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/*

 * linux/kernel/itimer.c

 *

 * Copyright (C) 1992 Darren Senn

 */

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

#include <linux/mm.h>

#include <linux/smp_lock.h>

#include <linux/interrupt.h>

#include <asm/uaccess.h>

/*

 * change timeval to jiffies, trying to avoid the

 * most obvious overflows..

 *

 * The tv_*sec values are signed, but nothing seems to

 * indicate whether we really should use them as signed values

 * when doing itimers. POSIX doesn't mention this (but if

 * alarm() uses itimers without checking, we have to use unsigned

 * arithmetic).

 */

static unsigned long tvtojiffies(struct timeval *value)

{

        unsigned long sec = (unsigned) value->tv_sec;

        unsigned long usec = (unsigned) value->tv_usec;

        if (sec > (ULONG_MAX / HZ))

                return ULONG_MAX;

        usec += 1000000 / HZ - 1;

        usec /= 1000000 / HZ;

        return HZ*sec+usec;

}

static void jiffiestotv(unsigned long jiffies, struct timeval *value)

{

        value->tv_usec = (jiffies % HZ) * (1000000 / HZ);

        value->tv_sec = jiffies / HZ;

}

int do_getitimer(int which, struct itimerval *value)

{

        register unsigned long val, interval;

        switch (which) {

        case ITIMER_REAL:

                interval = current->it_real_incr;

                val = 0;

                /*

                 * FIXME! This needs to be atomic, in case the kernel timer happens!

                 */

                if (timer_pending(&current->real_timer)) {

                        val = current->real_timer.expires - jiffies;

                        /* look out for negative/zero itimer.. */

                        if ((long) val <= 0)

                                val = 1;

                }

                break;

        case ITIMER_VIRTUAL:

                val = current->it_virt_value;

                interval = current->it_virt_incr;

                break;

        case ITIMER_PROF:

                val = current->it_prof_value;

                interval = current->it_prof_incr;

                break;

        default:

                return(-EINVAL);

        }

        jiffiestotv(val, &value->it_value);

        jiffiestotv(interval, &value->it_interval);

        return 0;

}

/* SMP: Only we modify our itimer values. */

asmlinkage long sys_getitimer(int which, struct itimerval *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;

}

void it_real_fn(unsigned long __data)

{

        struct task_struct * p = (struct task_struct *) __data;

        unsigned long interval;

        send_sig(SIGALRM, p, 1);

        interval = p->it_real_incr;

        if (interval) {

                if (interval > (unsigned long) LONG_MAX)

                        interval = LONG_MAX;

                p->real_timer.expires = jiffies + interval;

                add_timer(&p->real_timer);

        }

}

int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)

{

        register unsigned long i, j;

        int k;

        i = tvtojiffies(&value->it_interval);

        j = tvtojiffies(&value->it_value);

        if (ovalue && (k = do_getitimer(which, ovalue)) < 0)

                return k;

        switch (which) {

                case ITIMER_REAL:

                        del_timer_sync(&current->real_timer);

                        current->it_real_value = j;

                        current->it_real_incr = i;

                        if (!j)

                                break;

                        if (j > (unsigned long) LONG_MAX)

                                j = LONG_MAX;

                        i = j + jiffies;

                        current->real_timer.expires = i;

                        add_timer(&current->real_timer);

                        break;

                case ITIMER_VIRTUAL:

                        if (j)

                                j++;

                        current->it_virt_value = j;

                        current->it_virt_incr = i;

                        break;

                case ITIMER_PROF:

                        if (j)

                                j++;

                        current->it_prof_value = j;

                        current->it_prof_incr = i;

                        break;

                default:

                        return -EINVAL;

        }

        return 0;

}

/* SMP: Again, only we play with our itimers, and signals are SMP safe

 *      now so that is not an issue at all anymore.

 */

asmlinkage long sys_setitimer(int which, struct itimerval *value,

                              struct itimerval *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 : 0);

        if (error || !ovalue)

                return error;

        if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))

                return -EFAULT;

        return 0;

}