Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752995Ab0AJDTE (ORCPT ); Sat, 9 Jan 2010 22:19:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751242Ab0AJDTD (ORCPT ); Sat, 9 Jan 2010 22:19:03 -0500 Received: from mail-ew0-f214.google.com ([209.85.219.214]:63612 "EHLO mail-ew0-f214.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040Ab0AJDTB (ORCPT ); Sat, 9 Jan 2010 22:19:01 -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=ZEn16F6vi5OKQXNQfbepsreI8oNjCyDLmukh0uF3s3rAdgxK2qPYq+Plp40i//dWf7 pW825ys6lhWp7Ja751Kjq74ZHZ9CkAGb8V4POrKz8JENZBkc6mZSDk3m4ngTmtf8vgVm Ia1ZxFG2ar2uRRu25NQFO9yxc4gGnZV5R0gh0= Date: Sun, 10 Jan 2010 04:18:58 +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: <20100110031857.GB15195@nowhere> References: <20091226175533.149765731@linux.vnet.ibm.com> <20091226182833.GC9494@in.ibm.com> <20091231003808.GC23808@nowhere> <20091231190217.GC3676@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091231190217.GC3676@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: 2471 Lines: 68 On Fri, Jan 01, 2010 at 12:32:17AM +0530, K.Prasad wrote: > On Thu, Dec 31, 2009 at 01:38:09AM +0100, Frederic Weisbecker wrote: > > 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... > > > > Can you point me to the relevant code? I see various uses of DR6_VOLATILE and DR6_FIXED_1 in arch/x86/kvm/, DR6_FIXED_1 being the fixed unused bits in dr6. Not sure how this patch would affect what's set there. I'll wait for Jan's answer. Thanks. -- 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/