arm: ensure u-boot only uses relative relocations

Add a Makefile target ('checkarmreloc') which
fails if the ELF binary contains relocation records
of types other than R_ARM_RELATIVE.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Tested-by: Lubomir Popov <lpopov@mm-sol.com>
Tested-by: Jeroen Hofstee <jeroen@myspectrum.nl>
Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>

Makefile

@@ -743,6 +743,13 @@ tools: $(VERSION_FILE) $(TIMESTAMP_FILE)
 	$(MAKE) -C $@ all
 endif	# config.mk
 
+# ARM relocations should all be R_ARM_RELATIVE.
+checkarmreloc: $(obj)u-boot
+	@if test "R_ARM_RELATIVE" != \
+		"`readelf -r $< | cut -d ' ' -f 4 | grep R_ARM | sort -u`"; \
+		then echo "$< contains relocations other than \
+		R_ARM_RELATIVE"; false; fi
+
 $(VERSION_FILE):
 		@mkdir -p $(dir $(VERSION_FILE))
 		@( localvers='$(shell $(TOPDIR)/tools/setlocalversion $(TOPDIR))' ; \

arch/arm/config.mk

@@ -109,3 +109,8 @@ ifeq ($(GAS_BUG_12532),y)
 PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
 endif
 endif
+
+# check that only R_ARM_RELATIVE relocations are generated
+ifneq ($(CONFIG_SPL_BUILD),y)
+ALL-y	+= checkarmreloc
+endif