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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 CEEA1C43216 for ; Fri, 27 Aug 2021 18:46:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6F93260F6C for ; Fri, 27 Aug 2021 18:46:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6F93260F6C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id C5D216B0071; Fri, 27 Aug 2021 14:45:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B22D66B0072; Fri, 27 Aug 2021 14:45:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8895E8D0001; Fri, 27 Aug 2021 14:45:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0156.hostedemail.com [216.40.44.156]) by kanga.kvack.org (Postfix) with ESMTP id 6E83A6B0071 for ; Fri, 27 Aug 2021 14:45:59 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 17D2A18244EF7 for ; Fri, 27 Aug 2021 18:45:59 +0000 (UTC) X-FDA: 78521740038.01.AFE7EDA Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by imf11.hostedemail.com (Postfix) with ESMTP id C25E4F0000AF for ; Fri, 27 Aug 2021 18:45:58 +0000 (UTC) Received: from zn.tnic (p200300ec2f111700cf40790d4c46ba75.dip0.t-ipconnect.de [IPv6:2003:ec:2f11:1700:cf40:790d:4c46:ba75]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 645881EC0464; Fri, 27 Aug 2021 20:45:53 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1630089953; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=y0FEGpbT1o/usEWCQaIVd7WpX4gpA+I5TcpFa2iPS/c=; b=SHMA6G9AjxgkvlDD605FGB3xhf0BjvRxxmOo92lMF2ekx955Tjyy8uY4UbXlI7oyLe209g +JYuyJ2G360w9la3Fo0zaixmBftxHU0YDrMyaPumDFptRiuMFfbh/CP3tYATF87eJSLSql PtdHSUjwg7HnCzJzHi1aVTBWqnFKAak= Date: Fri, 27 Aug 2021 20:46:35 +0200 From: Borislav Petkov To: "Yu, Yu-cheng" 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 , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , Rick P Edgecombe Subject: Re: [PATCH v29 23/32] x86/cet/shstk: Add user-mode shadow stack support Message-ID: References: <20210820181201.31490-1-yu-cheng.yu@intel.com> <20210820181201.31490-24-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=alien8.de header.s=dkim header.b=SHMA6G9A; spf=pass (imf11.hostedemail.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) smtp.mailfrom=bp@alien8.de; dmarc=pass (policy=none) header.from=alien8.de X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C25E4F0000AF X-Stat-Signature: 3bxc6wtpfr75af7sfpy4n3xmko9gzinz X-HE-Tag: 1630089958-76469 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 27, 2021 at 11:37:34AM -0700, Yu, Yu-cheng wrote: > Right now, the kernel does lazy restore, and it waits until right before a > task goes back to ring-3 to restore xstates. If a task needs to write to > any xstate registers before that (e.g. for signals), it restores the whole > xstates first and clears TIF_NEED_FPU_LOAD, which will prevent xstates being > restored again later. shstk_setup() allocates a shadow stack for the task and puts its pointer in MSR_IA32_PL3_SSP. What does that have to do with a task having to write any xstate registers? -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette