Re: [PATCH] ARM: Implement Clang's SLS mitigation
From: Nathan Chancellor <nathan@kernel.org>
Date: 2021-02-12 05:56:15
Also in:
linux-security-module, lkml
Hi Jian, On Thu, Feb 11, 2021 at 09:14:58PM -0800, Jian Cai wrote:
This patch adds a config CONFIG_HARDEN_SLS_ALL that can be used to turn
Drop "a config".
on -mharden-sls=all, which mitigates the straight-line speculation vulnerability, or more commonly known as Spectre, Meldown.
^ I would drop "or" here
^ drop comma,
use "and",
typo: "Meltdown"
Although, is that a fair statement? SLS is not called Spectre or
Meltdown by ARM, it is a speculative processor vulnerabilty. It
might just be better to drop eerything after the first comma (although
maybe that is just being pedantic).
Notice -mharden-sls= has other options as below, and this config turns on the strongest option. all: enable all mitigations against Straight Line Speculation that are implemented. none: disable all mitigations against Straight Line Speculation. retbr: enable the mitigation against Straight Line Speculation for RET and BR instructions. blr: enable the mitigation against Straight Line Speculation for BLR instructions.
I cannot comment on whether or not this is worth doing, I will leave that up to Will, Catalin, et al. The following comments are more from a "regular kernel developer" perspective, rather than an "arm64 kernel developer" :)
Link: https://reviews.llvm.org/D93221 Link: https://reviews.llvm.org/D81404 Link: https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation
This is also a useful article it seems: https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/frequently-asked-questions#SLS2
Link: https://crbug.com/1171521
This crbug is private. If it is going into a commit message, please publicize it.
quoted hunk ↗ jump to hunk
Suggested-by: Manoj Gupta <redacted> Signed-off-by: Jian Cai <redacted> --- arch/arm/Makefile | 4 ++++ arch/arm64/Makefile | 5 +++++ security/Kconfig.hardening | 11 +++++++++++ 3 files changed, 20 insertions(+)diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 4aaec9599e8a..11d89ef32da9 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile@@ -48,6 +48,10 @@ CHECKFLAGS += -D__ARMEL__ KBUILD_LDFLAGS += -EL endif +ifeq ($(CONFIG_HARDEN_SLS_ALL), y) +KBUILD_CFLAGS += -mharden-sls=all +endif + # # The Scalar Replacement of Aggregates (SRA) optimization pass in GCC 4.9 and # later may result in code being generated that handles signed short and signeddiff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 90309208bb28..8fd0ccd87eca 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile@@ -34,6 +34,11 @@ $(warning LSE atomics not supported by binutils) endif endif +ifeq ($(CONFIG_HARDEN_SLS_ALL), y) +KBUILD_CFLAGS += -mharden-sls=all +endif + +
Extra space here
quoted hunk ↗ jump to hunk
cc_has_k_constraint := $(call try-run,echo \ 'int main(void) { \ asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 269967c4fc1b..d83c406c81a3 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening@@ -121,6 +121,17 @@ choice endchoice + +config CC_HAS_HARDEN_SLS_ALL + def_bool $(cc-option,-mharden-sls=all)
I do not think that CONFIG_CC_HAS_HARDEN_SLS_ALL serves much purpose. Moving the cc-option into CONFIG_HARDEN_SLS_ALL is just as clean. config HARDEN_SLS_ALL bool "enable SLS vulnerability hardening" depends on $(cc-option,-mharden-sls=all) help Enables straight-line speculation vulnerability hardening at highest level.
+ + config HARDEN_SLS_ALL + bool "enable SLS vulnerability hardening"
The spacing here seems messed up, I corrected it above.
+ depends on CC_HAS_HARDEN_SLS_ALL + help + Enables straight-line speculation vulnerability hardening + at highest level. + config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" depends on GCC_PLUGIN_STRUCTLEAK -- 2.30.0.478.g8a0d178c01-goog
Cheers, Nathan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel