xnu-6153.11.26.tar.gz

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

/*
 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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 *
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 */
/*
 * 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
 */
/*
 * NOTICE: This file was modified by McAfee Research in 2004 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 * Copyright (c) 2005-2006 SPARTA, Inc.
 */

#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>
#if CONFIG_MACF
#include <security/mac_framework.h>
#endif

#include <security/audit/audit.h>

#if SYSV_SEM


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

/* Uncomment this line to see MAC debugging output. */
/* #define      MAC_DEBUG */
#if CONFIG_MACF_DEBUG
#define MPRINTF(a)      printf(a)
#else
#define MPRINTF(a)
#endif

#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 = SEMMAP,        /* # of entries in semaphore map */
        .semmni = SEMMNI,        /* # of semaphore identifiers */
        .semmns = SEMMNS,        /* # of semaphores in system */
        .semmnu = SEMMNU,        /* # of undo structures in system */
        .semmsl = SEMMSL,        /* max # of semaphores per id */
        .semopm = SEMOPM,        /* max # of operations per semop call */
        .semume = SEMUME,        /* max # of undo entries per process */
        .semusz = SEMUSZ,        /* size in bytes of undo structure */
        .semvmx = SEMVMX,        /* semaphore maximum value */
        .semaem = 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 = SEMMAP,       /* Unused, # of entries in semaphore map */
        .semmni = 0,            /* # of semaphore identifiers */
        .semmns = 0,            /* # of semaphores in system */
        .semmnu = 0,            /* # of undo entries in system */
        .semmsl = SEMMSL,       /* max # of semaphores per id */
        .semopm = SEMOPM,       /* max # of operations per semop call */
        .semume = SEMUME,       /* max # of undo entries per process */
        .semusz = SEMUSZ,       /* size in bytes of undo structure */
        .semvmx = SEMVMX,       /* semaphore maximum value */
        .semaem = SEMAEM        /* adjust on exit max value */
};


static int semu_alloc(struct proc *p);
static int semundo_adjust(struct proc *p, int *supidx,
    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* const semcalls[] = {
        (sy_call_t *)semctl, (sy_call_t *)semget,
        (sy_call_t *)semop
};

static int              semtot = 0;             /* # of used semaphores */
struct semid_kernel     *sema = NULL;           /* semaphore id pool */
struct sem              *sem_pool =  NULL;      /* semaphore pool */
static int              semu_list_idx = -1;     /* 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();

        sysv_sem_subsys_lck_grp = lck_grp_alloc_init("sysv_sem_subsys_lock", sysv_sem_subsys_lck_grp_attr);

        sysv_sem_subsys_lck_attr = lck_attr_alloc_init();
        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_kernelto32(struct user_semid_ds *in, struct user32_semid_ds *out)
{
        out->sem_perm = in->sem_perm;
        out->sem_base = CAST_DOWN_EXPLICIT(__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 */
}

static void
semid_ds_kernelto64(struct user_semid_ds *in, struct user64_semid_ds *out)
{
        out->sem_perm = in->sem_perm;
        out->sem_base = CAST_DOWN_EXPLICIT(__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_32tokernel(struct user32_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 *)(uintptr_t)in->sem_base;
        out->sem_perm = in->sem_perm;
}

static void
semid_ds_64tokernel(struct user64_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 *)(uintptr_t)in->sem_base;
        out->sem_perm = in->sem_perm;
}


/*
 * semsys
 *
 * Entry point for all SEM calls: semctl, semget, semop
 *
 * Parameters:  p       Process requesting the call
 *              uap     User argument descriptor (see below)
 *              retval  Return value of the selected sem call
 *
 * Indirect parameters: uap->which      sem call to invoke (index in array of sem calls)
 *                      uap->a2         User argument descriptor
 *
 * Returns:     0       Success
 *              !0      Not success
 *
 * Implicit returns: retval     Return value of the selected sem call
 *
 * DEPRECATED:  This interface should not be used to call the other SEM
 *              functions (semctl, semget, semop). The correct usage is
 *              to call the other SEM functions directly.
 *
 */
int
semsys(struct proc *p, struct semsys_args *uap, int32_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);
}

/*
 * 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)
{
        int i;
        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)
{
        struct semid_kernel *newSema;
        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 semid_kernel *,
            sizeof(struct semid_kernel) * 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 semid_kernel pointer.
                 */
                if (sema[i].u.sem_perm.mode & SEM_ALLOC) {
                        wakeup((caddr_t)&sema[i]);
                }
        }

#if CONFIG_MACF
        for (i = seminfo.semmni; i < newSize; i++) {
                mac_sysvsem_label_init(&newSema[i]);
        }
#endif

        /*
         * 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 | M_NULL);
        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].u.sem_perm.mode & SEM_ALLOC) { /* ID in use */
                        sema[i].u.sem_base = new_sem_pool +
                            (sema[i].u.sem_base - 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 int
semu_alloc(struct proc *p)
{
        int i;
        struct sem_undo *suptr;
        int *supidx;
        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_idx = semu_list_idx;
                                semu_list_idx = i;
                                suptr->un_cnt = 0;
                                suptr->un_ent = NULL;
                                suptr->un_proc = p;
                                return i;
                        }
                }

                /*
                 * 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;

                        supidx = &semu_list_idx;
                        while (*supidx != -1) {
                                suptr = SEMU(*supidx);
                                if (suptr->un_cnt == 0) {
                                        suptr->un_proc = NULL;
                                        *supidx = suptr->un_next_idx;
                                        did_something = 1;
                                } else {
                                        supidx = &(suptr->un_next_idx);
                                }
                        }

                        /* 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 -1;
                                }
                        }
                } else {
                        /*
                         * The second pass failed even though we freed
                         * something after the first pass!
                         * This is IMPOSSIBLE!
                         */
                        panic("semu_alloc - second attempt failed");
                }
        }
        return -1;
}

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

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

        suidx = *supidx;
        if (suidx == -1) {
                for (suidx = semu_list_idx; suidx != -1;
                    suidx = suptr->un_next_idx) {
                        suptr = SEMU(suidx);
                        if (suptr->un_proc == p) {
                                *supidx = suidx;
                                break;
                        }
                }
                if (suidx == -1) {
                        if (adjval == 0) {
                                return 0;
                        }
                        suidx = semu_alloc(p);
                        if (suidx == -1) {
                                return ENOSPC;
                        }
                        *supidx = suidx;
                }
        }

        /*
         * Look for the requested entry and adjust it (delete if adjval becomes
         * 0).
         */
        suptr = SEMU(suidx);
        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;
        int suidx;

        for (suidx = semu_list_idx; suidx != -1; suidx = suptr->un_next_idx) {
                struct undo *sueptr;
                struct undo **suepptr;
                int i = 0;

                suptr = SEMU(suidx);
                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, int32_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 semid_kernel *semakptr;


        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;
        }

        semakptr = &sema[semid];
        if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0 ||
            semakptr->u.sem_perm._seq != IPCID_TO_SEQ(uap->semid)) {
                eval = EINVAL;
                goto semctlout;
        }
#if CONFIG_MACF
        eval = mac_sysvsem_check_semctl(cred, semakptr, cmd);
        if (eval) {
                goto semctlout;
        }
#endif

        eval = 0;
        rval = 0;

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

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

        case IPC_SET:
                if ((eval = ipcperm(cred, &semakptr->u.sem_perm, IPC_M))) {
                        goto semctlout;
                }

                if (IS_64BIT_PROCESS(p)) {
                        struct user64_semid_ds ds64;
                        eval = copyin(user_arg.buf, &ds64, sizeof(ds64));
                        semid_ds_64tokernel(&ds64, &sbuf);
                } else {
                        struct user32_semid_ds ds32;
                        eval = copyin(user_arg.buf, &ds32, sizeof(ds32));
                        semid_ds_32tokernel(&ds32, &sbuf);
                }

                if (eval != 0) {
                        goto semctlout;
                }

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

        case IPC_STAT:
                if ((eval = ipcperm(cred, &semakptr->u.sem_perm, IPC_R))) {
                        goto semctlout;
                }

                if (IS_64BIT_PROCESS(p)) {
                        struct user64_semid_ds semid_ds64;
                        bzero(&semid_ds64, sizeof(semid_ds64));
                        semid_ds_kernelto64(&semakptr->u, &semid_ds64);
                        eval = copyout(&semid_ds64, user_arg.buf, sizeof(semid_ds64));
                } else {
                        struct user32_semid_ds semid_ds32;
                        bzero(&semid_ds32, sizeof(semid_ds32));
                        semid_ds_kernelto32(&semakptr->u, &semid_ds32);
                        eval = copyout(&semid_ds32, user_arg.buf, sizeof(semid_ds32));
                }
                break;

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

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

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

        case GETALL:
                if ((eval = ipcperm(cred, &semakptr->u.sem_perm, IPC_R))) {
                        goto semctlout;
                }
/* XXXXXXXXXXXXXXXX TBD XXXXXXXXXXXXXXXX */
                for (i = 0; i < semakptr->u.sem_nsems; i++) {
                        /* XXX could be done in one go... */
                        eval = copyout((caddr_t)&semakptr->u.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, &semakptr->u.sem_perm, IPC_R))) {
                        goto semctlout;
                }
                if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
                        eval = EINVAL;
                        goto semctlout;
                }
                rval = semakptr->u.sem_base[semnum].semzcnt;
                break;

        case SETVAL:
                if ((eval = ipcperm(cred, &semakptr->u.sem_perm, IPC_W))) {
#ifdef SEM_DEBUG
                        printf("Invalid credentials for write\n");
#endif
                        goto semctlout;
                }
                if (semnum < 0 || semnum >= semakptr->u.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.
                 */
                u_int newsemval = CAST_DOWN_EXPLICIT(u_int, user_arg.buf);

                /*
                 * The check is being performed as unsigned values to match
                 * eventual destination
                 */
                if (newsemval > (u_int)seminfo.semvmx) {
#ifdef SEM_DEBUG
                        printf("Out of range sem value for set\n");
#endif
                        eval = ERANGE;
                        goto semctlout;
                }
                semakptr->u.sem_base[semnum].semval = newsemval;
                semakptr->u.sem_base[semnum].sempid = p->p_pid;
                /* XXX scottl Should there be a MAC call here? */
                semundo_clear(semid, semnum);
                wakeup((caddr_t)semakptr);
                break;

        case SETALL:
                if ((eval = ipcperm(cred, &semakptr->u.sem_perm, IPC_W))) {
                        goto semctlout;
                }
/*** XXXXXXXXXXXX TBD ********/
                for (i = 0; i < semakptr->u.sem_nsems; i++) {
                        /* XXX could be done in one go... */
                        eval = copyin(user_arg.array + (i * sizeof(unsigned short)),
                            (caddr_t)&semakptr->u.sem_base[i].semval,
                            sizeof(unsigned short));
                        if (eval != 0) {
                                break;
                        }
                        semakptr->u.sem_base[i].sempid = p->p_pid;
                }
                /* XXX scottl Should there be a MAC call here? */
                semundo_clear(semid, -1);
                wakeup((caddr_t)semakptr);
                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, int32_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].u.sem_perm.mode & SEM_ALLOC) &&
                            sema[semid].u.sem_perm._key == key) {
                                break;
                        }
                }
                if (semid < seminfo.semmni) {
#ifdef SEM_DEBUG
                        printf("found public key\n");
#endif
                        if ((eval = ipcperm(cred, &sema[semid].u.sem_perm,
                            semflg & 0700))) {
                                goto semgetout;
                        }
                        if (nsems < 0 || sema[semid].u.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;
                        }
#if CONFIG_MACF
                        eval = mac_sysvsem_check_semget(cred, &sema[semid]);
                        if (eval) {
                                goto semgetout;
                        }
#endif
                        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].u.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].u.sem_perm._key = key;
                sema[semid].u.sem_perm.cuid = kauth_cred_getuid(cred);
                sema[semid].u.sem_perm.uid = kauth_cred_getuid(cred);
                sema[semid].u.sem_perm.cgid = kauth_cred_getgid(cred);
                sema[semid].u.sem_perm.gid = kauth_cred_getgid(cred);
                sema[semid].u.sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
                sema[semid].u.sem_perm._seq =
                    (sema[semid].u.sem_perm._seq + 1) & 0x7fff;
                sema[semid].u.sem_nsems = nsems;
                sema[semid].u.sem_otime = 0;
                sema[semid].u.sem_ctime = sysv_semtime();
                sema[semid].u.sem_base = &sem_pool[semtot];
                semtot += nsems;
                bzero(sema[semid].u.sem_base,
                    sizeof(sema[semid].u.sem_base[0]) * nsems);
#if CONFIG_MACF
                mac_sysvsem_label_associate(cred, &sema[semid]);
#endif
#ifdef SEM_DEBUG
                printf("sembase = 0x%x, next = 0x%x\n", sema[semid].u.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].u.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, int32_t *retval)
{
        int semid = uap->semid;
        int nsops = uap->nsops;
        struct sembuf sops[seminfo.semopm];
        struct semid_kernel *semakptr;
        struct sembuf *sopptr = NULL;   /* protected by 'semptr' */
        struct sem *semptr = NULL;      /* protected by 'if' */
        int supidx = -1;
        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;
        }

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

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

        if (nsops < 0 || nsops > seminfo.semopm) {
#ifdef SEM_DEBUG
                printf("too many sops (max=%d, nsops=%d)\n",
                    seminfo.semopm, 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;
        }

#if CONFIG_MACF
        /*
         * Initial pass thru sops to see what permissions are needed.
         */
        j = 0;          /* permission needed */
        for (i = 0; i < nsops; i++) {
                j |= (sops[i].sem_op == 0) ? SEM_R : SEM_A;
        }

        /*
         * The MAC hook checks whether the thread has read (and possibly
         * write) permissions to the semaphore array based on the
         * sopptr->sem_op value.
         */
        eval = mac_sysvsem_check_semop(kauth_cred_get(), semakptr, j);
        if (eval) {
                goto semopout;
        }
#endif

        /*
         * 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 >= semakptr->u.sem_nsems) {
                                eval = EFBIG;
                                goto semopout;
                        }

                        semptr = &semakptr->u.sem_base[sopptr->sem_num];

#ifdef SEM_DEBUG
                        printf("semop:  semakptr=%x, sem_base=%x, semptr=%x, sem[%d]=%d : op=%d, flag=%s\n",
                            semakptr, semakptr->u.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++) {
                        semakptr->u.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)semakptr, &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.
                 */

                semptr = NULL;

                /*
                 * Make sure that the semaphore still exists
                 *
                 * XXX POSIX: Third test this 'if' and 'EINTR' precedence may
                 * fail testing; if so, we will need to revert this code.
                 */
                semakptr = &sema[semid];   /* sema may have been reallocated */
                if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0 ||
                    semakptr->u.sem_perm._seq != IPCID_TO_SEQ(uap->semid) ||
                    sopptr->sem_num >= semakptr->u.sem_nsems) {
                        /* The man page says to return EIDRM. */
                        /* Unfortunately, BSD doesn't define that code! */
                        if (eval == EINTR) {
                                /*
                                 * EINTR takes precedence over the fact that
                                 * the semaphore disappeared while we were
                                 * sleeping...
                                 */
                        } else {
#ifdef EIDRM
                                eval = EIDRM;
#else
                                eval = EINVAL;          /* Ancient past */
#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 = &semakptr->u.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, &supidx, 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, &supidx, semid,
                                    sops[j].sem_num, adjval) != 0) {
                                        panic("semop - can't undo undos");
                                }
                        }

                        for (j = 0; j < nsops; j++) {
                                semakptr->u.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 = &semakptr->u.sem_base[sopptr->sem_num];
                semptr->sempid = p->p_pid;
        }
        semakptr->u.sem_otime = sysv_semtime();

        if (do_wakeup) {
#ifdef SEM_DEBUG
                printf("semop:  doing wakeup\n");
#ifdef SEM_WAKEUP
                sem_wakeup((caddr_t)semakptr);
#else
                wakeup((caddr_t)semakptr);
#endif
                printf("semop:  back from wakeup\n");
#else
                wakeup((caddr_t)semakptr);
#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)
{
        struct sem_undo *suptr = NULL;
        int suidx;
        int *supidx;
        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 (supidx = &semu_list_idx; (suidx = *supidx) != -1;
            supidx = &suptr->un_next_idx) {
                suptr = SEMU(suidx);
                if (suptr->un_proc == p) {
                        break;
                }
        }

        if (suidx == -1) {
                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 semid_kernel *semakptr;

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

                        semakptr = &sema[semid];
                        if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0) {
                                panic("semexit - semid not allocated");
                        }
                        if (semnum >= semakptr->u.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,
                            semakptr->u.sem_base[semnum].semval);
#endif

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

                        /* Maybe we should build a list of semakptr's to wake
                         * up, finish all access to data structures, release the
                         * subsystem lock, and wake all the processes.  Something
                         * to think about.
                         */
#ifdef SEM_WAKEUP
                        sem_wakeup((caddr_t)semakptr);
#else
                        wakeup((caddr_t)semakptr);
#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;
        *supidx = suptr->un_next_idx;

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_idx == -1)) {
                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, OID_AUTO, semmni, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
    &limitseminfo.semmni, 0, &sysctl_seminfo, "I", "semmni");

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

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

SYSCTL_PROC(_kern_sysv, OID_AUTO, semmsl, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
    &limitseminfo.semmsl, 0, &sysctl_seminfo, "I", "semmsl");

SYSCTL_PROC(_kern_sysv, OID_AUTO, semume, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
    &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 user32_IPCS_command u32;
                struct user_IPCS_command u64;
        } ipcs;
        struct user32_semid_ds semid_ds32;      /* post conversion, 32 bit version */
        struct user64_semid_ds semid_ds64;      /* post conversion, 64 bit version */
        void *semid_dsp;
        size_t ipcs_sz;
        size_t semid_ds_sz;
        struct proc *p = current_proc();

        if (IS_64BIT_PROCESS(p)) {
                ipcs_sz = sizeof(struct user_IPCS_command);
                semid_ds_sz = sizeof(struct user64_semid_ds);
        } else {
                ipcs_sz = sizeof(struct user32_IPCS_command);
                semid_ds_sz = sizeof(struct user32_semid_ds);
        }

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

        if (!IS_64BIT_PROCESS(p)) { /* convert in place */
                ipcs.u64.ipcs_data = CAST_USER_ADDR_T(ipcs.u32.ipcs_data);
        }

        /* 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].u.sem_perm.mode & SEM_ALLOC) {
                                break;
                        }
                        continue;
                }
                if (cursor == seminfo.semmni) {
                        error = ENOENT;
                        break;
                }

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

                /*
                 * If necessary, convert the 64 bit kernel segment
                 * descriptor to a 32 bit user one.
                 */
                if (!IS_64BIT_PROCESS(p)) {
                        bzero(&semid_ds32, sizeof(semid_ds32));
                        semid_ds_kernelto32(semid_dsp, &semid_ds32);
                        semid_dsp = &semid_ds32;
                } else {
                        bzero(&semid_ds64, sizeof(semid_ds64));
                        semid_ds_kernelto64(semid_dsp, &semid_ds64);
                        semid_dsp = &semid_ds64;
                }

                error = copyout(semid_dsp, ipcs.u64.ipcs_data, ipcs.u64.ipcs_datalen);
                if (!error) {
                        /* update cursor */
                        ipcs.u64.ipcs_cursor = cursor + 1;

                        if (!IS_64BIT_PROCESS(p)) {     /* convert in place */
                                ipcs.u32.ipcs_data = CAST_DOWN_EXPLICIT(user32_addr_t, ipcs.u64.ipcs_data);
                        }

                        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 | CTLFLAG_LOCKED,
    0, 0, IPCS_sem_sysctl,
    "S,IPCS_sem_command",
    "ipcs sem command interface");

#endif /* SYSV_SEM */