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tty_ptm.c revision 1.42 
      1 /*	$NetBSD: tty_ptm.c,v 1.42 2020/05/23 22:16:17 ad 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 1.42 2020/05/23 22:16:17 ad 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 *);
     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 		vput(vp);
    145 		return error;
    146 	}
    147 
    148 	mutex_enter(vp->v_interlock);
    149 	vp->v_writecount++;
    150 	mutex_exit(vp->v_interlock);
    151 
    152 	return 0;
    153 }
    154 
    155 static int
    156 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp)
    157 {
    158 	int error;
    159 	struct file *fp;
    160 	struct vnode *vp;
    161 	int md;
    162 
    163 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    164 		DPRINTF(("fd_allocfile %d\n", error));
    165 		return error;
    166 	}
    167 retry:
    168 	/* Find and open a free master pty. */
    169 	*dev = pty_getfree();
    170 	md = minor(*dev);
    171 	if ((error = pty_check(md)) != 0) {
    172 		DPRINTF(("pty_check %d\n", error));
    173 		goto bad;
    174 	}
    175 	if (ptm == NULL) {
    176 		DPRINTF(("no ptm\n"));
    177 		error = EOPNOTSUPP;
    178 		goto bad;
    179 	}
    180 	if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
    181 		DPRINTF(("pty_allocvp %d\n", error));
    182 		goto bad;
    183 	}
    184 
    185 	if ((error = pty_vn_open(vp, l)) != 0) {
    186 		DPRINTF(("pty_vn_open %d\n", error));
    187 		/*
    188 		 * Check if the master open failed because we lost
    189 		 * the race to grab it.
    190 		 */
    191 		if (error != EIO)
    192 			goto bad;
    193 		error = !pty_isfree(md, 1);
    194 		DPRINTF(("pty_isfree %d\n", error));
    195 		if (error)
    196 			goto retry;
    197 		else
    198 			goto bad;
    199 	}
    200 	fp->f_flag = FREAD|FWRITE;
    201 	fp->f_type = DTYPE_VNODE;
    202 	fp->f_ops = &vnops;
    203 	fp->f_vnode = vp;
    204 	VOP_UNLOCK(vp);
    205 	fd_affix(curproc, fp, *fd);
    206 	return 0;
    207 bad:
    208 	fd_abort(curproc, fp, *fd);
    209 	return error;
    210 }
    211 
    212 int
    213 pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
    214 {
    215 	int error;
    216 	struct vnode *vp;
    217 
    218 	/*
    219 	 * Open the slave.
    220 	 * namei -> setattr -> unlock -> revoke -> vrele ->
    221 	 * namei -> open -> unlock
    222 	 * Three stage rocket:
    223 	 * 1. Change the owner and permissions on the slave.
    224 	 * 2. Revoke all the users of the slave.
    225 	 * 3. open the slave.
    226 	 */
    227 	if (ptm == NULL)
    228 		return EOPNOTSUPP;
    229 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    230 		return error;
    231 
    232 	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
    233 		struct vattr vattr;
    234 		(*ptm->getvattr)(mp, l, &vattr);
    235 		/* Do the VOP_SETATTR() as root. */
    236 		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
    237 		if (error) {
    238 			DPRINTF(("setattr %d\n", error));
    239 			vput(vp);
    240 			return error;
    241 		}
    242 	}
    243 	VOP_UNLOCK(vp);
    244 	VOP_REVOKE(vp, REVOKEALL);
    245 
    246 	/*
    247 	 * The vnode is useless after the revoke, we need to get it again.
    248 	 */
    249 	vrele(vp);
    250 	return 0;
    251 }
    252 
    253 static int
    254 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
    255 {
    256 	int error;
    257 	struct file *fp;
    258 	struct vnode *vp;
    259 
    260 	/* Grab a filedescriptor for the slave */
    261 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    262 		DPRINTF(("fd_allocfile %d\n", error));
    263 		return error;
    264 	}
    265 
    266 	if (ptm == NULL) {
    267 		error = EOPNOTSUPP;
    268 		goto bad;
    269 	}
    270 
    271 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    272 		goto bad;
    273 	if ((error = pty_vn_open(vp, l)) != 0)
    274 		goto bad;
    275 
    276 	fp->f_flag = FREAD|FWRITE;
    277 	fp->f_type = DTYPE_VNODE;
    278 	fp->f_ops = &vnops;
    279 	fp->f_vnode = vp;
    280 	VOP_UNLOCK(vp);
    281 	fd_affix(curproc, fp, *fd);
    282 	return 0;
    283 bad:
    284 	fd_abort(curproc, fp, *fd);
    285 	return error;
    286 }
    287 
    288 struct ptm_pty *
    289 pty_sethandler(struct ptm_pty *nptm)
    290 {
    291 	struct ptm_pty *optm = ptm;
    292 	ptm = nptm;
    293 	return optm;
    294 }
    295 
    296 int
    297 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
    298 {
    299 	struct ptmget *ptmg = data;
    300 	int error;
    301 
    302 	if (ptm == NULL)
    303 		return EOPNOTSUPP;
    304 
    305 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    306 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    307 
    308 	error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    309 	if (error)
    310 		return error;
    311 
    312 	return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    313 }
    314 
    315 void
    316 /*ARGSUSED*/
    317 ptmattach(int n)
    318 {
    319 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    320 	/* find the major and minor of the pty devices */
    321 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    322 		panic("ptmattach: Can't find pty slave in cdevsw");
    323 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    324 		panic("ptmattach: Can't find pty master in cdevsw");
    325 #ifdef COMPAT_BSDPTY
    326 	ptm = &ptm_bsdpty;
    327 #endif
    328 }
    329 
    330 static int
    331 /*ARGSUSED*/
    332 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    333 {
    334 	int error;
    335 	int fd;
    336 	dev_t ttydev;
    337 	struct mount *mp;
    338 
    339 	switch(minor(dev)) {
    340 	case 0:		/* /dev/ptmx */
    341 	case 2:		/* /emul/linux/dev/ptmx */
    342 		if ((error = pty_getmp(l, &mp)) != 0)
    343 			return error;
    344 		if ((error = pty_alloc_master(l, &fd, &ttydev, mp)) != 0)
    345 			return error;
    346 		if (minor(dev) == 2) {
    347 			/*
    348 			 * Linux ptyfs grants the pty right here.
    349 			 * Handle this case here, instead of writing
    350 			 * a new linux module.
    351 			 */
    352 			if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
    353 				file_t *fp = fd_getfile(fd);
    354 				if (fp != NULL) {
    355 					fd_close(fd);
    356 				}
    357 				return error;
    358 			}
    359 		}
    360 		curlwp->l_dupfd = fd;
    361 		return EMOVEFD;
    362 	case 1:		/* /dev/ptm */
    363 		return 0;
    364 	default:
    365 		return ENODEV;
    366 	}
    367 }
    368 
    369 static int
    370 /*ARGSUSED*/
    371 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    372 {
    373 
    374 	return (0);
    375 }
    376 
    377 static int
    378 /*ARGSUSED*/
    379 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    380 {
    381 	int error;
    382 	dev_t newdev;
    383 	int cfd, sfd;
    384 	file_t *fp;
    385 	struct mount *mp;
    386 
    387 	error = 0;
    388 	switch (cmd) {
    389 	case TIOCPTMGET:
    390 		if ((error = pty_getmp(l, &mp)) != 0)
    391 			return error;
    392 
    393 		if ((error = pty_alloc_master(l, &cfd, &newdev, mp)) != 0)
    394 			return error;
    395 
    396 		if ((error = pty_grant_slave(l, newdev, mp)) != 0)
    397 			goto bad;
    398 
    399 		if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
    400 			goto bad;
    401 
    402 		/* now, put the indices and names into struct ptmget */
    403 		if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
    404 			goto bad2;
    405 		return 0;
    406 	default:
    407 		MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
    408 		    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
    409 		if (error != EPASSTHROUGH)
    410 			return error;
    411 		DPRINTF(("ptmioctl EINVAL\n"));
    412 		return EINVAL;
    413 	}
    414 bad2:
    415 	fp = fd_getfile(sfd);
    416 	if (fp != NULL) {
    417 		fd_close(sfd);
    418 	}
    419  bad:
    420 	fp = fd_getfile(cfd);
    421 	if (fp != NULL) {
    422 		fd_close(cfd);
    423 	}
    424 	return error;
    425 }
    426 
    427 const struct cdevsw ptm_cdevsw = {
    428 	.d_open = ptmopen,
    429 	.d_close = ptmclose,
    430 	.d_read = noread,
    431 	.d_write = nowrite,
    432 	.d_ioctl = ptmioctl,
    433 	.d_stop = nullstop,
    434 	.d_tty = notty,
    435 	.d_poll = nopoll,
    436 	.d_mmap = nommap,
    437 	.d_kqfilter = nokqfilter,
    438 	.d_discard = nodiscard,
    439 	.d_flag = D_TTY
    440 };
    441 #endif
    442