[06/14] ARM: spectre-v2: harden branch predictor on context switches

Commit Message

Russell King (Oracle) May 22, 2018, 9:55 a.m. UTC

On Mon, May 21, 2018 at 08:21:58PM -0700, Florian Fainelli wrote:
> 
> 
> On 05/21/2018 04:44 AM, Russell King wrote:
> > Harden the branch predictor against Spectre v2 attacks on context
> > switches for ARMv7 and later CPUs.  We do this by:
> > 
> > Cortex A9, A12, A17, A73, A75: invalidating the BTB.
> > Cortex A15, Brahma B15: invalidating the instruction cache.
> > 
> > Cortex A57 and Cortex A72 are not addressed in this patch.
> > 
> > Cortex R7 and Cortex R8 are also not addressed as we do not enforce
> > memory protection on these cores.
> > 
> > Signed-off-by: Russell King <[e-mail]>
> 
> Reviewed-by: Florian Fainelli <[e-mail]>

It does need this additional patch to avoid some build errors - I'm
surprised that my autobuilder found it before the 0-day builder...

Patch

diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
index 0c37e6a2830d..526d07ab6b7a 100644
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@@ -127,4 +127,8 @@  void cpu_v7_bugs_init(void)
 		pr_info("CPU: Spectre v2: using %s workaround\n",
 			spectre_v2_method);
 }
+#else
+void cpu_v7_bugs_init(void)
+{
+}
 #endif