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=-7.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A77B7C433E9 for ; Thu, 3 Sep 2020 16:21:16 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 66DF920775 for ; Thu, 3 Sep 2020 16:21:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66DF920775 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 010566B0002; Thu, 3 Sep 2020 12:21:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EDB426B0003; Thu, 3 Sep 2020 12:21:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D571B6B0062; Thu, 3 Sep 2020 12:21:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0132.hostedemail.com [216.40.44.132]) by kanga.kvack.org (Postfix) with ESMTP id BCCBD6B0002 for ; Thu, 3 Sep 2020 12:21:15 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 526AC3622 for ; Thu, 3 Sep 2020 16:21:15 +0000 (UTC) X-FDA: 77222264910.13.cup66_081141f270ab Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 1DC9218140B67 for ; Thu, 3 Sep 2020 16:21:15 +0000 (UTC) X-HE-Tag: cup66_081141f270ab X-Filterd-Recvd-Size: 3852 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Thu, 3 Sep 2020 16:21:14 +0000 (UTC) IronPort-SDR: 1x09jcbMm1gRJZdyzFp3S2LeC4pCzXLfvUh8KOb8tbCm6x+/X9I2tfSXQvwkXQ2z7/zxkAlyBt uCe5rFx6RsAA== X-IronPort-AV: E=McAfee;i="6000,8403,9733"; a="155115882" X-IronPort-AV: E=Sophos;i="5.76,387,1592895600"; d="scan'208";a="155115882" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Sep 2020 09:21:12 -0700 IronPort-SDR: +Pe0zUpW7n8ydj/YOVTaKR79uc3vTuh90uRyD5Hw3BPUUqT/NnJucVFtliTUbdOkPMAUiK4O9f Kyp5qF3qstzg== X-IronPort-AV: E=Sophos;i="5.76,387,1592895600"; d="scan'208";a="503120164" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.209.173.133]) ([10.209.173.133]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Sep 2020 09:21:11 -0700 Subject: Re: [PATCH v11 6/9] x86/cet: Add PTRACE interface for CET To: Dave Hansen , Andy Lutomirski Cc: Jann Horn , the arch/x86 maintainers , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang References: <46e42e5e-0bca-5f3f-efc9-5ab15827cc0b@intel.com> <40BC093A-F430-4DCC-8DC0-2BA90A6FC3FA@amacapital.net> <88261152-2de1-fe8d-7ab0-acb108e97e04@intel.com> <1b51d89c-c7de-2032-df23-e138d1369ffa@intel.com> From: "Yu, Yu-cheng" Message-ID: <3967f126-f7ea-36fd-bec0-dfbbc46ef221@intel.com> Date: Thu, 3 Sep 2020 09:21:10 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <1b51d89c-c7de-2032-df23-e138d1369ffa@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Rspamd-Queue-Id: 1DC9218140B67 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable 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 9/3/2020 9:11 AM, Dave Hansen wrote: > On 9/3/20 9:09 AM, Yu, Yu-cheng wrote: >> If the debugger is going to write an MSR, only in the third case would >> this make a slight sense.=C2=A0 For example, if the system has CET ena= bled, >> but the task does not have CET enabled, and GDB is writing to a CET MS= R. >> =C2=A0But still, this is strange to me. >=20 > If this is strange, then why do we even _implement_ writes? >=20 For example, if the task has CET enabled, and it is in a control=20 protection fault, the debugger can clear the task's IBT state, or unwind=20 the shadow stack, etc. But if the task does not have CET enabled (its=20 CET MSRs are in INIT state), it would make sense for the PTRACE call to=20 return failure than doing something else, right?