Re: probe process.function on libc not working

[Laris Benkis <laris@tpn.cc>]

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On 04/01/2012 3:58 PM, Adrien Kunysz wrote:
> On Wed, Jan 04, 2012 at 09:09:51AM -0500, Laris Benkis wrote:
>>>> Warning: child process exited with signal 11 (Segmentation fault)
>>> What does the backtrace, the EIP and the code around the EIP in that
>>> core look like?
>> I've attached the core file.  Here are the registers and backtrace.  Thanks
>> Laris
>>
>> (gdb) info registers
>> eax            0xfffff000       -4096
>> ecx            0x2400   9216
>> edx            0x800000 8388608
>> ebx            0x44fdeff4       1157492724
>> esp            0xbf84c85c       0xbf84c85c
>> ebp            0x44e16000       0x44e16000
>> esi            0x8      8
>> edi            0x1      1
>> eip            0xbf850070       0xbf850070
>> eflags         0x10206  [ PF IF RF ]
>> cs             0x73     115
>> ss             0x7b     123
>> ds             0x7b     123
>> es             0x7b     123
>> fs             0x0      0
>> gs             0x33     51
>> (gdb) bt
>> #0  0xbf850070 in ?? ()
>> #1  0x0000000b in ?? ()
>> #2  0x44e16a54 in ?? ()
>> #3  0x44e0ee78 in ?? () from /lib/ld-2.14.90.so
>> Backtrace stopped: Not enough registers or memory available to unwind
>> further
> That core file is pretty much useless without de debug symbols and
> I don't have a Fedora machine. What do you see if you disassemble
> the code around the instruction pointer? (0xbf850070).
>
> Another idea to try to understand this would be to see whether probing
> only part of the libc functions cause the problem. Is this just with
> one execve()-related function? All the functions? Or does this happen
> only when probing many functions? If you are familiar with Python
> an adaptation of the script Timo posted last month might be helpful
> to explore this: http://sourceware.org/ml/systemtap/2011-q4/msg00402.html

This is pushing my gdb knowledge.  Here is what I get for the
disassemble command:
(gdb) disassemble 0xbf850070
No function contains specified address.

I guess thats probably not what you intended.  Can you give me some more
specific directions.

I've attached the ld-2.14.90.so, ls and libc debug symbols.  I hope that
helps.

I'm not familiar with python but  I'll have a look at it to see it I can
make it work.

Thanks

Laris

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