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tty_ptm.c revision 1.45 
      1 /*	$NetBSD: tty_ptm.c,v 1.45 2022/09/29 12:18:27 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2004, 2020 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 1.45 2022/09/29 12:18:27 christos Exp $");
     31 
     32 #ifdef _KERNEL_OPT
     33 #include "opt_compat_netbsd.h"
     34 #include "opt_ptm.h"
     35 #endif
     36 
     37 /* pty multiplexor driver /dev/ptm{,x} */
     38 
     39 #include <sys/param.h>
     40 #include <sys/systm.h>
     41 #include <sys/ioctl.h>
     42 #include <sys/proc.h>
     43 #include <sys/tty.h>
     44 #include <sys/stat.h>
     45 #include <sys/file.h>
     46 #include <sys/uio.h>
     47 #include <sys/kernel.h>
     48 #include <sys/vnode.h>
     49 #include <sys/namei.h>
     50 #include <sys/signalvar.h>
     51 #include <sys/filedesc.h>
     52 #include <sys/conf.h>
     53 #include <sys/poll.h>
     54 #include <sys/pty.h>
     55 #include <sys/kauth.h>
     56 #include <sys/compat_stub.h>
     57 
     58 #include <miscfs/specfs/specdev.h>
     59 
     60 #include <compat/sys/ttycom.h>
     61 
     62 #include "ioconf.h"
     63 
     64 #ifdef DEBUG_PTM
     65 #define DPRINTF(a)	printf a
     66 #else
     67 #define DPRINTF(a)
     68 #endif
     69 
     70 #ifdef NO_DEV_PTM
     71 const struct cdevsw ptm_cdevsw = {
     72 	.d_open = noopen,
     73 	.d_close = noclose,
     74 	.d_read = noread,
     75 	.d_write = nowrite,
     76 	.d_ioctl = noioctl,
     77 	.d_stop = nostop,
     78 	.d_tty = notty,
     79 	.d_poll = nopoll,
     80 	.d_mmap = nommap,
     81 	.d_kqfilter = nokqfilter,
     82 	.d_discard = nodiscard,
     83 	.d_flag = D_TTY
     84 };
     85 #else
     86 
     87 int pts_major, ptc_major;
     88 
     89 static dev_t pty_getfree(void);
     90 static int pty_alloc_master(struct lwp *, int *, dev_t *, struct mount *, int);
     91 static int pty_alloc_slave(struct lwp *, int *, dev_t, struct mount *);
     92 static int pty_vn_open(struct vnode *, struct lwp *);
     93 
     94 int
     95 pty_getmp(struct lwp *l, struct mount **mpp)
     96 {
     97 	if (ptm == NULL)
     98 		return EOPNOTSUPP;
     99 
    100 	return (*ptm->getmp)(l, mpp);
    101 }
    102 
    103 dev_t
    104 pty_makedev(char ms, int minor)
    105 {
    106 	return makedev(ms == 't' ? pts_major : ptc_major, minor);
    107 }
    108 
    109 
    110 static dev_t
    111 pty_getfree(void)
    112 {
    113 	extern kmutex_t pt_softc_mutex;
    114 	int i;
    115 
    116 	mutex_enter(&pt_softc_mutex);
    117 	for (i = 0; i < npty; i++) {
    118 		if (pty_isfree(i, 0))
    119 			break;
    120 	}
    121 	mutex_exit(&pt_softc_mutex);
    122 	return pty_makedev('t', i);
    123 }
    124 
    125 /*
    126  * Hacked up version of vn_open. We _only_ handle ptys and only open
    127  * them with FREAD|FWRITE and never deal with creat or stuff like that.
    128  *
    129  * We need it because we have to fake up root credentials to open the pty.
    130  */
    131 int
    132 pty_vn_open(struct vnode *vp, struct lwp *l)
    133 {
    134 	int error;
    135 
    136 	if (vp->v_type != VCHR) {
    137 		vput(vp);
    138 		return EINVAL;
    139 	}
    140 
    141 	error = VOP_OPEN(vp, FREAD|FWRITE, lwp0.l_cred);
    142 
    143 	if (error) {
    144 		/* only ptys mean we can't get these */
    145 		KASSERT(error != EDUPFD && error != EMOVEFD);
    146 		vput(vp);
    147 		return error;
    148 	}
    149 
    150 	mutex_enter(vp->v_interlock);
    151 	vp->v_writecount++;
    152 	mutex_exit(vp->v_interlock);
    153 
    154 	return 0;
    155 }
    156 
    157 static int
    158 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp,
    159     int flags)
    160 {
    161 	int error;
    162 	struct file *fp;
    163 	struct vnode *vp;
    164 	int md;
    165 
    166 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    167 		DPRINTF(("fd_allocfile %d\n", error));
    168 		return error;
    169 	}
    170 retry:
    171 	/* Find and open a free master pty. */
    172 	*dev = pty_getfree();
    173 	md = minor(*dev);
    174 	if ((error = pty_check(md)) != 0) {
    175 		DPRINTF(("pty_check %d\n", error));
    176 		goto bad;
    177 	}
    178 	if (ptm == NULL) {
    179 		DPRINTF(("no ptm\n"));
    180 		error = EOPNOTSUPP;
    181 		goto bad;
    182 	}
    183 	if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
    184 		DPRINTF(("pty_allocvp %d\n", error));
    185 		goto bad;
    186 	}
    187 
    188 	if ((error = pty_vn_open(vp, l)) != 0) {
    189 		DPRINTF(("pty_vn_open %d\n", error));
    190 		/*
    191 		 * Check if the master open failed because we lost
    192 		 * the race to grab it.
    193 		 */
    194 		if (error != EIO)
    195 			goto bad;
    196 		error = !pty_isfree(md, 1);
    197 		DPRINTF(("pty_isfree %d\n", error));
    198 		if (error)
    199 			goto retry;
    200 		else
    201 			goto bad;
    202 	}
    203 	fp->f_flag = FREAD|FWRITE|(flags&FMASK);
    204 	fp->f_type = DTYPE_VNODE;
    205 	fp->f_ops = &vnops;
    206 	fp->f_vnode = vp;
    207 
    208 	VOP_UNLOCK(vp);
    209 	fd_set_exclose(l, *fd, (flags & O_CLOEXEC) != 0);
    210 	fd_affix(curproc, fp, *fd);
    211 	return 0;
    212 bad:
    213 	fd_abort(curproc, fp, *fd);
    214 	return error;
    215 }
    216 
    217 int
    218 pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
    219 {
    220 	int error;
    221 	struct vnode *vp;
    222 
    223 	/*
    224 	 * Open the slave.
    225 	 * namei -> setattr -> unlock -> revoke -> vrele ->
    226 	 * namei -> open -> unlock
    227 	 * Three stage rocket:
    228 	 * 1. Change the owner and permissions on the slave.
    229 	 * 2. Revoke all the users of the slave.
    230 	 * 3. open the slave.
    231 	 */
    232 	if (ptm == NULL)
    233 		return EOPNOTSUPP;
    234 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    235 		return error;
    236 
    237 	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
    238 		struct vattr vattr;
    239 		(*ptm->getvattr)(mp, l, &vattr);
    240 		/* Do the VOP_SETATTR() as root. */
    241 		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
    242 		if (error) {
    243 			DPRINTF(("setattr %d\n", error));
    244 			vput(vp);
    245 			return error;
    246 		}
    247 	}
    248 	VOP_UNLOCK(vp);
    249 	VOP_REVOKE(vp, REVOKEALL);
    250 
    251 	/*
    252 	 * The vnode is useless after the revoke, we need to get it again.
    253 	 */
    254 	vrele(vp);
    255 	return 0;
    256 }
    257 
    258 static int
    259 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
    260 {
    261 	int error;
    262 	struct file *fp;
    263 	struct vnode *vp;
    264 
    265 	/* Grab a filedescriptor for the slave */
    266 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    267 		DPRINTF(("fd_allocfile %d\n", error));
    268 		return error;
    269 	}
    270 
    271 	if (ptm == NULL) {
    272 		error = EOPNOTSUPP;
    273 		goto bad;
    274 	}
    275 
    276 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    277 		goto bad;
    278 	if ((error = pty_vn_open(vp, l)) != 0)
    279 		goto bad;
    280 
    281 	fp->f_flag = FREAD|FWRITE;
    282 	fp->f_type = DTYPE_VNODE;
    283 	fp->f_ops = &vnops;
    284 	fp->f_vnode = vp;
    285 	VOP_UNLOCK(vp);
    286 	fd_affix(curproc, fp, *fd);
    287 	return 0;
    288 bad:
    289 	fd_abort(curproc, fp, *fd);
    290 	return error;
    291 }
    292 
    293 struct ptm_pty *
    294 pty_sethandler(struct ptm_pty *nptm)
    295 {
    296 	struct ptm_pty *optm = ptm;
    297 	ptm = nptm;
    298 	return optm;
    299 }
    300 
    301 int
    302 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
    303 {
    304 	struct ptmget *ptmg = data;
    305 	int error;
    306 
    307 	if (ptm == NULL)
    308 		return EOPNOTSUPP;
    309 
    310 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    311 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    312 
    313 	error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    314 	if (error)
    315 		return error;
    316 
    317 	return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    318 }
    319 
    320 void
    321 /*ARGSUSED*/
    322 ptmattach(int n)
    323 {
    324 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    325 	/* find the major and minor of the pty devices */
    326 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    327 		panic("%s: Can't find pty slave in cdevsw", __func__);
    328 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    329 		panic("%s: Can't find pty master in cdevsw", __func__);
    330 #ifdef COMPAT_BSDPTY
    331 	ptm = &ptm_bsdpty;
    332 #endif
    333 }
    334 
    335 static int
    336 /*ARGSUSED*/
    337 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    338 {
    339 	int error;
    340 	int fd;
    341 	dev_t ttydev;
    342 	struct mount *mp;
    343 
    344 	switch(minor(dev)) {
    345 	case 0:		/* /dev/ptmx */
    346 	case 2:		/* /emul/linux/dev/ptmx */
    347 		if ((error = pty_getmp(l, &mp)) != 0)
    348 			return error;
    349 		if ((error = pty_alloc_master(l, &fd, &ttydev, mp, flag)) != 0)
    350 			return error;
    351 		if (minor(dev) == 2) {
    352 			/*
    353 			 * Linux ptyfs grants the pty right here.
    354 			 * Handle this case here, instead of writing
    355 			 * a new linux module.
    356 			 */
    357 			if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
    358 				file_t *fp = fd_getfile(fd);
    359 				if (fp != NULL) {
    360 					fd_close(fd);
    361 				}
    362 				return error;
    363 			}
    364 		}
    365 		curlwp->l_dupfd = fd;
    366 		return EMOVEFD;
    367 	case 1:		/* /dev/ptm */
    368 		return 0;
    369 	default:
    370 		return ENODEV;
    371 	}
    372 }
    373 
    374 static int
    375 /*ARGSUSED*/
    376 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    377 {
    378 
    379 	return (0);
    380 }
    381 
    382 static int
    383 /*ARGSUSED*/
    384 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    385 {
    386 	int error;
    387 	dev_t newdev;
    388 	int cfd, sfd;
    389 	file_t *fp;
    390 	struct mount *mp;
    391 
    392 	error = 0;
    393 	switch (cmd) {
    394 	case TIOCPTMGET:
    395 		if ((error = pty_getmp(l, &mp)) != 0)
    396 			return error;
    397 
    398 		if ((error = pty_alloc_master(l, &cfd, &newdev, mp, 0)) != 0)
    399 			return error;
    400 
    401 		if ((error = pty_grant_slave(l, newdev, mp)) != 0)
    402 			goto bad;
    403 
    404 		if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
    405 			goto bad;
    406 
    407 		/* now, put the indices and names into struct ptmget */
    408 		if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
    409 			goto bad2;
    410 		return 0;
    411 	default:
    412 		MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
    413 		    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
    414 		if (error != EPASSTHROUGH)
    415 			return error;
    416 		DPRINTF(("ptmioctl EINVAL\n"));
    417 		return EINVAL;
    418 	}
    419 bad2:
    420 	fp = fd_getfile(sfd);
    421 	if (fp != NULL) {
    422 		fd_close(sfd);
    423 	}
    424  bad:
    425 	fp = fd_getfile(cfd);
    426 	if (fp != NULL) {
    427 		fd_close(cfd);
    428 	}
    429 	return error;
    430 }
    431 
    432 const struct cdevsw ptm_cdevsw = {
    433 	.d_open = ptmopen,
    434 	.d_close = ptmclose,
    435 	.d_read = noread,
    436 	.d_write = nowrite,
    437 	.d_ioctl = ptmioctl,
    438 	.d_stop = nullstop,
    439 	.d_tty = notty,
    440 	.d_poll = nopoll,
    441 	.d_mmap = nommap,
    442 	.d_kqfilter = nokqfilter,
    443 	.d_discard = nodiscard,
    444 	.d_flag = D_TTY
    445 };
    446 #endif
    447