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
 7struct {
 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
14struct {
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
21struct {
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
28SEC("raw_tp/sched_switch")
29int 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
55char LICENSE[] SEC("license") = "Dual BSD/GPL";