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dmesg.c revision 1.7 
      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 <err.h>
     48 #include <fcntl.h>
     49 #include <kvm.h>
     50 #include <limits.h>
     51 #include <nlist.h>
     52 #include <stdio.h>
     53 #include <stdlib.h>
     54 #include <time.h>
     55 #include <unistd.h>
     56 #include <vis.h>
     57 
     58 struct nlist nl[] = {
     59 #define	X_MSGBUF	0
     60 	{ "_msgbufp" },
     61 	{ NULL },
     62 };
     63 
     64 void usage __P((void));
     65 
     66 #define	KREAD(addr, var) \
     67 	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
     68 
     69 int
     70 main(argc, argv)
     71 	int argc;
     72 	char *argv[];
     73 {
     74 	register int ch, newl, skip;
     75 	register char *p, *ep;
     76 	struct msgbuf *bufp, cur;
     77 	char *memf, *nlistf;
     78 	kvm_t *kd;
     79 	char buf[5];
     80 
     81 	memf = nlistf = NULL;
     82 	while ((ch = getopt(argc, argv, "M:N:")) != EOF)
     83 		switch(ch) {
     84 		case 'M':
     85 			memf = optarg;
     86 			break;
     87 		case 'N':
     88 			nlistf = optarg;
     89 			break;
     90 		case '?':
     91 		default:
     92 			usage();
     93 		}
     94 	argc -= optind;
     95 	argv += optind;
     96 
     97 	/*
     98 	 * Discard setgid privileges if not the running kernel so that bad
     99 	 * guys can't print interesting stuff from kernel memory.
    100 	 */
    101 	if (memf != NULL || nlistf != NULL)
    102 		setgid(getgid());
    103 
    104 	/* Read in kernel message buffer, do sanity checks. */
    105 	if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
    106 		exit (1);
    107 	if (kvm_nlist(kd, nl) == -1)
    108 		errx(1, "kvm_nlist: %s", kvm_geterr(kd));
    109 	if (nl[X_MSGBUF].n_type == 0)
    110 		errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
    111 	if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
    112 		errx(1, "kvm_read: %s", kvm_geterr(kd));
    113 	kvm_close(kd);
    114 	if (cur.msg_magic != MSG_MAGIC)
    115 		errx(1, "magic number incorrect");
    116 	if (cur.msg_bufx >= MSG_BSIZE)
    117 		cur.msg_bufx = 0;
    118 
    119 	/*
    120 	 * The message buffer is circular; start at the read pointer, and
    121 	 * go to the write pointer - 1.
    122 	 */
    123 	p = cur.msg_bufc + cur.msg_bufx;
    124 	ep = cur.msg_bufc + cur.msg_bufx - 1;
    125 	for (newl = skip = 0; p != ep; ++p) {
    126 		if (p == cur.msg_bufc + MSG_BSIZE)
    127 			p = cur.msg_bufc;
    128 		ch = *p;
    129 		/* Skip "\n<.*>" syslog sequences. */
    130 		if (skip) {
    131 			if (ch == '>')
    132 				newl = skip = 0;
    133 			continue;
    134 		}
    135 		if (newl && ch == '<') {
    136 			skip = 1;
    137 			continue;
    138 		}
    139 		if (ch == '\0')
    140 			continue;
    141 		newl = ch == '\n';
    142 		(void)vis(buf, ch, 0, 0);
    143 		if (buf[1] == 0)
    144 			(void)putchar(buf[0]);
    145 		else
    146 			(void)printf("%s", buf);
    147 	}
    148 	if (!newl)
    149 		(void)putchar('\n');
    150 	exit(0);
    151 }
    152 
    153 void
    154 usage()
    155 {
    156 	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
    157 	exit(1);
    158 }
    159