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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 05A06C43387 for ; Wed, 9 Jan 2019 02:05:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C70B7214C6 for ; Wed, 9 Jan 2019 02:05:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546999508; bh=Ickqk2IZkIG8p04SgQek3hIsU1ZxkvWNSEhuLaJp8Mw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=iaU3NTZOcGTrG9zBypsycOfbZwYuI8PGQ0CIsrfBYz4xJOdtAdI69Pokw12pmS/fo OzQXs2cSk/UVCcb/kbxAyMbSBUYB7qa3x4kLGneTKcLMWZxF+uGSqF4mPqCe32Prvv vrtRxaCkHf7lL5qQEQkWk48PqUoZWdqfPxpCmjNM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729422AbfAICFI (ORCPT ); Tue, 8 Jan 2019 21:05:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:46650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729148AbfAICFH (ORCPT ); Tue, 8 Jan 2019 21:05:07 -0500 Received: from devnote (p103030-mobac01.tokyo.ocn.ne.jp [153.233.94.30]) (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 21085206BB; Wed, 9 Jan 2019 02:05:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546999506; bh=Ickqk2IZkIG8p04SgQek3hIsU1ZxkvWNSEhuLaJp8Mw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=2AigcZnMw1WQlONJhKEoRIJcREnBHjp7eqluXdmyCKIr5U8I9VVFR0H+7GAI1ciyO ciZqVwHQOi0ZHkjJ5/tblVIwzgGKd4/ZIRQ3rFcBsXeJgO9KBL2XUdsEDRFA4lfVZM keNRAWE9I4zF9m49i5lO0uXSP3vB0vU1wVbZZVWA= Date: Wed, 9 Jan 2019 11:05:00 +0900 From: Masami Hiramatsu To: James Morse Cc: Catalin Marinas , Will Deacon , Pratyush Anand , "David A . Long" , linux-arm-kernel@lists.infradead.org, linux-kernel Subject: Re: [PATCH 1/3] arm64: kprobes: Move extable address check into arch_prepare_kprobe() Message-Id: <20190109110500.b4b5049f4c67dfc85b9ced4e@kernel.org> In-Reply-To: References: <154502881646.30629.9938335052821665530.stgit@devbox> <154502884653.30629.3172839440883293817.stgit@devbox> <20190108113953.8bc0cc7d196ddba370377217@kernel.org> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; 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 James, On Tue, 8 Jan 2019 17:13:36 +0000 James Morse wrote: > Hi! > > On 08/01/2019 02:39, Masami Hiramatsu wrote: > > On Thu, 3 Jan 2019 17:05:18 +0000 > > James Morse wrote: > >> On 17/12/2018 06:40, Masami Hiramatsu wrote: > >>> Move extable address check into arch_prepare_kprobe() from > >>> arch_within_kprobe_blacklist(). > >> > >> I'm trying to work out the pattern for what should go in the blacklist, and what > >> should be rejected by the arch code. > >> > >> It seems address-ranges should be blacklisted as the contents don't matter. > >> easy-example: the idmap text. > > > > Yes, more precisely, the code smaller than a function (symbol), it must be > > rejected by arch_prepare_kprobe(), since blacklist is poplated based on > > kallsyms. > > Ah, okay, so the pattern is the blacklist should only be for whole symbols, > (which explains why its usually based on sections). Correct. Actually, the blacklist is generated based on the symbol info from symbol address. > I see kprobe_add_ksym_blacklist() would go wrong if you give it something like: > platform_drv_probe+0x50/0xb0, as it will log platform_drv_probe+0x50 as the > start_addr and platform_drv_probe+0x50+0xb0 as the end. Yes, it expects given address is the entry of a symbol. > > But how does anything from the arch code's blacklist get into the > kprobe_blacklist list? It should be done via arch_populate_kprobe_blacklist(). > > We don't have an arch_populate_kprobe_blacklist(), so rely on > within_kprobe_blacklist() calling arch_within_kprobe_blacklist() with the > address, as well as walking kprobe_blacklist. > > Is this cleanup ahead of a series that does away with > arch_within_kprobe_blacklist() so that debugfs list is always complete? Right, after this cleanup, I will send arch_populate_kprobe_blacklist() patch for arm64 and others. My plan is to move all arch_within_kprobe_blacklist() to arch_populate_kprobe_blacklist() so that user can get more precise blacklist via debugfs. > > As I pointed, the exception_table contains some range of code which inside > > functions, must be smaller than function. > > Since those instructions are expected to cause exception (that is main reason > > why it can not be probed on arm64), I thought such situation was similar to > > the limitation of instruction. > > > > So I think below will be better. > > ---- > > Please do not blacklisting instructions on exception_table, > > since those are smaller than one function. > > ---- > > I keep tripping over this because the exception_table lists addresses that are > allowed to fault. Nothing looks at the instruction, and we happily kprobe the > same instruction elsewhere. Thanks! > > (based on my assumptions about where you are going next!,), How about: > | The blacklist is exposed via debugfs as a list of symbols. extable entries are > | smaller, so must be filtered out by arch_prepare_kprobe(). This looks much better for me too :) Should I resend with the description? Thank you! > > (only we currently have more than one blacklist...) > > > Thanks, > > James -- Masami Hiramatsu