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subr_log.c revision 1.25 
      1 /*	$NetBSD: subr_log.c,v 1.25 2002/11/26 18:44:34 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. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  *
     35  *	@(#)subr_log.c	8.3 (Berkeley) 2/14/95
     36  */
     37 
     38 /*
     39  * Error log buffer for kernel printf's.
     40  */
     41 
     42 #include <sys/cdefs.h>
     43 __KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.25 2002/11/26 18:44:34 christos Exp $");
     44 
     45 #include <sys/param.h>
     46 #include <sys/systm.h>
     47 #include <sys/proc.h>
     48 #include <sys/vnode.h>
     49 #include <sys/ioctl.h>
     50 #include <sys/msgbuf.h>
     51 #include <sys/file.h>
     52 #include <sys/signalvar.h>
     53 #include <sys/syslog.h>
     54 #include <sys/conf.h>
     55 #include <sys/select.h>
     56 #include <sys/poll.h>
     57 
     58 #define LOG_RDPRI	(PZERO + 1)
     59 
     60 #define LOG_ASYNC	0x04
     61 #define LOG_RDWAIT	0x08
     62 
     63 struct logsoftc {
     64 	int	sc_state;		/* see above for possibilities */
     65 	struct	selinfo sc_selp;	/* process waiting on select call */
     66 	int	sc_pgid;		/* process/group for async I/O */
     67 } logsoftc;
     68 
     69 int	log_open;			/* also used in log() */
     70 int	msgbufmapped;			/* is the message buffer mapped */
     71 int	msgbufenabled;			/* is logging to the buffer enabled */
     72 struct	kern_msgbuf *msgbufp;		/* the mapped buffer, itself. */
     73 
     74 dev_type_open(logopen);
     75 dev_type_close(logclose);
     76 dev_type_read(logread);
     77 dev_type_ioctl(logioctl);
     78 dev_type_poll(logpoll);
     79 dev_type_kqfilter(logkqfilter);
     80 
     81 const struct cdevsw log_cdevsw = {
     82 	logopen, logclose, logread, nowrite, logioctl,
     83 	nostop, notty, logpoll, nommap, logkqfilter,
     84 };
     85 
     86 void
     87 initmsgbuf(buf, bufsize)
     88 	caddr_t buf;
     89 	size_t bufsize;
     90 {
     91 	struct kern_msgbuf *mbp;
     92 	long new_bufs;
     93 
     94 	/* Sanity-check the given size. */
     95 	if (bufsize < sizeof(struct kern_msgbuf))
     96 		return;
     97 
     98 	mbp = msgbufp = (struct kern_msgbuf *)buf;
     99 
    100 	new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc);
    101 	if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
    102 	    (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
    103 	    (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
    104 		/*
    105 		 * If the buffer magic number is wrong, has changed
    106 		 * size (which shouldn't happen often), or is
    107 		 * internally inconsistent, initialize it.
    108 		 */
    109 
    110 		memset(buf, 0, bufsize);
    111 		mbp->msg_magic = MSG_MAGIC;
    112 		mbp->msg_bufs = new_bufs;
    113 	}
    114 
    115 	/* mark it as ready for use. */
    116 	msgbufmapped = msgbufenabled = 1;
    117 }
    118 
    119 /*ARGSUSED*/
    120 int
    121 logopen(dev, flags, mode, p)
    122 	dev_t dev;
    123 	int flags, mode;
    124 	struct proc *p;
    125 {
    126 	struct kern_msgbuf *mbp = msgbufp;
    127 
    128 	if (log_open)
    129 		return (EBUSY);
    130 	log_open = 1;
    131 	logsoftc.sc_pgid = p->p_pid;		/* signal process only */
    132 	/*
    133 	 * The message buffer is initialized during system configuration.
    134 	 * If it's been clobbered, note that and return an error.  (This
    135 	 * allows a user to potentially read the buffer via /dev/kmem,
    136 	 * and try to figure out what clobbered it.
    137 	 */
    138 	if (mbp->msg_magic != MSG_MAGIC) {
    139 		msgbufenabled = 0;
    140 		return (ENXIO);
    141 	}
    142 
    143 	return (0);
    144 }
    145 
    146 /*ARGSUSED*/
    147 int
    148 logclose(dev, flag, mode, p)
    149 	dev_t dev;
    150 	int flag, mode;
    151 	struct proc *p;
    152 {
    153 
    154 	log_open = 0;
    155 	logsoftc.sc_state = 0;
    156 	return (0);
    157 }
    158 
    159 /*ARGSUSED*/
    160 int
    161 logread(dev, uio, flag)
    162 	dev_t dev;
    163 	struct uio *uio;
    164 	int flag;
    165 {
    166 	struct kern_msgbuf *mbp = msgbufp;
    167 	long l;
    168 	int s;
    169 	int error = 0;
    170 
    171 	s = splhigh();
    172 	while (mbp->msg_bufr == mbp->msg_bufx) {
    173 		if (flag & IO_NDELAY) {
    174 			splx(s);
    175 			return (EWOULDBLOCK);
    176 		}
    177 		logsoftc.sc_state |= LOG_RDWAIT;
    178 		error = tsleep((caddr_t)mbp, LOG_RDPRI | PCATCH,
    179 			       "klog", 0);
    180 		if (error) {
    181 			splx(s);
    182 			return (error);
    183 		}
    184 	}
    185 	splx(s);
    186 	logsoftc.sc_state &= ~LOG_RDWAIT;
    187 
    188 	while (uio->uio_resid > 0) {
    189 		l = mbp->msg_bufx - mbp->msg_bufr;
    190 		if (l < 0)
    191 			l = mbp->msg_bufs - mbp->msg_bufr;
    192 		l = min(l, uio->uio_resid);
    193 		if (l == 0)
    194 			break;
    195 		error = uiomove((caddr_t)&mbp->msg_bufc[mbp->msg_bufr],
    196 			(int)l, uio);
    197 		if (error)
    198 			break;
    199 		mbp->msg_bufr += l;
    200 		if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
    201 			mbp->msg_bufr = 0;
    202 	}
    203 	return (error);
    204 }
    205 
    206 /*ARGSUSED*/
    207 int
    208 logpoll(dev, events, p)
    209 	dev_t dev;
    210 	int events;
    211 	struct proc *p;
    212 {
    213 	int revents = 0;
    214 	int s = splhigh();
    215 
    216 	if (events & (POLLIN | POLLRDNORM)) {
    217 		if (msgbufp->msg_bufr != msgbufp->msg_bufx)
    218 			revents |= events & (POLLIN | POLLRDNORM);
    219 		else
    220 			selrecord(p, &logsoftc.sc_selp);
    221 	}
    222 
    223 	splx(s);
    224 	return (revents);
    225 }
    226 
    227 static void
    228 filt_logrdetach(struct knote *kn)
    229 {
    230 	int s;
    231 
    232 	s = splhigh();
    233 	SLIST_REMOVE(&logsoftc.sc_selp.sel_klist, kn, knote, kn_selnext);
    234 	splx(s);
    235 }
    236 
    237 static int
    238 filt_logread(struct knote *kn, long hint)
    239 {
    240 
    241 	if (msgbufp->msg_bufr == msgbufp->msg_bufx)
    242 		return (0);
    243 
    244 	if (msgbufp->msg_bufr < msgbufp->msg_bufx)
    245 		kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr;
    246 	else
    247 		kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) +
    248 		    msgbufp->msg_bufx;
    249 
    250 	return (1);
    251 }
    252 
    253 static const struct filterops logread_filtops =
    254 	{ 1, NULL, filt_logrdetach, filt_logread };
    255 
    256 int
    257 logkqfilter(dev_t dev, struct knote *kn)
    258 {
    259 	struct klist *klist;
    260 	int s;
    261 
    262 	switch (kn->kn_filter) {
    263 	case EVFILT_READ:
    264 		klist = &logsoftc.sc_selp.sel_klist;
    265 		kn->kn_fop = &logread_filtops;
    266 		break;
    267 
    268 	default:
    269 		return (1);
    270 	}
    271 
    272 	kn->kn_hook = NULL;
    273 
    274 	s = splhigh();
    275 	SLIST_INSERT_HEAD(klist, kn, kn_selnext);
    276 	splx(s);
    277 
    278 	return (0);
    279 }
    280 
    281 void
    282 logwakeup()
    283 {
    284 	struct proc *p;
    285 
    286 	if (!log_open)
    287 		return;
    288 	selnotify(&logsoftc.sc_selp, 0);
    289 	if (logsoftc.sc_state & LOG_ASYNC) {
    290 		if (logsoftc.sc_pgid < 0)
    291 			gsignal(-logsoftc.sc_pgid, SIGIO);
    292 		else if (logsoftc.sc_pgid > 0 &&
    293 		    (p = pfind(logsoftc.sc_pgid)) != NULL)
    294 			psignal(p, SIGIO);
    295 	}
    296 	if (logsoftc.sc_state & LOG_RDWAIT) {
    297 		wakeup((caddr_t)msgbufp);
    298 		logsoftc.sc_state &= ~LOG_RDWAIT;
    299 	}
    300 }
    301 
    302 /*ARGSUSED*/
    303 int
    304 logioctl(dev, com, data, flag, p)
    305 	dev_t dev;
    306 	u_long com;
    307 	caddr_t data;
    308 	int flag;
    309 	struct proc *p;
    310 {
    311 	long l;
    312 	int s;
    313 
    314 	switch (com) {
    315 
    316 	/* return number of characters immediately available */
    317 	case FIONREAD:
    318 		s = splhigh();
    319 		l = msgbufp->msg_bufx - msgbufp->msg_bufr;
    320 		splx(s);
    321 		if (l < 0)
    322 			l += msgbufp->msg_bufs;
    323 		*(int *)data = l;
    324 		break;
    325 
    326 	case FIONBIO:
    327 		break;
    328 
    329 	case FIOASYNC:
    330 		if (*(int *)data)
    331 			logsoftc.sc_state |= LOG_ASYNC;
    332 		else
    333 			logsoftc.sc_state &= ~LOG_ASYNC;
    334 		break;
    335 
    336 	case TIOCSPGRP:
    337 		logsoftc.sc_pgid = *(int *)data;
    338 		break;
    339 
    340 	case TIOCGPGRP:
    341 		*(int *)data = logsoftc.sc_pgid;
    342 		break;
    343 
    344 	default:
    345 		return (EPASSTHROUGH);
    346 	}
    347 	return (0);
    348 }
    349