StackMapParser.h

Go to the documentation of this file.

//===- StackMapParser.h - StackMap Parsing Support --------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_OBJECT_STACKMAPPARSER_H
#define LLVM_OBJECT_STACKMAPPARSER_H
 
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Object/ELF.h"
#include "llvm/Support/Endian.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <vector>
 
namespace llvm {
 
/// A parser for the latest stackmap format.  At the moment, latest=V3.
template <support::endianness Endianness>
class StackMapParser {
public:
  template <typename AccessorT>
  class AccessorIterator {
  public:
    AccessorIterator(AccessorT A) : A(A) {}
 
    AccessorIterator& operator++() { A = A.next(); return *this; }
    AccessorIterator operator++(int) {
      auto tmp = *this;
      ++*this;
      return tmp;
    }
 
    bool operator==(const AccessorIterator &Other) const {
      return A.P == Other.A.P;
    }
 
    bool operator!=(const AccessorIterator &Other) const {
      return !(*this == Other);
    }
 
    AccessorT& operator*() { return A; }
    AccessorT* operator->() { return &A; }
 
  private:
    AccessorT A;
  };
 
  /// Accessor for function records.
  class FunctionAccessor {
    friend class StackMapParser;
 
  public:
    /// Get the function address.
    uint64_t getFunctionAddress() const {
      return read<uint64_t>(P);
    }
 
    /// Get the function's stack size.
    uint64_t getStackSize() const {
      return read<uint64_t>(P + sizeof(uint64_t));
    }
 
    /// Get the number of callsite records.
    uint64_t getRecordCount() const {
      return read<uint64_t>(P + (2 * sizeof(uint64_t)));
    }
 
  private:
    FunctionAccessor(const uint8_t *P) : P(P) {}
 
    const static int FunctionAccessorSize = 3 * sizeof(uint64_t);
 
    FunctionAccessor next() const {
      return FunctionAccessor(P + FunctionAccessorSize);
    }
 
    const uint8_t *P;
  };
 
  /// Accessor for constants.
  class ConstantAccessor {
    friend class StackMapParser;
 
  public:
    /// Return the value of this constant.
    uint64_t getValue() const { return read<uint64_t>(P); }
 
  private:
    ConstantAccessor(const uint8_t *P) : P(P) {}
 
    const static int ConstantAccessorSize = sizeof(uint64_t);
 
    ConstantAccessor next() const {
      return ConstantAccessor(P + ConstantAccessorSize);
    }
 
    const uint8_t *P;
  };
 
  enum class LocationKind : uint8_t {
    Register = 1, Direct = 2, Indirect = 3, Constant = 4, ConstantIndex = 5
  };
 
  /// Accessor for location records.
  class LocationAccessor {
    friend class StackMapParser;
    friend class RecordAccessor;
 
  public:
    /// Get the Kind for this location.
    LocationKind getKind() const {
      return LocationKind(P[KindOffset]);
    }
 
    /// Get the Size for this location.
    unsigned getSizeInBytes() const {
        return read<uint16_t>(P + SizeOffset);
 
    }
 
    /// Get the Dwarf register number for this location.
    uint16_t getDwarfRegNum() const {
      return read<uint16_t>(P + DwarfRegNumOffset);
    }
 
    /// Get the small-constant for this location. (Kind must be Constant).
    uint32_t getSmallConstant() const {
      assert(getKind() == LocationKind::Constant && "Not a small constant.");
      return read<uint32_t>(P + SmallConstantOffset);
    }
 
    /// Get the constant-index for this location. (Kind must be ConstantIndex).
    uint32_t getConstantIndex() const {
      assert(getKind() == LocationKind::ConstantIndex &&
             "Not a constant-index.");
      return read<uint32_t>(P + SmallConstantOffset);
    }
 
    /// Get the offset for this location. (Kind must be Direct or Indirect).
    int32_t getOffset() const {
      assert((getKind() == LocationKind::Direct ||
              getKind() == LocationKind::Indirect) &&
             "Not direct or indirect.");
      return read<int32_t>(P + SmallConstantOffset);
    }
 
  private:
    LocationAccessor(const uint8_t *P) : P(P) {}
 
    LocationAccessor next() const {
      return LocationAccessor(P + LocationAccessorSize);
    }
 
    static const int KindOffset = 0;
    static const int SizeOffset = KindOffset + sizeof(uint16_t);
    static const int DwarfRegNumOffset = SizeOffset + sizeof(uint16_t);
    static const int SmallConstantOffset = DwarfRegNumOffset + sizeof(uint32_t);
    static const int LocationAccessorSize = sizeof(uint64_t) + sizeof(uint32_t);
 
    const uint8_t *P;
  };
 
  /// Accessor for stackmap live-out fields.
  class LiveOutAccessor {
    friend class StackMapParser;
    friend class RecordAccessor;
 
  public:
    /// Get the Dwarf register number for this live-out.
    uint16_t getDwarfRegNum() const {
      return read<uint16_t>(P + DwarfRegNumOffset);
    }
 
    /// Get the size in bytes of live [sub]register.
    unsigned getSizeInBytes() const {
      return read<uint8_t>(P + SizeOffset);
    }
 
  private:
    LiveOutAccessor(const uint8_t *P) : P(P) {}
 
    LiveOutAccessor next() const {
      return LiveOutAccessor(P + LiveOutAccessorSize);
    }
 
    static const int DwarfRegNumOffset = 0;
    static const int SizeOffset =
      DwarfRegNumOffset + sizeof(uint16_t) + sizeof(uint8_t);
    static const int LiveOutAccessorSize = sizeof(uint32_t);
 
    const uint8_t *P;
  };
 
  /// Accessor for stackmap records.
  class RecordAccessor {
    friend class StackMapParser;
 
  public:
    using location_iterator = AccessorIterator<LocationAccessor>;
    using liveout_iterator = AccessorIterator<LiveOutAccessor>;
 
    /// Get the patchpoint/stackmap ID for this record.
    uint64_t getID() const {
      return read<uint64_t>(P + PatchpointIDOffset);
    }
 
    /// Get the instruction offset (from the start of the containing function)
    /// for this record.
    uint32_t getInstructionOffset() const {
      return read<uint32_t>(P + InstructionOffsetOffset);
    }
 
    /// Get the number of locations contained in this record.
    uint16_t getNumLocations() const {
      return read<uint16_t>(P + NumLocationsOffset);
    }
 
    /// Get the location with the given index.
    LocationAccessor getLocation(unsigned LocationIndex) const {
      unsigned LocationOffset =
        LocationListOffset + LocationIndex * LocationSize;
      return LocationAccessor(P + LocationOffset);
    }
 
    /// Begin iterator for locations.
    location_iterator location_begin() const {
      return location_iterator(getLocation(0));
    }
 
    /// End iterator for locations.
    location_iterator location_end() const {
      return location_iterator(getLocation(getNumLocations()));
    }
 
    /// Iterator range for locations.
    iterator_range<location_iterator> locations() const {
      return make_range(location_begin(), location_end());
    }
 
    /// Get the number of liveouts contained in this record.
    uint16_t getNumLiveOuts() const {
      return read<uint16_t>(P + getNumLiveOutsOffset());
    }
 
    /// Get the live-out with the given index.
    LiveOutAccessor getLiveOut(unsigned LiveOutIndex) const {
      unsigned LiveOutOffset =
        getNumLiveOutsOffset() + sizeof(uint16_t) + LiveOutIndex * LiveOutSize;
      return LiveOutAccessor(P + LiveOutOffset);
    }
 
    /// Begin iterator for live-outs.
    liveout_iterator liveouts_begin() const {
      return liveout_iterator(getLiveOut(0));
    }
 
    /// End iterator for live-outs.
    liveout_iterator liveouts_end() const {
      return liveout_iterator(getLiveOut(getNumLiveOuts()));
    }
 
    /// Iterator range for live-outs.
    iterator_range<liveout_iterator> liveouts() const {
      return make_range(liveouts_begin(), liveouts_end());
    }
 
  private:
    RecordAccessor(const uint8_t *P) : P(P) {}
 
    unsigned getNumLiveOutsOffset() const {
      unsigned LocOffset = 
          ((LocationListOffset + LocationSize * getNumLocations()) + 7) & ~0x7; 
      return LocOffset + sizeof(uint16_t);
    }
 
    unsigned getSizeInBytes() const {
      unsigned RecordSize =
        getNumLiveOutsOffset() + sizeof(uint16_t) + getNumLiveOuts() * LiveOutSize;
      return (RecordSize + 7) & ~0x7;
    }
 
    RecordAccessor next() const {
      return RecordAccessor(P + getSizeInBytes());
    }
 
    static const unsigned PatchpointIDOffset = 0;
    static const unsigned InstructionOffsetOffset =
      PatchpointIDOffset + sizeof(uint64_t);
    static const unsigned NumLocationsOffset =
      InstructionOffsetOffset + sizeof(uint32_t) + sizeof(uint16_t);
    static const unsigned LocationListOffset =
      NumLocationsOffset + sizeof(uint16_t);
    static const unsigned LocationSize = sizeof(uint64_t) + sizeof(uint32_t);
    static const unsigned LiveOutSize = sizeof(uint32_t);
 
    const uint8_t *P;
  };
 
  /// Construct a parser for a version-3 stackmap. StackMap data will be read
  /// from the given array.
  StackMapParser(ArrayRef<uint8_t> StackMapSection)
      : StackMapSection(StackMapSection) {
    ConstantsListOffset = FunctionListOffset + getNumFunctions() * FunctionSize;
 
    assert(StackMapSection[0] == 3 &&
           "StackMapParser can only parse version 3 stackmaps");
 
    unsigned CurrentRecordOffset =
      ConstantsListOffset + getNumConstants() * ConstantSize;
 
    for (unsigned I = 0, E = getNumRecords(); I != E; ++I) {
      StackMapRecordOffsets.push_back(CurrentRecordOffset);
      CurrentRecordOffset +=
        RecordAccessor(&StackMapSection[CurrentRecordOffset]).getSizeInBytes();
    }
  }
 
  /// Validates the header of the specified stack map section.
  static Error validateHeader(ArrayRef<uint8_t> StackMapSection) {
    // See the comment for StackMaps::emitStackmapHeader().
    if (StackMapSection.size() < 16)
      return object::createError(
          "the stack map section size (" + Twine(StackMapSection.size()) +
          ") is less than the minimum possible size of its header (16)");
 
    unsigned Version = StackMapSection[0];
    if (Version != 3)
      return object::createError(
          "the version (" + Twine(Version) +
          ") of the stack map section is unsupported, the "
          "supported version is 3");
    return Error::success();
  }
 
  using function_iterator = AccessorIterator<FunctionAccessor>;
  using constant_iterator = AccessorIterator<ConstantAccessor>;
  using record_iterator = AccessorIterator<RecordAccessor>;
 
  /// Get the version number of this stackmap. (Always returns 3).
  unsigned getVersion() const { return 3; }
 
  /// Get the number of functions in the stack map.
  uint32_t getNumFunctions() const {
    return read<uint32_t>(&StackMapSection[NumFunctionsOffset]);
  }
 
  /// Get the number of large constants in the stack map.
  uint32_t getNumConstants() const {
    return read<uint32_t>(&StackMapSection[NumConstantsOffset]);
  }
 
  /// Get the number of stackmap records in the stackmap.
  uint32_t getNumRecords() const {
    return read<uint32_t>(&StackMapSection[NumRecordsOffset]);
  }
 
  /// Return an FunctionAccessor for the given function index.
  FunctionAccessor getFunction(unsigned FunctionIndex) const {
    return FunctionAccessor(StackMapSection.data() +
                            getFunctionOffset(FunctionIndex));
  }
 
  /// Begin iterator for functions.
  function_iterator functions_begin() const {
    return function_iterator(getFunction(0));
  }
 
  /// End iterator for functions.
  function_iterator functions_end() const {
    return function_iterator(
             FunctionAccessor(StackMapSection.data() +
                              getFunctionOffset(getNumFunctions())));
  }
 
  /// Iterator range for functions.
  iterator_range<function_iterator> functions() const {
    return make_range(functions_begin(), functions_end());
  }
 
  /// Return the large constant at the given index.
  ConstantAccessor getConstant(unsigned ConstantIndex) const {
    return ConstantAccessor(StackMapSection.data() +
                            getConstantOffset(ConstantIndex));
  }
 
  /// Begin iterator for constants.
  constant_iterator constants_begin() const {
    return constant_iterator(getConstant(0));
  }
 
  /// End iterator for constants.
  constant_iterator constants_end() const {
    return constant_iterator(
             ConstantAccessor(StackMapSection.data() +
                              getConstantOffset(getNumConstants())));
  }
 
  /// Iterator range for constants.
  iterator_range<constant_iterator> constants() const {
    return make_range(constants_begin(), constants_end());
  }
 
  /// Return a RecordAccessor for the given record index.
  RecordAccessor getRecord(unsigned RecordIndex) const {
    std::size_t RecordOffset = StackMapRecordOffsets[RecordIndex];
    return RecordAccessor(StackMapSection.data() + RecordOffset);
  }
 
  /// Begin iterator for records.
  record_iterator records_begin() const {
    if (getNumRecords() == 0)
      return record_iterator(RecordAccessor(nullptr));
    return record_iterator(getRecord(0));
  }
 
  /// End iterator for records.
  record_iterator records_end() const {
    // Records need to be handled specially, since we cache the start addresses
    // for them: We can't just compute the 1-past-the-end address, we have to
    // look at the last record and use the 'next' method.
    if (getNumRecords() == 0)
      return record_iterator(RecordAccessor(nullptr));
    return record_iterator(getRecord(getNumRecords() - 1).next());
  }
 
  /// Iterator range for records.
  iterator_range<record_iterator> records() const {
    return make_range(records_begin(), records_end());
  }
 
private:
  template <typename T>
  static T read(const uint8_t *P) {
    return support::endian::read<T, Endianness, 1>(P);
  }
 
  static const unsigned HeaderOffset = 0;
  static const unsigned NumFunctionsOffset = HeaderOffset + sizeof(uint32_t);
  static const unsigned NumConstantsOffset = NumFunctionsOffset + sizeof(uint32_t);
  static const unsigned NumRecordsOffset = NumConstantsOffset + sizeof(uint32_t);
  static const unsigned FunctionListOffset = NumRecordsOffset + sizeof(uint32_t);
 
  static const unsigned FunctionSize = 3 * sizeof(uint64_t);
  static const unsigned ConstantSize = sizeof(uint64_t);
 
  std::size_t getFunctionOffset(unsigned FunctionIndex) const {
    return FunctionListOffset + FunctionIndex * FunctionSize;
  }
 
  std::size_t getConstantOffset(unsigned ConstantIndex) const {
    return ConstantsListOffset + ConstantIndex * ConstantSize;
  }
 
  ArrayRef<uint8_t> StackMapSection;
  unsigned ConstantsListOffset;
  std::vector<unsigned> StackMapRecordOffsets;
};
 
} // end namespace llvm
 
#endif // LLVM_OBJECT_STACKMAPPARSER_H