linux-kernel - Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for ip_fast_csum and csum_ipv6

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Date: Thu, 15 Feb 2024 21:25:00 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Helge Deller <deller@....de>
Cc: Charlie Jenkins <charlie@...osinc.com>,
	David Laight <David.Laight@...lab.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Parisc List <linux-parisc@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/2] lib: checksum: Use aligned accesses for
 ip_fast_csum and csum_ipv6_magic tests

On Fri, Feb 16, 2024 at 06:54:55AM +0100, Helge Deller wrote:
> 
> Can you please give a pointer to this test code?
> I'm happy to try it on real hardware.
> 
See below.

Guenter

---
>From 0478f35f02224994e1d81e614b66219ab7539f7f Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@...ck-us.net>
Date: Wed, 14 Feb 2024 11:25:18 -0800
Subject: [PATCH] carry tests

Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 lib/checksum_kunit.c | 76 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/lib/checksum_kunit.c b/lib/checksum_kunit.c
index 72c313ba4c78..8f7925396e53 100644
--- a/lib/checksum_kunit.c
+++ b/lib/checksum_kunit.c
@@ -546,12 +546,88 @@ static void test_csum_ipv6_magic(struct kunit *test)
 #endif /* !CONFIG_NET */
 }
 
+#ifdef CONFIG_64BIT
+
+static __inline__ int get_carry64(void *addr)
+{
+	int carry = 0;
+	unsigned long sum = 0xffffffff;
+	unsigned long tmp;
+
+	__asm__ __volatile__ (
+"	add	%0, %0, %0\n"	/* clear carry			*/
+"	ldd	0(%2), %3\n"	/* load from memory		*/
+"	add	%1, %3, %1\n"	/* optionally generate carry	*/
+"	ldd	0(%2), %3\n"	/* load from memory again	*/
+"	add,dc	%0, %0, %0\n"	/* return carry			*/
+	: "=r" (carry), "=r" (sum), "=r" (addr), "=r" (tmp)
+	: "0" (carry), "1" (sum), "2" (addr)
+	: "memory");
+
+	return carry;
+}
+
+static __inline__ int get_carry32(void *addr)
+{
+	int carry = 0;
+	unsigned int sum = 0xffffffff;
+	unsigned int tmp;
+
+	__asm__ __volatile__ (
+"	add	%0, %0, %0\n"	/* clear carry			*/
+"	ldw	0(%2), %3\n"	/* load from memory		*/
+"	add	%1, %3, %1\n"	/* optionally generate carry	*/
+"	ldw	0(%2), %3\n"	/* load from memory again	*/
+"	addc	%0, %0, %0\n"	/* return carry			*/
+	: "=r" (carry), "=r" (sum), "=r" (addr), "=r" (tmp)
+	: "0" (carry), "1" (sum), "2" (addr)
+	: "memory");
+
+	return carry;
+}
+
+static void test_bad_carry(struct kunit *test)
+{
+	int carry;
+
+	memset(tmp_buf, 0xff, sizeof(tmp_buf));
+	carry = get_carry64(&tmp_buf[0]);
+	pr_info("#### carry64 aligned, expect 1 -> %d\n", carry);
+	carry = get_carry64(&tmp_buf[4]);
+	pr_info("#### carry64 unaligned 4, expect 1 -> %d\n", carry);
+
+	carry = get_carry64(&tmp_buf[2]);
+	pr_info("#### carry64 unaligned 2, expect 1 -> %d\n", carry);
+
+	carry = get_carry32(&tmp_buf[0]);
+	pr_info("#### carry32 aligned, expect 1 -> %d\n", carry);
+	carry = get_carry32(&tmp_buf[2]);
+	pr_info("#### carry64 unaligned, expect 1 -> %d\n", carry);
+
+	memset(tmp_buf, 0, sizeof(tmp_buf));
+	carry = get_carry64(&tmp_buf[0]);
+	pr_info("#### carry64 aligned, expect 0 -> %d\n", carry);
+	carry = get_carry64(&tmp_buf[4]);
+	pr_info("#### carry64 unaligned 4, expect 0 -> %d\n", carry);
+	carry = get_carry64(&tmp_buf[2]);
+	pr_info("#### carry64 unaligned 2, expect 0 -> %d\n", carry);
+
+	carry = get_carry32(&tmp_buf[0]);
+	pr_info("#### carry32 aligned, expect 0 -> %d\n", carry);
+	carry = get_carry32(&tmp_buf[2]);
+	pr_info("#### carry32 unaligned, expect 0 -> %d\n", carry);
+}
+#else
+static void test_bad_carry(struct kunit *test) {}
+#endif /* CONFIG_64BIT */
+
 static struct kunit_case __refdata checksum_test_cases[] = {
 	KUNIT_CASE(test_csum_fixed_random_inputs),
 	KUNIT_CASE(test_csum_all_carry_inputs),
 	KUNIT_CASE(test_csum_no_carry_inputs),
 	KUNIT_CASE(test_ip_fast_csum),
 	KUNIT_CASE(test_csum_ipv6_magic),
+	KUNIT_CASE(test_bad_carry),
 	{}
 };
 
-- 
2.39.2