1/* SPDX-License-Identifier: GPL-2.0 */
2/* Copyright (c) 2021 Hengqi Chen */
3
4#include "vmlinux.h"
5#include <bpf/bpf_helpers.h>
6#include <bpf/bpf_tracing.h>
7
8const volatile pid_t my_pid = 0;
9int value = 0;
10
11SEC("raw_tp/sys_enter")
12int tailcall_1(void *ctx)
13{
14	value = 42;
15	return 0;
16}
17
18struct {
19	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
20	__uint(max_entries, 2);
21	__uint(key_size, sizeof(__u32));
22	__array(values, int (void *));
23} prog_array_init SEC(".maps") = {
24	.values = {
25		[1] = (void *)&tailcall_1,
26	},
27};
28
29SEC("raw_tp/sys_enter")
30int entry(void *ctx)
31{
32	pid_t pid = bpf_get_current_pid_tgid() >> 32;
33
34	if (pid != my_pid)
35		return 0;
36
37	bpf_tail_call(ctx, &prog_array_init, 1);
38	return 0;
39}
40