1 //===- Target.cpp ---------------------------------------------------------===// 2 // 3 // The LLVM Linker 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // Machine-specific things, such as applying relocations, creation of 11 // GOT or PLT entries, etc., are handled in this file. 12 // 13 // Refer the ELF spec for the single letter variables, S, A or P, used 14 // in this file. 15 // 16 // Some functions defined in this file has "relaxTls" as part of their names. 17 // They do peephole optimization for TLS variables by rewriting instructions. 18 // They are not part of the ABI but optional optimization, so you can skip 19 // them if you are not interested in how TLS variables are optimized. 20 // See the following paper for the details. 21 // 22 // Ulrich Drepper, ELF Handling For Thread-Local Storage 23 // http://www.akkadia.org/drepper/tls.pdf 24 // 25 //===----------------------------------------------------------------------===// 26 27 #include "Target.h" 28 #include "InputFiles.h" 29 #include "OutputSections.h" 30 #include "SymbolTable.h" 31 #include "Symbols.h" 32 #include "lld/Common/ErrorHandler.h" 33 #include "llvm/Object/ELF.h" 34 35 using namespace llvm; 36 using namespace llvm::object; 37 using namespace llvm::ELF; 38 using namespace lld; 39 using namespace lld::elf; 40 41 TargetInfo *elf::Target; 42 43 std::string lld::toString(RelType Type) { 44 StringRef S = getELFRelocationTypeName(elf::Config->EMachine, Type); 45 if (S == "Unknown") 46 return ("Unknown (" + Twine(Type) + ")").str(); 47 return S; 48 } 49 50 TargetInfo *elf::getTarget() { 51 switch (Config->EMachine) { 52 case EM_386: 53 case EM_IAMCU: 54 return getX86TargetInfo(); 55 case EM_AARCH64: 56 return getAArch64TargetInfo(); 57 case EM_AMDGPU: 58 return getAMDGPUTargetInfo(); 59 case EM_ARM: 60 return getARMTargetInfo(); 61 case EM_AVR: 62 return getAVRTargetInfo(); 63 case EM_MIPS: 64 switch (Config->EKind) { 65 case ELF32LEKind: 66 return getMipsTargetInfo<ELF32LE>(); 67 case ELF32BEKind: 68 return getMipsTargetInfo<ELF32BE>(); 69 case ELF64LEKind: 70 return getMipsTargetInfo<ELF64LE>(); 71 case ELF64BEKind: 72 return getMipsTargetInfo<ELF64BE>(); 73 default: 74 fatal("unsupported MIPS target"); 75 } 76 case EM_PPC: 77 return getPPCTargetInfo(); 78 case EM_PPC64: 79 return getPPC64TargetInfo(); 80 case EM_SPARCV9: 81 return getSPARCV9TargetInfo(); 82 case EM_X86_64: 83 if (Config->EKind == ELF32LEKind) 84 return getX32TargetInfo(); 85 return getX86_64TargetInfo(); 86 } 87 fatal("unknown target machine"); 88 } 89 90 template <class ELFT> static std::string getErrorLoc(const uint8_t *Loc) { 91 for (InputSectionBase *D : InputSections) { 92 auto *IS = dyn_cast<InputSection>(D); 93 if (!IS || !IS->getParent()) 94 continue; 95 96 uint8_t *ISLoc = IS->getParent()->Loc + IS->OutSecOff; 97 if (ISLoc <= Loc && Loc < ISLoc + IS->getSize()) 98 return IS->template getLocation<ELFT>(Loc - ISLoc) + ": "; 99 } 100 return ""; 101 } 102 103 std::string elf::getErrorLocation(const uint8_t *Loc) { 104 switch (Config->EKind) { 105 case ELF32LEKind: 106 return getErrorLoc<ELF32LE>(Loc); 107 case ELF32BEKind: 108 return getErrorLoc<ELF32BE>(Loc); 109 case ELF64LEKind: 110 return getErrorLoc<ELF64LE>(Loc); 111 case ELF64BEKind: 112 return getErrorLoc<ELF64BE>(Loc); 113 default: 114 llvm_unreachable("unknown ELF type"); 115 } 116 } 117 118 TargetInfo::~TargetInfo() {} 119 120 int64_t TargetInfo::getImplicitAddend(const uint8_t *Buf, RelType Type) const { 121 return 0; 122 } 123 124 bool TargetInfo::usesOnlyLowPageBits(RelType Type) const { return false; } 125 126 bool TargetInfo::needsThunk(RelExpr Expr, RelType Type, const InputFile *File, 127 uint64_t BranchAddr, const Symbol &S) const { 128 return false; 129 } 130 131 bool TargetInfo::inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const { 132 return true; 133 } 134 135 void TargetInfo::writeIgotPlt(uint8_t *Buf, const Symbol &S) const { 136 writeGotPlt(Buf, S); 137 } 138 139 RelExpr TargetInfo::adjustRelaxExpr(RelType Type, const uint8_t *Data, 140 RelExpr Expr) const { 141 return Expr; 142 } 143 144 void TargetInfo::relaxGot(uint8_t *Loc, uint64_t Val) const { 145 llvm_unreachable("Should not have claimed to be relaxable"); 146 } 147 148 void TargetInfo::relaxTlsGdToLe(uint8_t *Loc, RelType Type, 149 uint64_t Val) const { 150 llvm_unreachable("Should not have claimed to be relaxable"); 151 } 152 153 void TargetInfo::relaxTlsGdToIe(uint8_t *Loc, RelType Type, 154 uint64_t Val) const { 155 llvm_unreachable("Should not have claimed to be relaxable"); 156 } 157 158 void TargetInfo::relaxTlsIeToLe(uint8_t *Loc, RelType Type, 159 uint64_t Val) const { 160 llvm_unreachable("Should not have claimed to be relaxable"); 161 } 162 163 void TargetInfo::relaxTlsLdToLe(uint8_t *Loc, RelType Type, 164 uint64_t Val) const { 165 llvm_unreachable("Should not have claimed to be relaxable"); 166 } 167 168 uint64_t TargetInfo::getImageBase() { 169 // Use -image-base if set. Fall back to the target default if not. 170 if (Config->ImageBase) 171 return *Config->ImageBase; 172 return Config->Pic ? 0 : DefaultImageBase; 173 } 174