Re: VAX addressing modes

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2017-07-27 05:28, Mouse wrote:
> > > 	R_VAX_RELATIVE   *ABS*+0x676cf
>
> > > My knowledge of VAX addressing modes is tiny, so [...]
>
> > I'm not sure I understand the problem.  This has nothing to do with
> > VAX addressing modes, but is a question of how relocatable symbols
> > are handled in the compiler, object file and linker.
>
> The part after the first comma is true - but relocations for a given
> architecture do have _something_ to do with the addressing modes that
> architecture makes available.  For example, you won't find a
> high-22-bits or low-10-bits relocation in a VAX file - but you may in a
> SPARC file, because of the SPARC sethi paradigm.

Right. There is a connection, in that it doesn't make sense to have some 
kind of relocation in the object file which cannot be realized in the 
architecture. But that only sets some constraints. It does not tell us 
anything about what a object file relocation means, and it does not have 
any direct connection to what addressing modes the architecture have. 
Hopefully, the linker or something like it, can take the object file 
symbols and relocations, and produce either some PIC or non-PIC code as 
a result, which is executable on the architecture. That's the point 
where this becomes something you might be able to look up in the VARM.

> (No, I can't speak to the original question, which is why I didn't
> respond.  I know the VAX addressing modes fairly well, but I know next
> to nothing about the relocations supported by the VAX toolchain.  The
> quoted relocation looks inconsistent to me, calling itself RELATIVE but
> describing the target as *ABS*, which looks like `absolute' to me.  So
> either it's broken, in which case I have no idea why or how it's
> broken, or it's not, in which case I don't understand VAX relocations
> enough to say anything useful.)

I can't guess either, but looking in VARM will not give any answers 
here, as this is not really about VAX addressing modes.

	Johnny

--
Johnny Billquist                  || "I'm on a bus
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