sys/kern/kern_fail.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright (c) 2009 Isilon Inc http://www.isilon.com/
   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 /**
  28  * @file
  29  *
  30  * fail(9) Facility.
  31  *
  32  * @ingroup failpoint_private
  33  */
  34 /**
  35  * @defgroup failpoint fail(9) Facility
  36  *
  37  * Failpoints allow for injecting fake errors into running code on the fly,
  38  * without modifying code or recompiling with flags.  Failpoints are always
  39  * present, and are very efficient when disabled.  Failpoints are described
  40  * in man fail(9).
  41  */
  42 /**
  43  * @defgroup failpoint_private Private fail(9) Implementation functions
  44  *
  45  * Private implementations for the actual failpoint code.
  46  *
  47  * @ingroup failpoint
  48  */
  49 /**
  50  * @addtogroup failpoint_private
  51  * @{
  52  */
  53
  54 #include <sys/cdefs.h>
  55 #include "opt_stack.h"
  56
  57 #include <sys/ctype.h>
  58 #include <sys/errno.h>
  59 #include <sys/fail.h>
  60 #include <sys/kernel.h>
  61 #include <sys/libkern.h>
  62 #include <sys/limits.h>
  63 #include <sys/lock.h>
  64 #include <sys/malloc.h>
  65 #include <sys/mutex.h>
  66 #include <sys/proc.h>
  67 #include <sys/sbuf.h>
  68 #include <sys/sleepqueue.h>
  69 #include <sys/sx.h>
  70 #include <sys/sysctl.h>
  71 #include <sys/types.h>
  72
  73 #include <machine/atomic.h>
  74 #include <machine/stdarg.h>
  75
  76 #ifdef ILOG_DEFINE_FOR_FILE
  77 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
  78 #endif
  79
  80 static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
  81 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
  82 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
  83 #define fs_free(ptr) fp_free(ptr)
  84 #define fs_malloc() fp_malloc(sizeof(struct fail_point_setting), \
  85     M_WAITOK | M_ZERO)
  86
  87 /**
  88  * These define the wchans that are used for sleeping, pausing respectively.
  89  * They are chosen arbitrarily but need to be distinct to the failpoint and
  90  * the sleep/pause distinction.
  91  */
  92 #define FP_SLEEP_CHANNEL(fp) (void*)(fp)
  93 #define FP_PAUSE_CHANNEL(fp) __DEVOLATILE(void*, &fp->fp_setting)
  94
  95 /**
  96  * Don't allow more than this many entries in a fail point set by sysctl.
  97  * The 99.99...% case is to have 1 entry.  I can't imagine having this many
  98  * entries, so it should not limit us.  Saves on re-mallocs while holding
  99  * a non-sleepable lock.
 100  */
 101 #define FP_MAX_ENTRY_COUNT 20
 102
 103 /* Used to drain sbufs to the sysctl output */
 104 int fail_sysctl_drain_func(void *, const char *, int);
 105
 106 /* Head of tailq of struct fail_point_entry */
 107 TAILQ_HEAD(fail_point_entry_queue, fail_point_entry);
 108
 109 /**
 110  * fp entries garbage list; outstanding entries are cleaned up in the
 111  * garbage collector
 112  */
 113 STAILQ_HEAD(fail_point_setting_garbage, fail_point_setting);
 114 static struct fail_point_setting_garbage fp_setting_garbage =
 115         STAILQ_HEAD_INITIALIZER(fp_setting_garbage);
 116 static struct mtx mtx_garbage_list;
 117 MTX_SYSINIT(mtx_garbage_list, &mtx_garbage_list, "fail point garbage mtx",
 118         MTX_SPIN);
 119
 120 static struct sx sx_fp_set;
 121 SX_SYSINIT(sx_fp_set, &sx_fp_set, "fail point set sx");
 122
 123 /**
 124  * Failpoint types.
 125  * Don't change these without changing fail_type_strings in fail.c.
 126  * @ingroup failpoint_private
 127  */
 128 enum fail_point_t {
 129         FAIL_POINT_OFF,         /**< don't fail */
 130         FAIL_POINT_PANIC,       /**< panic */
 131         FAIL_POINT_RETURN,      /**< return an errorcode */
 132         FAIL_POINT_BREAK,       /**< break into the debugger */
 133         FAIL_POINT_PRINT,       /**< print a message */
 134         FAIL_POINT_SLEEP,       /**< sleep for some msecs */
 135         FAIL_POINT_PAUSE,       /**< sleep until failpoint is set to off */
 136         FAIL_POINT_YIELD,       /**< yield the cpu */
 137         FAIL_POINT_DELAY,       /**< busy wait the cpu */
 138         FAIL_POINT_NUMTYPES,
 139         FAIL_POINT_INVALID = -1
 140 };
 141
 142 static struct {
 143         const char *name;
 144         int     nmlen;
 145 } fail_type_strings[] = {
 146 #define FP_TYPE_NM_LEN(s)       { s, sizeof(s) - 1 }
 147         [FAIL_POINT_OFF] =      FP_TYPE_NM_LEN("off"),
 148         [FAIL_POINT_PANIC] =    FP_TYPE_NM_LEN("panic"),
 149         [FAIL_POINT_RETURN] =   FP_TYPE_NM_LEN("return"),
 150         [FAIL_POINT_BREAK] =    FP_TYPE_NM_LEN("break"),
 151         [FAIL_POINT_PRINT] =    FP_TYPE_NM_LEN("print"),
 152         [FAIL_POINT_SLEEP] =    FP_TYPE_NM_LEN("sleep"),
 153         [FAIL_POINT_PAUSE] =    FP_TYPE_NM_LEN("pause"),
 154         [FAIL_POINT_YIELD] =    FP_TYPE_NM_LEN("yield"),
 155         [FAIL_POINT_DELAY] =    FP_TYPE_NM_LEN("delay"),
 156 };
 157
 158 #define FE_COUNT_UNTRACKED (INT_MIN)
 159
 160 /**
 161  * Internal structure tracking a single term of a complete failpoint.
 162  * @ingroup failpoint_private
 163  */
 164 struct fail_point_entry {
 165         volatile bool   fe_stale;
 166         enum fail_point_t       fe_type;        /**< type of entry */
 167         int             fe_arg;         /**< argument to type (e.g. return value) */
 168         int             fe_prob;        /**< likelihood of firing in millionths */
 169         int32_t         fe_count;       /**< number of times to fire, -1 means infinite */
 170         pid_t           fe_pid;         /**< only fail for this process */
 171         struct fail_point       *fe_parent;     /**< backpointer to fp */
 172         TAILQ_ENTRY(fail_point_entry)   fe_entries; /**< next entry ptr */
 173 };
 174
 175 struct fail_point_setting {
 176         STAILQ_ENTRY(fail_point_setting) fs_garbage_link;
 177         struct fail_point_entry_queue fp_entry_queue;
 178         struct fail_point * fs_parent;
 179         struct mtx feq_mtx; /* Gives fail_point_pause something to do.  */
 180 };
 181
 182 /**
 183  * Defines stating the equivalent of probablilty one (100%)
 184  */
 185 enum {
 186         PROB_MAX = 1000000,     /* probability between zero and this number */
 187         PROB_DIGITS = 6         /* number of zero's in above number */
 188 };
 189
 190 /* Get a ref on an fp's fp_setting */
 191 static inline struct fail_point_setting *fail_point_setting_get_ref(
 192         struct fail_point *fp);
 193 /* Release a ref on an fp_setting */
 194 static inline void fail_point_setting_release_ref(struct fail_point *fp);
 195 /* Allocate and initialize a struct fail_point_setting */
 196 static struct fail_point_setting *fail_point_setting_new(struct
 197         fail_point *);
 198 /* Free a struct fail_point_setting */
 199 static void fail_point_setting_destroy(struct fail_point_setting *fp_setting);
 200 /* Allocate and initialize a struct fail_point_entry */
 201 static struct fail_point_entry *fail_point_entry_new(struct
 202         fail_point_setting *);
 203 /* Free a struct fail_point_entry */
 204 static void fail_point_entry_destroy(struct fail_point_entry *fp_entry);
 205 /* Append fp setting to garbage list */
 206 static inline void fail_point_setting_garbage_append(
 207         struct fail_point_setting *fp_setting);
 208 /* Swap fp's setting with fp_setting_new */
 209 static inline struct fail_point_setting *
 210         fail_point_swap_settings(struct fail_point *fp,
 211         struct fail_point_setting *fp_setting_new);
 212 /* Free up any zero-ref setting in the garbage queue */
 213 static void fail_point_garbage_collect(void);
 214 /* If this fail point's setting are empty, then swap it out to NULL. */
 215 static inline void fail_point_eval_swap_out(struct fail_point *fp,
 216         struct fail_point_setting *fp_setting);
 217
 218 bool
 219 fail_point_is_off(struct fail_point *fp)
 220 {
 221         bool return_val;
 222         struct fail_point_setting *fp_setting;
 223         struct fail_point_entry *ent;
 224
 225         return_val = true;
 226
 227         fp_setting = fail_point_setting_get_ref(fp);
 228         if (fp_setting != NULL) {
 229                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue,
 230                     fe_entries) {
 231                         if (!ent->fe_stale) {
 232                                 return_val = false;
 233                                 break;
 234                         }
 235                 }
 236         }
 237         fail_point_setting_release_ref(fp);
 238
 239         return (return_val);
 240 }
 241
 242 /* Allocate and initialize a struct fail_point_setting */
 243 static struct fail_point_setting *
 244 fail_point_setting_new(struct fail_point *fp)
 245 {
 246         struct fail_point_setting *fs_new;
 247
 248         fs_new = fs_malloc();
 249         fs_new->fs_parent = fp;
 250         TAILQ_INIT(&fs_new->fp_entry_queue);
 251         mtx_init(&fs_new->feq_mtx, "fail point entries", NULL, MTX_SPIN);
 252
 253         fail_point_setting_garbage_append(fs_new);
 254
 255         return (fs_new);
 256 }
 257
 258 /* Free a struct fail_point_setting */
 259 static void
 260 fail_point_setting_destroy(struct fail_point_setting *fp_setting)
 261 {
 262         struct fail_point_entry *ent;
 263
 264         while (!TAILQ_EMPTY(&fp_setting->fp_entry_queue)) {
 265                 ent = TAILQ_FIRST(&fp_setting->fp_entry_queue);
 266                 TAILQ_REMOVE(&fp_setting->fp_entry_queue, ent, fe_entries);
 267                 fail_point_entry_destroy(ent);
 268         }
 269
 270         fs_free(fp_setting);
 271 }
 272
 273 /* Allocate and initialize a struct fail_point_entry */
 274 static struct fail_point_entry *
 275 fail_point_entry_new(struct fail_point_setting *fp_setting)
 276 {
 277         struct fail_point_entry *fp_entry;
 278
 279         fp_entry = fp_malloc(sizeof(struct fail_point_entry),
 280                 M_WAITOK | M_ZERO);
 281         fp_entry->fe_parent = fp_setting->fs_parent;
 282         fp_entry->fe_prob = PROB_MAX;
 283         fp_entry->fe_pid = NO_PID;
 284         fp_entry->fe_count = FE_COUNT_UNTRACKED;
 285         TAILQ_INSERT_TAIL(&fp_setting->fp_entry_queue, fp_entry,
 286                 fe_entries);
 287
 288         return (fp_entry);
 289 }
 290
 291 /* Free a struct fail_point_entry */
 292 static void
 293 fail_point_entry_destroy(struct fail_point_entry *fp_entry)
 294 {
 295
 296         fp_free(fp_entry);
 297 }
 298
 299 /* Get a ref on an fp's fp_setting */
 300 static inline struct fail_point_setting *
 301 fail_point_setting_get_ref(struct fail_point *fp)
 302 {
 303         struct fail_point_setting *fp_setting;
 304
 305         /* Invariant: if we have a ref, our pointer to fp_setting is safe */
 306         atomic_add_acq_32(&fp->fp_ref_cnt, 1);
 307         fp_setting = fp->fp_setting;
 308
 309         return (fp_setting);
 310 }
 311
 312 /* Release a ref on an fp_setting */
 313 static inline void
 314 fail_point_setting_release_ref(struct fail_point *fp)
 315 {
 316
 317         KASSERT(&fp->fp_ref_cnt > 0, ("Attempting to deref w/no refs"));
 318         atomic_subtract_rel_32(&fp->fp_ref_cnt, 1);
 319 }
 320
 321 /* Append fp entries to fp garbage list */
 322 static inline void
 323 fail_point_setting_garbage_append(struct fail_point_setting *fp_setting)
 324 {
 325
 326         mtx_lock_spin(&mtx_garbage_list);
 327         STAILQ_INSERT_TAIL(&fp_setting_garbage, fp_setting,
 328                 fs_garbage_link);
 329         mtx_unlock_spin(&mtx_garbage_list);
 330 }
 331
 332 /* Swap fp's entries with fp_setting_new */
 333 static struct fail_point_setting *
 334 fail_point_swap_settings(struct fail_point *fp,
 335         struct fail_point_setting *fp_setting_new)
 336 {
 337         struct fail_point_setting *fp_setting_old;
 338
 339         fp_setting_old = fp->fp_setting;
 340         fp->fp_setting = fp_setting_new;
 341
 342         return (fp_setting_old);
 343 }
 344
 345 static inline void
 346 fail_point_eval_swap_out(struct fail_point *fp,
 347         struct fail_point_setting *fp_setting)
 348 {
 349
 350         /* We may have already been swapped out and replaced; ignore. */
 351         if (fp->fp_setting == fp_setting)
 352                 fail_point_swap_settings(fp, NULL);
 353 }
 354
 355 /* Free up any zero-ref entries in the garbage queue */
 356 static void
 357 fail_point_garbage_collect(void)
 358 {
 359         struct fail_point_setting *fs_current, *fs_next;
 360         struct fail_point_setting_garbage fp_ents_free_list;
 361
 362         /**
 363           * We will transfer the entries to free to fp_ents_free_list while holding
 364           * the spin mutex, then free it after we drop the lock. This avoids
 365           * triggering witness due to sleepable mutexes in the memory
 366           * allocator.
 367           */
 368         STAILQ_INIT(&fp_ents_free_list);
 369
 370         mtx_lock_spin(&mtx_garbage_list);
 371         STAILQ_FOREACH_SAFE(fs_current, &fp_setting_garbage, fs_garbage_link,
 372             fs_next) {
 373                 if (fs_current->fs_parent->fp_setting != fs_current &&
 374                         fs_current->fs_parent->fp_ref_cnt == 0) {
 375                         STAILQ_REMOVE(&fp_setting_garbage, fs_current,
 376                                 fail_point_setting, fs_garbage_link);
 377                         STAILQ_INSERT_HEAD(&fp_ents_free_list, fs_current,
 378                                 fs_garbage_link);
 379                 }
 380         }
 381         mtx_unlock_spin(&mtx_garbage_list);
 382
 383         STAILQ_FOREACH_SAFE(fs_current, &fp_ents_free_list, fs_garbage_link,
 384                 fs_next)
 385                 fail_point_setting_destroy(fs_current);
 386 }
 387
 388 /* Drain out all refs from this fail point */
 389 static inline void
 390 fail_point_drain(struct fail_point *fp, int expected_ref)
 391 {
 392         struct fail_point_setting *entries;
 393
 394         entries = fail_point_swap_settings(fp, NULL);
 395         /**
 396          * We have unpaused all threads; so we will wait no longer
 397          * than the time taken for the longest remaining sleep, or
 398          * the length of time of a long-running code block.
 399          */
 400         while (fp->fp_ref_cnt > expected_ref) {
 401                 wakeup(FP_PAUSE_CHANNEL(fp));
 402                 tsleep(&fp, PWAIT, "fail_point_drain", hz / 100);
 403         }
 404         if (fp->fp_callout)
 405                 callout_drain(fp->fp_callout);
 406         fail_point_swap_settings(fp, entries);
 407 }
 408
 409 static inline void
 410 fail_point_pause(struct fail_point *fp, enum fail_point_return_code *pret,
 411         struct mtx *mtx_sleep)
 412 {
 413
 414         if (fp->fp_pre_sleep_fn)
 415                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 416
 417         msleep_spin(FP_PAUSE_CHANNEL(fp), mtx_sleep, "failpt", 0);
 418
 419         if (fp->fp_post_sleep_fn)
 420                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 421 }
 422
 423 static inline void
 424 fail_point_sleep(struct fail_point *fp, int msecs,
 425         enum fail_point_return_code *pret)
 426 {
 427         int timo;
 428
 429         /* Convert from millisecs to ticks, rounding up */
 430         timo = howmany((int64_t)msecs * hz, 1000L);
 431
 432         if (timo > 0) {
 433                 if (!(fp->fp_flags & FAIL_POINT_USE_TIMEOUT_PATH)) {
 434                         if (fp->fp_pre_sleep_fn)
 435                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 436
 437                         tsleep(FP_SLEEP_CHANNEL(fp), PWAIT, "failpt", timo);
 438
 439                         if (fp->fp_post_sleep_fn)
 440                                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 441                 } else {
 442                         if (fp->fp_pre_sleep_fn)
 443                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 444
 445                         callout_reset(fp->fp_callout, timo,
 446                             fp->fp_post_sleep_fn, fp->fp_post_sleep_arg);
 447                         *pret = FAIL_POINT_RC_QUEUED;
 448                 }
 449         }
 450 }
 451
 452 static char *parse_fail_point(struct fail_point_setting *, char *);
 453 static char *parse_term(struct fail_point_setting *, char *);
 454 static char *parse_number(int *out_units, int *out_decimal, char *);
 455 static char *parse_type(struct fail_point_entry *, char *);
 456
 457 /**
 458  * Initialize a fail_point.  The name is formed in a printf-like fashion
 459  * from "fmt" and subsequent arguments.  This function is generally used
 460  * for custom failpoints located at odd places in the sysctl tree, and is
 461  * not explicitly needed for standard in-line-declared failpoints.
 462  *
 463  * @ingroup failpoint
 464  */
 465 void
 466 fail_point_init(struct fail_point *fp, const char *fmt, ...)
 467 {
 468         va_list ap;
 469         char *name;
 470         int n;
 471
 472         fp->fp_setting = NULL;
 473         fp->fp_flags = 0;
 474
 475         /* Figure out the size of the name. */
 476         va_start(ap, fmt);
 477         n = vsnprintf(NULL, 0, fmt, ap);
 478         va_end(ap);
 479
 480         /* Allocate the name and fill it in. */
 481         name = fp_malloc(n + 1, M_WAITOK);
 482         if (name != NULL) {
 483                 va_start(ap, fmt);
 484                 vsnprintf(name, n + 1, fmt, ap);
 485                 va_end(ap);
 486         }
 487         fp->fp_name = name;
 488         fp->fp_location = "";
 489         fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
 490         fp->fp_pre_sleep_fn = NULL;
 491         fp->fp_pre_sleep_arg = NULL;
 492         fp->fp_post_sleep_fn = NULL;
 493         fp->fp_post_sleep_arg = NULL;
 494 }
 495
 496 void
 497 fail_point_alloc_callout(struct fail_point *fp)
 498 {
 499
 500         /**
 501          * This assumes that calls to fail_point_use_timeout_path()
 502          * will not race.
 503          */
 504         if (fp->fp_callout != NULL)
 505                 return;
 506         fp->fp_callout = fp_malloc(sizeof(*fp->fp_callout), M_WAITOK);
 507         callout_init(fp->fp_callout, CALLOUT_MPSAFE);
 508 }
 509
 510 /**
 511  * Free the resources held by a fail_point, and wake any paused threads.
 512  * Thou shalt not allow threads to hit this fail point after you enter this
 513  * function, nor shall you call this multiple times for a given fp.
 514  * @ingroup failpoint
 515  */
 516 void
 517 fail_point_destroy(struct fail_point *fp)
 518 {
 519
 520         fail_point_drain(fp, 0);
 521
 522         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
 523                 fp_free(__DECONST(void *, fp->fp_name));
 524                 fp->fp_name = NULL;
 525         }
 526         fp->fp_flags = 0;
 527         if (fp->fp_callout) {
 528                 fp_free(fp->fp_callout);
 529                 fp->fp_callout = NULL;
 530         }
 531
 532         sx_xlock(&sx_fp_set);
 533         fail_point_garbage_collect();
 534         sx_xunlock(&sx_fp_set);
 535 }
 536
 537 /**
 538  * This does the real work of evaluating a fail point. If the fail point tells
 539  * us to return a value, this function returns 1 and fills in 'return_value'
 540  * (return_value is allowed to be null). If the fail point tells us to panic,
 541  * we never return. Otherwise we just return 0 after doing some work, which
 542  * means "keep going".
 543  */
 544 enum fail_point_return_code
 545 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
 546 {
 547         bool execute = false;
 548         struct fail_point_entry *ent;
 549         struct fail_point_setting *fp_setting;
 550         enum fail_point_return_code ret;
 551         int cont;
 552         int count;
 553         int msecs;
 554         int usecs;
 555
 556         ret = FAIL_POINT_RC_CONTINUE;
 557         cont = 0; /* don't continue by default */
 558
 559         fp_setting = fail_point_setting_get_ref(fp);
 560         if (fp_setting == NULL)
 561                 goto abort;
 562
 563         TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 564                 if (ent->fe_stale)
 565                         continue;
 566
 567                 if (ent->fe_prob < PROB_MAX &&
 568                     ent->fe_prob < random() % PROB_MAX)
 569                         continue;
 570
 571                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
 572                         continue;
 573
 574                 if (ent->fe_count != FE_COUNT_UNTRACKED) {
 575                         count = ent->fe_count;
 576                         while (count > 0) {
 577                                 if (atomic_cmpset_32(&ent->fe_count, count, count - 1)) {
 578                                         count--;
 579                                         execute = true;
 580                                         break;
 581                                 }
 582                                 count = ent->fe_count;
 583                         }
 584                         if (execute == false)
 585                                 /* We lost the race; consider the entry stale and bail now */
 586                                 continue;
 587                         if (count == 0)
 588                                 ent->fe_stale = true;
 589                 }
 590
 591                 switch (ent->fe_type) {
 592                 case FAIL_POINT_PANIC:
 593                         panic("fail point %s panicking", fp->fp_name);
 594                         /* NOTREACHED */
 595
 596                 case FAIL_POINT_RETURN:
 597                         if (return_value != NULL)
 598                                 *return_value = ent->fe_arg;
 599                         ret = FAIL_POINT_RC_RETURN;
 600                         break;
 601
 602                 case FAIL_POINT_BREAK:
 603                         printf("fail point %s breaking to debugger\n",
 604                                 fp->fp_name);
 605                         breakpoint();
 606                         break;
 607
 608                 case FAIL_POINT_PRINT:
 609                         printf("fail point %s executing\n", fp->fp_name);
 610                         cont = ent->fe_arg;
 611                         break;
 612
 613                 case FAIL_POINT_SLEEP:
 614                         msecs = ent->fe_arg;
 615                         if (msecs)
 616                                 fail_point_sleep(fp, msecs, &ret);
 617                         break;
 618
 619                 case FAIL_POINT_PAUSE:
 620                         /**
 621                          * Pausing is inherently strange with multiple
 622                          * entries given our design.  That is because some
 623                          * entries could be unreachable, for instance in cases like:
 624                          * pause->return. We can never reach the return entry.
 625                          * The sysctl layer actually truncates all entries after
 626                          * a pause for this reason.
 627                          */
 628                         mtx_lock_spin(&fp_setting->feq_mtx);
 629                         fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
 630                         mtx_unlock_spin(&fp_setting->feq_mtx);
 631                         break;
 632
 633                 case FAIL_POINT_YIELD:
 634                         kern_yield(PRI_UNCHANGED);
 635                         break;
 636
 637                 case FAIL_POINT_DELAY:
 638                         usecs = ent->fe_arg;
 639                         DELAY(usecs);
 640                         break;
 641
 642                 default:
 643                         break;
 644                 }
 645
 646                 if (cont == 0)
 647                         break;
 648         }
 649
 650         if (fail_point_is_off(fp))
 651                 fail_point_eval_swap_out(fp, fp_setting);
 652
 653 abort:
 654         fail_point_setting_release_ref(fp);
 655
 656         return (ret);
 657 }
 658
 659 /**
 660  * Translate internal fail_point structure into human-readable text.
 661  */
 662 static void
 663 fail_point_get(struct fail_point *fp, struct sbuf *sb,
 664         bool verbose)
 665 {
 666         struct fail_point_entry *ent;
 667         struct fail_point_setting *fp_setting;
 668         struct fail_point_entry *fp_entry_cpy;
 669         int cnt_sleeping;
 670         int idx;
 671         int printed_entry_count;
 672
 673         cnt_sleeping = 0;
 674         idx = 0;
 675         printed_entry_count = 0;
 676
 677         fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
 678                 (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
 679
 680         fp_setting = fail_point_setting_get_ref(fp);
 681
 682         if (fp_setting != NULL) {
 683                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 684                         if (ent->fe_stale)
 685                                 continue;
 686
 687                         KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
 688                                 ("FP entry list larger than allowed"));
 689
 690                         fp_entry_cpy[printed_entry_count] = *ent;
 691                         ++printed_entry_count;
 692                 }
 693         }
 694         fail_point_setting_release_ref(fp);
 695
 696         /* This is our equivalent of a NULL terminator */
 697         fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
 698
 699         while (idx < printed_entry_count) {
 700                 ent = &fp_entry_cpy[idx];
 701                 ++idx;
 702                 if (ent->fe_prob < PROB_MAX) {
 703                         int decimal = ent->fe_prob % (PROB_MAX / 100);
 704                         int units = ent->fe_prob / (PROB_MAX / 100);
 705                         sbuf_printf(sb, "%d", units);
 706                         if (decimal) {
 707                                 int digits = PROB_DIGITS - 2;
 708                                 while (!(decimal % 10)) {
 709                                         digits--;
 710                                         decimal /= 10;
 711                                 }
 712                                 sbuf_printf(sb, ".%0*d", digits, decimal);
 713                         }
 714                         sbuf_printf(sb, "%%");
 715                 }
 716                 if (ent->fe_count >= 0)
 717                         sbuf_printf(sb, "%d*", ent->fe_count);
 718                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
 719                 if (ent->fe_arg)
 720                         sbuf_printf(sb, "(%d)", ent->fe_arg);
 721                 if (ent->fe_pid != NO_PID)
 722                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
 723                 if (TAILQ_NEXT(ent, fe_entries))
 724                         sbuf_printf(sb, "->");
 725         }
 726         if (!printed_entry_count)
 727                 sbuf_printf(sb, "off");
 728
 729         fp_free(fp_entry_cpy);
 730         if (verbose) {
 731 #ifdef STACK
 732                 /* Print number of sleeping threads. queue=0 is the argument
 733                  * used by msleep when sending our threads to sleep. */
 734                 sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
 735                 sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
 736                         &cnt_sleeping);
 737
 738                 sbuf_printf(sb, "},\n");
 739 #endif
 740                 sbuf_printf(sb, "sleeping_thread_count = %d,\n",
 741                         cnt_sleeping);
 742
 743 #ifdef STACK
 744                 sbuf_printf(sb, "paused_thread_stacks = {\n");
 745                 sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
 746                         &cnt_sleeping);
 747
 748                 sbuf_printf(sb, "},\n");
 749 #endif
 750                 sbuf_printf(sb, "paused_thread_count = %d\n",
 751                         cnt_sleeping);
 752         }
 753 }
 754
 755 /**
 756  * Set an internal fail_point structure from a human-readable failpoint string
 757  * in a lock-safe manner.
 758  */
 759 static int
 760 fail_point_set(struct fail_point *fp, char *buf)
 761 {
 762         struct fail_point_entry *ent, *ent_next;
 763         struct fail_point_setting *entries;
 764         bool should_wake_paused;
 765         bool should_truncate;
 766         int error;
 767
 768         error = 0;
 769         should_wake_paused = false;
 770         should_truncate = false;
 771
 772         /* Parse new entries. */
 773         /**
 774          * ref protects our new malloc'd stuff from being garbage collected
 775          * before we link it.
 776          */
 777         fail_point_setting_get_ref(fp);
 778         entries = fail_point_setting_new(fp);
 779         if (parse_fail_point(entries, buf) == NULL) {
 780                 STAILQ_REMOVE(&fp_setting_garbage, entries,
 781                         fail_point_setting, fs_garbage_link);
 782                 fail_point_setting_destroy(entries);
 783                 error = EINVAL;
 784                 goto end;
 785         }
 786
 787         /**
 788          * Transfer the entries we are going to keep to a new list.
 789          * Get rid of useless zero probability entries, and entries with hit
 790          * count 0.
 791          * If 'off' is present, and it has no hit count set, then all entries
 792          *       after it are discarded since they are unreachable.
 793          */
 794         TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next) {
 795                 if (ent->fe_prob == 0 || ent->fe_count == 0) {
 796                         printf("Discarding entry which cannot execute %s\n",
 797                                 fail_type_strings[ent->fe_type].name);
 798                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 799                                 fe_entries);
 800                         fp_free(ent);
 801                         continue;
 802                 } else if (should_truncate) {
 803                         printf("Discarding unreachable entry %s\n",
 804                                 fail_type_strings[ent->fe_type].name);
 805                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 806                                 fe_entries);
 807                         fp_free(ent);
 808                         continue;
 809                 }
 810
 811                 if (ent->fe_type == FAIL_POINT_OFF) {
 812                         should_wake_paused = true;
 813                         if (ent->fe_count == FE_COUNT_UNTRACKED) {
 814                                 should_truncate = true;
 815                                 TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 816                                         fe_entries);
 817                                 fp_free(ent);
 818                         }
 819                 } else if (ent->fe_type == FAIL_POINT_PAUSE) {
 820                         should_truncate = true;
 821                 } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
 822                         FAIL_POINT_NONSLEEPABLE)) {
 823                         /**
 824                          * If this fail point is annotated as being in a
 825                          * non-sleepable ctx, convert sleep to delay and
 826                          * convert the msec argument to usecs.
 827                          */
 828                         printf("Sleep call request on fail point in "
 829                                 "non-sleepable context; using delay instead "
 830                                 "of sleep\n");
 831                         ent->fe_type = FAIL_POINT_DELAY;
 832                         ent->fe_arg *= 1000;
 833                 }
 834         }
 835
 836         if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
 837                 entries = fail_point_swap_settings(fp, NULL);
 838                 if (entries != NULL)
 839                         wakeup(FP_PAUSE_CHANNEL(fp));
 840         } else {
 841                 if (should_wake_paused)
 842                         wakeup(FP_PAUSE_CHANNEL(fp));
 843                 fail_point_swap_settings(fp, entries);
 844         }
 845
 846 end:
 847 #ifdef IWARNING
 848         if (error)
 849                 IWARNING("Failed to set %s %s to %s",
 850                     fp->fp_name, fp->fp_location, buf);
 851         else
 852                 INOTICE("Set %s %s to %s",
 853                     fp->fp_name, fp->fp_location, buf);
 854 #endif /* IWARNING */
 855
 856         fail_point_setting_release_ref(fp);
 857         return (error);
 858 }
 859
 860 #define MAX_FAIL_POINT_BUF      1023
 861
 862 /**
 863  * Handle kernel failpoint set/get.
 864  */
 865 int
 866 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
 867 {
 868         struct fail_point *fp;
 869         char *buf;
 870         struct sbuf sb, *sb_check;
 871         int error;
 872
 873         buf = NULL;
 874         error = 0;
 875         fp = arg1;
 876
 877         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 878         if (sb_check != &sb)
 879                 return (ENOMEM);
 880
 881         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 882
 883         /* Setting */
 884         /**
 885          * Lock protects any new entries from being garbage collected before we
 886          * can link them to the fail point.
 887          */
 888         sx_xlock(&sx_fp_set);
 889         if (req->newptr) {
 890                 if (req->newlen > MAX_FAIL_POINT_BUF) {
 891                         error = EINVAL;
 892                         goto out;
 893                 }
 894
 895                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
 896
 897                 error = SYSCTL_IN(req, buf, req->newlen);
 898                 if (error)
 899                         goto out;
 900                 buf[req->newlen] = '\0';
 901
 902                 error = fail_point_set(fp, buf);
 903         }
 904
 905         fail_point_garbage_collect();
 906         sx_xunlock(&sx_fp_set);
 907
 908         /* Retrieving. */
 909         fail_point_get(fp, &sb, false);
 910
 911 out:
 912         sbuf_finish(&sb);
 913         sbuf_delete(&sb);
 914
 915         if (buf)
 916                 fp_free(buf);
 917
 918         return (error);
 919 }
 920
 921 int
 922 fail_point_sysctl_status(SYSCTL_HANDLER_ARGS)
 923 {
 924         struct fail_point *fp;
 925         struct sbuf sb, *sb_check;
 926
 927         fp = arg1;
 928
 929         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 930         if (sb_check != &sb)
 931                 return (ENOMEM);
 932
 933         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 934
 935         /* Retrieving. */
 936         fail_point_get(fp, &sb, true);
 937
 938         sbuf_finish(&sb);
 939         sbuf_delete(&sb);
 940
 941         /**
 942          * Lock protects any new entries from being garbage collected before we
 943          * can link them to the fail point.
 944          */
 945         sx_xlock(&sx_fp_set);
 946         fail_point_garbage_collect();
 947         sx_xunlock(&sx_fp_set);
 948
 949         return (0);
 950 }
 951
 952 int
 953 fail_sysctl_drain_func(void *sysctl_args, const char *buf, int len)
 954 {
 955         struct sysctl_req *sa;
 956         int error;
 957
 958         sa = sysctl_args;
 959
 960         error = SYSCTL_OUT(sa, buf, len);
 961
 962         if (error == ENOMEM)
 963                 return (-1);
 964         else
 965                 return (len);
 966 }
 967
 968 /**
 969  * Internal helper function to translate a human-readable failpoint string
 970  * into a internally-parsable fail_point structure.
 971  */
 972 static char *
 973 parse_fail_point(struct fail_point_setting *ents, char *p)
 974 {
 975         /*  <fail_point> ::
 976          *      <term> ( "->" <term> )*
 977          */
 978         uint8_t term_count;
 979
 980         term_count = 1;
 981
 982         p = parse_term(ents, p);
 983         if (p == NULL)
 984                 return (NULL);
 985
 986         while (*p != '\0') {
 987                 term_count++;
 988                 if (p[0] != '-' || p[1] != '>' ||
 989                         (p = parse_term(ents, p+2)) == NULL ||
 990                         term_count > FP_MAX_ENTRY_COUNT)
 991                         return (NULL);
 992         }
 993         return (p);
 994 }
 995
 996 /**
 997  * Internal helper function to parse an individual term from a failpoint.
 998  */
 999 static char *
1000 parse_term(struct fail_point_setting *ents, char *p)
1001 {
1002         struct fail_point_entry *ent;
1003
1004         ent = fail_point_entry_new(ents);
1005
1006         /*
1007          * <term> ::
1008          *     ( (<float> "%") | (<integer> "*" ) )*
1009          *     <type>
1010          *     [ "(" <integer> ")" ]
1011          *     [ "[pid " <integer> "]" ]
1012          */
1013
1014         /* ( (<float> "%") | (<integer> "*" ) )* */
1015         while (isdigit(*p) || *p == '.') {
1016                 int units, decimal;
1017
1018                 p = parse_number(&units, &decimal, p);
1019                 if (p == NULL)
1020                         return (NULL);
1021
1022                 if (*p == '%') {
1023                         if (units > 100) /* prevent overflow early */
1024                                 units = 100;
1025                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
1026                         if (ent->fe_prob > PROB_MAX)
1027                                 ent->fe_prob = PROB_MAX;
1028                 } else if (*p == '*') {
1029                         if (!units || units < 0 || decimal)
1030                                 return (NULL);
1031                         ent->fe_count = units;
1032                 } else
1033                         return (NULL);
1034                 p++;
1035         }
1036
1037         /* <type> */
1038         p = parse_type(ent, p);
1039         if (p == NULL)
1040                 return (NULL);
1041         if (*p == '\0')
1042                 return (p);
1043
1044         /* [ "(" <integer> ")" ] */
1045         if (*p != '(')
1046                 return (p);
1047         p++;
1048         if (!isdigit(*p) && *p != '-')
1049                 return (NULL);
1050         ent->fe_arg = strtol(p, &p, 0);
1051         if (*p++ != ')')
1052                 return (NULL);
1053
1054         /* [ "[pid " <integer> "]" ] */
1055 #define PID_STRING "[pid "
1056         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
1057                 return (p);
1058         p += sizeof(PID_STRING) - 1;
1059         if (!isdigit(*p))
1060                 return (NULL);
1061         ent->fe_pid = strtol(p, &p, 0);
1062         if (*p++ != ']')
1063                 return (NULL);
1064
1065         return (p);
1066 }
1067
1068 /**
1069  * Internal helper function to parse a numeric for a failpoint term.
1070  */
1071 static char *
1072 parse_number(int *out_units, int *out_decimal, char *p)
1073 {
1074         char *old_p;
1075
1076         /**
1077          *  <number> ::
1078          *      <integer> [ "." <integer> ] |
1079          *      "." <integer>
1080          */
1081
1082         /* whole part */
1083         old_p = p;
1084         *out_units = strtol(p, &p, 10);
1085         if (p == old_p && *p != '.')
1086                 return (NULL);
1087
1088         /* fractional part */
1089         *out_decimal = 0;
1090         if (*p == '.') {
1091                 int digits = 0;
1092                 p++;
1093                 while (isdigit(*p)) {
1094                         int digit = *p - '0';
1095                         if (digits < PROB_DIGITS - 2)
1096                                 *out_decimal = *out_decimal * 10 + digit;
1097                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
1098                                 (*out_decimal)++;
1099                         digits++;
1100                         p++;
1101                 }
1102                 if (!digits) /* need at least one digit after '.' */
1103                         return (NULL);
1104                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
1105                         *out_decimal *= 10;
1106         }
1107
1108         return (p); /* success */
1109 }
1110
1111 /**
1112  * Internal helper function to parse an individual type for a failpoint term.
1113  */
1114 static char *
1115 parse_type(struct fail_point_entry *ent, char *beg)
1116 {
1117         enum fail_point_t type;
1118         int len;
1119
1120         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
1121                 len = fail_type_strings[type].nmlen;
1122                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
1123                         ent->fe_type = type;
1124                         return (beg + len);
1125                 }
1126         }
1127         return (NULL);
1128 }
1129
1130 /* The fail point sysctl tree. */
1131 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
1132     "fail points");
1133
1134 /* Debugging/testing stuff for fail point */
1135 static int
1136 sysctl_test_fail_point(SYSCTL_HANDLER_ARGS)
1137 {
1138
1139         KFAIL_POINT_RETURN(DEBUG_FP, test_fail_point);
1140         return (0);
1141 }
1142 SYSCTL_OID(_debug_fail_point, OID_AUTO, test_trigger_fail_point,
1143     CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_NEEDGIANT, NULL, 0,
1144     sysctl_test_fail_point, "A",
1145     "Trigger test fail points");