[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

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--- Comment #11 from GitLab Migration User  ---
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This bug has been migrated to freedesktop.org's GitLab instance and has been
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You can subscribe and participate further through the new bug through this link
to our GitLab instance: https://gitlab.freedesktop.org/mesa/mesa/issues/171.

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #10 from Pekka Paalanen  ---
(In reply to Michael Olbrich from comment #9)
> (In reply to Pekka Paalanen from comment #1)
> > Any reason you cannot use EGL_KHR_platform_wayland?
> 
> It's not my code. It's somewhere in gstreamer-vaapi. I was just debugging
> why my application was crashing.

Ok, while this issue is being worked on in Mesa, I would very much recommend
filing a bug against gstreamer-vaapi to start using the EGL platform extensions
whenever available. It's the only reliable way forward.

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #9 from Michael Olbrich  ---
(In reply to Pekka Paalanen from comment #1)
> Any reason you cannot use EGL_KHR_platform_wayland?

It's not my code. It's somewhere in gstreamer-vaapi. I was just debugging why
my application was crashing.

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #8 from Michael Olbrich  ---
(In reply to Daniel Stone from comment #7)
> Good point - I guess it'd have to be if
> (_eglPointerIsDereferencable(child_pointer) &&
> _eglPointerIsDereferencable(((char *) child_pointer) + strlen("wl_display")
> + 1) && strcmp(interface->name, "wl_display") == 0) ... ugh. Does that work
> for you?

Yes that works.

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #7 from Daniel Stone  ---
(In reply to Michael Olbrich from comment #6)
> (In reply to Daniel Stone from comment #2)
> 
> > Michael, I'll attach a compiled but untested patch; can you please let me
> > know if it helps?
> 
> Looks good. It does the right thing for wayland and drm at least.
> is _eglPointerIsDereferencable() sufficient to ensure that the whole string
> is accessible?

Good point - I guess it'd have to be if
(_eglPointerIsDereferencable(child_pointer) &&
_eglPointerIsDereferencable(((char *) child_pointer) + strlen("wl_display") +
1) && strcmp(interface->name, "wl_display") == 0) ... ugh. Does that work for
you?

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #6 from Michael Olbrich  ---
(In reply to Daniel Stone from comment #2)

> Michael, I'll attach a compiled but untested patch; can you please let me
> know if it helps?

Looks good. It does the right thing for wayland and drm at least.
is _eglPointerIsDereferencable() sufficient to ensure that the whole string is
accessible?

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #5 from Daniel Stone  ---
(In reply to Emil Velikov from comment #4)
> 
> I do recall mentioning that exposing the same symbol(s) will lead to bad
> experiences. Followed by some ideas...
> 

Yep, as per the discussion on inlining wayland_drm_buffer_get. :)

It certainly hurts, but then again breaking ABI and forcing every single
Wayland user to rebuild - probably having to change every symbol name in the
API to make sure there was no clash between the two when loaded - would be
uncharted depths of pain.

On the other hand, the solution is the same: look at the interface name, rather
than ever compare pointers equally. Unfortunately, we can't use the same
solution since the wayland-drm one only works for wl_resource in
libwayland-server rather than a plain wl_interface or a wl_proxy ... oh well.

> A better heuristic would be to use dladdr() for eglGetDisplay. See the
> analogous GBM patch [1].

I don't think that would necessarily fix it, particularly if the
wayland-client.so.1 being loaded differed, e.g. due to people linking their own
copies?

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #4 from Emil Velikov  ---

I do recall mentioning that exposing the same symbol(s) will lead to bad
experiences. Followed by some ideas...


WRT eglGetDisplay - I'd recommend moving towards the EGL_*_platform_*
extensions ASAP - EGL_EXT_platform_wayland or EGL_KHR_platform_wayland in this
case.

A better heuristic would be to use dladdr() for eglGetDisplay. See the
analogous GBM patch [1].


https://patchwork.freedesktop.org/patch/187918/

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #3 from Daniel Stone  ---
Created attachment 135490
  --> https://bugs.freedesktop.org/attachment.cgi?id=135490=edit
egldisplay-try-interface-name-for-wl-display.patch

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #2 from Daniel Stone  ---
(In reply to Pekka Paalanen from comment #1)
> eglGetDisplay() is by definition broken on multi-platform implementations,
> yes.

Ugh. It is broken by definition, but Mesa does go to great lengths to try to
make it work by auto-detecting: see _eglNativePlatformDetectNativeDisplay()
inside src/egl/main/egldisplay.c.

Michael, I'll attach a compiled but untested patch; can you please let me know
if it helps?

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

--- Comment #1 from Pekka Paalanen  ---
eglGetDisplay() is by definition broken on multi-platform implementations, yes.

Any reason you cannot use EGL_KHR_platform_wayland?

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[Mesa-dev] [Bug 103757] eglGetDisplay() is broken for Wayland

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https://bugs.freedesktop.org/show_bug.cgi?id=103757

Bug ID: 103757
   Summary: eglGetDisplay() is broken for Wayland
   Product: Mesa
   Version: git
  Hardware: Other
OS: All
Status: NEW
  Severity: normal
  Priority: medium
 Component: EGL/Wayland
  Assignee: wayland-b...@lists.freedesktop.org
  Reporter: m.olbr...@pengutronix.de
QA Contact: mesa-dev@lists.freedesktop.org

_eglNativePlatformDetectNativeDisplay() (called by eglGetDisplay()) detects
Wayland by checking if the native display object starts with a pointer to
wl_display_interface.

Unfortunately wl_display_interface is defined in both libwayland-server.so and
libwayland-client.so. libEGL links to both and in all my tests it always picks
the one from libwayland-server.so.
The wl_display object passed as native display however contains the version
from libwayland-client.so so the check fails.

There is an old thread about this[1] on the wayland-devel list, but it seems
nothing happened since then.

[1]
https://lists.freedesktop.org/archives/wayland-devel/2014-October/017783.html

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