Re: [PATCH 3/5] arm64: dovetail: Allow early return from traps

[Richard Weinberger <richard@sigma-star.at>]

On Dienstag, 8. April 2025 19:06 Jan Kiszka wrote:
> On 08.04.25 14:34, Nikolaus Funk wrote:
> > From: Richard Weinberger <richard@nod.at>
> > 
> > Like on the x86 side, allow early return such that
> > handling the exception on the Linux can get avoided.
> > 
> 
> Which traps can be caught and fully handled in oob this way? From my
> past experiments, that list was not very long - and when I look at your
> Xenomai 3 changes, it still isn't. What was particularly hard: DABT and
> memory access faults.

The list is indeed short.
So far ARM64_TRAP_UNDI/BTI and ALIGN look good.
 
> Point is that we need to have some kind of consistency, between the
> archs and between the reporting information (Linux vs. OOB signals). Or
> we extensively need to document where all we are deviating (and ideally
> why).

I'd vote for the latter.
Plus improving the rt_signal_hist test such that others can
test whether some exception handling is good enough or nor.

So, I suggest exposing more exception but mark/document the known good
ones explicitly.

Thanks,
//richard

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