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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 834D1C47404 for ; Fri, 11 Oct 2019 08:39:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 579F42196E for ; Fri, 11 Oct 2019 08:39:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570783176; bh=/DrW5ph3A5E4Hgsb7Sd3CajDjM9gMywett8FftQi6PM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Ur5JSZSX2NFrUYtTI/GF88twS9bjgoSQlJ6OeI7+Y312Tm37IcNhL/l7mNbRKDDqp cIiV4pRyWPH714o6SvPJ+A998ZYyGnt8VexC6RAthZQQ+rJD5fTnhyLRkSKqwgaEBa YsYe6l4fLKB+Af7kQBJypnGYm3ga0+9VKZ1EkJEU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727488AbfJKIjf (ORCPT ); Fri, 11 Oct 2019 04:39:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:53500 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727066AbfJKIje (ORCPT ); Fri, 11 Oct 2019 04:39:34 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 1BA7820679; Fri, 11 Oct 2019 08:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570783174; bh=/DrW5ph3A5E4Hgsb7Sd3CajDjM9gMywett8FftQi6PM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=s0mQaGhluvgb8qCJ2TOMEfGY32AjQDL9MrXwsO8ByB4lc5WvP2EE8v3fg7uOSxoYa iEsY0b0R6mDLLwl5XwZrJZR8pHCbegt7rrilqksIJmCvcuKHRMaJ+hA2RnlvggPYRb 3x8zGilA3kzegeDzbIHb5RYqfzbW2LxKuu8Bf1j0= Date: Fri, 11 Oct 2019 17:39:29 +0900 From: Masami Hiramatsu To: Steven Rostedt 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: <20191011173929.9462a1414ff3a94ec93d6e98@kernel.org> In-Reply-To: <20191010175216.4ceb3cf1@gandalf.local.home> References: <20191010175216.4ceb3cf1@gandalf.local.home> X-Mailer: Sylpheed 3.5.1 (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 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) 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) Thank you, > ret = kprobe_add_ksym_blacklist(entry); > if (ret < 0) > return ret; -- Masami Hiramatsu