Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/samples/bpf/sampleip_user.c b/samples/bpf/sampleip_user.c
index 60c2b73..6b5dc26 100644
--- a/samples/bpf/sampleip_user.c
+++ b/samples/bpf/sampleip_user.c
@@ -1,15 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * sampleip: sample instruction pointer and frequency count in a BPF map.
  *
  * Copyright 2016 Netflix, Inc.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of version 2 of the GNU General Public
- * License as published by the Free Software Foundation.
  */
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <unistd.h>
 #include <errno.h>
 #include <signal.h>
@@ -110,6 +106,11 @@
 	for (i = 0; i < max; i++) {
 		if (counts[i].ip > PAGE_OFFSET) {
 			sym = ksym_search(counts[i].ip);
+			if (!sym) {
+				printf("ksym not found. Is kallsyms loaded?\n");
+				continue;
+			}
+
 			printf("0x%-17llx %-32s %u\n", counts[i].ip, sym->name,
 			       counts[i].count);
 		} else {