[PATCH v8 32/43] arm64: mte: Switch GCR_EL1 in kernel entry and exit

[Catalin Marinas]

On Thu, Nov 05, 2020 at 12:18:47AM +0100, Andrey Konovalov wrote:
> From: Vincenzo Frascino <vincenzo.frascino at arm.com>
> 
> When MTE is present, the GCR_EL1 register contains the tags mask that
> allows to exclude tags from the random generation via the IRG instruction.
> 
> With the introduction of the new Tag-Based KASAN API that provides a
> mechanism to reserve tags for special reasons, the MTE implementation
> has to make sure that the GCR_EL1 setting for the kernel does not affect
> the userspace processes and viceversa.
> 
> Save and restore the kernel/user mask in GCR_EL1 in kernel entry and exit.
> 
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
> Co-developed-by: Andrey Konovalov <andreyknvl at google.com>
> Signed-off-by: Andrey Konovalov <andreyknvl at google.com>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>