tools/perf/tests/bpf-script-example.c

   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_pwait")
  35 int 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 }
  47 char _license[] SEC("license") = "GPL";
  48 int _version SEC("version") = LINUX_VERSION_CODE;