lld/ELF/Relocations.h

   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 void addGotEntry(Symbol &sym);
 141
 142 void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections);
 143 bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
 144
 145 class ThunkSection;
 146 class Thunk;
 147 class InputSectionDescription;
 148
 149 class ThunkCreator {
 150 public:
 151   // Return true if Thunks have been added to OutputSections
 152   bool createThunks(uint32_t pass, ArrayRef<OutputSection *> outputSections);
 153
 154 private:
 155   void mergeThunks(ArrayRef<OutputSection *> outputSections);
 156
 157   ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
 158                                InputSectionDescription *isd,
 159                                const Relocation &rel, uint64_t src);
 160
 161   ThunkSection *getISThunkSec(InputSection *isec);
 162
 163   void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
 164
 165   std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
 166                                     uint64_t src);
 167
 168   ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
 169                                 uint64_t off);
 170
 171   bool normalizeExistingThunk(Relocation &rel, uint64_t src);
 172
 173   // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
 174   // is represented as a (section, offset) pair. There may be multiple
 175   // relocations sharing the same (section, offset + addend) pair. We may revert
 176   // a relocation back to its original non-Thunk target, and restore the
 177   // original addend, so we cannot fold offset + addend. A nested pair is used
 178   // because DenseMapInfo is not specialized for std::tuple.
 179   llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
 180                  std::vector<Thunk *>>
 181       thunkedSymbolsBySectionAndAddend;
 182   llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
 183       thunkedSymbols;
 184
 185   // Find a Thunk from the Thunks symbol definition, we can use this to find
 186   // the Thunk from a relocation to the Thunks symbol definition.
 187   llvm::DenseMap<Symbol *, Thunk *> thunks;
 188
 189   // Track InputSections that have an inline ThunkSection placed in front
 190   // an inline ThunkSection may have control fall through to the section below
 191   // so we need to make sure that there is only one of them.
 192   // The Mips LA25 Thunk is an example of an inline ThunkSection.
 193   llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
 194
 195   // The number of completed passes of createThunks this permits us
 196   // to do one time initialization on Pass 0 and put a limit on the
 197   // number of times it can be called to prevent infinite loops.
 198   uint32_t pass = 0;
 199 };
 200
 201 // Return a int64_t to make sure we get the sign extension out of the way as
 202 // early as possible.
 203 template <class ELFT>
 204 static inline int64_t getAddend(const typename ELFT::Rel &rel) {
 205   return 0;
 206 }
 207 template <class ELFT>
 208 static inline int64_t getAddend(const typename ELFT::Rela &rel) {
 209   return rel.r_addend;
 210 }
 211
 212 template <typename RelTy>
 213 ArrayRef<RelTy> sortRels(ArrayRef<RelTy> rels, SmallVector<RelTy, 0> &storage) {
 214   auto cmp = [](const RelTy &a, const RelTy &b) {
 215     return a.r_offset < b.r_offset;
 216   };
 217   if (!llvm::is_sorted(rels, cmp)) {
 218     storage.assign(rels.begin(), rels.end());
 219     llvm::stable_sort(storage, cmp);
 220     rels = storage;
 221   }
 222   return rels;
 223 }
 224
 225 // Returns true if Expr refers a GOT entry. Note that this function returns
 226 // false for TLS variables even though they need GOT, because TLS variables uses
 227 // GOT differently than the regular variables.
 228 bool needsGot(RelExpr expr);
 229 } // namespace lld::elf
 230
 231 #endif