xref: /netbsd-src/sys/kern/subr_log.c (revision 21e37cc72a480a47828990a439cde7ac9ffaf0c6)
1 /*	$NetBSD: subr_log.c,v 1.33 2003/09/22 12:59:57 christos Exp $	*/
2 
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	8.3 (Berkeley) 2/14/95
32  */
33 
34 /*
35  * Error log buffer for kernel printf's.
36  */
37 
38 #include <sys/cdefs.h>
39 __KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.33 2003/09/22 12:59:57 christos Exp $");
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/proc.h>
44 #include <sys/vnode.h>
45 #include <sys/ioctl.h>
46 #include <sys/msgbuf.h>
47 #include <sys/file.h>
48 #include <sys/signalvar.h>
49 #include <sys/syslog.h>
50 #include <sys/conf.h>
51 #include <sys/select.h>
52 #include <sys/poll.h>
53 
54 #define LOG_RDPRI	(PZERO + 1)
55 
56 #define LOG_ASYNC	0x04
57 #define LOG_RDWAIT	0x08
58 
59 struct logsoftc {
60 	int	sc_state;		/* see above for possibilities */
61 	struct	selinfo sc_selp;	/* process waiting on select call */
62 	pid_t	sc_pgid;		/* process/group for async I/O */
63 } logsoftc;
64 
65 int	log_open;			/* also used in log() */
66 int	msgbufmapped;			/* is the message buffer mapped */
67 int	msgbufenabled;			/* is logging to the buffer enabled */
68 struct	kern_msgbuf *msgbufp;		/* the mapped buffer, itself. */
69 
70 dev_type_open(logopen);
71 dev_type_close(logclose);
72 dev_type_read(logread);
73 dev_type_ioctl(logioctl);
74 dev_type_poll(logpoll);
75 dev_type_kqfilter(logkqfilter);
76 
77 const struct cdevsw log_cdevsw = {
78 	logopen, logclose, logread, nowrite, logioctl,
79 	nostop, notty, logpoll, nommap, logkqfilter,
80 };
81 
82 void
83 initmsgbuf(buf, bufsize)
84 	caddr_t buf;
85 	size_t bufsize;
86 {
87 	struct kern_msgbuf *mbp;
88 	long new_bufs;
89 
90 	/* Sanity-check the given size. */
91 	if (bufsize < sizeof(struct kern_msgbuf))
92 		return;
93 
94 	mbp = msgbufp = (struct kern_msgbuf *)buf;
95 
96 	new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc);
97 	if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
98 	    (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
99 	    (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
100 		/*
101 		 * If the buffer magic number is wrong, has changed
102 		 * size (which shouldn't happen often), or is
103 		 * internally inconsistent, initialize it.
104 		 */
105 
106 		memset(buf, 0, bufsize);
107 		mbp->msg_magic = MSG_MAGIC;
108 		mbp->msg_bufs = new_bufs;
109 	}
110 
111 	/* mark it as ready for use. */
112 	msgbufmapped = msgbufenabled = 1;
113 }
114 
115 /*ARGSUSED*/
116 int
117 logopen(dev, flags, mode, p)
118 	dev_t dev;
119 	int flags, mode;
120 	struct proc *p;
121 {
122 	struct kern_msgbuf *mbp = msgbufp;
123 
124 	if (log_open)
125 		return (EBUSY);
126 	log_open = 1;
127 	logsoftc.sc_pgid = p->p_pid;		/* signal process only */
128 	/*
129 	 * The message buffer is initialized during system configuration.
130 	 * If it's been clobbered, note that and return an error.  (This
131 	 * allows a user to potentially read the buffer via /dev/kmem,
132 	 * and try to figure out what clobbered it.
133 	 */
134 	if (mbp->msg_magic != MSG_MAGIC) {
135 		msgbufenabled = 0;
136 		return (ENXIO);
137 	}
138 
139 	return (0);
140 }
141 
142 /*ARGSUSED*/
143 int
144 logclose(dev, flag, mode, p)
145 	dev_t dev;
146 	int flag, mode;
147 	struct proc *p;
148 {
149 
150 	log_open = 0;
151 	logsoftc.sc_state = 0;
152 	return (0);
153 }
154 
155 /*ARGSUSED*/
156 int
157 logread(dev, uio, flag)
158 	dev_t dev;
159 	struct uio *uio;
160 	int flag;
161 {
162 	struct kern_msgbuf *mbp = msgbufp;
163 	long l;
164 	int s;
165 	int error = 0;
166 
167 	s = splhigh();
168 	while (mbp->msg_bufr == mbp->msg_bufx) {
169 		if (flag & IO_NDELAY) {
170 			splx(s);
171 			return (EWOULDBLOCK);
172 		}
173 		logsoftc.sc_state |= LOG_RDWAIT;
174 		error = tsleep((caddr_t)mbp, LOG_RDPRI | PCATCH,
175 			       "klog", 0);
176 		if (error) {
177 			splx(s);
178 			return (error);
179 		}
180 	}
181 	splx(s);
182 	logsoftc.sc_state &= ~LOG_RDWAIT;
183 
184 	while (uio->uio_resid > 0) {
185 		l = mbp->msg_bufx - mbp->msg_bufr;
186 		if (l < 0)
187 			l = mbp->msg_bufs - mbp->msg_bufr;
188 		l = min(l, uio->uio_resid);
189 		if (l == 0)
190 			break;
191 		error = uiomove((caddr_t)&mbp->msg_bufc[mbp->msg_bufr],
192 			(int)l, uio);
193 		if (error)
194 			break;
195 		mbp->msg_bufr += l;
196 		if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
197 			mbp->msg_bufr = 0;
198 	}
199 	return (error);
200 }
201 
202 /*ARGSUSED*/
203 int
204 logpoll(dev, events, p)
205 	dev_t dev;
206 	int events;
207 	struct proc *p;
208 {
209 	int revents = 0;
210 	int s = splhigh();
211 
212 	if (events & (POLLIN | POLLRDNORM)) {
213 		if (msgbufp->msg_bufr != msgbufp->msg_bufx)
214 			revents |= events & (POLLIN | POLLRDNORM);
215 		else
216 			selrecord(p, &logsoftc.sc_selp);
217 	}
218 
219 	splx(s);
220 	return (revents);
221 }
222 
223 static void
224 filt_logrdetach(struct knote *kn)
225 {
226 	int s;
227 
228 	s = splhigh();
229 	SLIST_REMOVE(&logsoftc.sc_selp.sel_klist, kn, knote, kn_selnext);
230 	splx(s);
231 }
232 
233 static int
234 filt_logread(struct knote *kn, long hint)
235 {
236 
237 	if (msgbufp->msg_bufr == msgbufp->msg_bufx)
238 		return (0);
239 
240 	if (msgbufp->msg_bufr < msgbufp->msg_bufx)
241 		kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr;
242 	else
243 		kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) +
244 		    msgbufp->msg_bufx;
245 
246 	return (1);
247 }
248 
249 static const struct filterops logread_filtops =
250 	{ 1, NULL, filt_logrdetach, filt_logread };
251 
252 int
253 logkqfilter(dev_t dev, struct knote *kn)
254 {
255 	struct klist *klist;
256 	int s;
257 
258 	switch (kn->kn_filter) {
259 	case EVFILT_READ:
260 		klist = &logsoftc.sc_selp.sel_klist;
261 		kn->kn_fop = &logread_filtops;
262 		break;
263 
264 	default:
265 		return (1);
266 	}
267 
268 	kn->kn_hook = NULL;
269 
270 	s = splhigh();
271 	SLIST_INSERT_HEAD(klist, kn, kn_selnext);
272 	splx(s);
273 
274 	return (0);
275 }
276 
277 void
278 logwakeup()
279 {
280 	if (!log_open)
281 		return;
282 	selnotify(&logsoftc.sc_selp, 0);
283 	if (logsoftc.sc_state & LOG_ASYNC)
284 		fownsignal(logsoftc.sc_pgid, SIGIO, 0, 0, NULL);
285 	if (logsoftc.sc_state & LOG_RDWAIT) {
286 		wakeup((caddr_t)msgbufp);
287 		logsoftc.sc_state &= ~LOG_RDWAIT;
288 	}
289 }
290 
291 /*ARGSUSED*/
292 int
293 logioctl(dev, com, data, flag, p)
294 	dev_t dev;
295 	u_long com;
296 	caddr_t data;
297 	int flag;
298 	struct proc *p;
299 {
300 	long l;
301 	int s;
302 
303 	switch (com) {
304 
305 	/* return number of characters immediately available */
306 	case FIONREAD:
307 		s = splhigh();
308 		l = msgbufp->msg_bufx - msgbufp->msg_bufr;
309 		splx(s);
310 		if (l < 0)
311 			l += msgbufp->msg_bufs;
312 		*(int *)data = l;
313 		break;
314 
315 	case FIONBIO:
316 		break;
317 
318 	case FIOASYNC:
319 		if (*(int *)data)
320 			logsoftc.sc_state |= LOG_ASYNC;
321 		else
322 			logsoftc.sc_state &= ~LOG_ASYNC;
323 		break;
324 
325 	case TIOCSPGRP:
326 	case FIOSETOWN:
327 		return fsetown(p, &logsoftc.sc_pgid, com, data);
328 
329 	case TIOCGPGRP:
330 	case FIOGETOWN:
331 		return fgetown(p, logsoftc.sc_pgid, com, data);
332 
333 	default:
334 		return (EPASSTHROUGH);
335 	}
336 	return (0);
337 }
338