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 15 static void *(*bpf_map_lookup_elem)(void *map, void *key) = 16 (void *) BPF_FUNC_map_lookup_elem; 17 static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) = 18 (void *) BPF_FUNC_map_update_elem; 19 20 struct 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)) 28 struct 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 35 SEC("func=do_epoll_wait") bpf_func__SyS_epoll_pwait(void * ctx)36 int 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 } 48 char _license[] SEC("license") = "GPL"; 49 int _version SEC("version") = LINUX_VERSION_CODE; 50