// SPDX-License-Identifier: GPL-2.0
/*
 * 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/sched/signal.h>
#include <linux/sched/cputime.h>
#include <linux/posix-timers.h>
#include <linux/hrtimer.h>
#include <trace/events/timer.h>
#include <linux/compat.h>

#include <linux/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 timespec64 itimer_get_remtime(struct hrtimer *timer)
{
        ktime_t rem = __hrtimer_get_remaining(timer, true);

        /*
         * 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 <= 0)
                        rem = NSEC_PER_USEC;
        } else
                rem = 0;

        return ktime_to_timespec64(rem);
}

static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
                           struct itimerspec64 *const value)
{
        u64 val, interval;
        struct cpu_itimer *it = &tsk->signal->it[clock_id];

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

        val = it->expires;
        interval = it->incr;
        if (val) {
                u64 t, samples[CPUCLOCK_MAX];

                thread_group_sample_cputime(tsk, samples);
                t = samples[clock_id];

                if (val < t)
                        /* about to fire */
                        val = TICK_NSEC;
                else
                        val -= t;
        }

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

        value->it_value = ns_to_timespec64(val);
        value->it_interval = ns_to_timespec64(interval);
}

static int do_getitimer(int which, struct itimerspec64 *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_timespec64(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;
}

static int put_itimerval(struct __kernel_old_itimerval __user *o,
                         const struct itimerspec64 *i)
{
        struct __kernel_old_itimerval v;

        v.it_interval.tv_sec = i->it_interval.tv_sec;
        v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
        v.it_value.tv_sec = i->it_value.tv_sec;
        v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
        return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0;
}


SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value)
{
        struct itimerspec64 get_buffer;
        int error = do_getitimer(which, &get_buffer);

        if (!error && put_itimerval(value, &get_buffer))
                error = -EFAULT;
        return error;
}

#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
struct old_itimerval32 {
        struct old_timeval32    it_interval;
        struct old_timeval32    it_value;
};

static int put_old_itimerval32(struct old_itimerval32 __user *o,
                               const struct itimerspec64 *i)
{
        struct old_itimerval32 v32;

        v32.it_interval.tv_sec = i->it_interval.tv_sec;
        v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC;
        v32.it_value.tv_sec = i->it_value.tv_sec;
        v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC;
        return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0;
}

COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
                       struct old_itimerval32 __user *, value)
{
        struct itimerspec64 get_buffer;
        int error = do_getitimer(which, &get_buffer);

        if (!error && put_old_itimerval32(value, &get_buffer))
                error = -EFAULT;
        return error;
}
#endif

/*
 * Invoked from dequeue_signal() when SIG_ALRM is delivered.
 *
 * Restart the ITIMER_REAL timer if it is armed as periodic timer.  Doing
 * this in the signal delivery path instead of self rearming prevents a DoS
 * with small increments in the high reolution timer case and reduces timer
 * noise in general.
 */
void posixtimer_rearm_itimer(struct task_struct *tsk)
{
        struct hrtimer *tmr = &tsk->signal->real_timer;

        if (!hrtimer_is_queued(tmr) && tsk->signal->it_real_incr != 0) {
                hrtimer_forward_now(tmr, tsk->signal->it_real_incr);
                hrtimer_restart(tmr);
        }
}

/*
 * Interval timers are restarted in the signal delivery path.  See
 * posixtimer_rearm_itimer().
 */
enum hrtimer_restart it_real_fn(struct hrtimer *timer)
{
        struct signal_struct *sig =
                container_of(timer, struct signal_struct, real_timer);
        struct pid *leader_pid = sig->pids[PIDTYPE_TGID];

        trace_itimer_expire(ITIMER_REAL, leader_pid, 0);
        kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid);

        return HRTIMER_NORESTART;
}

static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
                           const struct itimerspec64 *const value,
                           struct itimerspec64 *const ovalue)
{
        u64 oval, nval, ointerval, ninterval;
        struct cpu_itimer *it = &tsk->signal->it[clock_id];

        nval = timespec64_to_ns(&value->it_value);
        ninterval = timespec64_to_ns(&value->it_interval);

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

        oval = it->expires;
        ointerval = it->incr;
        if (oval || nval) {
                if (nval > 0)
                        nval += TICK_NSEC;
                set_process_cpu_timer(tsk, clock_id, &nval, &oval);
        }
        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) {
                ovalue->it_value = ns_to_timespec64(oval);
                ovalue->it_interval = ns_to_timespec64(ointerval);
        }
}

/*
 * 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))

static int do_setitimer(int which, struct itimerspec64 *value,
                        struct itimerspec64 *ovalue)
{
        struct task_struct *tsk = current;
        struct hrtimer *timer;
        ktime_t expires;

        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_timespec64(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);
                        hrtimer_cancel_wait_running(timer);
                        goto again;
                }
                expires = timespec64_to_ktime(value->it_value);
                if (expires != 0) {
                        tsk->signal->it_real_incr =
                                timespec64_to_ktime(value->it_interval);
                        hrtimer_start(timer, expires, HRTIMER_MODE_REL);
                } else
                        tsk->signal->it_real_incr = 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;
}

#ifdef CONFIG_SECURITY_SELINUX
void clear_itimer(void)
{
        struct itimerspec64 v = {};
        int i;

        for (i = 0; i < 3; i++)
                do_setitimer(i, &v, NULL);
}
#endif

#ifdef __ARCH_WANT_SYS_ALARM

/**
 * 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.
 */
static unsigned int alarm_setitimer(unsigned int seconds)
{
        struct itimerspec64 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_nsec = 0;
        it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 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_nsec) ||
              it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2))
                it_old.it_value.tv_sec++;

        return it_old.it_value.tv_sec;
}

/*
 * For backwards compatibility?  This can be done in libc so Alpha
 * and all newer ports shouldn't need it.
 */
SYSCALL_DEFINE1(alarm, unsigned int, seconds)
{
        return alarm_setitimer(seconds);
}

#endif

static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i)
{
        struct __kernel_old_itimerval v;

        if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval)))
                return -EFAULT;

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

        o->it_interval.tv_sec = v.it_interval.tv_sec;
        o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC;
        o->it_value.tv_sec = v.it_value.tv_sec;
        o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC;
        return 0;
}

SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value,
                struct __kernel_old_itimerval __user *, ovalue)
{
        struct itimerspec64 set_buffer, get_buffer;
        int error;

        if (value) {
                error = get_itimerval(&set_buffer, value);
                if (error)
                        return error;
        } else {
                memset(&set_buffer, 0, sizeof(set_buffer));
                printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
                            " Misfeature support will be removed\n",
                            current->comm);
        }

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

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

#if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA)
static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i)
{
        struct old_itimerval32 v32;

        if (copy_from_user(&v32, i, sizeof(struct old_itimerval32)))
                return -EFAULT;

        /* Validate the timevals in value.  */
        if (!timeval_valid(&v32.it_value) ||
            !timeval_valid(&v32.it_interval))
                return -EINVAL;

        o->it_interval.tv_sec = v32.it_interval.tv_sec;
        o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC;
        o->it_value.tv_sec = v32.it_value.tv_sec;
        o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC;
        return 0;
}

COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
                       struct old_itimerval32 __user *, value,
                       struct old_itimerval32 __user *, ovalue)
{
        struct itimerspec64 set_buffer, get_buffer;
        int error;

        if (value) {
                error = get_old_itimerval32(&set_buffer, value);
                if (error)
                        return error;
        } else {
                memset(&set_buffer, 0, sizeof(set_buffer));
                printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer."
                            " Misfeature support will be removed\n",
                            current->comm);
        }

        error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
        if (error || !ovalue)
                return error;
        if (put_old_itimerval32(ovalue, &get_buffer))
                return -EFAULT;
        return 0;
}
#endif