x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

x86/debug: Handle warnings before the notifier chain, to fix KGDB crash

Commit:

  9a93848fe787 ("x86/debug: Implement __WARN() using UD0")

turned warnings into UD0, but the fixup code only runs after the
notify_die() chain. This is a problem, in particular, with kgdb,
which kicks in as if it was a BUG().

Fix this by running the fixup code before the notifier chain in
the invalid op handler path.

Signed-off-by: Alexander Shishkin <[email protected]>
Tested-by: Ilya Dryomov <[email protected]>
Acked-by: Daniel Thompson <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Jason Wessel <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: <[email protected]> # v4.12+
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>