From patchwork Thu May 7 19:05:44 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: 11534755 X-Patchwork-Delegate: bhelgaas@google.com 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 3B6F2159A for ; Thu, 7 May 2020 19:01:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 245AD21835 for ; Thu, 7 May 2020 19:01:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878079; bh=Bd9ng0ejT5N0guis1pv/eylwB+4g3fX/7CGGNiSv4ns=; h=Date:From:To:Cc:Subject:List-ID:From; b=Ltcjsx0jDplw+zXoMIouyBsfYUJ6Ca7hQHTnTVGYnPvlKnXeRYJRtMSrM4ova3uQv GsGYxPSLGMq2fWkX5pfWRv0906JarMrvQTMVkyJd367bJOSuZm/ORP2oz3cOmrxO5A i4US5a+VaQJtPjfsXjF6XcYI0n98eXhCHj7xjXEw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728131AbgEGTBS (ORCPT ); Thu, 7 May 2020 15:01:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:60998 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726320AbgEGTBS (ORCPT ); Thu, 7 May 2020 15:01:18 -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 2F2912083B; Thu, 7 May 2020 19:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588878077; bh=Bd9ng0ejT5N0guis1pv/eylwB+4g3fX/7CGGNiSv4ns=; h=Date:From:To:Cc:Subject:From; b=K9d07fSnZ94nYK4zmbNDVzIrF6tgyErVnZUYBrXhugNE/ywoecfMuGXt9YpBaXCQC HtAZHWFFviBG1b8/8rkAWY3CaQxa9ZCM20CFYZQHTWL4DUWXFYrELuqcOr50D3wckM DUH3q20sCUwcbSd18JfFmWd9/EW7iqTl/itSkzVQ= Date: Thu, 7 May 2020 14:05:44 -0500 From: "Gustavo A. R. Silva" To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] PCI: Replace zero-length array with flexible-array Message-ID: <20200507190544.GA15633@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@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/pci/pci.c | 2 +- include/linux/pci.h | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 595fcf59843f..bb78f580814e 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1578,7 +1578,7 @@ EXPORT_SYMBOL(pci_restore_state); struct pci_saved_state { u32 config_space[16]; - struct pci_cap_saved_data cap[0]; + struct pci_cap_saved_data cap[]; }; /** diff --git a/include/linux/pci.h b/include/linux/pci.h index 83ce1cdf5676..0453ee458ab1 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -279,7 +279,7 @@ struct pci_cap_saved_data { u16 cap_nr; bool cap_extended; unsigned int size; - u32 data[0]; + u32 data[]; }; struct pci_cap_saved_state { @@ -532,7 +532,7 @@ struct pci_host_bridge { resource_size_t start, resource_size_t size, resource_size_t align); - unsigned long private[0] ____cacheline_aligned; + unsigned long private[] ____cacheline_aligned; }; #define to_pci_host_bridge(n) container_of(n, struct pci_host_bridge, dev)