Re: [RFC 07/14] drm/i915/pmu: Add fake regs

[Ben Widawsky <benjamin.widawsky@intel.com>]

On 17-07-18 15:36:11, Tvrtko Ursulin wrote:
>From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>
>Without this I can get a null ptr deref when trying to access
>our events with perf.
>
>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

This definitely seems unsafe, but should be squashed in somewhere earlier...

>---
> drivers/gpu/drm/i915/i915_pmu.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
>index 4d61a1e72ee6..4195d89b1c82 100644
>--- a/drivers/gpu/drm/i915/i915_pmu.c
>+++ b/drivers/gpu/drm/i915/i915_pmu.c
>@@ -183,8 +183,11 @@ static int engine_event_init(struct perf_event *event)
> 	return 0;
> }
>
>+static DEFINE_PER_CPU(struct pt_regs, i915_pmu_pt_regs);
>+
> static enum hrtimer_restart hrtimer_sample(struct hrtimer *hrtimer)
> {
>+	struct pt_regs *regs = this_cpu_ptr(&i915_pmu_pt_regs);
> 	struct perf_sample_data data;
> 	struct perf_event *event;
> 	u64 period;
>@@ -196,7 +199,7 @@ static enum hrtimer_restart hrtimer_sample(struct hrtimer *hrtimer)
> 	event->pmu->read(event);
>
> 	perf_sample_data_init(&data, 0, event->hw.last_period);
>-	perf_event_overflow(event, &data, NULL);
>+	perf_event_overflow(event, &data, regs);
>
> 	period = max_t(u64, 10000, event->hw.sample_period);
> 	hrtimer_forward_now(hrtimer, ns_to_ktime(period));
>-- 
>2.9.4
>

-- 
Ben Widawsky, Intel Open Source Technology Center
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