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 */ 13static bool block_transition; 14module_param(block_transition, bool, 0644); 15MODULE_PARM_DESC(block_transition, "block_transition (default=false)"); 16 17static void busymod_work_func(struct work_struct *work); 18static DECLARE_WORK(work, busymod_work_func); 19static DECLARE_COMPLETION(busymod_work_started); 20 21static 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 37static 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 59static 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 66module_init(test_klp_callbacks_busy_init); 67module_exit(test_klp_callbacks_busy_exit); 68MODULE_LICENSE("GPL"); 69MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>"); 70MODULE_DESCRIPTION("Livepatch test: busy target module"); 71