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tty_ptm.c revision 1.40 
      1 /*	$NetBSD: tty_ptm.c,v 1.40 2019/03/01 11:06:57 pgoyette 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 1.40 2019/03/01 11:06:57 pgoyette 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 			VOP_UNLOCK(vp);
    238 			vrele(vp);
    239 			return error;
    240 		}
    241 	}
    242 	VOP_UNLOCK(vp);
    243 	VOP_REVOKE(vp, REVOKEALL);
    244 
    245 	/*
    246 	 * The vnode is useless after the revoke, we need to get it again.
    247 	 */
    248 	vrele(vp);
    249 	return 0;
    250 }
    251 
    252 static int
    253 pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
    254 {
    255 	int error;
    256 	struct file *fp;
    257 	struct vnode *vp;
    258 
    259 	/* Grab a filedescriptor for the slave */
    260 	if ((error = fd_allocfile(&fp, fd)) != 0) {
    261 		DPRINTF(("fd_allocfile %d\n", error));
    262 		return error;
    263 	}
    264 
    265 	if (ptm == NULL) {
    266 		error = EOPNOTSUPP;
    267 		goto bad;
    268 	}
    269 
    270 	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
    271 		goto bad;
    272 	if ((error = pty_vn_open(vp, l)) != 0)
    273 		goto bad;
    274 
    275 	fp->f_flag = FREAD|FWRITE;
    276 	fp->f_type = DTYPE_VNODE;
    277 	fp->f_ops = &vnops;
    278 	fp->f_vnode = vp;
    279 	VOP_UNLOCK(vp);
    280 	fd_affix(curproc, fp, *fd);
    281 	return 0;
    282 bad:
    283 	fd_abort(curproc, fp, *fd);
    284 	return error;
    285 }
    286 
    287 struct ptm_pty *
    288 pty_sethandler(struct ptm_pty *nptm)
    289 {
    290 	struct ptm_pty *optm = ptm;
    291 	ptm = nptm;
    292 	return optm;
    293 }
    294 
    295 int
    296 pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
    297 {
    298 	struct ptmget *ptmg = data;
    299 	int error;
    300 
    301 	if (ptm == NULL)
    302 		return EOPNOTSUPP;
    303 
    304 	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
    305 	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
    306 
    307 	error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
    308 	if (error)
    309 		return error;
    310 
    311 	return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
    312 }
    313 
    314 void
    315 /*ARGSUSED*/
    316 ptmattach(int n)
    317 {
    318 	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
    319 	/* find the major and minor of the pty devices */
    320 	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
    321 		panic("ptmattach: Can't find pty slave in cdevsw");
    322 	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
    323 		panic("ptmattach: Can't find pty master in cdevsw");
    324 #ifdef COMPAT_BSDPTY
    325 	ptm = &ptm_bsdpty;
    326 #endif
    327 }
    328 
    329 static int
    330 /*ARGSUSED*/
    331 ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
    332 {
    333 	int error;
    334 	int fd;
    335 	dev_t ttydev;
    336 	struct mount *mp;
    337 
    338 	switch(minor(dev)) {
    339 	case 0:		/* /dev/ptmx */
    340 	case 2:		/* /emul/linux/dev/ptmx */
    341 		if ((error = pty_getmp(l, &mp)) != 0)
    342 			return error;
    343 		if ((error = pty_alloc_master(l, &fd, &ttydev, mp)) != 0)
    344 			return error;
    345 		if (minor(dev) == 2) {
    346 			/*
    347 			 * Linux ptyfs grants the pty right here.
    348 			 * Handle this case here, instead of writing
    349 			 * a new linux module.
    350 			 */
    351 			if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
    352 				file_t *fp = fd_getfile(fd);
    353 				if (fp != NULL) {
    354 					fd_close(fd);
    355 				}
    356 				return error;
    357 			}
    358 		}
    359 		curlwp->l_dupfd = fd;
    360 		return EMOVEFD;
    361 	case 1:		/* /dev/ptm */
    362 		return 0;
    363 	default:
    364 		return ENODEV;
    365 	}
    366 }
    367 
    368 static int
    369 /*ARGSUSED*/
    370 ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
    371 {
    372 
    373 	return (0);
    374 }
    375 
    376 static int
    377 /*ARGSUSED*/
    378 ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
    379 {
    380 	int error;
    381 	dev_t newdev;
    382 	int cfd, sfd;
    383 	file_t *fp;
    384 	struct mount *mp;
    385 
    386 	error = 0;
    387 	switch (cmd) {
    388 	case TIOCPTMGET:
    389 		if ((error = pty_getmp(l, &mp)) != 0)
    390 			return error;
    391 
    392 		if ((error = pty_alloc_master(l, &cfd, &newdev, mp)) != 0)
    393 			return error;
    394 
    395 		if ((error = pty_grant_slave(l, newdev, mp)) != 0)
    396 			goto bad;
    397 
    398 		if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
    399 			goto bad;
    400 
    401 		/* now, put the indices and names into struct ptmget */
    402 		if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
    403 			goto bad2;
    404 		return 0;
    405 	default:
    406 		MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
    407 		    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
    408 		if (error != EPASSTHROUGH)
    409 			return error;
    410 		DPRINTF(("ptmioctl EINVAL\n"));
    411 		return EINVAL;
    412 	}
    413 bad2:
    414 	fp = fd_getfile(sfd);
    415 	if (fp != NULL) {
    416 		fd_close(sfd);
    417 	}
    418  bad:
    419 	fp = fd_getfile(cfd);
    420 	if (fp != NULL) {
    421 		fd_close(cfd);
    422 	}
    423 	return error;
    424 }
    425 
    426 const struct cdevsw ptm_cdevsw = {
    427 	.d_open = ptmopen,
    428 	.d_close = ptmclose,
    429 	.d_read = noread,
    430 	.d_write = nowrite,
    431 	.d_ioctl = ptmioctl,
    432 	.d_stop = nullstop,
    433 	.d_tty = notty,
    434 	.d_poll = nopoll,
    435 	.d_mmap = nommap,
    436 	.d_kqfilter = nokqfilter,
    437 	.d_discard = nodiscard,
    438 	.d_flag = D_TTY
    439 };
    440 #endif
    441