From patchwork Thu Feb 13 00:14:01 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: 11379533 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 2C8EB1805 for ; Thu, 13 Feb 2020 01:06:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0269021739 for ; Thu, 13 Feb 2020 01:06:30 +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="E5A7ex1U" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729276AbgBMBGa (ORCPT ); Wed, 12 Feb 2020 20:06:30 -0500 Received: from gateway20.websitewelcome.com ([192.185.60.19]:35902 "EHLO gateway20.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729190AbgBMBGa (ORCPT ); Wed, 12 Feb 2020 20:06:30 -0500 X-Greylist: delayed 1679 seconds by postgrey-1.27 at vger.kernel.org; Wed, 12 Feb 2020 20:06:29 EST Received: from cm11.websitewelcome.com (cm11.websitewelcome.com [100.42.49.5]) by gateway20.websitewelcome.com (Postfix) with ESMTP id 793B6400C4A32 for ; Wed, 12 Feb 2020 17:00:29 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 228sjiIFoSl8q228sjQzTw; Wed, 12 Feb 2020 18:14:06 -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=3h2EV0nIxHBK7v9f5cUKRdwO80WBlvIZfyKilfYiuUg=; b=E5A7ex1Uu6r3pyb2y6Fl0Prond kgzSeEkFAMNZUnd42KQqtYjeDc8iO2quUxzYVZboPUVyxiXzSQAplCIdZyFsOMGW/UK7PpVwpcnqx t5wOERuAEXLy0V3D4b1Ssl5HsEtUDUEh0KJGRAn1LTOseqvWobgR9+kM4rhU8KwzGWD9J7yTVrI0h V02vJKAS+Sw0KMbr4fAYFCtEOdyJg2DHu9typZXfvnGGwqBYmbLQOYZZWqaxR0xnA7TRz394qsz0K iso3U/491+JPYKMSi3X3QHztXRNp9MgWc7tQ8UYZg5YRpvKRanycrsYULhM42DklNZ2yBuiV6u5g2 rF3z18hg==; Received: from [200.68.141.42] (port=9261 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j228r-003UE4-0h; Wed, 12 Feb 2020 18:14:05 -0600 Date: Wed, 12 Feb 2020 18:14:01 -0600 From: "Gustavo A. R. Silva" To: Rob Clark , Andy Gross , Bjorn Andersson , Joerg Roedel Cc: iommu@lists.linux-foundation.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] iommu/qcom: Replace zero-length array with flexible-array member Message-ID: <20200213001401.GA28587@embeddedor.com> 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: 200.68.141.42 X-Source-L: No X-Exim-ID: 1j228r-003UE4-0h X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.141.42]:9261 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 24 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@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/iommu/qcom_iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c index 39759db4f003..f1e175ca5e4a 100644 --- a/drivers/iommu/qcom_iommu.c +++ b/drivers/iommu/qcom_iommu.c @@ -48,7 +48,7 @@ struct qcom_iommu_dev { void __iomem *local_base; u32 sec_id; u8 num_ctxs; - struct qcom_iommu_ctx *ctxs[0]; /* indexed by asid-1 */ + struct qcom_iommu_ctx *ctxs[]; /* indexed by asid-1 */ }; struct qcom_iommu_ctx {