linux-kernel - Re: [PATCH 2/3] ARM: Select ARCH_USES_CFI_GENERIC_LLVM

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Message-ID: <20251028175243.GB1548965@ax162>
Date: Tue, 28 Oct 2025 10:52:43 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>, Kees Cook <kees@...nel.org>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Russell King <linux@...linux.org.uk>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Michal Kubiak <michal.kubiak@...el.com>,
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH 2/3] ARM: Select ARCH_USES_CFI_GENERIC_LLVM_PASS

On Mon, Oct 27, 2025 at 11:56:21PM +0100, Linus Walleij wrote:
> On Mon, Oct 27, 2025 at 4:54 PM Sami Tolvanen <samitolvanen@...gle.com> wrote:
> > Instead of working around issues with the generic pass, would it make
> > more sense to just disable arm32 CFI with older Clang versions
> > entirely? Linus, any thoughts?
> 
> We have people using this with the default compilers that come with
> Debiand and Fedora. I would say as soon as the latest release of
> the major distributions supports this, we can drop support for older
> compilers.

Okay, I think that is reasonable enough. This is not a very large
workaround and I do not expect these type of workarounds to be necessary
frequently so I think it is worth keeping this working if people are
actually using it. That means we could mandate the backend version of
kCFI for ARM with Debian Forky in 2027.

Cheers,
Nathan