linux-kernel - Re: [GIT PULL] objtool fixes

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Message-ID: <n7p2rtrq6vvfteu5szlubng4wj6akgn45suekjdxojrpuxr6dp@oxjfxawkv3xs>
Date: Thu, 3 Apr 2025 01:31:50 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org, 
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, Thomas Gleixner <tglx@...utronix.de>, 
	Borislav Petkov <bp@...en8.de>, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] objtool fixes

On Wed, Apr 02, 2025 at 10:58:15AM -0700, Linus Torvalds wrote:
>         911:
>         .pushsection .discard.annotate_insn,"M",@progbits,8
>         .long 911b - .
>         .long 6
>         .popsection
> 
> which is just pure unadulterated pointless noise.
> 
> That "annotation #6" is WORTHLESS.
> 
> Dammit, objtool could have figured that annotation out ON ITS OWN
> without generating shit in our code. It's not like it doesn't already
> look at alternatives, and it's not like it couldn't just have seen
> "oh, look, it's a nop instruction with a clac/stac instruction as an
> alternative".

Ugh, fragile hard-coded special cases like that are exactly what we're
trying to get away from.  They make the code unmaintainable and they end
up triggering false positives, just like the one fixed by that patch in
the first place.

-- 
Josh