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dmesg.c revision 1.10 
      1 /*	$NetBSD: dmesg.c,v 1.10 1997/05/03 17:18:05 mjacob Exp $	*/
      2 /*-
      3  * Copyright (c) 1991, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. All advertising materials mentioning features or use of this software
     15  *    must display the following acknowledgement:
     16  *	This product includes software developed by the University of
     17  *	California, Berkeley and its contributors.
     18  * 4. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #ifndef lint
     36 static char copyright[] =
     37 "@(#) Copyright (c) 1991, 1993\n\
     38 	The Regents of the University of California.  All rights reserved.\n";
     39 #endif /* not lint */
     40 
     41 #ifndef lint
     42 #if 0
     43 static char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
     44 #else
     45 static char rcsid[] = "$NetBSD: dmesg.c,v 1.10 1997/05/03 17:18:05 mjacob Exp $";
     46 #endif
     47 #endif /* not lint */
     48 
     49 #include <sys/cdefs.h>
     50 #include <sys/msgbuf.h>
     51 
     52 #include <err.h>
     53 #include <fcntl.h>
     54 #include <kvm.h>
     55 #include <limits.h>
     56 #include <nlist.h>
     57 #include <stdio.h>
     58 #include <stdlib.h>
     59 #include <time.h>
     60 #include <unistd.h>
     61 #include <vis.h>
     62 
     63 struct nlist nl[] = {
     64 #define	X_MSGBUF	0
     65 	{ "_msgbufp" },
     66 	{ NULL },
     67 };
     68 
     69 void usage __P((void));
     70 
     71 #define	KREAD(addr, var) \
     72 	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
     73 
     74 int
     75 main(argc, argv)
     76 	int argc;
     77 	char *argv[];
     78 {
     79 	register int ch, newl, skip;
     80 	register char *p, *ep;
     81 	struct msgbuf *bufp, cur;
     82 	char *memf, *nlistf;
     83 	kvm_t *kd;
     84 	char buf[5];
     85 
     86 	memf = nlistf = NULL;
     87 	while ((ch = getopt(argc, argv, "M:N:")) != EOF)
     88 		switch(ch) {
     89 		case 'M':
     90 			memf = optarg;
     91 			break;
     92 		case 'N':
     93 			nlistf = optarg;
     94 			break;
     95 		case '?':
     96 		default:
     97 			usage();
     98 		}
     99 	argc -= optind;
    100 	argv += optind;
    101 
    102 	/*
    103 	 * Discard setgid privileges if not the running kernel so that bad
    104 	 * guys can't print interesting stuff from kernel memory.
    105 	 */
    106 	if (memf != NULL || nlistf != NULL)
    107 		setgid(getgid());
    108 
    109 	/* Read in kernel message buffer, do sanity checks. */
    110 	if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
    111 		exit (1);
    112 	if (kvm_nlist(kd, nl) == -1)
    113 		errx(1, "kvm_nlist: %s", kvm_geterr(kd));
    114 	if (nl[X_MSGBUF].n_type == 0)
    115 		errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
    116 	if (KREAD(nl[X_MSGBUF].n_value, bufp))
    117 		errx(1, "kvm_read: %s (%lx)", kvm_geterr(kd),
    118 			nl[X_MSGBUF].n_value);
    119 	if (KREAD((long)bufp, cur))
    120 		errx(1, "kvm_read: %s (%lx)", kvm_geterr(kd), bufp);
    121 	kvm_close(kd);
    122 	if (cur.msg_magic != MSG_MAGIC)
    123 		errx(1, "magic number incorrect");
    124 	if (cur.msg_bufx >= MSG_BSIZE)
    125 		cur.msg_bufx = 0;
    126 
    127 	/*
    128 	 * The message buffer is circular; start at the read pointer, and
    129 	 * go to the write pointer - 1.
    130 	 */
    131 	p = ep = cur.msg_bufc + (cur.msg_bufx - 1 + MSG_BSIZE) % MSG_BSIZE;
    132 	newl = skip = 0;
    133 	do {
    134 		if (++p == cur.msg_bufc + MSG_BSIZE)
    135 			p = cur.msg_bufc;
    136 		ch = *p;
    137 		/* Skip "\n<.*>" syslog sequences. */
    138 		if (skip) {
    139 			if (ch == '>')
    140 				newl = skip = 0;
    141 			continue;
    142 		}
    143 		if (newl && ch == '<') {
    144 			skip = 1;
    145 			continue;
    146 		}
    147 		if (ch == '\0')
    148 			continue;
    149 		newl = ch == '\n';
    150 		(void)vis(buf, ch, 0, 0);
    151 		if (buf[1] == 0)
    152 			(void)putchar(buf[0]);
    153 		else
    154 			(void)printf("%s", buf);
    155 	} while (p != ep);
    156 	if (!newl)
    157 		(void)putchar('\n');
    158 	exit(0);
    159 }
    160 
    161 void
    162 usage()
    163 {
    164 	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
    165 	exit(1);
    166 }
    167