/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2012 Gleb Smirnoff <glebius@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <vm/uma.h>

#define IN_SUBR_COUNTER_C
#include <sys/counter.h>

static MALLOC_DEFINE(M_COUNTER_RATE, "counter_rate", "counter rate allocations");

void
counter_u64_zero(counter_u64_t c)
{

        counter_u64_zero_inline(c);
}

uint64_t
counter_u64_fetch(counter_u64_t c)
{

        return (counter_u64_fetch_inline(c));
}

counter_u64_t
counter_u64_alloc(int flags)
{

        return (uma_zalloc_pcpu(pcpu_zone_8, flags | M_ZERO));
}

void
counter_u64_free(counter_u64_t c)
{

        uma_zfree_pcpu(pcpu_zone_8, c);
}

int
sysctl_handle_counter_u64(SYSCTL_HANDLER_ARGS)
{
        uint64_t out;
        int error;

        out = counter_u64_fetch(*(counter_u64_t *)arg1);

        error = SYSCTL_OUT(req, &out, sizeof(uint64_t));

        if (error || !req->newptr)
                return (error);

        /*
         * Any write attempt to a counter zeroes it.
         */
        counter_u64_zero(*(counter_u64_t *)arg1);

        return (0);
}

int
sysctl_handle_counter_u64_array(SYSCTL_HANDLER_ARGS)
{
        uint64_t *out;
        int error;

        out = malloc(arg2 * sizeof(uint64_t), M_TEMP, M_WAITOK);
        for (int i = 0; i < arg2; i++)
                out[i] = counter_u64_fetch(((counter_u64_t *)arg1)[i]);

        error = SYSCTL_OUT(req, out, arg2 * sizeof(uint64_t));
        free(out, M_TEMP);

        if (error || !req->newptr)
                return (error);

        /*
         * Any write attempt to a counter zeroes it.
         */
        for (int i = 0; i < arg2; i++)
                counter_u64_zero(((counter_u64_t *)arg1)[i]);

        return (0);
}

/*
 * counter(9) based rate checking.
 */
struct counter_rate {
        counter_u64_t   cr_rate;        /* Events since last second */
        volatile int    cr_lock;        /* Lock to clean the struct */
        int             cr_ticks;       /* Ticks on last clean */
        int             cr_over;        /* Over limit since cr_ticks? */
        int             cr_period;      /* Allow cr_rate per cr_period seconds. */
};

struct counter_rate *
counter_rate_alloc(int flags, int period)
{
        struct counter_rate *new;

        new = malloc(sizeof(struct counter_rate), M_COUNTER_RATE,
            flags | M_ZERO);
        if (new == NULL)
                return (NULL);

        new->cr_rate = counter_u64_alloc(flags);
        if (new->cr_rate == NULL) {
                free(new, M_COUNTER_RATE);
                return (NULL);
        }
        new->cr_ticks = ticks;
        new->cr_period = period;

        return (new);
}

void
counter_rate_free(struct counter_rate *rate)
{
        if (rate == NULL)
                return;

        counter_u64_free(rate->cr_rate);
        free(rate, M_COUNTER_RATE);
}

uint64_t
counter_rate_get(struct counter_rate *cr)
{
        if (cr->cr_ticks < (tick - (hz * cr->cr_period)))
                return (0);

        return (counter_u64_fetch(cr->cr_rate));
}

/*
 * MP-friendly version of ppsratecheck().
 *
 * Returns non-negative if we are in the rate, negative otherwise.
 *  0 - rate limit not reached.
 * -1 - rate limit reached.
 * >0 - rate limit was reached before, and was just reset. The return value
 *      is number of events since last reset.
 */
int64_t
counter_ratecheck(struct counter_rate *cr, int64_t limit)
{
        int64_t val;
        int now;

        val = cr->cr_over;
        now = ticks;

        if ((u_int)(now - cr->cr_ticks) >= (hz * cr->cr_period)) {
                /*
                 * Time to clear the structure, we are in the next second.
                 * First try unlocked read, and then proceed with atomic.
                 */
                if ((cr->cr_lock == 0) &&
                    atomic_cmpset_acq_int(&cr->cr_lock, 0, 1)) {
                        /*
                         * Check if other thread has just went through the
                         * reset sequence before us.
                         */
                        if ((u_int)(now - cr->cr_ticks) >= (hz * cr->cr_period)) {
                                val = counter_u64_fetch(cr->cr_rate);
                                counter_u64_zero(cr->cr_rate);
                                cr->cr_over = 0;
                                cr->cr_ticks = now;
                                if (val <= limit)
                                        val = 0;
                        }
                        atomic_store_rel_int(&cr->cr_lock, 0);
                } else
                        /*
                         * We failed to lock, in this case other thread may
                         * be running counter_u64_zero(), so it is not safe
                         * to do an update, we skip it.
                         */
                        return (val);
        }

        counter_u64_add(cr->cr_rate, 1);
        if (cr->cr_over != 0)
                return (-1);
        if (counter_u64_fetch(cr->cr_rate) > limit)
                val = cr->cr_over = -1;

        return (val);
}

void
counter_u64_sysinit(void *arg)
{
        counter_u64_t *cp;

        cp = arg;
        *cp = counter_u64_alloc(M_WAITOK);
}

void
counter_u64_sysuninit(void *arg)
{
        counter_u64_t *cp;

        cp = arg;
        counter_u64_free(*cp);
}