include/llvm/MC/MCELFObjectWriter.h

   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 MCObjectWriter;
  27 class MCSymbol;
  28 class MCSymbolELF;
  29 class MCValue;
  30
  31 struct ELFRelocationEntry {
  32   uint64_t Offset; // Where is the relocation.
  33   const MCSymbolELF *Symbol; // The symbol to relocate with.
  34   unsigned Type;   // The type of the relocation.
  35   uint64_t Addend; // The addend to use.
  36   const MCSymbolELF *OriginalSymbol; // The original value of Symbol if we changed it.
  37   uint64_t OriginalAddend; // The original value of addend.
  38
  39   ELFRelocationEntry(uint64_t Offset, const MCSymbolELF *Symbol, unsigned Type,
  40                      uint64_t Addend, const MCSymbolELF *OriginalSymbol,
  41                      uint64_t OriginalAddend)
  42       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend),
  43         OriginalSymbol(OriginalSymbol), OriginalAddend(OriginalAddend) {}
  44
  45   void print(raw_ostream &Out) const {
  46     Out << "Off=" << Offset << ", Sym=" << Symbol << ", Type=" << Type
  47         << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol
  48         << ", OriginalAddend=" << OriginalAddend;
  49   }
  50
  51   void dump() const { print(errs()); }
  52 };
  53
  54 class MCELFObjectTargetWriter : public MCObjectTargetWriter {
  55   const uint8_t OSABI;
  56   const uint8_t ABIVersion;
  57   const uint16_t EMachine;
  58   const unsigned HasRelocationAddend : 1;
  59   const unsigned Is64Bit : 1;
  60
  61 protected:
  62   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_, uint16_t EMachine_,
  63                           bool HasRelocationAddend_, uint8_t ABIVersion_ = 0);
  64
  65 public:
  66   virtual ~MCELFObjectTargetWriter() = default;
  67
  68   virtual Triple::ObjectFormatType getFormat() const { return Triple::ELF; }
  69   static bool classof(const MCObjectTargetWriter *W) {
  70     return W->getFormat() == Triple::ELF;
  71   }
  72
  73   static uint8_t getOSABI(Triple::OSType OSType) {
  74     switch (OSType) {
  75       case Triple::CloudABI:
  76         return ELF::ELFOSABI_CLOUDABI;
  77       case Triple::HermitCore:
  78         return ELF::ELFOSABI_STANDALONE;
  79       case Triple::PS4:
  80       case Triple::FreeBSD:
  81         return ELF::ELFOSABI_FREEBSD;
  82       default:
  83         return ELF::ELFOSABI_NONE;
  84     }
  85   }
  86
  87   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
  88                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
  89
  90   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
  91                                        unsigned Type) const;
  92
  93   virtual void sortRelocs(const MCAssembler &Asm,
  94                           std::vector<ELFRelocationEntry> &Relocs);
  95
  96   virtual void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec);
  97
  98   /// \name Accessors
  99   /// @{
 100   uint8_t getOSABI() const { return OSABI; }
 101   uint8_t getABIVersion() const { return ABIVersion; }
 102   uint16_t getEMachine() const { return EMachine; }
 103   bool hasRelocationAddend() const { return HasRelocationAddend; }
 104   bool is64Bit() const { return Is64Bit; }
 105   /// @}
 106
 107   // Instead of changing everyone's API we pack the N64 Type fields
 108   // into the existing 32 bit data unsigned.
 109 #define R_TYPE_SHIFT 0
 110 #define R_TYPE_MASK 0xffffff00
 111 #define R_TYPE2_SHIFT 8
 112 #define R_TYPE2_MASK 0xffff00ff
 113 #define R_TYPE3_SHIFT 16
 114 #define R_TYPE3_MASK 0xff00ffff
 115 #define R_SSYM_SHIFT 24
 116 #define R_SSYM_MASK 0x00ffffff
 117
 118   // N64 relocation type accessors
 119   uint8_t getRType(uint32_t Type) const {
 120     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
 121   }
 122   uint8_t getRType2(uint32_t Type) const {
 123     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
 124   }
 125   uint8_t getRType3(uint32_t Type) const {
 126     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
 127   }
 128   uint8_t getRSsym(uint32_t Type) const {
 129     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
 130   }
 131
 132   // N64 relocation type setting
 133   unsigned setRType(unsigned Value, unsigned Type) const {
 134     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
 135   }
 136   unsigned setRType2(unsigned Value, unsigned Type) const {
 137     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
 138   }
 139   unsigned setRType3(unsigned Value, unsigned Type) const {
 140     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
 141   }
 142   unsigned setRSsym(unsigned Value, unsigned Type) const {
 143     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
 144   }
 145 };
 146
 147 /// Construct a new ELF writer instance.
 148 ///
 149 /// \param MOTW - The target specific ELF writer subclass.
 150 /// \param OS - The stream to write to.
 151 /// \returns The constructed object writer.
 152 std::unique_ptr<MCObjectWriter>
 153 createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
 154                       raw_pwrite_stream &OS, bool IsLittleEndian);
 155
 156 std::unique_ptr<MCObjectWriter>
 157 createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
 158                          raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
 159                          bool IsLittleEndian);
 160
 161 } // end namespace llvm
 162
 163 #endif // LLVM_MC_MCELFOBJECTWRITER_H