s390/bios: build with -fdelete-null-pointer-checks

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>
Message-Id: <1434363843-14576-1-git-send-email-aurelien@aurel32.net>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
index 009bb8d..746603a 100644 (file)
--- 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