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

   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")
  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;