Now available: 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 * * 4 * Copyright (c) David L. Mills 1993-2001 * 5 * * 6 * Permission to use, copy, modify, and distribute this software and * 7 * its documentation for any purpose and without fee is hereby * 8 * granted, provided that the above copyright notice appears in all * 9 * copies and that both the copyright notice and this permission * 10 * notice appear in supporting documentation, and that the name * 11 * University of Delaware not be used in advertising or publicity * 12 * pertaining to distribution of the software without specific, * 13 * written prior permission. The University of Delaware makes no * 14 * representations about the suitability this software for any * 15 * purpose. It is provided "as is" without express or implied * 16 * warranty. * 17 * * 18 **********************************************************************/ 19 20 /* 21 * Adapted from the original sources for FreeBSD and timecounters by: 22 * Poul-Henning Kamp <phk@FreeBSD.org>. 23 * 24 * The 32bit version of the "LP" macros seems a bit past its "sell by" 25 * date so I have retained only the 64bit version and included it directly 26 * in this file. 27 * 28 * Only minor changes done to interface with the timecounters over in 29 * sys/kern/kern_clock.c. Some of the comments below may be (even more) 30 * confusing and/or plain wrong in that context. 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include "opt_ntp.h" 37 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/sysproto.h> 41 #include <sys/eventhandler.h> 42 #include <sys/kernel.h> 43 #include <sys/priv.h> 44 #include <sys/proc.h> 45 #include <sys/lock.h> 46 #include <sys/mutex.h> 47 #include <sys/time.h> 48 #include <sys/timex.h> 49 #include <sys/timetc.h> 50 #include <sys/timepps.h> 51 #include <sys/syscallsubr.h> 52 #include <sys/sysctl.h> 53 54 #ifdef PPS_SYNC 55 FEATURE(pps_sync, "Support usage of external PPS signal by kernel PLL"); 56 #endif 57 58 /* 59 * Single-precision macros for 64-bit machines 60 */ 61 typedef int64_t l_fp; 62 #define L_ADD(v, u) ((v) += (u)) 63 #define L_SUB(v, u) ((v) -= (u)) 64 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 65 #define L_NEG(v) ((v) = -(v)) 66 #define L_RSHIFT(v, n) \ 67 do { \ 68 if ((v) < 0) \ 69 (v) = -(-(v) >> (n)); \ 70 else \ 71 (v) = (v) >> (n); \ 72 } while (0) 73 #define L_MPY(v, a) ((v) *= (a)) 74 #define L_CLR(v) ((v) = 0) 75 #define L_ISNEG(v) ((v) < 0) 76 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 77 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 78 79 /* 80 * Generic NTP kernel interface 81 * 82 * These routines constitute the Network Time Protocol (NTP) interfaces 83 * for user and daemon application programs. The ntp_gettime() routine 84 * provides the time, maximum error (synch distance) and estimated error 85 * (dispersion) to client user application programs. The ntp_adjtime() 86 * routine is used by the NTP daemon to adjust the system clock to an 87 * externally derived time. The time offset and related variables set by 88 * this routine are used by other routines in this module to adjust the 89 * phase and frequency of the clock discipline loop which controls the 90 * system clock. 91 * 92 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 93 * defined), the time at each tick interrupt is derived directly from 94 * the kernel time variable. When the kernel time is reckoned in 95 * microseconds, (NTP_NANO undefined), the time is derived from the 96 * kernel time variable together with a variable representing the 97 * leftover nanoseconds at the last tick interrupt. In either case, the 98 * current nanosecond time is reckoned from these values plus an 99 * interpolated value derived by the clock routines in another 100 * architecture-specific module. The interpolation can use either a 101 * dedicated counter or a processor cycle counter (PCC) implemented in 102 * some architectures. 103 * 104 * Note that all routines must run at priority splclock or higher. 105 */ 106 /* 107 * Phase/frequency-lock loop (PLL/FLL) definitions 108 * 109 * The nanosecond clock discipline uses two variable types, time 110 * variables and frequency variables. Both types are represented as 64- 111 * bit fixed-point quantities with the decimal point between two 32-bit 112 * halves. On a 32-bit machine, each half is represented as a single 113 * word and mathematical operations are done using multiple-precision 114 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 115 * used. 116 * 117 * A time variable is a signed 64-bit fixed-point number in ns and 118 * fraction. It represents the remaining time offset to be amortized 119 * over succeeding tick interrupts. The maximum time offset is about 120 * 0.5 s and the resolution is about 2.3e-10 ns. 121 * 122 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 123 * 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 1 124 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 * |s s s| ns | 126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 * | fraction | 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * 130 * A frequency variable is a signed 64-bit fixed-point number in ns/s 131 * and fraction. It represents the ns and fraction to be added to the 132 * kernel time variable at each second. The maximum frequency offset is 133 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 134 * 135 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 136 * 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 1 137 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 * |s s s s s s s s s s s s s| ns/s | 139 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 * | fraction | 141 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 */ 143 /* 144 * The following variables establish the state of the PLL/FLL and the 145 * residual time and frequency offset of the local clock. 146 */ 147 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 148 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 149 150 static int time_state = TIME_OK; /* clock state */ 151 int time_status = STA_UNSYNC; /* clock status bits */ 152 static long time_tai; /* TAI offset (s) */ 153 static long time_monitor; /* last time offset scaled (ns) */ 154 static long time_constant; /* poll interval (shift) (s) */ 155 static long time_precision = 1; /* clock precision (ns) */ 156 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 157 long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 158 static long time_reftime; /* uptime at last adjustment (s) */ 159 static l_fp time_offset; /* time offset (ns) */ 160 static l_fp time_freq; /* frequency offset (ns/s) */ 161 static l_fp time_adj; /* tick adjust (ns/s) */ 162 163 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 164 165 static struct mtx ntp_lock; 166 MTX_SYSINIT(ntp, &ntp_lock, "ntp", MTX_SPIN); 167 168 #define NTP_LOCK() mtx_lock_spin(&ntp_lock) 169 #define NTP_UNLOCK() mtx_unlock_spin(&ntp_lock) 170 #define NTP_ASSERT_LOCKED() mtx_assert(&ntp_lock, MA_OWNED) 171 172 #ifdef PPS_SYNC 173 /* 174 * The following variables are used when a pulse-per-second (PPS) signal 175 * is available and connected via a modem control lead. They establish 176 * the engineering parameters of the clock discipline loop when 177 * controlled by the PPS signal. 178 */ 179 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 180 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 181 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 182 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 183 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 184 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 185 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 186 187 static struct timespec pps_tf[3]; /* phase median filter */ 188 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 189 static long pps_fcount; /* frequency accumulator */ 190 static long pps_jitter; /* nominal jitter (ns) */ 191 static long pps_stabil; /* nominal stability (scaled ns/s) */ 192 static long pps_lastsec; /* time at last calibration (s) */ 193 static int pps_valid; /* signal watchdog counter */ 194 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 195 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 196 static int pps_intcnt; /* wander counter */ 197 198 /* 199 * PPS signal quality monitors 200 */ 201 static long pps_calcnt; /* calibration intervals */ 202 static long pps_jitcnt; /* jitter limit exceeded */ 203 static long pps_stbcnt; /* stability limit exceeded */ 204 static long pps_errcnt; /* calibration errors */ 205 #endif /* PPS_SYNC */ 206 /* 207 * End of phase/frequency-lock loop (PLL/FLL) definitions 208 */ 209 210 static void ntp_init(void); 211 static void hardupdate(long offset); 212 static void ntp_gettime1(struct ntptimeval *ntvp); 213 static bool ntp_is_time_error(int tsl); 214 215 static bool 216 ntp_is_time_error(int tsl) 217 { 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 ((tsl & (STA_UNSYNC | STA_CLOCKERR)) || 228 229 /* 230 * PPS signal lost when either time or frequency synchronization 231 * requested 232 */ 233 (tsl & (STA_PPSFREQ | STA_PPSTIME) && 234 !(tsl & STA_PPSSIGNAL)) || 235 236 /* 237 * PPS jitter exceeded when time synchronization requested 238 */ 239 (tsl & STA_PPSTIME && tsl & STA_PPSJITTER) || 240 241 /* 242 * PPS wander exceeded or calibration error when frequency 243 * synchronization requested 244 */ 245 (tsl & STA_PPSFREQ && 246 tsl & (STA_PPSWANDER | STA_PPSERROR))) 247 return (true); 248 249 return (false); 250 } 251 252 static void 253 ntp_gettime1(struct ntptimeval *ntvp) 254 { 255 struct timespec atv; /* nanosecond time */ 256 257 NTP_ASSERT_LOCKED(); 258 259 nanotime(&atv); 260 ntvp->time.tv_sec = atv.tv_sec; 261 ntvp->time.tv_nsec = atv.tv_nsec; 262 ntvp->maxerror = time_maxerror; 263 ntvp->esterror = time_esterror; 264 ntvp->tai = time_tai; 265 ntvp->time_state = time_state; 266 267 if (ntp_is_time_error(time_status)) 268 ntvp->time_state = TIME_ERROR; 269 } 270 271 /* 272 * ntp_gettime() - NTP user application interface 273 * 274 * See the timex.h header file for synopsis and API description. Note that 275 * the TAI offset is returned in the ntvtimeval.tai structure member. 276 */ 277 #ifndef _SYS_SYSPROTO_H_ 278 struct ntp_gettime_args { 279 struct ntptimeval *ntvp; 280 }; 281 #endif 282 /* ARGSUSED */ 283 int 284 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap) 285 { 286 struct ntptimeval ntv; 287 288 memset(&ntv, 0, sizeof(ntv)); 289 290 NTP_LOCK(); 291 ntp_gettime1(&ntv); 292 NTP_UNLOCK(); 293 294 td->td_retval[0] = ntv.time_state; 295 return (copyout(&ntv, uap->ntvp, sizeof(ntv))); 296 } 297 298 static int 299 ntp_sysctl(SYSCTL_HANDLER_ARGS) 300 { 301 struct ntptimeval ntv; /* temporary structure */ 302 303 memset(&ntv, 0, sizeof(ntv)); 304 305 NTP_LOCK(); 306 ntp_gettime1(&ntv); 307 NTP_UNLOCK(); 308 309 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req)); 310 } 311 312 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 313 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE | CTLFLAG_RD | 314 CTLFLAG_MPSAFE, 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", 315 ""); 316 317 #ifdef PPS_SYNC 318 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, 319 &pps_shiftmax, 0, "Max interval duration (sec) (shift)"); 320 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, 321 &pps_shift, 0, "Interval duration (sec) (shift)"); 322 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, 323 &time_monitor, 0, "Last time offset scaled (ns)"); 324 325 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD | CTLFLAG_MPSAFE, 326 &pps_freq, 0, 327 "Scaled frequency offset (ns/sec)"); 328 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD | CTLFLAG_MPSAFE, 329 &time_freq, 0, 330 "Frequency offset (ns/sec)"); 331 #endif 332 333 /* 334 * ntp_adjtime() - NTP daemon application interface 335 * 336 * See the timex.h header file for synopsis and API description. Note that 337 * the timex.constant structure member has a dual purpose to set the time 338 * constant and to set the TAI offset. 339 */ 340 int 341 kern_ntp_adjtime(struct thread *td, struct timex *ntv, int *retvalp) 342 { 343 long freq; /* frequency ns/s) */ 344 int modes; /* mode bits from structure */ 345 int error, retval; 346 347 /* 348 * Update selected clock variables - only the superuser can 349 * change anything. Note that there is no error checking here on 350 * the assumption the superuser should know what it is doing. 351 * Note that either the time constant or TAI offset are loaded 352 * from the ntv.constant member, depending on the mode bits. If 353 * the STA_PLL bit in the status word is cleared, the state and 354 * status words are reset to the initial values at boot. 355 */ 356 modes = ntv->modes; 357 error = 0; 358 if (modes) 359 error = priv_check(td, PRIV_NTP_ADJTIME); 360 if (error != 0) 361 return (error); 362 NTP_LOCK(); 363 if (modes & MOD_MAXERROR) 364 time_maxerror = ntv->maxerror; 365 if (modes & MOD_ESTERROR) 366 time_esterror = ntv->esterror; 367 if (modes & MOD_STATUS) { 368 if (time_status & STA_PLL && !(ntv->status & STA_PLL)) { 369 time_state = TIME_OK; 370 time_status = STA_UNSYNC; 371 #ifdef PPS_SYNC 372 pps_shift = PPS_FAVG; 373 #endif /* PPS_SYNC */ 374 } 375 time_status &= STA_RONLY; 376 time_status |= ntv->status & ~STA_RONLY; 377 } 378 if (modes & MOD_TIMECONST) { 379 if (ntv->constant < 0) 380 time_constant = 0; 381 else if (ntv->constant > MAXTC) 382 time_constant = MAXTC; 383 else 384 time_constant = ntv->constant; 385 } 386 if (modes & MOD_TAI) { 387 if (ntv->constant > 0) /* XXX zero & negative numbers ? */ 388 time_tai = ntv->constant; 389 } 390 #ifdef PPS_SYNC 391 if (modes & MOD_PPSMAX) { 392 if (ntv->shift < PPS_FAVG) 393 pps_shiftmax = PPS_FAVG; 394 else if (ntv->shift > PPS_FAVGMAX) 395 pps_shiftmax = PPS_FAVGMAX; 396 else 397 pps_shiftmax = ntv->shift; 398 } 399 #endif /* PPS_SYNC */ 400 if (modes & MOD_NANO) 401 time_status |= STA_NANO; 402 if (modes & MOD_MICRO) 403 time_status &= ~STA_NANO; 404 if (modes & MOD_CLKB) 405 time_status |= STA_CLK; 406 if (modes & MOD_CLKA) 407 time_status &= ~STA_CLK; 408 if (modes & MOD_FREQUENCY) { 409 freq = (ntv->freq * 1000LL) >> 16; 410 if (freq > MAXFREQ) 411 L_LINT(time_freq, MAXFREQ); 412 else if (freq < -MAXFREQ) 413 L_LINT(time_freq, -MAXFREQ); 414 else { 415 /* 416 * ntv->freq is [PPM * 2^16] = [us/s * 2^16] 417 * time_freq is [ns/s * 2^32] 418 */ 419 time_freq = ntv->freq * 1000LL * 65536LL; 420 } 421 #ifdef PPS_SYNC 422 pps_freq = time_freq; 423 #endif /* PPS_SYNC */ 424 } 425 if (modes & MOD_OFFSET) { 426 if (time_status & STA_NANO) 427 hardupdate(ntv->offset); 428 else 429 hardupdate(ntv->offset * 1000); 430 } 431 432 /* 433 * Retrieve all clock variables. Note that the TAI offset is 434 * returned only by ntp_gettime(); 435 */ 436 if (time_status & STA_NANO) 437 ntv->offset = L_GINT(time_offset); 438 else 439 ntv->offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 440 ntv->freq = L_GINT((time_freq / 1000LL) << 16); 441 ntv->maxerror = time_maxerror; 442 ntv->esterror = time_esterror; 443 ntv->status = time_status; 444 ntv->constant = time_constant; 445 if (time_status & STA_NANO) 446 ntv->precision = time_precision; 447 else 448 ntv->precision = time_precision / 1000; 449 ntv->tolerance = MAXFREQ * SCALE_PPM; 450 #ifdef PPS_SYNC 451 ntv->shift = pps_shift; 452 ntv->ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 453 if (time_status & STA_NANO) 454 ntv->jitter = pps_jitter; 455 else 456 ntv->jitter = pps_jitter / 1000; 457 ntv->stabil = pps_stabil; 458 ntv->calcnt = pps_calcnt; 459 ntv->errcnt = pps_errcnt; 460 ntv->jitcnt = pps_jitcnt; 461 ntv->stbcnt = pps_stbcnt; 462 #endif /* PPS_SYNC */ 463 retval = ntp_is_time_error(time_status) ? TIME_ERROR : time_state; 464 NTP_UNLOCK(); 465 466 *retvalp = retval; 467 return (0); 468 } 469 470 #ifndef _SYS_SYSPROTO_H_ 471 struct ntp_adjtime_args { 472 struct timex *tp; 473 }; 474 #endif 475 476 int 477 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 478 { 479 struct timex ntv; 480 int error, retval; 481 482 error = copyin(uap->tp, &ntv, sizeof(ntv)); 483 if (error == 0) { 484 error = kern_ntp_adjtime(td, &ntv, &retval); 485 if (error == 0) { 486 error = copyout(&ntv, uap->tp, sizeof(ntv)); 487 if (error == 0) 488 td->td_retval[0] = retval; 489 } 490 } 491 return (error); 492 } 493 494 /* 495 * second_overflow() - called after ntp_tick_adjust() 496 * 497 * This routine is ordinarily called immediately following the above 498 * routine ntp_tick_adjust(). While these two routines are normally 499 * combined, they are separated here only for the purposes of 500 * simulation. 501 */ 502 void 503 ntp_update_second(int64_t *adjustment, time_t *newsec) 504 { 505 int tickrate; 506 l_fp ftemp; /* 32/64-bit temporary */ 507 508 NTP_LOCK(); 509 510 /* 511 * On rollover of the second both the nanosecond and microsecond 512 * clocks are updated and the state machine cranked as 513 * necessary. The phase adjustment to be used for the next 514 * second is calculated and the maximum error is increased by 515 * the tolerance. 516 */ 517 time_maxerror += MAXFREQ / 1000; 518 519 /* 520 * Leap second processing. If in leap-insert state at 521 * the end of the day, the system clock is set back one 522 * second; if in leap-delete state, the system clock is 523 * set ahead one second. The nano_time() routine or 524 * external clock driver will insure that reported time 525 * is always monotonic. 526 */ 527 switch (time_state) { 528 529 /* 530 * No warning. 531 */ 532 case TIME_OK: 533 if (time_status & STA_INS) 534 time_state = TIME_INS; 535 else if (time_status & STA_DEL) 536 time_state = TIME_DEL; 537 break; 538 539 /* 540 * Insert second 23:59:60 following second 541 * 23:59:59. 542 */ 543 case TIME_INS: 544 if (!(time_status & STA_INS)) 545 time_state = TIME_OK; 546 else if ((*newsec) % 86400 == 0) { 547 (*newsec)--; 548 time_state = TIME_OOP; 549 time_tai++; 550 } 551 break; 552 553 /* 554 * Delete second 23:59:59. 555 */ 556 case TIME_DEL: 557 if (!(time_status & STA_DEL)) 558 time_state = TIME_OK; 559 else if (((*newsec) + 1) % 86400 == 0) { 560 (*newsec)++; 561 time_tai--; 562 time_state = TIME_WAIT; 563 } 564 break; 565 566 /* 567 * Insert second in progress. 568 */ 569 case TIME_OOP: 570 time_state = TIME_WAIT; 571 break; 572 573 /* 574 * Wait for status bits to clear. 575 */ 576 case TIME_WAIT: 577 if (!(time_status & (STA_INS | STA_DEL))) 578 time_state = TIME_OK; 579 } 580 581 /* 582 * Compute the total time adjustment for the next second 583 * in ns. The offset is reduced by a factor depending on 584 * whether the PPS signal is operating. Note that the 585 * value is in effect scaled by the clock frequency, 586 * since the adjustment is added at each tick interrupt. 587 */ 588 ftemp = time_offset; 589 #ifdef PPS_SYNC 590 /* XXX even if PPS signal dies we should finish adjustment ? */ 591 if (time_status & STA_PPSTIME && time_status & 592 STA_PPSSIGNAL) 593 L_RSHIFT(ftemp, pps_shift); 594 else 595 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 596 #else 597 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 598 #endif /* PPS_SYNC */ 599 time_adj = ftemp; 600 L_SUB(time_offset, ftemp); 601 L_ADD(time_adj, time_freq); 602 603 /* 604 * Apply any correction from adjtime(2). If more than one second 605 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500 PPM) 606 * until the last second is slewed the final < 500 usecs. 607 */ 608 if (time_adjtime != 0) { 609 if (time_adjtime > 1000000) 610 tickrate = 5000; 611 else if (time_adjtime < -1000000) 612 tickrate = -5000; 613 else if (time_adjtime > 500) 614 tickrate = 500; 615 else if (time_adjtime < -500) 616 tickrate = -500; 617 else 618 tickrate = time_adjtime; 619 time_adjtime -= tickrate; 620 L_LINT(ftemp, tickrate * 1000); 621 L_ADD(time_adj, ftemp); 622 } 623 *adjustment = time_adj; 624 625 #ifdef PPS_SYNC 626 if (pps_valid > 0) 627 pps_valid--; 628 else 629 time_status &= ~STA_PPSSIGNAL; 630 #endif /* PPS_SYNC */ 631 632 NTP_UNLOCK(); 633 } 634 635 /* 636 * ntp_init() - initialize variables and structures 637 * 638 * This routine must be called after the kernel variables hz and tick 639 * are set or changed and before the next tick interrupt. In this 640 * particular implementation, these values are assumed set elsewhere in 641 * the kernel. The design allows the clock frequency and tick interval 642 * to be changed while the system is running. So, this routine should 643 * probably be integrated with the code that does that. 644 */ 645 static void 646 ntp_init(void) 647 { 648 649 /* 650 * The following variables are initialized only at startup. Only 651 * those structures not cleared by the compiler need to be 652 * initialized, and these only in the simulator. In the actual 653 * kernel, any nonzero values here will quickly evaporate. 654 */ 655 L_CLR(time_offset); 656 L_CLR(time_freq); 657 #ifdef PPS_SYNC 658 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 659 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 660 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 661 pps_fcount = 0; 662 L_CLR(pps_freq); 663 #endif /* PPS_SYNC */ 664 } 665 666 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL); 667 668 /* 669 * hardupdate() - local clock update 670 * 671 * This routine is called by ntp_adjtime() to update the local clock 672 * phase and frequency. The implementation is of an adaptive-parameter, 673 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 674 * time and frequency offset estimates for each call. If the kernel PPS 675 * discipline code is configured (PPS_SYNC), the PPS signal itself 676 * determines the new time offset, instead of the calling argument. 677 * Presumably, calls to ntp_adjtime() occur only when the caller 678 * believes the local clock is valid within some bound (+-128 ms with 679 * NTP). If the caller's time is far different than the PPS time, an 680 * argument will ensue, and it's not clear who will lose. 681 * 682 * For uncompensated quartz crystal oscillators and nominal update 683 * intervals less than 256 s, operation should be in phase-lock mode, 684 * where the loop is disciplined to phase. For update intervals greater 685 * than 1024 s, operation should be in frequency-lock mode, where the 686 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 687 * is selected by the STA_MODE status bit. 688 */ 689 static void 690 hardupdate(offset) 691 long offset; /* clock offset (ns) */ 692 { 693 long mtemp; 694 l_fp ftemp; 695 696 NTP_ASSERT_LOCKED(); 697 698 /* 699 * Select how the phase is to be controlled and from which 700 * source. If the PPS signal is present and enabled to 701 * discipline the time, the PPS offset is used; otherwise, the 702 * argument offset is used. 703 */ 704 if (!(time_status & STA_PLL)) 705 return; 706 if (!(time_status & STA_PPSTIME && time_status & 707 STA_PPSSIGNAL)) { 708 if (offset > MAXPHASE) 709 time_monitor = MAXPHASE; 710 else if (offset < -MAXPHASE) 711 time_monitor = -MAXPHASE; 712 else 713 time_monitor = offset; 714 L_LINT(time_offset, time_monitor); 715 } 716 717 /* 718 * Select how the frequency is to be controlled and in which 719 * mode (PLL or FLL). If the PPS signal is present and enabled 720 * to discipline the frequency, the PPS frequency is used; 721 * otherwise, the argument offset is used to compute it. 722 */ 723 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 724 time_reftime = time_uptime; 725 return; 726 } 727 if (time_status & STA_FREQHOLD || time_reftime == 0) 728 time_reftime = time_uptime; 729 mtemp = time_uptime - time_reftime; 730 L_LINT(ftemp, time_monitor); 731 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 732 L_MPY(ftemp, mtemp); 733 L_ADD(time_freq, ftemp); 734 time_status &= ~STA_MODE; 735 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 736 MAXSEC)) { 737 L_LINT(ftemp, (time_monitor << 4) / mtemp); 738 L_RSHIFT(ftemp, SHIFT_FLL + 4); 739 L_ADD(time_freq, ftemp); 740 time_status |= STA_MODE; 741 } 742 time_reftime = time_uptime; 743 if (L_GINT(time_freq) > MAXFREQ) 744 L_LINT(time_freq, MAXFREQ); 745 else if (L_GINT(time_freq) < -MAXFREQ) 746 L_LINT(time_freq, -MAXFREQ); 747 } 748 749 #ifdef PPS_SYNC 750 /* 751 * hardpps() - discipline CPU clock oscillator to external PPS signal 752 * 753 * This routine is called at each PPS interrupt in order to discipline 754 * the CPU clock oscillator to the PPS signal. There are two independent 755 * first-order feedback loops, one for the phase, the other for the 756 * frequency. The phase loop measures and grooms the PPS phase offset 757 * and leaves it in a handy spot for the seconds overflow routine. The 758 * frequency loop averages successive PPS phase differences and 759 * calculates the PPS frequency offset, which is also processed by the 760 * seconds overflow routine. The code requires the caller to capture the 761 * time and architecture-dependent hardware counter values in 762 * nanoseconds at the on-time PPS signal transition. 763 * 764 * Note that, on some Unix systems this routine runs at an interrupt 765 * priority level higher than the timer interrupt routine hardclock(). 766 * Therefore, the variables used are distinct from the hardclock() 767 * variables, except for the actual time and frequency variables, which 768 * are determined by this routine and updated atomically. 769 * 770 * tsp - time at PPS 771 * nsec - hardware counter at PPS 772 */ 773 void 774 hardpps(struct timespec *tsp, long nsec) 775 { 776 long u_sec, u_nsec, v_nsec; /* temps */ 777 l_fp ftemp; 778 779 NTP_LOCK(); 780 781 /* 782 * The signal is first processed by a range gate and frequency 783 * discriminator. The range gate rejects noise spikes outside 784 * the range +-500 us. The frequency discriminator rejects input 785 * signals with apparent frequency outside the range 1 +-500 786 * PPM. If two hits occur in the same second, we ignore the 787 * later hit; if not and a hit occurs outside the range gate, 788 * keep the later hit for later comparison, but do not process 789 * it. 790 */ 791 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 792 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 793 pps_valid = PPS_VALID; 794 u_sec = tsp->tv_sec; 795 u_nsec = tsp->tv_nsec; 796 if (u_nsec >= (NANOSECOND >> 1)) { 797 u_nsec -= NANOSECOND; 798 u_sec++; 799 } 800 v_nsec = u_nsec - pps_tf[0].tv_nsec; 801 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - MAXFREQ) 802 goto out; 803 pps_tf[2] = pps_tf[1]; 804 pps_tf[1] = pps_tf[0]; 805 pps_tf[0].tv_sec = u_sec; 806 pps_tf[0].tv_nsec = u_nsec; 807 808 /* 809 * Compute the difference between the current and previous 810 * counter values. If the difference exceeds 0.5 s, assume it 811 * has wrapped around, so correct 1.0 s. If the result exceeds 812 * the tick interval, the sample point has crossed a tick 813 * boundary during the last second, so correct the tick. Very 814 * intricate. 815 */ 816 u_nsec = nsec; 817 if (u_nsec > (NANOSECOND >> 1)) 818 u_nsec -= NANOSECOND; 819 else if (u_nsec < -(NANOSECOND >> 1)) 820 u_nsec += NANOSECOND; 821 pps_fcount += u_nsec; 822 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 823 goto out; 824 time_status &= ~STA_PPSJITTER; 825 826 /* 827 * A three-stage median filter is used to help denoise the PPS 828 * time. The median sample becomes the time offset estimate; the 829 * difference between the other two samples becomes the time 830 * dispersion (jitter) estimate. 831 */ 832 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 833 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 834 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 835 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 836 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 837 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 838 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 839 } else { 840 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 841 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 842 } 843 } else { 844 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 845 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 846 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 847 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 848 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 849 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 850 } else { 851 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 852 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 853 } 854 } 855 856 /* 857 * Nominal jitter is due to PPS signal noise and interrupt 858 * latency. If it exceeds the popcorn threshold, the sample is 859 * discarded. otherwise, if so enabled, the time offset is 860 * updated. We can tolerate a modest loss of data here without 861 * much degrading time accuracy. 862 * 863 * The measurements being checked here were made with the system 864 * timecounter, so the popcorn threshold is not allowed to fall below 865 * the number of nanoseconds in two ticks of the timecounter. For a 866 * timecounter running faster than 1 GHz the lower bound is 2ns, just 867 * to avoid a nonsensical threshold of zero. 868 */ 869 if (u_nsec > lmax(pps_jitter << PPS_POPCORN, 870 2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) { 871 time_status |= STA_PPSJITTER; 872 pps_jitcnt++; 873 } else if (time_status & STA_PPSTIME) { 874 time_monitor = -v_nsec; 875 L_LINT(time_offset, time_monitor); 876 } 877 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 878 u_sec = pps_tf[0].tv_sec - pps_lastsec; 879 if (u_sec < (1 << pps_shift)) 880 goto out; 881 882 /* 883 * At the end of the calibration interval the difference between 884 * the first and last counter values becomes the scaled 885 * frequency. It will later be divided by the length of the 886 * interval to determine the frequency update. If the frequency 887 * exceeds a sanity threshold, or if the actual calibration 888 * interval is not equal to the expected length, the data are 889 * discarded. We can tolerate a modest loss of data here without 890 * much degrading frequency accuracy. 891 */ 892 pps_calcnt++; 893 v_nsec = -pps_fcount; 894 pps_lastsec = pps_tf[0].tv_sec; 895 pps_fcount = 0; 896 u_nsec = MAXFREQ << pps_shift; 897 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << pps_shift)) { 898 time_status |= STA_PPSERROR; 899 pps_errcnt++; 900 goto out; 901 } 902 903 /* 904 * Here the raw frequency offset and wander (stability) is 905 * calculated. If the wander is less than the wander threshold 906 * for four consecutive averaging intervals, the interval is 907 * doubled; if it is greater than the threshold for four 908 * consecutive intervals, the interval is halved. The scaled 909 * frequency offset is converted to frequency offset. The 910 * stability metric is calculated as the average of recent 911 * frequency changes, but is used only for performance 912 * monitoring. 913 */ 914 L_LINT(ftemp, v_nsec); 915 L_RSHIFT(ftemp, pps_shift); 916 L_SUB(ftemp, pps_freq); 917 u_nsec = L_GINT(ftemp); 918 if (u_nsec > PPS_MAXWANDER) { 919 L_LINT(ftemp, PPS_MAXWANDER); 920 pps_intcnt--; 921 time_status |= STA_PPSWANDER; 922 pps_stbcnt++; 923 } else if (u_nsec < -PPS_MAXWANDER) { 924 L_LINT(ftemp, -PPS_MAXWANDER); 925 pps_intcnt--; 926 time_status |= STA_PPSWANDER; 927 pps_stbcnt++; 928 } else { 929 pps_intcnt++; 930 } 931 if (pps_intcnt >= 4) { 932 pps_intcnt = 4; 933 if (pps_shift < pps_shiftmax) { 934 pps_shift++; 935 pps_intcnt = 0; 936 } 937 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 938 pps_intcnt = -4; 939 if (pps_shift > PPS_FAVG) { 940 pps_shift--; 941 pps_intcnt = 0; 942 } 943 } 944 if (u_nsec < 0) 945 u_nsec = -u_nsec; 946 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 947 948 /* 949 * The PPS frequency is recalculated and clamped to the maximum 950 * MAXFREQ. If enabled, the system clock frequency is updated as 951 * well. 952 */ 953 L_ADD(pps_freq, ftemp); 954 u_nsec = L_GINT(pps_freq); 955 if (u_nsec > MAXFREQ) 956 L_LINT(pps_freq, MAXFREQ); 957 else if (u_nsec < -MAXFREQ) 958 L_LINT(pps_freq, -MAXFREQ); 959 if (time_status & STA_PPSFREQ) 960 time_freq = pps_freq; 961 962 out: 963 NTP_UNLOCK(); 964 } 965 #endif /* PPS_SYNC */ 966 967 #ifndef _SYS_SYSPROTO_H_ 968 struct adjtime_args { 969 struct timeval *delta; 970 struct timeval *olddelta; 971 }; 972 #endif 973 /* ARGSUSED */ 974 int 975 sys_adjtime(struct thread *td, struct adjtime_args *uap) 976 { 977 struct timeval delta, olddelta, *deltap; 978 int error; 979 980 if (uap->delta) { 981 error = copyin(uap->delta, &delta, sizeof(delta)); 982 if (error) 983 return (error); 984 deltap = δ 985 } else 986 deltap = NULL; 987 error = kern_adjtime(td, deltap, &olddelta); 988 if (uap->olddelta && error == 0) 989 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta)); 990 return (error); 991 } 992 993 int 994 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta) 995 { 996 struct timeval atv; 997 int64_t ltr, ltw; 998 int error; 999 1000 if (delta != NULL) { 1001 error = priv_check(td, PRIV_ADJTIME); 1002 if (error != 0) 1003 return (error); 1004 ltw = (int64_t)delta->tv_sec * 1000000 + delta->tv_usec; 1005 } 1006 NTP_LOCK(); 1007 ltr = time_adjtime; 1008 if (delta != NULL) 1009 time_adjtime = ltw; 1010 NTP_UNLOCK(); 1011 if (olddelta != NULL) { 1012 atv.tv_sec = ltr / 1000000; 1013 atv.tv_usec = ltr % 1000000; 1014 if (atv.tv_usec < 0) { 1015 atv.tv_usec += 1000000; 1016 atv.tv_sec--; 1017 } 1018 *olddelta = atv; 1019 } 1020 return (0); 1021 } 1022 1023 static struct callout resettodr_callout; 1024 static int resettodr_period = 1800; 1025 1026 static void 1027 periodic_resettodr(void *arg __unused) 1028 { 1029 1030 /* 1031 * Read of time_status is lock-less, which is fine since 1032 * ntp_is_time_error() operates on the consistent read value. 1033 */ 1034 if (!ntp_is_time_error(time_status)) 1035 resettodr(); 1036 if (resettodr_period > 0) 1037 callout_schedule(&resettodr_callout, resettodr_period * hz); 1038 } 1039 1040 static void 1041 shutdown_resettodr(void *arg __unused, int howto __unused) 1042 { 1043 1044 callout_drain(&resettodr_callout); 1045 /* Another unlocked read of time_status */ 1046 if (resettodr_period > 0 && !ntp_is_time_error(time_status)) 1047 resettodr(); 1048 } 1049 1050 static int 1051 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS) 1052 { 1053 int error; 1054 1055 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req); 1056 if (error || !req->newptr) 1057 return (error); 1058 if (cold) 1059 goto done; 1060 if (resettodr_period == 0) 1061 callout_stop(&resettodr_callout); 1062 else 1063 callout_reset(&resettodr_callout, resettodr_period * hz, 1064 periodic_resettodr, NULL); 1065 done: 1066 return (0); 1067 } 1068 1069 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT | CTLFLAG_RWTUN | 1070 CTLFLAG_MPSAFE, &resettodr_period, 1800, sysctl_resettodr_period, "I", 1071 "Save system time to RTC with this period (in seconds)"); 1072 1073 static void 1074 start_periodic_resettodr(void *arg __unused) 1075 { 1076 1077 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL, 1078 SHUTDOWN_PRI_FIRST); 1079 callout_init(&resettodr_callout, 1); 1080 if (resettodr_period == 0) 1081 return; 1082 callout_reset(&resettodr_callout, resettodr_period * hz, 1083 periodic_resettodr, NULL); 1084 } 1085 1086 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE, 1087 start_periodic_resettodr, NULL);
Cache object: a11fa26cd1b368ca64fd338992a5eeea
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