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      1 //===- llvm/MC/MCELFObjectWriter.h - ELF Object Writer ----------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #ifndef LLVM_MC_MCELFOBJECTWRITER_H
     11 #define LLVM_MC_MCELFOBJECTWRITER_H
     12 
     13 #include "llvm/ADT/Triple.h"
     14 #include "llvm/BinaryFormat/ELF.h"
     15 #include "llvm/Support/Casting.h"
     16 #include "llvm/Support/raw_ostream.h"
     17 #include <cstdint>
     18 #include <vector>
     19 
     20 namespace llvm {
     21 
     22 class MCAssembler;
     23 class MCContext;
     24 class MCFixup;
     25 class MCObjectWriter;
     26 class MCSymbol;
     27 class MCSymbolELF;
     28 class MCValue;
     29 
     30 struct ELFRelocationEntry {
     31   uint64_t Offset; // Where is the relocation.
     32   const MCSymbolELF *Symbol; // The symbol to relocate with.
     33   unsigned Type;   // The type of the relocation.
     34   uint64_t Addend; // The addend to use.
     35   const MCSymbolELF *OriginalSymbol; // The original value of Symbol if we changed it.
     36   uint64_t OriginalAddend; // The original value of addend.
     37 
     38   ELFRelocationEntry(uint64_t Offset, const MCSymbolELF *Symbol, unsigned Type,
     39                      uint64_t Addend, const MCSymbolELF *OriginalSymbol,
     40                      uint64_t OriginalAddend)
     41       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend),
     42         OriginalSymbol(OriginalSymbol), OriginalAddend(OriginalAddend) {}
     43 
     44   void print(raw_ostream &Out) const {
     45     Out << "Off=" << Offset << ", Sym=" << Symbol << ", Type=" << Type
     46         << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol
     47         << ", OriginalAddend=" << OriginalAddend;
     48   }
     49 
     50   void dump() const { print(errs()); }
     51 };
     52 
     53 class MCELFObjectTargetWriter {
     54   const uint8_t OSABI;
     55   const uint16_t EMachine;
     56   const unsigned HasRelocationAddend : 1;
     57   const unsigned Is64Bit : 1;
     58   const unsigned IsN64 : 1;
     59 
     60 protected:
     61   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_, uint16_t EMachine_,
     62                           bool HasRelocationAddend, bool IsN64 = false);
     63 
     64 public:
     65   virtual ~MCELFObjectTargetWriter() = default;
     66 
     67   static uint8_t getOSABI(Triple::OSType OSType) {
     68     switch (OSType) {
     69       case Triple::CloudABI:
     70         return ELF::ELFOSABI_CLOUDABI;
     71       case Triple::PS4:
     72       case Triple::FreeBSD:
     73         return ELF::ELFOSABI_FREEBSD;
     74       default:
     75         return ELF::ELFOSABI_NONE;
     76     }
     77   }
     78 
     79   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
     80                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
     81 
     82   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
     83                                        unsigned Type) const;
     84 
     85   virtual void sortRelocs(const MCAssembler &Asm,
     86                           std::vector<ELFRelocationEntry> &Relocs);
     87 
     88   /// \name Accessors
     89   /// @{
     90   uint8_t getOSABI() const { return OSABI; }
     91   uint16_t getEMachine() const { return EMachine; }
     92   bool hasRelocationAddend() const { return HasRelocationAddend; }
     93   bool is64Bit() const { return Is64Bit; }
     94   bool isN64() const { return IsN64; }
     95   /// @}
     96 
     97   // Instead of changing everyone's API we pack the N64 Type fields
     98   // into the existing 32 bit data unsigned.
     99 #define R_TYPE_SHIFT 0
    100 #define R_TYPE_MASK 0xffffff00
    101 #define R_TYPE2_SHIFT 8
    102 #define R_TYPE2_MASK 0xffff00ff
    103 #define R_TYPE3_SHIFT 16
    104 #define R_TYPE3_MASK 0xff00ffff
    105 #define R_SSYM_SHIFT 24
    106 #define R_SSYM_MASK 0x00ffffff
    107 
    108   // N64 relocation type accessors
    109   uint8_t getRType(uint32_t Type) const {
    110     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    111   }
    112   uint8_t getRType2(uint32_t Type) const {
    113     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    114   }
    115   uint8_t getRType3(uint32_t Type) const {
    116     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    117   }
    118   uint8_t getRSsym(uint32_t Type) const {
    119     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    120   }
    121 
    122   // N64 relocation type setting
    123   unsigned setRType(unsigned Value, unsigned Type) const {
    124     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    125   }
    126   unsigned setRType2(unsigned Value, unsigned Type) const {
    127     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    128   }
    129   unsigned setRType3(unsigned Value, unsigned Type) const {
    130     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    131   }
    132   unsigned setRSsym(unsigned Value, unsigned Type) const {
    133     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    134   }
    135 };
    136 
    137 /// \brief Construct a new ELF writer instance.
    138 ///
    139 /// \param MOTW - The target specific ELF writer subclass.
    140 /// \param OS - The stream to write to.
    141 /// \returns The constructed object writer.
    142 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
    143                                       raw_pwrite_stream &OS,
    144                                       bool IsLittleEndian);
    145 
    146 } // end namespace llvm
    147 
    148 #endif // LLVM_MC_MCELFOBJECTWRITER_H
    149