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