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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/Support/DataTypes.h"
     15 #include "llvm/Support/ELF.h"
     16 #include <vector>
     17 
     18 namespace llvm {
     19 class MCAssembler;
     20 class MCFixup;
     21 class MCFragment;
     22 class MCObjectWriter;
     23 class MCSymbol;
     24 class MCValue;
     25 
     26 /// @name Relocation Data
     27 /// @{
     28 
     29 struct ELFRelocationEntry {
     30   // Make these big enough for both 32-bit and 64-bit
     31   uint64_t r_offset;
     32   int Index;
     33   unsigned Type;
     34   const MCSymbol *Symbol;
     35   uint64_t r_addend;
     36   const MCFixup *Fixup;
     37 
     38   ELFRelocationEntry()
     39     : r_offset(0), Index(0), Type(0), Symbol(0), r_addend(0), Fixup(0) {}
     40 
     41   ELFRelocationEntry(uint64_t RelocOffset, int Idx, unsigned RelType,
     42                      const MCSymbol *Sym, uint64_t Addend, const MCFixup &Fixup)
     43     : r_offset(RelocOffset), Index(Idx), Type(RelType), Symbol(Sym),
     44       r_addend(Addend), Fixup(&Fixup) {}
     45 };
     46 
     47 class MCELFObjectTargetWriter {
     48   const uint8_t OSABI;
     49   const uint16_t EMachine;
     50   const unsigned HasRelocationAddend : 1;
     51   const unsigned Is64Bit : 1;
     52   const unsigned IsN64 : 1;
     53 
     54 protected:
     55 
     56   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
     57                           uint16_t EMachine_,  bool HasRelocationAddend,
     58                           bool IsN64=false);
     59 
     60 public:
     61   static uint8_t getOSABI(Triple::OSType OSType) {
     62     switch (OSType) {
     63       case Triple::FreeBSD:
     64         return ELF::ELFOSABI_FREEBSD;
     65       case Triple::Linux:
     66         return ELF::ELFOSABI_LINUX;
     67       default:
     68         return ELF::ELFOSABI_NONE;
     69     }
     70   }
     71 
     72   virtual ~MCELFObjectTargetWriter() {}
     73 
     74   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
     75                                 bool IsPCRel, bool IsRelocWithSymbol,
     76                                 int64_t Addend) const = 0;
     77   virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
     78                                          const MCValue &Target,
     79                                          const MCFragment &F,
     80                                          const MCFixup &Fixup,
     81                                          bool IsPCRel) const;
     82   virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
     83                                                   const MCFixup &Fixup,
     84                                                   bool IsPCRel) const;
     85 
     86   virtual void sortRelocs(const MCAssembler &Asm,
     87                           std::vector<ELFRelocationEntry> &Relocs);
     88 
     89   /// @name Accessors
     90   /// @{
     91   uint8_t getOSABI() const { return OSABI; }
     92   uint16_t getEMachine() const { return EMachine; }
     93   bool hasRelocationAddend() const { return HasRelocationAddend; }
     94   bool is64Bit() const { return Is64Bit; }
     95   bool isN64() const { return IsN64; }
     96   /// @}
     97 
     98   // Instead of changing everyone's API we pack the N64 Type fields
     99   // into the existing 32 bit data unsigned.
    100 #define R_TYPE_SHIFT 0
    101 #define R_TYPE_MASK 0xffffff00
    102 #define R_TYPE2_SHIFT 8
    103 #define R_TYPE2_MASK 0xffff00ff
    104 #define R_TYPE3_SHIFT 16
    105 #define R_TYPE3_MASK 0xff00ffff
    106 #define R_SSYM_SHIFT 24
    107 #define R_SSYM_MASK 0x00ffffff
    108 
    109   // N64 relocation type accessors
    110   unsigned getRType(uint32_t Type) const {
    111     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    112   }
    113   unsigned getRType2(uint32_t Type) const {
    114     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    115   }
    116   unsigned getRType3(uint32_t Type) const {
    117     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    118   }
    119   unsigned getRSsym(uint32_t Type) const {
    120     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    121   }
    122 
    123   // N64 relocation type setting
    124   unsigned setRType(unsigned Value, unsigned Type) const {
    125     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    126   }
    127   unsigned setRType2(unsigned Value, unsigned Type) const {
    128     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    129   }
    130   unsigned setRType3(unsigned Value, unsigned Type) const {
    131     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    132   }
    133   unsigned setRSsym(unsigned Value, unsigned Type) const {
    134     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    135   }
    136 };
    137 
    138 /// \brief Construct a new ELF writer instance.
    139 ///
    140 /// \param MOTW - The target specific ELF writer subclass.
    141 /// \param OS - The stream to write to.
    142 /// \returns The constructed object writer.
    143 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
    144                                       raw_ostream &OS, bool IsLittleEndian);
    145 } // End llvm namespace
    146 
    147 #endif
    148