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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 58F6BC433DF for ; Thu, 14 May 2020 13:16:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C571206DA for ; Thu, 14 May 2020 13:16:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K1nuKyO9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727072AbgENNQL (ORCPT ); Thu, 14 May 2020 09:16:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726037AbgENNQK (ORCPT ); Thu, 14 May 2020 09:16:10 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DF0FC061A0C for ; Thu, 14 May 2020 06:16:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=TpLw4BdJT0JveDtO4r1F8bJeWxiAnJbyCG4f/8DEh+w=; b=K1nuKyO9v7e/WFY//uVAMPcEwp WJkX8ripvNzw4cpzMXS5ArXCwZKrcYEs+sIWd8kzPYCTpBQEcsHezZ9EFkUv9VaH5DGHTxgV1b8tg Du61eFF8etGcz5sT5bqOP41re+HBV9eAHnLjCT1i9o86+/WDGiGzMF4zyi8tv6JeUbZVoROf7UU09 GbARtX6P6qoiashn9XcLC5gaWETrYhjFms99a4VN8BRR6U5j7nxyXNe8LajLnj4syY4u+V9LLbhBJ VfuRY7tK5GvuFMSARfBklSW14Kn8h6cHwCBxoM8z0NEnXd0CrMGI5h+A9bpD+b1t+mzZKUoam7qHu 88SUcd/g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZDi0-0007nQ-O6; Thu, 14 May 2020 13:15:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 166C4300455; Thu, 14 May 2020 15:15:30 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C62A6213C8B61; Thu, 14 May 2020 15:15:30 +0200 (CEST) Date: Thu, 14 May 2020 15:15:30 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Andy Lutomirski , LKML , X86 ML , "Paul E. McKenney" , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon Subject: Re: [patch V4 part 4 02/24] x86/int3: Avoid atomic instrumentation Message-ID: <20200514131530.GQ2957@hirez.programming.kicks-ass.net> References: <20200505134926.578885807@linutronix.de> <20200505135313.517429268@linutronix.de> <20200514093257.GT2978@hirez.programming.kicks-ass.net> <87h7wiznl7.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h7wiznl7.fsf@nanos.tec.linutronix.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 14, 2020 at 02:51:32PM +0200, Thomas Gleixner wrote: > Peter Zijlstra writes: > > On Wed, May 13, 2020 at 09:57:52PM -0700, Andy Lutomirski wrote: > >> On Tue, May 5, 2020 at 7:15 AM Thomas Gleixner wrote: > >> > > >> > From: Peter Zijlstra > >> > > >> > Use arch_atomic_*() and READ_ONCE_NOCHECK() to ensure nothing untoward > >> > creeps in and ruins things. > >> > > >> > That is; this is the INT3 text poke handler, strictly limit the code > >> > that runs in it, lest it inadvertenly hits yet another INT3. > >> > >> > >> Acked-by: Andy Lutomirski > >> > >> Does objtool catch this error? > > > > It does not. I'll put it on the (endless) todo list.. > > Well, at least it detects when that code calls out into something which > is not in the non-instrumentable section. True, but the more specific problem is that noinstr code can use jump_label/static_call just fine. So a more specific test is validating none of that happens in the INT3 handler before poke_int3_handler(). Which is what I think Andy was after.