[ARM] dlopen and remote debugging

karthikeyan.s informkarthik@gmail.com
Thu Jul 1 05:02:00 GMT 2010


Can anyone give us a direction here? pointers to related code in gdb
would also be fine.

On Fri, Jun 25, 2010 at 8:47 PM, karthikeyan.s <informkarthik@gmail.com> wrote:
> Sorry I did not mention that we do start gdb with the binary app X.
> So in the host we start with:
> $ arm-none-linux-gnueabi-gdb <targetfs_path>/usr/bin/X
>
> and then
>  # (gdb) set sysroot <targetfs_path>
>  # (gdb) target remote 10.0.0.3:10000
>  # (gdb) continue
>
> I think one does not need to specify the source binary again.
>
> 1) One difference I see in the working and non-working case is that
> other libraries that X depends on are stripped in the failing case.
> So if X depends on x.so,y.so,our_driver.so. In the failing case, case
> x.so,y.so are stripped. Not that this is the reason for the failure,
> but just a difference in the conditions in succeeding and failing
> case.
> And X is stripped in both the cases.
>
> 2) Also, with the above method, I could manually specify the .text
> address (along with values of variables too by specifying other
> section addresses) of the library using add-file-symbol. And then was
> able to hit breakpoints disassemble the library.
>
> add-symbol-file <targetfs_path>/usr/lib/xorg/driver.so <text address>
> <text address> = library load address + text offset in the library.
>
> -Karthik
>
> On Fri, Jun 25, 2010 at 6:17 PM, Matthew Gretton-Dann
> <matthew.gretton-dann@arm.com> wrote:
>> Karthik,
>>
>> On Thu, 2010-06-24 at 23:42 +0530, karthikeyan.s wrote:
>>> Hi,
>>> We recently encountered an issue with gdb wherein it does not get the
>>> symbols from a shared library when loaded with dlopen. The following
>>> steps does not give us the shared library's symbols. The binary is
>>> Xorg.
>>>
>>> 1)
>>> <target> gdbserver :10000 /usr/bin/X -ac
>>> <host gdb> set sysroot <targetfs_path>
>>> <host gdb> target remote 10.0.0.3:10000
>>> <host gdb> continue
>>> <host> cntrl-C
>>> We do not get the library's symbols here. But with cat
>>> /proc/{x_pid}/maps we can see the library is loaded in memory.
>>>
>>> 2) But with the following steps, the libraries get loaded
>>> <target>  /usr/bin/X -ac &
>>> <target> gdbserver :10000 --attach <X_pid>
>>> <host gdb> set sysroot <targetfs_path>
>>> <host gdb> target remote 10.0.0.3:10000
>>>
>>> We can see the library's symbols and hit breakpoint, debug etc. etc.
>>>
>>
>> Section 20.3.2 of the gdb manual says that you need to load the symbols
>> for your application using the file command before you connect (see
>> http://sourceware.org/gdb/download/onlinedocs/gdb/Server.html#Server).
>> Can you try this, and report back if you are still having problems?
>>
>> I would imagine the commands to your host gdb would be something like:
>> (gdb) set sysroot <targetfs_path>
>> (gdb) file <program_being_debugged>
>> (gdb) target remote 10.0.0.3:10000
>> (gdb) continue
>>
>> Thanks,
>>
>> Matt
>>
>> --
>> Matthew Gretton-Dann
>> Principal Engineer - PDSW Tools
>> ARM Ltd
>>
>>
>
>
>
> --
> ---
> S. Karthikeyan | +919980814745
> ---
>



-- 
---
S. Karthikeyan | +919980814745
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