Re: kernel: building target-arch scripts/* to include in kernel-headers package

[Darren Hart <dvhart@linux.intel.com>]

On 06/25/2012 10:53 PM, Khem Raj wrote:
> On Mon, Jun 25, 2012 at 10:19 PM, Khem Raj <raj.khem@gmail.com> wrote:
>> On Mon, Jun 25, 2012 at 4:33 PM, Darren Hart <dvhart@linux.intel.com> wrote:
>>> I'm working on a patch series to provide a kernel-headers package which
>>> allows for the compilation of Linux kernel modules on the target. I
>>> currently have something working, but it requires that I first build the
>>> scripts/* binaries on the target, prior to trying to build a module.
>>>
>>>        # cd /usr/src/kernel-headers
>>>        # make scripts
>>>
>>> Then I can build modules:
>>>
>>>        # cd /home/root/hello-mod/files
>>>        # export KERNEL_SRC=/usr/src/kernel-headers
>>>        # make
>>>
>>> And test:
>>>
>>>        # insmod hello.ko
>>>        # rmmod hello.ko
>>>        # dmesg | tail -n2
>>>        Hello World!
>>>        Goodbye Cruel World!
>>>
>>> I would like to package the target-arch scripts binaries with the
>>> kernel-headers package, but I'm not sure how to go about building both
>>> the native and the target binaries as part of the kernel building
>>> process. Does it make sense to build these as part of the do_install()
>>> task after I've moved the files from the linux recipe's workdir and
>>> removed the host-arch binaries from scripts?
>>>
>>
>> the hostprogs there are a bit hairy. you could set HOSTCC to point to
>> cross compiler and build scripts dir in some O=foo after copying
>> .config into it but the problem would be that build system expects the
>> hosttools in build tree at exact same location
>> e.g. fixdep would be needed even to build other hosttools e.g.
>> recordmcount etc. and thats where you have to patch kbuild such that
>> it could reference another fixdep tool which then will be built for
>> the host you are compiling kernel on.
> 
> 
> another option is to add a completely new makefile to build
> the necessary tools the way we want them and not use make scripts target at all

While tempting, it sounds like a fragile mechanism with the potential
for maintenance issues.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel