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
14 static void *(*bpf_map_lookup_elem)(void *map, void *key) =
15 (void *) BPF_FUNC_map_lookup_elem;
16 static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
17 (void *) BPF_FUNC_map_update_elem;
18
19 struct 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))
27 struct 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
34 SEC("func=SyS_epoll_wait")
bpf_func__SyS_epoll_wait(void * ctx)35 int bpf_func__SyS_epoll_wait(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 }
47 char _license[] SEC("license") = "GPL";
48 int _version SEC("version") = LINUX_VERSION_CODE;
49