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subr_log.c revision 1.33 
      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 }
    338