LXR linux/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
  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_wait")
  35int 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}
  47char _license[] SEC("license") = "GPL";
  48int _version SEC("version") = LINUX_VERSION_CODE;
  49