lib/math: Add int_log test suite

This commit introduces KUnit tests for the intlog2 and intlog10
functions, which compute logarithms in base 2 and base 10, respectively.
The tests cover a range of inputs to ensure the correctness of these
functions across common and edge cases.

Signed-off-by: Bruno Sobreira França <brunofrancadevsec@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Link: https://lore.kernel.org/r/20241202075545.3648096-3-davidgow@google.com
Signed-off-by: Kees Cook <kees@kernel.org>

Author: Bruno Sobreira França

lib/Kconfig.debug

@@ -3197,6 +3197,17 @@ config INT_SQRT_KUNIT_TEST
 
 	  If unsure, say N
 
+config INT_LOG_KUNIT_TEST
+        tristate "Integer log (int_log) test" if !KUNIT_ALL_TESTS
+        depends on KUNIT
+        default KUNIT_ALL_TESTS
+        help
+          This option enables the KUnit test suite for the int_log library, which
+          provides two functions to compute the integer logarithm in base 2 and
+          base 10, called respectively as intlog2 and intlog10.
+
+          If unsure, say N
+
 endif # RUNTIME_TESTING_MENU
 
 config ARCH_USE_MEMTEST

lib/math/tests/Makefile

@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
+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_RATIONAL_KUNIT_TEST)	+= rational_kunit.o

lib/math/tests/int_log_kunit.c

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+#include <linux/int_log.h>
+
+struct test_case_params {
+	u32 value;
+	unsigned int expected_result;
+	const char *name;
+};
+
+
+/* The expected result takes into account the log error */
+static const struct test_case_params intlog2_params[] = {
+	{0, 0, "Log base 2 of 0"},
+	{1, 0, "Log base 2 of 1"},
+	{2, 16777216, "Log base 2 of 2"},
+	{3, 26591232, "Log base 2 of 3"},
+	{4, 33554432, "Log base 2 of 4"},
+	{8, 50331648, "Log base 2 of 8"},
+	{16, 67108864, "Log base 2 of 16"},
+	{32, 83886080, "Log base 2 of 32"},
+	{U32_MAX, 536870911, "Log base 2 of MAX"},
+};
+
+static const struct test_case_params intlog10_params[] = {
+	{0, 0, "Log base 10 of 0"},
+	{1, 0, "Log base 10 of 1"},
+	{6, 13055203, "Log base 10 of 6"},
+	{10, 16777225, "Log base 10 of 10"},
+	{100, 33554450, "Log base 10 of 100"},
+	{1000, 50331675, "Log base 10 of 1000"},
+	{10000, 67108862, "Log base 10 of 10000"},
+	{U32_MAX, 161614247, "Log base 10 of MAX"}
+};
+
+static void get_desc(const struct test_case_params *tc, char *desc)
+{
+	strscpy(desc, tc->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+
+KUNIT_ARRAY_PARAM(intlog2, intlog2_params, get_desc);
+
+static void intlog2_test(struct kunit *test)
+{
+	const struct test_case_params *tc = (const struct test_case_params *)test->param_value;
+
+	KUNIT_EXPECT_EQ(test, tc->expected_result, intlog2(tc->value));
+}
+
+KUNIT_ARRAY_PARAM(intlog10, intlog10_params, get_desc);
+
+static void intlog10_test(struct kunit *test)
+{
+	const struct test_case_params *tc = (const struct test_case_params *)test->param_value;
+
+	KUNIT_EXPECT_EQ(test, tc->expected_result, intlog10(tc->value));
+}
+
+static struct kunit_case math_int_log_test_cases[] = {
+	KUNIT_CASE_PARAM(intlog2_test, intlog2_gen_params),
+	KUNIT_CASE_PARAM(intlog10_test, intlog10_gen_params),
+	{}
+};
+
+static struct kunit_suite int_log_test_suite = {
+	.name = "math-int_log",
+	.test_cases =  math_int_log_test_cases,
+};
+
+kunit_test_suites(&int_log_test_suite);
+
+MODULE_DESCRIPTION("math.int_log KUnit test suite");
+MODULE_LICENSE("GPL");