[v2] kbuild: add -fcf-protection=none when using retpoline flags
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Message ID 20190717160626.26293-1-seth.forshee@canonical.com
State New
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Series
  • [v2] kbuild: add -fcf-protection=none when using retpoline flags
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Commit Message

Seth Forshee July 17, 2019, 4:06 p.m. UTC
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>
---
 Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Masahiro Yamada July 17, 2019, 5:22 p.m. UTC | #1
On Thu, Jul 18, 2019 at 1:07 AM Seth Forshee <seth.forshee@canonical.com> wrote:
>
> 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>

Applied to linux-kbuild. Thanks.

Patch
diff mbox series

diff --git a/Makefile b/Makefile
index 3e4868a6498b..73a94d1db2b6 100644
--- a/Makefile
+++ b/Makefile
@@ -878,6 +878,12 @@  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)