RISC-V Computer Emulator

Will Maclean

Let's build a RISC-V compliant emulator. Should be fun right?

Example

We can run C programs (no standard library support). For example, the following C program (found in sample_c/sample_c.c) can be build (using sample_c/build.sh) and run with the emulator.

#include "syscall.h"

void print_matrix(int m[3][3]){
    for(int i = 0; i < 3; i++){
        for(int j = 0; j < 3; j++){
            print_d(m[i][j]);
            if(j < 2){
                print_s(", ", 2);
            }
        }
        print_s("\n", 1);
    }
}

int main() {
    int x[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    print_matrix(x);

    return 0;
}

The Computer

Basic information about this computer:

• 32bit memory addressing
• stack pointer starts at 0xFFFFFFEF
• no c standard library support
• basic custom syscalls
• supported instruction sets:
  • rv32i
  • rv32ic (in progress)
• stdout captured in io_out.txt

Build instructions

mkdir build
cd build
cmake ..
make

Custom C program

You can modify sample_c/sample_c.c. You can then build the runnable binary with:

cd sample_c
./build.sh [rv32i|rv32ic]

Note the the ELF file format is not currently supported - we compile into binary format.

You can then rerun build/riscv_comp sample_c/test.bin (no rebuild required).