Re: [PATCH v3 1/2] x86_64,signal: Fix SS handling for signals delivered to 64-bit programs

Cyrill Gorcunov
2015-03-20T11:56:28Z

On Fri, Mar 20, 2015 at 12:43:14PM +0100, Denys Vlasenko wrote:
> On Thu, Mar 19, 2015 at 8:35 AM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> > On Wed, Mar 18, 2015 at 03:03:27PM -0700, Andy Lutomirski wrote:
> >> I don't have a great idea for how to work around this, unfortunately.
> >> Ideally we'd increment some kind of version counter or use an
> >> extension mechanism rather than shoving ss into a field that used to
> >> be padding.
> >
> > fwiw currently we're passing zero in this __pad0 (replying to your
> > previous email, so we can workaround in the kernel assuming zero
> > as a special case, not that good but better than nothing).
>
> Special-casing zero sounds not that bad to me.
> It can be removed after a few years - just don't forget
> to document it in a good comment: why we have special
> case? What software required it?
> In which version of that software the need to have this hack
> was eliminated?

To be fair, such special case would be ideal for us, so that
if noone object against such hack, i would cook a patch.