Re: [PATCH 5.15 746/913] ARM: ftrace: avoid redundant loads or clobbering IP
From: Ard Biesheuvel
Date: Wed Apr 06 2022 - 11:00:05 EST
On Wed, 6 Apr 2022 at 13:23, Sasha Levin <sashal@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxxxxxxxx> wrote:
> >> From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> >> [ 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@xxxxxxxxxx>
> >> Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> >> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> >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.
Yes, please. Just disregard all of my patches, unless they have a
fixes or cc:stable, or someone suggests them explicitly.
> >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
Yeah, we should really not be using a bot for that.