[Crash-utility] Re: source line numbers and modules (on x86_64)

[Dave Anderson]

Mike Snitzer wrote:
> On Wed, Apr 30, 2008 at 6:43 PM, Dave Anderson <anderson at redhat.com> wrote:
>   
>> Mike Snitzer wrote:
>>
>>     
>>> Hi,
>>>
>>> I searched the archives and found that you've discussed an issue I'm
>>> seeing with x86_64 kernels where crash doesn't have line numbers for
>>> modules' symbols:
>>> https://www.redhat.com/archives/crash-utility/2008-January/msg00021.html
>>>
>>> I'm using crash-4.0-6.3 on a RHEL5U1 x86_64 system with a custom
>>> 2.6.22.19 kernel.  Given that the RHEL5U1 x86_64 kernels clearly do
>>> provide accurate line numbers for modules, has anyone identified how
>>> that is?  I have to believe the redhat kernel is patched to fix this
>>> issue.
>>>
>>> I looked over the various redhat patches that are applied to RHEL5's
>>> 2.6.18 sources but can't see a patch that stands out as specifically
>>> addressing this x86_64 issue.  But I could easily be overlooking some
>>> patch.
>>>
>>> please advise, thanks.
>>> Mike
>>>
>>> ps. please cc me as I've not yet been able to join the list
>>>
>>>
>>>       
>>  You're on the list now...
>>
>>  Anyway, there are no kernel patches applied to RHEL5 kernels
>>  to make it work that I'm aware of.  That being said, I don't
>>  have an answer as to why they don't work for modules on your
>>  custom kernel (or why they don't work in RHEL4 kernels...).
>>     
>
> I configured my x86_64 kernel to be relocatable.  Could this be the
> reason for modules' line number debug data being off?  From:
> http://people.redhat.com/anderson/crash.changelog.html#4_0_4_5
>
> "Using /proc/kallsyms or a --reloc=[size] as a command line argument
>  is similar to using a System.map file, in that it results in the loss
>  of the use of line number debug data."
>   

No, that particular issue only applies to the base kernel, and is 
irrelevant with respect to modules.
(Note that the RHEL5 kernel is relocatable as well.)
> Still doesn't explain why RHEL4 isn't happy in this regard either...
>
> I'm trying a non-relocatable variant of my kernel now and will report
> back with the results.
>   

What you might confirm is whether you're getting any debuginfo data when 
you load
the module?  Are you sure that your modules are being built with -g?

Dave