From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753023AbaB0Pte (ORCPT ); Thu, 27 Feb 2014 10:49:34 -0500 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.230]:22937 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753404AbaB0Pt3 (ORCPT ); Thu, 27 Feb 2014 10:49:29 -0500 Message-Id: <20140227154922.957070805@goodmis.org> User-Agent: quilt/0.61-1 Date: Thu, 27 Feb 2014 10:46:17 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Peter Zijlstra , Frederic Weisbecker , Mathieu Desnoyers , Petr Mladek , "H. Peter Anvin" , Subject: [RFA][PATCH 1/5] ftrace/x86: Run a sync after fixup on failure References: <20140227154616.703252665@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=0001-ftrace-x86-Run-a-sync-after-fixup-on-failure.patch X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Request for Ack] From: "Steven Rostedt (Red Hat)" If a failure occurs while enabling a trace, it bails out and will remove the tracepoints to be back to what the code originally was. But the fix up had some bugs in it. By injecting a failure in the code, the fix up ran to completion, but shortly afterward the system rebooted. There was two bugs here. The first was that there was no final sync run across the CPUs after the fix up was done, and before the ftrace int3 handler flag was reset. That means that other CPUs could still see the breakpoint and trigger on it long after the flag was cleared, and the int3 handler would think it was a spurious interrupt. Worse yet, the int3 handler could hit other breakpoints because the ftrace int3 handler flag would have prevented the int3 handler from going further. The second bug was that the removal of the breakpoints required the "within()" logic updates instead of accessing the ip address directly. Link: http://lkml.kernel.org/r/1392650573-3390-1-git-send-email-pmladek@suse.cz Reported-by: Petr Mladek Cc: "H. Peter Anvin" Cc: stable@vger.kernel.org # 3.5+ Signed-off-by: Steven Rostedt --- arch/x86/kernel/ftrace.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index e625319..6b566c8 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -455,7 +455,7 @@ static int remove_breakpoint(struct dyn_ftrace *rec) } update: - return probe_kernel_write((void *)ip, &nop[0], 1); + return ftrace_write(ip, nop, 1); } static int add_update_code(unsigned long ip, unsigned const char *new) @@ -634,6 +634,7 @@ void ftrace_replace_code(int enable) rec = ftrace_rec_iter_record(iter); remove_breakpoint(rec); } + run_sync(); } static int @@ -664,7 +665,7 @@ ftrace_modify_code(unsigned long ip, unsigned const char *old_code, return ret; fail_update: - probe_kernel_write((void *)ip, &old_code[0], 1); + ftrace_write(ip, old_code, 1); goto out; } -- 1.8.5.3