subr_log.c revision 177253 
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 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 *	@(#)subr_log.c	8.1 (Berkeley) 6/10/93
30 */
31
32/*
33 * Error log buffer for kernel printf's.
34 */
35
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/sys/kern/subr_log.c 177253 2008-03-16 10:58:09Z rwatson $");
38
39#include <sys/param.h>
40#include <sys/systm.h>
41#include <sys/conf.h>
42#include <sys/proc.h>
43#include <sys/vnode.h>
44#include <sys/filio.h>
45#include <sys/ttycom.h>
46#include <sys/msgbuf.h>
47#include <sys/signalvar.h>
48#include <sys/kernel.h>
49#include <sys/poll.h>
50#include <sys/filedesc.h>
51#include <sys/sysctl.h>
52
53#define LOG_RDPRI	(PZERO + 1)
54
55#define LOG_ASYNC	0x04
56#define LOG_RDWAIT	0x08
57
58static	d_open_t	logopen;
59static	d_close_t	logclose;
60static	d_read_t	logread;
61static	d_ioctl_t	logioctl;
62static	d_poll_t	logpoll;
63
64static	void logtimeout(void *arg);
65
66static struct cdevsw log_cdevsw = {
67	.d_version =	D_VERSION,
68	.d_flags =	D_NEEDGIANT,
69	.d_open =	logopen,
70	.d_close =	logclose,
71	.d_read =	logread,
72	.d_ioctl =	logioctl,
73	.d_poll =	logpoll,
74	.d_name =	"log",
75};
76
77static struct logsoftc {
78	int	sc_state;		/* see above for possibilities */
79	struct	selinfo sc_selp;	/* process waiting on select call */
80	struct  sigio *sc_sigio;	/* information for async I/O */
81	struct	callout sc_callout;	/* callout to wakeup syslog  */
82} logsoftc;
83
84int	log_open;			/* also used in log() */
85
86/* Times per second to check for a pending syslog wakeup. */
87static int	log_wakeups_per_second = 5;
88SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
89    &log_wakeups_per_second, 0, "");
90
91/*ARGSUSED*/
92static	int
93logopen(struct cdev *dev, int flags, int mode, struct thread *td)
94{
95	if (log_open)
96		return (EBUSY);
97	log_open = 1;
98	callout_init(&logsoftc.sc_callout, 0);
99	fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);	/* signal process only */
100	if (log_wakeups_per_second < 1) {
101		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
102		log_wakeups_per_second = 1;
103	}
104	callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
105	    logtimeout, NULL);
106	return (0);
107}
108
109/*ARGSUSED*/
110static	int
111logclose(struct cdev *dev, int flag, int mode, struct thread *td)
112{
113
114	log_open = 0;
115	callout_stop(&logsoftc.sc_callout);
116	logsoftc.sc_state = 0;
117	funsetown(&logsoftc.sc_sigio);
118	return (0);
119}
120
121/*ARGSUSED*/
122static	int
123logread(struct cdev *dev, struct uio *uio, int flag)
124{
125	char buf[128];
126	struct msgbuf *mbp = msgbufp;
127	int error = 0, l, s;
128
129	s = splhigh();
130	while (msgbuf_getcount(mbp) == 0) {
131		if (flag & IO_NDELAY) {
132			splx(s);
133			return (EWOULDBLOCK);
134		}
135		logsoftc.sc_state |= LOG_RDWAIT;
136		if ((error = tsleep(mbp, LOG_RDPRI | PCATCH, "klog", 0))) {
137			splx(s);
138			return (error);
139		}
140	}
141	splx(s);
142	logsoftc.sc_state &= ~LOG_RDWAIT;
143
144	while (uio->uio_resid > 0) {
145		l = imin(sizeof(buf), uio->uio_resid);
146		l = msgbuf_getbytes(mbp, buf, l);
147		if (l == 0)
148			break;
149		error = uiomove(buf, l, uio);
150		if (error)
151			break;
152	}
153	return (error);
154}
155
156/*ARGSUSED*/
157static	int
158logpoll(struct cdev *dev, int events, struct thread *td)
159{
160	int s;
161	int revents = 0;
162
163	s = splhigh();
164
165	if (events & (POLLIN | POLLRDNORM)) {
166		if (msgbuf_getcount(msgbufp) > 0)
167			revents |= events & (POLLIN | POLLRDNORM);
168		else
169			selrecord(td, &logsoftc.sc_selp);
170	}
171	splx(s);
172	return (revents);
173}
174
175static void
176logtimeout(void *arg)
177{
178
179	if (!log_open)
180		return;
181	if (log_wakeups_per_second < 1) {
182		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
183		log_wakeups_per_second = 1;
184	}
185	if (msgbuftrigger == 0) {
186		callout_reset(&logsoftc.sc_callout,
187		    hz / log_wakeups_per_second, logtimeout, NULL);
188		return;
189	}
190	msgbuftrigger = 0;
191	selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
192	if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
193		pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
194	if (logsoftc.sc_state & LOG_RDWAIT) {
195		wakeup(msgbufp);
196		logsoftc.sc_state &= ~LOG_RDWAIT;
197	}
198	callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
199	    logtimeout, NULL);
200}
201
202/*ARGSUSED*/
203static	int
204logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
205{
206
207	switch (com) {
208
209	/* return number of characters immediately available */
210	case FIONREAD:
211		*(int *)data = msgbuf_getcount(msgbufp);
212		break;
213
214	case FIONBIO:
215		break;
216
217	case FIOASYNC:
218		if (*(int *)data)
219			logsoftc.sc_state |= LOG_ASYNC;
220		else
221			logsoftc.sc_state &= ~LOG_ASYNC;
222		break;
223
224	case FIOSETOWN:
225		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
226
227	case FIOGETOWN:
228		*(int *)data = fgetown(&logsoftc.sc_sigio);
229		break;
230
231	/* This is deprecated, FIOSETOWN should be used instead. */
232	case TIOCSPGRP:
233		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
234
235	/* This is deprecated, FIOGETOWN should be used instead */
236	case TIOCGPGRP:
237		*(int *)data = -fgetown(&logsoftc.sc_sigio);
238		break;
239
240	default:
241		return (ENOTTY);
242	}
243	return (0);
244}
245
246static void
247log_drvinit(void *unused)
248{
249
250	make_dev(&log_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
251}
252
253SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
254