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 "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         int             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()
 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         fail_point_swap_settings(fp, entries);
 405 }
 406
 407 static inline void
 408 fail_point_pause(struct fail_point *fp, enum fail_point_return_code *pret,
 409         struct mtx *mtx_sleep)
 410 {
 411
 412         if (fp->fp_pre_sleep_fn)
 413                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 414
 415         msleep_spin(FP_PAUSE_CHANNEL(fp), mtx_sleep, "failpt", 0);
 416
 417         if (fp->fp_post_sleep_fn)
 418                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 419 }
 420
 421 static inline void
 422 fail_point_sleep(struct fail_point *fp, int msecs,
 423         enum fail_point_return_code *pret)
 424 {
 425         int timo;
 426
 427         /* Convert from millisecs to ticks, rounding up */
 428         timo = howmany(msecs * hz, 1000);
 429
 430         if (timo > 0) {
 431                 if (!(fp->fp_flags & FAIL_POINT_USE_TIMEOUT_PATH)) {
 432                         if (fp->fp_pre_sleep_fn)
 433                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 434
 435                         tsleep(FP_SLEEP_CHANNEL(fp), PWAIT, "failpt", timo);
 436
 437                         if (fp->fp_post_sleep_fn)
 438                                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
 439                 } else {
 440                         if (fp->fp_pre_sleep_fn)
 441                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
 442
 443                         timeout(fp->fp_post_sleep_fn, fp->fp_post_sleep_arg,
 444                                 timo);
 445                         *pret = FAIL_POINT_RC_QUEUED;
 446                 }
 447         }
 448 }
 449
 450 static char *parse_fail_point(struct fail_point_setting *, char *);
 451 static char *parse_term(struct fail_point_setting *, char *);
 452 static char *parse_number(int *out_units, int *out_decimal, char *);
 453 static char *parse_type(struct fail_point_entry *, char *);
 454
 455 /**
 456  * Initialize a fail_point.  The name is formed in a printf-like fashion
 457  * from "fmt" and subsequent arguments.  This function is generally used
 458  * for custom failpoints located at odd places in the sysctl tree, and is
 459  * not explicitly needed for standard in-line-declared failpoints.
 460  *
 461  * @ingroup failpoint
 462  */
 463 void
 464 fail_point_init(struct fail_point *fp, const char *fmt, ...)
 465 {
 466         va_list ap;
 467         char *name;
 468         int n;
 469
 470         fp->fp_setting = NULL;
 471         fp->fp_flags = 0;
 472
 473         /* Figure out the size of the name. */
 474         va_start(ap, fmt);
 475         n = vsnprintf(NULL, 0, fmt, ap);
 476         va_end(ap);
 477
 478         /* Allocate the name and fill it in. */
 479         name = fp_malloc(n + 1, M_WAITOK);
 480         if (name != NULL) {
 481                 va_start(ap, fmt);
 482                 vsnprintf(name, n + 1, fmt, ap);
 483                 va_end(ap);
 484         }
 485         fp->fp_name = name;
 486         fp->fp_location = "";
 487         fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
 488         fp->fp_pre_sleep_fn = NULL;
 489         fp->fp_pre_sleep_arg = NULL;
 490         fp->fp_post_sleep_fn = NULL;
 491         fp->fp_post_sleep_arg = NULL;
 492 }
 493
 494 /**
 495  * Free the resources held by a fail_point, and wake any paused threads.
 496  * Thou shalt not allow threads to hit this fail point after you enter this
 497  * function, nor shall you call this multiple times for a given fp.
 498  * @ingroup failpoint
 499  */
 500 void
 501 fail_point_destroy(struct fail_point *fp)
 502 {
 503
 504         fail_point_drain(fp, 0);
 505
 506         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
 507                 fp_free(__DECONST(void *, fp->fp_name));
 508                 fp->fp_name = NULL;
 509         }
 510         fp->fp_flags = 0;
 511
 512         sx_xlock(&sx_fp_set);
 513         fail_point_garbage_collect();
 514         sx_xunlock(&sx_fp_set);
 515 }
 516
 517 /**
 518  * This does the real work of evaluating a fail point. If the fail point tells
 519  * us to return a value, this function returns 1 and fills in 'return_value'
 520  * (return_value is allowed to be null). If the fail point tells us to panic,
 521  * we never return. Otherwise we just return 0 after doing some work, which
 522  * means "keep going".
 523  */
 524 enum fail_point_return_code
 525 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
 526 {
 527         bool execute = false;
 528         struct fail_point_entry *ent;
 529         struct fail_point_setting *fp_setting;
 530         enum fail_point_return_code ret;
 531         int cont;
 532         int count;
 533         int msecs;
 534         int usecs;
 535
 536         ret = FAIL_POINT_RC_CONTINUE;
 537         cont = 0; /* don't continue by default */
 538
 539         fp_setting = fail_point_setting_get_ref(fp);
 540         if (fp_setting == NULL)
 541                 goto abort;
 542
 543         TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 544
 545                 if (ent->fe_stale)
 546                         continue;
 547
 548                 if (ent->fe_prob < PROB_MAX &&
 549                     ent->fe_prob < random() % PROB_MAX)
 550                         continue;
 551
 552                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
 553                         continue;
 554
 555                 if (ent->fe_count != FE_COUNT_UNTRACKED) {
 556                         count = ent->fe_count;
 557                         while (count > 0) {
 558                                 if (atomic_cmpset_32(&ent->fe_count, count, count - 1)) {
 559                                         count--;
 560                                         execute = true;
 561                                         break;
 562                                 }
 563                                 count = ent->fe_count;
 564                         }
 565                         if (execute == false)
 566                                 /* We lost the race; consider the entry stale and bail now */
 567                                 continue;
 568                         if (count == 0)
 569                                 ent->fe_stale = true;
 570                 }
 571
 572                 switch (ent->fe_type) {
 573                 case FAIL_POINT_PANIC:
 574                         panic("fail point %s panicking", fp->fp_name);
 575                         /* NOTREACHED */
 576
 577                 case FAIL_POINT_RETURN:
 578                         if (return_value != NULL)
 579                                 *return_value = ent->fe_arg;
 580                         ret = FAIL_POINT_RC_RETURN;
 581                         break;
 582
 583                 case FAIL_POINT_BREAK:
 584                         printf("fail point %s breaking to debugger\n",
 585                                 fp->fp_name);
 586                         breakpoint();
 587                         break;
 588
 589                 case FAIL_POINT_PRINT:
 590                         printf("fail point %s executing\n", fp->fp_name);
 591                         cont = ent->fe_arg;
 592                         break;
 593
 594                 case FAIL_POINT_SLEEP:
 595                         msecs = ent->fe_arg;
 596                         if (msecs)
 597                                 fail_point_sleep(fp, msecs, &ret);
 598                         break;
 599
 600                 case FAIL_POINT_PAUSE:
 601                         /**
 602                          * Pausing is inherently strange with multiple
 603                          * entries given our design.  That is because some
 604                          * entries could be unreachable, for instance in cases like:
 605                          * pause->return. We can never reach the return entry.
 606                          * The sysctl layer actually truncates all entries after
 607                          * a pause for this reason.
 608                          */
 609                         mtx_lock_spin(&fp_setting->feq_mtx);
 610                         fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
 611                         mtx_unlock_spin(&fp_setting->feq_mtx);
 612                         break;
 613
 614                 case FAIL_POINT_YIELD:
 615                         kern_yield(-1);
 616                         break;
 617
 618                 case FAIL_POINT_DELAY:
 619                         usecs = ent->fe_arg;
 620                         DELAY(usecs);
 621                         break;
 622
 623                 default:
 624                         break;
 625                 }
 626
 627                 if (cont == 0)
 628                         break;
 629         }
 630
 631         if (fail_point_is_off(fp))
 632                 fail_point_eval_swap_out(fp, fp_setting);
 633
 634 abort:
 635         fail_point_setting_release_ref(fp);
 636
 637         return (ret);
 638
 639 }
 640
 641 /**
 642  * Translate internal fail_point structure into human-readable text.
 643  */
 644 static void
 645 fail_point_get(struct fail_point *fp, struct sbuf *sb,
 646         bool verbose)
 647 {
 648         struct fail_point_entry *ent;
 649         struct fail_point_setting *fp_setting;
 650         struct fail_point_entry *fp_entry_cpy;
 651         int cnt_sleeping;
 652         int idx;
 653         int printed_entry_count;
 654
 655         cnt_sleeping = 0;
 656         idx = 0;
 657         printed_entry_count = 0;
 658
 659         fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
 660                 (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
 661
 662         fp_setting = fail_point_setting_get_ref(fp);
 663
 664         if (fp_setting != NULL) {
 665                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
 666                         if (ent->fe_stale)
 667                                 continue;
 668
 669                         KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
 670                                 ("FP entry list larger than allowed"));
 671
 672                         fp_entry_cpy[printed_entry_count] = *ent;
 673                         ++printed_entry_count;
 674                 }
 675         }
 676         fail_point_setting_release_ref(fp);
 677
 678         /* This is our equivalent of a NULL terminator */
 679         fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
 680
 681         while (idx < printed_entry_count) {
 682                 ent = &fp_entry_cpy[idx];
 683                 ++idx;
 684                 if (ent->fe_prob < PROB_MAX) {
 685                         int decimal = ent->fe_prob % (PROB_MAX / 100);
 686                         int units = ent->fe_prob / (PROB_MAX / 100);
 687                         sbuf_printf(sb, "%d", units);
 688                         if (decimal) {
 689                                 int digits = PROB_DIGITS - 2;
 690                                 while (!(decimal % 10)) {
 691                                         digits--;
 692                                         decimal /= 10;
 693                                 }
 694                                 sbuf_printf(sb, ".%0*d", digits, decimal);
 695                         }
 696                         sbuf_printf(sb, "%%");
 697                 }
 698                 if (ent->fe_count >= 0)
 699                         sbuf_printf(sb, "%d*", ent->fe_count);
 700                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
 701                 if (ent->fe_arg)
 702                         sbuf_printf(sb, "(%d)", ent->fe_arg);
 703                 if (ent->fe_pid != NO_PID)
 704                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
 705                 if (TAILQ_NEXT(ent, fe_entries))
 706                         sbuf_printf(sb, "->");
 707         }
 708         if (!printed_entry_count)
 709                 sbuf_printf(sb, "off");
 710
 711         fp_free(fp_entry_cpy);
 712         if (verbose) {
 713 #ifdef STACK
 714                 /* Print number of sleeping threads. queue=0 is the argument
 715                  * used by msleep when sending our threads to sleep. */
 716                 sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
 717                 sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
 718                         &cnt_sleeping);
 719
 720                 sbuf_printf(sb, "},\n");
 721 #endif
 722                 sbuf_printf(sb, "sleeping_thread_count = %d,\n",
 723                         cnt_sleeping);
 724
 725 #ifdef STACK
 726                 sbuf_printf(sb, "paused_thread_stacks = {\n");
 727                 sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
 728                         &cnt_sleeping);
 729
 730                 sbuf_printf(sb, "},\n");
 731 #endif
 732                 sbuf_printf(sb, "paused_thread_count = %d\n",
 733                         cnt_sleeping);
 734         }
 735 }
 736
 737 /**
 738  * Set an internal fail_point structure from a human-readable failpoint string
 739  * in a lock-safe manner.
 740  */
 741 static int
 742 fail_point_set(struct fail_point *fp, char *buf)
 743 {
 744         struct fail_point_entry *ent, *ent_next;
 745         struct fail_point_setting *entries;
 746         bool should_wake_paused;
 747         bool should_truncate;
 748         int error;
 749
 750         error = 0;
 751         should_wake_paused = false;
 752         should_truncate = false;
 753
 754         /* Parse new entries. */
 755         /**
 756          * ref protects our new malloc'd stuff from being garbage collected
 757          * before we link it.
 758          */
 759         fail_point_setting_get_ref(fp);
 760         entries = fail_point_setting_new(fp);
 761         if (parse_fail_point(entries, buf) == NULL) {
 762                 STAILQ_REMOVE(&fp_setting_garbage, entries,
 763                         fail_point_setting, fs_garbage_link);
 764                 fail_point_setting_destroy(entries);
 765                 error = EINVAL;
 766                 goto end;
 767         }
 768
 769         /**
 770          * Transfer the entries we are going to keep to a new list.
 771          * Get rid of useless zero probability entries, and entries with hit
 772          * count 0.
 773          * If 'off' is present, and it has no hit count set, then all entries
 774          *       after it are discarded since they are unreachable.
 775          */
 776         TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next) {
 777                 if (ent->fe_prob == 0 || ent->fe_count == 0) {
 778                         printf("Discarding entry which cannot execute %s\n",
 779                                 fail_type_strings[ent->fe_type].name);
 780                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 781                                 fe_entries);
 782                         fp_free(ent);
 783                         continue;
 784                 } else if (should_truncate) {
 785                         printf("Discarding unreachable entry %s\n",
 786                                 fail_type_strings[ent->fe_type].name);
 787                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 788                                 fe_entries);
 789                         fp_free(ent);
 790                         continue;
 791                 }
 792
 793                 if (ent->fe_type == FAIL_POINT_OFF) {
 794                         should_wake_paused = true;
 795                         if (ent->fe_count == FE_COUNT_UNTRACKED) {
 796                                 should_truncate = true;
 797                                 TAILQ_REMOVE(&entries->fp_entry_queue, ent,
 798                                         fe_entries);
 799                                 fp_free(ent);
 800                         }
 801                 } else if (ent->fe_type == FAIL_POINT_PAUSE) {
 802                         should_truncate = true;
 803                 } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
 804                         FAIL_POINT_NONSLEEPABLE)) {
 805                         /**
 806                          * If this fail point is annotated as being in a
 807                          * non-sleepable ctx, convert sleep to delay and
 808                          * convert the msec argument to usecs.
 809                          */
 810                         printf("Sleep call request on fail point in "
 811                                 "non-sleepable context; using delay instead "
 812                                 "of sleep\n");
 813                         ent->fe_type = FAIL_POINT_DELAY;
 814                         ent->fe_arg *= 1000;
 815                 }
 816         }
 817
 818         if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
 819                 entries = fail_point_swap_settings(fp, NULL);
 820                 if (entries != NULL)
 821                         wakeup(FP_PAUSE_CHANNEL(fp));
 822         } else {
 823                 if (should_wake_paused)
 824                         wakeup(FP_PAUSE_CHANNEL(fp));
 825                 fail_point_swap_settings(fp, entries);
 826         }
 827
 828 end:
 829 #ifdef IWARNING
 830         if (error)
 831                 IWARNING("Failed to set %s %s to %s",
 832                     fp->fp_name, fp->fp_location, buf);
 833         else
 834                 INOTICE("Set %s %s to %s",
 835                     fp->fp_name, fp->fp_location, buf);
 836 #endif /* IWARNING */
 837
 838         fail_point_setting_release_ref(fp);
 839         return (error);
 840 }
 841
 842 #define MAX_FAIL_POINT_BUF      1023
 843
 844 /**
 845  * Handle kernel failpoint set/get.
 846  */
 847
 848 int
 849 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
 850 {
 851         struct fail_point *fp;
 852         char *buf;
 853         struct sbuf *sb_check;
 854         struct sbuf sb;
 855         int error;
 856
 857         error = 0;
 858         fp = arg1;
 859         buf = NULL;
 860
 861         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 862         if (sb_check != &sb)
 863                 return (ENOMEM);
 864
 865         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 866
 867         /* Setting */
 868         /**
 869          * Lock protects any new entries from being garbage collected before we
 870          * can link them to the fail point.
 871          */
 872         sx_xlock(&sx_fp_set);
 873         if (req->newptr) {
 874                 if (req->newlen > MAX_FAIL_POINT_BUF) {
 875                         error = EINVAL;
 876                         goto out;
 877                 }
 878
 879                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
 880
 881                 error = SYSCTL_IN(req, buf, req->newlen);
 882                 if (error)
 883                         goto out;
 884                 buf[req->newlen] = '\0';
 885
 886                 error = fail_point_set(fp, buf);
 887         }
 888
 889         fail_point_garbage_collect();
 890         sx_xunlock(&sx_fp_set);
 891
 892         /* Retrieving. */
 893         fail_point_get(fp, &sb, false);
 894
 895 out:
 896         sbuf_finish(&sb);
 897         sbuf_delete(&sb);
 898
 899         if (buf)
 900                 fp_free(buf);
 901
 902         return (error);
 903 }
 904
 905 int
 906 fail_point_sysctl_status(SYSCTL_HANDLER_ARGS)
 907 {
 908         struct fail_point *fp;
 909         struct sbuf sb, *sb_check;
 910
 911         fp = arg1;
 912
 913         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
 914         if (sb_check != &sb)
 915                 return (ENOMEM);
 916
 917         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
 918
 919         /* Retrieving. */
 920         fail_point_get(fp, &sb, true);
 921
 922         sbuf_finish(&sb);
 923         sbuf_delete(&sb);
 924
 925         /**
 926          * Lock protects any new entries from being garbage collected before we
 927          * can link them to the fail point.
 928          */
 929         sx_xlock(&sx_fp_set);
 930         fail_point_garbage_collect();
 931         sx_xunlock(&sx_fp_set);
 932
 933         return (0);
 934 }
 935
 936 int
 937 fail_sysctl_drain_func(void *sysctl_args, const char *buf, int len)
 938 {
 939         struct sysctl_req *sa;
 940         int error;
 941
 942         sa = sysctl_args;
 943
 944         error = SYSCTL_OUT(sa, buf, len);
 945
 946         if (error == ENOMEM)
 947                 return (-1);
 948         else
 949                 return (len);
 950 }
 951
 952
 953 /**
 954  * Internal helper function to translate a human-readable failpoint string
 955  * into a internally-parsable fail_point structure.
 956  */
 957 static char *
 958 parse_fail_point(struct fail_point_setting *ents, char *p)
 959 {
 960         /*  <fail_point> ::
 961          *      <term> ( "->" <term> )*
 962          */
 963         uint8_t term_count;
 964
 965         term_count = 1;
 966
 967         p = parse_term(ents, p);
 968         if (p == NULL)
 969                 return (NULL);
 970
 971         while (*p != '\0') {
 972                 term_count++;
 973                 if (p[0] != '-' || p[1] != '>' ||
 974                         (p = parse_term(ents, p+2)) == NULL ||
 975                         term_count > FP_MAX_ENTRY_COUNT)
 976                         return (NULL);
 977         }
 978         return (p);
 979 }
 980
 981 /**
 982  * Internal helper function to parse an individual term from a failpoint.
 983  */
 984 static char *
 985 parse_term(struct fail_point_setting *ents, char *p)
 986 {
 987         struct fail_point_entry *ent;
 988
 989         ent = fail_point_entry_new(ents);
 990
 991         /*
 992          * <term> ::
 993          *     ( (<float> "%") | (<integer> "*" ) )*
 994          *     <type>
 995          *     [ "(" <integer> ")" ]
 996          *     [ "[pid " <integer> "]" ]
 997          */
 998
 999         /* ( (<float> "%") | (<integer> "*" ) )* */
1000         while (isdigit(*p) || *p == '.') {
1001                 int units, decimal;
1002
1003                 p = parse_number(&units, &decimal, p);
1004                 if (p == NULL)
1005                         return (NULL);
1006
1007                 if (*p == '%') {
1008                         if (units > 100) /* prevent overflow early */
1009                                 units = 100;
1010                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
1011                         if (ent->fe_prob > PROB_MAX)
1012                                 ent->fe_prob = PROB_MAX;
1013                 } else if (*p == '*') {
1014                         if (!units || units < 0 || decimal)
1015                                 return (NULL);
1016                         ent->fe_count = units;
1017                 } else
1018                         return (NULL);
1019                 p++;
1020         }
1021
1022         /* <type> */
1023         p = parse_type(ent, p);
1024         if (p == NULL)
1025                 return (NULL);
1026         if (*p == '\0')
1027                 return (p);
1028
1029         /* [ "(" <integer> ")" ] */
1030         if (*p != '(')
1031                 return (p);
1032         p++;
1033         if (!isdigit(*p) && *p != '-')
1034                 return (NULL);
1035         ent->fe_arg = strtol(p, &p, 0);
1036         if (*p++ != ')')
1037                 return (NULL);
1038
1039         /* [ "[pid " <integer> "]" ] */
1040 #define PID_STRING "[pid "
1041         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
1042                 return (p);
1043         p += sizeof(PID_STRING) - 1;
1044         if (!isdigit(*p))
1045                 return (NULL);
1046         ent->fe_pid = strtol(p, &p, 0);
1047         if (*p++ != ']')
1048                 return (NULL);
1049
1050         return (p);
1051 }
1052
1053 /**
1054  * Internal helper function to parse a numeric for a failpoint term.
1055  */
1056 static char *
1057 parse_number(int *out_units, int *out_decimal, char *p)
1058 {
1059         char *old_p;
1060
1061         /**
1062          *  <number> ::
1063          *      <integer> [ "." <integer> ] |
1064          *      "." <integer>
1065          */
1066
1067         /* whole part */
1068         old_p = p;
1069         *out_units = strtol(p, &p, 10);
1070         if (p == old_p && *p != '.')
1071                 return (NULL);
1072
1073         /* fractional part */
1074         *out_decimal = 0;
1075         if (*p == '.') {
1076                 int digits = 0;
1077                 p++;
1078                 while (isdigit(*p)) {
1079                         int digit = *p - '0';
1080                         if (digits < PROB_DIGITS - 2)
1081                                 *out_decimal = *out_decimal * 10 + digit;
1082                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
1083                                 (*out_decimal)++;
1084                         digits++;
1085                         p++;
1086                 }
1087                 if (!digits) /* need at least one digit after '.' */
1088                         return (NULL);
1089                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
1090                         *out_decimal *= 10;
1091         }
1092
1093         return (p); /* success */
1094 }
1095
1096 /**
1097  * Internal helper function to parse an individual type for a failpoint term.
1098  */
1099 static char *
1100 parse_type(struct fail_point_entry *ent, char *beg)
1101 {
1102         enum fail_point_t type;
1103         int len;
1104
1105         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
1106                 len = fail_type_strings[type].nmlen;
1107                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
1108                         ent->fe_type = type;
1109                         return (beg + len);
1110                 }
1111         }
1112         return (NULL);
1113 }
1114
1115 /* The fail point sysctl tree. */
1116 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
1117
1118 /* Debugging/testing stuff for fail point */
1119 static int
1120 sysctl_test_fail_point(SYSCTL_HANDLER_ARGS)
1121 {
1122
1123         KFAIL_POINT_RETURN(DEBUG_FP, test_fail_point);
1124         return (0);
1125 }
1126 SYSCTL_OID(_debug_fail_point, OID_AUTO, test_trigger_fail_point,
1127         CTLTYPE_STRING | CTLFLAG_RD, NULL, 0, sysctl_test_fail_point, "A",
1128         "Trigger test fail points");