Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754381Ab1E2O7c (ORCPT ); Sun, 29 May 2011 10:59:32 -0400 Received: from mail-pv0-f174.google.com ([74.125.83.174]:63822 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753154Ab1E2O7b convert rfc822-to-8bit (ORCPT ); Sun, 29 May 2011 10:59:31 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type :content-transfer-encoding; b=lEKrCiRh5TpV4lZUx3I9dYItu1TkN1fsgl8AWXlu8fUWm+sfz8QFOIKZ/3UmUfN+gH hwKSgwjuWzUC4hMd+vtOniwsGRLgEcAXJ8LLzmk2z6+JUUFhzUlU4sObPCgWv5V17rt7 fYnM1mnFhQira0KJsCYaxnmGrJqkv11B9U5mA= MIME-Version: 1.0 In-Reply-To: <19938.23219.306163.24059@pilspetsen.it.uu.se> References: <4DDEC589.3010201@mit.edu> <20110527061208.GB9260@elte.hu> <20110528153536.GB27104@elte.hu> <19938.23219.306163.24059@pilspetsen.it.uu.se> From: Andrew Lutomirski Date: Sun, 29 May 2011 10:59:11 -0400 X-Google-Sender-Auth: qQJs0SZ3LxE7wKJFe3pwSm4YCA8 Message-ID: Subject: Re: [GIT pull] x86 vdso updates To: Mikael Pettersson Cc: Ingo Molnar , Thomas Gleixner , Linus Torvalds , Andrew Morton , x86@kernel.org, LKML Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1454 Lines: 34 On Sun, May 29, 2011 at 10:39 AM, Mikael Pettersson wrote: > Ingo Molnar writes: > ?> > ?> * Andrew Lutomirski wrote: > ?> > ?> > On Fri, May 27, 2011 at 7:36 AM, Andrew Lutomirski wrote: > ?> > > 3. Add int 0xcc and use it from vgettimeofday. ?It will SIGSEGV if > ?> > > called from a user address (so it has no risk of ever becoming ABI) > ?> > > and it will do gettimeofday if called from the right address. ?(I like > ... > ?> > Make it a real syscall but with extra constraints. ?It would have the > ?> > same calling convention as the syscall instruction, but it would turn > ?> > into SIGKILL if the calling address isn't in the VSYSCALL page > > This will make things difficult for user-space dynamic binary instrumentation > applications, since these normally execute generated code at different > addresses than the original code. > > Is there a safe fallback for this particular vsyscall? All of the vsyscalls have vDSO versions that work like any other code. Alternatively, if the dynamic instrumentation code knew about vsyscalls, it could just not instrument addresses in the vsyscall page. What existing applications would get broken? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/