lib/livepatch/test_klp_callbacks_busy.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 // Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>
0003
0004 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0005
0006 #include <linux/module.h>
0007 #include <linux/kernel.h>
0008 #include <linux/sched.h>
0009 #include <linux/workqueue.h>
0010 #include <linux/delay.h>
0011
0012 /* load/run-time control from sysfs writer  */
0013 static bool block_transition;
0014 module_param(block_transition, bool, 0644);
0015 MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
0016
0017 static void busymod_work_func(struct work_struct *work);
0018 static DECLARE_WORK(work, busymod_work_func);
0019 static DECLARE_COMPLETION(busymod_work_started);
0020
0021 static void busymod_work_func(struct work_struct *work)
0022 {
0023     pr_info("%s enter\n", __func__);
0024     complete(&busymod_work_started);
0025
0026     while (READ_ONCE(block_transition)) {
0027         /*
0028          * Busy-wait until the sysfs writer has acknowledged a
0029          * blocked transition and clears the flag.
0030          */
0031         msleep(20);
0032     }
0033
0034     pr_info("%s exit\n", __func__);
0035 }
0036
0037 static int test_klp_callbacks_busy_init(void)
0038 {
0039     pr_info("%s\n", __func__);
0040     schedule_work(&work);
0041
0042     /*
0043      * To synchronize kernel messages, hold the init function from
0044      * exiting until the work function's entry message has printed.
0045      */
0046     wait_for_completion(&busymod_work_started);
0047
0048     if (!block_transition) {
0049         /*
0050          * Serialize output: print all messages from the work
0051          * function before returning from init().
0052          */
0053         flush_work(&work);
0054     }
0055
0056     return 0;
0057 }
0058
0059 static void test_klp_callbacks_busy_exit(void)
0060 {
0061     WRITE_ONCE(block_transition, false);
0062     flush_work(&work);
0063     pr_info("%s\n", __func__);
0064 }
0065
0066 module_init(test_klp_callbacks_busy_init);
0067 module_exit(test_klp_callbacks_busy_exit);
0068 MODULE_LICENSE("GPL");
0069 MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
0070 MODULE_DESCRIPTION("Livepatch test: busy target module");