drivers/s390/char/vmwatchdog.c

   1 /*
   2  * Watchdog implementation based on z/VM Watchdog Timer API
   3  *
   4  * The user space watchdog daemon can use this driver as
   5  * /dev/vmwatchdog to have z/VM execute the specified CP
   6  * command when the timeout expires. The default command is
   7  * "IPL", which which cause an immediate reboot.
   8  */
   9 #include <linux/init.h>
  10 #include <linux/fs.h>
  11 #include <linux/kernel.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/watchdog.h>
  16
  17 #include <asm/ebcdic.h>
  18 #include <asm/io.h>
  19 #include <asm/uaccess.h>
  20
  21 #define MAX_CMDLEN 240
  22 #define MIN_INTERVAL 15
  23 static char vmwdt_cmd[MAX_CMDLEN] = "IPL";
  24 static int vmwdt_conceal;
  25
  26 #ifdef CONFIG_WATCHDOG_NOWAYOUT
  27 static int vmwdt_nowayout = 1;
  28 #else
  29 static int vmwdt_nowayout = 0;
  30 #endif
  31
  32 MODULE_LICENSE("GPL");
  33 MODULE_AUTHOR("Arnd Bergmann <arndb@de.ibm.com>");
  34 MODULE_DESCRIPTION("z/VM Watchdog Timer");
  35 module_param_string(cmd, vmwdt_cmd, MAX_CMDLEN, 0644);
  36 MODULE_PARM_DESC(cmd, "CP command that is run when the watchdog triggers");
  37 module_param_named(conceal, vmwdt_conceal, bool, 0644);
  38 MODULE_PARM_DESC(conceal, "Enable the CONCEAL CP option while the watchdog "
  39                 " is active");
  40 module_param_named(nowayout, vmwdt_nowayout, bool, 0);
  41 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started"
  42                 " (default=CONFIG_WATCHDOG_NOWAYOUT)");
  43 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
  44
  45 static unsigned int vmwdt_interval = 60;
  46 static unsigned long vmwdt_is_open;
  47 static int vmwdt_expect_close;
  48
  49 enum vmwdt_func {
  50         /* function codes */
  51         wdt_init   = 0,
  52         wdt_change = 1,
  53         wdt_cancel = 2,
  54         /* flags */
  55         wdt_conceal = 0x80000000,
  56 };
  57
  58 static int __diag288(enum vmwdt_func func, unsigned int timeout,
  59                             char *cmd, size_t len)
  60 {
  61         register unsigned long __func asm("2");
  62         register unsigned long __timeout asm("3");
  63         register unsigned long __cmdp asm("4");
  64         register unsigned long __cmdl asm("5");
  65         int err;
  66
  67         __func = func;
  68         __timeout = timeout;
  69         __cmdp = virt_to_phys(cmd);
  70         __cmdl = len;
  71         err = 0;
  72         asm volatile (
  73 #ifdef __s390x__
  74                        "diag %2,%4,0x288\n"
  75                 "1:     \n"
  76                 ".section .fixup,\"ax\"\n"
  77                 "2:     lghi %0,%1\n"
  78                 "       jg 1b\n"
  79                 ".previous\n"
  80                 ".section __ex_table,\"a\"\n"
  81                 "       .align 8\n"
  82                 "       .quad 1b,2b\n"
  83                 ".previous\n"
  84 #else
  85                        "diag %2,%4,0x288\n"
  86                 "1:     \n"
  87                 ".section .fixup,\"ax\"\n"
  88                 "2:     lhi %0,%1\n"
  89                 "       bras 1,3f\n"
  90                 "       .long 1b\n"
  91                 "3:     l 1,0(1)\n"
  92                 "       br 1\n"
  93                 ".previous\n"
  94                 ".section __ex_table,\"a\"\n"
  95                 "       .align 4\n"
  96                 "       .long 1b,2b\n"
  97                 ".previous\n"
  98 #endif
  99                 : "+&d"(err)
 100                 : "i"(-EINVAL), "d"(__func), "d"(__timeout),
 101                   "d"(__cmdp), "d"(__cmdl)
 102                 : "1", "cc");
 103         return err;
 104 }
 105
 106 static int vmwdt_keepalive(void)
 107 {
 108         /* we allocate new memory every time to avoid having
 109          * to track the state. static allocation is not an
 110          * option since that might not be contiguous in real
 111          * storage in case of a modular build */
 112         static char *ebc_cmd;
 113         size_t len;
 114         int ret;
 115         unsigned int func;
 116
 117         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
 118         if (!ebc_cmd)
 119                 return -ENOMEM;
 120
 121         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
 122         ASCEBC(ebc_cmd, MAX_CMDLEN);
 123         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
 124
 125         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
 126         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
 127         kfree(ebc_cmd);
 128
 129         if (ret) {
 130                 printk(KERN_WARNING "%s: problem setting interval %d, "
 131                         "cmd %s\n", __FUNCTION__, vmwdt_interval,
 132                         vmwdt_cmd);
 133         }
 134         return ret;
 135 }
 136
 137 static int vmwdt_disable(void)
 138 {
 139         int ret = __diag288(wdt_cancel, 0, "", 0);
 140         if (ret) {
 141                 printk(KERN_WARNING "%s: problem disabling watchdog\n",
 142                         __FUNCTION__);
 143         }
 144         return ret;
 145 }
 146
 147 static int __init vmwdt_probe(void)
 148 {
 149         /* there is no real way to see if the watchdog is supported,
 150          * so we try initializing it with a NOP command ("BEGIN")
 151          * that won't cause any harm even if the following disable
 152          * fails for some reason */
 153         static char __initdata ebc_begin[] = {
 154                 194, 197, 199, 201, 213
 155         };
 156         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0) {
 157                 printk(KERN_INFO "z/VM watchdog not available\n");
 158                 return -EINVAL;
 159         }
 160         return vmwdt_disable();
 161 }
 162
 163 static int vmwdt_open(struct inode *i, struct file *f)
 164 {
 165         int ret;
 166         if (test_and_set_bit(0, &vmwdt_is_open))
 167                 return -EBUSY;
 168         ret = vmwdt_keepalive();
 169         if (ret)
 170                 clear_bit(0, &vmwdt_is_open);
 171         return ret ? ret : nonseekable_open(i, f);
 172 }
 173
 174 static int vmwdt_close(struct inode *i, struct file *f)
 175 {
 176         if (vmwdt_expect_close == 42)
 177                 vmwdt_disable();
 178         vmwdt_expect_close = 0;
 179         clear_bit(0, &vmwdt_is_open);
 180         return 0;
 181 }
 182
 183 static struct watchdog_info vmwdt_info = {
 184         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 185         .firmware_version = 0,
 186         .identity = "z/VM Watchdog Timer",
 187 };
 188
 189 static int vmwdt_ioctl(struct inode *i, struct file *f,
 190                           unsigned int cmd, unsigned long arg)
 191 {
 192         switch (cmd) {
 193         case WDIOC_GETSUPPORT:
 194                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 195                                         sizeof(vmwdt_info)))
 196                         return -EFAULT;
 197                 return 0;
 198         case WDIOC_GETSTATUS:
 199         case WDIOC_GETBOOTSTATUS:
 200                 return put_user(0, (int *)arg);
 201         case WDIOC_GETTEMP:
 202                 return -EINVAL;
 203         case WDIOC_SETOPTIONS:
 204                 {
 205                         int options, ret;
 206                         if (get_user(options, (int __user *)arg))
 207                                 return -EFAULT;
 208                         ret = -EINVAL;
 209                         if (options & WDIOS_DISABLECARD) {
 210                                 ret = vmwdt_disable();
 211                                 if (ret)
 212                                         return ret;
 213                         }
 214                         if (options & WDIOS_ENABLECARD) {
 215                                 ret = vmwdt_keepalive();
 216                         }
 217                         return ret;
 218                 }
 219         case WDIOC_GETTIMEOUT:
 220                 return put_user(vmwdt_interval, (int __user *)arg);
 221         case WDIOC_SETTIMEOUT:
 222                 {
 223                         int interval;
 224                         if (get_user(interval, (int __user *)arg))
 225                                 return -EFAULT;
 226                         if (interval < MIN_INTERVAL)
 227                                 return -EINVAL;
 228                         vmwdt_interval = interval;
 229                 }
 230                 return vmwdt_keepalive();
 231         case WDIOC_KEEPALIVE:
 232                 return vmwdt_keepalive();
 233         }
 234
 235         return -EINVAL;
 236 }
 237
 238 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 239                                 size_t count, loff_t *ppos)
 240 {
 241         if(count) {
 242                 if (!vmwdt_nowayout) {
 243                         size_t i;
 244
 245                         /* note: just in case someone wrote the magic character
 246                          * five months ago... */
 247                         vmwdt_expect_close = 0;
 248
 249                         for (i = 0; i != count; i++) {
 250                                 char c;
 251                                 if (get_user(c, buf+i))
 252                                         return -EFAULT;
 253                                 if (c == 'V')
 254                                         vmwdt_expect_close = 42;
 255                         }
 256                 }
 257                 /* someone wrote to us, we should restart timer */
 258                 vmwdt_keepalive();
 259         }
 260         return count;
 261 }
 262
 263 static struct file_operations vmwdt_fops = {
 264         .open    = &vmwdt_open,
 265         .release = &vmwdt_close,
 266         .ioctl   = &vmwdt_ioctl,
 267         .write   = &vmwdt_write,
 268         .owner   = THIS_MODULE,
 269 };
 270
 271 static struct miscdevice vmwdt_dev = {
 272         .minor      = WATCHDOG_MINOR,
 273         .name       = "watchdog",
 274         .fops       = &vmwdt_fops,
 275 };
 276
 277 static int __init vmwdt_init(void)
 278 {
 279         int ret;
 280
 281         ret = vmwdt_probe();
 282         if (ret)
 283                 return ret;
 284         return misc_register(&vmwdt_dev);
 285 }
 286 module_init(vmwdt_init);
 287
 288 static void __exit vmwdt_exit(void)
 289 {
 290         WARN_ON(misc_deregister(&vmwdt_dev) != 0);
 291 }
 292 module_exit(vmwdt_exit);