[PATCH net-next] kunit: Fix checksum tests on big endian CPUs

[Christophe Leroy <christophe.leroy@csgroup.eu>]

On powerpc64le checksum kunit tests work:

[    2.011457][    T1]     KTAP version 1
[    2.011662][    T1]     # Subtest: checksum
[    2.011848][    T1]     1..3
[    2.034710][    T1]     ok 1 test_csum_fixed_random_inputs
[    2.079325][    T1]     ok 2 test_csum_all_carry_inputs
[    2.127102][    T1]     ok 3 test_csum_no_carry_inputs
[    2.127202][    T1] # checksum: pass:3 fail:0 skip:0 total:3
[    2.127533][    T1] # Totals: pass:3 fail:0 skip:0 total:3
[    2.127956][    T1] ok 1 checksum

But on powerpc64 and powerpc32 they fail:

[    1.859890][    T1]     KTAP version 1
[    1.860041][    T1]     # Subtest: checksum
[    1.860201][    T1]     1..3
[    1.861927][   T58]     # test_csum_fixed_random_inputs: ASSERTION FAILED at lib/checksum_kunit.c:243
[    1.861927][   T58]     Expected result == expec, but
[    1.861927][   T58]         result == 54991 (0xd6cf)
[    1.861927][   T58]         expec == 33316 (0x8224)
[    1.863742][    T1]     not ok 1 test_csum_fixed_random_inputs
[    1.864520][   T60]     # test_csum_all_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:267
[    1.864520][   T60]     Expected result == expec, but
[    1.864520][   T60]         result == 255 (0xff)
[    1.864520][   T60]         expec == 65280 (0xff00)
[    1.868820][    T1]     not ok 2 test_csum_all_carry_inputs
[    1.869977][   T62]     # test_csum_no_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:306
[    1.869977][   T62]     Expected result == expec, but
[    1.869977][   T62]         result == 64515 (0xfc03)
[    1.869977][   T62]         expec == 0 (0x0)
[    1.872060][    T1]     not ok 3 test_csum_no_carry_inputs
[    1.872102][    T1] # checksum: pass:0 fail:3 skip:0 total:3
[    1.872458][    T1] # Totals: pass:0 fail:3 skip:0 total:3
[    1.872791][    T1] not ok 3 checksum

This is because all expected values were calculated for X86 which
is little endian. On big endian systems all precalculated 16 bits
halves must be byte swapped.

And this is confirmed by a huge amount of sparse errors when building
with C=2

So fix all sparse errors and it will naturally work on all endianness.

Fixes: 688eb8191b47 ("x86/csum: Improve performance of `csum_partial`")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 lib/checksum_kunit.c | 54 +++++++++++++++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 16 deletions(-)

diff --git a/lib/checksum_kunit.c b/lib/checksum_kunit.c
index ace3c4799fe1..0eed92b77ba3 100644
--- a/lib/checksum_kunit.c
+++ b/lib/checksum_kunit.c
@@ -10,7 +10,8 @@
 #define MAX_ALIGN 64
 #define TEST_BUFLEN (MAX_LEN + MAX_ALIGN)
 
-static const __wsum random_init_sum = 0x2847aab;
+/* Values for a little endian CPU. Byte swap each half on big endian CPU. */
+static const u32 random_init_sum = 0x2847aab;
 static const u8 random_buf[] = {
 	0xac, 0xd7, 0x76, 0x69, 0x6e, 0xf2, 0x93, 0x2c, 0x1f, 0xe0, 0xde, 0x86,
 	0x8f, 0x54, 0x33, 0x90, 0x95, 0xbf, 0xff, 0xb9, 0xea, 0x62, 0x6e, 0xb5,
@@ -56,7 +57,9 @@ static const u8 random_buf[] = {
 	0xe1, 0xdf, 0x4b, 0xe1, 0x81, 0xe2, 0x17, 0x02, 0x7b, 0x58, 0x8b, 0x92,
 	0x1a, 0xac, 0x46, 0xdd, 0x2e, 0xce, 0x40, 0x09
 };
-static const __sum16 expected_results[] = {
+
+/* Values for a little endian CPU. Byte swap on big endian CPU. */
+static const u16 expected_results[] = {
 	0x82d0, 0x8224, 0xab23, 0xaaad, 0x41ad, 0x413f, 0x4f3e, 0x4eab, 0x22ab,
 	0x228c, 0x428b, 0x41ad, 0xbbac, 0xbb1d, 0x671d, 0x66ea, 0xd6e9, 0xd654,
 	0x1754, 0x1655, 0x5d54, 0x5c6a, 0xfa69, 0xf9fb, 0x44fb, 0x4428, 0xf527,
@@ -115,7 +118,9 @@ static const __sum16 expected_results[] = {
 	0x1d47, 0x3c46, 0x3bc5, 0x59c4, 0x59ad, 0x57ad, 0x5732, 0xff31, 0xfea6,
 	0x6ca6, 0x6c8c, 0xc08b, 0xc045, 0xe344, 0xe316, 0x1516, 0x14d6,
 };
-static const __wsum init_sums_no_overflow[] = {
+
+/* Values for a little endian CPU. Byte swap each half on big endian CPU. */
+static const u32 init_sums_no_overflow[] = {
 	0xffffffff, 0xfffffffb, 0xfffffbfb, 0xfffffbf7, 0xfffff7f7, 0xfffff7f3,
 	0xfffff3f3, 0xfffff3ef, 0xffffefef, 0xffffefeb, 0xffffebeb, 0xffffebe7,
 	0xffffe7e7, 0xffffe7e3, 0xffffe3e3, 0xffffe3df, 0xffffdfdf, 0xffffdfdb,
@@ -208,7 +213,21 @@ static u8 tmp_buf[TEST_BUFLEN];
 
 #define full_csum(buff, len, sum) csum_fold(csum_partial(buff, len, sum))
 
-#define CHECK_EQ(lhs, rhs) KUNIT_ASSERT_EQ(test, lhs, rhs)
+#define CHECK_EQ(lhs, rhs) KUNIT_ASSERT_EQ(test, (__force u64)lhs, (__force u64)rhs)
+
+static __sum16 to_sum16(u16 x)
+{
+	return (__force __sum16)le16_to_cpu((__force __le16)x);
+}
+
+/* This function swaps the bytes inside each half of a __wsum */
+static __wsum to_wsum(u32 x)
+{
+	u16 hi = le16_to_cpu((__force __le16)(x >> 16));
+	u16 lo = le16_to_cpu((__force __le16)x);
+
+	return (__force __wsum)((hi << 16) | lo);
+}
 
 static void assert_setup_correct(struct kunit *test)
 {
@@ -226,7 +245,8 @@ static void assert_setup_correct(struct kunit *test)
 static void test_csum_fixed_random_inputs(struct kunit *test)
 {
 	int len, align;
-	__wsum result, expec, sum;
+	__wsum sum;
+	__sum16 result, expec;
 
 	assert_setup_correct(test);
 	for (align = 0; align < TEST_BUFLEN; ++align) {
@@ -237,9 +257,9 @@ static void test_csum_fixed_random_inputs(struct kunit *test)
 			/*
 			 * Test the precomputed random input.
 			 */
-			sum = random_init_sum;
+			sum = to_wsum(random_init_sum);
 			result = full_csum(&tmp_buf[align], len, sum);
-			expec = expected_results[len];
+			expec = to_sum16(expected_results[len]);
 			CHECK_EQ(result, expec);
 		}
 	}
@@ -251,7 +271,8 @@ static void test_csum_fixed_random_inputs(struct kunit *test)
 static void test_csum_all_carry_inputs(struct kunit *test)
 {
 	int len, align;
-	__wsum result, expec, sum;
+	__wsum sum;
+	__sum16 result, expec;
 
 	assert_setup_correct(test);
 	memset(tmp_buf, 0xff, TEST_BUFLEN);
@@ -261,9 +282,9 @@ static void test_csum_all_carry_inputs(struct kunit *test)
 			/*
 			 * All carries from input and initial sum.
 			 */
-			sum = 0xffffffff;
+			sum = to_wsum(0xffffffff);
 			result = full_csum(&tmp_buf[align], len, sum);
-			expec = (len & 1) ? 0xff00 : 0;
+			expec = to_sum16((len & 1) ? 0xff00 : 0);
 			CHECK_EQ(result, expec);
 
 			/*
@@ -272,11 +293,11 @@ static void test_csum_all_carry_inputs(struct kunit *test)
 			sum = 0;
 			result = full_csum(&tmp_buf[align], len, sum);
 			if (len & 1)
-				expec = 0xff00;
+				expec = to_sum16(0xff00);
 			else if (len)
 				expec = 0;
 			else
-				expec = 0xffff;
+				expec = to_sum16(0xffff);
 			CHECK_EQ(result, expec);
 		}
 	}
@@ -290,7 +311,8 @@ static void test_csum_all_carry_inputs(struct kunit *test)
 static void test_csum_no_carry_inputs(struct kunit *test)
 {
 	int len, align;
-	__wsum result, expec, sum;
+	__wsum sum;
+	__sum16 result, expec;
 
 	assert_setup_correct(test);
 	memset(tmp_buf, 0x4, TEST_BUFLEN);
@@ -300,7 +322,7 @@ static void test_csum_no_carry_inputs(struct kunit *test)
 			/*
 			 * Expect no carries.
 			 */
-			sum = init_sums_no_overflow[len];
+			sum = to_wsum(init_sums_no_overflow[len]);
 			result = full_csum(&tmp_buf[align], len, sum);
 			expec = 0;
 			CHECK_EQ(result, expec);
@@ -308,9 +330,9 @@ static void test_csum_no_carry_inputs(struct kunit *test)
 			/*
 			 * Expect one carry.
 			 */
-			sum = init_sums_no_overflow[len] + 1;
+			sum = to_wsum(init_sums_no_overflow[len] + 1);
 			result = full_csum(&tmp_buf[align], len, sum);
-			expec = len ? 0xfffe : 0xffff;
+			expec = to_sum16(len ? 0xfffe : 0xffff);
 			CHECK_EQ(result, expec);
 		}
 	}
-- 
2.41.0