From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= Subject: Re: alignment faults in 3.6 Date: Fri, 12 Oct 2012 12:18:08 +0100 Message-ID: References: <20121005082439.GF4625@n2100.arm.linux.org.uk> <201210120811.43290.arnd@arndb.de> <20121012090321.GA21164@n2100.arm.linux.org.uk> <20121012110750.GE21164@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, David Laight , Eric Dumazet , netdev@vger.kernel.org, Jon Masters To: Russell King - ARM Linux Return-path: Received: from unicorn.mansr.com ([78.86.181.103]:51210 "EHLO unicorn.mansr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718Ab2JLLSK convert rfc822-to-8bit (ORCPT ); Fri, 12 Oct 2012 07:18:10 -0400 In-Reply-To: <20121012110750.GE21164@n2100.arm.linux.org.uk> (Russell King's message of "Fri, 12 Oct 2012 12:07:50 +0100") Sender: netdev-owner@vger.kernel.org List-ID: Russell King - ARM Linux writes: > On Fri, Oct 12, 2012 at 12:00:03PM +0100, M=E5ns Rullg=E5rd wrote: >> Russell King - ARM Linux writes: >>=20 >> > On Fri, Oct 12, 2012 at 08:11:42AM +0000, Arnd Bergmann wrote: >> >> On Thursday 11 October 2012, M=E5ns Rullg=E5rd wrote: >> >> > > But, the IP header is expected to be aligned. >> >> >=20 >> >> > Everything tells the compiler the struct is perfectly aligned. = When the >> >> > buggy driver passes a misaligned pointer, bad things happen. >> >>=20 >> >> Would it be appropriate to add a WARN_ON_ONCE() in the alignment >> >> fault path then? >>=20 >> I think that's an excellent idea. > > Well, I get the last word here and it's no. Sadly, yes. >> >> If all alignment faults in the kernel are caused by broken driver= s, >> >> that would at least give us some hope of finding those drivers wh= ile >> >> at the same time not causing much overhead in the case where we n= eed >> >> to do the fixup in the meantime. >> > >> > No. It is my understanding that various IP option processing can = also >> > cause the alignment fault handler to be invoked, even when the pac= ket is >> > properly aligned, and then there's jffs2/mtd which also relies upo= n >> > alignment faults being fixed up. >>=20 >> As far as I'm concerned, this is all hearsay, and I've only ever hea= rd >> it from you. Why can't you let those who care fix these bugs instea= d? > > You know, I'm giving you the benefit of my _knowledge_ which has been > built over the course of the last 20 years. How proud you sound. Now could you say something of substance instead? > I've been in these discussions with networking people before. I ende= d > up having to develop the alignment fault handler because of those > discussions. And oh look, Eric confirmed that the networking code > isn't going to get "fixed" as you were demanding, which is exactly > what I said. =46unny, I saw him say the exact opposite: So if you find an offender, please report a bug, because I can guarantee you we will _fix_ it. > I've been in discussions with MTD people over these issues before, I'= ve > discussed this with David Woodhouse when it came up in JFFS2. I *KNO= W* > these things. In the same way you "know" the networking people won't fix their code, despite them _clearly_ stating the opposite? > You can call it hearsay if you wish, but it seems to be more accurate > than your wild outlandish and pathetic statements. So you're resorting to name-calling. Not taking that bait. --=20 M=E5ns Rullg=E5rd mans@mansr.com