lkml.org 
[lkml]   [2017]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 18/18] perf: arm_spe: Disallow userspace profiling when arm_kernel_unmapped_at_el0()
On 11/30, Will Deacon wrote:
> 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 <will.deacon@arm.com>
> ---
> 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");

Missing newline on that print?

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

\
 
 \ /
  Last update: 2017-12-01 17:27    [W:0.216 / U:25.608 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site