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 X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC837C3B1B1 for ; Fri, 14 Feb 2020 18:00:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B4D1F20848 for ; Fri, 14 Feb 2020 18:00:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="H6W/Fiys" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388666AbgBNSAS (ORCPT ); Fri, 14 Feb 2020 13:00:18 -0500 Received: from gateway31.websitewelcome.com ([192.185.143.40]:26227 "EHLO gateway31.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390670AbgBNSAJ (ORCPT ); Fri, 14 Feb 2020 13:00:09 -0500 X-Greylist: delayed 1502 seconds by postgrey-1.27 at vger.kernel.org; Fri, 14 Feb 2020 13:00:09 EST Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway31.websitewelcome.com (Postfix) with ESMTP id C0986F43A for ; Fri, 14 Feb 2020 11:10:25 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 2eTxjTyZVXVkQ2eTxjrj5J; Fri, 14 Feb 2020 11:10:25 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=BuEqONPSEjbS6nR+nsgUPfM1v5+Y+62xNXlUsAnUd/c=; b=H6W/Fiysye58hDJxiiYBMewzcd VBQLgnSAN28NP/JizT+q1WA/GLkUQjzDs71ZQcSDWPJUJqAbUNFgGTYDntMRyHou+3dCqT14qCXC1 PV27mRIl/oku9JMFvMq9eND7VNgLR6LBjVIw/Bse2pmxb84plypHp+xPIw9Ud2kHzlcCKobwbEBAq NYTs04MyY8ZSjljzrOCrBd3dMLne3zhsOKcySI0/KQTemQmjT4hT8qBufqJOqJ50JWsU5HhLEIVRr KT3SBt059LMfSFeiQEbZWgaHOdC6z8m5x3/Y/to+zL8qH1SXjaYVnEXSlNl4XfRwI1E6NiP+Y+WTa fhWfo0oA==; Received: from [200.68.140.137] (port=41921 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j2eTw-003don-BC; Fri, 14 Feb 2020 11:10:24 -0600 Date: Fri, 14 Feb 2020 11:13:02 -0600 From: "Gustavo A. R. Silva" To: Vinod Koul , Dan Williams Cc: dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] dmanegine: ioat/dca: Replace zero-length array with flexible-array member Message-ID: <20200214171302.GA20586@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) 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: 200.68.140.137 X-Source-L: No X-Exim-ID: 1j2eTw-003don-BC X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.137]:41921 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- drivers/dma/ioat/dca.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/ioat/dca.c b/drivers/dma/ioat/dca.c index be61c32a876f..0be385587c4c 100644 --- a/drivers/dma/ioat/dca.c +++ b/drivers/dma/ioat/dca.c @@ -102,7 +102,7 @@ struct ioat_dca_priv { int max_requesters; int requester_count; u8 tag_map[IOAT_TAG_MAP_LEN]; - struct ioat_dca_slot req_slots[0]; + struct ioat_dca_slot req_slots[]; }; static int ioat_dca_dev_managed(struct dca_provider *dca, -- 2.25.0