dmesg.c revision 70123 
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
35static const 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#if 0
42static const char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
43#endif
44static const char rcsid[] =
45  "$FreeBSD: head/sbin/dmesg/dmesg.c 70123 2000-12-17 19:05:17Z phk $";
46#endif /* not lint */
47
48#include <sys/msgbuf.h>
49
50#include <err.h>
51#include <fcntl.h>
52#include <kvm.h>
53#include <locale.h>
54#include <stdio.h>
55#include <stdlib.h>
56#include <unistd.h>
57#include <vis.h>
58#include <sys/syslog.h>
59
60struct nlist nl[] = {
61#define	X_MSGBUF	0
62	{ "_msgbufp" },
63	{ NULL },
64};
65
66void usage __P((void));
67
68#define	KREAD(addr, var) \
69	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
70
71int
72main(argc, argv)
73	int argc;
74	char *argv[];
75{
76	int ch, newl, skip;
77	char *p, *ep;
78	struct msgbuf *bufp, cur;
79	char *bp, *memf, *nlistf;
80	kvm_t *kd;
81	char buf[5];
82	int all = 0;
83	int pri;
84
85	(void) setlocale(LC_CTYPE, "");
86	memf = nlistf = NULL;
87	while ((ch = getopt(argc, argv, "aM:N:")) != -1)
88		switch(ch) {
89		case 'a':
90			all++;
91			break;
92		case 'M':
93			memf = optarg;
94			break;
95		case 'N':
96			nlistf = optarg;
97			break;
98		case '?':
99		default:
100			usage();
101		}
102	argc -= optind;
103	argv += optind;
104
105	/*
106	 * Discard setgid privileges if not the running kernel so that bad
107	 * guys can't print interesting stuff from kernel memory.
108	 */
109	if (memf != NULL || nlistf != NULL)
110		setgid(getgid());
111
112	/* Read in kernel message buffer, do sanity checks. */
113	if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
114		exit (1);
115	if (kvm_nlist(kd, nl) == -1)
116		errx(1, "kvm_nlist: %s", kvm_geterr(kd));
117	if (nl[X_MSGBUF].n_type == 0)
118		errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
119	if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
120		errx(1, "kvm_read: %s", kvm_geterr(kd));
121	if (cur.msg_magic != MSG_MAGIC)
122		errx(1, "kernel message buffer has different magic number");
123	bp = malloc(cur.msg_size);
124	if (!bp)
125		errx(1, "malloc failed");
126	if (kvm_read(kd, (long)cur.msg_ptr, bp, cur.msg_size) !=
127	    cur.msg_size)
128		errx(1, "kvm_read: %s", kvm_geterr(kd));
129	if (cur.msg_bufx >= cur.msg_size)
130		cur.msg_bufx = 0;
131	kvm_close(kd);
132
133	/*
134	 * The message buffer is circular.  If the buffer has wrapped, the
135	 * write pointer points to the oldest data.  Otherwise, the write
136	 * pointer points to \0's following the data.  Read the entire
137	 * buffer starting at the write pointer and ignore nulls so that
138	 * we effectively start at the oldest data.
139	 */
140	p = bp + cur.msg_bufx;
141	ep = (cur.msg_bufx == 0 ? bp + cur.msg_size : p);
142	newl = skip = 0;
143	do {
144		if (p == bp + cur.msg_size)
145			p = bp;
146		ch = *p;
147		/* Skip "\n<.*>" syslog sequences. */
148		if (skip) {
149			if (ch == '\n') {
150				skip = 0;
151				newl = 1;
152			} if (ch == '>') {
153				if (LOG_FAC(pri) == LOG_KERN || all)
154					newl = skip = 0;
155			} else if (ch >= '0' && ch <= '9') {
156				pri *= 10;
157				pri += ch - '0';
158			}
159			continue;
160		}
161		if (newl && ch == '<') {
162			pri = 0;
163			skip = 1;
164			continue;
165		}
166		if (ch == '\0')
167			continue;
168		newl = ch == '\n';
169		(void)vis(buf, ch, 0, 0);
170		if (buf[1] == 0)
171			(void)putchar(buf[0]);
172		else
173			(void)printf("%s", buf);
174	} while (++p != ep);
175	if (!newl)
176		(void)putchar('\n');
177	exit(0);
178}
179
180void
181usage()
182{
183	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
184	exit(1);
185}
186