From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100Ab2LRFgK (ORCPT ); Tue, 18 Dec 2012 00:36:10 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:43127 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858Ab2LRFgJ (ORCPT ); Tue, 18 Dec 2012 00:36:09 -0500 Date: Tue, 18 Dec 2012 11:06:03 +0530 From: Ananth N Mavinakayanahalli To: Oleg Nesterov Cc: "Suzuki K. Poulose" , bigeasy@linutronix.de, srikar@linux.vnet.ibm.com, peterz@infradead.org, benh@kernel.crashing.org, mingo@elte.hu, anton@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/4] uprobes/powerpc: Make use of generic routines to enable single step Message-ID: <20121218053603.GB6116@in.ibm.com> Reply-To: ananth@in.ibm.com References: <20121203150438.7727.74924.stgit@suzukikp> <20121203150946.7727.82735.stgit@suzukikp> <20121214200241.GA27195@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121214200241.GA27195@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12121805-9360-0000-0000-00000E168763 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 14, 2012 at 09:02:41PM +0100, Oleg Nesterov wrote: > On 12/03, Suzuki K. Poulose wrote: > > > > Replace the ptrace helpers with the powerpc generic routines to > > enable/disable single step. We save/restore the MSR (and DCBR for BookE) > > across for the operation. We don't have to disable the single step, > > as restoring the MSR/DBCR would restore the previous state. > > Obviously I can't review this series (although it looks fine to me). > > Just one note, > > > @@ -121,7 +132,7 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) > > > > WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR); > > > > - uprobe_restore_context_sstep(&utask->autask); > > + uprobe_restore_context_sstep(&utask->autask, regs); > > I am not sure ppc needs this, but note that x86 does a bit more. > > Not only we need to restore the "single-step" state, we need to > send SIGTRAP if it was not set by us. The same for _skip_sstep. Do you mean restoring the TF equivalent on powerpc to what it was before? If so, powerpc has always been unique in this aspect -- the single-step exception handler *always* resets the sstep bit in MSR. Any user needing to continue single-stepping has to explicitly set it again. Ananth