... so that it can mask args relative to its position, like the 'mode' arg
that may or not be printed according to the 'flags' (O_CREAT) value.

 [root@zoo ~]# perf trace -a -e openat,open_by_handle_at | head -1
    469.754 ( 0.034 ms): 1183 openat(dfd: -100, filename: 0x7fbde40014b0, flags: CLOEXEC|DIRECTORY|NONBLOCK) = 23
 [root@zoo ~]#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-bgokqpkufd4sio7ixxknf1ux@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>