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. 32 */ 33 34 #ifndef lint 35 static const char copyright[] = 36 "@(#) Copyright (c) 1991, 1993\n\ 37 The Regents of the University of California. All rights reserved.\n"; 38 #endif /* not lint */ 39 40 #ifndef lint 41 #if 0 42 static const char sccsid[] = "@(#)dmesg.c 8.1 (Berkeley) 6/5/93"; 43 #endif 44 static const char rcsid[] = 45 "$FreeBSD$"; 46 #endif /* not lint */ 47 48 #include <sys/msgbuf.h> 49 50 #include <err.h> 51 #include <fcntl.h> 52 #include <kvm.h> 53 #include <locale.h> 54 #include <stdio.h> 55 #include <stdlib.h> 56 #include <unistd.h> 57 #include <vis.h> 58 59 struct nlist nl[] = { 60 #define X_MSGBUF 0 61 { "_msgbufp" }, 62 { NULL }, 63 }; 64 65 void usage __P((void)); 66 67 #define KREAD(addr, var) \ 68 kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var) 69 70 int 71 main(argc, argv) 72 int argc; 73 char *argv[]; 74 { 75 register int ch, newl, skip; 76 register char *p, *ep; 77 struct msgbuf *bufp, cur; 78 char *bp, *memf, *nlistf; 79 kvm_t *kd; 80 char buf[5]; 81 82 (void) setlocale(LC_CTYPE, ""); 83 memf = nlistf = NULL; 84 while ((ch = getopt(argc, argv, "M:N:")) != -1) 85 switch(ch) { 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 argv += optind; 98 99 /* 100 * Discard setgid privileges if not the running kernel so that bad 101 * guys can't print interesting stuff from kernel memory. 102 */ 103 if (memf != NULL || nlistf != NULL) 104 setgid(getgid()); 105 106 /* Read in kernel message buffer, do sanity checks. */ 107 if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL) 108 exit (1); 109 if (kvm_nlist(kd, nl) == -1) 110 errx(1, "kvm_nlist: %s", kvm_geterr(kd)); 111 if (nl[X_MSGBUF].n_type == 0) 112 errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist"); 113 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur)) 114 errx(1, "kvm_read: %s", kvm_geterr(kd)); 115 if (cur.msg_magic != MSG_MAGIC) 116 errx(1, "kernel message buffer has different magic number"); 117 bp = malloc(cur.msg_size); 118 if (!bp) 119 errx(1, "malloc failed"); 120 if (kvm_read(kd, (long)cur.msg_ptr, bp, cur.msg_size) != 121 cur.msg_size) 122 errx(1, "kvm_read: %s", kvm_geterr(kd)); 123 if (cur.msg_bufx >= cur.msg_size) 124 cur.msg_bufx = 0; 125 kvm_close(kd); 126 127 /* 128 * The message buffer is circular. If the buffer has wrapped, the 129 * write pointer points to the oldest data. Otherwise, the write 130 * pointer points to \0's following the data. Read the entire 131 * buffer starting at the write pointer and ignore nulls so that 132 * we effectively start at the oldest data. 133 */ 134 p = bp + cur.msg_bufx; 135 ep = (cur.msg_bufx == 0 ? bp + cur.msg_size : p); 136 newl = skip = 0; 137 do { 138 if (p == bp + cur.msg_size) 139 p = bp; 140 ch = *p; 141 /* Skip "\n<.*>" syslog sequences. */ 142 if (skip) { 143 if (ch == '>') 144 newl = skip = 0; 145 continue; 146 } 147 if (newl && ch == '<') { 148 skip = 1; 149 continue; 150 } 151 if (ch == '\0') 152 continue; 153 newl = ch == '\n'; 154 (void)vis(buf, ch, 0, 0); 155 if (buf[1] == 0) 156 (void)putchar(buf[0]); 157 else 158 (void)printf("%s", buf); 159 } while (++p != ep); 160 if (!newl) 161 (void)putchar('\n'); 162 exit(0); 163 } 164 165 void 166 usage() 167 { 168 (void)fprintf(stderr, "usage: dmesg [-M core] [-N system]\n"); 169 exit(1); 170 } 171