From: Mark Brown Date: Wed, 6 May 2020 19:51:28 +0000 (+0100) Subject: arm64: Document why we enable PAC support for leaf functions X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=717b938e22f8dbf0c02d51cb8e74634fac9b57ef;p=linux.git 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 --- diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 85e4149cc5d5c..921c8ee8552b7 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