subr_log.c revision 116660 
1/*
2 * Copyright (c) 1982, 1986, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 *	@(#)subr_log.c	8.1 (Berkeley) 6/10/93
34 */
35
36/*
37 * Error log buffer for kernel printf's.
38 */
39
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/sys/kern/subr_log.c 116660 2003-06-22 02:18:31Z iedowse $");
42
43#include <sys/param.h>
44#include <sys/systm.h>
45#include <sys/conf.h>
46#include <sys/proc.h>
47#include <sys/vnode.h>
48#include <sys/filio.h>
49#include <sys/ttycom.h>
50#include <sys/msgbuf.h>
51#include <sys/signalvar.h>
52#include <sys/kernel.h>
53#include <sys/poll.h>
54#include <sys/filedesc.h>
55#include <sys/sysctl.h>
56
57#define LOG_RDPRI	(PZERO + 1)
58
59#define LOG_ASYNC	0x04
60#define LOG_RDWAIT	0x08
61
62static	d_open_t	logopen;
63static	d_close_t	logclose;
64static	d_read_t	logread;
65static	d_ioctl_t	logioctl;
66static	d_poll_t	logpoll;
67
68static	void logtimeout(void *arg);
69
70#define CDEV_MAJOR 7
71static struct cdevsw log_cdevsw = {
72	.d_open =	logopen,
73	.d_close =	logclose,
74	.d_read =	logread,
75	.d_ioctl =	logioctl,
76	.d_poll =	logpoll,
77	.d_name =	"log",
78	.d_maj =	CDEV_MAJOR,
79};
80
81static struct logsoftc {
82	int	sc_state;		/* see above for possibilities */
83	struct	selinfo sc_selp;	/* process waiting on select call */
84	struct  sigio *sc_sigio;	/* information for async I/O */
85	struct	callout sc_callout;	/* callout to wakeup syslog  */
86} logsoftc;
87
88int	log_open;			/* also used in log() */
89
90/* Times per second to check for a pending syslog wakeup. */
91static int	log_wakeups_per_second = 5;
92SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
93    &log_wakeups_per_second, 0, "");
94
95/*ARGSUSED*/
96static	int
97logopen(dev_t dev, int flags, int mode, struct thread *td)
98{
99	if (log_open)
100		return (EBUSY);
101	log_open = 1;
102	callout_init(&logsoftc.sc_callout, 0);
103	fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);	/* signal process only */
104	if (log_wakeups_per_second < 1) {
105		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
106		log_wakeups_per_second = 1;
107	}
108	callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
109	    logtimeout, NULL);
110	return (0);
111}
112
113/*ARGSUSED*/
114static	int
115logclose(dev_t dev, int flag, int mode, struct thread *td)
116{
117
118	log_open = 0;
119	callout_stop(&logsoftc.sc_callout);
120	logsoftc.sc_state = 0;
121	funsetown(&logsoftc.sc_sigio);
122	return (0);
123}
124
125/*ARGSUSED*/
126static	int
127logread(dev_t dev, struct uio *uio, int flag)
128{
129	char buf[128];
130	struct msgbuf *mbp = msgbufp;
131	int error = 0, l, s;
132
133	s = splhigh();
134	while (msgbuf_getcount(mbp) == 0) {
135		if (flag & IO_NDELAY) {
136			splx(s);
137			return (EWOULDBLOCK);
138		}
139		logsoftc.sc_state |= LOG_RDWAIT;
140		if ((error = tsleep(mbp, LOG_RDPRI | PCATCH, "klog", 0))) {
141			splx(s);
142			return (error);
143		}
144	}
145	splx(s);
146	logsoftc.sc_state &= ~LOG_RDWAIT;
147
148	while (uio->uio_resid > 0) {
149		l = imin(sizeof(buf), uio->uio_resid);
150		l = msgbuf_getbytes(mbp, buf, l);
151		if (l == 0)
152			break;
153		error = uiomove(buf, l, uio);
154		if (error)
155			break;
156	}
157	return (error);
158}
159
160/*ARGSUSED*/
161static	int
162logpoll(dev_t dev, int events, struct thread *td)
163{
164	int s;
165	int revents = 0;
166
167	s = splhigh();
168
169	if (events & (POLLIN | POLLRDNORM)) {
170		if (msgbuf_getcount(msgbufp) > 0)
171			revents |= events & (POLLIN | POLLRDNORM);
172		else
173			selrecord(td, &logsoftc.sc_selp);
174	}
175	splx(s);
176	return (revents);
177}
178
179static void
180logtimeout(void *arg)
181{
182
183	if (!log_open)
184		return;
185	if (log_wakeups_per_second < 1) {
186		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
187		log_wakeups_per_second = 1;
188	}
189	if (msgbuftrigger == 0) {
190		callout_reset(&logsoftc.sc_callout,
191		    hz / log_wakeups_per_second, logtimeout, NULL);
192		return;
193	}
194	msgbuftrigger = 0;
195	selwakeup(&logsoftc.sc_selp);
196	if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
197		pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
198	if (logsoftc.sc_state & LOG_RDWAIT) {
199		wakeup(msgbufp);
200		logsoftc.sc_state &= ~LOG_RDWAIT;
201	}
202	callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
203	    logtimeout, NULL);
204}
205
206/*ARGSUSED*/
207static	int
208logioctl(dev_t dev, u_long com, caddr_t data, int flag, struct thread *td)
209{
210
211	switch (com) {
212
213	/* return number of characters immediately available */
214	case FIONREAD:
215		*(int *)data = msgbuf_getcount(msgbufp);
216		break;
217
218	case FIONBIO:
219		break;
220
221	case FIOASYNC:
222		if (*(int *)data)
223			logsoftc.sc_state |= LOG_ASYNC;
224		else
225			logsoftc.sc_state &= ~LOG_ASYNC;
226		break;
227
228	case FIOSETOWN:
229		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
230
231	case FIOGETOWN:
232		*(int *)data = fgetown(&logsoftc.sc_sigio);
233		break;
234
235	/* This is deprecated, FIOSETOWN should be used instead. */
236	case TIOCSPGRP:
237		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
238
239	/* This is deprecated, FIOGETOWN should be used instead */
240	case TIOCGPGRP:
241		*(int *)data = -fgetown(&logsoftc.sc_sigio);
242		break;
243
244	default:
245		return (ENOTTY);
246	}
247	return (0);
248}
249
250static void
251log_drvinit(void *unused)
252{
253
254	make_dev(&log_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
255}
256
257SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE+CDEV_MAJOR,log_drvinit,NULL)
258