1 //===- Relocations.h -------------------------------------------*- C++ -*-===// 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 #ifndef LLD_ELF_RELOCATIONS_H 10 #define LLD_ELF_RELOCATIONS_H 11 12 #include "lld/Common/LLVM.h" 13 #include "llvm/ADT/DenseMap.h" 14 #include "llvm/ADT/STLExtras.h" 15 #include <vector> 16 17 namespace lld::elf { 18 class Symbol; 19 class InputSection; 20 class InputSectionBase; 21 class OutputSection; 22 class SectionBase; 23 24 // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL. 25 using RelType = uint32_t; 26 using JumpModType = uint32_t; 27 28 // List of target-independent relocation types. Relocations read 29 // from files are converted to these types so that the main code 30 // doesn't have to know about architecture-specific details. 31 enum RelExpr { 32 R_ABS, 33 R_ADDEND, 34 R_DTPREL, 35 R_GOT, 36 R_GOT_OFF, 37 R_GOT_PC, 38 R_GOTONLY_PC, 39 R_GOTPLTONLY_PC, 40 R_GOTPLT, 41 R_GOTPLTREL, 42 R_GOTREL, 43 R_GOTPLT_GOTREL, 44 R_GOTPLT_PC, 45 R_NONE, 46 R_PC, 47 R_PLT, 48 R_PLT_PC, 49 R_PLT_GOTPLT, 50 R_PLT_GOTREL, 51 R_RELAX_HINT, 52 R_RELAX_GOT_PC, 53 R_RELAX_GOT_PC_NOPIC, 54 R_RELAX_TLS_GD_TO_IE, 55 R_RELAX_TLS_GD_TO_IE_ABS, 56 R_RELAX_TLS_GD_TO_IE_GOT_OFF, 57 R_RELAX_TLS_GD_TO_IE_GOTPLT, 58 R_RELAX_TLS_GD_TO_LE, 59 R_RELAX_TLS_GD_TO_LE_NEG, 60 R_RELAX_TLS_IE_TO_LE, 61 R_RELAX_TLS_LD_TO_LE, 62 R_RELAX_TLS_LD_TO_LE_ABS, 63 R_SIZE, 64 R_TPREL, 65 R_TPREL_NEG, 66 R_TLSDESC, 67 R_TLSDESC_CALL, 68 R_TLSDESC_PC, 69 R_TLSDESC_GOTPLT, 70 R_TLSGD_GOT, 71 R_TLSGD_GOTPLT, 72 R_TLSGD_PC, 73 R_TLSIE_HINT, 74 R_TLSLD_GOT, 75 R_TLSLD_GOTPLT, 76 R_TLSLD_GOT_OFF, 77 R_TLSLD_HINT, 78 R_TLSLD_PC, 79 80 // The following is abstract relocation types used for only one target. 81 // 82 // Even though RelExpr is intended to be a target-neutral representation 83 // of a relocation type, there are some relocations whose semantics are 84 // unique to a target. Such relocation are marked with R_<TARGET_NAME>. 85 R_AARCH64_GOT_PAGE_PC, 86 R_AARCH64_GOT_PAGE, 87 R_AARCH64_PAGE_PC, 88 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC, 89 R_AARCH64_TLSDESC_PAGE, 90 R_ARM_PCA, 91 R_ARM_SBREL, 92 R_MIPS_GOTREL, 93 R_MIPS_GOT_GP, 94 R_MIPS_GOT_GP_PC, 95 R_MIPS_GOT_LOCAL_PAGE, 96 R_MIPS_GOT_OFF, 97 R_MIPS_GOT_OFF32, 98 R_MIPS_TLSGD, 99 R_MIPS_TLSLD, 100 R_PPC32_PLTREL, 101 R_PPC64_CALL, 102 R_PPC64_CALL_PLT, 103 R_PPC64_RELAX_TOC, 104 R_PPC64_TOCBASE, 105 R_PPC64_RELAX_GOT_PC, 106 R_RISCV_ADD, 107 R_RISCV_LEB128, 108 R_RISCV_PC_INDIRECT, 109 // Same as R_PC but with page-aligned semantics. 110 R_LOONGARCH_PAGE_PC, 111 // Same as R_PLT_PC but with page-aligned semantics. 112 R_LOONGARCH_PLT_PAGE_PC, 113 // In addition to having page-aligned semantics, LoongArch GOT relocs are 114 // also reused for TLS, making the semantics differ from other architectures. 115 R_LOONGARCH_GOT, 116 R_LOONGARCH_GOT_PAGE_PC, 117 R_LOONGARCH_TLSGD_PAGE_PC, 118 }; 119 120 // Architecture-neutral representation of relocation. 121 struct Relocation { 122 RelExpr expr; 123 RelType type; 124 uint64_t offset; 125 int64_t addend; 126 Symbol *sym; 127 }; 128 129 // Manipulate jump instructions with these modifiers. These are used to relax 130 // jump instruction opcodes at basic block boundaries and are particularly 131 // useful when basic block sections are enabled. 132 struct JumpInstrMod { 133 uint64_t offset; 134 JumpModType original; 135 unsigned size; 136 }; 137 138 // This function writes undefined symbol diagnostics to an internal buffer. 139 // Call reportUndefinedSymbols() after calling scanRelocations() to emit 140 // the diagnostics. 141 template <class ELFT> void scanRelocations(); 142 void reportUndefinedSymbols(); 143 void postScanRelocations(); 144 void addGotEntry(Symbol &sym); 145 146 void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections); 147 bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections); 148 149 class ThunkSection; 150 class Thunk; 151 class InputSectionDescription; 152 153 class ThunkCreator { 154 public: 155 // Return true if Thunks have been added to OutputSections 156 bool createThunks(uint32_t pass, ArrayRef<OutputSection *> outputSections); 157 158 private: 159 void mergeThunks(ArrayRef<OutputSection *> outputSections); 160 161 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec, 162 InputSectionDescription *isd, 163 const Relocation &rel, uint64_t src); 164 165 ThunkSection *getISThunkSec(InputSection *isec); 166 167 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections); 168 169 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel, 170 uint64_t src); 171 172 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *, 173 uint64_t off); 174 175 bool normalizeExistingThunk(Relocation &rel, uint64_t src); 176 177 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol 178 // is represented as a (section, offset) pair. There may be multiple 179 // relocations sharing the same (section, offset + addend) pair. We may revert 180 // a relocation back to its original non-Thunk target, and restore the 181 // original addend, so we cannot fold offset + addend. A nested pair is used 182 // because DenseMapInfo is not specialized for std::tuple. 183 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>, 184 std::vector<Thunk *>> 185 thunkedSymbolsBySectionAndAddend; 186 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>> 187 thunkedSymbols; 188 189 // Find a Thunk from the Thunks symbol definition, we can use this to find 190 // the Thunk from a relocation to the Thunks symbol definition. 191 llvm::DenseMap<Symbol *, Thunk *> thunks; 192 193 // Track InputSections that have an inline ThunkSection placed in front 194 // an inline ThunkSection may have control fall through to the section below 195 // so we need to make sure that there is only one of them. 196 // The Mips LA25 Thunk is an example of an inline ThunkSection. 197 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections; 198 199 // The number of completed passes of createThunks this permits us 200 // to do one time initialization on Pass 0 and put a limit on the 201 // number of times it can be called to prevent infinite loops. 202 uint32_t pass = 0; 203 }; 204 205 // Return a int64_t to make sure we get the sign extension out of the way as 206 // early as possible. 207 template <class ELFT> 208 static inline int64_t getAddend(const typename ELFT::Rel &rel) { 209 return 0; 210 } 211 template <class ELFT> 212 static inline int64_t getAddend(const typename ELFT::Rela &rel) { 213 return rel.r_addend; 214 } 215 216 template <typename RelTy> 217 ArrayRef<RelTy> sortRels(ArrayRef<RelTy> rels, SmallVector<RelTy, 0> &storage) { 218 auto cmp = [](const RelTy &a, const RelTy &b) { 219 return a.r_offset < b.r_offset; 220 }; 221 if (!llvm::is_sorted(rels, cmp)) { 222 storage.assign(rels.begin(), rels.end()); 223 llvm::stable_sort(storage, cmp); 224 rels = storage; 225 } 226 return rels; 227 } 228 229 // Returns true if Expr refers a GOT entry. Note that this function returns 230 // false for TLS variables even though they need GOT, because TLS variables uses 231 // GOT differently than the regular variables. 232 bool needsGot(RelExpr expr); 233 } // namespace lld::elf 234 235 #endif 236