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

[Mathieu Desnoyers]

Please refer to: 

http://lttng.org/docs/#doc-building-from-source 
which points to: 
https://github.com/lttng/lttng-modules/blob/master/README.md 

Thanks, 

Mathieu 

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

> Hi Mathieu,
> Thank you very much for your reply.
> Where in make file can I specify the full kernel source path? I found the
> following makefile snippet but I cannot locate where the $(srctree) variable
> is initialized. Could you please give me some insight or point to the
> related material? Thank you very much.
> ifneq ($(CONFIG_EXT4_FS),) ext4_dep = $(srctree) /fs/ext4/*.h ext4 =
> lttng-probe-ext4.o
> ifeq ($(wildcard $(ext4_dep)),) $(warning Files $(ext4_dep) not found. Probe
> "ext4" is disabled. Use full kernel source tree to enable it.) ext4 =
> endif
> obj-m += $(ext4)
> endif

> Regards,
> Rui
> On Mon, Mar 23, 2015 at 9:42 AM, Mathieu Desnoyers <
> mathieu.desnoyers at efficios.com > wrote:

> > > 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
> > 
> 

> > > _______________________________________________
> > 
> 
> > > 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
> 

> ​

-- 

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