From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 8D5356B004D for ; Tue, 29 Nov 2011 05:32:33 -0500 (EST) Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 29 Nov 2011 03:32:32 -0700 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id pATAWRiO148668 for ; Tue, 29 Nov 2011 03:32:27 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id pATAWPIe014603 for ; Tue, 29 Nov 2011 03:32:26 -0700 Date: Tue, 29 Nov 2011 16:00:40 +0530 From: Srikar Dronamraju Subject: Re: [PATCH RFC 0/5] uprobes: kill xol vma Message-ID: <20111129103040.GF13445@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20111118110631.10512.73274.sendpatchset@srdronam.in.ibm.com> <20111128190614.GA4602@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20111128190614.GA4602@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Oleg Nesterov Cc: Peter Zijlstra , Linus Torvalds , Andrew Morton , LKML , Linux-mm , Ingo Molnar , Andi Kleen , Christoph Hellwig , Steven Rostedt , Roland McGrath , Thomas Gleixner , Masami Hiramatsu , Arnaldo Carvalho de Melo , Anton Arapov , Ananth N Mavinakayanahalli , Jim Keniston , Stephen Wilson > > On top of this series, not for inclusion yet, just to explain what > I mean. May be someone can test it ;) > > This series kills xol_vma. Instead we use the per_cpu-like xol slots. > > This is much more simple and efficient. And this of course solves > many problems we currently have with xol_vma. > > For example, we simply can not trust it. We do not know what actually > we are going to execute in UTASK_SSTEP mode. An application can unmap > this area and then do mmap(PROT_EXEC|PROT_WRITE, MAP_FIXED) to fool > uprobes. > > The only disadvantage is that this adds a bit more arch-dependant > code. > > The main question, can this work? I know very little in this area. > And I am not sure if this can be ported to other architectures. Nice idea. I think this will help us in implementing boosted uprobes if tweak a bit. (i.e having a jump after the actual instruction that gets us back to the actual instruction stream). The current method of using a first cum-first-serve slot reservation doesnt work for booster because we have had to clear the slot in the post processing. I will apply your patches and test and let you know how it goes. (in a day or two). -- Thanks and Regards Srikar -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org