From: John Denker Subject: Re: better patch for linux/bitops.h Date: Wed, 4 May 2016 14:52:28 -0700 Message-ID: <572A6F1C.2080708@av8n.com> References: <1462170413-7164-1-git-send-email-tytso@mit.edu> <1462170413-7164-2-git-send-email-tytso@mit.edu> <20160504174901.GC3901@thunk.org> <20160504190723.GD3901@thunk.org> <572A6CDD.10503@av8n.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------010204000507020209040900" To: tytso@mit.edu, "H. Peter Anvin" , noloader@gmail.com, linux-kernel@vger.kernel.org, Stephan Mueller , Herbert Xu , andi@firstfloor.org, Sandy Harris , cryptography@lakedaemon.net, linux-crypto@vger.kernel.org Return-path: Received: from cloud.av8n.com ([174.136.99.130]:51334 "EHLO cloud.av8n.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754388AbcEDVw3 (ORCPT ); Wed, 4 May 2016 17:52:29 -0400 In-Reply-To: <572A6CDD.10503@av8n.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------010204000507020209040900 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit On 05/04/2016 02:42 PM, I wrote: > I find it very odd that the other seven functions were not > upgraded. I suggest the attached fix-others.diff would make > things more consistent. Here's a replacement patch. Same idea, less brain damage. Sorry for the confusion. --------------010204000507020209040900 Content-Type: text/x-patch; name="fix-others.diff" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="fix-others.diff" commit ba83b16d8430ee6104aa1feeed4ff7a82b02747a Author: John Denker Date: Wed May 4 13:55:51 2016 -0700 Make ror64, rol64, ror32, ror16, rol16, ror8, and rol8 consistent with rol32 in their handling of shifting by a zero amount. Same overall rationale as in d7e35dfa, just more consistently applied. Beware that shifting by an amount >= the number of bits in the word remains Undefined Behavior. This should be either documented or fixed. It could be fixed easily enough. diff --git a/include/linux/bitops.h b/include/linux/bitops.h index defeaac..90f389b 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -87,7 +87,7 @@ static __always_inline unsigned long hweight_long(unsigned long w) */ static inline __u64 rol64(__u64 word, unsigned int shift) { - return (word << shift) | (word >> (64 - shift)); + return (word << shift) | (word >> ((-shift) & 63)); } /** @@ -97,7 +97,7 @@ static inline __u64 rol64(__u64 word, unsigned int shift) */ static inline __u64 ror64(__u64 word, unsigned int shift) { - return (word >> shift) | (word << (64 - shift)); + return (word >> shift) | (word << ((-shift) & 63)); } /** @@ -117,7 +117,7 @@ static inline __u32 rol32(__u32 word, unsigned int shift) */ static inline __u32 ror32(__u32 word, unsigned int shift) { - return (word >> shift) | (word << (32 - shift)); + return (word >> shift) | (word << ((-shift) & 31)); } /** @@ -127,7 +127,7 @@ static inline __u32 ror32(__u32 word, unsigned int shift) */ static inline __u16 rol16(__u16 word, unsigned int shift) { - return (word << shift) | (word >> (16 - shift)); + return (word << shift) | (word >> ((-shift) & 15)); } /** @@ -137,7 +137,7 @@ static inline __u16 rol16(__u16 word, unsigned int shift) */ static inline __u16 ror16(__u16 word, unsigned int shift) { - return (word >> shift) | (word << (16 - shift)); + return (word >> shift) | (word << ((-shift) & 15)); } /** @@ -147,7 +147,7 @@ static inline __u16 ror16(__u16 word, unsigned int shift) */ static inline __u8 rol8(__u8 word, unsigned int shift) { - return (word << shift) | (word >> (8 - shift)); + return (word << shift) | (word >> ((-shift) & 7)); } /** @@ -157,7 +157,7 @@ static inline __u8 rol8(__u8 word, unsigned int shift) */ static inline __u8 ror8(__u8 word, unsigned int shift) { - return (word >> shift) | (word << (8 - shift)); + return (word >> shift) | (word << ((-shift) & 7)); } /** --------------010204000507020209040900--