[PATCH i-g-t v2 2/2] panthor: test dev_query buffer size variations

[Deborah Brouwer <deborah.brouwer@collabora.com>]

Add tests to check that the kernel driver will gracefully handle userspace
buffers that are smaller or larger than the kernel driver expected.

Also, add a test to ensure that the kernel driver will provide the size
when the userpointer is null.

This ensures UAPI compliance for DRM_IOCTL_PANTHOR_DEV_QUERY.

Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
---
 tests/panthor/panthor_query.c | 56 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/tests/panthor/panthor_query.c b/tests/panthor/panthor_query.c
index afd58a5bd..30e3a9cf3 100644
--- a/tests/panthor/panthor_query.c
+++ b/tests/panthor/panthor_query.c
@@ -7,6 +7,10 @@
 #include "panthor_drm.h"
 #include <stdint.h>
 
+#define GPU_INFO_MIN_SIZE \
+	(offsetof(struct drm_panthor_gpu_info, tiler_present) + \
+	 sizeof(((struct drm_panthor_gpu_info *)0)->tiler_present))
+
 int igt_main() {
 	int fd = -1;
 
@@ -20,10 +24,60 @@ int igt_main() {
 		struct drm_panthor_gpu_info gpu = {};
 
 		igt_panthor_query(fd, DRM_PANTHOR_DEV_QUERY_GPU_INFO, &gpu, sizeof(gpu), 0);
-
 		igt_assert_neq(gpu.gpu_id, 0);
 	}
 
+	igt_describe("Ensure kernel returns a GPU_INFO size.");
+	igt_subtest("query-size-null-pointer") {
+		uint32_t size;
+
+		size = igt_panthor_query(fd, DRM_PANTHOR_DEV_QUERY_GPU_INFO, NULL, 0, 0);
+
+		/*
+		 * The kernel returns its output structure size, which may be out
+		 * of sync with the header used to build these tests, so don't expect
+		 * that the sizes will match necessarily.
+		 */
+		igt_assert(size >= GPU_INFO_MIN_SIZE);
+	}
+
+	igt_describe("Ensure kernel enforces GPU_INFO minimum size.");
+	igt_subtest("query-size-too-small") {
+		struct drm_panthor_gpu_info gpu = {};
+
+		igt_panthor_query(fd, DRM_PANTHOR_DEV_QUERY_GPU_INFO,
+				  &gpu, GPU_INFO_MIN_SIZE - 1, EINVAL);
+	}
+
+	igt_describe("Ensure kernel zeros out unused part of buffer.");
+	igt_subtest("query-too-big") {
+		uint32_t size;
+		size_t buf_size;
+		uint8_t *buf;
+
+		/*
+		 * Create a buffer that is larger than necessary.
+		 * Start with the size returned by the kernel in case it is out of
+		 * sync with these tests. Then add an extra 16 bytes and initialize
+		 * the entire buffer to non-zero values.
+		 */
+		size = igt_panthor_query(fd, DRM_PANTHOR_DEV_QUERY_GPU_INFO,
+					 NULL, 0, 0);
+		buf_size = (size_t)size + 16;
+		buf = malloc(buf_size);
+		igt_assert(buf);
+		memset(buf, 0xff, buf_size);
+
+		igt_panthor_query(fd, DRM_PANTHOR_DEV_QUERY_GPU_INFO,
+				  buf, buf_size, 0);
+
+		/* Check that the extra bytes were zeroed. */
+		for (size_t i = size; i < buf_size; i++)
+			igt_assert_eq(buf[i], 0);
+
+		free(buf);
+	}
+
 	igt_fixture() {
 		drm_close_driver(fd);
 	}

-- 
2.56.0