livepatch-callbacks-demo.c 5.5 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /*
  3. * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
  4. */
  5. /*
  6. * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo
  7. *
  8. *
  9. * Purpose
  10. * -------
  11. *
  12. * Demonstration of registering livepatch (un)patching callbacks.
  13. *
  14. *
  15. * Usage
  16. * -----
  17. *
  18. * Step 1 - load the simple module
  19. *
  20. * insmod samples/livepatch/livepatch-callbacks-mod.ko
  21. *
  22. *
  23. * Step 2 - load the demonstration livepatch (with callbacks)
  24. *
  25. * insmod samples/livepatch/livepatch-callbacks-demo.ko
  26. *
  27. *
  28. * Step 3 - cleanup
  29. *
  30. * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
  31. * rmmod livepatch_callbacks_demo
  32. * rmmod livepatch_callbacks_mod
  33. *
  34. * Watch dmesg output to see livepatch enablement, callback execution
  35. * and patching operations for both vmlinux and module targets.
  36. *
  37. * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and
  38. * livepatch-callbacks-demo.ko to observe what happens when a
  39. * target module is loaded after a livepatch with callbacks.
  40. *
  41. * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch
  42. * callback return status. Try setting up a non-zero status
  43. * such as -19 (-ENODEV):
  44. *
  45. * # Load demo livepatch, vmlinux is patched
  46. * insmod samples/livepatch/livepatch-callbacks-demo.ko
  47. *
  48. * # Setup next pre-patch callback to return -ENODEV
  49. * echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret
  50. *
  51. * # Module loader refuses to load the target module
  52. * insmod samples/livepatch/livepatch-callbacks-mod.ko
  53. * insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device
  54. *
  55. * NOTE: There is a second target module,
  56. * livepatch-callbacks-busymod.ko, available for experimenting
  57. * with livepatch (un)patch callbacks. This module contains
  58. * a 'sleep_secs' parameter that parks the module on one of the
  59. * functions that the livepatch demo module wants to patch.
  60. * Modifying this value and tweaking the order of module loads can
  61. * effectively demonstrate stalled patch transitions:
  62. *
  63. * # Load a target module, let it park on 'busymod_work_func' for
  64. * # thirty seconds
  65. * insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30
  66. *
  67. * # Meanwhile load the livepatch
  68. * insmod samples/livepatch/livepatch-callbacks-demo.ko
  69. *
  70. * # ... then load and unload another target module while the
  71. * # transition is in progress
  72. * insmod samples/livepatch/livepatch-callbacks-mod.ko
  73. * rmmod samples/livepatch/livepatch-callbacks-mod.ko
  74. *
  75. * # Finally cleanup
  76. * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
  77. * rmmod samples/livepatch/livepatch-callbacks-demo.ko
  78. */
  79. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  80. #include <linux/module.h>
  81. #include <linux/kernel.h>
  82. #include <linux/livepatch.h>
  83. static int pre_patch_ret;
  84. module_param(pre_patch_ret, int, 0644);
  85. MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)");
  86. static const char *const module_state[] = {
  87. [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state",
  88. [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init",
  89. [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away",
  90. [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
  91. };
  92. static void callback_info(const char *callback, struct klp_object *obj)
  93. {
  94. if (obj->mod)
  95. pr_info("%s: %s -> %s\n", callback, obj->mod->name,
  96. module_state[obj->mod->state]);
  97. else
  98. pr_info("%s: vmlinux\n", callback);
  99. }
  100. /* Executed on object patching (ie, patch enablement) */
  101. static int pre_patch_callback(struct klp_object *obj)
  102. {
  103. callback_info(__func__, obj);
  104. return pre_patch_ret;
  105. }
  106. /* Executed on object unpatching (ie, patch disablement) */
  107. static void post_patch_callback(struct klp_object *obj)
  108. {
  109. callback_info(__func__, obj);
  110. }
  111. /* Executed on object unpatching (ie, patch disablement) */
  112. static void pre_unpatch_callback(struct klp_object *obj)
  113. {
  114. callback_info(__func__, obj);
  115. }
  116. /* Executed on object unpatching (ie, patch disablement) */
  117. static void post_unpatch_callback(struct klp_object *obj)
  118. {
  119. callback_info(__func__, obj);
  120. }
  121. static void patched_work_func(struct work_struct *work)
  122. {
  123. pr_info("%s\n", __func__);
  124. }
  125. static struct klp_func no_funcs[] = {
  126. { }
  127. };
  128. static struct klp_func busymod_funcs[] = {
  129. {
  130. .old_name = "busymod_work_func",
  131. .new_func = patched_work_func,
  132. }, { }
  133. };
  134. static struct klp_object objs[] = {
  135. {
  136. .name = NULL, /* vmlinux */
  137. .funcs = no_funcs,
  138. .callbacks = {
  139. .pre_patch = pre_patch_callback,
  140. .post_patch = post_patch_callback,
  141. .pre_unpatch = pre_unpatch_callback,
  142. .post_unpatch = post_unpatch_callback,
  143. },
  144. }, {
  145. .name = "livepatch_callbacks_mod",
  146. .funcs = no_funcs,
  147. .callbacks = {
  148. .pre_patch = pre_patch_callback,
  149. .post_patch = post_patch_callback,
  150. .pre_unpatch = pre_unpatch_callback,
  151. .post_unpatch = post_unpatch_callback,
  152. },
  153. }, {
  154. .name = "livepatch_callbacks_busymod",
  155. .funcs = busymod_funcs,
  156. .callbacks = {
  157. .pre_patch = pre_patch_callback,
  158. .post_patch = post_patch_callback,
  159. .pre_unpatch = pre_unpatch_callback,
  160. .post_unpatch = post_unpatch_callback,
  161. },
  162. }, { }
  163. };
  164. static struct klp_patch patch = {
  165. .mod = THIS_MODULE,
  166. .objs = objs,
  167. };
  168. static int livepatch_callbacks_demo_init(void)
  169. {
  170. return klp_enable_patch(&patch);
  171. }
  172. static void livepatch_callbacks_demo_exit(void)
  173. {
  174. }
  175. module_init(livepatch_callbacks_demo_init);
  176. module_exit(livepatch_callbacks_demo_exit);
  177. MODULE_LICENSE("GPL");
  178. MODULE_INFO(livepatch, "Y");