[Buildroot] Versioned symbols in elfutils and uClibc

[Buildroot] Versioned symbols in elfutils and uClibc

[Max Filippov]

Hi,

I'm debugging strange segfault running ltrace for xtensa:
it's caused by dwfl_report_elf recursively calling itself, resulting
in stack overflow. The symbol dwfl_report_elf is versioned, there
are versions ELFUTILS_0.122 and ELFUTILS_0.156, ltrace calls
0.122, but when 0.122 tries to resolve 0.156 it gets back pointer
to 0.122. AFAICS uClibc does not support symbol versioning.
Any idea what can be done about it?

-- 
Thanks.
-- Max

[Buildroot] Versioned symbols in elfutils and uClibc

[Thomas Petazzoni]

Max,

On Tue, 21 Apr 2015 04:30:12 +0300, Max Filippov wrote:

> I'm debugging strange segfault running ltrace for xtensa:
> it's caused by dwfl_report_elf recursively calling itself, resulting
> in stack overflow. The symbol dwfl_report_elf is versioned, there
> are versions ELFUTILS_0.122 and ELFUTILS_0.156, ltrace calls
> 0.122, but when 0.122 tries to resolve 0.156 it gets back pointer
> to 0.122. AFAICS uClibc does not support symbol versioning.
> Any idea what can be done about it?

I guess this is probably a question you should ask on the uClibc
mailing list rather than the Buildroot one.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] Versioned symbols in elfutils and uClibc

[Max Filippov]

On Tue, Apr 21, 2015 at 10:28 AM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
> Max,
>
> On Tue, 21 Apr 2015 04:30:12 +0300, Max Filippov wrote:
>
>> I'm debugging strange segfault running ltrace for xtensa:
>> it's caused by dwfl_report_elf recursively calling itself, resulting
>> in stack overflow. The symbol dwfl_report_elf is versioned, there
>> are versions ELFUTILS_0.122 and ELFUTILS_0.156, ltrace calls
>> 0.122, but when 0.122 tries to resolve 0.156 it gets back pointer
>> to 0.122. AFAICS uClibc does not support symbol versioning.
>> Any idea what can be done about it?
>
> I guess this is probably a question you should ask on the uClibc
> mailing list rather than the Buildroot one.

I'm asking here because it used to work with buildroot 2014.11,
but does not work now. The difference is in elfutils, back then its
dwfl_report_elf wasn't versioned.

-- 
Thanks.
-- Max

[Buildroot] Versioned symbols in elfutils and uClibc

[Peter Korsgaard]

>>>>> "Max" == Max Filippov <jcmvbkbc@gmail.com> writes:

 > Hi,
 > I'm debugging strange segfault running ltrace for xtensa:
 > it's caused by dwfl_report_elf recursively calling itself, resulting
 > in stack overflow. The symbol dwfl_report_elf is versioned, there
 > are versions ELFUTILS_0.122 and ELFUTILS_0.156, ltrace calls
 > 0.122, but when 0.122 tries to resolve 0.156 it gets back pointer
 > to 0.122. AFAICS uClibc does not support symbol versioning.
 > Any idea what can be done about it?

Without knowing much about this, have you tried commenting out the
#ifdef SHARED part in lib/eu-config.h (and possible the corresponding
part in libdwfl/dwfl_report_elf.c)?

-- 
Bye, Peter Korsgaard

[Buildroot] Versioned symbols in elfutils and uClibc

[Max Filippov]

On Tue, Apr 21, 2015 at 2:35 PM, Peter Korsgaard <peter@korsgaard.com> wrote:
>>>>>> "Max" == Max Filippov <jcmvbkbc@gmail.com> writes:
>
>  > Hi,
>  > I'm debugging strange segfault running ltrace for xtensa:
>  > it's caused by dwfl_report_elf recursively calling itself, resulting
>  > in stack overflow. The symbol dwfl_report_elf is versioned, there
>  > are versions ELFUTILS_0.122 and ELFUTILS_0.156, ltrace calls
>  > 0.122, but when 0.122 tries to resolve 0.156 it gets back pointer
>  > to 0.122. AFAICS uClibc does not support symbol versioning.
>  > Any idea what can be done about it?
>
> Without knowing much about this, have you tried commenting out the
> #ifdef SHARED part in lib/eu-config.h (and possible the corresponding
> part in libdwfl/dwfl_report_elf.c)?

It does help, thanks. Looks like this place needs to be patched to
account for missing symbol versioning in uclibc?

-- 
Thanks.
-- Max

[Buildroot] Versioned symbols in elfutils and uClibc

[Peter Korsgaard]

>>>>> "Max" == Max Filippov <jcmvbkbc@gmail.com> writes:

Hi,

>> Without knowing much about this, have you tried commenting out the
 >> #ifdef SHARED part in lib/eu-config.h (and possible the corresponding
 >> part in libdwfl/dwfl_report_elf.c)?

 > It does help, thanks. Looks like this place needs to be patched to
 > account for missing symbol versioning in uclibc?

Yes, it looks like it. Please consider submitting such patches to
elfutils upstream.

-- 
Bye, Peter Korsgaard