arm64: mte: add in-kernel tag fault handler

Add the implementation of the in-kernel fault handler.

When a tag fault happens on a kernel address:
* MTE is disabled on the current CPU,
* the execution continues.

When a tag fault happens on a user address:
* the kernel executes do_bad_area() and panics.

The tag fault handler for kernel addresses is currently empty and will be
filled in by a future commit.

  Link: https://lkml.kernel.org/r/20201203102628.GB2224@gaia

Link: https://lkml.kernel.org/r/ad31529b073e22840b7a2246172c2b67747ed7c4.1606161801.git.andreyknvl@google.com
Signed-off-by: Vincenzo Frascino <[email protected]>
Co-developed-by: Andrey Konovalov <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Tested-by: Vincenzo Frascino <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Branislav Rankov <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Evgenii Stepanov <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Will Deacon <[email protected]>
[[email protected]: ensure CONFIG_ARM64_PAN is enabled with MTE]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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