[Buildroot] compiler plugins & compiling the kernel

[Kenneth Adam Miller]

On Tue, Aug 23, 2016 at 8:46 PM, Arnout Vandecappelle <arnout at mind.be> wrote:
> On 21-08-16 05:43, Kenneth Adam Miller wrote:
>> On Sat, Aug 20, 2016 at 6:39 PM, Kenneth Adam Miller
>> <kennethadammiller at gmail.com> wrote:
>>> On Sat, Aug 20, 2016 at 2:01 PM, Thomas Petazzoni
>>> <thomas.petazzoni at free-electrons.com> wrote:
>>>> Hello,
>>>>
>>>> On Sat, 20 Aug 2016 13:10:07 -0400, Kenneth Adam Miller wrote:
> [snip]
>>>>> In addition, for some pax related options, it requires gcc plugins for
>>>>> the version being used. That means that I would have to have plugin
>>>>> support for my host, correct?
>>>>
>>>> No, you would need support for plugins in the cross-compiler.
>>>>
>>>
>>> We have been building gr-security modded kernels for some time on a
>>> different machine with gcc 4.8, but I'm having this confusion; does
>>> the buildroot internal compiler support that? Because I'm getting an
>>> error in buildroot indicating that compiler plugins must be supported,
>>> and I'm using the buildroot internal compiler with version 5.x, it
>>> confused me a little bit.
>>>
>>
>> I found the exact output that brought about the build error.
>>
>>>>> linux-headers 3.14.51 Configuring...
>> ...
>> make[2]: Entering directory ... build/linux-headers-3.14.51
>> Makefile:652 *** Your gcc installation does not support plugins. If
>> the necessary headers for plugin support are missing, they should be
>> installed. On Debian, apt-get install gcc-<ver>-plugin-dev. If you
>> choose to ignore this error and...
>
>  Ah, this is annoying...
>
>  When installing linux-headers, we don't pass the cross-compilation arguments,
> because the cross-compiler doesn't exist yet at that point. So the installation
> will use the host compiler instead for that check. Which is of course wrong.
>
>  Well, actually it's a bug in gr-security, because this check shouldn't be done
> for install_headers (gcc isn't even called).
>

Bummer, since gr security is no longer even being offered with a free
version anymore for it to be maintained there would have to be a
community consensus around what a good solution is and where
everything can be heaped. In any case, I was able to get past it and
get my kernel compiled. It was giving me some heartache for quite some
time though.

>>
>>>>> I don't believe that there is a way to
>>>>> enable plugin support for the buildroot toolchain or for crosstool. At
>>>>> least, when I looked and searched I didn't see any option that
>>>>> mentioned that. I just want to make sure that I have it correct in
>>>>> that my host compiler is being used to build the kernel.
>>>>
>>>> You're not correct. Support for plugins should be added to the
>>>> cross-compiler if you need plugin support to build your kernel.
>>>>
>>>
>>> That doesn't appear to be an option in buildroot.
>
>  Well, we pass --enable-plugins when BR2_GCC_ENABLE_LTO is set. We don't pass
> --disable-plugins so it really depends on the gcc defaults. But then, we don't
> install the plugin development headers to HOST_DIR, so it will probably be
> difficult to actually compile a plugin.
>
>  Regards,
>  Arnout
>
> --
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
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