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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 8C7EAC433E0 for ; Fri, 22 May 2020 16:53:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AA6C206D5 for ; Fri, 22 May 2020 16:53:08 +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="Pg7zV9Cm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730540AbgEVQxE (ORCPT ); Fri, 22 May 2020 12:53:04 -0400 Received: from merlin.infradead.org ([205.233.59.134]:45748 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730445AbgEVQxD (ORCPT ); Fri, 22 May 2020 12:53:03 -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; bh=DATMXvPBFN2+b2MxvEm54Fwd6smgejl5nHlaR7B/mQ0=; b=Pg7zV9Cm25CEnqqgnteZ4rkSsJ jW2xOn9ek07x0YLY9VOBqy/4T6f73bD7ddQVsHHMkRXrV7cpzYxoICoveu44T0Br4ZhNKlX3qlKSS aZErt43QdZUXpfE6yHIRby4AL78iDFQtFdl0tauMNHd4niRm4M4QgZNHSArC9OOBJOQeMiIKlLfKX yw2zOkesdkRGucqKlIxDGQvOc+hj1R2PdbWMzcs1mLYFL+t9kVLcYTwk0AU66ZB+7M1IpZvenY0YJ 6ruhazJA70OMSBAj97tUfjlrBUiYS+QT/ByLBhHHSzIChVTWXowwaKMLU/RVRKB62IM8sUfNltnqq DopPt9Gg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jcArr-0006XR-GU; Fri, 22 May 2020 16:49:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 8E3C93060FC; Fri, 22 May 2020 18:49:53 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7A55D20BDB125; Fri, 22 May 2020 18:49:53 +0200 (CEST) Date: Fri, 22 May 2020 18:49:53 +0200 From: Peter Zijlstra To: Andrew Cooper Cc: "H.J. Lu" , Dave Hansen , Yu-cheng Yu , the arch/x86 maintainers , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Subject: Re: [PATCH v10 01/26] Documentation/x86: Add CET description Message-ID: <20200522164953.GA411971@hirez.programming.kicks-ass.net> References: <20200429220732.31602-2-yu-cheng.yu@intel.com> <5cc163ff9058d1b27778e5f0a016c88a3b1a1598.camel@intel.com> <44c055342bda4fb4730703f987ae35195d1d0c38.camel@intel.com> <32235ffc-6e6c-fb3d-80c4-a0478e2d0e0f@intel.com> <6272c481-af90-05c5-7231-3ba44ff9bd02@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Sat, May 16, 2020 at 03:09:22PM +0100, Andrew Cooper wrote: > Sadly, the same is not true for kernel shadow stacks. > > SSP is 0 after SYSCALL, SYSENTER and CLRSSBSY, and you've got to be > careful to re-establish the shadow stack before a CALL, interrupt or > exception tries pushing a word onto the shadow stack at 0xfffffffffffffff8. Oh man, I can only imagine the joy that brings to #NM and friends :-(