1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright 2022, Athira Rajeev, IBM Corp.
4  */
5 
6 #include <stdio.h>
7 #include <stdlib.h>
8 
9 #include "../event.h"
10 #include "misc.h"
11 #include "utils.h"
12 
13 /*
14  * A perf sampling test for making sure
15  * enabling branch stack doesn't crash in any
16  * environment, say:
17  *  - With generic compat PMU
18  *  - without any PMU registered
19  *  - With platform specific PMU
20  *  A fix for bhrb sampling crash was added in kernel
21  *  via commit: b460b512417a ("powerpc/perf: Fix crashes
22  *  with generic_compat_pmu & BHRB")
23  *
24  * This testcase exercises this code by doing branch
25  * stack enable for software event. s/w event is used
26  * since software event will work even in platform
27  * without PMU.
28  */
29 static int bhrb_no_crash_wo_pmu_test(void)
30 {
31 	struct event event;
32 
33 	/*
34 	 * Init the event for the sampling test.
35 	 * This uses software event which works on
36 	 * any platform.
37 	 */
38 	event_init_opts(&event, 0, PERF_TYPE_SOFTWARE, "cycles");
39 
40 	event.attr.sample_period = 1000;
41 	event.attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
42 	event.attr.disabled = 1;
43 
44 	/*
45 	 * Return code of event_open is not
46 	 * considered since test just expects no crash from
47 	 * using PERF_SAMPLE_BRANCH_STACK. Also for environment
48 	 * like generic compat PMU, branch stack is unsupported.
49 	 */
50 	event_open(&event);
51 
52 	event_close(&event);
53 	return 0;
54 }
55 
56 int main(void)
57 {
58 	return test_harness(bhrb_no_crash_wo_pmu_test, "bhrb_no_crash_wo_pmu_test");
59 }
60