[PATCH v2 01/10] arm64: bti: Support building kernel C code using BTI

Mark Brown
2020-04-29T21:20:40Z

When running with BTI enabled we need to ask the compiler to enable
generation of BTI landing pads beyond those generated as a result of
pointer authentication instructions being landing pads. Since the two
features are practically speaking unlikely to be used separately we
will make kernel mode BTI depend on pointer authentication in order
to simplify the Makefile.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/Makefile | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 85e4149cc5d5..90150b5b180e 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -71,7 +71,11 @@ branch-prot-flags-y += $(call cc-option,-mbranch-protection=none)

ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
+ifeq ($(CONFIG_ARM64_BTI_KERNEL),y)
+branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET_BTI) := -mbranch-protection=pac-ret+leaf+bti
+else
branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
+endif
# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the
# compiler to generate them and consequently to break the single image contract
# we pass it only to the assembler. This option is utilized only in case of non
--
2.20.1