From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.6 required=5.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 718597D071 for ; Wed, 11 Jul 2018 09:30:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726392AbeGKJdY (ORCPT ); Wed, 11 Jul 2018 05:33:24 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51608 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726368AbeGKJdY (ORCPT ); Wed, 11 Jul 2018 05:33:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=HNfZeAyOUk6CW6jcqB/Fxzu6JdX1Qdcn48KtH6knTyA=; b=Stc7DE4qm7DUgMExJifJ6g72m XRgpSoJ3tR8xnZSiD/MA19wKq1as9PGJlZgRMdgbh6Aa5A41PJ9Bpa1tuq8+sF2x5RcizJv4qzBlc Qeb5RtPLCdq61vOAD4Zd/OyBPfDtEbpXx9iv/hvQ4IJB1gtDqflOMzAUtIb92QBOh0JDQVzJxR9T7 VTh82WrAgibyqXydHugtAuZB2poqrHr+2UpnaSAOmw9QoVDF68nFoxpSUKMMHTw+8oAzEEwBKgsYa I29JIkNLAXIxrnW/RFkjiaEjg+gkEZ/ze42j8X6bW1xO1LWXYHKPYdPK+d4GaO0gHBkTYtLvhb6z2 KsKwToA1g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fdBRZ-0004eh-67; Wed, 11 Jul 2018 09:29:53 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4F2F820291063; Wed, 11 Jul 2018 11:29:51 +0200 (CEST) Date: Wed, 11 Jul 2018 11:29:51 +0200 From: Peter Zijlstra To: Yu-cheng Yu 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 , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , "Ravi V. Shankar" , Vedvyas Shanbhogue Subject: Re: [RFC PATCH v2 16/27] mm: Modify can_follow_write_pte/pmd for shadow stack Message-ID: <20180711092951.GW2476@hirez.programming.kicks-ass.net> References: <20180710222639.8241-1-yu-cheng.yu@intel.com> <20180710222639.8241-17-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180710222639.8241-17-yu-cheng.yu@intel.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, Jul 10, 2018 at 03:26:28PM -0700, Yu-cheng Yu wrote: > There are three possible shadow stack PTE settings: > > Normal SHSTK PTE: (R/O + DIRTY_HW) > SHSTK PTE COW'ed: (R/O + DIRTY_HW) > SHSTK PTE shared as R/O data: (R/O + DIRTY_SW) I count _2_ distinct states there. > Update can_follow_write_pte/pmd for the shadow stack. So the below disallows can_follow_write when shstk && _PAGE_DIRTY_SW, but this here Changelog doesn't explain why. Doesn't even get close. Also, the code is a right mess :/ Can't we try harder to not let this shadow stack stuff escape arch code. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html