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=-17.3 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,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 D002DC433F5 for ; Wed, 15 Sep 2021 13:59:16 +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 8DD7461250 for ; Wed, 15 Sep 2021 13:59:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8DD7461250 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-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:Cc:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gdTGqRWX3h1MiNUZMWwLlHQZbl7WX9NtAJnf0vwlyKM=; b=LcLXsbgqmgV+S2nRxFSnhjEVL0 zIFLnmGjhZCCu+/we8NAsPHuMkifWhFLZdkCNivrSCDXWFuOqkWv4FMjm0vIC6FPN7FAPs8wVjAPf W3ZRimRmmGS0ZcCHhC8LHQyvnhCSWL3kyd8LCTbtgFdafV2Io+MEDYQdUPjC9D5zSdA/PpW+vCLKv boRa3g8hKadnqNhZ4K+6JGrM551Zi3+ULlc857qvN+mhpj2+zxJ183tC77AkGTcQYSwijDAmiLaqz 716tiwK7w4LjlcxaF6l/gfSjvTenb9MkRSrnqUBrsDMGvK38jGvqgISsWJxKN2Jw5m1sJ9bncejhk A6wn6uPw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mQVPR-009F3x-Dp; Wed, 15 Sep 2021 13:57:10 +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 1mQVPL-009F1z-NT for linux-arm-kernel@lists.infradead.org; Wed, 15 Sep 2021 13:57:05 +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 4F2236D; Wed, 15 Sep 2021 06:57:00 -0700 (PDT) Received: from [10.163.44.48] (unknown [10.163.44.48]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 281F43F719; Wed, 15 Sep 2021 06:56:57 -0700 (PDT) Subject: Re: [PATCH] arm64/traps: Avoid unnecessary kernel/user pointer conversion To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Vincenzo Frascino , Catalin Marinas , Will Deacon References: <20210914152742.27047-1-amit.kachhap@arm.com> <20210914160056.GA35239@C02TD0UTHF1T.local> From: Amit Kachhap Message-ID: <6662988b-b891-b6b0-cd7a-bd7f661fc737@arm.com> Date: Wed, 15 Sep 2021 19:26:55 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20210914160056.GA35239@C02TD0UTHF1T.local> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210915_065703_872946_B9CDFFD4 X-CRM114-Status: GOOD ( 24.28 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 9/14/21 9:30 PM, Mark Rutland wrote: > On Tue, Sep 14, 2021 at 08:57:42PM +0530, Amit Daniel Kachhap wrote: >> Annotating a pointer from kernel to __user and then back again might >> confuse sparse. In call_undef_hook() it can be avoided by not using the >> intermediate user pointer variable. > > When you say "might confuse sparse", does it complain today? If so, can > you include an example of what goes wrong? No it does not give warning. The __force option silences the warning. My idea is to remove the unwanted __force annotations and not mix user and kernel pointers. > >> Note: This patch adds no functional changes to code. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Signed-off-by: Amit Daniel Kachhap >> --- >> arch/arm64/kernel/traps.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c >> index b03e383d944a..357d10a8bbf5 100644 >> --- a/arch/arm64/kernel/traps.c >> +++ b/arch/arm64/kernel/traps.c >> @@ -404,7 +404,8 @@ static int call_undef_hook(struct pt_regs *regs) >> >> if (!user_mode(regs)) { >> __le32 instr_le; >> - if (get_kernel_nofault(instr_le, (__force __le32 *)pc)) >> + if (get_kernel_nofault(instr_le, >> + (__le32 *)instruction_pointer(regs))) > > Can we make `pc` an unsigned long, instead? I think it can be done. > > It'd be nice to handle all three cases consistently, even if that means > adding __force to the two user cases. Agree with your suggestion. Even in the 2 user cases, __force may not be needed as the typecast will be from from unsigned long to user pointer. BR, Amit > > Thanks, > Mark. > >> 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