C++ SectionRef类代码示例

MCMachObjectSymbolizer::MCMachObjectSymbolizer(
    MCContext &Ctx, std::unique_ptr<MCRelocationInfo> &RelInfo,
    const MachOObjectFile *MOOF)
    : MCObjectSymbolizer(Ctx, RelInfo, MOOF), MOOF(MOOF), StubsStart(0),
      StubsCount(0), StubSize(0), StubsIndSymIndex(0) {

  for (const SectionRef &Section : MOOF->sections()) {
    StringRef Name;
    Section.getName(Name);
    if (Name == "__stubs") {
      SectionRef StubsSec = Section;
      if (MOOF->is64Bit()) {
        MachO::section_64 S = MOOF->getSection64(StubsSec.getRawDataRefImpl());
        StubsIndSymIndex = S.reserved1;
        StubSize = S.reserved2;
      } else {
        MachO::section S = MOOF->getSection(StubsSec.getRawDataRefImpl());
        StubsIndSymIndex = S.reserved1;
        StubSize = S.reserved2;
      }
      assert(StubSize && "Mach-O stub entry size can't be zero!");
      StubsSec.getAddress(StubsStart);
      StubsSec.getSize(StubsCount);
      StubsCount /= StubSize;
    }
  }
}

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);
    SymbolTableMap::const_iterator SI =
      GlobalSymbolTable.find(TargetName.data());
    if (SI != GlobalSymbolTable.end()) {
      Value.SectionID = SI->second.first;
      Value.Offset = SI->second.second + RE.Addend;
    } else {
      Value.SymbolName = TargetName.data();
      Value.Offset = RE.Addend;
    }
  } else {
    SectionRef Sec = Obj.getRelocationSection(RelInfo);
    bool IsCode = Sec.isText();
    Value.SectionID = findOrEmitSection(Obj, Sec, IsCode, ObjSectionToID);
    uint64_t Addr = Sec.getAddress();
    Value.Offset = RE.Addend - Addr;
  }

  return Value;
}

static void getSectionsAndSymbols(const macho::Header &Header,
                                  MachOObjectFile *MachOObj,
                             InMemoryStruct<macho::SymtabLoadCommand> *SymtabLC,
                                  std::vector<SectionRef> &Sections,
                                  std::vector<SymbolRef> &Symbols,
                                  SmallVectorImpl<uint64_t> &FoundFns) {
  error_code ec;
  for (symbol_iterator SI = MachOObj->begin_symbols(),
       SE = MachOObj->end_symbols(); SI != SE; SI.increment(ec))
    Symbols.push_back(*SI);

  for (section_iterator SI = MachOObj->begin_sections(),
       SE = MachOObj->end_sections(); SI != SE; SI.increment(ec)) {
    SectionRef SR = *SI;
    StringRef SectName;
    SR.getName(SectName);
    Sections.push_back(*SI);
  }

  for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
    const MachOObject::LoadCommandInfo &LCI =
       MachOObj->getObject()->getLoadCommandInfo(i);
    if (LCI.Command.Type == macho::LCT_FunctionStarts) {
      // We found a function starts segment, parse the addresses for later
      // consumption.
      InMemoryStruct<macho::LinkeditDataLoadCommand> LLC;
      MachOObj->getObject()->ReadLinkeditDataLoadCommand(LCI, LLC);

      MachOObj->getObject()->ReadULEB128s(LLC->DataOffset, FoundFns);
    }
  }
}

// compute stub buffer size for the given section
unsigned RuntimeDyldImpl::computeSectionStubBufSize(ObjectImage &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.begin_sections(), SE = Obj.end_sections();
       SI != SE; ++SI) {
    section_iterator RelSecI = SI->getRelocatedSection();
    if (!(RelSecI == Section))
      continue;

    for (const RelocationRef &Reloc : SI->relocations()) {
      (void)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;
}

relocation_iterator RuntimeDyldMachO::processScatteredVANILLA(
                          unsigned SectionID, relocation_iterator RelI,
                          const ObjectFile &BaseObjT,
                          RuntimeDyldMachO::ObjSectionToIDMap &ObjSectionToID) {
  const MachOObjectFile &Obj =
    static_cast<const MachOObjectFile&>(BaseObjT);
  MachO::any_relocation_info RE =
    Obj.getRelocation(RelI->getRawDataRefImpl());

  SectionEntry &Section = Sections[SectionID];
  uint32_t RelocType = Obj.getAnyRelocationType(RE);
  bool IsPCRel = Obj.getAnyRelocationPCRel(RE);
  unsigned Size = Obj.getAnyRelocationLength(RE);
  uint64_t Offset = RelI->getOffset();
  uint8_t *LocalAddress = Section.getAddressWithOffset(Offset);
  unsigned NumBytes = 1 << Size;
  int64_t Addend = readBytesUnaligned(LocalAddress, NumBytes);

  unsigned SymbolBaseAddr = Obj.getScatteredRelocationValue(RE);
  section_iterator TargetSI = getSectionByAddress(Obj, SymbolBaseAddr);
  assert(TargetSI != Obj.section_end() && "Can't find section for symbol");
  uint64_t SectionBaseAddr = TargetSI->getAddress();
  SectionRef TargetSection = *TargetSI;
  bool IsCode = TargetSection.isText();
  uint32_t TargetSectionID =
    findOrEmitSection(Obj, TargetSection, IsCode, ObjSectionToID);

  Addend -= SectionBaseAddr;
  RelocationEntry R(SectionID, Offset, RelocType, Addend, IsPCRel, Size);

  addRelocationForSection(R, TargetSectionID);

  return ++RelI;
}

 explicit section(const SectionRef& sec) {
     StringRef name;
     if(error_code err = sec.getName(name))
         llvm_binary_fail(err);
     this->name_ = name.str();
     if (error_code err = sec.getAddress(this->addr_))
         llvm_binary_fail(err);
     
     if (error_code err = sec.getSize(this->size_))
         llvm_binary_fail(err);
 }

static void
getSectionsAndSymbols(const MachO::mach_header Header,
                      MachOObjectFile *MachOObj,
                      std::vector<SectionRef> &Sections,
                      std::vector<SymbolRef> &Symbols,
                      SmallVectorImpl<uint64_t> &FoundFns,
                      uint64_t &BaseSegmentAddress) {
  for (symbol_iterator SI = MachOObj->symbol_begin(),
                       SE = MachOObj->symbol_end();
       SI != SE; ++SI)
    Symbols.push_back(*SI);

  for (section_iterator SI = MachOObj->section_begin(),
                        SE = MachOObj->section_end();
       SI != SE; ++SI) {
    SectionRef SR = *SI;
    StringRef SectName;
    SR.getName(SectName);
    Sections.push_back(*SI);
  }

  MachOObjectFile::LoadCommandInfo Command =
    MachOObj->getFirstLoadCommandInfo();
  bool BaseSegmentAddressSet = false;
  for (unsigned i = 0; ; ++i) {
    if (Command.C.cmd == MachO::LC_FUNCTION_STARTS) {
      // We found a function starts segment, parse the addresses for later
      // consumption.
      MachO::linkedit_data_command LLC =
        MachOObj->getLinkeditDataLoadCommand(Command);

      MachOObj->ReadULEB128s(LLC.dataoff, FoundFns);
    }
    else if (Command.C.cmd == MachO::LC_SEGMENT) {
      MachO::segment_command SLC =
        MachOObj->getSegmentLoadCommand(Command);
      StringRef SegName = SLC.segname;
      if(!BaseSegmentAddressSet && SegName != "__PAGEZERO") {
        BaseSegmentAddressSet = true;
        BaseSegmentAddress = SLC.vmaddr;
      }
    }

    if (i == Header.ncmds - 1)
      break;
    else
      Command = MachOObj->getNextLoadCommandInfo(Command);
  }
}

void COFFDumper::printRelocation(const SectionRef &Section,
                                 const RelocationRef &Reloc) {
  uint64_t Offset;
  uint64_t RelocType;
  SmallString<32> RelocName;
  StringRef SymbolName;
  StringRef Contents;
  if (error(Reloc.getOffset(Offset)))
    return;
  if (error(Reloc.getType(RelocType)))
    return;
  if (error(Reloc.getTypeName(RelocName)))
    return;
  symbol_iterator Symbol = Reloc.getSymbol();
  if (error(Symbol->getName(SymbolName)))
    return;
  if (error(Section.getContents(Contents)))
    return;

  if (opts::ExpandRelocs) {
    DictScope Group(W, "Relocation");
    W.printHex("Offset", Offset);
    W.printNumber("Type", RelocName, RelocType);
    W.printString("Symbol", SymbolName.size() > 0 ? SymbolName : "-");
  } else {
    raw_ostream& OS = W.startLine();
    OS << W.hex(Offset)
       << " " << RelocName
       << " " << (SymbolName.size() > 0 ? SymbolName : "-")
       << "\n";
  }
}

static bool isRequiredForExecution(const SectionRef &Section) {
  const ObjectFile *Obj = Section.getObject();
  if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
    return ELFObj->getSectionFlags(Section) & ELF::SHF_ALLOC;
  assert(isa<MachOObjectFile>(Obj));
  return true;
 }

static bool isReadOnlyData(const SectionRef &Section) {
  const ObjectFile *Obj = Section.getObject();
  if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
    return !(ELFObj->getSectionFlags(Section) &
             (ELF::SHF_WRITE | ELF::SHF_EXECINSTR));
  assert(isa<MachOObjectFile>(Obj));
  return false;
}

/// Given a relocation from __compact_unwind, consisting of the RelocationRef
/// and data being relocated, determine the best base Name and Addend to use for
/// display purposes.
///
/// 1. An Extern relocation will directly reference a symbol (and the data is
///    then already an addend), so use that.
/// 2. Otherwise the data is an offset in the object file's layout; try to find
//     a symbol before it in the same section, and use the offset from there.
/// 3. Finally, if all that fails, fall back to an offset from the start of the
///    referenced section.
static void findUnwindRelocNameAddend(const MachOObjectFile *Obj,
                                      std::map<uint64_t, SymbolRef> &Symbols,
                                      const RelocationRef &Reloc,
                                      uint64_t Addr,
                                      StringRef &Name, uint64_t &Addend) {
  if (Reloc.getSymbol() != Obj->symbol_end()) {
    Reloc.getSymbol()->getName(Name);
    Addend = Addr;
    return;
  }

  auto RE = Obj->getRelocation(Reloc.getRawDataRefImpl());
  SectionRef RelocSection = Obj->getRelocationSection(RE);

  uint64_t SectionAddr;
  RelocSection.getAddress(SectionAddr);

  auto Sym = Symbols.upper_bound(Addr);
  if (Sym == Symbols.begin()) {
    // The first symbol in the object is after this reference, the best we can
    // do is section-relative notation.
    RelocSection.getName(Name);
    Addend = Addr - SectionAddr;
    return;
  }

  // Go back one so that SymbolAddress <= Addr.
  --Sym;

  section_iterator SymSection = Obj->section_end();
  Sym->second.getSection(SymSection);
  if (RelocSection == *SymSection) {
    // There's a valid symbol in the same section before this reference.
    Sym->second.getName(Name);
    Addend = Addr - Sym->first;
    return;
  }

  // There is a symbol before this reference, but it's in a different
  // section. Probably not helpful to mention it, so use the section name.
  RelocSection.getName(Name);
  Addend = Addr - SectionAddr;
}

static bool isZeroInit(const SectionRef &Section) {
  const ObjectFile *Obj = Section.getObject();
  if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
    return ELFObj->getSectionType(Section) == ELF::SHT_NOBITS;

  auto *MachO = cast<MachOObjectFile>(Obj);
  unsigned SectionType = MachO->getSectionType(Section);
  return SectionType == MachO::S_ZEROFILL ||
         SectionType == MachO::S_GB_ZEROFILL;
}

bool checked(const ELFObjectFile<T> &obj, SectionRef sec_ref) {
    typedef typename ELFObjectFile<T>::Elf_Shdr Elf_Shdr;

    auto &elf = *obj.getELFFile();
    const Elf_Shdr *RelSec = obj.getSection(sec_ref.getRawDataRefImpl());
    auto symsec = elf.getSection(RelSec->sh_link);
    if (!symsec) return false;
    uint32_t sec_typ = (*symsec)->sh_type;
    return
        (sec_typ == ELF::SHT_SYMTAB || sec_typ == ELF::SHT_DYNSYM);
}

void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
                                                       const SectionRef &Sec,
                                                       uint64_t Addr) {
  DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
  Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
                          reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));

  // This assumes the address passed in matches the target address bitness
  // The template-based type cast handles everything else.
  shdr->sh_addr = static_cast<addr_type>(Addr);
}

static void
getSectionsAndSymbols(const macho::Header Header,
                      MachOObjectFile *MachOObj,
                      std::vector<SectionRef> &Sections,
                      std::vector<SymbolRef> &Symbols,
                      SmallVectorImpl<uint64_t> &FoundFns) {
  error_code ec;
  for (symbol_iterator SI = MachOObj->begin_symbols(),
       SE = MachOObj->end_symbols(); SI != SE; SI.increment(ec))
    Symbols.push_back(*SI);

  for (section_iterator SI = MachOObj->begin_sections(),
       SE = MachOObj->end_sections(); SI != SE; SI.increment(ec)) {
    SectionRef SR = *SI;
    StringRef SectName;
    SR.getName(SectName);
    Sections.push_back(*SI);
  }

  MachOObjectFile::LoadCommandInfo Command =
    MachOObj->getFirstLoadCommandInfo();
  for (unsigned i = 0; ; ++i) {
    if (Command.C.Type == macho::LCT_FunctionStarts) {
      // We found a function starts segment, parse the addresses for later
      // consumption.
      macho::LinkeditDataLoadCommand LLC =
        MachOObj->getLinkeditDataLoadCommand(Command);

      MachOObj->ReadULEB128s(LLC.DataOffset, FoundFns);
    }

    if (i == Header.NumLoadCommands - 1)
      break;
    else
      Command = MachOObj->getNextLoadCommandInfo(Command);
  }
}