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 #endif 40 #include <sys/cdefs.h> 41 #include <sys/types.h> 42 #include <sys/msgbuf.h> 43 #include <sys/sysctl.h> 44 45 #include <ctype.h> 46 #include <err.h> 47 #include <errno.h> 48 #include <fcntl.h> 49 #include <kvm.h> 50 #include <limits.h> 51 #include <locale.h> 52 #include <nlist.h> 53 #include <stdio.h> 54 #include <stdbool.h> 55 #include <stdlib.h> 56 #include <string.h> 57 #include <unistd.h> 58 #include <vis.h> 59 #include <sys/syslog.h> 60 61 static struct nlist nl[] = { 62 #define X_MSGBUF 0 63 { "_msgbufp", 0, 0, 0, 0 }, 64 { NULL, 0, 0, 0, 0 }, 65 }; 66 67 void usage(void) __dead2; 68 69 #define KREAD(addr, var) \ 70 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var) 71 72 int 73 main(int argc, char *argv[]) 74 { 75 struct msgbuf *bufp, cur; 76 char *bp, *ep, *memf, *nextp, *nlistf, *p, *q, *visbp; 77 kvm_t *kd; 78 size_t buflen, bufpos; 79 long pri; 80 int ch, clear; 81 bool all; 82 83 all = false; 84 clear = false; 85 (void) setlocale(LC_CTYPE, ""); 86 memf = nlistf = NULL; 87 while ((ch = getopt(argc, argv, "acM:N:")) != -1) 88 switch(ch) { 89 case 'a': 90 all = true; 91 break; 92 case 'c': 93 clear = true; 94 break; 95 case 'M': 96 memf = optarg; 97 break; 98 case 'N': 99 nlistf = optarg; 100 break; 101 case '?': 102 default: 103 usage(); 104 } 105 argc -= optind; 106 if (argc != 0) 107 usage(); 108 109 if (memf == NULL) { 110 /* 111 * Running kernel. Use sysctl. This gives an unwrapped buffer 112 * as a side effect. Remove nulterm (if present) so the value 113 * returned by sysctl is formatted as the rest of the code 114 * expects (the same as the value read from a core file below). 115 */ 116 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1) 117 err(1, "sysctl kern.msgbuf"); 118 /* Allocate extra room for growth between the sysctl calls. */ 119 buflen += buflen/8; 120 /* Allocate more than sysctl sees, for room to append \n\0. */ 121 if ((bp = malloc(buflen + 2)) == NULL) 122 errx(1, "malloc failed"); 123 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1) 124 err(1, "sysctl kern.msgbuf"); 125 if (buflen > 0 && bp[buflen - 1] == '\0') 126 buflen--; 127 if (clear) 128 if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int))) 129 err(1, "sysctl kern.msgbuf_clear"); 130 } else { 131 /* Read in kernel message buffer and do sanity checks. */ 132 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg"); 133 if (kd == NULL) 134 exit (1); 135 if (kvm_nlist(kd, nl) == -1) 136 errx(1, "kvm_nlist: %s", kvm_geterr(kd)); 137 if (nl[X_MSGBUF].n_type == 0) 138 errx(1, "%s: msgbufp not found", 139 nlistf ? nlistf : "namelist"); 140 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur)) 141 errx(1, "kvm_read: %s", kvm_geterr(kd)); 142 if (cur.msg_magic != MSG_MAGIC) 143 errx(1, "kernel message buffer has different magic " 144 "number"); 145 if ((bp = malloc(cur.msg_size + 2)) == NULL) 146 errx(1, "malloc failed"); 147 148 /* Unwrap the circular buffer to start from the oldest data. */ 149 bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq); 150 if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp, 151 cur.msg_size - bufpos) != (ssize_t)(cur.msg_size - bufpos)) 152 errx(1, "kvm_read: %s", kvm_geterr(kd)); 153 if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr, 154 &bp[cur.msg_size - bufpos], bufpos) != (ssize_t)bufpos) 155 errx(1, "kvm_read: %s", kvm_geterr(kd)); 156 kvm_close(kd); 157 buflen = cur.msg_size; 158 } 159 160 /* 161 * Ensure that the buffer ends with a newline and a \0 to avoid 162 * complications below. We left space above. 163 */ 164 if (buflen == 0 || bp[buflen - 1] != '\n') 165 bp[buflen++] = '\n'; 166 bp[buflen] = '\0'; 167 168 if ((visbp = malloc(4 * buflen + 1)) == NULL) 169 errx(1, "malloc failed"); 170 171 /* 172 * The message buffer is circular, but has been unwrapped so that 173 * the oldest data comes first. The data will be preceded by \0's 174 * if the message buffer was not full. 175 */ 176 p = bp; 177 ep = &bp[buflen]; 178 if (*p == '\0') { 179 /* Strip leading \0's */ 180 while (*p == '\0') 181 p++; 182 } 183 for (; p < ep; p = nextp) { 184 nextp = memchr(p, '\n', ep - p); 185 nextp++; 186 187 /* Skip ^<[0-9]+> syslog sequences. */ 188 if (*p == '<' && isdigit(*(p+1))) { 189 errno = 0; 190 pri = strtol(p + 1, &q, 10); 191 if (*q == '>' && pri >= 0 && pri < INT_MAX && 192 errno == 0) { 193 if (LOG_FAC(pri) != LOG_KERN && !all) 194 continue; 195 p = q + 1; 196 } 197 } 198 199 (void)strvisx(visbp, p, nextp - p, 0); 200 (void)printf("%s", visbp); 201 } 202 exit(0); 203 } 204 205 void 206 usage(void) 207 { 208 fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n"); 209 exit(1); 210 } 211