1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 // Copyright (c) 2021 Facebook
3 #include <linux/bpf.h>
4 #include <linux/perf_event.h>
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include "bperf.h"
8 
9 struct {
10 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
11 	__uint(key_size, sizeof(__u32));
12 	__uint(value_size, sizeof(int));
13 	__uint(map_flags, BPF_F_PRESERVE_ELEMS);
14 } events SEC(".maps");
15 
16 reading_map prev_readings SEC(".maps");
17 reading_map diff_readings SEC(".maps");
18 
19 SEC("raw_tp/sched_switch")
20 int BPF_PROG(on_switch)
21 {
22 	struct bpf_perf_event_value val, *prev_val, *diff_val;
23 	__u32 key = bpf_get_smp_processor_id();
24 	__u32 zero = 0;
25 	long err;
26 
27 	prev_val = bpf_map_lookup_elem(&prev_readings, &zero);
28 	if (!prev_val)
29 		return 0;
30 
31 	diff_val = bpf_map_lookup_elem(&diff_readings, &zero);
32 	if (!diff_val)
33 		return 0;
34 
35 	err = bpf_perf_event_read_value(&events, key, &val, sizeof(val));
36 	if (err)
37 		return 0;
38 
39 	diff_val->counter = val.counter - prev_val->counter;
40 	diff_val->enabled = val.enabled - prev_val->enabled;
41 	diff_val->running = val.running - prev_val->running;
42 	*prev_val = val;
43 	return 0;
44 }
45 
46 char LICENSE[] SEC("license") = "Dual BSD/GPL";
47