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[dragonfly.git] / sys / kern / sys_mqueue.c

/*      $NetBSD: sys_mqueue.c,v 1.16 2009/04/11 23:05:26 christos Exp $ */

/*
 * Copyright (c) 2007, 2008 Mindaugas Rasiukevicius <rmind at NetBSD 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.
 */

/*
 * Implementation of POSIX message queues.
 * Defined in the Base Definitions volume of IEEE Std 1003.1-2001.
 *
 * Locking
 *
 * Global list of message queues (mqueue_head) and proc_t::p_mqueue_cnt
 * counter are protected by mqlist_mtx lock.  The very message queue and
 * its members are protected by mqueue::mq_mtx.
 *
 * Lock order:
 *      mqlist_mtx
 *        -> mqueue::mq_mtx
 */

#include <stdbool.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/ucred.h>
#include <sys/priv.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mplock2.h>
#include <sys/mqueue.h>
#include <sys/objcache.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/event.h>
#include <sys/serialize.h>
#include <sys/signal.h>
#include <sys/signalvar.h>
#include <sys/spinlock.h>
#include <sys/spinlock2.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/unistd.h>
#include <sys/vnode.h>

/* System-wide limits. */
static u_int                    mq_open_max = MQ_OPEN_MAX;
static u_int                    mq_prio_max = MQ_PRIO_MAX;
static u_int                    mq_max_msgsize = 16 * MQ_DEF_MSGSIZE;
static u_int                    mq_def_maxmsg = 32;
static u_int                    mq_max_maxmsg = 16 * 32;

struct lock                     mqlist_mtx;
static struct objcache *        mqmsg_cache;
static LIST_HEAD(, mqueue)      mqueue_head =
        LIST_HEAD_INITIALIZER(mqueue_head);

typedef struct  file file_t;    /* XXX: Should we put this in sys/types.h ? */

/* Function prototypes */
static int      mq_stat_fop(file_t *, struct stat *, struct ucred *cred);
static int      mq_close_fop(file_t *);
static int      mq_kqfilter_fop(struct file *fp, struct knote *kn);
static void     mqfilter_read_detach(struct knote *kn);
static void     mqfilter_write_detach(struct knote *kn);
static int      mqfilter_read(struct knote *kn, long hint);
static int      mqfilter_write(struct knote *kn, long hint);

/* Some time-related utility functions */
static int      itimespecfix(struct timespec *ts);
static int      tstohz(const struct timespec *ts);

/* File operations vector */
static struct fileops mqops = {
        .fo_read = badfo_readwrite,
        .fo_write = badfo_readwrite,
        .fo_ioctl = badfo_ioctl,
        .fo_stat = mq_stat_fop,
        .fo_close = mq_close_fop,
        .fo_kqfilter = mq_kqfilter_fop,
        .fo_shutdown = badfo_shutdown
};

/* Define a new malloc type for message queues */
MALLOC_DECLARE(M_MQBUF);
MALLOC_DEFINE(M_MQBUF, "mqueues", "Buffers to message queues");

/* Malloc arguments for object cache */
struct objcache_malloc_args mqueue_malloc_args = {
        sizeof(struct mqueue), M_MQBUF };

/*
 * Initialize POSIX message queue subsystem.
 */
void
mqueue_sysinit(void)
{
        mqmsg_cache = objcache_create("mqmsg_cache",
            0,          /* infinite depot's capacity */
            0,          /* default magazine's capacity */
            NULL,       /* constructor */
            NULL,       /* deconstructor */
            NULL,
            objcache_malloc_alloc,
            objcache_malloc_free,
            &mqueue_malloc_args);

        lockinit(&mqlist_mtx, "mqlist_mtx", 0, LK_CANRECURSE);
}

/*
 * Free the message.
 */
static void
mqueue_freemsg(struct mq_msg *msg, const size_t size)
{

        if (size > MQ_DEF_MSGSIZE) {
                kfree(msg, M_MQBUF);
        } else {
                objcache_put(mqmsg_cache, msg);
        }
}

/*
 * Destroy the message queue.
 */
static void
mqueue_destroy(struct mqueue *mq)
{
        struct mq_msg *msg;
        size_t msz;
        u_int i;

        /* Note MQ_PQSIZE + 1. */
        for (i = 0; i < MQ_PQSIZE + 1; i++) {
                while ((msg = TAILQ_FIRST(&mq->mq_head[i])) != NULL) {
                        TAILQ_REMOVE(&mq->mq_head[i], msg, msg_queue);
                        msz = sizeof(struct mq_msg) + msg->msg_len;
                        mqueue_freemsg(msg, msz);
                }
        }
        lockuninit(&mq->mq_mtx);
        kfree(mq, M_MQBUF);
}

/*
 * Lookup for file name in general list of message queues.
 *  => locks the message queue
 */
static void *
mqueue_lookup(char *name)
{
        struct mqueue *mq;

        KKASSERT(lockstatus(&mqlist_mtx, curthread));

        LIST_FOREACH(mq, &mqueue_head, mq_list) {
                if (strncmp(mq->mq_name, name, MQ_NAMELEN) == 0) {
                        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
                        return mq;
                }
        }

        return NULL;
}

/*
 * mqueue_get: get the mqueue from the descriptor.
 *  => locks the message queue, if found.
 *  => holds a reference on the file descriptor.
 */
static int
mqueue_get(struct lwp *l, mqd_t mqd, file_t **fpr)
{
        struct mqueue *mq;
        file_t *fp;

        fp = holdfp(curproc->p_fd, (int)mqd, -1);       /* XXX: Why -1 ? */
        if (__predict_false(fp == NULL))
                return EBADF;

        if (__predict_false(fp->f_type != DTYPE_MQUEUE)) {
                fdrop(fp);
                return EBADF;
        }
        mq = fp->f_data;
        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);

        *fpr = fp;
        return 0;
}

/*
 * mqueue_linear_insert: perform linear insert according to the message
 * priority into the reserved queue (MQ_PQRESQ).  Reserved queue is a
 * sorted list used only when mq_prio_max is increased via sysctl.
 */
static inline void
mqueue_linear_insert(struct mqueue *mq, struct mq_msg *msg)
{
        struct mq_msg *mit;

        TAILQ_FOREACH(mit, &mq->mq_head[MQ_PQRESQ], msg_queue) {
                if (msg->msg_prio > mit->msg_prio)
                        break;
        }
        if (mit == NULL) {
                TAILQ_INSERT_TAIL(&mq->mq_head[MQ_PQRESQ], msg, msg_queue);
        } else {
                TAILQ_INSERT_BEFORE(mit, msg, msg_queue);
        }
}

/*
 * Validate input.
 */
int
itimespecfix(struct timespec *ts)
{
        if (ts->tv_sec < 0 || ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
                return (EINVAL);
        if (ts->tv_sec == 0 && ts->tv_nsec != 0 && ts->tv_nsec < nstick)
                ts->tv_nsec = nstick;
        return (0);
}

/*
 * Compute number of ticks in the specified amount of time.
 */
int
tstohz(const struct timespec *ts)
{
        struct timeval tv;

        /*
         * usec has great enough resolution for hz, so convert to a
         * timeval and use tvtohz() above.
         */
        TIMESPEC_TO_TIMEVAL(&tv, ts);
        return tvtohz_high(&tv);        /* XXX Why _high() and not _low() ? */
}

/*
 * Converter from struct timespec to the ticks.
 * Used by mq_timedreceive(), mq_timedsend().
 */
int
abstimeout2timo(struct timespec *ts, int *timo)
{
        struct timespec tsd;
        int error;

        error = itimespecfix(ts);
        if (error) {
                return error;
        }
        getnanotime(&tsd);
        timespecsub(ts, &tsd);
        if (ts->tv_sec < 0 || (ts->tv_sec == 0 && ts->tv_nsec <= 0)) {
                return ETIMEDOUT;
        }
        *timo = tstohz(ts);
        KKASSERT(*timo != 0);

        return 0;
}

static int
mq_stat_fop(file_t *fp, struct stat *st, struct ucred *cred)
{
        struct mqueue *mq = fp->f_data;

        (void)memset(st, 0, sizeof(*st));

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
        st->st_mode = mq->mq_mode;
        st->st_uid = mq->mq_euid;
        st->st_gid = mq->mq_egid;
        st->st_atimespec = mq->mq_atime;
        st->st_mtimespec = mq->mq_mtime;
        /*st->st_ctimespec = st->st_birthtimespec = mq->mq_btime;*/
        st->st_uid = fp->f_cred->cr_uid;
        st->st_gid = fp->f_cred->cr_svgid;
        lockmgr(&mq->mq_mtx, LK_RELEASE);

        return 0;
}

static struct filterops mqfiltops_read =
        { FILTEROP_ISFD, NULL, mqfilter_read_detach, mqfilter_read };
static struct filterops mqfiltops_write =
        { FILTEROP_ISFD, NULL, mqfilter_write_detach, mqfilter_write };

static int
mq_kqfilter_fop(struct file *fp, struct knote *kn)
{
        struct mqueue *mq = fp->f_data;
        struct klist *klist;

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);

        switch (kn->kn_filter) {
        case EVFILT_READ:
                kn->kn_fop = &mqfiltops_read;
                kn->kn_hook = (caddr_t)mq;
                klist = &mq->mq_rkq.ki_note;
                break;
        case EVFILT_WRITE:
                kn->kn_fop = &mqfiltops_write;
                kn->kn_hook = (caddr_t)mq;
                klist = &mq->mq_wkq.ki_note;
                break;
        default:
                lockmgr(&mq->mq_mtx, LK_RELEASE);
                return (EOPNOTSUPP);
        }

        knote_insert(klist, kn);
        lockmgr(&mq->mq_mtx, LK_RELEASE);

        return (0);
}

static void
mqfilter_read_detach(struct knote *kn)
{
        struct mqueue *mq = (struct mqueue *)kn->kn_hook;

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
        struct klist *klist = &mq->mq_rkq.ki_note;
        knote_remove(klist, kn);
        lockmgr(&mq->mq_mtx, LK_RELEASE);
}

static void
mqfilter_write_detach(struct knote *kn)
{
        struct mqueue *mq = (struct mqueue *)kn->kn_hook;

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
        struct klist *klist = &mq->mq_wkq.ki_note;
        knote_remove(klist, kn);
        lockmgr(&mq->mq_mtx, LK_RELEASE);
}

static int
mqfilter_read(struct knote *kn, long hint)
{
        struct mqueue *mq = (struct mqueue *)kn->kn_hook;
        struct mq_attr *mqattr;
        int ready = 0;

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
        mqattr = &mq->mq_attrib;
        /* Ready for receiving, if there are messages in the queue */
        if (mqattr->mq_curmsgs)
                ready = 1;
        lockmgr(&mq->mq_mtx, LK_RELEASE);

        return (ready);
}

static int
mqfilter_write(struct knote *kn, long hint)
{
        struct mqueue *mq = (struct mqueue *)kn->kn_hook;
        struct mq_attr *mqattr;
        int ready = 0;

        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
        mqattr = &mq->mq_attrib;
        /* Ready for sending, if the message queue is not full */
        if (mqattr->mq_curmsgs < mqattr->mq_maxmsg)
                ready = 1;
        lockmgr(&mq->mq_mtx, LK_RELEASE);

        return (ready);
}

static int
mq_close_fop(file_t *fp)
{
        struct proc *p = curproc;
        struct mqueue *mq = fp->f_data;
        bool destroy;

        lockmgr(&mqlist_mtx, LK_EXCLUSIVE);
        lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);

        /* Decrease the counters */
        p->p_mqueue_cnt--;
        mq->mq_refcnt--;

        /* Remove notification if registered for this process */
        if (mq->mq_notify_proc == p)
                mq->mq_notify_proc = NULL;

        /*
         * If this is the last reference and mqueue is marked for unlink,
         * remove and later destroy the message queue.
         */
        if (mq->mq_refcnt == 0 && (mq->mq_attrib.mq_flags & MQ_UNLINK)) {
                LIST_REMOVE(mq, mq_list);
                destroy = true;
        } else
                destroy = false;

        lockmgr(&mq->mq_mtx, LK_RELEASE);
        lockmgr(&mqlist_mtx, LK_RELEASE);

        if (destroy)
                mqueue_destroy(mq);

        return 0;
}

/*
 * General mqueue system calls.
 */

int
sys_mq_open(struct mq_open_args *uap)
{
        /* {
                syscallarg(const char *) name;
                syscallarg(int) oflag;
                syscallarg(mode_t) mode;
                syscallarg(struct mq_attr) attr;
        } */
        struct thread *td = curthread;
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        struct mqueue *mq, *mq_new = NULL;
        file_t *fp;
        char *name;
        int mqd, error, oflag;

        /* Check access mode flags */
        oflag = SCARG(uap, oflag);
        if ((oflag & O_ACCMODE) == (O_WRONLY | O_RDWR)) {
                return EINVAL;
        }

        /* Get the name from the user-space */
        name = kmalloc(MQ_NAMELEN, M_MQBUF, M_WAITOK | M_ZERO);
        error = copyinstr(SCARG(uap, name), name, MQ_NAMELEN - 1, NULL);
        if (error) {
                kfree(name, M_MQBUF);
                return error;
        }

        if (oflag & O_CREAT) {
                struct mq_attr attr;
                u_int i;

                /* Check the limit */
                if (p->p_mqueue_cnt == mq_open_max) {
                        kfree(name, M_MQBUF);
                        return EMFILE;
                }

                /* Empty name is invalid */
                if (name[0] == '\0') {
                        kfree(name, M_MQBUF);
                        return EINVAL;
                }

                /* Check for mqueue attributes */
                if (SCARG(uap, attr)) {
                        error = copyin(SCARG(uap, attr), &attr,
                                sizeof(struct mq_attr));
                        if (error) {
                                kfree(name, M_MQBUF);
                                return error;
                        }
                        if (attr.mq_maxmsg <= 0 ||
                            attr.mq_maxmsg > mq_max_maxmsg ||
                            attr.mq_msgsize <= 0 ||
                            attr.mq_msgsize > mq_max_msgsize) {
                                kfree(name, M_MQBUF);
                                return EINVAL;
                        }
                        attr.mq_curmsgs = 0;
                } else {
                        memset(&attr, 0, sizeof(struct mq_attr));
                        attr.mq_maxmsg = mq_def_maxmsg;
                        attr.mq_msgsize =
                            MQ_DEF_MSGSIZE - sizeof(struct mq_msg);
                }

                /*
                 * Allocate new mqueue, initialize data structures,
                 * copy the name, attributes and set the flag.
                 */
                mq_new = kmalloc(sizeof(struct mqueue), M_MQBUF, M_WAITOK | M_ZERO);

                lockinit(&mq_new->mq_mtx, "mq_new->mq_mtx", 0, LK_CANRECURSE);
                for (i = 0; i < (MQ_PQSIZE + 1); i++) {
                        TAILQ_INIT(&mq_new->mq_head[i]);
                }

                strlcpy(mq_new->mq_name, name, MQ_NAMELEN);
                memcpy(&mq_new->mq_attrib, &attr, sizeof(struct mq_attr));

                /*CTASSERT((O_MASK & (MQ_UNLINK | MQ_RECEIVE)) == 0);*/
                /* mq_new->mq_attrib.mq_flags = (O_MASK & oflag); */
                mq_new->mq_attrib.mq_flags = oflag;

                /* Store mode and effective UID with GID */
                mq_new->mq_mode = ((SCARG(uap, mode) &
                    ~p->p_fd->fd_cmask) & ALLPERMS) & ~S_ISTXT;
                mq_new->mq_euid = td->td_ucred->cr_uid;
                mq_new->mq_egid = td->td_ucred->cr_svgid;
        }

        /* Allocate file structure and descriptor */
        error = falloc(td->td_lwp, &fp, &mqd);
        if (error) {
                if (mq_new)
                        mqueue_destroy(mq_new);
                kfree(name, M_MQBUF);
                return error;
        }
        fp->f_type = DTYPE_MQUEUE;
        fp->f_flag = FFLAGS(oflag) & (FREAD | FWRITE);
        fp->f_ops = &mqops;

        /* Look up for mqueue with such name */
        lockmgr(&mqlist_mtx, LK_EXCLUSIVE);
        mq = mqueue_lookup(name);
        if (mq) {
                int acc_mode;

                KKASSERT(lockstatus(&mq->mq_mtx, curthread));

                /* Check if mqueue is not marked as unlinking */
                if (mq->mq_attrib.mq_flags & MQ_UNLINK) {
                        error = EACCES;
                        goto exit;
                }
                /* Fail if O_EXCL is set, and mqueue already exists */
                if ((oflag & O_CREAT) && (oflag & O_EXCL)) {
                        error = EEXIST;
                        goto exit;
                }

                /*
                 * Check the permissions. Note the difference between
                 * VREAD/VWRITE and FREAD/FWRITE.
                 */
                acc_mode = 0;
                if (fp->f_flag & FREAD) {
                        acc_mode |= VREAD;
                }
                if (fp->f_flag & FWRITE) {
                        acc_mode |= VWRITE;
                }
                if (vaccess(VNON, mq->mq_mode, mq->mq_euid, mq->mq_egid,
                        acc_mode, td->td_ucred)) {

                        error = EACCES;
                        goto exit;
                }
        } else {
                /* Fail if mqueue neither exists, nor we create it */
                if ((oflag & O_CREAT) == 0) {
                        lockmgr(&mqlist_mtx, LK_RELEASE);
                        KKASSERT(mq_new == NULL);
                        fsetfd(fdp, NULL, mqd);
                        fp->f_ops = &badfileops;
                        fdrop(fp);
                        kfree(name, M_MQBUF);
                        return ENOENT;
                }

                /* Check the limit */
                if (p->p_mqueue_cnt == mq_open_max) {
                        error = EMFILE;
                        goto exit;
                }

                /* Insert the queue to the list */
                mq = mq_new;
                lockmgr(&mq->mq_mtx, LK_EXCLUSIVE);
                LIST_INSERT_HEAD(&mqueue_head, mq, mq_list);
                mq_new = NULL;
                getnanotime(&mq->mq_btime);
                mq->mq_atime = mq->mq_mtime = mq->mq_btime;
        }

        /* Increase the counters, and make descriptor ready */
        p->p_mqueue_cnt++;
        mq->mq_refcnt++;
        fp->f_data = mq;
exit:
        lockmgr(&mq->mq_mtx, LK_RELEASE);
        lockmgr(&mqlist_mtx, LK_RELEASE);

        if (mq_new)
                mqueue_destroy(mq_new);
        if (error) {
                fsetfd(fdp, NULL, mqd);
                fp->f_ops = &badfileops;
        } else {
                fsetfd(fdp, fp, mqd);
                uap->sysmsg_result = mqd;
        }
        fdrop(fp);
        kfree(name, M_MQBUF);

        return error;
}

int
sys_mq_close(struct mq_close_args *uap)
{
        return sys_close((void *)uap);
}

/*
 * Primary mq_receive1() function.
 */
int
mq_receive1(struct lwp *l, mqd_t mqdes, void *msg_ptr, size_t msg_len,
    unsigned *msg_prio, struct timespec *ts, ssize_t *mlen)
{
        file_t *fp = NULL;
        struct mqueue *mq;
        struct mq_msg *msg = NULL;
        struct mq_attr *mqattr;
        u_int idx;
        int error;

        /* Get the message queue */
        error = mqueue_get(l, mqdes, &fp);
        if (error) {
                return error;
        }
        mq = fp->f_data;
        if ((fp->f_flag & FREAD) == 0) {
                error = EBADF;
                goto error;
        }
        getnanotime(&mq->mq_atime);
        mqattr = &mq->mq_attrib;

        /* Check the message size limits */
        if (msg_len < mqattr->mq_msgsize) {
                error = EMSGSIZE;
                goto error;
        }

        /* Check if queue is empty */
        while (mqattr->mq_curmsgs == 0) {
                int t;

                if (mqattr->mq_flags & O_NONBLOCK) {
                        error = EAGAIN;
                        goto error;
                }
                if (ts) {
                        error = abstimeout2timo(ts, &t);
                        if (error)
                                goto error;
                } else
                        t = 0;
                /*
                 * Block until someone sends the message.
                 * While doing this, notification should not be sent.
                 */
                mqattr->mq_flags |= MQ_RECEIVE;
                error = lksleep(&mq->mq_send_cv, &mq->mq_mtx, PCATCH, "mqsend", t);
                mqattr->mq_flags &= ~MQ_RECEIVE;
                if (error || (mqattr->mq_flags & MQ_UNLINK)) {
                        error = (error == EWOULDBLOCK) ? ETIMEDOUT : EINTR;
                        goto error;
                }
        }


        /*
         * Find the highest priority message, and remove it from the queue.
         * At first, reserved queue is checked, bitmap is next.
         */
        msg = TAILQ_FIRST(&mq->mq_head[MQ_PQRESQ]);
        if (__predict_true(msg == NULL)) {
                idx = ffs(mq->mq_bitmap);
                msg = TAILQ_FIRST(&mq->mq_head[idx]);
                KKASSERT(msg != NULL);
        } else {
                idx = MQ_PQRESQ;
        }
        TAILQ_REMOVE(&mq->mq_head[idx], msg, msg_queue);

        /* Unmark the bit, if last message. */
        if (__predict_true(idx) && TAILQ_EMPTY(&mq->mq_head[idx])) {
                KKASSERT((MQ_PQSIZE - idx) == msg->msg_prio);
                mq->mq_bitmap &= ~(1 << --idx);
        }

        /* Decrement the counter and signal waiter, if any */
        mqattr->mq_curmsgs--;
        wakeup_one(&mq->mq_recv_cv);

        /* Ready for sending now */
        KNOTE(&mq->mq_wkq.ki_note, 0);
error:
        lockmgr(&mq->mq_mtx, LK_RELEASE);
        fdrop(fp);
        if (error)
                return error;

        /*
         * Copy the data to the user-space.
         * Note: According to POSIX, no message should be removed from the
         * queue in case of fail - this would be violated.
         */
        *mlen = msg->msg_len;
        error = copyout(msg->msg_ptr, msg_ptr, msg->msg_len);
        if (error == 0 && msg_prio)
                error = copyout(&msg->msg_prio, msg_prio, sizeof(unsigned));
        mqueue_freemsg(msg, sizeof(struct mq_msg) + msg->msg_len);

        return error;
}

int
sys_mq_receive(struct mq_receive_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(char *) msg_ptr;
                syscallarg(size_t) msg_len;
                syscallarg(unsigned *) msg_prio;
        } */
        ssize_t mlen;
        int error;

        error = mq_receive1(curthread->td_lwp, SCARG(uap, mqdes), SCARG(uap, msg_ptr),
            SCARG(uap, msg_len), SCARG(uap, msg_prio), 0, &mlen);
        if (error == 0)
                uap->sysmsg_result = mlen;

        return error;
}

int
sys_mq_timedreceive(struct mq_timedreceive_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(char *) msg_ptr;
                syscallarg(size_t) msg_len;
                syscallarg(unsigned *) msg_prio;
                syscallarg(const struct timespec *) abs_timeout;
        } */
        int error;
        ssize_t mlen;
        struct timespec ts, *tsp;

        /* Get and convert time value */
        if (SCARG(uap, abs_timeout)) {
                error = copyin(SCARG(uap, abs_timeout), &ts, sizeof(ts));
                if (error)
                        return error;
                tsp = &ts;
        } else {
                tsp = NULL;
        }

        error = mq_receive1(curthread->td_lwp, SCARG(uap, mqdes), SCARG(uap, msg_ptr),
            SCARG(uap, msg_len), SCARG(uap, msg_prio), tsp, &mlen);
        if (error == 0)
                uap->sysmsg_result = mlen;

        return error;
}

/*
 * Primary mq_send1() function.
 */
int
mq_send1(struct lwp *l, mqd_t mqdes, const char *msg_ptr, size_t msg_len,
    unsigned msg_prio, struct timespec *ts)
{
        file_t *fp = NULL;
        struct mqueue *mq;
        struct mq_msg *msg;
        struct mq_attr *mqattr;
        struct proc *notify = NULL;
        /*ksiginfo_t ksi;*/
        size_t size;
        int error;

        /* Check the priority range */
        if (msg_prio >= mq_prio_max)
                return EINVAL;

        /* Allocate a new message */
        size = sizeof(struct mq_msg) + msg_len;
        if (size > mq_max_msgsize)
                return EMSGSIZE;

        if (size > MQ_DEF_MSGSIZE) {
                msg = kmalloc(size, M_MQBUF, M_WAITOK);
        } else {
                msg = objcache_get(mqmsg_cache, M_WAITOK);
        }

        /* Get the data from user-space */
        error = copyin(msg_ptr, msg->msg_ptr, msg_len);
        if (error) {
                mqueue_freemsg(msg, size);
                return error;
        }
        msg->msg_len = msg_len;
        msg->msg_prio = msg_prio;

        /* Get the mqueue */
        error = mqueue_get(l, mqdes, &fp);
        if (error) {
                mqueue_freemsg(msg, size);
                return error;
        }
        mq = fp->f_data;
        if ((fp->f_flag & FWRITE) == 0) {
                error = EBADF;
                goto error;
        }
        getnanotime(&mq->mq_mtime);
        mqattr = &mq->mq_attrib;

        /* Check the message size limit */
        if (msg_len <= 0 || msg_len > mqattr->mq_msgsize) {
                error = EMSGSIZE;
                goto error;
        }

        /* Check if queue is full */
        while (mqattr->mq_curmsgs >= mqattr->mq_maxmsg) {
                int t;

                if (mqattr->mq_flags & O_NONBLOCK) {
                        error = EAGAIN;
                        goto error;
                }
                if (ts) {
                        error = abstimeout2timo(ts, &t);
                        if (error)
                                goto error;
                } else
                        t = 0;
                /* Block until queue becomes available */
                error = lksleep(&mq->mq_recv_cv, &mq->mq_mtx, PCATCH, "mqrecv", t);
                if (error || (mqattr->mq_flags & MQ_UNLINK)) {
                        error = (error == EWOULDBLOCK) ? ETIMEDOUT : error;
                        goto error;
                }
        }
        KKASSERT(mq->mq_attrib.mq_curmsgs < mq->mq_attrib.mq_maxmsg);

        /*
         * Insert message into the queue, according to the priority.
         * Note the difference between index and priority.
         */
        if (__predict_true(msg_prio < MQ_PQSIZE)) {
                u_int idx = MQ_PQSIZE - msg_prio;

                KKASSERT(idx != MQ_PQRESQ);
                TAILQ_INSERT_TAIL(&mq->mq_head[idx], msg, msg_queue);
                mq->mq_bitmap |= (1 << --idx);
        } else {
                mqueue_linear_insert(mq, msg);
        }

        /* Check for the notify */
        if (mqattr->mq_curmsgs == 0 && mq->mq_notify_proc &&
            (mqattr->mq_flags & MQ_RECEIVE) == 0 &&
            mq->mq_sig_notify.sigev_notify == SIGEV_SIGNAL) {
                /* Initialize the signal */
                /*KSI_INIT(&ksi);*/
                /*ksi.ksi_signo = mq->mq_sig_notify.sigev_signo;*/
                /*ksi.ksi_code = SI_MESGQ;*/
                /*ksi.ksi_value = mq->mq_sig_notify.sigev_value;*/
                /* Unregister the process */
                notify = mq->mq_notify_proc;
                mq->mq_notify_proc = NULL;
        }

        /* Increment the counter and signal waiter, if any */
        mqattr->mq_curmsgs++;
        wakeup_one(&mq->mq_send_cv);

        /* Ready for receiving now */
        KNOTE(&mq->mq_rkq.ki_note, 0);
error:
        lockmgr(&mq->mq_mtx, LK_RELEASE);
        fdrop(fp);

        if (error) {
                mqueue_freemsg(msg, size);
        } else if (notify) {
                /* Send the notify, if needed */
                lwkt_gettoken(&proc_token);
                /*kpsignal(notify, &ksi, NULL);*/
                ksignal(notify, mq->mq_sig_notify.sigev_signo);
                lwkt_reltoken(&proc_token);
        }

        return error;
}

int
sys_mq_send(struct mq_send_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(const char *) msg_ptr;
                syscallarg(size_t) msg_len;
                syscallarg(unsigned) msg_prio;
        } */

        return mq_send1(curthread->td_lwp, SCARG(uap, mqdes), SCARG(uap, msg_ptr),
            SCARG(uap, msg_len), SCARG(uap, msg_prio), 0);
}

int
sys_mq_timedsend(struct mq_timedsend_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(const char *) msg_ptr;
                syscallarg(size_t) msg_len;
                syscallarg(unsigned) msg_prio;
                syscallarg(const struct timespec *) abs_timeout;
        } */
        struct timespec ts, *tsp;
        int error;

        /* Get and convert time value */
        if (SCARG(uap, abs_timeout)) {
                error = copyin(SCARG(uap, abs_timeout), &ts, sizeof(ts));
                if (error)
                        return error;
                tsp = &ts;
        } else {
                tsp = NULL;
        }

        return mq_send1(curthread->td_lwp, SCARG(uap, mqdes), SCARG(uap, msg_ptr),
            SCARG(uap, msg_len), SCARG(uap, msg_prio), tsp);
}

int
sys_mq_notify(struct mq_notify_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(const struct sigevent *) notification;
        } */
        file_t *fp = NULL;
        struct mqueue *mq;
        struct sigevent sig;
        int error;

        if (SCARG(uap, notification)) {
                /* Get the signal from user-space */
                error = copyin(SCARG(uap, notification), &sig,
                    sizeof(struct sigevent));
                if (error)
                        return error;
                if (sig.sigev_notify == SIGEV_SIGNAL &&
                    (sig.sigev_signo <= 0 || sig.sigev_signo >= NSIG))
                        return EINVAL;
        }

        error = mqueue_get(curthread->td_lwp, SCARG(uap, mqdes), &fp);
        if (error)
                return error;
        mq = fp->f_data;

        if (SCARG(uap, notification)) {
                /* Register notification: set the signal and target process */
                if (mq->mq_notify_proc == NULL) {
                        memcpy(&mq->mq_sig_notify, &sig,
                            sizeof(struct sigevent));
                        mq->mq_notify_proc = curproc;
                } else {
                        /* Fail if someone else already registered */
                        error = EBUSY;
                }
        } else {
                /* Unregister the notification */
                mq->mq_notify_proc = NULL;
        }
        lockmgr(&mq->mq_mtx, LK_RELEASE);
        fdrop(fp);

        return error;
}

int
sys_mq_getattr(struct mq_getattr_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(struct mq_attr *) mqstat;
        } */
        file_t *fp = NULL;
        struct mqueue *mq;
        struct mq_attr attr;
        int error;

        /* Get the message queue */
        error = mqueue_get(curthread->td_lwp, SCARG(uap, mqdes), &fp);
        if (error)
                return error;
        mq = fp->f_data;
        memcpy(&attr, &mq->mq_attrib, sizeof(struct mq_attr));
        lockmgr(&mq->mq_mtx, LK_RELEASE);
        fdrop(fp);

        return copyout(&attr, SCARG(uap, mqstat), sizeof(struct mq_attr));
}

int
sys_mq_setattr(struct mq_setattr_args *uap)
{
        /* {
                syscallarg(mqd_t) mqdes;
                syscallarg(const struct mq_attr *) mqstat;
                syscallarg(struct mq_attr *) omqstat;
        } */
        file_t *fp = NULL;
        struct mqueue *mq;
        struct mq_attr attr;
        int error, nonblock;

        error = copyin(SCARG(uap, mqstat), &attr, sizeof(struct mq_attr));
        if (error)
                return error;
        nonblock = (attr.mq_flags & O_NONBLOCK);

        /* Get the message queue */
        error = mqueue_get(curthread->td_lwp, SCARG(uap, mqdes), &fp);
        if (error)
                return error;
        mq = fp->f_data;

        /* Copy the old attributes, if needed */
        if (SCARG(uap, omqstat)) {
                memcpy(&attr, &mq->mq_attrib, sizeof(struct mq_attr));
        }

        /* Ignore everything, except O_NONBLOCK */
        if (nonblock)
                mq->mq_attrib.mq_flags |= O_NONBLOCK;
        else
                mq->mq_attrib.mq_flags &= ~O_NONBLOCK;

        lockmgr(&mq->mq_mtx, LK_RELEASE);
        fdrop(fp);

        /*
         * Copy the data to the user-space.
         * Note: According to POSIX, the new attributes should not be set in
         * case of fail - this would be violated.
         */
        if (SCARG(uap, omqstat))
                error = copyout(&attr, SCARG(uap, omqstat),
                    sizeof(struct mq_attr));

        return error;
}

int
sys_mq_unlink(struct mq_unlink_args *uap)
{
        /* {
                syscallarg(const char *) name;
        } */
        struct thread *td = curthread;
        struct mqueue *mq;
        char *name;
        int error, refcnt = 0;

        /* Get the name from the user-space */
        name = kmalloc(MQ_NAMELEN, M_MQBUF, M_WAITOK | M_ZERO);
        error = copyinstr(SCARG(uap, name), name, MQ_NAMELEN - 1, NULL);
        if (error) {
                kfree(name, M_MQBUF);
                return error;
        }

        /* Lookup for this file */
        lockmgr(&mqlist_mtx, LK_EXCLUSIVE);
        mq = mqueue_lookup(name);
        if (mq == NULL) {
                error = ENOENT;
                goto error;
        }

        /* Check the permissions */
        if (td->td_ucred->cr_uid != mq->mq_euid &&
            priv_check(td, PRIV_ROOT) != 0) {
                lockmgr(&mq->mq_mtx, LK_RELEASE);
                error = EACCES;
                goto error;
        }

        /* Mark message queue as unlinking, before leaving the window */
        mq->mq_attrib.mq_flags |= MQ_UNLINK;

        /* Wake up all waiters, if there are such */
        wakeup(&mq->mq_send_cv);
        wakeup(&mq->mq_recv_cv);

        KNOTE(&mq->mq_rkq.ki_note, 0);
        KNOTE(&mq->mq_wkq.ki_note, 0);

        refcnt = mq->mq_refcnt;
        if (refcnt == 0)
                LIST_REMOVE(mq, mq_list);

        lockmgr(&mq->mq_mtx, LK_RELEASE);
error:
        lockmgr(&mqlist_mtx, LK_RELEASE);

        /*
         * If there are no references - destroy the message
         * queue, otherwise, the last mq_close() will do that.
         */
        if (error == 0 && refcnt == 0)
                mqueue_destroy(mq);

        kfree(name, M_MQBUF);
        return error;
}

/*
 * SysCtl.
 */
SYSCTL_NODE(_kern, OID_AUTO, mqueue,
    CTLFLAG_RW, 0, "Message queue options");

SYSCTL_INT(_kern_mqueue, OID_AUTO, mq_open_max,
    CTLFLAG_RW, &mq_open_max, 0,
    "Maximal number of message queue descriptors per process");

SYSCTL_INT(_kern_mqueue, OID_AUTO, mq_prio_max,
    CTLFLAG_RW, &mq_prio_max, 0,
    "Maximal priority of the message");

SYSCTL_INT(_kern_mqueue, OID_AUTO, mq_max_msgsize,
    CTLFLAG_RW, &mq_max_msgsize, 0,
    "Maximal allowed size of the message");

SYSCTL_INT(_kern_mqueue, OID_AUTO, mq_def_maxmsg,
    CTLFLAG_RW, &mq_def_maxmsg, 0,
    "Default maximal message count");

SYSCTL_INT(_kern_mqueue, OID_AUTO, mq_max_maxmsg,
    CTLFLAG_RW, &mq_max_maxmsg, 0,
    "Maximal allowed message count");

SYSINIT(sys_mqueue_init, SI_SUB_PRE_DRIVERS, SI_ORDER_ANY, mqueue_sysinit, NULL);