Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030717AbaDJMyA (ORCPT ); Thu, 10 Apr 2014 08:54:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:13120 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030515AbaDJMx6 (ORCPT ); Thu, 10 Apr 2014 08:53:58 -0400 Message-ID: <5346944F.2040709@redhat.com> Date: Thu, 10 Apr 2014 14:53:35 +0200 From: Denys Vlasenko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Oleg Nesterov , Ingo Molnar , Srikar Dronamraju CC: Ananth N Mavinakayanahalli , Anton Arapov , David Long , "Frank Ch. Eigler" , Jim Keniston , Jonathan Lebon , Masami Hiramatsu , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 4/6] uprobes/x86: Emulate rip-relative call's References: <20140409194434.GA6235@redhat.com> In-Reply-To: <20140409194434.GA6235@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/09/2014 09:44 PM, Oleg Nesterov wrote: > +static void ttt_clear_displacement(struct arch_uprobe *auprobe, struct insn *insn) Branch instruction's offset isn't called "displacement" on x86. How about ttt_clear_branch_offset? > +{ > + /* > + * Turn this insn into "call 1f; 1:", this is what we will execute > + * out-of-line if ->emulate() fails. > + * > + * In the likely case this will lead to arch_uprobe_abort_xol(), but > + * see the comment in ->emulate(). So we need to ensure that the new > + * ->ip can't fall into non-canonical area and trigger #GP. > + * > + * We could turn it into (say) "pushf", but then we would need to > + * divorce ->insn[] and ->ixol[]. We need to preserve the 1st byte > + * of ->insn[] for set_orig_insn(). > + */ > + memset(auprobe->insn + insn_offset_immediate(insn), > + 0, insn->immediate.nbytes); > +} -- 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/