Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 27 Mar 2023 18:32:51 +0300
From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     Willy Tarreau <w@1wt.eu>
Cc:     Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <thomas@t-8ch.de>,
        Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <linux@weissschuh.net>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector
Message-ID: <c0584807-511c-4496-b062-1263ea38f349@p183>
References: <89a960c7-0c9b-43ab-9fc8-a68405f7ed6a@p183>
 <8e156377-e7d9-48ec-a7ee-292aba002201@t-8ch.de>
 <ZCCSsFGqTFWknGBL@1wt.eu>
 <f141145c-fc73-4820-8a1b-98b722f1f28a@p183>
 <ZCCgJSEIqLQ9ZIOC@1wt.eu>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <ZCCgJSEIqLQ9ZIOC@1wt.eu>
Precedence: bulk

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.