mm/kasan: add support for memory hotplug

mm/kasan: add support for memory hotplug

KASAN doesn't happen work with memory hotplug because hotplugged memory
doesn't have any shadow memory.  So any access to hotplugged memory
would cause a crash on shadow check.

Use memory hotplug notifier to allocate and map shadow memory when the
hotplugged memory is going online and free shadow after the memory
offlined.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andrey Ryabinin <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>