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 #include <sys/types.h> 33 #include <sys/msgbuf.h> 34 #include <sys/sysctl.h> 35 36 #include <ctype.h> 37 #include <err.h> 38 #include <errno.h> 39 #include <fcntl.h> 40 #include <kvm.h> 41 #include <limits.h> 42 #include <locale.h> 43 #include <nlist.h> 44 #include <stdio.h> 45 #include <stdbool.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include <unistd.h> 49 #include <vis.h> 50 #include <sys/syslog.h> 51 52 static struct nlist nl[] = { 53 #define X_MSGBUF 0 54 { "_msgbufp", 0, 0, 0, 0 }, 55 { NULL, 0, 0, 0, 0 }, 56 }; 57 58 void usage(void) __dead2; 59 60 #define KREAD(addr, var) \ 61 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var) 62 63 int 64 main(int argc, char *argv[]) 65 { 66 struct msgbuf *bufp, cur; 67 char *bp, *ep, *memf, *nextp, *nlistf, *p, *q, *visbp; 68 kvm_t *kd; 69 size_t buflen, bufpos; 70 long pri; 71 int ch, clear; 72 bool all; 73 74 all = false; 75 clear = false; 76 (void) setlocale(LC_CTYPE, ""); 77 memf = nlistf = NULL; 78 while ((ch = getopt(argc, argv, "acM:N:")) != -1) 79 switch(ch) { 80 case 'a': 81 all = true; 82 break; 83 case 'c': 84 clear = true; 85 break; 86 case 'M': 87 memf = optarg; 88 break; 89 case 'N': 90 nlistf = optarg; 91 break; 92 case '?': 93 default: 94 usage(); 95 } 96 argc -= optind; 97 if (argc != 0) 98 usage(); 99 100 if (memf == NULL) { 101 /* 102 * Running kernel. Use sysctl. This gives an unwrapped buffer 103 * as a side effect. Remove nulterm (if present) so the value 104 * returned by sysctl is formatted as the rest of the code 105 * expects (the same as the value read from a core file below). 106 */ 107 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1) 108 err(1, "sysctl kern.msgbuf"); 109 /* Allocate extra room for growth between the sysctl calls. */ 110 buflen += buflen/8; 111 /* Allocate more than sysctl sees, for room to append \n\0. */ 112 if ((bp = malloc(buflen + 2)) == NULL) 113 errx(1, "malloc failed"); 114 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1) 115 err(1, "sysctl kern.msgbuf"); 116 if (buflen > 0 && bp[buflen - 1] == '\0') 117 buflen--; 118 if (clear) 119 if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int))) 120 err(1, "sysctl kern.msgbuf_clear"); 121 } else { 122 /* Read in kernel message buffer and do sanity checks. */ 123 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg"); 124 if (kd == NULL) 125 exit (1); 126 if (kvm_nlist(kd, nl) == -1) 127 errx(1, "kvm_nlist: %s", kvm_geterr(kd)); 128 if (nl[X_MSGBUF].n_type == 0) 129 errx(1, "%s: msgbufp not found", 130 nlistf ? nlistf : "namelist"); 131 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur)) 132 errx(1, "kvm_read: %s", kvm_geterr(kd)); 133 if (cur.msg_magic != MSG_MAGIC) 134 errx(1, "kernel message buffer has different magic " 135 "number"); 136 if ((bp = malloc(cur.msg_size + 2)) == NULL) 137 errx(1, "malloc failed"); 138 139 /* Unwrap the circular buffer to start from the oldest data. */ 140 bufpos = MSGBUF_SEQ_TO_POS(&cur, cur.msg_wseq); 141 if (kvm_read(kd, (long)&cur.msg_ptr[bufpos], bp, 142 cur.msg_size - bufpos) != (ssize_t)(cur.msg_size - bufpos)) 143 errx(1, "kvm_read: %s", kvm_geterr(kd)); 144 if (bufpos != 0 && kvm_read(kd, (long)cur.msg_ptr, 145 &bp[cur.msg_size - bufpos], bufpos) != (ssize_t)bufpos) 146 errx(1, "kvm_read: %s", kvm_geterr(kd)); 147 kvm_close(kd); 148 buflen = cur.msg_size; 149 } 150 151 /* 152 * Ensure that the buffer ends with a newline and a \0 to avoid 153 * complications below. We left space above. 154 */ 155 if (buflen == 0 || bp[buflen - 1] != '\n') 156 bp[buflen++] = '\n'; 157 bp[buflen] = '\0'; 158 159 if ((visbp = malloc(4 * buflen + 1)) == NULL) 160 errx(1, "malloc failed"); 161 162 /* 163 * The message buffer is circular, but has been unwrapped so that 164 * the oldest data comes first. The data will be preceded by \0's 165 * if the message buffer was not full. 166 */ 167 p = bp; 168 ep = &bp[buflen]; 169 if (*p == '\0') { 170 /* Strip leading \0's */ 171 while (*p == '\0') 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 } 195 196 void 197 usage(void) 198 { 199 fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n"); 200 exit(1); 201 } 202