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

[Tvrtko Ursulin]

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.

Regards,

Tvrtko