kbuild: add -fcf-protection=none when using retpoline flags
[ Upstream commit 29be86d7f9cb18df4123f309ac7857570513e8bc ]
The gcc -fcf-protection=branch option is not compatible with
-mindirect-branch=thunk-extern. The latter is used when
CONFIG_RETPOLINE is selected, and this will fail to build with
a gcc which has -fcf-protection=branch enabled by default. Adding
-fcf-protection=none when building with retpoline enabled
prevents such build failures.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/Makefile b/Makefile
index 62ce376..1d50905 100644
--- a/Makefile
+++ b/Makefile
@@ -840,6 +840,12 @@
# change __FILE__ to the relative path from the srctree
KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
+# ensure -fcf-protection is disabled when using retpoline as it is
+# incompatible with -mindirect-branch=thunk-extern
+ifdef CONFIG_RETPOLINE
+KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
+endif
+
# use the deterministic mode of AR if available
KBUILD_ARFLAGS := $(call ar-option,D)