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/BinaryFormat/ELF.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/MC/MCSectionELF.h"
17 #include "llvm/Support/Casting.h"
18 #include "llvm/Support/raw_ostream.h"
19 #include <cstdint>
20 #include <vector>
21 
22 namespace llvm {
23 
24 class MCAssembler;
25 class MCContext;
26 class MCFixup;
27 class MCObjectWriter;
28 class MCSymbol;
29 class MCSymbolELF;
30 class MCValue;
31 
32 struct ELFRelocationEntry {
33   uint64_t Offset; // Where is the relocation.
34   const MCSymbolELF *Symbol; // The symbol to relocate with.
35   unsigned Type;   // The type of the relocation.
36   uint64_t Addend; // The addend to use.
37   const MCSymbolELF *OriginalSymbol; // The original value of Symbol if we changed it.
38   uint64_t OriginalAddend; // The original value of addend.
39 
ELFRelocationEntryELFRelocationEntry40   ELFRelocationEntry(uint64_t Offset, const MCSymbolELF *Symbol, unsigned Type,
41                      uint64_t Addend, const MCSymbolELF *OriginalSymbol,
42                      uint64_t OriginalAddend)
43       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend),
44         OriginalSymbol(OriginalSymbol), OriginalAddend(OriginalAddend) {}
45 
printELFRelocationEntry46   void print(raw_ostream &Out) const {
47     Out << "Off=" << Offset << ", Sym=" << Symbol << ", Type=" << Type
48         << ", Addend=" << Addend << ", OriginalSymbol=" << OriginalSymbol
49         << ", OriginalAddend=" << OriginalAddend;
50   }
51 
dumpELFRelocationEntry52   void dump() const { print(errs()); }
53 };
54 
55 class MCELFObjectTargetWriter : public MCObjectTargetWriter {
56   const uint8_t OSABI;
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);
64 
65 public:
66   virtual ~MCELFObjectTargetWriter() = default;
67 
getFormat()68   virtual Triple::ObjectFormatType getFormat() const { return Triple::ELF; }
classof(const MCObjectTargetWriter * W)69   static bool classof(const MCObjectTargetWriter *W) {
70     return W->getFormat() == Triple::ELF;
71   }
72 
getOSABI(Triple::OSType OSType)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   /// @{
getOSABI()100   uint8_t getOSABI() const { return OSABI; }
getEMachine()101   uint16_t getEMachine() const { return EMachine; }
hasRelocationAddend()102   bool hasRelocationAddend() const { return HasRelocationAddend; }
is64Bit()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
getRType(uint32_t Type)118   uint8_t getRType(uint32_t Type) const {
119     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
120   }
getRType2(uint32_t Type)121   uint8_t getRType2(uint32_t Type) const {
122     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
123   }
getRType3(uint32_t Type)124   uint8_t getRType3(uint32_t Type) const {
125     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
126   }
getRSsym(uint32_t Type)127   uint8_t getRSsym(uint32_t Type) const {
128     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
129   }
130 
131   // N64 relocation type setting
setRType(unsigned Value,unsigned Type)132   unsigned setRType(unsigned Value, unsigned Type) const {
133     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
134   }
setRType2(unsigned Value,unsigned Type)135   unsigned setRType2(unsigned Value, unsigned Type) const {
136     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
137   }
setRType3(unsigned Value,unsigned Type)138   unsigned setRType3(unsigned Value, unsigned Type) const {
139     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
140   }
setRSsym(unsigned Value,unsigned Type)141   unsigned setRSsym(unsigned Value, unsigned Type) const {
142     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
143   }
144 };
145 
146 /// Construct a new ELF writer instance.
147 ///
148 /// \param MOTW - The target specific ELF writer subclass.
149 /// \param OS - The stream to write to.
150 /// \returns The constructed object writer.
151 std::unique_ptr<MCObjectWriter>
152 createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
153                       raw_pwrite_stream &OS, bool IsLittleEndian);
154 
155 std::unique_ptr<MCObjectWriter>
156 createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
157                          raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
158                          bool IsLittleEndian);
159 
160 } // end namespace llvm
161 
162 #endif // LLVM_MC_MCELFOBJECTWRITER_H
163