[Mesa-dev] [PATCH 2/2] gallium/util: libunwind support

[Thomas Hellstrom]

On 04/03/2017 11:09 PM, Rob Clark wrote:
> On Mon, Apr 3, 2017 at 4:57 PM, Rob Clark <robdclark at gmail.com> wrote:
>> On Mon, Apr 3, 2017 at 4:06 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>> On 04/03/2017 07:33 PM, Thomas Hellstrom wrote:
>>>> On 04/03/2017 07:13 PM, Rob Clark wrote:
>>>>> On Mon, Apr 3, 2017 at 12:56 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>>>>> Hi, Rob,
>>>>>>
>>>>>> On 03/24/2017 10:21 PM, Rob Clark wrote:
>>>>>>> It's kinda sad that (a) we don't have debug_backtrace support on !X86
>>>>>>> and that (b) we re-invent our own crude backtrace support in the first
>>>>>>> place.  If available, use libunwind instead.  The backtrace format is
>>>>>>> based on what xserver and weston use, since it is nice not to have to
>>>>>>> figure out a different format.
>>>>>>>
>>>>>>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>>>>>> Did you consider glibc "backtrace()", I think it's also available on ARM...
>>>>> I had not.. although xserver and weston are already using libunwind.
>>>>> I'm not sure about portability of libunwind to other libc
>>>>> implementations (but I guess it is at least not worse than using a
>>>>> glibc specific API).
>>>>>
>>>>> I suppose we could always add a fallback to backtrace().
>>>>>
>>> Hmm. This commit (bisected) appears to break svga/vmwgfx in DEBUG mode:
>>>
>>> *** Error in `glxgears': malloc(): memory corruption: 0x00000000025c09c0 ***
>>> Aborted (core dumped)
>>>
>>> The svga linux winsys makes extensive use of the backtrace functionality
>>> using u_debug_flush.c
>> ok, I can reproduce.. hopefully patch following shortly..
>>
> So, I found one other minor issue, but the big problem is
> debug_stack_frame size difference, because u_debug_flush.c doesn't
> #include config.h..  adding:
>
> #ifdef HAVE_CONFIG_H
> #include <config.h>
> #endif
Hmm,

Actually it seems we don't have a config.h, but rather -DHAVE_LIBUNWIND
is included in the compile command.
So the memory corruption should be solely due to not limiting the stack
walk.

/Thomas