[PATCH 1/6] drm/i915/pmu: Fix enable count array size and bounds checking

Tvrtko Ursulin
2018-02-12T18:57:52Z

Enable count array is supposed to have one counter for each possible
engine sampler. As such array sizing and bounds checking is not
correct when more engine samplers are added.

At the same time tidy the assert for readability and robustness.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: b46a33e271ed ("drm/i915/pmu: Expose a PMU interface for perf queries")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_pmu.c | 13 +++++++++----
drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 964467b03e4d..a0ae7ca220fd 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -576,7 +576,8 @@ static void i915_pmu_enable(struct perf_event *event)
* Update the bitmask of enabled events and increment
* the event reference counter.
*/
- GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
+ BUILD_BUG_ON(ARRAY_SIZE(i915->pmu.enable_count) != I915_PMU_MASK_BITS);
+ GEM_BUG_ON(bit >= ARRAY_SIZE(i915->pmu.enable_count));
GEM_BUG_ON(i915->pmu.enable_count[bit] == ~0);
i915->pmu.enable |= BIT_ULL(bit);
i915->pmu.enable_count[bit]++;
@@ -600,7 +601,10 @@ static void i915_pmu_enable(struct perf_event *event)
GEM_BUG_ON(!engine);
engine->pmu.enable |= BIT(sample);

- GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
+ BUILD_BUG_ON(ARRAY_SIZE(engine->pmu.enable_count) !=
+ (1 << I915_PMU_SAMPLE_BITS));
+ GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.enable_count));
+ GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.sample));
GEM_BUG_ON(engine->pmu.enable_count[sample] == ~0);
engine->pmu.enable_count[sample]++;
}
@@ -632,7 +636,8 @@ static void i915_pmu_disable(struct perf_event *event)
engine_event_class(event),
engine_event_instance(event));
GEM_BUG_ON(!engine);
- GEM_BUG_ON(sample >= I915_PMU_SAMPLE_BITS);
+ GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.enable_count));
+ GEM_BUG_ON(sample >= ARRAY_SIZE(engine->pmu.sample));
GEM_BUG_ON(engine->pmu.enable_count[sample] == 0);
/*
* Decrement the reference count and clear the enabled
@@ -642,7 +647,7 @@ static void i915_pmu_disable(struct perf_event *event)
engine->pmu.enable &= ~BIT(sample);
}

- GEM_BUG_ON(bit >= I915_PMU_MASK_BITS);
+ GEM_BUG_ON(bit >= ARRAY_SIZE(i915->pmu.enable_count));
GEM_BUG_ON(i915->pmu.enable_count[bit] == 0);
/*
* Decrement the reference count and clear the enabled
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 8f1a4badf812..3e98a589716a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -363,7 +363,7 @@ struct intel_engine_cs {
*
* Index number corresponds to the bit number from @enable.
*/
- unsigned int enable_count[I915_PMU_SAMPLE_BITS];
+ unsigned int enable_count[1 << I915_PMU_SAMPLE_BITS];
/**
* @sample: Counter values for sampling events.