[Xquartz-dev] Help requested debugging rgl under XQuartz

Wed Feb 24 09:46:31 PST 2021

Yes, I did get it wrong.  It looks like the error was detected before 
the call to IOAccelGLContextClearDrawable and the stack checking.  I'll 
see if I can figure out where.

Duncan Murdoch

On 24/02/2021 12:11 p.m., Duncan Murdoch wrote:
> I don't see any calls to __stack_chk_fail .  It's possible I
> misinterpreted what was going on after the IOAccelGLContextClearDrawable
> call.  I'll take another look.
> 
> Duncan Murdoch
> 
> On 24/02/2021 11:41 a.m., Jeremy Huddleston Sequoia wrote:
>> __stack_chk_guard is part of stack protector.
>>
>> If it's not liking the value in __stack_chk_guard, it means the stack
>> was smashed.
>>
>> When this is detected, the compiler runtime should
>> call __stack_chk_fail() if implemented or abort if not.  Given that
>> we're not crashing, I wonder if there's a handler somewhere that ends up
>> causing us to return the bad value instead of crashing.
>>
>> Can you break on __stack_chk_fail and see if that gives us anything useful?
>>
>>
>>
>>
>>> On Feb 24, 2021, at 06:26, Duncan Murdoch <murdoch.duncan at gmail.com
>>> <mailto:murdoch.duncan at gmail.com>> wrote:
>>>
>>> Tracing in with lldb, it appears to be this sequence of calls leading
>>> to the 10005 error value:
>>>
>>> r
>>>   * frame #0: 0x00007fff5afc19e0
>>> libGPUSupportMercury.dylib`gldAttachDrawable + 1
>>>     frame #1: 0x00007fff4467f396 GLEngine`gliAttachDrawableWithOptions
>>> + 251
>>>     frame #2: 0x00007fff4465d9f5
>>> OpenGL`___lldb_unnamed_symbol40$$OpenGL + 972
>>>     frame #3: 0x00007fff446618e2
>>> OpenGL`___lldb_unnamed_symbol59$$OpenGL + 82
>>>     frame #4: 0x00007fff44661c29 OpenGL`CGLSetSurface + 330
>>>     frame #5: 0x00007fff70c6ca63
>>> libXplugin.1.dylib`xp_attach_gl_context + 95
>>>     frame #6: 0x0000000108590dee libGL.1.dylib`surface_make_current + 206
>>>     frame #7: 0x000000010858df6a
>>> libGL.1.dylib`apple_glx_make_current_context + 1274
>>>     frame #8: 0x0000000108574579 libGL.1.dylib`applegl_bind_context + 185
>>>     frame #9: 0x000000010856237e libGL.1.dylib`MakeContextCurrent + 414
>>>     frame #10: 0x00000001085621d9 libGL.1.dylib`glXMakeCurrent + 41
>>>
>>>
>>> The libGPUSupportMercury.dylib`gldAttachDrawable function calls
>>>
>>> IOAccelGLContextClearDrawable
>>>
>>> then does some sort of check of __stack_chk_guard and doesn't like
>>> what it sees, and sets the error.
>>>
>>> Does this give any hint about what's wrong, or a way to fix it?
>>>
>>> Duncan Murdoch
>>>
>>>
>>>
>>> On 23/02/2021 4:31 p.m., Duncan Murdoch wrote:
>>>> On 23/02/2021 3:47 p.m., Jeremy Huddleston Sequoia wrote:
>>>>>
>>>>>
>>>>>> On Feb 23, 2021, at 06:14, Duncan Murdoch <murdoch.duncan at gmail.com
>>>>>> <mailto:murdoch.duncan at gmail.com>
>>>>>> <mailto:murdoch.duncan at gmail.com
>>>>>> <mailto:murdoch.duncan at gmail.com>>> wrote:
>>>>>>
>>>>>> On 23/02/2021 12:47 a.m., Jeremy Huddleston Sequoia wrote:
>>>>>>>> On Feb 22, 2021, at 14:38, Duncan Murdoch
>>>>>>>> <murdoch.duncan at gmail.com <mailto:murdoch.duncan at gmail.com>
>>>>>>>> <mailto:murdoch.duncan at gmail.com
>>>>>>>> <mailto:murdoch.duncan at gmail.com>>
>>>>>>>> <mailto:murdoch.duncan at gmail.com <mailto:murdoch.duncan at gmail.com>
>>>>>>>> <mailto:murdoch.duncan at gmail.com
>>>>>>>> <mailto:murdoch.duncan at gmail.com>>>> wrote:
>>>>>>>>
>>>>>>>> I've made a little bit of progress.
>>>>>>>>
>>>>>>>> The message "error: xp_attach_gl_context returned: 2" comes from the
>>>>>>>> Mesa routine surface_make_current, which calls xp_attach_gl_context.
>>>>>>>>   I haven't found where xp_attach_gl_context is defined.
>>>>>>> xp_attach_gl_context is in libXplugin (check Xplugin.h in the SDK).
>>>>>>> 2 is XP_BadValue, which is returned if cgl_ctx is NULL... so I'd
>>>>>>> suggest looking into why mesa is calling xp_attach_gl_context with a
>>>>>>> NULL context.
>>>>>>
>>>>>> Thanks, that's helpful.  The context is not NULL, so I need to think
>>>>>> of other ways it could be "bad".
>>>>>
>>>>> Ok, well xp_attach_gl_context is just a wrapper around CGLSetSurface(),
>>>>> which is an internal function to do exactly what we're trying to do
>>>>> here.  If it returns any error, xp_attach_gl_context returns bad value.
>>>>>
>>>>> Are you able to capture this in the debugger and figure out what the
>>>>> return value from CGLSetSurface() is?  That will tell us what the
>>>>> underlying CGLError is, which might help shed some light on this.
>>>> I believe it's returning  0x0000000000002715 when there's an error.
>>>> That's 10005, kCGLBadDrawable.  So now I need to find out what happened
>>>> to the drawable.
>>>> This feels like progress!  Thanks again.
>>>> Duncan
>>>>>
>>>>>> Here's what I see with LIBGL_DIAGNOSTIC=1.  For a successful open,
>>>>>>
>>>>>>> rgl.open()
>>>>>> function is no-op
>>>>>> Debug     ../src/glx/apple/apple_glx_context.c:205
>>>>>> apple_glx_create_context(4295810496): apple_glx_create_context: ac
>>>>>> 0x100a10a00 ac->context_obj 0x107cdce00
>>>>>> 2021-02-23 08:23:00.041711-0500 R[45754:1283995]
>>>>>> apple_glx_create_context: ac 0x100a10a00 ac->context_obj 0x107cdce00
>>>>>> Debug     ../src/glx/apple/apple_glx_drawable.c:342
>>>>>> apple_glx_drawable_create(4295810496): apple_glx_drawable_create: new
>>>>>> drawable 0x107ce0e00
>>>>>> 2021-02-23 08:23:00.042235-0500 R[45754:1283995]
>>>>>> apple_glx_drawable_create: new drawable 0x107ce0e00
>>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:154
>>>>>> create_surface(4295810496): create_surface: created a surface for
>>>>>> drawable 0x600066 with uid 621
>>>>>> 2021-02-23 08:23:00.044773-0500 R[45754:1283995] create_surface:
>>>>>> created a surface for drawable 0x600066 with uid 621
>>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:69
>>>>>> surface_make_current(4295810496): surface_make_current:
>>>>>> ac->context_obj 0x107cdce00 s->surface_id 9
>>>>>> 2021-02-23 08:23:00.044839-0500 R[45754:1283995] surface_make_current:
>>>>>> ac->context_obj 0x107cdce00 s->surface_id 9
>>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:89
>>>>>> surface_make_current(4295810496): surface_make_current: drawable
>>>>>> 0x600066
>>>>>> 2021-02-23 08:23:00.045680-0500 R[45754:1283995] surface_make_current:
>>>>>> drawable 0x600066
>>>>>> ... (more lines deleted)
>>>>>>
>>>>>> After I run quartz(), I see this:
>>>>>>
>>>>>>> rgl.open()
>>>>>> Debug     ../src/glx/apple/apple_glx_context.c:205
>>>>>> apple_glx_create_context(4295810496): apple_glx_create_context: ac
>>>>>> 0x10262bb00 ac->context_obj 0x1058c4800
>>>>>> 2021-02-23 08:23:35.666675-0500 R[45754:1283995]
>>>>>> apple_glx_create_context: ac 0x10262bb00 ac->context_obj 0x1058c4800
>>>>>> Debug     ../src/glx/apple/apple_glx_drawable.c:342
>>>>>> apple_glx_drawable_create(4295810496): apple_glx_drawable_create: new
>>>>>> drawable 0x107648000
>>>>>> 2021-02-23 08:23:35.667040-0500 R[45754:1283995]
>>>>>> apple_glx_drawable_create: new drawable 0x107648000
>>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:154
>>>>>> create_surface(4295810496): create_surface: created a surface for
>>>>>> drawable 0x6000c9 with uid 629
>>>>>> 2021-02-23 08:23:35.669119-0500 R[45754:1283995] create_surface:
>>>>>> created a surface for drawable 0x6000c9 with uid 629
>>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:69
>>>>>> surface_make_current(4295810496): surface_make_current:
>>>>>> ac->context_obj 0x1058c4800 s->surface_id 13
>>>>>> 2021-02-23 08:23:35.669195-0500 R[45754:1283995] surface_make_current:
>>>>>> ac->context_obj 0x1058c4800 s->surface_id 13
>>>>>> error: xp_attach_gl_context returned: 2
>>>>>> Debug     ../src/glx/applegl_glx.c:60
>>>>>> applegl_bind_context(4295810496): applegl_bind_context: error YES
>>>>>> 2021-02-23 08:23:35.669834-0500 R[45754:1283995] applegl_bind_context:
>>>>>> error YES
>>>>>>
>>>>>> and then I get my own messages from the failure of glXMakeCurrent().
>>>>>>   As far as I can see, everything appears fine until the call to
>>>>>> xp_attach_gl_context.
>>>>>>
>>>>>>
>>>>>> Everything looks very similar up to the failure of
>>>>>> xp_attach_gl_context.  Any idea I why the value returned a few lines
>>>>>> earlier from apple_glx_create_context() should be a bad value?
>>>>>>
>>>>>> Duncan Murdoch
>>>>>>
>>>>>>
>>>>>
>>>
>>
> 