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/Support/DataTypes.h"
15 #include "llvm/Support/ELF.h"
16 #include <vector>
17 
18 namespace llvm {
19 class MCAssembler;
20 class MCFixup;
21 class MCFragment;
22 class MCObjectWriter;
23 class MCSectionData;
24 class MCSymbol;
25 class MCSymbolData;
26 class MCValue;
27 class raw_pwrite_stream;
28 
29 struct ELFRelocationEntry {
30   uint64_t Offset; // Where is the relocation.
31   const MCSymbol *Symbol;       // The symbol to relocate with.
32   unsigned Type;   // The type of the relocation.
33   uint64_t Addend; // The addend to use.
34 
ELFRelocationEntryELFRelocationEntry35   ELFRelocationEntry(uint64_t Offset, const MCSymbol *Symbol, unsigned Type,
36                      uint64_t Addend)
37       : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
38 };
39 
40 class MCELFObjectTargetWriter {
41   const uint8_t OSABI;
42   const uint16_t EMachine;
43   const unsigned HasRelocationAddend : 1;
44   const unsigned Is64Bit : 1;
45   const unsigned IsN64 : 1;
46 
47 protected:
48 
49   MCELFObjectTargetWriter(bool Is64Bit_, uint8_t OSABI_,
50                           uint16_t EMachine_,  bool HasRelocationAddend,
51                           bool IsN64=false);
52 
53 public:
getOSABI(Triple::OSType OSType)54   static uint8_t getOSABI(Triple::OSType OSType) {
55     switch (OSType) {
56       case Triple::CloudABI:
57         return ELF::ELFOSABI_CLOUDABI;
58       case Triple::PS4:
59       case Triple::FreeBSD:
60         return ELF::ELFOSABI_FREEBSD;
61       case Triple::Linux:
62         return ELF::ELFOSABI_LINUX;
63       default:
64         return ELF::ELFOSABI_NONE;
65     }
66   }
67 
~MCELFObjectTargetWriter()68   virtual ~MCELFObjectTargetWriter() {}
69 
70   virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
71                                 bool IsPCRel) const = 0;
72 
73   virtual bool needsRelocateWithSymbol(const MCSymbolData &SD,
74                                        unsigned Type) const;
75 
76   virtual void sortRelocs(const MCAssembler &Asm,
77                           std::vector<ELFRelocationEntry> &Relocs);
78 
79   /// @name Accessors
80   /// @{
getOSABI()81   uint8_t getOSABI() const { return OSABI; }
getEMachine()82   uint16_t getEMachine() const { return EMachine; }
hasRelocationAddend()83   bool hasRelocationAddend() const { return HasRelocationAddend; }
is64Bit()84   bool is64Bit() const { return Is64Bit; }
isN64()85   bool isN64() const { return IsN64; }
86   /// @}
87 
88   // Instead of changing everyone's API we pack the N64 Type fields
89   // into the existing 32 bit data unsigned.
90 #define R_TYPE_SHIFT 0
91 #define R_TYPE_MASK 0xffffff00
92 #define R_TYPE2_SHIFT 8
93 #define R_TYPE2_MASK 0xffff00ff
94 #define R_TYPE3_SHIFT 16
95 #define R_TYPE3_MASK 0xff00ffff
96 #define R_SSYM_SHIFT 24
97 #define R_SSYM_MASK 0x00ffffff
98 
99   // N64 relocation type accessors
getRType(uint32_t Type)100   uint8_t getRType(uint32_t Type) const {
101     return (unsigned)((Type >> R_TYPE_SHIFT) & 0xff);
102   }
getRType2(uint32_t Type)103   uint8_t getRType2(uint32_t Type) const {
104     return (unsigned)((Type >> R_TYPE2_SHIFT) & 0xff);
105   }
getRType3(uint32_t Type)106   uint8_t getRType3(uint32_t Type) const {
107     return (unsigned)((Type >> R_TYPE3_SHIFT) & 0xff);
108   }
getRSsym(uint32_t Type)109   uint8_t getRSsym(uint32_t Type) const {
110     return (unsigned)((Type >> R_SSYM_SHIFT) & 0xff);
111   }
112 
113   // N64 relocation type setting
setRType(unsigned Value,unsigned Type)114   unsigned setRType(unsigned Value, unsigned Type) const {
115     return ((Type & R_TYPE_MASK) | ((Value & 0xff) << R_TYPE_SHIFT));
116   }
setRType2(unsigned Value,unsigned Type)117   unsigned setRType2(unsigned Value, unsigned Type) const {
118     return (Type & R_TYPE2_MASK) | ((Value & 0xff) << R_TYPE2_SHIFT);
119   }
setRType3(unsigned Value,unsigned Type)120   unsigned setRType3(unsigned Value, unsigned Type) const {
121     return (Type & R_TYPE3_MASK) | ((Value & 0xff) << R_TYPE3_SHIFT);
122   }
setRSsym(unsigned Value,unsigned Type)123   unsigned setRSsym(unsigned Value, unsigned Type) const {
124     return (Type & R_SSYM_MASK) | ((Value & 0xff) << R_SSYM_SHIFT);
125   }
126 };
127 
128 /// \brief Construct a new ELF writer instance.
129 ///
130 /// \param MOTW - The target specific ELF writer subclass.
131 /// \param OS - The stream to write to.
132 /// \returns The constructed object writer.
133 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
134                                       raw_pwrite_stream &OS,
135                                       bool IsLittleEndian);
136 } // End llvm namespace
137 
138 #endif
139