linux-hardening - Re: [PATCH 5/5] kcfi: Rename CONFIG_CFI_CLANG to CONFIG

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Message-ID: <CANiq72nX7d3XQtQKDdeUh2RFy5HqSg360m4pzesJyBP+y9K7FA@mail.gmail.com>
Date: Thu, 28 Aug 2025 14:11:51 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Randy Dunlap <rdunlap@...radead.org>, Kees Cook <kees@...flux.net>, Kees Cook <kees@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Mark Rutland <mark.rutland@....com>, 
	Puranjay Mohan <puranjay@...nel.org>, David Woodhouse <dwmw2@...radead.org>, 
	Jonathan Corbet <corbet@....net>, x86@...nel.org, linux-doc@...r.kernel.org, 
	linux-kbuild@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, llvm@...ts.linux.dev, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH 5/5] kcfi: Rename CONFIG_CFI_CLANG to CONFIG_CFI

On Wed, Aug 27, 2025 at 9:38 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> I am not sure I understand what you mean here. With the series as it is
> or Kees's suggested fix, oldconfig still prompts the user to enable
> CONFIG_CFI with CONFIG_CFI_CLANG=y in the old configuration. Both Miguel
> and I allude to that being fine but it would be really nice if users
> with CONFIG_CFI_CLANG=y were automatically transitioned to CONFIG_CFI=y
> without any action on their part. That seems to be in line with how
> Linus feels even as recently as this past merge window:
>
> https://lore.kernel.org/CAHk-=wgO0Rx2LcYT4f75Xs46orbJ4JxO2jbAFQnVKDYAjV5HeQ@mail.gmail.com/

Yeah, I think for pure renames one we should try to avoid churn if possible.

> Another idea I had to avoid this is introducing CONFIG_CFI_GCC as a user
> selectable symbol and making CONFIG_CFI the hidden symbol that both
> compiler symbols select. After a couple of releases (or maybe the next
> LTS), both CONFIG_CFI_CLANG and CONFIG_CFI_GCC could be eliminated with
> CONFIG_CFI becoming user selectable, which would keep things working
> since CONFIG_CFI=y will be present in the previous configuration.

If we are OK with something like this (i.e. waiting a few releases),
then isn't it simpler the `def_bool` approach I mentioned? i.e. it
means one less symbol and one less rename later, right?

Cheers,
Miguel