xnu-344.49.tar.gz

[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");