The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/dev/null/null.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
    5  * Copyright (c) 2001-2004 Mark R. V. Murray
    6  * Copyright (c) 2014 Eitan Adler
    7  * All rights reserved.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer
   14  *    in this position and unchanged.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
   20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   29  *
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD$");
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/conf.h>
   38 #include <sys/uio.h>
   39 #include <sys/kernel.h>
   40 #include <sys/malloc.h>
   41 #include <sys/module.h>
   42 #include <sys/disk.h>
   43 #include <sys/bus.h>
   44 #include <sys/filio.h>
   45 
   46 #include <machine/bus.h>
   47 #include <machine/vmparam.h>
   48 
   49 /* For use with destroy_dev(9). */
   50 static struct cdev *full_dev;
   51 static struct cdev *null_dev;
   52 static struct cdev *zero_dev;
   53 
   54 static d_write_t full_write;
   55 static d_write_t null_write;
   56 static d_ioctl_t null_ioctl;
   57 static d_ioctl_t zero_ioctl;
   58 static d_read_t zero_read;
   59 
   60 static struct cdevsw full_cdevsw = {
   61         .d_version =    D_VERSION,
   62         .d_read =       zero_read,
   63         .d_write =      full_write,
   64         .d_ioctl =      zero_ioctl,
   65         .d_name =       "full",
   66 };
   67 
   68 static struct cdevsw null_cdevsw = {
   69         .d_version =    D_VERSION,
   70         .d_read =       (d_read_t *)nullop,
   71         .d_write =      null_write,
   72         .d_ioctl =      null_ioctl,
   73         .d_name =       "null",
   74 };
   75 
   76 static struct cdevsw zero_cdevsw = {
   77         .d_version =    D_VERSION,
   78         .d_read =       zero_read,
   79         .d_write =      null_write,
   80         .d_ioctl =      zero_ioctl,
   81         .d_name =       "zero",
   82         .d_flags =      D_MMAP_ANON,
   83 };
   84 
   85 
   86 
   87 /* ARGSUSED */
   88 static int
   89 full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused)
   90 {
   91 
   92         return (ENOSPC);
   93 }
   94 
   95 /* ARGSUSED */
   96 static int
   97 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
   98 {
   99         uio->uio_resid = 0;
  100 
  101         return (0);
  102 }
  103 
  104 /* ARGSUSED */
  105 static int
  106 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
  107     int flags __unused, struct thread *td)
  108 {
  109         int error;
  110 
  111         error = 0;
  112         switch (cmd) {
  113 #ifdef COMPAT_FREEBSD11
  114         case DIOCSKERNELDUMP_FREEBSD11:
  115 #endif
  116         case DIOCSKERNELDUMP:
  117                 error = clear_dumper(td);
  118                 break;
  119         case FIONBIO:
  120                 break;
  121         case FIOASYNC:
  122                 if (*(int *)data != 0)
  123                         error = EINVAL;
  124                 break;
  125         default:
  126                 error = ENOIOCTL;
  127         }
  128         return (error);
  129 }
  130 
  131 /* ARGSUSED */
  132 static int
  133 zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
  134            int flags __unused, struct thread *td)
  135 {
  136         int error;
  137         error = 0;
  138 
  139         switch (cmd) {
  140         case FIONBIO:
  141                 break;
  142         case FIOASYNC:
  143                 if (*(int *)data != 0)
  144                         error = EINVAL;
  145                 break;
  146         default:
  147                 error = ENOIOCTL;
  148         }
  149         return (error);
  150 }
  151 
  152 
  153 /* ARGSUSED */
  154 static int
  155 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
  156 {
  157         void *zbuf;
  158         ssize_t len;
  159         int error = 0;
  160 
  161         KASSERT(uio->uio_rw == UIO_READ,
  162             ("Can't be in %s for write", __func__));
  163         zbuf = __DECONST(void *, zero_region);
  164         while (uio->uio_resid > 0 && error == 0) {
  165                 len = uio->uio_resid;
  166                 if (len > ZERO_REGION_SIZE)
  167                         len = ZERO_REGION_SIZE;
  168                 error = uiomove(zbuf, len, uio);
  169         }
  170 
  171         return (error);
  172 }
  173 
  174 /* ARGSUSED */
  175 static int
  176 null_modevent(module_t mod __unused, int type, void *data __unused)
  177 {
  178         switch(type) {
  179         case MOD_LOAD:
  180                 if (bootverbose)
  181                         printf("null: <full device, null device, zero device>\n");
  182                 full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0,
  183                     NULL, UID_ROOT, GID_WHEEL, 0666, "full");
  184                 null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
  185                     NULL, UID_ROOT, GID_WHEEL, 0666, "null");
  186                 zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
  187                     NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
  188                 break;
  189 
  190         case MOD_UNLOAD:
  191                 destroy_dev(full_dev);
  192                 destroy_dev(null_dev);
  193                 destroy_dev(zero_dev);
  194                 break;
  195 
  196         case MOD_SHUTDOWN:
  197                 break;
  198 
  199         default:
  200                 return (EOPNOTSUPP);
  201         }
  202 
  203         return (0);
  204 }
  205 
  206 DEV_MODULE(null, null_modevent, NULL);
  207 MODULE_VERSION(null, 1);

Cache object: 55080bc666c36f37a5f4e86e12554e71


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