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      1 //===- llvm/MC/MCELFObjectWriter.h - ELF Object Writer ----------*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_MC_MCELFOBJECTWRITER_H
     10 #define LLVM_MC_MCELFOBJECTWRITER_H
     11 
     12 #include "llvm/ADT/Triple.h"
     13 #include "llvm/BinaryFormat/ELF.h"
     14 #include "llvm/MC/MCObjectWriter.h"
     15 #include "llvm/MC/MCSectionELF.h"
     16 #include "llvm/Support/Casting.h"
     17 #include "llvm/Support/raw_ostream.h"
     18 #include <cstdint>
     19 #include <vector>
     20 
     21 namespace llvm {
     22 
     23 class MCAssembler;
     24 class MCContext;
     25 class MCFixup;
     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 : public MCObjectTargetWriter {
     54   const uint8_t OSABI;
     55   const uint8_t ABIVersion;
     56   const uint16_t EMachine;
     57   const unsigned HasRelocationAddend : 1;
     58   const unsigned Is64Bit : 1;
     59 
     60 protected:
     61   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_, uint16_t EMachine_,
     62                           bool HasRelocationAddend_, uint8_t ABIVersion_ = 0);
     63 
     64 public:
     65   virtual ~MCELFObjectTargetWriter() = default;
     66 
     67   Triple::ObjectFormatType getFormat() const override { return Triple::ELF; }
     68   static bool classof(const MCObjectTargetWriter *W) {
     69     return W->getFormat() == Triple::ELF;
     70   }
     71 
     72   static uint8_t getOSABI(Triple::OSType OSType) {
     73     switch (OSType) {
     74       case Triple::CloudABI:
     75         return ELF::ELFOSABI_CLOUDABI;
     76       case Triple::HermitCore:
     77         return ELF::ELFOSABI_STANDALONE;
     78       case Triple::PS4:
     79       case Triple::FreeBSD:
     80         return ELF::ELFOSABI_FREEBSD;
     81       default:
     82         return ELF::ELFOSABI_NONE;
     83     }
     84   }
     85 
     86   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
     87                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
     88 
     89   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
     90                                        unsigned Type) const;
     91 
     92   virtual void sortRelocs(const MCAssembler &Asm,
     93                           std::vector<ELFRelocationEntry> &Relocs);
     94 
     95   virtual void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec);
     96 
     97   /// \name Accessors
     98   /// @{
     99   uint8_t getOSABI() const { return OSABI; }
    100   uint8_t getABIVersion() const { return ABIVersion; }
    101   uint16_t getEMachine() const { return EMachine; }
    102   bool hasRelocationAddend() const { return HasRelocationAddend; }
    103   bool is64Bit() const { return Is64Bit; }
    104   /// @}
    105 
    106   // Instead of changing everyone's API we pack the N64 Type fields
    107   // into the existing 32 bit data unsigned.
    108 #define R_TYPE_SHIFT 0
    109 #define R_TYPE_MASK 0xffffff00
    110 #define R_TYPE2_SHIFT 8
    111 #define R_TYPE2_MASK 0xffff00ff
    112 #define R_TYPE3_SHIFT 16
    113 #define R_TYPE3_MASK 0xff00ffff
    114 #define R_SSYM_SHIFT 24
    115 #define R_SSYM_MASK 0x00ffffff
    116 
    117   // N64 relocation type accessors
    118   uint8_t getRType(uint32_t Type) const {
    119     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
    120   }
    121   uint8_t getRType2(uint32_t Type) const {
    122     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
    123   }
    124   uint8_t getRType3(uint32_t Type) const {
    125     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
    126   }
    127   uint8_t getRSsym(uint32_t Type) const {
    128     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
    129   }
    130 
    131   // N64 relocation type setting
    132   static unsigned setRTypes(unsigned Value1, unsigned Value2, unsigned Value3) {
    133     return ((Value1 & 0xff) << R_TYPE_SHIFT) |
    134            ((Value2 & 0xff) << R_TYPE2_SHIFT) |
    135            ((Value3 & 0xff) << R_TYPE3_SHIFT);
    136   }
    137   unsigned setRSsym(unsigned Value, unsigned Type) const {
    138     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
    139   }
    140 };
    141 
    142 /// Construct a new ELF writer instance.
    143 ///
    144 /// \param MOTW - The target specific ELF writer subclass.
    145 /// \param OS - The stream to write to.
    146 /// \returns The constructed object writer.
    147 std::unique_ptr<MCObjectWriter>
    148 createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
    149                       raw_pwrite_stream &OS, bool IsLittleEndian);
    150 
    151 std::unique_ptr<MCObjectWriter>
    152 createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
    153                          raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
    154                          bool IsLittleEndian);
    155 
    156 } // end namespace llvm
    157 
    158 #endif // LLVM_MC_MCELFOBJECTWRITER_H
    159