xref: /src/sys/rump/librump/rumpvfs/devnull.c

/*	$NetBSD: devnull.c,v 1.8 2018/09/03 16:29:37 riastradh Exp $	*/

/*
 * Copyright (c) 2009 Antti Kantee.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR OR CONTRIBUTORS 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.
 */

/*
 * /dev/null, the infamous bytesink.
 *
 * I can't imagine it being very different in the rump kernel than in
 * the host kernel.  But nonetheless it serves as a simple example.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: devnull.c,v 1.8 2018/09/03 16:29:37 riastradh Exp $");

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/stat.h>

#include <rump-sys/vfs.h>

static dev_type_open(rump_devnullopen);
static dev_type_read(rump_devnullrw);

static struct cdevsw null_cdevsw = {
	.d_open = rump_devnullopen,
	.d_close = nullclose,
	.d_read = rump_devnullrw,
	.d_write = rump_devnullrw,
	.d_ioctl = noioctl,
	.d_stop = nostop,
	.d_tty = notty,
	.d_poll = nopoll,
	.d_mmap = nommap,
	.d_kqfilter = nokqfilter,
	.d_discard = nodiscard,
	.d_flag = D_OTHER | D_MPSAFE
};

int
rump_devnull_init()
{
	devmajor_t null_bmaj, null_cmaj;
	int error;

	null_bmaj = null_cmaj = NODEVMAJOR;
	error = devsw_attach("null", NULL, &null_bmaj, &null_cdevsw,&null_cmaj);
	KASSERT(error || null_cmaj == 2);

	error = rump_vfs_makeonedevnode(S_IFCHR,
	    "/dev/null", null_cmaj, DEV_NULL);
	if (error)
		return error;
	return rump_vfs_makeonedevnode(S_IFCHR,
	    "/dev/zero", null_cmaj, DEV_ZERO);
}

static int
rump_devnullopen(dev_t dev, int flag, int mode, struct lwp *l)
{

	if (minor(dev) == DEV_ZERO || minor(dev) == DEV_NULL)
		return 0;
	return ENXIO;
}

static int
rump_devnullrw(dev_t dev, struct uio *uio, int flags)
{
	char zeros[512];
	int error;

	switch (minor(dev)) {
	case DEV_NULL:
		if (uio->uio_rw == UIO_WRITE)
			uio->uio_resid = 0;
		break;
	case DEV_ZERO:
		if (uio->uio_rw == UIO_WRITE) {
			uio->uio_resid = 0;
			break;
		}
		memset(zeros, 0, sizeof(zeros));
		while (uio->uio_resid > 0) {
			error = uiomove(zeros,
			    uimin(sizeof(zeros), uio->uio_resid), uio);
			if (error)
				return error;
		}
		break;
	default:
		return ENXIO; /* how? */
	}

	return 0;
}