linux-kernel - Re: [PATCH v2 2/2] objtool: dead_end function change for split functions

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Message-ID: <7cjkflvhay2lvdsqd5hiezhd3oybnhri6w3m34o6e7nendjdeq@wb6f6lmp6lyj>
Date: Mon, 17 Nov 2025 15:23:40 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Rong Xu <xur@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, 
	Sriraman Tallam <tmsriram@...gle.com>, Han Shen <shenhan@...gle.com>, 
	Krzysztof Pszeniczny <kpszeniczny@...gle.com>
Subject: Re: [PATCH v2 2/2] objtool: dead_end function change for split
 functions

On Mon, Nov 17, 2025 at 02:57:02PM -0800, Rong Xu wrote:
> Josh,
> 
> You're right, your fix makes a lot of sense. I wasn't aware that the
> split function was already handled for GCC.

FYI, GCC puts its cold functions in .text.unlikely[.*] rather than
.text.split.*.  And it does so automatically, without
-fsplit-machine-functions.

> Yes, clang sets the split part of the function as STT_NOTYPE, which is
> different from GCC.
> 
> I assume you will post the new patches (together with other fixes for
> clang's split function) soon. Any time line?
> 
> Also how about the other patch in this patch set. Does that make sense?

I think patch 1/2 looked ok, let me go stare at it again.

> Thanks for the advice on getting rid of objtool warnings in our
> builds! We tried but it's hard to get rid of all the warnings. But
> I'll keep close eyes on these unreachable code warnings.

Here's my work in progress:

  git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git objtool-split-fix

I hope to post the patches in a day or so if the bots don't complain.

If they don't fix all your warnings, let me know and I can help look.

-- 
Josh