xref: /freebsd/sys/kern/subr_log.c (revision ebacd8013fe5f7fdf9f6a5b286f6680dd2891036)
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 
59 static	d_open_t	logopen;
60 static	d_close_t	logclose;
61 static	d_read_t	logread;
62 static	d_ioctl_t	logioctl;
63 static	d_poll_t	logpoll;
64 static	d_kqfilter_t	logkqfilter;
65 
66 static	void logtimeout(void *arg);
67 
68 static 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 
79 static int	logkqread(struct knote *note, long hint);
80 static void	logkqdetach(struct knote *note);
81 
82 static struct filterops log_read_filterops = {
83 	.f_isfd =	1,
84 	.f_attach =	NULL,
85 	.f_detach =	logkqdetach,
86 	.f_event =	logkqread,
87 };
88 
89 static 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 
96 int			log_open;	/* also used in log() */
97 static struct cv	log_wakeup;
98 struct mtx		msgbuf_lock;
99 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
100 
101 static int	log_wakeups_per_second = 5;
102 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
103     &log_wakeups_per_second, 0,
104     "How often (times per second) to check for /dev/log waiters.");
105 
106 /*ARGSUSED*/
107 static	int
108 logopen(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*/
131 static	int
132 logclose(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*/
147 static	int
148 logread(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*/
182 static	int
183 logpoll(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 
198 static int
199 logkqfilter(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 
214 static int
215 logkqread(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 
223 static void
224 logkqdetach(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 
232 static void
233 logtimeout(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);
246 done:
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*/
256 static	int
257 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
258 {
259 
260 	switch (com) {
261 	/* return number of characters immediately available */
262 	case FIONREAD:
263 		*(int *)data = msgbuf_getcount(msgbufp);
264 		break;
265 
266 	case FIONBIO:
267 		break;
268 
269 	case FIOASYNC:
270 		mtx_lock(&msgbuf_lock);
271 		if (*(int *)data)
272 			logsoftc.sc_state |= LOG_ASYNC;
273 		else
274 			logsoftc.sc_state &= ~LOG_ASYNC;
275 		mtx_unlock(&msgbuf_lock);
276 		break;
277 
278 	case FIOSETOWN:
279 		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
280 
281 	case FIOGETOWN:
282 		*(int *)data = fgetown(&logsoftc.sc_sigio);
283 		break;
284 
285 	/* This is deprecated, FIOSETOWN should be used instead. */
286 	case TIOCSPGRP:
287 		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
288 
289 	/* This is deprecated, FIOGETOWN should be used instead */
290 	case TIOCGPGRP:
291 		*(int *)data = -fgetown(&logsoftc.sc_sigio);
292 		break;
293 
294 	default:
295 		return (ENOTTY);
296 	}
297 	return (0);
298 }
299 
300 static void
301 log_drvinit(void *unused)
302 {
303 
304 	cv_init(&log_wakeup, "klog");
305 	callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
306 	knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock);
307 	make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
308 	    GID_WHEEL, 0600, "klog");
309 }
310 
311 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
312