drm/i915: Use a slab for object allocation

The primary purpose of this was to debug some use-after-free memory
corruption that was causing an OOPS inside drm/i915. As it turned out
the corruption was being caused elsewhere and i915.ko as a major user of
many objects was being hit hardest.

Indeed as we do frequent the generic kmalloc caches, dedicating one to
ourselves (or at least naming one for us depending upon the core) aids
debugging our own slab usage.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1736,6 +1736,9 @@ int i915_driver_unload(struct drm_device *dev)
 
 	destroy_workqueue(dev_priv->wq);
 
+	if (dev_priv->slab)
+		kmem_cache_destroy(dev_priv->slab);
+
 	pci_dev_put(dev_priv->bridge_dev);
 	kfree(dev->dev_private);
 

drivers/gpu/drm/i915/i915_drv.h

@@ -614,6 +614,7 @@ struct intel_l3_parity {
 
 typedef struct drm_i915_private {
 	struct drm_device *dev;
+	struct kmem_cache *slab;
 
 	const struct intel_device_info *info;
 
@@ -1379,12 +1380,15 @@ int i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
 int i915_gem_wait_ioctl(struct drm_device *dev, void *data,
 			struct drm_file *file_priv);
 void i915_gem_load(struct drm_device *dev);
+void *i915_gem_object_alloc(struct drm_device *dev);
+void i915_gem_object_free(struct drm_i915_gem_object *obj);
 int i915_gem_init_object(struct drm_gem_object *obj);
 void i915_gem_object_init(struct drm_i915_gem_object *obj,
 			 const struct drm_i915_gem_object_ops *ops);
 struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 						  size_t size);
 void i915_gem_free_object(struct drm_gem_object *obj);
+
 int __must_check i915_gem_object_pin(struct drm_i915_gem_object *obj,
 				     uint32_t alignment,
 				     bool map_and_fenceable,

drivers/gpu/drm/i915/i915_gem.c

@@ -192,6 +192,18 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
 	return 0;
 }
 
+void *i915_gem_object_alloc(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	return kmem_cache_alloc(dev_priv->slab, GFP_KERNEL | __GFP_ZERO);
+}
+
+void i915_gem_object_free(struct drm_i915_gem_object *obj)
+{
+	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
+	kmem_cache_free(dev_priv->slab, obj);
+}
+
 static int
 i915_gem_create(struct drm_file *file,
 		struct drm_device *dev,
@@ -215,7 +227,7 @@ i915_gem_create(struct drm_file *file,
 	if (ret) {
 		drm_gem_object_release(&obj->base);
 		i915_gem_info_remove_obj(dev->dev_private, obj->base.size);
-		kfree(obj);
+		i915_gem_object_free(obj);
 		return ret;
 	}
 
@@ -3695,12 +3707,12 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
 	struct address_space *mapping;
 	u32 mask;
 
-	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	obj = i915_gem_object_alloc(dev);
 	if (obj == NULL)
 		return NULL;
 
 	if (drm_gem_object_init(dev, &obj->base, size) != 0) {
-		kfree(obj);
+		i915_gem_object_free(obj);
 		return NULL;
 	}
 
@@ -3783,7 +3795,7 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
 	i915_gem_info_remove_obj(dev_priv, obj->base.size);
 
 	kfree(obj->bit_17);
-	kfree(obj);
+	i915_gem_object_free(obj);
 }
 
 int
@@ -4101,8 +4113,14 @@ init_ring_lists(struct intel_ring_buffer *ring)
 void
 i915_gem_load(struct drm_device *dev)
 {
-	int i;
 	drm_i915_private_t *dev_priv = dev->dev_private;
+	int i;
+
+	dev_priv->slab =
+		kmem_cache_create("i915_gem_object",
+				  sizeof(struct drm_i915_gem_object), 0,
+				  SLAB_HWCACHE_ALIGN,
+				  NULL);
 
 	INIT_LIST_HEAD(&dev_priv->mm.active_list);
 	INIT_LIST_HEAD(&dev_priv->mm.inactive_list);

drivers/gpu/drm/i915/i915_gem_dmabuf.c

@@ -276,8 +276,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 	if (IS_ERR(attach))
 		return ERR_CAST(attach);
 
-
-	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	obj = i915_gem_object_alloc(dev);
 	if (obj == NULL) {
 		ret = -ENOMEM;
 		goto fail_detach;
@@ -285,7 +284,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 
 	ret = drm_gem_private_object_init(dev, &obj->base, dma_buf->size);
 	if (ret) {
-		kfree(obj);
+		i915_gem_object_free(obj);
 		goto fail_detach;
 	}
 

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -252,7 +252,7 @@ _i915_gem_object_create_stolen(struct drm_device *dev,
 {
 	struct drm_i915_gem_object *obj;
 
-	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	obj = i915_gem_object_alloc(dev);
 	if (obj == NULL)
 		return NULL;
 
@@ -277,7 +277,7 @@ _i915_gem_object_create_stolen(struct drm_device *dev,
 	return obj;
 
 cleanup:
-	kfree(obj);
+	i915_gem_object_free(obj);
 	return NULL;
 }