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