It is possible that the aligned address falls on no existing mapping,
however that does not mean that we can just align it down to that.
This test verifies that the "vma->vm_start != addr_to_align" check in
can_align_down() prevents disastrous results if aligning down when
source and dest are mutually aligned within a PMD but the source/dest
addresses requested are not at the beginning of the respective mapping
containing these addresses.
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/mremap_test.c | 189 ++++++++++++++++-------
1 file changed, 134 insertions(+), 55 deletions(-)
diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index f45d1abedc9c..c71ac8306c89 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -24,6 +24,7 @@
#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
#define SIZE_MB(m) ((size_t)m * (1024 * 1024))
+#define SIZE_KB(k) ((size_t)k * 1024)
struct config {
unsigned long long src_alignment;
@@ -148,6 +149,60 @@ static bool is_range_mapped(FILE *maps_fp, void *start, void *end)
return success;
}
+/*
+ * Returns the start address of the mapping on success, else returns
+ * NULL on failure.
+ */
+static void *get_source_mapping(struct config c)
+{
+ unsigned long long addr = 0ULL;
+ void *src_addr = NULL;
+ unsigned long long mmap_min_addr;
+
+ mmap_min_addr = get_mmap_min_addr();
+ /*
+ * For some tests, we need to not have any mappings below the
+ * source mapping. Add some headroom to mmap_min_addr for this.
+ */
+ mmap_min_addr += 10 * _4MB;
+
+retry:
+ addr += c.src_alignment;
+ if (addr < mmap_min_addr)
+ goto retry;
+
+ src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
+ MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
+ -1, 0);
+ if (src_addr == MAP_FAILED) {
+ if (errno == EPERM || errno == EEXIST)
+ goto retry;
+ goto error;
+ }
+ /*
+ * Check that the address is aligned to the specified alignment.
+ * Addresses which have alignments that are multiples of that
+ * specified are not considered valid. For instance, 1GB address is
+ * 2MB-aligned, however it will not be considered valid for a
+ * requested alignment of 2MB. This is done to reduce coincidental
+ * alignment in the tests.
+ */
+ if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
+ !((unsigned long long) src_addr & c.src_alignment)) {
+ munmap(src_addr, c.region_size);
+ goto retry;
+ }
+
+ if (!src_addr)
+ goto error;
+
+ return src_addr;
+error:
+ ksft_print_msg("Failed to map source region: %s\n",
+ strerror(errno));
+ return NULL;
+}
+
/*
* This test validates that merge is called when expanding a mapping.
* Mapping containing three pages is created, middle page is unmapped
@@ -300,60 +355,6 @@ static void mremap_move_within_range(char pattern_seed)
ksft_test_result_fail("%s\n", test_name);
}
-/*
- * Returns the start address of the mapping on success, else returns
- * NULL on failure.
- */
-static void *get_source_mapping(struct config c)
-{
- unsigned long long addr = 0ULL;
- void *src_addr = NULL;
- unsigned long long mmap_min_addr;
-
- mmap_min_addr = get_mmap_min_addr();
- /*
- * For some tests, we need to not have any mappings below the
- * source mapping. Add some headroom to mmap_min_addr for this.
- */
- mmap_min_addr += 10 * _4MB;
-
-retry:
- addr += c.src_alignment;
- if (addr < mmap_min_addr)
- goto retry;
-
- src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
- MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
- -1, 0);
- if (src_addr == MAP_FAILED) {
- if (errno == EPERM || errno == EEXIST)
- goto retry;
- goto error;
- }
- /*
- * Check that the address is aligned to the specified alignment.
- * Addresses which have alignments that are multiples of that
- * specified are not considered valid. For instance, 1GB address is
- * 2MB-aligned, however it will not be considered valid for a
- * requested alignment of 2MB. This is done to reduce coincidental
- * alignment in the tests.
- */
- if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
- !((unsigned long long) src_addr & c.src_alignment)) {
- munmap(src_addr, c.region_size);
- goto retry;
- }
-
- if (!src_addr)
- goto error;
-
- return src_addr;
-error:
- ksft_print_msg("Failed to map source region: %s\n",
- strerror(errno));
- return NULL;
-}
-
/* Returns the time taken for the remap on success else returns -1. */
static long long remap_region(struct config c, unsigned int threshold_mb,
char pattern_seed)
@@ -487,6 +488,83 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
return ret;
}
+/*
+ * Verify that an mremap aligning down does not destroy
+ * the beginning of the mapping just because the aligned
+ * down address landed on a mapping that maybe does not exist.
+ */
+static void mremap_move_1mb_from_start(char pattern_seed)
+{
+ char *test_name = "mremap move 1mb from start at 2MB+256KB aligned src";
+ void *src = NULL, *dest = NULL;
+ int i, success = 1;
+
+ /* Config to reuse get_source_mapping() to do an aligned mmap. */
+ struct config c = {
+ .src_alignment = SIZE_MB(1) + SIZE_KB(256),
+ .region_size = SIZE_MB(6)
+ };
+
+ src = get_source_mapping(c);
+ if (!src) {
+ success = 0;
+ goto out;
+ }
+
+ c.src_alignment = SIZE_MB(1) + SIZE_KB(256);
+ dest = get_source_mapping(c);
+ if (!dest) {
+ success = 0;
+ goto out;
+ }
+
+ /* Set byte pattern for source block. */
+ srand(pattern_seed);
+ for (i = 0; i < SIZE_MB(2); i++) {
+ ((char *)src)[i] = (char) rand();
+ }
+
+ /*
+ * Unmap the beginning of dest so that the aligned address
+ * falls on no mapping.
+ */
+ munmap(dest, SIZE_MB(1));
+
+ 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 (src && munmap(src, c.region_size) == -1)
+ perror("munmap src");
+
+ if (dest && munmap(dest, c.region_size) == -1)
+ perror("munmap dest");
+
+ if (success)
+ ksft_test_result_pass("%s\n", test_name);
+ else
+ ksft_test_result_fail("%s\n", test_name);
+}
+
static void run_mremap_test_case(struct test test_case, int *failures,
unsigned int threshold_mb,
unsigned int pattern_seed)
@@ -565,7 +643,7 @@ 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;
+ int num_misc_tests = 2;
struct test test_cases[MAX_TEST] = {};
struct test perf_test_cases[MAX_PERF_TEST];
int page_size;
@@ -666,6 +744,7 @@ int main(int argc, char **argv)
fclose(maps_fp);
mremap_move_within_range(pattern_seed);
+ mremap_move_1mb_from_start(pattern_seed);
if (run_perf_tests) {
ksft_print_msg("\n%s\n",
--
2.41.0.rc2.161.g9c6817b8e7-goog
