations.size() > 0) { 989 assert(OS.tell() == (*i)->Header.PointerToRelocations && 990 "Section::PointerToRelocations is insane!"); 991 992 if ((*i)->Relocations.size() >= 0xffff) { 993 // In case of overflow, write actual relocation count as first 994 // relocation. Including the synthetic reloc itself (+ 1). 995 COFF::relocation r; 996 r.VirtualAddress = (*i)->Relocations.size() + 1; 997 r.SymbolTableIndex = 0; 998 r.Type = 0; 999 WriteRelocation(r); 1000 } 1001 1002 for (const auto & Relocation : (*i)->Relocations) 1003 WriteRelocation(Relocation.Data); 1004 } else 1005 assert((*i)->Header.PointerToRelocations == 0 && 1006 "Section::PointerToRelocations is insane!"); 1007 } 1008 } 1009 1010 assert(OS.tell() == Header.PointerToSymbolTable && 1011 "Header::PointerToSymbolTable is insane!"); 1012 1013 for (auto & Symbol : Symbols) 1014 if (Symbol->Index != -1) 1015 WriteSymbol(*Symbol); 1016 1017 OS.write((char const *)&Strings.Data.front(), Strings.Data.size()); 1018 } 1019 1020 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) : 1021 Machine(Machine_) { 1022 } 1023 1024 // Pin the vtable to this file. 1025 void MCWinCOFFObjectTargetWriter::anchor() {} 1026 1027 //------------------------------------------------------------------------------ 1028 // WinCOFFObjectWriter factory function 1029 1030 namespace llvm { 1031 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, 1032 raw_ostream &OS) { 1033 return new WinCOFFObjectWriter(MOTW, OS); 1034 } 1035 } 1036
