kernel/time.c

   1 /*
   2  *  linux/kernel/time.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  This file contains the interface functions for the various
   7  *  time related system calls: time, stime, gettimeofday, settimeofday,
   8  *                             adjtime
   9  */
  10 /*
  11  * Modification history kernel/time.c
  12  *
  13  * 1993-09-02    Philip Gladstone
  14  *      Created file with time related functions from sched.c and adjtimex()
  15  * 1993-10-08    Torsten Duwe
  16  *      adjtime interface update and CMOS clock write code
  17  * 1995-08-13    Torsten Duwe
  18  *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
  19  * 1999-01-16    Ulrich Windl
  20  *      Introduced error checking for many cases in adjtimex().
  21  *      Updated NTP code according to technical memorandum Jan '96
  22  *      "A Kernel Model for Precision Timekeeping" by Dave Mills
  23  *      Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
  24  *      (Even though the technical memorandum forbids it)
  25  */
  26
  27 #include <linux/timex.h>
  28 #include <linux/errno.h>
  29 #include <linux/smp_lock.h>
  30
  31 #include <asm/uaccess.h>
  32
  33 /*
  34  * The timezone where the local system is located.  Used as a default by some
  35  * programs who obtain this value by using gettimeofday.
  36  */
  37 struct timezone sys_tz;
  38
  39 /* The xtime_lock is not only serializing the xtime read/writes but it's also
  40    serializing all accesses to the global NTP variables now. */
  41 extern rwlock_t xtime_lock;
  42 extern unsigned long last_time_offset;
  43
  44 #if !defined(__alpha__) && !defined(__ia64__)
  45
  46 /*
  47  * sys_time() can be implemented in user-level using
  48  * sys_gettimeofday().  Is this for backwards compatibility?  If so,
  49  * why not move it into the appropriate arch directory (for those
  50  * architectures that need it).
  51  *
  52  * XXX This function is NOT 64-bit clean!
  53  */
  54 asmlinkage long sys_time(int * tloc)
  55 {
  56         int i;
  57
  58         /* SMP: This is fairly trivial. We grab CURRENT_TIME and
  59            stuff it to user space. No side effects */
  60         i = CURRENT_TIME;
  61         if (tloc) {
  62                 if (put_user(i,tloc))
  63                         i = -EFAULT;
  64         }
  65         return i;
  66 }
  67
  68 /*
  69  * sys_stime() can be implemented in user-level using
  70  * sys_settimeofday().  Is this for backwards compatibility?  If so,
  71  * why not move it into the appropriate arch directory (for those
  72  * architectures that need it).
  73  */
  74
  75 asmlinkage long sys_stime(int * tptr)
  76 {
  77         int value;
  78
  79         if (!capable(CAP_SYS_TIME))
  80                 return -EPERM;
  81         if (get_user(value, tptr))
  82                 return -EFAULT;
  83         write_lock_irq(&xtime_lock);
  84         xtime.tv_sec = value;
  85         xtime.tv_nsec = 0;
  86         last_time_offset = 0;
  87         time_adjust = 0;        /* stop active adjtime() */
  88         time_status |= STA_UNSYNC;
  89         time_maxerror = NTP_PHASE_LIMIT;
  90         time_esterror = NTP_PHASE_LIMIT;
  91         write_unlock_irq(&xtime_lock);
  92         return 0;
  93 }
  94
  95 #endif
  96
  97 asmlinkage long sys_gettimeofday(struct timeval *tv, struct timezone *tz)
  98 {
  99         if (tv) {
 100                 struct timeval ktv;
 101                 do_gettimeofday(&ktv);
 102                 if (copy_to_user(tv, &ktv, sizeof(ktv)))
 103                         return -EFAULT;
 104         }
 105         if (tz) {
 106                 if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
 107                         return -EFAULT;
 108         }
 109         return 0;
 110 }
 111
 112 /*
 113  * Adjust the time obtained from the CMOS to be UTC time instead of
 114  * local time.
 115  *
 116  * This is ugly, but preferable to the alternatives.  Otherwise we
 117  * would either need to write a program to do it in /etc/rc (and risk
 118  * confusion if the program gets run more than once; it would also be
 119  * hard to make the program warp the clock precisely n hours)  or
 120  * compile in the timezone information into the kernel.  Bad, bad....
 121  *
 122  *                                              - TYT, 1992-01-01
 123  *
 124  * The best thing to do is to keep the CMOS clock in universal time (UTC)
 125  * as real UNIX machines always do it. This avoids all headaches about
 126  * daylight saving times and warping kernel clocks.
 127  */
 128 inline static void warp_clock(void)
 129 {
 130         write_lock_irq(&xtime_lock);
 131         xtime.tv_sec += sys_tz.tz_minuteswest * 60;
 132         last_time_offset = 0;
 133         write_unlock_irq(&xtime_lock);
 134 }
 135
 136 /*
 137  * In case for some reason the CMOS clock has not already been running
 138  * in UTC, but in some local time: The first time we set the timezone,
 139  * we will warp the clock so that it is ticking UTC time instead of
 140  * local time. Presumably, if someone is setting the timezone then we
 141  * are running in an environment where the programs understand about
 142  * timezones. This should be done at boot time in the /etc/rc script,
 143  * as soon as possible, so that the clock can be set right. Otherwise,
 144  * various programs will get confused when the clock gets warped.
 145  */
 146
 147 int do_sys_settimeofday(struct timeval *tv, struct timezone *tz)
 148 {
 149         static int firsttime = 1;
 150
 151         if (!capable(CAP_SYS_TIME))
 152                 return -EPERM;
 153
 154         if (tz) {
 155                 /* SMP safe, global irq locking makes it work. */
 156                 sys_tz = *tz;
 157                 if (firsttime) {
 158                         firsttime = 0;
 159                         if (!tv)
 160                                 warp_clock();
 161                 }
 162         }
 163         if (tv)
 164         {
 165                 /* SMP safe, again the code in arch/foo/time.c should
 166                  * globally block out interrupts when it runs.
 167                  */
 168                 do_settimeofday(tv);
 169         }
 170         return 0;
 171 }
 172
 173 asmlinkage long sys_settimeofday(struct timeval *tv, struct timezone *tz)
 174 {
 175         struct timeval  new_tv;
 176         struct timezone new_tz;
 177
 178         if (tv) {
 179                 if (copy_from_user(&new_tv, tv, sizeof(*tv)))
 180                         return -EFAULT;
 181         }
 182         if (tz) {
 183                 if (copy_from_user(&new_tz, tz, sizeof(*tz)))
 184                         return -EFAULT;
 185         }
 186
 187         return do_sys_settimeofday(tv ? &new_tv : NULL, tz ? &new_tz : NULL);
 188 }
 189
 190 long pps_offset;                /* pps time offset (us) */
 191 long pps_jitter = MAXTIME;      /* time dispersion (jitter) (us) */
 192
 193 long pps_freq;                  /* frequency offset (scaled ppm) */
 194 long pps_stabil = MAXFREQ;      /* frequency dispersion (scaled ppm) */
 195
 196 long pps_valid = PPS_VALID;     /* pps signal watchdog counter */
 197
 198 int pps_shift = PPS_SHIFT;      /* interval duration (s) (shift) */
 199
 200 long pps_jitcnt;                /* jitter limit exceeded */
 201 long pps_calcnt;                /* calibration intervals */
 202 long pps_errcnt;                /* calibration errors */
 203 long pps_stbcnt;                /* stability limit exceeded */
 204
 205 /* hook for a loadable hardpps kernel module */
 206 void (*hardpps_ptr)(struct timeval *);
 207
 208 /* adjtimex mainly allows reading (and writing, if superuser) of
 209  * kernel time-keeping variables. used by xntpd.
 210  */
 211 int do_adjtimex(struct timex *txc)
 212 {
 213         long ltemp, mtemp, save_adjust;
 214         int result;
 215
 216         /* In order to modify anything, you gotta be super-user! */
 217         if (txc->modes && !capable(CAP_SYS_TIME))
 218                 return -EPERM;
 219
 220         /* Now we validate the data before disabling interrupts */
 221
 222         if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
 223           /* singleshot must not be used with any other mode bits */
 224                 if (txc->modes != ADJ_OFFSET_SINGLESHOT)
 225                         return -EINVAL;
 226
 227         if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
 228           /* adjustment Offset limited to +- .512 seconds */
 229                 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
 230                         return -EINVAL;
 231
 232         /* if the quartz is off by more than 10% something is VERY wrong ! */
 233         if (txc->modes & ADJ_TICK)
 234                 if (txc->tick <  900000/USER_HZ ||
 235                     txc->tick > 1100000/USER_HZ)
 236                         return -EINVAL;
 237
 238         write_lock_irq(&xtime_lock);
 239         result = time_state;    /* mostly `TIME_OK' */
 240
 241         /* Save for later - semantics of adjtime is to return old value */
 242         save_adjust = time_adjust;
 243
 244 #if 0   /* STA_CLOCKERR is never set yet */
 245         time_status &= ~STA_CLOCKERR;           /* reset STA_CLOCKERR */
 246 #endif
 247         /* If there are input parameters, then process them */
 248         if (txc->modes)
 249         {
 250             if (txc->modes & ADJ_STATUS)        /* only set allowed bits */
 251                 time_status =  (txc->status & ~STA_RONLY) |
 252                               (time_status & STA_RONLY);
 253
 254             if (txc->modes & ADJ_FREQUENCY) {   /* p. 22 */
 255                 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
 256                     result = -EINVAL;
 257                     goto leave;
 258                 }
 259                 time_freq = txc->freq - pps_freq;
 260             }
 261
 262             if (txc->modes & ADJ_MAXERROR) {
 263                 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
 264                     result = -EINVAL;
 265                     goto leave;
 266                 }
 267                 time_maxerror = txc->maxerror;
 268             }
 269
 270             if (txc->modes & ADJ_ESTERROR) {
 271                 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
 272                     result = -EINVAL;
 273                     goto leave;
 274                 }
 275                 time_esterror = txc->esterror;
 276             }
 277
 278             if (txc->modes & ADJ_TIMECONST) {   /* p. 24 */
 279                 if (txc->constant < 0) {        /* NTP v4 uses values > 6 */
 280                     result = -EINVAL;
 281                     goto leave;
 282                 }
 283                 time_constant = txc->constant;
 284             }
 285
 286             if (txc->modes & ADJ_OFFSET) {      /* values checked earlier */
 287                 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
 288                     /* adjtime() is independent from ntp_adjtime() */
 289                     time_adjust = txc->offset;
 290                 }
 291                 else if ( time_status & (STA_PLL | STA_PPSTIME) ) {
 292                     ltemp = (time_status & (STA_PPSTIME | STA_PPSSIGNAL)) ==
 293                             (STA_PPSTIME | STA_PPSSIGNAL) ?
 294                             pps_offset : txc->offset;
 295
 296                     /*
 297                      * Scale the phase adjustment and
 298                      * clamp to the operating range.
 299                      */
 300                     if (ltemp > MAXPHASE)
 301                         time_offset = MAXPHASE << SHIFT_UPDATE;
 302                     else if (ltemp < -MAXPHASE)
 303                         time_offset = -(MAXPHASE << SHIFT_UPDATE);
 304                     else
 305                         time_offset = ltemp << SHIFT_UPDATE;
 306
 307                     /*
 308                      * Select whether the frequency is to be controlled
 309                      * and in which mode (PLL or FLL). Clamp to the operating
 310                      * range. Ugly multiply/divide should be replaced someday.
 311                      */
 312
 313                     if (time_status & STA_FREQHOLD || time_reftime == 0)
 314                         time_reftime = xtime.tv_sec;
 315                     mtemp = xtime.tv_sec - time_reftime;
 316                     time_reftime = xtime.tv_sec;
 317                     if (time_status & STA_FLL) {
 318                         if (mtemp >= MINSEC) {
 319                             ltemp = (time_offset / mtemp) << (SHIFT_USEC -
 320                                                               SHIFT_UPDATE);
 321                             if (ltemp < 0)
 322                                 time_freq -= -ltemp >> SHIFT_KH;
 323                             else
 324                                 time_freq += ltemp >> SHIFT_KH;
 325                         } else /* calibration interval too short (p. 12) */
 326                                 result = TIME_ERROR;
 327                     } else {    /* PLL mode */
 328                         if (mtemp < MAXSEC) {
 329                             ltemp *= mtemp;
 330                             if (ltemp < 0)
 331                                 time_freq -= -ltemp >> (time_constant +
 332                                                         time_constant +
 333                                                         SHIFT_KF - SHIFT_USEC);
 334                             else
 335                                 time_freq += ltemp >> (time_constant +
 336                                                        time_constant +
 337                                                        SHIFT_KF - SHIFT_USEC);
 338                         } else /* calibration interval too long (p. 12) */
 339                                 result = TIME_ERROR;
 340                     }
 341                     if (time_freq > time_tolerance)
 342                         time_freq = time_tolerance;
 343                     else if (time_freq < -time_tolerance)
 344                         time_freq = -time_tolerance;
 345                 } /* STA_PLL || STA_PPSTIME */
 346             } /* txc->modes & ADJ_OFFSET */
 347             if (txc->modes & ADJ_TICK) {
 348                 tick_usec = txc->tick;
 349                 tick_nsec = TICK_NSEC(tick_usec);
 350             }
 351         } /* txc->modes */
 352 leave:  if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
 353             || ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
 354                 && (time_status & STA_PPSSIGNAL) == 0)
 355             /* p. 24, (b) */
 356             || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 357                 == (STA_PPSTIME|STA_PPSJITTER))
 358             /* p. 24, (c) */
 359             || ((time_status & STA_PPSFREQ) != 0
 360                 && (time_status & (STA_PPSWANDER|STA_PPSERROR)) != 0))
 361             /* p. 24, (d) */
 362                 result = TIME_ERROR;
 363
 364         if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
 365             txc->offset    = save_adjust;
 366         else {
 367             if (time_offset < 0)
 368                 txc->offset = -(-time_offset >> SHIFT_UPDATE);
 369             else
 370                 txc->offset = time_offset >> SHIFT_UPDATE;
 371         }
 372         txc->freq          = time_freq + pps_freq;
 373         txc->maxerror      = time_maxerror;
 374         txc->esterror      = time_esterror;
 375         txc->status        = time_status;
 376         txc->constant      = time_constant;
 377         txc->precision     = time_precision;
 378         txc->tolerance     = time_tolerance;
 379         txc->tick          = tick_usec;
 380         txc->ppsfreq       = pps_freq;
 381         txc->jitter        = pps_jitter >> PPS_AVG;
 382         txc->shift         = pps_shift;
 383         txc->stabil        = pps_stabil;
 384         txc->jitcnt        = pps_jitcnt;
 385         txc->calcnt        = pps_calcnt;
 386         txc->errcnt        = pps_errcnt;
 387         txc->stbcnt        = pps_stbcnt;
 388         last_time_offset = 0;
 389         write_unlock_irq(&xtime_lock);
 390         do_gettimeofday(&txc->time);
 391         return(result);
 392 }
 393
 394 asmlinkage long sys_adjtimex(struct timex *txc_p)
 395 {
 396         struct timex txc;               /* Local copy of parameter */
 397         int ret;
 398
 399         /* Copy the user data space into the kernel copy
 400          * structure. But bear in mind that the structures
 401          * may change
 402          */
 403         if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
 404                 return -EFAULT;
 405         ret = do_adjtimex(&txc);
 406         return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
 407 }