linux-kernel - Re: [PATCH 5.15 746/913] ARM: ftrace: avoid redundant loads or clobbering IP

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Message-ID: <Yk14LhswMSlPGrmJ@sashalap>
Date:   Wed, 6 Apr 2022 07:23:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: Re: [PATCH 5.15 746/913] ARM: ftrace: avoid redundant loads or
 clobbering IP

On Tue, Apr 05, 2022 at 12:01:19PM +0200, Ard Biesheuvel wrote:
>On Tue, 5 Apr 2022 at 11:54, Greg Kroah-Hartman
><gregkh@...uxfoundation.org> wrote:
>>
>> From: Ard Biesheuvel <ardb@...nel.org>
>>
>> [ Upstream commit d11967870815b5ab89843980e35aab616c97c463 ]
>>
>> Tweak the ftrace return paths to avoid redundant loads of SP, as well as
>> unnecessary clobbering of IP.
>>
>> This also fixes the inconsistency of using MOV to perform a function
>> return, which is sub-optimal on recent micro-architectures but more
>> importantly, does not perform an interworking return, unlike compiler
>> generated function returns in Thumb2 builds.
>>
>> Let's fix this by popping PC from the stack like most ordinary code
>> does.
>>
>> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
>> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>Please drop all the 32-bit ARM patches authored by me from the stable
>queues except the ones that have fixes tags. These are highly likely

I can drop you from future selections as well.

>to cause an explosion of regressions, and they should have never been
>selected, as I don't remember anyone proposing these for stable.

They were proposed by the bot last week
(https://lore.kernel.org/lkml/20220330115005.1671090-22-sashal@kernel.org/).

-- 
Thanks,
Sasha