The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fail.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    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 __FBSDID("$FreeBSD: stable/12/sys/kern/kern_fail.c 326271 2017-11-27 15:20:12Z pfg $");
   56 
   57 #include "opt_stack.h"
   58 
   59 #include <sys/ctype.h>
   60 #include <sys/errno.h>
   61 #include <sys/fail.h>
   62 #include <sys/kernel.h>
   63 #include <sys/libkern.h>
   64 #include <sys/limits.h>
   65 #include <sys/lock.h>
   66 #include <sys/malloc.h>
   67 #include <sys/mutex.h>
   68 #include <sys/proc.h>
   69 #include <sys/sbuf.h>
   70 #include <sys/sleepqueue.h>
   71 #include <sys/sx.h>
   72 #include <sys/sysctl.h>
   73 #include <sys/types.h>
   74 
   75 #include <machine/atomic.h>
   76 #include <machine/stdarg.h>
   77 
   78 #ifdef ILOG_DEFINE_FOR_FILE
   79 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
   80 #endif
   81 
   82 static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
   83 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
   84 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
   85 #define fs_free(ptr) fp_free(ptr)
   86 #define fs_malloc() fp_malloc(sizeof(struct fail_point_setting), \
   87     M_WAITOK | M_ZERO)
   88 
   89 /**
   90  * These define the wchans that are used for sleeping, pausing respectively.
   91  * They are chosen arbitrarily but need to be distinct to the failpoint and
   92  * the sleep/pause distinction.
   93  */
   94 #define FP_SLEEP_CHANNEL(fp) (void*)(fp)
   95 #define FP_PAUSE_CHANNEL(fp) __DEVOLATILE(void*, &fp->fp_setting)
   96 
   97 /**
   98  * Don't allow more than this many entries in a fail point set by sysctl.
   99  * The 99.99...% case is to have 1 entry.  I can't imagine having this many
  100  * entries, so it should not limit us.  Saves on re-mallocs while holding
  101  * a non-sleepable lock.
  102  */
  103 #define FP_MAX_ENTRY_COUNT 20
  104 
  105 /* Used to drain sbufs to the sysctl output */
  106 int fail_sysctl_drain_func(void *, const char *, int);
  107 
  108 /* Head of tailq of struct fail_point_entry */
  109 TAILQ_HEAD(fail_point_entry_queue, fail_point_entry);
  110 
  111 /**
  112  * fp entries garbage list; outstanding entries are cleaned up in the
  113  * garbage collector
  114  */
  115 STAILQ_HEAD(fail_point_setting_garbage, fail_point_setting);
  116 static struct fail_point_setting_garbage fp_setting_garbage =
  117         STAILQ_HEAD_INITIALIZER(fp_setting_garbage);
  118 static struct mtx mtx_garbage_list;
  119 MTX_SYSINIT(mtx_garbage_list, &mtx_garbage_list, "fail point garbage mtx",
  120         MTX_SPIN);
  121 
  122 static struct sx sx_fp_set;
  123 SX_SYSINIT(sx_fp_set, &sx_fp_set, "fail point set sx");
  124 
  125 /**
  126  * Failpoint types.
  127  * Don't change these without changing fail_type_strings in fail.c.
  128  * @ingroup failpoint_private
  129  */
  130 enum fail_point_t {
  131         FAIL_POINT_OFF,         /**< don't fail */
  132         FAIL_POINT_PANIC,       /**< panic */
  133         FAIL_POINT_RETURN,      /**< return an errorcode */
  134         FAIL_POINT_BREAK,       /**< break into the debugger */
  135         FAIL_POINT_PRINT,       /**< print a message */
  136         FAIL_POINT_SLEEP,       /**< sleep for some msecs */
  137         FAIL_POINT_PAUSE,       /**< sleep until failpoint is set to off */
  138         FAIL_POINT_YIELD,       /**< yield the cpu */
  139         FAIL_POINT_DELAY,       /**< busy wait the cpu */
  140         FAIL_POINT_NUMTYPES,
  141         FAIL_POINT_INVALID = -1
  142 };
  143 
  144 static struct {
  145         const char *name;
  146         int     nmlen;
  147 } fail_type_strings[] = {
  148 #define FP_TYPE_NM_LEN(s)       { s, sizeof(s) - 1 }
  149         [FAIL_POINT_OFF] =      FP_TYPE_NM_LEN("off"),
  150         [FAIL_POINT_PANIC] =    FP_TYPE_NM_LEN("panic"),
  151         [FAIL_POINT_RETURN] =   FP_TYPE_NM_LEN("return"),
  152         [FAIL_POINT_BREAK] =    FP_TYPE_NM_LEN("break"),
  153         [FAIL_POINT_PRINT] =    FP_TYPE_NM_LEN("print"),
  154         [FAIL_POINT_SLEEP] =    FP_TYPE_NM_LEN("sleep"),
  155         [FAIL_POINT_PAUSE] =    FP_TYPE_NM_LEN("pause"),
  156         [FAIL_POINT_YIELD] =    FP_TYPE_NM_LEN("yield"),
  157         [FAIL_POINT_DELAY] =    FP_TYPE_NM_LEN("delay"),
  158 };
  159 
  160 #define FE_COUNT_UNTRACKED (INT_MIN)
  161 
  162 /**
  163  * Internal structure tracking a single term of a complete failpoint.
  164  * @ingroup failpoint_private
  165  */
  166 struct fail_point_entry {
  167         volatile bool   fe_stale;
  168         enum fail_point_t       fe_type;        /**< type of entry */
  169         int             fe_arg;         /**< argument to type (e.g. return value) */
  170         int             fe_prob;        /**< likelihood of firing in millionths */
  171         int32_t         fe_count;       /**< number of times to fire, -1 means infinite */
  172         pid_t           fe_pid;         /**< only fail for this process */
  173         struct fail_point       *fe_parent;     /**< backpointer to fp */
  174         TAILQ_ENTRY(fail_point_entry)   fe_entries; /**< next entry ptr */
  175 };
  176 
  177 struct fail_point_setting {
  178         STAILQ_ENTRY(fail_point_setting) fs_garbage_link;
  179         struct fail_point_entry_queue fp_entry_queue;
  180         struct fail_point * fs_parent;
  181         struct mtx feq_mtx; /* Gives fail_point_pause something to do.  */
  182 };
  183 
  184 /**
  185  * Defines stating the equivalent of probablilty one (100%)
  186  */
  187 enum {
  188         PROB_MAX = 1000000,     /* probability between zero and this number */
  189         PROB_DIGITS = 6         /* number of zero's in above number */
  190 };
  191 
  192 /* Get a ref on an fp's fp_setting */
  193 static inline struct fail_point_setting *fail_point_setting_get_ref(
  194         struct fail_point *fp);
  195 /* Release a ref on an fp_setting */
  196 static inline void fail_point_setting_release_ref(struct fail_point *fp);
  197 /* Allocate and initialize a struct fail_point_setting */
  198 static struct fail_point_setting *fail_point_setting_new(struct
  199         fail_point *);
  200 /* Free a struct fail_point_setting */
  201 static void fail_point_setting_destroy(struct fail_point_setting *fp_setting);
  202 /* Allocate and initialize a struct fail_point_entry */
  203 static struct fail_point_entry *fail_point_entry_new(struct
  204         fail_point_setting *);
  205 /* Free a struct fail_point_entry */
  206 static void fail_point_entry_destroy(struct fail_point_entry *fp_entry);
  207 /* Append fp setting to garbage list */
  208 static inline void fail_point_setting_garbage_append(
  209         struct fail_point_setting *fp_setting);
  210 /* Swap fp's setting with fp_setting_new */
  211 static inline struct fail_point_setting *
  212         fail_point_swap_settings(struct fail_point *fp,
  213         struct fail_point_setting *fp_setting_new);
  214 /* Free up any zero-ref setting in the garbage queue */
  215 static void fail_point_garbage_collect(void);
  216 /* If this fail point's setting are empty, then swap it out to NULL. */
  217 static inline void fail_point_eval_swap_out(struct fail_point *fp,
  218         struct fail_point_setting *fp_setting);
  219 
  220 bool
  221 fail_point_is_off(struct fail_point *fp)
  222 {
  223         bool return_val;
  224         struct fail_point_setting *fp_setting;
  225         struct fail_point_entry *ent;
  226 
  227         return_val = true;
  228 
  229         fp_setting = fail_point_setting_get_ref(fp);
  230         if (fp_setting != NULL) {
  231                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue,
  232                     fe_entries) {
  233                         if (!ent->fe_stale) {
  234                                 return_val = false;
  235                                 break;
  236                         }
  237                 }
  238         }
  239         fail_point_setting_release_ref(fp);
  240 
  241         return (return_val);
  242 }
  243 
  244 /* Allocate and initialize a struct fail_point_setting */
  245 static struct fail_point_setting *
  246 fail_point_setting_new(struct fail_point *fp)
  247 {
  248         struct fail_point_setting *fs_new;
  249 
  250         fs_new = fs_malloc();
  251         fs_new->fs_parent = fp;
  252         TAILQ_INIT(&fs_new->fp_entry_queue);
  253         mtx_init(&fs_new->feq_mtx, "fail point entries", NULL, MTX_SPIN);
  254 
  255         fail_point_setting_garbage_append(fs_new);
  256 
  257         return (fs_new);
  258 }
  259 
  260 /* Free a struct fail_point_setting */
  261 static void
  262 fail_point_setting_destroy(struct fail_point_setting *fp_setting)
  263 {
  264         struct fail_point_entry *ent;
  265 
  266         while (!TAILQ_EMPTY(&fp_setting->fp_entry_queue)) {
  267                 ent = TAILQ_FIRST(&fp_setting->fp_entry_queue);
  268                 TAILQ_REMOVE(&fp_setting->fp_entry_queue, ent, fe_entries);
  269                 fail_point_entry_destroy(ent);
  270         }
  271 
  272         fs_free(fp_setting);
  273 }
  274 
  275 /* Allocate and initialize a struct fail_point_entry */
  276 static struct fail_point_entry *
  277 fail_point_entry_new(struct fail_point_setting *fp_setting)
  278 {
  279         struct fail_point_entry *fp_entry;
  280 
  281         fp_entry = fp_malloc(sizeof(struct fail_point_entry),
  282                 M_WAITOK | M_ZERO);
  283         fp_entry->fe_parent = fp_setting->fs_parent;
  284         fp_entry->fe_prob = PROB_MAX;
  285         fp_entry->fe_pid = NO_PID;
  286         fp_entry->fe_count = FE_COUNT_UNTRACKED;
  287         TAILQ_INSERT_TAIL(&fp_setting->fp_entry_queue, fp_entry,
  288                 fe_entries);
  289 
  290         return (fp_entry);
  291 }
  292 
  293 /* Free a struct fail_point_entry */
  294 static void
  295 fail_point_entry_destroy(struct fail_point_entry *fp_entry)
  296 {
  297 
  298         fp_free(fp_entry);
  299 }
  300 
  301 /* Get a ref on an fp's fp_setting */
  302 static inline struct fail_point_setting *
  303 fail_point_setting_get_ref(struct fail_point *fp)
  304 {
  305         struct fail_point_setting *fp_setting;
  306 
  307         /* Invariant: if we have a ref, our pointer to fp_setting is safe */
  308         atomic_add_acq_32(&fp->fp_ref_cnt, 1);
  309         fp_setting = fp->fp_setting;
  310 
  311         return (fp_setting);
  312 }
  313 
  314 /* Release a ref on an fp_setting */
  315 static inline void
  316 fail_point_setting_release_ref(struct fail_point *fp)
  317 {
  318 
  319         KASSERT(&fp->fp_ref_cnt > 0, ("Attempting to deref w/no refs"));
  320         atomic_subtract_rel_32(&fp->fp_ref_cnt, 1);
  321 }
  322 
  323 /* Append fp entries to fp garbage list */
  324 static inline void
  325 fail_point_setting_garbage_append(struct fail_point_setting *fp_setting)
  326 {
  327 
  328         mtx_lock_spin(&mtx_garbage_list);
  329         STAILQ_INSERT_TAIL(&fp_setting_garbage, fp_setting,
  330                 fs_garbage_link);
  331         mtx_unlock_spin(&mtx_garbage_list);
  332 }
  333 
  334 /* Swap fp's entries with fp_setting_new */
  335 static struct fail_point_setting *
  336 fail_point_swap_settings(struct fail_point *fp,
  337         struct fail_point_setting *fp_setting_new)
  338 {
  339         struct fail_point_setting *fp_setting_old;
  340 
  341         fp_setting_old = fp->fp_setting;
  342         fp->fp_setting = fp_setting_new;
  343 
  344         return (fp_setting_old);
  345 }
  346 
  347 static inline void
  348 fail_point_eval_swap_out(struct fail_point *fp,
  349         struct fail_point_setting *fp_setting)
  350 {
  351 
  352         /* We may have already been swapped out and replaced; ignore. */
  353         if (fp->fp_setting == fp_setting)
  354                 fail_point_swap_settings(fp, NULL);
  355 }
  356 
  357 /* Free up any zero-ref entries in the garbage queue */
  358 static void
  359 fail_point_garbage_collect(void)
  360 {
  361         struct fail_point_setting *fs_current, *fs_next;
  362         struct fail_point_setting_garbage fp_ents_free_list;
  363 
  364         /**
  365           * We will transfer the entries to free to fp_ents_free_list while holding
  366           * the spin mutex, then free it after we drop the lock. This avoids
  367           * triggering witness due to sleepable mutexes in the memory
  368           * allocator.
  369           */
  370         STAILQ_INIT(&fp_ents_free_list);
  371 
  372         mtx_lock_spin(&mtx_garbage_list);
  373         STAILQ_FOREACH_SAFE(fs_current, &fp_setting_garbage, fs_garbage_link,
  374             fs_next) {
  375                 if (fs_current->fs_parent->fp_setting != fs_current &&
  376                         fs_current->fs_parent->fp_ref_cnt == 0) {
  377                         STAILQ_REMOVE(&fp_setting_garbage, fs_current,
  378                                 fail_point_setting, fs_garbage_link);
  379                         STAILQ_INSERT_HEAD(&fp_ents_free_list, fs_current,
  380                                 fs_garbage_link);
  381                 }
  382         }
  383         mtx_unlock_spin(&mtx_garbage_list);
  384 
  385         STAILQ_FOREACH_SAFE(fs_current, &fp_ents_free_list, fs_garbage_link,
  386                 fs_next)
  387                 fail_point_setting_destroy(fs_current);
  388 }
  389 
  390 /* Drain out all refs from this fail point */
  391 static inline void
  392 fail_point_drain(struct fail_point *fp, int expected_ref)
  393 {
  394         struct fail_point_setting *entries;
  395 
  396         entries = fail_point_swap_settings(fp, NULL);
  397         /**
  398          * We have unpaused all threads; so we will wait no longer
  399          * than the time taken for the longest remaining sleep, or
  400          * the length of time of a long-running code block.
  401          */
  402         while (fp->fp_ref_cnt > expected_ref) {
  403                 wakeup(FP_PAUSE_CHANNEL(fp));
  404                 tsleep(&fp, PWAIT, "fail_point_drain", hz / 100);
  405         }
  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                         timeout(fp->fp_post_sleep_fn, fp->fp_post_sleep_arg,
  446                             timo);
  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 /**
  497  * Free the resources held by a fail_point, and wake any paused threads.
  498  * Thou shalt not allow threads to hit this fail point after you enter this
  499  * function, nor shall you call this multiple times for a given fp.
  500  * @ingroup failpoint
  501  */
  502 void
  503 fail_point_destroy(struct fail_point *fp)
  504 {
  505 
  506         fail_point_drain(fp, 0);
  507 
  508         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
  509                 fp_free(__DECONST(void *, fp->fp_name));
  510                 fp->fp_name = NULL;
  511         }
  512         fp->fp_flags = 0;
  513 
  514         sx_xlock(&sx_fp_set);
  515         fail_point_garbage_collect();
  516         sx_xunlock(&sx_fp_set);
  517 }
  518 
  519 /**
  520  * This does the real work of evaluating a fail point. If the fail point tells
  521  * us to return a value, this function returns 1 and fills in 'return_value'
  522  * (return_value is allowed to be null). If the fail point tells us to panic,
  523  * we never return. Otherwise we just return 0 after doing some work, which
  524  * means "keep going".
  525  */
  526 enum fail_point_return_code
  527 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
  528 {
  529         bool execute = false;
  530         struct fail_point_entry *ent;
  531         struct fail_point_setting *fp_setting;
  532         enum fail_point_return_code ret;
  533         int cont;
  534         int count;
  535         int msecs;
  536         int usecs;
  537 
  538         ret = FAIL_POINT_RC_CONTINUE;
  539         cont = 0; /* don't continue by default */
  540 
  541         fp_setting = fail_point_setting_get_ref(fp);
  542         if (fp_setting == NULL)
  543                 goto abort;
  544 
  545         TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
  546 
  547                 if (ent->fe_stale)
  548                         continue;
  549 
  550                 if (ent->fe_prob < PROB_MAX &&
  551                     ent->fe_prob < random() % PROB_MAX)
  552                         continue;
  553 
  554                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
  555                         continue;
  556 
  557                 if (ent->fe_count != FE_COUNT_UNTRACKED) {
  558                         count = ent->fe_count;
  559                         while (count > 0) {
  560                                 if (atomic_cmpset_32(&ent->fe_count, count, count - 1)) {
  561                                         count--;
  562                                         execute = true;
  563                                         break;
  564                                 }
  565                                 count = ent->fe_count;
  566                         }
  567                         if (execute == false)
  568                                 /* We lost the race; consider the entry stale and bail now */
  569                                 continue;
  570                         if (count == 0)
  571                                 ent->fe_stale = true;
  572                 }
  573 
  574                 switch (ent->fe_type) {
  575                 case FAIL_POINT_PANIC:
  576                         panic("fail point %s panicking", fp->fp_name);
  577                         /* NOTREACHED */
  578 
  579                 case FAIL_POINT_RETURN:
  580                         if (return_value != NULL)
  581                                 *return_value = ent->fe_arg;
  582                         ret = FAIL_POINT_RC_RETURN;
  583                         break;
  584 
  585                 case FAIL_POINT_BREAK:
  586                         printf("fail point %s breaking to debugger\n",
  587                                 fp->fp_name);
  588                         breakpoint();
  589                         break;
  590 
  591                 case FAIL_POINT_PRINT:
  592                         printf("fail point %s executing\n", fp->fp_name);
  593                         cont = ent->fe_arg;
  594                         break;
  595 
  596                 case FAIL_POINT_SLEEP:
  597                         msecs = ent->fe_arg;
  598                         if (msecs)
  599                                 fail_point_sleep(fp, msecs, &ret);
  600                         break;
  601 
  602                 case FAIL_POINT_PAUSE:
  603                         /**
  604                          * Pausing is inherently strange with multiple
  605                          * entries given our design.  That is because some
  606                          * entries could be unreachable, for instance in cases like:
  607                          * pause->return. We can never reach the return entry.
  608                          * The sysctl layer actually truncates all entries after
  609                          * a pause for this reason.
  610                          */
  611                         mtx_lock_spin(&fp_setting->feq_mtx);
  612                         fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
  613                         mtx_unlock_spin(&fp_setting->feq_mtx);
  614                         break;
  615 
  616                 case FAIL_POINT_YIELD:
  617                         kern_yield(PRI_UNCHANGED);
  618                         break;
  619 
  620                 case FAIL_POINT_DELAY:
  621                         usecs = ent->fe_arg;
  622                         DELAY(usecs);
  623                         break;
  624 
  625                 default:
  626                         break;
  627                 }
  628 
  629                 if (cont == 0)
  630                         break;
  631         }
  632 
  633         if (fail_point_is_off(fp))
  634                 fail_point_eval_swap_out(fp, fp_setting);
  635 
  636 abort:
  637         fail_point_setting_release_ref(fp);
  638 
  639         return (ret);
  640 }
  641 
  642 /**
  643  * Translate internal fail_point structure into human-readable text.
  644  */
  645 static void
  646 fail_point_get(struct fail_point *fp, struct sbuf *sb,
  647         bool verbose)
  648 {
  649         struct fail_point_entry *ent;
  650         struct fail_point_setting *fp_setting;
  651         struct fail_point_entry *fp_entry_cpy;
  652         int cnt_sleeping;
  653         int idx;
  654         int printed_entry_count;
  655 
  656         cnt_sleeping = 0;
  657         idx = 0;
  658         printed_entry_count = 0;
  659 
  660         fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
  661                 (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
  662 
  663         fp_setting = fail_point_setting_get_ref(fp);
  664 
  665         if (fp_setting != NULL) {
  666                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
  667                         if (ent->fe_stale)
  668                                 continue;
  669 
  670                         KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
  671                                 ("FP entry list larger than allowed"));
  672 
  673                         fp_entry_cpy[printed_entry_count] = *ent;
  674                         ++printed_entry_count;
  675                 }
  676         }
  677         fail_point_setting_release_ref(fp);
  678 
  679         /* This is our equivalent of a NULL terminator */
  680         fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
  681 
  682         while (idx < printed_entry_count) {
  683                 ent = &fp_entry_cpy[idx];
  684                 ++idx;
  685                 if (ent->fe_prob < PROB_MAX) {
  686                         int decimal = ent->fe_prob % (PROB_MAX / 100);
  687                         int units = ent->fe_prob / (PROB_MAX / 100);
  688                         sbuf_printf(sb, "%d", units);
  689                         if (decimal) {
  690                                 int digits = PROB_DIGITS - 2;
  691                                 while (!(decimal % 10)) {
  692                                         digits--;
  693                                         decimal /= 10;
  694                                 }
  695                                 sbuf_printf(sb, ".%0*d", digits, decimal);
  696                         }
  697                         sbuf_printf(sb, "%%");
  698                 }
  699                 if (ent->fe_count >= 0)
  700                         sbuf_printf(sb, "%d*", ent->fe_count);
  701                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
  702                 if (ent->fe_arg)
  703                         sbuf_printf(sb, "(%d)", ent->fe_arg);
  704                 if (ent->fe_pid != NO_PID)
  705                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
  706                 if (TAILQ_NEXT(ent, fe_entries))
  707                         sbuf_printf(sb, "->");
  708         }
  709         if (!printed_entry_count)
  710                 sbuf_printf(sb, "off");
  711 
  712         fp_free(fp_entry_cpy);
  713         if (verbose) {
  714 #ifdef STACK
  715                 /* Print number of sleeping threads. queue=0 is the argument
  716                  * used by msleep when sending our threads to sleep. */
  717                 sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
  718                 sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
  719                         &cnt_sleeping);
  720 
  721                 sbuf_printf(sb, "},\n");
  722 #endif
  723                 sbuf_printf(sb, "sleeping_thread_count = %d,\n",
  724                         cnt_sleeping);
  725 
  726 #ifdef STACK
  727                 sbuf_printf(sb, "paused_thread_stacks = {\n");
  728                 sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
  729                         &cnt_sleeping);
  730 
  731                 sbuf_printf(sb, "},\n");
  732 #endif
  733                 sbuf_printf(sb, "paused_thread_count = %d\n",
  734                         cnt_sleeping);
  735         }
  736 }
  737 
  738 /**
  739  * Set an internal fail_point structure from a human-readable failpoint string
  740  * in a lock-safe manner.
  741  */
  742 static int
  743 fail_point_set(struct fail_point *fp, char *buf)
  744 {
  745         struct fail_point_entry *ent, *ent_next;
  746         struct fail_point_setting *entries;
  747         bool should_wake_paused;
  748         bool should_truncate;
  749         int error;
  750 
  751         error = 0;
  752         should_wake_paused = false;
  753         should_truncate = false;
  754 
  755         /* Parse new entries. */
  756         /**
  757          * ref protects our new malloc'd stuff from being garbage collected
  758          * before we link it.
  759          */
  760         fail_point_setting_get_ref(fp);
  761         entries = fail_point_setting_new(fp);
  762         if (parse_fail_point(entries, buf) == NULL) {
  763                 STAILQ_REMOVE(&fp_setting_garbage, entries,
  764                         fail_point_setting, fs_garbage_link);
  765                 fail_point_setting_destroy(entries);
  766                 error = EINVAL;
  767                 goto end;
  768         }
  769 
  770         /**
  771          * Transfer the entries we are going to keep to a new list.
  772          * Get rid of useless zero probability entries, and entries with hit
  773          * count 0.
  774          * If 'off' is present, and it has no hit count set, then all entries
  775          *       after it are discarded since they are unreachable.
  776          */
  777         TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next) {
  778                 if (ent->fe_prob == 0 || ent->fe_count == 0) {
  779                         printf("Discarding entry which cannot execute %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                 } else if (should_truncate) {
  786                         printf("Discarding unreachable entry %s\n",
  787                                 fail_type_strings[ent->fe_type].name);
  788                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
  789                                 fe_entries);
  790                         fp_free(ent);
  791                         continue;
  792                 }
  793 
  794                 if (ent->fe_type == FAIL_POINT_OFF) {
  795                         should_wake_paused = true;
  796                         if (ent->fe_count == FE_COUNT_UNTRACKED) {
  797                                 should_truncate = true;
  798                                 TAILQ_REMOVE(&entries->fp_entry_queue, ent,
  799                                         fe_entries);
  800                                 fp_free(ent);
  801                         }
  802                 } else if (ent->fe_type == FAIL_POINT_PAUSE) {
  803                         should_truncate = true;
  804                 } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
  805                         FAIL_POINT_NONSLEEPABLE)) {
  806                         /**
  807                          * If this fail point is annotated as being in a
  808                          * non-sleepable ctx, convert sleep to delay and
  809                          * convert the msec argument to usecs.
  810                          */
  811                         printf("Sleep call request on fail point in "
  812                                 "non-sleepable context; using delay instead "
  813                                 "of sleep\n");
  814                         ent->fe_type = FAIL_POINT_DELAY;
  815                         ent->fe_arg *= 1000;
  816                 }
  817         }
  818 
  819         if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
  820                 entries = fail_point_swap_settings(fp, NULL);
  821                 if (entries != NULL)
  822                         wakeup(FP_PAUSE_CHANNEL(fp));
  823         } else {
  824                 if (should_wake_paused)
  825                         wakeup(FP_PAUSE_CHANNEL(fp));
  826                 fail_point_swap_settings(fp, entries);
  827         }
  828 
  829 end:
  830 #ifdef IWARNING
  831         if (error)
  832                 IWARNING("Failed to set %s %s to %s",
  833                     fp->fp_name, fp->fp_location, buf);
  834         else
  835                 INOTICE("Set %s %s to %s",
  836                     fp->fp_name, fp->fp_location, buf);
  837 #endif /* IWARNING */
  838 
  839         fail_point_setting_release_ref(fp);
  840         return (error);
  841 }
  842 
  843 #define MAX_FAIL_POINT_BUF      1023
  844 
  845 /**
  846  * Handle kernel failpoint set/get.
  847  */
  848 int
  849 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
  850 {
  851         struct fail_point *fp;
  852         char *buf;
  853         struct sbuf sb, *sb_check;
  854         int error;
  855 
  856         buf = NULL;
  857         error = 0;
  858         fp = arg1;
  859 
  860         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
  861         if (sb_check != &sb)
  862                 return (ENOMEM);
  863 
  864         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
  865 
  866         /* Setting */
  867         /**
  868          * Lock protects any new entries from being garbage collected before we
  869          * can link them to the fail point.
  870          */
  871         sx_xlock(&sx_fp_set);
  872         if (req->newptr) {
  873                 if (req->newlen > MAX_FAIL_POINT_BUF) {
  874                         error = EINVAL;
  875                         goto out;
  876                 }
  877 
  878                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
  879 
  880                 error = SYSCTL_IN(req, buf, req->newlen);
  881                 if (error)
  882                         goto out;
  883                 buf[req->newlen] = '\0';
  884 
  885                 error = fail_point_set(fp, buf);
  886         }
  887 
  888         fail_point_garbage_collect();
  889         sx_xunlock(&sx_fp_set);
  890 
  891         /* Retrieving. */
  892         fail_point_get(fp, &sb, false);
  893 
  894 out:
  895         sbuf_finish(&sb);
  896         sbuf_delete(&sb);
  897 
  898         if (buf)
  899                 fp_free(buf);
  900 
  901         return (error);
  902 }
  903 
  904 int
  905 fail_point_sysctl_status(SYSCTL_HANDLER_ARGS)
  906 {
  907         struct fail_point *fp;
  908         struct sbuf sb, *sb_check;
  909 
  910         fp = arg1;
  911 
  912         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
  913         if (sb_check != &sb)
  914                 return (ENOMEM);
  915 
  916         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
  917 
  918         /* Retrieving. */
  919         fail_point_get(fp, &sb, true);
  920 
  921         sbuf_finish(&sb);
  922         sbuf_delete(&sb);
  923 
  924         /**
  925          * Lock protects any new entries from being garbage collected before we
  926          * can link them to the fail point.
  927          */
  928         sx_xlock(&sx_fp_set);
  929         fail_point_garbage_collect();
  930         sx_xunlock(&sx_fp_set);
  931 
  932         return (0);
  933 }
  934 
  935 int
  936 fail_sysctl_drain_func(void *sysctl_args, const char *buf, int len)
  937 {
  938         struct sysctl_req *sa;
  939         int error;
  940 
  941         sa = sysctl_args;
  942 
  943         error = SYSCTL_OUT(sa, buf, len);
  944 
  945         if (error == ENOMEM)
  946                 return (-1);
  947         else
  948                 return (len);
  949 }
  950 
  951 /**
  952  * Internal helper function to translate a human-readable failpoint string
  953  * into a internally-parsable fail_point structure.
  954  */
  955 static char *
  956 parse_fail_point(struct fail_point_setting *ents, char *p)
  957 {
  958         /*  <fail_point> ::
  959          *      <term> ( "->" <term> )*
  960          */
  961         uint8_t term_count;
  962 
  963         term_count = 1;
  964 
  965         p = parse_term(ents, p);
  966         if (p == NULL)
  967                 return (NULL);
  968 
  969         while (*p != '\0') {
  970                 term_count++;
  971                 if (p[0] != '-' || p[1] != '>' ||
  972                         (p = parse_term(ents, p+2)) == NULL ||
  973                         term_count > FP_MAX_ENTRY_COUNT)
  974                         return (NULL);
  975         }
  976         return (p);
  977 }
  978 
  979 /**
  980  * Internal helper function to parse an individual term from a failpoint.
  981  */
  982 static char *
  983 parse_term(struct fail_point_setting *ents, char *p)
  984 {
  985         struct fail_point_entry *ent;
  986 
  987         ent = fail_point_entry_new(ents);
  988 
  989         /*
  990          * <term> ::
  991          *     ( (<float> "%") | (<integer> "*" ) )*
  992          *     <type>
  993          *     [ "(" <integer> ")" ]
  994          *     [ "[pid " <integer> "]" ]
  995          */
  996 
  997         /* ( (<float> "%") | (<integer> "*" ) )* */
  998         while (isdigit(*p) || *p == '.') {
  999                 int units, decimal;
 1000 
 1001                 p = parse_number(&units, &decimal, p);
 1002                 if (p == NULL)
 1003                         return (NULL);
 1004 
 1005                 if (*p == '%') {
 1006                         if (units > 100) /* prevent overflow early */
 1007                                 units = 100;
 1008                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
 1009                         if (ent->fe_prob > PROB_MAX)
 1010                                 ent->fe_prob = PROB_MAX;
 1011                 } else if (*p == '*') {
 1012                         if (!units || units < 0 || decimal)
 1013                                 return (NULL);
 1014                         ent->fe_count = units;
 1015                 } else
 1016                         return (NULL);
 1017                 p++;
 1018         }
 1019 
 1020         /* <type> */
 1021         p = parse_type(ent, p);
 1022         if (p == NULL)
 1023                 return (NULL);
 1024         if (*p == '\0')
 1025                 return (p);
 1026 
 1027         /* [ "(" <integer> ")" ] */
 1028         if (*p != '(')
 1029                 return (p);
 1030         p++;
 1031         if (!isdigit(*p) && *p != '-')
 1032                 return (NULL);
 1033         ent->fe_arg = strtol(p, &p, 0);
 1034         if (*p++ != ')')
 1035                 return (NULL);
 1036 
 1037         /* [ "[pid " <integer> "]" ] */
 1038 #define PID_STRING "[pid "
 1039         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
 1040                 return (p);
 1041         p += sizeof(PID_STRING) - 1;
 1042         if (!isdigit(*p))
 1043                 return (NULL);
 1044         ent->fe_pid = strtol(p, &p, 0);
 1045         if (*p++ != ']')
 1046                 return (NULL);
 1047 
 1048         return (p);
 1049 }
 1050 
 1051 /**
 1052  * Internal helper function to parse a numeric for a failpoint term.
 1053  */
 1054 static char *
 1055 parse_number(int *out_units, int *out_decimal, char *p)
 1056 {
 1057         char *old_p;
 1058 
 1059         /**
 1060          *  <number> ::
 1061          *      <integer> [ "." <integer> ] |
 1062          *      "." <integer>
 1063          */
 1064 
 1065         /* whole part */
 1066         old_p = p;
 1067         *out_units = strtol(p, &p, 10);
 1068         if (p == old_p && *p != '.')
 1069                 return (NULL);
 1070 
 1071         /* fractional part */
 1072         *out_decimal = 0;
 1073         if (*p == '.') {
 1074                 int digits = 0;
 1075                 p++;
 1076                 while (isdigit(*p)) {
 1077                         int digit = *p - '';
 1078                         if (digits < PROB_DIGITS - 2)
 1079                                 *out_decimal = *out_decimal * 10 + digit;
 1080                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
 1081                                 (*out_decimal)++;
 1082                         digits++;
 1083                         p++;
 1084                 }
 1085                 if (!digits) /* need at least one digit after '.' */
 1086                         return (NULL);
 1087                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
 1088                         *out_decimal *= 10;
 1089         }
 1090 
 1091         return (p); /* success */
 1092 }
 1093 
 1094 /**
 1095  * Internal helper function to parse an individual type for a failpoint term.
 1096  */
 1097 static char *
 1098 parse_type(struct fail_point_entry *ent, char *beg)
 1099 {
 1100         enum fail_point_t type;
 1101         int len;
 1102 
 1103         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
 1104                 len = fail_type_strings[type].nmlen;
 1105                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
 1106                         ent->fe_type = type;
 1107                         return (beg + len);
 1108                 }
 1109         }
 1110         return (NULL);
 1111 }
 1112 
 1113 /* The fail point sysctl tree. */
 1114 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
 1115 
 1116 /* Debugging/testing stuff for fail point */
 1117 static int
 1118 sysctl_test_fail_point(SYSCTL_HANDLER_ARGS)
 1119 {
 1120 
 1121         KFAIL_POINT_RETURN(DEBUG_FP, test_fail_point);
 1122         return (0);
 1123 }
 1124 SYSCTL_OID(_debug_fail_point, OID_AUTO, test_trigger_fail_point,
 1125         CTLTYPE_STRING | CTLFLAG_RD, NULL, 0, sysctl_test_fail_point, "A",
 1126         "Trigger test fail points");

Cache object: e7c7f9983e1a2ae92d18777dfaeb643a


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