Genode and RISC OS demo
This is the demo I showed on the RISC OS Southwest show this spring.
It was a complete scenario running with several different components:
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RISC OS running on the second core. It is using a framebuffer window to display the graphics.
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The Unicorn CPU emulator running BBC Basic and a subset of RISC OS. Complete with graphics.
The RISC OS component uses the message unit on iMX8MQ to do inter core communication. I might say absuse it because I use it in a very unsupported way. The keyboard input is done with interrupts and the mouse movement is by pollling. RISC OS uses a fixed memory region as the framebuffer. The Genode part do copy that memory to the graphics window using a neon mem copy. It runs at 60hz , unless there are some heavy load in Genode. There is a RISC OS kernel module that provides a way to get files from Genode. At this point RISC OS doesn't have access to any mass storage. I used a RAM disc and copied in a self extracting archive with a basic harddisc install of RISC OS. I then start the RISC OS start sequence (!Boot) and get a full RISC OS experience.
The Unicorn port provides a 32-bit ARM. My code is a mix of ARM code and host code. The main interactive part is BBC BASIC. However you can run ARM RISC OS binaries. It is also possible to load RISC OS kernel modules, such as the c-library. The RISC OS programs can interact with the Genode graphics window in two ways. Through standard SWIs, syscalls in RISC OS is implemented with SWI handlers, and by accessing the graphics ram directly.
I have put the RISC OS Genode server on GitHub and it is my most hacky code I have ever published! You can find it here:
Obligatory screenshot:
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