perf auxtrace: Define auxtrace record alignment

Define auxtrace record alignment so that it can be referenced elsewhere.

Note this is preparation for patch "perf intel-pt: Fix overlap calculation
for padding"

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190206103947.15750-2-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/auxtrace.c

@@ -1279,9 +1279,9 @@ static int __auxtrace_mmap__read(struct perf_mmap *map,
 	}
 
 	/* padding must be written by fn() e.g. record__process_auxtrace() */
-	padding = size & 7;
+	padding = size & (PERF_AUXTRACE_RECORD_ALIGNMENT - 1);
 	if (padding)
-		padding = 8 - padding;
+		padding = PERF_AUXTRACE_RECORD_ALIGNMENT - padding;
 
 	memset(&ev, 0, sizeof(ev));
 	ev.auxtrace.header.type = PERF_RECORD_AUXTRACE;

tools/perf/util/auxtrace.h

@@ -40,6 +40,9 @@ struct record_opts;
 struct auxtrace_info_event;
 struct events_stats;
 
+/* Auxtrace records must have the same alignment as perf event records */
+#define PERF_AUXTRACE_RECORD_ALIGNMENT 8
+
 enum auxtrace_type {
 	PERF_AUXTRACE_UNKNOWN,
 	PERF_AUXTRACE_INTEL_PT,