Re: full dwarf backtracing kernel to user

[amouehsan <moussa dot ehsan at gmail dot com>]

Hi, 
I am trying systemtap and when probing a kernel function ("bio_endio") I
need to get the user backtrace. When I use 
probe kernel.function("bio_endio@fs/bio.c:1443").call 
{
   print_ubacktrace();
}
I get the following message. 
<no ubacktrace: kernel.function("bio_endio@fs/bio.c:1443").call>

I tried using --ldd but it didn't help. By what you have written:

Mark Wielaard-4 wrote:
> 
> I have been cleaning up the dwarf unwinder a bit, and after some small
> fixes (all in git trunk now) it is now finally possible to unwind fully
> from kernel space right into user space. This provides better user
> backtraces when a probe point triggered in kernel space. 
> 
>  With the new setup it is now possible to get a 
> full user space register set to start the user space dwarf unwinder and
> always do a full unwind. One example is setting a probe point on
> syscall.close and then doing a print_ubacktrace().
> 
I understand the feature I wanted to use was not implemented before. Is my
understanding right? If no, how can I do that? If yes, how I can have this
new feature enabled? Should I get a new code and re-compile systemtap?

Thanks,

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