[apple/xnu.git] / bsd / kern / tty_tty.c

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 * Copyright (c) 1997-2013 Apple Computer, Inc. All rights reserved.
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 * terms of an Apple operating system software license agreement.
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 * Please obtain a copy of the License at
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/*-
 * Copyright (c) 1982, 1986, 1991, 1993
 *      The Regents of the University of California.  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.
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 *
 *      @(#)tty_tty.c   8.2 (Berkeley) 9/23/93
 */

/*
 * Indirect driver for controlling tty.
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/ioctl.h>
#include <sys/proc_internal.h>
#include <sys/tty.h>
#include <sys/vnode_internal.h>
#include <sys/file_internal.h>
#include <sys/kauth.h>

/* Forward declarations for cdevsw[] entry */
/* XXX we should consider making these static */
int cttyopen(dev_t dev, int flag, int mode, proc_t p);
int cttyread(dev_t dev, struct uio *uio, int flag);
int cttywrite(dev_t dev, struct uio *uio, int flag);
int cttyioctl(dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p);
int cttyselect(dev_t dev, int flag, void* wql, proc_t p);
static vnode_t cttyvp(proc_t p);

int
cttyopen(dev_t dev, int flag, __unused int mode, proc_t p)
{
        vnode_t ttyvp = cttyvp(p);
        struct vfs_context context;
        int error = 0;
        int cttyflag, doclose = 0;
        struct session *sessp;

        if (ttyvp == NULL) {
                return ENXIO;
        }

        context.vc_thread = current_thread();
        context.vc_ucred = kauth_cred_proc_ref(p);

        sessp = proc_session(p);
        session_lock(sessp);
        cttyflag = sessp->s_flags & S_CTTYREF;
        session_unlock(sessp);

        /*
         * A little hack--this device, used by many processes,
         * happens to do an open on another device, which can
         * cause unhappiness if the second-level open blocks indefinitely
         * (as could be the case if the master side has hung up).  Since
         * we know that this driver doesn't care about the serializing
         * opens and closes, we can drop the lock. To avoid opencount leak,
         * open the vnode only for the first time.
         */
        if (cttyflag == 0) {
                devsw_unlock(dev, S_IFCHR);
                error = VNOP_OPEN(ttyvp, flag, &context);
                devsw_lock(dev, S_IFCHR);

                if (error) {
                        goto out;
                }

                /*
                 * If S_CTTYREF is set, some other thread did an open
                 * and was able to set the flag, now perform a close, else
                 * set the flag.
                 */
                session_lock(sessp);
                if (cttyflag == (sessp->s_flags & S_CTTYREF)) {
                        sessp->s_flags |= S_CTTYREF;
                } else {
                        doclose = 1;
                }
                session_unlock(sessp);

                /*
                 * We have to take a reference here to make sure a close
                 * gets called during revoke. Note that once a controlling
                 * tty gets opened by this driver, the only way close will
                 * get called is when the session leader , whose controlling
                 * tty is ttyvp, exits and vnode is revoked. We cannot
                 * redirect close from this driver because underlying controlling
                 * terminal might change and close may get redirected to a
                 * wrong vnode causing panic.
                 */
                if (doclose) {
                        devsw_unlock(dev, S_IFCHR);
                        VNOP_CLOSE(ttyvp, flag, &context);
                        devsw_lock(dev, S_IFCHR);
                } else {
                        error = vnode_ref(ttyvp);
                }
        }
out:
        session_rele(sessp);

        vnode_put(ttyvp);
        kauth_cred_unref(&context.vc_ucred);

        return error;
}

int
cttyread(__unused dev_t dev, struct uio *uio, int flag)
{
        vnode_t ttyvp = cttyvp(current_proc());
        struct vfs_context context;
        int error;

        if (ttyvp == NULL) {
                return EIO;
        }

        context.vc_thread = current_thread();
        context.vc_ucred = NOCRED;

        error = VNOP_READ(ttyvp, uio, flag, &context);
        vnode_put(ttyvp);

        return error;
}

int
cttywrite(__unused dev_t dev, struct uio *uio, int flag)
{
        vnode_t ttyvp = cttyvp(current_proc());
        struct vfs_context context;
        int error;

        if (ttyvp == NULL) {
                return EIO;
        }

        context.vc_thread = current_thread();
        context.vc_ucred = NOCRED;

        error = VNOP_WRITE(ttyvp, uio, flag, &context);
        vnode_put(ttyvp);

        return error;
}

int
cttyioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flag, proc_t p)
{
        vnode_t ttyvp = cttyvp(current_proc());
        struct vfs_context context;
        struct session *sessp;
        int error = 0;

        if (ttyvp == NULL) {
                return EIO;
        }
        if (cmd == TIOCSCTTY) {  /* don't allow controlling tty to be set    */
                error = EINVAL; /* to controlling tty -- infinite recursion */
                goto out;
        }
        if (cmd == TIOCNOTTY) {
                sessp = proc_session(p);
                if (!SESS_LEADER(p, sessp)) {
                        OSBitAndAtomic(~((uint32_t)P_CONTROLT), &p->p_flag);
                        if (sessp != SESSION_NULL) {
                                session_rele(sessp);
                        }
                        error = 0;
                        goto out;
                } else {
                        if (sessp != SESSION_NULL) {
                                session_rele(sessp);
                        }
                        error = EINVAL;
                        goto out;
                }
        }
        context.vc_thread = current_thread();
        context.vc_ucred = NOCRED;

        error = VNOP_IOCTL(ttyvp, cmd, addr, flag, &context);
out:
        vnode_put(ttyvp);
        return error;
}

int
cttyselect(__unused dev_t dev, int flag, void* wql, __unused proc_t p)
{
        vnode_t ttyvp = cttyvp(current_proc());
        struct vfs_context context;
        int error;

        context.vc_thread = current_thread();
        context.vc_ucred = NOCRED;

        if (ttyvp == NULL) {
                return 1;     /* try operation to get EOF/failure */
        }
        error = VNOP_SELECT(ttyvp, flag, FREAD | FWRITE, wql, &context);
        vnode_put(ttyvp);
        return error;
}

/* This returns vnode with ioref */
static vnode_t
cttyvp(proc_t p)
{
        vnode_t vp;
        int vid;
        struct session *sessp;

        sessp = proc_session(p);

        session_lock(sessp);
        vp = (p->p_flag & P_CONTROLT ? sessp->s_ttyvp : NULLVP);
        vid = sessp->s_ttyvid;
        session_unlock(sessp);

        session_rele(sessp);

        if (vp != NULLVP) {
                /* cannot get an IO reference, return NULLVP */
                if (vnode_getwithvid(vp, vid) != 0) {
                        vp = NULLVP;
                }
        }
        return vp;
}