lib/prime_numbers: convert self-test to KUnit

Extract a private header and convert the prime_numbers self-test to a
KUnit test. I considered parameterizing the test using
`KUNIT_CASE_PARAM` but didn't see how it was possible since the test
logic is entangled with the test parameter generation logic.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250208-prime_numbers-kunit-convert-v5-2-b0cb82ae7c7d@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>

2 files changed, 60 insertions, 0 deletions

diff --git a/lib/math/tests/Makefile b/lib/math/tests/Makefile
index 1d2dd6424df8..13dc96e48408 100644
--- a/lib/math/tests/Makefile
+++ b/lib/math/tests/Makefile
@@ -4,4 +4,5 @@ obj-$(CONFIG_GCD_KUNIT_TEST)		+= gcd_kunit.o
 obj-$(CONFIG_INT_LOG_KUNIT_TEST)	+= int_log_kunit.o
 obj-$(CONFIG_INT_POW_KUNIT_TEST)	+= int_pow_kunit.o
 obj-$(CONFIG_INT_SQRT_KUNIT_TEST)	+= int_sqrt_kunit.o
+obj-$(CONFIG_PRIME_NUMBERS_KUNIT_TEST)	+= prime_numbers_kunit.o
 obj-$(CONFIG_RATIONAL_KUNIT_TEST)	+= rational_kunit.o
diff --git a/lib/math/tests/prime_numbers_kunit.c b/lib/math/tests/prime_numbers_kunit.c
new file mode 100644
index 000000000000..2f1643208c66
--- /dev/null
+++ b/lib/math/tests/prime_numbers_kunit.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <kunit/test.h>
+#include <linux/module.h>
+#include <linux/prime_numbers.h>
+
+#include "../prime_numbers_private.h"
+
+static void dump_primes(void *ctx, const struct primes *p)
+{
+	static char buf[PAGE_SIZE];
+	struct kunit_suite *suite = ctx;
+
+	bitmap_print_to_pagebuf(true, buf, p->primes, p->sz);
+	kunit_info(suite, "primes.{last=%lu, .sz=%lu, .primes[]=...x%lx} = %s",
+		   p->last, p->sz, p->primes[BITS_TO_LONGS(p->sz) - 1], buf);
+}
+
+static void prime_numbers_test(struct kunit *test)
+{
+	const unsigned long max = 65536;
+	unsigned long x, last, next;
+
+	for (last = 0, x = 2; x < max; x++) {
+		const bool slow = slow_is_prime_number(x);
+		const bool fast = is_prime_number(x);
+
+		KUNIT_ASSERT_EQ_MSG(test, slow, fast, "is-prime(%lu)", x);
+
+		if (!slow)
+			continue;
+
+		next = next_prime_number(last);
+		KUNIT_ASSERT_EQ_MSG(test, next, x, "next-prime(%lu)", last);
+		last = next;
+	}
+}
+
+static void kunit_suite_exit(struct kunit_suite *suite)
+{
+	with_primes(suite, dump_primes);
+}
+
+static struct kunit_case prime_numbers_cases[] = {
+	KUNIT_CASE(prime_numbers_test),
+	{},
+};
+
+static struct kunit_suite prime_numbers_suite = {
+	.name = "math-prime_numbers",
+	.suite_exit = kunit_suite_exit,
+	.test_cases = prime_numbers_cases,
+};
+
+kunit_test_suite(prime_numbers_suite);
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_DESCRIPTION("Prime number library");
+MODULE_LICENSE("GPL");