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tty_ptm.c revision 1.27 
      1 /*	$NetBSD: tty_ptm.c,v 1.27 2010/06/24 13:03:11 hannken 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  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: tty_ptm.c,v 1.27 2010/06/24 13:03:11 hannken Exp $");
     31 
     32 #include "opt_ptm.h"
     33 
     34 /* pty multiplexor driver /dev/ptm{,x} */
     35 
     36 #include <sys/param.h>
     37 #include <sys/systm.h>
     38 #include <sys/ioctl.h>
     39 #include <sys/proc.h>
     40 #include <sys/tty.h>
     41 #include <sys/stat.h>
     42 #include <sys/file.h>
     43 #include <sys/uio.h>
     44 #include <sys/kernel.h>
     45 #include <sys/vnode.h>
     46 #include <sys/namei.h>
     47 #include <sys/signalvar.h>
     48 #include <sys/filedesc.h>
     49 #include <sys/conf.h>
     50 #include <sys/poll.h>
     51 #include <sys/pty.h>
     52 #include <sys/kauth.h>
     53 
     54 #include <miscfs/specfs/specdev.h>
     55 
     56 #ifdef DEBUG_PTM
     57 #define DPRINTF(a)	printf a
     58 #else
     59 #define DPRINTF(a)
     60 #endif
     61 
     62 #ifdef NO_DEV_PTM
     63 const struct cdevsw ptm_cdevsw = {
     64 	noopen, noclose, noread, nowrite, noioctl,
     65 	nostop, notty, nopoll, nommap, nokqfilter, D_TTY
     66 };
     67 #else
     68 
     69 static struct ptm_pty *ptm;
     70 int pts_major, ptc_major;
     71 
     72 static dev_t pty_getfree(void);
     73 static int pty_alloc_master(struct lwp *, int *, dev_t *);
     74 static int pty_alloc_slave(struct lwp *, int *, dev_t);
     75 
     76 void ptmattach(int);
     77 
     78 dev_t
     79 pty_makedev(char ms, int minor)
     80 {
     81 	return makedev(ms == 't' ? pts_major : ptc_major, minor);
     82 }
     83 
     84 
     85 static dev_t
     86 pty_getfree(void)
     87 {
     88 	extern kmutex_t pt_softc_mutex;
     89 	int i;
     90 
     91 	mutex_enter(&pt_softc_mutex);
     92 	for (i = 0; i < npty; i++) {
     93 		if (pty_isfree(i, 0))
     94 			break;
     95 	}
     96 	mutex_exit(&pt_softc_mutex);
     97 	return pty_makedev('t', i);
     98 }
     99 
    100 /*
    101  * Hacked up version of vn_open. We _only_ handle ptys and only open
    102  * them with FREAD|FWRITE and never deal with creat or stuff like that.
    103  *
    104  * We need it because we have to fake up root credentials to open the pty.
    105  */
    106 int
    107 pty_vn_open(struct vnode *vp, struct lwp *l)
    108 {
    109 	int error;
    110 
    111 	if (vp->v_type != VCHR) {
    112 		vput(vp);
    113 		return EINVAL;
    114 	}
    115 
    116 	error = VOP_OPEN(vp, FREAD|FWRITE, lwp0.l_cred);
    117 
    118 	if (error) {
    119 		vput(vp);
    120 		return error;
    121 	}
    122 
    123 	vp->v_writecount++;
    124 
    125 	return 0;
    126 }
    127 
    128 static int
    129 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev)
    130 {
    131 	int error;
    132 	struct file *fp;
    133 	struct vnode *vp;
    134 	int md;
    135 
    136 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    137 		DPRINTF(("fd_allocfile %d\n", error));
    138 		return error;
    139 	}
    140 retry:
    141 	/* Find and open a free master pty. */
    142 	*dev = pty_getfree();
    143 	md = minor(*dev);
    144 	if ((error = pty_check(md)) != 0) {
    145 		DPRINTF(("pty_check %d\n", error));
    146 		goto bad;
    147 	}
    148 	if (ptm == NULL) {
    149 		DPRINTF(("no ptm\n"));
    150 		error = EOPNOTSUPP;
    151 		goto bad;
    152 	}
    153 	if ((error = (*ptm->allocvp)(ptm, l, &vp, *dev, 'p')) != 0) {
    154 		DPRINTF(("pty_allocvp %d\n", error));
    155 		goto bad;
    156 	}
    157 
    158 	if ((error = pty_vn_open(vp, l)) != 0) {
    159 		DPRINTF(("pty_vn_open %d\n", error));
    160 		/*
    161 		 * Check if the master open failed because we lost
    162 		 * the race to grab it.
    163 		 */
    164 		if (error != EIO)
    165 			goto bad;
    166 		error = !pty_isfree(md, 1);
    167 		DPRINTF(("pty_isfree %d\n", error));
    168 		if (error)
    169 			goto retry;
    170 		else
    171 			goto bad;
    172 	}
    173 	fp->f_flag = FREAD|FWRITE;
    174 	fp->f_type = DTYPE_VNODE;
    175 	fp->f_ops = &vnops;
    176 	fp->f_data = vp;
    177 	VOP_UNLOCK(vp);
    178 	fd_affix(curproc, fp, *fd);
    179 	return 0;
    180 bad:
    181 	fd_abort(curproc, fp, *fd);
    182 	return error;
    183 }
    184 
    185 int
    186 pty_grant_slave(struct lwp *l, dev_t dev)
    187 {
    188 	int error;
    189 	struct vnode *vp;
    190 
    191 	/*
    192 	 * Open the slave.
    193 	 * namei -> setattr -> unlock -> revoke -> vrele ->
    194 	 * namei -> open -> unlock
    195 	 * Three stage rocket:
    196 	 * 1. Change the owner and permissions on the slave.
    197 	 * 2. Revoke all the users of the slave.
    198 	 * 3. open the slave.
    199 	 */
    200 	if (ptm == NULL)
    201 		return EOPNOTSUPP;
    202 	if ((error = (*ptm->allocvp)(ptm, l, &vp, dev, 't')) != 0)
    203 		return error;
    204 
    205 	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
    206 		struct vattr vattr;
    207 		(*ptm->getvattr)(ptm, l, &vattr);
    208 		/* Do the VOP_SETATTR() as root. */
    209 		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
    210 		if (error) {
    211 			DPRINTF(("setattr %d\n", error));
    212 			VOP_UNLOCK(vp);
    213 			vrele(vp);
    214 			return error;
    215 		}
    216 	}
    217 	VOP_UNLOCK(vp);
    218 	VOP_REVOKE(vp, REVOKEALL);
    219 
    220 	/*
    221 	 * The vnode is useless after the revoke, we need to get it again.
    222 	 */
    223 	vrele(vp);
    224 	return 0;
    225 }
    226 
    227 static int
    228 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev)
    229 {
    230 	int error;
    231 	struct file *fp;
    232 	struct vnode *vp;
    233 
    234 	/* Grab a filedescriptor for the slave */
    235 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    236 		DPRINTF(("fd_allocfile %d\n", error));
    237 		return error;
    238 	}
    239 
    240 	if (ptm == NULL) {
    241 		error = EOPNOTSUPP;
    242 		goto bad;
    243 	}
    244 
    245 	if ((error = (*ptm->allocvp)(ptm, l, &vp, dev, 't')) != 0)
    246 		goto bad;
    247 	if ((error = pty_vn_open(vp, l)) != 0)
    248 		goto bad;
    249 
    250 	fp->f_flag = FREAD|FWRITE;
    251 	fp->f_type = DTYPE_VNODE;
    252 	fp->f_ops = &vnops;
    253 	fp->f_data = vp;
    254 	VOP_UNLOCK(vp);
    255 	fd_affix(curproc, fp, *fd);
    256 	return 0;
    257 bad:
    258 	fd_abort(curproc, fp, *fd);
    259 	return error;
    260 }
    261 
    262 struct ptm_pty *
    263 pty_sethandler(struct ptm_pty *nptm)
    264 {
    265 	struct ptm_pty *optm = ptm;
    266 	ptm = nptm;
    267 	return optm;
    268 }
    269 
    270 int
    271 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data)
    272 {
    273 	struct ptmget *ptmg = data;
    274 	int error;
    275 
    276 	if (ptm == NULL)
    277 		return EOPNOTSUPP;
    278 
    279 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    280 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    281 
    282 	error = (*ptm->makename)(ptm, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    283 	if (error)
    284 		return error;
    285 
    286 	return (*ptm->makename)(ptm, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    287 }
    288 
    289 void
    290 /*ARGSUSED*/
    291 ptmattach(int n)
    292 {
    293 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    294 	/* find the major and minor of the pty devices */
    295 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    296 		panic("ptmattach: Can't find pty slave in cdevsw");
    297 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    298 		panic("ptmattach: Can't find pty master in cdevsw");
    299 #ifdef COMPAT_BSDPTY
    300 	ptm = &ptm_bsdpty;
    301 #endif
    302 }
    303 
    304 static int
    305 /*ARGSUSED*/
    306 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    307 {
    308 	int error;
    309 	int fd;
    310 	dev_t ttydev;
    311 
    312 	switch(minor(dev)) {
    313 	case 0:		/* /dev/ptmx */
    314 	case 2:		/* /emul/linux/dev/ptmx */
    315 		if ((error = pty_alloc_master(l, &fd, &ttydev)) != 0)
    316 			return error;
    317 		if (minor(dev) == 2) {
    318 			/*
    319 			 * Linux ptyfs grants the pty right here.
    320 			 * Handle this case here, instead of writing
    321 			 * a new linux module.
    322 			 */
    323 			if ((error = pty_grant_slave(l, ttydev)) != 0) {
    324 				file_t *fp = fd_getfile(fd);
    325 				if (fp != NULL) {
    326 					fd_close(fd);
    327 				}
    328 				return error;
    329 			}
    330 		}
    331 		curlwp->l_dupfd = fd;
    332 		return EMOVEFD;
    333 	case 1:		/* /dev/ptm */
    334 		return 0;
    335 	default:
    336 		return ENODEV;
    337 	}
    338 }
    339 
    340 static int
    341 /*ARGSUSED*/
    342 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    343 {
    344 
    345 	return (0);
    346 }
    347 
    348 static int
    349 /*ARGSUSED*/
    350 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    351 {
    352 	int error;
    353 	dev_t newdev;
    354 	int cfd, sfd;
    355 	file_t *fp;
    356 
    357 	error = 0;
    358 	switch (cmd) {
    359 	case TIOCPTMGET:
    360 		if ((error = pty_alloc_master(l, &cfd, &newdev)) != 0)
    361 			return error;
    362 
    363 		if ((error = pty_grant_slave(l, newdev)) != 0)
    364 			goto bad;
    365 
    366 		if ((error = pty_alloc_slave(l, &sfd, newdev)) != 0)
    367 			goto bad;
    368 
    369 		/* now, put the indices and names into struct ptmget */
    370 		return pty_fill_ptmget(l, newdev, cfd, sfd, data);
    371 	default:
    372 		DPRINTF(("ptmioctl EINVAL\n"));
    373 		return EINVAL;
    374 	}
    375  bad:
    376 	fp = fd_getfile(cfd);
    377 	if (fp != NULL) {
    378 		fd_close(cfd);
    379 	}
    380 	return error;
    381 }
    382 
    383 const struct cdevsw ptm_cdevsw = {
    384 	ptmopen, ptmclose, noread, nowrite, ptmioctl,
    385 	nullstop, notty, nopoll, nommap, nokqfilter, D_TTY
    386 };
    387 #endif
    388