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