Since I got into programming with Scratch, every time I see it capitalized in a HN title I get my hopes up that someone made something really cool in it. Alas, it never happens.
This [0] project might be one of my favourite ones I've seen in Scratch. I don't know how they managed to correctly keep everything together, considering the size of some of the internals.
This looks like a nice project, and I will check on its progress. So far only two of the advertised steps are there.
Reminds me, I started a RISC emulator project on a holiday - and then forgot about it when the holiday was over :o
Not sure if combining "learn rust" and "learn RISC V" at the same time is a good combination for a large audience, it will depend on the reader.
Maybe the intended audience is someone who knows enough basics and has plenty of motivation for/prior knowledge of/interest in both topics. And then, for good content, there will always be an audience.
The tricky part here comes when you have to run non-trivial programs. Mine currently passes the basic test suites, but it still fails in the C runtime startup when executing programs compiled with GCC. My next step is to do co-simulation with another emulator in order to find out where their execution states diverge.
The tests in riscv-tests are not complete enough to indicate strong compliance. I have found several bugs in my implementation that were not caught by them.
> but it still fails in the C runtime startup when executing programs compiled with GCC
The biggest issue I have seen with running C programs is that people don't have the system calls that C runs on startup. In a log from rv8, you need brk, uname, readlinkat, and mprotect. So without those you shouldn't be able to get a program into user code unless you make a custom entry point.
> The tests in riscv-tests are not complete enough to indicate strong compliance. I have found several bugs in my implementation that were not caught by them.
I've noticed that, yes. They got me pretty far, but there's something I'm doing wrong and I haven't been able to find what. That's why the next thing I'm going to try is co-simulation.
> The biggest issue I have seen with running C programs is that people don't have the system calls that C runs on startup. In a log from rv8, you need brk, uname, readlinkat, and mprotect. So without those you shouldn't be able to get a program into user code unless you make a custom entry point.
What does opcode 0x41 does? It's stopping the emulator when I try to run it on fib.text. Otherwise it's a pretty decent tutorial. I've also been following Stephen Marz's tutorial on bringing up a basic operating system on RiscV 64, going to use the two together.
The main difference between them is the number of instructions are supported. Rvemu supports RV64GC, while rvemu-for-book will support RV64I and instructions that xv6 uses (e.g. mul).
Also rvemu will support a device tree but rvemu-for-book won't.
Unfortunately it seems like the privileged instruction set is not yet covered. Also, I think that the arithmetic needs to have explicit wrapping? Otherwise it’ll overflow and cause a trap in debug builds I believe.
Next I want to see the book for writing a 64-bit RISC-V emulator from rust in Scratch ;)
The upper case S in the title made me believe for a second that they did it in Scratch :)