On Sat, Sep 08, 2001 at 05:44:22PM +0200, Kevin D. Kissell wrote:
> > Skip over copX instructions for X != 1 also.
> I'm sure there's a story behind this of which I am not aware,
> but surely skippling COP2 or COP3 instructions can't be
> correct behavior. Either there is no such coprocessor, in
> which case SIGILL would seem to me to be appropriate,
> or there really is some application-specific coprocessor
> on the COP2 interface. If such a coprocessor exists, and
> has context that the kernel doesn't know how to save and
> restore, until such time as we develop kernel modules to
> handle them, wouldn't it be more practical to allow exactly
> one processor to "own" the coprocessor? In that model,
> the first thread to issue a COP2 instruction would get it
> enabled and restart the instruction, but until that thread
> terminates, all other requestors would get nailed with
> SIGILL or some more appopriate signal.
Before this change the situation when we were trying to execute a copX
instruction (where X != 1) we would have re-executed the same instruction
again after returning from the signal handler / exception handler, ad
As for cop 0 this is the right thing to do because we treat it as
non-existant for userspace. To my knowledge only Sony Playstation
implements coprocessor 2 (and we don't support it) and cop3 is afaik unused
except MIPS IV recycling it, so I think we do the right thing.