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tty_ptm.c revision 1.21 
      1 /*	$NetBSD: tty_ptm.c,v 1.21 2007/11/26 19:02:05 pooka Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2004 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     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  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *        This product includes software developed by the NetBSD
     18  *        Foundation, Inc. and its contributors.
     19  * 4. Neither the name of The NetBSD Foundation nor the names of its
     20  *    contributors may be used to endorse or promote products derived
     21  *    from this software without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     24  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     25  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     26  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     27  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     28  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     29  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     30  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     31  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     32  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     33  * POSSIBILITY OF SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 __KERNEL_RCSID(0, "$NetBSD: tty_ptm.c,v 1.21 2007/11/26 19:02:05 pooka Exp $");
     38 
     39 #include "opt_ptm.h"
     40 
     41 /* pty multiplexor driver /dev/ptm{,x} */
     42 
     43 #include <sys/param.h>
     44 #include <sys/systm.h>
     45 #include <sys/ioctl.h>
     46 #include <sys/proc.h>
     47 #include <sys/tty.h>
     48 #include <sys/stat.h>
     49 #include <sys/file.h>
     50 #include <sys/uio.h>
     51 #include <sys/kernel.h>
     52 #include <sys/vnode.h>
     53 #include <sys/namei.h>
     54 #include <sys/signalvar.h>
     55 #include <sys/filedesc.h>
     56 #include <sys/conf.h>
     57 #include <sys/poll.h>
     58 #include <sys/malloc.h>
     59 #include <sys/pty.h>
     60 #include <sys/kauth.h>
     61 
     62 #ifdef DEBUG_PTM
     63 #define DPRINTF(a)	printf a
     64 #else
     65 #define DPRINTF(a)
     66 #endif
     67 
     68 #ifdef NO_DEV_PTM
     69 const struct cdevsw ptm_cdevsw = {
     70 	noopen, noclose, noread, nowrite, noioctl,
     71 	nostop, notty, nopoll, nommap, nokqfilter, D_TTY
     72 };
     73 #else
     74 
     75 static struct ptm_pty *ptm;
     76 int pts_major, ptc_major;
     77 
     78 static dev_t pty_getfree(void);
     79 static int pty_alloc_master(struct lwp *, int *, dev_t *);
     80 static int pty_alloc_slave(struct lwp *, int *, dev_t);
     81 
     82 void ptmattach(int);
     83 
     84 dev_t
     85 pty_makedev(char ms, int minor)
     86 {
     87 	return makedev(ms == 't' ? pts_major : ptc_major, minor);
     88 }
     89 
     90 
     91 static dev_t
     92 pty_getfree(void)
     93 {
     94 	extern kmutex_t pt_softc_mutex;
     95 	int i;
     96 
     97 	mutex_enter(&pt_softc_mutex);
     98 	for (i = 0; i < npty; i++) {
     99 		if (pty_isfree(i, 0))
    100 			break;
    101 	}
    102 	mutex_exit(&pt_softc_mutex);
    103 	return pty_makedev('t', i);
    104 }
    105 
    106 /*
    107  * Hacked up version of vn_open. We _only_ handle ptys and only open
    108  * them with FREAD|FWRITE and never deal with creat or stuff like that.
    109  *
    110  * We need it because we have to fake up root credentials to open the pty.
    111  */
    112 int
    113 pty_vn_open(struct vnode *vp, struct lwp *l)
    114 {
    115 	int error;
    116 
    117 	if (vp->v_type != VCHR) {
    118 		vput(vp);
    119 		return EINVAL;
    120 	}
    121 
    122 	error = VOP_OPEN(vp, FREAD|FWRITE, lwp0.l_cred);
    123 
    124 	if (error) {
    125 		vput(vp);
    126 		return error;
    127 	}
    128 
    129 	vp->v_writecount++;
    130 
    131 	return 0;
    132 }
    133 
    134 static int
    135 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev)
    136 {
    137 	int error;
    138 	struct file *fp;
    139 	struct vnode *vp;
    140 	int md;
    141 
    142 	if ((error = falloc(l, &fp, fd)) != 0) {
    143 		DPRINTF(("falloc %d\n", error));
    144 		return error;
    145 	}
    146 retry:
    147 	/* Find and open a free master pty. */
    148 	*dev = pty_getfree();
    149 	md = minor(*dev);
    150 	if ((error = pty_check(md)) != 0) {
    151 		DPRINTF(("pty_check %d\n", error));
    152 		goto bad;
    153 	}
    154 	if (ptm == NULL) {
    155 		DPRINTF(("no ptm\n"));
    156 		error = EOPNOTSUPP;
    157 		goto bad;
    158 	}
    159 	if ((error = (*ptm->allocvp)(ptm, l, &vp, *dev, 'p')) != 0) {
    160 		DPRINTF(("pty_allocvp %d\n", error));
    161 		goto bad;
    162 	}
    163 
    164 	if ((error = pty_vn_open(vp, l)) != 0) {
    165 		DPRINTF(("pty_vn_open %d\n", error));
    166 		/*
    167 		 * Check if the master open failed because we lost
    168 		 * the race to grab it.
    169 		 */
    170 		if (error != EIO)
    171 			goto bad;
    172 		error = !pty_isfree(md, 1);
    173 		DPRINTF(("pty_isfree %d\n", error));
    174 		if (error)
    175 			goto retry;
    176 		else
    177 			goto bad;
    178 	}
    179 	fp->f_flag = FREAD|FWRITE;
    180 	fp->f_type = DTYPE_VNODE;
    181 	fp->f_ops = &vnops;
    182 	fp->f_data = vp;
    183 	VOP_UNLOCK(vp, 0);
    184 	FILE_SET_MATURE(fp);
    185 	FILE_UNUSE(fp, l);
    186 	return 0;
    187 bad:
    188 	FILE_UNUSE(fp, l);
    189 	fdremove(l->l_proc->p_fd, *fd);
    190 	ffree(fp);
    191 	return error;
    192 }
    193 
    194 int
    195 pty_grant_slave(struct lwp *l, dev_t dev)
    196 {
    197 	int error;
    198 	bool revoke;
    199 	struct vnode *vp;
    200 
    201 	/*
    202 	 * Open the slave.
    203 	 * namei -> setattr -> unlock -> revoke -> vrele ->
    204 	 * namei -> open -> unlock
    205 	 * Three stage rocket:
    206 	 * 1. Change the owner and permissions on the slave.
    207 	 * 2. Revoke all the users of the slave.
    208 	 * 3. open the slave.
    209 	 */
    210 	if (ptm == NULL)
    211 		return EOPNOTSUPP;
    212 	if ((error = (*ptm->allocvp)(ptm, l, &vp, dev, 't')) != 0)
    213 		return error;
    214 
    215 	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
    216 		struct vattr vattr;
    217 		(*ptm->getvattr)(ptm, l, &vattr);
    218 		/* Do the VOP_SETATTR() as root. */
    219 		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
    220 		if (error) {
    221 			DPRINTF(("setattr %d\n", error));
    222 			VOP_UNLOCK(vp, 0);
    223 			vrele(vp);
    224 			return error;
    225 		}
    226 	}
    227 	simple_lock(&vp->v_interlock);
    228 	revoke = (vp->v_usecount > 1 || (vp->v_iflag & VI_ALIASED) ||
    229 	    (vp->v_iflag & VI_LAYER));
    230 	simple_unlock(&vp->v_interlock);
    231 	VOP_UNLOCK(vp, 0);
    232 	if (revoke)
    233 		VOP_REVOKE(vp, REVOKEALL);
    234 
    235 	/*
    236 	 * The vnode is useless after the revoke, we need to get it again.
    237 	 */
    238 	vrele(vp);
    239 	return 0;
    240 }
    241 
    242 static int
    243 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev)
    244 {
    245 	int error;
    246 	struct file *fp;
    247 	struct vnode *vp;
    248 
    249 	/* Grab a filedescriptor for the slave */
    250 	if ((error = falloc(l, &fp, fd)) != 0) {
    251 		DPRINTF(("falloc %d\n", error));
    252 		return error;
    253 	}
    254 
    255 	if (ptm == NULL) {
    256 		error = EOPNOTSUPP;
    257 		goto bad;
    258 	}
    259 
    260 	if ((error = (*ptm->allocvp)(ptm, l, &vp, dev, 't')) != 0)
    261 		goto bad;
    262 	if ((error = pty_vn_open(vp, l)) != 0)
    263 		goto bad;
    264 
    265 	fp->f_flag = FREAD|FWRITE;
    266 	fp->f_type = DTYPE_VNODE;
    267 	fp->f_ops = &vnops;
    268 	fp->f_data = vp;
    269 	VOP_UNLOCK(vp, 0);
    270 	FILE_SET_MATURE(fp);
    271 	FILE_UNUSE(fp, l);
    272 	return 0;
    273 bad:
    274 	FILE_UNUSE(fp, l);
    275 	fdremove(l->l_proc->p_fd, *fd);
    276 	ffree(fp);
    277 	return error;
    278 }
    279 
    280 struct ptm_pty *
    281 pty_sethandler(struct ptm_pty *nptm)
    282 {
    283 	struct ptm_pty *optm = ptm;
    284 	ptm = nptm;
    285 	return optm;
    286 }
    287 
    288 int
    289 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data)
    290 {
    291 	struct ptmget *ptmg = data;
    292 	int error;
    293 
    294 	if (ptm == NULL)
    295 		return EOPNOTSUPP;
    296 
    297 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    298 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    299 
    300 	error = (*ptm->makename)(ptm, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    301 	if (error)
    302 		return error;
    303 
    304 	return (*ptm->makename)(ptm, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    305 }
    306 
    307 void
    308 /*ARGSUSED*/
    309 ptmattach(int n)
    310 {
    311 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    312 	/* find the major and minor of the pty devices */
    313 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    314 		panic("ptmattach: Can't find pty slave in cdevsw");
    315 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    316 		panic("ptmattach: Can't find pty master in cdevsw");
    317 #ifdef COMPAT_BSDPTY
    318 	ptm = &ptm_bsdpty;
    319 #endif
    320 }
    321 
    322 static int
    323 /*ARGSUSED*/
    324 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    325 {
    326 	int error;
    327 	int fd;
    328 	dev_t ttydev;
    329 
    330 	switch(minor(dev)) {
    331 	case 0:		/* /dev/ptmx */
    332 	case 2:		/* /emul/linux/dev/ptmx */
    333 		if ((error = pty_alloc_master(l, &fd, &ttydev)) != 0)
    334 			return error;
    335 		if (minor(dev) == 2) {
    336 			/*
    337 			 * Linux ptyfs grants the pty right here.
    338 			 * Handle this case here, instead of writing
    339 			 * a new linux module.
    340 			 */
    341 			if ((error = pty_grant_slave(l, ttydev)) != 0) {
    342 				struct file *fp =
    343 				    fd_getfile(l->l_proc->p_fd, fd);
    344 				if (fp != NULL) {
    345 					FILE_UNUSE(fp, l);
    346 					fdremove(l->l_proc->p_fd, fd);
    347 					ffree(fp);
    348 				}
    349 				return error;
    350 			}
    351 		}
    352 		curlwp->l_dupfd = fd;
    353 		return EMOVEFD;
    354 	case 1:		/* /dev/ptm */
    355 		return 0;
    356 	default:
    357 		return ENODEV;
    358 	}
    359 }
    360 
    361 static int
    362 /*ARGSUSED*/
    363 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    364 {
    365 
    366 	return (0);
    367 }
    368 
    369 static int
    370 /*ARGSUSED*/
    371 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    372 {
    373 	int error;
    374 	dev_t newdev;
    375 	int cfd, sfd;
    376 	struct file *fp;
    377 	struct proc *p = l->l_proc;
    378 
    379 	error = 0;
    380 	switch (cmd) {
    381 	case TIOCPTMGET:
    382 		if ((error = pty_alloc_master(l, &cfd, &newdev)) != 0)
    383 			return error;
    384 
    385 		if ((error = pty_grant_slave(l, newdev)) != 0)
    386 			goto bad;
    387 
    388 		if ((error = pty_alloc_slave(l, &sfd, newdev)) != 0)
    389 			goto bad;
    390 
    391 		/* now, put the indices and names into struct ptmget */
    392 		return pty_fill_ptmget(l, newdev, cfd, sfd, data);
    393 	default:
    394 		DPRINTF(("ptmioctl EINVAL\n"));
    395 		return EINVAL;
    396 	}
    397 bad:
    398 	fp = fd_getfile(p->p_fd, cfd);
    399 	if (fp != NULL) {
    400 		FILE_UNUSE(fp, l);
    401 		fdremove(p->p_fd, cfd);
    402 		ffree(fp);
    403 	}
    404 	return error;
    405 }
    406 
    407 const struct cdevsw ptm_cdevsw = {
    408 	ptmopen, ptmclose, noread, nowrite, ptmioctl,
    409 	nullstop, notty, nopoll, nommap, nokqfilter, D_TTY
    410 };
    411 #endif
    412