dmesg.c revision 331722
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: stable/11/sbin/dmesg/dmesg.c 331722 2018-03-29 02:50:57Z eadler $"); 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 <stdbool.h> 58#include <stdlib.h> 59#include <string.h> 60#include <unistd.h> 61#include <vis.h> 62#include <sys/syslog.h> 63 64static struct nlist nl[] = { 65#define X_MSGBUF 0 66 { "_msgbufp", 0, 0, 0, 0 }, 67 { NULL, 0, 0, 0, 0 }, 68}; 69 70void usage(void) __dead2; 71 72#define KREAD(addr, var) \ 73 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var) 74 75int 76main(int argc, char *argv[]) 77{ 78 struct msgbuf *bufp, cur; 79 char *bp, *ep, *memf, *nextp, *nlistf, *p, *q, *visbp; 80 kvm_t *kd; 81 size_t buflen, bufpos; 82 long pri; 83 int ch, clear; 84 bool all; 85 86 all = false; 87 clear = false; 88 (void) setlocale(LC_CTYPE, ""); 89 memf = nlistf = NULL; 90 while ((ch = getopt(argc, argv, "acM:N:")) != -1) 91 switch(ch) { 92 case 'a': 93 all = true; 94 break; 95 case 'c': 96 clear = true; 97 break; 98 case 'M': 99 memf = optarg; 100 break; 101 case 'N': 102 nlistf = optarg; 103 break; 104 case '?': 105 default: 106 usage(); 107 } 108 argc -= optind; 109 if (argc != 0) 110 usage(); 111 112 if (memf == NULL) { 113 /* 114 * Running kernel. Use sysctl. This gives an unwrapped buffer 115 * as a side effect. Remove nulterm (if present) so the value 116 * returned by sysctl is formatted as the rest of the code 117 * expects (the same as the value read from a core file below). 118 */ 119 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1) 120 err(1, "sysctl kern.msgbuf"); 121 /* Allocate extra room for growth between the sysctl calls. */ 122 buflen += buflen/8; 123 /* Allocate more than sysctl sees, for room to append \n\0. */ 124 if ((bp = malloc(buflen + 2)) == NULL) 125 errx(1, "malloc failed"); 126 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1) 127 err(1, "sysctl kern.msgbuf"); 128 if (buflen > 0 && bp[buflen - 1] == '\0') 129 buflen--; 130 if (clear) 131 if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int))) 132 err(1, "sysctl kern.msgbuf_clear"); 133 } else { 134 /* Read in kernel message buffer and do sanity checks. */ 135 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg"); 136 if (kd == NULL) 137 exit (1); 138 if (kvm_nlist(kd, nl) == -1) 139 errx(1, "kvm_nlist: %s", kvm_geterr(kd)); 140 if (nl[X_MSGBUF].n_type == 0) 141 errx(1, "%s: msgbufp not found", 142 nlistf ? nlistf : "namelist"); 143 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur)) 144 errx(1, "kvm_read: %s", kvm_geterr(kd)); 145 if (cur.msg_magic != MSG_MAGIC) 146 errx(1, "kernel message buffer has different magic " 147 "number"); 148 if ((bp = malloc(cur.msg_size + 2)) == NULL) 149 errx(1, "malloc failed"); 150 151 /* Unwrap the circular buffer to start from the oldest data. */ 152 bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq); 153 if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp, 154 cur.msg_size - bufpos) != (ssize_t)(cur.msg_size - bufpos)) 155 errx(1, "kvm_read: %s", kvm_geterr(kd)); 156 if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr, 157 &bp[cur.msg_size - bufpos], bufpos) != (ssize_t)bufpos) 158 errx(1, "kvm_read: %s", kvm_geterr(kd)); 159 kvm_close(kd); 160 buflen = cur.msg_size; 161 } 162 163 /* 164 * Ensure that the buffer ends with a newline and a \0 to avoid 165 * complications below. We left space above. 166 */ 167 if (buflen == 0 || bp[buflen - 1] != '\n') 168 bp[buflen++] = '\n'; 169 bp[buflen] = '\0'; 170 171 if ((visbp = malloc(4 * buflen + 1)) == NULL) 172 errx(1, "malloc failed"); 173 174 /* 175 * The message buffer is circular, but has been unwrapped so that 176 * the oldest data comes first. The data will be preceded by \0's 177 * if the message buffer was not full. 178 */ 179 p = bp; 180 ep = &bp[buflen]; 181 if (*p == '\0') { 182 /* Strip leading \0's */ 183 while (*p == '\0') 184 p++; 185 } else if (!all) { 186 /* Skip the first line, since it is probably incomplete. */ 187 p = memchr(p, '\n', ep - p); 188 p++; 189 } 190 for (; p < ep; p = nextp) { 191 nextp = memchr(p, '\n', ep - p); 192 nextp++; 193 194 /* Skip ^<[0-9]+> syslog sequences. */ 195 if (*p == '<' && isdigit(*(p+1))) { 196 errno = 0; 197 pri = strtol(p + 1, &q, 10); 198 if (*q == '>' && pri >= 0 && pri < INT_MAX && 199 errno == 0) { 200 if (LOG_FAC(pri) != LOG_KERN && !all) 201 continue; 202 p = q + 1; 203 } 204 } 205 206 (void)strvisx(visbp, p, nextp - p, 0); 207 (void)printf("%s", visbp); 208 } 209 exit(0); 210} 211 212void 213usage(void) 214{ 215 fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n"); 216 exit(1); 217} 218