Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752662AbZLaAiN (ORCPT ); Wed, 30 Dec 2009 19:38:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751575AbZLaAiM (ORCPT ); Wed, 30 Dec 2009 19:38:12 -0500 Received: from mail-ew0-f219.google.com ([209.85.219.219]:63875 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751515AbZLaAiM (ORCPT ); Wed, 30 Dec 2009 19:38:12 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=pQbG3ndY2gG0C9rN6Do96x/lcjpmjXxdb4MJhEROJQ3n3QY59eLrMOi26BZQTvyRNa dLJtrDGcVQ2o4B99+LNPM1rgnDVN3/iqIpoi+o9CGElQoLldjCGDBvu7ANu5NdgcHMaz ziTF0ickkmfHMM5xgk/BBpnc5/5O2/jLBROlA= Date: Thu, 31 Dec 2009 01:38:09 +0100 From: Frederic Weisbecker To: "K.Prasad" Cc: LKML , Ingo Molnar , Alan Stern Subject: Re: [RFC Patch 2/2][Bugfix][x86][hw-breakpoint] Fix return-code to notifier chain in hw_breakpoint_handler Message-ID: <20091231003808.GC23808@nowhere> References: <20091226175533.149765731@linux.vnet.ibm.com> <20091226182833.GC9494@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091226182833.GC9494@in.ibm.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: 1889 Lines: 54 On Sat, Dec 26, 2009 at 11:58:33PM +0530, K.Prasad wrote: > The hw-breakpoint handler will return NOTIFY_DONE for user-space breakpoints > to generate SIGTRAP signal (and not for kernel-space addresses). > > Signed-off-by: K.Prasad > --- > arch/x86/kernel/hw_breakpoint.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > Index: linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c > =================================================================== > --- linux-2.6-tip.orig/arch/x86/kernel/hw_breakpoint.c > +++ linux-2.6-tip/arch/x86/kernel/hw_breakpoint.c > @@ -502,8 +502,6 @@ static int __kprobes hw_breakpoint_handl > rcu_read_lock(); > > bp = per_cpu(bp_per_reg[i], cpu); > - if (bp) > - rc = NOTIFY_DONE; > /* > * Reset the 'i'th TRAP bit in dr6 to denote completion of > * exception handling > @@ -517,6 +515,13 @@ static int __kprobes hw_breakpoint_handl > rcu_read_unlock(); > break; > } > + /* > + * Further processing in do_debug() is needed for a) user-space > + * breakpoints (to generate signals) and b) when the system has > + * taken exception due to multiple causes > + */ > + if (bp->attr.bp_addr < TASK_SIZE) > + rc = NOTIFY_DONE; > > perf_bp_event(bp, args->regs); > > Oh and now that I see this patch, the previous one indeed makes sense with this check: if (dr6 & (~DR_TRAP_BITS)) rc = NOTIFY_DONE; That said, it means thread.debugreg6 won't get the reserved bits anymore. I see some use of them from kvm (it restores the reserved bits on guest<->host switch). Not sure if this inconsistency could affect kvm... -- 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/