From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755956AbaIQP02 (ORCPT ); Wed, 17 Sep 2014 11:26:28 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:62192 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755862AbaIQP0X (ORCPT ); Wed, 17 Sep 2014 11:26:23 -0400 Message-ID: <5419A81B.2030705@converseincode.com> Date: Wed, 17 Sep 2014 08:26:19 -0700 From: Behan Webster User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 MIME-Version: 1.0 To: Herbert Xu , Dmitry Kasatkin CC: agk@redhat.com, clm@fb.com, davem@davemloft.net, dm-devel@redhat.com, fabf@skynet.be, jbacik@fb.com, snitzer@redhat.com, tadeusz.struk@intel.com, akpm@linux-foundation.org, bruce.w.allan@intel.com, james.l.morris@oracle.com, john.griffin@intel.com, linux-btrfs@vger.kernel.org, linux-crypto@vger.kernel.org, linux-ima-devel@lists.sourceforge.net, linux-ima-user@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, linux-security-module@vger.kernel.org, neilb@suse.de, qat-linux@intel.com, serge@hallyn.com, thomas.lendacky@amd.com, zohar@linux.vnet.ibm.com, torvalds@linux-foundation.org Subject: Re: [PATCH v3 01/12] crypto: LLVMLinux: Add macro to remove use of VLAIS in crypto code References: <1410766234-1634-1-git-send-email-behanw@converseincode.com> <1410766234-1634-2-git-send-email-behanw@converseincode.com> <20140917092212.GA1213@gondor.apana.org.au> <54196D5C.6040104@samsung.com> <20140917113035.GB2129@gondor.apana.org.au> In-Reply-To: <20140917113035.GB2129@gondor.apana.org.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/17/14 04:30, Herbert Xu wrote: > On Wed, Sep 17, 2014 at 02:15:40PM +0300, Dmitry Kasatkin wrote: >> On 17/09/14 12:22, Herbert Xu wrote: >>> On Mon, Sep 15, 2014 at 12:30:23AM -0700, behanw@converseincode.com wrote: >>>> From: Behan Webster >>>> >>>> Add a macro which replaces the use of a Variable Length Array In Struct (VLAIS) >>>> with a C99 compliant equivalent. This macro instead allocates the appropriate >>>> amount of memory using an char array. >>>> >>>> The new code can be compiled with both gcc and clang. >>>> >>>> struct shash_desc contains a flexible array member member ctx declared with >>>> CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning >>>> of the array declared after struct shash_desc with long long. >>>> >>>> No trailing padding is required because it is not a struct type that can >>>> be used in an array. >>>> >>>> The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long >>>> as would be the case for a struct containing a member with >>>> CRYPTO_MINALIGN_ATTR. >>>> >>>> Signed-off-by: Behan Webster >>> Acked-by: Herbert Xu >>> >>> Thanks, >> Just in case. >> I would still follow advice from "Michał Mirosław" to use shash##__desc[] Absolutely. I will be posting a v4 patchset . Just waiting a bit more for more comments on v3. The macro from v4 will look like this which I believe will satisfy the concern and indeed be safer than my previous version. +#define SHASH_DESC_ON_STACK(shash, tfm) \ + char __##shash##_desc[sizeof(struct shash_desc) + \ + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR; \ + struct shash_desc *shash = (struct shash_desc *)__##shash##_desc Hmm. Is it worth adding a comment with this macro explaining the reason this works? Essentially much of what is in the commit message? > Oh yes of course. My ack is more about the approach. Wonderful! Indeed. I would have asked for you to wait for v4 anyways. :) Thank you, Behan -- Behan Webster behanw@converseincode.com