1 //===-- lib/CodeGen/ELF.h - ELF constants and data structures ---*- 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 // This header contains common, non-processor-specific data structures and 11 // constants for the ELF file format. 12 // 13 // The details of the ELF32 bits in this file are largely based on the Tool 14 // Interface Standard (TIS) Executable and Linking Format (ELF) Specification 15 // Version 1.2, May 1995. The ELF64 is based on HP/Intel definition of the 16 // ELF-64 object file format document, Version 1.5 Draft 2 May 27, 1998 17 // 18 //===----------------------------------------------------------------------===// 19 20 #ifndef CODEGEN_ELF_H 21 #define CODEGEN_ELF_H 22 23 #include "llvm/CodeGen/BinaryObject.h" 24 #include "llvm/CodeGen/MachineRelocation.h" 25 #include "llvm/Support/ELF.h" 26 #include "llvm/Support/DataTypes.h" 27 28 namespace llvm { 29 class GlobalValue; 30 31 /// ELFSym - This struct contains information about each symbol that is 32 /// added to logical symbol table for the module. This is eventually 33 /// turned into a real symbol table in the file. 34 struct ELFSym { 35 36 // ELF symbols are related to llvm ones by being one of the two llvm 37 // types, for the other ones (section, file, func) a null pointer is 38 // assumed by default. 39 union { 40 const GlobalValue *GV; // If this is a pointer to a GV 41 const char *Ext; // If this is a pointer to a named symbol 42 } Source; 43 44 // Describes from which source type this ELF symbol comes from, 45 // they can be GlobalValue, ExternalSymbol or neither. 46 enum { 47 isGV, // The Source.GV field is valid. 48 isExtSym, // The Source.ExtSym field is valid. 49 isOther // Not a GlobalValue or External Symbol 50 }; 51 unsigned SourceType; 52 53 bool isGlobalValue() const { return SourceType == isGV; } 54 bool isExternalSym() const { return SourceType == isExtSym; } 55 56 // getGlobalValue - If this is a global value which originated the 57 // elf symbol, return a reference to it. 58 const GlobalValue *getGlobalValue() const { 59 assert(SourceType == isGV && "This is not a global value"); 60 return Source.GV; 61 } 62 63 // getExternalSym - If this is an external symbol which originated the 64 // elf symbol, return a reference to it. 65 const char *getExternalSymbol() const { 66 assert(SourceType == isExtSym && "This is not an external symbol"); 67 return Source.Ext; 68 } 69 70 // getGV - From a global value return a elf symbol to represent it 71 static ELFSym *getGV(const GlobalValue *GV, unsigned Bind, 72 unsigned Type, unsigned Visibility) { 73 ELFSym *Sym = new ELFSym(); 74 Sym->Source.GV = GV; 75 Sym->setBind(Bind); 76 Sym->setType(Type); 77 Sym->setVisibility(Visibility); 78 Sym->SourceType = isGV; 79 return Sym; 80 } 81 82 // getExtSym - Create and return an elf symbol to represent an 83 // external symbol 84 static ELFSym *getExtSym(const char *Ext) { 85 ELFSym *Sym = new ELFSym(); 86 Sym->Source.Ext = Ext; 87 Sym->setBind(ELF::STB_GLOBAL); 88 Sym->setType(ELF::STT_NOTYPE); 89 Sym->setVisibility(ELF::STV_DEFAULT); 90 Sym->SourceType = isExtSym; 91 return Sym; 92 } 93 94 // getSectionSym - Returns a elf symbol to represent an elf section 95 static ELFSym *getSectionSym() { 96 ELFSym *Sym = new ELFSym(); 97 Sym->setBind(ELF::STB_LOCAL); 98 Sym->setType(ELF::STT_SECTION); 99 Sym->setVisibility(ELF::STV_DEFAULT); 100 Sym->SourceType = isOther; 101 return Sym; 102 } 103 104 // getFileSym - Returns a elf symbol to represent the module identifier 105 static ELFSym *getFileSym() { 106 ELFSym *Sym = new ELFSym(); 107 Sym->setBind(ELF::STB_LOCAL); 108 Sym->setType(ELF::STT_FILE); 109 Sym->setVisibility(ELF::STV_DEFAULT); 110 Sym->SectionIdx = 0xfff1; // ELFSection::SHN_ABS; 111 Sym->SourceType = isOther; 112 return Sym; 113 } 114 115 // getUndefGV - Returns a STT_NOTYPE symbol 116 static ELFSym *getUndefGV(const GlobalValue *GV, unsigned Bind) { 117 ELFSym *Sym = new ELFSym(); 118 Sym->Source.GV = GV; 119 Sym->setBind(Bind); 120 Sym->setType(ELF::STT_NOTYPE); 121 Sym->setVisibility(ELF::STV_DEFAULT); 122 Sym->SectionIdx = 0; //ELFSection::SHN_UNDEF; 123 Sym->SourceType = isGV; 124 return Sym; 125 } 126 127 // ELF specific fields 128 unsigned NameIdx; // Index in .strtab of name, once emitted. 129 uint64_t Value; 130 unsigned Size; 131 uint8_t Info; 132 uint8_t Other; 133 unsigned short SectionIdx; 134 135 // Symbol index into the Symbol table 136 unsigned SymTabIdx; 137 138 ELFSym() : SourceType(isOther), NameIdx(0), Value(0), 139 Size(0), Info(0), Other(ELF::STV_DEFAULT), SectionIdx(0), 140 SymTabIdx(0) {} 141 142 unsigned getBind() const { return (Info >> 4) & 0xf; } 143 unsigned getType() const { return Info & 0xf; } 144 bool isLocalBind() const { return getBind() == ELF::STB_LOCAL; } 145 bool isFileType() const { return getType() == ELF::STT_FILE; } 146 147 void setBind(unsigned X) { 148 assert(X == (X & 0xF) && "Bind value out of range!"); 149 Info = (Info & 0x0F) | (X << 4); 150 } 151 152 void setType(unsigned X) { 153 assert(X == (X & 0xF) && "Type value out of range!"); 154 Info = (Info & 0xF0) | X; 155 } 156 157 void setVisibility(unsigned V) { 158 assert(V == (V & 0x3) && "Visibility value out of range!"); 159 Other = V; 160 } 161 }; 162 163 /// ELFSection - This struct contains information about each section that is 164 /// emitted to the file. This is eventually turned into the section header 165 /// table at the end of the file. 166 class ELFSection : public BinaryObject { 167 public: 168 // ELF specific fields 169 unsigned NameIdx; // sh_name - .shstrtab idx of name, once emitted. 170 unsigned Type; // sh_type - Section contents & semantics 171 unsigned Flags; // sh_flags - Section flags. 172 uint64_t Addr; // sh_addr - The mem addr this section is in. 173 unsigned Offset; // sh_offset - Offset from the file start 174 unsigned Size; // sh_size - The section size. 175 unsigned Link; // sh_link - Section header table index link. 176 unsigned Info; // sh_info - Auxiliary information. 177 unsigned Align; // sh_addralign - Alignment of section. 178 unsigned EntSize; // sh_entsize - Size of entries in the section e 179 180 /// SectionIdx - The number of the section in the Section Table. 181 unsigned short SectionIdx; 182 183 /// Sym - The symbol to represent this section if it has one. 184 ELFSym *Sym; 185 186 /// getSymIndex - Returns the symbol table index of the symbol 187 /// representing this section. 188 unsigned getSymbolTableIndex() const { 189 assert(Sym && "section not present in the symbol table"); 190 return Sym->SymTabIdx; 191 } 192 193 ELFSection(const std::string &name, bool isLittleEndian, bool is64Bit) 194 : BinaryObject(name, isLittleEndian, is64Bit), Type(0), Flags(0), Addr(0), 195 Offset(0), Size(0), Link(0), Info(0), Align(0), EntSize(0), Sym(0) {} 196 }; 197 198 /// ELFRelocation - This class contains all the information necessary to 199 /// to generate any 32-bit or 64-bit ELF relocation entry. 200 class ELFRelocation { 201 uint64_t r_offset; // offset in the section of the object this applies to 202 uint32_t r_symidx; // symbol table index of the symbol to use 203 uint32_t r_type; // machine specific relocation type 204 int64_t r_add; // explicit relocation addend 205 bool r_rela; // if true then the addend is part of the entry 206 // otherwise the addend is at the location specified 207 // by r_offset 208 public: 209 uint64_t getInfo(bool is64Bit) const { 210 if (is64Bit) 211 return ((uint64_t)r_symidx << 32) + ((uint64_t)r_type & 0xFFFFFFFFL); 212 else 213 return (r_symidx << 8) + (r_type & 0xFFL); 214 } 215 216 uint64_t getOffset() const { return r_offset; } 217 int64_t getAddend() const { return r_add; } 218 219 ELFRelocation(uint64_t off, uint32_t sym, uint32_t type, 220 bool rela = true, int64_t addend = 0) : 221 r_offset(off), r_symidx(sym), r_type(type), 222 r_add(addend), r_rela(rela) {} 223 }; 224 225 } // end namespace llvm 226 227 #endif 228
