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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 E30D5C5CFE7 for ; Wed, 11 Jul 2018 09:45:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9975920B6F for ; Wed, 11 Jul 2018 09:45:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OW0Mqczd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9975920B6F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726583AbeGKJsc (ORCPT ); Wed, 11 Jul 2018 05:48:32 -0400 Received: from merlin.infradead.org ([205.233.59.134]:60968 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726347AbeGKJsc (ORCPT ); Wed, 11 Jul 2018 05:48:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=35uc2c/EEdYEuEpYC3w2zjH12d59vutPkNXdCvFuokc=; b=OW0Mqczd3Y4p4iWRFDT6rdTwa 9m0Sy+l164x20ZSKPuBC7kNpBQMRo3zNdpe9JRJPDURD2XuylwTYjwKzA0huVrrKwKuJ32WeKKh0b e53w8yUc1OkFNBQpycDXXwV1iesJ74OHxBzw66YVwASgFbLL/p8fpP3kWb6n83BFQn8BRK6WjFT+h G61JLpDNJDhRbh7vKTjC7uCpb+Em126hNXeN873uf7EkYeXzVYIbK68MQB/dxmL9t+dlI60geuQVC C8cNkvMls0Mft8Z8NcBa1e/hGfo/DQC7cHcj5K6ltD7IaWUK0olomPJUIVrkByvQwjWmrSRrDTdr/ YlSdjxOYg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fdBg2-0006UE-LD; Wed, 11 Jul 2018 09:44:51 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8D43320291063; Wed, 11 Jul 2018 11:44:48 +0200 (CEST) Date: Wed, 11 Jul 2018 11:44:48 +0200 From: Peter Zijlstra To: Yu-cheng Yu Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , "Ravi V. Shankar" , Vedvyas Shanbhogue Subject: Re: [RFC PATCH v2 18/27] x86/cet/shstk: Introduce WRUSS instruction Message-ID: <20180711094448.GZ2476@hirez.programming.kicks-ass.net> References: <20180710222639.8241-1-yu-cheng.yu@intel.com> <20180710222639.8241-19-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180710222639.8241-19-yu-cheng.yu@intel.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 10, 2018 at 03:26:30PM -0700, Yu-cheng Yu wrote: > WRUSS is a new kernel-mode instruction but writes directly > to user shadow stack memory. This is used to construct > a return address on the shadow stack for the signal > handler. > > This instruction can fault if the user shadow stack is > invalid shadow stack memory. In that case, the kernel does > fixup. > > +static inline int write_user_shstk_64(unsigned long addr, unsigned long val) > +{ > + int err = 0; > + > + asm volatile("1: wrussq %[val], (%[addr])\n" > + "xor %[err], %[err]\n" this XOR is superfluous, you already cleared @err above. > + "2:\n" > + ".section .fixup,\"ax\"\n" > + "3: mov $-1, %[err]; jmp 2b\n" > + ".previous\n" > + _ASM_EXTABLE(1b, 3b) > + : [err] "=a" (err) > + : [val] "S" (val), [addr] "D" (addr)); > + > + return err; > +} > +#endif /* CONFIG_X86_INTEL_CET */ > + > #define nop() asm volatile ("nop") What happened to: https://lkml.kernel.org/r/1528729376.4526.0.camel@2b52.sc.intel.com