diff options
Diffstat (limited to 'contrib/llvm/lib/MC/WinCOFFObjectWriter.cpp')
| -rw-r--r-- | contrib/llvm/lib/MC/WinCOFFObjectWriter.cpp | 1110 |
1 files changed, 1110 insertions, 0 deletions
diff --git a/contrib/llvm/lib/MC/WinCOFFObjectWriter.cpp b/contrib/llvm/lib/MC/WinCOFFObjectWriter.cpp new file mode 100644 index 000000000000..53dee3e8b9f3 --- /dev/null +++ b/contrib/llvm/lib/MC/WinCOFFObjectWriter.cpp @@ -0,0 +1,1110 @@ +//===- llvm/MC/WinCOFFObjectWriter.cpp ------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains an implementation of a Win32 COFF object file writer. +// +//===----------------------------------------------------------------------===// + +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/ADT/Twine.h" +#include "llvm/BinaryFormat/COFF.h" +#include "llvm/MC/MCAsmLayout.h" +#include "llvm/MC/MCAssembler.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCFixup.h" +#include "llvm/MC/MCFragment.h" +#include "llvm/MC/MCObjectWriter.h" +#include "llvm/MC/MCSection.h" +#include "llvm/MC/MCSectionCOFF.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/MC/MCSymbolCOFF.h" +#include "llvm/MC/MCValue.h" +#include "llvm/MC/MCWinCOFFObjectWriter.h" +#include "llvm/MC/StringTableBuilder.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/Endian.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/JamCRC.h" +#include "llvm/Support/MathExtras.h" +#include "llvm/Support/raw_ostream.h" +#include <algorithm> +#include <cassert> +#include <cstddef> +#include <cstdint> +#include <cstring> +#include <ctime> +#include <memory> +#include <string> +#include <vector> + +using namespace llvm; +using llvm::support::endian::write32le; + +#define DEBUG_TYPE "WinCOFFObjectWriter" + +namespace { + +using name = SmallString<COFF::NameSize>; + +enum AuxiliaryType { + ATFunctionDefinition, + ATbfAndefSymbol, + ATWeakExternal, + ATFile, + ATSectionDefinition +}; + +struct AuxSymbol { + AuxiliaryType AuxType; + COFF::Auxiliary Aux; +}; + +class COFFSection; + +class COFFSymbol { +public: + COFF::symbol Data = {}; + + using AuxiliarySymbols = SmallVector<AuxSymbol, 1>; + + name Name; + int Index; + AuxiliarySymbols Aux; + COFFSymbol *Other = nullptr; + COFFSection *Section = nullptr; + int Relocations = 0; + const MCSymbol *MC = nullptr; + + COFFSymbol(StringRef Name) : Name(Name) {} + + void set_name_offset(uint32_t Offset); + + int64_t getIndex() const { return Index; } + void setIndex(int Value) { + Index = Value; + if (MC) + MC->setIndex(static_cast<uint32_t>(Value)); + } +}; + +// This class contains staging data for a COFF relocation entry. +struct COFFRelocation { + COFF::relocation Data; + COFFSymbol *Symb = nullptr; + + COFFRelocation() = default; + + static size_t size() { return COFF::RelocationSize; } +}; + +using relocations = std::vector<COFFRelocation>; + +class COFFSection { +public: + COFF::section Header = {}; + + std::string Name; + int Number; + MCSectionCOFF const *MCSection = nullptr; + COFFSymbol *Symbol = nullptr; + relocations Relocations; + + COFFSection(StringRef Name) : Name(Name) {} +}; + +class WinCOFFObjectWriter : public MCObjectWriter { +public: + using symbols = std::vector<std::unique_ptr<COFFSymbol>>; + using sections = std::vector<std::unique_ptr<COFFSection>>; + + using symbol_map = DenseMap<MCSymbol const *, COFFSymbol *>; + using section_map = DenseMap<MCSection const *, COFFSection *>; + + std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter; + + // Root level file contents. + COFF::header Header = {}; + sections Sections; + symbols Symbols; + StringTableBuilder Strings{StringTableBuilder::WinCOFF}; + + // Maps used during object file creation. + section_map SectionMap; + symbol_map SymbolMap; + + bool UseBigObj; + + WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS); + + void reset() override { + memset(&Header, 0, sizeof(Header)); + Header.Machine = TargetObjectWriter->getMachine(); + Sections.clear(); + Symbols.clear(); + Strings.clear(); + SectionMap.clear(); + SymbolMap.clear(); + MCObjectWriter::reset(); + } + + COFFSymbol *createSymbol(StringRef Name); + COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol); + COFFSection *createSection(StringRef Name); + + void defineSection(MCSectionCOFF const &Sec); + + COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol); + void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler, + const MCAsmLayout &Layout); + + void SetSymbolName(COFFSymbol &S); + void SetSectionName(COFFSection &S); + + bool IsPhysicalSection(COFFSection *S); + + // Entity writing methods. + + void WriteFileHeader(const COFF::header &Header); + void WriteSymbol(const COFFSymbol &S); + void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S); + void writeSectionHeaders(); + void WriteRelocation(const COFF::relocation &R); + uint32_t writeSectionContents(MCAssembler &Asm, const MCAsmLayout &Layout, + const MCSection &MCSec); + void writeSection(MCAssembler &Asm, const MCAsmLayout &Layout, + const COFFSection &Sec, const MCSection &MCSec); + + // MCObjectWriter interface implementation. + + void executePostLayoutBinding(MCAssembler &Asm, + const MCAsmLayout &Layout) override; + + bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, + const MCSymbol &SymA, + const MCFragment &FB, bool InSet, + bool IsPCRel) const override; + + void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, + const MCFragment *Fragment, const MCFixup &Fixup, + MCValue Target, bool &IsPCRel, + uint64_t &FixedValue) override; + + void createFileSymbols(MCAssembler &Asm); + void assignSectionNumbers(); + void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout); + + void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; +}; + +} // end anonymous namespace + +//------------------------------------------------------------------------------ +// Symbol class implementation + +// In the case that the name does not fit within 8 bytes, the offset +// into the string table is stored in the last 4 bytes instead, leaving +// the first 4 bytes as 0. +void COFFSymbol::set_name_offset(uint32_t Offset) { + write32le(Data.Name + 0, 0); + write32le(Data.Name + 4, Offset); +} + +//------------------------------------------------------------------------------ +// WinCOFFObjectWriter class implementation + +WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, + raw_pwrite_stream &OS) + : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) { + Header.Machine = TargetObjectWriter->getMachine(); +} + +COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) { + Symbols.push_back(make_unique<COFFSymbol>(Name)); + return Symbols.back().get(); +} + +COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) { + COFFSymbol *&Ret = SymbolMap[Symbol]; + if (!Ret) + Ret = createSymbol(Symbol->getName()); + return Ret; +} + +COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) { + Sections.emplace_back(make_unique<COFFSection>(Name)); + return Sections.back().get(); +} + +static uint32_t getAlignment(const MCSectionCOFF &Sec) { + switch (Sec.getAlignment()) { + case 1: + return COFF::IMAGE_SCN_ALIGN_1BYTES; + case 2: + return COFF::IMAGE_SCN_ALIGN_2BYTES; + case 4: + return COFF::IMAGE_SCN_ALIGN_4BYTES; + case 8: + return COFF::IMAGE_SCN_ALIGN_8BYTES; + case 16: + return COFF::IMAGE_SCN_ALIGN_16BYTES; + case 32: + return COFF::IMAGE_SCN_ALIGN_32BYTES; + case 64: + return COFF::IMAGE_SCN_ALIGN_64BYTES; + case 128: + return COFF::IMAGE_SCN_ALIGN_128BYTES; + case 256: + return COFF::IMAGE_SCN_ALIGN_256BYTES; + case 512: + return COFF::IMAGE_SCN_ALIGN_512BYTES; + case 1024: + return COFF::IMAGE_SCN_ALIGN_1024BYTES; + case 2048: + return COFF::IMAGE_SCN_ALIGN_2048BYTES; + case 4096: + return COFF::IMAGE_SCN_ALIGN_4096BYTES; + case 8192: + return COFF::IMAGE_SCN_ALIGN_8192BYTES; + } + llvm_unreachable("unsupported section alignment"); +} + +/// This function takes a section data object from the assembler +/// and creates the associated COFF section staging object. +void WinCOFFObjectWriter::defineSection(const MCSectionCOFF &MCSec) { + COFFSection *Section = createSection(MCSec.getSectionName()); + COFFSymbol *Symbol = createSymbol(MCSec.getSectionName()); + Section->Symbol = Symbol; + Symbol->Section = Section; + Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC; + + // Create a COMDAT symbol if needed. + if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) { + if (const MCSymbol *S = MCSec.getCOMDATSymbol()) { + COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S); + if (COMDATSymbol->Section) + report_fatal_error("two sections have the same comdat"); + COMDATSymbol->Section = Section; + } + } + + // In this case the auxiliary symbol is a Section Definition. + Symbol->Aux.resize(1); + Symbol->Aux[0] = {}; + Symbol->Aux[0].AuxType = ATSectionDefinition; + Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection(); + + // Set section alignment. + Section->Header.Characteristics = MCSec.getCharacteristics(); + Section->Header.Characteristics |= getAlignment(MCSec); + + // Bind internal COFF section to MC section. + Section->MCSection = &MCSec; + SectionMap[&MCSec] = Section; +} + +static uint64_t getSymbolValue(const MCSymbol &Symbol, + const MCAsmLayout &Layout) { + if (Symbol.isCommon() && Symbol.isExternal()) + return Symbol.getCommonSize(); + + uint64_t Res; + if (!Layout.getSymbolOffset(Symbol, Res)) + return 0; + + return Res; +} + +COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) { + if (!Symbol.isVariable()) + return nullptr; + + const MCSymbolRefExpr *SymRef = + dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue()); + if (!SymRef) + return nullptr; + + const MCSymbol &Aliasee = SymRef->getSymbol(); + if (!Aliasee.isUndefined()) + return nullptr; + return GetOrCreateCOFFSymbol(&Aliasee); +} + +/// This function takes a symbol data object from the assembler +/// and creates the associated COFF symbol staging object. +void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym, + MCAssembler &Assembler, + const MCAsmLayout &Layout) { + COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym); + const MCSymbol *Base = Layout.getBaseSymbol(MCSym); + COFFSection *Sec = nullptr; + if (Base && Base->getFragment()) { + Sec = SectionMap[Base->getFragment()->getParent()]; + if (Sym->Section && Sym->Section != Sec) + report_fatal_error("conflicting sections for symbol"); + } + + COFFSymbol *Local = nullptr; + if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) { + Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL; + + COFFSymbol *WeakDefault = getLinkedSymbol(MCSym); + if (!WeakDefault) { + std::string WeakName = (".weak." + MCSym.getName() + ".default").str(); + WeakDefault = createSymbol(WeakName); + if (!Sec) + WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; + else + WeakDefault->Section = Sec; + Local = WeakDefault; + } + + Sym->Other = WeakDefault; + + // Setup the Weak External auxiliary symbol. + Sym->Aux.resize(1); + memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0])); + Sym->Aux[0].AuxType = ATWeakExternal; + Sym->Aux[0].Aux.WeakExternal.TagIndex = 0; + Sym->Aux[0].Aux.WeakExternal.Characteristics = + COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY; + } else { + if (!Base) + Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE; + else + Sym->Section = Sec; + Local = Sym; + } + + if (Local) { + Local->Data.Value = getSymbolValue(MCSym, Layout); + + const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym); + Local->Data.Type = SymbolCOFF.getType(); + Local->Data.StorageClass = SymbolCOFF.getClass(); + + // If no storage class was specified in the streamer, define it here. + if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) { + bool IsExternal = MCSym.isExternal() || + (!MCSym.getFragment() && !MCSym.isVariable()); + + Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL + : COFF::IMAGE_SYM_CLASS_STATIC; + } + } + + Sym->MC = &MCSym; +} + +// Maximum offsets for different string table entry encodings. +enum : unsigned { Max7DecimalOffset = 9999999U }; +enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0 + +// Encode a string table entry offset in base 64, padded to 6 chars, and +// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ... +// Buffer must be at least 8 bytes large. No terminating null appended. +static void encodeBase64StringEntry(char *Buffer, uint64_t Value) { + assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset && + "Illegal section name encoding for value"); + + static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "abcdefghijklmnopqrstuvwxyz" + "0123456789+/"; + + Buffer[0] = '/'; + Buffer[1] = '/'; + + char *Ptr = Buffer + 7; + for (unsigned i = 0; i < 6; ++i) { + unsigned Rem = Value % 64; + Value /= 64; + *(Ptr--) = Alphabet[Rem]; + } +} + +void WinCOFFObjectWriter::SetSectionName(COFFSection &S) { + if (S.Name.size() <= COFF::NameSize) { + std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size()); + return; + } + + uint64_t StringTableEntry = Strings.getOffset(S.Name); + if (StringTableEntry <= Max7DecimalOffset) { + SmallVector<char, COFF::NameSize> Buffer; + Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer); + assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2); + std::memcpy(S.Header.Name, Buffer.data(), Buffer.size()); + return; + } + if (StringTableEntry <= MaxBase64Offset) { + // Starting with 10,000,000, offsets are encoded as base64. + encodeBase64StringEntry(S.Header.Name, StringTableEntry); + return; + } + report_fatal_error("COFF string table is greater than 64 GB."); +} + +void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) { + if (S.Name.size() > COFF::NameSize) + S.set_name_offset(Strings.getOffset(S.Name)); + else + std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size()); +} + +bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) { + return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == + 0; +} + +//------------------------------------------------------------------------------ +// entity writing methods + +void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) { + if (UseBigObj) { + writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN); + writeLE16(0xFFFF); + writeLE16(COFF::BigObjHeader::MinBigObjectVersion); + writeLE16(Header.Machine); + writeLE32(Header.TimeDateStamp); + writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic))); + writeLE32(0); + writeLE32(0); + writeLE32(0); + writeLE32(0); + writeLE32(Header.NumberOfSections); + writeLE32(Header.PointerToSymbolTable); + writeLE32(Header.NumberOfSymbols); + } else { + writeLE16(Header.Machine); + writeLE16(static_cast<int16_t>(Header.NumberOfSections)); + writeLE32(Header.TimeDateStamp); + writeLE32(Header.PointerToSymbolTable); + writeLE32(Header.NumberOfSymbols); + writeLE16(Header.SizeOfOptionalHeader); + writeLE16(Header.Characteristics); + } +} + +void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) { + writeBytes(StringRef(S.Data.Name, COFF::NameSize)); + writeLE32(S.Data.Value); + if (UseBigObj) + writeLE32(S.Data.SectionNumber); + else + writeLE16(static_cast<int16_t>(S.Data.SectionNumber)); + writeLE16(S.Data.Type); + write8(S.Data.StorageClass); + write8(S.Data.NumberOfAuxSymbols); + WriteAuxiliarySymbols(S.Aux); +} + +void WinCOFFObjectWriter::WriteAuxiliarySymbols( + const COFFSymbol::AuxiliarySymbols &S) { + for (const AuxSymbol &i : S) { + switch (i.AuxType) { + case ATFunctionDefinition: + writeLE32(i.Aux.FunctionDefinition.TagIndex); + writeLE32(i.Aux.FunctionDefinition.TotalSize); + writeLE32(i.Aux.FunctionDefinition.PointerToLinenumber); + writeLE32(i.Aux.FunctionDefinition.PointerToNextFunction); + WriteZeros(sizeof(i.Aux.FunctionDefinition.unused)); + if (UseBigObj) + WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); + break; + case ATbfAndefSymbol: + WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused1)); + writeLE16(i.Aux.bfAndefSymbol.Linenumber); + WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused2)); + writeLE32(i.Aux.bfAndefSymbol.PointerToNextFunction); + WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused3)); + if (UseBigObj) + WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); + break; + case ATWeakExternal: + writeLE32(i.Aux.WeakExternal.TagIndex); + writeLE32(i.Aux.WeakExternal.Characteristics); + WriteZeros(sizeof(i.Aux.WeakExternal.unused)); + if (UseBigObj) + WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); + break; + case ATFile: + writeBytes( + StringRef(reinterpret_cast<const char *>(&i.Aux), + UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size)); + break; + case ATSectionDefinition: + writeLE32(i.Aux.SectionDefinition.Length); + writeLE16(i.Aux.SectionDefinition.NumberOfRelocations); + writeLE16(i.Aux.SectionDefinition.NumberOfLinenumbers); + writeLE32(i.Aux.SectionDefinition.CheckSum); + writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number)); + write8(i.Aux.SectionDefinition.Selection); + WriteZeros(sizeof(i.Aux.SectionDefinition.unused)); + writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16)); + if (UseBigObj) + WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size); + break; + } + } +} + +// Write the section header. +void WinCOFFObjectWriter::writeSectionHeaders() { + // Section numbers must be monotonically increasing in the section + // header, but our Sections array is not sorted by section number, + // so make a copy of Sections and sort it. + std::vector<COFFSection *> Arr; + for (auto &Section : Sections) + Arr.push_back(Section.get()); + std::sort(Arr.begin(), Arr.end(), + [](const COFFSection *A, const COFFSection *B) { + return A->Number < B->Number; + }); + + for (auto &Section : Arr) { + if (Section->Number == -1) + continue; + + COFF::section &S = Section->Header; + if (Section->Relocations.size() >= 0xffff) + S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL; + writeBytes(StringRef(S.Name, COFF::NameSize)); + writeLE32(S.VirtualSize); + writeLE32(S.VirtualAddress); + writeLE32(S.SizeOfRawData); + writeLE32(S.PointerToRawData); + writeLE32(S.PointerToRelocations); + writeLE32(S.PointerToLineNumbers); + writeLE16(S.NumberOfRelocations); + writeLE16(S.NumberOfLineNumbers); + writeLE32(S.Characteristics); + } +} + +void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) { + writeLE32(R.VirtualAddress); + writeLE32(R.SymbolTableIndex); + writeLE16(R.Type); +} + +// Write MCSec's contents. What this function does is essentially +// "Asm.writeSectionData(&MCSec, Layout)", but it's a bit complicated +// because it needs to compute a CRC. +uint32_t WinCOFFObjectWriter::writeSectionContents(MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCSection &MCSec) { + // Save the contents of the section to a temporary buffer, we need this + // to CRC the data before we dump it into the object file. + SmallVector<char, 128> Buf; + raw_svector_ostream VecOS(Buf); + raw_pwrite_stream &OldStream = getStream(); + + // Redirect the output stream to our buffer and fill our buffer with + // the section data. + setStream(VecOS); + Asm.writeSectionData(&MCSec, Layout); + + // Reset the stream back to what it was before. + setStream(OldStream); + + // Write the section contents to the object file. + getStream() << Buf; + + // Calculate our CRC with an initial value of '0', this is not how + // JamCRC is specified but it aligns with the expected output. + JamCRC JC(/*Init=*/0); + JC.update(Buf); + return JC.getCRC(); +} + +void WinCOFFObjectWriter::writeSection(MCAssembler &Asm, + const MCAsmLayout &Layout, + const COFFSection &Sec, + const MCSection &MCSec) { + if (Sec.Number == -1) + return; + + // Write the section contents. + if (Sec.Header.PointerToRawData != 0) { + assert(getStream().tell() <= Sec.Header.PointerToRawData && + "Section::PointerToRawData is insane!"); + + unsigned PaddingSize = Sec.Header.PointerToRawData - getStream().tell(); + assert(PaddingSize < 4 && + "Should only need at most three bytes of padding!"); + WriteZeros(PaddingSize); + + uint32_t CRC = writeSectionContents(Asm, Layout, MCSec); + + // Update the section definition auxiliary symbol to record the CRC. + COFFSection *Sec = SectionMap[&MCSec]; + COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux; + assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition); + AuxSymbol &SecDef = AuxSyms[0]; + SecDef.Aux.SectionDefinition.CheckSum = CRC; + } + + // Write relocations for this section. + if (Sec.Relocations.empty()) { + assert(Sec.Header.PointerToRelocations == 0 && + "Section::PointerToRelocations is insane!"); + return; + } + + assert(getStream().tell() == Sec.Header.PointerToRelocations && + "Section::PointerToRelocations is insane!"); + + if (Sec.Relocations.size() >= 0xffff) { + // In case of overflow, write actual relocation count as first + // relocation. Including the synthetic reloc itself (+ 1). + COFF::relocation R; + R.VirtualAddress = Sec.Relocations.size() + 1; + R.SymbolTableIndex = 0; + R.Type = 0; + WriteRelocation(R); + } + + for (const auto &Relocation : Sec.Relocations) + WriteRelocation(Relocation.Data); +} + +//////////////////////////////////////////////////////////////////////////////// +// MCObjectWriter interface implementations + +void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm, + const MCAsmLayout &Layout) { + // "Define" each section & symbol. This creates section & symbol + // entries in the staging area. + for (const auto &Section : Asm) + defineSection(static_cast<const MCSectionCOFF &>(Section)); + + for (const MCSymbol &Symbol : Asm.symbols()) + if (!Symbol.isTemporary()) + DefineSymbol(Symbol, Asm, Layout); +} + +bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl( + const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB, + bool InSet, bool IsPCRel) const { + // MS LINK expects to be able to replace all references to a function with a + // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize + // away any relocations to functions. + uint16_t Type = cast<MCSymbolCOFF>(SymA).getType(); + if (Asm.isIncrementalLinkerCompatible() && + (Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION) + return false; + return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB, + InSet, IsPCRel); +} + +void WinCOFFObjectWriter::recordRelocation( + MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { + assert(Target.getSymA() && "Relocation must reference a symbol!"); + + const MCSymbol &A = Target.getSymA()->getSymbol(); + if (!A.isRegistered()) { + Asm.getContext().reportError(Fixup.getLoc(), + Twine("symbol '") + A.getName() + + "' can not be undefined"); + return; + } + if (A.isTemporary() && A.isUndefined()) { + Asm.getContext().reportError(Fixup.getLoc(), + Twine("assembler label '") + A.getName() + + "' can not be undefined"); + return; + } + + MCSection *MCSec = Fragment->getParent(); + + // Mark this symbol as requiring an entry in the symbol table. + assert(SectionMap.find(MCSec) != SectionMap.end() && + "Section must already have been defined in executePostLayoutBinding!"); + + COFFSection *Sec = SectionMap[MCSec]; + const MCSymbolRefExpr *SymB = Target.getSymB(); + bool CrossSection = false; + + if (SymB) { + const MCSymbol *B = &SymB->getSymbol(); + if (!B->getFragment()) { + Asm.getContext().reportError( + Fixup.getLoc(), + Twine("symbol '") + B->getName() + + "' can not be undefined in a subtraction expression"); + return; + } + + if (!A.getFragment()) { + Asm.getContext().reportError( + Fixup.getLoc(), + Twine("symbol '") + A.getName() + + "' can not be undefined in a subtraction expression"); + return; + } + + CrossSection = &A.getSection() != &B->getSection(); + + // Offset of the symbol in the section + int64_t OffsetOfB = Layout.getSymbolOffset(*B); + + // In the case where we have SymbA and SymB, we just need to store the delta + // between the two symbols. Update FixedValue to account for the delta, and + // skip recording the relocation. + if (!CrossSection) { + int64_t OffsetOfA = Layout.getSymbolOffset(A); + FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant(); + return; + } + + // Offset of the relocation in the section + int64_t OffsetOfRelocation = + Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); + + FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant(); + } else { + FixedValue = Target.getConstant(); + } + + COFFRelocation Reloc; + + Reloc.Data.SymbolTableIndex = 0; + Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); + + // Turn relocations for temporary symbols into section relocations. + if (A.isTemporary() || CrossSection) { + MCSection *TargetSection = &A.getSection(); + assert( + SectionMap.find(TargetSection) != SectionMap.end() && + "Section must already have been defined in executePostLayoutBinding!"); + Reloc.Symb = SectionMap[TargetSection]->Symbol; + FixedValue += Layout.getSymbolOffset(A); + } else { + assert( + SymbolMap.find(&A) != SymbolMap.end() && + "Symbol must already have been defined in executePostLayoutBinding!"); + Reloc.Symb = SymbolMap[&A]; + } + + ++Reloc.Symb->Relocations; + + Reloc.Data.VirtualAddress += Fixup.getOffset(); + Reloc.Data.Type = TargetObjectWriter->getRelocType( + Target, Fixup, CrossSection, Asm.getBackend()); + + // FIXME: Can anyone explain what this does other than adjust for the size + // of the offset? + if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && + Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || + (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && + Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) + FixedValue += 4; + + if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) { + switch (Reloc.Data.Type) { + case COFF::IMAGE_REL_ARM_ABSOLUTE: + case COFF::IMAGE_REL_ARM_ADDR32: + case COFF::IMAGE_REL_ARM_ADDR32NB: + case COFF::IMAGE_REL_ARM_TOKEN: + case COFF::IMAGE_REL_ARM_SECTION: + case COFF::IMAGE_REL_ARM_SECREL: + break; + case COFF::IMAGE_REL_ARM_BRANCH11: + case COFF::IMAGE_REL_ARM_BLX11: + // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for + // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid + // for Windows CE). + case COFF::IMAGE_REL_ARM_BRANCH24: + case COFF::IMAGE_REL_ARM_BLX24: + case COFF::IMAGE_REL_ARM_MOV32A: + // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are + // only used for ARM mode code, which is documented as being unsupported + // by Windows on ARM. Empirical proof indicates that masm is able to + // generate the relocations however the rest of the MSVC toolchain is + // unable to handle it. + llvm_unreachable("unsupported relocation"); + break; + case COFF::IMAGE_REL_ARM_MOV32T: + break; + case COFF::IMAGE_REL_ARM_BRANCH20T: + case COFF::IMAGE_REL_ARM_BRANCH24T: + case COFF::IMAGE_REL_ARM_BLX23T: + // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all + // perform a 4 byte adjustment to the relocation. Relative branches are + // offset by 4 on ARM, however, because there is no RELA relocations, all + // branches are offset by 4. + FixedValue = FixedValue + 4; + break; + } + } + + // The fixed value never makes sense for section indices, ignore it. + if (Fixup.getKind() == FK_SecRel_2) + FixedValue = 0; + + if (TargetObjectWriter->recordRelocation(Fixup)) + Sec->Relocations.push_back(Reloc); +} + +static std::time_t getTime() { + std::time_t Now = time(nullptr); + if (Now < 0 || !isUInt<32>(Now)) + return UINT32_MAX; + return Now; +} + +// Create .file symbols. +void WinCOFFObjectWriter::createFileSymbols(MCAssembler &Asm) { + for (const std::string &Name : Asm.getFileNames()) { + // round up to calculate the number of auxiliary symbols required + unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size; + unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize; + + COFFSymbol *File = createSymbol(".file"); + File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG; + File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE; + File->Aux.resize(Count); + + unsigned Offset = 0; + unsigned Length = Name.size(); + for (auto &Aux : File->Aux) { + Aux.AuxType = ATFile; + + if (Length > SymbolSize) { + memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize); + Length = Length - SymbolSize; + } else { + memcpy(&Aux.Aux, Name.c_str() + Offset, Length); + memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length); + break; + } + + Offset += SymbolSize; + } + } +} + +static bool isAssociative(const COFFSection &Section) { + return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection == + COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE; +} + +void WinCOFFObjectWriter::assignSectionNumbers() { + size_t I = 1; + auto Assign = [&](COFFSection &Section) { + Section.Number = I; + Section.Symbol->Data.SectionNumber = I; + Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I; + ++I; + }; + + // Although it is not explicitly requested by the Microsoft COFF spec, + // we should avoid emitting forward associative section references, + // because MSVC link.exe as of 2017 cannot handle that. + for (const std::unique_ptr<COFFSection> &Section : Sections) + if (!isAssociative(*Section)) + Assign(*Section); + for (const std::unique_ptr<COFFSection> &Section : Sections) + if (isAssociative(*Section)) + Assign(*Section); +} + +// Assign file offsets to COFF object file structures. +void WinCOFFObjectWriter::assignFileOffsets(MCAssembler &Asm, + const MCAsmLayout &Layout) { + unsigned Offset = getInitialOffset(); + + Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size; + Offset += COFF::SectionSize * Header.NumberOfSections; + + for (const auto &Section : Asm) { + COFFSection *Sec = SectionMap[&Section]; + + if (Sec->Number == -1) + continue; + + Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section); + + if (IsPhysicalSection(Sec)) { + // Align the section data to a four byte boundary. + Offset = alignTo(Offset, 4); + Sec->Header.PointerToRawData = Offset; + + Offset += Sec->Header.SizeOfRawData; + } + + if (!Sec->Relocations.empty()) { + bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff; + + if (RelocationsOverflow) { + // Signal overflow by setting NumberOfRelocations to max value. Actual + // size is found in reloc #0. Microsoft tools understand this. + Sec->Header.NumberOfRelocations = 0xffff; + } else { + Sec->Header.NumberOfRelocations = Sec->Relocations.size(); + } + Sec->Header.PointerToRelocations = Offset; + + if (RelocationsOverflow) { + // Reloc #0 will contain actual count, so make room for it. + Offset += COFF::RelocationSize; + } + + Offset += COFF::RelocationSize * Sec->Relocations.size(); + + for (auto &Relocation : Sec->Relocations) { + assert(Relocation.Symb->getIndex() != -1); + Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex(); + } + } + + assert(Sec->Symbol->Aux.size() == 1 && + "Section's symbol must have one aux!"); + AuxSymbol &Aux = Sec->Symbol->Aux[0]; + assert(Aux.AuxType == ATSectionDefinition && + "Section's symbol's aux symbol must be a Section Definition!"); + Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData; + Aux.Aux.SectionDefinition.NumberOfRelocations = + Sec->Header.NumberOfRelocations; + Aux.Aux.SectionDefinition.NumberOfLinenumbers = + Sec->Header.NumberOfLineNumbers; + } + + Header.PointerToSymbolTable = Offset; +} + +void WinCOFFObjectWriter::writeObject(MCAssembler &Asm, + const MCAsmLayout &Layout) { + if (Sections.size() > INT32_MAX) + report_fatal_error( + "PE COFF object files can't have more than 2147483647 sections"); + + UseBigObj = Sections.size() > COFF::MaxNumberOfSections16; + Header.NumberOfSections = Sections.size(); + Header.NumberOfSymbols = 0; + + assignSectionNumbers(); + createFileSymbols(Asm); + + for (auto &Symbol : Symbols) { + // Update section number & offset for symbols that have them. + if (Symbol->Section) + Symbol->Data.SectionNumber = Symbol->Section->Number; + Symbol->setIndex(Header.NumberOfSymbols++); + // Update auxiliary symbol info. + Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size(); + Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols; + } + + // Build string table. + for (const auto &S : Sections) + if (S->Name.size() > COFF::NameSize) + Strings.add(S->Name); + for (const auto &S : Symbols) + if (S->Name.size() > COFF::NameSize) + Strings.add(S->Name); + Strings.finalize(); + + // Set names. + for (const auto &S : Sections) + SetSectionName(*S); + for (auto &S : Symbols) + SetSymbolName(*S); + + // Fixup weak external references. + for (auto &Symbol : Symbols) { + if (Symbol->Other) { + assert(Symbol->getIndex() != -1); + assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!"); + assert(Symbol->Aux[0].AuxType == ATWeakExternal && + "Symbol's aux symbol must be a Weak External!"); + Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex(); + } + } + + // Fixup associative COMDAT sections. + for (auto &Section : Sections) { + if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection != + COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) + continue; + + const MCSectionCOFF &MCSec = *Section->MCSection; + + const MCSymbol *COMDAT = MCSec.getCOMDATSymbol(); + assert(COMDAT); + COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT); + assert(COMDATSymbol); + COFFSection *Assoc = COMDATSymbol->Section; + if (!Assoc) + report_fatal_error( + Twine("Missing associated COMDAT section for section ") + + MCSec.getSectionName()); + + // Skip this section if the associated section is unused. + if (Assoc->Number == -1) + continue; + + Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number; + } + + assignFileOffsets(Asm, Layout); + + // MS LINK expects to be able to use this timestamp to implement their + // /INCREMENTAL feature. + if (Asm.isIncrementalLinkerCompatible()) { + Header.TimeDateStamp = getTime(); + } else { + // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU. + Header.TimeDateStamp = 0; + } + + // Write it all to disk... + WriteFileHeader(Header); + writeSectionHeaders(); + + // Write section contents. + sections::iterator I = Sections.begin(); + sections::iterator IE = Sections.end(); + MCAssembler::iterator J = Asm.begin(); + MCAssembler::iterator JE = Asm.end(); + for (; I != IE && J != JE; ++I, ++J) + writeSection(Asm, Layout, **I, *J); + + assert(getStream().tell() == Header.PointerToSymbolTable && + "Header::PointerToSymbolTable is insane!"); + + // Write a symbol table. + for (auto &Symbol : Symbols) + if (Symbol->getIndex() != -1) + WriteSymbol(*Symbol); + + // Write a string table, which completes the entire COFF file. + Strings.write(getStream()); +} + +MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) + : Machine(Machine_) {} + +// Pin the vtable to this file. +void MCWinCOFFObjectTargetWriter::anchor() {} + +//------------------------------------------------------------------------------ +// WinCOFFObjectWriter factory function + +MCObjectWriter * +llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, + raw_pwrite_stream &OS) { + return new WinCOFFObjectWriter(MOTW, OS); +} |