1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 // Copyright (c) 2021 Facebook
3 #include "vmlinux.h"
4 #include <bpf/bpf_helpers.h>
5 #include <bpf/bpf_tracing.h>
6 
7 struct {
8 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
9 	__uint(key_size, sizeof(__u32));
10 	__uint(value_size, sizeof(int));
11 	__uint(map_flags, BPF_F_PRESERVE_ELEMS);
12 } events SEC(".maps");
13 
14 struct {
15 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
16 	__uint(key_size, sizeof(__u32));
17 	__uint(value_size, sizeof(struct bpf_perf_event_value));
18 	__uint(max_entries, 1);
19 } prev_readings SEC(".maps");
20 
21 struct {
22 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
23 	__uint(key_size, sizeof(__u32));
24 	__uint(value_size, sizeof(struct bpf_perf_event_value));
25 	__uint(max_entries, 1);
26 } diff_readings SEC(".maps");
27 
28 SEC("raw_tp/sched_switch")
BPF_PROG(on_switch)29 int BPF_PROG(on_switch)
30 {
31 	struct bpf_perf_event_value val, *prev_val, *diff_val;
32 	__u32 key = bpf_get_smp_processor_id();
33 	__u32 zero = 0;
34 	long err;
35 
36 	prev_val = bpf_map_lookup_elem(&prev_readings, &zero);
37 	if (!prev_val)
38 		return 0;
39 
40 	diff_val = bpf_map_lookup_elem(&diff_readings, &zero);
41 	if (!diff_val)
42 		return 0;
43 
44 	err = bpf_perf_event_read_value(&events, key, &val, sizeof(val));
45 	if (err)
46 		return 0;
47 
48 	diff_val->counter = val.counter - prev_val->counter;
49 	diff_val->enabled = val.enabled - prev_val->enabled;
50 	diff_val->running = val.running - prev_val->running;
51 	*prev_val = val;
52 	return 0;
53 }
54 
55 char LICENSE[] SEC("license") = "Dual BSD/GPL";
56