xref: /freebsd/sbin/dmesg/dmesg.c (revision 77c1fcec914bae1232762ca0b0462abd6957ff26)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
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. Neither the name of the University nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 #if 0
33 #ifndef lint
34 static const char copyright[] =
35 "@(#) Copyright (c) 1991, 1993\n\
36 	The Regents of the University of California.  All rights reserved.\n";
37 #endif /* not lint */
38 
39 #ifndef lint
40 static const char sccsid[] = "@(#)dmesg.c	8.1 (Berkeley) 6/5/93";
41 #endif /* not lint */
42 #endif
43 #include <sys/cdefs.h>
44 __FBSDID("$FreeBSD$");
45 
46 #include <sys/types.h>
47 #include <sys/msgbuf.h>
48 #include <sys/sysctl.h>
49 
50 #include <ctype.h>
51 #include <err.h>
52 #include <errno.h>
53 #include <fcntl.h>
54 #include <kvm.h>
55 #include <limits.h>
56 #include <locale.h>
57 #include <nlist.h>
58 #include <stdio.h>
59 #include <stdbool.h>
60 #include <stdlib.h>
61 #include <string.h>
62 #include <unistd.h>
63 #include <vis.h>
64 #include <sys/syslog.h>
65 
66 static struct nlist nl[] = {
67 #define	X_MSGBUF	0
68 	{ "_msgbufp", 0, 0, 0, 0 },
69 	{ NULL, 0, 0, 0, 0 },
70 };
71 
72 void usage(void) __dead2;
73 
74 #define	KREAD(addr, var) \
75 	kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
76 
77 int
78 main(int argc, char *argv[])
79 {
80 	struct msgbuf *bufp, cur;
81 	char *bp, *ep, *memf, *nextp, *nlistf, *p, *q, *visbp;
82 	kvm_t *kd;
83 	size_t buflen, bufpos;
84 	long pri;
85 	int ch, clear;
86 	bool all;
87 
88 	all = false;
89 	clear = false;
90 	(void) setlocale(LC_CTYPE, "");
91 	memf = nlistf = NULL;
92 	while ((ch = getopt(argc, argv, "acM:N:")) != -1)
93 		switch(ch) {
94 		case 'a':
95 			all = true;
96 			break;
97 		case 'c':
98 			clear = true;
99 			break;
100 		case 'M':
101 			memf = optarg;
102 			break;
103 		case 'N':
104 			nlistf = optarg;
105 			break;
106 		case '?':
107 		default:
108 			usage();
109 		}
110 	argc -= optind;
111 	if (argc != 0)
112 		usage();
113 
114 	if (memf == NULL) {
115 		/*
116 		 * Running kernel.  Use sysctl.  This gives an unwrapped buffer
117 		 * as a side effect.  Remove nulterm (if present) so the value
118 		 * returned by sysctl is formatted as the rest of the code
119 		 * expects (the same as the value read from a core file below).
120 		 */
121 		if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
122 			err(1, "sysctl kern.msgbuf");
123 		/* Allocate extra room for growth between the sysctl calls. */
124 		buflen += buflen/8;
125 		/* Allocate more than sysctl sees, for room to append \n\0. */
126 		if ((bp = malloc(buflen + 2)) == NULL)
127 			errx(1, "malloc failed");
128 		if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
129 			err(1, "sysctl kern.msgbuf");
130 		if (buflen > 0 && bp[buflen - 1] == '\0')
131 			buflen--;
132 		if (clear)
133 			if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int)))
134 				err(1, "sysctl kern.msgbuf_clear");
135 	} else {
136 		/* Read in kernel message buffer and do sanity checks. */
137 		kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
138 		if (kd == NULL)
139 			exit (1);
140 		if (kvm_nlist(kd, nl) == -1)
141 			errx(1, "kvm_nlist: %s", kvm_geterr(kd));
142 		if (nl[X_MSGBUF].n_type == 0)
143 			errx(1, "%s: msgbufp not found",
144 			    nlistf ? nlistf : "namelist");
145 		if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
146 			errx(1, "kvm_read: %s", kvm_geterr(kd));
147 		if (cur.msg_magic != MSG_MAGIC)
148 			errx(1, "kernel message buffer has different magic "
149 			    "number");
150 		if ((bp = malloc(cur.msg_size + 2)) == NULL)
151 			errx(1, "malloc failed");
152 
153 		/* Unwrap the circular buffer to start from the oldest data. */
154 		bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq);
155 		if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp,
156 		    cur.msg_size - bufpos) != (ssize_t)(cur.msg_size - bufpos))
157 			errx(1, "kvm_read: %s", kvm_geterr(kd));
158 		if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr,
159 		    &bp[cur.msg_size - bufpos], bufpos) != (ssize_t)bufpos)
160 			errx(1, "kvm_read: %s", kvm_geterr(kd));
161 		kvm_close(kd);
162 		buflen = cur.msg_size;
163 	}
164 
165 	/*
166 	 * Ensure that the buffer ends with a newline and a \0 to avoid
167 	 * complications below.  We left space above.
168 	 */
169 	if (buflen == 0 || bp[buflen - 1] != '\n')
170 		bp[buflen++] = '\n';
171 	bp[buflen] = '\0';
172 
173 	if ((visbp = malloc(4 * buflen + 1)) == NULL)
174 		errx(1, "malloc failed");
175 
176 	/*
177 	 * The message buffer is circular, but has been unwrapped so that
178 	 * the oldest data comes first.  The data will be preceded by \0's
179 	 * if the message buffer was not full.
180 	 */
181 	p = bp;
182 	ep = &bp[buflen];
183 	if (*p == '\0') {
184 		/* Strip leading \0's */
185 		while (*p == '\0')
186 			p++;
187 	} else if (!all) {
188 		/* Skip the first line, since it is probably incomplete. */
189 		p = memchr(p, '\n', ep - p);
190 		p++;
191 	}
192 	for (; p < ep; p = nextp) {
193 		nextp = memchr(p, '\n', ep - p);
194 		nextp++;
195 
196 		/* Skip ^<[0-9]+> syslog sequences. */
197 		if (*p == '<' && isdigit(*(p+1))) {
198 			errno = 0;
199 			pri = strtol(p + 1, &q, 10);
200 			if (*q == '>' && pri >= 0 && pri < INT_MAX &&
201 			    errno == 0) {
202 				if (LOG_FAC(pri) != LOG_KERN && !all)
203 					continue;
204 				p = q + 1;
205 			}
206 		}
207 
208 		(void)strvisx(visbp, p, nextp - p, 0);
209 		(void)printf("%s", visbp);
210 	}
211 	exit(0);
212 }
213 
214 void
215 usage(void)
216 {
217 	fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n");
218 	exit(1);
219 }
220