On Thu, Nov 05, 2020 at 12:18:47AM +0100, Andrey Konovalov wrote:

From: Vincenzo Frascino <vincenzo.frascino@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@arm.com>
Co-developed-by: Andrey Konovalov <redacted>
Signed-off-by: Andrey Konovalov <redacted>

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

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