From 717b938e22f8dbf0c02d51cb8e74634fac9b57ef Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 6 May 2020 20:51:28 +0100 Subject: arm64: Document why we enable PAC support for leaf functions Document the fact that we enable pointer authentication protection for leaf functions since there is some narrow potential for ROP protection benefits and little overhead has been observed. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20200506195138.22086-2-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/Makefile | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/arm64/Makefile') diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 85e4149cc5d5..921c8ee8552b 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -71,6 +71,9 @@ branch-prot-flags-y += $(call cc-option,-mbranch-protection=none) ifeq ($(CONFIG_ARM64_PTR_AUTH),y) branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all +# We enable additional protection for leaf functions as there is some +# narrow potential for ROP protection benefits and no substantial +# performance impact has been observed. branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf # -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 -- cgit