subr_log.c revision 198860 
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 198860 2009-11-03 21:06:19Z ed $");
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
57static	d_open_t	logopen;
58static	d_close_t	logclose;
59static	d_read_t	logread;
60static	d_ioctl_t	logioctl;
61static	d_poll_t	logpoll;
62
63static	void logtimeout(void *arg);
64
65static struct cdevsw log_cdevsw = {
66	.d_version =	D_VERSION,
67	.d_open =	logopen,
68	.d_close =	logclose,
69	.d_read =	logread,
70	.d_ioctl =	logioctl,
71	.d_poll =	logpoll,
72	.d_name =	"log",
73};
74
75static struct logsoftc {
76	int	sc_state;		/* see above for possibilities */
77	struct	selinfo sc_selp;	/* process waiting on select call */
78	struct  sigio *sc_sigio;	/* information for async I/O */
79	struct	callout sc_callout;	/* callout to wakeup syslog  */
80} logsoftc;
81
82int			log_open;	/* also used in log() */
83static struct cv	log_wakeup;
84struct mtx		msgbuf_lock;
85MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
86
87/* Times per second to check for a pending syslog wakeup. */
88static int	log_wakeups_per_second = 5;
89SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
90    &log_wakeups_per_second, 0, "");
91
92/*ARGSUSED*/
93static	int
94logopen(struct cdev *dev, int flags, int mode, struct thread *td)
95{
96
97	if (log_wakeups_per_second < 1) {
98		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
99		log_wakeups_per_second = 1;
100	}
101
102	mtx_lock(&msgbuf_lock);
103	if (log_open) {
104		mtx_unlock(&msgbuf_lock);
105		return (EBUSY);
106	}
107	log_open = 1;
108	callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
109	    logtimeout, NULL);
110	mtx_unlock(&msgbuf_lock);
111
112	fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);	/* signal process only */
113	return (0);
114}
115
116/*ARGSUSED*/
117static	int
118logclose(struct cdev *dev, int flag, int mode, struct thread *td)
119{
120
121	funsetown(&logsoftc.sc_sigio);
122
123	mtx_lock(&msgbuf_lock);
124	callout_stop(&logsoftc.sc_callout);
125	logsoftc.sc_state = 0;
126	log_open = 0;
127	mtx_unlock(&msgbuf_lock);
128
129	return (0);
130}
131
132/*ARGSUSED*/
133static	int
134logread(struct cdev *dev, struct uio *uio, int flag)
135{
136	char buf[128];
137	struct msgbuf *mbp = msgbufp;
138	int error = 0, l;
139
140	mtx_lock(&msgbuf_lock);
141	while (msgbuf_getcount(mbp) == 0) {
142		if (flag & IO_NDELAY) {
143			mtx_unlock(&msgbuf_lock);
144			return (EWOULDBLOCK);
145		}
146		if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
147			mtx_unlock(&msgbuf_lock);
148			return (error);
149		}
150	}
151
152	while (uio->uio_resid > 0) {
153		l = imin(sizeof(buf), uio->uio_resid);
154		l = msgbuf_getbytes(mbp, buf, l);
155		if (l == 0)
156			break;
157		mtx_unlock(&msgbuf_lock);
158		error = uiomove(buf, l, uio);
159		if (error || uio->uio_resid == 0)
160			return (error);
161		mtx_lock(&msgbuf_lock);
162	}
163	mtx_unlock(&msgbuf_lock);
164	return (error);
165}
166
167/*ARGSUSED*/
168static	int
169logpoll(struct cdev *dev, int events, struct thread *td)
170{
171	int revents = 0;
172
173	if (events & (POLLIN | POLLRDNORM)) {
174		mtx_lock(&msgbuf_lock);
175		if (msgbuf_getcount(msgbufp) > 0)
176			revents |= events & (POLLIN | POLLRDNORM);
177		else
178			selrecord(td, &logsoftc.sc_selp);
179		mtx_unlock(&msgbuf_lock);
180	}
181	return (revents);
182}
183
184static void
185logtimeout(void *arg)
186{
187
188	if (!log_open)
189		return;
190	if (log_wakeups_per_second < 1) {
191		printf("syslog wakeup is less than one.  Adjusting to 1.\n");
192		log_wakeups_per_second = 1;
193	}
194	if (msgbuftrigger == 0) {
195		callout_schedule(&logsoftc.sc_callout,
196		    hz / log_wakeups_per_second);
197		return;
198	}
199	msgbuftrigger = 0;
200	selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
201	if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
202		pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
203	cv_broadcastpri(&log_wakeup, LOG_RDPRI);
204	callout_schedule(&logsoftc.sc_callout, hz / log_wakeups_per_second);
205}
206
207/*ARGSUSED*/
208static	int
209logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
210{
211
212	switch (com) {
213
214	/* return number of characters immediately available */
215	case FIONREAD:
216		*(int *)data = msgbuf_getcount(msgbufp);
217		break;
218
219	case FIONBIO:
220		break;
221
222	case FIOASYNC:
223		mtx_lock(&msgbuf_lock);
224		if (*(int *)data)
225			logsoftc.sc_state |= LOG_ASYNC;
226		else
227			logsoftc.sc_state &= ~LOG_ASYNC;
228		mtx_unlock(&msgbuf_lock);
229		break;
230
231	case FIOSETOWN:
232		return (fsetown(*(int *)data, &logsoftc.sc_sigio));
233
234	case FIOGETOWN:
235		*(int *)data = fgetown(&logsoftc.sc_sigio);
236		break;
237
238	/* This is deprecated, FIOSETOWN should be used instead. */
239	case TIOCSPGRP:
240		return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
241
242	/* This is deprecated, FIOGETOWN should be used instead */
243	case TIOCGPGRP:
244		*(int *)data = -fgetown(&logsoftc.sc_sigio);
245		break;
246
247	default:
248		return (ENOTTY);
249	}
250	return (0);
251}
252
253static void
254log_drvinit(void *unused)
255{
256
257	cv_init(&log_wakeup, "klog");
258	callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
259	make_dev(&log_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
260}
261
262SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
263