Zhibin Li's GSoC status report - #2 of 12

Patrik Jakobsson pjakobsson at suse.de
Tue Jun 11 10:01:25 UTC 2019

On Mon, Jun 10, 2019 at 11:49:01PM +0800, Zhibin Li wrote:
> Hi all,
> I just finished my final so I didn't do much last week.
> Accomplishments:
> - Went through i915 source code to mark down what's missing in the original
> patch set.
> - Started to test i915 manually. But I came across some problems (I will
> mention them below in the questions section.
> Questions:
> When I started to test i915 ioctls, I found that it can't be integrated
> into strace's test suite. Please take a look at [1]. It makes sense that
> Patrik uses the driver name linked to the file descriptor to identify the
> specific device. After that the matched ioctl decoder will be invoked.
> Here's my question: Is there any way to tamper the path linked to the fd?
> Something like injection? I mean we usually use fd = -1 in the test but in
> this case it won't work because a valid driver name has to be obtained from
> the fd. Using -1 will simply match no devices.
> Or can we tamper the priv_data in struct tcb when we run tests? Because the
> driver name is stored in priv_data.
> I'm able to test those device specific ioctls by simply returning them. For
> example there is if...else clause to determine which (i915 or something
> else) decoder to invoke. When I want to test i915, I can temporarily remove
> the if...else and return i915_drm_ioctl(). In this way I can manually test
> if it works.

Hi Zhibin,
If you store the name of the driver (ie "i915") in tcb_priv_data before
drm_is_driver() gets called you would skip drm_get_driver_name()
entirely. Does that solve your problem?


> - As mentioned above, I'm still looking for a better way to test them.
> - Add missing functions in i915 decoder.
> BTW is the IRC logger robot absent? I can't see any logs from [2] anymore.
> [1] https://github.com/haoyouab/strace/blob/stuff/drm.c#L28
> [2] https://strace.io/logs
> Thanks,
> Zhibin Li

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