From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752130AbeCWTJu (ORCPT ); Fri, 23 Mar 2018 15:09:50 -0400 Received: from gateway24.websitewelcome.com ([192.185.50.45]:23027 "EHLO gateway24.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751595AbeCWTJt (ORCPT ); Fri, 23 Mar 2018 15:09:49 -0400 Subject: [RESEND] SHASH_DESC_ON_STACK macro References: To: Herbert Xu Cc: "David S. Miller" , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" From: "Gustavo A. R. Silva" X-Forwarded-Message-Id: Message-ID: Date: Fri, 23 Mar 2018 14:09:46 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.145.54.187 X-Source-L: No X-Exim-ID: 1ezS4R-002zip-T8 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.67]) [189.145.54.187]:43434 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 4 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Herbert, There is an ongoing effort to remove all VLAs from the code base [1] and while working on that I came across the following macro at include/crypto/hash.h:154: #define SHASH_DESC_ON_STACK(shash, ctx) \ char __##shash##_desc[sizeof(struct shash_desc) + \ crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \ struct shash_desc *shash = (struct shash_desc *)__##shash##_desc Currently, this macro is being used in 46 different places. I wonder how big can tfm->descsize can get? Do you think it is feasible to replace the call to crypto_shash_descsize with a constant value and get rid of 46 VLA warnings? I have sent some patches to replace the use of this macro with dynamic memory allocation instead, but it seems that this is not a suitable solution for all cases due to performance issues. [1] https://lkml.org/lkml/2018/3/7/621 I'd really appreciate any feedback. Thanks -- Gustavo