From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77488C47404 for ; Fri, 11 Oct 2019 13:12:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A83421D7F for ; Fri, 11 Oct 2019 13:12:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728444AbfJKNM5 (ORCPT ); Fri, 11 Oct 2019 09:12:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:46136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728404AbfJKNM4 (ORCPT ); Fri, 11 Oct 2019 09:12:56 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A38B9206A1; Fri, 11 Oct 2019 13:12:55 +0000 (UTC) Date: Fri, 11 Oct 2019 09:12:54 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: LKML , Ingo Molnar , Peter Zijlstra , "H. Peter Anvin" , Thomas Gleixner , Andrew Morton Subject: Re: [RFC][PATCH] kprobes/x86: While list ftrace locations in kprobe blacklist areas Message-ID: <20191011091254.3c4dd543@gandalf.local.home> In-Reply-To: <20191011173929.9462a1414ff3a94ec93d6e98@kernel.org> References: <20191010175216.4ceb3cf1@gandalf.local.home> <20191011173929.9462a1414ff3a94ec93d6e98@kernel.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Oct 2019 17:39:29 +0900 Masami Hiramatsu wrote: > Hi Steve, > > On Thu, 10 Oct 2019 17:52:16 -0400 > Steven Rostedt wrote: > > > From: Steven Rostedt (VMware) > > > > I noticed some of my old tests failing on kprobes, and realized that > > this was due to black listing irq_entry functions on x86 from being > > used by kprobes. IIRC, this was due to the cr2 being corrupted and > > such, and I believe other things were to cause. But black listing all > > irq_entry code is a big hammer to this. > > OK, I think if we can use ftrace for hooking, probing on "that address" > is good, but the function body still can not be probed. > > > > > (See commit 0eae81dc9f026 "x86/kprobes: Prohibit probing on IRQ > > handlers directly" for more details) > > > > Anyway, if kprobes is using ftrace as a hook, there shouldn't be any > > problems here. If we white list ftrace locations in the range of > > kprobe_add_area_blacklist(), it should be safe. > > Agreed. > > > > > Signed-off-by: Steven Rostedt (VMware) > > --- > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index d9770a5393c8..9d28a279282c 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -2124,6 +2124,11 @@ int kprobe_add_area_blacklist(unsigned long start, unsigned long end) > > int ret = 0; > > > > for (entry = start; entry < end; entry += ret) { > > +#ifdef CONFIG_KPROBES_ON_FTRACE > > + /* We are safe if using ftrace */ > > + if (ftrace_location(entry)) > > + continue; > > +#endif > > Have you tested the patch? it doesn't measure the entry function's size. > (kprobe_add_ksym_blacklist(entry) returns the function size) Yeah, I tested the patch, but it is obviously buggy. It fixed the issue I was having (was able to test against do_IRQ ;-) > > Could you do this in kprobe_add_ksym_blacklist()? > Instead of continue, increment ent->start_addr by MCOUNT size(?) will be OK. > (Note that since each blacklist symbol is managed independently, you can make > a "gap" between them as a safe area) OK, I'll move it to kprobe_add_ksym_blacklist. -- Steve > > Thank you, > > > ret = kprobe_add_ksym_blacklist(entry); > > if (ret < 0) > > return ret; > >