tools lib traceevent: Add plugin for decoding syscalls/sys_enter_futex

The futex syscall is a complicated one.  It supports thirteen
multiplexed operations, each with different semantics and encodings for
the syscalls six arguments.

Manually decoding these arguments is tedious and error prone.

This plugin provides symbolic names for futex operations, futex flags,
and tries to be intelligent about the intent of specific arguments (for
example, waking operations use 'val' as an integer count, not just an
arbitrary value).

It doesn't do a full decode of the FUTEX_WAKE_OP's 'val3' argument,
however, this is a good starting point.

Link: http://lkml.kernel.org/r/20171207025649.12160-1-julia@ni.com
Link: http://lore.kernel.org/linux-trace-devel/20200702174950.123454-3-tz.stoyanov@gmail.com

Signed-off-by: Julia Cartwright <julia@ni.com>
[ Ported from trace-cmd.git ]
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200702185705.127175788@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/plugins/Build

@@ -5,6 +5,7 @@ plugin_kvm-y          += plugin_kvm.o
 plugin_mac80211-y     += plugin_mac80211.o
 plugin_sched_switch-y += plugin_sched_switch.o
 plugin_function-y     += plugin_function.o
+plugin_futex-y        += plugin_futex.o
 plugin_xen-y          += plugin_xen.o
 plugin_scsi-y         += plugin_scsi.o
 plugin_cfg80211-y     += plugin_cfg80211.o