text: //===-- RuntimeDyldMachO.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-=//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // Implementation of the MC-JIT runtime dynamic linker.
  //
  //===----------------------------------------------------------------------===//
  
  #include "RuntimeDyldMachO.h"
  #include "Targets/RuntimeDyldMachOAArch64.h"
  #include "Targets/RuntimeDyldMachOARM.h"
  #include "Targets/RuntimeDyldMachOI386.h"
  #include "Targets/RuntimeDyldMachOX86_64.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/StringRef.h"
  
  using namespace llvm;
  using namespace llvm::object;
  
  #define DEBUG_TYPE "dyld"
  
  namespace {
  
  class LoadedMachOObjectInfo
      : public RuntimeDyld::LoadedObjectInfoHelper<LoadedMachOObjectInfo> {
  public:
    LoadedMachOObjectInfo(RuntimeDyldImpl &RTDyld, unsigned BeginIdx,
                          unsigned EndIdx)
        : LoadedObjectInfoHelper(RTDyld, BeginIdx, EndIdx) {}
  
    OwningBinary<ObjectFile>
    getObjectForDebug(const ObjectFile &Obj) const override {
      return OwningBinary<ObjectFile>();
    }
  };
  
  }
  
  namespace llvm {
  
  int64_t RuntimeDyldMachO::memcpyAddend(const RelocationEntry &RE) const {
    unsigned NumBytes = 1 << RE.Size;
    uint8_t *Src = Sections[RE.SectionID].Address + RE.Offset;
  
    return static_cast<int64_t>(readBytesUnaligned(Src, NumBytes));
  }
  
  RelocationValueRef RuntimeDyldMachO::getRelocationValueRef(
      const ObjectFile &BaseTObj, const relocation_iterator &RI,
      const RelocationEntry &RE, ObjSectionToIDMap &ObjSectionToID) {
  
    const MachOObjectFile &Obj =
        static_cast<const MachOObjectFile &>(BaseTObj);
    MachO::any_relocation_info RelInfo =
        Obj.getRelocation(RI->getRawDataRefImpl());
    RelocationValueRef Value;
  
    bool IsExternal = Obj.getPlainRelocationExternal(RelInfo);
    if (IsExternal) {
      symbol_iterator Symbol = RI->getSymbol();
      StringRef TargetName;
      Symbol->getName(TargetName);
      RTDyldSymbolTable::const_iterator SI =
        GlobalSymbolTable.find(TargetName.data());
      if (SI != GlobalSymbolTable.end()) {
        const auto &SymInfo = SI->second;
        Value.SectionID = SymInfo.getSectionID();
        Value.Offset = SymInfo.getOffset() + RE.Addend;
      } else {
        Value.SymbolName = TargetName.data();
        Value.Offset = RE.Addend;
      }
    } else {
      SectionRef Sec = Obj.getAnyRelocationSection(RelInfo);
      bool IsCode = Sec.isText();
      Value.SectionID = findOrEmitSection(Obj, Sec, IsCode, ObjSectionToID);
      uint64_t Addr = Sec.getAddress();
      Value.Offset = RE.Addend - Addr;
    }
  
    return Value;
  }
  
  void RuntimeDyldMachO::makeValueAddendPCRel(RelocationValueRef &Value,
                                              const ObjectFile &BaseTObj,
                                              const relocation_iterator &RI,
                                              unsigned OffsetToNextPC) {
    const MachOObjectFile &Obj =
        static_cast<const MachOObjectFile &>(BaseTObj);
    MachO::any_relocation_info RelInfo =
        Obj.getRelocation(RI->getRawDataRefImpl());
  
    bool IsPCRel = Obj.getAnyRelocationPCRel(RelInfo);
    if (IsPCRel) {
      uint64_t RelocAddr = 0;
      RI->getAddress(RelocAddr);
      Value.Offset += RelocAddr + OffsetToNextPC;
    }
  }
  
  void RuntimeDyldMachO::dumpRelocationToResolve(const RelocationEntry &RE,
                                                 uint64_t Value) const {
    const SectionEntry &Section = Sections[RE.SectionID];
    uint8_t *LocalAddress = Section.Address + RE.Offset;
    uint64_t FinalAddress = Section.LoadAddress + RE.Offset;
  
    dbgs() << "resolveRelocation Section: " << RE.SectionID
           << " LocalAddress: " << format("%p", LocalAddress)
           << " FinalAddress: " << format("0x%016" PRIx64, FinalAddress)
           << " Value: " << format("0x%016" PRIx64, Value) << " Addend: " << RE.Addend
           << " isPCRel: " << RE.IsPCRel << " MachoType: " << RE.RelType
           << " Size: " << (1 << RE.Size) << "\n";
  }
  
  section_iterator
  RuntimeDyldMachO::getSectionByAddress(const MachOObjectFile &Obj,
                                        uint64_t Addr) {
    section_iterator SI = Obj.section_begin();
    section_iterator SE = Obj.section_end();
  
    for (; SI != SE; ++SI) {
      uint64_t SAddr = SI->getAddress();
      uint64_t SSize = SI->getSize();
      if ((Addr >= SAddr) && (Addr < SAddr + SSize))
        return SI;
    }
  
    return SE;
  }
  
  
  // Populate __pointers section.
  void RuntimeDyldMachO::populateIndirectSymbolPointersSection(
                                                      const MachOObjectFile &Obj,
                                                      const SectionRef &PTSection,
                                                      unsigned PTSectionID) {
    assert(!Obj.is64Bit() &&
           "Pointer table section not supported in 64-bit MachO.");
  
    MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
    MachO::section Sec32 = Obj.getSection(PTSection.getRawDataRefImpl());
    uint32_t PTSectionSize = Sec32.size;
    unsigned FirstIndirectSymbol = Sec32.reserved1;
    const unsigned PTEntrySize = 4;
    unsigned NumPTEntries = PTSectionSize / PTEntrySize;
    unsigned PTEntryOffset = 0;
  
    assert((PTSectionSize % PTEntrySize) == 0 &&
           "Pointers section does not contain a whole number of stubs?");
  
    DEBUG(dbgs() << "Populating pointer table section "
                 << Sections[PTSectionID].Name
                 << ", Section ID " << PTSectionID << ", "
                 << NumPTEntries << " entries, " << PTEntrySize
                 << " bytes each:\n");
  
    for (unsigned i = 0; i < NumPTEntries; ++i) {
      unsigned SymbolIndex =
        Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
      symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
      StringRef IndirectSymbolName;
      SI->getName(IndirectSymbolName);
      DEBUG(dbgs() << "  " << IndirectSymbolName << ": index " << SymbolIndex
            << ", PT offset: " << PTEntryOffset << "\n");
      RelocationEntry RE(PTSectionID, PTEntryOffset,
                         MachO::GENERIC_RELOC_VANILLA, 0, false, 2);
      addRelocationForSymbol(RE, IndirectSymbolName);
      PTEntryOffset += PTEntrySize;
    }
  }
  
  bool RuntimeDyldMachO::isCompatibleFile(const object::ObjectFile &Obj) const {
    return Obj.isMachO();
  }
  
  template <typename Impl>
  void RuntimeDyldMachOCRTPBase<Impl>::finalizeLoad(const ObjectFile &Obj,
                                                    ObjSectionToIDMap &SectionMap) {
    unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
    unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
    unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
  
    for (const auto &Section : Obj.sections()) {
      StringRef Name;
      Section.getName(Name);
  
      // Force emission of the __text, __eh_frame, and __gcc_except_tab sections
      // if they're present. Otherwise call down to the impl to handle other
      // sections that have already been emitted.
      if (Name == "__text")
        TextSID = findOrEmitSection(Obj, Section, true, SectionMap);
      else if (Name == "__eh_frame")
        EHFrameSID = findOrEmitSection(Obj, Section, false, SectionMap);
      else if (Name == "__gcc_except_tab")
        ExceptTabSID = findOrEmitSection(Obj, Section, true, SectionMap);
      else {
        auto I = SectionMap.find(Section);
        if (I != SectionMap.end())
          impl().finalizeSection(Obj, I->second, Section);
      }
    }
    UnregisteredEHFrameSections.push_back(
      EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));
  }
  
  template <typename Impl>
  unsigned char *RuntimeDyldMachOCRTPBase<Impl>::processFDE(unsigned char *P,
                                                            int64_t DeltaForText,
                                                            int64_t DeltaForEH) {
    typedef typename Impl::TargetPtrT TargetPtrT;
  
    DEBUG(dbgs() << "Processing FDE: Delta for text: " << DeltaForText
                 << ", Delta for EH: " << DeltaForEH << "\n");
    uint32_t Length = readBytesUnaligned(P, 4);
    P += 4;
    unsigned char *Ret = P + Length;
    uint32_t Offset = readBytesUnaligned(P, 4);
    if (Offset == 0) // is a CIE
      return Ret;
  
    P += 4;
    TargetPtrT FDELocation = readBytesUnaligned(P, sizeof(TargetPtrT));
    TargetPtrT NewLocation = FDELocation - DeltaForText;
    writeBytesUnaligned(NewLocation, P, sizeof(TargetPtrT));
  
    P += sizeof(TargetPtrT);
  
    // Skip the FDE address range
    P += sizeof(TargetPtrT);
  
    uint8_t Augmentationsize = *P;
    P += 1;
    if (Augmentationsize != 0) {
      TargetPtrT LSDA = readBytesUnaligned(P, sizeof(TargetPtrT));
      TargetPtrT NewLSDA = LSDA - DeltaForEH;
      writeBytesUnaligned(NewLSDA, P, sizeof(TargetPtrT));
    }
  
    return Ret;
  }
  
  static int64_t computeDelta(SectionEntry *A, SectionEntry *B) {
    int64_t ObjDistance =
      static_cast<int64_t>(A->ObjAddress) - static_cast<int64_t>(B->ObjAddress);
    int64_t MemDistance = A->LoadAddress - B->LoadAddress;
    return ObjDistance - MemDistance;
  }
  
  template <typename Impl>
  void RuntimeDyldMachOCRTPBase<Impl>::registerEHFrames() {
  
    for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
      EHFrameRelatedSections &SectionInfo = UnregisteredEHFrameSections[i];
      if (SectionInfo.EHFrameSID == RTDYLD_INVALID_SECTION_ID ||
          SectionInfo.TextSID == RTDYLD_INVALID_SECTION_ID)
        continue;
      SectionEntry *Text = &Sections[SectionInfo.TextSID];
      SectionEntry *EHFrame = &Sections[SectionInfo.EHFrameSID];
      SectionEntry *ExceptTab = nullptr;
      if (SectionInfo.ExceptTabSID != RTDYLD_INVALID_SECTION_ID)
        ExceptTab = &Sections[SectionInfo.ExceptTabSID];
  
      int64_t DeltaForText = computeDelta(Text, EHFrame);
      int64_t DeltaForEH = 0;
      if (ExceptTab)
        DeltaForEH = computeDelta(ExceptTab, EHFrame);
  
      unsigned char *P = EHFrame->Address;
      unsigned char *End = P + EHFrame->Size;
      do {
        P = processFDE(P, DeltaForText, DeltaForEH);
      } while (P != End);
  
      MemMgr.registerEHFrames(EHFrame->Address, EHFrame->LoadAddress,
                              EHFrame->Size);
    }
    UnregisteredEHFrameSections.clear();
  }
  
  std::unique_ptr<RuntimeDyldMachO>
  RuntimeDyldMachO::create(Triple::ArchType Arch,
                           RuntimeDyld::MemoryManager &MemMgr,
                           RuntimeDyld::SymbolResolver &Resolver) {
    switch (Arch) {
    default:
      llvm_unreachable("Unsupported target for RuntimeDyldMachO.");
      break;
    case Triple::arm:
      return make_unique<RuntimeDyldMachOARM>(MemMgr, Resolver);
    case Triple::aarch64:
      return make_unique<RuntimeDyldMachOAArch64>(MemMgr, Resolver);
    case Triple::x86:
      return make_unique<RuntimeDyldMachOI386>(MemMgr, Resolver);
    case Triple::x86_64:
      return make_unique<RuntimeDyldMachOX86_64>(MemMgr, Resolver);
    }
  }
  
  std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
  RuntimeDyldMachO::loadObject(const object::ObjectFile &O) {
    unsigned SectionStartIdx, SectionEndIdx;
    std::tie(SectionStartIdx, SectionEndIdx) = loadObjectImpl(O);
    return llvm::make_unique<LoadedMachOObjectInfo>(*this, SectionStartIdx,
                                                    SectionEndIdx);
  }
  
  } // end namespace llvm
  