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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 MCSymbolELF;
     25 class MCValue;
     26 class raw_pwrite_stream;
     27 
     28 struct ELFRelocationEntry {
     29   uint64_t Offset; // Where is the relocation.
     30   const MCSymbolELF *Symbol; // The symbol to relocate with.
     31   unsigned Type;   // The type of the relocation.
     32   uint64_t Addend; // The addend to use.
     33 
     34   ELFRelocationEntry(uint64_t Offset, const MCSymbolELF *Symbol, unsigned Type,
     35                      uint64_t Addend)
     36       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
     37 };
     38 
     39 class MCELFObjectTargetWriter {
     40   const uint8_t OSABI;
     41   const uint16_t EMachine;
     42   const unsigned HasRelocationAddend : 1;
     43   const unsigned Is64Bit : 1;
     44   const unsigned IsN64 : 1;
     45 
     46 protected:
     47 
     48   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
     49                           uint16_t EMachine_,  bool HasRelocationAddend,
     50                           bool IsN64=false);
     51 
     52 public:
     53   static uint8_t getOSABI(Triple::OSType OSType) {
     54     switch (OSType) {
     55       case Triple::CloudABI:
     56         return ELF::ELFOSABI_CLOUDABI;
     57       case Triple::PS4:
     58       case Triple::FreeBSD:
     59         return ELF::ELFOSABI_FREEBSD;
     60       default:
     61         return ELF::ELFOSABI_NONE;
     62     }
     63   }
     64 
     65   virtual ~MCELFObjectTargetWriter() {}
     66 
     67   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
     68                                 bool IsPCRel) const = 0;
     69 
     70   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
     71                                        unsigned Type) const;
     72 
     73   virtual void sortRelocs(const MCAssembler &Asm,
     74                           std::vector<ELFRelocationEntry> &Relocs);
     75 
     76   /// \name Accessors
     77   /// @{
     78   uint8_t getOSABI() const { return OSABI; }
     79   uint16_t getEMachine() const { return EMachine; }
     80   bool hasRelocationAddend() const { return HasRelocationAddend; }
     81   bool is64Bit() const { return Is64Bit; }
     82   bool isN64() const { return IsN64; }
     83   /// @}
     84 
     85   // Instead of changing everyone's API we pack the N64 Type fields
     86   // into the existing 32 bit data unsigned.
     87 #define R_TYPE_SHIFT 0
     88 #define R_TYPE_MASK 0xffffff00
     89 #define R_TYPE2_SHIFT 8
     90 #define R_TYPE2_MASK 0xffff00ff
     91 #define R_TYPE3_SHIFT 16
     92 #define R_TYPE3_MASK 0xff00ffff
     93 #define R_SSYM_SHIFT 24
     94 #define R_SSYM_MASK 0x00ffffff
     95 
     96   // N64 relocation type accessors
     97   uint8_t getRType(uint32_t Type) const {
     98     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
     99   }
    100   uint8_t getRType2(uint32_t Type) const {
    101     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    102   }
    103   uint8_t getRType3(uint32_t Type) const {
    104     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    105   }
    106   uint8_t getRSsym(uint32_t Type) const {
    107     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    108   }
    109 
    110   // N64 relocation type setting
    111   unsigned setRType(unsigned Value, unsigned Type) const {
    112     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
    113   }
    114   unsigned setRType2(unsigned Value, unsigned Type) const {
    115     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
    116   }
    117   unsigned setRType3(unsigned Value, unsigned Type) const {
    118     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
    119   }
    120   unsigned setRSsym(unsigned Value, unsigned Type) const {
    121     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    122   }
    123 };
    124 
    125 /// \brief Construct a new ELF writer instance.
    126 ///
    127 /// \param MOTW - The target specific ELF writer subclass.
    128 /// \param OS - The stream to write to.
    129 /// \returns The constructed object writer.
    130 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
    131                                       raw_pwrite_stream &OS,
    132                                       bool IsLittleEndian);
    133 } // End llvm namespace
    134 
    135 #endif
    136