linux-kernel - Re: [PATCH 2/8] s390/alternatives: remove padding generation code

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Message-ID: <your-ad-here.call-01652433488-ext-2779@work.hours>
Date:   Fri, 13 May 2022 11:18:08 +0200
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Jonas Paulsson <paulsson@...ux.vnet.ibm.com>,
        Ulrich Weigand <ulrich.weigand@...ibm.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexander Egorenkov <egorenar@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andreas Krebbel <krebbel@...ux.ibm.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 2/8] s390/alternatives: remove padding generation code

On Wed, May 11, 2022 at 02:05:26PM +0200, Heiko Carstens wrote:
> clang fails to handle ".if" statements in inline assembly which are heavily
> used in the alternatives code.
> 
> To work around this remove this code, and enforce that users of
> alternatives must specify original and alternative instruction sequences
> which have identical sizes. Add a compile time check with two ".org"
> statements similar to arm64.
> 
> In result not only clang can handle this, but also quite a lot of code can
> be removed.
> 
> Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
> ---
>  arch/s390/include/asm/alternative-asm.h | 76 +++-----------------
>  arch/s390/include/asm/alternative.h     | 93 ++++++-------------------
>  arch/s390/kernel/alternative.c          | 61 +---------------
>  3 files changed, 31 insertions(+), 199 deletions(-)

Acked-by: Vasily Gorbik <gor@...ux.ibm.com>