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");
  58         register unsigned long __timeout asm("3");
  59         register unsigned long __cmdp asm("4");
  60         register unsigned long __cmdl asm("5");
  61         int err;
  62
  63         __func = func;
  64         __timeout = timeout;
  65         __cmdp = virt_to_phys(cmd);
  66         __cmdl = len;
  67         err = 0;
  68         asm volatile (
  69 #ifdef __s390x__
  70                        "diag %2,%4,0x288\n"
  71                 "1:     \n"
  72                 ".section .fixup,\"ax\"\n"
  73                 "2:     lghi %0,%1\n"
  74                 "       jg 1b\n"
  75                 ".previous\n"
  76                 ".section __ex_table,\"a\"\n"
  77                 "       .align 8\n"
  78                 "       .quad 1b,2b\n"
  79                 ".previous\n"
  80 #else
  81                        "diag %2,%4,0x288\n"
  82                 "1:     \n"
  83                 ".section .fixup,\"ax\"\n"
  84                 "2:     lhi %0,%1\n"
  85                 "       bras 1,3f\n"
  86                 "       .long 1b\n"
  87                 "3:     l 1,0(1)\n"
  88                 "       br 1\n"
  89                 ".previous\n"
  90                 ".section __ex_table,\"a\"\n"
  91                 "       .align 4\n"
  92                 "       .long 1b,2b\n"
  93                 ".previous\n"
  94 #endif
  95                 : "+&d"(err)
  96                 : "i"(-EINVAL), "d"(__func), "d"(__timeout),
  97                   "d"(__cmdp), "d"(__cmdl)
  98                 : "1", "cc");
  99         return err;
 100 }
 101
 102 static int vmwdt_keepalive(void)
 103 {
 104         /* we allocate new memory every time to avoid having
 105          * to track the state. static allocation is not an
 106          * option since that might not be contiguous in real
 107          * storage in case of a modular build */
 108         static char *ebc_cmd;
 109         size_t len;
 110         int ret;
 111         unsigned int func;
 112
 113         ebc_cmd = kmalloc(MAX_CMDLEN, GFP_KERNEL);
 114         if (!ebc_cmd)
 115                 return -ENOMEM;
 116
 117         len = strlcpy(ebc_cmd, vmwdt_cmd, MAX_CMDLEN);
 118         ASCEBC(ebc_cmd, MAX_CMDLEN);
 119         EBC_TOUPPER(ebc_cmd, MAX_CMDLEN);
 120
 121         func = vmwdt_conceal ? (wdt_init | wdt_conceal) : wdt_init;
 122         ret = __diag288(func, vmwdt_interval, ebc_cmd, len);
 123         kfree(ebc_cmd);
 124
 125         if (ret) {
 126                 printk(KERN_WARNING "%s: problem setting interval %d, "
 127                         "cmd %s\n", __FUNCTION__, vmwdt_interval,
 128                         vmwdt_cmd);
 129         }
 130         return ret;
 131 }
 132
 133 static int vmwdt_disable(void)
 134 {
 135         int ret = __diag288(wdt_cancel, 0, "", 0);
 136         if (ret) {
 137                 printk(KERN_WARNING "%s: problem disabling watchdog\n",
 138                         __FUNCTION__);
 139         }
 140         return ret;
 141 }
 142
 143 static int __init vmwdt_probe(void)
 144 {
 145         /* there is no real way to see if the watchdog is supported,
 146          * so we try initializing it with a NOP command ("BEGIN")
 147          * that won't cause any harm even if the following disable
 148          * fails for some reason */
 149         static char __initdata ebc_begin[] = {
 150                 194, 197, 199, 201, 213
 151         };
 152         if (__diag288(wdt_init, 15, ebc_begin, sizeof(ebc_begin)) != 0) {
 153                 printk(KERN_INFO "z/VM watchdog not available\n");
 154                 return -EINVAL;
 155         }
 156         return vmwdt_disable();
 157 }
 158
 159 static int vmwdt_open(struct inode *i, struct file *f)
 160 {
 161         int ret;
 162         if (test_and_set_bit(0, &vmwdt_is_open))
 163                 return -EBUSY;
 164         ret = vmwdt_keepalive();
 165         if (ret)
 166                 clear_bit(0, &vmwdt_is_open);
 167         return ret ? ret : nonseekable_open(i, f);
 168 }
 169
 170 static int vmwdt_close(struct inode *i, struct file *f)
 171 {
 172         if (vmwdt_expect_close == 42)
 173                 vmwdt_disable();
 174         vmwdt_expect_close = 0;
 175         clear_bit(0, &vmwdt_is_open);
 176         return 0;
 177 }
 178
 179 static struct watchdog_info vmwdt_info = {
 180         .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 181         .firmware_version = 0,
 182         .identity = "z/VM Watchdog Timer",
 183 };
 184
 185 static int vmwdt_ioctl(struct inode *i, struct file *f,
 186                           unsigned int cmd, unsigned long arg)
 187 {
 188         switch (cmd) {
 189         case WDIOC_GETSUPPORT:
 190                 if (copy_to_user((void __user *)arg, &vmwdt_info,
 191                                         sizeof(vmwdt_info)))
 192                         return -EFAULT;
 193                 return 0;
 194         case WDIOC_GETSTATUS:
 195         case WDIOC_GETBOOTSTATUS:
 196                 return put_user(0, (int *)arg);
 197         case WDIOC_GETTEMP:
 198                 return -EINVAL;
 199         case WDIOC_SETOPTIONS:
 200                 {
 201                         int options, ret;
 202                         if (get_user(options, (int __user *)arg))
 203                                 return -EFAULT;
 204                         ret = -EINVAL;
 205                         if (options & WDIOS_DISABLECARD) {
 206                                 ret = vmwdt_disable();
 207                                 if (ret)
 208                                         return ret;
 209                         }
 210                         if (options & WDIOS_ENABLECARD) {
 211                                 ret = vmwdt_keepalive();
 212                         }
 213                         return ret;
 214                 }
 215         case WDIOC_GETTIMEOUT:
 216                 return put_user(vmwdt_interval, (int __user *)arg);
 217         case WDIOC_SETTIMEOUT:
 218                 {
 219                         int interval;
 220                         if (get_user(interval, (int __user *)arg))
 221                                 return -EFAULT;
 222                         if (interval < MIN_INTERVAL)
 223                                 return -EINVAL;
 224                         vmwdt_interval = interval;
 225                 }
 226                 return vmwdt_keepalive();
 227         case WDIOC_KEEPALIVE:
 228                 return vmwdt_keepalive();
 229         }
 230
 231         return -EINVAL;
 232 }
 233
 234 static ssize_t vmwdt_write(struct file *f, const char __user *buf,
 235                                 size_t count, loff_t *ppos)
 236 {
 237         if(count) {
 238                 if (!vmwdt_nowayout) {
 239                         size_t i;
 240
 241                         /* note: just in case someone wrote the magic character
 242                          * five months ago... */
 243                         vmwdt_expect_close = 0;
 244
 245                         for (i = 0; i != count; i++) {
 246                                 char c;
 247                                 if (get_user(c, buf+i))
 248                                         return -EFAULT;
 249                                 if (c == 'V')
 250                                         vmwdt_expect_close = 42;
 251                         }
 252                 }
 253                 /* someone wrote to us, we should restart timer */
 254                 vmwdt_keepalive();
 255         }
 256         return count;
 257 }
 258
 259 static struct file_operations vmwdt_fops = {
 260         .open    = &vmwdt_open,
 261         .release = &vmwdt_close,
 262         .ioctl   = &vmwdt_ioctl,
 263         .write   = &vmwdt_write,
 264         .owner   = THIS_MODULE,
 265 };
 266
 267 static struct miscdevice vmwdt_dev = {
 268         .minor      = WATCHDOG_MINOR,
 269         .name       = "watchdog",
 270         .fops       = &vmwdt_fops,
 271 };
 272
 273 static int __init vmwdt_init(void)
 274 {
 275         int ret;
 276
 277         ret = vmwdt_probe();
 278         if (ret)
 279                 return ret;
 280         return misc_register(&vmwdt_dev);
 281 }
 282 module_init(vmwdt_init);
 283
 284 static void __exit vmwdt_exit(void)
 285 {
 286         WARN_ON(misc_deregister(&vmwdt_dev) != 0);
 287 }
 288 module_exit(vmwdt_exit);