riscv-hs

A RISC-V emulator written in Haskell. Currently supports the RV32I (32-bit integer) unprivileged ISA.

Common extensions such as M (multiplication) and C (compressed two-byte instructions) may be added later.

Run the simulator

cabal build && cabal run will run a small example program.

Alternatively, provide an ELF with cabal run riscv-hs -- <filepath>. Not all ELF features are supported; I've done my best to raise an error if something unsupported is detected.

Compiling input programs

riscv64-unknown-elf-gcc -O2 -march=rv32i -mabi=ilp32 <program>.c -o <program>

You will need the riscv toolchain installed. For mac, this can be found here: homebrew-riscv

Some test programs (compiled and not) are found in test/c. You can find out what the compiler does with no multiplication instruction in test/c/mul: cabal run riscv-hs -- /test/c/mul

See the disaster in /test for other things we tried and other possible program inputs.

Current implementation quirks

• The program counter starts at 0x0 unless an ELF (with entry point) is provided
• The stack pointer starts at 0x0 (the first item pushed will appear at the highest available address)
• ECALL and any undefined instructions according to the RV32I spec are treated as halt instructions
  • By their design, any instruction with all bits set to zero is undefined. Accessing uninitialized memory will always produce zero (by our design).