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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37FF0C433FE for ; Mon, 21 Nov 2022 14:48:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229774AbiKUOse (ORCPT ); Mon, 21 Nov 2022 09:48:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232052AbiKUOrK (ORCPT ); Mon, 21 Nov 2022 09:47:10 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23B93D29A3; Mon, 21 Nov 2022 06:41:21 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 41017B8106E; Mon, 21 Nov 2022 14:40:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE78BC433C1; Mon, 21 Nov 2022 14:40:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669041628; bh=adn/oebRPSLoCRPxZEVPB8mg0QA8QCN70vqucPnJ/uo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=sV0pofivIR9RlYIUXkTCnGWYK4YjbLiM4kYu/V8Gjn5+uJuQGTqu4kOgSRqIFPrif PGSbno7Et5no0hFBLW6dSFJTIrqadajvIBecYfdx8jfEeKiTJlKhkvw8tC6FWxdUl8 /f2eaDpr7UVzW41AF+BX8paNYu8EEC+6tfQikJAoN+1UBmwQOf/jFPmL2p2MtIFJTK If4tARvrH3cQe45iLjOY3o7KrTURnEMv7j41qpsh2sBfL1sFI4XyQy0Ap4f83GF2bG jAN5ckQ1wleA6sXHgfFAegki1cMNROb/HJ+ESYOUzEcuQ3S0gG21TNamZI+KgT5mt0 rN2ozM3c8jKYA== Date: Mon, 21 Nov 2022 23:40:23 +0900 From: Masami Hiramatsu (Google) To: Peter Zijlstra Cc: Steven Rostedt , Chris Mason , Mark Rutland , Alexei Starovoitov , Florent Revest , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , KP Singh , Brendan Jackman , markowsky@google.com, Masami Hiramatsu , Xu Kuohai , LKML , Greg Kroah-Hartman , Linus Torvalds , Christoph Hellwig Subject: Re: [RFC 0/1] BPF tracing for arm64 using fprobe Message-Id: <20221121234023.0a8d3a89bf26ad463cf11ad4@kernel.org> In-Reply-To: References: <20221108220651.24492-1-revest@chromium.org> <20221117121617.4e1529d3@gandalf.local.home> <20221117174030.0170cd36@gandalf.local.home> <20221118114519.2711d890@gandalf.local.home> <43d5d1f5-c01d-c0db-b421-386331c2b8c1@meta.com> <20221118130608.5ba89bd8@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 21 Nov 2022 11:09:21 +0100 Peter Zijlstra wrote: > On Fri, Nov 18, 2022 at 01:06:08PM -0500, Steven Rostedt wrote: > > How do I know that a function return was modified by BPF? If I'm debugging > > something, is it obvious to the developer that is debugging an issue > > (perhaps unaware of what BPF programs are loaded on the users machine), > > that the return of a function was tweaked by BPF and that could be the > > source of the bug? > > Have it taint the kernel if something is overridden ;-) Then we can all > ignore the report until it comes back without taint. Hmm, indeed. BTW, error injection should set that too. Thanks, -- Masami Hiramatsu (Google)