linux-kernel - Re: [tip: objtool/urgent] objtool, pwm: mediatek: Prevent theoretical divide-by-zero in pwm_mediatek

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Message-ID: <20250326111129.GC5880@noisy.programming.kicks-ass.net>
Date: Wed, 26 Mar 2025 12:11:29 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Uwe Kleine-König <ukleinek@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	linux-tip-commits@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org
Subject: Re: [tip: objtool/urgent] objtool, pwm: mediatek: Prevent
 theoretical divide-by-zero in pwm_mediatek_config()

On Wed, Mar 26, 2025 at 11:35:28AM +0100, Uwe Kleine-König wrote:

> and the build works fine for me and there is no warning about
> drivers/pwm/pwm-mediatek.o. What am I missing?

Could be compiler related; IIRC it is mostly clang that does this. When
it finds /0 it simply stops code-gen.

I *really* dislike this behaviour, but since C declares this UB, they're
basically free to do whatever.

IMO it should just emit the code; kernel has exceptions to deal with
this and userspace gets signals.

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