text: //===-- DWARFUnit.cpp -----------------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  
  #include "DWARFUnit.h"
  #include "DWARFContext.h"
  #include "llvm/DebugInfo/DWARFFormValue.h"
  #include "llvm/Support/Dwarf.h"
  #include "llvm/Support/Path.h"
  #include <cstdio>
  
  using namespace llvm;
  using namespace dwarf;
  
  void DWARFUnitSectionBase::parse(DWARFContext &C, const DWARFSection &Section) {
    parseImpl(C, Section, C.getDebugAbbrev(), C.getRangeSection(),
              C.getStringSection(), StringRef(), C.getAddrSection(),
              C.isLittleEndian());
  }
  
  void DWARFUnitSectionBase::parseDWO(DWARFContext &C,
                                      const DWARFSection &DWOSection) {
    parseImpl(C, DWOSection, C.getDebugAbbrevDWO(), C.getRangeDWOSection(),
              C.getStringDWOSection(), C.getStringOffsetDWOSection(),
              C.getAddrSection(), C.isLittleEndian());
  }
  
  DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
                       const DWARFDebugAbbrev *DA, StringRef RS, StringRef SS,
                       StringRef SOS, StringRef AOS, bool LE,
                       const DWARFUnitSectionBase &UnitSection)
      : Context(DC), InfoSection(Section), Abbrev(DA), RangeSection(RS),
        StringSection(SS), StringOffsetSection(SOS), AddrOffsetSection(AOS),
        isLittleEndian(LE), UnitSection(UnitSection) {
    clear();
  }
  
  DWARFUnit::~DWARFUnit() {
  }
  
  bool DWARFUnit::getAddrOffsetSectionItem(uint32_t Index,
                                                  uint64_t &Result) const {
    uint32_t Offset = AddrOffsetSectionBase + Index * AddrSize;
    if (AddrOffsetSection.size() < Offset + AddrSize)
      return false;
    DataExtractor DA(AddrOffsetSection, isLittleEndian, AddrSize);
    Result = DA.getAddress(&Offset);
    return true;
  }
  
  bool DWARFUnit::getStringOffsetSectionItem(uint32_t Index,
                                                    uint32_t &Result) const {
    // FIXME: string offset section entries are 8-byte for DWARF64.
    const uint32_t ItemSize = 4;
    uint32_t Offset = Index * ItemSize;
    if (StringOffsetSection.size() < Offset + ItemSize)
      return false;
    DataExtractor DA(StringOffsetSection, isLittleEndian, 0);
    Result = DA.getU32(&Offset);
    return true;
  }
  
  bool DWARFUnit::extractImpl(DataExtractor debug_info, uint32_t *offset_ptr) {
    Length = debug_info.getU32(offset_ptr);
    Version = debug_info.getU16(offset_ptr);
    uint64_t AbbrOffset = debug_info.getU32(offset_ptr);
    AddrSize = debug_info.getU8(offset_ptr);
  
    bool LengthOK = debug_info.isValidOffset(getNextUnitOffset() - 1);
    bool VersionOK = DWARFContext::isSupportedVersion(Version);
    bool AddrSizeOK = AddrSize == 4 || AddrSize == 8;
  
    if (!LengthOK || !VersionOK || !AddrSizeOK)
      return false;
  
    Abbrevs = Abbrev->getAbbreviationDeclarationSet(AbbrOffset);
    if (Abbrevs == nullptr)
      return false;
  
    return true;
  }
  
  bool DWARFUnit::extract(DataExtractor debug_info, uint32_t *offset_ptr) {
    clear();
  
    Offset = *offset_ptr;
  
    if (debug_info.isValidOffset(*offset_ptr)) {
      if (extractImpl(debug_info, offset_ptr))
        return true;
  
      // reset the offset to where we tried to parse from if anything went wrong
      *offset_ptr = Offset;
    }
  
    return false;
  }
  
  bool DWARFUnit::extractRangeList(uint32_t RangeListOffset,
                                          DWARFDebugRangeList &RangeList) const {
    // Require that compile unit is extracted.
    assert(DieArray.size() > 0);
    DataExtractor RangesData(RangeSection, isLittleEndian, AddrSize);
    uint32_t ActualRangeListOffset = RangeSectionBase + RangeListOffset;
    return RangeList.extract(RangesData, &ActualRangeListOffset);
  }
  
  void DWARFUnit::clear() {
    Offset = 0;
    Length = 0;
    Version = 0;
    Abbrevs = nullptr;
    AddrSize = 0;
    BaseAddr = 0;
    RangeSectionBase = 0;
    AddrOffsetSectionBase = 0;
    clearDIEs(false);
    DWO.reset();
  }
  
  const char *DWARFUnit::getCompilationDir() {
    extractDIEsIfNeeded(true);
    if (DieArray.empty())
      return nullptr;
    return DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, nullptr);
  }
  
  uint64_t DWARFUnit::getDWOId() {
    extractDIEsIfNeeded(true);
    const uint64_t FailValue = -1ULL;
    if (DieArray.empty())
      return FailValue;
    return DieArray[0]
        .getAttributeValueAsUnsignedConstant(this, DW_AT_GNU_dwo_id, FailValue);
  }
  
  void DWARFUnit::setDIERelations() {
    if (DieArray.size() <= 1)
      return;
  
    std::vector<DWARFDebugInfoEntryMinimal *> ParentChain;
    DWARFDebugInfoEntryMinimal *SiblingChain = nullptr;
    for (auto &DIE : DieArray) {
      if (SiblingChain) {
        SiblingChain->setSibling(&DIE);
      }
      if (const DWARFAbbreviationDeclaration *AbbrDecl =
              DIE.getAbbreviationDeclarationPtr()) {
        // Normal DIE.
        if (AbbrDecl->hasChildren()) {
          ParentChain.push_back(&DIE);
          SiblingChain = nullptr;
        } else {
          SiblingChain = &DIE;
        }
      } else {
        // NULL entry terminates the sibling chain.
        SiblingChain = ParentChain.back();
        ParentChain.pop_back();
      }
    }
    assert(SiblingChain == nullptr || SiblingChain == &DieArray[0]);
    assert(ParentChain.empty());
  }
  
  void DWARFUnit::extractDIEsToVector(
      bool AppendCUDie, bool AppendNonCUDies,
      std::vector<DWARFDebugInfoEntryMinimal> &Dies) const {
    if (!AppendCUDie && !AppendNonCUDies)
      return;
  
    // Set the offset to that of the first DIE and calculate the start of the
    // next compilation unit header.
    uint32_t DIEOffset = Offset + getHeaderSize();
    uint32_t NextCUOffset = getNextUnitOffset();
    DWARFDebugInfoEntryMinimal DIE;
    uint32_t Depth = 0;
    bool IsCUDie = true;
  
    while (DIEOffset < NextCUOffset && DIE.extractFast(this, &DIEOffset)) {
      if (IsCUDie) {
        if (AppendCUDie)
          Dies.push_back(DIE);
        if (!AppendNonCUDies)
          break;
        // The average bytes per DIE entry has been seen to be
        // around 14-20 so let's pre-reserve the needed memory for
        // our DIE entries accordingly.
        Dies.reserve(Dies.size() + getDebugInfoSize() / 14);
        IsCUDie = false;
      } else {
        Dies.push_back(DIE);
      }
  
      if (const DWARFAbbreviationDeclaration *AbbrDecl =
              DIE.getAbbreviationDeclarationPtr()) {
        // Normal DIE
        if (AbbrDecl->hasChildren())
          ++Depth;
      } else {
        // NULL DIE.
        if (Depth > 0)
          --Depth;
        if (Depth == 0)
          break;  // We are done with this compile unit!
      }
    }
  
    // Give a little bit of info if we encounter corrupt DWARF (our offset
    // should always terminate at or before the start of the next compilation
    // unit header).
    if (DIEOffset > NextCUOffset)
      fprintf(stderr, "warning: DWARF compile unit extends beyond its "
                      "bounds cu 0x%8.8x at 0x%8.8x'\n", getOffset(), DIEOffset);
  }
  
  size_t DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
    if ((CUDieOnly && DieArray.size() > 0) ||
        DieArray.size() > 1)
      return 0; // Already parsed.
  
    bool HasCUDie = DieArray.size() > 0;
    extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
  
    if (DieArray.empty())
      return 0;
  
    // If CU DIE was just parsed, copy several attribute values from it.
    if (!HasCUDie) {
      uint64_t BaseAddr =
          DieArray[0].getAttributeValueAsAddress(this, DW_AT_low_pc, -1ULL);
      if (BaseAddr == -1ULL)
        BaseAddr = DieArray[0].getAttributeValueAsAddress(this, DW_AT_entry_pc, 0);
      setBaseAddress(BaseAddr);
      AddrOffsetSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
          this, DW_AT_GNU_addr_base, 0);
      RangeSectionBase = DieArray[0].getAttributeValueAsSectionOffset(
          this, DW_AT_ranges_base, 0);
      // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
      // skeleton CU DIE, so that DWARF users not aware of it are not broken.
    }
  
    setDIERelations();
    return DieArray.size();
  }
  
  DWARFUnit::DWOHolder::DWOHolder(StringRef DWOPath)
      : DWOFile(), DWOContext(), DWOU(nullptr) {
    auto Obj = object::ObjectFile::createObjectFile(DWOPath);
    if (!Obj)
      return;
    DWOFile = std::move(Obj.get());
    DWOContext.reset(
        cast<DWARFContext>(DIContext::getDWARFContext(*DWOFile.getBinary())));
    if (DWOContext->getNumDWOCompileUnits() > 0)
      DWOU = DWOContext->getDWOCompileUnitAtIndex(0);
  }
  
  bool DWARFUnit::parseDWO() {
    if (DWO.get())
      return false;
    extractDIEsIfNeeded(true);
    if (DieArray.empty())
      return false;
    const char *DWOFileName =
        DieArray[0].getAttributeValueAsString(this, DW_AT_GNU_dwo_name, nullptr);
    if (!DWOFileName)
      return false;
    const char *CompilationDir =
        DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, nullptr);
    SmallString<16> AbsolutePath;
    if (sys::path::is_relative(DWOFileName) && CompilationDir != nullptr) {
      sys::path::append(AbsolutePath, CompilationDir);
    }
    sys::path::append(AbsolutePath, DWOFileName);
    DWO = llvm::make_unique<DWOHolder>(AbsolutePath);
    DWARFUnit *DWOCU = DWO->getUnit();
    // Verify that compile unit in .dwo file is valid.
    if (!DWOCU || DWOCU->getDWOId() != getDWOId()) {
      DWO.reset();
      return false;
    }
    // Share .debug_addr and .debug_ranges section with compile unit in .dwo
    DWOCU->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
    uint32_t DWORangesBase = DieArray[0].getRangesBaseAttribute(this, 0);
    DWOCU->setRangesSection(RangeSection, DWORangesBase);
    return true;
  }
  
  void DWARFUnit::clearDIEs(bool KeepCUDie) {
    if (DieArray.size() > (unsigned)KeepCUDie) {
      // std::vectors never get any smaller when resized to a smaller size,
      // or when clear() or erase() are called, the size will report that it
      // is smaller, but the memory allocated remains intact (call capacity()
      // to see this). So we need to create a temporary vector and swap the
      // contents which will cause just the internal pointers to be swapped
      // so that when temporary vector goes out of scope, it will destroy the
      // contents.
      std::vector<DWARFDebugInfoEntryMinimal> TmpArray;
      DieArray.swap(TmpArray);
      // Save at least the compile unit DIE
      if (KeepCUDie)
        DieArray.push_back(TmpArray.front());
    }
  }
  
  void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
    // First, check if CU DIE describes address ranges for the unit.
    const auto &CUDIERanges = getCompileUnitDIE()->getAddressRanges(this);
    if (!CUDIERanges.empty()) {
      CURanges.insert(CURanges.end(), CUDIERanges.begin(), CUDIERanges.end());
      return;
    }
  
    // This function is usually called if there in no .debug_aranges section
    // in order to produce a compile unit level set of address ranges that
    // is accurate. If the DIEs weren't parsed, then we don't want all dies for
    // all compile units to stay loaded when they weren't needed. So we can end
    // up parsing the DWARF and then throwing them all away to keep memory usage
    // down.
    const bool ClearDIEs = extractDIEsIfNeeded(false) > 1;
    DieArray[0].collectChildrenAddressRanges(this, CURanges);
  
    // Collect address ranges from DIEs in .dwo if necessary.
    bool DWOCreated = parseDWO();
    if (DWO.get())
      DWO->getUnit()->collectAddressRanges(CURanges);
    if (DWOCreated)
      DWO.reset();
  
    // Keep memory down by clearing DIEs if this generate function
    // caused them to be parsed.
    if (ClearDIEs)
      clearDIEs(true);
  }
  
  const DWARFDebugInfoEntryMinimal *
  DWARFUnit::getSubprogramForAddress(uint64_t Address) {
    extractDIEsIfNeeded(false);
    for (const DWARFDebugInfoEntryMinimal &DIE : DieArray) {
      if (DIE.isSubprogramDIE() &&
          DIE.addressRangeContainsAddress(this, Address)) {
        return &DIE;
      }
    }
    return nullptr;
  }
  
  DWARFDebugInfoEntryInlinedChain
  DWARFUnit::getInlinedChainForAddress(uint64_t Address) {
    // First, find a subprogram that contains the given address (the root
    // of inlined chain).
    const DWARFUnit *ChainCU = nullptr;
    const DWARFDebugInfoEntryMinimal *SubprogramDIE =
        getSubprogramForAddress(Address);
    if (SubprogramDIE) {
      ChainCU = this;
    } else {
      // Try to look for subprogram DIEs in the DWO file.
      parseDWO();
      if (DWO.get()) {
        SubprogramDIE = DWO->getUnit()->getSubprogramForAddress(Address);
        if (SubprogramDIE)
          ChainCU = DWO->getUnit();
      }
    }
  
    // Get inlined chain rooted at this subprogram DIE.
    if (!SubprogramDIE)
      return DWARFDebugInfoEntryInlinedChain();
    return SubprogramDIE->getInlinedChainForAddress(ChainCU, Address);
  }
  