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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 3CB16C3B18B for ; Thu, 13 Feb 2020 14:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AC5324649 for ; Thu, 13 Feb 2020 14:00:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730190AbgBMOA1 (ORCPT ); Thu, 13 Feb 2020 09:00:27 -0500 Received: from foss.arm.com ([217.140.110.172]:46972 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730055AbgBMOA1 (ORCPT ); Thu, 13 Feb 2020 09:00:27 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 69FF91045; Thu, 13 Feb 2020 06:00:26 -0800 (PST) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id B800D3F68F; Thu, 13 Feb 2020 06:00:25 -0800 (PST) From: Robin Murphy To: joro@8bytes.org Cc: iommu@lists.linux-foundation.org, gustavo@embeddedor.com, linux-kernel@vger.kernel.org Subject: [PATCH] iommu: Use C99 flexible array in fwspec Date: Thu, 13 Feb 2020 14:00:21 +0000 Message-Id: <7364595699c37d2ef53636c8af6dcefa6602529b.1581601149.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.23.0.dirty MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Although the 1-element array was a typical pre-C99 way to implement variable-length structures, and indeed is a fundamental construct in the APIs of certain other popular platforms, there's no good reason for it here (and in particular the sizeof() trick is far too "clever" for its own good). We can just as easily implement iommu_fwspec's preallocation behaviour using a standard flexible array member, so let's make it look the way most readers would expect. Signed-off-by: Robin Murphy --- Before the Coccinelle police catch up with me... :) Deliberately no fixes tag, since the original code predates struct_size(), and it's really just a cosmetic cleanup that shouldn't be backported anyway. Robin. drivers/iommu/iommu.c | 15 ++++++++------- include/linux/iommu.h | 2 +- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 3e3528436e0b..660eea8d1d2f 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -2405,7 +2405,8 @@ int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode, if (fwspec) return ops == fwspec->ops ? 0 : -EINVAL; - fwspec = kzalloc(sizeof(*fwspec), GFP_KERNEL); + /* Preallocate for the overwhelmingly common case of 1 ID */ + fwspec = kzalloc(struct_size(fwspec, ids, 1), GFP_KERNEL); if (!fwspec) return -ENOMEM; @@ -2432,15 +2433,15 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_free); int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids) { struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev); - size_t size; - int i; + int i, new_num; if (!fwspec) return -EINVAL; - size = offsetof(struct iommu_fwspec, ids[fwspec->num_ids + num_ids]); - if (size > sizeof(*fwspec)) { - fwspec = krealloc(fwspec, size, GFP_KERNEL); + new_num = fwspec->num_ids + num_ids; + if (new_num > 1) { + fwspec = krealloc(fwspec, struct_size(fwspec, ids, new_num), + GFP_KERNEL); if (!fwspec) return -ENOMEM; @@ -2450,7 +2451,7 @@ int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids) for (i = 0; i < num_ids; i++) fwspec->ids[fwspec->num_ids + i] = ids[i]; - fwspec->num_ids += num_ids; + fwspec->num_ids = new_num; return 0; } EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids); diff --git a/include/linux/iommu.h b/include/linux/iommu.h index d1b5f4d98569..4d1ba76c9a64 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -592,7 +592,7 @@ struct iommu_fwspec { u32 flags; u32 num_pasid_bits; unsigned int num_ids; - u32 ids[1]; + u32 ids[]; }; /* ATS is supported */ -- 2.23.0.dirty