From patchwork Thu Nov 3 05:10:55 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Mackerras X-Patchwork-Id: 690676 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3t8Y9d1t61z9t0v for ; Thu, 3 Nov 2016 16:16:53 +1100 (AEDT) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3t8Y9d14LLzDvYn for ; Thu, 3 Nov 2016 16:16:53 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3t8Y8Z5mjtzDvQM for ; Thu, 3 Nov 2016 16:15:58 +1100 (AEDT) Received: by ozlabs.org (Postfix) id 3t8Y8Z4xLXz9t2g; Thu, 3 Nov 2016 16:15:58 +1100 (AEDT) Delivered-To: linuxppc-dev@ozlabs.org Received: by ozlabs.org (Postfix, from userid 1003) id 3t8Y8Z4WNmz9t1Q; Thu, 3 Nov 2016 16:15:58 +1100 (AEDT) Date: Thu, 3 Nov 2016 16:10:55 +1100 From: Paul Mackerras To: linuxppc-dev@ozlabs.org Subject: [PATCH 1/2] powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold Message-ID: <20161103051055.GA8368@fergus.ozlabs.ibm.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" These functions compute an IP checksum by computing a 64-bit sum and folding it to 32 bits (the "nofold" in their names refers to folding down to 16 bits). However, doing (u32) (s + (s >> 32)) is not sufficient to fold a 64-bit sum to 32 bits correctly. The addition can produce a carry out from bit 31, which needs to be added in to the sum to produce the correct result. To fix this, we copy the from64to32() function from lib/checksum.c and use that. Signed-off-by: Paul Mackerras --- arch/powerpc/include/asm/checksum.h | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h index ee655ed..c16c6f8 100644 --- a/arch/powerpc/include/asm/checksum.h +++ b/arch/powerpc/include/asm/checksum.h @@ -53,19 +53,27 @@ static inline __sum16 csum_fold(__wsum sum) return (__force __sum16)(~((__force u32)sum + tmp) >> 16); } +static inline u32 from64to32(u64 x) +{ + /* add up 32-bit and 32-bit for 32+c bit */ + x = (x & 0xffffffff) + (x >> 32); + /* add up carry.. */ + x = (x & 0xffffffff) + (x >> 32); + return (u32)x; +} + static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr, unsigned short len, unsigned short proto, __wsum sum) { #ifdef __powerpc64__ - unsigned long s = (__force u32)sum; + u64 s = (__force u32)sum; s += (__force u32)saddr; s += (__force u32)daddr; s += proto + len; - s += (s >> 32); - return (__force __wsum) s; + return (__force __wsum) from64to32(s); #else __asm__("\n\ addc %0,%0,%1 \n\ @@ -127,8 +135,7 @@ static inline __wsum ip_fast_csum_nofold(const void *iph, unsigned int ihl) for (i = 0; i < ihl - 1; i++, ptr++) s += *ptr; - s += (s >> 32); - return (__force __wsum)s; + return (__force __wsum)from64to32(s); #else __wsum sum, tmp;