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Message-ID: <Zsb9z2giUQbUTH5a@arm.com>
Date: Thu, 22 Aug 2024 09:58:55 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Mark Brown <broonie@...nel.org>
Cc: Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
Shuah Khan <shuah@...nel.org>,
"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>,
Szabolcs Nagy <Szabolcs.Nagy@....com>, Kees Cook <kees@...nel.org>,
"H.J. Lu" <hjl.tools@...il.com>,
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Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Florian Weimer <fweimer@...hat.com>,
Christian Brauner <brauner@...nel.org>,
Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
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Wilco Dijkstra <wilco.dijkstra@....com>,
linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
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Subject: Re: [PATCH v11 05/39] arm64: Document boot requirements for Guarded
Control Stacks
On Thu, Aug 22, 2024 at 02:15:08AM +0100, Mark Brown wrote:
> FEAT_GCS introduces a number of new system registers, we require that
> access to these registers is not trapped when we identify that the feature
> is present. There is also a HCRX_EL2 control to make GCS operations
> functional.
>
> Since if GCS is enabled any function call instruction will cause a fault
> we also require that the feature be specifically disabled, existing
> kernels implicitly have this requirement and especially given that the
> MMU must be disabled it is difficult to see a situation where leaving
> GCS enabled would be reasonable.
>
> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@...aro.org>
> Signed-off-by: Mark Brown <broonie@...nel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
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