1 files changed, 323 insertions, 150 deletions

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index 901e950f9138..8d874c4754f3 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -21,21 +21,30 @@
 #include <sys/wait.h>
 #include <linux/userfaultfd.h>
 
-#include "../kselftest.h"
+#include "kselftest.h"
 #include "vm_util.h"
 
 #define KiB 1024u
 #define MiB (1024 * KiB)
+#define FORK_EXEC_CHILD_PRG_NAME "ksm_fork_exec_child"
+
+#define MAP_MERGE_FAIL ((void *)-1)
+#define MAP_MERGE_SKIP ((void *)-2)
+
+enum ksm_merge_mode {
+	KSM_MERGE_PRCTL,
+	KSM_MERGE_MADVISE,
+	KSM_MERGE_NONE, /* PRCTL already set */
+};
 
 static int mem_fd;
-static int ksm_fd;
-static int ksm_full_scans_fd;
-static int proc_self_ksm_stat_fd;
-static int proc_self_ksm_merging_pages_fd;
-static int ksm_use_zero_pages_fd;
+static int pages_to_scan_fd;
+static int sleep_millisecs_fd;
 static int pagemap_fd;
 static size_t pagesize;
 
+static void init_global_file_handles(void);
+
 static bool range_maps_duplicates(char *addr, unsigned long size)
 {
 	unsigned long offs_a, offs_b, pfn_a, pfn_b;
@@ -63,115 +72,34 @@ static bool range_maps_duplicates(char *addr, unsigned long size)
 	return false;
 }
 
-static long get_my_ksm_zero_pages(void)
-{
-	char buf[200];
-	char *substr_ksm_zero;
-	size_t value_pos;
-	ssize_t read_size;
-	unsigned long my_ksm_zero_pages;
-
-	if (!proc_self_ksm_stat_fd)
-		return 0;
-
-	read_size = pread(proc_self_ksm_stat_fd, buf, sizeof(buf) - 1, 0);
-	if (read_size < 0)
-		return -errno;
-
-	buf[read_size] = 0;
-
-	substr_ksm_zero = strstr(buf, "ksm_zero_pages");
-	if (!substr_ksm_zero)
-		return 0;
-
-	value_pos = strcspn(substr_ksm_zero, "0123456789");
-	my_ksm_zero_pages = strtol(substr_ksm_zero + value_pos, NULL, 10);
-
-	return my_ksm_zero_pages;
-}
-
-static long get_my_merging_pages(void)
-{
-	char buf[10];
-	ssize_t ret;
-
-	if (proc_self_ksm_merging_pages_fd < 0)
-		return proc_self_ksm_merging_pages_fd;
-
-	ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
-	if (ret <= 0)
-		return -errno;
-	buf[ret] = 0;
-
-	return strtol(buf, NULL, 10);
-}
-
-static long ksm_get_full_scans(void)
-{
-	char buf[10];
-	ssize_t ret;
-
-	ret = pread(ksm_full_scans_fd, buf, sizeof(buf) - 1, 0);
-	if (ret <= 0)
-		return -errno;
-	buf[ret] = 0;
-
-	return strtol(buf, NULL, 10);
-}
-
-static int ksm_merge(void)
-{
-	long start_scans, end_scans;
-
-	/* Wait for two full scans such that any possible merging happened. */
-	start_scans = ksm_get_full_scans();
-	if (start_scans < 0)
-		return start_scans;
-	if (write(ksm_fd, "1", 1) != 1)
-		return -errno;
-	do {
-		end_scans = ksm_get_full_scans();
-		if (end_scans < 0)
-			return end_scans;
-	} while (end_scans < start_scans + 2);
-
-	return 0;
-}
-
-static int ksm_unmerge(void)
-{
-	if (write(ksm_fd, "2", 1) != 1)
-		return -errno;
-	return 0;
-}
-
-static char *mmap_and_merge_range(char val, unsigned long size, int prot,
-				  bool use_prctl)
+static char *__mmap_and_merge_range(char val, unsigned long size, int prot,
+				  enum ksm_merge_mode mode)
 {
 	char *map;
+	char *err_map = MAP_MERGE_FAIL;
 	int ret;
 
 	/* Stabilize accounting by disabling KSM completely. */
-	if (ksm_unmerge()) {
-		ksft_test_result_fail("Disabling (unmerging) KSM failed\n");
-		goto unmap;
+	if (ksm_stop() < 0) {
+		ksft_print_msg("Disabling (unmerging) KSM failed\n");
+		return err_map;
 	}
 
-	if (get_my_merging_pages() > 0) {
-		ksft_test_result_fail("Still pages merged\n");
-		goto unmap;
+	if (ksm_get_self_merging_pages() > 0) {
+		ksft_print_msg("Still pages merged\n");
+		return err_map;
 	}
 
 	map = mmap(NULL, size, PROT_READ|PROT_WRITE,
 		   MAP_PRIVATE|MAP_ANON, -1, 0);
 	if (map == MAP_FAILED) {
-		ksft_test_result_fail("mmap() failed\n");
-		return MAP_FAILED;
+		ksft_print_msg("mmap() failed\n");
+		return err_map;
 	}
 
 	/* Don't use THP. Ignore if THP are not around on a kernel. */
 	if (madvise(map, size, MADV_NOHUGEPAGE) && errno != EINVAL) {
-		ksft_test_result_fail("MADV_NOHUGEPAGE failed\n");
+		ksft_print_msg("MADV_NOHUGEPAGE failed\n");
 		goto unmap;
 	}
 
@@ -179,27 +107,36 @@ static char *mmap_and_merge_range(char val, unsigned long size, int prot,
 	memset(map, val, size);
 
 	if (mprotect(map, size, prot)) {
-		ksft_test_result_skip("mprotect() failed\n");
+		ksft_print_msg("mprotect() failed\n");
+		err_map = MAP_MERGE_SKIP;
 		goto unmap;
 	}
 
-	if (use_prctl) {
+	switch (mode) {
+	case KSM_MERGE_PRCTL:
 		ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
 		if (ret < 0 && errno == EINVAL) {
-			ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
+			ksft_print_msg("PR_SET_MEMORY_MERGE not supported\n");
+			err_map = MAP_MERGE_SKIP;
 			goto unmap;
 		} else if (ret) {
-			ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
+			ksft_print_msg("PR_SET_MEMORY_MERGE=1 failed\n");
 			goto unmap;
 		}
-	} else if (madvise(map, size, MADV_MERGEABLE)) {
-		ksft_test_result_fail("MADV_MERGEABLE failed\n");
-		goto unmap;
+		break;
+	case KSM_MERGE_MADVISE:
+		if (madvise(map, size, MADV_MERGEABLE)) {
+			ksft_print_msg("MADV_MERGEABLE failed\n");
+			goto unmap;
+		}
+		break;
+	case KSM_MERGE_NONE:
+		break;
 	}
 
 	/* Run KSM to trigger merging and wait. */
-	if (ksm_merge()) {
-		ksft_test_result_fail("Running KSM failed\n");
+	if (ksm_start() < 0) {
+		ksft_print_msg("Running KSM failed\n");
 		goto unmap;
 	}
 
@@ -207,15 +144,32 @@ static char *mmap_and_merge_range(char val, unsigned long size, int prot,
 	 * Check if anything was merged at all. Ignore the zero page that is
 	 * accounted differently (depending on kernel support).
 	 */
-	if (val && !get_my_merging_pages()) {
-		ksft_test_result_fail("No pages got merged\n");
+	if (val && !ksm_get_self_merging_pages()) {
+		ksft_print_msg("No pages got merged\n");
 		goto unmap;
 	}
 
 	return map;
 unmap:
 	munmap(map, size);
-	return MAP_FAILED;
+	return err_map;
+}
+
+static char *mmap_and_merge_range(char val, unsigned long size, int prot,
+				  enum ksm_merge_mode mode)
+{
+	char *map;
+	char *ret = MAP_FAILED;
+
+	map = __mmap_and_merge_range(val, size, prot, mode);
+	if (map == MAP_MERGE_FAIL)
+		ksft_test_result_fail("Merging memory failed");
+	else if (map == MAP_MERGE_SKIP)
+		ksft_test_result_skip("Merging memory skipped");
+	else
+		ret = map;
+
+	return ret;
 }
 
 static void test_unmerge(void)
@@ -225,7 +179,7 @@ static void test_unmerge(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, false);
+	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
 	if (map == MAP_FAILED)
 		return;
 
@@ -237,6 +191,7 @@ static void test_unmerge(void)
 	ksft_test_result(!range_maps_duplicates(map, size),
 			 "Pages were unmerged\n");
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 
@@ -249,27 +204,24 @@ static void test_unmerge_zero_pages(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	if (proc_self_ksm_stat_fd < 0) {
-		ksft_test_result_skip("open(\"/proc/self/ksm_stat\") failed\n");
-		return;
-	}
-	if (ksm_use_zero_pages_fd < 0) {
-		ksft_test_result_skip("open \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
+	if (ksm_get_self_zero_pages() < 0) {
+		ksft_test_result_skip("accessing \"/proc/self/ksm_stat\" failed\n");
 		return;
 	}
-	if (write(ksm_use_zero_pages_fd, "1", 1) != 1) {
+
+	if (ksm_use_zero_pages() < 0) {
 		ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
 		return;
 	}
 
 	/* Let KSM deduplicate zero pages. */
-	map = mmap_and_merge_range(0x00, size, PROT_READ | PROT_WRITE, false);
+	map = mmap_and_merge_range(0x00, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
 	if (map == MAP_FAILED)
 		return;
 
 	/* Check if ksm_zero_pages is updated correctly after KSM merging */
 	pages_expected = size / pagesize;
-	if (pages_expected != get_my_ksm_zero_pages()) {
+	if (pages_expected != ksm_get_self_zero_pages()) {
 		ksft_test_result_fail("'ksm_zero_pages' updated after merging\n");
 		goto unmap;
 	}
@@ -282,7 +234,7 @@ static void test_unmerge_zero_pages(void)
 
 	/* Check if ksm_zero_pages is updated correctly after unmerging */
 	pages_expected /= 2;
-	if (pages_expected != get_my_ksm_zero_pages()) {
+	if (pages_expected != ksm_get_self_zero_pages()) {
 		ksft_test_result_fail("'ksm_zero_pages' updated after unmerging\n");
 		goto unmap;
 	}
@@ -292,7 +244,7 @@ static void test_unmerge_zero_pages(void)
 		*((unsigned int *)&map[offs]) = offs;
 
 	/* Now we should have no zeropages remaining. */
-	if (get_my_ksm_zero_pages()) {
+	if (ksm_get_self_zero_pages()) {
 		ksft_test_result_fail("'ksm_zero_pages' updated after write fault\n");
 		goto unmap;
 	}
@@ -301,6 +253,7 @@ static void test_unmerge_zero_pages(void)
 	ksft_test_result(!range_maps_duplicates(map, size),
 			"KSM zero pages were unmerged\n");
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 
@@ -311,7 +264,7 @@ static void test_unmerge_discarded(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, false);
+	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
 	if (map == MAP_FAILED)
 		return;
 
@@ -329,6 +282,7 @@ static void test_unmerge_discarded(void)
 	ksft_test_result(!range_maps_duplicates(map, size),
 			 "Pages were unmerged\n");
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 
@@ -343,7 +297,7 @@ static void test_unmerge_uffd_wp(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, false);
+	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
 	if (map == MAP_FAILED)
 		return;
 
@@ -356,9 +310,13 @@ static void test_unmerge_uffd_wp(void)
 
 	/* See if UFFD-WP is around. */
 	uffdio_api.api = UFFD_API;
-	uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+	uffdio_api.features = 0;
 	if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
-		ksft_test_result_fail("UFFDIO_API failed\n");
+		if (errno == EINVAL)
+			ksft_test_result_skip("The API version requested is not supported\n");
+		else
+			ksft_test_result_fail("UFFDIO_API failed: %s\n", strerror(errno));
+
 		goto close_uffd;
 	}
 	if (!(uffdio_api.features & UFFD_FEATURE_PAGEFAULT_FLAG_WP)) {
@@ -366,6 +324,26 @@ static void test_unmerge_uffd_wp(void)
 		goto close_uffd;
 	}
 
+	/*
+	 * UFFDIO_API must only be called once to enable features.
+	 * So we close the old userfaultfd and create a new one to
+	 * actually enable UFFD_FEATURE_PAGEFAULT_FLAG_WP.
+	 */
+	close(uffd);
+	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+	if (uffd < 0) {
+		ksft_test_result_fail("__NR_userfaultfd failed\n");
+		goto unmap;
+	}
+
+	/* Now, enable it ("two-step handshake") */
+	uffdio_api.api = UFFD_API;
+	uffdio_api.features = UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+	if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
+		ksft_test_result_fail("UFFDIO_API failed: %s\n", strerror(errno));
+		goto close_uffd;
+	}
+
 	/* Register UFFD-WP, no need for an actual handler. */
 	if (uffd_register(uffd, map, size, false, true, false)) {
 		ksft_test_result_fail("UFFDIO_REGISTER_MODE_WP failed\n");
@@ -391,6 +369,7 @@ static void test_unmerge_uffd_wp(void)
 close_uffd:
 	close(uffd);
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 #endif
@@ -438,6 +417,39 @@ static void test_prctl(void)
 	ksft_test_result_pass("Setting/clearing PR_SET_MEMORY_MERGE works\n");
 }
 
+static int test_child_ksm(void)
+{
+	const unsigned int size = 2 * MiB;
+	char *map;
+
+	/* Test if KSM is enabled for the process. */
+	if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1)
+		return 1;
+
+	/* Test if merge could really happen. */
+	map = __mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_NONE);
+	if (map == MAP_MERGE_FAIL)
+		return 2;
+	else if (map == MAP_MERGE_SKIP)
+		return 3;
+
+	ksm_stop();
+	munmap(map, size);
+	return 0;
+}
+
+static void test_child_ksm_err(int status)
+{
+	if (status == 1)
+		ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
+	else if (status == 2)
+		ksft_test_result_fail("Merge in child failed\n");
+	else if (status == 3)
+		ksft_test_result_skip("Merge in child skipped\n");
+	else if (status == 4)
+		ksft_test_result_fail("Binary not found\n");
+}
+
 /* Verify that prctl ksm flag is inherited. */
 static void test_prctl_fork(void)
 {
@@ -457,7 +469,8 @@ static void test_prctl_fork(void)
 
 	child_pid = fork();
 	if (!child_pid) {
-		exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0));
+		init_global_file_handles();
+		exit(test_child_ksm());
 	} else if (child_pid < 0) {
 		ksft_test_result_fail("fork() failed\n");
 		return;
@@ -466,8 +479,106 @@ static void test_prctl_fork(void)
 	if (waitpid(child_pid, &status, 0) < 0) {
 		ksft_test_result_fail("waitpid() failed\n");
 		return;
-	} else if (WEXITSTATUS(status) != 1) {
-		ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result in child\n");
+	}
+
+	status = WEXITSTATUS(status);
+	if (status) {
+		test_child_ksm_err(status);
+		return;
+	}
+
+	if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
+		ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
+		return;
+	}
+
+	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
+}
+
+static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms)
+{
+	int ksm_fd;
+
+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+	if (ksm_fd < 0)
+		return -errno;
+
+	if (write(ksm_fd, "1", 1) != 1)
+		return -errno;
+
+	if (write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)) <= 0)
+		return -errno;
+
+	if (write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0)
+		return -errno;
+
+	return 0;
+}
+
+static int stop_ksmd_and_restore_frequency(void)
+{
+	int ksm_fd;
+
+	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
+	if (ksm_fd < 0)
+		return -errno;
+
+	if (write(ksm_fd, "2", 1) != 1)
+		return -errno;
+
+	if (write(pages_to_scan_fd, "100", 3) <= 0)
+		return -errno;
+
+	if (write(sleep_millisecs_fd, "20", 2) <= 0)
+		return -errno;
+
+	return 0;
+}
+
+static void test_prctl_fork_exec(void)
+{
+	int ret, status;
+	pid_t child_pid;
+
+	ksft_print_msg("[RUN] %s\n", __func__);
+
+	if (start_ksmd_and_set_frequency("2000", "0"))
+		ksft_test_result_fail("set ksmd's scanning frequency failed\n");
+
+	ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
+	if (ret < 0 && errno == EINVAL) {
+		ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
+		return;
+	} else if (ret) {
+		ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
+		return;
+	}
+
+	child_pid = fork();
+	if (child_pid == -1) {
+		ksft_test_result_skip("fork() failed\n");
+		return;
+	} else if (child_pid == 0) {
+		char *prg_name = "./ksm_functional_tests";
+		char *argv_for_program[] = { prg_name, FORK_EXEC_CHILD_PRG_NAME, NULL };
+
+		execv(prg_name, argv_for_program);
+		exit(4);
+	}
+
+	if (waitpid(child_pid, &status, 0) > 0) {
+		if (WIFEXITED(status)) {
+			status = WEXITSTATUS(status);
+			if (status) {
+				test_child_ksm_err(status);
+				return;
+			}
+		} else {
+			ksft_test_result_fail("program didn't terminate normally\n");
+			return;
+		}
+	} else {
+		ksft_test_result_fail("waitpid() failed\n");
 		return;
 	}
 
@@ -476,6 +587,11 @@ static void test_prctl_fork(void)
 		return;
 	}
 
+	if (stop_ksmd_and_restore_frequency()) {
+		ksft_test_result_fail("restore ksmd frequency failed\n");
+		return;
+	}
+
 	ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
 }
 
@@ -486,7 +602,7 @@ static void test_prctl_unmerge(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, true);
+	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_PRCTL);
 	if (map == MAP_FAILED)
 		return;
 
@@ -498,6 +614,7 @@ static void test_prctl_unmerge(void)
 	ksft_test_result(!range_maps_duplicates(map, size),
 			 "Pages were unmerged\n");
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 
@@ -509,7 +626,7 @@ static void test_prot_none(void)
 
 	ksft_print_msg("[RUN] %s\n", __func__);
 
-	map = mmap_and_merge_range(0x11, size, PROT_NONE, false);
+	map = mmap_and_merge_range(0x11, size, PROT_NONE, KSM_MERGE_MADVISE);
 	if (map == MAP_FAILED)
 		goto unmap;
 
@@ -531,14 +648,83 @@ static void test_prot_none(void)
 	ksft_test_result(!range_maps_duplicates(map, size),
 			 "Pages were unmerged\n");
 unmap:
+	ksm_stop();
 	munmap(map, size);
 }
 
+static void test_fork_ksm_merging_page_count(void)
+{
+	const unsigned int size = 2 * MiB;
+	char *map;
+	pid_t child_pid;
+	int status;
+
+	ksft_print_msg("[RUN] %s\n", __func__);
+
+	map = mmap_and_merge_range(0xcf, size, PROT_READ | PROT_WRITE, KSM_MERGE_MADVISE);
+	if (map == MAP_FAILED)
+		return;
+
+	child_pid = fork();
+	if (!child_pid) {
+		init_global_file_handles();
+		exit(ksm_get_self_merging_pages());
+	} else if (child_pid < 0) {
+		ksft_test_result_fail("fork() failed\n");
+		goto unmap;
+	}
+
+	if (waitpid(child_pid, &status, 0) < 0) {
+		ksft_test_result_fail("waitpid() failed\n");
+		goto unmap;
+	}
+
+	status = WEXITSTATUS(status);
+	if (status) {
+		ksft_test_result_fail("ksm_merging_page in child: %d\n", status);
+		goto unmap;
+	}
+
+	ksft_test_result_pass("ksm_merging_pages is not inherited after fork\n");
+
+unmap:
+	ksm_stop();
+	munmap(map, size);
+}
+
+static void init_global_file_handles(void)
+{
+	mem_fd = open("/proc/self/mem", O_RDWR);
+	if (mem_fd < 0)
+		ksft_exit_fail_msg("opening /proc/self/mem failed\n");
+	if (ksm_stop() < 0)
+		ksft_exit_skip("accessing \"/sys/kernel/mm/ksm/run\") failed\n");
+	if (ksm_get_full_scans() < 0)
+		ksft_exit_skip("accessing \"/sys/kernel/mm/ksm/full_scans\") failed\n");
+	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
+	if (pagemap_fd < 0)
+		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
+	if (ksm_get_self_merging_pages() < 0)
+		ksft_exit_skip("accessing \"/proc/self/ksm_merging_pages\") failed\n");
+
+	pages_to_scan_fd = open("/sys/kernel/mm/ksm/pages_to_scan", O_RDWR);
+	if (pages_to_scan_fd < 0)
+		ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/pages_to_scan failed\n");
+	sleep_millisecs_fd = open("/sys/kernel/mm/ksm/sleep_millisecs", O_RDWR);
+	if (sleep_millisecs_fd < 0)
+		ksft_exit_fail_msg("opening /sys/kernel/mm/ksm/sleep_millisecs failed\n");
+}
+
 int main(int argc, char **argv)
 {
-	unsigned int tests = 7;
+	unsigned int tests = 9;
 	int err;
 
+	if (argc > 1 && !strcmp(argv[1], FORK_EXEC_CHILD_PRG_NAME)) {
+		init_global_file_handles();
+		exit(test_child_ksm());
+	}
+
 #ifdef __NR_userfaultfd
 	tests++;
 #endif
@@ -548,22 +734,7 @@ int main(int argc, char **argv)
 
 	pagesize = getpagesize();
 
-	mem_fd = open("/proc/self/mem", O_RDWR);
-	if (mem_fd < 0)
-		ksft_exit_fail_msg("opening /proc/self/mem failed\n");
-	ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR);
-	if (ksm_fd < 0)
-		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/run\") failed\n");
-	ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
-	if (ksm_full_scans_fd < 0)
-		ksft_exit_skip("open(\"/sys/kernel/mm/ksm/full_scans\") failed\n");
-	pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
-	if (pagemap_fd < 0)
-		ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
-	proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
-	proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
-					      O_RDONLY);
-	ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
+	init_global_file_handles();
 
 	test_unmerge();
 	test_unmerge_zero_pages();
@@ -576,11 +747,13 @@ int main(int argc, char **argv)
 
 	test_prctl();
 	test_prctl_fork();
+	test_prctl_fork_exec();
 	test_prctl_unmerge();
+	test_fork_ksm_merging_page_count();
 
 	err = ksft_get_fail_cnt();
 	if (err)
 		ksft_exit_fail_msg("%d out of %d tests failed\n",
 				   err, ksft_test_num());
-	return ksft_exit_pass();
+	ksft_exit_pass();
 }