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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 5F6DDC33C9E for ; Tue, 14 Jan 2020 03:25:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C0A6214AF for ; Tue, 14 Jan 2020 03:25:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578972316; bh=QkHyKAGTddSsShkAKK/9wz9s/LBEIbe4rXene2Ocgcw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=lW8UQ/A8punaR6rQfAGZm6+xjxX5jfRrYxFNv9qS9jAzT5Xmn77fHIjLzWXJplYQv 4YUHhhS5d/6STMM8BKhe7M09t0DKctnItrJPnGEdFJS5p4INlMSAHObai6esr98wC+ l8xZCu2JIaxFB+a+byol3I79TfTZtuhqwa3dZyH0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729308AbgANDZP (ORCPT ); Mon, 13 Jan 2020 22:25:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:53920 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728802AbgANDZP (ORCPT ); Mon, 13 Jan 2020 22:25:15 -0500 Received: from devnote2 (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 E500420CC7; Tue, 14 Jan 2020 03:25:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578972314; bh=QkHyKAGTddSsShkAKK/9wz9s/LBEIbe4rXene2Ocgcw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=P/oeRpMLF2bpU9nSUQIoi6OYhsI/JtCANb5Pqun4pmvjYHBs7iMrEF+jFM0p99K5J 9Vi0fL0G6yVxBBlCqCZKTylkfO4ZfpLayfsRohavJxscGdKhB7RSASxW8zY1uijujf 6uDPYCefy+oYQMT3d2EYhKpa1jdmy1aUOBRfXGok= Date: Tue, 14 Jan 2020 12:25:06 +0900 From: Masami Hiramatsu To: Alexey Budankov Cc: arnaldo.melo@gmail.com, Song Liu , Peter Zijlstra , Ingo Molnar , "jani.nikula@linux.intel.com" , "joonas.lahtinen@linux.intel.com" , "rodrigo.vivi@intel.com" , Alexei Starovoitov , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "james.bottomley@hansenpartnership.com" , Serge Hallyn , James Morris , Will Deacon , Mark Rutland , Casey Schaufler , Robert Richter , Jiri Olsa , Andi Kleen , Stephane Eranian , Igor Lubashev , Alexander Shishkin , Namhyung Kim , linux-kernel Subject: Re: [PATCH v4 2/9] perf/core: open access for CAP_SYS_PERFMON privileged process Message-Id: <20200114122506.3cf442dc189a649d4736f86e@kernel.org> In-Reply-To: <158a4033-f8d6-8af7-77b0-20e62ec913b0@linux.intel.com> References: <20200108160713.GI2844@hirez.programming.kicks-ass.net> <20200110140234.GO2844@hirez.programming.kicks-ass.net> <20200111005213.6dfd98fb36ace098004bde0e@kernel.org> <20200110164531.GA2598@kernel.org> <20200111084735.0ff01c758bfbfd0ae2e1f24e@kernel.org> <2B79131A-3F76-47F5-AAB4-08BCA820473F@fb.com> <5e191833.1c69fb81.8bc25.a88c@mx.google.com> <158a4033-f8d6-8af7-77b0-20e62ec913b0@linux.intel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-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 Sat, 11 Jan 2020 12:57:18 +0300 Alexey Budankov wrote: > > On 11.01.2020 3:35, arnaldo.melo@gmail.com wrote: > > Message-ID: > > > > On January 10, 2020 9:23:27 PM GMT-03:00, Song Liu wrote: > >> > >> > >>> On Jan 10, 2020, at 3:47 PM, Masami Hiramatsu > >> wrote: > >>> > >>> On Fri, 10 Jan 2020 13:45:31 -0300 > >>> Arnaldo Carvalho de Melo wrote: > >>> > >>>> Em Sat, Jan 11, 2020 at 12:52:13AM +0900, Masami Hiramatsu escreveu: > >>>>> On Fri, 10 Jan 2020 15:02:34 +0100 Peter Zijlstra > >> wrote: > >>>>>> Again, this only allows attaching to previously created kprobes, > >> it does > >>>>>> not allow creating kprobes, right? > >>>> > >>>>>> That is; I don't think CAP_SYS_PERFMON should be allowed to create > >>>>>> kprobes. > >>>> > >>>>>> As might be clear; I don't actually know what the user-ABI is for > >>>>>> creating kprobes. > >>>> > >>>>> There are 2 ABIs nowadays, ftrace and ebpf. perf-probe uses ftrace > >> interface to > >>>>> define new kprobe events, and those events are treated as > >> completely same as > >>>>> tracepoint events. On the other hand, ebpf tries to define new > >> probe event > >>>>> via perf_event interface. Above one is that interface. IOW, it > >> creates new kprobe. > >>>> > >>>> Masami, any plans to make 'perf probe' use the perf_event_open() > >>>> interface for creating kprobes/uprobes? > >>> > >>> Would you mean perf probe to switch to perf_event_open()? > >>> No, perf probe is for setting up the ftrace probe events. I think we > >> can add an > >>> option to use perf_event_open(). But current kprobe creation from > >> perf_event_open() > >>> is separated from ftrace by design. > >> > >> I guess we can extend event parser to understand kprobe directly. > >> Instead of > >> > >> perf probe kernel_func > >> perf stat/record -e probe:kernel_func ... > >> > >> We can just do > >> > >> perf stat/record -e kprobe:kernel_func ... > > > > > > You took the words from my mouth, exactly, that is a perfect use case, an alternative to the 'perf probe' one of making a disabled event that then gets activated via record/stat/trace, in many cases it's better, removes the explicit probe setup case. > > Arnaldo, Masami, Song, > > What do you think about making this also open to CAP_SYS_PERFMON privileged processes? > Could you please also review and comment on patch 5/9 for bpf_trace.c? As we talked at RFC series of CAP_SYS_TRACING last year, I just expected to open it for enabling/disabling kprobes, not for creation. If we can accept user who has no admin priviledge but the CAP_SYS_PERFMON, to shoot their foot by their own risk, I'm OK to allow it. (Even though, it should check the max number of probes to be created by something like ulimit) I think nowadays we have fixed all such kernel crash problems on x86, but not sure for other archs, especially on the devices I can not reach. I need more help to stabilize it. Thank you, -- Masami Hiramatsu