path: root/drivers/perf
diff options
authorWill Deacon <will.deacon@arm.com>2017-11-27 15:49:53 +0000
committerWill Deacon <will.deacon@arm.com>2017-12-11 13:41:13 +0000
commit7a4a0c1555b824e0d3dd72942481b1190abea604 (patch)
tree0d82f6fa778dd826c1e448f56e6bcbbdf9e2be89 /drivers/perf
parent084eb77cd3a81134d02500977dc0ecc9277dc97d (diff)
perf: arm_spe: Fail device probe when arm64_kernel_unmapped_at_el0()
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 and potentially also when writing back kernel samples unless an expensive drain operation is performed on exception return. For now, fail the SPE driver probe when arm64_kernel_unmapped_at_el0(). Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Tested-by: Shanker Donthineni <shankerd@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'drivers/perf')
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 8ce262fc2561..51b40aecb776 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -1164,6 +1164,15 @@ static int arm_spe_pmu_device_dt_probe(struct platform_device *pdev)
struct arm_spe_pmu *spe_pmu;
struct device *dev = &pdev->dev;
+ /*
+ * 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()) {
+ dev_warn_once(dev, "profiling buffer inaccessible. Try passing \"kpti=off\" on the kernel command line\n");
+ return -EPERM;
+ }
spe_pmu = devm_kzalloc(dev, sizeof(*spe_pmu), GFP_KERNEL);
if (!spe_pmu) {
dev_err(dev, "failed to allocate spe_pmu\n");

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