linux-kernel - Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

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Date:   Mon, 27 Mar 2023 18:32:51 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     Thomas Weißschuh <thomas@...ch.de>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

On Sun, Mar 26, 2023 at 09:42:29PM +0200, Willy Tarreau wrote:
> On Sun, Mar 26, 2023 at 10:38:39PM +0300, Alexey Dobriyan wrote:
> > > I'm not seeing any issue with your approach instead, let's
> > > keep it as-is for now (also it does what the stack protector is supposed
> > > to catch anyway).
> > 
> > There are no guarantess about stack layout and dead writes.
> > The test doesn't corrupt stack reliably, just 99.99% reliably.
> 
> Sure but it's for a regtest which can easily be adjusted and its
> posrtability and ease of maintenance outweights its reliability,
> especially when in practice what the code does is what we want to
> test for. And if an extra zero needs to be added to the loop, it
> can be at a lower cost than maintaining arch-specific asm code.

For the record, I disagree. Use volatile writes at least.