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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 489A2C433EF for ; Tue, 16 Nov 2021 09:46:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1890761B98 for ; Tue, 16 Nov 2021 09:46:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233484AbhKPJtV (ORCPT ); Tue, 16 Nov 2021 04:49:21 -0500 Received: from foss.arm.com ([217.140.110.172]:42726 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231770AbhKPJtU (ORCPT ); Tue, 16 Nov 2021 04:49:20 -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 A34D61FB; Tue, 16 Nov 2021 01:46:23 -0800 (PST) Received: from [10.57.76.160] (unknown [10.57.76.160]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 637873F766; Tue, 16 Nov 2021 01:46:22 -0800 (PST) Message-ID: <07dbd4ac-5847-96cf-eb3c-d24561bb052c@arm.com> Date: Tue, 16 Nov 2021 09:46:20 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v1 3/4] coresight: etm4x: Don't trace contextID for non-root namespace in perf mode To: Leo Yan , Mathieu Poirier , Mike Leach , Alexander Shishkin , James Clark , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20211031144214.237879-1-leo.yan@linaro.org> <20211031144214.237879-4-leo.yan@linaro.org> From: Suzuki K Poulose In-Reply-To: <20211031144214.237879-4-leo.yan@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Leo, On 31/10/2021 14:42, Leo Yan wrote: > When runs in perf mode, the driver always enables the contextID tracing. > This can lead to confusion if the program runs in non-root PID namespace > and potentially leak kernel information. > > When programs running in perf mode, this patch changes to only enable > contextID tracing for root PID namespace. > The only concern with the patch here is we silently ignore the CTXTID flag and the perf assumes the CTXTID is traced, when traced from a non-root namespace. Does the decoder handle this case gracefully ? We are fine if that is the case. Either way, we don't want to enforce the policy in the perf tool, if we can transparently handle the missing CTXTID and allow the trace session and decode complete. That said, your approach is the safe bet here. > Signed-off-by: Leo Yan > --- > drivers/hwtracing/coresight/coresight-etm4x-core.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index e24252eaf8e4..6e614bfb38c6 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -615,7 +615,9 @@ static int etm4_parse_event_config(struct coresight_device *csdev, > config->cfg |= BIT(11); > } > > - if (attr->config & BIT(ETM_OPT_CTXTID)) > + /* Only trace contextID when runs in root PID namespace */ > + if ((attr->config & BIT(ETM_OPT_CTXTID)) && > + (task_active_pid_ns(current) == &init_pid_ns)) > /* bit[6], Context ID tracing bit */ > config->cfg |= BIT(ETM4_CFG_BIT_CTXTID); > As mentioned in the previous comment, please add a helper here, than open coding the check. Kind regards Suzuki