UPSTREAM: kcov: support compat processes

Support compat processes in KCOV by providing compat_ioctl callback.
Compat mode uses the same ioctl callback: we have 2 commands that do not
use the argument and 1 that already checks that the arg does not overflow
INT_MAX.  This allows to use KCOV-guided fuzzing in compat processes.

Link: http://lkml.kernel.org/r/20170823100553.55812-1-dvyukov@google.com


Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <syzkaller@googlegroups.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Bug: 64145065
(cherry-picked from 7483e5d420d9d5aa1732c5efb0da59e095a8b24e)
Change-Id:I74b62f01941091649ce6e88b3130e4ca4274a8de
Signed-off-by: Paul Lawrence <paullawrence@google.com>