Re: MicroBlaze symver attribute support

[Vincent Fazio <vfazio@gmail.com>]

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All

On Mon, Feb 20, 2023 at 7:35 PM Michael Eager <eager@eagercon.com> wrote:

> On 2/20/23 06:54, Joel Sherrill wrote:
> >
> >
> > On Mon, Feb 20, 2023 at 7:56 AM Vincent Fazio via Gcc <gcc@gcc.gnu.org
> > <mailto:gcc@gcc.gnu.org>> wrote:
> >
> >     Michael, all,
> >
> >     Regarding:
> >     https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766
> >     <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766>
> >     https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102110
> >     <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102110>
> >
> >     If I understand correctly, since the GCC MicroBlaze targets generate
> ELF
> >     images, it would seem there's no technical reason why `__attribute__
> >     ((symver ...))` cannot be supported?
> >
> >     The issue seems to be that the MicroBlaze targets in config.gcc do
> not
> >     include elfos.h
> >     https://github.com/gcc-mirror/gcc/blob/master/gcc/config.gcc#L2369
> >     <https://github.com/gcc-mirror/gcc/blob/master/gcc/config.gcc#L2369>
> >
> >     Which defines `ASM_OUTPUT_SYMVER_DIRECTIVE`
> >
> https://github.com/gcc-mirror/gcc/blob/master/gcc/config/elfos.h#L259 <
> https://github.com/gcc-mirror/gcc/blob/master/gcc/config/elfos.h#L259>
> >
> >     Which is necessary for
> >     https://github.com/gcc-mirror/gcc/blob/master/gcc/varasm.cc#L6260
> >     <https://github.com/gcc-mirror/gcc/blob/master/gcc/varasm.cc#L6260>
> >
> >     Changing the targets to include elfos.h leads to a number of
> >     conflicts with
> >     the target specific header (config/microblaze/microblaze.h).
> >
> >     Should `ASM_OUTPUT_SYMVER_DIRECTIVE` be copied into
> >     config/microblaze/microblaze.h or should the MicroBlaze targets and
> >     header
> >     be reworked to support elfos.h?
> >
> >
> > IMO reworked to include elfos.h. During the RTEMS port, we noticed that
> > some quirks on the microblaze gcc because it isn't using elfos.h. This
> > likely
> > will mean it will be updated as a side-effect of normal GCC maintenance
> > instead of being an odd singleton which doesn't share.
> >
> >
> >     I'm asking because I've seen a number of projects run into this
> >     issue (xz,
> >     elfutils, libfuse, libkcapi, cryptsetup).
> >
> >
> > And RTEMS.
> >
> > --joel
>
>
> Joel -- do you have a patch to add elfos.h to MicroBlaze?
>
>

I have a very crude commit here off of 11.3.0:

https://github.com/vfazio/gcc/commit/e65fea47b881b136f6753001791ebf68a4874dd6

I've tested it as a patch on Buildroot's toolchain and dropped the patch we
used to hack
around the previous lack of symver support for XZ. I was able to boot the
resultant kernel
and rootfs via qemu-system-microblaze and the symbol versions XZ expects
are included
based on discussions with the maintainer
https://github.com/tukaani-project/xz/pull/32#issuecomment-1424531920

I doubt the work is "complete" but it's a starting point.

-- 
> Michael Eager
>