Building kernel modules fails for Debian Jessie Linux Arm 4.1.6

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1

I tried a couple of different ways to build the “hello world” kernel module, but I seem to be lacking the proper “build” to use in my makefiles.

So, I installed the linux headers, but I seem to be missing a “classmap.h” file.

I also managed to get past git crashing by downloading the repo and then rsync’ing it to the BBB. So, after 8 hours(!), the BBB fully compiled a 4.1.6-ti-r12 build. So, if there is something I can do to build a kernel module using that tree and scripts, I can do that, too.

What obvious thing am I missing?

Thanks.

`

The following NEW packages will be installed:
linux-headers-4.1.6-ti-r11
0 upgraded, 1 newly installed, 0 to remove and 9 not upgraded.
Need to get 6,992 kB of archives.
After this operation, 52.9 MB of additional disk space will be used.
Get:1 http://repos.rcn-ee.com/debian/ jessie/main linux-headers-4.1.6-ti-r11 armhf 1jessie [6,992 kB]
Fetched 6,992 kB in 3s (2,199 kB/s)
Selecting previously unselected package linux-headers-4.1.6-ti-r11.
(Reading database … 84339 files and directories currently installed.)
Preparing to unpack …/linux-headers-4.1.6-ti-r11_1jessie_armhf.deb …
Unpacking linux-headers-4.1.6-ti-r11 (1jessie) …
Setting up linux-headers-4.1.6-ti-r11 (1jessie) …
root@arm:~/kernels# cd /lib/modules/uname -r/build
root@arm:/lib/modules/4.1.6-ti-r11/build# ls
arch block crypto Documentation drivers firmware fs include init ipc Kconfig kernel lib Makefile mm Module.symvers net samples scripts security sound tools usr virt
root@arm:/lib/modules/4.1.6-ti-r11/build# make scripts
scripts/kconfig/conf --silentoldconfig Kconfig
HOSTCC scripts/selinux/genheaders/genheaders
scripts/selinux/genheaders/genheaders.c:13:22: fatal error: classmap.h: No such file or directory
#include “classmap.h”
^
compilation terminated.
scripts/Makefile.host:91: recipe for target ‘scripts/selinux/genheaders/genheaders’ failed
make[3]: *** [scripts/selinux/genheaders/genheaders] Error 1
scripts/Makefile.build:403: recipe for target ‘scripts/selinux/genheaders’ failed
make[2]: *** [scripts/selinux/genheaders] Error 2
scripts/Makefile.build:403: recipe for target ‘scripts/selinux’ failed
make[1]: *** [scripts/selinux] Error 2
Makefile:555: recipe for target ‘scripts’ failed
make: *** [scripts] Error 2

`

`

root@arm:~/bb-kernel/mymodules# cat makefile

obj-m += hello.o

all:
make -C /root/bb-kernel/KERNEL/tools/build M=$(PWD) modules

clean:
make -C /root/bb-kernel/KERNEL/tools/build M=$(PWD) clean

root@arm:~/bb-kernel/mymodules# make
make -C /root/bb-kernel/KERNEL/tools/build M=/root/bb-kernel/mymodules modules
make[1]: Entering directory ‘/root/bb-kernel/KERNEL/tools/build’
make[1]: *** No rule to make target ‘modules’. Stop.
make[1]: Leaving directory ‘/root/bb-kernel/KERNEL/tools/build’
makefile:5: recipe for target ‘all’ failed
make: *** [all] Error 2
root@arm:~/bb-kernel/mymodules#

`

2

This just means, for your external module, you need more then just the
'headers" you need the full kernel source..

Regards,

3

After I clean up my own two very stupid errors of not capitalizing the name of the Makefile and installing the r12 headers (I had r11), it compiles and inserts.

During my experiments, though, I came across something odd. As the missing piece appeared to be this symlink:

`

root@arm:~/mymodules# ls -al /lib/modules/4.1.6-ti-r12/build
lrwxrwxrwx 1 root root 35 Aug 26 21:17 /lib/modules/4.1.6-ti-r12/build → /usr/src/linux-headers-4.1.6-ti-r12

`

To make r12 compile, I tried creating this symlink:

`

root@arm:/# ln -s /root/bb-kernel/KERNEL /lib/modules/4.1.6-ti-r12/build

`

Which does compile, but unfortunately doesn’t seem to get the module info correct, so I can’t insmod:

`

root@arm:~/mymodules# insmod hello.ko
insmod: ERROR: could not insert module hello.ko: Invalid module format
root@arm:~/mymodules# modinfo hello.ko
filename: /root/mymodules/hello.ko
description: A Simple Hello World module
depends:
vermagic: 4.1.6-bone15 mod_unload modversions ARMv7 thumb2 p2v8
root@arm:~/mymodules# uname -r
4.1.6-ti-r12

`

The conflict appears to be that vermagic gets set to 4.1.6-bone15 instead of r12.

Anyway, thanks for the advice.

For the record, here is my new Makefile (careful copying as make is nuts about tabs vs spaces):

`

root@arm:~/mymodules# cat Makefile

obj-m += hello.o

all:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

`

4

"bb-kernel" repo has w.x.y-bonez kernel names...

https://github.com/RobertCNelson/ti-linux-kernel-dev

has what your are looking for kernel source...

Regards,

5

Aha!

Thank you. That was the piece I was missing.