[lttng-dev] How to compile lttng-modules using full kernel source tree.

Jonathan Rajotte Julien Jonathan.rajotte-julien at efficios.com
Fri Mar 20 10:36:36 EDT 2015

See comments below.

On 2015-03-20 09:34 AM, Rui Han wrote:
> Hi,
> I have encountered following output when I try to run make from the 
> lttng-modules source cloned from git repo. I have tried in a clean 
> install of both 12.04 and 14.04.
> |make -C /lib/modules/3.13.0-45-generic/build M=/home/troguard32/lttng/lttng-modules modules
> make[1]: Entering directory `/usr/src/linux-headers-3.13.0-45-generic'
> /home/troguard32/lttng/lttng-modules/probes/Makefile:30: File /usr/src/linux-headers-3.13.0-45-generic/virt/kvm/iodev.h not found. Probe "kvm" x86-specific is disabled. Use full kernel source tree to enable it.
> /home/troguard32/lttng/lttng-modules/probes/Makefile:142: Files /usr/src/linux-headers-3.13.0-45-generic/fs/btrfs/*.h not found. Probe "btrfs" is disabled. Use full kernel source tree to enable it.
> /home/troguard32/lttng/lttng-modules/probes/Makefile:158: Files /usr/src/linux-headers-3.13.0-45-generic/fs/ext4/*.h not found. Probe "ext4" is disabled. Use full kernel source tree to enable it.
>    Building modules, stage 2.
>    MODPOST 43 modules
> make[1]: Leaving directory `/usr/src/linux-headers-3.13.0-45-generic'
> |
> when run make modules_install, it seem the installation is successful, 
> but the output is abnormal, giving repeated “Can’t read private key” 
> messages.
> If I ignore this message and install all other lttng components, it 
> seems lttng kernel tracer is working fine.
> My question is,
>  1. How to completely remove this abnormal message? where to specify
>     the full kernel source path in make file? (I am a makefile beginner)
Abnormal message being the key related one? We are looking into but this 
does not in any way change behavior.

As for the warning for kvm/btrfs/ext4. Nothing to worry about you simply 
don't have these components installed on your system.
>  1. How to check whether the lttng-modules installed is fully
>     functional or not?
A quick check is the one you probably did: lttng list -k. You can also 
run the root_regression tests from lttng-tools. Under ./tests you can 
run ./run.sh root_regression while being root.
>  1. Does the above message is just telling me that I will be able to
>     use the full function of lttng-modules except those file system
>     probe mentioned in the make output?
> Thank you very much.
> Best regards,
> Rui
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Jonathan R. Julien

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