[IPV4]: Avoid common branch misprediction while checking csum in ip_rcv()

[hh.org.git] / kernel / time.c

/*
 *  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-1589)
 * 1999-01-16    Ulrich Windl
 *      Introduced error checking for many cases in adjtimex().
 *      Updated NTP code according to technical memorandum Jan '96
 *      "A Kernel Model for Precision Timekeeping" by Dave Mills
 *      Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
 *      (Even though the technical memorandum forbids it)
 * 2004-07-14    Christoph Lameter
 *      Added getnstimeofday to allow the posix timer functions to return
 *      with nanosecond accuracy
 */

#include <linux/module.h>
#include <linux/timex.h>
#include <linux/errno.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/module.h>

#include <asm/uaccess.h>
#include <asm/unistd.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;

EXPORT_SYMBOL(sys_tz);

#ifdef __ARCH_WANT_SYS_TIME

/*
 * 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 long sys_time(time_t __user * tloc)
{
        time_t i;
        struct timeval tv;

        do_gettimeofday(&tv);
        i = tv.tv_sec;

        if (tloc) {
                if (put_user(i,tloc))
                        i = -EFAULT;
        }
        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 long sys_stime(time_t __user *tptr)
{
        struct timespec tv;
        int err;

        if (get_user(tv.tv_sec, tptr))
                return -EFAULT;

        tv.tv_nsec = 0;

        err = security_settime(&tv, NULL);
        if (err)
                return err;

        do_settimeofday(&tv);
        return 0;
}

#endif /* __ARCH_WANT_SYS_TIME */

asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
{
        if (likely(tv != NULL)) {
                struct timeval ktv;
                do_gettimeofday(&ktv);
                if (copy_to_user(tv, &ktv, sizeof(ktv)))
                        return -EFAULT;
        }
        if (unlikely(tz != NULL)) {
                if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
                        return -EFAULT;
        }
        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.
 */
static inline void warp_clock(void)
{
        write_seqlock_irq(&xtime_lock);
        wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
        xtime.tv_sec += sys_tz.tz_minuteswest * 60;
        time_interpolator_reset();
        write_sequnlock_irq(&xtime_lock);
        clock_was_set();
}

/*
 * 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.
 */

int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
{
        static int firsttime = 1;
        int error = 0;

        error = security_settime(tv, tz);
        if (error)
                return error;

        if (tz) {
                /* SMP safe, global irq locking makes it work. */
                sys_tz = *tz;
                if (firsttime) {
                        firsttime = 0;
                        if (!tv)
                                warp_clock();
                }
        }
        if (tv)
        {
                /* SMP safe, again the code in arch/foo/time.c should
                 * globally block out interrupts when it runs.
                 */
                return do_settimeofday(tv);
        }
        return 0;
}

asmlinkage long sys_settimeofday(struct timeval __user *tv,
                                struct timezone __user *tz)
{
        struct timeval user_tv;
        struct timespec new_ts;
        struct timezone new_tz;

        if (tv) {
                if (copy_from_user(&user_tv, tv, sizeof(*tv)))
                        return -EFAULT;
                new_ts.tv_sec = user_tv.tv_sec;
                new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
        }
        if (tz) {
                if (copy_from_user(&new_tz, tz, sizeof(*tz)))
                        return -EFAULT;
        }

        return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
}

long pps_offset;                /* pps time offset (us) */
long pps_jitter = MAXTIME;      /* time dispersion (jitter) (us) */

long pps_freq;                  /* 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;                /* jitter limit exceeded */
long pps_calcnt;                /* calibration intervals */
long pps_errcnt;                /* calibration errors */
long pps_stbcnt;                /* stability limit exceeded */

/* hook for a loadable hardpps kernel module */
void (*hardpps_ptr)(struct timeval *);

/* we call this to notify the arch when the clock is being
 * controlled.  If no such arch routine, do nothing.
 */
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;
        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_next_adjust ? time_next_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 = txc->freq - pps_freq;
            }

            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 = txc->constant;
            }

            if (txc->modes & ADJ_OFFSET) {      /* values checked earlier */
                if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
                    /* adjtime() is independent from ntp_adjtime() */
                    if ((time_next_adjust = txc->offset) == 0)
                         time_adjust = 0;
                }
                else if ( time_status & (STA_PLL | STA_PPSTIME) ) {
                    ltemp = (time_status & (STA_PPSTIME | STA_PPSSIGNAL)) ==
                            (STA_PPSTIME | 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 /* calibration interval too short (p. 12) */
                                result = TIME_ERROR;
                    } else {    /* PLL mode */
                        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);
                        } else /* calibration interval too long (p. 12) */
                                result = TIME_ERROR;
                    }
                    if (time_freq > time_tolerance)
                        time_freq = time_tolerance;
                    else if (time_freq < -time_tolerance)
                        time_freq = -time_tolerance;
                } /* STA_PLL || STA_PPSTIME */
            } /* txc->modes & ADJ_OFFSET */
            if (txc->modes & ADJ_TICK) {
                tick_usec = txc->tick;
                tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
            }
        } /* txc->modes */
leave:  if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
            || ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
                && (time_status & STA_PPSSIGNAL) == 0)
            /* p. 24, (b) */
            || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
                == (STA_PPSTIME|STA_PPSJITTER))
            /* p. 24, (c) */
            || ((time_status & STA_PPSFREQ) != 0
                && (time_status & (STA_PPSWANDER|STA_PPSERROR)) != 0))
            /* p. 24, (d) */
                result = TIME_ERROR;
        
        if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
            txc->offset    = save_adjust;
        else {
            if (time_offset < 0)
                txc->offset = -(-time_offset >> SHIFT_UPDATE);
            else
                txc->offset = time_offset >> SHIFT_UPDATE;
        }
        txc->freq          = time_freq + pps_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->tick          = tick_usec;
        txc->ppsfreq       = pps_freq;
        txc->jitter        = pps_jitter >> PPS_AVG;
        txc->shift         = pps_shift;
        txc->stabil        = pps_stabil;
        txc->jitcnt        = pps_jitcnt;
        txc->calcnt        = pps_calcnt;
        txc->errcnt        = pps_errcnt;
        txc->stbcnt        = pps_stbcnt;
        write_sequnlock_irq(&xtime_lock);
        do_gettimeofday(&txc->time);
        notify_arch_cmos_timer();
        return(result);
}

asmlinkage long sys_adjtimex(struct timex __user *txc_p)
{
        struct timex txc;               /* Local copy of parameter */
        int ret;

        /* Copy the user data space into the kernel copy
         * structure. But bear in mind that the structures
         * may change
         */
        if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
                return -EFAULT;
        ret = do_adjtimex(&txc);
        return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
}

inline struct timespec current_kernel_time(void)
{
        struct timespec now;
        unsigned long seq;

        do {
                seq = read_seqbegin(&xtime_lock);
                
                now = xtime;
        } while (read_seqretry(&xtime_lock, seq));

        return now; 
}

EXPORT_SYMBOL(current_kernel_time);

/**
 * current_fs_time - Return FS time
 * @sb: Superblock.
 *
 * Return the current time truncated to the time granuality supported by
 * the fs.
 */
struct timespec current_fs_time(struct super_block *sb)
{
        struct timespec now = current_kernel_time();
        return timespec_trunc(now, sb->s_time_gran);
}
EXPORT_SYMBOL(current_fs_time);

/**
 * timespec_trunc - Truncate timespec to a granuality
 * @t: Timespec
 * @gran: Granuality in ns.
 *
 * Truncate a timespec to a granuality. gran must be smaller than a second.
 * Always rounds down.
 *
 * This function should be only used for timestamps returned by
 * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
 * it doesn't handle the better resolution of the later.
 */
struct timespec timespec_trunc(struct timespec t, unsigned gran)
{
        /*
         * Division is pretty slow so avoid it for common cases.
         * Currently current_kernel_time() never returns better than
         * jiffies resolution. Exploit that.
         */
        if (gran <= jiffies_to_usecs(1) * 1000) {
                /* nothing */
        } else if (gran == 1000000000) {
                t.tv_nsec = 0;
        } else {
                t.tv_nsec -= t.tv_nsec % gran;
        }
        return t;
}
EXPORT_SYMBOL(timespec_trunc);

#ifdef CONFIG_TIME_INTERPOLATION
void getnstimeofday (struct timespec *tv)
{
        unsigned long seq,sec,nsec;

        do {
                seq = read_seqbegin(&xtime_lock);
                sec = xtime.tv_sec;
                nsec = xtime.tv_nsec+time_interpolator_get_offset();
        } while (unlikely(read_seqretry(&xtime_lock, seq)));

        while (unlikely(nsec >= NSEC_PER_SEC)) {
                nsec -= NSEC_PER_SEC;
                ++sec;
        }
        tv->tv_sec = sec;
        tv->tv_nsec = nsec;
}
EXPORT_SYMBOL_GPL(getnstimeofday);

int do_settimeofday (struct timespec *tv)
{
        time_t wtm_sec, sec = tv->tv_sec;
        long wtm_nsec, nsec = tv->tv_nsec;

        if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
                return -EINVAL;

        write_seqlock_irq(&xtime_lock);
        {
                wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
                wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

                set_normalized_timespec(&xtime, sec, nsec);
                set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

                time_adjust = 0;                /* stop active adjtime() */
                time_status |= STA_UNSYNC;
                time_maxerror = NTP_PHASE_LIMIT;
                time_esterror = NTP_PHASE_LIMIT;
                time_interpolator_reset();
        }
        write_sequnlock_irq(&xtime_lock);
        clock_was_set();
        return 0;
}

void do_gettimeofday (struct timeval *tv)
{
        unsigned long seq, nsec, usec, sec, offset;
        do {
                seq = read_seqbegin(&xtime_lock);
                offset = time_interpolator_get_offset();
                sec = xtime.tv_sec;
                nsec = xtime.tv_nsec;
        } while (unlikely(read_seqretry(&xtime_lock, seq)));

        usec = (nsec + offset) / 1000;

        while (unlikely(usec >= USEC_PER_SEC)) {
                usec -= USEC_PER_SEC;
                ++sec;
        }

        tv->tv_sec = sec;
        tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);


#else
/*
 * Simulate gettimeofday using do_gettimeofday which only allows a timeval
 * and therefore only yields usec accuracy
 */
void getnstimeofday(struct timespec *tv)
{
        struct timeval x;

        do_gettimeofday(&x);
        tv->tv_sec = x.tv_sec;
        tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
}
#endif

#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void)
{
        unsigned long seq;
        u64 ret;

        do {
                seq = read_seqbegin(&xtime_lock);
                ret = jiffies_64;
        } while (read_seqretry(&xtime_lock, seq));
        return ret;
}

EXPORT_SYMBOL(get_jiffies_64);
#endif

EXPORT_SYMBOL(jiffies);