Re: sigaltstack breaks swapcontext()

[Stas Sergeev]

07.01.2016 20:23, Andy Lutomirski ÐÐÑÐÑ:
> On Thu, Jan 7, 2016 at 7:33 AM, Stas Sergeev <stsp@xxxxxxx> wrote:
> > 06.01.2016 22:53, Andy Lutomirski ÐÐÑÐÑ:
> > > On Wed, Jan 6, 2016 at 11:31 AM, Stas Sergeev <stsp@xxxxxxx> wrote:
> > > > Exactly.
> > > > Do you think this can be ignored?
> > > > A man page should then be corrected with EPERM and the
> > > > above note removed, right?
> > > I think it can be ignored.  I'd go the SS_FORCE route, though, to
> > > maintain POSIX compliance.
> > I think such a flag would be a wrong thing to do.
> > Allowing only SS_DISABLE (without any new flags) keeps
> > you still "compatible with posix", and anything beyond
> > SS_DISABLE in a sighandler is not needed.
> >
> > So I think we only have the following options:
> > 1. Remove the check and forget (if anything, glibc can
> > add the EPERM check to stay compatible with crap).
> > 2. Allow only SS_DISABLE. This will mean a large patch,
> > touching all arches, but the bonus is the compatibility
> > with posix, that no one needs in this particular case.
> Why does allowing SS_DISABLE require touching all arches?
I mean, if we also consistently return SA_ONSTACK even
after SS_DISABLE. This will require kernel to save the
ss_flags separately, and not to use "if (ss_size)" checks.
Of course if we don't want to return SA_ONSTACK, we
should just remove EPERM as I don't think it serves any
other purpose than that.