NetBSD/sys/kern/kern_lkm.c

/*	$NetBSD: kern_lkm.c,v 1.55 2001/02/24 10:16:46 jdolecek Exp $	*/

/*
 * Copyright (c) 1994 Christopher G. Demetriou
 * Copyright (c) 1992 Terrence R. Lambert.
 * 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 Terrence R. Lambert.
 * 4. The name Terrence R. Lambert may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TERRENCE R. LAMBERT ``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 TERRENCE R. LAMBERT 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.
 */

/*
 * XXX it's not really safe to unload *any* of the types which are
 * currently loadable; e.g. you could unload a syscall which was being
 * blocked in, etc.  In the long term, a solution should be come up
 * with, but "not right now." -- cgd
 */

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/file.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/exec.h>
#include <sys/syscallargs.h>
#include <sys/conf.h>

#include <sys/lkm.h>
#include <sys/syscall.h>
#ifdef DDB
#include <machine/db_machdep.h>
#include <ddb/db_sym.h>
#endif

#include <uvm/uvm_extern.h>

#if !defined(DEBUG) && defined(LKMDEBUG)
# define DEBUG
#endif

#ifdef DEBUG
# define LKMDB_INFO	0x01
# define LKMDB_LOAD	0x02
int	lkmdebug = 0;
#endif

#define PAGESIZE 1024		/* kmem_alloc() allocation quantum */

#define	LKM_ALLOC	0x01
#define	LKM_WANT	0x02

#define	LKMS_IDLE	0x00
#define	LKMS_RESERVED	0x01
#define	LKMS_LOADING	0x02
#define	LKMS_UNLOADING	0x08

static int	lkm_v = 0;
static int	lkm_state = LKMS_IDLE;

#ifndef MAXLKMS
#define	MAXLKMS		20
#endif

static struct lkm_table	lkmods[MAXLKMS];	/* table of loaded modules */
static struct lkm_table	*curp;			/* global for in-progress ops */

static void lkmunreserve __P((void));
static int _lkm_syscall __P((struct lkm_table *, int));
static int _lkm_vfs __P((struct lkm_table *, int));
static int _lkm_dev __P((struct lkm_table *, int));
#ifdef STREAMS
static int _lkm_strmod __P((struct lkm_table *, int));
#endif
static int _lkm_exec __P((struct lkm_table *, int));
static int _lkm_compat __P((struct lkm_table *, int));


/*ARGSUSED*/
int
lkmopen(dev, flag, devtype, p)
	dev_t dev;
	int flag;
	int devtype;
	struct proc *p;
{
	int error;

	if (minor(dev) != 0)
		return (ENXIO);		/* bad minor # */

	/*
	 * Use of the loadable kernel module device must be exclusive; we
	 * may try to remove this restriction later, but it's really no
	 * hardship.
	 */
	while (lkm_v & LKM_ALLOC) {
		if (flag & FNONBLOCK)		/* don't hang */
			return (EBUSY);
		lkm_v |= LKM_WANT;
		/*
		 * Sleep pending unlock; we use tsleep() to allow
		 * an alarm out of the open.
		 */
		error = tsleep((caddr_t)&lkm_v, TTIPRI|PCATCH, "lkmopn", 0);
		if (error)
			return (error);	/* leave LKM_WANT set -- no problem */
	}
	lkm_v |= LKM_ALLOC;

	return (0);		/* pseudo-device open */
}

/*
 * Unreserve the memory associated with the current loaded module; done on
 * a coerced close of the lkm device (close on premature exit of modload)
 * or explicitly by modload as a result of a link failure.
 */
static void
lkmunreserve()
{

	if (lkm_state == LKMS_IDLE)
		return;

	if (curp && curp->syms) {
#ifdef DDB
		db_del_symbol_table(curp->private.lkm_any->lkm_name);
#endif
		uvm_km_free(kernel_map, curp->syms, curp->sym_size);/**/
		curp->syms = 0;
	}
	/*
	 * Actually unreserve the memory
	 */
	if (curp && curp->area) {
		uvm_km_free(kernel_map, curp->area, curp->size);/**/
		curp->area = 0;
	}
	lkm_state = LKMS_IDLE;
}

int
lkmclose(dev, flag, mode, p)
	dev_t dev;
	int flag;
	int mode;
	struct proc *p;
{

	if (!(lkm_v & LKM_ALLOC)) {
#ifdef DEBUG
		if (lkmdebug & LKMDB_INFO)
			printf("LKM: close before open!\n");
#endif	/* DEBUG */
		return (EBADF);
	}

	/* do this before waking the herd... */
	if (curp && !curp->used) {
		/*
		 * If we close before setting used, we have aborted
		 * by way of error or by way of close-on-exit from
		 * a premature exit of "modload".
		 */
		lkmunreserve();	/* coerce state to LKM_IDLE */
	}

	lkm_v &= ~LKM_ALLOC;
	wakeup((caddr_t)&lkm_v);	/* thundering herd "problem" here */

	return (0);		/* pseudo-device closed */
}

/*ARGSUSED*/
int
lkmioctl(dev, cmd, data, flag, p)
	dev_t dev;
	u_long cmd;
	caddr_t data;
	int flag;
	struct proc *p;
{
	int error = 0;
	int i;
	struct lmc_resrv *resrvp;
	struct lmc_loadbuf *loadbufp;
	struct lmc_unload *unloadp;
	struct lmc_stat	 *statp;
	char istr[MAXLKMNAME];

	switch(cmd) {
	case LMRESERV:		/* reserve pages for a module */
	case LMRESERV_O:	/* reserve pages for a module */
		if (securelevel > 0)
			return EPERM;

		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		resrvp = (struct lmc_resrv *)data;

		/*
		 * Find a free slot.
		 */
		for (i = 0; i < MAXLKMS; i++)
			if (!lkmods[i].used)
				break;
		if (i == MAXLKMS) {
			error = ENOMEM;		/* no slots available */
			break;
		}
		curp = &lkmods[i];
		curp->id = i;		/* self reference slot offset */
		curp->ver = (cmd == LMRESERV) ? LKM_VERSION : LKM_OLDVERSION;

		resrvp->slot = i;		/* return slot */

		/*
		 * Get memory for module
		 */
		curp->size = resrvp->size;

		curp->area = uvm_km_alloc(kernel_map, curp->size);/**/

		curp->offset = 0;		/* load offset */

		resrvp->addr = curp->area; /* ret kernel addr */

		if (cmd == LMRESERV && resrvp->sym_size) {
			curp->sym_size = resrvp->sym_size;
			curp->sym_symsize = resrvp->sym_symsize;
			curp->syms = (u_long)uvm_km_alloc(kernel_map, curp->sym_size);/**/
			curp->sym_offset = 0;
			resrvp->sym_addr = curp->syms; /* ret symbol addr */
		} else {
			curp->sym_size = 0;
			curp->syms = 0;
			curp->sym_offset = 0;
			if (cmd == LMRESERV)
				resrvp->sym_addr = 0;
		}

#ifdef DEBUG
		if (lkmdebug & LKMDB_INFO) {
			printf("LKM: LMRESERV (actual   = 0x%08lx)\n",
			    curp->area);
			printf("LKM: LMRESERV (syms     = 0x%08lx)\n",
			       curp->syms);
			printf("LKM: LMRESERV (adjusted = 0x%08lx)\n",
			    trunc_page(curp->area));
		}
#endif /* DEBUG */
		lkm_state = LKMS_RESERVED;
		break;

	case LMLOADBUF:		/* Copy in; stateful, follows LMRESERV */
		if (securelevel > 0)
			return EPERM;

		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		loadbufp = (struct lmc_loadbuf *)data;
		i = loadbufp->cnt;
		if ((lkm_state != LKMS_RESERVED && lkm_state != LKMS_LOADING)
		    || i < 0
		    || i > MODIOBUF
		    || i > curp->size - curp->offset) {
			error = ENOMEM;
			break;
		}

		/* copy in buffer full of data */
		error = copyin(loadbufp->data, 
			       (caddr_t)curp->area + curp->offset, i);
		if (error)
			break;

		if ((curp->offset + i) < curp->size) {
			lkm_state = LKMS_LOADING;
#ifdef DEBUG
			if (lkmdebug & LKMDB_LOAD)
		printf("LKM: LMLOADBUF (loading @ %ld of %ld, i = %d)\n",
			    curp->offset, curp->size, i);
#endif /* DEBUG */
		}
		curp->offset += i;
		break;

	case LMLOADSYMS:	/* Copy in; stateful, follows LMRESERV*/
		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		loadbufp = (struct lmc_loadbuf *)data;
		i = loadbufp->cnt;
		if ((lkm_state != LKMS_LOADING)
		    || i < 0
		    || i > MODIOBUF
		    || i > curp->sym_size - curp->sym_offset) {
			error = ENOMEM;
			break;
		}

		/* copy in buffer full of data*/
		if ((error = copyin(loadbufp->data,
				   (caddr_t)(curp->syms) + curp->sym_offset,
				   i)) != 0)
			break;

		if ((curp->sym_offset + i) < curp->sym_size) {
			lkm_state = LKMS_LOADING;
#ifdef DEBUG
			if (lkmdebug & LKMDB_LOAD)
		printf( "LKM: LMLOADSYMS (loading @ %ld of %ld, i = %d)\n",
			curp->sym_offset, curp->sym_size, i);
#endif	/* DEBUG*/
		}
		curp->sym_offset += i;
		break;

	case LMUNRESRV:		/* discard reserved pages for a module */
		if (securelevel > 0)
			return EPERM;

		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		lkmunreserve();	/* coerce state to LKM_IDLE */
#ifdef DEBUG
		if (lkmdebug & LKMDB_INFO)
			printf("LKM: LMUNRESERV\n");
#endif /* DEBUG */
		break;

	case LMREADY:		/* module loaded: call entry */
		if (securelevel > 0)
			return EPERM;

		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		if (lkm_state != LKMS_LOADING) {
#ifdef DEBUG
			if (lkmdebug & LKMDB_INFO)
				printf("lkm_state is %02x\n", lkm_state);
#endif /* DEBUG */
			return ENXIO;
		}

		if (curp->size - curp->offset > 0) 
			/* The remainder must be bss, so we clear it */
			memset((caddr_t)curp->area + curp->offset, 0,
			       curp->size - curp->offset);

		curp->entry = (int (*) __P((struct lkm_table *, int, int)))
				(*((long *) (data)));

		/* call entry(load)... (assigns "private" portion) */
		error = (*(curp->entry))(curp, LKM_E_LOAD, curp->ver);
		if (error) {
			/*
			 * Module may refuse loading or may have a
			 * version mismatch...
			 */
			lkm_state = LKMS_UNLOADING;	/* for lkmunreserve */
			lkmunreserve();			/* free memory */
			curp->used = 0;			/* free slot */
			break;
		}

		curp->used = 1;
#ifdef DEBUG
		if (lkmdebug & LKMDB_INFO)
			printf("LKM: LMREADY\n");
#endif /* DEBUG */
#ifdef DDB
		if (curp->syms && curp->sym_offset >= curp->sym_size) {
		    db_add_symbol_table((caddr_t)curp->syms,
					(caddr_t)curp->syms + curp->sym_symsize,
					curp->private.lkm_any->lkm_name,
					(caddr_t)curp->syms);
#ifdef DEBUG
		    if (lkmdebug & LKMDB_INFO)
			printf( "DDB symbols added!\n" );
#endif
		}
#endif



		lkm_state = LKMS_IDLE;
		break;

	case LMUNLOAD:		/* unload a module */
		if (securelevel > 0)
			return EPERM;

		if ((flag & FWRITE) == 0) /* only allow this if writing */
			return EPERM;

		unloadp = (struct lmc_unload *)data;

		if ((i = unloadp->id) == -1) {		/* unload by name */
			/*
			 * Copy name and lookup id from all loaded
			 * modules.  May fail.
			 */
		 	error = copyinstr(unloadp->name, istr, MAXLKMNAME-1,
					  NULL);
			if (error)
				break;

			/*
			 * look up id...
			 */
			for (i = 0; i < MAXLKMS; i++) {
				if (!lkmods[i].used)
					continue;
				if (!strcmp(istr,
				        lkmods[i].private.lkm_any->lkm_name))
					break;
			}
		}

		/*
		 * Range check the value; on failure, return EINVAL
		 */
		if (i < 0 || i >= MAXLKMS) {
			error = EINVAL;
			break;
		}

		curp = &lkmods[i];

		if (!curp->used) {
			error = ENOENT;
			break;
		}

		/* call entry(unload) */
		if ((*(curp->entry))(curp, LKM_E_UNLOAD, curp->ver)) {
			error = EBUSY;
			break;
		}

		lkm_state = LKMS_UNLOADING;	/* non-idle for lkmunreserve */
		lkmunreserve();			/* free memory */
		curp->used = 0;			/* free slot */
		break;

	case LMSTAT:		/* stat a module by id/name */
		/* allow readers and writers to stat */

		statp = (struct lmc_stat *)data;

		if ((i = statp->id) == -1) {		/* stat by name */
			/*
			 * Copy name and lookup id from all loaded
			 * modules.
			 */
		 	copystr(statp->name, istr, MAXLKMNAME-1, (size_t *)0);
			/*
			 * look up id...
			 */
			for (i = 0; i < MAXLKMS; i++) {
				if (!lkmods[i].used)
					continue;
				if (!strcmp(istr,
				        lkmods[i].private.lkm_any->lkm_name))
					break;
			}

			if (i == MAXLKMS) {		/* Not found */
				error = ENOENT;
				break;
			}
		}

		/*
		 * Range check the value; on failure, return EINVAL
		 */
		if (i < 0 || i >= MAXLKMS) {
			error = EINVAL;
			break;
		}

		curp = &lkmods[i];

		if (!curp->used) {			/* Not found */
			error = ENOENT;
			break;
		}

		if ((error = (*curp->entry)(curp, LKM_E_STAT, curp->ver)))
			break;

		/*
		 * Copy out stat information for this module...
		 */
		statp->id	= curp->id;
		statp->offset	= curp->private.lkm_any->lkm_offset;
		statp->type	= curp->private.lkm_any->lkm_type;
		statp->area	= curp->area;
		statp->size	= curp->size / PAGESIZE;
		statp->private	= (unsigned long)curp->private.lkm_any;
		statp->ver	= curp->private.lkm_any->lkm_ver;
		copystr(curp->private.lkm_any->lkm_name, 
			  statp->name,
			  MAXLKMNAME - 2,
			  (size_t *)0);

		break;

	default:		/* bad ioctl()... */
		error = ENOTTY;
		break;
	}

	return (error);
}

/*
 * Acts like "nosys" but can be identified in sysent for dynamic call
 * number assignment for a limited number of calls.
 *
 * Place holder for system call slots reserved for loadable modules.
 */
int
sys_lkmnosys(p, v, retval)
	struct proc *p;
	void *v;
	register_t *retval;
{

	return (sys_nosys(p, v, retval));
}

/*
 * Acts like "enodev", but can be identified in cdevsw and bdevsw for
 * dynamic driver major number assignment for a limited number of
 * drivers.
 *
 * Place holder for device switch slots reserved for loadable modules.
 */
int
lkmenodev()
{

	return (enodev());
}

/*
 * A placeholder function for load/unload/stat calls; simply returns zero.
 * Used where people don't want to specify a special function.
 */
int
lkm_nofunc(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{

	return (0);
}

int
lkmexists(lkmtp)
	struct lkm_table *lkmtp;
{
	int i;

	/*
	 * see if name exists...
	 */
	for (i = 0; i < MAXLKMS; i++) {
		/*
		 * An unused module and the one we are testing are not
		 * considered.
		 */
		if (!lkmods[i].used || &lkmods[i] == lkmtp)
			continue;
		if (!strcmp(lkmtp->private.lkm_any->lkm_name,
			lkmods[i].private.lkm_any->lkm_name))
			return (1);		/* already loaded... */
	}

	return (0);		/* module not loaded... */
}

/*
 * For the loadable system call described by the structure pointed to
 * by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_syscall(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_syscall *args = lkmtp->private.lkm_syscall;
	int i;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);

		if ((i = args->lkm_offset) == -1) {	/* auto */
			/*
			 * Search the table looking for a slot...
			 */
			for (i = 0; i < SYS_MAXSYSCALL; i++)
				if (sysent[i].sy_call == sys_lkmnosys)
					break;		/* found it! */
			/* out of allocable slots? */
			if (i == SYS_MAXSYSCALL) {
				error = ENFILE;
				break;
			}
		} else {				/* assign */
			if (i < 0 || i >= SYS_MAXSYSCALL) {
				error = EINVAL;
				break;
			}
		}

		/* save old */
		memcpy(&args->lkm_oldent, &sysent[i], sizeof(struct sysent));

		/* replace with new */
		memcpy(&sysent[i], args->lkm_sysent, sizeof(struct sysent));

		/* done! */
		args->lkm_offset = i;	/* slot in sysent[] */

		break;

	case LKM_E_UNLOAD:
		/* current slot... */
		i = args->lkm_offset;

		/* replace current slot contents with old contents */
		memcpy(&sysent[i], &args->lkm_oldent, sizeof(struct sysent));

		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}

/*
 * For the loadable virtual file system described by the structure pointed
 * to by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_vfs(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_vfs *args = lkmtp->private.lkm_vfs;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);

		/* Establish the file system. */
		if ((error = vfs_attach(args->lkm_vfsops)) != 0)
			return (error);

		/* done! */
		break;

	case LKM_E_UNLOAD:
		/* Disestablish the file system. */
		if ((error = vfs_detach(args->lkm_vfsops)) != 0)
			return (error);
		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}

/*
 * For the loadable device driver described by the structure pointed to
 * by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_dev(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_dev *args = lkmtp->private.lkm_dev;
	int i;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);

		switch(args->lkm_devtype) {
		case LM_DT_BLOCK:
			if ((i = args->lkm_offset) == -1) {	/* auto */
				/*
				 * Search the table looking for a slot...
				 */
				for (i = 0; i < nblkdev; i++)
					if (bdevsw[i].d_open == 
					    (dev_type_open((*))) lkmenodev)
						break;		/* found it! */
				/* out of allocable slots? */
				if (i == nblkdev) {
					error = ENFILE;
					break;
				}
			} else {				/* assign */
				if (i < 0 || i >= nblkdev) {
					error = EINVAL;
					break;
				}
			}

			/* save old */
			memcpy(&args->lkm_olddev.bdev, &bdevsw[i], sizeof(struct bdevsw));

			/* replace with new */
			memcpy(&bdevsw[i], args->lkm_dev.bdev, sizeof(struct bdevsw));

			/* done! */
			args->lkm_offset = i;	/* slot in bdevsw[] */
			break;

		case LM_DT_CHAR:
			if ((i = args->lkm_offset) == -1) {	/* auto */
				/*
				 * Search the table looking for a slot...
				 */
				for (i = 0; i < nchrdev; i++)
					if (cdevsw[i].d_open ==
					    (dev_type_open((*))) lkmenodev)
						break;		/* found it! */
				/* out of allocable slots? */
				if (i == nchrdev) {
					error = ENFILE;
					break;
				}
			} else {				/* assign */
				if (i < 0 || i >= nchrdev) {
					error = EINVAL;
					break;
				}
			}

			/* save old */
			memcpy(&args->lkm_olddev.cdev, &cdevsw[i], sizeof(struct cdevsw));

			/* replace with new */
			memcpy(&cdevsw[i], args->lkm_dev.cdev, sizeof(struct cdevsw));

			/* done! */
			args->lkm_offset = i;	/* slot in cdevsw[] */

			break;

		default:
			error = ENODEV;
			break;
		}
		break;

	case LKM_E_UNLOAD:
		/* current slot... */
		i = args->lkm_offset;

		switch(args->lkm_devtype) {
		case LM_DT_BLOCK:
			/* replace current slot contents with old contents */
			memcpy(&bdevsw[i], &args->lkm_olddev.bdev, sizeof(struct bdevsw));
			break;

		case LM_DT_CHAR:
			/* replace current slot contents with old contents */
			memcpy(&cdevsw[i], &args->lkm_olddev.cdev, sizeof(struct cdevsw));
			break;

		default:
			error = ENODEV;
			break;
		}
		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}

#ifdef STREAMS
/*
 * For the loadable streams module described by the structure pointed to
 * by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_strmod(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_strmod *args = lkmtp->private.lkm_strmod;
	int i;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);
		break;

	case LKM_E_UNLOAD:
		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}
#endif	/* STREAMS */

/*
 * For the loadable execution class described by the structure pointed to
 * by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_exec(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_exec *args = lkmtp->private.lkm_exec;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);

		/* this would also fill in the emulation pointer in
		 * args->lkm_execsw */
		error = exec_add(args->lkm_execsw, args->lkm_emul);
		break;

	case LKM_E_UNLOAD:
		error = exec_remove(args->lkm_execsw);
		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}

/*
 * For the loadable compat/emulation class described by the structure pointed to
 * by lkmtp, load/unload/stat it depending on the cmd requested.
 */
static int
_lkm_compat(lkmtp, cmd)
	struct lkm_table *lkmtp;
	int cmd;
{
	struct lkm_compat *args = lkmtp->private.lkm_compat;
	int error = 0;

	switch(cmd) {
	case LKM_E_LOAD:
		/* don't load twice! */
		if (lkmexists(lkmtp))
			return (EEXIST);

		error = emul_register(args->lkm_compat, 0);
		break;

	case LKM_E_UNLOAD:
		error = emul_unregister(args->lkm_compat->e_name);
		break;

	case LKM_E_STAT:	/* no special handling... */
		break;
	}

	return (error);
}

/*
 * This code handles the per-module type "wiring-in" of loadable modules
 * into existing kernel tables.  For "LM_MISC" modules, wiring and unwiring
 * is assumed to be done in their entry routines internal to the module
 * itself.
 */
int
lkmdispatch(lkmtp, cmd)
	struct lkm_table *lkmtp;	
	int cmd;
{
	int error = 0;		/* default = success */
#ifdef DEBUG
	if (lkmdebug & LKMDB_INFO)
		printf( "lkmdispatch: %p %d\n", lkmtp, cmd );
#endif

	switch(lkmtp->private.lkm_any->lkm_type) {
	case LM_SYSCALL:
		error = _lkm_syscall(lkmtp, cmd);
		break;

	case LM_VFS:
		error = _lkm_vfs(lkmtp, cmd);
		break;

	case LM_DEV:
		error = _lkm_dev(lkmtp, cmd);
		break;

#ifdef STREAMS
	case LM_STRMOD:
	    {
		struct lkm_strmod *args = lkmtp->private.lkm_strmod;
	    }
		break;

#endif	/* STREAMS */

	case LM_EXEC:
		error = _lkm_exec(lkmtp, cmd);
		break;

	case LM_COMPAT:
		error = _lkm_compat(lkmtp, cmd);
		break;

	case LM_MISC:	/* ignore content -- no "misc-specific" procedure */
		break;

	default:
		error = ENXIO;	/* unknown type */
		break;
	}

	return (error);
}