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

     /*-
      * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
      * Copyright (c) 2001-2004 Mark R. V. Murray
      * 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
     *    in this position and unchanged.
     * 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 AUTHORS ``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 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.
     *
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/9.0/sys/dev/null/null.c 221855 2011-05-13 19:35:01Z mdf $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/conf.h>
    #include <sys/uio.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/module.h>
    #include <sys/priv.h>
    #include <sys/disk.h>
    #include <sys/bus.h>
    
    #include <machine/bus.h>
    #include <machine/vmparam.h>
    
    /* For use with destroy_dev(9). */
    static struct cdev *null_dev;
    static struct cdev *zero_dev;
    
    static d_write_t null_write;
    static d_ioctl_t null_ioctl;
    static d_read_t zero_read;
    
    static struct cdevsw null_cdevsw = {
            .d_version =    D_VERSION,
            .d_read =       (d_read_t *)nullop,
            .d_write =      null_write,
            .d_ioctl =      null_ioctl,
            .d_name =       "null",
    };
    
    static struct cdevsw zero_cdevsw = {
            .d_version =    D_VERSION,
            .d_read =       zero_read,
            .d_write =      null_write,
            .d_name =       "zero",
            .d_flags =      D_MMAP_ANON,
    };
    
    /* ARGSUSED */
    static int
    null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
    {
            uio->uio_resid = 0;
    
            return (0);
    }
    
    /* ARGSUSED */
    static int
    null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
        int flags __unused, struct thread *td)
    {
            int error;
    
            if (cmd != DIOCSKERNELDUMP)
                    return (ENOIOCTL);
            error = priv_check(td, PRIV_SETDUMPER);
            if (error)
                    return (error);
            return (set_dumper(NULL));
    }
    
    /* ARGSUSED */
    static int
    zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
    {
            void *zbuf;
            ssize_t len;
           int error = 0;
   
           KASSERT(uio->uio_rw == UIO_READ,
               ("Can't be in %s for write", __func__));
           zbuf = __DECONST(void *, zero_region);
           while (uio->uio_resid > 0 && error == 0) {
                   len = uio->uio_resid;
                   if (len > ZERO_REGION_SIZE)
                           len = ZERO_REGION_SIZE;
                   error = uiomove(zbuf, len, uio);
           }
   
           return (error);
   }
   
   /* ARGSUSED */
   static int
   null_modevent(module_t mod __unused, int type, void *data __unused)
   {
           switch(type) {
           case MOD_LOAD:
                   if (bootverbose)
                           printf("null: <null device, zero device>\n");
                   null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
                       NULL, UID_ROOT, GID_WHEEL, 0666, "null");
                   zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
                       NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
                   break;
   
           case MOD_UNLOAD:
                   destroy_dev(null_dev);
                   destroy_dev(zero_dev);
                   break;
   
           case MOD_SHUTDOWN:
                   break;
   
           default:
                   return (EOPNOTSUPP);
           }
   
           return (0);
   }
   
   DEV_MODULE(null, null_modevent, NULL);
   MODULE_VERSION(null, 1);

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