1 /*
2 * Stress userfaultfd syscall.
3 *
4 * Copyright (C) 2015 Red Hat, Inc.
5 *
6 * This work is licensed under the terms of the GNU GPL, version 2. See
7 * the COPYING file in the top-level directory.
8 *
9 * This test allocates two virtual areas and bounces the physical
10 * memory across the two virtual areas (from area_src to area_dst)
11 * using userfaultfd.
12 *
13 * There are three threads running per CPU:
14 *
15 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
16 * page of the area_dst (while the physical page may still be in
17 * area_src), and increments a per-page counter in the same page,
18 * and checks its value against a verification region.
19 *
20 * 2) another per-CPU thread handles the userfaults generated by
21 * thread 1 above. userfaultfd blocking reads or poll() modes are
22 * exercised interleaved.
23 *
24 * 3) one last per-CPU thread transfers the memory in the background
25 * at maximum bandwidth (if not already transferred by thread
26 * 2). Each cpu thread takes cares of transferring a portion of the
27 * area.
28 *
29 * When all threads of type 3 completed the transfer, one bounce is
30 * complete. area_src and area_dst are then swapped. All threads are
31 * respawned and so the bounce is immediately restarted in the
32 * opposite direction.
33 *
34 * per-CPU threads 1 by triggering userfaults inside
35 * pthread_mutex_lock will also verify the atomicity of the memory
36 * transfer (UFFDIO_COPY).
37 *
38 * The program takes two parameters: the amounts of physical memory in
39 * megabytes (MiB) of the area and the number of bounces to execute.
40 *
41 * # 100MiB 99999 bounces
42 * ./userfaultfd 100 99999
43 *
44 * # 1GiB 99 bounces
45 * ./userfaultfd 1000 99
46 *
47 * # 10MiB-~6GiB 999 bounces, continue forever unless an error triggers
48 * while ./userfaultfd $[RANDOM % 6000 + 10] 999; do true; done
49 */
50
51 #define _GNU_SOURCE
52 #include <stdio.h>
53 #include <errno.h>
54 #include <unistd.h>
55 #include <stdlib.h>
56 #include <sys/types.h>
57 #include <sys/stat.h>
58 #include <fcntl.h>
59 #include <time.h>
60 #include <signal.h>
61 #include <poll.h>
62 #include <string.h>
63 #include <sys/mman.h>
64 #include <sys/syscall.h>
65 #include <sys/ioctl.h>
66 #include <pthread.h>
67 #include <linux/userfaultfd.h>
68
69 #ifdef __NR_userfaultfd
70
71 static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
72
73 #define BOUNCE_RANDOM (1<<0)
74 #define BOUNCE_RACINGFAULTS (1<<1)
75 #define BOUNCE_VERIFY (1<<2)
76 #define BOUNCE_POLL (1<<3)
77 static int bounces;
78
79 static unsigned long long *count_verify;
80 static int uffd, finished, *pipefd;
81 static char *area_src, *area_dst;
82 static char *zeropage;
83 pthread_attr_t attr;
84
85 /* pthread_mutex_t starts at page offset 0 */
86 #define area_mutex(___area, ___nr) \
87 ((pthread_mutex_t *) ((___area) + (___nr)*page_size))
88 /*
89 * count is placed in the page after pthread_mutex_t naturally aligned
90 * to avoid non alignment faults on non-x86 archs.
91 */
92 #define area_count(___area, ___nr) \
93 ((volatile unsigned long long *) ((unsigned long) \
94 ((___area) + (___nr)*page_size + \
95 sizeof(pthread_mutex_t) + \
96 sizeof(unsigned long long) - 1) & \
97 ~(unsigned long)(sizeof(unsigned long long) \
98 - 1)))
99
my_bcmp(char * str1,char * str2,size_t n)100 static int my_bcmp(char *str1, char *str2, size_t n)
101 {
102 unsigned long i;
103 for (i = 0; i < n; i++)
104 if (str1[i] != str2[i])
105 return 1;
106 return 0;
107 }
108
locking_thread(void * arg)109 static void *locking_thread(void *arg)
110 {
111 unsigned long cpu = (unsigned long) arg;
112 struct random_data rand;
113 unsigned long page_nr = *(&(page_nr)); /* uninitialized warning */
114 int32_t rand_nr;
115 unsigned long long count;
116 char randstate[64];
117 unsigned int seed;
118 time_t start;
119
120 if (bounces & BOUNCE_RANDOM) {
121 seed = (unsigned int) time(NULL) - bounces;
122 if (!(bounces & BOUNCE_RACINGFAULTS))
123 seed += cpu;
124 bzero(&rand, sizeof(rand));
125 bzero(&randstate, sizeof(randstate));
126 if (initstate_r(seed, randstate, sizeof(randstate), &rand))
127 fprintf(stderr, "srandom_r error\n"), exit(1);
128 } else {
129 page_nr = -bounces;
130 if (!(bounces & BOUNCE_RACINGFAULTS))
131 page_nr += cpu * nr_pages_per_cpu;
132 }
133
134 while (!finished) {
135 if (bounces & BOUNCE_RANDOM) {
136 if (random_r(&rand, &rand_nr))
137 fprintf(stderr, "random_r 1 error\n"), exit(1);
138 page_nr = rand_nr;
139 if (sizeof(page_nr) > sizeof(rand_nr)) {
140 if (random_r(&rand, &rand_nr))
141 fprintf(stderr, "random_r 2 error\n"), exit(1);
142 page_nr |= (((unsigned long) rand_nr) << 16) <<
143 16;
144 }
145 } else
146 page_nr += 1;
147 page_nr %= nr_pages;
148
149 start = time(NULL);
150 if (bounces & BOUNCE_VERIFY) {
151 count = *area_count(area_dst, page_nr);
152 if (!count)
153 fprintf(stderr,
154 "page_nr %lu wrong count %Lu %Lu\n",
155 page_nr, count,
156 count_verify[page_nr]), exit(1);
157
158
159 /*
160 * We can't use bcmp (or memcmp) because that
161 * returns 0 erroneously if the memory is
162 * changing under it (even if the end of the
163 * page is never changing and always
164 * different).
165 */
166 #if 1
167 if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
168 page_size))
169 fprintf(stderr,
170 "my_bcmp page_nr %lu wrong count %Lu %Lu\n",
171 page_nr, count,
172 count_verify[page_nr]), exit(1);
173 #else
174 unsigned long loops;
175
176 loops = 0;
177 /* uncomment the below line to test with mutex */
178 /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
179 while (!bcmp(area_dst + page_nr * page_size, zeropage,
180 page_size)) {
181 loops += 1;
182 if (loops > 10)
183 break;
184 }
185 /* uncomment below line to test with mutex */
186 /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
187 if (loops) {
188 fprintf(stderr,
189 "page_nr %lu all zero thread %lu %p %lu\n",
190 page_nr, cpu, area_dst + page_nr * page_size,
191 loops);
192 if (loops > 10)
193 exit(1);
194 }
195 #endif
196 }
197
198 pthread_mutex_lock(area_mutex(area_dst, page_nr));
199 count = *area_count(area_dst, page_nr);
200 if (count != count_verify[page_nr]) {
201 fprintf(stderr,
202 "page_nr %lu memory corruption %Lu %Lu\n",
203 page_nr, count,
204 count_verify[page_nr]), exit(1);
205 }
206 count++;
207 *area_count(area_dst, page_nr) = count_verify[page_nr] = count;
208 pthread_mutex_unlock(area_mutex(area_dst, page_nr));
209
210 if (time(NULL) - start > 1)
211 fprintf(stderr,
212 "userfault too slow %ld "
213 "possible false positive with overcommit\n",
214 time(NULL) - start);
215 }
216
217 return NULL;
218 }
219
copy_page(unsigned long offset)220 static int copy_page(unsigned long offset)
221 {
222 struct uffdio_copy uffdio_copy;
223
224 if (offset >= nr_pages * page_size)
225 fprintf(stderr, "unexpected offset %lu\n",
226 offset), exit(1);
227 uffdio_copy.dst = (unsigned long) area_dst + offset;
228 uffdio_copy.src = (unsigned long) area_src + offset;
229 uffdio_copy.len = page_size;
230 uffdio_copy.mode = 0;
231 uffdio_copy.copy = 0;
232 if (ioctl(uffd, UFFDIO_COPY, &uffdio_copy)) {
233 /* real retval in ufdio_copy.copy */
234 if (uffdio_copy.copy != -EEXIST)
235 fprintf(stderr, "UFFDIO_COPY error %Ld\n",
236 uffdio_copy.copy), exit(1);
237 } else if (uffdio_copy.copy != page_size) {
238 fprintf(stderr, "UFFDIO_COPY unexpected copy %Ld\n",
239 uffdio_copy.copy), exit(1);
240 } else
241 return 1;
242 return 0;
243 }
244
uffd_poll_thread(void * arg)245 static void *uffd_poll_thread(void *arg)
246 {
247 unsigned long cpu = (unsigned long) arg;
248 struct pollfd pollfd[2];
249 struct uffd_msg msg;
250 int ret;
251 unsigned long offset;
252 char tmp_chr;
253 unsigned long userfaults = 0;
254
255 pollfd[0].fd = uffd;
256 pollfd[0].events = POLLIN;
257 pollfd[1].fd = pipefd[cpu*2];
258 pollfd[1].events = POLLIN;
259
260 for (;;) {
261 ret = poll(pollfd, 2, -1);
262 if (!ret)
263 fprintf(stderr, "poll error %d\n", ret), exit(1);
264 if (ret < 0)
265 perror("poll"), exit(1);
266 if (pollfd[1].revents & POLLIN) {
267 if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
268 fprintf(stderr, "read pipefd error\n"),
269 exit(1);
270 break;
271 }
272 if (!(pollfd[0].revents & POLLIN))
273 fprintf(stderr, "pollfd[0].revents %d\n",
274 pollfd[0].revents), exit(1);
275 ret = read(uffd, &msg, sizeof(msg));
276 if (ret < 0) {
277 if (errno == EAGAIN)
278 continue;
279 perror("nonblocking read error"), exit(1);
280 }
281 if (msg.event != UFFD_EVENT_PAGEFAULT)
282 fprintf(stderr, "unexpected msg event %u\n",
283 msg.event), exit(1);
284 if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
285 fprintf(stderr, "unexpected write fault\n"), exit(1);
286 offset = (char *)(unsigned long)msg.arg.pagefault.address -
287 area_dst;
288 offset &= ~(page_size-1);
289 if (copy_page(offset))
290 userfaults++;
291 }
292 return (void *)userfaults;
293 }
294
295 pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
296
uffd_read_thread(void * arg)297 static void *uffd_read_thread(void *arg)
298 {
299 unsigned long *this_cpu_userfaults;
300 struct uffd_msg msg;
301 unsigned long offset;
302 int ret;
303
304 this_cpu_userfaults = (unsigned long *) arg;
305 *this_cpu_userfaults = 0;
306
307 pthread_mutex_unlock(&uffd_read_mutex);
308 /* from here cancellation is ok */
309
310 for (;;) {
311 ret = read(uffd, &msg, sizeof(msg));
312 if (ret != sizeof(msg)) {
313 if (ret < 0)
314 perror("blocking read error"), exit(1);
315 else
316 fprintf(stderr, "short read\n"), exit(1);
317 }
318 if (msg.event != UFFD_EVENT_PAGEFAULT)
319 fprintf(stderr, "unexpected msg event %u\n",
320 msg.event), exit(1);
321 if (bounces & BOUNCE_VERIFY &&
322 msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
323 fprintf(stderr, "unexpected write fault\n"), exit(1);
324 offset = (char *)(unsigned long)msg.arg.pagefault.address -
325 area_dst;
326 offset &= ~(page_size-1);
327 if (copy_page(offset))
328 (*this_cpu_userfaults)++;
329 }
330 return (void *)NULL;
331 }
332
background_thread(void * arg)333 static void *background_thread(void *arg)
334 {
335 unsigned long cpu = (unsigned long) arg;
336 unsigned long page_nr;
337
338 for (page_nr = cpu * nr_pages_per_cpu;
339 page_nr < (cpu+1) * nr_pages_per_cpu;
340 page_nr++)
341 copy_page(page_nr * page_size);
342
343 return NULL;
344 }
345
stress(unsigned long * userfaults)346 static int stress(unsigned long *userfaults)
347 {
348 unsigned long cpu;
349 pthread_t locking_threads[nr_cpus];
350 pthread_t uffd_threads[nr_cpus];
351 pthread_t background_threads[nr_cpus];
352 void **_userfaults = (void **) userfaults;
353
354 finished = 0;
355 for (cpu = 0; cpu < nr_cpus; cpu++) {
356 if (pthread_create(&locking_threads[cpu], &attr,
357 locking_thread, (void *)cpu))
358 return 1;
359 if (bounces & BOUNCE_POLL) {
360 if (pthread_create(&uffd_threads[cpu], &attr,
361 uffd_poll_thread, (void *)cpu))
362 return 1;
363 } else {
364 if (pthread_create(&uffd_threads[cpu], &attr,
365 uffd_read_thread,
366 &_userfaults[cpu]))
367 return 1;
368 pthread_mutex_lock(&uffd_read_mutex);
369 }
370 if (pthread_create(&background_threads[cpu], &attr,
371 background_thread, (void *)cpu))
372 return 1;
373 }
374 for (cpu = 0; cpu < nr_cpus; cpu++)
375 if (pthread_join(background_threads[cpu], NULL))
376 return 1;
377
378 /*
379 * Be strict and immediately zap area_src, the whole area has
380 * been transferred already by the background treads. The
381 * area_src could then be faulted in in a racy way by still
382 * running uffdio_threads reading zeropages after we zapped
383 * area_src (but they're guaranteed to get -EEXIST from
384 * UFFDIO_COPY without writing zero pages into area_dst
385 * because the background threads already completed).
386 */
387 if (madvise(area_src, nr_pages * page_size, MADV_DONTNEED)) {
388 perror("madvise");
389 return 1;
390 }
391
392 for (cpu = 0; cpu < nr_cpus; cpu++) {
393 char c;
394 if (bounces & BOUNCE_POLL) {
395 if (write(pipefd[cpu*2+1], &c, 1) != 1) {
396 fprintf(stderr, "pipefd write error\n");
397 return 1;
398 }
399 if (pthread_join(uffd_threads[cpu], &_userfaults[cpu]))
400 return 1;
401 } else {
402 if (pthread_cancel(uffd_threads[cpu]))
403 return 1;
404 if (pthread_join(uffd_threads[cpu], NULL))
405 return 1;
406 }
407 }
408
409 finished = 1;
410 for (cpu = 0; cpu < nr_cpus; cpu++)
411 if (pthread_join(locking_threads[cpu], NULL))
412 return 1;
413
414 return 0;
415 }
416
userfaultfd_stress(void)417 static int userfaultfd_stress(void)
418 {
419 void *area;
420 char *tmp_area;
421 unsigned long nr;
422 struct uffdio_register uffdio_register;
423 struct uffdio_api uffdio_api;
424 unsigned long cpu;
425 int uffd_flags, err;
426 unsigned long userfaults[nr_cpus];
427
428 if (posix_memalign(&area, page_size, nr_pages * page_size)) {
429 fprintf(stderr, "out of memory\n");
430 return 1;
431 }
432 area_src = area;
433 if (posix_memalign(&area, page_size, nr_pages * page_size)) {
434 fprintf(stderr, "out of memory\n");
435 return 1;
436 }
437 area_dst = area;
438
439 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
440 if (uffd < 0) {
441 fprintf(stderr,
442 "userfaultfd syscall not available in this kernel\n");
443 return 1;
444 }
445 uffd_flags = fcntl(uffd, F_GETFD, NULL);
446
447 uffdio_api.api = UFFD_API;
448 uffdio_api.features = 0;
449 if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
450 fprintf(stderr, "UFFDIO_API\n");
451 return 1;
452 }
453 if (uffdio_api.api != UFFD_API) {
454 fprintf(stderr, "UFFDIO_API error %Lu\n", uffdio_api.api);
455 return 1;
456 }
457
458 count_verify = malloc(nr_pages * sizeof(unsigned long long));
459 if (!count_verify) {
460 perror("count_verify");
461 return 1;
462 }
463
464 for (nr = 0; nr < nr_pages; nr++) {
465 *area_mutex(area_src, nr) = (pthread_mutex_t)
466 PTHREAD_MUTEX_INITIALIZER;
467 count_verify[nr] = *area_count(area_src, nr) = 1;
468 /*
469 * In the transition between 255 to 256, powerpc will
470 * read out of order in my_bcmp and see both bytes as
471 * zero, so leave a placeholder below always non-zero
472 * after the count, to avoid my_bcmp to trigger false
473 * positives.
474 */
475 *(area_count(area_src, nr) + 1) = 1;
476 }
477
478 pipefd = malloc(sizeof(int) * nr_cpus * 2);
479 if (!pipefd) {
480 perror("pipefd");
481 return 1;
482 }
483 for (cpu = 0; cpu < nr_cpus; cpu++) {
484 if (pipe2(&pipefd[cpu*2], O_CLOEXEC | O_NONBLOCK)) {
485 perror("pipe");
486 return 1;
487 }
488 }
489
490 if (posix_memalign(&area, page_size, page_size)) {
491 fprintf(stderr, "out of memory\n");
492 return 1;
493 }
494 zeropage = area;
495 bzero(zeropage, page_size);
496
497 pthread_mutex_lock(&uffd_read_mutex);
498
499 pthread_attr_init(&attr);
500 pthread_attr_setstacksize(&attr, 16*1024*1024);
501
502 err = 0;
503 while (bounces--) {
504 unsigned long expected_ioctls;
505
506 printf("bounces: %d, mode:", bounces);
507 if (bounces & BOUNCE_RANDOM)
508 printf(" rnd");
509 if (bounces & BOUNCE_RACINGFAULTS)
510 printf(" racing");
511 if (bounces & BOUNCE_VERIFY)
512 printf(" ver");
513 if (bounces & BOUNCE_POLL)
514 printf(" poll");
515 printf(", ");
516 fflush(stdout);
517
518 if (bounces & BOUNCE_POLL)
519 fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
520 else
521 fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);
522
523 /* register */
524 uffdio_register.range.start = (unsigned long) area_dst;
525 uffdio_register.range.len = nr_pages * page_size;
526 uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
527 if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
528 fprintf(stderr, "register failure\n");
529 return 1;
530 }
531 expected_ioctls = (1 << _UFFDIO_WAKE) |
532 (1 << _UFFDIO_COPY) |
533 (1 << _UFFDIO_ZEROPAGE);
534 if ((uffdio_register.ioctls & expected_ioctls) !=
535 expected_ioctls) {
536 fprintf(stderr,
537 "unexpected missing ioctl for anon memory\n");
538 return 1;
539 }
540
541 /*
542 * The madvise done previously isn't enough: some
543 * uffd_thread could have read userfaults (one of
544 * those already resolved by the background thread)
545 * and it may be in the process of calling
546 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
547 * area_src and it would map a zero page in it (of
548 * course such a UFFDIO_COPY is perfectly safe as it'd
549 * return -EEXIST). The problem comes at the next
550 * bounce though: that racing UFFDIO_COPY would
551 * generate zeropages in the area_src, so invalidating
552 * the previous MADV_DONTNEED. Without this additional
553 * MADV_DONTNEED those zeropages leftovers in the
554 * area_src would lead to -EEXIST failure during the
555 * next bounce, effectively leaving a zeropage in the
556 * area_dst.
557 *
558 * Try to comment this out madvise to see the memory
559 * corruption being caught pretty quick.
560 *
561 * khugepaged is also inhibited to collapse THP after
562 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
563 * required to MADV_DONTNEED here.
564 */
565 if (madvise(area_dst, nr_pages * page_size, MADV_DONTNEED)) {
566 perror("madvise 2");
567 return 1;
568 }
569
570 /* bounce pass */
571 if (stress(userfaults))
572 return 1;
573
574 /* unregister */
575 if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) {
576 fprintf(stderr, "register failure\n");
577 return 1;
578 }
579
580 /* verification */
581 if (bounces & BOUNCE_VERIFY) {
582 for (nr = 0; nr < nr_pages; nr++) {
583 if (*area_count(area_dst, nr) != count_verify[nr]) {
584 fprintf(stderr,
585 "error area_count %Lu %Lu %lu\n",
586 *area_count(area_src, nr),
587 count_verify[nr],
588 nr);
589 err = 1;
590 bounces = 0;
591 }
592 }
593 }
594
595 /* prepare next bounce */
596 tmp_area = area_src;
597 area_src = area_dst;
598 area_dst = tmp_area;
599
600 printf("userfaults:");
601 for (cpu = 0; cpu < nr_cpus; cpu++)
602 printf(" %lu", userfaults[cpu]);
603 printf("\n");
604 }
605
606 return err;
607 }
608
main(int argc,char ** argv)609 int main(int argc, char **argv)
610 {
611 if (argc < 3)
612 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
613 nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
614 page_size = sysconf(_SC_PAGE_SIZE);
615 if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
616 > page_size)
617 fprintf(stderr, "Impossible to run this test\n"), exit(2);
618 nr_pages_per_cpu = atol(argv[1]) * 1024*1024 / page_size /
619 nr_cpus;
620 if (!nr_pages_per_cpu) {
621 fprintf(stderr, "invalid MiB\n");
622 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
623 }
624 bounces = atoi(argv[2]);
625 if (bounces <= 0) {
626 fprintf(stderr, "invalid bounces\n");
627 fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
628 }
629 nr_pages = nr_pages_per_cpu * nr_cpus;
630 printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
631 nr_pages, nr_pages_per_cpu);
632 return userfaultfd_stress();
633 }
634
635 #else /* __NR_userfaultfd */
636
637 #warning "missing __NR_userfaultfd definition"
638
main(void)639 int main(void)
640 {
641 printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
642 return 0;
643 }
644
645 #endif /* __NR_userfaultfd */
646