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/MC/MCValue.h"
15 #include "llvm/Support/DataTypes.h"
16 #include "llvm/Support/ELF.h"
17 #include "llvm/Support/raw_ostream.h"
18 #include <vector>
19 
20 namespace llvm {
21 class MCAssembler;
22 class MCContext;
23 class MCFixup;
24 class MCFragment;
25 class MCObjectWriter;
26 class MCSymbol;
27 class MCSymbolELF;
28 class MCValue;
29 class raw_pwrite_stream;
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 
ELFRelocationEntryELFRelocationEntry39   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 
printELFRelocationEntry45   void print(raw_ostream &Out) const {
46     Out << "Off=" << Offset << ", Sym=" << Symbol << ", Type=" << Type
47         << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol
48         << ", OriginalAddend=" << OriginalAddend;
49   }
dumpELFRelocationEntry50   void dump() const { print(errs()); }
51 };
52 
53 class MCELFObjectTargetWriter {
54   const uint8_t OSABI;
55   const uint16_t EMachine;
56   const unsigned HasRelocationAddend : 1;
57   const unsigned Is64Bit : 1;
58   const unsigned IsN64 : 1;
59 
60 protected:
61 
62   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
63                           uint16_t EMachine_,  bool HasRelocationAddend,
64                           bool IsN64=false);
65 
66 public:
getOSABI(Triple::OSType OSType)67   static uint8_t getOSABI(Triple::OSType OSType) {
68     switch (OSType) {
69       case Triple::CloudABI:
70         return ELF::ELFOSABI_CLOUDABI;
71       case Triple::PS4:
72       case Triple::FreeBSD:
73         return ELF::ELFOSABI_FREEBSD;
74       default:
75         return ELF::ELFOSABI_NONE;
76     }
77   }
78 
~MCELFObjectTargetWriter()79   virtual ~MCELFObjectTargetWriter() {}
80 
81   virtual unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
82                                 const MCFixup &Fixup, bool IsPCRel) const = 0;
83 
84   virtual bool needsRelocateWithSymbol(const MCSymbol &Sym,
85                                        unsigned Type) const;
86 
87   virtual void sortRelocs(const MCAssembler &Asm,
88                           std::vector<ELFRelocationEntry> &Relocs);
89 
90   /// \name Accessors
91   /// @{
getOSABI()92   uint8_t getOSABI() const { return OSABI; }
getEMachine()93   uint16_t getEMachine() const { return EMachine; }
hasRelocationAddend()94   bool hasRelocationAddend() const { return HasRelocationAddend; }
is64Bit()95   bool is64Bit() const { return Is64Bit; }
isN64()96   bool isN64() const { return IsN64; }
97   /// @}
98 
99   // Instead of changing everyone's API we pack the N64 Type fields
100   // into the existing 32 bit data unsigned.
101 #define R_TYPE_SHIFT 0
102 #define R_TYPE_MASK 0xffffff00
103 #define R_TYPE2_SHIFT 8
104 #define R_TYPE2_MASK 0xffff00ff
105 #define R_TYPE3_SHIFT 16
106 #define R_TYPE3_MASK 0xff00ffff
107 #define R_SSYM_SHIFT 24
108 #define R_SSYM_MASK 0x00ffffff
109 
110   // N64 relocation type accessors
getRType(uint32_t Type)111   uint8_t getRType(uint32_t Type) const {
112     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
113   }
getRType2(uint32_t Type)114   uint8_t getRType2(uint32_t Type) const {
115     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
116   }
getRType3(uint32_t Type)117   uint8_t getRType3(uint32_t Type) const {
118     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
119   }
getRSsym(uint32_t Type)120   uint8_t getRSsym(uint32_t Type) const {
121     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
122   }
123 
124   // N64 relocation type setting
setRType(unsigned Value,unsigned Type)125   unsigned setRType(unsigned Value, unsigned Type) const {
126     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
127   }
setRType2(unsigned Value,unsigned Type)128   unsigned setRType2(unsigned Value, unsigned Type) const {
129     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
130   }
setRType3(unsigned Value,unsigned Type)131   unsigned setRType3(unsigned Value, unsigned Type) const {
132     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
133   }
setRSsym(unsigned Value,unsigned Type)134   unsigned setRSsym(unsigned Value, unsigned Type) const {
135     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
136   }
137 };
138 
139 /// \brief Construct a new ELF writer instance.
140 ///
141 /// \param MOTW - The target specific ELF writer subclass.
142 /// \param OS - The stream to write to.
143 /// \returns The constructed object writer.
144 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
145                                       raw_pwrite_stream &OS,
146                                       bool IsLittleEndian);
147 } // End llvm namespace
148 
149 #endif
150