linux-kernel - Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

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Message-ID: <CAPhsuW5VCmuPLd8wwzBp_Divnu=uaZQcrRLsjsEOJ9GmA0TR5A@mail.gmail.com>
Date: Wed, 12 Feb 2025 23:37:45 -0800
From: Song Liu <song@...nel.org>
To: Puranjay Mohan <puranjay@...nel.org>
Cc: Indu Bhagat <indu.bhagat@...cle.com>, Weinan Liu <wnliu@...gle.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Peter Zijlstra <peterz@...radead.org>, Mark Rutland <mark.rutland@....com>, roman.gushchin@...ux.dev, 
	Will Deacon <will@...nel.org>, Ian Rogers <irogers@...gle.com>, linux-toolchains@...r.kernel.org, 
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org, 
	joe.lawrence@...hat.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/8] unwind, arm64: add sframe unwinder for kernel

On Wed, Feb 12, 2025 at 11:26 PM Puranjay Mohan <puranjay@...nel.org> wrote:
>
> Song Liu <song@...nel.org> writes:
>
> > On Wed, Feb 12, 2025 at 4:10 PM Indu Bhagat <indu.bhagat@...cle.com> wrote:
> >>
> >> On 2/12/25 3:32 PM, Song Liu wrote:
> >> > I run some tests with this set and my RFC set [1]. Most of
> >> > the test is done with kpatch-build. I tested both Puranjay's
> >> > version [3] and my version [4].
> >> >
> >> > For gcc 14.2.1, I have seen the following issue with this
> >> > test [2]. This happens with both upstream and 6.13.2.
> >> > The livepatch loaded fine, but the system spilled out the
> >> > following warning quickly.
> >> >
> >>
> >> In presence of the issue
> >> https://sourceware.org/bugzilla/show_bug.cgi?id=32666, I'd expect bad
> >> data in SFrame section.  Which may be causing this symptom?
> >>
> >> To be clear, the issue affects loaded kernel modules.  I cannot tell for
> >> certain - is there module loading involved in your test ?
> >
> > The KLP is a module, I guess that is also affected?
> >
> > During kpatch-build, we added some logic to drop the .sframe section.
> > I guess this is wrong, as we need the .sframe section when we apply
> > the next KLP. However, I don't think the issue is caused by missing
> > .sframe section.
>
> Hi, I did the same testing and did not get the Warning.
>
> I am testing on the 6.12.11 kernel with GCC 11.4.1.

Could you please also try kernel 6.13.2?

> Just to verify, the patch we are testing is:

Yes, this is the test patch.
>
> --- >8 ---
[...]
> --- 8< ---
>
> P.S. - I have a downstream patch for create-diff-object to generate .sframe sections for
> livepatch module, will add it to the PR after some cleanups.

Yeah, I think the .sframe section is still needed.

Thanks,
Song