Re: [WIP/RFC] MIPS registers overhaul

Daniel Jacobowitz
2003-05-22T00:32:02Z

On Wed, May 21, 2003 at 03:15:00PM -0400, Andrew Cagney wrote:
> >On May 21, 12:58pm, Daniel Jacobowitz wrote:
> >
> >
> >>> From GDB's view point, the ISA is 64 bit.
> >>>
> >>> The fact that a specific remote debug agent choses to use 32 bit
> >>> registers is a limitation of that debug agent / kernel. An embedded
> >>> target, and I'm pretty sure IRIX 6.5, for instance, don't do that.
> >
> >>
> >>No, from GDB's view point in this situation, the target ISA is _NOT_ 64
> >>bit. Nothing 64-bit is available, either to the inferior or to the
> >>debugger. Period.
> >>
> >>I would be a little surprised if IRIX didn't work that way too, but I
> >>don't have access to IRIX to poke around.
> >
> >
> >I too would be surprised. I should think that SGI would want to
> >ensure that legacy programs (i.e, those using the o32 ABI) behave the
> >same when run on 64-bit hardware as they do when run on 32-bit
> >hardware. One of the implications of this is that illegal
> >instructions in the 32-bit ISA should continue to be illegal when run
> >on the 64-bit hardware.
>
> Er, it's the same deal as for SPARC. If GDB is built against the 64 bit
> debug interface, it can debug both 32 and 64 bit applications. This is
> the debuggers view, not the program being run's view.

But the point is that the debugger's view of a 32-bit application on
MIPS is of a 32-bit ISA. That's all that's available. You get 32-bit
registers from the kernel.

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer