linux-kernel - Re: [PATCH v2 43/62] x86/alternative: Define ELF section entry size for alternatives

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Message-ID: <20250509221236.GGaB591CVcWMLiMJN5@fat_crate.local>
Date: Sat, 10 May 2025 00:12:36 +0200
From: Borislav Petkov <bp@...en8.de>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 43/62] x86/alternative: Define ELF section entry size
 for alternatives

On Fri, May 09, 2025 at 02:54:00PM -0700, Josh Poimboeuf wrote:
> On Fri, May 09, 2025 at 11:36:35PM +0200, Borislav Petkov wrote:
> > On Fri, May 09, 2025 at 01:17:07PM -0700, Josh Poimboeuf wrote:
> > > +#define ALTINSTR_SIZE		14
> > 
> > We have sizeof(struct alt_instr) to offer...
> 
> Right, but IIRC, sizeof(struct alt_instr) isn't available at macro
> expansion time so it would have to be provided as an input constraint.
> 
> That doesn't really work for the ALTERNATIVE macro, where the asm
> constraints are out of our control because they're set by the caller.

Bah, that doesn't work. And you're enforcing it with BUILD_BUG_ON(). Oh well,
ignore the noise.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette