time.c
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/*
* linux/kernel/time.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* This file contains the interface functions for the various
* time related system calls: time, stime, gettimeofday, settimeofday,
* adjtime
*/
/*
* Modification history kernel/time.c
*
* 1993-09-02 Philip Gladstone
* Created file with time related functions from sched.c and adjtimex()
* 1993-10-08 Torsten Duwe
* adjtime interface update and CMOS clock write code
* 1995-08-13 Torsten Duwe
* kernel PLL updated to 1994-12-13 specs (rfc-1489)
*/
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/timex.h>
#include <asm/segment.h>
/*
* The timezone where the local system is located. Used as a default by some
* programs who obtain this value by using gettimeofday.
*/
struct timezone sys_tz = { 0, 0};
#ifndef __alpha__
/*
* sys_time() can be implemented in user-level using
* sys_gettimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage int sys_time(int * tloc)
{
int i;
i = CURRENT_TIME;
if (tloc) {
int error = verify_area(VERIFY_WRITE, tloc, sizeof(*tloc));
if (error)
return error;
put_user(i,tloc);
}
return i;
}
/*
* sys_stime() can be implemented in user-level using
* sys_settimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage int sys_stime(int * tptr)
{
int error, value;
if (!suser())
return -EPERM;
error = verify_area(VERIFY_READ, tptr, sizeof(*tptr));
if (error)
return error;
value = get_user(tptr);
cli();
xtime.tv_sec = value;
xtime.tv_usec = 0;
time_state = TIME_ERROR;
time_maxerror = MAXPHASE;
time_esterror = MAXPHASE;
sti();
return 0;
}
#endif
asmlinkage int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
{
int error;
if (tv) {
struct timeval ktv;
error = verify_area(VERIFY_WRITE, tv, sizeof *tv);
if (error)
return error;
do_gettimeofday(&ktv);
memcpy_tofs(tv, &ktv, sizeof(ktv));
}
if (tz) {
error = verify_area(VERIFY_WRITE, tz, sizeof *tz);
if (error)
return error;
memcpy_tofs(tz, &sys_tz, sizeof(sys_tz));
}
return 0;
}
/*
* Adjust the time obtained from the CMOS to be UTC time instead of
* local time.
*
* This is ugly, but preferable to the alternatives. Otherwise we
* would either need to write a program to do it in /etc/rc (and risk
* confusion if the program gets run more than once; it would also be
* hard to make the program warp the clock precisely n hours) or
* compile in the timezone information into the kernel. Bad, bad....
*
* - TYT, 1992-01-01
*
* The best thing to do is to keep the CMOS clock in universal time (UTC)
* as real UNIX machines always do it. This avoids all headaches about
* daylight saving times and warping kernel clocks.
*/
inline static void warp_clock(void)
{
cli();
xtime.tv_sec += sys_tz.tz_minuteswest * 60;
sti();
}
/*
* In case for some reason the CMOS clock has not already been running
* in UTC, but in some local time: The first time we set the timezone,
* we will warp the clock so that it is ticking UTC time instead of
* local time. Presumably, if someone is setting the timezone then we
* are running in an environment where the programs understand about
* timezones. This should be done at boot time in the /etc/rc script,
* as soon as possible, so that the clock can be set right. Otherwise,
* various programs will get confused when the clock gets warped.
*/
asmlinkage int sys_settimeofday(struct timeval *tv, struct timezone *tz)
{
static int firsttime = 1;
struct timeval new_tv;
struct timezone new_tz;
if (!suser())
return -EPERM;
if (tv) {
int error = verify_area(VERIFY_READ, tv, sizeof(*tv));
if (error)
return error;
memcpy_fromfs(&new_tv, tv, sizeof(*tv));
}
if (tz) {
int error = verify_area(VERIFY_READ, tz, sizeof(*tz));
if (error)
return error;
memcpy_fromfs(&new_tz, tz, sizeof(*tz));
}
if (tz) {
sys_tz = new_tz;
if (firsttime) {
firsttime = 0;
if (!tv)
warp_clock();
}
}
if (tv)
do_settimeofday(&new_tv);
return 0;
}
long pps_offset = 0; /* pps time offset (us) */
long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */
long pps_freq = 0; /* frequency offset (scaled ppm) */
long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
long pps_valid = PPS_VALID; /* pps signal watchdog counter */
int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
long pps_jitcnt = 0; /* jitter limit exceeded */
long pps_calcnt = 0; /* calibration intervals */
long pps_errcnt = 0; /* calibration errors */
long pps_stbcnt = 0; /* stability limit exceeded */
/* hook for a loadable hardpps kernel module */
void (*hardpps_ptr)(struct timeval *) = (void (*)(struct timeval *))0;
/* adjtimex mainly allows reading (and writing, if superuser) of
* kernel time-keeping variables. used by xntpd.
*/
asmlinkage int sys_adjtimex(struct timex *txc_p)
{
long ltemp, mtemp, save_adjust;
int error;
/* Local copy of parameter */
struct timex txc;
error = verify_area(VERIFY_WRITE, txc_p, sizeof(struct timex));
if (error)
return error;
/* Copy the user data space into the kernel copy
* structure. But bear in mind that the structures
* may change
*/
memcpy_fromfs(&txc, txc_p, sizeof(struct timex));
/* In order to modify anything, you gotta be super-user! */
if (txc.modes && !suser())
return -EPERM;
/* Now we validate the data before disabling interrupts
*/
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/HZ || txc.tick > 1100000/HZ)
return -EINVAL;
cli();
/* Save for later - semantics of adjtime is to return old value */
save_adjust = time_adjust;
/* If there are input parameters, then process them */
if (txc.modes)
{
if (time_state == TIME_BAD)
time_state = TIME_OK;
if (txc.modes & ADJ_STATUS)
time_status = txc.status;
if (txc.modes & ADJ_FREQUENCY)
time_freq = txc.freq;
if (txc.modes & ADJ_MAXERROR)
time_maxerror = txc.maxerror;
if (txc.modes & ADJ_ESTERROR)
time_esterror = txc.esterror;
if (txc.modes & ADJ_TIMECONST)
time_constant = txc.constant;
if (txc.modes & ADJ_OFFSET)
if ((txc.modes == ADJ_OFFSET_SINGLESHOT)
|| !(time_status & STA_PLL))
{
time_adjust = txc.offset;
}
else if ((time_status & STA_PLL)||(time_status & STA_PPSTIME))
{
ltemp = (time_status & STA_PPSTIME &&
time_status & STA_PPSSIGNAL) ?
pps_offset : txc.offset;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
if (ltemp > MAXPHASE)
time_offset = MAXPHASE << SHIFT_UPDATE;
else if (ltemp < -MAXPHASE)
time_offset = -(MAXPHASE << SHIFT_UPDATE);
else
time_offset = ltemp << SHIFT_UPDATE;
/*
* 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;
if (time_status & STA_FLL)
{
if (mtemp >= MINSEC)
{
ltemp = ((time_offset / mtemp) << (SHIFT_USEC -
SHIFT_UPDATE));
if (ltemp < 0)
time_freq -= -ltemp >> SHIFT_KH;
else
time_freq += ltemp >> SHIFT_KH;
}
}
else
{
if (mtemp < MAXSEC)
{
ltemp *= mtemp;
if (ltemp < 0)
time_freq -= -ltemp >> (time_constant +
time_constant + SHIFT_KF -
SHIFT_USEC);
else
time_freq += ltemp >> (time_constant +
time_constant + SHIFT_KF -
SHIFT_USEC);
}
}
if (time_freq > time_tolerance)
time_freq = time_tolerance;
else if (time_freq < -time_tolerance)
time_freq = -time_tolerance;
} /* STA_PLL || STA_PPSTIME */
if (txc.modes & ADJ_TICK)
tick = txc.tick;
}
txc.offset = save_adjust;
txc.freq = time_freq;
txc.maxerror = time_maxerror;
txc.esterror = time_esterror;
txc.status = time_status;
txc.constant = time_constant;
txc.precision = time_precision;
txc.tolerance = time_tolerance;
txc.time = xtime;
txc.tick = tick;
txc.ppsfreq = pps_freq;
txc.jitter = pps_jitter;
txc.shift = pps_shift;
txc.stabil = pps_stabil;
txc.jitcnt = pps_jitcnt;
txc.calcnt = pps_calcnt;
txc.errcnt = pps_errcnt;
txc.stbcnt = pps_stbcnt;
sti();
memcpy_tofs(txc_p, &txc, sizeof(struct timex));
return time_state;
}