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

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Message-ID: <mb61pr0411o57.fsf@kernel.org>
Date: Thu, 13 Feb 2025 22:21:56 +0000
From: Puranjay Mohan <puranjay@...nel.org>
To: Song Liu <song@...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

Song Liu <song@...nel.org> writes:

> On Thu, Feb 13, 2025 at 12:38 AM Puranjay Mohan <puranjay@...nel.org> wrote:
> [...]
>>
>> P.S. - The livepatch doesn't have copy_process() but only copy_signal(),
>> yours had copy_process() somehow.
>
> In my build, copy_signal is inlined to copy_process, unless I add noinline.
> If I do add noinline, the issue will not reproduce.
>
> I tried more combinations. The issue doesn't reproduce if I either
> 1) add noinline to copy_signal, so we are not patching the whole
>    copy_process function;
> or
> 2) Switch compiler from gcc 14.2.1 to gcc 11.5.0.
>
> So it appears something in gcc 14.2.1 is causing live patch to fail
> for copy_process().

So, can you test your RFC set (without SFRAME) with gcc 14.2.1, so we
can be sure that it is not a sframe problem?

And about having the .sframe section in the livepatch module, I realised
that this set doesn't include support for reading/using sframe data from
any module(livepatches included), so the patch I added for generating
.sframe in kpatch is irrelevant because it is a no-op with the current setup.

Thanks,
Puranjay

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