Re: [WIP/RFC] MIPS registers overhaul

Andrew Cagney
2003-05-21T15:34:58Z

> At Tue, 20 May 2003 16:52:23 -0400, Andrew Cagney wrote:
>
>> > At Sat, 17 May 2003 00:41:10 +0000 (UTC), "Kevin Buettner" wrote:
>> >
>
>> >> Unfortunately, it isn't reasonable to use an ABI-specific RDA to debug
>> >> an application which uses a different ABI. It might kind of, sort of
>> >> work some of the time, but there are various things that won't work.
>> >> You've just identified one of the problems.
>
>> >
>> >
>> > BTW, because of this kind of problem, does it even make sense that
>> > when talking to a mips64 kernel but using an o32 rda (or gdbserver
>> > 8-), you'd use a "mips64" protocol? I.e., why wouldn't it just use
>> > the 32-bit mips protocol, since from you're debugging a 32-bit binary
>> > with a 32-bit debugging daemon...
>
>>
>> Ignoring the FP registers, I think it does make sense. o32 code does
>> run on a 64 bit ISA. Who is GDB to decide what the ISA should be.

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''.

Andrew

> I think even w.r.t. FP registers it makes sense. 8-)
>
> in o32, there are exactly (32 * 32 bits) worth of FP registers.
>
> They've got a very strange organization, and different operations on
> them set them in non-obvious ways, but they're still 32*32 bits.
>
>
>
> cgd
>
>