[lttng-dev] loading modules with modprobe
François Belias
beliasossim at gmail.com
Wed Jul 17 20:44:11 EDT 2024
Hello Kienan,
Thanks to your advice, I managed to load some modules. However, I
encountered errors like these when running `dmesg | grep lttng`:
```
[ 218.043672] module lttng_kretprobes: .gnu.linkonce.this_module section
size must match the kernel's built struct module size at run time
[ 650.560883] lttng_kretprobes: module verification failed: signature
and/or required key missing - tainting kernel
[ 1468.329988] module lttng_ring_buffer_client_discard:
.gnu.linkonce.this_module section size must match the kernel's built struct
module size at run time
```
I'm unsure of their meaning. After loading my module, how can I be certain
that my tracepoints are active? I read online that people use `sudo lttng
list -k` for this purpose, but when I tried it, I got the error: "Error:
Unable to list kernel events: Kernel tracer not available". Is there
another way?
Thank you for your assistance.
Le mer. 17 juill. 2024, à 12 h 08, Kienan Stewart <kstewart at efficios.com> a
écrit :
> Hi François,
>
> On 7/17/24 11:47 AM, François Belias wrote:
> > Hello, Kienan
> >
> >
> > *Right. Which kernel are you actually running at this time? You can check
> > using: `uname -a`*
> > Linux philippe 6.5.0-41-generic #41~22.04.2-Ubuntu SMP PREEMPT_DYNAMIC
> > Mon Jun 3 11:32:55 UTC 2 x86_64 x86_64 x86_64 GNU/Linux
> >
> > *Since you've got a few different images and headers installed, it is
> > possible to check that same info the linux-source package: `dpkg -l |
> > grep linux-source`.*
> > ii linux-source 5.15.0.116.116
> > all Linux kernel source with
> > Ubuntu patches
> > ii linux-source-5.15.0 5.15.0-116.126
> > all Linux kernel source for version
> > 5.15.0 with Ubuntu patches
> > ii linux-source-6.5.0 6.5.0-44.44~22.04.1
> > all Linux kernel source for version
>
> Your currently running `6.5.0-41-generic #41~22.04.2-Ubuntu`
>
> You have source installed for `6.5.0-44.44~22.04.1`. From your previous
> e-mail, there is also a linux image installed:
>
> ```
> linux-image-6.5.0-44-generic 6.5.0-44.44~22.04.1
> ```
>
> Assuming you are using grub, could you verify that one of the options
> for booting in `/boot/grub/grub.cfg` is linux 6.5.0-44.44. Look for the
> lines similar to the following inside a menu entry block:
>
> (Note my example is 5.15.0-116, but you will be lookng for 6.5.0-44 or
> 6.5.0-44.44)
>
> ```
> linux /boot/vmlinuz-5.15.0-116-generic root=....
> initrd /boot/initrd.img-5.15.0-116-generic
> ```
>
> If you have a grub entry for linux 6.5.0-44.44, could you reboot to run
> on the linux 6.5.0-44.44.
>
> After rebooting verify with `uname -a` that your kernel version is
> 6.5.0-44.44.
>
> Make sure you have unpacked the linux sources:
>
> ```
> # Approximating the version numbers, since I don't have 6.5.0 installed
> cd /usr/src/linux-source-6.5.0
> bunzip2 linux-source-6.5.0.tar.bz2
> tar -xf linux-source-6.5.0.tar
> ```
>
> Then retry the build with
> `KERNELDIR=/usr/src/linux-source-6.5.0/linux-source-6.5.0/`
>
> I haven't personally tried the full steps on an Ubuntu installation so
> you may still need to tweak a couple of things, but I think this should
> get you on the right path.
>
> Really the important thing is to make sure that the kernel source code
> matches the kernel you are running.
>
> > 6.5.0 with Ubuntu patches
> > *Could you run either `apt-cache policy` or `apt policy` and `apt-mark
> > showhold` in order to know which sources you have configured.*
> > For this part, /*apt-mark showhold*/ gave me nothing I don't know what
> > is means.
>
> `apt-mark showhold` will show any packages that are on hold - it is a
> way of marking packages that shouldn't be updated.
>
> As you have the linux-source for 6.5.0-44.44~22.04.1, I don't think it
> will be necessary to have the output of `apt-cache policy`.
>
> thanks,
> kienan
>
> >
> > I am looking at the links, but nothing seems to match my kernel version.
> >
> > Thanks for your assistance.
> >
> > Le mer. 17 juill. 2024, à 11 h 46, François Belias
> > <beliasossim at gmail.com <mailto:beliasossim at gmail.com>> a écrit :
> >
> > Hello, Kienan
> >
> >
> > *Right. Which kernel are you actually running at this time? You can
> > check
> > using: `uname -a`*
> > Linux philippe 6.5.0-41-generic #41~22.04.2-Ubuntu SMP
> > PREEMPT_DYNAMIC Mon Jun 3 11:32:55 UTC 2 x86_64 x86_64 x86_64
> GNU/Linux
> >
> > *Since you've got a few different images and headers installed, it is
> > possible to check that same info the linux-source package: `dpkg -l |
> > grep linux-source`.*
> > ii linux-source 5.15.0.116.116
> > all Linux kernel source
> > with Ubuntu patches
> > ii linux-source-5.15.0 5.15.0-116.126
> > all Linux kernel source for
> > version 5.15.0 with Ubuntu patches
> > ii linux-source-6.5.0 6.5.0-44.44~22.04.1
> > all Linux kernel source for
> > version 6.5.0 with Ubuntu patches
> > *Could you run either `apt-cache policy` or `apt policy` and
> `apt-mark
> > showhold` in order to know which sources you have configured.*
> > For this part, /*apt-mark showhold*/ gave me nothing I don't know
> > what is means.
> >
> > I am looking at the links, but nothing seems to match my kernel
> > version.
> >
> > Thanks for your assistance.
> >
> > Le mer. 17 juill. 2024, à 10 h 55, Kienan Stewart
> > <kstewart at efficios.com <mailto:kstewart at efficios.com>> a écrit :
> >
> > Hi François,
> >
> > On 7/16/24 4:34 PM, François Belias wrote:
> > > Hello Kienan,
> > >
> > > When I proceed with the following steps:
> > >
> > > ```
> > > # Warning: this removes all untracked content from the
> > lttng-modules
> > > directory
> > > cd /path/to/lttng-modules-source
> > > git clean -dxf
> > >
> > > make
> > > sudo make modules_install
> > > sudo depmod -a
> > > ```
> > >
> > > I encounter a warning in
> > > `/home/philippe/lttng-modules/src/probes/Kbuild:79` stating
> > "File
> > > ./arch/x86/kvm/lapic.h not found. Probe 'kvm' x86-specific is
> > disabled.
> > > Use full kernel source tree to enable it." Although
> > everything compiles
> > > fine and I'm able to load modules, when I execute `sudo lttng
> > list -k`,
> > > I don't see the tracepoints `kvm_entry` and `kvm_exit`, which
> > I believe
> > > should be available. Could this be due to not using my full
> > kernel tree
> > > during compilation?
> >
> >
> > Exactly. Those probes depend on having the full kernel source as
> > they
> > require private headers which aren't shipped as part of the
> > `linux-headers` package.
> >
> > >
> > > Here are the answers to your questions:
> > >
> > > - *Where did `/usr/src/linux-source-6.5.0` come from?*
> > > I initially attempted `sudo apt-get update && sudo apt-get
> > install
> > > linux-source`, but it gave me this answer */linux-source is
> > already the
> > > newest version (5.15.0.116.116)/*`, which doesn't match my
> > current
> > > kernel version. So, I downloaded it directly from kernel.org
> > <http://kernel.org>
> > > <http://kernel.org <http://kernel.org>> using this command:
> > `wget
> > >
> > https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz`
> <https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz>
> > <https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz>
> > >
> > <https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz`
> <https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz>
> > <https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.5.tar.xz
> >>.
> > >
> >
> > Right. Which kernel are you actually running at this time? You
> > can check
> > using: `uname -a`
> >
> > In any case, Linux upstream 6.5 is not the same as Ubuntus's 6.5.
> >
> > > - *Which Linux distribution and version are you using?*
> > > Running `lsb_release -a` gives me:
> > > ```
> > > No LSB modules are available.
> > > Distributor ID: Ubuntu
> > > Description: Ubuntu 22.04.4 LTS
> > > Release: 22.04
> > > Codename: jammy
> > > ```
> > >
> > > - *Assuming your distribution has kernel packages, which do
> > you have
> > > installed, and do you have the corresponding kernel headers
> > package
> > > installed?*
> > >
> > > Running `dpkg -l | grep linux-image` shows these installed
> > packages:
> > > ```
> > > ii linux-image-5.15.0-116-generic 5.15.0-116.126
> > > amd64 Signed kernel image generic
> > > ii linux-image-6.5.0-28-generic
> > 6.5.0-28.29~22.04.1
> > > amd64 Signed kernel image generic
> > > ii linux-image-6.5.0-41-generic
> > 6.5.0-41.41~22.04.2
> > > amd64 Signed kernel image generic
> > > ii linux-image-6.5.0-44-generic
> > 6.5.0-44.44~22.04.1
> > > amd64 Signed kernel image generic
> > > ii linux-image-generic 5.15.0.116.116
> > > amd64 Generic Linux kernel image
> > > ii linux-image-generic-hwe-22.04
> > 6.5.0.44.44~22.04.1
> > > amd64 Generic Linux kernel image
> > > ```
> > >
> > > And `dpkg -l | grep linux-headers` shows these installed
> > header packages:
> > > ```
> > > ii linux-headers-5.15.0-116
> > 5.15.0-116.126 all
> > > Header files related to Linux kernel version 5.15.0
> > > ii linux-headers-5.15.0-116-generic 5.15.0-116.126
> > > amd64 Linux kernel headers for version 5.15.0 on 64 bit
> > x86 SMP
> > > ii linux-headers-6.5.0-28-generic
> > 6.5.0-28.29~22.04.1
> > > amd64 Linux kernel headers for version 6.5.0 on 64 bit
> > x86 SMP
> > > ii linux-headers-6.5.0-41-generic
> > 6.5.0-41.41~22.04.2
> > > amd64 Linux kernel headers for version 6.5.0 on 64 bit
> > x86 SMP
> > > ii linux-headers-6.5.0-44-generic
> > 6.5.0-44.44~22.04.1
> > > amd64 Linux kernel headers for version 6.5.0 on 64 bit
> > x86 SMP
> > > ii linux-headers-generic 5.15.0.116.116
> > > amd64 Generic Linux kernel headers
> > > ii linux-headers-generic-hwe-22.04
> > 6.5.0.44.44~22.04.1
> > > amd64 Generic Linux kernel headers
> > > ```
> > >
> >
> > Since you've got a few different images and headers installed,
> > it is
> > possible to check that same info the linux-source package: `dpkg
> > -l |
> > grep linux-source`.
> >
> > Maybe one thing tripping this process up is that you don't have
> > an apt
> > source that provides linux-source that matches the kernel you
> > are using.
> > Could you run either `apt-cache policy` or `apt policy` and
> > `apt-mark
> > showhold` in order to know which sources you have configured.
> >
> > There are also alternative sources for the full source tree:
> >
> > - You could download the specific package from
> > packages.ubuntu.com <http://packages.ubuntu.com>. See
> > https://packages.ubuntu.com <https://packages.ubuntu.com> and
> > use `apt install ./downloaded_package.deb`
> >
> > - You could clone the kernel source for Ubuntu and checkout the
> > appropriate tag. See
> >
> https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/jammy/refs/tags
> <
> https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/jammy/refs/tags
> >
> >
> > thanks,
> > kienan
> >
>
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