[Query] Re: dwarf unwinder (only works on i386/x86_64)

[Prerna Saxena <prerna@linux.vnet.ibm.com>]

Hi Mark,
An elementary query regarding the dwarf-unwinder implementation...

Mark Wielaard wrote:
> ......
>   
> I am working on using the dwarf unwinder also for user space
> backtracing. First using the debug_frame tables that we also are using
> for the kernel case, but maybe switching to the eh_frame tables (it
> isn't clear which one is really the most accurate at the moment, we
> might need to consult both, but I am trying to avoid doing that for
> now).
>
>   
I was trying to contrast the ".eh_frame" vs ".debug_frame" 
specifications for keeping track of stack backtraces. Both appear rather 
similar wrt information they maintain.

The Exception header ".eh_frame" section seems to be present in vmlinux 
even when kernel is compiled without debuginfo.

i. what gcc flags cause this section to be compiled ?
ii. This section seemingly appears to be a better bet than DWARF to base 
the unwinder on--- because a ".debug_frame" based unwinder might not be 
useful in case of a kernel complied without debuginfo.

Looks like I'm missing some reasoning here, could you throw some light ? 
:-)
> Cheers,
>
> Mark
>
>   
Regards,

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India