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?

Answer 1

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

1. Prepare the source code by running

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

2. Go to the build directory, for example by:

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

3. Edit Makefile and set EXTRAVERSION to something like:

   EXTRAVERSION = -200.fc20.x86_64
   

4. Enable the modules. I suggest starting with the corresponding file underneath the configs directory (I used kernel-3.14.8-x86_64.config).

5. Prepare the kernel for modules:

   make modules_prepare
   

6. Build the module:

   make M=drivers/net/can
   

7. Profit! Insert the module:

   insmod can-dev.ko
   

Answer 2

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..

1. you might want to update your kernel now in order to not having to do it twice

   sudo yum update
   reboot
   

2. 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
   

3. 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
   

4. 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
   

5. Build the modules

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

6. Install and load

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