[PATCH v2 2/2] selftests/nolibc: test the memory allocator

Thomas Weißschuh
2026-04-04T11:50:29Z

The memory allocator has not seen any testing so far.

Add a simple testcase for it.

Suggested-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/lkml/adDRK8D6YBZgv36H@1wt.eu/
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

---
This is the proposal from Willy with some improvements:
* Check that calloc() returns zeroed memory
* Test the page-based invariants for all page sizes
* Use named variables instead of hardcoded values
* Fix a segfault
---
tools/testing/selftests/nolibc/nolibc-test.c | 55 ++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 91d95a152568..dd10402267ee 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1555,6 +1555,60 @@ int test_time_types(void)
return 0;
}

+int test_malloc(void)
+{
+ size_t sz_array1, sz_array2, sz_array3;
+ int *array1, *array2, *array3;
+ int pagesize = getpagesize();
+ size_t idx;
+
+ if (pagesize < 0)
+ return 1;
+
+ /* Dependent on the page size, as that is the granularity of our allocator. */
+ sz_array1 = pagesize / 2;
+ array1 = malloc(sz_array1 * sizeof(*array1));
+ if (!array1)
+ return 2;
+
+ for (idx = 0; idx < sz_array1; idx++)
+ array1[idx] = idx;
+
+ sz_array2 = pagesize * 2;
+ array2 = calloc(sz_array2, sizeof(*array2));
+ if (!array2) {
+ free(array1);
+ return 3;
+ }
+
+ for (idx = 0; idx < sz_array2; idx++) {
+ if (array2[idx] != 0) {
+ free(array2);
+ return 4;
+ }
+ array2[idx] = idx + sz_array1;
+ }
+
+ /* Resize array1 into array3 and append array2 at the end. */
+ sz_array3 = sz_array1 + sz_array2;
+ array3 = realloc(array1, sz_array3 * sizeof(*array3));
+ if (!array3) {
+ free(array2);
+ free(array1);
+ return 5;
+ }
+ memcpy(array3 + sz_array1, array2, sizeof(*array2) * sz_array2);
+ free(array2);
+
+ /* The contents must be contiguous now. */
+ for (idx = 0; idx < sz_array3; idx++)
+ if (array3[idx] != (int)idx)
+ return 6;
+
+ free(array3);
+ return 0;
+}
+
int run_stdlib(int min, int max)
{
int test;
@@ -1687,6 +1741,7 @@ int run_stdlib(int min, int max)
CASE_TEST(makedev_big); EXPECT_EQ(1, makedev(0x11223344, 0x55667788), 0x1122355667734488); break;
CASE_TEST(major_big); EXPECT_EQ(1, major(0x1122355667734488), 0x11223344); break;
CASE_TEST(minor_big); EXPECT_EQ(1, minor(0x1122355667734488), 0x55667788); break;
+ CASE_TEST(malloc); EXPECT_ZR(1, test_malloc()); break;

case __LINE__:
return ret; /* must be last */

--
2.53.0