bitfield: add tests

Add tests for the bitfield helpers. The constant ones will all
be folded to nothing by the compiler (if everything is correct
in the header file), and the variable ones do some tests against
open-coding the necessary shifts.

A few test cases that should fail/warn compilation are provided
under ifdef.
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

lib/Kconfig.debug

@@ -1802,6 +1802,13 @@ config TEST_BITMAP
 
 	  If unsure, say N.
 
+config TEST_BITFIELD
+	tristate "Test bitfield functions at runtime"
+	help
+	  Enable this option to test the bitfield functions at boot.
+
+	  If unsure, say N.
+
 config TEST_UUID
 	tristate "Test functions located in the uuid module at runtime"
 

lib/Makefile

@@ -68,6 +68,7 @@ obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_keys.o
 obj-$(CONFIG_TEST_STATIC_KEYS) += test_static_key_base.o
 obj-$(CONFIG_TEST_PRINTF) += test_printf.o
 obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
+obj-$(CONFIG_TEST_BITFIELD) += test_bitfield.o
 obj-$(CONFIG_TEST_UUID) += test_uuid.o
 obj-$(CONFIG_TEST_PARMAN) += test_parman.o
 obj-$(CONFIG_TEST_KMOD) += test_kmod.o

lib/test_bitfield.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Test cases for bitfield helpers.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/bitfield.h>
+
+#define CHECK_ENC_GET_U(tp, v, field, res) do {				\
+		{							\
+			u##tp _res;					\
+									\
+			_res = u##tp##_encode_bits(v, field);		\
+			if (_res != res) {				\
+				pr_warn("u" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != " #res "\n",\
+					(u64)_res);			\
+				return -EINVAL;				\
+			}						\
+			if (u##tp##_get_bits(_res, field) != v)		\
+				return -EINVAL;				\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET_LE(tp, v, field, res) do {			\
+		{							\
+			__le##tp _res;					\
+									\
+			_res = le##tp##_encode_bits(v, field);		\
+			if (_res != cpu_to_le##tp(res)) {		\
+				pr_warn("le" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != 0x%llx\n",\
+					(u64)le##tp##_to_cpu(_res),	\
+					(u64)(res));			\
+				return -EINVAL;				\
+			}						\
+			if (le##tp##_get_bits(_res, field) != v)	\
+				return -EINVAL;				\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET_BE(tp, v, field, res) do {			\
+		{							\
+			__be##tp _res;					\
+									\
+			_res = be##tp##_encode_bits(v, field);		\
+			if (_res != cpu_to_be##tp(res)) {		\
+				pr_warn("be" #tp "_encode_bits(" #v ", " #field ") is 0x%llx != 0x%llx\n",\
+					(u64)be##tp##_to_cpu(_res),	\
+					(u64)(res));			\
+				return -EINVAL;				\
+			}						\
+			if (be##tp##_get_bits(_res, field) != v)	\
+				return -EINVAL;				\
+		}							\
+	} while (0)
+
+#define CHECK_ENC_GET(tp, v, field, res) do {				\
+		CHECK_ENC_GET_U(tp, v, field, res);			\
+		CHECK_ENC_GET_LE(tp, v, field, res);			\
+		CHECK_ENC_GET_BE(tp, v, field, res);			\
+	} while (0)
+
+static int test_constants(void)
+{
+	/*
+	 * NOTE
+	 * This whole function compiles (or at least should, if everything
+	 * is going according to plan) to nothing after optimisation.
+	 */
+
+	CHECK_ENC_GET(16,  1, 0x000f, 0x0001);
+	CHECK_ENC_GET(16,  3, 0x00f0, 0x0030);
+	CHECK_ENC_GET(16,  5, 0x0f00, 0x0500);
+	CHECK_ENC_GET(16,  7, 0xf000, 0x7000);
+	CHECK_ENC_GET(16, 14, 0x000f, 0x000e);
+	CHECK_ENC_GET(16, 15, 0x00f0, 0x00f0);
+
+	CHECK_ENC_GET_U(8,  1, 0x0f, 0x01);
+	CHECK_ENC_GET_U(8,  3, 0xf0, 0x30);
+	CHECK_ENC_GET_U(8, 14, 0x0f, 0x0e);
+	CHECK_ENC_GET_U(8, 15, 0xf0, 0xf0);
+
+	CHECK_ENC_GET(32,  1, 0x00000f00, 0x00000100);
+	CHECK_ENC_GET(32,  3, 0x0000f000, 0x00003000);
+	CHECK_ENC_GET(32,  5, 0x000f0000, 0x00050000);
+	CHECK_ENC_GET(32,  7, 0x00f00000, 0x00700000);
+	CHECK_ENC_GET(32, 14, 0x0f000000, 0x0e000000);
+	CHECK_ENC_GET(32, 15, 0xf0000000, 0xf0000000);
+
+	CHECK_ENC_GET(64,  1, 0x00000f0000000000ull, 0x0000010000000000ull);
+	CHECK_ENC_GET(64,  3, 0x0000f00000000000ull, 0x0000300000000000ull);
+	CHECK_ENC_GET(64,  5, 0x000f000000000000ull, 0x0005000000000000ull);
+	CHECK_ENC_GET(64,  7, 0x00f0000000000000ull, 0x0070000000000000ull);
+	CHECK_ENC_GET(64, 14, 0x0f00000000000000ull, 0x0e00000000000000ull);
+	CHECK_ENC_GET(64, 15, 0xf000000000000000ull, 0xf000000000000000ull);
+
+	return 0;
+}
+
+#define CHECK(tp, mask) do {						\
+		u64 v;							\
+									\
+		for (v = 0; v < 1 << hweight32(mask); v++)		\
+			if (tp##_encode_bits(v, mask) != v << __ffs64(mask)) \
+				return -EINVAL;				\
+	} while (0)
+
+static int test_variables(void)
+{
+	CHECK(u8, 0x0f);
+	CHECK(u8, 0xf0);
+	CHECK(u8, 0x38);
+
+	CHECK(u16, 0x0038);
+	CHECK(u16, 0x0380);
+	CHECK(u16, 0x3800);
+	CHECK(u16, 0x8000);
+
+	CHECK(u32, 0x80000000);
+	CHECK(u32, 0x7f000000);
+	CHECK(u32, 0x07e00000);
+	CHECK(u32, 0x00018000);
+
+	CHECK(u64, 0x8000000000000000ull);
+	CHECK(u64, 0x7f00000000000000ull);
+	CHECK(u64, 0x0001800000000000ull);
+	CHECK(u64, 0x0000000080000000ull);
+	CHECK(u64, 0x000000007f000000ull);
+	CHECK(u64, 0x0000000018000000ull);
+	CHECK(u64, 0x0000001f8000000ull);
+
+	return 0;
+}
+
+static int __init test_bitfields(void)
+{
+	int ret = test_constants();
+
+	if (ret) {
+		pr_warn("constant tests failed!\n");
+		return ret;
+	}
+
+	ret = test_variables();
+	if (ret) {
+		pr_warn("variable tests failed!\n");
+		return ret;
+	}
+
+#ifdef TEST_BITFIELD_COMPILE
+	/* these should fail compilation */
+	CHECK_ENC_GET(16, 16, 0x0f00, 0x1000);
+	u32_encode_bits(7, 0x06000000);
+
+	/* this should at least give a warning */
+	u16_encode_bits(0, 0x60000);
+#endif
+
+	pr_info("tests passed\n");
+
+	return 0;
+}
+module_init(test_bitfields)
+
+MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
+MODULE_LICENSE("GPL");