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=-14.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_NONE,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=no 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 F36E1C04FE4 for ; Thu, 1 Apr 2021 17:46:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 60C7661286 for ; Thu, 1 Apr 2021 17:46:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235587AbhDARpy (ORCPT ); Thu, 1 Apr 2021 13:45:54 -0400 Received: from linux.microsoft.com ([13.77.154.182]:33150 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235935AbhDARn0 (ORCPT ); Thu, 1 Apr 2021 13:43:26 -0400 Received: from [192.168.254.32] (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id 756E020B5680; Thu, 1 Apr 2021 10:43:26 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 756E020B5680 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1617299007; bh=SXrslQ5h2CELNvXp37RVjh4DI/73D8F1okC67YGXnNE=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Y4rHwdh5CynAQxFVFMiaX5GOsqqKumJgAktfCoA4eqp/vqaUjt76xJy2kDaEq24Qx b5RwCjL5zXBxgQzfCRx5U28X/gE0Q1oJCf19zlZ8ao/jCvpKsz36fTkaxC+pkuJDAl /CHFdpal5kN6kllSEZCrknTG5uqaVGQAEMYNXBWo= Subject: Re: [RFC PATCH v1 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable To: Mark Brown Cc: mark.rutland@arm.com, jpoimboe@redhat.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <77bd5edeea72d44533c769b1e8c0fea7a9d7eb3a> <20210330190955.13707-1-madvenka@linux.microsoft.com> <20210330190955.13707-4-madvenka@linux.microsoft.com> <20210401142759.GJ4758@sirena.org.uk> From: "Madhavan T. Venkataraman" Message-ID: <0bece48b-5fee-2bd1-752e-66d2b89cc5ad@linux.microsoft.com> Date: Thu, 1 Apr 2021 12:43:25 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210401142759.GJ4758@sirena.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 4/1/21 9:27 AM, Mark Brown wrote: > On Tue, Mar 30, 2021 at 02:09:54PM -0500, madvenka@linux.microsoft.com wrote: > >> + * FTRACE trampolines. >> + */ >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS >> + { (unsigned long) &ftrace_graph_call, 0 }, >> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER >> + { (unsigned long) ftrace_graph_caller, 0 }, >> + { (unsigned long) return_to_handler, 0 }, >> +#endif >> +#endif > > It's weird that we take the address of ftrace_graph_call but not the > other functions - we should be consistent or explain why. It'd probably > also look nicer to not nest the ifdefs, the dependencies in Kconfig will > ensure we only get things when we should. > I have explained it in the comment in the FTRACE trampoline right above ftrace_graph_call(). /* * The only call in the FTRACE trampoline code is above. The above * instruction is patched to call a tracer function. Its return * address is below (ftrace_graph_call). In a stack trace taken from * a tracer function, ftrace_graph_call() will show. The unwinder * checks this for reliable stack trace. Please see the comments * in stacktrace.c. If another call is added in the FTRACE * trampoline code, the special_functions[] array in stacktrace.c * must be updated. */ I also noticed that I have to fix something here. The label ftrace_graph_call is defined like this: #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); nop // If enabled, this will be replaced // "b ftrace_graph_caller" #endif So, it is only defined if CONFIG_FUNCTION_GRAPH_TRACER is defined. I can address this as well as your comment by defining another label whose name is more meaningful to our use: +SYM_INNER_LABEL(ftrace_trampoline, SYM_L_GLOBAL) // checked by the unwinder #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); nop // If enabled, this will be replaced // "b ftrace_graph_caller" #endif Is this acceptable? Thanks. Madhavan 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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 443F0C433B4 for ; Thu, 1 Apr 2021 17:45:21 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 BAAE161165 for ; Thu, 1 Apr 2021 17:45:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BAAE161165 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com 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=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:Cc:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ml5gqziESLdlVrUyqzOnkTxOfOnOertonH7J5BKcZKw=; b=EbydQNcpVNPADF3KRvvi0GBCF sYRBd4sY2A+OYeR+hQAVlOR2IwkerKbsexvQ7gzI///hiDbnRJVXBTEcvtPN0VdNktKFP3KQN5GO8 ztLXUP0aoM0xLZdB7lqWVGUBSr58RwC1YmsHeI9zqJnYo9wncnqyof6O6B8GAu+g4Dzmbs32GRa12 4YIlgZjOK9cNMvtUxpW+s4HcLtkh+vpkpt40gMJWfOfqooKBo2s9BeGZpFz87nixs6CXtWWNPwaiK auBSLaHXioRnmOlXpbLUHiPhGWx/rKRdqbseKmQTKbur9EXOtLg3KhDARVlZQGlWt1tKT/iR+OTcp UkIGwHYCA==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lS1M3-00AZfH-DN; Thu, 01 Apr 2021 17:43:39 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lS1Ly-00AZeR-H8 for linux-arm-kernel@lists.infradead.org; Thu, 01 Apr 2021 17:43:36 +0000 Received: from [192.168.254.32] (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id 756E020B5680; Thu, 1 Apr 2021 10:43:26 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 756E020B5680 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1617299007; bh=SXrslQ5h2CELNvXp37RVjh4DI/73D8F1okC67YGXnNE=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Y4rHwdh5CynAQxFVFMiaX5GOsqqKumJgAktfCoA4eqp/vqaUjt76xJy2kDaEq24Qx b5RwCjL5zXBxgQzfCRx5U28X/gE0Q1oJCf19zlZ8ao/jCvpKsz36fTkaxC+pkuJDAl /CHFdpal5kN6kllSEZCrknTG5uqaVGQAEMYNXBWo= Subject: Re: [RFC PATCH v1 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable To: Mark Brown Cc: mark.rutland@arm.com, jpoimboe@redhat.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <77bd5edeea72d44533c769b1e8c0fea7a9d7eb3a> <20210330190955.13707-1-madvenka@linux.microsoft.com> <20210330190955.13707-4-madvenka@linux.microsoft.com> <20210401142759.GJ4758@sirena.org.uk> From: "Madhavan T. Venkataraman" Message-ID: <0bece48b-5fee-2bd1-752e-66d2b89cc5ad@linux.microsoft.com> Date: Thu, 1 Apr 2021 12:43:25 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210401142759.GJ4758@sirena.org.uk> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210401_184334_829393_875C977B X-CRM114-Status: GOOD ( 14.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 On 4/1/21 9:27 AM, Mark Brown wrote: > On Tue, Mar 30, 2021 at 02:09:54PM -0500, madvenka@linux.microsoft.com wrote: > >> + * FTRACE trampolines. >> + */ >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS >> + { (unsigned long) &ftrace_graph_call, 0 }, >> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER >> + { (unsigned long) ftrace_graph_caller, 0 }, >> + { (unsigned long) return_to_handler, 0 }, >> +#endif >> +#endif > > It's weird that we take the address of ftrace_graph_call but not the > other functions - we should be consistent or explain why. It'd probably > also look nicer to not nest the ifdefs, the dependencies in Kconfig will > ensure we only get things when we should. > I have explained it in the comment in the FTRACE trampoline right above ftrace_graph_call(). /* * The only call in the FTRACE trampoline code is above. The above * instruction is patched to call a tracer function. Its return * address is below (ftrace_graph_call). In a stack trace taken from * a tracer function, ftrace_graph_call() will show. The unwinder * checks this for reliable stack trace. Please see the comments * in stacktrace.c. If another call is added in the FTRACE * trampoline code, the special_functions[] array in stacktrace.c * must be updated. */ I also noticed that I have to fix something here. The label ftrace_graph_call is defined like this: #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); nop // If enabled, this will be replaced // "b ftrace_graph_caller" #endif So, it is only defined if CONFIG_FUNCTION_GRAPH_TRACER is defined. I can address this as well as your comment by defining another label whose name is more meaningful to our use: +SYM_INNER_LABEL(ftrace_trampoline, SYM_L_GLOBAL) // checked by the unwinder #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); nop // If enabled, this will be replaced // "b ftrace_graph_caller" #endif Is this acceptable? Thanks. Madhavan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel