[Bug 97909] X-Plane 10 crashes with SIGSEGV on radeonsi

[bugzilla-daemon@freedesktop.org]

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https://bugs.freedesktop.org/show_bug.cgi?id=97909

--- Comment #5 from Nicolai Hähnle <nhaehnle@gmail.com> ---
Okay, so I could reproduce this after all with the web demo.

There is a bug in X-Plane and also questionable behaviour of the driver. The
bug in X-Plane is that it uses GL_AMD_pinned_memory with a size that is not a
multiple of a page; as per the spec, the driver is allowed to reject that, and
we do (apparently unlike the closed source driver...). X-Plane doesn't check
this error condition, and continues rendering, hence the crash, which would
also happen with a simple sequence of:

  glGenBuffers(1, &bo);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo);
  glDrawElements(...);

Somewhat surprisingly, the OpenGL spec never states that a draw call that goes
outside the element/index buffer should flag a GL_INVALID_OPERATION. There is
also no mention of this in the GL_ARB_robust_buffer_access_behavior extension,
which is surprising.

The patch you provide may or may not go in the right direction - I'm not sure.
If we want to check that, we should do it in api_validate.c, but I'm not
convinced that we should. Meanwhile, that check wouldn't properly fix the issue
in X-Plane. To work around the bug in X-Plane, you need to run with:

MESA_EXTENSION_OVERRIDE=-GL_AMD_pinned_memory ./X-Plane-x86_64 --force_run

which will work with an unmodified driver.

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