fmash16 / riscv_emulator

A basic working RISCV emulator written in C

A RISCV Emulator written in C

This is written as a personal project, with a view to learning more about computer architecture. This is being implemented following the RISCV specs in pure C. The ultimate goal is to run linux for riscv on this emulator.

Currently, the following has been implemented: 1. RV32i base instruction set 2. RV64i base instruction set 3. RV32/64 Zicsr standard extension 4. RV32M standart extension 5. RV64M standart extension

TODO

1. Fully implement RV64G (IMAFD extensions)
2. Interrupt handling
3. Trap handling
4. UART
5. VIRTIO
6. Run xv6 unix 
7. Run linux for riscv

Build and run

In order to build and run the emulator, clone the repo and simply do the following

make
./main <binary.bin>

The binary.bin is the binary file to be run. A test code can be written in c in the tests directory. Then in the tests directory, you can run make which will produce the required binary test.bin file to be supplied to the emulator. Then you can run the produced file.

cd ./tests && make
cd ../ & ./main tests/test.bin

Testing with riscv-tests

There is an official repo by riscv here. This contains the tests for each cpu operation for different sets of modular impplemnetations. In order to run the riscv-tests on this emulator, clone the repo and build the test executables in the isa folder. The tests are grouped in directories.

For example, in order to test the rv64ui(user mode, integer), run the following

git clone https://github.com/riscv/riscv-tests/
cd riscv-tests/isa
make rv64ui

This is going to produce the riscv executables for all the instructions for the rv64ui implmenetation and dumpfiles to check the operation for the respective instructions. In order to produce the bin file, objcopy for riscv is required. For that, install riscv-tools from here; Simply run:

git  clone https://github.com/riscv/riscv-tools/
cd riscv-tools & make & make linux

The executables going to be installed under /opt/riscv/bin by default. Addn the path to your PATH variable in your .bashrc file.

export PATH=$PATH:/opt/riscv/bin

Now, you can generate the binary file running the following

riscv64-unknown-elf-objcopy -O binary riscv-tests/isa/rv32ui-p-ori tests/ori.bin

test.py

A simple python script that I wrote to build all the tests in the riscv-tests directory. You can run the following to get all the binary files in you provided destination folder

./test.py <riscv-tests-dir> <destination-dir>

Currently, the emulator passes the following tests: 1. rv32ui 2. rv64ui 3. rv64um