[PATCH v1 2/3] selftests/ksm: ksm_functional_tests: add prctl unmerge test

David Hildenbrand
2023-04-18T15:30:42Z

Let's test whether setting PR_SET_MEMORY_MERGE to 0 after setting it to
1 will unmerge pages, similar to how setting MADV_UNMERGEABLE after setting
MADV_MERGEABLE would.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
.../selftests/mm/ksm_functional_tests.c | 46 ++++++++++++++++---
1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index 7bc9fc17c9f0..26853badae70 100644
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -91,9 +91,10 @@ static int ksm_merge(void)
return 0;
}

-static char *mmap_and_merge_range(char val, unsigned long size)
+static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
{
char *map;
+ int ret;

map = mmap(NULL, size, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANON, -1, 0);
@@ -110,7 +111,17 @@ static char *mmap_and_merge_range(char val, unsigned long size)

/* Make sure each page contains the same values to merge them. */
memset(map, val, size);
- if (madvise(map, size, MADV_MERGEABLE)) {
+
+ if (use_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");
+ goto unmap;
+ } else if (ret) {
+ ksft_test_result_fail("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;
}
@@ -133,7 +144,7 @@ static void test_unmerge(void)

ksft_print_msg("[RUN] %s\n", __func__);

- map = mmap_and_merge_range(0xcf, size);
+ map = mmap_and_merge_range(0xcf, size, false);
if (map == MAP_FAILED)
return;

@@ -155,7 +166,7 @@ static void test_unmerge_discarded(void)

ksft_print_msg("[RUN] %s\n", __func__);

- map = mmap_and_merge_range(0xcf, size);
+ map = mmap_and_merge_range(0xcf, size, false);
if (map == MAP_FAILED)
return;

@@ -187,7 +198,7 @@ static void test_unmerge_uffd_wp(void)

ksft_print_msg("[RUN] %s\n", __func__);

- map = mmap_and_merge_range(0xcf, size);
+ map = mmap_and_merge_range(0xcf, size, false);
if (map == MAP_FAILED)
return;

@@ -323,9 +334,31 @@ static void test_prctl_fork(void)
ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
}

+static void test_prctl_unmerge(void)
+{
+ const unsigned int size = 2 * MiB;
+ char *map;
+
+ ksft_print_msg("[RUN] %s\n", __func__);
+
+ map = mmap_and_merge_range(0xcf, size, true);
+ if (map == MAP_FAILED)
+ return;
+
+ if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
+ ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
+ goto unmap;
+ }
+
+ ksft_test_result(!range_maps_duplicates(map, size),
+ "Pages were unmerged\n");
+unmap:
+ munmap(map, size);
+}
+
int main(int argc, char **argv)
{
- unsigned int tests = 4;
+ unsigned int tests = 5;
int err;

#ifdef __NR_userfaultfd
@@ -355,6 +388,7 @@ int main(int argc, char **argv)

test_prctl();
test_prctl_fork();
+ test_prctl_unmerge();

err = ksft_get_fail_cnt();
if (err)
--
2.39.2