netdev - Re: [PATCH v9 1/2] lib: checksum: Fix type casting in checksum kunits

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Message-ID: <cd631754-86fc-4f82-a9f3-560a60515302@csgroup.eu>
Date: Fri, 23 Feb 2024 09:13:53 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Charlie Jenkins <charlie@...osinc.com>, Guenter Roeck
	<linux@...ck-us.net>, David Laight <David.Laight@...lab.com>, Palmer Dabbelt
	<palmer@...belt.com>, Andrew Morton <akpm@...ux-foundation.org>, Helge Deller
	<deller@....de>, "James E.J. Bottomley"
	<James.Bottomley@...senpartnership.com>, Parisc List
	<linux-parisc@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, kernel test
 robot <lkp@...el.com>, "linuxppc-dev@...ts.ozlabs.org"
	<linuxppc-dev@...ts.ozlabs.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v9 1/2] lib: checksum: Fix type casting in checksum kunits



Le 22/02/2024 à 03:55, Charlie Jenkins a écrit :
> The checksum functions use the types __wsum and __sum16. These need to
> be explicitly casted to, because will cause sparse errors otherwise.

This is not the correct fix. When you forcibly cast, you shut up sparse 
and hide warnings but you don't fix the problem on big endian 
architectures which is what sparse reports to you.

In order to fix both the sparse warnings and the related issues, you 
have to perform proper endian conversion, similar to what was done with 
commit b38460bc463c ("kunit: Fix checksum tests on big endian CPUs")

The following change is what your patch should do:

diff --git a/lib/checksum_kunit.c b/lib/checksum_kunit.c
index 225bb7701460..bf70850035c7 100644
--- a/lib/checksum_kunit.c
+++ b/lib/checksum_kunit.c
@@ -215,7 +215,7 @@ static const u32 init_sums_no_overflow[] = {
  	0xffff0000, 0xfffffffb,
  };

-static const __sum16 expected_csum_ipv6_magic[] = {
+static const u16 expected_csum_ipv6_magic[] = {
  	0x18d4, 0x3085, 0x2e4b, 0xd9f4, 0xbdc8, 0x78f,	0x1034, 0x8422, 0x6fc0,
  	0xd2f6, 0xbeb5, 0x9d3,	0x7e2a, 0x312e, 0x778e, 0xc1bb, 0x7cf2, 0x9d1e,
  	0xca21, 0xf3ff, 0x7569, 0xb02e, 0xca86, 0x7e76, 0x4539, 0x45e3, 0xf28d,
@@ -241,7 +241,7 @@ static const __sum16 expected_csum_ipv6_magic[] = {
  	0x3845, 0x1014
  };

-static const __sum16 expected_fast_csum[] = {
+static const u16 expected_fast_csum[] = {
  	0xda83, 0x45da, 0x4f46, 0x4e4f, 0x34e,	0xe902, 0xa5e9, 0x87a5, 0x7187,
  	0x5671, 0xf556, 0x6df5, 0x816d, 0x8f81, 0xbb8f, 0xfbba, 0x5afb, 0xbe5a,
  	0xedbe, 0xabee, 0x6aac, 0xe6b,	0xea0d, 0x67ea, 0x7e68, 0x8a7e, 0x6f8a,
@@ -577,7 +577,8 @@ static void test_csum_no_carry_inputs(struct kunit 
*test)

  static void test_ip_fast_csum(struct kunit *test)
  {
-	__sum16 csum_result, expected;
+	__sum16 csum_result;
+	u16 expected;

  	for (int len = IPv4_MIN_WORDS; len < IPv4_MAX_WORDS; len++) {
  		for (int index = 0; index < NUM_IP_FAST_CSUM_TESTS; index++) {
@@ -586,7 +587,7 @@ static void test_ip_fast_csum(struct kunit *test)
  				expected_fast_csum[(len - IPv4_MIN_WORDS) *
  						   NUM_IP_FAST_CSUM_TESTS +
  						   index];
-			CHECK_EQ(expected, csum_result);
+			CHECK_EQ(to_sum16(expected), csum_result);
  		}
  	}
  }
@@ -598,7 +599,7 @@ static void test_csum_ipv6_magic(struct kunit *test)
  	const struct in6_addr *daddr;
  	unsigned int len;
  	unsigned char proto;
-	unsigned int csum;
+	__wsum csum;

  	const int daddr_offset = sizeof(struct in6_addr);
  	const int len_offset = sizeof(struct in6_addr) + sizeof(struct in6_addr);
@@ -611,10 +612,10 @@ static void test_csum_ipv6_magic(struct kunit *test)
  		saddr = (const struct in6_addr *)(random_buf + i);
  		daddr = (const struct in6_addr *)(random_buf + i +
  						  daddr_offset);
-		len = *(unsigned int *)(random_buf + i + len_offset);
+		len = le32_to_cpu(*(__le32 *)(random_buf + i + len_offset));
  		proto = *(random_buf + i + proto_offset);
-		csum = *(unsigned int *)(random_buf + i + csum_offset);
-		CHECK_EQ(expected_csum_ipv6_magic[i],
+		csum = *(__wsum *)(random_buf + i + csum_offset);
+		CHECK_EQ(to_sum16(expected_csum_ipv6_magic[i]),
  			 csum_ipv6_magic(saddr, daddr, len, proto, csum));
  	}
  #endif /* !CONFIG_NET */
---

Christophe