1 //===- llvm/MC/WinCOFFObjectWriter.cpp ------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains an implementation of a Win32 COFF object file writer.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallString.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/BinaryFormat/COFF.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/MCFixup.h"
26 #include "llvm/MC/MCFragment.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCSectionCOFF.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/MC/MCSymbolCOFF.h"
32 #include "llvm/MC/MCValue.h"
33 #include "llvm/MC/MCWinCOFFObjectWriter.h"
34 #include "llvm/MC/StringTableBuilder.h"
35 #include "llvm/Support/Casting.h"
36 #include "llvm/Support/Endian.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/JamCRC.h"
39 #include "llvm/Support/MathExtras.h"
40 #include "llvm/Support/raw_ostream.h"
52 using llvm::support::endian::write32le;
54 #define DEBUG_TYPE "WinCOFFObjectWriter"
58 using name = SmallString<COFF::NameSize>;
69 AuxiliaryType AuxType;
77 COFF::symbol Data = {};
79 using AuxiliarySymbols = SmallVector<AuxSymbol, 1>;
84 COFFSymbol *Other = nullptr;
85 COFFSection *Section = nullptr;
87 const MCSymbol *MC = nullptr;
89 COFFSymbol(StringRef Name) : Name(Name) {}
91 void set_name_offset(uint32_t Offset);
93 int64_t getIndex() const { return Index; }
94 void setIndex(int Value) {
97 MC->setIndex(static_cast<uint32_t>(Value));
101 // This class contains staging data for a COFF relocation entry.
102 struct COFFRelocation {
103 COFF::relocation Data;
104 COFFSymbol *Symb = nullptr;
106 COFFRelocation() = default;
108 static size_t size() { return COFF::RelocationSize; }
111 using relocations = std::vector<COFFRelocation>;
115 COFF::section Header = {};
119 MCSectionCOFF const *MCSection = nullptr;
120 COFFSymbol *Symbol = nullptr;
121 relocations Relocations;
123 COFFSection(StringRef Name) : Name(Name) {}
126 class WinCOFFObjectWriter : public MCObjectWriter {
128 using symbols = std::vector<std::unique_ptr<COFFSymbol>>;
129 using sections = std::vector<std::unique_ptr<COFFSection>>;
131 using symbol_map = DenseMap<MCSymbol const *, COFFSymbol *>;
132 using section_map = DenseMap<MCSection const *, COFFSection *>;
134 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
136 // Root level file contents.
137 COFF::header Header = {};
140 StringTableBuilder Strings{StringTableBuilder::WinCOFF};
142 // Maps used during object file creation.
143 section_map SectionMap;
144 symbol_map SymbolMap;
148 WinCOFFObjectWriter(std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW,
149 raw_pwrite_stream &OS);
151 void reset() override {
152 memset(&Header, 0, sizeof(Header));
153 Header.Machine = TargetObjectWriter->getMachine();
159 MCObjectWriter::reset();
162 COFFSymbol *createSymbol(StringRef Name);
163 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
164 COFFSection *createSection(StringRef Name);
166 void defineSection(MCSectionCOFF const &Sec);
168 COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
169 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
170 const MCAsmLayout &Layout);
172 void SetSymbolName(COFFSymbol &S);
173 void SetSectionName(COFFSection &S);
175 bool IsPhysicalSection(COFFSection *S);
177 // Entity writing methods.
179 void WriteFileHeader(const COFF::header &Header);
180 void WriteSymbol(const COFFSymbol &S);
181 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
182 void writeSectionHeaders();
183 void WriteRelocation(const COFF::relocation &R);
184 uint32_t writeSectionContents(MCAssembler &Asm, const MCAsmLayout &Layout,
185 const MCSection &MCSec);
186 void writeSection(MCAssembler &Asm, const MCAsmLayout &Layout,
187 const COFFSection &Sec, const MCSection &MCSec);
189 // MCObjectWriter interface implementation.
191 void executePostLayoutBinding(MCAssembler &Asm,
192 const MCAsmLayout &Layout) override;
194 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
195 const MCSymbol &SymA,
196 const MCFragment &FB, bool InSet,
197 bool IsPCRel) const override;
199 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
200 const MCFragment *Fragment, const MCFixup &Fixup,
201 MCValue Target, uint64_t &FixedValue) override;
203 void createFileSymbols(MCAssembler &Asm);
204 void assignSectionNumbers();
205 void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout);
207 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
210 } // end anonymous namespace
212 //------------------------------------------------------------------------------
213 // Symbol class implementation
215 // In the case that the name does not fit within 8 bytes, the offset
216 // into the string table is stored in the last 4 bytes instead, leaving
217 // the first 4 bytes as 0.
218 void COFFSymbol::set_name_offset(uint32_t Offset) {
219 write32le(Data.Name + 0, 0);
220 write32le(Data.Name + 4, Offset);
223 //------------------------------------------------------------------------------
224 // WinCOFFObjectWriter class implementation
226 WinCOFFObjectWriter::WinCOFFObjectWriter(
227 std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
228 : MCObjectWriter(OS, true), TargetObjectWriter(std::move(MOTW)) {
229 Header.Machine = TargetObjectWriter->getMachine();
232 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
233 Symbols.push_back(make_unique<COFFSymbol>(Name));
234 return Symbols.back().get();
237 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
238 COFFSymbol *&Ret = SymbolMap[Symbol];
240 Ret = createSymbol(Symbol->getName());
244 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
245 Sections.emplace_back(make_unique<COFFSection>(Name));
246 return Sections.back().get();
249 static uint32_t getAlignment(const MCSectionCOFF &Sec) {
250 switch (Sec.getAlignment()) {
252 return COFF::IMAGE_SCN_ALIGN_1BYTES;
254 return COFF::IMAGE_SCN_ALIGN_2BYTES;
256 return COFF::IMAGE_SCN_ALIGN_4BYTES;
258 return COFF::IMAGE_SCN_ALIGN_8BYTES;
260 return COFF::IMAGE_SCN_ALIGN_16BYTES;
262 return COFF::IMAGE_SCN_ALIGN_32BYTES;
264 return COFF::IMAGE_SCN_ALIGN_64BYTES;
266 return COFF::IMAGE_SCN_ALIGN_128BYTES;
268 return COFF::IMAGE_SCN_ALIGN_256BYTES;
270 return COFF::IMAGE_SCN_ALIGN_512BYTES;
272 return COFF::IMAGE_SCN_ALIGN_1024BYTES;
274 return COFF::IMAGE_SCN_ALIGN_2048BYTES;
276 return COFF::IMAGE_SCN_ALIGN_4096BYTES;
278 return COFF::IMAGE_SCN_ALIGN_8192BYTES;
280 llvm_unreachable("unsupported section alignment");
283 /// This function takes a section data object from the assembler
284 /// and creates the associated COFF section staging object.
285 void WinCOFFObjectWriter::defineSection(const MCSectionCOFF &MCSec) {
286 COFFSection *Section = createSection(MCSec.getSectionName());
287 COFFSymbol *Symbol = createSymbol(MCSec.getSectionName());
288 Section->Symbol = Symbol;
289 Symbol->Section = Section;
290 Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
292 // Create a COMDAT symbol if needed.
293 if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
294 if (const MCSymbol *S = MCSec.getCOMDATSymbol()) {
295 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
296 if (COMDATSymbol->Section)
297 report_fatal_error("two sections have the same comdat");
298 COMDATSymbol->Section = Section;
302 // In this case the auxiliary symbol is a Section Definition.
303 Symbol->Aux.resize(1);
305 Symbol->Aux[0].AuxType = ATSectionDefinition;
306 Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection();
308 // Set section alignment.
309 Section->Header.Characteristics = MCSec.getCharacteristics();
310 Section->Header.Characteristics |= getAlignment(MCSec);
312 // Bind internal COFF section to MC section.
313 Section->MCSection = &MCSec;
314 SectionMap[&MCSec] = Section;
317 static uint64_t getSymbolValue(const MCSymbol &Symbol,
318 const MCAsmLayout &Layout) {
319 if (Symbol.isCommon() && Symbol.isExternal())
320 return Symbol.getCommonSize();
323 if (!Layout.getSymbolOffset(Symbol, Res))
329 COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
330 if (!Symbol.isVariable())
333 const MCSymbolRefExpr *SymRef =
334 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
338 const MCSymbol &Aliasee = SymRef->getSymbol();
339 if (!Aliasee.isUndefined())
341 return GetOrCreateCOFFSymbol(&Aliasee);
344 /// This function takes a symbol data object from the assembler
345 /// and creates the associated COFF symbol staging object.
346 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
347 MCAssembler &Assembler,
348 const MCAsmLayout &Layout) {
349 COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym);
350 const MCSymbol *Base = Layout.getBaseSymbol(MCSym);
351 COFFSection *Sec = nullptr;
352 if (Base && Base->getFragment()) {
353 Sec = SectionMap[Base->getFragment()->getParent()];
354 if (Sym->Section && Sym->Section != Sec)
355 report_fatal_error("conflicting sections for symbol");
358 COFFSymbol *Local = nullptr;
359 if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
360 Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
362 COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
364 std::string WeakName = (".weak." + MCSym.getName() + ".default").str();
365 WeakDefault = createSymbol(WeakName);
367 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
369 WeakDefault->Section = Sec;
373 Sym->Other = WeakDefault;
375 // Setup the Weak External auxiliary symbol.
377 memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
378 Sym->Aux[0].AuxType = ATWeakExternal;
379 Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
380 Sym->Aux[0].Aux.WeakExternal.Characteristics =
381 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
384 Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
391 Local->Data.Value = getSymbolValue(MCSym, Layout);
393 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym);
394 Local->Data.Type = SymbolCOFF.getType();
395 Local->Data.StorageClass = SymbolCOFF.getClass();
397 // If no storage class was specified in the streamer, define it here.
398 if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
399 bool IsExternal = MCSym.isExternal() ||
400 (!MCSym.getFragment() && !MCSym.isVariable());
402 Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
403 : COFF::IMAGE_SYM_CLASS_STATIC;
410 // Maximum offsets for different string table entry encodings.
411 enum : unsigned { Max7DecimalOffset = 9999999U };
412 enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0
414 // Encode a string table entry offset in base 64, padded to 6 chars, and
415 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
416 // Buffer must be at least 8 bytes large. No terminating null appended.
417 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
418 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
419 "Illegal section name encoding for value");
421 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
422 "abcdefghijklmnopqrstuvwxyz"
428 char *Ptr = Buffer + 7;
429 for (unsigned i = 0; i < 6; ++i) {
430 unsigned Rem = Value % 64;
432 *(Ptr--) = Alphabet[Rem];
436 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
437 if (S.Name.size() <= COFF::NameSize) {
438 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
442 uint64_t StringTableEntry = Strings.getOffset(S.Name);
443 if (StringTableEntry <= Max7DecimalOffset) {
444 SmallVector<char, COFF::NameSize> Buffer;
445 Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
446 assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
447 std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
450 if (StringTableEntry <= MaxBase64Offset) {
451 // Starting with 10,000,000, offsets are encoded as base64.
452 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
455 report_fatal_error("COFF string table is greater than 64 GB.");
458 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
459 if (S.Name.size() > COFF::NameSize)
460 S.set_name_offset(Strings.getOffset(S.Name));
462 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
465 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
466 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
470 //------------------------------------------------------------------------------
471 // entity writing methods
473 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
475 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
477 writeLE16(COFF::BigObjHeader::MinBigObjectVersion);
478 writeLE16(Header.Machine);
479 writeLE32(Header.TimeDateStamp);
480 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic)));
485 writeLE32(Header.NumberOfSections);
486 writeLE32(Header.PointerToSymbolTable);
487 writeLE32(Header.NumberOfSymbols);
489 writeLE16(Header.Machine);
490 writeLE16(static_cast<int16_t>(Header.NumberOfSections));
491 writeLE32(Header.TimeDateStamp);
492 writeLE32(Header.PointerToSymbolTable);
493 writeLE32(Header.NumberOfSymbols);
494 writeLE16(Header.SizeOfOptionalHeader);
495 writeLE16(Header.Characteristics);
499 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
500 writeBytes(StringRef(S.Data.Name, COFF::NameSize));
501 writeLE32(S.Data.Value);
503 writeLE32(S.Data.SectionNumber);
505 writeLE16(static_cast<int16_t>(S.Data.SectionNumber));
506 writeLE16(S.Data.Type);
507 write8(S.Data.StorageClass);
508 write8(S.Data.NumberOfAuxSymbols);
509 WriteAuxiliarySymbols(S.Aux);
512 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
513 const COFFSymbol::AuxiliarySymbols &S) {
514 for (const AuxSymbol &i : S) {
516 case ATFunctionDefinition:
517 writeLE32(i.Aux.FunctionDefinition.TagIndex);
518 writeLE32(i.Aux.FunctionDefinition.TotalSize);
519 writeLE32(i.Aux.FunctionDefinition.PointerToLinenumber);
520 writeLE32(i.Aux.FunctionDefinition.PointerToNextFunction);
521 WriteZeros(sizeof(i.Aux.FunctionDefinition.unused));
523 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
525 case ATbfAndefSymbol:
526 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused1));
527 writeLE16(i.Aux.bfAndefSymbol.Linenumber);
528 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused2));
529 writeLE32(i.Aux.bfAndefSymbol.PointerToNextFunction);
530 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused3));
532 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
535 writeLE32(i.Aux.WeakExternal.TagIndex);
536 writeLE32(i.Aux.WeakExternal.Characteristics);
537 WriteZeros(sizeof(i.Aux.WeakExternal.unused));
539 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
543 StringRef(reinterpret_cast<const char *>(&i.Aux),
544 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
546 case ATSectionDefinition:
547 writeLE32(i.Aux.SectionDefinition.Length);
548 writeLE16(i.Aux.SectionDefinition.NumberOfRelocations);
549 writeLE16(i.Aux.SectionDefinition.NumberOfLinenumbers);
550 writeLE32(i.Aux.SectionDefinition.CheckSum);
551 writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number));
552 write8(i.Aux.SectionDefinition.Selection);
553 WriteZeros(sizeof(i.Aux.SectionDefinition.unused));
554 writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16));
556 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
562 // Write the section header.
563 void WinCOFFObjectWriter::writeSectionHeaders() {
564 // Section numbers must be monotonically increasing in the section
565 // header, but our Sections array is not sorted by section number,
566 // so make a copy of Sections and sort it.
567 std::vector<COFFSection *> Arr;
568 for (auto &Section : Sections)
569 Arr.push_back(Section.get());
570 std::sort(Arr.begin(), Arr.end(),
571 [](const COFFSection *A, const COFFSection *B) {
572 return A->Number < B->Number;
575 for (auto &Section : Arr) {
576 if (Section->Number == -1)
579 COFF::section &S = Section->Header;
580 if (Section->Relocations.size() >= 0xffff)
581 S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
582 writeBytes(StringRef(S.Name, COFF::NameSize));
583 writeLE32(S.VirtualSize);
584 writeLE32(S.VirtualAddress);
585 writeLE32(S.SizeOfRawData);
586 writeLE32(S.PointerToRawData);
587 writeLE32(S.PointerToRelocations);
588 writeLE32(S.PointerToLineNumbers);
589 writeLE16(S.NumberOfRelocations);
590 writeLE16(S.NumberOfLineNumbers);
591 writeLE32(S.Characteristics);
595 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
596 writeLE32(R.VirtualAddress);
597 writeLE32(R.SymbolTableIndex);
601 // Write MCSec's contents. What this function does is essentially
602 // "Asm.writeSectionData(&MCSec, Layout)", but it's a bit complicated
603 // because it needs to compute a CRC.
604 uint32_t WinCOFFObjectWriter::writeSectionContents(MCAssembler &Asm,
605 const MCAsmLayout &Layout,
606 const MCSection &MCSec) {
607 // Save the contents of the section to a temporary buffer, we need this
608 // to CRC the data before we dump it into the object file.
609 SmallVector<char, 128> Buf;
610 raw_svector_ostream VecOS(Buf);
611 raw_pwrite_stream &OldStream = getStream();
613 // Redirect the output stream to our buffer and fill our buffer with
616 Asm.writeSectionData(&MCSec, Layout);
618 // Reset the stream back to what it was before.
619 setStream(OldStream);
621 // Write the section contents to the object file.
624 // Calculate our CRC with an initial value of '0', this is not how
625 // JamCRC is specified but it aligns with the expected output.
626 JamCRC JC(/*Init=*/0);
631 void WinCOFFObjectWriter::writeSection(MCAssembler &Asm,
632 const MCAsmLayout &Layout,
633 const COFFSection &Sec,
634 const MCSection &MCSec) {
635 if (Sec.Number == -1)
638 // Write the section contents.
639 if (Sec.Header.PointerToRawData != 0) {
640 assert(getStream().tell() <= Sec.Header.PointerToRawData &&
641 "Section::PointerToRawData is insane!");
643 unsigned PaddingSize = Sec.Header.PointerToRawData - getStream().tell();
644 assert(PaddingSize < 4 &&
645 "Should only need at most three bytes of padding!");
646 WriteZeros(PaddingSize);
648 uint32_t CRC = writeSectionContents(Asm, Layout, MCSec);
650 // Update the section definition auxiliary symbol to record the CRC.
651 COFFSection *Sec = SectionMap[&MCSec];
652 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
653 assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition);
654 AuxSymbol &SecDef = AuxSyms[0];
655 SecDef.Aux.SectionDefinition.CheckSum = CRC;
658 // Write relocations for this section.
659 if (Sec.Relocations.empty()) {
660 assert(Sec.Header.PointerToRelocations == 0 &&
661 "Section::PointerToRelocations is insane!");
665 assert(getStream().tell() == Sec.Header.PointerToRelocations &&
666 "Section::PointerToRelocations is insane!");
668 if (Sec.Relocations.size() >= 0xffff) {
669 // In case of overflow, write actual relocation count as first
670 // relocation. Including the synthetic reloc itself (+ 1).
672 R.VirtualAddress = Sec.Relocations.size() + 1;
673 R.SymbolTableIndex = 0;
678 for (const auto &Relocation : Sec.Relocations)
679 WriteRelocation(Relocation.Data);
682 ////////////////////////////////////////////////////////////////////////////////
683 // MCObjectWriter interface implementations
685 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
686 const MCAsmLayout &Layout) {
687 // "Define" each section & symbol. This creates section & symbol
688 // entries in the staging area.
689 for (const auto &Section : Asm)
690 defineSection(static_cast<const MCSectionCOFF &>(Section));
692 for (const MCSymbol &Symbol : Asm.symbols())
693 if (!Symbol.isTemporary())
694 DefineSymbol(Symbol, Asm, Layout);
697 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
698 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
699 bool InSet, bool IsPCRel) const {
700 // MS LINK expects to be able to replace all references to a function with a
701 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
702 // away any relocations to functions.
703 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
704 if (Asm.isIncrementalLinkerCompatible() &&
705 (Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
707 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
711 void WinCOFFObjectWriter::recordRelocation(MCAssembler &Asm,
712 const MCAsmLayout &Layout,
713 const MCFragment *Fragment,
714 const MCFixup &Fixup, MCValue Target,
715 uint64_t &FixedValue) {
716 assert(Target.getSymA() && "Relocation must reference a symbol!");
718 const MCSymbol &A = Target.getSymA()->getSymbol();
719 if (!A.isRegistered()) {
720 Asm.getContext().reportError(Fixup.getLoc(),
721 Twine("symbol '") + A.getName() +
722 "' can not be undefined");
725 if (A.isTemporary() && A.isUndefined()) {
726 Asm.getContext().reportError(Fixup.getLoc(),
727 Twine("assembler label '") + A.getName() +
728 "' can not be undefined");
732 MCSection *MCSec = Fragment->getParent();
734 // Mark this symbol as requiring an entry in the symbol table.
735 assert(SectionMap.find(MCSec) != SectionMap.end() &&
736 "Section must already have been defined in executePostLayoutBinding!");
738 COFFSection *Sec = SectionMap[MCSec];
739 const MCSymbolRefExpr *SymB = Target.getSymB();
742 const MCSymbol *B = &SymB->getSymbol();
743 if (!B->getFragment()) {
744 Asm.getContext().reportError(
746 Twine("symbol '") + B->getName() +
747 "' can not be undefined in a subtraction expression");
751 // Offset of the symbol in the section
752 int64_t OffsetOfB = Layout.getSymbolOffset(*B);
754 // Offset of the relocation in the section
755 int64_t OffsetOfRelocation =
756 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
758 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
760 FixedValue = Target.getConstant();
763 COFFRelocation Reloc;
765 Reloc.Data.SymbolTableIndex = 0;
766 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
768 // Turn relocations for temporary symbols into section relocations.
769 if (A.isTemporary()) {
770 MCSection *TargetSection = &A.getSection();
772 SectionMap.find(TargetSection) != SectionMap.end() &&
773 "Section must already have been defined in executePostLayoutBinding!");
774 Reloc.Symb = SectionMap[TargetSection]->Symbol;
775 FixedValue += Layout.getSymbolOffset(A);
778 SymbolMap.find(&A) != SymbolMap.end() &&
779 "Symbol must already have been defined in executePostLayoutBinding!");
780 Reloc.Symb = SymbolMap[&A];
783 ++Reloc.Symb->Relocations;
785 Reloc.Data.VirtualAddress += Fixup.getOffset();
786 Reloc.Data.Type = TargetObjectWriter->getRelocType(
787 Asm.getContext(), Target, Fixup, SymB, Asm.getBackend());
789 // FIXME: Can anyone explain what this does other than adjust for the size
791 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
792 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
793 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
794 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
797 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
798 switch (Reloc.Data.Type) {
799 case COFF::IMAGE_REL_ARM_ABSOLUTE:
800 case COFF::IMAGE_REL_ARM_ADDR32:
801 case COFF::IMAGE_REL_ARM_ADDR32NB:
802 case COFF::IMAGE_REL_ARM_TOKEN:
803 case COFF::IMAGE_REL_ARM_SECTION:
804 case COFF::IMAGE_REL_ARM_SECREL:
806 case COFF::IMAGE_REL_ARM_BRANCH11:
807 case COFF::IMAGE_REL_ARM_BLX11:
808 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
809 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
811 case COFF::IMAGE_REL_ARM_BRANCH24:
812 case COFF::IMAGE_REL_ARM_BLX24:
813 case COFF::IMAGE_REL_ARM_MOV32A:
814 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
815 // only used for ARM mode code, which is documented as being unsupported
816 // by Windows on ARM. Empirical proof indicates that masm is able to
817 // generate the relocations however the rest of the MSVC toolchain is
818 // unable to handle it.
819 llvm_unreachable("unsupported relocation");
821 case COFF::IMAGE_REL_ARM_MOV32T:
823 case COFF::IMAGE_REL_ARM_BRANCH20T:
824 case COFF::IMAGE_REL_ARM_BRANCH24T:
825 case COFF::IMAGE_REL_ARM_BLX23T:
826 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
827 // perform a 4 byte adjustment to the relocation. Relative branches are
828 // offset by 4 on ARM, however, because there is no RELA relocations, all
829 // branches are offset by 4.
830 FixedValue = FixedValue + 4;
835 // The fixed value never makes sense for section indices, ignore it.
836 if (Fixup.getKind() == FK_SecRel_2)
839 if (TargetObjectWriter->recordRelocation(Fixup))
840 Sec->Relocations.push_back(Reloc);
843 static std::time_t getTime() {
844 std::time_t Now = time(nullptr);
845 if (Now < 0 || !isUInt<32>(Now))
850 // Create .file symbols.
851 void WinCOFFObjectWriter::createFileSymbols(MCAssembler &Asm) {
852 for (const std::string &Name : Asm.getFileNames()) {
853 // round up to calculate the number of auxiliary symbols required
854 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
855 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
857 COFFSymbol *File = createSymbol(".file");
858 File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
859 File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
860 File->Aux.resize(Count);
863 unsigned Length = Name.size();
864 for (auto &Aux : File->Aux) {
865 Aux.AuxType = ATFile;
867 if (Length > SymbolSize) {
868 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
869 Length = Length - SymbolSize;
871 memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
872 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
876 Offset += SymbolSize;
881 static bool isAssociative(const COFFSection &Section) {
882 return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection ==
883 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
886 void WinCOFFObjectWriter::assignSectionNumbers() {
888 auto Assign = [&](COFFSection &Section) {
890 Section.Symbol->Data.SectionNumber = I;
891 Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I;
895 // Although it is not explicitly requested by the Microsoft COFF spec,
896 // we should avoid emitting forward associative section references,
897 // because MSVC link.exe as of 2017 cannot handle that.
898 for (const std::unique_ptr<COFFSection> &Section : Sections)
899 if (!isAssociative(*Section))
901 for (const std::unique_ptr<COFFSection> &Section : Sections)
902 if (isAssociative(*Section))
906 // Assign file offsets to COFF object file structures.
907 void WinCOFFObjectWriter::assignFileOffsets(MCAssembler &Asm,
908 const MCAsmLayout &Layout) {
909 unsigned Offset = getInitialOffset();
911 Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size;
912 Offset += COFF::SectionSize * Header.NumberOfSections;
914 for (const auto &Section : Asm) {
915 COFFSection *Sec = SectionMap[&Section];
917 if (Sec->Number == -1)
920 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
922 if (IsPhysicalSection(Sec)) {
923 // Align the section data to a four byte boundary.
924 Offset = alignTo(Offset, 4);
925 Sec->Header.PointerToRawData = Offset;
927 Offset += Sec->Header.SizeOfRawData;
930 if (!Sec->Relocations.empty()) {
931 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
933 if (RelocationsOverflow) {
934 // Signal overflow by setting NumberOfRelocations to max value. Actual
935 // size is found in reloc #0. Microsoft tools understand this.
936 Sec->Header.NumberOfRelocations = 0xffff;
938 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
940 Sec->Header.PointerToRelocations = Offset;
942 if (RelocationsOverflow) {
943 // Reloc #0 will contain actual count, so make room for it.
944 Offset += COFF::RelocationSize;
947 Offset += COFF::RelocationSize * Sec->Relocations.size();
949 for (auto &Relocation : Sec->Relocations) {
950 assert(Relocation.Symb->getIndex() != -1);
951 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
955 assert(Sec->Symbol->Aux.size() == 1 &&
956 "Section's symbol must have one aux!");
957 AuxSymbol &Aux = Sec->Symbol->Aux[0];
958 assert(Aux.AuxType == ATSectionDefinition &&
959 "Section's symbol's aux symbol must be a Section Definition!");
960 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
961 Aux.Aux.SectionDefinition.NumberOfRelocations =
962 Sec->Header.NumberOfRelocations;
963 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
964 Sec->Header.NumberOfLineNumbers;
967 Header.PointerToSymbolTable = Offset;
970 void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
971 const MCAsmLayout &Layout) {
972 if (Sections.size() > INT32_MAX)
974 "PE COFF object files can't have more than 2147483647 sections");
976 UseBigObj = Sections.size() > COFF::MaxNumberOfSections16;
977 Header.NumberOfSections = Sections.size();
978 Header.NumberOfSymbols = 0;
980 assignSectionNumbers();
981 createFileSymbols(Asm);
983 for (auto &Symbol : Symbols) {
984 // Update section number & offset for symbols that have them.
986 Symbol->Data.SectionNumber = Symbol->Section->Number;
987 Symbol->setIndex(Header.NumberOfSymbols++);
988 // Update auxiliary symbol info.
989 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
990 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
993 // Build string table.
994 for (const auto &S : Sections)
995 if (S->Name.size() > COFF::NameSize)
996 Strings.add(S->Name);
997 for (const auto &S : Symbols)
998 if (S->Name.size() > COFF::NameSize)
999 Strings.add(S->Name);
1003 for (const auto &S : Sections)
1005 for (auto &S : Symbols)
1008 // Fixup weak external references.
1009 for (auto &Symbol : Symbols) {
1010 if (Symbol->Other) {
1011 assert(Symbol->getIndex() != -1);
1012 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
1013 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
1014 "Symbol's aux symbol must be a Weak External!");
1015 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
1019 // Fixup associative COMDAT sections.
1020 for (auto &Section : Sections) {
1021 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
1022 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1025 const MCSectionCOFF &MCSec = *Section->MCSection;
1027 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
1029 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
1030 assert(COMDATSymbol);
1031 COFFSection *Assoc = COMDATSymbol->Section;
1034 Twine("Missing associated COMDAT section for section ") +
1035 MCSec.getSectionName());
1037 // Skip this section if the associated section is unused.
1038 if (Assoc->Number == -1)
1041 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
1044 assignFileOffsets(Asm, Layout);
1046 // MS LINK expects to be able to use this timestamp to implement their
1047 // /INCREMENTAL feature.
1048 if (Asm.isIncrementalLinkerCompatible()) {
1049 Header.TimeDateStamp = getTime();
1051 // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
1052 Header.TimeDateStamp = 0;
1055 // Write it all to disk...
1056 WriteFileHeader(Header);
1057 writeSectionHeaders();
1059 // Write section contents.
1060 sections::iterator I = Sections.begin();
1061 sections::iterator IE = Sections.end();
1062 MCAssembler::iterator J = Asm.begin();
1063 MCAssembler::iterator JE = Asm.end();
1064 for (; I != IE && J != JE; ++I, ++J)
1065 writeSection(Asm, Layout, **I, *J);
1067 assert(getStream().tell() == Header.PointerToSymbolTable &&
1068 "Header::PointerToSymbolTable is insane!");
1070 // Write a symbol table.
1071 for (auto &Symbol : Symbols)
1072 if (Symbol->getIndex() != -1)
1073 WriteSymbol(*Symbol);
1075 // Write a string table, which completes the entire COFF file.
1076 Strings.write(getStream());
1079 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1080 : Machine(Machine_) {}
1082 // Pin the vtable to this file.
1083 void MCWinCOFFObjectTargetWriter::anchor() {}
1085 //------------------------------------------------------------------------------
1086 // WinCOFFObjectWriter factory function
1088 std::unique_ptr<MCObjectWriter> llvm::createWinCOFFObjectWriter(
1089 std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS) {
1090 return llvm::make_unique<WinCOFFObjectWriter>(std::move(MOTW), OS);