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_LOONGARCH: 66 return getLoongArchTargetInfo(); 67 case EM_MIPS: 68 switch (config->ekind) { 69 case ELF32LEKind: 70 return getMipsTargetInfo<ELF32LE>(); 71 case ELF32BEKind: 72 return getMipsTargetInfo<ELF32BE>(); 73 case ELF64LEKind: 74 return getMipsTargetInfo<ELF64LE>(); 75 case ELF64BEKind: 76 return getMipsTargetInfo<ELF64BE>(); 77 default: 78 llvm_unreachable("unsupported MIPS target"); 79 } 80 case EM_MSP430: 81 return getMSP430TargetInfo(); 82 case EM_PPC: 83 return getPPCTargetInfo(); 84 case EM_PPC64: 85 return getPPC64TargetInfo(); 86 case EM_RISCV: 87 return getRISCVTargetInfo(); 88 case EM_SPARCV9: 89 return getSPARCV9TargetInfo(); 90 case EM_X86_64: 91 return getX86_64TargetInfo(); 92 } 93 llvm_unreachable("unknown target machine"); 94 } 95 96 ErrorPlace elf::getErrorPlace(const uint8_t *loc) { 97 assert(loc != nullptr); 98 for (InputSectionBase *d : ctx.inputSections) { 99 auto *isec = dyn_cast<InputSection>(d); 100 if (!isec || !isec->getParent() || (isec->type & SHT_NOBITS)) 101 continue; 102 103 const uint8_t *isecLoc = 104 Out::bufferStart 105 ? (Out::bufferStart + isec->getParent()->offset + isec->outSecOff) 106 : isec->contentMaybeDecompress().data(); 107 if (isecLoc == nullptr) { 108 assert(isa<SyntheticSection>(isec) && "No data but not synthetic?"); 109 continue; 110 } 111 if (isecLoc <= loc && loc < isecLoc + isec->getSize()) { 112 std::string objLoc = isec->getLocation(loc - isecLoc); 113 // Return object file location and source file location. 114 // TODO: Refactor getSrcMsg not to take a variable. 115 Undefined dummy(nullptr, "", STB_LOCAL, 0, 0); 116 return {isec, objLoc + ": ", 117 isec->file ? isec->getSrcMsg(dummy, loc - isecLoc) : ""}; 118 } 119 } 120 return {}; 121 } 122 123 TargetInfo::~TargetInfo() {} 124 125 int64_t TargetInfo::getImplicitAddend(const uint8_t *buf, RelType type) const { 126 internalLinkerError(getErrorLocation(buf), 127 "cannot read addend for relocation " + toString(type)); 128 return 0; 129 } 130 131 bool TargetInfo::usesOnlyLowPageBits(RelType type) const { return false; } 132 133 bool TargetInfo::needsThunk(RelExpr expr, RelType type, const InputFile *file, 134 uint64_t branchAddr, const Symbol &s, 135 int64_t a) const { 136 return false; 137 } 138 139 bool TargetInfo::adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end, 140 uint8_t stOther) const { 141 llvm_unreachable("Target doesn't support split stacks."); 142 } 143 144 bool TargetInfo::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { 145 return true; 146 } 147 148 RelExpr TargetInfo::adjustTlsExpr(RelType type, RelExpr expr) const { 149 return expr; 150 } 151 152 RelExpr TargetInfo::adjustGotPcExpr(RelType type, int64_t addend, 153 const uint8_t *data) const { 154 return R_GOT_PC; 155 } 156 157 void TargetInfo::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const { 158 const unsigned bits = config->is64 ? 64 : 32; 159 uint64_t secAddr = sec.getOutputSection()->addr; 160 if (auto *s = dyn_cast<InputSection>(&sec)) 161 secAddr += s->outSecOff; 162 for (const Relocation &rel : sec.relocs()) { 163 uint8_t *loc = buf + rel.offset; 164 const uint64_t val = SignExtend64( 165 sec.getRelocTargetVA(sec.file, rel.type, rel.addend, 166 secAddr + rel.offset, *rel.sym, rel.expr), 167 bits); 168 if (rel.expr != R_RELAX_HINT) 169 relocate(loc, rel, val); 170 } 171 } 172 173 uint64_t TargetInfo::getImageBase() const { 174 // Use --image-base if set. Fall back to the target default if not. 175 if (config->imageBase) 176 return *config->imageBase; 177 return config->isPic ? 0 : defaultImageBase; 178 } 179