usr.bin/ktrdump/ktrdump.c

   1 /*-
   2  * Copyright (c) 2002 Jake Burkholder
   3  * Copyright (c) 2004 Robert Watson
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  *
  27  * $FreeBSD: src/usr.bin/ktrdump/ktrdump.c,v 1.10 2005/05/21 09:55:06 ru Exp $
  28  * $DragonFly: src/usr.bin/ktrdump/ktrdump.c,v 1.13 2008/11/10 02:05:31 swildner Exp $
  29  */
  30
  31 #include <sys/cdefs.h>
  32
  33 #include <sys/types.h>
  34 #include <sys/ktr.h>
  35 #include <sys/mman.h>
  36 #include <sys/stat.h>
  37 #include <sys/queue.h>
  38
  39 #include <err.h>
  40 #include <fcntl.h>
  41 #include <kvm.h>
  42 #include <limits.h>
  43 #include <nlist.h>
  44 #include <stdint.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48 #include <unistd.h>
  49
  50 #define SBUFLEN 128
  51
  52 struct ktr_buffer {
  53         struct ktr_entry *ents;
  54         int modified;
  55         int reset;
  56         int beg_idx;            /* Beginning index */
  57         int end_idx;            /* Ending index */
  58 };
  59
  60 static struct nlist nl[] = {
  61         { .n_name = "_ktr_version" },
  62         { .n_name = "_ktr_entries" },
  63         { .n_name = "_ktr_idx" },
  64         { .n_name = "_ktr_buf" },
  65         { .n_name = "_ncpus" },
  66         { .n_name = NULL }
  67 };
  68 static struct nlist nl2[] = {
  69         { .n_name = "_tsc_frequency" },
  70         { .n_name = NULL }
  71 };
  72
  73 static int cflag;
  74 static int fflag;
  75 static int iflag;
  76 static int lflag;
  77 static int nflag;
  78 static int qflag;
  79 static int rflag;
  80 static int sflag;
  81 static int tflag;
  82 static int xflag;
  83 static int pflag;
  84 static int Mflag;
  85 static int Nflag;
  86 static double tsc_frequency;
  87 static double correction_factor = 0.0;
  88
  89 static char corefile[PATH_MAX];
  90 static char execfile[PATH_MAX];
  91
  92 static char errbuf[_POSIX2_LINE_MAX];
  93 static int ncpus;
  94 static kvm_t *kd;
  95 static int entries_per_buf;
  96 static int fifo_mask;
  97
  98 static void usage(void);
  99 static int earliest_ts(struct ktr_buffer *);
 100 static void print_header(FILE *, int);
 101 static void print_entry(FILE *, int, int, struct ktr_entry *, u_int64_t *);
 102 static struct ktr_info *kvm_ktrinfo(void *);
 103 static const char *kvm_string(const char *);
 104 static const char *trunc_path(const char *, int);
 105 static void read_symbols(const char *);
 106 static const char *address_to_symbol(void *);
 107 static struct ktr_buffer *ktr_bufs_init(void);
 108 static void get_indices(int *);
 109 static void load_bufs(struct ktr_buffer *, struct ktr_entry **);
 110 static void print_buf(FILE *, struct ktr_buffer *, int, u_int64_t *);
 111 static void print_bufs_timesorted(FILE *, struct ktr_buffer *, u_int64_t *);
 112
 113
 114 /*
 115  * Reads the ktr trace buffer from kernel memory and prints the trace entries.
 116  */
 117 int
 118 main(int ac, char **av)
 119 {
 120         struct ktr_buffer *ktr_bufs;
 121         struct ktr_entry **ktr_kbuf;
 122         FILE *fo;
 123         int64_t tts;
 124         int *ktr_start_index;
 125         int version;
 126         int c;
 127         int n;
 128
 129         /*
 130          * Parse commandline arguments.
 131          */
 132         fo = stdout;
 133         while ((c = getopt(ac, av, "acfinqrtxpslA:N:M:o:")) != -1) {
 134                 switch (c) {
 135                 case 'a':
 136                         cflag = 1;
 137                         iflag = 1;
 138                         rflag = 1;
 139                         xflag = 1;
 140                         pflag = 1;
 141                         rflag = 1;
 142                         sflag = 1;
 143                         break;
 144                 case 'c':
 145                         cflag = 1;
 146                         break;
 147                 case 'N':
 148                         if (strlcpy(execfile, optarg, sizeof(execfile))
 149                             >= sizeof(execfile))
 150                                 errx(1, "%s: File name too long", optarg);
 151                         Nflag = 1;
 152                         break;
 153                 case 'f':
 154                         fflag = 1;
 155                         break;
 156                 case 'l':
 157                         lflag = 1;
 158                         break;
 159                 case 'i':
 160                         iflag = 1;
 161                         break;
 162                 case 'A':
 163                         correction_factor = strtod(optarg, NULL);
 164                         break;
 165                 case 'M':
 166                         if (strlcpy(corefile, optarg, sizeof(corefile))
 167                             >= sizeof(corefile))
 168                                 errx(1, "%s: File name too long", optarg);
 169                         Mflag = 1;
 170                         break;
 171                 case 'n':
 172                         nflag = 1;
 173                         break;
 174                 case 'o':
 175                         if ((fo = fopen(optarg, "w")) == NULL)
 176                                 err(1, "%s", optarg);
 177                         break;
 178                 case 'p':
 179                         pflag++;
 180                         break;
 181                 case 'q':
 182                         qflag++;
 183                         break;
 184                 case 'r':
 185                         rflag = 1;
 186                         break;
 187                 case 's':
 188                         sflag = 1;      /* sort across the cpus */
 189                         break;
 190                 case 't':
 191                         tflag = 1;
 192                         break;
 193                 case 'x':
 194                         xflag = 1;
 195                         break;
 196                 case '?':
 197                 default:
 198                         usage();
 199                 }
 200         }
 201         if (cflag + iflag + tflag + xflag + fflag + pflag == 0) {
 202                 cflag = 1;
 203                 iflag = 1;
 204                 tflag = 1;
 205                 pflag = 1;
 206         }
 207         if (correction_factor != 0.0 && (rflag == 0 || nflag)) {
 208                 fprintf(stderr, "Correction factor can only be applied with -r and without -n\n");
 209                 exit(1);
 210         }
 211         ac -= optind;
 212         av += optind;
 213         if (ac != 0)
 214                 usage();
 215
 216         /*
 217          * Open our execfile and corefile, resolve needed symbols and read in
 218          * the trace buffer.
 219          */
 220         if ((kd = kvm_openfiles(Nflag ? execfile : NULL,
 221             Mflag ? corefile : NULL, NULL, O_RDONLY, errbuf)) == NULL)
 222                 errx(1, "%s", errbuf);
 223         if (kvm_nlist(kd, nl) != 0)
 224                 errx(1, "%s", kvm_geterr(kd));
 225         if (kvm_read(kd, nl[0].n_value, &version, sizeof(version)) == -1)
 226                 errx(1, "%s", kvm_geterr(kd));
 227         if (kvm_read(kd, nl[4].n_value, &ncpus, sizeof(ncpus)) == -1)
 228                 errx(1, "%s", kvm_geterr(kd));
 229         ktr_start_index = malloc(sizeof(*ktr_start_index) * ncpus);
 230         if (version >= 3 && kvm_nlist(kd, nl2) == 0) {
 231                 if (kvm_read(kd, nl2[0].n_value, &tts, sizeof(tts)) == -1)
 232                         errx(1, "%s", kvm_geterr(kd));
 233                 tsc_frequency = (double)tts;
 234         }
 235         if (version > KTR_VERSION)
 236                 errx(1, "ktr version too high for us to handle");
 237         if (kvm_read(kd, nl[1].n_value, &entries_per_buf,
 238                                 sizeof(entries_per_buf)) == -1)
 239                 errx(1, "%s", kvm_geterr(kd));
 240         fifo_mask = entries_per_buf - 1;
 241
 242         printf("TSC frequency is %6.3f MHz\n", tsc_frequency / 1000000.0);
 243
 244         ktr_kbuf = malloc(sizeof(*ktr_kbuf) * ncpus);
 245
 246         if (nflag == 0)
 247                 read_symbols(Nflag ? execfile : NULL);
 248
 249         if (kvm_read(kd, nl[3].n_value, ktr_kbuf, sizeof(*ktr_kbuf) * ncpus) == -1)
 250                 errx(1, "%s", kvm_geterr(kd));
 251
 252         ktr_bufs = ktr_bufs_init();
 253
 254         if (sflag) {
 255                 u_int64_t last_timestamp = 0;
 256                 do {
 257                         load_bufs(ktr_bufs, ktr_kbuf);
 258                         print_bufs_timesorted(fo, ktr_bufs, &last_timestamp);
 259                         if (lflag)
 260                                 usleep(1000000 / 10);
 261                 } while (lflag);
 262         } else {
 263                 u_int64_t *last_timestamp = calloc(sizeof(u_int64_t), ncpus);
 264                 do {
 265                         load_bufs(ktr_bufs, ktr_kbuf);
 266                         for (n = 0; n < ncpus; ++n)
 267                                 print_buf(fo, ktr_bufs, n, &last_timestamp[n]);
 268                         if (lflag)
 269                                 usleep(1000000 / 10);
 270                 } while (lflag);
 271         }
 272         return (0);
 273 }
 274
 275 static void
 276 print_header(FILE *fo, int row)
 277 {
 278         if (qflag == 0 && (u_int32_t)row % 20 == 0) {
 279                 fprintf(fo, "%-6s ", "index");
 280                 if (cflag)
 281                         fprintf(fo, "%-3s ", "cpu");
 282                 if (tflag || rflag)
 283                         fprintf(fo, "%-16s ", "timestamp");
 284                 if (xflag) {
 285                         if (nflag)
 286                             fprintf(fo, "%-10s %-10s", "caller2", "caller1");
 287                         else
 288                             fprintf(fo, "%-20s %-20s", "caller2", "caller1");
 289                 }
 290                 if (iflag)
 291                         fprintf(fo, "%-20s ", "ID");
 292                 if (fflag)
 293                         fprintf(fo, "%10s%-30s ", "", "file and line");
 294                 if (pflag)
 295                         fprintf(fo, "%s", "trace");
 296                 fprintf(fo, "\n");
 297         }
 298 }
 299
 300 static void
 301 print_entry(FILE *fo, int n, int row, struct ktr_entry *entry,
 302             u_int64_t *last_timestamp)
 303 {
 304         struct ktr_info *info = NULL;
 305
 306         fprintf(fo, " %06x ", row & 0x00FFFFFF);
 307         if (cflag)
 308                 fprintf(fo, "%-3d ", n);
 309         if (tflag || rflag) {
 310                 if (rflag && !nflag && tsc_frequency != 0.0) {
 311                         fprintf(fo, "%13.3f uS ",
 312                                 (double)(entry->ktr_timestamp - *last_timestamp) * 1000000.0 / tsc_frequency - correction_factor);
 313                 } else if (rflag) {
 314                         fprintf(fo, "%-16ju ",
 315                             (uintmax_t)(entry->ktr_timestamp - *last_timestamp));
 316                 } else {
 317                         fprintf(fo, "%-16ju ",
 318                             (uintmax_t)entry->ktr_timestamp);
 319                 }
 320         }
 321         if (xflag) {
 322                 if (nflag) {
 323                     fprintf(fo, "%p %p ",
 324                             entry->ktr_caller2, entry->ktr_caller1);
 325                 } else {
 326                     fprintf(fo, "%-20s ",
 327                             address_to_symbol(entry->ktr_caller2));
 328                     fprintf(fo, "%-20s ",
 329                             address_to_symbol(entry->ktr_caller1));
 330                 }
 331         }
 332         if (iflag) {
 333                 info = kvm_ktrinfo(entry->ktr_info);
 334                 if (info)
 335                         fprintf(fo, "%-20s ", kvm_string(info->kf_name));
 336                 else
 337                         fprintf(fo, "%-20s ", "<empty>");
 338         }
 339         if (fflag)
 340                 fprintf(fo, "%34s:%-4d ", trunc_path(kvm_string(entry->ktr_file), 34), entry->ktr_line);
 341         if (pflag) {
 342                 if (info == NULL)
 343                         info = kvm_ktrinfo(entry->ktr_info);
 344                 if (info) {
 345                         fprintf(fo, kvm_string(info->kf_format),
 346                                 entry->ktr_data[0], entry->ktr_data[1],
 347                                 entry->ktr_data[2], entry->ktr_data[3],
 348                                 entry->ktr_data[4], entry->ktr_data[5],
 349                                 entry->ktr_data[6], entry->ktr_data[7],
 350                                 entry->ktr_data[8], entry->ktr_data[9]);
 351                 }
 352         }
 353         fprintf(fo, "\n");
 354         *last_timestamp = entry->ktr_timestamp;
 355 }
 356
 357 static
 358 struct ktr_info *
 359 kvm_ktrinfo(void *kptr)
 360 {
 361         static struct ktr_info save_info;
 362         static void *save_kptr;
 363
 364         if (kptr == NULL)
 365                 return(NULL);
 366         if (save_kptr != kptr) {
 367                 if (kvm_read(kd, (uintptr_t)kptr, &save_info, sizeof(save_info)) == -1) {
 368                         bzero(&save_info, sizeof(save_info));
 369                 } else {
 370                         save_kptr = kptr;
 371                 }
 372         }
 373         return(&save_info);
 374 }
 375
 376 static
 377 const char *
 378 kvm_string(const char *kptr)
 379 {
 380         static char save_str[128];
 381         static const char *save_kptr;
 382         u_int l;
 383         u_int n;
 384
 385         if (kptr == NULL)
 386                 return("?");
 387         if (save_kptr != kptr) {
 388                 save_kptr = kptr;
 389                 l = 0;
 390                 while (l < sizeof(save_str) - 1) {
 391                         n = 256 - ((intptr_t)(kptr + l) & 255);
 392                         if (n > sizeof(save_str) - l - 1)
 393                                 n = sizeof(save_str) - l - 1;
 394                         if (kvm_read(kd, (uintptr_t)(kptr + l), save_str + l, n) < 0)
 395                                 break;
 396                         while (l < sizeof(save_str) && n) {
 397                             if (save_str[l] == 0)
 398                                     break;
 399                             --n;
 400                             ++l;
 401                         }
 402                         if (n)
 403                             break;
 404                 }
 405                 save_str[l] = 0;
 406         }
 407         return(save_str);
 408 }
 409
 410 static
 411 const char *
 412 trunc_path(const char *str, int maxlen)
 413 {
 414         int len = strlen(str);
 415
 416         if (len > maxlen)
 417                 return(str + len - maxlen);
 418         else
 419                 return(str);
 420 }
 421
 422 struct symdata {
 423         TAILQ_ENTRY(symdata) link;
 424         const char *symname;
 425         char *symaddr;
 426         char symtype;
 427 };
 428
 429 static TAILQ_HEAD(symlist, symdata) symlist;
 430 static struct symdata *symcache;
 431 static char *symbegin;
 432 static char *symend;
 433
 434 static
 435 void
 436 read_symbols(const char *file)
 437 {
 438         char buf[256];
 439         char cmd[256];
 440         size_t buflen = sizeof(buf);
 441         FILE *fp;
 442         struct symdata *sym;
 443         char *s1;
 444         char *s2;
 445         char *s3;
 446
 447         TAILQ_INIT(&symlist);
 448
 449         if (file == NULL) {
 450                 if (sysctlbyname("kern.bootfile", buf, &buflen, NULL, 0) < 0)
 451                         file = "/boot/kernel";
 452                 else
 453                         file = buf;
 454         }
 455         snprintf(cmd, sizeof(cmd), "nm -n %s", file);
 456         if ((fp = popen(cmd, "r")) != NULL) {
 457                 while (fgets(buf, sizeof(buf), fp) != NULL) {
 458                     s1 = strtok(buf, " \t\n");
 459                     s2 = strtok(NULL, " \t\n");
 460                     s3 = strtok(NULL, " \t\n");
 461                     if (s1 && s2 && s3) {
 462                         sym = malloc(sizeof(struct symdata));
 463                         sym->symaddr = (char *)strtoul(s1, NULL, 16);
 464                         sym->symtype = s2[0];
 465                         sym->symname = strdup(s3);
 466                         if (strcmp(s3, "kernbase") == 0)
 467                                 symbegin = sym->symaddr;
 468                         if (strcmp(s3, "end") == 0)
 469                                 symend = sym->symaddr;
 470                         TAILQ_INSERT_TAIL(&symlist, sym, link);
 471                     }
 472                 }
 473                 pclose(fp);
 474         }
 475         symcache = TAILQ_FIRST(&symlist);
 476 }
 477
 478 static
 479 const char *
 480 address_to_symbol(void *kptr)
 481 {
 482         static char buf[64];
 483
 484         if (symcache == NULL ||
 485            (char *)kptr < symbegin || (char *)kptr >= symend
 486         ) {
 487                 snprintf(buf, sizeof(buf), "%p", kptr);
 488                 return(buf);
 489         }
 490         while ((char *)symcache->symaddr < (char *)kptr) {
 491                 if (TAILQ_NEXT(symcache, link) == NULL)
 492                         break;
 493                 symcache = TAILQ_NEXT(symcache, link);
 494         }
 495         while ((char *)symcache->symaddr > (char *)kptr) {
 496                 if (symcache != TAILQ_FIRST(&symlist))
 497                         symcache = TAILQ_PREV(symcache, symlist, link);
 498         }
 499         snprintf(buf, sizeof(buf), "%s+%d", symcache->symname,
 500                 (int)((char *)kptr - symcache->symaddr));
 501         return(buf);
 502 }
 503
 504 static
 505 struct ktr_buffer *
 506 ktr_bufs_init(void)
 507 {
 508         struct ktr_buffer *ktr_bufs, *it;
 509         int i;
 510
 511         ktr_bufs = malloc(sizeof(*ktr_bufs) * ncpus);
 512         if (!ktr_bufs)
 513                 err(1, "can't allocate data structures\n");
 514         for (i = 0; i < ncpus; ++i) {
 515                 it = ktr_bufs + i;
 516                 it->ents = malloc(sizeof(struct ktr_entry) * entries_per_buf);
 517                 if (it->ents == NULL)
 518                         err(1, "can't allocate data structures\n");
 519                 it->reset = 1;
 520                 it->beg_idx = -1;
 521                 it->end_idx = -1;
 522         }
 523         return ktr_bufs;
 524 }
 525
 526 static
 527 void
 528 get_indices(int *idx)
 529 {
 530         if (kvm_read(kd, nl[2].n_value, idx, sizeof(*idx) * ncpus) == -1)
 531                 errx(1, "%s", kvm_geterr(kd));
 532 }
 533
 534 /*
 535  * Get the trace buffer data from the kernel
 536  */
 537 static
 538 void
 539 load_bufs(struct ktr_buffer *ktr_bufs, struct ktr_entry **kbufs)
 540 {
 541         static int *kern_idx;
 542         struct ktr_buffer *kbuf;
 543         int i;
 544
 545         if (!kern_idx) {
 546                 kern_idx = malloc(sizeof(*kern_idx) * ncpus);
 547                 if (!kern_idx) {
 548                         err(1, "can't allocate data structures\n");
 549                 }
 550         }
 551
 552         get_indices(kern_idx);
 553         for (i = 0; i < ncpus; ++i) {
 554                 kbuf = &ktr_bufs[i];
 555                 if (kern_idx[i] == kbuf->end_idx)
 556                         continue;
 557                 kbuf->end_idx = kern_idx[i];
 558
 559                 /*
 560                  * If we do not have a notion of the beginning index, assume
 561                  * it is entries_per_buf before the ending index.  Don't
 562                  * worry about underflows/negative numbers, the indices will
 563                  * be masked.
 564                  */
 565                 if (kbuf->reset) {
 566                         kbuf->beg_idx = kbuf->end_idx - entries_per_buf + 1;
 567                         kbuf->reset = 0;
 568                 }
 569                 if (kvm_read(kd, (uintptr_t)kbufs[i], ktr_bufs[i].ents,
 570                                 sizeof(struct ktr_entry) * entries_per_buf)
 571                                                                         == -1)
 572                         errx(1, "%s", kvm_geterr(kd));
 573                 kbuf->modified = 1;
 574                 kbuf->beg_idx = earliest_ts(kbuf);
 575         }
 576
 577 }
 578
 579 /*
 580  * Locate the earliest timestamp iterating backwards from end_idx, but
 581  * not going further back then beg_idx.  We have to do this because
 582  * the kernel uses a circulating buffer.
 583  */
 584 static
 585 int
 586 earliest_ts(struct ktr_buffer *buf)
 587 {
 588         struct ktr_entry *save;
 589         int count, scan, i, earliest;
 590
 591         count = 0;
 592         earliest = buf->end_idx - 1;
 593         save = &buf->ents[earliest & fifo_mask];
 594         for (scan = buf->end_idx - 1; scan != buf->beg_idx -1; --scan) {
 595                 i = scan & fifo_mask;
 596                 if (buf->ents[i].ktr_timestamp <= save->ktr_timestamp)
 597                         earliest = scan;
 598                 /*
 599                  * We may have gotten so far behind that beg_idx wrapped
 600                  * more then once around the buffer.  Just stop
 601                  */
 602                 if (++count == entries_per_buf)
 603                         break;
 604         }
 605         return earliest;
 606 }
 607
 608 static
 609 void
 610 print_buf(FILE *fo, struct ktr_buffer *ktr_bufs, int cpu,
 611           u_int64_t *last_timestamp)
 612 {
 613         struct ktr_buffer *buf = ktr_bufs + cpu;
 614
 615         if (buf->modified == 0)
 616                 return;
 617         if (*last_timestamp == 0) {
 618                 *last_timestamp =
 619                         buf->ents[buf->beg_idx & fifo_mask].ktr_timestamp;
 620         }
 621         while (buf->beg_idx != buf->end_idx) {
 622                 print_header(fo, buf->beg_idx);
 623                 print_entry(fo, cpu, buf->beg_idx,
 624                             &buf->ents[buf->beg_idx & fifo_mask],
 625                             last_timestamp);
 626                 ++buf->beg_idx;
 627         }
 628         buf->modified = 0;
 629 }
 630
 631 static
 632 void
 633 print_bufs_timesorted(FILE *fo, struct ktr_buffer *ktr_bufs,
 634                       u_int64_t *last_timestamp)
 635 {
 636         struct ktr_entry *ent;
 637         struct ktr_buffer *buf;
 638         int n, bestn;
 639         u_int64_t ts;
 640         static int row = 0;
 641
 642         for (;;) {
 643                 ts = 0;
 644                 bestn = -1;
 645                 for (n = 0; n < ncpus; ++n) {
 646                         buf = ktr_bufs + n;
 647                         if (buf->beg_idx == buf->end_idx)
 648                                 continue;
 649                         ent = &buf->ents[buf->beg_idx & fifo_mask];
 650                         if (ts == 0 || (ts >= ent->ktr_timestamp)) {
 651                                 ts = ent->ktr_timestamp;
 652                                 bestn = n;
 653                         }
 654                 }
 655                 if ((bestn < 0) || (ts < *last_timestamp))
 656                         break;
 657                 buf = ktr_bufs + bestn;
 658                 print_header(fo, row);
 659                 print_entry(fo, bestn, row,
 660                             &buf->ents[buf->beg_idx & fifo_mask],
 661                             last_timestamp);
 662                 ++buf->beg_idx;
 663                 *last_timestamp = ts;
 664                 ++row;
 665         }
 666 }
 667
 668 static void
 669 usage(void)
 670 {
 671         fprintf(stderr, "usage: ktrdump [-acfilnpqrstx] [-A factor] [-N execfile] "
 672                         "[-M corefile] [-o outfile]\n");
 673         exit(1);
 674 }