FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_log.c
1 /* $NetBSD: subr_log.c,v 1.33 2003/09/22 12:59:57 christos Exp $ */
2
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 8.3 (Berkeley) 2/14/95
32 */
33
34 /*
35 * Error log buffer for kernel printf's.
36 */
37
38 #include <sys/cdefs.h>
39 __KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.33 2003/09/22 12:59:57 christos Exp $");
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/proc.h>
44 #include <sys/vnode.h>
45 #include <sys/ioctl.h>
46 #include <sys/msgbuf.h>
47 #include <sys/file.h>
48 #include <sys/signalvar.h>
49 #include <sys/syslog.h>
50 #include <sys/conf.h>
51 #include <sys/select.h>
52 #include <sys/poll.h>
53
54 #define LOG_RDPRI (PZERO + 1)
55
56 #define LOG_ASYNC 0x04
57 #define LOG_RDWAIT 0x08
58
59 struct logsoftc {
60 int sc_state; /* see above for possibilities */
61 struct selinfo sc_selp; /* process waiting on select call */
62 pid_t sc_pgid; /* process/group for async I/O */
63 } logsoftc;
64
65 int log_open; /* also used in log() */
66 int msgbufmapped; /* is the message buffer mapped */
67 int msgbufenabled; /* is logging to the buffer enabled */
68 struct kern_msgbuf *msgbufp; /* the mapped buffer, itself. */
69
70 dev_type_open(logopen);
71 dev_type_close(logclose);
72 dev_type_read(logread);
73 dev_type_ioctl(logioctl);
74 dev_type_poll(logpoll);
75 dev_type_kqfilter(logkqfilter);
76
77 const struct cdevsw log_cdevsw = {
78 logopen, logclose, logread, nowrite, logioctl,
79 nostop, notty, logpoll, nommap, logkqfilter,
80 };
81
82 void
83 initmsgbuf(buf, bufsize)
84 caddr_t buf;
85 size_t bufsize;
86 {
87 struct kern_msgbuf *mbp;
88 long new_bufs;
89
90 /* Sanity-check the given size. */
91 if (bufsize < sizeof(struct kern_msgbuf))
92 return;
93
94 mbp = msgbufp = (struct kern_msgbuf *)buf;
95
96 new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc);
97 if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
98 (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
99 (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
100 /*
101 * If the buffer magic number is wrong, has changed
102 * size (which shouldn't happen often), or is
103 * internally inconsistent, initialize it.
104 */
105
106 memset(buf, 0, bufsize);
107 mbp->msg_magic = MSG_MAGIC;
108 mbp->msg_bufs = new_bufs;
109 }
110
111 /* mark it as ready for use. */
112 msgbufmapped = msgbufenabled = 1;
113 }
114
115 /*ARGSUSED*/
116 int
117 logopen(dev, flags, mode, p)
118 dev_t dev;
119 int flags, mode;
120 struct proc *p;
121 {
122 struct kern_msgbuf *mbp = msgbufp;
123
124 if (log_open)
125 return (EBUSY);
126 log_open = 1;
127 logsoftc.sc_pgid = p->p_pid; /* signal process only */
128 /*
129 * The message buffer is initialized during system configuration.
130 * If it's been clobbered, note that and return an error. (This
131 * allows a user to potentially read the buffer via /dev/kmem,
132 * and try to figure out what clobbered it.
133 */
134 if (mbp->msg_magic != MSG_MAGIC) {
135 msgbufenabled = 0;
136 return (ENXIO);
137 }
138
139 return (0);
140 }
141
142 /*ARGSUSED*/
143 int
144 logclose(dev, flag, mode, p)
145 dev_t dev;
146 int flag, mode;
147 struct proc *p;
148 {
149
150 log_open = 0;
151 logsoftc.sc_state = 0;
152 return (0);
153 }
154
155 /*ARGSUSED*/
156 int
157 logread(dev, uio, flag)
158 dev_t dev;
159 struct uio *uio;
160 int flag;
161 {
162 struct kern_msgbuf *mbp = msgbufp;
163 long l;
164 int s;
165 int error = 0;
166
167 s = splhigh();
168 while (mbp->msg_bufr == mbp->msg_bufx) {
169 if (flag & IO_NDELAY) {
170 splx(s);
171 return (EWOULDBLOCK);
172 }
173 logsoftc.sc_state |= LOG_RDWAIT;
174 error = tsleep((caddr_t)mbp, LOG_RDPRI | PCATCH,
175 "klog", 0);
176 if (error) {
177 splx(s);
178 return (error);
179 }
180 }
181 splx(s);
182 logsoftc.sc_state &= ~LOG_RDWAIT;
183
184 while (uio->uio_resid > 0) {
185 l = mbp->msg_bufx - mbp->msg_bufr;
186 if (l < 0)
187 l = mbp->msg_bufs - mbp->msg_bufr;
188 l = min(l, uio->uio_resid);
189 if (l == 0)
190 break;
191 error = uiomove((caddr_t)&mbp->msg_bufc[mbp->msg_bufr],
192 (int)l, uio);
193 if (error)
194 break;
195 mbp->msg_bufr += l;
196 if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
197 mbp->msg_bufr = 0;
198 }
199 return (error);
200 }
201
202 /*ARGSUSED*/
203 int
204 logpoll(dev, events, p)
205 dev_t dev;
206 int events;
207 struct proc *p;
208 {
209 int revents = 0;
210 int s = splhigh();
211
212 if (events & (POLLIN | POLLRDNORM)) {
213 if (msgbufp->msg_bufr != msgbufp->msg_bufx)
214 revents |= events & (POLLIN | POLLRDNORM);
215 else
216 selrecord(p, &logsoftc.sc_selp);
217 }
218
219 splx(s);
220 return (revents);
221 }
222
223 static void
224 filt_logrdetach(struct knote *kn)
225 {
226 int s;
227
228 s = splhigh();
229 SLIST_REMOVE(&logsoftc.sc_selp.sel_klist, kn, knote, kn_selnext);
230 splx(s);
231 }
232
233 static int
234 filt_logread(struct knote *kn, long hint)
235 {
236
237 if (msgbufp->msg_bufr == msgbufp->msg_bufx)
238 return (0);
239
240 if (msgbufp->msg_bufr < msgbufp->msg_bufx)
241 kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr;
242 else
243 kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) +
244 msgbufp->msg_bufx;
245
246 return (1);
247 }
248
249 static const struct filterops logread_filtops =
250 { 1, NULL, filt_logrdetach, filt_logread };
251
252 int
253 logkqfilter(dev_t dev, struct knote *kn)
254 {
255 struct klist *klist;
256 int s;
257
258 switch (kn->kn_filter) {
259 case EVFILT_READ:
260 klist = &logsoftc.sc_selp.sel_klist;
261 kn->kn_fop = &logread_filtops;
262 break;
263
264 default:
265 return (1);
266 }
267
268 kn->kn_hook = NULL;
269
270 s = splhigh();
271 SLIST_INSERT_HEAD(klist, kn, kn_selnext);
272 splx(s);
273
274 return (0);
275 }
276
277 void
278 logwakeup()
279 {
280 if (!log_open)
281 return;
282 selnotify(&logsoftc.sc_selp, 0);
283 if (logsoftc.sc_state & LOG_ASYNC)
284 fownsignal(logsoftc.sc_pgid, SIGIO, 0, 0, NULL);
285 if (logsoftc.sc_state & LOG_RDWAIT) {
286 wakeup((caddr_t)msgbufp);
287 logsoftc.sc_state &= ~LOG_RDWAIT;
288 }
289 }
290
291 /*ARGSUSED*/
292 int
293 logioctl(dev, com, data, flag, p)
294 dev_t dev;
295 u_long com;
296 caddr_t data;
297 int flag;
298 struct proc *p;
299 {
300 long l;
301 int s;
302
303 switch (com) {
304
305 /* return number of characters immediately available */
306 case FIONREAD:
307 s = splhigh();
308 l = msgbufp->msg_bufx - msgbufp->msg_bufr;
309 splx(s);
310 if (l < 0)
311 l += msgbufp->msg_bufs;
312 *(int *)data = l;
313 break;
314
315 case FIONBIO:
316 break;
317
318 case FIOASYNC:
319 if (*(int *)data)
320 logsoftc.sc_state |= LOG_ASYNC;
321 else
322 logsoftc.sc_state &= ~LOG_ASYNC;
323 break;
324
325 case TIOCSPGRP:
326 case FIOSETOWN:
327 return fsetown(p, &logsoftc.sc_pgid, com, data);
328
329 case TIOCGPGRP:
330 case FIOGETOWN:
331 return fgetown(p, logsoftc.sc_pgid, com, data);
332
333 default:
334 return (EPASSTHROUGH);
335 }
336 return (0);
337 }
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