1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com> 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 <joe.lawrence@redhat.com>"); 70 MODULE_DESCRIPTION("Livepatch test: busy target module"); 71