The kernel is pretty much from scratch. It provides a FreeBSD compatible syscall interface for the syscalls that BEAM calls, as well as the FreeBSD runtime loader. I do make healthy use of FreeBSD libraries to provide the OS, you can get an idea of what I pull from the file names in the Makefile [1]. Building an OS is a lot, so I tried to stick to the parts I find fun and interesting. Things like a NIC driver in Erlang [2] (with NIFs to copy to/from device memory). But process / thread creation is original, memory management is original (not necessarily good), time keeping is original, etc. I used existing code and interfaces so I didn't have to write a bootloader, memcpy, and lots of other stuff.
DragonFlyBSD would be really interesting here as well since its kernel has Light Weight Kernel Threads that use message passing. Similar in shape to Erlang/BEAM. Though I guess you've built the kernel in Erlang... so wrong abstraction.
My kernel is in C. BEAM is in userspace. Most of the drivers are in userspace too. Turns out, if you let userspace mmap whatever address it wants to, and have access to all the i/o ports, plus have a way to hook interrupts, you can write drivers in userspace.
You could run beam as init with an existing kernel, but I wanted to explore something with less kernel.
I've thought about doing something like this but I am only very recently getting into low-level OS stuff.
I can't remember who said this, but they called "Erlang an operating system for your code", and I think that's fairly accurate. When I build an Erlang app, I don't build it the same way as I would with Rust; I have a lot of independent gen_servers that do operate independent from each other.
The Erlang VM is (roughly) preemptive multitasking, and even each process has its own GC, so it does feel like it could be a natural fit for its own operating system without having to live on top of Linux.
I don't think v86 [1] is based on qemu, but it's a javascript (well javascript + rust->wasm) virtual PC. Not my project, it's super lovely for hobby os demos though. (And they've taken a couple of my PRs!)
mixedbit | 13 hours ago
[OP] toast0 | 13 hours ago
[1] https://github.com/russor/crazierl/blob/main/Makefile#L23
[2] https://github.com/russor/crazierl/blob/main/src/rtl_8168.er...
asenchi | 10 hours ago
[OP] toast0 | 9 hours ago
You could run beam as init with an existing kernel, but I wanted to explore something with less kernel.
tombert | 13 hours ago
I can't remember who said this, but they called "Erlang an operating system for your code", and I think that's fairly accurate. When I build an Erlang app, I don't build it the same way as I would with Rust; I have a lot of independent gen_servers that do operate independent from each other.
The Erlang VM is (roughly) preemptive multitasking, and even each process has its own GC, so it does feel like it could be a natural fit for its own operating system without having to live on top of Linux.
calvinmorrison | 12 hours ago
https://www.erlang-factory.com/static/upload/media/149858389...
tombert | 12 hours ago
Not that it's not interesting, just that my brain is dumb sometimes.
[OP] toast0 | 12 hours ago
lightandlight | 11 hours ago
Wait, so is the browser running a JavaScript build of Qemu? /
alhazrod | 11 hours ago
[0]: https://github.com/copy/v86
[OP] toast0 | 11 hours ago
[1] https://copy.sh/v86/ https://github.com/copy/v86