From 035f7f87b7295a342577aebd7b5b451f1e2a353c Mon Sep 17 00:00:00 2001 From: Kees Cook <keescook@chromium.org> Date: Tue, 3 May 2022 13:55:03 -0700 Subject: randstruct: Enable Clang support Clang 15 will support randstruct via the -frandomize-layout-seed-file=... option. Update the Kconfig and Makefile to recognize this feature. Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: linux-kbuild@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220503205503.3054173-7-keescook@chromium.org --- security/Kconfig.hardening | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'security') diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 0277ba578779..bd2aabb2c60f 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -266,9 +266,12 @@ config ZERO_CALL_USED_REGS endmenu +config CC_HAS_RANDSTRUCT + def_bool $(cc-option,-frandomize-layout-seed-file=/dev/null) + choice prompt "Randomize layout of sensitive kernel structures" - default RANDSTRUCT_FULL if COMPILE_TEST && GCC_PLUGINS + default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT) default RANDSTRUCT_NONE help If you enable this, the layouts of structures that are entirely @@ -297,13 +300,20 @@ choice config RANDSTRUCT_FULL bool "Fully randomize structure layout" - depends on GCC_PLUGINS + depends on CC_HAS_RANDSTRUCT || GCC_PLUGINS select MODVERSIONS if MODULES help Fully randomize the member layout of sensitive structures as much as possible, which may have both a memory size and performance impact. + One difference between the Clang and GCC plugin + implementations is the handling of bitfields. The GCC + plugin treats them as fully separate variables, + introducing sometimes significant padding. Clang tries + to keep adjacent bitfields together, but with their bit + ordering randomized. + config RANDSTRUCT_PERFORMANCE bool "Limit randomization of structure layout to cache-lines" depends on GCC_PLUGINS -- cgit