source/Plugins/Trace/intel-pt/DecodedThread.h

//===-- DecodedThread.h -----------------------------------------*- 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 LLDB_SOURCE_PLUGINS_TRACE_INTEL_PT_DECODEDTHREAD_H
#define LLDB_SOURCE_PLUGINS_TRACE_INTEL_PT_DECODEDTHREAD_H

#include <vector>

#include "llvm/Support/Errc.h"
#include "llvm/Support/Error.h"

#include "lldb/Target/Trace.h"

#include "intel-pt.h"

namespace lldb_private {
namespace trace_intel_pt {

/// Class for representing a libipt decoding error.
class IntelPTError : public llvm::ErrorInfo<IntelPTError> {
public:
  static char ID;

  /// \param[in] libipt_error_code
  ///     Negative number returned by libipt when decoding the trace and
  ///     signaling errors.
  ///
  /// \param[in] address
  ///     Optional instruction address. When decoding an individual instruction,
  ///     its address might be available in the \a pt_insn object, and should be
  ///     passed to this constructor. Other errors don't have an associated
  ///     address.
  IntelPTError(int libipt_error_code,
               lldb::addr_t address = LLDB_INVALID_ADDRESS);

  std::error_code convertToErrorCode() const override {
    return llvm::errc::not_supported;
  }

  void log(llvm::raw_ostream &OS) const override;

private:
  int m_libipt_error_code;
  lldb::addr_t m_address;
};

/// \class IntelPTInstruction
/// An instruction obtained from decoding a trace. It is either an actual
/// instruction or an error indicating a gap in the trace.
///
/// Gaps in the trace can come in a few flavors:
///   - tracing gaps (e.g. tracing was paused and then resumed)
///   - tracing errors (e.g. buffer overflow)
///   - decoding errors (e.g. some memory region couldn't be decoded)
/// As mentioned, any gap is represented as an error in this class.
class IntelPTInstruction {
public:
  IntelPTInstruction(const pt_insn &pt_insn) : m_pt_insn(pt_insn) {}

  /// Error constructor
  ///
  /// libipt errors should use the underlying \a IntelPTError class.
  IntelPTInstruction(llvm::Error err) {
    llvm::handleAllErrors(std::move(err),
                          [&](std::unique_ptr<llvm::ErrorInfoBase> info) {
                            m_error = std::move(info);
                          });
  }

  /// Check if this object represents an error (i.e. a gap).
  ///
  /// \return
  ///     Whether this object represents an error.
  bool IsError() const;

  /// \return
  ///     The instruction pointer address, or an \a llvm::Error if it is an
  ///     error.
  llvm::Expected<lldb::addr_t> GetLoadAddress() const;

  /// \return
  ///     An \a llvm::Error object if this class corresponds to an Error, or an
  ///     \a llvm::Error::success otherwise.
  llvm::Error ToError() const;

  IntelPTInstruction(IntelPTInstruction &&other) = default;

private:
  IntelPTInstruction(const IntelPTInstruction &other) = delete;
  const IntelPTInstruction &operator=(const IntelPTInstruction &other) = delete;

  pt_insn m_pt_insn;
  std::unique_ptr<llvm::ErrorInfoBase> m_error;
};

/// \class DecodedThread
/// Class holding the instructions and function call hierarchy obtained from
/// decoding a trace, as well as a position cursor used when reverse debugging
/// the trace.
///
/// Each decoded thread contains a cursor to the current position the user is
/// stopped at. See \a Trace::GetCursorPosition for more information.
class DecodedThread {
public:
  DecodedThread(std::vector<IntelPTInstruction> &&instructions)
      : m_instructions(std::move(instructions)), m_position(GetLastPosition()) {
  }

  /// Get the instructions from the decoded trace. Some of them might indicate
  /// errors (i.e. gaps) in the trace.
  ///
  /// \return
  ///   The instructions of the trace.
  llvm::ArrayRef<IntelPTInstruction> GetInstructions() const;

  /// \return
  ///   The current position of the cursor of this trace, or 0 if there are no
  ///   instructions.
  size_t GetCursorPosition() const;

  /// Change the position of the cursor of this trace. If this value is to high,
  /// the new position will be set as the last instruction of the trace.
  ///
  /// \return
  ///     The effective new position.
  size_t SetCursorPosition(size_t new_position);
  /// \}

private:
  /// \return
  ///     The index of the last element of the trace, or 0 if empty.
  size_t GetLastPosition() const;

  std::vector<IntelPTInstruction> m_instructions;
  size_t m_position;
};

} // namespace trace_intel_pt
} // namespace lldb_private

#endif // LLDB_SOURCE_PLUGINS_TRACE_INTEL_PT_DECODEDTHREAD_H