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)
45 static int bounces;
46 
47 /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
48 #define ALARM_INTERVAL_SECS 10
49 static char *zeropage;
50 pthread_attr_t attr;
51 
52 #define swap(a, b) \
53 	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
54 
55 const char *examples =
56     "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
57     "./userfaultfd anon 100 99999\n\n"
58     "# Run share memory test on 1GiB region with 99 bounces:\n"
59     "./userfaultfd shmem 1000 99\n\n"
60     "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
61     "./userfaultfd hugetlb 256 50\n\n"
62     "# Run the same hugetlb test but using private file:\n"
63     "./userfaultfd hugetlb-private 256 50\n\n"
64     "# 10MiB-~6GiB 999 bounces anonymous test, "
65     "continue forever unless an error triggers\n"
66     "while ./userfaultfd anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";
67 
68 static void usage(void)
69 {
70 	fprintf(stderr, "\nUsage: ./userfaultfd <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 
78 static 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 
91 static 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 
123 static int copy_page_retry(int ufd, unsigned long offset)
124 {
125 	return __copy_page(ufd, offset, true, test_uffdio_wp);
126 }
127 
128 pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
129 
130 static 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 
147 static 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 
179 static 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,
193 					   uffd_poll_thread,
194 					   (void *)&args[cpu]))
195 				return 1;
196 		} else {
197 			if (pthread_create(&uffd_threads[cpu], &attr,
198 					   uffd_read_thread,
199 					   (void *)&args[cpu]))
200 				return 1;
201 			pthread_mutex_lock(&uffd_read_mutex);
202 		}
203 		if (pthread_create(&background_threads[cpu], &attr,
204 				   background_thread, (void *)cpu))
205 			return 1;
206 	}
207 	for (cpu = 0; cpu < nr_cpus; cpu++)
208 		if (pthread_join(background_threads[cpu], NULL))
209 			return 1;
210 
211 	/*
212 	 * Be strict and immediately zap area_src, the whole area has
213 	 * been transferred already by the background treads. The
214 	 * area_src could then be faulted in a racy way by still
215 	 * running uffdio_threads reading zeropages after we zapped
216 	 * area_src (but they're guaranteed to get -EEXIST from
217 	 * UFFDIO_COPY without writing zero pages into area_dst
218 	 * because the background threads already completed).
219 	 */
220 	uffd_test_ops->release_pages(area_src);
221 
222 	finished = 1;
223 	for (cpu = 0; cpu < nr_cpus; cpu++)
224 		if (pthread_join(locking_threads[cpu], NULL))
225 			return 1;
226 
227 	for (cpu = 0; cpu < nr_cpus; cpu++) {
228 		char c;
229 		if (bounces & BOUNCE_POLL) {
230 			if (write(pipefd[cpu*2+1], &c, 1) != 1)
231 				err("pipefd write error");
232 			if (pthread_join(uffd_threads[cpu],
233 					 (void *)&args[cpu]))
234 				return 1;
235 		} else {
236 			if (pthread_cancel(uffd_threads[cpu]))
237 				return 1;
238 			if (pthread_join(uffd_threads[cpu], NULL))
239 				return 1;
240 		}
241 	}
242 
243 	return 0;
244 }
245 
246 static int userfaultfd_stress(void)
247 {
248 	void *area;
249 	unsigned long nr;
250 	struct uffd_args args[nr_cpus];
251 	uint64_t mem_size = nr_pages * page_size;
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 			return 1;
328 
329 		/* Clear all the write protections if there is any */
330 		if (test_uffdio_wp)
331 			wp_range(uffd, (unsigned long)area_dst,
332 				 nr_pages * page_size, false);
333 
334 		/* unregister */
335 		if (uffd_unregister(uffd, area_dst, mem_size))
336 			err("unregister failure");
337 		if (area_dst_alias) {
338 			if (uffd_unregister(uffd, area_dst_alias, mem_size))
339 				err("unregister failure alias");
340 		}
341 
342 		/* verification */
343 		if (bounces & BOUNCE_VERIFY)
344 			for (nr = 0; nr < nr_pages; nr++)
345 				if (*area_count(area_dst, nr) != count_verify[nr])
346 					err("error area_count %llu %llu %lu\n",
347 					    *area_count(area_src, nr),
348 					    count_verify[nr], nr);
349 
350 		/* prepare next bounce */
351 		swap(area_src, area_dst);
352 
353 		swap(area_src_alias, area_dst_alias);
354 
355 		uffd_stats_report(args, nr_cpus);
356 	}
357 
358 	return 0;
359 }
360 
361 static void set_test_type(const char *type)
362 {
363 	if (!strcmp(type, "anon")) {
364 		test_type = TEST_ANON;
365 		uffd_test_ops = &anon_uffd_test_ops;
366 	} else if (!strcmp(type, "hugetlb")) {
367 		test_type = TEST_HUGETLB;
368 		uffd_test_ops = &hugetlb_uffd_test_ops;
369 		map_shared = true;
370 	} else if (!strcmp(type, "hugetlb-private")) {
371 		test_type = TEST_HUGETLB;
372 		uffd_test_ops = &hugetlb_uffd_test_ops;
373 	} else if (!strcmp(type, "shmem")) {
374 		map_shared = true;
375 		test_type = TEST_SHMEM;
376 		uffd_test_ops = &shmem_uffd_test_ops;
377 	} else if (!strcmp(type, "shmem-private")) {
378 		test_type = TEST_SHMEM;
379 		uffd_test_ops = &shmem_uffd_test_ops;
380 	}
381 }
382 
383 static void parse_test_type_arg(const char *raw_type)
384 {
385 	uint64_t features = UFFD_API_FEATURES;
386 
387 	set_test_type(raw_type);
388 
389 	if (!test_type)
390 		err("failed to parse test type argument: '%s'", raw_type);
391 
392 	if (test_type == TEST_HUGETLB)
393 		page_size = default_huge_page_size();
394 	else
395 		page_size = sysconf(_SC_PAGE_SIZE);
396 
397 	if (!page_size)
398 		err("Unable to determine page size");
399 	if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
400 	    > page_size)
401 		err("Impossible to run this test");
402 
403 	/*
404 	 * Whether we can test certain features depends not just on test type,
405 	 * but also on whether or not this particular kernel supports the
406 	 * feature.
407 	 */
408 
409 	if (userfaultfd_open(&features))
410 		err("Userfaultfd open failed");
411 
412 	test_uffdio_wp = test_uffdio_wp &&
413 		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
414 
415 	close(uffd);
416 	uffd = -1;
417 }
418 
419 static void sigalrm(int sig)
420 {
421 	if (sig != SIGALRM)
422 		abort();
423 	test_uffdio_copy_eexist = true;
424 	alarm(ALARM_INTERVAL_SECS);
425 }
426 
427 int main(int argc, char **argv)
428 {
429 	size_t bytes;
430 
431 	if (argc < 4)
432 		usage();
433 
434 	if (signal(SIGALRM, sigalrm) == SIG_ERR)
435 		err("failed to arm SIGALRM");
436 	alarm(ALARM_INTERVAL_SECS);
437 
438 	parse_test_type_arg(argv[1]);
439 	bytes = atol(argv[2]) * 1024 * 1024;
440 
441 	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
442 
443 	nr_pages_per_cpu = bytes / page_size / nr_cpus;
444 	if (!nr_pages_per_cpu) {
445 		_err("invalid MiB");
446 		usage();
447 	}
448 
449 	bounces = atoi(argv[3]);
450 	if (bounces <= 0) {
451 		_err("invalid bounces");
452 		usage();
453 	}
454 	nr_pages = nr_pages_per_cpu * nr_cpus;
455 
456 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
457 	       nr_pages, nr_pages_per_cpu);
458 	return userfaultfd_stress();
459 }
460 
461 #else /* __NR_userfaultfd */
462 
463 #warning "missing __NR_userfaultfd definition"
464 
465 int main(void)
466 {
467 	printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
468 	return KSFT_SKIP;
469 }
470 
471 #endif /* __NR_userfaultfd */
472