From patchwork Fri May 8 21:08:05 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: 11537599 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 77A3181 for ; Fri, 8 May 2020 21:03:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5694A2173E for ; Fri, 8 May 2020 21:03:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588971819; bh=pfu8cwd9Mnmh9wwYakprq15dAD5AtNJSX5L+uHwmI58=; h=Date:From:To:Cc:Subject:List-ID:From; b=t7paCGGVCivEHauTTqexamy1e6zEC3ZeAgVojOMA1NS0vxwJGOmKxy+lnP41FT0R1 J+Ev5AmvzfHFVx7iOC3UhzIPYyz3pLz6++xlr5RZjeaUCkxaZYwIJri9cRTd1lvIot 8fep7uD/E/jsTzVt7s3x9DkoZ4yNVL8aFFjVfpSs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727088AbgEHVDi (ORCPT ); Fri, 8 May 2020 17:03:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:33558 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726883AbgEHVDi (ORCPT ); Fri, 8 May 2020 17:03:38 -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 97F52206B8; Fri, 8 May 2020 21:03:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588971818; bh=pfu8cwd9Mnmh9wwYakprq15dAD5AtNJSX5L+uHwmI58=; h=Date:From:To:Cc:Subject:From; b=00MwkRBPLeUh1u1MuDYSlhMpmye5mAA2D+5XxoMuGjwsOYMv0k9SU/+kCbpCzlb7W /YAIUcMX7Nq1U1qhY/3i5AmHdMBpfO/CpMSWlGfstCMkR2zr6t4v2rynzUH8hNdT0X J4X/QgAiRGCLaQwfSd0qBnwTsu/OTwXh0lngm8lE= Date: Fri, 8 May 2020 16:08:05 -0500 From: "Gustavo A. R. Silva" To: Andy Gross , Bjorn Andersson , Jeffrey Hugo Cc: linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] firmware: qcom_scm-legacy: Replace zero-length array with flexible-array Message-ID: <20200508210805.GA24170@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) 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] 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") Reviewed-by: Jeffrey Hugo Signed-off-by: Gustavo A. R. Silva --- drivers/firmware/qcom_scm-legacy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/firmware/qcom_scm-legacy.c b/drivers/firmware/qcom_scm-legacy.c index 8532e7c78ef7..eba6b60bfb61 100644 --- a/drivers/firmware/qcom_scm-legacy.c +++ b/drivers/firmware/qcom_scm-legacy.c @@ -56,7 +56,7 @@ struct scm_legacy_command { __le32 buf_offset; __le32 resp_hdr_offset; __le32 id; - __le32 buf[0]; + __le32 buf[]; }; /**