arm64: Add skeleton to harden the branch predictor against aliasing attacks
Aliasing attacks against CPU branch predictors can allow an attacker to
redirect speculative control flow on some CPUs and potentially divulge
information from one context to another.
This patch adds initial skeleton code behind a new Kconfig option to
enable implementation-specific mitigations against these attacks for
CPUs that are affected.
Co-developed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[ckadabi@codeaurora.org: Add changes to include header files for per cpu
declarations in mmu.h and use raw_cpu_ptr instead of this_cpu_ptr.
Disable branch predictor hardening by default.]
Patch-mainline: linux-arm-kernel @ 01/05/18, 5:12
Change-Id: Ic8cafac0db223ba3cfe7b55419b29cea7b297a72
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ddeb098..32a80d6 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -793,6 +793,22 @@
If unsure, say Y.
+config HARDEN_BRANCH_PREDICTOR
+ bool "Harden the branch predictor against aliasing attacks" if EXPERT
+ help
+ Speculation attacks against some high-performance processors rely on
+ being able to manipulate the branch predictor for a victim context by
+ executing aliasing branches in the attacker context. Such attacks
+ can be partially mitigated against by clearing internal branch
+ predictor state and limiting the prediction logic in some situations.
+
+ This config option will take CPU-specific actions to harden the
+ branch predictor against aliasing attacks and may rely on specific
+ instruction sequences or control bits being set by the system
+ firmware.
+
+ If unsure, say Y.
+
menuconfig ARMV8_DEPRECATED
bool "Emulate deprecated/obsolete ARMv8 instructions"
depends on COMPAT