1/*	$NetBSD: tty_ptm.c,v 1.46 2023/04/09 09:18:09 riastradh 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 1.46 2023/04/09 09:18:09 riastradh 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
71const 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
87int pts_major, ptc_major;
88
89static dev_t pty_getfree(void);
90static int pty_alloc_master(struct lwp *, int *, dev_t *, struct mount *, int);
91static int pty_alloc_slave(struct lwp *, int *, dev_t, struct mount *);
92static int pty_vn_open(struct vnode *, struct lwp *);
93
94int
95pty_getmp(struct lwp *l, struct mount **mpp)
96{
97	if (ptm == NULL)
98		return EOPNOTSUPP;
99
100	return (*ptm->getmp)(l, mpp);
101}
102
103dev_t
104pty_makedev(char ms, int minor)
105{
106	return makedev(ms == 't' ? pts_major : ptc_major, minor);
107}
108
109
110static dev_t
111pty_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 */
131int
132pty_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);
146		KASSERT(error != EMOVEFD);
147		vput(vp);
148		return error;
149	}
150
151	mutex_enter(vp->v_interlock);
152	vp->v_writecount++;
153	mutex_exit(vp->v_interlock);
154
155	return 0;
156}
157
158static int
159pty_alloc_master(struct lwp *l, int *fd, dev_t *dev, struct mount *mp,
160    int flags)
161{
162	int error;
163	struct file *fp;
164	struct vnode *vp;
165	int md;
166
167	if ((error = fd_allocfile(&fp, fd)) != 0) {
168		DPRINTF(("fd_allocfile %d\n", error));
169		return error;
170	}
171retry:
172	/* Find and open a free master pty. */
173	*dev = pty_getfree();
174	md = minor(*dev);
175	if ((error = pty_check(md)) != 0) {
176		DPRINTF(("pty_check %d\n", error));
177		goto bad;
178	}
179	if (ptm == NULL) {
180		DPRINTF(("no ptm\n"));
181		error = EOPNOTSUPP;
182		goto bad;
183	}
184	if ((error = (*ptm->allocvp)(mp, l, &vp, *dev, 'p')) != 0) {
185		DPRINTF(("pty_allocvp %d\n", error));
186		goto bad;
187	}
188
189	if ((error = pty_vn_open(vp, l)) != 0) {
190		DPRINTF(("pty_vn_open %d\n", error));
191		/*
192		 * Check if the master open failed because we lost
193		 * the race to grab it.
194		 */
195		if (error != EIO)
196			goto bad;
197		error = !pty_isfree(md, 1);
198		DPRINTF(("pty_isfree %d\n", error));
199		if (error)
200			goto retry;
201		else
202			goto bad;
203	}
204	fp->f_flag = FREAD|FWRITE|(flags&FMASK);
205	fp->f_type = DTYPE_VNODE;
206	fp->f_ops = &vnops;
207	fp->f_vnode = vp;
208
209	VOP_UNLOCK(vp);
210	fd_set_exclose(l, *fd, (flags & O_CLOEXEC) != 0);
211	fd_affix(curproc, fp, *fd);
212	return 0;
213bad:
214	fd_abort(curproc, fp, *fd);
215	return error;
216}
217
218int
219pty_grant_slave(struct lwp *l, dev_t dev, struct mount *mp)
220{
221	int error;
222	struct vnode *vp;
223
224	/*
225	 * Open the slave.
226	 * namei -> setattr -> unlock -> revoke -> vrele ->
227	 * namei -> open -> unlock
228	 * Three stage rocket:
229	 * 1. Change the owner and permissions on the slave.
230	 * 2. Revoke all the users of the slave.
231	 * 3. open the slave.
232	 */
233	if (ptm == NULL)
234		return EOPNOTSUPP;
235	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
236		return error;
237
238	if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
239		struct vattr vattr;
240		(*ptm->getvattr)(mp, l, &vattr);
241		/* Do the VOP_SETATTR() as root. */
242		error = VOP_SETATTR(vp, &vattr, lwp0.l_cred);
243		if (error) {
244			DPRINTF(("setattr %d\n", error));
245			vput(vp);
246			return error;
247		}
248	}
249	VOP_UNLOCK(vp);
250	VOP_REVOKE(vp, REVOKEALL);
251
252	/*
253	 * The vnode is useless after the revoke, we need to get it again.
254	 */
255	vrele(vp);
256	return 0;
257}
258
259static int
260pty_alloc_slave(struct lwp *l, int *fd, dev_t dev, struct mount *mp)
261{
262	int error;
263	struct file *fp;
264	struct vnode *vp;
265
266	/* Grab a filedescriptor for the slave */
267	if ((error = fd_allocfile(&fp, fd)) != 0) {
268		DPRINTF(("fd_allocfile %d\n", error));
269		return error;
270	}
271
272	if (ptm == NULL) {
273		error = EOPNOTSUPP;
274		goto bad;
275	}
276
277	if ((error = (*ptm->allocvp)(mp, l, &vp, dev, 't')) != 0)
278		goto bad;
279	if ((error = pty_vn_open(vp, l)) != 0)
280		goto bad;
281
282	fp->f_flag = FREAD|FWRITE;
283	fp->f_type = DTYPE_VNODE;
284	fp->f_ops = &vnops;
285	fp->f_vnode = vp;
286	VOP_UNLOCK(vp);
287	fd_affix(curproc, fp, *fd);
288	return 0;
289bad:
290	fd_abort(curproc, fp, *fd);
291	return error;
292}
293
294struct ptm_pty *
295pty_sethandler(struct ptm_pty *nptm)
296{
297	struct ptm_pty *optm = ptm;
298	ptm = nptm;
299	return optm;
300}
301
302int
303pty_fill_ptmget(struct lwp *l, dev_t dev, int cfd, int sfd, void *data, struct mount *mp)
304{
305	struct ptmget *ptmg = data;
306	int error;
307
308	if (ptm == NULL)
309		return EOPNOTSUPP;
310
311	ptmg->cfd = cfd == -1 ? minor(dev) : cfd;
312	ptmg->sfd = sfd == -1 ? minor(dev) : sfd;
313
314	error = (*ptm->makename)(mp, l, ptmg->cn, sizeof(ptmg->cn), dev, 'p');
315	if (error)
316		return error;
317
318	return (*ptm->makename)(mp, l, ptmg->sn, sizeof(ptmg->sn), dev, 't');
319}
320
321void
322/*ARGSUSED*/
323ptmattach(int n)
324{
325	extern const struct cdevsw pts_cdevsw, ptc_cdevsw;
326	/* find the major and minor of the pty devices */
327	if ((pts_major = cdevsw_lookup_major(&pts_cdevsw)) == -1)
328		panic("%s: Can't find pty slave in cdevsw", __func__);
329	if ((ptc_major = cdevsw_lookup_major(&ptc_cdevsw)) == -1)
330		panic("%s: Can't find pty master in cdevsw", __func__);
331#ifdef COMPAT_BSDPTY
332	ptm = &ptm_bsdpty;
333#endif
334}
335
336static int
337/*ARGSUSED*/
338ptmopen(dev_t dev, int flag, int mode, struct lwp *l)
339{
340	int error;
341	int fd;
342	dev_t ttydev;
343	struct mount *mp;
344
345	switch(minor(dev)) {
346	case 0:		/* /dev/ptmx */
347	case 2:		/* /emul/linux/dev/ptmx */
348		if ((error = pty_getmp(l, &mp)) != 0)
349			return error;
350		if ((error = pty_alloc_master(l, &fd, &ttydev, mp, flag)) != 0)
351			return error;
352		if (minor(dev) == 2) {
353			/*
354			 * Linux ptyfs grants the pty right here.
355			 * Handle this case here, instead of writing
356			 * a new linux module.
357			 */
358			if ((error = pty_grant_slave(l, ttydev, mp)) != 0) {
359				file_t *fp = fd_getfile(fd);
360				if (fp != NULL) {
361					fd_close(fd);
362				}
363				return error;
364			}
365		}
366		curlwp->l_dupfd = fd;
367		return EMOVEFD;
368	case 1:		/* /dev/ptm */
369		return 0;
370	default:
371		return ENODEV;
372	}
373}
374
375static int
376/*ARGSUSED*/
377ptmclose(dev_t dev, int flag, int mode, struct lwp *l)
378{
379
380	return (0);
381}
382
383static int
384/*ARGSUSED*/
385ptmioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
386{
387	int error;
388	dev_t newdev;
389	int cfd, sfd;
390	file_t *fp;
391	struct mount *mp;
392
393	error = 0;
394	switch (cmd) {
395	case TIOCPTMGET:
396		if ((error = pty_getmp(l, &mp)) != 0)
397			return error;
398
399		if ((error = pty_alloc_master(l, &cfd, &newdev, mp, 0)) != 0)
400			return error;
401
402		if ((error = pty_grant_slave(l, newdev, mp)) != 0)
403			goto bad;
404
405		if ((error = pty_alloc_slave(l, &sfd, newdev, mp)) != 0)
406			goto bad;
407
408		/* now, put the indices and names into struct ptmget */
409		if ((error = pty_fill_ptmget(l, newdev, cfd, sfd, data, mp)) != 0)
410			goto bad2;
411		return 0;
412	default:
413		MODULE_HOOK_CALL(tty_ptmioctl_60_hook,
414		    (dev, cmd, data, flag, l), EPASSTHROUGH, error);
415		if (error != EPASSTHROUGH)
416			return error;
417		DPRINTF(("ptmioctl EINVAL\n"));
418		return EINVAL;
419	}
420bad2:
421	fp = fd_getfile(sfd);
422	if (fp != NULL) {
423		fd_close(sfd);
424	}
425 bad:
426	fp = fd_getfile(cfd);
427	if (fp != NULL) {
428		fd_close(cfd);
429	}
430	return error;
431}
432
433const struct cdevsw ptm_cdevsw = {
434	.d_open = ptmopen,
435	.d_close = ptmclose,
436	.d_read = noread,
437	.d_write = nowrite,
438	.d_ioctl = ptmioctl,
439	.d_stop = nullstop,
440	.d_tty = notty,
441	.d_poll = nopoll,
442	.d_mmap = nommap,
443	.d_kqfilter = nokqfilter,
444	.d_discard = nodiscard,
445	.d_flag = D_TTY
446};
447#endif
448