s390: introduce compile time check for empty .bss section

Introduce compile time check for files which should avoid using .bss
section, because of the following reasons:
- .bss section has not been zeroed yet,
- initrd has not been moved to a safe location and could be overlapping
with .bss section.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/Makefile

@@ -98,3 +98,6 @@ obj-$(CONFIG_TRACEPOINTS)	+= trace.o
 # vdso
 obj-y				+= vdso64/
 obj-$(CONFIG_COMPAT)		+= vdso32/
+
+chkbss := head.o head64.o als.o early_nobss.o
+include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/lib/Makefile

@@ -8,3 +8,6 @@ obj-y += mem.o xor.o
 lib-$(CONFIG_SMP) += spinlock.o
 lib-$(CONFIG_KPROBES) += probes.o
 lib-$(CONFIG_UPROBES) += probes.o
+
+chkbss := mem.o
+include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/scripts/Makefile.chkbss

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+
+quiet_cmd_chkbss = CHKBSS  $<
+define cmd_chkbss
+	if ! $(OBJDUMP) -j .bss -w -h $< | awk 'END { if ($$3) exit 1 }'; then \
+		echo "error: $< .bss section is not empty" >&2; exit 1; \
+	fi; \
+	touch $@;
+endef
+
+$(obj)/built-in.a: $(patsubst %, $(obj)/%.chkbss, $(chkbss))
+
+%.o.chkbss: %.o
+	$(call cmd,chkbss)

drivers/s390/char/Makefile

@@ -54,3 +54,6 @@ obj-$(CONFIG_CRASH_DUMP) += sclp_sdias.o zcore.o
 
 hmcdrv-objs := hmcdrv_mod.o hmcdrv_dev.o hmcdrv_ftp.o hmcdrv_cache.o diag_ftp.o sclp_ftp.o
 obj-$(CONFIG_HMC_DRV) += hmcdrv.o
+
+chkbss := sclp_early_core.o
+include $(srctree)/arch/s390/scripts/Makefile.chkbss