The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_ntptime.c

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    1 /*      $NetBSD: kern_ntptime.c,v 1.49 2008/04/28 20:24:03 martin Exp $ */
    2 
    3 /*-
    4  * Copyright (c) 2008 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   26  * POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 /*-
   30  ***********************************************************************
   31  *                                                                     *
   32  * Copyright (c) David L. Mills 1993-2001                              *
   33  *                                                                     *
   34  * Permission to use, copy, modify, and distribute this software and   *
   35  * its documentation for any purpose and without fee is hereby         *
   36  * granted, provided that the above copyright notice appears in all    *
   37  * copies and that both the copyright notice and this permission       *
   38  * notice appear in supporting documentation, and that the name        *
   39  * University of Delaware not be used in advertising or publicity      *
   40  * pertaining to distribution of the software without specific,        *
   41  * written prior permission. The University of Delaware makes no       *
   42  * representations about the suitability this software for any         *
   43  * purpose. It is provided "as is" without express or implied          *
   44  * warranty.                                                           *
   45  *                                                                     *
   46  **********************************************************************/
   47 
   48 /*
   49  * Adapted from the original sources for FreeBSD and timecounters by:
   50  * Poul-Henning Kamp <phk@FreeBSD.org>.
   51  *
   52  * The 32bit version of the "LP" macros seems a bit past its "sell by" 
   53  * date so I have retained only the 64bit version and included it directly
   54  * in this file.
   55  *
   56  * Only minor changes done to interface with the timecounters over in
   57  * sys/kern/kern_clock.c.   Some of the comments below may be (even more)
   58  * confusing and/or plain wrong in that context.
   59  */
   60 
   61 #include <sys/cdefs.h>
   62 /* __FBSDID("$FreeBSD: src/sys/kern/kern_ntptime.c,v 1.59 2005/05/28 14:34:41 rwatson Exp $"); */
   63 __KERNEL_RCSID(0, "$NetBSD: kern_ntptime.c,v 1.49 2008/04/28 20:24:03 martin Exp $");
   64 
   65 #include "opt_ntp.h"
   66 #include "opt_compat_netbsd.h"
   67 
   68 #include <sys/param.h>
   69 #include <sys/resourcevar.h>
   70 #include <sys/systm.h>
   71 #include <sys/kernel.h>
   72 #include <sys/proc.h>
   73 #include <sys/sysctl.h>
   74 #include <sys/timex.h>
   75 #include <sys/vnode.h>
   76 #include <sys/kauth.h>
   77 #include <sys/mount.h>
   78 #include <sys/syscallargs.h>
   79 #include <sys/cpu.h>
   80 
   81 #ifdef COMPAT_30
   82 #include <compat/sys/timex.h>
   83 #endif
   84 
   85 /*
   86  * Single-precision macros for 64-bit machines
   87  */
   88 typedef int64_t l_fp;
   89 #define L_ADD(v, u)     ((v) += (u))
   90 #define L_SUB(v, u)     ((v) -= (u))
   91 #define L_ADDHI(v, a)   ((v) += (int64_t)(a) << 32)
   92 #define L_NEG(v)        ((v) = -(v))
   93 #define L_RSHIFT(v, n) \
   94         do { \
   95                 if ((v) < 0) \
   96                         (v) = -(-(v) >> (n)); \
   97                 else \
   98                         (v) = (v) >> (n); \
   99         } while (0)
  100 #define L_MPY(v, a)     ((v) *= (a))
  101 #define L_CLR(v)        ((v) = 0)
  102 #define L_ISNEG(v)      ((v) < 0)
  103 #define L_LINT(v, a)    ((v) = (int64_t)(a) << 32)
  104 #define L_GINT(v)       ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
  105 
  106 #ifdef NTP
  107 /*
  108  * Generic NTP kernel interface
  109  *
  110  * These routines constitute the Network Time Protocol (NTP) interfaces
  111  * for user and daemon application programs. The ntp_gettime() routine
  112  * provides the time, maximum error (synch distance) and estimated error
  113  * (dispersion) to client user application programs. The ntp_adjtime()
  114  * routine is used by the NTP daemon to adjust the system clock to an
  115  * externally derived time. The time offset and related variables set by
  116  * this routine are used by other routines in this module to adjust the
  117  * phase and frequency of the clock discipline loop which controls the
  118  * system clock.
  119  *
  120  * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
  121  * defined), the time at each tick interrupt is derived directly from
  122  * the kernel time variable. When the kernel time is reckoned in
  123  * microseconds, (NTP_NANO undefined), the time is derived from the
  124  * kernel time variable together with a variable representing the
  125  * leftover nanoseconds at the last tick interrupt. In either case, the
  126  * current nanosecond time is reckoned from these values plus an
  127  * interpolated value derived by the clock routines in another
  128  * architecture-specific module. The interpolation can use either a
  129  * dedicated counter or a processor cycle counter (PCC) implemented in
  130  * some architectures.
  131  *
  132  * Note that all routines must run at priority splclock or higher.
  133  */
  134 /*
  135  * Phase/frequency-lock loop (PLL/FLL) definitions
  136  *
  137  * The nanosecond clock discipline uses two variable types, time
  138  * variables and frequency variables. Both types are represented as 64-
  139  * bit fixed-point quantities with the decimal point between two 32-bit
  140  * halves. On a 32-bit machine, each half is represented as a single
  141  * word and mathematical operations are done using multiple-precision
  142  * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
  143  * used.
  144  *
  145  * A time variable is a signed 64-bit fixed-point number in ns and
  146  * fraction. It represents the remaining time offset to be amortized
  147  * over succeeding tick interrupts. The maximum time offset is about
  148  * 0.5 s and the resolution is about 2.3e-10 ns.
  149  *
  150  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  151  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  152  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  153  * |s s s|                       ns                                |
  154  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  155  * |                        fraction                               |
  156  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  157  *
  158  * A frequency variable is a signed 64-bit fixed-point number in ns/s
  159  * and fraction. It represents the ns and fraction to be added to the
  160  * kernel time variable at each second. The maximum frequency offset is
  161  * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
  162  *
  163  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  164  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  165  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  166  * |s s s s s s s s s s s s s|            ns/s                     |
  167  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  168  * |                        fraction                               |
  169  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  170  */
  171 /*
  172  * The following variables establish the state of the PLL/FLL and the
  173  * residual time and frequency offset of the local clock.
  174  */
  175 #define SHIFT_PLL       4               /* PLL loop gain (shift) */
  176 #define SHIFT_FLL       2               /* FLL loop gain (shift) */
  177 
  178 static int time_state = TIME_OK;        /* clock state */
  179 static int time_status = STA_UNSYNC;    /* clock status bits */
  180 static long time_tai;                   /* TAI offset (s) */
  181 static long time_monitor;               /* last time offset scaled (ns) */
  182 static long time_constant;              /* poll interval (shift) (s) */
  183 static long time_precision = 1;         /* clock precision (ns) */
  184 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
  185 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
  186 static long time_reftime;               /* time at last adjustment (s) */
  187 static l_fp time_offset;                /* time offset (ns) */
  188 static l_fp time_freq;                  /* frequency offset (ns/s) */
  189 #endif /* NTP */
  190 
  191 static l_fp time_adj;                   /* tick adjust (ns/s) */
  192 int64_t time_adjtime;           /* correction from adjtime(2) (usec) */
  193 
  194 extern int time_adjusted;       /* ntp might have changed the system time */
  195 
  196 #ifdef NTP
  197 #ifdef PPS_SYNC
  198 /*
  199  * The following variables are used when a pulse-per-second (PPS) signal
  200  * is available and connected via a modem control lead. They establish
  201  * the engineering parameters of the clock discipline loop when
  202  * controlled by the PPS signal.
  203  */
  204 #define PPS_FAVG        2               /* min freq avg interval (s) (shift) */
  205 #define PPS_FAVGDEF     8               /* default freq avg int (s) (shift) */
  206 #define PPS_FAVGMAX     15              /* max freq avg interval (s) (shift) */
  207 #define PPS_PAVG        4               /* phase avg interval (s) (shift) */
  208 #define PPS_VALID       120             /* PPS signal watchdog max (s) */
  209 #define PPS_MAXWANDER   100000          /* max PPS wander (ns/s) */
  210 #define PPS_POPCORN     2               /* popcorn spike threshold (shift) */
  211 
  212 static struct timespec pps_tf[3];       /* phase median filter */
  213 static l_fp pps_freq;                   /* scaled frequency offset (ns/s) */
  214 static long pps_fcount;                 /* frequency accumulator */
  215 static long pps_jitter;                 /* nominal jitter (ns) */
  216 static long pps_stabil;                 /* nominal stability (scaled ns/s) */
  217 static long pps_lastsec;                /* time at last calibration (s) */
  218 static int pps_valid;                   /* signal watchdog counter */
  219 static int pps_shift = PPS_FAVG;        /* interval duration (s) (shift) */
  220 static int pps_shiftmax = PPS_FAVGDEF;  /* max interval duration (s) (shift) */
  221 static int pps_intcnt;                  /* wander counter */
  222 
  223 /*
  224  * PPS signal quality monitors
  225  */
  226 static long pps_calcnt;                 /* calibration intervals */
  227 static long pps_jitcnt;                 /* jitter limit exceeded */
  228 static long pps_stbcnt;                 /* stability limit exceeded */
  229 static long pps_errcnt;                 /* calibration errors */
  230 #endif /* PPS_SYNC */
  231 /*
  232  * End of phase/frequency-lock loop (PLL/FLL) definitions
  233  */
  234 
  235 static void hardupdate(long offset);
  236 
  237 /*
  238  * ntp_gettime() - NTP user application interface
  239  */
  240 void
  241 ntp_gettime(struct ntptimeval *ntv)
  242 {
  243 
  244         mutex_spin_enter(&timecounter_lock);
  245         nanotime(&ntv->time);
  246         ntv->maxerror = time_maxerror;
  247         ntv->esterror = time_esterror;
  248         ntv->tai = time_tai;
  249         ntv->time_state = time_state;
  250         mutex_spin_exit(&timecounter_lock);
  251 }
  252 
  253 /* ARGSUSED */
  254 /*
  255  * ntp_adjtime() - NTP daemon application interface
  256  */
  257 int
  258 sys_ntp_adjtime(struct lwp *l, const struct sys_ntp_adjtime_args *uap, register_t *retval)
  259 {
  260         /* {
  261                 syscallarg(struct timex *) tp;
  262         } */
  263         struct timex ntv;
  264         int error = 0;
  265 
  266         error = copyin((void *)SCARG(uap, tp), (void *)&ntv, sizeof(ntv));
  267         if (error != 0)
  268                 return (error);
  269 
  270         if (ntv.modes != 0 && (error = kauth_authorize_system(l->l_cred,
  271             KAUTH_SYSTEM_TIME, KAUTH_REQ_SYSTEM_TIME_NTPADJTIME, NULL,
  272             NULL, NULL)) != 0)
  273                 return (error);
  274 
  275         ntp_adjtime1(&ntv);
  276 
  277         error = copyout((void *)&ntv, (void *)SCARG(uap, tp), sizeof(ntv));
  278         if (!error)
  279                 *retval = ntp_timestatus();
  280 
  281         return error;
  282 }
  283 
  284 void
  285 ntp_adjtime1(struct timex *ntv)
  286 {
  287         long freq;
  288         int modes;
  289 
  290         /*
  291          * Update selected clock variables - only the superuser can
  292          * change anything. Note that there is no error checking here on
  293          * the assumption the superuser should know what it is doing.
  294          * Note that either the time constant or TAI offset are loaded
  295          * from the ntv.constant member, depending on the mode bits. If
  296          * the STA_PLL bit in the status word is cleared, the state and
  297          * status words are reset to the initial values at boot.
  298          */
  299         mutex_spin_enter(&timecounter_lock);
  300         modes = ntv->modes;
  301         if (modes != 0)
  302                 /* We need to save the system time during shutdown */
  303                 time_adjusted |= 2;
  304         if (modes & MOD_MAXERROR)
  305                 time_maxerror = ntv->maxerror;
  306         if (modes & MOD_ESTERROR)
  307                 time_esterror = ntv->esterror;
  308         if (modes & MOD_STATUS) {
  309                 if (time_status & STA_PLL && !(ntv->status & STA_PLL)) {
  310                         time_state = TIME_OK;
  311                         time_status = STA_UNSYNC;
  312 #ifdef PPS_SYNC
  313                         pps_shift = PPS_FAVG;
  314 #endif /* PPS_SYNC */
  315                 }
  316                 time_status &= STA_RONLY;
  317                 time_status |= ntv->status & ~STA_RONLY;
  318         }
  319         if (modes & MOD_TIMECONST) {
  320                 if (ntv->constant < 0)
  321                         time_constant = 0;
  322                 else if (ntv->constant > MAXTC)
  323                         time_constant = MAXTC;
  324                 else
  325                         time_constant = ntv->constant;
  326         }
  327         if (modes & MOD_TAI) {
  328                 if (ntv->constant > 0)  /* XXX zero & negative numbers ? */
  329                         time_tai = ntv->constant;
  330         }
  331 #ifdef PPS_SYNC
  332         if (modes & MOD_PPSMAX) {
  333                 if (ntv->shift < PPS_FAVG)
  334                         pps_shiftmax = PPS_FAVG;
  335                 else if (ntv->shift > PPS_FAVGMAX)
  336                         pps_shiftmax = PPS_FAVGMAX;
  337                 else
  338                         pps_shiftmax = ntv->shift;
  339         }
  340 #endif /* PPS_SYNC */
  341         if (modes & MOD_NANO)
  342                 time_status |= STA_NANO;
  343         if (modes & MOD_MICRO)
  344                 time_status &= ~STA_NANO;
  345         if (modes & MOD_CLKB)
  346                 time_status |= STA_CLK;
  347         if (modes & MOD_CLKA)
  348                 time_status &= ~STA_CLK;
  349         if (modes & MOD_FREQUENCY) {
  350                 freq = (ntv->freq * 1000LL) >> 16;
  351                 if (freq > MAXFREQ)
  352                         L_LINT(time_freq, MAXFREQ);
  353                 else if (freq < -MAXFREQ)
  354                         L_LINT(time_freq, -MAXFREQ);
  355                 else {
  356                         /*
  357                          * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
  358                          * time_freq is [ns/s * 2^32]
  359                          */
  360                         time_freq = ntv->freq * 1000LL * 65536LL;
  361                 }
  362 #ifdef PPS_SYNC
  363                 pps_freq = time_freq;
  364 #endif /* PPS_SYNC */
  365         }
  366         if (modes & MOD_OFFSET) {
  367                 if (time_status & STA_NANO)
  368                         hardupdate(ntv->offset);
  369                 else
  370                         hardupdate(ntv->offset * 1000);
  371         }
  372 
  373         /*
  374          * Retrieve all clock variables. Note that the TAI offset is
  375          * returned only by ntp_gettime();
  376          */
  377         if (time_status & STA_NANO)
  378                 ntv->offset = L_GINT(time_offset);
  379         else
  380                 ntv->offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
  381         ntv->freq = L_GINT((time_freq / 1000LL) << 16);
  382         ntv->maxerror = time_maxerror;
  383         ntv->esterror = time_esterror;
  384         ntv->status = time_status;
  385         ntv->constant = time_constant;
  386         if (time_status & STA_NANO)
  387                 ntv->precision = time_precision;
  388         else
  389                 ntv->precision = time_precision / 1000;
  390         ntv->tolerance = MAXFREQ * SCALE_PPM;
  391 #ifdef PPS_SYNC
  392         ntv->shift = pps_shift;
  393         ntv->ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
  394         if (time_status & STA_NANO)
  395                 ntv->jitter = pps_jitter;
  396         else
  397                 ntv->jitter = pps_jitter / 1000;
  398         ntv->stabil = pps_stabil;
  399         ntv->calcnt = pps_calcnt;
  400         ntv->errcnt = pps_errcnt;
  401         ntv->jitcnt = pps_jitcnt;
  402         ntv->stbcnt = pps_stbcnt;
  403 #endif /* PPS_SYNC */
  404         mutex_spin_exit(&timecounter_lock);
  405 }
  406 #endif /* NTP */
  407 
  408 /*
  409  * second_overflow() - called after ntp_tick_adjust()
  410  *
  411  * This routine is ordinarily called immediately following the above
  412  * routine ntp_tick_adjust(). While these two routines are normally
  413  * combined, they are separated here only for the purposes of
  414  * simulation.
  415  */
  416 void
  417 ntp_update_second(int64_t *adjustment, time_t *newsec)
  418 {
  419         int tickrate;
  420         l_fp ftemp;             /* 32/64-bit temporary */
  421 
  422         KASSERT(mutex_owned(&timecounter_lock));
  423 
  424 #ifdef NTP
  425 
  426         /*
  427          * On rollover of the second both the nanosecond and microsecond
  428          * clocks are updated and the state machine cranked as
  429          * necessary. The phase adjustment to be used for the next
  430          * second is calculated and the maximum error is increased by
  431          * the tolerance.
  432          */
  433         time_maxerror += MAXFREQ / 1000;
  434 
  435         /*
  436          * Leap second processing. If in leap-insert state at
  437          * the end of the day, the system clock is set back one
  438          * second; if in leap-delete state, the system clock is
  439          * set ahead one second. The nano_time() routine or
  440          * external clock driver will insure that reported time
  441          * is always monotonic.
  442          */
  443         switch (time_state) {
  444 
  445                 /*
  446                  * No warning.
  447                  */
  448                 case TIME_OK:
  449                 if (time_status & STA_INS)
  450                         time_state = TIME_INS;
  451                 else if (time_status & STA_DEL)
  452                         time_state = TIME_DEL;
  453                 break;
  454 
  455                 /*
  456                  * Insert second 23:59:60 following second
  457                  * 23:59:59.
  458                  */
  459                 case TIME_INS:
  460                 if (!(time_status & STA_INS))
  461                         time_state = TIME_OK;
  462                 else if ((*newsec) % 86400 == 0) {
  463                         (*newsec)--;
  464                         time_state = TIME_OOP;
  465                         time_tai++;
  466                 }
  467                 break;
  468 
  469                 /*
  470                  * Delete second 23:59:59.
  471                  */
  472                 case TIME_DEL:
  473                 if (!(time_status & STA_DEL))
  474                         time_state = TIME_OK;
  475                 else if (((*newsec) + 1) % 86400 == 0) {
  476                         (*newsec)++;
  477                         time_tai--;
  478                         time_state = TIME_WAIT;
  479                 }
  480                 break;
  481 
  482                 /*
  483                  * Insert second in progress.
  484                  */
  485                 case TIME_OOP:
  486                         time_state = TIME_WAIT;
  487                 break;
  488 
  489                 /*
  490                  * Wait for status bits to clear.
  491                  */
  492                 case TIME_WAIT:
  493                 if (!(time_status & (STA_INS | STA_DEL)))
  494                         time_state = TIME_OK;
  495         }
  496 
  497         /*
  498          * Compute the total time adjustment for the next second
  499          * in ns. The offset is reduced by a factor depending on
  500          * whether the PPS signal is operating. Note that the
  501          * value is in effect scaled by the clock frequency,
  502          * since the adjustment is added at each tick interrupt.
  503          */
  504         ftemp = time_offset;
  505 #ifdef PPS_SYNC
  506         /* XXX even if PPS signal dies we should finish adjustment ? */
  507         if (time_status & STA_PPSTIME && time_status &
  508             STA_PPSSIGNAL)
  509                 L_RSHIFT(ftemp, pps_shift);
  510         else
  511                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  512 #else
  513                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  514 #endif /* PPS_SYNC */
  515         time_adj = ftemp;
  516         L_SUB(time_offset, ftemp);
  517         L_ADD(time_adj, time_freq);
  518         
  519 #ifdef PPS_SYNC
  520         if (pps_valid > 0)
  521                 pps_valid--;
  522         else
  523                 time_status &= ~STA_PPSSIGNAL;
  524 #endif /* PPS_SYNC */
  525 #else  /* !NTP */
  526         L_CLR(time_adj);
  527 #endif /* !NTP */
  528 
  529         /*
  530          * Apply any correction from adjtime(2).  If more than one second
  531          * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
  532          * until the last second is slewed the final < 500 usecs.
  533          */
  534         if (time_adjtime != 0) {
  535                 if (time_adjtime > 1000000)
  536                         tickrate = 5000;
  537                 else if (time_adjtime < -1000000)
  538                         tickrate = -5000;
  539                 else if (time_adjtime > 500)
  540                         tickrate = 500;
  541                 else if (time_adjtime < -500)
  542                         tickrate = -500;
  543                 else
  544                         tickrate = time_adjtime;
  545                 time_adjtime -= tickrate;
  546                 L_LINT(ftemp, tickrate * 1000);
  547                 L_ADD(time_adj, ftemp);
  548         }
  549         *adjustment = time_adj;
  550 }
  551 
  552 /*
  553  * ntp_init() - initialize variables and structures
  554  *
  555  * This routine must be called after the kernel variables hz and tick
  556  * are set or changed and before the next tick interrupt. In this
  557  * particular implementation, these values are assumed set elsewhere in
  558  * the kernel. The design allows the clock frequency and tick interval
  559  * to be changed while the system is running. So, this routine should
  560  * probably be integrated with the code that does that.
  561  */
  562 void
  563 ntp_init(void)
  564 {
  565 
  566         /*
  567          * The following variables are initialized only at startup. Only
  568          * those structures not cleared by the compiler need to be
  569          * initialized, and these only in the simulator. In the actual
  570          * kernel, any nonzero values here will quickly evaporate.
  571          */
  572         L_CLR(time_adj);
  573 #ifdef NTP
  574         L_CLR(time_offset);
  575         L_CLR(time_freq);
  576 #ifdef PPS_SYNC
  577         pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
  578         pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
  579         pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
  580         pps_fcount = 0;
  581         L_CLR(pps_freq);
  582 #endif /* PPS_SYNC */
  583 #endif
  584 }
  585 
  586 #ifdef NTP
  587 /*
  588  * hardupdate() - local clock update
  589  *
  590  * This routine is called by ntp_adjtime() to update the local clock
  591  * phase and frequency. The implementation is of an adaptive-parameter,
  592  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
  593  * time and frequency offset estimates for each call. If the kernel PPS
  594  * discipline code is configured (PPS_SYNC), the PPS signal itself
  595  * determines the new time offset, instead of the calling argument.
  596  * Presumably, calls to ntp_adjtime() occur only when the caller
  597  * believes the local clock is valid within some bound (+-128 ms with
  598  * NTP). If the caller's time is far different than the PPS time, an
  599  * argument will ensue, and it's not clear who will lose.
  600  *
  601  * For uncompensated quartz crystal oscillators and nominal update
  602  * intervals less than 256 s, operation should be in phase-lock mode,
  603  * where the loop is disciplined to phase. For update intervals greater
  604  * than 1024 s, operation should be in frequency-lock mode, where the
  605  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
  606  * is selected by the STA_MODE status bit.
  607  *
  608  * Note: splclock() is in effect.
  609  */
  610 void
  611 hardupdate(long offset)
  612 {
  613         long mtemp;
  614         l_fp ftemp;
  615 
  616         KASSERT(mutex_owned(&timecounter_lock));
  617 
  618         /*
  619          * Select how the phase is to be controlled and from which
  620          * source. If the PPS signal is present and enabled to
  621          * discipline the time, the PPS offset is used; otherwise, the
  622          * argument offset is used.
  623          */
  624         if (!(time_status & STA_PLL))
  625                 return;
  626         if (!(time_status & STA_PPSTIME && time_status &
  627             STA_PPSSIGNAL)) {
  628                 if (offset > MAXPHASE)
  629                         time_monitor = MAXPHASE;
  630                 else if (offset < -MAXPHASE)
  631                         time_monitor = -MAXPHASE;
  632                 else
  633                         time_monitor = offset;
  634                 L_LINT(time_offset, time_monitor);
  635         }
  636 
  637         /*
  638          * Select how the frequency is to be controlled and in which
  639          * mode (PLL or FLL). If the PPS signal is present and enabled
  640          * to discipline the frequency, the PPS frequency is used;
  641          * otherwise, the argument offset is used to compute it.
  642          */
  643         if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
  644                 time_reftime = time_second;
  645                 return;
  646         }
  647         if (time_status & STA_FREQHOLD || time_reftime == 0)
  648                 time_reftime = time_second;
  649         mtemp = time_second - time_reftime;
  650         L_LINT(ftemp, time_monitor);
  651         L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
  652         L_MPY(ftemp, mtemp);
  653         L_ADD(time_freq, ftemp);
  654         time_status &= ~STA_MODE;
  655         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
  656             MAXSEC)) {
  657                 L_LINT(ftemp, (time_monitor << 4) / mtemp);
  658                 L_RSHIFT(ftemp, SHIFT_FLL + 4);
  659                 L_ADD(time_freq, ftemp);
  660                 time_status |= STA_MODE;
  661         }
  662         time_reftime = time_second;
  663         if (L_GINT(time_freq) > MAXFREQ)
  664                 L_LINT(time_freq, MAXFREQ);
  665         else if (L_GINT(time_freq) < -MAXFREQ)
  666                 L_LINT(time_freq, -MAXFREQ);
  667 }
  668 
  669 #ifdef PPS_SYNC
  670 /*
  671  * hardpps() - discipline CPU clock oscillator to external PPS signal
  672  *
  673  * This routine is called at each PPS interrupt in order to discipline
  674  * the CPU clock oscillator to the PPS signal. It measures the PPS phase
  675  * and leaves it in a handy spot for the hardclock() routine. It
  676  * integrates successive PPS phase differences and calculates the
  677  * frequency offset. This is used in hardclock() to discipline the CPU
  678  * clock oscillator so that intrinsic frequency error is cancelled out.
  679  * The code requires the caller to capture the time and hardware counter
  680  * value at the on-time PPS signal transition.
  681  *
  682  * Note that, on some Unix systems, this routine runs at an interrupt
  683  * priority level higher than the timer interrupt routine hardclock().
  684  * Therefore, the variables used are distinct from the hardclock()
  685  * variables, except for certain exceptions: The PPS frequency pps_freq
  686  * and phase pps_offset variables are determined by this routine and
  687  * updated atomically. The time_tolerance variable can be considered a
  688  * constant, since it is infrequently changed, and then only when the
  689  * PPS signal is disabled. The watchdog counter pps_valid is updated
  690  * once per second by hardclock() and is atomically cleared in this
  691  * routine.
  692  */
  693 void
  694 hardpps(struct timespec *tsp,           /* time at PPS */
  695         long nsec                       /* hardware counter at PPS */)
  696 {
  697         long u_sec, u_nsec, v_nsec; /* temps */
  698         l_fp ftemp;
  699 
  700         KASSERT(mutex_owned(&timecounter_lock));
  701 
  702         /*
  703          * The signal is first processed by a range gate and frequency
  704          * discriminator. The range gate rejects noise spikes outside
  705          * the range +-500 us. The frequency discriminator rejects input
  706          * signals with apparent frequency outside the range 1 +-500
  707          * PPM. If two hits occur in the same second, we ignore the
  708          * later hit; if not and a hit occurs outside the range gate,
  709          * keep the later hit for later comparison, but do not process
  710          * it.
  711          */
  712         time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
  713         time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
  714         pps_valid = PPS_VALID;
  715         u_sec = tsp->tv_sec;
  716         u_nsec = tsp->tv_nsec;
  717         if (u_nsec >= (NANOSECOND >> 1)) {
  718                 u_nsec -= NANOSECOND;
  719                 u_sec++;
  720         }
  721         v_nsec = u_nsec - pps_tf[0].tv_nsec;
  722         if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
  723             MAXFREQ)
  724                 return;
  725         pps_tf[2] = pps_tf[1];
  726         pps_tf[1] = pps_tf[0];
  727         pps_tf[0].tv_sec = u_sec;
  728         pps_tf[0].tv_nsec = u_nsec;
  729 
  730         /*
  731          * Compute the difference between the current and previous
  732          * counter values. If the difference exceeds 0.5 s, assume it
  733          * has wrapped around, so correct 1.0 s. If the result exceeds
  734          * the tick interval, the sample point has crossed a tick
  735          * boundary during the last second, so correct the tick. Very
  736          * intricate.
  737          */
  738         u_nsec = nsec;
  739         if (u_nsec > (NANOSECOND >> 1))
  740                 u_nsec -= NANOSECOND;
  741         else if (u_nsec < -(NANOSECOND >> 1))
  742                 u_nsec += NANOSECOND;
  743         pps_fcount += u_nsec;
  744         if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
  745                 return;
  746         time_status &= ~STA_PPSJITTER;
  747 
  748         /*
  749          * A three-stage median filter is used to help denoise the PPS
  750          * time. The median sample becomes the time offset estimate; the
  751          * difference between the other two samples becomes the time
  752          * dispersion (jitter) estimate.
  753          */
  754         if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
  755                 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
  756                         v_nsec = pps_tf[1].tv_nsec;     /* 0 1 2 */
  757                         u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
  758                 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
  759                         v_nsec = pps_tf[0].tv_nsec;     /* 2 0 1 */
  760                         u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
  761                 } else {
  762                         v_nsec = pps_tf[2].tv_nsec;     /* 0 2 1 */
  763                         u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
  764                 }
  765         } else {
  766                 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
  767                         v_nsec = pps_tf[1].tv_nsec;     /* 2 1 0 */
  768                         u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
  769                 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
  770                         v_nsec = pps_tf[0].tv_nsec;     /* 1 0 2 */
  771                         u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
  772                 } else {
  773                         v_nsec = pps_tf[2].tv_nsec;     /* 1 2 0 */
  774                         u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
  775                 }
  776         }
  777 
  778         /*
  779          * Nominal jitter is due to PPS signal noise and interrupt
  780          * latency. If it exceeds the popcorn threshold, the sample is
  781          * discarded. otherwise, if so enabled, the time offset is
  782          * updated. We can tolerate a modest loss of data here without
  783          * much degrading time accuracy.
  784          */
  785         if (u_nsec > (pps_jitter << PPS_POPCORN)) {
  786                 time_status |= STA_PPSJITTER;
  787                 pps_jitcnt++;
  788         } else if (time_status & STA_PPSTIME) {
  789                 time_monitor = -v_nsec;
  790                 L_LINT(time_offset, time_monitor);
  791         }
  792         pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
  793         u_sec = pps_tf[0].tv_sec - pps_lastsec;
  794         if (u_sec < (1 << pps_shift))
  795                 return;
  796 
  797         /*
  798          * At the end of the calibration interval the difference between
  799          * the first and last counter values becomes the scaled
  800          * frequency. It will later be divided by the length of the
  801          * interval to determine the frequency update. If the frequency
  802          * exceeds a sanity threshold, or if the actual calibration
  803          * interval is not equal to the expected length, the data are
  804          * discarded. We can tolerate a modest loss of data here without
  805          * much degrading frequency accuracy.
  806          */
  807         pps_calcnt++;
  808         v_nsec = -pps_fcount;
  809         pps_lastsec = pps_tf[0].tv_sec;
  810         pps_fcount = 0;
  811         u_nsec = MAXFREQ << pps_shift;
  812         if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
  813             pps_shift)) {
  814                 time_status |= STA_PPSERROR;
  815                 pps_errcnt++;
  816                 return;
  817         }
  818 
  819         /*
  820          * Here the raw frequency offset and wander (stability) is
  821          * calculated. If the wander is less than the wander threshold
  822          * for four consecutive averaging intervals, the interval is
  823          * doubled; if it is greater than the threshold for four
  824          * consecutive intervals, the interval is halved. The scaled
  825          * frequency offset is converted to frequency offset. The
  826          * stability metric is calculated as the average of recent
  827          * frequency changes, but is used only for performance
  828          * monitoring.
  829          */
  830         L_LINT(ftemp, v_nsec);
  831         L_RSHIFT(ftemp, pps_shift);
  832         L_SUB(ftemp, pps_freq);
  833         u_nsec = L_GINT(ftemp);
  834         if (u_nsec > PPS_MAXWANDER) {
  835                 L_LINT(ftemp, PPS_MAXWANDER);
  836                 pps_intcnt--;
  837                 time_status |= STA_PPSWANDER;
  838                 pps_stbcnt++;
  839         } else if (u_nsec < -PPS_MAXWANDER) {
  840                 L_LINT(ftemp, -PPS_MAXWANDER);
  841                 pps_intcnt--;
  842                 time_status |= STA_PPSWANDER;
  843                 pps_stbcnt++;
  844         } else {
  845                 pps_intcnt++;
  846         }
  847         if (pps_intcnt >= 4) {
  848                 pps_intcnt = 4;
  849                 if (pps_shift < pps_shiftmax) {
  850                         pps_shift++;
  851                         pps_intcnt = 0;
  852                 }
  853         } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
  854                 pps_intcnt = -4;
  855                 if (pps_shift > PPS_FAVG) {
  856                         pps_shift--;
  857                         pps_intcnt = 0;
  858                 }
  859         }
  860         if (u_nsec < 0)
  861                 u_nsec = -u_nsec;
  862         pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
  863 
  864         /*
  865          * The PPS frequency is recalculated and clamped to the maximum
  866          * MAXFREQ. If enabled, the system clock frequency is updated as
  867          * well.
  868          */
  869         L_ADD(pps_freq, ftemp);
  870         u_nsec = L_GINT(pps_freq);
  871         if (u_nsec > MAXFREQ)
  872                 L_LINT(pps_freq, MAXFREQ);
  873         else if (u_nsec < -MAXFREQ)
  874                 L_LINT(pps_freq, -MAXFREQ);
  875         if (time_status & STA_PPSFREQ)
  876                 time_freq = pps_freq;
  877 }
  878 #endif /* PPS_SYNC */
  879 #endif /* NTP */
  880 
  881 #ifdef NTP
  882 int
  883 ntp_timestatus(void)
  884 {
  885         int rv;
  886 
  887         /*
  888          * Status word error decode. If any of these conditions
  889          * occur, an error is returned, instead of the status
  890          * word. Most applications will care only about the fact
  891          * the system clock may not be trusted, not about the
  892          * details.
  893          *
  894          * Hardware or software error
  895          */
  896         mutex_spin_enter(&timecounter_lock);
  897         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
  898 
  899         /*
  900          * PPS signal lost when either time or frequency
  901          * synchronization requested
  902          */
  903             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
  904              !(time_status & STA_PPSSIGNAL)) ||
  905 
  906         /*
  907          * PPS jitter exceeded when time synchronization
  908          * requested
  909          */
  910             (time_status & STA_PPSTIME &&
  911              time_status & STA_PPSJITTER) ||
  912 
  913         /*
  914          * PPS wander exceeded or calibration error when
  915          * frequency synchronization requested
  916          */
  917             (time_status & STA_PPSFREQ &&
  918              time_status & (STA_PPSWANDER | STA_PPSERROR)))
  919                 rv = TIME_ERROR;
  920         else
  921                 rv = time_state;
  922         mutex_spin_exit(&timecounter_lock);
  923 
  924         return rv;
  925 }
  926 
  927 /*ARGSUSED*/
  928 /*
  929  * ntp_gettime() - NTP user application interface
  930  */
  931 int
  932 sys___ntp_gettime30(struct lwp *l, const struct sys___ntp_gettime30_args *uap, register_t *retval)
  933 {
  934         /* {
  935                 syscallarg(struct ntptimeval *) ntvp;
  936         } */
  937         struct ntptimeval ntv;
  938         int error = 0;
  939 
  940         if (SCARG(uap, ntvp)) {
  941                 ntp_gettime(&ntv);
  942 
  943                 error = copyout((void *)&ntv, (void *)SCARG(uap, ntvp),
  944                                 sizeof(ntv));
  945         }
  946         if (!error) {
  947                 *retval = ntp_timestatus();
  948         }
  949         return(error);
  950 }
  951 
  952 #ifdef COMPAT_30
  953 int
  954 compat_30_sys_ntp_gettime(struct lwp *l, const struct compat_30_sys_ntp_gettime_args *uap, register_t *retval)
  955 {
  956         /* {
  957                 syscallarg(struct ntptimeval30 *) ontvp;
  958         } */
  959         struct ntptimeval ntv;
  960         struct ntptimeval30 ontv;
  961         int error = 0;
  962 
  963         if (SCARG(uap, ntvp)) {
  964                 ntp_gettime(&ntv);
  965                 TIMESPEC_TO_TIMEVAL(&ontv.time, &ntv.time);
  966                 ontv.maxerror = ntv.maxerror;
  967                 ontv.esterror = ntv.esterror;
  968 
  969                 error = copyout((void *)&ontv, (void *)SCARG(uap, ntvp),
  970                                 sizeof(ontv));
  971         }
  972         if (!error)
  973                 *retval = ntp_timestatus();
  974 
  975         return (error);
  976 }
  977 #endif
  978 
  979 /*
  980  * return information about kernel precision timekeeping
  981  */
  982 static int
  983 sysctl_kern_ntptime(SYSCTLFN_ARGS)
  984 {
  985         struct sysctlnode node;
  986         struct ntptimeval ntv;
  987 
  988         ntp_gettime(&ntv);
  989 
  990         node = *rnode;
  991         node.sysctl_data = &ntv;
  992         node.sysctl_size = sizeof(ntv);
  993         return (sysctl_lookup(SYSCTLFN_CALL(&node)));
  994 }
  995 
  996 SYSCTL_SETUP(sysctl_kern_ntptime_setup, "sysctl kern.ntptime node setup")
  997 {
  998 
  999         sysctl_createv(clog, 0, NULL, NULL,
 1000                        CTLFLAG_PERMANENT,
 1001                        CTLTYPE_NODE, "kern", NULL,
 1002                        NULL, 0, NULL, 0,
 1003                        CTL_KERN, CTL_EOL);
 1004 
 1005         sysctl_createv(clog, 0, NULL, NULL,
 1006                        CTLFLAG_PERMANENT,
 1007                        CTLTYPE_STRUCT, "ntptime",
 1008                        SYSCTL_DESCR("Kernel clock values for NTP"),
 1009                        sysctl_kern_ntptime, 0, NULL,
 1010                        sizeof(struct ntptimeval),
 1011                        CTL_KERN, KERN_NTPTIME, CTL_EOL);
 1012 }
 1013 #else /* !NTP */
 1014 /* For some reason, raising SIGSYS (as sys_nosys would) is problematic. */
 1015 
 1016 int
 1017 sys___ntp_gettime30(struct lwp *l, const struct sys___ntp_gettime30_args *uap, register_t *retval)
 1018 {
 1019 
 1020         return(ENOSYS);
 1021 }
 1022 
 1023 #ifdef COMPAT_30
 1024 int
 1025 compat_30_sys_ntp_gettime(struct lwp *l, const struct compat_30_sys_ntp_gettime_args *uap, register_t *retval)
 1026 {
 1027 
 1028         return(ENOSYS);
 1029 }
 1030 #endif
 1031 #endif /* !NTP */

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