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 *	@(#)subr_log.c	8.1 (Berkeley) 6/10/93
32 */
33
34/*
35 * Error log buffer for kernel printf's.
36 */
37
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD$");
40
41#include <sys/param.h>
42#include <sys/systm.h>
43#include <sys/conf.h>
44#include <sys/proc.h>
45#include <sys/vnode.h>
46#include <sys/filio.h>
47#include <sys/ttycom.h>
48#include <sys/msgbuf.h>
49#include <sys/signalvar.h>
50#include <sys/kernel.h>
51#include <sys/poll.h>
52#include <sys/filedesc.h>
53#include <sys/sysctl.h>
54
55#define LOG_RDPRI	(PZERO + 1)
56
57#define LOG_ASYNC	0x04
58
59static	d_open_t	logopen;
60static	d_close_t	logclose;
61static	d_read_t	logread;
62static	d_ioctl_t	logioctl;
63static	d_poll_t	logpoll;
64static	d_kqfilter_t	logkqfilter;
65
66static	void logtimeout(void *arg);
67
68static struct cdevsw log_cdevsw = {
69	.d_version =	D_VERSION,
70	.d_open =	logopen,
71	.d_close =	logclose,
72	.d_read =	logread,
73	.d_ioctl =	logioctl,
74	.d_poll =	logpoll,
75	.d_kqfilter =	logkqfilter,
76	.d_name =	"log",
77};
78
79static int	logkqread(struct knote *note, long hint);
80static void	logkqdetach(struct knote *note);
81
82static struct filterops log_read_filterops = {
83	.f_isfd =	1,
84	.f_attach =	NULL,
85	.f_detach =	logkqdetach,
86	.f_event =	logkqread,
87};
88
89static struct logsoftc {
90	int	sc_state;		/* see above for possibilities */
91	struct	selinfo sc_selp;	/* process waiting on select call */
92	struct  sigio *sc_sigio;	/* information for async I/O */
93	struct	callout sc_callout;	/* callout to wakeup syslog  */
94} logsoftc;
95
96int			log_open;	/* also used in log() */
97static struct cv	log_wakeup;
98struct mtx		msgbuf_lock;
99MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
100
101/* Times per second to check for a pending syslog wakeup. */
102static int	log_wakeups_per_second = 5;
103SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
104    &log_wakeups_per_second, 0, "");
105
106/*ARGSUSED*/
107static	int
108logopen(struct cdev *dev, int flags, int mode, struct thread *td)
109{
110
111	if (log_wakeups_per_second < 1) {
112		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
113		log_wakeups_per_second = 1;
114	}
115
116	mtx_lock(&msgbuf_lock);
117	if (log_open) {
118		mtx_unlock(&msgbuf_lock);
119		return (EBUSY);
120	}
121	log_open = 1;
122	callout_reset_sbt(&logsoftc.sc_callout,
123	    SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
124	mtx_unlock(&msgbuf_lock);
125
126	fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);	/* signal process only */
127	return (0);
128}
129
130/*ARGSUSED*/
131static	int
132logclose(struct cdev *dev, int flag, int mode, struct thread *td)
133{
134
135	funsetown(&logsoftc.sc_sigio);
136
137	mtx_lock(&msgbuf_lock);
138	callout_stop(&logsoftc.sc_callout);
139	logsoftc.sc_state = 0;
140	log_open = 0;
141	mtx_unlock(&msgbuf_lock);
142
143	return (0);
144}
145
146/*ARGSUSED*/
147static	int
148logread(struct cdev *dev, struct uio *uio, int flag)
149{
150	char buf[128];
151	struct msgbuf *mbp = msgbufp;
152	int error = 0, l;
153
154	mtx_lock(&msgbuf_lock);
155	while (msgbuf_getcount(mbp) == 0) {
156		if (flag & IO_NDELAY) {
157			mtx_unlock(&msgbuf_lock);
158			return (EWOULDBLOCK);
159		}
160		if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
161			mtx_unlock(&msgbuf_lock);
162			return (error);
163		}
164	}
165
166	while (uio->uio_resid > 0) {
167		l = imin(sizeof(buf), uio->uio_resid);
168		l = msgbuf_getbytes(mbp, buf, l);
169		if (l == 0)
170			break;
171		mtx_unlock(&msgbuf_lock);
172		error = uiomove(buf, l, uio);
173		if (error || uio->uio_resid == 0)
174			return (error);
175		mtx_lock(&msgbuf_lock);
176	}
177	mtx_unlock(&msgbuf_lock);
178	return (error);
179}
180
181/*ARGSUSED*/
182static	int
183logpoll(struct cdev *dev, int events, struct thread *td)
184{
185	int revents = 0;
186
187	if (events & (POLLIN | POLLRDNORM)) {
188		mtx_lock(&msgbuf_lock);
189		if (msgbuf_getcount(msgbufp) > 0)
190			revents |= events & (POLLIN | POLLRDNORM);
191		else
192			selrecord(td, &logsoftc.sc_selp);
193		mtx_unlock(&msgbuf_lock);
194	}
195	return (revents);
196}
197
198static int
199logkqfilter(struct cdev *dev, struct knote *kn)
200{
201
202	if (kn->kn_filter != EVFILT_READ)
203		return (EINVAL);
204
205	kn->kn_fop = &log_read_filterops;
206	kn->kn_hook = NULL;
207
208	mtx_lock(&msgbuf_lock);
209	knlist_add(&logsoftc.sc_selp.si_note, kn, 1);
210	mtx_unlock(&msgbuf_lock);
211	return (0);
212}
213
214static int
215logkqread(struct knote *kn, long hint)
216{
217
218	mtx_assert(&msgbuf_lock, MA_OWNED);
219	kn->kn_data = msgbuf_getcount(msgbufp);
220	return (kn->kn_data != 0);
221}
222
223static void
224logkqdetach(struct knote *kn)
225{
226
227	mtx_lock(&msgbuf_lock);
228	knlist_remove(&logsoftc.sc_selp.si_note, kn, 1);
229	mtx_unlock(&msgbuf_lock);
230}
231
232static void
233logtimeout(void *arg)
234{
235
236	if (!log_open)
237		return;
238	if (msgbuftrigger == 0)
239		goto done;
240	msgbuftrigger = 0;
241	selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
242	KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0);
243	if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
244		pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
245	cv_broadcastpri(&log_wakeup, LOG_RDPRI);
246done:
247	if (log_wakeups_per_second < 1) {
248		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
249		log_wakeups_per_second = 1;
250	}
251	callout_reset_sbt(&logsoftc.sc_callout,
252	    SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
253}
254
255/*ARGSUSED*/
256static	int
257logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
258{
259
260	switch (com) {
261
262	/* return number of characters immediately available */
263	case FIONREAD:
264		*(int *)data = msgbuf_getcount(msgbufp);
265		break;
266
267	case FIONBIO:
268		break;
269
270	case FIOASYNC:
271		mtx_lock(&msgbuf_lock);
272		if (*(int *)data)
273			logsoftc.sc_state |= LOG_ASYNC;
274		else
275			logsoftc.sc_state &= ~LOG_ASYNC;
276		mtx_unlock(&msgbuf_lock);
277		break;
278
279	case FIOSETOWN:
280		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
281
282	case FIOGETOWN:
283		*(int *)data = fgetown(&logsoftc.sc_sigio);
284		break;
285
286	/* This is deprecated, FIOSETOWN should be used instead. */
287	case TIOCSPGRP:
288		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
289
290	/* This is deprecated, FIOGETOWN should be used instead */
291	case TIOCGPGRP:
292		*(int *)data = -fgetown(&logsoftc.sc_sigio);
293		break;
294
295	default:
296		return (ENOTTY);
297	}
298	return (0);
299}
300
301static void
302log_drvinit(void *unused)
303{
304
305	cv_init(&log_wakeup, "klog");
306	callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
307	knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock);
308	make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
309	    GID_WHEEL, 0600, "klog");
310}
311
312SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
313