//===- lib/ReaderWriter/ELF/SegmentChunks.h -------------------------------===//
//
//                             The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "SegmentChunks.h"
#include "TargetLayout.h"

namespace lld {
namespace elf {

template <class ELFT>
bool SegmentSlice<ELFT>::compare_slices(SegmentSlice<ELFT> *a,
                                        SegmentSlice<ELFT> *b) {
  return a->startSection() < b->startSection();
}

template <class ELFT>
Segment<ELFT>::Segment(const ELFLinkingContext &ctx, StringRef name,
                       const typename TargetLayout<ELFT>::SegmentType type)
    : Chunk<ELFT>(name, Chunk<ELFT>::Kind::ELFSegment, ctx), _segmentType(type),
      _flags(0), _atomflags(0) {
  this->_alignment = 1;
  this->_fsize = 0;
  _outputMagic = ctx.getOutputMagic();
}

// This function actually is used, but not in all instantiations of Segment.
LLVM_ATTRIBUTE_UNUSED
static DefinedAtom::ContentPermissions toAtomPerms(uint64_t flags) {
  switch (flags & (SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR)) {
  case SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR:
    return DefinedAtom::permRWX;
  case SHF_ALLOC | SHF_EXECINSTR:
    return DefinedAtom::permR_X;
  case SHF_ALLOC:
    return DefinedAtom::permR__;
  case SHF_ALLOC | SHF_WRITE:
    return DefinedAtom::permRW_;
  default:
    return DefinedAtom::permUnknown;
  }
}

template <class ELFT> void Segment<ELFT>::append(Chunk<ELFT> *chunk) {
  _sections.push_back(chunk);
  Section<ELFT> *section = dyn_cast<Section<ELFT>>(chunk);
  if (!section)
    return;
  if (_flags < section->getFlags())
    _flags |= section->getFlags();
  if (_atomflags < toAtomPerms(_flags))
    _atomflags = toAtomPerms(_flags);
  if (this->_alignment < section->alignment())
    this->_alignment = section->alignment();
}

template <class ELFT>
bool Segment<ELFT>::compareSegments(Segment<ELFT> *sega, Segment<ELFT> *segb) {
  int64_t type1 = sega->segmentType();
  int64_t type2 = segb->segmentType();

  if (type1 == type2)
    return sega->atomflags() < segb->atomflags();

  // The single PT_PHDR segment is required to precede any loadable
  // segment.  We simply make it always first.
  if (type1 == llvm::ELF::PT_PHDR)
    return true;
  if (type2 == llvm::ELF::PT_PHDR)
    return false;

  // The single PT_INTERP segment is required to precede any loadable
  // segment.  We simply make it always second.
  if (type1 == llvm::ELF::PT_INTERP)
    return true;
  if (type2 == llvm::ELF::PT_INTERP)
    return false;

  // We then put PT_LOAD segments before any other segments.
  if (type1 == llvm::ELF::PT_LOAD)
    return true;
  if (type2 == llvm::ELF::PT_LOAD)
    return false;

  // We put the PT_GNU_RELRO segment last, because that is where the
  // dynamic linker expects to find it
  if (type1 == llvm::ELF::PT_GNU_RELRO)
    return false;
  if (type2 == llvm::ELF::PT_GNU_RELRO)
    return true;

  // We put the PT_TLS segment last except for the PT_GNU_RELRO
  // segment, because that is where the dynamic linker expects to find
  if (type1 == llvm::ELF::PT_TLS)
    return false;
  if (type2 == llvm::ELF::PT_TLS)
    return true;

  // Otherwise compare the types to establish an arbitrary ordering.
  // FIXME: Should figure out if we should just make all other types compare
  // equal, but if so, we should probably do the same for atom flags and change
  // users of this to use stable_sort.
  return type1 < type2;
}

template <class ELFT>
void Segment<ELFT>::assignFileOffsets(uint64_t startOffset) {
  uint64_t fileOffset = startOffset;
  uint64_t curSliceFileOffset = fileOffset;
  bool isDataPageAlignedForNMagic = false;
  bool alignSegments = this->_ctx.alignSegments();
  uint64_t p_align = this->_ctx.getPageSize();
  uint64_t lastVirtualAddress = 0;

  this->setFileOffset(startOffset);
  for (auto &slice : slices()) {
    bool isFirstSection = true;
    for (auto section : slice->sections()) {
      // Handle linker script expressions, which may change the offset
      if (!isFirstSection)
        if (auto expr = dyn_cast<ExpressionChunk<ELFT>>(section))
          fileOffset += expr->virtualAddr() - lastVirtualAddress;
      // Align fileoffset to the alignment of the section.
      fileOffset = llvm::RoundUpToAlignment(fileOffset, section->alignment());
      // If the linker outputmagic is set to OutputMagic::NMAGIC, align the Data
      // to a page boundary
      if (isFirstSection &&
          _outputMagic != ELFLinkingContext::OutputMagic::NMAGIC &&
          _outputMagic != ELFLinkingContext::OutputMagic::OMAGIC) {
        // Align to a page only if the output is not
        // OutputMagic::NMAGIC/OutputMagic::OMAGIC
        if (alignSegments)
          fileOffset = llvm::RoundUpToAlignment(fileOffset, p_align);
        else {
          // Align according to ELF spec.
          // in p75, http://www.sco.com/developers/devspecs/gabi41.pdf
          uint64_t virtualAddress = slice->virtualAddr();
          Section<ELFT> *sect = dyn_cast<Section<ELFT>>(section);
          if (sect && sect->isLoadableSection() &&
              ((virtualAddress & (p_align - 1)) !=
               (fileOffset & (p_align - 1))))
            fileOffset = llvm::RoundUpToAlignment(fileOffset, p_align) +
                         (virtualAddress % p_align);
        }
      } else if (!isDataPageAlignedForNMagic && needAlign(section)) {
        fileOffset =
            llvm::RoundUpToAlignment(fileOffset, this->_ctx.getPageSize());
        isDataPageAlignedForNMagic = true;
      }
      if (isFirstSection) {
        slice->setFileOffset(fileOffset);
        isFirstSection = false;
        curSliceFileOffset = fileOffset;
      }
      section->setFileOffset(fileOffset);
      fileOffset += section->fileSize();
      lastVirtualAddress = section->virtualAddr() + section->memSize();
    }
    slice->setFileSize(fileOffset - curSliceFileOffset);
  }
  this->setFileSize(fileOffset - startOffset);
}

/// \brief Assign virtual addresses to the slices
template <class ELFT> void Segment<ELFT>::assignVirtualAddress(uint64_t addr) {
  int startSection = 0;
  int currSection = 0;
  SectionIter startSectionIter;

  // slice align is set to the max alignment of the chunks that are
  // contained in the slice
  uint64_t sliceAlign = 0;
  // Current slice size
  uint64_t curSliceSize = 0;
  // Current Slice File Offset
  uint64_t curSliceAddress = 0;

  startSectionIter = _sections.begin();
  startSection = 0;
  bool isFirstSection = true;
  bool isDataPageAlignedForNMagic = false;
  uint64_t startAddr = addr;
  SegmentSlice<ELFT> *slice = nullptr;
  uint64_t tlsStartAddr = 0;
  bool alignSegments = this->_ctx.alignSegments();
  StringRef prevOutputSectionName = StringRef();

  for (auto si = _sections.begin(); si != _sections.end(); ++si) {
    // If this is first section in the segment, page align the section start
    // address. The linker needs to align the data section to a page boundary
    // only if NMAGIC is set.
    if (isFirstSection) {
      isFirstSection = false;
      if (alignSegments &&
          _outputMagic != ELFLinkingContext::OutputMagic::NMAGIC &&
          _outputMagic != ELFLinkingContext::OutputMagic::OMAGIC)
        // Align to a page only if the output is not
        // OutputMagic::NMAGIC/OutputMagic::OMAGIC
        startAddr =
            llvm::RoundUpToAlignment(startAddr, this->_ctx.getPageSize());
      else if (!isDataPageAlignedForNMagic && needAlign(*si)) {
        // If the linker outputmagic is set to OutputMagic::NMAGIC, align the
        // Data to a page boundary.
        startAddr =
            llvm::RoundUpToAlignment(startAddr, this->_ctx.getPageSize());
        isDataPageAlignedForNMagic = true;
      }
      // align the startOffset to the section alignment
      uint64_t newAddr =
          llvm::RoundUpToAlignment(startAddr, (*si)->alignment());
      // Handle linker script expressions, which *may update newAddr* if the
      // expression assigns to "."
      if (auto expr = dyn_cast<ExpressionChunk<ELFT>>(*si))
        expr->evalExpr(newAddr);
      curSliceAddress = newAddr;
      sliceAlign = (*si)->alignment();
      (*si)->setVirtualAddr(curSliceAddress);

      // Handle TLS.
      if (auto section = dyn_cast<Section<ELFT>>(*si)) {
        if (section->getSegmentType() == llvm::ELF::PT_TLS) {
          tlsStartAddr =
              llvm::RoundUpToAlignment(tlsStartAddr, (*si)->alignment());
          section->assignVirtualAddress(tlsStartAddr);
          tlsStartAddr += (*si)->memSize();
        } else {
          section->assignVirtualAddress(newAddr);
        }
      }
      // TBSS section is special in that it doesn't contribute to memory of any
      // segment. If we see a tbss section, don't add memory size to addr The
      // fileOffset is automatically taken care of since TBSS section does not
      // end up using file size
      if ((*si)->order() != TargetLayout<ELFT>::ORDER_TBSS)
        curSliceSize = (*si)->memSize();
    } else {
      uint64_t curAddr = curSliceAddress + curSliceSize;
      if (!isDataPageAlignedForNMagic && needAlign(*si)) {
        // If the linker outputmagic is set to OutputMagic::NMAGIC, align the
        // Data
        // to a page boundary
        curAddr = llvm::RoundUpToAlignment(curAddr, this->_ctx.getPageSize());
        isDataPageAlignedForNMagic = true;
      }
      uint64_t newAddr = llvm::RoundUpToAlignment(curAddr, (*si)->alignment());
      // Handle linker script expressions, which *may update newAddr* if the
      // expression assigns to "."
      if (auto expr = dyn_cast<ExpressionChunk<ELFT>>(*si))
        expr->evalExpr(newAddr);
      Section<ELFT> *sec = dyn_cast<Section<ELFT>>(*si);
      StringRef curOutputSectionName;
      if (sec)
        curOutputSectionName = sec->outputSectionName();
      else {
        // If this is a linker script expression, propagate the name of the
        // previous section instead
        if (isa<ExpressionChunk<ELFT>>(*si))
          curOutputSectionName = prevOutputSectionName;
        else
          curOutputSectionName = (*si)->name();
      }
      bool autoCreateSlice = true;
      if (curOutputSectionName == prevOutputSectionName)
        autoCreateSlice = false;
      // If the newAddress computed is more than a page away, let's create
      // a separate segment, so that memory is not used up while running.
      // Dont create a slice, if the new section falls in the same output
      // section as the previous section.
      if (autoCreateSlice && ((newAddr - curAddr) > this->_ctx.getPageSize()) &&
          (_outputMagic != ELFLinkingContext::OutputMagic::NMAGIC &&
           _outputMagic != ELFLinkingContext::OutputMagic::OMAGIC)) {
        auto sliceIter =
            std::find_if(_segmentSlices.begin(), _segmentSlices.end(),
                         [startSection](SegmentSlice<ELFT> *s) -> bool {
                           return s->startSection() == startSection;
                         });
        if (sliceIter == _segmentSlices.end()) {
          slice = new (_segmentAllocate.Allocate<SegmentSlice<ELFT>>())
              SegmentSlice<ELFT>();
          _segmentSlices.push_back(slice);
        } else {
          slice = (*sliceIter);
        }
        slice->setStart(startSection);
        slice->setSections(make_range(startSectionIter, si));
        slice->setMemSize(curSliceSize);
        slice->setAlign(sliceAlign);
        slice->setVirtualAddr(curSliceAddress);
        // Start new slice
        curSliceAddress = newAddr;
        (*si)->setVirtualAddr(curSliceAddress);
        startSectionIter = si;
        startSection = currSection;
        if (auto section = dyn_cast<Section<ELFT>>(*si))
          section->assignVirtualAddress(newAddr);
        curSliceSize = newAddr - curSliceAddress + (*si)->memSize();
        sliceAlign = (*si)->alignment();
      } else {
        if (sliceAlign < (*si)->alignment())
          sliceAlign = (*si)->alignment();
        (*si)->setVirtualAddr(newAddr);
        // Handle TLS.
        if (auto section = dyn_cast<Section<ELFT>>(*si)) {
          if (section->getSegmentType() == llvm::ELF::PT_TLS) {
            tlsStartAddr =
                llvm::RoundUpToAlignment(tlsStartAddr, (*si)->alignment());
            section->assignVirtualAddress(tlsStartAddr);
            tlsStartAddr += (*si)->memSize();
          } else {
            section->assignVirtualAddress(newAddr);
          }
        }
        // TBSS section is special in that it doesn't contribute to memory of
        // any segment. If we see a tbss section, don't add memory size to addr
        // The fileOffset is automatically taken care of since TBSS section does
        // not end up using file size.
        if ((*si)->order() != TargetLayout<ELFT>::ORDER_TBSS)
          curSliceSize = newAddr - curSliceAddress + (*si)->memSize();
        else
          curSliceSize = newAddr - curSliceAddress;
      }
      prevOutputSectionName = curOutputSectionName;
    }
    currSection++;
  }
  auto sliceIter = std::find_if(_segmentSlices.begin(), _segmentSlices.end(),
                                [startSection](SegmentSlice<ELFT> *s) -> bool {
                                  return s->startSection() == startSection;
                                });
  if (sliceIter == _segmentSlices.end()) {
    slice = new (_segmentAllocate.Allocate<SegmentSlice<ELFT>>())
        SegmentSlice<ELFT>();
    _segmentSlices.push_back(slice);
  } else {
    slice = (*sliceIter);
  }
  slice->setStart(startSection);
  slice->setVirtualAddr(curSliceAddress);
  slice->setMemSize(curSliceSize);
  slice->setSections(make_range(startSectionIter, _sections.end()));
  slice->setAlign(sliceAlign);

  // Set the segment memory size and the virtual address.
  this->setMemSize(curSliceAddress - startAddr + curSliceSize);
  this->setVirtualAddr(curSliceAddress);
  std::stable_sort(_segmentSlices.begin(), _segmentSlices.end(),
                   SegmentSlice<ELFT>::compare_slices);
}

// Write the Segment
template <class ELFT>
void Segment<ELFT>::write(ELFWriter *writer, TargetLayout<ELFT> &layout,
                          llvm::FileOutputBuffer &buffer) {
  for (auto slice : slices())
    for (auto section : slice->sections())
      section->write(writer, layout, buffer);
}

template <class ELFT> int64_t Segment<ELFT>::flags() const {
  int64_t fl = 0;
  if (_flags & llvm::ELF::SHF_ALLOC)
    fl |= llvm::ELF::PF_R;
  if (_flags & llvm::ELF::SHF_WRITE)
    fl |= llvm::ELF::PF_W;
  if (_flags & llvm::ELF::SHF_EXECINSTR)
    fl |= llvm::ELF::PF_X;
  return fl;
}

template <class ELFT> void Segment<ELFT>::finalize() {
  // We want to finalize the segment values for now only for non loadable
  // segments, since those values are not set in the Layout
  if (_segmentType == llvm::ELF::PT_LOAD)
    return;
  // The size is the difference of the
  // last section to the first section, especially for TLS because
  // the TLS segment contains both .tdata/.tbss
  this->setFileOffset(_sections.front()->fileOffset());
  this->setVirtualAddr(_sections.front()->virtualAddr());
  size_t startFileOffset = _sections.front()->fileOffset();
  size_t startAddr = _sections.front()->virtualAddr();
  for (auto ai : _sections) {
    this->_fsize = ai->fileOffset() + ai->fileSize() - startFileOffset;
    this->_msize = ai->virtualAddr() + ai->memSize() - startAddr;
  }
}

template <class ELFT> int Segment<ELFT>::getContentType() const {
  int64_t fl = flags();
  switch (_segmentType) {
  case llvm::ELF::PT_LOAD: {
    if (fl && llvm::ELF::PF_X)
      return Chunk<ELFT>::ContentType::Code;
    if (fl && llvm::ELF::PF_W)
      return Chunk<ELFT>::ContentType::Data;
  }
  case llvm::ELF::PT_TLS:
    return Chunk<ELFT>::ContentType::TLS;
  case llvm::ELF::PT_NOTE:
    return Chunk<ELFT>::ContentType::Note;
  default:
    return Chunk<ELFT>::ContentType::Unknown;
  }
}

template <class ELFT> int64_t Segment<ELFT>::atomflags() const {
  switch (_atomflags) {
  case DefinedAtom::permUnknown:
    return permUnknown;
  case DefinedAtom::permRWX:
    return permRWX;
  case DefinedAtom::permR_X:
    return permRX;
  case DefinedAtom::permR__:
    return permR;
  case DefinedAtom::permRW_L:
    return permRWL;
  case DefinedAtom::permRW_:
    return permRW;
  case DefinedAtom::perm___:
  default:
    return permNonAccess;
  }
}

/// \brief Check if the chunk needs to be aligned
template <class ELFT> bool Segment<ELFT>::needAlign(Chunk<ELFT> *chunk) const {
  if (chunk->getContentType() == Chunk<ELFT>::ContentType::Data &&
      _outputMagic == ELFLinkingContext::OutputMagic::NMAGIC)
    return true;
  return false;
}

template <class ELFT> void ProgramHeaderSegment<ELFT>::finalize() {
  // If the segment is of type Program Header, then the values fileOffset
  // and the fileSize need to be picked up from the last section, the first
  // section points to the ELF header and the second chunk points to the
  // actual program headers
  this->setFileOffset(this->_sections.back()->fileOffset());
  this->setVirtualAddr(this->_sections.back()->virtualAddr());
  this->_fsize = this->_sections.back()->fileSize();
  this->_msize = this->_sections.back()->memSize();
}

#define INSTANTIATE(klass)        \
  template class klass<ELF32LE>;  \
  template class klass<ELF32BE>;  \
  template class klass<ELF64LE>;  \
  template class klass<ELF64BE>;

INSTANTIATE(ExpressionChunk);
INSTANTIATE(ProgramHeaderSegment);
INSTANTIATE(Segment);
INSTANTIATE(SegmentSlice);

} // end namespace elf
} // end namespace lld