FreeBSD/Linux Kernel Cross Reference
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: releng/8.4/sys/kern/kern_fail.c 224190 2011-07-18 18:06:39Z mdf $");
54
55 #include <sys/ctype.h>
56 #include <sys/errno.h>
57 #include <sys/fail.h>
58 #include <sys/kernel.h>
59 #include <sys/libkern.h>
60 #include <sys/lock.h>
61 #include <sys/malloc.h>
62 #include <sys/mutex.h>
63 #include <sys/proc.h>
64 #include <sys/sbuf.h>
65
66 #include <machine/stdarg.h>
67
68 #ifdef ILOG_DEFINE_FOR_FILE
69 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
70 #endif
71
72 MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
73 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
74 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
75
76 static struct mtx g_fp_mtx;
77 MTX_SYSINIT(g_fp_mtx, &g_fp_mtx, "fail point mtx", MTX_DEF);
78 #define FP_LOCK() mtx_lock(&g_fp_mtx)
79 #define FP_UNLOCK() mtx_unlock(&g_fp_mtx)
80
81 /**
82 * Failpoint types.
83 * Don't change these without changing fail_type_strings in fail.c.
84 * @ingroup failpoint_private
85 */
86 enum fail_point_t {
87 FAIL_POINT_OFF, /**< don't fail */
88 FAIL_POINT_PANIC, /**< panic */
89 FAIL_POINT_RETURN, /**< return an errorcode */
90 FAIL_POINT_BREAK, /**< break into the debugger */
91 FAIL_POINT_PRINT, /**< print a message */
92 FAIL_POINT_SLEEP, /**< sleep for some msecs */
93 FAIL_POINT_NUMTYPES
94 };
95
96 static struct {
97 const char *name;
98 int nmlen;
99 } fail_type_strings[] = {
100 #define FP_TYPE_NM_LEN(s) { s, sizeof(s) - 1 }
101 [FAIL_POINT_OFF] = FP_TYPE_NM_LEN("off"),
102 [FAIL_POINT_PANIC] = FP_TYPE_NM_LEN("panic"),
103 [FAIL_POINT_RETURN] = FP_TYPE_NM_LEN("return"),
104 [FAIL_POINT_BREAK] = FP_TYPE_NM_LEN("break"),
105 [FAIL_POINT_PRINT] = FP_TYPE_NM_LEN("print"),
106 [FAIL_POINT_SLEEP] = FP_TYPE_NM_LEN("sleep"),
107 };
108
109 /**
110 * Internal structure tracking a single term of a complete failpoint.
111 * @ingroup failpoint_private
112 */
113 struct fail_point_entry {
114 enum fail_point_t fe_type; /**< type of entry */
115 int fe_arg; /**< argument to type (e.g. return value) */
116 int fe_prob; /**< likelihood of firing in millionths */
117 int fe_count; /**< number of times to fire, 0 means always */
118 pid_t fe_pid; /**< only fail for this process */
119 TAILQ_ENTRY(fail_point_entry) fe_entries; /**< next entry in fail point */
120 };
121
122 static inline void
123 fail_point_sleep(struct fail_point *fp, struct fail_point_entry *ent,
124 int msecs, enum fail_point_return_code *pret)
125 {
126 /* convert from millisecs to ticks, rounding up */
127 int timo = ((msecs * hz) + 999) / 1000;
128
129 if (timo > 0) {
130 if (fp->fp_sleep_fn == NULL) {
131 msleep(fp, &g_fp_mtx, PWAIT, "failpt", timo);
132 } else {
133 timeout(fp->fp_sleep_fn, fp->fp_sleep_arg, timo);
134 *pret = FAIL_POINT_RC_QUEUED;
135 }
136 }
137 }
138
139
140 /**
141 * Defines stating the equivalent of probablilty one (100%)
142 */
143 enum {
144 PROB_MAX = 1000000, /* probability between zero and this number */
145 PROB_DIGITS = 6, /* number of zero's in above number */
146 };
147
148 static char *parse_fail_point(struct fail_point_entries *, char *);
149 static char *parse_term(struct fail_point_entries *, char *);
150 static char *parse_number(int *out_units, int *out_decimal, char *);
151 static char *parse_type(struct fail_point_entry *, char *);
152 static void free_entry(struct fail_point_entries *, struct fail_point_entry *);
153 static void clear_entries(struct fail_point_entries *);
154
155 /**
156 * Initialize a fail_point. The name is formed in a printf-like fashion
157 * from "fmt" and subsequent arguments. This function is generally used
158 * for custom failpoints located at odd places in the sysctl tree, and is
159 * not explicitly needed for standard in-line-declared failpoints.
160 *
161 * @ingroup failpoint
162 */
163 void
164 fail_point_init(struct fail_point *fp, const char *fmt, ...)
165 {
166 va_list ap;
167 char *name;
168 int n;
169
170 TAILQ_INIT(&fp->fp_entries);
171 fp->fp_flags = 0;
172
173 /* Figure out the size of the name. */
174 va_start(ap, fmt);
175 n = vsnprintf(NULL, 0, fmt, ap);
176 va_end(ap);
177
178 /* Allocate the name and fill it in. */
179 name = fp_malloc(n + 1, M_WAITOK);
180 if (name != NULL) {
181 va_start(ap, fmt);
182 vsnprintf(name, n + 1, fmt, ap);
183 va_end(ap);
184 }
185 fp->fp_name = name;
186 fp->fp_location = "";
187 fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
188 fp->fp_sleep_fn = NULL;
189 fp->fp_sleep_arg = NULL;
190 }
191
192 /**
193 * Free the resources held by a fail_point.
194 *
195 * @ingroup failpoint
196 */
197 void
198 fail_point_destroy(struct fail_point *fp)
199 {
200
201 if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
202 fp_free(__DECONST(void *, fp->fp_name));
203 fp->fp_name = NULL;
204 }
205 fp->fp_flags = 0;
206 clear_entries(&fp->fp_entries);
207 }
208
209 /**
210 * This does the real work of evaluating a fail point. If the fail point tells
211 * us to return a value, this function returns 1 and fills in 'return_value'
212 * (return_value is allowed to be null). If the fail point tells us to panic,
213 * we never return. Otherwise we just return 0 after doing some work, which
214 * means "keep going".
215 */
216 enum fail_point_return_code
217 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
218 {
219 enum fail_point_return_code ret = FAIL_POINT_RC_CONTINUE;
220 struct fail_point_entry *ent, *next;
221 int msecs;
222
223 FP_LOCK();
224
225 TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, next) {
226 int cont = 0; /* don't continue by default */
227
228 if (ent->fe_prob < PROB_MAX &&
229 ent->fe_prob < random() % PROB_MAX)
230 continue;
231 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
232 continue;
233
234 switch (ent->fe_type) {
235 case FAIL_POINT_PANIC:
236 panic("fail point %s panicking", fp->fp_name);
237 /* NOTREACHED */
238
239 case FAIL_POINT_RETURN:
240 if (return_value != NULL)
241 *return_value = ent->fe_arg;
242 ret = FAIL_POINT_RC_RETURN;
243 break;
244
245 case FAIL_POINT_BREAK:
246 printf("fail point %s breaking to debugger\n",
247 fp->fp_name);
248 breakpoint();
249 break;
250
251 case FAIL_POINT_PRINT:
252 printf("fail point %s executing\n", fp->fp_name);
253 cont = ent->fe_arg;
254 break;
255
256 case FAIL_POINT_SLEEP:
257 /*
258 * Free the entry now if necessary, since
259 * we're about to drop the mutex and sleep.
260 */
261 msecs = ent->fe_arg;
262 if (ent->fe_count > 0 && --ent->fe_count == 0) {
263 free_entry(&fp->fp_entries, ent);
264 ent = NULL;
265 }
266
267 if (msecs)
268 fail_point_sleep(fp, ent, msecs, &ret);
269 break;
270
271 default:
272 break;
273 }
274
275 if (ent != NULL && ent->fe_count > 0 && --ent->fe_count == 0)
276 free_entry(&fp->fp_entries, ent);
277 if (cont == 0)
278 break;
279 }
280
281 /* Get rid of "off"s at the end. */
282 while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
283 ent->fe_type == FAIL_POINT_OFF)
284 free_entry(&fp->fp_entries, ent);
285
286 FP_UNLOCK();
287
288 return (ret);
289 }
290
291 /**
292 * Translate internal fail_point structure into human-readable text.
293 */
294 static void
295 fail_point_get(struct fail_point *fp, struct sbuf *sb)
296 {
297 struct fail_point_entry *ent;
298
299 FP_LOCK();
300
301 TAILQ_FOREACH(ent, &fp->fp_entries, fe_entries) {
302 if (ent->fe_prob < PROB_MAX) {
303 int decimal = ent->fe_prob % (PROB_MAX / 100);
304 int units = ent->fe_prob / (PROB_MAX / 100);
305 sbuf_printf(sb, "%d", units);
306 if (decimal) {
307 int digits = PROB_DIGITS - 2;
308 while (!(decimal % 10)) {
309 digits--;
310 decimal /= 10;
311 }
312 sbuf_printf(sb, ".%0*d", digits, decimal);
313 }
314 sbuf_printf(sb, "%%");
315 }
316 if (ent->fe_count > 0)
317 sbuf_printf(sb, "%d*", ent->fe_count);
318 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
319 if (ent->fe_arg)
320 sbuf_printf(sb, "(%d)", ent->fe_arg);
321 if (ent->fe_pid != NO_PID)
322 sbuf_printf(sb, "[pid %d]", ent->fe_pid);
323 if (TAILQ_NEXT(ent, fe_entries))
324 sbuf_printf(sb, "->");
325 }
326 if (TAILQ_EMPTY(&fp->fp_entries))
327 sbuf_printf(sb, "off");
328
329 FP_UNLOCK();
330 }
331
332 /**
333 * Set an internal fail_point structure from a human-readable failpoint string
334 * in a lock-safe manner.
335 */
336 static int
337 fail_point_set(struct fail_point *fp, char *buf)
338 {
339 int error = 0;
340 struct fail_point_entry *ent, *ent_next;
341 struct fail_point_entries new_entries;
342
343 /* Parse new entries. */
344 TAILQ_INIT(&new_entries);
345 if (!parse_fail_point(&new_entries, buf)) {
346 clear_entries(&new_entries);
347 error = EINVAL;
348 goto end;
349 }
350
351 FP_LOCK();
352
353 /* Move new entries in. */
354 TAILQ_SWAP(&fp->fp_entries, &new_entries, fail_point_entry, fe_entries);
355 clear_entries(&new_entries);
356
357 /* Get rid of useless zero probability entries. */
358 TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, ent_next) {
359 if (ent->fe_prob == 0)
360 free_entry(&fp->fp_entries, ent);
361 }
362
363 /* Get rid of "off"s at the end. */
364 while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
365 ent->fe_type == FAIL_POINT_OFF)
366 free_entry(&fp->fp_entries, ent);
367
368 FP_UNLOCK();
369
370 end:
371 #ifdef IWARNING
372 if (error)
373 IWARNING("Failed to set %s %s to %s",
374 fp->fp_name, fp->fp_location, buf);
375 else
376 INOTICE("Set %s %s to %s",
377 fp->fp_name, fp->fp_location, buf);
378 #endif /* IWARNING */
379
380 return (error);
381 }
382
383 #define MAX_FAIL_POINT_BUF 1023
384
385 /**
386 * Handle kernel failpoint set/get.
387 */
388 int
389 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
390 {
391 struct fail_point *fp = arg1;
392 char *buf = NULL;
393 struct sbuf sb;
394 int error;
395
396 /* Retrieving */
397 sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
398 fail_point_get(fp, &sb);
399 sbuf_trim(&sb);
400 sbuf_finish(&sb);
401 error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
402 sbuf_delete(&sb);
403
404 /* Setting */
405 if (!error && req->newptr) {
406 if (req->newlen > MAX_FAIL_POINT_BUF) {
407 error = EINVAL;
408 goto out;
409 }
410
411 buf = fp_malloc(req->newlen + 1, M_WAITOK);
412
413 error = SYSCTL_IN(req, buf, req->newlen);
414 if (error)
415 goto out;
416 buf[req->newlen] = '\0';
417
418 error = fail_point_set(fp, buf);
419 }
420
421 out:
422 fp_free(buf);
423 return (error);
424 }
425
426 /**
427 * Internal helper function to translate a human-readable failpoint string
428 * into a internally-parsable fail_point structure.
429 */
430 static char *
431 parse_fail_point(struct fail_point_entries *ents, char *p)
432 {
433 /* <fail_point> ::
434 * <term> ( "->" <term> )*
435 */
436 p = parse_term(ents, p);
437 if (p == NULL)
438 return (NULL);
439 while (*p != '\0') {
440 if (p[0] != '-' || p[1] != '>')
441 return (NULL);
442 p = parse_term(ents, p + 2);
443 if (p == NULL)
444 return (NULL);
445 }
446 return (p);
447 }
448
449 /**
450 * Internal helper function to parse an individual term from a failpoint.
451 */
452 static char *
453 parse_term(struct fail_point_entries *ents, char *p)
454 {
455 struct fail_point_entry *ent;
456
457 ent = fp_malloc(sizeof *ent, M_WAITOK | M_ZERO);
458 ent->fe_prob = PROB_MAX;
459 ent->fe_pid = NO_PID;
460 TAILQ_INSERT_TAIL(ents, ent, fe_entries);
461
462 /*
463 * <term> ::
464 * ( (<float> "%") | (<integer> "*" ) )*
465 * <type>
466 * [ "(" <integer> ")" ]
467 * [ "[pid " <integer> "]" ]
468 */
469
470 /* ( (<float> "%") | (<integer> "*" ) )* */
471 while (isdigit(*p) || *p == '.') {
472 int units, decimal;
473
474 p = parse_number(&units, &decimal, p);
475 if (p == NULL)
476 return (NULL);
477
478 if (*p == '%') {
479 if (units > 100) /* prevent overflow early */
480 units = 100;
481 ent->fe_prob = units * (PROB_MAX / 100) + decimal;
482 if (ent->fe_prob > PROB_MAX)
483 ent->fe_prob = PROB_MAX;
484 } else if (*p == '*') {
485 if (!units || decimal)
486 return (NULL);
487 ent->fe_count = units;
488 } else
489 return (NULL);
490 p++;
491 }
492
493 /* <type> */
494 p = parse_type(ent, p);
495 if (p == NULL)
496 return (NULL);
497 if (*p == '\0')
498 return (p);
499
500 /* [ "(" <integer> ")" ] */
501 if (*p != '(')
502 return p;
503 p++;
504 if (!isdigit(*p) && *p != '-')
505 return (NULL);
506 ent->fe_arg = strtol(p, &p, 0);
507 if (*p++ != ')')
508 return (NULL);
509
510 /* [ "[pid " <integer> "]" ] */
511 #define PID_STRING "[pid "
512 if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
513 return (p);
514 p += sizeof(PID_STRING) - 1;
515 if (!isdigit(*p))
516 return (NULL);
517 ent->fe_pid = strtol(p, &p, 0);
518 if (*p++ != ']')
519 return (NULL);
520
521 return (p);
522 }
523
524 /**
525 * Internal helper function to parse a numeric for a failpoint term.
526 */
527 static char *
528 parse_number(int *out_units, int *out_decimal, char *p)
529 {
530 char *old_p;
531
532 /*
533 * <number> ::
534 * <integer> [ "." <integer> ] |
535 * "." <integer>
536 */
537
538 /* whole part */
539 old_p = p;
540 *out_units = strtol(p, &p, 10);
541 if (p == old_p && *p != '.')
542 return (NULL);
543
544 /* fractional part */
545 *out_decimal = 0;
546 if (*p == '.') {
547 int digits = 0;
548 p++;
549 while (isdigit(*p)) {
550 int digit = *p - '';
551 if (digits < PROB_DIGITS - 2)
552 *out_decimal = *out_decimal * 10 + digit;
553 else if (digits == PROB_DIGITS - 2 && digit >= 5)
554 (*out_decimal)++;
555 digits++;
556 p++;
557 }
558 if (!digits) /* need at least one digit after '.' */
559 return (NULL);
560 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
561 *out_decimal *= 10;
562 }
563
564 return (p); /* success */
565 }
566
567 /**
568 * Internal helper function to parse an individual type for a failpoint term.
569 */
570 static char *
571 parse_type(struct fail_point_entry *ent, char *beg)
572 {
573 enum fail_point_t type;
574 int len;
575
576 for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
577 len = fail_type_strings[type].nmlen;
578 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
579 ent->fe_type = type;
580 return (beg + len);
581 }
582 }
583 return (NULL);
584 }
585
586 /**
587 * Internal helper function to free an individual failpoint term.
588 */
589 static void
590 free_entry(struct fail_point_entries *ents, struct fail_point_entry *ent)
591 {
592 TAILQ_REMOVE(ents, ent, fe_entries);
593 fp_free(ent);
594 }
595
596 /**
597 * Internal helper function to clear out all failpoint terms for a single
598 * failpoint.
599 */
600 static void
601 clear_entries(struct fail_point_entries *ents)
602 {
603 struct fail_point_entry *ent, *ent_next;
604
605 TAILQ_FOREACH_SAFE(ent, ents, fe_entries, ent_next)
606 fp_free(ent);
607 TAILQ_INIT(ents);
608 }
609
610 /* The fail point sysctl tree. */
611 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
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