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SubjectRe: [RFC][PATCH 0/3] signal: Move si_trapno into the _si_fault union
On Sat, 1 May 2021 at 02:37, Marco Elver <elver@google.com> wrote:
> On Sat, 1 May 2021 at 01:48, Eric W. Biederman <ebiederm@xmission.com> wrote:
> >
> > Well with 7 patches instead of 3 that was a little more than I thought
> > I was going to send.
> >
> > However that does demonstrate what I am thinking, and I think most of
> > the changes are reasonable at this point.
> >
> > I am very curious how synchronous this all is, because if this code
> > is truly synchronous updating signalfd to handle this class of signal
> > doesn't really make sense.

Just a note on this: the reason for adding signalfd support was based
on the comment at SIL_FAULT_PKUERR:

> /*
> * Fall through to the SIL_FAULT case. Both SIL_FAULT_BNDERR
> * and SIL_FAULT_PKUERR are only generated by faults that
> * deliver them synchronously to userspace. In case someone
> * injects one of these signals and signalfd catches it treat
> * it as SIL_FAULT.
> */

The same would hold for SIL_FAULT_PERF_EVENT, where somebody injects
(re-injects perhaps?) such an event. But otherwise, yes,
non-synchronous handling of SIGTRAP/TRAP_PERF is pretty useless for
almost all usecases I can think of.

Thanks,
-- Marco

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