linux-kernel - Re: [PATCH] sched-ext: Use correct annotation for strings in kfuncs

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Message-ID: <ZxlJKC16Kp4aX6uL@slm.duckdns.org>
Date: Wed, 23 Oct 2024 09:06:16 -1000
From: Tejun Heo <tj@...nel.org>
To: Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched-ext: Use correct annotation for strings in kfuncs

On Mon, Oct 21, 2024 at 01:11:43PM -0700, Kumar Kartikeya Dwivedi wrote:
> The sched-ext kfuncs with bstr suffix need to take a string, but that
> requires annotating the parameters with __str suffix, as right now the
> verifier will treat this parameter as a one-byte memory region.
> 
> Fixes: f0e1a0643a59 ("sched_ext: Implement BPF extensible scheduler class")
> Fixes: 07814a9439a3 ("sched_ext: Print debug dump after an error exit")
> Cc: Tejun Heo <tj@...nel.org>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>

I popped this patch from sched_ext/for-6.12-fixes along with the follow-up
fix. This breaks compatibility in a way which is difficult to work around.
If we want to do this, I think we should do it by introducing new set of
kfuncs and than phasing out the old ones. Also, it's unclear what the
practical benefits of the change are anyway.

Thanks.

-- 
tejun