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devnull.c revision 1.7.2.2 
      1 /*	$NetBSD: devnull.c,v 1.7.2.2 2016/07/19 06:27:00 pgoyette Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2009 Antti Kantee.  All Rights Reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
     16  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     18  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     21  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  */
     27 
     28 /*
     29  * /dev/null, the infamous bytesink.
     30  *
     31  * I can't imagine it being very different in the rump kernel than in
     32  * the host kernel.  But nonetheless it serves as a simple example.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 __KERNEL_RCSID(0, "$NetBSD: devnull.c,v 1.7.2.2 2016/07/19 06:27:00 pgoyette Exp $");
     37 
     38 #include <sys/param.h>
     39 #include <sys/conf.h>
     40 #include <sys/device.h>
     41 #include <sys/stat.h>
     42 #include <sys/localcount.h>
     43 
     44 #include <rump-sys/vfs.h>
     45 
     46 static dev_type_open(rump_devnullopen);
     47 static dev_type_read(rump_devnullrw);
     48 
     49 static struct cdevsw null_cdevsw = {
     50 	LOCALCOUNT_INITIALIZER
     51 	.d_open = rump_devnullopen,
     52 	.d_close = nullclose,
     53 	.d_read = rump_devnullrw,
     54 	.d_write = rump_devnullrw,
     55 	.d_ioctl = noioctl,
     56 	.d_stop = nostop,
     57 	.d_tty = notty,
     58 	.d_poll = nopoll,
     59 	.d_mmap = nommap,
     60 	.d_kqfilter = nokqfilter,
     61 	.d_discard = nodiscard,
     62 	.d_flag = D_OTHER | D_MPSAFE
     63 };
     64 
     65 int
     66 rump_devnull_init()
     67 {
     68 	devmajor_t null_bmaj, null_cmaj;
     69 	int error;
     70 
     71 	null_bmaj = null_cmaj = NODEVMAJOR;
     72 	error = devsw_attach("null", NULL, &null_bmaj, &null_cdevsw,&null_cmaj);
     73 	KASSERT(error || null_cmaj == 2);
     74 
     75 	error = rump_vfs_makeonedevnode(S_IFCHR,
     76 	    "/dev/null", null_cmaj, DEV_NULL);
     77 	if (error)
     78 		return error;
     79 	return rump_vfs_makeonedevnode(S_IFCHR,
     80 	    "/dev/zero", null_cmaj, DEV_ZERO);
     81 }
     82 
     83 static int
     84 rump_devnullopen(dev_t dev, int flag, int mode, struct lwp *l)
     85 {
     86 
     87 	if (minor(dev) == DEV_ZERO || minor(dev) == DEV_NULL)
     88 		return 0;
     89 	return ENXIO;
     90 }
     91 
     92 static int
     93 rump_devnullrw(dev_t dev, struct uio *uio, int flags)
     94 {
     95 	char zeros[512];
     96 	int error;
     97 
     98 	switch (minor(dev)) {
     99 	case DEV_NULL:
    100 		if (uio->uio_rw == UIO_WRITE)
    101 			uio->uio_resid = 0;
    102 		break;
    103 	case DEV_ZERO:
    104 		if (uio->uio_rw == UIO_WRITE) {
    105 			uio->uio_resid = 0;
    106 			break;
    107 		}
    108 		memset(zeros, 0, sizeof(zeros));
    109 		while (uio->uio_resid > 0) {
    110 			error = uiomove(zeros,
    111 			    min(sizeof(zeros), uio->uio_resid), uio);
    112 			if (error)
    113 				return error;
    114 		}
    115 		break;
    116 	default:
    117 		return ENXIO; /* how? */
    118 	}
    119 
    120 	return 0;
    121 }
    122