1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2020 Facebook */
 3
 4#include "vmlinux.h"
 5
 6#include <bpf/bpf_helpers.h>
 7
 8extern const struct rq runqueues __ksym; /* struct type global var. */
 9extern const int bpf_prog_active __ksym; /* int type global var. */
10
11SEC("raw_tp/sys_enter")
12int handler(const void *ctx)
13{
14	struct rq *rq;
15	int *active;
16	__u32 cpu;
17
18	cpu = bpf_get_smp_processor_id();
19	rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, cpu);
20	active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
21	if (active) {
22		/* READ_ONCE */
23		*(volatile int *)active;
24		/* !rq has not been tested, so verifier should reject. */
25		*(volatile int *)(&rq->cpu);
26	}
27
28	return 0;
29}
30
31char _license[] SEC("license") = "GPL";