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[209.132.180.67]) by mx.google.com with ESMTP id d6si2775108pgu.400.2018.03.01.10.39.39; Thu, 01 Mar 2018 10:39:54 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=fail header.i=@gmail.com header.s=20161025 header.b=O4qiNA7t; dkim=fail header.i=@linux-foundation.org header.s=google header.b=AHSt6fUN; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034064AbeCASiZ (ORCPT + 99 others); Thu, 1 Mar 2018 13:38:25 -0500 Received: from mail-io0-f195.google.com ([209.85.223.195]:38952 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1033978AbeCASiX (ORCPT ); Thu, 1 Mar 2018 13:38:23 -0500 Received: by mail-io0-f195.google.com with SMTP id b34so8154678ioj.6 for ; Thu, 01 Mar 2018 10:38:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=E/9pCxAqP3dGVNcNNKoTGFGiiXGo7HPgsxST8EX9WGc=; b=O4qiNA7tnNXX8ozjTzWOs3+qHxsRxSAiYm3SqTXBdh7jDMFuvialdSlcyGccDxtKOp 45lt0tT4Wio+mcTH8Mmv+dwVBTnaTfM6t9RdhVzGMV1B1eFWuUkF+c9oETKpSVSaxBls LqDoDxEWShoGyN/Ys5hspfek0R1U0KF5PKSCpCyK1z1N2GsMZ8pWJ4Gjuw/8yd8fSpo+ pkDBXg47u4vh2MSE69sJSx1FV0jzFpddK6TXqIRQIbtq3hRt5JFVh5waWadpAt6o2kBo UiJsTQplNDByj0xBlx2HfU3QpTyjdsVNzzGpU1FiN9raUEyZ43aKBgOSMfv0/rVTkYfr bI1w== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=E/9pCxAqP3dGVNcNNKoTGFGiiXGo7HPgsxST8EX9WGc=; b=AHSt6fUNjoIAt/AxiF0xxKD/ZgzBpMYqkAPA4Gymy0O4tSQKnT5IDTLxJf8rHFsKCM oG08LfVyQMDosv6Gr2kjNFVKdDm182QPN3e9AOnF0kXzqQ5NfjmILa96rRa1GVAUkvcK tRLd8QDH5Wl7yj/P9Q/dELiYBTK9EhNeRmndU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=E/9pCxAqP3dGVNcNNKoTGFGiiXGo7HPgsxST8EX9WGc=; b=Zt0YaaFNWpoSnRYb30saaHvqLarA8kNnHKkx9NfYSedNGnYbv/lgJ8LuPDWFQyvNMG fRL3n0vvpWGBUqSAnekbQuGBEO1LhQNRsQR2I30iEMCtfhi/4wh7LOzXNMimx7lilJ9R ye2MFvXI+yn6YEGsfzeKiDkon7pR5TL7CFtDOoBY0iqszv0eH6mBvH7n2BIyhFTGJh62 kVIUmrZebdfyYVBvJ4wj4gdf1C7vNaYf8/cR+F9Geg7iynExX3xUYQTkyC5b0E1yztQ/ jxN/hwCwTrw19NgKstJ7bL2/QN9+C+rtJVlm/TTDIfVyeB3Zsx+paeDh2jKeYj3D6Rg/ JdRg== X-Gm-Message-State: APf1xPBho9XSOsQ1MVLyQfk+Ra7aWCnKPz26oGj9Qe2afRS+Wxwv2CC0 NUyT8jfXRx+8m8GyYxdoZMNNwzfsbHDYNelQgF8= X-Received: by 10.107.10.155 with SMTP id 27mr3278200iok.259.1519929502350; Thu, 01 Mar 2018 10:38:22 -0800 (PST) MIME-Version: 1.0 Received: by 10.107.135.221 with HTTP; Thu, 1 Mar 2018 10:38:21 -0800 (PST) In-Reply-To: References: <1518168340-9392-1-git-send-email-joro@8bytes.org> <1518168340-9392-13-git-send-email-joro@8bytes.org> <20180301133430.wda4qesqhxnww7d6@8bytes.org> <2ae8b01f-844b-b8b1-3198-5db70c3e083b@redhat.com> <20180301165019.kuynvb6fkcwdpxjx@suse.de> From: Linus Torvalds Date: Thu, 1 Mar 2018 10:38:21 -0800 X-Google-Sender-Auth: RNdYufNge33fC6cUVDvE1AO0ids Message-ID: Subject: Re: [PATCH 12/31] x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points To: Brian Gerst Cc: Joerg Roedel , Waiman Long , Joerg Roedel , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , "the arch/x86 maintainers" , Linux Kernel Mailing List , Linux-MM , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , "Liguori, Anthony" , Daniel Gruss , Hugh Dickins , Kees Cook , Andrea Arcangeli , Waiman Long , Pavel Machek Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 1, 2018 at 10:24 AM, Brian Gerst wrote: > > The IF flag only affects external maskable interrupts, not traps or > faults. You do need to check CR3 because SYSENTER does not clear TF > and will immediately cause a debug trap on kernel entry (with user > CR3) if set. That is why the code existed before to check for the > entry stack for debug/NMI. Note that debug traps can happen regardless of TF, Think kgdb etc. Arguably kgdb users get what they deserve, but still.. I think root can set kernel breakpoints too. Linus