From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753325AbdK3Qkd (ORCPT ); Thu, 30 Nov 2017 11:40:33 -0500 Received: from foss.arm.com ([217.140.101.70]:57586 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753382AbdK3Qjr (ORCPT ); Thu, 30 Nov 2017 11:39:47 -0500 From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, sboyd@codeaurora.org, dave.hansen@linux.intel.com, keescook@chromium.org, msalter@redhat.com, labbott@redhat.com, tglx@linutronix.de, Will Deacon Subject: [PATCH v2 18/18] perf: arm_spe: Disallow userspace profiling when arm_kernel_unmapped_at_el0() Date: Thu, 30 Nov 2017 16:39:46 +0000 Message-Id: <1512059986-21325-19-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1512059986-21325-1-git-send-email-will.deacon@arm.com> References: <1512059986-21325-1-git-send-email-will.deacon@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running with the kernel unmapped whilst at EL0, the virtually-addressed SPE buffer is also unmapped, which can lead to buffer faults if userspace profiling is enabled. This patch prohibits SPE profiling of userspace when arm_kernel_unmapped_at_el0(). Signed-off-by: Will Deacon --- drivers/perf/arm_spe_pmu.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c index 8ce262fc2561..c028db8973a4 100644 --- a/drivers/perf/arm_spe_pmu.c +++ b/drivers/perf/arm_spe_pmu.c @@ -675,6 +675,13 @@ static int arm_spe_pmu_event_init(struct perf_event *event) return -EOPNOTSUPP; /* + * If kernelspace is unmapped when running at EL0, then the SPE + * buffer will fault and prematurely terminate the AUX session. + */ + if (arm64_kernel_unmapped_at_el0() && !attr->exclude_user) + dev_warn_once(&spe_pmu->pdev->dev, "unable to write to profiling buffer from EL0. Try passing \"kaiser=off\" on the kernel command line"); + + /* * Feedback-directed frequency throttling doesn't work when we * have a buffer of samples. We'd need to manually count the * samples in the buffer when it fills up and adjust the event -- 2.1.4