kasan: improve vmalloc tests

kasan: improve vmalloc tests

Update the existing vmalloc_oob() test to account for the specifics of the
tag-based modes.  Also add a few new checks and comments.

Add new vmalloc-related tests:

- vmalloc_helpers_tags() to check that exported vmalloc helpers can
  handle tagged pointers.
- vmap_tags() to check that SW_TAGS mode properly tags vmap() mappings.
- vm_map_ram_tags() to check that SW_TAGS mode properly tags
  vm_map_ram() mappings.
- vmalloc_percpu() to check that SW_TAGS mode tags regions allocated
  for __alloc_percpu(). The tagging of per-cpu mappings is best-effort;
  proper tagging is tracked in [1].

[1] https://bugzilla.kernel.org/show_bug.cgi?id=215019

Link: https://lkml.kernel.org/r/bbdc1c0501c5275e7f26fdb8e2a7b14a40a9f36b.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>