Re: [WIP/RFC] MIPS registers overhaul

Daniel Jacobowitz
2003-05-21T16:58:23Z

On Wed, May 21, 2003 at 12:04:35PM -0400, Andrew Cagney wrote:
>
> >>That came out wrong.
> >>
> >>I think a GDB debugging a remote 64 bit MIPS ISA should always expect 64
> >>bit GPRs and 64 bit FPRs when the ISA is 64 bits, regardless of the ABI.
> >>
> >>It is quite legitimate, for instance, for GDB to do something as sick-o
> >>as clearing the FR bit and then resume the thread. The register
> >>save/restore code needs to correctly handle this - be it reject the
> >>operation or ``do the right thing''.
> >
> >
> >But when using rda or gdbserver to debug an o32 application, then for
> >all intents and purposes we are debugging a 32-bit ISA. The kernel
> >will not allow us to change the FR bit. The app will never see 64-bit
> >registers. The 32-bit protocol makes more sense here IMO.
>
> 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.

Certainly straight embedded is different. For those obviously the
64-bit protocol is appropriate.

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer