What's this?

A simple RISCV32I/RISCV64I emulator that can execute an ELF executable file compiled with gnu tool chain and Newlib.

Supported Instructions

• RV32I (Including compressed instructions)
• RV32M (Including compressed instructions)
• RV64I (Including compressed instructions)
• RV64M (Including compressed instructions)

Following instructions are partially supported

• RV32A (except LR and SC)
• RV64A (except LR and SC)

Support of privilege instruction is partial and not complete.

Some system calls are emulated with limitation

Usage

Build

1. Run the following command

$ make 

How to generate executable for the emulator.

1. Install GNU tool chain for RISCV 32bit with support of ilp.

$ ./configure --prefix=/opt/riscv --with-arch=rv32i --with-abi=ilp32
$ make -j

2. Compile the target code for rv32i and ilp32 with static option. For example.

$ riscv32-unknown-elf-gcc file_name.c -o file_name -Wall -march=rv32i -mabi=ilp32 -static

3. Run the emulator.

Move to the emulator folder, then run the following command.

$ ./RISCV_Emulator file_name

Test

Compiling the RISCV-Tests

To run the RISCV tests with this emulator, first set $RISCV to the location of where m99_riscv_emulator is placed.

$ RISCV=/folder/where/the/emulator/is/placed

Then, follow the instruction on riscv-tests page as below.

$ git clone https://github.com/riscv/riscv-tests
$ cd riscv-tests
$ git submodule update --init --recursive
$ autoconf
$ ./configure --prefix=$RISCV/target
$ make
$ make install

The test suite is generated under $RISCV/target/

Now you can run test.

Running Test

1. Run the following command

$ make test

Details

Runtime options

-v: Verbose. Emulator output the current PC, disassembled instruction, register status
-e: System call emulation enabled. See the next section.
-64: Run in 64 bit mode.
-m: Disable machine interrupt delegation to supervisor mode. This is for compatibility with QEMU.
-h: Use "tohost" and "fromhost" functions in riscv-test suite. This is only for riscv-test purpose.
-d: Device emulation. Enable uart output, virtio disk, and interrupt timer. Press Ctrl-a to exit. (This option is work-in-progress.)
-s <filename>: Load as disk iamge. You need to enable device emulation with -d option.
-p: Paging enabled. This is for testing purpose.

System Call emulation

Following system calls are supported with -e option with limitation.

• open (1024)
• close (57)
• fstat (80)
• write (64)
• read (63)
• lseek (62)
• brk (214)
• exit (93)

Running xv6 for riscv

Support of xv6 is still under development.

This emulator is able to run xv6 for riscv to show sh prompt.

You first need to compile xv6 for riscv with CPUS=1 option. Then, you need to copy kernel/kernel in the Emulator directory.
Also, you need fs.img (disk image) from xv6 too. fs.img is generated when running xv6 with QEMU option.

Run the emulator with -64 -m -d -s fs.img options (64 bit mode, disable machine interrupt delegation, device emulation, load fs.img as storage image).

$ ./RISCV_Emulator -64 -m -d -s fs.img kernel

You will eventually see the prompt ($) pops up.
You can run the commands, for example by typing ls or cat README.
Press Ctrl-a to exit.