linux-hardening - Re: [PATCH 3/5] x86/cfi: Add option for cfi=debug bootparam

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Message-ID: <202508281848.A6EE3E4BA@keescook>
Date: Thu, 28 Aug 2025 18:49:26 -0700
From: Kees Cook <kees@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Kees Cook <kees@...flux.net>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Puranjay Mohan <puranjay@...nel.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 3/5] x86/cfi: Add option for cfi=debug bootparam

On Wed, Aug 27, 2025 at 12:57:53PM -0700, Nathan Chancellor wrote:
> On Mon, Aug 25, 2025 at 07:25:50AM -0700, Kees Cook wrote:
> > From: Kees Cook <kees@...flux.net>
> > 
> > Add "debug" option for "cfi=" bootparam to get details on early CFI
> > initialization steps. Standardize CFI pr_info() lines to use "CFI:"
> > prefix. Standardize "CFI: Using ..." to always report which CFI mode is
> > being used, regardless of CONFIG_FINEIBT. Document all the "cfi=" options.
> > 
> > Signed-off-by: Kees Cook <kees@...flux.net>
> 
> I am not sure if the x86 maintainers are "patch count adverse" but it
> feels like this would be a little easier to review as four separate
> patches. Every sentence in the commit message is basically its own
> change.
> 
> 1. The initial documentation for cfi= and its current values.
> 2. Standardization of pr_info() calls to use "CFI:"
> 3. Adding "CFI: Using" to __apply_fineibt()
> 4. Adding cfi=debug
> 
> Patch four would become much simpler to understand, especially with
> Peter's suggested change.

Yeah, that's entirely fair. :) I will split this up.

-- 
Kees Cook