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=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 B16DBC43387 for ; Tue, 8 Jan 2019 02:39:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 732F1218B0 for ; Tue, 8 Jan 2019 02:39:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546915198; bh=VT0+XNUdZwsmaGLxFPXM9zwdwnbcsTw9cqA1fMecFRc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=OvN0vlRbC77r7QPFP1paTCi9cSjvp1E/x68G5TPpE1R6fI0PrYl7nRpccEy7mIhAj FZPpm3W2S2LCPnqQ1iWZh9ffFgawiG9srPi4koq/jsKnyKo27Dj5qwIalgL8EZs/IQ MBOjIjlf2SVgiyNGg563qvgKEFU17kQ0nY0By9OM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727472AbfAHCj5 (ORCPT ); Mon, 7 Jan 2019 21:39:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:53466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727147AbfAHCj5 (ORCPT ); Mon, 7 Jan 2019 21:39:57 -0500 Received: from devbox (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 0B312206A3; Tue, 8 Jan 2019 02:39:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546915196; bh=VT0+XNUdZwsmaGLxFPXM9zwdwnbcsTw9cqA1fMecFRc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=kxdHCejoo7hs1seGOIlYhPyhqOgP6q4raLbVYdBr9TZ879haspLbpoPKnS3ot4hfv 7TgO+x/UAwi6Vq2F3Y4TLDhYDH/m0ul+YrDM06Ep/V3NSktzs53+vCQG13POcdaGHs tsHAuPnTwt7OXyYtuJHzuzldmRBZpoEMJbeB1WQU= Date: Tue, 8 Jan 2019 11:39:53 +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: <20190108113953.8bc0cc7d196ddba370377217@kernel.org> In-Reply-To: References: <154502881646.30629.9938335052821665530.stgit@devbox> <154502884653.30629.3172839440883293817.stgit@devbox> 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Jan 2019 17:05:18 +0000 James Morse wrote: > Hi! > > 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. > The arch code should also reject instructions that can't be probed from > arch_prepare_kprobe(). easy-example: exclusive load or store. > > > > Please do not blacklisting instructions on exception_table, > > since it is a kind of architectural unsupported instruction. > > This doesn't fit the pattern, ... what should it be? Some kind of instructions can not be instrumented by kprobes, such instruction level rejection must be done in arch_prepare_kprobe(), instead of blacklist. > The instructions in the exception_table don't matter, its the address that > indicates there is a fixup for page-faults that occur here. We don't need to > look at the instruction to determine this, why can't we treated these as a > blacklisted range? Sorry for your confusion, it was my mis-describing. 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. ---- Thank you, > > > Thanks, > > James > > > > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > > index 2a5b338b2542..b2d4b7428ebc 100644 > > --- a/arch/arm64/kernel/probes/kprobes.c > > +++ b/arch/arm64/kernel/probes/kprobes.c > > @@ -102,6 +102,10 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) > > > > if (in_exception_text(probe_addr)) > > return -EINVAL; > > + > > + if (search_exception_tables(probe_addr)) > > + return -EINVAL; > > + > > if (probe_addr >= (unsigned long) __start_rodata && > > probe_addr <= (unsigned long) __end_rodata) > > return -EINVAL; > > @@ -477,8 +481,7 @@ bool arch_within_kprobe_blacklist(unsigned long addr) > > (addr >= (unsigned long)__entry_text_start && > > addr < (unsigned long)__entry_text_end) || > > (addr >= (unsigned long)__idmap_text_start && > > - addr < (unsigned long)__idmap_text_end) || > > - !!search_exception_tables(addr)) > > + addr < (unsigned long)__idmap_text_end)) > > return true; > > > > if (!is_kernel_in_hyp_mode()) { > > > -- Masami Hiramatsu