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dmesg.c revision 1.6 
      1 /*-
      2  * Copyright (c) 1991, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #ifndef lint
     35 static char copyright[] =
     36 "@(#) Copyright (c) 1991, 1993\n\
     37 	The Regents of the University of California.  All rights reserved.\n";
     38 #endif /* not lint */
     39 
     40 #ifndef lint
     41 static char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
     42 #endif /* not lint */
     43 
     44 #include <sys/cdefs.h>
     45 #include <sys/msgbuf.h>
     46 
     47 #include <fcntl.h>
     48 #include <kvm.h>
     49 #include <limits.h>
     50 #include <nlist.h>
     51 #include <stdio.h>
     52 #include <stdlib.h>
     53 #include <time.h>
     54 #include <unistd.h>
     55 #include <vis.h>
     56 
     57 struct nlist nl[] = {
     58 #define	X_MSGBUF	0
     59 	{ "_msgbufp" },
     60 	{ NULL },
     61 };
     62 
     63 void usage __P((void));
     64 
     65 #define	KREAD(addr, var) \
     66 	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
     67 
     68 int
     69 main(argc, argv)
     70 	int argc;
     71 	char *argv[];
     72 {
     73 	register int ch, newl, skip;
     74 	register char *p, *ep;
     75 	struct msgbuf *bufp, cur;
     76 	char *memf, *nlistf;
     77 	kvm_t *kd;
     78 	char buf[5];
     79 
     80 	memf = nlistf = NULL;
     81 	while ((ch = getopt(argc, argv, "M:N:")) != EOF)
     82 		switch(ch) {
     83 		case 'M':
     84 			memf = optarg;
     85 			break;
     86 		case 'N':
     87 			nlistf = optarg;
     88 			break;
     89 		case '?':
     90 		default:
     91 			usage();
     92 		}
     93 	argc -= optind;
     94 	argv += optind;
     95 
     96 	/*
     97 	 * Discard setgid privileges if not the running kernel so that bad
     98 	 * guys can't print interesting stuff from kernel memory.
     99 	 */
    100 	if (memf != NULL || nlistf != NULL)
    101 		setgid(getgid());
    102 
    103 	/* Read in kernel message buffer, do sanity checks. */
    104 	if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
    105 		exit (1);
    106 	if (kvm_nlist(kd, nl) == -1)
    107 		errx(1, "kvm_nlist: %s", kvm_geterr(kd));
    108 	if (nl[X_MSGBUF].n_type == 0)
    109 		errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
    110 	if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
    111 		errx(1, "kvm_read: %s", kvm_geterr(kd));
    112 	kvm_close(kd);
    113 	if (cur.msg_magic != MSG_MAGIC)
    114 		errx(1, "magic number incorrect");
    115 	if (cur.msg_bufx >= MSG_BSIZE)
    116 		cur.msg_bufx = 0;
    117 
    118 	/*
    119 	 * The message buffer is circular; start at the read pointer, and
    120 	 * go to the write pointer - 1.
    121 	 */
    122 	p = cur.msg_bufc + cur.msg_bufx;
    123 	ep = cur.msg_bufc + cur.msg_bufx - 1;
    124 	for (newl = skip = 0; p != ep; ++p) {
    125 		if (p == cur.msg_bufc + MSG_BSIZE)
    126 			p = cur.msg_bufc;
    127 		ch = *p;
    128 		/* Skip "\n<.*>" syslog sequences. */
    129 		if (skip) {
    130 			if (ch == '>')
    131 				newl = skip = 0;
    132 			continue;
    133 		}
    134 		if (newl && ch == '<') {
    135 			skip = 1;
    136 			continue;
    137 		}
    138 		if (ch == '\0')
    139 			continue;
    140 		newl = ch == '\n';
    141 		(void)vis(buf, ch, 0, 0);
    142 		if (buf[1] == 0)
    143 			(void)putchar(buf[0]);
    144 		else
    145 			(void)printf("%s", buf);
    146 	}
    147 	if (!newl)
    148 		(void)putchar('\n');
    149 	exit(0);
    150 }
    151 
    152 void
    153 usage()
    154 {
    155 	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
    156 	exit(1);
    157 }
    158