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 * 3. 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 * $FreeBSD: src/sys/kern/subr_log.c,v 1.39.2.2 2001/06/02 08:11:25 phk Exp $
31 */
32
33 /*
34 * Error log buffer for kernel printf's.
35 */
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/uio.h>
40 #include <sys/conf.h>
41 #include <sys/device.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/event.h>
50 #include <sys/filedesc.h>
51 #include <sys/sysctl.h>
52 #include <sys/thread2.h>
53
54 #define LOG_ASYNC 0x04
55 #define LOG_RDWAIT 0x08
56
57 static d_open_t logopen;
58 static d_close_t logclose;
59 static d_read_t logread;
60 static d_ioctl_t logioctl;
61 static d_kqfilter_t logkqfilter;
62
63 static void logtimeout(void *arg);
64 static void logfiltdetach(struct knote *kn);
65 static int logfiltread(struct knote *kn, long hint);
66
67 #define CDEV_MAJOR 7
68 static struct dev_ops log_ops = {
69 { "log", 0, 0 },
70 .d_open = logopen,
71 .d_close = logclose,
72 .d_read = logread,
73 .d_ioctl = logioctl,
74 .d_kqfilter = logkqfilter
75 };
76
77 static struct logsoftc {
78 int sc_state; /* see above for possibilities */
79 struct kqinfo sc_kqp; /* processes waiting on I/O */
80 struct sigio *sc_sigio; /* information for async I/O */
81 struct callout sc_callout; /* callout to wakeup syslog */
82 } logsoftc;
83
84 int log_open; /* also used in log() */
85
86 /* Times per second to check for a pending syslog wakeup. */
87 static int log_wakeups_per_second = 5;
88 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
89 &log_wakeups_per_second, 0, "");
90
91 /*ARGSUSED*/
92 static int
logopen(struct dev_open_args * ap)93 logopen(struct dev_open_args *ap)
94 {
95 struct proc *p = curproc;
96
97 KKASSERT(p != NULL);
98 if (log_open)
99 return (EBUSY);
100 log_open = 1;
101 callout_init_mp(&logsoftc.sc_callout);
102 fsetown(p->p_pid, &logsoftc.sc_sigio); /* signal process only */
103 callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
104 logtimeout, NULL);
105 return (0);
106 }
107
108 /*ARGSUSED*/
109 static int
logclose(struct dev_close_args * ap)110 logclose(struct dev_close_args *ap)
111 {
112 log_open = 0;
113 callout_cancel(&logsoftc.sc_callout);
114 logsoftc.sc_state = 0;
115 funsetown(&logsoftc.sc_sigio);
116 return (0);
117 }
118
119 /*ARGSUSED*/
120 static int
logread(struct dev_read_args * ap)121 logread(struct dev_read_args *ap)
122 {
123 struct uio *uio = ap->a_uio;
124 struct msgbuf *mbp = msgbufp;
125 int error = 0;
126 u_int lindex;
127 u_int xindex;
128 u_int lindex_modulo;
129 u_int n;
130
131 /*
132 * Handle blocking
133 */
134 while (mbp->msg_bufl == mbp->msg_bufx) {
135 crit_enter();
136 if (ap->a_ioflag & IO_NDELAY) {
137 crit_exit();
138 return (EWOULDBLOCK);
139 }
140 atomic_set_int(&logsoftc.sc_state, LOG_RDWAIT);
141 if ((error = tsleep((caddr_t)mbp, PCATCH, "klog", 0))) {
142 crit_exit();
143 return (error);
144 }
145 /* don't bother clearing LOG_RDWAIT */
146 crit_exit();
147 }
148
149 /*
150 * Loop reading data
151 */
152 while (uio->uio_resid > 0 && mbp->msg_bufl != mbp->msg_bufx) {
153 lindex = mbp->msg_bufl;
154 xindex = mbp->msg_bufx;
155 cpu_ccfence();
156
157 /*
158 * Clean up if too much time has passed causing us to wrap
159 * the buffer. This will lose some data. If more than ~4GB
160 * then this will lose even more data.
161 */
162 n = xindex - lindex;
163 if (n > mbp->msg_size - 1024) {
164 lindex = xindex - mbp->msg_size + 2048;
165 n = xindex - lindex;
166 }
167
168 /*
169 * Calculates contiguous bytes we can read in one loop.
170 */
171 lindex_modulo = lindex % mbp->msg_size;
172 n = mbp->msg_size - lindex_modulo;
173 if (n > xindex - lindex)
174 n = xindex - lindex;
175 if ((size_t)n > uio->uio_resid)
176 n = (u_int)uio->uio_resid;
177
178 /*
179 * Copy (n) bytes of data.
180 */
181 error = uiomove((caddr_t)msgbufp->msg_ptr + lindex_modulo,
182 (size_t)n, uio);
183 if (error)
184 break;
185 mbp->msg_bufl = lindex + n;
186 }
187 return (error);
188 }
189
190 static struct filterops logread_filtops =
191 { FILTEROP_ISFD, NULL, logfiltdetach, logfiltread };
192
193 static int
logkqfilter(struct dev_kqfilter_args * ap)194 logkqfilter(struct dev_kqfilter_args *ap)
195 {
196 struct knote *kn = ap->a_kn;
197 struct klist *klist = &logsoftc.sc_kqp.ki_note;
198
199 ap->a_result = 0;
200 switch (kn->kn_filter) {
201 case EVFILT_READ:
202 kn->kn_fop = &logread_filtops;
203 break;
204 default:
205 ap->a_result = EOPNOTSUPP;
206 return (0);
207 }
208
209 knote_insert(klist, kn);
210
211 return (0);
212 }
213
214 static void
logfiltdetach(struct knote * kn)215 logfiltdetach(struct knote *kn)
216 {
217 struct klist *klist = &logsoftc.sc_kqp.ki_note;
218
219 knote_remove(klist, kn);
220 }
221
222 static int
logfiltread(struct knote * kn,long hint)223 logfiltread(struct knote *kn, long hint)
224 {
225 int ret = 0;
226
227 crit_enter();
228 if (msgbufp->msg_bufl != msgbufp->msg_bufx)
229 ret = 1;
230 crit_exit();
231
232 return (ret);
233 }
234
235 static void
logtimeout(void * arg)236 logtimeout(void *arg)
237 {
238 if (!log_open)
239 return;
240 if (msgbuftrigger == 0) {
241 callout_reset(&logsoftc.sc_callout,
242 hz / log_wakeups_per_second, logtimeout, NULL);
243 return;
244 }
245 msgbuftrigger = 0;
246 KNOTE(&logsoftc.sc_kqp.ki_note, 0);
247 if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
248 pgsigio(logsoftc.sc_sigio, SIGIO, 0);
249 if (logsoftc.sc_state & LOG_RDWAIT) {
250 atomic_clear_int(&logsoftc.sc_state, LOG_RDWAIT);
251 wakeup((caddr_t)msgbufp);
252 }
253 callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
254 logtimeout, NULL);
255 }
256
257 /*ARGSUSED*/
258 static int
logioctl(struct dev_ioctl_args * ap)259 logioctl(struct dev_ioctl_args *ap)
260 {
261 struct msgbuf *mbp = msgbufp;
262 u_int lindex;
263 u_int xindex;
264 u_int n;
265
266 switch (ap->a_cmd) {
267 case FIONREAD:
268 lindex = mbp->msg_bufl;
269 xindex = mbp->msg_bufx;
270 cpu_ccfence();
271
272 /*
273 * Clean up if too much time has passed causing us to wrap
274 * the buffer. This will lose some data. If more than ~4GB
275 * then this will lose even more data.
276 */
277 n = xindex - lindex;
278 if (n > mbp->msg_size - 1024) {
279 lindex = xindex - mbp->msg_size + 2048;
280 n = xindex - lindex;
281 }
282 *(int *)ap->a_data = n;
283 break;
284
285 case FIOASYNC:
286 if (*(int *)ap->a_data)
287 atomic_set_int(&logsoftc.sc_state, LOG_ASYNC);
288 else
289 atomic_clear_int(&logsoftc.sc_state, LOG_ASYNC);
290 break;
291
292 case FIOSETOWN:
293 return (fsetown(*(int *)ap->a_data, &logsoftc.sc_sigio));
294
295 case FIOGETOWN:
296 *(int *)ap->a_data = fgetown(&logsoftc.sc_sigio);
297 break;
298
299 /* This is deprecated, FIOSETOWN should be used instead. */
300 case TIOCSPGRP:
301 return (fsetown(-(*(int *)ap->a_data), &logsoftc.sc_sigio));
302
303 /* This is deprecated, FIOGETOWN should be used instead */
304 case TIOCGPGRP:
305 *(int *)ap->a_data = -fgetown(&logsoftc.sc_sigio);
306 break;
307
308 default:
309 return (ENOTTY);
310 }
311 return (0);
312 }
313
314 static void
log_drvinit(void * unused)315 log_drvinit(void *unused)
316 {
317 make_dev(&log_ops, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
318 }
319
320 SYSINIT(logdev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR, log_drvinit,
321 NULL);
322