sys/kern/kern_fail.c

   1 /*-
   2  * Copyright (c) 2009 Isilon Inc http://www.isilon.com/
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  23  * SUCH DAMAGE.
  24  */
  25 /**
  26  * @file
  27  *
  28  * fail(9) Facility.
  29  *
  30  * @ingroup failpoint_private
  31  */
  32 /**
  33  * @defgroup failpoint fail(9) Facility
  34  *
  35  * Failpoints allow for injecting fake errors into running code on the fly,
  36  * without modifying code or recompiling with flags.  Failpoints are always
  37  * present, and are very efficient when disabled.  Failpoints are described
  38  * in man fail(9).
  39  */
  40 /**
  41  * @defgroup failpoint_private Private fail(9) Implementation functions
  42  *
  43  * Private implementations for the actual failpoint code.
  44  *
  45  * @ingroup failpoint
  46  */
  47 /**
  48  * @addtogroup failpoint_private
  49  * @{
  50  */
  51
  52 #include <sys/cdefs.h>
  53 __FBSDID("$FreeBSD$");
  54
  55 #include <sys/ctype.h>
  56 #include <sys/errno.h>
  57 #include <sys/fail.h>
  58 #include <sys/kernel.h>
  59 #include <sys/libkern.h>
  60 #include <sys/lock.h>
  61 #include <sys/malloc.h>
  62 #include <sys/mutex.h>
  63 #include <sys/proc.h>
  64 #include <sys/sbuf.h>
  65
  66 #include <machine/stdarg.h>
  67
  68 #ifdef ILOG_DEFINE_FOR_FILE
  69 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
  70 #endif
  71
  72 static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
  73 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
  74 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
  75
  76 static struct mtx g_fp_mtx;
  77 MTX_SYSINIT(g_fp_mtx, &g_fp_mtx, "fail point mtx", MTX_DEF);
  78 #define FP_LOCK()       mtx_lock(&g_fp_mtx)
  79 #define FP_UNLOCK()     mtx_unlock(&g_fp_mtx)
  80
  81 /**
  82  * Failpoint types.
  83  * Don't change these without changing fail_type_strings in fail.c.
  84  * @ingroup failpoint_private
  85  */
  86 enum fail_point_t {
  87         FAIL_POINT_OFF,         /**< don't fail */
  88         FAIL_POINT_PANIC,       /**< panic */
  89         FAIL_POINT_RETURN,      /**< return an errorcode */
  90         FAIL_POINT_BREAK,       /**< break into the debugger */
  91         FAIL_POINT_PRINT,       /**< print a message */
  92         FAIL_POINT_SLEEP,       /**< sleep for some msecs */
  93         FAIL_POINT_NUMTYPES
  94 };
  95
  96 static struct {
  97         const char *name;
  98         int     nmlen;
  99 } fail_type_strings[] = {
 100 #define FP_TYPE_NM_LEN(s)       { s, sizeof(s) - 1 }
 101         [FAIL_POINT_OFF] =      FP_TYPE_NM_LEN("off"),
 102         [FAIL_POINT_PANIC] =    FP_TYPE_NM_LEN("panic"),
 103         [FAIL_POINT_RETURN] =   FP_TYPE_NM_LEN("return"),
 104         [FAIL_POINT_BREAK] =    FP_TYPE_NM_LEN("break"),
 105         [FAIL_POINT_PRINT] =    FP_TYPE_NM_LEN("print"),
 106         [FAIL_POINT_SLEEP] =    FP_TYPE_NM_LEN("sleep"),
 107 };
 108
 109 /**
 110  * Internal structure tracking a single term of a complete failpoint.
 111  * @ingroup failpoint_private
 112  */
 113 struct fail_point_entry {
 114         enum fail_point_t fe_type;      /**< type of entry */
 115         int             fe_arg;         /**< argument to type (e.g. return value) */
 116         int             fe_prob;        /**< likelihood of firing in millionths */
 117         int             fe_count;       /**< number of times to fire, 0 means always */
 118         pid_t           fe_pid;         /**< only fail for this process */
 119         TAILQ_ENTRY(fail_point_entry) fe_entries; /**< next entry in fail point */
 120 };
 121
 122 static inline void
 123 fail_point_sleep(struct fail_point *fp, struct fail_point_entry *ent,
 124     int msecs, enum fail_point_return_code *pret)
 125 {
 126         /* convert from millisecs to ticks, rounding up */
 127         int timo = ((msecs * hz) + 999) / 1000;
 128
 129         if (timo > 0) {
 130                 if (fp->fp_sleep_fn == NULL) {
 131                         msleep(fp, &g_fp_mtx, PWAIT, "failpt", timo);
 132                 } else {
 133                         timeout(fp->fp_sleep_fn, fp->fp_sleep_arg, timo);
 134                         *pret = FAIL_POINT_RC_QUEUED;
 135                 }
 136         }
 137 }
 138
 139
 140 /**
 141  * Defines stating the equivalent of probablilty one (100%)
 142  */
 143 enum {
 144         PROB_MAX = 1000000,     /* probability between zero and this number */
 145         PROB_DIGITS = 6,        /* number of zero's in above number */
 146 };
 147
 148 static char *parse_fail_point(struct fail_point_entries *, char *);
 149 static char *parse_term(struct fail_point_entries *, char *);
 150 static char *parse_number(int *out_units, int *out_decimal, char *);
 151 static char *parse_type(struct fail_point_entry *, char *);
 152 static void free_entry(struct fail_point_entries *, struct fail_point_entry *);
 153 static void clear_entries(struct fail_point_entries *);
 154
 155 /**
 156  * Initialize a fail_point.  The name is formed in a printf-like fashion
 157  * from "fmt" and subsequent arguments.  This function is generally used
 158  * for custom failpoints located at odd places in the sysctl tree, and is
 159  * not explicitly needed for standard in-line-declared failpoints.
 160  *
 161  * @ingroup failpoint
 162  */
 163 void
 164 fail_point_init(struct fail_point *fp, const char *fmt, ...)
 165 {
 166         va_list ap;
 167         char *name;
 168         int n;
 169
 170         TAILQ_INIT(&fp->fp_entries);
 171         fp->fp_flags = 0;
 172
 173         /* Figure out the size of the name. */
 174         va_start(ap, fmt);
 175         n = vsnprintf(NULL, 0, fmt, ap);
 176         va_end(ap);
 177
 178         /* Allocate the name and fill it in. */
 179         name = fp_malloc(n + 1, M_WAITOK);
 180         if (name != NULL) {
 181                 va_start(ap, fmt);
 182                 vsnprintf(name, n + 1, fmt, ap);
 183                 va_end(ap);
 184         }
 185         fp->fp_name = name;
 186         fp->fp_location = "";
 187         fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
 188         fp->fp_sleep_fn = NULL;
 189         fp->fp_sleep_arg = NULL;
 190 }
 191
 192 /**
 193  * Free the resources held by a fail_point.
 194  *
 195  * @ingroup failpoint
 196  */
 197 void
 198 fail_point_destroy(struct fail_point *fp)
 199 {
 200
 201         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
 202                 fp_free(__DECONST(void *, fp->fp_name));
 203                 fp->fp_name = NULL;
 204         }
 205         fp->fp_flags = 0;
 206         clear_entries(&fp->fp_entries);
 207 }
 208
 209 /**
 210  * This does the real work of evaluating a fail point. If the fail point tells
 211  * us to return a value, this function returns 1 and fills in 'return_value'
 212  * (return_value is allowed to be null). If the fail point tells us to panic,
 213  * we never return. Otherwise we just return 0 after doing some work, which
 214  * means "keep going".
 215  */
 216 enum fail_point_return_code
 217 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
 218 {
 219         enum fail_point_return_code ret = FAIL_POINT_RC_CONTINUE;
 220         struct fail_point_entry *ent, *next;
 221         int msecs;
 222
 223         FP_LOCK();
 224
 225         TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, next) {
 226                 int cont = 0; /* don't continue by default */
 227
 228                 if (ent->fe_prob < PROB_MAX &&
 229                     ent->fe_prob < random() % PROB_MAX)
 230                         continue;
 231                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
 232                         continue;
 233
 234                 switch (ent->fe_type) {
 235                 case FAIL_POINT_PANIC:
 236                         panic("fail point %s panicking", fp->fp_name);
 237                         /* NOTREACHED */
 238
 239                 case FAIL_POINT_RETURN:
 240                         if (return_value != NULL)
 241                                 *return_value = ent->fe_arg;
 242                         ret = FAIL_POINT_RC_RETURN;
 243                         break;
 244
 245                 case FAIL_POINT_BREAK:
 246                         printf("fail point %s breaking to debugger\n",
 247                             fp->fp_name);
 248                         breakpoint();
 249                         break;
 250
 251                 case FAIL_POINT_PRINT:
 252                         printf("fail point %s executing\n", fp->fp_name);
 253                         cont = ent->fe_arg;
 254                         break;
 255
 256                 case FAIL_POINT_SLEEP:
 257                         /*
 258                          * Free the entry now if necessary, since
 259                          * we're about to drop the mutex and sleep.
 260                          */
 261                         msecs = ent->fe_arg;
 262                         if (ent->fe_count > 0 && --ent->fe_count == 0) {
 263                                 free_entry(&fp->fp_entries, ent);
 264                                 ent = NULL;
 265                         }
 266
 267                         if (msecs)
 268                                 fail_point_sleep(fp, ent, msecs, &ret);
 269                         break;
 270
 271                 default:
 272                         break;
 273                 }
 274
 275                 if (ent != NULL && ent->fe_count > 0 && --ent->fe_count == 0)
 276                         free_entry(&fp->fp_entries, ent);
 277                 if (cont == 0)
 278                         break;
 279         }
 280
 281         /* Get rid of "off"s at the end. */
 282         while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
 283                ent->fe_type == FAIL_POINT_OFF)
 284                 free_entry(&fp->fp_entries, ent);
 285
 286         FP_UNLOCK();
 287
 288         return (ret);
 289 }
 290
 291 /**
 292  * Translate internal fail_point structure into human-readable text.
 293  */
 294 static void
 295 fail_point_get(struct fail_point *fp, struct sbuf *sb)
 296 {
 297         struct fail_point_entry *ent;
 298
 299         FP_LOCK();
 300
 301         TAILQ_FOREACH(ent, &fp->fp_entries, fe_entries) {
 302                 if (ent->fe_prob < PROB_MAX) {
 303                         int decimal = ent->fe_prob % (PROB_MAX / 100);
 304                         int units = ent->fe_prob / (PROB_MAX / 100);
 305                         sbuf_printf(sb, "%d", units);
 306                         if (decimal) {
 307                                 int digits = PROB_DIGITS - 2;
 308                                 while (!(decimal % 10)) {
 309                                         digits--;
 310                                         decimal /= 10;
 311                                 }
 312                                 sbuf_printf(sb, ".%0*d", digits, decimal);
 313                         }
 314                         sbuf_printf(sb, "%%");
 315                 }
 316                 if (ent->fe_count > 0)
 317                         sbuf_printf(sb, "%d*", ent->fe_count);
 318                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
 319                 if (ent->fe_arg)
 320                         sbuf_printf(sb, "(%d)", ent->fe_arg);
 321                 if (ent->fe_pid != NO_PID)
 322                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
 323                 if (TAILQ_NEXT(ent, fe_entries))
 324                         sbuf_printf(sb, "->");
 325         }
 326         if (TAILQ_EMPTY(&fp->fp_entries))
 327                 sbuf_printf(sb, "off");
 328
 329         FP_UNLOCK();
 330 }
 331
 332 /**
 333  * Set an internal fail_point structure from a human-readable failpoint string
 334  * in a lock-safe manner.
 335  */
 336 static int
 337 fail_point_set(struct fail_point *fp, char *buf)
 338 {
 339         int error = 0;
 340         struct fail_point_entry *ent, *ent_next;
 341         struct fail_point_entries new_entries;
 342
 343         /* Parse new entries. */
 344         TAILQ_INIT(&new_entries);
 345         if (!parse_fail_point(&new_entries, buf)) {
 346                 clear_entries(&new_entries);
 347                 error = EINVAL;
 348                 goto end;
 349         }
 350
 351         FP_LOCK();
 352
 353         /* Move new entries in. */
 354         TAILQ_SWAP(&fp->fp_entries, &new_entries, fail_point_entry, fe_entries);
 355         clear_entries(&new_entries);
 356
 357         /* Get rid of useless zero probability entries. */
 358         TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, ent_next) {
 359                 if (ent->fe_prob == 0)
 360                         free_entry(&fp->fp_entries, ent);
 361         }
 362
 363         /* Get rid of "off"s at the end. */
 364         while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
 365                 ent->fe_type == FAIL_POINT_OFF)
 366                 free_entry(&fp->fp_entries, ent);
 367
 368         FP_UNLOCK();
 369
 370  end:
 371 #ifdef IWARNING
 372         if (error)
 373                 IWARNING("Failed to set %s %s to %s",
 374                     fp->fp_name, fp->fp_location, buf);
 375         else
 376                 INOTICE("Set %s %s to %s",
 377                     fp->fp_name, fp->fp_location, buf);
 378 #endif /* IWARNING */
 379
 380         return (error);
 381 }
 382
 383 #define MAX_FAIL_POINT_BUF      1023
 384
 385 /**
 386  * Handle kernel failpoint set/get.
 387  */
 388 int
 389 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
 390 {
 391         struct fail_point *fp = arg1;
 392         char *buf = NULL;
 393         struct sbuf sb;
 394         int error;
 395
 396         /* Retrieving */
 397         sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
 398         fail_point_get(fp, &sb);
 399         sbuf_trim(&sb);
 400         sbuf_finish(&sb);
 401         error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
 402         sbuf_delete(&sb);
 403
 404         /* Setting */
 405         if (!error && req->newptr) {
 406                 if (req->newlen > MAX_FAIL_POINT_BUF) {
 407                         error = EINVAL;
 408                         goto out;
 409                 }
 410
 411                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
 412
 413                 error = SYSCTL_IN(req, buf, req->newlen);
 414                 if (error)
 415                         goto out;
 416                 buf[req->newlen] = '\0';
 417
 418                 error = fail_point_set(fp, buf);
 419         }
 420
 421 out:
 422         fp_free(buf);
 423         return (error);
 424 }
 425
 426 /**
 427  * Internal helper function to translate a human-readable failpoint string
 428  * into a internally-parsable fail_point structure.
 429  */
 430 static char *
 431 parse_fail_point(struct fail_point_entries *ents, char *p)
 432 {
 433         /*  <fail_point> ::
 434          *      <term> ( "->" <term> )*
 435          */
 436         p = parse_term(ents, p);
 437         if (p == NULL)
 438                 return (NULL);
 439         while (*p != '\0') {
 440                 if (p[0] != '-' || p[1] != '>')
 441                         return (NULL);
 442                 p = parse_term(ents, p + 2);
 443                 if (p == NULL)
 444                         return (NULL);
 445         }
 446         return (p);
 447 }
 448
 449 /**
 450  * Internal helper function to parse an individual term from a failpoint.
 451  */
 452 static char *
 453 parse_term(struct fail_point_entries *ents, char *p)
 454 {
 455         struct fail_point_entry *ent;
 456
 457         ent = fp_malloc(sizeof *ent, M_WAITOK | M_ZERO);
 458         ent->fe_prob = PROB_MAX;
 459         ent->fe_pid = NO_PID;
 460         TAILQ_INSERT_TAIL(ents, ent, fe_entries);
 461
 462         /*
 463          * <term> ::
 464          *     ( (<float> "%") | (<integer> "*" ) )*
 465          *     <type>
 466          *     [ "(" <integer> ")" ]
 467          *     [ "[pid " <integer> "]" ]
 468          */
 469
 470         /* ( (<float> "%") | (<integer> "*" ) )* */
 471         while (isdigit(*p) || *p == '.') {
 472                 int units, decimal;
 473
 474                 p = parse_number(&units, &decimal, p);
 475                 if (p == NULL)
 476                         return (NULL);
 477
 478                 if (*p == '%') {
 479                         if (units > 100) /* prevent overflow early */
 480                                 units = 100;
 481                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
 482                         if (ent->fe_prob > PROB_MAX)
 483                                 ent->fe_prob = PROB_MAX;
 484                 } else if (*p == '*') {
 485                         if (!units || decimal)
 486                                 return (NULL);
 487                         ent->fe_count = units;
 488                 } else
 489                         return (NULL);
 490                 p++;
 491         }
 492
 493         /* <type> */
 494         p = parse_type(ent, p);
 495         if (p == NULL)
 496                 return (NULL);
 497         if (*p == '\0')
 498                 return (p);
 499
 500         /* [ "(" <integer> ")" ] */
 501         if (*p != '(')
 502                 return p;
 503         p++;
 504         if (!isdigit(*p) && *p != '-')
 505                 return (NULL);
 506         ent->fe_arg = strtol(p, &p, 0);
 507         if (*p++ != ')')
 508                 return (NULL);
 509
 510         /* [ "[pid " <integer> "]" ] */
 511 #define PID_STRING      "[pid "
 512         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
 513                 return (p);
 514         p += sizeof(PID_STRING) - 1;
 515         if (!isdigit(*p))
 516                 return (NULL);
 517         ent->fe_pid = strtol(p, &p, 0);
 518         if (*p++ != ']')
 519                 return (NULL);
 520
 521         return (p);
 522 }
 523
 524 /**
 525  * Internal helper function to parse a numeric for a failpoint term.
 526  */
 527 static char *
 528 parse_number(int *out_units, int *out_decimal, char *p)
 529 {
 530         char *old_p;
 531
 532         /*
 533          *  <number> ::
 534          *      <integer> [ "." <integer> ] |
 535          *      "." <integer>
 536          */
 537
 538         /* whole part */
 539         old_p = p;
 540         *out_units = strtol(p, &p, 10);
 541         if (p == old_p && *p != '.')
 542                 return (NULL);
 543
 544         /* fractional part */
 545         *out_decimal = 0;
 546         if (*p == '.') {
 547                 int digits = 0;
 548                 p++;
 549                 while (isdigit(*p)) {
 550                         int digit = *p - '0';
 551                         if (digits < PROB_DIGITS - 2)
 552                                 *out_decimal = *out_decimal * 10 + digit;
 553                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
 554                                 (*out_decimal)++;
 555                         digits++;
 556                         p++;
 557                 }
 558                 if (!digits) /* need at least one digit after '.' */
 559                         return (NULL);
 560                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
 561                         *out_decimal *= 10;
 562         }
 563
 564         return (p); /* success */
 565 }
 566
 567 /**
 568  * Internal helper function to parse an individual type for a failpoint term.
 569  */
 570 static char *
 571 parse_type(struct fail_point_entry *ent, char *beg)
 572 {
 573         enum fail_point_t type;
 574         int len;
 575
 576         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
 577                 len = fail_type_strings[type].nmlen;
 578                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
 579                         ent->fe_type = type;
 580                         return (beg + len);
 581                 }
 582         }
 583         return (NULL);
 584 }
 585
 586 /**
 587  * Internal helper function to free an individual failpoint term.
 588  */
 589 static void
 590 free_entry(struct fail_point_entries *ents, struct fail_point_entry *ent)
 591 {
 592         TAILQ_REMOVE(ents, ent, fe_entries);
 593         fp_free(ent);
 594 }
 595
 596 /**
 597  * Internal helper function to clear out all failpoint terms for a single
 598  * failpoint.
 599  */
 600 static void
 601 clear_entries(struct fail_point_entries *ents)
 602 {
 603         struct fail_point_entry *ent, *ent_next;
 604
 605         TAILQ_FOREACH_SAFE(ent, ents, fe_entries, ent_next)
 606                 fp_free(ent);
 607         TAILQ_INIT(ents);
 608 }
 609
 610 /* The fail point sysctl tree. */
 611 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");