I already succeeded to run xv6 in my RISC-V emulator and wrote a blog post "Made a RISC-V Emulator Running Xv6": https://d0iasm.github.io/blog/risc-v/2020/04/03/xv6-on-my-ri...
I have 2 different RISC-V emulators and its goals are different:
rvemu (https://github.com/d0iasm/rvemu): Can run xv6. It's trying to support Linux and make it faster in the future.
rvemu-for-book (https://github.com/d0iasm/rvemu-for-book): Reference implementation for the book. Simpler than original one.
Also rvemu will support a device tree but rvemu-for-book won't.
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 :)
But it does do almost everything I would expect.
https://github.com/michaelmelanson/riscy
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.
Source: I am the maintainer of RARS (https://github.com/TheThirdOne/rars)
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.
Yes, that hasn't been a problem so far. I've written minimal implementations of a few (so far: fstat, brk, exit) as I've gone along. https://github.com/michaelmelanson/riscy/blob/master/emulato...
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.
Heh, this is _exactly_ the combination that appeals to me, or at least would have before I learned either of them.
As it is now, it is just a skeleton, and thus not worth the light of day.
