riscairo

RISC-V ELF interpreter in cairo 2.

Intro

This is my first program in cairo ! It implements an ELF file parser and a RISC-V virtual machine. The machine implements the RV32i instruction set, without extensions for now.

WARNING: do not use in production, this is a POC project for now.

Run a basic test

Running the command scarb cairo-run should trigger a basic run that loads the following RISC-V program compiled as ELF:

.global _start

_start:
    
    # run only one instance
    csrr    t0, mhartid
    bnez    t0, forever
    
    # prepare for the loop
    li      s1, 0x10000000  # output offset   
    la      s2, hello       # load string start addr into s2
    addi    s3, s2, 13      # set up string end addr in s3

loop:
    lb      s4, 0(s2)       # load next byte at s2 into s4
    sb      s4, 0(s1)       # write byte to output 
    addi    s2, s2, 1       # increase s2
    addi    s1, s1, 1       # increase s1
    blt     s2, s3, loop    # branch back until end addr (s3) reached

forever:
    wfi
    j       forever


.section .data

hello:
    .string "hello world!\n"

the expected output of the run is:

$ scarb cairo-run
   Compiling riscairo v0.1.0
    Finished release target(s) in 10 seconds
     Running riscairo
The RISC-V ELF was executed and sent the following output: hello world!

Run completed successfully, returning [0]