C++ SectionRef::getAlignment方法代码示例

// 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;
}

unsigned RuntimeDyldImpl::emitSection(ObjectImage &Obj,
                                      const SectionRef &Section,
                                      bool IsCode) {

  unsigned StubBufSize = 0,
           StubSize = getMaxStubSize();
  error_code err;
  const ObjectFile *ObjFile = Obj.getObjectFile();
  // 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.
  if (StubSize > 0) {
    for (section_iterator SI = ObjFile->begin_sections(),
           SE = ObjFile->end_sections();
         SI != SE; SI.increment(err), Check(err)) {
      section_iterator RelSecI = SI->getRelocatedSection();
      if (!(RelSecI == Section))
        continue;

      for (relocation_iterator I = SI->begin_relocations(),
             E = SI->end_relocations(); I != E; I.increment(err), Check(err)) {
        StubBufSize += StubSize;
      }
    }
  }

  StringRef data;
  uint64_t Alignment64;
  Check(Section.getContents(data));
  Check(Section.getAlignment(Alignment64));

  unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
  bool IsRequired;
  bool IsVirtual;
  bool IsZeroInit;
  bool IsReadOnly;
  uint64_t DataSize;
  StringRef Name;
  Check(Section.isRequiredForExecution(IsRequired));
  Check(Section.isVirtual(IsVirtual));
  Check(Section.isZeroInit(IsZeroInit));
  Check(Section.isReadOnlyData(IsReadOnly));
  Check(Section.getSize(DataSize));
  Check(Section.getName(Name));
  if (StubSize > 0) {
    unsigned StubAlignment = getStubAlignment();
    unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
    if (StubAlignment > EndAlignment)
      StubBufSize += StubAlignment - EndAlignment;
  }

  unsigned Allocate;
  unsigned SectionID = Sections.size();
  uint8_t *Addr;
  const char *pData = 0;

  // Some sections, such as debug info, don't need to be loaded for execution.
  // Leave those where they are.
  if (IsRequired) {
    Allocate = DataSize + StubBufSize;
    Addr = IsCode
      ? MemMgr->allocateCodeSection(Allocate, Alignment, SectionID)
      : MemMgr->allocateDataSection(Allocate, Alignment, SectionID, IsReadOnly);
    if (!Addr)
      report_fatal_error("Unable to allocate section memory!");

    // Virtual sections have no data in the object image, so leave pData = 0
    if (!IsVirtual)
      pData = data.data();

    // Zero-initialize or copy the data from the image
    if (IsZeroInit || IsVirtual)
      memset(Addr, 0, DataSize);
    else
      memcpy(Addr, pData, DataSize);

    DEBUG(dbgs() << "emitSection SectionID: " << SectionID
                 << " Name: " << Name
                 << " obj addr: " << format("%p", pData)
                 << " new addr: " << format("%p", Addr)
                 << " DataSize: " << DataSize
                 << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate
                 << "\n");
    Obj.updateSectionAddress(Section, (uint64_t)Addr);
  }
  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 = 0;
    DEBUG(dbgs() << "emitSection SectionID: " << SectionID
                 << " Name: " << Name
                 << " obj addr: " << format("%p", data.data())
                 << " new addr: 0"
                 << " DataSize: " << DataSize
                 << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate
                 << "\n");
//.........这里部分代码省略.........

unsigned RuntimeDyldImpl::emitSection(const SectionRef &Section,
                                      bool IsCode) {

  unsigned StubBufSize = 0,
           StubSize = getMaxStubSize();
  error_code err;
  if (StubSize > 0) {
    for (relocation_iterator i = Section.begin_relocations(),
         e = Section.end_relocations(); i != e; i.increment(err), Check(err))
      StubBufSize += StubSize;
  }
  StringRef data;
  uint64_t Alignment64;
  Check(Section.getContents(data));
  Check(Section.getAlignment(Alignment64));

  unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
  bool IsRequired;
  bool IsVirtual;
  bool IsZeroInit;
  uint64_t DataSize;
  Check(Section.isRequiredForExecution(IsRequired));
  Check(Section.isVirtual(IsVirtual));
  Check(Section.isZeroInit(IsZeroInit));
  Check(Section.getSize(DataSize));

  unsigned Allocate;
  unsigned SectionID = Sections.size();
  uint8_t *Addr;
  const char *pData = 0;

  // Some sections, such as debug info, don't need to be loaded for execution.
  // Leave those where they are.
  if (IsRequired) {
    Allocate = DataSize + StubBufSize;
    Addr = IsCode
      ? MemMgr->allocateCodeSection(Allocate, Alignment, SectionID)
      : MemMgr->allocateDataSection(Allocate, Alignment, SectionID);
    if (!Addr)
      report_fatal_error("Unable to allocate section memory!");

    // Virtual sections have no data in the object image, so leave pData = 0
    if (!IsVirtual)
      pData = data.data();

    // Zero-initialize or copy the data from the image
    if (IsZeroInit || IsVirtual)
      memset(Addr, 0, DataSize);
    else
      memcpy(Addr, pData, DataSize);

    DEBUG(dbgs() << "emitSection SectionID: " << SectionID
                 << " 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 = 0;
    DEBUG(dbgs() << "emitSection SectionID: " << SectionID
                 << " obj addr: " << format("%p", data.data())
                 << " new addr: 0"
                 << " DataSize: " << DataSize
                 << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate
                 << "\n");
  }

  Sections.push_back(SectionEntry(Addr, Allocate, DataSize,(uintptr_t)pData));
  return SectionID;
}

unsigned RuntimeDyldImpl::emitSection(ObjectImage &Obj,
                                      const SectionRef &Section, bool IsCode) {

  StringRef data;
  uint64_t Alignment64;
  Check(Section.getContents(data));
  Check(Section.getAlignment(Alignment64));

  unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
  bool IsRequired;
  bool IsVirtual;
  bool IsZeroInit;
  bool IsReadOnly;
  uint64_t DataSize;
  unsigned PaddingSize = 0;
  unsigned StubBufSize = 0;
  StringRef Name;
  Check(Section.isRequiredForExecution(IsRequired));
  Check(Section.isVirtual(IsVirtual));
  Check(Section.isZeroInit(IsZeroInit));
  Check(Section.isReadOnlyData(IsReadOnly));
  Check(Section.getSize(DataSize));
  Check(Section.getName(Name));

  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 = 0;

  // Some sections, such as debug info, don't need to be loaded for execution.
  // Leave those where they are.
  if (IsRequired) {
    Allocate = DataSize + PaddingSize + StubBufSize;
    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!");

    // Virtual sections have no data in the object image, so leave pData = 0
    if (!IsVirtual)
      pData = data.data();

    // 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 so that the stub offset is set correctly.
      DataSize += PaddingSize;
    }

    DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
                 << " obj addr: " << format("%p", pData)
                 << " new addr: " << format("%p", Addr)
                 << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate << "\n");
    Obj.updateSectionAddress(Section, (uint64_t)Addr);
  } 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 = 0;
    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, (uintptr_t)pData));
  return SectionID;
}