llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h

//===-- RuntimeDyldMachO.h - 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.
//
//===----------------------------------------------------------------------===//
//
// MachO support for MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_RUNTIME_DYLD_MACHO_H
#define LLVM_RUNTIME_DYLD_MACHO_H

#include "ObjectImageCommon.h"
#include "RuntimeDyldImpl.h"
#include "llvm/Object/MachO.h"
#include "llvm/Support/Format.h"

#define DEBUG_TYPE "dyld"

using namespace llvm;
using namespace llvm::object;

namespace llvm {
class RuntimeDyldMachO : public RuntimeDyldImpl {
protected:
  struct SectionOffsetPair {
    unsigned SectionID;
    uint64_t Offset;
  };

  struct EHFrameRelatedSections {
    EHFrameRelatedSections()
        : EHFrameSID(RTDYLD_INVALID_SECTION_ID),
          TextSID(RTDYLD_INVALID_SECTION_ID),
          ExceptTabSID(RTDYLD_INVALID_SECTION_ID) {}
    EHFrameRelatedSections(SID EH, SID T, SID Ex)
        : EHFrameSID(EH), TextSID(T), ExceptTabSID(Ex) {}
    SID EHFrameSID;
    SID TextSID;
    SID ExceptTabSID;
  };

  // When a module is loaded we save the SectionID of the EH frame section
  // in a table until we receive a request to register all unregistered
  // EH frame sections with the memory manager.
  SmallVector<EHFrameRelatedSections, 2> UnregisteredEHFrameSections;

  RuntimeDyldMachO(RTDyldMemoryManager *mm) : RuntimeDyldImpl(mm) {}

  /// Extract the addend encoded in the instruction.
  int64_t decodeAddend(uint8_t *LocalAddress, unsigned NumBytes,
                       uint32_t RelType) const;

  /// Construct a RelocationValueRef representing the relocation target.
  /// For Symbols in known sections, this will return a RelocationValueRef
  /// representing a (SectionID, Offset) pair.
  /// For Symbols whose section is not known, this will return a
  /// (SymbolName, Offset) pair, where the Offset is taken from the instruction
  /// immediate (held in RE.Addend).
  /// In both cases the Addend field is *NOT* fixed up to be PC-relative. That
  /// should be done by the caller where appropriate by calling makePCRel on
  /// the RelocationValueRef.
  RelocationValueRef getRelocationValueRef(ObjectImage &ObjImg,
                                           const relocation_iterator &RI,
                                           const RelocationEntry &RE,
                                           ObjSectionToIDMap &ObjSectionToID,
                                           const SymbolTableMap &Symbols);

  /// Make the RelocationValueRef addend PC-relative.
  void makeValueAddendPCRel(RelocationValueRef &Value, ObjectImage &ObjImg,
                            const relocation_iterator &RI);

  /// Dump information about the relocation entry (RE) and resolved value.
  void dumpRelocationToResolve(const RelocationEntry &RE, uint64_t Value) const;

public:
  /// Create an ObjectImage from the given ObjectBuffer.
  static ObjectImage *createObjectImage(ObjectBuffer *InputBuffer) {
    return new ObjectImageCommon(InputBuffer);
  }

  /// Create an ObjectImage from the given ObjectFile.
  static ObjectImage *
  createObjectImageFromFile(std::unique_ptr<object::ObjectFile> InputObject) {
    return new ObjectImageCommon(std::move(InputObject));
  }

  /// Create a RuntimeDyldMachO instance for the given target architecture.
  static std::unique_ptr<RuntimeDyldMachO> create(Triple::ArchType Arch,
                                                  RTDyldMemoryManager *mm);

  /// Write the least significant 'Size' bytes in 'Value' out at the address
  /// pointed to by Addr. Check for overflow.
  bool writeBytesUnaligned(uint8_t *Addr, uint64_t Value, unsigned Size);

  SectionEntry &getSection(unsigned SectionID) { return Sections[SectionID]; }

  bool isCompatibleFormat(const ObjectBuffer *Buffer) const override;
  bool isCompatibleFile(const object::ObjectFile *Obj) const override;
  void registerEHFrames() override;
};

/// RuntimeDyldMachOTarget - Templated base class for generic MachO linker
/// algorithms and data structures.
///
/// Concrete, target specific sub-classes can be accessed via the impl()
/// methods. (i.e. the RuntimeDyldMachO hierarchy uses the Curiously
/// Recurring Template Idiom). Concrete subclasses for each target
/// can be found in ./Targets.
template <typename Impl>
class RuntimeDyldMachOCRTPBase : public RuntimeDyldMachO {
private:
  Impl &impl() { return static_cast<Impl &>(*this); }
  const Impl &impl() const { return static_cast<const Impl &>(*this); }

protected:

  /// Parse the given relocation, which must be a non-scattered, and
  /// return a RelocationEntry representing the information. The 'Addend' field
  /// will contain the unmodified instruction immediate.
  RelocationEntry getBasicRelocationEntry(unsigned SectionID,
                                          ObjectImage &ObjImg,
                                          const relocation_iterator &RI) const {
    const MachOObjectFile &Obj =
      static_cast<const MachOObjectFile &>(*ObjImg.getObjectFile());
    MachO::any_relocation_info RelInfo =
      Obj.getRelocation(RI->getRawDataRefImpl());

    const SectionEntry &Section = Sections[SectionID];
    bool IsPCRel = Obj.getAnyRelocationPCRel(RelInfo);
    unsigned Size = Obj.getAnyRelocationLength(RelInfo);
    uint64_t Offset;
    RI->getOffset(Offset);
    uint8_t *LocalAddress = Section.Address + Offset;
    unsigned NumBytes = 1 << Size;
    uint32_t RelType = Obj.getAnyRelocationType(RelInfo);
    int64_t Addend = impl().decodeAddend(LocalAddress, NumBytes, RelType);

    return RelocationEntry(SectionID, Offset, RelType, Addend, IsPCRel, Size);
  }

public:
  RuntimeDyldMachOCRTPBase(RTDyldMemoryManager *mm) : RuntimeDyldMachO(mm) {}

  void finalizeLoad(ObjectImage &ObjImg, ObjSectionToIDMap &SectionMap) {
    unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
    unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
    unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
    ObjSectionToIDMap::iterator i, e;

    for (i = SectionMap.begin(), e = SectionMap.end(); i != e; ++i) {
      const SectionRef &Section = i->first;
      StringRef Name;
      Section.getName(Name);
      if (Name == "__eh_frame")
        EHFrameSID = i->second;
      else if (Name == "__text")
        TextSID = i->second;
      else if (Name == "__gcc_except_tab")
        ExceptTabSID = i->second;
      else
        impl().finalizeSection(ObjImg, i->second, Section);
    }
    UnregisteredEHFrameSections.push_back(
        EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));
  }
};

} // end namespace llvm

#undef DEBUG_TYPE

#endif