text: //===-- RuntimeDyld.cpp - 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
  //
  //===----------------------------------------------------------------------===//
  //
  // Implementation of the MC-JIT runtime dynamic linker.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ExecutionEngine/RuntimeDyld.h"
  #include "RuntimeDyldCOFF.h"
  #include "RuntimeDyldELF.h"
  #include "RuntimeDyldImpl.h"
  #include "RuntimeDyldMachO.h"
  #include "llvm/Object/COFF.h"
  #include "llvm/Object/ELFObjectFile.h"
  #include "llvm/Support/Alignment.h"
  #include "llvm/Support/MSVCErrorWorkarounds.h"
  #include "llvm/Support/ManagedStatic.h"
  #include "llvm/Support/MathExtras.h"
  #include <mutex>
  
  #include <future>
  
  using namespace llvm;
  using namespace llvm::object;
  
  #define DEBUG_TYPE "dyld"
  
  namespace {
  
  enum RuntimeDyldErrorCode {
    GenericRTDyldError = 1
  };
  
  // FIXME: This class is only here to support the transition to llvm::Error. It
  // will be removed once this transition is complete. Clients should prefer to
  // deal with the Error value directly, rather than converting to error_code.
  class RuntimeDyldErrorCategory : public std::error_category {
  public:
    const char *name() const noexcept override { return "runtimedyld"; }
  
    std::string message(int Condition) const override {
      switch (static_cast<RuntimeDyldErrorCode>(Condition)) {
        case GenericRTDyldError: return "Generic RuntimeDyld error";
      }
      llvm_unreachable("Unrecognized RuntimeDyldErrorCode");
    }
  };
  
  static ManagedStatic<RuntimeDyldErrorCategory> RTDyldErrorCategory;
  
  }
  
  char RuntimeDyldError::ID = 0;
  
  void RuntimeDyldError::log(raw_ostream &OS) const {
    OS << ErrMsg << "\n";
  }
  
  std::error_code RuntimeDyldError::convertToErrorCode() const {
    return std::error_code(GenericRTDyldError, *RTDyldErrorCategory);
  }
  
  // Empty out-of-line virtual destructor as the key function.
  RuntimeDyldImpl::~RuntimeDyldImpl() {}
  
  // Pin LoadedObjectInfo's vtables to this file.
  void RuntimeDyld::LoadedObjectInfo::anchor() {}
  
  namespace llvm {
  
  void RuntimeDyldImpl::registerEHFrames() {}
  
  void RuntimeDyldImpl::deregisterEHFrames() {
    MemMgr.deregisterEHFrames();
  }
  
  #ifndef NDEBUG
  static void dumpSectionMemory(const SectionEntry &S, StringRef State) {
    dbgs() << "----- Contents of section " << S.getName() << " " << State
           << " -----";
  
    if (S.getAddress() == nullptr) {
      dbgs() << "\n          <section not emitted>\n";
      return;
    }
  
    const unsigned ColsPerRow = 16;
  
    uint8_t *DataAddr = S.getAddress();
    uint64_t LoadAddr = S.getLoadAddress();
  
    unsigned StartPadding = LoadAddr & (ColsPerRow - 1);
    unsigned BytesRemaining = S.getSize();
  
    if (StartPadding) {
      dbgs() << "\n" << format("0x%016" PRIx64,
                               LoadAddr & ~(uint64_t)(ColsPerRow - 1)) << ":";
      while (StartPadding--)
        dbgs() << "   ";
    }
  
    while (BytesRemaining > 0) {
      if ((LoadAddr & (ColsPerRow - 1)) == 0)
        dbgs() << "\n" << format("0x%016" PRIx64, LoadAddr) << ":";
  
      dbgs() << " " << format("%02x", *DataAddr);
  
      ++DataAddr;
      ++LoadAddr;
      --BytesRemaining;
    }
  
    dbgs() << "\n";
  }
  #endif
  
  // Resolve the relocations for all symbols we currently know about.
  void RuntimeDyldImpl::resolveRelocations() {
    std::lock_guard<sys::Mutex> locked(lock);
  
    // Print out the sections prior to relocation.
    LLVM_DEBUG(for (int i = 0, e = Sections.size(); i != e; ++i)
                   dumpSectionMemory(Sections[i], "before relocations"););
  
    // First, resolve relocations associated with external symbols.
    if (auto Err = resolveExternalSymbols()) {
      HasError = true;
      ErrorStr = toString(std::move(Err));
    }
  
    resolveLocalRelocations();
  
    // Print out sections after relocation.
    LLVM_DEBUG(for (int i = 0, e = Sections.size(); i != e; ++i)
                   dumpSectionMemory(Sections[i], "after relocations"););
  }
  
  void RuntimeDyldImpl::resolveLocalRelocations() {
    // Iterate over all outstanding relocations
    for (auto it = Relocations.begin(), e = Relocations.end(); it != e; ++it) {
      // The Section here (Sections[i]) refers to the section in which the
      // symbol for the relocation is located.  The SectionID in the relocation
      // entry provides the section to which the relocation will be applied.
      int Idx = it->first;
      uint64_t Addr = Sections[Idx].getLoadAddress();
      LLVM_DEBUG(dbgs() << "Resolving relocations Section #" << Idx << "\t"
                        << format("%p", (uintptr_t)Addr) << "\n");
      resolveRelocationList(it->second, Addr);
    }
    Relocations.clear();
  }
  
  void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
                                          uint64_t TargetAddress) {
    std::lock_guard<sys::Mutex> locked(lock);
    for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
      if (Sections[i].getAddress() == LocalAddress) {
        reassignSectionAddress(i, TargetAddress);
        return;
      }
    }
    llvm_unreachable("Attempting to remap address of unknown section!");
  }
  
  static Error getOffset(const SymbolRef &Sym, SectionRef Sec,
                         uint64_t &Result) {
    Expected<uint64_t> AddressOrErr = Sym.getAddress();
    if (!AddressOrErr)
      return AddressOrErr.takeError();
    Result = *AddressOrErr - Sec.getAddress();
    return Error::success();
  }
  
  Expected<RuntimeDyldImpl::ObjSectionToIDMap>
  RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
    std::lock_guard<sys::Mutex> locked(lock);
  
    // Save information about our target
    Arch = (Triple::ArchType)Obj.getArch();
    IsTargetLittleEndian = Obj.isLittleEndian();
    setMipsABI(Obj);
  
    // Compute the memory size required to load all sections to be loaded
    // and pass this information to the memory manager
    if (MemMgr.needsToReserveAllocationSpace()) {
      uint64_t CodeSize = 0, RODataSize = 0, RWDataSize = 0;
      uint32_t CodeAlign = 1, RODataAlign = 1, RWDataAlign = 1;
      if (auto Err = computeTotalAllocSize(Obj,
                                           CodeSize, CodeAlign,
                                           RODataSize, RODataAlign,
                                           RWDataSize, RWDataAlign))
        return std::move(Err);
      MemMgr.reserveAllocationSpace(CodeSize, CodeAlign, RODataSize, RODataAlign,
                                    RWDataSize, RWDataAlign);
    }
  
    // Used sections from the object file
    ObjSectionToIDMap LocalSections;
  
    // Common symbols requiring allocation, with their sizes and alignments
    CommonSymbolList CommonSymbolsToAllocate;
  
    uint64_t CommonSize = 0;
    uint32_t CommonAlign = 0;
  
    // First, collect all weak and common symbols. We need to know if stronger
    // definitions occur elsewhere.
    JITSymbolResolver::LookupSet ResponsibilitySet;
    {
      JITSymbolResolver::LookupSet Symbols;
      for (auto &Sym : Obj.symbols()) {
        uint32_t Flags = Sym.getFlags();
        if ((Flags & SymbolRef::SF_Common) || (Flags & SymbolRef::SF_Weak)) {
          // Get symbol name.
          if (auto NameOrErr = Sym.getName())
            Symbols.insert(*NameOrErr);
          else
            return NameOrErr.takeError();
        }
      }
  
      if (auto ResultOrErr = Resolver.getResponsibilitySet(Symbols))
        ResponsibilitySet = std::move(*ResultOrErr);
      else
        return ResultOrErr.takeError();
    }
  
    // Parse symbols
    LLVM_DEBUG(dbgs() << "Parse symbols:\n");
    for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
         ++I) {
      uint32_t Flags = I->getFlags();
  
      // Skip undefined symbols.
      if (Flags & SymbolRef::SF_Undefined)
        continue;
  
      // Get the symbol type.
      object::SymbolRef::Type SymType;
      if (auto SymTypeOrErr = I->getType())
        SymType = *SymTypeOrErr;
      else
        return SymTypeOrErr.takeError();
  
      // Get symbol name.
      StringRef Name;
      if (auto NameOrErr = I->getName())
        Name = *NameOrErr;
      else
        return NameOrErr.takeError();
  
      // Compute JIT symbol flags.
      auto JITSymFlags = getJITSymbolFlags(*I);
      if (!JITSymFlags)
        return JITSymFlags.takeError();
  
      // If this is a weak definition, check to see if there's a strong one.
      // If there is, skip this symbol (we won't be providing it: the strong
      // definition will). If there's no strong definition, make this definition
      // strong.
      if (JITSymFlags->isWeak() || JITSymFlags->isCommon()) {
        // First check whether there's already a definition in this instance.
        if (GlobalSymbolTable.count(Name))
          continue;
  
        // If we're not responsible for this symbol, skip it.
        if (!ResponsibilitySet.count(Name))
          continue;
  
        // Otherwise update the flags on the symbol to make this definition
        // strong.
        if (JITSymFlags->isWeak())
          *JITSymFlags &= ~JITSymbolFlags::Weak;
        if (JITSymFlags->isCommon()) {
          *JITSymFlags &= ~JITSymbolFlags::Common;
          uint32_t Align = I->getAlignment();
          uint64_t Size = I->getCommonSize();
          if (!CommonAlign)
            CommonAlign = Align;
          CommonSize = alignTo(CommonSize, Align) + Size;
          CommonSymbolsToAllocate.push_back(*I);
        }
      }
  
      if (Flags & SymbolRef::SF_Absolute &&
          SymType != object::SymbolRef::ST_File) {
        uint64_t Addr = 0;
        if (auto AddrOrErr = I->getAddress())
          Addr = *AddrOrErr;
        else
          return AddrOrErr.takeError();
  
        unsigned SectionID = AbsoluteSymbolSection;
  
        LLVM_DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
                          << " SID: " << SectionID
                          << " Offset: " << format("%p", (uintptr_t)Addr)
                          << " flags: " << Flags << "\n");
        GlobalSymbolTable[Name] = SymbolTableEntry(SectionID, Addr, *JITSymFlags);
      } else if (SymType == object::SymbolRef::ST_Function ||
                 SymType == object::SymbolRef::ST_Data ||
                 SymType == object::SymbolRef::ST_Unknown ||
                 SymType == object::SymbolRef::ST_Other) {
  
        section_iterator SI = Obj.section_end();
        if (auto SIOrErr = I->getSection())
          SI = *SIOrErr;
        else
          return SIOrErr.takeError();
  
        if (SI == Obj.section_end())
          continue;
  
        // Get symbol offset.
        uint64_t SectOffset;
        if (auto Err = getOffset(*I, *SI, SectOffset))
          return std::move(Err);
  
        bool IsCode = SI->isText();
        unsigned SectionID;
        if (auto SectionIDOrErr =
                findOrEmitSection(Obj, *SI, IsCode, LocalSections))
          SectionID = *SectionIDOrErr;
        else
          return SectionIDOrErr.takeError();
  
        LLVM_DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
                          << " SID: " << SectionID
                          << " Offset: " << format("%p", (uintptr_t)SectOffset)
                          << " flags: " << Flags << "\n");
        GlobalSymbolTable[Name] =
            SymbolTableEntry(SectionID, SectOffset, *JITSymFlags);
      }
    }
  
    // Allocate common symbols
    if (auto Err = emitCommonSymbols(Obj, CommonSymbolsToAllocate, CommonSize,
                                     CommonAlign))
      return std::move(Err);
  
    // Parse and process relocations
    LLVM_DEBUG(dbgs() << "Parse relocations:\n");
    for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
         SI != SE; ++SI) {
      StubMap Stubs;
  
      Expected<section_iterator> RelSecOrErr = SI->getRelocatedSection();
      if (!RelSecOrErr)
        return RelSecOrErr.takeError();
  
      section_iterator RelocatedSection = *RelSecOrErr;
      if (RelocatedSection == SE)
        continue;
  
      relocation_iterator I = SI->relocation_begin();
      relocation_iterator E = SI->relocation_end();
  
      if (I == E && !ProcessAllSections)
        continue;
  
      bool IsCode = RelocatedSection->isText();
      unsigned SectionID = 0;
      if (auto SectionIDOrErr = findOrEmitSection(Obj, *RelocatedSection, IsCode,
                                                  LocalSections))
        SectionID = *SectionIDOrErr;
      else
        return SectionIDOrErr.takeError();
  
      LLVM_DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
  
      for (; I != E;)
        if (auto IOrErr = processRelocationRef(SectionID, I, Obj, LocalSections, Stubs))
          I = *IOrErr;
        else
          return IOrErr.takeError();
  
      // If there is a NotifyStubEmitted callback set, call it to register any
      // stubs created for this section.
      if (NotifyStubEmitted) {
        StringRef FileName = Obj.getFileName();
        StringRef SectionName = Sections[SectionID].getName();
        for (auto &KV : Stubs) {
  
          auto &VR = KV.first;
          uint64_t StubAddr = KV.second;
  
          // If this is a named stub, just call NotifyStubEmitted.
          if (VR.SymbolName) {
            NotifyStubEmitted(FileName, SectionName, VR.SymbolName, SectionID,
                              StubAddr);
            continue;
          }
  
          // Otherwise we will have to try a reverse lookup on the globla symbol table.
          for (auto &GSTMapEntry : GlobalSymbolTable) {
            StringRef SymbolName = GSTMapEntry.first();
            auto &GSTEntry = GSTMapEntry.second;
            if (GSTEntry.getSectionID() == VR.SectionID &&
                GSTEntry.getOffset() == VR.Offset) {
              NotifyStubEmitted(FileName, SectionName, SymbolName, SectionID,
                                StubAddr);
              break;
            }
          }
        }
      }
    }
  
    // Process remaining sections
    if (ProcessAllSections) {
      LLVM_DEBUG(dbgs() << "Process remaining sections:\n");
      for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
           SI != SE; ++SI) {
  
        /* Ignore already loaded sections */
        if (LocalSections.find(*SI) != LocalSections.end())
          continue;
  
        bool IsCode = SI->isText();
        if (auto SectionIDOrErr =
                findOrEmitSection(Obj, *SI, IsCode, LocalSections))
          LLVM_DEBUG(dbgs() << "\tSectionID: " << (*SectionIDOrErr) << "\n");
        else
          return SectionIDOrErr.takeError();
      }
    }
  
    // Give the subclasses a chance to tie-up any loose ends.
    if (auto Err = finalizeLoad(Obj, LocalSections))
      return std::move(Err);
  
  //   for (auto E : LocalSections)
  //     llvm::dbgs() << "Added: " << E.first.getRawDataRefImpl() << " -> " << E.second << "\n";
  
    return LocalSections;
  }
  
  // A helper method for computeTotalAllocSize.
  // Computes the memory size required to allocate sections with the given sizes,
  // assuming that all sections are allocated with the given alignment
  static uint64_t
  computeAllocationSizeForSections(std::vector<uint64_t> &SectionSizes,
                                   uint64_t Alignment) {
    uint64_t TotalSize = 0;
    for (size_t Idx = 0, Cnt = SectionSizes.size(); Idx < Cnt; Idx++) {
      uint64_t AlignedSize =
          (SectionSizes[Idx] + Alignment - 1) / Alignment * Alignment;
      TotalSize += AlignedSize;
    }
    return TotalSize;
  }
  
  static bool isRequiredForExecution(const SectionRef Section) {
    const ObjectFile *Obj = Section.getObject();
    if (isa<object::ELFObjectFileBase>(Obj))
      return ELFSectionRef(Section).getFlags() & ELF::SHF_ALLOC;
    if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj)) {
      const coff_section *CoffSection = COFFObj->getCOFFSection(Section);
      // Avoid loading zero-sized COFF sections.
      // In PE files, VirtualSize gives the section size, and SizeOfRawData
      // may be zero for sections with content. In Obj files, SizeOfRawData
      // gives the section size, and VirtualSize is always zero. Hence
      // the need to check for both cases below.
      bool HasContent =
          (CoffSection->VirtualSize > 0) || (CoffSection->SizeOfRawData > 0);
      bool IsDiscardable =
          CoffSection->Characteristics &
          (COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_LNK_INFO);
      return HasContent && !IsDiscardable;
    }
  
    assert(isa<MachOObjectFile>(Obj));
    return true;
  }
  
  static bool isReadOnlyData(const SectionRef Section) {
    const ObjectFile *Obj = Section.getObject();
    if (isa<object::ELFObjectFileBase>(Obj))
      return !(ELFSectionRef(Section).getFlags() &
               (ELF::SHF_WRITE | ELF::SHF_EXECINSTR));
    if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
      return ((COFFObj->getCOFFSection(Section)->Characteristics &
               (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
               | COFF::IMAGE_SCN_MEM_READ
               | COFF::IMAGE_SCN_MEM_WRITE))
               ==
               (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
               | COFF::IMAGE_SCN_MEM_READ));
  
    assert(isa<MachOObjectFile>(Obj));
    return false;
  }
  
  static bool isZeroInit(const SectionRef Section) {
    const ObjectFile *Obj = Section.getObject();
    if (isa<object::ELFObjectFileBase>(Obj))
      return ELFSectionRef(Section).getType() == ELF::SHT_NOBITS;
    if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
      return COFFObj->getCOFFSection(Section)->Characteristics &
              COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
  
    auto *MachO = cast<MachOObjectFile>(Obj);
    unsigned SectionType = MachO->getSectionType(Section);
    return SectionType == MachO::S_ZEROFILL ||
           SectionType == MachO::S_GB_ZEROFILL;
  }
  
  // Compute an upper bound of the memory size that is required to load all
  // sections
  Error RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
                                               uint64_t &CodeSize,
                                               uint32_t &CodeAlign,
                                               uint64_t &RODataSize,
                                               uint32_t &RODataAlign,
                                               uint64_t &RWDataSize,
                                               uint32_t &RWDataAlign) {
    // Compute the size of all sections required for execution
    std::vector<uint64_t> CodeSectionSizes;
    std::vector<uint64_t> ROSectionSizes;
    std::vector<uint64_t> RWSectionSizes;
  
    // Collect sizes of all sections to be loaded;
    // also determine the max alignment of all sections
    for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
         SI != SE; ++SI) {
      const SectionRef &Section = *SI;
  
      bool IsRequired = isRequiredForExecution(Section) || ProcessAllSections;
  
      // Consider only the sections that are required to be loaded for execution
      if (IsRequired) {
        uint64_t DataSize = Section.getSize();
        uint64_t Alignment64 = Section.getAlignment();
        unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
        bool IsCode = Section.isText();
        bool IsReadOnly = isReadOnlyData(Section);
  
        Expected<StringRef> NameOrErr = Section.getName();
        if (!NameOrErr)
          return NameOrErr.takeError();
        StringRef Name = *NameOrErr;
  
        uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
  
        uint64_t PaddingSize = 0;
        if (Name == ".eh_frame")
          PaddingSize += 4;
        if (StubBufSize != 0)
          PaddingSize += getStubAlignment() - 1;
  
        uint64_t SectionSize = DataSize + PaddingSize + StubBufSize;
  
        // The .eh_frame section (at least on Linux) needs an extra four bytes
        // padded
        // with zeroes added at the end.  For MachO objects, this section has a
        // slightly different name, so this won't have any effect for MachO
        // objects.
        if (Name == ".eh_frame")
          SectionSize += 4;
  
        if (!SectionSize)
          SectionSize = 1;
  
        if (IsCode) {
          CodeAlign = std::max(CodeAlign, Alignment);
          CodeSectionSizes.push_back(SectionSize);
        } else if (IsReadOnly) {
          RODataAlign = std::max(RODataAlign, Alignment);
          ROSectionSizes.push_back(SectionSize);
        } else {
          RWDataAlign = std::max(RWDataAlign, Alignment);
          RWSectionSizes.push_back(SectionSize);
        }
      }
    }
  
    // Compute Global Offset Table size. If it is not zero we
    // also update alignment, which is equal to a size of a
    // single GOT entry.
    if (unsigned GotSize = computeGOTSize(Obj)) {
      RWSectionSizes.push_back(GotSize);
      RWDataAlign = std::max<uint32_t>(RWDataAlign, getGOTEntrySize());
    }
  
    // Compute the size of all common symbols
    uint64_t CommonSize = 0;
    uint32_t CommonAlign = 1;
    for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
         ++I) {
      uint32_t Flags = I->getFlags();
      if (Flags & SymbolRef::SF_Common) {
        // Add the common symbols to a list.  We'll allocate them all below.
        uint64_t Size = I->getCommonSize();
        uint32_t Align = I->getAlignment();
        // If this is the first common symbol, use its alignment as the alignment
        // for the common symbols section.
        if (CommonSize == 0)
          CommonAlign = Align;
        CommonSize = alignTo(CommonSize, Align) + Size;
      }
    }
    if (CommonSize != 0) {
      RWSectionSizes.push_back(CommonSize);
      RWDataAlign = std::max(RWDataAlign, CommonAlign);
    }
  
    // Compute the required allocation space for each different type of sections
    // (code, read-only data, read-write data) assuming that all sections are
    // allocated with the max alignment. Note that we cannot compute with the
    // individual alignments of the sections, because then the required size
    // depends on the order, in which the sections are allocated.
    CodeSize = computeAllocationSizeForSections(CodeSectionSizes, CodeAlign);
    RODataSize = computeAllocationSizeForSections(ROSectionSizes, RODataAlign);
    RWDataSize = computeAllocationSizeForSections(RWSectionSizes, RWDataAlign);
  
    return Error::success();
  }
  
  // compute GOT size
  unsigned RuntimeDyldImpl::computeGOTSize(const ObjectFile &Obj) {
    size_t GotEntrySize = getGOTEntrySize();
    if (!GotEntrySize)
      return 0;
  
    size_t GotSize = 0;
    for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
         SI != SE; ++SI) {
  
      for (const RelocationRef &Reloc : SI->relocations())
        if (relocationNeedsGot(Reloc))
          GotSize += GotEntrySize;
    }
  
    return GotSize;
  }
  
  // compute stub buffer size for the given section
  unsigned RuntimeDyldImpl::computeSectionStubBufSize(const ObjectFile &Obj,
                                                      const SectionRef &Section) {
    unsigned StubSize = getMaxStubSize();
    if (StubSize == 0) {
      return 0;
    }
    // FIXME: this is an inefficient way to handle this. We should computed the
    // necessary section allocation size in loadObject by walking all the sections
    // once.
    unsigned StubBufSize = 0;
    for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
         SI != SE; ++SI) {
  
      Expected<section_iterator> RelSecOrErr = SI->getRelocatedSection();
      if (!RelSecOrErr)
        report_fatal_error(toString(RelSecOrErr.takeError()));
  
      section_iterator RelSecI = *RelSecOrErr;
      if (!(RelSecI == Section))
        continue;
  
      for (const RelocationRef &Reloc : SI->relocations())
        if (relocationNeedsStub(Reloc))
          StubBufSize += StubSize;
    }
  
    // Get section data size and alignment
    uint64_t DataSize = Section.getSize();
    uint64_t Alignment64 = Section.getAlignment();
  
    // Add stubbuf size alignment
    unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
    unsigned StubAlignment = getStubAlignment();
    unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
    if (StubAlignment > EndAlignment)
      StubBufSize += StubAlignment - EndAlignment;
    return StubBufSize;
  }
  
  uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
                                               unsigned Size) const {
    uint64_t Result = 0;
    if (IsTargetLittleEndian) {
      Src += Size - 1;
      while (Size--)
        Result = (Result << 8) | *Src--;
    } else
      while (Size--)
        Result = (Result << 8) | *Src++;
  
    return Result;
  }
  
  void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
                                            unsigned Size) const {
    if (IsTargetLittleEndian) {
      while (Size--) {
        *Dst++ = Value & 0xFF;
        Value >>= 8;
      }
    } else {
      Dst += Size - 1;
      while (Size--) {
        *Dst-- = Value & 0xFF;
        Value >>= 8;
      }
    }
  }
  
  Expected<JITSymbolFlags>
  RuntimeDyldImpl::getJITSymbolFlags(const SymbolRef &SR) {
    return JITSymbolFlags::fromObjectSymbol(SR);
  }
  
  Error RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
                                           CommonSymbolList &SymbolsToAllocate,
                                           uint64_t CommonSize,
                                           uint32_t CommonAlign) {
    if (SymbolsToAllocate.empty())
      return Error::success();
  
    // Allocate memory for the section
    unsigned SectionID = Sections.size();
    uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, CommonAlign, SectionID,
                                               "<common symbols>", false);
    if (!Addr)
      report_fatal_error("Unable to allocate memory for common symbols!");
    uint64_t Offset = 0;
    Sections.push_back(
        SectionEntry("<common symbols>", Addr, CommonSize, CommonSize, 0));
    memset(Addr, 0, CommonSize);
  
    LLVM_DEBUG(dbgs() << "emitCommonSection SectionID: " << SectionID
                      << " new addr: " << format("%p", Addr)
                      << " DataSize: " << CommonSize << "\n");
  
    // Assign the address of each symbol
    for (auto &Sym : SymbolsToAllocate) {
      uint32_t Alignment = Sym.getAlignment();
      uint64_t Size = Sym.getCommonSize();
      StringRef Name;
      if (auto NameOrErr = Sym.getName())
        Name = *NameOrErr;
      else
        return NameOrErr.takeError();
      if (Alignment) {
        // This symbol has an alignment requirement.
        uint64_t AlignOffset =
            offsetToAlignment((uint64_t)Addr, Align(Alignment));
        Addr += AlignOffset;
        Offset += AlignOffset;
      }
      auto JITSymFlags = getJITSymbolFlags(Sym);
  
      if (!JITSymFlags)
        return JITSymFlags.takeError();
  
      LLVM_DEBUG(dbgs() << "Allocating common symbol " << Name << " address "
                        << format("%p", Addr) << "\n");
      GlobalSymbolTable[Name] =
          SymbolTableEntry(SectionID, Offset, std::move(*JITSymFlags));
      Offset += Size;
      Addr += Size;
    }
  
    return Error::success();
  }
  
  Expected<unsigned>
  RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
                               const SectionRef &Section,
                               bool IsCode) {
    StringRef data;
    uint64_t Alignment64 = Section.getAlignment();
  
    unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
    unsigned PaddingSize = 0;
    unsigned StubBufSize = 0;
    bool IsRequired = isRequiredForExecution(Section);
    bool IsVirtual = Section.isVirtual();
    bool IsZeroInit = isZeroInit(Section);
    bool IsReadOnly = isReadOnlyData(Section);
    uint64_t DataSize = Section.getSize();
  
    // An alignment of 0 (at least with ELF) is identical to an alignment of 1,
    // while being more "polite".  Other formats do not support 0-aligned sections
    // anyway, so we should guarantee that the alignment is always at least 1.
    Alignment = std::max(1u, Alignment);
  
    Expected<StringRef> NameOrErr = Section.getName();
    if (!NameOrErr)
      return NameOrErr.takeError();
    StringRef Name = *NameOrErr;
  
    StubBufSize = computeSectionStubBufSize(Obj, Section);
  
    // The .eh_frame section (at least on Linux) needs an extra four bytes padded
    // with zeroes added at the end.  For MachO objects, this section has a
    // slightly different name, so this won't have any effect for MachO objects.
    if (Name == ".eh_frame")
      PaddingSize = 4;
  
    uintptr_t Allocate;
    unsigned SectionID = Sections.size();
    uint8_t *Addr;
    const char *pData = nullptr;
  
    // If this section contains any bits (i.e. isn't a virtual or bss section),
    // grab a reference to them.
    if (!IsVirtual && !IsZeroInit) {
      // In either case, set the location of the unrelocated section in memory,
      // since we still process relocations for it even if we're not applying them.
      if (Expected<StringRef> E = Section.getContents())
        data = *E;
      else
        return E.takeError();
      pData = data.data();
    }
  
    // If there are any stubs then the section alignment needs to be at least as
    // high as stub alignment or padding calculations may by incorrect when the
    // section is remapped.
    if (StubBufSize != 0) {
      Alignment = std::max(Alignment, getStubAlignment());
      PaddingSize += getStubAlignment() - 1;
    }
  
    // Some sections, such as debug info, don't need to be loaded for execution.
    // Process those only if explicitly requested.
    if (IsRequired || ProcessAllSections) {
      Allocate = DataSize + PaddingSize + StubBufSize;
      if (!Allocate)
        Allocate = 1;
      Addr = IsCode ? MemMgr.allocateCodeSection(Allocate, Alignment, SectionID,
                                                 Name)
                    : MemMgr.allocateDataSection(Allocate, Alignment, SectionID,
                                                 Name, IsReadOnly);
      if (!Addr)
        report_fatal_error("Unable to allocate section memory!");
  
      // Zero-initialize or copy the data from the image
      if (IsZeroInit || IsVirtual)
        memset(Addr, 0, DataSize);
      else
        memcpy(Addr, pData, DataSize);
  
      // Fill in any extra bytes we allocated for padding
      if (PaddingSize != 0) {
        memset(Addr + DataSize, 0, PaddingSize);
        // Update the DataSize variable to include padding.
        DataSize += PaddingSize;
  
        // Align DataSize to stub alignment if we have any stubs (PaddingSize will
        // have been increased above to account for this).
        if (StubBufSize > 0)
          DataSize &= -(uint64_t)getStubAlignment();
      }
  
      LLVM_DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: "
                        << Name << " obj addr: " << format("%p", pData)
                        << " new addr: " << format("%p", Addr) << " DataSize: "
                        << DataSize << " StubBufSize: " << StubBufSize
                        << " Allocate: " << Allocate << "\n");
    } else {
      // Even if we didn't load the section, we need to record an entry for it
      // to handle later processing (and by 'handle' I mean don't do anything
      // with these sections).
      Allocate = 0;
      Addr = nullptr;
      LLVM_DEBUG(
          dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
                 << " obj addr: " << format("%p", data.data()) << " new addr: 0"
                 << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate << "\n");
    }
  
    Sections.push_back(
        SectionEntry(Name, Addr, DataSize, Allocate, (uintptr_t)pData));
  
    // Debug info sections are linked as if their load address was zero
    if (!IsRequired)
      Sections.back().setLoadAddress(0);
  
    return SectionID;
  }
  
  Expected<unsigned>
  RuntimeDyldImpl::findOrEmitSection(const ObjectFile &Obj,
                                     const SectionRef &Section,
                                     bool IsCode,
                                     ObjSectionToIDMap &LocalSections) {
  
    unsigned SectionID = 0;
    ObjSectionToIDMap::iterator i = LocalSections.find(Section);
    if (i != LocalSections.end())
      SectionID = i->second;
    else {
      if (auto SectionIDOrErr = emitSection(Obj, Section, IsCode))
        SectionID = *SectionIDOrErr;
      else
        return SectionIDOrErr.takeError();
      LocalSections[Section] = SectionID;
    }
    return SectionID;
  }
  
  void RuntimeDyldImpl::addRelocationForSection(const RelocationEntry &RE,
                                                unsigned SectionID) {
    Relocations[SectionID].push_back(RE);
  }
  
  void RuntimeDyldImpl::addRelocationForSymbol(const RelocationEntry &RE,
                                               StringRef SymbolName) {
    // Relocation by symbol.  If the symbol is found in the global symbol table,
    // create an appropriate section relocation.  Otherwise, add it to
    // ExternalSymbolRelocations.
    RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(SymbolName);
    if (Loc == GlobalSymbolTable.end()) {
      ExternalSymbolRelocations[SymbolName].push_back(RE);
    } else {
      // Copy the RE since we want to modify its addend.
      RelocationEntry RECopy = RE;
      const auto &SymInfo = Loc->second;
      RECopy.Addend += SymInfo.getOffset();
      Relocations[SymInfo.getSectionID()].push_back(RECopy);
    }
  }
  
  uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr,
                                               unsigned AbiVariant) {
    if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be ||
        Arch == Triple::aarch64_32) {
      // This stub has to be able to access the full address space,
      // since symbol lookup won't necessarily find a handy, in-range,
      // PLT stub for functions which could be anywhere.
      // Stub can use ip0 (== x16) to calculate address
      writeBytesUnaligned(0xd2e00010, Addr,    4); // movz ip0, #:abs_g3:<addr>
      writeBytesUnaligned(0xf2c00010, Addr+4,  4); // movk ip0, #:abs_g2_nc:<addr>
      writeBytesUnaligned(0xf2a00010, Addr+8,  4); // movk ip0, #:abs_g1_nc:<addr>
      writeBytesUnaligned(0xf2800010, Addr+12, 4); // movk ip0, #:abs_g0_nc:<addr>
      writeBytesUnaligned(0xd61f0200, Addr+16, 4); // br ip0
  
      return Addr;
    } else if (Arch == Triple::arm || Arch == Triple::armeb) {
      // TODO: There is only ARM far stub now. We should add the Thumb stub,
      // and stubs for branches Thumb - ARM and ARM - Thumb.
      writeBytesUnaligned(0xe51ff004, Addr, 4); // ldr pc, [pc, #-4]
      return Addr + 4;
    } else if (IsMipsO32ABI || IsMipsN32ABI) {
      // 0:   3c190000        lui     t9,%hi(addr).
      // 4:   27390000        addiu   t9,t9,%lo(addr).
      // 8:   03200008        jr      t9.
      // c:   00000000        nop.
      const unsigned LuiT9Instr = 0x3c190000, AdduiT9Instr = 0x27390000;
      const unsigned NopInstr = 0x0;
      unsigned JrT9Instr = 0x03200008;
      if ((AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_32R6 ||
          (AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_64R6)
        JrT9Instr = 0x03200009;
  
      writeBytesUnaligned(LuiT9Instr, Addr, 4);
      writeBytesUnaligned(AdduiT9Instr, Addr + 4, 4);
      writeBytesUnaligned(JrT9Instr, Addr + 8, 4);
      writeBytesUnaligned(NopInstr, Addr + 12, 4);
      return Addr;
    } else if (IsMipsN64ABI) {
      // 0:   3c190000        lui     t9,%highest(addr).
      // 4:   67390000        daddiu  t9,t9,%higher(addr).
      // 8:   0019CC38        dsll    t9,t9,16.
      // c:   67390000        daddiu  t9,t9,%hi(addr).
      // 10:  0019CC38        dsll    t9,t9,16.
      // 14:  67390000        daddiu  t9,t9,%lo(addr).
      // 18:  03200008        jr      t9.
      // 1c:  00000000        nop.
      const unsigned LuiT9Instr = 0x3c190000, DaddiuT9Instr = 0x67390000,
                     DsllT9Instr = 0x19CC38;
      const unsigned NopInstr = 0x0;
      unsigned JrT9Instr = 0x03200008;
      if ((AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_64R6)
        JrT9Instr = 0x03200009;
  
      writeBytesUnaligned(LuiT9Instr, Addr, 4);
      writeBytesUnaligned(DaddiuT9Instr, Addr + 4, 4);
      writeBytesUnaligned(DsllT9Instr, Addr + 8, 4);
      writeBytesUnaligned(DaddiuT9Instr, Addr + 12, 4);
      writeBytesUnaligned(DsllT9Instr, Addr + 16, 4);
      writeBytesUnaligned(DaddiuT9Instr, Addr + 20, 4);
      writeBytesUnaligned(JrT9Instr, Addr + 24, 4);
      writeBytesUnaligned(NopInstr, Addr + 28, 4);
      return Addr;
    } else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
      // Depending on which version of the ELF ABI is in use, we need to
      // generate one of two variants of the stub.  They both start with
      // the same sequence to load the target address into r12.
      writeInt32BE(Addr,    0x3D800000); // lis   r12, highest(addr)
      writeInt32BE(Addr+4,  0x618C0000); // ori   r12, higher(addr)
      writeInt32BE(Addr+8,  0x798C07C6); // sldi  r12, r12, 32
      writeInt32BE(Addr+12, 0x658C0000); // oris  r12, r12, h(addr)
      writeInt32BE(Addr+16, 0x618C0000); // ori   r12, r12, l(addr)
      if (AbiVariant == 2) {
        // PowerPC64 stub ELFv2 ABI: The address points to the function itself.
        // The address is already in r12 as required by the ABI.  Branch to it.
        writeInt32BE(Addr+20, 0xF8410018); // std   r2,  24(r1)
        writeInt32BE(Addr+24, 0x7D8903A6); // mtctr r12
        writeInt32BE(Addr+28, 0x4E800420); // bctr
      } else {
        // PowerPC64 stub ELFv1 ABI: The address points to a function descriptor.
        // Load the function address on r11 and sets it to control register. Also
        // loads the function TOC in r2 and environment pointer to r11.
        writeInt32BE(Addr+20, 0xF8410028); // std   r2,  40(r1)
        writeInt32BE(Addr+24, 0xE96C0000); // ld    r11, 0(r12)
        writeInt32BE(Addr+28, 0xE84C0008); // ld    r2,  0(r12)
        writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
        writeInt32BE(Addr+36, 0xE96C0010); // ld    r11, 16(r2)
        writeInt32BE(Addr+40, 0x4E800420); // bctr
      }
      return Addr;
    } else if (Arch == Triple::systemz) {
      writeInt16BE(Addr,    0xC418);     // lgrl %r1,.+8
      writeInt16BE(Addr+2,  0x0000);
      writeInt16BE(Addr+4,  0x0004);
      writeInt16BE(Addr+6,  0x07F1);     // brc 15,%r1
      // 8-byte address stored at Addr + 8
      return Addr;
    } else if (Arch == Triple::x86_64) {
      *Addr      = 0xFF; // jmp
      *(Addr+1)  = 0x25; // rip
      // 32-bit PC-relative address of the GOT entry will be stored at Addr+2
    } else if (Arch == Triple::x86) {
      *Addr      = 0xE9; // 32-bit pc-relative jump.
    }
    return Addr;
  }
  
  // Assign an address to a symbol name and resolve all the relocations
  // associated with it.
  void RuntimeDyldImpl::reassignSectionAddress(unsigned SectionID,
                                               uint64_t Addr) {
    // The address to use for relocation resolution is not
    // the address of the local section buffer. We must be doing
    // a remote execution environment of some sort. Relocations can't
    // be applied until all the sections have been moved.  The client must
    // trigger this with a call to MCJIT::finalize() or
    // RuntimeDyld::resolveRelocations().
    //
    // Addr is a uint64_t because we can't assume the pointer width
    // of the target is the same as that of the host. Just use a generic
    // "big enough" type.
    LLVM_DEBUG(
        dbgs() << "Reassigning address for section " << SectionID << " ("
               << Sections[SectionID].getName() << "): "
               << format("0x%016" PRIx64, Sections[SectionID].getLoadAddress())
               << " -> " << format("0x%016" PRIx64, Addr) << "\n");
    Sections[SectionID].setLoadAddress(Addr);
  }
  
  void RuntimeDyldImpl::resolveRelocationList(const RelocationList &Relocs,
                                              uint64_t Value) {
    for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
      const RelocationEntry &RE = Relocs[i];
      // Ignore relocations for sections that were not loaded
      if (Sections[RE.SectionID].getAddress() == nullptr)
        continue;
      resolveRelocation(RE, Value);
    }
  }
  
  void RuntimeDyldImpl::applyExternalSymbolRelocations(
      const StringMap<JITEvaluatedSymbol> ExternalSymbolMap) {
    while (!ExternalSymbolRelocations.empty()) {
  
      StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();
  
      StringRef Name = i->first();
      if (Name.size() == 0) {
        // This is an absolute symbol, use an address of zero.
        LLVM_DEBUG(dbgs() << "Resolving absolute relocations."
                          << "\n");
        RelocationList &Relocs = i->second;
        resolveRelocationList(Relocs, 0);
      } else {
        uint64_t Addr = 0;
        JITSymbolFlags Flags;
        RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(Name);
        if (Loc == GlobalSymbolTable.end()) {
          auto RRI = ExternalSymbolMap.find(Name);
          assert(RRI != ExternalSymbolMap.end() && "No result for symbol");
          Addr = RRI->second.getAddress();
          Flags = RRI->second.getFlags();
          // The call to getSymbolAddress may have caused additional modules to
          // be loaded, which may have added new entries to the
          // ExternalSymbolRelocations map.  Consquently, we need to update our
          // iterator.  This is also why retrieval of the relocation list
          // associated with this symbol is deferred until below this point.
          // New entries may have been added to the relocation list.
          i = ExternalSymbolRelocations.find(Name);
        } else {
          // We found the symbol in our global table.  It was probably in a
          // Module that we loaded previously.
          const auto &SymInfo = Loc->second;
          Addr = getSectionLoadAddress(SymInfo.getSectionID()) +
                 SymInfo.getOffset();
          Flags = SymInfo.getFlags();
        }
  
        // FIXME: Implement error handling that doesn't kill the host program!
        if (!Addr)
          report_fatal_error("Program used external function '" + Name +
                             "' which could not be resolved!");
  
        // If Resolver returned UINT64_MAX, the client wants to handle this symbol
        // manually and we shouldn't resolve its relocations.
        if (Addr != UINT64_MAX) {
  
          // Tweak the address based on the symbol flags if necessary.
          // For example, this is used by RuntimeDyldMachOARM to toggle the low bit
          // if the target symbol is Thumb.
          Addr = modifyAddressBasedOnFlags(Addr, Flags);
  
          LLVM_DEBUG(dbgs() << "Resolving relocations Name: " << Name << "\t"
                            << format("0x%lx", Addr) << "\n");
          // This list may have been updated when we called getSymbolAddress, so
          // don't change this code to get the list earlier.
          RelocationList &Relocs = i->second;
          resolveRelocationList(Relocs, Addr);
        }
      }
  
      ExternalSymbolRelocations.erase(i);
    }
  }
  
  Error RuntimeDyldImpl::resolveExternalSymbols() {
    StringMap<JITEvaluatedSymbol> ExternalSymbolMap;
  
    // Resolution can trigger emission of more symbols, so iterate until
    // we've resolved *everything*.
    {
      JITSymbolResolver::LookupSet ResolvedSymbols;
  
      while (true) {
        JITSymbolResolver::LookupSet NewSymbols;
  
        for (auto &RelocKV : ExternalSymbolRelocations) {
          StringRef Name = RelocKV.first();
          if (!Name.empty() && !GlobalSymbolTable.count(Name) &&
              !ResolvedSymbols.count(Name))
            NewSymbols.insert(Name);
        }
  
        if (NewSymbols.empty())
          break;
  
  #ifdef _MSC_VER
        using ExpectedLookupResult =
            MSVCPExpected<JITSymbolResolver::LookupResult>;
  #else
        using ExpectedLookupResult = Expected<JITSymbolResolver::LookupResult>;
  #endif
  
        auto NewSymbolsP = std::make_shared<std::promise<ExpectedLookupResult>>();
        auto NewSymbolsF = NewSymbolsP->get_future();
        Resolver.lookup(NewSymbols,
                        [=](Expected<JITSymbolResolver::LookupResult> Result) {
                          NewSymbolsP->set_value(std::move(Result));
                        });
  
        auto NewResolverResults = NewSymbolsF.get();
  
        if (!NewResolverResults)
          return NewResolverResults.takeError();
  
        assert(NewResolverResults->size() == NewSymbols.size() &&
               "Should have errored on unresolved symbols");
  
        for (auto &RRKV : *NewResolverResults) {
          assert(!ResolvedSymbols.count(RRKV.first) && "Redundant resolution?");
          ExternalSymbolMap.insert(RRKV);
          ResolvedSymbols.insert(RRKV.first);
        }
      }
    }
  
    applyExternalSymbolRelocations(ExternalSymbolMap);
  
    return Error::success();
  }
  
  void RuntimeDyldImpl::finalizeAsync(
      std::unique_ptr<RuntimeDyldImpl> This,
      unique_function<void(Error)> OnEmitted,
      std::unique_ptr<MemoryBuffer> UnderlyingBuffer) {
  
    auto SharedThis = std::shared_ptr<RuntimeDyldImpl>(std::move(This));
    auto PostResolveContinuation =
        [SharedThis, OnEmitted = std::move(OnEmitted),
         UnderlyingBuffer = std::move(UnderlyingBuffer)](
            Expected<JITSymbolResolver::LookupResult> Result) mutable {
          if (!Result) {
            OnEmitted(Result.takeError());
            return;
          }
  
          /// Copy the result into a StringMap, where the keys are held by value.
          StringMap<JITEvaluatedSymbol> Resolved;
          for (auto &KV : *Result)
            Resolved[KV.first] = KV.second;
  
          SharedThis->applyExternalSymbolRelocations(Resolved);
          SharedThis->resolveLocalRelocations();
          SharedThis->registerEHFrames();
          std::string ErrMsg;
          if (SharedThis->MemMgr.finalizeMemory(&ErrMsg))
            OnEmitted(make_error<StringError>(std::move(ErrMsg),
                                              inconvertibleErrorCode()));
          else
            OnEmitted(Error::success());
        };
  
    JITSymbolResolver::LookupSet Symbols;
  
    for (auto &RelocKV : SharedThis->ExternalSymbolRelocations) {
      StringRef Name = RelocKV.first();
      assert(!Name.empty() && "Symbol has no name?");
      assert(!SharedThis->GlobalSymbolTable.count(Name) &&
             "Name already processed. RuntimeDyld instances can not be re-used "
             "when finalizing with finalizeAsync.");
      Symbols.insert(Name);
    }
  
    if (!Symbols.empty()) {
      SharedThis->Resolver.lookup(Symbols, std::move(PostResolveContinuation));
    } else
      PostResolveContinuation(std::map<StringRef, JITEvaluatedSymbol>());
  }
  
  //===----------------------------------------------------------------------===//
  // RuntimeDyld class implementation
  
  uint64_t RuntimeDyld::LoadedObjectInfo::getSectionLoadAddress(
                                            const object::SectionRef &Sec) const {
  
    auto I = ObjSecToIDMap.find(Sec);
    if (I != ObjSecToIDMap.end())
      return RTDyld.Sections[I->second].getLoadAddress();
  
    return 0;
  }
  
  void RuntimeDyld::MemoryManager::anchor() {}
  void JITSymbolResolver::anchor() {}
  void LegacyJITSymbolResolver::anchor() {}
  
  RuntimeDyld::RuntimeDyld(RuntimeDyld::MemoryManager &MemMgr,
                           JITSymbolResolver &Resolver)
      : MemMgr(MemMgr), Resolver(Resolver) {
    // FIXME: There's a potential issue lurking here if a single instance of
    // RuntimeDyld is used to load multiple objects.  The current implementation
    // associates a single memory manager with a RuntimeDyld instance.  Even
    // though the public class spawns a new 'impl' instance for each load,
    // they share a single memory manager.  This can become a problem when page
    // permissions are applied.
    Dyld = nullptr;
    ProcessAllSections = false;
  }
  
  RuntimeDyld::~RuntimeDyld() {}
  
  static std::unique_ptr<RuntimeDyldCOFF>
  createRuntimeDyldCOFF(
                       Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
                       JITSymbolResolver &Resolver, bool ProcessAllSections,
                       RuntimeDyld::NotifyStubEmittedFunction NotifyStubEmitted) {
    std::unique_ptr<RuntimeDyldCOFF> Dyld =
      RuntimeDyldCOFF::create(Arch, MM, Resolver);
    Dyld->setProcessAllSections(ProcessAllSections);
    Dyld->setNotifyStubEmitted(std::move(NotifyStubEmitted));
    return Dyld;
  }
  
  static std::unique_ptr<RuntimeDyldELF>
  createRuntimeDyldELF(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
                       JITSymbolResolver &Resolver, bool ProcessAllSections,
                       RuntimeDyld::NotifyStubEmittedFunction NotifyStubEmitted) {
    std::unique_ptr<RuntimeDyldELF> Dyld =
        RuntimeDyldELF::create(Arch, MM, Resolver);
    Dyld->setProcessAllSections(ProcessAllSections);
    Dyld->setNotifyStubEmitted(std::move(NotifyStubEmitted));
    return Dyld;
  }
  
  static std::unique_ptr<RuntimeDyldMachO>
  createRuntimeDyldMachO(
                       Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
                       JITSymbolResolver &Resolver,
                       bool ProcessAllSections,
                       RuntimeDyld::NotifyStubEmittedFunction NotifyStubEmitted) {
    std::unique_ptr<RuntimeDyldMachO> Dyld =
      RuntimeDyldMachO::create(Arch, MM, Resolver);
    Dyld->setProcessAllSections(ProcessAllSections);
    Dyld->setNotifyStubEmitted(std::move(NotifyStubEmitted));
    return Dyld;
  }
  
  std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
  RuntimeDyld::loadObject(const ObjectFile &Obj) {
    if (!Dyld) {
      if (Obj.isELF())
        Dyld =
            createRuntimeDyldELF(static_cast<Triple::ArchType>(Obj.getArch()),
                                 MemMgr, Resolver, ProcessAllSections,
                                 std::move(NotifyStubEmitted));
      else if (Obj.isMachO())
        Dyld = createRuntimeDyldMachO(
                 static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
                 ProcessAllSections, std::move(NotifyStubEmitted));
      else if (Obj.isCOFF())
        Dyld = createRuntimeDyldCOFF(
                 static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
                 ProcessAllSections, std::move(NotifyStubEmitted));
      else
        report_fatal_error("Incompatible object format!");
    }
  
    if (!Dyld->isCompatibleFile(Obj))
      report_fatal_error("Incompatible object format!");
  
    auto LoadedObjInfo = Dyld->loadObject(Obj);
    MemMgr.notifyObjectLoaded(*this, Obj);
    return LoadedObjInfo;
  }
  
  void *RuntimeDyld::getSymbolLocalAddress(StringRef Name) const {
    if (!Dyld)
      return nullptr;
    return Dyld->getSymbolLocalAddress(Name);
  }
  
  unsigned RuntimeDyld::getSymbolSectionID(StringRef Name) const {
    assert(Dyld && "No RuntimeDyld instance attached");
    return Dyld->getSymbolSectionID(Name);
  }
  
  JITEvaluatedSymbol RuntimeDyld::getSymbol(StringRef Name) const {
    if (!Dyld)
      return nullptr;
    return Dyld->getSymbol(Name);
  }
  
  std::map<StringRef, JITEvaluatedSymbol> RuntimeDyld::getSymbolTable() const {
    if (!Dyld)
      return std::map<StringRef, JITEvaluatedSymbol>();
    return Dyld->getSymbolTable();
  }
  
  void RuntimeDyld::resolveRelocations() { Dyld->resolveRelocations(); }
  
  void RuntimeDyld::reassignSectionAddress(unsigned SectionID, uint64_t Addr) {
    Dyld->reassignSectionAddress(SectionID, Addr);
  }
  
  void RuntimeDyld::mapSectionAddress(const void *LocalAddress,
                                      uint64_t TargetAddress) {
    Dyld->mapSectionAddress(LocalAddress, TargetAddress);
  }
  
  bool RuntimeDyld::hasError() { return Dyld->hasError(); }
  
  StringRef RuntimeDyld::getErrorString() { return Dyld->getErrorString(); }
  
  void RuntimeDyld::finalizeWithMemoryManagerLocking() {
    bool MemoryFinalizationLocked = MemMgr.FinalizationLocked;
    MemMgr.FinalizationLocked = true;
    resolveRelocations();
    registerEHFrames();
    if (!MemoryFinalizationLocked) {
      MemMgr.finalizeMemory();
      MemMgr.FinalizationLocked = false;
    }
  }
  
  StringRef RuntimeDyld::getSectionContent(unsigned SectionID) const {
    assert(Dyld && "No Dyld instance attached");
    return Dyld->getSectionContent(SectionID);
  }
  
  uint64_t RuntimeDyld::getSectionLoadAddress(unsigned SectionID) const {
    assert(Dyld && "No Dyld instance attached");
    return Dyld->getSectionLoadAddress(SectionID);
  }
  
  void RuntimeDyld::registerEHFrames() {
    if (Dyld)
      Dyld->registerEHFrames();
  }
  
  void RuntimeDyld::deregisterEHFrames() {
    if (Dyld)
      Dyld->deregisterEHFrames();
  }
  // FIXME: Kill this with fire once we have a new JIT linker: this is only here
  // so that we can re-use RuntimeDyld's implementation without twisting the
  // interface any further for ORC's purposes.
  void jitLinkForORC(object::ObjectFile &Obj,
                     std::unique_ptr<MemoryBuffer> UnderlyingBuffer,
                     RuntimeDyld::MemoryManager &MemMgr,
                     JITSymbolResolver &Resolver, bool ProcessAllSections,
                     unique_function<Error(
                         std::unique_ptr<RuntimeDyld::LoadedObjectInfo> LoadedObj,
                         std::map<StringRef, JITEvaluatedSymbol>)>
                         OnLoaded,
                     unique_function<void(Error)> OnEmitted) {
  
    RuntimeDyld RTDyld(MemMgr, Resolver);
    RTDyld.setProcessAllSections(ProcessAllSections);
  
    auto Info = RTDyld.loadObject(Obj);
  
    if (RTDyld.hasError()) {
      OnEmitted(make_error<StringError>(RTDyld.getErrorString(),
                                        inconvertibleErrorCode()));
      return;
    }
  
    if (auto Err = OnLoaded(std::move(Info), RTDyld.getSymbolTable()))
      OnEmitted(std::move(Err));
  
    RuntimeDyldImpl::finalizeAsync(std::move(RTDyld.Dyld), std::move(OnEmitted),
                                   std::move(UnderlyingBuffer));
  }
  
  } // end namespace llvm
  