From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0546FC433F5 for ; Thu, 21 Apr 2022 07:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385954AbiDUHn2 convert rfc822-to-8bit (ORCPT ); Thu, 21 Apr 2022 03:43:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1386108AbiDUHnY (ORCPT ); Thu, 21 Apr 2022 03:43:24 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E49D31BEBA for ; Thu, 21 Apr 2022 00:40:29 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-320-RjXwMqAnPfqhoyE6QW4dlQ-1; Thu, 21 Apr 2022 08:40:26 +0100 X-MC-Unique: RjXwMqAnPfqhoyE6QW4dlQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Thu, 21 Apr 2022 08:40:25 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.033; Thu, 21 Apr 2022 08:40:25 +0100 From: David Laight To: 'Yury Norov' , "linux-kernel@vger.kernel.org" , Alexander Gordeev , Andy Shevchenko , Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Heiko Carstens , Janosch Frank , Rasmus Villemoes , Sven Schnelle , "Vasily Gorbik" , "linux-s390@vger.kernel.org" , "kvm@vger.kernel.org" Subject: RE: [PATCH 2/4] lib: add bitmap_{from,to}_arr64 Thread-Topic: [PATCH 2/4] lib: add bitmap_{from,to}_arr64 Thread-Index: AQHYVQdrgrXWaR3sCEGGbig0LA6aC6z5+Nxw Date: Thu, 21 Apr 2022 07:40:25 +0000 Message-ID: References: <20220420222530.910125-1-yury.norov@gmail.com> <20220420222530.910125-3-yury.norov@gmail.com> In-Reply-To: <20220420222530.910125-3-yury.norov@gmail.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org From: Yury Norov > Sent: 20 April 2022 23:25 > > Manipulating 64-bit arrays with bitmap functions is potentially dangerous > because on 32-bit BE machines the order of halfwords doesn't match. Another > issue is that compiler may throw a warning about out-of-boundary access. > > This patch adds bitmap_{from,to}_arr64 functions in addition to existing > bitmap_{from,to}_arr32. > > Signed-off-by: Yury Norov > --- > include/linux/bitmap.h | 23 +++++++++++++++++---- > lib/bitmap.c | 47 ++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 66 insertions(+), 4 deletions(-) > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > index 10d805c2893c..f78c534fb814 100644 > --- a/include/linux/bitmap.h > +++ b/include/linux/bitmap.h > @@ -292,6 +292,24 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, > (const unsigned long *) (bitmap), (nbits)) > #endif > > +/* > + * On 64-bit systems bitmaps are represented as u64 arrays internally. On LE32 > + * machines the order of hi and lo parts of nubmers match the bitmap structure. > + * In both cases conversion is not needed when copying data from/to arrays of > + * u64. > + */ > +#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) I think I'd change the condition to (inverting it): #if (BITS_PER_LONG == 64) || defined(__LITTLE_ENDIAN) since that is the condition when the layout matches. > +void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits); > +void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits); > +#else > +#define bitmap_from_arr64(bitmap, buf, nbits) \ > + bitmap_copy_clear_tail((unsigned long *) (bitmap), \ > + (const unsigned long *) (buf), (nbits)) > +#define bitmap_to_arr64(buf, bitmap, nbits) \ > + bitmap_copy_clear_tail((unsigned long *) (buf), \ > + (const unsigned long *) (bitmap), (nbits)) > +#endif > + > static inline int bitmap_and(unsigned long *dst, const unsigned long *src1, > const unsigned long *src2, unsigned int nbits) > { > @@ -596,10 +614,7 @@ static inline void bitmap_next_set_region(unsigned long *bitmap, > */ > static inline void bitmap_from_u64(unsigned long *dst, u64 mask) > { > - dst[0] = mask & ULONG_MAX; > - > - if (sizeof(mask) > sizeof(unsigned long)) > - dst[1] = mask >> 32; > + bitmap_from_arr64(dst, &mask, 64); > } I'd leave this alone. > > /** > diff --git a/lib/bitmap.c b/lib/bitmap.c > index d9a4480af5b9..aea9493f4216 100644 > --- a/lib/bitmap.c > +++ b/lib/bitmap.c > @@ -1533,5 +1533,52 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) > buf[halfwords - 1] &= (u32) (UINT_MAX >> ((-nbits) & 31)); > } > EXPORT_SYMBOL(bitmap_to_arr32); > +#endif > + > +#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) > +/** > + * bitmap_from_arr64 - copy the contents of u64 array of bits to bitmap > + * @bitmap: array of unsigned longs, the destination bitmap > + * @buf: array of u64 (in host byte order), the source bitmap > + * @nbits: number of bits in @bitmap > + */ > +void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits) > +{ > + while (nbits > 0) { This looks like a for look to me... > + u64 val = *buf++; > + > + *bitmap++ = (unsigned long)val; > + if (nbits > 32) > + *bitmap++ = (unsigned long)(val >> 32); No need for either cast. > + nbits -= 64; > + } > > + /* Clear tail bits in last word beyond nbits. */ > + if (nbits % BITS_PER_LONG) > + bitmap[-1] &= BITMAP_LAST_WORD_MASK(nbits); > +} > +EXPORT_SYMBOL(bitmap_from_arr64); > + > +/** > + * bitmap_to_arr64 - copy the contents of bitmap to a u64 array of bits > + * @buf: array of u64 (in host byte order), the dest bitmap > + * @bitmap: array of unsigned longs, the source bitmap > + * @nbits: number of bits in @bitmap > + */ > +void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits) > +{ > + unsigned long *end = bitmap + BITS_TO_LONGS(nbits); > + > + while (bitmap < end) { Another for loop... > + *buf = *bitmap++; > + if (bitmap < end) > + *buf |= *bitmap++ << 32; That is UB. Did you even compile this?? David > + buf++; > + } > + > + /* Clear tail bits in last element of array beyond nbits. */ > + if (nbits % 64) > + buf[-1] &= GENMASK_ULL(nbits, 0); > +} > +EXPORT_SYMBOL(bitmap_to_arr64); > #endif > -- > 2.32.0 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)