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 173A2C433EF for ; Tue, 18 Jan 2022 14:14:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235514AbiAROOi (ORCPT ); Tue, 18 Jan 2022 09:14:38 -0500 Received: from foss.arm.com ([217.140.110.172]:57870 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235517AbiAROOA (ORCPT ); Tue, 18 Jan 2022 09:14:00 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 502B81FB; Tue, 18 Jan 2022 06:13:59 -0800 (PST) Received: from [10.57.35.29] (unknown [10.57.35.29]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 681EC3F766; Tue, 18 Jan 2022 06:13:58 -0800 (PST) Subject: Re: [RFC PATCH 2/2] perf: arm_spe: Enable CONTEXT packets in SPE traces if the profiler runs in CPU mode. To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, james.clark@arm.com, leo.yan@linaro.org References: <20220117124432.3119132-1-german.gomez@arm.com> <20220117124432.3119132-3-german.gomez@arm.com> <20220118095258.GA16547@willie-the-truck> From: German Gomez Message-ID: Date: Tue, 18 Jan 2022 14:13:42 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20220118095258.GA16547@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/01/2022 09:52, Will Deacon wrote: > On Mon, Jan 17, 2022 at 12:44:32PM +0000, German Gomez wrote: >> Enable CONTEXT packets in SPE traces if the profiler runs in CPU mode. >> This is no less permissive than the existing behavior for the following >> reason: >> >> If perf_event_paranoid <= 0, then non perfmon_capable() users can open >> a per-CPU event. With a per-CPU event, unpriviledged users are allowed >> to profile _all_ processes, even ones owned by root. >> >> Without this change, users could see kernel addresses, root processes, >> etc, but not gather the PIDs of those processes. The PID is probably the >> least sensitive of all the information. >> >> It would be more idiomatic to check the perf_event_paranoid level with >> perf_allow_cpu(), but this function is not exported so cannot be used >> from a module. Looking for cpu != -1 is the indirect way of checking >> the same thing as it could never get to arm_spe_pmu_event_init() without >> perf_event_paranoid <= 0. > perf_allow_cpu() is a static inline so there's no need to export it. What's > missing? We were still running into build errors: ERROR: modpost: "security_perf_event_open" [drivers/perf/arm_spe_pmu.ko] undefined! ERROR: modpost: "sysctl_perf_event_paranoid" [drivers/perf/arm_spe_pmu.ko] undefined > > Will