DWARFUnit.cpp

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//===-- 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;

DWARFUnit::DWARFUnit(const DWARFDebugAbbrev *DA, StringRef IS, StringRef AS,
                     StringRef RS, StringRef SS, StringRef SOS, StringRef AOS,
                     const RelocAddrMap *M, bool LE)
    : Abbrev(DA), InfoSection(IS), AbbrevSection(AS), RangeSection(RS),
      StringSection(SS), StringOffsetSection(SOS), AddrOffsetSection(AOS),
      RelocMap(M), isLittleEndian(LE) {
  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 abbrOffsetOK = AbbrevSection.size() > abbrOffset;
  bool addrSizeOK = AddrSize == 4 || AddrSize == 8;

  if (!lengthOK || !versionOK || !addrSizeOK || !abbrOffsetOK)
    return false;

  Abbrevs = Abbrev->getAbbreviationDeclarationSet(abbrOffset);
  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 = 0;
  AddrSize = 0;
  BaseAddr = 0;
  RangeSectionBase = 0;
  AddrOffsetSectionBase = 0;
  clearDIEs(false);
  DWO.reset();
}

const char *DWARFUnit::getCompilationDir() {
  extractDIEsIfNeeded(true);
  if (DieArray.empty())
    return 0;
  return DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, 0);
}

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.empty())
    return;
  DWARFDebugInfoEntryMinimal *die_array_begin = &DieArray.front();
  DWARFDebugInfoEntryMinimal *die_array_end = &DieArray.back();
  DWARFDebugInfoEntryMinimal *curr_die;
  // We purposely are skipping the last element in the array in the loop below
  // so that we can always have a valid next item
  for (curr_die = die_array_begin; curr_die < die_array_end; ++curr_die) {
    // Since our loop doesn't include the last element, we can always
    // safely access the next die in the array.
    DWARFDebugInfoEntryMinimal *next_die = curr_die + 1;

    const DWARFAbbreviationDeclaration *curr_die_abbrev =
      curr_die->getAbbreviationDeclarationPtr();

    if (curr_die_abbrev) {
      // Normal DIE
      if (curr_die_abbrev->hasChildren())
        next_die->setParent(curr_die);
      else
        curr_die->setSibling(next_die);
    } else {
      // NULL DIE that terminates a sibling chain
      DWARFDebugInfoEntryMinimal *parent = curr_die->getParent();
      if (parent)
        parent->setSibling(next_die);
    }
  }

  // Since we skipped the last element, we need to fix it up!
  if (die_array_begin < die_array_end)
    curr_die->setParent(die_array_begin);
}

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 Offset = getFirstDIEOffset();
  uint32_t NextCUOffset = getNextUnitOffset();
  DWARFDebugInfoEntryMinimal DIE;
  uint32_t Depth = 0;
  bool IsCUDie = true;

  while (Offset < NextCUOffset && DIE.extractFast(this, &Offset)) {
    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);
    }

    const DWARFAbbreviationDeclaration *AbbrDecl =
      DIE.getAbbreviationDeclarationPtr();
    if (AbbrDecl) {
      // 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 (Offset > NextCUOffset)
    fprintf(stderr, "warning: DWARF compile unit extends beyond its "
                    "bounds cu 0x%8.8x at 0x%8.8x'\n", getOffset(), Offset);
}

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_GNU_ranges_base, 0);
  }

  setDIERelations();
  return DieArray.size();
}

DWARFUnit::DWOHolder::DWOHolder(object::ObjectFile *DWOFile)
    : DWOFile(DWOFile),
      DWOContext(cast<DWARFContext>(DIContext::getDWARFContext(DWOFile))),
      DWOU(0) {
  if (DWOContext->getNumDWOCompileUnits() > 0)
    DWOU = DWOContext->getDWOCompileUnitAtIndex(0);
}

bool DWARFUnit::parseDWO() {
  if (DWO.get() != 0)
    return false;
  extractDIEsIfNeeded(true);
  if (DieArray.empty())
    return false;
  const char *DWOFileName =
      DieArray[0].getAttributeValueAsString(this, DW_AT_GNU_dwo_name, 0);
  if (DWOFileName == 0)
    return false;
  const char *CompilationDir =
      DieArray[0].getAttributeValueAsString(this, DW_AT_comp_dir, 0);
  SmallString<16> AbsolutePath;
  if (sys::path::is_relative(DWOFileName) && CompilationDir != 0) {
    sys::path::append(AbsolutePath, CompilationDir);
  }
  sys::path::append(AbsolutePath, DWOFileName);
  object::ObjectFile *DWOFile =
      object::ObjectFile::createObjectFile(AbsolutePath);
  if (!DWOFile)
    return false;
  // Reset DWOHolder.
  DWO.reset(new DWOHolder(DWOFile));
  DWARFUnit *DWOCU = DWO->getUnit();
  // Verify that compile unit in .dwo file is valid.
  if (DWOCU == 0 || DWOCU->getDWOId() != getDWOId()) {
    DWO.reset();
    return false;
  }
  // Share .debug_addr and .debug_ranges section with compile unit in .dwo
  DWOCU->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
  DWOCU->setRangesSection(RangeSection, RangeSectionBase);
  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::buildAddressRangeTable(DWARFDebugAranges *debug_aranges,
                                         bool clear_dies_if_already_not_parsed,
                                         uint32_t CUOffsetInAranges) {
  // 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 clear_dies = extractDIEsIfNeeded(false) > 1 &&
                          clear_dies_if_already_not_parsed;
  DieArray[0].buildAddressRangeTable(this, debug_aranges, CUOffsetInAranges);
  bool DWOCreated = parseDWO();
  if (DWO.get()) {
    // If there is a .dwo file for this compile unit, then skeleton CU DIE
    // doesn't have children, and we should instead build address range table
    // from DIEs in the .debug_info.dwo section of .dwo file.
    DWO->getUnit()->buildAddressRangeTable(
        debug_aranges, clear_dies_if_already_not_parsed, CUOffsetInAranges);
  }
  if (DWOCreated && clear_dies_if_already_not_parsed)
    DWO.reset();

  // Keep memory down by clearing DIEs if this generate function
  // caused them to be parsed.
  if (clear_dies)
    clearDIEs(true);
}

const DWARFDebugInfoEntryMinimal *
DWARFUnit::getSubprogramForAddress(uint64_t Address) {
  extractDIEsIfNeeded(false);
  for (size_t i = 0, n = DieArray.size(); i != n; i++)
    if (DieArray[i].isSubprogramDIE() &&
        DieArray[i].addressRangeContainsAddress(this, Address)) {
      return &DieArray[i];
    }
  return 0;
}

DWARFDebugInfoEntryInlinedChain
DWARFUnit::getInlinedChainForAddress(uint64_t Address) {
  // First, find a subprogram that contains the given address (the root
  // of inlined chain).
  const DWARFUnit *ChainCU = 0;
  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);
}