[GSoC - x86_64 BSP] Using fPIC to compile RTEMS as a shared library

[Amaan Cheval]

Hi! Thanks for the guidance, both of you! I think we're quite close
now to integrating gnu-efi in and finally having the stub port boot as
a UEFI application image. All the test exe's generated on my local
tree are now dynamic libraries, so both Newlib and crtbeginS/crtendS
issues have been resolved (see point 2 below for the relevant WIP
patches).

Here's what I've done:

- Updated amd64.cfg as Joel instructed earlier - here I put "-shared"
in LDFLAGS instead of CPU_CFLAGS because of configure trying to use
CPU_CFLAGS in general, running into unresolved symbols coming from
GCC's stub crt0.c, and falling down. Putting it in LDFLAGS lets me
work around this, but I'd appreciate a thumbs-up on this being okay:

https://github.com/AmaanC/rtems-gsoc18/commit/547ef85a7f176046b2cb06a34b1e312c4986e97f#diff-c64f46c71f828120e08bc4c8667f0525R18

- Updated GCC as follows, building on top of Joel's WIP patch to
minimize bsp_specs:

https://github.com/AmaanC/gcc/pull/1

I made it a PR on my fork so viewing it commit-wise or as a whole diff
is easier for you to review. I'll look into how to make and use
multilib variants next.

Let me know what you think (about the LDFLAGS workaround, and the
approach for the GCC patch so far).

On Mon, Jun 4, 2018 at 6:42 PM, Joel Sherrill <joel at rtems.org> wrote:
>
>
> On Mon, Jun 4, 2018 at 5:44 AM, Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
>>
>>
>>
>> ----- Am 4. Jun 2018 um 12:20 schrieb Amaan Cheval amaan.cheval at gmail.com:
>>
>> > That's a good idea. That way based on the multilib variant, Newlib would
>> > be
>> > compiled using fPIC, yes?
>>
>> Yes.
>
>
> This would be desirable for the i386 as well. Having the RTEMS libraries as
> dynamic libraries would be more natural under Deos.
>
> Just a statement. Not a requirement on the GSoC project.
>>
>>
>> >
>> > Then I could simply figure out how to solve the crtbegin and crtend
>> > dilemma
>> > (which I believe should be easier), and use those to have a
>> > dynamic/shared
>> > RTEMS kernel + user application.
>>
>> These files will be compiled with -fPIC as well.
>
>
>
>>
>>
>> >
>> > If that sounds right, I'll look into that first. Not familiar with the
>> > GCC
>> > source yet, but it should be doable.
>>
>> Sorry, I have no idea how the x86_64 configuration of GCC works for RTEMS.
>>
>> >
>> >
>> > On Mon, Jun 4, 2018, 3:43 PM Sebastian Huber <
>> > sebastian.huber at embedded-brains.de> wrote:
>> >
>> >> Hello Amaan,
>> >>
>> >> can't you add a new multilib variant which includes -fPIC to the GCC
>> >> configuration for RTEMS?
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>
>