dmesg.c revision 227081
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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30#if 0 31#ifndef lint 32static const char copyright[] = 33"@(#) Copyright (c) 1991, 1993\n\ 34 The Regents of the University of California. All rights reserved.\n"; 35#endif /* not lint */ 36 37#ifndef lint 38static const char sccsid[] = "@(#)dmesg.c 8.1 (Berkeley) 6/5/93"; 39#endif /* not lint */ 40#endif 41#include <sys/cdefs.h> 42__FBSDID("$FreeBSD: head/sbin/dmesg/dmesg.c 227081 2011-11-04 13:36:02Z ed $"); 43 44#include <sys/types.h> 45#include <sys/msgbuf.h> 46#include <sys/sysctl.h> 47 48#include <ctype.h> 49#include <err.h> 50#include <errno.h> 51#include <fcntl.h> 52#include <kvm.h> 53#include <limits.h> 54#include <locale.h> 55#include <nlist.h> 56#include <stdio.h> 57#include <stdlib.h> 58#include <string.h> 59#include <unistd.h> 60#include <vis.h> 61#include <sys/syslog.h> 62 63static struct nlist nl[] = { 64#define X_MSGBUF 0 65 { "_msgbufp", 0, 0, 0, 0 }, 66 { NULL, 0, 0, 0, 0 }, 67}; 68 69void usage(void) __dead2; 70 71#define KREAD(addr, var) \ 72 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var) 73 74int 75main(int argc, char *argv[]) 76{ 77 struct msgbuf *bufp, cur; 78 char *bp, *ep, *memf, *nextp, *nlistf, *p, *q, *visbp; 79 kvm_t *kd; 80 size_t buflen, bufpos; 81 long pri; 82 int all, ch; 83 84 all = 0; 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 if (argc != 0) 104 usage(); 105 106 if (memf == NULL) { 107 /* 108 * Running kernel. Use sysctl. This gives an unwrapped 109 * buffer as a side effect. 110 */ 111 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1) 112 err(1, "sysctl kern.msgbuf"); 113 if ((bp = malloc(buflen + 2)) == NULL) 114 errx(1, "malloc failed"); 115 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1) 116 err(1, "sysctl kern.msgbuf"); 117 } else { 118 /* Read in kernel message buffer and do sanity checks. */ 119 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg"); 120 if (kd == NULL) 121 exit (1); 122 if (kvm_nlist(kd, nl) == -1) 123 errx(1, "kvm_nlist: %s", kvm_geterr(kd)); 124 if (nl[X_MSGBUF].n_type == 0) 125 errx(1, "%s: msgbufp not found", 126 nlistf ? nlistf : "namelist"); 127 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur)) 128 errx(1, "kvm_read: %s", kvm_geterr(kd)); 129 if (cur.msg_magic != MSG_MAGIC) 130 errx(1, "kernel message buffer has different magic " 131 "number"); 132 if ((bp = malloc(cur.msg_size + 2)) == NULL) 133 errx(1, "malloc failed"); 134 135 /* Unwrap the circular buffer to start from the oldest data. */ 136 bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq); 137 if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp, 138 cur.msg_size - bufpos) != (ssize_t)(cur.msg_size - bufpos)) 139 errx(1, "kvm_read: %s", kvm_geterr(kd)); 140 if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr, 141 &bp[cur.msg_size - bufpos], bufpos) != (ssize_t)bufpos) 142 errx(1, "kvm_read: %s", kvm_geterr(kd)); 143 kvm_close(kd); 144 buflen = cur.msg_size; 145 } 146 147 /* 148 * Ensure that the buffer ends with a newline and a \0 to avoid 149 * complications below. We left space above. 150 */ 151 if (buflen == 0 || bp[buflen - 1] != '\n') 152 bp[buflen++] = '\n'; 153 bp[buflen] = '\0'; 154 155 if ((visbp = malloc(4 * buflen + 1)) == NULL) 156 errx(1, "malloc failed"); 157 158 /* 159 * The message buffer is circular, but has been unwrapped so that 160 * the oldest data comes first. The data will be preceded by \0's 161 * if the message buffer was not full. 162 */ 163 p = bp; 164 ep = &bp[buflen]; 165 if (*p == '\0') { 166 /* Strip leading \0's */ 167 while (*p == '\0') 168 p++; 169 } else if (!all) { 170 /* Skip the first line, since it is probably incomplete. */ 171 p = memchr(p, '\n', ep - p); 172 p++; 173 } 174 for (; p < ep; p = nextp) { 175 nextp = memchr(p, '\n', ep - p); 176 nextp++; 177 178 /* Skip ^<[0-9]+> syslog sequences. */ 179 if (*p == '<' && isdigit(*(p+1))) { 180 errno = 0; 181 pri = strtol(p + 1, &q, 10); 182 if (*q == '>' && pri >= 0 && pri < INT_MAX && 183 errno == 0) { 184 if (LOG_FAC(pri) != LOG_KERN && !all) 185 continue; 186 p = q + 1; 187 } 188 } 189 190 (void)strvisx(visbp, p, nextp - p, 0); 191 (void)printf("%s", visbp); 192 } 193 exit(0); 194} 195 196void 197usage(void) 198{ 199 (void)fprintf(stderr, "usage: dmesg [-a] [-M core [-N system]]\n"); 200 exit(1); 201} 202