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/limits.h>
  61 #include <sys/lock.h>
  62 #include <sys/malloc.h>
  63 #include <sys/mutex.h>
  64 #include <sys/proc.h>
  65 #include <sys/sbuf.h>
  66 #include <sys/sleepqueue.h>
  67 #include <sys/sx.h>
  68 #include <sys/sysctl.h>
  69 #include <sys/types.h>
  70
  71 #include <machine/atomic.h>
  72 #include <machine/stdarg.h>
  73
  74 #ifdef ILOG_DEFINE_FOR_FILE
  75 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
  76 #endif
  77
  78 static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
  79 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
  80 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
  81 #define fs_free(ptr) fp_free(ptr)
  82 #define fs_malloc() fp_malloc(sizeof(struct fail_point_setting), \
  83         M_WAITOK | M_ZERO)
  84
  85  /**
  86   * These define the wchans that are used for sleeping, pausing respectively.
  87   * They are chosen arbitrarily but need to be distinct to the failpoint and
  88   * the sleep/pause distinction.
  89   */
  90 #define FP_SLEEP_CHANNEL(fp) (void*)(fp)
  91 #define FP_PAUSE_CHANNEL(fp) __DEVOLATILE(void*, &fp->fp_setting)
  92
  93 /**
  94  * Don't allow more than this many entries in a fail point set by sysctl.
  95  * The 99.99...% case is to have 1 entry.  I can't imagine having this many
  96  * entries, so it should not limit us.  Saves on re-mallocs while holding
  97  * a non-sleepable lock.
  98  */
  99 #define FP_MAX_ENTRY_COUNT 20
 100
 101 /* Used to drain sbufs to the sysctl output */
 102 int fail_sysctl_drain_func(void *, const char *, int);
 103
 104 /* Head of tailq of struct fail_point_entry */
 105 TAILQ_HEAD(fail_point_entry_queue, fail_point_entry);
 106
 107 /**
 108  * fp entries garbage list; outstanding entries are cleaned up in the
 109  * garbage collector
 110  */
 111 STAILQ_HEAD(fail_point_setting_garbage, fail_point_setting);
 112 static struct fail_point_setting_garbage fp_setting_garbage =
 113         STAILQ_HEAD_INITIALIZER(fp_setting_garbage);
 114 static struct mtx mtx_garbage_list;
 115 MTX_SYSINIT(mtx_garbage_list, &mtx_garbage_list, "fail point garbage mtx",
 116         MTX_SPIN);
 117
 118 static struct sx sx_fp_set;
 119 SX_SYSINIT(sx_fp_set, &sx_fp_set, "fail point set sx");
 120
 121 /**
 122  * Failpoint types.
 123  * Don't change these without changing fail_type_strings in fail.c.
 124  * @ingroup failpoint_private
 125  */
 126 enum fail_point_t {
 127         FAIL_POINT_OFF,         /**< don't fail */
 128         FAIL_POINT_PANIC,       /**< panic */
 129         FAIL_POINT_RETURN,      /**< return an errorcode */
 130         FAIL_POINT_BREAK,       /**< break into the debugger */
 131         FAIL_POINT_PRINT,       /**< print a message */
 132         FAIL_POINT_SLEEP,       /**< sleep for some msecs */
 133         FAIL_POINT_PAUSE,       /**< sleep until failpoint is set to off */
 134         FAIL_POINT_YIELD,       /**< yield the cpu */
 135         FAIL_POINT_DELAY,       /**< busy wait the cpu */
 136         FAIL_POINT_NUMTYPES,
 137         FAIL_POINT_INVALID = -1
 138 };
 139
 140 static struct {
 141         const char *name;
 142         int     nmlen;
 143 } fail_type_strings[] = {
 144 #define FP_TYPE_NM_LEN(s)       { s, sizeof(s) - 1 }
 145         [FAIL_POINT_OFF] =      FP_TYPE_NM_LEN("off"),
 146         [FAIL_POINT_PANIC] =    FP_TYPE_NM_LEN("panic"),
 147         [FAIL_POINT_RETURN] =   FP_TYPE_NM_LEN("return"),
 148         [FAIL_POINT_BREAK] =    FP_TYPE_NM_LEN("break"),
 149         [FAIL_POINT_PRINT] =    FP_TYPE_NM_LEN("print"),
 150         [FAIL_POINT_SLEEP] =    FP_TYPE_NM_LEN("sleep"),
 151         [FAIL_POINT_PAUSE] =    FP_TYPE_NM_LEN("pause"),
 152         [FAIL_POINT_YIELD] =    FP_TYPE_NM_LEN("yield"),
 153         [FAIL_POINT_DELAY] =    FP_TYPE_NM_LEN("delay"),
 154 };
 155
 156 #define FE_COUNT_UNTRACKED (INT_MIN)
 157
 158 /**
 159  * Internal structure tracking a single term of a complete failpoint.
 160  * @ingroup failpoint_private
 161  */
 162 struct fail_point_entry {
 163         volatile bool   fe_stale;
 164         enum fail_point_t       fe_type;        /**< type of entry */
 165         int             fe_arg;         /**< argument to type (e.g. return value) */
 166         int             fe_prob;        /**< likelihood of firing in millionths */
 167         int             fe_count;       /**< number of times to fire, -1 means infinite */
 168         pid_t           fe_pid;         /**< only fail for this process */
 169         struct fail_point       *fe_parent;     /**< backpointer to fp */
 170         TAILQ_ENTRY(fail_point_entry)   fe_entries; /**< next entry ptr */
 171 };
 172
 173 struct fail_point_setting {
 174         STAILQ_ENTRY(fail_point_setting) fs_garbage_link;
 175         struct fail_point_entry_queue fp_entry_queue;
 176         struct fail_point * fs_parent;
 177         struct mtx feq_mtx; /* Gives fail_point_pause something to do.  */
 178 };
 179
 180 /**
 181  * Defines stating the equivalent of probablilty one (100%)
 182  */
 183 enum {
 184         PROB_MAX = 1000000,     /* probability between zero and this number */
 185         PROB_DIGITS = 6         /* number of zero's in above number */
 186 };
 187
 188 /* Get a ref on an fp's fp_setting */
 189 static inline struct fail_point_setting *fail_point_setting_get_ref(
 190         struct fail_point *fp);
 191 /* Release a ref on an fp_setting */
 192 static inline void fail_point_setting_release_ref(struct fail_point *fp);
 193 /* Allocate and initialize a struct fail_point_setting */
 194 static struct fail_point_setting *fail_point_setting_new(struct
 195         fail_point *);
 196 /* Free a struct fail_point_setting */
 197 static void fail_point_setting_destroy(struct fail_point_setting *fp_setting);
 198 /* Allocate and initialize a struct fail_point_entry */
 199 static struct fail_point_entry *fail_point_entry_new(struct
 200         fail_point_setting *);
 201 /* Free a struct fail_point_entry */
 202 static void fail_point_entry_destroy(struct fail_point_entry *fp_entry);
 203 /* Append fp setting to garbage list */
 204 static inline void fail_point_setting_garbage_append(
 205         struct fail_point_setting *fp_setting);
 206 /* Swap fp's setting with fp_setting_new */
 207 static inline struct fail_point_setting *
 208         fail_point_swap_settings(struct fail_point *fp,
 209         struct fail_point_setting *fp_setting_new);
 210 /* Free up any zero-ref setting in the garbage queue */
 211 static void fail_point_garbage_collect(void);
 212 /* If this fail point's setting are empty, then swap it out to NULL. */
 213 static inline void fail_point_eval_swap_out(struct fail_point *fp,
 214         struct fail_point_setting *fp_setting);
 215
 216 bool
 217 fail_point_is_off(struct fail_point *fp)
 218 {
 219         bool return_val;
 220         struct fail_point_setting *fp_setting;
 221         struct fail_point_entry *ent;
 222
 223         return_val = true;
 224
 225         fp_setting = fail_point_setting_get_ref(fp);
 226         if (fp_setting != NULL) {
 227                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue,
 228                     fe_entries) {
 229                         if (!ent->fe_stale) {
 230                                 return_val = false;
 231                                 break;
 232                         }
 233                 }
 234         }
 235         fail_point_setting_release_ref(fp);
 236
 237         return (return_val);
 238 }
 239
 240 /* Allocate and initialize a struct fail_point_setting */
 241 static struct fail_point_setting *
 242 fail_point_setting_new(struct fail_point *fp)
 243 {
 244         struct fail_point_setting *fs_new;
 245
 246         fs_new = fs_malloc();
 247         fs_new->fs_parent = fp;
 248         TAILQ_INIT(&fs_new->fp_entry_queue);
 249         mtx_init(&fs_new->feq_mtx, "fail point entries", NULL, MTX_SPIN);
 250
 251         fail_point_setting_garbage_append(fs_new);
 252
 253         return (fs_new);
 254 }
 255
 256 /* Free a struct fail_point_setting */
 257 static void
 258 fail_point_setting_destroy(struct fail_point_setting *fp_setting)
 259 {
 260         struct fail_point_entry *ent;
 261
 262         while (!TAILQ_EMPTY(&fp_setting->fp_entry_queue)) {
 263                 ent = TAILQ_FIRST(&fp_setting->fp_entry_queue);
 264                 TAILQ_REMOVE(&fp_setting->fp_entry_queue, ent, fe_entries);
 265                 fail_point_entry_destroy(ent);
 266         }
 267
 268         fs_free(fp_setting);
 269 }
 270
 271 /* Allocate and initialize a struct fail_point_entry */
 272 static struct fail_point_entry *
 273 fail_point_entry_new(struct fail_point_setting *fp_setting)
 274 {
 275         struct fail_point_entry *fp_entry;
 276
 277         fp_entry = fp_malloc(sizeof(struct fail_point_entry),
 278                 M_WAITOK | M_ZERO);
 279         fp_entry->fe_parent = fp_setting->fs_parent;
 280         fp_entry->fe_prob = PROB_MAX;
 281         fp_entry->fe_pid = NO_PID;
 282         fp_entry->fe_count = FE_COUNT_UNTRACKED;
 283         TAILQ_INSERT_TAIL(&fp_setting->fp_entry_queue, fp_entry,
 284                 fe_entries);
 285
 286         return (fp_entry);
 287 }
 288
 289 /* Free a struct fail_point_entry */
 290 static void
 291 fail_point_entry_destroy(struct fail_point_entry *fp_entry)
 292 {
 293
 294         fp_free(fp_entry);
 295 }
 296
 297 /* Get a ref on an fp's fp_setting */
 298 static inline struct fail_point_setting *
 299 fail_point_setting_get_ref(struct fail_point *fp)
 300 {
 301         struct fail_point_setting *fp_setting;
 302
 303         /* Invariant: if we have a ref, our pointer to fp_setting is safe */
 304         atomic_add_acq_32(&fp->fp_ref_cnt, 1);
 305         fp_setting = fp->fp_setting;
 306
 307         return (fp_setting);
 308 }
 309
 310 /* Release a ref on an fp_setting */
 311 static inline void
 312 fail_point_setting_release_ref(struct fail_point *fp)
 313 {
 314
 315         KASSERT(&fp->fp_ref_cnt > 0, ("Attempting to deref w/no refs"));
 316         atomic_subtract_rel_32(&fp->fp_ref_cnt, 1);
 317 }
 318
 319 /* Append fp entries to fp garbage list */
 320 static inline void
 321 fail_point_setting_garbage_append(struct fail_point_setting *fp_setting)
 322 {
 323
 324         mtx_lock_spin(&mtx_garbage_list);
 325         STAILQ_INSERT_TAIL(&fp_setting_garbage, fp_setting,
 326                 fs_garbage_link);
 327         mtx_unlock_spin(&mtx_garbage_list);
 328 }
 329
 330 /* Swap fp's entries with fp_setting_new */
 331 static struct fail_point_setting *
 332 fail_point_swap_settings(struct fail_point *fp,
 333         struct fail_point_setting *fp_setting_new)
 334 {
 335         struct fail_point_setting *fp_setting_old;
 336
 337         fp_setting_old = fp->fp_setting;
 338         fp->fp_setting = fp_setting_new;
 339
 340         return (fp_setting_old);
 341 }
 342
 343 static inline void
 344 fail_point_eval_swap_out(struct fail_point *fp,
 345         struct fail_point_setting *fp_setting)
 346 {
 347
 348         /* We may have already been swapped out and replaced; ignore. */
 349         if (fp->fp_setting == fp_setting)
 350                 fail_point_swap_settings(fp, NULL);
 351 }
 352
 353 /* Free up any zero-ref entries in the garbage queue */
 354 static void
 355 fail_point_garbage_collect()
 356 {
 357         struct fail_point_setting *fs_current, *fs_next;
 358         struct fail_point_setting_garbage fp_ents_free_list;
 359
 360         /**
 361           * We will transfer the entries to free to fp_ents_free_list while holding
 362           * the spin mutex, then free it after we drop the lock. This avoids
 363           * triggering witness due to sleepable mutexes in the memory
 364           * allocator.
 365           */
 366         STAILQ_INIT(&fp_ents_free_list);
 367
 368         mtx_lock_spin(&mtx_garbage_list);
 369         STAILQ_FOREACH_SAFE(fs_current, &fp_setting_garbage, fs_garbage_link,
 370             fs_next) {
 371                 if (fs_current->fs_parent->fp_setting != fs_current &&
 372                         fs_current->fs_parent->fp_ref_cnt == 0) {
 373                         STAILQ_REMOVE(&fp_setting_garbage, fs_current,
 374                                 fail_point_setting, fs_garbage_link);
 375                         STAILQ_INSERT_HEAD(&fp_ents_free_list, fs_current,
 376                                 fs_garbage_link);
 377                 }
 378         }
 379         mtx_unlock_spin(&mtx_garbage_list);
 380
 381         STAILQ_FOREACH_SAFE(fs_current, &fp_ents_free_list, fs_garbage_link,
 382                 fs_next)
 383                 fail_point_setting_destroy(fs_current);
 384 }
 385
 386 /* Drain out all refs from this fail point */
 387 static inline void
 388 fail_point_drain(struct fail_point *fp, int expected_ref)
 389 {
 390         struct fail_point_setting *entries;
 391
 392         entries = fail_point_swap_settings(fp, NULL);
 393         /**
 394          * We have unpaused all threads; so we will wait no longer
 395          * than the time taken for the longest remaining sleep, or
 396          * the length of time of a long-running code block.
 397          */
 398         while (fp->fp_ref_cnt > expected_ref) {
 399                 wakeup(FP_PAUSE_CHANNEL(fp));
 400                 tsleep(&fp, PWAIT, "fail_point_drain", hz / 100);
 401         }
 402         fail_point_swap_settings(fp, entries);
 403 }
 404
 405 static inline void
 406 fail_point_pause(struct fail_point *fp, enum fail_point_return_code *pret,
 407         struct mtx *mtx_sleep)
 408 {
 409
 410         if (fp->fp_pre_sleep_fn)
 411                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 412
 413         msleep_spin(FP_PAUSE_CHANNEL(fp), mtx_sleep, "failpt", 0);
 414
 415         if (fp->fp_post_sleep_fn)
 416                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 417 }
 418
 419 static inline void
 420 fail_point_sleep(struct fail_point *fp, int msecs,
 421         enum fail_point_return_code *pret)
 422 {
 423         int timo;
 424
 425         /* Convert from millisecs to ticks, rounding up */
 426         timo = howmany(msecs * hz, 1000);
 427
 428         if (timo > 0) {
 429                 if (!(fp->fp_flags & FAIL_POINT_USE_TIMEOUT_PATH)) {
 430                         if (fp->fp_pre_sleep_fn)
 431                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 432
 433                         tsleep(FP_SLEEP_CHANNEL(fp), PWAIT, "failpt", timo);
 434
 435                         if (fp->fp_post_sleep_fn)
 436                                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 437                 } else {
 438                         if (fp->fp_pre_sleep_fn)
 439                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 440
 441                         timeout(fp->fp_post_sleep_fn, fp->fp_post_sleep_arg,
 442                                 timo);
 443                         *pret = FAIL_POINT_RC_QUEUED;
 444                 }
 445         }
 446 }
 447
 448 static char *parse_fail_point(struct fail_point_setting *, char *);
 449 static char *parse_term(struct fail_point_setting *, char *);
 450 static char *parse_number(int *out_units, int *out_decimal, char *);
 451 static char *parse_type(struct fail_point_entry *, char *);
 452
 453 /**
 454  * Initialize a fail_point.  The name is formed in a printf-like fashion
 455  * from "fmt" and subsequent arguments.  This function is generally used
 456  * for custom failpoints located at odd places in the sysctl tree, and is
 457  * not explicitly needed for standard in-line-declared failpoints.
 458  *
 459  * @ingroup failpoint
 460  */
 461 void
 462 fail_point_init(struct fail_point *fp, const char *fmt, ...)
 463 {
 464         va_list ap;
 465         char *name;
 466         int n;
 467
 468         fp->fp_setting = NULL;
 469         fp->fp_flags = 0;
 470
 471         /* Figure out the size of the name. */
 472         va_start(ap, fmt);
 473         n = vsnprintf(NULL, 0, fmt, ap);
 474         va_end(ap);
 475
 476         /* Allocate the name and fill it in. */
 477         name = fp_malloc(n + 1, M_WAITOK);
 478         if (name != NULL) {
 479                 va_start(ap, fmt);
 480                 vsnprintf(name, n + 1, fmt, ap);
 481                 va_end(ap);
 482         }
 483         fp->fp_name = name;
 484         fp->fp_location = "";
 485         fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
 486         fp->fp_pre_sleep_fn = NULL;
 487         fp->fp_pre_sleep_arg = NULL;
 488         fp->fp_post_sleep_fn = NULL;
 489         fp->fp_post_sleep_arg = NULL;
 490 }
 491
 492 /**
 493  * Free the resources held by a fail_point, and wake any paused threads.
 494  * Thou shalt not allow threads to hit this fail point after you enter this
 495  * function, nor shall you call this multiple times for a given fp.
 496  * @ingroup failpoint
 497  */
 498 void
 499 fail_point_destroy(struct fail_point *fp)
 500 {
 501
 502         fail_point_drain(fp, 0);
 503
 504         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
 505                 fp_free(__DECONST(void *, fp->fp_name));
 506                 fp->fp_name = NULL;
 507         }
 508         fp->fp_flags = 0;
 509
 510         sx_xlock(&sx_fp_set);
 511         fail_point_garbage_collect();
 512         sx_xunlock(&sx_fp_set);
 513 }
 514
 515 /**
 516  * This does the real work of evaluating a fail point. If the fail point tells
 517  * us to return a value, this function returns 1 and fills in 'return_value'
 518  * (return_value is allowed to be null). If the fail point tells us to panic,
 519  * we never return. Otherwise we just return 0 after doing some work, which
 520  * means "keep going".
 521  */
 522 enum fail_point_return_code
 523 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
 524 {
 525         bool execute = false;
 526         struct fail_point_entry *ent;
 527         struct fail_point_setting *fp_setting;
 528         enum fail_point_return_code ret;
 529         int cont;
 530         int count;
 531         int msecs;
 532         int usecs;
 533
 534         ret = FAIL_POINT_RC_CONTINUE;
 535         cont = 0; /* don't continue by default */
 536
 537         fp_setting = fail_point_setting_get_ref(fp);
 538         if (fp_setting == NULL)
 539                 goto abort;
 540
 541         TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 542
 543                 if (ent->fe_stale)
 544                         continue;
 545
 546                 if (ent->fe_prob < PROB_MAX &&
 547                     ent->fe_prob < random() % PROB_MAX)
 548                         continue;
 549
 550                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
 551                         continue;
 552
 553                 if (ent->fe_count != FE_COUNT_UNTRACKED) {
 554                         count = ent->fe_count;
 555                         while (count > 0) {
 556                                 if (atomic_cmpset_32(&ent->fe_count, count, count - 1)) {
 557                                         count--;
 558                                         execute = true;
 559                                         break;
 560                                 }
 561                                 count = ent->fe_count;
 562                         }
 563                         if (execute == false)
 564                                 /* We lost the race; consider the entry stale and bail now */
 565                                 continue;
 566                         if (count == 0)
 567                                 ent->fe_stale = true;
 568                 }
 569
 570                 switch (ent->fe_type) {
 571                 case FAIL_POINT_PANIC:
 572                         panic("fail point %s panicking", fp->fp_name);
 573                         /* NOTREACHED */
 574
 575                 case FAIL_POINT_RETURN:
 576                         if (return_value != NULL)
 577                                 *return_value = ent->fe_arg;
 578                         ret = FAIL_POINT_RC_RETURN;
 579                         break;
 580
 581                 case FAIL_POINT_BREAK:
 582                         printf("fail point %s breaking to debugger\n",
 583                                 fp->fp_name);
 584                         breakpoint();
 585                         break;
 586
 587                 case FAIL_POINT_PRINT:
 588                         printf("fail point %s executing\n", fp->fp_name);
 589                         cont = ent->fe_arg;
 590                         break;
 591
 592                 case FAIL_POINT_SLEEP:
 593                         msecs = ent->fe_arg;
 594                         if (msecs)
 595                                 fail_point_sleep(fp, msecs, &ret);
 596                         break;
 597
 598                 case FAIL_POINT_PAUSE:
 599                         /**
 600                          * Pausing is inherently strange with multiple
 601                          * entries given our design.  That is because some
 602                          * entries could be unreachable, for instance in cases like:
 603                          * pause->return. We can never reach the return entry.
 604                          * The sysctl layer actually truncates all entries after
 605                          * a pause for this reason.
 606                          */
 607                         mtx_lock_spin(&fp_setting->feq_mtx);
 608                         fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
 609                         mtx_unlock_spin(&fp_setting->feq_mtx);
 610                         break;
 611
 612                 case FAIL_POINT_YIELD:
 613                         kern_yield(-1);
 614                         break;
 615
 616                 case FAIL_POINT_DELAY:
 617                         usecs = ent->fe_arg;
 618                         DELAY(usecs);
 619                         break;
 620
 621                 default:
 622                         break;
 623                 }
 624
 625                 if (cont == 0)
 626                         break;
 627         }
 628
 629         if (fail_point_is_off(fp))
 630                 fail_point_eval_swap_out(fp, fp_setting);
 631
 632 abort:
 633         fail_point_setting_release_ref(fp);
 634
 635         return (ret);
 636
 637 }
 638
 639 /**
 640  * Translate internal fail_point structure into human-readable text.
 641  */
 642 static void
 643 fail_point_get(struct fail_point *fp, struct sbuf *sb,
 644         bool verbose)
 645 {
 646         struct fail_point_entry *ent;
 647         struct fail_point_setting *fp_setting;
 648         struct fail_point_entry *fp_entry_cpy;
 649         int cnt_sleeping;
 650         int idx;
 651         int printed_entry_count;
 652
 653         cnt_sleeping = 0;
 654         idx = 0;
 655         printed_entry_count = 0;
 656
 657         fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
 658                 (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
 659
 660         fp_setting = fail_point_setting_get_ref(fp);
 661
 662         if (fp_setting != NULL) {
 663                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 664                         if (ent->fe_stale)
 665                                 continue;
 666
 667                         KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
 668                                 ("FP entry list larger than allowed"));
 669
 670                         fp_entry_cpy[printed_entry_count] = *ent;
 671                         ++printed_entry_count;
 672                 }
 673         }
 674         fail_point_setting_release_ref(fp);
 675
 676         /* This is our equivalent of a NULL terminator */
 677         fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
 678
 679         while (idx < printed_entry_count) {
 680                 ent = &fp_entry_cpy[idx];
 681                 ++idx;
 682                 if (ent->fe_prob < PROB_MAX) {
 683                         int decimal = ent->fe_prob % (PROB_MAX / 100);
 684                         int units = ent->fe_prob / (PROB_MAX / 100);
 685                         sbuf_printf(sb, "%d", units);
 686                         if (decimal) {
 687                                 int digits = PROB_DIGITS - 2;
 688                                 while (!(decimal % 10)) {
 689                                         digits--;
 690                                         decimal /= 10;
 691                                 }
 692                                 sbuf_printf(sb, ".%0*d", digits, decimal);
 693                         }
 694                         sbuf_printf(sb, "%%");
 695                 }
 696                 if (ent->fe_count >= 0)
 697                         sbuf_printf(sb, "%d*", ent->fe_count);
 698                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
 699                 if (ent->fe_arg)
 700                         sbuf_printf(sb, "(%d)", ent->fe_arg);
 701                 if (ent->fe_pid != NO_PID)
 702                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
 703                 if (TAILQ_NEXT(ent, fe_entries))
 704                         sbuf_printf(sb, "->");
 705         }
 706         if (!printed_entry_count)
 707                 sbuf_printf(sb, "off");
 708
 709         fp_free(fp_entry_cpy);
 710         if (verbose) {
 711                 /* Print number of sleeping threads. queue=0 is the argument
 712                  * used by msleep when sending our threads to sleep. */
 713                 sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
 714                 sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
 715                         &cnt_sleeping);
 716
 717                 sbuf_printf(sb, "},\n");
 718                 sbuf_printf(sb, "sleeping_thread_count = %d,\n",
 719                         cnt_sleeping);
 720
 721                 sbuf_printf(sb, "paused_thread_stacks = {\n");
 722                 sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
 723                         &cnt_sleeping);
 724
 725                 sbuf_printf(sb, "},\n");
 726                 sbuf_printf(sb, "paused_thread_count = %d\n",
 727                         cnt_sleeping);
 728         }
 729 }
 730
 731 /**
 732  * Set an internal fail_point structure from a human-readable failpoint string
 733  * in a lock-safe manner.
 734  */
 735 static int
 736 fail_point_set(struct fail_point *fp, char *buf)
 737 {
 738         struct fail_point_entry *ent, *ent_next;
 739         struct fail_point_setting *entries;
 740         bool should_wake_paused;
 741         bool should_truncate;
 742         int error;
 743
 744         error = 0;
 745         should_wake_paused = false;
 746         should_truncate = false;
 747
 748         /* Parse new entries. */
 749         /**
 750          * ref protects our new malloc'd stuff from being garbage collected
 751          * before we link it.
 752          */
 753         fail_point_setting_get_ref(fp);
 754         entries = fail_point_setting_new(fp);
 755         if (parse_fail_point(entries, buf) == NULL) {
 756                 STAILQ_REMOVE(&fp_setting_garbage, entries,
 757                         fail_point_setting, fs_garbage_link);
 758                 fail_point_setting_destroy(entries);
 759                 error = EINVAL;
 760                 goto end;
 761         }
 762
 763         /**
 764          * Transfer the entries we are going to keep to a new list.
 765          * Get rid of useless zero probability entries, and entries with hit
 766          * count 0.
 767          * If 'off' is present, and it has no hit count set, then all entries
 768          *       after it are discarded since they are unreachable.
 769          */
 770         TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next) {
 771                 if (ent->fe_prob == 0 || ent->fe_count == 0) {
 772                         printf("Discarding entry which cannot execute %s\n",
 773                                 fail_type_strings[ent->fe_type].name);
 774                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 775                                 fe_entries);
 776                         fp_free(ent);
 777                         continue;
 778                 } else if (should_truncate) {
 779                         printf("Discarding unreachable entry %s\n",
 780                                 fail_type_strings[ent->fe_type].name);
 781                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 782                                 fe_entries);
 783                         fp_free(ent);
 784                         continue;
 785                 }
 786
 787                 if (ent->fe_type == FAIL_POINT_OFF) {
 788                         should_wake_paused = true;
 789                         if (ent->fe_count == FE_COUNT_UNTRACKED) {
 790                                 should_truncate = true;
 791                                 TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 792                                         fe_entries);
 793                                 fp_free(ent);
 794                         }
 795                 } else if (ent->fe_type == FAIL_POINT_PAUSE) {
 796                         should_truncate = true;
 797                 } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
 798                         FAIL_POINT_NONSLEEPABLE)) {
 799                         /**
 800                          * If this fail point is annotated as being in a
 801                          * non-sleepable ctx, convert sleep to delay and
 802                          * convert the msec argument to usecs.
 803                          */
 804                         printf("Sleep call request on fail point in "
 805                                 "non-sleepable context; using delay instead "
 806                                 "of sleep\n");
 807                         ent->fe_type = FAIL_POINT_DELAY;
 808                         ent->fe_arg *= 1000;
 809                 }
 810         }
 811
 812         if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
 813                 entries = fail_point_swap_settings(fp, NULL);
 814                 if (entries != NULL)
 815                         wakeup(FP_PAUSE_CHANNEL(fp));
 816         } else {
 817                 if (should_wake_paused)
 818                         wakeup(FP_PAUSE_CHANNEL(fp));
 819                 fail_point_swap_settings(fp, entries);
 820         }
 821
 822 end:
 823 #ifdef IWARNING
 824         if (error)
 825                 IWARNING("Failed to set %s %s to %s",
 826                     fp->fp_name, fp->fp_location, buf);
 827         else
 828                 INOTICE("Set %s %s to %s",
 829                     fp->fp_name, fp->fp_location, buf);
 830 #endif /* IWARNING */
 831
 832         fail_point_setting_release_ref(fp);
 833         return (error);
 834 }
 835
 836 #define MAX_FAIL_POINT_BUF      1023
 837
 838 /**
 839  * Handle kernel failpoint set/get.
 840  */
 841
 842 int
 843 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
 844 {
 845         struct fail_point *fp;
 846         char *buf;
 847         struct sbuf *sb_check;
 848         struct sbuf sb;
 849         int error;
 850
 851         error = 0;
 852         fp = arg1;
 853         buf = NULL;
 854
 855         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 856         if (sb_check != &sb)
 857                 return (ENOMEM);
 858
 859         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 860
 861         /* Setting */
 862         /**
 863          * Lock protects any new entries from being garbage collected before we
 864          * can link them to the fail point.
 865          */
 866         sx_xlock(&sx_fp_set);
 867         if (req->newptr) {
 868                 if (req->newlen > MAX_FAIL_POINT_BUF) {
 869                         error = EINVAL;
 870                         goto out;
 871                 }
 872
 873                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
 874
 875                 error = SYSCTL_IN(req, buf, req->newlen);
 876                 if (error)
 877                         goto out;
 878                 buf[req->newlen] = '\0';
 879
 880                 error = fail_point_set(fp, buf);
 881         }
 882
 883         fail_point_garbage_collect();
 884         sx_xunlock(&sx_fp_set);
 885
 886         /* Retrieving. */
 887         fail_point_get(fp, &sb, false);
 888
 889 out:
 890         sbuf_finish(&sb);
 891         sbuf_delete(&sb);
 892
 893         if (buf)
 894                 fp_free(buf);
 895
 896         return (error);
 897 }
 898
 899 int
 900 fail_point_sysctl_status(SYSCTL_HANDLER_ARGS)
 901 {
 902         struct fail_point *fp;
 903         struct sbuf sb, *sb_check;
 904
 905         fp = arg1;
 906
 907         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 908         if (sb_check != &sb)
 909                 return (ENOMEM);
 910
 911         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 912
 913         /* Retrieving. */
 914         fail_point_get(fp, &sb, true);
 915
 916         sbuf_finish(&sb);
 917         sbuf_delete(&sb);
 918
 919         /**
 920          * Lock protects any new entries from being garbage collected before we
 921          * can link them to the fail point.
 922          */
 923         sx_xlock(&sx_fp_set);
 924         fail_point_garbage_collect();
 925         sx_xunlock(&sx_fp_set);
 926
 927         return (0);
 928 }
 929
 930 int
 931 fail_sysctl_drain_func(void *sysctl_args, const char *buf, int len)
 932 {
 933         struct sysctl_req *sa;
 934         int error;
 935
 936         sa = sysctl_args;
 937
 938         error = SYSCTL_OUT(sa, buf, len);
 939
 940         if (error == ENOMEM)
 941                 return (-1);
 942         else
 943                 return (len);
 944 }
 945
 946
 947 /**
 948  * Internal helper function to translate a human-readable failpoint string
 949  * into a internally-parsable fail_point structure.
 950  */
 951 static char *
 952 parse_fail_point(struct fail_point_setting *ents, char *p)
 953 {
 954         /*  <fail_point> ::
 955          *      <term> ( "->" <term> )*
 956          */
 957         uint8_t term_count;
 958
 959         term_count = 1;
 960
 961         p = parse_term(ents, p);
 962         if (p == NULL)
 963                 return (NULL);
 964
 965         while (*p != '\0') {
 966                 term_count++;
 967                 if (p[0] != '-' || p[1] != '>' ||
 968                         (p = parse_term(ents, p+2)) == NULL ||
 969                         term_count > FP_MAX_ENTRY_COUNT)
 970                         return (NULL);
 971         }
 972         return (p);
 973 }
 974
 975 /**
 976  * Internal helper function to parse an individual term from a failpoint.
 977  */
 978 static char *
 979 parse_term(struct fail_point_setting *ents, char *p)
 980 {
 981         struct fail_point_entry *ent;
 982
 983         ent = fail_point_entry_new(ents);
 984
 985         /*
 986          * <term> ::
 987          *     ( (<float> "%") | (<integer> "*" ) )*
 988          *     <type>
 989          *     [ "(" <integer> ")" ]
 990          *     [ "[pid " <integer> "]" ]
 991          */
 992
 993         /* ( (<float> "%") | (<integer> "*" ) )* */
 994         while (isdigit(*p) || *p == '.') {
 995                 int units, decimal;
 996
 997                 p = parse_number(&units, &decimal, p);
 998                 if (p == NULL)
 999                         return (NULL);
1000
1001                 if (*p == '%') {
1002                         if (units > 100) /* prevent overflow early */
1003                                 units = 100;
1004                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
1005                         if (ent->fe_prob > PROB_MAX)
1006                                 ent->fe_prob = PROB_MAX;
1007                 } else if (*p == '*') {
1008                         if (!units || units < 0 || decimal)
1009                                 return (NULL);
1010                         ent->fe_count = units;
1011                 } else
1012                         return (NULL);
1013                 p++;
1014         }
1015
1016         /* <type> */
1017         p = parse_type(ent, p);
1018         if (p == NULL)
1019                 return (NULL);
1020         if (*p == '\0')
1021                 return (p);
1022
1023         /* [ "(" <integer> ")" ] */
1024         if (*p != '(')
1025                 return (p);
1026         p++;
1027         if (!isdigit(*p) && *p != '-')
1028                 return (NULL);
1029         ent->fe_arg = strtol(p, &p, 0);
1030         if (*p++ != ')')
1031                 return (NULL);
1032
1033         /* [ "[pid " <integer> "]" ] */
1034 #define PID_STRING "[pid "
1035         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
1036                 return (p);
1037         p += sizeof(PID_STRING) - 1;
1038         if (!isdigit(*p))
1039                 return (NULL);
1040         ent->fe_pid = strtol(p, &p, 0);
1041         if (*p++ != ']')
1042                 return (NULL);
1043
1044         return (p);
1045 }
1046
1047 /**
1048  * Internal helper function to parse a numeric for a failpoint term.
1049  */
1050 static char *
1051 parse_number(int *out_units, int *out_decimal, char *p)
1052 {
1053         char *old_p;
1054
1055         /**
1056          *  <number> ::
1057          *      <integer> [ "." <integer> ] |
1058          *      "." <integer>
1059          */
1060
1061         /* whole part */
1062         old_p = p;
1063         *out_units = strtol(p, &p, 10);
1064         if (p == old_p && *p != '.')
1065                 return (NULL);
1066
1067         /* fractional part */
1068         *out_decimal = 0;
1069         if (*p == '.') {
1070                 int digits = 0;
1071                 p++;
1072                 while (isdigit(*p)) {
1073                         int digit = *p - '0';
1074                         if (digits < PROB_DIGITS - 2)
1075                                 *out_decimal = *out_decimal * 10 + digit;
1076                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
1077                                 (*out_decimal)++;
1078                         digits++;
1079                         p++;
1080                 }
1081                 if (!digits) /* need at least one digit after '.' */
1082                         return (NULL);
1083                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
1084                         *out_decimal *= 10;
1085         }
1086
1087         return (p); /* success */
1088 }
1089
1090 /**
1091  * Internal helper function to parse an individual type for a failpoint term.
1092  */
1093 static char *
1094 parse_type(struct fail_point_entry *ent, char *beg)
1095 {
1096         enum fail_point_t type;
1097         int len;
1098
1099         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
1100                 len = fail_type_strings[type].nmlen;
1101                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
1102                         ent->fe_type = type;
1103                         return (beg + len);
1104                 }
1105         }
1106         return (NULL);
1107 }
1108
1109 /* The fail point sysctl tree. */
1110 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
1111
1112 /* Debugging/testing stuff for fail point */
1113 static int
1114 sysctl_test_fail_point(SYSCTL_HANDLER_ARGS)
1115 {
1116
1117         KFAIL_POINT_RETURN(DEBUG_FP, test_fail_point);
1118         return (0);
1119 }
1120 SYSCTL_OID(_debug_fail_point, OID_AUTO, test_trigger_fail_point,
1121         CTLTYPE_STRING | CTLFLAG_RD, NULL, 0, sysctl_test_fail_point, "A",
1122         "Trigger test fail points");