| //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements ELF object file writer information. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/MC/MCELFObjectWriter.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/ADT/StringMap.h" |
| #include "llvm/MC/MCAsmBackend.h" |
| #include "llvm/MC/MCAsmInfo.h" |
| #include "llvm/MC/MCAsmLayout.h" |
| #include "llvm/MC/MCAssembler.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCELF.h" |
| #include "llvm/MC/MCELFSymbolFlags.h" |
| #include "llvm/MC/MCExpr.h" |
| #include "llvm/MC/MCFixupKindInfo.h" |
| #include "llvm/MC/MCObjectWriter.h" |
| #include "llvm/MC/MCSectionELF.h" |
| #include "llvm/MC/MCValue.h" |
| #include "llvm/MC/StringTableBuilder.h" |
| #include "llvm/Support/Compression.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/Endian.h" |
| #include "llvm/Support/ELF.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include <vector> |
| using namespace llvm; |
| |
| #undef DEBUG_TYPE |
| #define DEBUG_TYPE "reloc-info" |
| |
| namespace { |
| class FragmentWriter { |
| bool IsLittleEndian; |
| |
| public: |
| FragmentWriter(bool IsLittleEndian); |
| template <typename T> void write(MCDataFragment &F, T Val); |
| }; |
| |
| typedef DenseMap<const MCSectionELF *, uint32_t> SectionIndexMapTy; |
| |
| class SymbolTableWriter { |
| MCAssembler &Asm; |
| FragmentWriter &FWriter; |
| bool Is64Bit; |
| SectionIndexMapTy &SectionIndexMap; |
| |
| // The symbol .symtab fragment we are writting to. |
| MCDataFragment *SymtabF; |
| |
| // .symtab_shndx fragment we are writting to. |
| MCDataFragment *ShndxF; |
| |
| // The numbel of symbols written so far. |
| unsigned NumWritten; |
| |
| void createSymtabShndx(); |
| |
| template <typename T> void write(MCDataFragment &F, T Value); |
| |
| public: |
| SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter, bool Is64Bit, |
| SectionIndexMapTy &SectionIndexMap, |
| MCDataFragment *SymtabF); |
| |
| void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size, |
| uint8_t other, uint32_t shndx, bool Reserved); |
| }; |
| |
| struct ELFRelocationEntry { |
| uint64_t Offset; // Where is the relocation. |
| bool UseSymbol; // Relocate with a symbol, not the section. |
| union { |
| const MCSymbol *Symbol; // The symbol to relocate with. |
| const MCSectionData *Section; // The section to relocate with. |
| }; |
| unsigned Type; // The type of the relocation. |
| uint64_t Addend; // The addend to use. |
| |
| ELFRelocationEntry(uint64_t Offset, const MCSymbol *Symbol, unsigned Type, |
| uint64_t Addend) |
| : Offset(Offset), UseSymbol(true), Symbol(Symbol), Type(Type), |
| Addend(Addend) {} |
| |
| ELFRelocationEntry(uint64_t Offset, const MCSectionData *Section, |
| unsigned Type, uint64_t Addend) |
| : Offset(Offset), UseSymbol(false), Section(Section), Type(Type), |
| Addend(Addend) {} |
| }; |
| |
| class ELFObjectWriter : public MCObjectWriter { |
| FragmentWriter FWriter; |
| |
| protected: |
| |
| static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); |
| static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant); |
| static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout); |
| static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolData &Data, |
| bool Used, bool Renamed); |
| static bool isLocal(const MCSymbolData &Data, bool isUsedInReloc); |
| static bool IsELFMetaDataSection(const MCSectionData &SD); |
| static uint64_t DataSectionSize(const MCSectionData &SD); |
| static uint64_t GetSectionFileSize(const MCAsmLayout &Layout, |
| const MCSectionData &SD); |
| static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout, |
| const MCSectionData &SD); |
| |
| void WriteDataSectionData(MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCSectionELF &Section); |
| |
| /*static bool isFixupKindX86RIPRel(unsigned Kind) { |
| return Kind == X86::reloc_riprel_4byte || |
| Kind == X86::reloc_riprel_4byte_movq_load; |
| }*/ |
| |
| /// ELFSymbolData - Helper struct for containing some precomputed |
| /// information on symbols. |
| struct ELFSymbolData { |
| MCSymbolData *SymbolData; |
| uint64_t StringIndex; |
| uint32_t SectionIndex; |
| StringRef Name; |
| |
| // Support lexicographic sorting. |
| bool operator<(const ELFSymbolData &RHS) const { |
| return Name < RHS.Name; |
| } |
| }; |
| |
| /// The target specific ELF writer instance. |
| std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter; |
| |
| SmallPtrSet<const MCSymbol *, 16> UsedInReloc; |
| SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc; |
| DenseMap<const MCSymbol *, const MCSymbol *> Renames; |
| |
| llvm::DenseMap<const MCSectionData *, std::vector<ELFRelocationEntry>> |
| Relocations; |
| StringTableBuilder ShStrTabBuilder; |
| |
| /// @} |
| /// @name Symbol Table Data |
| /// @{ |
| |
| StringTableBuilder StrTabBuilder; |
| std::vector<uint64_t> FileSymbolData; |
| std::vector<ELFSymbolData> LocalSymbolData; |
| std::vector<ELFSymbolData> ExternalSymbolData; |
| std::vector<ELFSymbolData> UndefinedSymbolData; |
| |
| /// @} |
| |
| bool NeedsGOT; |
| |
| // This holds the symbol table index of the last local symbol. |
| unsigned LastLocalSymbolIndex; |
| // This holds the .strtab section index. |
| unsigned StringTableIndex; |
| // This holds the .symtab section index. |
| unsigned SymbolTableIndex; |
| |
| unsigned ShstrtabIndex; |
| |
| |
| // TargetObjectWriter wrappers. |
| bool is64Bit() const { return TargetObjectWriter->is64Bit(); } |
| bool hasRelocationAddend() const { |
| return TargetObjectWriter->hasRelocationAddend(); |
| } |
| unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, |
| bool IsPCRel) const { |
| return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel); |
| } |
| |
| public: |
| ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_ostream &_OS, |
| bool IsLittleEndian) |
| : MCObjectWriter(_OS, IsLittleEndian), FWriter(IsLittleEndian), |
| TargetObjectWriter(MOTW), NeedsGOT(false) {} |
| |
| virtual ~ELFObjectWriter(); |
| |
| void WriteWord(uint64_t W) { |
| if (is64Bit()) |
| Write64(W); |
| else |
| Write32(W); |
| } |
| |
| template <typename T> void write(MCDataFragment &F, T Value) { |
| FWriter.write(F, Value); |
| } |
| |
| void WriteHeader(const MCAssembler &Asm, |
| uint64_t SectionDataSize, |
| unsigned NumberOfSections); |
| |
| void WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD, |
| const MCAsmLayout &Layout); |
| |
| void WriteSymbolTable(MCDataFragment *SymtabF, MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| SectionIndexMapTy &SectionIndexMap); |
| |
| bool shouldRelocateWithSymbol(const MCAssembler &Asm, |
| const MCSymbolRefExpr *RefA, |
| const MCSymbolData *SD, uint64_t C, |
| unsigned Type) const; |
| |
| void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, |
| const MCFragment *Fragment, const MCFixup &Fixup, |
| MCValue Target, bool &IsPCRel, |
| uint64_t &FixedValue) override; |
| |
| uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm, |
| const MCSymbol *S); |
| |
| // Map from a group section to the signature symbol |
| typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy; |
| // Map from a signature symbol to the group section |
| typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy; |
| // Map from a section to the section with the relocations |
| typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy; |
| // Map from a section to its offset |
| typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy; |
| |
| /// Compute the symbol table data |
| /// |
| /// \param Asm - The assembler. |
| /// \param SectionIndexMap - Maps a section to its index. |
| /// \param RevGroupMap - Maps a signature symbol to the group section. |
| /// \param NumRegularSections - Number of non-relocation sections. |
| void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout, |
| const SectionIndexMapTy &SectionIndexMap, |
| RevGroupMapTy RevGroupMap, |
| unsigned NumRegularSections); |
| |
| void ComputeIndexMap(MCAssembler &Asm, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap); |
| |
| void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout, |
| RelMapTy &RelMap); |
| |
| void CompressDebugSections(MCAssembler &Asm, MCAsmLayout &Layout); |
| |
| void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, |
| const RelMapTy &RelMap); |
| |
| void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap); |
| |
| // Create the sections that show up in the symbol table. Currently |
| // those are the .note.GNU-stack section and the group sections. |
| void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout, |
| GroupMapTy &GroupMap, |
| RevGroupMapTy &RevGroupMap, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap); |
| |
| void ExecutePostLayoutBinding(MCAssembler &Asm, |
| const MCAsmLayout &Layout) override; |
| |
| void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap, |
| const MCAsmLayout &Layout, |
| const SectionIndexMapTy &SectionIndexMap, |
| const SectionOffsetMapTy &SectionOffsetMap); |
| |
| void ComputeSectionOrder(MCAssembler &Asm, |
| std::vector<const MCSectionELF*> &Sections); |
| |
| void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags, |
| uint64_t Address, uint64_t Offset, |
| uint64_t Size, uint32_t Link, uint32_t Info, |
| uint64_t Alignment, uint64_t EntrySize); |
| |
| void WriteRelocationsFragment(const MCAssembler &Asm, |
| MCDataFragment *F, |
| const MCSectionData *SD); |
| |
| bool |
| IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, |
| const MCSymbolData &DataA, |
| const MCFragment &FB, |
| bool InSet, |
| bool IsPCRel) const override; |
| |
| void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; |
| void WriteSection(MCAssembler &Asm, |
| const SectionIndexMapTy &SectionIndexMap, |
| uint32_t GroupSymbolIndex, |
| uint64_t Offset, uint64_t Size, uint64_t Alignment, |
| const MCSectionELF &Section); |
| }; |
| } |
| |
| FragmentWriter::FragmentWriter(bool IsLittleEndian) |
| : IsLittleEndian(IsLittleEndian) {} |
| |
| template <typename T> void FragmentWriter::write(MCDataFragment &F, T Val) { |
| if (IsLittleEndian) |
| Val = support::endian::byte_swap<T, support::little>(Val); |
| else |
| Val = support::endian::byte_swap<T, support::big>(Val); |
| const char *Start = (const char *)&Val; |
| F.getContents().append(Start, Start + sizeof(T)); |
| } |
| |
| void SymbolTableWriter::createSymtabShndx() { |
| if (ShndxF) |
| return; |
| |
| MCContext &Ctx = Asm.getContext(); |
| const MCSectionELF *SymtabShndxSection = |
| Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, |
| SectionKind::getReadOnly(), 4, ""); |
| MCSectionData *SymtabShndxSD = |
| &Asm.getOrCreateSectionData(*SymtabShndxSection); |
| SymtabShndxSD->setAlignment(4); |
| ShndxF = new MCDataFragment(SymtabShndxSD); |
| unsigned Index = SectionIndexMap.size() + 1; |
| SectionIndexMap[SymtabShndxSection] = Index; |
| |
| for (unsigned I = 0; I < NumWritten; ++I) |
| write(*ShndxF, uint32_t(0)); |
| } |
| |
| template <typename T> |
| void SymbolTableWriter::write(MCDataFragment &F, T Value) { |
| FWriter.write(F, Value); |
| } |
| |
| SymbolTableWriter::SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter, |
| bool Is64Bit, |
| SectionIndexMapTy &SectionIndexMap, |
| MCDataFragment *SymtabF) |
| : Asm(Asm), FWriter(FWriter), Is64Bit(Is64Bit), |
| SectionIndexMap(SectionIndexMap), SymtabF(SymtabF), ShndxF(nullptr), |
| NumWritten(0) {} |
| |
| void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value, |
| uint64_t size, uint8_t other, |
| uint32_t shndx, bool Reserved) { |
| bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved; |
| |
| if (LargeIndex) |
| createSymtabShndx(); |
| |
| if (ShndxF) { |
| if (LargeIndex) |
| write(*ShndxF, shndx); |
| else |
| write(*ShndxF, uint32_t(0)); |
| } |
| |
| uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx; |
| |
| raw_svector_ostream OS(SymtabF->getContents()); |
| |
| if (Is64Bit) { |
| write(*SymtabF, name); // st_name |
| write(*SymtabF, info); // st_info |
| write(*SymtabF, other); // st_other |
| write(*SymtabF, Index); // st_shndx |
| write(*SymtabF, value); // st_value |
| write(*SymtabF, size); // st_size |
| } else { |
| write(*SymtabF, name); // st_name |
| write(*SymtabF, uint32_t(value)); // st_value |
| write(*SymtabF, uint32_t(size)); // st_size |
| write(*SymtabF, info); // st_info |
| write(*SymtabF, other); // st_other |
| write(*SymtabF, Index); // st_shndx |
| } |
| |
| ++NumWritten; |
| } |
| |
| bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { |
| const MCFixupKindInfo &FKI = |
| Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind); |
| |
| return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; |
| } |
| |
| bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) { |
| switch (Variant) { |
| default: |
| return false; |
| case MCSymbolRefExpr::VK_GOT: |
| case MCSymbolRefExpr::VK_PLT: |
| case MCSymbolRefExpr::VK_GOTPCREL: |
| case MCSymbolRefExpr::VK_GOTOFF: |
| case MCSymbolRefExpr::VK_TPOFF: |
| case MCSymbolRefExpr::VK_TLSGD: |
| case MCSymbolRefExpr::VK_GOTTPOFF: |
| case MCSymbolRefExpr::VK_INDNTPOFF: |
| case MCSymbolRefExpr::VK_NTPOFF: |
| case MCSymbolRefExpr::VK_GOTNTPOFF: |
| case MCSymbolRefExpr::VK_TLSLDM: |
| case MCSymbolRefExpr::VK_DTPOFF: |
| case MCSymbolRefExpr::VK_TLSLD: |
| return true; |
| } |
| } |
| |
| ELFObjectWriter::~ELFObjectWriter() |
| {} |
| |
| // Emit the ELF header. |
| void ELFObjectWriter::WriteHeader(const MCAssembler &Asm, |
| uint64_t SectionDataSize, |
| unsigned NumberOfSections) { |
| // ELF Header |
| // ---------- |
| // |
| // Note |
| // ---- |
| // emitWord method behaves differently for ELF32 and ELF64, writing |
| // 4 bytes in the former and 8 in the latter. |
| |
| Write8(0x7f); // e_ident[EI_MAG0] |
| Write8('E'); // e_ident[EI_MAG1] |
| Write8('L'); // e_ident[EI_MAG2] |
| Write8('F'); // e_ident[EI_MAG3] |
| |
| Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS] |
| |
| // e_ident[EI_DATA] |
| Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); |
| |
| Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] |
| // e_ident[EI_OSABI] |
| Write8(TargetObjectWriter->getOSABI()); |
| Write8(0); // e_ident[EI_ABIVERSION] |
| |
| WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); |
| |
| Write16(ELF::ET_REL); // e_type |
| |
| Write16(TargetObjectWriter->getEMachine()); // e_machine = target |
| |
| Write32(ELF::EV_CURRENT); // e_version |
| WriteWord(0); // e_entry, no entry point in .o file |
| WriteWord(0); // e_phoff, no program header for .o |
| WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) : |
| sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes |
| |
| // e_flags = whatever the target wants |
| Write32(Asm.getELFHeaderEFlags()); |
| |
| // e_ehsize = ELF header size |
| Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr)); |
| |
| Write16(0); // e_phentsize = prog header entry size |
| Write16(0); // e_phnum = # prog header entries = 0 |
| |
| // e_shentsize = Section header entry size |
| Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr)); |
| |
| // e_shnum = # of section header ents |
| if (NumberOfSections >= ELF::SHN_LORESERVE) |
| Write16(ELF::SHN_UNDEF); |
| else |
| Write16(NumberOfSections); |
| |
| // e_shstrndx = Section # of '.shstrtab' |
| if (ShstrtabIndex >= ELF::SHN_LORESERVE) |
| Write16(ELF::SHN_XINDEX); |
| else |
| Write16(ShstrtabIndex); |
| } |
| |
| uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data, |
| const MCAsmLayout &Layout) { |
| if (Data.isCommon() && Data.isExternal()) |
| return Data.getCommonAlignment(); |
| |
| uint64_t Res; |
| if (!Layout.getSymbolOffset(&Data, Res)) |
| return 0; |
| |
| if (Layout.getAssembler().isThumbFunc(&Data.getSymbol())) |
| Res |= 1; |
| |
| return Res; |
| } |
| |
| void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| // The presence of symbol versions causes undefined symbols and |
| // versions declared with @@@ to be renamed. |
| |
| for (MCSymbolData &OriginalData : Asm.symbols()) { |
| const MCSymbol &Alias = OriginalData.getSymbol(); |
| |
| // Not an alias. |
| if (!Alias.isVariable()) |
| continue; |
| auto *Ref = dyn_cast<MCSymbolRefExpr>(Alias.getVariableValue()); |
| if (!Ref) |
| continue; |
| const MCSymbol &Symbol = Ref->getSymbol(); |
| MCSymbolData &SD = Asm.getSymbolData(Symbol); |
| |
| StringRef AliasName = Alias.getName(); |
| size_t Pos = AliasName.find('@'); |
| if (Pos == StringRef::npos) |
| continue; |
| |
| // Aliases defined with .symvar copy the binding from the symbol they alias. |
| // This is the first place we are able to copy this information. |
| OriginalData.setExternal(SD.isExternal()); |
| MCELF::SetBinding(OriginalData, MCELF::GetBinding(SD)); |
| |
| StringRef Rest = AliasName.substr(Pos); |
| if (!Symbol.isUndefined() && !Rest.startswith("@@@")) |
| continue; |
| |
| // FIXME: produce a better error message. |
| if (Symbol.isUndefined() && Rest.startswith("@@") && |
| !Rest.startswith("@@@")) |
| report_fatal_error("A @@ version cannot be undefined"); |
| |
| Renames.insert(std::make_pair(&Symbol, &Alias)); |
| } |
| } |
| |
| static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) { |
| uint8_t Type = newType; |
| |
| // Propagation rules: |
| // IFUNC > FUNC > OBJECT > NOTYPE |
| // TLS_OBJECT > OBJECT > NOTYPE |
| // |
| // dont let the new type degrade the old type |
| switch (origType) { |
| default: |
| break; |
| case ELF::STT_GNU_IFUNC: |
| if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT || |
| Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS) |
| Type = ELF::STT_GNU_IFUNC; |
| break; |
| case ELF::STT_FUNC: |
| if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE || |
| Type == ELF::STT_TLS) |
| Type = ELF::STT_FUNC; |
| break; |
| case ELF::STT_OBJECT: |
| if (Type == ELF::STT_NOTYPE) |
| Type = ELF::STT_OBJECT; |
| break; |
| case ELF::STT_TLS: |
| if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE || |
| Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC) |
| Type = ELF::STT_TLS; |
| break; |
| } |
| |
| return Type; |
| } |
| |
| void ELFObjectWriter::WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD, |
| const MCAsmLayout &Layout) { |
| MCSymbolData &OrigData = *MSD.SymbolData; |
| assert((!OrigData.getFragment() || |
| (&OrigData.getFragment()->getParent()->getSection() == |
| &OrigData.getSymbol().getSection())) && |
| "The symbol's section doesn't match the fragment's symbol"); |
| const MCSymbol *Base = Layout.getBaseSymbol(OrigData.getSymbol()); |
| |
| // This has to be in sync with when computeSymbolTable uses SHN_ABS or |
| // SHN_COMMON. |
| bool IsReserved = !Base || OrigData.isCommon(); |
| |
| // Binding and Type share the same byte as upper and lower nibbles |
| uint8_t Binding = MCELF::GetBinding(OrigData); |
| uint8_t Type = MCELF::GetType(OrigData); |
| MCSymbolData *BaseSD = nullptr; |
| if (Base) { |
| BaseSD = &Layout.getAssembler().getSymbolData(*Base); |
| Type = mergeTypeForSet(Type, MCELF::GetType(*BaseSD)); |
| } |
| uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); |
| |
| // Other and Visibility share the same byte with Visibility using the lower |
| // 2 bits |
| uint8_t Visibility = MCELF::GetVisibility(OrigData); |
| uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift); |
| Other |= Visibility; |
| |
| uint64_t Value = SymbolValue(OrigData, Layout); |
| uint64_t Size = 0; |
| |
| const MCExpr *ESize = OrigData.getSize(); |
| if (!ESize && Base) |
| ESize = BaseSD->getSize(); |
| |
| if (ESize) { |
| int64_t Res; |
| if (!ESize->EvaluateAsAbsolute(Res, Layout)) |
| report_fatal_error("Size expression must be absolute."); |
| Size = Res; |
| } |
| |
| // Write out the symbol table entry |
| Writer.writeSymbol(MSD.StringIndex, Info, Value, Size, Other, |
| MSD.SectionIndex, IsReserved); |
| } |
| |
| void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF, |
| MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| SectionIndexMapTy &SectionIndexMap) { |
| // The string table must be emitted first because we need the index |
| // into the string table for all the symbol names. |
| |
| // FIXME: Make sure the start of the symbol table is aligned. |
| |
| SymbolTableWriter Writer(Asm, FWriter, is64Bit(), SectionIndexMap, SymtabF); |
| |
| // The first entry is the undefined symbol entry. |
| Writer.writeSymbol(0, 0, 0, 0, 0, 0, false); |
| |
| for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) { |
| Writer.writeSymbol(FileSymbolData[i], ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, |
| ELF::STV_DEFAULT, ELF::SHN_ABS, true); |
| } |
| |
| // Write the symbol table entries. |
| LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1; |
| |
| for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) { |
| ELFSymbolData &MSD = LocalSymbolData[i]; |
| WriteSymbol(Writer, MSD, Layout); |
| } |
| |
| // Write out a symbol table entry for each regular section. |
| for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; |
| ++i) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(i->getSection()); |
| if (Section.getType() == ELF::SHT_RELA || |
| Section.getType() == ELF::SHT_REL || |
| Section.getType() == ELF::SHT_STRTAB || |
| Section.getType() == ELF::SHT_SYMTAB || |
| Section.getType() == ELF::SHT_SYMTAB_SHNDX) |
| continue; |
| Writer.writeSymbol(0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, |
| SectionIndexMap.lookup(&Section), false); |
| LastLocalSymbolIndex++; |
| } |
| |
| for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { |
| ELFSymbolData &MSD = ExternalSymbolData[i]; |
| MCSymbolData &Data = *MSD.SymbolData; |
| assert(((Data.getFlags() & ELF_STB_Global) || |
| (Data.getFlags() & ELF_STB_Weak)) && |
| "External symbol requires STB_GLOBAL or STB_WEAK flag"); |
| WriteSymbol(Writer, MSD, Layout); |
| if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) |
| LastLocalSymbolIndex++; |
| } |
| |
| for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { |
| ELFSymbolData &MSD = UndefinedSymbolData[i]; |
| MCSymbolData &Data = *MSD.SymbolData; |
| WriteSymbol(Writer, MSD, Layout); |
| if (MCELF::GetBinding(Data) == ELF::STB_LOCAL) |
| LastLocalSymbolIndex++; |
| } |
| } |
| |
| // It is always valid to create a relocation with a symbol. It is preferable |
| // to use a relocation with a section if that is possible. Using the section |
| // allows us to omit some local symbols from the symbol table. |
| bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm, |
| const MCSymbolRefExpr *RefA, |
| const MCSymbolData *SD, |
| uint64_t C, |
| unsigned Type) const { |
| // A PCRel relocation to an absolute value has no symbol (or section). We |
| // represent that with a relocation to a null section. |
| if (!RefA) |
| return false; |
| |
| MCSymbolRefExpr::VariantKind Kind = RefA->getKind(); |
| switch (Kind) { |
| default: |
| break; |
| // The .odp creation emits a relocation against the symbol ".TOC." which |
| // create a R_PPC64_TOC relocation. However the relocation symbol name |
| // in final object creation should be NULL, since the symbol does not |
| // really exist, it is just the reference to TOC base for the current |
| // object file. Since the symbol is undefined, returning false results |
| // in a relocation with a null section which is the desired result. |
| case MCSymbolRefExpr::VK_PPC_TOCBASE: |
| return false; |
| |
| // These VariantKind cause the relocation to refer to something other than |
| // the symbol itself, like a linker generated table. Since the address of |
| // symbol is not relevant, we cannot replace the symbol with the |
| // section and patch the difference in the addend. |
| case MCSymbolRefExpr::VK_GOT: |
| case MCSymbolRefExpr::VK_PLT: |
| case MCSymbolRefExpr::VK_GOTPCREL: |
| case MCSymbolRefExpr::VK_Mips_GOT: |
| case MCSymbolRefExpr::VK_PPC_GOT_LO: |
| case MCSymbolRefExpr::VK_PPC_GOT_HI: |
| case MCSymbolRefExpr::VK_PPC_GOT_HA: |
| return true; |
| } |
| |
| // An undefined symbol is not in any section, so the relocation has to point |
| // to the symbol itself. |
| const MCSymbol &Sym = SD->getSymbol(); |
| if (Sym.isUndefined()) |
| return true; |
| |
| unsigned Binding = MCELF::GetBinding(*SD); |
| switch(Binding) { |
| default: |
| llvm_unreachable("Invalid Binding"); |
| case ELF::STB_LOCAL: |
| break; |
| case ELF::STB_WEAK: |
| // If the symbol is weak, it might be overridden by a symbol in another |
| // file. The relocation has to point to the symbol so that the linker |
| // can update it. |
| return true; |
| case ELF::STB_GLOBAL: |
| // Global ELF symbols can be preempted by the dynamic linker. The relocation |
| // has to point to the symbol for a reason analogous to the STB_WEAK case. |
| return true; |
| } |
| |
| // If a relocation points to a mergeable section, we have to be careful. |
| // If the offset is zero, a relocation with the section will encode the |
| // same information. With a non-zero offset, the situation is different. |
| // For example, a relocation can point 42 bytes past the end of a string. |
| // If we change such a relocation to use the section, the linker would think |
| // that it pointed to another string and subtracting 42 at runtime will |
| // produce the wrong value. |
| auto &Sec = cast<MCSectionELF>(Sym.getSection()); |
| unsigned Flags = Sec.getFlags(); |
| if (Flags & ELF::SHF_MERGE) { |
| if (C != 0) |
| return true; |
| |
| // It looks like gold has a bug (http://sourceware.org/PR16794) and can |
| // only handle section relocations to mergeable sections if using RELA. |
| if (!hasRelocationAddend()) |
| return true; |
| } |
| |
| // Most TLS relocations use a got, so they need the symbol. Even those that |
| // are just an offset (@tpoff), require a symbol in some linkers (gold, |
| // but not bfd ld). |
| if (Flags & ELF::SHF_TLS) |
| return true; |
| |
| // If the symbol is a thumb function the final relocation must set the lowest |
| // bit. With a symbol that is done by just having the symbol have that bit |
| // set, so we would lose the bit if we relocated with the section. |
| // FIXME: We could use the section but add the bit to the relocation value. |
| if (Asm.isThumbFunc(&Sym)) |
| return true; |
| |
| if (TargetObjectWriter->needsRelocateWithSymbol(*SD, Type)) |
| return true; |
| return false; |
| } |
| |
| static const MCSymbol *getWeakRef(const MCSymbolRefExpr &Ref) { |
| const MCSymbol &Sym = Ref.getSymbol(); |
| |
| if (Ref.getKind() == MCSymbolRefExpr::VK_WEAKREF) |
| return &Sym; |
| |
| if (!Sym.isVariable()) |
| return nullptr; |
| |
| const MCExpr *Expr = Sym.getVariableValue(); |
| const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr); |
| if (!Inner) |
| return nullptr; |
| |
| if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) |
| return &Inner->getSymbol(); |
| return nullptr; |
| } |
| |
| void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| bool &IsPCRel, |
| uint64_t &FixedValue) { |
| const MCSectionData *FixupSection = Fragment->getParent(); |
| uint64_t C = Target.getConstant(); |
| uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); |
| |
| if (const MCSymbolRefExpr *RefB = Target.getSymB()) { |
| assert(RefB->getKind() == MCSymbolRefExpr::VK_None && |
| "Should not have constructed this"); |
| |
| // Let A, B and C being the components of Target and R be the location of |
| // the fixup. If the fixup is not pcrel, we want to compute (A - B + C). |
| // If it is pcrel, we want to compute (A - B + C - R). |
| |
| // In general, ELF has no relocations for -B. It can only represent (A + C) |
| // or (A + C - R). If B = R + K and the relocation is not pcrel, we can |
| // replace B to implement it: (A - R - K + C) |
| if (IsPCRel) |
| Asm.getContext().FatalError( |
| Fixup.getLoc(), |
| "No relocation available to represent this relative expression"); |
| |
| const MCSymbol &SymB = RefB->getSymbol(); |
| |
| if (SymB.isUndefined()) |
| Asm.getContext().FatalError( |
| Fixup.getLoc(), |
| Twine("symbol '") + SymB.getName() + |
| "' can not be undefined in a subtraction expression"); |
| |
| assert(!SymB.isAbsolute() && "Should have been folded"); |
| const MCSection &SecB = SymB.getSection(); |
| if (&SecB != &FixupSection->getSection()) |
| Asm.getContext().FatalError( |
| Fixup.getLoc(), "Cannot represent a difference across sections"); |
| |
| const MCSymbolData &SymBD = Asm.getSymbolData(SymB); |
| uint64_t SymBOffset = Layout.getSymbolOffset(&SymBD); |
| uint64_t K = SymBOffset - FixupOffset; |
| IsPCRel = true; |
| C -= K; |
| } |
| |
| // We either rejected the fixup or folded B into C at this point. |
| const MCSymbolRefExpr *RefA = Target.getSymA(); |
| const MCSymbol *SymA = RefA ? &RefA->getSymbol() : nullptr; |
| const MCSymbolData *SymAD = SymA ? &Asm.getSymbolData(*SymA) : nullptr; |
| |
| unsigned Type = GetRelocType(Target, Fixup, IsPCRel); |
| bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymAD, C, Type); |
| if (!RelocateWithSymbol && SymA && !SymA->isUndefined()) |
| C += Layout.getSymbolOffset(SymAD); |
| |
| uint64_t Addend = 0; |
| if (hasRelocationAddend()) { |
| Addend = C; |
| C = 0; |
| } |
| |
| FixedValue = C; |
| |
| // FIXME: What is this!?!? |
| MCSymbolRefExpr::VariantKind Modifier = |
| RefA ? RefA->getKind() : MCSymbolRefExpr::VK_None; |
| if (RelocNeedsGOT(Modifier)) |
| NeedsGOT = true; |
| |
| if (!RelocateWithSymbol) { |
| const MCSection *SecA = |
| (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr; |
| const MCSectionData *SecAD = SecA ? &Asm.getSectionData(*SecA) : nullptr; |
| ELFRelocationEntry Rec(FixupOffset, SecAD, Type, Addend); |
| Relocations[FixupSection].push_back(Rec); |
| return; |
| } |
| |
| if (SymA) { |
| if (const MCSymbol *R = Renames.lookup(SymA)) |
| SymA = R; |
| |
| if (const MCSymbol *WeakRef = getWeakRef(*RefA)) |
| WeakrefUsedInReloc.insert(WeakRef); |
| else |
| UsedInReloc.insert(SymA); |
| } |
| ELFRelocationEntry Rec(FixupOffset, SymA, Type, Addend); |
| Relocations[FixupSection].push_back(Rec); |
| return; |
| } |
| |
| |
| uint64_t |
| ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm, |
| const MCSymbol *S) { |
| const MCSymbolData &SD = Asm.getSymbolData(*S); |
| return SD.getIndex(); |
| } |
| |
| bool ELFObjectWriter::isInSymtab(const MCAsmLayout &Layout, |
| const MCSymbolData &Data, bool Used, |
| bool Renamed) { |
| const MCSymbol &Symbol = Data.getSymbol(); |
| if (Symbol.isVariable()) { |
| const MCExpr *Expr = Symbol.getVariableValue(); |
| if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) { |
| if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF) |
| return false; |
| } |
| } |
| |
| if (Used) |
| return true; |
| |
| if (Renamed) |
| return false; |
| |
| if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_") |
| return true; |
| |
| if (Symbol.isVariable()) { |
| const MCSymbol *Base = Layout.getBaseSymbol(Symbol); |
| if (Base && Base->isUndefined()) |
| return false; |
| } |
| |
| bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL; |
| if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal) |
| return false; |
| |
| if (Symbol.isTemporary()) |
| return false; |
| |
| return true; |
| } |
| |
| bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isUsedInReloc) { |
| if (Data.isExternal()) |
| return false; |
| |
| const MCSymbol &Symbol = Data.getSymbol(); |
| if (Symbol.isDefined()) |
| return true; |
| |
| if (isUsedInReloc) |
| return false; |
| |
| return true; |
| } |
| |
| void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap) { |
| unsigned Index = 1; |
| for (MCAssembler::iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(it->getSection()); |
| if (Section.getType() != ELF::SHT_GROUP) |
| continue; |
| SectionIndexMap[&Section] = Index++; |
| } |
| |
| for (MCAssembler::iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(it->getSection()); |
| if (Section.getType() == ELF::SHT_GROUP || |
| Section.getType() == ELF::SHT_REL || |
| Section.getType() == ELF::SHT_RELA) |
| continue; |
| SectionIndexMap[&Section] = Index++; |
| const MCSectionELF *RelSection = RelMap.lookup(&Section); |
| if (RelSection) |
| SectionIndexMap[RelSection] = Index++; |
| } |
| } |
| |
| void |
| ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout, |
| const SectionIndexMapTy &SectionIndexMap, |
| RevGroupMapTy RevGroupMap, |
| unsigned NumRegularSections) { |
| // FIXME: Is this the correct place to do this? |
| // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed? |
| if (NeedsGOT) { |
| StringRef Name = "_GLOBAL_OFFSET_TABLE_"; |
| MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); |
| MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); |
| Data.setExternal(true); |
| MCELF::SetBinding(Data, ELF::STB_GLOBAL); |
| } |
| |
| // Add the data for the symbols. |
| for (MCSymbolData &SD : Asm.symbols()) { |
| const MCSymbol &Symbol = SD.getSymbol(); |
| |
| bool Used = UsedInReloc.count(&Symbol); |
| bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol); |
| bool isSignature = RevGroupMap.count(&Symbol); |
| |
| if (!isInSymtab(Layout, SD, |
| Used || WeakrefUsed || isSignature, |
| Renames.count(&Symbol))) |
| continue; |
| |
| ELFSymbolData MSD; |
| MSD.SymbolData = &SD; |
| const MCSymbol *BaseSymbol = Layout.getBaseSymbol(Symbol); |
| |
| // Undefined symbols are global, but this is the first place we |
| // are able to set it. |
| bool Local = isLocal(SD, Used); |
| if (!Local && MCELF::GetBinding(SD) == ELF::STB_LOCAL) { |
| assert(BaseSymbol); |
| MCSymbolData &BaseData = Asm.getSymbolData(*BaseSymbol); |
| MCELF::SetBinding(SD, ELF::STB_GLOBAL); |
| MCELF::SetBinding(BaseData, ELF::STB_GLOBAL); |
| } |
| |
| if (!BaseSymbol) { |
| MSD.SectionIndex = ELF::SHN_ABS; |
| } else if (SD.isCommon()) { |
| assert(!Local); |
| MSD.SectionIndex = ELF::SHN_COMMON; |
| } else if (BaseSymbol->isUndefined()) { |
| if (isSignature && !Used) |
| MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]); |
| else |
| MSD.SectionIndex = ELF::SHN_UNDEF; |
| if (!Used && WeakrefUsed) |
| MCELF::SetBinding(SD, ELF::STB_WEAK); |
| } else { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(BaseSymbol->getSection()); |
| MSD.SectionIndex = SectionIndexMap.lookup(&Section); |
| assert(MSD.SectionIndex && "Invalid section index!"); |
| } |
| |
| // The @@@ in symbol version is replaced with @ in undefined symbols and |
| // @@ in defined ones. |
| StringRef Name = Symbol.getName(); |
| SmallString<32> Buf; |
| size_t Pos = Name.find("@@@"); |
| if (Pos != StringRef::npos) { |
| Buf += Name.substr(0, Pos); |
| unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1; |
| Buf += Name.substr(Pos + Skip); |
| Name = Buf; |
| } |
| MSD.Name = StrTabBuilder.add(Name); |
| |
| if (MSD.SectionIndex == ELF::SHN_UNDEF) |
| UndefinedSymbolData.push_back(MSD); |
| else if (Local) |
| LocalSymbolData.push_back(MSD); |
| else |
| ExternalSymbolData.push_back(MSD); |
| } |
| |
| for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i) |
| StrTabBuilder.add(*i); |
| |
| StrTabBuilder.finalize(); |
| |
| for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i) |
| FileSymbolData.push_back(StrTabBuilder.getOffset(*i)); |
| |
| for (ELFSymbolData& MSD : LocalSymbolData) |
| MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name); |
| for (ELFSymbolData& MSD : ExternalSymbolData) |
| MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name); |
| for (ELFSymbolData& MSD : UndefinedSymbolData) |
| MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name); |
| |
| // Symbols are required to be in lexicographic order. |
| array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end()); |
| array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); |
| array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); |
| |
| // Set the symbol indices. Local symbols must come before all other |
| // symbols with non-local bindings. |
| unsigned Index = FileSymbolData.size() + 1; |
| for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) |
| LocalSymbolData[i].SymbolData->setIndex(Index++); |
| |
| Index += NumRegularSections; |
| |
| for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) |
| ExternalSymbolData[i].SymbolData->setIndex(Index++); |
| for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) |
| UndefinedSymbolData[i].SymbolData->setIndex(Index++); |
| } |
| |
| void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm, |
| MCAsmLayout &Layout, |
| RelMapTy &RelMap) { |
| for (MCAssembler::const_iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionData &SD = *it; |
| if (Relocations[&SD].empty()) |
| continue; |
| |
| MCContext &Ctx = Asm.getContext(); |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(SD.getSection()); |
| |
| const StringRef SectionName = Section.getSectionName(); |
| std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel"; |
| RelaSectionName += SectionName; |
| |
| unsigned EntrySize; |
| if (hasRelocationAddend()) |
| EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela); |
| else |
| EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel); |
| |
| unsigned Flags = 0; |
| StringRef Group = ""; |
| if (Section.getFlags() & ELF::SHF_GROUP) { |
| Flags = ELF::SHF_GROUP; |
| Group = Section.getGroup()->getName(); |
| } |
| |
| const MCSectionELF *RelaSection = |
| Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ? |
| ELF::SHT_RELA : ELF::SHT_REL, Flags, |
| SectionKind::getReadOnly(), |
| EntrySize, Group); |
| RelMap[&Section] = RelaSection; |
| Asm.getOrCreateSectionData(*RelaSection); |
| } |
| } |
| |
| static SmallVector<char, 128> |
| getUncompressedData(MCAsmLayout &Layout, |
| MCSectionData::FragmentListType &Fragments) { |
| SmallVector<char, 128> UncompressedData; |
| for (const MCFragment &F : Fragments) { |
| const SmallVectorImpl<char> *Contents; |
| switch (F.getKind()) { |
| case MCFragment::FT_Data: |
| Contents = &cast<MCDataFragment>(F).getContents(); |
| break; |
| case MCFragment::FT_Dwarf: |
| Contents = &cast<MCDwarfLineAddrFragment>(F).getContents(); |
| break; |
| case MCFragment::FT_DwarfFrame: |
| Contents = &cast<MCDwarfCallFrameFragment>(F).getContents(); |
| break; |
| default: |
| llvm_unreachable( |
| "Not expecting any other fragment types in a debug_* section"); |
| } |
| UncompressedData.append(Contents->begin(), Contents->end()); |
| } |
| return UncompressedData; |
| } |
| |
| // Include the debug info compression header: |
| // "ZLIB" followed by 8 bytes representing the uncompressed size of the section, |
| // useful for consumers to preallocate a buffer to decompress into. |
| static bool |
| prependCompressionHeader(uint64_t Size, |
| SmallVectorImpl<char> &CompressedContents) { |
| static const StringRef Magic = "ZLIB"; |
| if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size()) |
| return false; |
| if (sys::IsLittleEndianHost) |
| sys::swapByteOrder(Size); |
| CompressedContents.insert(CompressedContents.begin(), |
| Magic.size() + sizeof(Size), 0); |
| std::copy(Magic.begin(), Magic.end(), CompressedContents.begin()); |
| std::copy(reinterpret_cast<char *>(&Size), |
| reinterpret_cast<char *>(&Size + 1), |
| CompressedContents.begin() + Magic.size()); |
| return true; |
| } |
| |
| // Return a single fragment containing the compressed contents of the whole |
| // section. Null if the section was not compressed for any reason. |
| static std::unique_ptr<MCDataFragment> |
| getCompressedFragment(MCAsmLayout &Layout, |
| MCSectionData::FragmentListType &Fragments) { |
| std::unique_ptr<MCDataFragment> CompressedFragment(new MCDataFragment()); |
| |
| // Gather the uncompressed data from all the fragments, recording the |
| // alignment fragment, if seen, and any fixups. |
| SmallVector<char, 128> UncompressedData = |
| getUncompressedData(Layout, Fragments); |
| |
| SmallVectorImpl<char> &CompressedContents = CompressedFragment->getContents(); |
| |
| zlib::Status Success = zlib::compress( |
| StringRef(UncompressedData.data(), UncompressedData.size()), |
| CompressedContents); |
| if (Success != zlib::StatusOK) |
| return nullptr; |
| |
| if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) |
| return nullptr; |
| |
| return CompressedFragment; |
| } |
| |
| typedef DenseMap<const MCSectionData *, std::vector<MCSymbolData *>> |
| DefiningSymbolMap; |
| |
| static void UpdateSymbols(const MCAsmLayout &Layout, |
| const std::vector<MCSymbolData *> &Symbols, |
| MCFragment &NewFragment) { |
| for (MCSymbolData *Sym : Symbols) { |
| Sym->setOffset(Sym->getOffset() + |
| Layout.getFragmentOffset(Sym->getFragment())); |
| Sym->setFragment(&NewFragment); |
| } |
| } |
| |
| static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout, |
| const DefiningSymbolMap &DefiningSymbols, |
| const MCSectionELF &Section, |
| MCSectionData &SD) { |
| StringRef SectionName = Section.getSectionName(); |
| MCSectionData::FragmentListType &Fragments = SD.getFragmentList(); |
| |
| std::unique_ptr<MCDataFragment> CompressedFragment = |
| getCompressedFragment(Layout, Fragments); |
| |
| // Leave the section as-is if the fragments could not be compressed. |
| if (!CompressedFragment) |
| return; |
| |
| // Update the fragment+offsets of any symbols referring to fragments in this |
| // section to refer to the new fragment. |
| auto I = DefiningSymbols.find(&SD); |
| if (I != DefiningSymbols.end()) |
| UpdateSymbols(Layout, I->second, *CompressedFragment); |
| |
| // Invalidate the layout for the whole section since it will have new and |
| // different fragments now. |
| Layout.invalidateFragmentsFrom(&Fragments.front()); |
| Fragments.clear(); |
| |
| // Complete the initialization of the new fragment |
| CompressedFragment->setParent(&SD); |
| CompressedFragment->setLayoutOrder(0); |
| Fragments.push_back(CompressedFragment.release()); |
| |
| // Rename from .debug_* to .zdebug_* |
| Asm.getContext().renameELFSection(&Section, |
| (".z" + SectionName.drop_front(1)).str()); |
| } |
| |
| void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm, |
| MCAsmLayout &Layout) { |
| if (!Asm.getContext().getAsmInfo()->compressDebugSections()) |
| return; |
| |
| DefiningSymbolMap DefiningSymbols; |
| |
| for (MCSymbolData &SD : Asm.symbols()) |
| if (MCFragment *F = SD.getFragment()) |
| DefiningSymbols[F->getParent()].push_back(&SD); |
| |
| for (MCSectionData &SD : Asm) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(SD.getSection()); |
| StringRef SectionName = Section.getSectionName(); |
| |
| // Compressing debug_frame requires handling alignment fragments which is |
| // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow |
| // for writing to arbitrary buffers) for little benefit. |
| if (!SectionName.startswith(".debug_") || SectionName == ".debug_frame") |
| continue; |
| |
| CompressDebugSection(Asm, Layout, DefiningSymbols, Section, SD); |
| } |
| } |
| |
| void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout, |
| const RelMapTy &RelMap) { |
| for (MCAssembler::const_iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionData &SD = *it; |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(SD.getSection()); |
| |
| const MCSectionELF *RelaSection = RelMap.lookup(&Section); |
| if (!RelaSection) |
| continue; |
| MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); |
| RelaSD.setAlignment(is64Bit() ? 8 : 4); |
| |
| MCDataFragment *F = new MCDataFragment(&RelaSD); |
| WriteRelocationsFragment(Asm, F, &*it); |
| } |
| } |
| |
| void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, |
| uint64_t Flags, uint64_t Address, |
| uint64_t Offset, uint64_t Size, |
| uint32_t Link, uint32_t Info, |
| uint64_t Alignment, |
| uint64_t EntrySize) { |
| Write32(Name); // sh_name: index into string table |
| Write32(Type); // sh_type |
| WriteWord(Flags); // sh_flags |
| WriteWord(Address); // sh_addr |
| WriteWord(Offset); // sh_offset |
| WriteWord(Size); // sh_size |
| Write32(Link); // sh_link |
| Write32(Info); // sh_info |
| WriteWord(Alignment); // sh_addralign |
| WriteWord(EntrySize); // sh_entsize |
| } |
| |
| // ELF doesn't require relocations to be in any order. We sort by the r_offset, |
| // just to match gnu as for easier comparison. The use type is an arbitrary way |
| // of making the sort deterministic. |
| static int cmpRel(const ELFRelocationEntry *AP, const ELFRelocationEntry *BP) { |
| const ELFRelocationEntry &A = *AP; |
| const ELFRelocationEntry &B = *BP; |
| if (A.Offset != B.Offset) |
| return B.Offset - A.Offset; |
| if (B.Type != A.Type) |
| return A.Type - B.Type; |
| llvm_unreachable("ELFRelocs might be unstable!"); |
| } |
| |
| static void sortRelocs(const MCAssembler &Asm, |
| std::vector<ELFRelocationEntry> &Relocs) { |
| array_pod_sort(Relocs.begin(), Relocs.end(), cmpRel); |
| } |
| |
| void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm, |
| MCDataFragment *F, |
| const MCSectionData *SD) { |
| std::vector<ELFRelocationEntry> &Relocs = Relocations[SD]; |
| |
| sortRelocs(Asm, Relocs); |
| |
| for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { |
| const ELFRelocationEntry &Entry = Relocs[e - i - 1]; |
| |
| unsigned Index; |
| if (Entry.UseSymbol) { |
| Index = getSymbolIndexInSymbolTable(Asm, Entry.Symbol); |
| } else { |
| const MCSectionData *Sec = Entry.Section; |
| if (Sec) |
| Index = Sec->getOrdinal() + FileSymbolData.size() + |
| LocalSymbolData.size() + 1; |
| else |
| Index = 0; |
| } |
| |
| if (is64Bit()) { |
| write(*F, Entry.Offset); |
| if (TargetObjectWriter->isN64()) { |
| write(*F, uint32_t(Index)); |
| |
| write(*F, TargetObjectWriter->getRSsym(Entry.Type)); |
| write(*F, TargetObjectWriter->getRType3(Entry.Type)); |
| write(*F, TargetObjectWriter->getRType2(Entry.Type)); |
| write(*F, TargetObjectWriter->getRType(Entry.Type)); |
| } else { |
| struct ELF::Elf64_Rela ERE64; |
| ERE64.setSymbolAndType(Index, Entry.Type); |
| write(*F, ERE64.r_info); |
| } |
| if (hasRelocationAddend()) |
| write(*F, Entry.Addend); |
| } else { |
| write(*F, uint32_t(Entry.Offset)); |
| |
| struct ELF::Elf32_Rela ERE32; |
| ERE32.setSymbolAndType(Index, Entry.Type); |
| write(*F, ERE32.r_info); |
| |
| if (hasRelocationAddend()) |
| write(*F, uint32_t(Entry.Addend)); |
| } |
| } |
| } |
| |
| void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm, |
| MCAsmLayout &Layout, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap) { |
| MCContext &Ctx = Asm.getContext(); |
| MCDataFragment *F; |
| |
| unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; |
| |
| // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. |
| const MCSectionELF *ShstrtabSection = |
| Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, |
| SectionKind::getReadOnly()); |
| MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); |
| ShstrtabSD.setAlignment(1); |
| |
| const MCSectionELF *SymtabSection = |
| Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, |
| SectionKind::getReadOnly(), |
| EntrySize, ""); |
| MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); |
| SymtabSD.setAlignment(is64Bit() ? 8 : 4); |
| |
| const MCSectionELF *StrtabSection; |
| StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, |
| SectionKind::getReadOnly()); |
| MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); |
| StrtabSD.setAlignment(1); |
| |
| ComputeIndexMap(Asm, SectionIndexMap, RelMap); |
| |
| ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection); |
| SymbolTableIndex = SectionIndexMap.lookup(SymtabSection); |
| StringTableIndex = SectionIndexMap.lookup(StrtabSection); |
| |
| // Symbol table |
| F = new MCDataFragment(&SymtabSD); |
| WriteSymbolTable(F, Asm, Layout, SectionIndexMap); |
| |
| F = new MCDataFragment(&StrtabSD); |
| F->getContents().append(StrTabBuilder.data().begin(), |
| StrTabBuilder.data().end()); |
| |
| F = new MCDataFragment(&ShstrtabSD); |
| |
| // Section header string table. |
| for (auto it = Asm.begin(), ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(it->getSection()); |
| ShStrTabBuilder.add(Section.getSectionName()); |
| } |
| ShStrTabBuilder.finalize(); |
| F->getContents().append(ShStrTabBuilder.data().begin(), |
| ShStrTabBuilder.data().end()); |
| } |
| |
| void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm, |
| MCAsmLayout &Layout, |
| GroupMapTy &GroupMap, |
| RevGroupMapTy &RevGroupMap, |
| SectionIndexMapTy &SectionIndexMap, |
| const RelMapTy &RelMap) { |
| // Create the .note.GNU-stack section if needed. |
| MCContext &Ctx = Asm.getContext(); |
| if (Asm.getNoExecStack()) { |
| const MCSectionELF *GnuStackSection = |
| Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0, |
| SectionKind::getReadOnly()); |
| Asm.getOrCreateSectionData(*GnuStackSection); |
| } |
| |
| // Build the groups |
| for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); |
| it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(it->getSection()); |
| if (!(Section.getFlags() & ELF::SHF_GROUP)) |
| continue; |
| |
| const MCSymbol *SignatureSymbol = Section.getGroup(); |
| Asm.getOrCreateSymbolData(*SignatureSymbol); |
| const MCSectionELF *&Group = RevGroupMap[SignatureSymbol]; |
| if (!Group) { |
| Group = Ctx.CreateELFGroupSection(); |
| MCSectionData &Data = Asm.getOrCreateSectionData(*Group); |
| Data.setAlignment(4); |
| MCDataFragment *F = new MCDataFragment(&Data); |
| write(*F, uint32_t(ELF::GRP_COMDAT)); |
| } |
| GroupMap[Group] = SignatureSymbol; |
| } |
| |
| ComputeIndexMap(Asm, SectionIndexMap, RelMap); |
| |
| // Add sections to the groups |
| for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); |
| it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF&>(it->getSection()); |
| if (!(Section.getFlags() & ELF::SHF_GROUP)) |
| continue; |
| const MCSectionELF *Group = RevGroupMap[Section.getGroup()]; |
| MCSectionData &Data = Asm.getOrCreateSectionData(*Group); |
| // FIXME: we could use the previous fragment |
| MCDataFragment *F = new MCDataFragment(&Data); |
| uint32_t Index = SectionIndexMap.lookup(&Section); |
| write(*F, Index); |
| } |
| } |
| |
| void ELFObjectWriter::WriteSection(MCAssembler &Asm, |
| const SectionIndexMapTy &SectionIndexMap, |
| uint32_t GroupSymbolIndex, |
| uint64_t Offset, uint64_t Size, |
| uint64_t Alignment, |
| const MCSectionELF &Section) { |
| uint64_t sh_link = 0; |
| uint64_t sh_info = 0; |
| |
| switch(Section.getType()) { |
| case ELF::SHT_DYNAMIC: |
| sh_link = ShStrTabBuilder.getOffset(Section.getSectionName()); |
| sh_info = 0; |
| break; |
| |
| case ELF::SHT_REL: |
| case ELF::SHT_RELA: { |
| const MCSectionELF *SymtabSection; |
| const MCSectionELF *InfoSection; |
| SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, |
| 0, |
| SectionKind::getReadOnly()); |
| sh_link = SectionIndexMap.lookup(SymtabSection); |
| assert(sh_link && ".symtab not found"); |
| |
| // Remove ".rel" and ".rela" prefixes. |
| unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5; |
| StringRef SectionName = Section.getSectionName().substr(SecNameLen); |
| StringRef GroupName = |
| Section.getGroup() ? Section.getGroup()->getName() : ""; |
| |
| InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS, |
| 0, SectionKind::getReadOnly(), |
| 0, GroupName); |
| sh_info = SectionIndexMap.lookup(InfoSection); |
| break; |
| } |
| |
| case ELF::SHT_SYMTAB: |
| case ELF::SHT_DYNSYM: |
| sh_link = StringTableIndex; |
| sh_info = LastLocalSymbolIndex; |
| break; |
| |
| case ELF::SHT_SYMTAB_SHNDX: |
| sh_link = SymbolTableIndex; |
| break; |
| |
| case ELF::SHT_PROGBITS: |
| case ELF::SHT_STRTAB: |
| case ELF::SHT_NOBITS: |
| case ELF::SHT_NOTE: |
| case ELF::SHT_NULL: |
| case ELF::SHT_ARM_ATTRIBUTES: |
| case ELF::SHT_INIT_ARRAY: |
| case ELF::SHT_FINI_ARRAY: |
| case ELF::SHT_PREINIT_ARRAY: |
| case ELF::SHT_X86_64_UNWIND: |
| case ELF::SHT_MIPS_REGINFO: |
| case ELF::SHT_MIPS_OPTIONS: |
| case ELF::SHT_MIPS_ABIFLAGS: |
| // Nothing to do. |
| break; |
| |
| case ELF::SHT_GROUP: |
| sh_link = SymbolTableIndex; |
| sh_info = GroupSymbolIndex; |
| break; |
| |
| default: |
| llvm_unreachable("FIXME: sh_type value not supported!"); |
| } |
| |
| if (TargetObjectWriter->getEMachine() == ELF::EM_ARM && |
| Section.getType() == ELF::SHT_ARM_EXIDX) { |
| StringRef SecName(Section.getSectionName()); |
| if (SecName == ".ARM.exidx") { |
| sh_link = SectionIndexMap.lookup( |
| Asm.getContext().getELFSection(".text", |
| ELF::SHT_PROGBITS, |
| ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, |
| SectionKind::getText())); |
| } else if (SecName.startswith(".ARM.exidx")) { |
| StringRef GroupName = |
| Section.getGroup() ? Section.getGroup()->getName() : ""; |
| sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection( |
| SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS, |
| ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0, |
| GroupName)); |
| } |
| } |
| |
| WriteSecHdrEntry(ShStrTabBuilder.getOffset(Section.getSectionName()), |
| Section.getType(), |
| Section.getFlags(), 0, Offset, Size, sh_link, sh_info, |
| Alignment, Section.getEntrySize()); |
| } |
| |
| bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) { |
| return SD.getOrdinal() == ~UINT32_C(0) && |
| !SD.getSection().isVirtualSection(); |
| } |
| |
| uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) { |
| uint64_t Ret = 0; |
| for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; |
| ++i) { |
| const MCFragment &F = *i; |
| assert(F.getKind() == MCFragment::FT_Data); |
| Ret += cast<MCDataFragment>(F).getContents().size(); |
| } |
| return Ret; |
| } |
| |
| uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout, |
| const MCSectionData &SD) { |
| if (IsELFMetaDataSection(SD)) |
| return DataSectionSize(SD); |
| return Layout.getSectionFileSize(&SD); |
| } |
| |
| uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout, |
| const MCSectionData &SD) { |
| if (IsELFMetaDataSection(SD)) |
| return DataSectionSize(SD); |
| return Layout.getSectionAddressSize(&SD); |
| } |
| |
| void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCSectionELF &Section) { |
| const MCSectionData &SD = Asm.getOrCreateSectionData(Section); |
| |
| uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment()); |
| WriteZeros(Padding); |
| |
| if (IsELFMetaDataSection(SD)) { |
| for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e; |
| ++i) { |
| const MCFragment &F = *i; |
| assert(F.getKind() == MCFragment::FT_Data); |
| WriteBytes(cast<MCDataFragment>(F).getContents()); |
| } |
| } else { |
| Asm.writeSectionData(&SD, Layout); |
| } |
| } |
| |
| void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm, |
| const GroupMapTy &GroupMap, |
| const MCAsmLayout &Layout, |
| const SectionIndexMapTy &SectionIndexMap, |
| const SectionOffsetMapTy &SectionOffsetMap) { |
| const unsigned NumSections = Asm.size() + 1; |
| |
| std::vector<const MCSectionELF*> Sections; |
| Sections.resize(NumSections - 1); |
| |
| for (SectionIndexMapTy::const_iterator i= |
| SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) { |
| const std::pair<const MCSectionELF*, uint32_t> &p = *i; |
| Sections[p.second - 1] = p.first; |
| } |
| |
| // Null section first. |
| uint64_t FirstSectionSize = |
| NumSections >= ELF::SHN_LORESERVE ? NumSections : 0; |
| uint32_t FirstSectionLink = |
| ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0; |
| WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0); |
| |
| for (unsigned i = 0; i < NumSections - 1; ++i) { |
| const MCSectionELF &Section = *Sections[i]; |
| const MCSectionData &SD = Asm.getOrCreateSectionData(Section); |
| uint32_t GroupSymbolIndex; |
| if (Section.getType() != ELF::SHT_GROUP) |
| GroupSymbolIndex = 0; |
| else |
| GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, |
| GroupMap.lookup(&Section)); |
| |
| uint64_t Size = GetSectionAddressSize(Layout, SD); |
| |
| WriteSection(Asm, SectionIndexMap, GroupSymbolIndex, |
| SectionOffsetMap.lookup(&Section), Size, |
| SD.getAlignment(), Section); |
| } |
| } |
| |
| void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm, |
| std::vector<const MCSectionELF*> &Sections) { |
| for (MCAssembler::iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(it->getSection()); |
| if (Section.getType() == ELF::SHT_GROUP) |
| Sections.push_back(&Section); |
| } |
| |
| for (MCAssembler::iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(it->getSection()); |
| if (Section.getType() != ELF::SHT_GROUP && |
| Section.getType() != ELF::SHT_REL && |
| Section.getType() != ELF::SHT_RELA) |
| Sections.push_back(&Section); |
| } |
| |
| for (MCAssembler::iterator it = Asm.begin(), |
| ie = Asm.end(); it != ie; ++it) { |
| const MCSectionELF &Section = |
| static_cast<const MCSectionELF &>(it->getSection()); |
| if (Section.getType() == ELF::SHT_REL || |
| Section.getType() == ELF::SHT_RELA) |
| Sections.push_back(&Section); |
| } |
| } |
| |
| void ELFObjectWriter::WriteObject(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| GroupMapTy GroupMap; |
| RevGroupMapTy RevGroupMap; |
| SectionIndexMapTy SectionIndexMap; |
| |
| unsigned NumUserSections = Asm.size(); |
| |
| CompressDebugSections(Asm, const_cast<MCAsmLayout &>(Layout)); |
| |
| DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap; |
| CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); |
| |
| const unsigned NumUserAndRelocSections = Asm.size(); |
| CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap, |
| RevGroupMap, SectionIndexMap, RelMap); |
| const unsigned AllSections = Asm.size(); |
| const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections; |
| |
| unsigned NumRegularSections = NumUserSections + NumIndexedSections; |
| |
| // Compute symbol table information. |
| computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap, |
| NumRegularSections); |
| |
| WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap); |
| |
| CreateMetadataSections(const_cast<MCAssembler&>(Asm), |
| const_cast<MCAsmLayout&>(Layout), |
| SectionIndexMap, |
| RelMap); |
| |
| uint64_t NaturalAlignment = is64Bit() ? 8 : 4; |
| uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) : |
| sizeof(ELF::Elf32_Ehdr); |
| uint64_t FileOff = HeaderSize; |
| |
| std::vector<const MCSectionELF*> Sections; |
| ComputeSectionOrder(Asm, Sections); |
| unsigned NumSections = Sections.size(); |
| SectionOffsetMapTy SectionOffsetMap; |
| for (unsigned i = 0; i < NumRegularSections + 1; ++i) { |
| const MCSectionELF &Section = *Sections[i]; |
| const MCSectionData &SD = Asm.getOrCreateSectionData(Section); |
| |
| FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); |
| |
| // Remember the offset into the file for this section. |
| SectionOffsetMap[&Section] = FileOff; |
| |
| // Get the size of the section in the output file (including padding). |
| FileOff += GetSectionFileSize(Layout, SD); |
| } |
| |
| FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); |
| |
| const unsigned SectionHeaderOffset = FileOff - HeaderSize; |
| |
| uint64_t SectionHeaderEntrySize = is64Bit() ? |
| sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr); |
| FileOff += (NumSections + 1) * SectionHeaderEntrySize; |
| |
| for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) { |
| const MCSectionELF &Section = *Sections[i]; |
| const MCSectionData &SD = Asm.getOrCreateSectionData(Section); |
| |
| FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); |
| |
| // Remember the offset into the file for this section. |
| SectionOffsetMap[&Section] = FileOff; |
| |
| // Get the size of the section in the output file (including padding). |
| FileOff += GetSectionFileSize(Layout, SD); |
| } |
| |
| // Write out the ELF header ... |
| WriteHeader(Asm, SectionHeaderOffset, NumSections + 1); |
| |
| // ... then the regular sections ... |
| // + because of .shstrtab |
| for (unsigned i = 0; i < NumRegularSections + 1; ++i) |
| WriteDataSectionData(Asm, Layout, *Sections[i]); |
| |
| uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment); |
| WriteZeros(Padding); |
| |
| // ... then the section header table ... |
| WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap, |
| SectionOffsetMap); |
| |
| // ... and then the remaining sections ... |
| for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) |
| WriteDataSectionData(Asm, Layout, *Sections[i]); |
| } |
| |
| bool |
| ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, |
| const MCSymbolData &DataA, |
| const MCFragment &FB, |
| bool InSet, |
| bool IsPCRel) const { |
| if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC) |
| return false; |
| return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl( |
| Asm, DataA, FB,InSet, IsPCRel); |
| } |
| |
| MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW, |
| raw_ostream &OS, |
| bool IsLittleEndian) { |
| return new ELFObjectWriter(MOTW, OS, IsLittleEndian); |
| } |