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.dea...@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");
+
+ /*
* 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
