sbin/dmesg/dmesg.c

   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  * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
  34  * @(#)dmesg.c  8.1 (Berkeley) 6/5/93
  35  * $FreeBSD: src/sbin/dmesg/dmesg.c,v 1.11.2.3 2001/08/08 22:32:15 obrien Exp $
  36  * $DragonFly: src/sbin/dmesg/dmesg.c,v 1.7 2005/01/14 06:38:41 cpressey Exp $
  37  */
  38
  39 #include <sys/types.h>
  40 #include <sys/msgbuf.h>
  41 #include <sys/sysctl.h>
  42
  43 #include <err.h>
  44 #include <fcntl.h>
  45 #include <kvm.h>
  46 #include <locale.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <unistd.h>
  50 #include <vis.h>
  51 #include <sys/syslog.h>
  52
  53 struct nlist nl[] = {
  54 #define X_MSGBUF        0
  55         { "_msgbufp",   0, 0, 0, 0 },
  56         { NULL,         0, 0, 0, 0 },
  57 };
  58
  59 void usage(void);
  60
  61 #define KREAD(addr, var) \
  62         kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
  63
  64 int
  65 main(int argc, char **argv)
  66 {
  67         int ch, newl, skip;
  68         char *p, *ep;
  69         struct msgbuf *bufp, cur;
  70         char *bp, *memf, *nlistf;
  71         kvm_t *kd;
  72         char buf[5];
  73         int all = 0;
  74         int pri = 0;
  75         size_t buflen, bufpos;
  76
  77         setlocale(LC_CTYPE, "");
  78         memf = nlistf = NULL;
  79         while ((ch = getopt(argc, argv, "aM:N:")) != -1)
  80                 switch(ch) {
  81                 case 'a':
  82                         all++;
  83                         break;
  84                 case 'M':
  85                         memf = optarg;
  86                         break;
  87                 case 'N':
  88                         nlistf = optarg;
  89                         break;
  90                 case '?':
  91                 default:
  92                         usage();
  93                 }
  94         argc -= optind;
  95         argv += optind;
  96
  97         if (memf == NULL && nlistf == NULL) {
  98                 /* Running kernel. Use sysctl. */
  99                 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
 100                         err(1, "sysctl kern.msgbuf");
 101                 buflen += 4096;         /* add some slop */
 102                 if ((bp = malloc(buflen)) == NULL)
 103                         errx(1, "malloc failed");
 104                 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
 105                         err(1, "sysctl kern.msgbuf");
 106                 /* We get a dewrapped buffer using sysctl. */
 107                 bufpos = 0;
 108         } else {
 109                 /* Read in kernel message buffer, do sanity checks. */
 110                 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
 111                 if (kd == NULL)
 112                         exit (1);
 113                 if (kvm_nlist(kd, nl) == -1)
 114                         errx(1, "kvm_nlist: %s", kvm_geterr(kd));
 115                 if (nl[X_MSGBUF].n_type == 0)
 116                         errx(1, "%s: msgbufp not found",
 117                             nlistf ? nlistf : "namelist");
 118                 if (KREAD(nl[X_MSGBUF].n_value, bufp) || KREAD((long)bufp, cur))
 119                         errx(1, "kvm_read: %s", kvm_geterr(kd));
 120                 if (cur.msg_magic != MSG_MAGIC)
 121                         errx(1, "kernel message buffer has different magic "
 122                             "number");
 123                 bp = malloc(cur.msg_size);
 124                 if (!bp)
 125                         errx(1, "malloc failed");
 126                 if (kvm_read(kd, (long)cur.msg_ptr, bp, cur.msg_size) !=
 127                     (ssize_t)cur.msg_size)
 128                         errx(1, "kvm_read: %s", kvm_geterr(kd));
 129                 kvm_close(kd);
 130                 buflen = cur.msg_size;
 131                 bufpos = cur.msg_bufx;
 132                 if (bufpos >= buflen)
 133                         bufpos = 0;
 134         }
 135
 136         /*
 137          * The message buffer is circular.  If the buffer has wrapped, the
 138          * write pointer points to the oldest data.  Otherwise, the write
 139          * pointer points to \0's following the data.  Read the entire
 140          * buffer starting at the write pointer and ignore nulls so that
 141          * we effectively start at the oldest data.
 142          */
 143         p = bp + bufpos;
 144         ep = (bufpos == 0 ? bp + buflen : p);
 145         newl = skip = 0;
 146         do {
 147                 if (p == bp + buflen)
 148                         p = bp;
 149                 ch = *p;
 150                 /* Skip "\n<.*>" syslog sequences. */
 151                 if (skip) {
 152                         if (ch == '\n') {
 153                                 skip = 0;
 154                                 newl = 1;
 155                         } if (ch == '>') {
 156                                 if (LOG_FAC(pri) == LOG_KERN || all)
 157                                         newl = skip = 0;
 158                         } else if (ch >= '0' && ch <= '9') {
 159                                 pri *= 10;
 160                                 pri += ch - '0';
 161                         }
 162                         continue;
 163                 }
 164                 if (newl && ch == '<') {
 165                         pri = 0;
 166                         skip = 1;
 167                         continue;
 168                 }
 169                 if (ch == '\0')
 170                         continue;
 171                 newl = ch == '\n';
 172                 vis(buf, ch, 0, 0);
 173                 if (buf[1] == 0)
 174                         putchar(buf[0]);
 175                 else
 176                         printf("%s", buf);
 177         } while (++p != ep);
 178         if (!newl)
 179                 putchar('\n');
 180         exit(0);
 181 }
 182
 183 void
 184 usage(void)
 185 {
 186         fprintf(stderr, "usage: dmesg [-a] [-M core] [-N system]\n");
 187         exit(1);
 188 }