Move a block of memory within a memory range. Any alignment optimization
on the source address may cause corruption. Verify using kselftest that
it works. I have also verified with tracing that such optimization does
not happen due to this check in can_align_down():
if (!for_stack && vma->vm_start <= addr_masked)
return false;
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/mremap_test.c | 79 +++++++++++++++++++++++-
1 file changed, 78 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index d7366074e2a8..f45d1abedc9c 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -23,6 +23,7 @@
#define VALIDATION_NO_THRESHOLD 0 /* Verify the entire region */
#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
+#define SIZE_MB(m) ((size_t)m * (1024 * 1024))
struct config {
unsigned long long src_alignment;
@@ -226,6 +227,79 @@ static void mremap_expand_merge_offset(FILE *maps_fp, unsigned long page_size)
ksft_test_result_fail("%s\n", test_name);
}
+/*
+ * Verify that an mremap within a range does not cause corruption
+ * of unrelated part of range.
+ *
+ * Consider the following range which is 2MB aligned and is
+ * a part of a larger 10MB range which is not shown. Each
+ * character is 256KB below making the source and destination
+ * 2MB each. The lower case letters are moved (s to d) and the
+ * upper case letters are not moved. The below test verifies
+ * that the upper case S letters are not corrupted by the
+ * adjacent mremap.
+ *
+ * |DDDDddddSSSSssss|
+ */
+static void mremap_move_within_range(char pattern_seed)
+{
+ char *test_name = "mremap mremap move within range";
+ void *src, *dest;
+ int i, success = 1;
+
+ size_t size = SIZE_MB(20);
+ void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (ptr == MAP_FAILED) {
+ perror("mmap");
+ success = 0;
+ goto out;
+ }
+ memset(ptr, 0, size);
+
+ src = ptr + SIZE_MB(6);
+ src = (void *)((unsigned long)src & ~(SIZE_MB(2) - 1));
+
+ /* Set byte pattern for source block. */
+ srand(pattern_seed);
+ for (i = 0; i < SIZE_MB(2); i++) {
+ ((char *)src)[i] = (char) rand();
+ }
+
+ dest = src - SIZE_MB(2);
+
+ void *new_ptr = mremap(src + SIZE_MB(1), SIZE_MB(1), SIZE_MB(1),
+ MREMAP_MAYMOVE | MREMAP_FIXED, dest + SIZE_MB(1));
+ if (new_ptr == MAP_FAILED) {
+ perror("mremap");
+ success = 0;
+ goto out;
+ }
+
+ /* Verify byte pattern after remapping */
+ srand(pattern_seed);
+ for (i = 0; i < SIZE_MB(1); i++) {
+ char c = (char) rand();
+
+ if (((char *)src)[i] != c) {
+ ksft_print_msg("Data at src at %d got corrupted due to unrelated mremap\n",
+ i);
+ ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
+ ((char *) src)[i] & 0xff);
+ success = 0;
+ }
+ }
+
+out:
+ if (munmap(ptr, size) == -1)
+ perror("munmap");
+
+ if (success)
+ ksft_test_result_pass("%s\n", test_name);
+ else
+ ksft_test_result_fail("%s\n", test_name);
+}
+
/*
* Returns the start address of the mapping on success, else returns
* NULL on failure.
@@ -491,6 +565,7 @@ int main(int argc, char **argv)
unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
unsigned int pattern_seed;
int num_expand_tests = 2;
+ int num_misc_tests = 1;
struct test test_cases[MAX_TEST] = {};
struct test perf_test_cases[MAX_PERF_TEST];
int page_size;
@@ -572,7 +647,7 @@ int main(int argc, char **argv)
(threshold_mb * _1MB >= _1GB);
ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
- ARRAY_SIZE(perf_test_cases) : 0) + num_expand_tests);
+ ARRAY_SIZE(perf_test_cases) : 0) + num_expand_tests + num_misc_tests);
for (i = 0; i < ARRAY_SIZE(test_cases); i++)
run_mremap_test_case(test_cases[i], &failures, threshold_mb,
@@ -590,6 +665,8 @@ int main(int argc, char **argv)
fclose(maps_fp);
+ mremap_move_within_range(pattern_seed);
+
if (run_perf_tests) {
ksft_print_msg("\n%s\n",
"mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
--
2.42.0.rc1.204.g551eb34607-goog
