drm/i915/pmu: Avoid using globals for PMU events

Attempting to bind / unbind module from devices where we have both
integrated and discreete GPU handled by i915, will cause us to try and
double free the global state, hitting null ptr deref in free_event_attributes.

Let's move it to i915_pmu.

Fixes: 05488673 ("drm/i915/pmu: Support multiple GPUs")
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200219161822.24592-2-michal.winiarski@intel.com

drivers/gpu/drm/i915/i915_pmu.c

@@ -822,11 +822,6 @@ static ssize_t i915_pmu_event_show(struct device *dev,
 	return sprintf(buf, "config=0x%lx\n", eattr->val);
 }
 
-static struct attribute_group i915_pmu_events_attr_group = {
-	.name = "events",
-	/* Patch in attrs at runtime. */
-};
-
 static ssize_t
 i915_pmu_get_attr_cpumask(struct device *dev,
 			  struct device_attribute *attr,
@@ -846,13 +841,6 @@ static const struct attribute_group i915_pmu_cpumask_attr_group = {
 	.attrs = i915_cpumask_attrs,
 };
 
-static const struct attribute_group *i915_pmu_attr_groups[] = {
-	&i915_pmu_format_attr_group,
-	&i915_pmu_events_attr_group,
-	&i915_pmu_cpumask_attr_group,
-	NULL
-};
-
 #define __event(__config, __name, __unit) \
 { \
 	.config = (__config), \
@@ -1026,16 +1014,16 @@ err:;
 
 static void free_event_attributes(struct i915_pmu *pmu)
 {
-	struct attribute **attr_iter = i915_pmu_events_attr_group.attrs;
+	struct attribute **attr_iter = pmu->events_attr_group.attrs;
 
 	for (; *attr_iter; attr_iter++)
 		kfree((*attr_iter)->name);
 
-	kfree(i915_pmu_events_attr_group.attrs);
+	kfree(pmu->events_attr_group.attrs);
 	kfree(pmu->i915_attr);
 	kfree(pmu->pmu_attr);
 
-	i915_pmu_events_attr_group.attrs = NULL;
+	pmu->events_attr_group.attrs = NULL;
 	pmu->i915_attr = NULL;
 	pmu->pmu_attr = NULL;
 }
@@ -1117,6 +1105,13 @@ static bool is_igp(struct drm_i915_private *i915)
 void i915_pmu_register(struct drm_i915_private *i915)
 {
 	struct i915_pmu *pmu = &i915->pmu;
+	const struct attribute_group *attr_groups[] = {
+		&i915_pmu_format_attr_group,
+		&pmu->events_attr_group,
+		&i915_pmu_cpumask_attr_group,
+		NULL
+	};
+
 	int ret = -ENOMEM;
 
 	if (INTEL_GEN(i915) <= 2) {
@@ -1143,11 +1138,16 @@ void i915_pmu_register(struct drm_i915_private *i915)
 	if (!pmu->name)
 		goto err;
 
-	i915_pmu_events_attr_group.attrs = create_event_attributes(pmu);
-	if (!i915_pmu_events_attr_group.attrs)
+	pmu->events_attr_group.name = "events";
+	pmu->events_attr_group.attrs = create_event_attributes(pmu);
+	if (!pmu->events_attr_group.attrs)
 		goto err_name;
 
-	pmu->base.attr_groups	= i915_pmu_attr_groups;
+	pmu->base.attr_groups = kmemdup(attr_groups, sizeof(attr_groups),
+					GFP_KERNEL);
+	if (!pmu->base.attr_groups)
+		goto err_attr;
+
 	pmu->base.task_ctx_nr	= perf_invalid_context;
 	pmu->base.event_init	= i915_pmu_event_init;
 	pmu->base.add		= i915_pmu_event_add;
@@ -1159,7 +1159,7 @@ void i915_pmu_register(struct drm_i915_private *i915)
 
 	ret = perf_pmu_register(&pmu->base, pmu->name, -1);
 	if (ret)
-		goto err_attr;
+		goto err_groups;
 
 	ret = i915_pmu_register_cpuhp_state(pmu);
 	if (ret)
@@ -1169,6 +1169,8 @@ void i915_pmu_register(struct drm_i915_private *i915)
 
 err_unreg:
 	perf_pmu_unregister(&pmu->base);
+err_groups:
+	kfree(pmu->base.attr_groups);
 err_attr:
 	pmu->base.event_init = NULL;
 	free_event_attributes(pmu);
@@ -1194,6 +1196,7 @@ void i915_pmu_unregister(struct drm_i915_private *i915)
 
 	perf_pmu_unregister(&pmu->base);
 	pmu->base.event_init = NULL;
+	kfree(pmu->base.attr_groups);
 	if (!is_igp(i915))
 		kfree(pmu->name);
 	free_event_attributes(pmu);

drivers/gpu/drm/i915/i915_pmu.h

@@ -107,6 +107,10 @@ struct i915_pmu {
 	 * @sleep_last: Last time GT parked for RC6 estimation.
 	 */
 	ktime_t sleep_last;
+	/**
+	 * @events_attr_group: Device events attribute group.
+	 */
+	struct attribute_group events_attr_group;
 	/**
 	 * @i915_attr: Memory block holding device attributes.
 	 */