From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753730AbdJSVjK (ORCPT ); Thu, 19 Oct 2017 17:39:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:34096 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752744AbdJSViQ (ORCPT ); Thu, 19 Oct 2017 17:38:16 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 388862191E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org Date: Fri, 20 Oct 2017 06:38:12 +0900 From: Masami Hiramatsu To: "Naveen N. Rao" Cc: Ingo Molnar , Masami Hiramatsu , Michael Ellerman , Ananth N Mavinakayanahalli , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Revert "kprobes: Warn if optprobe handler tries to change execution path" Message-Id: <20171020063812.ca0b931fb88df393772acbba@kernel.org> In-Reply-To: <20171017081834.3629-1-naveen.n.rao@linux.vnet.ibm.com> References: <20171017081834.3629-1-naveen.n.rao@linux.vnet.ibm.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 17 Oct 2017 13:48:34 +0530 "Naveen N. Rao" wrote: > This reverts commit e863d539614641 ("kprobes: Warn if optprobe handler > tries to change execution path"). > > On powerpc, we place a probe at kretprobe_trampoline to catch function > returns and with CONFIG_OPTPROBES, this probe gets optimized. This > works for us due to the way we handle the optprobe as described in > commit 762df10bad6954 ("powerpc/kprobes: Optimize kprobe > in kretprobe_trampoline()"). With the above commit, we end up with a > warning. As such, revert this change. OK, so for ppc, optprobe can handle nip change. Acked-by: Masami Hiramatsu I'll update the document too. Thanks, > > Reported-by: Michael Ellerman > Signed-off-by: Naveen N. Rao > --- > Discussion here: > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1510995.html > > kernel/kprobes.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 2d28377a0e32..15fba7fe57c8 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -387,10 +387,7 @@ void opt_pre_handler(struct kprobe *p, struct pt_regs *regs) > list_for_each_entry_rcu(kp, &p->list, list) { > if (kp->pre_handler && likely(!kprobe_disabled(kp))) { > set_kprobe_instance(kp); > - if (kp->pre_handler(kp, regs)) { > - if (WARN_ON_ONCE(1)) > - pr_err("Optprobe ignores instruction pointer changing.(%pF)\n", p->addr); > - } > + kp->pre_handler(kp, regs); > } > reset_kprobe_instance(); > } > -- > 2.14.2 > -- Masami Hiramatsu