[yocto] Debugging shared libraries

[Gary Thomas]

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.


-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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