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tty_ptm.c revision 1.41 
      1 /*	$NetBSD: tty_ptm.c,v 1.41 2019/11/30 20:45:49 ad 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 1.41 2019/11/30 20:45:49 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 	vp->v_writecount++;
    149 
    150 	return 0;
    151 }
    152 
    153 static int
    154 pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp)
    155 {
    156 	int error;
    157 	struct file *fp;
    158 	struct vnode *vp;
    159 	int md;
    160 
    161 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    162 		DPRINTF(("fd_allocfile %d\n", error));
    163 		return error;
    164 	}
    165 retry:
    166 	/* Find and open a free master pty. */
    167 	*dev = pty_getfree();
    168 	md = minor(*dev);
    169 	if ((error = pty_check(md)) != 0) {
    170 		DPRINTF(("pty_check %d\n", error));
    171 		goto bad;
    172 	}
    173 	if (ptm == NULL) {
    174 		DPRINTF(("no ptm\n"));
    175 		error = EOPNOTSUPP;
    176 		goto bad;
    177 	}
    178 	if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
    179 		DPRINTF(("pty_allocvp %d\n", error));
    180 		goto bad;
    181 	}
    182 
    183 	if ((error = pty_vn_open(vp, l)) != 0) {
    184 		DPRINTF(("pty_vn_open %d\n", error));
    185 		/*
    186 		 * Check if the master open failed because we lost
    187 		 * the race to grab it.
    188 		 */
    189 		if (error != EIO)
    190 			goto bad;
    191 		error = !pty_isfree(md, 1);
    192 		DPRINTF(("pty_isfree %d\n", error));
    193 		if (error)
    194 			goto retry;
    195 		else
    196 			goto bad;
    197 	}
    198 	fp->f_flag = FREAD|FWRITE;
    199 	fp->f_type = DTYPE_VNODE;
    200 	fp->f_ops = &vnops;
    201 	fp->f_vnode = vp;
    202 	VOP_UNLOCK(vp);
    203 	fd_affix(curproc, fp, *fd);
    204 	return 0;
    205 bad:
    206 	fd_abort(curproc, fp, *fd);
    207 	return error;
    208 }
    209 
    210 int
    211 pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
    212 {
    213 	int error;
    214 	struct vnode *vp;
    215 
    216 	/*
    217 	 * Open the slave.
    218 	 * namei -> setattr -> unlock -> revoke -> vrele ->
    219 	 * namei -> open -> unlock
    220 	 * Three stage rocket:
    221 	 * 1. Change the owner and permissions on the slave.
    222 	 * 2. Revoke all the users of the slave.
    223 	 * 3. open the slave.
    224 	 */
    225 	if (ptm == NULL)
    226 		return EOPNOTSUPP;
    227 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    228 		return error;
    229 
    230 	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
    231 		struct vattr vattr;
    232 		(*ptm->getvattr)(mp, l, &vattr);
    233 		/* Do the VOP_SETATTR() as root. */
    234 		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
    235 		if (error) {
    236 			DPRINTF(("setattr %d\n", error));
    237 			vput(vp);
    238 			return error;
    239 		}
    240 	}
    241 	VOP_UNLOCK(vp);
    242 	VOP_REVOKE(vp, REVOKEALL);
    243 
    244 	/*
    245 	 * The vnode is useless after the revoke, we need to get it again.
    246 	 */
    247 	vrele(vp);
    248 	return 0;
    249 }
    250 
    251 static int
    252 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
    253 {
    254 	int error;
    255 	struct file *fp;
    256 	struct vnode *vp;
    257 
    258 	/* Grab a filedescriptor for the slave */
    259 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    260 		DPRINTF(("fd_allocfile %d\n", error));
    261 		return error;
    262 	}
    263 
    264 	if (ptm == NULL) {
    265 		error = EOPNOTSUPP;
    266 		goto bad;
    267 	}
    268 
    269 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    270 		goto bad;
    271 	if ((error = pty_vn_open(vp, l)) != 0)
    272 		goto bad;
    273 
    274 	fp->f_flag = FREAD|FWRITE;
    275 	fp->f_type = DTYPE_VNODE;
    276 	fp->f_ops = &vnops;
    277 	fp->f_vnode = vp;
    278 	VOP_UNLOCK(vp);
    279 	fd_affix(curproc, fp, *fd);
    280 	return 0;
    281 bad:
    282 	fd_abort(curproc, fp, *fd);
    283 	return error;
    284 }
    285 
    286 struct ptm_pty *
    287 pty_sethandler(struct ptm_pty *nptm)
    288 {
    289 	struct ptm_pty *optm = ptm;
    290 	ptm = nptm;
    291 	return optm;
    292 }
    293 
    294 int
    295 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
    296 {
    297 	struct ptmget *ptmg = data;
    298 	int error;
    299 
    300 	if (ptm == NULL)
    301 		return EOPNOTSUPP;
    302 
    303 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    304 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    305 
    306 	error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    307 	if (error)
    308 		return error;
    309 
    310 	return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    311 }
    312 
    313 void
    314 /*ARGSUSED*/
    315 ptmattach(int n)
    316 {
    317 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    318 	/* find the major and minor of the pty devices */
    319 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    320 		panic("ptmattach: Can't find pty slave in cdevsw");
    321 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    322 		panic("ptmattach: Can't find pty master in cdevsw");
    323 #ifdef COMPAT_BSDPTY
    324 	ptm = &ptm_bsdpty;
    325 #endif
    326 }
    327 
    328 static int
    329 /*ARGSUSED*/
    330 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    331 {
    332 	int error;
    333 	int fd;
    334 	dev_t ttydev;
    335 	struct mount *mp;
    336 
    337 	switch(minor(dev)) {
    338 	case 0:		/* /dev/ptmx */
    339 	case 2:		/* /emul/linux/dev/ptmx */
    340 		if ((error = pty_getmp(l, &mp)) != 0)
    341 			return error;
    342 		if ((error = pty_alloc_master(l, &fd, &ttydev, mp)) != 0)
    343 			return error;
    344 		if (minor(dev) == 2) {
    345 			/*
    346 			 * Linux ptyfs grants the pty right here.
    347 			 * Handle this case here, instead of writing
    348 			 * a new linux module.
    349 			 */
    350 			if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
    351 				file_t *fp = fd_getfile(fd);
    352 				if (fp != NULL) {
    353 					fd_close(fd);
    354 				}
    355 				return error;
    356 			}
    357 		}
    358 		curlwp->l_dupfd = fd;
    359 		return EMOVEFD;
    360 	case 1:		/* /dev/ptm */
    361 		return 0;
    362 	default:
    363 		return ENODEV;
    364 	}
    365 }
    366 
    367 static int
    368 /*ARGSUSED*/
    369 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    370 {
    371 
    372 	return (0);
    373 }
    374 
    375 static int
    376 /*ARGSUSED*/
    377 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    378 {
    379 	int error;
    380 	dev_t newdev;
    381 	int cfd, sfd;
    382 	file_t *fp;
    383 	struct mount *mp;
    384 
    385 	error = 0;
    386 	switch (cmd) {
    387 	case TIOCPTMGET:
    388 		if ((error = pty_getmp(l, &mp)) != 0)
    389 			return error;
    390 
    391 		if ((error = pty_alloc_master(l, &cfd, &newdev, mp)) != 0)
    392 			return error;
    393 
    394 		if ((error = pty_grant_slave(l, newdev, mp)) != 0)
    395 			goto bad;
    396 
    397 		if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
    398 			goto bad;
    399 
    400 		/* now, put the indices and names into struct ptmget */
    401 		if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
    402 			goto bad2;
    403 		return 0;
    404 	default:
    405 		MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
    406 		    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
    407 		if (error != EPASSTHROUGH)
    408 			return error;
    409 		DPRINTF(("ptmioctl EINVAL\n"));
    410 		return EINVAL;
    411 	}
    412 bad2:
    413 	fp = fd_getfile(sfd);
    414 	if (fp != NULL) {
    415 		fd_close(sfd);
    416 	}
    417  bad:
    418 	fp = fd_getfile(cfd);
    419 	if (fp != NULL) {
    420 		fd_close(cfd);
    421 	}
    422 	return error;
    423 }
    424 
    425 const struct cdevsw ptm_cdevsw = {
    426 	.d_open = ptmopen,
    427 	.d_close = ptmclose,
    428 	.d_read = noread,
    429 	.d_write = nowrite,
    430 	.d_ioctl = ptmioctl,
    431 	.d_stop = nullstop,
    432 	.d_tty = notty,
    433 	.d_poll = nopoll,
    434 	.d_mmap = nommap,
    435 	.d_kqfilter = nokqfilter,
    436 	.d_discard = nodiscard,
    437 	.d_flag = D_TTY
    438 };
    439 #endif
    440