livepatch-sample.c 1.3 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /*
  3. * livepatch-sample.c - Kernel Live Patching Sample Module
  4. *
  5. * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
  6. */
  7. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8. #include <linux/module.h>
  9. #include <linux/kernel.h>
  10. #include <linux/livepatch.h>
  11. /*
  12. * This (dumb) live patch overrides the function that prints the
  13. * kernel boot cmdline when /proc/cmdline is read.
  14. *
  15. * Example:
  16. *
  17. * $ cat /proc/cmdline
  18. * <your cmdline>
  19. *
  20. * $ insmod livepatch-sample.ko
  21. * $ cat /proc/cmdline
  22. * this has been live patched
  23. *
  24. * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
  25. * $ cat /proc/cmdline
  26. * <your cmdline>
  27. */
  28. #include <linux/seq_file.h>
  29. static int livepatch_cmdline_proc_show(struct seq_file *m, void *v)
  30. {
  31. seq_printf(m, "%s\n", "this has been live patched");
  32. return 0;
  33. }
  34. static struct klp_func funcs[] = {
  35. {
  36. .old_name = "cmdline_proc_show",
  37. .new_func = livepatch_cmdline_proc_show,
  38. }, { }
  39. };
  40. static struct klp_object objs[] = {
  41. {
  42. /* name being NULL means vmlinux */
  43. .funcs = funcs,
  44. }, { }
  45. };
  46. static struct klp_patch patch = {
  47. .mod = THIS_MODULE,
  48. .objs = objs,
  49. };
  50. static int livepatch_init(void)
  51. {
  52. return klp_enable_patch(&patch);
  53. }
  54. static void livepatch_exit(void)
  55. {
  56. }
  57. module_init(livepatch_init);
  58. module_exit(livepatch_exit);
  59. MODULE_LICENSE("GPL");
  60. MODULE_INFO(livepatch, "Y");