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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 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
     83                                          const MCValue &Target,
     84                                          const MCFragment &F,
     85                                          const MCFixup &Fixup,
     86                                          bool IsPCRel) const;
     87   virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
     88                                                   const MCFixup &Fixup,
     89                                                   bool IsPCRel) const;
     90   virtual void adjustFixupOffset(const MCFixup &Fixup,
     91                                  uint64_t &RelocOffset);
     92 
     93   virtual void sortRelocs(const MCAssembler &Asm,
     94                           std::vector<ELFRelocationEntry> &Relocs);
     95 
     96   /// @name Accessors
     97   /// @{
     98   uint8_t getOSABI() const { return OSABI; }
     99   uint16_t getEMachine() const { return EMachine; }
    100   bool hasRelocationAddend() const { return HasRelocationAddend; }
    101   bool is64Bit() const { return Is64Bit; }
    102   bool isN64() const { return IsN64; }
    103   /// @}
    104 
    105   // Instead of changing everyone's API we pack the N64 Type fields
    106   // into the existing 32 bit data unsigned.
    107 #define R_TYPE_SHIFT 0
    108 #define R_TYPE_MASK 0xffffff00
    109 #define R_TYPE2_SHIFT 8
    110 #define R_TYPE2_MASK 0xffff00ff
    111 #define R_TYPE3_SHIFT 16
    112 #define R_TYPE3_MASK 0xff00ffff
    113 #define R_SSYM_SHIFT 24
    114 #define R_SSYM_MASK 0x00ffffff
    115 
    116   // N64 relocation type accessors
    117   unsigned getRType(uint32_t Type) const {
    118     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    119   }
    120   unsigned getRType2(uint32_t Type) const {
    121     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    122   }
    123   unsigned getRType3(uint32_t Type) const {
    124     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    125   }
    126   unsigned getRSsym(uint32_t Type) const {
    127     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    128   }
    129 
    130   // N64 relocation type setting
    131   unsigned setRType(unsigned Value, unsigned Type) const {
    132     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    133   }
    134   unsigned setRType2(unsigned Value, unsigned Type) const {
    135     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    136   }
    137   unsigned setRType3(unsigned Value, unsigned Type) const {
    138     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    139   }
    140   unsigned setRSsym(unsigned Value, unsigned Type) const {
    141     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    142   }
    143 };
    144 
    145 /// \brief Construct a new ELF writer instance.
    146 ///
    147 /// \param MOTW - The target specific ELF writer subclass.
    148 /// \param OS - The stream to write to.
    149 /// \returns The constructed object writer.
    150 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
    151                                       raw_ostream &OS, bool IsLittleEndian);
    152 } // End llvm namespace
    153 
    154 #endif
    155