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,SPF_PASS,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 43265C433B4 for ; Thu, 1 Apr 2021 18:42:11 +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 CD87160FD9 for ; Thu, 1 Apr 2021 18:42:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CD87160FD9 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=CoIF/xJQoMvIz0tz2BUB7x/IRczs+UtmyjbB1XQLPEM=; b=go+YhY16VaA5JYEAO1QX99IBz mqVC2Hy14/9sjbFgQ7gM70hUDMKd2FN2htqKLHSl9pbuZ3Uycq3sbYR2yGuULek03iDm7UhYu0HrE HCAh0L/rx0F+2EQuaJSZtbsSan1k78loUm+akpsFab+2LNIsOn9JLNVzI9Rv6zmxeERxgNoF6hCXz CRtp4ggqUvZwGl+jpcLGAcK5gnSLI5ORbKaB2C++ILjgIRS6QEO3rpsJzEuu5PYm0GYy4SUP+iLjn XpYI+Kz3s8rejj2HayLElR1duNGpW1idAX8tkx4LbcYijFmMVd+ECQq4u/VJybESOcR42WE92QJYQ mgLWURKVg==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lS2F5-00Aimn-GA; Thu, 01 Apr 2021 18:40:32 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lS2F0-00AimB-DC for linux-arm-kernel@lists.infradead.org; Thu, 01 Apr 2021 18:40:28 +0000 Received: from [192.168.254.32] (unknown [47.187.194.202]) by linux.microsoft.com (Postfix) with ESMTPSA id BDFDF20ABC25; Thu, 1 Apr 2021 11:40:24 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com BDFDF20ABC25 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1617302425; bh=SOlvCGNF2qL5Q3qgj9PLqYCmEQf62InHHijTjNlIusI=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=PnrhJu9LCcT59AvJiHeY+krR88BIg5ss+Vm+tOQZcJ+rklhu2M8B38Qvj5bnMgCyT O66WxUU29Ta/gNMB+kWtkN6uCu+FU0EsFnFIlSy4xbDWNI6nMkQK+F3EhHOft3iAmO zx7iV8lXhO2Y5OLAwpQgTmfPaGhtpV7VcF9PFkeg= 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> <0bece48b-5fee-2bd1-752e-66d2b89cc5ad@linux.microsoft.com> <20210401182810.GO4758@sirena.org.uk> From: "Madhavan T. Venkataraman" Message-ID: <2a56fe4b-9929-0d8b-aa49-c2b1c1b82b79@linux.microsoft.com> Date: Thu, 1 Apr 2021 13:40:23 -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: <20210401182810.GO4758@sirena.org.uk> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210401_194026_852978_30EA0BED X-CRM114-Status: GOOD ( 20.29 ) 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 1:28 PM, Mark Brown wrote: > On Thu, Apr 01, 2021 at 12:43:25PM -0500, Madhavan T. Venkataraman wrote: > >>>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS >>>> + { (unsigned long) &ftrace_graph_call, 0 }, >>>> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER >>>> + { (unsigned long) ftrace_graph_caller, 0 }, > >>> 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(). > > Ah, right - it's a result of it being an inner label. I'd suggest > putting a brief note right at that line of code explaining this (eg, > "Inner label, not a function"), it wasn't confusing due to the use of > that symbol but rather due to it being different from everything else > in the list and that's kind of lost in the main comment. > OK, So, I will add a note in the main comment above the list. I will add the comment line you have suggested at the exact line. >> 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 > > I'm not sure we need to bother with that, you'd still need the & I think. I think we need to bother with that. If CONFIG_FUNCTION_GRAPH_TRACER is not on but CONFIG_DYNAMIC_FTRACE_WITH_REGS is, then ftrace_graph_call() will not occur in the stack trace taken from a tracer function. The unwinder still needs to recognize an ftrace frame. I don't want to assume ftrace_common_return which is the label that currently follows the above code. So, we need a different label outside the above ifdef. As for the &, I needed it because ftrace_graph_call is currently defined elsewhere as: extern unsigned long ftrace_graph_call; I did not want to change that. Thanks, Madhavan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel