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 /***********************************************************************
    2  *                                                                     *
    3  * Copyright (c) David L. Mills 1993-2001                              *
    4  *                                                                     *
    5  * Permission to use, copy, modify, and distribute this software and   *
    6  * its documentation for any purpose and without fee is hereby         *
    7  * granted, provided that the above copyright notice appears in all    *
    8  * copies and that both the copyright notice and this permission       *
    9  * notice appear in supporting documentation, and that the name        *
   10  * University of Delaware not be used in advertising or publicity      *
   11  * pertaining to distribution of the software without specific,        *
   12  * written prior permission. The University of Delaware makes no       *
   13  * representations about the suitability this software for any         *
   14  * purpose. It is provided "as is" without express or implied          *
   15  * warranty.                                                           *
   16  *                                                                     *
   17  **********************************************************************/
   18 
   19 /*
   20  * Adapted from the original sources for FreeBSD and timecounters by:
   21  * Poul-Henning Kamp <phk@FreeBSD.org>.
   22  *
   23  * The 32bit version of the "LP" macros seems a bit past its "sell by" 
   24  * date so I have retained only the 64bit version and included it directly
   25  * in this file.
   26  *
   27  * Only minor changes done to interface with the timecounters over in
   28  * sys/kern/kern_clock.c.   Some of the comments below may be (even more)
   29  * confusing and/or plain wrong in that context.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/5.3/sys/kern/kern_ntptime.c 136588 2004-10-16 08:43:07Z cvs2svn $");
   34 
   35 #include "opt_ntp.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/sysproto.h>
   40 #include <sys/kernel.h>
   41 #include <sys/proc.h>
   42 #include <sys/lock.h>
   43 #include <sys/mutex.h>
   44 #include <sys/time.h>
   45 #include <sys/timex.h>
   46 #include <sys/timetc.h>
   47 #include <sys/timepps.h>
   48 #include <sys/sysctl.h>
   49 
   50 /*
   51  * Single-precision macros for 64-bit machines
   52  */
   53 typedef int64_t l_fp;
   54 #define L_ADD(v, u)     ((v) += (u))
   55 #define L_SUB(v, u)     ((v) -= (u))
   56 #define L_ADDHI(v, a)   ((v) += (int64_t)(a) << 32)
   57 #define L_NEG(v)        ((v) = -(v))
   58 #define L_RSHIFT(v, n) \
   59         do { \
   60                 if ((v) < 0) \
   61                         (v) = -(-(v) >> (n)); \
   62                 else \
   63                         (v) = (v) >> (n); \
   64         } while (0)
   65 #define L_MPY(v, a)     ((v) *= (a))
   66 #define L_CLR(v)        ((v) = 0)
   67 #define L_ISNEG(v)      ((v) < 0)
   68 #define L_LINT(v, a)    ((v) = (int64_t)(a) << 32)
   69 #define L_GINT(v)       ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
   70 
   71 /*
   72  * Generic NTP kernel interface
   73  *
   74  * These routines constitute the Network Time Protocol (NTP) interfaces
   75  * for user and daemon application programs. The ntp_gettime() routine
   76  * provides the time, maximum error (synch distance) and estimated error
   77  * (dispersion) to client user application programs. The ntp_adjtime()
   78  * routine is used by the NTP daemon to adjust the system clock to an
   79  * externally derived time. The time offset and related variables set by
   80  * this routine are used by other routines in this module to adjust the
   81  * phase and frequency of the clock discipline loop which controls the
   82  * system clock.
   83  *
   84  * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
   85  * defined), the time at each tick interrupt is derived directly from
   86  * the kernel time variable. When the kernel time is reckoned in
   87  * microseconds, (NTP_NANO undefined), the time is derived from the
   88  * kernel time variable together with a variable representing the
   89  * leftover nanoseconds at the last tick interrupt. In either case, the
   90  * current nanosecond time is reckoned from these values plus an
   91  * interpolated value derived by the clock routines in another
   92  * architecture-specific module. The interpolation can use either a
   93  * dedicated counter or a processor cycle counter (PCC) implemented in
   94  * some architectures.
   95  *
   96  * Note that all routines must run at priority splclock or higher.
   97  */
   98 /*
   99  * Phase/frequency-lock loop (PLL/FLL) definitions
  100  *
  101  * The nanosecond clock discipline uses two variable types, time
  102  * variables and frequency variables. Both types are represented as 64-
  103  * bit fixed-point quantities with the decimal point between two 32-bit
  104  * halves. On a 32-bit machine, each half is represented as a single
  105  * word and mathematical operations are done using multiple-precision
  106  * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
  107  * used.
  108  *
  109  * A time variable is a signed 64-bit fixed-point number in ns and
  110  * fraction. It represents the remaining time offset to be amortized
  111  * over succeeding tick interrupts. The maximum time offset is about
  112  * 0.5 s and the resolution is about 2.3e-10 ns.
  113  *
  114  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  115  *  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
  116  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  117  * |s s s|                       ns                                |
  118  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  119  * |                        fraction                               |
  120  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  121  *
  122  * A frequency variable is a signed 64-bit fixed-point number in ns/s
  123  * and fraction. It represents the ns and fraction to be added to the
  124  * kernel time variable at each second. The maximum frequency offset is
  125  * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
  126  *
  127  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  128  *  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
  129  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  130  * |s s s s s s s s s s s s s|            ns/s                     |
  131  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  132  * |                        fraction                               |
  133  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  134  */
  135 /*
  136  * The following variables establish the state of the PLL/FLL and the
  137  * residual time and frequency offset of the local clock.
  138  */
  139 #define SHIFT_PLL       4               /* PLL loop gain (shift) */
  140 #define SHIFT_FLL       2               /* FLL loop gain (shift) */
  141 
  142 static int time_state = TIME_OK;        /* clock state */
  143 static int time_status = STA_UNSYNC;    /* clock status bits */
  144 static long time_tai;                   /* TAI offset (s) */
  145 static long time_monitor;               /* last time offset scaled (ns) */
  146 static long time_constant;              /* poll interval (shift) (s) */
  147 static long time_precision = 1;         /* clock precision (ns) */
  148 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
  149 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
  150 static long time_reftime;               /* time at last adjustment (s) */
  151 static l_fp time_offset;                /* time offset (ns) */
  152 static l_fp time_freq;                  /* frequency offset (ns/s) */
  153 static l_fp time_adj;                   /* tick adjust (ns/s) */
  154 
  155 static int64_t time_adjtime;            /* correction from adjtime(2) (usec) */
  156 
  157 #ifdef PPS_SYNC
  158 /*
  159  * The following variables are used when a pulse-per-second (PPS) signal
  160  * is available and connected via a modem control lead. They establish
  161  * the engineering parameters of the clock discipline loop when
  162  * controlled by the PPS signal.
  163  */
  164 #define PPS_FAVG        2               /* min freq avg interval (s) (shift) */
  165 #define PPS_FAVGDEF     8               /* default freq avg int (s) (shift) */
  166 #define PPS_FAVGMAX     15              /* max freq avg interval (s) (shift) */
  167 #define PPS_PAVG        4               /* phase avg interval (s) (shift) */
  168 #define PPS_VALID       120             /* PPS signal watchdog max (s) */
  169 #define PPS_MAXWANDER   100000          /* max PPS wander (ns/s) */
  170 #define PPS_POPCORN     2               /* popcorn spike threshold (shift) */
  171 
  172 static struct timespec pps_tf[3];       /* phase median filter */
  173 static l_fp pps_freq;                   /* scaled frequency offset (ns/s) */
  174 static long pps_fcount;                 /* frequency accumulator */
  175 static long pps_jitter;                 /* nominal jitter (ns) */
  176 static long pps_stabil;                 /* nominal stability (scaled ns/s) */
  177 static long pps_lastsec;                /* time at last calibration (s) */
  178 static int pps_valid;                   /* signal watchdog counter */
  179 static int pps_shift = PPS_FAVG;        /* interval duration (s) (shift) */
  180 static int pps_shiftmax = PPS_FAVGDEF;  /* max interval duration (s) (shift) */
  181 static int pps_intcnt;                  /* wander counter */
  182 
  183 /*
  184  * PPS signal quality monitors
  185  */
  186 static long pps_calcnt;                 /* calibration intervals */
  187 static long pps_jitcnt;                 /* jitter limit exceeded */
  188 static long pps_stbcnt;                 /* stability limit exceeded */
  189 static long pps_errcnt;                 /* calibration errors */
  190 #endif /* PPS_SYNC */
  191 /*
  192  * End of phase/frequency-lock loop (PLL/FLL) definitions
  193  */
  194 
  195 static void ntp_init(void);
  196 static void hardupdate(long offset);
  197 
  198 /*
  199  * ntp_gettime() - NTP user application interface
  200  *
  201  * See the timex.h header file for synopsis and API description. Note
  202  * that the TAI offset is returned in the ntvtimeval.tai structure
  203  * member.
  204  */
  205 static int
  206 ntp_sysctl(SYSCTL_HANDLER_ARGS)
  207 {
  208         struct ntptimeval ntv;  /* temporary structure */
  209         struct timespec atv;    /* nanosecond time */
  210 
  211         nanotime(&atv);
  212         ntv.time.tv_sec = atv.tv_sec;
  213         ntv.time.tv_nsec = atv.tv_nsec;
  214         ntv.maxerror = time_maxerror;
  215         ntv.esterror = time_esterror;
  216         ntv.tai = time_tai;
  217         ntv.time_state = time_state;
  218 
  219         /*
  220          * Status word error decode. If any of these conditions occur,
  221          * an error is returned, instead of the status word. Most
  222          * applications will care only about the fact the system clock
  223          * may not be trusted, not about the details.
  224          *
  225          * Hardware or software error
  226          */
  227         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
  228 
  229         /*
  230          * PPS signal lost when either time or frequency synchronization
  231          * requested
  232          */
  233             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
  234             !(time_status & STA_PPSSIGNAL)) ||
  235 
  236         /*
  237          * PPS jitter exceeded when time synchronization requested
  238          */
  239             (time_status & STA_PPSTIME &&
  240             time_status & STA_PPSJITTER) ||
  241 
  242         /*
  243          * PPS wander exceeded or calibration error when frequency
  244          * synchronization requested
  245          */
  246             (time_status & STA_PPSFREQ &&
  247             time_status & (STA_PPSWANDER | STA_PPSERROR)))
  248                 ntv.time_state = TIME_ERROR;
  249         return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
  250 }
  251 
  252 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
  253 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
  254         0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
  255 
  256 #ifdef PPS_SYNC
  257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
  258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
  259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
  260 
  261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
  262 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
  263 #endif
  264 /*
  265  * ntp_adjtime() - NTP daemon application interface
  266  *
  267  * See the timex.h header file for synopsis and API description. Note
  268  * that the timex.constant structure member has a dual purpose to set
  269  * the time constant and to set the TAI offset.
  270  */
  271 #ifndef _SYS_SYSPROTO_H_
  272 struct ntp_adjtime_args {
  273         struct timex *tp;
  274 };
  275 #endif
  276 
  277 /*
  278  * MPSAFE
  279  */
  280 int
  281 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
  282 {
  283         struct timex ntv;       /* temporary structure */
  284         long freq;              /* frequency ns/s) */
  285         int modes;              /* mode bits from structure */
  286         int s;                  /* caller priority */
  287         int error;
  288 
  289         error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
  290         if (error)
  291                 return(error);
  292 
  293         /*
  294          * Update selected clock variables - only the superuser can
  295          * change anything. Note that there is no error checking here on
  296          * the assumption the superuser should know what it is doing.
  297          * Note that either the time constant or TAI offset are loaded
  298          * from the ntv.constant member, depending on the mode bits. If
  299          * the STA_PLL bit in the status word is cleared, the state and
  300          * status words are reset to the initial values at boot.
  301          */
  302         mtx_lock(&Giant);
  303         modes = ntv.modes;
  304         if (modes)
  305                 error = suser(td);
  306         if (error)
  307                 goto done2;
  308         s = splclock();
  309         if (modes & MOD_MAXERROR)
  310                 time_maxerror = ntv.maxerror;
  311         if (modes & MOD_ESTERROR)
  312                 time_esterror = ntv.esterror;
  313         if (modes & MOD_STATUS) {
  314                 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
  315                         time_state = TIME_OK;
  316                         time_status = STA_UNSYNC;
  317 #ifdef PPS_SYNC
  318                         pps_shift = PPS_FAVG;
  319 #endif /* PPS_SYNC */
  320                 }
  321                 time_status &= STA_RONLY;
  322                 time_status |= ntv.status & ~STA_RONLY;
  323         }
  324         if (modes & MOD_TIMECONST) {
  325                 if (ntv.constant < 0)
  326                         time_constant = 0;
  327                 else if (ntv.constant > MAXTC)
  328                         time_constant = MAXTC;
  329                 else
  330                         time_constant = ntv.constant;
  331         }
  332         if (modes & MOD_TAI) {
  333                 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
  334                         time_tai = ntv.constant;
  335         }
  336 #ifdef PPS_SYNC
  337         if (modes & MOD_PPSMAX) {
  338                 if (ntv.shift < PPS_FAVG)
  339                         pps_shiftmax = PPS_FAVG;
  340                 else if (ntv.shift > PPS_FAVGMAX)
  341                         pps_shiftmax = PPS_FAVGMAX;
  342                 else
  343                         pps_shiftmax = ntv.shift;
  344         }
  345 #endif /* PPS_SYNC */
  346         if (modes & MOD_NANO)
  347                 time_status |= STA_NANO;
  348         if (modes & MOD_MICRO)
  349                 time_status &= ~STA_NANO;
  350         if (modes & MOD_CLKB)
  351                 time_status |= STA_CLK;
  352         if (modes & MOD_CLKA)
  353                 time_status &= ~STA_CLK;
  354         if (modes & MOD_FREQUENCY) {
  355                 freq = (ntv.freq * 1000LL) >> 16;
  356                 if (freq > MAXFREQ)
  357                         L_LINT(time_freq, MAXFREQ);
  358                 else if (freq < -MAXFREQ)
  359                         L_LINT(time_freq, -MAXFREQ);
  360                 else {
  361                         /*
  362                          * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
  363                          * time_freq is [ns/s * 2^32]
  364                          */
  365                         time_freq = ntv.freq * 1000LL * 65536LL;
  366                 }
  367 #ifdef PPS_SYNC
  368                 pps_freq = time_freq;
  369 #endif /* PPS_SYNC */
  370         }
  371         if (modes & MOD_OFFSET) {
  372                 if (time_status & STA_NANO)
  373                         hardupdate(ntv.offset);
  374                 else
  375                         hardupdate(ntv.offset * 1000);
  376         }
  377 
  378         /*
  379          * Retrieve all clock variables. Note that the TAI offset is
  380          * returned only by ntp_gettime();
  381          */
  382         if (time_status & STA_NANO)
  383                 ntv.offset = L_GINT(time_offset);
  384         else
  385                 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
  386         ntv.freq = L_GINT((time_freq / 1000LL) << 16);
  387         ntv.maxerror = time_maxerror;
  388         ntv.esterror = time_esterror;
  389         ntv.status = time_status;
  390         ntv.constant = time_constant;
  391         if (time_status & STA_NANO)
  392                 ntv.precision = time_precision;
  393         else
  394                 ntv.precision = time_precision / 1000;
  395         ntv.tolerance = MAXFREQ * SCALE_PPM;
  396 #ifdef PPS_SYNC
  397         ntv.shift = pps_shift;
  398         ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
  399         if (time_status & STA_NANO)
  400                 ntv.jitter = pps_jitter;
  401         else
  402                 ntv.jitter = pps_jitter / 1000;
  403         ntv.stabil = pps_stabil;
  404         ntv.calcnt = pps_calcnt;
  405         ntv.errcnt = pps_errcnt;
  406         ntv.jitcnt = pps_jitcnt;
  407         ntv.stbcnt = pps_stbcnt;
  408 #endif /* PPS_SYNC */
  409         splx(s);
  410 
  411         error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
  412         if (error)
  413                 goto done2;
  414 
  415         /*
  416          * Status word error decode. See comments in
  417          * ntp_gettime() routine.
  418          */
  419         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
  420             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
  421             !(time_status & STA_PPSSIGNAL)) ||
  422             (time_status & STA_PPSTIME &&
  423             time_status & STA_PPSJITTER) ||
  424             (time_status & STA_PPSFREQ &&
  425             time_status & (STA_PPSWANDER | STA_PPSERROR))) {
  426                 td->td_retval[0] = TIME_ERROR;
  427         } else {
  428                 td->td_retval[0] = time_state;
  429         }
  430 done2:
  431         mtx_unlock(&Giant);
  432         return (error);
  433 }
  434 
  435 /*
  436  * second_overflow() - called after ntp_tick_adjust()
  437  *
  438  * This routine is ordinarily called immediately following the above
  439  * routine ntp_tick_adjust(). While these two routines are normally
  440  * combined, they are separated here only for the purposes of
  441  * simulation.
  442  */
  443 void
  444 ntp_update_second(int64_t *adjustment, time_t *newsec)
  445 {
  446         int tickrate;
  447         l_fp ftemp;             /* 32/64-bit temporary */
  448 
  449         /*
  450          * On rollover of the second both the nanosecond and microsecond
  451          * clocks are updated and the state machine cranked as
  452          * necessary. The phase adjustment to be used for the next
  453          * second is calculated and the maximum error is increased by
  454          * the tolerance.
  455          */
  456         time_maxerror += MAXFREQ / 1000;
  457 
  458         /*
  459          * Leap second processing. If in leap-insert state at
  460          * the end of the day, the system clock is set back one
  461          * second; if in leap-delete state, the system clock is
  462          * set ahead one second. The nano_time() routine or
  463          * external clock driver will insure that reported time
  464          * is always monotonic.
  465          */
  466         switch (time_state) {
  467 
  468                 /*
  469                  * No warning.
  470                  */
  471                 case TIME_OK:
  472                 if (time_status & STA_INS)
  473                         time_state = TIME_INS;
  474                 else if (time_status & STA_DEL)
  475                         time_state = TIME_DEL;
  476                 break;
  477 
  478                 /*
  479                  * Insert second 23:59:60 following second
  480                  * 23:59:59.
  481                  */
  482                 case TIME_INS:
  483                 if (!(time_status & STA_INS))
  484                         time_state = TIME_OK;
  485                 else if ((*newsec) % 86400 == 0) {
  486                         (*newsec)--;
  487                         time_state = TIME_OOP;
  488                         time_tai++;
  489                 }
  490                 break;
  491 
  492                 /*
  493                  * Delete second 23:59:59.
  494                  */
  495                 case TIME_DEL:
  496                 if (!(time_status & STA_DEL))
  497                         time_state = TIME_OK;
  498                 else if (((*newsec) + 1) % 86400 == 0) {
  499                         (*newsec)++;
  500                         time_tai--;
  501                         time_state = TIME_WAIT;
  502                 }
  503                 break;
  504 
  505                 /*
  506                  * Insert second in progress.
  507                  */
  508                 case TIME_OOP:
  509                         time_state = TIME_WAIT;
  510                 break;
  511 
  512                 /*
  513                  * Wait for status bits to clear.
  514                  */
  515                 case TIME_WAIT:
  516                 if (!(time_status & (STA_INS | STA_DEL)))
  517                         time_state = TIME_OK;
  518         }
  519 
  520         /*
  521          * Compute the total time adjustment for the next second
  522          * in ns. The offset is reduced by a factor depending on
  523          * whether the PPS signal is operating. Note that the
  524          * value is in effect scaled by the clock frequency,
  525          * since the adjustment is added at each tick interrupt.
  526          */
  527         ftemp = time_offset;
  528 #ifdef PPS_SYNC
  529         /* XXX even if PPS signal dies we should finish adjustment ? */
  530         if (time_status & STA_PPSTIME && time_status &
  531             STA_PPSSIGNAL)
  532                 L_RSHIFT(ftemp, pps_shift);
  533         else
  534                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  535 #else
  536                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  537 #endif /* PPS_SYNC */
  538         time_adj = ftemp;
  539         L_SUB(time_offset, ftemp);
  540         L_ADD(time_adj, time_freq);
  541         
  542         /*
  543          * Apply any correction from adjtime(2).  If more than one second
  544          * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
  545          * until the last second is slewed the final < 500 usecs.
  546          */
  547         if (time_adjtime != 0) {
  548                 if (time_adjtime > 1000000)
  549                         tickrate = 5000;
  550                 else if (time_adjtime < -1000000)
  551                         tickrate = -5000;
  552                 else if (time_adjtime > 500)
  553                         tickrate = 500;
  554                 else if (time_adjtime < -500)
  555                         tickrate = -500;
  556                 else
  557                         tickrate = time_adjtime;
  558                 time_adjtime -= tickrate;
  559                 L_LINT(ftemp, tickrate * 1000);
  560                 L_ADD(time_adj, ftemp);
  561         }
  562         *adjustment = time_adj;
  563                 
  564 #ifdef PPS_SYNC
  565         if (pps_valid > 0)
  566                 pps_valid--;
  567         else
  568                 time_status &= ~STA_PPSSIGNAL;
  569 #endif /* PPS_SYNC */
  570 }
  571 
  572 /*
  573  * ntp_init() - initialize variables and structures
  574  *
  575  * This routine must be called after the kernel variables hz and tick
  576  * are set or changed and before the next tick interrupt. In this
  577  * particular implementation, these values are assumed set elsewhere in
  578  * the kernel. The design allows the clock frequency and tick interval
  579  * to be changed while the system is running. So, this routine should
  580  * probably be integrated with the code that does that.
  581  */
  582 static void
  583 ntp_init()
  584 {
  585 
  586         /*
  587          * The following variables are initialized only at startup. Only
  588          * those structures not cleared by the compiler need to be
  589          * initialized, and these only in the simulator. In the actual
  590          * kernel, any nonzero values here will quickly evaporate.
  591          */
  592         L_CLR(time_offset);
  593         L_CLR(time_freq);
  594 #ifdef PPS_SYNC
  595         pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
  596         pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
  597         pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
  598         pps_fcount = 0;
  599         L_CLR(pps_freq);
  600 #endif /* PPS_SYNC */      
  601 }
  602 
  603 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
  604 
  605 /*
  606  * hardupdate() - local clock update
  607  *
  608  * This routine is called by ntp_adjtime() to update the local clock
  609  * phase and frequency. The implementation is of an adaptive-parameter,
  610  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
  611  * time and frequency offset estimates for each call. If the kernel PPS
  612  * discipline code is configured (PPS_SYNC), the PPS signal itself
  613  * determines the new time offset, instead of the calling argument.
  614  * Presumably, calls to ntp_adjtime() occur only when the caller
  615  * believes the local clock is valid within some bound (+-128 ms with
  616  * NTP). If the caller's time is far different than the PPS time, an
  617  * argument will ensue, and it's not clear who will lose.
  618  *
  619  * For uncompensated quartz crystal oscillators and nominal update
  620  * intervals less than 256 s, operation should be in phase-lock mode,
  621  * where the loop is disciplined to phase. For update intervals greater
  622  * than 1024 s, operation should be in frequency-lock mode, where the
  623  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
  624  * is selected by the STA_MODE status bit.
  625  */
  626 static void
  627 hardupdate(offset)
  628         long offset;            /* clock offset (ns) */
  629 {
  630         long mtemp;
  631         l_fp ftemp;
  632 
  633         /*
  634          * Select how the phase is to be controlled and from which
  635          * source. If the PPS signal is present and enabled to
  636          * discipline the time, the PPS offset is used; otherwise, the
  637          * argument offset is used.
  638          */
  639         if (!(time_status & STA_PLL))
  640                 return;
  641         if (!(time_status & STA_PPSTIME && time_status &
  642             STA_PPSSIGNAL)) {
  643                 if (offset > MAXPHASE)
  644                         time_monitor = MAXPHASE;
  645                 else if (offset < -MAXPHASE)
  646                         time_monitor = -MAXPHASE;
  647                 else
  648                         time_monitor = offset;
  649                 L_LINT(time_offset, time_monitor);
  650         }
  651 
  652         /*
  653          * Select how the frequency is to be controlled and in which
  654          * mode (PLL or FLL). If the PPS signal is present and enabled
  655          * to discipline the frequency, the PPS frequency is used;
  656          * otherwise, the argument offset is used to compute it.
  657          */
  658         if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
  659                 time_reftime = time_second;
  660                 return;
  661         }
  662         if (time_status & STA_FREQHOLD || time_reftime == 0)
  663                 time_reftime = time_second;
  664         mtemp = time_second - time_reftime;
  665         L_LINT(ftemp, time_monitor);
  666         L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
  667         L_MPY(ftemp, mtemp);
  668         L_ADD(time_freq, ftemp);
  669         time_status &= ~STA_MODE;
  670         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
  671             MAXSEC)) {
  672                 L_LINT(ftemp, (time_monitor << 4) / mtemp);
  673                 L_RSHIFT(ftemp, SHIFT_FLL + 4);
  674                 L_ADD(time_freq, ftemp);
  675                 time_status |= STA_MODE;
  676         }
  677         time_reftime = time_second;
  678         if (L_GINT(time_freq) > MAXFREQ)
  679                 L_LINT(time_freq, MAXFREQ);
  680         else if (L_GINT(time_freq) < -MAXFREQ)
  681                 L_LINT(time_freq, -MAXFREQ);
  682 }
  683 
  684 #ifdef PPS_SYNC
  685 /*
  686  * hardpps() - discipline CPU clock oscillator to external PPS signal
  687  *
  688  * This routine is called at each PPS interrupt in order to discipline
  689  * the CPU clock oscillator to the PPS signal. There are two independent
  690  * first-order feedback loops, one for the phase, the other for the
  691  * frequency. The phase loop measures and grooms the PPS phase offset
  692  * and leaves it in a handy spot for the seconds overflow routine. The
  693  * frequency loop averages successive PPS phase differences and
  694  * calculates the PPS frequency offset, which is also processed by the
  695  * seconds overflow routine. The code requires the caller to capture the
  696  * time and architecture-dependent hardware counter values in
  697  * nanoseconds at the on-time PPS signal transition.
  698  *
  699  * Note that, on some Unix systems this routine runs at an interrupt
  700  * priority level higher than the timer interrupt routine hardclock().
  701  * Therefore, the variables used are distinct from the hardclock()
  702  * variables, except for the actual time and frequency variables, which
  703  * are determined by this routine and updated atomically.
  704  */
  705 void
  706 hardpps(tsp, nsec)
  707         struct timespec *tsp;   /* time at PPS */
  708         long nsec;              /* hardware counter at PPS */
  709 {
  710         long u_sec, u_nsec, v_nsec; /* temps */
  711         l_fp ftemp;
  712 
  713         /*
  714          * The signal is first processed by a range gate and frequency
  715          * discriminator. The range gate rejects noise spikes outside
  716          * the range +-500 us. The frequency discriminator rejects input
  717          * signals with apparent frequency outside the range 1 +-500
  718          * PPM. If two hits occur in the same second, we ignore the
  719          * later hit; if not and a hit occurs outside the range gate,
  720          * keep the later hit for later comparison, but do not process
  721          * it.
  722          */
  723         time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
  724         time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
  725         pps_valid = PPS_VALID;
  726         u_sec = tsp->tv_sec;
  727         u_nsec = tsp->tv_nsec;
  728         if (u_nsec >= (NANOSECOND >> 1)) {
  729                 u_nsec -= NANOSECOND;
  730                 u_sec++;
  731         }
  732         v_nsec = u_nsec - pps_tf[0].tv_nsec;
  733         if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
  734             MAXFREQ)
  735                 return;
  736         pps_tf[2] = pps_tf[1];
  737         pps_tf[1] = pps_tf[0];
  738         pps_tf[0].tv_sec = u_sec;
  739         pps_tf[0].tv_nsec = u_nsec;
  740 
  741         /*
  742          * Compute the difference between the current and previous
  743          * counter values. If the difference exceeds 0.5 s, assume it
  744          * has wrapped around, so correct 1.0 s. If the result exceeds
  745          * the tick interval, the sample point has crossed a tick
  746          * boundary during the last second, so correct the tick. Very
  747          * intricate.
  748          */
  749         u_nsec = nsec;
  750         if (u_nsec > (NANOSECOND >> 1))
  751                 u_nsec -= NANOSECOND;
  752         else if (u_nsec < -(NANOSECOND >> 1))
  753                 u_nsec += NANOSECOND;
  754         pps_fcount += u_nsec;
  755         if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
  756                 return;
  757         time_status &= ~STA_PPSJITTER;
  758 
  759         /*
  760          * A three-stage median filter is used to help denoise the PPS
  761          * time. The median sample becomes the time offset estimate; the
  762          * difference between the other two samples becomes the time
  763          * dispersion (jitter) estimate.
  764          */
  765         if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
  766                 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
  767                         v_nsec = pps_tf[1].tv_nsec;     /* 0 1 2 */
  768                         u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
  769                 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
  770                         v_nsec = pps_tf[0].tv_nsec;     /* 2 0 1 */
  771                         u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
  772                 } else {
  773                         v_nsec = pps_tf[2].tv_nsec;     /* 0 2 1 */
  774                         u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
  775                 }
  776         } else {
  777                 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
  778                         v_nsec = pps_tf[1].tv_nsec;     /* 2 1 0 */
  779                         u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
  780                 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
  781                         v_nsec = pps_tf[0].tv_nsec;     /* 1 0 2 */
  782                         u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
  783                 } else {
  784                         v_nsec = pps_tf[2].tv_nsec;     /* 1 2 0 */
  785                         u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
  786                 }
  787         }
  788 
  789         /*
  790          * Nominal jitter is due to PPS signal noise and interrupt
  791          * latency. If it exceeds the popcorn threshold, the sample is
  792          * discarded. otherwise, if so enabled, the time offset is
  793          * updated. We can tolerate a modest loss of data here without
  794          * much degrading time accuracy.
  795          */
  796         if (u_nsec > (pps_jitter << PPS_POPCORN)) {
  797                 time_status |= STA_PPSJITTER;
  798                 pps_jitcnt++;
  799         } else if (time_status & STA_PPSTIME) {
  800                 time_monitor = -v_nsec;
  801                 L_LINT(time_offset, time_monitor);
  802         }
  803         pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
  804         u_sec = pps_tf[0].tv_sec - pps_lastsec;
  805         if (u_sec < (1 << pps_shift))
  806                 return;
  807 
  808         /*
  809          * At the end of the calibration interval the difference between
  810          * the first and last counter values becomes the scaled
  811          * frequency. It will later be divided by the length of the
  812          * interval to determine the frequency update. If the frequency
  813          * exceeds a sanity threshold, or if the actual calibration
  814          * interval is not equal to the expected length, the data are
  815          * discarded. We can tolerate a modest loss of data here without
  816          * much degrading frequency accuracy.
  817          */
  818         pps_calcnt++;
  819         v_nsec = -pps_fcount;
  820         pps_lastsec = pps_tf[0].tv_sec;
  821         pps_fcount = 0;
  822         u_nsec = MAXFREQ << pps_shift;
  823         if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
  824             pps_shift)) {
  825                 time_status |= STA_PPSERROR;
  826                 pps_errcnt++;
  827                 return;
  828         }
  829 
  830         /*
  831          * Here the raw frequency offset and wander (stability) is
  832          * calculated. If the wander is less than the wander threshold
  833          * for four consecutive averaging intervals, the interval is
  834          * doubled; if it is greater than the threshold for four
  835          * consecutive intervals, the interval is halved. The scaled
  836          * frequency offset is converted to frequency offset. The
  837          * stability metric is calculated as the average of recent
  838          * frequency changes, but is used only for performance
  839          * monitoring.
  840          */
  841         L_LINT(ftemp, v_nsec);
  842         L_RSHIFT(ftemp, pps_shift);
  843         L_SUB(ftemp, pps_freq);
  844         u_nsec = L_GINT(ftemp);
  845         if (u_nsec > PPS_MAXWANDER) {
  846                 L_LINT(ftemp, PPS_MAXWANDER);
  847                 pps_intcnt--;
  848                 time_status |= STA_PPSWANDER;
  849                 pps_stbcnt++;
  850         } else if (u_nsec < -PPS_MAXWANDER) {
  851                 L_LINT(ftemp, -PPS_MAXWANDER);
  852                 pps_intcnt--;
  853                 time_status |= STA_PPSWANDER;
  854                 pps_stbcnt++;
  855         } else {
  856                 pps_intcnt++;
  857         }
  858         if (pps_intcnt >= 4) {
  859                 pps_intcnt = 4;
  860                 if (pps_shift < pps_shiftmax) {
  861                         pps_shift++;
  862                         pps_intcnt = 0;
  863                 }
  864         } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
  865                 pps_intcnt = -4;
  866                 if (pps_shift > PPS_FAVG) {
  867                         pps_shift--;
  868                         pps_intcnt = 0;
  869                 }
  870         }
  871         if (u_nsec < 0)
  872                 u_nsec = -u_nsec;
  873         pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
  874 
  875         /*
  876          * The PPS frequency is recalculated and clamped to the maximum
  877          * MAXFREQ. If enabled, the system clock frequency is updated as
  878          * well.
  879          */
  880         L_ADD(pps_freq, ftemp);
  881         u_nsec = L_GINT(pps_freq);
  882         if (u_nsec > MAXFREQ)
  883                 L_LINT(pps_freq, MAXFREQ);
  884         else if (u_nsec < -MAXFREQ)
  885                 L_LINT(pps_freq, -MAXFREQ);
  886         if (time_status & STA_PPSFREQ)
  887                 time_freq = pps_freq;
  888 }
  889 #endif /* PPS_SYNC */
  890 
  891 #ifndef _SYS_SYSPROTO_H_
  892 struct adjtime_args {
  893         struct timeval *delta;
  894         struct timeval *olddelta;
  895 };
  896 #endif
  897 /*
  898  * MPSAFE
  899  */
  900 /* ARGSUSED */
  901 int
  902 adjtime(struct thread *td, struct adjtime_args *uap)
  903 {
  904         struct timeval atv;
  905         int error;
  906 
  907         if ((error = suser(td)))
  908                 return (error);
  909 
  910         mtx_lock(&Giant);
  911         if (uap->olddelta) {
  912                 atv.tv_sec = time_adjtime / 1000000;
  913                 atv.tv_usec = time_adjtime % 1000000;
  914                 if (atv.tv_usec < 0) {
  915                         atv.tv_usec += 1000000;
  916                         atv.tv_sec--;
  917                 }
  918                 error = copyout(&atv, uap->olddelta, sizeof(atv));
  919                 if (error)
  920                         goto done2;
  921         }
  922         if (uap->delta) {
  923                 error = copyin(uap->delta, &atv, sizeof(atv));
  924                 if (error)
  925                         goto done2;
  926                 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec;
  927         }
  928 done2:
  929         mtx_unlock(&Giant);
  930         return (error);
  931 }
  932 

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