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Message-ID: <4e215e53-c7d1-4338-8df9-3f9bf783ced9@sirena.org.uk>
Date: Thu, 10 Aug 2023 12:41:09 +0100
From: Mark Brown <broonie@...nel.org>
To: Szabolcs Nagy <Szabolcs.Nagy@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
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Eric Biederman <ebiederm@...ssion.com>,
Kees Cook <keescook@...omium.org>,
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"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
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"H.J. Lu" <hjl.tools@...il.com>,
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Subject: Re: [PATCH v4 03/36] arm64/gcs: Document the ABI for Guarded Control
Stacks
On Thu, Aug 10, 2023 at 09:55:50AM +0100, Szabolcs Nagy wrote:
> The 08/09/2023 16:34, Mark Brown wrote:
> > It's actually based on bitrot that I'd initially chosen a smaller value
> > since it's likely that functions will push at least something as you
> > suggest, the patches now just use RLIMIT_STACK. I'll fix.
> the pcs requires 16byte aligned stack frames, with 8byte per gcs entry
> there is no need for same gcs size as stack size in userspace.
I agree that it's going to be excessive for pretty much all
applications, I adjusted it to match x86 as part of the general effort
to avoid divergence and because I was a bit concerned about non-PCS
cases (eg, JITed code) potentially running into trouble, especially with
smaller stack limits. It's not an issue I have super strong opinions on
though, as you can see I had implemented it both ways at various times.
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