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

[Mathieu Desnoyers]

----- Original Message -----

> Hey,
> 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.
It's because you are building against your distribution kernel, for which 
only your distribution has the signing key. Therefore, the build complains 
that the modules are not signed. But since your distro kernel allows 
loading unsigned modules, it works fine, but outputs a warning. 

> As for the warning for kvm/btrfs/ext4. Nothing to worry about you simply
> don't have these components installed on your system.
A small correction: you may have kvm/btrfs/ext4 on your system. However, lttng-modules 
is letting you know that it cannot build the probes to attach to those subsystem, because 
you build against the installed kernel headers, rather than against the full kernel source tree. 
This is because those subsystem place their instrumentation headers into subdirectories of 
the Linux kernel tree that are not installed on the system. 

Thanks, 

Mathieu 

> > 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?
> 

> Exactly.

> > Thank you very much.
> 

> > Best regards,
> 
> > Rui
> 
> > ​
> 

> > _______________________________________________
> 
> > lttng-dev mailing list lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> 

> --
> Jonathan R. Julien
> Efficios

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-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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