1 //===- Target.cpp ---------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // Machine-specific things, such as applying relocations, creation of 10 // GOT or PLT entries, etc., are handled in this file. 11 // 12 // Refer the ELF spec for the single letter variables, S, A or P, used 13 // in this file. 14 // 15 // Some functions defined in this file has "relaxTls" as part of their names. 16 // They do peephole optimization for TLS variables by rewriting instructions. 17 // They are not part of the ABI but optional optimization, so you can skip 18 // them if you are not interested in how TLS variables are optimized. 19 // See the following paper for the details. 20 // 21 // Ulrich Drepper, ELF Handling For Thread-Local Storage 22 // http://www.akkadia.org/drepper/tls.pdf 23 // 24 //===----------------------------------------------------------------------===// 25 26 #include "Target.h" 27 #include "InputFiles.h" 28 #include "OutputSections.h" 29 #include "SymbolTable.h" 30 #include "Symbols.h" 31 #include "lld/Common/ErrorHandler.h" 32 #include "llvm/Object/ELF.h" 33 34 using namespace llvm; 35 using namespace llvm::object; 36 using namespace llvm::ELF; 37 using namespace lld; 38 using namespace lld::elf; 39 40 const TargetInfo *elf::Target; 41 42 std::string lld::toString(RelType Type) { 43 StringRef S = getELFRelocationTypeName(elf::Config->EMachine, Type); 44 if (S == "Unknown") 45 return ("Unknown (" + Twine(Type) + ")").str(); 46 return S; 47 } 48 49 TargetInfo *elf::getTarget() { 50 switch (Config->EMachine) { 51 case EM_386: 52 case EM_IAMCU: 53 return getX86TargetInfo(); 54 case EM_AARCH64: 55 return getAArch64TargetInfo(); 56 case EM_AMDGPU: 57 return getAMDGPUTargetInfo(); 58 case EM_ARM: 59 return getARMTargetInfo(); 60 case EM_AVR: 61 return getAVRTargetInfo(); 62 case EM_HEXAGON: 63 return getHexagonTargetInfo(); 64 case EM_MIPS: 65 switch (Config->EKind) { 66 case ELF32LEKind: 67 return getMipsTargetInfo<ELF32LE>(); 68 case ELF32BEKind: 69 return getMipsTargetInfo<ELF32BE>(); 70 case ELF64LEKind: 71 return getMipsTargetInfo<ELF64LE>(); 72 case ELF64BEKind: 73 return getMipsTargetInfo<ELF64BE>(); 74 default: 75 llvm_unreachable("unsupported MIPS target"); 76 } 77 case EM_MSP430: 78 return getMSP430TargetInfo(); 79 case EM_PPC: 80 return getPPCTargetInfo(); 81 case EM_PPC64: 82 return getPPC64TargetInfo(); 83 case EM_RISCV: 84 return getRISCVTargetInfo(); 85 case EM_SPARCV9: 86 return getSPARCV9TargetInfo(); 87 case EM_X86_64: 88 return getX86_64TargetInfo(); 89 } 90 llvm_unreachable("unknown target machine"); 91 } 92 93 template <class ELFT> static ErrorPlace getErrPlace(const uint8_t *Loc) { 94 for (InputSectionBase *D : InputSections) { 95 auto *IS = cast<InputSection>(D); 96 if (!IS->getParent()) 97 continue; 98 99 uint8_t *ISLoc = Out::BufferStart + IS->getParent()->Offset + IS->OutSecOff; 100 if (ISLoc <= Loc && Loc < ISLoc + IS->getSize()) 101 return {IS, IS->template getLocation<ELFT>(Loc - ISLoc) + ": "}; 102 } 103 return {}; 104 } 105 106 ErrorPlace elf::getErrorPlace(const uint8_t *Loc) { 107 switch (Config->EKind) { 108 case ELF32LEKind: 109 return getErrPlace<ELF32LE>(Loc); 110 case ELF32BEKind: 111 return getErrPlace<ELF32BE>(Loc); 112 case ELF64LEKind: 113 return getErrPlace<ELF64LE>(Loc); 114 case ELF64BEKind: 115 return getErrPlace<ELF64BE>(Loc); 116 default: 117 llvm_unreachable("unknown ELF type"); 118 } 119 } 120 121 TargetInfo::~TargetInfo() {} 122 123 int64_t TargetInfo::getImplicitAddend(const uint8_t *Buf, RelType Type) const { 124 return 0; 125 } 126 127 bool TargetInfo::usesOnlyLowPageBits(RelType Type) const { return false; } 128 129 bool TargetInfo::needsThunk(RelExpr Expr, RelType Type, const InputFile *File, 130 uint64_t BranchAddr, const Symbol &S) const { 131 return false; 132 } 133 134 bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *Loc, uint8_t *End, 135 uint8_t StOther) const { 136 llvm_unreachable("Target doesn't support split stacks."); 137 } 138 139 bool TargetInfo::inBranchRange(RelType Type, uint64_t Src, uint64_t Dst) const { 140 return true; 141 } 142 143 void TargetInfo::writeIgotPlt(uint8_t *Buf, const Symbol &S) const { 144 writeGotPlt(Buf, S); 145 } 146 147 RelExpr TargetInfo::adjustRelaxExpr(RelType Type, const uint8_t *Data, 148 RelExpr Expr) const { 149 return Expr; 150 } 151 152 void TargetInfo::relaxGot(uint8_t *Loc, uint64_t Val) const { 153 llvm_unreachable("Should not have claimed to be relaxable"); 154 } 155 156 void TargetInfo::relaxTlsGdToLe(uint8_t *Loc, RelType Type, 157 uint64_t Val) const { 158 llvm_unreachable("Should not have claimed to be relaxable"); 159 } 160 161 void TargetInfo::relaxTlsGdToIe(uint8_t *Loc, RelType Type, 162 uint64_t Val) const { 163 llvm_unreachable("Should not have claimed to be relaxable"); 164 } 165 166 void TargetInfo::relaxTlsIeToLe(uint8_t *Loc, RelType Type, 167 uint64_t Val) const { 168 llvm_unreachable("Should not have claimed to be relaxable"); 169 } 170 171 void TargetInfo::relaxTlsLdToLe(uint8_t *Loc, RelType Type, 172 uint64_t Val) const { 173 llvm_unreachable("Should not have claimed to be relaxable"); 174 } 175 176 uint64_t TargetInfo::getImageBase() const { 177 // Use -image-base if set. Fall back to the target default if not. 178 if (Config->ImageBase) 179 return *Config->ImageBase; 180 return Config->Pic ? 0 : DefaultImageBase; 181 } 182