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=-16.6 required=3.0 tests=BAYES_00,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=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 972F4C433E2 for ; Tue, 14 Jul 2020 15:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 751CF22285 for ; Tue, 14 Jul 2020 15:39:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594741165; bh=415lbHSeClwZCtpjlS68bKbmwLWmlia7bSW5KCVq2Mc=; h=Date:From:To:Cc:Subject:List-ID:From; b=CelBWt3pQ2j4OBkA29wKR3YblMxQzGH5YqqObAkSNhaB/42n6eD6WMQccKxU4P3iD rGJ+Fpv9587ewjN+TAkaOHKUbi32jYek4KbwMu6ZiFWrfyQ3JcUHiIC7Huvg3DQDZk EcMr5e9JMgPLpJ2tjChyt6cdzCj9UmJiG+nYogcs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726752AbgGNPjU (ORCPT ); Tue, 14 Jul 2020 11:39:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:52446 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725280AbgGNPjT (ORCPT ); Tue, 14 Jul 2020 11:39:19 -0400 Received: from embeddedor (unknown [201.162.240.73]) (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 2393622285; Tue, 14 Jul 2020 15:39:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594741158; bh=415lbHSeClwZCtpjlS68bKbmwLWmlia7bSW5KCVq2Mc=; h=Date:From:To:Cc:Subject:From; b=L6gBkn/qS+Aaz8ESC53BwR7g+RF+HsoAypwMOJzMRDMgLjoGi76E+3PJLYCRUXi9X dQcjWjX/EkZ9Il7sc+7twvEjEBcCepeMiypNAubKVjJ/h1WRiJ6e4Qtf1TAJDPrQXU +oaE2ICT/CVvA9KcHgzeZgURrUq34B4F3qHiYNsI= Date: Tue, 14 Jul 2020 10:44:49 -0500 From: "Gustavo A. R. Silva" To: Arnd Bergmann , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] hpilo: Replace one-element array with flexible-array member Message-ID: <20200714154449.GA26153@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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 There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. For this particular case, it is important to notice that the cachelines change from 7 to 6 after the flexible-array conversion: $ pahole -C 'fifo' drivers/misc/hpilo.o struct fifo { u64 nrents; /* 0 8 */ u64 imask; /* 8 8 */ u64 merge; /* 16 8 */ u64 reset; /* 24 8 */ u8 pad_0[96]; /* 32 96 */ /* --- cacheline 2 boundary (128 bytes) --- */ u64 head; /* 128 8 */ u8 pad_1[120]; /* 136 120 */ /* --- cacheline 4 boundary (256 bytes) --- */ u64 tail; /* 256 8 */ u8 pad_2[120]; /* 264 120 */ /* --- cacheline 6 boundary (384 bytes) --- */ u64 fifobar[1]; /* 384 8 */ /* size: 392, cachelines: 7, members: 10 */ /* last cacheline: 8 bytes */ }; $ pahole -C 'fifo' drivers/misc/hpilo.o struct fifo { u64 nrents; /* 0 8 */ u64 imask; /* 8 8 */ u64 merge; /* 16 8 */ u64 reset; /* 24 8 */ u8 pad_0[96]; /* 32 96 */ /* --- cacheline 2 boundary (128 bytes) --- */ u64 head; /* 128 8 */ u8 pad_1[120]; /* 136 120 */ /* --- cacheline 4 boundary (256 bytes) --- */ u64 tail; /* 256 8 */ u8 pad_2[120]; /* 264 120 */ /* --- cacheline 6 boundary (384 bytes) --- */ u64 fifobar[]; /* 384 0 */ /* size: 384, cachelines: 6, members: 10 */ }; Lastly, remove unnecessary parentheses in fifo_sz() and fix the following checkpatch.pl warning for the whole fifo structure: WARNING: please, no spaces at the start of a line [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://github.com/KSPP/linux/issues/79 Tested-by: kernel test robot Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/kernel-ci/hpilo-20200714.md Signed-off-by: Gustavo A. R. Silva --- drivers/misc/hpilo.c | 2 +- drivers/misc/hpilo.h | 22 +++++++++++----------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/drivers/misc/hpilo.c b/drivers/misc/hpilo.c index 927309b86bab..10c975662f8b 100644 --- a/drivers/misc/hpilo.c +++ b/drivers/misc/hpilo.c @@ -207,7 +207,7 @@ static void ctrl_setup(struct ccb *ccb, int nr_desc, int l2desc_sz) static inline int fifo_sz(int nr_entry) { /* size of a fifo is determined by the number of entries it contains */ - return (nr_entry * sizeof(u64)) + FIFOHANDLESIZE; + return nr_entry * sizeof(u64) + FIFOHANDLESIZE; } static void fifo_setup(void *base_addr, int nr_entry) diff --git a/drivers/misc/hpilo.h b/drivers/misc/hpilo.h index 1aa433a7f66c..f69ff645cac9 100644 --- a/drivers/misc/hpilo.h +++ b/drivers/misc/hpilo.h @@ -160,23 +160,23 @@ struct ccb_data { #define ILO_START_ALIGN 4096 #define ILO_CACHE_SZ 128 struct fifo { - u64 nrents; /* user requested number of fifo entries */ - u64 imask; /* mask to extract valid fifo index */ - u64 merge; /* O/C bits to merge in during enqueue operation */ - u64 reset; /* set to non-zero when the target device resets */ - u8 pad_0[ILO_CACHE_SZ - (sizeof(u64) * 4)]; + u64 nrents; /* user requested number of fifo entries */ + u64 imask; /* mask to extract valid fifo index */ + u64 merge; /* O/C bits to merge in during enqueue operation */ + u64 reset; /* set to non-zero when the target device resets */ + u8 pad_0[ILO_CACHE_SZ - (sizeof(u64) * 4)]; - u64 head; - u8 pad_1[ILO_CACHE_SZ - (sizeof(u64))]; + u64 head; + u8 pad_1[ILO_CACHE_SZ - (sizeof(u64))]; - u64 tail; - u8 pad_2[ILO_CACHE_SZ - (sizeof(u64))]; + u64 tail; + u8 pad_2[ILO_CACHE_SZ - (sizeof(u64))]; - u64 fifobar[1]; + u64 fifobar[]; }; /* convert between struct fifo, and the fifobar, which is saved in the ccb */ -#define FIFOHANDLESIZE (sizeof(struct fifo) - sizeof(u64)) +#define FIFOHANDLESIZE (sizeof(struct fifo)) #define FIFOBARTOHANDLE(_fifo) \ ((struct fifo *)(((char *)(_fifo)) - FIFOHANDLESIZE)) -- 2.27.0