linux-kernel - Re: [PATCH] x86/signals: Fix save/restore signal stack to correctly support sigset

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Message-ID: <CADCN6nx3oqNcYxa7xCAybK2Aygv1GugTnMxs=EO2bQMStiejzQ@mail.gmail.com>
Date:   Sun, 29 Nov 2020 08:27:42 -0800
From:   Walt Drummond <walt@...mmond.us>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, brgerst@...il.com, linux@...inikbrodowski.net,
        gustavoars@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/signals: Fix save/restore signal stack to correctly
 support sigset_t

Got it.  Thanks again Al.

On Sat, Nov 28, 2020 at 7:28 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Sat, Nov 28, 2020 at 06:19:31PM -0800, Walt Drummond wrote:
> > Thanks Al.  I want to understand the nuance, so please bear with me as I
> > reason this out.   The cast in stone nature of this is due to both the need
> > to keep userspace and kernel space in sync (ie, you'd have to coordinate
> > libc and kernel changes super tightly to pull this off), and any change in
> > the size of struct rt_sigframe would break backwards compatibility with
> > older binaries, is that correct?
>
> Pretty much so.  I would expect gdb and friends to be very unhappy about
> that, for starters, along with a bunch of fun stuff like JVM, etc.
>
> Ask the userland folks (libc, gdb, etc.) how would they feel about such
> changes.  I'm fairly sure that it's _not_ going to be a matter of
> changing _NSIG, rebuilding the kernel and living happily ever after.