drm/test: drm_exec: use kzalloc() to allocate GEM objects

Since commit e7fa80e ("drm_gem: add mutex to drm_gem_object.gpuva")
it is possible for test_prepare_array() to exceed a stack frame size of
2048 bytes depending on the exact configuration of the kernel.

  drivers/gpu/drm/tests/drm_exec_test.c: In function ‘test_prepare_array’:
  drivers/gpu/drm/tests/drm_exec_test.c:171:1: error: the frame size of 2128 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
    171 | }
        | ^
  cc1: all warnings being treated as errors
  make[6]: *** [scripts/Makefile.build:287: drivers/gpu/drm/tests/drm_exec_test.o] Error 1
  make[6]: *** Waiting for unfinished jobs....

In order to fix this, allocate the GEM objects in test_prepare_array()
with kzalloc(), rather than placing them on the stack.

Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Christian König <christian.koenig@amd.com>
Fixes: e7fa80e ("drm_gem: add mutex to drm_gem_object.gpuva")
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Nirmoy Das <nirmoyd@nvidia.com>
Link: https://lore.kernel.org/r/20250829075633.2306-1-dakr@kernel.org
[ Use kunit_kzalloc() instead of kzalloc(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Danilo Krummrich

drivers/gpu/drm/tests/drm_exec_test.c

@@ -150,14 +150,22 @@ static void test_prepare(struct kunit *test)
 static void test_prepare_array(struct kunit *test)
 {
 	struct drm_exec_priv *priv = test->priv;
-	struct drm_gem_object gobj1 = { };
-	struct drm_gem_object gobj2 = { };
-	struct drm_gem_object *array[] = { &gobj1, &gobj2 };
+	struct drm_gem_object *gobj1;
+	struct drm_gem_object *gobj2;
+	struct drm_gem_object *array[] = {
+		(gobj1 = kunit_kzalloc(test, sizeof(*gobj1), GFP_KERNEL)),
+		(gobj2 = kunit_kzalloc(test, sizeof(*gobj2), GFP_KERNEL)),
+	};
 	struct drm_exec exec;
 	int ret;
 
-	drm_gem_private_object_init(priv->drm, &gobj1, PAGE_SIZE);
-	drm_gem_private_object_init(priv->drm, &gobj2, PAGE_SIZE);
+	if (!gobj1 || !gobj2) {
+		KUNIT_FAIL(test, "Failed to allocate GEM objects.\n");
+		return;
+	}
+
+	drm_gem_private_object_init(priv->drm, gobj1, PAGE_SIZE);
+	drm_gem_private_object_init(priv->drm, gobj2, PAGE_SIZE);
 
 	drm_exec_init(&exec, DRM_EXEC_INTERRUPTIBLE_WAIT, 0);
 	drm_exec_until_all_locked(&exec)
@@ -166,8 +174,8 @@ static void test_prepare_array(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, ret, 0);
 	drm_exec_fini(&exec);
 
-	drm_gem_private_object_fini(&gobj1);
-	drm_gem_private_object_fini(&gobj2);
+	drm_gem_private_object_fini(gobj1);
+	drm_gem_private_object_fini(gobj2);
 }
 
 static void test_multiple_loops(struct kunit *test)