null.c

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    1 /*-
    2  * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
    3  * Copyright (c) 2001-2004 Mark R. V. Murray
    4  * 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  *    in this position and unchanged.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
   17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  *
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD$");
   31 
   32 #include <sys/param.h>
   33 #include <sys/systm.h>
   34 #include <sys/conf.h>
   35 #include <sys/uio.h>
   36 #include <sys/kernel.h>
   37 #include <sys/malloc.h>
   38 #include <sys/module.h>
   39 #include <sys/disk.h>
   40 #include <sys/bus.h>
   41 #include <machine/bus.h>
   42 
   43 /* For use with destroy_dev(9). */
   44 static struct cdev *null_dev;
   45 static struct cdev *zero_dev;
   46 
   47 static d_write_t null_write;
   48 static d_ioctl_t null_ioctl;
   49 static d_read_t zero_read;
   50 
   51 #define NULL_MINOR      2
   52 #define ZERO_MINOR      12
   53 
   54 static struct cdevsw null_cdevsw = {
   55         .d_version =    D_VERSION,
   56         .d_read =       (d_read_t *)nullop,
   57         .d_write =      null_write,
   58         .d_ioctl =      null_ioctl,
   59         .d_name =       "null",
   60 };
   61 
   62 static struct cdevsw zero_cdevsw = {
   63         .d_version =    D_VERSION,
   64         .d_read =       zero_read,
   65         .d_write =      null_write,
   66         .d_name =       "zero",
   67         .d_flags =      D_MMAP_ANON,
   68 };
   69 
   70 static void *zbuf;
   71 
   72 /* ARGSUSED */
   73 static int
   74 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
   75 {
   76         uio->uio_resid = 0;
   77 
   78         return (0);
   79 }
   80 
   81 /* ARGSUSED */
   82 static int
   83 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
   84     int flags __unused, struct thread *td)
   85 {
   86         int error;
   87 
   88         if (cmd != DIOCSKERNELDUMP)
   89                 return (ENOIOCTL);
   90         error = suser(td);
   91         if (error)
   92                 return (error);
   93         return (set_dumper(NULL));
   94 }
   95 
   96 /* ARGSUSED */
   97 static int
   98 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
   99 {
  100         int error = 0;
  101 
  102         while (uio->uio_resid > 0 && error == 0)
  103                 error = uiomove(zbuf, MIN(uio->uio_resid, PAGE_SIZE), uio);
  104 
  105         return (error);
  106 }
  107 
  108 /* ARGSUSED */
  109 static int
  110 null_modevent(module_t mod __unused, int type, void *data __unused)
  111 {
  112         switch(type) {
  113         case MOD_LOAD:
  114                 if (bootverbose)
  115                         printf("null: <null device, zero device>\n");
  116                 zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
  117                 null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT,
  118                         GID_WHEEL, 0666, "null");
  119                 zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT,
  120                         GID_WHEEL, 0666, "zero");
  121                 break;
  122 
  123         case MOD_UNLOAD:
  124                 destroy_dev(null_dev);
  125                 destroy_dev(zero_dev);
  126                 free(zbuf, M_TEMP);
  127                 break;
  128 
  129         case MOD_SHUTDOWN:
  130                 break;
  131 
  132         default:
  133                 return (EOPNOTSUPP);
  134         }
  135 
  136         return (0);
  137 }
  138 
  139 DEV_MODULE(null, null_modevent, NULL);
  140 MODULE_VERSION(null, 1);

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

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