linux-kernel - Re: [PATCH] s390/jump_label: Correct asm contraint

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Date:   Sat, 9 Feb 2019 12:34:20 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     Andreas Krebbel <krebbel@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/jump_label: Correct asm contraint

On 2/5/19 12:43 PM, Heiko Carstens wrote:
> On Tue, Jan 29, 2019 at 08:25:58AM +0100, Laura Abbott wrote:
>> On 1/23/19 5:24 AM, Heiko Carstens wrote:
>>> On Wed, Jan 23, 2019 at 01:55:13PM +0100, Laura Abbott wrote:
>>>> There's a build failure with gcc9:
>>>>
>>>>   ./arch/s390/include/asm/jump_label.h: Assembler messages:
>>>>   ./arch/s390/include/asm/jump_label.h:23: Error: bad expression
>>>>   ./arch/s390/include/asm/jump_label.h:23: Error: junk at end of line, first unrecognized character is `r'
>>>>   make[1]: *** [scripts/Makefile.build:277: init/main.o] Error 1
> ...
>> I've had to turn off s390 in Fedora until this gets fixed :(
> 
> Laura, the patch below should fix this (temporarily). If possible,
> could you give it a try? It seems to work for me.
> 
> rom 4067027c2ccc8d3f1dc3bb19fe2d00da0c65bcd8 Mon Sep 17 00:00:00 2001
> From: Heiko Carstens <heiko.carstens@...ibm.com>
> Date: Tue, 5 Feb 2019 13:21:56 +0100
> Subject: [PATCH] s390: disable section anchors
> 
> Disable section anchors to allow to compile with the current gcc 9
> experimental version. The section anchors is a new feature for s390
> with gcc 9, however it breaks our current usage of the 'X' constraint
> within the asm goto construct within our jump label implementation.
> 
> Fixing this seems to be non-trivial, therefore (hopefully) temporarily
> disable section anchors. We will hopefully have a better solution
> before gcc 9 is released, so that this can be removed again.
> 
> Reported-by: Laura Abbott <labbott@...hat.com>
> Suggested-by: Ilya Leoshkevich <iii@...ux.ibm.com>
> Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
> ---
>   arch/s390/Makefile | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/arch/s390/Makefile b/arch/s390/Makefile
> index e21053e5e0da..1eac75bc3a29 100644
> --- a/arch/s390/Makefile
> +++ b/arch/s390/Makefile
> @@ -62,6 +62,14 @@ cflags-y += -Wa,-I$(srctree)/arch/$(ARCH)/include
>   #
>   cflags-$(CONFIG_FRAME_POINTER) += -fno-optimize-sibling-calls
>   
> +#
> +# Disable section anchors. This gcc 9 feature currently breaks the 'X'
> +# constraint like it is used in the asm goto construct.
> +#
> +ifeq ($(call cc-option-yn,-fno-section-anchors),y)
> +cflags-y += -fno-section-anchors
> +endif
> +
>   ifeq ($(call cc-option-yn,-mpacked-stack),y)
>   cflags-$(CONFIG_PACK_STACK)  += -mpacked-stack -D__PACK_STACK
>   aflags-$(CONFIG_PACK_STACK)  += -D__PACK_STACK
> 

Tested-by: Laura Abbott <labbott@...hat.com><