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 // SPDX-License-Identifier: GPL-2.0
 /*
  *  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:
  *
  * 1993-09-02    Philip Gladstone
  *      Created file with time related functions from sched/core.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/export.h>
 #include <linux/kernel.h>
 #include <linux/timex.h>
 #include <linux/capability.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/errno.h>
 #include <linux/syscalls.h>
 #include <linux/security.h>
 #include <linux/fs.h>
 #include <linux/math64.h>
 #include <linux/ptrace.h>
 
 #include <linux/uaccess.h>
 #include <linux/compat.h>
 #include <asm/unistd.h>
 
 #include <generated/timeconst.h>
 #include "timekeeping.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).
  */
 SYSCALL_DEFINE1(time, __kernel_old_time_t __user *, tloc)
 {
     __kernel_old_time_t i = (__kernel_old_time_t)ktime_get_real_seconds();
 
     if (tloc) {
         if (put_user(i,tloc))
             return -EFAULT;
     }
     force_successful_syscall_return();
     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).
  */
 
 SYSCALL_DEFINE1(stime, __kernel_old_time_t __user *, tptr)
 {
     struct timespec64 tv;
     int err;
 
     if (get_user(tv.tv_sec, tptr))
         return -EFAULT;
 
     tv.tv_nsec = 0;
 
     err = security_settime64(&tv, NULL);
     if (err)
         return err;
 
     do_settimeofday64(&tv);
     return 0;
 }
 
 #endif /* __ARCH_WANT_SYS_TIME */
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 #ifdef __ARCH_WANT_SYS_TIME32
 
 /* old_time32_t is a 32 bit "long" and needs to get converted. */
 SYSCALL_DEFINE1(time32, old_time32_t __user *, tloc)
 {
     old_time32_t i;
 
     i = (old_time32_t)ktime_get_real_seconds();
 
     if (tloc) {
         if (put_user(i,tloc))
             return -EFAULT;
     }
     force_successful_syscall_return();
     return i;
 }
 
 SYSCALL_DEFINE1(stime32, old_time32_t __user *, tptr)
 {
     struct timespec64 tv;
     int err;
 
     if (get_user(tv.tv_sec, tptr))
         return -EFAULT;
 
     tv.tv_nsec = 0;
 
     err = security_settime64(&tv, NULL);
     if (err)
         return err;
 
     do_settimeofday64(&tv);
     return 0;
 }
 
 #endif /* __ARCH_WANT_SYS_TIME32 */
 #endif
 
 SYSCALL_DEFINE2(gettimeofday, struct __kernel_old_timeval __user *, tv,
         struct timezone __user *, tz)
 {
     if (likely(tv != NULL)) {
         struct timespec64 ts;
 
         ktime_get_real_ts64(&ts);
         if (put_user(ts.tv_sec, &tv->tv_sec) ||
             put_user(ts.tv_nsec / 1000, &tv->tv_usec))
             return -EFAULT;
     }
     if (unlikely(tz != NULL)) {
         if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
             return -EFAULT;
     }
     return 0;
 }
 
 /*
  * 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_settimeofday64(const struct timespec64 *tv, const struct timezone *tz)
 {
     static int firsttime = 1;
     int error = 0;
 
     if (tv && !timespec64_valid_settod(tv))
         return -EINVAL;
 
     error = security_settime64(tv, tz);
     if (error)
         return error;
 
     if (tz) {
         /* Verify we're within the +-15 hrs range */
         if (tz->tz_minuteswest > 15*60 || tz->tz_minuteswest < -15*60)
             return -EINVAL;
 
         sys_tz = *tz;
         update_vsyscall_tz();
         if (firsttime) {
             firsttime = 0;
             if (!tv)
                 timekeeping_warp_clock();
         }
     }
     if (tv)
         return do_settimeofday64(tv);
     return 0;
 }
 
 SYSCALL_DEFINE2(settimeofday, struct __kernel_old_timeval __user *, tv,
         struct timezone __user *, tz)
 {
     struct timespec64 new_ts;
     struct timezone new_tz;
 
     if (tv) {
         if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
             get_user(new_ts.tv_nsec, &tv->tv_usec))
             return -EFAULT;
 
         if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
             return -EINVAL;
 
         new_ts.tv_nsec *= NSEC_PER_USEC;
     }
     if (tz) {
         if (copy_from_user(&new_tz, tz, sizeof(*tz)))
             return -EFAULT;
     }
 
     return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
 }
 
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE2(gettimeofday, struct old_timeval32 __user *, tv,
                struct timezone __user *, tz)
 {
     if (tv) {
         struct timespec64 ts;
 
         ktime_get_real_ts64(&ts);
         if (put_user(ts.tv_sec, &tv->tv_sec) ||
             put_user(ts.tv_nsec / 1000, &tv->tv_usec))
             return -EFAULT;
     }
     if (tz) {
         if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
             return -EFAULT;
     }
 
     return 0;
 }
 
 COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
                struct timezone __user *, tz)
 {
     struct timespec64 new_ts;
     struct timezone new_tz;
 
     if (tv) {
         if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
             get_user(new_ts.tv_nsec, &tv->tv_usec))
             return -EFAULT;
 
         if (new_ts.tv_nsec > USEC_PER_SEC || new_ts.tv_nsec < 0)
             return -EINVAL;
 
         new_ts.tv_nsec *= NSEC_PER_USEC;
     }
     if (tz) {
         if (copy_from_user(&new_tz, tz, sizeof(*tz)))
             return -EFAULT;
     }
 
     return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
 }
 #endif
 
 #ifdef CONFIG_64BIT
 SYSCALL_DEFINE1(adjtimex, struct __kernel_timex __user *, txc_p)
 {
     struct __kernel_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 __kernel_timex)))
         return -EFAULT;
     ret = do_adjtimex(&txc);
     return copy_to_user(txc_p, &txc, sizeof(struct __kernel_timex)) ? -EFAULT : ret;
 }
 #endif
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 int get_old_timex32(struct __kernel_timex *txc, const struct old_timex32 __user *utp)
 {
     struct old_timex32 tx32;
 
     memset(txc, 0, sizeof(struct __kernel_timex));
     if (copy_from_user(&tx32, utp, sizeof(struct old_timex32)))
         return -EFAULT;
 
     txc->modes = tx32.modes;
     txc->offset = tx32.offset;
     txc->freq = tx32.freq;
     txc->maxerror = tx32.maxerror;
     txc->esterror = tx32.esterror;
     txc->status = tx32.status;
     txc->constant = tx32.constant;
     txc->precision = tx32.precision;
     txc->tolerance = tx32.tolerance;
     txc->time.tv_sec = tx32.time.tv_sec;
     txc->time.tv_usec = tx32.time.tv_usec;
     txc->tick = tx32.tick;
     txc->ppsfreq = tx32.ppsfreq;
     txc->jitter = tx32.jitter;
     txc->shift = tx32.shift;
     txc->stabil = tx32.stabil;
     txc->jitcnt = tx32.jitcnt;
     txc->calcnt = tx32.calcnt;
     txc->errcnt = tx32.errcnt;
     txc->stbcnt = tx32.stbcnt;
 
     return 0;
 }
 
 int put_old_timex32(struct old_timex32 __user *utp, const struct __kernel_timex *txc)
 {
     struct old_timex32 tx32;
 
     memset(&tx32, 0, sizeof(struct old_timex32));
     tx32.modes = txc->modes;
     tx32.offset = txc->offset;
     tx32.freq = txc->freq;
     tx32.maxerror = txc->maxerror;
     tx32.esterror = txc->esterror;
     tx32.status = txc->status;
     tx32.constant = txc->constant;
     tx32.precision = txc->precision;
     tx32.tolerance = txc->tolerance;
     tx32.time.tv_sec = txc->time.tv_sec;
     tx32.time.tv_usec = txc->time.tv_usec;
     tx32.tick = txc->tick;
     tx32.ppsfreq = txc->ppsfreq;
     tx32.jitter = txc->jitter;
     tx32.shift = txc->shift;
     tx32.stabil = txc->stabil;
     tx32.jitcnt = txc->jitcnt;
     tx32.calcnt = txc->calcnt;
     tx32.errcnt = txc->errcnt;
     tx32.stbcnt = txc->stbcnt;
     tx32.tai = txc->tai;
     if (copy_to_user(utp, &tx32, sizeof(struct old_timex32)))
         return -EFAULT;
     return 0;
 }
 
 SYSCALL_DEFINE1(adjtimex_time32, struct old_timex32 __user *, utp)
 {
     struct __kernel_timex txc;
     int err, ret;
 
     err = get_old_timex32(&txc, utp);
     if (err)
         return err;
 
     ret = do_adjtimex(&txc);
 
     err = put_old_timex32(utp, &txc);
     if (err)
         return err;
 
     return ret;
 }
 #endif
 
 /*
  * Convert jiffies to milliseconds and back.
  *
  * Avoid unnecessary multiplications/divisions in the
  * two most common HZ cases:
  */
 unsigned int jiffies_to_msecs(const unsigned long j)
 {
 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
     return (MSEC_PER_SEC / HZ) * j;
 #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
     return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
 #else
 # if BITS_PER_LONG == 32
     return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >>
            HZ_TO_MSEC_SHR32;
 # else
     return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
 # endif
 #endif
 }
 EXPORT_SYMBOL(jiffies_to_msecs);
 
 unsigned int jiffies_to_usecs(const unsigned long j)
 {
     /*
      * Hz usually doesn't go much further MSEC_PER_SEC.
      * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
      */
     BUILD_BUG_ON(HZ > USEC_PER_SEC);
 
 #if !(USEC_PER_SEC % HZ)
     return (USEC_PER_SEC / HZ) * j;
 #else
 # if BITS_PER_LONG == 32
     return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
 # else
     return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
 # endif
 #endif
 }
 EXPORT_SYMBOL(jiffies_to_usecs);
 
 /*
  * mktime64 - Converts date to seconds.
  * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
  * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
  *
  * [For the Julian calendar (which was used in Russia before 1917,
  * Britain & colonies before 1752, anywhere else before 1582,
  * and is still in use by some communities) leave out the
  * -year/100+year/400 terms, and add 10.]
  *
  * This algorithm was first published by Gauss (I think).
  *
  * A leap second can be indicated by calling this function with sec as
  * 60 (allowable under ISO 8601).  The leap second is treated the same
  * as the following second since they don't exist in UNIX time.
  *
  * An encoding of midnight at the end of the day as 24:00:00 - ie. midnight
  * tomorrow - (allowable under ISO 8601) is supported.
  */
 time64_t mktime64(const unsigned int year0, const unsigned int mon0,
         const unsigned int day, const unsigned int hour,
         const unsigned int min, const unsigned int sec)
 {
     unsigned int mon = mon0, year = year0;
 
     /* 1..12 -> 11,12,1..10 */
     if (0 >= (int) (mon -= 2)) {
         mon += 12;  /* Puts Feb last since it has leap day */
         year -= 1;
     }
 
     return ((((time64_t)
           (year/4 - year/100 + year/400 + 367*mon/12 + day) +
           year*365 - 719499
         )*24 + hour /* now have hours - midnight tomorrow handled here */
       )*60 + min /* now have minutes */
     )*60 + sec; /* finally seconds */
 }
 EXPORT_SYMBOL(mktime64);
 
 struct __kernel_old_timeval ns_to_kernel_old_timeval(s64 nsec)
 {
     struct timespec64 ts = ns_to_timespec64(nsec);
     struct __kernel_old_timeval tv;
 
     tv.tv_sec = ts.tv_sec;
     tv.tv_usec = (suseconds_t)ts.tv_nsec / 1000;
 
     return tv;
 }
 EXPORT_SYMBOL(ns_to_kernel_old_timeval);
 
 /**
  * set_normalized_timespec - set timespec sec and nsec parts and normalize
  *
  * @ts:     pointer to timespec variable to be set
  * @sec:    seconds to set
  * @nsec:   nanoseconds to set
  *
  * Set seconds and nanoseconds field of a timespec variable and
  * normalize to the timespec storage format
  *
  * Note: The tv_nsec part is always in the range of
  *  0 <= tv_nsec < NSEC_PER_SEC
  * For negative values only the tv_sec field is negative !
  */
 void set_normalized_timespec64(struct timespec64 *ts, time64_t sec, s64 nsec)
 {
     while (nsec >= NSEC_PER_SEC) {
         /*
          * The following asm() prevents the compiler from
          * optimising this loop into a modulo operation. See
          * also __iter_div_u64_rem() in include/linux/time.h
          */
         asm("" : "+rm"(nsec));
         nsec -= NSEC_PER_SEC;
         ++sec;
     }
     while (nsec < 0) {
         asm("" : "+rm"(nsec));
         nsec += NSEC_PER_SEC;
         --sec;
     }
     ts->tv_sec = sec;
     ts->tv_nsec = nsec;
 }
 EXPORT_SYMBOL(set_normalized_timespec64);
 
 /**
  * ns_to_timespec64 - Convert nanoseconds to timespec64
  * @nsec:       the nanoseconds value to be converted
  *
  * Returns the timespec64 representation of the nsec parameter.
  */
 struct timespec64 ns_to_timespec64(s64 nsec)
 {
     struct timespec64 ts = { 0, 0 };
     s32 rem;
 
     if (likely(nsec > 0)) {
         ts.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
         ts.tv_nsec = rem;
     } else if (nsec < 0) {
         /*
          * With negative times, tv_sec points to the earlier
          * second, and tv_nsec counts the nanoseconds since
          * then, so tv_nsec is always a positive number.
          */
         ts.tv_sec = -div_u64_rem(-nsec - 1, NSEC_PER_SEC, &rem) - 1;
         ts.tv_nsec = NSEC_PER_SEC - rem - 1;
     }
 
     return ts;
 }
 EXPORT_SYMBOL(ns_to_timespec64);
 
 /**
  * msecs_to_jiffies: - convert milliseconds to jiffies
  * @m:  time in milliseconds
  *
  * conversion is done as follows:
  *
  * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
  *
  * - 'too large' values [that would result in larger than
  *   MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
  *
  * - all other values are converted to jiffies by either multiplying
  *   the input value by a factor or dividing it with a factor and
  *   handling any 32-bit overflows.
  *   for the details see __msecs_to_jiffies()
  *
  * msecs_to_jiffies() checks for the passed in value being a constant
  * via __builtin_constant_p() allowing gcc to eliminate most of the
  * code, __msecs_to_jiffies() is called if the value passed does not
  * allow constant folding and the actual conversion must be done at
  * runtime.
  * the _msecs_to_jiffies helpers are the HZ dependent conversion
  * routines found in include/linux/jiffies.h
  */
 unsigned long __msecs_to_jiffies(const unsigned int m)
 {
     /*
      * Negative value, means infinite timeout:
      */
     if ((int)m < 0)
         return MAX_JIFFY_OFFSET;
     return _msecs_to_jiffies(m);
 }
 EXPORT_SYMBOL(__msecs_to_jiffies);
 
 unsigned long __usecs_to_jiffies(const unsigned int u)
 {
     if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
         return MAX_JIFFY_OFFSET;
     return _usecs_to_jiffies(u);
 }
 EXPORT_SYMBOL(__usecs_to_jiffies);
 
 /*
  * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
  * that a remainder subtract here would not do the right thing as the
  * resolution values don't fall on second boundaries.  I.e. the line:
  * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding.
  * Note that due to the small error in the multiplier here, this
  * rounding is incorrect for sufficiently large values of tv_nsec, but
  * well formed timespecs should have tv_nsec < NSEC_PER_SEC, so we're
  * OK.
  *
  * Rather, we just shift the bits off the right.
  *
  * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec
  * value to a scaled second value.
  */
 
 unsigned long
 timespec64_to_jiffies(const struct timespec64 *value)
 {
     u64 sec = value->tv_sec;
     long nsec = value->tv_nsec + TICK_NSEC - 1;
 
     if (sec >= MAX_SEC_IN_JIFFIES){
         sec = MAX_SEC_IN_JIFFIES;
         nsec = 0;
     }
     return ((sec * SEC_CONVERSION) +
         (((u64)nsec * NSEC_CONVERSION) >>
          (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
 
 }
 EXPORT_SYMBOL(timespec64_to_jiffies);
 
 void
 jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
 {
     /*
      * Convert jiffies to nanoseconds and separate with
      * one divide.
      */
     u32 rem;
     value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
                     NSEC_PER_SEC, &rem);
     value->tv_nsec = rem;
 }
 EXPORT_SYMBOL(jiffies_to_timespec64);
 
 /*
  * Convert jiffies/jiffies_64 to clock_t and back.
  */
 clock_t jiffies_to_clock_t(unsigned long x)
 {
 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
 # if HZ < USER_HZ
     return x * (USER_HZ / HZ);
 # else
     return x / (HZ / USER_HZ);
 # endif
 #else
     return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
 #endif
 }
 EXPORT_SYMBOL(jiffies_to_clock_t);
 
 unsigned long clock_t_to_jiffies(unsigned long x)
 {
 #if (HZ % USER_HZ)==0
     if (x >= ~0UL / (HZ / USER_HZ))
         return ~0UL;
     return x * (HZ / USER_HZ);
 #else
     /* Don't worry about loss of precision here .. */
     if (x >= ~0UL / HZ * USER_HZ)
         return ~0UL;
 
     /* .. but do try to contain it here */
     return div_u64((u64)x * HZ, USER_HZ);
 #endif
 }
 EXPORT_SYMBOL(clock_t_to_jiffies);
 
 u64 jiffies_64_to_clock_t(u64 x)
 {
 #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
 # if HZ < USER_HZ
     x = div_u64(x * USER_HZ, HZ);
 # elif HZ > USER_HZ
     x = div_u64(x, HZ / USER_HZ);
 # else
     /* Nothing to do */
 # endif
 #else
     /*
      * There are better ways that don't overflow early,
      * but even this doesn't overflow in hundreds of years
      * in 64 bits, so..
      */
     x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
 #endif
     return x;
 }
 EXPORT_SYMBOL(jiffies_64_to_clock_t);
 
 u64 nsec_to_clock_t(u64 x)
 {
 #if (NSEC_PER_SEC % USER_HZ) == 0
     return div_u64(x, NSEC_PER_SEC / USER_HZ);
 #elif (USER_HZ % 512) == 0
     return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
 #else
     /*
          * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
          * overflow after 64.99 years.
          * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
          */
     return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
 #endif
 }
 
 u64 jiffies64_to_nsecs(u64 j)
 {
 #if !(NSEC_PER_SEC % HZ)
     return (NSEC_PER_SEC / HZ) * j;
 # else
     return div_u64(j * HZ_TO_NSEC_NUM, HZ_TO_NSEC_DEN);
 #endif
 }
 EXPORT_SYMBOL(jiffies64_to_nsecs);
 
 u64 jiffies64_to_msecs(const u64 j)
 {
 #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
     return (MSEC_PER_SEC / HZ) * j;
 #else
     return div_u64(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
 #endif
 }
 EXPORT_SYMBOL(jiffies64_to_msecs);
 
 /**
  * nsecs_to_jiffies64 - Convert nsecs in u64 to jiffies64
  *
  * @n:  nsecs in u64
  *
  * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
  * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
  * for scheduler, not for use in device drivers to calculate timeout value.
  *
  * note:
  *   NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
  *   ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
  */
 u64 nsecs_to_jiffies64(u64 n)
 {
 #if (NSEC_PER_SEC % HZ) == 0
     /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
     return div_u64(n, NSEC_PER_SEC / HZ);
 #elif (HZ % 512) == 0
     /* overflow after 292 years if HZ = 1024 */
     return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
 #else
     /*
      * Generic case - optimized for cases where HZ is a multiple of 3.
      * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
      */
     return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
 #endif
 }
 EXPORT_SYMBOL(nsecs_to_jiffies64);
 
 /**
  * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
  *
  * @n:  nsecs in u64
  *
  * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
  * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
  * for scheduler, not for use in device drivers to calculate timeout value.
  *
  * note:
  *   NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
  *   ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
  */
 unsigned long nsecs_to_jiffies(u64 n)
 {
     return (unsigned long)nsecs_to_jiffies64(n);
 }
 EXPORT_SYMBOL_GPL(nsecs_to_jiffies);
 
 /*
  * Add two timespec64 values and do a safety check for overflow.
  * It's assumed that both values are valid (>= 0).
  * And, each timespec64 is in normalized form.
  */
 struct timespec64 timespec64_add_safe(const struct timespec64 lhs,
                 const struct timespec64 rhs)
 {
     struct timespec64 res;
 
     set_normalized_timespec64(&res, (timeu64_t) lhs.tv_sec + rhs.tv_sec,
             lhs.tv_nsec + rhs.tv_nsec);
 
     if (unlikely(res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)) {
         res.tv_sec = TIME64_MAX;
         res.tv_nsec = 0;
     }
 
     return res;
 }
 
 int get_timespec64(struct timespec64 *ts,
            const struct __kernel_timespec __user *uts)
 {
     struct __kernel_timespec kts;
     int ret;
 
     ret = copy_from_user(&kts, uts, sizeof(kts));
     if (ret)
         return -EFAULT;
 
     ts->tv_sec = kts.tv_sec;
 
     /* Zero out the padding in compat mode */
     if (in_compat_syscall())
         kts.tv_nsec &= 0xFFFFFFFFUL;
 
     /* In 32-bit mode, this drops the padding */
     ts->tv_nsec = kts.tv_nsec;
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(get_timespec64);
 
 int put_timespec64(const struct timespec64 *ts,
            struct __kernel_timespec __user *uts)
 {
     struct __kernel_timespec kts = {
         .tv_sec = ts->tv_sec,
         .tv_nsec = ts->tv_nsec
     };
 
     return copy_to_user(uts, &kts, sizeof(kts)) ? -EFAULT : 0;
 }
 EXPORT_SYMBOL_GPL(put_timespec64);
 
 static int __get_old_timespec32(struct timespec64 *ts64,
                    const struct old_timespec32 __user *cts)
 {
     struct old_timespec32 ts;
     int ret;
 
     ret = copy_from_user(&ts, cts, sizeof(ts));
     if (ret)
         return -EFAULT;
 
     ts64->tv_sec = ts.tv_sec;
     ts64->tv_nsec = ts.tv_nsec;
 
     return 0;
 }
 
 static int __put_old_timespec32(const struct timespec64 *ts64,
                    struct old_timespec32 __user *cts)
 {
     struct old_timespec32 ts = {
         .tv_sec = ts64->tv_sec,
         .tv_nsec = ts64->tv_nsec
     };
     return copy_to_user(cts, &ts, sizeof(ts)) ? -EFAULT : 0;
 }
 
 int get_old_timespec32(struct timespec64 *ts, const void __user *uts)
 {
     if (COMPAT_USE_64BIT_TIME)
         return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
     else
         return __get_old_timespec32(ts, uts);
 }
 EXPORT_SYMBOL_GPL(get_old_timespec32);
 
 int put_old_timespec32(const struct timespec64 *ts, void __user *uts)
 {
     if (COMPAT_USE_64BIT_TIME)
         return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
     else
         return __put_old_timespec32(ts, uts);
 }
 EXPORT_SYMBOL_GPL(put_old_timespec32);
 
 int get_itimerspec64(struct itimerspec64 *it,
             const struct __kernel_itimerspec __user *uit)
 {
     int ret;
 
     ret = get_timespec64(&it->it_interval, &uit->it_interval);
     if (ret)
         return ret;
 
     ret = get_timespec64(&it->it_value, &uit->it_value);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(get_itimerspec64);
 
 int put_itimerspec64(const struct itimerspec64 *it,
             struct __kernel_itimerspec __user *uit)
 {
     int ret;
 
     ret = put_timespec64(&it->it_interval, &uit->it_interval);
     if (ret)
         return ret;
 
     ret = put_timespec64(&it->it_value, &uit->it_value);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(put_itimerspec64);
 
 int get_old_itimerspec32(struct itimerspec64 *its,
             const struct old_itimerspec32 __user *uits)
 {
 
     if (__get_old_timespec32(&its->it_interval, &uits->it_interval) ||
         __get_old_timespec32(&its->it_value, &uits->it_value))
         return -EFAULT;
     return 0;
 }
 EXPORT_SYMBOL_GPL(get_old_itimerspec32);
 
 int put_old_itimerspec32(const struct itimerspec64 *its,
             struct old_itimerspec32 __user *uits)
 {
     if (__put_old_timespec32(&its->it_interval, &uits->it_interval) ||
         __put_old_timespec32(&its->it_value, &uits->it_value))
         return -EFAULT;
     return 0;
 }
 EXPORT_SYMBOL_GPL(put_old_itimerspec32);

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