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


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



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