Add watchdog support to the ABI

[g2p]

(I'm trying to figure out a good first issue to expand the ABIs)

A watchdog ABI could work like this:

• watchdog_setup(tick_interval)
• watchdog_alive()

An interrupt is programmed for the given tick interval, and the process is killed if it doesn't call watchdog_alive before the interrupt triggers. Each call to watchdog_alive resets the interrupt.

[g2p]

Looking at https://wiki.osdev.org/Timer_Interrupt_Sources , this may be too complex for a first issue.
Does Nebulet have some kind of global tick that could be used here?

[g2p]

Looking at irq.rs and the PIT section, that seems like a good place to integrate it.

[lachlansneff]

What would this abi be used for?

[g2p]

It would be used to increase reliability of services. A process that opts into it could prevent bugs from making it appear alive when it has hit a bug that spins the CPU or makes it wait forever. This would generally be hooked into the main loop of the program.