1// SPDX-License-Identifier: GPL-2.0
 2// Copyright (c) 2018 Facebook
 3
 4#include <linux/bpf.h>
 5#include "bpf_helpers.h"
 6
 7#ifndef PERF_MAX_STACK_DEPTH
 8#define PERF_MAX_STACK_DEPTH         127
 9#endif
10
11struct bpf_map_def SEC("maps") control_map = {
12	.type = BPF_MAP_TYPE_ARRAY,
13	.key_size = sizeof(__u32),
14	.value_size = sizeof(__u32),
15	.max_entries = 1,
16};
17
18struct bpf_map_def SEC("maps") stackid_hmap = {
19	.type = BPF_MAP_TYPE_HASH,
20	.key_size = sizeof(__u32),
21	.value_size = sizeof(__u32),
22	.max_entries = 10000,
23};
24
25struct bpf_map_def SEC("maps") stackmap = {
26	.type = BPF_MAP_TYPE_STACK_TRACE,
27	.key_size = sizeof(__u32),
28	.value_size = sizeof(__u64) * PERF_MAX_STACK_DEPTH,
29	.max_entries = 10000,
30};
31
32/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
33struct sched_switch_args {
34	unsigned long long pad;
35	char prev_comm[16];
36	int prev_pid;
37	int prev_prio;
38	long long prev_state;
39	char next_comm[16];
40	int next_pid;
41	int next_prio;
42};
43
44SEC("tracepoint/sched/sched_switch")
45int oncpu(struct sched_switch_args *ctx)
46{
47	__u32 key = 0, val = 0, *value_p;
48
49	value_p = bpf_map_lookup_elem(&control_map, &key);
50	if (value_p && *value_p)
51		return 0; /* skip if non-zero *value_p */
52
53	/* The size of stackmap and stackid_hmap should be the same */
54	key = bpf_get_stackid(ctx, &stackmap, 0);
55	if ((int)key >= 0)
56		bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
57
58	return 0;
59}
60
61char _license[] SEC("license") = "GPL";
62__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */