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