llvm-project/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

//===-- DWARFUnit.cpp -----------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/DWARF/DWARFDebugAbbrev.h"
#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/DataExtractor.h"
#include "llvm/Support/Path.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstdio>
#include <vector>

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.getLineSection().Data, C.isLittleEndian(), false);
}

void DWARFUnitSectionBase::parseDWO(DWARFContext &C,
                                    const DWARFSection &DWOSection,
                                    DWARFUnitIndex *Index) {
  parseImpl(C, DWOSection, C.getDebugAbbrevDWO(), C.getRangeDWOSection(),
            C.getStringDWOSection(), C.getStringOffsetDWOSection(),
            C.getAddrSection(), C.getLineDWOSection().Data, C.isLittleEndian(),
            true);
}

DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
                     const DWARFDebugAbbrev *DA, StringRef RS, StringRef SS,
                     StringRef SOS, StringRef AOS, StringRef LS, bool LE,
                     bool IsDWO, const DWARFUnitSectionBase &UnitSection,
                     const DWARFUnitIndex::Entry *IndexEntry)
    : Context(DC), InfoSection(Section), Abbrev(DA), RangeSection(RS),
      LineSection(LS), StringSection(SS), StringOffsetSection([&]() {
        if (IndexEntry)
          if (const auto *C = IndexEntry->getOffset(DW_SECT_STR_OFFSETS))
            return SOS.slice(C->Offset, C->Offset + C->Length);
        return SOS;
      }()),
      AddrOffsetSection(AOS), isLittleEndian(LE), isDWO(IsDWO),
      UnitSection(UnitSection), IndexEntry(IndexEntry) {
  clear();
}

DWARFUnit::~DWARFUnit() = default;

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);
  if (IndexEntry) {
    if (AbbrOffset)
      return false;
    auto *UnitContrib = IndexEntry->getOffset();
    if (!UnitContrib || UnitContrib->Length != (Length + 4))
      return false;
    auto *AbbrEntry = IndexEntry->getOffset(DW_SECT_ABBREV);
    if (!AbbrEntry)
      return false;
    AbbrOffset = AbbrEntry->Offset;
  }
  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);
  return Abbrevs != nullptr;
}

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.empty());
  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() {
  return getUnitDIE().getAttributeValueAsString(DW_AT_comp_dir, nullptr);
}

Optional<uint64_t> DWARFUnit::getDWOId() {
  return getUnitDIE().getAttributeValueAsUnsignedConstant(DW_AT_GNU_dwo_id);
}

void DWARFUnit::extractDIEsToVector(
    bool AppendCUDie, bool AppendNonCUDies,
    std::vector<DWARFDebugInfoEntry> &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();
  DWARFDebugInfoEntry DIE;
  DataExtractor DebugInfoData = getDebugInfoExtractor();
  uint32_t Depth = 0;
  bool IsCUDie = true;

  while (DIE.extractFast(*this, &DIEOffset, DebugInfoData, NextCUOffset,
                         Depth)) {
    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.empty()) ||
      DieArray.size() > 1)
    return 0; // Already parsed.

  bool HasCUDie = !DieArray.empty();
  extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);

  if (DieArray.empty())
    return 0;

  // If CU DIE was just parsed, copy several attribute values from it.
  if (!HasCUDie) {
    DWARFDie UnitDie = getUnitDIE();
    auto BaseAddr = UnitDie.getAttributeValueAsAddress(DW_AT_low_pc);
    if (!BaseAddr)
      BaseAddr = UnitDie.getAttributeValueAsAddress(DW_AT_entry_pc);
    if (BaseAddr)
      setBaseAddress(*BaseAddr);
    AddrOffsetSectionBase = UnitDie.getAttributeValueAsSectionOffset(
        DW_AT_GNU_addr_base, 0);
    RangeSectionBase = UnitDie.getAttributeValueAsSectionOffset(
        DW_AT_rnglists_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.
  }

  return DieArray.size();
}

DWARFUnit::DWOHolder::DWOHolder(StringRef DWOPath)
    : DWOU(nullptr) {
  auto Obj = object::ObjectFile::createObjectFile(DWOPath);
  if (!Obj) {
    // TODO: Actually report errors helpfully.
    consumeError(Obj.takeError());
    return;
  }
  DWOFile = std::move(Obj.get());
  DWOContext.reset(
      cast<DWARFContext>(new DWARFContextInMemory(*DWOFile.getBinary())));
  if (DWOContext->getNumDWOCompileUnits() > 0)
    DWOU = DWOContext->getDWOCompileUnitAtIndex(0);
}

bool DWARFUnit::parseDWO() {
  if (isDWO)
    return false;
  if (DWO.get())
    return false;
  DWARFDie UnitDie = getUnitDIE();
  if (!UnitDie)
    return false;
  const char *DWOFileName =
      UnitDie.getAttributeValueAsString(DW_AT_GNU_dwo_name, nullptr);
  if (!DWOFileName)
    return false;
  const char *CompilationDir =
      UnitDie.getAttributeValueAsString(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);
  auto DWORangesBase = UnitDie.getRangesBaseAttribute();
  DWOCU->setRangesSection(RangeSection, DWORangesBase ? *DWORangesBase : 0);
  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<DWARFDebugInfoEntry> TmpArray;
    DieArray.swap(TmpArray);
    // Save at least the compile unit DIE
    if (KeepCUDie)
      DieArray.push_back(TmpArray.front());
  }
}

void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
  DWARFDie UnitDie = getUnitDIE();
  if (!UnitDie)
    return;
  // First, check if unit DIE describes address ranges for the whole unit.
  const auto &CUDIERanges = UnitDie.getAddressRanges();
  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;
  getUnitDIE().collectChildrenAddressRanges(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);
}

DWARFDie
DWARFUnit::getSubprogramForAddress(uint64_t Address) {
  extractDIEsIfNeeded(false);
  for (const DWARFDebugInfoEntry &D : DieArray) {
    DWARFDie DIE(this, &D);
    if (DIE.isSubprogramDIE() &&
        DIE.addressRangeContainsAddress(Address)) {
      return DIE;
    }
  }
  return DWARFDie();
}

void
DWARFUnit::getInlinedChainForAddress(uint64_t Address,
                                     SmallVectorImpl<DWARFDie> &InlinedChain) {
  // First, find a subprogram that contains the given address (the root
  // of inlined chain).
  DWARFDie SubprogramDIE;
  // Try to look for subprogram DIEs in the DWO file.
  parseDWO();
  if (DWO)
    SubprogramDIE = DWO->getUnit()->getSubprogramForAddress(Address);
  else
    SubprogramDIE = getSubprogramForAddress(Address);

  // Get inlined chain rooted at this subprogram DIE.
  if (SubprogramDIE)
    SubprogramDIE.getInlinedChainForAddress(Address, InlinedChain);
  else
    InlinedChain.clear();
}

const DWARFUnitIndex &getDWARFUnitIndex(DWARFContext &Context,
                                        DWARFSectionKind Kind) {
  if (Kind == DW_SECT_INFO)
    return Context.getCUIndex();
  assert(Kind == DW_SECT_TYPES);
  return Context.getTUIndex();
}

DWARFDie DWARFUnit::getParent(const DWARFDebugInfoEntry *Die) {
  if (!Die)
    return DWARFDie();
  const uint32_t Depth = Die->getDepth();
  // Unit DIEs always have a depth of zero and never have parents.
  if (Depth == 0)
    return DWARFDie();
  // Depth of 1 always means parent is the compile/type unit.
  if (Depth == 1)
    return getUnitDIE();
  // Look for previous DIE with a depth that is one less than the Die's depth.
  const uint32_t ParentDepth = Depth - 1;
  for (uint32_t I = getDIEIndex(Die) - 1; I > 0; --I) {
    if (DieArray[I].getDepth() == ParentDepth)
      return DWARFDie(this, &DieArray[I]);
  }
  return DWARFDie();
}

DWARFDie DWARFUnit::getSibling(const DWARFDebugInfoEntry *Die) {
  if (!Die)
    return DWARFDie();
  uint32_t Depth = Die->getDepth();
  // Unit DIEs always have a depth of zero and never have siblings.
  if (Depth == 0)
    return DWARFDie();
  // NULL DIEs don't have siblings.
  if (Die->getAbbreviationDeclarationPtr() == nullptr)
    return DWARFDie();
  
  // Find the next DIE whose depth is the same as the Die's depth.
  for (size_t I=getDIEIndex(Die)+1, EndIdx = DieArray.size(); I<EndIdx; ++I) {
    if (DieArray[I].getDepth() == Depth)
      return DWARFDie(this, &DieArray[I]);
  }
  return DWARFDie();
}

} // end namespace llvm