[PATCH 2/4] ARM: Introduce ability to enable invalidate of BTB with ICIALLU on Cortex-A15 for CVE-2017-5715
From: f.fainelli@gmail.com (Florian Fainelli)
Date: 2018-06-13 00:30:36
Also in:
u-boot
On June 12, 2018 1:24:09 PM PDT, Nishanth Menon [off-list ref] wrote:
As recommended by Arm in [1], ACTLR[0] (Enable invalidates of BTB) needs to be set[2] for BTB to be invalidated on ICIALLU. This needs to be done unconditionally for Cortex-A15 processors. Provide a config option for platforms to enable this option based on impact analysis for products. NOTE: This patch in itself is NOT the final solution, this requires: a) Implementation of v7_arch_cp15_set_acr on SoCs which may not provide direct access to ACR register. b) Operating Systems such as Linux to provide adequate workaround in the right locations.
This is the case as of 4.18 so you could probably reference CONFIG_CPU_SPECTRE and CONFIG_HARDEN_BRANCH_PREDICTOR in a v2.
c) This workaround applies to only the boot processor. It is important to apply workaround as necessary (context-save-restore) around low power context loss OR additional processors as necessary in either firmware support OR elsewhere in OS.
About that, I don't know enough of uboot but are there existing PSCI or other seemingly standard secondary core support in uboot that would make us go through the same initialization as the boot CPU? If not, is everything going to be largely implementation specific and scattered between uboot and the hypervisors or kernel? FWIW, this is what prompted me to submit this: https://patchwork.kernel.org/patch/10453643/
quoted hunk ↗ jump to hunk
[1] https://developer.arm.com/support/security-update [2] http://infocenter.arm.com/help/topic/com.arm.doc.ddi0438c/BABGHIBG.html Cc: Marc Zyngier <redacted> Cc: Russell King <redacted> Cc: Tony Lindgren <tony@atomide.com> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <redacted> Cc: Christoffer Dall <redacted> Cc: Andre Przywara <Andre.Przywara@arm.com> Cc: Ard Biesheuvel <redacted> Cc: Tom Rini <redacted> Cc: Michael Nazzareno Trimarchi <michael@amarulasolutions.com> Signed-off-by: Nishanth Menon <nm@ti.com> --- arch/arm/Kconfig | 4 ++++ arch/arm/cpu/armv7/start.S | 8 ++++++++ 2 files changed, 12 insertions(+)diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 9e32d5b43cb0..98f58fd27696 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig@@ -109,6 +109,7 @@ config SYS_ARM_MPU# CONFIG_ARM_ERRATA_798870 # CONFIG_ARM_ERRATA_801819 # CONFIG_ARM_CORTEX_A8_CVE_2017_5715 +# CONFIG_ARM_CORTEX_A15_CVE_2017_5715 config ARM_ERRATA_430973 bool@@ -182,6 +183,9 @@ config ARM_ERRATA_855873config ARM_CORTEX_A8_CVE_2017_5715 bool +config ARM_CORTEX_A15_CVE_2017_5715 + bool + config CPU_ARM720T bool select SYS_CACHE_SHIFT_5diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S index 3beaf5a93d81..81edec01bf32 100644 --- a/arch/arm/cpu/armv7/start.S +++ b/arch/arm/cpu/armv7/start.S@@ -241,6 +241,14 @@ skip_errata_798870:skip_errata_801819: #endif +#ifdef CONFIG_ARM_CORTEX_A15_CVE_2017_5715 + mrc p15, 0, r0, c1, c0, 1 @ read auxilary control register + orr r0, r0, #1 << 0 @ Enable invalidates of BTB + push {r1-r5} @ Save the cpu info registers + bl v7_arch_cp15_set_acr + pop {r1-r5} @ Restore the cpu info - fall through +#endif + #ifdef CONFIG_ARM_ERRATA_454179 mrc p15, 0, r0, c1, c0, 1 @ Read ACR
-- Florian