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/kernel.h> 42 #include <sys/priv.h> 43 #include <sys/proc.h> 44 #include <sys/lock.h> 45 #include <sys/mutex.h> 46 #include <sys/time.h> 47 #include <sys/timex.h> 48 #include <sys/timetc.h> 49 #include <sys/timepps.h> 50 #include <sys/syscallsubr.h> 51 #include <sys/sysctl.h> 52 53 /* 54 * Single-precision macros for 64-bit machines 55 */ 56 typedef int64_t l_fp; 57 #define L_ADD(v, u) ((v) += (u)) 58 #define L_SUB(v, u) ((v) -= (u)) 59 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 60 #define L_NEG(v) ((v) = -(v)) 61 #define L_RSHIFT(v, n) \ 62 do { \ 63 if ((v) < 0) \ 64 (v) = -(-(v) >> (n)); \ 65 else \ 66 (v) = (v) >> (n); \ 67 } while (0) 68 #define L_MPY(v, a) ((v) *= (a)) 69 #define L_CLR(v) ((v) = 0) 70 #define L_ISNEG(v) ((v) < 0) 71 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 72 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 73 74 /* 75 * Generic NTP kernel interface 76 * 77 * These routines constitute the Network Time Protocol (NTP) interfaces 78 * for user and daemon application programs. The ntp_gettime() routine 79 * provides the time, maximum error (synch distance) and estimated error 80 * (dispersion) to client user application programs. The ntp_adjtime() 81 * routine is used by the NTP daemon to adjust the system clock to an 82 * externally derived time. The time offset and related variables set by 83 * this routine are used by other routines in this module to adjust the 84 * phase and frequency of the clock discipline loop which controls the 85 * system clock. 86 * 87 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 88 * defined), the time at each tick interrupt is derived directly from 89 * the kernel time variable. When the kernel time is reckoned in 90 * microseconds, (NTP_NANO undefined), the time is derived from the 91 * kernel time variable together with a variable representing the 92 * leftover nanoseconds at the last tick interrupt. In either case, the 93 * current nanosecond time is reckoned from these values plus an 94 * interpolated value derived by the clock routines in another 95 * architecture-specific module. The interpolation can use either a 96 * dedicated counter or a processor cycle counter (PCC) implemented in 97 * some architectures. 98 * 99 * Note that all routines must run at priority splclock or higher. 100 */ 101 /* 102 * Phase/frequency-lock loop (PLL/FLL) definitions 103 * 104 * The nanosecond clock discipline uses two variable types, time 105 * variables and frequency variables. Both types are represented as 64- 106 * bit fixed-point quantities with the decimal point between two 32-bit 107 * halves. On a 32-bit machine, each half is represented as a single 108 * word and mathematical operations are done using multiple-precision 109 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 110 * used. 111 * 112 * A time variable is a signed 64-bit fixed-point number in ns and 113 * fraction. It represents the remaining time offset to be amortized 114 * over succeeding tick interrupts. The maximum time offset is about 115 * 0.5 s and the resolution is about 2.3e-10 ns. 116 * 117 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 118 * 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 1 119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 * |s s s| ns | 121 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 * | fraction | 123 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 124 * 125 * A frequency variable is a signed 64-bit fixed-point number in ns/s 126 * and fraction. It represents the ns and fraction to be added to the 127 * kernel time variable at each second. The maximum frequency offset is 128 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 129 * 130 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 131 * 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 1 132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 * |s s s s s s s s s s s s s| ns/s | 134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 * | fraction | 136 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 */ 138 /* 139 * The following variables establish the state of the PLL/FLL and the 140 * residual time and frequency offset of the local clock. 141 */ 142 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 143 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 144 145 static int time_state = TIME_OK; /* clock state */ 146 static int time_status = STA_UNSYNC; /* clock status bits */ 147 static long time_tai; /* TAI offset (s) */ 148 static long time_monitor; /* last time offset scaled (ns) */ 149 static long time_constant; /* poll interval (shift) (s) */ 150 static long time_precision = 1; /* clock precision (ns) */ 151 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 152 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 153 static long time_reftime; /* time at last adjustment (s) */ 154 static l_fp time_offset; /* time offset (ns) */ 155 static l_fp time_freq; /* frequency offset (ns/s) */ 156 static l_fp time_adj; /* tick adjust (ns/s) */ 157 158 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 159 160 #ifdef PPS_SYNC 161 /* 162 * The following variables are used when a pulse-per-second (PPS) signal 163 * is available and connected via a modem control lead. They establish 164 * the engineering parameters of the clock discipline loop when 165 * controlled by the PPS signal. 166 */ 167 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 168 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 169 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 170 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 171 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 172 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 173 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 174 175 static struct timespec pps_tf[3]; /* phase median filter */ 176 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 177 static long pps_fcount; /* frequency accumulator */ 178 static long pps_jitter; /* nominal jitter (ns) */ 179 static long pps_stabil; /* nominal stability (scaled ns/s) */ 180 static long pps_lastsec; /* time at last calibration (s) */ 181 static int pps_valid; /* signal watchdog counter */ 182 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 183 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 184 static int pps_intcnt; /* wander counter */ 185 186 /* 187 * PPS signal quality monitors 188 */ 189 static long pps_calcnt; /* calibration intervals */ 190 static long pps_jitcnt; /* jitter limit exceeded */ 191 static long pps_stbcnt; /* stability limit exceeded */ 192 static long pps_errcnt; /* calibration errors */ 193 #endif /* PPS_SYNC */ 194 /* 195 * End of phase/frequency-lock loop (PLL/FLL) definitions 196 */ 197 198 static void ntp_init(void); 199 static void hardupdate(long offset); 200 static void ntp_gettime1(struct ntptimeval *ntvp); 201 202 static void 203 ntp_gettime1(struct ntptimeval *ntvp) 204 { 205 struct timespec atv; /* nanosecond time */ 206 207 GIANT_REQUIRED; 208 209 nanotime(&atv); 210 ntvp->time.tv_sec = atv.tv_sec; 211 ntvp->time.tv_nsec = atv.tv_nsec; 212 ntvp->maxerror = time_maxerror; 213 ntvp->esterror = time_esterror; 214 ntvp->tai = time_tai; 215 ntvp->time_state = time_state; 216 217 /* 218 * Status word error decode. If any of these conditions occur, 219 * an error is returned, instead of the status word. Most 220 * applications will care only about the fact the system clock 221 * may not be trusted, not about the details. 222 * 223 * Hardware or software error 224 */ 225 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 226 227 /* 228 * PPS signal lost when either time or frequency synchronization 229 * requested 230 */ 231 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 232 !(time_status & STA_PPSSIGNAL)) || 233 234 /* 235 * PPS jitter exceeded when time synchronization requested 236 */ 237 (time_status & STA_PPSTIME && 238 time_status & STA_PPSJITTER) || 239 240 /* 241 * PPS wander exceeded or calibration error when frequency 242 * synchronization requested 243 */ 244 (time_status & STA_PPSFREQ && 245 time_status & (STA_PPSWANDER | STA_PPSERROR))) 246 ntvp->time_state = TIME_ERROR; 247 } 248 249 /* 250 * ntp_gettime() - NTP user application interface 251 * 252 * See the timex.h header file for synopsis and API description. Note that 253 * the TAI offset is returned in the ntvtimeval.tai structure member. 254 */ 255 #ifndef _SYS_SYSPROTO_H_ 256 struct ntp_gettime_args { 257 struct ntptimeval *ntvp; 258 }; 259 #endif 260 /* ARGSUSED */ 261 int 262 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap) 263 { 264 struct ntptimeval ntv; 265 266 mtx_lock(&Giant); 267 ntp_gettime1(&ntv); 268 mtx_unlock(&Giant); 269 270 td->td_retval[0] = ntv.time_state; 271 return (copyout(&ntv, uap->ntvp, sizeof(ntv))); 272 } 273 274 static int 275 ntp_sysctl(SYSCTL_HANDLER_ARGS) 276 { 277 struct ntptimeval ntv; /* temporary structure */ 278 279 ntp_gettime1(&ntv); 280 281 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req)); 282 } 283 284 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 285 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 286 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 287 288 #ifdef PPS_SYNC 289 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 290 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 291 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 292 293 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 294 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 295 #endif 296 297 /* 298 * ntp_adjtime() - NTP daemon application interface 299 * 300 * See the timex.h header file for synopsis and API description. Note that 301 * the timex.constant structure member has a dual purpose to set the time 302 * constant and to set the TAI offset. 303 */ 304 #ifndef _SYS_SYSPROTO_H_ 305 struct ntp_adjtime_args { 306 struct timex *tp; 307 }; 308 #endif 309 310 int 311 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 312 { 313 struct timex ntv; /* temporary structure */ 314 long freq; /* frequency ns/s) */ 315 int modes; /* mode bits from structure */ 316 int s; /* caller priority */ 317 int error; 318 319 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 320 if (error) 321 return(error); 322 323 /* 324 * Update selected clock variables - only the superuser can 325 * change anything. Note that there is no error checking here on 326 * the assumption the superuser should know what it is doing. 327 * Note that either the time constant or TAI offset are loaded 328 * from the ntv.constant member, depending on the mode bits. If 329 * the STA_PLL bit in the status word is cleared, the state and 330 * status words are reset to the initial values at boot. 331 */ 332 mtx_lock(&Giant); 333 modes = ntv.modes; 334 if (modes) 335 error = priv_check(td, PRIV_NTP_ADJTIME); 336 if (error) 337 goto done2; 338 s = splclock(); 339 if (modes & MOD_MAXERROR) 340 time_maxerror = ntv.maxerror; 341 if (modes & MOD_ESTERROR) 342 time_esterror = ntv.esterror; 343 if (modes & MOD_STATUS) { 344 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 345 time_state = TIME_OK; 346 time_status = STA_UNSYNC; 347 #ifdef PPS_SYNC 348 pps_shift = PPS_FAVG; 349 #endif /* PPS_SYNC */ 350 } 351 time_status &= STA_RONLY; 352 time_status |= ntv.status & ~STA_RONLY; 353 } 354 if (modes & MOD_TIMECONST) { 355 if (ntv.constant < 0) 356 time_constant = 0; 357 else if (ntv.constant > MAXTC) 358 time_constant = MAXTC; 359 else 360 time_constant = ntv.constant; 361 } 362 if (modes & MOD_TAI) { 363 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 364 time_tai = ntv.constant; 365 } 366 #ifdef PPS_SYNC 367 if (modes & MOD_PPSMAX) { 368 if (ntv.shift < PPS_FAVG) 369 pps_shiftmax = PPS_FAVG; 370 else if (ntv.shift > PPS_FAVGMAX) 371 pps_shiftmax = PPS_FAVGMAX; 372 else 373 pps_shiftmax = ntv.shift; 374 } 375 #endif /* PPS_SYNC */ 376 if (modes & MOD_NANO) 377 time_status |= STA_NANO; 378 if (modes & MOD_MICRO) 379 time_status &= ~STA_NANO; 380 if (modes & MOD_CLKB) 381 time_status |= STA_CLK; 382 if (modes & MOD_CLKA) 383 time_status &= ~STA_CLK; 384 if (modes & MOD_FREQUENCY) { 385 freq = (ntv.freq * 1000LL) >> 16; 386 if (freq > MAXFREQ) 387 L_LINT(time_freq, MAXFREQ); 388 else if (freq < -MAXFREQ) 389 L_LINT(time_freq, -MAXFREQ); 390 else { 391 /* 392 * ntv.freq is [PPM * 2^16] = [us/s * 2^16] 393 * time_freq is [ns/s * 2^32] 394 */ 395 time_freq = ntv.freq * 1000LL * 65536LL; 396 } 397 #ifdef PPS_SYNC 398 pps_freq = time_freq; 399 #endif /* PPS_SYNC */ 400 } 401 if (modes & MOD_OFFSET) { 402 if (time_status & STA_NANO) 403 hardupdate(ntv.offset); 404 else 405 hardupdate(ntv.offset * 1000); 406 } 407 408 /* 409 * Retrieve all clock variables. Note that the TAI offset is 410 * returned only by ntp_gettime(); 411 */ 412 if (time_status & STA_NANO) 413 ntv.offset = L_GINT(time_offset); 414 else 415 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 416 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 417 ntv.maxerror = time_maxerror; 418 ntv.esterror = time_esterror; 419 ntv.status = time_status; 420 ntv.constant = time_constant; 421 if (time_status & STA_NANO) 422 ntv.precision = time_precision; 423 else 424 ntv.precision = time_precision / 1000; 425 ntv.tolerance = MAXFREQ * SCALE_PPM; 426 #ifdef PPS_SYNC 427 ntv.shift = pps_shift; 428 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 429 if (time_status & STA_NANO) 430 ntv.jitter = pps_jitter; 431 else 432 ntv.jitter = pps_jitter / 1000; 433 ntv.stabil = pps_stabil; 434 ntv.calcnt = pps_calcnt; 435 ntv.errcnt = pps_errcnt; 436 ntv.jitcnt = pps_jitcnt; 437 ntv.stbcnt = pps_stbcnt; 438 #endif /* PPS_SYNC */ 439 splx(s); 440 441 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 442 if (error) 443 goto done2; 444 445 /* 446 * Status word error decode. See comments in 447 * ntp_gettime() routine. 448 */ 449 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 450 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 451 !(time_status & STA_PPSSIGNAL)) || 452 (time_status & STA_PPSTIME && 453 time_status & STA_PPSJITTER) || 454 (time_status & STA_PPSFREQ && 455 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 456 td->td_retval[0] = TIME_ERROR; 457 } else { 458 td->td_retval[0] = time_state; 459 } 460 done2: 461 mtx_unlock(&Giant); 462 return (error); 463 } 464 465 /* 466 * second_overflow() - called after ntp_tick_adjust() 467 * 468 * This routine is ordinarily called immediately following the above 469 * routine ntp_tick_adjust(). While these two routines are normally 470 * combined, they are separated here only for the purposes of 471 * simulation. 472 */ 473 void 474 ntp_update_second(int64_t *adjustment, time_t *newsec) 475 { 476 int tickrate; 477 l_fp ftemp; /* 32/64-bit temporary */ 478 479 /* 480 * On rollover of the second both the nanosecond and microsecond 481 * clocks are updated and the state machine cranked as 482 * necessary. The phase adjustment to be used for the next 483 * second is calculated and the maximum error is increased by 484 * the tolerance. 485 */ 486 time_maxerror += MAXFREQ / 1000; 487 488 /* 489 * Leap second processing. If in leap-insert state at 490 * the end of the day, the system clock is set back one 491 * second; if in leap-delete state, the system clock is 492 * set ahead one second. The nano_time() routine or 493 * external clock driver will insure that reported time 494 * is always monotonic. 495 */ 496 switch (time_state) { 497 498 /* 499 * No warning. 500 */ 501 case TIME_OK: 502 if (time_status & STA_INS) 503 time_state = TIME_INS; 504 else if (time_status & STA_DEL) 505 time_state = TIME_DEL; 506 break; 507 508 /* 509 * Insert second 23:59:60 following second 510 * 23:59:59. 511 */ 512 case TIME_INS: 513 if (!(time_status & STA_INS)) 514 time_state = TIME_OK; 515 else if ((*newsec) % 86400 == 0) { 516 (*newsec)--; 517 time_state = TIME_OOP; 518 time_tai++; 519 } 520 break; 521 522 /* 523 * Delete second 23:59:59. 524 */ 525 case TIME_DEL: 526 if (!(time_status & STA_DEL)) 527 time_state = TIME_OK; 528 else if (((*newsec) + 1) % 86400 == 0) { 529 (*newsec)++; 530 time_tai--; 531 time_state = TIME_WAIT; 532 } 533 break; 534 535 /* 536 * Insert second in progress. 537 */ 538 case TIME_OOP: 539 time_state = TIME_WAIT; 540 break; 541 542 /* 543 * Wait for status bits to clear. 544 */ 545 case TIME_WAIT: 546 if (!(time_status & (STA_INS | STA_DEL))) 547 time_state = TIME_OK; 548 } 549 550 /* 551 * Compute the total time adjustment for the next second 552 * in ns. The offset is reduced by a factor depending on 553 * whether the PPS signal is operating. Note that the 554 * value is in effect scaled by the clock frequency, 555 * since the adjustment is added at each tick interrupt. 556 */ 557 ftemp = time_offset; 558 #ifdef PPS_SYNC 559 /* XXX even if PPS signal dies we should finish adjustment ? */ 560 if (time_status & STA_PPSTIME && time_status & 561 STA_PPSSIGNAL) 562 L_RSHIFT(ftemp, pps_shift); 563 else 564 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 565 #else 566 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 567 #endif /* PPS_SYNC */ 568 time_adj = ftemp; 569 L_SUB(time_offset, ftemp); 570 L_ADD(time_adj, time_freq); 571 572 /* 573 * Apply any correction from adjtime(2). If more than one second 574 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 575 * until the last second is slewed the final < 500 usecs. 576 */ 577 if (time_adjtime != 0) { 578 if (time_adjtime > 1000000) 579 tickrate = 5000; 580 else if (time_adjtime < -1000000) 581 tickrate = -5000; 582 else if (time_adjtime > 500) 583 tickrate = 500; 584 else if (time_adjtime < -500) 585 tickrate = -500; 586 else 587 tickrate = time_adjtime; 588 time_adjtime -= tickrate; 589 L_LINT(ftemp, tickrate * 1000); 590 L_ADD(time_adj, ftemp); 591 } 592 *adjustment = time_adj; 593 594 #ifdef PPS_SYNC 595 if (pps_valid > 0) 596 pps_valid--; 597 else 598 time_status &= ~STA_PPSSIGNAL; 599 #endif /* PPS_SYNC */ 600 } 601 602 /* 603 * ntp_init() - initialize variables and structures 604 * 605 * This routine must be called after the kernel variables hz and tick 606 * are set or changed and before the next tick interrupt. In this 607 * particular implementation, these values are assumed set elsewhere in 608 * the kernel. The design allows the clock frequency and tick interval 609 * to be changed while the system is running. So, this routine should 610 * probably be integrated with the code that does that. 611 */ 612 static void 613 ntp_init() 614 { 615 616 /* 617 * The following variables are initialized only at startup. Only 618 * those structures not cleared by the compiler need to be 619 * initialized, and these only in the simulator. In the actual 620 * kernel, any nonzero values here will quickly evaporate. 621 */ 622 L_CLR(time_offset); 623 L_CLR(time_freq); 624 #ifdef PPS_SYNC 625 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 626 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 627 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 628 pps_fcount = 0; 629 L_CLR(pps_freq); 630 #endif /* PPS_SYNC */ 631 } 632 633 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL); 634 635 /* 636 * hardupdate() - local clock update 637 * 638 * This routine is called by ntp_adjtime() to update the local clock 639 * phase and frequency. The implementation is of an adaptive-parameter, 640 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 641 * time and frequency offset estimates for each call. If the kernel PPS 642 * discipline code is configured (PPS_SYNC), the PPS signal itself 643 * determines the new time offset, instead of the calling argument. 644 * Presumably, calls to ntp_adjtime() occur only when the caller 645 * believes the local clock is valid within some bound (+-128 ms with 646 * NTP). If the caller's time is far different than the PPS time, an 647 * argument will ensue, and it's not clear who will lose. 648 * 649 * For uncompensated quartz crystal oscillators and nominal update 650 * intervals less than 256 s, operation should be in phase-lock mode, 651 * where the loop is disciplined to phase. For update intervals greater 652 * than 1024 s, operation should be in frequency-lock mode, where the 653 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 654 * is selected by the STA_MODE status bit. 655 */ 656 static void 657 hardupdate(offset) 658 long offset; /* clock offset (ns) */ 659 { 660 long mtemp; 661 l_fp ftemp; 662 663 /* 664 * Select how the phase is to be controlled and from which 665 * source. If the PPS signal is present and enabled to 666 * discipline the time, the PPS offset is used; otherwise, the 667 * argument offset is used. 668 */ 669 if (!(time_status & STA_PLL)) 670 return; 671 if (!(time_status & STA_PPSTIME && time_status & 672 STA_PPSSIGNAL)) { 673 if (offset > MAXPHASE) 674 time_monitor = MAXPHASE; 675 else if (offset < -MAXPHASE) 676 time_monitor = -MAXPHASE; 677 else 678 time_monitor = offset; 679 L_LINT(time_offset, time_monitor); 680 } 681 682 /* 683 * Select how the frequency is to be controlled and in which 684 * mode (PLL or FLL). If the PPS signal is present and enabled 685 * to discipline the frequency, the PPS frequency is used; 686 * otherwise, the argument offset is used to compute it. 687 */ 688 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 689 time_reftime = time_second; 690 return; 691 } 692 if (time_status & STA_FREQHOLD || time_reftime == 0) 693 time_reftime = time_second; 694 mtemp = time_second - time_reftime; 695 L_LINT(ftemp, time_monitor); 696 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 697 L_MPY(ftemp, mtemp); 698 L_ADD(time_freq, ftemp); 699 time_status &= ~STA_MODE; 700 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 701 MAXSEC)) { 702 L_LINT(ftemp, (time_monitor << 4) / mtemp); 703 L_RSHIFT(ftemp, SHIFT_FLL + 4); 704 L_ADD(time_freq, ftemp); 705 time_status |= STA_MODE; 706 } 707 time_reftime = time_second; 708 if (L_GINT(time_freq) > MAXFREQ) 709 L_LINT(time_freq, MAXFREQ); 710 else if (L_GINT(time_freq) < -MAXFREQ) 711 L_LINT(time_freq, -MAXFREQ); 712 } 713 714 #ifdef PPS_SYNC 715 /* 716 * hardpps() - discipline CPU clock oscillator to external PPS signal 717 * 718 * This routine is called at each PPS interrupt in order to discipline 719 * the CPU clock oscillator to the PPS signal. There are two independent 720 * first-order feedback loops, one for the phase, the other for the 721 * frequency. The phase loop measures and grooms the PPS phase offset 722 * and leaves it in a handy spot for the seconds overflow routine. The 723 * frequency loop averages successive PPS phase differences and 724 * calculates the PPS frequency offset, which is also processed by the 725 * seconds overflow routine. The code requires the caller to capture the 726 * time and architecture-dependent hardware counter values in 727 * nanoseconds at the on-time PPS signal transition. 728 * 729 * Note that, on some Unix systems this routine runs at an interrupt 730 * priority level higher than the timer interrupt routine hardclock(). 731 * Therefore, the variables used are distinct from the hardclock() 732 * variables, except for the actual time and frequency variables, which 733 * are determined by this routine and updated atomically. 734 */ 735 void 736 hardpps(tsp, nsec) 737 struct timespec *tsp; /* time at PPS */ 738 long nsec; /* hardware counter at PPS */ 739 { 740 long u_sec, u_nsec, v_nsec; /* temps */ 741 l_fp ftemp; 742 743 /* 744 * The signal is first processed by a range gate and frequency 745 * discriminator. The range gate rejects noise spikes outside 746 * the range +-500 us. The frequency discriminator rejects input 747 * signals with apparent frequency outside the range 1 +-500 748 * PPM. If two hits occur in the same second, we ignore the 749 * later hit; if not and a hit occurs outside the range gate, 750 * keep the later hit for later comparison, but do not process 751 * it. 752 */ 753 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 754 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 755 pps_valid = PPS_VALID; 756 u_sec = tsp->tv_sec; 757 u_nsec = tsp->tv_nsec; 758 if (u_nsec >= (NANOSECOND >> 1)) { 759 u_nsec -= NANOSECOND; 760 u_sec++; 761 } 762 v_nsec = u_nsec - pps_tf[0].tv_nsec; 763 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 764 MAXFREQ) 765 return; 766 pps_tf[2] = pps_tf[1]; 767 pps_tf[1] = pps_tf[0]; 768 pps_tf[0].tv_sec = u_sec; 769 pps_tf[0].tv_nsec = u_nsec; 770 771 /* 772 * Compute the difference between the current and previous 773 * counter values. If the difference exceeds 0.5 s, assume it 774 * has wrapped around, so correct 1.0 s. If the result exceeds 775 * the tick interval, the sample point has crossed a tick 776 * boundary during the last second, so correct the tick. Very 777 * intricate. 778 */ 779 u_nsec = nsec; 780 if (u_nsec > (NANOSECOND >> 1)) 781 u_nsec -= NANOSECOND; 782 else if (u_nsec < -(NANOSECOND >> 1)) 783 u_nsec += NANOSECOND; 784 pps_fcount += u_nsec; 785 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 786 return; 787 time_status &= ~STA_PPSJITTER; 788 789 /* 790 * A three-stage median filter is used to help denoise the PPS 791 * time. The median sample becomes the time offset estimate; the 792 * difference between the other two samples becomes the time 793 * dispersion (jitter) estimate. 794 */ 795 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 796 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 797 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 798 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 799 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 800 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 801 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 802 } else { 803 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 804 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 805 } 806 } else { 807 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 808 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 809 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 810 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 811 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 812 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 813 } else { 814 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 815 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 816 } 817 } 818 819 /* 820 * Nominal jitter is due to PPS signal noise and interrupt 821 * latency. If it exceeds the popcorn threshold, the sample is 822 * discarded. otherwise, if so enabled, the time offset is 823 * updated. We can tolerate a modest loss of data here without 824 * much degrading time accuracy. 825 */ 826 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 827 time_status |= STA_PPSJITTER; 828 pps_jitcnt++; 829 } else if (time_status & STA_PPSTIME) { 830 time_monitor = -v_nsec; 831 L_LINT(time_offset, time_monitor); 832 } 833 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 834 u_sec = pps_tf[0].tv_sec - pps_lastsec; 835 if (u_sec < (1 << pps_shift)) 836 return; 837 838 /* 839 * At the end of the calibration interval the difference between 840 * the first and last counter values becomes the scaled 841 * frequency. It will later be divided by the length of the 842 * interval to determine the frequency update. If the frequency 843 * exceeds a sanity threshold, or if the actual calibration 844 * interval is not equal to the expected length, the data are 845 * discarded. We can tolerate a modest loss of data here without 846 * much degrading frequency accuracy. 847 */ 848 pps_calcnt++; 849 v_nsec = -pps_fcount; 850 pps_lastsec = pps_tf[0].tv_sec; 851 pps_fcount = 0; 852 u_nsec = MAXFREQ << pps_shift; 853 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 854 pps_shift)) { 855 time_status |= STA_PPSERROR; 856 pps_errcnt++; 857 return; 858 } 859 860 /* 861 * Here the raw frequency offset and wander (stability) is 862 * calculated. If the wander is less than the wander threshold 863 * for four consecutive averaging intervals, the interval is 864 * doubled; if it is greater than the threshold for four 865 * consecutive intervals, the interval is halved. The scaled 866 * frequency offset is converted to frequency offset. The 867 * stability metric is calculated as the average of recent 868 * frequency changes, but is used only for performance 869 * monitoring. 870 */ 871 L_LINT(ftemp, v_nsec); 872 L_RSHIFT(ftemp, pps_shift); 873 L_SUB(ftemp, pps_freq); 874 u_nsec = L_GINT(ftemp); 875 if (u_nsec > PPS_MAXWANDER) { 876 L_LINT(ftemp, PPS_MAXWANDER); 877 pps_intcnt--; 878 time_status |= STA_PPSWANDER; 879 pps_stbcnt++; 880 } else if (u_nsec < -PPS_MAXWANDER) { 881 L_LINT(ftemp, -PPS_MAXWANDER); 882 pps_intcnt--; 883 time_status |= STA_PPSWANDER; 884 pps_stbcnt++; 885 } else { 886 pps_intcnt++; 887 } 888 if (pps_intcnt >= 4) { 889 pps_intcnt = 4; 890 if (pps_shift < pps_shiftmax) { 891 pps_shift++; 892 pps_intcnt = 0; 893 } 894 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 895 pps_intcnt = -4; 896 if (pps_shift > PPS_FAVG) { 897 pps_shift--; 898 pps_intcnt = 0; 899 } 900 } 901 if (u_nsec < 0) 902 u_nsec = -u_nsec; 903 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 904 905 /* 906 * The PPS frequency is recalculated and clamped to the maximum 907 * MAXFREQ. If enabled, the system clock frequency is updated as 908 * well. 909 */ 910 L_ADD(pps_freq, ftemp); 911 u_nsec = L_GINT(pps_freq); 912 if (u_nsec > MAXFREQ) 913 L_LINT(pps_freq, MAXFREQ); 914 else if (u_nsec < -MAXFREQ) 915 L_LINT(pps_freq, -MAXFREQ); 916 if (time_status & STA_PPSFREQ) 917 time_freq = pps_freq; 918 } 919 #endif /* PPS_SYNC */ 920 921 #ifndef _SYS_SYSPROTO_H_ 922 struct adjtime_args { 923 struct timeval *delta; 924 struct timeval *olddelta; 925 }; 926 #endif 927 /* ARGSUSED */ 928 int 929 adjtime(struct thread *td, struct adjtime_args *uap) 930 { 931 struct timeval delta, olddelta, *deltap; 932 int error; 933 934 if (uap->delta) { 935 error = copyin(uap->delta, &delta, sizeof(delta)); 936 if (error) 937 return (error); 938 deltap = δ 939 } else 940 deltap = NULL; 941 error = kern_adjtime(td, deltap, &olddelta); 942 if (uap->olddelta && error == 0) 943 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta)); 944 return (error); 945 } 946 947 int 948 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta) 949 { 950 struct timeval atv; 951 int error; 952 953 mtx_lock(&Giant); 954 if (olddelta) { 955 atv.tv_sec = time_adjtime / 1000000; 956 atv.tv_usec = time_adjtime % 1000000; 957 if (atv.tv_usec < 0) { 958 atv.tv_usec += 1000000; 959 atv.tv_sec--; 960 } 961 *olddelta = atv; 962 } 963 if (delta) { 964 if ((error = priv_check(td, PRIV_ADJTIME))) { 965 mtx_unlock(&Giant); 966 return (error); 967 } 968 time_adjtime = (int64_t)delta->tv_sec * 1000000 + 969 delta->tv_usec; 970 } 971 mtx_unlock(&Giant); 972 return (0); 973 } 974
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