Spice86 – A PC Emulator For Real Mode Reverse Engineering

Spice86 is an advanced PC emulator designed for reverse engineering and rewriting real-mode DOS programs, especially when the source code is unavailable.

Built on .NET 8, it is compatible with Windows, macOS, and Linux, offering a robust platform for developers and researchers to dissect and reimplement legacy software. Below is an overview of its primary functions and capabilities.

Key Features And Functions

1. Emulation for Reverse Engineering

Spice86 emulates real-mode DOS programs, allowing users to execute binaries in a controlled environment.

During execution, it generates runtime data such as memory dumps and execution flow information. This data serves as the foundation for reverse engineering efforts.

2. Integration with Ghidra

Spice86 works seamlessly with the Ghidra reverse engineering tool via the spice86-ghidra-plugin. The plugin translates assembly instructions from memory dumps into C# code.

This enables developers to gradually replace low-level assembly code with high-level C# implementations, simplifying the reverse engineering process.

3. Methodical Reimplementation

The tool employs a divide-and-conquer approach to rewriting programs. Developers can statically analyze small sequences of assembly code, translate them into C#, and integrate these translations into the emulator.

This iterative process ensures that the program remains functional throughout development, making debugging and intent discovery more straightforward.

4. Debugging Capabilities

Spice86 includes a built-in debugger and supports integration with GDB (GNU Debugger). Users can set breakpoints, inspect memory, view disassembly, and analyze execution flow dynamically.

Custom GDB commands enhance debugging by providing specialized tools for runtime analysis.

5. Support for DOS Program Features

Spice86 emulates various DOS functionalities, including:

• CPU instructions (16-bit fully supported; partial 32-bit support).
• Graphics modes (VGA, EGA, CGA).
• Input devices (keyboard and mouse).
• Sound systems (PC Speaker, Adlib/SoundBlaster MIDI/PCM).

6. Data Dumping and Analysis

The emulator can dump runtime data such as memory snapshots and execution flow information. This data is crucial for understanding program behavior and facilitates seamless integration with external tools like Ghidra.

7. Code Overrides

Developers can override original assembly code with custom C# implementations using IOverrideSupplier. This allows precise control over program behavior and enables modular reimplementation of legacy software.

Spice86 is particularly useful for:

• Analyzing old DOS games or software.
• Rewriting legacy applications into modern programming languages.
• Debugging complex binaries with incomplete documentation.
• Preserving historical software by converting it into maintainable codebases.

In summary, Spice86 bridges the gap between legacy DOS programs and modern development practices by providing powerful tools for emulation, reverse engineering, debugging, and reimplementation.

Its ability to combine low-level analysis with high-level language translation makes it an invaluable resource for software preservationists and developers alike.