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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 
     59 protected:
     60   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_, uint16_t EMachine_,
     61                           bool HasRelocationAddend);
     62 
     63 public:
     64   virtual ~MCELFObjectTargetWriter() = default;
     65 
     66   static uint8_t getOSABI(Triple::OSType OSType) {
     67     switch (OSType) {
     68       case Triple::CloudABI:
     69         return ELF::ELFOSABI_CLOUDABI;
     70       case Triple::PS4:
     71       case Triple::FreeBSD:
     72         return ELF::ELFOSABI_FREEBSD;
     73       default:
     74         return ELF::ELFOSABI_NONE;
     75     }
     76   }
     77 
     78   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
     79                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
     80 
     81   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
     82                                        unsigned Type) const;
     83 
     84   virtual void sortRelocs(const MCAssembler &Asm,
     85                           std::vector<ELFRelocationEntry> &Relocs);
     86 
     87   /// \name Accessors
     88   /// @{
     89   uint8_t getOSABI() const { return OSABI; }
     90   uint16_t getEMachine() const { return EMachine; }
     91   bool hasRelocationAddend() const { return HasRelocationAddend; }
     92   bool is64Bit() const { return Is64Bit; }
     93   /// @}
     94 
     95   // Instead of changing everyone's API we pack the N64 Type fields
     96   // into the existing 32 bit data unsigned.
     97 #define R_TYPE_SHIFT 0
     98 #define R_TYPE_MASK 0xffffff00
     99 #define R_TYPE2_SHIFT 8
    100 #define R_TYPE2_MASK 0xffff00ff
    101 #define R_TYPE3_SHIFT 16
    102 #define R_TYPE3_MASK 0xff00ffff
    103 #define R_SSYM_SHIFT 24
    104 #define R_SSYM_MASK 0x00ffffff
    105 
    106   // N64 relocation type accessors
    107   uint8_t getRType(uint32_t Type) const {
    108     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    109   }
    110   uint8_t getRType2(uint32_t Type) const {
    111     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    112   }
    113   uint8_t getRType3(uint32_t Type) const {
    114     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    115   }
    116   uint8_t getRSsym(uint32_t Type) const {
    117     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    118   }
    119 
    120   // N64 relocation type setting
    121   unsigned setRType(unsigned Value, unsigned Type) const {
    122     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    123   }
    124   unsigned setRType2(unsigned Value, unsigned Type) const {
    125     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    126   }
    127   unsigned setRType3(unsigned Value, unsigned Type) const {
    128     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    129   }
    130   unsigned setRSsym(unsigned Value, unsigned Type) const {
    131     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    132   }
    133 };
    134 
    135 /// \brief Construct a new ELF writer instance.
    136 ///
    137 /// \param MOTW - The target specific ELF writer subclass.
    138 /// \param OS - The stream to write to.
    139 /// \returns The constructed object writer.
    140 std::unique_ptr<MCObjectWriter>
    141 createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
    142                       raw_pwrite_stream &OS, bool IsLittleEndian);
    143 
    144 } // end namespace llvm
    145 
    146 #endif // LLVM_MC_MCELFOBJECTWRITER_H
    147