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  * 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
  32 static 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
  38 static const char sccsid[] = "@(#)dmesg.c       8.1 (Berkeley) 6/5/93";
  39 #endif /* not lint */
  40 #endif
  41 #include <sys/cdefs.h>
  42 __FBSDID("$FreeBSD$");
  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
  64 static struct nlist nl[] = {
  65 #define X_MSGBUF        0
  66         { "_msgbufp", 0, 0, 0, 0 },
  67         { NULL, 0, 0, 0, 0 },
  68 };
  69
  70 void usage(void) __dead2;
  71
  72 #define KREAD(addr, var) \
  73         kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
  74
  75 int
  76 main(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
 212 void
 213 usage(void)
 214 {
 215         fprintf(stderr, "usage: dmesg [-ac] [-M core [-N system]]\n");
 216         exit(1);
 217 }