[apple/xnu.git] / bsd / kern / sysv_sem.c

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Implementation of SVID semaphores
 *
 * Author:  Daniel Boulet
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 */
/*
 * John Bellardo modified the implementation for Darwin. 12/2000
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/sem_internal.h>
#include <sys/malloc.h>
#include <mach/mach_types.h>

#include <sys/filedesc.h>
#include <sys/file_internal.h>
#include <sys/sysctl.h>
#include <sys/ipcs.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>

#include <bsm/audit_kernel.h>


/* Uncomment this line to see the debugging output */
/* #define SEM_DEBUG */

#define M_SYSVSEM       M_TEMP


/* Hard system limits to avoid resource starvation / DOS attacks.
 * These are not needed if we can make the semaphore pages swappable.
 */
static struct seminfo limitseminfo = {
        SEMMAP,        /* # of entries in semaphore map */
        SEMMNI,        /* # of semaphore identifiers */
        SEMMNS,        /* # of semaphores in system */
        SEMMNU,        /* # of undo structures in system */
        SEMMSL,        /* max # of semaphores per id */
        SEMOPM,        /* max # of operations per semop call */
        SEMUME,        /* max # of undo entries per process */
        SEMUSZ,        /* size in bytes of undo structure */
        SEMVMX,        /* semaphore maximum value */
        SEMAEM         /* adjust on exit max value */
};

/* Current system allocations.  We use this structure to track how many
 * resources we have allocated so far.  This way we can set large hard limits
 * and not allocate the memory for them up front.
 */
struct seminfo seminfo = {
        SEMMAP, /* Unused, # of entries in semaphore map */
        0,      /* # of semaphore identifiers */
        0,      /* # of semaphores in system */
        0,      /* # of undo entries in system */
        SEMMSL, /* max # of semaphores per id */
        SEMOPM, /* max # of operations per semop call */
        SEMUME, /* max # of undo entries per process */
        SEMUSZ, /* size in bytes of undo structure */
        SEMVMX, /* semaphore maximum value */
        SEMAEM  /* adjust on exit max value */
};


static struct sem_undo *semu_alloc(struct proc *p);
static int semundo_adjust(struct proc *p, struct sem_undo **supptr, 
                int semid, int semnum, int adjval);
static void semundo_clear(int semid, int semnum);

/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *semcalls[] = {
        (sy_call_t *)semctl, (sy_call_t *)semget,
        (sy_call_t *)semop, (sy_call_t *)semconfig
};

static int              semtot = 0;             /* # of used semaphores */
struct user_semid_ds    *sema = NULL;           /* semaphore id pool */
struct sem              *sem_pool =  NULL;      /* semaphore pool */
static struct sem_undo  *semu_list = NULL;      /* active undo structures */
struct sem_undo         *semu = NULL;           /* semaphore undo pool */


void sysv_sem_lock_init(void);
static lck_grp_t       *sysv_sem_subsys_lck_grp;
static lck_grp_attr_t  *sysv_sem_subsys_lck_grp_attr;
static lck_attr_t      *sysv_sem_subsys_lck_attr;
static lck_mtx_t        sysv_sem_subsys_mutex;

#define SYSV_SEM_SUBSYS_LOCK() lck_mtx_lock(&sysv_sem_subsys_mutex)
#define SYSV_SEM_SUBSYS_UNLOCK() lck_mtx_unlock(&sysv_sem_subsys_mutex)


__private_extern__ void
sysv_sem_lock_init( void )
{

    sysv_sem_subsys_lck_grp_attr = lck_grp_attr_alloc_init();
    lck_grp_attr_setstat(sysv_sem_subsys_lck_grp_attr);

    sysv_sem_subsys_lck_grp = lck_grp_alloc_init("sysv_shm_subsys_lock", sysv_sem_subsys_lck_grp_attr);

    sysv_sem_subsys_lck_attr = lck_attr_alloc_init();
    lck_attr_setdebug(sysv_sem_subsys_lck_attr); 
    lck_mtx_init(&sysv_sem_subsys_mutex, sysv_sem_subsys_lck_grp, sysv_sem_subsys_lck_attr);
}

static __inline__ user_time_t
sysv_semtime(void)
{
        struct timeval  tv;
        microtime(&tv);
        return (tv.tv_sec);
}

/*
 * XXX conversion of internal user_time_t to external tume_t loses
 * XXX precision; not an issue for us now, since we are only ever
 * XXX setting 32 bits worth of time into it.
 *
 * pad field contents are not moved correspondingly; contents will be lost
 *
 * NOTE: Source and target may *NOT* overlap! (target is smaller)
 */
static void
semid_ds_64to32(struct user_semid_ds *in, struct semid_ds *out)
{
        out->sem_perm = in->sem_perm;
        out->sem_base = (__int32_t)in->sem_base;
        out->sem_nsems = in->sem_nsems;
        out->sem_otime = in->sem_otime;         /* XXX loses precision */
        out->sem_ctime = in->sem_ctime;         /* XXX loses precision */
}

/*
 * pad field contents are not moved correspondingly; contents will be lost
 *
 * NOTE: Source and target may are permitted to overlap! (source is smaller);
 * this works because we copy fields in order from the end of the struct to
 * the beginning.
 *
 * XXX use CAST_USER_ADDR_T() for lack of a CAST_USER_TIME_T(); net effect
 * XXX is the same.
 */
static void
semid_ds_32to64(struct semid_ds *in, struct user_semid_ds *out)
{
        out->sem_ctime = in->sem_ctime;
        out->sem_otime = in->sem_otime;
        out->sem_nsems = in->sem_nsems;
        out->sem_base = (void *)in->sem_base;
        out->sem_perm = in->sem_perm;
}


/*
 * Entry point for all SEM calls
 *
 * In Darwin this is no longer the entry point.  It will be removed after
 *  the code has been tested better.
 */
/* XXX actually varargs. */
int
semsys(struct proc *p, struct semsys_args *uap, register_t *retval)
{

        /* The individual calls handling the locking now */

        if (uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
                return (EINVAL);
        return ((*semcalls[uap->which])(p, &uap->a2, retval));
}

/*
 * Lock or unlock the entire semaphore facility.
 *
 * This will probably eventually evolve into a general purpose semaphore
 * facility status enquiry mechanism (I don't like the "read /dev/kmem"
 * approach currently taken by ipcs and the amount of info that we want
 * to be able to extract for ipcs is probably beyond what the capability
 * of the getkerninfo facility.
 *
 * At the time that the current version of semconfig was written, ipcs is
 * the only user of the semconfig facility.  It uses it to ensure that the
 * semaphore facility data structures remain static while it fishes around
 * in /dev/kmem.
 */

int
semconfig(__unused struct proc *p, struct semconfig_args *uap, register_t *retval)
{
        int eval = 0;

        switch (uap->flag) {
        case SEM_CONFIG_FREEZE:
                SYSV_SEM_SUBSYS_LOCK();
                break;

        case SEM_CONFIG_THAW:
                SYSV_SEM_SUBSYS_UNLOCK();
                break;

        default:
                printf("semconfig: unknown flag parameter value (%d) - ignored\n",
                    uap->flag);
                eval = EINVAL;
                break;
        }

        *retval = 0;
        return(eval);
}

/*
 * Expand the semu array to the given capacity.  If the expansion fails
 * return 0, otherwise return 1.
 *
 * Assumes we already have the subsystem lock.
 */
static int
grow_semu_array(int newSize)
{
        register int i;
        register struct sem_undo *newSemu;

        if (newSize <= seminfo.semmnu)
                return 1;
        if (newSize > limitseminfo.semmnu) /* enforce hard limit */
        {
#ifdef SEM_DEBUG
                printf("undo structure hard limit of %d reached, requested %d\n",
                        limitseminfo.semmnu, newSize);
#endif
                return 0;
        }
        newSize = (newSize/SEMMNU_INC + 1) * SEMMNU_INC;
        newSize = newSize > limitseminfo.semmnu ? limitseminfo.semmnu : newSize;

#ifdef SEM_DEBUG
        printf("growing semu[] from %d to %d\n", seminfo.semmnu, newSize);
#endif
        MALLOC(newSemu, struct sem_undo *, sizeof (struct sem_undo) * newSize,
               M_SYSVSEM, M_WAITOK | M_ZERO);
        if (NULL == newSemu)
        {
#ifdef SEM_DEBUG
                printf("allocation failed.  no changes made.\n");
#endif
                return 0;
        }

        /* copy the old data to the new array */
        for (i = 0; i < seminfo.semmnu; i++)
        {
                newSemu[i] = semu[i];
        }
        /*
         * The new elements (from newSemu[i] to newSemu[newSize-1]) have their
         * "un_proc" set to 0 (i.e. NULL) by the M_ZERO flag to MALLOC() above,
         * so they're already marked as "not in use".
         */

        /* Clean up the old array */
        if (semu)
                FREE(semu, M_SYSVSEM);

        semu = newSemu;
        seminfo.semmnu = newSize;
#ifdef SEM_DEBUG
        printf("expansion successful\n");
#endif
        return 1;
}

/*
 * Expand the sema array to the given capacity.  If the expansion fails
 * we return 0, otherwise we return 1.
 *
 * Assumes we already have the subsystem lock.
 */
static int
grow_sema_array(int newSize)
{
        register struct user_semid_ds *newSema;
        register int i;

        if (newSize <= seminfo.semmni)
                return 0;
        if (newSize > limitseminfo.semmni) /* enforce hard limit */
        {
#ifdef SEM_DEBUG
                printf("identifier hard limit of %d reached, requested %d\n",
                        limitseminfo.semmni, newSize);
#endif
                return 0;
        }
        newSize = (newSize/SEMMNI_INC + 1) * SEMMNI_INC;
        newSize = newSize > limitseminfo.semmni ? limitseminfo.semmni : newSize;

#ifdef SEM_DEBUG
        printf("growing sema[] from %d to %d\n", seminfo.semmni, newSize);
#endif
        MALLOC(newSema, struct user_semid_ds *,
               sizeof (struct user_semid_ds) * newSize,
               M_SYSVSEM, M_WAITOK | M_ZERO);
        if (NULL == newSema)
        {
#ifdef SEM_DEBUG
                printf("allocation failed.  no changes made.\n");
#endif
                return 0;
        }

        /* copy over the old ids */
        for (i = 0; i < seminfo.semmni; i++)
        {
                newSema[i] = sema[i];
                /* This is a hack.  What we really want to be able to
                 * do is change the value a process is waiting on
                 * without waking it up, but I don't know how to do
                 * this with the existing code, so we wake up the
                 * process and let it do a lot of work to determine the
                 * semaphore set is really not available yet, and then
                 * sleep on the correct, reallocated user_semid_ds pointer.
                 */
                if (sema[i].sem_perm.mode & SEM_ALLOC)
                        wakeup((caddr_t)&sema[i]);
        }
        /*
         * The new elements (from newSema[i] to newSema[newSize-1]) have their
         * "sem_base" and "sem_perm.mode" set to 0 (i.e. NULL) by the M_ZERO
         * flag to MALLOC() above, so they're already marked as "not in use".
         */

        /* Clean up the old array */
        if (sema)
                FREE(sema, M_SYSVSEM);

        sema = newSema;
        seminfo.semmni = newSize;
#ifdef SEM_DEBUG
        printf("expansion successful\n");
#endif
        return 1;
}

/*
 * Expand the sem_pool array to the given capacity.  If the expansion fails
 * we return 0 (fail), otherwise we return 1 (success).
 *
 * Assumes we already hold the subsystem lock.
 */
static int
grow_sem_pool(int new_pool_size)
{
        struct sem *new_sem_pool = NULL;
        struct sem *sem_free;
        int i;

        if (new_pool_size < semtot)
                return 0;
        /* enforce hard limit */
        if (new_pool_size > limitseminfo.semmns) {
#ifdef SEM_DEBUG
                printf("semaphore hard limit of %d reached, requested %d\n",
                        limitseminfo.semmns, new_pool_size);
#endif
                return 0;
        }

        new_pool_size = (new_pool_size/SEMMNS_INC + 1) * SEMMNS_INC;
        new_pool_size = new_pool_size > limitseminfo.semmns ? limitseminfo.semmns : new_pool_size;

#ifdef SEM_DEBUG
        printf("growing sem_pool array from %d to %d\n", seminfo.semmns, new_pool_size);
#endif
        MALLOC(new_sem_pool, struct sem *, sizeof (struct sem) * new_pool_size,
               M_SYSVSEM, M_WAITOK | M_ZERO);
        if (NULL == new_sem_pool) {
#ifdef SEM_DEBUG
                printf("allocation failed.  no changes made.\n");
#endif
                return 0;
        }

        /* We have our new memory, now copy the old contents over */
        if (sem_pool)
                for(i = 0; i < seminfo.semmns; i++)
                        new_sem_pool[i] = sem_pool[i];

        /* Update our id structures to point to the new semaphores */
        for(i = 0; i < seminfo.semmni; i++) {
                if (sema[i].sem_perm.mode & SEM_ALLOC)  /* ID in use */
                        sema[i].sem_base += (new_sem_pool - sem_pool);
        }

        sem_free = sem_pool;
        sem_pool = new_sem_pool;

        /* clean up the old array */
        if (sem_free != NULL)
                FREE(sem_free, M_SYSVSEM);

        seminfo.semmns = new_pool_size;
#ifdef SEM_DEBUG
        printf("expansion complete\n");
#endif
        return 1;
}

/*
 * Allocate a new sem_undo structure for a process
 * (returns ptr to structure or NULL if no more room)
 *
 * Assumes we already hold the subsystem lock.
 */

static struct sem_undo *
semu_alloc(struct proc *p)
{
        register int i;
        register struct sem_undo *suptr;
        register struct sem_undo **supptr;
        int attempt;

        /*
         * Try twice to allocate something.
         * (we'll purge any empty structures after the first pass so
         * two passes are always enough)
         */

        for (attempt = 0; attempt < 2; attempt++) {
                /*
                 * Look for a free structure.
                 * Fill it in and return it if we find one.
                 */

                for (i = 0; i < seminfo.semmnu; i++) {
                        suptr = SEMU(i);
                        if (suptr->un_proc == NULL) {
                                suptr->un_next = semu_list;
                                semu_list = suptr;
                                suptr->un_cnt = 0;
                                suptr->un_ent = NULL;
                                suptr->un_proc = p;
                                return(suptr);
                        }
                }

                /*
                 * We didn't find a free one, if this is the first attempt
                 * then try to free some structures.
                 */

                if (attempt == 0) {
                        /* All the structures are in use - try to free some */
                        int did_something = 0;

                        supptr = &semu_list;
                        while ((suptr = *supptr) != NULL) {
                                if (suptr->un_cnt == 0)  {
                                        suptr->un_proc = NULL;
                                        *supptr = suptr->un_next;
                                        did_something = 1;
                                } else
                                        supptr = &(suptr->un_next);
                        }

                        /* If we didn't free anything. Try expanding
                         * the semu[] array.  If that doesn't work
                         * then fail.  We expand last to get the
                         * most reuse out of existing resources.
                         */
                        if (!did_something)
                                if (!grow_semu_array(seminfo.semmnu + 1))
                                        return(NULL);
                } else {
                        /*
                         * The second pass failed even though we freed
                         * something after the first pass!
                         * This is IMPOSSIBLE!
                         */
                        panic("semu_alloc - second attempt failed");
                }
        }
        return (NULL);
}

/*
 * Adjust a particular entry for a particular proc
 *
 * Assumes we already hold the subsystem lock.
 */
static int
semundo_adjust(struct proc *p, struct sem_undo **supptr, int semid,
        int semnum, int adjval)
{
        register struct sem_undo *suptr;
        register struct undo *sueptr, **suepptr, *new_sueptr;
        int i;

        /*
         * Look for and remember the sem_undo if the caller doesn't provide it
         */

        suptr = *supptr;
        if (suptr == NULL) {
                for (suptr = semu_list; suptr != NULL;
                    suptr = suptr->un_next) {
                        if (suptr->un_proc == p) {
                                *supptr = suptr;
                                break;
                        }
                }
                if (suptr == NULL) {
                        if (adjval == 0)
                                return(0);
                        suptr = semu_alloc(p);
                        if (suptr == NULL)
                                return(ENOSPC);
                        *supptr = suptr;
                }
        }

        /*
         * Look for the requested entry and adjust it (delete if adjval becomes
         * 0).
         */
        new_sueptr = NULL;
        for (i = 0, suepptr = &suptr->un_ent, sueptr = suptr->un_ent;
             i < suptr->un_cnt;
             i++, suepptr = &sueptr->une_next, sueptr = sueptr->une_next) {
                if (sueptr->une_id != semid || sueptr->une_num != semnum)
                        continue;
                if (adjval == 0)
                        sueptr->une_adjval = 0;
                else
                        sueptr->une_adjval += adjval;
                if (sueptr->une_adjval == 0) {
                        suptr->un_cnt--;
                        *suepptr = sueptr->une_next;
                        FREE(sueptr, M_SYSVSEM);
                        sueptr = NULL;
                }
                return 0;
        }

        /* Didn't find the right entry - create it */
        if (adjval == 0) {
                /* no adjustment: no need for a new entry */
                return 0;
        }

        if (suptr->un_cnt == limitseminfo.semume) {
                /* reached the limit number of semaphore undo entries */
                return EINVAL;
        }

        /* allocate a new semaphore undo entry */
        MALLOC(new_sueptr, struct undo *, sizeof (struct undo),
               M_SYSVSEM, M_WAITOK);
        if (new_sueptr == NULL) {
                return ENOMEM;
        }

        /* fill in the new semaphore undo entry */
        new_sueptr->une_next = suptr->un_ent;
        suptr->un_ent = new_sueptr;
        suptr->un_cnt++;
        new_sueptr->une_adjval = adjval;
        new_sueptr->une_id = semid;
        new_sueptr->une_num = semnum;

        return 0;
}

/* Assumes we already hold the subsystem lock.
 */
static void
semundo_clear(int semid, int semnum)
{
        struct sem_undo *suptr;

        for (suptr = semu_list; suptr != NULL; suptr = suptr->un_next) {
                struct undo *sueptr;
                struct undo **suepptr;
                int i = 0;

                sueptr = suptr->un_ent;
                suepptr = &suptr->un_ent;
                while (i < suptr->un_cnt) {
                        if (sueptr->une_id == semid) {
                                if (semnum == -1 || sueptr->une_num == semnum) {
                                        suptr->un_cnt--;
                                        *suepptr = sueptr->une_next;
                                        FREE(sueptr, M_SYSVSEM);
                                        sueptr = *suepptr;
                                        continue;
                                }
                                if (semnum != -1)
                                        break;
                        }
                        i++;
                        suepptr = &sueptr->une_next;
                        sueptr = sueptr->une_next;
                }
        }
}

/*
 * Note that the user-mode half of this passes a union coerced to a
 * user_addr_t.  The union contains either an int or a pointer, and
 * so we have to coerce it back, variant on whether the calling
 * process is 64 bit or not.  The coercion works for the 'val' element
 * because the alignment is the same in user and kernel space.
 */
int
semctl(struct proc *p, struct semctl_args *uap, register_t *retval)
{
        int semid = uap->semid;
        int semnum = uap->semnum;
        int cmd = uap->cmd;
        user_semun_t user_arg = (user_semun_t)uap->arg;
        kauth_cred_t cred = kauth_cred_get();
        int i, rval, eval;
        struct user_semid_ds sbuf;
        struct user_semid_ds *semaptr;
        struct user_semid_ds uds;
        

        AUDIT_ARG(svipc_cmd, cmd);
        AUDIT_ARG(svipc_id, semid);

        SYSV_SEM_SUBSYS_LOCK();

#ifdef SEM_DEBUG
        printf("call to semctl(%d, %d, %d, 0x%qx)\n", semid, semnum, cmd, user_arg);
#endif

        semid = IPCID_TO_IX(semid);

        if (semid < 0 || semid >= seminfo.semmni) {
#ifdef SEM_DEBUG
                printf("Invalid semid\n");
#endif
                eval = EINVAL;
                goto semctlout;
        }

        semaptr = &sema[semid];
        if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
            semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
                eval = EINVAL;
                goto semctlout;
        }

        eval = 0;
        rval = 0;

        switch (cmd) {
        case IPC_RMID:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_M))) 
                        goto semctlout;

                semaptr->sem_perm.cuid = kauth_cred_getuid(cred);
                semaptr->sem_perm.uid = kauth_cred_getuid(cred);
                semtot -= semaptr->sem_nsems;
                for (i = semaptr->sem_base - sem_pool; i < semtot; i++)
                        sem_pool[i] = sem_pool[i + semaptr->sem_nsems];
                for (i = 0; i < seminfo.semmni; i++) {
                        if ((sema[i].sem_perm.mode & SEM_ALLOC) &&
                            sema[i].sem_base > semaptr->sem_base)
                                sema[i].sem_base -= semaptr->sem_nsems;
                }
                semaptr->sem_perm.mode = 0;
                semundo_clear(semid, -1);
                wakeup((caddr_t)semaptr);
                break;

        case IPC_SET:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_M)))
                                goto semctlout;

                if (IS_64BIT_PROCESS(p)) {
                        eval = copyin(user_arg.buf, &sbuf, sizeof(struct user_semid_ds));
                } else {
                        eval = copyin(user_arg.buf, &sbuf, sizeof(struct semid_ds));
                        /* convert in place; ugly, but safe */
                        semid_ds_32to64((struct semid_ds *)&sbuf, &sbuf);
                }
                
                if (eval != 0) {
                        goto semctlout;
                }

                semaptr->sem_perm.uid = sbuf.sem_perm.uid;
                semaptr->sem_perm.gid = sbuf.sem_perm.gid;
                semaptr->sem_perm.mode = (semaptr->sem_perm.mode & ~0777) |
                    (sbuf.sem_perm.mode & 0777);
                semaptr->sem_ctime = sysv_semtime();
                break;

        case IPC_STAT:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
                bcopy(semaptr, &uds, sizeof(struct user_semid_ds));
                if (IS_64BIT_PROCESS(p)) {
                        eval = copyout(&uds, user_arg.buf, sizeof(struct user_semid_ds));
                } else {
                        struct semid_ds semid_ds32;
                        semid_ds_64to32(&uds, &semid_ds32);
                        eval = copyout(&semid_ds32, user_arg.buf, sizeof(struct semid_ds));
                }
                break;

        case GETNCNT:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
                if (semnum < 0 || semnum >= semaptr->sem_nsems) {
                        eval = EINVAL;
                        goto semctlout;
                }
                rval = semaptr->sem_base[semnum].semncnt;
                break;

        case GETPID:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
                if (semnum < 0 || semnum >= semaptr->sem_nsems) {
                        eval = EINVAL;
                        goto semctlout;
                }
                rval = semaptr->sem_base[semnum].sempid;
                break;

        case GETVAL:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
                if (semnum < 0 || semnum >= semaptr->sem_nsems) {
                        eval = EINVAL;
                        goto semctlout;
                }
                rval = semaptr->sem_base[semnum].semval;
                break;

        case GETALL:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
/* XXXXXXXXXXXXXXXX TBD XXXXXXXXXXXXXXXX */
                for (i = 0; i < semaptr->sem_nsems; i++) {
                        /* XXX could be done in one go... */
                        eval = copyout((caddr_t)&semaptr->sem_base[i].semval,
                            user_arg.array + (i * sizeof(unsigned short)),
                            sizeof(unsigned short));
                        if (eval != 0)
                                break;
                }
                break;

        case GETZCNT:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_R)))
                                goto semctlout;
                if (semnum < 0 || semnum >= semaptr->sem_nsems) {
                        eval = EINVAL;
                        goto semctlout;
                }
                rval = semaptr->sem_base[semnum].semzcnt;
                break;

        case SETVAL:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
                {
#ifdef SEM_DEBUG
                        printf("Invalid credentials for write\n");
#endif
                                goto semctlout;
                }
                if (semnum < 0 || semnum >= semaptr->sem_nsems)
                {
#ifdef SEM_DEBUG
                        printf("Invalid number out of range for set\n");
#endif
                        eval = EINVAL;
                        goto semctlout;
                }
                /*
                 * Cast down a pointer instead of using 'val' member directly
                 * to avoid introducing endieness and a pad field into the
                 * header file.  Ugly, but it works.
                 */
                semaptr->sem_base[semnum].semval = CAST_DOWN(int,user_arg.buf);
                semundo_clear(semid, semnum);
                wakeup((caddr_t)semaptr);
                break;

        case SETALL:
                if ((eval = ipcperm(cred, &semaptr->sem_perm, IPC_W)))
                                goto semctlout;
/*** XXXXXXXXXXXX TBD ********/
                for (i = 0; i < semaptr->sem_nsems; i++) {
                        /* XXX could be done in one go... */
                        eval = copyin(user_arg.array + (i * sizeof(unsigned short)),
                            (caddr_t)&semaptr->sem_base[i].semval,
                            sizeof(unsigned short));
                        if (eval != 0)
                                break;
                }
                semundo_clear(semid, -1);
                wakeup((caddr_t)semaptr);
                break;

        default:
                        eval = EINVAL;
                        goto semctlout;
        }

        if (eval == 0)
                *retval = rval;
semctlout:
        SYSV_SEM_SUBSYS_UNLOCK();
        return(eval);
}

int
semget(__unused struct proc *p, struct semget_args *uap, register_t *retval)
{
        int semid, eval;
        int key = uap->key;
        int nsems = uap->nsems;
        int semflg = uap->semflg;
        kauth_cred_t cred = kauth_cred_get();

#ifdef SEM_DEBUG
        if (key != IPC_PRIVATE)
                printf("semget(0x%x, %d, 0%o)\n", key, nsems, semflg);
        else
                printf("semget(IPC_PRIVATE, %d, 0%o)\n", nsems, semflg);
#endif


        SYSV_SEM_SUBSYS_LOCK();

    
        if (key != IPC_PRIVATE) {
                for (semid = 0; semid < seminfo.semmni; semid++) {
                        if ((sema[semid].sem_perm.mode & SEM_ALLOC) &&
                            sema[semid].sem_perm.key == key)
                                break;
                }
                if (semid < seminfo.semmni) {
#ifdef SEM_DEBUG
                        printf("found public key\n");
#endif
                        if ((eval = ipcperm(cred, &sema[semid].sem_perm,
                            semflg & 0700)))
                                goto semgetout;
                        if (nsems < 0 || sema[semid].sem_nsems < nsems) {
#ifdef SEM_DEBUG
                                printf("too small\n");
#endif
                                eval = EINVAL;
                                goto semgetout;
                        }
                        if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
#ifdef SEM_DEBUG
                                printf("not exclusive\n");
#endif
                                eval = EEXIST;
                                goto semgetout;
                        }
                        goto found;
                }
        }

#ifdef SEM_DEBUG
        printf("need to allocate an id for the request\n");
#endif
        if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
                if (nsems <= 0 || nsems > limitseminfo.semmsl) {
#ifdef SEM_DEBUG
                        printf("nsems out of range (0<%d<=%d)\n", nsems,
                            seminfo.semmsl);
#endif
                        eval = EINVAL;
                        goto semgetout;
                }
                if (nsems > seminfo.semmns - semtot) {
#ifdef SEM_DEBUG
                        printf("not enough semaphores left (need %d, got %d)\n",
                            nsems, seminfo.semmns - semtot);
#endif
                        if (!grow_sem_pool(semtot + nsems)) {
#ifdef SEM_DEBUG
                                printf("failed to grow the sem array\n");
#endif
                                eval = ENOSPC;
                                goto semgetout;
                        }
                }
                for (semid = 0; semid < seminfo.semmni; semid++) {
                        if ((sema[semid].sem_perm.mode & SEM_ALLOC) == 0)
                                break;
                }
                if (semid == seminfo.semmni) {
#ifdef SEM_DEBUG
                        printf("no more id's available\n");
#endif
                        if (!grow_sema_array(seminfo.semmni + 1))
                        {
#ifdef SEM_DEBUG
                                printf("failed to grow sema array\n");
#endif
                                eval = ENOSPC;
                                goto semgetout;
                        }
                }
#ifdef SEM_DEBUG
                printf("semid %d is available\n", semid);
#endif
                sema[semid].sem_perm.key = key;
                sema[semid].sem_perm.cuid = kauth_cred_getuid(cred);
                sema[semid].sem_perm.uid = kauth_cred_getuid(cred);
                sema[semid].sem_perm.cgid = cred->cr_gid;
                sema[semid].sem_perm.gid = cred->cr_gid;
                sema[semid].sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
                sema[semid].sem_perm.seq =
                    (sema[semid].sem_perm.seq + 1) & 0x7fff;
                sema[semid].sem_nsems = nsems;
                sema[semid].sem_otime = 0;
                sema[semid].sem_ctime = sysv_semtime();
                sema[semid].sem_base = &sem_pool[semtot];
                semtot += nsems;
                bzero(sema[semid].sem_base,
                    sizeof(sema[semid].sem_base[0])*nsems);
#ifdef SEM_DEBUG
                printf("sembase = 0x%x, next = 0x%x\n", sema[semid].sem_base,
                    &sem_pool[semtot]);
#endif
        } else {
#ifdef SEM_DEBUG
                printf("didn't find it and wasn't asked to create it\n");
#endif
                eval = ENOENT;
                goto semgetout;
        }

found:
        *retval = IXSEQ_TO_IPCID(semid, sema[semid].sem_perm);
        AUDIT_ARG(svipc_id, *retval);
#ifdef SEM_DEBUG
        printf("semget is done, returning %d\n", *retval);
#endif
        eval = 0;

semgetout:
        SYSV_SEM_SUBSYS_UNLOCK();
        return(eval);
}

int
semop(struct proc *p, struct semop_args *uap, register_t *retval)
{
        int semid = uap->semid;
        int nsops = uap->nsops;
        struct sembuf sops[MAX_SOPS];
        register struct user_semid_ds *semaptr;
        register struct sembuf *sopptr = NULL;  /* protected by 'semptr' */
        register struct sem *semptr = NULL;     /* protected by 'if' */
        struct sem_undo *suptr = NULL;
        int i, j, eval;
        int do_wakeup, do_undos;

        AUDIT_ARG(svipc_id, uap->semid);

        SYSV_SEM_SUBSYS_LOCK();

#ifdef SEM_DEBUG
        printf("call to semop(%d, 0x%x, %d)\n", semid, sops, nsops);
#endif

        semid = IPCID_TO_IX(semid);     /* Convert back to zero origin */

        if (semid < 0 || semid >= seminfo.semmni) {
                eval = EINVAL;
                goto semopout;
        }

        semaptr = &sema[semid];
        if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0) {
                eval = EINVAL;
                goto semopout;
        }
        if (semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
                eval = EINVAL;
                goto semopout;
        }

        if ((eval = ipcperm(kauth_cred_get(), &semaptr->sem_perm, IPC_W))) {
#ifdef SEM_DEBUG
                printf("eval = %d from ipaccess\n", eval);
#endif
                goto semopout;
        }

        if (nsops < 0 || nsops > MAX_SOPS) {
#ifdef SEM_DEBUG
                printf("too many sops (max=%d, nsops=%d)\n", MAX_SOPS, nsops);
#endif
                eval = E2BIG;
                goto semopout;
        }

        /*  OK for LP64, since sizeof(struct sembuf) is currently invariant */
        if ((eval = copyin(uap->sops, &sops, nsops * sizeof(struct sembuf))) != 0) {
#ifdef SEM_DEBUG
                printf("eval = %d from copyin(%08x, %08x, %ld)\n", eval,
                    uap->sops, &sops, nsops * sizeof(struct sembuf));
#endif
                goto semopout;
        }

        /*
         * Loop trying to satisfy the vector of requests.
         * If we reach a point where we must wait, any requests already
         * performed are rolled back and we go to sleep until some other
         * process wakes us up.  At this point, we start all over again.
         *
         * This ensures that from the perspective of other tasks, a set
         * of requests is atomic (never partially satisfied).
         */
        do_undos = 0;

        for (;;) {
                do_wakeup = 0;

                for (i = 0; i < nsops; i++) {
                        sopptr = &sops[i];

                        if (sopptr->sem_num >= semaptr->sem_nsems) {
                                eval = EFBIG;
                                goto semopout;
                        }

                        semptr = &semaptr->sem_base[sopptr->sem_num];

#ifdef SEM_DEBUG
                        printf("semop:  semaptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n",
                            semaptr, semaptr->sem_base, semptr,
                            sopptr->sem_num, semptr->semval, sopptr->sem_op,
                            (sopptr->sem_flg & IPC_NOWAIT) ? "nowait" : "wait");
#endif

                        if (sopptr->sem_op < 0) {
                                if (semptr->semval + sopptr->sem_op < 0) {
#ifdef SEM_DEBUG
                                        printf("semop:  can't do it now\n");
#endif
                                        break;
                                } else {
                                        semptr->semval += sopptr->sem_op;
                                        if (semptr->semval == 0 &&
                                            semptr->semzcnt > 0)
                                                do_wakeup = 1;
                                }
                                if (sopptr->sem_flg & SEM_UNDO)
                                        do_undos = 1;
                        } else if (sopptr->sem_op == 0) {
                                if (semptr->semval > 0) {
#ifdef SEM_DEBUG
                                        printf("semop:  not zero now\n");
#endif
                                        break;
                                }
                        } else {
                                if (semptr->semncnt > 0)
                                        do_wakeup = 1;
                                semptr->semval += sopptr->sem_op;
                                if (sopptr->sem_flg & SEM_UNDO)
                                        do_undos = 1;
                        }
                }

                /*
                 * Did we get through the entire vector?
                 */
                if (i >= nsops)
                        goto done;

                /*
                 * No ... rollback anything that we've already done
                 */
#ifdef SEM_DEBUG
                printf("semop:  rollback 0 through %d\n", i-1);
#endif
                for (j = 0; j < i; j++)
                        semaptr->sem_base[sops[j].sem_num].semval -=
                            sops[j].sem_op;

                /*
                 * If the request that we couldn't satisfy has the
                 * NOWAIT flag set then return with EAGAIN.
                 */
                if (sopptr->sem_flg & IPC_NOWAIT) {
                        eval = EAGAIN;
                        goto semopout;
                }

                if (sopptr->sem_op == 0)
                        semptr->semzcnt++;
                else
                        semptr->semncnt++;

#ifdef SEM_DEBUG
                printf("semop:  good night!\n");
#endif
                /* Release our lock on the semaphore subsystem so
                 * another thread can get at the semaphore we are
                 * waiting for. We will get the lock back after we
                 * wake up.
                 */
                eval = msleep((caddr_t)semaptr, &sysv_sem_subsys_mutex , (PZERO - 4) | PCATCH,
                    "semwait", 0);
                
#ifdef SEM_DEBUG
                printf("semop:  good morning (eval=%d)!\n", eval);
#endif
                if (eval != 0) {
                        eval = EINTR;
                }

                /*
                 * IMPORTANT: while we were asleep, the semaphore array might
                 * have been reallocated somewhere else (see grow_sema_array()).
                 * When we wake up, we have to re-lookup the semaphore 
                 * structures and re-validate them.
                 */

                suptr = NULL;   /* sem_undo may have been reallocated */
                semaptr = &sema[semid];    /* sema may have been reallocated */

                /*
                 * Make sure that the semaphore still exists
                 */
                if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0 ||
                    semaptr->sem_perm.seq != IPCID_TO_SEQ(uap->semid) ||
                    sopptr->sem_num >= semaptr->sem_nsems) {
                        if (eval == EINTR) {
                                /*
                                 * EINTR takes precedence over the fact that
                                 * the semaphore disappeared while we were
                                 * sleeping...
                                 */
                        } else {
                                /*
                                 * The man page says to return EIDRM.
                                 * Unfortunately, BSD doesn't define that code!
                                 */
#ifdef EIDRM
                                eval = EIDRM;
#else
                                eval = EINVAL;
#endif
                        }
                        goto semopout;
                }

                /*
                 * The semaphore is still alive.  Readjust the count of
                 * waiting processes. semptr needs to be recomputed
                 * because the sem[] may have been reallocated while
                 * we were sleeping, updating our sem_base pointer.
                 */
                semptr = &semaptr->sem_base[sopptr->sem_num];
                if (sopptr->sem_op == 0)
                        semptr->semzcnt--;
                else
                        semptr->semncnt--;

                if (eval != 0) { /* EINTR */
                        goto semopout;
                }
        }

done:
        /*
         * Process any SEM_UNDO requests.
         */
        if (do_undos) {
                for (i = 0; i < nsops; i++) {
                        /*
                         * We only need to deal with SEM_UNDO's for non-zero
                         * op's.
                         */
                        int adjval;

                        if ((sops[i].sem_flg & SEM_UNDO) == 0)
                                continue;
                        adjval = sops[i].sem_op;
                        if (adjval == 0)
                                continue;
                        eval = semundo_adjust(p, &suptr, semid,
                            sops[i].sem_num, -adjval);
                        if (eval == 0)
                                continue;

                        /*
                         * Oh-Oh!  We ran out of either sem_undo's or undo's.
                         * Rollback the adjustments to this point and then
                         * rollback the semaphore ups and down so we can return
                         * with an error with all structures restored.  We
                         * rollback the undo's in the exact reverse order that
                         * we applied them.  This guarantees that we won't run
                         * out of space as we roll things back out.
                         */
                        for (j = i - 1; j >= 0; j--) {
                                if ((sops[j].sem_flg & SEM_UNDO) == 0)
                                        continue;
                                adjval = sops[j].sem_op;
                                if (adjval == 0)
                                        continue;
                                if (semundo_adjust(p, &suptr, semid,
                                    sops[j].sem_num, adjval) != 0)
                                        panic("semop - can't undo undos");
                        }

                        for (j = 0; j < nsops; j++)
                                semaptr->sem_base[sops[j].sem_num].semval -=
                                    sops[j].sem_op;

#ifdef SEM_DEBUG
                        printf("eval = %d from semundo_adjust\n", eval);
#endif
                        goto semopout;
                } /* loop through the sops */
        } /* if (do_undos) */

        /* We're definitely done - set the sempid's */
        for (i = 0; i < nsops; i++) {
                sopptr = &sops[i];
                semptr = &semaptr->sem_base[sopptr->sem_num];
                semptr->sempid = p->p_pid;
        }

        if (do_wakeup) {
#ifdef SEM_DEBUG
                printf("semop:  doing wakeup\n");
#ifdef SEM_WAKEUP
                sem_wakeup((caddr_t)semaptr);
#else
                wakeup((caddr_t)semaptr);
#endif
                printf("semop:  back from wakeup\n");
#else
                wakeup((caddr_t)semaptr);
#endif
        }
#ifdef SEM_DEBUG
        printf("semop:  done\n");
#endif
        *retval = 0;
        eval = 0;
semopout:
        SYSV_SEM_SUBSYS_UNLOCK();
        return(eval);
}

/*
 * Go through the undo structures for this process and apply the adjustments to
 * semaphores.
 */
void
semexit(struct proc *p)
{
        register struct sem_undo *suptr;
        register struct sem_undo **supptr;
        int did_something;

        /* If we have not allocated our semaphores yet there can't be
         * anything to undo, but we need the lock to prevent
         * dynamic memory race conditions.
         */
        SYSV_SEM_SUBSYS_LOCK();

        if (!sem_pool)
        {
                SYSV_SEM_SUBSYS_UNLOCK();
                return;
        }
        did_something = 0;

        /*
         * Go through the chain of undo vectors looking for one
         * associated with this process.
         */

        for (supptr = &semu_list; (suptr = *supptr) != NULL;
            supptr = &suptr->un_next) {
                if (suptr->un_proc == p)
                        break;
        }

        if (suptr == NULL)
                goto unlock;

#ifdef SEM_DEBUG
        printf("proc @%08x has undo structure with %d entries\n", p,
            suptr->un_cnt);
#endif

        /*
         * If there are any active undo elements then process them.
         */
        if (suptr->un_cnt > 0) {
                while (suptr->un_ent != NULL) {
                        struct undo *sueptr;
                        int semid;
                        int semnum;
                        int adjval;
                        struct user_semid_ds *semaptr;

                        sueptr = suptr->un_ent;
                        semid = sueptr->une_id;
                        semnum = sueptr->une_num;
                        adjval = sueptr->une_adjval;

                        semaptr = &sema[semid];
                        if ((semaptr->sem_perm.mode & SEM_ALLOC) == 0)
                                panic("semexit - semid not allocated");
                        if (semnum >= semaptr->sem_nsems)
                                panic("semexit - semnum out of range");

#ifdef SEM_DEBUG
                        printf("semexit:  %08x id=%d num=%d(adj=%d) ; sem=%d\n",
                               suptr->un_proc,
                               semid,
                               semnum,
                               adjval,
                               semaptr->sem_base[semnum].semval);
#endif

                        if (adjval < 0) {
                                if (semaptr->sem_base[semnum].semval < -adjval)
                                        semaptr->sem_base[semnum].semval = 0;
                                else
                                        semaptr->sem_base[semnum].semval +=
                                            adjval;
                        } else
                                semaptr->sem_base[semnum].semval += adjval;

                /* Maybe we should build a list of semaptr's to wake
                 * up, finish all access to data structures, release the
                 * subsystem lock, and wake all the processes.  Something
                 * to think about.  It wouldn't buy us anything unless
                 * wakeup had the potential to block, or the syscall
                 * funnel state was changed to allow multiple threads
                 * in the BSD code at once.
                 */
#ifdef SEM_WAKEUP
                        sem_wakeup((caddr_t)semaptr);
#else
                        wakeup((caddr_t)semaptr);
#endif
#ifdef SEM_DEBUG
                        printf("semexit:  back from wakeup\n");
#endif
                        suptr->un_cnt--;
                        suptr->un_ent = sueptr->une_next;
                        FREE(sueptr, M_SYSVSEM);
                        sueptr = NULL;
                }
        }

        /*
         * Deallocate the undo vector.
         */
#ifdef SEM_DEBUG
        printf("removing vector\n");
#endif
        suptr->un_proc = NULL;
        *supptr = suptr->un_next;

unlock:
        /*
         * There is a semaphore leak (i.e. memory leak) in this code.
         * We should be deleting the IPC_PRIVATE semaphores when they are
         * no longer needed, and we dont. We would have to track which processes
         * know about which IPC_PRIVATE semaphores, updating the list after
         * every fork.  We can't just delete them semaphore when the process
         * that created it dies, because that process may well have forked
         * some children.  So we need to wait until all of it's children have
         * died, and so on.  Maybe we should tag each IPC_PRIVATE sempahore
         * with the creating group ID, count the number of processes left in
         * that group, and delete the semaphore when the group is gone.
         * Until that code gets implemented we will leak IPC_PRIVATE semaphores.
         * There is an upper bound on the size of our semaphore array, so   
         * leaking the semaphores should not work as a DOS attack.
         *
         * Please note that the original BSD code this file is based on had the
         * same leaky semaphore problem.
         */

        SYSV_SEM_SUBSYS_UNLOCK();
}


/* (struct sysctl_oid *oidp, void *arg1, int arg2, \
        struct sysctl_req *req) */
static int
sysctl_seminfo(__unused struct sysctl_oid *oidp, void *arg1,
        __unused int arg2, struct sysctl_req *req)
{
        int error = 0;

        error = SYSCTL_OUT(req, arg1, sizeof(int));
        if (error || req->newptr == USER_ADDR_NULL)
                return(error);

        SYSV_SEM_SUBSYS_LOCK();

        /* Set the values only if shared memory is not initialised */
        if ((sem_pool == NULL) && 
                (sema == NULL) && 
                (semu == NULL) && 
                (semu_list == NULL)) {
                        if ((error = SYSCTL_IN(req, arg1, sizeof(int)))) {
                                goto out;
                        }
        } else 
                error = EINVAL;
out:
        SYSV_SEM_SUBSYS_UNLOCK();
        return(error);
        
}

/* SYSCTL_NODE(_kern, KERN_SYSV, sysv, CTLFLAG_RW, 0, "SYSV"); */
extern struct sysctl_oid_list sysctl__kern_sysv_children;
SYSCTL_PROC(_kern_sysv, KSYSV_SEMMNI, semmni, CTLTYPE_INT | CTLFLAG_RW,
    &limitseminfo.semmni, 0, &sysctl_seminfo ,"I","semmni");

SYSCTL_PROC(_kern_sysv, KSYSV_SEMMNS, semmns, CTLTYPE_INT | CTLFLAG_RW,
    &limitseminfo.semmns, 0, &sysctl_seminfo ,"I","semmns");

SYSCTL_PROC(_kern_sysv, KSYSV_SEMMNU, semmnu, CTLTYPE_INT | CTLFLAG_RW,
    &limitseminfo.semmnu, 0, &sysctl_seminfo ,"I","semmnu");

SYSCTL_PROC(_kern_sysv, KSYSV_SEMMSL, semmsl, CTLTYPE_INT | CTLFLAG_RW,
    &limitseminfo.semmsl, 0, &sysctl_seminfo ,"I","semmsl");
    
SYSCTL_PROC(_kern_sysv, KSYSV_SEMUNE, semume, CTLTYPE_INT | CTLFLAG_RW,
    &limitseminfo.semume, 0, &sysctl_seminfo ,"I","semume");


static int
IPCS_sem_sysctl(__unused struct sysctl_oid *oidp, __unused void *arg1,
        __unused int arg2, struct sysctl_req *req)
{
        int error;
        int cursor;
        union {
                struct IPCS_command u32;
                struct user_IPCS_command u64;
        } ipcs;
        struct semid_ds semid_ds32;     /* post conversion, 32 bit version */
        void *semid_dsp;
        size_t ipcs_sz = sizeof(struct user_IPCS_command);
        size_t semid_ds_sz = sizeof(struct user_semid_ds);
        struct proc *p = current_proc();

        /* Copy in the command structure */
        if ((error = SYSCTL_IN(req, &ipcs, ipcs_sz)) != 0) {
                return(error);
        }

        if (!IS_64BIT_PROCESS(p)) {
                ipcs_sz = sizeof(struct IPCS_command);
                semid_ds_sz = sizeof(struct semid_ds);
        }

        /* Let us version this interface... */
        if (ipcs.u64.ipcs_magic != IPCS_MAGIC) {
                return(EINVAL);
        }

        SYSV_SEM_SUBSYS_LOCK();
        switch(ipcs.u64.ipcs_op) {
        case IPCS_SEM_CONF:     /* Obtain global configuration data */
                if (ipcs.u64.ipcs_datalen != sizeof(struct seminfo)) {
                        error = ERANGE;
                        break;
                }
                if (ipcs.u64.ipcs_cursor != 0) {        /* fwd. compat. */
                        error = EINVAL;
                        break;
                }
                error = copyout(&seminfo, ipcs.u64.ipcs_data, ipcs.u64.ipcs_datalen);
                break;

        case IPCS_SEM_ITER:     /* Iterate over existing segments */
                cursor = ipcs.u64.ipcs_cursor;
                if (cursor < 0 || cursor >= seminfo.semmni) {
                        error = ERANGE;
                        break;
                }
                if (ipcs.u64.ipcs_datalen != (int)semid_ds_sz ) {
                        error = EINVAL;
                        break;
                }
                for( ; cursor < seminfo.semmni; cursor++) {
                        if (sema[cursor].sem_perm.mode & SEM_ALLOC)
                                break;
                        continue;
                }
                if (cursor == seminfo.semmni) {
                        error = ENOENT;
                        break;
                }

                semid_dsp = &sema[cursor];      /* default: 64 bit */

                /*
                 * If necessary, convert the 64 bit kernel segment
                 * descriptor to a 32 bit user one.
                 */
                if (!IS_64BIT_PROCESS(p)) {
                        semid_ds_64to32(semid_dsp, &semid_ds32);
                        semid_dsp = &semid_ds32;
                }
                error = copyout(semid_dsp, ipcs.u64.ipcs_data, ipcs.u64.ipcs_datalen);
                if (!error) {
                        /* update cursor */
                        ipcs.u64.ipcs_cursor = cursor + 1;
                        error = SYSCTL_OUT(req, &ipcs, ipcs_sz);
                }
                break;

        default:
                error = EINVAL;
                break;
        }
        SYSV_SEM_SUBSYS_UNLOCK();
        return(error);
}

SYSCTL_DECL(_kern_sysv_ipcs);
SYSCTL_PROC(_kern_sysv_ipcs, OID_AUTO, sem, CTLFLAG_RW|CTLFLAG_ANYBODY,
        0, 0, IPCS_sem_sysctl,
        "S,IPCS_sem_command",
        "ipcs sem command interface");