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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.   LLVM_DUMP_METHOD 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.       case Triple::Solaris:
  82.         return ELF::ELFOSABI_SOLARIS;
  83.       default:
  84.         return ELF::ELFOSABI_NONE;
  85.     }
  86.   }
  87.  
  88.   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
  89.                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
  90.  
  91.   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
  92.                                        unsigned Type) const;
  93.  
  94.   virtual void sortRelocs(const MCAssembler &Asm,
  95.                           std::vector<ELFRelocationEntry> &Relocs);
  96.  
  97.   virtual void addTargetSectionFlags(MCContext &Ctx, MCSectionELF &Sec);
  98.  
  99.   /// \name Accessors
  100.   /// @{
  101.   uint8_t getOSABI() const { return OSABI; }
  102.   uint8_t getABIVersion() const { return ABIVersion; }
  103.   uint16_t getEMachine() const { return EMachine; }
  104.   bool hasRelocationAddend() const { return HasRelocationAddend; }
  105.   bool is64Bit() const { return Is64Bit; }
  106.   /// @}
  107.  
  108.   // Instead of changing everyone's API we pack the N64 Type fields
  109.   // into the existing 32 bit data unsigned.
  110. #define R_TYPE_SHIFT 0
  111. #define R_TYPE_MASK 0xffffff00
  112. #define R_TYPE2_SHIFT 8
  113. #define R_TYPE2_MASK 0xffff00ff
  114. #define R_TYPE3_SHIFT 16
  115. #define R_TYPE3_MASK 0xff00ffff
  116. #define R_SSYM_SHIFT 24
  117. #define R_SSYM_MASK 0x00ffffff
  118.  
  119.   // N64 relocation type accessors
  120.   uint8_t getRType(uint32_t Type) const {
  121.     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
  122.   }
  123.   uint8_t getRType2(uint32_t Type) const {
  124.     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
  125.   }
  126.   uint8_t getRType3(uint32_t Type) const {
  127.     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
  128.   }
  129.   uint8_t getRSsym(uint32_t Type) const {
  130.     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
  131.   }
  132.  
  133.   // N64 relocation type setting
  134.   static unsigned setRTypes(unsigned Value1, unsigned Value2, unsigned Value3) {
  135.     return ((Value1 & 0xff) << R_TYPE_SHIFT) |
  136.            ((Value2 & 0xff) << R_TYPE2_SHIFT) |
  137.            ((Value3 & 0xff) << R_TYPE3_SHIFT);
  138.   }
  139.   unsigned setRSsym(unsigned Value, unsigned Type) const {
  140.     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
  141.   }
  142.  
  143.   // On AArch64, return a new section to be added to the ELF object that
  144.   // contains relocations used to describe every symbol that should have memory
  145.   // tags applied. Returns nullptr if no such section is necessary (i.e. there's
  146.   // no tagged globals).
  147.   virtual MCSectionELF *getMemtagRelocsSection(MCContext &Ctx) const {
  148.     return nullptr;
  149.   }
  150. };
  151.  
  152. /// Construct a new ELF writer instance.
  153. ///
  154. /// \param MOTW - The target specific ELF writer subclass.
  155. /// \param OS - The stream to write to.
  156. /// \returns The constructed object writer.
  157. std::unique_ptr<MCObjectWriter>
  158. createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
  159.                       raw_pwrite_stream &OS, bool IsLittleEndian);
  160.  
  161. std::unique_ptr<MCObjectWriter>
  162. createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
  163.                          raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
  164.                          bool IsLittleEndian);
  165.  
  166. } // end namespace llvm
  167.  
  168. #endif // LLVM_MC_MCELFOBJECTWRITER_H
  169.