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. 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  * @(#) Copyright (c) 1991, 1993 The Regents of the University of California.  All rights reserved.
  30  * @(#)dmesg.c  8.1 (Berkeley) 6/5/93
  31  * $FreeBSD: src/sbin/dmesg/dmesg.c,v 1.11.2.3 2001/08/08 22:32:15 obrien Exp $
  32  */
  33
  34 #include <sys/types.h>
  35 #include <sys/msgbuf.h>
  36 #include <sys/sysctl.h>
  37 #include <sys/stat.h>
  38
  39 #include <err.h>
  40 #include <fcntl.h>
  41 #include <kvm.h>
  42 #include <locale.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <unistd.h>
  46 #include <vis.h>
  47 #include <sys/syslog.h>
  48
  49 static struct nlist nl[] = {
  50 #define X_MSGBUF        0
  51         { "_msgbufp",   0, 0, 0, 0 },
  52         { NULL,         0, 0, 0, 0 },
  53 };
  54
  55 static void dumpbuf(char *bp, size_t bufpos, size_t buflen,
  56                     int *newl, int *skip, int *pri);
  57 static void usage(void) __dead2;
  58
  59 #define KREAD(addr, var) \
  60         kvm_read(kd, addr, &var, sizeof(var)) != sizeof(var)
  61
  62 #define INCRBUFSIZE     65536
  63
  64 static int all_opt;
  65
  66 int
  67 main(int argc, char **argv)
  68 {
  69         int newl, skip;
  70         struct msgbuf *bufp, cur;
  71         char *bp, *memf, *nlistf;
  72         kvm_t *kd;
  73         int ch;
  74         int clear = 0;
  75         int pri = 0;
  76         int tailmode = 0;
  77         int kno;
  78         size_t buflen, bufpos;
  79         struct stat st;
  80
  81         setlocale(LC_CTYPE, "");
  82         memf = nlistf = NULL;
  83         while ((ch = getopt(argc, argv, "acfM:N:n:")) != -1) {
  84                 switch(ch) {
  85                 case 'a':
  86                         all_opt++;
  87                         break;
  88                 case 'c':
  89                         clear = 1;
  90                         break;
  91                 case 'f':
  92                         ++tailmode;
  93                         break;
  94                 case 'M':
  95                         memf = optarg;
  96                         break;
  97                 case 'N':
  98                         nlistf = optarg;
  99                         break;
 100                 case 'n':
 101                         kno = strtol(optarg, NULL, 0);
 102                         asprintf(&memf, "vmcore.%d", kno);
 103                         asprintf(&nlistf, "kern.%d", kno);
 104                         if (stat(memf, &st) || stat(nlistf, &st)) {
 105                                 free(memf);
 106                                 free(nlistf);
 107                                 asprintf(&memf, "/var/crash/vmcore.%d", kno);
 108                                 asprintf(&nlistf, "/var/crash/kern.%d", kno);
 109                         }
 110                         break;
 111                 case '?':
 112                 default:
 113                         usage();
 114                 }
 115         }
 116         argc -= optind;
 117         argv += optind;
 118
 119         newl = 1;
 120         skip = 0;
 121         pri = 0;
 122
 123         if (memf == NULL && nlistf == NULL && tailmode == 0) {
 124                 /* Running kernel. Use sysctl. */
 125                 buflen = 0;
 126                 if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
 127                         err(1, "sysctl kern.msgbuf");
 128                 if (buflen == 0)        /* can happen if msgbuf was cleared */
 129                         buflen = 1;
 130
 131                 if ((bp = malloc(buflen)) == NULL)
 132                         errx(1, "malloc failed");
 133                 if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
 134                         err(1, "sysctl kern.msgbuf");
 135                 /* We get a dewrapped buffer using sysctl. */
 136                 bufpos = 0;
 137                 dumpbuf(bp, bufpos, buflen, &newl, &skip, &pri);
 138         } else {
 139                 u_int rindex;
 140                 u_int xindex;
 141                 u_int ri;
 142                 u_int xi;
 143                 u_int n;
 144
 145                 /* Read in kernel message buffer, do sanity checks. */
 146                 kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
 147                 if (kd == NULL)
 148                         exit (1);
 149                 if (kvm_nlist(kd, nl) == -1)
 150                         errx(1, "kvm_nlist: %s", kvm_geterr(kd));
 151                 if (nl[X_MSGBUF].n_type == 0)
 152                         errx(1, "%s: msgbufp not found",
 153                             nlistf ? nlistf : "namelist");
 154                 bp = malloc(INCRBUFSIZE);
 155                 if (!bp)
 156                         errx(1, "malloc failed");
 157                 if (KREAD(nl[X_MSGBUF].n_value, bufp))
 158                         errx(1, "kvm_read: %s", kvm_geterr(kd));
 159                 if (KREAD((long)bufp, cur))
 160                         errx(1, "kvm_read: %s", kvm_geterr(kd));
 161                 if (cur.msg_magic != MSG_MAGIC && cur.msg_magic != MSG_OMAGIC)
 162                         errx(1, "kernel message buffer has different magic "
 163                             "number");
 164
 165                 /*
 166                  * NOTE: current algorithm is compatible with both old and
 167                  *       new msgbuf structures.  The new structure doesn't
 168                  *       modulo the indexes (so we do), and adds a separate
 169                  *       log index which we don't access here.
 170                  */
 171
 172                 rindex = cur.msg_bufr;
 173
 174                 for (;;) {
 175                         /*
 176                          * Calculate index for dump and do sanity clipping.
 177                          */
 178                         xindex = cur.msg_bufx;
 179                         n = xindex - rindex;
 180                         if (n > cur.msg_size - 1024) {
 181                                 rindex = xindex - cur.msg_size + 2048;
 182                                 n = xindex - rindex;
 183                         }
 184                         ri = rindex % cur.msg_size;
 185                         xi = xindex % cur.msg_size;
 186
 187                         if (ri < xi)
 188                                 buflen = xi - ri;
 189                         else
 190                                 buflen = cur.msg_size - ri;
 191                         if (buflen > n)
 192                                 buflen = n;
 193                         if (buflen > INCRBUFSIZE)
 194                                 buflen = INCRBUFSIZE;
 195
 196                         if (kvm_read(kd, (long)cur.msg_ptr + ri,
 197                                      bp, buflen) != (ssize_t)buflen) {
 198                                 errx(1, "kvm_read: %s", kvm_geterr(kd));
 199                         }
 200                         if (buflen)
 201                                 dumpbuf(bp, 0, buflen, &newl, &skip, &pri);
 202                         ri = (ri + buflen) % cur.msg_size;
 203                         n = n - buflen;
 204                         rindex += buflen;
 205                         if ((int)n <= 0) {
 206                                 if (tailmode == 0)
 207                                         break;
 208                                 fflush(stdout);
 209                                 if (tailmode == 1)
 210                                         sleep(1);
 211                         }
 212                         if (KREAD((long)bufp, cur))
 213                                 errx(1, "kvm_read: %s", kvm_geterr(kd));
 214                 }
 215                 kvm_close(kd);
 216         }
 217         if (!newl)
 218                 putchar('\n');
 219         if (clear) {
 220                 if (sysctlbyname("kern.msgbuf_clear", NULL, NULL,
 221                                  &clear, sizeof(int)) != 0) {
 222                         err(1, "sysctl kern.msgbuf_clear");
 223                 }
 224         }
 225         return(0);
 226 }
 227
 228 static
 229 void
 230 dumpbuf(char *bp, size_t bufpos, size_t buflen,
 231         int *newl, int *skip, int *pri)
 232 {
 233         int ch;
 234         char *p, *ep;
 235         char buf[5];
 236
 237         /*
 238          * The message buffer is circular.  If the buffer has wrapped, the
 239          * write pointer points to the oldest data.  Otherwise, the write
 240          * pointer points to \0's following the data.  Read the entire
 241          * buffer starting at the write pointer and ignore nulls so that
 242          * we effectively start at the oldest data.
 243          */
 244         p = bp + bufpos;
 245         ep = (bufpos == 0 ? bp + buflen : p);
 246         do {
 247                 if (p == bp + buflen)
 248                         p = bp;
 249                 ch = *p;
 250                 /* Skip "\n<.*>" syslog sequences. */
 251                 if (*skip) {
 252                         if (ch == '\n') {
 253                                 *skip = 0;
 254                                 *newl = 1;
 255                         } if (ch == '>') {
 256                                 if (LOG_FAC(*pri) == LOG_KERN)
 257                                         *newl = *skip = 0;
 258                         } else if (ch >= '0' && ch <= '9') {
 259                                 *pri *= 10;
 260                                 *pri += ch - '0';
 261                         }
 262                         continue;
 263                 }
 264                 if (*newl && ch == '<' && all_opt == 0) {
 265                         *pri = 0;
 266                         *skip = 1;
 267                         continue;
 268                 }
 269                 if (ch == '\0')
 270                         continue;
 271                 *newl = (ch == '\n');
 272                 vis(buf, ch, VIS_NOSLASH, 0);
 273                 if (buf[1] == 0)
 274                         putchar(buf[0]);
 275                 else
 276                         printf("%s", buf);
 277         } while (++p != ep);
 278 }
 279
 280 static void
 281 usage(void)
 282 {
 283         fprintf(stderr, "usage: dmesg [-ac] [-M core] [-N system]\n");
 284         exit(1);
 285 }