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 "SyntheticSections.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 const 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 std::string(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_HEXAGON: 64 return getHexagonTargetInfo(); 65 case EM_MIPS: 66 switch (config->ekind) { 67 case ELF32LEKind: 68 return getMipsTargetInfo<ELF32LE>(); 69 case ELF32BEKind: 70 return getMipsTargetInfo<ELF32BE>(); 71 case ELF64LEKind: 72 return getMipsTargetInfo<ELF64LE>(); 73 case ELF64BEKind: 74 return getMipsTargetInfo<ELF64BE>(); 75 default: 76 llvm_unreachable("unsupported MIPS target"); 77 } 78 case EM_MSP430: 79 return getMSP430TargetInfo(); 80 case EM_PPC: 81 return getPPCTargetInfo(); 82 case EM_PPC64: 83 return getPPC64TargetInfo(); 84 case EM_RISCV: 85 return getRISCVTargetInfo(); 86 case EM_SPARCV9: 87 return getSPARCV9TargetInfo(); 88 case EM_X86_64: 89 return getX86_64TargetInfo(); 90 } 91 llvm_unreachable("unknown target machine"); 92 } 93 94 template <class ELFT> static ErrorPlace getErrPlace(const uint8_t *loc) { 95 assert(loc != nullptr); 96 for (InputSectionBase *d : inputSections) { 97 auto *isec = cast<InputSection>(d); 98 if (!isec->getParent() || (isec->type & SHT_NOBITS)) 99 continue; 100 101 const uint8_t *isecLoc = 102 Out::bufferStart 103 ? (Out::bufferStart + isec->getParent()->offset + isec->outSecOff) 104 : isec->data().data(); 105 if (isecLoc == nullptr) { 106 assert(isa<SyntheticSection>(isec) && "No data but not synthetic?"); 107 continue; 108 } 109 if (isecLoc <= loc && loc < isecLoc + isec->getSize()) { 110 auto objLoc = isec->template getLocation<ELFT>(loc - isecLoc); 111 // Return object file location and source file location. 112 // TODO: Refactor getSrcMsg not to take a variable. 113 Undefined dummy(nullptr, "", STB_LOCAL, 0, 0); 114 return {isec, objLoc + ": ", 115 isec->file ? isec->getSrcMsg(dummy, loc - isecLoc) : ""}; 116 } 117 } 118 return {}; 119 } 120 121 ErrorPlace elf::getErrorPlace(const uint8_t *loc) { 122 switch (config->ekind) { 123 case ELF32LEKind: 124 return getErrPlace<ELF32LE>(loc); 125 case ELF32BEKind: 126 return getErrPlace<ELF32BE>(loc); 127 case ELF64LEKind: 128 return getErrPlace<ELF64LE>(loc); 129 case ELF64BEKind: 130 return getErrPlace<ELF64BE>(loc); 131 default: 132 llvm_unreachable("unknown ELF type"); 133 } 134 } 135 136 TargetInfo::~TargetInfo() {} 137 138 int64_t TargetInfo::getImplicitAddend(const uint8_t *buf, RelType type) const { 139 internalLinkerError(getErrorLocation(buf), 140 "cannot read addend for relocation " + toString(type)); 141 return 0; 142 } 143 144 bool TargetInfo::usesOnlyLowPageBits(RelType type) const { return false; } 145 146 bool TargetInfo::needsThunk(RelExpr expr, RelType type, const InputFile *file, 147 uint64_t branchAddr, const Symbol &s, 148 int64_t a) const { 149 return false; 150 } 151 152 bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end, 153 uint8_t stOther) const { 154 llvm_unreachable("Target doesn't support split stacks."); 155 } 156 157 bool TargetInfo::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 158 return true; 159 } 160 161 RelExpr TargetInfo::adjustTlsExpr(RelType type, RelExpr expr) const { 162 return expr; 163 } 164 165 RelExpr TargetInfo::adjustGotPcExpr(RelType type, int64_t addend, 166 const uint8_t *data) const { 167 return R_GOT_PC; 168 } 169 170 void TargetInfo::relaxGot(uint8_t *loc, const Relocation &rel, 171 uint64_t val) const { 172 llvm_unreachable("Should not have claimed to be relaxable"); 173 } 174 175 void TargetInfo::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel, 176 uint64_t val) const { 177 llvm_unreachable("Should not have claimed to be relaxable"); 178 } 179 180 void TargetInfo::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel, 181 uint64_t val) const { 182 llvm_unreachable("Should not have claimed to be relaxable"); 183 } 184 185 void TargetInfo::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel, 186 uint64_t val) const { 187 llvm_unreachable("Should not have claimed to be relaxable"); 188 } 189 190 void TargetInfo::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel, 191 uint64_t val) const { 192 llvm_unreachable("Should not have claimed to be relaxable"); 193 } 194 195 uint64_t TargetInfo::getImageBase() const { 196 // Use --image-base if set. Fall back to the target default if not. 197 if (config->imageBase) 198 return *config->imageBase; 199 return config->isPic ? 0 : defaultImageBase; 200 } 201