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=-13.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 21B0EC38A24 for ; Thu, 7 May 2020 19:18:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D52C92063A for ; Thu, 7 May 2020 19:18:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879117; bh=PmaRvWKL0WGLgfjQ1uvdyt1NSJQfqavoNxrgKWSaeQk=; h=Date:From:To:Cc:Subject:List-ID:From; b=uT/dankAkvb+KP0JrRYOBcdy7hBaG4wxBxSZO49REEwJNaszJIsVj0jN/1QTt5B9e +xzNRCf/OFwBssV+K62Up8ReSEZGMCWaWT9gAmX/LL6bFXsxgOYjHi0VZb82K/jbLv sVT16S6Ve7YaqTnvVpXIgA6jOgHL+1yWoWlxPdD8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728691AbgEGTSh (ORCPT ); Thu, 7 May 2020 15:18:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:41400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726367AbgEGTSg (ORCPT ); Thu, 7 May 2020 15:18:36 -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 409EA2063A; Thu, 7 May 2020 19:18:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588879115; bh=PmaRvWKL0WGLgfjQ1uvdyt1NSJQfqavoNxrgKWSaeQk=; h=Date:From:To:Cc:Subject:From; b=C3Kelkzg4jGnKUJAti5PEFqSI042uFT80iLvvdSVCw3XhrJby/ZYUfBPVkFl5kZlj ynKQnuPOAzSq7MPWh8KjZ6E8mjgM5nmLYoaVewBuUbUNNggTlkSJgbVx4HLzEUowUk syh9hvRxFT7UkK8LnoTwCP6EFjf79wiDIAWi54Ao= Date: Thu, 7 May 2020 14:23:02 -0500 From: "Gustavo A. R. Silva" To: "David S. Miller" Cc: sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] sparc64: Replace zero-length array with flexible-array Message-ID: <20200507192302.GA16402@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 --- arch/sparc/kernel/cpumap.c | 2 +- arch/sparc/kernel/ds.c | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c index 1cb62bfeaa1f..f07ea88a83af 100644 --- a/arch/sparc/kernel/cpumap.c +++ b/arch/sparc/kernel/cpumap.c @@ -50,7 +50,7 @@ struct cpuinfo_tree { /* Offsets into nodes[] for each level of the tree */ struct cpuinfo_level level[CPUINFO_LVL_MAX]; - struct cpuinfo_node nodes[0]; + struct cpuinfo_node nodes[]; }; diff --git a/arch/sparc/kernel/ds.c b/arch/sparc/kernel/ds.c index 75232cbd58bf..522e5b51050c 100644 --- a/arch/sparc/kernel/ds.c +++ b/arch/sparc/kernel/ds.c @@ -87,7 +87,7 @@ struct ds_reg_req { __u64 handle; __u16 major; __u16 minor; - char svc_id[0]; + char svc_id[]; }; struct ds_reg_ack { @@ -701,12 +701,12 @@ struct ds_var_hdr { struct ds_var_set_msg { struct ds_var_hdr hdr; - char name_and_value[0]; + char name_and_value[]; }; struct ds_var_delete_msg { struct ds_var_hdr hdr; - char name[0]; + char name[]; }; struct ds_var_resp { @@ -989,7 +989,7 @@ struct ds_queue_entry { struct ds_info *dp; int req_len; int __pad; - u64 req[0]; + u64 req[]; }; static void process_ds_work(void)