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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   // Support lexicographic sorting.
     47   bool operator<(const ELFRelocationEntry &RE) const {
     48     return RE.r_offset < r_offset;
     49   }
     50 };
     51 
     52 class MCELFObjectTargetWriter {
     53   const uint8_t OSABI;
     54   const uint16_t EMachine;
     55   const unsigned HasRelocationAddend : 1;
     56   const unsigned Is64Bit : 1;
     57   const unsigned IsN64 : 1;
     58 
     59 protected:
     60 
     61   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
     62                           uint16_t EMachine_,  bool HasRelocationAddend,
     63                           bool IsN64=false);
     64 
     65 public:
     66   static uint8_t getOSABI(Triple::OSType OSType) {
     67     switch (OSType) {
     68       case Triple::FreeBSD:
     69         return ELF::ELFOSABI_FREEBSD;
     70       case Triple::Linux:
     71         return ELF::ELFOSABI_LINUX;
     72       default:
     73         return ELF::ELFOSABI_NONE;
     74     }
     75   }
     76 
     77   virtual ~MCELFObjectTargetWriter() {}
     78 
     79   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
     80                                 bool IsPCRel, bool IsRelocWithSymbol,
     81                                 int64_t Addend) const = 0;
     82   virtual unsigned getEFlags() const;
     83   virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
     84                                          const MCValue &Target,
     85                                          const MCFragment &F,
     86                                          const MCFixup &Fixup,
     87                                          bool IsPCRel) const;
     88   virtual void adjustFixupOffset(const MCFixup &Fixup,
     89                                  uint64_t &RelocOffset);
     90 
     91   virtual void sortRelocs(const MCAssembler &Asm,
     92                           std::vector<ELFRelocationEntry> &Relocs);
     93 
     94   /// @name Accessors
     95   /// @{
     96   uint8_t getOSABI() { return OSABI; }
     97   uint16_t getEMachine() { return EMachine; }
     98   bool hasRelocationAddend() { return HasRelocationAddend; }
     99   bool is64Bit() const { return Is64Bit; }
    100   bool isN64() const { return IsN64; }
    101   /// @}
    102 
    103   // Instead of changing everyone's API we pack the N64 Type fields
    104   // into the existing 32 bit data unsigned.
    105 #define R_TYPE_SHIFT 0
    106 #define R_TYPE_MASK 0xffffff00
    107 #define R_TYPE2_SHIFT 8
    108 #define R_TYPE2_MASK 0xffff00ff
    109 #define R_TYPE3_SHIFT 16
    110 #define R_TYPE3_MASK 0xff00ffff
    111 #define R_SSYM_SHIFT 24
    112 #define R_SSYM_MASK 0x00ffffff
    113 
    114   // N64 relocation type accessors
    115   unsigned getRType(uint32_t Type) const {
    116     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    117   }
    118   unsigned getRType2(uint32_t Type) const {
    119     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    120   }
    121   unsigned getRType3(uint32_t Type) const {
    122     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    123   }
    124   unsigned getRSsym(uint32_t Type) const {
    125     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    126   }
    127 
    128   // N64 relocation type setting
    129   unsigned setRType(unsigned Value, unsigned Type) const {
    130     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    131   }
    132   unsigned setRType2(unsigned Value, unsigned Type) const {
    133     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    134   }
    135   unsigned setRType3(unsigned Value, unsigned Type) const {
    136     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    137   }
    138   unsigned setRSsym(unsigned Value, unsigned Type) const {
    139     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    140   }
    141 };
    142 
    143 /// \brief Construct a new ELF writer instance.
    144 ///
    145 /// \param MOTW - The target specific ELF writer subclass.
    146 /// \param OS - The stream to write to.
    147 /// \returns The constructed object writer.
    148 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
    149                                       raw_ostream &OS, bool IsLittleEndian);
    150 } // End llvm namespace
    151 
    152 #endif
    153