drm/i915/gem: consolidate 2big error checking for object sizes

Throw it into a simple helper, and throw a warning if we encounter an
object which has been initialised with an object size that exceeds our
limit of INT_MAX pages.
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@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/20210122181514.541436-2-matthew.auld@intel.comSigned-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c

@@ -244,14 +244,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
 		}
 	}
 
-	/*
-	 * XXX: There is a prevalence of the assumption that we fit the
-	 * object's page count inside a 32bit _signed_ variable. Let's document
-	 * this and catch if we ever need to fix it. In the meantime, if you do
-	 * spot such a local variable, please consider fixing!
-	 */
-
-	if (dma_buf->size >> PAGE_SHIFT > INT_MAX)
+	if (i915_gem_object_size_2big(dma_buf->size))
 		return ERR_PTR(-E2BIG);
 
 	/* need to attach */

drivers/gpu/drm/i915/gem/i915_gem_object.h

@@ -16,6 +16,32 @@
 #include "i915_gem_gtt.h"
 #include "i915_vma_types.h"
 
+/*
+ * XXX: There is a prevalence of the assumption that we fit the
+ * object's page count inside a 32bit _signed_ variable. Let's document
+ * this and catch if we ever need to fix it. In the meantime, if you do
+ * spot such a local variable, please consider fixing!
+ *
+ * Aside from our own locals (for which we have no excuse!):
+ * - sg_table embeds unsigned int for num_pages
+ * - get_user_pages*() mixed ints with longs
+ */
+#define GEM_CHECK_SIZE_OVERFLOW(sz) \
+	GEM_WARN_ON((sz) >> PAGE_SHIFT > INT_MAX)
+
+static inline bool i915_gem_object_size_2big(u64 size)
+{
+	struct drm_i915_gem_object *obj;
+
+	if (GEM_CHECK_SIZE_OVERFLOW(size))
+		return true;
+
+	if (overflows_type(size, obj->base.size))
+		return true;
+
+	return false;
+}
+
 void i915_gem_init__objects(struct drm_i915_private *i915);
 
 struct drm_i915_gem_object *i915_gem_object_alloc(void);

drivers/gpu/drm/i915/gem/i915_gem_region.c

@@ -161,17 +161,7 @@ i915_gem_object_create_region(struct intel_memory_region *mem,
 	GEM_BUG_ON(!size);
 	GEM_BUG_ON(!IS_ALIGNED(size, I915_GTT_MIN_ALIGNMENT));
 
-	/*
-	 * XXX: There is a prevalence of the assumption that we fit the
-	 * object's page count inside a 32bit _signed_ variable. Let's document
-	 * this and catch if we ever need to fix it. In the meantime, if you do
-	 * spot such a local variable, please consider fixing!
-	 */
-
-	if (size >> PAGE_SHIFT > INT_MAX)
-		return ERR_PTR(-E2BIG);
-
-	if (overflows_type(size, obj->base.size))
+	if (i915_gem_object_size_2big(size))
 		return ERR_PTR(-E2BIG);
 
 	obj = i915_gem_object_alloc();

drivers/gpu/drm/i915/gem/i915_gem_userptr.c

@@ -770,21 +770,7 @@ i915_gem_userptr_ioctl(struct drm_device *dev,
 			    I915_USERPTR_UNSYNCHRONIZED))
 		return -EINVAL;
 
-	/*
-	 * XXX: There is a prevalence of the assumption that we fit the
-	 * object's page count inside a 32bit _signed_ variable. Let's document
-	 * this and catch if we ever need to fix it. In the meantime, if you do
-	 * spot such a local variable, please consider fixing!
-	 *
-	 * Aside from our own locals (for which we have no excuse!):
-	 * - sg_table embeds unsigned int for num_pages
-	 * - get_user_pages*() mixed ints with longs
-	 */
-
-	if (args->user_size >> PAGE_SHIFT > INT_MAX)
-		return -E2BIG;
-
-	if (overflows_type(args->user_size, obj->base.size))
+	if (i915_gem_object_size_2big(args->user_size))
 		return -E2BIG;
 
 	if (!args->user_size)