From: Kees Cook <keescook@chromium.org>
To: Bill Wendling <morbo@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Masahiro Yamada <masahiroy@kernel.org>,
linux-kbuild@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
David Howells <dhowells@redhat.com>,
Jeff Layton <jlayton@kernel.org>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
llvm@lists.linux.dev
Subject: [PATCH 6/6] randstruct: Enable Clang support
Date: Tue, 3 May 2022 13:55:03 -0700 [thread overview]
Message-ID: <20220503205503.3054173-7-keescook@chromium.org> (raw)
In-Reply-To: <20220503205503.3054173-1-keescook@chromium.org>
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>
---
scripts/Makefile.randstruct | 3 +++
security/Kconfig.hardening | 14 ++++++++++++--
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/scripts/Makefile.randstruct b/scripts/Makefile.randstruct
index 4d741e6db554..24e283e89893 100644
--- a/scripts/Makefile.randstruct
+++ b/scripts/Makefile.randstruct
@@ -7,6 +7,9 @@ randstruct-cflags-y \
+= -fplugin=$(objtree)/scripts/gcc-plugins/randomize_layout_plugin.so
randstruct-cflags-$(CONFIG_RANDSTRUCT_PERFORMANCE) \
+= -fplugin-arg-randomize_layout_plugin-performance-mode
+else
+randstruct-cflags-y \
+ += -frandomize-layout-seed-file=$(objtree)/scripts/basic/randstruct.seed
endif
export RANDSTRUCT_CFLAGS := $(randstruct-cflags-y)
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
--
2.32.0
prev parent reply other threads:[~2022-05-03 20:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-03 20:54 [PATCH 0/6] randstruct: Enable Clang support Kees Cook
2022-05-03 20:54 ` [PATCH 1/6] netfs: Eliminate Clang randstruct warning Kees Cook
2022-05-03 21:31 ` Jeff Layton
2022-05-03 20:54 ` [PATCH 2/6] sancov: Split plugin build from plugin CFLAGS Kees Cook
2022-05-03 20:55 ` [PATCH 3/6] randstruct: Reorganize Kconfigs and attribute macros Kees Cook
2022-05-03 20:55 ` [PATCH 4/6] randstruct: Split randstruct Makefile and CFLAGS Kees Cook
2022-05-03 20:55 ` [PATCH 5/6] randstruct: Move seed generation into scripts/basic/ Kees Cook
2022-05-03 20:55 ` Kees Cook [this message]
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