1 /* 2 * SoftDog 0.07: A Software Watchdog Device 3 * 4 * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>, 5 * All Rights Reserved. 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 10 * 2 of the License, or (at your option) any later version. 11 * 12 * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide 13 * warranty for any of this software. This material is provided 14 * "AS-IS" and at no charge. 15 * 16 * (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk> 17 * 18 * Software only watchdog driver. Unlike its big brother the WDT501P 19 * driver this won't always recover a failed machine. 20 * 21 * 03/96: Angelo Haritsis <ah@doc.ic.ac.uk> : 22 * Modularised. 23 * Added soft_margin; use upon insmod to change the timer delay. 24 * NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate 25 * minors. 26 * 27 * 19980911 Alan Cox 28 * Made SMP safe for 2.3.x 29 * 30 * 20011127 Joel Becker (jlbec@evilplan.org> 31 * Added soft_noboot; Allows testing the softdog trigger without 32 * requiring a recompile. 33 * Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT. 34 * 35 * 20020530 Joel Becker <joel.becker@oracle.com> 36 * Added Matt Domsch's nowayout module option. 37 */ 38 39 #include <linux/module.h> 40 #include <linux/moduleparam.h> 41 #include <linux/types.h> 42 #include <linux/timer.h> 43 #include <linux/miscdevice.h> 44 #include <linux/watchdog.h> 45 #include <linux/fs.h> 46 #include <linux/notifier.h> 47 #include <linux/reboot.h> 48 #include <linux/init.h> 49 #include <linux/jiffies.h> 50 #include <linux/uaccess.h> 51 52 #define PFX "SoftDog: " 53 54 #define TIMER_MARGIN 60 /* Default is 60 seconds */ 55 static int soft_margin = TIMER_MARGIN; /* in seconds */ 56 module_param(soft_margin, int, 0); 57 MODULE_PARM_DESC(soft_margin, 58 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default=" 59 __MODULE_STRING(TIMER_MARGIN) ")"); 60 61 static int nowayout = WATCHDOG_NOWAYOUT; 62 module_param(nowayout, int, 0); 63 MODULE_PARM_DESC(nowayout, 64 "Watchdog cannot be stopped once started (default=" 65 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 66 67 #ifdef ONLY_TESTING 68 static int soft_noboot = 1; 69 #else 70 static int soft_noboot = 0; 71 #endif /* ONLY_TESTING */ 72 73 module_param(soft_noboot, int, 0); 74 MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)"); 75 76 /* 77 * Our timer 78 */ 79 80 static void watchdog_fire(unsigned long); 81 82 static struct timer_list watchdog_ticktock = 83 TIMER_INITIALIZER(watchdog_fire, 0, 0); 84 static unsigned long driver_open, orphan_timer; 85 static char expect_close; 86 87 88 /* 89 * If the timer expires.. 90 */ 91 92 static void watchdog_fire(unsigned long data) 93 { 94 if (test_and_clear_bit(0, &orphan_timer)) 95 module_put(THIS_MODULE); 96 97 if (soft_noboot) 98 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n"); 99 else { 100 printk(KERN_CRIT PFX "Initiating system reboot.\n"); 101 emergency_restart(); 102 printk(KERN_CRIT PFX "Reboot didn't ?????\n"); 103 } 104 } 105 106 /* 107 * Softdog operations 108 */ 109 110 static int softdog_keepalive(void) 111 { 112 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ)); 113 return 0; 114 } 115 116 static int softdog_stop(void) 117 { 118 del_timer(&watchdog_ticktock); 119 return 0; 120 } 121 122 static int softdog_set_heartbeat(int t) 123 { 124 if ((t < 0x0001) || (t > 0xFFFF)) 125 return -EINVAL; 126 127 soft_margin = t; 128 return 0; 129 } 130 131 /* 132 * /dev/watchdog handling 133 */ 134 135 static int softdog_open(struct inode *inode, struct file *file) 136 { 137 if (test_and_set_bit(0, &driver_open)) 138 return -EBUSY; 139 if (!test_and_clear_bit(0, &orphan_timer)) 140 __module_get(THIS_MODULE); 141 /* 142 * Activate timer 143 */ 144 softdog_keepalive(); 145 return nonseekable_open(inode, file); 146 } 147 148 static int softdog_release(struct inode *inode, struct file *file) 149 { 150 /* 151 * Shut off the timer. 152 * Lock it in if it's a module and we set nowayout 153 */ 154 if (expect_close == 42) { 155 softdog_stop(); 156 module_put(THIS_MODULE); 157 } else { 158 printk(KERN_CRIT PFX 159 "Unexpected close, not stopping watchdog!\n"); 160 set_bit(0, &orphan_timer); 161 softdog_keepalive(); 162 } 163 clear_bit(0, &driver_open); 164 expect_close = 0; 165 return 0; 166 } 167 168 static ssize_t softdog_write(struct file *file, const char __user *data, 169 size_t len, loff_t *ppos) 170 { 171 /* 172 * Refresh the timer. 173 */ 174 if (len) { 175 if (!nowayout) { 176 size_t i; 177 178 /* In case it was set long ago */ 179 expect_close = 0; 180 181 for (i = 0; i != len; i++) { 182 char c; 183 184 if (get_user(c, data + i)) 185 return -EFAULT; 186 if (c == 'V') 187 expect_close = 42; 188 } 189 } 190 softdog_keepalive(); 191 } 192 return len; 193 } 194 195 static long softdog_ioctl(struct file *file, unsigned int cmd, 196 unsigned long arg) 197 { 198 void __user *argp = (void __user *)arg; 199 int __user *p = argp; 200 int new_margin; 201 static const struct watchdog_info ident = { 202 .options = WDIOF_SETTIMEOUT | 203 WDIOF_KEEPALIVEPING | 204 WDIOF_MAGICCLOSE, 205 .firmware_version = 0, 206 .identity = "Software Watchdog", 207 }; 208 switch (cmd) { 209 case WDIOC_GETSUPPORT: 210 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 211 case WDIOC_GETSTATUS: 212 case WDIOC_GETBOOTSTATUS: 213 return put_user(0, p); 214 case WDIOC_KEEPALIVE: 215 softdog_keepalive(); 216 return 0; 217 case WDIOC_SETTIMEOUT: 218 if (get_user(new_margin, p)) 219 return -EFAULT; 220 if (softdog_set_heartbeat(new_margin)) 221 return -EINVAL; 222 softdog_keepalive(); 223 /* Fall */ 224 case WDIOC_GETTIMEOUT: 225 return put_user(soft_margin, p); 226 default: 227 return -ENOTTY; 228 } 229 } 230 231 /* 232 * Notifier for system down 233 */ 234 235 static int softdog_notify_sys(struct notifier_block *this, unsigned long code, 236 void *unused) 237 { 238 if (code == SYS_DOWN || code == SYS_HALT) 239 /* Turn the WDT off */ 240 softdog_stop(); 241 return NOTIFY_DONE; 242 } 243 244 /* 245 * Kernel Interfaces 246 */ 247 248 static const struct file_operations softdog_fops = { 249 .owner = THIS_MODULE, 250 .llseek = no_llseek, 251 .write = softdog_write, 252 .unlocked_ioctl = softdog_ioctl, 253 .open = softdog_open, 254 .release = softdog_release, 255 }; 256 257 static struct miscdevice softdog_miscdev = { 258 .minor = WATCHDOG_MINOR, 259 .name = "watchdog", 260 .fops = &softdog_fops, 261 }; 262 263 static struct notifier_block softdog_notifier = { 264 .notifier_call = softdog_notify_sys, 265 }; 266 267 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n"; 268 269 static int __init watchdog_init(void) 270 { 271 int ret; 272 273 /* Check that the soft_margin value is within it's range; 274 if not reset to the default */ 275 if (softdog_set_heartbeat(soft_margin)) { 276 softdog_set_heartbeat(TIMER_MARGIN); 277 printk(KERN_INFO PFX 278 "soft_margin must be 0 < soft_margin < 65536, using %d\n", 279 TIMER_MARGIN); 280 } 281 282 ret = register_reboot_notifier(&softdog_notifier); 283 if (ret) { 284 printk(KERN_ERR PFX 285 "cannot register reboot notifier (err=%d)\n", ret); 286 return ret; 287 } 288 289 ret = misc_register(&softdog_miscdev); 290 if (ret) { 291 printk(KERN_ERR PFX 292 "cannot register miscdev on minor=%d (err=%d)\n", 293 WATCHDOG_MINOR, ret); 294 unregister_reboot_notifier(&softdog_notifier); 295 return ret; 296 } 297 298 printk(banner, soft_noboot, soft_margin, nowayout); 299 300 return 0; 301 } 302 303 static void __exit watchdog_exit(void) 304 { 305 misc_deregister(&softdog_miscdev); 306 unregister_reboot_notifier(&softdog_notifier); 307 } 308 309 module_init(watchdog_init); 310 module_exit(watchdog_exit); 311 312 MODULE_AUTHOR("Alan Cox"); 313 MODULE_DESCRIPTION("Software Watchdog Device Driver"); 314 MODULE_LICENSE("GPL"); 315 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 316