Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756047AbZLRCQa (ORCPT ); Thu, 17 Dec 2009 21:16:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752773AbZLRCQ3 (ORCPT ); Thu, 17 Dec 2009 21:16:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:8601 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272AbZLRCQ2 (ORCPT ); Thu, 17 Dec 2009 21:16:28 -0500 Date: Fri, 18 Dec 2009 03:10:42 +0100 From: Oleg Nesterov To: Roland McGrath Cc: "K.Prasad" , Alan Stern , Frederic Weisbecker , Ingo Molnar , linux-kernel@vger.kernel.org, utrace-devel@redhat.com Subject: Re: x86: do_debug && PTRACE_SINGLESTEP broken by 08d68323d1f0c34452e614263b212ca556dae47f Message-ID: <20091218021042.GA508@redhat.com> References: <20091218005650.GA20667@redhat.com> <20091218014021.CB474135F@magilla.sf.frob.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091218014021.CB474135F@magilla.sf.frob.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1555 Lines: 45 On 12/17, Roland McGrath wrote: > > Comparing to the old (2.6.32) logic, I think it might be this (untested). > I also note this is the sole use of get_si_code, seems like it should > just be rolled in here. Well, it is too late for me to even try to read this patch ;) but... > @@ -569,14 +568,15 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) > * We already checked v86 mode above, so we can check for kernel mode > * by just checking the CPL of CS. > */ > + dr6 = tsk->thread.debugreg6; why? we have "tsk->thread.debugreg6 = dr6" above > if ((dr6 & DR_STEP) && !user_mode(regs)) { > tsk->thread.debugreg6 &= ~DR_STEP; > set_tsk_thread_flag(tsk, TIF_SINGLESTEP); > regs->flags &= ~X86_EFLAGS_TF; this looks strange... we set TIF_SINGLESTEP but clear X86_EFLAGS_TF > + } else if (dr6 & (DR_STEP | DR_TRAP_BITS)) { > + send_sigtrap(tsk, regs, error_code, get_si_code(dr6)); > } > - si_code = get_si_code(tsk->thread.debugreg6); > - if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS)) > - send_sigtrap(tsk, regs, error_code, si_code); > + can't understand how this change can fix the problem. We should always send SIGTRAP if the task returns to user-mode with X86_EFLAGS_TF? OK. I blindly applied this patch, step-simple still fails. Oleg. -- 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/