1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1993
5 *	The Regents of the University of California.  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 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32/*
33 * Error log buffer for kernel printf's.
34 */
35
36#include <sys/param.h>
37#include <sys/systm.h>
38#include <sys/conf.h>
39#include <sys/proc.h>
40#include <sys/vnode.h>
41#include <sys/filio.h>
42#include <sys/ttycom.h>
43#include <sys/msgbuf.h>
44#include <sys/signalvar.h>
45#include <sys/kernel.h>
46#include <sys/poll.h>
47#include <sys/filedesc.h>
48#include <sys/sysctl.h>
49
50#define LOG_RDPRI	(PZERO + 1)
51
52#define LOG_ASYNC	0x04
53
54static	d_open_t	logopen;
55static	d_close_t	logclose;
56static	d_read_t	logread;
57static	d_ioctl_t	logioctl;
58static	d_poll_t	logpoll;
59static	d_kqfilter_t	logkqfilter;
60
61static	void logtimeout(void *arg);
62
63static struct cdevsw log_cdevsw = {
64	.d_version =	D_VERSION,
65	.d_open =	logopen,
66	.d_close =	logclose,
67	.d_read =	logread,
68	.d_ioctl =	logioctl,
69	.d_poll =	logpoll,
70	.d_kqfilter =	logkqfilter,
71	.d_name =	"log",
72};
73
74static int	logkqread(struct knote *note, long hint);
75static void	logkqdetach(struct knote *note);
76
77static struct filterops log_read_filterops = {
78	.f_isfd =	1,
79	.f_attach =	NULL,
80	.f_detach =	logkqdetach,
81	.f_event =	logkqread,
82};
83
84static struct logsoftc {
85	int	sc_state;		/* see above for possibilities */
86	struct	selinfo sc_selp;	/* process waiting on select call */
87	struct  sigio *sc_sigio;	/* information for async I/O */
88	struct	callout sc_callout;	/* callout to wakeup syslog  */
89} logsoftc;
90
91int			log_open;	/* also used in log() */
92static struct cv	log_wakeup;
93struct mtx		msgbuf_lock;
94MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
95
96static int	log_wakeups_per_second = 5;
97SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
98    &log_wakeups_per_second, 0,
99    "How often (times per second) to check for /dev/log waiters.");
100
101/*ARGSUSED*/
102static	int
103logopen(struct cdev *dev, int flags, int mode, struct thread *td)
104{
105
106	if (log_wakeups_per_second < 1) {
107		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
108		log_wakeups_per_second = 1;
109	}
110
111	mtx_lock(&msgbuf_lock);
112	if (log_open) {
113		mtx_unlock(&msgbuf_lock);
114		return (EBUSY);
115	}
116	log_open = 1;
117	callout_reset_sbt(&logsoftc.sc_callout,
118	    SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
119	mtx_unlock(&msgbuf_lock);
120
121	fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);	/* signal process only */
122	return (0);
123}
124
125/*ARGSUSED*/
126static	int
127logclose(struct cdev *dev, int flag, int mode, struct thread *td)
128{
129
130	funsetown(&logsoftc.sc_sigio);
131
132	mtx_lock(&msgbuf_lock);
133	callout_stop(&logsoftc.sc_callout);
134	logsoftc.sc_state = 0;
135	log_open = 0;
136	mtx_unlock(&msgbuf_lock);
137
138	return (0);
139}
140
141/*ARGSUSED*/
142static	int
143logread(struct cdev *dev, struct uio *uio, int flag)
144{
145	char buf[128];
146	struct msgbuf *mbp = msgbufp;
147	int error = 0, l;
148
149	mtx_lock(&msgbuf_lock);
150	while (msgbuf_getcount(mbp) == 0) {
151		if (flag & IO_NDELAY) {
152			mtx_unlock(&msgbuf_lock);
153			return (EWOULDBLOCK);
154		}
155		if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
156			mtx_unlock(&msgbuf_lock);
157			return (error);
158		}
159	}
160
161	while (uio->uio_resid > 0) {
162		l = imin(sizeof(buf), uio->uio_resid);
163		l = msgbuf_getbytes(mbp, buf, l);
164		if (l == 0)
165			break;
166		mtx_unlock(&msgbuf_lock);
167		error = uiomove(buf, l, uio);
168		if (error || uio->uio_resid == 0)
169			return (error);
170		mtx_lock(&msgbuf_lock);
171	}
172	mtx_unlock(&msgbuf_lock);
173	return (error);
174}
175
176/*ARGSUSED*/
177static	int
178logpoll(struct cdev *dev, int events, struct thread *td)
179{
180	int revents = 0;
181
182	if (events & (POLLIN | POLLRDNORM)) {
183		mtx_lock(&msgbuf_lock);
184		if (msgbuf_getcount(msgbufp) > 0)
185			revents |= events & (POLLIN | POLLRDNORM);
186		else
187			selrecord(td, &logsoftc.sc_selp);
188		mtx_unlock(&msgbuf_lock);
189	}
190	return (revents);
191}
192
193static int
194logkqfilter(struct cdev *dev, struct knote *kn)
195{
196
197	if (kn->kn_filter != EVFILT_READ)
198		return (EINVAL);
199
200	kn->kn_fop = &log_read_filterops;
201	kn->kn_hook = NULL;
202
203	mtx_lock(&msgbuf_lock);
204	knlist_add(&logsoftc.sc_selp.si_note, kn, 1);
205	mtx_unlock(&msgbuf_lock);
206	return (0);
207}
208
209static int
210logkqread(struct knote *kn, long hint)
211{
212
213	mtx_assert(&msgbuf_lock, MA_OWNED);
214	kn->kn_data = msgbuf_getcount(msgbufp);
215	return (kn->kn_data != 0);
216}
217
218static void
219logkqdetach(struct knote *kn)
220{
221
222	mtx_lock(&msgbuf_lock);
223	knlist_remove(&logsoftc.sc_selp.si_note, kn, 1);
224	mtx_unlock(&msgbuf_lock);
225}
226
227static void
228logtimeout(void *arg)
229{
230
231	if (!log_open)
232		return;
233	if (msgbuftrigger == 0)
234		goto done;
235	msgbuftrigger = 0;
236	selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
237	KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0);
238	if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
239		pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
240	cv_broadcastpri(&log_wakeup, LOG_RDPRI);
241done:
242	if (log_wakeups_per_second < 1) {
243		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
244		log_wakeups_per_second = 1;
245	}
246	callout_reset_sbt(&logsoftc.sc_callout,
247	    SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
248}
249
250/*ARGSUSED*/
251static	int
252logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
253{
254
255	switch (com) {
256	/* return number of characters immediately available */
257	case FIONREAD:
258		*(int *)data = msgbuf_getcount(msgbufp);
259		break;
260
261	case FIONBIO:
262		break;
263
264	case FIOASYNC:
265		mtx_lock(&msgbuf_lock);
266		if (*(int *)data)
267			logsoftc.sc_state |= LOG_ASYNC;
268		else
269			logsoftc.sc_state &= ~LOG_ASYNC;
270		mtx_unlock(&msgbuf_lock);
271		break;
272
273	case FIOSETOWN:
274		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
275
276	case FIOGETOWN:
277		*(int *)data = fgetown(&logsoftc.sc_sigio);
278		break;
279
280	/* This is deprecated, FIOSETOWN should be used instead. */
281	case TIOCSPGRP:
282		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
283
284	/* This is deprecated, FIOGETOWN should be used instead */
285	case TIOCGPGRP:
286		*(int *)data = -fgetown(&logsoftc.sc_sigio);
287		break;
288
289	default:
290		return (ENOTTY);
291	}
292	return (0);
293}
294
295static void
296log_drvinit(void *unused)
297{
298
299	cv_init(&log_wakeup, "klog");
300	callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
301	knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock);
302	make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
303	    GID_WHEEL, 0600, "klog");
304}
305
306SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
307