[Intel-gfx] [PATCH i-g-t 4/4] gem_create: Convert stolen test to uABI checking

[Chris Wilson]

On Fri, Mar 31, 2017 at 08:11:10AM +0100, Tvrtko Ursulin wrote:
> 
> On 30/03/2017 18:25, Chris Wilson wrote:
> >On Thu, Mar 30, 2017 at 05:58:09PM +0100, Tvrtko Ursulin wrote:
> >>From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>
> >>Stolen never materialized so convert this test into checking
> >>that the garbage in padding remains legal.
> >>
> >>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>---
> >> tests/gem_create.c | 39 ++++++++++++---------------------------
> >> 1 file changed, 12 insertions(+), 27 deletions(-)
> >>
> >>diff --git a/tests/gem_create.c b/tests/gem_create.c
> >>index 21df13f7b655..0dad06c784c5 100644
> >>--- a/tests/gem_create.c
> >>+++ b/tests/gem_create.c
> >>@@ -27,8 +27,7 @@
> >>
> >> /** @file gem_create.c
> >>  *
> >>- * This is a test for the extended and old gem_create ioctl, that
> >>- * includes allocation of object from stolen memory and shmem.
> >>+ * This is a test for the gem_create ioctl.
> >>  *
> >>  * The goal is to simply ensure that basics work and invalid input
> >>  * combinations are rejected.
> >>@@ -62,36 +61,22 @@ IGT_TEST_DESCRIPTION("This is a test for the extended & old gem_create ioctl,"
> >> 		     " that includes allocation of object from stolen memory"
> >> 		     " and shmem.");
> >>
> >>-#define CLEAR(s) memset(&s, 0, sizeof(s))
> >> #define PAGE_SIZE 4096
> >>
> >>-struct local_i915_gem_create_v2 {
> >>-	uint64_t size;
> >>-	uint32_t handle;
> >>-	uint32_t pad;
> >>-#define I915_CREATE_PLACEMENT_STOLEN (1<<0)
> >>-	uint32_t flags;
> >>-} create;
> >>-
> >>-#define LOCAL_IOCTL_I915_GEM_CREATE       DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_GEM_CREATE, struct local_i915_gem_create_v2)
> >>-
> >>-static void invalid_flag_test(int fd)
> >>+/*
> >>+ * Verify that historical omission of checking for garbage in the padding
> >>+ * field still holds.
> >>+ */
> >>+static void test_pad_garbage(int fd)
> >> {
> >>+	struct drm_i915_gem_create create = { };
> >> 	int ret;
> >>
> >>-	gem_require_stolen_support(fd);
> >>-
> >> 	create.handle = 0;
> >> 	create.size = PAGE_SIZE;
> >>-	create.flags = ~I915_CREATE_PLACEMENT_STOLEN;
> >>-	ret = drmIoctl(fd, LOCAL_IOCTL_I915_GEM_CREATE, &create);
> >>-
> >>-	igt_assert(ret <= 0);
> >>-
> >>-	create.flags = ~0;
> >>-	ret = drmIoctl(fd, LOCAL_IOCTL_I915_GEM_CREATE, &create);
> >>-
> >>-	igt_assert(ret <= 0);
> >>+	create.pad = 1;
> >>+	ret = drmIoctl(fd, DRM_IOCTL_I915_GEM_CREATE, &create);
> >>+	igt_assert_eq(ret, 0);
> >> }
> >>
> >> static void invalid_size_test(int fd)
> >>@@ -134,8 +119,8 @@ igt_main
> >> 		fd = drm_open_driver(DRIVER_INTEL);
> >> 	}
> >>
> >>-	igt_subtest("stolen-invalid-flag")
> >>-		invalid_flag_test(fd);
> >>+	igt_subtest("basic-pad-garbage")
> >>+		test_pad_garbage(fd);
> >
> >Not basic though. I just dislike having negative tests that we intend to
> >break be part of basic. (I dislike negative tests in general as they are
> >restrictive and limit creativity, a false limitation in terms of ABI.)
> 
> My understanding is that we can never break this now. I mean that we
> have to allow userspace putting garbage in the padding field forever
> now.
> 
> I don't fully understand right now then how createv2 implementation
> was suggesting to re-purpose half of the padding for flags at the
> moment as well.

It's simple, the code here doesn't reflect the kernel interface :)
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre