[lttng-dev] New LTTNG user : Question about Kprobe and function commandline options

[tarek slaymia]

Hi,

can we retrieve kernel data structures addresses or contents using LTTng ?

regards.


2013/6/23 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>

> * Jessica Foest (jessica.foest at gmail.com) wrote:
> > Hi,
> > i tried to apply kprobe to a system call , so i used probe and function
> > option :
> >
> > lttng enable-event aname -k --probe sys_open+0x0
> > this command returns ip value
> >
> > lttng enable-event aname -k --function sys_open
> > this command returns ip and parent_ip values .
> >
> > what does these values ip and parent_ip means ?
>
> ip: instruction pointer of the function,
> parent_ip: instruction pointer of the caller.
>
> >
> > I try to apply probe and function options to some kernel symbols like
> > initialized date (like xen_vcpu_info symbol), read only data (like
> > linux_prob_banner symbol) and code (like reserve_ebda_region symbol) it
> > displays to me : Enable kernel event failed ,warning some command went(s)
> > wrong.
> > Did i make a mistake or it's a limitation in LTTng ?
>
> It's kprobes: you can only add breakpoints to code, not data.
>
> Thanks,
>
> Mathieu
>
> > regards.
>
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>
> _______________________________________________
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> lttng-dev at lists.lttng.org
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>
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