Make kernel modules available that have been deactivated on Fedora

Question

Edit: I turned Cristians answer into a script which does everything automatically: https://github.com/frans-fuerst/magic/blob/master/fedora-activate-can.sh

I need some kernel modules which are available in the Linux source but deactivated on Fedora 20 and I wonder what's the easiest and most forward way to do make them available. (namely then net/CAN suport resulting in some can_* modules)

are there fedora-repos/rpms which make deactivated modules available?
or do I have to compile these modules manually?
in this case - is there some mechanism to automate this in case of a kernel update or do i have to compile them over and over again?

I've already followed this HowTo (and there are many more very similar out there) but the "build a module only" section seems to work only for modules which haven't been disabled because in that case even the module sources are missing.

Here is what I tried following the mentioned HowTo:

First I tried to follow the Out Of Tree Modules section but in that damn source tree shipped with kernel-devel even the sources for CAN support are missing. So I try to build the modules from the src.rpm:

$ yumdownloader --source kernel
$ sudo yum-builddep kernel-3.14.8-200.fc20.src.rpm
$ rpm -Uvh kernel-3.14.8-200.fc20.src.rpm
$ cd ~/rpmbuild/SPECS
$ rpmbuild -bp --target=$(uname -m) kernel.special
$ cd ~/rpmbuild/BUILD/<kerneldir>/<linuxdir>
$ <configure the kernel using menuconfig>
$ make prepare

Then I build and get some warnings:

$ make -C /lib/modules/`uname -r`/build M=`pwd`/net/can modules
make: Entering directory `<rpmbuild-BUILD-kernel-linux-dir>'

  WARNING: Symbol version dump <rpmbuild-BUILD-kernel-linux-dir>/Module.symvers
           is missing; modules will have no dependencies and modversions.

  CC [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/bcm.o
  CC [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/gw.o
  CC [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/raw.o
  CC [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/af_can.o
  CC [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/proc.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-raw.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-bcm.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-gw.o
  Building modules, stage 2.
  MODPOST 4 modules
  CC      <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-bcm.mod.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-bcm.ko
  CC      <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-gw.mod.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-gw.ko
  CC      <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-raw.mod.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-raw.ko
  CC      <rpmbuild-BUILD-kernel-linux-dir>/net/can/can.mod.o
  LD [M]  <rpmbuild-BUILD-kernel-linux-dir>/net/can/can.ko
make: Leaving directory `<rpmbuild-BUILD-kernel-linux-dir>'

$ sudo make -C /lib/modules/`uname -r`/build M=`pwd`/net/can modules_install
make: Entering directory `<rpmbuild-BUILD-kernel-linux-dir>'
  INSTALL <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-bcm.ko
Can't read private key
  INSTALL <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-gw.ko
Can't read private key
  INSTALL <rpmbuild-BUILD-kernel-linux-dir>/net/can/can-raw.ko
Can't read private key
  INSTALL <rpmbuild-BUILD-kernel-linux-dir>/net/can/can.ko
Can't read private key
  DEPMOD  3.14.8
make: Leaving directory `<rpmbuild-BUILD-kernel-linux-dir>'

I don't get the first warning when I just run make modules but this costs me about an hour.

However after installing, the .ko files are located in the wrong directory (/usr/lib/modules/3.14.8 rather than /usr/lib/modules/3.14.8-200.fc20.x86_64) and after depmod -a and modprobe can I get

modprobe: ERROR: could not insert 'can': Exec format error

What am I doing wrong?

Are the modules that you want included in the src.rpm? If so, why not install the src.rpm, patch the `.config` to enable them and then build the RPM? You could also probably build just those modules by following the "Building Only Kernel Modules (Out Of Tree Modules)" section of that howto. — Cristian Ciupitu, Jun 23 '14 at 11:57
I did so. But maybe I need some detailed instructions for that. I'm unable to just build the required modules running `make M='pwd'/net/can modules`. I get `WARNING: Symbol version dump /Module.symvers is missing; modules will have no dependencies and modversions.` When I just run `make modules` the modules are built but I can't install them to the correct location. When I copy them manually and try to load them I get `modprobe: ERROR: could not insert 'can': Exec format error` — frans, Jun 23 '14 at 12:04
There's a similar question on Ask Ubuntu: ["How do I build a single in-tree kernel module?"](http://askubuntu.com/q/168279/74792) (and it also happens to be about `CONFIG_CAN_PEAK_USB`). — Cristian Ciupitu, Jun 23 '14 at 14:14
Unfortunately this is a different situation - On Ubuntu everything is fine because the source for the CAN modules exists. The .symvers file shipped with Fedora does not contain information about the CAN modules. Looks like I have to migrate to Ubuntu if I don't want to compile very single kernel which is being released.. — frans, Jun 23 '14 at 14:27

Cristian Ciupitu · Accepted Answer · 2014-06-23T19:18:03.993

6

I think I got it, although it's probably far from perfect.

Prepare the source code by running

rpmbuild -bp --target=$(uname -m) kernel.spec

Go to the build directory, for example by:

cd ~/rpmbuild/BUILD/kernel-3.14.fc20/linux-3.14.8-200.fc20.x86_64

Edit Makefile and set EXTRAVERSION to something like:
```
EXTRAVERSION = -200.fc20.x86_64
```
Enable the modules. I suggest starting with the corresponding file underneath the configs directory (I used kernel-3.14.8-x86_64.config).
Prepare the kernel for modules:
```
make modules_prepare
```
Build the module:
```
make M=drivers/net/can
```
Profit! Insert the module:
```
insmod can-dev.ko
```

edited Jun 23 '14 at 19:18

answered Jun 23 '14 at 19:02

Cristian Ciupitu

6,226
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I'll check this tomorrow and in case that works you really deserve this bounty :) But at the same time I'm really gutted about how Fedora treats people who want to modify their system.. https://bugzilla.redhat.com/show_bug.cgi?id=871655 also demonstrates this attitude. – frans Jun 23 '14 at 19:18
Markdown links are vice-versa `[...](...)`. You could request to include the modules in the **kernel-modules-extra** package (although they're probably gonna refuse on the same grounds) or perhaps ask the guys from [RPM Fusion](http://rpmfusion.org/). – Cristian Ciupitu Jun 23 '14 at 19:21

score 0 · Answer 2 · answered Jun 24 '14 at 10:03

For the sake of completeness here is a complete list of steps you need to make the CAN modules (or any other module) available which has been disabled on Fedora (removing the sources, so just using the kernel-devel-approach does not do it).

This procedure might not be perfect but it works for me and enables peak_usb and vcan as well as base CAN modules on Fedora.

Improvements are appreciated and will be honored since I will have to do this very often..

you might want to update your kernel now in order to not having to do it twice
```
sudo yum update
reboot
```

prepare, get and install the Fedora kernel source tree

rpmdev-setuptree
yumdownloader --source kernel
sudo yum-builddep kernel-3.14.8-200.fc20.src.rpm
rpm -Uvh kernel-3.14.8-200.fc20.src.rpm
cd ~/rpmbuild/SPECS
rpmbuild -bp --target=$(uname -m) kernel.spec

Edit Makefile and set EXTRAVERSION to something like:

cd ~/rpmbuild/BUILD/kernel-3.14.fc20/linux-3.14.8-200.fc20.x86_64
EXTRAVERSION = -200.fc20.x86_64

Configure the kernel by first fetching a base configuration e.g.
```
cp /boot/config-3.14.8-200.fc20.x86_64 .config
```
or
```
cp configs/kernel-3.14.8-x86_64.config .config
```
and configure it by activating the needed modules, e.g.
```
make menuconfig
```

Build the modules

make modules_prepare
make M=net/can modules
make M=drivers/net/can modules

Install and load

sudo make M=net/can modules_install
sudo make M=drivers/net/can modules_install
sudo depmod -a
sudo modprobe can

Make kernel modules available that have been deactivated on Fedora

2 Answers2