linux-kernel - [PATCH bpf-next v3 1/4] net: checksum: move from32to16() to generic header

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Message-Id: <20241026125339.26459-2-puranjay@kernel.org>
Date: Sat, 26 Oct 2024 12:53:36 +0000
From: Puranjay Mohan <puranjay@...nel.org>
To: Albert Ou <aou@...s.berkeley.edu>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	bpf@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eduard Zingerman <eddyz87@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Helge Deller <deller@....de>,
	Jakub Kicinski <kuba@...nel.org>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-parisc@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Mykola Lysenko <mykolal@...com>,
	netdev@...r.kernel.org,
	Palmer Dabbelt <palmer@...belt.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Puranjay Mohan <puranjay12@...il.com>,
	Puranjay Mohan <puranjay@...nel.org>,
	Shuah Khan <shuah@...nel.org>,
	Song Liu <song@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Yonghong Song <yonghong.song@...ux.dev>
Subject: [PATCH bpf-next v3 1/4] net: checksum: move from32to16() to generic header

from32to16() is used by lib/checksum.c and also by
arch/parisc/lib/checksum.c. The next patch will use it in the
bpf_csum_diff helper.

Move from32to16() to the include/net/checksum.h as csum_from32to16() and
remove other implementations.

Signed-off-by: Puranjay Mohan <puranjay@...nel.org>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 arch/parisc/lib/checksum.c | 13 ++-----------
 include/net/checksum.h     |  6 ++++++
 lib/checksum.c             | 11 +----------
 3 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/arch/parisc/lib/checksum.c b/arch/parisc/lib/checksum.c
index 4818f3db84a5c..59d8c15d81bd0 100644
--- a/arch/parisc/lib/checksum.c
+++ b/arch/parisc/lib/checksum.c
@@ -25,15 +25,6 @@
 	: "=r"(_t)                      \
 	: "r"(_r), "0"(_t));
 
-static inline unsigned short from32to16(unsigned int x)
-{
-	/* 32 bits --> 16 bits + carry */
-	x = (x & 0xffff) + (x >> 16);
-	/* 16 bits + carry --> 16 bits including carry */
-	x = (x & 0xffff) + (x >> 16);
-	return (unsigned short)x;
-}
-
 static inline unsigned int do_csum(const unsigned char * buff, int len)
 {
 	int odd, count;
@@ -85,7 +76,7 @@ static inline unsigned int do_csum(const unsigned char * buff, int len)
 	}
 	if (len & 1)
 		result += le16_to_cpu(*buff);
-	result = from32to16(result);
+	result = csum_from32to16(result);
 	if (odd)
 		result = swab16(result);
 out:
@@ -102,7 +93,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 {
 	unsigned int result = do_csum(buff, len);
 	addc(result, sum);
-	return (__force __wsum)from32to16(result);
+	return (__force __wsum)csum_from32to16(result);
 }
 
 EXPORT_SYMBOL(csum_partial);
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 1338cb92c8e72..243f972267b8d 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -151,6 +151,12 @@ static inline void csum_replace(__wsum *csum, __wsum old, __wsum new)
 	*csum = csum_add(csum_sub(*csum, old), new);
 }
 
+static inline unsigned short csum_from32to16(unsigned int sum)
+{
+	sum += (sum >> 16) | (sum << 16);
+	return (unsigned short)(sum >> 16);
+}
+
 struct sk_buff;
 void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 			      __be32 from, __be32 to, bool pseudohdr);
diff --git a/lib/checksum.c b/lib/checksum.c
index 6860d6b05a171..025ba546e1ec6 100644
--- a/lib/checksum.c
+++ b/lib/checksum.c
@@ -34,15 +34,6 @@
 #include <asm/byteorder.h>
 
 #ifndef do_csum
-static inline unsigned short from32to16(unsigned int x)
-{
-	/* add up 16-bit and 16-bit for 16+c bit */
-	x = (x & 0xffff) + (x >> 16);
-	/* add up carry.. */
-	x = (x & 0xffff) + (x >> 16);
-	return x;
-}
-
 static unsigned int do_csum(const unsigned char *buff, int len)
 {
 	int odd;
@@ -90,7 +81,7 @@ static unsigned int do_csum(const unsigned char *buff, int len)
 #else
 		result += (*buff << 8);
 #endif
-	result = from32to16(result);
+	result = csum_from32to16(result);
 	if (odd)
 		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 out:
-- 
2.40.1