1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (C) 2023. Huawei Technologies Co., Ltd */
3#include <linux/bpf.h>
4#include <time.h>
5#include <bpf/bpf_helpers.h>
6
7#include "bpf_misc.h"
8
9struct inner_map_type {
10	__uint(type, BPF_MAP_TYPE_ARRAY);
11	__uint(key_size, 4);
12	__uint(value_size, 4);
13	__uint(max_entries, 1);
14} inner_map SEC(".maps");
15
16struct {
17	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
18	__type(key, int);
19	__type(value, int);
20	__uint(max_entries, 1);
21	__array(values, struct inner_map_type);
22} outer_array_map SEC(".maps") = {
23	.values = {
24		[0] = &inner_map,
25	},
26};
27
28struct {
29	__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
30	__type(key, int);
31	__type(value, int);
32	__uint(max_entries, 1);
33	__array(values, struct inner_map_type);
34} outer_htab_map SEC(".maps") = {
35	.values = {
36		[0] = &inner_map,
37	},
38};
39
40char _license[] SEC("license") = "GPL";
41
42int tgid = 0;
43
44static int acc_map_in_map(void *outer_map)
45{
46	int i, key, value = 0xdeadbeef;
47	void *inner_map;
48
49	if ((bpf_get_current_pid_tgid() >> 32) != tgid)
50		return 0;
51
52	/* Find nonexistent inner map */
53	key = 1;
54	inner_map = bpf_map_lookup_elem(outer_map, &key);
55	if (inner_map)
56		return 0;
57
58	/* Find the old inner map */
59	key = 0;
60	inner_map = bpf_map_lookup_elem(outer_map, &key);
61	if (!inner_map)
62		return 0;
63
64	/* Wait for the old inner map to be replaced */
65	for (i = 0; i < 2048; i++)
66		bpf_map_update_elem(inner_map, &key, &value, 0);
67
68	return 0;
69}
70
71SEC("?kprobe/" SYS_PREFIX "sys_getpgid")
72int access_map_in_array(void *ctx)
73{
74	return acc_map_in_map(&outer_array_map);
75}
76
77SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
78int sleepable_access_map_in_array(void *ctx)
79{
80	return acc_map_in_map(&outer_array_map);
81}
82
83SEC("?kprobe/" SYS_PREFIX "sys_getpgid")
84int access_map_in_htab(void *ctx)
85{
86	return acc_map_in_map(&outer_htab_map);
87}
88
89SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
90int sleepable_access_map_in_htab(void *ctx)
91{
92	return acc_map_in_map(&outer_htab_map);
93}
94