R2: RISC OS kernel reimplementation

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hjalfi
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R2: RISC OS kernel reimplementation

Postby hjalfi » Mon May 15, 2017 6:11 pm

It's not really an emulator, but... a long time ago I wrote this as an experiment:

http://cowlark.com/r2/

It's a RISC OS kernel clone. It runs entirely in userspace, with a tiny supervisor-mode dispatcher to send SWIs; everything else happens inside modules. It's very much a prototype, so right now the whole thing runs in an ARM emulator (I didn't have any ARM hardware back then), but there's enough there to run a very basic OS image with Basic in it; there are unmodified versions of BASIC, BASICTrans, FileSwitch, MessageTrans, ResourceFS, TerritoryManager and UK.

I have no idea whether it's of any actual use to anyone, but I didn't write it to be useful...

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davidb
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Re: R2: RISC OS kernel reimplementation

Postby davidb » Mon May 15, 2017 6:52 pm

I was fascinated by your project when I first heard of it, but I've never managed to make the time to explore further. :(

Have you seen the unrelated effort to run RISC OS in userspace on Linux?

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hjalfi
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Re: R2: RISC OS kernel reimplementation

Postby hjalfi » Mon May 15, 2017 7:07 pm

That's really, really impressive! The core's a similar idea to mine, although extended amazingly. Simulation of supervisor mode in usermode code! Hardware emulation! I'm really impressed.

My code wouldn't get that far; I mainly wanted to prove a point about microkernels and user-mode, so there's no support at all for changing processor modes. So actually making it do anything useful would involve huge amounts of work replacing all the direct hardware access with software drivers. In addition I don't have the patience to cope with RISC OS innards, which... uh... is less good on the inside than it looks on the outside.


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