linux-kernel - Re: [PATCH 1/4] arm64/sve: Remove bitrotted comment about syscall behaviour

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Tue, 23 Jan 2024 18:11:52 +0000
From: Mark Brown <broonie@...nel.org>
To: Dave Martin <Dave.Martin@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Edmund Grimley-Evans <edmund.grimley-evans@....com>
Subject: Re: [PATCH 1/4] arm64/sve: Remove bitrotted comment about syscall
 behaviour

On Tue, Jan 23, 2024 at 05:54:17PM +0000, Dave Martin wrote:

> I still feel that it is iffy practice for userspace to rely on the
> extra bits being zeroed -- I think the architecture hides this
> guarantee anyway whenever you go through a function call confirming to
> the regular procedure call standard (including the syscall wrappers).
> But there may not be a lot of point trying to put people off if we
> can't force them not to rely on it.

I do tend to agree that the requirement to zero is excessively zealous
and that the risk from relaxing it is minor (it's stricter than the
function call ABI), I did leave a sysctl as a mechanism for restoring
compatibility in the case where we did run into issues in my original
series but I didn't expect to need it.  If you convince everyone else
I'd be happy to relax things but I don't super care either way.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)