From patchwork Thu May 7 19:19:48 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: 11534773 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 DC4EC1392 for ; Thu, 7 May 2020 19:15:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB5C421835 for ; Thu, 7 May 2020 19:15:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878923; bh=XgVvt1I6zgp7hLrKdR8zya9BZUOMROQtmE4xGkXj+ss=; h=Date:From:To:Cc:Subject:List-ID:From; b=qY9zHD76XjiqyaMcpJ0tT1YLDPaLNUy5uQ7JYmRwnueUE5A9J+IQoPDs2q2e+A5Ca QaWlOMrw9mBQqNtKudnbmAgC5rLyA8+74zfQIQd+wYAhNtB0phFBN/5Bml62hV+hS1 yLpa0MJKJ0DVJs4BKw8QG21VfWfbhVRF6tbHR8DU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726860AbgEGTPX (ORCPT ); Thu, 7 May 2020 15:15:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:39048 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGTPW (ORCPT ); Thu, 7 May 2020 15:15:22 -0400 Received: from embeddedor (unknown [189.207.59.248]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BA536208E4; Thu, 7 May 2020 19:15:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878922; bh=XgVvt1I6zgp7hLrKdR8zya9BZUOMROQtmE4xGkXj+ss=; h=Date:From:To:Cc:Subject:From; b=wLn2qSA4qpYqsA72eamB1zrIXEE6uFQx70pjJyUNZlsYUB5Xh+6Q9BNNHv3pGthwf LKxFzO7YPbb5uelvKtb5IGuBejb38oM2LsuinYVvrSJRLy+rDc2fMk5HBefXqSJfOj yTSbeRzKcLaOa6xgWLsmsywvdpnOzqaakoIpRsn8= Date: Thu, 7 May 2020 14:19:48 -0500 From: "Gustavo A. R. Silva" To: Ohad Ben-Cohen , Bjorn Andersson Cc: linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] rpmsg: Replace zero-length array with flexible-array Message-ID: <20200507191948.GA16053@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-remoteproc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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/rpmsg/virtio_rpmsg_bus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c index 376ebbf880d6..07d4f3374098 100644 --- a/drivers/rpmsg/virtio_rpmsg_bus.c +++ b/drivers/rpmsg/virtio_rpmsg_bus.c @@ -89,7 +89,7 @@ struct rpmsg_hdr { u32 reserved; u16 len; u16 flags; - u8 data[0]; + u8 data[]; } __packed; /**