bpf-script-example.c 1.3 KB

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  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. 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. struct bpf_map_def {
  19. unsigned int type;
  20. unsigned int key_size;
  21. unsigned int value_size;
  22. unsigned int max_entries;
  23. };
  24. #define SEC(NAME) __attribute__((section(NAME), used))
  25. struct bpf_map_def SEC("maps") flip_table = {
  26. .type = BPF_MAP_TYPE_ARRAY,
  27. .key_size = sizeof(int),
  28. .value_size = sizeof(int),
  29. .max_entries = 1,
  30. };
  31. SEC("func=do_epoll_wait")
  32. int bpf_func__SyS_epoll_pwait(void *ctx)
  33. {
  34. int ind =0;
  35. int *flag = bpf_map_lookup_elem(&flip_table, &ind);
  36. int new_flag;
  37. if (!flag)
  38. return 0;
  39. /* flip flag and store back */
  40. new_flag = !*flag;
  41. bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
  42. return new_flag;
  43. }
  44. char _license[] SEC("license") = "GPL";
  45. int _version SEC("version") = LINUX_VERSION_CODE;