diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 0550194b3252740bbee8ffc8c38adbb4cdc031c8..53869bbd8b5d8afb7b00730cd432e229bde9a4b0 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -198,6 +198,7 @@ struct hw_perf_event {
 	 */
 	u64				sample_period;
 
+#ifndef __GENKSYMS__
 	union {
 		struct { /* Sampling */
 			/*
@@ -218,6 +219,20 @@ struct hw_perf_event {
 			u64				saved_slots;
 		};
 	};
+#else
+	/*
+	 * The period we started this sample with.
+	 */
+	u64				last_period;
+
+	/*
+	 * However much is left of the current period;
+	 * note that this is a full 64bit value and
+	 * allows for generation of periods longer
+	 * than hardware might allow.
+	 */
+	local64_t			period_left;
+#endif
 
 	/*
 	 * State for throttling the event, see __perf_event_overflow() and