SEMU

A simple RISC-V 32 emulator for fun and practice, inspired by NEMU.
This project is the final project for CPL2024.

Installation

1. Set up the environment

Install necessary packages from your distro's package manager:

sudo apt update
sudo apt install build-essential man gdb git libreadline-dev -y

Install SDL3: https://wiki.libsdl.org/SDL3/Installation

2. Build SEMU

Clone the repository and set up the environment:

git clone <repository-url>
cd semu
. scripts/envsetup.sh

Generate .config:

make perf_defconfig

or

make menuconfig

Build:

make

3. Run SEMU

Once the build is complete, you can run the emulator:

make run

To load a program, you can download prebuilt ones from https://github.com/snnbyyds/semu-examples

make run IMG=/path/fceux-mario.bin

Feature Overview

SEMU Infrastructure

kbuild system (tools/kconfig, synced from NEMU)

debuggers (src/monitor)

• sdb (builtin simple debugger with some simple commands)
• gdbstub (an implementation of the GDB Remote Serial Protocol to help debug programs with GDB)

snapshot utility (src/utils)

• snapshot backup & restore

trace (src/utils)

• exception / interruption trace
• instruction trace (Powered by capstone 6)
• function trace (NOT implemented)

expression calculation

• expression calculator (NOT implemented)

difftest

• difftest with NEMU (DUT: SEMU, REF: https://github.com/ics-ext/nemu-ref)
• serve as a REF for difftest (NOT implemented)

CPU Simulation src/cpu

• Common RV32IM instructions (src/cpu/inst.c)
• GPRs
• CSRs (Basic ones)
• Fetch, decode, execute cycle (src/cpu/cpu.c)
• Basic privileged ISA

( TODO: Make it running even FASTER )

Memory Simulation src/memory

• Basic read and write operations
• RV32 Sv32 paging (Basic)
• TLB (NOT implemented)
• MMIO src/device/mmio

Device Simulation src/device

• audio (src/device/audio.c)
• disk (src/device/disk.c)
• keyboard (src/device/keyboard.c)
• serial (src/device/serial.c, Input not implemented)
• timer (src/device/timer.c)
• vga (src/device/vga.c)

About HALs and programs

I haven’t had the chance to develop our own Hardware Abstraction Layer, the SAL yet, so for now, I’ve only ported the abstract-machine as the abstraction layer. However, since the code in abstract-machine, nanos-lite, and navy-apps is related to the ICS2024 Programming Assignment, it cannot be made public. Therefore, they will only be distributed in the form of precompiled binaries.

Contributing

Feel free to fork the repository and submit a pull request if you’d like to contribute. Bug fixes, performance improvements, and new features are always welcome! Please ensure your contributions follow the coding standards and include appropriate tests.