RawMemProfReader.cpp

//===- RawMemProfReader.cpp - Instrumented memory profiling reader --------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains support for reading MemProf profiling data.
//
//===----------------------------------------------------------------------===//

#include <cstdint>
#include <type_traits>

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/DebugInfo/Symbolize/SymbolizableModule.h"
#include "llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/ProfileData/MemProf.h"
#include "llvm/ProfileData/MemProfData.inc"
#include "llvm/ProfileData/RawMemProfReader.h"
#include "llvm/Support/MD5.h"

namespace llvm {
namespace memprof {
namespace {

struct Summary {
  uint64_t Version;
  uint64_t TotalSizeBytes;
  uint64_t NumSegments;
  uint64_t NumMIBInfo;
  uint64_t NumStackOffsets;
};

template <class T = uint64_t> inline T alignedRead(const char *Ptr) {
  static_assert(std::is_pod<T>::value, "Not a pod type.");
  assert(reinterpret_cast<size_t>(Ptr) % sizeof(T) == 0 && "Unaligned Read");
  return *reinterpret_cast<const T *>(Ptr);
}

Summary computeSummary(const char *Start) {
  auto *H = reinterpret_cast<const Header *>(Start);

  // Check alignment while reading the number of items in each section.
  return Summary{
      H->Version,
      H->TotalSize,
      alignedRead(Start + H->SegmentOffset),
      alignedRead(Start + H->MIBOffset),
      alignedRead(Start + H->StackOffset),
  };
}

Error checkBuffer(const MemoryBuffer &Buffer) {
  if (!RawMemProfReader::hasFormat(Buffer))
    return make_error<InstrProfError>(instrprof_error::bad_magic);

  if (Buffer.getBufferSize() == 0)
    return make_error<InstrProfError>(instrprof_error::empty_raw_profile);

  if (Buffer.getBufferSize() < sizeof(Header)) {
    return make_error<InstrProfError>(instrprof_error::truncated);
  }

  // The size of the buffer can be > header total size since we allow repeated
  // serialization of memprof profiles to the same file.
  uint64_t TotalSize = 0;
  const char *Next = Buffer.getBufferStart();
  while (Next < Buffer.getBufferEnd()) {
    auto *H = reinterpret_cast<const Header *>(Next);
    if (H->Version != MEMPROF_RAW_VERSION) {
      return make_error<InstrProfError>(instrprof_error::unsupported_version);
    }

    TotalSize += H->TotalSize;
    Next += H->TotalSize;
  }

  if (Buffer.getBufferSize() != TotalSize) {
    return make_error<InstrProfError>(instrprof_error::malformed);
  }
  return Error::success();
}

// A generic method to read binary data for type T where the first 8b indicate
// the number of elements of type T to be read.
template <typename T> llvm::SmallVector<T, 16> readInfo(const char *Begin) {
  const uint64_t NumItemsToRead = *reinterpret_cast<const uint64_t *>(Begin);
  const char *Ptr = Begin + sizeof(uint64_t);
  llvm::SmallVector<T, 16> Items;
  for (uint64_t I = 0; I < NumItemsToRead; I++) {
    Items.emplace_back(*reinterpret_cast<const T *>(Ptr + I * sizeof(T)));
  }
  return Items;
}

CallStackMap readStackInfo(const char *Begin) {
  const uint64_t NumItemsToRead = *reinterpret_cast<const uint64_t *>(Begin);
  char *Ptr = const_cast<char *>(Begin) + sizeof(uint64_t);
  CallStackMap Items;

  uint64_t Count = 0;
  do {
    const uint64_t StackId = alignedRead(Ptr);
    Ptr += sizeof(uint64_t);

    const uint64_t NumPCs = alignedRead(Ptr);
    Ptr += sizeof(uint64_t);

    SmallVector<uint64_t, 32> CallStack;
    for (uint64_t I = 0; I < NumPCs; I++) {
      CallStack.push_back(alignedRead(Ptr));
      Ptr += sizeof(uint64_t);
    }

    Items[StackId] = CallStack;
  } while (++Count < NumItemsToRead);
  return Items;
}

// Merges the contents of stack information in \p From to \p To. Returns true if
// any stack ids observed previously map to a different set of program counter
// addresses.
bool mergeStackMap(const CallStackMap &From, CallStackMap &To) {
  for (const auto &IdStack : From) {
    auto I = To.find(IdStack.first);
    if (I == To.end()) {
      To[IdStack.first] = IdStack.second;
    } else {
      // Check that the PCs are the same (in order).
      if (IdStack.second != I->second)
        return true;
    }
  }
  return false;
}

StringRef trimSuffix(const StringRef Name) {
  const auto Pos = Name.find(".llvm.");
  return Name.take_front(Pos);
}

Error report(Error E, const StringRef Context) {
  return joinErrors(createStringError(inconvertibleErrorCode(), Context),
                    std::move(E));
}
} // namespace

Expected<std::unique_ptr<RawMemProfReader>>
RawMemProfReader::create(const Twine &Path, const StringRef ProfiledBinary) {
  auto BufferOr = MemoryBuffer::getFileOrSTDIN(Path);
  if (std::error_code EC = BufferOr.getError())
    return report(errorCodeToError(EC), Path.getSingleStringRef());

  std::unique_ptr<MemoryBuffer> Buffer(BufferOr.get().release());
  if (Error E = checkBuffer(*Buffer))
    return report(std::move(E), Path.getSingleStringRef());

  if (ProfiledBinary.empty())
    return report(
        errorCodeToError(make_error_code(std::errc::invalid_argument)),
        "Path to profiled binary is empty!");

  auto BinaryOr = llvm::object::createBinary(ProfiledBinary);
  if (!BinaryOr) {
    return report(BinaryOr.takeError(), ProfiledBinary);
  }

  std::unique_ptr<RawMemProfReader> Reader(
      new RawMemProfReader(std::move(Buffer), std::move(BinaryOr.get())));
  if (Error E = Reader->initialize()) {
    return std::move(E);
  }
  return std::move(Reader);
}

bool RawMemProfReader::hasFormat(const StringRef Path) {
  auto BufferOr = MemoryBuffer::getFileOrSTDIN(Path);
  if (!BufferOr)
    return false;

  std::unique_ptr<MemoryBuffer> Buffer(BufferOr.get().release());
  return hasFormat(*Buffer);
}

bool RawMemProfReader::hasFormat(const MemoryBuffer &Buffer) {
  if (Buffer.getBufferSize() < sizeof(uint64_t))
    return false;
  // Aligned read to sanity check that the buffer was allocated with at least 8b
  // alignment.
  const uint64_t Magic = alignedRead(Buffer.getBufferStart());
  return Magic == MEMPROF_RAW_MAGIC_64;
}

void RawMemProfReader::printYAML(raw_ostream &OS) {
  OS << "MemprofProfile:\n";
  printSummaries(OS);
  // Print out the merged contents of the profiles.
  OS << "  Records:\n";
  for (const auto &Record : *this) {
    OS << "  -\n";
    Record.print(OS);
  }
}

void RawMemProfReader::printSummaries(raw_ostream &OS) const {
  const char *Next = DataBuffer->getBufferStart();
  while (Next < DataBuffer->getBufferEnd()) {
    auto Summary = computeSummary(Next);
    OS << "  -\n";
    OS << "  Header:\n";
    OS << "    Version: " << Summary.Version << "\n";
    OS << "    TotalSizeBytes: " << Summary.TotalSizeBytes << "\n";
    OS << "    NumSegments: " << Summary.NumSegments << "\n";
    OS << "    NumMibInfo: " << Summary.NumMIBInfo << "\n";
    OS << "    NumStackOffsets: " << Summary.NumStackOffsets << "\n";
    // TODO: Print the build ids once we can record them using the
    // sanitizer_procmaps library for linux.

    auto *H = reinterpret_cast<const Header *>(Next);
    Next += H->TotalSize;
  }
}

Error RawMemProfReader::initialize() {
  const StringRef FileName = Binary.getBinary()->getFileName();

  auto *ElfObject = dyn_cast<object::ELFObjectFileBase>(Binary.getBinary());
  if (!ElfObject) {
    return report(make_error<StringError>(Twine("Not an ELF file: "),
                                          inconvertibleErrorCode()),
                  FileName);
  }

  auto Triple = ElfObject->makeTriple();
  if (!Triple.isX86())
    return report(make_error<StringError>(Twine("Unsupported target: ") +
                                              Triple.getArchName(),
                                          inconvertibleErrorCode()),
                  FileName);

  auto *Object = cast<object::ObjectFile>(Binary.getBinary());
  std::unique_ptr<DIContext> Context = DWARFContext::create(
      *Object, DWARFContext::ProcessDebugRelocations::Process);

  auto SOFOr = symbolize::SymbolizableObjectFile::create(
      Object, std::move(Context), /*UntagAddresses=*/false);
  if (!SOFOr)
    return report(SOFOr.takeError(), FileName);
  Symbolizer = std::move(SOFOr.get());

  return readRawProfile();
}

Error RawMemProfReader::readRawProfile() {
  const char *Next = DataBuffer->getBufferStart();

  while (Next < DataBuffer->getBufferEnd()) {
    auto *Header = reinterpret_cast<const memprof::Header *>(Next);

    // Read in the segment information, check whether its the same across all
    // profiles in this binary file.
    if (SegmentInfo.empty()) {
      SegmentInfo = readInfo<SegmentEntry>(Next + Header->SegmentOffset);
    } else {
      auto Info = readInfo<SegmentEntry>(Next + Header->SegmentOffset);
      // We do not expect segment information to change when deserializing from
      // the same binary profile file. This can happen if dynamic libraries are
      // loaded/unloaded between profile dumping.
      if (SegmentInfo != Info) {
        return make_error<InstrProfError>(instrprof_error::malformed);
      }
    }

    // Read in the MemInfoBlocks. Merge them based on stack id - we assume that
    // raw profiles in the same binary file are from the same process so the
    // stackdepot ids are the same.
    PACKED(struct IDAndMIB {
      uint64_t Id;
      MemInfoBlock MIB;
    });
    for (const auto &Value : readInfo<IDAndMIB>(Next + Header->MIBOffset)) {
      if (ProfileData.count(Value.Id)) {
        ProfileData[Value.Id].Merge(Value.MIB);
      } else {
        ProfileData[Value.Id] = Value.MIB;
      }
    }

    // Read in the callstack for each ids. For multiple raw profiles in the same
    // file, we expect that the callstack is the same for a unique id.
    const CallStackMap CSM = readStackInfo(Next + Header->StackOffset);
    if (StackMap.empty()) {
      StackMap = CSM;
    } else {
      if (mergeStackMap(CSM, StackMap))
        return make_error<InstrProfError>(instrprof_error::malformed);
    }

    Next += Header->TotalSize;
  }

  return Error::success();
}

object::SectionedAddress
RawMemProfReader::getModuleOffset(const uint64_t VirtualAddress) {
  SegmentEntry *ContainingSegment = nullptr;
  for (auto &SE : SegmentInfo) {
    if (VirtualAddress > SE.Start && VirtualAddress <= SE.End) {
      ContainingSegment = &SE;
    }
  }

  // Ensure that the virtual address is valid.
  assert(ContainingSegment && "Could not find a segment entry");

  // TODO: Compute the file offset based on the maps and program headers. For
  // now this only works for non PIE binaries.
  return object::SectionedAddress{VirtualAddress};
}

Error RawMemProfReader::fillRecord(const uint64_t Id, const MemInfoBlock &MIB,
                                   MemProfRecord &Record) {
  auto &CallStack = StackMap[Id];
  DILineInfoSpecifier Specifier(
      DILineInfoSpecifier::FileLineInfoKind::RawValue,
      DILineInfoSpecifier::FunctionNameKind::LinkageName);
  for (const uint64_t Address : CallStack) {
    Expected<DIInliningInfo> DIOr = Symbolizer->symbolizeInlinedCode(
        getModuleOffset(Address), Specifier, /*UseSymbolTable=*/false);

    if (!DIOr)
      return DIOr.takeError();
    DIInliningInfo DI = DIOr.get();

    for (size_t I = 0; I < DI.getNumberOfFrames(); I++) {
      const auto &Frame = DI.getFrame(I);
      Record.CallStack.emplace_back(
          std::to_string(llvm::MD5Hash(trimSuffix(Frame.FunctionName))),
          Frame.Line - Frame.StartLine, Frame.Column,
          // Only the first entry is not an inlined location.
          I != 0);
    }
  }
  Record.Info = MIB;
  return Error::success();
}

Error RawMemProfReader::readNextRecord(MemProfRecord &Record) {
  if (ProfileData.empty())
    return make_error<InstrProfError>(instrprof_error::empty_raw_profile);

  if (Iter == ProfileData.end())
    return make_error<InstrProfError>(instrprof_error::eof);

  Record.clear();
  if (Error E = fillRecord(Iter->first, Iter->second, Record)) {
    return E;
  }
  Iter++;
  return Error::success();
}

} // namespace memprof
} // namespace llvm