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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2C5F8C433FE for ; Tue, 18 Jan 2022 09:54:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=YBK4Qazzxs7uP5b+GBspuhT2ovFKhmVnXaLr+HiCR/M=; b=bM0Ud+CR6vkVgy qyVTsj7Dfm0ZuiGC0tt5CjoqDJ1eQyjNT3pvpuMuO0usLwr3LaXFefy8WecSxbO0IF+gRar3p1SXK 8RrGicwod5U0X52H9L4eiL0gL6bucBVp1H1INkscsQQDuGz0b9WWSQEwGqgfUOQJzOWf6SdWRzKfp cQsAuWyKvh1OIX65Mf3bPzxgIOKmTvzXIv5cNceisyratsjlWaCGObkW/qR/a6Iqaoe2TRltDWhcg 8Dh/hh0DpK8kBQE79IuyQmlXRSJ6/zgXp+lxOk8UUqS9m40trsZK3rOLA3VouTEBePGdi7NkoC/sL skkf77zZ0TWDHm03vPJw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n9lAr-000zeU-07; Tue, 18 Jan 2022 09:53:09 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1n9lAn-000zcj-Ap for linux-arm-kernel@lists.infradead.org; Tue, 18 Jan 2022 09:53:06 +0000 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 dfw.source.kernel.org (Postfix) with ESMTPS id 215A361251; Tue, 18 Jan 2022 09:53:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC096C00446; Tue, 18 Jan 2022 09:53:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1642499584; bh=gMdBtQYDJLAK8ioF6FJ5GqmvRCsOVfKh/Bd5dSM7Cd0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=I9nWilbQvN2UPwJIXW9PqFf3H7iD1TSxSZcRurbKlePMLcQqrX31PuyHQR0UqavMx 0r09/g8K20ggi18Dja3gtc8Q5YFUsBfKn0FG9qx1+7XZQabl0UKau1r0JAM8KsE9Ha oe7x4Ii2iKDXIn4yir9f0VO6qpDgUHuXj6vW7hWTSJyhH0zlZ/zZeihQVwtZLtBFjs N6KOpukL46F8DC6gfQvr48vd6/q/m/uvwBHW6pmH/7zDMFcHq0+FiIIXg/3ZNgMXfJ lc09/KIkZPGol7P6pXzvbmCZpWpKzKTYATk7UKAx5RDMAfif4TwtW7U0yD+TkOsMY9 QYe8iydunVhnw== Date: Tue, 18 Jan 2022 09:52:58 +0000 From: Will Deacon To: German Gomez Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, james.clark@arm.com, leo.yan@linaro.org Subject: Re: [RFC PATCH 2/2] perf: arm_spe: Enable CONTEXT packets in SPE traces if the profiler runs in CPU mode. Message-ID: <20220118095258.GA16547@willie-the-truck> References: <20220117124432.3119132-1-german.gomez@arm.com> <20220117124432.3119132-3-german.gomez@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220117124432.3119132-3-german.gomez@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220118_015305_468299_50C06E51 X-CRM114-Status: GOOD ( 18.10 ) 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 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? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel