A software implementation of a RISC-V computer.
You can run the emulator using cargo and give it a file to run:
cargo run --bin riscy-emulator -- path/to/binary
The binary must be a RISC-V executable in ELF format. Binaries produced by Selfie should work, as long as they are very simple. There is one subsystem supported which supplies a very limited set of POSIX-compliant system calls. Currently only a couple system calls are supported:
| # | System call | Current support |
|---|---|---|
| 57 | close | No effect. Always returns success. |
| 64 | write | Prints the buffer as a string to standard output (regardless of which file descriptor is given). |
| 80 | fstat | If file descriptor 1 (standard output) is requested, then it returns a refcount of 0. Other descriptors are not supported. |
| 93 | exit | Terminates with a status code. |
| 214 | program break | Supports updating the program break and returning the current program break, as documented in the brk man page. However, the program break is not actually used for memory protection. |
Any other system calls will fail with an "unknown system call" error.
The emulator will only print out a couple lines by default, but you can turn on more verbose logging with the -d flag:
cargo run --bin riscy-emulator -- -d debug path/to/binary
tl;dr it might run your program, if you're super generous with your definition of "run".
This repository contains binary versions of the riscv-tests test suite from
https://github.com/riscv/riscv-tests and uses these to test compliance with the
RISC-V standard:
| Instruction Set | Test suites passing | Notes |
|---|---|---|
| RV64I Base instruction set | 100% 🎉 | |
| "M" Integer multiplication & division | 12 / 13 test suites (92%) | Exception is MULHSU which is a pain in the ass |
| "A" Atomic operations | 18 / 19 test suites (94%) | Load-Reserved and Store-Condition are not implemented |
| "Zicsr" Control & Status Register | 2 / 11 test suites (18%) | Some CSRs work |
| "C" Compressed instructions | 100% 🎉 | Not including re-encoding |
tl;dr super rudimentary
The emulator can execute simple programs compiled with Selfie. Notably it does not yet support output, so you're limited to using the status code to output data.