Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20201119221132.1515696-1-walt@drummond.us> <20201128052317.GY3576660@ZenIV.linux.org.uk>
 <CADCN6nyGW0=QS=J+704n-mtAqTxgVrKZC=P8d01NZ_pjssptew@mail.gmail.com> <20201129032823.GA3579531@ZenIV.linux.org.uk>
In-Reply-To: <20201129032823.GA3579531@ZenIV.linux.org.uk>
From:   Walt Drummond <walt@drummond.us>
Date:   Sun, 29 Nov 2020 08:27:42 -0800
Message-ID: <CADCN6nx3oqNcYxa7xCAybK2Aygv1GugTnMxs=EO2bQMStiejzQ@mail.gmail.com>
Subject: Re: [PATCH] x86/signals: Fix save/restore signal stack to correctly
 support sigset_t
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org,
        hpa@zytor.com, brgerst@gmail.com, linux@dominikbrodowski.net,
        gustavoars@kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Got it.  Thanks again Al.

On Sat, Nov 28, 2020 at 7:28 PM Al Viro <viro@zeniv.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.