|  | /* | 
|  | * linux/kernel/time/ntp.c | 
|  | * | 
|  | * NTP state machine interfaces and logic. | 
|  | * | 
|  | * This code was mainly moved from kernel/timer.c and kernel/time.c | 
|  | * Please see those files for relevant copyright info and historical | 
|  | * changelogs. | 
|  | */ | 
|  |  | 
|  | #include <linux/mm.h> | 
|  | #include <linux/time.h> | 
|  | #include <linux/timex.h> | 
|  |  | 
|  | #include <asm/div64.h> | 
|  | #include <asm/timex.h> | 
|  |  | 
|  | /* | 
|  | * Timekeeping variables | 
|  | */ | 
|  | unsigned long tick_usec = TICK_USEC; 		/* USER_HZ period (usec) */ | 
|  | unsigned long tick_nsec;			/* ACTHZ period (nsec) */ | 
|  | static u64 tick_length, tick_length_base; | 
|  |  | 
|  | #define MAX_TICKADJ		500		/* microsecs */ | 
|  | #define MAX_TICKADJ_SCALED	(((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \ | 
|  | TICK_LENGTH_SHIFT) / HZ) | 
|  |  | 
|  | /* | 
|  | * phase-lock loop variables | 
|  | */ | 
|  | /* TIME_ERROR prevents overwriting the CMOS clock */ | 
|  | static int time_state = TIME_OK;	/* clock synchronization status	*/ | 
|  | int time_status = STA_UNSYNC;		/* clock status bits		*/ | 
|  | static long time_offset;		/* time adjustment (ns)		*/ | 
|  | static long time_constant = 2;		/* pll time constant		*/ | 
|  | long time_maxerror = NTP_PHASE_LIMIT;	/* maximum error (us)		*/ | 
|  | long time_esterror = NTP_PHASE_LIMIT;	/* estimated error (us)		*/ | 
|  | long time_freq;				/* frequency offset (scaled ppm)*/ | 
|  | static long time_reftime;		/* time at last adjustment (s)	*/ | 
|  | long time_adjust; | 
|  |  | 
|  | #define CLOCK_TICK_OVERFLOW	(LATCH * HZ - CLOCK_TICK_RATE) | 
|  | #define CLOCK_TICK_ADJUST	(((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \ | 
|  | (s64)CLOCK_TICK_RATE) | 
|  |  | 
|  | static void ntp_update_frequency(void) | 
|  | { | 
|  | tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT; | 
|  | tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT; | 
|  | tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC); | 
|  |  | 
|  | do_div(tick_length_base, HZ); | 
|  |  | 
|  | tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT; | 
|  | } | 
|  |  | 
|  | /** | 
|  | * ntp_clear - Clears the NTP state variables | 
|  | * | 
|  | * Must be called while holding a write on the xtime_lock | 
|  | */ | 
|  | void ntp_clear(void) | 
|  | { | 
|  | time_adjust = 0;		/* stop active adjtime() */ | 
|  | time_status |= STA_UNSYNC; | 
|  | time_maxerror = NTP_PHASE_LIMIT; | 
|  | time_esterror = NTP_PHASE_LIMIT; | 
|  |  | 
|  | ntp_update_frequency(); | 
|  |  | 
|  | tick_length = tick_length_base; | 
|  | time_offset = 0; | 
|  | } | 
|  |  | 
|  | /* | 
|  | * this routine handles the overflow of the microsecond field | 
|  | * | 
|  | * The tricky bits of code to handle the accurate clock support | 
|  | * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. | 
|  | * They were originally developed for SUN and DEC kernels. | 
|  | * All the kudos should go to Dave for this stuff. | 
|  | */ | 
|  | void second_overflow(void) | 
|  | { | 
|  | long time_adj; | 
|  |  | 
|  | /* Bump the maxerror field */ | 
|  | time_maxerror += MAXFREQ >> SHIFT_USEC; | 
|  | if (time_maxerror > NTP_PHASE_LIMIT) { | 
|  | time_maxerror = NTP_PHASE_LIMIT; | 
|  | time_status |= STA_UNSYNC; | 
|  | } | 
|  |  | 
|  | /* | 
|  | * Leap second processing. If in leap-insert state at the end of the | 
|  | * day, the system clock is set back one second; if in leap-delete | 
|  | * state, the system clock is set ahead one second. The microtime() | 
|  | * routine or external clock driver will insure that reported time is | 
|  | * always monotonic. The ugly divides should be replaced. | 
|  | */ | 
|  | switch (time_state) { | 
|  | case TIME_OK: | 
|  | if (time_status & STA_INS) | 
|  | time_state = TIME_INS; | 
|  | else if (time_status & STA_DEL) | 
|  | time_state = TIME_DEL; | 
|  | break; | 
|  | case TIME_INS: | 
|  | if (xtime.tv_sec % 86400 == 0) { | 
|  | xtime.tv_sec--; | 
|  | wall_to_monotonic.tv_sec++; | 
|  | /* | 
|  | * The timer interpolator will make time change | 
|  | * gradually instead of an immediate jump by one second | 
|  | */ | 
|  | time_interpolator_update(-NSEC_PER_SEC); | 
|  | time_state = TIME_OOP; | 
|  | clock_was_set(); | 
|  | printk(KERN_NOTICE "Clock: inserting leap second " | 
|  | "23:59:60 UTC\n"); | 
|  | } | 
|  | break; | 
|  | case TIME_DEL: | 
|  | if ((xtime.tv_sec + 1) % 86400 == 0) { | 
|  | xtime.tv_sec++; | 
|  | wall_to_monotonic.tv_sec--; | 
|  | /* | 
|  | * Use of time interpolator for a gradual change of | 
|  | * time | 
|  | */ | 
|  | time_interpolator_update(NSEC_PER_SEC); | 
|  | time_state = TIME_WAIT; | 
|  | clock_was_set(); | 
|  | printk(KERN_NOTICE "Clock: deleting leap second " | 
|  | "23:59:59 UTC\n"); | 
|  | } | 
|  | break; | 
|  | case TIME_OOP: | 
|  | time_state = TIME_WAIT; | 
|  | break; | 
|  | case TIME_WAIT: | 
|  | if (!(time_status & (STA_INS | STA_DEL))) | 
|  | time_state = TIME_OK; | 
|  | } | 
|  |  | 
|  | /* | 
|  | * Compute the phase adjustment for the next second. The offset is | 
|  | * reduced by a fixed factor times the time constant. | 
|  | */ | 
|  | tick_length = tick_length_base; | 
|  | time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); | 
|  | time_offset -= time_adj; | 
|  | tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); | 
|  |  | 
|  | if (unlikely(time_adjust)) { | 
|  | if (time_adjust > MAX_TICKADJ) { | 
|  | time_adjust -= MAX_TICKADJ; | 
|  | tick_length += MAX_TICKADJ_SCALED; | 
|  | } else if (time_adjust < -MAX_TICKADJ) { | 
|  | time_adjust += MAX_TICKADJ; | 
|  | tick_length -= MAX_TICKADJ_SCALED; | 
|  | } else { | 
|  | tick_length += (s64)(time_adjust * NSEC_PER_USEC / | 
|  | HZ) << TICK_LENGTH_SHIFT; | 
|  | time_adjust = 0; | 
|  | } | 
|  | } | 
|  | } | 
|  |  | 
|  | /* | 
|  | * Return how long ticks are at the moment, that is, how much time | 
|  | * update_wall_time_one_tick will add to xtime next time we call it | 
|  | * (assuming no calls to do_adjtimex in the meantime). | 
|  | * The return value is in fixed-point nanoseconds shifted by the | 
|  | * specified number of bits to the right of the binary point. | 
|  | * This function has no side-effects. | 
|  | */ | 
|  | u64 current_tick_length(void) | 
|  | { | 
|  | return tick_length; | 
|  | } | 
|  |  | 
|  |  | 
|  | void __attribute__ ((weak)) notify_arch_cmos_timer(void) | 
|  | { | 
|  | return; | 
|  | } | 
|  |  | 
|  | /* adjtimex mainly allows reading (and writing, if superuser) of | 
|  | * kernel time-keeping variables. used by xntpd. | 
|  | */ | 
|  | int do_adjtimex(struct timex *txc) | 
|  | { | 
|  | long ltemp, mtemp, save_adjust; | 
|  | s64 freq_adj, temp64; | 
|  | int result; | 
|  |  | 
|  | /* In order to modify anything, you gotta be super-user! */ | 
|  | if (txc->modes && !capable(CAP_SYS_TIME)) | 
|  | return -EPERM; | 
|  |  | 
|  | /* Now we validate the data before disabling interrupts */ | 
|  |  | 
|  | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | 
|  | /* singleshot must not be used with any other mode bits */ | 
|  | if (txc->modes != ADJ_OFFSET_SINGLESHOT) | 
|  | return -EINVAL; | 
|  |  | 
|  | if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET)) | 
|  | /* adjustment Offset limited to +- .512 seconds */ | 
|  | if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE ) | 
|  | return -EINVAL; | 
|  |  | 
|  | /* if the quartz is off by more than 10% something is VERY wrong ! */ | 
|  | if (txc->modes & ADJ_TICK) | 
|  | if (txc->tick <  900000/USER_HZ || | 
|  | txc->tick > 1100000/USER_HZ) | 
|  | return -EINVAL; | 
|  |  | 
|  | write_seqlock_irq(&xtime_lock); | 
|  | result = time_state;	/* mostly `TIME_OK' */ | 
|  |  | 
|  | /* Save for later - semantics of adjtime is to return old value */ | 
|  | save_adjust = time_adjust; | 
|  |  | 
|  | #if 0	/* STA_CLOCKERR is never set yet */ | 
|  | time_status &= ~STA_CLOCKERR;		/* reset STA_CLOCKERR */ | 
|  | #endif | 
|  | /* If there are input parameters, then process them */ | 
|  | if (txc->modes) | 
|  | { | 
|  | if (txc->modes & ADJ_STATUS)	/* only set allowed bits */ | 
|  | time_status =  (txc->status & ~STA_RONLY) | | 
|  | (time_status & STA_RONLY); | 
|  |  | 
|  | if (txc->modes & ADJ_FREQUENCY) {	/* p. 22 */ | 
|  | if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) { | 
|  | result = -EINVAL; | 
|  | goto leave; | 
|  | } | 
|  | time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC); | 
|  | } | 
|  |  | 
|  | if (txc->modes & ADJ_MAXERROR) { | 
|  | if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) { | 
|  | result = -EINVAL; | 
|  | goto leave; | 
|  | } | 
|  | time_maxerror = txc->maxerror; | 
|  | } | 
|  |  | 
|  | if (txc->modes & ADJ_ESTERROR) { | 
|  | if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) { | 
|  | result = -EINVAL; | 
|  | goto leave; | 
|  | } | 
|  | time_esterror = txc->esterror; | 
|  | } | 
|  |  | 
|  | if (txc->modes & ADJ_TIMECONST) {	/* p. 24 */ | 
|  | if (txc->constant < 0) {	/* NTP v4 uses values > 6 */ | 
|  | result = -EINVAL; | 
|  | goto leave; | 
|  | } | 
|  | time_constant = min(txc->constant + 4, (long)MAXTC); | 
|  | } | 
|  |  | 
|  | if (txc->modes & ADJ_OFFSET) {	/* values checked earlier */ | 
|  | if (txc->modes == ADJ_OFFSET_SINGLESHOT) { | 
|  | /* adjtime() is independent from ntp_adjtime() */ | 
|  | time_adjust = txc->offset; | 
|  | } | 
|  | else if (time_status & STA_PLL) { | 
|  | ltemp = txc->offset * NSEC_PER_USEC; | 
|  |  | 
|  | /* | 
|  | * Scale the phase adjustment and | 
|  | * clamp to the operating range. | 
|  | */ | 
|  | time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC); | 
|  | time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC); | 
|  |  | 
|  | /* | 
|  | * Select whether the frequency is to be controlled | 
|  | * and in which mode (PLL or FLL). Clamp to the operating | 
|  | * range. Ugly multiply/divide should be replaced someday. | 
|  | */ | 
|  |  | 
|  | if (time_status & STA_FREQHOLD || time_reftime == 0) | 
|  | time_reftime = xtime.tv_sec; | 
|  | mtemp = xtime.tv_sec - time_reftime; | 
|  | time_reftime = xtime.tv_sec; | 
|  |  | 
|  | freq_adj = (s64)time_offset * mtemp; | 
|  | freq_adj = shift_right(freq_adj, time_constant * 2 + | 
|  | (SHIFT_PLL + 2) * 2 - SHIFT_NSEC); | 
|  | if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { | 
|  | temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL); | 
|  | if (time_offset < 0) { | 
|  | temp64 = -temp64; | 
|  | do_div(temp64, mtemp); | 
|  | freq_adj -= temp64; | 
|  | } else { | 
|  | do_div(temp64, mtemp); | 
|  | freq_adj += temp64; | 
|  | } | 
|  | } | 
|  | freq_adj += time_freq; | 
|  | freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC); | 
|  | time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC); | 
|  | time_offset = (time_offset / HZ) << SHIFT_UPDATE; | 
|  | } /* STA_PLL */ | 
|  | } /* txc->modes & ADJ_OFFSET */ | 
|  | if (txc->modes & ADJ_TICK) | 
|  | tick_usec = txc->tick; | 
|  |  | 
|  | if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) | 
|  | ntp_update_frequency(); | 
|  | } /* txc->modes */ | 
|  | leave:	if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) | 
|  | result = TIME_ERROR; | 
|  |  | 
|  | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | 
|  | txc->offset	   = save_adjust; | 
|  | else | 
|  | txc->offset    = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000; | 
|  | txc->freq	   = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC); | 
|  | txc->maxerror	   = time_maxerror; | 
|  | txc->esterror	   = time_esterror; | 
|  | txc->status	   = time_status; | 
|  | txc->constant	   = time_constant; | 
|  | txc->precision	   = 1; | 
|  | txc->tolerance	   = MAXFREQ; | 
|  | txc->tick	   = tick_usec; | 
|  |  | 
|  | /* PPS is not implemented, so these are zero */ | 
|  | txc->ppsfreq	   = 0; | 
|  | txc->jitter	   = 0; | 
|  | txc->shift	   = 0; | 
|  | txc->stabil	   = 0; | 
|  | txc->jitcnt	   = 0; | 
|  | txc->calcnt	   = 0; | 
|  | txc->errcnt	   = 0; | 
|  | txc->stbcnt	   = 0; | 
|  | write_sequnlock_irq(&xtime_lock); | 
|  | do_gettimeofday(&txc->time); | 
|  | notify_arch_cmos_timer(); | 
|  | return(result); | 
|  | } |