Re: bfd_perform_relocation() and split fields

[Eric DeVolder <devolder at evsx dot com>]

Ian Lance Taylor wrote:

>    Date: Tue, 16 Nov 1999 17:56:45 -0600
>    From: Eric DeVolder <devolder@evsx.com>
>
>    The function bfd_perform_relocation() is oriented for inserting a
>    resolved relocation into a contiguous set of bits. I find myself in
>    perhaps a rather unique situation in which I need a resolved relocation
>    to appear in two non-contiguous fields within an instruction, i.e. the
>    most-significant portion of the reloc appears in field A, and the
>    least-significant portion of the reloc appears in field B, where other
>    bits separate field A from field B.
>
>    Function bfd_perform_relocation() as it stands today wont do this, so I
>    have two options as I see it:
>
>       * Generate two relocs, one for field A and one for field B
>       * Add somekind of CPU-specific hook to bfd_perform_relocation()
>
> The CPU specific hook is already there: the special_function field in
> the howto structure.  Just make that do whatever you need your
> relocation to do.

The call to special_function occurs way too early in bfd_perform_relocation().
There are several statements that perform calculations or modify reloc_entry
that would not be able to "preserve" a split-field value all the way thru to
where the bits are actually placed back into the insn. What I'm suggesting is
a hook right before the switch(howto-size) statement that gives you a chance
to munge the reloc value before it gets inserted.

> Note that in the ``new'' linker approach, bfd_perform_relocation is
> not used while linking.

I'm not familiar with this...is there a pointer available? or email thread?

>
>
> Ian