[PATCH v6 (resend) 0/3] bitfield fixes and tests

[PATCH v6 (resend) 0/3] bitfield fixes and tests

[Johannes Berg]

This is just a resend of v5, to Cc linux-wireless - we decided that
since we have the user coming in through the wireless-drivers tree,
it'll avoid all the usual problems if we'll take these also through
that tree.

johannes

[PATCH v6 (resend) 1/3] bitfield: fix *_encode_bits()

[Johannes Berg]

There's a bug in *_encode_bits() in using ~field_multiplier() for
the check whether or not the constant value fits into the field,
this is wrong and clearly ~field_mask() was intended. This was
triggering for me for both constant and non-constant values.

Additionally, make this case actually into an compile error.
Declaring the extern function that will never exist with just a
warning is pointless as then later we'll just get a link error.

While at it, also fix the indentation in those lines I'm touching.

Finally, as suggested by Andy Shevchenko, add some tests and for
that introduce also u8 helpers. The tests don't compile without
the fix, showing that it's necessary.

Fixes: 00b0c9b82663 ("Add primitives for manipulating bitfields both in host- and fixed-endian.")
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
---
v2: replace stray tab by space
v3: u8 helpers, tests
v4: minor cleanup (Andy)
    split into two patches (Andy)
---
 include/linux/bitfield.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index cf2588d81148..147a7bb341dd 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -104,7 +104,7 @@
 		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask));	\
 	})
 
-extern void __compiletime_warning("value doesn't fit into mask")
+extern void __compiletime_error("value doesn't fit into mask")
 __field_overflow(void);
 extern void __compiletime_error("bad bitfield mask")
 __bad_mask(void);
@@ -121,8 +121,8 @@ static __always_inline u64 field_mask(u64 field)
 #define ____MAKE_OP(type,base,to,from)					\
 static __always_inline __##type type##_encode_bits(base v, base field)	\
 {									\
-        if (__builtin_constant_p(v) &&	(v & ~field_multiplier(field)))	\
-			    __field_overflow();				\
+	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
+		__field_overflow();					\
 	return to((v & field_mask(field)) * field_multiplier(field));	\
 }									\
 static __always_inline __##type type##_replace_bits(__##type old,	\
-- 
2.14.4

Re: [v6,(resend),1/3] bitfield: fix *_encode_bits()

[Kalle Valo]

Johannes Berg <johannes@sipsolutions.net> wrote:

> There's a bug in *_encode_bits() in using ~field_multiplier() for
> the check whether or not the constant value fits into the field,
> this is wrong and clearly ~field_mask() was intended. This was
> triggering for me for both constant and non-constant values.
> 
> Additionally, make this case actually into an compile error.
> Declaring the extern function that will never exist with just a
> warning is pointless as then later we'll just get a link error.
> 
> While at it, also fix the indentation in those lines I'm touching.
> 
> Finally, as suggested by Andy Shevchenko, add some tests and for
> that introduce also u8 helpers. The tests don't compile without
> the fix, showing that it's necessary.
> 
> Fixes: 00b0c9b82663 ("Add primitives for manipulating bitfields both in host- and fixed-endian.")
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

3 patches applied to wireless-drivers-next.git, thanks.

e7d4a95da86e bitfield: fix *_encode_bits()
37a3862e1238 bitfield: add u8 helpers
0e2dc70e3d0d bitfield: add tests

-- 
https://patchwork.kernel.org/patch/10476545/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

[PATCH v6 (resend) 2/3] bitfield: add u8 helpers

[Johannes Berg]

There's no reason why we shouldn't pack/unpack bits into/from
u8 values/registers/etc., so add u8 helpers.

Use the ____MAKE_OP() macro directly to avoid having nonsense
le8_encode_bits() and similar functions.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
---
 include/linux/bitfield.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 147a7bb341dd..65a6981eef7b 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -143,6 +143,7 @@ static __always_inline base type##_get_bits(__##type v, base field)	\
 	____MAKE_OP(le##size,u##size,cpu_to_le##size,le##size##_to_cpu)	\
 	____MAKE_OP(be##size,u##size,cpu_to_be##size,be##size##_to_cpu)	\
 	____MAKE_OP(u##size,u##size,,)
+____MAKE_OP(u8,u8,,)
 __MAKE_OP(16)
 __MAKE_OP(32)
 __MAKE_OP(64)
-- 
2.14.4

[PATCH v6 (resend) 3/3] bitfield: add tests

[Johannes Berg]

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>
---
 lib/Kconfig.debug   |   7 +++
 lib/Makefile        |   1 +
 lib/test_bitfield.c | 168 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 176 insertions(+)
 create mode 100644 lib/test_bitfield.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index eb885942eb0f..b0870377b4d1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1799,6 +1799,13 @@ 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"
 
diff --git a/lib/Makefile b/lib/Makefile
index 84c6dcb31fbb..02ab4c1a64d1 100644
--- a/lib/Makefile
+++ b/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
diff --git a/lib/test_bitfield.c b/lib/test_bitfield.c
new file mode 100644
index 000000000000..5b8f4108662d
--- /dev/null
+++ b/lib/test_bitfield.c
@@ -0,0 +1,168 @@
+// 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");
-- 
2.14.4