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=-10.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 5CA45C56202 for ; Wed, 25 Nov 2020 16:12:56 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CD8A12087C for ; Wed, 25 Nov 2020 16:12:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OWjCMERI"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="anLcyluN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CD8A12087C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XHNHP5GGvQDqIzQZST7iwUOQsmxQnG6xqb7AOx59O94=; b=OWjCMERIm8N2alpX/JNRkP/kH 4M8D+grCHi23jXh805dRKen6lkMKtXzVHEiG8Sco5aS3/quGEvcIoc9tnEQ1jhdFtUZgZDJlO5xwi mGc0hiV1d71d9PTxQXuhZm/oh0QPKctxS8GSrWZ0fDKpJZoclFAvnx5HtzAGdkF9v8QwveZ5TorF9 j5ZZqveIR80Rkj2RLcVNeRy1KRyQle/vvBc9+m88iD7nyItdb222COOYWdctlafGT4DzT/2SRRxw9 a/xJwyX/zsRlEfH1KgSuakL10UIlaA4TSXVt+K6t6rMZPYBz/TjOB17UDlLFlxTYzHAdiMGuclRvl sgbN1Boyw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1khxOQ-0007Me-I3; Wed, 25 Nov 2020 16:11:42 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1khxON-0007LV-Hk for linux-arm-kernel@lists.infradead.org; Wed, 25 Nov 2020 16:11:40 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 4F68B2083E; Wed, 25 Nov 2020 16:11:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606320698; bh=zqxG+srv9flwDsXaJ5dZ33rGmkR4F3z92RJcZAORSOc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=anLcyluNEUQrUemE091M1NzU1uVh+hvW8K9neThLAhwnyKs6HH+KimRNLOwpDv29j RY+g7J0h1mfN6as7VPzqKeqZTWGNYSv4PJadJvcmjL4zkrzrz1bsml+wVZl71BZizS bbwio1qh7oqjlMChQFm3vsT/ynGYc94FOjUeQgf8= Date: Wed, 25 Nov 2020 16:11:34 +0000 From: Will Deacon To: Masami Hiramatsu Subject: Re: [PATCH] arm64: Fix early single-stepping Message-ID: <20201125161133.GA16924@willie-the-truck> References: <20201026172907.1468294-1-jean-philippe@linaro.org> <20201027191318.aba935f7ccf00af9acd89388@kernel.org> <20201027194258.43b157ac0bbccd918fc8756a@kernel.org> <20201027115909.GB1514990@myrica> <20201027123317.GA26351@willie-the-truck> <20201027224922.7b032857d53bbfdc4484f768@kernel.org> <20201028082820.GA2328726@myrica> <20201028083643.GA27678@willie-the-truck> <20201126010906.dd56ca668e30de6be9380028@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201126010906.dd56ca668e30de6be9380028@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201125_111139_822495_CB79CA71 X-CRM114-Status: GOOD ( 20.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , Steven Rostedt , dianders@chromium.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Masami, On Thu, Nov 26, 2020 at 01:09:06AM +0900, Masami Hiramatsu wrote: > On Wed, 28 Oct 2020 08:36:44 +0000 > Will Deacon wrote: > > Cheers. An alternative (which I think would be better in the long run > > anyway) would be to avoid using hardware step in kprobes and instead rely > > on a BRK instruction to trap after running the trampoline. > > We started working on using the BRK instead of hardware step in kprobes > in other threads. However, there still be a bug in the kernel. > I would like to fix or at least mitigate this issue until this is released > (since it's a bug) > > Would you think we can push the BRK only kprobes until it or in stable kernel? > Or, we should add a mitigation patch for this bug? > For the mitigation, I think we can introduce a kconfig flag which indicates > the arch doesn't support early kprobes, in that case we defer the kprobe and > boot-time trace later stage. This flag will be removed after we introduce the > BRK-only kprobes. The BRK stuff is merged upstream: http://git.kernel.org/linus/7ee31a3aa8f49 Are you saying that this isn't sufficient to fix the problem? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel