[lttng-dev] LTTng Support for Mount Namespace

[Mohammad Kavousi]

Michael,

Thank you for your swift response. However, for the first part, I'm not
sure what it means by "using" the full kernel source. How would I use it
with lttng-modules?

As for the quick hack part, I grabbed the kernel source and copied the
mount.h onto the folder you mentioned, and it did not help. I don't expect
lttng to automatically find that file and use it; also there are no other
header files in the package build directory. Could you kindly give us more
instructions?

Thanks,
Mohammad

On Wed, Jan 6, 2021 at 11:02 AM Michael Jeanson <mjeanson at efficios.com>
wrote:

> On 2021-01-06 10 h 50, Mohammad Kavousi via lttng-dev wrote:
> > Dear LTTng developers,
> >
> > Our group at Northwestern has been using your amazing tool for the
> > purpose of provenance tracking on Linux-based systems and we are very
> > fond of the performance and accuracy it provides.
> >
> > Our analysis shows that mnt_ns context is supported in the 2.12 version
> > of LTTng. However, though, adding the mnt_ns context using
> > the add-context command produces this error:
> >
> > Error: mnt_ns: Context unavailable on this kernel
> >
> > We have tried adding the context to the more recent version of the
> > kernel (5.8) on Ubuntu 20.04, as well as older kernel versions such as
> > the 4.4 version on Ubuntu 16.04. However, we always receive the above
> > error trying to add the mnt_ns context.
> >
> > We could not find which kernel versions are supported for adding this
> > context, or whether they need to be built with special flags. I would
> > appreciate your guidance on resolving this issue.
> >
> >
> > Thank you,
> > Mohammad
>
> Hi,
>
> Unfortunately the definition of 'struct mnt_namespace' is in a private
> kernel header (fs/mount.h) unlike other namespaces.  Private headers are
> not included in the kernel headers package of distributions like Ubuntu,
> to build support for this namespace context in lttng-modules you need to
> use the full kernel source tree.
>
> Or as a quick hack, you could copy 'fs/mount.h' from the original source
> tree to your kernel headers package build directory, which on Ubuntu is
> usually '/lib/modules/$(uname -r)/build'.
>
> Hoe this helps,
>
> Michael
>
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