Writing a RISC-V Emulator from Scratch
book.rvemu.app
Writing a RISC-V Emulator from Scratch
1–10 of 16 posts
Re: Writing a RISC-V Emulator from Scratch
#2This 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.
Re: Writing a RISC-V Emulator from Scratch
#3Unfortunately 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.
Re: Writing a RISC-V Emulator from Scratch
#4It looks like it's the season for hobby RISC-V emulators, because I've also been working on one.
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.
Re: Writing a RISC-V Emulator from Scratch
#5It looks like it's the season for hobby RISC-V emulators, because I've also been working on one. 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 w…
> Mine currently passes the basic test suites
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)
Re: Writing a RISC-V Emulator from Scratch
#6It looks like it's the season for hobby RISC-V emulators, because I've also been working on one. 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 w…
> Mine currently passes the basic test suites 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…
> 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.
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...
Re: Writing a RISC-V Emulator from Scratch
#7> This is the book for writing a 64-bit RISC-V emulator from scratch in Rust.
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 :)
Re: Writing a RISC-V Emulator from Scratch
#8> This is the book for writing a 64-bit RISC-V emulator from scratch in Rust. 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 :)
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.
Re: Writing a RISC-V Emulator from Scratch
#9Making an OS for RISC-V in Rust: http://osblog.stephenmarz.com/
Re: Writing a RISC-V Emulator from Scratch
#10This 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…
> 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.
Heh, this is _exactly_ the combination that appeals to me, or at least would have before I learned either of them.