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=-13.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 E2952C4BA3B for ; Thu, 27 Feb 2020 13:12:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDCFD2469C for ; Thu, 27 Feb 2020 13:12:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729117AbgB0NMC (ORCPT ); Thu, 27 Feb 2020 08:12:02 -0500 Received: from mga03.intel.com ([134.134.136.65]:31938 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729056AbgB0NMC (ORCPT ); Thu, 27 Feb 2020 08:12:02 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Feb 2020 05:12:01 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,492,1574150400"; d="scan'208";a="231834432" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.167]) ([10.237.72.167]) by orsmga008.jf.intel.com with ESMTP; 27 Feb 2020 05:12:00 -0800 Subject: Re: [PATCH] mmc: Replace zero-length array with flexible-array member To: "Gustavo A. R. Silva" , Ulf Hansson Cc: linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200226223125.GA20630@embeddedor> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: Date: Thu, 27 Feb 2020 15:11:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200226223125.GA20630@embeddedor> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/02/20 12:31 am, Gustavo A. R. Silva wrote: > 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 Acked-by: Adrian Hunter > --- > drivers/mmc/host/sdhci-acpi.c | 2 +- > drivers/mmc/host/sdhci-cadence.c | 2 +- > drivers/mmc/host/sdhci-pci.h | 2 +- > drivers/mmc/host/sdhci-pltfm.h | 2 +- > drivers/mmc/host/sdhci.h | 2 +- > drivers/mmc/host/vub300.c | 2 +- > include/linux/mmc/host.h | 2 +- > include/linux/mmc/sdio_func.h | 2 +- > include/uapi/linux/mmc/ioctl.h | 2 +- > 9 files changed, 9 insertions(+), 9 deletions(-) > > diff --git a/drivers/mmc/host/sdhci-acpi.c b/drivers/mmc/host/sdhci-acpi.c > index 9651dca6863e..ea0e4fda3a9e 100644 > --- a/drivers/mmc/host/sdhci-acpi.c > +++ b/drivers/mmc/host/sdhci-acpi.c > @@ -72,7 +72,7 @@ struct sdhci_acpi_host { > const struct sdhci_acpi_slot *slot; > struct platform_device *pdev; > bool use_runtime_pm; > - unsigned long private[0] ____cacheline_aligned; > + unsigned long private[] ____cacheline_aligned; > }; > > static inline void *sdhci_acpi_priv(struct sdhci_acpi_host *c) > diff --git a/drivers/mmc/host/sdhci-cadence.c b/drivers/mmc/host/sdhci-cadence.c > index 5827d3751b81..9af3fe48d62f 100644 > --- a/drivers/mmc/host/sdhci-cadence.c > +++ b/drivers/mmc/host/sdhci-cadence.c > @@ -67,7 +67,7 @@ struct sdhci_cdns_priv { > void __iomem *hrs_addr; > bool enhanced_strobe; > unsigned int nr_phy_params; > - struct sdhci_cdns_phy_param phy_params[0]; > + struct sdhci_cdns_phy_param phy_params[]; > }; > > struct sdhci_cdns_phy_cfg { > diff --git a/drivers/mmc/host/sdhci-pci.h b/drivers/mmc/host/sdhci-pci.h > index 981bbbe63aff..42ccd123b046 100644 > --- a/drivers/mmc/host/sdhci-pci.h > +++ b/drivers/mmc/host/sdhci-pci.h > @@ -163,7 +163,7 @@ struct sdhci_pci_slot { > bool cd_override_level; > > void (*hw_reset)(struct sdhci_host *host); > - unsigned long private[0] ____cacheline_aligned; > + unsigned long private[] ____cacheline_aligned; > }; > > struct sdhci_pci_chip { > diff --git a/drivers/mmc/host/sdhci-pltfm.h b/drivers/mmc/host/sdhci-pltfm.h > index 2af445b8c325..6301b81cf573 100644 > --- a/drivers/mmc/host/sdhci-pltfm.h > +++ b/drivers/mmc/host/sdhci-pltfm.h > @@ -25,7 +25,7 @@ struct sdhci_pltfm_host { > unsigned int clock; > u16 xfer_mode_shadow; > > - unsigned long private[0] ____cacheline_aligned; > + unsigned long private[] ____cacheline_aligned; > }; > > #ifdef CONFIG_MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER > diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h > index cac2d97782e6..249635692112 100644 > --- a/drivers/mmc/host/sdhci.h > +++ b/drivers/mmc/host/sdhci.h > @@ -614,7 +614,7 @@ struct sdhci_host { > > u64 data_timeout; > > - unsigned long private[0] ____cacheline_aligned; > + unsigned long private[] ____cacheline_aligned; > }; > > struct sdhci_ops { > diff --git a/drivers/mmc/host/vub300.c b/drivers/mmc/host/vub300.c > index 6ced1b7f642f..a5a90d133f1f 100644 > --- a/drivers/mmc/host/vub300.c > +++ b/drivers/mmc/host/vub300.c > @@ -95,7 +95,7 @@ struct sd_response_header { > u8 port_number; > u8 command_type; > u8 command_index; > - u8 command_response[0]; > + u8 command_response[]; > } __packed; > > struct sd_status_header { > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h > index 562ed06881b0..2629329ab9f2 100644 > --- a/include/linux/mmc/host.h > +++ b/include/linux/mmc/host.h > @@ -465,7 +465,7 @@ struct mmc_host { > /* Host Software Queue support */ > bool hsq_enabled; > > - unsigned long private[0] ____cacheline_aligned; > + unsigned long private[] ____cacheline_aligned; > }; > > struct device_node; > diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h > index 5a177f7a83c3..fa2aaab5e57a 100644 > --- a/include/linux/mmc/sdio_func.h > +++ b/include/linux/mmc/sdio_func.h > @@ -25,7 +25,7 @@ struct sdio_func_tuple { > struct sdio_func_tuple *next; > unsigned char code; > unsigned char size; > - unsigned char data[0]; > + unsigned char data[]; > }; > > /* > diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h > index 00c08120f3ba..98e29e7f54ac 100644 > --- a/include/uapi/linux/mmc/ioctl.h > +++ b/include/uapi/linux/mmc/ioctl.h > @@ -57,7 +57,7 @@ struct mmc_ioc_cmd { > */ > struct mmc_ioc_multi_cmd { > __u64 num_of_cmds; > - struct mmc_ioc_cmd cmds[0]; > + struct mmc_ioc_cmd cmds[]; > }; > > #define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd) >