1/*	$NetBSD: dmesg.c,v 1.26 2008/07/20 01:20:22 lukem 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. Neither the name of the University nor the names of its contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#include <sys/cdefs.h>
32#ifndef lint
33__COPYRIGHT("@(#) Copyright (c) 1991, 1993\
34 The Regents of the University of California.  All rights reserved.");
35#endif /* not lint */
36
37#ifndef lint
38#if 0
39static char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
40#else
41__RCSID("$NetBSD: dmesg.c,v 1.26 2008/07/20 01:20:22 lukem Exp $");
42#endif
43#endif /* not lint */
44
45#include <sys/param.h>
46#include <sys/msgbuf.h>
47#include <sys/sysctl.h>
48
49#include <err.h>
50#include <fcntl.h>
51#include <kvm.h>
52#include <nlist.h>
53#include <stdio.h>
54#include <stddef.h>
55#include <stdlib.h>
56#include <unistd.h>
57#include <vis.h>
58
59#ifndef SMALL
60static struct nlist nl[] = {
61#define	X_MSGBUF	0
62	{ .n_name = "_msgbufp" },
63	{ .n_name = NULL },
64};
65
66__dead static void	usage(void);
67
68#define	KREAD(addr, var) \
69	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
70#endif
71
72int
73main(int argc, char *argv[])
74{
75	struct kern_msgbuf cur;
76	int ch, newl, skip, i;
77	char *p, *bufdata;
78#ifndef SMALL
79	char *memf, *nlistf;
80#endif
81	char buf[5];
82
83#ifndef SMALL
84	memf = nlistf = NULL;
85	while ((ch = getopt(argc, argv, "M:N:")) != -1)
86		switch(ch) {
87		case 'M':
88			memf = optarg;
89			break;
90		case 'N':
91			nlistf = optarg;
92			break;
93		case '?':
94		default:
95			usage();
96		}
97	argc -= optind;
98	argv += optind;
99
100	if (memf == NULL) {
101#endif
102		size_t size;
103		int mib[2];
104
105		mib[0] = CTL_KERN;
106		mib[1] = KERN_MSGBUF;
107
108		if (sysctl(mib, 2, NULL, &size, NULL, 0) == -1 ||
109		    (bufdata = malloc(size)) == NULL ||
110		    sysctl(mib, 2, bufdata, &size, NULL, 0) == -1)
111			err(1, "can't get msgbuf");
112
113		/* make a dummy struct msgbuf for the display logic */
114		cur.msg_bufx = 0;
115		cur.msg_bufs = size;
116#ifndef SMALL
117	} else {
118		kvm_t *kd;
119		struct kern_msgbuf *bufp;
120
121		/*
122		 * Read in message buffer header and data, and do sanity
123		 * checks.
124		 */
125		kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
126		if (kd == NULL)
127			exit (1);
128		if (kvm_nlist(kd, nl) == -1)
129			errx(1, "kvm_nlist: %s", kvm_geterr(kd));
130		if (nl[X_MSGBUF].n_type == 0)
131			errx(1, "%s: msgbufp not found", nlistf ? nlistf :
132			    "namelist");
133		if (KREAD(nl[X_MSGBUF].n_value, bufp))
134			errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
135			    nl[X_MSGBUF].n_value);
136		if (kvm_read(kd, (long)bufp, &cur,
137		    offsetof(struct kern_msgbuf, msg_bufc)) !=
138		    offsetof(struct kern_msgbuf, msg_bufc))
139			errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
140			    (unsigned long)bufp);
141		if (cur.msg_magic != MSG_MAGIC)
142			errx(1, "magic number incorrect");
143		bufdata = malloc(cur.msg_bufs);
144		if (bufdata == NULL)
145			errx(1, "couldn't allocate space for buffer data");
146		if (kvm_read(kd, (long)&bufp->msg_bufc, bufdata,
147		    cur.msg_bufs) != cur.msg_bufs)
148			errx(1, "kvm_read: %s", kvm_geterr(kd));
149		kvm_close(kd);
150		if (cur.msg_bufx >= cur.msg_bufs)
151			cur.msg_bufx = 0;
152	}
153#endif
154
155	/*
156	 * The message buffer is circular; start at the write pointer
157	 * (which points the oldest character), and go to the write
158	 * pointer - 1 (which points the newest character).  I.e, loop
159	 * over cur.msg_bufs times.  Unused area is skipped since it
160	 * contains nul.
161	 */
162	for (newl = skip = i = 0, p = bufdata + cur.msg_bufx;
163	    i < cur.msg_bufs; i++, p++) {
164#ifndef SMALL
165		if (p == bufdata + cur.msg_bufs)
166			p = bufdata;
167#endif
168		ch = *p;
169		/* Skip "\n<.*>" syslog sequences. */
170		if (skip) {
171			if (ch == '>')
172				newl = skip = 0;
173			continue;
174		}
175		if (newl && ch == '<') {
176			skip = 1;
177			continue;
178		}
179		if (ch == '\0')
180			continue;
181		newl = ch == '\n';
182		(void)vis(buf, ch, VIS_NOSLASH, 0);
183#ifndef SMALL
184		if (buf[1] == 0)
185			(void)putchar(buf[0]);
186		else
187#endif
188			(void)printf("%s", buf);
189	}
190	if (!newl)
191		(void)putchar('\n');
192	exit(0);
193}
194
195#ifndef SMALL
196static void
197usage(void)
198{
199
200	(void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n");
201	exit(1);
202}
203#endif
204