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=-2.2 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 85033C04AAD for ; Tue, 7 May 2019 11:32:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55E6820989 for ; Tue, 7 May 2019 11:32:17 +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="bv9hlo2+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726586AbfEGLcQ (ORCPT ); Tue, 7 May 2019 07:32:16 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38388 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726276AbfEGLcQ (ORCPT ); Tue, 7 May 2019 07:32:16 -0400 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: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=0G0Op7qzdUllIx217BDIX7hQDFmNR1hjBEmN3uH/wmM=; b=bv9hlo2+IqIluXyx1IyzYf4+2 XhumvYALMGJMgM81v5ZLGPqY5LRZT67zik8hBt/625x5jxWyUACHPwDUiRtMLRjyLFvSehE0YE9hA WGGaAEm4Vl0gGDXvotmBnc3tECB82fSuKQ8Sex3m4R/NZ4WI2ti48nUQA8iUYzqb3GENub4IxQS9M xUX1h7wMqORpAYUeAvaWgn5ss/K6KKU3WqkmIEqdjHnLl1vrosMXNaFZEhI6TOJsXytb/c3vdR6P3 dD4e/QeMf+TEl7i2H86GUAZAY5cVEe9letJOB7J9cES996O5TlJTAZ3VCmQ+UyU3Pmz+Q62/LWc8F 7dDh57edQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hNyJB-0006Sy-Su; Tue, 07 May 2019 11:30:54 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id D03FC2063D744; Tue, 7 May 2019 13:30:50 +0200 (CEST) Date: Tue, 7 May 2019 13:30:50 +0200 From: Peter Zijlstra To: David Laight Cc: Linus Torvalds , Andy Lutomirski , Steven Rostedt , Linux List Kernel Mailing , Ingo Molnar , Andrew Morton , Andy Lutomirski , Nicolai Stange , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , the arch/x86 maintainers , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , "open list:KERNEL SELFTEST FRAMEWORK" , stable Subject: Re: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions Message-ID: <20190507113050.GR2606@hirez.programming.kicks-ass.net> References: <20190502185225.0cdfc8bc@gandalf.local.home> <20190502193129.664c5b2e@gandalf.local.home> <20190502195052.0af473cf@gandalf.local.home> <20190503092959.GB2623@hirez.programming.kicks-ass.net> <20190503092247.20cc1ff0@gandalf.local.home> <2045370D-38D8-406C-9E94-C1D483E232C9@amacapital.net> <20190506081951.GJ2606@hirez.programming.kicks-ass.net> <20190507085753.GO2606@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 07, 2019 at 09:18:51AM +0000, David Laight wrote: > From: Peter Zijlstra > > Sent: 07 May 2019 09:58 > ... > > + /* > > + * When we're here from kernel mode; the (exception) stack looks like: > > + * > > + * 4*4(%esp) - > > + * 3*4(%esp) - flags > > + * 2*4(%esp) - cs > > + * 1*4(%esp) - ip > > + * 0*4(%esp) - orig_eax > > Am I right in thinking that this is the only 'INT3' stack frame that > needs to be 'fiddled' with? > And that the 'emulate a call instruction' has verified that is the case?? > So the %cs is always the kernel %cs. Only the INT3 thing needs 'the gap', but the far bigger change here is that kernel frames now have a complete pt_regs set and all sorts of horrible crap can go away. For 32bit 'the gap' happens naturally when building a 5 entry frame. Yes it is possible to build a 5 entry frame on top of the old 3 entry one, but why bother... From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz at infradead.org (Peter Zijlstra) Date: Tue, 7 May 2019 13:30:50 +0200 Subject: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions In-Reply-To: References: <20190502185225.0cdfc8bc@gandalf.local.home> <20190502193129.664c5b2e@gandalf.local.home> <20190502195052.0af473cf@gandalf.local.home> <20190503092959.GB2623@hirez.programming.kicks-ass.net> <20190503092247.20cc1ff0@gandalf.local.home> <2045370D-38D8-406C-9E94-C1D483E232C9@amacapital.net> <20190506081951.GJ2606@hirez.programming.kicks-ass.net> <20190507085753.GO2606@hirez.programming.kicks-ass.net> Message-ID: <20190507113050.GR2606@hirez.programming.kicks-ass.net> On Tue, May 07, 2019 at 09:18:51AM +0000, David Laight wrote: > From: Peter Zijlstra > > Sent: 07 May 2019 09:58 > ... > > + /* > > + * When we're here from kernel mode; the (exception) stack looks like: > > + * > > + * 4*4(%esp) - > > + * 3*4(%esp) - flags > > + * 2*4(%esp) - cs > > + * 1*4(%esp) - ip > > + * 0*4(%esp) - orig_eax > > Am I right in thinking that this is the only 'INT3' stack frame that > needs to be 'fiddled' with? > And that the 'emulate a call instruction' has verified that is the case?? > So the %cs is always the kernel %cs. Only the INT3 thing needs 'the gap', but the far bigger change here is that kernel frames now have a complete pt_regs set and all sorts of horrible crap can go away. For 32bit 'the gap' happens naturally when building a 5 entry frame. Yes it is possible to build a 5 entry frame on top of the old 3 entry one, but why bother... From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz@infradead.org (Peter Zijlstra) Date: Tue, 7 May 2019 13:30:50 +0200 Subject: [RFC][PATCH 1/2] x86: Allow breakpoints to emulate call functions In-Reply-To: References: <20190502185225.0cdfc8bc@gandalf.local.home> <20190502193129.664c5b2e@gandalf.local.home> <20190502195052.0af473cf@gandalf.local.home> <20190503092959.GB2623@hirez.programming.kicks-ass.net> <20190503092247.20cc1ff0@gandalf.local.home> <2045370D-38D8-406C-9E94-C1D483E232C9@amacapital.net> <20190506081951.GJ2606@hirez.programming.kicks-ass.net> <20190507085753.GO2606@hirez.programming.kicks-ass.net> Message-ID: <20190507113050.GR2606@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" Message-ID: <20190507113050.J_9TFgt39p_tqmbzjGFJfeqN3ly25ATzms-VwuO54PM@z> On Tue, May 07, 2019@09:18:51AM +0000, David Laight wrote: > From: Peter Zijlstra > > Sent: 07 May 2019 09:58 > ... > > + /* > > + * When we're here from kernel mode; the (exception) stack looks like: > > + * > > + * 4*4(%esp) - > > + * 3*4(%esp) - flags > > + * 2*4(%esp) - cs > > + * 1*4(%esp) - ip > > + * 0*4(%esp) - orig_eax > > Am I right in thinking that this is the only 'INT3' stack frame that > needs to be 'fiddled' with? > And that the 'emulate a call instruction' has verified that is the case?? > So the %cs is always the kernel %cs. Only the INT3 thing needs 'the gap', but the far bigger change here is that kernel frames now have a complete pt_regs set and all sorts of horrible crap can go away. For 32bit 'the gap' happens naturally when building a 5 entry frame. Yes it is possible to build a 5 entry frame on top of the old 3 entry one, but why bother...