linux-kernel - Re: [PATCH v2 01/12] objtool: Generic annotation infrastructure

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Message-ID: <20241120160308.o24km3zwrpbqn7m4@jpoimboe>
Date: Wed, 20 Nov 2024 08:03:08 -0800
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
	jthoughton@...gle.com
Subject: Re: [PATCH v2 01/12] objtool: Generic annotation infrastructure

On Wed, Nov 20, 2024 at 09:52:54AM +0100, Peter Zijlstra wrote:
> On Tue, Nov 19, 2024 at 05:04:24PM -0800, Josh Poimboeuf wrote:
> > On Tue, Nov 19, 2024 at 04:31:25PM -0800, Josh Poimboeuf wrote:
> > > On Sat, Nov 16, 2024 at 10:33:31AM +0100, Peter Zijlstra wrote:
> > > > On Fri, Nov 15, 2024 at 10:38:28AM -0800, Josh Poimboeuf wrote:
> > > > > On Mon, Nov 11, 2024 at 12:59:36PM +0100, Peter Zijlstra wrote:
> > > > > > +#define ASM_ANNOTATE(x)						\
> > > > > > +	"911:\n\t"						\
> > > > > > +	".pushsection .discard.annotate,\"M\",@progbits,8\n\t"	\
> > > > > > +	".long 911b - .\n\t"					\
> > > > > > +	".long " __stringify(x) "\n\t"				\
> > > > > > +	".popsection\n\t"
> > > > > 
> > > > > Why mergeable and progbits?
> > > > 
> > > > In order to get sh_entsize ?
> > > 
> > > Is that a guess?  If so, it's not very convincing as I don't see what
> > > entsize would have to do with it.
> > 
> > Oh, nevermind... I see it's a gas syntax issue.
> 
> Not a guess, only mergable gets entsize, and progbits is a required
> argument per the syntax in order to specify entsize.

If you look at "readelf -WS vmlinux" there are plenty of non-mergeable
sections with entsize.

-- 
Josh