--- /dev/null
+/*
+ * 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/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/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 <asm/uaccess.h>
+#include <asm/unistd.h>
+
+#include "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, time_t __user *, tloc)
+{
+ time_t i = get_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, 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 */
+
+SYSCALL_DEFINE2(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;
+}
+
+/*
+ * Indicates if there is an offset between the system clock and the hardware
+ * clock/persistent clock/rtc.
+ */
+int persistent_clock_is_local;
+
+/*
+ * 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)
+{
+ if (sys_tz.tz_minuteswest != 0) {
+ struct timespec adjust;
+
+ persistent_clock_is_local = 1;
+ adjust.tv_sec = sys_tz.tz_minuteswest * 60;
+ adjust.tv_nsec = 0;
+ timekeeping_inject_offset(&adjust);
+ }
+}
+
+/*
+ * 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(const struct timespec *tv, const struct timezone *tz)
+{
+ static int firsttime = 1;
+ int error = 0;
+
+ if (tv && !timespec_valid(tv))
+ return -EINVAL;
+
+ error = security_settime(tv, tz);
+ if (error)
+ return error;
+
+ if (tz) {
+ sys_tz = *tz;
+ update_vsyscall_tz();
+ if (firsttime) {
+ firsttime = 0;
+ if (!tv)
+ warp_clock();
+ }
+ }
+ if (tv)
+ return do_settimeofday(tv);
+ return 0;
+}
+
+SYSCALL_DEFINE2(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;
+
+ if (!timeval_valid(&user_tv))
+ return -EINVAL;
+
+ 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);
+}
+
+SYSCALL_DEFINE1(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;
+}
+
+/**
+ * current_fs_time - Return FS time
+ * @sb: Superblock.
+ *
+ * Return the current time truncated to the time granularity 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);
+
+/*
+ * 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) >> HZ_TO_MSEC_SHR32;
+# else
+ return (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)
+{
+#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+ return (USEC_PER_SEC / HZ) * j;
+#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
+ return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
+#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);
+
+/**
+ * timespec_trunc - Truncate timespec to a granularity
+ * @t: Timespec
+ * @gran: Granularity in ns.
+ *
+ * Truncate a timespec to a granularity. 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 latter.
+ */
+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);
+
+/*
+ * 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).
+ */
+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 */
+ )*60 + min /* now have minutes */
+ )*60 + sec; /* finally seconds */
+}
+EXPORT_SYMBOL(mktime64);
+
+/**
+ * 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_timespec(struct timespec *ts, time_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_timespec);
+
+/**
+ * ns_to_timespec - Convert nanoseconds to timespec
+ * @nsec: the nanoseconds value to be converted
+ *
+ * Returns the timespec representation of the nsec parameter.
+ */
+struct timespec ns_to_timespec(const s64 nsec)
+{
+ struct timespec ts;
+ s32 rem;
+
+ if (!nsec)
+ return (struct timespec) {0, 0};
+
+ ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
+ if (unlikely(rem < 0)) {
+ ts.tv_sec--;
+ rem += NSEC_PER_SEC;
+ }
+ ts.tv_nsec = rem;
+
+ return ts;
+}
+EXPORT_SYMBOL(ns_to_timespec);
+
+/**
+ * ns_to_timeval - Convert nanoseconds to timeval
+ * @nsec: the nanoseconds value to be converted
+ *
+ * Returns the timeval representation of the nsec parameter.
+ */
+struct timeval ns_to_timeval(const s64 nsec)
+{
+ struct timespec ts = ns_to_timespec(nsec);
+ struct timeval tv;
+
+ tv.tv_sec = ts.tv_sec;
+ tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000;
+
+ return tv;
+}
+EXPORT_SYMBOL(ns_to_timeval);
+
+#if BITS_PER_LONG == 32
+/**
+ * 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(const s64 nsec)
+{
+ struct timespec64 ts;
+ s32 rem;
+
+ if (!nsec)
+ return (struct timespec64) {0, 0};
+
+ ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem);
+ if (unlikely(rem < 0)) {
+ ts.tv_sec--;
+ rem += NSEC_PER_SEC;
+ }
+ ts.tv_nsec = rem;
+
+ return ts;
+}
+EXPORT_SYMBOL(ns_to_timespec64);
+#endif
+/*
+ * When we convert to jiffies then we interpret incoming values
+ * the following way:
+ *
+ * - 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
+ *
+ * We must also be careful about 32-bit overflows.
+ */
+unsigned long msecs_to_jiffies(const unsigned int m)
+{
+ /*
+ * Negative value, means infinite timeout:
+ */
+ if ((int)m < 0)
+ return MAX_JIFFY_OFFSET;
+
+#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
+ /*
+ * HZ is equal to or smaller than 1000, and 1000 is a nice
+ * round multiple of HZ, divide with the factor between them,
+ * but round upwards:
+ */
+ return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
+#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
+ /*
+ * HZ is larger than 1000, and HZ is a nice round multiple of
+ * 1000 - simply multiply with the factor between them.
+ *
+ * But first make sure the multiplication result cannot
+ * overflow:
+ */
+ if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+ return MAX_JIFFY_OFFSET;
+
+ return m * (HZ / MSEC_PER_SEC);
+#else
+ /*
+ * Generic case - multiply, round and divide. But first
+ * check that if we are doing a net multiplication, that
+ * we wouldn't overflow:
+ */
+ if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
+ return MAX_JIFFY_OFFSET;
+
+ return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
+ >> MSEC_TO_HZ_SHR32;
+#endif
+}
+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;
+#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+ return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
+#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
+ return u * (HZ / USEC_PER_SEC);
+#else
+ return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
+ >> USEC_TO_HZ_SHR32;
+#endif
+}
+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 boundries. 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.
+ */
+static unsigned long
+__timespec_to_jiffies(unsigned long sec, long nsec)
+{
+ nsec = nsec + TICK_NSEC - 1;
+
+ if (sec >= MAX_SEC_IN_JIFFIES){
+ sec = MAX_SEC_IN_JIFFIES;
+ nsec = 0;
+ }
+ return (((u64)sec * SEC_CONVERSION) +
+ (((u64)nsec * NSEC_CONVERSION) >>
+ (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC;
+
+}
+
+unsigned long
+timespec_to_jiffies(const struct timespec *value)
+{
+ return __timespec_to_jiffies(value->tv_sec, value->tv_nsec);
+}
+
+EXPORT_SYMBOL(timespec_to_jiffies);
+
+void
+jiffies_to_timespec(const unsigned long jiffies, struct timespec *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_timespec);
+
+/*
+ * We could use a similar algorithm to timespec_to_jiffies (with a
+ * different multiplier for usec instead of nsec). But this has a
+ * problem with rounding: we can't exactly add TICK_NSEC - 1 to the
+ * usec value, since it's not necessarily integral.
+ *
+ * We could instead round in the intermediate scaled representation
+ * (i.e. in units of 1/2^(large scale) jiffies) but that's also
+ * perilous: the scaling introduces a small positive error, which
+ * combined with a division-rounding-upward (i.e. adding 2^(scale) - 1
+ * units to the intermediate before shifting) leads to accidental
+ * overflow and overestimates.
+ *
+ * At the cost of one additional multiplication by a constant, just
+ * use the timespec implementation.
+ */
+unsigned long
+timeval_to_jiffies(const struct timeval *value)
+{
+ return __timespec_to_jiffies(value->tv_sec,
+ value->tv_usec * NSEC_PER_USEC);
+}
+EXPORT_SYMBOL(timeval_to_jiffies);
+
+void jiffies_to_timeval(const unsigned long jiffies, struct timeval *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_usec = rem / NSEC_PER_USEC;
+}
+EXPORT_SYMBOL(jiffies_to_timeval);
+
+/*
+ * 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
+}
+
+/**
+ * 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 timespec values and do a safety check for overflow.
+ * It's assumed that both values are valid (>= 0)
+ */
+struct timespec timespec_add_safe(const struct timespec lhs,
+ const struct timespec rhs)
+{
+ struct timespec res;
+
+ set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec,
+ lhs.tv_nsec + rhs.tv_nsec);
+
+ if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec)
+ res.tv_sec = TIME_T_MAX;
+
+ return res;
+}
Code Review / kvmfornfv.git / blobdiff