Nifty! Fun to pull up the module for ELF and have it be so easy to read.
Some day I want to write an RTOS in Nim. I enjoy writing embedded programs in Nim and it’d be fun to make an RTOS.
Some day I want to write an RTOS in Nim. I enjoy writing embedded programs in Nim and it’d be fun to make an RTOS.
For this to work properly, user tasks need to be able to respond to completed syscalls async as well. That's why my idea of user tasks is that they should be modeled as state machines, with channel-based events as the core mechanism by which code gets executed in a deterministic manner. The equivalent of signals in Unix (which many find one of the bad aspects of Unix design) would be receiving events on one or more channels for various purposes (e.g. IO completion, timers, abort, interrupt, GUI events, etc.).
Good minds think alike, I guess.
But as a sibling comment says, this is essentially what io_uring is. Read Lord of the io_uring [1] if you want to know more. Polling mode is the key.
The reason I mentioned it after elcritch's RTOS mention is partly that the way the little interpreter has no backward jumps means there are no loops and so no halting problem issue. So, you can still embed conditional error handling logic in system call batches, but the overall call is bounded by the time of its component calls (that is, if they are bounded, anyway...). That might be a useful property for higher levels of the system to guarantee meeting a real-time budget in many situations with very low complexity. I'm not sure if any of this is original with that github repo, but I haven't seen it before in this specific context.
Perhaps the most complete example of "adding a new sys_batch-based syscall" is https://github.com/c-blake/batch/blob/master/examples/total.... which adds a `mapall` that can mmap a whole file or fail trying (at a couple points) for the purpose of just totaling the bytes as an example calculation.