dmesg - Don't fail when the kernel is adding to the dmesg quickly
[dragonfly.git] / sbin / dmesg / dmesg.c
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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.
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32 *
33 * @(#) Copyright (c) 1991, 1993 The Regents of the University of California. All rights reserved.
34 * @(#)dmesg.c 8.1 (Berkeley) 6/5/93
35 * $FreeBSD: src/sbin/dmesg/dmesg.c,v 1.11.2.3 2001/08/08 22:32:15 obrien Exp $
f44d99cd 36 * $DragonFly: src/sbin/dmesg/dmesg.c,v 1.7 2005/01/14 06:38:41 cpressey Exp $
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37 */
38
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39#include <sys/types.h>
40#include <sys/msgbuf.h>
41#include <sys/sysctl.h>
42
43#include <err.h>
44#include <fcntl.h>
45#include <kvm.h>
46#include <locale.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include <unistd.h>
50#include <vis.h>
51#include <sys/syslog.h>
52
53struct nlist nl[] = {
54#define X_MSGBUF 0
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55 { "_msgbufp", 0, 0, 0, 0 },
56 { NULL, 0, 0, 0, 0 },
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57};
58
9a76cd75 59void usage(void);
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60
61#define KREAD(addr, var) \
62 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
63
64int
b5744197 65main(int argc, char **argv)
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66{
67 int ch, newl, skip;
68 char *p, *ep;
69 struct msgbuf *bufp, cur;
70 char *bp, *memf, *nlistf;
71 kvm_t *kd;
72 char buf[5];
73 int all = 0;
8af0d623 74 int pri = 0;
f44d99cd 75 size_t buflen, bufpos;
984263bc 76
7cee7052 77 setlocale(LC_CTYPE, "");
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78 memf = nlistf = NULL;
79 while ((ch = getopt(argc, argv, "aM:N:")) != -1)
80 switch(ch) {
81 case 'a':
82 all++;
83 break;
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 if (memf == NULL && nlistf == NULL) {
98 /* Running kernel. Use sysctl. */
99 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
100 err(1, "sysctl kern.msgbuf");
35bb81ce 101 buflen += 4096; /* add some slop */
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102 if ((bp = malloc(buflen)) == NULL)
103 errx(1, "malloc failed");
104 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
105 err(1, "sysctl kern.msgbuf");
106 /* We get a dewrapped buffer using sysctl. */
107 bufpos = 0;
108 } else {
109 /* Read in kernel message buffer, do sanity checks. */
110 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
111 if (kd == NULL)
112 exit (1);
113 if (kvm_nlist(kd, nl) == -1)
114 errx(1, "kvm_nlist: %s", kvm_geterr(kd));
115 if (nl[X_MSGBUF].n_type == 0)
116 errx(1, "%s: msgbufp not found",
117 nlistf ? nlistf : "namelist");
118 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
119 errx(1, "kvm_read: %s", kvm_geterr(kd));
120 if (cur.msg_magic != MSG_MAGIC)
121 errx(1, "kernel message buffer has different magic "
122 "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) !=
f44d99cd 127 (ssize_t)cur.msg_size)
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128 errx(1, "kvm_read: %s", kvm_geterr(kd));
129 kvm_close(kd);
130 buflen = cur.msg_size;
131 bufpos = cur.msg_bufx;
132 if (bufpos >= buflen)
133 bufpos = 0;
134 }
135
136 /*
137 * The message buffer is circular. If the buffer has wrapped, the
138 * write pointer points to the oldest data. Otherwise, the write
139 * pointer points to \0's following the data. Read the entire
140 * buffer starting at the write pointer and ignore nulls so that
141 * we effectively start at the oldest data.
142 */
143 p = bp + bufpos;
144 ep = (bufpos == 0 ? bp + buflen : p);
145 newl = skip = 0;
146 do {
147 if (p == bp + buflen)
148 p = bp;
149 ch = *p;
150 /* Skip "\n<.*>" syslog sequences. */
151 if (skip) {
152 if (ch == '\n') {
153 skip = 0;
154 newl = 1;
155 } if (ch == '>') {
156 if (LOG_FAC(pri) == LOG_KERN || all)
157 newl = skip = 0;
158 } else if (ch >= '0' && ch <= '9') {
159 pri *= 10;
160 pri += ch - '0';
161 }
162 continue;
163 }
164 if (newl && ch == '<') {
165 pri = 0;
166 skip = 1;
167 continue;
168 }
169 if (ch == '\0')
170 continue;
171 newl = ch == '\n';
7cee7052 172 vis(buf, ch, 0, 0);
984263bc 173 if (buf[1] == 0)
7cee7052 174 putchar(buf[0]);
984263bc 175 else
7cee7052 176 printf("%s", buf);
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177 } while (++p != ep);
178 if (!newl)
7cee7052 179 putchar('\n');
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180 exit(0);
181}
182
183void
b5744197 184usage(void)
984263bc 185{
7cee7052 186 fprintf(stderr, "usage: dmesg [-a] [-M core] [-N system]\n");
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187 exit(1);
188}