FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_log.c
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);
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