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
32 /*
33 * Error log buffer for kernel printf's.
34 */
35
36 #include <sys/param.h>
37 #include <sys/systm.h>
38 #include <sys/conf.h>
39 #include <sys/proc.h>
40 #include <sys/vnode.h>
41 #include <sys/filio.h>
42 #include <sys/ttycom.h>
43 #include <sys/msgbuf.h>
44 #include <sys/signalvar.h>
45 #include <sys/kernel.h>
46 #include <sys/poll.h>
47 #include <sys/filedesc.h>
48 #include <sys/sysctl.h>
49
50 #define LOG_RDPRI PZERO
51
52 #define LOG_ASYNC 0x04
53
54 static d_open_t logopen;
55 static d_close_t logclose;
56 static d_read_t logread;
57 static d_ioctl_t logioctl;
58 static d_poll_t logpoll;
59 static d_kqfilter_t logkqfilter;
60
61 static void logtimeout(void *arg);
62
63 static struct cdevsw log_cdevsw = {
64 .d_version = D_VERSION,
65 .d_open = logopen,
66 .d_close = logclose,
67 .d_read = logread,
68 .d_ioctl = logioctl,
69 .d_poll = logpoll,
70 .d_kqfilter = logkqfilter,
71 .d_name = "log",
72 };
73
74 static int logkqread(struct knote *note, long hint);
75 static void logkqdetach(struct knote *note);
76
77 static const struct filterops log_read_filterops = {
78 .f_isfd = 1,
79 .f_attach = NULL,
80 .f_detach = logkqdetach,
81 .f_event = logkqread,
82 .f_copy = knote_triv_copy,
83 };
84
85 static struct logsoftc {
86 int sc_state; /* see above for possibilities */
87 struct selinfo sc_selp; /* process waiting on select call */
88 struct sigio *sc_sigio; /* information for async I/O */
89 struct callout sc_callout; /* callout to wakeup syslog */
90 } logsoftc;
91
92 int log_open; /* also used in log() */
93 static struct cv log_wakeup;
94 struct mtx msgbuf_lock;
95 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
96
97 static int log_wakeups_per_second = 5;
98 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
99 &log_wakeups_per_second, 0,
100 "How often (times per second) to check for /dev/log waiters.");
101
102 /*ARGSUSED*/
103 static int
logopen(struct cdev * dev,int flags,int mode,struct thread * td)104 logopen(struct cdev *dev, int flags, int mode, struct thread *td)
105 {
106
107 if (log_wakeups_per_second < 1) {
108 printf("syslog wakeup is less than one. Adjusting to 1.\n");
109 log_wakeups_per_second = 1;
110 }
111
112 mtx_lock(&msgbuf_lock);
113 if (log_open) {
114 mtx_unlock(&msgbuf_lock);
115 return (EBUSY);
116 }
117 log_open = 1;
118 callout_reset_sbt(&logsoftc.sc_callout,
119 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
120 mtx_unlock(&msgbuf_lock);
121
122 fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio); /* signal process only */
123 return (0);
124 }
125
126 /*ARGSUSED*/
127 static int
logclose(struct cdev * dev,int flag,int mode,struct thread * td)128 logclose(struct cdev *dev, int flag, int mode, struct thread *td)
129 {
130
131 funsetown(&logsoftc.sc_sigio);
132
133 mtx_lock(&msgbuf_lock);
134 callout_stop(&logsoftc.sc_callout);
135 logsoftc.sc_state = 0;
136 log_open = 0;
137 mtx_unlock(&msgbuf_lock);
138
139 return (0);
140 }
141
142 /*ARGSUSED*/
143 static int
logread(struct cdev * dev,struct uio * uio,int flag)144 logread(struct cdev *dev, struct uio *uio, int flag)
145 {
146 char buf[128];
147 struct msgbuf *mbp = msgbufp;
148 int error = 0, l;
149
150 mtx_lock(&msgbuf_lock);
151 while (msgbuf_getcount(mbp) == 0) {
152 if (flag & IO_NDELAY) {
153 mtx_unlock(&msgbuf_lock);
154 return (EWOULDBLOCK);
155 }
156 if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
157 mtx_unlock(&msgbuf_lock);
158 return (error);
159 }
160 }
161
162 while (uio->uio_resid > 0) {
163 l = imin(sizeof(buf), uio->uio_resid);
164 l = msgbuf_getbytes(mbp, buf, l);
165 if (l == 0)
166 break;
167 mtx_unlock(&msgbuf_lock);
168 error = uiomove(buf, l, uio);
169 if (error || uio->uio_resid == 0)
170 return (error);
171 mtx_lock(&msgbuf_lock);
172 }
173 mtx_unlock(&msgbuf_lock);
174 return (error);
175 }
176
177 /*ARGSUSED*/
178 static int
logpoll(struct cdev * dev,int events,struct thread * td)179 logpoll(struct cdev *dev, int events, struct thread *td)
180 {
181 int revents = 0;
182
183 if (events & (POLLIN | POLLRDNORM)) {
184 mtx_lock(&msgbuf_lock);
185 if (msgbuf_getcount(msgbufp) > 0)
186 revents |= events & (POLLIN | POLLRDNORM);
187 else
188 selrecord(td, &logsoftc.sc_selp);
189 mtx_unlock(&msgbuf_lock);
190 }
191 return (revents);
192 }
193
194 static int
logkqfilter(struct cdev * dev,struct knote * kn)195 logkqfilter(struct cdev *dev, struct knote *kn)
196 {
197
198 if (kn->kn_filter != EVFILT_READ)
199 return (EINVAL);
200
201 kn->kn_fop = &log_read_filterops;
202 kn->kn_hook = NULL;
203
204 mtx_lock(&msgbuf_lock);
205 knlist_add(&logsoftc.sc_selp.si_note, kn, 1);
206 mtx_unlock(&msgbuf_lock);
207 return (0);
208 }
209
210 static int
logkqread(struct knote * kn,long hint)211 logkqread(struct knote *kn, long hint)
212 {
213
214 mtx_assert(&msgbuf_lock, MA_OWNED);
215 kn->kn_data = msgbuf_getcount(msgbufp);
216 return (kn->kn_data != 0);
217 }
218
219 static void
logkqdetach(struct knote * kn)220 logkqdetach(struct knote *kn)
221 {
222
223 mtx_lock(&msgbuf_lock);
224 knlist_remove(&logsoftc.sc_selp.si_note, kn, 1);
225 mtx_unlock(&msgbuf_lock);
226 }
227
228 static void
logtimeout(void * arg)229 logtimeout(void *arg)
230 {
231
232 if (!log_open)
233 return;
234 if (msgbuftrigger == 0)
235 goto done;
236 msgbuftrigger = 0;
237 selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
238 KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0);
239 if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
240 pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
241 cv_broadcastpri(&log_wakeup, LOG_RDPRI);
242 done:
243 if (log_wakeups_per_second < 1) {
244 printf("syslog wakeup is less than one. Adjusting to 1.\n");
245 log_wakeups_per_second = 1;
246 }
247 callout_reset_sbt(&logsoftc.sc_callout,
248 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
249 }
250
251 /*ARGSUSED*/
252 static int
logioctl(struct cdev * dev,u_long com,caddr_t data,int flag,struct thread * td)253 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
254 {
255
256 switch (com) {
257 /* return number of characters immediately available */
258 case FIONREAD:
259 *(int *)data = msgbuf_getcount(msgbufp);
260 break;
261
262 case FIONBIO:
263 break;
264
265 case FIOASYNC:
266 mtx_lock(&msgbuf_lock);
267 if (*(int *)data)
268 logsoftc.sc_state |= LOG_ASYNC;
269 else
270 logsoftc.sc_state &= ~LOG_ASYNC;
271 mtx_unlock(&msgbuf_lock);
272 break;
273
274 case FIOSETOWN:
275 return (fsetown(*(int *)data, &logsoftc.sc_sigio));
276
277 case FIOGETOWN:
278 *(int *)data = fgetown(&logsoftc.sc_sigio);
279 break;
280
281 /* This is deprecated, FIOSETOWN should be used instead. */
282 case TIOCSPGRP:
283 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
284
285 /* This is deprecated, FIOGETOWN should be used instead */
286 case TIOCGPGRP:
287 *(int *)data = -fgetown(&logsoftc.sc_sigio);
288 break;
289
290 default:
291 return (ENOTTY);
292 }
293 return (0);
294 }
295
296 static void
log_drvinit(void * unused)297 log_drvinit(void *unused)
298 {
299
300 cv_init(&log_wakeup, "klog");
301 callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
302 knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock);
303 make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
304 GID_WHEEL, 0600, "klog");
305 }
306
307 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
308