FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_log.c
1 /* $NetBSD: subr_log.c,v 1.39 2006/11/01 10:17:58 yamt 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 1.39 2006/11/01 10:17:58 yamt 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 void
71 initmsgbuf(void *bf, size_t bufsize)
72 {
73 struct kern_msgbuf *mbp;
74 long new_bufs;
75
76 /* Sanity-check the given size. */
77 if (bufsize < sizeof(struct kern_msgbuf))
78 return;
79
80 mbp = msgbufp = (struct kern_msgbuf *)bf;
81
82 new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc);
83 if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
84 (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
85 (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
86 /*
87 * If the buffer magic number is wrong, has changed
88 * size (which shouldn't happen often), or is
89 * internally inconsistent, initialize it.
90 */
91
92 memset(bf, 0, bufsize);
93 mbp->msg_magic = MSG_MAGIC;
94 mbp->msg_bufs = new_bufs;
95 }
96
97 /* mark it as ready for use. */
98 msgbufmapped = msgbufenabled = 1;
99 }
100
101 /*ARGSUSED*/
102 static int
103 logopen(dev_t dev, int flags, int mode, struct lwp *l)
104 {
105 struct kern_msgbuf *mbp = msgbufp;
106
107 if (log_open)
108 return (EBUSY);
109 log_open = 1;
110 logsoftc.sc_pgid = l->l_proc->p_pid; /* signal process only */
111 /*
112 * The message buffer is initialized during system configuration.
113 * If it's been clobbered, note that and return an error. (This
114 * allows a user to potentially read the buffer via /dev/kmem,
115 * and try to figure out what clobbered it.
116 */
117 if (mbp->msg_magic != MSG_MAGIC) {
118 msgbufenabled = 0;
119 return (ENXIO);
120 }
121
122 return (0);
123 }
124
125 /*ARGSUSED*/
126 static int
127 logclose(dev_t dev, int flag, int mode, struct lwp *l)
128 {
129
130 log_open = 0;
131 logsoftc.sc_state = 0;
132 return (0);
133 }
134
135 /*ARGSUSED*/
136 static int
137 logread(dev_t dev, struct uio *uio, int flag)
138 {
139 struct kern_msgbuf *mbp = msgbufp;
140 long l;
141 int s;
142 int error = 0;
143
144 s = splhigh();
145 while (mbp->msg_bufr == mbp->msg_bufx) {
146 if (flag & IO_NDELAY) {
147 splx(s);
148 return (EWOULDBLOCK);
149 }
150 logsoftc.sc_state |= LOG_RDWAIT;
151 error = tsleep((caddr_t)mbp, LOG_RDPRI | PCATCH,
152 "klog", 0);
153 if (error) {
154 splx(s);
155 return (error);
156 }
157 }
158 splx(s);
159 logsoftc.sc_state &= ~LOG_RDWAIT;
160
161 while (uio->uio_resid > 0) {
162 l = mbp->msg_bufx - mbp->msg_bufr;
163 if (l < 0)
164 l = mbp->msg_bufs - mbp->msg_bufr;
165 l = min(l, uio->uio_resid);
166 if (l == 0)
167 break;
168 error = uiomove((caddr_t)&mbp->msg_bufc[mbp->msg_bufr],
169 (int)l, uio);
170 if (error)
171 break;
172 mbp->msg_bufr += l;
173 if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
174 mbp->msg_bufr = 0;
175 }
176 return (error);
177 }
178
179 /*ARGSUSED*/
180 static int
181 logpoll(dev_t dev, int events, struct lwp *l)
182 {
183 int revents = 0;
184 int s = splhigh();
185
186 if (events & (POLLIN | POLLRDNORM)) {
187 if (msgbufp->msg_bufr != msgbufp->msg_bufx)
188 revents |= events & (POLLIN | POLLRDNORM);
189 else
190 selrecord(l, &logsoftc.sc_selp);
191 }
192
193 splx(s);
194 return (revents);
195 }
196
197 static void
198 filt_logrdetach(struct knote *kn)
199 {
200 int s;
201
202 s = splhigh();
203 SLIST_REMOVE(&logsoftc.sc_selp.sel_klist, kn, knote, kn_selnext);
204 splx(s);
205 }
206
207 static int
208 filt_logread(struct knote *kn, long hint)
209 {
210
211 if (msgbufp->msg_bufr == msgbufp->msg_bufx)
212 return (0);
213
214 if (msgbufp->msg_bufr < msgbufp->msg_bufx)
215 kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr;
216 else
217 kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) +
218 msgbufp->msg_bufx;
219
220 return (1);
221 }
222
223 static const struct filterops logread_filtops =
224 { 1, NULL, filt_logrdetach, filt_logread };
225
226 static int
227 logkqfilter(dev_t dev, struct knote *kn)
228 {
229 struct klist *klist;
230 int s;
231
232 switch (kn->kn_filter) {
233 case EVFILT_READ:
234 klist = &logsoftc.sc_selp.sel_klist;
235 kn->kn_fop = &logread_filtops;
236 break;
237
238 default:
239 return (1);
240 }
241
242 kn->kn_hook = NULL;
243
244 s = splhigh();
245 SLIST_INSERT_HEAD(klist, kn, kn_selnext);
246 splx(s);
247
248 return (0);
249 }
250
251 void
252 logwakeup(void)
253 {
254 if (!log_open)
255 return;
256 selnotify(&logsoftc.sc_selp, 0);
257 if (logsoftc.sc_state & LOG_ASYNC)
258 fownsignal(logsoftc.sc_pgid, SIGIO, 0, 0, NULL);
259 if (logsoftc.sc_state & LOG_RDWAIT) {
260 wakeup((caddr_t)msgbufp);
261 logsoftc.sc_state &= ~LOG_RDWAIT;
262 }
263 }
264
265 /*ARGSUSED*/
266 static int
267 logioctl(dev_t dev, u_long com, caddr_t data, int flag, struct lwp *lwp)
268 {
269 struct proc *p = lwp->l_proc;
270 long l;
271 int s;
272
273 switch (com) {
274
275 /* return number of characters immediately available */
276 case FIONREAD:
277 s = splhigh();
278 l = msgbufp->msg_bufx - msgbufp->msg_bufr;
279 splx(s);
280 if (l < 0)
281 l += msgbufp->msg_bufs;
282 *(int *)data = l;
283 break;
284
285 case FIONBIO:
286 break;
287
288 case FIOASYNC:
289 if (*(int *)data)
290 logsoftc.sc_state |= LOG_ASYNC;
291 else
292 logsoftc.sc_state &= ~LOG_ASYNC;
293 break;
294
295 case TIOCSPGRP:
296 case FIOSETOWN:
297 return fsetown(p, &logsoftc.sc_pgid, com, data);
298
299 case TIOCGPGRP:
300 case FIOGETOWN:
301 return fgetown(p, logsoftc.sc_pgid, com, data);
302
303 default:
304 return (EPASSTHROUGH);
305 }
306 return (0);
307 }
308
309 const struct cdevsw log_cdevsw = {
310 logopen, logclose, logread, nowrite, logioctl,
311 nostop, notty, logpoll, nommap, logkqfilter, D_OTHER,
312 };
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