lib/livepatch/test_klp_callbacks_busy.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2018 Joe Lawrence <[email protected]>
   3
   4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   5
   6 #include <linux/module.h>
   7 #include <linux/kernel.h>
   8 #include <linux/sched.h>
   9 #include <linux/workqueue.h>
  10 #include <linux/delay.h>
  11
  12 /* load/run-time control from sysfs writer  */
  13 static bool block_transition;
  14 module_param(block_transition, bool, 0644);
  15 MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
  16
  17 static void busymod_work_func(struct work_struct *work);
  18 static DECLARE_WORK(work, busymod_work_func);
  19 static DECLARE_COMPLETION(busymod_work_started);
  20
  21 static void busymod_work_func(struct work_struct *work)
  22 {
  23         pr_info("%s enter\n", __func__);
  24         complete(&busymod_work_started);
  25
  26         while (READ_ONCE(block_transition)) {
  27                 /*
  28                  * Busy-wait until the sysfs writer has acknowledged a
  29                  * blocked transition and clears the flag.
  30                  */
  31                 msleep(20);
  32         }
  33
  34         pr_info("%s exit\n", __func__);
  35 }
  36
  37 static int test_klp_callbacks_busy_init(void)
  38 {
  39         pr_info("%s\n", __func__);
  40         schedule_work(&work);
  41
  42         /*
  43          * To synchronize kernel messages, hold the init function from
  44          * exiting until the work function's entry message has printed.
  45          */
  46         wait_for_completion(&busymod_work_started);
  47
  48         if (!block_transition) {
  49                 /*
  50                  * Serialize output: print all messages from the work
  51                  * function before returning from init().
  52                  */
  53                 flush_work(&work);
  54         }
  55
  56         return 0;
  57 }
  58
  59 static void test_klp_callbacks_busy_exit(void)
  60 {
  61         WRITE_ONCE(block_transition, false);
  62         flush_work(&work);
  63         pr_info("%s\n", __func__);
  64 }
  65
  66 module_init(test_klp_callbacks_busy_init);
  67 module_exit(test_klp_callbacks_busy_exit);
  68 MODULE_LICENSE("GPL");
  69 MODULE_AUTHOR("Joe Lawrence <[email protected]>");
  70 MODULE_DESCRIPTION("Livepatch test: busy target module");