xref: /linux/tools/testing/selftests/mm/ksm_functional_tests.c (revision 55d0969c451159cff86949b38c39171cab962069)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * KSM functional tests
4  *
5  * Copyright 2022, Red Hat, Inc.
6  *
7  * Author(s): David Hildenbrand <david@redhat.com>
8  */
9 #define _GNU_SOURCE
10 #include <stdlib.h>
11 #include <string.h>
12 #include <stdbool.h>
13 #include <stdint.h>
14 #include <asm-generic/unistd.h>
15 #include <errno.h>
16 #include <fcntl.h>
17 #include <sys/mman.h>
18 #include <sys/prctl.h>
19 #include <sys/syscall.h>
20 #include <sys/ioctl.h>
21 #include <sys/wait.h>
22 #include <linux/userfaultfd.h>
23 
24 #include "../kselftest.h"
25 #include "vm_util.h"
26 
27 #define KiB 1024u
28 #define MiB (1024 * KiB)
29 #define FORK_EXEC_CHILD_PRG_NAME "ksm_fork_exec_child"
30 
31 #define MAP_MERGE_FAIL ((void *)-1)
32 #define MAP_MERGE_SKIP ((void *)-2)
33 
34 enum ksm_merge_mode {
35 	KSM_MERGE_PRCTL,
36 	KSM_MERGE_MADVISE,
37 	KSM_MERGE_NONE, /* PRCTL already set */
38 };
39 
40 static int mem_fd;
41 static int ksm_fd;
42 static int ksm_full_scans_fd;
43 static int proc_self_ksm_stat_fd;
44 static int proc_self_ksm_merging_pages_fd;
45 static int ksm_use_zero_pages_fd;
46 static int pagemap_fd;
47 static size_t pagesize;
48 
49 static bool range_maps_duplicates(char *addr, unsigned long size)
50 {
51 	unsigned long offs_a, offs_b, pfn_a, pfn_b;
52 
53 	/*
54 	 * There is no easy way to check if there are KSM pages mapped into
55 	 * this range. We only check that the range does not map the same PFN
56 	 * twice by comparing each pair of mapped pages.
57 	 */
58 	for (offs_a = 0; offs_a < size; offs_a += pagesize) {
59 		pfn_a = pagemap_get_pfn(pagemap_fd, addr + offs_a);
60 		/* Page not present or PFN not exposed by the kernel. */
61 		if (pfn_a == -1ul || !pfn_a)
62 			continue;
63 
64 		for (offs_b = offs_a + pagesize; offs_b < size;
65 		     offs_b += pagesize) {
66 			pfn_b = pagemap_get_pfn(pagemap_fd, addr + offs_b);
67 			if (pfn_b == -1ul || !pfn_b)
68 				continue;
69 			if (pfn_a == pfn_b)
70 				return true;
71 		}
72 	}
73 	return false;
74 }
75 
76 static long get_my_ksm_zero_pages(void)
77 {
78 	char buf[200];
79 	char *substr_ksm_zero;
80 	size_t value_pos;
81 	ssize_t read_size;
82 	unsigned long my_ksm_zero_pages;
83 
84 	if (!proc_self_ksm_stat_fd)
85 		return 0;
86 
87 	read_size = pread(proc_self_ksm_stat_fd, buf, sizeof(buf) - 1, 0);
88 	if (read_size < 0)
89 		return -errno;
90 
91 	buf[read_size] = 0;
92 
93 	substr_ksm_zero = strstr(buf, "ksm_zero_pages");
94 	if (!substr_ksm_zero)
95 		return 0;
96 
97 	value_pos = strcspn(substr_ksm_zero, "0123456789");
98 	my_ksm_zero_pages = strtol(substr_ksm_zero + value_pos, NULL, 10);
99 
100 	return my_ksm_zero_pages;
101 }
102 
103 static long get_my_merging_pages(void)
104 {
105 	char buf[10];
106 	ssize_t ret;
107 
108 	if (proc_self_ksm_merging_pages_fd < 0)
109 		return proc_self_ksm_merging_pages_fd;
110 
111 	ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
112 	if (ret <= 0)
113 		return -errno;
114 	buf[ret] = 0;
115 
116 	return strtol(buf, NULL, 10);
117 }
118 
119 static long ksm_get_full_scans(void)
120 {
121 	char buf[10];
122 	ssize_t ret;
123 
124 	ret = pread(ksm_full_scans_fd, buf, sizeof(buf) - 1, 0);
125 	if (ret <= 0)
126 		return -errno;
127 	buf[ret] = 0;
128 
129 	return strtol(buf, NULL, 10);
130 }
131 
132 static int ksm_merge(void)
133 {
134 	long start_scans, end_scans;
135 
136 	/* Wait for two full scans such that any possible merging happened. */
137 	start_scans = ksm_get_full_scans();
138 	if (start_scans < 0)
139 		return start_scans;
140 	if (write(ksm_fd, "1", 1) != 1)
141 		return -errno;
142 	do {
143 		end_scans = ksm_get_full_scans();
144 		if (end_scans < 0)
145 			return end_scans;
146 	} while (end_scans < start_scans + 2);
147 
148 	return 0;
149 }
150 
151 static int ksm_unmerge(void)
152 {
153 	if (write(ksm_fd, "2", 1) != 1)
154 		return -errno;
155 	return 0;
156 }
157 
158 static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
159 				  enum ksm_merge_mode mode)
160 {
161 	char *map;
162 	char *err_map = MAP_MERGE_FAIL;
163 	int ret;
164 
165 	/* Stabilize accounting by disabling KSM completely. */
166 	if (ksm_unmerge()) {
167 		ksft_print_msg("Disabling (unmerging) KSM failed\n");
168 		return err_map;
169 	}
170 
171 	if (get_my_merging_pages() > 0) {
172 		ksft_print_msg("Still pages merged\n");
173 		return err_map;
174 	}
175 
176 	map = mmap(NULL, size, PROT_READ|PROT_WRITE,
177 		   MAP_PRIVATE|MAP_ANON, -1, 0);
178 	if (map == MAP_FAILED) {
179 		ksft_print_msg("mmap() failed\n");
180 		return err_map;
181 	}
182 
183 	/* Don't use THP. Ignore if THP are not around on a kernel. */
184 	if (madvise(map, size, MADV_NOHUGEPAGE) && errno != EINVAL) {
185 		ksft_print_msg("MADV_NOHUGEPAGE failed\n");
186 		goto unmap;
187 	}
188 
189 	/* Make sure each page contains the same values to merge them. */
190 	memset(map, val, size);
191 
192 	if (mprotect(map, size, prot)) {
193 		ksft_print_msg("mprotect() failed\n");
194 		err_map = MAP_MERGE_SKIP;
195 		goto unmap;
196 	}
197 
198 	switch (mode) {
199 	case KSM_MERGE_PRCTL:
200 		ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
201 		if (ret < 0 && errno == EINVAL) {
202 			ksft_print_msg("PR_SET_MEMORY_MERGE not supported\n");
203 			err_map = MAP_MERGE_SKIP;
204 			goto unmap;
205 		} else if (ret) {
206 			ksft_print_msg("PR_SET_MEMORY_MERGE=1 failed\n");
207 			goto unmap;
208 		}
209 		break;
210 	case KSM_MERGE_MADVISE:
211 		if (madvise(map, size, MADV_MERGEABLE)) {
212 			ksft_print_msg("MADV_MERGEABLE failed\n");
213 			goto unmap;
214 		}
215 		break;
216 	case KSM_MERGE_NONE:
217 		break;
218 	}
219 
220 	/* Run KSM to trigger merging and wait. */
221 	if (ksm_merge()) {
222 		ksft_print_msg("Running KSM failed\n");
223 		goto unmap;
224 	}
225 
226 	/*
227 	 * Check if anything was merged at all. Ignore the zero page that is
228 	 * accounted differently (depending on kernel support).
229 	 */
230 	if (val && !get_my_merging_pages()) {
231 		ksft_print_msg("No pages got merged\n");
232 		goto unmap;
233 	}
234 
235 	return map;
236 unmap:
237 	munmap(map, size);
238 	return err_map;
239 }
240 
241 static char *mmap_and_merge_range(char val, unsigned long size, int prot,
242 				  enum ksm_merge_mode mode)
243 {
244 	char *map;
245 	char *ret = MAP_FAILED;
246 
247 	map = __mmap_and_merge_range(val, size, prot, mode);
248 	if (map == MAP_MERGE_FAIL)
249 		ksft_test_result_fail("Merging memory failed");
250 	else if (map == MAP_MERGE_SKIP)
251 		ksft_test_result_skip("Merging memory skipped");
252 	else
253 		ret = map;
254 
255 	return ret;
256 }
257 
258 static void test_unmerge(void)
259 {
260 	const unsigned int size = 2 * MiB;
261 	char *map;
262 
263 	ksft_print_msg("[RUN] %s\n", __func__);
264 
265 	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
266 	if (map == MAP_FAILED)
267 		return;
268 
269 	if (madvise(map, size, MADV_UNMERGEABLE)) {
270 		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
271 		goto unmap;
272 	}
273 
274 	ksft_test_result(!range_maps_duplicates(map, size),
275 			 "Pages were unmerged\n");
276 unmap:
277 	munmap(map, size);
278 }
279 
280 static void test_unmerge_zero_pages(void)
281 {
282 	const unsigned int size = 2 * MiB;
283 	char *map;
284 	unsigned int offs;
285 	unsigned long pages_expected;
286 
287 	ksft_print_msg("[RUN] %s\n", __func__);
288 
289 	if (proc_self_ksm_stat_fd < 0) {
290 		ksft_test_result_skip("open(\"/proc/self/ksm_stat\") failed\n");
291 		return;
292 	}
293 	if (ksm_use_zero_pages_fd < 0) {
294 		ksft_test_result_skip("open \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
295 		return;
296 	}
297 	if (write(ksm_use_zero_pages_fd, "1", 1) != 1) {
298 		ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
299 		return;
300 	}
301 
302 	/* Let KSM deduplicate zero pages. */
303 	map = mmap_and_merge_range(0x00, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
304 	if (map == MAP_FAILED)
305 		return;
306 
307 	/* Check if ksm_zero_pages is updated correctly after KSM merging */
308 	pages_expected = size / pagesize;
309 	if (pages_expected != get_my_ksm_zero_pages()) {
310 		ksft_test_result_fail("'ksm_zero_pages' updated after merging\n");
311 		goto unmap;
312 	}
313 
314 	/* Try to unmerge half of the region */
315 	if (madvise(map, size / 2, MADV_UNMERGEABLE)) {
316 		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
317 		goto unmap;
318 	}
319 
320 	/* Check if ksm_zero_pages is updated correctly after unmerging */
321 	pages_expected /= 2;
322 	if (pages_expected != get_my_ksm_zero_pages()) {
323 		ksft_test_result_fail("'ksm_zero_pages' updated after unmerging\n");
324 		goto unmap;
325 	}
326 
327 	/* Trigger unmerging of the other half by writing to the pages. */
328 	for (offs = size / 2; offs < size; offs += pagesize)
329 		*((unsigned int *)&map[offs]) = offs;
330 
331 	/* Now we should have no zeropages remaining. */
332 	if (get_my_ksm_zero_pages()) {
333 		ksft_test_result_fail("'ksm_zero_pages' updated after write fault\n");
334 		goto unmap;
335 	}
336 
337 	/* Check if ksm zero pages are really unmerged */
338 	ksft_test_result(!range_maps_duplicates(map, size),
339 			"KSM zero pages were unmerged\n");
340 unmap:
341 	munmap(map, size);
342 }
343 
344 static void test_unmerge_discarded(void)
345 {
346 	const unsigned int size = 2 * MiB;
347 	char *map;
348 
349 	ksft_print_msg("[RUN] %s\n", __func__);
350 
351 	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
352 	if (map == MAP_FAILED)
353 		return;
354 
355 	/* Discard half of all mapped pages so we have pte_none() entries. */
356 	if (madvise(map, size / 2, MADV_DONTNEED)) {
357 		ksft_test_result_fail("MADV_DONTNEED failed\n");
358 		goto unmap;
359 	}
360 
361 	if (madvise(map, size, MADV_UNMERGEABLE)) {
362 		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
363 		goto unmap;
364 	}
365 
366 	ksft_test_result(!range_maps_duplicates(map, size),
367 			 "Pages were unmerged\n");
368 unmap:
369 	munmap(map, size);
370 }
371 
372 static void test_unmerge_uffd_wp(void)
373 {
374 	struct uffdio_writeprotect uffd_writeprotect;
375 	const unsigned int size = 2 * MiB;
376 	struct uffdio_api uffdio_api;
377 	char *map;
378 	int uffd;
379 
380 	ksft_print_msg("[RUN] %s\n", __func__);
381 
382 	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
383 	if (map == MAP_FAILED)
384 		return;
385 
386 	/* See if UFFD is around. */
387 	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
388 	if (uffd < 0) {
389 		ksft_test_result_skip("__NR_userfaultfd failed\n");
390 		goto unmap;
391 	}
392 
393 	/* See if UFFD-WP is around. */
394 	uffdio_api.api = UFFD_API;
395 	uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
396 	if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
397 		ksft_test_result_fail("UFFDIO_API failed\n");
398 		goto close_uffd;
399 	}
400 	if (!(uffdio_api.features & UFFD_FEATURE_PAGEFAULT_FLAG_WP)) {
401 		ksft_test_result_skip("UFFD_FEATURE_PAGEFAULT_FLAG_WP not available\n");
402 		goto close_uffd;
403 	}
404 
405 	/* Register UFFD-WP, no need for an actual handler. */
406 	if (uffd_register(uffd, map, size, false, true, false)) {
407 		ksft_test_result_fail("UFFDIO_REGISTER_MODE_WP failed\n");
408 		goto close_uffd;
409 	}
410 
411 	/* Write-protect the range using UFFD-WP. */
412 	uffd_writeprotect.range.start = (unsigned long) map;
413 	uffd_writeprotect.range.len = size;
414 	uffd_writeprotect.mode = UFFDIO_WRITEPROTECT_MODE_WP;
415 	if (ioctl(uffd, UFFDIO_WRITEPROTECT, &uffd_writeprotect)) {
416 		ksft_test_result_fail("UFFDIO_WRITEPROTECT failed\n");
417 		goto close_uffd;
418 	}
419 
420 	if (madvise(map, size, MADV_UNMERGEABLE)) {
421 		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
422 		goto close_uffd;
423 	}
424 
425 	ksft_test_result(!range_maps_duplicates(map, size),
426 			 "Pages were unmerged\n");
427 close_uffd:
428 	close(uffd);
429 unmap:
430 	munmap(map, size);
431 }
432 
433 /* Verify that KSM can be enabled / queried with prctl. */
434 static void test_prctl(void)
435 {
436 	int ret;
437 
438 	ksft_print_msg("[RUN] %s\n", __func__);
439 
440 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
441 	if (ret < 0 && errno == EINVAL) {
442 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
443 		return;
444 	} else if (ret) {
445 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
446 		return;
447 	}
448 
449 	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
450 	if (ret < 0) {
451 		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
452 		return;
453 	} else if (ret != 1) {
454 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 not effective\n");
455 		return;
456 	}
457 
458 	ret = prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0);
459 	if (ret) {
460 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
461 		return;
462 	}
463 
464 	ret = prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0);
465 	if (ret < 0) {
466 		ksft_test_result_fail("PR_GET_MEMORY_MERGE failed\n");
467 		return;
468 	} else if (ret != 0) {
469 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 not effective\n");
470 		return;
471 	}
472 
473 	ksft_test_result_pass("Setting/clearing PR_SET_MEMORY_MERGE works\n");
474 }
475 
476 static int test_child_ksm(void)
477 {
478 	const unsigned int size = 2 * MiB;
479 	char *map;
480 
481 	/* Test if KSM is enabled for the process. */
482 	if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1)
483 		return -1;
484 
485 	/* Test if merge could really happen. */
486 	map = __mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_NONE);
487 	if (map == MAP_MERGE_FAIL)
488 		return -2;
489 	else if (map == MAP_MERGE_SKIP)
490 		return -3;
491 
492 	munmap(map, size);
493 	return 0;
494 }
495 
496 static void test_child_ksm_err(int status)
497 {
498 	if (status == -1)
499 		ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
500 	else if (status == -2)
501 		ksft_test_result_fail("Merge in child failed\n");
502 	else if (status == -3)
503 		ksft_test_result_skip("Merge in child skipped\n");
504 }
505 
506 /* Verify that prctl ksm flag is inherited. */
507 static void test_prctl_fork(void)
508 {
509 	int ret, status;
510 	pid_t child_pid;
511 
512 	ksft_print_msg("[RUN] %s\n", __func__);
513 
514 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
515 	if (ret < 0 && errno == EINVAL) {
516 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
517 		return;
518 	} else if (ret) {
519 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
520 		return;
521 	}
522 
523 	child_pid = fork();
524 	if (!child_pid) {
525 		exit(test_child_ksm());
526 	} else if (child_pid < 0) {
527 		ksft_test_result_fail("fork() failed\n");
528 		return;
529 	}
530 
531 	if (waitpid(child_pid, &status, 0) < 0) {
532 		ksft_test_result_fail("waitpid() failed\n");
533 		return;
534 	}
535 
536 	status = WEXITSTATUS(status);
537 	if (status) {
538 		test_child_ksm_err(status);
539 		return;
540 	}
541 
542 	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
543 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
544 		return;
545 	}
546 
547 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
548 }
549 
550 static void test_prctl_fork_exec(void)
551 {
552 	int ret, status;
553 	pid_t child_pid;
554 
555 	ksft_print_msg("[RUN] %s\n", __func__);
556 
557 	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
558 	if (ret < 0 && errno == EINVAL) {
559 		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
560 		return;
561 	} else if (ret) {
562 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
563 		return;
564 	}
565 
566 	child_pid = fork();
567 	if (child_pid == -1) {
568 		ksft_test_result_skip("fork() failed\n");
569 		return;
570 	} else if (child_pid == 0) {
571 		char *prg_name = "./ksm_functional_tests";
572 		char *argv_for_program[] = { prg_name, FORK_EXEC_CHILD_PRG_NAME };
573 
574 		execv(prg_name, argv_for_program);
575 		return;
576 	}
577 
578 	if (waitpid(child_pid, &status, 0) > 0) {
579 		if (WIFEXITED(status)) {
580 			status = WEXITSTATUS(status);
581 			if (status) {
582 				test_child_ksm_err(status);
583 				return;
584 			}
585 		} else {
586 			ksft_test_result_fail("program didn't terminate normally\n");
587 			return;
588 		}
589 	} else {
590 		ksft_test_result_fail("waitpid() failed\n");
591 		return;
592 	}
593 
594 	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
595 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
596 		return;
597 	}
598 
599 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
600 }
601 
602 static void test_prctl_unmerge(void)
603 {
604 	const unsigned int size = 2 * MiB;
605 	char *map;
606 
607 	ksft_print_msg("[RUN] %s\n", __func__);
608 
609 	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_PRCTL);
610 	if (map == MAP_FAILED)
611 		return;
612 
613 	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
614 		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
615 		goto unmap;
616 	}
617 
618 	ksft_test_result(!range_maps_duplicates(map, size),
619 			 "Pages were unmerged\n");
620 unmap:
621 	munmap(map, size);
622 }
623 
624 static void test_prot_none(void)
625 {
626 	const unsigned int size = 2 * MiB;
627 	char *map;
628 	int i;
629 
630 	ksft_print_msg("[RUN] %s\n", __func__);
631 
632 	map = mmap_and_merge_range(0x11, size, PROT_NONE, KSM_MERGE_MADVISE);
633 	if (map == MAP_FAILED)
634 		goto unmap;
635 
636 	/* Store a unique value in each page on one half using ptrace */
637 	for (i = 0; i < size / 2; i += pagesize) {
638 		lseek(mem_fd, (uintptr_t) map + i, SEEK_SET);
639 		if (write(mem_fd, &i, sizeof(i)) != sizeof(i)) {
640 			ksft_test_result_fail("ptrace write failed\n");
641 			goto unmap;
642 		}
643 	}
644 
645 	/* Trigger unsharing on the other half. */
646 	if (madvise(map + size / 2, size / 2, MADV_UNMERGEABLE)) {
647 		ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
648 		goto unmap;
649 	}
650 
651 	ksft_test_result(!range_maps_duplicates(map, size),
652 			 "Pages were unmerged\n");
653 unmap:
654 	munmap(map, size);
655 }
656 
657 static void init_global_file_handles(void)
658 {
659 	mem_fd = open("/proc/self/mem", O_RDWR);
660 	if (mem_fd < 0)
661 		ksft_exit_fail_msg("opening /proc/self/mem failed\n");
662 	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
663 	if (ksm_fd < 0)
664 		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/run\") failed\n");
665 	ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
666 	if (ksm_full_scans_fd < 0)
667 		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/full_scans\") failed\n");
668 	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
669 	if (pagemap_fd < 0)
670 		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
671 	proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
672 	proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
673 						O_RDONLY);
674 	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
675 }
676 
677 int main(int argc, char **argv)
678 {
679 	unsigned int tests = 8;
680 	int err;
681 
682 	if (argc > 1 && !strcmp(argv[1], FORK_EXEC_CHILD_PRG_NAME)) {
683 		init_global_file_handles();
684 		exit(test_child_ksm());
685 	}
686 
687 	tests++;
688 
689 	ksft_print_header();
690 	ksft_set_plan(tests);
691 
692 	pagesize = getpagesize();
693 
694 	init_global_file_handles();
695 
696 	test_unmerge();
697 	test_unmerge_zero_pages();
698 	test_unmerge_discarded();
699 	test_unmerge_uffd_wp();
700 
701 	test_prot_none();
702 
703 	test_prctl();
704 	test_prctl_fork();
705 	test_prctl_fork_exec();
706 	test_prctl_unmerge();
707 
708 	err = ksft_get_fail_cnt();
709 	if (err)
710 		ksft_exit_fail_msg("%d out of %d tests failed\n",
711 				   err, ksft_test_num());
712 	ksft_exit_pass();
713 }
714