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Asked: 2026-05-11T17:31:49+00:00

Is it possible to compile a linux kernel(2.6) module that includes functionality defined by

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Is it possible to compile a linux kernel(2.6) module that includes functionality defined by non-kernel includes?

For example:

kernelmodule.h

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>   // printk()
// ...
#include <openssl/sha.h>
// ...

Makefile

obj-m := kernelmodule.o
all:
    $(MAKE) -C /lib/modules/`uname -r`/build M=`pwd` modules

clean:
    $(MAKE) -C /lib/modules/`uname -r`/build M=`pwd` clean
    $(RM) Module.markers modules.order

The kernel module I have written and are trying to compile contains functionality found in a number of openssl include files.

The standard makefile presented above doesn’t allow includes outside of the linux headers. Is it possible to include this functionality, and if so, could you please point me in the right direction.

Thanks,
Mike

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1 Answer

  1. Editorial Team

    The kernel cannot use userspace code and must stand alone (i.e. be completely self contained, no libraries), therefore it does not pick up standard headers.

    It is not clear what benefit trying to pick up userspace headers is. If there are things in there that it would be valid to use (constants, some macros perhaps provided they don’t call any userspace functions), then it may be better to duplicate them and include only the kernel-compatible parts that you need.

    It is not possible to link the kernel with libraries designed for userspace use – even if they don’t make any OS calls – because the linking environment in the kernel cannot pick them up.

    Instead, recompile any functions to be used in the kernel (assuming they don’t make any OS or library calls – e.g. malloc – in which case they’ll need to be modified anyway). Incorporate them into your own library to be used in your kernel modules.

    Recent versions of linux contain cryptographic functions anyway, including various SHA hashes – perhaps you can use one of those instead.

    Another idea would be to stop trying to do crypto in kernel-space and move the code to userspace. Userspace code is easier to write / debug / maintain etc.

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