Commit 0446b030 authored Jul 17, 2019 by Seth Forshee Committed by Greg Kroah-Hartman Nov 10, 2019

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>

parent 2e1dff7b

Makefile

+6 −0

Original line number	Diff line number	Diff line
		@@ -840,6 +840,12 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init)
		# 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)