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