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