text: //===- Relocations.h -------------------------------------------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLD_ELF_RELOCATIONS_H
  #define LLD_ELF_RELOCATIONS_H
  
  #include "lld/Common/LLVM.h"
  #include "llvm/ADT/DenseMap.h"
  #include <map>
  #include <vector>
  
  namespace lld {
  namespace elf {
  class Symbol;
  class InputSection;
  class InputSectionBase;
  class OutputSection;
  class SectionBase;
  
  // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
  using RelType = uint32_t;
  
  // List of target-independent relocation types. Relocations read
  // from files are converted to these types so that the main code
  // doesn't have to know about architecture-specific details.
  enum RelExpr {
    R_ABS,
    R_ADDEND,
    R_DTPREL,
    R_GOT,
    R_GOT_OFF,
    R_GOT_PC,
    R_GOTONLY_PC,
    R_GOTPLTONLY_PC,
    R_GOTPLT,
    R_GOTPLTREL,
    R_GOTREL,
    R_HINT,
    R_NEG_TLS,
    R_NONE,
    R_PC,
    R_PLT,
    R_PLT_PC,
    R_RELAX_GOT_PC,
    R_RELAX_GOT_PC_NOPIC,
    R_RELAX_TLS_GD_TO_IE,
    R_RELAX_TLS_GD_TO_IE_ABS,
    R_RELAX_TLS_GD_TO_IE_GOT_OFF,
    R_RELAX_TLS_GD_TO_IE_GOTPLT,
    R_RELAX_TLS_GD_TO_LE,
    R_RELAX_TLS_GD_TO_LE_NEG,
    R_RELAX_TLS_IE_TO_LE,
    R_RELAX_TLS_LD_TO_LE,
    R_RELAX_TLS_LD_TO_LE_ABS,
    R_SIZE,
    R_TLS,
    R_TLSDESC,
    R_TLSDESC_CALL,
    R_TLSDESC_PC,
    R_TLSGD_GOT,
    R_TLSGD_GOTPLT,
    R_TLSGD_PC,
    R_TLSIE_HINT,
    R_TLSLD_GOT,
    R_TLSLD_GOTPLT,
    R_TLSLD_GOT_OFF,
    R_TLSLD_HINT,
    R_TLSLD_PC,
  
    // The following is abstract relocation types used for only one target.
    //
    // Even though RelExpr is intended to be a target-neutral representation
    // of a relocation type, there are some relocations whose semantics are
    // unique to a target. Such relocation are marked with R_<TARGET_NAME>.
    R_AARCH64_GOT_PAGE_PC,
    R_AARCH64_PAGE_PC,
    R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
    R_AARCH64_TLSDESC_PAGE,
    R_ARM_SBREL,
    R_MIPS_GOTREL,
    R_MIPS_GOT_GP,
    R_MIPS_GOT_GP_PC,
    R_MIPS_GOT_LOCAL_PAGE,
    R_MIPS_GOT_OFF,
    R_MIPS_GOT_OFF32,
    R_MIPS_TLSGD,
    R_MIPS_TLSLD,
    R_PPC32_PLTREL,
    R_PPC64_CALL,
    R_PPC64_CALL_PLT,
    R_PPC64_RELAX_TOC,
    R_PPC64_TOCBASE,
    R_RISCV_ADD,
    R_RISCV_PC_INDIRECT,
  };
  
  // Architecture-neutral representation of relocation.
  struct Relocation {
    RelExpr expr;
    RelType type;
    uint64_t offset;
    int64_t addend;
    Symbol *sym;
  };
  
  // This function writes undefined symbol diagnostics to an internal buffer.
  // Call reportUndefinedSymbols() after calling scanRelocations() to emit
  // the diagnostics.
  template <class ELFT> void scanRelocations(InputSectionBase &);
  
  template <class ELFT> void reportUndefinedSymbols();
  
  void addIRelativeRelocs();
  
  class ThunkSection;
  class Thunk;
  struct InputSectionDescription;
  
  class ThunkCreator {
  public:
    // Return true if Thunks have been added to OutputSections
    bool createThunks(ArrayRef<OutputSection *> outputSections);
  
    // The number of completed passes of createThunks this permits us
    // to do one time initialization on Pass 0 and put a limit on the
    // number of times it can be called to prevent infinite loops.
    uint32_t pass = 0;
  
  private:
    void mergeThunks(ArrayRef<OutputSection *> outputSections);
  
    ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
                                 InputSectionDescription *isd, uint32_t type,
                                 uint64_t src);
  
    ThunkSection *getISThunkSec(InputSection *isec);
  
    void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
  
    std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
                                      uint64_t src);
  
    ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
                                  uint64_t off);
  
    bool normalizeExistingThunk(Relocation &rel, uint64_t src);
  
    // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
    // is represented as a (section, offset) pair. There may be multiple
    // relocations sharing the same (section, offset + addend) pair. We may revert
    // a relocation back to its original non-Thunk target, and restore the
    // original addend, so we cannot fold offset + addend. A nested pair is used
    // because DenseMapInfo is not specialized for std::tuple.
    llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
                   std::vector<Thunk *>>
        thunkedSymbolsBySectionAndAddend;
    llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
        thunkedSymbols;
  
    // Find a Thunk from the Thunks symbol definition, we can use this to find
    // the Thunk from a relocation to the Thunks symbol definition.
    llvm::DenseMap<Symbol *, Thunk *> thunks;
  
    // Track InputSections that have an inline ThunkSection placed in front
    // an inline ThunkSection may have control fall through to the section below
    // so we need to make sure that there is only one of them.
    // The Mips LA25 Thunk is an example of an inline ThunkSection.
    llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
  };
  
  // Return a int64_t to make sure we get the sign extension out of the way as
  // early as possible.
  template <class ELFT>
  static inline int64_t getAddend(const typename ELFT::Rel &rel) {
    return 0;
  }
  template <class ELFT>
  static inline int64_t getAddend(const typename ELFT::Rela &rel) {
    return rel.r_addend;
  }
  } // namespace elf
  } // namespace lld
  
  #endif
  