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: releng/8.0/sys/dev/null/null.c 164033 2006-11-06 13:42:10Z rwatson $");
   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/priv.h>
   40 #include <sys/disk.h>
   41 #include <sys/bus.h>
   42 #include <machine/bus.h>
   43 
   44 /* For use with destroy_dev(9). */
   45 static struct cdev *null_dev;
   46 static struct cdev *zero_dev;
   47 
   48 static d_write_t null_write;
   49 static d_ioctl_t null_ioctl;
   50 static d_read_t zero_read;
   51 
   52 #define NULL_MINOR      2
   53 #define ZERO_MINOR      12
   54 
   55 static struct cdevsw null_cdevsw = {
   56         .d_version =    D_VERSION,
   57         .d_read =       (d_read_t *)nullop,
   58         .d_write =      null_write,
   59         .d_ioctl =      null_ioctl,
   60         .d_name =       "null",
   61 };
   62 
   63 static struct cdevsw zero_cdevsw = {
   64         .d_version =    D_VERSION,
   65         .d_read =       zero_read,
   66         .d_write =      null_write,
   67         .d_name =       "zero",
   68         .d_flags =      D_MMAP_ANON,
   69 };
   70 
   71 static void *zbuf;
   72 
   73 /* ARGSUSED */
   74 static int
   75 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
   76 {
   77         uio->uio_resid = 0;
   78 
   79         return (0);
   80 }
   81 
   82 /* ARGSUSED */
   83 static int
   84 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
   85     int flags __unused, struct thread *td)
   86 {
   87         int error;
   88 
   89         if (cmd != DIOCSKERNELDUMP)
   90                 return (ENOIOCTL);
   91         error = priv_check(td, PRIV_SETDUMPER);
   92         if (error)
   93                 return (error);
   94         return (set_dumper(NULL));
   95 }
   96 
   97 /* ARGSUSED */
   98 static int
   99 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
  100 {
  101         int error = 0;
  102 
  103         while (uio->uio_resid > 0 && error == 0)
  104                 error = uiomove(zbuf, MIN(uio->uio_resid, PAGE_SIZE), uio);
  105 
  106         return (error);
  107 }
  108 
  109 /* ARGSUSED */
  110 static int
  111 null_modevent(module_t mod __unused, int type, void *data __unused)
  112 {
  113         switch(type) {
  114         case MOD_LOAD:
  115                 if (bootverbose)
  116                         printf("null: <null device, zero device>\n");
  117                 zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
  118                 null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT,
  119                         GID_WHEEL, 0666, "null");
  120                 zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT,
  121                         GID_WHEEL, 0666, "zero");
  122                 break;
  123 
  124         case MOD_UNLOAD:
  125                 destroy_dev(null_dev);
  126                 destroy_dev(zero_dev);
  127                 free(zbuf, M_TEMP);
  128                 break;
  129 
  130         case MOD_SHUTDOWN:
  131                 break;
  132 
  133         default:
  134                 return (EOPNOTSUPP);
  135         }
  136 
  137         return (0);
  138 }
  139 
  140 DEV_MODULE(null, null_modevent, NULL);
  141 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