[U-Boot] [PATCH][v2] mpc85xx/u-boot*.lds: remove _GLOBAL_OFFSET_TABLE_ definition

Joakim Tjernlund
2015-11-02T18:48:18Z

[Resending with old email address]

I want to add why PROVIDE was added in the first place:
In theory it is possible to build an u-boot without ld defining
_GLOBAL_OFFSET_TABLE_, in that case we create _GLOBAL_OFFSET_TABLE_ ourself.

Should we start using -fPIC* one day this will we will be close to
an u-boot without _GLOBAL_OFFSET_TABLE_ and the __got2_entries calculation
will fail.

*older gcc's will automatically promote -fpic to -fPIC when used with -mrelocatable
I wrote a small patch in 2010 to fix this:
https://gcc.gnu.org/ml/gcc-patches/2010-10/msg02301.html
Cannot remember what gcc version(4.6?) that went into.

About the same time support for -msingle-pic-base was added to powerpc gcc
This would reduce code size further, possibly interesting for SPL?
I sent som patches for that but there were something holding them
back.

On Mon, 2015-11-02 at 17:17 +0100, Joakim Tjernlund wrote:
> On Fri, 2015-10-30 at 10:12 -0700, York Sun wrote:
> >
> > On 10/24/2015 10:02 PM, Prabhakar Kushwaha wrote:
> > > From: Zhenhua Luo <zhenhua.luo@freescale.com>
> > >
> > > In binutils-2.25, the _GLOBAL_OFFSET_TABLE_ symbols defined by PROVIDE in
> > > u-boot.lds overrides the linker built-in symbols
> > > (https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;
> > > h=b893397a4b1316610f49819344817715e4305de9),
>
> hmm, what was the reson for this change in binutils? As I recall, PROVIDE should
> only add a symbol when there is none and now binutils just ignores this, strange.
>
> > > so the linker is treating _GLOBAL_OFFSET_TABLE_ as a definition into the
> > > .reloc section.
>
> Yes, where do you want it instead? what is the difference with/without PROVIDE?
>
> > >
> > > To align with the change of binutils-2.25, the _GLOBAL_OFFSET_TABLE_ symbol
> > > should not be defined in sections, and the symbols in linker generated .got
> > > section should be used(https://sourceware.org/ml/binutils/2008-09/
> > > msg00122.html)
> > > Fixed the following build errors with binutils-2.25:
> > > > powerpc-poky-linux-gnuspe-ld.bfd: _GLOBAL_OFFSET_TABLE_ not defined in
> > > linker created .got
> > >
> > > Signed-off-by: Zhenhua Luo <zhenhua.luo@freescale.com>
> > > Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
> > > ---
> > > Changes for v2: Updated Subject
> > >
> >
> > Prabhakar/Zhenghua,
> >
> > Have you addressed Tom's comment (on rev 1 patch)? Quote, "What happens when we
> > use older binutils? I'd like some run-time testing too please".
> >
> > York
> >
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