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/kern/tty_tty.c

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    1 /*-
    2  * Copyright (c) 2003 Poul-Henning Kamp.  All rights reserved.
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  *
   13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   23  * SUCH DAMAGE.
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 __FBSDID("$FreeBSD$");
   28 
   29 #include <sys/param.h>
   30 #include <sys/systm.h>
   31 #include <sys/conf.h>
   32 #include <sys/kernel.h>
   33 #include <sys/proc.h>
   34 #include <sys/sx.h>
   35 #include <sys/vnode.h>
   36 
   37 #include <fs/devfs/devfs.h>
   38 #include <fs/devfs/devfs_int.h>
   39 
   40 static  d_open_t        cttyopen;
   41 
   42 static struct cdevsw ctty_cdevsw = {
   43         .d_version =    D_VERSION,
   44         .d_open =       cttyopen,
   45         .d_name =       "ctty",
   46         .d_flags =      D_TTY | D_NEEDGIANT,
   47 };
   48 
   49 static struct cdev *ctty;
   50 
   51 static  int
   52 cttyopen(struct cdev *dev, int flag, int mode, struct thread *td)
   53 {
   54 
   55         return (ENXIO);
   56 }
   57 
   58 static void
   59 ctty_clone(void *arg, struct ucred *cred, char *name, int namelen,
   60     struct cdev **dev)
   61 {
   62 
   63         if (*dev != NULL)
   64                 return;
   65         if (strcmp(name, "tty"))
   66                 return;
   67         sx_sunlock(&clone_drain_lock);
   68         mtx_lock(&Giant);
   69         sx_slock(&proctree_lock);
   70         sx_slock(&clone_drain_lock);
   71         dev_lock();
   72         if (!(curthread->td_proc->p_flag & P_CONTROLT))
   73                 *dev = ctty;
   74         else if (curthread->td_proc->p_session->s_ttyvp == NULL)
   75                 *dev = ctty;
   76         else if (curthread->td_proc->p_session->s_ttyvp->v_type == VBAD ||
   77             curthread->td_proc->p_session->s_ttyvp->v_rdev == NULL) {
   78                 /* e.g. s_ttyvp was revoked */
   79                 *dev = ctty;
   80         } else
   81                 *dev = curthread->td_proc->p_session->s_ttyvp->v_rdev;
   82         dev_refl(*dev);
   83         dev_unlock();
   84         sx_sunlock(&proctree_lock);
   85         mtx_unlock(&Giant);
   86 }
   87 
   88 static void
   89 ctty_drvinit(void *unused)
   90 {
   91 
   92         EVENTHANDLER_REGISTER(dev_clone, ctty_clone, 0, 1000);
   93         ctty = make_dev(&ctty_cdevsw, 0, 0, 0, 0666, "ctty");
   94 }
   95 
   96 SYSINIT(cttydev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,ctty_drvinit,NULL)

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