1// SPDX-License-Identifier: GPL-2.0
2/*
3 * bpf-script-example.c
4 * Test basic LLVM building
5 */
6#ifndef LINUX_VERSION_CODE
7# error Need LINUX_VERSION_CODE
8# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
9#endif
10#define BPF_ANY 0
11#define BPF_MAP_TYPE_ARRAY 2
12#define BPF_FUNC_map_lookup_elem 1
13#define BPF_FUNC_map_update_elem 2
14
15static void *(*bpf_map_lookup_elem)(void *map, void *key) =
16	(void *) BPF_FUNC_map_lookup_elem;
17static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
18	(void *) BPF_FUNC_map_update_elem;
19
20struct bpf_map_def {
21	unsigned int type;
22	unsigned int key_size;
23	unsigned int value_size;
24	unsigned int max_entries;
25};
26
27#define SEC(NAME) __attribute__((section(NAME), used))
28struct bpf_map_def SEC("maps") flip_table = {
29	.type = BPF_MAP_TYPE_ARRAY,
30	.key_size = sizeof(int),
31	.value_size = sizeof(int),
32	.max_entries = 1,
33};
34
35SEC("func=do_epoll_wait")
36int bpf_func__SyS_epoll_pwait(void *ctx)
37{
38	int ind =0;
39	int *flag = bpf_map_lookup_elem(&flip_table, &ind);
40	int new_flag;
41	if (!flag)
42		return 0;
43	/* flip flag and store back */
44	new_flag = !*flag;
45	bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
46	return new_flag;
47}
48char _license[] SEC("license") = "GPL";
49int _version SEC("version") = LINUX_VERSION_CODE;
50