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dmesg.c revision 1.8 
      1 /*	$NetBSD: dmesg.c,v 1.8 1995/03/18 14:54:49 cgd Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 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 
     36 #ifndef lint
     37 static char copyright[] =
     38 "@(#) Copyright (c) 1991, 1993\n\
     39 	The Regents of the University of California.  All rights reserved.\n";
     40 #endif /* not lint */
     41 
     42 #ifndef lint
     43 #if 0
     44 static char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
     45 #else
     46 static char rcsid[] = "$NetBSD: dmesg.c,v 1.8 1995/03/18 14:54:49 cgd Exp $";
     47 #endif
     48 #endif /* not lint */
     49 
     50 #include <sys/cdefs.h>
     51 #include <sys/msgbuf.h>
     52 
     53 #include <err.h>
     54 #include <fcntl.h>
     55 #include <kvm.h>
     56 #include <limits.h>
     57 #include <nlist.h>
     58 #include <stdio.h>
     59 #include <stdlib.h>
     60 #include <time.h>
     61 #include <unistd.h>
     62 #include <vis.h>
     63 
     64 struct nlist nl[] = {
     65 #define	X_MSGBUF	0
     66 	{ "_msgbufp" },
     67 	{ NULL },
     68 };
     69 
     70 void usage __P((void));
     71 
     72 #define	KREAD(addr, var) \
     73 	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
     74 
     75 int
     76 main(argc, argv)
     77 	int argc;
     78 	char *argv[];
     79 {
     80 	register int ch, newl, skip;
     81 	register char *p, *ep;
     82 	struct msgbuf *bufp, cur;
     83 	char *memf, *nlistf;
     84 	kvm_t *kd;
     85 	char buf[5];
     86 
     87 	memf = nlistf = NULL;
     88 	while ((ch = getopt(argc, argv, "M:N:")) != EOF)
     89 		switch(ch) {
     90 		case 'M':
     91 			memf = optarg;
     92 			break;
     93 		case 'N':
     94 			nlistf = optarg;
     95 			break;
     96 		case '?':
     97 		default:
     98 			usage();
     99 		}
    100 	argc -= optind;
    101 	argv += optind;
    102 
    103 	/*
    104 	 * Discard setgid privileges if not the running kernel so that bad
    105 	 * guys can't print interesting stuff from kernel memory.
    106 	 */
    107 	if (memf != NULL || nlistf != NULL)
    108 		setgid(getgid());
    109 
    110 	/* Read in kernel message buffer, do sanity checks. */
    111 	if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
    112 		exit (1);
    113 	if (kvm_nlist(kd, nl) == -1)
    114 		errx(1, "kvm_nlist: %s", kvm_geterr(kd));
    115 	if (nl[X_MSGBUF].n_type == 0)
    116 		errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
    117 	if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
    118 		errx(1, "kvm_read: %s", kvm_geterr(kd));
    119 	kvm_close(kd);
    120 	if (cur.msg_magic != MSG_MAGIC)
    121 		errx(1, "magic number incorrect");
    122 	if (cur.msg_bufx >= MSG_BSIZE)
    123 		cur.msg_bufx = 0;
    124 
    125 	/*
    126 	 * The message buffer is circular; start at the read pointer, and
    127 	 * go to the write pointer - 1.
    128 	 */
    129 	p = cur.msg_bufc + cur.msg_bufx;
    130 	ep = cur.msg_bufc + cur.msg_bufx - 1;
    131 	for (newl = skip = 0; p != ep; ++p) {
    132 		if (p == cur.msg_bufc + MSG_BSIZE)
    133 			p = cur.msg_bufc;
    134 		ch = *p;
    135 		/* Skip "\n<.*>" syslog sequences. */
    136 		if (skip) {
    137 			if (ch == '>')
    138 				newl = skip = 0;
    139 			continue;
    140 		}
    141 		if (newl && ch == '<') {
    142 			skip = 1;
    143 			continue;
    144 		}
    145 		if (ch == '\0')
    146 			continue;
    147 		newl = ch == '\n';
    148 		(void)vis(buf, ch, 0, 0);
    149 		if (buf[1] == 0)
    150 			(void)putchar(buf[0]);
    151 		else
    152 			(void)printf("%s", buf);
    153 	}
    154 	if (!newl)
    155 		(void)putchar('\n');
    156 	exit(0);
    157 }
    158 
    159 void
    160 usage()
    161 {
    162 	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
    163 	exit(1);
    164 }
    165