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=-14.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 476EBC433F5 for ; Fri, 17 Sep 2021 09:38:57 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 119B860F43 for ; Fri, 17 Sep 2021 09:38:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 119B860F43 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=LRMGo2VhxJYpuYaqA4HHJahpmku41MSB68RidKsSOHU=; b=sbQDfpbnUcbXAz jMklPhJ8ktr3wwk6/F6mGTo65KoT5rCeww0HtlFaRTw44Sq+C2C7A50mGFNBQkSvi7DGvU1WhFQWq GA9GnCZ83UnCiPnhKnQD2IKD2NqQ8MnGbHPcrohjQd0TK+NDe3hS/4Kjl4qfpc6swfYzLEtTas80p zXqfdhL8bHZ/FhPmWsvo9A2EglO7hzXgtjaE2Aemt8hhOrM+COdb2gbUa+nSfyDvfTL+cY62y9q1s UDg3ieRBCiTI75f9B9w8OXC4B/2QT8dMKxMbxqgEmKWWIS+VFBq/HhpSmtYTl/BNHYDVoTbXmlva3 WYpLJLjzGDXPfz2YJ1Rg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mRAIY-00De0g-NB; Fri, 17 Sep 2021 09:36:46 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mRAIU-00De09-MI for linux-arm-kernel@lists.infradead.org; Fri, 17 Sep 2021 09:36:44 +0000 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 92122101E; Fri, 17 Sep 2021 02:36:36 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.20.241]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 428D43F59C; Fri, 17 Sep 2021 02:36:35 -0700 (PDT) Date: Fri, 17 Sep 2021 10:36:28 +0100 From: Mark Rutland To: Amit Daniel Kachhap Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Vincenzo Frascino , Kevin Brodsky , Catalin Marinas , Will Deacon Subject: Re: [PATCH v2] arm64/traps: Avoid unnecessary kernel/user pointer conversion Message-ID: <20210917093628.GB75427@C02TD0UTHF1T.local> References: <20210917055811.22341-1-amit.kachhap@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210917055811.22341-1-amit.kachhap@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210917_023642_818441_56195B44 X-CRM114-Status: GOOD ( 21.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Sep 17, 2021 at 11:28:11AM +0530, Amit Daniel Kachhap wrote: > Annotating a pointer from kernel to __user and then back again requires > an extra __force annotation to silent sparse warning. In call_undef_hook() > this unnecessary complexity can be avoided by modifying the intermediate > user pointer to unsigned long. > > This way there is no inter-changeable use of user and kernel pointers > and the code is consistent. > > Note: This patch adds no functional changes to code. > > Cc: Catalin Marinas > Cc: Will Deacon > Signed-off-by: Amit Daniel Kachhap I like that this clarifies that `pc` is not necessarily a user pointer, and this makes the relevant lines shorter and eaier to read, so FWIW: Acked-by: Mark Rutland Thanks, Mark. > --- > Changes from v1: > * Instead of directly using instruction_pointer() for kernel pointers, > modified the pc type from void __user * to unsigned long as suggested > by Mark Rutland. > > arch/arm64/kernel/traps.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > index b03e383d944a..09236751283e 100644 > --- a/arch/arm64/kernel/traps.c > +++ b/arch/arm64/kernel/traps.c > @@ -400,11 +400,11 @@ static int call_undef_hook(struct pt_regs *regs) > unsigned long flags; > u32 instr; > int (*fn)(struct pt_regs *regs, u32 instr) = NULL; > - void __user *pc = (void __user *)instruction_pointer(regs); > + unsigned long pc = instruction_pointer(regs); > > if (!user_mode(regs)) { > __le32 instr_le; > - if (get_kernel_nofault(instr_le, (__force __le32 *)pc)) > + if (get_kernel_nofault(instr_le, (__le32 *)pc)) > goto exit; > instr = le32_to_cpu(instr_le); > } else if (compat_thumb_mode(regs)) { > -- > 2.17.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel