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	git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239174 91177308-0d34-0410-b5e6-96231b3b80d8
		
			
				
	
	
		
			1352 lines
		
	
	
		
			46 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
			
		
		
	
	
			1352 lines
		
	
	
		
			46 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
//===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
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//
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//                     The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements ELF object file writer information.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCSymbolELF.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/MC/StringTableBuilder.h"
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#include "llvm/Support/Compression.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ELF.h"
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#include "llvm/Support/Endian.h"
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#include "llvm/Support/ErrorHandling.h"
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#include <vector>
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using namespace llvm;
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#undef  DEBUG_TYPE
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#define DEBUG_TYPE "reloc-info"
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namespace {
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typedef DenseMap<const MCSectionELF *, uint32_t> SectionIndexMapTy;
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class ELFObjectWriter;
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class SymbolTableWriter {
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  ELFObjectWriter &EWriter;
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  bool Is64Bit;
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  // indexes we are going to write to .symtab_shndx.
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  std::vector<uint32_t> ShndxIndexes;
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  // The numbel of symbols written so far.
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  unsigned NumWritten;
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  void createSymtabShndx();
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  template <typename T> void write(T Value);
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public:
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  SymbolTableWriter(ELFObjectWriter &EWriter, bool Is64Bit);
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  void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
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                   uint8_t other, uint32_t shndx, bool Reserved);
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  ArrayRef<uint32_t> getShndxIndexes() const { return ShndxIndexes; }
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};
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class ELFObjectWriter : public MCObjectWriter {
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    static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
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    static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
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    static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
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                           bool Used, bool Renamed);
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    /// Helper struct for containing some precomputed information on symbols.
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    struct ELFSymbolData {
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      const MCSymbolELF *Symbol;
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      uint32_t SectionIndex;
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      StringRef Name;
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      // Support lexicographic sorting.
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      bool operator<(const ELFSymbolData &RHS) const {
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        unsigned LHSType = Symbol->getType();
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        unsigned RHSType = RHS.Symbol->getType();
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        if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
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          return false;
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        if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
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          return true;
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        if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
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          return SectionIndex < RHS.SectionIndex;
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        return Name < RHS.Name;
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      }
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    };
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    /// The target specific ELF writer instance.
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    std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
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    DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
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    llvm::DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>>
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        Relocations;
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    /// @}
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    /// @name Symbol Table Data
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    /// @{
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    StringTableBuilder StrTabBuilder;
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    /// @}
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    // This holds the symbol table index of the last local symbol.
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    unsigned LastLocalSymbolIndex;
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    // This holds the .strtab section index.
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    unsigned StringTableIndex;
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    // This holds the .symtab section index.
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    unsigned SymbolTableIndex;
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    // This holds the .symtab_shndx section index.
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    unsigned SymtabShndxSectionIndex = 0;
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    // Sections in the order they are to be output in the section table.
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    std::vector<const MCSectionELF *> SectionTable;
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    unsigned addToSectionTable(const MCSectionELF *Sec);
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    // TargetObjectWriter wrappers.
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    bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
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    bool hasRelocationAddend() const {
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      return TargetObjectWriter->hasRelocationAddend();
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    }
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    unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
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                          bool IsPCRel) const {
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      return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel);
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    }
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    void align(unsigned Alignment);
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  public:
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    ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_pwrite_stream &OS,
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                    bool IsLittleEndian)
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        : MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {}
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    void reset() override {
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      Renames.clear();
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      Relocations.clear();
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      StrTabBuilder.clear();
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      SectionTable.clear();
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      MCObjectWriter::reset();
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    }
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    ~ELFObjectWriter() override;
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    void WriteWord(uint64_t W) {
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      if (is64Bit())
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        write64(W);
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      else
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        write32(W);
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    }
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    template <typename T> void write(T Val) {
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      if (IsLittleEndian)
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        support::endian::Writer<support::little>(OS).write(Val);
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      else
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        support::endian::Writer<support::big>(OS).write(Val);
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    }
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    void writeHeader(const MCAssembler &Asm);
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    void writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
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                     ELFSymbolData &MSD, const MCAsmLayout &Layout);
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    // Start and end offset of each section
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    typedef std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>
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        SectionOffsetsTy;
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    bool shouldRelocateWithSymbol(const MCAssembler &Asm,
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                                  const MCSymbolRefExpr *RefA,
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                                  const MCSymbol *Sym, uint64_t C,
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                                  unsigned Type) const;
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    void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
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                          const MCFragment *Fragment, const MCFixup &Fixup,
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                          MCValue Target, bool &IsPCRel,
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                          uint64_t &FixedValue) override;
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    // Map from a signature symbol to the group section index
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    typedef DenseMap<const MCSymbol *, unsigned> RevGroupMapTy;
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    /// Compute the symbol table data
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    ///
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    /// \param Asm - The assembler.
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    /// \param SectionIndexMap - Maps a section to its index.
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    /// \param RevGroupMap - Maps a signature symbol to the group section.
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    void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
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                            const SectionIndexMapTy &SectionIndexMap,
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                            const RevGroupMapTy &RevGroupMap,
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                            SectionOffsetsTy &SectionOffsets);
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    MCSectionELF *createRelocationSection(MCContext &Ctx,
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                                          const MCSectionELF &Sec);
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    const MCSectionELF *createStringTable(MCContext &Ctx);
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    void executePostLayoutBinding(MCAssembler &Asm,
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                                  const MCAsmLayout &Layout) override;
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    void writeSectionHeader(const MCAsmLayout &Layout,
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                            const SectionIndexMapTy &SectionIndexMap,
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                            const SectionOffsetsTy &SectionOffsets);
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    void writeSectionData(const MCAssembler &Asm, MCSection &Sec,
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                          const MCAsmLayout &Layout);
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    void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
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                          uint64_t Address, uint64_t Offset, uint64_t Size,
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                          uint32_t Link, uint32_t Info, uint64_t Alignment,
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                          uint64_t EntrySize);
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    void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
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    bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
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                                                const MCSymbol &SymA,
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                                                const MCFragment &FB,
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                                                bool InSet,
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                                                bool IsPCRel) const override;
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    bool isWeak(const MCSymbol &Sym) const override;
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    void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
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    void writeSection(const SectionIndexMapTy &SectionIndexMap,
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                      uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
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                      const MCSectionELF &Section);
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  };
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}
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void ELFObjectWriter::align(unsigned Alignment) {
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  uint64_t Padding = OffsetToAlignment(OS.tell(), Alignment);
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  WriteZeros(Padding);
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}
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unsigned ELFObjectWriter::addToSectionTable(const MCSectionELF *Sec) {
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  SectionTable.push_back(Sec);
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  StrTabBuilder.add(Sec->getSectionName());
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  return SectionTable.size();
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}
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void SymbolTableWriter::createSymtabShndx() {
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  if (!ShndxIndexes.empty())
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    return;
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  ShndxIndexes.resize(NumWritten);
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}
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template <typename T> void SymbolTableWriter::write(T Value) {
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  EWriter.write(Value);
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}
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SymbolTableWriter::SymbolTableWriter(ELFObjectWriter &EWriter, bool Is64Bit)
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    : EWriter(EWriter), Is64Bit(Is64Bit), NumWritten(0) {}
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void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
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                                    uint64_t size, uint8_t other,
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                                    uint32_t shndx, bool Reserved) {
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  bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
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  if (LargeIndex)
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    createSymtabShndx();
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  if (!ShndxIndexes.empty()) {
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    if (LargeIndex)
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      ShndxIndexes.push_back(shndx);
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    else
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      ShndxIndexes.push_back(0);
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  }
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  uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
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  if (Is64Bit) {
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    write(name);  // st_name
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    write(info);  // st_info
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    write(other); // st_other
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    write(Index); // st_shndx
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    write(value); // st_value
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    write(size);  // st_size
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  } else {
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    write(name);            // st_name
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    write(uint32_t(value)); // st_value
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    write(uint32_t(size));  // st_size
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    write(info);            // st_info
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    write(other);           // st_other
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    write(Index);           // st_shndx
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  }
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  ++NumWritten;
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}
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bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
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  const MCFixupKindInfo &FKI =
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    Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
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  return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
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}
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ELFObjectWriter::~ELFObjectWriter()
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{}
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// Emit the ELF header.
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void ELFObjectWriter::writeHeader(const MCAssembler &Asm) {
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  // ELF Header
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  // ----------
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  //
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  // Note
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  // ----
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  // emitWord method behaves differently for ELF32 and ELF64, writing
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  // 4 bytes in the former and 8 in the latter.
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  writeBytes(ELF::ElfMagic); // e_ident[EI_MAG0] to e_ident[EI_MAG3]
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  write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
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  // e_ident[EI_DATA]
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  write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
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  write8(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
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  // e_ident[EI_OSABI]
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  write8(TargetObjectWriter->getOSABI());
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  write8(0);                  // e_ident[EI_ABIVERSION]
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  WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
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  write16(ELF::ET_REL);             // e_type
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  write16(TargetObjectWriter->getEMachine()); // e_machine = target
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  write32(ELF::EV_CURRENT);         // e_version
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  WriteWord(0);                    // e_entry, no entry point in .o file
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  WriteWord(0);                    // e_phoff, no program header for .o
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  WriteWord(0);                     // e_shoff = sec hdr table off in bytes
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  // e_flags = whatever the target wants
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  write32(Asm.getELFHeaderEFlags());
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  // e_ehsize = ELF header size
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  write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
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  write16(0);                  // e_phentsize = prog header entry size
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  write16(0);                  // e_phnum = # prog header entries = 0
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  // e_shentsize = Section header entry size
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  write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
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  // e_shnum     = # of section header ents
 | 
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  write16(0);
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 | 
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  // e_shstrndx  = Section # of '.shstrtab'
 | 
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  assert(StringTableIndex < ELF::SHN_LORESERVE);
 | 
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  write16(StringTableIndex);
 | 
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}
 | 
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 | 
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uint64_t ELFObjectWriter::SymbolValue(const MCSymbol &Sym,
 | 
						|
                                      const MCAsmLayout &Layout) {
 | 
						|
  if (Sym.isCommon() && Sym.isExternal())
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						|
    return Sym.getCommonAlignment();
 | 
						|
 | 
						|
  uint64_t Res;
 | 
						|
  if (!Layout.getSymbolOffset(Sym, Res))
 | 
						|
    return 0;
 | 
						|
 | 
						|
  if (Layout.getAssembler().isThumbFunc(&Sym))
 | 
						|
    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 (const MCSymbol &A : Asm.symbols()) {
 | 
						|
    const auto &Alias = cast<MCSymbolELF>(A);
 | 
						|
    // Not an alias.
 | 
						|
    if (!Alias.isVariable())
 | 
						|
      continue;
 | 
						|
    auto *Ref = dyn_cast<MCSymbolRefExpr>(Alias.getVariableValue());
 | 
						|
    if (!Ref)
 | 
						|
      continue;
 | 
						|
    const auto &Symbol = cast<MCSymbolELF>(Ref->getSymbol());
 | 
						|
 | 
						|
    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.
 | 
						|
    Alias.setExternal(Symbol.isExternal());
 | 
						|
    Alias.setBinding(Symbol.getBinding());
 | 
						|
 | 
						|
    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,
 | 
						|
                                  uint32_t StringIndex, ELFSymbolData &MSD,
 | 
						|
                                  const MCAsmLayout &Layout) {
 | 
						|
  const auto &Symbol = cast<MCSymbolELF>(*MSD.Symbol);
 | 
						|
  assert((!Symbol.getFragment() ||
 | 
						|
          (Symbol.getFragment()->getParent() == &Symbol.getSection())) &&
 | 
						|
         "The symbol's section doesn't match the fragment's symbol");
 | 
						|
  const MCSymbolELF *Base =
 | 
						|
      cast_or_null<MCSymbolELF>(Layout.getBaseSymbol(Symbol));
 | 
						|
 | 
						|
  // This has to be in sync with when computeSymbolTable uses SHN_ABS or
 | 
						|
  // SHN_COMMON.
 | 
						|
  bool IsReserved = !Base || Symbol.isCommon();
 | 
						|
 | 
						|
  // Binding and Type share the same byte as upper and lower nibbles
 | 
						|
  uint8_t Binding = Symbol.getBinding();
 | 
						|
  uint8_t Type = Symbol.getType();
 | 
						|
  if (Base) {
 | 
						|
    Type = mergeTypeForSet(Type, Base->getType());
 | 
						|
  }
 | 
						|
  uint8_t Info = (Binding << 4) | Type;
 | 
						|
 | 
						|
  // Other and Visibility share the same byte with Visibility using the lower
 | 
						|
  // 2 bits
 | 
						|
  uint8_t Visibility = Symbol.getVisibility();
 | 
						|
  uint8_t Other = Symbol.getOther() | Visibility;
 | 
						|
 | 
						|
  uint64_t Value = SymbolValue(*MSD.Symbol, Layout);
 | 
						|
  uint64_t Size = 0;
 | 
						|
 | 
						|
  const MCExpr *ESize = MSD.Symbol->getSize();
 | 
						|
  if (!ESize && Base)
 | 
						|
    ESize = Base->getSize();
 | 
						|
 | 
						|
  if (ESize) {
 | 
						|
    int64_t Res;
 | 
						|
    if (!ESize->evaluateKnownAbsolute(Res, Layout))
 | 
						|
      report_fatal_error("Size expression must be absolute.");
 | 
						|
    Size = Res;
 | 
						|
  }
 | 
						|
 | 
						|
  // Write out the symbol table entry
 | 
						|
  Writer.writeSymbol(StringIndex, Info, Value, Size, Other, MSD.SectionIndex,
 | 
						|
                     IsReserved);
 | 
						|
}
 | 
						|
 | 
						|
// 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 MCSymbol *S, uint64_t C,
 | 
						|
                                               unsigned Type) const {
 | 
						|
  const auto *Sym = cast_or_null<MCSymbolELF>(S);
 | 
						|
  // 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.
 | 
						|
  assert(Sym && "Expected a symbol");
 | 
						|
  if (Sym->isUndefined())
 | 
						|
    return true;
 | 
						|
 | 
						|
  unsigned Binding = Sym->getBinding();
 | 
						|
  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 gold versions before
 | 
						|
  // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
 | 
						|
  // http://sourceware.org/PR16773.
 | 
						|
  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(*Sym, Type))
 | 
						|
    return true;
 | 
						|
  return false;
 | 
						|
}
 | 
						|
 | 
						|
// True if the assembler knows nothing about the final value of the symbol.
 | 
						|
// This doesn't cover the comdat issues, since in those cases the assembler
 | 
						|
// can at least know that all symbols in the section will move together.
 | 
						|
static bool isWeak(const MCSymbolELF &Sym) {
 | 
						|
  if (Sym.getType() == ELF::STT_GNU_IFUNC)
 | 
						|
    return true;
 | 
						|
 | 
						|
  switch (Sym.getBinding()) {
 | 
						|
  default:
 | 
						|
    llvm_unreachable("Unknown binding");
 | 
						|
  case ELF::STB_LOCAL:
 | 
						|
    return false;
 | 
						|
  case ELF::STB_GLOBAL:
 | 
						|
    return false;
 | 
						|
  case ELF::STB_WEAK:
 | 
						|
  case ELF::STB_GNU_UNIQUE:
 | 
						|
    return true;
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
 | 
						|
                                       const MCAsmLayout &Layout,
 | 
						|
                                       const MCFragment *Fragment,
 | 
						|
                                       const MCFixup &Fixup, MCValue Target,
 | 
						|
                                       bool &IsPCRel, uint64_t &FixedValue) {
 | 
						|
  const MCSectionELF &FixupSection = cast<MCSectionELF>(*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().reportFatalError(
 | 
						|
          Fixup.getLoc(),
 | 
						|
          "No relocation available to represent this relative expression");
 | 
						|
 | 
						|
    const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
 | 
						|
 | 
						|
    if (SymB.isUndefined())
 | 
						|
      Asm.getContext().reportFatalError(
 | 
						|
          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)
 | 
						|
      Asm.getContext().reportFatalError(
 | 
						|
          Fixup.getLoc(), "Cannot represent a difference across sections");
 | 
						|
 | 
						|
    if (::isWeak(SymB))
 | 
						|
      Asm.getContext().reportFatalError(
 | 
						|
          Fixup.getLoc(), "Cannot represent a subtraction with a weak symbol");
 | 
						|
 | 
						|
    uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
 | 
						|
    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 auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
 | 
						|
 | 
						|
  bool ViaWeakRef = false;
 | 
						|
  if (SymA && SymA->isVariable()) {
 | 
						|
    const MCExpr *Expr = SymA->getVariableValue();
 | 
						|
    if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
 | 
						|
      if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
 | 
						|
        SymA = cast<MCSymbolELF>(&Inner->getSymbol());
 | 
						|
        ViaWeakRef = true;
 | 
						|
      }
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  unsigned Type = GetRelocType(Target, Fixup, IsPCRel);
 | 
						|
  bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
 | 
						|
  if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
 | 
						|
    C += Layout.getSymbolOffset(*SymA);
 | 
						|
 | 
						|
  uint64_t Addend = 0;
 | 
						|
  if (hasRelocationAddend()) {
 | 
						|
    Addend = C;
 | 
						|
    C = 0;
 | 
						|
  }
 | 
						|
 | 
						|
  FixedValue = C;
 | 
						|
 | 
						|
  if (!RelocateWithSymbol) {
 | 
						|
    const MCSection *SecA =
 | 
						|
        (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
 | 
						|
    auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
 | 
						|
    const auto *SectionSymbol =
 | 
						|
        ELFSec ? cast<MCSymbolELF>(ELFSec->getBeginSymbol()) : nullptr;
 | 
						|
    if (SectionSymbol)
 | 
						|
      SectionSymbol->setUsedInReloc();
 | 
						|
    ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend);
 | 
						|
    Relocations[&FixupSection].push_back(Rec);
 | 
						|
    return;
 | 
						|
  }
 | 
						|
 | 
						|
  if (SymA) {
 | 
						|
    if (const MCSymbolELF *R = Renames.lookup(SymA))
 | 
						|
      SymA = R;
 | 
						|
 | 
						|
    if (ViaWeakRef)
 | 
						|
      SymA->setIsWeakrefUsedInReloc();
 | 
						|
    else
 | 
						|
      SymA->setUsedInReloc();
 | 
						|
  }
 | 
						|
  ELFRelocationEntry Rec(FixupOffset, SymA, Type, Addend);
 | 
						|
  Relocations[&FixupSection].push_back(Rec);
 | 
						|
  return;
 | 
						|
}
 | 
						|
 | 
						|
bool ELFObjectWriter::isInSymtab(const MCAsmLayout &Layout,
 | 
						|
                                 const MCSymbolELF &Symbol, bool Used,
 | 
						|
                                 bool Renamed) {
 | 
						|
  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.isVariable() && Symbol.isUndefined()) {
 | 
						|
    // FIXME: this is here just to diagnose the case of a var = commmon_sym.
 | 
						|
    Layout.getBaseSymbol(Symbol);
 | 
						|
    return false;
 | 
						|
  }
 | 
						|
 | 
						|
  if (Symbol.isUndefined() && !Symbol.isBindingSet())
 | 
						|
    return false;
 | 
						|
 | 
						|
  if (Symbol.isTemporary())
 | 
						|
    return false;
 | 
						|
 | 
						|
  if (Symbol.getType() == ELF::STT_SECTION)
 | 
						|
    return false;
 | 
						|
 | 
						|
  return true;
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::computeSymbolTable(
 | 
						|
    MCAssembler &Asm, const MCAsmLayout &Layout,
 | 
						|
    const SectionIndexMapTy &SectionIndexMap, const RevGroupMapTy &RevGroupMap,
 | 
						|
    SectionOffsetsTy &SectionOffsets) {
 | 
						|
  MCContext &Ctx = Asm.getContext();
 | 
						|
  SymbolTableWriter Writer(*this, is64Bit());
 | 
						|
 | 
						|
  // Symbol table
 | 
						|
  unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
 | 
						|
  MCSectionELF *SymtabSection =
 | 
						|
      Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
 | 
						|
  SymtabSection->setAlignment(is64Bit() ? 8 : 4);
 | 
						|
  SymbolTableIndex = addToSectionTable(SymtabSection);
 | 
						|
 | 
						|
  align(SymtabSection->getAlignment());
 | 
						|
  uint64_t SecStart = OS.tell();
 | 
						|
 | 
						|
  // The first entry is the undefined symbol entry.
 | 
						|
  Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
 | 
						|
 | 
						|
  std::vector<ELFSymbolData> LocalSymbolData;
 | 
						|
  std::vector<ELFSymbolData> ExternalSymbolData;
 | 
						|
 | 
						|
  // Add the data for the symbols.
 | 
						|
  bool HasLargeSectionIndex = false;
 | 
						|
  for (const MCSymbol &S : Asm.symbols()) {
 | 
						|
    const auto &Symbol = cast<MCSymbolELF>(S);
 | 
						|
    bool Used = Symbol.isUsedInReloc();
 | 
						|
    bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
 | 
						|
    bool isSignature = Symbol.isSignature();
 | 
						|
 | 
						|
    if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
 | 
						|
                    Renames.count(&Symbol)))
 | 
						|
      continue;
 | 
						|
 | 
						|
    ELFSymbolData MSD;
 | 
						|
    MSD.Symbol = cast<MCSymbolELF>(&Symbol);
 | 
						|
 | 
						|
    bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
 | 
						|
    if (Symbol.isAbsolute()) {
 | 
						|
      MSD.SectionIndex = ELF::SHN_ABS;
 | 
						|
    } else if (Symbol.isCommon()) {
 | 
						|
      assert(!Local);
 | 
						|
      MSD.SectionIndex = ELF::SHN_COMMON;
 | 
						|
    } else if (Symbol.isUndefined()) {
 | 
						|
      if (isSignature && !Used) {
 | 
						|
        MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
 | 
						|
        if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
 | 
						|
          HasLargeSectionIndex = true;
 | 
						|
      } else {
 | 
						|
        MSD.SectionIndex = ELF::SHN_UNDEF;
 | 
						|
      }
 | 
						|
    } else {
 | 
						|
      const MCSectionELF &Section =
 | 
						|
          static_cast<const MCSectionELF &>(Symbol.getSection());
 | 
						|
      MSD.SectionIndex = SectionIndexMap.lookup(&Section);
 | 
						|
      assert(MSD.SectionIndex && "Invalid section index!");
 | 
						|
      if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
 | 
						|
        HasLargeSectionIndex = true;
 | 
						|
    }
 | 
						|
 | 
						|
    // The @@@ in symbol version is replaced with @ in undefined symbols and @@
 | 
						|
    // in defined ones.
 | 
						|
    //
 | 
						|
    // FIXME: All name handling should be done before we get to the writer,
 | 
						|
    // including dealing with GNU-style version suffixes.  Fixing this isn't
 | 
						|
    // trivial.
 | 
						|
    //
 | 
						|
    // We thus have to be careful to not perform the symbol version replacement
 | 
						|
    // blindly:
 | 
						|
    //
 | 
						|
    // The ELF format is used on Windows by the MCJIT engine.  Thus, on
 | 
						|
    // Windows, the ELFObjectWriter can encounter symbols mangled using the MS
 | 
						|
    // Visual Studio C++ name mangling scheme. Symbols mangled using the MSVC
 | 
						|
    // C++ name mangling can legally have "@@@" as a sub-string. In that case,
 | 
						|
    // the EFLObjectWriter should not interpret the "@@@" sub-string as
 | 
						|
    // specifying GNU-style symbol versioning. The ELFObjectWriter therefore
 | 
						|
    // checks for the MSVC C++ name mangling prefix which is either "?", "@?",
 | 
						|
    // "__imp_?" or "__imp_@?".
 | 
						|
    //
 | 
						|
    // It would have been interesting to perform the MS mangling prefix check
 | 
						|
    // only when the target triple is of the form *-pc-windows-elf. But, it
 | 
						|
    // seems that this information is not easily accessible from the
 | 
						|
    // ELFObjectWriter.
 | 
						|
    StringRef Name = Symbol.getName();
 | 
						|
    if (!Name.startswith("?") && !Name.startswith("@?") &&
 | 
						|
        !Name.startswith("__imp_?") && !Name.startswith("__imp_@?")) {
 | 
						|
      // This symbol isn't following the MSVC C++ name mangling convention. We
 | 
						|
      // can thus safely interpret the @@@ in symbol names as specifying symbol
 | 
						|
      // versioning.
 | 
						|
      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;
 | 
						|
      }
 | 
						|
    }
 | 
						|
 | 
						|
    // Sections have their own string table
 | 
						|
    if (Symbol.getType() != ELF::STT_SECTION)
 | 
						|
      MSD.Name = StrTabBuilder.add(Name);
 | 
						|
 | 
						|
    if (Local)
 | 
						|
      LocalSymbolData.push_back(MSD);
 | 
						|
    else
 | 
						|
      ExternalSymbolData.push_back(MSD);
 | 
						|
  }
 | 
						|
 | 
						|
  if (HasLargeSectionIndex) {
 | 
						|
    MCSectionELF *SymtabShndxSection =
 | 
						|
        Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
 | 
						|
    SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
 | 
						|
    SymtabShndxSection->setAlignment(4);
 | 
						|
  }
 | 
						|
 | 
						|
  ArrayRef<std::string> FileNames = Asm.getFileNames();
 | 
						|
  for (const std::string &Name : FileNames)
 | 
						|
    StrTabBuilder.add(Name);
 | 
						|
 | 
						|
  StrTabBuilder.finalize(StringTableBuilder::ELF);
 | 
						|
 | 
						|
  for (const std::string &Name : FileNames)
 | 
						|
    Writer.writeSymbol(StrTabBuilder.getOffset(Name),
 | 
						|
                       ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
 | 
						|
                       ELF::SHN_ABS, true);
 | 
						|
 | 
						|
  // Symbols are required to be in lexicographic order.
 | 
						|
  array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
 | 
						|
  array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
 | 
						|
 | 
						|
  // Set the symbol indices. Local symbols must come before all other
 | 
						|
  // symbols with non-local bindings.
 | 
						|
  unsigned Index = FileNames.size() + 1;
 | 
						|
 | 
						|
  for (ELFSymbolData &MSD : LocalSymbolData) {
 | 
						|
    unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
 | 
						|
                               ? 0
 | 
						|
                               : StrTabBuilder.getOffset(MSD.Name);
 | 
						|
    MSD.Symbol->setIndex(Index++);
 | 
						|
    writeSymbol(Writer, StringIndex, MSD, Layout);
 | 
						|
  }
 | 
						|
 | 
						|
  // Write the symbol table entries.
 | 
						|
  LastLocalSymbolIndex = Index;
 | 
						|
 | 
						|
  for (ELFSymbolData &MSD : ExternalSymbolData) {
 | 
						|
    unsigned StringIndex = StrTabBuilder.getOffset(MSD.Name);
 | 
						|
    MSD.Symbol->setIndex(Index++);
 | 
						|
    writeSymbol(Writer, StringIndex, MSD, Layout);
 | 
						|
    assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
 | 
						|
  }
 | 
						|
 | 
						|
  uint64_t SecEnd = OS.tell();
 | 
						|
  SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
 | 
						|
 | 
						|
  ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
 | 
						|
  if (ShndxIndexes.empty()) {
 | 
						|
    assert(SymtabShndxSectionIndex == 0);
 | 
						|
    return;
 | 
						|
  }
 | 
						|
  assert(SymtabShndxSectionIndex != 0);
 | 
						|
 | 
						|
  SecStart = OS.tell();
 | 
						|
  const MCSectionELF *SymtabShndxSection =
 | 
						|
      SectionTable[SymtabShndxSectionIndex - 1];
 | 
						|
  for (uint32_t Index : ShndxIndexes)
 | 
						|
    write(Index);
 | 
						|
  SecEnd = OS.tell();
 | 
						|
  SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
 | 
						|
}
 | 
						|
 | 
						|
MCSectionELF *
 | 
						|
ELFObjectWriter::createRelocationSection(MCContext &Ctx,
 | 
						|
                                         const MCSectionELF &Sec) {
 | 
						|
  if (Relocations[&Sec].empty())
 | 
						|
    return nullptr;
 | 
						|
 | 
						|
  const StringRef SectionName = Sec.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;
 | 
						|
  if (Sec.getFlags() & ELF::SHF_GROUP)
 | 
						|
    Flags = ELF::SHF_GROUP;
 | 
						|
 | 
						|
  MCSectionELF *RelaSection = Ctx.createELFRelSection(
 | 
						|
      RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
 | 
						|
      Flags, EntrySize, Sec.getGroup(), &Sec);
 | 
						|
  RelaSection->setAlignment(is64Bit() ? 8 : 4);
 | 
						|
  return RelaSection;
 | 
						|
}
 | 
						|
 | 
						|
static SmallVector<char, 128>
 | 
						|
getUncompressedData(const MCAsmLayout &Layout,
 | 
						|
                    const MCSection::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) {
 | 
						|
  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;
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
 | 
						|
                                       const MCAsmLayout &Layout) {
 | 
						|
  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
 | 
						|
  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 (!Asm.getContext().getAsmInfo()->compressDebugSections() ||
 | 
						|
      !SectionName.startswith(".debug_") || SectionName == ".debug_frame") {
 | 
						|
    Asm.writeSectionData(&Section, Layout);
 | 
						|
    return;
 | 
						|
  }
 | 
						|
 | 
						|
  // Gather the uncompressed data from all the fragments.
 | 
						|
  const MCSection::FragmentListType &Fragments = Section.getFragmentList();
 | 
						|
  SmallVector<char, 128> UncompressedData =
 | 
						|
      getUncompressedData(Layout, Fragments);
 | 
						|
 | 
						|
  SmallVector<char, 128> CompressedContents;
 | 
						|
  zlib::Status Success = zlib::compress(
 | 
						|
      StringRef(UncompressedData.data(), UncompressedData.size()),
 | 
						|
      CompressedContents);
 | 
						|
  if (Success != zlib::StatusOK) {
 | 
						|
    Asm.writeSectionData(&Section, Layout);
 | 
						|
    return;
 | 
						|
  }
 | 
						|
 | 
						|
  if (!prependCompressionHeader(UncompressedData.size(), CompressedContents)) {
 | 
						|
    Asm.writeSectionData(&Section, Layout);
 | 
						|
    return;
 | 
						|
  }
 | 
						|
  Asm.getContext().renameELFSection(&Section,
 | 
						|
                                    (".z" + SectionName.drop_front(1)).str());
 | 
						|
  OS << CompressedContents;
 | 
						|
}
 | 
						|
 | 
						|
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
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::writeRelocations(const MCAssembler &Asm,
 | 
						|
                                       const MCSectionELF &Sec) {
 | 
						|
  std::vector<ELFRelocationEntry> &Relocs = Relocations[&Sec];
 | 
						|
 | 
						|
  // Sort the relocation entries. Most targets just sort by Offset, but some
 | 
						|
  // (e.g., MIPS) have additional constraints.
 | 
						|
  TargetObjectWriter->sortRelocs(Asm, Relocs);
 | 
						|
 | 
						|
  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
 | 
						|
    const ELFRelocationEntry &Entry = Relocs[e - i - 1];
 | 
						|
    unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
 | 
						|
 | 
						|
    if (is64Bit()) {
 | 
						|
      write(Entry.Offset);
 | 
						|
      if (TargetObjectWriter->isN64()) {
 | 
						|
        write(uint32_t(Index));
 | 
						|
 | 
						|
        write(TargetObjectWriter->getRSsym(Entry.Type));
 | 
						|
        write(TargetObjectWriter->getRType3(Entry.Type));
 | 
						|
        write(TargetObjectWriter->getRType2(Entry.Type));
 | 
						|
        write(TargetObjectWriter->getRType(Entry.Type));
 | 
						|
      } else {
 | 
						|
        struct ELF::Elf64_Rela ERE64;
 | 
						|
        ERE64.setSymbolAndType(Index, Entry.Type);
 | 
						|
        write(ERE64.r_info);
 | 
						|
      }
 | 
						|
      if (hasRelocationAddend())
 | 
						|
        write(Entry.Addend);
 | 
						|
    } else {
 | 
						|
      write(uint32_t(Entry.Offset));
 | 
						|
 | 
						|
      struct ELF::Elf32_Rela ERE32;
 | 
						|
      ERE32.setSymbolAndType(Index, Entry.Type);
 | 
						|
      write(ERE32.r_info);
 | 
						|
 | 
						|
      if (hasRelocationAddend())
 | 
						|
        write(uint32_t(Entry.Addend));
 | 
						|
    }
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
const MCSectionELF *ELFObjectWriter::createStringTable(MCContext &Ctx) {
 | 
						|
  const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
 | 
						|
  OS << StrTabBuilder.data();
 | 
						|
  return StrtabSection;
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
 | 
						|
                                   uint32_t GroupSymbolIndex, uint64_t Offset,
 | 
						|
                                   uint64_t Size, const MCSectionELF &Section) {
 | 
						|
  uint64_t sh_link = 0;
 | 
						|
  uint64_t sh_info = 0;
 | 
						|
 | 
						|
  switch(Section.getType()) {
 | 
						|
  default:
 | 
						|
    // Nothing to do.
 | 
						|
    break;
 | 
						|
 | 
						|
  case ELF::SHT_DYNAMIC:
 | 
						|
    llvm_unreachable("SHT_DYNAMIC in a relocatable object");
 | 
						|
 | 
						|
  case ELF::SHT_REL:
 | 
						|
  case ELF::SHT_RELA: {
 | 
						|
    sh_link = SymbolTableIndex;
 | 
						|
    assert(sh_link && ".symtab not found");
 | 
						|
    const MCSectionELF *InfoSection = Section.getAssociatedSection();
 | 
						|
    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_GROUP:
 | 
						|
    sh_link = SymbolTableIndex;
 | 
						|
    sh_info = GroupSymbolIndex;
 | 
						|
    break;
 | 
						|
  }
 | 
						|
 | 
						|
  if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
 | 
						|
      Section.getType() == ELF::SHT_ARM_EXIDX)
 | 
						|
    sh_link = SectionIndexMap.lookup(Section.getAssociatedSection());
 | 
						|
 | 
						|
  WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
 | 
						|
                   Section.getType(), Section.getFlags(), 0, Offset, Size,
 | 
						|
                   sh_link, sh_info, Section.getAlignment(),
 | 
						|
                   Section.getEntrySize());
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::writeSectionHeader(
 | 
						|
    const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap,
 | 
						|
    const SectionOffsetsTy &SectionOffsets) {
 | 
						|
  const unsigned NumSections = SectionTable.size();
 | 
						|
 | 
						|
  // Null section first.
 | 
						|
  uint64_t FirstSectionSize =
 | 
						|
      (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
 | 
						|
  WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
 | 
						|
 | 
						|
  for (const MCSectionELF *Section : SectionTable) {
 | 
						|
    uint32_t GroupSymbolIndex;
 | 
						|
    unsigned Type = Section->getType();
 | 
						|
    if (Type != ELF::SHT_GROUP)
 | 
						|
      GroupSymbolIndex = 0;
 | 
						|
    else
 | 
						|
      GroupSymbolIndex = Section->getGroup()->getIndex();
 | 
						|
 | 
						|
    const std::pair<uint64_t, uint64_t> &Offsets =
 | 
						|
        SectionOffsets.find(Section)->second;
 | 
						|
    uint64_t Size;
 | 
						|
    if (Type == ELF::SHT_NOBITS)
 | 
						|
      Size = Layout.getSectionAddressSize(Section);
 | 
						|
    else
 | 
						|
      Size = Offsets.second - Offsets.first;
 | 
						|
 | 
						|
    writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
 | 
						|
                 *Section);
 | 
						|
  }
 | 
						|
}
 | 
						|
 | 
						|
void ELFObjectWriter::writeObject(MCAssembler &Asm,
 | 
						|
                                  const MCAsmLayout &Layout) {
 | 
						|
  MCContext &Ctx = Asm.getContext();
 | 
						|
  MCSectionELF *StrtabSection =
 | 
						|
      Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
 | 
						|
  StringTableIndex = addToSectionTable(StrtabSection);
 | 
						|
 | 
						|
  RevGroupMapTy RevGroupMap;
 | 
						|
  SectionIndexMapTy SectionIndexMap;
 | 
						|
 | 
						|
  std::map<const MCSymbol *, std::vector<const MCSectionELF *>> GroupMembers;
 | 
						|
 | 
						|
  // Write out the ELF header ...
 | 
						|
  writeHeader(Asm);
 | 
						|
 | 
						|
  // ... then the sections ...
 | 
						|
  SectionOffsetsTy SectionOffsets;
 | 
						|
  std::vector<MCSectionELF *> Groups;
 | 
						|
  std::vector<MCSectionELF *> Relocations;
 | 
						|
  for (MCSection &Sec : Asm) {
 | 
						|
    MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
 | 
						|
 | 
						|
    align(Section.getAlignment());
 | 
						|
 | 
						|
    // Remember the offset into the file for this section.
 | 
						|
    uint64_t SecStart = OS.tell();
 | 
						|
 | 
						|
    const MCSymbolELF *SignatureSymbol = Section.getGroup();
 | 
						|
    writeSectionData(Asm, Section, Layout);
 | 
						|
 | 
						|
    uint64_t SecEnd = OS.tell();
 | 
						|
    SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
 | 
						|
 | 
						|
    MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
 | 
						|
 | 
						|
    if (SignatureSymbol) {
 | 
						|
      Asm.registerSymbol(*SignatureSymbol);
 | 
						|
      unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
 | 
						|
      if (!GroupIdx) {
 | 
						|
        MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
 | 
						|
        GroupIdx = addToSectionTable(Group);
 | 
						|
        Group->setAlignment(4);
 | 
						|
        Groups.push_back(Group);
 | 
						|
      }
 | 
						|
      std::vector<const MCSectionELF *> &Members =
 | 
						|
          GroupMembers[SignatureSymbol];
 | 
						|
      Members.push_back(&Section);
 | 
						|
      if (RelSection)
 | 
						|
        Members.push_back(RelSection);
 | 
						|
    }
 | 
						|
 | 
						|
    SectionIndexMap[&Section] = addToSectionTable(&Section);
 | 
						|
    if (RelSection) {
 | 
						|
      SectionIndexMap[RelSection] = addToSectionTable(RelSection);
 | 
						|
      Relocations.push_back(RelSection);
 | 
						|
    }
 | 
						|
  }
 | 
						|
 | 
						|
  for (MCSectionELF *Group : Groups) {
 | 
						|
    align(Group->getAlignment());
 | 
						|
 | 
						|
    // Remember the offset into the file for this section.
 | 
						|
    uint64_t SecStart = OS.tell();
 | 
						|
 | 
						|
    const MCSymbol *SignatureSymbol = Group->getGroup();
 | 
						|
    assert(SignatureSymbol);
 | 
						|
    write(uint32_t(ELF::GRP_COMDAT));
 | 
						|
    for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
 | 
						|
      uint32_t SecIndex = SectionIndexMap.lookup(Member);
 | 
						|
      write(SecIndex);
 | 
						|
    }
 | 
						|
 | 
						|
    uint64_t SecEnd = OS.tell();
 | 
						|
    SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
 | 
						|
  }
 | 
						|
 | 
						|
  // Compute symbol table information.
 | 
						|
  computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap, SectionOffsets);
 | 
						|
 | 
						|
  for (MCSectionELF *RelSection : Relocations) {
 | 
						|
    align(RelSection->getAlignment());
 | 
						|
 | 
						|
    // Remember the offset into the file for this section.
 | 
						|
    uint64_t SecStart = OS.tell();
 | 
						|
 | 
						|
    writeRelocations(Asm, *RelSection->getAssociatedSection());
 | 
						|
 | 
						|
    uint64_t SecEnd = OS.tell();
 | 
						|
    SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
 | 
						|
  }
 | 
						|
 | 
						|
  {
 | 
						|
    uint64_t SecStart = OS.tell();
 | 
						|
    const MCSectionELF *Sec = createStringTable(Ctx);
 | 
						|
    uint64_t SecEnd = OS.tell();
 | 
						|
    SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
 | 
						|
  }
 | 
						|
 | 
						|
  uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
 | 
						|
  align(NaturalAlignment);
 | 
						|
 | 
						|
  const unsigned SectionHeaderOffset = OS.tell();
 | 
						|
 | 
						|
  // ... then the section header table ...
 | 
						|
  writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
 | 
						|
 | 
						|
  uint16_t NumSections = (SectionTable.size() + 1 >= ELF::SHN_LORESERVE)
 | 
						|
                             ? (uint16_t)ELF::SHN_UNDEF
 | 
						|
                             : SectionTable.size() + 1;
 | 
						|
  if (sys::IsLittleEndianHost != IsLittleEndian)
 | 
						|
    sys::swapByteOrder(NumSections);
 | 
						|
  unsigned NumSectionsOffset;
 | 
						|
 | 
						|
  if (is64Bit()) {
 | 
						|
    uint64_t Val = SectionHeaderOffset;
 | 
						|
    if (sys::IsLittleEndianHost != IsLittleEndian)
 | 
						|
      sys::swapByteOrder(Val);
 | 
						|
    OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
 | 
						|
              offsetof(ELF::Elf64_Ehdr, e_shoff));
 | 
						|
    NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
 | 
						|
  } else {
 | 
						|
    uint32_t Val = SectionHeaderOffset;
 | 
						|
    if (sys::IsLittleEndianHost != IsLittleEndian)
 | 
						|
      sys::swapByteOrder(Val);
 | 
						|
    OS.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
 | 
						|
              offsetof(ELF::Elf32_Ehdr, e_shoff));
 | 
						|
    NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
 | 
						|
  }
 | 
						|
  OS.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
 | 
						|
            NumSectionsOffset);
 | 
						|
}
 | 
						|
 | 
						|
bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
 | 
						|
    const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
 | 
						|
    bool InSet, bool IsPCRel) const {
 | 
						|
  const auto &SymA = cast<MCSymbolELF>(SA);
 | 
						|
  if (IsPCRel) {
 | 
						|
    assert(!InSet);
 | 
						|
    if (::isWeak(SymA))
 | 
						|
      return false;
 | 
						|
  }
 | 
						|
  return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
 | 
						|
                                                                InSet, IsPCRel);
 | 
						|
}
 | 
						|
 | 
						|
bool ELFObjectWriter::isWeak(const MCSymbol &S) const {
 | 
						|
  const auto &Sym = cast<MCSymbolELF>(S);
 | 
						|
  if (::isWeak(Sym))
 | 
						|
    return true;
 | 
						|
 | 
						|
  // It is invalid to replace a reference to a global in a comdat
 | 
						|
  // with a reference to a local since out of comdat references
 | 
						|
  // to a local are forbidden.
 | 
						|
  // We could try to return false for more cases, like the reference
 | 
						|
  // being in the same comdat or Sym being an alias to another global,
 | 
						|
  // but it is not clear if it is worth the effort.
 | 
						|
  if (Sym.getBinding() != ELF::STB_GLOBAL)
 | 
						|
    return false;
 | 
						|
 | 
						|
  if (!Sym.isInSection())
 | 
						|
    return false;
 | 
						|
 | 
						|
  const auto &Sec = cast<MCSectionELF>(Sym.getSection());
 | 
						|
  return Sec.getGroup();
 | 
						|
}
 | 
						|
 | 
						|
MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
 | 
						|
                                            raw_pwrite_stream &OS,
 | 
						|
                                            bool IsLittleEndian) {
 | 
						|
  return new ELFObjectWriter(MOTW, OS, IsLittleEndian);
 | 
						|
}
 |