DwarfTransformer.cpp

Go to the documentation of this file.

//===- DwarfTransformer.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include <thread>
#include <unordered_set>
 
#include "llvm/DebugInfo/DIContext.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Support/raw_ostream.h"
 
#include "llvm/DebugInfo/GSYM/DwarfTransformer.h"
#include "llvm/DebugInfo/GSYM/FunctionInfo.h"
#include "llvm/DebugInfo/GSYM/GsymCreator.h"
#include "llvm/DebugInfo/GSYM/GsymReader.h"
#include "llvm/DebugInfo/GSYM/InlineInfo.h"
 
using namespace llvm;
using namespace gsym;
 
struct llvm::gsym::CUInfo {
  const DWARFDebugLine::LineTable *LineTable;
  const char *CompDir;
  std::vector<uint32_t> FileCache;
  uint64_t Language = 0;
  uint8_t AddrSize = 0;
 
  CUInfo(DWARFContext &DICtx, DWARFCompileUnit *CU) {
    LineTable = DICtx.getLineTableForUnit(CU);
    CompDir = CU->getCompilationDir();
    FileCache.clear();
    if (LineTable)
      FileCache.assign(LineTable->Prologue.FileNames.size() + 1, UINT32_MAX);
    DWARFDie Die = CU->getUnitDIE();
    Language = dwarf::toUnsigned(Die.find(dwarf::DW_AT_language), 0);
    AddrSize = CU->getAddressByteSize();
  }
 
  /// Return true if Addr is the highest address for a given compile unit. The
  /// highest address is encoded as -1, of all ones in the address. These high
  /// addresses are used by some linkers to indicate that a function has been
  /// dead stripped or didn't end up in the linked executable.
  bool isHighestAddress(uint64_t Addr) const {
    if (AddrSize == 4)
      return Addr == UINT32_MAX;
    else if (AddrSize == 8)
      return Addr == UINT64_MAX;
    return false;
  }
 
  /// Convert a DWARF compile unit file index into a GSYM global file index.
  ///
  /// Each compile unit in DWARF has its own file table in the line table
  /// prologue. GSYM has a single large file table that applies to all files
  /// from all of the info in a GSYM file. This function converts between the
  /// two and caches and DWARF CU file index that has already been converted so
  /// the first client that asks for a compile unit file index will end up
  /// doing the conversion, and subsequent clients will get the cached GSYM
  /// index.
  uint32_t DWARFToGSYMFileIndex(GsymCreator &Gsym, uint32_t DwarfFileIdx) {
    if (!LineTable)
      return 0;
    assert(DwarfFileIdx < FileCache.size());
    uint32_t &GsymFileIdx = FileCache[DwarfFileIdx];
    if (GsymFileIdx != UINT32_MAX)
      return GsymFileIdx;
    std::string File;
    if (LineTable->getFileNameByIndex(
            DwarfFileIdx, CompDir,
            DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, File))
      GsymFileIdx = Gsym.insertFile(File);
    else
      GsymFileIdx = 0;
    return GsymFileIdx;
  }
};
 
 
static DWARFDie GetParentDeclContextDIE(DWARFDie &Die) {
  if (DWARFDie SpecDie =
          Die.getAttributeValueAsReferencedDie(dwarf::DW_AT_specification)) {
    if (DWARFDie SpecParent = GetParentDeclContextDIE(SpecDie))
      return SpecParent;
  }
  if (DWARFDie AbstDie =
          Die.getAttributeValueAsReferencedDie(dwarf::DW_AT_abstract_origin)) {
    if (DWARFDie AbstParent = GetParentDeclContextDIE(AbstDie))
      return AbstParent;
  }
 
  // We never want to follow parent for inlined subroutine - that would
  // give us information about where the function is inlined, not what
  // function is inlined
  if (Die.getTag() == dwarf::DW_TAG_inlined_subroutine)
    return DWARFDie();
 
  DWARFDie ParentDie = Die.getParent();
  if (!ParentDie)
    return DWARFDie();
 
  switch (ParentDie.getTag()) {
  case dwarf::DW_TAG_namespace:
  case dwarf::DW_TAG_structure_type:
  case dwarf::DW_TAG_union_type:
  case dwarf::DW_TAG_class_type:
  case dwarf::DW_TAG_subprogram:
    return ParentDie; // Found parent decl context DIE
  case dwarf::DW_TAG_lexical_block:
    return GetParentDeclContextDIE(ParentDie);
  default:
    break;
  }
 
  return DWARFDie();
}
 
/// Get the GsymCreator string table offset for the qualified name for the
/// DIE passed in. This function will avoid making copies of any strings in
/// the GsymCreator when possible. We don't need to copy a string when the
/// string comes from our .debug_str section or is an inlined string in the
/// .debug_info. If we create a qualified name string in this function by
/// combining multiple strings in the DWARF string table or info, we will make
/// a copy of the string when we add it to the string table.
static Optional<uint32_t> getQualifiedNameIndex(DWARFDie &Die,
                                                uint64_t Language,
                                                GsymCreator &Gsym) {
  // If the dwarf has mangled name, use mangled name
  if (auto LinkageName =
          dwarf::toString(Die.findRecursively({dwarf::DW_AT_MIPS_linkage_name,
                                               dwarf::DW_AT_linkage_name}),
                          nullptr))
    return Gsym.insertString(LinkageName, /* Copy */ false);
 
  StringRef ShortName(Die.getName(DINameKind::ShortName));
  if (ShortName.empty())
    return llvm::None;
 
  // For C++ and ObjC, prepend names of all parent declaration contexts
  if (!(Language == dwarf::DW_LANG_C_plus_plus ||
        Language == dwarf::DW_LANG_C_plus_plus_03 ||
        Language == dwarf::DW_LANG_C_plus_plus_11 ||
        Language == dwarf::DW_LANG_C_plus_plus_14 ||
        Language == dwarf::DW_LANG_ObjC_plus_plus ||
        // This should not be needed for C, but we see C++ code marked as C
        // in some binaries. This should hurt, so let's do it for C as well
        Language == dwarf::DW_LANG_C))
    return Gsym.insertString(ShortName, /* Copy */ false);
 
  // Some GCC optimizations create functions with names ending with .isra.<num>
  // or .part.<num> and those names are just DW_AT_name, not DW_AT_linkage_name
  // If it looks like it could be the case, don't add any prefix
  if (ShortName.startswith("_Z") &&
      (ShortName.contains(".isra.") || ShortName.contains(".part.")))
    return Gsym.insertString(ShortName, /* Copy */ false);
 
  DWARFDie ParentDeclCtxDie = GetParentDeclContextDIE(Die);
  if (ParentDeclCtxDie) {
    std::string Name = ShortName.str();
    while (ParentDeclCtxDie) {
      StringRef ParentName(ParentDeclCtxDie.getName(DINameKind::ShortName));
      if (!ParentName.empty()) {
        // "lambda" names are wrapped in < >. Replace with { }
        // to be consistent with demangled names and not to confuse with
        // templates
        if (ParentName.front() == '<' && ParentName.back() == '>')
          Name = "{" + ParentName.substr(1, ParentName.size() - 2).str() + "}" +
                "::" + Name;
        else
          Name = ParentName.str() + "::" + Name;
      }
      ParentDeclCtxDie = GetParentDeclContextDIE(ParentDeclCtxDie);
    }
    // Copy the name since we created a new name in a std::string.
    return Gsym.insertString(Name, /* Copy */ true);
  }
  // Don't copy the name since it exists in the DWARF object file.
  return Gsym.insertString(ShortName, /* Copy */ false);
}
 
static bool hasInlineInfo(DWARFDie Die, uint32_t Depth) {
  bool CheckChildren = true;
  switch (Die.getTag()) {
  case dwarf::DW_TAG_subprogram:
    // Don't look into functions within functions.
    CheckChildren = Depth == 0;
    break;
  case dwarf::DW_TAG_inlined_subroutine:
    return true;
  default:
    break;
  }
  if (!CheckChildren)
    return false;
  for (DWARFDie ChildDie : Die.children()) {
    if (hasInlineInfo(ChildDie, Depth + 1))
      return true;
  }
  return false;
}
 
static void parseInlineInfo(GsymCreator &Gsym, CUInfo &CUI, DWARFDie Die,
                            uint32_t Depth, FunctionInfo &FI,
                            InlineInfo &parent) {
  if (!hasInlineInfo(Die, Depth))
    return;
 
  dwarf::Tag Tag = Die.getTag();
  if (Tag == dwarf::DW_TAG_inlined_subroutine) {
    // create new InlineInfo and append to parent.children
    InlineInfo II;
    DWARFAddressRange FuncRange =
        DWARFAddressRange(FI.startAddress(), FI.endAddress());
    Expected<DWARFAddressRangesVector> RangesOrError = Die.getAddressRanges();
    if (RangesOrError) {
      for (const DWARFAddressRange &Range : RangesOrError.get()) {
        // Check that the inlined function is within the range of the function
        // info, it might not be in case of split functions
        if (FuncRange.LowPC <= Range.LowPC && Range.HighPC <= FuncRange.HighPC)
          II.Ranges.insert(AddressRange(Range.LowPC, Range.HighPC));
      }
    }
    if (II.Ranges.empty())
      return;
 
    if (auto NameIndex = getQualifiedNameIndex(Die, CUI.Language, Gsym))
      II.Name = *NameIndex;
    II.CallFile = CUI.DWARFToGSYMFileIndex(
        Gsym, dwarf::toUnsigned(Die.find(dwarf::DW_AT_call_file), 0));
    II.CallLine = dwarf::toUnsigned(Die.find(dwarf::DW_AT_call_line), 0);
    // parse all children and append to parent
    for (DWARFDie ChildDie : Die.children())
      parseInlineInfo(Gsym, CUI, ChildDie, Depth + 1, FI, II);
    parent.Children.emplace_back(std::move(II));
    return;
  }
  if (Tag == dwarf::DW_TAG_subprogram || Tag == dwarf::DW_TAG_lexical_block) {
    // skip this Die and just recurse down
    for (DWARFDie ChildDie : Die.children())
      parseInlineInfo(Gsym, CUI, ChildDie, Depth + 1, FI, parent);
  }
}
 
static void convertFunctionLineTable(raw_ostream &Log, CUInfo &CUI,
                                     DWARFDie Die, GsymCreator &Gsym,
                                     FunctionInfo &FI) {
  std::vector<uint32_t> RowVector;
  const uint64_t StartAddress = FI.startAddress();
  const uint64_t EndAddress = FI.endAddress();
  const uint64_t RangeSize = EndAddress - StartAddress;
  const object::SectionedAddress SecAddress{
      StartAddress, object::SectionedAddress::UndefSection};
 
 
  if (!CUI.LineTable->lookupAddressRange(SecAddress, RangeSize, RowVector)) {
    // If we have a DW_TAG_subprogram but no line entries, fall back to using
    // the DW_AT_decl_file an d DW_AT_decl_line if we have both attributes.
    std::string FilePath = Die.getDeclFile(
        DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath);
    if (FilePath.empty())
      return;
    if (auto Line =
            dwarf::toUnsigned(Die.findRecursively({dwarf::DW_AT_decl_line}))) {
      LineEntry LE(StartAddress, Gsym.insertFile(FilePath), *Line);
      FI.OptLineTable = LineTable();
      FI.OptLineTable->push(LE);
    }
    return;
  }
 
  FI.OptLineTable = LineTable();
  DWARFDebugLine::Row PrevRow;
  for (uint32_t RowIndex : RowVector) {
    // Take file number and line/column from the row.
    const DWARFDebugLine::Row &Row = CUI.LineTable->Rows[RowIndex];
    const uint32_t FileIdx = CUI.DWARFToGSYMFileIndex(Gsym, Row.File);
    uint64_t RowAddress = Row.Address.Address;
    // Watch out for a RowAddress that is in the middle of a line table entry
    // in the DWARF. If we pass an address in between two line table entries
    // we will get a RowIndex for the previous valid line table row which won't
    // be contained in our function. This is usually a bug in the DWARF due to
    // linker problems or LTO or other DWARF re-linking so it is worth emitting
    // an error, but not worth stopping the creation of the GSYM.
    if (!FI.Range.contains(RowAddress)) {
      if (RowAddress < FI.Range.Start) {
        Log << "error: DIE has a start address whose LowPC is between the "
          "line table Row[" << RowIndex << "] with address "
          << HEX64(RowAddress) << " and the next one.\n";
        Die.dump(Log, 0, DIDumpOptions::getForSingleDIE());
        RowAddress = FI.Range.Start;
      } else {
        continue;
      }
    }
 
    LineEntry LE(RowAddress, FileIdx, Row.Line);
    if (RowIndex != RowVector[0] && Row.Address < PrevRow.Address) {
      // We have seen full duplicate line tables for functions in some
      // DWARF files. Watch for those here by checking the the last
      // row was the function's end address (HighPC) and that the
      // current line table entry's address is the same as the first
      // line entry we already have in our "function_info.Lines". If
      // so break out after printing a warning.
      auto FirstLE = FI.OptLineTable->first();
      if (FirstLE && *FirstLE == LE) {
        if (!Gsym.isQuiet()) {
          Log << "warning: duplicate line table detected for DIE:\n";
          Die.dump(Log, 0, DIDumpOptions::getForSingleDIE());
        }
      } else {
        // Print out (ignore if os == nulls as this is expensive)
        Log << "error: line table has addresses that do not "
             << "monotonically increase:\n";
        for (uint32_t RowIndex2 : RowVector) {
          CUI.LineTable->Rows[RowIndex2].dump(Log);
        }
        Die.dump(Log, 0, DIDumpOptions::getForSingleDIE());
      }
      break;
    }
 
    // Skip multiple line entries for the same file and line.
    auto LastLE = FI.OptLineTable->last();
    if (LastLE && LastLE->File == FileIdx && LastLE->Line == Row.Line)
        continue;
    // Only push a row if it isn't an end sequence. End sequence markers are
    // included for the last address in a function or the last contiguous
    // address in a sequence.
    if (Row.EndSequence) {
      // End sequence means that the next line entry could have a lower address
      // that the previous entries. So we clear the previous row so we don't
      // trigger the line table error about address that do not monotonically
      // increase.
      PrevRow = DWARFDebugLine::Row();
    } else {
      FI.OptLineTable->push(LE);
      PrevRow = Row;
    }
  }
  // If not line table rows were added, clear the line table so we don't encode
  // on in the GSYM file.
  if (FI.OptLineTable->empty())
    FI.OptLineTable = llvm::None;
}
 
void DwarfTransformer::handleDie(raw_ostream &OS, CUInfo &CUI, DWARFDie Die) {
  switch (Die.getTag()) {
  case dwarf::DW_TAG_subprogram: {
    Expected<DWARFAddressRangesVector> RangesOrError = Die.getAddressRanges();
    if (!RangesOrError) {
      consumeError(RangesOrError.takeError());
      break;
    }
    const DWARFAddressRangesVector &Ranges = RangesOrError.get();
    if (Ranges.empty())
      break;
    auto NameIndex = getQualifiedNameIndex(Die, CUI.Language, Gsym);
    if (!NameIndex) {
      OS << "error: function at " << HEX64(Die.getOffset())
         << " has no name\n ";
      Die.dump(OS, 0, DIDumpOptions::getForSingleDIE());
      break;
    }
 
    // Create a function_info for each range
    for (const DWARFAddressRange &Range : Ranges) {
      // The low PC must be less than the high PC. Many linkers don't remove
      // DWARF for functions that don't get linked into the final executable.
      // If both the high and low pc have relocations, linkers will often set
      // the address values for both to the same value to indicate the function
      // has been remove. Other linkers have been known to set the one or both
      // PC values to a UINT32_MAX for 4 byte addresses and UINT64_MAX for 8
      // byte addresses to indicate the function isn't valid. The check below
      // tries to watch for these cases and abort if it runs into them.
      if (Range.LowPC >= Range.HighPC || CUI.isHighestAddress(Range.LowPC))
        break;
 
      // Many linkers can't remove DWARF and might set the LowPC to zero. Since
      // high PC can be an offset from the low PC in more recent DWARF versions
      // we need to watch for a zero'ed low pc which we do using
      // ValidTextRanges below.
      if (!Gsym.IsValidTextAddress(Range.LowPC)) {
        // We expect zero and -1 to be invalid addresses in DWARF depending
        // on the linker of the DWARF. This indicates a function was stripped
        // and the debug info wasn't able to be stripped from the DWARF. If
        // the LowPC isn't zero or -1, then we should emit an error.
        if (Range.LowPC != 0) {
          if (!Gsym.isQuiet()) {
            // Unexpected invalid address, emit a warning
            OS << "warning: DIE has an address range whose start address is "
                  "not in any executable sections ("
               << *Gsym.GetValidTextRanges()
               << ") and will not be processed:\n";
            Die.dump(OS, 0, DIDumpOptions::getForSingleDIE());
          }
        }
        break;
      }
 
      FunctionInfo FI;
      FI.setStartAddress(Range.LowPC);
      FI.setEndAddress(Range.HighPC);
      FI.Name = *NameIndex;
      if (CUI.LineTable) {
        convertFunctionLineTable(OS, CUI, Die, Gsym, FI);
      }
      if (hasInlineInfo(Die, 0)) {
        FI.Inline = InlineInfo();
        FI.Inline->Name = *NameIndex;
        FI.Inline->Ranges.insert(FI.Range);
        parseInlineInfo(Gsym, CUI, Die, 0, FI, *FI.Inline);
      }
      Gsym.addFunctionInfo(std::move(FI));
    }
  } break;
  default:
    break;
  }
  for (DWARFDie ChildDie : Die.children())
    handleDie(OS, CUI, ChildDie);
}
 
Error DwarfTransformer::convert(uint32_t NumThreads) {
  size_t NumBefore = Gsym.getNumFunctionInfos();
  if (NumThreads == 1) {
    // Parse all DWARF data from this thread, use the same string/file table
    // for everything
    for (const auto &CU : DICtx.compile_units()) {
      DWARFDie Die = CU->getUnitDIE(false);
      CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
      handleDie(Log, CUI, Die);
    }
  } else {
    // LLVM Dwarf parser is not thread-safe and we need to parse all DWARF up
    // front before we start accessing any DIEs since there might be
    // cross compile unit references in the DWARF. If we don't do this we can
    // end up crashing.
 
    // We need to call getAbbreviations sequentially first so that getUnitDIE()
    // only works with its local data.
    for (const auto &CU : DICtx.compile_units())
      CU->getAbbreviations();
 
    // Now parse all DIEs in case we have cross compile unit references in a
    // thread pool.
    ThreadPool pool(hardware_concurrency(NumThreads));
    for (const auto &CU : DICtx.compile_units())
      pool.async([&CU]() { CU->getUnitDIE(false /*CUDieOnly*/); });
    pool.wait();
 
    // Now convert all DWARF to GSYM in a thread pool.
    std::mutex LogMutex;
    for (const auto &CU : DICtx.compile_units()) {
      DWARFDie Die = CU->getUnitDIE(false /*CUDieOnly*/);
      if (Die) {
        CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
        pool.async([this, CUI, &LogMutex, Die]() mutable {
          std::string ThreadLogStorage;
          raw_string_ostream ThreadOS(ThreadLogStorage);
          handleDie(ThreadOS, CUI, Die);
          ThreadOS.flush();
          if (!ThreadLogStorage.empty()) {
            // Print ThreadLogStorage lines into an actual stream under a lock
            std::lock_guard<std::mutex> guard(LogMutex);
            Log << ThreadLogStorage;
          }
        });
      }
    }
    pool.wait();
  }
  size_t FunctionsAddedCount = Gsym.getNumFunctionInfos() - NumBefore;
  Log << "Loaded " << FunctionsAddedCount << " functions from DWARF.\n";
  return Error::success();
}
 
llvm::Error DwarfTransformer::verify(StringRef GsymPath) {
  Log << "Verifying GSYM file \"" << GsymPath << "\":\n";
 
  auto Gsym = GsymReader::openFile(GsymPath);
  if (!Gsym)
    return Gsym.takeError();
 
  auto NumAddrs = Gsym->getNumAddresses();
  DILineInfoSpecifier DLIS(
      DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath,
      DILineInfoSpecifier::FunctionNameKind::LinkageName);
  std::string gsymFilename;
  for (uint32_t I = 0; I < NumAddrs; ++I) {
    auto FuncAddr = Gsym->getAddress(I);
    if (!FuncAddr)
        return createStringError(std::errc::invalid_argument,
                                  "failed to extract address[%i]", I);
 
    auto FI = Gsym->getFunctionInfo(*FuncAddr);
    if (!FI)
      return createStringError(std::errc::invalid_argument,
                            "failed to extract function info for address 0x%"
                            PRIu64, *FuncAddr);
 
    for (auto Addr = *FuncAddr; Addr < *FuncAddr + FI->size(); ++Addr) {
      const object::SectionedAddress SectAddr{
          Addr, object::SectionedAddress::UndefSection};
      auto LR = Gsym->lookup(Addr);
      if (!LR)
        return LR.takeError();
 
      auto DwarfInlineInfos =
          DICtx.getInliningInfoForAddress(SectAddr, DLIS);
      uint32_t NumDwarfInlineInfos = DwarfInlineInfos.getNumberOfFrames();
      if (NumDwarfInlineInfos == 0) {
        DwarfInlineInfos.addFrame(
            DICtx.getLineInfoForAddress(SectAddr, DLIS));
      }
 
      // Check for 1 entry that has no file and line info
      if (NumDwarfInlineInfos == 1 &&
          DwarfInlineInfos.getFrame(0).FileName == "<invalid>") {
        DwarfInlineInfos = DIInliningInfo();
        NumDwarfInlineInfos = 0;
      }
      if (NumDwarfInlineInfos > 0 &&
          NumDwarfInlineInfos != LR->Locations.size()) {
        Log << "error: address " << HEX64(Addr) << " has "
            << NumDwarfInlineInfos << " DWARF inline frames and GSYM has "
            << LR->Locations.size() << "\n";
        Log << "    " << NumDwarfInlineInfos << " DWARF frames:\n";
        for (size_t Idx = 0; Idx < NumDwarfInlineInfos; ++Idx) {
          const auto &dii = DwarfInlineInfos.getFrame(Idx);
          Log << "    [" << Idx << "]: " << dii.FunctionName << " @ "
              << dii.FileName << ':' << dii.Line << '\n';
        }
        Log << "    " << LR->Locations.size() << " GSYM frames:\n";
        for (size_t Idx = 0, count = LR->Locations.size();
              Idx < count; ++Idx) {
          const auto &gii = LR->Locations[Idx];
          Log << "    [" << Idx << "]: " << gii.Name << " @ " << gii.Dir
              << '/' << gii.Base << ':' << gii.Line << '\n';
        }
        DwarfInlineInfos = DICtx.getInliningInfoForAddress(SectAddr, DLIS);
        Gsym->dump(Log, *FI);
        continue;
      }
 
      for (size_t Idx = 0, count = LR->Locations.size(); Idx < count;
            ++Idx) {
        const auto &gii = LR->Locations[Idx];
        if (Idx < NumDwarfInlineInfos) {
          const auto &dii = DwarfInlineInfos.getFrame(Idx);
          gsymFilename = LR->getSourceFile(Idx);
          // Verify function name
          if (dii.FunctionName.find(gii.Name.str()) != 0)
            Log << "error: address " << HEX64(Addr) << " DWARF function \""
                << dii.FunctionName.c_str()
                << "\" doesn't match GSYM function \"" << gii.Name << "\"\n";
          // Verify source file path
          if (dii.FileName != gsymFilename)
            Log << "error: address " << HEX64(Addr) << " DWARF path \""
                << dii.FileName.c_str() << "\" doesn't match GSYM path \""
                << gsymFilename.c_str() << "\"\n";
          // Verify source file line
          if (dii.Line != gii.Line)
            Log << "error: address " << HEX64(Addr) << " DWARF line "
                << dii.Line << " != GSYM line " << gii.Line << "\n";
        }
      }
    }
  }
  return Error::success();
}