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Date: Mon, 15 Jun 2015 12:54:12 +0200
From: Christian Borntraeger <borntraeger@de.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH] s390/bios: build with
	-fdelete-null-pointer-checks
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To: Aurelien Jarno <aurelien@aurel32.net>, qemu-devel@nongnu.org
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, Alexander Graf <agraf@suse.de>

Am 15.06.2015 um 12:24 schrieb Aurelien Jarno:
> Starting with version 4.9, GCC assumes it can't safely dereference null
> pointers, and uses this for some optimizations. On s390, the lowcore
> memory is located at address 0, so this assumption is wrong and breaks
> the s390-ccw firmware. Pass -fdelete-null-pointer-checks to avoid that.
> 
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Alexander Graf <agraf@suse.de>
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  pc-bios/s390-ccw/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
> index 009bb8d..746603a 100644
> --- a/pc-bios/s390-ccw/Makefile
> +++ b/pc-bios/s390-ccw/Makefile
> @@ -10,7 +10,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
>  .PHONY : all clean build-all
> 
>  OBJECTS = start.o main.o bootmap.o sclp-ascii.o virtio.o
> -CFLAGS += -fPIE -fno-stack-protector -ffreestanding
> +CFLAGS += -fPIE -fno-stack-protector -ffreestanding -fno-delete-null-pointer-checks
>  LDFLAGS += -Wl,-pie -nostdlib
> 
>  build-all: s390-ccw.img
> 

applied thanks.