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 <map> 15 #include <vector> 16 17 namespace lld { 18 namespace elf { 19 class Symbol; 20 class InputSection; 21 class InputSectionBase; 22 class OutputSection; 23 class SectionBase; 24 25 // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL. 26 using RelType = 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_NEG_TLS, 44 R_NONE, 45 R_PC, 46 R_PLT, 47 R_PLT_PC, 48 R_RELAX_GOT_PC, 49 R_RELAX_GOT_PC_NOPIC, 50 R_RELAX_TLS_GD_TO_IE, 51 R_RELAX_TLS_GD_TO_IE_ABS, 52 R_RELAX_TLS_GD_TO_IE_GOT_OFF, 53 R_RELAX_TLS_GD_TO_IE_GOTPLT, 54 R_RELAX_TLS_GD_TO_LE, 55 R_RELAX_TLS_GD_TO_LE_NEG, 56 R_RELAX_TLS_IE_TO_LE, 57 R_RELAX_TLS_LD_TO_LE, 58 R_RELAX_TLS_LD_TO_LE_ABS, 59 R_SIZE, 60 R_TLS, 61 R_TLSDESC, 62 R_TLSDESC_CALL, 63 R_TLSDESC_PC, 64 R_TLSGD_GOT, 65 R_TLSGD_GOTPLT, 66 R_TLSGD_PC, 67 R_TLSIE_HINT, 68 R_TLSLD_GOT, 69 R_TLSLD_GOTPLT, 70 R_TLSLD_GOT_OFF, 71 R_TLSLD_HINT, 72 R_TLSLD_PC, 73 74 // The following is abstract relocation types used for only one target. 75 // 76 // Even though RelExpr is intended to be a target-neutral representation 77 // of a relocation type, there are some relocations whose semantics are 78 // unique to a target. Such relocation are marked with R_<TARGET_NAME>. 79 R_AARCH64_GOT_PAGE_PC, 80 R_AARCH64_PAGE_PC, 81 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC, 82 R_AARCH64_TLSDESC_PAGE, 83 R_ARM_SBREL, 84 R_MIPS_GOTREL, 85 R_MIPS_GOT_GP, 86 R_MIPS_GOT_GP_PC, 87 R_MIPS_GOT_LOCAL_PAGE, 88 R_MIPS_GOT_OFF, 89 R_MIPS_GOT_OFF32, 90 R_MIPS_TLSGD, 91 R_MIPS_TLSLD, 92 R_PPC32_PLTREL, 93 R_PPC64_CALL, 94 R_PPC64_CALL_PLT, 95 R_PPC64_RELAX_TOC, 96 R_PPC64_TOCBASE, 97 R_RISCV_ADD, 98 R_RISCV_PC_INDIRECT, 99 }; 100 101 // Architecture-neutral representation of relocation. 102 struct Relocation { 103 RelExpr expr; 104 RelType type; 105 uint64_t offset; 106 int64_t addend; 107 Symbol *sym; 108 }; 109 110 // This function writes undefined symbol diagnostics to an internal buffer. 111 // Call reportUndefinedSymbols() after calling scanRelocations() to emit 112 // the diagnostics. 113 template <class ELFT> void scanRelocations(InputSectionBase &); 114 115 template <class ELFT> void reportUndefinedSymbols(); 116 117 class ThunkSection; 118 class Thunk; 119 struct InputSectionDescription; 120 121 class ThunkCreator { 122 public: 123 // Return true if Thunks have been added to OutputSections 124 bool createThunks(ArrayRef<OutputSection *> outputSections); 125 126 // The number of completed passes of createThunks this permits us 127 // to do one time initialization on Pass 0 and put a limit on the 128 // number of times it can be called to prevent infinite loops. 129 uint32_t pass = 0; 130 131 private: 132 void mergeThunks(ArrayRef<OutputSection *> outputSections); 133 134 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec, 135 InputSectionDescription *isd, uint32_t type, 136 uint64_t src); 137 138 ThunkSection *getISThunkSec(InputSection *isec); 139 140 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections); 141 142 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel, 143 uint64_t src); 144 145 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *, 146 uint64_t off); 147 148 bool normalizeExistingThunk(Relocation &rel, uint64_t src); 149 150 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol 151 // is represented as a (section, offset) pair. There may be multiple 152 // relocations sharing the same (section, offset + addend) pair. We may revert 153 // a relocation back to its original non-Thunk target, and restore the 154 // original addend, so we cannot fold offset + addend. A nested pair is used 155 // because DenseMapInfo is not specialized for std::tuple. 156 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>, 157 std::vector<Thunk *>> 158 thunkedSymbolsBySectionAndAddend; 159 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>> 160 thunkedSymbols; 161 162 // Find a Thunk from the Thunks symbol definition, we can use this to find 163 // the Thunk from a relocation to the Thunks symbol definition. 164 llvm::DenseMap<Symbol *, Thunk *> thunks; 165 166 // Track InputSections that have an inline ThunkSection placed in front 167 // an inline ThunkSection may have control fall through to the section below 168 // so we need to make sure that there is only one of them. 169 // The Mips LA25 Thunk is an example of an inline ThunkSection. 170 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections; 171 }; 172 173 // Return a int64_t to make sure we get the sign extension out of the way as 174 // early as possible. 175 template <class ELFT> 176 static inline int64_t getAddend(const typename ELFT::Rel &rel) { 177 return 0; 178 } 179 template <class ELFT> 180 static inline int64_t getAddend(const typename ELFT::Rela &rel) { 181 return rel.r_addend; 182 } 183 } // namespace elf 184 } // namespace lld 185 186 #endif 187