From patchwork Fri Feb 14 17:16:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 11382783 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 94CD2930 for ; Fri, 14 Feb 2020 18:00:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7454820873 for ; Fri, 14 Feb 2020 18:00:13 +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="OpQNwq3c" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390800AbgBNSAM (ORCPT ); Fri, 14 Feb 2020 13:00:12 -0500 Received: from gateway31.websitewelcome.com ([192.185.143.40]:17742 "EHLO gateway31.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390784AbgBNSAL (ORCPT ); Fri, 14 Feb 2020 13:00:11 -0500 Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway31.websitewelcome.com (Postfix) with ESMTP id 7B4913B32D for ; Fri, 14 Feb 2020 11:14:21 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 2eXljU3tKXVkQ2eXljroNJ; Fri, 14 Feb 2020 11:14:21 -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=k+QU65CHLZoLG7AfwTnQ5YtDbA20JGLnCMfo7U4sik4=; b=OpQNwq3cCqz8SZD6hAvLref+Y6 lMllw7ioVUPsYynpCRVpJGfyWvhnsmOA+BrGswNXwTMNRi7yD6i0AXXYikW7kjcOIlx5A39W9SSMP 5Q5VGYluBnUMY5C7vzBaU2Ep6ryr74VmdSO+sQutg4Tlc/ouI/YHh6XAvTXxYmqZBinqu7r5HmVbZ iFQM8+f+Qhgj/1HAzMYj8rRSONhIBxAkUJniCHe6TVCNwU1OpEg8p3p5SWuU9bW6SQG3/r9o4KUDO cJOKrMw5ZVqS45ItrIgxaucsN8gWZwmimFtkfRR9SKyu+uS3p/gJoAB9HBlKSoStWvHif21BAvKIL 7zOktwHQ==; Received: from [200.68.140.137] (port=25415 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j2eXj-003fsi-RY; Fri, 14 Feb 2020 11:14:20 -0600 Date: Fri, 14 Feb 2020 11:16:57 -0600 From: "Gustavo A. R. Silva" To: Laxman Dewangan , Jon Hunter , Dan Williams , Vinod Koul , Thierry Reding Cc: dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] dmaengine: tegra210-adma: Replace zero-length array with flexible-array member Message-ID: <20200214171657.GA25663@embeddedor> MIME-Version: 1.0 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: 1j2eXj-003fsi-RY X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.137]:25415 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 21 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/tegra210-adma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c index 6e1268552f74..c4ce5dfb149b 100644 --- a/drivers/dma/tegra210-adma.c +++ b/drivers/dma/tegra210-adma.c @@ -164,7 +164,7 @@ struct tegra_adma { const struct tegra_adma_chip_data *cdata; /* Last member of the structure */ - struct tegra_adma_chan channels[0]; + struct tegra_adma_chan channels[]; }; static inline void tdma_write(struct tegra_adma *tdma, u32 reg, u32 val)