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 #include <linux/kernel.h> 52 53 #define PFX "SoftDog: " 54 55 #define TIMER_MARGIN 60 /* Default is 60 seconds */ 56 static int soft_margin = TIMER_MARGIN; /* in seconds */ 57 module_param(soft_margin, int, 0); 58 MODULE_PARM_DESC(soft_margin, 59 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default=" 60 __MODULE_STRING(TIMER_MARGIN) ")"); 61 62 static int nowayout = WATCHDOG_NOWAYOUT; 63 module_param(nowayout, int, 0); 64 MODULE_PARM_DESC(nowayout, 65 "Watchdog cannot be stopped once started (default=" 66 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 67 68 #ifdef ONLY_TESTING 69 static int soft_noboot = 1; 70 #else 71 static int soft_noboot = 0; 72 #endif /* ONLY_TESTING */ 73 74 module_param(soft_noboot, int, 0); 75 MODULE_PARM_DESC(soft_noboot, 76 "Softdog action, set to 1 to ignore reboots, 0 to reboot " 77 "(default depends on ONLY_TESTING)"); 78 79 static int soft_panic; 80 module_param(soft_panic, int, 0); 81 MODULE_PARM_DESC(soft_panic, 82 "Softdog action, set to 1 to panic, 0 to reboot (default=0)"); 83 84 /* 85 * Our timer 86 */ 87 88 static void watchdog_fire(unsigned long); 89 90 static struct timer_list watchdog_ticktock = 91 TIMER_INITIALIZER(watchdog_fire, 0, 0); 92 static unsigned long driver_open, orphan_timer; 93 static char expect_close; 94 95 96 /* 97 * If the timer expires.. 98 */ 99 100 static void watchdog_fire(unsigned long data) 101 { 102 if (test_and_clear_bit(0, &orphan_timer)) 103 module_put(THIS_MODULE); 104 105 if (soft_noboot) 106 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n"); 107 else if (soft_panic) { 108 printk(KERN_CRIT PFX "Initiating panic.\n"); 109 panic("Software Watchdog Timer expired."); 110 } else { 111 printk(KERN_CRIT PFX "Initiating system reboot.\n"); 112 emergency_restart(); 113 printk(KERN_CRIT PFX "Reboot didn't ?????\n"); 114 } 115 } 116 117 /* 118 * Softdog operations 119 */ 120 121 static int softdog_keepalive(void) 122 { 123 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ)); 124 return 0; 125 } 126 127 static int softdog_stop(void) 128 { 129 del_timer(&watchdog_ticktock); 130 return 0; 131 } 132 133 static int softdog_set_heartbeat(int t) 134 { 135 if ((t < 0x0001) || (t > 0xFFFF)) 136 return -EINVAL; 137 138 soft_margin = t; 139 return 0; 140 } 141 142 /* 143 * /dev/watchdog handling 144 */ 145 146 static int softdog_open(struct inode *inode, struct file *file) 147 { 148 if (test_and_set_bit(0, &driver_open)) 149 return -EBUSY; 150 if (!test_and_clear_bit(0, &orphan_timer)) 151 __module_get(THIS_MODULE); 152 /* 153 * Activate timer 154 */ 155 softdog_keepalive(); 156 return nonseekable_open(inode, file); 157 } 158 159 static int softdog_release(struct inode *inode, struct file *file) 160 { 161 /* 162 * Shut off the timer. 163 * Lock it in if it's a module and we set nowayout 164 */ 165 if (expect_close == 42) { 166 softdog_stop(); 167 module_put(THIS_MODULE); 168 } else { 169 printk(KERN_CRIT PFX 170 "Unexpected close, not stopping watchdog!\n"); 171 set_bit(0, &orphan_timer); 172 softdog_keepalive(); 173 } 174 clear_bit(0, &driver_open); 175 expect_close = 0; 176 return 0; 177 } 178 179 static ssize_t softdog_write(struct file *file, const char __user *data, 180 size_t len, loff_t *ppos) 181 { 182 /* 183 * Refresh the timer. 184 */ 185 if (len) { 186 if (!nowayout) { 187 size_t i; 188 189 /* In case it was set long ago */ 190 expect_close = 0; 191 192 for (i = 0; i != len; i++) { 193 char c; 194 195 if (get_user(c, data + i)) 196 return -EFAULT; 197 if (c == 'V') 198 expect_close = 42; 199 } 200 } 201 softdog_keepalive(); 202 } 203 return len; 204 } 205 206 static long softdog_ioctl(struct file *file, unsigned int cmd, 207 unsigned long arg) 208 { 209 void __user *argp = (void __user *)arg; 210 int __user *p = argp; 211 int new_margin; 212 static const struct watchdog_info ident = { 213 .options = WDIOF_SETTIMEOUT | 214 WDIOF_KEEPALIVEPING | 215 WDIOF_MAGICCLOSE, 216 .firmware_version = 0, 217 .identity = "Software Watchdog", 218 }; 219 switch (cmd) { 220 case WDIOC_GETSUPPORT: 221 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 222 case WDIOC_GETSTATUS: 223 case WDIOC_GETBOOTSTATUS: 224 return put_user(0, p); 225 case WDIOC_KEEPALIVE: 226 softdog_keepalive(); 227 return 0; 228 case WDIOC_SETTIMEOUT: 229 if (get_user(new_margin, p)) 230 return -EFAULT; 231 if (softdog_set_heartbeat(new_margin)) 232 return -EINVAL; 233 softdog_keepalive(); 234 /* Fall */ 235 case WDIOC_GETTIMEOUT: 236 return put_user(soft_margin, p); 237 default: 238 return -ENOTTY; 239 } 240 } 241 242 /* 243 * Notifier for system down 244 */ 245 246 static int softdog_notify_sys(struct notifier_block *this, unsigned long code, 247 void *unused) 248 { 249 if (code == SYS_DOWN || code == SYS_HALT) 250 /* Turn the WDT off */ 251 softdog_stop(); 252 return NOTIFY_DONE; 253 } 254 255 /* 256 * Kernel Interfaces 257 */ 258 259 static const struct file_operations softdog_fops = { 260 .owner = THIS_MODULE, 261 .llseek = no_llseek, 262 .write = softdog_write, 263 .unlocked_ioctl = softdog_ioctl, 264 .open = softdog_open, 265 .release = softdog_release, 266 }; 267 268 static struct miscdevice softdog_miscdev = { 269 .minor = WATCHDOG_MINOR, 270 .name = "watchdog", 271 .fops = &softdog_fops, 272 }; 273 274 static struct notifier_block softdog_notifier = { 275 .notifier_call = softdog_notify_sys, 276 }; 277 278 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 " 279 "initialized. soft_noboot=%d soft_margin=%d sec soft_panic=%d " 280 "(nowayout= %d)\n"; 281 282 static int __init watchdog_init(void) 283 { 284 int ret; 285 286 /* Check that the soft_margin value is within it's range; 287 if not reset to the default */ 288 if (softdog_set_heartbeat(soft_margin)) { 289 softdog_set_heartbeat(TIMER_MARGIN); 290 printk(KERN_INFO PFX 291 "soft_margin must be 0 < soft_margin < 65536, using %d\n", 292 TIMER_MARGIN); 293 } 294 295 ret = register_reboot_notifier(&softdog_notifier); 296 if (ret) { 297 printk(KERN_ERR PFX 298 "cannot register reboot notifier (err=%d)\n", ret); 299 return ret; 300 } 301 302 ret = misc_register(&softdog_miscdev); 303 if (ret) { 304 printk(KERN_ERR PFX 305 "cannot register miscdev on minor=%d (err=%d)\n", 306 WATCHDOG_MINOR, ret); 307 unregister_reboot_notifier(&softdog_notifier); 308 return ret; 309 } 310 311 printk(banner, soft_noboot, soft_margin, soft_panic, nowayout); 312 313 return 0; 314 } 315 316 static void __exit watchdog_exit(void) 317 { 318 misc_deregister(&softdog_miscdev); 319 unregister_reboot_notifier(&softdog_notifier); 320 } 321 322 module_init(watchdog_init); 323 module_exit(watchdog_exit); 324 325 MODULE_AUTHOR("Alan Cox"); 326 MODULE_DESCRIPTION("Software Watchdog Device Driver"); 327 MODULE_LICENSE("GPL"); 328 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 329