[PATCH 1/2] kern_ntptime.c: Import from FreeBSD

Sebastian Huber sebastian.huber at embedded-brains.de
Tue Feb 8 15:16:21 UTC 2022


The file was imported from this repository:

https://github.com/freebsd/freebsd.git

This commit was used:

commit 3ec0dc367bff27c345ad83240625b2057af391b9
Author: Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:   Mon Feb 7 14:16:16 2022 -0700

    kern_ntptime.c: Remove ntp_init()

    The ntp_init() function did set a couple of global objects to zero.  These
    objects are in the .bss section and already initialized to zero during kernel
    or module loading.

Update #2348.
---
 cpukit/score/src/kern_ntptime.c | 1053 +++++++++++++++++++++++++++++++
 1 file changed, 1053 insertions(+)
 create mode 100644 cpukit/score/src/kern_ntptime.c

diff --git a/cpukit/score/src/kern_ntptime.c b/cpukit/score/src/kern_ntptime.c
new file mode 100644
index 0000000000..96f14a408b
--- /dev/null
+++ b/cpukit/score/src/kern_ntptime.c
@@ -0,0 +1,1053 @@
+/*-
+ ***********************************************************************
+ *								       *
+ * Copyright (c) David L. Mills 1993-2001			       *
+ *								       *
+ * Permission to use, copy, modify, and distribute this software and   *
+ * its documentation for any purpose and without fee is hereby	       *
+ * granted, provided that the above copyright notice appears in all    *
+ * copies and that both the copyright notice and this permission       *
+ * notice appear in supporting documentation, and that the name	       *
+ * University of Delaware not be used in advertising or publicity      *
+ * pertaining to distribution of the software without specific,	       *
+ * written prior permission. The University of Delaware makes no       *
+ * representations about the suitability this software for any	       *
+ * purpose. It is provided "as is" without express or implied	       *
+ * warranty.							       *
+ *								       *
+ **********************************************************************/
+
+/*
+ * Adapted from the original sources for FreeBSD and timecounters by:
+ * Poul-Henning Kamp <phk at FreeBSD.org>.
+ *
+ * The 32bit version of the "LP" macros seems a bit past its "sell by" 
+ * date so I have retained only the 64bit version and included it directly
+ * in this file.
+ *
+ * Only minor changes done to interface with the timecounters over in
+ * sys/kern/kern_clock.c.   Some of the comments below may be (even more)
+ * confusing and/or plain wrong in that context.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_ntp.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/sysproto.h>
+#include <sys/eventhandler.h>
+#include <sys/kernel.h>
+#include <sys/priv.h>
+#include <sys/proc.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/time.h>
+#include <sys/timex.h>
+#include <sys/timetc.h>
+#include <sys/timepps.h>
+#include <sys/syscallsubr.h>
+#include <sys/sysctl.h>
+
+#ifdef PPS_SYNC
+FEATURE(pps_sync, "Support usage of external PPS signal by kernel PLL");
+#endif
+
+/*
+ * Single-precision macros for 64-bit machines
+ */
+typedef int64_t l_fp;
+#define L_ADD(v, u)	((v) += (u))
+#define L_SUB(v, u)	((v) -= (u))
+#define L_ADDHI(v, a)	((v) += (int64_t)(a) << 32)
+#define L_NEG(v)	((v) = -(v))
+#define L_RSHIFT(v, n) \
+	do { \
+		if ((v) < 0) \
+			(v) = -(-(v) >> (n)); \
+		else \
+			(v) = (v) >> (n); \
+	} while (0)
+#define L_MPY(v, a)	((v) *= (a))
+#define L_CLR(v)	((v) = 0)
+#define L_ISNEG(v)	((v) < 0)
+#define L_LINT(v, a)	((v) = (int64_t)(a) << 32)
+#define L_GINT(v)	((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
+
+/*
+ * Generic NTP kernel interface
+ *
+ * These routines constitute the Network Time Protocol (NTP) interfaces
+ * for user and daemon application programs. The ntp_gettime() routine
+ * provides the time, maximum error (synch distance) and estimated error
+ * (dispersion) to client user application programs. The ntp_adjtime()
+ * routine is used by the NTP daemon to adjust the system clock to an
+ * externally derived time. The time offset and related variables set by
+ * this routine are used by other routines in this module to adjust the
+ * phase and frequency of the clock discipline loop which controls the
+ * system clock.
+ *
+ * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
+ * defined), the time at each tick interrupt is derived directly from
+ * the kernel time variable. When the kernel time is reckoned in
+ * microseconds, (NTP_NANO undefined), the time is derived from the
+ * kernel time variable together with a variable representing the
+ * leftover nanoseconds at the last tick interrupt. In either case, the
+ * current nanosecond time is reckoned from these values plus an
+ * interpolated value derived by the clock routines in another
+ * architecture-specific module. The interpolation can use either a
+ * dedicated counter or a processor cycle counter (PCC) implemented in
+ * some architectures.
+ *
+ * Note that all routines must run at priority splclock or higher.
+ */
+/*
+ * Phase/frequency-lock loop (PLL/FLL) definitions
+ *
+ * The nanosecond clock discipline uses two variable types, time
+ * variables and frequency variables. Both types are represented as 64-
+ * bit fixed-point quantities with the decimal point between two 32-bit
+ * halves. On a 32-bit machine, each half is represented as a single
+ * word and mathematical operations are done using multiple-precision
+ * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
+ * used.
+ *
+ * A time variable is a signed 64-bit fixed-point number in ns and
+ * fraction. It represents the remaining time offset to be amortized
+ * over succeeding tick interrupts. The maximum time offset is about
+ * 0.5 s and the resolution is about 2.3e-10 ns.
+ *
+ *			1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
+ *  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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |s s s|			 ns				   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |			    fraction				   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * A frequency variable is a signed 64-bit fixed-point number in ns/s
+ * and fraction. It represents the ns and fraction to be added to the
+ * kernel time variable at each second. The maximum frequency offset is
+ * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
+ *
+ *			1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
+ *  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
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |s s s s s s s s s s s s s|	          ns/s			   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |			    fraction				   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+/*
+ * The following variables establish the state of the PLL/FLL and the
+ * residual time and frequency offset of the local clock.
+ */
+#define SHIFT_PLL	4		/* PLL loop gain (shift) */
+#define SHIFT_FLL	2		/* FLL loop gain (shift) */
+
+static int time_state = TIME_OK;	/* clock state */
+int time_status = STA_UNSYNC;	/* clock status bits */
+static long time_tai;			/* TAI offset (s) */
+static long time_monitor;		/* last time offset scaled (ns) */
+static long time_constant;		/* poll interval (shift) (s) */
+static long time_precision = 1;		/* clock precision (ns) */
+static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
+long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
+static long time_reftime;		/* uptime at last adjustment (s) */
+static l_fp time_offset;		/* time offset (ns) */
+static l_fp time_freq;			/* frequency offset (ns/s) */
+static l_fp time_adj;			/* tick adjust (ns/s) */
+
+static int64_t time_adjtime;		/* correction from adjtime(2) (usec) */
+
+static struct mtx ntp_lock;
+MTX_SYSINIT(ntp, &ntp_lock, "ntp", MTX_SPIN);
+
+#define	NTP_LOCK()		mtx_lock_spin(&ntp_lock)
+#define	NTP_UNLOCK()		mtx_unlock_spin(&ntp_lock)
+#define	NTP_ASSERT_LOCKED()	mtx_assert(&ntp_lock, MA_OWNED)
+
+#ifdef PPS_SYNC
+/*
+ * The following variables are used when a pulse-per-second (PPS) signal
+ * is available and connected via a modem control lead. They establish
+ * the engineering parameters of the clock discipline loop when
+ * controlled by the PPS signal.
+ */
+#define PPS_FAVG	2		/* min freq avg interval (s) (shift) */
+#define PPS_FAVGDEF	8		/* default freq avg int (s) (shift) */
+#define PPS_FAVGMAX	15		/* max freq avg interval (s) (shift) */
+#define PPS_PAVG	4		/* phase avg interval (s) (shift) */
+#define PPS_VALID	120		/* PPS signal watchdog max (s) */
+#define PPS_MAXWANDER	100000		/* max PPS wander (ns/s) */
+#define PPS_POPCORN	2		/* popcorn spike threshold (shift) */
+
+static struct timespec pps_tf[3];	/* phase median filter */
+static l_fp pps_freq;			/* scaled frequency offset (ns/s) */
+static long pps_fcount;			/* frequency accumulator */
+static long pps_jitter;			/* nominal jitter (ns) */
+static long pps_stabil;			/* nominal stability (scaled ns/s) */
+static long pps_lastsec;		/* time at last calibration (s) */
+static int pps_valid;			/* signal watchdog counter */
+static int pps_shift = PPS_FAVG;	/* interval duration (s) (shift) */
+static int pps_shiftmax = PPS_FAVGDEF;	/* max interval duration (s) (shift) */
+static int pps_intcnt;			/* wander counter */
+
+/*
+ * PPS signal quality monitors
+ */
+static long pps_calcnt;			/* calibration intervals */
+static long pps_jitcnt;			/* jitter limit exceeded */
+static long pps_stbcnt;			/* stability limit exceeded */
+static long pps_errcnt;			/* calibration errors */
+#endif /* PPS_SYNC */
+/*
+ * End of phase/frequency-lock loop (PLL/FLL) definitions
+ */
+
+static void hardupdate(long offset);
+static void ntp_gettime1(struct ntptimeval *ntvp);
+static bool ntp_is_time_error(int tsl);
+
+static bool
+ntp_is_time_error(int tsl)
+{
+
+	/*
+	 * Status word error decode. If any of these conditions occur,
+	 * an error is returned, instead of the status word. Most
+	 * applications will care only about the fact the system clock
+	 * may not be trusted, not about the details.
+	 *
+	 * Hardware or software error
+	 */
+	if ((tsl & (STA_UNSYNC | STA_CLOCKERR)) ||
+
+	/*
+	 * PPS signal lost when either time or frequency synchronization
+	 * requested
+	 */
+	    (tsl & (STA_PPSFREQ | STA_PPSTIME) &&
+	    !(tsl & STA_PPSSIGNAL)) ||
+
+	/*
+	 * PPS jitter exceeded when time synchronization requested
+	 */
+	    (tsl & STA_PPSTIME && tsl & STA_PPSJITTER) ||
+
+	/*
+	 * PPS wander exceeded or calibration error when frequency
+	 * synchronization requested
+	 */
+	    (tsl & STA_PPSFREQ &&
+	    tsl & (STA_PPSWANDER | STA_PPSERROR)))
+		return (true);
+
+	return (false);
+}
+
+static void
+ntp_gettime1(struct ntptimeval *ntvp)
+{
+	struct timespec atv;	/* nanosecond time */
+
+	NTP_ASSERT_LOCKED();
+
+	nanotime(&atv);
+	ntvp->time.tv_sec = atv.tv_sec;
+	ntvp->time.tv_nsec = atv.tv_nsec;
+	ntvp->maxerror = time_maxerror;
+	ntvp->esterror = time_esterror;
+	ntvp->tai = time_tai;
+	ntvp->time_state = time_state;
+
+	if (ntp_is_time_error(time_status))
+		ntvp->time_state = TIME_ERROR;
+}
+
+/*
+ * ntp_gettime() - NTP user application interface
+ *
+ * See the timex.h header file for synopsis and API description.  Note that
+ * the TAI offset is returned in the ntvtimeval.tai structure member.
+ */
+#ifndef _SYS_SYSPROTO_H_
+struct ntp_gettime_args {
+	struct ntptimeval *ntvp;
+};
+#endif
+/* ARGSUSED */
+int
+sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
+{	
+	struct ntptimeval ntv;
+
+	memset(&ntv, 0, sizeof(ntv));
+
+	NTP_LOCK();
+	ntp_gettime1(&ntv);
+	NTP_UNLOCK();
+
+	td->td_retval[0] = ntv.time_state;
+	return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
+}
+
+static int
+ntp_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	struct ntptimeval ntv;	/* temporary structure */
+
+	memset(&ntv, 0, sizeof(ntv));
+
+	NTP_LOCK();
+	ntp_gettime1(&ntv);
+	NTP_UNLOCK();
+
+	return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
+}
+
+SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
+    "");
+SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE | CTLFLAG_RD |
+    CTLFLAG_MPSAFE, 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval",
+    "");
+
+#ifdef PPS_SYNC
+SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW,
+    &pps_shiftmax, 0, "Max interval duration (sec) (shift)");
+SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW,
+    &pps_shift, 0, "Interval duration (sec) (shift)");
+SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD,
+    &time_monitor, 0, "Last time offset scaled (ns)");
+
+SYSCTL_S64(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
+    &pps_freq, 0,
+    "Scaled frequency offset (ns/sec)");
+SYSCTL_S64(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
+    &time_freq, 0,
+    "Frequency offset (ns/sec)");
+#endif
+
+/*
+ * ntp_adjtime() - NTP daemon application interface
+ *
+ * See the timex.h header file for synopsis and API description.  Note that
+ * the timex.constant structure member has a dual purpose to set the time
+ * constant and to set the TAI offset.
+ */
+int
+kern_ntp_adjtime(struct thread *td, struct timex *ntv, int *retvalp)
+{
+	long freq;		/* frequency ns/s) */
+	int modes;		/* mode bits from structure */
+	int error, retval;
+
+	/*
+	 * Update selected clock variables - only the superuser can
+	 * change anything. Note that there is no error checking here on
+	 * the assumption the superuser should know what it is doing.
+	 * Note that either the time constant or TAI offset are loaded
+	 * from the ntv.constant member, depending on the mode bits. If
+	 * the STA_PLL bit in the status word is cleared, the state and
+	 * status words are reset to the initial values at boot.
+	 */
+	modes = ntv->modes;
+	error = 0;
+	if (modes)
+		error = priv_check(td, PRIV_NTP_ADJTIME);
+	if (error != 0)
+		return (error);
+	NTP_LOCK();
+	if (modes & MOD_MAXERROR)
+		time_maxerror = ntv->maxerror;
+	if (modes & MOD_ESTERROR)
+		time_esterror = ntv->esterror;
+	if (modes & MOD_STATUS) {
+		if (time_status & STA_PLL && !(ntv->status & STA_PLL)) {
+			time_state = TIME_OK;
+			time_status = STA_UNSYNC;
+#ifdef PPS_SYNC
+			pps_shift = PPS_FAVG;
+#endif /* PPS_SYNC */
+		}
+		time_status &= STA_RONLY;
+		time_status |= ntv->status & ~STA_RONLY;
+	}
+	if (modes & MOD_TIMECONST) {
+		if (ntv->constant < 0)
+			time_constant = 0;
+		else if (ntv->constant > MAXTC)
+			time_constant = MAXTC;
+		else
+			time_constant = ntv->constant;
+	}
+	if (modes & MOD_TAI) {
+		if (ntv->constant > 0) /* XXX zero & negative numbers ? */
+			time_tai = ntv->constant;
+	}
+#ifdef PPS_SYNC
+	if (modes & MOD_PPSMAX) {
+		if (ntv->shift < PPS_FAVG)
+			pps_shiftmax = PPS_FAVG;
+		else if (ntv->shift > PPS_FAVGMAX)
+			pps_shiftmax = PPS_FAVGMAX;
+		else
+			pps_shiftmax = ntv->shift;
+	}
+#endif /* PPS_SYNC */
+	if (modes & MOD_NANO)
+		time_status |= STA_NANO;
+	if (modes & MOD_MICRO)
+		time_status &= ~STA_NANO;
+	if (modes & MOD_CLKB)
+		time_status |= STA_CLK;
+	if (modes & MOD_CLKA)
+		time_status &= ~STA_CLK;
+	if (modes & MOD_FREQUENCY) {
+		freq = (ntv->freq * 1000LL) >> 16;
+		if (freq > MAXFREQ)
+			L_LINT(time_freq, MAXFREQ);
+		else if (freq < -MAXFREQ)
+			L_LINT(time_freq, -MAXFREQ);
+		else {
+			/*
+			 * ntv->freq is [PPM * 2^16] = [us/s * 2^16]
+			 * time_freq is [ns/s * 2^32]
+			 */
+			time_freq = ntv->freq * 1000LL * 65536LL;
+		}
+#ifdef PPS_SYNC
+		pps_freq = time_freq;
+#endif /* PPS_SYNC */
+	}
+	if (modes & MOD_OFFSET) {
+		if (time_status & STA_NANO)
+			hardupdate(ntv->offset);
+		else
+			hardupdate(ntv->offset * 1000);
+	}
+
+	/*
+	 * Retrieve all clock variables. Note that the TAI offset is
+	 * returned only by ntp_gettime();
+	 */
+	if (time_status & STA_NANO)
+		ntv->offset = L_GINT(time_offset);
+	else
+		ntv->offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
+	ntv->freq = L_GINT((time_freq / 1000LL) << 16);
+	ntv->maxerror = time_maxerror;
+	ntv->esterror = time_esterror;
+	ntv->status = time_status;
+	ntv->constant = time_constant;
+	if (time_status & STA_NANO)
+		ntv->precision = time_precision;
+	else
+		ntv->precision = time_precision / 1000;
+	ntv->tolerance = MAXFREQ * SCALE_PPM;
+#ifdef PPS_SYNC
+	ntv->shift = pps_shift;
+	ntv->ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
+	if (time_status & STA_NANO)
+		ntv->jitter = pps_jitter;
+	else
+		ntv->jitter = pps_jitter / 1000;
+	ntv->stabil = pps_stabil;
+	ntv->calcnt = pps_calcnt;
+	ntv->errcnt = pps_errcnt;
+	ntv->jitcnt = pps_jitcnt;
+	ntv->stbcnt = pps_stbcnt;
+#endif /* PPS_SYNC */
+	retval = ntp_is_time_error(time_status) ? TIME_ERROR : time_state;
+	NTP_UNLOCK();
+
+	*retvalp = retval;
+	return (0);
+}
+
+#ifndef _SYS_SYSPROTO_H_
+struct ntp_adjtime_args {
+	struct timex *tp;
+};
+#endif
+
+int
+sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
+{
+	struct timex ntv;
+	int error, retval;
+
+	error = copyin(uap->tp, &ntv, sizeof(ntv));
+	if (error == 0) {
+		error = kern_ntp_adjtime(td, &ntv, &retval);
+		if (error == 0) {
+			error = copyout(&ntv, uap->tp, sizeof(ntv));
+			if (error == 0)
+				td->td_retval[0] = retval;
+		}
+	}
+	return (error);
+}
+
+/*
+ * second_overflow() - called after ntp_tick_adjust()
+ *
+ * This routine is ordinarily called immediately following the above
+ * routine ntp_tick_adjust(). While these two routines are normally
+ * combined, they are separated here only for the purposes of
+ * simulation.
+ */
+void
+ntp_update_second(int64_t *adjustment, time_t *newsec)
+{
+	int tickrate;
+	l_fp ftemp;		/* 32/64-bit temporary */
+
+	NTP_LOCK();
+
+	/*
+	 * On rollover of the second both the nanosecond and microsecond
+	 * clocks are updated and the state machine cranked as
+	 * necessary. The phase adjustment to be used for the next
+	 * second is calculated and the maximum error is increased by
+	 * the tolerance.
+	 */
+	time_maxerror += MAXFREQ / 1000;
+
+	/*
+	 * 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 nano_time() routine or
+	 * external clock driver will insure that reported time
+	 * is always monotonic.
+	 */
+	switch (time_state) {
+		/*
+		 * No warning.
+		 */
+		case TIME_OK:
+		if (time_status & STA_INS)
+			time_state = TIME_INS;
+		else if (time_status & STA_DEL)
+			time_state = TIME_DEL;
+		break;
+
+		/*
+		 * Insert second 23:59:60 following second
+		 * 23:59:59.
+		 */
+		case TIME_INS:
+		if (!(time_status & STA_INS))
+			time_state = TIME_OK;
+		else if ((*newsec) % 86400 == 0) {
+			(*newsec)--;
+			time_state = TIME_OOP;
+			time_tai++;
+		}
+		break;
+
+		/*
+		 * Delete second 23:59:59.
+		 */
+		case TIME_DEL:
+		if (!(time_status & STA_DEL))
+			time_state = TIME_OK;
+		else if (((*newsec) + 1) % 86400 == 0) {
+			(*newsec)++;
+			time_tai--;
+			time_state = TIME_WAIT;
+		}
+		break;
+
+		/*
+		 * Insert second in progress.
+		 */
+		case TIME_OOP:
+			time_state = TIME_WAIT;
+		break;
+
+		/*
+		 * Wait for status bits to clear.
+		 */
+		case TIME_WAIT:
+		if (!(time_status & (STA_INS | STA_DEL)))
+			time_state = TIME_OK;
+	}
+
+	/*
+	 * Compute the total time adjustment for the next second
+	 * in ns. The offset is reduced by a factor depending on
+	 * whether the PPS signal is operating. Note that the
+	 * value is in effect scaled by the clock frequency,
+	 * since the adjustment is added at each tick interrupt.
+	 */
+	ftemp = time_offset;
+#ifdef PPS_SYNC
+	/* XXX even if PPS signal dies we should finish adjustment ? */
+	if (time_status & STA_PPSTIME && time_status &
+	    STA_PPSSIGNAL)
+		L_RSHIFT(ftemp, pps_shift);
+	else
+		L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
+#else
+		L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
+#endif /* PPS_SYNC */
+	time_adj = ftemp;
+	L_SUB(time_offset, ftemp);
+	L_ADD(time_adj, time_freq);
+
+	/*
+	 * Apply any correction from adjtime(2).  If more than one second
+	 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500 PPM)
+	 * until the last second is slewed the final < 500 usecs.
+	 */
+	if (time_adjtime != 0) {
+		if (time_adjtime > 1000000)
+			tickrate = 5000;
+		else if (time_adjtime < -1000000)
+			tickrate = -5000;
+		else if (time_adjtime > 500)
+			tickrate = 500;
+		else if (time_adjtime < -500)
+			tickrate = -500;
+		else
+			tickrate = time_adjtime;
+		time_adjtime -= tickrate;
+		L_LINT(ftemp, tickrate * 1000);
+		L_ADD(time_adj, ftemp);
+	}
+	*adjustment = time_adj;
+		
+#ifdef PPS_SYNC
+	if (pps_valid > 0)
+		pps_valid--;
+	else
+		time_status &= ~STA_PPSSIGNAL;
+#endif /* PPS_SYNC */
+
+	NTP_UNLOCK();
+}
+
+/*
+ * hardupdate() - local clock update
+ *
+ * This routine is called by ntp_adjtime() to update the local clock
+ * phase and frequency. The implementation is of an adaptive-parameter,
+ * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
+ * time and frequency offset estimates for each call. If the kernel PPS
+ * discipline code is configured (PPS_SYNC), the PPS signal itself
+ * determines the new time offset, instead of the calling argument.
+ * Presumably, calls to ntp_adjtime() occur only when the caller
+ * believes the local clock is valid within some bound (+-128 ms with
+ * NTP). If the caller's time is far different than the PPS time, an
+ * argument will ensue, and it's not clear who will lose.
+ *
+ * For uncompensated quartz crystal oscillators and nominal update
+ * intervals less than 256 s, operation should be in phase-lock mode,
+ * where the loop is disciplined to phase. For update intervals greater
+ * than 1024 s, operation should be in frequency-lock mode, where the
+ * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
+ * is selected by the STA_MODE status bit.
+ */
+static void
+hardupdate(offset)
+	long offset;		/* clock offset (ns) */
+{
+	long mtemp;
+	l_fp ftemp;
+
+	NTP_ASSERT_LOCKED();
+
+	/*
+	 * Select how the phase is to be controlled and from which
+	 * source. If the PPS signal is present and enabled to
+	 * discipline the time, the PPS offset is used; otherwise, the
+	 * argument offset is used.
+	 */
+	if (!(time_status & STA_PLL))
+		return;
+	if (!(time_status & STA_PPSTIME && time_status &
+	    STA_PPSSIGNAL)) {
+		if (offset > MAXPHASE)
+			time_monitor = MAXPHASE;
+		else if (offset < -MAXPHASE)
+			time_monitor = -MAXPHASE;
+		else
+			time_monitor = offset;
+		L_LINT(time_offset, time_monitor);
+	}
+
+	/*
+	 * Select how the frequency is to be controlled and in which
+	 * mode (PLL or FLL). If the PPS signal is present and enabled
+	 * to discipline the frequency, the PPS frequency is used;
+	 * otherwise, the argument offset is used to compute it.
+	 */
+	if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
+		time_reftime = time_uptime;
+		return;
+	}
+	if (time_status & STA_FREQHOLD || time_reftime == 0)
+		time_reftime = time_uptime;
+	mtemp = time_uptime - time_reftime;
+	L_LINT(ftemp, time_monitor);
+	L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
+	L_MPY(ftemp, mtemp);
+	L_ADD(time_freq, ftemp);
+	time_status &= ~STA_MODE;
+	if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
+	    MAXSEC)) {
+		L_LINT(ftemp, (time_monitor << 4) / mtemp);
+		L_RSHIFT(ftemp, SHIFT_FLL + 4);
+		L_ADD(time_freq, ftemp);
+		time_status |= STA_MODE;
+	}
+	time_reftime = time_uptime;
+	if (L_GINT(time_freq) > MAXFREQ)
+		L_LINT(time_freq, MAXFREQ);
+	else if (L_GINT(time_freq) < -MAXFREQ)
+		L_LINT(time_freq, -MAXFREQ);
+}
+
+#ifdef PPS_SYNC
+/*
+ * hardpps() - discipline CPU clock oscillator to external PPS signal
+ *
+ * This routine is called at each PPS interrupt in order to discipline
+ * the CPU clock oscillator to the PPS signal. There are two independent
+ * first-order feedback loops, one for the phase, the other for the
+ * frequency. The phase loop measures and grooms the PPS phase offset
+ * and leaves it in a handy spot for the seconds overflow routine. The
+ * frequency loop averages successive PPS phase differences and
+ * calculates the PPS frequency offset, which is also processed by the
+ * seconds overflow routine. The code requires the caller to capture the
+ * time and architecture-dependent hardware counter values in
+ * nanoseconds at the on-time PPS signal transition.
+ *
+ * Note that, on some Unix systems this routine runs at an interrupt
+ * priority level higher than the timer interrupt routine hardclock().
+ * Therefore, the variables used are distinct from the hardclock()
+ * variables, except for the actual time and frequency variables, which
+ * are determined by this routine and updated atomically.
+ *
+ * tsp  - time at PPS
+ * nsec - hardware counter at PPS
+ */
+void
+hardpps(struct timespec *tsp, long nsec)
+{
+	long u_sec, u_nsec, v_nsec; /* temps */
+	l_fp ftemp;
+
+	NTP_LOCK();
+
+	/*
+	 * The signal is first processed by a range gate and frequency
+	 * discriminator. The range gate rejects noise spikes outside
+	 * the range +-500 us. The frequency discriminator rejects input
+	 * signals with apparent frequency outside the range 1 +-500
+	 * PPM. If two hits occur in the same second, we ignore the
+	 * later hit; if not and a hit occurs outside the range gate,
+	 * keep the later hit for later comparison, but do not process
+	 * it.
+	 */
+	time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
+	time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
+	pps_valid = PPS_VALID;
+	u_sec = tsp->tv_sec;
+	u_nsec = tsp->tv_nsec;
+	if (u_nsec >= (NANOSECOND >> 1)) {
+		u_nsec -= NANOSECOND;
+		u_sec++;
+	}
+	v_nsec = u_nsec - pps_tf[0].tv_nsec;
+	if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - MAXFREQ)
+		goto out;
+	pps_tf[2] = pps_tf[1];
+	pps_tf[1] = pps_tf[0];
+	pps_tf[0].tv_sec = u_sec;
+	pps_tf[0].tv_nsec = u_nsec;
+
+	/*
+	 * Compute the difference between the current and previous
+	 * counter values. If the difference exceeds 0.5 s, assume it
+	 * has wrapped around, so correct 1.0 s. If the result exceeds
+	 * the tick interval, the sample point has crossed a tick
+	 * boundary during the last second, so correct the tick. Very
+	 * intricate.
+	 */
+	u_nsec = nsec;
+	if (u_nsec > (NANOSECOND >> 1))
+		u_nsec -= NANOSECOND;
+	else if (u_nsec < -(NANOSECOND >> 1))
+		u_nsec += NANOSECOND;
+	pps_fcount += u_nsec;
+	if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
+		goto out;
+	time_status &= ~STA_PPSJITTER;
+
+	/*
+	 * A three-stage median filter is used to help denoise the PPS
+	 * time. The median sample becomes the time offset estimate; the
+	 * difference between the other two samples becomes the time
+	 * dispersion (jitter) estimate.
+	 */
+	if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
+		if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
+			v_nsec = pps_tf[1].tv_nsec;	/* 0 1 2 */
+			u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
+		} else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
+			v_nsec = pps_tf[0].tv_nsec;	/* 2 0 1 */
+			u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
+		} else {
+			v_nsec = pps_tf[2].tv_nsec;	/* 0 2 1 */
+			u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
+		}
+	} else {
+		if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
+			v_nsec = pps_tf[1].tv_nsec;	/* 2 1 0 */
+			u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
+		} else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
+			v_nsec = pps_tf[0].tv_nsec;	/* 1 0 2 */
+			u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
+		} else {
+			v_nsec = pps_tf[2].tv_nsec;	/* 1 2 0 */
+			u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
+		}
+	}
+
+	/*
+	 * Nominal jitter is due to PPS signal noise and interrupt
+	 * latency. If it exceeds the popcorn threshold, the sample is
+	 * discarded. otherwise, if so enabled, the time offset is
+	 * updated. We can tolerate a modest loss of data here without
+	 * much degrading time accuracy.
+	 *
+	 * The measurements being checked here were made with the system
+	 * timecounter, so the popcorn threshold is not allowed to fall below
+	 * the number of nanoseconds in two ticks of the timecounter.  For a
+	 * timecounter running faster than 1 GHz the lower bound is 2ns, just
+	 * to avoid a nonsensical threshold of zero.
+	*/
+	if (u_nsec > lmax(pps_jitter << PPS_POPCORN,
+	    2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) {
+		time_status |= STA_PPSJITTER;
+		pps_jitcnt++;
+	} else if (time_status & STA_PPSTIME) {
+		time_monitor = -v_nsec;
+		L_LINT(time_offset, time_monitor);
+	}
+	pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
+	u_sec = pps_tf[0].tv_sec - pps_lastsec;
+	if (u_sec < (1 << pps_shift))
+		goto out;
+
+	/*
+	 * At the end of the calibration interval the difference between
+	 * the first and last counter values becomes the scaled
+	 * frequency. It will later be divided by the length of the
+	 * interval to determine the frequency update. If the frequency
+	 * exceeds a sanity threshold, or if the actual calibration
+	 * interval is not equal to the expected length, the data are
+	 * discarded. We can tolerate a modest loss of data here without
+	 * much degrading frequency accuracy.
+	 */
+	pps_calcnt++;
+	v_nsec = -pps_fcount;
+	pps_lastsec = pps_tf[0].tv_sec;
+	pps_fcount = 0;
+	u_nsec = MAXFREQ << pps_shift;
+	if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << pps_shift)) {
+		time_status |= STA_PPSERROR;
+		pps_errcnt++;
+		goto out;
+	}
+
+	/*
+	 * Here the raw frequency offset and wander (stability) is
+	 * calculated. If the wander is less than the wander threshold
+	 * for four consecutive averaging intervals, the interval is
+	 * doubled; if it is greater than the threshold for four
+	 * consecutive intervals, the interval is halved. The scaled
+	 * frequency offset is converted to frequency offset. The
+	 * stability metric is calculated as the average of recent
+	 * frequency changes, but is used only for performance
+	 * monitoring.
+	 */
+	L_LINT(ftemp, v_nsec);
+	L_RSHIFT(ftemp, pps_shift);
+	L_SUB(ftemp, pps_freq);
+	u_nsec = L_GINT(ftemp);
+	if (u_nsec > PPS_MAXWANDER) {
+		L_LINT(ftemp, PPS_MAXWANDER);
+		pps_intcnt--;
+		time_status |= STA_PPSWANDER;
+		pps_stbcnt++;
+	} else if (u_nsec < -PPS_MAXWANDER) {
+		L_LINT(ftemp, -PPS_MAXWANDER);
+		pps_intcnt--;
+		time_status |= STA_PPSWANDER;
+		pps_stbcnt++;
+	} else {
+		pps_intcnt++;
+	}
+	if (pps_intcnt >= 4) {
+		pps_intcnt = 4;
+		if (pps_shift < pps_shiftmax) {
+			pps_shift++;
+			pps_intcnt = 0;
+		}
+	} else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
+		pps_intcnt = -4;
+		if (pps_shift > PPS_FAVG) {
+			pps_shift--;
+			pps_intcnt = 0;
+		}
+	}
+	if (u_nsec < 0)
+		u_nsec = -u_nsec;
+	pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
+
+	/*
+	 * The PPS frequency is recalculated and clamped to the maximum
+	 * MAXFREQ. If enabled, the system clock frequency is updated as
+	 * well.
+	 */
+	L_ADD(pps_freq, ftemp);
+	u_nsec = L_GINT(pps_freq);
+	if (u_nsec > MAXFREQ)
+		L_LINT(pps_freq, MAXFREQ);
+	else if (u_nsec < -MAXFREQ)
+		L_LINT(pps_freq, -MAXFREQ);
+	if (time_status & STA_PPSFREQ)
+		time_freq = pps_freq;
+
+out:
+	NTP_UNLOCK();
+}
+#endif /* PPS_SYNC */
+
+#ifndef _SYS_SYSPROTO_H_
+struct adjtime_args {
+	struct timeval *delta;
+	struct timeval *olddelta;
+};
+#endif
+/* ARGSUSED */
+int
+sys_adjtime(struct thread *td, struct adjtime_args *uap)
+{
+	struct timeval delta, olddelta, *deltap;
+	int error;
+
+	if (uap->delta) {
+		error = copyin(uap->delta, &delta, sizeof(delta));
+		if (error)
+			return (error);
+		deltap = δ
+	} else
+		deltap = NULL;
+	error = kern_adjtime(td, deltap, &olddelta);
+	if (uap->olddelta && error == 0)
+		error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
+	return (error);
+}
+
+int
+kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
+{
+	struct timeval atv;
+	int64_t ltr, ltw;
+	int error;
+
+	if (delta != NULL) {
+		error = priv_check(td, PRIV_ADJTIME);
+		if (error != 0)
+			return (error);
+		ltw = (int64_t)delta->tv_sec * 1000000 + delta->tv_usec;
+	}
+	NTP_LOCK();
+	ltr = time_adjtime;
+	if (delta != NULL)
+		time_adjtime = ltw;
+	NTP_UNLOCK();
+	if (olddelta != NULL) {
+		atv.tv_sec = ltr / 1000000;
+		atv.tv_usec = ltr % 1000000;
+		if (atv.tv_usec < 0) {
+			atv.tv_usec += 1000000;
+			atv.tv_sec--;
+		}
+		*olddelta = atv;
+	}
+	return (0);
+}
+
+static struct callout resettodr_callout;
+static int resettodr_period = 1800;
+
+static void
+periodic_resettodr(void *arg __unused)
+{
+
+	/*
+	 * Read of time_status is lock-less, which is fine since
+	 * ntp_is_time_error() operates on the consistent read value.
+	 */
+	if (!ntp_is_time_error(time_status))
+		resettodr();
+	if (resettodr_period > 0)
+		callout_schedule(&resettodr_callout, resettodr_period * hz);
+}
+
+static void
+shutdown_resettodr(void *arg __unused, int howto __unused)
+{
+
+	callout_drain(&resettodr_callout);
+	/* Another unlocked read of time_status */
+	if (resettodr_period > 0 && !ntp_is_time_error(time_status))
+		resettodr();
+}
+
+static int
+sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+
+	error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
+	if (error || !req->newptr)
+		return (error);
+	if (cold)
+		goto done;
+	if (resettodr_period == 0)
+		callout_stop(&resettodr_callout);
+	else
+		callout_reset(&resettodr_callout, resettodr_period * hz,
+		    periodic_resettodr, NULL);
+done:
+	return (0);
+}
+
+SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT | CTLFLAG_RWTUN |
+    CTLFLAG_MPSAFE, &resettodr_period, 1800, sysctl_resettodr_period, "I",
+    "Save system time to RTC with this period (in seconds)");
+
+static void
+start_periodic_resettodr(void *arg __unused)
+{
+
+	EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
+	    SHUTDOWN_PRI_FIRST);
+	callout_init(&resettodr_callout, 1);
+	if (resettodr_period == 0)
+		return;
+	callout_reset(&resettodr_callout, resettodr_period * hz,
+	    periodic_resettodr, NULL);
+}
+
+SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE,
+	start_periodic_resettodr, NULL);
-- 
2.26.2



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