[yocto] Debugging shared libraries

[Mark Hatle]

On 2/10/16 9:41 PM, Gary Thomas wrote:
> On 2016-02-10 21:08, Khem Raj wrote:
>>
>>> On Feb 10, 2016, at 8:35 AM, Mark Hatle <mark.hatle at windriver.com> wrote:
>>>
>>> On 2/10/16 1:31 AM, Gary Thomas wrote:
>>>> I'm trying to debug some code (mplayer) which uses some shared
>>>> libraries from ffmpeg.  When I use GDB (via gdbserver), I don't
>>>> get all the debug information I need - note that many of the shared
>>>> libraries do not have any symbolic debugging info:
>>>
>>> Is your system using the the split debug binaries, and if so, do you have them
>>> all installed on the system that GDB is running on?
>>>
>>> (When GDB starts, you should see it load the symbols, or error it can't find them.)
>>>
>>> Assuming you DO have the symbol files available, and some things are lacking
>>> debuginfo, it's possible those recipes are not properly building with full
>>> symbols (they should be, the whole system should be.)
>>>
>>> Easiest way to check is do a readelf/objdump on the .debug version of the
>>> library and check that there are dwarf symbols present... if not, it's probably
>>> a recipe error.
>>>
>>> --Mark
>>>
>>>> (gdb) info sharedlibrary
>>>>  From        To          Syms Read   Shared Object Library
>>>> 0xb6fcf800  0xb6feaf08  Yes         /tmp/p0382.img/lib/ld-linux-armhf.so.3
>>>> 0xb6fa6fa8  0xb6fb2b40  Yes (*)     /tmp/p0382.img/lib/libtinfo.so.5
>>>> 0xb6f6d210  0xb6f8c200  Yes         /tmp/p0382.img/usr/lib/libpng16.so.16
>>>> 0xb6f488e8  0xb6f54a60  Yes         /tmp/p0382.img/lib/libz.so.1
>>>> 0xb6f069f0  0xb6f34264  Yes         /tmp/p0382.img/usr/lib/libjpeg.so.8
>>>> 0xb6edbaf0  0xb6eee29c  Yes         /tmp/p0382.img/usr/lib/libdvdread.so.4
>>>> 0xb6eb6108  0xb6ec7ae8  Yes         /tmp/p0382.img/usr/lib/libass.so.4
>>>> 0xb6e808b8  0xb6e95384  Yes         /tmp/p0382.img/usr/lib/libvorbis.so.0
>>>> 0xb6e6b4b4  0xb6e6d7e4  Yes         /tmp/p0382.img/usr/lib/libogg.so.0
>>>> 0xb6e48978  0xb6e55eb4  Yes         /tmp/p0382.img/usr/lib/libspeex.so.1
>>>> 0xb6dfe818  0xb6e1b8b4  Yes (*)     /tmp/p0382.img/usr/lib/libfaad.so.2
>>>> 0xb6d92df0  0xb6dd4e78  Yes (*)     /tmp/p0382.img/usr/lib/libavutil.so.54
>>>> 0xb5de0640  0xb64a2e18  Yes (*)     /tmp/p0382.img/usr/lib/libavcodec.so.56
>>>> 0xb5c17528  0xb5d65840  Yes (*)     /tmp/p0382.img/usr/lib/libavformat.so.56
>>>> 0xb5b81688  0xb5be8db8  Yes (*)     /tmp/p0382.img/usr/lib/libswscale.so.3
>>>> 0xb5b5f578  0xb5b6c718  Yes (*)     /tmp/p0382.img/usr/lib/libswresample.so.1
>>>> 0xb5b44998  0xb5b4b490  Yes (*)     /tmp/p0382.img/usr/lib/libpostproc.so.53
>>>> 0xb5b1f0e0  0xb5b2e194  Yes         /tmp/p0382.img/lib/libpthread.so.0
>>>> 0xb5aa4c00  0xb5ad46d0  Yes         /tmp/p0382.img/lib/libm.so.6
>>>> 0xb5a859ec  0xb5a8fc34  Yes         /tmp/p0382.img/usr/lib/libXext.so.6
>>>> 0xb597b728  0xb59f92bc  Yes         /tmp/p0382.img/usr/lib/libX11.so.6
>>>> 0xb5946fc8  0xb59573d0  Yes         /tmp/p0382.img/usr/lib/libtheoradec.so.1
>>>> 0xb5887910  0xb591bbb8  Yes (*)     /tmp/p0382.img/usr/lib/libasound.so.2
>>>> 0xb58579f8  0xb58586ac  Yes         /tmp/p0382.img/usr/lib/libXss.so.1
>>>> 0xb5844ca0  0xb5846bac  Yes         /tmp/p0382.img/usr/lib/libXv.so.1
>>>> 0xb57e7700  0xb58265e0  Yes         /tmp/p0382.img/usr/lib/libSDL-1.2.so.0
>>>> 0xb56bae00  0xb57abb28  Yes         /tmp/p0382.img/lib/libc.so.6
>>>> 0xb569292c  0xb5693724  Yes         /tmp/p0382.img/lib/libdl.so.2
>>>> 0xb5650a70  0xb566e6a4  Yes         /tmp/p0382.img/usr/lib/libfontconfig.so.1
>>>> 0xb561e324  0xb563951c  Yes         /tmp/p0382.img/usr/lib/libexpat.so.1
>>>> 0xb559d36c  0xb55f5cb4  Yes         /tmp/p0382.img/usr/lib/libfreetype.so.6
>>>> 0xb55622b0  0xb5567e84  Yes         /tmp/p0382.img/usr/lib/libenca.so.0
>>>> 0xb541fbc0  0xb54b5a08  Yes (*)     /tmp/p0382.img/usr/lib/libx264.so.144
>>>> 0xb53d4df0  0xb53fa0b0  Yes         /tmp/p0382.img/usr/lib/libtheoraenc.so.1
>>>> 0xb53a72b0  0xb53bd258  Yes (*)     /tmp/p0382.img/usr/lib/liblzma.so.5
>>>> 0xb5386050  0xb5392cc0  Yes (*)     /tmp/p0382.img/usr/lib/libbz2.so.0
>>>> 0xb5367810  0xb5373b30  Yes         /tmp/p0382.img/usr/lib/libxcb.so.1
>>>> 0xb534da00  0xb534e5a8  Yes         /tmp/p0382.img/usr/lib/libXau.so.6
>>>> 0xb5339f80  0xb533b69c  Yes         /tmp/p0382.img/usr/lib/libXdmcp.so.6
>>>> 0xb5323720  0xb5326ea0  Yes         /tmp/p0382.img/lib/librt.so.1
>>>> 0xb530b6e0  0xb5311234  Yes         /tmp/p0382.img/usr/lib/libXrandr.so.2
>>>> 0xb52f3530  0xb52f9060  Yes         /tmp/p0382.img/usr/lib/libXrender.so.1
>>>> 0xb52d3160  0xb52e18a4  Yes         /tmp/p0382.img/lib/libgcc_s.so.1
>>>> (*): Shared library is missing debugging information.
>>>>
>>>> Is this a function of how those libraries were built (by the recipe)
>>>> or something else?  How can I get the symbolic debugging info enabled?
>>>>
>>>> Thanks for any pointers
>>
>>
>> Usually it works well if you add
>>
>> EXTRA_IMAGE_FEATURES_append = “ dbg-pkgs”
>>
>> image size grows but you get good debug view on target.
>>
>> another option, I usually use is setup feeds
>> and then
>>
>> opkg install <package>-dbg
>>
>> which pulls in a section of debug info needed to debug a given package.
>>
> 
> I've done all this already.  The problem is that for the libraries which
> have no symbols there are no corresponding -dbg packages :-(  I looked
> at the ffmpeg recipe (where the libswresample library I'm most interested
> in comes from) and there is serious magic involved in the packaging.  I'm
> pretty sure that's where the discrepancy lies...  Any help understanding
> how to fix that would be appreciated.

If the package is being built from source, I'd expect -dbg to be generated.. if
it's not, we definitely should investigate.

The intention has always been to generate -dbg for the core pieces..  External
layers can disable it if they're packaging binaries or commercial, but that is
different.

--Mark

>