fkvm_get_regs: missing break in switch statement

[freebsd-src/fkvm-freebsd.git] / sys / kern / sysv_msg.c

/*-
 * Implementation of SVID messages
 *
 * Author:  Daniel Boulet
 *
 * Copyright 1993 Daniel Boulet and RTMX Inc.
 *
 * This system call was implemented by Daniel Boulet under contract from RTMX.
 *
 * Redistribution and use in source forms, with and without modification,
 * are permitted provided that this entire comment appears intact.
 *
 * Redistribution in binary form may occur without any restrictions.
 * Obviously, it would be nice if you gave credit where credit is due
 * but requiring it would be too onerous.
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 */
/*-
 * Copyright (c) 2003-2005 McAfee, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project in part by McAfee
 * Research, the Security Research Division of McAfee, Inc under DARPA/SPAWAR
 * contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS research
 * program.
 *
 * 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/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_sysvipc.h"
#include "opt_mac.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/module.h>
#include <sys/msg.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/jail.h>

#include <security/mac/mac_framework.h>

static MALLOC_DEFINE(M_MSG, "msg", "SVID compatible message queues");

static void msginit(void);
static int msgunload(void);
static int sysvmsg_modload(struct module *, int, void *);

#ifdef MSG_DEBUG
#define DPRINTF(a)      printf a
#else
#define DPRINTF(a)
#endif

static void msg_freehdr(struct msg *msghdr);

/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *msgcalls[] = {
        (sy_call_t *)msgctl, (sy_call_t *)msgget,
        (sy_call_t *)msgsnd, (sy_call_t *)msgrcv
};

#ifndef MSGSSZ
#define MSGSSZ  8               /* Each segment must be 2^N long */
#endif
#ifndef MSGSEG
#define MSGSEG  2048            /* must be less than 32767 */
#endif
#define MSGMAX  (MSGSSZ*MSGSEG)
#ifndef MSGMNB
#define MSGMNB  2048            /* max # of bytes in a queue */
#endif
#ifndef MSGMNI
#define MSGMNI  40
#endif
#ifndef MSGTQL
#define MSGTQL  40
#endif

/*
 * Based on the configuration parameters described in an SVR2 (yes, two)
 * config(1m) man page.
 *
 * Each message is broken up and stored in segments that are msgssz bytes
 * long.  For efficiency reasons, this should be a power of two.  Also,
 * it doesn't make sense if it is less than 8 or greater than about 256.
 * Consequently, msginit in kern/sysv_msg.c checks that msgssz is a power of
 * two between 8 and 1024 inclusive (and panic's if it isn't).
 */
struct msginfo msginfo = {
                MSGMAX,         /* max chars in a message */
                MSGMNI,         /* # of message queue identifiers */
                MSGMNB,         /* max chars in a queue */
                MSGTQL,         /* max messages in system */
                MSGSSZ,         /* size of a message segment */
                                /* (must be small power of 2 greater than 4) */
                MSGSEG          /* number of message segments */
};

/*
 * macros to convert between msqid_ds's and msqid's.
 * (specific to this implementation)
 */
#define MSQID(ix,ds)    ((ix) & 0xffff | (((ds).msg_perm.seq << 16) & 0xffff0000))
#define MSQID_IX(id)    ((id) & 0xffff)
#define MSQID_SEQ(id)   (((id) >> 16) & 0xffff)

/*
 * The rest of this file is specific to this particular implementation.
 */

struct msgmap {
        short   next;           /* next segment in buffer */
                                /* -1 -> available */
                                /* 0..(MSGSEG-1) -> index of next segment */
};

#define MSG_LOCKED      01000   /* Is this msqid_ds locked? */

static int nfree_msgmaps;       /* # of free map entries */
static short free_msgmaps;      /* head of linked list of free map entries */
static struct msg *free_msghdrs;/* list of free msg headers */
static char *msgpool;           /* MSGMAX byte long msg buffer pool */
static struct msgmap *msgmaps;  /* MSGSEG msgmap structures */
static struct msg *msghdrs;     /* MSGTQL msg headers */
static struct msqid_kernel *msqids;     /* MSGMNI msqid_kernel struct's */
static struct mtx msq_mtx;      /* global mutex for message queues. */

static void
msginit()
{
        register int i;

        TUNABLE_INT_FETCH("kern.ipc.msgseg", &msginfo.msgseg);
        TUNABLE_INT_FETCH("kern.ipc.msgssz", &msginfo.msgssz);
        msginfo.msgmax = msginfo.msgseg * msginfo.msgssz;
        TUNABLE_INT_FETCH("kern.ipc.msgmni", &msginfo.msgmni);
        TUNABLE_INT_FETCH("kern.ipc.msgmnb", &msginfo.msgmnb);
        TUNABLE_INT_FETCH("kern.ipc.msgtql", &msginfo.msgtql);

        msgpool = malloc(msginfo.msgmax, M_MSG, M_WAITOK);
        if (msgpool == NULL)
                panic("msgpool is NULL");
        msgmaps = malloc(sizeof(struct msgmap) * msginfo.msgseg, M_MSG, M_WAITOK);
        if (msgmaps == NULL)
                panic("msgmaps is NULL");
        msghdrs = malloc(sizeof(struct msg) * msginfo.msgtql, M_MSG, M_WAITOK);
        if (msghdrs == NULL)
                panic("msghdrs is NULL");
        msqids = malloc(sizeof(struct msqid_kernel) * msginfo.msgmni, M_MSG,
            M_WAITOK);
        if (msqids == NULL)
                panic("msqids is NULL");

        /*
         * msginfo.msgssz should be a power of two for efficiency reasons.
         * It is also pretty silly if msginfo.msgssz is less than 8
         * or greater than about 256 so ...
         */

        i = 8;
        while (i < 1024 && i != msginfo.msgssz)
                i <<= 1;
        if (i != msginfo.msgssz) {
                DPRINTF(("msginfo.msgssz=%d (0x%x)\n", msginfo.msgssz,
                    msginfo.msgssz));
                panic("msginfo.msgssz not a small power of 2");
        }

        if (msginfo.msgseg > 32767) {
                DPRINTF(("msginfo.msgseg=%d\n", msginfo.msgseg));
                panic("msginfo.msgseg > 32767");
        }

        if (msgmaps == NULL)
                panic("msgmaps is NULL");

        for (i = 0; i < msginfo.msgseg; i++) {
                if (i > 0)
                        msgmaps[i-1].next = i;
                msgmaps[i].next = -1;   /* implies entry is available */
        }
        free_msgmaps = 0;
        nfree_msgmaps = msginfo.msgseg;

        if (msghdrs == NULL)
                panic("msghdrs is NULL");

        for (i = 0; i < msginfo.msgtql; i++) {
                msghdrs[i].msg_type = 0;
                if (i > 0)
                        msghdrs[i-1].msg_next = &msghdrs[i];
                msghdrs[i].msg_next = NULL;
#ifdef MAC
                mac_sysvmsg_init(&msghdrs[i]);
#endif
        }
        free_msghdrs = &msghdrs[0];

        if (msqids == NULL)
                panic("msqids is NULL");

        for (i = 0; i < msginfo.msgmni; i++) {
                msqids[i].u.msg_qbytes = 0;     /* implies entry is available */
                msqids[i].u.msg_perm.seq = 0;   /* reset to a known value */
                msqids[i].u.msg_perm.mode = 0;
#ifdef MAC
                mac_sysvmsq_init(&msqids[i]);
#endif
        }
        mtx_init(&msq_mtx, "msq", NULL, MTX_DEF);
}

static int
msgunload()
{
        struct msqid_kernel *msqkptr;
        int msqid;
#ifdef MAC
        int i;
#endif

        for (msqid = 0; msqid < msginfo.msgmni; msqid++) {
                /*
                 * Look for an unallocated and unlocked msqid_ds.
                 * msqid_ds's can be locked by msgsnd or msgrcv while
                 * they are copying the message in/out.  We can't
                 * re-use the entry until they release it.
                 */
                msqkptr = &msqids[msqid];
                if (msqkptr->u.msg_qbytes != 0 ||
                    (msqkptr->u.msg_perm.mode & MSG_LOCKED) != 0)
                        break;
        }
        if (msqid != msginfo.msgmni)
                return (EBUSY);

#ifdef MAC
        for (i = 0; i < msginfo.msgtql; i++)
                mac_sysvmsg_destroy(&msghdrs[i]);
        for (msqid = 0; msqid < msginfo.msgmni; msqid++)
                mac_sysvmsq_destroy(&msqids[msqid]);
#endif
        free(msgpool, M_MSG);
        free(msgmaps, M_MSG);
        free(msghdrs, M_MSG);
        free(msqids, M_MSG);
        mtx_destroy(&msq_mtx);
        return (0);
}


static int
sysvmsg_modload(struct module *module, int cmd, void *arg)
{
        int error = 0;

        switch (cmd) {
        case MOD_LOAD:
                msginit();
                break;
        case MOD_UNLOAD:
                error = msgunload();
                break;
        case MOD_SHUTDOWN:
                break;
        default:
                error = EINVAL;
                break;
        }
        return (error);
}

static moduledata_t sysvmsg_mod = {
        "sysvmsg",
        &sysvmsg_modload,
        NULL
};

SYSCALL_MODULE_HELPER(msgsys);
SYSCALL_MODULE_HELPER(msgctl);
SYSCALL_MODULE_HELPER(msgget);
SYSCALL_MODULE_HELPER(msgsnd);
SYSCALL_MODULE_HELPER(msgrcv);

DECLARE_MODULE(sysvmsg, sysvmsg_mod,
        SI_SUB_SYSV_MSG, SI_ORDER_FIRST);
MODULE_VERSION(sysvmsg, 1);

/*
 * Entry point for all MSG calls.
 */
int
msgsys(td, uap)
        struct thread *td;
        /* XXX actually varargs. */
        struct msgsys_args /* {
                int     which;
                int     a2;
                int     a3;
                int     a4;
                int     a5;
                int     a6;
        } */ *uap;
{
        int error;

        if (!jail_sysvipc_allowed && jailed(td->td_ucred))
                return (ENOSYS);
        if (uap->which < 0 ||
            uap->which >= sizeof(msgcalls)/sizeof(msgcalls[0]))
                return (EINVAL);
        error = (*msgcalls[uap->which])(td, &uap->a2);
        return (error);
}

static void
msg_freehdr(msghdr)
        struct msg *msghdr;
{
        while (msghdr->msg_ts > 0) {
                short next;
                if (msghdr->msg_spot < 0 || msghdr->msg_spot >= msginfo.msgseg)
                        panic("msghdr->msg_spot out of range");
                next = msgmaps[msghdr->msg_spot].next;
                msgmaps[msghdr->msg_spot].next = free_msgmaps;
                free_msgmaps = msghdr->msg_spot;
                nfree_msgmaps++;
                msghdr->msg_spot = next;
                if (msghdr->msg_ts >= msginfo.msgssz)
                        msghdr->msg_ts -= msginfo.msgssz;
                else
                        msghdr->msg_ts = 0;
        }
        if (msghdr->msg_spot != -1)
                panic("msghdr->msg_spot != -1");
        msghdr->msg_next = free_msghdrs;
        free_msghdrs = msghdr;
#ifdef MAC
        mac_sysvmsg_cleanup(msghdr);
#endif
}

#ifndef _SYS_SYSPROTO_H_
struct msgctl_args {
        int     msqid;
        int     cmd;
        struct  msqid_ds *buf;
};
#endif
int
msgctl(td, uap)
        struct thread *td;
        register struct msgctl_args *uap;
{
        int msqid = uap->msqid;
        int cmd = uap->cmd;
        struct msqid_ds msqbuf;
        int error;

        DPRINTF(("call to msgctl(%d, %d, %p)\n", msqid, cmd, uap->buf));
        if (cmd == IPC_SET &&
            (error = copyin(uap->buf, &msqbuf, sizeof(msqbuf))) != 0)
                return (error);
        error = kern_msgctl(td, msqid, cmd, &msqbuf);
        if (cmd == IPC_STAT && error == 0)
                error = copyout(&msqbuf, uap->buf, sizeof(struct msqid_ds));
        return (error);
}

int
kern_msgctl(td, msqid, cmd, msqbuf)
        struct thread *td;
        int msqid;
        int cmd;
        struct msqid_ds *msqbuf;
{
        int rval, error, msqix;
        register struct msqid_kernel *msqkptr;

        if (!jail_sysvipc_allowed && jailed(td->td_ucred))
                return (ENOSYS);

        msqix = IPCID_TO_IX(msqid);

        if (msqix < 0 || msqix >= msginfo.msgmni) {
                DPRINTF(("msqid (%d) out of range (0<=msqid<%d)\n", msqix,
                    msginfo.msgmni));
                return (EINVAL);
        }

        msqkptr = &msqids[msqix];

        mtx_lock(&msq_mtx);
        if (msqkptr->u.msg_qbytes == 0) {
                DPRINTF(("no such msqid\n"));
                error = EINVAL;
                goto done2;
        }
        if (msqkptr->u.msg_perm.seq != IPCID_TO_SEQ(msqid)) {
                DPRINTF(("wrong sequence number\n"));
                error = EINVAL;
                goto done2;
        }
#ifdef MAC
        error = mac_sysvmsq_check_msqctl(td->td_ucred, msqkptr, cmd);
        if (error != 0)
                goto done2;
#endif

        error = 0;
        rval = 0;

        switch (cmd) {

        case IPC_RMID:
        {
                struct msg *msghdr;
                if ((error = ipcperm(td, &msqkptr->u.msg_perm, IPC_M)))
                        goto done2;

#ifdef MAC
                /*
                 * Check that the thread has MAC access permissions to
                 * individual msghdrs.  Note: We need to do this in a
                 * separate loop because the actual loop alters the
                 * msq/msghdr info as it progresses, and there is no going
                 * back if half the way through we discover that the
                 * thread cannot free a certain msghdr.  The msq will get
                 * into an inconsistent state.
                 */
                for (msghdr = msqkptr->u.msg_first; msghdr != NULL;
                    msghdr = msghdr->msg_next) {
                        error = mac_sysvmsq_check_msgrmid(td->td_ucred, msghdr);
                        if (error != 0)
                                goto done2;
                }
#endif

                /* Free the message headers */
                msghdr = msqkptr->u.msg_first;
                while (msghdr != NULL) {
                        struct msg *msghdr_tmp;

                        /* Free the segments of each message */
                        msqkptr->u.msg_cbytes -= msghdr->msg_ts;
                        msqkptr->u.msg_qnum--;
                        msghdr_tmp = msghdr;
                        msghdr = msghdr->msg_next;
                        msg_freehdr(msghdr_tmp);
                }

                if (msqkptr->u.msg_cbytes != 0)
                        panic("msg_cbytes is screwed up");
                if (msqkptr->u.msg_qnum != 0)
                        panic("msg_qnum is screwed up");

                msqkptr->u.msg_qbytes = 0;      /* Mark it as free */

#ifdef MAC
                mac_sysvmsq_cleanup(msqkptr);
#endif

                wakeup(msqkptr);
        }

                break;

        case IPC_SET:
                if ((error = ipcperm(td, &msqkptr->u.msg_perm, IPC_M)))
                        goto done2;
                if (msqbuf->msg_qbytes > msqkptr->u.msg_qbytes) {
                        error = priv_check(td, PRIV_IPC_MSGSIZE);
                        if (error)
                                goto done2;
                }
                if (msqbuf->msg_qbytes > msginfo.msgmnb) {
                        DPRINTF(("can't increase msg_qbytes beyond %d"
                            "(truncating)\n", msginfo.msgmnb));
                        msqbuf->msg_qbytes = msginfo.msgmnb;    /* silently restrict qbytes to system limit */
                }
                if (msqbuf->msg_qbytes == 0) {
                        DPRINTF(("can't reduce msg_qbytes to 0\n"));
                        error = EINVAL;         /* non-standard errno! */
                        goto done2;
                }
                msqkptr->u.msg_perm.uid = msqbuf->msg_perm.uid; /* change the owner */
                msqkptr->u.msg_perm.gid = msqbuf->msg_perm.gid; /* change the owner */
                msqkptr->u.msg_perm.mode = (msqkptr->u.msg_perm.mode & ~0777) |
                    (msqbuf->msg_perm.mode & 0777);
                msqkptr->u.msg_qbytes = msqbuf->msg_qbytes;
                msqkptr->u.msg_ctime = time_second;
                break;

        case IPC_STAT:
                if ((error = ipcperm(td, &msqkptr->u.msg_perm, IPC_R))) {
                        DPRINTF(("requester doesn't have read access\n"));
                        goto done2;
                }
                *msqbuf = msqkptr->u;
                break;

        default:
                DPRINTF(("invalid command %d\n", cmd));
                error = EINVAL;
                goto done2;
        }

        if (error == 0)
                td->td_retval[0] = rval;
done2:
        mtx_unlock(&msq_mtx);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct msgget_args {
        key_t   key;
        int     msgflg;
};
#endif
int
msgget(td, uap)
        struct thread *td;
        register struct msgget_args *uap;
{
        int msqid, error = 0;
        int key = uap->key;
        int msgflg = uap->msgflg;
        struct ucred *cred = td->td_ucred;
        register struct msqid_kernel *msqkptr = NULL;

        DPRINTF(("msgget(0x%x, 0%o)\n", key, msgflg));

        if (!jail_sysvipc_allowed && jailed(td->td_ucred))
                return (ENOSYS);

        mtx_lock(&msq_mtx);
        if (key != IPC_PRIVATE) {
                for (msqid = 0; msqid < msginfo.msgmni; msqid++) {
                        msqkptr = &msqids[msqid];
                        if (msqkptr->u.msg_qbytes != 0 &&
                            msqkptr->u.msg_perm.key == key)
                                break;
                }
                if (msqid < msginfo.msgmni) {
                        DPRINTF(("found public key\n"));
                        if ((msgflg & IPC_CREAT) && (msgflg & IPC_EXCL)) {
                                DPRINTF(("not exclusive\n"));
                                error = EEXIST;
                                goto done2;
                        }
                        if ((error = ipcperm(td, &msqkptr->u.msg_perm,
                            msgflg & 0700))) {
                                DPRINTF(("requester doesn't have 0%o access\n",
                                    msgflg & 0700));
                                goto done2;
                        }
#ifdef MAC
                        error = mac_sysvmsq_check_msqget(cred, msqkptr);
                        if (error != 0)
                                goto done2;
#endif
                        goto found;
                }
        }

        DPRINTF(("need to allocate the msqid_ds\n"));
        if (key == IPC_PRIVATE || (msgflg & IPC_CREAT)) {
                for (msqid = 0; msqid < msginfo.msgmni; msqid++) {
                        /*
                         * Look for an unallocated and unlocked msqid_ds.
                         * msqid_ds's can be locked by msgsnd or msgrcv while
                         * they are copying the message in/out.  We can't
                         * re-use the entry until they release it.
                         */
                        msqkptr = &msqids[msqid];
                        if (msqkptr->u.msg_qbytes == 0 &&
                            (msqkptr->u.msg_perm.mode & MSG_LOCKED) == 0)
                                break;
                }
                if (msqid == msginfo.msgmni) {
                        DPRINTF(("no more msqid_ds's available\n"));
                        error = ENOSPC;
                        goto done2;
                }
                DPRINTF(("msqid %d is available\n", msqid));
                msqkptr->u.msg_perm.key = key;
                msqkptr->u.msg_perm.cuid = cred->cr_uid;
                msqkptr->u.msg_perm.uid = cred->cr_uid;
                msqkptr->u.msg_perm.cgid = cred->cr_gid;
                msqkptr->u.msg_perm.gid = cred->cr_gid;
                msqkptr->u.msg_perm.mode = (msgflg & 0777);
                /* Make sure that the returned msqid is unique */
                msqkptr->u.msg_perm.seq = (msqkptr->u.msg_perm.seq + 1) & 0x7fff;
                msqkptr->u.msg_first = NULL;
                msqkptr->u.msg_last = NULL;
                msqkptr->u.msg_cbytes = 0;
                msqkptr->u.msg_qnum = 0;
                msqkptr->u.msg_qbytes = msginfo.msgmnb;
                msqkptr->u.msg_lspid = 0;
                msqkptr->u.msg_lrpid = 0;
                msqkptr->u.msg_stime = 0;
                msqkptr->u.msg_rtime = 0;
                msqkptr->u.msg_ctime = time_second;
#ifdef MAC
                mac_sysvmsq_create(cred, msqkptr);
#endif
        } else {
                DPRINTF(("didn't find it and wasn't asked to create it\n"));
                error = ENOENT;
                goto done2;
        }

found:
        /* Construct the unique msqid */
        td->td_retval[0] = IXSEQ_TO_IPCID(msqid, msqkptr->u.msg_perm);
done2:
        mtx_unlock(&msq_mtx);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct msgsnd_args {
        int     msqid;
        const void      *msgp;
        size_t  msgsz;
        int     msgflg;
};
#endif
int
kern_msgsnd(td, msqid, msgp, msgsz, msgflg, mtype)
        struct thread *td;
        int msqid;
        const void *msgp;       /* XXX msgp is actually mtext. */
        size_t msgsz;
        int msgflg;
        long mtype;
{
        int msqix, segs_needed, error = 0;
        register struct msqid_kernel *msqkptr;
        register struct msg *msghdr;
        short next;

        if (!jail_sysvipc_allowed && jailed(td->td_ucred))
                return (ENOSYS);

        mtx_lock(&msq_mtx);
        msqix = IPCID_TO_IX(msqid);

        if (msqix < 0 || msqix >= msginfo.msgmni) {
                DPRINTF(("msqid (%d) out of range (0<=msqid<%d)\n", msqix,
                    msginfo.msgmni));
                error = EINVAL;
                goto done2;
        }

        msqkptr = &msqids[msqix];
        if (msqkptr->u.msg_qbytes == 0) {
                DPRINTF(("no such message queue id\n"));
                error = EINVAL;
                goto done2;
        }
        if (msqkptr->u.msg_perm.seq != IPCID_TO_SEQ(msqid)) {
                DPRINTF(("wrong sequence number\n"));
                error = EINVAL;
                goto done2;
        }

        if ((error = ipcperm(td, &msqkptr->u.msg_perm, IPC_W))) {
                DPRINTF(("requester doesn't have write access\n"));
                goto done2;
        }

#ifdef MAC
        error = mac_sysvmsq_check_msqsnd(td->td_ucred, msqkptr);
        if (error != 0)
                goto done2;
#endif

        segs_needed = (msgsz + msginfo.msgssz - 1) / msginfo.msgssz;
        DPRINTF(("msgsz=%zu, msgssz=%d, segs_needed=%d\n", msgsz,
            msginfo.msgssz, segs_needed));
        for (;;) {
                int need_more_resources = 0;

                /*
                 * check msgsz
                 * (inside this loop in case msg_qbytes changes while we sleep)
                 */

                if (msgsz > msqkptr->u.msg_qbytes) {
                        DPRINTF(("msgsz > msqkptr->u.msg_qbytes\n"));
                        error = EINVAL;
                        goto done2;
                }

                if (msqkptr->u.msg_perm.mode & MSG_LOCKED) {
                        DPRINTF(("msqid is locked\n"));
                        need_more_resources = 1;
                }
                if (msgsz + msqkptr->u.msg_cbytes > msqkptr->u.msg_qbytes) {
                        DPRINTF(("msgsz + msg_cbytes > msg_qbytes\n"));
                        need_more_resources = 1;
                }
                if (segs_needed > nfree_msgmaps) {
                        DPRINTF(("segs_needed > nfree_msgmaps\n"));
                        need_more_resources = 1;
                }
                if (free_msghdrs == NULL) {
                        DPRINTF(("no more msghdrs\n"));
                        need_more_resources = 1;
                }

                if (need_more_resources) {
                        int we_own_it;

                        if ((msgflg & IPC_NOWAIT) != 0) {
                                DPRINTF(("need more resources but caller "
                                    "doesn't want to wait\n"));
                                error = EAGAIN;
                                goto done2;
                        }

                        if ((msqkptr->u.msg_perm.mode & MSG_LOCKED) != 0) {
                                DPRINTF(("we don't own the msqid_ds\n"));
                                we_own_it = 0;
                        } else {
                                /* Force later arrivals to wait for our
                                   request */
                                DPRINTF(("we own the msqid_ds\n"));
                                msqkptr->u.msg_perm.mode |= MSG_LOCKED;
                                we_own_it = 1;
                        }
                        DPRINTF(("msgsnd:  goodnight\n"));
                        error = msleep(msqkptr, &msq_mtx, (PZERO - 4) | PCATCH,
                            "msgsnd", hz);
                        DPRINTF(("msgsnd:  good morning, error=%d\n", error));
                        if (we_own_it)
                                msqkptr->u.msg_perm.mode &= ~MSG_LOCKED;
                        if (error == EWOULDBLOCK) {
                                DPRINTF(("msgsnd:  timed out\n"));
                                continue;
                        }
                        if (error != 0) {
                                DPRINTF(("msgsnd:  interrupted system call\n"));
                                error = EINTR;
                                goto done2;
                        }

                        /*
                         * Make sure that the msq queue still exists
                         */

                        if (msqkptr->u.msg_qbytes == 0) {
                                DPRINTF(("msqid deleted\n"));
                                error = EIDRM;
                                goto done2;
                        }

                } else {
                        DPRINTF(("got all the resources that we need\n"));
                        break;
                }
        }

        /*
         * We have the resources that we need.
         * Make sure!
         */

        if (msqkptr->u.msg_perm.mode & MSG_LOCKED)
                panic("msg_perm.mode & MSG_LOCKED");
        if (segs_needed > nfree_msgmaps)
                panic("segs_needed > nfree_msgmaps");
        if (msgsz + msqkptr->u.msg_cbytes > msqkptr->u.msg_qbytes)
                panic("msgsz + msg_cbytes > msg_qbytes");
        if (free_msghdrs == NULL)
                panic("no more msghdrs");

        /*
         * Re-lock the msqid_ds in case we page-fault when copying in the
         * message
         */

        if ((msqkptr->u.msg_perm.mode & MSG_LOCKED) != 0)
                panic("msqid_ds is already locked");
        msqkptr->u.msg_perm.mode |= MSG_LOCKED;

        /*
         * Allocate a message header
         */

        msghdr = free_msghdrs;
        free_msghdrs = msghdr->msg_next;
        msghdr->msg_spot = -1;
        msghdr->msg_ts = msgsz;
        msghdr->msg_type = mtype;
#ifdef MAC
        /*
         * XXXMAC: Should the mac_sysvmsq_check_msgmsq check follow here
         * immediately?  Or, should it be checked just before the msg is
         * enqueued in the msgq (as it is done now)?
         */
        mac_sysvmsg_create(td->td_ucred, msqkptr, msghdr);
#endif

        /*
         * Allocate space for the message
         */

        while (segs_needed > 0) {
                if (nfree_msgmaps <= 0)
                        panic("not enough msgmaps");
                if (free_msgmaps == -1)
                        panic("nil free_msgmaps");
                next = free_msgmaps;
                if (next <= -1)
                        panic("next too low #1");
                if (next >= msginfo.msgseg)
                        panic("next out of range #1");
                DPRINTF(("allocating segment %d to message\n", next));
                free_msgmaps = msgmaps[next].next;
                nfree_msgmaps--;
                msgmaps[next].next = msghdr->msg_spot;
                msghdr->msg_spot = next;
                segs_needed--;
        }

        /*
         * Validate the message type
         */

        if (msghdr->msg_type < 1) {
                msg_freehdr(msghdr);
                msqkptr->u.msg_perm.mode &= ~MSG_LOCKED;
                wakeup(msqkptr);
                DPRINTF(("mtype (%ld) < 1\n", msghdr->msg_type));
                error = EINVAL;
                goto done2;
        }

        /*
         * Copy in the message body
         */

        next = msghdr->msg_spot;
        while (msgsz > 0) {
                size_t tlen;
                if (msgsz > msginfo.msgssz)
                        tlen = msginfo.msgssz;
                else
                        tlen = msgsz;
                if (next <= -1)
                        panic("next too low #2");
                if (next >= msginfo.msgseg)
                        panic("next out of range #2");
                mtx_unlock(&msq_mtx);
                if ((error = copyin(msgp, &msgpool[next * msginfo.msgssz],
                    tlen)) != 0) {
                        mtx_lock(&msq_mtx);
                        DPRINTF(("error %d copying in message segment\n",
                            error));
                        msg_freehdr(msghdr);
                        msqkptr->u.msg_perm.mode &= ~MSG_LOCKED;
                        wakeup(msqkptr);
                        goto done2;
                }
                mtx_lock(&msq_mtx);
                msgsz -= tlen;
                msgp = (const char *)msgp + tlen;
                next = msgmaps[next].next;
        }
        if (next != -1)
                panic("didn't use all the msg segments");

        /*
         * We've got the message.  Unlock the msqid_ds.
         */

        msqkptr->u.msg_perm.mode &= ~MSG_LOCKED;

        /*
         * Make sure that the msqid_ds is still allocated.
         */

        if (msqkptr->u.msg_qbytes == 0) {
                msg_freehdr(msghdr);
                wakeup(msqkptr);
                error = EIDRM;
                goto done2;
        }

#ifdef MAC
        /*
         * Note: Since the task/thread allocates the msghdr and usually
         * primes it with its own MAC label, for a majority of policies, it
         * won't be necessary to check whether the msghdr has access
         * permissions to the msgq.  The mac_sysvmsq_check_msqsnd check would
         * suffice in that case.  However, this hook may be required where
         * individual policies derive a non-identical label for the msghdr
         * from the current thread label and may want to check the msghdr
         * enqueue permissions, along with read/write permissions to the
         * msgq.
         */
        error = mac_sysvmsq_check_msgmsq(td->td_ucred, msghdr, msqkptr);
        if (error != 0) {
                msg_freehdr(msghdr);
                wakeup(msqkptr);
                goto done2;
        }
#endif

        /*
         * Put the message into the queue
         */
        if (msqkptr->u.msg_first == NULL) {
                msqkptr->u.msg_first = msghdr;
                msqkptr->u.msg_last = msghdr;
        } else {
                msqkptr->u.msg_last->msg_next = msghdr;
                msqkptr->u.msg_last = msghdr;
        }
        msqkptr->u.msg_last->msg_next = NULL;

        msqkptr->u.msg_cbytes += msghdr->msg_ts;
        msqkptr->u.msg_qnum++;
        msqkptr->u.msg_lspid = td->td_proc->p_pid;
        msqkptr->u.msg_stime = time_second;

        wakeup(msqkptr);
        td->td_retval[0] = 0;
done2:
        mtx_unlock(&msq_mtx);
        return (error);
}

int
msgsnd(td, uap)
        struct thread *td;
        register struct msgsnd_args *uap;
{
        int error;
        long mtype;

        DPRINTF(("call to msgsnd(%d, %p, %zu, %d)\n", uap->msqid, uap->msgp,
            uap->msgsz, uap->msgflg));

        if ((error = copyin(uap->msgp, &mtype, sizeof(mtype))) != 0) {
                DPRINTF(("error %d copying the message type\n", error));
                return (error);
        }
        return (kern_msgsnd(td, uap->msqid,
            (const char *)uap->msgp + sizeof(mtype),
            uap->msgsz, uap->msgflg, mtype));
}

#ifndef _SYS_SYSPROTO_H_
struct msgrcv_args {
        int     msqid;
        void    *msgp;
        size_t  msgsz;
        long    msgtyp;
        int     msgflg;
};
#endif
int
kern_msgrcv(td, msqid, msgp, msgsz, msgtyp, msgflg, mtype)
        struct thread *td;
        int msqid;
        void *msgp;     /* XXX msgp is actually mtext. */
        size_t msgsz;
        long msgtyp;
        int msgflg;
        long *mtype;
{
        size_t len;
        register struct msqid_kernel *msqkptr;
        register struct msg *msghdr;
        int msqix, error = 0;
        short next;

        if (!jail_sysvipc_allowed && jailed(td->td_ucred))
                return (ENOSYS);

        msqix = IPCID_TO_IX(msqid);

        if (msqix < 0 || msqix >= msginfo.msgmni) {
                DPRINTF(("msqid (%d) out of range (0<=msqid<%d)\n", msqix,
                    msginfo.msgmni));
                return (EINVAL);
        }

        msqkptr = &msqids[msqix];
        mtx_lock(&msq_mtx);
        if (msqkptr->u.msg_qbytes == 0) {
                DPRINTF(("no such message queue id\n"));
                error = EINVAL;
                goto done2;
        }
        if (msqkptr->u.msg_perm.seq != IPCID_TO_SEQ(msqid)) {
                DPRINTF(("wrong sequence number\n"));
                error = EINVAL;
                goto done2;
        }

        if ((error = ipcperm(td, &msqkptr->u.msg_perm, IPC_R))) {
                DPRINTF(("requester doesn't have read access\n"));
                goto done2;
        }

#ifdef MAC
        error = mac_sysvmsq_check_msqrcv(td->td_ucred, msqkptr);
        if (error != 0)
                goto done2;
#endif

        msghdr = NULL;
        while (msghdr == NULL) {
                if (msgtyp == 0) {
                        msghdr = msqkptr->u.msg_first;
                        if (msghdr != NULL) {
                                if (msgsz < msghdr->msg_ts &&
                                    (msgflg & MSG_NOERROR) == 0) {
                                        DPRINTF(("first message on the queue "
                                            "is too big (want %zu, got %d)\n",
                                            msgsz, msghdr->msg_ts));
                                        error = E2BIG;
                                        goto done2;
                                }
#ifdef MAC
                                error = mac_sysvmsq_check_msgrcv(td->td_ucred,
                                    msghdr);
                                if (error != 0)
                                        goto done2;
#endif
                                if (msqkptr->u.msg_first == msqkptr->u.msg_last) {
                                        msqkptr->u.msg_first = NULL;
                                        msqkptr->u.msg_last = NULL;
                                } else {
                                        msqkptr->u.msg_first = msghdr->msg_next;
                                        if (msqkptr->u.msg_first == NULL)
                                                panic("msg_first/last screwed up #1");
                                }
                        }
                } else {
                        struct msg *previous;
                        struct msg **prev;

                        previous = NULL;
                        prev = &(msqkptr->u.msg_first);
                        while ((msghdr = *prev) != NULL) {
                                /*
                                 * Is this message's type an exact match or is
                                 * this message's type less than or equal to
                                 * the absolute value of a negative msgtyp?
                                 * Note that the second half of this test can
                                 * NEVER be true if msgtyp is positive since
                                 * msg_type is always positive!
                                 */

                                if (msgtyp == msghdr->msg_type ||
                                    msghdr->msg_type <= -msgtyp) {
                                        DPRINTF(("found message type %ld, "
                                            "requested %ld\n",
                                            msghdr->msg_type, msgtyp));
                                        if (msgsz < msghdr->msg_ts &&
                                            (msgflg & MSG_NOERROR) == 0) {
                                                DPRINTF(("requested message "
                                                    "on the queue is too big "
                                                    "(want %zu, got %hu)\n",
                                                    msgsz, msghdr->msg_ts));
                                                error = E2BIG;
                                                goto done2;
                                        }
#ifdef MAC
                                        error = mac_sysvmsq_check_msgrcv(
                                            td->td_ucred, msghdr);
                                        if (error != 0)
                                                goto done2;
#endif
                                        *prev = msghdr->msg_next;
                                        if (msghdr == msqkptr->u.msg_last) {
                                                if (previous == NULL) {
                                                        if (prev !=
                                                            &msqkptr->u.msg_first)
                                                                panic("msg_first/last screwed up #2");
                                                        msqkptr->u.msg_first =
                                                            NULL;
                                                        msqkptr->u.msg_last =
                                                            NULL;
                                                } else {
                                                        if (prev ==
                                                            &msqkptr->u.msg_first)
                                                                panic("msg_first/last screwed up #3");
                                                        msqkptr->u.msg_last =
                                                            previous;
                                                }
                                        }
                                        break;
                                }
                                previous = msghdr;
                                prev = &(msghdr->msg_next);
                        }
                }

                /*
                 * We've either extracted the msghdr for the appropriate
                 * message or there isn't one.
                 * If there is one then bail out of this loop.
                 */

                if (msghdr != NULL)
                        break;

                /*
                 * Hmph!  No message found.  Does the user want to wait?
                 */

                if ((msgflg & IPC_NOWAIT) != 0) {
                        DPRINTF(("no appropriate message found (msgtyp=%ld)\n",
                            msgtyp));
                        /* The SVID says to return ENOMSG. */
                        error = ENOMSG;
                        goto done2;
                }

                /*
                 * Wait for something to happen
                 */

                DPRINTF(("msgrcv:  goodnight\n"));
                error = msleep(msqkptr, &msq_mtx, (PZERO - 4) | PCATCH,
                    "msgrcv", 0);
                DPRINTF(("msgrcv:  good morning (error=%d)\n", error));

                if (error != 0) {
                        DPRINTF(("msgrcv:  interrupted system call\n"));
                        error = EINTR;
                        goto done2;
                }

                /*
                 * Make sure that the msq queue still exists
                 */

                if (msqkptr->u.msg_qbytes == 0 ||
                    msqkptr->u.msg_perm.seq != IPCID_TO_SEQ(msqid)) {
                        DPRINTF(("msqid deleted\n"));
                        error = EIDRM;
                        goto done2;
                }
        }

        /*
         * Return the message to the user.
         *
         * First, do the bookkeeping (before we risk being interrupted).
         */

        msqkptr->u.msg_cbytes -= msghdr->msg_ts;
        msqkptr->u.msg_qnum--;
        msqkptr->u.msg_lrpid = td->td_proc->p_pid;
        msqkptr->u.msg_rtime = time_second;

        /*
         * Make msgsz the actual amount that we'll be returning.
         * Note that this effectively truncates the message if it is too long
         * (since msgsz is never increased).
         */

        DPRINTF(("found a message, msgsz=%zu, msg_ts=%hu\n", msgsz,
            msghdr->msg_ts));
        if (msgsz > msghdr->msg_ts)
                msgsz = msghdr->msg_ts;
        *mtype = msghdr->msg_type;

        /*
         * Return the segments to the user
         */

        next = msghdr->msg_spot;
        for (len = 0; len < msgsz; len += msginfo.msgssz) {
                size_t tlen;

                if (msgsz - len > msginfo.msgssz)
                        tlen = msginfo.msgssz;
                else
                        tlen = msgsz - len;
                if (next <= -1)
                        panic("next too low #3");
                if (next >= msginfo.msgseg)
                        panic("next out of range #3");
                mtx_unlock(&msq_mtx);
                error = copyout(&msgpool[next * msginfo.msgssz], msgp, tlen);
                mtx_lock(&msq_mtx);
                if (error != 0) {
                        DPRINTF(("error (%d) copying out message segment\n",
                            error));
                        msg_freehdr(msghdr);
                        wakeup(msqkptr);
                        goto done2;
                }
                msgp = (char *)msgp + tlen;
                next = msgmaps[next].next;
        }

        /*
         * Done, return the actual number of bytes copied out.
         */

        msg_freehdr(msghdr);
        wakeup(msqkptr);
        td->td_retval[0] = msgsz;
done2:
        mtx_unlock(&msq_mtx);
        return (error);
}

int
msgrcv(td, uap)
        struct thread *td;
        register struct msgrcv_args *uap;
{
        int error;
        long mtype;

        DPRINTF(("call to msgrcv(%d, %p, %zu, %ld, %d)\n", uap->msqid,
            uap->msgp, uap->msgsz, uap->msgtyp, uap->msgflg));

        if ((error = kern_msgrcv(td, uap->msqid,
            (char *)uap->msgp + sizeof(mtype), uap->msgsz,
            uap->msgtyp, uap->msgflg, &mtype)) != 0)
                return (error);
        if ((error = copyout(&mtype, uap->msgp, sizeof(mtype))) != 0)
                DPRINTF(("error %d copying the message type\n", error));
        return (error);
}

static int
sysctl_msqids(SYSCTL_HANDLER_ARGS)
{

        return (SYSCTL_OUT(req, msqids,
            sizeof(struct msqid_kernel) * msginfo.msgmni));
}

SYSCTL_INT(_kern_ipc, OID_AUTO, msgmax, CTLFLAG_RD, &msginfo.msgmax, 0,
    "Maximum message size");
SYSCTL_INT(_kern_ipc, OID_AUTO, msgmni, CTLFLAG_RDTUN, &msginfo.msgmni, 0,
    "Number of message queue identifiers");
SYSCTL_INT(_kern_ipc, OID_AUTO, msgmnb, CTLFLAG_RDTUN, &msginfo.msgmnb, 0,
    "Maximum number of bytes in a queue");
SYSCTL_INT(_kern_ipc, OID_AUTO, msgtql, CTLFLAG_RDTUN, &msginfo.msgtql, 0,
    "Maximum number of messages in the system");
SYSCTL_INT(_kern_ipc, OID_AUTO, msgssz, CTLFLAG_RDTUN, &msginfo.msgssz, 0,
    "Size of a message segment");
SYSCTL_INT(_kern_ipc, OID_AUTO, msgseg, CTLFLAG_RDTUN, &msginfo.msgseg, 0,
    "Number of message segments");
SYSCTL_PROC(_kern_ipc, OID_AUTO, msqids, CTLFLAG_RD,
    NULL, 0, sysctl_msqids, "", "Message queue IDs");