linux-kernel - Re: [PATCH v2] kconfig: Add transitional symbol attribute for migration support

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Message-ID: <202509050921.2398728EE2@keescook>
Date: Fri, 5 Sep 2025 09:23:55 -0700
From: Kees Cook <kees@...nel.org>
To: Vegard Nossum <vegard.nossum@...cle.com>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Jonathan Corbet <corbet@....net>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>, Arnd Bergmann <arnd@...db.de>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	linux-kbuild@...r.kernel.org, linux-doc@...r.kernel.org,
	Miguel Ojeda <ojeda@...nel.org>,
	Stephen Brennan <stephen.s.brennan@...cle.com>,
	Marco Bonelli <marco@...eim.net>, Petr Vorel <pvorel@...e.cz>,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] kconfig: Add transitional symbol attribute for
 migration support

On Thu, Sep 04, 2025 at 07:03:56PM +0200, Vegard Nossum wrote:
> 
> On 04/09/2025 04:51, Kees Cook wrote:
> > On Mon, Sep 01, 2025 at 08:44:56PM +0200, Vegard Nossum wrote:
> > > If you change sym_calc_visibility() to always return 'yes' for
> > > transitional values then I don't think you need to touch
> > > sym_calc_value() at all.
> > 
> > Hm, it looks like sym_calc_visibility() doesn't strictly just look at
> > visibility. And visibility seems to "last"? And I think the "tri" still
> > can't just be "yes", don't we need the other stuff handled?
> > 
> > Do you see a way to do it how you're suggesting? And now I wrote the
> > regression tests so we can test any alternatives! ;)
> 
> Here's what I had in mind (on top of your kcfi patchset), see the
> attachment.
> 
> It basically undoes all your additions to sym_calc_value() in favour of
> two straightforward additions:
> 
> @@ -214,6 +214,11 @@ static void sym_calc_visibility(struct symbol *sym)
>         struct property *prop;
>         tristate tri;
> 
> +       if (sym->flags & SYMBOL_HIDDEN) {
> +               sym->visible = yes;
> +               return;
> +       }
> +

If this doesn't break "m" choices and the config doesn't show up in
menuconfig, then yeah, I can do this.

I'll give it a spin!

-- 
Kees Cook