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kbuild: add -fcf-protection=none when using retpoline flags

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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>
This commit is contained in:
Seth Forshee 2019-07-17 11:06:26 -05:00 committed by Masahiro Yamada
parent 67bf47452e
commit 29be86d7f9
1 changed files with 6 additions and 0 deletions
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6
Makefile
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@ -882,6 +882,12 @@ 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)