linux-kernel - Re: [PATCH] gcc-plugins: Disable GCC plugins for compile test builds

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Message-ID: <8cbe0cac-2952-47b6-9b0d-1400aec0bf25@sirena.org.uk>
Date: Mon, 7 Apr 2025 23:02:15 +0100
From: Mark Brown <broonie@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Kees Cook <kees@...nel.org>,
	Mickaël Salaün <mic@...ikod.net>,
	Günther Noack <gnoack@...gle.com>,
	Arnd Bergmann <arnd@...db.de>, linux-hardening@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH] gcc-plugins: Disable GCC plugins for compile test builds

On Mon, Apr 07, 2025 at 02:33:40PM -0700, Linus Torvalds wrote:
> On Mon, 7 Apr 2025 at 14:10, Mark Brown <broonie@...nel.org> wrote:

> > Arnd bisected this to c56f649646ec ("landlock: Log mount-related
> > denials") but that commit is fairly obviously not really at fault here,
> > most likely this is an issue in the plugin.  Given how disruptive having
> > key configs like this failing let's disable the plugins for compile test
> > builds until a fix is found.

> I'm not against this, but I do want to bring up the "are the plugins
> worth having at all" discussion again.

> They've been a pain before. Afaik, the actual useful cases are now
> done by actual real compiler support (and by clang, at that).

> Who actually *uses* the gcc plugins? They just worry me in general,
> and this is not the first time they have caused ICE problems.

There was a bit of discussion of that on IRC which didn't summon up huge
enthusiasm for them.  Arnd noted that:

    https://github.com/nyrahul/linux-kernel-configs

indicates that Talos 1.9.1 uses latent_entropy (but we didn't check how
accurate that survey is).  He also noted that GCC_PLUGIN_SANCOV is
obsolete as of GCC 6 (!) and both CC_HAVE_STACKPROTECTOR_TLS and
GCC_PLUGIN_STRUCTLEAK_BYREF_ALL as of GCC 12, Ard indicated he wasn't
worried about loosing CC_HAVE_STACKPROTECTOR_TLS.

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