[U-Boot-Users] Fixup entries

Joakim Tjernlund
2008-04-09T16:19:59Z

> -----Original Message-----
> From: Kenneth Johansson [mailto:kenneth at southpole.se]
> Sent: den 9 april 2008 16:47
> To: joakim.tjernlund at transmode.se
> Cc: u-boot-users at lists.sourceforge.net
> Subject: Re: [U-Boot-Users] Fixup entries
>
>
> On Wed, 2008-04-09 at 13:23 +0200, Joakim Tjernlund wrote:
> > On Wed, 2008-04-09 at 11:32 +0200, Kenneth Johansson wrote:
> > > What is the fixup section used for ?
> > >
> > > of the 274 cards that build on my MAKEALL not one has any entries into
> > > this section.
> >
> > These are needed for relocation of function pointers(and possible some
> > think more). There was an attempt by Grant Likely to enable this
> > functionalty, but some toolchains had problems with so the function
> > was disabled. If you undo commit
> > 1c3dd43338a077165e7e0309cb3994e65d2bdbf8 you will enable it again for
> > powerpc.
> >
> > Jocke
>
> aaahhaa so that is how it's working.
>
> I remember having problem understanding this when I did the command
> section and ended up doing a manual relocation of the command table. But
> compiling with -mrelocatable and going over the .fixup section instead I
> can now remove that extra code and it works fine.
>
> It's not easy to understand the ABI.
>
> I removed the -fPIC and only used -mrelocatable and that works too.
>
> Wonder if there is something else in u-boot that use function pointers
> and work by accident due to the fact that the old address in flash is
> still valid.

Oh yes, there are a few such pointers. And the conversion to using fixups instead
is a bit lazy. Several manual relocations has only been nullified by setting
gd->reloc_off=0 instead of #ifdef:ing out the relevant code. Feel
free to send patches :)

Jocke