time.h

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#ifndef _LINUX_TIME_H
#define _LINUX_TIME_H

# include <linux/cache.h>
# include <linux/seqlock.h>
# include <linux/math64.h>
#include <uapi/linux/time.h>

extern struct timezone sys_tz;

/* Parameters used to convert the timespec values: */
#define MSEC_PER_SEC    1000L
#define USEC_PER_MSEC   1000L
#define NSEC_PER_USEC   1000L
#define NSEC_PER_MSEC   1000000L
#define USEC_PER_SEC    1000000L
#define NSEC_PER_SEC    1000000000L
#define FSEC_PER_SEC    1000000000000000LL

#define TIME_T_MAX  (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)

static inline int timespec_equal(const struct timespec *a,
                                 const struct timespec *b)
{
    return (a->tv_sec == b->tv_sec) && (a->tv_nsec == b->tv_nsec);
}

/*
 * lhs < rhs:  return <0
 * lhs == rhs: return 0
 * lhs > rhs:  return >0
 */
static inline int timespec_compare(const struct timespec *lhs, const struct timespec *rhs)
{
    if (lhs->tv_sec < rhs->tv_sec)
        return -1;
    if (lhs->tv_sec > rhs->tv_sec)
        return 1;
    return lhs->tv_nsec - rhs->tv_nsec;
}

static inline int timeval_compare(const struct timeval *lhs, const struct timeval *rhs)
{
    if (lhs->tv_sec < rhs->tv_sec)
        return -1;
    if (lhs->tv_sec > rhs->tv_sec)
        return 1;
    return lhs->tv_usec - rhs->tv_usec;
}

extern unsigned long mktime(const unsigned int year, const unsigned int mon,
                const unsigned int day, const unsigned int hour,
                const unsigned int min, const unsigned int sec);

extern void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec);

/*
 * timespec_add_safe assumes both values are positive and checks
 * for overflow. It will return TIME_T_MAX if the reutrn would be
 * smaller then either of the arguments.
 */
extern struct timespec timespec_add_safe(const struct timespec lhs,
                     const struct timespec rhs);


static inline struct timespec timespec_add(struct timespec lhs,
                        struct timespec rhs)
{
    struct timespec ts_delta;
    set_normalized_timespec(&ts_delta, lhs.tv_sec + rhs.tv_sec,
                lhs.tv_nsec + rhs.tv_nsec);
    return ts_delta;
}

/*
 * sub = lhs - rhs, in normalized form
 */
static inline struct timespec timespec_sub(struct timespec lhs,
                        struct timespec rhs)
{
    struct timespec ts_delta;
    set_normalized_timespec(&ts_delta, lhs.tv_sec - rhs.tv_sec,
                lhs.tv_nsec - rhs.tv_nsec);
    return ts_delta;
}

#define KTIME_MAX           ((s64)~((u64)1 << 63))
#if (BITS_PER_LONG == 64)
# define KTIME_SEC_MAX          (KTIME_MAX / NSEC_PER_SEC)
#else
# define KTIME_SEC_MAX          LONG_MAX
#endif

/*
 * Returns true if the timespec is norm, false if denorm:
 */
static inline bool timespec_valid(const struct timespec *ts)
{
    /* Dates before 1970 are bogus */
    if (ts->tv_sec < 0)
        return false;
    /* Can't have more nanoseconds then a second */
    if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
        return false;
    return true;
}

static inline bool timespec_valid_strict(const struct timespec *ts)
{
    if (!timespec_valid(ts))
        return false;
    /* Disallow values that could overflow ktime_t */
    if ((unsigned long long)ts->tv_sec >= KTIME_SEC_MAX)
        return false;
    return true;
}

extern void read_persistent_clock(struct timespec *ts);
extern void read_boot_clock(struct timespec *ts);
extern int update_persistent_clock(struct timespec now);
void timekeeping_init(void);
extern int timekeeping_suspended;

unsigned long get_seconds(void);
struct timespec current_kernel_time(void);
struct timespec __current_kernel_time(void); /* does not take xtime_lock */
struct timespec get_monotonic_coarse(void);
void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
                struct timespec *wtom, struct timespec *sleep);
void timekeeping_inject_sleeptime(struct timespec *delta);

#define CURRENT_TIME        (current_kernel_time())
#define CURRENT_TIME_SEC    ((struct timespec) { get_seconds(), 0 })

/* Some architectures do not supply their own clocksource.
 * This is mainly the case in architectures that get their
 * inter-tick times by reading the counter on their interval
 * timer. Since these timers wrap every tick, they're not really
 * useful as clocksources. Wrapping them to act like one is possible
 * but not very efficient. So we provide a callout these arches
 * can implement for use with the jiffies clocksource to provide
 * finer then tick granular time.
 */
#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
extern u32 arch_gettimeoffset(void);
#else
static inline u32 arch_gettimeoffset(void) { return 0; }
#endif

extern void do_gettimeofday(struct timeval *tv);
extern int do_settimeofday(const struct timespec *tv);
extern int do_sys_settimeofday(const struct timespec *tv,
                   const struct timezone *tz);
#define do_posix_clock_monotonic_gettime(ts) ktime_get_ts(ts)
extern long do_utimes(int dfd, const char __user *filename, struct timespec *times, int flags);
struct itimerval;
extern int do_setitimer(int which, struct itimerval *value,
            struct itimerval *ovalue);
extern unsigned int alarm_setitimer(unsigned int seconds);
extern int do_getitimer(int which, struct itimerval *value);
extern void getnstimeofday(struct timespec *tv);
extern void getrawmonotonic(struct timespec *ts);
extern void getnstime_raw_and_real(struct timespec *ts_raw,
        struct timespec *ts_real);
extern void getboottime(struct timespec *ts);
extern void monotonic_to_bootbased(struct timespec *ts);
extern void get_monotonic_boottime(struct timespec *ts);

extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
extern u64 timekeeping_max_deferment(void);
extern int timekeeping_inject_offset(struct timespec *ts);

struct tms;
extern void do_sys_times(struct tms *);

/*
 * Similar to the struct tm in userspace <time.h>, but it needs to be here so
 * that the kernel source is self contained.
 */
struct tm {
    /*
     * the number of seconds after the minute, normally in the range
     * 0 to 59, but can be up to 60 to allow for leap seconds
     */
    int tm_sec;
    /* the number of minutes after the hour, in the range 0 to 59*/
    int tm_min;
    /* the number of hours past midnight, in the range 0 to 23 */
    int tm_hour;
    /* the day of the month, in the range 1 to 31 */
    int tm_mday;
    /* the number of months since January, in the range 0 to 11 */
    int tm_mon;
    /* the number of years since 1900 */
    long tm_year;
    /* the number of days since Sunday, in the range 0 to 6 */
    int tm_wday;
    /* the number of days since January 1, in the range 0 to 365 */
    int tm_yday;
};

void time_to_tm(time_t totalsecs, int offset, struct tm *result);

static inline s64 timespec_to_ns(const struct timespec *ts)
{
    return ((s64) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
}

static inline s64 timeval_to_ns(const struct timeval *tv)
{
    return ((s64) tv->tv_sec * NSEC_PER_SEC) +
        tv->tv_usec * NSEC_PER_USEC;
}

extern struct timespec ns_to_timespec(const s64 nsec);

extern struct timeval ns_to_timeval(const s64 nsec);

static __always_inline void timespec_add_ns(struct timespec *a, u64 ns)
{
    a->tv_sec += __iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns);
    a->tv_nsec = ns;
}

#endif