/*
 * linux/kernel/itimer.c
 *
 * Copyright (C) 1992 Darren Senn
 */

/* These are all the functions necessary to implement itimers */

#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/posix-timers.h>
#include <linux/hrtimer.h>
#include <trace/events/timer.h>

#include <asm/uaccess.h>

/**
 * itimer_get_remtime - get remaining time for the timer
 *
 * @timer: the timer to read
 *
 * Returns the delta between the expiry time and now, which can be
 * less than zero or 1usec for an pending expired timer
 */
static struct timeval itimer_get_remtime(struct hrtimer *timer)
{
        ktime_t rem = hrtimer_get_remaining(timer);

        /*
         * Racy but safe: if the itimer expires after the above
         * hrtimer_get_remtime() call but before this condition
         * then we return 0 - which is correct.
         */
        if (hrtimer_active(timer)) {
                if (rem.tv64 <= 0)
                        rem.tv64 = NSEC_PER_USEC;
        } else
                rem.tv64 = 0;

        return ktime_to_timeval(rem);
}

static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
                           struct itimerval *const value)
{
        cputime_t cval, cinterval;
        struct cpu_itimer *it = &tsk->signal->it[clock_id];

        spin_lock_irq(&tsk->sighand->siglock);

        cval = it->expires;
        cinterval = it->incr;
        if (!cputime_eq(cval, cputime_zero)) {
                struct task_cputime cputime;
                cputime_t t;

                thread_group_cputimer(tsk, &cputime);
                if (clock_id == CPUCLOCK_PROF)
                        t = cputime_add(cputime.utime, cputime.stime);
                else
                        /* CPUCLOCK_VIRT */
                        t = cputime.utime;

                if (cputime_le(cval, t))
                        /* about to fire */
                        cval = cputime_one_jiffy;
                else
                        cval = cputime_sub(cval, t);
        }

        spin_unlock_irq(&tsk->sighand->siglock);

        cputime_to_timeval(cval, &value->it_value);
        cputime_to_timeval(cinterval, &value->it_interval);
}

int do_getitimer(int which, struct itimerval *value)
{
        struct task_struct *tsk = current;

        switch (which) {
        case ITIMER_REAL:
                spin_lock_irq(&tsk->sighand->siglock);
                value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
                value->it_interval =
                        ktime_to_timeval(tsk->signal->it_real_incr);
                spin_unlock_irq(&tsk->sighand->siglock);
                break;
        case ITIMER_VIRTUAL:
                get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
                break;
        case ITIMER_PROF:
                get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
                break;
        default:
                return(-EINVAL);
        }
        return 0;
}

SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
{
        int error = -EFAULT;
        struct itimerval get_buffer;

        if (value) {
                error = do_getitimer(which, &get_buffer);
                if (!error &&
                    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
                        error = -EFAULT;
        }
        return error;
}


/*
 * The timer is automagically restarted, when interval != 0
 */
enum hrtimer_restart it_real_fn(struct hrtimer *timer)
{
        struct signal_struct *sig =
                container_of(timer, struct signal_struct, real_timer);

        trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
        kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);

        return HRTIMER_NORESTART;
}

static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
{
        struct timespec ts;
        s64 cpu_ns;

        cputime_to_timespec(ct, &ts);
        cpu_ns = timespec_to_ns(&ts);

        return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
}

static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
                           const struct itimerval *const value,
                           struct itimerval *const ovalue)
{
        cputime_t cval, nval, cinterval, ninterval;
        s64 ns_ninterval, ns_nval;
        struct cpu_itimer *it = &tsk->signal->it[clock_id];

        nval = timeval_to_cputime(&value->it_value);
        ns_nval = timeval_to_ns(&value->it_value);
        ninterval = timeval_to_cputime(&value->it_interval);
        ns_ninterval = timeval_to_ns(&value->it_interval);

        it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
        it->error = cputime_sub_ns(nval, ns_nval);

        spin_lock_irq(&tsk->sighand->siglock);

        cval = it->expires;
        cinterval = it->incr;
        if (!cputime_eq(cval, cputime_zero) ||
            !cputime_eq(nval, cputime_zero)) {
                if (cputime_gt(nval, cputime_zero))
                        nval = cputime_add(nval, cputime_one_jiffy);
                set_process_cpu_timer(tsk, clock_id, &nval, &cval);
        }
        it->expires = nval;
        it->incr = ninterval;
        trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
                           ITIMER_VIRTUAL : ITIMER_PROF, value, nval);

        spin_unlock_irq(&tsk->sighand->siglock);

        if (ovalue) {
                cputime_to_timeval(cval, &ovalue->it_value);
                cputime_to_timeval(cinterval, &ovalue->it_interval);
        }
}

/*
 * Returns true if the timeval is in canonical form
 */
#define timeval_valid(t) \
        (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))

int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
{
        struct task_struct *tsk = current;
        struct hrtimer *timer;
        ktime_t expires;

        /*
         * Validate the timevals in value.
         */
        if (!timeval_valid(&value->it_value) ||
            !timeval_valid(&value->it_interval))
                return -EINVAL;

        switch (which) {
        case ITIMER_REAL:
again:
                spin_lock_irq(&tsk->sighand->siglock);
                timer = &tsk->signal->real_timer;
                if (ovalue) {
                        ovalue->it_value = itimer_get_remtime(timer);
                        ovalue->it_interval
                                = ktime_to_timeval(tsk->signal->it_real_incr);
                }
                /* We are sharing ->siglock with it_real_fn() */
                if (hrtimer_try_to_cancel(timer) < 0) {
                        spin_unlock_irq(&tsk->sighand->siglock);
                        goto again;
                }
                expires = timeval_to_ktime(value->it_value);
                if (expires.tv64 != 0) {
                        tsk->signal->it_real_incr =
                                timeval_to_ktime(value->it_interval);
                        hrtimer_start(timer, expires, HRTIMER_MODE_REL);
                } else
                        tsk->signal->it_real_incr.tv64 = 0;

                trace_itimer_state(ITIMER_REAL, value, 0);
                spin_unlock_irq(&tsk->sighand->siglock);
                break;
        case ITIMER_VIRTUAL:
                set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
                break;
        case ITIMER_PROF:
                set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
                break;
        default:
                return -EINVAL;
        }
        return 0;
}

/**
 * alarm_setitimer - set alarm in seconds
 *
 * @seconds:    number of seconds until alarm
 *              0 disables the alarm
 *
 * Returns the remaining time in seconds of a pending timer or 0 when
 * the timer is not active.
 *
 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 * negative timeval settings which would cause immediate expiry.
 */
unsigned int alarm_setitimer(unsigned int seconds)
{
        struct itimerval it_new, it_old;

#if BITS_PER_LONG < 64
        if (seconds > INT_MAX)
                seconds = INT_MAX;
#endif
        it_new.it_value.tv_sec = seconds;
        it_new.it_value.tv_usec = 0;
        it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;

        do_setitimer(ITIMER_REAL, &it_new, &it_old);

        /*
         * We can't return 0 if we have an alarm pending ...  And we'd
         * better return too much than too little anyway
         */
        if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
              it_old.it_value.tv_usec >= 500000)
                it_old.it_value.tv_sec++;

        return it_old.it_value.tv_sec;
}

SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
                struct itimerval __user *, ovalue)
{
        struct itimerval set_buffer, get_buffer;
        int error;

        if (value) {
                if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
                        return -EFAULT;
        } else
                memset((char *) &set_buffer, 0, sizeof(set_buffer));

        error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
        if (error || !ovalue)
                return error;

        if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
                return -EFAULT;
        return 0;
}