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authorDev Jain <dev.jain@arm.com>2026-04-15 10:15:09 +0530
committerAndrew Morton <akpm@linux-foundation.org>2026-05-28 21:04:53 -0700
commit7e8983f317ab0efd13aa573e166d7ad69e36a429 (patch)
tree547caac5fc409cbc5ecd00b2cc89c4e57be6b90c /tools
parent8aa442cfce79e2d69e72fc8e0c0864ac2971149d (diff)
downloadlinux-next-history-7e8983f317ab0efd13aa573e166d7ad69e36a429.tar.gz
selftests/mm: simplify byte pattern checking in mremap_test
The original version of mremap_test (7df666253f26: "kselftests: vm: add mremap tests") validated remapped contents byte-by-byte and printed a mismatch index in case the bytes streams didn't match. That was rather inefficient, especially also if the test passed. Later, commit 7033c6cc9620 ("selftests/mm: mremap_test: optimize execution time from minutes to seconds using chunkwise memcmp") used memcmp() on bigger chunks, to fallback to byte-wise scanning to detect the problematic index only if it discovered a problem. However, the implementation is overly complicated (e.g., get_sqrt() is currently not optimal) and we don't really have to report the exact index: whoever debugs the failing test can figure that out. Let's simplify by just comparing both byte streams with memcmp() and not detecting the exact failed index. Link: https://lore.kernel.org/20260415044509.579428-1-dev.jain@arm.com Signed-off-by: Dev Jain <dev.jain@arm.com> Reported-by: Sarthak Sharma <sarthak.sharma@arm.com> Tested-by: Sarthak Sharma <sarthak.sharma@arm.com> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Liam Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: David Laight <david.laight.linux@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/mm/mremap_test.c109
1 files changed, 10 insertions, 99 deletions
diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index 308576437228c..131d9d6db8679 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -76,27 +76,6 @@ enum {
.expect_failure = should_fail \
}
-/* compute square root using binary search */
-static unsigned long get_sqrt(unsigned long val)
-{
- unsigned long low = 1;
-
- /* assuming rand_size is less than 1TB */
- unsigned long high = (1UL << 20);
-
- while (low <= high) {
- unsigned long mid = low + (high - low) / 2;
- unsigned long temp = mid * mid;
-
- if (temp == val)
- return mid;
- if (temp < val)
- low = mid + 1;
- high = mid - 1;
- }
- return low;
-}
-
/*
* Returns false if the requested remap region overlaps with an
* existing mapping (e.g text, stack) else returns true.
@@ -995,11 +974,9 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
char *rand_addr)
{
void *addr, *tmp_addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
- unsigned long long t, d;
struct timespec t_start = {0, 0}, t_end = {0, 0};
long long start_ns, end_ns, align_mask, ret, offset;
unsigned long long threshold;
- unsigned long num_chunks;
if (threshold_mb == VALIDATION_NO_THRESHOLD)
threshold = c.region_size;
@@ -1068,87 +1045,21 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
goto clean_up_dest_preamble;
}
- /*
- * Verify byte pattern after remapping. Employ an algorithm with a
- * square root time complexity in threshold: divide the range into
- * chunks, if memcmp() returns non-zero, only then perform an
- * iteration in that chunk to find the mismatch index.
- */
- num_chunks = get_sqrt(threshold);
- for (unsigned long i = 0; i < num_chunks; ++i) {
- size_t chunk_size = threshold / num_chunks;
- unsigned long shift = i * chunk_size;
-
- if (!memcmp(dest_addr + shift, rand_addr + shift, chunk_size))
- continue;
-
- /* brute force iteration only over mismatch segment */
- for (t = shift; t < shift + chunk_size; ++t) {
- if (((char *) dest_addr)[t] != rand_addr[t]) {
- ksft_print_msg("Data after remap doesn't match at offset %llu\n",
- t);
- ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[t] & 0xff,
- ((char *) dest_addr)[t] & 0xff);
- ret = -1;
- goto clean_up_dest;
- }
- }
- }
-
- /*
- * if threshold is not divisible by num_chunks, then check the
- * last chunk
- */
- for (t = num_chunks * (threshold / num_chunks); t < threshold; ++t) {
- if (((char *) dest_addr)[t] != rand_addr[t]) {
- ksft_print_msg("Data after remap doesn't match at offset %llu\n",
- t);
- ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[t] & 0xff,
- ((char *) dest_addr)[t] & 0xff);
- ret = -1;
- goto clean_up_dest;
- }
+ /* Verify byte pattern after remapping */
+ if (memcmp(dest_addr, rand_addr, threshold)) {
+ ksft_print_msg("Data after remap doesn't match\n");
+ ret = -1;
+ goto clean_up_dest;
}
/* Verify the dest preamble byte pattern after remapping */
- if (!c.dest_preamble_size)
- goto no_preamble;
-
- num_chunks = get_sqrt(c.dest_preamble_size);
-
- for (unsigned long i = 0; i < num_chunks; ++i) {
- size_t chunk_size = c.dest_preamble_size / num_chunks;
- unsigned long shift = i * chunk_size;
-
- if (!memcmp(dest_preamble_addr + shift, rand_addr + shift,
- chunk_size))
- continue;
-
- /* brute force iteration only over mismatched segment */
- for (d = shift; d < shift + chunk_size; ++d) {
- if (((char *) dest_preamble_addr)[d] != rand_addr[d]) {
- ksft_print_msg("Preamble data after remap doesn't match at offset %llu\n",
- d);
- ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[d] & 0xff,
- ((char *) dest_preamble_addr)[d] & 0xff);
- ret = -1;
- goto clean_up_dest;
- }
- }
- }
-
- for (d = num_chunks * (c.dest_preamble_size / num_chunks); d < c.dest_preamble_size; ++d) {
- if (((char *) dest_preamble_addr)[d] != rand_addr[d]) {
- ksft_print_msg("Preamble data after remap doesn't match at offset %llu\n",
- d);
- ksft_print_msg("Expected: %#x\t Got: %#x\n", rand_addr[d] & 0xff,
- ((char *) dest_preamble_addr)[d] & 0xff);
- ret = -1;
- goto clean_up_dest;
- }
+ if (c.dest_preamble_size &&
+ memcmp(dest_preamble_addr, rand_addr, c.dest_preamble_size)) {
+ ksft_print_msg("Preamble data after remap doesn't match\n");
+ ret = -1;
+ goto clean_up_dest;
}
-no_preamble:
start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
ret = end_ns - start_ns;
generated by cgit 1.3-korg (git 2.53.0) at 2026-06-01 03:58:19 +0000