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