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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 B3FE1C43461 for ; Thu, 3 Sep 2020 16:15:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 94E3C20829 for ; Thu, 3 Sep 2020 16:15:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599149748; bh=M4de8VIlN5oGko56PdnQYFxQoRWoIZixfSOt8ZIRpmc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=n1r/dBJhrOBybguAMl7KOHucUBW/AHj7UVTWzu24i4mjy76LiAp6dz/t90P6S2zXr 7R2DiyBlgkAaxYJPYX3ewmnk4NuyloDDHmVUC9vERWAMJyS3nxkXsIIe3E5eGjhKz1 oyx4qo6ykgtUHJd63WMD1K+lAdWXPp2z4S7+Isg0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727786AbgICQPl (ORCPT ); Thu, 3 Sep 2020 12:15:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:42010 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728085AbgICQPj (ORCPT ); Thu, 3 Sep 2020 12:15:39 -0400 Received: from mail-wr1-f49.google.com (mail-wr1-f49.google.com [209.85.221.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4E5D0208C7 for ; Thu, 3 Sep 2020 16:15:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599149738; bh=M4de8VIlN5oGko56PdnQYFxQoRWoIZixfSOt8ZIRpmc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=HUHyfNdaaBJXPriZlf3Ts2pJyj08I/ktPKdyfOn7ewAQ8zlUBn1eHxblXyok+MwmN Cn2QhTZnlkuJ0mfrATrWHnY35H3F9z4nd+P2u4UtlnIOm7OtR6ZH+dIl0N99ifRiOE dfYckGpTHxSmqtAurJcSq4FJh0Zga6d3lGbOhCqg= Received: by mail-wr1-f49.google.com with SMTP id c18so3839509wrm.9 for ; Thu, 03 Sep 2020 09:15:38 -0700 (PDT) X-Gm-Message-State: AOAM530If1hPN3wdIpEcKH4m6bfpPExjmNm3v98/kdIOAuGVTVso2b0T 3PEqkESdJBzcOc9pYrK7IZ3R2jc8Q15hsEWfXZNh8w== X-Google-Smtp-Source: ABdhPJzxk51W165I8aXmQ7ZsFkeOfAM9XM8FPpX1on1tLbF9c0ZcoI90VLnKqRN+zu5Iz7T/J1VzvJy8Uq4K7qJhTOU= X-Received: by 2002:a5d:5111:: with SMTP id s17mr3244344wrt.70.1599149736897; Thu, 03 Sep 2020 09:15:36 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: <1b51d89c-c7de-2032-df23-e138d1369ffa@intel.com> From: Andy Lutomirski Date: Thu, 3 Sep 2020 09:15:25 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v11 6/9] x86/cet: Add PTRACE interface for CET To: Dave Hansen Cc: "Yu, Yu-cheng" , Jann Horn , "the arch/x86 maintainers" , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , "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 , "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 Content-Type: text/plain; charset="UTF-8" Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Sep 3, 2020 at 9:12 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. For example, if the system has CET enabled, > > but the task does not have CET enabled, and GDB is writing to a CET MSR. > > But still, this is strange to me. > > If this is strange, then why do we even _implement_ writes? Well, if gdb wants to force a tracee to return early from a function, wouldn't it want the ability to modify SSP? --Andy