[yocto] Debugging shared libraries

Thu Feb 11 19:11:06 PST 2016

On 2016-02-11 22:48, Mark Hatle wrote:
> 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.

Definitely standard (OE-core) package, being built from sources.  No -dbg for
the libraries in question.

>
> 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.

https://bugzilla.yoctoproject.org/show_bug.cgi?id=9104

As obvious from the list above, there are other packages with libraries that
have no -dbg as well.  This bug was filed against ffmpeg only, perhaps it should
be more generic...

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