[lttng-dev] Undefined symbol error fix

[Kienan Stewart]

Hi François,

On 7/12/24 12:21 PM, François Belias wrote:
> Hello Kienan,
>    Thanks for your reply. I'm working on analyzing a virtual machine by 
> tracing both the host and the guest. I need these tracepoints to 
> synchronize the traces and begin my analysis. Could you provide any 
> steps or recommendations for making these add-ons compatible with the 
> current version of LTTng so that I don't have the error I 
> mentioned earlier?

I think you will also have to modify the Kbuild file so that it builds 
the new modules that are in the addons folder.

I assume there will be other changes to make but to go over all the 
details is beyond the scope of what I think I can effectively help you with.

You may want to consult a resource like 
https://sysprog21.github.io/lkmpg/#functions-available-to-modules to see 
how it works to configure and write kernel modules.

thanks,
kienan

P.S. Could you please keep lttng-dev in CC? thanks

> 
> Thanks,
> 
> François
> 
> Le ven. 12 juill. 2024, à 10 h 33, Kienan Stewart <kstewart at efficios.com 
> <mailto:kstewart at efficios.com>> a écrit :
> 
>     Hi François,
> 
>     On 7/11/24 6:06 PM, François Belias wrote:
>      > Hello Kienan, thanks for the reply. For my analysis, I am also
>     looking
>      > for these tracepoints:
>      >      - vmsync_gh_guest
>      >      - vmsync_hg_guest
>      >      - vmsync_gh_host
>      >      - vmsync_hg_host
>      >   does the canonical upstream version have them ? thanks.
>      >
> 
>     No, it doesn't. Those tracepoints are custom by the looks of it, and
>     not
>     tracepoints that exist in the mainline linux kernel.
> 
>     thanks,
>     kienan
> 
>      > François
>      >
>      > Le jeu. 11 juill. 2024, à 16 h 55, Kienan Stewart
>     <kstewart at efficios.com <mailto:kstewart at efficios.com>
>      > <mailto:kstewart at efficios.com <mailto:kstewart at efficios.com>>> a
>     écrit :
>      >
>      >     Hi François,
>      >
>      >     We don't support the forked version of LTTng modules that you
>     are using
>      >     (https://github.com/tahini/lttng-modules
>     <https://github.com/tahini/lttng-modules>
>      >     <https://github.com/tahini/lttng-modules
>     <https://github.com/tahini/lttng-modules>>)
>      >
>      >     The canonical upstream version available at
>      > https://github.com/lttng/lttng-modules
>     <https://github.com/lttng/lttng-modules>
>      >     <https://github.com/lttng/lttng-modules
>     <https://github.com/lttng/lttng-modules>> has tracepoints such as
>      >     kvm_entry
>      >     and kvm_exit.
>      >
>      >     E.g.
>      >
>     https://github.com/lttng/lttng-modules/blob/06a1fc639b10b40c0ffc412f3fb663632e42dae6/include/instrumentation/events/arch/x86/kvm/trace.h#L20 <https://github.com/lttng/lttng-modules/blob/06a1fc639b10b40c0ffc412f3fb663632e42dae6/include/instrumentation/events/arch/x86/kvm/trace.h#L20> <https://github.com/lttng/lttng-modules/blob/06a1fc639b10b40c0ffc412f3fb663632e42dae6/include/instrumentation/events/arch/x86/kvm/trace.h#L20 <https://github.com/lttng/lttng-modules/blob/06a1fc639b10b40c0ffc412f3fb663632e42dae6/include/instrumentation/events/arch/x86/kvm/trace.h#L20>>
>      >
>      >     thanks,
>      >     kienan
>      >
>      >     On 7/11/24 4:06 PM, François Belias via lttng-dev wrote:
>      >      > Hello,
>      >      >
>      >      >      I am trying to access tracepoints from this website
>      >      >
>      >
>     https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html> <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html>> <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html> <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html <https://archive.eclipse.org/tracecompass.incubator/doc/org.eclipse.tracecompass.incubator.virtual.machine.analysis.doc.user/Virtual-Machine-Analysis-User-Documentation.html>>> (kmv_entry, kmv_exit) for my analysis. I added the "addons" folder from the "addons_vm" branch of this repository: https://github.com/tahini/lttng-modules <https://github.com/tahini/lttng-modules> <https://github.com/tahini/lttng-modules <https://github.com/tahini/lttng-modules>> <https://github.com/tahini/lttng-modules <https://github.com/tahini/lttng-modules> <https://github.com/tahini/lttng-modules <https://github.com/tahini/lttng-modules>>> to the current version of lttng-module github repository. However, I am encountering these errors when compiling
>      >      > ERROR: modpost: "lttng_tracepoint_probe_register"
>      >      > [lttng-modules/src/addons/lttng-vmsync-guest.ko] undefined!
>      >      > ERROR: modpost: "lttng_tracepoint_probe_unregister"
>      >      > [Desktop/lttng-modules/src/addons/lttng-vmsync-guest.ko]
>     undefined!
>      >      > ERROR: modpost: "lttng_tracepoint_probe_register"
>      >      > [Desktop/lttng-modules/src/addons/lttng-vmsync-host.ko]
>     undefined!
>      >      > ERROR: modpost: "lttng_tracepoint_probe_unregister"
>      >      > [Desktop/lttng-modules/src/addons/lttng-vmsync-host.ko]
>     undefined!
>      >      >
>      >      > I am not sure how to resolve this issue. Can someone
>     please help me?
>      >      >
>      >      > Thanks.
>      >      >
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