/*
 * Copyright (c) 1982, 1986, 1993
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      @(#)subr_log.c  8.1 (Berkeley) 6/10/93
 * $FreeBSD: src/sys/kern/subr_log.c,v 1.39.2.2 2001/06/02 08:11:25 phk Exp $
 */

/*
 * Error log buffer for kernel printf's.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/filio.h>
#include <sys/ttycom.h>
#include <sys/msgbuf.h>
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/event.h>
#include <sys/filedesc.h>
#include <sys/sysctl.h>
#include <sys/thread2.h>

#define LOG_ASYNC       0x04
#define LOG_RDWAIT      0x08

static  d_open_t        logopen;
static  d_close_t       logclose;
static  d_read_t        logread;
static  d_ioctl_t       logioctl;
static  d_kqfilter_t    logkqfilter;

static  void logtimeout(void *arg);
static  void logfiltdetach(struct knote *kn);
static  int  logfiltread(struct knote *kn, long hint);

#define CDEV_MAJOR 7
static struct dev_ops log_ops = {
        { "log", 0, 0 },
        .d_open =       logopen,
        .d_close =      logclose,
        .d_read =       logread,
        .d_ioctl =      logioctl,
        .d_kqfilter =   logkqfilter
};

static struct logsoftc {
        int     sc_state;               /* see above for possibilities */
        struct  kqinfo  sc_kqp;         /* processes waiting on I/O */
        struct  sigio *sc_sigio;        /* information for async I/O */
        struct  callout sc_callout;     /* callout to wakeup syslog  */
} logsoftc;

int     log_open;                       /* also used in log() */

/* Times per second to check for a pending syslog wakeup. */
static int      log_wakeups_per_second = 5;
SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
    &log_wakeups_per_second, 0, "");

/*ARGSUSED*/
static  int
logopen(struct dev_open_args *ap)
{
        struct proc *p = curproc;

        KKASSERT(p != NULL);
        if (log_open)
                return (EBUSY);
        log_open = 1;
        callout_init_mp(&logsoftc.sc_callout);
        fsetown(p->p_pid, &logsoftc.sc_sigio);  /* signal process only */
        callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
                      logtimeout, NULL);
        return (0);
}

/*ARGSUSED*/
static  int
logclose(struct dev_close_args *ap)
{
        log_open = 0;
        callout_terminate(&logsoftc.sc_callout);
        logsoftc.sc_state = 0;
        funsetown(&logsoftc.sc_sigio);
        return (0);
}

/*ARGSUSED*/
static  int
logread(struct dev_read_args *ap)
{
        struct uio *uio = ap->a_uio;
        struct msgbuf *mbp = msgbufp;
        int error = 0;
        u_int lindex;
        u_int xindex;
        u_int lindex_modulo;
        u_int n;

        /*
         * Handle blocking
         */
        while (mbp->msg_bufl == mbp->msg_bufx) {
                crit_enter();
                if (ap->a_ioflag & IO_NDELAY) {
                        crit_exit();
                        return (EWOULDBLOCK);
                }
                atomic_set_int(&logsoftc.sc_state, LOG_RDWAIT);
                if ((error = tsleep((caddr_t)mbp, PCATCH, "klog", 0))) {
                        crit_exit();
                        return (error);
                }
                /* don't bother clearing LOG_RDWAIT */
                crit_exit();
        }

        /*
         * Loop reading data
         */
        while (uio->uio_resid > 0 && mbp->msg_bufl != mbp->msg_bufx) {
                lindex = mbp->msg_bufl;
                xindex = mbp->msg_bufx;
                cpu_ccfence();

                /*
                 * Clean up if too much time has passed causing us to wrap
                 * the buffer.  This will lose some data.  If more than ~4GB
                 * then this will lose even more data.
                 */
                n = xindex - lindex;
                if (n > mbp->msg_size - 1024) {
                        lindex = xindex - mbp->msg_size + 2048;
                        n = xindex - lindex;
                }

                /*
                 * Calculates contiguous bytes we can read in one loop.
                 */
                lindex_modulo = lindex % mbp->msg_size;
                n = mbp->msg_size - lindex_modulo;
                if (n > xindex - lindex)
                        n = xindex - lindex;
                if ((size_t)n > uio->uio_resid)
                        n = (u_int)uio->uio_resid;

                /*
                 * Copy (n) bytes of data.
                 */
                error = uiomove((caddr_t)msgbufp->msg_ptr + lindex_modulo,
                                (size_t)n, uio);
                if (error)
                        break;
                mbp->msg_bufl = lindex + n;
        }
        return (error);
}

static struct filterops logread_filtops =
        { FILTEROP_ISFD, NULL, logfiltdetach, logfiltread };

static int
logkqfilter(struct dev_kqfilter_args *ap)
{
        struct knote *kn = ap->a_kn;
        struct klist *klist = &logsoftc.sc_kqp.ki_note;

        ap->a_result = 0;
        switch (kn->kn_filter) {
        case EVFILT_READ:
                kn->kn_fop = &logread_filtops;
                break;
        default:
                ap->a_result = EOPNOTSUPP;
                return (0);
        }

        knote_insert(klist, kn);

        return (0);
}

static void
logfiltdetach(struct knote *kn)
{
        struct klist *klist = &logsoftc.sc_kqp.ki_note;

        knote_remove(klist, kn);
}

static int
logfiltread(struct knote *kn, long hint)
{
        int ret = 0;

        crit_enter();
        if (msgbufp->msg_bufl != msgbufp->msg_bufx)
                ret = 1;
        crit_exit();

        return (ret);
}

static void
logtimeout(void *arg)
{
        if (!log_open)
                return;
        if (msgbuftrigger == 0) {
                callout_reset(&logsoftc.sc_callout,
                              hz / log_wakeups_per_second, logtimeout, NULL);
                return;
        }
        msgbuftrigger = 0;
        KNOTE(&logsoftc.sc_kqp.ki_note, 0);
        if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
                pgsigio(logsoftc.sc_sigio, SIGIO, 0);
        if (logsoftc.sc_state & LOG_RDWAIT) {
                atomic_clear_int(&logsoftc.sc_state, LOG_RDWAIT);
                wakeup((caddr_t)msgbufp);
        }
        callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
                      logtimeout, NULL);
}

/*ARGSUSED*/
static  int
logioctl(struct dev_ioctl_args *ap)
{
        struct msgbuf *mbp = msgbufp;
        u_int lindex;
        u_int xindex;
        u_int n;

        switch (ap->a_cmd) {
        case FIONREAD:
                lindex = mbp->msg_bufl;
                xindex = mbp->msg_bufx;
                cpu_ccfence();

                /*
                 * Clean up if too much time has passed causing us to wrap
                 * the buffer.  This will lose some data.  If more than ~4GB
                 * then this will lose even more data.
                 */
                n = xindex - lindex;
                if (n > mbp->msg_size - 1024) {
                        lindex = xindex - mbp->msg_size + 2048;
                        n = xindex - lindex;
                }
                *(int *)ap->a_data = n;
                break;

        case FIOASYNC:
                if (*(int *)ap->a_data)
                        atomic_set_int(&logsoftc.sc_state, LOG_ASYNC);
                else
                        atomic_clear_int(&logsoftc.sc_state, LOG_ASYNC);
                break;

        case FIOSETOWN:
                return (fsetown(*(int *)ap->a_data, &logsoftc.sc_sigio));

        case FIOGETOWN:
                *(int *)ap->a_data = fgetown(&logsoftc.sc_sigio);
                break;

        /* This is deprecated, FIOSETOWN should be used instead. */
        case TIOCSPGRP:
                return (fsetown(-(*(int *)ap->a_data), &logsoftc.sc_sigio));

        /* This is deprecated, FIOGETOWN should be used instead */
        case TIOCGPGRP:
                *(int *)ap->a_data = -fgetown(&logsoftc.sc_sigio);
                break;

        default:
                return (ENOTTY);
        }
        return (0);
}

static void
log_drvinit(void *unused)
{
        make_dev(&log_ops, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
}

SYSINIT(logdev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR, log_drvinit,
    NULL);