1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Stress userfaultfd syscall.
4 *
5 * Copyright (C) 2015 Red Hat, Inc.
6 *
7 * This test allocates two virtual areas and bounces the physical
8 * memory across the two virtual areas (from area_src to area_dst)
9 * using userfaultfd.
10 *
11 * There are three threads running per CPU:
12 *
13 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
14 * page of the area_dst (while the physical page may still be in
15 * area_src), and increments a per-page counter in the same page,
16 * and checks its value against a verification region.
17 *
18 * 2) another per-CPU thread handles the userfaults generated by
19 * thread 1 above. userfaultfd blocking reads or poll() modes are
20 * exercised interleaved.
21 *
22 * 3) one last per-CPU thread transfers the memory in the background
23 * at maximum bandwidth (if not already transferred by thread
24 * 2). Each cpu thread takes cares of transferring a portion of the
25 * area.
26 *
27 * When all threads of type 3 completed the transfer, one bounce is
28 * complete. area_src and area_dst are then swapped. All threads are
29 * respawned and so the bounce is immediately restarted in the
30 * opposite direction.
31 *
32 * per-CPU threads 1 by triggering userfaults inside
33 * pthread_mutex_lock will also verify the atomicity of the memory
34 * transfer (UFFDIO_COPY).
35 */
36
37#include "uffd-common.h"
38
39#ifdef __NR_userfaultfd
40
41#define BOUNCE_RANDOM (1<<0)
42#define BOUNCE_RACINGFAULTS (1<<1)
43#define BOUNCE_VERIFY (1<<2)
44#define BOUNCE_POLL (1<<3)
45static int bounces;
46
47/* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
48#define ALARM_INTERVAL_SECS 10
49static char *zeropage;
50pthread_attr_t attr;
51
52#define swap(a, b) \
53 do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
54
55const char *examples =
56 "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
57 "./uffd-stress anon 100 99999\n\n"
58 "# Run share memory test on 1GiB region with 99 bounces:\n"
59 "./uffd-stress shmem 1000 99\n\n"
60 "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
61 "./uffd-stress hugetlb 256 50\n\n"
62 "# Run the same hugetlb test but using private file:\n"
63 "./uffd-stress hugetlb-private 256 50\n\n"
64 "# 10MiB-~6GiB 999 bounces anonymous test, "
65 "continue forever unless an error triggers\n"
66 "while ./uffd-stress anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";
67
68static void usage(void)
69{
70 fprintf(stderr, "\nUsage: ./uffd-stress <test type> <MiB> <bounces>\n\n");
71 fprintf(stderr, "Supported <test type>: anon, hugetlb, "
72 "hugetlb-private, shmem, shmem-private\n\n");
73 fprintf(stderr, "Examples:\n\n");
74 fprintf(stderr, "%s", examples);
75 exit(1);
76}
77
78static void uffd_stats_reset(struct uffd_args *args, unsigned long n_cpus)
79{
80 int i;
81
82 for (i = 0; i < n_cpus; i++) {
83 args[i].cpu = i;
84 args[i].apply_wp = test_uffdio_wp;
85 args[i].missing_faults = 0;
86 args[i].wp_faults = 0;
87 args[i].minor_faults = 0;
88 }
89}
90
91static void *locking_thread(void *arg)
92{
93 unsigned long cpu = (unsigned long) arg;
94 unsigned long page_nr;
95 unsigned long long count;
96
97 if (!(bounces & BOUNCE_RANDOM)) {
98 page_nr = -bounces;
99 if (!(bounces & BOUNCE_RACINGFAULTS))
100 page_nr += cpu * nr_pages_per_cpu;
101 }
102
103 while (!finished) {
104 if (bounces & BOUNCE_RANDOM) {
105 if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr))
106 err("getrandom failed");
107 } else
108 page_nr += 1;
109 page_nr %= nr_pages;
110 pthread_mutex_lock(area_mutex(area_dst, page_nr));
111 count = *area_count(area_dst, page_nr);
112 if (count != count_verify[page_nr])
113 err("page_nr %lu memory corruption %llu %llu",
114 page_nr, count, count_verify[page_nr]);
115 count++;
116 *area_count(area_dst, page_nr) = count_verify[page_nr] = count;
117 pthread_mutex_unlock(area_mutex(area_dst, page_nr));
118 }
119
120 return NULL;
121}
122
123static int copy_page_retry(int ufd, unsigned long offset)
124{
125 return __copy_page(ufd, offset, true, test_uffdio_wp);
126}
127
128pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
129
130static void *uffd_read_thread(void *arg)
131{
132 struct uffd_args *args = (struct uffd_args *)arg;
133 struct uffd_msg msg;
134
135 pthread_mutex_unlock(&uffd_read_mutex);
136 /* from here cancellation is ok */
137
138 for (;;) {
139 if (uffd_read_msg(uffd, &msg))
140 continue;
141 uffd_handle_page_fault(&msg, args);
142 }
143
144 return NULL;
145}
146
147static void *background_thread(void *arg)
148{
149 unsigned long cpu = (unsigned long) arg;
150 unsigned long page_nr, start_nr, mid_nr, end_nr;
151
152 start_nr = cpu * nr_pages_per_cpu;
153 end_nr = (cpu+1) * nr_pages_per_cpu;
154 mid_nr = (start_nr + end_nr) / 2;
155
156 /* Copy the first half of the pages */
157 for (page_nr = start_nr; page_nr < mid_nr; page_nr++)
158 copy_page_retry(uffd, page_nr * page_size);
159
160 /*
161 * If we need to test uffd-wp, set it up now. Then we'll have
162 * at least the first half of the pages mapped already which
163 * can be write-protected for testing
164 */
165 if (test_uffdio_wp)
166 wp_range(uffd, (unsigned long)area_dst + start_nr * page_size,
167 nr_pages_per_cpu * page_size, true);
168
169 /*
170 * Continue the 2nd half of the page copying, handling write
171 * protection faults if any
172 */
173 for (page_nr = mid_nr; page_nr < end_nr; page_nr++)
174 copy_page_retry(uffd, page_nr * page_size);
175
176 return NULL;
177}
178
179static int stress(struct uffd_args *args)
180{
181 unsigned long cpu;
182 pthread_t locking_threads[nr_cpus];
183 pthread_t uffd_threads[nr_cpus];
184 pthread_t background_threads[nr_cpus];
185
186 finished = 0;
187 for (cpu = 0; cpu < nr_cpus; cpu++) {
188 if (pthread_create(&locking_threads[cpu], &attr,
189 locking_thread, (void *)cpu))
190 return 1;
191 if (bounces & BOUNCE_POLL) {
192 if (pthread_create(&uffd_threads[cpu], &attr, uffd_poll_thread, &args[cpu]))
193 err("uffd_poll_thread create");
194 } else {
195 if (pthread_create(&uffd_threads[cpu], &attr,
196 uffd_read_thread,
197 (void *)&args[cpu]))
198 return 1;
199 pthread_mutex_lock(&uffd_read_mutex);
200 }
201 if (pthread_create(&background_threads[cpu], &attr,
202 background_thread, (void *)cpu))
203 return 1;
204 }
205 for (cpu = 0; cpu < nr_cpus; cpu++)
206 if (pthread_join(background_threads[cpu], NULL))
207 return 1;
208
209 /*
210 * Be strict and immediately zap area_src, the whole area has
211 * been transferred already by the background treads. The
212 * area_src could then be faulted in a racy way by still
213 * running uffdio_threads reading zeropages after we zapped
214 * area_src (but they're guaranteed to get -EEXIST from
215 * UFFDIO_COPY without writing zero pages into area_dst
216 * because the background threads already completed).
217 */
218 uffd_test_ops->release_pages(area_src);
219
220 finished = 1;
221 for (cpu = 0; cpu < nr_cpus; cpu++)
222 if (pthread_join(locking_threads[cpu], NULL))
223 return 1;
224
225 for (cpu = 0; cpu < nr_cpus; cpu++) {
226 char c;
227 if (bounces & BOUNCE_POLL) {
228 if (write(pipefd[cpu*2+1], &c, 1) != 1)
229 err("pipefd write error");
230 if (pthread_join(uffd_threads[cpu],
231 (void *)&args[cpu]))
232 return 1;
233 } else {
234 if (pthread_cancel(uffd_threads[cpu]))
235 return 1;
236 if (pthread_join(uffd_threads[cpu], NULL))
237 return 1;
238 }
239 }
240
241 return 0;
242}
243
244static int userfaultfd_stress(void)
245{
246 void *area;
247 unsigned long nr;
248 struct uffd_args args[nr_cpus];
249 uint64_t mem_size = nr_pages * page_size;
250
251 memset(args, 0, sizeof(struct uffd_args) * nr_cpus);
252
253 if (uffd_test_ctx_init(UFFD_FEATURE_WP_UNPOPULATED, NULL))
254 err("context init failed");
255
256 if (posix_memalign(&area, page_size, page_size))
257 err("out of memory");
258 zeropage = area;
259 bzero(zeropage, page_size);
260
261 pthread_mutex_lock(&uffd_read_mutex);
262
263 pthread_attr_init(&attr);
264 pthread_attr_setstacksize(&attr, 16*1024*1024);
265
266 while (bounces--) {
267 printf("bounces: %d, mode:", bounces);
268 if (bounces & BOUNCE_RANDOM)
269 printf(" rnd");
270 if (bounces & BOUNCE_RACINGFAULTS)
271 printf(" racing");
272 if (bounces & BOUNCE_VERIFY)
273 printf(" ver");
274 if (bounces & BOUNCE_POLL)
275 printf(" poll");
276 else
277 printf(" read");
278 printf(", ");
279 fflush(stdout);
280
281 if (bounces & BOUNCE_POLL)
282 fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
283 else
284 fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);
285
286 /* register */
287 if (uffd_register(uffd, area_dst, mem_size,
288 true, test_uffdio_wp, false))
289 err("register failure");
290
291 if (area_dst_alias) {
292 if (uffd_register(uffd, area_dst_alias, mem_size,
293 true, test_uffdio_wp, false))
294 err("register failure alias");
295 }
296
297 /*
298 * The madvise done previously isn't enough: some
299 * uffd_thread could have read userfaults (one of
300 * those already resolved by the background thread)
301 * and it may be in the process of calling
302 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
303 * area_src and it would map a zero page in it (of
304 * course such a UFFDIO_COPY is perfectly safe as it'd
305 * return -EEXIST). The problem comes at the next
306 * bounce though: that racing UFFDIO_COPY would
307 * generate zeropages in the area_src, so invalidating
308 * the previous MADV_DONTNEED. Without this additional
309 * MADV_DONTNEED those zeropages leftovers in the
310 * area_src would lead to -EEXIST failure during the
311 * next bounce, effectively leaving a zeropage in the
312 * area_dst.
313 *
314 * Try to comment this out madvise to see the memory
315 * corruption being caught pretty quick.
316 *
317 * khugepaged is also inhibited to collapse THP after
318 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
319 * required to MADV_DONTNEED here.
320 */
321 uffd_test_ops->release_pages(area_dst);
322
323 uffd_stats_reset(args, nr_cpus);
324
325 /* bounce pass */
326 if (stress(args)) {
327 uffd_test_ctx_clear();
328 return 1;
329 }
330
331 /* Clear all the write protections if there is any */
332 if (test_uffdio_wp)
333 wp_range(uffd, (unsigned long)area_dst,
334 nr_pages * page_size, false);
335
336 /* unregister */
337 if (uffd_unregister(uffd, area_dst, mem_size))
338 err("unregister failure");
339 if (area_dst_alias) {
340 if (uffd_unregister(uffd, area_dst_alias, mem_size))
341 err("unregister failure alias");
342 }
343
344 /* verification */
345 if (bounces & BOUNCE_VERIFY)
346 for (nr = 0; nr < nr_pages; nr++)
347 if (*area_count(area_dst, nr) != count_verify[nr])
348 err("error area_count %llu %llu %lu\n",
349 *area_count(area_src, nr),
350 count_verify[nr], nr);
351
352 /* prepare next bounce */
353 swap(area_src, area_dst);
354
355 swap(area_src_alias, area_dst_alias);
356
357 uffd_stats_report(args, nr_cpus);
358 }
359 uffd_test_ctx_clear();
360
361 return 0;
362}
363
364static void set_test_type(const char *type)
365{
366 if (!strcmp(type, "anon")) {
367 test_type = TEST_ANON;
368 uffd_test_ops = &anon_uffd_test_ops;
369 } else if (!strcmp(type, "hugetlb")) {
370 test_type = TEST_HUGETLB;
371 uffd_test_ops = &hugetlb_uffd_test_ops;
372 map_shared = true;
373 } else if (!strcmp(type, "hugetlb-private")) {
374 test_type = TEST_HUGETLB;
375 uffd_test_ops = &hugetlb_uffd_test_ops;
376 } else if (!strcmp(type, "shmem")) {
377 map_shared = true;
378 test_type = TEST_SHMEM;
379 uffd_test_ops = &shmem_uffd_test_ops;
380 } else if (!strcmp(type, "shmem-private")) {
381 test_type = TEST_SHMEM;
382 uffd_test_ops = &shmem_uffd_test_ops;
383 }
384}
385
386static void parse_test_type_arg(const char *raw_type)
387{
388 uint64_t features = UFFD_API_FEATURES;
389
390 set_test_type(raw_type);
391
392 if (!test_type)
393 err("failed to parse test type argument: '%s'", raw_type);
394
395 if (test_type == TEST_HUGETLB)
396 page_size = default_huge_page_size();
397 else
398 page_size = sysconf(_SC_PAGE_SIZE);
399
400 if (!page_size)
401 err("Unable to determine page size");
402 if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
403 > page_size)
404 err("Impossible to run this test");
405
406 /*
407 * Whether we can test certain features depends not just on test type,
408 * but also on whether or not this particular kernel supports the
409 * feature.
410 */
411
412 if (userfaultfd_open(&features))
413 err("Userfaultfd open failed");
414
415 test_uffdio_wp = test_uffdio_wp &&
416 (features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
417
418 close(uffd);
419 uffd = -1;
420}
421
422static void sigalrm(int sig)
423{
424 if (sig != SIGALRM)
425 abort();
426 test_uffdio_copy_eexist = true;
427 alarm(ALARM_INTERVAL_SECS);
428}
429
430int main(int argc, char **argv)
431{
432 size_t bytes;
433
434 if (argc < 4)
435 usage();
436
437 if (signal(SIGALRM, sigalrm) == SIG_ERR)
438 err("failed to arm SIGALRM");
439 alarm(ALARM_INTERVAL_SECS);
440
441 parse_test_type_arg(argv[1]);
442 bytes = atol(argv[2]) * 1024 * 1024;
443
444 if (test_type == TEST_HUGETLB &&
445 get_free_hugepages() < bytes / page_size) {
446 printf("skip: Skipping userfaultfd... not enough hugepages\n");
447 return KSFT_SKIP;
448 }
449
450 nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
451
452 nr_pages_per_cpu = bytes / page_size / nr_cpus;
453 if (!nr_pages_per_cpu) {
454 _err("invalid MiB");
455 usage();
456 }
457
458 bounces = atoi(argv[3]);
459 if (bounces <= 0) {
460 _err("invalid bounces");
461 usage();
462 }
463 nr_pages = nr_pages_per_cpu * nr_cpus;
464
465 printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
466 nr_pages, nr_pages_per_cpu);
467 return userfaultfd_stress();
468}
469
470#else /* __NR_userfaultfd */
471
472#warning "missing __NR_userfaultfd definition"
473
474int main(void)
475{
476 printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
477 return KSFT_SKIP;
478}
479
480#endif /* __NR_userfaultfd */
481

source code of linux/tools/testing/selftests/mm/uffd-stress.c