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=-5.2 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 7E2EFC2F3A0 for ; Mon, 21 Jan 2019 13:26:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EA4020870 for ; Mon, 21 Jan 2019 13:26:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548077164; bh=pn8NvDkjUXZxm5vucToeMhlBwtPcbI5F3xg+Z+D2ics=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=UEgrbqpihPPjnBl90Db6WIzilf7vBVis9VWK6r/++KaJgxzYjjGOhxpAT5RLz40cE ZS/d9QarwyGYyrz8IEgv24TaQD9nniOfswRmrpRzH40gM0q7pfChezN0kC8+6U6Nm4 saz6WYsCcJP75HorQyM6yZya33sxiQi1UwbskYwg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729006AbfAUN0C (ORCPT ); Mon, 21 Jan 2019 08:26:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:47062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728570AbfAUN0C (ORCPT ); Mon, 21 Jan 2019 08:26:02 -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 5B40C2085A; Mon, 21 Jan 2019 13:26:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548077161; bh=pn8NvDkjUXZxm5vucToeMhlBwtPcbI5F3xg+Z+D2ics=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FUeHwPeQ5nFLt5HD7NicHyHtjx6By4fg3ObhnySxQPDKO9LARuobbpOcZ6Ib7aLMq WNOJh1GfiAM7GH61i63NPm27ge7qxxNMpWdP99kRj8V6CCLeZDgeLYTikq1Za53puI 9H8u3NL3mLQoFKvL7gePmkdTiyauZ77NiGuRFkhg= Date: Mon, 21 Jan 2019 22:25:58 +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 v2 4/4] arm64: kprobes: Use arch_populate_kprobe_blacklist() Message-Id: <20190121222558.1ef0abc89a704597d6c3de7f@kernel.org> In-Reply-To: <7f840cc8-4e62-e1d7-9035-4361204fc134@arm.com> References: <154753341900.31541.8135985235882849464.stgit@devbox> <154753353370.31541.14485875717131836689.stgit@devbox> <7f840cc8-4e62-e1d7-9035-4361204fc134@arm.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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 21 Jan 2019 12:20:07 +0000 James Morse wrote: > Hello, > > On 15/01/2019 06:25, Masami Hiramatsu wrote: > > Use arch_populate_kprobe_blacklist() instead of > > arch_within_kprobe_blacklist() so that we can see the full > > blacklisted symbols under the debugfs. > > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > > index b9e9758b6534..6c066c34c8a4 100644 > > --- a/arch/arm64/kernel/probes/kprobes.c > > +++ b/arch/arm64/kernel/probes/kprobes.c > > @@ -465,26 +465,30 @@ kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) > > return DBG_HOOK_HANDLED; > > } > > > > -bool arch_within_kprobe_blacklist(unsigned long addr) > > +int __init arch_populate_kprobe_blacklist(void) > > { > > - if ((addr >= (unsigned long)__kprobes_text_start && > > - addr < (unsigned long)__kprobes_text_end) || > > - (addr >= (unsigned long)__entry_text_start && > > - addr < (unsigned long)__entry_text_end) || > > - (addr >= (unsigned long)__idmap_text_start && > > - addr < (unsigned long)__idmap_text_end) || > > > - in_exception_text(addr)) > > You added this one in the previous patch, but it disappears here. Yes, it is easy to explain how we transcribe from arch_within_kprobe_blacklist() to arch_populate_kprobe_blacklist(). > > > > - return true; > > - > > - if (!is_kernel_in_hyp_mode()) { > > - if ((addr >= (unsigned long)__hyp_text_start && > > - addr < (unsigned long)__hyp_text_end) || > > - (addr >= (unsigned long)__hyp_idmap_text_start && > > - addr < (unsigned long)__hyp_idmap_text_end)) > > - return true; > > - } > > - > > - return false; > > + int ret; > > > > + ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start, > > + (unsigned long)__kprobes_text_end); > > + if (ret) > > + return ret; > > Now that we have arch_populate_kprobe_blacklist(), does the arch-code need to > blacklist the kprobes section itself? Ah, good catch! No, we don't need it here. Sorry I worked on older patch. I'll update it. > The weak arch_within_kprobe_blacklist() will test it at kprobe-load time, and > populate_kprobe_blacklist() adds it to the list before it calls > arch_populate_kprobe_blacklist(). > > Won't this result in duplicate entries? yes, so it should not. > > > > + ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start, > > + (unsigned long)__entry_text_end); > > + if (ret) > > + return ret; > > > + ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start, > > + (unsigned long)__idmap_text_end); > > > + if (ret || is_kernel_in_hyp_mode()) > > + return ret; > > > Hmmm, I think we have a bug here today. OK. > > This is saying we can kprobe KVM when we have VHE, because all of KVMs code runs > at the same exception-level as the kernel. Which is true... > But KVM switches VBAR_EL1, so if we run over one of kprobes BRK instructions, > we're going to hyp-panic, because KVM doesn't handle synchronous exceptions from > EL2. > > The __hyp_text also contains the guest entry/exit code, which we mustn't probe, > even on VHE. Hmm, I'm not sure when the original code decided this. But it sounds reasonable. > > I think we should always blacklist the __hyp_text, and KVM should mark its > vhe-only functions with __kprobes. I'll post patches for this. OK, then I should wait for that, because this series is a kind of improvement. But your's is a bugfix, that should be backported to stable. Thank you, > > > Thanks, > > James > > > > + ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start, > > + (unsigned long)__hyp_text_end); > > + if (ret) > > + return ret; > > + ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start, > > + (unsigned long)__hyp_idmap_text_end); > > + return ret; > > } > > > > void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) > > > -- Masami Hiramatsu