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

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * 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. 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.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*      $NetBSD: sysv_shm.c,v 1.23 1994/07/04 23:25:12 glass Exp $      */

/*
 * Copyright (c) 1994 Adam Glass and Charles Hannum.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Adam Glass and Charles
 *      Hannum.
 * 4. The names of the authors may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <sys/appleapiopts.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/shm.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/sysctl.h>

#include <mach/mach_types.h>
#include <mach/vm_inherit.h>
#include <vm/vm_map.h>

struct shmat_args;
extern int shmat __P((struct proc *p, struct shmat_args *uap, int *retval));
struct shmctl_args;
extern int shmctl __P((struct proc *p, struct shmctl_args *uap, int *retval));
struct shmdt_args;
extern int shmdt __P((struct proc *p, struct shmdt_args *uap, int *retval));
struct shmget_args;
extern int shmget __P((struct proc *p, struct shmget_args *uap, int *retval));

#if 0
static void shminit __P((void *));
SYSINIT(sysv_shm, SI_SUB_SYSV_SHM, SI_ORDER_FIRST, shminit, NULL)
#endif 0

struct oshmctl_args;
static int oshmctl __P((struct proc *p, struct oshmctl_args *uap, int * retval));
static int shmget_allocate_segment __P((struct proc *p, struct shmget_args *uap, int mode, int * retval));
static int shmget_existing __P((struct proc *p, struct shmget_args *uap, int mode, int segnum, int  * retval));

typedef int     sy_call_t __P((struct proc *, void *, int *));

/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *shmcalls[] = {
        (sy_call_t *)shmat, (sy_call_t *)oshmctl,
        (sy_call_t *)shmdt, (sy_call_t *)shmget,
        (sy_call_t *)shmctl
};

#define SHMSEG_FREE             0x0200
#define SHMSEG_REMOVED          0x0400
#define SHMSEG_ALLOCATED        0x0800
#define SHMSEG_WANTED           0x1000

static int shm_last_free, shm_nused, shm_committed;
struct shmid_ds *shmsegs;
static int shm_inited = 0;

struct shm_handle {
        /* vm_offset_t kva; */
        void * shm_object;
};

struct shmmap_state {
        vm_offset_t va;
        int shmid;
};

static void shm_deallocate_segment __P((struct shmid_ds *));
static int shm_find_segment_by_key __P((key_t));
static struct shmid_ds *shm_find_segment_by_shmid __P((int));
static int shm_delete_mapping __P((struct proc *, struct shmmap_state *));

#ifdef __APPLE_API_PRIVATE
struct  shminfo shminfo = {
        -1,     /* SHMMAX 4096 *1024 */
        -1,     /* SHMMIN = 1 */
        -1,     /* SHMMNI = 1 */
        -1,     /* SHMSEG = 8 */
        -1      /* SHMALL = 1024 */
};
#endif /* __APPLE_API_PRIVATE */

static int
shm_find_segment_by_key(key)
        key_t key;
{
        int i;

        for (i = 0; i < shminfo.shmmni; i++)
                if ((shmsegs[i].shm_perm.mode & SHMSEG_ALLOCATED) &&
                    shmsegs[i].shm_perm.key == key)
                        return i;
        return -1;
}

static struct shmid_ds *
shm_find_segment_by_shmid(shmid)
        int shmid;
{
        int segnum;
        struct shmid_ds *shmseg;

        segnum = IPCID_TO_IX(shmid);
        if (segnum < 0 || segnum >= shminfo.shmmni)
                return NULL;
        shmseg = &shmsegs[segnum];
        if ((shmseg->shm_perm.mode & (SHMSEG_ALLOCATED | SHMSEG_REMOVED))
            != SHMSEG_ALLOCATED ||
            shmseg->shm_perm.seq != IPCID_TO_SEQ(shmid))
                return NULL;
        return shmseg;
}

static void
shm_deallocate_segment(shmseg)
        struct shmid_ds *shmseg;
{
        struct shm_handle *shm_handle;
        struct shmmap_state *shmmap_s=NULL;
        size_t size;
        char * ptr;

        shm_handle = shmseg->shm_internal;
        size = round_page(shmseg->shm_segsz);
        mach_destroy_memory_entry(shm_handle->shm_object);
        FREE((caddr_t)shm_handle, M_SHM);
        shmseg->shm_internal = NULL;
        shm_committed -= btoc(size);
        shm_nused--;
        shmseg->shm_perm.mode = SHMSEG_FREE;
}

static int
shm_delete_mapping(p, shmmap_s)
        struct proc *p;
        struct shmmap_state *shmmap_s;
{
        struct shmid_ds *shmseg;
        int segnum, result;
        size_t size;

        segnum = IPCID_TO_IX(shmmap_s->shmid);
        shmseg = &shmsegs[segnum];
        size = round_page(shmseg->shm_segsz);
        result = vm_deallocate(current_map(), shmmap_s->va, size);
        if (result != KERN_SUCCESS)
                return EINVAL;
        shmmap_s->shmid = -1;
        shmseg->shm_dtime = time_second;
        if ((--shmseg->shm_nattch <= 0) &&
            (shmseg->shm_perm.mode & SHMSEG_REMOVED)) {
                shm_deallocate_segment(shmseg);
                shm_last_free = segnum;
        }
        return 0;
}

struct shmdt_args {
        void *shmaddr;
};

int
shmdt(p, uap, retval)
        struct proc *p;
        struct shmdt_args *uap;
        register_t *retval;
{
        struct shmmap_state *shmmap_s;
        int i;

        if (!shm_inited)
                return(EINVAL);
        shmmap_s = (struct shmmap_state *)p->vm_shm;
        if (shmmap_s == NULL)
            return EINVAL;
        for (i = 0; i < shminfo.shmseg; i++, shmmap_s++)
                if (shmmap_s->shmid != -1 &&
                    shmmap_s->va == (vm_offset_t)uap->shmaddr)
                        break;
        if (i == shminfo.shmseg)
                return EINVAL;
        return shm_delete_mapping(p, shmmap_s);
}

#ifndef _SYS_SYSPROTO_H_
struct shmat_args {
        int shmid;
        void *shmaddr;
        int shmflg;
};
#endif

int
shmat(p, uap, retval)
        struct proc *p;
        struct shmat_args *uap;
        register_t *retval;
{
        int error, i, flags;
        struct ucred *cred = p->p_ucred;
        struct shmid_ds *shmseg;
        struct shmmap_state *shmmap_s = NULL;
        struct shm_handle *shm_handle;
        vm_offset_t attach_va;
        vm_prot_t prot;
        vm_size_t size;
        kern_return_t rv;

        if (!shm_inited)
                return(EINVAL);
        shmmap_s = (struct shmmap_state *)p->vm_shm;
        if (shmmap_s == NULL) {
                size = shminfo.shmseg * sizeof(struct shmmap_state);
                shmmap_s = (struct shmmap_state *)_MALLOC(size, M_SHM, M_WAITOK);
                for (i = 0; i < shminfo.shmseg; i++)
                        shmmap_s[i].shmid = -1;
                p->vm_shm = (caddr_t)shmmap_s;
        }
        shmseg = shm_find_segment_by_shmid(uap->shmid);
        if (shmseg == NULL)
                return EINVAL;
        error = ipcperm(cred, &shmseg->shm_perm,
            (uap->shmflg & SHM_RDONLY) ? IPC_R : IPC_R|IPC_W);
        if (error)
                return error;
        for (i = 0; i < shminfo.shmseg; i++) {
                if (shmmap_s->shmid == -1)
                        break;
                shmmap_s++;
        }
        if (i >= shminfo.shmseg)
                return EMFILE;
        size = round_page(shmseg->shm_segsz);
        prot = VM_PROT_READ;
        if ((uap->shmflg & SHM_RDONLY) == 0)
                prot |= VM_PROT_WRITE;
        flags = MAP_ANON | MAP_SHARED;
        if (uap->shmaddr) {
                flags |= MAP_FIXED;
                if (uap->shmflg & SHM_RND)
                        attach_va = (vm_offset_t)uap->shmaddr & ~(SHMLBA-1);
                else if (((vm_offset_t)uap->shmaddr & (SHMLBA-1)) == 0)
                        attach_va = (vm_offset_t)uap->shmaddr;
                else
                        return EINVAL;
        } else {
                attach_va = round_page(uap->shmaddr);
        }

        shm_handle = shmseg->shm_internal;
        rv = vm_map(current_map(), &attach_va, size, 0, (flags & MAP_FIXED)? FALSE: TRUE,
                shm_handle->shm_object, 0, FALSE, prot, prot, VM_INHERIT_DEFAULT);
        if (rv != KERN_SUCCESS) 
                        goto out;
        rv = vm_inherit(current_map(), attach_va, size,
                        VM_INHERIT_SHARE);
        if (rv != KERN_SUCCESS) {
                (void) vm_deallocate(current_map(), attach_va, size);
                goto out;
        }

        shmmap_s->va = attach_va;
        shmmap_s->shmid = uap->shmid;
        shmseg->shm_lpid = p->p_pid;
        shmseg->shm_atime = time_second;
        shmseg->shm_nattch++;
        *retval = attach_va;
        return( 0);
out:
        switch (rv) {
        case KERN_INVALID_ADDRESS:
        case KERN_NO_SPACE:
                return (ENOMEM);
        case KERN_PROTECTION_FAILURE:
                return (EACCES);
        default:
                return (EINVAL);
        }

}

struct oshmid_ds {
        struct  ipc_perm shm_perm;      /* operation perms */
        int     shm_segsz;              /* size of segment (bytes) */
        ushort  shm_cpid;               /* pid, creator */
        ushort  shm_lpid;               /* pid, last operation */
        short   shm_nattch;             /* no. of current attaches */
        time_t  shm_atime;              /* last attach time */
        time_t  shm_dtime;              /* last detach time */
        time_t  shm_ctime;              /* last change time */
        void    *shm_handle;            /* internal handle for shm segment */
};

struct oshmctl_args {
        int shmid;
        int cmd;
        struct oshmid_ds *ubuf;
};

static int
oshmctl(p, uap, retval)
        struct proc *p;
        struct oshmctl_args *uap;
        register_t *retval;
{
#ifdef COMPAT_43
        int error;
        struct ucred *cred = p->p_ucred;
        struct shmid_ds *shmseg;
        struct oshmid_ds outbuf;

        if (!shm_inited)
                return(EINVAL);
        shmseg = shm_find_segment_by_shmid(uap->shmid);
        if (shmseg == NULL)
                return EINVAL;
        switch (uap->cmd) {
        case IPC_STAT:
                error = ipcperm(cred, &shmseg->shm_perm, IPC_R);
                if (error)
                        return error;
                outbuf.shm_perm = shmseg->shm_perm;
                outbuf.shm_segsz = shmseg->shm_segsz;
                outbuf.shm_cpid = shmseg->shm_cpid;
                outbuf.shm_lpid = shmseg->shm_lpid;
                outbuf.shm_nattch = shmseg->shm_nattch;
                outbuf.shm_atime = shmseg->shm_atime;
                outbuf.shm_dtime = shmseg->shm_dtime;
                outbuf.shm_ctime = shmseg->shm_ctime;
                outbuf.shm_handle = shmseg->shm_internal;
                error = copyout((caddr_t)&outbuf, uap->ubuf, sizeof(outbuf));
                if (error)
                        return error;
                break;
        default:
                /* XXX casting to (sy_call_t *) is bogus, as usual. */
                return ((sy_call_t *)shmctl)(p, uap, retval);
        }
        return 0;
#else
        return EINVAL;
#endif
}

#ifndef _SYS_SYSPROTO_H_
struct shmctl_args {
        int shmid;
        int cmd;
        struct shmid_ds *buf;
};
#endif

int
shmctl(p, uap,  retval)
        struct proc *p;
        struct shmctl_args *uap;
        register_t *retval;
{
        int error;
        struct ucred *cred = p->p_ucred;
        struct shmid_ds inbuf;
        struct shmid_ds *shmseg;

        if (!shm_inited)
                return(EINVAL);
        shmseg = shm_find_segment_by_shmid(uap->shmid);
        if (shmseg == NULL)
                return EINVAL;
        switch (uap->cmd) {
        case IPC_STAT:
                error = ipcperm(cred, &shmseg->shm_perm, IPC_R);
                if (error)
                        return error;
                error = copyout((caddr_t)shmseg, uap->buf, sizeof(inbuf));
                if (error)
                        return error;
                break;
        case IPC_SET:
                error = ipcperm(cred, &shmseg->shm_perm, IPC_M);
                if (error)
                        return error;
                error = copyin(uap->buf, (caddr_t)&inbuf, sizeof(inbuf));
                if (error)
                        return error;
                shmseg->shm_perm.uid = inbuf.shm_perm.uid;
                shmseg->shm_perm.gid = inbuf.shm_perm.gid;
                shmseg->shm_perm.mode =
                    (shmseg->shm_perm.mode & ~ACCESSPERMS) |
                    (inbuf.shm_perm.mode & ACCESSPERMS);
                shmseg->shm_ctime = time_second;
                break;
        case IPC_RMID:
                error = ipcperm(cred, &shmseg->shm_perm, IPC_M);
                if (error)
                        return error;
                shmseg->shm_perm.key = IPC_PRIVATE;
                shmseg->shm_perm.mode |= SHMSEG_REMOVED;
                if (shmseg->shm_nattch <= 0) {
                        shm_deallocate_segment(shmseg);
                        shm_last_free = IPCID_TO_IX(uap->shmid);
                }
                break;
#if 0
        case SHM_LOCK:
        case SHM_UNLOCK:
#endif
        default:
                return EINVAL;
        }
        return 0;
}

#ifndef _SYS_SYSPROTO_H_
struct shmget_args {
        key_t key;
        size_t size;
        int shmflg;
};
#endif

static int
shmget_existing(p, uap, mode, segnum, retval)
        struct proc *p;
        struct shmget_args *uap;
        int mode;
        int segnum;
        int *retval;
{
        struct shmid_ds *shmseg;
        struct ucred *cred = p->p_ucred;
        int error;

        shmseg = &shmsegs[segnum];
        if (shmseg->shm_perm.mode & SHMSEG_REMOVED) {
                /*
                 * This segment is in the process of being allocated.  Wait
                 * until it's done, and look the key up again (in case the
                 * allocation failed or it was freed).
                 */
                shmseg->shm_perm.mode |= SHMSEG_WANTED;
                error = tsleep((caddr_t)shmseg, PLOCK | PCATCH, "shmget", 0);
                if (error)
                        return error;
                return EAGAIN;
        }
        error = ipcperm(cred, &shmseg->shm_perm, mode);
        if (error)
                return error;
        if (uap->size && uap->size > shmseg->shm_segsz)
                return EINVAL;
       if ((uap->shmflg & (IPC_CREAT | IPC_EXCL)) == (IPC_CREAT | IPC_EXCL))
                return EEXIST;
        *retval = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
        return 0;
}

static int
shmget_allocate_segment(p, uap, mode, retval)
        struct proc *p;
        struct shmget_args *uap;
        int mode;
        int * retval;
{
        int i, segnum, shmid, size;
        struct ucred *cred = p->p_ucred;
        struct shmid_ds *shmseg;
        struct shm_handle *shm_handle;
        kern_return_t kret;
        vm_offset_t user_addr;
        void * mem_object;

        if (uap->size < shminfo.shmmin || uap->size > shminfo.shmmax)
                return EINVAL;
        if (shm_nused >= shminfo.shmmni) /* any shmids left? */
                return ENOSPC;
        size = round_page(uap->size);
        if (shm_committed + btoc(size) > shminfo.shmall)
                return ENOMEM;
        if (shm_last_free < 0) {
                for (i = 0; i < shminfo.shmmni; i++)
                        if (shmsegs[i].shm_perm.mode & SHMSEG_FREE)
                                break;
                if (i == shminfo.shmmni)
                        panic("shmseg free count inconsistent");
                segnum = i;
        } else  {
                segnum = shm_last_free;
                shm_last_free = -1;
        }
        shmseg = &shmsegs[segnum];
        /*
         * In case we sleep in malloc(), mark the segment present but deleted
         * so that noone else tries to create the same key.
         */
        kret = vm_allocate(current_map(), &user_addr, size, TRUE);
        if (kret != KERN_SUCCESS) 
                goto out;

        kret = mach_make_memory_entry (current_map(), &size,
                        user_addr, VM_PROT_DEFAULT, &mem_object, 0);

        if (kret != KERN_SUCCESS) 
                goto out;
        shmseg->shm_perm.mode = SHMSEG_ALLOCATED | SHMSEG_REMOVED;
        shmseg->shm_perm.key = uap->key;
        shmseg->shm_perm.seq = (shmseg->shm_perm.seq + 1) & 0x7fff;
        shm_handle = (struct shm_handle *)
            _MALLOC(sizeof(struct shm_handle), M_SHM, M_WAITOK);
        shm_handle->shm_object = mem_object;
        shmid = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);

        shmseg->shm_internal = shm_handle;
        shmseg->shm_perm.cuid = shmseg->shm_perm.uid = cred->cr_uid;
        shmseg->shm_perm.cgid = shmseg->shm_perm.gid = cred->cr_gid;
        shmseg->shm_perm.mode = (shmseg->shm_perm.mode & SHMSEG_WANTED) |
            (mode & ACCESSPERMS) | SHMSEG_ALLOCATED;
        shmseg->shm_segsz = uap->size;
        shmseg->shm_cpid = p->p_pid;
        shmseg->shm_lpid = shmseg->shm_nattch = 0;
        shmseg->shm_atime = shmseg->shm_dtime = 0;
        shmseg->shm_ctime = time_second;
        shm_committed += btoc(size);
        shm_nused++;
        if (shmseg->shm_perm.mode & SHMSEG_WANTED) {
                /*
                 * Somebody else wanted this key while we were asleep.  Wake
                 * them up now.
                 */
                shmseg->shm_perm.mode &= ~SHMSEG_WANTED;
                wakeup((caddr_t)shmseg);
        }
        *retval = shmid;
        return 0;
out: 
        switch (kret) {
        case KERN_INVALID_ADDRESS:
        case KERN_NO_SPACE:
                return (ENOMEM);
        case KERN_PROTECTION_FAILURE:
                return (EACCES);
        default:
                return (EINVAL);
        }

}

int
shmget(p, uap, retval)
        struct proc *p;
        struct shmget_args *uap;
        register_t *retval;
{
        int segnum, mode, error;

        if (!shm_inited)
                return(EINVAL);

        mode = uap->shmflg & ACCESSPERMS;
        if (uap->key != IPC_PRIVATE) {
        again:
                segnum = shm_find_segment_by_key(uap->key);
                if (segnum >= 0) {
                        error = shmget_existing(p, uap, mode, segnum, retval);
                        if (error == EAGAIN)
                                goto again;
                        return(error);
                }
                if ((uap->shmflg & IPC_CREAT) == 0)
                        return ENOENT;
        }
        return( shmget_allocate_segment(p, uap, mode, retval));;
        /*NOTREACHED*/

}

struct shmsys_args  {
        u_int   which;
        int     a2;
        int     a3;
        int     a4;
};
int
shmsys(p, uap, retval)
        struct proc *p;
        /* XXX actually varargs. */
        struct shmsys_args *uap;
        register_t *retval;
{

        if (!shm_inited)
                return(EINVAL);

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

void
shmfork(p1, p2)
        struct proc *p1, *p2;
{
        struct shmmap_state *shmmap_s;
        size_t size;
        int i;

        if (!shm_inited)
                return;
        size = shminfo.shmseg * sizeof(struct shmmap_state);
        shmmap_s = (struct shmmap_state *)_MALLOC(size, M_SHM, M_WAITOK);
        bcopy((caddr_t)p1->vm_shm, (caddr_t)shmmap_s, size);
        p2->vm_shm = (caddr_t)shmmap_s;
        for (i = 0; i < shminfo.shmseg; i++, shmmap_s++)
                if (shmmap_s->shmid != -1)
                        shmsegs[IPCID_TO_IX(shmmap_s->shmid)].shm_nattch++;
}

void
shmexit(p)
        struct proc *p;
{
        struct shmmap_state *shmmap_s;
        int i;

        shmmap_s = (struct shmmap_state *)p->vm_shm;
        for (i = 0; i < shminfo.shmseg; i++, shmmap_s++)
                if (shmmap_s->shmid != -1)
                        shm_delete_mapping(p, shmmap_s);
        FREE((caddr_t)p->vm_shm, M_SHM);
        p->vm_shm = NULL;
}

void
shminit(dummy)
        void *dummy;
{
        int i;
        int s;

        if (!shm_inited) {
                s = sizeof(struct shmid_ds) * shminfo.shmmni;

                MALLOC(shmsegs, struct shmid_ds *, s, 
                        M_SHM, M_WAITOK);
                for (i = 0; i < shminfo.shmmni; i++) {
                        shmsegs[i].shm_perm.mode = SHMSEG_FREE;
                        shmsegs[i].shm_perm.seq = 0;
                }
                shm_last_free = 0;
                shm_nused = 0;
                shm_committed = 0;
                shm_inited = 1;
        }
}

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

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

        /* Set the values only if shared memory is not initialised */
        if (!shm_inited) {
                if (error = SYSCTL_IN(req, arg1, sizeof(int)))
                        return(error);
                if (arg1 == &shminfo.shmmax) {
                        if (shminfo.shmmax & PAGE_MASK) {
                                shminfo.shmmax = -1;
                                return(EINVAL);
                        }
                }

                /* Initialize only when all values are set */
                if ((shminfo.shmmax != -1) &&
                        (shminfo.shmmin != -1) &&       
                        (shminfo.shmmni != -1) &&
                        (shminfo.shmseg != -1) &&
                        (shminfo.shmall != -1)) {
                                shminit();
                }
        }
        return(0);
}

SYSCTL_NODE(_kern, KERN_SYSV, sysv, CTLFLAG_RW, 0, "SYSV");

SYSCTL_PROC(_kern_sysv, KSYSV_SHMMAX, shmmax, CTLTYPE_INT | CTLFLAG_RW,
    &shminfo.shmmax, 0, &sysctl_shminfo ,"I","shmmax");

SYSCTL_PROC(_kern_sysv, KSYSV_SHMMIN, shmmin, CTLTYPE_INT | CTLFLAG_RW,
    &shminfo.shmmin, 0, &sysctl_shminfo ,"I","shmmin");

SYSCTL_PROC(_kern_sysv, KSYSV_SHMMNI, shmmni, CTLTYPE_INT | CTLFLAG_RW,
    &shminfo.shmmni, 0, &sysctl_shminfo ,"I","shmmni");

SYSCTL_PROC(_kern_sysv, KSYSV_SHMSEG, shmseg, CTLTYPE_INT | CTLFLAG_RW,
    &shminfo.shmseg, 0, &sysctl_shminfo ,"I","shmseg");

SYSCTL_PROC(_kern_sysv, KSYSV_SHMALL, shmall, CTLTYPE_INT | CTLFLAG_RW,
    &shminfo.shmall, 0, &sysctl_shminfo ,"I","shmall");