text: //===-- RuntimeDyldImpl.h - Run-time dynamic linker for MC-JIT --*- 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
  //
  //===----------------------------------------------------------------------===//
  //
  // Interface for the implementations of runtime dynamic linker facilities.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
  #define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
  
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringMap.h"
  #include "llvm/ADT/Triple.h"
  #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
  #include "llvm/ExecutionEngine/RuntimeDyld.h"
  #include "llvm/ExecutionEngine/RuntimeDyldChecker.h"
  #include "llvm/Object/ObjectFile.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/Format.h"
  #include "llvm/Support/Host.h"
  #include "llvm/Support/Mutex.h"
  #include "llvm/Support/SwapByteOrder.h"
  #include <deque>
  #include <map>
  #include <system_error>
  #include <unordered_map>
  
  using namespace llvm;
  using namespace llvm::object;
  
  namespace llvm {
  
  class Twine;
  
  #define UNIMPLEMENTED_RELOC(RelType) \
    case RelType: \
      return make_error<RuntimeDyldError>("Unimplemented relocation: " #RelType)
  
  /// SectionEntry - represents a section emitted into memory by the dynamic
  /// linker.
  class SectionEntry {
    /// Name - section name.
    std::string Name;
  
    /// Address - address in the linker's memory where the section resides.
    uint8_t *Address;
  
    /// Size - section size. Doesn't include the stubs.
    size_t Size;
  
    /// LoadAddress - the address of the section in the target process's memory.
    /// Used for situations in which JIT-ed code is being executed in the address
    /// space of a separate process.  If the code executes in the same address
    /// space where it was JIT-ed, this just equals Address.
    uint64_t LoadAddress;
  
    /// StubOffset - used for architectures with stub functions for far
    /// relocations (like ARM).
    uintptr_t StubOffset;
  
    /// The total amount of space allocated for this section.  This includes the
    /// section size and the maximum amount of space that the stubs can occupy.
    size_t AllocationSize;
  
    /// ObjAddress - address of the section in the in-memory object file.  Used
    /// for calculating relocations in some object formats (like MachO).
    uintptr_t ObjAddress;
  
  public:
    SectionEntry(StringRef name, uint8_t *address, size_t size,
                 size_t allocationSize, uintptr_t objAddress)
        : Name(std::string(name)), Address(address), Size(size),
          LoadAddress(reinterpret_cast<uintptr_t>(address)), StubOffset(size),
          AllocationSize(allocationSize), ObjAddress(objAddress) {
      // AllocationSize is used only in asserts, prevent an "unused private field"
      // warning:
      (void)AllocationSize;
    }
  
    StringRef getName() const { return Name; }
  
    uint8_t *getAddress() const { return Address; }
  
    /// Return the address of this section with an offset.
    uint8_t *getAddressWithOffset(unsigned OffsetBytes) const {
      assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
      return Address + OffsetBytes;
    }
  
    size_t getSize() const { return Size; }
  
    uint64_t getLoadAddress() const { return LoadAddress; }
    void setLoadAddress(uint64_t LA) { LoadAddress = LA; }
  
    /// Return the load address of this section with an offset.
    uint64_t getLoadAddressWithOffset(unsigned OffsetBytes) const {
      assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
      return LoadAddress + OffsetBytes;
    }
  
    uintptr_t getStubOffset() const { return StubOffset; }
  
    void advanceStubOffset(unsigned StubSize) {
      StubOffset += StubSize;
      assert(StubOffset <= AllocationSize && "Not enough space allocated!");
    }
  
    uintptr_t getObjAddress() const { return ObjAddress; }
  };
  
  /// RelocationEntry - used to represent relocations internally in the dynamic
  /// linker.
  class RelocationEntry {
  public:
    /// SectionID - the section this relocation points to.
    unsigned SectionID;
  
    /// Offset - offset into the section.
    uint64_t Offset;
  
    /// RelType - relocation type.
    uint32_t RelType;
  
    /// Addend - the relocation addend encoded in the instruction itself.  Also
    /// used to make a relocation section relative instead of symbol relative.
    int64_t Addend;
  
    struct SectionPair {
        uint32_t SectionA;
        uint32_t SectionB;
    };
  
    /// SymOffset - Section offset of the relocation entry's symbol (used for GOT
    /// lookup).
    union {
      uint64_t SymOffset;
      SectionPair Sections;
    };
  
    /// True if this is a PCRel relocation (MachO specific).
    bool IsPCRel;
  
    /// The size of this relocation (MachO specific).
    unsigned Size;
  
    // ARM (MachO and COFF) specific.
    bool IsTargetThumbFunc = false;
  
    RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend)
        : SectionID(id), Offset(offset), RelType(type), Addend(addend),
          SymOffset(0), IsPCRel(false), Size(0), IsTargetThumbFunc(false) {}
  
    RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                    uint64_t symoffset)
        : SectionID(id), Offset(offset), RelType(type), Addend(addend),
          SymOffset(symoffset), IsPCRel(false), Size(0),
          IsTargetThumbFunc(false) {}
  
    RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                    bool IsPCRel, unsigned Size)
        : SectionID(id), Offset(offset), RelType(type), Addend(addend),
          SymOffset(0), IsPCRel(IsPCRel), Size(Size), IsTargetThumbFunc(false) {}
  
    RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                    unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
                    uint64_t SectionBOffset, bool IsPCRel, unsigned Size)
        : SectionID(id), Offset(offset), RelType(type),
          Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
          Size(Size), IsTargetThumbFunc(false) {
      Sections.SectionA = SectionA;
      Sections.SectionB = SectionB;
    }
  
    RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
                    unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
                    uint64_t SectionBOffset, bool IsPCRel, unsigned Size,
                    bool IsTargetThumbFunc)
        : SectionID(id), Offset(offset), RelType(type),
          Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
          Size(Size), IsTargetThumbFunc(IsTargetThumbFunc) {
      Sections.SectionA = SectionA;
      Sections.SectionB = SectionB;
    }
  };
  
  class RelocationValueRef {
  public:
    unsigned SectionID = 0;
    uint64_t Offset = 0;
    int64_t Addend = 0;
    const char *SymbolName = nullptr;
    bool IsStubThumb = false;
  
    inline bool operator==(const RelocationValueRef &Other) const {
      return SectionID == Other.SectionID && Offset == Other.Offset &&
             Addend == Other.Addend && SymbolName == Other.SymbolName &&
             IsStubThumb == Other.IsStubThumb;
    }
    inline bool operator<(const RelocationValueRef &Other) const {
      if (SectionID != Other.SectionID)
        return SectionID < Other.SectionID;
      if (Offset != Other.Offset)
        return Offset < Other.Offset;
      if (Addend != Other.Addend)
        return Addend < Other.Addend;
      if (IsStubThumb != Other.IsStubThumb)
        return IsStubThumb < Other.IsStubThumb;
      return SymbolName < Other.SymbolName;
    }
  };
  
  /// Symbol info for RuntimeDyld.
  class SymbolTableEntry {
  public:
    SymbolTableEntry() = default;
  
    SymbolTableEntry(unsigned SectionID, uint64_t Offset, JITSymbolFlags Flags)
        : Offset(Offset), SectionID(SectionID), Flags(Flags) {}
  
    unsigned getSectionID() const { return SectionID; }
    uint64_t getOffset() const { return Offset; }
    void setOffset(uint64_t NewOffset) { Offset = NewOffset; }
  
    JITSymbolFlags getFlags() const { return Flags; }
  
  private:
    uint64_t Offset = 0;
    unsigned SectionID = 0;
    JITSymbolFlags Flags = JITSymbolFlags::None;
  };
  
  typedef StringMap<SymbolTableEntry> RTDyldSymbolTable;
  
  class RuntimeDyldImpl {
    friend class RuntimeDyld::LoadedObjectInfo;
  protected:
    static const unsigned AbsoluteSymbolSection = ~0U;
  
    // The MemoryManager to load objects into.
    RuntimeDyld::MemoryManager &MemMgr;
  
    // The symbol resolver to use for external symbols.
    JITSymbolResolver &Resolver;
  
    // A list of all sections emitted by the dynamic linker.  These sections are
    // referenced in the code by means of their index in this list - SectionID.
    // Because references may be kept while the list grows, use a container that
    // guarantees reference stability.
    typedef std::deque<SectionEntry> SectionList;
    SectionList Sections;
  
    typedef unsigned SID; // Type for SectionIDs
  #define RTDYLD_INVALID_SECTION_ID ((RuntimeDyldImpl::SID)(-1))
  
    // Keep a map of sections from object file to the SectionID which
    // references it.
    typedef std::map<SectionRef, unsigned> ObjSectionToIDMap;
  
    // A global symbol table for symbols from all loaded modules.
    RTDyldSymbolTable GlobalSymbolTable;
  
    // Keep a map of common symbols to their info pairs
    typedef std::vector<SymbolRef> CommonSymbolList;
  
    // For each symbol, keep a list of relocations based on it. Anytime
    // its address is reassigned (the JIT re-compiled the function, e.g.),
    // the relocations get re-resolved.
    // The symbol (or section) the relocation is sourced from is the Key
    // in the relocation list where it's stored.
    typedef SmallVector<RelocationEntry, 64> RelocationList;
    // Relocations to sections already loaded. Indexed by SectionID which is the
    // source of the address. The target where the address will be written is
    // SectionID/Offset in the relocation itself.
    std::unordered_map<unsigned, RelocationList> Relocations;
  
    // Relocations to external symbols that are not yet resolved.  Symbols are
    // external when they aren't found in the global symbol table of all loaded
    // modules.  This map is indexed by symbol name.
    StringMap<RelocationList> ExternalSymbolRelocations;
  
  
    typedef std::map<RelocationValueRef, uintptr_t> StubMap;
  
    Triple::ArchType Arch;
    bool IsTargetLittleEndian;
    bool IsMipsO32ABI;
    bool IsMipsN32ABI;
    bool IsMipsN64ABI;
  
    // True if all sections should be passed to the memory manager, false if only
    // sections containing relocations should be. Defaults to 'false'.
    bool ProcessAllSections;
  
    // This mutex prevents simultaneously loading objects from two different
    // threads.  This keeps us from having to protect individual data structures
    // and guarantees that section allocation requests to the memory manager
    // won't be interleaved between modules.  It is also used in mapSectionAddress
    // and resolveRelocations to protect write access to internal data structures.
    //
    // loadObject may be called on the same thread during the handling of of
    // processRelocations, and that's OK.  The handling of the relocation lists
    // is written in such a way as to work correctly if new elements are added to
    // the end of the list while the list is being processed.
    sys::Mutex lock;
  
    using NotifyStubEmittedFunction =
      RuntimeDyld::NotifyStubEmittedFunction;
    NotifyStubEmittedFunction NotifyStubEmitted;
  
    virtual unsigned getMaxStubSize() const = 0;
    virtual unsigned getStubAlignment() = 0;
  
    bool HasError;
    std::string ErrorStr;
  
    void writeInt16BE(uint8_t *Addr, uint16_t Value) {
      if (IsTargetLittleEndian)
        sys::swapByteOrder(Value);
      *Addr       = (Value >> 8) & 0xFF;
      *(Addr + 1) = Value & 0xFF;
    }
  
    void writeInt32BE(uint8_t *Addr, uint32_t Value) {
      if (IsTargetLittleEndian)
        sys::swapByteOrder(Value);
      *Addr       = (Value >> 24) & 0xFF;
      *(Addr + 1) = (Value >> 16) & 0xFF;
      *(Addr + 2) = (Value >> 8) & 0xFF;
      *(Addr + 3) = Value & 0xFF;
    }
  
    void writeInt64BE(uint8_t *Addr, uint64_t Value) {
      if (IsTargetLittleEndian)
        sys::swapByteOrder(Value);
      *Addr       = (Value >> 56) & 0xFF;
      *(Addr + 1) = (Value >> 48) & 0xFF;
      *(Addr + 2) = (Value >> 40) & 0xFF;
      *(Addr + 3) = (Value >> 32) & 0xFF;
      *(Addr + 4) = (Value >> 24) & 0xFF;
      *(Addr + 5) = (Value >> 16) & 0xFF;
      *(Addr + 6) = (Value >> 8) & 0xFF;
      *(Addr + 7) = Value & 0xFF;
    }
  
    virtual void setMipsABI(const ObjectFile &Obj) {
      IsMipsO32ABI = false;
      IsMipsN32ABI = false;
      IsMipsN64ABI = false;
    }
  
    /// Endian-aware read Read the least significant Size bytes from Src.
    uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const;
  
    /// Endian-aware write. Write the least significant Size bytes from Value to
    /// Dst.
    void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const;
  
    /// Generate JITSymbolFlags from a libObject symbol.
    virtual Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &Sym);
  
    /// Modify the given target address based on the given symbol flags.
    /// This can be used by subclasses to tweak addresses based on symbol flags,
    /// For example: the MachO/ARM target uses it to set the low bit if the target
    /// is a thumb symbol.
    virtual uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
                                               JITSymbolFlags Flags) const {
      return Addr;
    }
  
    /// Given the common symbols discovered in the object file, emit a
    /// new section for them and update the symbol mappings in the object and
    /// symbol table.
    Error emitCommonSymbols(const ObjectFile &Obj,
                            CommonSymbolList &CommonSymbols, uint64_t CommonSize,
                            uint32_t CommonAlign);
  
    /// Emits section data from the object file to the MemoryManager.
    /// \param IsCode if it's true then allocateCodeSection() will be
    ///        used for emits, else allocateDataSection() will be used.
    /// \return SectionID.
    Expected<unsigned> emitSection(const ObjectFile &Obj,
                                   const SectionRef &Section,
                                   bool IsCode);
  
    /// Find Section in LocalSections. If the secton is not found - emit
    ///        it and store in LocalSections.
    /// \param IsCode if it's true then allocateCodeSection() will be
    ///        used for emmits, else allocateDataSection() will be used.
    /// \return SectionID.
    Expected<unsigned> findOrEmitSection(const ObjectFile &Obj,
                                         const SectionRef &Section, bool IsCode,
                                         ObjSectionToIDMap &LocalSections);
  
    // Add a relocation entry that uses the given section.
    void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
  
    // Add a relocation entry that uses the given symbol.  This symbol may
    // be found in the global symbol table, or it may be external.
    void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName);
  
    /// Emits long jump instruction to Addr.
    /// \return Pointer to the memory area for emitting target address.
    uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
  
    /// Resolves relocations from Relocs list with address from Value.
    void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
  
    /// A object file specific relocation resolver
    /// \param RE The relocation to be resolved
    /// \param Value Target symbol address to apply the relocation action
    virtual void resolveRelocation(const RelocationEntry &RE, uint64_t Value) = 0;
  
    /// Parses one or more object file relocations (some object files use
    ///        relocation pairs) and stores it to Relocations or SymbolRelocations
    ///        (this depends on the object file type).
    /// \return Iterator to the next relocation that needs to be parsed.
    virtual Expected<relocation_iterator>
    processRelocationRef(unsigned SectionID, relocation_iterator RelI,
                         const ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID,
                         StubMap &Stubs) = 0;
  
    void applyExternalSymbolRelocations(
        const StringMap<JITEvaluatedSymbol> ExternalSymbolMap);
  
    /// Resolve relocations to external symbols.
    Error resolveExternalSymbols();
  
    // Compute an upper bound of the memory that is required to load all
    // sections
    Error computeTotalAllocSize(const ObjectFile &Obj,
                                uint64_t &CodeSize, uint32_t &CodeAlign,
                                uint64_t &RODataSize, uint32_t &RODataAlign,
                                uint64_t &RWDataSize, uint32_t &RWDataAlign);
  
    // Compute GOT size
    unsigned computeGOTSize(const ObjectFile &Obj);
  
    // Compute the stub buffer size required for a section
    unsigned computeSectionStubBufSize(const ObjectFile &Obj,
                                       const SectionRef &Section);
  
    // Implementation of the generic part of the loadObject algorithm.
    Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
  
    // Return size of Global Offset Table (GOT) entry
    virtual size_t getGOTEntrySize() { return 0; }
  
    // Return true if the relocation R may require allocating a GOT entry.
    virtual bool relocationNeedsGot(const RelocationRef &R) const {
      return false;
    }
  
    // Return true if the relocation R may require allocating a stub.
    virtual bool relocationNeedsStub(const RelocationRef &R) const {
      return true;    // Conservative answer
    }
  
  public:
    RuntimeDyldImpl(RuntimeDyld::MemoryManager &MemMgr,
                    JITSymbolResolver &Resolver)
      : MemMgr(MemMgr), Resolver(Resolver),
        ProcessAllSections(false), HasError(false) {
    }
  
    virtual ~RuntimeDyldImpl();
  
    void setProcessAllSections(bool ProcessAllSections) {
      this->ProcessAllSections = ProcessAllSections;
    }
  
    virtual std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
    loadObject(const object::ObjectFile &Obj) = 0;
  
    uint64_t getSectionLoadAddress(unsigned SectionID) const {
      return Sections[SectionID].getLoadAddress();
    }
  
    uint8_t *getSectionAddress(unsigned SectionID) const {
      return Sections[SectionID].getAddress();
    }
  
    StringRef getSectionContent(unsigned SectionID) const {
      return StringRef(reinterpret_cast<char *>(Sections[SectionID].getAddress()),
                       Sections[SectionID].getStubOffset() + getMaxStubSize());
    }
  
    uint8_t* getSymbolLocalAddress(StringRef Name) const {
      // FIXME: Just look up as a function for now. Overly simple of course.
      // Work in progress.
      RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
      if (pos == GlobalSymbolTable.end())
        return nullptr;
      const auto &SymInfo = pos->second;
      // Absolute symbols do not have a local address.
      if (SymInfo.getSectionID() == AbsoluteSymbolSection)
        return nullptr;
      return getSectionAddress(SymInfo.getSectionID()) + SymInfo.getOffset();
    }
  
    unsigned getSymbolSectionID(StringRef Name) const {
      auto GSTItr = GlobalSymbolTable.find(Name);
      if (GSTItr == GlobalSymbolTable.end())
        return ~0U;
      return GSTItr->second.getSectionID();
    }
  
    JITEvaluatedSymbol getSymbol(StringRef Name) const {
      // FIXME: Just look up as a function for now. Overly simple of course.
      // Work in progress.
      RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
      if (pos == GlobalSymbolTable.end())
        return nullptr;
      const auto &SymEntry = pos->second;
      uint64_t SectionAddr = 0;
      if (SymEntry.getSectionID() != AbsoluteSymbolSection)
        SectionAddr = getSectionLoadAddress(SymEntry.getSectionID());
      uint64_t TargetAddr = SectionAddr + SymEntry.getOffset();
  
      // FIXME: Have getSymbol should return the actual address and the client
      //        modify it based on the flags. This will require clients to be
      //        aware of the target architecture, which we should build
      //        infrastructure for.
      TargetAddr = modifyAddressBasedOnFlags(TargetAddr, SymEntry.getFlags());
      return JITEvaluatedSymbol(TargetAddr, SymEntry.getFlags());
    }
  
    std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const {
      std::map<StringRef, JITEvaluatedSymbol> Result;
  
      for (auto &KV : GlobalSymbolTable) {
        auto SectionID = KV.second.getSectionID();
        uint64_t SectionAddr = 0;
        if (SectionID != AbsoluteSymbolSection)
          SectionAddr = getSectionLoadAddress(SectionID);
        Result[KV.first()] =
          JITEvaluatedSymbol(SectionAddr + KV.second.getOffset(), KV.second.getFlags());
      }
  
      return Result;
    }
  
    void resolveRelocations();
  
    void resolveLocalRelocations();
  
    static void finalizeAsync(
        std::unique_ptr<RuntimeDyldImpl> This,
        unique_function<void(object::OwningBinary<object::ObjectFile>, Error)>
            OnEmitted,
        object::OwningBinary<object::ObjectFile> O);
  
    void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
  
    void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
  
    // Is the linker in an error state?
    bool hasError() { return HasError; }
  
    // Mark the error condition as handled and continue.
    void clearError() { HasError = false; }
  
    // Get the error message.
    StringRef getErrorString() { return ErrorStr; }
  
    virtual bool isCompatibleFile(const ObjectFile &Obj) const = 0;
  
    void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
      this->NotifyStubEmitted = std::move(NotifyStubEmitted);
    }
  
    virtual void registerEHFrames();
  
    void deregisterEHFrames();
  
    virtual Error finalizeLoad(const ObjectFile &ObjImg,
                               ObjSectionToIDMap &SectionMap) {
      return Error::success();
    }
  };
  
  } // end namespace llvm
  
  #endif
  