From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.72 #1 (Red Hat Linux)) id 1Oz7p3-000381-Cd for barebox@lists.infradead.org; Fri, 24 Sep 2010 12:56:18 +0000 Date: Fri, 24 Sep 2010 14:56:15 +0200 From: Sascha Hauer Message-ID: <20100924125615.GT23406@pengutronix.de> References: <1285075689-11071-1-git-send-email-plagnioj@jcrosoft.com> <1285075689-11071-2-git-send-email-plagnioj@jcrosoft.com> <4C9C4C9A.7010504@gmail.com> <20100924074303.GO23406@pengutronix.de> <20100924083438.GE16813@game.jcrosoft.org> <4C9C7A6C.2060802@gmail.com> <20100924110045.GF16813@game.jcrosoft.org> <20100924111512.GR23406@pengutronix.de> <20100924114350.GG16813@game.jcrosoft.org> <20100924125254.GS23406@pengutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100924125254.GS23406@pengutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: barebox-bounces@lists.infradead.org Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH 2/2] sha1/sha256: use be32_to_cpu and cpu_to_be32 To: Jean-Christophe PLAGNIOL-VILLARD Cc: barebox@lists.infradead.org, Andre On Fri, Sep 24, 2010 at 02:52:55PM +0200, Sascha Hauer wrote: > On Fri, Sep 24, 2010 at 01:43:50PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > On 13:15 Fri 24 Sep , Sascha Hauer wrote: > > > On Fri, Sep 24, 2010 at 01:00:45PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > > > > > >>>>- | ( (uint32_t) (b)[(i) + 3] ); \ > > > > > >>>>-} > > > > > >>>>-#endif > > > > > >>>>- > > > > > >>>>-#ifndef PUT_UINT32_BE > > > > > >>>>-#define PUT_UINT32_BE(n,b,i) { \ > > > > > >>>>- (b)[(i) ] = (unsigned char) ( (n)>> 24 ); \ > > > > > >>>>- (b)[(i) + 1] = (unsigned char) ( (n)>> 16 ); \ > > > > > >>>>- (b)[(i) + 2] = (unsigned char) ( (n)>> 8 ); \ > > > > > >>>>- (b)[(i) + 3] = (unsigned char) ( (n) ); \ > > > > > >>>>-} > > > > > >>>>-#endif > > > > > >>>>+#define GET_UINT32_BE(n,b,i) (n) = be32_to_cpu(((uint32_t*)(b))[i / 4]) > > > > > >>>>+#define PUT_UINT32_BE(n,b,i) ((uint32_t*)(b))[i / 4] = cpu_to_be32(n) > > > > > >>>> > > > > > >>>> > > > > > >>> > > > > > >>>The previous macros served two purposes: endian swapping and performing > > > > > >>>the memory accesses byte-by-byte. New versions are unsafe for CPUs which > > > > > >>>do not support misaligned 32bit memory accesses. > > > > > >> > > > > > >>Indeed. We have get_unaligned_be32() / put_unaligned_be32(). These should be > > > > > >>the correct functions, right? > > > > > > > > > > > >no-nned IIRC as be32_to_cpu and cpu_to_be32 already handle this > > > > > >depending on the arch > > > > > > > > > > > > > > > > I think get_unaligned_be32() / put_unaligned_be32() are correct in > > > > > this case. be32_to_cpu / cpu_to_be32 perform endian swapping (if > > > > > required) with source and destination both being 32bit variables, > > > > > not memory locations ? > > > > no the arch have to handle this > > > > > > No. As Andre mentioned cpu_to_be32 operates on variables, not on > > > pointers. with ((uint32_t*)(b))[i / 4] you cast b to a pointer to > > > uint32_t which you dereference with [i / 4]. This has nothing to do > > > with cpu_to_be32 and will crash if the architecture does not allow > > > unaligned accesses. > > except cpu_to_be 32 do a swapb so it's safe > > cpu_to_be32 does a __swap32 and not a swapb. > > And I can only repeat myself: The problem is *not* cpu_to_be32 but the > argument you pass *to* cpu_to_be32. Let me put it in other words: > > x = be32_to_cpu(((uint32_t*)(b))[i / 4]) > > can be written as > > u32 y = ((uint32_t*)(b))[i / 4]; > x = be32_to_cpu(y); > > which can also be written as: > > u32 *z = (uint32_t *)b; > u32 y = z[i / 4]; > x = be32_to_cpu(y); > > And this will crash in the first line if b is not aligned. I mean in the second line because that's where the pointer is dereferenced. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox