Re: [PATCH 26/35] kasan, arm64: Enable TBI EL1

[Catalin Marinas]

On Thu, Aug 27, 2020 at 12:05:55PM +0100, Vincenzo Frascino wrote:
> On 8/27/20 11:40 AM, Catalin Marinas wrote:
> > On Fri, Aug 14, 2020 at 07:27:08PM +0200, Andrey Konovalov wrote:
> >> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> >> index 152d74f2cc9c..6880ddaa5144 100644
> >> --- a/arch/arm64/mm/proc.S
> >> +++ b/arch/arm64/mm/proc.S
> >> @@ -38,7 +38,7 @@
> >>  /* PTWs cacheable, inner/outer WBWA */
> >>  #define TCR_CACHE_FLAGS	TCR_IRGN_WBWA | TCR_ORGN_WBWA
> >>  
> >> -#ifdef CONFIG_KASAN_SW_TAGS
> >> +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> >>  #define TCR_KASAN_FLAGS TCR_TBI1
> >>  #else
> >>  #define TCR_KASAN_FLAGS 0
> > 
> > I prefer to turn TBI1 on only if MTE is present. So on top of the v8
> > user series, just do this in __cpu_setup.
> 
> Not sure I understand... Enabling TBI1 only if MTE is present would break
> KASAN_SW_TAGS which is based on TBI1 but not on MTE.

You keep the KASAN_SW_TAGS as above but for HW_TAGS, only set TBI1 later
in __cpu_setup().

-- 
Catalin