[PATCH] x86: Enable IBT in Rust if enabled in C

[Matthew Maurer]

These flags are not made conditional on compiler support because at the
moment exactly one version of rustc supported, and that one supports
these flags.

Building without these additional flags will manifest as objtool
printing a large number of errors about missing ENDBR and if CFI is
enabled (not currently possible) will result in incorrectly structured
function prefixes.

Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx>
---

Split out the IBT additions as per
https://lkml.kernel.org/linux-fsdevel/CANiq72kK6ppBE7j=z7uua1cJMKaLoR5U3NUAZXT5MrNEs9ZhfQ@xxxxxxxxxxxxxx/

arch/x86/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 5bfe5caaa444..941f7abf6dbf 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -81,6 +81,7 @@ ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816
 #
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=branch -fno-jump-tables)
+KBUILD_RUSTFLAGS += -Zcf-protection=branch -Zno-jump-tables
 else
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
 endif
-- 
2.42.0.609.gbb76f46606-goog